iliiiiiiiiiiipiiiiiiiiliiii fjiiisiiiiiijiiiiPiiili Marine Biological Laboratory Received A-T. 11. 1950 Accession No. 64455 Given By Ccmstock Publ. Co., Inc. ., Place. It.h3ca, i:. Y. AN INTRODUCTION TO ENTOMOLOGY AN INTRODUCTION TO ENTOMOLOGY BY JOHN HENRY COMSTOCK LATE PROFESSOR OF ENTOMOLOGY AND GENERAL INVERTEBRATE ZOOLOGY IN CORNELL UNIVERSITY NINTH EDITION REVISED ITHACA X^^^ NEW YORK COMSTOCK PUBLISHING COMPANY, INC. 1949 COPYRIGHT 1920 BY COMSTOCK PUBLISHING COMPANY COPYRIGHT 1924 BY J. H. COMSTOCK COPYRIGHT 1933, 1936, 1940 BY COMSTOCK PUBLISHING COMPANY, INC. PRINTED IN THE UNITED STATES OF AMERICA BY THE VAIL-BALLOU PRESS, INC., BINGHAMTON, N. Y. TO MY OLD STUDENTS WHOSE YOUTHFUL ENTHUSIASM WAS A CONSTANT INSPIRATION DURING THE LONG PERIOD OF MY SERVICE AS A TEACHER THIS EFFORT TO CONTINUE TO AID THEM IS AFFECTIONATELY INSCRIBED PREFACE TO THE 1940 EDITION INCREASING interest in the biological control of insects has cre- ated an insistent demand for a wider knowledge of the parasitic forms active in destroying those insects which are injurious to agriculture. The greater number of these parasitic species is found in the order Hymenoptera. Opportunity has, therefore, been taken in this edition (1940) to revise and extend the discussion of the superf ami- lies Ichneumonoidea, Proctotrupoidea and Chalcidoidea, the groups which contain the most important parasites. In addition, a shorter key to the commoner families of the suborder Clistogastra together with keys to the subfamilies of the Ichneumonidae and Chalcididas have been included. The text for the keys and for the new matter on the parasitic Hymenoptera has been contributed by Dr. Henry K. Townes, who has given much study to these groups. It is hoped that the keys will prove helpful to those interested in the parasitic forms. Glenn W. Herrick Ithaca, June IQ40. PREFACE TO THE 1936 EDITION IT SEEMED opportune with this reprinting (1936) of the Intro- duction to make some slight revision, more specifically of the orders of the wingless insects. The class Myrientomata of Berlese has been advanced to its more logical position as the order Protura of Silvestri, under the Hexapoda. This has been done with some reservation, but in accord with the trend of opinion among morphologists and probably most systematists. Probably the data for treating the suborder Entognatha of the Thysanura as a definite order are more numerous and more reliable than for the foregoing change in position of the Protura. Out of respect, however, for the careful conservatism of Professor Comstock, the writer has retained the Entognatha as a subordinate group in the Thysanura. This is, no doubt, illogical because Professor Comstock always kept pace with legitimate progress in his field of science. PREFACE The Hemimeridae has been advanced to its place in the Dermap- tera and the discussion briefly extended on the basis of the paper by Rehn and Rehn. At the suggestion of Dr. J. C. Bradley the suborder Idiogastra has been abandoned and the family Oryssidae included among the Chalastogastra. Glenn W. Herrick Ithaca, July iQj6. THE ORIGINAL PREFACE IT IS now nearly thirty years since "A Manual for the Study of Insects," in the preparation of which I was aided by Mrs. Com- stock, was published. The great advances in the science of ento- mology during this period have made a revision of that work desirable. In the revision of the "Manual " so many changes and additions have been found necessary that the result is a book differing greatly from the original work; for this reason, it is published under a different title. The title selected is that of an earlier work, an "Introduction to Entomology" published in 1888 and long out of print. Part I of the present volume was published separately in 1919, in order that it might be available for the use of classes in insect mor- phology and also that an opportunity might be offered for the sugges- tion of desirable changes to be made before the incorporation of it in the completed work. Such suggestions have been received, with the result that some very important changes have been made in the text. In the preparation of this work I have received much help from my colleagues in the entomological department of Cornell University, for which I wish to make grateful acknowledgment, and especially to Dr. J. G. Needham for aid in the study of wing- venation, to Dr. O. A. Johannsen for help in the preparation of the chapter on the Diptera, to Dr. W. T. M. Forbes for help in the preparation of the chapter on the Lepidoptera, to Dr. J. C. Bradley for help in the prep- aration of the chapter on the Hymenoptera, and to Dr. J. T. Lloyd for the use of his figures of the cases of caddice worms. From the published works of Professors Herrick, Crosby and Slingerland, Crosby and Leonard, Sanderson, and Matheson I have gleaned much information; references to these and to the more im- portant of the other sources from which material has been drawn are indicated in the text and in the bibliography at the end of the volume. PRE FA CE References to the bibliography are made in the text by citing the name of the author and the year in which the paper quoted was pubHshed. The wood cuts used in the text were engraved from nature by Mrs. Anna B. Comstock for our joint work, "A Manual for the Study of Insects." The other original figures and the copies of published figures were drawn by Miss Anna C. Stryke, Miss Ellen Edmonson, Miss Mary Mekeel, Mr. Albert Force, Mrs. Louise Nash, and Miss E. L. Keyes. I am deeply indebted to each of these artists for the painstaking care shown in their work. As an aid to the pronunciation of the technical terms used and of the Latin names of insects, the accented syllable is marked with a sign indicating the quality of the vowel according to the English sys- tem of pronouncing Latin. Two objects have been kept constantly in mind in the preparation of this book: first, to aid the student in laying a firm foundation for his entomological studies; and second, to make available, so far as possible in the limited space of a handbook, a knowledge of the varied phenomena of the insect world. It is hoped that those who use this book will find delight in acquiring a more intimate acquaintance with these phenomena. John Henry Comstock Entomological Department Cornell University August IQ24. TABLE OF CONTENTS PART I. THE STRUCTURE AND METAMORPHOSIS OF INSECTS CHAPTER I Pages The Characteristics of Insects and Their Near Relatives i Phylum Arthropoda i List of the classes of the Arthropoda 2 Table of the classes of the Arthropoda 3 Class Onychophora 4 Class Crustacea 6 Class Palaeostracha 8 Class Arachnida 9 Class Pycnogonida 10 Class Tardigrada 12 Class Pentastomida 14 Class Diplopoda 15 Class Pauropoda 14 Class Chilopoda 28 Class Symphyla 23 Class Myrientomata 24 Class Hexapoda 26 CHAPTER II The External Anatomy of Insects 29 I. the structure of the body-wall a. The three layers of the body-wall 29 The hypodermis 29 The trichogens 3° The cuticula 3" Chitin 30 Chitinized and non-chitinized cuticula 30 The epidermis and the dermis 3^ The basement membrane 3 1 b. The external apophyses of the cuticula 31 The cuticular nodules 3^ The fixed hairs 3i The spines 32 c. The appendages of the cuticula 32 The spurs 32 64455 TABLE OF CONTENTS The setce 32 The taxonomic value of setae 33 A classification of setae 33 (i) The clothing hairs 33 (2) The glandular hairs 33 (3) The sense-hairs 33 The segmentation of the body 34 The body-segments, somites or metamcrcs 34 The transverse conjunctivae 34 The segmentation of the appendages 34 The divisions of a body-segment 34 The tergum, the pleura, and the sternum 34 The lateral conjunctivae 35 The sclerites 35 The sutures 35 The median sutures 35 The piliferous tubercles of larvae 35 The homologizing of sclerites 35 The regions of the body > 36 2. THE HEAD The corneas of the eyes 36 The corneas of the compound eyes 36 The corneas of the ocelli 37 The areas of the surface of the head 37 The front 37 The clypeus 38 The labrum 38 The epicranium 38 The vertex 39 The occiput 39 The genag 39 The postgenas 39 The gula 39 The ocular sclerites 39 The antennal sclerites 39 The trochantin of the mandible 40 The maxillary pleurites 40 The cervical sclerites 40 The appendages of the hsad 40 The antennas 40 The mouth-parts 42 The labrum 42 The mandibles 42 The maxillulae 42 The maxillae 42 The labium or second maxillas 45 TABLE OF CONTENTS xi The epipharynx 46 The hypopharynx 47 d. The segments of the head 47 3. THE THORAX c. The segments of the thorax 48 The prothorax, mesothorax, and metathorax 48 The alitrunk 49 The propodeum or the median segment 49 b. The sclerites of a thoracic segment 49 The sclerites of a tergum 49 The notum 49 The postnotum or the postscutellum 50 The divisions of the notum 50 The patagia 50 The parapsides 51 The sclerites of the pleura 51 The episternum 51 The epimerum 51 The preepistemum 51 The paraptera , 51 The spiracles 52 The peritremes 52 The acetabula 52 The sclerites of a sternum 52 c. The articular sclerites of the appendages 53 The articular sclerites of the legs 53 The trochantin 53 The antecoxal piece 54 The second antecoxal piece 54 The articular sclerites of the wings 54 The tegula 54 The axillaries 54 d. The appendages of the thorax 55 The legs 56 The coxa 56 The styli 56 The trochanter 57 The f emiu: 57 The tibia 57 The tarsus 57 The wings 58 The different types of wings 59 The margins of wings 60 The angles of wings 60 The axillary cord 60 The axillary membrane 60 The alula 60 The axillary excision 61 TABLE OF CONTENTS The posterior lobe 6i The methods of uniting the two wings of each side 6i The hamuli 6i The frenulum and the frenulum hook 6i The jugum 6i The fibula 62 The hypothetical type of the primitive wing-venation 62 Longitudinal veins and cross-veins 64 The principal wing-veins 64 The chief branches of the wing-veins 64 The veins of the anal area 65 The reduction of the number of the wing-veins 65 Serial veins 67 The increase of the number of the wing- veins 68 The accessory veins 68 The intercalary veins 69 The adventitious veins 7° The anastomosis of veins 70 The named cross-veins 71 The arculus 72 The terminology of the cells of the wing 72 The corrugations of the wings 73 Convex and concave veins 73 The furrows of the wing 73 The bullae 74 The ambient vein 74 The humeral veins 74 The pterostigma or stigma 74 The epiplurae 74 The discal cell and the discal vein 74 The anal area and the preanal area of the wing 75 4. THE ABDOMEN 75 a. The segments of the abdomen 75 b. The appendages of the abdomen 7^ The styli or vestigial legs of certain Thysanura 76 The coUophore of the Collembola 7^ The spring of the Collembola 7^ The genitalia 7^ The cerci 77 The median caudal filament 7^ The prolegs of larvae 7^ 5. THE MUSIC AND THE MUSICAL ORGANS Cr INSECTS 78 a. Sounds produced by striking objects outside of the body 79 b. The music of flight 80 TABLE OF CONTENTS xiii c. Stridulating organs of the rasping type 8i The stridulating organs of the Locustidse 82 The stridulating organs of the Gryllidae and the Tettigoniidag 83 Rasping organs of other than orthopterous insects 87 d. The musical organs of a cicada 89 e. The spiracular musical organs 91 /. The acute buzzing of flies and bees 91 g. Musical notation of the songs of insects 92 h. Insect choruses 93 CHAPTER III The Internal Anatomy of Insects 94 i. the hypodermal structures 95 a. The internal skeleton 95 Sources of the internal skeleton 95 Chitinized tendons 95 Invaginations of the body-wall or apodemes 95 The tentorium 96 The posterior arms of the tentorium 96 The anterior arms of the tentorium 97 The dorsal arms of the tentorium 97 The frontal plate of the tentoritun 97 The endothorax 97 The pragmas 97 The lateral apodemes 98 The furcae 98 b. The hypodermal glands 98 The molting-fluid glands 99 Glands connected with setae 99 Venomous setae and spines 100 Androconia 100 The specific scent-glands of females 100 Tenent hairs 100 The osmeteria loi Glands opening on the surface of the body 102 Wax-glands 102 Froth-glands of spittle insects 102 Stink -glands 102 The cephalic silk-glands 103 The salivary glands 104 2. THE MUSCLES IO4 3. THE ALIMENTARY CANAL AND ITS APPENDAGES IO7 a. The more general features 107 The principal divisions 108 Imperforate intestines in the larvae of certain insects 108 TABLE OF CONTENTS b. The fore-intestine 109 The layers of the fore-intestine 109 The intima 109 The epithelium 109 The basement membrane 109 The longitudinal muscles 109 The circular muscles 109 The peritoneal membrane 109 The regions of the fore-intestine 109 The pharynx 109 The oesophagus 1 10 The crop no The proventriculus no The oesophageal valve in c. The mid-intestine Ill The layers of the mid-intestine in The epithelium 112 The peritrophic membrane 112 d. The hind-intestine 112 The layers of the hind-intestine 112 The regions of the hind-intestine 113 The Malpighian vessels 113 The Malpighian vessels as silk-glands 113 The caecum 113 The anus 113 4. THE RESPIRATORY SYSTEM II3 a. The open or holopneustic type of respiratory organs 114 1. The spiracles 114 The position of the spiracles 114 The number of spiracles 114 Terms indicating the distribution of the spiracles 115 The structure of spiracles 116 The closing apparatus of the tracheae 116 2. The trachece 116 The structure of the trachea 117 3. The tracheoles 118 4. The air-sacs 118 5. Modifications of the open type of respiratory organs 119 b. The closed or apneustic type of respiratory organs • 119 /. The Tracheal gills 119 2. Respiration of parasites 120 3. The blood-gills 120 TABLE OF CONTENTS XV 5. THE CIRCULATORY SYSTEM 121 The general features of the circulatory system 12 1 The heart 121 The pulsations of the heart 122 The aorta 122 The circulation of the blood 122 Accessory circulatory organs 122 6. THE BLOOD 122 7. THE ADIPOSE TISSUE I23 8. THE NERVOUS SYSTEM 123 The central nervous system 123 The oesophageal sympathetic nervous system 125 The ventral sympathetic nervous system 127 The peripheral sensory nervous system 128 9. GENERALIZATIONS REGARDING THE SENSE-ORGANS OF INSECTS.. . 1 29 A classification of the sense-organs 129 The cuticular part of the sense-organs 130 10. THE ORGANS OF TOUCH I3I 11. THE ORGANS OF TASTE AND SMELL I32 12. THE ORGANS OF SIGHT 134 The general features I34 The two types of eyes I34 The distinction between ocelli and compound eyes 134 The absence of compound eyes in most of the Apterygota 135 The absence of compound eyes in larvae I35 The ocelH I35 The primary ocelli i35 The adaptive ocelli 136 The structure of a visual cell I37 The structure of a primary ocellus I37 Ocelli of Ephemerida i39 The compound eyes I39 The physiology of compound eyes 141 The theory of mosaic vision 14^ Day-eyes 14^ Night-eyes H3 Eyes with double function i43 Divided eyes H4 The tapetum ^44 TABLE OF CONTENTS 13. THE ORGANS OF HEARING 145 The general featiires 145 The tympana 145 The chordotonal organs 145 The scolopale and the scolopophore 146 The integumental and the subintegumental scolopophores 146 The structure of a scolopophore 146 The structure of a scolopale 147 The simpler forms of chordotonal organs 147 The chordotonal ligament 147 The chordotonal organs of larvse 148 The chordotonal organs of the Locustidae 148 The chordotonal organs of the Tettigoniidae and of the Gryllida;. . . 149 The trachea of the leg 1 50 The spaces of the leg 151 The supra-tympanal or subgenual organ 151 The intermediate organ 152 Siebold's organ or the crista acustica 152 Johnston's organ 1 52 14. SENSE-ORGANS OF UNKNOWN FUNCTIONS The sense-domes or the olfactory pores 154 15. THE REPRODUCTIVE ORGANS The general features 156 Secondary sexual characters 157 The reproductive organs of the female 157 The general features of the ovary 157 The wall of an ovarian tube 158 The zones of an ovarian tube 158 The contents of an ovarian tube 158 The egg-follicles 158 The functions of the follicular epithelium 159 The ligament of the ovary 1 59 The oviduct 1 59 The egg-calyx 1 59 The vagina 1 59 The spsrmatheca 159 The bursa copulatrix 1 59 The colleterial glands 160 The reproductive organs of the male 160 The general features of the testes 160 The structure of a testicular follicle 161 The spermatophores 1 62 Otlier structures 162 TABLE OF CONTENTS xvii l6. THE SUSPENSORIA OF THE VISCERA The dorsal diaphragm 1 62 The ventral diaphragm 165 The thread-like suspensoria of the viscera 163 17. SUPPLEMENTARY DEFINITIONS The oenocytes 163 The pericardial cells 164 The phagocytic organs 164 The light-organs 165 CHAPTER IV The Metamorphosis of Insects 166 I. the EXTERNAL CHARACTERISTICS OF THE METAMORPHOSIS OF INSECTS a. The egg 1 66 The shape of the egg 167 The sculpture of the shell 167 The microphyle 167 The number of eggs produced by insects 168 Modes of laying eggs 168 Duration of the egg-state 170 b. The hatching of young insects 171 The hatching spines 171 c. The molting of insects 171 General features of the molting of insects 171 The molting fluid 172 The number of postembryonic molts 172 Stadia 172 Instars 172 Head measurements of larva; 173 The reproduction of lost limbs 173 d. Development without metamorphosis 174 The Ametabola 174 e. Gradual metamorphosis 175 The Paurometabola 176 The term nymph 176 Deviations from the usual type 176 The Saltitorial Orthoptera 177 The Cicadas 177 The Coccidae 177 The Aleyrodida; 177 The Aphididse 177 The Thysanoptera . 177 /. Incomplete metamorphosis 178 The Hemimetabola 179 The term naiad 179 Deviations from the usual type 1 80 The Odonata 180, The Ephemerida ,,.,,... 180 i TABLE OF CONTENTS g. Complete metamorphosis l8o The Holometabola i8o The term larva l8o The adaptive characteristics of larvae i8i The different types of larvae 183 The prepupa 185 The pupa 186 The chrysalis 186 Active pupae 187 The cremaster 187 The cocoon 188 Modes of escape from the cocoon 188 The puparium 190 Modes of escape from the puparium 190 The different types of pupae 190 The imago 191 h. Hypermetamorphosis 191 i. Viviparous insects 191 Viviparity with parthenogenetic reproduction 192 Viviparity with sexual reproduction 193 j. Neoteinia 194 2. THE DEVELOPMENT OF APPENDAGES I94 a. The development of wings 195 The development of the wings of nymphs and naiads 195 The development of the wings in insects with a complete meta- morphosis 195 b. The development of legs 197 The development of the legs of nymphs and naiads 198 The development of the legs in insects with a complete meta- morphosis 198 c. The development of antennae 199 d. The development of mouth-parts 200 e. The development of the genital appendages 201 3. THE DEVELOPMENT OF THE HEAD IN THE MUSCID^ 202 4. THE TRANSFORMATION OF THE INTERNAL ORGANS 204 TABLE OF CONTENTS PART II. THE CLASSIFICATION AND THE LIFE-HISTORIES OF INSECTS Chapter V. — The sub-classes and the orders of the class Hexapoda . . 206 Chapter VI. — Class Hexapoda 217 Chapter VII.— The Apterygota 218 Chapter VII. —Order Protura 218 Chapter VII. — Order Thysanura 219 Chapter VII. — Order Collembola 225 Chapter VIIL— The Pterygota Chapter VIIL — Order Orthoptera 230 Chapter IX. — Order Zoraptera 270 Chapter X. — Order Isoptera 273 Chapter XL — Order Neuroptera 281 Chapter XII. — Order Ephemerida 308 Chapter XIIL — Order Odonata 314 Chapter XIV. — Order Plecoptera , 325 Chapter XV. — Order Corrodentia 331 Chapter XVI. — Order Mallophaga 335 Chapter XVII. —Order Embiidina 338 Chapter XVIII. — Order Thysanoptera 341 Chapter XIX. — Order Anoplura 347 Chapter XX. — Order Hemiptera 350 Chapter XXI. — Order Homoptera 394 Chapter XXII. — Order Dermaptera 460 Chapter XXIII. — Order Coleoptera 464 Chapter XXIV. — Order Strepsiptera 546 Chapter XXV. — Order Mecoptera 550 Chapter XXVL -Order Trichoptera 555 Chapter XXVIL — Order Lepidoptera 571 Chapter XXVIIL —Order Diptera 773 Chapter XXIX. — Order Siphonaptera 877 Chapter XXX. — Order Hymenoptera 884 Bibliography 1008 Index 1029 PART I THE STRUCTURE AND METAMORPHOSIS OF INSECTS CHAPTER I THE CHARACTERISTICS OF INSECTS AND OF THEIR NEAR RELATIVES Phylum ARTHROPODA The Arthr If an insect, a scorpion, a centipede, or a lobster be examined, the body will be found to be composed of a series of more or less similar rings or segments joined together; and some of these seg- ments will be found to bear jointed legs (Fig. i) . All animals possess- ing these characteristics are classed together as the Arthr opoda, one of the chief divisions or phyla of the animal kingdom. A similar segmented form of body is found among worms; but these are distinguished from the Arthropoda by the absence of legs. It should be remembered that many animals commonly called worms, as the tomato-worm, the cabbage-worm, and others, are not true worms, but are the larvae of insects (Fig. 2). The angle-worm is the most familiar example of a true worm. In the case of certain arthropods the dis- tinctive characteristics of the phylum are not evident from a ciu-sory examination. This may be due to a very generalized condi- tion, as perhaps is true of Peripatus; but in Fig. I. — An arthropod, most instances it is due to a secondary modifi- cation of form, the result of adaptation to special modes of life. Thus the segmentation of the body may be Fig. 2. — ^A larva of an insect. (1) .v^^^<^ AN INTRODUCTION TO ENTOMOLOGY many other insects. obscured, as in spiders and in mites (Fig. 3) ; or the jointed append- ages may be absent, as in the larvae of flies (Fig. 4), of bees, and of In all of these cases, however, a careful study of the structure of the animal, or of its complete life-history, or of other animals that are evidently closely allied to it removes any doubt regarding its being an arthropod. The phylum Arthropoda is the largest of the phyla of the animal kingdom, including many more known species than all the other phyla taken together. This Fig. 3.— A mite, an arth- vast assemblage of animals in- ropod in which the ^^^^^g f^^^g differing widely in segmentation or the " -^ body is obscured. The structure, all agreemg, however, in the possession of the essential characteristics of the Arthropoda. Several distinct types of arthropods are recognized; and those of each type are grouped together as a class. The number of distinct classes that should be recog- nized, and the relation of these classes to each other are matters regarding which there are still differences of opinion ; we must have much more knowledge than we now possess before we can speak with any degree of certainty regarding them. Each of the classes enumerated below is regarded by all as a distinct group of animals ; but in some cases there may be a question whether the group should be given the rank of a distinct class or not. The order in which the classes are discussed in this chapter is indicated in the following list. southern cattle-tick, Boophilus annulatus. LIST OF THE CLASSES OF THE ARTHROPODA THE MOST PRIMITIVE ARTHROPODS Class Onychophora, page 4 THE AQUATIC SERIES Class Crustacea, page 6 Class Palaeostracha, page 8 AN OFFSHOOT OF THE AQUATIC SERIES, SECONDARILY AERIAL Class Arachnida, page 9 CHARA CTERISTICS OF INSECTS AND THEIR RELA TIVES 3 IV. DEGENERATE ARTHROPODS OF DOUBTFUL POSITION Class Pycnogonida, page lo Class Tardigrada, page 12 Class Pentastomida, page 14 V. THE PRIMARILY AERIAL SERIES Class Onychophora (See above) Class Diplopoda, page 15 Class Pauropoda, page 18 Class Chilopoda, page 20 Class Symphyla, page 23 Class Myrientomata, page 24 Class Hexapoda, page 26 TABLE OF CLASSES OF THE ARTHROPODA A. Worm-like animals, with an unsegmented body, but with many unjointed legs Onychophora AA. Body more or less distinctly segmented except in a few degen- erate forms. B. With two pairs of antennae and at least five pairs of legs; respiration aquatic Crustacea BB. Without or apparently without antenucE. C. With well-developed aquatic respiratory organs. PaL/EOSTRACHA CC. With well-developed aerial respiratory organs or with- out distinct respiratory organs. D. With well-developed aerial respiratory organs. E. Body not resembhng that of the Thysanura in form. Arachnida EE. Body resembling that of the Thysanura in form (Family Eosentomidas) Myrientomata DD. Without distinct respiratory organs. E. With di"tinctly segmented legs. F. Body resembling that of the Thysanura in form, but without antennas, and with three pairs of thoracic legs and three pairs of vestigial abdominal legs (Family Acerentomidcs) Myrientomata FF. With four or five pairs of ambulatory legs; abdomen vestigial Pycnogonida EE. Legs not distinctly segmented. F. With four pairs of legs in the adult instar. Tardigrada AN INTRODUCTION TO ENTOMOLOGY FF. Larva with two pairs of legs, adult without legs Pentastomida BBB. With one pair, and only one, of feeler-like antennae. Respiration aerial. C. With more than three pairs of legs, and without wings. D, With two pairs of legs on some of the body-segments. DiPLOPODA DD . With only one pair of legs on each segment of the body. E. Antennas branched Pauropoda EE. Antennae not branched. F. Head without a Y-shaped epicranial suture. Tarsi of legs with a single claw each. Opening of the reproductive organs near the caudal end of the body Chilopoda FF. Head with a Y-shaped epicranial suture, as in insects. Tarsi of legs with two claws each. Opening of the reproductive organs near the head. Symphyla CC. With only three pairs of legs, and usually with wings in the adult state Hexapoda Class ONYCHOPHORA The genus Peripatus of authors The members of this class are air-breathing animals, with a nearly cylindrical, unsegmented body, which is furnished with many pairs of unjo-'ntcd legs. The reproductive organs open near thehindend ofthebody. The class Onychophora occupies the position of a connecting link between the Arthropoda and the phylum Annulata or worms; and is therefore of the highest interest to students of systematic zoology. All known members of this class have been included until recently in a single genus Pertpatus; but now the fifty or more known species are distributed among nearly a dozen genera. The body (Fig. 5) is nearly cylindrical, cat- erpillar - like in form, but is un- segmented ex- ternally. It is I^ig. 5- — Peripatoides novcB-zealandicce. furnished with many pairs of legs, the number of which varies in different species. The legs have a ringed appearance, but are not distinctly jointed. CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 5 The head bears a pair of ringed antennae (Fi^. 6) ; behind these on the sides of the head, there is a pair of short appendages termed oral papillae. The mouth opening is surrounded by a row of lobes which constitute the lips, and between these in the anterior part of the mouth-cavity there is an obtuse pro- jection, which bears a row of chitinous points. Within the mouth cavity there are two pairs of hooked plates, which have been termed the mandibles, the two plates of each side being regarded a? a single mandible. Although the body is unsegmented externally, internally there are evi- dences of a metameric arrangement of parts. The ventral nerve cords, which at first sight appear to be without ^r/ ganglia, are enlarged opposite each pair of legs, and these enlargments are regarded as rudimentary ganglia. Fig. 6.-Ventral view of the head We can, therefore speak of each sec- and first pair of legs of Peri- ,• i: u J J- 4. paloides; a, antenna; o, oral tion of a body corresponding to a papilla. pair of appendages as a segment. The metameric condition is farther indicated by the fact that most of these segments contain each a pair of nephridia; each nephridium opening at the base of a leg. The respiratory organs are short tracheae, which are rareiy branched, and in which the t^nidia appear to be rudimentary.* In some species, the spiracles are distributed irregularly; in others, they are in longitudinal rows. The sexes are distinct. The reproductive organs open near the hind end of the body, either between the last or the next to the last pair of legs. The various species are found in damp situations, under the bark of rotten stumps, under stones or other objects on the ground. They have been found in Africa, in Australia, in South America, and in the West Indies. Their relationship to the Arthropoda is shown by the presence of paired appendages, one, or perhaps two, pairs of which are modified as jaws; the presence of tracheae which are found nowhere else except *It is quite possible that the "short trachese" described by writers on the structure of these animals are tracheoles. See the account of the distinguishing features of tracheae and tracheoles m Chapter III. 6 AN INTRODUCTION TO ENTOMOLOGY in the Arthropoda; the presence of paired ostia in the wall of the heart ; and the presence of a vascular body cavity and pericardium. They resemble the Annulata in having a pair of nephridia in most of the segments of the body corresponding to the pairs of legs, and in having ciha in the generative tracts. An extended monograph of the Onychophora v/as published by Bouvier ('05-07). Class CRUSTACEA The Crustaceans The members of this class are aquatic arthropods, which breathe by true gills. They have two pairs of antennce and at least five pairs of legs. The position of the openings of the reproductive organs varies greatly; hut as a rule they are situated far forward. The most familiar examples of the Crustacea are the cray- fishes, the lobsters, the shrimps, and the crabs, Cray-fishes (Fig. 7) abound in our brooks, and are often improperly called crabs. The lobsters, the shrimps, and the true crabs live in salt water. Excepting Llmulus, the sole living representative of the class described next, the Crus- tacea are distinguished from all other arthro- pods by their mode of respiration, being the only ones that breathe by true gills. Many in- sects live in water and are furnished with gill- like organs; but these are either tracheal gills or blood-gills, organs which differ essentially in struc- ture from true gills, as Cypndopsis, c, Cyclops. A cray-iish. Daphnia; CHARACTERISTICS OF INSECTS AND THEIR RELATIVES described later. The Crustacea also differ from other Arthropoda in having two pairs of antennae. Rudiments of two pairs of antennae have been observed in the embryos of many other arthropods ; but in these cases one or the other of the two pairs of antennas fail to develop. The examples of crustaceans named above are the more con- spicuous members of the class; but many other smaller forms abound both in the sea and in fresh water. Some of the more minute fresh- water forms are almost sure to occur in any fresh-water aquarium. In Figure 8 are repre- sented three of these greatly enlarged. The minute crustaceans form an important element in the food of fishes. Some crustaceans live in damp places on land, and are often found by c(;llectors of insects; those most often ob- served are the sow-bugs (Oniscoida), which fre- quently occur about water-soaked wood. Figure 9 represents one of these. As there are several, most excellent text books devoted to the Crustacea, it is unnecessary to discuss farther this class in this place. Fig. 9. — A sow -bug, Cylisticus convexus (From Richardson after Sars). AN INTRODUCTION TO ENTOMOLOGY Class PAL^OSTRACHA The King-crabs or Horseshoe-crabs The members of this class are aquatic arthropods, which resemble the Crustacea in that they breathe by true gills, but in other respects are closely allied to the Arachnida. They are apparently without antenna, the appendages hom- ologous to antenncB being not feeler-like. The reproductive organs open near the base of the abdomen. The class Palseostracha is composed almost entirely of extinct forms, there being living representatives of only a single order, the Xiphosura, and this order is nearly extinct; for of it there re- mains only the genu? Lhnulus, represented b / only five known species. The members of this genus are known as king- crabs or horseshoe-crabs ; the former name is sug- gested by the great size of some of the species; the latter, by shape of the cephalothorax (Fig. lo). The king-crabs are marine; they are found on our Atlantic Coast from Maine to Florida, in the West Indies, and on the eastern shores of Asia. They are found in from two to six fathoms of water on sandy and muddy shores; they burrow a short distance in the sand or mud and feed chiefly on worms. The single species of our coast is Ltmulus polyphemus. Fig. 10. — A horseshoe crab, Limulus (After Packard). the CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 3 Class ARACHNIDA Scorpions, Harvestmen, Spiders, Mites, and others The members of this class are air-breathing arthropods, in which the head and thorax are usually grown to getlier, forming a cephalothorax, which have four pairs of legs, and which apparently have no antennce. The reproductive organs open near the base of the abdomen. Fig. II. — Arachnids: a, a scorpion; b, a harvestman. c, a spider; d, an itch-mite, from below and from above. The Arachnida abound wherever insects occur, and are often mistaken for insects. But they can be easily distinguished by the characters given above, even in those cases where an exception occurs to some one of them. The more important of the exceptions are the following: in one order, the Solpugida, the head is distinct from the 10 AN INTRODUCTION TO ENTOMOLOGY thorax; as a rule the young of mites have only six legs, but a fourth pair is added during growth ; and in the gall-mites there are only four legs. The Arachnida are air-breathing; but it is believed that they have been evclved from aquatic progenitors. Two forms of respira- tory organs exist in this class : first, book-lungs ; and second, tubular trachea. Some members of it possess only one of these types • but the greater number of spiders possess both. A striking characteristic of the Arachnida, which, however, is also possessed by the Palaeostracha, is the absence of true jaws In other arthropods ore or more pairs of appcndag es a e jaw-like i form and are used exclusively as jaws ; but in the Arachnida the p- e^ is crushed either by the modified antennas alone or by these organs and other more or less leg-like appendages. The arachnids suck the blood of their victims by means of a sucking stomach; they crush their prey, but do not masticate it so as to swallow the solid parts. In the Arachnida there exist only simple eyes. The reproductive organs open near the base of the abdomen on the ventral side. In this respect the Arachnida resemble Limidus, the millipedes, and the Crustacea, and differ from the centipedes and insects. Among the more familiar representatives of this class are the scorpions (Fig. ii, a), the harvestmen (Fig. ii, b), the spiders (Fig. II, c), and the mites (Fig. ii, d). As the writer has devoted a separate volume (Comstock, '12) to the Arachnida, it will not be discussed farther in this place. Class PYCNOGONIDA The Pycnogonids The members of this class are marine arachnid-like arthropods, in •which the cephaloihorax bears typically seven pairs 0} jointed appen- dages, but in afewfcrms there are eight pairs, and in some the anterior two or three pairs are absent; and in which the abdomen is reduced to a legless, unsegmented condition. They possess a circulatory system, but no evident respiratory organs. The reproductive organs open through the second segment of the legs; the number of legs bearing these opening varies f rem one to five pairs. The Pycnogonida or pycnogonids are marine animals, which bear a superficial resemblance to spiders (Fig. 12). Some of them are f oimd under stones, near the low water line, on sea shores ; but they CHARA CTERISTICS OF INSECTS A ND THEIR RELA TIVES 1 1 are more abundant in deep water. Some are found attached to sea- anemones, upon which they probably prey; others are found climbing Fig. 12. — A pycnogonid, Nymphon hispidiim: c, chelophore; p, palpus; o, ovigerous legs; /, /, I, I, ambulatory legs; ab, abdo- men (After Hoeck). over sea-weeds and Hydroids; and sometimes they are dredged in great numbers from deep water. They possess a suctorial proboscis. In none of the appendages are the basal segments modified into organs for crushing the prey. The cephalothorax comprises almost tl e entire body ; the abdomen being reduced to a mere vestige, without appendages, and with no external indication of segmentation. But the presence of two pairs of abdominal ganglia indicates that originally the abdomen consisted of more than one segment. There are typically seven pairs of appendages; but a few forms possess eight pairs ; and in some the first two or three pairs are absent. The appendages, when all are present, consist of a pair of chelophores, each of which when well-developed consists of one or two basal seg- ments and a chelate "hand"; the palpi, which are supposed to be tactile, and which have from five to ten joints when well-developed; the ovigerous legs, which are so-called because in the males they are used for holding the mass of eggs beneath the body; and the ambula- tory legs, of which there are usually four pairs, but a few forms possess a fifth pair. The ambulatory legs consist each of eight segments and a terminal claw. The only organs of special sense that have been found in these animals are the eyes. These are absent or at least very poorly 12 ^A^ INTRODUCTION TO ENTOMOLOGY developed in some forms, especially those that are found in very deep water, i.e. below four or five hundred fathoms. When well-developed they are simple, and consist of two pairs, situated on a tubercle, on the head or the first compound segment of the body, the segment that bears the first four pairs of appendages. The reproductive organs open in the second segment of the legs. In some these openings occur only in the last pair of legs; in others, in all of the ambulatory legs. Very little is known regarding the habits of these animals. The most interesting features that have been observed are perhaps the facts that the males carry the eggs in a mass, held beneath the body by the third pair of appendages, the ovigerous legs, and also carry the young for a time. As to the systematic position of the class Pycnogonida, very little can be said. These animals are doubtless arthropods, and they are commonly placed near the Arachnida. Class TARDIGRADA The Tardigrades or Bear Animalcules The members of this class are very minute segmented animals, with four pairs of legs, hut without antenna; or mouth-appendages, and without special circulatory or respiratory organs; the reproductive organs open into the intestine. The Tardigrada or tardigrades are microscopic animals, measuring from one seventy-fifth to one twenty-fifth of an inch in length. They are somewhat mite-like in appearance; but are very different from mites in structure (Fig. 13 and 14). The head bears neither antennae nor mouth-appendages. The four pairs of legs are short, unjointed, and are distributed along the entire length of the body, the fourth pair being at the cau- dal end. Each leg is termin- ated by claws, which differ in number and form in different genera. The more striking features of the internal structure of Fig. 13.-A tardigrade (After Doyere). these animals is the absence of special circulatory and respiratory organs; the presence of a pair of chitinous teeth, either in the oral cavity or a short distance back of CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 13 it ; the presence of Malpighian tubules ; the unpaired condition of the reproductive organs of both sexes; and the fact that these organs open into the intestine. The central nervous system consists of a brain, a suboesophageal ganghon, and a ventral chain of four ganglia, connected by widely separated connectives. The tardigrades are very abundant, and are very widely dis- tributed. Some live in fresh water, a few are marine, but most of them live in damp places, and especially on the roots of moss, growing in gutters, on roofs or trees, or in ditches. But although they are common, their minute size and retiring habits result in their being rarely seen except by those who are seeking them. Many of them have the power of withstanding desiccation for a long period. This has been demonstrated artificially by placing them on a microscopic slide and allowing the mositure to evaporate slowly. The body shrinks, its skin becomes wrinkled, and finally it assumes the appearance of a grain of sand in which no parts can be distinguished. In this state they can remain, it is said, for years; after which, if water be added, the body swells, assumes its normal form, and after a time, the creatures resume their activities. Regarding the systematic position of this class of animals nothing definite can be stated beyond the fact that they are doubtless arthropods. Their relationship to the other classes of arthropods has been masked by degenerative modifications. They are placed here near the end of the series of classes of arthropods, merely as a matter of convenience, in what may be termed an appendix to the arthropod series, which includes animals of doubtful relationships. Fig. 14. — A tardigrade (After Doyere). 14 AN INTRODUCTION TO ENTOMOLOGY Class PENTASTOMIDA The Pentastomids or Linguatulids The members of this class are degenerate, worm-like, parasitic q/fthropods , which in the adidt state have no appendages, except two pairs of hooks near the mouth; the larvce have two pairs of short legs. These animals possess neither circidatory nor respiratory organs. The reproductive organs of t!ie male open a short distance behind the mouth; those of the female near the caudal end of the body. The Pentastomida or pentastomids are worm-like creatures, whose form has been greatly modified by their parasitic life. The adults bear little resemblance to any other arthropods. Representatives of three genera are known. These are Lingudtula in which the body is fluke-like in form(Fig. 15) and superficially annulated; Porocephalus, in which the body is cylindrical (Fig. 16) and ringed; and Re igJidrdia, which is devoid of annulations, and with poorly developed hooks and a mouth-armature. The arthropodan nature of these animals is indicated by the form of the larvae, which although greatly degenerate, are less so than the adults, having two pairs of legs (Fig. 17). Fig. 15. — A pertasto- mid, I.ini^ uattila t a ni oilers, f irnle at the time of copula- tion: //, hooks; oe, cesopliaur.s, rs. re- ceptanila seniini?, one of which is still empty; i, ir.testine; 07', ovary; fa, vagina (From Lang after Leuckart), Fig. 1 6. — A pentastomid, Porocephalus annulaius; a, ventral view of head, greatly enlarged; b, ventral view of animal, slighlly enlarged (After Shipley). Fig. 17 — A pentastomid, larva of Poroi fpJialus proboscidens, seen from below, highly magnified: I, boring anterior end; 2, first pair of chitinons processes seen be- tween the fo'ks of the second pair; 3, ventral nerve ganglion; 4, ali- mentary canal, 5, mouth; 6 anc 7, gland cells (From Shipley after Stiles). CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 15 Like many of the parasitic worms, these animals, in soma cases at least, pass their larval life in one host, and complete their development in another of a different species ; some larvae being found in the bodies of herbivorous animals and the adults in predacious animals that feed on these herbivorous hosts. The systematic position of the pentastomids is very uncertain. They have been considered by some writers to be allied to the mites. But it seems better to merely place them in this appendix to the arthropod series until more is known of their relationships. Class DIPLOPODA The Millipedes or Diplopods The members of this class are air-breathing arthropods in which the head is distinct, and the remaining segments of the body form a continuous region. The greater number of the body-segments are so grouped that each apparent segment bears two pairs of legs. The antennce are short and very similar to the legs. The openings of the reproductive organs are paired, and situated behind the second pair of legs. i^'ig. 1 8. — A millipede, Spiroholus marginatus. The Diplopoda and the three following classes were formerly grouped together as a single class, the Myridpoda. But this grouping has been abandoned, because it has been found that the Chilopoda are more closely allied to the insects than they are to the DiplopDda; and the Pauropoda and Symphyla are both very distinct from the Diplo- poda on the one hand and the Chilopoda on the other. Owing to the very general and long continued use of the term Myriapoda, the student who wishes to look up the literature on these four classes should consult the references under this older name. The most distinctive feature of the millipedes is that which sug- gested the name Diplopoda for the class, the fact that throughout the greater part of the length of the body there appears to be two pairs of legs borne by each segment (Fig. i8). This apparent doubling of the appendages is due to a grouping of the segments in pairs and either a consolidation of the two terga of 16 AN INTRODUCTION TO ENTOMOLOGY each pair or the non-development of one of them; which of these alternatives is the case has not been definitely determined. It is clear, however, that there has been a grouping of the seg- ments in pairs in the region where the appendages are doubled, for corresponding with each tergum there are two sterna and two pairs of spiracles. A few of the anterior body segments, usually three or four in number, and sometimes one or two of the caudal segments remain single. Frequently one of the anterior single segments is legless, but the particular segment that lacks legs differs in the different families. The head, which is as distinct as is the head of insects, bears the antennae, the eyes, and the mouth-parts. The antennas are short, and usually consist each of seven segments. The eyes are usually represented by a group of ocelli on each side of the head; but the ocelli vary greatly in ntimber, and are '^ sometimes absent. The mouth-parts consist of an P upper lip or labrum; a pair of mandibles; and a pair of jaws, which are united at the base, forming a large plate, which is known as the gnaihochilarium. In the genus Polyxenus there is a pair of lobes between s the mandibles and the gnathochilarium, which have been named the maxillulcB. (paragnatha?). The labrum is merely the anterior part of the ^j^- '^9-— A mandi- 11 r .1 1 -1 1 • • • Die of Julus; c, upper wall of the head and, as m insects, is not an cardo; d,d,teeth; appendage. The mandibles, in the forms in which ^' muscle; ma, they are best developed, are fitted for biting, and nate ' plate; s, consist of several parts (Fig. 19) ; but in some forms ? ^f^i^ ^ (After they are vestigial. The gnathochilarium (Fig. 20) is complicated in structure, the details of which vary greatly in different genera. Pig. 20. — The gnathochilarium or second jaws of three diplopods; A, Spirostrtp- tus; B, Julus; C, Glomeris: c, cardo; h, liypostoma; Ig, linguce; m, ment'om. pm, promentum; st, stipes (After Silvestri). CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 17 In one subdivision of the class Diplopoda, which is represented by the genus Polyxenus and a few others, the mandibles are one- jointed; and be- mxt tween the mandi- »'^-l'> ' bles and the gnathochilarium there is a pair of one-jointed lobes, which have not been found in other diplopods; these are the "max- illulas" (Fig. 21). The correspondence of the parts of the gnathochilarium of Polyxenus and its allies with the parts of the gnathocil- larium of other di- plopods has not been satisfactorily determined. Most of our more common millipedes possess stink-glands, which open by pores on a greater or less nimiber of the body segments. These glands are the only means of defence possessed by millipedes, except the hard cuticula protecting the body. The millipedes as a rule are harmless, living in damp places and feeding on decaying vegetable matter; but there are a few species that occasionally feed upon growing plants. For a more detailed account of the Diplopoda see Pocock ('11). Fig. 21. — The second pair of jaws, maxillulae, and the third pair of jaws, maxillas or gnathochilarium, of Polyxenus; the parts of the maxillae or gnathochila- rium are stippled and some are omitted on the right side of the figure: mh, basal membrane of the labium ; la, "labium" of Carpenter, perhaps the mentum and promentum of the gnathochilarium; mx, basal seg- ment of the maxilla, perhaps the stipes of the gnathochilarium; w:x;. /o, lobe of the maxilla; mx.p, maxillary palpus; A, tongue or hypopharynx; mxl, maxillula; fl. flagellate process (After Carpenter). 18 AN INTRODUCTION TO ENTOMOLOGY Class PAUROPODA The Pauropods The members of this class are small arthropods in which the head is distinct, and the segments of the body form a single continuous region. Most of the body-segments bear each a single pair of legs. Although most of the terga of the body-segments are usually fused in couples, the legs are not grouped in double pairs as in the Diplopoda. The antennce are branched. The reproductive organs open in the third segment back of the head. The Pauropoda or pauropods are minute creatures, the described species measuring only about one twenty-fifth inch in length, more or less. They resemble centipedes in the elongated form of the body and in the fact that the legs are not grouped in double pairs as in the Diplopoda, although the terga of the body-region are usually fused in couples. These characteris- tics are well-shown by the dorsal and ventral views of Pauropus (Fig. 22 and 23). Although the pauropods resemble the chilopods in the distribution of their legs, they differ widely in the position of the openings of the reproductive organs. These open in the third seg- ment back of the head ; that of the female is single, those of the male are double. The head is distinct from the body-region. It bears one pair of antennae and two pairs of jaws; the eyes are absent but there is an eye- like spot on each side of the head (Fig. 24). The first pair of jaws are large, one- jointed mandibles; the second pair are short pear-shaped organs. Between these two pairs Fig. 22. — A pauropod, Pauropus huxleyi, dor- sal aspect (After Ken- yon). Fig. 23. — Pauropus huxleyi, ventral aspect (After Lubbock). CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 19 Fig. 24 — Eurypauropus spina- sus; face showing the base of the antennas, the mandibles, and the eye-lilce spots (After Kenyon) . of jaws, there is a horny framework forming a kind of lower Hp to the mouth (Fig. 25). The homologies of the mouth-parts with those of the allied classes of arthropods have not been determined. The body-region consists of twelve segments. This is most clearly seen by an examination of the ventral aspect of the body. When the body is viewed from above the mmiber of segments appears to be less, owing to the fact that the terga of the first ten segments are fused in couples. Nine of the body-segments bear well-developed legs. The appendages of the first segment are vestigial, and the last two segments bear no appendages. The most distinctive feature of mem- bers of this class is the form of the antennae, which differ from those of all other arthropods in structure. Each antenna (Fig. 26) consists of four short basal segments and a pair of one-jointed branches borne by the fourth segment. One of these branches bears a long, many- ringed filament with a rounded apical knob; and the other branch bears two such filaments with a globular or pear- shaped body between them. This is prob- ably an organ of special sense. The pauropods live under leaves and stones and in other damp situations. Representatives of two quite distinct families are found in this country and in various other parts of the world. In addition to these a third family, the BrachypauropodidcB, is foimd in Europe. In this family the pairs of terga consist each of two distinct plates. Our two „. ^ A .. r 17 . . .■ families are the fol- rig. 26. — Antenna 01 hurypauropus spmosus (After Kenyon) . lowmg : Fig. 25. — Mouth-parts of Eury- pauropus ornatus; md, man- dible; mx, second iaws; /, lower lip (After Latzel). 20 AN INTROD UCTION TO ENTOMOLOG Y Family Pauropodidce. — In members of this family the head is not covered by the first tergal plate and the anal segment is not covered by the sixth tergal plate. The best known representatives of this family belong to the genus Pauropus (Fig. 22). This genus is widely distributed, represen- tatives having been found in Europe and in both North and South America. They are active, measure about one twenty-fifth inch in length, "s^^^ and are white. Family EiirypauropidcB. — The members of this family are characterized by the wide form of the body, which bears some resemblance to that of a sow-bug. The head is concealed by the first tergum of the body-region; and the anal segment, by the penultimate tergum. Our most familiar representative is Eiirypanropus spinosus ^'l-^7.—Euryparcro- (pig_ ) ^^is, unlike Pauropus, is slow in its pus spinosus (After ^ »^ ' ^ -r > Kenyon). movements. Class CHILOPODA The Centipedes or Chilopods The members of this class are air-breathing arthropods in which the head is distinct, and the remaining segments of the body form a continuous region. The numerous pairs of legs are not grouped in double pairs, as in the Diplopcda. The antennae are long and many-jointed. The appendages of the first body-segment are jaw-like and function as organs of offense, the poison-jaws. The opening of the reproductive organs is in the next to the last segment of the body. The animals constituting the class Chilopoda or chilopods are commonly known as centipedes. They vary to a considerable degree in the form of the body, but in all except perhaps the sub-class Notostigma the body-segments are distinct, not grouped in couples as in the diplopods (Fig. 28). They are sharply distinguished from the three preceding classes in the possession of poison-jaws and in having the opening of the reproductive organs at the caudal end of the body. The antennae are large, flexible, and consist of fourteen or more segments. There are four pairs of jaws including the jaw-like CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 21 appendages of the first body-segment. These are the mandibles (Fig. 29, A), which are stout and consist each of two segments; the maxillcs (Fig. 29, B, a), which are foHaceous, and usually regarded as biramous; the second maxill(B or palpognaihs, which are leg-like in form, consisting of five or six segments, and usually have the coxae united on the middle line of the body (Fig. 29, B, 6), and the poison- claws or toxicognaths, which are the appendages of the first body-segment (Fig. 29, C). The poison-claws consist each of six seg- ments, of which the basal one, or coxa is usually fused with its fellow, the two forming a large coxal plate, and the distal one is a strong pierc- ing fang in which there is the opening of the duct leading from a poison gland, which is in the appendage. The legs consist typically of six segments, of which the last, the tarsus, is armed with a -A centipede single terminal claw. The last pair of legs are directed backwards, and are often greatly modified in form. The class Chilopoda includes two quite distinct groups of animals which are regarded by Pocock ('11) as sub-classes, the Pleuro- stigma and theNoto- stigma. The names I^J^. J^%.^\ C of the sub-classes refer to the position ^ a of the spiracles. Sub-Class PLEUROSTIGMA The typical Centipedes In the typical cen- tipedes, the sub-class Pleurostigma, the spiracles are paired and are situated in the sides of the segments that bear them. Each leg-bearing segment contains a distinct tergiim and sternum, the number of sterna never exceeding that of the terga. The eyes Buthropolys multi- dentatus. Fig. 29. — Mouth-parts of a centipede, Geophilus flavi' dus. A, right mandible, greatly enlarged. B, the two pairs of maxillae, less enlarged; a, the united 00X33 of the maxillse; b, the united coxae of the second maxillae or palpognaths. C, the poison claws or toxicognaths (After Latzel) 22 AN INTRODUCTION TO ENTOMOLOGY when present are simple ocelli; but there may be a group of ocelli on each side of the head. Figure 28 represents a typical centipede. Sub-Class NOTOSTIGMA Scutigera and its Allies In the genus Scuttgera and its allies, which constitute the sub-class Notostigma, there is a very distinctive type of respiratory- organs. There is a single spiracle in each of the spiracle-bearing segments, which are seven in number. These spiracles open in the middle line of the back, each in the hind margin of one of the seven prominent terga cf the body-region. Each spiracle leads into a short sac from which the tracheal tubes extend into the pericardial blood-sinus. There are fifteen leg-bearing segments in the body region; but the terga of these segments are reduced to seven by fusion and suppression. The eyes differ from those of afl other members of the old group Myriapoda in being compoimd, the ommatidia resembling in structure the ommatidia of the compound eyes of insects. The following species is the most familiar representative of the Notostigma. The house centipede, Scutigera forceps. — This centipede attracts attention on account of the great length of its appendages (Fig. 30), and the fact that it is often seen, in the regions where it is common, running on the walls of rooms in dwelling houses, where it himts for flies and other insects. It prefers damp situations; in houses it is most frequently foimd in cellars, bathrooms, and closets. Sometimes it becomes very abundant in conservatories, living among the stored pots and about the heating pipes. It is much more common in the South than in the North. Fig. 30. — Scutigera forceps. CHARA CTERISTICS OF INSECTS A ND THEIR RELA TI VES 23 The body of the adult measures an inch or a little more in length. It is difficult to obtain perfect specimens, as they shed their legs when seized. Class SYMPHYLA The Symphylids The members of this class are small arthropods in which the head is distinct, and the segments of the body form a single con- tinuous region. Most of the body-segments bear a single pair of legs. The antenncB are very long and many-jointed. The head bears a Y-shaped epicranial suture, as in insects. The opening of the reproductive organs is in the third segment behind the head. The class Symphyla includes a small number of many-legged arthropods which exhibit striking affinities with insects, and especially with the Thysanura. The body is centipede-Hke in form (Fig. 31). The head is distinct, and is not bent down Fig . 31. — Scolopendrella (After Latzel). as it is in the diplopods and pauro- pods; it is shaped as in Thysanura and bears a Y-shaped epicranial suture. The body-region bears fifteen terga, which are distinct, not grouped in couples as in the two preceding classes; and there are eleven or twelve pairs of legs. The antennae are long and vary greatly in the number of the segments. There are no eyes. The mandibles, the "maxillulae" (paragnatha) , the maxillae, and the sec- ond maxillae or labium are present. Fig. 32. — Mouth-parts of Scolopendrella seen from below; md, mandible; mx, maxillae; s, stipes; p, pal- pus; /, second maxillee or labium. The mandible on the right side of the figure is omitted (After Hansen). The mandibles (Fig. 32, md) are two- jointed; the maxillulcB (Fig. 33, m) are small, not segmented, and are attached to a median lobe or hypopharynx (Fig. 33, h); they are hidden when the mouth-parts are viewed from below as represented in Figure 3 2 ; the maxillce (Fig. 24 AN INTRODUCTION TO ENTOMOLOGY 2,2, mx) resemble in a striking degree the maxillae of insects, consisting of a long stipes, (5), which bears a minute palpus, {p), and an outer and inner lobe ; the second maxillce or labium (Fig. 32,/) also resembles the corresponding part of the more generalized insects, being composed of a pair of united gnathites. The legs of the first pair are reduced in size and in the number of their segments. The other legs ^^pophl'i^i^^^ ^h) consist each of five segments; the last segment andmaxillulaeCm) bears a pair of claws. Excepting the first two (Iftt/'filntent pairs of legs, each leg bears on its proximal seg- ment a slender cylindrical process, the parapodium (Fig. 34, p). These parapodia appear to correspond with the styli of the Thysanura. At the caudal end of the body there is a pair of appendages, which are believed to be homologous / '■"^^^^rfH^ with the cerci of insects (Fig. 35, c). A striking peculiarity of the symphylids is that Fig- 34-— A ieg of ^-j^gy possess only a single pair of tracheal tubes, Scolopendrella; ,., , . ff, . ^ . />, parapodium. which Open by a pair of spiracles, situated in the head beneath the insertion of the antennae. The members of this class are of small size, the larger ones measiuing about one-fourth inch in length. They live in earth under stones and decay- ing wood, and in other damp situations. Imma- ture individuals possess fewer body-segments and legs than do adults. Less than thirty species have been described; but doubtless many more remain to be discovered. The known species are classed in two genera : pig. j^.—The caudal Scolopendrella and Scutigerella. In the former the ^nd of the body of , . ^ r j_, j_ 1 -1 •, Scolopendrella; I, posterior angles of the terga are produced and leg; c, cercus (After angular; while in the latter they are rounded. Latzel). A monograph of the Symphyla has been published by Hansen ('03). Class MYRIENTOMATA Professor Comstock, in the former editions of this book, gave this group of arthropods the rank of a class, coordinate with the other classes of the Arthropoda. The position and rank of these animals were uncertain at the time the Introduction was written. Indeed, the affinities of the CHARACTERISTICS OF INSECTS AND THEIR RELATIVES 25 Protura are not yet clearly understood, but the general opinion among morphologists and sys- tematists is tending more and more to place these tiny crea- tures in an ordinal group, the Protura, among the insects in the class Hexapoda. It has seemed best to follow this general trend and we have, therefore, trans- ferred this group to the class Hexapoda, order Protura, on p. 220. In commenting on the posi- tion of the group in the original edition of the Introduction, Pro- fessor Comstock gave the follow- ing discussion and explanation of his conclusions at that time : "The first discovered species was described in 1907 by Profes- sor F. Silvestri of Portici, who regarded it as the type of a dis- tinct order of insects, for which he proposed the name Protura. Later Professor Antonio Berlese of Florence described several additional species, and pubHshed pjg_ ^e.—Acerentomon doderoi: A, dor- an extended monograph of the sal aspect; B, ventral aspect; 1, 1, 1, A /-D ^ > z,\ vestigial abdominal legs (After order (Berlese 09 h). Berime). "Professor Berlese concluded that these arthopods are more closely allied to the Myriapoda and especially to the Pauropoda than they are to the insects, and changed the name of the order, in an arbitrary manner, to Myrientomata. "It seems clear to me that in either case whether the order is classed among the insects or assigned to some other position it should be known by the name first given to it, that is, the Protura. "In the present state of our knowledge of the affinities of the classes of arthropods, it seems best to regard the Protura as representing a separate class, of rank equal to that of the Pauropoda, Symphyla, etc.; and for this class I have adopted the name proposed for the group by Berlese, that is the Myrientomata." 26 AN INTRODUCTION TO ENTOMOLOGY Class HEXAPODA The Insects The members of this class are air-breathing arthropods, with distinct head, thorax, and abdomen. They have one pair of antennae, three pairs of legs, and usually one or two pairs of wings in the adult state. The opening of the reproductive organs is near the caudal end of the body. We have now reached in our hasty review of the classes of arthro- pods the class of animals to which this book is chiefly devoted, the Hexapoda,* or Insects, the study of which is termed entomology. The number of species of insects now known is around 600,000, perhaps more rather than less. The number of species yet undescribed is purely problematical. Probably there are hundreds of thousands of unknown forms distributed over the tropical portions of the earth. Insects vary greatly in size. Folsom says that some insects are smaller than the largest protozoans, while some are larger than the smallest vertebrates. A beetle, Dynastes hercules from Vene- zuela, which may be 155mm. long, and a Venezuelan grasshopper, Tropidacris latreillei, which may attain a length of i66mm., are among the largest insects. Some moths of the genus Attacus may have a wing expanse of from 240 to 2 5 5mm. while a BraziHan noctuid, Erebus agrippina, is said to have a wing expanse of 280mm. On the other hand, certain beetles of the family Trichopterygidae may be but .25mm. in length, and some hymenopterous egg parasites are even smaller. Insects are essentially terrestrial ; and in the struggle for existence they are the most successful of all terrestrial animals, outnumbering both in species and individuals all others together. On the land they abound under the greatest variety of conditions, special forms having been evolved fitted to live in each of the various situations where other animals and plants can live; but insects are not restricted to dry land, for many aquatic forms have been developed. The aquatic insects are almost entirely restricted to small bodies of fresh water, as streams and ponds, where they exist in great num- bers. Larger bodies of fresh water and the seas are nearly destitute of them except at the shores. *Hexapoda: hex (?|), six', pons (ttoi/s), a foot. CHARACTERISTICS OF INSECTS AND THEIR RELA TIVES 27 As might be inferred from a consideration of the immense number of insects, the part they play in the economy of nature is an exceed- ingly important one. Whether this part is to be considered a bene- ficial or an injurious one when judged from the human standpoint would be an exceedingly difificult question to determine. For if insects were to be removed from the earth the whole face of nature would be changed. While the removal of insects from the earth would eliminate many pests that prey on vegetation, would relieve many animals of annoying parasites, and would remove some of the most terrible diseases to which oiu- race is subject, it would result in the destruction of many groups of animals that depend, either directly or indirectly, upon insects for food, and the destruction of many flowering plants that depend upon insects for the fertilization of their blossoms. Truly this world would speedily become a very differ- ent one if insects were exterminated. It may seem idle to consider what would be the result of the total destruction of insects; but it is not wholly so. A care- ful study of this question will do much to open our eyes to an appreciation of the wonderful "web of life" of which we are a part. Most adult insects can be readily dis- tinguished from other arthropods by the form of the body, the segments being grouped into three distinct regions, head, thorax, and abdomen (Fig. 37), by the possession of only three pairs of legs, and in most cases by the presence of wings. The head bears a single pair of antennas, the organs of sight, and the mouth-parts. To the thorax, are articulated the organs of locomotion, the legs and the wings when they are present. The abdomen is usually without organs of locomotion but frequently bears other appendages at the caudal end. These characteristics are also possessed by the immature forms of several of the orders of insects ; although with these the wings are Fig. 37. — Wasp with head, thorax, and abdomen separated. Fig. 38. — Nymph of the red- legged locust. 28 AN INTRODUCTION TO ENTOMOLOGY rudimentary (Fig. 38). But in other orders of insects the immature forms have been greatly modified to adapt them to special modes of life, with the result that they depart widely from the insect type. For example, the larvae of bees, wasps, flies, and many beetles are legless and more or less worm-like in form (Fig. 4) ; while the larvae of butter- flies and moths possess abdominal as well as thoracic legs (Fig. 39). Fig- 39-~~A. larva of a handmaid moth, Datana. Although the presence of wings in the adult state is characteristic of most insects, there are two orders of insects, the Thysanura and the CoUembola, in which wings are absent. These orders represent a branch of the insect series that separated from the main stem before the evolution of wings took place; their wing- less condition is, therefore, a primitive one. There are also certain other insects, as the lice and bird-lice, that are wingless. But it is believed that these have descended from winged insects, and have been degraded by their parasitic life; in these cases the wingless condition is an acquired one. Beside these there are many species belonging to orders in which most of the species are winged that have acquired a wingless condition in one or both sexes. Familiar examples of these are the females of the Coccidas (Fig. 40), and the females of the canker-worm moths. In fact, wingless forms occur in most of the orders of winged insects. As the structure and transformations of insects are described in detail in the following chapters, it is unnecessary to dwell farther on the characteristics of the Hexapoda in this place. Fig. 40. — A mealy-bug, Dactylopius. CHAPTER II. THE EXTERNAL ANATOMY OF INSECTS I. THE STRUCTURE OF THE BODY-WALL a. THE THREE LAYERS OF THE BODY-WALL Three, more or less distinct, layers can be recognized in the body- wall of an insect: first, the outer, protecting layer, the cuticula; second, an intermediate, cellular layer, the hypodermis; and third, an inner, delicate, membranous layer, the basement membrane. These layers can be distinguished only by a study of carefully prepared, microscopic sec- tions of the body- wall. Figure 41 represents the ap- pearance of such a section. As the outer and inner layers are derived from the hypo- dermis, this layer will be described first. The hypodermis. — The ac- tive living part of the body- wall consists of a layer of cells, which is termed the hypo- dermis (Fig. 41, /^). The hypodermis is a portion of one of the germ-layers, the ectoderm. In other words, that portion of the ectoderm which in the course of the development of the insect comes to form a part of the body- wall is termed the hypodermis; while to invaginated portions of the ectoderm other terms are appHed, as the epithehal layer of the trachea?, the epithelial layer of the fore-intestine, and the epithelial layer 01 the hind-intestine. The cells of which the hypodermis is composed vary in shape ; but they are usually columnar in form, constituting what is known to histologists as a columnar epithelium. Sometimes the cells are so flattened that they form a simple pavement epithelium. I know of no case in which the hypodermis consists of more than a single layer of cells; although in wing-buds and buds of other appendages, where the cells are fusiform, and are much crowded, it appears to be irregu- (29) Fig. 41. — A section of the body- wall of an insect: c, cuticula; h, hypodermis; hm, basement membrane; e, epidermis, d, dermis; tr, trichogen; s, seta. 30 AN INTROD UCTION TO ENTOMOLOG V larly stratified. This is due to the fact that the nuclei of the different cells are at different levels. The Trichogens. — Certain of the hypodermal cells become highly- specialized and produce hollow, hair-like organs, the setae, with which they remain connected through pores in the cuticula. Such a hair-forming cell is termed a trtchogen (Fig. 41, tr)\ and the pore in the cuticula is termed a Mchopore. The cuticula. — Outside of the hypodermis there is a firm layer which protects the body and serves as a support for the internal organs; this is the cuticula (Fig. 41, c). The cuticula is produced by the hypodermis; the method of its production is discussed on p. 171, where the molting of insects is treated. The cuticula is not destroyed by caustic potash; it is easy, therefore, to separate it from the tissues of the body by boiling or soaking it in an aqueous solution of this substance. Chitin. — This word was introduced into entomology by Odier in 1823 for the colorless, flexible covering of the arthropods after the integument had been boiled in caustic potash and the albuminous, oily, coloring and mineral substances had been removed thereby. By a not unusual turn in the use of words, chitin has come to mean, as stated by Newport (1836-1839): "The peculiar substance that constitutes the hard portion of the dermo-skeleton [in insects]." From 1870 and onward the words chitinize and chitinization have come to mean the hardening of the cuticula by the incorporation of chitin; and they are used with that meaning throughout this work. (For references to chitin, see p. 10 10). Rigid and flexible cuticula. — When freshly formed by the hypo- dermis, the cuticula is flexible and elastic, and certain portions of it, as at the nodes of the body and of the appendages, remain so. But the greater part of the cuticula, especially in adult insects, usually becomes firm and inelastic; this is due to a change in which the hardening substance is developed within or upon the original soft cuticula. What the exact nature of this change is or how it is pro- duced is not known. This change is usually spoken of as chitinization ; and the hard parts of the cuticula are then said to be chitinized, and the soft parts, as at the nodes, non-chitinized. The hardened or chitinized cuticula is rigid and inelastic while the soft or non-chitinized cuticula is flexible and elastic. The elasticity of the soft cuticula is well shown by the stretching of the body wall after a molt. It is also strikingly shown by the expansion of the soft, intersegmental cuticula to accommodate the growing eggs, as in the queens of Termites. THE EX TERN A L ANATOMY OF INSE CTS 3 1 The formation of chitin is not restricted to the hypodermis, but is a property of the invaginated portions of the ectoderm; the fore- intestine, the hind-intestine, and the tracheee are all lined with a cuticular layer, which is continuous with the cuticula of the body-wall and is chitinized. The most marked case of internal formation of chitin is the development of large and powerful teeth in the proven- triculus of many insects. The epidermis and the dermis. — Two quite distinct parts of the cuticula are recognized by recent writers ; these are distinguished as the epidermis and the dermis respectively. The epidermis is the external portion ; in it are located all of the cuticular pigments; and from it are formed all scales, hairs, and other surface structures. It is designated by some writers as the primary cuticula (Fig. 41, e). The dermis is situated beneath the epidermis. It is formed in layers, which give sections of the cuticula the well-known laminate appearance. It is sometimes termed the secondary cuticula (Fig. 41, <^)- The basement membrane. — The inner ends of the hypodermal cells are bounded by a more or less distinct membrane ; this is termed the basement membrane (Fig. 4 1 , bm) . The basement membrane is most easily seen in those places where the inner ends of the hypodermal cells are much smaller than the outer ends ; here it is a continuous sheet connecting the tips of the hypodermal cells. b. THE EXTERNAL APOPHYSES OF THE CUTICULA The outer surface of the cuticula bears a wonderful variety of pro- jections. These, however, can be grouped under two heads: first, those that form an integral part of the cuticula; and second, those that are connected with the cuticula by a joint. Those that form an integral part of the cuticula are termed apophyses; those that are con- nected by a joint are termed appendages of the cuticula. The cuticular nodules. — The most frequently occurring out- growths of the cuticula are small, more or less conical nodules. These vary greatly in size, form, and distribution over the surface of the body in different species of insects, and are frequently of taxonomic value. The fixed hairs. — On the wings of some insects, as the Trichoptera and certain of the Lepidoptera, there are in addition to the more obvious setse and scales many very small, hair-like structures, which 32 AN INTRODUCTION TO ENTOMOLOGY differ from setae in being directly continuous with the cuticula, and not connected with it by a joint; these are termed the fixed hairs, or aculese. The mode of origin and development of the fixed hairs has not been studied. The spines. — The term spine has been used loosely by writers on entomology. Frequently large setae are termed spines. In this work such setae are called spine-like setse; and the term spine is applied only to outgrowths of the cuticula that are not separated from it by a joint. Spines differ also from spine-like setae in being produced by undifferentiated hypodermal cells and are usually if not always of multicellular origin, while each seta is produced by a single trichogen cell. The accompanying diagram (Fig. 42) illustrates this difference. C. THE APPENDAGES OF THE CUTICULA Under this head are included those outgrowths of the cuticula that are connected with it by a joint. Of these there are two quite dis- tinct types represented by the spurs and the setas respectively. The spurs. — There exist upon the legs of many insects appendages which on account of their form and position have been termed spurs. Spurs resemble the true spines described above and differ from setas in being of multicellular origin; they differ from spines in being appendages, that is, in being connected with the body-wall by a joint. The setae. — The setae are what are commonly called the hairs of in- sects. Each seta (Fig. 42, s) is an appendage of the body- wall, which arises from a cup-like cavity in the cuticula, the alveolus, situated at the outer end of a per- foration of the cuticula, the trtchopore; and each seta is united at its base with the wall of the trichopore by a ring of thin membrane, the articular membrane of the seta. The setae are hollow ; each is the product of a single hypodermal cell, a trichogen (Fig. 42), and is an extension of the epidermal layer of the cuticula. Fig. 42. — Diagram illustrating the diflference be- tween a spine (sp) and a seta (s). THE EXTERNAL ANATOMY OF INSECTS 33 In addition to the trichogen there may be a gland-cell opening into the seta, thus forming a glandular hair, or a nerv^e may extend to the seta, forming a sense-hair; each of these types is discussed later. The most common type of seta is bristle-like in form; familiar examples of this type are the hairs of many larvae. But numerous modifications of this form exist. Frequently the setae are stout and firm, such are the spine-like setcB; others are furnished with lateral prolongations, these are the plumose hairs; and still others are flat, wide, and comparatively short, examples of this form are the scales of the Lepidoptera and of many other insects. The taxonomic value of setcB. — In many cases the form of the setae and in others their -arrangement on the cuticula afford useful charac- teristics for the classification of insects. Thus the scale-like form of the setas on the wing-veins of mosquitoes serves to distinguish these insects from closely alHed midges; and the clothing of scales is one of the most striking of the characteristics of the Lepidoptera. The arrangement of the setas upon the cuticula, in some cases at least, is a very definite one. Thus Dyar ('94) was able to work out a classification of lepidopterous larvai by a study of the setas v\.ith which the body is clothed. A classifu,ation of setce. — If only their function be considered the hairs or setae of insects can be grouped in the three following classes ; (i) The clothing hairs. — Under this head are grouped those hairs and scales whose primary function appears to be merely the- protection of the body or of its appendages. So far as is known, such hairs con- tain only a prolongation of the trichogen cell that produced them. It should be stated, however, that this group is merely a provisional one; for as yet comparatively little is known regarding the relation of these hairs to the activities of the insects possessing them. In some cases the clothing hairs have a secondary fimction. Thus the highly specialized overlapping scales of the wings of Lepidoptera. which are modified setae, may serv^e to strengthen the wings; and the markings of insects are due almost entirely to hairs and scales. The fringes on the wmgs of many insects doubtless aid in flight, and the fringes on the legs of certain aquatic insects also aid in locomotion. (2) The glandular hairs. — Under this head are grouped those hairs that serve as the outlets of gland cells. They are discussed in the next chapter, imder the head of hypodermal glands. (3) The sense-hairs — In many case a seta, more or less modified in form, constitutes a part of a sense-organ, either of touch, taste, or smell : examples of these are discussed in the next chapter. 34 AN INTRODUCTION TO ENTOMOLOGY d. THE SEGMENTATION OF THE BODY The cuticular layer of the body-wall, being more or less rigid, forms an external skeleton; but this skeleton is flexible along certain transverse lines, thus admitting of the movements of the body, and producing the jointed appearance characteristic of insects and of other arthropods. An examination of a longitudinal section of the body-wall shows that it is a continuous layer and that the apparent segmentation is due to infoldings of it (Fig. 43), The body-seg- ments, somites, or metameres . — Each section of the body „. ^. , , . ,. . ^. , ^, r 1 Fi?- 43- — Diagram of a longitudinal section of the between two of the body-wall of an insect. infoldings described above is termed a body-segment, or somite, or metamere. The transverse conjunctivae. — The infolded portion of the body- wall connecting two segments is termed a conjunctiva. These con- junctivae may be distinguished from others described later as the transverse conjunctivce. The conjunctivae are less densely chitinized than the other portions of the cuticula; their flexibility is due to this fact, rather than to a comparative thinness as has been commonly described. e. THE SEGMENTATION OF THE APPENDAGES The segmentation of the legs and of certain other appendages is produced in the same way as that of the body. At each node of an appendage there is an infolded, flexible portion of the wall of the appendage, a conjunctiva, which renders possible the movements of the appendage. /. THE DIVISIONS OF A BODY-SEGMENT In many larvae, the cuticula of a large part of the body-wall is of the non-chitinized type ; in this case the wall of a segment may form a ring which is not divided into parts. But in most nymphs, naiads, and adult insects, there are several densely chitinized parts in the wall of each segment; this enables us to separate it into well-defined portions. The tergum, the pleura, and the sternum. — The larger divisions of a segment that are commonly recognized are a dorsal division, the THE EXTERNAL ANATOMY OF INSECTS 35 tergum; two lateral divisions, one on each side of the body, the pleura; and a ventral division, the sternum. Each of these divisions may include several definite areas of chitinization. In this case the sclerites of the tergum are referred to collectively as the tergites, those of each pleurum, as the pleurites, and those constituting the sternum, as the sternites. The division of a segment into a tergum, two pleura, and a sternum are most easily seen in the wing-bearing segments, but it can be recognized also in the prothorax of certain generalized insects. This is especially the case in many Orthoptera, as cockroaches and walking- sticks, where the pleura of the prothorax are distinct from the tergum and the sternum. In the abdomen it is evident that correlated with the loss of the abdominal appendages a reduction of the pleura has taken place. The lateral conjunctivae. — On each side of each abdominal segment of adults the tergum and the sternum are united by a strip of non- chitinized cuticula; these are the lateral conjtmctivae. Like the transverse conjunctivee, the lateral ones are more or less infolded. The sclerites. — Each definite area of chitinization of the cuticula is termed a sclerite. The sutures. — The lines of separation between the sclerites are termed sutures. Sutures vary greatly in form ; they may be infolded conjunctiva; or they may be mere lines indicating the place of union between two sclerites. Frequently adjacent sclerites grow together so completely that there is no indication of the suture ; in such cases the suture is said to be obsolete. The median sutures. — On the middle line of the tergites and also of the sternites there frequently exist longitudinal sutures. These are termed the median sutures. They represent the lines of the closure of the embryo, and are not taken into account in determining the number of the sclerites. The dorsal median suture has been well-preserved in the head and thorax, as it is the chief line of rupture of the cuticula at the time of molting. The piUf erous tubercles of larvae. — The setae of larvae are usually borne en slightly elevated annular sclerites; these are termed pilif- erous tubercles. The homologizing of the sclerites. — While it is probable that the more important sclerites of the body in winged insects have been derived from a common winged ancestor and, therefore, can be homologized, miany secondary sclerites occur which can not be thus homoiogized. 36 AN INTRODUCTION TO ENTOMOLOGY g. THE REGIONS OF THE BODY The segments of the body in an adult insect are grouped into three, more or less well-marked regions: the head, the thorax, and the abdomen. Each of these regions consists of several segments more or less closely united. The head is the first of these regions; it bears the mouth-parts, the eyes, and the antennas. The thorax is the second region ; it bears the legs and the wings if they are present. The abdomen is the third region; it may bear appendages connected with the organs of repro- duction. II. THE HEAD The external skeleton of the head of an insect is composed of several sclerites more or less closely united, forming a capsule, which includes a portion of the viscera, and to which are art'culated certain appendages. a. THE CORNEAS OF THE EYES The external layer of the organs of vision, the corneas of the eyes, is, in each case, a translucent portion of the cuticula. It is a portion of the skeleton of the head, which serves not merely for the admission of light but also to support the more delicate parts of the visual apparatus. The corneas of the compound eyes. — The compound eyes are the more commonly observed eyes of insects. They are situated one on each side of the head, and are usually conspicuous. Sometimes, as in dragon-flies, they occupy the larger part of the surface of the head. The compound eyes are easily recognized as eyes; but when one of them is examined with a microscope it is found to present an appearance very different from that of the eyes of higher animals, its surface being divided into a large number of six-sided divisions (Fig. 44) ; hence the term ccmpound eyes applied to them. A study of the internal structure of this organ has shown that each of these hexagonal divisions is the outer end of a distinct element of the eye. Each of these elements is termed an ommattdium. The number of ommatidia of which a compound p. '^^ ^^ ^^r eye is composed varies greatly; there may be not cornea of a com- more than fifty, as in certain ants, or there may pound eye. |-,g j^^ny thousand, as in a butterfly or a dragon-fly. As a rule, the immature stages of insects with a gradual metamor- phosis end also those of insects with an incomplete metamorphosis, THE EXTERNAL A NA TOM Y OF INSECTS 37 that is to say nymphs and naiads possess compound eyes. But the larvee of insects with a complete metamorphosis, do not possess well- developed compound eyes; although there are frequently a few sep- arate ommatidia on each side of the head. These are usually termed ocelli ; but the ocelli of larvae should not be confused with the ocelli of nymphs, naiads, and adults. The corneas of the ocelli. — In addition to the compound eyes most nymphs, naiads, and adult insects possess other eyes, which are termed ocelli. The cornea of each ocellus is usually a more or less nearly circular, convex area, which is not divided into facets. The typical number of ocelli is four; but this number is rarely found. The usual number is three, a median ocellus, which has been derived from a pair of ocelli united, and a distinct pair of ocelli. Frequently the median ocellus is lacking, and less frequently, all of the ocelli have been lost. The position of the ocelli is discussed later. h. THE AREAS OF THE SURFACE OF THE HEAD In descriptions of insects it is frequently necessary to refer to the different regions of the surface of the head. Most of these regions were named by the early insect anatomists; and others have been described by more recent writers. This terminology is really of comparatively little morphological value; for in some cases a named area includes several sclerites, while in others only a portion of a sclerite is included. This is due to the fact that but few of the primitive sclerites of the head have remained distinct, and some of them greatly over- shadow others in their development. The terms used, however, are sufficiently accurate to meet the needs of describers of species, and will doubtless continue in use. It is necessary, therefore, that students of entomology become familiar with them. The best landmark from which to start in a study of the areas of the surface of the head is the epicranial suture, the inverted Y-shaped suture on the dorsal part of the head, in the more generalized insects (Fig. 45, e. sit). Behind the arms of this suture there is a series of paired sclerites, which meet on the dorsal wall of the head, the line of union being the stem of the Y, a median suture ; and between the arms of the Y and the mouth there are typically three single sclerites (Fig. 45, F, C, L). It is with these unpaired sclerites that we will begin our definitions of the areas of the head. ^ Fig. 45.-Head of a The front. — The front is the unpaired cricket. sclerite between the arms of the epicranial suture (Fig. 45, F). 38 AN INTRODUCTION TO ENTOMOLOGY Fig. 46.— Head of a cockroach; m, muscle impres- sions. In the more generalized insects at least, if not in all, the front bears the median ocellus; and in the Plecoptera, the paired ocelli also. Frequently the suture between the front and the following sclerite, the clypeus, is obsolete ; but as it ends on each side in the invagination which forms an anterior arm of the tentorium or endo-skeleton (Fig. 46, at), its former position can be inferred, at least in the more generalized insects, even when no other trace of it remains. In Figure 46 this is indicated by a dotted line. The clypeus. — The clypeus is the intermediate of the three unpaired sclerites between the epi- cranial suture and the mouth (fig. 46, c). To this part one condyle of the mandible articulates. Although the clypeus almost always appears to be a single sclerite, except when divided trans- versely as indicated below, it really consists of a transverse row of three sclerites, one on the median line, and one on each side articulating with the mandible. The median sclerite may be designated the clypeus proper, and each lateral sclerite, the ante- coxal piece of the mandible. Usually there are no indications of the sutures separating the clypeus proper from the antecoxal pieces ; but in some insects they are distinct. In the larva of Corydalus, the ante- coxal pieces are not only distinct but are quite large (Fig. 47, ac, ac). In some insects the clypeus is completely or partly divided by a transverse suture into two parts (Fig. 45). These may be designated as the first clypeus and the second clypeus, respectively; the first clypeus being the part next the front (Fig. 45, Ci) and the second clypeus being that next the labrum (Fig. 45, C2). The suture between the clypeus and the epicranium is termed the clypeal suture. The labrum. — The labrum is the movable flap which constitutes the upper lip of the mouth (Fig. 45, L). The labrum is the last of the series of unpaired sclerites between the epicranial suture and the mouth. It has the appearance of an appendage but is really a portion of one of the head segments. The epicranium. — Under the term epi- cranium are included all of the paired sclerites of the skull, and some- times also the front. The paired sclerites constitute the sides of Fi^. 47.— Head of a larva of Corydalus, dorsal aspect. THE EXTERNAL ANATOMY OF INSECTS 39 the head and that portion of the dorsal surface that is behind the arms of the epicranial suture. The sclerites constituting this region are so closely united that they were regarded as a single piece by Straus-Durckheim (1828), who also included the front in this region, the epicranial suture being obsolete in the May beetle, which he used as a type. The vertex. — The dorsal portion of the epicranium; or, more specifically, that portion which is next the front and between the compound eyes is known as the vertex (Fig. 45, V, V). In many insects the vertex bears the paired ocelli. It is not a definite sclerite; but the term vertex is a very useful one and will doubtless be retained. The occiput. — ^The hind part of the dorsal surface of the head is the occiput. When a distinct sclerite, it is formed from the tergal portion of the united postgenae described below (Fig. 47, 0, 0). The genae. — The gems are the lateral portions of the epicranium. Each gena, in the sense in which the word was used by the older writers, includes a portion of several sclerites. Like vertex, however, the term is a useful one. The postgenae. — In many insects each gena is divided by a well-marked suture. This led the writer, in an earher work ('95), to restrict the term gena to the part in front of the suture (Fig. 48, G), and to propose the term postgena for the part behind the suture (Fig. 48, Pg). The gula. — The gtila is a sclerite forming the ventral wall of the hind part of the head in certain orders of insects, and bearing the labium or second maxillae (Fig. 49, Gu). In the more generalized orders, the sclerite corresponding to the gula does not form a part of the skull. The sutures forming the lateral boundaries of the gula are termed the gular sutures. The ocular sclerites. — In many insects each compound eye is situated in the axis of an annular sclerite; these sclerites bearing the compound eyes are the ocular sclerites (Fig. 50, os). The antennal sclerites. — In some insects there is at the base of ench antenna an annular sclerite; these are the antennal sclerites (Fig. 50, as). The antennal sclerites are most distinct in the Plecoptera. Fig. 48. — Head and neck of a cock- roach. -Head of Coryd'ilus, adult, ventral aspect. 40 AN INTROD UCTION TO ENTOMOLOG Y The trochantin of the mandible. — In some insects, as Orthoptera there is a distinct sclerite between each mandible and the gena: this is the trochantin of the mandible (Fig. 45, tr). The maxillary pleurites. — In some of the more generaHzed insects, as certain cockroaches and crickets, it can be seen that each maxilla is articulated at the ventral end of a pair of sclerites, between which is the invagination that forms the posterior arm of the tentorium; these are the maxillary pleurites; the pos- terior member of this pair of sclerites can be seen in the lateral view of the head of a cockroach (Fig. 48, m. em). The cervical sclerites. — The cervical scler- ites are the small sclerites found in the neck of many insects. Of these there are dorsal, lateral, and ventral sclerites. The cervical sclerites were so named by Huxley ('78); Pig_ 50.— Head of a recently they have been termed the t7i/(?r5^g- cricket, ental surface mental plates by Crampton ('17), who con- wa . siders them to be homologous with sclerites found in the intersegmental regions of the thorax of some generalized insects. The lateral cervical sclerites have long been known as the jugular sclerites {pieces jugulaires, Straus Durckheim, 1828). C. THE APPENDAGES OF THE HEAD Under this category are classed a pair of jointed appendages termed the antennce, and the organs known collectively as the mouth- parts. The antemiae. — The antennae are a pair of jointed appendages articulated with the head in front of the eyes or between them. The antennse vary greatly in form; in some insects they are thread-like, consisting of a series of similar segments ; in others certain segments are greatly modified. The thread-like form is the more generalized. In descriptive works names have been given to particular parts of the antennae, as follows (Fig. 51): The Scape. — The first or proximal segment of an antenna is called the scape (a). The proximal end of this segment is often subglobose, appearing like a distinct segment; in such cases it is called the bulb (a'). THE EXTERNAL ANATOMY OF INSECTS 41 a- The Pedicel.— The. pedicel is the second segment of an antenna {b). In some insects it differs greatl}^ in form from the other segments. The Cldvola.— The term cla- y^ ,'-' '-.^ vola is applied to that part of ;■ ^--'' """-,^ the antenna distad of the pedi- cel (c); in other words, to all of the antenna except the first and second segments. In some insects certain parts of the cla- vola are specialized and have received particular names. These are the ring- joints, the funicle, and the club. Tne Eing-joints. ^In certain Fig. 51.— Antennaofachalcis-fly. insects (e..?., Chalcididse) the proximal segment or segments of the clavola are much shorter than the suc- ceeding segments; in such cases they have received the name of ring-joints (c*). The Club.— In many insects the distal seg- ments of the antennas are more or less enlarged. In such cases they are termed the club (c^). The Funicle. — The funicle (c^) is that part of the clavola between the club and the ring- joints; or, when the latter are not specialized, between the club and the pedicel. The various forms of antenna; are designated by special terms. The more common of these forms are represented in Fig. 52. They are as follows: 1. Setaceous or bristle-like, in which the segments are successively smaller and smaller, the whole organ tapering to a point. 2. Filiform or thread-like, in which the segments are of nearly uniform thickness. 3. Mbmliform or necklace-form, in which the segments are more or less globose, suggesting a string of beads. 4. Serrate or saw-like, in which the segments are triangular and project like the teeth of a saw. 5. Pectinate or comb-like, in which the seg- ments have long processes on one side, like the teeth of a comb. 6. Clavile or club-shaped, in which the segments becon3 gradually broader, so that the whole organ assumes the form of a club. 7. Capitate or with a head, in which the terminal segment or segments form a large knob. 8. Lamellate in which the segments that compose the knob are extended on one side into broad plates. When an antenna is bent abruptly at an angle like a bent knee (Fig. 51) it is said to be geniculate. Fig. 52. — Various forms "of antennae. 42 AN INTRODUCTION TO ENTOMOLOGY The mouth-parts. — The mouth-parts consist typically of an uppe:.' lip, lahrum, an under lip, labium, and two pairs of jaws acting hori- zontally between them. The upper jaws are called the mandibles; the lower pair, the maxillos. The maxillae and labium are each furnished with a pair of feelers, called respectively the maxillary palpi, and the labial palpi. There may be also within the mouth one or two tongue- like organs, the epipharynx and the hypopharynx. The mouth-parts of a locust will serve as an example of the typical form of the mouth- parts (Fig. 53). The mouth-parts enumer- ated in the preceding paragraph are those commonly recognized in insects; but in certain insects there exist vestiges of a pair of lobes between the mandibles and the maxillae, these are the parag- natha. No set of organs in the body of an insect vary in form to a greater degree than do the mouth-parts. Thus with some the mouth is formed for chewing, while with others it is formed for sucking. Among the chewing insects some are predaceous, and have jaws fitted for seizing and tearing their prey; others feed upon vegetable matter, and have jaws for chewing this kind of food. Among the sucking insects the butterfly merely sips the nectar from flowers, while the mosquito needs a powerful instniment for piercing its victim. In this chapter the typical form of the mouth-parts as illustrated by the biting insects is described. The various modifications of it presented by the sucking insects are described later, in the discussions of the characters of those insects. Fig. 53. — Mouth-parts of rum; md, mandible; mx, pharynx; /, labium. a locust: la, lab- maxilla; h, hypo- THE EXTERNAL ANATOMY OF INSECTS 43 The lahrum. — The Idbrum or upper lip (Fig. 53), is a more or less flap-like organ above the opening of the mouth. As it is often freely- movable, it has the appearance of an appendage of the body; but it is not a true appendage, being a part of one of the body segments that enter into the composition of the head. The mandibles. — The mandibles are the upper pair of jaws (Fig. 53). They represent the appendages of one of the segments of the head. In most cases they are reduced to a single segment; but in some insects, as in certain beetles of the family Scarabceidae, each mandible consists of several more or less distinct sclerites. The pardgnatha. — In some insects there is between the mandibles and the maxillae a pair of more or less appendage-like organs borne by the hypopharynx. These are the "paraglossas" of writers on the Thysanura and Collembola and the "superhnguae" of Fol- som ('00). They were termed the maxillulae, a diminutive of maxillas by Hansen ('93), who regards them as homologous with the first maxillae of the Crustacea. But it has been shown by Cramp ton ('21) that they are homologous with the paragnatha of Crustacea. In Figure 54, A. represents a ventral view of the hypopharynx, parag- natha, and mandibles of the crustacean Ligyda; and B. the same parts of a naiad of a May-fly, Heptagenia. Paragnatha have been found in the Thysanura, Dermoptera, Orthoptera, Corrodentia, the naiads of Ephemerida, and the lar\^£e of Coleoptera. The MaxillcB. — The maxUlcB are the second pair of jaws of insects. Like the mandibles they are the appendages of one of the segments of the head. Fig. 54. — A. Posterior (ventral) view of mandibles and hypopharynx of the crustacean Ligyda; h, hypopharynx; p, paragnatha; m, mandibles; B. Same of a nymph of the Mayfly Heptagenia (From Crampton). The maxilte are much more complicated than the mandibles, each maxilla consisting, when all of the parts are present, of five primary parts and three appendages. The primary parts are the cardo or hin^e, the stipes for foot- stalk, the palpifer or palpus-bearer, the subgalea or helmet-bearer, and the lacinia or blade. The appendages are the maxillaiy palpus or feeler, the galea 44 AN INTRODUCTION TO ENTOMOLOGY or superior lobe, and the digitus or finger. The maxilla may also bear claw-like or tooth-Hke projections, spines, bristles, and hairs. In the following description of the parts of the maxillae, only very general statements can be made. Not only is there an infinite variation in the form of these parts, but the same part may have a very different outline on the dorsal aspect of the maxilla from what it has on the ventral. Compare Fi . 55 and Fig. 56, which represent the two aspects of the maxilla of Hydrophikis. Excepting Fig. 56, the figures of maxillas represent the ventral aspect of this organ. The cardo or hinge {a) is the first or proximal part of the maxilla. It is usually more or less triangular in outline, and is the part upon which nearly all of the motions of this organ depend In many cases, hov/ever, it is not th: only naxt directly joined to the body; for frequently muscles extend direct to '.e :b.";alea, without passing through the cardo. The stipes or footstaUc {h) is the part next in order proceeding distad. It is usually triangular, and articulates with the cardo by its base, with the palpifer by its lateral margin, and with the subgalea by its mesal side. In many insects the stipes is united with the subgalea, and the two form the larger portion of the body of the maxilla (Fig. 53). The stipes has no appendages; but the palipfer on the one side, and the subgalea on the other, may become united to the stipes without any trace of sutvire remaining, and their appendages will then appear to be borne by the stipes. Thus in Fig. 53 it appears to be the stipes that bears the galea, and that receives muscles from the body. The palpifer or palpus-bearer (c) is situated upon the lateral (outer) side of the stipes; it does not, however, extend to the base of this organ, and frequently projects distad beyond it. It is often much more developed on the dorsal side of the maxilla than on the ventral (Figs. 55 and 56). It can bereadily distinguished when it is distinct by the ^. ,, , T>- ^ T^ 1 insertion upon it of the ap- Fig. 5S. — \entral as- Fig. 56. — Dorsal as- , t.- t, • ^ -4. pect of a maxilla of pect of a maxilla of Pondage which gives to it Hydrophilus. Hydrophilus. its name. The maxillary palpus or feeler {d) is the most conspicuous of the appendages of the maxilla. It is an organ composed of from one to six freely movable segments, and is articulated to the palpifer on the latero-distal angle of the body of the maxilla. The subgalea or heknet-bearer (e) when developed as a distinct sclerite is most easily distinguished as the one that bears the galea. It bounds the stipes more or less completely on its mesal (inner) side, and is often directly connected with the body by muscles. In many Coleoptera it is closely united to the lacinia; this gives the lacinia the appearance of bearing the galea, and of being connected with the body (Fig. 56). In several orders the subgalea is united to the stipes; consequently in these orders the stipes appears to bear the galea, and to be joined directly to the body if any part besides the cardo is so connected. THE EXTERNAL ANATOMY OF INSECTS 45 Fig- 57- — Maxilla oiCicindela. The galea or helmet (/) is the second in prominence of the appendages of the maxilla. It consists of one or two segments, and is joined to the maxilla ^ mesad of the palpus. The galea varies greatly in form: it is often more or less flattened, with the distal segment concave, and overlapping the lacinia like a hood. It was this form that suggested the name galea or helmet. In other ^-A>'*SJ ' \ 4 r^ t^^"^ cases the galea resembles a palpus in form (Fig. rX- \ \ \ V* r^~^ 57)- The galea is also known as the otiter lobe, '~'~^S\x^ ^^^"Z^ the upper lobe, or the superior lobe. The lacinia or blade (g) is borne on the mesal (inner) margin of the subgalea. It is the cutting or chewing part of the maxilla, and is often furnished with teeth and spines. The lacinia is also known as the inner lobe, or the inferior lobe. The digitus or finger {h) is a small appendage sometimes borne by the lacinia at its distal end. In the Cicindelidas it is in the form of an articu- lated claw (Fig. 57) ; but in certain other beetles it is more obviously one of the segments of the maxilla (Figs. 55 and 56). The labium or second maxillce. — The labium or under lip (Fig. 53), is attached to the cephaHc border of the gula, and is the most ventral of the mouth-parts. It appears to be a single organ, although some- times cleft at its distal extremity; it is, however, composed of a pair of appendages grown together on the middle line of the body. In the Crustacea the parts corresponding to the labiimi of insects consists of two distinct organs, resembling the maxillae; and in the embryos of insects the labium arises as a pair of append- ages. In naming the parts of the labium, entomo- logists have usually taken some form of it in which the two parts are completely grown together, that is, one which is not cleft on the middle line (Fig. 58). I will first describe such a labium, and later one into two parts is carried as far as we find it in insects. Fig. 58. — Labium of Harpalus. in which the division ^£4^^ LISRARY V! %^ 46 AN INTRODUCTION TO ENTOMOLOGY The labium is usually described as consisting of three principal parts and a oair of appendages. The principal parts are the sv.b'r.icvAv.m, the mentum, and the Ugida; the appendages are the labial palpi. The submentum. The basal part of the labium consists of Lwo transverse sclerites; the proximal one, which is attached to the cephalic border ol the gula, is the submetitutn (a). This is often the most prominent part of the body of the labium. The mentum is the more distal of the two primary parts of the labium (b). It is articulated to the cephahc border of the submentum, and is often so slightly developed that it is concealed by the submentum. The ligula includes the remaining parts of the labium except the labial palpi. It is a compound organ; but in the higher insects the sutures between the different sclerites of which it is composed are usually obsolete. Three parts, however, are commonly distinguished (Fig. 58), a central part, often greatly prolonged, the glossa (c^) and two parts, usually small membranous projections, one on each side of the base of the glossa, the paraglossce (c^) . Sometimes, how- ever, the paraglossas are large, exceeding the glossa in size. The labial palpi. From the base of the ligula arise a pair of appendages, the labial palpi. Each labial palpus consists of from one to four freely movable segments. In the forms of the labium just described, the correspondence of its parts to the parts of the maxillae is not easily seen; but this is much more evident in the labium of some of the lower insects, as for example a cockroach (Fig. 59). Here the organ is very deeply cleft; only the submentum and mentum remain united on the median line; while the ligula consists of two distinct maxilla-like parts. It is easy in this case to trace the correspondence referred to above. Each lateral hr.lf of the submentum corresponds to the cardo of a maxilla; each half of the mentum, to the stipes; while the remaining parts of a maxilla are represented by each half of the ligula, as follows: near th base of the ligula there is a part (c') which bears the labial palpus; this appears in the figure like a basal segment of the palpus; but in many msects it is easily seen that it is undoubtc '.ly one of the primary parts of the organ; it has been named Pig, gg, Labium of a ^^^^ palpiger, and is the homologue of the palpifer of cockroach. a maxilla. The trunk of each half of the ligula is formed by a large sclerite (c*) ; this evidently corres- ponds to the subgalea. At the distal extremity of this subgalea of the labium there are two appendages. The lateral one of these (c^) is the paraglossa. and obviously corresponds to the galea. The mesal one (c^) corresponds to the lacinia or inner lobe. This part is probably wanting in those insects in which the glossa consists of an undivided part; and in this case the glossa probably represents the united and more or less elongated subgaleag. The epipharynx. — In some insects there is borne on the ental sur- face of the labtum, within the cavity of the mouth, an unpaired fold, which is membranous and more or less chitinized' this is the epi- phdrynx. THE EXTERNAL A NA TOMY OF INSECTS 47 The hypopharynx. — The hypophdrynx is usually a tongue-like organ borne on the floor of the mouth cavity. This more simple form of it is well-shown in the Orthoptera (Fig. 53). To the hypopharnyx are articulated the paragnatha when they are present. The hypo- pharynx is termed the lingua by some writers. d. THE SEGMENTS OF THE HEAD The determination of the number of segments in the head of an insect is a problem that has been much discussed since the early days of entomology. The first important step towards its solution was made by Savigny (18 16), who sug- gested that the movable appendages of the head were homodyanmous with legs. This conclusion has been accepted by all ; and as each segment in the body of an insect bears only a single pair of appendages, there are at least four segments in the head; i. e., the antennal, the mandibular, the maxillary, and the second maxillary or labial. In more recent times workers on the embryology of insects have demonstrated the presence of two additional segments. First, there has been found in the embryos of many insects a pair of evanescent appendages situated between the antennse and the mandibles. These evidently correspond to the second antennee of Crustacea, and indicate the presence of a second antennal segment in the head of an insect. This conclusion is confirmed by a study of the development of the nervous system. And in the Thysanura and CoUembola vestiges of the second a.ntennas persist in the adults of certain members of these orders. Second, as the compound eyes are borne on movable stalks in certain Crusta- cea, it was held by Milne-Edwards that they represent another pair of appendages; but this view has not been generally accepted. It is not necessary, however, to discuss whether the eyes represent appendages or not ; the existence of an ocular segment has been demonstrated by a study of the development of the nervous system. It has been shown that the brain of an insect is formed from three pairs of primary ganglia, which correspond to the three principal divisions of the brain, the protecerebrum, the deutocerebrum, and the tritocerebrum . And it has also been shown that the protocerebrum innervates the compound eyes and ocelli; the deutocerebrum, the antenns; and the tritocerebrum, the labrum. This demon- strates the existence of three premandibular segments: an ocular segment or protocerebral segment, without appendages, unless the compound eyes repre- sent them; an antennal or deutocerebral segment, bearing antennae; and a second antennal or tritocerebral segment, of which the labrum is a part, and to which the evanescent appendages between the antennse and the mandibles doubt- less belong. As Viallanes has shown that the tritocerebrum of Crustacea inner- vates the second antennae, we are warranted in considering the tritocerebral segment of insects to be the second antennal segment. Folsom ('00) in his work on the development of the mouth-parts of Anurida described a pair of primary ganglia which he believed indicated the presence of a segment between the mandibular and maxillary segments. He named the ap- pendages of this segment the superlingucc; they are the paragnatha described above. The existence of the supposed ganglia indicating the presence of a super- lingual segment has not been confirmed by other investigators and is no longer maintained by Folsom. 48 AN INTRODUCTION TO ENTOMOLOGY The suboesophageal ganglion is formed by the union of three pairs of primitive ganglia, pertaining respectively to the mandibular, the maxillary, and the labial segments of the embryo. LIST OF THE SEGMENTS OF THE HEAD First, ocular, or protocerebral. Second, antennal, or deutocerebral. Third, second antennal, or tritocerebral. Fourth, mandibular. Fifth, maxillary. Sixth, labial, or second maxillary. III. THE THORAX a. THE SEGMENTS OF THE THORAX The prothorax, the mesothorax, and the metathorax. — The thorax is the second or intermediate region of the body ; it is the region that in nymphs, naiads, and adults bears the organs of locomotion, the legs, and the wings when they are present. This region is composed of three of the body-segments more or less firmly joined together; the segments are most readily distinguished by the fact that each bears a pair of legs. In winged insects, the wings are borne by the second and third segments. The first segment of the thorax, the one next the head, is named the prothorax; the second thoracic segment is the mesothorax; and the third, the metathorax. The simplest form of the thorax in adult insects occurs in the Apterygota (the Thysanura and the Collembola) where although the seg- ments differ in size and proportions, they are distinct and quite similar (Fig. 60). In the Pterygota, or winged insects, the prothorax is either free or closely united to the mesothorax ; in many cases it is greatly reduced in size; it bears the first pair of legs. The meso- thorax and the metathorax are more or less closely united, forming a box, which bears the wings and the second and third pairs of legs. This union of these two segments is often so close that it is very difficult to distin- guish their limits. Sometimes the matter is farther complicated by a union with the thorax of a part or of the whole of the first Pig. 60. — Lepisma saccharina (After Lubbock). THE EXTERNAL ANATOMY OF INSECTS 49 abdominal segment. In the Acridiidae, for example, the sternum of the first abdominal segment forms a part of the intermediate region of the body, and in the Hymenoptera the entire first abdominal segment pertains to this region. The alitrunk. — ^When, as in the Hymenoptera, the intermediate region of the body includes more than the three true thoracic seg- ments it is designated the dlitrnnk. The propodeum or the median segment. — ^When the alitrunk con- sists of four segments the abdominal segment that f omis a part of it is teniied the propodeum or the median segment. In such cases the true second abdominal segment is termed the first. h. THE SCLERITES OF A THORACIC SEGMENT The parts of the thorax most generally recognized by entomologists were described nearly a century ago by Audouin (1824) ; some addi- tional parts not observed by Audouin have been described in recent times, by the writer ('02), Verhoeff ('03), Crampton ('og), and Snodgrass ('09, '10 a, and '10 h). The following account is based on all of these works. In designating the parts of the thorax the prefixes pro, meso, and meta are used for designating the three thoracic segments or corres- ponding parts of them; and the prefixes pre and post are used to designate parts of any one of the segments. Thus the scutum of the prothorax is designated the proscutum; while the term prescutum is applied to the sclerite immediately in front of the scutum in each of the thoracic segments. This system leads to the UL^e of a number of hybrid combinations of Latin and Greek terms, but it is so firmly established that it would not be Vv^ise to attempt to change it on this account. Reference has already been made to the division of a body-segment into a tergum, two pleura, and a sterntun ; each of these divisions will be considered separately; and as the maximum number of parts are found in the wing-bearing segments, one of these will be taken as an illustration. The sclerites of a tergum. — In this discussion of the external ana- tomy of the thorax reference is made only to those parts that form the external covering of this region of the body. The infoldings of the body- wall that constitute the internal skeleton are discussed in the next chapter. The notum. — In nymphs and in the adults of certain generalized insects the tergum of each wing-bearing segment contains a single 50 AN INTRODUCTION TO ENTOMOLOGY chitinized plate; this sclerite is designated the notum. The term notum is also applied to the tergal plate of the prothorax and to that of each abdominal segment. The three thoracic nota are designated as the pronotum, the mesonotum, and the metanotum respectively. The notum of a wing-bearing segment is the part that bears the wings of that segment, even when the tergum contains more than one sclerite. Each wing is attached to two processes of the notum, the anterior notal process (Fig. 6i, a n p) and the posterior notal process (Fig. 61, p n p); and the posterior angles of the notum are produced into the axillary cords, which form the posterior margins of the basal membranes of the wings. The postnotmn or postscutellum. — In the wing-bearing segments of most adult insects the tergum consists of two principal sclerites ; the notum already described, and behind this a narrower, transverse sclerite which is commonly known as the postscutellum, and to which Snodgrass has applied the term postnotum (Fig. 61, P N). The divisions of the notum. — In most specialized insects the notum of each wing-bearing segment is more or less distinctly divided by transverse lines or sutures into three parts; these are known as the prescUtum (Fig. 61, Psc), the scutum (Fig. 61, Set), and the scutellum (Fig. 61, Scl). It has been commonly held, since the days of Audouin, that "the tergum of each thoracic segment is composed typically of four sclerites, the prescutum, scutum, scutellum, , -^^-> and postscutellum. But the investigations of Snodgrass indicate that in its more genera- lized form the tergum contains a single ^" sclerite, the notum; that the postscutellum ^^ or postnotum is a secondary tergal chitini- zation in the dorsal membrane behind the j^- notum, in more specialized insects; and that £p^ the separation of the notum into three parts, the prescutum, scutimi, and scutellum, is a still later specialization that has arisen independently in different orders, and does not indicate a division into homologous parts in all orders where it exists. The patagia. — In many of the more specialized Lepidoptera the pronotum Fig. 61. — Diagram of a generalized is produced on each side into a flat thoracic segment (From Snod- 1 u t,- 1, • • grass), lobe, which m some cases is even con- stricted at the base so as to become a stalked plate, these lobes are the patagia. THE EXTERNAL ANATOMY OF INSECTS 51 The parapsides. — In some Hymenoptera the scutum of the meso- thorax is divided into two parts by the prescutum; these separated halves of the scutum are called the parapsides (see Fig. 1 130A). The sclerites of the pleura. — In the accompanying figure (Fig. 61) the sclerites of the left pleunim of a wing-bearing segment are repre- sented diagrammatically ; these sclerites are the following: The episternum. — Each pleurum is composed chiefly of two sclerites, which typically occupy a nearly vertical position, but usually are more or less oblique. In most insects the dorsal end of these sclerites extends farther forward than the ventral end, but in the Odonata the reverse may be true. The more anterior in position of these two sclerites is the episternum (Fig. 61, Eps). In several of the orders of insects one or more of the episterna are divided by a distinct suture into an upper and a lower part. These two parts have been designated by Crampton ('09) as the anepister- num and the katepisternum respectively (Fig. 62). The epimerum. — The epimerum is the more posterior of the two principal sclerites of a pleurum (Fig. 61). It is separated from the episternum by the pleural suture (Fig. 61, PS) which extends from the pleural wing process above (Fig. 61, Wp) to the pleural coxal process below (Fig. 61, CxP). In some of the orders of insects one or more of the epimera are divided by a distinct suture into an upper and a lower part. These two parts have been desig- nated by Crampton ('09) as the anepimerum and the katepimeruni respectively (Fig. 62). The preepisternum. — In some of the more generalized insects there is a sclerite situated in front of the episternum; this is the pre- episternum. The paraptera. — In many insects there is on each side a small sclerite between the upper end of the episternum and the base of the wing ; these have long been known as the paraptera. Snodgrass (10 o) has shown that there are in some insects two sclerites in this region, which, he designates the episternal paraptera. or preparaptera (Fig. 61, iP and 2P); and that one or occasionally two are similarly situated between the epimerum and the base of the wing, the epimeral paraptera or postparaptera (Fig. 61, 3P). Fig. 62. — Lateral aspect of the meso- and meta- thorax of Mantis pa rugicollis; i, i, anepis- ternum ;2, 2, katepister- num; 3,3, anepimer- um; 4,4,katepimerum; c, c, coxa. 52 AN INTRODUCTION TO ENTOMOLOGY The spiracles. — The external openings of the respiratory system are termed spiracles. Of these there are two pairs in the thorax. The first pair of thoracic spiracles open, typically, one on each side in the transverse conjunctiva between the prothorax and the meso- thorax ; the second pair open in similar positions between the meso- thorax and the me athorax. In some cases the spiracles have migrated either fonvard or backward upon the adjacent segment. For a discussion of the number and distribution of the spiracles, see the next chapter. The periiremes. — In many cases a spiracle is surrounded by a cir- cular sclerite; such a sclerite is termed a peritreme. The acelabula or coxal cavities. — In some of the m.ore specialized insects, as many beetles for example, the basal segment of the legs is inserted in a distinct cavity ; such a cavity is termed an aceidbuhtfn or ^uxal cavity. When the epimera of the prothorax extend behind the coxae and reach the prostemum, the coxal cavities are said to be closed (Fig. 63) ; when the epimera do not extend behind the coxa to the prosterum, the coxal cavities are described as open (Fig. 54) . The sclerites of a sternum. — In the more generalized insects the sternimi of a wing-bearing segment may consist of three or four sclerites. These have been designated, beginning with the anterior one, the presternum (Fig. 61, Ps), the sternum or eusternum (Fig. 61, 5), the sternellum (Fig. 61, SI) , and the postsiernellum. (Fig. 61, Pst). In the more special- ized insects only one of these, the sternum, re- mains distinctly visible. It is an interesting fact that while in the speciali- zation of tue tergum there is an increase in the nimiber of the scleri- tes in this division of a segment, in the specialization of the sternimi there is a reduction. It is a somewhat unfortunate fact that the term sternum has been used in two senses : first, it is applied to the entire ventral division of a segment ; and second, it is applied to one of the sclerites entering Fig. 63. — Prothorax of Harpa.,is, ventral aspect; c, coxa; em, epimerum; is, episternum; /, femur; n, pronotum; s, s, s, prostemum. THE EXTERNAL ANATOMY OF INSECTS 53 Fig. 64. — Prothorax of Penlhe; c, coxa; cc, coxal cavity ;/, femur ; 5, prosternum; ngs. Beginning with the front edge of this joint and passing backward these sclerites are as follows: The iegula. — In several orders of insects there is at the base of the costal vein a small, hairy, slightly chitinized pad; this is the tegula (Fig. 66, Tg). In the more highly specialized orders, the Lepidoptera, the Hymenoptera, and the Diptera, the tegula is largely developed so as to form a scale-like plate overlapping the base of the wing. The tegulag of the front wings of Lepidoptera are specially large and are carried by special tegular plates of the notum. These, in turn, are supported by special internal tegular arms from the bases of the pleural wing -processes (Snodgrass, '09) The axillaries. — Excepting the tegula, which is at the front edg3 of the wing-joint, the articular sclerites of the wings have been termed collectively the axillaries. Much has been written about these sclerites, and many names have been applied to them. The simplest terminology is that of Snodgrass ('09 and '10 a) which I here adopt. THE EXTERNAL ANATOMY OF INSECTS 55 The first axillary. — This sclerite (Fig. 66, i Ax) articulates with the anterior notal wing-process and is specially connected with the base of the subcostal vein of the wing. In rare cases it is divided into two. The second axillary. — The second axillary (Fig. 66, 2 Ax) articulates with the first axillary proximally and usually with the base. of the radius distally; it also articulates below with the wing-process of the pleurum, constituting thus a sort of pivotal element. The third axillary. — The third axillary (Fig. 66, 3 Ax) is interposed between the bases of the anal veins and the fourth axillary when this sclerite is present. When the fourth axillary is absent, as it is in Fig. 66. — Diagram of a generalized wing and its articular sclerites (From Snodgrass). nearly all insects except Orthoptera and Hymenoptera, the third axillary articulates directly with the posterior notal wing-process. The fourth axillary. — When this sclerite is present it articulates with the posterior notal wing-process proximally and with the third axillary distally (Fig. 66, 4 Ax). Usually this sclerite is absent; it occurs principally in Orthoptera and Hymenoptera. The median plates. — The median plates of the wing-joint are not of constant shape and occurrence; when present, these plates are associated with the bases of the media, the cubitus, and the first anal vein when the latter is separated from the other anals. Often one of them is fused with the third axillary and sometimes none of them^ are present. THE APPENDAGES OF THE THORAX The appendages of the thorax are the organs of locomotion. They consist of the legs and the u ings. Of the former there are three 56 AN INTRODUCTION TO ENTOMOLOGY pairs, a pair borne by each of the three thoracic segments; of the latter there are never more than two pairs, a pair borne by the meso- thorax and a pair borne by the metathorax. One or both pairs of wings may be wanting. The legs. — Each leg consists of the following named parts and their appendages: coxa, trochanter, femur, tibia, and tarsus. The coxa. — The coxa is the proximal segment of the leg; it is the one by which the leg is articulated to the body (Fig. 67). The coxa varies much in form, but it is usually a truncated cone or nearly globular. In some insects the coxae of the third pair of legs are more or less flattened and immovably attached to the metasternum; this is the case in beetles of the family Carabidas for example. In such cases the coxas really form a part of the body-wall, and are liable to be mistaken for primary parts of the metathorax instead of the proximal segments of appendages. In several of the orders of insects the coxa is apparently composed of two, more or less dis- tinct, parallel parts; this is the case, for example, inin- sects of the trichopterous genus Neuro- ma (Fig. 68, Cx and epm). But it has been shown by Snodgrass ('09) that the posterior part of the sup- posed double coxa, the "meron"(Fig. 68, epm) is a detached por- tion of the epimerimi. The styli. — In certain generalized insects, as Machilis of the order Fig. 67. — Legs of insects: A, wasp; B, ichneumon-fly; C, bee; c, coxa; tr, trochanter; /, femur; ti, tibia; to, tarsus; m, metatarsus. THE EXTERNAL ANATOMY OF INSECTS 57 Thysanura, the coxa of each middle and hind leg bears a small appendage, the stylus (Fig. 69). The styli are of great interest as they are believed to correspond to one of the two branches of the legs of Crustacea; thus indicating that insects have descended from forms in which the legs were biramous. In several genera of the Thysanura one or more of the abdominal segments bear each a pair of styli ; in Machilis they are found on the second to the ninth abdominal segments. These styli are regarded as vestiges of abdominal legs. The trochanter. — The trochanter is the second part of the leg. It consists usually of a very short, triangular or quadrangular segment, between the coxa and the femur. Sometimes the femur appears to articulate directly with the coxa ; and the trochanter to be merely an appendage of the prox'mal end of the femur {e. g. Carabidas). But the fact is that in these insects, although the femur may touch the coxa, it does not articulate with it; and the organs that pass from the cavity of the coxa to that of the femur must pass through the trochanter. In some Hymenoptera the tro- chanter consists of two segments (67, B). The femur. — The femur is the third part of the leg; and is usually the largest part. It consists of a single segment. The tibia. — The tibia is the fourth part of the leg. It consists of a single segment; and Fig. 68.— Lateral aspect ^^ usually a little more slender than the femur, of the mesothorax of although it often equals or exceeds it in length. In such species as burrow in the ground, the distal extremity is greatly broadened and shaped more or less like a hand. Near the distal end of the tibia there are in most insects one or more spurs, which are much larger than the hairs and spines which arm the leg; these are called the tibial spurs, and are much used in classification. The tarsus. — The tarsus is the fifth and most distal part of the leg, that which is popularly called the foot. It consists of a series of segments, var^dng in number from one to six. The most common num- ber of segments in the tarsus is five. In many insects, the first segment of the tarsus is much longer, Neuronia (From Snod- grass). Fig. 69. — A leg of Machilis; s, stylus. 58 AN INTRODUCTION TO ENTOMOLOGY and sometimes much broader, than the other segments. In such cases this segment is frequently designated as the metatarsus (Fig. 67, C, m). In some insects the claws borne by the distal end of the tarsus are outgrowths of a small terminal portion of the leg, the sixth segment of the tarsus of some authors. This terminal part with its appendages has received the name prcetarsus (De Meijere '01). As a rule the prsetarsus is withdrawn into the fifth segment of the tarsus or is not piesent as a distinct segment. On the ventral surface of the segments of the tarsus in many insects are cushion-like structures; these are called pulvUli. The cuticula of the pulvilli is traversed by nvimerous pores which open either at the surface of the cuticula or through hollow hairs, the tenent-hairs, and from which exudes an adhesive fluid that enables the insect to walk on the lower surface of objects. With many insects (e. g. most Diptera) the distal segment of the tarsus bears a pair of pulvilli, one beneath each claw. In such cases there is frequently between these pulvilli a third single appendage of similar structure; this is called the empoiium; writers on the Orthop- tera commonly called the appendage between the claws the arolium. In other insects the empodium is bristle-like or altogether wanting. In many insects the pulvillus of the distal segment of the tarsus is a circular pad projecting between the tarsal claws. In many descriptive works this is referred to as the pulvillus , even though the other pulvilli are well-developed. The pulvilli are called the onychii by some writers. The claws borne at the tip of the tarsus are termed the tarsal claws or ungues; they vary much in form; they are usually two in nimiber, but sometimes there is only one on each tarsus. The wings. — The wings of insects are typically two pairs of mem- branous appendages, one pair borne by the mesothorax and one pair by the metathorax; prothoracic wings are unknown in living insects but they existed in certain paleozoic forms. Excepting in the subclass Apterygota which includes the orders Thysanura and Collembola, wings are usually present in adult insects. Their absence in the Apterygota is due to the fact that they have not been evolved in this division of the class Hexapoda; but when they are absent in adult members of the subclass Pterygo- ta, which includes the other orders of insects, their absence is due to a degradation, which has resulted in their loss. THE EXTERNAL ANATOMY OF INSECTS 59 The loss of wings is often confined to one sex of a species; thus with the canker-worm moths, for example, the females are wingless, while the males have well-developed wings; on the other hand, with the fig-insects, Blastophaga, the female is winged and the male wingless. Studies of the development of wings have shown that each wing is a saclike fold of the body-wall; but in the fully developed wing, its saclike nature is not obvious; the upper and lower walls become closely applied throughout the greater part of their extent ; and since they become very thin, they present the appearance of a single delicate membrane. Along certain lines, however, the walls remain separate, and are thickened, forming the firmer framework of the wing. These thickened and hollow lines are termed the veins of the wing ; and their arrangement is described as the venation of the wing. The thin spaces of the wings which are bounded by veins are called cells. When a cell is completely surrounded by veins it is said to be closed; and when it extends to the margin of the wing it is said to be open. The different types of insect wings. — What may be regarded as the typical form of insect wing is a nearly flat, deHcate, membranous appendage of the body, which is stiffened by the so-called wing-veins ; but striking modifications of this form exist; and to certain of them distinctive names have been applied, as follows: In the Coleoptera and in the Dermaptera, the front wings are thickened and ser^'e chiefly to protect the dorsal wall of the body and the membranous hind wings, which are folded beneath them when not in use. Front wings of this type are termed wing-covers or elytra. The front wings of the Hemiptera, which are thickened at the base like elytra, are often desig- nated the hemelytra. The thickened fore wings of Orthoptera are termed tegmina by many writers. The hind wings of Diptera, which are knobbed, thread-like organs, are termed haltcres. The hind wings of the males of the family Coccidse are also thread- Fig. 70. — Diasrram of a wing showing like, margins and angk^s. ,^1 -, -, ^ The reduced front wmgs of the Strepsiptera are known as the pseudo-halteres. 60 AN INTRODUCTION TO ENTOMOLOGY The margivs of wings. — -Most insect wings are more or less triangular in outline; they, therefore, present three margins: the costal margin or costa (Fig. 70, a-h)\ the outer margin (Fig. 70, h-c)\ and the inner margin (Fig. 70, c-d). The angles of wings. — The angle at the base of the costal margin of a wing is the humeral angle (Fig. 70, a) ; that between the costal margin and the outer margin is the apex of the wing (Fig. 70, h)\ 2dA*Cu, Fig. 71. — Wing of Conops; ac, axillary excision; /, posterior lobe. and that between the outer margin and the inner margin is the anal a?gle (Fig. 70, c). The axillary cord. — The posterior margin of the membrane at the base of the wing is usually thickened and corrugated; this cord-like structure is termed the axillary cord. The axillary cord normally arises, on each side, from the posterior lateral angle of the notum, and thus serves as a mark for determining the posterior limits of the notum. The axillary membrane. — The membrane of the wing base is termed the axillary membrane; it extends from the tegula at the base of the costal margin to the axillary cord ; in it are found the axillary sclerites. The alula. — In certain families of the Diptera and of the Coleop- tera the axillary membrane is expanded so as to form a lobe or lobes which fold beneath the base of the wing when the wings are closed; this part of the wing is the alula or alulet. The alulas are termed the sgi^amcB by some writers, and the calypteres by others. Fig. 72. — Wings of the honeybee; A, hamuli. THE EXTERNAL ANATOMY OF INSECTS 61 The axillary excision. — In the wings of most Diptera and in the wings of many other insects there is a notch in the inner margin of the wing near its base (Fig. 71, ae), this is the axillary excision. The posterior lobe of the wing. — That part of the wing lying between the axillary excision when it exists, and the axillary membrane is the posterior lobe of the wing. The posterior lobe of the wing and an alula are easily differentiated as the alula is margined by the axillary cord. The methods of uniting the two wings of each side. — It is obvious that a provision for ensuring the synchronous action of the fore and hind wings adds to their efficiency; it is as important that the two pairs of wings should act as a unit as it is that the members of a boat's crew should pull together. In many insects the synchronous action of the wings is ensured by the fore wing overlapping the hind wing. But in other insects special structures have been developed which fasten together the two wings of each side. The different types of these structures have received special names as follows: The hamuli. — With certain insects the costal margin of the hind wings bears a row of hooks, which fasten into a fold on the inner margin of the fore wings (Fig. 72) ; these hooks are named the hamuli. The frenulum and the frenulum hook. — In most moths there is a strong spine-like organ or a bunch of bristles borne by the hind wing at the humeral angle (Fig. 73,/); this is the frenulum or little bridle. As a rule the frenulum of the female consists of several bristles ; that of the male, of a single, strong, spine-like organ. In the males of certain moths, where the frenulimi is highly developed, there is a membranous fold on the fore wing for recei\-ing the end of the frenulum, this is the frenulum hook (Fig. ^Sffh). The jugum. — In one family of moths, the Hepialidse, the posterior lobe of the fore wing is a slender, finger-like organ which is stiffened by a branch of the third anal vein, and which projects beneath the costal margin of the hind wing. As the greater part of the inner margin of the fore Fig- 73- — Wings of Thyridnpteryx ephemercB- formis; f, frpnulum; fh, frenulum hook. 62 AN INTRODUCTION TO ENTOMOLOGY wing overlaps the hind wing, the hind wing is held between the two (Fig. 74). This type of the posterior lobe of the fore wing is termed the jugum or yoke. The structure of the jugum is shown in Figure 75. The fibula. — In several groups of insects an organ has been developed that serves to unite the fore and hind wings, but which functions in a way quite different from that of the jugum. Like the jugum it is f oimd at the base of the fore wing ; but unlike the jugum it extends back above the base of the hind wing and is clasped over an elevated part of the hind wing; this organ is the fibula or clasp. In some insects, as in the Trichoptera, the fibula consists only of a specialized posterior lobe of the fore wing; in others, as in the genus Corydalns of the order Neuroptera, the proximal part of the fibula is margined by the axillary cord, showing that the axillary membrane enters into the composition of this organ (Fig. 76). The hypothetical type of the primitive wing-venation. — A careful study of the wings of many insects has shown that the fundamental type of venation is the same in all of the orders of winged insects. But this fact is evident only when the more primitive or generalized members of different orders are compared with each other. In most of the orders of insects the greater number of species have become so modified or specialized as regards the structure of their wings that it is diffi- cult at first to trace out the primitive type. This agreement in the important features of the venation of the wings of the generalized members of the different orders of insects is still more evident when the wings of nymphs, naiads, and pupae are studied. It has been demonstrated that in the development of wings of generalized insects the longitudinal wing-veins are formed about preexisting tracheae. In the develop- ment of the wing, these tracheee grow out into the wing-bud, and later the wing-veins are formed about them. Fig. 74. — Wings of a hepialid, seen from below; a, accessory vein. THE EXTERNAL ANATOMY OF INSECTS 63 The wings of nymphs, naiads, and pupae are broad at the base, and consequently the tracheag that precede the wing-veins are not crowded together as are the wing-veins at the base of the wings of Fig- 75- — Jugum of a hepialid Fibula of Corydalus. adults. For this reason the identity of the wing- veins can be deter- mined more surely in the wings of immature insects than they can be in the wings of adults. This is especially true where two or more veins coalesce in the adult wing while the tracheag that precede these veins are distinctly separate in the immature wing. A study was made of the tracheation of the wings of immature insects of representatives of most of the orders of insects, and, assum- ing that those features that are possessed by all of them must have been inherited from a common ancestor, a diagram was made repre- senting the hypothetical tracheation of a nymph of the primitive winged insect (Fig. 77). In this diagram the tracheag are lettered Fig. 77.— Hypothetical tracheation of a wing of the primitive nymph. with the abbreviations used in designating the veins that are formed about them in the course of the development of the wing. The dia- gram will serve, therefore, to indicate the typical venation of an insect 64 AN INTRODUCTION TO ENTOMOLOGY wing, except that the tracheae are not crowded together at the base of the wing as are the veins in the wings of adults.* Longitudinal veins and cross-veins. — The veins of the wing can be grouped under two heads: first, longitudinal veins, those that normally extend lengthwise the wing; and second, cross-veins, those that normally extend in a transverse direction. The insertion of the word normally in the above definitions is important; for it is only in comparatively generalized wings that the direction of a vein can be depended upon for determining to which of these two classes it belongs. The principal wing-veins.— The longitudinal wing-veins constitute the principal framework of the wings. In the diagram representing the typical venation of an insect wing (Fig. 77), only longitudinal veins are indicated; this is due to the fact that the diagram was based on a study of the tracheation of wings, and in the more generalized wings the cross-veins are not preceded by tracheae; moreover in the wings of more generalized paleozoic insects there were no definite cross-veins, but merely an irregular network of thickened lines [)etween the longitudinal veins. There are eight principal veins; and of these the second, third, fourth, and fifth are branched. The names of these veins and the t bbreviations by which they are known are as follows, beginning with ' he on3 nearest the costal margin of the wing: Nam?s of vsins Abbreditions Costa C Subcosta So Radius R Media M Cubitus Cu First Anal ist A Second Anal 2dA Third Anal 3dA The chief branches of the voing-veins. — The chief branches of the principal veins are numbered, beginning with the branch nearest to the costal margin of the wing. The term used to designate a branch of a vein is formed by compounding the name of the vein with a *For many details regarding the development of the wings of insects, their structure, and the terminology of the wing-veins, that can not be included in this work, see a volume by the writer entitled The Wings of Insects. This is published by The Comstock Publishing Company, Ithaca, N. Y. THE EXTERNAL ANATOMY OF INSECTS 63 numeral indicating the number cf the branch ; thus, for example, the first branch of the radius is radius-one or vein Ri. In the case of radius and media, each of which has more than two branches, each division of the vein that bears two or more branches has received a special name. Thus after the separation of radius-one from the main stem of radius there remains a division which is typi- cally four-branched; this division is termed the radial sector, or vein Rsi the first division of the radial sector, which later separates into radius-two and radius-three, is designated as radius-two-plus- three or vein R2+3; and the second division is termed radius-four- plus-five or vein R4+5. Media is typically separated into two divi- sions, each of which is two-branched; the first division is media-one- plUs two or vein Mi +2, the second is media-three-plus-four or vein M3+4. The veins of the anal area.— The three anal veins exhibit a wide range of variation both as to their persistence and to their form when Fig. 78. — A wing of Rhyphns. present. In those cases where the anal veins are branched there is no indication that the branching has been derived from a uniform primitive type of branching. For this reason in describing a branched anal vein merely the nimiber of branches is indicated. In some cases, as in the Odonata, there is a single anal vein the identity of which can not be determined. In such cases this vein is designated merely as the anal vein or vein A, and its branches as Ax, Ai, Az, etc. The reduction of the number of wing-veins. — In many wings the nimiber of the veins is less than it is in the hypothetical type. In some cases this is due to the fact that one or more veins have faded out in the course of the evolution of the insects showing this deficiency; frequently in such wings vestiges of the lacking veins remain, either as faint line-s in the positions formerly occupied by the veins or as 66 AN INTRODUCTION TO ENTOMOLOGY short fragments of the veins. A much more common way in which the number of veins has been reduced is by the coalescence of adja- cent veins. In many wings the basal parts of two or more principal veins are united so as to appear as a single vein; and the number of the branches of a vein has been reduced in very many cases by two or more branches becoming united throughout their entire length. When a vein consists of two or more of the primitive veins united, the name applied to the compound vein should indicate this fact. In the wing of Rhyphus (Fig. 78), for example, radius is only three- branched; but it would be misleading to designate these branches as Ri, R2, and R3, for this would indicate that veins R4 and R5 are lacking. The first branch is evidently Ri ; the second branch is composed of the Fig. 79. — A wing of Tabanus. coalesced R2 and R3, it is, therefore, designated as R2+3; and the third branch, which consists of the coalesced R4 and R5, is designated as R4+5. A second method of coalescence of veins is illustrated by a wing of Tabanus (Fig. 79). In this wing the tips of cubitus-two and the second anal vein are united ; here the coalescence began at the margin of the wing and is progressing towards the base. The united portions of the two veins are designated as 2d A+Cu2. When it is desired to indicate the composition of a compound vein it can be readily done by combining the terms indicating its elements. But in descriptions of hymenopterous wings where a compound vein may be formed by the coalescence of several veins the logical carrying out of this plan would result in a very cumbersome terminology, one that it is impracticable to use in ordinary descrip- tions. In such cases the compound vein is designated by the term indicating its most obvious element. Thus, for example, in the fore THE EXTERNAL ANATOMY OF INSECTS 67 wing of Pamphilius, where veins M4, Cu,, and Cu^ coalesce with the first anal vein, the united tips of these veins is designated as vein ist A, the first anal vein being its most obvious element (Fig. 80), although it is really vein M4+Cui+Cu2 + ist A. Serial veins. — In the wings of some insects, where the wing-vena- tion has been greatly modified, as in certain Hymenoptera, there exist what appears to be simple veins that in reality are compound veins composed of sections of two or more veins joined end to end with no indication of the point of union. Compound veins formed in this Fig. 80. — Wings of Pamphilius. manner are termed serial veins. Examples of wings in which there are serial veins are figured in the chapter treating of the Hymenoptera. In designating serial veins either the sign & or a dash is used between the terms indicating the elements of the vein, instead of the sign -f as the latter is used in designating compound veins formed by the coalescence of veins side by side. If the serial vein consists of only two elements the sign & is used; thus the serial vein in the wings of braconids, which consists of the medial cross-vein and vein M„ is designated as m & M2. In those cases where sections of several veins enter into the com- position of a serial vein, the serial vein is designated by the abbrevia- tion of the name of the basal element connected by a dash with the 68 AN INTRODUCTION TO ENTOMOLOGY abbreviation of the name of the terminal element. Thus a serial vein, the basal element of which is the cubitus and the terminal ele- ment vein Ml, is designated as vein Cit — Mi. A serial vein thus formed exists in the hind wings of certain ichneumon flies. The increase of the number of wing-veins. In the wings of many- insects the number of veins is greater than it is in the hypothetical type. This multiplication of veins is due either to an increase in the Fig. 8 1 . — Wings of Osmylus hyalinatus. nimiber of the branches of the principal veins by the addition of secondary branches, termed accessory veins, or to the development of secondary longitudinal veins between these branches, termed inter- calary veins. In no case is there an increase in the number of principal veins. The accessory veins. — The wings of Osmylus (Fig. 8i) are an exam- ple of wings in which accessory veins have been developed; here the radial sector bears many more branches than the typical number; those branches that are regarded as the primitive branches are lettered Ri, Ro, R3, R4, and R5 respectively (Fig. 82); the other THE EXTERNAL ANATOMY OF INSECTS 69 branches are the secondarily developed accessor}^ veins. Two types of accessory veins are recognized the marginal accessory veins and the definitive accessory veins. The marginal accessory veins are twig-like branches that are the result of bifurcations of veins that have not extended far back from the margin of the wing; many such short branches of veins exist in the wings of Osmylus (Fig. 8i). The nimiber and position of the marginal accessory veins are not constant, differing in the wings of the two sides of the same individual. The definitive accessory veins differ from the marginal accessory Fig. 82. — Base of fore wing shown in Figure 81. veins in having attained a position that is comparable in stability to that of the primitive branches of the principal veins. In those cases where the accessory veins are believed to have been developed in regular order they are designated by the addition of a letter to the abbreviation of the name of the vein that bears them; thus if vein R2 bears three accessory veins they are designated as veins R2a, Rsb, and Rac, respectively. The intercalary veins. — The intercalary veins are secondarily developed longitudinal veins that did not arise as branches of the primitive veins, but were developed in each case as a thickened fold in a corrugated wing, more or less nearly midway between two pre- existing veins, with which primarily it was connected only by cross- veins. Excellent examples of unmodified intercalary veins are com- 70 AN INTRODUCTION TO ENTOMOLOGY Fig. 83. — Wing of a May-fly (After Morgan). mon in the Ephemerida, where most of the intercalary veins remain distinct from the veins between which they were developed, being connected with them only by cross-veins, the proximal end of the intercalary vein being free (Fig. 83). ^ When it is desirable to re- fer to a parti- cular interca- lary vein it can be done by combining the initial /, indicating intercalary, with the designation of the area of the wing in which the intercalary vein occurs. For example, in the wings of most May-flies there is an intercalary vein between veins Cui and Cu2, i e. in the area Cui ; this intercalary vein is desig- nated as ICui. The adven- titious veins. — In certain in- sects there are secon d ary veins that are neither acces- sory veins nor intercalary veins as de- fined above; these are termed adven- titious veins. Examples of these are the supplements of the wings of St A 3dA 2d A '^ Fig. 84. — Wings of Prionoxystus. certain Odonata and the spurious vein of the Syrphidae. The anastomosis of veins. — The typical arrangement of wing-veins is often modified by an anastomosis of adjacent veins; that is, two THE EXTERNAL ANATOMY OF INSECTS 71 veins will come together at some point more or less remote from their extremities and merge into one for a greater or less distance, while their extremities remain separate. In the fore wing of Prionoxystus (Fig. 84), for example, there is an anastomosis of veins R3 and R4+5. The named cross-veins. — In the wings of certain insects, as the dragon-flies, May-fiies, and others, there are many cross-veins; it is impracticable in cases of this kind to name them. But in several of the orders of insects there are only a few cross-veins, and these have been named. Figure 85 represents the hypothetical primitive type •5^> Sc^ Fig. 85. — The hypothetical primitive type of wing-venation with the named cross-veins added. of wing-venation with the named cross-veins added in the positions in which they normally occm-; these are the following: The humeral cross-vein (h) extends from the subcosta to costa near the humeral angle of the wing. The radial cross-vein (r) extends between the two principal divi- sions of radius, i. e. from vein Ri to vein Rg. The sectorial cross-vein {s) extends between the principal divisions of the radial sector — ■ i. e., from vein R2+3 to vein R4+5 or from vein R3 to vein R4. The radio-medial cross-vein (r — m) extends from radius to media, usually near the center of the wing. When in its typical position this cross- vein extends from vein R4+5 to vein Mi +2. The medial cross-vein (m) extends from vein M2 to vein M3. This cross-vein divides cell M2 into cells, ist M2 and 2d M2; see Figure 87 where the cells are lettered. The medio-cubital cross-vein (m — cu) extends from media to cubitus. 72 AN INTRODUCTION TO ENTOMOLOGY The arculus. — In many insects there is what appears to be a cross- vein extending from the radius to the cubitus near the base of the wing; this is the arculus. The arculus is designated in figures of wings by the abbreviation ar. Usually when the arculus is present the media appears to arise from it; the fact is, the arculus is com- pound, being composed of a section of media and a cross-vein. Figure 86 is a dia- e+yl/ Fig. 86. — Diagram of a:i arculus of a dragon-fly. gram representing the typical struc- ture of the arculus. That part of the arculus which is a section of media is designated as the anterior arculus (aa) and that part formed by a cross-vein, the posterior arculus (pa) . The terminology of the cells of the wing. — Each cell of the wing is designated by the name of the vein that normally forms its front margin when the wings are spread. See Figure 87 where both the veins and the cells of the wing are lettered. The cells of the wing fall naturally into two groups: first, those on the basal part of the wing; and second, those nearer the distal end of the wing. The former are bounded by the stems of the principal veins, the latter, by the branches of these veins; a corresponding distinction is made in designating the cells. Thus a cell lying behind the main stem of radius and in the basal part of the wing is designated as cell R; while a cell lying behind radius-one is designated as cell Ri. zdA Fig. 87. — A wing of Rhyphus. It should be remembered that the coalescence of two veins results in the obliteration of the cell that was between them. Thus when THE EXTERNAL ANATOMY OF INSECTS 73 veins Ri and Rz coalesce, as in the wings of RJtyphus (Fig. 87), the cell lying behind vein i?2+3 is cell Rz, and not cell i?2+3, cell i?2 having been obliterated. When one of the principal cells is divided into two or more parts by one or more cross-veins, the parts may be mmibered, beginning v\^ith the proximal one. Thus in Rhyphus (Fig. 87), cell M2 is divided by the medial cross-vein into cell istM-i and cell 2dM2. When two or more cells are united by the atrophy of the vein or veins separating them, the compound cell thus formed is designated by a combination of the terms applied to the elements of the com- pound cell. When, for example, the stem of media is atrophied, the cell resulting from the combination of cells R and M is designated as cell R+M. The application of this system of naming the cells of the wing is an easy matter in those orders where there are but few cross- veins; but in those orders where there are many cross-veins it is not practicable 10 apply it. In the latter case we have to do with areas of the wing rather than with separate cells. These areas are designated as are the cells of the few- veined wings with which they correspond; thus the area immediately behind vein R2 is area R2. The corrugations of the wings. — The wings of comparatively few insects present a flat surface ; in most cases the membrane is thrown into a series of folds or corrugations. This corrugating of the wing in some cases adds greatly to its strength, as in the wings of dragon-fiies; in other cases the corrugations are the result of a folding of the wing when not in use, as in the anal area when this part is broadly ex- panded. It rarely happens that there is occasion to refer to individual members of either of these classes of folds, except perhaps the one between the costa and the radius, which is the subcostal fold and that which is normally between the cubitus and the first anal vein, the cubito-anal fold. Convex and concave veins. — ^When the wings are corrugated, the wing-veins that follow the crests of ridges are termed convex veins; and those that follow the furrows, concave veins. The furrows of the wing. — There are found in the wings of many insects one or more suture-like grooves in the membrane of the wing; these are termed the furrows of the wing. The more important of these furrows are the four following: The anal furrow when present is usually developed in the cubito anal fold ; but in the Heteroptera it is found in front of the cubitus. 74 AN INTRODUCTION TO ENTOMOLOGY The median furrow is usually between radius and media. The nodal furrow is a transverse suture beginning at a point in the costal margin of the wing corresponding to the nodus of the Odonata and extending towards the inner margin of the wing across a varjdng number of veins in the different orders of insects. The axillary furrow is a Hne that serves as a hinge which facilitates the folding of the posterior lobe of the wing of many insects under that ^^^^^^ part of the wing \ \ ^"\^ J^cr^^^*^*"'^"""'"'^--^^/"'^'''^ wing where they VJ ^■-~— J^N ^^r^"""^^ ^""""""^y^ ^'"^ crossed by ^^^^---—JN ^^^^--^"^^ furrows. The bullae are usually Fig. 88. — Wings of Myrmeaa; b, b, b, hullse. , . , paler m color than the other portions of the wing; they are common in the wings of the Hymenoptera (Fig. 88), and of some other insects. The ambient vein. — Sometimes the entire margin of the wing is stiffened by a vein-like structure; this is known as the ambient vein. The humeral veins. — In certain Lepidoptera and especially in the Lasiocampidae, the humeral area of the hind wings is greatly expanded and in many cases is strengthened by the development of secondary veins. These are termed the humeral veins. TJie pterostigma or stigma. — A thickened, opaque spot which exists near the costal margin of the outer part of the wing in many insects is known as the pterostigma or stigma. The epipleurcB. — A part of the outer margin of the elytra of beetles when turned down on the side of the thorax is termed the epipleura. The discal cell and the discal vein. — The term discal cell is applied to a large cell which is situated near the center of the wing ; and the term discal vein, to the vein or series of veins that limits the outer end of the discal cell. These terms are not a part of the uniform terminol- ogy used in this book, and can not be made so, being applied to different parts of the wing by writers on different orders of insects. They are included here as they are frequently used, as a matter of convenience, by those who have adopted the uniform terminology. The discal cell of the Lepidoptera is cell R+M+ISIM2; that of th-* Diptera is cell ist M2; and that of the Trichoptera is cell R2+3. THE EXTERNAL ANATOMY OF INSECTS 75 The anal area and the preanal area of the wing. — In descriptions of wings it is frequently necessary to refer to that part of the wing supported by the anal veins ; this is designated as the anal area of the wing; and that part lying in front of the anal area, including all cf the wing except the anal area, is termed the preanal area. IV. THE ABDOMEN a. THE SEGMENTS OF THE ABDOMEN The third and terminal region of the bDdy, the abdomen, consists of a series of approximately similar segments, which as a rule are without appendages excepting certain segments near the caudal end of the body. The body-wall of an abdominal segment is usually comparatively simple, consisting in adults of a tergum and a sternum, united by lateral conjunctivas. Somstimas there are one or two small sclerites on each lateral aspect of a segment; these are probably reduced pleura. The nimiber of segments of which the abdomen appears to be composed varies greatly in different insects. In the cuckoo-flies (Chrysididag) there are usually only three or four visible; while in many insects ten or eleven can be distinguished. All intergrades between these extremes occur. The apparent variation in the nimiber of abdominal segments is due to two causes: in some cases, some of the segments are tele- scoped ; and in others, adjacent segments coalesce, so that two or more segments appear as one. A study of embryos of insects has shown that the abdomen con- sists typically of eleven segments; although this number may be reduced during the development of the insect by the coalescence of adjacent segments. In some insects there is what appears to be a segment caudad of the eleventh segment; this is termed the telson. The telson differs from the segments preceding it in that it never bears appendages. Special terms have been applied, especially by writers on the Coleoptera, to the caudal segments of the abdomen. Thus the terminal segment of a beetle's abdomen when exposed beyond the elytra is termed the pygidium; the tergite cephalad of the pygidium, especially in beetles with short elytra, the propygidium; and the last abdominal stemite, the hypopygium. The term hypopygium is also applied to the genitalia of male Diptera by writers on that order of insects. 76 AN INTRODUCTION TO ENTOMOLOGY b. THE APPENDAGES OF THE ABDOMEN In the early embryonic stages of insects, each segment of the abdomen, except the telson, bears a pair of appendages (Fig. 89) . This indicates that the primitive ancestor of insects possessed many legs, like a centipede. But the appendages of the first seven abdominal segments are usually lost during embryonic life, these segments being without appen- dages in postembryonic stages, except in certain Thysanura and Collembola, and in some larvae. Reference is made here merely to the primary appendages of the segments, those that are homodyna- mous with the thoracic legs; secondarily developed appendages, as for example, the tracheal gills, are present in the immature instars of many insects. The styli or vestigial legs of certain Thysanura. — ^In certain Thysanura the coxa of each middle and hind thoracic leg bears a small appendage, the stylus (Fig. 90) ; and on from one to nine abdominal segments there is a pair of similar styli. These abdominal styli are believed to be homodynamous with those of the thoracic legs, and must, therefore, be regarded as vestiges of abdominal legs. The collophore of the CoUembola.— Although in the postembryonic stages of Collembola the collophore is an unpaired organ on the middle line of the ventral aspect of the first abdominal segment, the fact that it arises in the embryo as a pair of appendages comparable in position to the thoracic legs, has led to the beHef that it represents the legs of this segment. The structiire of the collophore is described more fully later in the chapter treating of the Collembola. The spring of the Collembola. — The spring of the Collembola, like the collophore, is believed to represent a pair of primary append- ages. This organ is discussed in the chapter treating of the Col- lembola. The genitalia. — In most insects there are more or less prominent appendages connected with the reproductive organs. These append- ages constitute in males the genital claspers and in females the ovi- positor; to them have been applied the general term genitalia, they are also known as the gonapophyses. The genitalia, when all are developed consist of three pairs or appendages. Writers vary greatly in their views regarding the seg- Fig. 89.- Em- bryo of Hy- dro philus showing ab- dominal ap- pendages. THE EXTERNAL ANATOMY OF INSECTS 77 ments of the abdomen to which these appendages belong. One cause of difference is that some writers regard the last segment of the abdo- men as the tenth abdominal segment while others believe it to be the eleventh, which is the view adopted in this work, this segment bears the cerci when they are present. The three pairs of appendages that constitute the genitalia are borne by the eighth and ninth segments, two pairs being borne by the ninth segment. The outer pair of the ninth segment constitute the sheath of the ovipositor. See ac- count of the genitalia of the Orthoptera in Chapter eight. The genitalia of many in- sects have been carefully fig- ured and described and special terms have been applied to each of the parts. But as most of these descriptions have been based upon studies of repre- sentatives of a single order of insects or even of some smaller group, there is a great lack of uniformity in the terms applied to homologous parts in the different orders of in- sects; such of these terms as are commonly used are defined later in the characterizations of the several orders of insects. The cerci. — In many insects there is a pair of caudal appendages which are known as the cerci; these are the appendages of the eleventh abdominal segment, the last segment of the body except in the few cases where a telson is presemt. The cerci vary greatly in form ; in some insects, as in most Thy- sanura, in the Plecoptera, and in the Ephermerida, they are long and Fig. 90. — Ventral aspect of Machilis; c, cer- cus; Ip, labial palpus; mf, median caudal filament; mp, maxillary palpus; 0, oviposi- tor; .s, s, styli. That part of the figure representing the abdomen is after Oude- mans. 78 AN INTRODUCTION TO ENTOMOLOGY many jointed; while in others they are short and not segmented. The function of the cerci is different in different insects ; they are beheved to be tactile in some, olfactory in others, and in some males they aid in holding the female during copulation. The median caudal filament. — In many of the Ephemerida and in some of the Thysanura, the last abdominal segment bears a long, median filament, which resembles the many-jointed cerci of these insects (Fig. 91); this filament is believed to be a prolongation of the tergum of this segment and not a true appendage like the cerci. The prolegs of larvae. — ^The question whether the prolegs of larv^ee represent true appendages or are merely hypodermal outgrowths has been much dis- cussed. Several embryologists have shown that in embryos of Lepidoptera and of saw-flies limb-rudi- ments appear on all or most of the abdominal seg- ments; and that they very soon disappear on those segments which in the larva have no legs while on other segments they are transferred into functional prolegs. If this view is estab- lished we must regard such prolegs as representing primitive abdo- minal appendages, that is as true abdominal legs. Fig. 91. — Lepis- ma saccharina. V. THE MUSIC AND THE MUSICAL ORGANS OF INSECTS Much has been written about music ; but the greater part of this literature refers to music made by man for human ears. Man, how- ever, is only one of many musical animals; and, although he excels all others in musical accomplishments, a study of what is done by our htmibler relatives is not without interest. The songs of birds command the attention of all observers. But there is a great orchestra which is performing constantly through the warmer portions of the year, which is almost unnoticed by man.. Occasionally there is a performer that cannot be ignored, as: — • "The shy Cicada, whose noon- voice rings So piercing shrill that it almost stings The sense of hearing." (Elizabeth Akers.) But the great majority fiddle or drum away unnoticed by human ears. THE EXTERNAL ANATOMY OF INSECTS 79 Musical sounds are produced by many different insects, and in various ways. These sounds are commonly referred to as the songs of insects; but properly speaking few if any insects sing; for, with some possible exceptions, the note of an insect is always at one pitch, lacking musical modulations like those of the songs of man and of birds. The sound produced by an insect may be a prolonged note, or it may consist of a series of short notes of varying length, with intervals of rest of varying lengths. These variations with differences in pitch give the wide range of insect calls that exists. In some cicadas where the chambers containing the musical organs are covered by opercvda, the insect can give its call a rhythmic increase and decrease of loudness, by opening and closing these chambers. As most insect calls are strident, organs specialized for the pro- duction of these calls are commonly known as stridulating organs. But many sounds of insects are produced without the aid of organs specialized for the production of sound. The various ways in which insects produce sounds can be grouped under the following heads : First. — By striking blows with some part of the body upon sur- roimding objects. Second. — By rapid movements of the wings. In this way is produced what may be termed the music of flight. Third. — By rasping one hard part of the body upon another. Under this head fall the greater number of stridulating organs. Fourth. — By the rapid vibration of a membrane moved by a muscle attached to it. This is the type found in the cicadas. Fifth. — By the vibration of msmbranss set in motion by th^ rush of air through spiracles. The reality of this method has been ques- tioned. Sixth. — By rapid changes of the outline of the thorax due to the action of the wing muscles. a. SOUNDS PRODUCED BY STRIKING OBJECTS OUTSIDE THE BODY Although th3 sDunis prolu^sl by in332'3 by stri'.clng blows with some part of ths bDiy upon surrounding objects are not rapid enough to give a musical note, they are referred to here for the sake of completeness. The most familiar SDunis of this kind are those produced by the insects known as the dsath-watch. These are small beetles of the family Ptinidas, and espscially those of the genus Anobium. These are wood-boring insects, frequently found in the woodwork of old 80 AN INTRODUCTION TO ENTOMOLOGY houses and in furniture, where they make a ticking sound by striking their heads against the walls of their burrows. The sound consists of several, sharp, distinct ticks, followed by an interval of silence, and is beheved to be a sexual call. The name death-watch was applied to these insects by supersti- tious people who believed that it presaged the death of some person in the house where it is heard. This belief probably arose from the fact that the sound is most likely to be heard in the quiet of the night, and would consequently be observed by watchers by sick-beds. The name death-watch has also been applied to some species of the Psocidas, Clothilla pulsatoria and Atropos divinatoria, which have been believed to make a ticking sound. This, however, is doubted by some writers, who urge that it is difficult to believe that such minute and soft insects can produce sounds audible to human ears. The death-watches produce their sounds individually; but an interesting example of an insect chorus is cited by Sharp ('99, p. 156), who, quoting a Mr. Peal, states that an ant, presimiably an Assamese species, "makes a concerted noise loud enough to be heard by a human being at twenty or thirty feet distance, the sound being produced by each ant scraping the horny apex of the abdomen three times in rapid succession on the dry, crisp leaves of which the nest is usually com- posed." h. THE MUSIC OF FLIGHT The most obvious method by which insects produce sounds is by beating the air with their wings during flight. It can be readily seen that if the wing-strokes are sufficiently rapid and are uniform, they will produce, like the flapping reeds of a mouth organ, a musical note. When, however, we take into account the fact that to produce the lowest note regularly employed in music, the C of the lowest octave, requires 32 vibrations a second, i. e., nearly 2,000 vibrations per minute, it will seem marvellous that muscular action can be rapid enough to produce musical notes. Nevertheless, it is a fact that many insects sing in this way ; and too their notes are not confined to the lower octaves. For example, the common house fly hums F of the middle octave, to produce which, it must vibrate its wings 345 times per second or 20,700 times per minute. As a rule, the note produced by the wings is constant in each species of insect. Still with insects, as with us, the physical condition of the singer has its influence. The vigorous honey-bee makes the A of 435 vibrations, while the tired one hums on the E of ^26 vibrations. THE EXTERNAL ANATOMY OF INSECTS 81 While it is only necessary to determine the note produced by vibrating wings to ascertain the rate of vibration, a graphical demon- stration of the rate is more convincing. Such a demonstration has been made by Marey ('69) who fixed a fly so that the tip of the wing just touched the smoked surface of a revolving cylinder, and thus obtained a wavy line, showing that there were actually 320 strokes in a second. This agrees almost exactly with the number inferred from the note produced. The music of flight may be, in many cases, a mere accidental result of the rapid movement, and in no sense the object of that movement, like the hwoa of a trolley car; but there are cases where the song seems to be the object of the movement. The honeybee produces different sounds, which can be understood by man, and probably by bees, as indicating different conditions. The contented hum of the worker collecting nectar may be a song, like the well-known song of a hen wandering about on a pleasant day, or may be an accidental sound. But the honeybee produces other sounds that communicate ideas. The swarming sound, the hiim of the queenless colony, and the note of anger of a belligerent bee can be easily distinguished by the experi- enced beekeeper, and doubtless also by the bee colony. It seems probable, therefore, that in each of these cases the rate of vibration of the wings is adjusted so as to produce a desired note. This is also probably true of the song of the female mosquito, which is pitched so as to set the antennal hairs of the male in vibration. While the music of flight is a common phenomenon, many insects have a silent flight on account of the slowness of the wing-movement. C. STRIDULATING ORGANS OF THE RASPING TYPE The greater number of the insect sounds that attract our attention are produced by the friction of hard parts of the cuticula by which a vibrating surface is set in motion. In some cases, as in many of the Orthoptera, the vibrating surface is apart of the wings that is special- ized for this purpose; but in other cases, a specialized vibrating sur- face has not been observed. Stridulating organs of the rasping type are possessed by represen- tatives of several of the orders of insects ; but they are most common in the order Orthoptera, and especially in the families Acridiidae, Locustidffi, and Gryllidae, where the males of very many species possess them. Very few other Orthoptera stridulate; and with few exceptions it is only the males that sing. 82 AN INTRODUCTION TO ENTOMOLOGY In each of these famiHes the vibrating element of the stridulating organ is a portion of one or of both of the fore wings ; but this is set in motion in several different ways. In some exotic Acridiidas abdominal stridulating organs exist. The stridulating organs of the Locustidae. — With many species of the Locustidffi we find the males furnished with stridulating organs ; but these are comparatively simple, and are used only in the day time. Two methods of stridulation are used by members of this family. The simpler of these two methods is employed by several common species belonging to the (Edipodinae; one of which is the Carolina locust, Dissosteira Carolina, whose crackling flight is a common feature of country roadsides. These locusts, as they fly, rub the upper sur- face of the costal margin of the hind wings upon the lower surface of the thickened veins of the fore wings, and thus produce a loud but not musical sound. The second method of stridulation practiced by locusts consists in rubbing the inner surface of the hind femora, upon each of which there is a series of bead-like prominences (Fig. 92), against the outer surface of the fore wings. With these insects, there is a thickening of the radius in the basal third of each fore wing, and a widening of the two areas between this vein and the costal margin of the wing, which serves as a sounding board (Fig. 93). The two wings and femora constitute a pair of violin-like organs; the thickened radius in each case cor- responding to the strings; the membrane of the wing, to the body of the instrument ; and the file of the femur, to the bow. These two organs are used simultaneously. When about to stridulate, the insect B-- Fig. 92. — A, hind femora of Stenobothrus ; B, file greatly enlarged. Fig- 93- — Fore wing of a male of Stenobothrus. R, radius; Sc, subcosta; C, costa. THE EXTERNAL ANATOMY OF INSECTS 83 places itself in a nearly horizontal position, and raising both hind legs at once rasps the femora against the outer surface of the wings. The most common representatives of insects that stridulate in this way belong to the genus Steno- bothrus. The stridulating organs of the Gryllidae and the Tettigoniidae. — The stridulating organs of the Gryllidae and the Tettigoniidae are of the same type, and are the most highly specialized found in the Orthoptera. They consist of modified portions of the fore wings ; both the vibrating and the rasp- ing elements of the organs pertaining to the wings. It is by rubbing the two fore wings together that sound is produced. In what is probably the more generalized con- dition of the organs, as seen in Gryllns, each fore wing bears a rasping organ, the file (Fig. ; 94, /) a hardened area, the scraper (Fig. 94, s), \:,^^^^^^ 1,^-4^ against which the file of the other wing acts, and 'Itli 'Eli 1:1:^0 vibrating areas, the tympana (Fig. 94, /, t). As rm^^?^'^?^^'^^^ the file of either wing can be used to set the C tympana of the wings in vibration, we may say Fig.94.— Fore wing of that Grylliis is ambidextrous. Grvllus; A, as seen 1 , • 1,1 from above, that When the cncket wishes to make his call, he part of the wmg elevates his fore wings so that thev make an angle which IS bent down ^° .'i,, , on the side of the of about forty-five degrees with the body; then abdomen is not holding them in such a position that the scraper shown; 5, scraper;/, , „, ^ , - , t, tympana. B,base of one rests on the file of the other, he moves the of wing seen from ^^jngg ^^ck and forth laterally, so that the file and below; s, scraper; , , ^, . , /.file. C, file great- scraper rasp upon each other. Ihis throws the ly enlarged. wings into vibration and produces the call. It is easy to observe the chirping of crickets. If one will move slowly towards a cricket that is making his call, and stop when the cricket stops chirping until he gains confidence and begins again, one can get sufficiently near to see the operation clearly. This can be done either in the day time or at night with the aid of a light. The songs of the different genera of crickets can be easily dis- tinguished, and that of each species, with more care. Writers on the Orthoptera have carefully described the songs of our more common crickets, and especially those of the tree crickets. The rate of chirping 84 AN INTRODUCTION TO ENTOMOLOGY is often influenced by temperature, being slower in cool nights than in warm ones; and becoming slower towards morning if the tem- perature falls. In certain genera of crickets as Nemohins and QLcanthus, while each fore wing is furnished with a file and tympana, the scraper of the right wing is poorly formed and evidently not functional. As these insects use only the file of the right wing to set the tympana of the wings in vibration, they may be said to be right-handed. Fig- 95- — Wings of a female nymph of CEcanthus (From Comstock and Needham). In the Locustidag a similar modification of the function of the stridulating organs has taken place. In all of our common represen- tatives of the family, at least, only one of the files is used. But in these cases it is the file of the left wing that is functional ; we may say, therefore, that so far as observed the Locustidas are left-handed. Different genera exhibit great differences as to the extent of the reduc- tion of the unused parts of the stridulating organs. The file is present in both wings of all of the forms that I have studied; but th2 unused file is sometimes in a vestigial condition. The scraper is less persistent, being frequently entirely lacking in one of the wings. In some cases, the tjmipana of one wing have been lost; but in others the tympana of both wings are well preserved, although only one file THE EXTERNAL ANATOMY OF INSECTS 85 is used. In these cases it is probable that the tympana of both wings are set in vibration by the action of the single functional file. The determination of the homologies of the parts of the wing that enter into the composition of the stridulating organs was accomplished by a study of the tracheation of the wings of nymphs (Comstock and Needliam, 'gS-'gg). The results obtained by a study of the wings of CEcanthus will serve as an illustration. Figure 95 represents the wings of a female n3miph of this genus, with the tracheag lettered. The only parts to which we need to give attention in this discussion are the cubital and anal areas of the fore wing; for it is this part of the wing that is modified in the male to form the musical organ. Both branches of cubitus are present, and Cui bears three accessory branches. The three anal tracheae are present and are quite simple. Fig. 96. — Fore wing of a male nymph of CEcanthus (From Comstock and Needham). The homologies of the tracheae of the fore wing of a male nymph, Figure 96, were easily determined by a comparison with the trachese of the female. The most striking difference between the two sexes is a great expanding of the area between the two branches of cubitus in the male, brought about by the bending back of the basal part of CU2. The next step in this study was to compare the wing of an adult male, Figure 97, with that of the n5nnph of the same sex; and the solution of the problem was soon reached. It can be easily seen that the file is on that part of Cu2 that is bent back toward the inner mar- gin of the wing (Fig. 97, /); the tympana are formed between the branches of cubitus (Fig. 97, /, t); and the scraper is formed at the outer end of the anal area (Fig. 97,5). 86 AN INTRODUCTION TO ENTOMOLOGY A similar study was made of the wings of Conocephalus, as an example of the Tettigoniidse, Figure 98 represents the wings of a male nymph; and Figure 99 the fore wing of an adult. The most striking fea- ture and one characteris- tic of the fam- ily, is that the musical organ occupies an area near the base of the wing which is small corn- Fig. 97. — Fore wing of an adult male of CEcanthus;f, vein bearing the file; s, scraper; t, t, tympana. pared with the area occupied by the musical organs of the Gryllidffi. But here, as in the Gryllidse, the file is borne by the basal part of CU2, Pig. 98. — Wings of a male nymph of Conocephalus, (From Comstock and Needham). the tympana are formed between the branches of cubitus, and the scraper is formed at the outer end of the anal area. THE EXTERNAL ANATOMY OF INSECTS 87 Rasping organs of other than orthopterous insects. — Rasping organs are found in many other than orthopterous insects and vary M Fig. 99. — Right fore wing of an adult male of Conocephalus, seen from below; /, file; s, scraper. greatly in form and in their location on the body. Lack of space for- bids any attempt to enimierate these variations here ; but examples of various types of stridulating organs will be described in later chapters when treating of the insects that possess them. As in the Orthoptera, they consist of a rasp and a scraper. The rasp is a file-like area of the surface of a segment of the body or of an appendage; and the scraper is a hard ridge or point so situated that it can be drawn across the rasp by movements of the body or of an append- age. In some cases the ap- paratus con- sists of two rasps so situ- ated that they can be rubbed together. With many beetles one of a- Fig. 100. — Stridulating organ of an ant, (From Sharp after Janet); d, scraper; Myrmica rubra e, file. the two parts of the stridulating organ is situated upon the elytra; and it is quite probable that in these cases the elytra acts as vibrating surfaces, as do the wings of locusts and crickets. But in many cases as where a part of a leg is rubbed against a portion of a thoracic segment, there appears to be no vibrating surface unless it is the wall of the body or of the appendage that acts as a sounding board. In the stridulating organ of Myrmica rubra, var. IcBvinodis, figured by Janet (Fig. 100), the scraper is the posterior border of one abdominal segment, and the file is situated on the dorsimi of the following segment. It is quite conceivable that in this case 88 AN INTROD UCTION TO ENTOMOLOG Y the dorsal wall of the segment bearing the file is made to vibrate by the successive impacts of the scraper upon the ridges of the file. In fact this seems to me more probable than that the sound produced is merely that of the scraper striking against the successive ridges of the file. There is at least one recorded case where the body wall is specialized to act as a sounding board. According to Sharp ('95, p. 200), in the males of the Pneumorides, a tribe of South African AcridiidcC, where the phonetic organ is situated on the abdomen, this part is inflated and tense, no doubt with the result of increasing the volume and quality of the sound. Ordinarily the stridulating organs of insects are fitted to produce notes of a single degree of pitch; but Gahan ('00) figures those of some beetles that are evidently fitted to produce sounds of more than one degree of pitch ; the file of Hispopria foveicollis, consists of three parts, one very finely striated, followed by one in which the striae are much coarser, and this in turn followed by one in which the striation is intermediate in character between the other two. While the stridulating organs of the Orthoptera are possessed almost exclusively by the males, in the Coleoptera, very many species of which stridulate, the phonetic organs are very commonly possessed by both sexes, and serve as a mutual call. In one genus of beetles, Phonapate, stridulating organs have been found only in the females (Gahan, '00). It seems evident that in the great majority of cases the sounds produced by insects are sexual calls; but this is not always so. It was pointed out long ago by Charles Darwin that "beetles stridulate under various emotions, in the same manner as birds use their voices for many purposes besides singing to their mates. The great Chiasog- nathus stridulates in anger or defiance ; many species do the same from distress or fear, if held so that they cannot escape; by striking the hollow stems of trees in the Canary Islands, Messrs. Wollaston and Crotch were able to discover the presence of beetles belonging to the genus Acalles by their stridulation. Lastly the male Ateuchus stridulates to encourage the female in her work and from distress when she is removed" {The Descent of Man). The most remarkable case where stridulating organs have been developed for other than sexual purposes is that of the larvae of certain Lucanidas and Scarabaeidas described by Schiodte ('74). In these larvae there is a file on the coxa of each middle leg, and the hind legs are shortened and modified so as to act as scrapers. The most highly THE EXTERNAL ANATOMY OF INSECTS 89 Specialized example of this type of stridulating organ is possessed by the larvae of Passalus, in which the legs of the third pair are so much shortened that the f.-^...4 , larvae appear to have only four legs ; each hind leg is a paw-like structure fitted for rasping the file (Fig. loi). These insects are social, a pair of beetles and their progeny living to- gether in decaying wood. The adults prepare food for the larv«; and the col- ony is able to keep together by stridu- latory signals. d. THE MUSICAL ORGANS OF A CICADA With the cica- das there exists a type of stridulating organ peculiar to them, and one that is the most complicated organ of sound found in the animal kingdom. Yet, while the cicadas are the most noisy of the insect world, the results obtained by their com- plicated musical apparatus are not comparable with those pro- duced by the comparatively simple vocal organs of birds and of Fig. loi. — Stridulating organ of a larva of Passalus; a, b, oortions of the metathorax; c. coxa of the second leg; d. file; e. basal part of femur of middle le?; /, hairs with chitinous process at base of each; g, the diminutive third leg modified for scratching the file (From Sharp). It is said that in some species of Cicada both sexes stridulate; but as a rule the females are mute, possessing only vestiges of the musical apparatus. The structure of the stridulating organs varies somewhat in details in different species of Cicada; but those of Cicada pleheia, which were described and figured by Carlet ('77), may be taken as an example of the more perfect f orn: . In the male of this species there is a pair of large plates, on the ventral side of the body, that extend back 90 AN INTRODUCTION TO ENTOMOLOGY Fig. 1 02. — The musical apparatus of a cicada; fm, folded membrane; /, base of leg; Ic, lateral cavity; m, mirror; o, operculum, that of the opposite side removed; sp, spiracle; t, timbal; vc, ventral cavity (After Carlet). from the hind border of the thorax and overlap the basal part of the abdomen; these are the opercula (Fig. 102, o). The opercula are expansions of the ster- nellum of the meta- / thorax, and each • serves as a lid covering a pair of cavities, con- taining the external parts of the musical apparatus of one side of the body. The two cavities covered by a single operculum may be de- signated as the ventral cavity (Fig. 102, v. c.) and the lateral cavity (Fig. 102, /. c.) respec- tively. Each cavity is form.ed by an infolding of the body-wall. In the walls of these cavities are three membranous areas; these are known as the timbal, the folded membrane, and the mirror. The timbal is in the lateral cavity on the lateral wall of the parti- tion separating the two cavities (Fig. 102, t); the other two mem- branes are in the ventral cavity. The folded membrane is in the anterior wall of the ventral cavity (Fig. 102, /. m.); and the mirror is in the posterior wall of the same cavity (Fig. 102, w). Within the body, there is in the region of the musical apparatus a large thoraco- abdominal air chamber, which communicates with the exterior through a pair of spiracles (Fig. 102 sp); and a large muscle, which extends from the furca of the second abdominal segment to the inner face of the timbal. By the contraction of this muscle the timbal is pulled towards the center of the body ; and when the muscle is relaxed, the elasticity of the chitinous ring supporting the timbal causes it to regain its former position. By a very rapid repetition of these movements of the timbal the sound is produced. It is probable that the vibrations of the timbal are transmitted to the folded membrane and to the mirror by the air contained in the large air chamber mentioned above; as the strings of a piano are made to vibrate by the notes of a near-by violin. The sound, how- ever, is produced primarily by the timbal, the destruction of which THE EXTERNAL ANATOMY OF INSECTS 91 renders the insect a mute; while the destruction of the other mem- branes, the timbal remaining intact, simply reduces the sound. The chief function of the opercula is doubtless the protecting of the delicate parts of the musical organ; but as they can be lifted slightly and as the abdomen can be moved away from them to some extent, the chambers containing the vibrating parts of the organ can be opened and closed, thus giving a rhythmic increase and decrease of the loudness of the call. e. THE SPIRACULAR MUSICAL ORGANS There has been much discussion of the question whether insects, and especially Diptera and Hymenoptera, possess a sound -producing organ connected with the spiracles or not. Landois ('67) believed that he found such an organ and figures and describes it in several insects. It varies greatly in form in different insects. In the Diptera it consists of a series of leaf-like folds of the intima of the trachea; these are held against each other by a special himiming ring, which lies close under the opening of the spiracle; and is found within two or all four of the thoracic spiracles. These membranous folds of the intima are set in vibration by the rush of air through the spiracles. In the May-beetle, according to Landois, a buzzing organ is found near each of the fourteen abdominal spiracles. It is a tongue-like fold projecting into the lumen of the trachea under the base of the closing apparatus. On its upper surface it is marked with very fine arched furrows. He concludes that this tongue is put in vibration by tlie breathing of the insect, and hence the buzzing of the flying beetle. If insects produce sounds in the way described by Landois they have a voice quite analogous to our own. But the validity of the conclusions of Landois has been seriously questioned; the subject, therefore, demands further investigation. See also Duncan ('24). /. THE ACUTE BUZZING OF FLIES AND BEES Many observers have found that when the wings of a fly or of a bee are removed or held so that they can not vibrate the insect can still produce a sound. The sound produced under these circumstances is higher, usually an octave higher, than that produced by the w:n;^^s. It is evident, therefore, that these insects can produce sounds in two ways; and an extended search has been made for the organ or organj producing the higher note. 92 AN INTRODUCTION TO ENTOMOLOGY Landois believed that the spiracular organs referred to above were the source of the acute sound. But more recently Perez ('78) and Bellesme ('78) have shown that when the spiracles are closed artifi- cially the insect can still produce the high tone. Perez attributes the sound to the vibrations of the stumps of the wings against the solid parts which surround them or of the sclerites of the base of the wing against each other. But Bellesme maintains that the sound is pro- duced by changes in the form of the thorax due to the action of the wing-muscles.* When the wing-muscles are at rest the section of this region, according to this writer, represent an ellipse elongated ver- tically; the contraction of the muscles transforms it to an ellipse elongated laterally; the thorax, therefore, constitutes a vibrating body which moves the air like a tine of a tuning fork. Bellesme states that by fastening a style to the dorsal wall of the thorax he obtained a record of the rate of its vibrations, the ntmiber of which corresponded exactly to that required to produce the acute sound which the ear perceives. The fact that the note produced when the wings are removed is higher than that produced by the wings is supposed by Bellesme to be due to the absence of the resistance of air against the wings, which admits of the maximum rate of contraction of the wing-muscles. g. MUSICAL NOTATION OF THE SONGS OF INSECTS Mr. S. H. Scudder ('93) devised a musical notation by which the songs of stridulating insects can be recorded. As the notes are always at one pitch the staff in this notation consists of a single horizontal line, the pitch being indicated by a separate statement. Each bar represents a second of time, and is occupied by the equivalent of a semibreve ; consequently a quarter note 1, or a quarter rest *1, repre- 0 ^ sents a quarter of a second ; a sixteenth note t, or a sixteenth rest \ a sixteenth of a second and so on. For convenience's sake he intro- duced a new form of rest, shown in the second example given below, which indicates silence through the remainder of a measure; this differs from the whole rest commonly employed in musical notation by being cut off obliquely at one end. *This view was maintained by Siebold at a much earlier date in his Anatomy of the Invertebrates. THE EXTERNAL ANATOMY OF INSECTS 93 The following examples taken from his paper on "The Songs of our Grasshoppers and Crickets" will serve to illustrate this method of notation. The chirp of Gryllotalpa horealis (Fig. 103) "is a guttural sort of sound, like grii or greeu, repeated in a trill indefinitely, but seldom grQ gru gru gru grS grfl grQ prn gru grtt^ Fig. 103. — The chirp of Gryllotalpa horealis (From Scudder). lor more than two or three minutes, and often for less time. It is pitched at two octaves above middle C." Fig. 104. — The chirp of the katydid (From Scudder). The note of the true katydid, Cyrtophylhis concavus, (Fig. 104) "which sounds like xr, has a shocking lack of melody; the poets who have sung its praises must have heard it at a distance that lends enchantment." "They ordinarily call 'Katy' or say 'She did' rather than 'Katy did'; that is they rasp their fore wings twice more fre- quently than thrice." Mr. Scudder in his account of this song fails to indicate its pitch. h. INSECT CHORUSES Most insect singers are soloists, singing without reference to other singers or in rivalry with them. But there are a few species the members of which sing in unison with others of their kind that are near them. The most familiar sound of autumn evenings in rural places in this country is a chorus of the snowy tree cricket, CEcanthus niveus. Very many individuals of this species, in fact all that are chirping in any locality, chirp in unison. Early in the evening, when the chirping first begins, there may be a lack of unanimity in keeping time; but this lasts only for a short period, soon all chirp in unison, and the monotonous beat of their call is kept up uninterrupted throughout the night. Individual singers will stop to rest, but when they start again they keep time with those that have continued the chorus. Other instances of insect choruses have been recorded. Sharp ('99, 156) quotes accounts of two produced by ants; one of these is given on an earlier page (p. 80). CHAPTER III THE INTERNAL ANATOMY OF INSECTS Before making a more detailed study of the internal anatomy of insects, it is well to take a glance at the relative positions of the differ- ent systems of organs within the body of insects and other arthropods. One of the most striking features in the structure of these animals is that the body-wall ser\^es as a skeleton, being hard, and giving sup- port to the other organs of the body. This skeleton may be repre- sented, therefore, as a hollow cylinder. We have now to consider the arrangement and the general form of the organs contained in this cylinder. The accompanying diagram (Fig. 105), which represents a vertical, longitudinal section of the body, will enable the student to gain an Fig. 105. — Diagram showing the relations of the internal organs; a, alimentary canal; A, heart; w, muscle; n, nervous system; r, reproductive organs. idea of the relative positions of some of the more important organs. The parts shown in the diagram are as follows: The body-wall, or skeleton; this is made up of a series of overlapping segments; that part of it between the segments is not hardened with chitin, thus remaining flexible and allowing for the movements of the body. Just within the body-wall, and attached to it, are represented a few of the muscles (m) ; it will be seen that these muscles are so arranged that the contraction of those on the lower side of the body would bend it down, while the contraction of those on the opposite side would act in the opposite direction, other muscles not shown in the figure provide for movements in other directions. The alimentary canal (a) occupies the centre of the body, and extends from one end to the other. The heart (/z) is a tube open at both ends, and lying between the alimentary canal and the muscles of the back. The central part of the nervous system (w) is a series of small masses of nervous matter connected by (94) THE INTERNAL ANATOMY OF INSECTS 95 two longitudinal cords: one of these masses, the brain, lies in the head above the alimentary canal ; the others are situated, one in each segment, between the alimentary canal and the layer of muscles of the ventral side of the body; the two cords connecting these masses, or ganglia, pass one on each side of the oesophagus to the brain. The reproductive organs (r) lie in the cavity of the abdomen and open near the caudal end of the body. The respiratory organs are omitted from this diagram for the sake of simplicity. We will now pass to a more detailed study of the different systems of organs. I. THE HYPODERMAL STRUCTURES The active living part of the body-wall is the hypodermis, already described in the discussion of the external anatomy of insects. In addition to the external skeleton, there are derived from the hypo- dermis an internal skeleton and several types of glands. a, THE INTERNAL SKELETON Although the skeleton of an insect is chiefly an external one, there are prolongations of it extending into the body-cavity. These inwardly directed processes, which serve for the attachment of muscles and for the support of other viscera are termed collectively the internal skeleton or endo-skeleton. The internal skeleton is much more highly developed in adult insects than it is in the immature instars. Sources of the internal skeleton. — The parts of the internal skele- ton are formed in two ways : first by the chitinization of tendons of muscles; and second, by invaginations of the body -wall. Chitinized tendons. — Chitinized tendons of the muscles that move the mouth-parts, of muscles that move the legs, and of other muscles are of frequent occurrence. As these chitinized tendons help support the internal organs they are considered as a part of the internal skeleton. Invaginations of the body-wall or apodemes. — The second and more important soiu-ce of the parts of the internal skeleton consists of invaginations of the body- wall. Such an invagination is termed an dpodeme. The more important apodemes, if not all, arise as invagina- tions of the body-wall between sclerites or at the edge of a sclerite on the margin of a body-segment; although by the fusion of sclerites about an apodeme, it may appear to arise from the disc of a sclerite. 96 AN INTRODUCTION TO ENTOMOLOGY Frequently, in the more generalized insects, the mouth of an apodeme remains open in the adult insects. In Figure io6 are represented two apodemes that exist in the thorax of a locust, Melanoplus. Each of these {ap and ap) is an invagination of the body- wall, between the epistemimi and the epimeron of a segment, immediately above the base of a leg. These are known as the lateral apodemes of the thorax and serve as points of attachment of muscles. The number of apodemes may be very ^\,'%^^lt'1l!tL!i. large, and it varies greatly in different and metathorax of Melano- insects. Among the more important apo- apodemes,^c^^ ap^ demes are the following: — The tentorium. — The chief part of the internal skeleton of the head is termed the tentorium. This was studied by Comstock and Kochi ('02). We found that in the generalized insects studied by us it is composed of two or three pairs of apodemes that, extend- ing far into the head, meet and coalesce. The three pairs of apodemes that may enter into the formation of the tentoriimi were termed the anterior, the posterior, and the dorsal arms of the tentorium respectively. The coalesced and more or less expanded tips of these apodemes constitute the body of the tentorium. From the body of the tentoritmi there extend a variable munber of processes or chitinized tendons. The posterior arms of the tentorium. — The posterior arms of the tentorium (Fig. 107, 109, no, pt) are the lateral apodemes of the Fig. 107. — Tentorium of a co::kroach, dor- sal aspect. Fig. 108.— Part of the tentorium of a cric- ket, ventral aspect. maxillary segment. In many Orthoptera the open mouth of the apodeme can be seen on the lateral aspect of the head, jtist above the THE INTERNAL ANATOMY OF INSECTS 97 Fig. 109. — Head of Melajnplus, cau- dal aspect. articulation of the maxilla (Fig. 48). In the Acridiidae (Fig. 109) these apodemes bear a striking resemblance to the lateral apodemes of the thorax (Fig. 106), except that the ventral process of the maxil- lary apodeme is much more prominent, and the two from the opposite sides of the head meet and coalesce, thus forming the caudal part of the body of the tentorium. The anterior arms of the tentorium. — Each anterior arm of the tentorium (Fig. 107, 108, no, at) is an invagination of the body-wall which opens on the margin of the antecoxal piece of the mandible when it is distinct ; if this part is not distinct the apodeme opens between the clypeus and the front (Fig. 46, at). The dorsal arms of the tentorium. — Each dorsal arm of the tentorium arises from the side of the body of the tentorium between the anterior and posterior arms and extends either to the front or to the margin of the antennal sclerite (Fig. 107, 108, no, dt). The frontal plate of the tentorium. — In the cockroaches the anterior arms of the tentorium meet and fuse, forming a broad plate situated between the crura cerebri and the mouth ; this plate was termed by us the frontal plate of the tentorium (Fig. 107,/^). On each side, an extension of this plate connects it with the body of the tentorium; these enclose a circular opening through which pass the crura cerebri. Other cervical apodemes and some chitinized tendons are described in the paper cited above. The endothorax. — The internal skeleton of the thorax is commonly termed the endothorax; under this head are not included the internal processes of the appendages. The endothorax is composed of invaginations of each of the sections of a thoracic ring. Those por- tions that are derived from tergites are termed phragmas; those derived from the pleurites, lateral apodemes; and those, from the stemites, furcce. The phragmas. — A phragma is a transverse partition extending entad from the front or the hind margin of a tergite ; three of them are commonly recognized; these were designated by Kirby and Spence (1826) the propkragma, the mesophragma, and the meta- phragma; but, as they do not arise one from each segment of the Fig. I 10. — Ten- torium of Mela- nopliis, cephalic aspect. Thedistal end of the dorsal arms detached. AN INTRODUCTION TO ENTOMOLOGY thorax, and arise differently in different insects, these terms are mis- leading. No phragma is borne by the prothorax; the mesothorax may bear two and the metathorax one, or the mesothorax one and the metathorax two. A more definite terminology is that used by Snod- grass ('09) by which the anterior phragma of any segment is termed the prephragma of that segment, and the posterior phragma of any segment is termed the postphragma of that segment. The lateral apodemes. — Each lat- eral apodeme is an invagination of the body-wall between the epister- num and the epimeron. The lateral apodemes are referred to above (Fig. 106). ThefurccB. — Each fiu*ca is an invagination of the body-wall arising between the sternum and the stemellimi (Fig. 1 1 1) ; when the sternel- lum is obsolete, as it is in most insects, the furca arises at the caudal margin of the segment (Fig. 112). Pig. Ill . — Ventral aspect of the metathorax of Stenopelmatus. The _ position of the furca within the body is represented by a dotted line. h. THE HYPODERMAL GLANDS A gland is an organ that pDssesses the function of either trans- forming nutritive substances, which it derives from the blood, into some useful substance, as mucus, wax, or venom, or of assimilating and removing from the body waste material. The different glands vary greatly in structure; many are unicellular, the gland consisting of a single cell, which differs from the other cells of the epithe- lium of which it is a part in being larger and in possessing the secreting and ex- creting functions; others are multicel- lular, consisting of more than one cell. Fig. 112.— Ventral aspect of the usually of many cells. In these cases ^^^^fhepo^tfordthl the glandular area usually becomes furcae wit'iin the body are invaginated, and provided with an indicated by dotted lines, efferent duct; and often the invagination is much branched. The glands found in the body of an insect can be grouped under three heads; the hypodermal glands, the glands of the alimentary THE INTERNAL ANATOMY OF INSECTS canal, and the glands of the reproductive organs. In this place reference is made only to the hypodermal glands, those developed from the hypodermis. The Molting-fluid glands. — Under this head are classed those unicellular, h^/po- dermal glands that secrete a fluid that facilitates the process of molting, as des- cribed in the next chapter (Fig. 113). While molting-fluid glands are very numerous and conspicuous in certain insects, those living freely exposed where there exists the greatest liability to rapid Fig. 113. — Molting-fluid glands desiccation, Tower ('06) states that he of the last larvalinstar of j^as never found these glands in larva Leptinolarsa dectmhtieata , ]ust ° before pupation; le, larval that live m burrows, or m the soil, or in epidermis; Id larval dermis; ^ells; in these cases the molting fluid is ot/, moltmg fluid; ^e, formmg , , , r pupal epidermis; h, hypoder- apparently secreted by the entire hypo- ?lt= S'^"^°l^^"g fl^i^ gl^'^^ dermal layer. (After Tower). ^, , , . , Glands connected with setae. — There are in insects several kinds of glands in which the outlet of the gland is through the limien of a seta. The function of the excretions of these glands is various as indicated below. There are also differences in the manner of issuance of the excre- tion from the seta. In some cases, as in the tenent hairs on the feet of certain insects, the excretion can be seen to issue through a pore at the tip of the seta. In some kinds of venomous setag the tip of the seta breaks off in the wound made by it and thus sets free the venom. But in most cases the manner of issuance has not been deter- mined, although it is commonly believed to be by means of a minute pore or pores in the seta, the thickness of the wall of the seta making it improbable that the excretion passes from the seta by osmosis. The structure of a glandular seta is illustrated by Figure 114; the essential difference between such a seta and an ordinary one, that is a Fig. 114. — Glandular s^ta; 5, seta; c, cuticula; h, hypodermis; bm, basement membrane; tr, tricho- gen; g, gland (After Holmgren). 100 AN INTRODUCTION TO ENTOMOLOGY clothing hair, is that there is connected with it, in addition to the trichogen cell which produced it, the gland cell which opens through it. In most of the published figures of glandular setae there is no indi- cation that these organs are supplied with nerves ; but in some cases a nerve extending to the gland cell is clearly shown. This condition may be found to be general when more extended investigations of glandular cells have been made. The best known kinds of glandular setce are the following : Venomous setce and spines. — These are best known in larvae of Lepidoptera, several common species of which possess stinging hairs; among these are Lagoa crispata, Sihine stimulea, Automeris to, and the brown-tail moth, Euproctis chrysorrhcea. Androconia. — The term androconia* is applied to some peculiarly modified scales on the wings of certain male butterflies. These are the outlets of glands, which secrete a fluid with an agreeable odor; the supposed function of which is to attract the opposite sex, like the beautiful pltimage and songs of male birds. The androconia differ marvelously from ordinary scales in the variety of their forms (Fig. 115). They usually occur in patches on the upper sur- face of the fore wings; and are usually concealed by other scales; but they are scattered in some butterflies. The most familiar examples of grouped androconia are those that occur in the discal stigma of the hair-streaks, in the brand of certain skippers and in the costal fold of others, and in the scent-pouch of the male of the monarch butterfly The specific scent-glands of females. — The well-known fact that if an unfertilized female moth be confined in a cage or otherwise in the open many males of the Fig._ 115.— Androconia from the same species as the female will be attracted wmgsof male butterflies (After . ^ . .. , . Kellogg). to it, and sometimes evidently from a great distance, leads to the conclusion that there must emanate from the female a specific odor. The special glands producing this odor have not been recognized. Tenent hairs. — In many insects the pulvilli or the empodia are clothed with numerous hairs that are the outlets of glands which I I I ^Androconia: andro- {dvT/jp,dpdp6s), male; conia (xoi'ia), dust. THE INTERNAL ANATOMY OF INSECTS 101 secrete ai adhesive fluid ; this enables the insect to walk on the lower surface of objects (Fig. ii6). Fig. Ii6. — A, terminal part of a tenent hair from Eupolus, showing canal in the hair and opeaing near the tip; B, cross-section throu.^h a tarsal segment of Telephorus; c, cuticula; g, gland of tenent hair; h, h, tactile hairs; hy, hypo- dermis; n, nerve; s, sense-cell of tactile hair; t, t, tenent hairs (After Dewitz). The osmeteria. — In many insects there are hypodermal glands that open into sac-like invaginations of the body- wall which can be evaginated when the insect wishes to make use of the secretion pro- duced by these glands; such an organ i§ termed an osmeterium. The invagination of the osmeterium admits of an accumulation of the products of the gland within the cavity of the sac thus formed; when the osmeterium is evaginated the secretion becomes exposed to the air, being then on the outside of the osmeterium, and rapid diffusion of the secretion results. The most familiar examples of osmeteria are those of the larvas of the swallow-tailed butterflies, which are forked, and are thrust out from the upper part of the prothorax when the caterpillar is disturbed, and which diffuse a dis- agreeable odor (Fig. 117). They are ob- viously organs of defense. Osmeteria are present in the larvae of certain blue butterflies, Lycaenidce. These are in the seventh and eighth abdominal segments, and secrete a honey-dew, which attracts ants that attend and probably protect the larvae. The osmeteria of many other caterpillars have been described. Fig. 117 — Larva of Papilio thoas; 0, osmeterium expanded. 102 AN INTRODUCTION TO ENTOMOLOGY Fig. IT 8. — Wax-plates of Lhe honeybee (After Cheshire). Glands opening on the surface of the body. — There are several kinds of hypodermal glands, differing widely in function, that open on the surface of the body; among the best known of these are the following : Wax-glands. — The worker honeybee has fotn* pairs of wax-glands; these are situated on the ventral wall of the second, third, fourth, and fifth abdominal segments, and on that part of the segment which is overlapped by the preceding segment; each gland is simply a disc- like area of the hypodermis (Fig. 1 1 8). The cuticle covering each gland is smooth and delicate, and is known as a wax plate. The wax exudes through these plates and accumu- lates, forming little scales, which are used in making the honey-comb. Wax -glands exist in many of the Homoptera. In some of these the unicellular wax- glands are distributed nearly all over the body; and the product of these glands forms, in some, a powdery covering; in others, a clothing of threads; and in still others a series of plates (Fig. 119). Certain coccids excrete wax in con- siderable quantities. China wax, which was formerly an article of commerce, is the excretion of a coccid known as Pe-la (Ericerus Pe-la). Froth-glands of spittle-insects. — In the spittle-insects (Cercopidcc) there are large hypodermal glands in the pleural regions of the seventh and eighth abdominal segments, which open through numerous minute pores in the cuticula. These glands secrete a muci- laginous substance, which is mixed with a fluid excreted from the anus, and thus fits it for the retention of bubbles of air included in it by means of abdominal appendages (Guilbeau '08). Stink-glands. — Glands that secrete a liquid having a fetid odor and that are doubtless defensive exist in many insects. In the stink-bugs Fig. 119. — Orthcsia, greatly en- larged. THE INTERNAL ANATOMY OF INSECTS 103 (PentatoniicUe) the fluid is excreted through two openings, one on each side of the lower side of the body near the middle coxse ; in the bed- bug (Cimcx), the stink-glands open in the dorsal wall of the first three abdominal segments ; in Dytiscus, the glands open on the prothorax ; and in certain Coleoptera they open near the caudal end of the bodv. These are merely a few examples of the many glands of this type that are known. The cephalic silk-glaiids. — In the Lepidoptera, Trichoptera, and Hymenoptera, there is a pair of glands that secrete silk, and which open through the lower lip. These glands are designated as the cephalic silk-glands to distinguish them from the silk-glands of certain Neuroptera and Coleoptera in which the silk is produced by modified Malpighian vessels and is spun from the anus. The cephalic silk-glands are elongate and coiled ; they often extend nearly the whole length of the body ; the two ducts unite and the single terminal duct opens through the lower lip, and is not connected with the mouth cavity. These glands are a pair of salivary glands which have been transformed into silk organs. According to Carriere Fig. 1 20. — The salivary glands of the honeybee (After Cheshire). Fig. 121. — Theman- viibular gland of a honeybee. and Burger ('97), who studied their development in the embryo of a bee, they are developed from the rudiments of the spiracles of the first thoracic segment. In the later development they move 104 AN INTRODUCTION TO ENTOMOLOGY cephalad and the paired openings become a single one. This is the reason that in the adult there are no spiracles in the prothorax. The Salivary glands. — The term saUvary glands is a general one, applied to various glands opening in the vicinity of the mouth. The number of these varies greatly in different insects; the maximum number is found in the Hymenoptera. In the adult worker honey- bee, for example, there are four pairs of glands opening into the mouth; three of these are represented in Figure 120 and the fourth in Figure 121. These are designated as the supracerebral glands (Fig. 120, j), the postcerebral glands (Fig. 120, 2), the thoracic glands (Fig. 120, 3), and the mandibulary glands (Fig. 121), respectively. II. THE MUSCLES There exist in insects a wonderfully large number of muscles; some of these move the segments of the body, others move the appen- dages of the body, and still others are found in the viscera. Those of the viscera are described later in the accounts of the organs in which they occur. The muscles that move the segments of the body form several layers just within the body-wall, to which thsy are attached. The inner layer of these is well shown in Figure 122, which is a copy of one of the plates in the great work by Lyonet (1762) on the anatomy of a caterpillar, Cossus ligniperda. The two figures on this plate represent two larvae which have been split open lengthwise, one on the middle line of the back (Fig. 5), and one on the middle line of the ventral surface (Fig. 4) ; in each case the alimentary canal has been removed, so that only those organs that are attached quite closely to the body-wall are left. The bands of parallel fibers are the muscles that move the segments. It should be borne in mind, however, that only a single layer of muscles is represented in these figures, the layer that would be seen if a caterpillar were opened in the way indicated. When these muscles are cut away many other muscles are found extending obliquely in various directions between these muscles and the body-wall. In the head and thorax of adult insects the arrangement of the muscles is even more complicated ; for here the muscles that move the appendages add to the complexity of the muscular system. As a rule, the muscles of insects are composed of many distinct fibers, which are not enclosed in tendinous sheaths as with Verte- THE INTERNAL ANATOMY OF INSECTS 105 r mmii Fig. 122. — Internal anatomy of a caterpillar, Cossus ligniperda; i, principal longitudinal trachce; 2, central nervous system; j, aorta; 4, longitudinal dorsal muscles; 5, longtiudinal ventral muscles; 6, wings of the heart; 7, tracheal trunks arising near the spiracles; 8, reproductive organs; 9, vertical muscles; 10, last abdominal ganglion (From Lyonet). 106 A N INTROD UCTION TO ENTOMOLOG Y are lurnisnea witn a tendon at tne end brates. But the muscles that move the appendages of the body- are furnished with a tendon at the end farthest from the body (Fig- 123). The muscles of in- sects appear very differ- ently from those of Ver- tebrates. In insects, the Fig. 123— A leg of a May-beetle (After Straus- muscles are either Color- Durckheim). l^^g ^^^ transparent, or yellowish white ; and they are soft, almost of a gelatinous consistency ; notwithstanding this they are very efficient. The fibers of insect muscles are usually, if not always, of the striated type. Much has been written regarding the muscular power of insects, which has been supposed to be extraordinarily great; the power of leaping possessed by many and the great loads, compared to the weight of the body of the insect, that insects have drawn when harnessed to them by experimenters, have been cited as illustrating this. But it has been pointed out that these conclusions are not warranted; that the comparative contractile force of muscles of the same kind depends on the number and thickness of the fibers, that is, on the comparative areas of the cross-sections of the muscles com- pared ; that this sectional area increases as the square of any linear dimension, while the weight of similar bodies increases as the cube of any linear dimension; and consequently, that the muscles of the legs of an insect one fourth inch long and supporting a load 399 times its own weight, would be subjected to the same stress, per square inch of cross-section, as they would be in an insect 100 inches long of precisely similar shape, that carried only its own weight. We thus see that it is the small size of insects rather than an unusual strength of their muscles, that makes possible the apparently marvelous exhibitions of muscular power. Detailed accounts of the arrangement of the muscles in particular insects have been published by various writers: among the more important of these monographs are the following Lyonet (1762), on the larva of a cossid moth; Straus-Durckheim (1828), on a May- beetle; Newport (1839), on the larva of a Sphinx moth; Lubbock (1858), on the larva Pygaera bucephala; Berlese ('09a), on several insects; and Forbes ('14) on caterpillars. THE INTERNAL ANATOMY OF INSECTS 107 III. THE ALIMENTARY CANAL AND ITS APPENDAGES a. THE MORE GENERAL FEATURES The alimentary canal is a tube extending from one end of the body to the other. In some larvee, its length is about the same as that of the body; in this case it extends in a nearly straight line, occupying a iivnnsa Fig. 124. — Internal anatomy of a cockroach, Periplanela orientalis; a, antennas; bi, ^2, 63, first, second, and third legs; c, cerci: d, ventricular ganglion; e, salivary duct; f, salivary bladder, g, gizzard or proventriculus ; h, hepatic coeca; i, mid-intestine; j, Malpighian vessels; k, small intestine; /, large intestine: m, rectum; », first abdominal ganglion; 0, ovary; p, sebaceous glands (From RoUeston). 108 AN INTRODUCTION TO ENTOMOLOGY the longitudinal axis of the body, as is represented in the diagram given above (Fig. 105). In most insects, however, it is longer than the body, and is consequently more or less convoluted (Fig. 124); great variations exist in the length of the alimentary canal as com- pared to the length of the body; it is longer in herbivorous insects than it is in those that are carnivorous. The principal divisions. — Three chief divisions of the alimentary- canal are recognized ; these are termed the fore-intestine, the mid- intestine, and the hind-intestine, respectively. In the embryological development of the alimentary canal, the fore-intestine and the hind- intestine each arises as an invagination of the ectoderm, the germ layer from which the hypodermis of the body- wall is derived (p. 29). The invagination at the anterior end of the body, which develops into the fore-intestine, is termed the stomodceum; that at the posterior end, which develops into the hind-intestine, the proctodceum. Between these two deep invaginations of the outer germ layer of the embryo, the stomodffitmi and the proctodaeum, and ultimately connecting them, there is developed an entodermal tube, the mesenteron, which becomes the mid-intestine. These embryological facts are briefly stated here merely to elucidate two important features of the alimentary canal : first, the fore-intestine and the hind-intestine are invaginations of the body wall and consequently resemble it in structure, the chitinous lining of these two parts of the alimentary canal is directly continuous with the cuticula of the body wall, and the epithelium of these two parts and the hypodermis are also directly continuous; and second, the striking differences, pointed out later, in the structure of the mid- intestine from that of the fore- and hind-intestines are not surprising when the differences in origin are considered. Imperforate intestines in the larvae of certain insects. — ^Inthelarvse of certain insects the lumen of the alimentary canal is not a continuous passage; in these larvse, while food passes freely from the fore- intestine to the mid-intestine, there is no passage of the waste from the mid-intestine to the hind-intestine; there being a constriction at the point where the mid-intestine and hind-intestine join, v/hich closes the passage during a part or the whole of the larval life. This condition has been observed in the following families: — (a) Hymenoptera. — Proctotrypidag (in the first larval instar), Ichneumonidee, Formicidae, Vespidac, and Apidas. {b) Diptera. — Hippoboscidse. THE INTERNAL ANATOMY OF INSECTS 109 (c) Neuroptera. — Myrmeleonidce, Osmylidae, Sisyridce, and Chrysopidas. In these families the larvas spin silk from the anus. {d) Coleoptera. — In the Campodeiform larvse of Stylopidse and Meloidce. b. THE FORE-INTESTINE The layers of the fore-intestine. — The following layers have been recognized in the fore-intestine : The intima. — This is a chitinous layer which lines the cavity of the fore-intestine; it is directly continuous with the cuticula of the body-wall ; and is molted with the cuticula when this is molted. The epithelium. — This is a cell layer which is continuous with the h37podermis; it is sometimes quite delicate so that it is difficult to demonstrate it. The basement membrane. — Like the hypodermis the epitheliimi is bounded on one side by a chitinous layer and on the other by a base- ment membrane. The longitudinal ynuscles. — Next to the basement membrane there is a layer of longitudinal muscles. The circular muscles. — Out- side of the longitudinal muscles there is a layer of circular muscles. The peritoneal membrane. — Surrounding the alimentary canal there is a coat of con- nective tissue, which is termed the peritoneal membrane. This is one of a few places in which connective tissue, so abundant in Vertebrates, is found in in- sects. The regions of the fore- intestine. — Several distinct reg- ions of the fore-intestine are recognized; but the extent of these regions differ greatly in different insects. The pharynx. — The phar3mx is not a well-defined region of the intestine ; the term pharynx is commonly applied to a region between the mouth and the oesophagus; in mandibulate insects the pharynx Fig. 125. — Longitudinal section through the head of A nosa ptexippns, showing the interior of the left half; mx, left maxilla, the canal of which leads into the pharynx; ph, pharynx; 0, oesophagus; m, m, muscles of the pharynx; sd, salivary duct (After Burges). no AN INTRODUCTION TO ENTOMOLOGY is not distinct from the mouth-cavity; but in sucking insects the pharynx is a highly speciaHzed organ, being greatly enlarged, muscu- lar, and attached to the wall of the head by muscles. It is the pump- ing organ by which the liquid food is drawn into the alimentary canal. The pharnyx of the milkweed butterfly (Fig. 125) is a good example of this type of pharynx. The oesophagMS. — The oeso- phagus is a simple tube which traverses the caudal part of the head and the cephalic part of the thorax. There are variations in the application of the term oesophagus depending on the presence or absence of a crop and of a proventriculus, which are modified portions of the oesophagus; when either or both of these are present, the term oesophagus is commonly restricted to the unmodified part ot the fore-intestine. The crop. — In many insects a portion of the oesophagus is dilated and serves as a reservoir of food ; this expanded part, when present, is termed the crop. In the cock- roach (Fig. 124) it is very large, comprising the greater part of the fore-intestine ; in the ground-beetle Carabus (Fig. 126, c), it is much more restricted; this is the case also in the honeybee, where it is a nearly spherical sac in which the nectar is stored as it is col- lected from flowers and carried to the hive. In some insects the crop is a lateral dilatation of the oesophagus, and in some of these it is stalked. The proventriculus. — In certain insects that feed on hard sub- stances, the terminal portion of the fore-intestine, that part im- Fig. 126. — ^Alimentary canal oi Carabus auralus; h, head; oe, oesophagus; c, crop; pv, proventriculus; mi, mid- intestine covered with viiUform gastric cceca; mv, Malpighian vessels; hi, part of hind-intestine; r, rectum; ag, anal glands; mr, muscular reservoir (After Dufour). THE INTERNAL ANATOMY OF INSECTS 111 Fig. 127. — Cross-section of the proventriculus of a larva of Corydalus. mediately in front of the mid-intestine or ventriculus, is a highly speciaHzed organ in which the food is prepared for entrance into the more delicate ventriculus ; such an organ is termed the proventriculus (Fig. 126, pv). The characteristic features of a proventriculus are a remarkable development of the chitinous mtima into folds and teeth and a great in- crease in the size of the muscles of this region. The details of the structure of this organ vary greatly in different insects; a cross-section of the proven- triculus of the larva of Corydalus (Fig. 127) will serve to illustrate its form. In the proventriculus, the food is both masticated and more thoroughly mixed with the digestive fluids. The oesophageal valve.—Wh&n the fore-intestine projects into the mid- intestine, as shown in Figure 128, the folded end of the fore-intestine is termed the (esophageal valve. C. THE MID-INTESTINE The mid-intestine is the inter- mediate of the three principal divisions of the alimentary canal, which are distinguished by differ- ences in their embryological origins, as stated above. The mid-intestine is termed by different writers the mese liter on, the stomach, the chylific ventricle, the chyle stomach, and the ventriculus. The layers of the mid-intestine. — The structure of the mid-intestine differs markedly from that of the fore-intestine. In the mid-intestine there is no chitinous intima, and the relative positions of the circular and longitudinal muscles are reversed. Fig. 128. — The cesophageal valve of a larva of Simulium; F, fore-intestine: M, mid-intestine; u, point of uriion of fore-intestine and mid-intestiner p, peritoneal membrane; i, intima of fore- intestine; e, epithe- Hum of fore-intestine; pt, peritrophic membrane; m, muscles. 112 AN INTRODUCTION TO ENTOMOLOGY The sequence of the different layers is as follows : a lining epithelium, which is supported by a basement membrane, a layer of circular muscles, a layer of longitudinal muscles, and a peritoneal membrane. The epithelium. — The epitheliiun of the mid-intestine is very con- spicuous, being composed of large cells, which secrete a digestive fluid. These cells break when they discharge their secretion and are replaced by new cells, which are developed in centers termed nidi (Fig. 129, w). The extent of the digestive epithelium is increased in many insects by the development of pouch-like diverticula of the mid-intestine, these are the gastric cceca (Fig. 124, h). These differ greatly in niun- ber in different insects and are wanting in some. In some predaceous beetles they are villiform and very numerous (Fig. 126, mi). The peritrophic membrane. ■ — In many insects there is a membranous tube which is form- ed at or near the point of union of the fore-intestine and the mid- intestine and which incloses the food so that it does not come in contact with the delicate epithe- lium of the mid-intestine; this is known as the peritrophic mem- brane (Fig. 128, pt). As a rule this membrane is found in insects that eat solid food and is lacking in those that eat liquid food. It is obvious that the digestive fluid and the products of digestion pass through this membrane. It is continuously formed at its point of origin and passes from the body inclosing the excrement. d. THE HIND-INTESTINE The layers cf the hind-intes- tine.— The layers of the hind-in- testine are the same as those of the fore-intestine described above, except that a greater or less number of circular muscles exist between the basement membrane of the eoithelial layer and the layer of longitudinal muscles. The 129. — Resting epitheHum of mid- Intestine of a dragon-fly naiad; b, bases of large cells filled with digestive fluid; cm, space filled by circular mus- cles, /m . longitudinal muscles ; «, nidus in which new cells are developing (From Needham). THE INTERNAL ANATOMY OF INSECTS 113 sequence of the layers of the hind-intestine is, therefore, as follows: the intima, the epithelium, the basement membrane, the ental circular muscles, the longitudinal muscles, the ecial circular muscles, and the peritoneal membrane. The regions of the hind-intestine. — Three distinct regions are commonly recognized in the hind-intestine, these are the small intestine (Fig. 124, k), the large intestine (Fig. 124, /), and the rectum (Fig. 124, w). The Malpighian vessels.^ — There open into the beginning of the hind-intestine two or more simple or branched tubes (Fig. 124, ;), these are the Malpighian vessels. The number of these vessels varies in different insects but is very constant within groups; there are either two, four, or six of them; but, as a result of branching, there may appear to be one hundred or more. The function of the Mal- pighian vessels has been much discussed ; it was formerly believed to be hepatic, but now it is known that normally it is urinary. The Malpighian vessels as silk-glands. — There are certain larvas that in making their cocoons spin the silk used from the anus. These larvas are chiefly found among those in which the passage from the mid-intestine to the hind-intestine is closed. The silk spun from the anus is secreted by the Malpighian vessels. Among the larvag in which the Malpighian vessels are known to secrete silk are those of the Myrmeleonidas, Osmylus (Hagen 1852), Sisyra (Anthony '02), Lebia scapularis (Silvestri '05), and the Coccidag (Berlese '96). Berlese states that the Malpighian vessels secrete the woof of the scale of the Coccidas. The caecum. — In some insects there is a pouch-like diverticulum of the rectum, this is the ccecum. The anus. — The posterior opening of the alimentary canal, the anus, is situated at the caudal end of the abdomen. IV. THE RESPIRATORY SYSTEM Insects breathe by means of a system of air-tubes, which ramify in all parts of the body and its appendages ; these air-tubes are of two kinds, which are termed irachece and tracheoles, respectively. In adult insects and in most nymphs and larvce, the air is received through openings in the sides of the segments of the body, which are known as spiracles or stigmata. Many insects that live in water are furnished with special devices for obtaining air from above the water; but with naiads and a few 114 AN INTRODUCTION TO ENTOMOLOGY aquatic larv^ the spiracles are closed; in these insects the air is purified by means of gill-like organs, termed tracheal gills. A few insects have blood-gills. Two types of respiratory systems, therefore, can be recognized: first, the open type, in which the air is received through spiracles ; and second, the closed type, in which the spiracles are not functional. a. THE OPEN OR HOLOPNEUSTIC TYPE OR RESPIRATORY ORGANS That form of respiratory organs in which the trachae communicate freely with the air outside the body through open spiracles is termed the open or holopneustic type.* As the open type of respiratory organs is the most common one, those features that are common to both types will be discussed under this head as well as those that are peculiar to this type. Under the head of closed respiratory organs will be discussed only those features distinctly characteristic of that type. /. The Spiracles The position of the spiracles. — The spiracles are situated one on each side of the segments that bear them or are situated on the lateral aspects of the body in the transverse conjunctivae. The question of the position of the spiracles has not been thor- oughly investigated ; but I believe that normally the tracheae, of which Pig. 130. — Lateral view of a silk worm showing the spiracles (After Verson). i:he spiracles are the mouths, are invaginations of the transverse conjunctivae between segments. From this normal position a spiracle may migrate either forward or backward upon an adjacent segment (Fig. 130). The number of spiracles. — The normal number of spiracles is ten pairs; when in their normal position, there is a pair in front of the ^Holopneustic: holo (5Xos), whole; pneuma {/rveOna), breath. THE INTERNAL ANATOMY OF INSECTS 115 second and third thoracic segments and the first to the eighth abdom- inal segments, respectively. There are none in the corresponding position in front of the first thoracic segment. See account of cephaHc silk-glands p. 103. The two pairs of thoracic spiracles are commonly distinguished as the mesothoracic and the metathoracic spiracles ; that is each pair of spiracles is attributed to the segment in front of which it is normally situated. Following this terminology there are no prothoracic spiracles; although sometimes the first pair of spiracles is situated in the hind margin of the prothorax, having migrated forward from its normal position. It would be better to designate the thoracic spiracles as the first and second pairs of thoracic spiracles, respec- tively; in this way the same term would be applied to a pair of spiracles whatever its position. There are many references in entomological works to "prothoracic spiracles," but these refer to the pair of spiracles that are more commonly designated the mesothoracic spiracles. In many cases the abdominal spiracles have migrated back upon the segment in front of which they are normally situated, being fre- quently situated upon the middle of the segment. The statements made above refer to the normal number and dis- tribution of spiracles; but a very wide range of variations from this type exists. Perhaps the most abnormal condition is that found in the genus Smi nthurus of the Collembola, where there is a single pair of spiracles which is borne by the neck. In the Podurid^, also of the Collembola, the respiratory system has been lost, there being neither tracheas nor spiracles. Terms indicating the distribution of the spiracles. — The following terms are used for indicating the distribution of the spiracles; they have been used most frequently in descriptions of lan^as of Diptera. These terms were formed by combining with pneustic (from pneo, to breathe) the following prefixes: peri-, around, about; pro-, before; meta- after; and aniphi, both. Peripneustic. — Having spiracles in a row on each side of the body, the normal type. Propneustic. — ^With only the first pair of spiracles. Metapneustic. — With only the last pair of spiracles. Amphipneustic. — With a pair of spiracles at each end of the body. 116 AN INTRODUCTION TO ENTOMOLOG\ a Fig. 13 Spiracles; a, of the larva of Corydalus; b, of the larva of Droso- phila amcena. The Structure of spiracles. — In their simplest form the spiracles or stigmata are small round or oval openings in the body-wall. In many- cases they are provided with hairs to exclude dust; in some, as in the larva of Corydalus, each spiracle is furnished with a lid (Fig. 131, a); in fact, very many forms of spiracles exist. Usually each spir- acle opens by a single aperture; but in some larvas and pupae of Diptera they have several openings (Fig. 131, &)■ The closing apparatus of the tracheae. — Within the body, a short distance back of the spiracle, there is an apparatus consisting of several chitinous parts, surrounding the trachea, and moved by a muscle, by which the trachea can be closed by compression (Fig. 132). This is the closing apparatus of the trachea. The closing of this appara- tus and the contraction of the body by the respiratory muscles is sup- posed to force the air into thetracheoles, which are the essential res- piratory or- gans. Fig. I -52. — -Diagrams representing the closing apparatus of the trache.-p; a, b, c, chitinous parts of the apparatus; m, muscle; A, apparatus open; B, apparatus closed; C, spiracle and trunk of trachea showing the position of the apparatus. (From Judeich and Nitsche). 2. THE TRACHEA • Each spiracle is the opening of an air-tube or trachea. The main tracheal trunk which arises from the spiracle soon divides into several branches, these in turn divide, and by repeated divisions an immense number of branches are formed. Every part of the Dody is supplied with tracheae. In a few insects the group of tracheee arising from a spiracle is not connected with the groups arising from other spiracles; this is the case in Machilis (Fig. 133). In most insects, however, each group of tracheae is connected with the corresponding groups in adiacent seg- THE INTERNAL ANATOMY OF INSECTS 117 ments by one or more longitudinal tracheas, and is also connected Fig. 133. — The trachcce of Machilis (From Oudemans). with the group on the opposite side of the same segment by one or more transverse trachese (Fig. 134). The structure of the tracheae. — The fact that in their embryological development the tracheas arise as invaginations of the body-wall, makes it easy to understand the structure of the tracheas. The three layers of the body-wall are directly continuous with corresponding layers in the wall of a trachea (Fig. 135). These layers of -a trachea are designated as the intima, the epithe- lium, and the basement membrane. The mtima is the chitinous inner layer of the trachese. It is directly continuous with the cuticula of the body- wall, and like the cuticula is molted at each ecdysis. A peculiar feature of the intima of trachea is the fact that it is furnished with thickenings which extend spirally. These give the 1 34-— Larva of tracheae their charac- Fig. 135.— Section of a ixachea teristic transversely ^",<^ ^^^f body-v/all; c, Cantharis vesicatorta, showing the distribu- tion of tracheae (From striated appearance. the larger trachea be pulled apart the intima will tear between the folds of the spiral thickening, and the latter will uncoil from within the trachea like a basement membrane; sp, spiral thickening of the in- tima, the tasnidium. 118 AN INTRODUCTION TO ENTOMOLOGY thread (Fig. 135). The spiral thickening of the intima of a trachea is termed the tcBrndium. In some insects there are several parallel tasnidia; so that when an attempt is made to uncoil the thread a ribbon-like band is produced, composed of several parallel threads. This condition exists in the larger tracheae of the larva Corydalus. The epithelium of the trachea is a cellular layer, which is directly- continuous with the hypodermis of the body-wall. The basement membrane is a delicate layer, which supports the epitheliinn, as the basement membrane of the body-wall supports the hypodermis. 3. The Tracheoles The tracheoles are minute tubes that are connected with the tips of trachea or arise from their sides, but which differ from trachese in their appearance, structure, and mode of origin; they are not small tracheae, but structures that differ both histologically and in their origin from tracheae. The tracheoles are exceedingly slender, measuring less than one micron in diameter; ordinarily they do not taper as do trachese; they contain no tsenidia; and they rarely branch, but often anasto- mose which gives them a branched appearance (Fig. 136, t and 138 B, /)• Each tracheole is of unicellular origin, and is, at first, intracellular in position, being developed coiled within a single cell of the epithelium of a trachea. In this stage of its development it has no connection with the liunen of the trachea in the wall of which it is developing, being separated from it by the intima of the trachea. A subsequent molting of the intimia of the trachea opens a connection between the lumen of the tracheole and the trachea. At the same time or a little later the tracheole breaks forth from its mother cell, uncoils, and extends far beyond the cell in which it was developed. The tracheoles are probably the essential organs of respiration, the trachea acting merely as conduits of air to the tracheoles. 4. The Air-Sacs In many winged insects there are expansions of the tracheae, which are termed air-sacs. These vary greatly in nimiber and size. In the honeybee there are two large air-sacs which occupy a consider- able part of the abdominal cavity; while in a May-beetle there are hundreds cf small air-sacs. The air-sacs differ from tracheae in lacking tanidia. THE INTERNAL ANATOMY OF INSECTS 119 As the air-sacs lessen the specific gravity of the insect they proba- bly aid in flight ; as filling the lungs with air makes it easier for a man to float in water ; in each case there is a greater volimie for the same weight. 5. Modifications of the open type of respiratory organs in aquatic insects There are many insects in which the spiracles are open that live in water ; these insects breathe air obtained from above the surface of the water. Some of these insects breathe at the surface of the water, Fig. 136. — Part of a tracheal gill of the larva of Corydalus; T, trachea; t, tracheoles. as the larvcB and pupae of mosquitoes, the larvae of Eristalis, and the Nepidse; others get a supply of air and carry it about with them beneath the surface of the water, as the Dytiscidae, the Notonectidae and the Corisidae. The methods of respiration of these and of other aquatic insects with open spiracles are described in the accounts of these insects given later. b. THE CLOSED OR APNEUSTIC TYPE OF RESPIRATORY ORGANS That type of respiratory organs in which the spiracles do not function is termed the closed or apneustic* type; it exists in naiads and in a few aquatic lar\'ae. I. The Traclieal Gills In the immature insects mentioned p;. 137. — Part of a tuft of tracheal gills of a larva of Corydalus. above, the air m the body is purified by means of organs known as tracheal gills. *ApneQstic: apneustos {dirvevffTos), without breath 120 AN INTRODUCTION TO ENTOMOLOGY These are hair-like or more or less plate-like expansions of the body- wall, abundantly suppHed with trachege and tracheoles. Figures 136 and 137 represent a part of a tuft of hair-like tracheal gills of a larva of Cory dolus and figure 13S a naiad of a are separated damsel-fly. from the air In these the a plate-like tracheal gill of tracheal gills the tracheoles water only by the deHcate wall of the tracheal gill which admits of the transfer of gases between the air in the tracheoles and the air in the water. Tracheal gills are usually borne by the abdomen, sometimes by the thorax, and in case of one genus of stone-flies by the head. They pertain almost exclusively to the immature stages of insects ; but stone- flies of the genus Pteronarcys retain them throughout their existence. In the naiads of the Odonata the rectum is supplied with many tracheae and functions as a tracheal gill. 138. — Tracheal gill of a damsel- fly: A, entire gill showing the tracheae; B, part of gill more magnified showing both tracheae (T) and tracheoles (t). 2. Respiration of Parasites It is believed that internal parasitic larvse derive their air from air that is contained in the blood of their hosts, and that this is done by osmosis through the cuticula of the larva, the skin of the larva being furnished with a network of fine tracheae (Seurat '99). J. The blood-gills Certain aquatic larvas possess thin transparent extensions of the body wall, which are filled with blood, and serve as respiratory organs. These are termed blood-gills. Blood-gills have been observed in comparatively few insects; among them are certain trichopterous larvae; the larva of an exotic beetle, Pelobius; and a few aquatic dipterous larvae, Chironomus and Simulium. It is probable that the ventral sacs of the Thysanura, described in the account of that order, are also blood-gills. THE INTERNAL ANATOMY OF INSECTS 121 V. THE CIRCULATORY SYSTEM The general features of the circulatory system. — In insects the cir- culatory system is not a closed one, the blood flowing in vessels during only a part of its course. The greater part of the circulation of this fluid takes place in the cavities of the body and of its appendages, where it fills the space not occupied by the internal organs. Almost the only blood-vessel that exists in insects lies just beneath the body-wall, above the alimentary canal (Fig. 105, h). It extends from near the caudal end of the abdomen through the thorax into the head. That part of it that lies in the abdomen is the heart; the more slender portion, which traverses the thorax and extends into the head is the aorta. On each side of the heart, there is a series L %J^ of triangular muscles extending from the heart to the lateral wall of the body. These con- stitute the dorsal diaphragm or the wings of the heart. They are discussed later under the head : Suspensoria of the Viscera. The heart. — The heart is a tube, which is usually closed at its posterior end; at its anterior end it is continuous with the aorta. The heart is divided by constrictions into chambers which are separated by valves (Fig. 139). The nimiber of these chambers varies greatly in different insects; in some, as in Phasma and in the larva of Corethra, there is only one, in others, as in the cockroach, there are as many as thirteen, but usually there are not more than eight. The blood is admitted to the heart through sKt-like openings, the ostia of the heart; usually there is a pair of ostia in the lateral walls of each chamber. Each ostitmi is furnished with a valve which closes it when the chamber contracts. The wall of the heart is composed of two dis- Fig. 139. — Heart of a May -beetle; a, lateral aspect of the aorta; b, interior of the heart showing valves; c, ventral aspect of the heart and wing-mus- cles, the muscles are represented as cut away from the caudal part of the heart; d, dorsal tinct layers: an inner muscular layer ; and an outer, connective tissue or peritoneal layer. The muscular layer consists chiefly of annular muscles; but longitudinal fibers have also been observed. aspect of the (After Straus-Durck- heim). 122 AN INTRODUCTION TO ENTOMOLOGY The pulsations of the heart. — When a heart consists of several chambers, they contract one after another, the wave of contraction passing from the caudal end of the heart forwards. As the valves between the chambers permit the blood to move forward but not in the opposite direction, the successive contraction of the chambers causes the blood received through the ostia to flow toward the head, into the aorta. The aorta. — The cephalic prolongation of the heart, the aorta (Fig. 139, a), is a simple tube, which extends through the thorax into the head, where it opens in the vicinity of the brain. In some cases, at least, there are \'alves in the aorta. The circulation of the blood. — The circiilation of the blood can be observed in certain transparent insects, as in young naiads, in larv£e of Trichoptera, and in insects that have just molted. The blood flows from the open, cephalic end of the aorta and passes in quite definite streams to the various parts of the body-cavity and into the cavities of the appendages. These streams, like the ocean currents, have no walls but flow in the spaces between the internal organs. After bathing these organs, the blood returns to the sides of the heart, which it enters through the ostia. Accessory circulatory organs. — Accessory pulsating circulatory organs have been described in several insects. These are sac-like structures which contract independently of the contractions of the heart. They have been found in the head in several Orthoptera; in the legs of Hemiptera, and in the caudal filaments of Ephemerida. VI. THE BLOOD The blood of insects is a fluid, which fills the perivisceral cavity, bathing all of the internal organs of the body, and flowing out into the cavities of the appendages of the body. In only a comparatively small portion of its course, is the blood enclosed in definite blood- vessels; these, the heart and the aorta are described abo^^e. The blood consists of two elements, a fluid plasma and cells similar to th.e white corpuscles of the blood of vertebrates, the leucocytes. The blood of insects differs greatly in appearance from the blood of vertebrates, on account of the absence of red blood-corpuscles. In most insects the blood is colorless ; but in many species it has a yellow- ish, greenish, or reddish color. In the latter case, however, the color is not due to corpuscles of the type which gives the characteristic color to the blood of vertebrates. THE INTERNAL ANATOMY OF INSECTS 123 The leucocytes are nucleated, colorless, amoeboid cells similar to the white corpuscles of vertebrates, in appearance and function ; they take up and destroy foreign bodies and feed upon disintegrating tissue. It is believed that the products of digestion of disintegrating tissue by the leucocytes pass into the blood and serve to nourish new tissue. The blood receives the products of digestion of food, which pass in a liquid form, by osmosis, through the walls of the alimentary canal. On the other hand it gives up to the tissues which it bathes the materials needed for their growth. In insects oxygen is supplied to the tissues and gaseous wastes are removed chiefly by the respiratory system and not by means of the blood as in vertebrates. VII. THE ADIPOSE TISSUE On opening the body of an insect, especially of a larva, one of the most conspicuous things to be seen is fatty tissue, in large masses. These often completely siuround the alimentary canal, and are held in place by niimerous branches of the trachese with which they are supplied. Other and smaller masses of this tissue adhere to the inner surface of the abdominal wall, in the vicinity of the nervous system, and at the sides of the body. In adult insects it usually exists in much less quantity than in larvae. The chief function of the adipose tissue is the storage of nutriment ; but it is believed that it also has a urinary function, as concretions of uric acid accumulate in it during the life of the insect. VIII. THE NERVOUS SYSTEM a. THE CENTRAL NERVOUS SYSTEM The more obvious parts of the central nerv^ous system are the following: a ganglion in the head above the oesophagus, the brain; a ganglion in the head below the oesophagus, the subcesophageal ganglion; a series of ganglia, lying on the floor of the body cavity in the thorax and in the abdomen, the thoracic and the abdominal ganglia; two longitudinal cords, the connectives, uniting all of these ganglia in a series ; and many nerves radiating from the ganglia to the various parts of the body. The connectives between the brain and the subcesophageal ganglion pass one on each side of the oesophagus ; these are termed the crura cerebri, or the legs of the brain; in the remainder of their course, the two connectives are quite closely parallel (Fig. 124), 124 AN INTRODUCTION TO ENTOMOLOGY The series of ganglia is really a double one, there being typically a pair of ganglia in each segment of the body ; but each pair of ganglia is more or less closely united on the middle line of the body, and often appear to be a single ganglion. In some cases the ganglia of adjacent segments coalesce, thus reducing the nimiber of distinct ganglia in the series. It has been demonstrated that the brain is composed of the coalesced ganglia of three of the head segments, and the suboesophageal ganglion of the coalesced ganglia of the remaining four segments. Fig. 140. — Successive stages in the coalescence of thoracic and of abdominal gangUa in Diptera; A, Chironomus; B, Empis; C, Tahanus; D, Sar- cophaga (From Henneguy after Brandt). The three parts of the brain, each of which is composed of the pair of ganglia of a head segment, are designated as the protocerebruni, the deutocerebrum, and the tritocerebrum, respectively. The protocere- brum innervates the compound eyes; the deutocerebrum, the antennas; and the tritocerebrum, the labnmi. The subcesophageal ganglion is composed of four pairs of primary ganglia ; these are the ganglia of the segments of which the mandibles, the maxillulae, the maxilla, and the labium, respectively, are the appendages. The three pairs of thoracic ganglia often coalesce so as to form a single ganghonic mass; and usually in adult insects the number of abdominal ganglia is reduced in a similar way. THE INTERNAL ANATOMY OF INSECTS 125 Successive stages in the coalescence of the thoracic and abdominal ganglia can be seen by a study of the nervous system of the larva, pupa, and adult of the same species, a distinct cephalization of the central nervous system taking place during the development of the insect. Varying degrees of coalescence of the thoracic and of the abdominal ganglia can be seen by a comparative study of the nervous systems of different adult insects (Fig. 140). The transverse band of fibers that unite the two members of a pair of ganglia is termed a commissure. In addition to the commissures that pass directly from one member of a pair of ganglia to the other, there is in the head a com- missure that encircles the oesophagus in its passage from one side of the brain to the other, this is the suh- osophageal commissure (Fig. 141). The nerves that extend ^i-' Fig. 141.— Lateral view of the oesophagus of a r ^t^ pptitral chain nf caterpillar, showing the suboesophageal com- ^^°^ ^^^ central cnam ot missure; b, brain; oe, oesophagus; sc, sub- oesophageal commissure; sg, suboesophageal ganglion; pg, paired ganglion (After Lienard). gangHa to the different parts of the body are a part of the central nervous sys- tem ; the core of each nerve fiber being merely a process of a ganglionic cell, however long it ^ may be. ^^, ,^ b. THE CESOPHAGEAL SYMPATHETIC NER- VOUS SYSTEM In addition to the central nervous sys- tem as defined above there are three other nervous complexes which are commonly described as separate systems although they are connected to the central nervous system by nerves. These are the oeso- phageal sympathetic Fig. 142. — Lateral view of the nerves of the head in the larva of Corydalus; a, antennal nerve; ao, aorta; ar paired nerves connecting the frontal ganglion with the brain; h, brain; d, clypeo-labral nerve; con, connective; cr, crura cerebri; fg, frontal ganglion; fn, frontal nerve; i, unpaired nerve connecting the frontal ganglion with the brain; /, labial nerve; Ig, the paired gangHa; md, mandibular nerve; m, p, q, s, u, z, nerves of the oesopha- geal sympathetic system; mx, maxillary nerve; o, optic nerves; oes, oesophagus; ph, pharynx; pn, phar>'ngeal nerve; r, recurrent nerve; sc, suboesophageal commis- sure; sg, suboesophageal ganglion; st, stomagastric nerve; v, ventricular ganglion (From Hammar). nervous system, the ventral sympathetic nervous 126 AN INTRODUCTION TO ENTOMOLOGY system, and the peripheral sensory nervous system. The first of these is connected with the brain; the other two, with the thoracic and abdominal gangha of the central nervous system. The oesophageal sympathetic nervous system is intimately associated with the oesophagus and, as just stated, is connected with the brain. It is described by different writers under various names; among these are visceral, vagus, and stomato gastric. It consists of two, more or less distinct, divisions, an unpaired median division and a paired lateral division. The unpaired division of the oesophageal sympathetic nervous system is composed of the following parts, which are represented in Figures 141, 143, 143, and 144: the frontal ganglion (Jg), this is a minute gang- lion situated above the oesophagus a short distance in front of the brain; the unpaired nerve connecting the frontal ganglion with the brain (i), this is a small nerve extending from the brain to the frontal ganglion ; the paired nerves connecting the frontal ganglion with the brain (ar), these are arching nerves, one on each side, extending from the upper ends of the crura cerebri to the frontal gangHon; the frontal nerve (fn) , this nerve arises from the anterior bor- der of the frontal ganglion and extends cephalad into the clypeus, where it bifur- cates; the pharyngeal nerves (pn), these extend, one on each side, from the frontal ganglion to the lower portions of the pharynx; the recurrent nerve (r), this is a single median nerve, which arises from the caudal border of the frontal >;anglion, and extends back, passing under the brain and betv»-een the Fig. 143. — Dorsal view of the nerves of the head in the larva of Corydalus; e, ocelli; mnd. mandible; other lettering as in Figtire 142 (From Hammar). THE INTERNAL ANATOMY OF INSECTS 127 aorta and the oesophagus, to terminate in the ventricular ganghon; the ventricular ganglion (v), this is a minute ganghon on the middle line, a short distance cauda of the brain, and between the aorta and the oesophagus; and the stomogastric nerves (st), these are two nerves which extend back from the caudal border of the ventricular ganglion, they are parallel for a short distance, then they separate and pass, one on each side, to the sides of the alimentary canal which they follow to the proventriculus. The paired division of the oesophageal sympathetic nervous system varies greatly in form in different insects. In the larv^a of Corydalus, there is a single pair of ganglia (Fig. 142 and 143, Ig), one on each side of the oesophagus; each of these ganglia is connected with the brain by two nerves {m and u) but they are not connected with each other nor with the unpaired division of this system. In a cockroach (Fig. 144), there are two pairs of ganglia {ag and pg); the two ganglia of each side are connected with each '\ other and with the recurrent nerve of the unpaired division. As yet comparatively little is known regarding the function of the oesophageal sympathetic nerv^ous sys- tem of insects ; nerves extending from it have been traced to the clypeus, the muscles of the pharynx, the oeso- phagus, the mid-intestine, the salivary glands, the aorta, and the heart. Its function is probably analogous to that of the sympathetic nervous sys- tem of Vertebrates. Fig. 144. — The oesophageal sympa- thetic nervous system of Peri- planeta orientalis; the outhnes of the brain {b) and the roots of the antennal nerve which cover a por- tion of the sympathetic nervous system are given in dotted lines; ag, anterior ganglion; pg, posterior ganghon; /g, frontal ganghon; sn, nerves of the salivary glands; r, recurrent nerve (After Hofer). THE VENTRAL SYMPATIlETIC NERV- OUS SYSTEM The ventral sjonpathetic nervous system consists of a series of more or less similar elements, each connected with a ganglion of the ventral chain of the central nervous system. Typi- cally there is an element of this system arising in each thoracic and 128 AN INTRODUCTION TO ENTOMOLOGY abdominal ganglion; and each element consists of a median nerve extending from the ganglion of its origin caudad between the two connectives, a pair of lateral branches of this median nerve, and one or more ganglionic enlargements of each lateral branch. Frequently the median nerve extends to the ganglion of the following segment. A simple form of this system exists in the larva of Cossiis ligniperda (Fig. 122); and a more compli- cated one, in Locusia viridissima (Fig. 145). Frcm each lateral branch of the median nerve a slender twig extends to the closing apparatus of the tracheae. d. THE PERIPHERAL SENSORY NERVOUS SYSTEM Immediately beneath the hypodermal layer of the body -wall, there are many bipolar and multipolar ^,^;^O^rt^1^^\ nerve-cells whose prolongations form a network of // \y{\\gs nerves; these constitute the peripheral sensory nervous system or the subhypodermal nerve plexus. The fine nerves of this system are branches of larger nerves which arise in the central nervous sys- tem; and the terminal prolongations of the bipolar trai sympathetic nerve-cells innervate the sense-hairs of the body- nervous sys- ^^n tern; g, ganglion . r • r 11 of the central l^igure 146 represents a surface view 01 a small nervous system; p^j.^ q£ ^^le peripheral sensory nervous system of the n, nerve; c, con- . t^ 7 ■ r- ttm /> nective; m, me- sukworm, Bomoyx men, as figured by Hilton ( 02); dian nerve of the ^-^q bases of several sense hairs are also shown. The sympathetic sys- tem; gs, gang- details of this figure are as follows: h, h, h, the bases lion of the sym- ^f sense-hairs; s, s, s, bipolar nerve cells; m, m, m, pathetic svstem » > > ; r- (From Beriese). multipolar cells; n, n, n, nerves. All of these struc- tures are united, forming a net work. Of especial interest is the fact that the terminal prolongation of each bipolar nerve-cell enters the cavity of a sense-hair and that the other pro- longation is a branch of a larger nerve which comes from the central nervous system. The peripheral sensory nervous system is so delicate that it can not be seen except when it is stained by some dye that differentiates nervous matter from other tissues. For this purpose the intravitam methylen blue method of staining is commonly used. Fig. 145. — Part of the ventral chain of ganglia of Lo- custa viridissima and of the ven- THE INTERNAL ANATOMY OF INSECTS 129 IX. GENERALIZATIONS REGARDING THE SENSE- ORGANS OF INSECTS The sense-organs of insects present a great variety of forms, some of which are still incompletely understood, in spite of the fact that they have been investigated by many careful observers. In the limited space that can be devoted to these organs here only the more general features of them can be described and some of the disputed questions regarding them briefly indicated. A classification of the sense-organs. — The different kinds of sense- organs are distinguished by the nature of the stimulus that acts on Fig. 146. — Surface view of subhypodermal nerves and nerve-cells from the silkworm (From Hilton) each. This stimulus may be either a mechanical stimulus, a chemicEil one, or light. The organs of touch and of hearing respond to mechani- cal stimuli; the former, to simple contact with other objects; the latter, to vibratory motion caused by waves of sound. The organs of taste and of smell are influenced only by soluble substances and it seems probable that chemical changes are set up in the sense-cells by these substances ; hence these organs are commonly referred to as the chemical sense-organs; no criterion has been discovered by which the organs of taste and of smell in insects can be distinguished. The organs of sight are acted upon by light ; it is possible that the action of light in this case is a chemical one, as it is on a photographic plate, 130 AN INTRODUCTION TO ENTOMOLOGY but the eyes have not been classed among the chemical sense-organs. For these reasons the following groups of sense-organs are recognized: The mechanical sense-organs. — The organs of touch and of hearing. The chemical sense-organs. — The organs of taste and of smell. The organs of sight. — The compound eyes and the ocelH. The cuticular part of the sense-organs. — In most if not all of the sense-organs of insects there exists one or more parts that are of cuti- cular formation. The cuticular parts of the organs of sight and of hearing are described later, in the accounts of these organs; in this place, a few of the modifications of the cuticula found in other sense- organs are described. Each of the cuticular formations described here is found either within or at the outer end of a pore in the cuticula ; as some of these formations are obviously setae and others are regarded as modified setae, this pore is usually termed the trichopore; it has also been termed the neuropore, as it is penetrated by a nerve-ending. As the cuticular part of this group of sense-organs, those other than the organs of hearing and of sight, is regarded as a seta, more or less modified, these organs are often referred to as the setiferous sense-organs; they are termed the Hautsinnesorgane by German writers. Special terms have been applied to the different types of setiferous sense-organs, based on the form of the cuticUlar part of each; but these types cannot be sharply differentiated as intergrades exist between them. In Figure 147 are represented the cuticular parts of several of these different types; these are designated as follows : The thick-walled sense-hair, sensillum trichodeum. — In this type the cuticular part is a seta, the base of which is in an alveolus at the end of a trichopore and is connected with the wall of the trichopore by a thin articular mem- brane (Fig. 147, a.) Fig. 147. — Various forms of the cuticular portion of the setiferous sense-organs. The lettering is explained in the text. THE INTERNAL ANATOMY OF INSECTS 131 If the sense-hair is short and stout, it is termed by some writers a sense-bristle, sensilhtm chceticum; but there is little use for this dis- tinction. In the thick-walled sense-hairs, the wall of the seta is fitted to receive only mechanical stimuli, being relatively thick, and as these organs lack the characteristic features of the organs of hearing, they are believed to be organs of touch. The sense-cones - — -The sense-cones vary greatly in form and in their relation xo the cuticula of the body- wall ; their distinctive feature is that they are thin-walled. For this reason, they are believed to be chemical sense-organs, the thinness of the wall of the cone permitting osmosis to take place through it. In the sense-cones, too, there is no joint at the base, as in the sense-hairs, the articular membrane being of the same thickness as the wall of the cone ; there is, therefore, no provision for movement in response to mechanical stimuli. In one type of sense-cone, the sensillum basiconicum, the base of the cone is at the surface of the body- wall (Fig. 147, 6). In another type, sensillum caloconicum, the cone is in a pit in the cuticula of the body-wall (Fig. 147, c). Two forms of this type are represented in the figure; in one, the sense-cone is conical; in the other, it is fungi- form. Intergrades between the basiconicum and the coeloconictmi types exist (Fig. 147, d). The flask-like sense-organ, sensillum ampullaceum. — This is a modification of the sense-cone type, the characteristic featiu^e of which is that the cone is at the bottom of an invagination of the articu- lar membrane; in some cases the invagination is very deep so that the cone is far within tlie body- wall (Fig. 147, ^) ; intergrades between this fonn and the more common sensillum coeloconicum exist (Fig. 147, /). The pore-plate, sensillum placodeum. — In this type the cuticular part of the organ is a plate closing the opening of the trichopore ; in some cases, this plate is of considerable thickness with a thin articular membrane (Fig. 147, g); in others it is thin throughout (Fig. 147, h). The olfactory pores. — This type of sense-organ is described later. X. THE ORGANS OF TOUCH The organs of touc. . are the simplest of the organs of special sense of insects. They are widely distributed over the surface of the body and cf its appendages. Fach consists of a seta, with all the character- istics of setae already ar^scnoed, a tricho|,en cell, which excreted the 132 AN INTRODUCTION TO ENTOMOLOGY seta, and a bipolar nerv^e-cell. These organs are of the type known as sensillum trichodeum referred to in the preceding section of this chapter. According to the observations of Hilton (02) the terminal pro- longation of the nerve-cell enters the hair and ends on one side of it at some distance from its base (Fig. 148). The proximal part of this nerve-cell is connected with the peripheral sensory nervous system, as already described (page 128). The presence of this nervous connection is believed to distinguish tactile hairs from those termed clothing hairs, and from the scales that are modified setee. If this distinction is a good one, it is quite probable that many hairs and scales that are now regarded as merely clothing will be found to be sense-organs, when studied by improved histological methods. In fact Guenther (01) and others have shown that some of the scales on the wings of Lepidoptera, especially those on the veins of the wings, are supplied with nerves ; but the function of these scales is unknown. Hilton states that he "found no evidence to indicate nerves ending in gland cells or trichogen cells by such branches as have been described and figured by Blanc ('90), but in every case the very fine nerve termination could be traced up past the hypodermal cell la^-er with no branches." Many figures of unbranched nerve fibers ending in sense-hairs are also given by O. vom Rath ('96). A very different form of nerve-endings in sense-hairs is given by Berlese ('09, a). This author represents the nerv^e extending to a sense-hair as dividing into many bipolar nen^e-endings. XL THE ORGANS OF TASTE AND OF SMELL {The chemical sense-organs) It is necessary to discuss together the organs of taste and of smell, as no morphological distinction between them has been discovered. If a chemical sense-organ is so located that it comes in contact with the food of the insect, it is commonly regarded as an organ of taste, if not so situated, it is thought to be an organ of smell. In the present state of our knowledge, this is the only distinction that can be made between these two kinds of organs. Many experiments have been made to determine the function of the various chemical sense-organs but the results are, as yet, far from conclusive. The problem is made difficult by the fact that these THE INTERNAL ANATOMY OF INSECTS 133 organs are widely distributed over the body and its appendages, and in some parts, as on the antenna of many insects, several different types of sense-organs are closely associated. Those organs that are characterized by the presence of a thin- walled sense-cone (Fig. 147, h-f) or by a pore-plate (Fig. 147, g, h) are believed to be chemical sense-organs. It is maintained by Berlese ('09, a) that an essential feature of these chemical sense-organs is the presence of a gland -cell, the excretion ofwhich, passing through the thin wall of the cuticular part, keeps the outer surface of this part, the sense-cone or pore-plate, moist and thus fitted for the reception of chemical stimuli. According to this view a chemical sense-organ consists of a cuticular part, a trichogen cell or cells which produced Fig. 148. — Sections through the body-wall and sense-hairs of the silk- worm; c, cuticula; h, hair; hy, hypodermis; n, nerve; 5, bipolar nerve-cell (From Hilton). The line at the right of the figure indi- cates one tenth miUimeter. this part, a gland-cell which excretes a fluid which keeps the part moist, and a nerve-ending. It is interesting to note that tactile hairs may be regarded as specialized clothing hairs, specialized by the addition of a nervous connection, and that sense-cones and pore-plates may be regarded as specialized glandular hairs with a nervous connection; in the latter case, the specialization involves a thinning of the wall of the hair so as to permit of osmosis through it. In the diiTerent accounts of chemical sense-organs there are marked differences as regards the form of the nerve-endings. In many of the descriptions and figures of these organs the nerv^e-ending is represented as extending unbranched to the chitinous part of the organ, resembling in this respect those represented in Figure 148. In other accounts the gland-cell is surrounded by an involucre of nerve-cells (Fig. 149). 13-t AN INTRODUCTION TO ENTOMOLOGY In the types of chemical sense-organs described above the action of the chemical stimuli is supposed to be dependent upon osmosis through a delicate cuticular membrane. It should be noted, however, that sev- eral writers have de- scribed sense-cones in which there is a pore ; but the accuracy of these observations is doubted by other writers. A very different type of sense-organs which has been termed olfactory pores is de- scribed in the conclud- ing section of this chapter. Fig. 149.— Section of the external layers of the wall of an antenna of A crida turrita; Ct, cuticula; Ip, hypo- dermis; N, nerve; Nv, involucre of nerve-cells sur- rounding the glandular part of a sense-organ; Sbc, sensillum basiconicum; Sec, sensillum coeloconicum. Three sense-organs are figured; a surface view of the first is represented, the other two are shown in sec- tion. (From Berlese). XII. THE ORGANS OF SIGHT a. THE GENERAL FEATURES The two types of eyes of insects. — It is shown in the preceding chapter that insects possess two types of eyes, the ocelli or simple eyes and the compound or facetted eyes. Typically both types of eyes are present in the same insect, but either may be wanting. Thus many adult insects lack ocelli, while the larvae of insects with a complete metamorphosis lack compound eyes. When all are present there are two compound eyes and, typically two pairs of ocelli ; but almost invariably the members of one pair of ocelli are united and form a single median ocellus. The median ocel- lus is wanting in many insects that possess the other two ocelli. The distinction between ocelli and compound eyes. — The most obvious distinction between ocelli and compound eyes is the fact that in an ocellus there is a single cornea while in a compound eye there are many. Other features of compound eyes have been regarded as dis- tinctively characteristic of them; but in the case of each of these features it is found that they exist in some ocelli. THE INTERNAL ANATOMY OF INSECTS 135 Each ommatidium of a compound eye has been considered as a separate eye because its nerve-endings constituting the retinula are isolated from the retinulse of other ommatidia by surrounding acces- sory pigment cells; but a similar isolation of retinulas exist in some ocelli. It has also been held that in compound eyes there is a layer of cells between the corneal hypodermis and the retina, the crystalline-cone- cells, which is absent in ocelli ; but in the ocelli of adult Ephemerida there is a layer of cells between the lens and the retina, which, at least, is in a position analogous to that of the crystalline-cone-cells; the two may have had a different origin, but regarding this, we have, as yet, no conclusive data. The absence of compound eyes in most of the Apterygota. — Typically insects possess both ocelli and compound eyes ; when either kind of eyes is wanting it is evidently due to a loss of these organs and not to a generalized condition. Although compound eyes are almost universally absent in the Apterygota in the few cases where they are present in this group they are of a highly developed type and not rudimentary; the compound eyes of Machilis, for example, are as perfect as those of winged insects. The absence of compound eyes in larvae. — The absence of com- pound eyes in larvse is evidently a secondary adaptation to ilieir particular mode of life, like the internal development of wings in the same forms. In the case of the compound eyes of larvae, the develop- ment of the organs is retarded, taking place in the pupal stage instead of in an embryonic stage, as is the case with nymphs and naiads. While the development of the compound eyes as a whole is retarded in larvffi, a few ommatidia may be developed and function as ocelli during larval life. h. THE OCELLI There are two classes of ocelli found in insects : first, the ocelli of adult insects and of nymphs and naiads, which may be termed the primary ocelli; and second, the ocelli of most larvag possessing ocelli, which may be termed adaptive ocelli. The primary ocelli. — The ocelli of adult insects and of nymphs and naiads having been orig'nally developed as ocelli are termed the primary ocelli. Of these there are typically two pairs; but usually when they are present there are only three of them, and in many cases only a single pair. 136 AN INTRODUCTION TO ENTOMOLOGY When there are three ocelH, the double nature of the median ocel- lus is shown by the fact that the root of the nerve is double, while that of each of the other two is single. In certain generalized insects, as some Plecoptera, (Fig. 150) all of the ocelli are situated in the front; but in most insects, the paired ocelli have either migrated into the suture between the front and the vertex (Fig. 151), or have proceeded farther and are situated in the vertex. The structure of primary ocelli is described later. The adaptive ocelli. — Some larvae, as those of the Tenthredinidae, possess a single pair of ocelli, which in their position and in their structure agree with the ocelli of the adult insects ; these are doubtless primary ocelli. But most larvae have lost the primary ocelli; and if they possess ocelli the position of them and their structure differ greatly from the positions and structure of primary ocelli. Except in the few cases where primary ocelli have been retained by larvae, the ocelli of larvae are situated in a position corresponding to the position of the compound eyes of the adult (Fig. 152); and there are frequently several of these ocelli on each side of the head. This has led to the belief that they represent a few degenerate ommatidia, which have been retained by the larva, while the development of the greater nimiber of ommatidia has been retarded. For this reason they are termed Fig. 150. — Head of naiad of Pteronacys; dt, spots in the cnti- cula beneath which the dorsal arms of the adaptive ocelli. tached; the three The number of adaptive ocelli varies greatly, oceUi are on the front and sometimes is not con- (F), between these , , . . ,, two spots. stant m a species; thus in the larva of Corydalus, there may be either six or seven ocelli on each side of the head. There are also great variations in the struct- ure of adaptive ocelli. These variations pro- bably represent different degrees of degeneration or of retardation of development. The extreme of simplicity is found in certain dipterous lar\^as ; according to Hesse ('01) an ocellus of Cerato- pogon consists of only two sense-cells. As examples of com- plicated adaptive ocelli, those of lepidopterous larv^ae can be cited. Fig. 151. — Head of cricket. THE INTERNAL ANATOMY OF INSECTS 137 Fig. 152. — Head of a larva of Corydalus, dorsal aspect. The ocellus cf Gastropacha rubi, which is described and figured by Pankrath ('90), resembles in structure, to a remarkable degree, an ommatidium, and the same is true of the ocellus of the lar\^a of Arctia caja figured by Hesse (01). The structure of a visual cell. — The dis- tinctively characteristic feature of eyes is the presence of what is termed visual cells. In insects, and in other arthropods, a visual cell is a nerve-end-cell, which contains a nucleus and a greater or less amount of pigment, and bears a characteristic border, termed the rhabdomere; this is so called because it forms a part of a rhab- dom. The visual cells are grouped in such a way that the rhabdomeres of two or more of them are united to form what is known as a rhabdcm or optic rod. A group of two visual cells with therhabdom formed by their united rhabdomeres is shown in Figure 153, AandB. The form of the rhabdomere varies greatly in the visual cells of different insect eyes; and the number of rhab- domeres that enter into the composi- tion of a rhabdom also varies. Figure 153, C represents in a dia- grammatic manner the structure of rhabdomere as described by Hesse ('01). The rhabdomere (r) consists of many minute rodleti each with a minute knob at its base and connected with a nerve fibril. The structure cf a primary ocellus. — The primary ocelli vary greatly in the details of the form of their parts, but the essential features of their structure are illustrated by the accompanying diagram (Fig. 154). In some ocelli, as for example the lateral ocelli of scorpions, the visual cells are interpolated among ordinary hypodermal cells. Fig. 153. — Two visual cells from an ocellus of a pupa of Apis mellifica. A, longitudinal sec- tion ; B, transverse section; n, n, nerves; iiu, nucleus; r, rhabdom; p, pigment (After Redikorzew), C, diagram il- lustrating the structure of a rhabdomere; r, rhabdomere; c, cell-body (From Berlese after Hesse). 138 AN INTRODUCTION TO ENTOMOLOGY Fig. 154. — A diagram illustrating the structtire of a primary ocellus; c, cornea; c. hy, corneal hypodermis; ret, retina; n, ocellar nerve; p, accessory pigment cell; r, rhabdom. the two kinds forming a single layer of cells beneath the cornea; but in the ocelli of insects, the sense-cells form a distinct layer beneath the hypo- dermal cells. In this type of ocellus the fol- lowing parts can be dis- tinguished : The cornea. — T h e cornea (Fig. 154, c) is a transparent portion of the cuticula of the body- wall ; this may be lenti- cular in form or not. Tlie corneal hypoder- mis.— The hypodermis of the body-wall is con- tinued beneath the cornea (Fig. 154, c. hy.) ; this part of the hypo- dermis is termed by many writers the vitrecus layer of the ocellus; but the term corneal hypodermis, being a self- explanatory term, is preferable. Other terms have been applied to it, as the lentigen layer and the corneagen, both referring to the fact that this part of the hypodermis produces the cornea. The retina. — Beneath the corneal hypodermis is a second cellular layer, which is termed the retina, being composed chiefly or entirely of visual cells (Fig. 154, ret). The visual cells of the retina are grouped, as described above (Fig. 153), so that the rhabdomeres of several of them, two, three or four, unite to form a rhabdom; such a group of retinal cells is termed a retinula. The visual cells are nerve-end-cells, each constituting the termina- tion of a fiber of the ocellar nerve, and are thus connected with the central nervous system. Accessory pigment cells. — In some ocelli there are densely pig- mented cells between the retinulas, which serve to isolate them in a similar way to that in which the retinula of an ommatidium of a com- pound eye is isolated (Fig. 154, p). Even in cases where accessory pigment cells are wanting a degree of isolation of the rhabdoms of the retinulse of an ocellus is secured by pigment within the visual cells (Fig. 153, P)- THE INTERNAL ANATOMY OF INSECTS 139 Ocelli of Ephemerida. — It has been found that the ocelli of certain adult Ephemerida differ remarkably from the more com-mon type of ocelli described above. These peculiar ocelli have been described and figured by Hesse ('oi) and Seiler ('05). In them the cuticula over the ocellus, the comea, is arched but not thickened and the corneal hypo- dermis is a thin layer of cells immediately beneath it. Under the hypodermis there is a lens-shaped mass of large polygonal cells; and between this lens and the retina there is a layer of closely crowded columnar cells. The development of these ocelli has not been studied; hence the origin of the lens-shaped mass of cells and of the layer of cells between it and the retina is not known. C. THE COMPOUND EYES A compound eye consists of many quite distinct elements, the ommatidia, each represented externally by one of the many facets of which the cuticular layer of the eye is composed. As the ommatidia of a given eye are similar, a description of the structure of one will serve to illustrate the structure of the eye as a whole. The structure of an ommatidium. — The compound eyes of different insects vary in the details of their structure; but these variations are merely modi- fications of a common plan ; this plan is well -illustrated by the compound eyes of Machilis, the structure of which was worked out by Seaton ('03). Figure 155 represents a longitudinal section and a seiies of transverse sections of an ommatidium in an eye of this insect, which consists of the following parts. Ml , The cornea. — The cornea is a hexa- inr-» gonal portion of the cuticular layer of the eye and is biconvex in form (Fig. 155, c). The corneal hypodermis. — Beneath each facet of the cuticular layer of the eye are twe hypodermal cells Fig- 155- — An ommatidium of Machilis. The lettering is ex- plained in the text. 140 AN INTRODUCTION TO ENTOMOLOGY which constitute the corneal hypodermis of the ommatidium. These cells are quite distinct in Machilis and their nuclei are prominent (Fig. 155, hy); but in many insects they are greatly reduced, and consequently are not represented in many of the published figures of compound eyes. The crystalline-cone-ceUs. — Next to the corneal hypodermis there are four cells, which in one type of compound eyes, the eucone eyes, form a body known as the crystalline-cone, for this reason these cells are termed the crystalline-conc-cells (Fig. 155, cc). Two of these cells are represented in the figure of a longitudinal section and all four, in that of a transverse section. In each cell there is a prominent nucleus at its distal end. The iris -pigment-cells. — Surrounding the crystalline-cone-cells and the corneal hypodermis, there is a curtain of densely pigmented cells, which serves to exclude from the cone light entering other ommatidia; for this reason these cells are termed the iris -pigment (Fig. 155, i). They are also known as the distal retinula cells; but as they are not a part of the retina this term is misleading. There are six iris -pigment -cells surrounding each crystalline -cone; but as each of these cells forms a part of the iris of three adjacent ommatidia, there are only twice as many of these cells as there are ommatidia. This is indicated in the diagram of a transverse section (Fig. 15s, ^). The retinula. — At the base of each ommatidium, there is a group of visual cells forming a retinula (Fig. 1 55, r) ; of these there are seven in Machilis; but they vary in number in the eyes of different insects. The visual cells are so grouped that their united rhabdomeres form a rhabdom, which extends along the longitudinal axis of the ommati- dium (Fig. 155, r/j). The distal end of the rhabdom abuts against the proximal end of the crystalline-cone ; and the nerve-fibers of which the visual cells are the endings pass through the basement membrane (Fig. 155, b) to the optic nerve. The visual cells are pigmented and thus aid in the isolation of the ommatidium. The accessory pigment -cells. — In addition to the two kinds of pig- ment-cells described above there is a variable niunber of accessory pigment -cells (Fig. 155, ap), which lie outside of and overlap them. From the above it will be seen that each ommatidium of a eucone eye is composed of five kinds of cells, three of which, the corneal hypo- dermis, the crystalline-cone-cells, and the retinular cells produce solid structures; and three of them are pigmented. THE INTERNAL ANATOMY OF INSECTS 141 Three types of compound eyes are recognized: first, the eucone eyes, in these each ommatidium contains a true cry staUine -cone, as described above, and the nuclei of the cone-cells are in front of the cone; second, the pseudocone eyes, in these the four cone-cells are filled with a transparent fluid medium, and the nuclei of these cells are behind the refracting body; and third, the acone eyes, in which although the four cone -cells are present they do not form a cone, either solid or liquid. d. THE PHYSIOLOGY OF COMPOUND EYES The compound eyes of insects and of Crustacea are the most com- plicated organs of vision known to us. It is not strange therefore, that the manner in which they function has been the subject of much dis- cussion. It is now, however, comparatively well-understood; although much remains to be determined. In studying the physiology of compound eyes, three sets of struc- tures, found in each ommatidium, are to be considered: first, the dioptric apparatus, consisting of the cornea and the crystalline -cone; second, the percipient portion, the retinula, and especially the rhab- dom; and third, the envelope of pigment, which is found in three sets of cells, the iris pigment -cells, the retinular cells, and the accessory or secondary pigment- cells. The dioptrics of compound eyes is an exceedingly complicated subject ; a discussion of it would require too much space to be intro- duced here. It has been quite fully treated by Exner ('91). to whose work those especially interested in this subject are referred. The im.portant point for our present discussion is that by means of the cornea and the crystalline-cone, light entering the cornea from within the limits of a certain angle passes through the cornea and the crystal- line-cone to the rhabdom, which is formed of the combined rhab- domeres of the nerve-end-cells, constituting the retinula, the precipient portion of the ommatidium. The theory of mosaic vision. — The first two questions suggested by a study of physiology of compound eyes have reference to the nature of the vision of such an eye. What kind of an image is thrown upon the retinula of each ommatidium? And how are these images com- bined to form the image perceived by the insect? Does an insect with a thousand ommatidia perceive a thousand images of the object viewed or only one? The theory of mosaic vision gives the answers to these questions. This theory was proposed by J. Muller in 1826; and the most recent 142 j^N INTRODUCTION TO ENTOMOLOGY investigations confirm it. The essential features of it are the follow- ing: only the rays of light that pass through the cornea and the crystalline -cones reach the precipient portion of the eye, the others fall on the pigment of the eye and are absorbed by it ; in each ommatidium the cornea transmits to the crystalline -cone light from a very limited field of vision, and when this light reaches the apex of the crystalline- cone it forms a point of light, not an image; hence the image formed upon the combined retinute is a mosaic of points of light, which com- bined make a single image, and this rmage is an erect one. Figure 156 will serve to illustrate the mosaic theory of vision. In this figi-ire are represented the corneas (c), the crystalline -cones (cc), and the rhabdoms (r.) of several adja- cent ommatidia. It can be seen, from this diagram, that each rhabdom receives a point of light which comes from a limited portion of the object viewed (O) ; and that the image (I) received by the percipient portion of the eye is a single erect image, formed by points of light, each of which corresponds in density and color to the corresponding part of the object viewed. The distinctness of vision of a com- pound eye depends in part upon the num- ber and size of the ommatidia. It ca n be readily seen that the image formed by many small ommatidia will represent the details of the object better than one formed by a smaller number of larger ommatidia ; the smaller the portion of the object viewed by each ommatidium the more detailed -will be the image. The distinctness of the vision of a compound eye depends also on the degree of isolation of the light received by each ommatidium, which is determined by the amount and distribution of the pigment. Two types of compound eyes, differing in the degree of isolation of the light received by each ommatidiiun, are recognized; to one type has been applied the term day-eyes, and to the other, night-eyes. Day-eyes. — The type of eyes known as day-eyes are so-called because they are fitted for use in the day-time, when there is an abundance of light. In these eyes the envelope of pigment sur- rounding the transparent parts of each ommatidiimi is so complete that only the light that has traversed the cornea and crystalline-cone Fig. 156. — Diagram illustrat- ing the theory of mosaic vision. THE INTERNAL ANATOMY OF INSECTS 143 of that ommatidimn reaches its rhabdom. The image fonned in such an eye is termed by Exner an apposed image; because it is former^ by apposed points of Hght, falHng side by side and not overlapping. Such an image is a distinct one. Night-eyes. — In the night-eyes the envelope of pigment surround- ing the transparent parts of each ommatidiimi is incomplete ; so that rays of light entering several adjacent corneas can reach the same retinula. In such an eye there will be an overlapping of the points of light; the image thus formed is termed by Exner a superimposed image. It is obvious that such an image is not as distinct as an ap- posed image. It is also obvious that a limited amount of light will produce a greater impression in this type of eye than in one where a considerable part of the light is absorbed by pigment. Night-eyes are fitted to perceive objects and the movement of objects in a dim light, but only the more general features of the object can be perceived by them. Eyes with double function. — It is a remarkable fact that with many insects and Crustacea the compound eyes function in a bright ^ p light as day-eyes and in a dim light as night- eyes. This is brought about by movements in the pigment. If an insect having eyes of this kind be kept in a light place for a time and then killed while still in the light, its eyes will be found to be day-eyes, that is eyes fitted to form apposed images. But if another insect of the same species be kept in a dark place for a time and then killed while still in the dark, its eyes will be found to be night-eyes, that is eyes fitted to form superimposed images. Figure 157 represents two preparations showing the structure of the compound eyes of a diving-beetle, studied by Exner. In one (Fig. 157, A), each rhabdom is surrounded by an envelope of pigment, so that it can receive only the light passing through the crystalline-cone of the ommatidium of which this rhabdom is a part. This is the condition found in the individual killed in the light, and illustrates well the struct- ure of a day-eye. In the other preparation (Fig. 157, i5), which is from an individual killed in the dark, it can be seen that the pigment has moved up between the crystalline -cones so that Fig. 157. — Ommatidia from eyes of Colym- betes; A, day-eye condition; B, night- eye condition (From Exner). 144 AN INTRODUCTION TO ENTOMOLOGY the light passing from the tip of a cone may reach several rhabdoms, making the eye a night-eye. These changes in the position of the pigment are probably due to amoeboid movements of the cells. Divided Eyes. — In many insects each compound eye is divided into two parts; one of which is a day-eye, and the other a night-eye. The two parts of such an eye can be readily distinguished by a differ- ence in the size of the facets ; the portion of the eye that functions as a day-eye being composed of much smaller facets than that which functions as a night-eye. A study of the internal structure of a divided eye shows that the distribution of the pigment in the part composed of smaller facets is that characteristic of day-eyes ; while the part of the eye composed of larger facets is fitted to produce a superimposed image, which is the distinctive characteristic of night-eyes. Great differences exist in the extent to which the two parts of a divided eye are separated. In many dragon-flies the facets of a part of each compound eye are small, while those of the remainder of the eye are much larger ; but the two fields are not sharply separated. In some Blepharocera the two fields are separated by a narrow band in which there are no facets, and the difference in the size of the facets of the two areas is very marked. The extreme condition is reached in certain May-flies, where the two parts of the eye are so widely separa- ted that the insect appears to have two pairs of compound eyes (Fig 158). The tapetum. — In the eyes of many ariimals there is a structure that reflects back the light that has entered the eye, causing the well- known shining of the eyes in the dark. This is often observed in the Fig. i58.-Front of head of Cloeon, ^f ^^^g ^^^ ^^ ^^le eyes of moths showing divided eyes; a, night-eye; ; , i- 1 i, day-eye; c, ocellus (From Sharp), that are attracted to our light at night. The part of the eye that causes this reflection is termed a tapetum. The supposed function of a tapetimi is to increase the effect of a faint light, the light being caused to pass through the retina a second time, when it is reflected from the tapetimi. The structure of the tapetum varies greatly in different animals; in the cat and other carnivores it is a thick layer of wavy fibrous tissue; in spiders it consists of a layer of cells behind the retina containing THE INTERNAL ANATOMY OF INSECTS 145 small crystals that reflect the light ; and in insects it is a mass of fine tracheae surrounding the retinula of each ommatidium. XIII. THE ORGANS OF HEARING Fig. 159. — Side view of a locust with the wings removed; t, tympanum. a. THE GENERAL FEATURES The fact that in many insects there are highly specialized organs for the production of sounds indicates that insects possess also organs of hearing; but in only a few cases are these organs of such form that they have been gen- erally recognized as ears. The tympana. — In most of the jimiping Orthoptera there are thinned portions of the cuticula, which are of a structure fitted to be put in vibration by waves of sound. For this reason these have been commonly regarded as organs of hearing, and have been termed tympana. In the Acridiidae, there is a tympanum on each side of the first abdominal segment (Fig. 159); and in the Locustidee and in the Gryllidas, there is a pair of tympana near the proximal end of each tibia of the first pair of legs (Fig. 160). The chordotonal organs. — An ear to be effective must consist of something more than a membrane that will be put in vibration by means of sound; the vibrations of such a tympantmi must be trans- ferred in some way to a nerv- vous structure that will be influenced by them if the sound is to be perceived. Such structures, closely associated with the tympana of Orthoptera, were discovered more than a half century ago by Von Siebold (1844) and have been studied since by many investigators . The morphological unit of these essential auditory Fig. 160. — Fore leg of a katydid; /, tympa- num. 146 AN INTRODUCTION TO ENTOMOLOGY Fig. i6i. — Diagrammatic representation of the auditory organs of a locustid (After Graber). structures of insects is a more or less peg-like rod contained in a tubular nerve-ending (Fig. i6i, A and B); this nerve-ending may or may not be associated with a specialized t5rmpanum. To all sense-organs char- acterized by the presence of these auditory pegs, Graber ('82) applied the term chordotonal organs or fiddle-string-like organs. The scolopale and the scolopophore. — The peg-like rod characteris- tic of a chor- dotonal organ of an insect was named by Graber the scolopale; and to the tubular nerve-ending containing the scolopale, he applied the term scolopophore. The integumental and the subintegumental scolopo- phores. — ^With respect to their position there are two types of scolopophores ; in one, the nerve-ending is attached to the body-wall (Fig. 161, A); in the other, it ends free in the body-cavity (Fig. 161, B). These two types are designated respectively as integumental scolo- pophores and subintegumental scolopophores. The structure of a scolopophore. — In a scolopophore there can be distinguished an outer sheath (Fig. 161, I), which appears to be continuous either with the basement membrane of the hypodermis or with that of the epitheliirm of a trachea, and within this sheath the complicated nerve-ending; this nerve-ending is repre- sented diagrammatically in Figure 161 from Graber and in detail in Figure 162 from Hess ('17). In Figure 162 the following parts are represented: a bipolar sense-cell {sc) with its nucleus (sen) ; the proximal pole of this sense -cell is connected with the central nerv- ous system by a nerve; and its distal pole is connected phoreof the with the scolopale {s) by an axis -fiber (a/); surrounding mental type the distal prolongation of the sense-cell and the scolopale (From there is an enveloping or accessory cell {ec), in which ^^^s). there is a prominent nucleus {ecu) ; distad of the enveloping cell is THE INTERNAL ANA.TOMY OF INSECTS 147 the cap-cell {c:), in which there is a nucleus {ecu); extending from the end -knob (ek) of the scolopale and surrounded by the cap -cell there is an attacliment fiber or terminal ligament {tl) , by which the scolopophore is attached to the body-wall, the scolopophore repre- sented being of the integumental type; at the base of the scolopale and partly surrounding it, there is a vacuole (v) . The structure of a scolopale. — The scolopalas or auditory pegs are exceedingly minute and are quite uniform in size, regardless of the size of the insect in which they are ; but they vary in form in different insects. They are hollow (Fig. 162,5); but the wall of the scolopale is almost always thickened at its distal end, this forming an end-knob (Fig. 162, ^^). They are traversed by the axis -fiber of the sense -cell. The vacuole at the base of the scolopale connects with the limien of the scolopale; this vacuole is filled with watery fluid. In Figure 163 is shown a part of the scolopo- phore represented in Figure 162, more enlarged @(A), and three cross-sections (B, C, D) of the '■ scolopale. The wall of the scolopale is composed at either end of seven ribs (r), each of which is -(.^ij.;- divided in the central portion, making fourteen ^--— ^ ribs in this part. The entire scolopale, except possibly the terminal ligament, is bathed in the watery liquid, and is free to vibrate (Hess '17). Fig. i63.-Part of the j^ g^o^ld be remembered that the scolopate of scolopophore shown . . . in Figure 162 more different insects vary greatly in form; the one enlarged (From figu^j-ed here is merely given as an example of one type. The simpler forms of chordotonal organs. — In the simplest form of a chordotonal organ there is a single scolopophore; usually, how- ever, there are two or more closely parallel scolopophores. In figure 164, which represents a chordotonal organ found in the next to the last segment of the body of a larv^a of ChironomMS, these two types are represented, one part of the organ being composed of a single scolopo- phore, the other of several. The chordotonal ligament. — In Figure 164 the nerve connecting the chordotonal organ with the central nervous system is represented at n; and at U is shown a structure not yet mentioned, the chordo- tonal ligament, which is found in many chordotonal organs. Figure 165 is a diagrammatic representation of the relations of the chordo- tonal organs of a larva of Chironomus to the central nen.^ous system 148 AN INTRODUCTION TO ENTOMOLOGY and to the body-wall. Here each chordotonal organ is approxi- mately T-shaped; the proximal nerve forming the body of the T; the scolopophore, one arm; and the chor- dotonal ligament, the other arm. It will be observed that in this type of chordotonal organ the scolopophore and the ligament form a fiddle-string-like structure between two points in the wall of a single segment. It is believed that in cases of this kind the integument acts as a tympanum or sounding board. Fig. 164. — Chordotonal organ of a larva of Chironomus (From Graber). Fig. 165. — Diagram representing the chordotonal organs of a larva of Chiro- nomus (After Gra- ber). h. THE CHORDOTONAL ORGANS OF LARV^ Chordotonal organs have been observed in so many larvae that we may infer that they are commonly present in larvse. These organs are very simple compared with those of certain adult insects, described later. Those figured in the preceding paragraphs will serve to illus- trate the typical form of larval chordotonal organs. Even in the more complicated ones, there are comparatively few scolopophores ; and, as a rule, they are not connected with specialized tympana, but extend between distant parts of the body-wall, which probably acts as a sounding board. In certain larvse, however, the scolopophores are attached to specialized areas of the body -wall. Hess ('17) has shown that the pleural discs of cerambycid larvee, which are situated one on each side of several of the abdominal segments, serve as points of attachment of scolopophores. C. THE CHORDOTONAL ORGANS OF THE LOCUSTID^ In the Locustidae there are highly specialized ears situated one on each side of the first abdominal segment. The external vibrating THE INTERNAL ANA TOMY OF INSECTS 149 Fig. 1 66. — Side view of a locust with the wings removed; /, tympanum. part of these organs, the tympanum, is conspicuous, being a thinned portion of the body-wall (Fig. i66). Closely applied to the inner surface of each tympanum (Fig. 167, T), there is a ganglion known as Muller's organ {go), first described by Miiller (1826). This gan- glion contains many ganglion-cells and scolopalae and is the termination of a nerve extend- ing from the central nervous system, the auditory nerve (w). Figure 168 represents a section of Miiller's organ, showing the ganglion-cells and scolopalcE. Intimately associated with the Miiller's organ are two horny processes (Fig. 167,6' and m) and a pear-shaped vesicle (Fig. 167, hi)\ and near the margin of the tympanum, there is a spiracle (Fig. 167, St), which admits air to a space inside of the tympa- num, the tympanal air-chamber. As the nerve-end- ings in Miiller's or- gan are attached to the tympanum, it is a chordotonal organ of the integumental type; it is attached to a vibratile mem- brane, between two air-spaces. Fig. 167. — Ear of a locust, Caloptenus itallcus, seen from inner side; T, tympanum; TR, its border; o, u, two horn-like processes; bi, pear-shaped vesicle; n, audi- tory nerve; ga, terminal ganglion or Muller's organ; st, spiracle; M, tensor muscle of the tympanum (From Packard after Graber). d. THE CHORDOTONAL ORGANS OF THE TETTIGONIID^ AND OF THE GRYLLID^ In the long-horned grasshoppers and in the crickets, there is a pair of tympana near the proximal end of the tibia of each fore leg. In 150 AN INTRODUCTION TO ENTOMOLOGY --S many genera, these t}Tnpana are exposed and easily observed (Fig. 169) ; but in some genera each is covered by a fold of the body-wall and is consequently within a cavity, which communicates with the out- side air by an elongated opening (Fig. 170, a and b). Within the legs bearing these tympana, there are complicated chordotonal organs. Very de- tailed accounts of these organs have been pubhshed by Graber ('76), Adelung ('92) and Schwabe ('06); in this place, for lack of space, only their more general features can be described. Figure 171 represents a longi- tudinal section of that part of a fore tibia of Decticus verrucivorus in which the chordotonal organs are situated, and Figure 172 represents a cross-section of the same tibia, passing through the tympana and s, s, scolo- ii^Q air-chambers formed by the folds of the body-wall. In the fol- lowing account the references, in most cases, are to both of these figures. Fig. 168. — Section of Mullet's organ ganglion-cells; n, nerve; palie (After Graber). Fig. 169. — Fore leg of a katydid; i, tympa- ntun. a Fig. 1 70. — Tibia of a locustid with covered tympana; a, front view; &, side view; 0, opening (After Schwabe). The trachea of the leg.— The trachea of the leg figured in part here is remarkable for its great size and for its division into two branches, THE INTERNAL ANATOMY OF INSECTS 151 the front trachea (Ti) and the hind trachea (Tc) ; these two branches reunite a short distance beyond the end cf the chordotonal organs. It is an interesting fact that these large tracheae of the legs containing the chor- dotonal organs open through a pair of supemumery spir- acles, differing in this respect from the tra- chea cf the other legs. The spaces cf the leg. — ^ By reference to Figure 172, it will be seen that the two branches of the leg trachea occupy the middle space of the leg between the two tympana (Tie and ^ Tii) and separate an outer space, the upper one in the figure, from an inner space. The outer space (E) con- tains a chordotonal organ, of which the scolopale is repre- sented at S ; and the inner space contains small tracheae (t), muscles (m), the tibial nerve (Ntb), and a tendon (Tn). The interstices of the outer and inner spaces are filled with blood. In the outer space some leucocytes and fat-cells (Gr) are represented. The supra-tympanal or subgenual organ. — In the outer space of the tibia, a short distance above the tympana, there is a ganglion (Fig. Fig. 171. — Longitudinal section of a fore tibia of Decticus verrucivoms (From Berlese after Schwabe). 152 AN INTRODUCTION TO ENTOMOLOGY 171, Os) composed of nerve-endings, which are scolopophores of the integumental type. Two nerves extend to this ganglion, one from each side of the leg, and each divides into many scolopophores. The attachment fibers of the scolopophores converge and are attached to the wall of the leg. Two terms have been applied to this organ, both indicat- ing its position in the leg; one refers to the fact that it is above the tympana, the other, that it is below the knee. The intermediate or- gan.— Immediately below Fig. 172.— Transverse section of the fore tibia of +>ip ^inra tvmnanfll nrran Decticus verrucivorus (From Berlese after the supra-tympanal organ, Schwabe). In comparing this figure with the and between it and the preceding, note that in that one the external ^^„^^ described in the next parts are at the left, in this one, at the right. °^g^^ aescriDea mtnenext paragraph, is a ganglion composed of scolopophores of the subintegumental type; this is termed the intermediate organ (Fig. 171, Oi). Siebold's organ or the crista acustica. — On the outer face of the front branch of the large trachea of the leg there is a third chordo- tonal organ, the Siebold's organ or the crista acustica. A surface view of the organ is given in Figure 171 and a cross-section is represented in Figure 172. It consists of a series of scolopophores of the subintegu- mental type, which diminish in length toward the distal end of the organ (Fig. 171). The relation of Siebold's organ to the trachea is shown in Figure 172. It forms a ridge or crest on the trachea, shown in setion at cr in Figure 172; this suggested the name crista acustica, used by some writers. e. THE Johnston's organ There has been found in the pedicel of the antenna of many insects, representing several of the orders, an organ of hearing, which is known as the Johnston's organ, having been pointed out by Christopher Johnston (1855). This organ varies somewhat in form in different THE INTERNAL ANATOMY OF INSECTS 153 insects and in the two sexes of the same species; but that of a male mosquito will serv^e as an example illustrating its essential features. The following account is based on an in- vestigation by Professor Ch. / M. Child ('94). In an an- tenna of a mos- quito (Fig. 173) the scape or first segment, which contains the muscles of the antenna, is much smaller than the pedicel or second seg- ment, and is usually over- looked, being concealed b y the large, glob- ular pedicel; the clavola con- sists of thirteen slender seg- ments. Excepting one or two terminal segments, each segment of the clavola bears a whorl of long, slender setae; these are more prominent in the male than in the female. Figure 174 represents a longitudinal section of the base of an antenna; in this the following parts are shown: S, scape; P, pedicel, C, base of the first segment of the clavola; cp, conjunctival plate connecting the pedicel with the first segment of the clavola; pr, chitinous processes of the conjunctival plate; m, muscles of the antenna; N, principal antennal nerve; n, nerve of the clavola; immediately within the wall of the segments there is a thin layer of hypodermis; the lumen of the pedicel is largely occupied by a" ganglion composed of scolopophores, the attachment fibers of which are attached to the chitinous proce'-ses of the conjunctival plate. Fig. 173. — Antennas of mosquitoes, Culex; female; s, scape; p, pedicel. 154 AN INTRODUCTION TO ENTOMOLOGY As to the action of the auditory apparatus as a whole, it was shown experimentally by Mayer ('74) that the different whorls of setae borne by the segments of the clavola, and which gradually decrease in length on successive segments, are caused to vibrate by different notes ; and it is believed that the vibrations of the setse are transferred to the conjunctival plate by the clavola, and thence to the nerve-end- ings. It was formerly believed that the great specialization of the Johnston's or- gan in male mosqui- toes enabled the males to hear the songs of the females and thus more readily to find their mates. But it has been found that in some species, at least, of mosqui- toes and of midges in which the males have this organ high- ly specialized the fe- males seek the males. This has led some writers to doubt that the Johnston's organ is auditory in function. But the fact remains that its distinctive feature is the presence of scolopalae, which is the dis- tinctive characteristic of the auditory organs of other insects. Fig. 1 74. — Longitudinal section of the base of an anten- na of a male mosquito, Corethra culiciformis (After Child). XIV. SENSE-ORGANS OF UNKNOWN FUNCTIONS In addition to the sense-organs discussed in the foregoing account there have been described several types of supposed sense-organs which are as yet very imperfectly understood. Among these there is one that merits a brief discussion here on account of the frequent references to it in entomological literature. Many different names have been applied to the organs of this type; of these that of sense domes is as appropriate as any, unless the conclusions of Mclndoo, referred to on the following page, are confirmed, in which case his term olfactory pores will be more descriptive. THE INTERNAL ANATOMY OF INSECTS 155 a b Fig. 175. — Sense-domes (From Berlese). The sense-domes are found in various situations, but they occur chiefly on the bases of the wings and on the legs. Each sense-dome consists of a thin, hemispherical or more nearly spherical membrane, which either projects from the outer end of a pore in the cuticula (Fig. 175, a) or is more or less deeply enclosed in such a pore (Fig. 175, h)\ intergrades between the two types represented in the accom- panying figures occur. When a sense-dome is viewed in section a nerve- ending is seen to be connected with the dome-shaped or bell- like membrane. A striking feature of these organs is the absence of any gland -cells connected with them, such as are found in the chemical sense-organs described on an earlier page. In one very important respect there is a marked difference in the accounts of these organs that have been published. The organs were first discovered long ago by Hicks ('57); but they have been more carefully studied in recent years by several writers, who have been able to make use of a greatly improved histological technic; among these writers are Berlese (09 a), Vogel ('11), Hochreuter (12'), Lehr ('14), and Mclndoo ('14). All of the writers mentioned above except the last named maintain that the sense-cell ends in a structure, in the middle of the sense-dome, which differs in appearance from both the membrane of the sense- dome and the body of the sense-cell. This structure varies in form in different sense- domes; in some it is cyHndrical, and is consequently described as a peg; in others, it is greatly flattened so that it is semilunar in form when seen in section. In Figure 175, ^. which represents a section made transversely to the long axis of this part it appears peglike ; but in Figure 175,0, which represents a longitudinal view of it, it is semilunar in form. According to Mclndoo (Fig. 176) no structure of this kind is Fig. 176 — Olfactory pore of Mclndoo (From Mclndoo) 156 AN INTROD UCTION TO ENTOMOLOG Y present, but the sense-fiber of the sense-cell pierces the bottom of the cone and enters the round, oblong, or slit-like pore-aperture. "It is thus seen that the cytoplasm in the peripheral end of the sense- fiber comes in direct contact with the air containing odorous par- ticles and that odors do not have to pass through a hard membrane in order to stimulate the sense-cell as is claimed for the antennal organs." XV. THE REPRODUCTIVE ORGANS a. THE GENERAL FEATURES In insects the sexes are distinct. Formerly Termitoxenia, a genus of wingless, very aberrant Diptera, the members of which live in nests of Termites, was believed to be hermaphroditic, but this is now doubted. Individuals in which one side has the external characters of the male and the other those of the female are not rare ; such an individual is termed a gyndndromorph; in some gynandromorphs, both testes and ovaries are present but in no case are both functional ; these there- fore are not true hermaphrodites. In females the essential reproductive organs consist of a pair of ovaries, the organs in which the ova or eggs are developed, and a tube leading from each ovary to an external opening, the oviduct. In the male, the essential reproductive organs are a pair of testes, in which the spermatozoa are developed and a tube leading from each testis to an external opening, the vas deferens. In addition to these essential organs, there are in most insects accessory organs, these consist of glands and of reservoirs for the reproductive elements. The form of the essential reproductive organs and the number and form of the accessory organs vary greatly in different insects. It is impossible to indicate the extent of these variations in the limited space that can be devoted to this subject in this work. Instead of attempting this it seems more profitable to indicate by diagrams, one for each sex, the relations of the accessory organs that may exist to the essential organs. In adult insects the external opening of the reproductive organs is on the ventral side of the abdomen near the caudal end of the body. The position of the opening appears to differ in different insects and in some cases in the two sexes of the same species. The lack of uni- formity in the published accounts bearing on this point is partly due to differences in numbering the abdominal segments; some authors describing the last segment of the abdomen as the tenth while others THE INTERNAL ANATOMY OF INSECTS 157 believe it to be the eleventh; embryological evidence supports the latter view. In most insects there is a single external opening of the reproduc- tive organs; but in the Ephemerida and in a few other insects the two efferent ducts open separately. Secondary sexual characters. — In addition to differences in the essential reproductive organs and in the genital appendages of the two sexes, many insects exhibit what are termed secondary sexual characters. Among the more striking of these are differences in size, coloring, and in the form of certain organs. Female insects are usually larger than the males of the same species; this is due to the fact that the females carry the eggs ; but in those cases where the males fight for their mates, as stag-beetles, the males are the larger. ing differences in the color- ing of the two sexes are common, especially in the Lepidoptera. In many insects the antennee of the male are more highly specialized than those of the female; and this is true also of the eyes of certain insects. These are merely a few of the many known secondary sexual characters found in insects. Strik- Fig. 178- Repro- ductive organs of Japyx, female (After Grassi) . b. THE REPRODUCTIVE ORGANS OF THE FEMALE The general features of ^~. . - --^5^ the ovajy.— In the more ^JJ^^ p^^^^^**^^^^s==^ usual form of the ovaries of insects, each ovary is a compact, more or less spindle- shaped body composed of many paral- lel ovarian tubes (Fig. 177, 0), which open into a common efferent tube, the oviduct. In CampoJ^a, however, there is a single ovarian tube; and in certain other Thysanura the ovarian tubes have a metameric arrangement (Fig. 178). The nvim- Fig. 177. — Diagram of thereproduc- tive organs of a female insect; 0, ovary; od, oviduct; c, egg-calyx; v, vagina; 5,spermatheca; 6c, bursa copulatrix; sg, spermathecal gland; eg, colleterial glands. 158 AN INTRODUCTION TO ENTOMOLOGY ber of ovarian tubes differs greatly in different insects; in many Lepidoptera there are only four in each ovary; in the honeybee, about 150; and in some Termites, 3000 or more. The wall of an ovarian tube..— The ovarian tubes are lined with an epithelial layer, which is supported by a basement membrane; out- side of this there is a peritoneal envelope, composed of connective tis- sue; and sometimes there are muscles in the peritoneal envelope. The zones of an ovarian tube. — Three different sections or zones are recognized in an ovarian tube; first, the terminal filament, which is the slender portion which is farthest from the oviduct (Fig. 179, /); second, the germarium, this is a comparatively short chamber, between the other two zones (Fig. 179, g); and third, the vitellarium, which constitutes the greater portion of the ovarian tube. The contents of an ovarian tube. — In the germarium are found the primordial germ-cells from which the eggs are devel- oped; and in the vitellarium are found the developing eggs. In addition to the cells that develop into eggs there are found, in the ovarian tubes of many insects, cells whose function is to furnish nutriment to the developing eggs; these are termed nurse-cells. Depending upon the presence cr ab- sence of nurse-cells and on the location of the nurse-cells when present, three types of ovarian tubes are recognized: first, those without distinct nurse-cells (Fig. 1 79, A) ; second, those in which the eggs and masses of nurse-cells alternate in the ovarian tube (Fig. 179, B); and third, those in which the nurse-cells are restricted to the germarium (Fig. 179, C), which thus becomes a nutri- tive chamber. In the latter type the developing eggs are each con- nected by a thread with the nutritive chamber. The egg-follicles. — The epithelium lining of the ovarian tube becomes invaginated between the eggs in such a way that each egg is Fig. 179. — Three ovarian tubes; e, e, e, eggs; n, n, n, nurse-cells (After Berlese). THE INTERNAL ANA TOMY OF INSECTS 159 enclosed in an epithelial sac or egg-follicle, which passes down the tube with the egg (Fig. 179). There is thus a tendency to strip the tube of its epithelium, but a new one is constantly formed. The functions of the follicular epithelium. — It is believed that in some cases, and especially where the nurse-cells are wanting, the follicular epithelium serves a nutritive function. Eut the most obvious function cf this epithelium is the formation cf the chorion or egg-shell, which is secreted on its inner surface. The pit-like mark- ings so common on the shells of insect eggs indicate the outlines of the cells of the follicular epithelium. The ligament of the ovary. — In many insects, the terminal fila- ments of the several ovarian tubes of an ovary unite and form a slender cord, the ligament of the ovary, which is attached to the dorsal diaphragm; but in other insects this ligament is wanting, the terminal filaments ending free in the body cavity. The oviduct. — The common outlet of the ovarian tubes is the ovi- duct (Fig. jj-j, od). In most insects the oviducts of the two ovaries unite and join a common outlet, the vagina; but in the Ephemerida and in some Dermaptera each oviduct has a separate opening. The egg-calyx. — In some insects each oviduct is enlarged so as to form a pouch for storing the eggs, these pouches are termed the egg- calyces (Fig. 177, c.) The vagina. — The tube into which the oviducts open is the vagina (Fig. 177, v). The vagina differs in structure from the oviducts, due to the fact that it is an invagination of the body-wall, and, like other invaginations of the body- wall, is lined with a cuticular layer The spermatheca. — The spermatheca is a sac for the storage of the seminal fluid (Fig. 177,5). As the pairing of the sexes takes place only once in most insects and as the egg-laying period may extend over a long time, it is essential that provision be made for the fertilization of the eggs developed after the union of the sexes. The eggs become full- grown and each is provided with a shell before leaving the ovarian tubes. At the time an egg is laid a spermatozoan may pass from the spermatheca, where thousands of them are stored, into the egg through an opening in the shell, the micropyle, which is described in the next chapter (Figs. 184 and 185). In some social insects, eggs that are developed years after the pairing took place are fertilized by spermatozoa that have been stored in the spermatheca. The bi'rsa copulatrix. — In many insects there is a pouch for the reception of the seminal fluid before it passes to the spermatheca. 160 AN INTRODUCTION TO ENTOMOLOGY This pouch is known as the bursa copulatrix or copulatory pouch. In some insects this pouch is a diverticulimi of the vagina (Fig. 177, he); in others it has a distinct external opening, there being two external openings of the reproductive organs, the opening of the vagina and the opening of the bursa copulatrix. When the bursa copulatrix has a distinct external opening there may or may not be a passage from it to the vagina. In at least some Orthoptera (Melanoplus) there is no connection between the two; ^^ when the eggs are laid they are w^ ^ — "J^^ »■ — V. pushed past the opening of the ^^""V^'-''^ V-^"" bursa copulatrix where they are 4/\ j^-^'.i ■5"'m^.-'#' fertilized. '^^''^f^^^^^^''^^^^S^^^^^m..o:r In the Lepidoptera (Fig. 180), Tj^n feB^^==£=:^E^^^i:^^ there is a passage from the bursa ^' {^^dfjJ^-^'^ ^^^^^^^^^^^^^^^ copulatrix to the vagina. In J^§^-ov ^ this case the seminal fluid is Fig. i8o.-Reproductive organs of the I'eceived by the bursa copulatrix femaleof the milkweed butterfly; a, at the time of pairing, later it anus; ft, opening of the bursa copula- . .1^ Qnermathprfl anrl trix; ov, ovarian tubes; /, terminal passes to tne spermatneca, ana filaments of the ovary; v, opening from here it passes to the Vagina, of the vagina (After Burgess). ^ ^^^^^ copulatrix is said to be wanting in Hymenoptera, Diptera, Heteroptera and Homoptera except the Cicadas. The coUeterial glands.— There are one or two pairs of glands that open into the vagina near its outlet (Fig. 177, eg); to these has been applied the general term coUeterial glands. Their function differs in different insects ; in some insects they secrete a cement for gluing the eggs together, in others they produce a capsule or other covering which protects the eggs. The spermathecal gland. — In many insects there is a gland that opens either into the spermatheca or near the opening of the sperma- theca, this is the spermathecal gland (Fig. 177, sg). C. THE REPRODUCTIVE ORGANS OF THE MALE The reproductive organs of the male are quite similar in their more general features to those of the female; but there are striking differ- ences in details of form. The general features of the testes. — As the reproductive elements developed in the testes, the spermatazoa, always remain small, the testes of a male are usually much smaller than the ovaries of the female of the same species. THE INTERNAL ANATOMY OF INSECTS 161 In the more common form, each testis is a compact body (Fig. i8i, t) composed of a variable number of tubes corresponding with the ovarian tubes, these are commonly called the testicular follicles; but it would have been better to have termed them the testicular tubes, reserving the term follicle for their divisions. The testicular follicles vary in number, form, and in their arrangement. In many insects as the Neuroptera, the Hemiptera, the Diptera, and in Campodea and Japyx, each testis is composed of a single follicle. In some beetles, Carabidse and Elateridae, the follicle is long and rolled into a ball. In some Thy- sanura the testicular follicles have a metameric arrangement. In some Coleoptera, each testis is separated into several masses, each having its own outlet leading to the vas deferens; while in some other insects the two testes approach each other during the pupal stage and constitute in the adult a single mass. The structure of a testicular follicle. — Like the ovarian tubes, the testicular follicles are lined with an epithelial layer, which is sup- ported by a basement membrane, outside of which there is a peritoneal envelope composed And in these follicles a series of zones are distinguished in which the genital cells are found in different stages of development, corresponding to the successive generations of these cells. In addition to the terminal filament four zones are recog- nized as follows: The germarium. — This includes the primordial germ-cells and the spermatogonia. The zone of growth. — Here are produced the spermatocytes of the first order and the spermatocytes of the second order. The zone of division and reduction. — In this zone are produced the Spermatids or immature spermatozoa. The zone of transformation. — Here the spermatids become sper- matozoa. A discussion of the details of the development of the successive generations of the genital cells of the male, or spermatogenesis, does not fall within the scope of this volume. Fig. 1 8 1 . — D i agram of the reproductive or- gans of a male insect ; the right testis is shown in section; ag, acces- sory glands; ed, eja- culatory duct; ^i^, semi- nal vesicles; t, testes; vd, vasa deferentia. of connective tissue. 162 AN INTRODUCTION TO ENTOMOLOGY The spermatophores. — In some insects the spermatozoa become enveloped in a sac in which they are transferred to the female; this sac is the spermatophore. Spermatophores have been observed in Gryllidse, Locustidae, and certain Lepidoptera. Other structures. — A ligament of the testis, corresponding to the ligament of the ovary, is often present ; the common outlet of the testi- cular follicles, corresponding to the oviduct is termed the vas deferens (Fig. i&i, vd); an enlarged portion of the vas deferens serving as a reservoir for the products of the testis is known as a seminal vesicle (Fig. i8i, sv); the invaginated portion of the body-wall, correspond- ing with the vagina of the female, is the ejaculatory duct (Fig. i8i, ed); accessory glands, corresponding to the colleterial glands of the female, are present (Fig. i8i, ag); the function of these glands has not been determined, they may secrete the fluid part of the semen, and they probably secrete the spermatophore when one is formed; the penis, this is merely the chitinized terminal portion of the ejaculatory duct, which can be evaginated with a part of the invaginated portion of the body-wall. It is furnished with powerful muscles for its protrusion and retraction. XVI. THE SUSPENSORIA OF THE VISCERA The organs discussed here do not constitute a well-defined system, but are isolated structures connected with different viscera. As in most cases they appear to serve a suspensory function, they are grouped together provisionally as the sus- pensoria of the viscera. The dorsal diaphragm. — This is a mem- branous structure which extends across the . _ , abdominal cavity immediately below the ^. , heart, to which it is attached along its median -„. -Diagram shov/- 0^11.1 • <• ^1 • j- 1 ing the relation of the hne. i he lateral margms 01 this diaphragm dorsal diaphragrn and are attached to the sides of the body by a the ventral diaphragm . . . , , . , • 1 1 to other viscera; a, series of triangular prolongations, which have alimentary canal; d, been commonly known as the -wings of the dorsal diaphragm; h, , ,^. s ^1 -, 11-1 heart; n, ventral nerv- heart (Fig. 139, c). The dorsal diaphragm IS ous system; v, ventral composed largely of very delicate muscles, diaphragm. ^ , . / , . .,, -, , .1 Its relation to the heart is illustrated by the accompanying diagram (Fig. 182, d). There are differences of opinion as to the function of the dorsal diaphragm. An important function is probabh^ to protect the heart THE INTERNAL A NA TOM Y OF INSECTS 163 from the peristaltic movements of the ahmentary canal. It also supports the heart; and it may play a part in its expansion. The dorsal diaphragm is also known as the pericardial diaphragm. The ventral diaphragm. — The ventral diaphragm is a very delicate membrane which extends across the abdominal cavity immediately above the ganglia of the central nervous system. It is quite similar in form to the dorsal diaphragm ; it is attached along each side of the body, just laterad of the great ventral muscles, by a series of pro- longations resembling in form the wings of the heart. The position of the ventral diaphragm is illustrated in Figure 182, v. This diaphragm has been described as a ventral heart; but I believe that its function is to protect the abdominal ganglia of the central nervous system from the peristaltic movements of the alimen- tary canal. The thread-like suspensoria of the viscera. — Under this head may be classed the ligament of the ovary and the ligament of the testis, already described. In addition to these, there is, in some insects at least, a thread-like ligament that is attached to the intestine. XVII. SUPPLEMENTARY DEFINITIONS There are found in the bodies of insects certain organs not referred to in the foregoing general account of the internal anatomy of insects. These organs, though doubtless very important to the insects in which they occur, are not likely to be studied in an elementary course in entom-ology and, therefore, a detailed account of them may well be omitted from an introductory text -book. This is especially true as our knowledge of the structure and functions of these organs is so incomplete that an adequate discussion of the conflicting views now held v/ould require more space than can be devoted to it here. The organs in question are the following : The oenocytes. — The term cenocytes is applied to certain very large cells, that are found in clusters, often metamerically arranged, and connected with the tracheae and the fat body of insects. The name was suggested by the light yellow color which often characterizes these cells, the color of certain wines; but the name is not a good one, as oenocytes vary greatly in color. Several other names have been applied to them but they are generally known by the name used here. Two types of oenocytes are recognized: first, the larval oenocytes; and second, the imaginal oenocytes. 164 AN INTRODUCTION TO ENTOMOLOGY The lar\^al oenocytes are believed by Verson and Bisson ('91) to be ductless glands which take up, elaborate, and return to the blood definite substances, which may then be taken up by other cells of the body. Other views are held by other writers, but the view given above seems, as this time to be the one best supported by the evidence at hand. As to the function of the imaginal oenocytes, there are some obser- vations that seem to show that they are excretory organs without ducts, cells that serve as storehouses for excretory products, becoming more filled with these products with the advancing age of the insect. The pericardial cells. — The term fericardial cells is applied to a distinct type of cells that are found on either side of the heart in the pericardial sinus or crowded between the fibers of the pericardial diaphragm. These cells can be rendered very conspicuous by injecting ammonia carmine into the living insect some time before killing and dissecting it ; by this method the pericardial cells are stained deeply while the other cells of the body remain uncolored. It is believed that the pericardial cells absorb albuminoids origina- ting from the food and transform them into assimilable substances. The phagocytic organs. — The term phagocyte is commonly applied to any leucocyte or white blood corpuscle that shows special activity in ingesting and digesting waste and harmful materials, as disinte- grating tissue, bacteria, etc. The action of phagocytes is termed phagocytosis; an excellent example of phagocytosis is the part played by the leucocytes in the breaking down and rebuilding of tissues in the course of the metamorphosis of insects ; this is discussed in the next chapter. Phagocytosis may take place in any part of the body bathed by the blood and thus reached by leucocytes. In addition to this widely distributed phagocytosis, it is beheved that in certain insects there are localized masses of cells which perform a similar function; these masses of cells are known as the phagocytic organs. Phagocytic organs have been found in many Orthoptera and in earwigs; they are situated in the pericardial region; and can be made conspicuous by injecting a mixture of ammonia carmine and India ink into the body cavity; by this method the pericardial cells are stained red and the phagocytic organs black. The light-organs. — The presence of organs for producing light is widely distributed among living forms both animal and vegetable. THE INTERNAL ANA TOMY OF INSECTS 165 The most commonly observed examples of light-producing insects are certain members of the Lampyridas, the fireflies and the glow-worms, and a member of the Elateridas, the "cucujo" of the tropics. With these insects the production of light is a normal function of highly specialized organs, the light-organs. Examples of insects in which the production of light is occasionally observed are larvee of mosquitoes, and certain lepidopterous larvae. In these cases the production of light is abnormal, being due either to the presence in the body of light-producing bacteria or to the ingestion of luminescent food. The position of the specialized light-organs of insects varies greatly; in the fireflies, they are situated on the ventral side of the abdomen; in the glow-worms, along the sides of the abdomen; and in the cucujo, the principal organs are in a pair of tubercles on the dorsal side of the prothorax and in a patch in the ventral region of the metathorax. The structure of the light-organs of insects varies in different insects, as is shown by the investigations of several authors. A good example of highly specialized light-organs are those of Photinus marginellus, one of our common fireflies. An excellent account of these is that of Miss Townsend ('04), to which the reader is referred. A detailed account of the origin and development of the light-organs of Photurus pennsylvanica is given by Hess ('22). CHAPTER IV. THE METAMORPHOSIS OF INSECTS Many insects in the course of their lives undergo remarkable changes in form ; a butterfly was once a caterpillar, a bee lived first the life of a climisy footless grub, and flies, which are so graceful and activ e, are developed from maggots. In the following chapters considerable attention is given to descriptions of the changes through which various insects pass; the object of this chapter is merely to discuss the more general features of the metamorphosis of insects, and to define the terms commonly used in descriptions of insect transformations. I. THE EXTERNAL CHARACTERISTICS OF THE META- MORPHOSIS OF INSECTS The more obvious characteristics of the metamorphosis of insects are those changes in the external form of the body that occur during postembryonic development. In some cases there appears to be but little in common between the successive forms presented by the same insect, as the caterpillar, chrysalis, and adult stages of a butterfly. On the other hand, in certain insects, the change in the form of the body during the postembryonic life is comparatively little. Based on these differences, several distinct types of metamorphosis have been recognized; and in those cases where the insect in its successive stages assumes different forms, distinctive terms are applied to the different stages. a. THE EGG Strictly speaking, all insects are developed from eggs, which are formed from the primordial germ-cells in the ovary of the female. As a rule, each egg is surrounded by a shell, formed by the follicular epithelium of the ovarian tube in which the egg is developed; and this egg, enclosed in its shell, is deposited by the female insect, usually on or near the food upon which the young insect is to feed. In some cases, however, the egg is retained by the female until it is hatched; thus flesh-flies frequently deposit active larvag upon meat, especially when they have had difficulty in finding it; and t'.ere are other vivi- parous insects, which are discussed later. In tl" ! s place is discussed (166) THE METAMORPHOSIS OF INSECTS 167 the more common type of insect eggs, those that are laid while still enclosed in their shell. The shape of the egg. — The terms ovoid and ovate have a definite meaning which has been derived from the shape of the eggs of birds ; but while many eggs of insects are ovate in form, many others are not. The more common form of insect eggs is an elongate oval, some- what curved; this type is illustrated by the eggs of crickets (Fig. 183, i); many eggs; are approx- imately spherical, as those of some butterflies (Fig. 183, 2) ; while some are of remarkable shape, two of these are represented in Figure 183,3, 4. The sculpture of the shell. — Almost always the external surface of the shell gonal areas; these are the Fig. 183. — Eggs of insects; 1 , CEcanthus nigri- cornis; 2, CEnis semidea; 3, Piezoslerum subidatum; 4, Hydromeira martini. of an insect egg is marked with small, hex imprints of the cells of the follicular epi- thelium, which formed the shell. In many cases the ornamentation of the shell is very conspicuous, consisting of prominent ridges or series of tubercles ; this is well -shown in the eggs of many Lepidoptera (Fig. 184). The micropyle. — It has been shown, in the course of the discussion of the reproductive organs of the female, that the egg becomes full-grown, and the protecting chorion or egg-shell is formed about it before it is fertilized. This renders necessary some provision for the entrance of the male germ -cell into the egg; this provision consists of one or more openings in the shell through which a spermatozoan may enter. This opening or group of openings is termed the micropyle. Fig. 184.— Egg of the cotton- worm moth; the micropyle is shown in the center of the lower figure. 168 AN INTRODUCTION TO ENTOMOLOGY Fig. 185.— Egg Drosophila melan- ogaster; m, micro- pyle. The number and position of the micropylar openings varies greatly in the eggs of different insects. Frequently they present an elaborate pattern at one pole of the egg (Fig. 184); and sometimes they open through more or less elongated papillae (Fig. 185). While in most cases it is necessary that an egg be fertilized in order that development may continue, there are many instances of par- thenogenesis among insects. The number of eggs produced by insects. — A very wide variation exists in the number of eggs produced by insects. In the sheep-tick, for example, a single large egg is produced at a time, and but few are produced during the life of the insect; on the other hand, in social insects, as ants, bees, and termites, a single queen may produce hundreds of thousands of eggs during her lifetime. These, however, are extreme examples; the peculiar mode of development of the larva of the sheep-tick within the body of the female makes possible the production of but few eggs; while the division of labor in the colonies of social insects, by which the func- tion of the queen is merely the production of eggs, makes it possible for her to produce an immense number ; this is especially true where the egg-laying period of the queen extends over several years. The following may be taken as less extreme examples. In the solitary nest-building insects, as the fossores, the solitary wasps, and the solitary bees, the great labor involved in making and provisioning the nest results in the reduction of the number of eggs produced to a comparatively small number; while many insects that make no pro- vision for their young, as moths, for example, may lay several hundred eggs. With certain chalcis-flies the number of young produced is not dependent upon the number of eggs laid ; for with these insects many embryos are developed from a single egg. This type of development is termed polyembryony. Modes of laying eggs. — Perhaps in no respect are the wonderful instincts of insects exhibited in a more remarkable way than in the manner of laying their eggs. If insects were reasoning beings, and if each female knew the needs of her young to be, she could not more accurately make provision for them than is now done by the great majority of insects. THE METAMORPHOSIS OF INSECTS 169 This is especially striking where the life of the young is entirely different from that of the adult. The butterfly or moth may sip nectar from any flower; but when the female lays her eggs, she selects with unerring accuracy the particular kind of plant upon which her larvae feed. The dragonfly which hunts its prey over the field, returns to water and lays her eggs in such a position that the young when it leaves the egg is either in or can readily find the element in which alone it is fitted to live. The ichneumon-flies frequent flowers; but when the time comes for a female to lay her eggs, she seeks the particular kind of larva upon which the species is parasitic, and will lay her eggs in no other. It' is a remarkable fact that no larva leads so secluded a life that it cannot be found by its parasites. Thus the larvae of Tremex columba bore in solid wood, where they are out of sight and protected by a layer of wood and the bark of the tree in which they are boring; nevertheless the ichneumon-fly Megarhyssa lunator, which is parasitic upon it, places her eggs in the burrows of the Tremex by means of her long drill-like ovipositor (Fig. i86). In contrast with the exam- ples just cited, some insects exhibit no remarkable instinct in their egg-laying. Our com- mon northern walking-stick, Diapheromera, drops its eggs on the ground under the shrubs and trees upon which it feeds. This, however, is sufficient pro- vision, for the eggs are pro- tected throughout the winter by the fallen leaves, and the young when hatched, readily find their food. Many species, the young of which feed upon foliage, lay their eggs singly upon leaves; but many others, and this is especially tine of those, the young of which are gregarious, lay their eggs in clusters. In some cases, as in the squash bug, the mass of eggs is not protected (Fig. 187) ; in others, where the duration of the egg-state is long, the eggs are protected by some covering. The females of our tent- caterpillars cover their eggs with a water-proof coating; and the tussock moths of the genus Hemerocampa covertheir egg-clusters with a frothy mass. Fig. 186. — Megarhyssa lunator. 170 AN INTRODUCTION TO ENTOMOLOGY The laying of eggs in compact masses, however, is not correlated, in most cases, with gregarious habits of the larvas. The water- scavenger beetles, Hydrophilidae, make egg-sacks out of a hardened silk-like secretion (Fig. i! the locusts, Acridiidas, lay their eggs in oval masses and cover them with a tough substance; the scale-insects of the genus Puhinaria excrete a large cottony egg-sac (Fig. 189); ^^ Fig. 187 — Egg-mass of the squash-bug. Fig. 188. — Egg-ssLCot Hydrophilus (After Miall). Fig. 189. — Pulvinan'atnnumerabUis, females on grape with egg sacb the eggs of the praying mantis are laid in masses and overlaid with a hard covering of silk (Fig. igo) ; and cockroaches produce pod-like egg-cases, termed ootheca, each containing many eggs (Fig. 191). Among the more remarkable of the methods of caring for eggs is that of the lace-winged flies, Chrysopa. These insects place each of their eggs on the summit of a stiff stalk of hard silk (Fig. 192). Duration of the egg-state. — In the life-cycle of most insects, a few days, and only a few, intervene between the laying of an egg and the emergence of the nymph, naiad, or larva from it. In some the duration of the egg-state is even shorter, the hatching of the egg taking place very soon after it is laid, or pray- even, as sometimes in flesh-flies, before it is laid. On the m a i> *^^^*^^ hand, in certain species, the greater part of the life of an tis. individual is passed within the egg-shell. The common apple-tree tent-caterpillars, Clisiocampa americana, lays its eggs in early summer; but these eggs do not hatch till the fol- lowing spring ; while the remainder of the life-cycle occupies only a i:)D. o f THE METAMORPHOSIS OF INSECTS 171 few weeks. The eggs of Bittacus are said to remain unhatched for two years; and a similar statement is made regarding the eggs of our common walking-stick. b. THE HATCHING OF YOUNG INSECTS Only a few accounts have been published ■regarding the manner in which a young insect frees itself from the embryonic envelopes. In ^'^cockmad?!^^''''^ °^ ^ some cases it is evident that the lar\^a cuts its way out from the egg-shell by means of its mandibles ; but in others, a specialized organ has been developed for this purpose. The hatching spines. — An organ for rupturing the embryonic envelopes is probably commonly pre- sent. It has been des- cribed under several names. It was termed an egg-burster by Hagen, the niptor ovi by C. V. Riley an egg-tooth by Heymons, and the hatching spines by Wheeler. Fig. 192. — Eggs, larva, cocoon, and adult of Chrysopa. C. THE MOLTING OF INSECTS The young of insects cast periodically the outer parts of the cuticula; this process is termed molting or ecdysis. General features of the molting of insects.— The chitinization of the epidermis or primary cuticula adds to its efficiency as an armor, but it prevents the expansion of the body-v/all rendered necessary by the growth of the insect; consequently as the body grows, its cuticula becomes too small for it. When this occurs a second epidermis is formed by the hypodermis; after which the old epidermis splits open, usually along the back of the head and thorax, and the insect works itself out from it. The new epidermis being elastic, accommodates itself to the increased size of the body ; but in a short time it becomes chitinized; and as the insect grows it in turn is cast off. The cast skin of an insect is termed the exuvice, the plural noun being used as in English is the word clothes. 172 AN INTRODUCTION TO ENTOMOLOGY Coincident with the formation of the new epidermis, new setae are formed beneath the old epidermis; these He closely appressed to the outer surface of the new epidermis until released by the molting of the old epidermis. In the above account only the more general features of the process of molting are indicated, the details, according to the observations of Tower ('06) are as follows. (See Figure 1 13, p. 99). In the formation of the new epidermis it appears as a thin, delicate lamella, spread evenly over the entire outer surface of the hypodermis; it grows rapidly in thickness until finally, just before ecdysis takes place, it reaches its final thickness. After ecdysis the epidermis hardens rapidly and its coloration is developed. As soon as ecdysis is over the deposition of the dermis or secondary cuticula begins. This layer is a carbohydrate related to cellulose, and is deposited in layers of alternating composition, through the period of reconstruction and growth, during which it reaches its maximum thick- ness. Preliminary to ecdysis a thin layer of molting fluid is formed, and through its action the old dermis is corroded and often almost entirely destroyed, thus facilitating ecdysis. This dissolving of the dermis, is, according to Tower, a most constant phenomenon in ecdysis and has been found in all insects examined by him in varying degrees. It is said that the Collembola molt after reaching sexual maturity, in this respect agreeing with the Crustacea and the "Myriapoda," and differing from the Arachnida and from all other insects (Brindley '98). The molting fluid. — As indicated above, the process of molting is facilitated by the excretion of a fluid known as the molting fluid. This is produced by unicellular glands (Fig. 1 13, p. 99) which are modified hypodermal cells. These glands are found all through the life of the insect and upon all parts of the body; but are most abundant upon the pronotum, and are more abundant at pupation than at any other period. The number of postembryonic molts. — A very wide range of vari- ation exists as to number of molts undergone by insects after they leave the egg-shell. According to Grassi ('98, p. 292), there is only a single partial molt with Campodea and Japyx, while the May-fly Chloeon molts twenty times. Between these extremes every condition exists. Probably the majority of insects molt from four to six times ; but there are many records of insects that molt many more times than this. Stadia. — The intervals between the ecdyses are called stadia. In numbering the stadia, the first stadium is the period between hatching and the first postembryonic ecdysis. Instars. — The term instar is applied to the form of an insect during a stadium; in numbering the instars, the form assumed by the insect between hatching and the first postembryonic molt is termed the first instar. THE METAMORPHOSIS OF INSECTS 173 Head measurements of larvse. — It was demonstratedby Dyar ('90) that the widths of the head of a larva in its successive instars follow a regular geometric progression in their increase. The head was selected as a part not subject to growth during a stadium; and the width as the most convenient measurement to take. By means of this criterion, it is possible to determine, when studying the transfor- mations of an insect, whether an ecdysis has been overlooked or not. Experience has shown that slight variations between the computed and the actual widths may occur; but these differences are so slight that the overlooking of an ecdysis can be readily discovered. The following example will serve to illustrate the method employed. A lan^a of Papilio thoas was reared from the egg; and the widths of the head in the successive instars was found to be, expressed in milhmeters, as follov/s: .6; i.i; 1.6; 2.2; 3.4. By dividing 2.2. by 3.4 (two successive members of this series), the ratio of increase was found to be .676+ ; the number, .68 was taken, therefore, as sufficiently near the ratio for practical purposes. By using this ratio as a factor the following results were obtained: Width foimd in fifth instar = 3.4 Calculated width in fourth instar (3.4 X .68) = 2.312 " "third " (2.312 X .68) =... . 1.57 " " " second " (1.57 X .68) = 1.067 " " first (1.067 X .68) = 72s By comparing the two series, as is done bslow, so close a correspond- ence is found that it is evident that no ecdysis was overlooked. Widths found: — .6; i.i; 1.6; 2.2; 3.4 " calculated: — .7; 1.1-; 1.6-; 2.3. The reproduction of lost limbs. — The repro- duction of lost limbs has been observ^ed in many insects ; but such reproduction occurs here much less frequently than in the other classes of the Arthropoda. The reproduction takes place dur- ing the period of ecdysis, the reproduced part becoming larger and larger with each molt; hence with insects, and with Arachnida as well, the power of reproducing lost limbs ceases with the attainment of sexual maturity; but not so with the Crustacea and the "Myriapoda" which molt after becoming sexually mature. In none Fig. 93-— A spider in Qf ^he observed examples of the reproduction which lost legs we: e . , , ^- 1 1 j j being reproduced of appendages has an entire leg been reproduced. 174 AN I NT ROD UCTION TO ENTOAIOLOCY It appears to be necessary that the original coxa be not removed in order that the reproduction may take place. Figure 193 represents a spider in our collection in which two legs, the left fore leg and the right hind leg, were being reproduced when the specimen was captured. d. DEVELOPMENT WITHOUT METAMORPHOSIS (Anietabolous* Development) While most insects undergo remarkable changes in form during their postembryonic development, there are some in which this is not the case. In these the young insect just hatched from the egg is of practically the same form as the adult insect. These insects grow larger and may undergo slight changes in form of the body and its appendages; but these changes are not sufficiently marked to merit being termed a metamorphosis. This type of development is known technically as ametdholoiis development. Development without metamorphosis is characteristic of the two orders Thysanura and Collembola, which in other respects, also, are the most generalized of insects. The nature of the changes in form undergone by an insect with an ametabolous development is iUustratcd by the development of Machilis alternata, one of the Thysanura. The first instar of this insect, according to Heymons ('07), lacks the clothing of scales, the styli on the thoracic legs, and the lateral rows of eversi- ble sacs on the abdominal segments; and the antennae and cerci are relatively shorter and consist of a much smaller rumber of segments than those of the adult. These changes, however, are comparable with those undergone by many animals in the course of their development that are not regarded as having a metamorpho- sis. In common usage in works on Entomology the term metamorphosis is used to indicate those m^arked changes that take place in the appearance of an insect that are correlated with the development of wings. In addition to the Thysanura and the Collembola there are certain insects that develop without metamorphosis, as the Mallophaga and the Pediculida^. But their ametabolous condition is believed to be an acquired one. In other words, it is believed that the bird-lice and the true Hce are descendants of winged insects whose form of body and mode of development have been modified as a result of parasitic life. The Ametabola. — Those insects that develop without meta- morphosis are sometim.es referred to as the Ametabola. This term was first proposed by Leach (18 15), who included under it the lice as well as the Thysanura and Collembola. But with our present knowledge, if it is used it should be restricted to the Thysanura and Collembola, those insects in which a development without metamorphosis is a primitive not an acquired conditicn. *Ametabolous: Greek a, without; metabole (fieTa^o\-n), change. 2 HE METAMORPHOSIS OF INS.iCTS 175 e. GRADUAL METAMORPH ) IS {Paurometaboloits* Development) In several orders of insects there exists a type of development that is characterized by the fact that the young resemble the adult in the general form ot the body and in manner of life. There is a gradual growth of the body and of the wing rudiments and genital appendages. Fig. 194. — Nymph of Mela- noplus, first instar (After Emerton). Fig. 195. — Nymph of Mela- noplus, second instar (After Emerton). Fig. 196. — Nymph of Melano- plus, third instar (After Emer- ton) Fig, 198. — Nymph of Melano- plus, fifth instar (After Emer- ton), Fig. 197. — Nymph of Melano- plus, fourth instar (After Emerton). Fig. 199. — Melanoplus, adult. But the changes in form take place gradually and are not very great between any two successive instars except that at the last ecdysis there takes place a greater change, especially in the wings, than at any of the preceding ecdyses. This type of metamorphosis is desig- nated as gradual metamorphosis or paurometabolous development. The characteristic features oi paurometabolous development are correlated with the fact that the mode of life of the young and of the *Paurometabolous : pauros (TraCpos), little; nietahole {fiera^o'Ki^)^ change. 176 AN INTROD UCTION TO ENTOMOLOG Y adult are essentially the same; the two living in the same situation, and feeding on the same food. The adult has increased power of loco- motion, due to the completion of the development of the wings; this enables it to more readily perform the functions of the adult, the spread of the species, and the making of provision for its continuance; but otherwise the life of the adult is very similar to that of the young. The development of a locust or short-homed grasshopper will serve as an example of gradual metamorphosis. Each of the instars of our common red-legged locust, Alclanoplus feniur-rtibrttm, is repre- sented in the accompanying series of figures. The adult (Fig. 199) is represented natural size; each of the other instars somewhat enlarged; the hair line above the figure in each case indicates the length of the insect. The young locust just out from the egg-shell can be easily recog- nized as a locust (Fig. 194). It is of course much smaller than the adult ; the proportion of the different regions of the body are some- what different ; and it is not furnished with wings ; still the form of the body is essentially the same as that of the adult. In the second and third instars (Fig. 195 and 196) there are sHght indications of the development of wing-rudiments; and these rudimentary wings are quite conspicuous in the fourth and fifth instars (Fig. 197 and 198). The change at the last ecdysis, that from the fifth instar to the adult, is more striking than that at any preceding ecdysis ; this is due to the complete expansion of the wings, which takes place at this time. The Paurometabola, — Those orders of insects that are characterized by a gradual metamorphosis are grouped together as the Paurometa- bola. This is not a natural division of the class Hexapoda but merely indicates a similarity in the nature of the metamorphosis in the orders included. This group includes the Isoptera, Dermaptera, Orthop- tera, Corrodentia, Thysanoptera, Homoptera, and Hemiptera. The term nymph. — An immature instar of an insect that undergoes a gradual metamorphosis is termed a nymph. In old entomological works, and especially in those written in the early part of the last century, the term nymph was used as a synonym of pupa ; but in more recent works it is applied to the immature instar of insects that undergo either a gradual or incomplete metamorphosis. In this book I restrict the use of this term to designate an immature instar of an insect that undergoes a gradual metamorphosis. Deviation from the usual type. — It is to be expected that within so large a group of organisms as the Paurometabola there should have THE ME TA MORPHOSIS OF INSECTS 177 been evolved forms that exhibit deviations from the usual type of development. The more familiar examples of these are the following: The Saltatorial Orthoptera. — In the crickets, locusts, and long- homed grasshoppers, the wings of the nymphs are developed in an inverted position ; that surface of the wing which is on the outside in the adult is next to the body in the nymphal instars; and the rudi- mentary hind wings are outside of the fore wings, instead of beneath them, as in the adult. At the last ecdysis the wings assume the normal position. The Cicadas. — In the Cicadas there exists a greater difference between the nymphal instars and the adult than is usual with insects in which the metamorphosis is gradual. The nymphs live below the surface of the ground, feeding upon the roots of plants; the adults live in the open air, chiefly among the branches of trees. The forelegs of the nymphs are fossorial (Fig. 200) ; this is an adaptation for subterranean life, which is not needed and not possessed by the adults. And it is said that the last nymphal instar is quiescent for a period. The CoccidcB. — In the Coccidae the mode of devel- opment of the two sexes differ greatly. The female never acquires wings, and in so far as external form is concerned the adult is degenerate. The male, on the other hand, exhibits a striking approach to com- plete metamorphosis, the last nymphal instar being enclosed in a cocoon, and the legs of the adult are not those of the nymph, being developed from imaginal Pig. 200. — disks. But the wings are developed externally. ^iSdai After ^^^ AleyrodidcB.—ln this family the type of meta- Riley). morphosis corresponds quite closely with that described later as complete metamorphosis; con- sequently the term larva is applied to the immature instars except the last, which is designated the pupa. The wings arise as histoblasts in the late embryo, and the growth of the wing-buds during the larval stadia takes place inside the body- wall. The change to the pupal instar, in which the wing-buds are external, takes place beneath the last larval skin, which is known as the pupa case or puparium. The adult emerges through a T-shaped opening on the dorsum of the puparium. Both sexes are winged. The Aphididce. — In the Aphididae there exists a remarkable type of development known as heterogamy or cyclic reproduction. This is characterized by an alternation of several parthenogenetic generations 178 AN INTRODUCTION TO ENTOMOLOGY with a sexual generation. And within the series of parthenogenetic forms there may be an alternation of winged and wingless forms. In some cases the reproductive cycle is an exceedingly complicated one ; and different parts of it occur on different food plants. The Thysanoptera. — In the Thysanoptera, as in most other insects with a gradual metamorphosis, the nymphs resemble the adults in the form of the body, and the wings are developed externally; but the last nymphal instar is quiescent or nearly so and takes no nourishment. This instar is commonly described as the pupa. /. INCOMPLETE METAMORPHOSIS (Hemimetabolous* Development) In three of the orders of insects, the Plecoptera, Ephemerida, and Odonata, there exists a type of metamorphosis in which the changes Fig. 20I -Transformation of a May-fly, Ephemera varia; A, adult; B, naiad (After Needham). that take place in the form of the body are greater than in gradual metamorphosis but much less marked than in complete metamorpho- sis. For this reason the terms incomplete metamorphosis and hemi- metaboloiis development have been applied to it. Both incomplete metamorphosis and complete metamorphosis are characterized by the fact that the immature instars exhibit adaptive modifications of form and structure, fitting them for a very different mode of life than that followed by the adult. This is often expressed by the statement that the im.mature instars are "sidewise developed" ; for it is believed that in these cases the development of the individual does not repeat the history of the race to which the individual belongs. *Hemimetabolous : hemi {vM-^), half; metabole (/ucto^oX'^), change. THE ME TA MORPHOSIS 0 F INSECTS 1 79 This mode of development is termed cenogenesis* It contrasts strongly with gradual metamorphosis, where there is a direct develop- ment from the egg to the adult. In each of the orders that are characterized by an incomplete metamorphosis, the adaptive characteristics of the young insects fit them for aquatic life; while the adults lead an aerial existence. The transformations of a May-fly (Fig. 201) will serve to illustrate this type of metamorphosis. The primitive insects were doubtless terrestrial ; this is shown by the nature of the respiratory system, which is aerial in all insects. In the course of the evolution of the different orders of insects, the immature forms of some of them invaded the water in search of food. This resulted in a sidewise development of these immature forms to better fit them to live in this medium; while the adult continued their development in, what may be termed by contrast, a direct line. In some of the Plecoptera, as Capnia and others, the results of the ceno- genetic development are not marked except that the immature forms are aquatic. In the three orders in which the metamorphosis is incomplete, the cenogenetic development of the immature instars involved neither a change in the manner of development of the wings nor a retarding of the development of the compound eyes; consequently these immature forms, although sidewise developed, constitute a class quite distinct from larvae. The Hemimetabola. — The three orders in which the development is a hemimetabolous one are grouped together as the Hemimetabola; these are the Plecoptera, Ephemerida, and Odonata. This grouping together of these three orders is merely for convenience in discussions of types of metamorphosis and does not indicate a natural division of the class Hexapoda. The radical differences in the three types of aquatic respiratory organs characteristic of the three orders indicate that they were evolved independently. The term naiad. — The immature instars of insects with an incom- plete metamorphosis have been termed nymphs; but as a result of their sidewise development they do not properly belong in the same class as the immature instars of insects with a gradual metamorphosis. I, therefore, proposed to designate them as naiads (Comstock '18, h). The adoption of the term naiad in this sense affords a distinctive term for each of the three classes of immature insects corresponding to the three types of metamorphosis, i. e., nymphs, naiads, and larvae. "Cenogenesis: kainos (Kaivos), new; genesis. 180 AN INTRODUCTION TO ENTOMOLOGY Deviation from the usual type of incomplete metamorphosis. — The more striking deviations from the usual type of hemimetabolous devel- opment are the following: The Odonata. — In theOdonata the wings of the naiads are inverted; these insects resembling in this respect the Saltitorial Orthoptera. What is the upper surface of the wings with naiads becomes the lower surface in the adults, the change taking place at the last ecdysis. The Ephemerida. — In the Ephemerida, there exists the remarkable phenomenon of an ecdysis taking place after the insect has left the water and acquired functional wings. The winged instar that is interpolated between the last aquatic one and the adult is termed the sub-imago. g. COMPLETE METAMORPHOSIS (Holometabolus* Development) The representatives of several orders of insects leave the egg-shell in an entirely different form from that they assume when they reach maturity; familiar examples of these are caterpillars which develop into butterflies, maggots which develop into flies, and grubs which develop into beetles. These insects and others that when they emerge from the egg-shell bear almost no resemblance in form to the adult are said to undergo a complete metamorphosis or a holometdbolous development. The Holometabola. — Those orders that are characterized by a holometabolous development are grouped together as the Holometab- ola. This group includes the Neuroptera, Mecoptera, Trichoptera, Lepidoptera, Diptera, Siphonaptera, Coleoptera, and Hymenoptera. This grouping together of these orders, while convenient for dis- cussions of metamorphosis, is doubtless artificial. It is not at all probable that the Holometabola is a monophylitic group. In other words complete metamorphosis doubtless arose several times inde- pendently in the evolution of insects. The term larva. — The form in which a holometabolous insect leaves the egg is called larva. The term was suggested by a belief of the ancients that the form of the perfect insect was masked, the Latin word larva meaning a mask. Formerly the term larva was applied to the immatiu-e stages of all insects; but more recent writers restrict its use to the immature in- *Holometabolous : Jiolos {&'>^oi), complete; metabole (/ieTo^oX^), change. THE METAMORPHOSIS OF INSECTS 181 stars of insects with a complete metamorphosis; and in this sense only is it used in this book. The adaptive characteristics of larvae. — The larvas of insects with complete metamorphosis, like the naiads of those with incomplete metamorphosis, exhibit an acquired form of body adapting them to special modes of life; and in this case the cenogenetic or "sidewise development" is much more marked than it is in insects with an incomplete metamorphosis. Here the form of the body bears but little relation to the form to be assumed by the adult, the nature of the larval life being the controlling factor. The differences in form between larvae and adults are augmented by the fact that not only have larvae been modified for special modes of life, but in most cases the adults have been highly specialized for a different mode of life; and so great are these differences that a quiescent pupa stage, during which certain parts of the body can be made over, is necessary. Here, as in the case of insects with an incomplete metamorphosis, we have an illustration of the fact that natural selection can act on any stage in the develop- ment of animal to better adapt that particular stage to the conditions under which it e-cists. Darwin pointed out in his "Origin of Species" that at whatever age a variation first appears in the parent it tends to reappear at a corresponding age in the offspring. This tendency is termed homochronous heredity* . It is obvious that the greater the adaptive characteristics of the immature forms, the less does the ontogeny of a species represent the phylogeny of the race to which it belongs. This fact led Fritz MuUer, in his "Facts for Darwin", to make the aphorism "There were perfect insects before larv£e and pupje." The overlooking of this principle frequently results in the drawing of unwarranted con- clusions, by those writers on insects who cite adaptive larval characteristics as being more generalized than the corresponding features of the adult. The more obvious of the adaptive characteristics of larvae are the following : The form of the body. — As indicated above the form of the body of a larva bears but httle relation to the form to be assumed by the adult, the nature of the larval life being the controlling factor in determining the form of the body. As different larvae live under widely differing situations, various types of lar\^as have been developed; the more important of these types are described later. The greater or less reduction of the thoracic legs. — In the evolution of most larvce there has taken place a greater or less reduction of the thoracic legs; but the extent of this reduction varies greatly. The larvae of certain Neuroptera, as Cory dolus for example, have as perfect "Homochronous: homos ipixo's), one and the same; chronos (xp^vos), time. 182 AN INTRODUCTION TO ENTOMOLOGY legs as do naiads of insects with an incomplete m etamorphosis. The larv£e of Lepidoptera have short legs which correspond to only a part of the legs of the adidt. While the larvae of Diptera have no external indications of legs. The development of prolegs in some larvce. — A striking feature of many larvae is the presence of abdominal organs of locomotion; these have been termed prolegs; the prolegs of caterpillars are the most familiar examples of these organs. The prolegs were so named because they were believed to be merely adaptive cuticular formations and not true legs; this belief arose from the fact that they are shed with the last larval skin. Some recent writers, however, regard the prolegs as true legs. It is now known that abdominal appendages are common in the embryos of insects; and these writers believe that the prolegs are developed from these embryonic appendages, and that, therefore, they must be regarded as true legs. If this is true, there has taken place a remarkable reversal in the course ot development. The abdominal legs, except those that were modified into append- ages of the reproductive organs, the gonapophyses, were lost early in the phylogeny of the Hexapoda. The origin of complete metamorphosis must have taken place at a much later period; when, according to this belief, the abdominal appendages^ which had been latent for a long time, were redeveloped into functional organs. The development of tracheal gills. — A striking feature of many larvae is the possession of tracheal gills. This is obviously an adaptive characteristic the development of which was correlated with the assumption of aquatic life by forms that were primarily aerial; and it is also obvious that the development of tracheal gills has arisen indepandently many times; for they exist in widely separated families belonging to different orders of insects that are chiefly aerial. They are pDsssssed by a few lepidopterous larvas, and by the representatives of several families of Neuroptera, Coleoptera and Diptera. On the other hand, in the Trichoptera the possession of tracheal gills by the larvce is characteristic of nearly all members of the order. The internal developnent of wings. — This is perhaps the most re- markable of the sidewise developments of larvae. Although larvae exhibit no external indications of wings, it has been found that the rudiments of these organs arise at as early a period in insects with a complete metamorphosis as they do in those with an incomplete m.etamorphosis ; and that during lan^al life the wing rudiments attain an advanced stage in their development. But as these rudiments are invaginated there are no external indications of their presence during larval life. The details of the internal development of wings are dis- cussed later. THE MET A MORPHOSIS OF INSECTS 183 Occasionally atavistic individual larvse are found which have external wing-buds. As to the causes that brought about the internal development of wings we can only make conjectures. It has occurred to the writer that this type of wing- development may have arisen as a result of boring habits, or habits of an analogous nature, of the stem forms from which the orders of the Holometabola sprang. Projecting wing-buds would interfere with the progress of a boring insect; and, therefore, an embedding of them in the body, thus leaving a smooth contour, would be advantageous. In support of this theory attention may be called to the fact that the larvag of the most generalized Lepidoptera, the Hepialidaj, are borers; the larva2 'A the Siricidas, which are among the more generalized of the Hymenoptera are oorers; so too are many Coleoptera; most larvae of Diptera are burrowers; and -he larvae of Trichoptera live in cases. The retarding of the development of the compound eyes.— One of the most distinctively characteristic features of larvze is the absence of compound eyes. The life of most larvse is such that only limited vision is necessary for them; and correlated with this fact is a retard- ing of the development of the greater portion of the compound eyes ; only a few separate ommatidia being functional during larval life. In striking contrast with this condition are the well-developed eyes of nymphs and naiads. The larvae of Corethra and Panorpa are the only larv^as known to me that possess compound eyes. The invaginated conditions of the head in the larvcB of the more specialized Diptera. — The extreme of sidewise development is exhib- ited by the larvae of the more specialized Diptera. Here not only are the legs and wings developed internally but also the head. This phenomenon is discussed later. The different types of larvae. — As a rule, the larvae of the insects of any order resemble each other in their more general characteristics, although they bear but little resemblance to the adult forms. Thus the grubs of Coleoptera, the caterpillars of Lepidoptera, or the mag- gots of Diptera, in most ca^es, can be recognized as such. Still in each of these orders there are larvse that bear almost no resemblance to the usual type. As examples of these may be cited the water- pennies (Parnidae, Coleoptera), the slug-caterpillars (Cochlidiidae, Lepidoptera), and the larvae of Microdon (Diptera). To understand the variations in form of larvae it should be borne in mind that the form of the body in all larvae is the result of secondary adaptations to peculiar modes of life; and that this modification of form has proceeded in different directions and in varying degrees in different insects. 184 ^A^ INTRODUCTION TO ENTOMOLOGY Among the many types of larvs, there are a few that are of such common occurrence as to merit distinctive names; the more im- portant of these are the following: Campodeiform. — In many paurometabolous insects and in some holometabolous ones, the early instars resemble Campodea more or less in the form of the body (Fig. 202); such naiads and larvae are described as campodeiform. In this type, the body is long, more or less flattened, and with or without caudal setae ; the mandibles are well developed; and the legs are not greatly reduced. Among the examples of this type are the larvae of most Neuroptera, and the active larvas of many Coleoptera (Cara- bidas, Dysticidas, and the first instar of Me- loidae). Eruciform. — The eruciform type of larvae is well-illustrated by most larv« of Lepidoptera and of Mecoptera; it is the caterpillar form (Fig. 203). In this type the body is cylindrical; the thoracic legs are short, having only the terminal portions of them developed; and the abdomen is furnished with prolegs or with proleg-like cuticular folds. Although these larvae move freely, their powers of locomo- tion are much less than in the campodeiform type. Scarabeiform. — The common white grub, the larva of the May- beetle (Fig, 204) is the most familiar example of a scarabeiform larva. Fig. 202. — Campodea slaphylinus (After Lubbock). Fig. 203. — The silk-worm, an eruciform larva (After Verson). In this type the body is nearly cylindrical, but usually, especially when at rest, its longitudinal axis is curved ; the legs are short ; and THE METAMORPHOSIS OF INSECTS 185 prolegs are wanting. This type is quite characteristic of the lar\^£e of the Scarabaeidag, hence the name ; but it occurs in other groups of insects. The movements of these larvae are slow; most of them live in the ground, or in wood, or in decaying animal or vegetable matter. Vermiform. — Those larvae that are more or less worm-like in form are termed vermiform. The most striking features of this type are the elongated Fig. 204. — Larva of Melolontha form of the body and an absence of vukaris (After Schiodte). locomotive appendages (Fig. 205). Naupliiform. — The term naupliiform is applied to the first instar of the larva of Platygaster (Fig. 206), on account of its resemblance to the nauplius of certain Crustacea. The prepupa. — Usually the existence of an instar between the last lan.^al one and the pupal instar is not recognized. But such a form exists; and the recogni- tion of it becomes important when a careful study is made of the development of holometabolous insects. As is shown later, during larval life the develop- ment of the wings is going on within the body. As the larva approaches maturity, the wings reach an advanced stage of development within sac-like invagi- nations of the body-wall. Near the close of the last larval stadium the insect makes preparation for the change to the pupa state. Some form a cell within which the pupa state is passed, the larvae of butter- flies suspend themselves, and most larvae of moths spin a cocoon. Then follows a period of apparent rest before the last larv^al skm is shed and the pupal state assumed. But this period is far from being a quiet one; within the apparently motionless body important changes p^ ^^ take place. The most easily observed of these Larva of a changes is a change in the position of the wings, crane-fly. Each of these passes out through the mouth of the sac in which it has been developed, and lies outside of the newly developed pupal cuti- cula, but beneath the last larval cuticula. Then follows a period of variable duration in different insects, in which the wings are really 186 AN INTRODUCTION TO ENTOMOLOGY outside of the body although still covered by the last larval cuticula , this period is 206. — Larva of Platygaster (After Ganin.) the prepupal stadium. The prepupal instar differs markedly from both the last larval one and from the pupa ; for after the shedding of the last larval cuticula important changes in the form of the body take place before the pupal instar is assimied. The pupa. — The most obvious characteristics of the pupa state are, except in a few cases, inactivity and help- lessness. The organs of locom.otion are functionless, and may even be soldered to the body throughout their entire length, as is usual with the pupae of Lepidoptera (Fig. 207). In other cases, as in the Coleoptera (Fig. 208) and in the Hymenoptera, the wings and legs are free, but enclosed in more or less sac-like cuticular sheaths, which put them in the condition of the pro- verbial cat in gloves. More than this, in most cases, the legs of the adult are not fully formed till near the end of the pupal stadium. The term pupa, meaning girl, was applied to this instar by Linnseus on account of its resemblance to a baby that has been swathed or bound up, as is the custom with many peoples. Although the insect during the pupal stadiun^. is apparently at rest, this, from a physiological point of view, is the most active period of its postembryonic exist- encp; for wonderful changes in the struc- p-„ 207.— Pupa of a moth. cure of the body take piaffe at this time. In the development of a larva the primitive form of the body has been greatly modified to adapt it to its peculiar mode of life; tl-iis sidewise development results in the production of a type of body that is not at all fitted for the duties of adult life. In the case of an insect with incomplete meta- morphosis, the full grown naiad needs to be modified comparatively little to fit it for adult life; but the change from a maggot to a fly, or from a caterpiller to a butterfly, involves not merely a change in external form but a greater or less remodeling of its entire structure. These changes take place during the period of apparent . est, the prepupal and pupal stadia. The chrymlis.— The term chrysalis is often applied to the pupffi of butterflies. It was suggested by the golden ^ spots with which the pups of certain butterflies are ornamented. Two forms of this word are in use: first, chrysalis, the plural of which is chrysalides; and second, chrysalid, the pltiral of which is THE METAMORPHOSIS OF INSECTS 187 chrysalids. The singular of the first form and the plural of the second are those most often used. Active piipcB. — The pupae of mosquitoes and of certain midges are remarkable for being active. Although the wings and legs are func- tionless, as with other pupae, these creatures are able to swim by means of movements of the caudal end of the body. In several genera of the Neuroptera (Chrysopa, Hemerobius, and Raphidia) the pupa becomes active and crawls about just before transforming to the adult state. Movements of a less striking character are made by many pups, which work their way out of the ground, or from burrows in wood, before transforming. In some cases, as in the pup« of the carpenter- moths (Cossidce) the pupa is armed with rows of backward projecting teeth on the abdominal segments, which facilitate the movements within the burrow. The creniaster. — Many pupae, and especially those of most Lepidop- tera, are provided with a variously shaped process of the posterior end of the body, to which the term creniaster is applied. This process is often provided with hooks which serve to suspend the pupa, as in butterflies, or to hold it in place, after it has partly emerged from the cocoon, and while the adult is emerging from the pupal skin, as in cocoon-making moths. In its more simple form, where hooks are lacking, it aids the pupa in working its way out of the earth, or from other closed situations. The method of fixing the cremaster in the disk of silk from which the pupa of a butterfly is suspended was well-illustrated by C. V. Riley ('79). The full grown larva spins this disk and hangs from it during the prepupal stadium by means of its anal prolegs (Fig. 209, a). When the last larval skin is shed, it is worked back to the caudal end of the body (Fig. 209, b); and is then grasped between two of the abdominal segments (Fig. 209, c,) while the caudal end of the body is removed from it ; and thus the cremaster is freed, and is in a position from which it can be inserted in the disk of silk. Fig. 209. — Transformations of the milkweed butter- fly (From Riley). 188 AN INTRODUCTION TO ENTOMOLOGY The cocoon. — The pupal instar is an especially vulnerable one. During the pupal life the insect has no means of offence, and having exceedingly limited powers of motion, it has almost no means of defense unless an armor has been provided. Many larvae merely retreat to some secluded place in which the pupal stadium is passed ; others bury themselves in the ground ; and still others make provision for this helpless period by spinning a silken armor about their bodies. Such an armor is termed a cocoon. The cocoon is made by the full-grown larva; and this usually takes place only a short time before the beginning of the pupal stadium. But in some cases several months elapse between the spinning of the cocoon and the change to pupa, the cocoon being made in the autimm and the change to pupa taking place in the spring. Of course a greater or less portion of this period is occupied by the prepupal stadium. Cocoons are usually made of silk, which is spun from glands already described. In some cases, as in the cocoons of Bomhyx, the silk can be unwound and utilized by man. While silk is the chief material used in the making of cocoons, it is by no means the only material. Many wood-boring larvas make cocoons largely of chips. Many insects that undergo their transformation in the ground incorporate earth in the walls of their cocoons. And hairy cater- pillars use silk merely as a warp to hold together a woof of hair, the hairs of the larva being the most con- spicuous element in the cocoon. In those cases in which silk alone is used there is a great variation in the nature of the silk, and in the den- sity of the cocoon. The well-known cocoons of the saturniids illustrate one extreme in density, the cocoons of certain Hymenoptera, the other. The fiberous nature of the cocoon is usually obvious ; but the cocoons of saw-flies appear parchment -like, and Fig. 2IO.— the cocoons of the sphecids appear like a delicate foil. cocoon^ of While in the more common tjrpe of cocoons the Trichostibas wall is a closely woven sheet, there are cocoons that from ^ which ^^^ lace-like in texture (Fig. 210). the adult has Modes of escape from the cocoon. — The insect, having ^^ ■ walled itself in with a firm layer of silk, is forced to meet the problem of a means of escape from this inclosure; a problem which is solved in greatly varied ways. THE METAMORPHOSIS OF INSECTS 189 In many insects in which the adult has biting mouth parts, the adult merely gnaws its way out by means of its mandibles In some cases, as the Cynipidce, it is said that this is the only use made of its mandibles by the adult. In some cases the mandibles with which the cocoon is pierced per- tain to the pupal instar, this is true of Chrysopa and Hemerobius; and the Trichoptera break out from their cases, by means of their mandibles, while yet in the pupal state. For those insects in which the adult has sucking mouth parts, the problem is even more difficult. Here it has been met in several quite distinct ways. The pupse of many Lepidop- tera possess a specialized organ for breaking through the cocoon; in some the anterior end of the pupa is furnished with a toothed crest (LithocoUetes hamadryella) ; in certain satur- niids there is a pair of large, stout, black spines, one on each side of the thorax, at the base of the fore wings with which the adult cuts a sHt in the cocoon through which the moth emerges, this was obser\'ed by Packard in Tropcea luna; but as these spines are present in other saturniids, where the cocoon is too . ^._ ,^i. dense to be cut by them, and where an opening is h^^i^mil made in some other way, it is probable that, as a rule, their function is loco- motive, aiding the.moth to work its way out from the cocoon, by a wriggling motion. One of the ways in which saturniids pierce their cocoons is that practiced by Bombyx and Telea. These insects soften one end of the cocoon by a liquid, which issues from the mouth; and then, by- forcing the threads apart or by breaking them, make an opening. Cocoon of Megalopyge oper- Fig. 211. — Longi- tudinal section of a cocoon of Callosamia pro- melhea;v, valve- like arrange- ment for the escape of the adult. Fig. 213. — Old cocoon of Megalopyge opercularis. 190 AN INTRODUCTION TO ENTOMOLOGY Far more wonderful than any of the methods of emergence from the cocoon described above are those in which the larva makes pro- vision for the escape of the adult. The most familiar of these is that practiced by the larv^as of Samia cecropia and Callosamia promethea. These larvae when they spin their cocoons construct at one end a coni- cal valve-like arrangement, which allows the adult to emerge without the necessity of making a hole through the cocoon (Fig. 211, v). A less familiar example, but one that is fully as wonderful, is that of a Megalopyge. The larva of this species makes a cocoon of the form shown in Figure 212. After an outer layer of the cocoon has been made, the larva constructs, near one end of it, a hinged partition ; this serves as a trap door, through which the moth emerges. That part of the cocoon that is outside of the partition is quite delicate and is easily destroyed. Hence most specimens of the cocoons in col- lections present the appearance represented in Figure 213. The puparium. — The pupal stadiimi of most Diptera is passed within the last larval skin, which is not broken till the adult fly is ready to emerge. In this case the larval skin, which becomes hard and brown, and which serves as a cocoon, is termed a puparium. In some families the puparium retains the form of the larva; in others the body of the larva shortens, assuming a more or less barrel-shaped form, before the change to a pupa takes place (Fig. 214). Modes of escape from the puparium. — The pupse of the more generalized Diptera escape from the pupa- rium through a T-shaped opening, which is formed by a lengthwise split on the back near the head end and a crosswise split at the front end of this (Fig. 215), or rarely, through a cross-wise split between the seventh -Pupa- and eighth abdominal segments. In the more special- ■'^''^''ized Diptera there is developed a large bladder-like organ, which is pushed out from the front of the head, through what is known as the frontal suture, and by which the head end of the puparium is forced off. This organ is known as the ptilinum. After the adult escapes, the ptilinum is withdrawn into the head. The Different types of pupaB. — Three types of pupce are commonly recognized; these are the following: Fig. 215.— Puparium of a Exarate pupcB. — Pupae which, like those ^ ''^ lomyu of the Coleoptera and Hymenoptera, have the legs and. vnngs free, are termed exarate pupag. THE METAMORPHOSIS OF INSECTS 191 Oocected pupce. — Pups which like the pupse of Lepidoptera, have the limbs glued to the surface of the body, are termed obtected pupas. Coarctate Pupce. — Pupas that are enclosed within the hardened larval skin, as is the case with the pupae of most of the Diptera, are termed coarctate pupae. The imago — The fully developed or adult insect is termed the imago. The life of the imago is devoted to making provision for the perpetuation of the species. It is during the imaginal stadium that the sexes pair, and the females lay their eggs. With many species this is done very soon after the last ecdysis ; but with others the egg- laying is continued over a long period; this is especially true with females of the social Hymenoptera. h. HYPERMETAMORPHOSIS There are certain insects, representatives of several different orders that exhibit the remarkable peculiarity in their development that the successive larval instars represent different types of larvae. Such insects are said to undergo a hypermetamorphosis. The transformations of several of these insects will be described later in the accounts of the families to which they belong; and for this reason, in order to avoid repetition, are not discussed here. The more striking examples are Mantispa, Meloe, Stylops, and Platy- gaster. i. VIVIPAROUS INSECTS There are many insects that produce either nymphs or larvae instead of laying eggs. Such insects are termed viviparous. This term is opposed to oviparous, which is applied to those insects that lay eggs that hatch after exclusion from the body. It has been pointed out in the discussion of the reproductive organs that, from the primordial germ -cells, there are developed in one sex spermatoza and in the other eggs; and it should be borne in mind that the germ-cells produced in the ovary of a female from the primordial germ-cells are eggs. These eggs grow and mature; in some cases they become covered with a shell, in others they are not so covered; in some cases they are fertilized by the union of a spermatozoan with them, and in others they are never fertilized; but in all these cases they are eggs. We may say, therefore, that all insects are developed from eggs. A failure to recognize this fact has introduced confusion into entomological literature. Some writers have termed the germ-cells produced by agamic aphids pseudova or false eggs. But these germ-cells are as truly eggs as are those from which the males of the honeybee develop; they are merely unfertilized eggs. The term pseudovum conveys a false impression; while the phrase, an unfer- tilized egg, clearly states a fact. 192 AN INTRODUCTION TO ENTOMOLOGY Some writers make use of the term ovoviviparous indicating the production of eggs that have a well -developed shell or covering, but whicK hatch within the body of the parent; but the distinction is not fundamental, since viviparous ani- mals also produce eggs as indicated above. Among viviparous insects there are found every gradation from those in which the larvse are born when very young to those in which the entire larval life is passed within the body of the parent. There also exist examples of viviparous larvae, viviparous pupae, and vivi- parous adults. And still another distinction can be made; in some viviparous insects the reproduction is parthenogenetic ; in others it is sexual. Viviparity with parthenogenetic reproduction. — In certain vivipar- ous insects the reproduction is parthenogenetic ; that is, the young are produced from eggs that are not fertilized. This type of reproduction occurs in larvae, pupas, and apparently in adults. Pcsdogenetic Larvae. — In 1862 Nicholas Wagner made the remark- able discovery that certain larvae belonging to the Cecidomyiidae give birth to living young. This discovery has been confirmed by other observers, and for this type of reproduction the term pcsdogenesis, proposed by Von Baer, has come into general use. This term is also spelled pedogenesis; the word is from pcedo or pedo, a child, and genesis. The phenomenon of paedogenesis is discussed later in the accounts of the Cecidomyiidae and of the Micromalthidas. Pcedogenetic pupce. — The most frequently observed examples of paedogenetic reproduction are by larv^ae ; but that pupae also are some- times capable of reproduction is shown by the fact that Grimm ('70) found that eggs laid by a pupa of Chironomus grimrni, and of coxu"se not fertilized, hatched. Anton Schneider ('85) found that the adults of this same species of Chironomus reproduced parthenogenetically. This species, therefore, exhibits a transition from pedogenesis to normal parthenogenesis. Viviparous adult agamic females. — There may be classed under this class provisionally, the agamic females of the Aphididae; as these are commonly regarded as adults. It has been suggested, however, that the agamic reproduction of the Aphids may be a kind of pasdogenesis ; the agamic females being looked upon as nymphs. This however, is not so evident in the case of the winged agamic generation. On the other hand, the reproductive organs of the agamic aphids are incom- pletely developed, as compared with those of the sexual forms, lacking a spermatheca and colleterial glands. THE MET A MORPHOSIS OF INSECTS 193 This discussion illustrates the difficulty of attempting to make sharp distinc- tions, whereas in nature all gradations exist between different types of structure and of development. Thus Leydig ('67) found a certain aphid to be both ovipar- ous and viviparous; the eggs and the individuals born as nymphs being produced from neighboring tubes of the same ovary. Viviparity with sexual reproduction. — Although most insects that reproduce sexually are oviparous, there are a considerable number in which sexual reproduction is associated with viviparity. Among these sexual viviparous insects there exist great differences in method of reproduction ; with some the young are born in a very immature stage of development, a stage corresponding to that in which the young of oviparous insects emerge from the egg; while with others the young attain an advanced stage of development within the body of the mother. Sexual viviparous insects giving birth to nymphs or larvce. — That type of viviparity in which sexual females give birth to very immature nymphs or larvae exists in more or less isolated members of widely separated groups of insects. As the assumption of this type of repro- duction involves no change in the structure of the parent, but merely a precocious hatching of the egg, it is not strange that it has arisen sporadically and many times. In some cases, however, the change is not so slight as the foregoing statement would imply; as, for example, in the case of the viviparous cockroach, which does not secrete oothecae as do other cockroaches. Among the recorded examples of this type of viviparity are representatives of the Ephemerida, Orthoptera, Hemiptera, Lepi- doptera, Coleoptera, Strepsiptera, and Diptera. Sexual viviparous insects giving birth to old larvce. — The mode of reproduction exhibited by these insects is doubtless the most excep- tional that occurs in the Hexapoda, involving, as it does, very impor- tant changes in the structure of the reproductive organs of the fe- males. With these insects the larvae reach maturity within the body of the parent, undergoing what is analogous to an intra-uterine develop- ment, and are born as full-grown larvae. This involves the secretion of a "milk" for the nourishment of the young. This mode of reproduction is characteristic of a group of flies, including several families, and known as the Pupipara. This name was suggested for this group by the old belief that the young are born as pupas ; but it has been found that the change to pupa does not take place till after the birth of the larva. 194 AN INTROD UCTION TO ENTOMOLOG Y The reproduction of the sheep-tick, Melophagns oviniis, may be taken as an illustration of this type of development ; this is described in the discussion of the Hippoboscidse, the family to which this insect belongs. The giving birth to old larvce is not restricted to the Pupipara. Surgeon Bruce (quoted by Sharp, 'gg) has shown that the Tsetse fly, Glossina morsitans, reproduces in this way, the young changing to pupee immediately after birth. An intermediate type of development is illustrated by Hylemyia strigosa, a dung-frequenting fly belonging to the Anthomyiidse. This insect, according to Sharp ('99), produces living larvee, one at a time. "These larvae are so large that it would be supposed they are full-grown, but this is not the case, they are really only in the first stage, an unusual amount of growth being accomplished in this stadium." j. NEOTEINIA The persistence with adult animals of larval characteristics has been termed neoteinia* or neotenia. When this term first came into use it was applied to certain amphibians, as the axolotle, which retains its gills after becoming sexually mature; but it is now used also in entomology. The most familiar examples of neoteinic insects are the glow- worms, which are the adult females of certain beetles, the complemen- tal females of Termites, and the females of the Strepsiptera. II. THE DEVELOPMENT OF APPENDAGES In the preceding pages the more obvious of the changes in the external form of the body during the metamorphosis of insects and some deviations from the more common types of development have been discussed. The changes in the form of the trunk that have been described are those that can be seen without dissection; but it is impracticable to limit a discussion of the development of the appen- dages of the body in this way, for in the more specialized types of metamorphosis a considerable part of the development of the appen- dages takes place within the body -wall. •^Neoteinia: neos (v^os), youthful; teinein {rebeiv), to stretch. THE METAMORPHOSIS OF INSECTS 195 a. THE DEVELOPMENT OP WINGS Two quite distinct methods of development of wings exist in msects; by one method, the wings are developed as outward project- ing appendages of the body; by the other, they reach an advanced stage of development within the body. The former method of development takes place with nymphs and naiads, the latter with larvct* I. The Development oj the Wings of Nymphs and Naiads In insects with a gradual or with an incomplete metamorphosis the development of the appendages proceeds in a direct manner. The wings of nymphs and naiads are sac-like outgrowths of the body-wall, which appear comparatively early in life and become larger and larger with successive molts, the expanding of the wing-buds taking place immediately after the molt ; an illustration of this has been given in the discussion of gradual metamorphosis, page 175. 2. Development of the Wings in Insects vuith a Complete Metamorphosis Although there are differences in details in the development of the wings in the different insects undergoing a complete metamorphosis, the essential features are the same in all. The most striking feature is that the rudiments of the wings, the wing-buds, arise within the body and become exposed for the first time when the last larval skin is shed. The development of the wings of the cabbage butterfly {Pontia rapce) will serve as an example of this type of development of wings. The tracing of that part of this development which takes place during the larval life can be obsen^ed by making sections of the body-wall of the wing-bearing segments of the successive instars of this insect. The fiisc indication of a wing-bud is a thickening of the hypo- dermis; this thickening, known as a histoblast or an imaginal disc, has been observed in the embryos of certain insects, in the first larval instar of the cabbage butterfly it is quite prominent (Fig. 216, a). During the second stadium, it becomes more prominent and is invaginated, forming a pocket-like structure (Fig. 216, 6). During the third stadium a part of this invagination becomes thickened and evaginated into the pocket formed by the thinner *Only the more general features of the development of wings are discussed here. For a fuUer account see "The Wings of Insects" (Comstock '18, a). 196 AN INTRODUCTION TO ENTOMOLOGY portions of tne invagination (Fig. 216, c). During the fourth stadium, the evaginated part of the histoblast becomes greatly- extended (Fig. 216, d). It is this evaginated portion of the histo- blast that later be- comes the wing. Dur- ing the fifth stadium the wing-bud attains the form shown in Figure 216, e, which represents it dissected out of the wing-pocket At the close of the last larval stadium, the fifth , the wing is pushed out from the wing-poc- ket, and Hes under the old larval cuticula dur- ing the prepupal sta- dium. It is then of the form shown in Figure 216, /. The molt that marks the beginning of the pupal stadium, exposes the wing-buds, which in the Lepidoptera be- come closely soldered to the sides and breast of the pupa. Imme- diately after the last molt when the adult emerges, the wings Fig. 216.— Several stages in the development of the expand greatly and wings of a cabbage butterfly (After Mercer). assume their definitive form. While this increase in size and changes in form of the developing wing are taking place, there occur other remarkable developments in its structure. A connection is made with a large trachea near which the histoblast is developed, shown in cross-section in the first four THE METAMORPHOSIS OF INSECTS 197 parts (a, b, c, and d) of Figure 216; temporary respiratoiy organs, consisting of bundles of tracheoles, are developed (e and/) ; and later, near the close of the larval period, the trachese of the wing are devel- oped, and the bundles of tracheoles disappear. During the later stages in the development of the wing the basement membranes of the hypodermis of the upper and lower sides of the wing come together, except along the lines where the veins are to be developed later, and become united. In this way the wing is transformed from a bag-like organ to a sheet-like one. The hnes along which the two sides of the wing remain separate are the vein cavities ; in these the trunks of the wing-tracheag extend. During the final stages of the development of the wing, the walls of the vein-cavities are thickened, thus the wing- veins are formed; and the spaces between the wing-veins become thin. By reference to Figure 216, c and d, it will be seen that the histo- blast consists of two quite distinct parts, a greatly thickened portion which is the wing-bud and a thinner portion which connects the wing- bud with the hypodermis of the body-wall, and which constitutes the neck of the sac-like histoblast, this is termed the peripodal membrane, a term suggested by the similar part of the histoblast of a leg ; and the enclosed cavity is known as the peripodal cavity. In the more specialized Diptera, the peripodal membranes are very long and both the wing-buds and the leg-buds are far removed from the body-wall. A condition intermediate between that which exists in the Lepidoptera, as shown in Figure 216, and that of the more speciaHzed Diptera was found by Kellogg (07) in the larva of Holorusia rubiginosa, one of the crane-flies (Fig. 217). b. THE DEVELOPMENT OF LEGS The development of the legs pi oceeds in widely different ways in different insects. In the ^. „,. , , . , , ^ ,, ,. , . , Fig. 217. — Wing- bud m the larva of the more generalized forms, the giant crane-fly, Holorusia rubiginosa; legs of the embryo reach an ^3-, hypodermis; pm peripodal mem- brane;/, trachea; wo, wmg-bud (Alter advanced stage of development Kellogg). before the nymph or naiad leaves the egg-shell, and are functional when the insect is born; on the other hand, in those specialized insects that have vermiform larvas, the development of the legs is retarded, and these organs do not become functional until the adult stage is reached. Almost every conceivable intergrade between these two extremes exist. 198 AN INTRODUCTION TO ENTOMOLOGY I. The Development of the Legs of Nymphs and of Naiads In insects with a gradual metamorphosis and also in those with an incomplete metamorphosis the nymph or naiad when it emerges from the eggshell has well-developed legs, which resemble quite closely those of the adult. The changes that take place in the form of the legs during the postembyronic development are comparatively slight ; there may be changes in the relative sizes of the different parts ; and in some cases there is an increase in the number of the segments of the tarsus ; but the changes are not sufficiently great to require a descrip- tion of them here. 2. The Development of the Legs in Insects with a Complete Metamor- phosis It is a characteristic of most larvse that the development of their legs is retarded to a greater or less extent. This retardation is least in campodeiform larvae, more marked in cruciform larv^, and reaches its extreme in vermiform larvee. The development of the legs of insects with campodeiform larvae. — Among the larvae classed as campodeiform the legs are more or less like those of the adults of the same species ; there may be differences in the proportions of the different segments of the leg, in the number of the tarsal segments, and in the number and form of the tarsal claws ; but these differences are not of a nature to warrant a discussion of them here. These larvs lead an active life, like that of nymphs, and consequently the form of legs has not been greatly modified from the paurometabolous type. The development of the legs of insects with erucif orm larvae. — In caterpillars and other cruciform larvee the thoracic legs are short and fitted for creeping ; this mode of locomotion being best suited to their mode of life, either in burrows or clinging to foliage. This form of leg is evidently an acquired one being, like the internal development of wings, the result of those adaptive changes that fit these XsltvcQ to lead a very different life from that of the adults. In the case of caterpillars the thoracic legs are short, they taper greatly, and each consists of only three segments. It has been com- monly believed and often stated that the three segments of the larval leg correspond to the terminal portion of the adult leg ; but studies of the development of the legs of adults have shown that the divisions of the larval leg have no relation to the five divisions of the adult leg. THB METAMORPHOSIS OF INSECTS 199 It has been shown by Gonin ('92), Kellogg ('01 and '04), and Verson (04) that histoblasts which are the rudiments of the legs of the adult exist within the body-wall of the caterpillar at the base of the larval legs. Late in the larval life the extremity of the legs of the adult are contained in the legs of the caterpillar. It has been shown that the cutting off of a leg of a caterpillar at this time results in a mutilation of the terminal part of the leg of the adult. The development of the legs of the adult within the body of cater- pillars has not been studied as thoroughly as has been the develop- ment of the wings ; but enough is known to show that in some respects the two are quite similar; this is especially true of the development of the tracheoles and of the tracheas. The development of the legs in insects with vermiform larvae. — In vermiform larvae the development of the entire leg is retarded. The leg arises as a histoblast, which is within the body and bears, in its more general features, a resemblance to the wing-buds of the same insect. The development of the legs of vermiform larvae has been studied most carefully in the larvse of Diptera. During the larval life the leg becomes quite fully developed within the peripodal cavity; in Corethra, they are spirally coiled; in Musca, the different segments telescope into each other. At the close of the larval period, the evagination of the legs takes place. C. THE DEVELOPMENT OF ANTENNA I. The Transformation of the Antennaz of Nymphs and of Naiads In the case of n3Tiiphs and of naiads the insect when it emerges from the eggshell has well-developed antennee. The changes that take place during the postembryonic development are, as a rule, com- paratively slight; in most insects, an increase in the number of the segments of the antennse takes place ; but in the Ephemerida, a reduc- tion in number of the antennal segments occurs. 2. The Development of the Antennce in Insects with a Complete Metamorphosis One of the marked characteristics of larvae is the reduced condition of the antennse; even in the campodeiform larvas of the Neuroptera, where the legs are comparatively w^ell-developed, the antennae are greatly reduced. In cruciform larvae the development of the antennas follows a course quite similar to that of the legs. The larval antennas are small: 200 AN INTRODUCTION TO ENTOMOLOGY the antennae of the adult are developed from histoblasts within the head and during the latter part of the larval life are folded like the bellows of a closed accor- dian; at the close of this period they become eva- ginated, but the definitive form is not assumed until the emergence of the adult. A similar course of devel- / m^ opment of the antennae takes place in vermiform larvae (Fig. 218). d. THE DEVELOPMENT OF Fig. 218. — .Sagittal section through headof old THE MOUTH-PARTS lan^a of 5/;«u/^'mw, showing forming imaginal head paits within. Ic, larval cuticula; id. Great differences exist imagi-al head-wall; la, larval antenna; ia, among insects with refer- imagmal antenna; ie, imagmal eye; Imd, ° larval mandible; imd, imaginal mandible; ence tO the comparative h:x larval maxilla; imx, imaginal maxilla; structure of their mouth- Ih, larval labmm; tit, imagmal labium (rrom Kellogg). parts in their immature and adult instars. In some insects the immature instars have essentially the same type of mouth-parts as the adults ; in most of these cases, the mouth-parts are of the biting types, but in the Homoptera and Heteroptera both nymphs and adults have them fitted for sucking; in many other insects, the mouth-parts of the larvae are fitted for biting while those of adults are fitted for sucking; and in still others, as certain maggots, the development of the mouth-parts is so retarded that they are first functional in the adult insect. Correlated with these differences are differences in the method of development of these organs. In those insects that have a gradual or incomplete metamorphosis and in the Neuroptera, the Coleoptera, and the Hymenoptera in part, the mouth-parts of the immature and adult instars are essentially of the same type. In these insects the mouth-parts of each instar are developed within the corresponding mouth-parts of the preceding instar. At each ecdysis there is a molting of the old cuticula, a stretching of the new one before it is hardened, a result of the growth in size of the appendages, and sometimes an increase in the number of the segments of the appendage. In a word, the mouth-parts of the adult are developed from those of the immature instar in a compara- tively direct manner. In some cases, however, where the mouth- THE METAMORPHOSIS OF INSECTS 201 parts of the larva are small and those of the adult are large, only the tips of the developing adult organs are within those of the larva at the close of the larval period, a considerable part of the adult organs being embedded in the head of the old larva. In a few Coleoptera and Neuroptera (the Dytiscidas, Myrme- leonidae, and Hemerobiidas) the larvae, although mandibulate, have the mouth-parts fitted for sucking. In these cases the form of the mouth-parts have been modified to fit them for a peculiar method of taking nourishment during the larval life. The mouth-parts of the adults are of the form characteristic of the orders to which these insects belong. In those insects in which the larvag have biting mouth-parts and the adults those fitted for sucking, the development is less direct. In the Lepidoptera, for example, to take an extreme case, there are great differences in the developmeoc oi the different organs; within the mandibles of the old larvae there are no developing mandibles, these organs being atrophied in the adult; but at the base of each larval maxilla, there is a very large, invaginated histoblast, the developing maxilla of the adult; these histoblasts become evaginated at the close of the larval period, but the maxillae do not assimie their defini- tive form till after the last ecdysis. The extreme modification of the more usual course of development of the mouth-parts is found in the footless and headless larvae of the more specialized Diptera. Here the mouth-parts do not appear externally until during the pupal stadium and become functional only when the adult condition is reached. See the figures illustrating the development of the head in the Muscidas (Fig. 220). It should be noted that the oral hooks possessed by the larvae of the more specialized Diptera are secondarily developed organs and not mouth-parts in the sense in which this term is commonly used. These oral hooks serve as organs of fixation in the larv^as of the CEstridae and as rasping organs in other larvas. e. THE DEVELOPMENT OF THE GENITAL APPENDAGES The development of the genital appendages of insects has been studied comparatively little and the results obtained by the different investigators are not entirely in accord ; it is too early therefore to do more than to make a few general statements. In the nymphs of insects with a gradual metamorphosis rudimen- tary genital appendages are more or less prominent and their develop- 202 AN INTRODUCTION TO ENTOMOLOGY ment follows a course quite similar to that of the other appendages of the body. In insects with a complete metamorphosis the genital appendages are represented in the larv« by invaginated histoblasts; the develop- ing appendages become evaginated in the transformation to the pupa state and asstime their definitive form after the last ecdysis. III. THE DEVELOPMENT OF THE HEAD IN THE MUSCID^ In the more generalized Diptera the head of the larva becomes, with more or less change, the head of the adult ; the more important of these changes pertain to the perfecting of the organs of sight and the development of the appendages, the antennse and mouth-parts. But in the more specialized Diptera there is an anomalous retard- ing of the development of the head, which is so great that the larvae of these insects are commonly referred to as being acephalous. This retarded development of the head has been carefully studied by Weis- man ('64), Van Rees ('88) and Kowalevsky ('87). The accompanying diagrams (Fig. 220) based on those given by the last two authors illus- trate the development of the head in Musca, which will serve as an illustration of this type of development of the head. The larvas of Musca are conical (Fig. 219); and the head-region is repre- sented externally only by the minute apical segment Fig.2l9.— Larva of the house-fly, If M5ca of the conical body. It do we5/tca (After Hewitt). .„ , , , ,1 . Will be shown later that this segment is the neck of the insect, the developing head being invaginated within this and the following segments. This invagina- tion of the head takes place during the later embryonic stages. In Figure 220 are given diagrams, adapted from Kowalevsky and Van Rees. representing three stages in the development of the head of Musca. Diagram A represents the cephaHc end of the body of a larva; and diagram B and C, the corresponding region in a young and in an old pupa respectively; the parts are lettered uniformly in the three diagrams. The three thoracic segments (1,2, and 3) can be identified by the rudiments of the legs (/^ /-, and P). In the larva (A) the leg-buds are far within the body, the peripodal membrane being connected with THE METAMORPHOSIS OF INSECTS 203 the hypodermis of the body-wall by a slender stalk-like portion. In the young pupa (B) the pcripodal membranes of the histoblasts of the legs are greatly shortened and the leg-buds are near the surface of the body; and in the old pupa (C) the leg -buds are evaginated. The wing-buds are omitted in all of the diagrams. In the first two segments of the body of the larva (A) there is a cavity (ph) which has been termed the "pharynx" ; this is the part in which the oral hooks characteristic of the larvas of the Muscidas develop. The name pharynx is unfortunate as this is not a part of the alimentary canal; it is an invaginated section of the head, into the base of which the oesophagus (a) now opens. In the figure of the lar\^a (A) note the following parts: the oesophagus (cb) ; the ventral chain of ganglia (vg), the brain (b), and a Fig. 220. — Development of the head in the Muscidae. A, larva; B, youn^ pupa ; C, old pupa (From Korschelt and Heider after Kowalevsky and Van Rees). sac (ba) extending from the so-called pharynx to the brain. There are two of these sacs, one applied to each half of the brain, but only one of these would appear in such a section as is represented by the diagram. These sacs were termed the brain-appendages by Weismann. In each of the "brain-appendages" there is a disc-like thickening near the brain, the optic disc (od) ; this is a histoblast which develops into a compound eye ; in front of the optic disc there is another prominent histoblast ; the frontal disc (fd), upon which the rudiment of an antenna (at) is developed. In the larA^a the brain and a considerable part of the "brain- appendages" lie within the third thoracic segment. In the young pupa (B) these parts have moved forward a considerable distance; and in the old pupa (C) the head has become completely evaginated. The part marked p in the two diagrams of the pupa is the rudiment of the proboscis. 204 AN INTRODUCTION TO ENTOMOLOGY By comparing diagrams B and C it will be seen that what was the tip of the first segment of the larva and of the young pupa (++) becomes the neck of the insect after the head is evaginated. IV. THE TRANSFORMATIONS OF THE INTERNAL ORGANS Great as are the changes in the external form of the body during the life of insects with a complete metamorphosis, even greater changes take place in the internal organs of some of them. In the space that can be devoted to this subject in this work, only the more general features of the transformation of the internal organs can be discussed; there is an extensive and constantly increasing literature on this subject which is available for those who wish to study it more thoroughly. In insects with a gradual or with an incomplete metamorphosis there is a continuous transformation of the internal organs, the changes in form taking place gradually : being quite comparable to the gradual de velopment of the external organs ; but in insects with a complete metamorphosis, where the manner of life of the larva and the adult are very different, extensive changes take place during the pupal stadium. The life of a butterfly, for example, is very different from that it led as a caterpillar; the organs of the larva are not fitted to perform the functions of the adult ; there is consequently a necessity for the reconstruction of certain of them; hence the need of a pupal stadium. Pupae are of ten referred to as being quiet ; but physiologi- cally the pupal period is the most active one in the post-embryonic life of the insect. In those cases where a very marked change takes place in the structure of internal organs, there is a degeneration and dissolution of tissue, this breaking down of tissues is termed histolysis- In the course of histolysis some cells, whicii are irequentiy leu- cocytes or white blood corpuscles, feed upon the debris of the disin- tegrating tissue ; such a cell is termed a phagocyte, and the process :1s termed phagocytosis. It is believed that the products of the digestion of disintegrating tissue by the phagocytes pass by diffusion into the surrounding blood and serve to nourish new tissue. After an organ has been raore or less broken down by histolysis, the extent of the disintegration differing greatly :r different organs and in different insects, ther3 follows a growth ci new tissue; this process is termed histogenesis. THE MET A MORPHOSIS OF INSECTS 205 The histogenetic reproduction of a tissue begins in the differentia- tion and multiplication of small groups of cells, which were not affected by the histolysis of the old tissue; such a group of cells is termed an imaginal disc or a Mstoblast. They were termed imaginal discs on account of the disc-like form of those that were first described and because they are rudiments of organs that do not become func- tional till the imago stage ; but the term histoblast is of more general application and is to be preferred. The extent of the transformation of the internal organs differs greatly in dift'erent insects. In the Coleoptera, the Lepidoptera, the Hymenoptera, and the Diptera Nemocera, the mid-intestine and some other larval organs are greatly modified, but there is no general histolysis. On the other hand, in the Diptera Brachycera, there is a general histolysis. In Mtisca all organs break down and are reformed except the central nervous system, the heart, the reproductive organs, and three pairs of thoracic muscles. Regarding the extent of the transformations in the other orders where the metamorphosis is com- plete we have, as yet, but little data. For a more detailed and exhaustive discussion of the morphology of insects the special student should consult the authoritative book by R. E. Snodgrass, "Principles of Insect Morphology" (1935). PART II THE CLASSIFICATION AND THE LIFE- HISTORIES OF INSECTS Class HEXAPODA The Insects The members of this class are air-breathing arthropods, with distinct head, thorax, and abdomen. They have one pair of antennce, three pairs of legs, and usually one or two pairs of wings in the adidt state. In most adult insects the head bears a pair of compound eyes. The opening of the reproductive organs is near the caudal end of the body. The more general character of insects, together with their structure and morphology, has been discussed at some length in Part I of this book. It is now appropriate to consider the classification, habits and life histories of insects. Part II will therefore be devoted to a dis- cussion of the subclasses, orders, and families of this great group of animals. The class Hexapoda is divided into two subclasses, the small wingless insects, Apterygota, and the winged insects, Pterygoia. The subclass Apterygota is a small one, containing but three orders (four by some authors) and mostly unfamiliar forms except to those especially interested in these tiny creatures. The subclass Pterygota is a very large group including all of the remaining twenty-three orders discussed in this book. This subclass contains all of the more familiar forms, such as grasshoppers, beetles, butterflies, moths, flies, wasps, and bees. CHAPTER V THE SUBCLASSES AND THE ORDERS OF THE CLASS HEXAPODA Insects constitute one of the classes of the Arthropoda, that division of the animal kingdom in which the body is composed of a series of more or less similar segments and in which some of these segments bear jointed legs. This class is known as the Hexapoda. The distinctive characteristics of the Class Hexapoda and its relation to the other classes of the Arthropoda are discussed in the first chapter of this work; we have now to consider the division of this class into subclasses and orders. The orders that constitute the Hexapoda represent two well-marked groups; this class is divided, therefore, into two subclasses. This division was first proposed by Brauer ('85), who recognized the fact that while the wingless condition of certain insects, the fleas, lice, bird-lice, and the wingless members of orders in which the wings are usually present, is an acquired one, the wingless condition of the Thysanura and Collembola is a primitive one. In other words, from the primitive insects, which were wingless, there were evolved on the one hand the orders Thysanura and Collembola, which remained wingless, and on the other hand, a winged form from which have descended all other orders of insects. An extended study of the wings of insects has shown that the wings of all of the orders of winged insects are modifications of a single type ; it is believed, therefore, that all of the orders of winged insects have descended from a common winged ancestor. As to the lice, bird-lice, and fleas, the relation of each of these groups to certain winged insects, as shown by their structure, has led to the belief that their wingless condition is an acquired one, being the result of parasitic habits. The lice or Anoplura are commonly regarded as closely allied to the Homoptera and Heteroptera ; the bird-lice or Mallophaga to the Corrodentia; and the fleas or Siphonaptera to the Diptera. Hence these wingless insects are placed with the winged insects in a single subclass. The two subclasses thus recognized were named by Brauer the Apter^^gogenea and the Pterygogenea respectively. The cumber- someness of these names led to the substitution for them of the shorter names Apterygota and Pter3'gota. The Apterygota includes the orders Thysanura and Collembola; and the Pterygota, all other orders of insects. Some writers regard the Th\'sanura and Collem- bola as suborders of a single order, which they term the Aptera. The distribution of insects into orders is based on the classification of Linnaeus, as set forth in his "Systema Naturse" (i 735-1 768). Linnaeus, who has been called the Adam of zoological science, divided (206) HEX A POD A 207 his class Insecta into seven orders; these he named Coleoptera, Hemiptera, Lepidoptera, Neuroptera, H}Tnenoptera, Diptera, and Aptera, respectively. Since the time of Linnasusmany modifications of his classification of insects have been proposed; and new ones are constantly appear- ing. The result is that now there is a great lack of uniformity in the classification used by dift'erent writers. The modifications of the Linnaean distribution of insects into orders are based on the belief that in certain cases Linnteus grouped into a single order forais that really represent two or more distinct orders. The result has been a great increase in the number of orders recognized. Linnajus included in his class Insecta, under the order Aptera, not only wingless insects but also arachnids, crustaceans, centipedes, and millipedes. The animals thus grouped by LinncTus are now dis- tributed into several classes; and to the class composed of the animals now commonly known as insects, those characterized by the posses- sion of only six legs, the term Hexapoda is commonly applied. Some writers, however, apply the term Insecta to the class of insects as now limited. Some of the more recently recognized orders of insects are repre- sented among living insects by comparatively few species; but in each case the structure of the insects included in the group is so differ- ent from that of all other insects that we are led to belie\'e that they represent a division of the class Hexapoda that is of ordinal value. There are given below the names of the orders of insects recognized in this work. The sequence in which these orders are discussed is of necessity a more or less arbitrary one. In general the plan adopted here is to make the series an ascending one; that is, the more gen- eralized or primitive insects are placed first and the more highly specialized ones later in the series; but as the different orders of insects have been specialized in very different ways, the relative de- grees of their specialization cannot be shown by arranging them in a single linear series, as must be done in a book. To indicate the different wa}-s in which the dift'erent members of a group have been specialized and the relative rank of those specialized in a similar way, use must be made of a diagram representing a genealogical tree. Many such diagrams have been made, but no one of them has re- ceived general acceptance; much remains to be learned before such a diagram can be made that will inspire confidence in its accuracy. In the course of the preparation of a special treatise on the wings of insects (Comstock ' 1 8 a) , I wrote a table indicating the more strik- ing of the methods of specialization of the wings characteristic of each of the orders of winged insects; and in the discussion of the different orders, I followed the sequence indicated by tnis table. In doing this I did not advocate the basing of a classification of insects upon the characters presented by the wings alone, but merely made use of these characters for the purposes of that work. 208 AN INTRODUCTION TO ENTOMOLOGY A renewed study of the relationships of the different orders to each other, in which an effort has been made to correlate other characters with those presented by the wings, has not indicated the desirability of changes in the sequence of the orders indicated in that table, ex- cept in the allocation of those orders in which wings are wanting. The importance of the wings of insects for taxonomic purposes was early recognized by entomologists, as is well shown by the fact that the names of the Linnsean orders are all drawn from the nature of the wings, except one, Aptera, and that from the absence of wings. The different methods of specialization of the wings arose very early in that part of the geological history of insects that is known to us. And as most of the fossil remains of the older insects consist of wings, we are forced to depend very largely on the characters presented by these organs for data regarding the separation of the primitive insects into the groups from which the orders of recent insects have been developed. But in characterizing the orders as they now exist all the results of the study of the structure of insects and of their transformations are available. Aside from the structure of the wings, the characters most used in characterizing the orders of insects are those presented by the structure of the mouth-parts and the nature of the post-embryonic development. While these characters are of value in defining the orders, but little use has been made of them, as yet, in working out the lines of descent of the various orders from the primitive insects. The primitive insects had chewing mouth-parts and this type has been retained in the greater mmiber of the orders. But although many detailed accounts of the structure of the mouth-parts of chew- ing insects have been published, no one has worked out the various ways in which they have been specialized in such a manner as to in- dicate the phylogeny of the orders. Several different types of sucking mouth-parts exist among living insects; but these are apparently of comparatively late origin, and while they are of great value in defining the orders in which they occur, they do not afford characters for determining the primitive divisions of the Pterygota. The nature of the post-embryonic development of insects, like the structure of the mouth-parts, affords characters for defining the orders of recent insects, but is of little value in determining the phylogeny of the orders. The primitive insects doubtless developed without any marked metamorphosis as do the Thysanura and Collembola of today. With the development of wings, there arose that type of development known as gradual metamorphosis, and this type is retained by eight of the orders recognized in this work. Incomplete metamorphosis is the result of a sidewise development of the immature instars of the insects exhibiting it, in order to fit them for life in the water, and it doubtless arose independently in each of the three orders in which it occurs; it is therefore an ordinal characteristic in each case and not one indicating a natural group of orders. This is also true of com- HEX A POD A 209 plete metamorphosis, which also doubtless arose independently in different divisions of the insect series, as, for example, intheNeurop- tera, which it is believed is a very ancient order, the origin of which was much earlier than the attainment of complete metamorphosis. TABLE OF THE METHODS OF SPECIALIZATION OF THE WINGS CHARACTERISTIC OF THE ORDERS OF WINGED INSECTS* This table is merely the result of an eflfort to indicate the more striking of the methods of specialization of the wings characteristic of each of the orders of insects. It is not a key for determining the orders of insects. It is not avail- able for this purpose; because, in many cases, the wings of an insect do not show the type of specialization characteristic of the order to which the insect belongs. Thus, for example, while the most characteristic modification of the courses of the wing-veins in the Diptera and Hymenoptera is due to the coales- cence of veins proceeding from the margin of the wing towards the base of the wing, there is no indication of this type of coalescence of veins in some of the nemocerous Diptera. A. Wings specialized by the development of supernumerary veins in the preanal area. B. Supernumerary veins of the accessory type. C. Wings developed externally. D. Wings retained throughout life. Wings without a striking contrast in the thickness of the veins of the anterior part of the wing and those of the middle portion Orthoptera DD. Wings deciduous, there being near the base of each wing a trans- verse suture along which the wing is broken off after the swarming flight. Wings with the veins of the anterior part of the wing greatly thickened and those of the middle portion reduced to narrow lines ISOPTERA CC. Wings developed internally Neuroptera BB. Supernumerary veins of the intercalary type. C. Flight -function cephalized; the hind wings being greatly reduced in size Ephemerida CC. Flight-function not cephalized; the hind wings as large as or larger than the fore wings Odonata AA. Wings speciaHzed by a reduction in the number of veins in the preanal area. B. Wings developed externally. C. The two pairs of wings similar in texture. D. With the tendency to develop accessory veins retained. . Plecoptera DD. With the tendency to develop accessory veins in the preanal area lost, E. With the courses of some of the longitudinal veins modified so that they function as cross-veins Corrodentia EE. The transverse bracing of the wing attained in the usual way. F. The veins of the wing bordered with dark bands.. .Embiidina FF. The veins of the wing not bordered with dark bands. G. Wings long and narrow, supplemented by a wide fringe of hairs Thysanoptera GG. Wings not greatly narrowed and not supplemented by a wide fringe of hairs Homoptera CC. The front wings more or less thickened. D. The front wings not greatly reduced in length as compared with the hind wings. E. The front wings thickened throughout Homoptera EE. The front wings thickened at the base, the terminal portion membranous Heteroptera DD. The front wings greatly reduced in length Dermaptera *From "The Wings of Insects," pp. 120-122. 210 AN INTRODUCTION TO ENTOMOLOGY BB. Wings developed internally. C. Fore wings greatly thickened. D. Fore wings modified so as to serve as covers of the posterior wings COLEOPTERA DD. Fore wings reduced to slender, leathery, club-shaped appendages Strepsiptera CC. The two pairs of wings similar in texture. D. With the tendency to develop accessory veins retained. .Mecoptera DD. With the tendency to develop accessory veins lost. E. The most characteristic method of reduction of the wing-veins of the preanal area being by coalescence outward. F. Anal veins of the fore wings tending to coalesce at the tip. Wings usually clothed with hairs Trichoptera FF. Anal veins of the fore wings not tending to coalesce at the tip. Wings clothed with scales Lepidoptera EE. The most characteristic method of reduction of the wing-veins of the preanal area being by coalescence from the margin of the wing inward. F. With only one pair of wings Diptera FF. With two pairs of wings Hymenoptera The sequence in which the orders of insects are discussed in the following chapters has been determined by the above table. This sequence, lil^e all linear arrangements of groups of organisms, is more or less arbitrary. Thus while there is an effort to place first the more generalized orders and later those that are more specialized, the putting together of orders exhibiting the same type of specialization results in some cases in the placing of comparatively generalized forms after those that are obviously more highly specialized. The position of the Plecoptera is an illustration of this. The insects of this order are evidently more generalized than, for example, the Neuroptera or the Odonata, which are placed earlier in the linear series. The comparatively high position assigned to the Plecoptera is, however, only apparent. A reference to the table will show that the orders of insects are grouped in two series, "A" and "AA". Under "A" are placed those orders in which the wings are specialized by addition in the preanal area, and under "AA" those orders in which the wings are specialized by reduction in the preanal area. Each of these series includes some quite generalized insects and others that are highly specialized. The completion of the discussion of the first series before taking up the second series results in the generalized members of the second series following the highly specialized members of the first series. The more generalized members of these two series, the Orthoptera of the first series and the Plecoptera of the second series, are probably more closely allied to each other than is either of these orders to the more specialized orders of the series in which it is placed; the two series arose from a common starting point, the Palaeodictyoptera, but have widely diverged in the course of their development. An even more striking illustration of the difficulty of indicating the relative ranks of orders by the use of a single linear series is the position of the Isoptera in the above table. This order is a very HEX APOD A 211 ancient one; it separated from the Palasodictyoptera before definite cross-veins in the wings had been developed and has not attained them. It is placed in the table next to the Orthoptera because the wings are specialized by the development of supernumerary veins of the accessory t3pe and are developed externally; but the peculiar specialization of the wings is very different from that of the Orthop- tera as is indicated in the table. And in other respects the termites have reached a stage of development far in advance of that shown by any of the Orthoptera. They have attained a social mode of life, with the correlated separation of the species into several castes and the development of remarkable instincts. In this respect they rival the social H^Tnenoptera. In fact the living members of each of the orders of insects must be regarded as a group of organisms representing the results of speciali- zation in a direction different from that of any other order; and to attempt to decide which order is the "highest" seems as futile as the discussion by children of the question: "Which is better, sugar or salt?" The "list below indicates the sequence in which the orders are discussed in the following chapters. THE SUBCLASSES AND ORDERS OF THE HEXAPODA SUBCLASS A'^TFRYGOTA. — Wingless insects in which the wingless condition is believed to oe a primitive one, there being no indication that they descended from winged ancestors. ORDER PROTURA. — The Telson-tails. p. 218. ORDER THYSANURA. — The Bristle-tails. p. 219. ORDER COLLEMBOLA. — The Spring-tails. p. 225. SUBCLASS PTERYGOTA. — Winged insects and wingless insects in which the wingless condition is believed to be an acquired one. ORDER ORTHOPTERA. — The Cockroaches, Crickets, Grasshoppers, and others, p. 230. ORDER ZORAPTERA. — The genus Zorotypus. p. 270. ORDER isoPTERA. — The Termites or White Ants. p. 273. ORDER NEUROPTERA. — The Dobson, Aphis-lions, Ant-lions, and others, p. 281. ORDER EPHEMERiDA. — The May-flies. p. 303. ORDER ODONATA. — The Dragon-flies and ths Damsel-flies, p. 314. ORDER PLECOPTERA. — The Stone-flies. p. 325. ORDER CORRODENTIA. — The Psocids. p. 33 1. ORDER MALLOPHAGA. — The Bird-lice. p. 335. ORDER EMBUDINA. — The Embiids. p. 338. ORDER THYSANOPTERA. — The Thrips. p. 341. ORDER ANOPLURA. — The Lice. p. 347. ORDER HOMOPTER.\. — The Cicadas, Leaf-hoppers, Aphids, Scale-bugs, and others, p. 394. ORDER HEMiPTERA. — The True Bugs. p. 350. ORDER DERMAPTERA. — The Earwigs. p. 460. ORDER COLEOPTERA. — The Beetles, p. 464. ORDER STREPSIPTERA. — The Twisted Winged Insects, p. 546. ORDER MECOPTERA. — The Scorpion-flies. p. 550. ORDER TRICHOPTERA. — The Caddice-flies. p. 555. ORDER LEPIDOPTERA. — The Moths, the Skippers, and the Butterflies, p. 571. ORDER DIPTERA. — The Flies. p. 773. .. . -.---. ORDER SIPHONAPTERA. — The Fleas. p. 877. '^tSlQii^A/ ORDER HYMENOPTERA. — The Bees, Wasps, Ants, and others, p. 884. lXV_ -_^ ^ '• t 212 AN INTRODUCTION TO ENTOMOLOGY TA BLE FOR DETERMINING THE ORDERS OF THE HEX A POD A This table is merely intended to aid the students in determining to which of the orders a specimen that he is examining belongs. No effort has been made to indicate in the table the relation of the orders to one another. A. Winged. (The wing-covers, Elytra, of beetles and of earwigs are wings.) B. With two wings. C. Wings horny, leathery, or parchment-like. D. Mouth-parts formed for sucking. Wings leathery, shortened, or membranous at the tip. p. 350 Hemiptera DD. Mouth-parts formed for biting. Jaws distinct. E. Wings horny, without veins. Hind legs not fitted for jumping. p. 464 COLEOPTERA EE. Wings parchment-lilce with a network of veins. Hind legs fitted for jumping, p. 230 Orthoptera CC. Wings membranous. . D. Abdomen with caudal filaments. Mouth-parts vestigial. E. Halteres wanting, p. 308 Ephemerida EE. Halteres present (males of Coccidas). p. 394 Homoptera DD. Abdomen without caudal filaments. Halteres in place of second wings. Mouth-parts formed for sucking, p. 773 Diptera BB. With four wings. C. The two pairs of wings unlike in structure. D. Fore wings reduced to slender club-shaped appendages; hind wings fan-shaped with radiating veins. Minute insects, p. 546. .Strepsiptera DD. Front wings leathery at base, and membranous at tip, often over- lapping. Mouth-parts formed for sucking, p. 350. . .Hemiptera DDD. Front wings of same texture throughout. E. Front wings horny or leathery, being veinless wing-covers. (Ely- tra). F. Abdomen with- caudal appendages in form of movable forceps. p. 460 Dermaptera FF. Abdomen without forceps-like appendages, p. 464. Coleoptera EE. Front wings leathery or parchment-like with a network of veins. F. Under wings not folded; mouth-parts formed for sucking. G. Beak arising from the front part of the head. p. 350. Hemiptera GG. Beak arising from the hind part of the lower side of the head. p. 394 Homoptera FF. Under wings folded lengthwise. Mouth-parts formed for chewing, p. 230 Orthoptera CC. The two pairs of wings similar, membranous. D. Last joint of tarsi bladder-like or hoof-like in form and without claws, p. 341 Thysanoptera DD. Last joint of tarsi not bladder-lilce. E. Wings entirely or for the greater part clothed with scales. Mouth- parts formed for sucking, p. 571 Lepidoptera EE. Wings naked, transparent, or thinly clothed with hairs. F. Mouth-parts arising from the hinder part of the lower surface of the head, and consisting of bristle-lil<;e organs inclosed in a jointed sheath, p. 394 Homoptera FF. Mouth-parts in normal position. Mandibles not bristle-like. G. Wings net-veined, with many veins and cross-veins. H. Tarsi consisting of less than five segments. I. Antennas inconspicuous, awl-shaped, short and slender. J. First and second pairs of wings of nearly the same length; tarsi three-jointed, p. 314 Odonata JJ. Second pair of wings either small or wanting; tarsi four-jointed, p. 308 Ephemerida II. Antenna usually conspicuous, setiform, filiform clavate, capitate, or pectinate. J. Tarsi two- or three- jointed. K. Second pair of wings the smaller. Pc 33 1 . Corrodentia HEX A POD A 213 KK. Second pair of wings broader, or at least the same size as the first pair. p. 325. . . .Plecoptera JJ. Tarsi four-jointed; wings equal, p. 273. .Isoptera HH. Tarsi consisting of five segments. I. Abdomen with setiform, many-]ointed anal filaments. (Certain May-flies), p. 308 Ephemerida II. Abdomen without many-jointed anal filaments. J. Head prolonged into a trunk-like beak. p. 550.MECOPTERA J J. Head not prolonged into a beak. p. 281.. .Neuroptera GG. Wings with branching veins and comparatively few cross- veins, or veinless. H. Each of the veins of the wing extending along the middle of a brown line. p. 338 Embiidina HH. Wings not marked with brown lines. I. Tarsi two-or three- jointed. J. Hind wings smaller than the fore wings. K. Cerci present; body less than three millimeters in length, p. 270 ZORAPTERA KK. Cerci absent; larger insects, p. 331..C0RRODENTIA JJ. Posterior wings as large as or larger than the anterior ones. (Certain Stone-flies), p. 325 Plecoptera II. Tarsi four- or five-jointed. J. Abdomen with setiform, many-]ointed anal filaments. (Certain May-flies), p. 308 Ephemerida JJ. Abdomen without many-jointed anal filaments. K. Prothorax horny. First wings larger than the second, naked or imperceptibly hairy. Second wings without, or with few, unusually simple, veins. Jaws (mandibles) well developed. Palpi small, p. 884. . . . Hvmenoptera KK. Prothorax membranous or, at the most, parchment- like. Second wings as large as or larger than the first, folded lengthwise, with many branching veins. First wings naked or thinly clothed with hair. Jaws (mandibles) inconspicuous. Palpi long. JVIoth-like insects, p. 555 Trichoptera AA. Wingless or with vestigial or rudimentary wings. B. Insects with a distinct head and jointed legs, and capable of locomotion. C. Aquatic insects. D. Mouth-parts fitted for piercing and sucking. E. Free-swimming nymphs, p. 350 Hemiptera EE. Larvae parasitic in sponges (Sisyridae). p. 281 Neuroptera DD. Mouth-parts fitted for chewing. E. Either somewhat caterpillar-like larvae that live in portable cases or campodeiform larvae that spin nets for catching their food. (Caddice- worms). p. 555 Trichoptera EE. Neither case-bearing nor net-spinning larvae. F. Naiads, that is, immature insects that resemble adults in having the thorax sharply differentiated from the abdomen, and, except in very young individuals, with rudimentary wings. G. Lower lip greatly elongated, jointed, capable of being thrust for- ward, and armed at its extremity with sharp hooks, p. 314.ODONATA GG. Lower lip not capable of being thrust forward. H. Usually with filamentous tracheal gills on the ventral side of the thorax, p. 325 Plecoptera HH. Tracheal gills borne by the first seven abdominal seg- ments, p. 308 Ephemerida FF. Larvae, that is, immature forms that do not resemble adults in the form of the body, and in which the developing wings are not visible externally. G. Several segments of the abdomen fiu-nished with prolegs. p. 571 Lepidoptera GG. With only anal prolegs or with none. 214 AN INTRODUCTION TO ENTOMOLOGY H. With paired lateral filaments on most or on all of the ab- dominal segments. (SiaHdas). p. 281 Neuroptera See also Haliplidas and Gyrinidas. p. 464 Coleoptera HH. Without paired lateral filaments on the abdomen, p. 464. Coleoptera CC. Terrestrial insects. D. External parasites. E. Infesting the honey-bee. (Braula). p. 773 Diptera EE. Infesting birds or mammals. F. Body strongly compressed. (Fleas), p. 877 Siphonaptera FF. Body not strongly compressed. G. Mouth-parts formed for chewing. (Bird-lice), p. 335. Mallophaga GG. Mouth-parts formed for piercing and sucking. H. Antennre inserted in pits, not visible from above. (Pupi- para). p. 773 Diptera HH. Antennae exserted, visible from above. G. Tarsi with a single claw which is opposed by a toothed pro- jection of the tibia. (Lice), p. 347 Anoplura GG. Tarsi two-clawed, p. 350 Hemiptera DD. Terrestrial insects not parasites. E. Mouth-parts apparently retracted within the cavity of the head so that only their apices are visible, being overgrown by folds of the genae. F. Abdomen consisting of ten or eleven segments. (Campodeidce and Japygidae). p. 220 Thysanura FF, Abdomen consisting of not more than six segments, p. 225. Collembola EE. Mouth-parts mandibulate, either fitted for chewing or with sickle-shaped mandibles formed for seizing prey. (See also EEE.) F. Larvffi with abdominal prolegs. G. Prolegs armed at the extremity with numerous minute hooks. (Caterpillars), p. 571 Lepidoptera GG. Prolegs not armed with minute hooks. H. With a pair of ocelH, one on each side. (Larvas of saw-flies). p. 884 Hymenoptera HH. With many ocelli on each side of the head. p. 550 Mecoptera FF. Without abdominal prolegs. G. Body clothed with scales. (Machihdas and Lepismatidae). p. 220 Thysanura GG. Body not clothed with scales. H. Antennae long and distinct. I. Abdomen terminated by strong movable forceps, p. 460. Dermaptera II. Abdomen not terminated by forceps. J. Abdomen strongly constricted at base. (Ants. etc.). p. 884 Hymenoptera JJ. Abdomen not strongly constricted at base. K. Head with a long trunk-like beak. {Boreus). p. ^50. Mecoptera KK. Head not prolonged into a trunk. L. Insects of small size, more or less louse-like in form, with a very small prothorax, and without cerci. (Book-lice and Psocids). p. 331 CorrodExNTIA LL. Insects of various forms, but not louse-like, prothorax not extremely small; cerci present. M. Hind legs fitted for jumping, hind femora en- larged. (Wingless locusts, grasshoppers, and crickets), p. 230 Orthoptera MM. Hind femora not greatly enlarged, not fitted for jumping. HEX A POD A 215 N. Prothorax much longer than the mesc thorax; front legs fitted for grasping prey. (Mantidas). p. 230 Orthoptera NN. Prothorax not greatly lengthened. O. Cerci present; antennas usually with more than fifteen joints, often many-jointed. P. Cerci with more than three joints. Q. Body flattened and oval. (Blattidas). p. 230 Orthoptera QQ. Body elongate. R. Head very large. (Termopsis) . p. 273. ISOPTERA RR. Head of moderate size. p. 268. Grylloblattid^ PP. Cerci short, with one to three joints. Q. Body hnear with very long linear legs. (Walking-sticks), p. 230 ... Orthoptera QQ. Body elongate or not, if elongate the legs are not linear. R. Body elongate, front tarsi with first joint swollen, p. 338. . . Embiidina RR. Front tarsi not enlarged. S. Minute insects, less than 3 mm, in length; antennae nine-jointed. p. 270 Zoraptera SS. Larger insects,; antennae usually more than nine- jointed. (White-ants) . p. 273 Isoptera 00. Cerci absent; antennse usually with eleven joints, p. 464 Coleoptera HH. Antennae short, not pronounced; larval forms. I. Body cylindrical, caterpillar-like. p. 550.MECOPTERA II. Body not caterpillar-like. J. Mandibles sickle-shaped; each mandible with a furrow over which the maxilla of that side fits, the two forming an organ for piercing and sucking. (Ant-lions, aphis- lions, hemerobiids). p. 281 Neuroptera JJ. Mouth-parts not of the ant-lion type. K. Larva of Raphidia. p. 281 Neuroptera KK. Larvae of beetles, p. 464 Coleoptera EEE. Mouth-parts haustellate, fitted for sucking; mandibles not sickle-shaped. F. Body covered with a waxy powder or with tufts or plates of wax. (Mealy-bugs, Orthezia). p. 350 Hemiptera FF. Body more or less covered with minute scales, or with thick- long hairs; proboscis if present coiled beneath the head: (Moths). p. 57 1 Lepidoptera FFF. Body naked, or with isolated or bristle-like hairs. G. Prothorax not well developed, inconspicuous or invisible from above, p. 773 Diptera GG. Prothorax well developed. H. Last joint of tarsi bladder-like or hoof-like in form and usually without claws; mouth-parts forming a triangular unjointed beak. p. 550 Thysanoptera HH. Last joint of tarsi not bladder-like, and ftunished with one or two claws; mouth-parts forming a slender; usually jointed beak. I. Beak arising from the front part of the head. p. 350. Hemiptera II. Beak arising from the back part of the head. p. 394 . . . .0 HOMOPTERA 216 AN INTRODUCTION TO ENTOMOLOGY BB. Either without a distinct head, or without jointed legs, or incapable of locomotion. C. Forms that are legless but capable of locomotion; in some the head is distinct, in others not. Here belong many larvae representing several of the orders, and the active pupse of mosquitoes and certain midges. It is impracticable to separate them in this key. CC. Sedentary forms, incapable of locomotion. D. Small abnormal insects in which the body is either scale-like or gall- like in form, or grub-like clothed with wax. The waxy covering may be in the form of powder, or large tufts or plates, or a continuous layer, or of a thin scale, beneath which the insect lives. (Coccidse). p. 350.HEMIPTERA DD. Pupae, the inactive stage of insects with a complete metamor- phosis; capable only of a wriggling motion, and incapable of feeding. E. Obtected pupae, pupae in which the legs and wings are glued to the surface of the body; either in a cocoon or naked, p. 571 . Lepidoptera EE. Coarctate pupae, pupae enclosed in the hardened larval skin. p. 773 DiPTERA EEE. Exarate pupae, pupas that have the legs and wings free; either in a cocoon or naked. This type of pupa is characteristic of all of the orders in which the metamorphosis is complete except the Lepidop- tera and Diptera. The order Protura does not occur in the foregoing table because it has only now, in this edition (1936), been placed among the Hexapoda. Since the members of the order are uncommon insects rarely met with it did not seem advisable to incur the added expense of rearranging and reprinting a large part of the table. CHAPTER VI Subclass I. APTERYGOTA Wingless Insects The members of this subclass are small wingless insects in which the wingless condition is believed to be a primitive one, there being no indication that they have descended from winged ancestors. The month- parts vary. In some they are sucking, in others chewing. The meta- morphosis is always slight and in some cases absent. This subclass contains but the three orders, Protura, Thysanura, and Collembola. These insects are all primitive and usually general- ized. They are all small and wingless and because of their usually concealed habits are not as generally known as the winged forms. They are widely distributed and about 1200 species are now known. Probably many more remain to be discovered. A characteristic feature of these primitive insects is the abdominal appendages, especially the abdominal styli present in the Machilidae and in others of the Thysanura. (217) CHAPTER VII ORDER PROTURA The Tclson-Tails The members of this order are small arthropods in which the body is elongate, as in the Thysanura, fusiform, pointed behind, and depressed; it may be greatly extended and retracted. The antennce, cerci and compound eyes are absent. The oral apparatus is suctorial, and consists of three pairs of gnathites. There are three pairs of thoracic legs, and three pairs of vestigial abdominal legs. The abdomen is composed of eleven segments and a telson. The opening of ihe reproductive organs is unpaired, and near ihe hind end of the body. The head bears a pair of organs, termed pseitdocidi, the nature of which has not been definitely determined. The metamorphosis is slight, consisting of an increase in the number of abdominal segments. The known members of this order are very small arthropods, the body measuring fron one fiftieth to three-fiftieths of an inch in length. The form, of the body is shown by Figure 36, p. 25. These exceedingly interesting creatures are found in damp situa- tions, as in the humus of gardens. They are widely distributed: they are now known to occur in India, England, Italy, and other European countries. A number of species have been described from the southwestern United States. The mouthparts are withdrawn into the head and the mandibles are stylet-like and fitted for piercing. In the newly hatched insect the abdomen is 9-segmented, but during later growth three more segments are added between the last two segments. This mode of change in form is known as anamorphosis. The systematic position of the Protura is still unsettled. The differentiated thorax with three pairs of legs and the form of the mouthparts are characteristic of insects. The lack of antennae and the intercalary addition of body segments during growth (ana- morphosis) are very unlike insects. The name Protura refers to the last telson-like segment of the abdomen. The order contains two families as follows : Family i. Acerentomid^, in which the tracheae and spiracles are absent and the second and third abdominal appendages are i- jointed. This family includes the two genera Acerentomon and Acerentidus. Family 2. Eosentomidae, in which tracheae are present with two pairs of thoracic spiracles and the second and third abdominal appendages are 2-jointed. This family includes the genus Eosen- tomon and probably Protapteron. (218) THYSANURA 219 ORDER THYSANURA* The Bristle-Tails The members of this order are wingless insects in which the wingless condition is believed to he a primitive one, there being no indication that they have descended from winged ancestors; the month-parts ore formed for cheiving; and the adult insects resemble the young in form. In these three respects, these insects resemble the next order, the Collembola; but they differ from the Collembola in that the abdominal segments are not reduced in number and the cerci are usually filiform and many-jointed; some members of the order have also a caudal fila- ment. The members of this order are known as bristle-tails, a name suggested by the pres- ence, in most of them, of either two or three many- jointed filiform appendages at the cau- dal end of the body (Fig. 221, c, and m f) . The paired caudal appendages are the cerci; the median one, when three are present, is the median caudal filament, a prolongation of the eleventh abdominal segment. In fdpyx (Fig. 222), the cerci are not jointed but are strong, curved appendages, resembling the forceps of earwigs. The bristle-tails are most often found under stones and other objects lying on the ground; but some species live in houses. While most species prefer cool situations, there is one, the fire-brat, that fre- quents warm ones, about fire- places and in bakehouses. The antennae are long and many- jointed. In the Machilidas Fig. 221. — Machilis, ventral aspect: c, cer- cus ; Ip, labial palpus ; mf, median caudal filament: mp, maxillary palpus; 0, ovi- positor; s, s, styli. "Thysanura: thysanos (Svpavos), a tassel; oiira {ovpd), the tail. 220 AN INTRODUCTION TO ENTOMOLOGY Fig. 222. — Japyx sol- ifugus. (After Lub- bock.) (Machilts), the eyes are very perfect; for this reason, they are used in Chapter III to illustrate the structure of the compound eyes of insects. In all other Apterygota they are more or less degenerate or are lost entirely. In the Lepismatidas (Lepisma) , the degeneration of the eyes has progressed far, they being reduced to a group of a dozen ommatidia, on each side of the head. In the Campodeidas and the Jap}^gidae, the eyes have disappeared. The mouth-parts are formed for chewing ; those of Machilis will serve to illustrate their form. The mandibles are elongate with a toothed apex and a sub-apical projection teimi- nated by a grinding surface (Fig. 223, A); the paragnatha are comparatively well developed (Fig. 224); on the outer edge of each there is a small lobe, which Carpenter ('03), who regarded the organs as true appendages, believed to be a vestigial palpus, and at the tip there are two dis- tinct lobes, which this author homologized with the galea and the lacinia of a typical maxilla; the maxillge (Fig. 223, B) bear prominent palpi. In the Campodeidas and the Japygidas, the jaws are apparently sunk in the head. This con- dition is due to their being overgrown by folds of the genae. In the Machilidffi and the Lepismatidas the jaws are not overgrown; these two families are known, on this account, as the Ectotrophi or Ectotro- phous Thysanura; while the Campodeidas and the Japygidas are grouped together as the Ento- trophi or Entotrophous Thysanura. The over- growing of the mouth- parts by folds of the gense is characteristic of the Collembola also and is discussed more fully in the next chapter. The three thoracic segments are distincth' separate. There is noth- ing in the structure of the thorax to indicate that these insects have descended from winged ancestors. The three pairs of legs are well developed. In the genus Machilis the cox^ of the second and third pairs of legs each bears a stylus (Fig. 221, s). Fig. 223. — A, mandibles of Machilis; B, maxilla of Machilis. (After Oudemans.) THYSANURA 221 The abdomen consists of eleven segments. The eleventh segment bears the cerci, which are filiform and many-jointed except in th(j Japygidge, where they are forceps-like. In the Machilidee and the Lepismatids the eleventh abdominal segment bears a long, many-jointed median caudal filament; styli and eversible ventral sacs are also usually present ; these vary in number in difi'erent genera. The styli are slender appendages (Fig. 221, s). Each stylus consists of two segments, a very short basal one and a much longer termi- nal one. The maximimi number of styli is found in Machilis (Fig. 221), where they are borne by the second and third thoracic legs and the second to the ninth abdominal seg- ments. In Lepisma there are only three pairs; these are borne by the seventh, eighth, and ninth abdominal segments. The abdominal styli are borne by large plates, one on each side of the ventral aspect of each abdominal segment. These plates are termed coxites, as they are believed to be flat- tened coxae of abdominal legs which have otherwise disappeared. A result of the large size and position of the coxites is a reduction in the size of the sternum in the abdominal segments. This is well shown in Machilis (Fig. 221) ; in the first seven abdominal segments, there is in each a median triangular sclerite; this is the stemimi; in the eighth and ninth segments no sternum is visible. Fig. 224. — One of the paragnatha of Ma- chilis. (After Car- penter.) Fig. 225. — Cross-section of an abdominal segment of Machilis showing the styli and the ventral sacs. The ventral sacs of the left side are retracted ; those of the right side, expanded. (After Oudemans.) In the families Machilidas and Lepismatidas the females have an ovipositor, which consists of two pairs of filiform gonapophyses aris- ing from between the coxites of the eighth and ninth aiadominal segments respectively. 222 AN INTRODUCTION TO ENTOMOLOGY The ventral sacs are sac-like expansions of the wall of the coxites which can be everted, probably by blood -pressure, and are withdrawn into the cavity of the coxite by muscles (Fig. 225). In Figure 221, the openings into the retracted ventral sacs are represented ; there is one pair in the first abdominal seg- ment; two pairs in each of the four following segments; and a single pair each in the seventh and eighth ab- dominal segments. In Lepisma the ventral sacs are wanting. The func- tion of the ventral sacs has not been definitely determined; but it seems probable that they are blood-gills. The presence in the Thysanura of styli and of ventral sacs, which are evidently homologous with those of the Symphyla, is an indication of the primitive condition of these insects. The generalized form of the reproductive organs of the Thy- sanura is another indication of this. In Japyx the ovarian tubes have a metameric arrangement (Fig. 226); and in Machilis (Fig. 227) we find an intermediate form between a metameric arrange- ment of the ovarian tubes and a compact ovary. These facts, and especially the presence of styli and ventral sacs, are opposed to the view held by some writers that the Thysanura are degenerate instead of primitive insects. It is true that degenerate fea- tures are present in the order, as the loss of eyes in Japyx and Campodea; but this loss is correlated with the life of these insects in dark places, like the loss of eyes in certain cave-beetles, and is not important in the determination of the zoological position of the order. The young of the Thysanura resemble the adults in form, there being no marked metamorphosis. In Campodea and Japyx the molt is partial (Grassi '89). This is a small order; less than twenty American species have been described. The classification is as follows : Fig. 226. — Ovary of Ja- pyx. (After Grassi.) Fig.227.— Ovary of Machilis: c, coxite of the eighth abdomi- nal segment; s, stylus; o, ovi- positor. (After Oudemans.) Suborder I. ECTOGNATHA Body usually clothed with scales; monthparts outside of the head, not overgrown with folds of the genae; caudal end of abdomen with three long, filiform appendages; compound eyes present. Family i, Machilidae. The abdominal tergites reflexed to the under surface so as to form an imbrication covering the sides of the THYSANURA 223 coxites (Fig. 221). Compound eyes large and contiguous. Pro- thorax smaller than the mesothorax. Middle and hind legs with vStyli. Saltatorial insects. This family is represented by the genus Machilis, of which several species occur in North America. These insects are found in heaps of stones and in other concealed places; they are very active and leap with agility when disturbed. They are about 12 mm. in length. Family 2, Lepismatidae. Abdominal tergites not covering the sides of the coxites. Eyes small and distant. Prothorax as large as or larger than the mesothorax. Middle and hind legs without styli. Not saltatorial insects. The best-known representative of this family is the silverfish or fish-moth Leptsma sacchanna (Fig. 228). It is silvery white with a yellowish tinge about the antennas and legs and measures about Fig. 228. — Lepisma saccharina. (After Lubbock.) 8 mm. in length. It is often a troublesome pest in laundries, li- braries, and museums, as it injures starched clothes, the bindings of books, labels, and other things on which paste or gkie is used. The popular names were suggested by the clothing of scales with which the body is covered. Another common representative of this family is the fire-brat, Thermobia domcstica. This species resembles the fish-moth in general appearance except that it has dusky markings on its upper surface. It is remarkable for frequenting warm and even hot places about ovens, ranges, and fireplaces. 224 AN INTRODUCTION TO ENTOMOLOGY Suborder II. ENTOGNATHA* Body not clothed with scales; mouthparts within the head, being overgrown by folds of the gence; median caudal filament wanting; com- pound eyes absent. Family 3, Campodeid^. Cerci filiform, long and many-jointed; first abdominal segment without styli. The best-known member of this family is Campodea staphylmus (Fig. 229). It lives in damp places under stones, fallen trees, or in rotten wood and leaves. It is a very delicate, small, white insect, about 6 mm. in length. It has on the first abdominal segment a pair of appendages which occupy a position corre- sponding to that of the thoracic legs and each consists of two or three segments. Family 4, Projapygidae. Cerci short, rather stout, few-jointed; first abdominal seg- ment with styli. This family is represented by the genera Projapyx and Anajapyx. The species A. vesiculosus described by Silvestri may be considered representative. Family 5, Japygidae. Cerci forceps-like; styli present on first abdominal segment. This family is represented by the genus Jdpyx, of which two species have been found in this country. These insects can be recognized i7,-„ -,^„ ^ >, J by the forceps-like form of the cerci (Fig. 222). -big. 229. — Campodea rJ, n j i- .. • / staphylmus. (After They are small, delicate, uncommon msects Lubbock.) found under stones. *This suborder is raised to the rank of an order, Diplura, by Silvestri. Other systeraatists believe it should rank as a definite order. COLLEMBOLA 225 ORDER COLLEMBOLA* The Spring-Tails The members of this order resemble the Thysanura in being wingless insects in which the wingless condition is believed to be a primitive one, there being no indication that they have descended from winged ancestors, and in that the adtdt insects resemble the young in form. They differ Fig. 230. — Side view of Tomocerus plumbens: co, coUophore; c, catch; s spring. (Aftar Willem.) from the Thysanura as follows: the abdominal segments are reduced in number, there being only six of them; the first abdcnninal segment bears a ventral tube, the coUophore, furnished with a pair of eversible sacs which assist the insects in walking on smooth surfaces; the fourth abdominal segment usually bears a pair of appendages, which constitute a spring- ing organ; and the third abdominal segment usually bears a short pair of appendages, the catch, which hold the spring when it is folded under the abdomen. The common name spring-tails has been appHed to these insects on account of the caudal springing organ that is possessed by most members of the order. The spring- tails are minute insects, often of microscopic size and rarely as large as 5 mm. in length. Most of the species live on decaying matter. These insects are common under stones and decayed leaves and wood, in the chinks and crevices of bark, among moss, and on herbage in damp places. Sometimes they occur abundantly in winter on the surface Fig. 231. — An ommatid- ium of Podiira aqual- ica. (After Willem.) *Collembola: collophores. colla {K6X\a), glue; embolon {iix^oKov), a bolt, bar; — from their 226 AN INTRODUCTION TO ENTOMOLOGY of snow, where they appear as minute black specks, which spring away on either side from our feet as we walk; and some species collect in great numbers on the surface of standing water. Sev- eral species are known to be photogenic. The body consists of the head, three thoracic segments, and six abdominal segments (Fig. 230). The prothorax is usually small and in several genera is overlapped by the tergum of the mesothorax ; in theSminthuridffi the body-segrnents are more or less fused together. The structure of the abdomen is remarkable, as it consists of only six segments; there is no indication of the manner in which the reduc- tion of the number of segments has taken place. The anus is at the caudal end of the body; the genital opening is on a small papilla on the fifth abdominal segment. The antenna consist of from four to six segments, usually of four. They vary greatly in their comparative length; in some genera the last segment or the last two segments are divided into many rings orsubsegments(Fig.23o). The eyes of the Col- lembola are commonly described as a group of eight, or fewer, distinct simple eyes on each side of the head. But these so-called simple eyes are not ocelli; they are more or less degenerate omma- tidia, each group being the vestige of a com- pound eye. In Podura aquatica, these eyes, as figured by Willem ('00), are clearly ommatidia of the eucone type (Fig. 231). In some other Col- lembola, as in Anurida niaritima (Fig. 232, O), the reduction of the om- matidia has progressed so far that they present the appearance of ocelli; and in still others the eyes are lost entire- ly. Primary ocelli have not been found in the Collembola. The mouth-parts are typically mandibulate; the jaws consisting of a pair each of mandibles, paragnatha, and maxillae. The parag- natha of Orchesella cincta were described by Folsom ('99) ; and those of Anurida niaritima by the same writer ('00). These organs were termed the siiperlingiiCB by Folsom. One of the most striking characteristics of the Collembola is that the jaws are apparently retracted into the cavity of the head so that only their tips are visible. But it has been shown by Folsom ('00), Fig. 232. — A, longitudinal section of an ommatid- ium and of the postantennal organ of Anurida niaritima; B, a surface view of the postantennal organ. (After Willem.) O, ommatidium ; Pa, post- antennal organ; hy, hypodemial cells; N, optic nerve; n, branch of the optic nerve; /, t, tuber- cles surrounding the postantennal organ;,, g, nerve-end-cell of the postantennal organ. (After Willem.) COLLEMBOLA 227 Fig. 233.— Hind foot of Ach- orutes maturus. (After Fol- som.) who studied the development of the mouth-parts of Anurida maritima, that, strictly speaking, the jaws are not "retracted," as is usually stated , but are overgrown by the genas. In an early embryonic stage, a downward projection of the gena ap- pears on each side of the head, and these "mouth -folds" become larger and larger in successive stages until the condition seen in the fully developed insect is reached. The development of mouth-folds is not restricted to the Collembola, but occurs also in the Entotrophous Thysan- ura, and to a less marked extent in many of the Pterygota, especially in some Orthoptera, where the gena of each side is prolonged into a small, but distinct, flat fold over the base of the mandible. In some of the Poduridas the mouth- parts are fitted for piercing and sucking, the mandibles and maxillae being styliform and projecting in a conspicuous cone. In some of the Collembola there is a sense organ situated between the base of the antenna and the ocular field; this is known as the postantennal organ; its presence o^ absence and its form when present afford characters used in the description of these insects. In its simplest form it is a claviform hyaline tubercle {Sminihurus) . A more complicated type is that of Anurida maritima, which has been figured by Willem ('00). In Figure 232, Pa repre- sents a longitudinal section of this organ. It is a nerve-end-cell, branching from the optic nerve and extending to the surface of the body, where it is covered by a very thin cuticular layer. It is pro- tected by a ring of tubercles {t, t), two of which are shown in the sectional view (A) and eight in the surface view (B). The function of this organ has not been determined; it has been suggested that it is an organ of smell. The legs of the Collembola consist each of five segments, which correspond to the five principal divisions of the legs of the higher insects. Willem ('00) considers the two antecoxal pieces as segments of the legs and consequently states that the legs are composed of seven segments The tarsi in most genera bear two claws, an outer, larger one, the unguis, and an inner, smaller one, the unguiadus; these claws are apposable (Fig. 22,^); in some genera the inner claw is wanting. One of the most characteristic features of the Collembola is the collophore, or ventral tube, which is situated on the ventral aspect of the first abdominal segment (Fig. 230, co). This organ varies greatly in form in the different genera; in some it is a simple tubercle, di- vided into two halves by a central slit; in others it is enlarged and becomes a jointed tube divided at its free end into two lobes. The 228 AN INTRODUCTION TO ENTOMOLOGY collophore bears at its extremity a pair of eversible sacs through the walls of which exude a viscid fluid. By means of this organ these insects are enabled to cling to the lower surface of smooth objects. The collophore is developed from a pair of appendages, which in the course of their development become fused together at their base. The third abdominal segment usually bears a pair of short append- ages, whose basal segments are fused; this is the tenaculum, or catch (Fig. 230, c), which holds thespring when it is folded under the abdomen. The spring or furcula (Fig. 230, s) is formed by the appendages of the fourth abdominal segment which are united at the base but separate distally. These ap- pendages are three-jointed. The united basal seg- ment is termed the manubrium (Fig. 234, ma); the intermediate segments, the denies (Fig. 234, d); and the terminal segments, the mucrones (Fig. 234, mu). In the Entomobryidse the furcula appears to be formed by the appendages of the fifth abdominal seg- ment; but a study of the muscles that move it shows that it really pertains to the fourth segment. In some genera of the Podurid^ the furcula is wanting. The order Collembola includes two quite distinct types of insects; in one of these types the body is elongate w4th distinct segmentation; in the other the body is shortened, the abdomen globose and its segments in part fused. Based on this distinction the order is divided into two suborders as follows : Fig. 234.— The furcula of Pa- pirius: ma, manubrium; d, left dens; mil, left muc- ro. (After Lubbock,) A. Body elongate Suborder Arthropleona. AA. Body globose Suborder Symphypleona. Fig. 235. — The rnow- flea, A chorutes ni'vi- cola. (After Fol- som.) Suborder I. ARTHROPLEONA* Body elongate with distinct segmentation, rare- ly with the last two or three segments of abdomen partially fused; tracheae absent. Family i, Poduridae. Furcula, when pres- ent, clearly appended to the fourth abdominal segment; prothorax well developed; cuticula usually granulated. Among the better-known members of this family are the following: The "Snow -flea," Achoriites nivicola, which occurs abundantly in winter on the surface of snow (Fig. 235); this species is also known as Achoriites socidlis. Achoriites armdtus is often found on fungi. *Arthropleona : arthron (dpdov), stacean's abdomen. joint; pleon, a cru- SYMPHYPLEONA 229 Anurida marUima occurs abundantly on the seashore, chiefly between tide marks; several important embryological and anatomical mono- graphs have been published regarding this species. Podiira aqiiatica is one of the most abundant members of the Collembola; it occurs on the surface of standing water on the margins of ponds and streams. Family 2, Entomobryidae. Furcula present and apparently appended to the fifth abdominal segment; prothorax reduced and cuticula not granulated. This is the largest family of the Collembola, containing many genera and species. In some genera the body is clothed with scales. To this family belongs the genus Orchesella, the only genus in the Collembola in which the antennae consist of six segments. Suborder II. SYMPHYPLEONA* Body shortened, sitbglobniar in shape with segments of body, except the last two, fused closely together and segmentation mostly obliterated; trachecB present in some genera. Family 3, Neelidae. Antennae short and stout; thorax large and longer than abdomen. The principal genera are Neehis and Ne elides. Family 4, Sminthuridae. Antennse long and slender; thorax shorter than abdomen. The principal genera Smin- thurus and Papirius. In Sminthurns, trachea are present; in Fig. 236. — Papirius fuscus- the other genera they are absent or ex- (After Lubbock.) tremely vestigial. The presence of tra- cheae in Sminthurns enables these insects to live in drier situations than can other Collembola. The " garden-^ea" S^mnthiirus hortensis is found upon the leaves of young cabbage, turnip, cucumber, and various other plants. *Symphypleona ; symphyo, to grow together; pleon, a crustacean's ab- domen. %g^ /^l^^^^ Subclass II. PTERYGOTA Winged Insects The members of this subclass are winged; or, if without wings, they have had winged ancestors and this is an acquired condition. The mouthparts vary; in some they are sucking, in others chewing. The metamorphosis varies from slight to gradual to complete. Much the greater number of species of insects belong to this subclass and much the greater number of them possess wings, for example, the beetles, flies, wasps, bees, and many others. Many aphids, all fleas, lice, worker ants, female scale insects, and some others have no wings. The wingless condition of these forms, how- ever, is an acquired one, for the evidence is clear that they have de- scended from winged ancestors. The subclass Pterygota contains all of the remaining twenty -three orders discussed in this book. CHAPTER Vlir ORDER ORTHOPTERA* Grasshoppers, Crickets, Cockroaches, and others The winged members of this order have two pairs of wings; the fore wings are more or less thickened, hut have a distinct venation; the hind wings are folded in plaits like a fan when at rest; there are many forms in which the wings are vestigial or even wanting. The month-parts are formed for chewing. The metamorphosis is gradual (paurometabolous) ; the nymphs are terrestrial. The order Orthoptera includes some of the veiy common and best- known insects. The most famiHar representatives are the long-homed grasshoppers, locusts, crickets, katydids, and cockroaches. With the exception of a single family, the Mantidae, the members of this order are as a rule injurious to vegetation; and many species are quite apt to multiply to such an extent that their destruction of plant life becomes of great economic importance. The two pairs of wings of the Orthoptera differ in structure. The front wings are leathery or parchment-like, forming covers for the more delicate hind wings. These wing-covers have received the special name tegmina. The tegmina usually overlap, at least at the tips, when at rest. The hind wings are thinner than the tegmina and usually have a broadly expanded anal area, which is folded in plaits like a fan when at rest. Many Orthoptera have vestigial wings, and many are wingless. In the males of the Saltatorial Orthoptera, the Locustidse, the Tettigoniidae, and the Gryllidae, musical organs have been formed by modifications of certain parts of the wings; these have been described in Chapter II. The mouth-parts are of the mandibulate type, that is, they are formed for chewing. The mouth-parts of a locust are figured on page 42. In the Orthoptera the metamorphosis is gradual, paurometabo- lous. In the case of those species in which the wings of the adult are either vestigial or wanting, the adults resemble very greatly immature insects. It is often important to determine whether a short-winged specimen is an adult or not. Fortunately this determination can usually be made with ease with the Saltatorial Orthoptera, the Locustidae, the Tettigoniidae, and the Gryllidae. In these three families the wing-pads of the nymphs are inverted, as shown by the curving down of the extremities of the wing-veins, instead of up as with the adult; and the rudimentary hind-wings are outside of the tegmina, instead of beneath them. The development of the wings of a locust is described in Chapter IV, p. 175. *0rth6ptera: orthos (dpdos), straight; pteron {irrepbv), a wing. (230) ORTHOPTERA 23 i The segmentation of the abdomen and the development and structure of tlie genitaha or gonapophyses in the jumping Orthoptera are of especial interest; as, on account of the generalized condition of these parts in these insects, they can serve as a type with which the corresponding parts in more specialized insects can be compared. In some members of this group of families all of the abdominal segments are preserved more or less distinct, and in nearh^ all of them the genitalia are well-developed.* The segmentation of the abdomen can be seen best on the dorsal aspect of this region; for in some cases the tergiun of a segment is well-pre- served while the sternum Fig. 237. — Side view of a locust with the wings re- is vestigial. Figure 237 moved: /, tympanum. represents a side view of a female locust with the wings removed in order to show the segmentation of the abdomen. The first eight segments of the abdomen of this insect are very distinct; but the caudal segments are much less so. Figure 238 represents the caudal part of the abdomen of the same insect more enlarged, in order to . _ facilitate the lettering of the parts. In this insect the eighth abdominal tergum resembles the preceding ones. The ninth and tenth abdominal terga are shorter and are joined together on each side; but in many other jumping Orthoptera these terga are not thus o..^^\ \ \JLy united. Caudad of the tenth abdomi- nal tergum there is a shield-shaped part, which is commonly known as the Fig. 238.- Side view of the caudal supra-anal plate; this plate is divided end of the abdomen of a female into two sclerites by a transverse su- ture; the first of these sclerites is be- lieved to be the tergum of the eleventh abdominal segment, and the other the telson (Fig. 238, t). Thus all of the abdominal segments are preserved, in part at least, in this insect. locust: 8, p, 10, II, the tergites of the eighth, ninth, tenth, and eleventh abdominal segments; /, telson; p^ podical plate; c, cer- cus; d, i, V, dorsal, inner, and ventral valves of the oviposi- tor. The last two abdominal segments, the eleventh and the telson, are even more distinctly preserved in the early instars of some orthopterous insects than they are in the adult (Fig. 239). In many adult Orthop- tera there is no suture between the eleventh tergum and the telson. On each side of the body, in the angle between the supra-anal plate and the lateral part of the tenth tergum, there is a triangular sclerite (Fig. 238, p); this pair of sclerites has long been *The genitalia are vestigial in Tridaclylus and are entirely wanting in Gryllo- talpa. In these genera the reduction or loss of the genitaliu is probably correlated with the subterranean life of these insects, they having no need for an ovi]:ositor. 232 AN INTRODUCTION TO ENTOMOLOGY known as the podical plates; but they have recently been named the para prods because they are situated one on each side of the anus. They are the sternum of the eleventh abdominal segment, which is divided on the midventral line, to admit of the expansion of the poste- rior end of the alimentan,' canal during defecation. In this insect the cerci (Fig. 238, c) project from beneath the caudal border of the tenth tergum ; they appear, there- fore, to be appendages of the tenth ab- dominal segment; but it is believed that in all insects where cerci are pres- ent they are appendages of the elev- enth abdominal segment. This, for example, is obviously the case in the Plecoptera (Fig. 240). The homology Fig. 239.-Caudal segments of a o^ the paraprocts IS also well shown in nymph of a female locust, dorsal this figure. aspect: 11, eleventh abdominal 'phg ovipositor consists of three segment; /, telson; r, cercus. ^^^-^^ ^^ processes or gonapophyses ; these are termed the valves or valvula of the ovipositor; they are dis- tinguished as the dorsal, ventral, and inner valvulae, respectively. In the locust the dorsal valvulae (Fig. 238, ,? uj -f t ^t? ^ .-. .. rig. 246. — Amblycoryphaobiongtfolia. (From subfamily. Lugger.) ^ ^'^ *■' Blatchley ('20) describes twenty species and varieties of the false katydids that are found in northeastern America; these represent eight genera. Among our common species there are representatives of three genera; these can be separated as follows. A. Tegmina broadened in the middle; the extreme point of the vertex much broader than the first segment of the antennas. ORTHOPTERA 237 —Scudderia septentr (From Lugger.) B, Hind femora much shorter than the tegmina; ovipositor short and turned abruptly upward (Fig. 245). p. 237 Microcentrlim BB. Hind femora but Httle if any shorter than the tegmina; ovipositor well developed, and curved gradually upward, p. 237 Amblycorypha AA. Tegmina of nearly equal breadth throughout; the extreme point of the vertex but little if any broader than the first segment of the antennae, p. 237. Scudderia Microcentmm. — Two species of this genus are found in the United States east of the Rocky Mountains; these are known as the angular- winged katydids. Figure 245 repre- sents the female of the larger angular- winged katydid, Microcentmm rhombi- folium, and the remarkable way in which it deposits its eggs on leaves and twigs. In this species the slightly hol- lowed front of the pronotum has a very small central tooth, which is lacking in smaller species. The smaller angular- winged katydid, Microcentrum retinerve, is only slightly smaller than the larger one. Amblycorypha. — The three most common species of the genus are the following: The oblong-winged katydid, Amblycorypha oblongi- Jolia (Fig. 246), is the largest of the three most common species. The tegmina measure from 34 to 37 mm. in length; the ovipositor is less ser- rate and less curved than in the next species. The round-winged katydid, Amblycorypha roHmdifdlia, is a smaller species ; the tegmina are not more than 30 mm. in length and are wnde for their length, as indicated by the specific name; the ovipositor is quite broad, much curved, and roughly serrated. Uhler's katydid, Amblycorypha tihleri, is our smallest species; the body meas- ures from 14 to 16 mm. in length; the tegmina from 24 to 26 mm.; and the ovipositor about 8 mm. Scudderia. — Species of this genus are found throughout the United States and in Canada; but the greater number of our species are found east of the Great Plains. One species, Scudderia mexicdna, is found in Cali- fornia and Oregon. A common eastern species which may serve as an ex- am-ple of the insects of this genus, is the northern bush-katydid, Scudderia septentriondlis. Figure 247 represents Pterophvlla caniellifo- (After Harris.) the male of this species, natural size. 238 AN INTRODUCTION TO ENTOMOLOGY Subfamily PSEUDOPHYLLIN^ The True Katydids The best -known representative of this subfamily in the United States is the northern true katydid, Pterophylla camellijolia (Fig. 248). This insect is found throughout the United States east of the Rocky Mountains; but in the North it Hves in colonies which occupy quite limited areas. This is the insect whose song suggested the popular name katydid. It differs from members of the preceding subfamily in having the hind wings shorter than the tegmina, and in having the tegmina very convex, so that it has an inflated appearance. Subfamily CONOCEPHALIN^. The Meadow Grasshoppers From the middle of the summer to the autumn there can be found upon the grass in our meadows and moist pastures many light-green long-horned grasshoppers of various sizes; these, on ac- count of the situations in which they are usually found, are termed the meadow- grass- hoppers. Our common species represent only two genera ; but each of these includes many species. Orchelimum. — This genus includes the larger and stouter species of meadow grasshoppers; but they are of medium size com- pared with other Tettigoniidae. In these the ovipositor is usually Fig. 249. — Orchelimum vulgare, mal; (Prom Lugger.) Fig. 251. — CoiiocephalHs Fig. 250. — Orchelimum vulgare, female. (From Lugger.) up-curved. Our most abundant species is the common meadow grasshopper, Orchelimum vulgare. This is found from the Rocky Mountains to the Atlantic Coast. Figure 249 represents the male, natural size; and Figure 250, the female. Conocephalns.— This genus comprises the smaller and slenderer- species of this subfamily. In these the ovipositor is slender, and straight or slightly curved (Fig. 251). Until recently this genus has been generally known as Xiphidium.* *It is unfortunate that according to the rules of nomenclature the name Conocephalus must be applied to this genus instead of to the typical genus of the next subfamily, now known as Nsoconocephalus, with the result that the sub- family name ConocephaUnje is applied to the meadow grasshoppers instead of to the cone-headed grasshoppers. ORTHOPTERA Subfamily COPIPHORIN.E 239 The Cone-headed Grasshoppers The cone-headed grasshoppers are so called because the vertex is prolonged forward and upward into a cone. These are much larger insects than the meadow grass- hoppers and are found in trees as well as upon grass. This sub- family is represented in our fauna by four genera; but three of these are found only in the South. All of the northern species belong to the genus Neoconocephaltis, of which eleven species occur in the United States. The most com- mon species in the north, east of Fig. 252. — Neoconocephaltis ensiger, male. (From Lugger.) the Rocky Mountains, is the sword-bearer, Neoconocephalus ensiger. Figure 252 represents the male of this species, and Figure 253 the female. Both sexes have very long wings, and the ovipositor of the female is remarkable for its length. Fig. 253. — Neoconocephalus ensiger, female. (From Lugger.) In most of the species of Neoconocephalus there are two distinct forms : one pea-green in color and the other of a brownish straw-color. Subfamily DECTICINiE The Shield-backed Grasshoppers A few members of this subfamily have well-developed wings ; but in most species the wings are small, especially in the female, where they are sometimes even absent. Most of the species bear some resemblance to crickets. They present, however, a strange appear- ance, due to the pronotum extending backward over the rest of the thorax, like a sun-bonnet worn over the shoulders with the 240 AN INTRODUCTION TO ENTOMOLOGY Fig. 254. — Atlantictis testacens, (From Lugger.) male. back side forward. It was the large size of the pronotum that sug- gested for the group the popular name the shield-hacked grass- hoppers. These insects live in grassy fields or in open woods, where they hop about in exposed posi- tions. Even in some of the short- winged forms the stridulating or- gans of the tegmina of the males are well deiveloped. The North American species represent twenty genera ; most of these are found west of the Mississippi River, a few species occur m the east; nearly all of these belong to the germs A tldnticus. Figure 254 represents the male of At- IdnticMS testdceus, and Figure 255 the female of Atlanticus davisi. Most of the species of this subfamily are local or very rare and not of economic im- portance; but species of the genus Anabrus and of Perana- brus at times invade cultivated areas in the western United States and do immense damage. Many popular names have been applied to these insects; perhaps the one in most general use is the western cricket. A very complete monograph of the North American species of this subfamily has been pubHshed by Caudell ('07). Fig. 255. — A tlanticus davisi, female. Subfamily GRYLLACRIN.^ The Leaf -rolling Grasshoppers The members of this subfamily agree with the preceding sub- families and differ from the two following in having the tarsi more or less depressed. They agree with the fol- lowing subfamilies and differ from the preceding in the ab- sence of auditory t>Tnpana in the fore tibias and in the ab- sence of stridulating organs even when the tegmina are present. Only a single spe- Fig. 256. — Camptonotus carolinensis, female. Blatchley.) (From ORTHOPTERA 241 cies, the Carolina leaf-roller, Camptondtus carolinensis (Fig. 256), occurs in our fauna. This species is wingless; it measures from 13 mm. to 15 mm. in length. Its known range extends from New- Jersey west to Indiana and south to Florida. This insect is very remarkable in its habits,which have been de- scribed by Caudell ('04) and McAfee ('08). It makes a nest by rolling a leaf and fastening the roll with silken threads which it spins from its mouth. It remains in its nest during the day and emerges at night to capture aphids upon which it feeds. Subfamily RHAPHIDOPHORIN^ The Cave-Crickets or Camel-Crickets Many common names have been applied to members of this sub- family; SLxnong these are cave-crickets, because they abound in caves and are found in other dark places; camel-crick- ets, because of the high, arched back of some species (Fig. 257); and stone-crickets, from their habit of hiding beneath stones. This last name is not at all distinctive. These are wingless long-horned grass- hoppers that bear some resemblance to the true crickets (Fig. 258). They have a short, thick body and remark- ably stout hind femora, like a cricket, but are entirely destitute of tegmina and wings, and the females, like other Tettigoniidse, have a sword-shaped ovipositor. The more common species are either of a pale brown or a dirty white color and more or less mottled with either lighter or darker shades. Fig. 257. — Ceuthophilus uhleri, male. (From Blatchley.) Fig. 258. — Ceuthophilus, female. Fig. 259. — Ceuthophilus niaculatus, female. (From Lugger.) These insects live in dark and moist places, under stones and rubbish, especially in woods, in cellars, in the walls of wells, and in caves. On one occasion I saw many thousands of them on the :oof of a cave in Texas. Caudell ('16) in his monograph of this subfamily lists twelve gen- era including many species that occur in the United States. Most of 242 AN INTRODUCTION TO ENTOMOLOGY our common species in the East belong to the genus Ceuthophilus. Figure 257 represents themale oi Ceuthophilus uhleri, and Figure 2 i,g the female of Ceuthophilus maculdtus. Subfamily STENOPELMATIN^ The Sand-Crickets These are large, clumsy- creatures with big heads (Fig. 260). They live under stones and in loose soil. They are represented in our fauna by a single genus, Stenopelmatus, several species of which are found in the Far West and pjg. 260. -Stenopelmatus. especially on the Pacmc Coast. Family GRYLLIDAE* The Crickets Although the word cricket forms a part of some popular com- pound names of members of the Tettigoniidee, as "western crickets" and "sand-crickets," when the word is used alone it is correctly ap- plied only to members of this family. In the more typical crickets, the hind legs are fitted for leaping; the antennas are long and slender; the tegmina lie flat on the back and are bent down abruptly at the sides of the body; the ovipositor is spear-shaped; and the tarsi are three-jointed. Wingless forms are common. The more striking departures from these characteristics are the following: in the Tridactylinae the antennas are short; in the Tri- gonidiinas the ovipositor is sword-shaped; in the Gryllotalpinas and the Tridactylinae the ovipositor is wanting in our species; and in the Tridactylinas the tarsi are reduced. It is evident that one step in the reduction of the nimiber of tarsal segments is the growing together of the metatarsus and the second segment. This is shown in the hind tarsi of Anaxlpha, CEcdnthus, Nemohius, and doubtless others, where the suture between these two segments can be seen although the segments are anchylosed. Tjonpana are usually present in the fore tibiae, one on each side of each tibia, as in the Tettigoniidce. In some genera one tjinpanimi of each pair is wanting ; this is sometimes the outer and sometimes the inner one; in the wingless, and therefore mute, species, the tympana are wanting; and in the Tridactylince there are none. *This family is termed the Achetidae by some writers. ORTHOPTERA 243 With most species of crickets the two sexes differ greatly in ap- pearance; the female has a long ovipositor and the venation of the wings is simple, while the male has the horizontal part of the fore wings modified to form musical organs. The structure of these has been described in Chapter 11. The Gryllidse includes eight subfamilies, all of which are repre- sented in the United States. These subfamilies can be separated by the following table. A. The next to the last segment of the tarsi distinct, depressed, and heart- shaped. B. Hind tibiae armed with two series of spines without teeth between them. p. 243 Trigonidiin^ BB. Hind tibiae with teeth between the spines, p. 244 Eneopterin^ AA. Tarsi compressed, the next to the last segment minute, compressed. B. Fore legs fitted for walking. C. Hind tibiae without spines except the apical spurs. D. With well-developed wings; hind tibias with only two very small apical spurs. (Neoxabea.) p. 245 QJcanthin^ DD. Wingless or subapterous; hind tibias with three pairs of apical spurs, p. 250 MOGOPLISTIN^ CC. Hind tibiae armed with two series of spines. D. Body subspherical ; wingless; hind femora ovate, very strongly swollen, p. 249 Myrmecophilin^ DD. Body more elongate, usually winged; hind femora more elongate, not exceptionally swollen. E. Hind tibiae with minute teeth between the spines, p. 245 CEcanthin^ EE. Hind tibiae without teeth between the spines, p. 247 Gryllin^ BB. Fore legs fitted for digging. C. Antennae many-jointed ; all of the tarsi three-jointed, p. 250 Gryllotalpin^ CC. Antennae el even- jointed; fore and middle tarsi two-jointed, hind tarsi one-jointed or wanting, p. 251 Tridactylin^ Subfamily TRIGONIDIIN^ The Sword-bearing Crickets These are small crickets, our species measuring from 4 mm. to 8.5 mm. in length of body. They live chiefly on shrubs and tall grasses and weeds growing in or near water. Their distinguishing features are the following : The next to the last segment of the tarsi is distinct, depressed, and heart-shaped, the hind tibias are slender with three pairs of mobile spines besides the terminal spurs, and with no teeth between these spines; and the ovipositor of the female is compressed and curved upwards. In the sword-shaped form of the ovipositor these crickets present a striking exception to the character- istics of the Gryllidas. The following are our best-known representatives of this sub- family. Anaxtpha extgua.— This cricket resembles somewhat in general appearance the common small field-crickets (Nemobius), but unlike 244 AN INTRODUCTION TO ENTOMOLOGY them it does not live on the ground. The antennae are very long (Fig. 261); the ovipositor is one half as long as the hind femora; the hind femora of the male are longer than the tegmina; and the stridu- lating area of the tegmina is large. The length of the body is 5-8 mm. There are two forms of this species: in one, the hind wings are wanting and only the tympana on the outer face of the fore tibise are present ; in the other, long hind wings are present and there is a tympanum on each face of the fore tibiae. This species is found from southern New England west to Minnesota and Nebraska and south to Florida and Texas. Falctcula hebdrdi. — This is a smaller species than the preceding, the body measuring only 4-5 mm. in length. It is uniform pale yellowish brown in color. The hind wings are wanting. The stridulating area is small, confined to the basal fourth of the tegmina. The fore tibiae are without visible t^Tnpana. Its range extends from New Jersey south and southwest to Florida and Texas. Cyrtoxipha colmnbidna. — This is a small, pale green fading to brownish yellow, cricket; it is found on shrubs and small trees, usually near water. The wings are always present and pro- longed in the form of a tail or queue. Tjonpana are present on both faces of the fore tibiae. The tegmina extend 2-3 mm. beyond the end of the abdomen. The length of the body to apices of Fig. 26i.--^jwA:i^/m ^gjyjnina is 8.^ mm. Its range extends from extgua. (From Lug- Washington. D. C, to Florida and Texas. Phylloscyrtus pulchellus. — This cricket differs from the three preceding species in having the last segment of the maxillary palpi spoon-shaped. The head and the thorax are bright crimson-red; the margin of the thorax is pale yellow; the abdomen is black, and the tegmina are chestnut-brown. The length of the body is 6-7 mm. This species is found throughout the United States east of the Mississippi River, except in the northern portions. Subfamily ENEOPTERIN^ The Larger Brown Bush-Crickets These crickets resemble those of the preceding subfamily in the heart-shaped form of the next to the last segment of the tarsi ; but differ in having teeth between the spines of the tibise, and in the ovipositor being spear-shaped. ORTHOPTERA 245 These represent Only a few species are found in our fauna, three genera: Orocharis, in which both t^in- pana of the fore tibiae are present ; Hdpithus, with a tympanum on the inner face only of the fore tibiae; and Tafaltsca, with no tympana and no stridulating organs. The most common species is Orocharis saltdtor (Fig. 262). This is usually pale reddish brown, but some individuals are grayish. The length of the body is 14-16 mm. It is foimd from New Jersey west to Nebraska and south to Florida and Texas. The only common species of Hapithus is H. agitator, which is found from Long Island west to Nebraska and south to Florida _ and Texas. Our only species of Tafalisca is T. lUrida, which is found in southern Florida. Subfamily CECANTHIN^ The Tree-Crickets Fig. 262.— Orocharis saltaior. (From These are delicate crickets, many of which are Lugger.) of a light green color, with the body and legs sometimes dusky. Figure 263 represents a male; in the females the front wings are miore closely wrapped about the body, giving the insect a narrower appearance. They live in more or less elevated positions, varying, according to the species, from among herbaceous plants to the higher parts of fruit and forest trees, hence the name tree-crickets commonly applied to them. Their frequent occurrence among flowers suggested the name of the principal genus, CEcdfithus, implying / dwell in flowers. Two genera of tree-crickets are represented in our fauna, Neoxahea and CEcanthus; these can be distinguished by differ- ences in the armature of the hind tibi«. Neoxahea. — In this genus the hind tibiae bear neither teeth nor spines except the apical spurs, and the first segment of the antennae is armed in front with a stout, blunt tooth (Fig. 264, h). Neoxahea bipunctdta is the only species known. In this species the hind wings are almost twice as long as the fore wings; the fore wings of the fe- male are each marked with two rather large blackish spots; the wings of the male are un- marked. The general color is pale pinkish brown. The length of the body is about 16 mm. CEcanthus .—In this genus the hind tibiae bear both spines and teeth. Several species occur in F" 26 —CEcanthus the United States and Canada; these differ in the ^%veus male"" "'^ color of the body, in the markings on the first two segments of the antennas, in their song, and in the 246 AN INTRODUCTION TO ENTOMOLOGY elevation above the surface of the ground in which they are usually found. Most of our species are found east of the Great Plains; one, CEcanthus calif ornicus, occurs in California; and one, CEcanthus & « t Fig. 264. — Basal segments of antennae of QLcanthus and Neoxabea. (The lettering is explained in the text. (After Lugger and Fulton.) argentinus, in Texas. The species of eastern North America can be distinguished by the following table, which is copied from a de- tailed account of these insects by B. B. Fulton ('15). A. Basal segment of antennas with a swelling on the front and inner side. First and second segments each with a single lalack mark. B. Basal antennal segment with a round black spot. (Fig. 264, a). . ffi. nlveus BB. Basal antennal segment with a J-shaped black mark. (Fig. 264, b) CE. angustipcnnis BBB. Basal antennal segment with a straight club-shaped black mark. (Fig. 264, e) ffi. exclamationis AA. Basal antennal segment without a swelling on the front and inner side. First and second antennal segments each with two black marks or entirely black. Tegmina of males 5 mm. or less in width. B. Head and thorax pale yellowish green or black or marked with both colors. C. First antennal segment with a narrow black line along inner edge and a black spot near the distal end. Body entirely pale yellowish green. (Fig. 264, d) ffi, quadripunctatus CC. First antennal segment with black markings similar to above, but broader and usually confluent, sometimes covering the whole segment. Head and thorax often with three longitudinal black stripes; ventral side of abdomen always solid black in life. (Fig. 264, c) . . CE. nigricornis BB. Head, thorax, and antennas reddish brown. Wings in life with conspicuous green veins. Marks on basal antennal segment broad but seldom con. fluent. (Fig. 264, f) (E. pini AAA. Basal antennal segment without a swelling on the front and inner side. Basal portion of antenna red unmarked with black. (Fig. 264, g). Teg- mina of male about 8 mm. wide (E. latipennis The species of CEcanthus that most often attracts attention is the snowy tree-cricket, CEcanthus niveus (Fig. 263). The pres- ence of this insect, though usually unseen, is made very evident in late ORTHOPTERA 247 summer and in the autumn by the song of th e males . This song is begun early in the evening and is continued through- out the night ; it consists of a monotonous series of high-pitched trills rhythmically repeated in- definitely. It is a remarkable fact that all of these crickets that are chirping in any locality chirp in unison. Individual singers will stop to rest, but when they start again they keep time with those that have continued the chorus , Except where the true katydid is heard, this is the most conspicuous insect song heard in the night in the regions where this species occurs. This cricket inhabits chiefly high shrubs and trees; it deposits its eggs singly in the bark or cambiiun of trees and bushes. While the presence of the snowy tree-cricket is made evident by its song, there is another species that has attracted much attention by its manner of oviposition; this is Qicanthus nigricornis. The female lays her eggs in a longitudinal series in the twigs or canes of various plants (Fig. 265). She selects the rasp- berry more often than any other plant; and as that portion of the cane beyond the incisions made for the eggs usually dies, it often happens that these crickets materially injure the plants. Fig. 265.— Stem of black In such cases the dead canes should be cut out raspberry with the eggs 1 . J 1 • ^1 • 1 r xi of (Ecanthus mgrtcor- and burned early m the sprmg before the eggs „^-^ . ^^ ^^ ggg enlarged. hatch. (From Riley.) Subfamily GRYLLIN^ TJw Field-Crickets The field-crickets abound everywhere, in pastures, meadows, and gardens; and certain species enter our dwellings. They lurk imder stones or other objects on the ground or burrow into the earth. They are chiefly solitary, nocturnal insects; yet many can be seen in the fields in the daytime. They usually feed upon plants but are sometimes predacious. With most species the eggs are laid in the autumn, usually in the grotmd, and are hatched in the following summer. The greater number of the old crickets die on the approach of winter; but a few survive the cold season. In many of the species there are both short-winged and long-winged forms. This subfamily is represented in our fauna by several genera; but nearly all of our common species are included in the two genera Gryllus and Nemohius. 248 AN INTRODUCTION TO ENTOMOLOGY Fig. 266 sus. -Gryllus assimilis luctuo- The larger field-crickets, Gryllus. — The members of this genus are dark-colored, thick-bodied insects of medium or large size. In these the hind tibiae are armed with strong fixed spines and the first segment of the hind tarsi is armed with two rows of teeth above. There are two auditory tympana in each fore tibia. The length of the body is rarely less than 14 mm. Many supposedly distinct species of Gryllus have been de- scribed as occurring in our faima; but now all of our native forms are believed to be merely varieties of one species, Gryllus assimilis, and the different varieties are distin- guished by subspecific names. Six of these varieties that occur in the East are described by Blatchley ('20). Two of these will serve to illustrate our native forms. Gryllus assimilis luciudsus. — This is one of our more common forms of the genus. It is distinguished by the great length of the ovipositor of the female, which is nearly or fully half as long again as the hind femora (Fig. 266) ; and by the fact that the head of the male is distinctly wider than the front of the pronotum. Gryllus assimilis pennsylvanicus. — In this variety the ovipositor is less than half as long again as the hind femora, and the head of the male is but little if any wider than the front of the pronotum (Fig. 267). In fresh specimens the color is not shining black, but with a very fine grayish pubes- cence. In addition to our native forms of Gryllus, there is an Old World species that has been introduced into this country; this is the house-cricket, Gryllus domesticus. Refer- ences to the "cricket of the hearth" are common in English literature and refer to this species, which is now widely distributed in this country, though it is rarely abundant. It is pale yellowish browTi or straw-colored, and slender in form (Fig. 268). The length of the body is 15-17 mm. Our native field-crickets sometimes enter our dwellings in the autumn; but the house-cricket can be easily distinguished from these. The smaller field-crickets, Nemobius. — To this genus belong the little field-crickets, which are the most abundant of all of our crickets. In these the hind tibiae are furnished with long, mobile, hairy spines. Fig. 267. — Gryllus assim- ilis pennsylvani- cus. (From Lugger.) ORTHOPTERA 249 and the first segment of the hind tarsi is unarmed above or with only one row of teeth. There is only one tympantim in each fore tibia. The length of the body is less than 1 2 mm. There are many species and varieties of this genus in our fauna. The following enlarged figures of two of our species will serve to illustrate the form of these insects. (Fig. 269 and 270.) Fig. 268.— Gryllus do- mesticus. (From Lug- ger.) Fig. 269. — • Nemo- bius fasciatus. (From Lugger.) Fig. 270. — Nemo- bins pahistris. (Fom Blatch- ley.) Subfamily MYRMECOPHILIN^ The Ant-loving Crickets The members of this subfamily are very small crickets, which live as guests in the nests of ants. The form of these crickets is very remarkable. The body is ovate, greatly convex above, and wing- less (Fig. 271); the hind femora are ovate and greatly enlarged, the cerci are long; and the ovi- positor is short and stout. Wheeler ('00) states that these crickets feed on an oily secretion covering the surface of the body of the ants; they also obtain this substance from the greasy walls of the ant-burrows. Apparently the ants derive no benefit from the presence of these Fig. 271. — Myrmecophila pergandei. (From Lugger.) 250 AN INTRODUCTION TO ENTOMOLOGY guests, and destroy them when they can; but the crickets are very agile. These are the smallest of the true Orthoptera. This subfamily includes a single genus, Myrmecophila, of which five species have been described from the United States. Only one species has been found in the East; this is Myrmecophila pergdndei. In this species the length of the body is 3-5 mm. Subfamily MOGOPLISTIN.E The Wingless Bush-Crickets These crickets are found chiefly on bushes or among rubbish under bushes; some are found beneath debris in sandy places. They are small; those found in the United States measure from 5 mm. to 13 mm. in length of body. They are either wing- less or furnished in the male sex with short tegmina, in which the stridulating organs are well developed. The body is covered with translucent, easily abraded scales. Most of the species are tropical or subtropical in dis- tribution; our species are found chiefly in the South and Fig. 2j2.^Cryptopti- Southwest; but the range of him trigonipalpiim. one of them extends north to Fig- 273. — Holosphy- (From Rehn and Long Island. Only four spe- rum boreale {From Hebard. ^:^^u^,.^u ^^r,L:u^A ^'^ Rehn and He- cies have been described from bard.) the East and one of these is restricted to Florida. A few others are known from the western part of our countr>\ A monograph of the North American species was published by Rehn and Hebard ('12). Figure 272 represents the male of Cryptoptilum trigonipdlpum, sl wingless species found from Virginia southward; and Figure 273, the male of Holosphyrum boreale, found in the Southwest. Subfamily GRYLLOTALPIN^ The Mole-Crickets The mole-crickets differ greatly in appearance from the more typical crickets, the form of the body and of the fore legs being adapted to burrowing in the ground. The front tibiae, especially, are fitted for digging; they are greatly broadened and shaped some- ORTHOPTERA 251 what like a hand or a foot of a mole ; they are terminated by strong blade-like teeth, termed the dactyls (Fig. 274). Two of the tarsal segments are blade-like and so situated that they can be moved across the dactyls like the cutting blades of a mowing machine (Fig. 275). Sharpe ('95) states that this organ enables the mole-cricket to cut the small roots it meets in digging its burrows ; but this is doubted by Morse ('20), who believes that the roots are cut by the powerful mandibles. The antennse of mole-crickets are much shorter than the body; the hind femora are but little enlarged, not well fitted for jumping; and the ovipositor is not visible externally. The name of the type genus, Gryllotalpa, is from Grylhis, a cricket, and talpa, a mole. Two genera of mole-crickets are found in the United States: Gryllotalpa, in which the front tibias are furnished with four dactyls; and Scap- tenscus, in which each fore tibia bears only two dactyls. Each of these genera is represented in our fauna by several species. Our best-known and most widely distributed species is Gryllotalpa hexaddctyla (Fig. 274). This species has been generally known in this country as Gryllotalpa horedlis; but this name is now be- lieved to be a synonym. The range of this species extends from British America to the southern part of South America. The length of the body is 20-30 mm. The mole-crickets are not common insects in this country; but occasionally they are found in great numbers in a limited lo- cality. They make burrows in moist places from six to eight inches below the surface of the ground, and feed upon the tender roots of various plants, and also on other insects. The eggs are deposited in a neatly constructed subterranean chamber, about the size of a hen's eee. Fig. 274. — Gryllotal- pa hexadactyla. Fig. 275. — Front leg of a mole-cricket; A, inner aspect; B, outer aspect; e, ear-slit. (Prom Sharp.) Subfamily TRIDACTYLIN^ The Pigmy Mole-Crickets The members of this subfamily resemble the mole-crickets in the form of the body and in their burrowing habits; but they are much 252 A N INTROD UCTION TO ENTOMOLOG Y smaller, the larger species measuring only lo mm. in length; and the hind femora are greatly enlarged, being strongly saltatorial (Fig. 276). The antennae are short and composed of only eleven segments. The fore wings are usually short and never extend to the end of the abdomen; they are horny, are almost veinless, and are not furnished with stridulating organs in the male. The hind wings are much longer, usually extending beyond the end of the abdomen. The fore tibiae lack auditory tympana. The first four tarsi, in our genera, are two- jointed; the hind tarsi are one- jointed or want- ing. The hind tibiae are furnished with movable plates, "natatory lamellae," near the distal end; these are ordinarily closely appressed to the tibia but can be spread out like a fan. It is probable that these p- 2-5 tH- plates are used to aid the insect in leaping from the dactylns apica- surf ace of water upon which they have jumped ; lis. (From Lug- they may also serve a similar purpose on land, mak- sev.) ing a firm planting of the end of the leg upon the ground. The ovipositor is vestigial in our species; but Walker ('19) states that in the exotic genus Ripipteryx there is a well-developed ovipositor, which is remarkably similar to that of the short-horned grasshoppers. These insects apparently have two pairs of cerci; this is due to the fact that in addition to the true cerci each of the two podical plates is greatly elongated and bears a terminal segment, which appears like a stylus or cercus. These insects burrow rapidly in sand and possess great powers of leaping. They live on and in the damp sand on the shores of ponds and streams. Their burrows extend only a short distance below the surface of the ground. Only two genera, each represented by a single species, have been found in America north of Mexico. Triddctylus. — In this genus the hind tibiae are furnished with four pairs of long, slender plates, the "natatory lamellae;" and the hind tarsi are one-jointed. Our species is Triddctylus apicdlis (Fig. 276). Thejength of the body is 6-9.5 m^i- Ellipes. — In this genus the hind tibiae are furnished with a single pair of "natatory lamellae"; and the hind tarsi are wanting. Our vSpecies is Ellipes minida. The length of the body is 4-5 mm. Walker ('19) as a result of his studies of the genitalia of Ripi- pteryx believes that the pigmy mole-crickets are more closely allied to the Locus tidae than they are to the Gryllidae, and ranks them as constituting a distinct family, the Tridactylidae. Family LOCUSTID^* The Locusts or Short-horned Grasshoppers The family Locustidae includes the locusts or short-horned grass- *This family is termed the Acrididse by some writers, this name being based on the generic name Acrida of Linnaeus; other writers use the family name Aery- ORTHOPTERA 253 hoppers. These are common and well-loiown insects. They differ from most of the members of the two preceding famiHes in having the antennee much shorter than the body, and consisting of not more than twenty-five segments. The ovipositor of the female is snort and composed of separate plates; and the basal segment of the abdomen is furnished on each side with a tympanum, the external parts of the organs of hearing (Fig. 277, t). It is to these insects that the term locust is properly applied; for the locusts of which we read in the Bible, and in other books published in the older countries, are members of this family. Unfortunately, in the United States the term locust has been applied to the Periodical Cicada, a member of the order Homoptera, described later. And, what is more unfortunate, the scientific name Locus- tidse has been applied by many writers to the long-homed grasshoppers. Locusts lay their eggs in oval masses and cover them with a tough substance. Some species lay their eggs in the ground. The female makes a hole in the ground with her ovipositor, which is a good digging tool. Some species even make holes in fence-rails, logs, and stumps; then, after the eggs are laid the hole is covered up with a plug of gummy material. There is but one generation a year, and in most cases the winter is passed in the egg-state. This family is of great economic importance, as the members of it usually appear in great numbers in nearly every region where plants grow, and often do much damage. With many species of the Locustidae the males are furnished with stridulating organs. These have been described in Chapter II, page 82. There are very many species of locusts in the United States and Canada; these represent four of the subfamilies of the family Locus- tidae, which can be separated by the following table. A. Claws of the tarsi with a small pad (arolium) between them; pronotum ex- tending at most over the extreme base of the abdomen. B . Prosternum armed anteriorly with a distinct conical or cylindrical tubercle. p. 254 LoCUSTINiE. BB. Prosternum without a distinct tubercle; arolium usually small or rather small. C. Head rounded at the union of the vertex and front ; front perpendicular or nearly so. p. 257 CEdipodin^. CC. Vertex and front of head meeting at an acute angle; vertex extending horizontally; front strongly receding, p. 259 Truxalin^. AA. Claws of tarsi without an arolium between them; pronotum extending over the abdomen, p. 259 Acrydiin^. diidse, based on the generic name Acrydium of Fabricius; and still others use the family name Acridiidae, based on Acridium, an emended spelling of Acrydium. The oldest name given to this family is Acrydiana, applied to it by Latreille in 1802; but the group of insects that Latreille used as the type of the family is the Locusta of Linnaeus (1758); for this reason the name given to the family by Latreille has been changed to Locustidae. See also the footnote on page 234. 254 AN INTRODUCTION TO ENTOMOLOGY Subfamily LOCUSTIN^ The Spur-throated Locusts The members of this subfamily are distinguished from other North American locusts by the presence of a tubercle on the pro- sternum. Here belong many of our more com- mon species; and among them are found the most injurious insects of the order Orthoptera. Among our best -known species are the following. The Rocky Mountain locust or western grasshopper, Melanoplus spretus. — The most terrible of insect scourges that this country has known have been the invasions Fig. 277. — Side view of a female locust with the wings removed. Fig. 278. — Egg-laying of the Rocky Mountain Locust : a, a, a, female in different positions, ovipositing; b, egg-pod extracted from the ground with the end broken open; c, a few eggs lying loose on the ground; d, e, show the earth partially removed, to illustrate an egg-mass already in place, and one being placed; / shows where such a mass has been covered up. (From Riley.) of this species. Large areas of coimtry have been devastated, and the inhabitants reduced to a state of starvation. The cause of all this stiff ering is not a large insect. It is represented in natural size by Figure 278. It measures to the tip of its wing-covers 20-35 mm., and resembles very closely our common red-legged lo- cust, the most abundant of all our species. It can easily be distinguished from this species by the greater length of the wings, which extend about one-third of their length beyond the tip of the abdomen, and by the fact that the apex of the last abdominal segment in the males is distinctly notched. Fig. 279. — Melanoplus femur- rubrum. ORTHOPTERA 255 Fig. 280.- Riley.) -Melanoplus bivittatus. (From The permanent home or breeding grounds of this species is in the high, drylands on the eastern slope of the Rocky Mountains, extend- ing from the southern limit of the true forests in British America south through Montana, Wyoming, the western part of the Dakotas, and the Parks of Colorado. There are also regions in which the species exists permanently west of the Rocky Mountains in Idaho and Utah. When the food of this insect becomes scarce in its mountain home, it migrates to lower and more fertile re- gions. Its long wings en- able it to travel great dis- tances; and thus the larger part of the region west of the Mississippi River is liable to be invaded by it. Fortunately, the species cannot long survive in the low, moist regions of the valleys. Although the hordes of locusts which reach these sections retain their vigor, and frequently consume every bit of green vegetation, the yoimg, which hatch from the eggs that they lay, perish before reaching maturity. In this way the invaded region is freed from the pest until it is stocked again by another in- cursion. There is, however, a large sec- tion of country lying immediately east of the great area indicated above as the permanent home of this species, w^hich it frequently invades and in which it can perpetuate itself for several years, but from which it in time disappears. This sub-permanent region, as it has been termed, extends east in British America so as to include nearly one-third of Mani- toba; and, in the United States, it em- braces nearly the whole of the Dakotas, the western half of Nebraska, and the northeast fourth of Colorado. The temporary region, or that only periodically visited and from which the species generally disappears within a year, extends east and south so as to include more than half of Minnesota and Iowa, the western tier of counties of Missouri, the whole of Kansas and Oklahoma, and the greater part of Texas. The country lying east of the section thus indicated has never been invaded by this locust, and there is no probability that It will ever be reached by it. Fig. 281. — Melanoplus bivitta- tus killed by a fungus. (From Lugger.) 256 AN INTRODUCTION TO ENTOMOLOGY Detailed directions for the control of this pest have been pub- lished in many State and Federal Government reports. Among these methods of control are the plowing of land in which its eggs have been deposited, the use of poisoned bran- mash as a bait, and catching of the insects Fig. 282. — Melanoplus differentialis. (From Riley.) j^y machines com- monly known as "hopper dozers." The red-legged locust, Melanoplus femur-rubrum. — This is the Fig. 283. — Schistocerca americana. (From Riley.) most common short-horned grasshopper throughout the United vStates, except where Melanoplus spretus occurs. It ravages our meadows and pastures more than all other species combined. It is ioxmd in most parts of North America. The female is represented, natural size, by Figure 279. Melanoplus hivittdtus. — This species is also found from the Atlantic to the Pacific. It is marked with a yellowish stripe, extending along each side from the upper angle of the eye to the tip of the front wing (Fig. 280). The length of the body varies from 23 mm. to 40 mm. This locust is often killed by a para- sitic fungus. Dead fungus-infected in- dividuals are frequently found clinging to weeds, up which they have climbed to die (Fig. 281). Melanoplus differentialis. — This spe- cies is slightly larger than the preceding; and it lacks the prominent yellow stripe (Fig. 282). Schistocerca americana. — This magnifi- cent species occurs in the Southern States pjg. 2H^-Brachystoi^ mafKa. and has been foimd as far north as Con- (From Riley.) ORTHOPTERA 257 necfcicut and Iowa. It can be recognized by Figure 283, which rep- i-esents it natural size. This locust sometimes assumes the migratory ' - injurious to agriculture. habit, and is sometimes The lubber grasshopper, Erachystola magna. — This clumsy species in which the wings are vestigial (Fig. confined to the central portion of North America. Leptysma marginicollis. — In most of the spur-throated locusts the face is nearly ver- tical; but in a few species it is very oblique. This species is a good illustration of this type (Fig. 285); it is foimd in the Southern States east of the Mississippi River. is a large, 284); it is Fig. 28^.— Lcplysma marrinicollis. Subfamily CEDIPODIN^ The Bard-winged Locusts In this subfamily the prosternum is without a distinct tubercle; the head is rounded at the union of the vertex and the front; and the f'-ont is perpendicular or nearly so. In most of our species the hind wings are in part black, and a portion of them yellow or red; this gives them a banded appearance. There are many representatives of this subfamily in our fauna: the following are some of the more common ones. The clouded locust, Encoptolophus sordidus. — This species (Fig. 286) is very common in the eastern United States during the autumn. It abounds in meadows and pas- tures, and attracts attention by the crackling somid made by the males during flight. It is of a dirty brown color, mottled with spots of a darker shade. The length of the body of the male is 1 9- -Encoptolophus sordidus. 22 mm.; of the female, 24-32 mm. The northern green-striped locust, Chortophaga viridifascidta. — This is a. very common species in the United States and Canada east of the Rocky Moim tains. There are two well-marked varieties, .'n one. the typical form, the head, thorax, and femora are green, and there is a broad green stripe on each fore wing, extend- Fig. 286. 258 AN INTRODUCTION TO ENTOMOLOGY ing to beyond t^^e middle; this often includes two dusky spots on the edge. In the other vari- ety, the ground color is dusky brown. Intergrades occur, in which the head and thorax are of a reddish velvety brown. The length of the body is 17-32 mm. The Carolina locust, D-issostetra Carolina. — Not- withstanding its specific name, this species is com- mon throughout the United vStates and Canada. It is a large species; the length of the body of the males is 24-33 mm., of the females 33-40 mm. It abounds in highways and in barren _,.__,.. ,- /T7 T ^ places. It takes flight Fig. 287.-Z)z..../.zraca../^na. (From Lugger.) ^^^^.^^^ ^^^ ^^^ ^^^^^ stridulate while in the air. The color of this insect varies greatly, simulating that of the soil upon which it is foimd. It is usually of a pale yel- lowish or reddish brown, with small dusky spots. The hind wings are black, with a broad yellow margin which is covered with dusky spots at the tip (Fig. 287). Boll's locust, Sphardgernon bolli. — This species is widely distributed in the United States and southern Ontario east of the Rocky Motrntains. The length of the body of the male is 20-28 mm., of the female 27-36 mm. The hind wings are pale greenish yellow at the base and are crossed by a dark band; the apical third is transparent smoky in color (Fig. 288). The coral-winged locust, Hipptscus apiculdtus. — This is one of the larger of our band-winged locusts (Fig. 289). The length of the body of the male is 25-30 mm., of the female 36-44 mm. The general color is ash-brown. The basal portion of the hind wings is bright coral-red, rarely yellow; this part is bordered without by a dark band. This species is widely distributed east of the Rocky Mountains. Fig. 288. — -Spharagemoji bolli. (From Lugger.) ORTHOPTERA 259 Fig. 289. — Hippiscus apiciilatus. (From Lugger.) Subfamily TRUXALIN^ The Slant-faced Locusts Fig. 2go.^Chloealtis conspersa, male. (From Lugger.) In this subfamily, as in the preceding one, the prostemum is unarmed but the head is of a different form. In the TruxaHnae, the v^ertex and the front meet on an acute angle. In some species this angle is a sharp one, the shape of the head being similar to that of Leptysnia (Fig. 285). In other species, however, the front is less receding ; this is the case in the fol- lowing species. The sprinkled locust, Chlo'ealtis conspersa. — This is a veryabimdant species in the northern United States and Canada east of the Great Plains. It is brown, with the sides of the pronotum and the first two or three abdominal seg- ments shining black in the male; and with the body and tegmina of the female sprinkled or mottled with darker brown. The teg- mina and hind wings are a little shorter than the abdomen in the male (Fig. 290), and much shorter in the female (Fig. 291). The males measure 15-20 mm. in length; the females, 20-28 mm. Fig. 2gi .—Chloealtis conspersa, female. (From Lugger.) Subfamily ACRYDIIN^ The Pigmy Locusts The Acry^diinae includes small locusts of very unusual form. They differ so much from other locustids that some students of the 260 AN INTRODUCTION TO ENTOMOLOGY Fig. 292.— A pig- my locust. Fig. 293. — Acrydium granula'.um. ley, after Kirby.) (From Blatch- Orthoptera believe they constitute a separate family. The most striking character of the subfamily is the shape of the pronotum. This is prolong- ed backwards over the abdomen to or beyond its extremity (Fig. 292). The head is deeply set in the pronotum; and the prosternum is ex- panded into a broad border, which partly envelops the mouth-parts like a muffler. The antennee are very slender and short. The tegmina are vestigial, being in the form of small, rough scales; while the wings are usually well-developed. These locusts differ, also, from all others in having no arolium between the claws of the tarsi. The pigmy locusts are commonly found in low, wet places, and on the borders of streams. Their colors are usually dark, and are often pro- tective, closely resem- bling the soil upon which the insects occur. They are very active and pos- sess great leaping powers. Some of the species vary greatly in coloring; this has resulted often in a single species being described under two or more names. This is an exceedingly difficult group in which to deteiTnine the species. Figure 293 represents Acrydium granuldtum with its wings spread, and the pronota of two color varieties. Figure 294 represents Acrydium arenosum obsciirum, greatly enlarged, with its wings closed. Family PHASMID^* The Walking-Sticks and tJie Leaf -Insects The Phasmidee is of especial interest on ac- count of the remarkable mimetic forms of the insects comprising it. In those species that are fotmd in the United States, except one in Florida, the body is linear (Fig. 295), wingless, and furnished with long legs and antennae. This peculiar form has suggested the name walking-sticks which is commonly applied *This family is separated from the Orthoptera by Handlirsch ('o6-'o8) and made to constitute a distinct order, the Phasmoidea. Fig. 294. — Acrydium arenosum obscurum. (From Hancock.) ORTHOPTERA 261 to these insects; they are also kno\\ai as stick-insects. In some exotic species the body has the appearance of being covered with moss or with Hchens. which increases the resemblance to a stick or a piece of bark. While our species are all wingless, except Aplopus mayeri, found in southern Florida, many exotic species are furnished with wings; and with some of these the wings resemble leaves. Among the more remarkable of the leaf-insects, as they are kno\\Ti, are those of the genus PhylUum (Fig. 296), the members of which occur in the tropical regions of the Old World. In the walking-sticks, the body is elongate and subcylindrical. the abdomen consists of ten segments, but the basal segment is small and usually coalesced with the meta thorax and sometimes it is entirely invisible; the legs are all fitted for walking, the tarsi are five-jointed except in the genus Timema, where they are three= jointed; the cerci are without joints. _ These insects are strictly herbivorous; they are slow in their motions, and often remain quiet for a long time in one place. They evidenth' depend on their mimetic form for protection. In addition to this some species have the power of ejecting a stinking fluid, which is said to be very acrid ; this fluid comes from glands placed in the thorax. The eggs are scattered on the ground beneath the plants upon which the insects feed, the female, unlike most Orthoptera, making no provision for their safety. In our common northern species the eggs are dropped late in the summer and do not hatch till the following spring, and they often remain till the second spring before they hatch. About 600 species of phasmids have been described; but they are largely restricted to the tropical and subtropical regions. Caudell ('03) in his monograph of the species of the United States enu- merates sixteen species that occur in our fauna; but these are found chiefly in the southern part of the country. Our common northern walking-stick is Diapheromera femordta (Fig. 295). The range of this species extends into Canada. It is a quite common insect, and on sev- eral occasions has appeared in such great numbers as to be seriously destructive to the foliage of forest trees; but these outbreaks have been temporary. Diapheromera fem 262 AN INTRODUCTION TO ENTOMOLOGY Among the more striking in ap- pearance of the walking-sticks found in the South are Me gaphdsma de^itricus , our largest species, measuring from 125 to 150 mm. in length, and Anisomorpha buprestoides, a yellowish brown species, about half as long as the preceding, with conspicuous, broad, black stripes extending from the front of the head to the tip of the abdomen. The reproduction of lost legs occurs frequently in this family. Family MANTID^^ The Praying Mantes or Soothsayers The praying mantes are easily rec- Fig. 296.— Phyllium scythe. (From ognized by the imusual forrn of the Sharp, after Westwood.) prothoraxand of the first pair of legs (Fig. 297). The prothorax is elongate, sometimes nearly as long as the remainder of the body; and the front legs are large and fitted for seizing prey. The coxee of the front legs are very long, pre- senting the appearance of femora; and the femora and tibi« of these legs are armed with spines; the tibia of each leg can be folded back against the femur so that the spines of the two will securely hold any insect seized by the praying mantis. The second and third pairs of legs are simple and similar; the tarsi are five-jointed; and the cerci are jointed. With some species the wings resemble leaves of plants in form and coloring. This resemblance is protective, causing the insects to resemble twigs of the plants upon which they are. All of the species are carnivorous, feeding on other insects. They do not pursue their prey but wait patiently with the front legs raised like uplifted hands in prayer, until it comes within reach, when they seize it. This position, which they assume while waiting, gives them most of their popular names, of which there are many. The eggs of the Mantidae are encased in chambered oothecas, which are usually fastened to the stems or twigs of plants (Fig. 298). In the case of the species that occur in the North, there is only one generation in a year and the winter is passed in the egg-state. Most of the members of this family are tropical insects ; a few species, probably less than twenty, live in the southern half of *This family is separated from the Orthoptera by Handlirsch ('o6-'o8) and made to constitute a distinct order, the Mantoidea. ORTHOPTERA 263 the United States; and one of our native species, Stagmomdntis Fig. 297. — Stagmomantis Carolina Carolina (Fig. 297), is found as far north as Maryland and southern Indiana. Recently two exotic species have been introduced into the Northern States, probably by the irnporta- tion of oothecce on nursery stock, and have become established here. These are the Mantis religidsa of Europe, which was first observed in this country near Rochester, N. Y., in 1899, and Paratenodera sinensis of China and Japan, which was first ob- served here at Philadelphia about 1895. Family BLATTID^E* The Cockroaches The cockroaches are such well-known insects that there is but little need for a detailed account of their characteristics. As already indicated in the table of families, the body is oval and depressed; the head is nearly horizontal, and wholly or almost wholly withdrawn beneath the pronotum; the head is bent so that the mouth-parts project caudad between the bases of the first pair of legs; the antennas are long and bristle-like; and the pronotum is shield-like. This family includes only the cockroaches ; but these Fig. 298. — Egg- insects are known in some localities as "black ^^^^^ °f. ^^^^' , , ,, 1 J • • J.1 momantts car- beetles, and our most common species m the ^^^^^ (From northern cities bears the name of Croton-bug. Riley.) *This family is separated from the Orthoptera by Handlirsch ('o6-'o8) and made to constitute a distinct order, the Blattoidea. 264 AN INTRODUCTION TO ENTOMOLOGY In the Northern States our native species are usually foimd in the fields or forests under sticks, stones, or other rubbish. But certain imported species become pests in dwell- ings. In the warmer parts of the coimtry, how- ever, native and foreign species alike swarm in Fig. 299.— Ootheca of a buildings of all kinds, and are very common out of doors. cockroach. Cockroaches are very general feeders; they destroy nearly all forms of provisions, and injure many other kinds of merchandise. They often deface the covers of cloth-bound books, eating blotches upon them for the sake of the sizing used in their manufacture ; and I have had them eat even the g\m\ from postage stamps. They thrive best in warm, damp situations; in dwellings they prefer the kitchens and laundries, and the neighborhood of steam and water pipes. They are chiefly nocturnal insects. They conceal themselves during the day beneath furniture or the floors, or within the spaces in the walls of a house; and at night they emerge in search of food. The de- pressed form of their bodies enables them to enter small cracks in the floors or walls. Not only are these insects very destructive to our possessions, but owing to their fetid odor merely the sight of them awakens disgust ; but it is due them to state that they are said to devour greedily bed- bugs. This will better enable us to abide their presence in our staterooms on ocean voyages, or in our chambers when we are forced to stop at poor hotels. The eggs of cockroaches are enclosed in purse-like capsules (Fig. 299). These capsules, or oothecae, vary in form in different genera, but are more or less bean-shaped. Within, the ootheca is divided into two parallel spaces, in each of which there is a row of separate chambers, each chamber enclosing an egg. The female often carries an ootheca protruding from the end of the abdomen for several days. It has been found that a single female may produce several oothecae. The nymphs resemble the adults except in size, and, in the case of winged species, in the degree of develop- ment of the wings. In adults also of some species the wings are reduced, atrophied, or absent; this condi- tion exists more frequently in females than in males (Fig. 300). As in most other insects, the homologies of the wing-veins can be most easily determined by a study of the tracheation of the wings of nymphs; Figure 301 will serve to illustrate this. Experiments conducted by the Bureau of Ento- mology at Washington have shown that one of the Fig-.3oo- — A most effective means of ridding premises of cockroaches wingless is dusting the places they frequent with commercial sodium fluorid. Several other substances are used for this purpose; ORTHOPTERA 265 among these are borax, p}'rethnun, sulphur, and phosphorus paste. Cockroaches are chiefly inhabitants of warm countries ; although nearly one thousand species have been described, few are found in the Fig. 301. — Fore wirg of a nymph of a cockroach. temperate regions. Only forty-three species have been found in North America north of the Mexican boimdary, and ten of these are probably introduced species (Hebard '17). ^ The cockroaches that are most often found in buildings are two introduced species, the Croton-bug and the Oriental cockroach, and two native species, the American cockroach and the common wood-cockroach. The adults Fig. 302. — The Croton-bug: a, first instar; h, second instar; c, third instar; d, fourth instar; e, adult; /, adult female with egg-case; g, egg-case, enlarged; h, adult with the wings spread. All natural size except g. (From Howard and Marlatt.) of these four species can be separated by the following table. For tables separating all North American species see Hebard ('17). A. With well-developed tegmina. B. Tegmina extending to or beyond the tip of the abdomen. C. Body about 12 mm. in length The Crototi-bug CC. Body 16 mm. or more in length. 266 AN INTRODUCTION TO ENTOMOLOGY D. Margin of the pronotum light in color while the disk is dark. . . The common wood-cockroach, male DD. Pronotum reddish-brown with two blotches of a lighter color. The American cockroach BB. Wings not extending to the tip of the abdomen. C. With a, light band on each lateral border of the pronotum The common wood-cockroach, female CC. With no bands on the pronotum The Oriental cockroach, male AA. Tegmina represented by small ovate pads The Oriental cockroach, female The Croton-bug, Blattella genndnica (Fig. 302), is the best-known of all of the cockroaches in our northern cities. It is easily recognized _ by its small size, about ^- ,-— ^^ >V ^ ' 12 mm. in length, and ^ '^^ by its pale color with two dark, parallel bands on the prono- tum. Its popular name originated in New York City, and was suggested by the fact that this pest is •^ \/ very abundant, in ** '^ ^ houses, about water pipes connected with the Croton Aqueduct. This is a species intro- duced from Europe; it has spread to nearly ^ ^ ^ r ^ y ^11 parts of the world, living upon ships, and Fig. 303.— The oriental cockroach: a, female; b, spreading from them. male, ^. side view of female; rf, half-grown sped- ^^j^e oriental cock- men. All natural size. (From Howard and Mar- , t,t-,, ■ j-i- latt.) roach, BLatta onentaUs (Fig. 303), is also a cosmopolitan species ; its original habitat is supposed to have been in Asia; but it has been distributed by commerce throughout the world except in the colder regions. In this country it is most abun- dant in the central latitudes of the United States; it has been foimd in only a few places in Canada. It measures from 18 to 25 mm. in length. It is blackish brown in color. In the male the wings cover about two-thirds of the abdomen ; while in the female they are small, ovate-lanceolate, lateral j^ads. The American cockroach, Periplaneta americdna (Fig. 304), is a native of tropical or subtropical America that has become distributed both in tropical and mild climates over the entire world. This is a large species measuring from 25 to 33 mm. in length. The common wood-cockroach, Parcobldtta pennsylvdnica, is a common species throughout the eastern half of the United States, ORTHOPTERA 267 and its ranre extends into southern Canada. It is a na- The American cockroach. (From Howard and Marlatt.) tive of our woods but is frequently attracted to lights in our houses The two sexes differ so greatly in appear- ance that they were long believed to be distinct species. In both sexes the lateral margins of the prono- tum are light in color while the disk is dark. In the male the body measures from 15 to 25 mm. in length and the wings extend be- yond the tip of the ab- domen (Fig. 305). The female is smaller and the wings are much shorter than in the mal (Fig. 306) Fig. 305. — The common wood-cockroach, male. (From Lugger.) Fig. 306. — The com- m o n wood-cock- roach , female. (From Blatchley.) ORTHOPTEROID INSECTS OF UNCERTAIN KINSHIP Under this head is placed a family of insects the zoological po- sition of which has not been definitely determined. 268 ^A^ INTRODUCTION TO ENTOMOLOGY Family GRYLLOBLATTID^ This family was recently established by Dr. E. M. Walker ('14) for the reception of the species described below, which, while showing striking affinities to the Orthoptera, differs remarkably from all other known members of this order. Some writers who favor the breaking up of the order Orthoptera into several orders, regard this species as the type of a distinct order of insects, the Notoptera. Gryllobldtta campodeiformis. — In this the only species of the family known, the body is elongate, slender, depressed, and thysanuriform Fig. 307. — GrylloUatta campodeiformis. (After Walker.) (Fig. 307). The legs are fitted for rimning, the tarsi are five-jointed and lack pulvilli. The cerci are long, about as long as the hind tibiae, slender, and eight-jointed. The ovipositor is exserted and resembles that of the Tettigoniidas. The eyes are small and the ocelli are absent. The adult male measures 16.5 mm. in length; the female, 30 mm. As yet, this species has been fotmd only in the vicinity of Banff, Alberta, and in Plumas Coimty, California. It is found under stones, at high altitudes, and nms like a centipede. ORTHOPTERA 269 Family HEMIMERID^ Further studies of this family during the years since the pubHcation of former editions of the Introduction seem clearly to have estab- lished the affinity of the Hemimeridae with the order Dermaptera. Recent explorations and collections from rats of Africa have brought to light several new species in the family and much additional knowledge concerning their habits. We have, therefore, placed the family with a brief discussion of it under the Dermap- tera, on page 463. In 1925 Professor Comstock said concerning this family, "although these are exotic insects, they are mentioned here on account of their exceptional manner of devel- opment and mode of life." The additional knowledge concerning them emphasizes this observation and justifies retaining a brief discussion of the family among its proper relatives. Fig. 308. — Hemimerus hans eni. (From Hansen.) CHAPTER IX ORDER ZORAPTERA* So little is known regarding the insects of this order, only a single genus having been found, that it would be premature at this time to define definitely the characters of the order. This is well shown by the fact that recent discoveries have greatly modified our views regarding the ordinal characters of these insects. This order was established by Silvestri in i g 13 . At that time only wingless individuals were known; and it was supposed by this author that the wingless condition was a distinctive ordinal character; he, therefore, proposed the name Zoraptera for the order. But recently Caudell ('20) has described winged individuals of each of the two species fotmd in this country. The name Zoraptera, however, must be retained even though it is inappropriate. Family ZOROTYPIDiE The single known genus, Zorotypus, is the type of this family and imtil other genera are found the characters of this genus must be taken as those of this family and of the order Zoraptera as well. At the time this is written, only six species of Zorotypus have been described. These have been found in widely separated parts of the world, one each in Africa, Ceylon, Java, and Costa Rica, and two in Florida. One of the species from Florida has been found also in Texas. The knowTi species are all minute, the largest measuring only 2.5 mm. in length. In our two species both wingless and winged adults have been foimd ; and it is probable that these two forms exist in the other species. The winged adults that have been observed are all females; but it would not be wise to conclude that only this sex is winged. Of the wingless form both male and female have been found. As these are social insects, living in colonies of various sizes, it may be that the wingless and the winged adults represent distinct castes, analogous to the castes of termites. Another similarity to termites is that the winged individuals shed their wings as do the winged termites. The wingless adults (Figure 309, 4) resemble in general appear- ance small worker termites ; but they have longer legs and are more active. The legs are formed for running; the tarsi are two-jointed and each bears two claws. The mandibles are strong. The antennae are moniliform and nine-jointed. Compound eyes and ocelli are wanting. The cerci are short, fleshy, and unsegmented. The winged adult female (Fig. 309, i) has large compound eyes, three ocelli, nine-jointed antennae, and two pairs of wings. The vena- *Zoraptera: zoros {suphs), pure; apterous (dTrrepos), without wings. (270) ZORAPTERA 271 tion of the wings is represented in the figure. As the tracheation of the wings of n\Tnphs has not been studied, I will not venture to make any suggestions regarding the homologies of the wing-veins. Pig n^oQ.—Zorotypus hubbardi: i, winged adult female; 2, adult female that had shed her wings; 3, nvmph of winged form; 4, wingless adult female. 5 -An- tenna of adult wingless Zorotypus snyderi. (From Caudell,m Proc. lint. boc. Wash., Vol. 22.) 272 AN INTRODUCTION TO ENTOMOLOGY Figure 309, 2, represents an adult female that had shed her wings; and Figure 309, 3, a nymph with well-developed wing pads. The two known American species are Zorotypus hubhardi and Zorotypus snyderi. Detailed descriptions of each of the forms of each of these species are given by Caudell ('20), and the external anatomy of Zorotypus hubhardi is described by Crampton ('20 a), who also discusses the relationships of the order Zoraptera to the other orders of insects. The colonies of Zorotypus are found under the bark of logs and stumps and frequently near the galleries of termites. For this reason they were formerly believed to live as inquilines in the nests of termites ; but recent observations do not support this view« CHAPTER X ORDER ISOPTERA* The Termites or White- Ants The members of this order are social insects, living in colonies like ants. Each species consists of several distinct castes, the number of which differs in different species. Each caste includes both male and female individuals. In most species there are four castes as follows: first, the first reproductive caste, in which the wings become fidly de- veloped and are used for a swarming flight and then shed; second, the second reproductive caste, in which the wing-buds remain short; the members of this caste are neoteinic, becoming sexually mature while retaining the nymphal form of the body; third, the worker caste; and fourth, the soldier caste. Except in a single Australian genus, the two pairs of wings are similar in form and in the more general features of their venation; they are long and narrow, and are laid flat on the back when not in use. The abdomen is broadly joined to the thorax; the mouth-parts are formed for chewing; the metamorphosis is gradual. The termites or white-ants are chiefly tropical insects; but some species live in the temperate zones. These insects can be easily recognized by the fact that they live in ant-like colonies, by the pale color of the greater nimiber of individuals of which a colony is com- posed, and by the form of the abdomen, which is broadly joined to the thorax instead of being pedunculate as in ants. The termites are commonly called white-ants on account of their color and of a resemblance in form and habits to the true ants. These resemblances, however, are only very general. In structure the termites and ants are widely separated. In habits there is little more in common than that both are social, and the fact that in each the function of reproduction is restricted to a few individuals, while the greater number differ in form from the sexually perfect males and females, and are especially adapted to the performance of the labors and defense of the colony. The cuticula of termites is delicate even in adults; the mature winged forms can withstand exposure to dry air for a limited period, as is necessary during their swarming flight; but other members of a colony quickly become shriveled and die if exposed. It is for this reason that they build tubes constructed of earth and excrement for passage-ways, and only rarely appear in the open, and then merely for a brief period. The mouth-parts, which are fitted for chewing, are quite general- ized, resembling somewhat those of the Orthoptera; but in the case of the soldier caste the mandibles are very large and vary greatly in form in the different species. *Is6ptera: isos (f% each by a single species. These genera are distinguished as follows : A. Costal area of the fore wings greatly expanded before the middle (Fig.3i8j. SlALIS AA. Costal area of the fore wings slightly expanded before the middle Protosialis Fig. 318. — Wings of Sialis infumata. 286 AN INTRODUCTION TO ENTOMOLOGY The smoky alder-fly, 5iafo injumdta. — This is a small insect hav- ing a wing-expanse of about 2 5 mm. ; the males are sometimes smaller than this, and the females slightly larger. It is dusky brownish in color. It can be easily recognized by the form and venation of its wings (Fig. 318). The costal area of the fore wings is greatly expanded before the middle, and most of the wing-veins are stout. A striking feature of these wings, one that is characteristic of the subfamily Sialinae, is that the radial sector is nearly typical in form; the only modification being the development of one or more marginal accessory veins upon it. These accessory veins, however, are in a quite different position from that occupied by the accessory veins borne by the radial sector in the Corydalinse, where a pectinately branched radial sector has been developed. The larva (Fig. 319) is furnished with the paired lateral filaments characteristic of the larvce of the Sialidas on the first seven abdominal segments. These filaments are more or less distinctly five-segmented. The last abdominal segment is prolonged into a taper- ing lash-like filament. The larvas are found in swiftly flowing streams adhering to the lower side of stones in the bed of the streams and in trashy places filled with aquatic plants in the borders of streams and ponds; they are very active. The larvae transform in earthen cells at some little distance from the water. Two or three weeks after the making of the pupal cell the adult fly emerges. The eggs are laid in patches, each consisting of a single layer of eggs. The females frequently add their eggs to patches of eggs that have been laid by other females. The eggs when first laid are lighter in color than later. Several specific names have been given to what are now believed to be merely varieties of this species. Protoslalis americana. — In this species the costal area of the fore wings is only slightly expanded before the middle; and the wing- veins are not as stout as in Sialis. The early stages have not been described. Fig. 319. — Larva of Sialis inju- mata. (After Needham.) Subfamily CORYDALIN^ Corydalus and the Fish-Flies The subfamily Corydallnas is represented in this country by the well-known homed coiydalus and several smaller species, commonly known as the fish-flies. In these insects there are three ocelli; the fourth tarsal segment is not bilobed; and the radial sector is pec- tinately branched (Fig. 320). The larvae are distinguished by the NEUROPTERA 287 presence of a pair of anal prolegs, each of which bears a pair of hooks. Six species are found in the United States and Canada; these repre- sent four genera, which can be separated as follows. A. Latero-caudal angles of the head with a sharp tooth. Large insects, p. 287 CORYDALUS AA. Latero-caudal angles of the head unarmed. Insects moderately large; the fish-flies. B. Wings somewhat ashy in color with more or less dusky markings. C. Veins of fore wings marked with dark and light, uniformly alternate. p. 288 Chauliodes CC. Veins of fore wings uniform in color except where dusky markings cross them. p. 288 Neohermes BB. Wings black or brown with white markings, p. 288 Nigronia Corydalus. — The only member of this genus in our fatma is Corydalus cornutus. This is a magnificent insect, which has a wing- expanse of from 100 to 130 mm. Figure 321 represents the male, jcf^ 2d A Cui Cuia Fig. 320. — Fore wing of a pupa of Corydalus. which has remarkably long mandibles. The female resembles the male, except that the mandibles are comparatively short. The larv^ are called dobsons or hellgrammttes by anglers and are used by them for bait, especially for bass. Figure 322 represents a full-grown dobson, natural size. These larvae live under stones in the beds of streams. They are most abrmdant where the water flows swiftest. They feed upon the naiads of stone-flies and May-flies and on other insects. The larvas of Corydalus dift'er from those of the following genera in the possession of a tuft of hair-like tracheal gills at the base of each of the lateral appendages on the first seven abdominal segments. When about two years and eleven months old, the larva leaves the water and makes a cell under a stone or some other object on or near the bank of the stream. This occurs during the early part of the summer ; here the larva changes to a pupa. In about a month after the larva leaves the water, the adult insect appears. The eggs are then soon laid; these are attached to stones or other objects overhanging the water. They are laid in blotch-like masses, which are chalky white in color and measure from 12 mm. to nearly 25 mm. in diameter. A single mass contains from two thousand to three thousand eggs. When the larvas hatch they at once find their way into the water, where they remain imtil full-grown. 288 AN INTRODUCTION TO ENTOMOLOGY Chauliodes. — See the table on page 287 for the discinguishing characteristics of this genus. There are two species in our fauna; these are distinguished as follows: Chauliodes rastricornis. — In this species the antennas are serrate; the embossed markings on the head and prothorax are black on a paler groimd; and the prothorax is longer than wide. Fig. 322. — Larva of Corydahis. Fig. 321. — Corydalns coniiUus, male. Chauliodes pectinicornis . — In this species the antennae are serrate; the embossed markings on the head and prothorax are yellow on a black groimd; and the prothorax is not longer than wide. Neohennes. — This genus is represented by Neohermes caHformcus. In addition to the characters given in the table of genera above, this species is distinguished by the great length of its antenna, which are about two-thirds as long as the fore wings. Nigronia. — In this genus the wings are black or brown with white markings. Two species only are knowm; these can be distinguished by the form of the white markings on the wings. Nigronia fascidtus. — In this species there is a continuous, broad, somewhat arcuate, white band extending across the middle of each wing and almost attaining the hind margin. Nigronia serricornis. — In this species there is an irregular band of white spots, generally broadest in front, extending across the middle NEUROPTERA 289 of each front wing. On the hind wings, the white band is representee^ by only a few minute dots or is entirely wanting. Family RAPHIDIID^* The Snake-Flies Fig. 323.^ — Raphidia, female. The members of the RaphidiidcC are found in this country only in the Far West. They are strange-appearing insects, the prothorax being greatly elongate, like the neck of a camel (Fig. 323). The female bears a long, slender, sickle-shaped ovipositor at the end of the ab- domen. The fore legs resemble the other pairs of legs, and are borne at the hind end of the pro- thorax. The wings are long and narrow and fur- nished with a pterostigma. The wing-venation of a representative of each of the two genera belonging to this family is figured by the writer in his "The Wings of Insects." The larvce are found under bark and are carnivorous. They are common in Cali- fornia imder the loose bark of the eucalyp- tus. They also occur in orchards, and doubtless do good by destroying the larvae and pupae of the codlin-moth. The pupas are not enclosed in silken cocoons but lie concealed in sheltered places. Figure 324 represents a larva and a pupa of Raphtdia as figured by Professor Kellogg. This family includes only two genera, Raphidia and Inocellia. In the former there are three ocelli on the top of the head be- Fig._ 324.— Larva^and pupa tween the compound eyes ; in the latter these ocelli are waa'ting. Six species of Raphidia and three of Inocellia are found in America north of Mexico. of Raphidia. (From Kel- logg.) Family MANTISPID^ The Mantis-like Nenroptera The members of the Mantispida) are even more strange in appear- ance than are those of the preceding family. Here, as in that family, *This family is separated from the Neuroptera by Handlirsch ('o6-'o8 ) and • "aade to constitute a separate order, the Raphidioidea. 290 AN INTRODUCTION TO ENTOMOLOGY the prothorax is greatly elongated ; but the members of this family can be easily recognized by their re- markable fore legs, which are great- ly enlarged and resemble those of the praying mantes in form (Fig. 325). These legs are fitted for seiz- ing prey; and, in order that they may reach farther forward, they are joined to the front end of the long prothorax. In the adult stage, these insects are predacious; while the larvae, so far as is known, are parasitic. Brauer ('69) described the trans- formations of Mantispa styriaca, a European species. This insect undergoes a hypermetamorphosis. It was accidentally discovered that the larvffi were parasitic in the egg-sacs of spiders of the genus Lycosa. These are the large black Fig. 325. — Mantispa. In the speci- men figured the fore legs were twisted somewhat in order to show the form of the parts. Fig. 326. — ^Hypermetamorphosisof ilfaw.'i5/?a. (From Henneguy, after Brauer.) spiders which are common tinder stones, and which carry their egg-sacs with them. Brauer obtained eggs from a female Mantispa kept in confinement. These eggs were rose-red in color, and fastened upon stalks, like the eggs of Chrysopa. The eggs were laid in July; and the larvfe emerged 2 1 days later. The yoimg larvee are campodeiform (Fig. 326, A); they are very agile creatures, with a long, slender body, well-developed legs, and long, slender antennas. They pass the winter without food. In the spring they find their way into the egg- sacs of the above-nam.ed spiders. Here they feed upon the yotmg spiders; and the body becomes proportionately thicker. Later the larva molts and undergoes a remarkable change in form, becom- ing what is known as the second larva; in this stage the larva is NEUROPTERA 291 scarabeiform (Fig. 326, B); the legs are much reduced in size; the antenna are short ; and the head is very small. When fullv grown this larva measures from 7 to 10 mm. in length. It then spins a cocoon, and changes to a pupa within the skin of the larva. Later the larval skin is cast; and, finally, after being in the cocoon about a month, the pupa becomes active, pierces the cocoon and the egg-sac, and crawls about for a time (Fig. 326, C) ; later it changes to the adult form (Fig. 326, D). The life-history of Symphasis vdria, a Bradlian species, is partly known. The larv£e of this species live parasiticallv i 1 the nests of wasps; when full-grown each larva spins a cocoon "in one of the cells of the nest. Only a few representatives of this family occur in the United States, and all are rare insects. Family SISYRID^ The Spoil gilla-Flies The Sisyridce in- clude a very limited number of small, smoky brown insects, of the form shown in Figure 327. They are called Spongilla-jiies because the larvae live as parasites in fresh- water sponges, the typical genus of which is Spongilla. Two interesting features of these insects are the comparative simplicity of the wing-venation of the adults, and the anomalous habits of the larvae. The more striking characteristics of the wings (Fig. 3 28) are the following : The costal area of the fore wings is not greatly broadened ; the humeral vein is not recurrent and is not branched. Veins Sc and Ri coalesce near the apex of the wing. The radial sector is pectinately branched; but no definitive accessory veins have been developed; this is the simplest form of pectinately branched radial sector foimd in the fore wings in this order. Marginal accessory veins are present. The larvce are aquatic and live in fresh-water sponges, upon which they feed. The life-history of a representative of each of the two genera, Sisyra and Climacia, which constitute this family, was worked out by Professor Needham ('01); and the anatomy and transfonnations of a species of Sisyra were carefully studied by Miss Anthony ('02). The following notes are based on the accounts published by these authors. Sisyra mnbrdta. — The form of the adult is shown in Figure 327; its color is nearly unifoiTn blackish brown. The legs and the apex of the abdomen are dirty 3'ellowish. The length of the male to the tips of the wings is 6 mm ; that of the female, 8 mm. Fig. 327. — Sisyra nmbrata, greatly enlarged. (From Anthony.) 292 AN INTRODUCTION TO ENTOMOLOGY The larva (Fig. 329) is campodeiform. Its mouth-parts are formed for sucking as in the larvcC of ant-Hons (see page 282) ; they Fig. 328. — Wings of Sisyra flavicornis . are very long; and two sucking organs, each formed of the mandible and maxilla of one side, are closely parallel for the greater part of their length. Each of the first seven abdominal segments bears on the ventral side a pair of jointed filaments which are believed to be tracheal gills. When full-grown, the larva leaves the water and spins over itself, on some object near the water, a hemi- r;pheric cover of close- ly woven silk, at- tached by its edges to the supporting surface, and a complete inner cocoon of consider- ably smaller size, like- wise closdy Vv^oven. The silk-organs of the larva are described on pages 282-3. Climdcia dictyona. — This species resem- bles the preceding in size but is yellowish Fig. 330. — Cocoon and cocoon-cover of Cli- macia. Fig. 329. — Larva of Sisy- ra umbrata. (After An- thony.) NEUROPTERA 293 in coloration ; the two can be distinguished by the form of the labia (Fig. 331). In the larva of this species the setae on the dorsum of the tho- rax are situated on tubercles; they are sessile in the larva of 5^5 jra. The habits of the larva are similar to those of Sisyra. Fig. 331. — Labia of Spongilla-flies: a, Climacia dictyona; h, Sisyra umbrata. (After Needham.) Before spuming its cocoon this larva spins a hemispheric cover beneath which the cocoon is made, as does the larva of Sisyra. But in the case of Climacia this cocoon-cover is lace-like; it is a beautiful object (Fig. 330). Excepting the sialids, the larva of Sisyra and Climacia are the only known aquatic neuropterous larva? foimd in this country. Family SYMPHEROBIID^ The Sympherohiids This family includes certain insects which were formerly classed with the Hemerobiida? but which exhibit a type of specialization of the wings that is quite different from that which is distinctively characteristic of that family. The distinctive characteristic of the Sympherobiidas is that vein R2+.3 of the fore wings has become separated from the remainder of the radial sector and is attached separately to vein Ri. This results in the radius of the fore wing having two sectors, each of which is forked (Fig. 332). In this family the number of the branches of the radial sector has not been increased, this vein being four-branched in both fore and hind wings ; but the tips of all of the branches are forked. The costal area of the fore wing is broad towards the base of the wing; and the himieral vein is recurved and branched. The North American species of this family represent two genera. 294 AN INTRODUCTION TO ENTOMOLOGY Sympherobius. — In this genus there are two series of gradate veins in the fore wings; the outer series consists of four cross-veins (Fig. 332). Seven American species have been described. The wing-expanse of these insects ranges from 9 mm. to 1 2 mm. Fig. 332. — Wings of Sympherobius amiculus. Psectra. — In this genus there is only one series of gradate veins in the fore wings. The only species is Psectra dtptera. The specific name of this species was suggested by the fact that in the female the hind wings are atrophied. This is a widely distributed species both in this coimtry and in Europe. Its wing expanse is from 5 mm. to 6 mm. Family HEMEROBIID^ The Hemer. hiids The Hemerobiids include insects of moderate size; in most of our species the wing-expanse is between 12 mm. and 22 mm.; in one species of Megalomus it is only 6 mm. In most of the species the body is brown or blackish and is often marked with yellow; in some NEUROPTERA 295 the body is pale yellow. The wings are usually hyaline or pale yellowish. This farnily has been greatly restricted in recent times ; formerly there were included in it the members of the two preceding and the three following families. ^^^^^^^^^ Fig. 333. — Wings of Hemerobius humuli As now restricted this family is composed of a group of genera that are characterized by a distinctive manner of specialization of the radius of the fore wings. This feature is a coalescence of vein Ri and the stem of the pectinately branched radial sector, which results in what I have termed the suppression of the stem of the radial sector. A comparatively simple example of this condition is exhibited by Hemerobius humuli; in the fore wings of this species (Fig. 333), veins R5, R4, and R2+3 arise separately from what appears to be the main stem of the radius but which is really vein Ri and the basal part of the radial sector coalesced. An early stage in the suppression of the stem of the radial sector is shown in the hind wing oi Hemerobius humuli (Fig. 333). Here 29G AN INTRODUCTION TO ENTOMOLOGY vein Ro+3-r4 is bent forward near its base and is joined to vein Ri. The extending of the union of veins Ri and R2+3+4 from the point where they now anastomose towards the base of the wing, so as to obhterate the small cell between them, and also towards the apex of Fig. 334.- — Wings of Megalomus mosstus. the wing for a certain distance, would produce the condition that exists in the fore wing. The wings of Hemerobius represent a comparatively simple type of hemerobiid wings; those of Megalomus mcestus (Fig. 334), a more complicated one. Here there have been developed a larger number of definitive accessory veins and of marginal accessory veins. Under the title "A Revision of the Nearctic Hemerobiidse" Mr.N. Banks ('05) has published an account of this family, the two preceding families, and the three following families, in which all of our species known at that time are described. NEUROPTERA 297 The larvas of the hemerobiids, as far as they are known, resemble in their general appearance aphis-lions (Chrysopidae) , and, like the aphis-lions, feed on plant-lice and other small insects. Their mouth -parts are formed for piercing and sucking (see page 282), and the posterior part of the alimentary ca- nal is transformed into a silk-organ, as in Sisyra (see page 283). They are found most often running about on trees, and especial- ly on coniferous trees. Some, like the aphis-lions, are ^% naked ; but the lar- vae of some species, at least, of Hemcro- hius cover them- selves with a cloak, composed of the empty skins of their victims and other debris (Fig. 335). These larvae are furnished at the sides with projections which serve as pedicels to elongate, divergent hairs that help to keej^ the cloak in place. There are thirty described American species belonging to this family; these represent four genera, Hemerobius, Boriomyia, Megalo- mus, and Micromus. Family DILARIDyE 335. — Larva of Hemerobius: A, the larva bare; B, the same partially concealed by the remains of its victims, etc.; a portion of the covering has been re- moved in order to show the head. (From Sharp.) The Dilaridse is a small family, representatives of which are found chiefly in the Old World. In this family the antennas of the male are pectinate ; and the female is furnished with an exerted ovipositor. Only a single, exceedingly rare species, Dllar americdnus, has been foimd in North America; and of this only a single female individual is known. This is a small insect ; the length of the body, not includ- ing the ovipositor, is about 3 mm.; the length of the ovipositor is a little greater than that of the body ; the expanse of the wings is about 1 4 mm. There is a single five-branched radial sector in both fore and hind wings. In several exotic species the radius of the fore wings bears two or more sectors. The type of our species was taken at Bee Spring, Kentucky, in June, 1874. 298 AN INTRODUCTION TO ENTOMOLOGY Family BEROTHID^ The Berothidas is a small family, which is represented in Ncrth America by a single genus, Lomamyia, of which only two species are Fig. 336. — Wings of Berotha insoliia. known. Figure 336 represents the venation of the wings of the type species of the family, Berotha insolita, which is found in India, and to which our species are closely allied. The fore wings are falcate, which is not true of certain exotic genera ; the humeral cross-vein is not recurved ; many of the transverse veins between the costa and the subcosta are forked ; the radial sector bears definitive accessory veins; and there is a single series of gradate veins in the radial area. In the hind wings the first radio-medial cross-vein is transverse; vein Cu2 is wanting; and the area between the margin of the wing and veins ist A and Cui is narrow and largely occupied by the fanlike tips of the accessory veins. Nothing is known regarding the early stages of these insects. Family POLYSTCECHOTID^ The family Polystoechotidse was established to receive the genus Polystoechotes ,oi\Nh{c\\ only two species, both American, are known. These are larger insects than are the members of the allied families. Fig- 337. — Polystachotes puncta tus. NEUROPTERA 299 measuring in wing-expanse from 40 mm. to 75 mm., vars-ing greatly in size. They are nocturnal and are attracted to lights. The two species can be distinguished as follows : PolystoEchotes piinctdtiis (Fig. 337). This is blackish, with three longitudinal lines on the prothorax, and with the lateral margins of this segment yellowish. Pig. 338. — Wings of Polystcschotes punctatus. Polystoschotes vittdtus. — This is pale yellowish, with a black stripe on the sides of the thorax, and with the abdomen dark brown. The larva of neither of these species is known. This is a strange fact considering the size and the abundance of these insects. The wings oi Polystachotes punctatus (Fig. 338) represent the type of wing-venation characteristic of this family. In these wings the humeral cross-vein is recurved and branched; veins Sc and Ri co- alesce at the tip; the radial sector is pectinately branched; the nimi- ber of cross-veins is greatly reduced; but there is in both fore and hind wings a very perfect series of gradate veins. In these wings the development of definitive accessory veins on the radial sector and the regularity of the border of marginal accessory veins have reached a very high degree of perfection. Family CHRYSOPID^ The Lacewing-Flies or Aphis-Lions The family Chrysopidas includes the insects commonly known as lacewing-fiies; these and their larvee, the aphis-lions, are common 300 AN INTRODUCTION TO ENTOMOLOGY and well-known insects; they are found upon herbage and the foliage of shrubs and trees throughout the summer months (Fig. 339). The adults are easily recognized by their deli- cate lacelike wings and their green or yellowish green color. Members of several of the preceding families have delicate lacelike wings; but with those insects the wings are more or less brown or are hyaline. While these insects are most commonly known as the lacewing- fiies, other popular names have been applied to them; they are some- times called golden-eyed flies, on account of the peculiar metallic color of their eyes while alive; and as some species, when handled, emit a very disagreeable odor, they have been called stink-flies, an undesirable name for such beautiful insects. The wings of the Chrysopidse are characterized by a very re- markable and distinctive type of specialization, the details of which Fig. 339-— Eggs, Chrysopa. larva, cocoon, and adult of Fig. 340. — Fore wing of Chrysopa nigricornis: ]M', pseudo-media; Cui', pseudo- cubitus. can be understood only by a study of the tracheation of the wings of the pupas. Such a study has been made by McClendon ('06), Tillyard ('16), and R. C. Smith ('22). A superficial examination of a wing of Chrysopa (Fig. 340) reveals the presence of two longitudinal veins between the radial sector and the inner margin of the wing, one of which appears to be the media and the other vein Cui; but each of these, as is shown later, is a serial vein composed of sections of several veins. NEUROPTERA 301 As it would be impracticable to apply to these serial veins names indicating their composition, they have been termed the pseudo- media or vein M' and the pseudo-ciibitus-one or vein Cui', re- spectively (Fig. 340, ]\r and Cu/). Fig. 341. — Tracheation of the wings of a pupa of Chrysopa nigricornis. An examination of the tracheation of the wings of a pupa of Chrysopa nigricornis reveals the nature of the two serial veins M' and Cui' (Fig. 341). In order to show more definitely the composition of the two serial veins, a diagram of an adult wing is given (Fig. 342). in which the elements of the coalesced veins are represented slightly separated, and the cross-veins connecting the coalesced veins are represented by dotted lines. By comparing this diagramwith Figiire 340 the homologies of the different veins can be recognized. The larvce of the lacewing-fiies are known as aphis-lions, because they feed upon aphids; they are found on the foliage of plants in- fested by these pests; they also feed upon other small insects and the eggs' of insects; they are spindle-shaped (Fig. 339) and arefur- nished with piercing and sucking mouth-parts like those of ant-lions. Nearly all aphis-lions are naked; but a few species cover them- selves with the skins of their victims and other debris, as do the larvs of Hemerobius. This has l^een obser^'ed by European writers (Sharp 302 AN INTRODUCTION TO ENTOMOLOGY '95); and recently Mr. R. C. Smith ('21) has found that the larvae of several of our native species have a similar habit. The cocoons are generally found on the lower sides of leaves or on the supports of plants; they are spherical and composed of dense layers of silk. In order to emerge the insect cuts a circular lid from ^'+^^r':^r^r^ Fig. 342. — Diagram of the wings of Chrysopa nigricornis, showing the coalesced veins slightly separated. one side of the cocoon ; this is done by the pupa by means of its mandibles. After emerging from its cocoon, the pupa crawls about for a short time before changing to the adult state. The adults are often attracted to lights at night. A remarkable fact in the life-history of these insects is the way in which the female cares for her eggs. When about to lay an egg she emits from the end of her body a minute drop of a tenacious substance, which is probably a product of the colleterial glands; this she applies to the object on which she is standing and then draws it out into a slender thread by lifting the abdomen ; then an egg is placed on the stmimit of this thread. The thread dries at once and firmly holds the egg in mid-air. These threads are usually about 12 mm. in length, and occur singly or in groups; a group is represented attached to a leaf in Figure 339. About fifty species belonging to this family have been found in the United States and Canada; the greater number of these belong to the genus Chrysopa. NEUROPTERA 303 Fig- 343- — Larva, cocoon with pupa-skin projecting, and adult, of an ant-lion. Family MYRMELEONID^ The Ant-Lions The members of the family Myrmeleonidas are commonly known as ant-lions. This name was suggested by the fact that the larvee of the best-known species, those that dig pitfalls, feed chiefly on ants. The adults are graceful creatures. The body is long and slender (Fig. 343); the antenucB are short and en- larged towards the end ; the wings are long and narrow and delicate in structure ; they are furnished with many accessory veins, both definitive and marginal, and with very many cross-veins. A distinctive feature of the wings of these insects is the presence of an elongated cell behind the point of fusion of veins Sc and Ri (Fig. 344); this characteristic serves to distinguish this family from the closely allied Ascalaphidas. The determination of the homologies of the wing-veins of the Myrmeleonidse was completed only recently. The results of this de- termination are set forth in detail by the writer in his "The Wings of Insects," where they are illustrated by many figures. Our native species, as a rule, are not striking in appearance; the wings are hyaline and are often more or less spotted with black or brown marks; iDut certain exotic forms, as those of the genus Pal- pares, are large and have conspicuously marked wings. The larvae have broad and somewhat depressed bodies which taper towards each end (Fig. 343). The mouth-parts are large and powerful and are of the piercing and sucking type; they are described on page 282. The pupa state is passed in a spherical cocoon, made of sand fastened together with silk, and neatly lined with the same material (Fig. 343). The silk is spun from the posterior end of the alimentary canal and is secreted by modified Malpighian vessels, as in Sisyra (see page 283.) This is a large family including several hundred described species. In his "Catalogue of the Neuropteroid Insects of the United States," Banks ('07) lists fifty-eight species of this family known at that time to occur in our fauna; these are distributed among eleven genera. The life-histories of comparatively few of the species are known ; but certain species, the larvae of which dig pitfalls in sandy places, have attracted much attention since the earliest days of entomology. 304 AN INTRODUCTION TO ENTOMOLOGY Ant-lions are much more common in the Southern and Southwest- ern States than they are in the North. The pitfalls of the larvae are usually found in sandy places that are protected from rain, as beneath buildings or overhanging rocks. In making these pitfalls the sand is thrown out by an upward jerk of the head, this part of the body Fig. 344. — Wings of Myrmeleon. serving as a shovel. The pits dififer greatly in depth, according to the nature of the soil in which they are made. Their sides are as steep as the sand will lie. When an ant or other wingless insect steps upon the brink of one of these pits, the sand crumbles beneath its feet, and it is precipitated into the jaws of the ant-lion, which is buried in the sand, with its jaws at the bottom of the pit (Fig. 345). Incase the ant does not fall to the bottom of the pit, the ant-lion undermines it by throwing out some sand beneath it. I have even seen an ant-lion throw the sand in such a way that in falling it would tend to hit the ant and knock it down the side of the pit. These larvae can be easily kept in a dish of sand, and their habits watched. The most common ant-lion in the North is Myrmeleon im- maculdtus; the larva of this species makes a pitfall. The habits of the larvas of Glenurus, Dendroleon, and Acanthdclisis, three genera that are repre- sented in this country, have been described by European writers. These larvae do not dig pitfalls, but partially bury themselves in the sand, from which position they throw themselves quickly upon their victims. Fig. 345.— Pitfall of an ant-lion. NEUROPTERA 305 Family ASCALAPHID^ The Ascalaphids The family Ascalaphidse is quite closely allied to the preceding family; but the members of this family can be easily distinguished from myrmeleonids by the greater length of the antennas (Fig. 346) and by the fact that in the wings there is not an elongate cell behind the point of fusion of veins ScandRi; compare Fig- ures 347 and 344. Fig. z^6.— Ululodes hyalina. (From Kellogg, after McClendon.) The adults are pre- dacious; some species fly in the daytime in bright sunshine, but it is said that others fly in the twilight. Some species resemble mymieleon- I r ca Fig. 347. — Wings of Ululodes hyalina. ids in appearance, while others resemble dragon-flies. When at rest they remain motionless on some small branch or stalk, head down, with the wings and antennae closely applied to the branch, and the abdomen erected and often bent so as to resemble a short brown twig or branch (Fig. 346). 306 AN INTRODUCTION TO ENTOMOLOGY The larvae resemble ant-lions in the form of the body and possess the same type of mouth-parts (Fig. 348). They have on each segment of the body a pair of lateral finger-like appendages, which are clothed with hairs. They do not dig pitfalls, but lie in ambush on the surface of the ground, with the body more or less covered, and wait for small insects to come near them. When a larva is full-grown, it spins a spherical silken cocoon. An account of the life-history of one of our native species, Ululodes hydlina, has been published by McClendon ('02). The Ascalaphidae of the world have been mon- ographed by H. W. Van der Weele ('08). In this monograph more than two hundred species are de- scribed. The members of this family are chiefly p. ^ y ^ tropical insects, but a few species occur in the Ululodes hyatina. United States; these represent three genera, which (After McClendon.) can be separated by the following table. A. Eyes entire Neuroptynx AA. Each eye divided into two parts by a groove. B. Hind margin of wings entire Ululodes BB. Hind margin of wings excised Colobopterus Fig. 349. — Wings of Semidalis aleurodiformis. (After Enderlein.) NEUROPTERA 3o; Family CONIOPTERYGID^ The Mealy-winged Neuroptera The Coniopterygidas is a family of limited extent ; and it includes only small insects, the smallest of the Nenroptera; the described American species measure only 3 mm. or less in length. They are characterized by a reduced wing-venation (Fig. 349) and by having the body and wings covered by a whitish powder. While the adults resemble very slightly other neuropterous insects, the larvae resemble those of the Hemerobiidae and allied families in form, in the structure of their mouth-parts, in their predacious habits, and in their metamorphosis. The larvas have been seen to feed upon coccids, aphids, and the eggs of the red-spider; they doubtless feed on other small insects. When full-grown they make a double cocoon consisting of an outer flat layer and an inner spherical case. Mr. Nathan Banks ('07) has published a revision of the species that have been found in our fauna. This includes eight species, representing five genera. CHAPTER XII ORDER EPHEMERIDA* The May-Flies The rAembers of this order have delicate membranous wings, which arc triangular in outline and are usually furnished with a considerable number of intercalary veins and withmany cross-veins; the hind wings are much small- er than the fore wings and arc sometimes wanting. The matt th-parts of the adults are vestigial; those of the naiads are fitted for chewing. The metamorphosis is incomplete. The May -flies or ephemerids are of ten very common insects in the vicinity of streams, ponds, and lakes; frequently the surface of such bodies of water is thickly strewn with them. They are attracted by lights; and it is not an uncommon occur- rence in summertime to see hundreds of them flying about a single street-lamp. The May-flies are easily distinguished from other net-winged insects by the shape of the wings and the relative sizes of the two pairs (Fig. 350). The mouth-parts of the adult are vestigial, as these insects eat nothing in are very small; they are composed of Fig- 350-— A May-fly. The antennas stout this state, two short segments s u c- ceededbya slen- der, many-joint- ed bristle. The thorax is robust, with the meso- thorax predomi- nant; the great development of this segment is correlated with the large size of the fore wings. The abdomen is Fig long, soft, and composed of ten 351. — Caudal end of abdomen of Siphlurus alternatus, male: g, 10, 11, abdominal segments; c, cerci; mf, median caudal filament ; p, penis ;/, forceps-limbs. (After Morgan.) *Ephemerida, Ephemera: ephemeron {icp-nM^pov) , (308) May-fly. EPHEMERIDA 309 visible segments; the eleventh segment, which bears the cerci, is overlapped by the tenth (Fig. 351). The cerci are long, slender, and many-jointed; and in some species there is a median caudal filament, which resembles the cerci inform; these three organs, the two cerci and the median caudal filament, are commonly referred to as the caudal setse. In the male there is a pair of clasping organs placed ventrally at the extremity of the tenth segment ; these are usually two-, three-, or four-jointed and are termed the forceps- limbs. Each vas deferens and each oviduct has a separate opening; in the male these openings are at the caudal end of the body; in the female, between the seventh and eighth stemites. In some May-flies the compound eyes are divided; one part of each, in such cases, is a day-eye, and the other a night-eye (seepage 144). As the adult May-fly takes no food, its alimentary canal is not needed in this stage for purposes of digestion, and, instead of serving this function, acts as a balloon, being inflated with air, thus lessening the specific gravity of the body and aid- ing in flight. In this order a marked cephalization of the flight function has taken place, which has resulted in a great reduction of the hind wings in all Hving forms. In some cases (CcBnis et al.), this has gone so far that the hind wings are wanting (Fig. 352); but at least one pair of wings is present in all members of this order. When at rest, the wings are held upright; they are never folded over the abdomen. No anal furrow has been developed . A striking feature of the wings of May -flies is their well-known corrugated or fan -like form, there being a remarkably ■^^ Fig. 353. — Fore wing of Chirotonetes alhomanicatus . perfect alternation of so-called convex and concave veins. Correlated with the development of the fan-like form of the wings has been the development of intercalary veins, that is, veins that did not arise as branches of the primitive veins, but were developed in each case as a thickened fold, more or less nearly midway between two preexisting 310 AN INTRODUCTION TO ENTOMOLOGY veins, with which primarily it was connected only by cross-veins. The veins labeled IMi, IM3, and ICui in Figures 353 and 354 are good illustrations of this type of veins. The initial I in these designa- tions is an abbreviation of the word intercalary. Thus the intercalary vein between veins Cui and Cu2, i. e., in the area Cui, is designated as vein ICui. Figures 353 and 354 will aid in the determination of the homol- ogies of the wing-veins of May-flies. In these figures convex veins are designated by plus signs and con- cave veins by minus signs. In attempt- ing to determine the homology of a vein in a wing where the venation is reduced, it should first be determined whether the vein is convex or concave, as the corrugations of the wings of May-flies are the most persistent fea- tures of them. For a more detailed ac- count of this subject, see Chapter X of "The Wings of Insects." The Greek name Ephemeron applied to these insects in the days of Aristotle was derived from ephemeras, signifying lasting but a day; and from that time to this, frequent references have been made to the insects that live only a single day. This brevity of the life of these insects is true only of their existence in the adult state. Strictly speak- ing, the May-flies are long-lived insects; some species pass through their life-cycle in a few weeks in midsummer ; but as a rule one, two, or even three years are required for the development of a generation. The greater part of this time is passed, however, beneath the surface of water, and after the insect emerges into the air and assumes the adult form its existence is very brief. With many species the indi- viduals leave the water, molt twice, mate, lay their eggs, and die in the course of an evening or early morning; and although the adults of many genera live several days, the existence of these insects is very short compared with that of the adults of other insects. The females lay their eggs in water. Some short-Hved species discharge the contents of each ovary in a mass. Individuals are often found in which there project from the caudal end of the body two parallel subcylindrical masses of eggs, one protruding from each of the openings of the oviducts. "The less perishable species extrude their eggs gradually, part at a time, and deposit them in one or the other of the following manners: either the mother alights upon the water 354. — Hind wing of Chirolonetes alhomanicatiis. EPHEMERIDA 311 at intervals to wash off the eggs that have issued from the mouths of the oviducts during her flight or else she creeps down into the water — enclosed within a film of air with her wings collapsed so as to overhe the abdomen in the form of an acute narrowly linear bundle, and with her setae closed together — to lay her eggs upon the under side of the stones, disposing of them in rounded patches, in a single layer evenly spread, and in mutual contiguity." (Eaton '83). Fig- 355- — Metamorphosis of a May-fly, Ephemera varia: A, adult; B, naiad. (After Needham.) The metamorphosis of May-flies is incomplete. The wings are developed externally, as in the Orthoptera; the development of the compound eyes is not retarded; but the immature forms, or naiads, are "sidewise developed" to fit them for aquatic life. In most species the form of the body of the naiads is elongate and furnished with two or three long "caudal set^," that is, cerci and in some a median caudal filament; in these respects the naiads resemble, to a greater or less degree, the adults (Fig. 355); but except in the early instars the abdomen of a naiad is furnished with tracheal gills (Figs. 355 a.nd 356.) The tracheal gills are usually large and prominent; in most species there are seven pairs, borne by the first seven abdominal segments. They vary greatly in form in the different genera. In some each gill is divided into two long narrow branches, which lie in one plane (Fig. 355); in others the gills consist of a scoop-shaped covering piece beneath which is a more delicate part consisting of many thread-like branches. A detailed account of the various forms of tracheal gills of May -flies is given by Miss Morgan ('13). The naiads of May -flies are all aquatic; they are very active; and are almost entirely herbivorous, -p. ^ feeding largely on the decaying stems and leaves of iad of a May- aquatic plants, the epidermis of moss and of roots, fly. 312 AN INTRODUCTION TO ENTOMOLOGY algse, and diatoms. The variations in the details of their habits are described as follows by Dr. Needham ('i8). "A few, like Hexagenia, Ephemera, and Po/jmz7a/-cv5 are burrowers beneath the bottom silt. A few like Canis and Ephemerella, are of sedentary habits and live rather inactively on the bottom, and on silt-covered stems. Alany are active climbers among green vegetation; such are Callibcetis and Blasturns; and some of these can swim and dart about by means of synchronous strokes of tail and gills with the swiftness of a minnow. The species of Leptophlebia love the beds of i.-jOW-flowing streams, and all the flattened nymphs of the Heptageninse live in swiftly moving water, and manifest various degrees of adaptation to withstanding the wash of strong currents. The form is depressed, and margins of the head and body are thin and flaring, and can be appressed closely to the stones to deflect the current." There are two features of special interest in the structure of the naiads of May -flies: first, the hypopharynx bears a pair of lateral lobes, which are believed to be : . vestiges of paragnatha ; and sec- ond, the presence of accessory circulatory organs in the cerci and median caudal filament 'Fig. 3 57)- May-fiies exhibit a remark- able peculiarity in their develop- ment. After the insect leaves the water and has apparently as- sumed the adult form, that is, after the wings have become fully expanded, it molts again. These are the only insects that molt af- ter the}^ have attained functional wings. The term 5«6wzag(9 is ap- plied to the instar between the naiad and the final form of the insect, the adult. With some Fig. 357. — A, caudal end of abdomen of Clo'eon dipterum: h, heart; a, acces- sory circulatory organs. B, twer.ty- sixth segment of a cercus: 0, orifice in blood vessel. (After Zimmerman.) species the duration of the sub imago stage is only a few minutes; the insect molts on leaving the water; flies a short distance; and molts again. In others this stage lasts twenty-four hours or more. With many species of May-flies there is great uniformity in the date of maturing of the individuals. Thus immense swarms of them will leave the water at about the same time, and in the course of a few days pass away, this being the only appearance of the species until another generation has been developed. The great swarms of "lake- flies," Ephemera shnulans, which appear along our northern lakes about the third week of July, afford good illustration of this peculi- aritv. Family EPHEMERID^ The May-Flies The oraer Ephemerida includes a single family, the Ephemeridas; the characteristics of this family, therefore, are those of the order, which are given above. EPHEMERIDA 313 Comparatively few writers have made extended studies of the classification of the ephemerids ; this is doubtless partly due to the fact that pinned specimens usually become shriveled and are very fragile ; consequently this order is poorly represented in most collections of insects. In spite of this, more than one hundred species have been described from the United States. An important paper on the classification of May-flies is that by Dr. Needham ('05) in Bulletin 86 of the New York State Museum. Here are given keys for separating the North American genera, one for the adult insects and one for the naiads. CHAPTER XIII ORDER ODONATA=' The Dragon-Flies and the Damsel-Flies The members of this order have four membranous wings, which are finely netted with veins; the hind wings are as large as or larger than the fore wings; and each wing has near the middle of the costal margin a joint-like structure, the nodus. There are no wingless species. The mouth-parts are formed for chewing. The metamorphosis is incomplete. Dragon-flies and damsel-flies are very common insects in the vicinity of streams, ponds, and lakes; they are well known to all who frequent such places. The dragon-flies, especially, attract attention on account of their largesize(Fig. 358) and rapid flight, back and forth, over the water and the shores ; the damsel-flies (Fig, 359) are less likely to be noticed, on account of their less vigorous flight. The name of this order is evi- dently from the Greek word odous, a tooth; but the reason for applying it to these insects is obscure; it may refer to the tusk-like form of the abdomen. In these insects, the head is large; it differs in shape in the two suborders as described below. The compound eyes are large; they often occupy the greater part of the surface of the head ; in many cases the upper facets of the eye are larger than the lower, and in a few forms the line of division between the two kinds is sharply marked. It is probable that the ommatidia with the larger facets are night-eyes, and those with the smaller facets, day-eyes. See pages 142 and 1 43 . Three ocelli are present. The antennae are short ; they consist of from five to eight segments; of these the two basal ones are thick, the others form a bristle-like organ. The mouth- parts are well developed; the labrum is prominent; the mandibles and maxillas are both strongly toothed; and the labiiun consists of Fig. 358. — A dragon-fly, Plathemis lydia. (From San- born.) "Odonata: odous (65oi5s), a tooth. (314) ODONA TA 315 A damsel-fly. three large lobes, which with the labrum nearly enclose the jaws when at rest. The thorax is large. The wings are, as a rule, of nearly- similar size and structure ; they are richly netted with veins; and the costal border of each is divided into basal and apical parts by what is termed the nodtis (Fig. 364, n). The legs are rarely used for walking, but are used chiefly for perching, and are set far forward ; the tarsi are three- jointed. The abdomen is long, slender, and more or less cylindrical; the caudal end is furnished with clasping organs in the males. A remarkable peculiarity of the order is the fact that the copulatory organs of the male are distinct from the opening of the vasa deferentia; the former are situated on the second abdominal segment, the latter on the ninth. Before pairing, the male conveys the seminal fluid to a bladder-like cavity on the second abdominal segment; this is done by bending the tip of the abdomen forward. Except in the subfamily Gomphinse, the pair- ing takes place during flight. The male seizes the prothorax or hind part of the head of the female with his anal clasping organs; the female then curves the end of the abdomen to the organs on the second abdominal segment of the male. Pairs of dragon-flies thus united and flying over water are a common sight. The Odonata are predacious, both in the immature instars and as adults. The adults feed on a great variety of insects, which they capture by flight; and the larger dragon -flies habitually eat the smaller ones, but a large part of their food consists of mosquitoes and other small Diptera. The eggs are laid in or near water. All of the damsel-flies and many dragon-flies are provided with an ovipositor, by means of which punctures are made in the stems of aquatic plants, in logs, in wet mud, etc., for the reception of the eggs. The females of those dragon-flies that lack a well-developed ovipositor deposit their eggs in various ways. In some species the female flies back and forth over the surface of the water, sweeping down at interv-als to touch it with the tip of her abdomen and thus wash off one or more eggs into it. In other species the eggs are laid in a mass on some object just below the surface of the water; some species do this by alighting upon a water-plant, and, pushing the end of the abdomen below the surface of the water, glue a bunch of eggs to the submerged stem or leaf; in other species the mass of eggs is built up gradually; the female will poise in the air a short distance above the point where the mass of eggs is being laid, and at frequent intervals descend with a swift curved motion and add to the egg-mass and then return to her former position to repeat the operation. Still other species hang their .IG AN INTRODUCTION TO ENTOMOLOGY eggs in long gelatinous strings, on some plant stem at the surface of the water. The metamorphosis is incomplete. The naiads are all aquatic except those of a few Hawaiian damsel-flies, which live on moist soil under the leaves of liliaceous plants. The wings are developed externally, and the development of the compound eyes is not retarded, as it is with larvas. The adaptations for aquatic life differ in the two suborders and are described later. All naiads of the Odonata are predacious. The mouth is furnished with well-developed mandibles and maxillae, all of which are armed with strong teeth. But none of these is visible when the insect is at rest. The lower lip is greatly enlarged, and so formed that it closes over the jaws, conceahng them. For this reason it has been termed the mask. But it is much more than a mask; it is a powerful weapon of oft'ence. It is greatly elongated and is jointed in such a way that it can be thrust out forward in front of the head. It is armed at its extremity with sharp hooks, for seizing and retaining its prey (Fig. 360). The order Odonata is divided into three sub- orders. One of these suborders, the Anisozygop- Under side tera, is composed almost entirely of fossil forms, of head of a naiad being represented among living insects by a single of adamseU^with genus, Epiophlebia, which is found in Japan. The (Afte™Sharp.*) ^ ' other two suborders are well represented in this country ; one of them consists of the dragon-flies, the other of the damsel-flies. Suborder ANISOPTERA* The Dragon-Flies The dragon-flies are easily recognized by the relative size of the two pairs of wings, and by the attitude of the wings when at rest (Fig. 361). The hind wings are larger than the fore wings and are of a somewhat dift'erent shape; but the most striking characteristic is the fact that the wings are extended horizontally when at rest. 4 Fig. 360, Fig. 361. — A dragon-fly, Libellula luduosa. "Anisoptera : anisos (Hvktos), unequal; pteron {wTep6v), a wing. ODONATA 317 The head is large, broad, often semi-globose, and concave behind. The wings are very strong. An important factor in the strengthening Fig. 362. — -Wings of naiads of Gomphus descriptus, early stages. (From Comstock and Needham.) of the wings of these insects is the development of a series of cor- rugations, which has resulted in certain veins becoming convex and others concave; this has progressed so far that there is a very perfect alternation of convex and concave veins. The habits of dragon -flies have been carefully studied by Professor Needham ('18), who writes as follows: "Among the dragon-flies are many superb flyers. The speed on the wing of Trdmea and Anax equals, and their agility exceeds, that of swallows. They all capture their prey in flight; and are dependent on their wings for getting a living. But the habit of flight is very different in different groups. Only a few of the Fig. 363. — Tracheation of the wings of a grown naiad of Gomphus descriptus. (After Needham.) 318 AN INTRODUCTION TO ENTOMOLOGY strongest forms roam the upper air at will. There is a host of beautiful species, the skimmers or Libellulidce, that hover over ponds in horizontal flight, the larger species on tireless wings, keeping to the higher levels. The stronger flying ^schni- dae course along streams on more or less regular beats; but the Gomphines are less constantly on the wing, flying usually in short sallies, from one resting place to another, and alighting oftener on stones or other flat surfaces than on vertical stems." The characters presented by the venation of the wings of the Odonata are much used in the classification of these insects. In general the veins and areas of the wings are designated as in the accounts of the wings of other orders of insects ; but there are certain features in the wings of these insects that are peculiar to them. The most distinctive feature of the wings of the Odonata is the fact that in the course of their development one or more branches, usually two, of the medial trachea invade the area of the radial sector. Fig. 364. — Wings of Gomphus descriptus. In the front wing, cells or areas are labeled; in the hind wing, veins. This results in vein Rg occupying a position behind one or more, usually two, of the branches of media. Figure 362 represents the tracheation of the wings of two naiads of Gomphus descriptus; the wing shown at A is of a very young naiad ; that at B is of a somewhat older one. In the wing shown at A, the branches of trachea M are in their typical position; in the wing shown at B, trachea Mi is in front of trachea Rs. Figure 363 represents the tracheation of a full-grown naiad of the same species. In this stage of the development of the wings, both tracheas Mi and Mo are in front of trachea Rs; and it is in this position that the veins of the adult wing are developed (Fig. 364)- ODONA TA 319 By comparing the figure of the wing of an adult (Fig. 364) with that of the full-grown naiad (Fig. 363), it will be seen that the chlique vein marked o is not a cross-vein but a section of vein R?; so too, what appears to be another cross-vein, labeled 5 «, is also a section of vein Rg; this section of vein Rs is known as the subnodus. It will also be seen that what appears to be the base of the radial sector, labeled b r, isa secondarily developed vein which connects the radial sector with a branch of media ; this secondary vein is known as the bridge. The beginning of the formation of the bridge is shown in Figure 363.* The more important of the other special terms used in descriptions of the wings of dragon-flies are the following : Much use is made in taxonomic work of the two series of cross-veins that are nearest the costal margin of the wing ; those of these cross-veins that are situated between the base of the wing and the nodus are termed the antenodal cross-veins; the first of these two series of antenodal cross-veins ex- tend from the costa to the subcosta; the second from the subcosta to the radius; the antenodal cross-veins are termed the antecubital cross-veins b}^ some writers. The two series of cross- veins nearest to the costal margin of the wing and between the nodus and the apex of the wing are termed the postnodal cross- veins; the first of the two series of postnodal cross-veins extend from the costa to vein R] ; the second, from , vein Ri to vein Mr, the postnodal cross- veins are teimed the postciibital cross-veins by some writers. Near tlie base of the wing there is in dragon-flies a well-marked area of the wing, which is usu- ally triangular in out- line (Fig. 364, t); this. is the triangle; fre- . ■ ^ t a ,1 ,1 , ^. 1 . of a naiad of a drag- quently the triangle is ^j^.f iy_ Tetrago- divided by one or neuHa. Fig.365.-Hind-intestineand part more cross-veins into of the tracheal system of a naiad two or more cells. The area lying imme- ot /EscJmacyanea: R, R, R, R,vec- diatelv in f ront of the triangle (Fig. 364, rif,;.T„\vS^tctaUubS! f.'' terrnedthe ™f.rt™„gfe; like the M, Malpighian tubes. (From triangle this area may consist of a single Sharp, after Oustalet.) cell or may be divided by one or more Fig. 366. — • Exuviae *The conclusions regarding the homologies of the wing-veins given here are based on investigations by Dr. Needham the results of which were published by 320 AN INTRODUCTION TO ENTOMOLOGY cross-veins. Other named areas are thebasal anal area (Fig. 364, ha) and the cubital area (Fig. 364, ca). The writer has given in his "The Wings of Insects" an extended discussion of the wings of Odonata, illustrated by many figures, in- cluding a plate in which adjacent veins are represented in different colors, so that the course of each can be easily followed. With the naiads of dragon-fiies there is a remarkable modification of the organs of respiration, which fits these insects for aquatic life. The caudal part of the alimentary canal, the rectum, is modified so as to constitute a tracheal gill. It is somewhat enlarged ; and its walls are abundantly supplied with tracheae and tracheoles (Fig. 365). Water is alternately taken in and forced out through the anal opening; by this process the air in the tracheae, with which the walls of the rectum are supplied, is purified in the same manner as in an ordinary tracheal gill. The rectal tracheal gill of the naiads of dragon-flies is an organ of locomotion, as well as of respiration. By drawing water into the rec- tiun gradually, and expelling it forcibly, the insect is able to dart through the water with considerable rapidity. This can be easily observed when naiads are kept in an aquarium. When the naiad of a dragon-fly is fully grown it leaves the water to transform. The skin of the naiad splits open on the back of the thorax and head, and the adult emerges, leaving the empty skin of the naiad clinging to the object upon which the transformation took place. Figure 366 represents such a skin clinging to the stem of a water plant. The suborder Anisoptera includes two families, the ^Eschnidag and the Libellulidae ; each of these families is represented in our fauna by many genera and species. These are enumerated in the "Catalogue of the Odonata of North America" by Muttkowski ('10). The two families can be separated by the characters given below. Family ^SCHNID^ The Mschnids In this family the triangle (Fig. 364, t) is about equally distant from the arculus (Fig. 364, ar) in the fore and hind wings; and, except in the genus Cordulegdster, there is an oblique brace-vein extending back from the inner end of the stigma (Fig. 364). The aeschnids are mostly large species ; among them are the largest, fleetest, and most voracious of our dragon-flies. Some of them roam far from water and are commonly seen coursing over lawns in the evening twilight; but most of them fly over clear water. Comstock and Needham ('gS-'gg) and by Needham ('03). These conclusions have been questioned by Tillyard ('22) and by Schmieder ('22); but I do not feel that it would be wise to modify them before a much more extended investigation of the subject has been made. ODONA TA 321 Family LIBELLULID^ The Ltbellulids or Skimmers In this family the triangle in the hind wing is much nearer the arculus than is the triangle of the fore wing ; and there is no oblique brace-vein extending back from the inner end of the stigma, as in the ceschnids. This is a large family including many of our commonest and best-known species of dragon-flies; many of them are familiar figures flying over ponds and ditches and by roadsides. Most of them are of well-sustained flight, and are seen continually hovering over the surface of still water; this suggested the common name skimmers which has been applied to them. Fig- 367. — A damsel-fly. Suborder ZYGOPTERA* The Damsel-Flies The damsel-flies differ from the dragon-flies in that the two pairs of wing:s are similar in form and are either folded parallel with the abdomen when at rest (Fig. 367) or uptilted (Testes). The head is transverse, each eye being borne by a lateral prolongation of the head. The females possess an ovipositor by means of which the eggs are placed in the stems of aquatic plants, sometimes beneath the surface of the water. The name of the suborder probably refers to the fact that the wings are brought together when at rest. Fig. 368. — Wing of Lestes rectangularis : 0, oblique vein; br, the bridge. ''Zygoptera: zygon (,^vy6v), yoke; pteron {irrepdv), a wing. 322 AN INTRODUCTION TO ENTOMOLOGY Unlike the dragon-flies, the damsel-flies are comparatively feeble in their flight. They are found near the margins of streams and ponds, in which the immature stages are passed. Most of the features in the venation of the wings of dragon-fliti described on earlier pages are also characteristic of the wings of damse'i- flies. Figure 368 represents an entire wing of Lestes rectangularis; Fig. 369. — Base of fore wing of Lestes rectangularis: br, the bridge; q, quadrangle; sq, subquadrangle. in this figure o indicates the oblique vein, and hr the bridge. In Figure 369 the base of this wing is represented more enlarged, and the principal veins are lettered. In the suborder Zygoptera the cubitus and the first branch, vein Cui, extend in a comparatively direct course from the base of the wing outward (Fig. 369); the abrupt bends in these veins in the region of the triangle, which are so characteristic of the Anisop- tera, are only slightly developed here. This results in the areas corresponding to the triangle and the supertriangle of the Anisop- tera being in direct line and forming an area which is often quadrangular; this area is termed the quadrangle (Fig. 369, q). In a large part of this or- der the cross-vein sep^ arating the parts of the quadrangle corre- spond ingto th e triangle and the supertriangle of the Anisoptera is lacking, in which case the quadrangle con- sists of a single cell Fig. 370.— Base of wing of Heliocharis. ^~*~-^ (Fig. 369, g). In SOme members of this sub- order it is present; in Figure 370, representing the base of a wing of Heliocharis, the two cells of the quadrangle are labeled t and .j to ODONA TA 323 facilitate comparison with figures of wings of Anisoptera. In certain other members of this subor- der the quadrangle is divided into several cells by cross- veins (Fig. 37i). The cubital area of the wing is usually quadrangular in outline in the Zygoptera, and is termed the subquad- rangle (Fig. 369, sq). Like the quadrangle, it may con- sist of a single cell or it may be divided by cross-veins (Fig. 371)- The naiads of damsel-flies have three plate-like tracheal gills at the caudal end of the body (Fig. 372). The structure of these gills is illustrated by Figure 373 ; at A is represented an entire gillshowing the trachea; and at B, part of a gill more magnified, showing both tracheae (T) and tracheoles (t). Fig. 371. of wing of He.'cprina. Fig. 373. — Tracheal gill of a damsel-fly: A, entire gill showing the tracheae; B, part of gill more magnified , show- ing both tracheae (T) and tracheoles (t). Fig. 372. — Naiad of a damsel-fly, Argia. The suborder Zygoptera includes two families, the Agrionidee and the Coenagrionidas. The genera and species of these families are enumerated by Muttkowski ('10). The two families can be separated as follows. A. Wings with many, at least five, antenodal cross-veins Agrionid.-e AA. Wings usually with only two antenodal cross- veins, rarely with three or four CCENAGRIONID/E 324 AN INTRODUCTION TO ENTOMOLOGY Family AGRIONID^ The True Agrionids In the Agrionidse the wings are furnished with many antenodal cross-veins; and, although the wings are narrow at the base, they are not so distinctly petiolate as in the next family. These insects may be termed the true agrionids, as owing to a misapplication of the generic name Agrioti the members of the next family have been incorrectly known as the agrionids. Here belong the most beautiful of our damsel-flies, whose metallic blue or green colors are sure to attract attention. They are feeble in flight and do not go far from the banks of the pond or stream in which they were developed. There are only two genera of this family in our fauna. These are Agrion, which has been commonly known as Calopteryx, and Hetce- rina. In Agrion the wings are broad and spoon-shaped. In HetcB- nna the wings are rather narrow, and in the males the base of one or both pairs is red. Family CCENAGRIONID^ The Stalked-winged Damsel-Flies The members of this famiily are easily recognized by the shape of their wings, which are long, narrow, and very distinctly petiolate (Fig. 368); and by the fact that in each wing there are only two antenodal cross-veins, except in a few cases where there are three or four. To this family belong the smallest of our damsel-flies; but while our species are of small or moderate size, there exist in the tropics species that are the largest of the Odonata. Some of our species are dull in color; but many are brilliant, being colored with green, blue, or yellow. This family includes the greater number of our damsel-flies. CHAPTER XIV ORDER PLECOPTERA* The Stone-Flies The members of this order have four membranous wings. In some genera the branches of the principal veins are reduced in number and there are comparatively few cross-veins; in others, accessory veins are developed and there are many cross-veins; in most genera the hind wings are much larger than the fore wings, and are folded in plaits and lie upon the abdomen when at rest. The mouth-parts are of the chewing type of structure, but are frequently vestigial in the adidt. The cerci are usually long and many-jointed. The metamorphosis is incomplete. Members of this order are common insects in the vicinity of rapid streams and on wave-washed rocky shores of lakes ; but they attract Httle attention on account of their inconspicuous colors and secretive habits. They are called stone-flies because the immature forms are very abundant under stones in the beds of streams. In the adults the body is depressed, elongate, and with the sides nearly parallel (Fig. 374). The prothorax is large. The antenna are long, tapering, and many-jointed. The mouth-parts are usually greatly reduced. In some genera the mandibles are al- most membranous, but in others they are firm and toothed, being well fitted for biting. The maxillae exhibit variations in the degree of their reduction similar to those shown by the mandibles. The maxil- lary palpi are five-jointed. The labial palpi are three- jointed. The legs are widely separated, except the fore legs in the Pteronarcidse; the tarsi are three-jointed. The hind wings are a little shorter than the fore wings, but usually, owing to the expansion of the anal area, they are considerably larger than the fore wings ; in a f ev\^ genera the hind wings are smaller than the fore wings ; in some species the wings of the male are greatly reduced in size, and in others the males are wingless. When at rest, the wings are folded in plaits and lie upon the *Plecoptera: pieces (wXiKo^), plaited; pteron (irTepdv), a win^. Cb25) A stone-fly, Pteronarcys dorsata. 326 AN INTRODUCTION TO ENTOMOLOGY abdomen, as shown on the left side of Figure 374. The cerci are u'^u- ally long and many -jointed; but they are rudimentary in the Nemouridas. The stone-flies are unattractive in appearance ; in most of them the colors are obscure, being predominantly black, brown, or gray ; but some of them that are active in the da}i;ime and inhabit foliage are green. Their powers of flight are quite limited; they are usually found crawling about on stones or on plants near streams. Several of the smaller species appear in the adult state upon snow on warm days in the latter half of winter. They become more numerous in early spring and often find their way into our houses. The most common one of these in central New York is the small snow-fly, Cdpnia pygmcea. It is probable that most adult stone-flies eat nothing; this can be inferred from the reduced condition of their mouth-parts. But it has been shown by Newcomer ('18) that several species of Tmiiopteryx, which are equipped with well-developed mouth-parts, feed upon the buds and leaves of plants. One species in particular, T. pactfica, is a serious pest in the Wenatchee Valley, Wash., where it bites into the buds of fruit trees. One of the more striking features of the venation of the wings of the Plecoptera is a lack of uniformity in the number and courses of the subordinate veins. Not only are striking differences in wing-venation to be observed between different individuals of the same species, but frequently the wings of the two sides of an individual will vary greatly in venation. This is especially true as to the number of cross-veins and the branching of the veins in the distal parts of the wings. On the other hand, the characters presented by the trunks of the principal veins are quite constant. There is one characteristic of the wings of the Plecoptera that is so constant that it may be considered an ordinal character. This is the fact that in the wings of the adult the radial sector of the hind wings is attached to media instead of to radius (Fig. 3766). This switching of the radial sector of the hind wings is true only of the venation of the adult. In the wings of naiads the trachea Rs is a branch of trachea R. There are certain features of the wings of Plecoptera, which, although not always constant, occur in so large a portion of the members of the order that they may be considered characteristic; these are the following, all of which are repre- sented in Figure 3766; The presence of the radial cross-vein {r). The absence of cross- veins in cell R and in the basal part of area Ri. (Cross- veins are found in cell R in Pteronarcys.) The strengthening in the fore wings of the area between media and vein Cui and of that between veins Cuj and Cuj by the development of many cross- veins. The reduction of media to a two-branched condition. The reduction of the radial sector to a two-branched condition. (This reduction of the i-adial sector is apparent only after an extended study of the wings of stone-flies. In many cases, of which the form represented by Figure 3766 is one, accessory veins have been developed on vein R2 +3 which appear to be the primitive branches of the radial sector; but these accessory veins are very inconstant in number and position.) And the unbranched condition of the first anal vein. In concluding this brief summary of the special features of the wings of the Plecoptera it seems desirable to define some terms frequently used by writers on this order. The transverse cord. — In many genera of this order there is a nearly continuous series of cross-veins extending across each wing just beyond the middle of its length; this series of cross- veins is termed the anastomosis by many writers On the Plecoptera. As it is not formed by an anastomosing of veins, the use of the term transverse cord is preferable. PLECOPTERA 327 The pterosligma. — In most members of this order a specialized pterostigma has not been developed; but the term pterostigma is commonly applied to the cell beyond the end of the subcosta and between the costa and vein Ri, even though it is of the same color and texture as the remainder of the wing. The basal anal cell. — A very constant feature of the anal area of the wings of Plecoptera is the presence of a cross- vein near the base of the wing, which extends from the first anal vein to the second. The cell that is closed by this cross- vein is termed the basal anal cell (Fig. 376^, ba). The females drop their eggs in a mass in water. I have taken females of Perla and of Pteronarcys at lights, each with a mass of eggs hanging from the abdomen. The metamorphosis is incomplete. The immature forms are all aquatic. These naiads are common on the lower surface of stones in rapids. They can be found easily by lifting stones from such situations and turning them over quickly, when the na- iads will be found clinging to the stones with their fiat bodies closely appressed to them and their legs, antenna, and cerci ra- diating on the surface of the stone , but they are apt to run away quickly. The naiads of stone-flies live only in well-aerated water; they are not found in stagnant water or in foul streams. They are said to feed on other aquatic insects, includ- ing smaller individuals of their own species; but according to the observations of Dr. P. W. Claassen they are largely vegetable feeders. The body is depressed (Fig. 375); the antenna are long, so too are the cerci Most species possess tracheal gills, situated usually on the ventral side of the thorax just be- hind the base of each leg ; but tracheal gills are found in some species either on the un- der side of the head, on the basal abdom- inal segments, or at the tip of the abdo- men. A large nimiber of the smaller species are destitute of tracheal gills; in these the air supply is absorbed through the thin cuticula of the ventral surface. The colors of naiads are often brighter than those of adults. When full-grown the naiads leave the water and transform on some near-by object. The empty exuviae are often found clinging to stones or logs projecting from water or on the banks of streams. According to a recent classification of this order, that of Tillyard ('21), it includes seven families; but only four of these families are represented in our fauna. A monograph of the North American species of the order is in preparation by Professor J. G. Needham and Professor P. W. Claassen; this is nearly completed and probably will be published soon. The four families of our fauna can be separat- ed by the following table. Fig. 375. — Naiad of a stone-fly, Acroneura. 328 AN INTRODUCTION TO ENTOMOLOGY A. Anal area of the fore wings with two or more series of cross-veins (Fig. 376a). p. 328 PTERONARCID.E AA. Anal area of the fore wings with not more than a single series of cross- veins, usually with no cross-veins beyond the basal anal cell. B . Media of the fore wings separating from radius gradually, the two forming a sharp angle (Fig. 3766). p. 328 Perlid^ BB, Media of the fore wings separating from radius abruptly, the two form- ing a blunt angle (Fig. 376c), C. Anal area of the fore wings with a forked vein arising from the basal anal cell (Fig. 376a). Cerci vestigial, p. 330. Nemourid^ CC. Anal area of the fore wings with only simple veins arising from the basal anal cell (Fig. 376c?). Cerci well developed, p. 330 Capniid^ Family PTERONARCID^ This is a small family which is represented in North America by only two genera and by but few species. Pterondrcys. — This genus includes the largest of our stone-flies. Figure 374 represents a common species. The venation of the wings ^Tm Sr, Fig. 376a. — Wings of Pteronarcella badia. is reticulate ; the reticulation is irregular and extends in the fore vnngs from the costa through the anal area. A remarkable feature of members of this genus is that vestiges of tracheal gills are retained by the adults. Pteronarcella. — This genus includes smaller species than the pre- ceding one, and the venation of the wings is more regular than in Pteronarcys (Fig. 376a). Family PERLID^ The members of this family differ from the Pteronarcidae in the smaller niunber of cross- veins in the anal area of the fore wings. PLECOPTERA 329 there being usually no cross-veins beyond the basal anal cells (Fig. 3766); and they differ from the following families in that media of , 2dA Fig. 376^. — Wings of Isogenus sp. 2^^ Fig. 376c. — Wings of Nemoura sp. 330 ^A^ INTRODUCTION TO ENTOMOLOGY the fore wings separates from radius gradually, the two forming a sharp angle (Fig. 37 6b). This is the largest of the families, including a large portion of the genera and species found in our fauna; fourteen genera have been described from this region. Family NEMOURID^ In this and the following family the media of the fore wings separates from radius abruptly, the two forming a blunt angle (Fig. 376c). In this family the second and third anal veins of the fore wings coalesce for some distance beyond the basal anal cell, forming a forked vein (Fig. 376c), and the cerci are vestigial. The family is represented in our fauna by nine genera. Our more common representatives are small, dusky, and grayish species that are found emerging throughout the spring of the year. Family CAPNIID^ In this family, as in the Nemouridae, the media of the fore wings separates from radius abruptly, the two forming a blunb angle (Fig. 3,7 6d); but in this family there are in the anal area of the fore wings ^•4+5 Fig. 376^. — Wing of Capnia sp. only simple veins arising from the basal anal cell (Fig. 376(f), and the cerci are well developed. This is a small family which is represented in our fauna by only three genera. The members of this family that are most often seen are the little black species of Capnia that appear on snow on warm days in the latter half of winter and in early spring. The naiads of these live chiefly in small brooks. CHAPTER XV OPJ)ER CORRODENTIA* The Psocids and the Book-Lice Fig- 377- — A winged psocid, Cerastipsocus venosus. The winged members of this order have Jour membranous wings, wiTn the veins prominent, but, with comparatively Jew cross-veins; the Jore wings are larger than the hind wings; and both pairs when not in use are placed rooj-like over the body, being almost vertical, and not Jolded in plaits. The mouth-parts are formed Jor chewing. The metamorphosis is gradual. The best-known representatives of this order are the minute, soft-bodied insects which are common in old papers, books, and neglected collections and which have received the popular name book-lice. These low, wingless creatures form, how- ever, but a small part of the order. The more typical winged forms (Fig. 377) bear a strong resemblance to plant-lice or aphids. The body- is oval, the head free, and the protho- rax small. The fore wings are larger than the hind wings; and both pairs when not in use are placed roof- like over the body, being almost vertical, and not folded in plaits. The wing-veins are prominent, but the venation of the wings is reduced. The tarsi are two- or three-jointed. Cerci are wanting. The mouth-parts are of especial interest on account of the presence of well-preserved paragnatha. Fig- ure 378 represents the mouth-parts of the common book-louse, Troctes divinatorius , as figured by Snodgrass ('05). The mandibles 0) are of the ordinary, strong, heavy, biting type. The maxillag (m) consist each of a body piece, a weakly chitinized terminal lobe, and a four-jointed palpus. The paragnathus if, J) is represented in the figure at A, with the maxilla; it lies above the maxilla and is, therefore, in its typical position between the maxilla and the mandible of the same *Corrodentia: Latin corrodens, gnawing. r331) Fig. 378. — Mouth-parts of a book- louse, Troctes divinatorius: A , max- illa and paragnathus of right side, ventral view; w, maxilla; /, /, paragnathus; p, protractor mus- cle; r, retractor muscle. .B, man- dibles. C, labium, ventral view; p, palpus. (After Snodgrass.) 332 AN INTRODUCTION TO ENTOMOLOGY side. Note that the figure is a ventral view, hence the paragnathus is represented as passing beneath the maxilla. The paragnatha have Fig. 379. — The wings of a psocid. been known as the fur ecu maxillares. The labium (C) bears a pair of one-jointed palpi. The venation of the wings is distinctively characteristic in this order. The venation is more or less reduced; but its most characteristic feature is the bracing of the wing by anastom.oses of the principal Fore v.'ing of a full-grown nymph of a psocid. veins instead of by cross-veins. This is well shown by the wings of Psocus (Fig. 379). The determination of the homologies of the wing-veins in this insect was accomplished by a study of the trachea- tion of the wings of nymphs. Figure 3 So represents the tracheation of a fore wing of a full-grown nymph of Psocus. There are no cross-veins in the wings of Psocus; the arculus (ar) in the fore wing is merely the base of media, and what appear as CORRODENTIA 333 cross-veins in the central portion of the wing are sections of rr.edia and cubitus. In some genera, however, the radial cross-vein is present, and in some, instead of an anastomosis of veins M and Cui, these veins are connected by a medio-cubital cross- vein. The metamorphosis is gradual. The nymphs resemble the adults in the form of the body, but lack wings and ocelli in those species that are winged in the adult; in the wingless species the differences between the young and the adult are even less marked. The Corrodentia of the United vStates and Canada represent tvvo families, which can be separated as follows. A. Wings well developed ; ocelli present Psocid^ AA. Wings absent or vestigial; ocelli absent Atropid^ Family PSOCID^E The P sec ids The family Psocidae includes the more typical members of the Corrodentia, those in which the wings are well developed (Fig. 377). Usually the wings extend much be>'ond the end of th.e abdomen; but short -winged forms occur in species which ordinarib/ are long-winged. Of course the young of all are wingless, and there is a gradual develop- ment as the insect matures. The antennge consist of onlv' thirteen segments; this will enable one to separate the immature forms from the Atropids, in which the antennas have a greater number of segments. The psocids occur upon the trunks and leaves of trees, and on stones, walls, and fences. They feed upon lichens, fungi, and probabl ;^ other dry vegetable matter. They are sometimes gregarious. I have often seen communities of a hundred or more closely huddled together on the trunks of trees, feeding on lichens. The eggs are laid in heaps on leaves, branches, and the bark of trunks of trees. The female covers them with a tissue of threads. It is believed that both sexes have the power of spinning threads. The silk is spun from the labium. More than seventy species, representing eleven genera, have been described from our fauna. Family ATROPID^ The Book-Lice and Their Allies The family Atropidse includes small Corrodentia, which are wingless or possess only vestigial wings. The most commonly ob- served species are those known as book-lice, which are the minute soft-bodied insects often found in old books (Fig. 381). Of these the two following species are the best known. Troctes divinatorius. — This is a wingless species which measuies about I mm. in length; it is grayish white, with black eyes. 334 AN INTRODUCTION TO ENTOMOLOGY Atropos pulsatoria. — In this species the fore wings are represented by small convex scales ; it is of a pale yellowish white color and is a little more than i mm. in length. Each of these species has been known as the death-watch, as they have been believed by superstitious people to make a ticking sound that presaged the death of some person in the house where it is heard. It is not probable that such minute and soft insects can produce sounds audible to human ears. The sounds heard were prob- ably made by some wood-boring beetles, Anohiidce, which are also known as the death-watch. Book-lice are found chiefly in damp, well-shaded rooms, not in general use. They do not attack man, but feed upon dead vegetable and animal matter, as the paste in book-bindings, wall-paper, and photo- graphs. They rarely occur in sufficient numbers to do serious injury. They can be destroyed by fumigating the infected room with hydrocyanic acid gas. This, however, should be used only by experienced persons. Ordinarily a prolonged heating and drying of the roam will be sufficient to destrov them. Fig. 381.— A book-louse. CHAPTER XVI ORDER MALLOPHAGA* The Bird-Lice The members of this order are wingless parasitic insects with chewing mouth-parts. Their development is without metamorphosis. The bird-lice resemble the true lice in form, being wingless, and having the body more or less flattened; certain species that infest domestic fowls are well-known examples. These insects differ from the true hce in having chewing mouth-parts. They feed upon feath- ers, hair, and dermal scales, while the true lice, which constitute the order Anoplura, have sucking mouth- parts, feed upon blood, and infest only mammals. The Mallophaga infest chiefly birds, and on this account the term bird-lice is applied to the entire group; a few genera, however, are parasitic upon mammals. Some writers term the Mallo- phaga the biting lice, which is a more accurate designation; but the name bird-lice is more generally used. The bird-lice are small insects. The more common species range from I mm. to 5 mm. in length. The mouth-parts are on the under side of the head, the most anterior part of the head being a greatly enlarged clypeus ; they are of the mandibulate type; and paragnatha ("furcce maxillares") have been found in several species (Snod- grass '05). There is a pair of "simple eyes" located in the lateral margins of the head. The structure of these eyes has not been de- scribed; but judging from their position they are probably degenerate ommatidia and not oceUi. The front legs are shorter than the others and are used to convey food to the mouth. There is an interesting correlation between the habits of these insects and the structure of their feet. The tarsi of those species that feed on mammals are one-clawed and fitted for folding against the tibiffi; they are organs well adapted for clinging to hairs. Those species that feed on birds have two-clawed tarsi and are better fitted for running. The above distinction is not quite accurate, as a few two-clawed species feed on kangaroos, wallabies, and wombats. *Mall6phaga: mallos {na\\6s), wool; phagein {(payeip), to eat. (335) -336 • AN INTRODUCTION TO ENTOMOLOGY The accompanying figures represent some of our common species. Fig. 2)^2.—Goniodes stylif- er. (From Law.) Fig- 383. — Tricho- d e c t e s I at u s. (From Law.) Fig 384 — Trichodectes spheroceph- aliis. (From Law.) Fig. 2,^^. — Tri- chodectes sca- Hris. (From Law.) Fig 386 —Tncho dectes equt. (From Law.) Gcniodes stylifer (Fig. 382) infests turkeys; Trichodectes Idtus (Fig. 383), dogs; Trichodectes spherocephalus (Fig. 384), sheep; Trichodectes scaldris (Fig. 385), domestic cat- tle; and Trichodectes equi (Fig. 386), horses and asses. The eggs of the Mallophaga are glued to the hairs or feathers of their hosts. The development takes place on the body of the host and is without metamorphosis. The young are not so dark in color as the adults and the cuticula is less densely chitin- ized. The ametabolous condition of these insects is believed to be an acquired one, a result of their parasitic habits. The bird-lice are well known to most people who have pet birds or who keep poultry. It is to free themselves from these pests that birds wallow in dust. When poultry are kept in closed houses they should be provided with a dust-bath. AH poultry houses should be cleaned at least twice a year, and the old straw burned. Sprinkling powdered sulphur in the nests and oiling the perches with kerosene will tend to keep the pests in check. If a poultry house becomes badly infected, it should be cleaned thoroughly, ever>^ part whitewashed, and the poultr}^ dust- ed with either insect-powder or sodium fluoride. The Mallophaga is a small order. Professor V. L. Kellogg in his "Mallophaga" (Kellogg '08 b) estimates the number of known species to be 1250; these represent twenty-seven genera. But there are doubtless many species not yet discovered, as comparatively few birds and mammals have been thoroughly searched for these pests. The work just quoted is the latest and most complete systematic treatise on this order. It followed a long series of papers on these insects published by this author. A more generally accessible ac- count of the species that have been found in North America is a MALLOPHAGA 337 chapter in Professor Herbert Osborn's "Insects Affecting Domestic Animals" (Osborn '96). The chief divisions of the order adopted by Kellogg ('08 b) are as follows. A.. With filiform, 3- or 5-segmented, exposed antennas; no maxillary palpi; mandibles vertical Suborder Ischnocera B. With 3-segmented antennae; tarsi with one claw; infesting mammals. Family Trichodectid.e BB. With 5-segmented antennee; tarsi with two claws; infesting birds Family Philopterid^s AA. With clavateor capitate, 4-segmented, concealed antennae; with 4-segmented maxillary palpi; mandibles horizontal Suborder Amblycera B. Tarsi with one claw; infesting mammals Family Gyropid^ BB, Tarsi with two claws; infesting birds, excepting a few species that infest kangaroos, wallabies, and wombats Family Liotheii.-^ CHAPTER XVII ORDER EMBIIDINA=' The Embiids This order is composed of small and feeble insects in which the body IS elongate and depressed. The winged members of the order have two pairs of wings, which are quite similar in form and structure; they are elongate, membranous, extremely delicate, and folded on the back when at rest; the venation of the wings is considerably reduced. The mouth- parts are formed for chewing. Cerci are present and consist each of two segments. The metamorphosis is of a peculiar type. This is a small order of insects; Enderlein ('12 a) in his monograph of the Embiidina of the world lists only sixty-one species. The body is elongate and depressed (Figs. 387 and 388). Only the males are winged ; and in some genera this sex also is wingless. The venation of the wings is re- ■ """ ; duced; this reduction has been brought •'"' Fig- 3^7- — Embia sabulosa, male. (After En- derlein.) Fig. 388. — Embia sabulosa, female. (After Enderlein.) about both by the coalescence of veins and by the atrophy of veins. Each of the veins of the wings extends along the middle of a brown band ; between these bands the membrane of the wing is pale in color. The alternating brown and pale bands give the wing a very characteristic *Embiidina: Embiidae, Embia, embios (ffi^ios), lively. (338) RMBIIDINA 339 appearance (Fig. 389). In those forms where the venation of the wings has been reduced by the atrophy of veins, the brown bands persist after the veins have faded out; hence it is easy to determine by these bands the former position of veins that have been lost. A discussion of the venation of the wings of the Embiidina is given in my "The Wings of Insects." The antennae are fiHform and are composed of from sixteen to thirty-two segments. The compound eyes consist of many ommatidia, Fig. 389. — Fore wing of Oligoloma saundersi: A, the wing; B, outline of the wing showing the existing venation; C, outline of the wing showing the venation restored. (After Wood-Mason.) which are of the eucone type. Ocelli are always wanting. The mouth-parts are mandibulate; the maxillary palpi are five-jointed and the labial palpi three-jointed. The abdomen is composed of ten distinct segments and bears at its tig a pair of two-jointed cerci. Figure 387 represents the male of Embia sabulosa, with the wing of one side removed; and Figure 388, the female of this species. The metamorphosis is of a type intermediate between gradual and complete. This was shown by Melander ('02 b), who vStudied the development of Embia texdna. The }^oung resemble the adults in the form of the body, except that the body is cylindrical instead of depressed; and the cuticula of the young is less densely chitinized and pigmented than is that of the adult. In the case of the females 340 AN INTRODUCTION TO ENTOMOLOGY and of those males that are wingless in the adult instar, it might be said that these insects develop without metamorphosis. But in the case of the winged males the development resembles that of insects with a complete metamorphosis in one important respect; that is, the development of the wings is internal until the penultimate molt is reached. Melander states that he sectioned the fully grown larva and found the wings as large invaginated pockets completely beneath the hypodermis. In the penultimate instar of the winged females there are well-developed, external wing-pads. This instar may well be termed a pupa. The embiids are very active insects both in running and in flight. They are often gregarious. They live in silken nests or galleries under stones or other objects lying on the ground, and burrow into the soil when the surface becomes too dry. Imms found in his studies of Embia major in the Himalayas that maternal care on behalf of the ova and larvae is strongly exhibited by the females, in much the same .manner as is known to occur among the Dermaptera. Writers differ as to the source of the sillv of which the nests are made. Melander ('02 a) and others have described glands in the metatarsi of the forelegs, which open through hairs, and have ob- served that in spinning its nest the insect uses its fore feet. But Enderlein maintains that the chief source of the silk is from glands that open through a spinneret on the labium, although the secretion of the metatarsal glands may play a part in the formation of the silken tissues. The embiids are widely distributed in the warmer parts of the world. A few species have been found in Florida, Texas, and California. CHAPTER XVIII ORDER THYSANOPTERA* The Thrips The members of this order are minute insects with wings or wingless. The winged species have four wings; these are similar in form, long, narrow, membranous, not plaited, with but few or with no veins, and only rarely with cross-veins; they are fringed with long hairs, and in some species are armed with spines along the veins or along the lines from which veins have disappeared. The mouth-parts are formed for piercing and sucking. The tarsi are usually two-jointed and are bladder- like at the tip. The metamorphosis is gradual, but deviates from the usual type. These insects are of minute size, rarely exceeding 2 mm. or 3 mm. in length. They can be obtained easily, however, from various flowers, especially those of the daisy and clover. Ordinarily it is only necessary to pull apart one of these flowers to find several thrips. They are in many cases very active insects, leaping or taking flight with great agility. In case they do not leap or take flight when alarmed, they are apt to run about and at the same time turn up the end of the abdomen in a threatening manner, as if to sting. In this respect they resemble the rove-beetles. The body is long (Fig. 390). The head is narrower than the thorax, without any distinct neck. The antenuce are filiform or moniliform and consist of from six to nine segments ; they are alwaj'S much longer than the head and may be two or three times as long. The compound eyes are large, with conspicuous facets, which are circular, oval, or reniform in outline. Three ocelli are usually present in the winged forms, but sometimes there are only two ocelli ; wing- less species lack ocelli. The mouth parts are fitted for piercing and sucking ; they are in the form of a cone which encloses the piercing or- gans. The cone is composed of the clypeus, . . , . labnmi, maxillary sclerites, and labium. The ^^' ^^^' "^^' piercing organs consist of the left mandible (the right mandible is vestigial) and the two maxillae. Each maxilla is composed of two parts: first, the palpus-bearing maxillary sclerite; and second, the maxillary seta. For detailed accounts of the mouth-parts see Hinds ('02) and Peterson ('15). The above statement regarding the mouth- parts is based on the paper by Peterson. The mouth-parts of the Thysanoptera bear a striking resemblance to those of the Hemiptera *Thysan6ptera: ihysanos (dvaavos), fringe; pteron {irr^f^bv), a wing. (341) 342 AN INTRODUCTION TO ENTOMOLOGY and the Homoptera, which are described in detail in later chapters. The three thoracic segments are well developed. The wings are laid horizontally on the back when not in use; they are very narrow, but are fringed with long hairs (Fig. 391), which, diverging in flight, compensate for the smallness of the membrane. The fringing of the wings suggested the name Thysanoptera, by which the order is known The two longitudinal veins that traverse the disk of the wing in Fig. 391. — Fore wing of Mlothrips nasturlii. (After Jones.) The lettering is original. the more generalized forms I believe to be the radius and the media respectively. The costal vein is continued by an ambient vein, which margins the entire preanal area of the wing (Fig. 391, am). The ambient vein is termed the "ring vein" by writers on this order, al- though the term ambient vein has been long in use for veins in this position. There is a short longitudinal vein separating the anal and preanal areas; this is doubtless the anal vein (Fig. 391, A). An organ for uniting the two wings of each side, and consisting of hooked spines situated near the base of the wings and a membranous fold on the under side of the anal area of the fore wing, is described byHinds ('02). In some species one or both sexes are wingless in the adult state; and in others, short-winged forms occur. The legs are well developed, but are furnished with very peculiar tarsi. These are usually composed of two segments; the last seg- ment terminates in a cup-shaped or hoof-like end and is usually without claws. Fitted into the cup-shaped end of the tarsus there is a very delicate, protrusile, membranous lobe or bladder, which is withdrawn into the cup when not in use but is protruded when the tarsus is brought into contact with an object. This is one of the most distinctively characteristic features of the members of this order. It was this feature that suggested the name Physopoda which is ap- plied to this order by some writers.* The abdomen consists of ten distinct segments. The form of the caudal segments differs in the two suborders as indicated below. The manner of oviposition differs in the two suborders. In the Terebrantia the female cuts slits with her saw-like ovipositor and deposits her eggs singly in the tissue of the infested plant. In the Tubulifera it is evident that the eggs must be deposited on the surface. *Physopoda: physao {(pvcrdu), to blow up; pons (tows), a foot. THYSANOPTERA 343 The metamorphosis of these insects is in some respects peculiar; but it conforms more closely to the paurometabolous type than to any other, the newly hatched young resembling the adult in the form of its body (Fig. 392, A) and in having similar mouth-parts and food habits. The first two or three instars have no external wings; these instars are commonly referred to as larvcB. The use of the term larva in this connection is not inappropriate if the wings are de- veloping internally during these early stadia. That this may be the case is indicated by the large size of the wing-pads when they first Fig. 392. — Immature forms of the citrus thrips: A, first larval instar ; B, second larval instar; C, propupa; P, pupa. (After Horton.) appear externally. After the last larval molt the insect assumes a form known as the propupa (Fig. 392, C). This resembles the larva in form ; the antennae are slender, and the insect is moderately active. Its most striking feature is the presence of large wing-pads, which extend at first to about the end of the second abdominal segment and increase in length somewhat during this stadium. With the next molt the insect becomes what is known as the pupa. In this stage the wing-pads are longer (Fig. 392, D), the antennee extend back over the head and prothorax, and the insect is quiescent. With the next molt the adult form is assumed. The different species of thrips vary greatly in habits, some being injurious to vegetation, while others are carnivorous, feeding on aphids and other small insects, the eggs of insects, and mites, es- peciall}^ the "red spider." Their most important economic role, how- ever, is that of pests of cultivated plants. The thrips that infest plants puncture the tissue of the plant by their piercing mouth-parts and suck out the sap. The order Thysanoptera is divided into two suborders, which can be separated as follows : A. Female with a saw-like ovipositor; terminal abdominal segment of female conical; that of the male bluntly rounded Terebrantia AA. Female without a saw-like ovipositor; terminal abdominal segment tubular in both sexes, p. 345 Tubulifera 344 AN INTRODUCTION TO ENTOMOLOGY Suborder TEREBRANTIA* In this suborder the female has a four-valved, saw-Hke ovipositor; the terminal abdominal segment of the female is conical ; that of the male bluntly rounded. Wings are usually present; the front wings are stronger than the hind wings and usually have more or less well- developed veins; the membrane of the wings is clothed with micro- scopic hairs. The members of this suborder are more agile than those of the other one. They run rapidly; and spring, by bending under the tip of the abdomen and suddenly straightening it out. This suborder includes two families. Fig- 393- — Fore wing of Erythrothrips arizonce. (After Moulton.) Family ^OLOTHRIPID^ In this family the wings are comparatively broad. Each fore wing has two longitudinal veins extending from its base to near the tip, where they unite with a prominent - / /^^z^i^Z^ ambient vein on each side of the tip (Fig. 391) ;four or five cross-veins are present in each fore wing, in some species (Fig. 393); in others, cross- veins are want- ing (Fig. 391). The ovipositor is upcurved. Comparatively few species belonging to this family have been found in our fauna; the best-known one is the following. The banded thrips, ALolothrips fascidtus.- — -This species is widely distributed both in this country and in Europe. The adult is yellow- ish brown to dark brown in color, with three white bands on the wings, one at the base, one m the middle, and one at the tip. The larva is yellow with the abdomen deeper orange behind. This species infests many plants; it is common in the heads of red clover. Family THRIPID^ In this family the wings, when present, are usually narrow and pointed at the tip. The radius and cubitus of the front wings, when present, usually coalesce for about one third their length, so that cubitus appears to be a branch of radius. The ovipositor is down- curved. To this family belong most of the species of thrips that have at- tracted attention on account of their economic importance. The better-known of these are the following. *Terebrantia : terebro, to bore through. TH YSA NOP TERA 345 The onion thrips, Thrips tabdci. — This is a serious pest of the onion. It is found on the bulbs in loose soil and at the axils of leaves, causing the disease known as white blast on account of the whitish appearance of the infested fields. Although called the onion thrips, it infests a great variety of plants. The greenhouse thrips, Heltothrips hmnorrhoidalis . — This is a tropical insect, which is often a serious pest in greenhouses; it is also found out of doors in the milder California climate. Drops of a reddish fluid which turns black cover the infested leaves. The bean thrips, Heliothrips fascidtus.- — This is a serious pest on oranges, alfalfa, pear trees, and various garden crops in California. The orange thrips, Euthrips citri. — This is a serious orange pest in California and Arizona ; it deforms the new growth of foliage and causes scabbing and scarring of the fruits. The pear thrips, Euthrips pyri. — This thrips infests pears, prunes, peaches, and other deciduous fruits, both in California and in the East. It infests the opening buds and blossoms, stunting the leaves and blasting the blossoms. The tobacco thrips, Euthrips fusctis . — This is a destructive enemy of shade-grown tobacco causing the injury known as white vein. The white veins of the leaves show in the wrapper when manufactured into cigars. The strawberry thrips, Euthrips trltici. — This species was first described as a pest of wheat, hence its specific name; but on account of its extensive injury to the flowers of strawberry it is now known as the strawberry thrips. It is found in the flowers of almost all wild and cultivated plants and is the commonest and most widely distribut- ed of all American species of thrips. The grass thrips, Andph: thrips stridtus. — This species infests June grass, timothy, and other grasses by destroying the heads of the infested plants. The young insect pierces the stem just above the upper node, where it is tender, causing it to shrivel and all the parts above the injury to die. The dead and yellow heads of grasses thus destroyed can be seen in early summer every^where in grass-growing regions. This disease is known as silver-top. Control. — Thrips are destro3^ed in those cases where it is prac- ticable to spray the infested plants by the use of contact poisons, such as nicotine or kerosene emulsion, and soap solution. Detailed di- rections for making and applying these sprays are given in many published bulletins and in special text-books. The burning of old grass in early spring would probably destroy the hibernating grass thrips. Suborder TUBULIFERA* In this suborder the female is without a saw-like ovipositor and the terminal abdominal segment is tubular in both sexes. The wings are usually present ; the fore pair only with a single vestigial, longi- *Tubulifera: tubulns, a little tube; Jero, to bear. 346 AN INTRODUCTION TO ENTOMOLOGY tudinal vein; the membrane of the wings is not clothed with micro- scopic hairs. This suborder includes a single family. Family PHLCEOTHRIPID^ The members of this family are, as a rule, considerably larger and more powerfully formed than the Terebrantia, some of them being the giants of the order. They live usually in secluded places, as be- tween the parts of composite flowers, under the bark of trees, on the underside of foliage, in galls, moss, turf, fungi, etc. Their movements are very deliberate and they never run or spring (Hinds '02). Nearly as many species and genera of this family have been found in this country as of the other suborder; but this family appears to be of much less economic importance than is the Thripidse. One species, Aleurddothripsfasciapennis, which is common in Florida, feeds on the eggs, larvae, and pup^ of the citrus white fly, Dialeurodes citri. CHAPTER XIX ORDER ANOPLURA* The Tnie Lice The members of this order are wingless parasitic insects with piercing and sucking mouth-parts. Their development is without metamorphosis. The order Anoplura is composed of the true lice. These are small wingless insects, which live on the skin of mammals and suck their blood. They are sharply distinguished from the Mallophaga or bird- lice by the possession of piercing and sucking mouth -parts. The most familiar examples of the Anoplura are three species that infest man and several species that are found on domestic animals. The name Siphunculata was proposed for this order by Meinert in 1 89 1 and is now used by some authors; but the name Anoplura is much the older name, having been proposed by Leach in 181 5, and is more generally used. The body is more or less flattened (Fig. 394). The head is free and horizontal. The compound eyes are vestigial or are wanting. There are no ocelli. The antennas are three-, four-, or five- jointed. The mouth is furnished with a fleshy, unjointed proboscis, which can be withdrawn into the head or extended to a considerable length. Within this proboscis are two knife-like stylets; and at its base, when extended, there is a wreath of recurved hooks. These hooks serve to anchor firmly the proboscis when inserted in the skin of the infested animal. Authors do not agree as to the homologies of the different mouth -parts of these insects. The thoracic segments are fused. The legs are similar; the tarsi consist of a single segment, which is often greatly reduced. There is a single tarsal claw, which is opposed by a toothed projection of the tibia, forming an efficient organ for clinging to the hairs of the host. The abdomen consists of nine segments; there are no cerci. The eggs of the true lice are commonly known as "nits." Thej'' are attached to the hairs of the host by a glue-like substance. The young lice resemble the adults except in size. As with the Mallophaga, the ametabolous condition of these insects is beheved to be an ac- quired one, a result of their parasitic life. This is a small order. Dalla Torre ('08) in his monograph of the Anoplura of the world lists only sixty-five species. These represent fifteen genera, which are grouped in four families. The two following families include all of the species that infest man and the common domestic animals. *Anoplura: anoplos (AkottXcj) , unarmed; our a {piipd), tail. (347) AN INTRODUCTION TO ENTOMOLOGY Family PEDICULID^ In this family the eyes are comparatively large, convex, and dis- tinctly pigmented; and the proboscis is short, hardly reaching the thorax. Here belong the three well-known species of lice that are parasites of man. These are the following. The head-louse, Pediciilus capitis. — This is the most common species infesting man. It lives in the hair of the head, and is most common on the heads of neglected children. Under ordinary circum- stances, cleanliness and the use of a fine-toothed comb are all that is necessary to insure freedom from this disgusting pest. But sometimes adults of most cleanly habits become infested by it. It can be destroyed by the use of tincture of larkspur or a larkspur lotion, which can be obtained from druggists. The body-louse, Pediculus corporis. — This insect lives upon the skin of most parts of the body, but especiaUy on the chest and back. It is often troublesome on ships, in military camps, in prisons, and in the apartments of uncleanly people who neglect to change their clothes. It was a terrible scourge during the World War, when troops were obliged to live under most unsanitary conditions in trenches and camps. The female attaches her eggs to fibers in the seams of under- garments, from which the young hatch in about a week. This species is exceedingly prolific. It and the preceding species transmit several human diseases, including typhus fever, trench fever, and relapsing fever. The method of destroying these vermin commonly employed in hospitals and poorhouses is to rub mercurial ointment in the seams Fig. 394. — The short- nosed ox-louse. (From Law.) Fig. 395. — The horse- louse. (From Law.) Fig. 396. — The hog- louse. (From Law.) of undergarments. During the World War much attention was de- voted to the problem of control of this pest and hundreds of papers were published on this subject. It has been found that both the lice and their eggs are destroyed by the ordinary laundering process used in washing clothes. ANOPLURA 349 The crab-louse, Phthtrius pubis.- — The common name of this spe- cies is suggested by the form of the bod}% which is nearly as broad as long. When highly magnified, the resemblance of this insect to a crab is quite striking ; but to the unaided eye it appears more like a large scale of dandruff. These offensive vermin affect the pubic region and armpits of man, stretching themselves out flat, holding tight to the cuticle, and inflicting most irritating punctiires. They can be destro^'ed b\' mercurial ointment. Family H^MATOPINID^ In this family the eyes are vestigial or wanting and the proboscis is very long. Here belong the true lice that infest our common domes- tic animals; the more important of these are the following. The short -nosed ox-louse, HcEmatopmus eurysternus (Fig. 394). The horse-louse, Hmnatoptmis asini (Fig. 395). The hog-louse, Hcematophius suis (Fig. 396). The long-nosed ox-louse, Linognathus vthtli (Fig. 397). The dog-louse, Linognathus piliferus (Fig. 398). For the destruction of these pests upon cattle, poisonous sub- stances must not be used, as injury would result from the animals licking themselves. They may be safely treated by washing with a strong in- fusion of tobacco leaves, or by rubbing with an oint- ment made of one part sul- phur and four parts lard, or by sprinkling with Scotch snuff or powdered wood- ashes. Stavesacre lotion and larkspur lotion are also used. The insecticide should be applied thoroughly, leaving no spot untouched where the lice can gather and remain and from which they can spread over the body again. The applica- tion should be repeated several times at intervals of three or four days, in order to destroy the young which may hatch after the first applica- tion. It is also necessary, in order to make sure of eradicating the pests, to dress with similar agents, or with strong lye or kerosene, all places where the cattle have been in the habit of rubbing, and the cracks in the stables where they have stood; or to whitewash the stables and rubbing-places. For a more extended account of the true lice found in North America, see Professor Herbert Osbom's "Insects Affecting Domestic Animals," pp. 164-188 (Osborn '96). Fig. 397.— The long-nosed ox- louse. (From Law.) ^V^"^ Fig. 398.— The dog- louse. (From Law.) CHAPTER XX ORDER HEMIPTERA* The True Bugs The winged members of this order have jour wtngs; the first pair of wings are thickened at the base, with thinner extremities which overlap on the back. The mouth-parts are formed for piercing and sucking; the beak arises from the front part of the head. The metamorphosis is gradual. People who know but little regarding entomology are apt to apply the term bug to any kind of insect ; but strictly speaking, only mem- bers of the order Hemiptera are bugs. The bugs are very common insects. Many species abound on grass and on the foliage of other plants; some species live on the surface of water; others live within water; and a few are parasitic on birds and mammals. This order is a ven^ important one; it includes many species in- jurious to vegetation ; among these are some of our more important pests of cultivated plants. On the other hand, some of the species are ranked among beneficial insects on account of their predac'ous habits; for many of them feed upon noxious insects. The name Hemiptera was suggested by the form of the front wings. In these the basal half is thickened so as to resemble the elytra of beetles, only the terminal half being wing-like. The hind wings are membranous, and are folded beneath the front wings. On this account the front wings are often termed wing-covers; they are also termed hemelytra, a word suggested by their structure. Formerly, when the Homoptera was included in the order Hemip- tera, the true bugs constituted the suborder Heteroptera; this name indicated the remarkable difference in the texture of the two pairs of wings of the true bugs and served to contrast this condition with that found in the Homoptera, where the two pairs of wings are usually similar in structure. In the Hemiptera the front wings present characters much used in the classification of these insects ; and consequently special names have been applied to the diif erent parts of them The thickened basal portion is composed of two pieces joined together at their sides; one of these is narrow and is the part next to the scutellum when the wings are closed; this is distinguished as the clavus (Fig. 399, cl) ; the other part is the corium (Fig. 399, co). The terminal portion of the front wing is termed the membrane (Fig. 399, m). In certain families, the Anthocoridas for example, a narrow piece along the costal margin of the wing is separated by a suture from the remainder of the *Hemiptera: hemi- (vixi), half; pteron {■KTepbv), a wing. The order Hemiptera as now restricted includes only one of the suborders of the old order Hemiptera, the suborder Heteroptera. The following order, the Homoptera, was formerly regarded as a suborder of the Hemiptera. (350) HEMIPTERA 351 corirnn; this is the embolium (Fig. 400, e). In certain other cases, as the Miridse for example, a triangular portion of the terminal part of Fig. 399. — Diagram of a front wing of a bug: cl, clavus; co, coriuin; m, membrane. Fig. 400. — Diagram of a front wing of an anthocorid: e, embolium. the corium is separated as a distinct piece; this is the cuneus (Fig. 401, cu). The wings of the Hemiptera exhibit remarkable departures from the primitive type of wing-venation. So great are these that, at first, one sees very little in com- mon between the wings of a bug and those of insects of any other order. But an examina- tion of the tracheation of the wings of nymphs of bugs shows that these wings are merely modifications of the primitive type of insect wings. This is more obvious in some families than in others; it is well shown Fig- 401.— Diagram of a front wing of a in the tracheation of a fore ™"^= "'• ^""^"^• wing of a pentatomid nymph (Fig. 402). The head in the Hemiptera varies greatly in form in the different families; but the accompanying figures of the head of one of the Belostomatidas, Lethocerus (Figs. 403 and 404), will serve to illustrate the position and form of the parts that are commonly referred to in descriptions of members of this order. There are two factors which make difficult the determination of the areas of the surface of the head in these insects that have been recognized and defined in the more generalized insects (see pages 3 7 to 40) : first, in some cases the sutures that limit these areas in the more generalized insects are here obsolete; second, the basal part of each mandible and of each maxilla enters into the composition of the wall of the head. A similar modification of the head and mouth-parts exists in the Hoinoptera, and the students of the Hemiptera should study the relations of the mouth-parts to the head -capsule in that order, where they are more easily seen than in the Hemiptera. S52 AN INTRODUCTION TO ENTOMOLOGY An important feature of the head in the Hemiptera is the extended development of the gular regions, which results in the beak being Fig. 402. — Tracheation of a fore wing of a pentatomid nymph. borne by the front part of the head. This contrasts strongly with the condition found in the Homoptera, where the gula is so reduced that Fig. 403. — Head of Lemocertis, aorsal Fig. 404.^ — Head of Lethocerus, ventral aspect. asoect. the beak arises from the hind part of the lower side of the head. In Lethocerus the occiput (Fig. 403, o) is separated from the vertex by a distinct transverse suture. The vertex (Fig. 403, v, v) is very HEMIPTERA 353 short on the middle Hne of the body but is much longer on each side next to the compound eye ; the epicranial suture is very indistinct in the adult. In those bugs in which the paired ocelli are present they are borne by the vertex. Immediately in front of the vertex is the front or frons (Fig. 403, /). The clypeus is a narrow, elliptical sclerite which is well defined (Fig. 403, c). Some writers on the Hemiptera and Homoptera term the ch'peus the tylns; but, for the sake of uniformity, the use of this name should be discontinued. The four regions of the head referred to in the preceding paragraph, the occiput, the vertex, the front, and the clypeus, are easily homol- ogized with the corresponding regions in the more generalized insects. We will now consider certain modifications of the structure of the wall of the head that are correlated with the development of the type of mouth-parts characteristic of the Hemiptera and Homoptera. On either side of the clypeus there is what appears to be a pro- longation of the front. In Lethocerus (Fig. 403, x, x), each of these prolongations extends about half the length of the clypeus and bounds the eye in front. It is believed that each of them represents the basal part of a mandible; they are termed, therefore, the mandibu- lar sclerites. In some Homoptera the mandibular sclerites are dis- tinct ; this condition exists in the head of a cicada figured in the next chapter (Fig. 463). The mandibular sclerites were so named by Smith ('92), who first recognized that they pertain to the mandibles. Before that time several different names were applied to them, which are still in use by some writers; these are jugcB, lorcB, and fulcra. In Lethocerus there is a pair of sclerites in front of the mandibular sclerites and bounding the distal end of the clypeus; each of these is the basal part of a maxilla; for this reason they are termed the maxillary sclerites (Fig. 403, y, y) In Lethocerus the tips of these sclerites meet on the dorsal wall of the head covering the tip of the clypeus. On the ventral aspect of the head, the gula occupies the median area (Fig. 404, gu); and the gen(Z, the lateral areas (Fig. 404, ge). In each gena there is a deep groove in which the very remarkable antenna rests. At the front end of the ventral wall of the head there is a pair of sclerites, each of which is articulated with a maxillary sclerite; these are known as the bucculce and are believed to represent the maxillary palpi (Fig. 404, bu). In Lethocerus the caudal margin of each buccula is solidly joined to the front end of the gula. From the above account it can be seen that only a portion of the mouth-parts enters into the constitution of the beak. The beak consists of the following parts: the labrum, the labium, and four very slender lancet-like organs enclosed in the labrum and labivim, the mandibular setae and the maxillary setae. The labrum is joined to the distal end of the clypeus ; in Lethocerus the base of the labrum is covered by the maxillary sclerites, where they overlap the tip of the clypeus, and its distal end extends into the furrow of the labiiun, but the intermediate portion is exposed 354 AN INTRODUCTION TO ENTOMOLOGY (Fig. 403, /). It is a slender, pointed, transversely striated organ. The Icoium constitutes the most prominent part of the beak; in most Hemiptera it consists of four segments ; but in several families it is reduced to three segments. At the distal end of the third segment in Lethocerus and some other aquatic Hemiptera there is a pair of small append- ages, each of which consists of a single seg- ment (Fig. 403, Ip); these were described by Leon ('97) as vestiges of the labial palpi.* The dorsal surface of the labium is deeply grooved, forming a channel which encloses the mandibular and maxillary set^e. The labiimi is not a piercing organ; its function is to protect and direct the sets and to de- termine, by means of tactile hairs at its tip, the place where the puncture should be made by the setae (Fig. 405, t). The mandibular setos and the maxillary setcB are four slender, lance-like organs which arise within the head-capsule and pass out from the head through a furrow in the lower side of the la- brum and extend in a furrow on the upper m side of thelabiimito the tip of this organ, from which they are pushed out when not in use (Fig. 405). As the four seta3 emerge from the head they lie side by side; the outer pair are the mandibular setce, the inner Fig. 406. — Cross-section pair the maxillary setas. Farther from the head the maxillary setag become twisted so that one of them lies above the other. Figure 406 repre- sents a cross-section of the setae of a squash- bug as figured by Tower ('14); the setae are fastened together by interlocking grooves *There has been much discussion regarding the homologies of the parts of the labium in the Hemiptera and the Homoptera. The early entomologists believed that the lower lip of bugs was composed of the labium and the grown-together labial palpi; but this view is no longer held. Leon, who published a series of papers on the labium of aquatic bugs, believes that the first two segments of the labium consists of the submentum and the mentum; the third segment, of the palpiger, which bears vestiges of the labial palpi; and the fourth segment, of the remainder of the ligula. Heymons ('99) argues at great length against the con- clusions of Leon. He believes that the segmentation of the labium is merely the result of secondary divisions of this organ and that labial palpi do not exist in the Hemiptera and Homootera. Fig. 405. — Last segment of the beak of Lethocerus, with setae projecting : md, mandibular seta; mx, maxillary seta. md" of the setae of Anasa Iris'.is: md, mandibular setae; ot, maxillary se- tae; fc, food canal; sc, salivarv canal. (From Towerj IIEMIPTERA S55 and ridges ; and between the maxillary setee are two canals, the upper one (/c) for the passage in of food, the lower one {sc) for the passage out of saliva. The tip of the mandibular setas are barbed (Fig. 405, md) ; their function is that of piercing the tissue fed upon and holding the seta^in place; while the tips of th'5 maxillary setse, which are acute and fluted, probe the tissue, take up the fluid food, and eject the saliva. Within the head each seta is connected with a chitinous lever, or with a series of two levers which in turn articulate with the head- capsule; the in and -out move- ments of the setffi are produced by muscles extending from the head-capsule to them and to the levers connecting them with the wall of the head. Fig- ure 407 represents the articu- lation of a mandibular seta of a squash-bug, as represented by Tower; and in the next chapter the relations of both the mandibular setae and the maxillary setae to the head- Fig- 407 •— Articulation of a mandibular capsule in a cicada are rep- seta with tlie wall of the head: md,man- J /-n- ^ \ dibular seta; c and 6, chitmous levers; g, resented (l^lg. 465). wall of the head; rw, retractor muscles; Correlated with the de- pm, protractor muscle. (From Tower.) velopment of the hemipterous type of mouth-parts there is a remarkable specialization of the phar- ynx, which fits it as a sucking organ, and the development of an organ for forcing out the saliva, which is known as the salivary pump. A detailed account of these organs is given by Bugnion and Popoff (•11). Most of the Hemiptera protect themselves by the emission of a disagreeable odor. In the adult stink-bugs (Pentatomidaj) this is caused by a fluid which is excreted through two openings, one on each side of the ventral aspect of the thorax, behind or near the middle coxa. These openings are termed the osteoles. Each of these is usually in some kind of an open channel styled the osteolar canal, and this is surrounded by a more or less rugged and granulated space, the evaporating surface. In the nymphs the stink-glands open on the dorsal aspect of the abdomen. In the bedbug {Cimex), the stink -glands open in the dorsal wall of the first three abdominal segments. The legs of the Hemiptera vary greatly in form, but the tarsi are rarely more than three-jointed. The lateral margin of the abdominal segments is much developed in several families, and forms a flat, reflexed or vertical border to the abdomen, which is called the connexivum. In the Hemiptera the metamorphosis is gradual; the newly hatched young resembles the adult in the form of its body but lacks wings. After one or two molts the wing-buds appear and become larger and larger at successive molts. With the last molt there takes 356 AN INTRODUCTION TO ENTOMOLOGY place a great expansion of the wings, the change at this time being much greater than at either of the previous molts. There are many forms in this order in which wings are not developed. In some species all individuals are wingless; in others there are two forms of adults, the winged and the wingless. In this order we find variations in structure which correspond closely with variations in habits. There are certain families the members of which are truly aquatic, living within the water, through which they swim and to the surface of which they come occasionally for air. There are others which are truly terrestrial, living upon the surface of plants, or in other positions away from water. There are still other families the members of which hold an intermediate position between the aquatic and the terrestrial forms, living upon the surface of water or in marshy places. In the systematic arrangement of the families of the Hemiptera adopted here the aquatic forms are placed first; the terrestrial forms, last; and the semiaquatic forms hold an intermediate position. The sequence of the families is more fully indicated in the following synopsis. SYNOPSIS OF FAAIILIES The Short-horned Bugs. Bugs with short antennae, which are nearly or quite concealed beneath the head. Bugs that live within water. The Water- boatmen, Family Corixid^. p. 360. The Back-swimmers, Family Notonectid^. p. 362. The Water-scorpions, Family Nepid^. p. 364. The Giant Water-bugs, Family Belostomatid.e. p. 365. The Creeping Water-bugs, Family NaucoriDvE. p. 367. Bugs that live near water. ■ The Toad-shaped Bugs, Family Gelastocorid^. p. 368. The Ochterids, Family Ochterid.e. p. 368. The Long-horned Bugs. Bugs with antennae at least as long as the head, and prominent except in the Phymatids, where they are concealed under the sides of the prothorax. The Semi-aquatic Bugs. The Shore-bugs, Family Saldid^. p. 369. The Broad-shouldered Water-striders, Family Veluzje. p. 369. The Water-striders, Family Gerrid^. p. 370. The Mesoveliids, Family Mesovelhd^. p. 372. The Hebrids, Family Hebrid^. p. 372. The Water-measurers, Family Hydrometrid.e. p. 373. The Land-bugs. The Land-bugs with four-jointed antenticE. The Schizopterids, Family Schizopterid^. p. 373. The Dipsocorids, Family Dipsocorid^. p. 374. The Isometopids, Family Isometopid^. p. 374. The Leaf-bugs, Family M1RID.E. p. 375. The TermatophyHds, Family Termatophvlid^. p. 377. The Flower-bugs, Family Anthocorid^. p. 377. The Bedbugs, Family Cimicid^. p. 378. The Many- combed Bugs, Family Polyctenid^. p. 379. The Nabids, Family Nabid^. p. 380. The Assassin-bugs, Family Reduvud^. p. 380. The Ambush-bugs, Family Phymatid^. p. 382. The Unique-headed Bugs, Family Enicocephahd.e. p. J83. HEMIPTERA 357 The Lace-bugs, Family Tingid^. p. 384. The Cotton-stainer Family, Family Pyrrhocorid^. p. 385. The Chinch-bug Family, Family Lyg^id^. p. 386. The Stilt-bugs, Family NeididJe. p. 388. The Flat-bugs, Family Aradid.e. p. 388. The Squash-bug Family, Family Coreid^. p. 389. The Land-bugs with five-jointed antennce. The Stink-bug Family, Family Pentatomid^. p. 390. The Burrower-bugs and the Negro-bugs, Family Cydnid^. p. 391. The Shield-backed-bugs, Family Scutellerid^. p. 392. TABLE FOR SEPARATING THE FAMILIES OF THE HEMIPTERA h.. Antenna shorter than the head, and nearly or quite concealed in a cavity beneath the eyes. B. Hind tarsi with indistinct setiform claws (except in Plea, of the family Notonectidse, which is less than 3 mm. in length). C. Fore tarsi consisting of one segment, which is flattened or shovel-shaped, and without claws; head overlapping the prothorax dorsally. p. 360. CORIXID^ CC. Fore tarsi of the usual form, and with two claws; head inserted in the prothorax. p. 362 Notonectid^ BB. Hind tarsi with distinct claws. C. Ocelli absent; bugs that live within water. D. Membrane of the hemelytra with distinct veins. E. Caudal appendages of the abdomen long and slender; tarsi one- segmented, p. 364 Nepid^ EE. Caudal appendages of the abdomen short, flat, and retractile; tarsi two-segmented, p. 365 Belostomatid^ DD. Membrane of the hemel}i;ra without veins. p. 367..NAucoRiDiE CC. Ocelli present ; bugs that live on shores of streams and ponds. D. Fore legs stout, fitted for grasping; antennae concealed, p. 368. Gelastocorid^ DD. Fore legs slender, fitted for running; antennae exposed, p. 368. OCHTERIDiE AA. Antennae at least as long as the head, usually free, rarely (P hymatidae) fitting in a groove under the lateral margin of the pronotum. B. Body linear; head as long as the three thoracic segments, p. 373. Hydrometrid^ BB. Body of various forms, but, when linear, with the head shorter than the thorax. C. Last segment of the tarsi more or less split, and with the claws of at least the front tarsi inserted before the apex. D. Hind femora extending much beyond the apex of the abdomen; intermediate and hind pairs of legs approximated, very distant from the front pair; beak four-jointed, v. 370 Gerrid^ DD. Hind femora not extending much beyond the apex of the ab- domen ; intermediate pair of legs about equidistant from front and hind pairs (except in Rhagovelia) ; beak three-jointed. p. 369 VeliidvE CC. Last segment of the tarsi entire, and with the claws inserted at the apex. D. Antennse four- jointed.* E. Hemelytra resembling network, and very rarely with any dis- tinction between the corium and the membrane, p. 384. TlNGID^ EE. Hemelytra of various forms or absent, but not of the form presented by the Tingidae. *In certain families there are minute intermediate joints between the principal joints of the antennae; for the purposes of this table, these intermediate joints are not. counted. 358 AN INTRODUCTION TO ENTOMOLOGY F. Beak three-jointed. G. Hemelytra when well-developed with an emboLam (Fig. 408); those forms in which the adult has vestigial hemelytra have no ocelli. H. Hemelytra vestigial; parasitic bugs preying on man, bats, and birds, p. 378 Cimicid.^ HH. Hemelytra usually well developed; not parasitic bugs. p. 377 Anthocorid^ GG. Hemelytra when well developed without an embolium; those forms in which the adult has vestigial hemely- tra have ocelli. H. Ocelli wanting. I. Body greatly flattened, p. 388 Aradid^ II. Body not greatly flattened, p. 38o..Reduviid^ HH. Ocelli present, though sometimes difficult to see. I. Antennas whip-like, the first two segments short and thick, the third and fourth long and very slender and clothed with long hairs, the third segment thickened towards the base. J. Head when viewed from above wider than long, strongly deflexed; beak short, p. 373. SCHIZOPTERID^ JJ. Head extended horizontally or slightly de- flexed; beak long. p. 374. . . Dipsocorid^ II. Antennae not of the form described above. J. Beak long, reaching to or beyond the inter- mediate coxag. K. Membrane of hemelytra with looped veins. p. 369 Saldid^e KK. Alembrane of hemelytra without veins. L. Hemelytra with the clavus similar in texture to the membrane (Fig. 409). p. 372 Hebrid^ LL. Clavus and membrane distinct, p. 372 Mesoveliid^ JJ. Beak not reaching the intermediate coxae. K. Front legs with greatly thickened fem- ora, p. 382 Phymatid^ KK. Front femora somewhat thickened, but much less than half as wide as long. p. 380 Reduviid^ '3F. Beak four-jointed. G. Front legs fitted for grasping prey. H. The fore tarsi, which are one-jointed, capable of be- ing closed upon the end of the broad tibice. p. 383. Enicocephalid^ HH. The fore tibiae armed with spines andcpable of being closed tightly upon the femora, wahich are stout. In the forms with long wings the mem- brane is usually furnished with four long veins bounding three discal cells which are often open. From these cells diverge veins which form sev- eral marginal cells (Fig. 410). p. 380..NABID.E GG. Front legs fitted for walking. H. Hemelytra with a cuneus; membrane with one or two closed cells at its base, otherwise without veins (Fig. 411). I. Ocelli wanting. J. Membrane of the hemelytra with two closed cells, p. 375 MiRiD.E JJ. Membrane with only one closed cell. HEMIPTERA 359 K. Tarsi furnished with an aroHum. p. 375. MlRID^ KK. Tarsi without an aroHum. p. 377 Termatophylid^ II. OcelU present, p. 374 Isometopid^ HH. Hemelytra without a cuneus; meinbrane with four or five simple or anastomosing veins aris- ing from the base, or with a large number of veins arising from a cross-vein at the base. I. Ocelli w£.iting. J. Exceedingly flat bugs, p. 388 Aradid^ J J. Rather stout and heavily formed bugs. p. 385 Pyrrhocorid^ II. Ocelli usually present. J. Head with a transverse incision in front of the ocelli, which are always present (Fig. 449). p. 388 Neidid^ JJ. Head without transverse incision. K. Membrane with four or five simple veins arising from the base of the membrane, the two inner ones sometimes joined to a cell near the base (Fig. 413). p. 386. LYG^IDiE KK. Membrane with many, usually forked veins, springing from a transverse basal vein (Fig. 414). p. 389. . . . CoREID/E HHH. Hemelytra vestigial; parasitic bugs preying on bats. p. 379 POLYCTENIDiE DD. Antennas five- jointed.* E . Hemelytra with the clavus similar in texture to the membrane, which is without veins (Fig. 409) ; small semiaquatic bugs, measuring less than 3 mm. in length {Hebrus). p. 372 Hebrid^ EE. Hemelytra with the clavus markedly thicker than the membrane. F. Tibiae armed with strong cpines. p. 391 Cydnid^ FF. Tibije smooth or with small spines. G. Scutellum narrowed behind, only rarely almost cover- ing the abdomen, p. 390 Pentatomid^ GG. Scutellum not narrowed as in the Pentatomidag, very convex, nearly or quite covering the ab- domen, p. 392 SCUTELLERID^ *In some cases there are minute intermediate joints between the principal joints of the antennas; for the purposes of this table these intermediate joints are not counted. 360 AN INTRODUCTION TO ENTOMOLOGY Fig. 410. — Nabidae. Fig. 411. — JMiridEe. Fig. 412, — Pyrrhocorid^. Fig. 413.— Lygaeidae. Fig. 414. — Coreidae. Figures 408 to 414. — Diagrams illustrating the types of hemelytra characteristic of several families of Hemiptera. • Family CORIXID^* The Water-Boatmen The family Corixidffi includes oval, gray-and-black mottled bugs, usually less than half an inch in length, which live in lakes, ponds, and streams, in both stagnant and running water. The characteristic form and markings of these insects are shown in Figure 415. The name of the typical genus of this family, Corixa, is evidently from the Greek word coris, meaning a bug. For this reason many writers have spelled the generic name Corisa and the family name Corisidce. This name was probably given to these insects because they have an odor like that of the bedbug. The water-boatmen exhibit some striking peculiarities in struc- *Corixidae, Corixa, a misspelling of Corisa: coris («6/"s)i a bug. HEMIPTERA 361 ture: the head overlaps the prothorax instead of being inserted in that segment; the beak is very short and scarcely distinguishable from the face, the opening to the mouth being on the front of the so- called beak; the tarsi of the front legs (termed palce) are flattened or scoop-like in form; each consists of a single segment and bears a comb-like fringe of bristles; the middle legs are long, slender, and end in two claws ; the hind legs are flattened and fringed for swimming ; and, in the males, the abdominal sterna, especially the four caudal ones, are very uns\Tnmetrical, being on one side broken into irregular- shaped fragments. The water-boatmen have the body flattened above, and swim upon their ventral surface; they differ in these respects from the members of the next family. They swim with a quick, darting motion; they use for this purpose chiefly their long, oar-like, posterior legs. When in their favorite attitude, they are anchored to some object near the bottom of the pond or aquarium by the tips of their long, slender, intermediate legs; at such times the fore legs hang slightly folded, and the posterior legs are stretched out horizontally at right angles to the length of the body. The body of these insects, with the air which chngs to it, is much lighter than water; consequently whenever they lose hold upon the object to which they have been clinging, they rise quickly to the surface, unless they prevent it by swimming. They occasionally float on the surface of the water, and can leap into the air from the water and take flight. Fig. 415.— A water-boat- The bodies of these insects, as they swim through the water, are almost completely enveloped in air. The coating of air upon the ventral surface and sides can be easily seen, for it glistens like silver. By watching the insects carefully when they are bending their bodies, the air can be seen to fill the spaces between the head and the prothorax, and between the pro- thorax and the mesothorax. The space beneath the wings is also filled with air. When these insects are in impure water, they must come to the surface at intervals to change this supply of air. But I have demonstrated that in good water it is not necessary for them to do this. The air with which the body is clothed is purified by contact with the fine particles of air in the water ; so that the insect can breathe its coat of air again and again indefinitely. It has been commonly believed that the corixids are carnivorous ; but Hungerford ('19) has shown, by an extended series of experiments, that these insects gather their food supply from the ooze at the bottom of pools in which they live. This flocculent material they sweep into their mouths by means of the flat rakes of their fore tarsi. This material is largely of plant origin; but the protozoa and other minute animals living on it are also consimied. This author also found that the corixids feed on the chlorophyll of Spirogyra. 362 AN INTRODUCTION TO ENTOMOLOGY In most cases the eggs of corixids are attached to the stems of aquatic plants; but Ramphocorixa acuminata usually attaches its eggs to the body of a crayiish. The males of most of the Corixidse are furnished with stridulating organs. These consist of one or two rows of chitinous "pegs" on the fore tarsi and a roughened area on the inner surface of the fore femora near the base. By rubbing the tarsal comb of one leg over the roughened area of the femur of the opposite leg, a chirping sound is produced. These stridulating organs differ in form in different species. In addition to the stridulating organs of the fore legs there is in certain species a more or less currv'-comb-like organ near the lateral margin of the dorsal wall of the sixth abdominal segment ; this has been termed the "strigil." It is situated, when present, on the left side in Corixa and on the right side in several other genera. Its func- tion has not been definitely determined. Both the adults and the eggs of Corixa are used for food for man and for birds in Mexico and in EgA-pt. The eggs are gathered from water-plants. Glover states that in Mexico the natives cultivate a sedge upon which the insects will deposit their eggs; this sedge is made into bundles, which are floated in the water of a lake until covered with eggs; the bundles are then taken out, dried, and beaten over a cloth ; the eggs, being thus disengaged, are cleaned and powdered into flour. Kirkaldy ('98) reports the importation into England of Corixa mercenaria and its eggs for food of insectivorous birds, game, fish, etc., by the ton; and computes "that each ton of the adults will contain little short of 250 million individuals!! As to the ova, they are beyond computation." The adults are captured at night with nets when they leave the water in swarms. It is difficult to separate the different species of water-boatmen on account of their close resemblance to each other; this is especially true of the females. Fifty-five species are listed in the Van Duzee check -list; these represent six genera. Family NOTONECTID^ The Back-Swimmers The Notonectidae differ from all other aquatic Hemiptera in the fact that they always swim on their backs ; and there is a corresponding difference in the form of these in- sects. The body is much deeper than in the allied families, and is more boat-shaped. The back, from the peculiar attitude of the insect when in the water, ■^^8- 416.— iVo/o- corresponds to the bottom of a boat, and is sloped necta unduLata. ^^ ^^ ^^ greatly resemble in form this part (Fig. 416). The eyes are large, reniform, twice sinuated on the outer side, and project a little way over the front margin of the prothorax. Ocelli are absent. The prothorax has the lateral margins sharp and pro- HEMIPTERA 363 jecting. The legs are all long ; the hind pair are much the longest and fitted for swimming. The tarsi consist each of three segments, but the basal segment is so small that it is often overlooked. There is a ridge along the middle line of the venter which is clothed with hairs, and along each side of this a furrow. Along the upper edge of the outside of this furrow and a short distance from the side of the body, there is a fringe of long hairs, and beneath this fringe the abdominal spiracles are situated. The features presented by the ventral side of the abdomen just referred to can be seen on dead specimens; but it is well to examine them on living insects. This can be done by placing a back-swimmer in a glass of water, and, when it is resting at the surface of the water, studying it by means of a lens of low power. Under these conditions it can be seen that the furrow on either side of the venter is an air- chamber, which is enclosed by the two fringes of hairs, one borne by the ridge of the middle line on the body and the other by the outer margin of the furrow. It can also be seen that there is a hole near the tip of the abdomen through which the air passes into the chambers beneath the fringes of hairs. Sometimes when watching an individual under these conditions it will be seen to force the air out of the chambers beneath the fringes of hair, using the hind legs for this purpose, and sometimes an entire fringe will be lifted like a lid. By examining the first ventral abdominal segment of a dead indi- vidual a little furrow can be seen on each side; these are air-passages extending between the chambers on the ventral side of the abdomen to that beneath the wings. Air is also carried among the hairs on the lower side of the thorax, and in the spaces between the head and the prothorax and between the prothorax and the mesothorax; this is probably expired air. In collecting back-swimmers, care must be taken or they will inflict painful stings with the stylets of their beak. The manner of oviposition of these insects differs in different spe- cies. Some merely attach their eggs to the surface of aquatic plants by means of acolorless, water-proof glue; others have a long oviposi- tor by means of which they insert their eggs in the tissue of these plants. The males of some back-swimmers possess stridulating areas; these are located on the femora and tibiae of the fore legs and on the sides of the face at the base of the beak. The notonectids of our fauna represent three genera ; these can be separated by the following table : A. Legs dissimilar; hind legs flattened and fringed for swimminfr. B. Last segment of the antennas much shorter than the penultimate segment. NOTONECTA BB. Last segment of the antennae longer than the penultimate segment. BUENOA AA. Legs quite similar Plea Noionecta. — To this genus belong the greater number of our species, of which twelve have been described. These are the back- 364 AN INTRODUCTION TO ENTOMOLOGY swimmers that are commonly seen floating at the surface of the water, with the caudal part projecting sufficiently to admit of the air being drawn into the air chambers. When in this position, their long, oar-like, hind legs are stretched outward and forward ready for action ; when disturbed they dart away toward the bottom of the pond, carrying a supply of air with them. Buenoa. — This genus, of which six species have been found in this country, is composed of much more slender forms than is the preceding. The habits of two of our species have been studied by Hungerford (' 1 9) . These insects do not rest at the surface of the water as do some species of Notonecta, but may be seen swimming slowly, or even poising in midwater some distance beneath the surface. They abound in water teeming with Entomostraca, upon which they largely feed. Plea. — The members of this genus are small insects, not exceeding 3 mm. in length. The shape of the body is quite different from that of other back-swimmers, being highly arched behind. They are found in tangles of aquatic vegetation, to thefilaments of which they cling when at rest. They feed on small Crustacea. Only one species, Plea siriola, has been described from our fauna. Family NEPID^ The Water-Scorpions The members of this family can be distinguished from other aquatic Hemiptera by the presence of a long respiratory tube at the end of the abdomen. This tube consists of two long filaments, each with a groove on its mesal side. By applying these filaments together the grooves form a tube, which conducts the air to two spiracles situated at the caudal end of the abdomen. By means of this ap- paratus these insects are able to rest on the bottom of a shallow pond, or among rubbish or plants in water, and by projecting this tube to the surface obtain what air they need. With regard to the form of the body, two very different types exist in this family. In one, repre- sented by the genus Nepa, the body is a long oval, Yig.^iT.—Nepa ^^^' ^"^ ^^^^ (^^S- 4^ 7) I ^" ^^^ other, represented a'piculata. by the genus Ranatra, the body is almost linear and cylindrical (Fig. 418). An intermediate form, Curicta, represented by two species, is found in Louisiana, Texas, and Arizona. The water-scorpions are carnivorous; and with them the first pair of legs is fitted for seizing prey. In these legs the cox^ are very long, especially in Ranatra; the femora are furnished with a groove into which the tibias and tarsi fit like the blade of a pocket-knife into its handle. HEMIPTERA 365 Although the Nepidae are aquatic insects, the second and third pairs of legs are fitted for walking rather than for swimming. Of the genus Nepa we have only a single species, Nepa apiculdta. This insect is about i6 mm. in length, not including the respiratory tube, which measures a little more than 6 mm. It lives in shallow water concealed in the mud or among the dead leaves and twigs, lying in wait for its prey. The eggs are inserted in the tissues of decaying plants ; they are an elongate oval and bear near one end a crown of eleven slender fila- ments. Of the genus Rdnatra eight American species have been described. These in- sects are found in the same situations as Nepa; where, owing to the linear form of the body and to the dirt with which it is usually covered, it is quite difficult to de- tect their presence. They have also been observed in deep water clinging to the stems of rushes and grasses, with the re- spiratory tube piercing the surface film (Bueno) ; and also upon floating dead leaves and stalks of cat-tail, where the}' were basking in the sun and entirely dry (Hungerford). Ranatra has stridulating organs; these consist of a roughened patch on the outside of each fore coxa and a rasp on the inner margin of each shoulder of the prothorax ; b}' means of these organs a squeak- ing sound is produced. The eggs of Ranatra have been described by Pettit; they are elongate oval, about 3.5 mm. in length, and bear at one end a pair of slender appendages, about 4 mm. long; they are embedded in the rotting stems of aquatic plants, from which the appendages of the eggs project. A monograph of the Nepidfe of North America was published by Himgerford ('22). Fig. 418. — Ranatra ftisca. Family BELOSTOMATID^ The Giant Water-Bugs The common name "giant water-bugs" was applied to this family because to it belong the largest of the Hemiptera now living; a species that is found in Guiana and Brazil measures from 75 to 100 mm. in length; and the larger of our species exceed in s^'ze our other water-bugs. 366 AN INTRODUCTION TO ENTOMOLOGY Lethocerus america- The members of this family are all wide and flat-bodied aquatic insects, of more or less ovate outline. The fore legs are raptorial ; the middle and hind legs are fitted for swimming, being flattened and ciliated; this is especially true of the hind legs. At the caudal end of the body there is, in the adult, a pair of narrow, strap-like respiratory appendages, which are re- tractile. These insects are rapacious creatures, feeding on other insects, snails, and small fish. Like other water-bugs, they fly fi om pond to pond and are frequently attracted to lights. This is especially the case where electric lights are used, into which they sometimes fly and are killed by hundreds. On this account they are known in many parts of the country as "electric-light bugs." The family Belostomatidas is repre- sented in this country by four genera. Recent studies of the nomenclature of the genera of this family have resulted in the making of changes in some of the generic names. This should be kept in mind when using the older text-books. Our genera are separated by Hungerford ('19) as follows: A. Mesothorax with a strong midventral keel; membrane of the hemelytra re- duced Abedus AA. Mesothorax without a midventral keel; membrane of the hemelytra not reduced. B. Basal segment of the beak longer than the second; base of the wing- membrane nearly or quite straight. Body about 25 mm. or less in length Belostoma BB. Basal segment of the beak shorter than the second; base of the wing- membrane sinuous. Body more than 37 mm. in length. C. Anterior femora grooved for the reception of the tibia. ..Lethocerus CC. Anterior femora not grooved for the reception of the tibia.. Benacus Lethocerus. — To this genus and the following one belong our larger members of this family. The appearance of these insects is indicated by Figure 419, which represents Lethocerus americdnus. In this genus the anterior femora are furnished with a groove for the reception of the tibia. Five species have been described from the United States and Canada. In most of the references to these insects in our literature the gener- Fig. 420. — Belos- toma fltmiinea. ic name Belostoma is used. Benacus. — Only a single spe- Abedus, with eggs. HEMIPTERA 367 ciesof this genus, i?ewacM5 gnseus, is found in our fauna. This close- ly resembles Lethocerus americanus (Fig. 419), but can be distinguish- ed from that species by the absence of the groove in the femora of the fore legs. Belostoma. — To this genus as now recognized belong our more com- mon representatives of the smaller members of this family. These have long been known incorrectly under the generic name Zaitha. Our most common species is Belostoma flummea (Fig. 420). In this genus and the following one the eggs are carried by the males on their backs, where they are placed by the females, sometimes in spite of vigorous opposition on the part of the male. Abedus. — Five species of this genus have been found in the south- western parts of the United States. Figure 421 represents the male of one of these carrying his load of eggs. Family NAUCORID^ The Creeping Water-Bugs The Naucoridffi includes fiat-bodied, chiefly oval insects, of moderate size. The abdomen is without caudal appendages. The front legs are fitted for grasping, the femora being greatly enlarged; the middle and hind legs are suited for crawling rather than for swimming. There are no ocelli ; the antennae are very short, and well concealed beneath the eyes; the beak is three-jointed and covered at the base by the large labrum ; and the hemelytra are furnished with a distinct embolium. Although these are aquatic insects, they have been comparatively little modified for such a life. They carry air beneath their wings and obtain this air by pushing the tip of the abdomen above the surface of the water. They are predacious and are fond of reedy and grassy, quiet waters, where they creep about like the dytiscid beetles, creeping and swimming around and Fig. 422. — Pel- between the leaves and sprays of the submerged plants, ocorisfemor- seeking their prey. Only two genera of this family are represented in our fauna ; these are Pelocoris and Amhrysus. In Ambry sus the front margin of the prothorax is deeply excavated for the reception of the head; in Pelocoris this is not the case. Pelocoris. — Only three speciesof thisgenus are found in this country and these are restricted to the eastern half of the United States. The most common one is Pelocoris femordtus (Fig. 422). It measures about Q mm. in length, and when alive is more or less greenish testa- ceous in color; but after death it is pale yellow or brownish in color, with black or dark brown markings. Ambrysus. — Ten species of this genus have been found in this coimtry; they are restricted to the Far West. ^ 368 AN INTRODUCTION TO ENTOMOLOGY Family GELASTOCORID^ The Toad-shaped Bugs The Gelastocoridas was formerly known as the Galguhd«; conse- quently most of the references to these insects will be found under the older family name, which has been dropped, as the generic name Galgulus, on which it was based, is not tenable. In these insects the body is broad and short, and the eyes are prominent and projecting; the form of the body and the protuberant eyes remind one of a toad (Fig. 423). Ocelli are present. The an- tennae are short and nearly or quite concealed beneath the eyes. The beak is short, stout, and four-segmented. The fore legs are raptorial. The toad-shaped bugs live on the muddy margins of streams or other bodies of water. Some of them make holes for themselves, and live for a part of the time beneath the ground. They feed upon other insects, which they capture by leaping suddenly upon them. Their colors are protective and vary so as to agree with Fig-423 — G^^- the color of the soil on which they live. Hungerford Tatus!^^ °"^' ^3-S found that the eggs are buried' in the sand. Only five species are known to occur in this country. The most common and most widely distributed representative of the family found in this country is Gelasiocoris oculdtus (Fig. 423). Two other species of Gelastocoris are found in the Southern and Western States. In this genus the hemelytra are not fused and the fore tarsi are two-clawed. In the genus Mononyx, of which a single species, Mononyxfuscipes, is found in California, the hemelytra are free, but the fore tarsi are one-clawed. The genus Ncrthra is also represented in this country by a single species, Nerihra stygtea, which is found in Georgia and Florida. In this genus the hemelytra are fused together along a straight suture indicated by a groove. Family OCHTERID^ The Ochterids These are shore-inhabiting bugs, which are closely allied to the preceding family, in which they were formerly classed. They differ from the toad-shaped bugs in having the fore legs slender and fitted for running, and in having the short antenn£e exposed. They resemble the following family, the Saldidae, in having the beak long, reaching the hind coxs. The eyes are prominent, and two ocelli are present. The family includes a single genus, Ochterus, which, due to an error, has been commonly known as Pelogonus. Only three species occur in the United States; one of these was described from Virginia, one from Florida, and the third is widely distributed from the At- lantic Coast to Arizona. HEMIPTERA 3G9 The widely distributed species is Ochterus americdnus . It measures 5 mm. in length, and is blackish in color sprinkled with golden yellow points. On each side of the prothorax, behind the front angles, there is a bright yellow spot. The members of this family arc predacious. Family SALDID^E The Shore-Bugs With the Saldidag we reach the beginning of the extensive series of families of Hemiptera in which the antennse are prominent and are not concealed beneath the head. In this family the insects are of small size, and of dark colors with white or yellow markings. The head stands out free from the thorax on a cylindrical base. The an- tennse are four-jointed; there are two ocelli; the rostrum is three- jointed and very long, reaching to or beyond the middle coxae. The membrane of the wing-covers is furnished with looped veins, forming four or five long cells placed side by side. Occasionally there is little or no distinc- tion between the coriimi and the membrane. Two forms sometimes occur in the same species, one with a dis- tinct membrane, and another with the membrane thick- ^^2- 424- A ened and almost as coriaceous as the corium proper. ^ °'^^" ^^' The shape of these shore-bugs is shown by Figure 424. These insects abound in the vicinity of streams and other bodies of water, and upon damp soils, especially of marshes near our coasts. Some of the shore bugs dig burrows, and live for a part of the time beneath the ground. They take flight quickly when disturbed, but alight after flying a short distance, taking care also to slip quickly into the shade of some projecting tuft of grass or clod where the soil agrees with the color of their bodies. Thirty-three species belonging to this family have been found in the United States and Canada; these represent eight genera. m Family VELIID^ The Broad-shouldered Water-Striders The Velliidse includes insects which are very closely allied to the following family, the water-striders, both in structure and in habits. In both families the distal segment of the tarsi, at least of the fore tarsi, is more or less bifid, and the claws are inserted before the apex; these characters distinguish these two families from all other Hemip- tera. In the Veliidag the body is usually stout, oval, and broadest across the prothorax (Fig. 425). The beak is three-jointed; the legs are not extremely long, the hind femora not extending much beyond 370 AN INTRODUCTION TO ENTOMOLOGY the end of the abdomen. In fact, the legs are fitted for running over the water, instead of for rowing, as with the Gerridje. The intermedi- ate legs are about equidistant from the front and hind pairs, except in Rhagovelia. These insects are dimor]3hic, both fully winged and short-winged or wingless adults occurring in the same species. About twenty species of this family have been found in America north of Mexico; these represent four genera. The broad-shouldered water-striders are found both on the banks of streams and ponds and on the surface of water. About one-half of our species belong to the genus Microvelia. These are very small, plump-bodied bugs, which are usually black and silvery in color or mottled with brown. They are found at the water's edge but run out on the water when disturbed ; and they are also often found upon rafts of floating vegetation. To the genus Rhagovelia belong somewhat larger forms, which are characterized by the long, deeply split, terminal segment of the tarsi of the middle legs. Our most common species of this genus is Rhagovelia obesa (Fig. 425). These bugs are found running over the surface of rapidly moving waters in streams. They can also dive and swim well under water. Four species of Rhagovelia are found in this p- . ^Rj^^^ovelia country-. _ ohesa. The genus Velia includes the larger members of the family. In these the tarsi of the middle legs are not cleft. Four species of this genus occur in our fauna. They are found on moderately rapid streams or little bogs and eddies connected there- with. The fourth genus occurring in our fauna is represented by a single species, Macrovelia harrhii, which is restricted to the Far West. Family GERRID.E The Water-Stnders This family includes elongated or oval insects which live upon the surface of water. Their legs are long and slender; the hind femora extend much beyond the apex of the abdomen ; the middle and hind pairs of legs are approximated and distant from the fore legs; the terminal segment of the tarsi, at least of the fore tarsi, is more or less bifid, and the claws are inserted before the apex. The beak is four-jointed. The antennae are long and four-jointed. The water-striders prefer quiet waters, upon which they rest or over which they skim rapidly; they often congregate in great nimibers. There are commonly two forms of adults belonging to the same species, the winged and the wingless; sometimes a third form occurs in which the adult has short wings. These insects are predacious; they feed on insects that fall into the water, and I have seen them jump from the water to capture flies and other insects that were flying near them. HEMIPTERA 371 Twenty species of water-striders have been found in America north of Mexico; these represent seven genera. These genera are .separated by Hungerford ('19) as follows: A. Inner margin of the eyes sinuate behind the middle. Body comparatively long and narrow; abdomen long. (Subfamily Gerrinac). B. Pronotum sericeous, dull; antennae comparatively short and stout. C. First segment of the antennae shorter than the second and third taken together. D. Antennas half as long as the body; sixth abdominal segment of the male roundly emarginate Limnoporus DD. Antennae not half as long as the body, not extending beyond the thorax; sixth abdominal segment of the male doubly emarginate. Gerris CO. First segment of the antennae longer than the second and third taken together Gerris BB. Pronotum glabrous, shining; antennae long and slender. . .Tenagogonus AA. Inner margin of the eyes convexly rounded. Body comparatively short and broad ; abdomen so short as to appear almost nymphal in some forms. (Subfamily Halobatinae). B. First antennal segment much shorter than the other three taken together; not much longer than the second and third taken together, and some times shorter. C. Fourth (apical) segment of the antennas longer than the third. D. Eyes fairly prominent; colors of body black and yellow. .Trepobates DD. Eyes smaller, widely separated; body lead-colored, sericeous. ocean dwellers Halobates CO. Fourth segment of antennae never more than equal to the third; basal segm.ent of anterior tarsi much shorter than the second; hind femur equal to or much shorter than the hind tibia and tarsus taken together Rheumatobates BB. First antennal segment nearly equal to the remaining three taken to- gether, much longer than the second and third; antennae almost as long as the entire body; hind femur twice as long as hind tibia. Metrobates Gerris. — Of the twenty species of water-striders found in this country, nine belong to this genus; a common species in the East is Gerris conformis (Fig. 426). Fig. 426. — Gerris conformis. Limnoporus. — We have only a single species of this genus, L. ru- foscutilldhis. Tenagogonus. — Three species are listed from oiu* fauna, only one of which has been found in the North; this is T. gillettei, which is reported from Ohio. The others are found in Florida and California. Metrobates. — Our only species, M. hesperius, is found in Ontario and the eastern part of the United States. 372 AN INTRODUCTION TO ENTOMOLOGY Trepobates. — This genus is represented only by T. pictus. This is a beautiful vellow and black species, which is quite widely distribut- ed. Rheumatobates.— Three species of this genus have been described. The males are remarkable for the strange form of the posterior femora, which are strongly bent, and the shape of the antennae, which are fitted for clasping. Halobates. — These are truly pelagic insects, living on the surface of the ocean, often hundreds of miles from land. They are most abundant in the region of calms near the equator; they feed on the juices of dead animals floating on the surface, and probably attach their eggs to floating sea-weed (Sargassum). H. micans is found off the coast of Florida and H. senceus off the coast of California. Family MESOVELIID^ The Mesoveliids This is a small family of which only two species have been found in North America. These are the following . Mesovelia mulsdnti. — This is a small bug, measuring only 4 or 5 mm. in length; it is of a pale yellow color marked with brown. The antennae are long, filiform, and four-jointed; the beak is three- jointed; the legs are moderately long and slender; and the tarsi are three-jointed. This species is dimorphic, the adults being either winged or wingless. In the winged form, the membrane of the hemelytra is without veins. This species lives on the surface of quiet waters and on rafts of floating vegetation and is predacious. It is furnished with an ovi- positor and embeds its eggs in the stems of aquatic plants. Mesovelia douglasensis. — This is a smaller species than the pre- ceding; the length of the female is 2.1 mm., of the male 1.8 mm. It is olive-brown in color. It was recently discovered and described by Professor Hungerford ('24). It was found near Douglas Lake, Michi- Family HEBRIDiE The Hebrids This family includes very small plump-bodied bugs, measuring less than 3 mm. in length. The antennas are either four-jointed or five- jointed; the beak is three-jointed; and the tarsi are two-jointed. Ocelli are present. The head and thorax are sulcate beneath. The clavus of the hemelytra is similar in texture to the membrane, which is without ^'uehru's ^^"'''^^'^'■°'' °^ veins (Fig. 427). Two genera of this family are found in the United States. HEMIPTERA 373 Hebrus. — In this genus the antennas consist of five segments, not counting a minute segment at the base of the third. The adults are always winged. Four species occur in our fauna. These bugs are found on moist earth at the margins of pools and run out upon the water when disturbed; they are also found on floating vegetation. Merragdta. — In this genus the antennas are four-jointed not count- ing the small segment at the base of the third. The adults are dimor- phic, short-winged and long-winged forms occcurring in the same species. These insects inhabit still and stagnant waters and often descend beneath the surface; at such times the body is surrounded by a film of air. Only two species have been found, as yet, in this country. Family HYDROMETRID^ The Water-Measurers The members of this family are very slender insects, with linear legs andantennee (Fig. 428). The head is as long as the entire thorax, although this region is long also. The eyes are round, projecting, and placed a little nearer the base than the tip of the head. Ocelli are absent. The antennas are four-jointed; the beak is three- jointed; and the tarsi are three-jointed. These insects creep slowly upon the surface of the water; they carr>' the body considerably ele- vated, and are found mostly where plants are growing in quiet waters. It was probably their deliberate gait when walking on water that sug- gested the generic name Hydrometra, or water- measurer. In this country these insects have been commonly known under the generic name Limnobaies, or marsh-treaders ; but Hydrometra is much the older name. Only three species have been found in the United States. One of these, Hydrometra martini Fig. 428.— Hydrome- (Fig. 428), is widely distributed. The other two, ''« marfini. Hydrometra anstralis and Hydrometra wileyi, are found in the South. These insects are dimorphic both winged and wingless forms occurring in the same species. Descriptions of the three species are given by Hungerford ('23). The egg of Hydrometra martini is remarkable in form; it is figured on page 167. Family SCHIZOPTERID^ The Schizopterids This family and the following one, the Dipsocoridce, constitute a quite distinct superfamily, the members of which are most easily rec- 374 AN INTRODUCTION TO ENTOMOLOGY ognized by the form of the antennae (Fig. 429, h). These are four- iointed; the first two segments are short and thick; the third and for.rth segments are long, slender, and clothed with long hairs; the third segm.ent is thickened toward the base. In these two families ocelli are present; the beak is three- jointed; the legs are quite slender, and the tarsi are three-jointed. The species are small or very minute. The Schizopterid^ is distinguished from the following family by the shape of the head and the form of the cavities in which the front legs are inserted. The head when viewed from above is wider than long and is strongly deflexed; the fore coxal cavities are very prominent and timiidly formed. The beak is short. ¥ig. ^2C).-GlvptocombHssaUator: The Schizopteridaj is represented in a, dorsal aspect ; b, antenna, our fauna by a single species, Glyptocom- (Aftcr Heidemann.) hus saltdtor (Fig. 429). This is a minute bug, measuring only 1.2 mm. in length and .6 mm. in width. The known specimens were taken on Plummers Island, Md. The describer of this species, Mr. O. Heidemann, states: "This species is most difficult to collect and is only to be found by sifting fallen leaves, rubbish and earth. The collector must watch patiently until the minute insect makes its presence known by jumping, and even then it takes a skillful hand to secure it in a vial." Family DIPSOCORID^ The Dipsocorids This family is closely allied to the preceding family; the dis- tinguishing features common to the two famiHes are indicated in the account of that family. In the Dipsocoridse the head is extended horizontally or slightly deflexed, and the fore coxal cavities are not at all prominent. The beak is long. This family is represented in our fauna by a single genus, Cera- tocombus, of which two or three species have been found in New Mexico; and one of these is doubtfully reported from Florida. These measure less than 2 mm. in length. Family ISOMETOPID.E The Isometopids This is a family of limited extent, there being very few species known in the entire world. It includes very small bugs, those found in this country ranging from 2 mm. to 2.6 mm. in length. HEMIPTERA 375 The Isometopldae is closely allied to the following family, the Mirid^; by some writers it has been classed as a subfamily of that family. In both families the antennae are four-jointed; the beak is four-jointed; the hemelytra are composed of clavus, coriimi, cuneus, and membrane; at the base of the membrane there are one or two cells; otherwise the membrane is with out veins. The Isometopidae is dis- tinguished from the following family by the presence of ocelli, two in number. Only four species of this family have been found in our fauna; one in Texas, one in Arizona, and two in the East. The Eastern species are Myiomma cixii- Jormis, which is dull black in color with a narrow white band across the base of the cuneus; and Isometopus pulchellns, which is easily recognizable by its contrasting colors of dark brown and yellowish white (Fig. 430). Both are exceedingly rare in- sects. Family MIRID^ The Leaf -Bugs Fig. 430. — Isometopus pulchel- lus. (After Heidemann.) This family, which has been known as the Capsidas, is more large- ly represented' in this country than any other family of the Hemiptera. Van Duzee in his "Catalogue of the Hemiptera North of Mexico" lists 398 species, which represent 129 genera. The species are usually of medium or small size. The form of the body varies greath^ in the different genera, which makes it difficult to characterize the family. The most available char- acter for distinguishing these insects is the structure of the hemelytra. These are almost always complete, and com- posed of clavus, corium, cuneus, and membrane. At the base of the membrane there are one or two cells; otherwise the membrane is without veins (Fig. 431). Other characters of the family are as follows: the ocelli are wanting; the beak and the antennae are each four-jointed ; the coxk are subelongate ; and the tarsi are three-jointed. It is impracticable to discuss here the divisions of this family; reference can be made to only a few of the more common species. The four-lined leaf-bug, Pcecilocdpsus linedtus. — This is a bright Fig. 431. — Hemelytron of Pcecilocapsus lineatus. 370 AN INTRODUCTION TO ENTOMOLOCV yellow bug, marked with black. It measures about 8 mm. in length. There are four longitudinal black lines which extend over the prothoraxand the greater part of the hemeMra (Fig. 432). There is in many individuals a black dot on the cuneus of each hemelytron; and the membrane is also black. This insect infests various plants, but abounds most on the leaves of currant, gooseberry, mint, parsnip, Weigela, Dahlia, and rose. It punctures the young and tender leaves, causing small brown spots; but these are sometimes so numerous and closely placed that the leaves become completely withered. It is a widely distributed species, its range extending from Canada to Georgia and westward to the Rocky Mountains. There is only one generation a year. The eggs are laid in the terminal twigs of currant and other bushes in midsummer and hatch the following spring. They are laid in clusters, each containing six or eight eggs; these egg-clusters are forced out of the stem somewhat by the growth of the surrounding plant tissue; and as the projecting part of the egg is white, they can be easily found. The methods of control are the pruning and burning of twigs containing egg-clusters, and, early in the season . fu^^cal^su's ^^^ destruction of the nvTuphs by the use of kerosene lineatus. emulsion or some one of the tobacco extracts. The tarnished plant-bug, Lygus pratensis. — The tarnished plant-bug is a very common species which is found through- out the United States and in Canada. It is smaller than the preceding species, measuring 5 mm. in length and 2.5 mm. in its greatest width. It is exceedingly variable in color and markings ; its color varies from a dull dark-brown to a greenish or dirty yellowish brown. In the more typical forms the prothorax has a yellowish margin and several longitudinal yellowish lines; there i^ a V-shaped yellowish mark on the scutelltim ; the distal end of the corium is dark ; and the cuneus is pale, with a black point at the apex. This pest is a very general feeder; it has been recorded as injuring about fifty species of plants of economic value; its injuries to the buds of Aster, Dahlia, and Chr^^santhemum, and to the buds and blossoms of orchard-trees, and to nursery stock, are well-known. As yet no practical method of control of this pest has been foimd. The apple-redbug, Heterocordylus mdliniis. — This species and the following one are sometimes a serious pest in apple orchards. They cause spotting of the leaves; but, what is far more serious, they punc- ture the young fruit, which results either in the dropping of the fruit or in its becoming badly deformed so as to be unmarketable. The eggs are inserted into the bark of the smaller branches late in June or early in Jul}^; they hatch in the following spring soon after the opening of the leaves of the fruit-buds. The nymphs are tomato- red in color. They first attack the tender leaves, but as soon as the fruit sets they attack it. The young nymphs can be killed by an HEMIPTERA 377 application of "black leaf 40" tobacco-extract diluted at the rate of I pint in 100 gallons of water; the efficiency of this spray is increased by the addition of about 4 pounds of soap to each 100 gallons. Two applications of the spray should be made: the first, just before the blossoms open; the second, just after the petals fall. The spraying should be done on bright warm days, for in cool weather many of the n^TTLphs hide away in the opening leaves. The adult apple-redbug is about 6 mm. long. The general color varies from red to nearly black. Usually the thorax is black in front and red behind. The wings are red, usually black along the inner edge and with a pointed ovate black spot near the outer margin. The scutellimi, legs, and antenna are black. The entire dorsal sur- face is sparsely covered with conspicuous white, flattened, scale-like hairs. The false apple-redbug, Lygideamendax.- — -This species resembles the preceding one in general appearance and in habits. The nymphs can be distinguished by their brighter red color, by the absence of dusky markings on the thorax, and by having the body clothed with fine, short, black hairs. The adult of this species is lighter-colored and lacks the scale-like hairs on the dorsal surface. The above account of these two species is an abstract of one pub- lished by Professor C. R. Crosby ('11). The hop-redbug, Paracalocoris hawleyi.— The leaves of hop plants are sometimes perforated and the stems stunted and deformed by the nymphs of this species, which are red with white markings. The adult is 6 mm. long, black, with hemehi:ra hyaline or pale yellowish, and the cuneus reddish. For a detailed account see Hawley ('17). Family TERMATOPHYLID^ The Termatophylids This family is closely allied to the following one, the Anthocoridse, but differs in that the beak is four-jointed and ocelli are wanting. The hemelytra are well developed, furnished with an embolium, and usually with a single large cell in the membrane. The tarsi are three- jointed and are not furnished with an aroliimi. The Termatophylidas is a very small family, but it is world-wide in its distribution. A single ver\' rare species has been found in this country. This is Hesperophylum heidemanni, which has been taken in New Hampshire and Arizona. Only the female of this species has been described. It is dark brown with the scutellum yellowish white; the cell in the membrane of the hemelytra is semicircular; the length of the body is 4 mm. Family ANTHOCORIDSE The Flower-Bugs This family is closely allied to the following one; but in the flower-bugs ocelli are present, though sometimes difficult to see, 378 AN INTRODUCTION TO ENTOMOLOGY and the hemelytra are almost always fully developed and are furnished with an emboliirm (Fig. 433). As in the following family, the beak consists of three segments; the antennse, of four; and the tarsi, of three. The species are small. They are found in a great variety of situations, often upon trees and on flowers, sometimes under bark or rubbish. They are predacious. Fig- 433.— Hemelytron of Triphelps. Thirty-six species have been catalogued in our fauna; these represent thirteen genera. The following species will serve as an example. The insidious flower-bug, Triphelps insidiosus. — This is perhaps the best-known of our species. It is a small black bug, measuring only 2 mm. in length; the hemelytra are yellowish white on the corium, at the tip of which is a large, triangular, blackish spot; the membrane is milky white. This species is widely distributed; it is common on flowers, and is often found preying upon the leaf -inhabit- ing form of the grape Phylloxera; it is also often found in company with the chinch-bug, upon which it preys and for which it is some- times mistaken. Family CIMICIT>M The Bedbug Family The members of this family are parasitic bugs, which are either wingless or possess only vestigial hemelytra. In these insects the ocelli are absent, the antennce are four-jointed, the beak is three- jointed, and the tarsi are three-jointed. Only four species belonging to this family have been found in America north of Mexico. These can be separated by the following table, which is based on a more detailed one given by Riley and Johannsen ('15). A. Beak short, reaching to about the anterior coxae. B. Pronotum with the anterior margin very deeply sinuate. The genus Ctmex. C. Body covered with very short hairs; second segment of the antennae shorter than the third; hemelytra with the inner margin rounded and shorter than the scutellum. The common bedbug. . .C. led uldrius CC. Body covered with longer hairs; second and third segments of the an- tennae of equal length; hemelytra with the inner margin straight and longer than the scutellum. Species found on bats. . .C.pilosellus BB. Anterior margin of the pronotum very slightly sinuate or nearly straight in the middle. Species found in swallows' nest?,. . .CEclacus vicar ius AA. Beak long, reaching to the posterior coxae. Infests poultry in southwest United States and in Mexico Hcematosiphon inodorus The common bedbug, Clmex lectuldrius. — The body is ovate in outline and is very flat (Fig. 434) ; it is reddish brown in color, and is 4-5 mm. long by 3 mm. broad when full-grown. This pest is a noc- IJEMIPTERA 379 Fig.434.— Cfwex lectularius. tumal insect, hiding by day in cracks of furniture and beneath various objects. Ordinarily it is found only in the dwellings of man; but it has been known to infest chicken houses. The means commonly employed to destroy this pest is to wet ~^^^ the cracks of the bedstead and other places in which T ^"Pffl«^ ^^ hides with corrosive sublimate dissolved in alco- f^^'x" ^*-*^' '^^^^ ^^ ^^^"^ ^^' druggists under the name of /^^\ bedbug poison. As this substance is a virulent poison, it should be used with great care. In case a room is badly infested, it should be thoroughly cleaned; fumigated with sulphur or with hydro- cyanic acid gas; the walls repapered, kalsomined, or whitewashed ; and the woodwork repainted. Detailed directions for the use ot gases against household insects are given by Herrick {'14). In traveling, where one is forced to lodge at places in- fested by this insect or by fleas, protection from them can be had by sprinkling a small quantity of pyrethrum powder between the sheets of the bed on retiring. The other members of this family found in this country can be distinguished from the com- mon bedbug b}' means of the table given above. Family POLYCTENID^ The Many-combed Bugs The Polyctenidas includes a small number of very rare species of bugs that are parasitic upon bats. Until recently it was not known to be represented in America north of Mexico; but Ferris ('19) records the finding of one species, Hesperoctenes longi- ceps, on the bat Eumops calif orni- ctis, near San Bernardino, Cali- fornia. Figure 435 is a reduced copy of a figure of this insect by Ferris. The left half of the figure represents the dorsal aspect of this insect; the right half, the ventral aspect. This carefully made figure renders a detailed description unnecessary. The length of the body of the female is 4.5 mm.; of the male, 3.8 mm. rig. 435. — Hesperoctenes longiceps: A, female, left half dorsal, right half ven- tral; B, posterior tarsus; C, anterior tarsus; D, dorsal aspect of second an- tennal segment, distal end upward. (After Ferris.) ScSn AN INTRODUCTION TO ENTOMOLOGY In this family the hemelytra are vestigial and the hind and middle tarsi are four-jointed. The name of the typical genus, Polyctenes, was probably suggested by the presence of several comb-like series of spines on the body. Family NABID^ The Nabids In this family the body is oblong and somewhat oval behind. The beak is long, slender, and four-jointed. The hemelytra are longer than the abdomen, or are very short. Some species are di- morphic, being represented by both long-winged and short-wing- ed forms. In the forms with long wings the membrane is usually furnished with four long veins -Hemelytron of Nahs ferns, bo^^ding three discal cells, which are often open; from these discal cells diverge veins which form several marginal cells (Fig. 436). The fore tibi^ are armed with spines and are capable of being closed tightly upon the femora, which are stout; they are thus fitted for grasping prey. Nearly all of our common species belong to the genus Nobis; in fact this genus includes twenty-six of the thirty-one species found in this country. Due to an error made long ago, this genus has been commonly known as Corhcus; and most of the references to these insects are under this name. Nobis ferus: — This is one of our most common species. It measures about 8 mm. in length. It is pale yellow with numerous minute brown dots; the veins of the membrane are also brownish. This species is distributed from the Atlantic Coast to the Pacific. It secretes itself in the flowers or among the foliage of various herbaceous plants, and captures small insects upon which it feeds. Nobis subcoleopirdtus. — The short-winged form of this species is another very common insect (Fig. 437). This is of a shining jet-black color, with the edge of the abdomen and legs yellowish. The hemelytra barely extend to the second abdominal segment. The long-winged form of this species is not common; it is much narrower behind, and the hemel>i;ra and the ab- domen are rather dusky , or piceous, instead of jet-black. Family REDUVIID^ The Assassin-Bugs The Reduviida2 is a large family, including numerous genera of diverse forms. Many of the members of it are insects of considerable HEMIPTERA 381 size, and some are gayly colored. They are predacious, living on the blood of insects. In some cases they attack the higher animals; and, occasionally, even man suffers from them. Fig. 438. — Arilus cristatus. (From Glover.) In this family the beak is short, three-jointed, attached to the tip of the head, and with the distal end, when not in use, resting upon the prostemimi, which is grooved to receive it. Except in a few spe_ cies, ocelli are present in the winged forms. The anten- HcB are four-jointed. More than one hundred species occur in our fauna ; these represent forty-four genera. The following species will serve to illustrate the great diversity in form of members of this family. The wheel-bug, Arilus cristatus. — The wheel-bug is so called on account of the cogwheel-like crest on the prothorax (Fig. 438). It is a common insect south of New York City, and is found as far west as Texas and New Mexico. The adult, a cluster of eggs, and several n>Tnphs, are represented in the figure. The nymphs when young are blood-red, with black marks. The masked bedbug-hunter, Reduvius persondtus. — The adult of this species is represented by Figure 439; it measures from 15 to 20 mm. in length, and is black or very dark brown in colo- 382 A N I NT ROD UCTION TO ENTOMOLOG Y There are two marked peculiarities of this species that have caused it to attract much attention : first, in its immature instars the body is covered with a viscid substance which causes particles of dust and fibers to adhere to it ; not only the body, but the legs and antenna also, are masked in this way; in fact the nymph resembles a mass of lint, and attracts attention only when it moves; second, this species infests houses for the sake of preying upon the bedbug. It feeds also upon flies and other insects. The big bedbug, Tridtoma sanguisuga. — Closely allied to the masked bedbug-hunter is a large bug which insinuates itself into beds for a less commendable purpose than that of its ally, for it seeks human blood at first hand. This insect measures 25 mm. in length; it is black marked with red; there are six red spots on each side of the abdomen, both above and below. It inflicts a most painful wound. This is one of several species of the Reduviidse that received the name of "kissing-bug" as a result of sensational newspaper accounts which were widely published in the summer of 1899 and which stated that a new and deadly bug had made its appearance, which had the habit of choosing the lips or cheeks for its point of attack on man. It is found from New Jersey south to Florida and west to Illinois and Texas. The genus Triatoma was renamed Conbrhimis and most of the references to this species are under this generic name. The thread-legged bug, Eniesa brevipennis. — This is our most common representative cf one of the subfamilies of the Redu- viidffi in which the body is slen- der and the middle and hind legs are thread-like (Fig. 440). The front legs are less thread- like, and are fitted for grasp- ing ; they suggest by their form the front legs of the Mantidae; the coxa is greatly elongated, more than four times as long as -Emesa brevipennis. thick; the femur is spined; and the tibia shuts back upon the femur. In Figure 440 they are represented beneath the thread- like antennae. Emesa brevipennis measures about 33 mm. in length; it is found upon trees, or sometimes swinging by its long legs from the roofs of sheds or barns. A monograph of the Reduviidc^ of North America has been published by Fracker ('12). Family PHYMATID^ The Ambush-Bugs The Phymatidse is poorly represented in this country but some of the species are very common. Here we find the body extended HEMIPTERA 383 w^ Fig. 44I- — Phymata er- osa. laterally into angular or rounded projections, suggesting the name of the "typical genus. But the most striking character which dis- tinguishes this group is the remarkable form of the front legs. These are fitted for seizing prey. The coxa is somewhat elongated ; the femur is greatly thickened, so that it is half or two thirds as broad as long; the tibia is sickle-shaped, and fits closely upon the broadened and curved end of the femur; both tibia and femur are armed with a series of close-set teeth, so that the unlucky insect that is grasped by this organ is firmly held between two saws; the apparently useless tarsus is bent back into a groove in the tibia. Another striking character is presented by the antennas, the terminal segment being more or less enlarged into a knob. Under the lateral margin of the pronotum in Phymata there is on each side a groove into which the antenna fits. Only two genera are represented in our fauna, each by six species. These are Phymata and Macrocephalus. In Phymata the scutellimi is of ordinary size; in Macro- cephalus it is very large and extends to the tip of the abdomen. Our most common species is Phymata erosa (Fig. 441). It is a yellow insect, greenish when fresh, marked with a broad black band across the expanded part of the abdomen. It conceals itself in the flowers of various plants, and captures the insects which come to sip nectar. It is remarkable what large insects it can overcome and destroy; cabbage butterflies, honey-bees, and large wasps are over- powered by it. Family ENICOCEPHALID^ The Unique-headed Bugs In this family the hemelytra are wholly mem- branous and provided with longitudinal veins and a few cross-veins (Fig. 442). The head is constricted at its base and behind the eyes, and is swollen between these two constrictions. This is a form of head not found in any other Hemip- tera. Ocelli are present. The antennce are four- jointed; the first, second, and third segments are each followed by a small ring-joint. The beak is four-jointed. The front tarsi are one-jointed, the middle and hind tarsi two-jointed. The front legs are fitted for grasping prey, the fore tarsi being capable of closing upon the end of the broad tibiae.^ This is a small family ; but few species are known from the entire world, and only two have been described from America north of Mexico. These are Enicocephalus formicina, found in California, and Systelloderus bleeps, which has been found from New York to Utah. Fig. 442. — Systello - derus biceps. (Af- ter Johannsen.) 3S4 AN INTRODUCTION TO ENTOMOLOGY But little has been published regarding the habits of these insects. It is evident, from the structure of their fore legs, that they are predacious. Professor Johannsen ('09 b) found Systelloderus biceps {Henicocephalus culicis) flying in small swarms near Ithaca, N. Y. Their manner of flight resembled that of chironomids. They were observed repeatedly from July 5 to the last week in August, always in the latter part of the afternoon. This species measures 4 mm. in length. The type genus of this family was first named Enicocephalus ; this name was later emended to Henicocephalus ; but the older form of the name, though incorrectly formed, is now used. Family TINGID.E The Lace-Bugs The Tingida? are doubtless the most easily recognized of all Hemip- tera. The reticulated and gauze-like structure of the hemelytra, usually accompanied by expansions of the pro- thorax of a similar form, gives these insects a characteristic appearance which needs only to be once seen to be recognized in the future. Figure 443 represents one of these insects greatly enlarged, the hair-line at the side indicating the natural size of the insect. They are generally very small insects. But they occur in great numbers on the leaves of trees and shrubs, which they puncture in order to suck their nourishment from them. In this family the ocelli are wanting; the beak and antennse are four-jointed; the scu- Fig- A\2>-—Corythucha tellimi is usually wanting or vestigial, replaced "''""^'^- by the angular hind portions of the pronotum; and the tarsi are tw^o-jointed. About seventy-five species of lace-bugs, representing twenty-three genera, are now listed from this country. There are two well-marked subfamilies. Subfamily TINGING This division includes nearly all of the known species. Here the scutellum is usually covered by an angular projection of the pronotum ; and the hemelytra have no distinction between the clavus, corium, and membrane. The following species will serve as an il- lustration of this subfamily. ' _ The hawthorn lace-bug, Corythucha arcudta. — This is a widely distributed species, which punctures the under surface of the leaves of different species of Cratcegus. The infested leaves have a brown and sunburnt appearance. Eggs, nymphs, and adults are found together. The adult is represented, much enlarged, in Figure 443. HEMIPTERA 385 In Figure 444 the eggs and a nymph are shown. The eggs are covered uy a brown substance, which hardens soon after oviposition. Subfamily PIESMIN.E In this subfamily the scutellum is not covered; the hemelytra have a distinct clavus, with a well-marked claval suture; the clavus is furnished with one, and the coriimi with three, longitudinal veins which are much stronger than the network of veins between them. In long- winged individuals the tip of the membrane lacks the network of veins and appears like the mem- brane in other families. As yet but a single American species has been described. The ash-gray Piesma, Piesma cinerea. — This species measures about 3 mm. in length, and is of an ash-gray color. The prothorax is deeply pitted, so that it presents the same appearance as the base of the wing-covers. The head is deeply bifid at tip, and there is a short robust spine be- tween the eye and the antenna on each side. This species sometimes infests vineyards to an injurious extent, destroying the fiower-buds in early spring. Family PYRRHOCORID^ Fig. 444.— Eggs and nymph of Cory- thucha arcuata. The Cotton-Stainer Family In this family the antennae are four-jointed; the beak is also four-jointed; ocelli are absent ; and the hemelytra are not furnished with a cuneus. The members of the family are stout and heavily built insects, and are generally rather large and marked with strongly contrasting colors, in which red and black play a con- spicuous part, in this respect re- sembling some of the larger species of the following family. The Pyrrhocoridee can be dis- tinguished from the Lygaeidas by the absence of ocelli, and by the venation of the membrane of the hemelytra (Fig. 445). At the base of the membrane there are two or three large cells, and from these arise branching veins. Only twenty-two species, representing five genera, have been found in our fauna, and these are restricted to the Southern and Western States. Our most important species, from an economic standpoint, is the red-bug or cotton-stainer, Dysdercus suturellus (Fig. 446). It is Fig. 445. — Hemelytron of Euryopthal mus succinctiis. 386 AN INTRODUCTION TO ENTOMOLOGY oblong-oval in form, of a red color; the hemelytra and an arc on the base of the prothorax, and also the scutelltim, are pale brown. The hemel>i:ra have the costal margin, a narrow line bordering the base of the membrane and continuing diagonally along the outer margin of the clavus, and also a slender streak on the inner margin of the clavus, pale yellow. It varies much in size, ranging from _io mm. to 1 6 mm. in length. The young bugs are bright red with black legs and antennas. From time immemorial this has been one of the worst pests with which the cotton-planters of Florida and the West Indies have had to contend. It does much damage by piercing the stems and bolls with its beak and sucking the sap ; but the principal injury to the crop is from staining the cotton in the opening boll by its excrement. It is also injurious to oranges ; it punctures the rind of the fruit with its beak; and soon decay sets in, and the fruit drops. These insects can be trapped in cotton-flelds by laying chips of sugar-cane upon the earth near the plants ; in orange-groves small heaps of cotton-seed will be found useful, as well as pieces of sugar-cane. The insects that collect upon these traps can be destroyed with hot water . The species whose range extends farthest north is Euryophthdlntus succinctus. This is found from New Jersey south to Florida and west to Arizona. It is brownish black, with the lateral and Fig. 446.- — Dys- dercus suturelliis hind margins of the prothorax, elytra, and the edge of the abdomen, margined with orange or red. It measures about 15 mm. in length. Family LYG^ID^ The Chinch-Bug Family the costal margin of the hem- Fig. 447. — Hemelytron of Lygaus kalmii. The Lygseidas is one of the larger families of the Hemiptera. It includes certain forms which closely resemble members of the pre- ceding family in size, form, and strongly contrasting colors. But the great majority of the species are of smaller size and less brightly col- ored ; and all differ from that family in presenting distinct ocelli. The membrane of the hemelytra is furnished with four or five simple veins, which arise from the base of the membrane ; sometimes the two inner veins are joined to a cell near the base (Fig. 447). Nearly two hundred species belonging to this family have been found in our fauna; these represent fifty-five genera and seven subfamilies. Although these insects feed on vegetation, they have attracted but little attention as pests of cultivated plants excepting the following species. HEMIPTERA 387 The chinch-bug, Bltssus leiicopterus. — This well-known pest of grain-fields is a small bug, which when fully grown measures a little less than 4 rrjn. in length. It is blackish in color, with conspicuous, snowy white hemel\ tra. There is on the costal margin of each hemeh'tron near the middle of its length a black spot ; from each of these spots there extends towards the head a some- what Y-shaped dusky line. The body is clothed with numerous microscopic hairs. In Figure 448 this insect is represented natural size and enlarged. The species is dimorphic, there being a short-winged form. There are two generations of the chinch-bug each p^g ^^^,—Blissus year. The insects winter in the adult state, hiding leucoptems. beneath rubbish of any kind; they even penetrate forests and creep under leaves, and into crevices in bark. In early spring they emerge from their winter quarters and pair; soon after, the females begin to lay eggs; this they do leisurely, the process being carried on for two or three weeks. The eggs are yellowish ; about 500 are laid by a single insect; they are deposited in fields of grain, be- neath the ground upon the roots, or on the stem near the surface. The eggs hatch in about two weeks after being laid. The newly hatched bugs are red; they feed at first on the roots of the plant which they infest, sucking the juices; afterw^ards they attack the stalks. The bugs become full-grown in from forty to fifty days. Before the females of this brood deposit their eggs, they leave their original quarters and migrate in search of a more abundant supply of food. About this time the wheat becomes dry and hard; and the migration appears to be a very general one. Although the insects sometimes go in different directions, as a general rule the masses take one direction, which is towards the nearest field of oats, corn, or some other cereal or grass that is still in a succulent state. At this time many of the bugs have not reached the adult state ; and even in the case of the fully winged individuals the migration is usually on foot. In their new quarters the bugs lay the eggs for the second or fall brood. The methods of control of this pest that are used are the fol- lowing : the burning in autumn of all rubbish about fields, in fence comers, and in other places where the bugs have congregated to pass the winter; the stopping of the marching of the spring brood into new fields by means of a furrow or ditch with vertical sides, and with holes like post -holes at intervals of a few rods in the bottom of the furrow or ditch, in which the bugs are trapped; the use of a line of gas-tar on the ground to stop the marching of the spring brood ; in some cases kerosene emulsion has been used to advantage ; the sowing of decoy plots of attractive grains in early spring, and the later plowing under of the bugs and their food and harrowing and rolling the ground to keep the bugs from escaping; and the artificial dissemination of the fungus Sporotrichum globuliferum, which is the cause of a contagious disease of the chinch-bug. 388 AN INTRODUCTION TO ENTOMOLOGY Family NEIDID^ The Stilt-Bugs The family Neididse consists of a small number of species, which on account of their attenuated forms are very striking in appearance (Fig. 449). The body is long and narrow; the legs and antennae are also long and extremely slender. There is a transverse incision in the vertex in front of the ocelli. The antennae are four-jointed, elbowed at the base of the second segment, and with f/\\x/A the tip of the first segment enlarged. The y \X/ \_ beak is four-jointed; and the membrane r JT ^ r of the hemelytra is furnished with a very I /H\ \ few veins, r* / H \ ^ -i Only eight species of this family have been found in our fauna; but these repre- sent six genera. Only two of the species are widely distributed in the United States and Canada. These are sluggish insects, found in the undergrowth of woods and in meadows and pastures. Jalysus spindsus. — This is the best- known member of this family. It is distributed from the Atlantic to the Pacific in both the United States and Canada. It is as slender as a crane-fly (Fig. 449) and of a pale tawny color. The front of the head tapers off to an almost acute, upturned point. An erect spine projects from the base of the scutellum, and another from each side of the mesopleura, just in front of the posterior coxas. The body is about 8 mm. in length. Jalysus perclavdtus. — This is one of the southern members of the family, but it has been found in New Jersey and the District of Columbia. It is smaller than the preceding species; the length of the male is 5 mm., of the female 6 mm. There is an erect spine be- tween the bases of the antennas; and the last segment of the antennae is shorter and thicker than in J. spinosus. Neides miiticus .—L^ke Jalysus spinosus, this species is found from the Atlantic to the Pacific in both the United States and Canada. It lacks the spines of the scutellum and thorax; and the front of the head is bent down, in the form of a little horn. The other representatives of this family in our fauna are found in Florida, Arizona, New Mexico, and California. Fig. 449. — Jalysus spinosus. Family ARADIDiE The Flat-Bugs The members of this family are very flat insects; in fact they are the flattest of all Hemiotera. The-/ live in the cracks or beneath HEMIPTERA 389 the bark of decaying trees; and the form of the body is especially adapted for gliding about in these cramped situations. They are usually dull brown or black ; sometimes they are varied with reddish or pale markings. The hemelytra are usually well developed, with distinct corium, clavus, and mem- brane; but they are reduced in size, so that when folded they cover only the disk of the abdomen (Fig. 450). Ocelli are lacking; the antennas are four-jointed ; the tarsi are two-jointed; and the beak is four-jointed, but often apparently three-jointed. These insects are supposed to feed upon fungi or upon the juices of decaying wood and bark. The family is well represented in this country; fifty-nine species, repre- senting nine genera, are now known, and doubtless many remain to be discovered. * Fig. 450.— ^r- adiis acutus. Fig. 451. — Hemely trivittattis. Leptocoris Family COREID^ The Squash-Bug Family The members of this family vary greatly in form. Some of the species are among the most formidable in appearance of all of our Hem.iptera ; while others are comparatively weak and inconspicuous. The family is characterized as follows : the antenna are insert- ed above an ideal line extending from the eye to the base of the rostrum, and are four-jointed ; the vertex is not transversely im- pressed; the ocelli are present; the beak is four-jointed; the scutellum is small or of mediiim size; the hemelytra are usually complete and composed of clavus, coriiim, and membrane; the membi ane is furnished with many veins, which spring from a transverse basal vein, and are usually forked (Fig. 451); the tarsi are three-jointed. This is a large family ; one hundred and twenty- four species, representing forty-eight genera, have been found in our fauna. It contains both vegetable feeders and carnivorous forms ; in some cases the same species will feed upon both insects and plants. The most common and best-known species is the following. The squash-bug, Anzsa trhtis. — The form of the body of the adult insect is represented in Figure 452. In this stage the insect appears blackish brown above and dirty yellow beneath. The ground color is really ochre-yellow, darkened by numerous minute black punctures. Upon the head are two longitudinal black stripes; the lateral margins of the prothorax ars } ellow, owing to the absence of the punctures along a narrow Fig. 45 2. — Anasa Irislis. 390 AN INTRODUCTION TO ENTOMOLOGY space; and the margin of the abdomen is spotted with yellow from. a similar cause; the membrane of the hemelytra is black. This species winters in the adult state. In early simmier it lays its eggs in little patches on the young leaves of squash and allied plants. The young bugs are short and more rounded than the adult insects. There are several generations of this /^•^mt^m^'**^ species each year. J^^^^^^ This is one of the most annoying of JJ^i/W^ \^ the many pests of the kitchen-garden; .J^im^m ^ and, unfortunately, no satisfactory meth- od of control has been devised. The egg masses are conspicuous and can be col- lected and destroyed ; the young nymphs can be killed by spraying with io% kerosene emulsion; the adults can be trapped under bits of boards and stones; and many nymphs can be killed by de- stroying "the vines as soon as the crop is harvested. Acanthocephala femordta (Fig. 453) will serve as an example of one of the larger members of this family. This species is distribut- ed from North Carolina to Florida and Texas. It has been known to destroy the cotton-worm, and is said to injure the fruit of the cherry by puncturing it with its beak and sucking the juices. Fig. 453. — Acanthocephala femorata. (From Glover.) Family PENTATOMID^ The Stink-Bug Family With the Pentatomidas we reach a series of families, three in number, in which the antennas are usually five-jointed, differing in this respect from all of the preceding families. _ The form of the body presented by the great majority of the members of the Pentatomidse is well shown by Figure 454. It is broad, short, and but slightly convex; the head and prothorax form a triangle. The scutellum is narrowed behind ; it is large and in a few forms nearly covers the abdomen. The tibias are unarmed or are furnished with very fine short spines. As with the Coreidae, the members of this family Fig. 454.— A varv^ greatly in their habits; some are injurious to pentatomid. vegetation; others are predacious; while some species feed indifferently upon animal or vegetable matter. vSome species are often found on berries and have received the popular name of HEMIPTERA 391 stink-hugs on account of their fetid odor, which they are apt to impart to the berries over which they crawl. This nauseous odor is caused by a fluid which is excreted through two openings, one on each side of the lower side of the body near the middle coxae. The harleqtiin cabbage-bug, Murgdntia histrionica. — Among the species of the Pentatomidas that feed upon cultivated plants, the harlequin cabbage-bug or "calico-back" is the most important pest. It is very destructive to cabbage and other cruciferous plants in the vSouthern States and on the Pacific Coast. It is black, with bands, stripes, and margins of red or orange or yellow. Its bizarre coloring has suggested the popular names given above. The full-grown bugs live through the winter, and in the early spring each female lays on the under surface of the young leaves of its food-plants about twelve eggs in two parallel rows. The eggs are barrel-shaped and are white banded with black. The young bugs are pale green with black spots. They mature rapidly; and it is said that there are several generations in one season. This is an exceedingly difficult species to contend against. Much can be done by cleaning up the cabbage stalks and other remnants as soon as the crop is harvested, and, in the following spring, trapping the bugs that have hiber- nated by placing turnip or cabbage leaves in the in- fested gardens or fields, or by planting trap-crops of mustard or other cruciferous plants. The bugs that are not collected by these methods and their eggs should be collected by hand; this can be easily done Fig. 455.- P«(/- as both the bugs and their eggs are conspicuous. "''^^ . ^y"l^- As if to atone for the destruction caused by their Gfover.) relative, the harlequin cabbage-bug, there are many members of this family that aid the agriculturist by destroying noxious insects. The species of the genus Podisus have been reported often as destroying the Colorado potato-beetle, currant worms, and other well-known pests. Figure 455 represents a member of this genus, Podisus niactiliventris Family CYDNID^ The Bnrrower-Biigs and the Negro-Bugs The Cydnidfe is the second of the series of families in which the antennae are five-jointed. In this family the outline of the body is more generally oval, rounded, or elliptical, and the form more convex, than in the Pentatomidae. The scutellum is large but varies greatly in size and in outline. Each lateral margin of the scutellum is fur- nished with a furrow into which the margin of the hemelytron of that side fits. In this respect the Cydnidas agrees with the preceding family and differs from the following one. The tibiae are armed with strong spines. The family includes two well-marked subfamilies. 392 AN INTRODUCTION TO ENTOMOLOGY Subfamily CYDNIN^ The Burrower-Bugs The subfamily Cydninaa includes the greater niunber of the mem- bers of the Cydnidag found in the United States and Canada ; of these there are twenty-nine species now listed, representing nine genera ; most of these are restricted to the South and the Far West. In this subfamily the scutellum is either broad and bluntly rounded, or triangular with the apex pressed down. The species are generally black or very dark brown. They are found burrowing in sandy places, or on the surface of the ground beneath sticks and stones, or at the roots of grass and other herbage. A European species is said to suck the sap from various plants near the ground. It is desirable that further observations be made upon the habits of this subfamily. Figure 456 represents Cyrtomenus mirabilis, a species found in the South and the Southwest. Subfamily THYREOCORIN^ The Negro-Bugs The subfamily Thyreocorinaj is represented in our fauna by a single genus, Thyreocoris, of which sixteen species have been found in this country. They are mostly black and beetle-like in appearance, some have a bluish or greenish tinge, and all are very convex. The body is short, broad, and very convex, in fact almost hemispherical. The scutellum is very convex and covers nearly the whole of the abdomen. These insects infest various plants, and often in- jure raspberries and other fruits by imparting a dis- agreeable, bedbug-lilce odor to them. A common and widely distributed species is Thyreocoris ater (Fig. 457). Another species often found on berries is T. pulicarins; this species is some- times a serious celery pest. It is shiny black and has a white stripe on each side of the body; it measures 3 mm. in length. Family SCUTELLERID^ The Shield-hacked Bugs The members of this family are turtle-shaped bugs; that is, the HEMIPTERA 393 body is short, broad, and ver\^ convex. The scutellum is very covering nearly the whole of the abdomen. The lateral margins of the scutellum are not furnished with grooves for receiving the edges of the hemelytra as is the case in the two preceding families. The tibise are smooth or furnished with small spines. Figure 458 represents Eurygdster alterndtus somewhat enlarged, and serv^es to illustrate the typical form of members of this family. The family is represented in this country b}' fourteen genera including twenty-six species. I have met no account of any of our species occurring in sufficient numbers to be of economic importance. large, CHAPTER XXI ORDER HOMOPTERA* Cicadas, Leaf-Hoppers, Aphids, Scale-Bugs, and others The winged members of this order have four wings, except in the family Coccidce; the wings are of the same thickness throughout, and usually are held sloping at the sides of the body when at rest. The mouth-parts are formed for piercing and sucking; the beak arises from the hind part of the lower side of the head. The metamorphosis is gradual except in some highly specialized forms. Although the Homoptera is a well-defined order, the families of which it is composed differ greatly in the appearance of their members. For this reason there is no popular name that is applied to the order as a whole. The Homoptera was formerly regarded as a suborder of the Hemip- tera, that order being divided into two suborders, the Heteroptera and the Homoptera. But these two groups of insects differ so mark- edly in structure that it seems best to regard them as distinct orders. The Hemiptera is, therefore, restricted to what was formerly known as the suborder Heteroptera, and the suborder Homoptera is raised to the rank of a separate order. The wings of the Homoptera are usually membranous, but in some the front wings are subcoriaceous. In these cases, however, they are of quite uniform texture throughout, and not thickened at the base as in the Hemiptera. Many wingless forms exist in this order; in the family Coccidas the females are always wingless; and in the family Aphididas the males may be either winged or wingless, while the sexually perfect females and certain generations of the agamic fem^ales are wingless. In the Coccidas the males have only a single pair of wings, the hind wings being represented by a pair of club-like halteres. Each of these is furnished with a bristle, which is hooked and fits in a pocket on the hind margin of the fore wing of the same side. In several of the families of the Homoptera the wing-venation is greatly reduced; and even in the case of the more generalized forms, if only the wings of adults be studied the venation of these wings appears to depart widely from the hypothetical primitive type; but by examining the tracheae that precede the wing-veins in the wings of the nymphs, it is easy to determine the homologies of the wing-veins. This has now been done in the case of representatives of each of the families. The most generalized condition was found in the wings of a cicada, which will serve as the type of homopterous wing-venation. *Hom6ptera: homos (6/u6s), same, pteron (irTepdv), a wing. (394) HOMOPTERA 395 Figure 459 represents the tracheation of the fore wing of a young nymph of a cicada. The dotted Hne a-h indicates approximate- ly the line along which the hinge of the wing of the adult is formed. In this wing the only departures from the typical branching of the tracheee are the following: trachea Ri coalesces with the ra- dial sector to a point beyond the separation of trachea R 1+5 from the sector; the first anal trachea coalesces with trachea Cu for a short distance; and the second and third anal tracheae are unit- ed at the base. These differences are remark- ably slight compared with the great changes that have taken place in the specialization of the mouth -parts and other organs of the adult cicada. Figure 460 represents the fore wing of a mature nymph of a cicada. In this wing trachea Ri is completely aborted. In fact one of the Fig. 459. — Tracheation of a fore wing of a young nymph of a cicada. Fig. 460. — Tracheation of a fore wing of a mature nymph of a cicada. most characteristic features in the venation of the Homoptera, and of the Hemiptera also, is the absence or very great reduction of vein Ri in the adult wings of most members of these two orders. In the stage represented in this figure the developing cross-veins appear as pale bands. 396 AN INTRODUCTION TO ENTOMOLOGY Figure 461 represents the wings of an adult cicada. In this figure, where the veins are not numbered their homologies are indicated by the numbering of the cells behind them. In the adult wing there is a massing of several veins along the costal margin of the wing, and the cross-veins have the same appearance as the branches of the primary veins. Further details regarding the development of the wings of a cicada, and accounts of the development of the wings of representatives of other families of the Homoptera, are given in "The Wings of Insects" (Comstock '18). In the Homoptera the front part of the head is bent under and back so that the beak arises from the hind part of the lower side of the head. There is no distinct neck; and so closely is the head applied to the thorax that usually the front coxas are in contact The wings of a cicada. with the sides of the head, and in many forms the beak appears to arise from between the front legs. The mouth-parts are formed for piercing and sucking. The piercing organs consist of four long, bristle-like setae, the mandibular and maxillary setse; these are enclosed in a long, jointed sheath, which is the labium. The labium and the enclosed setee constitute what is commonly termed the beak. The beak, however, corresponds to only a portion of the mouth- parts of a chewing insect, each mandibular and maxillary seta being only a part of a mandible or maxilla; in each case another part of the organ enters into the composition of the head-capsule. As an example of the homopterous type of head and mouth-parts those of a cicada are probably the most available, on account of the large size of these insects and the comparative ease with which the HOMOPTERA 397 parts of the head can be distinguished. Figure 462 represents a lateral Fig. 462. — Head and prothorax of a Fig. 463. — Head of a cicada, front view: cicada, lateral aspect: a, antenna; md, mandibular seta; mx, maxillary c, clypeus; e, compound eye; ep, seta; other letters as in Fig. 462. epipharynx; /, labrum; o, ocelli; 2, (After Marlatt, with changes in the 3, second and third segments of the lettering.) labium. (After Marlatt, with changes in the lettering.) view of the head and prothorax of a cicada, and Figure 463 a front view. The corresponding parts are lettered the same in the two figures. The compound eyes (Figs . 46 2 and 463 , ^) , the an - tennse (Figs. 462 and 463 , a) , and the three ocelli (Figs. 466 and 467, o),can be easily recognized and need not be described in detail. The front is a small scle- rite near the stunmit of the head. It can be most easily recognized by the fact that it bears the median ocellus. In the adult insect the su- ture between it and the ver- tex is indistinct; but in the exuviae of a nymph, where the epicranial suture has been opened by the emergence of the adult, the outline of this sclerite is evident (Fig. 464). In many homopterous insects the front is vestigial or wanting. The vertex (Figs. 462 and 463, v) bears the paired ocelli. The clypeus (Figs. 462 and 463, c) is very large, occupying the greater part of the anterior surface of the head. In several of the Fig. 464. — Part of the exuviae of the head of a nymph of a cicada: a, antennas; as, antennal sclerite; c, clypeus; e, e, com- pound eyes; /, front; v, v, vertex. (After Berlese.) 398 AN INTRODUCTION TO ENTOMOLOGY CO - published accounts of the head of homopterous insects the clypeuS has been incorrectly identified as the front. The lahnmi (Figs. 462 and 463, /) is joined to the lower end of the clypeus; at its distal end it forms a sheath covering the base of the labium and the enclosed setae. This part is described as the clypeus by those who have incorrectly identified the clypeus as the front. The epipharynx (Figs. 462 and 463, ^) arises at its normal position on the ental surface of the labrum; but it is greatly developed and projects beyond the end of the labrum. The projecting part has been mistaken for the labrum by some writers, those who have failed to recognize the front and have termed the clypeus the front and the labrum the clypeus. The mandibular sclerites are easily recognized in the cicada. On each lateral as- pect of the head there are two quite distinct sclerites; the one that is next to the clypeus and the base of the labium is the mandibular sclerite(Figs.462and463,:i;), This sclerite is termed the lora by some writers on the Homoptera. The mandibular sclerites are believed to be in each case the basal part of a man- dible. They were first rec- ognized as such by Profes- sor J. B. Smith ('92); and this conclusion has been adopted by Marlatt ('95), Heymons ('99), Meek ('03), Berlese ('09), and Bugnion and Popoff ('11). On the other hand, Muir and Ker- shaw ('12) regard the lors as "lateral developments of the clypeal region" and not parts of mandibles. The structure of the mandible as a whole has been worked out by Meek ('03) and is shown in the left half of Figure 465. Within the cavity of the head the maxillary seta is enlarged, and to it are attached a retractor muscle {mdr) and a protractor muscle (mdp) . The seta is attached to the dorsal end of the mandibular sclerite (Fig. 465, mds) by a quadrangular sclerite (Fig. 465, co). The maxillary sclerites (Figs. 462 and 463, y) are closely parallel with the mandibular sclerites, but extend farther down, joining the Fig. 465. — Caudal view of the head of a cicada, with part of the head-capsule and muscles re- moved so as to show the left mandible and the right maxilla. (Prom Meek.) HO MOP T ERA 399 terminal part of the labrum. Each maxillan- sclerite is a part of a maxilla. This is clearly shown by the fact that in the embryo each maxilla is at first a bilobed appendage; from one of these lobes the maxillary sclerite is developed, and from the other the maxillary seta (see Heymons '99). In the adult insect the maxillary sclerites are not separated from the epicranium by sutures as are the mandibular sclerites (Figs. 462 and 463). The form and relations of the different parts of a maxilla, as worked out by Meek ('03), are shown in the right half of Figure 465. From the enlarged base of the maxillary seta a crescent -shaped sclerite (Fig. 465, ca) extends to the maxillar\^ sclerite (Fig. 465, mxs). In this figure the maxillary retractor muscles {mxr), the maxillary protractor muscles (mxp), and a tendon (mc) connecting the crescent- shaped sclerite with the tentoriim:i, are also represented. It is interesting to note the similarity in the structure of the mandibles and the maxillae. Each consists of a basal part which forms a portion of the wall of the head; a terminal piercing organ, the seta; and a sclerite connecting these two parts. The labium forms the outer wall of the beak; it consists of three segments; the second and third are lettered in Figures 462 and 463. The proximal segment is probably homologous with the submentum of the chewing insect mouth; the second segment, with the menttmi; and the third segment, with the ligula (see footnote, page 354). The dorsal surface of the labium, which is the lower surface, isdeeply grooved, forming a channel which enclos- es the mandibular and maxillary setae. The labium, which is all that is commonly seen of the beak in either hemipterous or homopterous insects, is not a piercing or- gan; it is not pushed into the food sub- stance of the insect, but serves merely as a sheath for the mandib- ular and maxillary setse, which are the piercing organs and which are worked by the protractor and retractor muscles within the head (Fig. 465). Figure 466 represents a cross-section of the third segment of the beak of a cicada as figured by Meek ('03), and shows the relation of the labitmi to the mandibular and maxillar}^ setae. Each seta is crescent-shaped in cross-section; the mandibular setae lie outside of the maxillary setae; the maxillary setae, which extend side by side at Fig. 466. — Cross-section of the third segment of the beak of a cicada: lah, labium; md, mandibular seta; mx, maxillary seta; /, /, lumina in the seta. (From Aleek.) 400 AN INTRODUCTION TO ENTOMOLOGY the base of the beak, are twisted so that at this point one lies above the other. The two are fastened together by interlocking grooves and ridges ; and between them is a channel for the passage of the food. Within each of the four setae, there is a lumen (Fig. 466, /, /). The hypopharynx is a funnel-shaped, chitinized organ found near the base of the ental surface of the labitmi, at the end of the phar\'nx. The nature of the metamorphosis differs to a considerable degree in the different families; in most cases it is gradual, but marked modifications of this type have been developed in the Aleyrodidee and in the Coccidae. The members of this order feed on vegetation and to it belong some of our more important insect pests. This order includes ten families, which are designated as follows : The Cicadas, Family Cicadid^, p. 401. The Spittle-insects, Family Cercopid^, p. 402. The Tree-hoppers, Family Membracid^, p. 404. The Leaf-hoppers, Family Cicadellid^, p. 406. The Lantern-fly Family, Family Fulgorid^, p. 408. The Jumping Plant-hce, Family Chermid^, p. 410. The Typical Aphids, Family Aphidid^, p. 415. The Adelgids andthePhylloxerids, Family Phylloxerid^, p. 428. The Aleyrodids, Family Aleyrodid^, p. 437. The Scale-bugs, Family Coccid^, p. 440. TABLE FOR DETERMINING THE FAMILIES OF THE HOMOPTERA A. Beak evidently arising from the head; tarsi three- jointed; antennas minute, bristle-Hke. B. With three ocelH, and the males with musical organs. Usually large insects, with all the wings entirely membranous, p. 401 Cicadid^ BB. Ocelli only two in number or wanting; males without musical organs. C. Antenn-^ inserted on the sides of the cheeks beneath the eyes. p. 408 FULGORID^ CC. Antennae inserted in front of and between the eyes. D. Prothorax not prolonged above the abdomen. E. Hind tibiae armed with one or two stout teeth, and the tip crowned with short, stout spines, p. 402 Cercopid^ EE. Hind tibiae having a row of spines below, p. 4o6.Cicadellid^ DD. Prothorax prolonged into a horn or point above the abdomen, p. 404 Membracid^ AA. Beak apparently arising from between the front legs, or absent ; tarsi one- or two- jointed; antennae usually prominent and threadlike, sometimes wanting. B. Tarsi usually two- jointed; wings when present four in number. C. Wings transparent. D. Hind legs fitted for leaping; antennas nine- or ten-jointed, p. 410.. Chermid^ DD. Legs long an slender, not fitted for leaping; antennas three- to seven-jointed. 412 Superfamily Aphidoidea CC. Wings opaque, whitish; wings and body covered with a whitish powder, p. 437 Aleyrodids HOMOPTERA 401 BB. Tarsi usually one-jointed; adult male without any beak, and with only two wings; female wingless, with the body either scale-like or gall-Hke in form, or grub-like and clothed with wax. The waxy covering may be in the form of powder, of large tufts or plates, of a continuous layer, or of a . „ thin scale beneath which the insect lives, p. 440 CocciDiE ^iC^/fl/ "\ F MiLY CICADID^ \»i\ The Cicadas \j^ The large size and well-known songs of the more common species of this family render them familiar objects. It is only necessary to refer to the periodical cicada and to the harvest- flies, one of which is represented by Figure 467, to give an idea of the more striking character- istics of this family. We have species of cicadas much smaller than either of these; but their characteristic form is sufficient to distinguish them from members of the other families of this order. The species are generally of large size, with a subconical body. The head is wide and blunt, with prominent eyes on the outer angles, and three bead-like ocelli arranged in a triangle be- tween the eyes. The stntcture of the mouth- parts is described on an earlier page and illus- trated by several figures; and the form and venation of the wings are shown by Figure 461. But the most distinctive peculiarity is the form „. „ ., . , . of the musical organs of the males ; an example of ^ '^„et ~ "" these is described and figured on pages 89 to 9 1 . The family Cicadid^ is well represented in this country ; seventy- four species, representing sixteen genera, are now listed from our fauna. The two following species will serve as illustrations. There are several species of cicadas that are commonly known as dog-day cicadas or harvest -flies ; the most abundant of these is the species that has received the popular name of the lyreman; this is Tih'icen linnet (Fig. 467). The shrill cry of this species, which is the most prominent of the various insect sounds heard during the latter part of the summer, has brought its author into prominent notice. This insect varies both in size and colors. It commonly measures 50 mm. to the tip of the closed wings; it is black and green, and more or less powdered with white beneath. The transformations of this insect are similar to those of the following species, except that it probably completes its development in a much shorter period. It 402 AN INTRODUCTION TO ENTOMOLOGY differs also in seldom, if ever, occurring in sufficient numbers to be of economic importance ; but a brood of it appears each year. The member of this family that has attracted most attention is the periodical cicada, Tihicina septcndecim. This species is commonly known as the seventeen-year locust; but the term locust when applied to this insect is a misnomer, the true locusts being members of the order Orthoptera. The improper application of the term locust to this species was doubtless due to the fact that it appears in great swarms, which reminded the early observers in this country of the hordes of migratory locusts or grasshoppers of the Old World. This species is remarkable for the long time required for it to attain its maturity. The eggs are laid in the twigs of various trees ; the female makes a series of slits in the twig, into which the eggs are placed. vSometimes this cicada occurs in such great mmibers that they seriously injure small fruit trees, by ovipositing in the twigs and smaller branches. The n^-mphs hatch in about six weeks. They soon volun- tarily drop to the ground, where they bury themselves. Here they obtain nourishment by sucking the juices from the roots of forest and fruit trees. And here they remain till the seventeenth year following. They emerge from the ground during the last half of Alay, at which time the empty pupa-skins may be found in great numbers, clinging to the bark of trees and other objects. It is at this period that the cicadas attract attention by the shrill cries of the m.ales. The insects soon pair, the females oviposit, and all disappear in a few weeks. More than twenty distinct broods of this species have been traced out; so that one or more broods appear somewhere in the United States nearly every year. In many localities, several broods co-exist; in some cases there are as many as seven distinct broods in the same place, each brood appearing in distinct years. There is a variety of the species in which the period of development is only thirteen years. This variety is chiefly a southern form, while the seventeen-year broods occur in the North. Family CERCOPID^ The Spittle-Insects cr Frog-Hoppers During the summer months one often finds upon various shrubs, grass, and other herbs, masses of white froth. In the midst of each of these masses there lives a young insect, a member of this family. In some cases as many as four or five insects inhabit the same mass of froth. It is asserted that these insects undergo all their trans- formations within this mass; that when one is about to molt for the last time, a clear space is formed about its body and the superficial part of the froth dries, so as to form a vaulted roof to a closed chamber within which the last molt is made. The adult insects wander about on herbage, shrubs, and trees. They have the power of leaping well. The name frog-hoppers has IIOMOPTERA 403 doubtless grown out of the fact that formerly the froth was called "frog-spittle" and was supposed to have been voided by tree-frogs from their mouths. The name is not, however, inappropriate, for the broad and depressed form of our more common species is somewhat like that of a frog. The origin and formation of the froth of spittle-insects has been discussed by many writers. Guilbeau ('08) found by many experi- ments that the froth is derived from two sources. The greater part of the fluid is voided from the anus; to this fluid is added a mucilagi- nous substance which renders it viscous and causes the retention of air bubbles, which are introduced into it by the insect by means of its caudal appendages. The mucilaginous substance is the excretion of large hypodermal glands, which are in the pleural region of the seventh and eighth abdominal segments. These are known as the glands of Batelli; they open through numerous minute pores in the cuticula. It is evident that the covering of froth protects the spittle-insects from parasites and other enemies. In this family the antennas are inserted in front of and between the eyes; the prothorax is not prolonged back of the abdomen, as in the Membracidas ; the tibise are armed with one or two stout teeth, and the tip is crowned with short, stout spines, as shown in Figure 468. The Cercopidas is represented in our fauna by six genera, which include twenty-five species. The follow- Fig. 468.-1,5- ing species will serve as examples. p y r 0 m a One of the more common and very widely distribut- ^^^^ ''^nlin- ed species is Lepyronia quadranguldris (Fig. 468). The ral size, and adult of this species is a brownish insect, densely one tibia en- covered with microscopic hairs, and black beneath; larged. the hemelytra are marked with two oblique brown bands, which are confluent near the middle of the costal margin; the humeral region is dusky; and the tip of each hemelytron is marked with a small blackish curve; the ocelli are black, but indistinct. This species measures from 6 mm. to 8 mm. in length. Somewhat resembling the preceding species, and also common and widely distributed, is Aphrophora quadranotdta. In this species the body is pale; the hemelytra are dusky, each with two large hya- line costal spots, margined with dark brown ; the ocelli are blood-red ; and the head and pronotimi are furnished with a slightly elevated, median, longitudinal line. To the genus Clastopiera belong certain other common members of this family. In this genus the body is short and plump, some- times nearly hemispherical; the species are small, our common forms ranging from 3 mm. to 6 mm. in length. Clastopiera proteus is a conspicuous species on account of its bright yellow markings. It varies greatly in color and markings; but the most striking forms are black, with three transverse yellow bands, two on the head and one on the thorax, and with the scutellum and a large oblique band 404 AN INTRODUCTION TO ENTOMOLOGY on each hemelytron yellow. Another common species is Clasloptera ohtusa. This occurs on black alder in summer and autumn. It is of a claret-brown color above, marked with two pale bands on the vertex, two on the prothorax, and a wavy, broader band on the hemelytra. The membrane is often whitish, the waved band is extended exteriorly, and there is a pale V-shaped figure on the end of the scutellum. Family MEMBRACID.^ The Tree-Hoppers Spongophorus hallista; B, Spongophorns The most useful character for distinguishing members of this family is the prolongation of the prothorax backward above the abdomen; some- times it extends back to the tip of the abdomen and completely cov- ers the wings. This develop- ment of the prothorax re- sembles that which occurs in the pigmy lo- custs, the sub- familyAcrydiinag of the order Or- thoptera. In many of the Membracidae, however, the prothorax is not only prolonged backward but is extended sidewise or upwards, with the result that in some cases the insect presents a most bizarre appearance ; this is especially true of certain tropical forms ; Figure 469 represents two species found in Central America. Many species of the Membracidae live upon bushes or small trees; others inhabit grass and other herbaceous plants. Although these insects subsist upon the juices of plants, they rare- ly occur in sufficient numbers to be of economic impor- tance. Sometimes the females injure young trees by lay- ing their eggs in the bark of the smaller branches and in buds and stems. Many members of this family excrete honey -dew and are attended by ants, especially in the nymphal stages, as are the aphids. The adults are good leapers ; hence the common name tree-hoppers. This family is well represented in this countr\' ; one hundred eighty-five species, representing forty-three genera, are now listed. Among our more common species are the following. The Buffalo tree-hopper, Ceresa hubalus. — The popular name of this species refers to the lateral prolongations of the prothorax, which suggest the horns of a buffalo (Fig. 470). The life-history of f Fig. 470.— Cer- esa hubalus. HOMOPTERA 405 this insect has been worked out by Funkhouser ('17). The n}TTiphs feed on succulent herbs, particularly sweet clover; the eggs are laid on young trees, particularly elm and apple, the stems of which are injured by the egg-punctures. Oviposition occurs most commonly in early September, at Ithaca, N. Y. The eggs hatch early in the following May. The young nymphs leave the trees on which the eggs were deposited and migrate to succulent weeds. The early life of the adult is spent on the weeds ; but later the females migrate to trees for egg-laying. The two-homed tree-hopper, Ceresa dicer os.- — This species re- sembles the buffalo tree-hopper in size and form. It is a pale dirty yellow, spotted with brown; the lateral and caudal aspect of each horn is brown; the caudal tip of the prothorax, and a large spot midway between the tip and the horns, are also brown. The insect is densely clothed with hairs. It is common on black elder, Sambucus canadensis. Funkhouser followed the life-history from the egg to the adult on this plant. The eggs are laid about the middle of August in the second-year stems, and hatch about the middle of May. The two-marked tree-hopper, Enchendpa binotdta.- — In this spe- cies the pronotum is prolonged in an upward- and forward- projecting horn (Fig. 471). This insect is very abundant on trees, shrubs, and vines. It is gregarious, and both adult and immature forms are found clustered together. The eggs are usually laid in frothy masses, which are very white and appear like wax. Funkhouser states that a variety of this species found on butternut lays its eggs in the buds and does not cover them with the heavy froth. The specific name of this species refers to the fact there are two yellow spots on the dorsal line of the pronotum. Another very common species, and one that is closely allied to the preceding, is Campylenchia Idtipes. This is brownish, unspotted, and has a rather longer horn than that of the two-marked tree-hopper; but it varies much in color and in the length of the pronotal horn. This is a grass-inhabiting species and is common in pastures and especially on alfalfa. It is often taken by sweeping. Telamona. — To this genus belong our humpback Fig. 471.— £w- chenopa bi- notata. Fig. 472. — Tel- amona. 406 AN INTRODUCTION TO ENTOMOLOGY forms (Fig. 472), of which about thirty species have been found in our fauna. They Hve chiefly on oaks, hickories, basswood, and other forest trees. The adults generally rest singly on the limbs and branches of the trees; they are strong flyers and are difficult to capture. The immature forms keep together in small groups. Figure 473 represents a front viev/ of several membracids in our collection. Family CICADELLID^* J he Leaf -Hoppers This family is a very large one, and it is also of considerable economic importance; for it includes a ntimber of species that are very injurious to cultivated plants. The members of it are of small or moderate size. The antennae are inserted in front of and between the eyes; the pronotum is not prolonged above the abdomen; and the hind tibiae are nearly or quite as long as the abdomen, curv^ed, and armed with a row of spines on each margin. The form and armature of the hind tibiae are the most salient characters of this family. The form of the body is commonly long and slender, often spindle-shaped; but "_ some are plump. ^fcc/J/ exitt- These insects are able to leap powerfully; and, as osus. they are more often found on the leaves of herbage and on grass than elsewhere, they have been named leaf-hoppers. They infest a great variety of plants; some of them are important pests in gardens, orchards, and vineyards; but they are most destruc- tive as pests of grains and grasses. Although this is true, much less attention has been paid to injuries caused by them to grains and grasses than to those inflicted upon vineyards and rose bushes. More than seven hundred species, representing about seventy genera, have been found in the United vSiates and Canada. Among the more important members of the family from an economic standpoint are the following. The destructive leaf-hopper, Eiiscelis exitiosus, which is repre- sented, greatly enlarged, in Figure 474, sometimes infests winter wheat to a serious extent. It is a widely distributed species, its range including nearly the whole of the United States. It is a small, active, brownish insect, which measures with its wings folded about 5 mm. in length. It injures grass or grain b}^ piercing the midrib of the leaf and sucking the juices from it. The grape-vine leaf -hopper, Erythroneura comes, is a well-known pest which infests the leaves of grape, in all parts of this country where this vine is grown. It is a little more than 3 mm. in length, and has the back and wings marked in a peculiar manner with yellow and red. In the winter the darker markings are a dark orange-red, but after feeding has been resumed for a short time in the spring they change to a light lemon-yellow. The darker markings on the *This family has been commonly known as the Jassidae, but Cicadellidae is the older name. HO MO PT ERA 407 adults var>^ so much that eleven distinct varieties are now recognized ; two of these are represented at b and c in Figure 475. The rose leaf-hopper, Empoa toscb, is a well-known pest of the rose. Swarms of these insects may be found, in various stages of growth, on the leaves of the rose-bush through the greater part of the summer, and their nu- merous cast skins ma}^ be seen adhering to the low- er sides of the leaves; in fact attention is most fre- quently called to this pest by these white ex- uviae. The adult meas- ures less than 3 rrsn. in length. Its body is yel- lowish white, its wings are white and transpar- ent, and its eyes, claws, and ovipositor are brown. The apple leaf-hop- per, Enipodsca JahcB. — Al- though this species is named the apple leaf- hopper, it infests to an in- jurious extent man}^ dif- ferent plants, both cultivated and wild. Slingerland and Crosby ('14) state that it infests apple, currant, gooseberry, raspberry, potato, sugar-beets, beans, celery, grains, grasses, shade trees, and weeds. The adult insect measures about 3 mm. in length, and is of a pale yellowish green color with six or eight distinguishing white spots on the front margin of the pronotirm. The genus Drccailaccphala includes grass-green or pale green, spindle-shaped species, in which the head ai seen from above is long and triangular. One of the species, D. reticulata, sometimes greatly injures fields of grain in the South. The genus Oncometopia includes species in which the head is more blunt than in the preceding genus and is wider across the eyes than the thorax. O. tmddta (Fig. 476) is a common /^^ species. Its body, head, fore part of the thorax, scutel- ^./^^^ lum, and legs are bright yellow, with circular lines of yWl black on the head, thorax, and scutellimi. The fore ^ wings are bluish purple, when fresh, coated with whitish powder. It measures 12 mm. in length. It is said to lay its eggs in grape canes, and to puncture with its beak the stems of the bunches of grapes, causing the stems to wither and the bunches to drop off. One division of this family, the subfamily Gyponinge, includes forms which resemble certain genera belonging to the Cercopidsby their Fig. 475. — Ery'.hroiieiira cor.zes: a and h, female and male of the typical corr.es variety; c, the vi'As variety. (From Slingerland.) Fig. 476. — On ■ come t o pia undata. 408 AN INTRODCUTION TO ENTOMOLOGY plump proportions. Among these are Penthima americdna, which is a plump, short-bodied insect, resembling a Clastoptera; and the genus Gypona includes a large niimber of species, some of which resemble very closely certain species of Aphrophora. A glance at the posterior tibiae of these leaf-hoppers will enable one to distinguish them from the cercopids, which they so closely resemble. Methods of combating leaf-hoppers. — Leaf-hoppers, being sucking insects, are fought with contact insecticides. But it is difficult to destroy the adults, for they are so well-protected by their wings that applications strong enough to kill them are liable to injure the foliage of the host-plant; and, too, they are very active and fly away when approached. The most effective remedial measures are those directed against the nymphs. These consist of the use of some spray, as a ten- per-cent. kerosene emulsion or a soap solution made by dissolving one pound of soap in six or eight gallons of water, or a solution made of one ounce of "black leaf 40" tobacco extract and six gallons of water in which has been dissolved a piece of soap the size of a hen's egg. The application should be so applied as to wet the lower surface of every leaf. Family FULGORID^ The Lantern-Fly Family This family is remarkable for certain exotic forms which it includes. Chief among these is the great lantem-fiy of Brazil, Laterndria phos- phorea. This is the largest species of the family and is one of the most striking in appearance of all insects (Fig. 477). It has immense wings, which expand nearly six inches; upon each hind wing there is Fig. 477. — The lantern-fly, Lalernaria phosphorea. a large eye-like spot. But the character that makes this insect es- pecially prominent is the form of the head. This has a great bladder- like prolongation extending forward, which has been aptly compared to the pod of a peanut. Maria Sibylla Merian, a careful observer, who wrote more than two hundred years ago (1705), stated that this prolongation of the head is limiinescent. This statement was ac- cepted by Linnseus without question ; and he made use of names for this and some allied species, such as laternaria, phosphorea, candelar- ia, etc., to illustrate the supposed light-producing powers of these insects. The common name lantern-fly is based on the same belief. HOMOPTERA 409 (Aftei Fig Scolops 479-- The Brazilian lantern-fly has been studied by many more recent observers, and all have failed to find that it is luminescent. It may be that the individuals observed by Madame Merianwere infested by luminescent bacteria, as has been observed to be the case occasionally in certain other insects. No member of this fam- ily is known to be kmii- nescent. The Chinese candle- Fig. 478. — Antenna of Megamelus nottila fly, Fulgoria candeldria, Hansen.) is another very promi- nent member of this family, which is commonly represented in col- lections of exotic insects and is often figured by the Chinese. This too has been reputed to give light. Certain fulgorids found in China excrete large quantities of a white, flocculent wax, which is used by the Chinese for candles and other purposes. There does not seem to be any typical form of the body characteristic of this family. The different genera differ so greatly that on superficial examination they appear to have very little in common. The most useful character for recognizing, these insects is the form and position of the antennae. These are situated on the side of the cheeks beneath the eyes; the two proximal segments, the scape and pedicel, are stout (Fig. 478); the clavola consists of a small, nearly pear-shaped basal segment and a slender, segmented or un- segmented, bristle-like ter- minal part. The pedicel is provided with numerous sense-organs. So far as numbers are concerned this family is well represented in our fauna, three hundred fifty- seven species and seventy- seven genera having been listed; but our species are all small compared with the exotics mentioned above. The following of our native genera will serve to illustrate some of the variations in form represented in this country. The species all feed on the juices of plants. Scolops.- — In this genus the head is greatly prolonged (Fig. 479), as with the Chinese candle-fly. Our more common species, however, measure only about 8 mm. in length. Otiocerus. — In this genus the body is oblong; the head is com- pressed, with a double edge both above and below. Otiocerus coque- bertii (Fig. 480) is a gay lemon-yellow or cream-colored species, with Fig. 480.- ler.) -Otiocerus coquehertii. (From Uh- 410 AN INTRODUCTION TO ENTOMOLOGY wavy red lines on the fore wings. It measures about 8 mm. to the tips of the wings, and Hves upon the leaves of grape-vines, oaks, and hickory. Ormenis. — In our common representatives of this genus the wing -covers are broad, and closely applied to each other in a vertical position ; they are more or less truncate, and give the insects a wedge-shaped outline. 0. septentriondlis (Fig. 481) is a beautiful, pale green species powdered with white, which feeds on wild grape-vines, drawing nourish- ment from the tender shoots and midribs of the leaves, during its young stages. Fig. 481. — Ormems sep- tentrionalis. Family CHERMID.E* The Jumping Plant-Lice The jumping plant-lice are small insects ; many of them measure less than 2 mm. in length ; and the larger of our species, less than 5 mm. They resemble somewhat the winged aphids; but they look more like miniature cicadas (Fig. 482). They differ from aphids in the firmer texture of the body, in the stouter legs, in having the hind legs fitted for jumping, and in the antennge being ten-jointed or rarely nine- or eleven-jointed. The terminal segment of the antenucC bears two thick setae of unequal length. Both sexes are winged in the adult. The front wings are ample, and, while often transparent, are inuch thicker than the hind wings. The homologies of the wing-veins of the fore wings of Psyllia floccosa are indi- cated in Figure 4S3. Fig. 482.-P5W- lia. itf,+2 Fig. 483. — The venation of a fore wing of Psy'dia floccosa. (x^fter Patch.) The beak is short and three-jointed. The basal segment of the beak is held rigidlv between the fore coxae. *This family has been quite commonly known as the PsyUidae, a result of an incorrect application of the name Chermes to a genus of the Phylloxeridse. HOMOPTERA 411 The jumping plant-lice are very active little creatures, jumping and taking flight when disturbed; but their flight is not a prolonged one. They subsist en- tirely upon the juices of plants; some species form galls ; but it is rare that any of the species appear on cultivated plants in sufficient num- bers to attract attention, except in case of the pear- tree Psylla. The family Chermi- das is of moderate size; in our latest list onc- hundrcd thirty-seven species representing twenty-four genera, are enumerated from our fauna. The two fol- lowing species will ser^^e to illustrate variations in habits of these insects. Pachypsylla celtidis- mdmma. — This is a gall- making species which in- fests the leaves of hack- berry (Ccltis occidentalis). Figure 4S4 represents an infested leaf with galls, and a single gall and a nymph enlarged. The adult insect (Fig. 485) has a wing expanse of about 6 mm. The pear-tree psyllia, Psyllia pyricola. — This is our most impor- Fig. 484. — Gall of Pachypsylla celtidis-niamma: a,leaf with galls, from under-side; ^, section of gall enlarged and insect in cavity; c, nymph, enlarged . (From Riley . ) Fig. 485. — Pachypsylla celtidis-mamma. (From Packard.) Fig. 486. — Psyllia pyricola. tant species from an economic standpoint, being a serious enemy of the pear. It is a small species (Fig. 486) ; the summer generations 412 AN INTRODUCTION TO ENTOMOLOGY measure to the tips of the folded wings from 2.1 mm. to 2.8mm., the hibernating form 3.3 mm. to 4 mm. The general color is light orange to reddish brown, with darker markings. The eggs are laid early in the spring in the creases of the bark, in old leaf-scars, and about the base of the terminal buds. The young n^Tnphs migrate to the axils of the leaf petioles and the stems of the forming fruit; later they spread to the under side of the leaves. They secrete large quantities of honey -dew, upon which a blackish fungus grows; this is often the first indication of the presence of the pest. There are at least four generations each year. Badly infested trees shed their leaves and yoimg fruit in midsummer. In some cases orchards have been so badly injured by this pest that they have been cut down by their owners. The methods of control that are recommended are the following : the scraping off of the rough bark from the trunks and larger branches of the trees and burning it, in order to destroy the hibernating adults ; and thorough spraying of the trees with kerosene emulsion or "black leaf 40" tobacco extract when the petals have fallen from the blossoms, in order to destroy the newly hatched nymphs; this spray- ing should be repeated in three or four days; later sprayings are not so effective on account of the protection afforded the insects by the expanded leaves and by their covering of honey-dew. A monograph of the North American species of this family has been pubHshed by Crawford ('14). SUPERFAMILY APHIDOIDEA The Plant-Lice cr Aphids and their Allies The plant-lice or aphids are well-known insects; they infest nearly all kinds of vegetation in all parts of the countr}'. Our most common examples are minute, soft -bodied, green insects, with long legs and antenna, which appear on various plants in the house and in the field. Usually, at least, in each species there are both winged and wingless forms (Fig. 487). There are many species of aphids, nearly all of which are of small Fig. 487.— A group of size; some measure less than i mm. in aphids. length; and our largest species, only 5 or 6 mm. The body in most species is more or less pear-shaped. The winged forms have two pairs of delicate, transparent wrings. These are furnished with a few simple or branched veins; but the venation is more extended than in either of the two following families. The fore wings are larger than the hind wings; and the two wings of each side are connected by a small group of hamuli. The wings are usually held roof -like when at rest (Fig. 488, ab\ but are laid flat on the abdomen in some genera. The beak is four-jointed and varies greatl}- HOMOPTERA 413 in length ; in some species it is longer than the body. The antennae consist of from three to six segments; the last segment is usually provided with a narrowed prolongation (Fig. 488, aa). The first two segments of the antennas are always short, but the other segments show a great specific variation in length and are therefore very useful as systematic characters. Excepting the first two, the seg- ments of the antennas are usually provided with sense-organs, the sensoria, which vary in nimiber and shape in different species and are Fig. 488. — The melon aphis, Aphis gossypi: a, winged agamic female; aa, en- larged antenna of same; ab, winged agamic female, with wings closed, sucking juice from leaf; b, young nymph; c, last nymphal instar of winged form; d, wingless agamic female. (From Chittenden.) much used in the classification of these insects. On the back of the sixth abdominal segment there is, in many species, a pair of tubes, the cornicles, through which a wax-like material is excreted. In some genera these organs are merely perforated tubercles, while in still other genera they are wanting. It was formerly believed that the honey-dew excreted by aphids came from the cornicles ; for this reason they are termed the honey-tubes in many of the older books. The honey-dew of aphids is excreted from the posterior end of the alimentary canal. It is sometimes produced in such quantities that it forms a glistening coating on the leaves of the branches below the aphids, and stone walks beneath shade-trees are often densely spotted 414 AN INTRODUCTION TO ENTOMOLOGY with it. This honey-dew is fed upon by bees, wasps, and ants. The bees and wasps take the food where they find it, paying Uttle if any attention to its source ; but the ants recognize in the plant-Hce useful auxiharies, and often care for them as men care for their herds. This curious relationship is discussed later, under the head of Ants. In addition to honeydew, many aphids excrete a white waxy sub- stance. This may be in the form of powder, scattered over the Sc^R^M+Cu,^lstA Fig. 489. — The wings of Eriosoma americana. (From Patch.) surface of the body, or it may be in large flocculent or downy masses; ever}^ gradation between these forms exists. The superfamily Aphidoidea includes two families, the Aphididas and the Phylloxeridas. These two families differ in the life-histories of their species and in the venation of the wings of the winged forms, as follows : A. Only the sexually perfect females lay eggs; the parthenogenetic forms give birth to developed young, which, however, in some cases, are each enclosed in a pellicle. The radius of the fore wings is branched; and the outer part of the stigma is bounded behind by vein Ri (Fig. 489) Aphidid^ AA. Both the sexually perfect females and the parthenogenetic forms lay eggs. Vein Ri of the fore wings is wanting; and the outer part of the stigma is bounded behind by the radial sector (Fig. 490) Phylloxerid.,e Sc^R^M^Cu + istA Fig. 490. — The wings of Adelges. (From Patch.) HOMOPTERA 415 Family APHIDID^ The Typical Aphids To this family belong the far greater ntimber of the genera and species of the Aphidoidea. The distinctive characters of this family are given under A in the table above. For a detailed discussion of the wing-venation of these insects, see Patch ('09). In the Aphididce there exists a remarkable type of developrnent known as heterogamy or cyclic reproduction. This is characterized by an alternation of parthenogenetic generations with a sexual generation. And within the series of parthenogenetic generations there may be an alternation of winged and wingless forms. In some cases the reproductive cycle is an exceedingly complicated one, and differ- ent parts of it occur on different species of food plants. In those cases where different parts of the reproductive cycle occur on different food-plants, the plant on which the over-wintering fertilized egg is normally deposited and upon which the stem-mother and her immediate progeny develop is termed the primary host; a.nd that plant to which the migrants fly and from which a later form in the series migrates to the primary host is known as the secondary host. Different species of aphids differ greatly in the details of their development; it is difficult, therefore, to make generalizations re- garding this matter. The following account will serve to indicate the sequence of the forms occurring in the reproductive cycle of a migrat- ing aphid, one in which the different parts of the cycle occur on different food-plants. This account refers to what occurs in the North, where the winter interrupts the production of young, and eggs are developed which continue the life of the species through the inclement season. In hot climates also, where there is a wet and a dry season, eggs are produced to carry the species over the period when succulent food is lacking. And in some cases in the North, on ex- hausted vegetation the non-migratory species produce eggs during the summer months. The stem-mother.- — In the spring there hatches from an over- wintering egg a parthenogenetic, viviparous female, which lives on the primar}^ host. As this female is the stock from which the summer generations spring, she is known as the stem-mother or fundatrix. The stem-mother is winged in some species of one of the tribes (Callipterini) ; but usually she is wingless. The wingless agamic form. — In most species the stem-mother gives birth to young which do not develop wings and which are all females. These reproduce parthenogetically and are known as the wingless agamic form or spurice aptercc.* These reproduce their kind for a variable number of generations and then produce the next form. All of these generations live on the primary host. In a few species the wingless agamic form rarely appears if at all. *Sptiricc (New Latin, fern, pi.); Lat. spurius, an iHegitimate or spurious child. 416 AN INTRODUCTION TO ENTOMOLOGY The winged agamic form. — After a variable number of generations of the wingless agamic form have been developed and tiie food-plant has become overstocked by them, there appears a generation which becomes winged and which migrates to the secondary host. These are all parthenogenetic, viviparous females. They are known as the winged agamic form or spur ice alatce or migrants or migrantes. In some species, the second generation, the offspring of the stem-mother, are winged migrants. When the migrating winged agamic form becomes established on the secondary host, it produces young which are all females of the wingless agamic form. After a variable number of generations of this form have been developed, there is produced a generation of winged agamic females which migrate from the secondary host to the primary host. The two forms developed on the secondary host, the wingless and the winged agamic forms, may closely resemble the corresponding forms previously developed on the primary host or may differ markedly from them. The members of the last generation of the series of partheno- genetic forms, which produce the males and the oviparous females, are termed the sexuparce. In some non-migrating species this genera- tion is wingless. The males and the oviparous females . — The winged agamic females that have migrated from the secondary host to the primary one, here give birth to true sexual forms, male and female. These pair, and each female produces one or more eggs. These are sometimes designated as gamogenetic eggs to distinguish them from the so-called }va developed in agamic females. See note on page 191. The males and the oviparous females are termed collectively the sexuales; and some writers refer to the oviparous females as the ovipara. (Note that ovtpara is a plural noun.) The sexuales differ greatly in form and habits in the different tribes of aphids. In the more generalized aphids the ovipara of some species are winged, and the males are very commonly winged; both sexes have beaks and feed in the same way as do the other forms; and each female produces several eggs. In some of the more specialized aphids the sexuales are small, wingless, and beakless; consequently they can take no food. Each female produces a single egg, which in some cases is not deposited but remains throughout the winter within the shriveled body of the female. In some cases the young produced by the agamic females aie each enclosed in a pellicle when born ; this is soon ruptured and the young aphid escapes from it. The young thus enclosed are termed pseudova by many writers. The foregoing account, omitting exceptions and variations, can be summarized as follows : A. DIFFERENT TYPES OF INDIVIDUALS IN THE APHIDID.E First type. — The stem-mother or fundatrix, which is hatched from a fertihzed egg, is usually wingless, and reproduces parthenogenetically. Second type. — The parthenogenetically produced wingless agamic females. HOMOPTERA 417 Third type.— The parthenogenetically produced winged agamic females. Fourth type. — The sexual forms, males and oviparous females. B. SEQUENCE OF GENERATIONS IN A MIGRATING SPECIES Only the first of a series of similar generations is counted. First generation. — The stem-mother. Second generation. — Wingless agamic females. There may be a series of generations of this form here. Third generation. — Winged agamic females. These migrate to the secondary host. Fourth generation. — -Wingless agamic females. There may be a series of generations of this form here. Fifth generation. — Winged agamic females. These migrate to the primary host and are the sexuparae. Sixth generation. — Males and oviparous females. The females produce the fertilized eggs from which the stem-mothers are hatched, thus completing the life- cycle. A remarkable fact that has been demonstrated by several ob- servers is that the ntmiber of generations of the wingless agamic form may be influenced by the conditions under which the aphids live. In an experiment conducted under my direction by Mr. Slingerland, in the insectary at Cornell University, we reared 98 generations of the wingless agamic form without the appearance of any other form. The experiment was carried on for four years and three months without any apparent change in the fecundity of the aphids, and was discontinued owing to the press of other duties. As the aphids were kept in a hothouse throughout the winters, seasonal influences were practically eliminated ; and as members of each gen- eration were placed singly on aphid-free plants and their young re- moved as soon as born, there was no crowding. In order to determine the influence of crowding, members of the sixtieth generation were placed on separate plants and their young not removed. At the end of three weeks the winged agamic form ap- peared, evidently in response to need of migration to less densely populated plants ; while in other cages where the young were removed promptly, no migrants appeared up to the end of the experiment. The family Aphididse includes a very large number of genera and species. The genera are grouped into tribes and these into subfamilies in various ways by different authors. Recent classifications by American authors are those of Oestlund ('18) and Baker ('20). Four subfamilies are recognized by Baker. The characters of these sub- families given below are largely compiled from this author. Subfamily APHIDIN.E To this subfamily belong most of the species of aphids that are commonly seen living free {i. e., not in galls) upon the foliage of plants. But while most of the species feed on foliage, some of them attack stems and roots. Their attacks on foliage in some cases merely cause a weakening of it; in other cases, the leaves become curled or otherwise distorted; such distortions are termed pseudo galls. True galls formed by aphids are described in the accounts of the last two subfamilies. 418 AN INTRODUCTION TO ENTOMOLOGY In the Aphidinas the males and the oviparous females are com- paratively generalized; they are furnished with functioning mouth- parts and feed as do the other forms; the females lay several eggs; in a few species the oviparous females are winged ; and winged males are common. Wax-glands are not abundant in members of this sub- family ; and the antennal sensoria are oval or subcircular. The following are a few of the more common representatives of the Aphidinse. These are selected to illustrate some of the more striking differences in habits exhibited by the different species. a. BARK-FEEDING APHIDIN^ The following species will serve as an example of the bark -feeding species belonging to this subfamily, and also of the maximum size reached by any aphid. The giant hickory-aphid, Longistigma cdrycB. — This is a very large species, one of the largest aphids known, measuring to the tip of the abdomen 6 mm., and more than lo mm. to the tips of the wings (Fig. 491). It can be distinguished by the shape of the stigma of the fore wings, which is drawn out at the tip to an acute point extending Fig. 491.— LoKgi- aknost to the tip of the wing. The top of the thorax s tgma carycB. ^^^ ^-^^ veins of the wings are black and there are four rows of little transverse black spots on the back. The body is covered with a bluish white substance like the bloom of a plum. This is a bark-feeding species; it is found clustered on the under side of limbs in summer. It infests hickory^ maple, and several other forest trees. The oviparous female is wingless; the male, winged. b. LEAF-FEEDING APHIDIN^ Examples of the leaf-feeding species belonging to this subfamily can be found on a great variety of plants. Among those most easily observed are the species infesting the leaves of fniit trees, and especially the following. The apple-leaf aphis. Aphis pomi. — This is a bright green species, the entire life-cycle of which is passed on the apple. The migrants fly to other parts of the infested tree or to other apple-trees. As a result of the attacks of this species the leaves of the apple are often badly curled and sometimes drop off the tree. The rosy apple-aphis, Anuraphis rdseus. — -The common name of this species refers to the fact that the agamic females are usually of a pinkish color; but they may vary in color to a light brown, slaty gray, or greenish black, with the body covered with a whitish coating. This species is most common on apple; but it infests also pear, white thorn, and three species of Sorbus. It is a migrating spe- cies. HOMOPTERA 419 The appie-bud aphis, Rhopalosiphum pruniJolicB. — This is the species that most commonly infests the opening apple-buds, often nearly covering them. It also infests pear, plimi, quince, and many other plants. It is a migrating species; various species of grain serve as its secondary host. C. ROOT-FEEDING APHIDIN^ The corn-root aphis, Anuraphis maidi-radtcis . — This is a serious pest of corn throughout the principal corn-growing States, sometimes totally ruining fields of corn. Broom-corn and sorghum are the only other cultivated crops injured by it ; but it infests many species of weeds that grow in corn-fields. Our knowledge of this species is largely the result of investigations of Professor S. A. Forbes, who has published several detailed accounts of it in his reports as State Entomologist of Illinois. This author found that this aphid is largely dependent on a small brown ant, the corn-field ant (Ldsitis americdims), the nests of which are common in corn-fields. The ants store the winter eggs of the aphids in their nests and care for them throughout the winter. In the spring, when the stem-mothers hatch, they are trans- ferred by the ants to the roots of the weeds upon which they feed. As soon as corn-plants are available, the ants transfer the aphids to the roots of the corn, the ants digging burrows along the roots of the corn for this purpose. The ants in return for their labors derive honey-dew from the aphids. One can understand how these ants that attend aphids that are excreting honey -dew should learn to drive away the enemies of the aphids, as is often done ; but is it not wonderful that Lasius americanus should recognize the importance of preserving the eggs from which their herds are to develop ! The strawberr}^-root aphid, Aphis forhesi. — The winter eggs of this species are found upon the stems and along the midribs of the green leaves of strawberry plants. The stem-mothers and one or more generations of the offspring feed upon the leaves in the early spring. But a little later in the season the corn-field ant appears and transfers the aphids to the roots of the strawberry, where it cares for them in the same way that in corn-fields it cares for the corn-root aphis. This ant is entirely responsible for the infesting of the roots by the aphids; and it is here that the greatest injury to the plants is done. Subfamily AIINDARIN^ This subfamily was established by Baker ('20) for the reception of the genus Mindarus, which can be distinguished from all other living aphids by the venation of the wings. In this genus the radial sector of the fore wings separates from vein R^ at the base of the 420 AN INTRODUCTION TO ENTOMOLOGY long, narrow stig- ma (Fig. 492). In all other living aphids the origin of the ra- dial sector is much nearer the tip of the wing; but in many of the fossil aphid wings it is as in Mindarus . The males and the oviparous females are small and wing- less; but they retain the beak, at least in most individuals, and feed. The female lays several eggs. Only one species, Mindarus ahietinus, is known. This lives free upon the twigs of spruce and other conifers, which become somewhat distorted and are often killed by the attack of the insects. When disturbed this insect secretes large quantities of honeydew. The life-cycle of this species usually includes only three genera- tions, the stem-mother, the winged agamic females {sexuparce), and the sexual forms. Sometimes there is a generation of wingless agamic females. This species was redescribed by Thomas as Schizoneura pinicola. Fig. 492. — Wings of Mindarus. (After Patch.) Subfamily ERIOSOMATIN^ This subfamily includes those genera of aphids in which the males and the oviparous females are greatly specialized by reduction. They do not have functioning mouth-parts; some have a beak when born but lose it at the first molting; in others the beak is vestigial at birth. As they cannot feed, they remain small. Both sexes are wingless. The oviparous females produce each a single egg, which in some species is not laid but remains throughout the winter in the shriveled body of the female. In this subfamily, the cornicles are much reduced or are wanting ; wax-glands are abundantly developed; and the antennal sensoria are prominent. These are often annular. The members of this subfamily that are most likely to attract attention can be grouped under two heads: a, the woolly aphids; and b, the gall-making Erisomatinse. These groups, however, do not represent natural divisions of the subfamily and do not include all members of it. They are merely used for convenience in the present discussion. a. THE WOOLLY APHIDS The woolly aphids are the most conspicuous members of the Aphididae, on account of the abundant, white, waxy excretion that HOMOPTERA 421 covers colonies of them. The three following species are widely dis- tributed and are common. The woolly apple aphis, Eriosdnia lamgera. — This plant-louse, on account of its woolly covering and the fact that it is a serious pest of the apple, is known as the woolly apple aphis, although the apple is its secondary host. This insect not only has a complicated series of generations but the life-cycle is subject to variations ; its usual course is as follows : The winter-eggs are deposited in crevices of the bark of elm. From these eggs stem-mothers hatch in the spring and pass to the young leaves, where they produce either the well-known leaf-curl of the ekn or, when a group of terminal leaves are affected, what has been termed a rosette, which is a cluster of deformed leaves. Within these pseudogalls the second generation is produced ; this consists of vv^ingless agamic females. The offspring of these, the third generation, become winged and migrate from the elm to the apple. Here they produce the fourth generation, the members of which live on the water-shoots or the tender bark of the apple, and are wingless. The fifth generation also consists of wingless agamic females. Some of these develop on the bark of the branches, which apparently ceases to grow at the point of attack but swells into a large ridge about the cluster of plant-lice, leaving them in a sheltered pit ; the aphids also frequently congregate in the axils of the leaves and the forks of the branches. Other members of this generation pass to the roots of the tree, where they produce knotty swellings on the fibrous roots. The sixth generation consists, in part, of winged agamic females which migrate from the apple to the elm, where they produce the seventh generation. This generation, the last in the series, consists of the males and oviparous females, both of which are beakless and wing- less. These pair and each female produces a single egg, which is found in a crevice of the bark with the remains of the body of the female. The course of events outlined above may be modified in two ways : first, it is said that the sexual forms are sometimes produced on the apple; and second, some members of the sixth generation do not develop wings and migrate, but are wingless and produce young that hibernate on the apple. This species infests also mountain ash and hawthorn, as secondary hosts. The elm-feeding generations of this species that cause the leaf- curls and rosettes have been known as Schizoneura americdna. And there are also found during the summer aphids on tender elm bark which are believed to belong to this species and which have been described under the name Schizoneura rileyi. In the Pacific Coast States there is another species of aphid that produces leaf curl on elm. This is Schizoneura ulmi, a European species, which in Europe has been found to migrate to Ribes. The alder-blight, Proctphilus tesselldtus. — ^A woolly aphid that is found in dense masses on the branches o£ several species of alder is known as the alder-blight. Colonies of this species are easily found 422 AN INTRODUCTION TO ENTOMOLOGY in the regions where it occurs, as their covering of flocculent excretion renders them very conspicuous. These colonies are of especial in- terest, as within them is found the predacious larva of the wanderer butterfly, Feniseca tarquiniiis, which feeds on the aphids. In the late stunmer or early autumn the last generation of wingless agamic females bring forth young, which winter among the fallen leaves at the base of the alder and return to the branches in the spring. From this there appears to be no need of an alternate host. But it was found by Dr. Patch that at the same time that the form that hibernates at the base of the alder is produced, winged migrants appear and fly to maple trees, where they give birth, in the crevices and rough places in the bark, to males and oviparous females. Each of these females produces a single egg. From these eggs there hatch in the spring aphids which pass to the lower side of the leaves of the maple, where they become conspicuous on accotmt of their abundant and long woolly excretion. In this period of its existence this species is the well-known pest of the maple that has long been known as Pemphigus acerjdlii, which name must now be regarded as a synon^mi of Proctphilus tesselldtus, the older name. In July winged migrants are developed on maple which fly to alder. The alder-blight excretes honeydew abundantly; the result is that the branches infested by this insect, and those beneath the cluster of aphids, become blackened with fungi that grow upon this excretion. There is also a curious fungus which grows in large spongy masses immediately beneath the cluster of plant-lice; this is known to bot- anists asScorias spongiosa. It is evidently fed by the honeydew that falls upon it. The beech-tree blight, Prociphilus imbricdtor . — This infests both twigs and leaves of beech. Lilce the preceding species it occurs in clusters of individuals, each of which is clothed with a conspicuous downy excretion. These clusters often attract attention by the curious habit which the insects have of waving their bodies up and down when disturbed. When an infested limb is jarred, the aphids emit a shower of honeydew. Owing to the abundance of this excretion, the branches and leaves of an infested tree become blackened by growths of fungi, as with the preceding species. The life-cycle of this species has not been determined. h. THE GALL-MAKING ERIOSOMATIN^ Certain members of this subfamily cause the growth of remarkable galls, resembling in this respect certain members of the following subfamily. Among the gall-making Eriosomatinee that are most likely to attract attention are the following. The cockscomb elm-gall colopha, Colopha ulmtcola. — There are two species of aphids that make similar galls on the leaves of elm. These galls are commonly known as cockscomb ekn -galls on account of their shape. Those made by the two species of aphids are so similar that a description of one will apply to the other. In each case HO MOP T ERA 423 the gall is an excrescence resembling a cock's conib in form, which rises abruptly from the upper surface of the leaf (Fig. 493, a). It is compressed, and has its sides wrinkled perpendicularly and its summit irregularly gashed and toothed. It opens on the under side of the leaf by a long slit-like orifice. The winter eggs can be found during the winter in the crevices of the bark of the elm; each egg is usually enclosed in the dry skin of the oviparous female (Fig. 493, h). In the spring the stem-mothers ^^=p=F^ Fig. 493. — Colopha ulmicola: a, leaf showing galls from above and beneath; b, fertilized egg surrounded by the skin of the female; c, newly born young of the second generation; h, its antenna; d, full-grown nymph of the second genera- tion; e, adult of second generation; /, antenna of migrant ; g, antenna of stem- mother. (From Riley.) pass to the leaves and each causes by its attack the growth of a gall. The second generation is produced within the gall; it consists of winged agamic females (Fig. 493, e). These migrants can be dis- tinguished from those of the other cockscomb elm-gall aphid by the fact that in this species vein M of the fore wings is forked. The migrants of this species pass from the elm to certain grasses, among them species of Eragrostis and Panicum. The forms found on these secondary hosts have been described under the name Colopha eragrostidis, but this is a much later name than Colopha ulmtcola. 424 AN INTRODUCTION TO ENTOMOLOGY The cockscomb elm-gall tetraneura, Tetraneura gramlnis. — The life-cycle of this species is quite similar to that of the preceding one. The primary host is elm. The stem-mothers cause the growth of cockscomb-like galls; and the migrants produced in these galls pass to grasses. These migrants differ from those of the preceding species in that vein M of the fore wings is not forked. This species was first described from individu- als found on the second- ary hosts and was named Tetraneura gramlnis . Lat- er, forms found on elms were named Tetraneura colophoides . For a detailed ac- count of the gall-aphids of the elm, see Patch Cio). The poplar-leaf gall- aphid, Thecdhius populi- caulis. — This aphid is common on several spe- cies of poplar. It makes a swelling the size of a small marble on the leaf at the junction of the petiole with the blade. This gall is of a reddish tint, and has on one side a slit-like opening. In the early part of the season each gall is occu- pied by a single wingless female, probably the agamic stem-mother, which by midsummer becomes the mother of niunerous progeny. These are winged and probably migrate to some other host-plant; but the life-cycle of this species has not been determined. The vagabond gall-aphid, Mordwilkoja vagabunda.- — This species infests the tips of the twigs of several species of poplar; here it causes the growth of large corrugated galls, which resemble somewhat the flower of the double cockscomb of our gardens. The galls are at first bright green, but later turn black, become woody, and remain on the trees during the winter (Fig. 494). Very little is known regarding the life-cycle of this species. Fig. 494. — The vagabond i)oplar-gall. Walsh and Riley.) (From Subfamily HORMAPHIDIN^ The members of this subfamily are usually gall-makers, resembling in this respect certain members of the Eriosomatinse, and also re- sembling them in that the antennal sensoria are annular. But in this subfamily the sexual forms are not so specialized by reduction as in the preceding one. In the Hormaphidinffi, although the males and the oviparous females are small and wingless, they possess HOMOPTERA 425 beaks, they feed, and the oviparous female lays more than one egg. In this subfamily great specialization of wax-producing organs occurs. In many species some of the agamic generations become greatly modi- fied in form so that they do not resemble the more typical aphids. In some species these modified forms have the appearance of an Aleyrodes; in other species, that of a coccid. Our best-known representatives of this subfamily are two species of gall-makers, each of which infests alternately witch-hazel and birch. The life-histories of these were ver\' carefullv worked out bv Fig. 495. — The witch-hazel cone-gall: a, natural size; b, section of gall, enlarged. (From Pergande.) Pergande ('01); the followini:: accounts are greatly condensed from that author. The witch-hazel cone-gall aphid, Hormaphis hamamelidis. — The winter-egg is deposited on the branches and twigs of witch-hazel and hatches early in the spring. The stem -mother, which hatches from this egg, attacks the lower surface of the leaf, causing the growth of a conical gall on the upper surface of the leaf with a mouth on the lower surface (Fig. 495). The second generation, the offspring of the stem-mother, consists of many individuals; these are pro- duced within the gall, which becomes crowded with them. These are agamic females, which become winged, leave the gall, and mi- grate to birches, where they deposit their young on the lower side of the leaves. The first instar of the third generation, the offspring of the migrants, is broadly oval, with the entire margin of the body 42G AN INTRODUCTION TO ENTOMOLOGY studded with short and stout excretory tubercles (Fig. 496); from each of these there issues a short, glassy, beautifully iridescent, waxy rod. The second and third instars of this generation are marked by a reduction of the antennae, beak, and legs. The fourth instar, which is found about the middle of June, is aley- rodiform (Fig. 497). The fourth and fifth generations resemble the third, there be- ing three aleyrodiform gen- erations. The members of the sixth generation become winged and are the return migrants. These fly to witch-hazel, where they give birth to the seventh genera- tion, which consists of males and oviparous females. These pair and the females lay the winter eggs; each female produces from five to ten eggs. The males and In this species the antenna Fig. 496.^ — Hormaphis hamamelidis , first instar of the third generation. (From Pergande.) the oviparous females are both wingless. of the winged forms are three-jointed. Later experiments by Alorgan and Shull ('10) indicate that this species can complete its life-cycle on the witch-hazel. According to these ,,r"',-T7 authors there are only three genera- , "^ ''■"",' '"*'''- /, tions; first, the stem-mother, which causes the growth of the cone-gall; second, the winged forms, which are developed in the gall and which spread to the leaves ; and third, the males and oviparous females. No aleyrodiform individuals were found on the witch- hazel. The spiny witch-hazel-gall aphid, Hamameltstes spinosus.— The winter eggs of this species are commonly de- posited near the flower-buds of witch- hazel, late in June or early in July, but they do not hatch till May or June of the following year. The stem-mother attacks the flower-bud. which becomes transformed into a large gall of the form shown in Figure 498. Within this gall the stem-mother produces the second generation; these crowd the gall and develop into winged migrants, which leave the gall, from July to late fall, and fly to birches. The Fig. 497. — Hormaphis hamamel- idis, foiirth instar of the third generation. (After Pergande.) HOMOPTERA 427 young of the migrants, the third generation, feed a short time and then settle close to the leaf-buds, where they hibernate; the last in- Fig. 498. — The spiny witch-hazel gall: a, mature gall; b, section of gall. (From Pergande.) star of this generation resembles a coccid (Fig. 499). The fourth generation is produced early in the spring ; the young of this genera- tion move to the young and tender leaves of the birch, which, as a Fig. 499- — Hamamelistes spinosus, last instar of the third generation, much enlarged: a, dorsal view; b, lateral view; c, ventral view; d, antenna; <5 /, g, legs. (From Pergande.) result of the attack, become corrugated, the upper surface bulging out between the veins, and the folds closing up below. In these 428 AN INTRODUCTION TO ENTOMOLOGY pseudogalls the fifth generation is produced; the members of this generation become winged and migrate to witch-hazel in early summer, where they produce the seventh and last generation of the series, the males and oviparous females. These pair and the females soon lay their eggs. Both sexes are wingless. The winged migrants of this species can be distinguished from those of the preceding species by their five-jointed antennae Family PHYLLOXERID^ The Adelgids and the Phylloxerids The members of this family differ from the typical aphids in that both the sexually perfect females and the parthenogenetic forms lay eggs, in lacking vein Ri of the fore wings, and in that the outer part of the stigma is bounded behind by the radial sector (Fig. 500). Sc.-R^M^Cu^li^-^ g^ Fig. 500. — Wings of Adelges. (From Patch.) In this family the cornicles are always wanting; and the males and sexually perfect females are dwarfed and wingless. This family includes two subfamilies, which can be separated by the following table. These subfamilies are regarded as distinct families by some writers. A. The wingless agamic females excrete a waxy flocculence. The winged forms have five-jointed antennae, the last three segments of which bear each a single sensorium. The wings are held roof-like when at rest. The free part of vein Cu of the fore wings is separate from vein 1st A (Fig. 500). The sexual forms have a beak. The alimentary canal is normal, producing a fluid excrement. The species infest only conifers Adelgin^ AA. The wingless agamic females do not secrete a waxy flocculence, but in the genus Phylloxerina they excrete a waxy powder. The winged forms have three-jointed antenna, the second segment of which bears two sensoria. The wings when at rest are laid flat upon the abdomen. The free parts of veins Cu HOMOPTERA 429 and 1st A of the fore wings coalesce at base (Fig. 501). The sexual forms have no beak. The anus is closed. The species do not infest conifers Phylloxerin^ Sc+lt+Jf+Cif + IsfA Fig. 501 . — Wings of Phylloxera. (From Patch.) Subfamily ADELGINvE The Adelgids This subfamily includes those insects found on conifers that have been quite generally known under the generic name Chermes. But it has been determined that this name should be applied to certain jumping plant-lice of the family Chermidce, formerly known as the Psyllidae. The necessity of this change is very unfortunate, as much has been published regarding members of the Adelginae and in most of these accounts they are described under the name Chermes. All the species of this subfamily infest conifers; and in all cases in which the sexual generation is known, this generation lives on spruce. The secondary host may be either larch, pine, or fir. Much has been written regarding the life-histories of these insects. It has been found that what may be regarded as the t^'pical life-cycle of an Adelges or ''Chermes' is a very complex one, including the developing of two parallel series of forms differing in habits ; that in one of these series a single host-plant, spruce, is infested and the life- cycle is completed in one year; while in the other series the life-cycle extends over two years and is passed in part upon spruce and in part upon larch or some other host-plant. In this typical life-cycle, beginning with the individual that hatches from a fertilized egg, there are developed five generations, the members of which differ in either form or habits or both from those of the other generations, before the cycle is completed by the production again of fertilized eggs. The actual number of generations may be greater than this, owing to the fact that in a part of the cycle there may be a series of similar generations only the first of which is counted in this enumeration. 430 AN INTRODUCTION TO ENTOMOLOGY This indicating of a typical life-cycle is an effort to outline as simply as possible the life-history of these insects. In some species it is much more complicated; thus, for example, Borner ('08) in his account of the life-history of Cnaphalodes strohildhius recognizes seven parallel series of forms. The distinctive characters of the five differing generations in the typical life-cycle are indicated below. A. GENERATIONS ON SPRUCE (Picea) A one-year cycle or the first year of a two-year cycle. First generation. — This consists of the true stem-mother {fimdatrix vera), a wingless agamic female. In the case of those supposed parthenogenetic species vvhich do not migrate to another host-plant and which complete their life-cycle in one year, this form is the offspring of the second generation, an agamic fortn; in the case of species that migrate to a secondary host-plant, and where there are two parallel series, the stem-mother is the offspring of either the second generation or the fifth generation, the sexual forms. The stem-mothers hatch in the autumn; they hibernate immature in crevices at the bases of buds, complete their growth in the spring, and by their attack upon the buds cause the beginning of the growth of galls. Each stem-mother lays a large number of eggs. Second generation. — The members of this generation hatch from the eggs laid by the stem-mothers, and by their attack upon the buds cause the completion of the growth of the galls. The galls are formed by the hypertrophy and coalescence of the spruce-needles. The members of this generation have been termed the gallicolce, because they inhabit the galls. They reach the last nymphal instar within the galls. When this stage is reached, the galls open and the nymphs emerge and soon molt, becoming winged agamic females. As to their habits, there are two types of gallicolae: first, the non-migrants, which remain on the spruce and lay the eggs from which the stem-mothers of the one-year cycle are hatched; and second, the migrants, which fly to a secondary host-plant, which is not spruce, and where they lay many eggs, but not so many as are laid by the stem-mothers. B. GENERATIONS ON A SECONDARY HOST Part of the second year of a two-year cycle. The secondary host may be a species of either larch {Larix), pine (Pinus), or fir (Abies); but no galls are produced on any of these. Third generation. — The members of this generation hatch from eggs laid by migrants of the second generation that have flown from spruce to larch or other secondary host and laid their eggs there. The young that hatch from these eggs hibernate in crevices in the bark and complete their growth in the spring, becom- ing wingless agamic females. The members of this generation and of similar generations which follow immediately but which are not numbered here, are termed colonici, because they are settlers in a new region, or exsides, that is, exiles. Some writers term the first of this series of generations false stem-mothers {fundatrices spiirice) to distinguish them from the true stem-mother, which is the beginning of the two-year cycle. The members of the third generation resemble those of the first generation, but usually lay fewer eggs and do not cause the growth of galls. The offspring of the third generation are all wingless agamic females, which reproduce their kind. Of these there may be a series of generations, which are not numbered in this generalized statement; and there may be among these several parallel series of generations, differing in the life-cycle but all reproducing parthenogenetically on the secondary host. The secondary host may be thus infested throughout the year; while the primary host, if there is not an annua] series, will be free during the interval between the migration of the second genera- tion and the return migration of the fourth generation. HO MO PT ERA 431 Among the offspring of the third generation two types are recognized by ^larchal ('13): first, nymphs which remain undeveloped for a time, the sistens type; and second, nymphs which develop at once into wingless agamic females, the progrediens type.* Fourth generation. — The members of this generation are produced by indi- viduals of the progrediens type of the third generation. They develop into winged agamic females. The adults migrate to spruce and there lay a small number of eggs. Since their offspring are the sexual forms, this generation is known as the sexuparcB. C. A GENERATION ON SPRUCE The completion of the second year of a two-year cycle. Fifth generation. — From eggs laid by the sexuparas that have migrated from the secondary host to spruce, there are developed males and sexually perfect females, termed the sexuales; both of these forms are wingless. They pair and each female lays a single egg. These eggs hatch in the autumn; the young hibernate and become the true stem-mothers. Thus is completed the two- year life-cycle. Omitting the annual series, the typical two-year life-cycle includes the follow- ing series of generations, which are described above. First. — The wingless agamic stem-mother. Second. — The winged agamic migrants. Third. — The wingless agamic colonici or exsules. (a) The sistentes, several generations. (b) The progredientes, several generations. Fourth. — The winged agamic sexuparae. Fifth. — The wingless sexuales, males and sexually perfect females. Each female produces a single fertilized egg, from which hatches a stem-mother, thus completing the life-cycle. In the case of some species, which have been studied very carefully by different observers, only an annual series, consisting of the first and second generations described above, is known. It should be noted that in a lif e-c>xle of this kind there are no sexual forms and that although a winged form appears it is not known to migrate. These facts indicate that either some members of the winged generation migrate to a secondary host-plant which has not been discovered, or that the species in question have become, by adaptation, purely par- thenogenetic. Which of these alternatives is true has been much dis- cussed. The following species are some of the more common of our repre- sentatives of this subfamily. The pine-leaf adelges, Adelges pinijolice. — Our knowledge of the life-history of this species is still fragmentar>^ In one part of its life- cycle it infests the leaves of white pine {Pinus strobus). The genera- tions found here are winged agamic females. These attach them- selves firmly to the pine-needles, each with its head directed towards the base of the needle. Within each there are developed about one hundred eggs, which are not extruded. After the death of the female, the mass of eggs remains adhering to the leaf, covered over and "Sistens, Latin sisto, to stand; progrediens, Latin pro, forth, gradior, to go. 432 AN INTRODUCTION TO ENTOMOLOGY g. 502. — Gall of Adelges pinifolicB on spruce. protected by the remains of the body and closed wings of the dead insect. It has been determined that these plant- lice infesting the pine leaves are specifically identical with those that issue from a cone- like gall found on several species of spruce (Fig. 502). The spruce-inhabiting form has been known as Chermes abieticolens; but -piniJolicB is the older specific namo and should be used for all forms of this species. It is probable that this species has a two- year life-cycle and that spruce is its primary host and pine its secondary host. The green-winged adelges, Adelges ahle- tis. — This species causes the growth of pine- apple-shaped galls on several species of spruce (Fig. 503). It is a European species and its life-history has been the subject of m.uch controversy. It is held by Borner ('08) that it has a typical life-cycle in which there are two parallel series: first, an annual series on spruce alone; and second, a two-year series in which larch is used as a secondary host. On the other hand, Cholodkovsky ('15) maintains that it is a parthenogenetic species; that its life- cycle includes only two generations, the agamic hibernating stem-mothers and the gallicolae; and that the form with a typical life-cycle is a distinct species {Chermes viridis). Dr. Patch ('09) has studied Adel- ges abietis in Maine and has found only the parthenogenetic forms, the hibernating stem- mothers and the gallicolse; thus confirming the conclusion that it may have become a parthenogenetic species. The pine-bark adelges, Adelges pinicorti- cis. — This species infests several species of pine, but especially white pine. The trunks and larger limbs of the infested trees often -Gall of Adelges ^PPff^ ^^ '^ whitewashed; this is due to the woolly excretion which covers the bodies 01 the insects. But little is known regarding the life-cycle of the species. Wingless females, which are doubtless agamic as they lay many eggs, hibernate on the pine and feed on the bark in the spring. They lay their eggs in April; these soon hatch and the young develop into winged agamic females in May. These soon dis- appear and the pine is said to be free from the pest during the simimer. Return migrants to the pine have not been observed; but there must be a generation of these, the parents of the wingless hibernating Fig. 503-- ahietis. no MO PT ERA 433 generation, if, as stated, the pines are free from the pest during the summer. Subfamily PHYLLOXERIN^ The Phylloxerids The distinguishing characters of this subfamily are given under AA in the table on page 428 and need not be repeated here. It in- cludes two genera, Phylloxera and Phylloxerina. The genus Phylloxerina is distinguished by the fact that the wingless agamic females excrete a waxy powder, which gives them the appearance of mealy-bugs. Species of this genus have been found in this countn^ on poplar, willow, and sour-gum. The genus Phylloxera is represented by the grape Phylloxera and thirty or more described species that infest forest-trees — hickory, oak, and cnestnut. Most of these are found on hickory. Those on hickory cause the growth of galls either on the leaves or on the tender twigs and petioles. Other species produce either pseudogalls or white or yellowish circular spots on the infested leaves. The species infesting forest -trees were monographed by Pergande ('04). Although in this subfamily there is a generation of winged mi- grants in the life-cycle of each species, few if any of them have a secondary host. The migrants fly to other parts of the infested plant or to other plants of the same species. So far as is known, the life-c3-cle of the species infesting forest-trees is a comparatively simple one. The stem-mother hatches in the spring from an over-wintering, fertilized egg and causes the growth of a gall; she develops within the gall and produces unfertilized eggs. From these eggs hatch young that develop into winged agamic females. These produce eggs of two sizes; from the smaller eggs hatch males; and from the larger ones, females. The sexes pair and each female lays a single fertilized egg. In some species these eggs are laid in June and do not hatch till the following April. The grape Phylloxera, Phylloxera vastdtrix. — From an economic standpoint this species is the most important member of the Phyl- loxerinse; millions of acres of vineyards have been destroyed by it.* The most extensive ravages of this pest have occurred in France and in California. This species is a native of the eastern United States, where it infests various species of wild grapes. It does not injure these seriously; but when it was introduced into France it was found that the European grape, Vitis vinifera, is extremely sus- ceptible to its attack. The great injury to the vineyards of California is due to the fact that it is the European grape that is chiefly grown there. The presence of this insect is manifested by the infested vines in two ways: first, in the case of certain species of grapes, there *"The Phylloxera when at its worst had destroyed in France some 2,500,000 acres of vineyards, representing an annual loss in wine products of the value of 150,000,000." (Marlatt '98.) 434 AN INTRODUCTION TO ENTOMOLOGY ^>^# Fig. 504. — Leaf of grapewith galls of Phylloxera. (From Riley.) appear upon the lower surface of the leaves galls, which are more or less wrinkled and hairy (Fig. 504), which open upon the upper surface of the leaf, and each of which contains a wingless, agamic plant-louse and her eggs; second, when the fi- brous roots of a sickly vine are examined, we find, if the disease is due to this insect, that the minute fibers have become swollen and knotty; or, if the disease is far ad- vanced, they may be en- tirely decayed (Fig. 505, c). Upon these root-swellings there may be found wing- less, agamic, egg-laying plant-lice, the authors of the mischief. The life-history of this species is a complicated one, due to the fact that parallel series of generations with different life-cycles may be developed at the same time. While a fertilized winter egg may be considered a part of the typical life-cycle, some of the agamic females hibernate on the roots of the vine and form a part of a series of agamic generations that apparently may continue indefinitely year after year. The typical life-cycle, that one in which males and sexually perfect females form a part, extends over two years and includes four forms as follows : The gallicolcB. — From an over-wintering fertilized egg, there hatches in the spring a wingless agamic stem-mother, which passes to a leaf and by her attack causes the growth of a gall, within which she passes the remainder of her life. She reaches maturity in about fifteen days, fills the gall with eggs, and soon dies. The young that hatch from the eggs laid by the stem-mother resemble her in being wingless agamic females; they escape from the gall, spread over the leaves, and in turn cause the growth of galls. Six or seven generations of this form (Fig. 506) are developed during the simimer. They are termed the gallicolcs. The radicicolce or colonici. — On the appearance of cold weather, young hatched from eggs laid by the gall-inhabiting form pass down the vines to the roots, where they hibernate. This completes the first year of the two-year cycle. In the following spring these colonici, that is, settlers in a new region, attack the fibrous roots, and cause the growth of knotty swellings on them (Fig. 505, b, c) and ultimately their destruction. This is the most serious injury to the vine caused by this species. There is a series of generations of the root-inhabiting HO MOP T ERA 435 form all of which are wingless agamic females. This form (Fig. 507) differs somewhat in appearance from the gallicolae. The migrants or sexuparcB.- — -During the late summer and fall there are hatched from eggs laid by some individuals of the root-inhabiting Fig. 505. — Phylloxera, root-inhabiting form: a, shows a healthy root; b, one on which the hce are working, representing the knots and swellings caused by their punctures; c, a root that has been deserted by them, and where the rootlets have commenced to decay; d, d, d, show how the lice are found on the larger roots; e, agamic female nymph, dorsal view; /, same, ventral view; g, winged agamic female, dorsal view; h, same, ventral view; i, magnified antenna of winged insect; j, side view of the wingless agamic female, laying eggs on roots; k, shows how the punctures of the lice cause the large roots to rot. (From Riley.) form, young that develop into winged agamic females (Fig. 505, g, h). These come forth from the ground, fly to neighboring vines, and lay eggs in cracks in the bark or under loose bark. They lay only a few eggs, from three to eight. 436 A IS INTRODUCTION TO ENTOMOLOGY Fig. 506. — Phylloxera, gall-inhabiting form: a, b, newly hatched nymph, ventral and dorsal views ; c, egg ; d, section of gall ; e, swelling of tendril ; /, g, h, mother gall-louse, lateral, dorsal, and ventral views; i, her antenna; j, her two-jointed tarsus. Natural sizes indicated at sides. (From Riley.) The sexuales. — The eggs laid by the winged migrants are of two sizes ; from the smaller eggs there hatch males ; and from the larger eggs, sexually perfect fe- males. These pair and each female pro- duces a single egg, which is laid in the fall on old wood. Here it remains over winter, and from it in the fol- lowing spring a stem- mother is hatched. This completes the two-year life-cycle. Control.- — Owing to the great injury that this species has done to vineyards, hundreds of memoirs have been published regarding it; but, as yet, no satisfactory means of destroying it that can be generally used has been discovered. Where the soil conditions are favor- able it can be destroyed by the use of carbon-bi- sulphide, but this is an expensive method ; where the vineyards are so situ- ated that they can be submerged with water at certain seasons of the year, the insect can be drowned ; and it has been found that vines growing in very sandy soil are less liable to be seriously in- jured by this pest. While it is usually im- practicable to destroy this pest in an infested vineyard, there is a pre- ventative measure that has given good results. Fig. 507. — Phylloxera, root-inhabiting form: a, roots of Clinton vine showing the relation of swellings to leaf -galls, and power of resisting de- composition; b, nymph as it appears when hibernating; c, d, antenna and leg of same; e, f, g, forms of more mature lice; h, granulations of skin; i, tubercle; j, transverse folds at border of joints; k, simple eyes. (From Riley.) HOMOP TERA 437 Certain varieties of American grapes are not seriously injured by the root-form of the Phylloxera. By growing these varieties, or by using the roots of them as stocks on which to graft the susceptible European varieties, the danger of injur^^ by this pest is greatl}' reduced. Fig. 509. besii. -Aleurochiton for- Family ALEYRODID^ The Aleyrodids or White Flies The members of this family are small or minute insects ; our more common species have a wing-expanse of about 3 mm. In the adult state both sexes have four wings, differing in this respect from the Coccidag, with which they were classed by the early entomologists. The wings are transparent, white, clouded or mottled with spots or bands. The wings, and the body as well, are covered with a whitish powder. It is this character that suggested the name of the typical genus,* and the common name white flies. In the immature stages, these insects Fig- 508. — Analeyrodid are scale-like in form and often resemble somewhat certain species of the genus Lecanium of the family Coccidas. Except during the first stadium, the larvae remain quiescent upon the leaves of the infested plant and in most species are sur- rounded or covered by a waxy excretion. In Figure 508 there is represented one of the many forms of this excretion. Here it consists of parallel fibers, which ra- diate from the margin of the body, and its white color contrasts strongly with the dark color of the insect. In some species the fringe of excretion is wanting; and in others, the excretion from the margin of the body, in- stead of extending laterally and forming a fringe, is di- rected toward the leaf upon which the insect rests, and Fig. 510. — Wings of Udamoselis. (After En- derlein, with changed lettering.) *Aleyrodes (a\evpd)8r]s), like flour. 438 AN INTRODUCTION TO ENTOMOLOGY thus the body is Hfted away from the leaf and is perched upon an exquisite pahsade of white wax (Fig. 509). The members of this family feed exclusively on the leaves of the host-plants. With few exceptions they are not of economic impor- tance ; and also with few exceptions, the injurious species are not wide- ly distributed over the world as are many aphids and coccids. This is probably due to the fact that as they live exclusively on leaves they are not so liable to be transported on cuttings and nursery stock. They are most abundant in tropical and semi-tropical regions. The adults present the following characters : The compound eyes are usually constricted in the middle and in some species each eye is completely divided. In some cases the facets of the two parts of a divided eye are different in size ; it is probable that in such cases one part is a day-eye and the other part a night-eye (see page 1 44) . The ocelli are two in number; each ocellus is situated near the anterior margin of a compound eye. The antennae are usually seven-jointed. The labium is composed of three segments. The fore wings are larger than the hind wings; when at rest the wings are carried nearly horizontally. The venation of the wings is greatly reduced; the maximiun number of wing-veins found in the family is in the fore wings of the genus Udamoselis (Fig. 510). The three pairs of legs are similar in form; the tarsi are two-jointed; and each tarsus is furnished with a pair of claws and an empoditim or paronychium. The anus opens on the dorsal wall of the abdomen at some distance from the caudal end of the body and within a tubular structure, which is termed the vasiform orifice. A tongue-like organ, the lingtda, projects from the vasiform orifice; and at the base of the lingula there is a broad plate, the operculum; the anus opens beneath these two organs. In this family the type of metamorphosis corresponds quite closely with that known as complete metamorphosis; consequently the term larva is applied to the immature instars except the last, which is designated the pupa. The eggs are elongate-oval in shape and are stalked. The larvse during the first stadiimi are active, after which they remain quiescent. There are four larval and one pupal instars. The wings arise as histoblasts in the late embryo, and the growth of the wing-buds during the larval stadia takes place inside the body-wall. The change to the pupal instar, in which the wing-buds are external, takes place beneath the last larval skin, which is known as the pupa- case or puparium. In matiy descriptions of these insects only three larval instars are recognized, the fourth being described as the pupa. As the change to a pupa takes place beneath the last larval skin, the puparium, and as the adult emerges through a T-shaped opening in the dorsal wall of the puparium, the pupa itself is rarely observed. Parthenogenesis occurs in this family; but according to the observations of Morrill, unfertilized eggs produce only males. As with the adults, the anus of the immature forms opens in a vasiform orifice on the dorsal aspect of the body at some distance HOMOPTERA 439 from the caudal end of the body. The excrement is in the form of honey-dew, of which much is excreted. Formerly all the members of this family were included in a single genus, Aleyrodes; consequently, except in comparatively recent works, the various species are described under this generic name. In later days, very extended studies have been made of the family ; and the Fig. 511. — AsterocUton vaporariorum: a, egg; b, larva, first instar; c, puparium, dorsal view; d, puparium, lateral view; e, adult. (After Morrill.) genus Aleyrodes has been divided into many genera, which are now grouped into three subfamilies. The most complete systematic works on the family are those of Quaintance and Baker ('13 and '17). The following species are among our more common representatives of the family. The greenhouse white fly, Asterochiton vaporariorum. — One of the most important of the greenhouse pests is this insect, which infests very many species of plants that are grown under glass ; and some- times it is a serious pest in the open on tomato and other plants that are set out after the weather is warm. The adult measures about 1.5 mm. in length, and like other aleyrodids is covered with a white, waxy powder. The eggs are only .2 mm. in length, and are suspended from the leaf by a short stalk (Fig. 511, a). In the first instar the larva is flat, oval in outline, and with each margin of the body furnished with eighteen spines (Fig. 511, b), of which the last is much the longest. In the second and third instars there are only three pairs of marginal spines, a very small pair near the cephalic end of the body and two somewhat larger ones near the caudal end. The marginal fringe of wax is 440 AN INTRODUCTION TO ENTOMOLOGY narrow. The puparium is box-like, the body of the insect being elevated on a paHsade of vertical wax rods (Fig. 511, d). There are other rods of wax represented in the dorsal view of the puparium (Fig. 511, c). The most successful means of destroying this pest is by fumigation of infested greenhouses with hydrocyanic acid gas. The strawberry white fly, Asterochiton packardi. — This species is closely allied to the greenhouse white fly, but differs in minute char- acters presented by the spines and wax rods of the immature forms. It infests strawberry plants, and is a hardy species, passing the winter in the egg state out of doors. The citrus white fly, Dialeurodes cUri. — This is a well-known pest in the orange-growing sections of our country, and is also found in greenhouses in the North. It infests all citrus fruits grown in this countr}^ and is found on several other plants. This insect injures its host in two ways: first directly, by sucking the sap from the leaves; and second indirectly, by furnishing nourish- ment, in the form of honeydew.to a fungus, the sooty mold {Meliola camellia), which forms a dark -brown or black membranous coating on the leaves and fruit, and thus interfering with the functioning of the leaves, retarding the ripening of the fruit, and decreasing the yield of the fruit. There are from two to six generations of this species in a year. An extended account of it is given by Morrill and Back('ii). The maple white fly, Aleurochiton Jorhesii. — Figure 509 represents this species, which is fairly common on maple, but rarely in sufficient numbers to do serious injury. Family COCCID^ The Scale-Insects or Bark-Lice, Mealy-Bugs, and others The family Coccidge includes the scale-insects or bark-lice, the mealy-bugs, and certain other insects for which there are no popular names. To this family belong many of the most serious pests of horticulturists; scarcely any kind of fruit is free from their attacks; and certain species of scale-insects and of mealy-bugs are constant pests in greenhouses. Most of the species live on the leaves and stems of plants; but some species infest the roots of the host-plants. The great majority of the species remain fixed upon their host during a part of their life-cycle, and can thus be transported long distances while 3 et alive, on fruit or on nursery stock ; this has resulted in many species becoming world-wide in distribution. Most of the species are minute or of moderate size ; but some members of the family found in Australia measure 25 mm. or more in length. While the economic importance of this family is due chiefly to the noxious species that belong to it, it contains several useful species. The most important useful species at this time is the lac-insect, Tachardia Idcca. The stick-lac of commerce, from which shell-lac HOMOPTERA 441 or shellac is prepared, is a resinous substance excreted by this species, which lives on the young branches of many tiopical trees, most of which belong to the genus Ficus, the figs. In the past, several coccids have been important as coloring agents. The bodies of the lac-insects, which are obtained from stick-lac in the manufacture of shellac, are the source of lac-dye. Another coccid, Kernies Uicis, which lives on a species of oak in southern Europe, has been used as a dye from very early times. And the well-known Pig. 512. — Chionaspis furfura: /, scales on pear, natural size; Ja, scale of male, lb, adult male, ic, scale of female, enlarged. cochineal is composed of the dried bodies of a coccid, Coccus cacti, which lives on various species of cactus. Recently these dyes have been largely supplanted by those obtained from coal-tar. China-wax is also produced by a coccid. It is the excretion of an insect known as pe-la, Ericerus pe-la, and was formerly much used in China in the manufacture of candles, before the introduction of paraffin. In the adult state, the two sexes of coccids differ greatly in form. The males are usually winged (Fig. 512); in a few species they 442 AN INTRODUCTION TO ENTOMOLOGY are either wingless or have vestigial wings. The fore wings are usually large, com- pared with the size of the body ; the hind wings are always greatly reduced in size; usually they are a pair of club-shaped hal- teres, but in a few forms they are more or less wing -like. Each hind Fig. 5I3-— Wing of P seudococcus . (From Patch.) ^-^^^ -g f^j-nished with a bristle, which is hooked at the end and fits into a pocket or fold on the inner margin of the fore wing of the same side; in a few spe- cies there are two or three or more of these hamuli. The venation of the fore wings is greatly reduced; a wing of Pseudococcus (Fig. 513) will serve to illustrate the usual type of wing- venation found in this family. The legs are wanting in many adult females, having been lost during the metamorphosis. In adult males they are of ordinary form; except in a few species, the tarsi are one-jointed, and each is furnished with a single claw^ Accompanying the tarsal claw there are often a few long, clubbed setae, the digitules (Fig. 514) ; these are tenent hairs ; some of the digi- tules arise from the tip of the ^.-—7 ^-^""X"""- — -^ d tarsus, and some from the claw. The caudal end of the ab- domen of the male usually bears a slender tubular pro- cess, the s^j'/h 5. In some spe- cies the stylus is as long as or even longer than the abdomen ; in others it is short, and in some it is apparently wanting. The stylus serves as a support for the penis, which is protruded from it and in some species is very long. The female coccid is always wingless, and the body is either scale- like or gall-like in form, or grub-like and clothed with wax. The waxy covering may be in the form of powder, of large tufts or plates, of a continuous layer, or of a thin scale, beneath which the insect lives. The eyes of coccids exhibit varying degrees of degeneration and retardation of development. The extreme of degeneration is found in the females, where there is only a single simple eye on each side of the head; this is probably a vestige of a compound eye. In the adult males of the more generalized forms, compound eyes are present ; and in some of these forms, there are also ocelli, two in some and three in others. When compound eyes are present the facets are usually large, and not closely associated. In the more specialized forms, instead of compound eyes there are on each lateral half of the head from two to eight widely separated simple eyes, which may be scattered vestiges of compound eyes. Fig. 514. — Leg of a female Lecanium: digitules. no MO PT ERA 443 Fig. 515. — A depigmented "acces- sory eye" of Psetidococcus de- structor: c, cornea; h, corneal hypodermis ; i, iris cell; r, reti- nal cells; n, nerve. The structure and development of the eyes of the male of the common mealy- bug, Pseudococciis (Dactylopms) destructor, was studied by Krecker ('09). In this insect there is on each side of the head a very small eye; since these are the only eyes possessed by the young nymphs, they were termed by Krecker the primary eyes. In the adult, in addition to the primary eyes, there are two pairs of eyes, one pair on the dorsal aspect of the head, and a second pair on the ventral aspect; these he termed the accessory eyes. The so-called primary eyes are very de- generate, in the adult at least. There is a lens below which there are a few retinal cells; but there is no corneal hypodermis, no rhab- doms, and no iris. The development of the so-called acces- sory eyes is greatly retarded. The histo- blasts from which they are developed appear in the latter part of the second nymphal stadium or in the beginning of the third; these are thickenings of the hypodermis. When fully developed as seen in the adult, the accessory eyes (Fig. 515) have a large circular cornea, followed by a comparatively thin layer of corneal hypodermis, encircling which is a single row of large iris cells. Below the corneal hypodermis there is a crescent- shaped area of polygonal rods (rhabdoms), which are terminally situated upon the ret- inal cells. From the proximal end of the retinal cells extend the nerve fibrils which join to form the optic nerve, which follows the contour of the head to enter the bram lateral- ly. Reddish brown pigment fills the retina, the iris, and also a ridge surrounding the eyes. There are no cells which function as pigment cells alone. The antennas of the males are lon^ and slender, and consist of from six to thirteen segments; in some of the Margarodinag they are branched or fiabellate. The antennce of adult females exhibit great variations in structure; they may be well developed and consist of as many as eleven segments; or they may be greatly reduced in size and in the number of segments; in some species they are either vestigial or entirely wanting in adult females. The mouth-parts are situated on the hind part of the ventral aspect of the head, and often extend caudad of the first pair of legs. In front of the beak there is a densely chitinized area, which includes the clypeus, Fig. 516.— Mouth-parts of a ^^gjabj^jj^ and themandibularandmaxillary cWtwied'Jfin ftrS^elerites. In cleared specimens there can be the beak; B, the beak; /, seen withm this area a complicated endo- labrum; 0, oesophagus; skeleton (Fig. 516, A). s, loop of mandibular and 'pj^g labium (Fig. 516, B), which is com- maxillary sete^Jn ^the^^^^^ termed the beak or rostrum, ^consists crumena lese.) of three segments in a few forms found in 444 AN INTRODUCTION TO ENTOMOLOGY New Zealand, but usually it is more or less reduced, consisting either of two segments or of only one ; in a few subfamilies it is wanting in the adult. The mandibular and maxillary setae are wanting in the later nj-mphal instars of some forms, in some adult females, and in all adult males. These set£e, when present, are usually long, frequently longer than the body, and in some species sev- eral times as long. When not exserted, they are coiled within a pouch, termed the crumena, only their united tips extending to the labium. The crumena is a deep invagination of the body-wall, which extends far back into the body-cavity. Its walls are delicate, and not easily observed; but the coiled setae within it can be easily seen in cleared specimens (Fig. 516, s). In the classification of coccids, the characters most used are those presented by the female, although those of the male are used to some extent . The most available characters of the female are the following : first, the general form of the body; second, the form of the waxy excretions; third, the structure of the caudal end of the body; and fourth, the form and position of the pores through which the wax is excreted. To study the third and fourth classes of characters listed above, it is necessary to remove the wax, to clarify the body, and, in some cases, to stain it. The method most commonly used for removing the wax and clarifying the body is to boil the specimen in a ten per cent, aqueous solution of caustic potash. P'or staining the body. Gage ('19) found that a solution of saurefuchsin was most satisfactory; his formula for the preparation of this solution is as follows: Saurefuchsin 0-5 gf- Hydrochloric acid, 10% 25.0 c.c. Distilled water 300.0 c.c. The cleaned and stained specimens are usually mounted in Canada balsam for micro- scopic examination. Within the family Coccidae there are to be found most re- markable variations in struc- '^1 1 UTU// 1 I ture; this is especially true of the form of the caudal end of the body and of the form of the parts through which the wax and other excretions are exud- ed. These characters have been described by many authors; but, unfortunately, there is a great lack of uniformity in the Fig. 517. — Caudal end of female of Erzococ- terminology used by them. cus araucaricE: r^^n^X ring; 5, anal-ring j^^ ^j^is place, only sufficient setae; /, anal lobe; as, anal seta. Be- -u \ ^ u. a n tween the bases of the anal-ring setse space can be taken to define there are openings of wax-glands. the more important StfUC- HOMOPTERA 445 tures, using the terms that are more generally applied to them. The anal ring. — In the mealy-bugs, the tortoise-scales, and the lac-insects, and in the nymphs of some others, the anus is surrounded by a well-defined ring, the anal ring (Fig. 517, r). The anal-ring setce. — The anal ring bears several, from two to thirty but usually six, long and stout setae, the anal-ring setce (Fig. 517.^)- The anal lobes. — 'In many coccids, the caudal end of the body is terminated by a pair of lobes, the anal lobes (Fig. 517, /). The anal setce. — Each anal lobe bears one or more prominent setae, the anal setce (Fig. 517, as). The anal plates. — In the subfamily Lecaniinse, the abdomen of the female is cleft at the caudal end, and, at the cephalic end of the cleft, there is a pair of tri- angular, or sometimes semi-cir- cular plates, the anal plates (Fig. 518, ap). The pygidium. — In the sub- family Diaspidinae, the abdo- men of the adult female is ter- minated by a strongly chi- tinizedunsegmented region, which consists of four co- alesced segments (Fig. 519); this region is termed the pygid- ium by writers on the Coccidae. This application of the term pygidium is quite different from that used in descriptions of other insects, where it refers only to the tergite of the last abdominal segment. A more detailed account of the charac- ters presented by the pygidium ofthe Diaspidinae isgiven later. The spines and the setce. — -The position and number of spines and of setae are often indicated in specific descriptions. Care should be taken to distinguish between these two kinds of structures. A seta can be recognized by the cup-like cavity in the cuticula, the alveolus, within which it is jointed to the body; while a spine is an outgrowth of the cuticula that is not separated from it by a joint. See figure 42, page 32. The writer in his early works on the Coccidae ('81, '82, '83) termed certain spine-like setae spines. The outlets of wax-glands. — In the Coccidae there are many minute openings in the cuticula through which wax is excreted; these vary greatly in form, in position on the body, and in the structure of the part of the cuticula through which they open. As the characters presented by these openings are much used in the classification of coccids, a very elaborate terminology referring to them has been developed. Unfortunately different authors use quite different terms, Fig. 518.— A Lecanium, enlarged : c^, anal plates. Fig. 519. — Adult female Lepidosaphes: p, py- gidium. 446 AN INTRODUCTION TO ENTOMOLOGY and, therefore, it is necessary to learn the terms used by an author in order to understand his descriptions. The most detailed and sys- tematic terminology that has been proposed is that of MacGillivray ('21). Some of the many terms adopted by this author are defined below. The cerattibcB. — In the Diaspidinse and in some species of several other subfamilies, the terminal portion of the outlet of some of the wax-glands is an invaginated cuticular tube. The inner end of this tube is truncate, and, in the Diaspidinse, bears a perforated knob. This invaginated cuticular tube is termed a ceratuha. The ceratubae vary greatly in length and in shape; in some the greater part of the tube is reduced to a fine thread, with a bulb-like inner end. A few ceratubse are represented in a diagram given later (Fig. 522), The openings of most ceratubae are flush with the body-wall, but some of them open through plates in the marginal fringe. The dif- -Several types of openings of ferent types of ceratubas have re- ceived distinguishing names formed by combining a prefix with the word ceratubae. The cerores. — The various types of outlets of the wax-glands in which the cuticula is not invaginated so as to form a ceratuba are termed cerores. The openings of cerores through the cuticula vary ©o Fig. 521. — Diagram of a pygidium of a diaspid: o, anus showing through the body; d, densarise; g, genacerores; i, incisions; /, first pair of lobes; pe, pectinas; pi, plate; 5, setas; v, vagina. greatly in form; several types of these openings are represented in Figure 520. While in most cases the openings of cerores are flush with the general surface of the cuticula, in some coccids (Ortheziinas) the cerores open through spines. There are also variations in the grouping of the cerores. Each of the various types has received a technical name formed by combining a prefix with the word cerores. HOMOPTERA 447 Thus, for example, the cerores that occur in four or five groups about the genital opening in many of the Diaspidinas (Fig. 52 1 , g) are temled genacerores. The features of the pygidium. — The pygidia of adult female diaspids present characters that are much used in distinguishing the species of this subfamily; among these are the following. Fig. 522. — A composite diagram of a pygidium: a, anus; b, marginal ceratubse, with elongated openings; d, ceratubae opening through plates; e, linear ceratubae; /, /, /, lobes; the lobes of the second and third pairs are divided. The position of the anus, which opens on the dorsal aspect of the pygidium at varying distances from the end of the body (Fig. 522,0). The opening of the vagina, on the ventral aspect of the pygidium (Fig. 521, ^0- The presence or absence of groups of genacerores (Fig. 521, g), the number of these groups when present, and the number of cerores in each group. The different groups are distinguished as the median group (niesogenacerores) , the cephalo-lateral groups, one on each side (pregnacerores) , and the caudo-lateral groups, one on each side (post genacerores), respectively. These all open on the ventral aspect of the pygidium. Each genaceroris has several openings. The position and number of openings of ceratuba?, and the t^^pes of ceratubae that are present (Fig. 522). The number of pairs of lobes borne by the margin, the shape of the lobes, and whether they are divided or not (Fig. 522, /, /, /). The pairs of lobes are numbered, beginning with the pair at the end of the body; in some species this pair is represented by a single lobe. The number of pairs of incisions {incisnrce) in the margin of the pygidium (Fig. 521, i). The presence or absence of thickenings of the margins of the incisions (densarice); these are thickenings of the ventral wall (Fig. 521, d). 448 AN INTRODUCTION TO ENTOMOLOGY The presence or absence of club-shaped thickenings of the dorsal wall (paraphyses) that extend forward from near the bases of the lobes (Fig. 523. :P)- The presence or absence of a thickening of the lateral margin of the pygidium cephalad of the region in which the lobes are situated, and resembling the lobes in structure (Fig. 523, m). The nimiber and shape of the thin projections of the margin, known as plates. Two quite distinct types of plates can be dis- tinguished: in one they are broad and fringed (Fig. 521, pe); the plates of this type have been termed pectince; in the other type they are spine-like in form (Fig. $21, pi); some writers restrict the term plate to this type, and use pectince for the first type. Each plate contains the outlet of a wax-gland. Fig. 523. — Part of the pygidium of Chrysomphalus tenebricosus , ventral aspect, with the paraphyses {pp) of the dorsal wall showing through: /, /, /, lobes; m, thickened margin; s, spine-like setee. The metamorphosis of coccids. — In this family the two sexes are indistinguishable during the first nymphal stadium. Both are fur- nished with legs, antenna, and functional mouth-parts. It is during this period that the sedentary species spread over the plants that they infest. In their subsequent development the sexes differ greatly; hence the metamorphosis of each can be best discussed separately. The females never become winged. Some, as the mealy-bugs and Orthezia, continue active throughout their entire or almost entire life; but most forms become sedentary early in life and remain fixed upon their host. Many species lose their legs and antennas when they assume the quiescent form ; and in some the mandibular and maxillary setse are wanting in the adult. The number of n>TTiphal instars in females varies from two to four; the smaller number occurs in the more specialized subfamilies. In the males there are usually four njonphal instars. During the latter part of the nymphal life the male is quiescent, having formed a cocoon or a scale within or beneath which it remiains till it emerges as an adult. The stage of development at which the quiescent HOMOPTERA 449 period begins varies greatly. Thus,- while in the mealy-bugs the cocoon is made during the second stadium, in I eery a it is not made till near the end of the third. In the Diaspidinffi the formation of the scale begins either at the close of the first stadium or immediately after the first molt. With the molt at the beginning of the quiescent period the male loses its legs, antennae, and mandibular and maxillary set«. The setcc are not replaced ; and, consequently, the adult m^ales can take no food. The legs and antennae of the adult are developed from histoblasts, as in insects with a complete metamorphosis; the wing- buds appear in the last nymphal stadium; but they are developed externally, as in insects with a gradual metamorphosis. The type of metamorphosis of the male coccid is, therefore, neither strictly com- plete nor gradual. This illustrates the difificulty of attempting to make sharp distinctions; for in nature all gradations exist between the different types of structure and of development. The classification of the Coccidce. — The different writers on the Coccidas have grouped the genera into a variable number of sub- families. In the classification by MacGillivray ('21), this author recognizes seventeen subfamilies, and gives two tables for separating them, one based on the characters presented by the first nymphal instar, and one on those of adult females. Tables are also given for separating the genera and species of the different subfamilies. The following are a few of the better-known representatives of this family found in this country. Several subfamilies not mentioned here are represented in our fauna. Subfamily MONOPHLEBIN^ The Giant Coccids The common name of this family was suggested by the large size of many of the exotic species. The best-known species found in North America is of moderate size ; this is the cottony-cushion scale, Icerya purchasi (Fig. 524). The adult fe- male measures from 4 to 8 mm. in length, is scale-like, dark orange- red, and has the dorsal surface more or less covered with a white or yel- lowish white powder. It secretes a large, longitudinally ribbed egg-sac, which is white tinged with yellow This beautiful insect was at one time the most dangerous insect pest in California , and did a great amount of injury. It is an introduced Austra- pjg ^,2^.— Icerya purchasi: females, lian species, and has been subdued adults, and young on orange. 450 AN INTRODUCTION TO ENTOMOLOGY to a great extent by the introduction of an Australian lady-bug, Roddlia cardindlis. Subfamily COCCIN^ The Cochineal Coccids This subfamily is of especial interest because it includes the cochineal insect, Coccus cacti. This is a native of Mexico, but occurs in the southern United States. It feeds upon various species of the Cactaceae. It has been extensively cultivated in India, Spain, and other countries. The adult female bears some resemblance to a mealy-bug, but differs in lacking anal lobes and an anal ring. It excretes a mass of white cottony threads, within which the eggs are laid. The dye-stuff consists of the female insects, which, when mature, are brushed off the plants, killed, and dried. The entire insect is used. Cochineal is now being superseded by aniline dyes, which are made from coal-tar. Subfamily ORTHEZIIN^ Fig. 525. — Orthezia, greatly larged. The Ensign Coccids Members of this subfamily occur not uncommonly on various weeds. They are remarkable for the sym- metrically arranged, glistening, white plates of excretion with which the body is clothed. Figure 525 represents a nymph; in the adult female, the ex- cretion becomes more elongated pos- teriorly, and forms a sac containing the eggs mixed with fine down. Later, when the young are born, they excrete a sufficient amount of the lamellar excretion to cover them. In many species the egg-sac is held in a more or less elevated position; this fact suggested the common name ensign- coccids for these insects. Most of our species belong to the genus Orthezia, Subfamily ERIOCOCCIN^ The Mealy-Bugs This subfamily includes many genera and species; the best -known members of it are certain mealy-bugs, which are the most common and noxious of greenhouse pests. These insects have received the HOMOPTERA 451 Fig. 527. — Pseiidococcus cilri. Fig. 526. — Pseiidococcus longispinosus. name mealy-bugs because their bodies are covered with a fine granular excretion, appearing as if the}' had been dusted with flour. The females are active nearly throughout their entire life. The males make a cocoon early in their nymphal life in which they remain till they emerge as adults. Figure 526 represents Pseiidococcus longispinosus, a common species in greenh ouses ; and Figure 527, Pseudococcits citri, another species that is found in greenhouses in the North. The latter species is also a well-known pest of orange trees in the South. Several species of mealy- bugs of the genus Ripersia are found in the nests of ants of the genus Lasius. Subfamily LECANIIN^ The Tortoise-Scales The tortoise-scales are so named on account of the form pig. ^28.-Lccanium hesperidum, adult fe- of the body in many species. males, natural size. 452 AN INTRODUCTION TO ENTOMOLOGY The most striking characteristic of this subfamily is that the abdomen of the female is cleft at the caudal end, and at the cephalic end of this cleft there is a pair of triangular or semicircular plates, the anal plates (Fig. 518). This is a large subfamily including many genera and species. While the various forms agree in the distinguishing characteristics given above, there are great differences in the appearance of the adult females. Many of them excrete very little wax, the body being practically naked, and the eggs, or the young in the viviparous species, Fig. 529. Saissetia olece: enlarged. I, adult females on olive, natural size; /a, female, are deposited beneath the body ; in other species, although the body is nearly naked, the adult female excretes a large, cottony egg-sac; and in still others the body is deeply encased in wax. The three following species will serve as examples of those in which the body is naked and which do not form an egg-sac. The soft scale, Lecdnium hesperidum. — This is the commonest and most widely spread member of this subfamily; it infests a great variety of plants; in the North, it is very common in greenhouses; in the" warmer parts of the countr}' it lives out of doors. The adult female is nearly flat (Fig. 528), and is viviparous. HOMOPTERA 453 The black scale, Saissetia dlece. — This is a well-known pest, es- pecially in California, where it infests various kinds of fruit-trees and other plants. The adult fe- male is dark brown, nearly black, in color; nearly hemi- spherical in form (Fig. 529), often, however, quite a little longer than broad. There is a median longitudinal ridge on the back, and two transverse ridges, the three forming a raised surface of the form of a capital H. The hemispherical scale, Saissetia hemisphcerica.— The adult female is nearly hemi- spherical in form, with the edges of the body flattened (Fig. 530). This species is found in conserv^atories every- where, and in the open air in warmer regions. Pulvindria. — Those mem- bers of this subfamily in which the adult female is nearly naked but excretes a large cottony egg-sac beneath or be- hind the body, are represented in this/ country by the genus Pulvinaria, of which we have many species. Our best-known species are the two following. The cottony maple-scale, Pulvindria vitis. — This species is common on maple, osage orange, grape, and other plants. Figure 531 represents several adult females with their egg-sacs on a cane of grape. The maple-leaf pulvinaria, Pulvindria acerlcola . — This species is also found on maple. It differs from the preceding Fig. 53 1 .—Pulvinaria vitir. Species in that the egg- sac is much longer than the body of the female, and is formed on the leaves instead of on the stem of the host. Ceroplastes. — In this genus the body of the female is covered with thick plates of wax. Alore than sixty species have been described, JkaraJd Fig. 530. — Saissetia hemispharica: 3, adult females on orange, natural size; 3a, adult female, enlarged. 454 AN INTRODUCTION TO ENTOMOLOGY several of which are found in the southern United States; the follow- ing will serve as an example of these beautiful insects. The barnacle scale, Ceropldstes cir- ripediformis. — Several individuals of this species are represented natural size, and one enlarged, in Figure 532. It infests orange, quince, and many other plants. Subfamily KERMESIIN^ The Pseudogall Coccids This subfamily includes only one genus, Kermes. Species of this genus are common on oaks wherever they grow. These insects are remarkable for the wonderful gall-like form of the adult females. So striking is this re- semblance, that they have been mis- taken for galls by many entomologists. Fig. 533 represents a species of this genus upon Qtiercus agrijolia. The gall- like bodies on the stem are adult fe- males, the smaller scales on the leaves are immature males. Subfamily DIASPIDIN^ The Armored Scales Fig. 532. — Ceroplastes cirripedi formis. The Diaspidinas includes those coc- cids that form a scale, composed in part of molted skins and partly of an excretion of the insect, beneath which the insect lives. It is on account of this covering that these scale-insects are named the armored scales. The Diaspidinae are also characterized by a coalescence of the last four abdominal segments so as to form what is known as the pygidium ; this peculiar structure is described on an earlier page. The formation of the scale begins immediately after the close of the active period of the first m-mphal instar. At this time the young insect settles and begins to draw nourishment from its host. Soon after, there exude from the body fine threads of wax, the commence- ment of the formation of the scale. At the close of the first stadiimi, the molted skin is added to the scale and forms a part of it. This is also true, except as noted below, of the second molted skin of the female (Fig. 534, 2b and 2c). In the formation of the scale of the male only the first molted skin is added to the scale (Fig. 534, 2d). The scales of males can be distinguished by this fact, and, too, they are much smaller than the scales of females. HOMOPTERA 455 In a few genera the female does not molt the second exuviae*; the body shrinks away from it, and transforms within it. In such cases is it termed a puparimn. Figure 535 represents the scale of Fionnia fionnicB; here the puparium can be seen through the trans- parent scale. Fig. 533. — Kermes sp. on Querciis agrifolia : adult females on the stem ; immature males on the leaves. The shape of the scale, and the position of the exuviae on it, fur- nish characters that are very useful in the classification of the Diaspidinas. To this subfamily belong some of the most serious pests of shrubs and trees, as, for example, the San Jose scale and the oyster-shell scale. The following are a few of the many well-known species of this very important subfamily. *The term exuvice is a Latin word which had no singular form, the plural noun being used as is in Enghsh the word clothes. Some recent writers use the term extivia for a single molted skin. 456 AN INTRODUCTION TO ENTOMOLOGY The purple scale, Leptdosaphes pinncBjormis. — This scale-insect is well known in the orange-growing sections of this and of other ImUS. Fig. 534. — Chionaspis pinifolicE: 2, scales on Pinus strobus, natural size, leaves stunted; 2a, leaves not stunted by coccids; 2h, scale of female, usual form, enlarged; 2c, scale of female, wide form, enlarged; 2^, scale of male, enlarged. countries. It is one of the two most common scale-insects found on citrus trees in Florida. The scales of this species are represented in Figure 536; they are represented natural size on the leaf, and greatly enlarged in the other figures. The scale of the female is long, more or less curved, and widened posteriorly (Fig. 536, zaand/fe); the first of these two figures repre- sents the dorsal scale, and the second the ventral scale, which is well developed in this species. Some eggs can be seen through a gap in the ventral scale. The scale of the male (Fig. 536, ic) is usually straight or nearly so. At about one-quarter of the length of the scale from the posterior extremity, the scale is thin, forming a hinge which allows the posterior part of it to be lifted by the male as he emerges. While this insect is chiefly known as a pest of citrus trees, it has been fotmd on several other species of plants. It has been described under several different names; for a long time it was known as Mytilaspis citricola. Fig. 535-—-^^ orinia fiorimcB HOMOPTERA 45^ Glover's scale, Lepidosaphes gloverii. — This is the second of the two most common species of scale-insects found on citrus trees in Florida. In this species the scale of the female is much narrower than that of the preceding species. This species is widely distributed over the warmer parts of the world. The oyster-shell scale, Lepidosaphes ulmi. — This is a northern rep- resentative of the genus to which the two preceding species belong. It is closely allied to the purple scale; in fact Figure 536 would serve to illustrate this species except that it does not occur on orange and that it is found chiefly on the trunk of its host. The two species differ in the characters presented by the pygidium. The oyster-shell scale is Fig. 536. — Lepidosaphes pinnceformis : i, scales on orange, natural size; la, scale of female, dorsal view, enlarged ; ib, scale of female with ventral scale and eggs, enlarged; ic, scale of male, enlarged. a cosmopolitan insect, and it infests very many species of shrubs and trees. In the North it is the commonest and best-known scale-insect infesting fruit-trees and various ornamental shrubs. It is discussed in all of our manuals of fruit-insects; in some of them it is described under the name Mytilaspis pomorum. The scurfy scale, Chiondspis furfura. — This, like the preceding species, is a very common pest of the apple and various other trees and shrubs; but usually it is not very destructive. In this species the scale of the female is widened posteriorly, and bears the exuviee at the anterior end (Fig. 512, ic). The scale of the male is very small, being only .75 mm. in length, narrow, and tricarinated (Fig. 512, la). 458 AN INTRODUCTION TO ENTOMOLOGY The pine-leaf scale, Chiondspis pinifdlia;. — This is a very common pest of pine, spruce, and other coniferous trees, throughout the United States and Canada. It infests the leaves of its various hosts. The scale of the female is snowy white in color, with the exuvias light yellow ; it is usually long and narrow, as represented in Figure 534, 2h; but on the broader-leaved pines it is often of the form shown Fig. 537. — Aulacaspis toscb: I, scales on rose, natural size; la, scale of female, enlarged; ib, scale of male, enlarged. at 2c in the figure; this is the typical form of the scale of the female in the genus Chionaspis. The rose-scale, Aulacaspis rdscs. — This species infests the stems of roses, blackberry, raspberr>', dewberry, and some other plants. The infested stems often become densely coated with the scales. The scale of the female is circular, snowy white, with the exu vise light yellow and upon one side (Fig. 53 7, la). The scale of the male is also white; it is long, tricarinated, and with the exuvise at one end (Fig. S37> J^i>); it measures 1.25 mm. in length. The San Jose scale, Comstockaspis pernicidsa. — The San Jose scale was first described by the writer in 1881, under the name Aspidiotus pernicidsus. It has since been made the type of a new genus, Com- stockaspis, by MacGillivray ('21). At the time it was described it was known only in Santa Clara County, California. But in describing HOMOPTERA 459 it, notwithstanding its limited distribution, I stated: "From what I have seen of it, I think that it is the most pernicious scale-insect known in this countr}\" Since that time it has become widely dis- tributed. Slingerland and Crosby write of it as follows: "The San Jose scale has attained greater notoriety, has been the cause of more legislation, both foreign and interstate, and has demonstrated its capabilities of doing more injury to the fruit interests of the United States and Canada than any other insect." This species infests various fruit-trees and ornamental shrubs; it infests the bark, leaves, and fruit of its hosts, and usually causes reddish discolorations of the bark and of the skin of the fruit. This species can be distinguished from the other scale-insects that are important pests of our fruit-trees by the form of the scales. The scale of the female is circular and flat, with the exuviae central, or nearly so. The scale is gray, excepting the central part, that which covers the exuviae, which varies from a pale yellow to a reddish yellow. It measures 2 mm. in diameter. The scale of the male is black, and is somewhat elongate when fully formed. The exuviae is covered with secretion; its position is marked by a nipple-like prominence which is between the center and the anterior margin of the scale. Control of scale-insects . — The extensive damage that has been done by scale-insects to fruit-trees and to cultivated shrubs has led to many experiments in the destruction of these insects. The results have been quite satisf actor}' ; with proper care, it is now possible to keep in check the ravages of these pests. Detailed accounts of the methods to be employed are given in many easily available publications, and especially in bulletins of experiment stations. In the case of deciduous trees and shrubs, the best time to destroy scale-insects infesting them is during the winter, when the trees are bare and in a dormant state. At this time the entire tree can be reached w4th sprays, without the interference of leaves; and, too, certain sprays can be safely used that are liable to injure the trees during the growing season. This is especially true of the lime-sulphur mixture, which is ver\' widely used for the destruction of scale-insects, and is very effective. Among the other insecticides used for this purpose are kerosene emulsion and dilute miscible oils. For summer spraying, whale-oil soap, one pound dissolved in four or five gallons of water, can be safely used. In the case of trees that are constantly clothed with foliage, tha effective use of sprays is more difficult. In the orange-growing sections of California the trees are fumigated with hydrocyanic acid gas, t\i$ tree to be treated being first covered with a large tent. CHAPTER XXII ORDER DERMAPTERA* The Earwigs The winged members oj this order usually have four wings; but in some of them the wings are wanting. The fore wings are leathery, very small, without veins, and when at rest meet in a straight line on the back; the hind wings, when well developed, are large, with radiating veins, and when at rest are folded both lengthwise and crosswise. The mouth-parts are formed for chewing. The caudal end of the body is furnished with a pair of appendages, the cerci, which usually resemble forceps. The metamorphosis is gradual or wanting. This order includes three families, Forficulidae, Arixeniidae and Hemimeridse. The order is made up largely of the earwigs of the family Forficulidae. These are long and narrow insects resembling rove-beetles in the form of the body and in having short and thickened fore wings (Fig. 538) ; but the earwigs are easily distinguished from rove-beetles by the presence of a pair of forceps-like appendages at the caudal end of the body. The common name, earwig, was given to these insects in England, and has reference to a widely spread fancy that these insects creep w H K^^ 1 into the ears of sleeping persons. Other similar ifL rJ^^^TS names are applied to them in Europe, Ohr- /f\ ilfflSi A Wurm in Germany and perceoreille in France. The earwigs are rare in the northeastern United States and Canada, but are more often found in the South and on the Pacific Coast. In Europe they are common, and often trouble- some pests, feeding upon the corollas of fiowers, fruits, and other vegetable substances. Some species are carnivorous, feeding on other in- sects and some are probably scavengers. They are nocturnal, hiding in the day-time among leaves and in all kinds of crevices, and coming out by night ; sometimes they are attracted to lights. Earwigs are small or of moderate size; the living species measure from 2.5 to 37 mm. in length. The body is narrow and flat. The mouth-parts are fitted for chewing, and resemble in their more general features those of the Orthoptera ; minute but distinct parag- natha are present; and the second maxillae are incompletely fused. *Dermaptera : derma {Upua) , skin ; pteron {irrepov) , a wing. (460) Fig. 538.— An Labia minor, earwig, male. DERMAPTERA 461 The compound eyes are rather large; but the ocelli are wanting. The antennae are slender, and consist of from ten to thirty-five seg- ments ; the second segment is always small. The fore wings are leath- ery, very short, without veins, and when at rest meet in a straight line on the back. This pair of wings is commonly termed the tegmina or the elytra. The hind wings when at rest are folded both length- wise and crosswise and project a short distance behind the fore wings (Fig. 538). The radiating veins of the hind wings extend from a point near the middle of the length of the wing (Fig. 539). When the wing is not in use, that part over which the radiating veins ex- tend is folded in plaits hke a fan. This part of the wing is the greatly expanded anal area. The preanal area is much reduced with but two longitudinal veins, and is quite densely chitinized. The trachea- tion of the hind wings has been described and figured by the writer Fig. 539. — liind wing of an earwig: «/, nodal furrow. (Comstock '18). The wings vary much in size and development even in the same species; and there are many species that are wingless. The legs are similar in form, and the tarsi are three-jointed. The most distinctive feature of earwigs is the form of the cerci, which are forceps-like, and usually very prominent. A similar form of cerci is found, however, in the genus Japyx of the order Thysanura. The size and shape of the forceps of earwigs differ in the different species and in the two sexes of the same species; they are usually more highly developed in the male than in the female ; they are used as organs of defense and offense, in pairing, and are sometimes used as an aid in folding the wings. 462 AN INTRODUCTION TO ENTOMOLOGY Certain earwigs possess stink-glands, which open through tuber- cles situated one on each side near the hind margins of the second and third visible abdominal segments, from which, it is said, they can squirt a foul-smelling fluid to a distance of three or four inches. The female earwig has smaller for- ceps and but six visible abdominal sterna while the male has eight. In some earwigs the two efferent ducts of the reproductive organs open separate- ly. The metamorphosis is gradual, the wings developing externally. The female is said to brood over the eggs but to abandon them soon after hatch- ing. ig- 5.41 Pro- labia pulchella burgessi, male. (From Rehn and Hebard.) Earwigs are cosmopolitan insects, and are easily transported by com- merce ; consequently exotic species are liable to be found near seaports; and some such species have become established in this country. The species of the world have been mono- graphed by B urr ('11). Fig. _ ^^o.— Labia The order is a comparatively small one ; only about minor, female, four hundred living species have been described, and dom^n of the ^^^^e are mostly tropical or semitropical. The native male. (From and the exotic species that have become established Lugger.) in America north of Mexico number together only fifteen. The seaside earwig, Anisoldhis mantinia. — In this species both pairs of wings a-^e wanting, the antennae are 24-jointed, and the length of the body is from 18 to 20 mm. This earwig is found along the coast from Maine to Texas. The ring-legged earwig, Anisoldhis ammlipes. — This is also a wingless species. The antennae are only 15- or i6-jointed, the body is about 10 mm. long and the legs are ringed with fuscous. Its range does not extend as far north as that of the seaside earwig, but it extends farther inland. The little earwig. Labia minor. — In this species the body is thickly clothed with fine yellowish pubescence. The body measures only from 4 to 5 mm. in length. Figure 538 represents the male, and Figure 540, the female. This species is widely distributed in the United States and is established in Canada. The handsome earwig, Proldhia pulchella. — This species is widely distributed over the southern United States; it is found under the bark of dead trees. The body is dark chestnut-brown, shining and glabrous. It measures from 6 to 6.5 mm. in length. This species is dimorphic; in one form, known as burgsssi (Fig. J41), the hind wings are shorter than the tegmina. DERMAPTERA 463 The spine-tailed earwig, Doru acidedtnm. — In the genus Dom the pygidium of the male is armed with a distinct spine (Fig. 542). This species is dark chestnut-brown, with the palpi, legs, edges of pronotum, and the outer two-thirds of the tegmina yellow. The hind wings are usually aborted. The length of the body is 7.5 to 1 1 mm. It is distributed from New Jersey and southern Michigan to Nebraska, Georgia, and Louisiana. The common European earwig, Forficida aitriculdria. — In this species and in the preceding one as well, the second tarsal segment is lobed and prolonged beneath the third; but tha two species can be distinguished by the shape of the forceps of the male (Fig. 543). The males of this species are dimorphic; in one form the forceps average about 4 mm. in length, in the other about 7 mm. This common European species appeared in great numbers at Newport, Rhode Island, about 191 2. Family Arixeniidae. — This family contains but a single genus, Arixenia, which, up to 1913 at least, contained but two species. One, A. esau, was taken from the breast-pouch of a bat, Chetromeles tor- quatus, in Sarawak, Borneo. The other, A. jacohsoni, was taken on guano in a cave in Java which was frequented by bats. This species occurred in large numbers crawling over the ground and on the walls of the cave. The adults are very hairy, wingless, and viviparous. The antennas have fourteen segments but the eyes are greatly reduced with from 70 to 80 facets. The mandibles are flattened and the cerci are rather long, unsegmented and curved, thus having the appearance of weak forceps. See Burr and Jordan, Trans. 2nd En- tom. Cong., p. 398, 1913. Family Hemimeridae. — This family includes but a single genus, Hemimerus, which now contains eight species, hanseni (see Figure 308, p. 269), bouvieri, talpoides, viciniis, advectus, vosseleri, sessor, and deceptiis. These insects are small (from 8.5mm. to 15mm. in length), wingless, viviparous ectoparasites on rats of the genus Cricetomys. The known species are distributed throughout equatorial Africa as far south as the Transvaal. The eyes are absent and the cerci are elon- gated, unsegmented but not formed into forceps. The antennas are well developed and have eleven segments while the legs, although short and stout, are fitted for rather rapid running among the hairs of the hosts. The body is broad and flattened, convex above and below, and uniformly orange-ochraceous in color, and the surface bears minute hairs. S?e Rehn and Rehn, Proc. Acad. Nat. SC. Phila., Vol. 87, pp. 457-508, 1936. Fig. 542. — Doru acii- leatum, male. (From Blatchley.) ^''ig- 543- — Forficula auricularia: A, male with short forceps; 5, forceps of female; C, long type of forceps of male. (After Morse.) CHAPTER XXIII ORDER COLEOPTERA* The Beetles The winged members of this order have four wings; hut the first pair of wings are greatly thickened, forming a pair of ''wing-covers'' or elytra, beneath which the membranous hind wings are folded when at rest. The elytra meet in a straight line along the middle of the back and serve as armor, protecting that part of the body which they cover. The mouth- parts are formed for chewing. The metamorphosis is complete. The order Coleoptera includes only the beetles. These insects can be readily distinguished from all others except the earwigs by the structure of the fore wings, these being homy, veinless "wing-covers" or elytra, which meet in a straight line along the middle of the back (Fig. 544); and they differ from ear- wigs in lacking pincer-like appendages at the caudal end of the body. Beetles also differ from earwigs in having a complete metamorphosis. Only a few modifications of the typical characteristics exist in this order; among the Fig. ^^.—Desmocerus pal- "lore familiar of these are the following : in liattis. some of the Meloidae the elytra do not meet in a straight line; in many of the Carabidae, Curculionidee, et al., the hind wings are wanting, and in some of these the elytra are grown together; in a few females of the Lampyridaeand Phengodidas both pairs of wings are wanting. The different mouth-parts are very evenly developed ; we do not find some of them greatly enlarged at the expense of others, as in several other orders of insects. The upper lip, or labrum, is usually distinct; the mandibles are powerful jaw^s fitted either for seizing prey or for gnaw^ing; the maxillse are also well developed and are quite complicated, consisting of several distinct pieces; the maxillary palpi are usually prominent; and the lower lip,- or labium, is also well Lleveloped and complicated, consisting of several parts and bearing prominent labial palpi. Detailed figures of the maxillae and labium of beetles are given in Chapter II. In the classification of beetles much use is being made of the variations in form of the ventral and lateral sclerites of the thorax. Figure 545 will serve as an illustration of these sclerites. One feature merits special mention: the coxae of the hind legs are flattened and immovably attached to the thorax so that they appear to be a part of the thorax instead of the basal segment of an appendage. Coleoptera: coleos (KoXe6s), a sheath; pleron (irTepSv), a wing. (464) COLEOPTERA 465 Almost the only use that has been made of the characteristics of the wings has been restricted to certain features of the elytra, those that can be seen with- out spreading the wings. These are the shape of the elytra, the presence or ab- sence of striae, the pres- ence or absence of punctures and their distribution when present, and the pres- ence or absence of setae, pubescence, or scales on the surface of the elytra. A beginning has been made, however, to make use of the venation of the hind wings; this, as yet, is restricted to an indi- cation of the type of wing-venation charac- teristic in each case of the superfamilies. The venation of the wings of the Cole- optera has become greatly modified, and, consequently, the de- termination of the ho- mologies of the wing- veins is a difficult mat- Fig. 545.— Ventral aspect of a beetle, Enchroma gigan- ter The transforma- /ea; ^, prothorax; 5, mesothorax; C, metathorax; , . ■ J. ,, J. . c, c, c, coxae; em, em, em, epimera; es, es, es, epis- tion Of the tore wmgs ^ema; s, s, s, sterna; /, ;, trochantins; x, elytrum; into ehi:ra has result- y, antecoxal piece of metasternum. ed in a great reduction of their venation; and the foldings of the hind wings interrupt the veins and cause distortions in their courses. It is only recently that extended studies of the wing-venation of the Coleoptera have been made, and the conclusions reached by the different investigators are not fully in accord. But much progress has been made, and so much interest is being shown in the subject that we can confidently expect that conclusions will soon be reached that can be generally accepted. Among the recent studies of the subject is an extended one by Dr. Wm. T. M. Forbes ('22 6), in which the venation of the hind wings of more than fifty species of beetles are figured. The accompanying figures (Figs. 546-547), copied from Dr. Forbes' paper, will serve to illustrate his conclusions regarding the homologies of the wing-veins 466 AN INTRODUCTION TO ENTOMOLOGY of beetles. Another recent paper in which the venation of the wings of many beetles is figured is that of Graham ('22). Sc R, Fig. 546. — Tracheation of wing of imago of Calosoma. (From Forbes.) Fig- 547- — Tracheation of wing of imago of Dytiscus verticalis. (From Forbes.) Beetles undergo a complete metamorphosis. The larvae, which are commonly called grubs, vary greatly in form; some are campodeiform, others are scarabeiform, and some are vermiform. In some members of the order there is a hypermetamorphosis, the successive larval instars representing different types of larvae; this is true of members of the Meloidee and Micromalthidae. Oc- casionally individuals of Tenebrio molitor are found in which the wings are developed externally. The pupae Fig. 548.— Pu- are exarate, that is, the limbs are free (Fig. 548) . These pa of a bee- insects usually transform in rude cocoons made of earth or of bits of wood fastened together by a viscid substance excreted by the larvae. Many wood-burrowing species transform in the tunnels made by the larvae; and some of the Dermes- COLEOPTERA 467 tidce as well as some of the Coccinellidas transform in the last larval skin. Both larvce and adults present a very wide range of habits. While the majority of the species are terrestrial, the members of several families are aquatic ; and while some feed on vegetable matter, others feed upon animal matter. The vegetable feeders include those that eat the living parts of plants, those that bore in dead wood, and those that feed upon decaying vegetable substances. Among the animal feeders are those that are predacious, those that feed on dried parts of animals, and those that act as scavengers, feeding on decaying animal matter. Viewed from the human standpoint, some species are very beneficial, others are extremely noxious. The Coleoptera is a very large order; in the "Catalogue of the Coleoptera of America, North of Mexico" by Leng ('20), 18,547 species are listed; these represent 109 families. The order is divided into two suborders, the Adephaga and the Polyphaga. In each of the suborders the families are grouped into superfamilies, two in the Adephaga and twenty in the Poh-phaga; and in the suborder Polyphaga the superfamilies are grouped into seven series of superfamilies. Students of the Coleoptera are not fully agreed as to some of the details of this classification; but as this catalogue will doubtless serve, for a long time, in this country, as a guide for the arrangement of collections, it seems best to follow it in this introductory text-book. Some of the places where there is a lack of agreement among the authorities are indicated in the conspectus on page 38 of the Catalogue. SYNOPSIS OF THE COLEOPTERA {Tables for determining the families are given below) I. SUBORDER ADEPHAGA This suborder includes the first seven f amiHes, the Cicindelidas to the Gyrinidag inclusive, pages 476 to 484. The family Rhysodidae (page 508) is also included in this suborder by some writers. II. SUBORDER POLYPHAGA This suborder includes all but the first seven families, or the first eight if the Rhysodidas be included in the Adephaga. The families of this suborder are grouped into seven series, as follows: — SERIES I. — THE PALPICORNIA This series includes a single family, the Hy drophilidce ; page 485. SERIES II. — THE BRACHELYTRA This series includes fifteen families, the Platypsyllidae to the Histeridae, in- clusive, pages 486 to 490. SERIES III. — THE POLYFORMIA This series includes forty-three families, the Lycidse to the Nosodendridae, inclusive, pages 491 to 508. SERIES IV. — THE CLAVICORNIA This series includes thirty families, if the Rhysodidae be placed here instead of in the suborder Adephaga; these are the families Rhysodidas to Cisidae, in- clusive, pages 508 to 515. 468 AN INTRODUCTION TO ENTOMOLOGY SERIES V. — THE LAMELLICORNIA This series includes four families, th3 Scarabaeidas, theTrogidae, the Lucanidae, and the Passalidae, pages 515 to 524. SERIES VI. — THE PHYTOPHAGA This series includes three families, the Cerambycidae, the Chrysomelidae, and the Mylabridae, pages 524 to 535. SERIES VII. — THE RHYNCHOPHORA This series includes six families, the Brentidae to the Scolytidas, inclusive, pages 536 to 542. TABLES FOR DETERMINING THE FAMILIES OF THE COLEOPTERA TABLE I.— THE SUBORDERS AND THE SERIES OF SUPERFAMILIES A. Ventral part of the first segment of the abdomen divided by the hind coxal cavities, so that the sides are separated from the very small medial part. Suborder Adephaga; see Table II, below. AA. Ventral part of the first segment of the abdomen visible for its entire breadth. Suborder Polyphaga. Fig. 549. — Head of Harpalus, ven- tral aspect: a, antenna; g, g, gula; ga, galea or outer lobe of the maxilla; gs, gular suture; Ip, labial palpus; m, m, mandibles; mp, maxillary palpus; s, submen- tum. Fig. 550. — Prothorax of Harpalus, ventral aspect: c, coxa; em, epi- merum ; es, episternum ; /, femur ; n, pronotum; s, s, 5, prosternum. B. Head not prolonged into a narrow beak, palpi always flexible; two gula sutures at least before and behind (Fig. 549) ; sutures between the prosternum and the episterna and epimera distinct (Fig. 550) ; the epimera of the pro- thorax not meeting on the middle line behind the prosternum (Fig. 550). C. Abdomen with at least three corneous segments dorsally, and exposed more or less by the short elytra. Hind wings with simple, straight veins; antennae variable, but never lamellate. Series Brachelytra, See Table III, below. CC. Abdomen with at most two corneous segments dorsally, usually com- pletely covered by the elytra; hind wings with veins in part connected by recurrent veins. D. Antennae clubbed or not, but if clubbed not lamellate. E. Tarsi usually apparently four-jointed, the real fourth segment being reduced in size so as to form an indistinct segment at the base of the last segment, with which it is immovably united (Fig. 551, A); the first three segments of the tarsi dilated and brush-like beneath; the third segment bilobed. In two genera, Parandra and COLEOPTEM 460 Spondyiis, the fourth segment of che tarsus, altnough much reduced and immovably united with the fifth, is distinctly visible, the first three Fig- 551- — Tarsi of Phytophaga: ,4, typical; B, Spondyiis; C, Parandra. BB segments are but slightly dilated, and the third is either bilobed, Spondyiis (Fig. 551, 5), or not, Parandra (Fig. 551, C). Series Phytophaga. See Table VI, below. EE. Tarsi varying in form and in the number of the segments, but when five-jointed not of the type described under E above, the joint be- tween the fourth and fifth segments being flexible. Series Palpicornia, Polyformia, and Clavicornia. See Table IV, below. DD. Antenna with a lamellate club. Series Lam- ellicornia. See Table V, below. Head either prolonged into a beak or not; palpi usually short and rigid; gular sutures confluent on the median line (Fig. 552, gs); prosternal sutures wanting; the epimera of the prothorax meeting on the middle line behind the presternum (Fig. 552, em). Series Rhynchophora. See Table VII, below. TABLE II. -THE FAMILIES OF THE SUB- ORDER ADEPHAGA Fig. 552. — Head and prothorax of Rhyn- chophorus: gs, con- fluent gular su- tures; s, prester- num; etn, epime- rum; c, coxa; /, fe- mur. A. Metasternum with an antecoxal piece, separated by a well-marked suture reaching from one side to the other and extending in a triangular process between the hind coxae. B. Antennae eleven-jointed; hind coxae mobile, and of the usual form; habits terrestrial. C. Antennae inserted on the front above the base of the mandibles, p. 476. CiCINDELIDiE 470 AN TNTRODUCTION TO ENTOMOLOGY CC. Antennae arising at the side of the head between the base of the mandi- bles and the eyes. D. Beetles of a round convex form in which the scutellum is entirely concealed, p. 481 Omophronid^ DD. Not such beetles, p. 478 Carabid^ BB. Antennae ten- jointed; hind coxas fixed and greatly expanded so as to conceal the basal half of the hind femora and from three to six of the ab- dominal segments; habits aquatic, p. 481 Haliplid^ AA. Metasternum either with a very short antecoxal piece, which is separated by an indistinct suture and which is not prolonged posteriorly between the coxae, or without an antecoxal piece. B. Metasternum with a very short antecoxal piece, p. 481 .Amphizoid^ BB. Metasternum without an antecoxal piece. C. Legs fitted for swimming. D. With only two eyes. p. 482 Dytiscid^ DD. With four eyes, two above and two below, p. 484. .Gyrinid^ CC. Legs fitted for walking, p. 508 RHYSODiDiE* TABLE III.— THE FAMILIES OF THE BRACHELYTRA A. Elytra short, leaving the greater part of the abdomen exposed; the suture between the elytra when closed straight; wings present, and when not in use folded beneath the short elytra; the dorsal part of the abdominal segments en- tirely horny. B. Abdomen flexible, and with seven or eight segments visible below, p. 488. Staphylinid^ BB. Abdomen not flexible, and with only five or six ventral segments visible. C. Antennas with less than six joints, p. 490 Clavigerid^ CC. Antennae eleven-jointed, rarely ten-jointed, p. 489..PSELAPHID.E AA. Elytra usually long, covering the greater part of the abdomen; when short the wings are wanting, or, if present, may or may not be folded under the short elytra when at rest; the dorsal part of the abdominal segments partly membranous. B. Hind tarsi five-jointed. C. Antennas elbowed, and clavate. p. 490 Histerid^ CC. Antennae rarely elbowed, and then not clavate. D. Abdomen with not more than five ventral segments. E. Antennae capitate, the last three segments forming an abrupt club. p. 490 SPH^RITID^t EE. Antennae but slightly clavate if at all. p. 490.. . .Scaphidiid^ DD. Abdomen with six or more ventral segments. E. Anterior coxae flat. p. 486 Platypsyllid^ EE. Anterior coxs either globular or conical. F. Anterior coxae globular, p. 487 Leptinid^ FF. Anterior coxas conical. G. Posterior coxae widely separated. H. Eyes wanting or inconspicuous, p. 487 Silphid^ HH. With well-developed eyes. I. Elytra covering the abdomen, p. 488 . . . ScYDM^ENiDiE II. Elytra not covering the entire abdomen, p. 490 SCAPHIDIID^ GG. Posterior coxae approximate. H. Posterior .coxae laminate, p. 488 Clambid^ HH. Posterior cox® not laminate. *The Rhysodidas is a very aberrant family, and its affinities have been much discussed. The form of the ventral part of the first abdominal segment is similar to that characteristic of the Adephaga; hence, according to Table I, this family should be placed in this suborder. But other characters led Leconte and Horn ('83) to place it in the Clavicornia, in which view they are followed by recent writers. fSee also p. 508, the Nitidulidas of the series Clavicornia. COLEOPTERA 471 I. Eyes with large facets, p. 486 Brathinid^ II. Eyes with small facets, p. 487 Silphid^ BB. Hind tarsi either only three-jointed or four-jointed, but apparently three- jointed, the third segment being small and concealed in a notch at the end of the second segment. (See also BBB and BBBB.) C. Abdomen with six or seven ventral segments. D. Tarsi four-jointed, the third segment small and concealed in a notch at the end of the second segment, p. 488 Corylophid^e DD. Tarsi three-jointed, p. 490 Trichopterygid^ CC. Abdomen with only three ventral segments, p. 490. Sph^riid^ BBB. All tarsi four-jointed. (See also BBBB.) C. Hind coxae contiguous and with plates covering the femora entirely or in part. p. 487 Silphid^ CC. Hind coxas separate and not covering the femora, p. 488 CoRYLOPHiDiE BBBB. Hind tarsi with only four segments; the fore tarsi, and almost always the middle tarsi also, with five segments, p. 487 Silphid^e TABLE IV.— THE FAMILIES OF THE PALPICORNIA, POLYFORMIA, AND CLAVICORNIA It is impracticable to separate these three series of families in these tables, owing to the fact that characters sharply separating them have not been found. A. Hind tarsi five-jointed. B. Maxillary palpi as long as or longer than the antennae, p. 485 Hydrophilid.e BB. Maxillary palpi much shorter than the antennas. C. Tarsal claws very large; the first three abdominal segments grown together on the ventral side. D. Abdomen with more than five ventral segments; anterior coxas with very large trochantin. p. 503 PsepheniD/E DD. Abdomen with five ventral segments. E. Anteriorcoxae transverse, with distinct trochantin. p.504.Dryopid^ EE. Anterior coxae rounded, without trochantin. p. 504 . . . Elmid^ CC. farsal claws of usual size; ventral abdominal segments usually free, sometimes (Buprestidae) the first two grown together. D. Abdomen with not more than five ventral segments. E. Femur joined to the apex or very near the apex of the trochanter. F. Antennae inserted upon the front, p. 514 Ptinid^e FF. Antennffi inserted before the eyes. G. Tibiae without spurs, p. 514 Anobiid^ GG. Tibiae with distinct spurs. H. First ventral segment scarcely longer than the second. p. 515 BOSTRICHID^ HH. First ventral segment elongated, p. 515 Lyctid.e EE. Femur joined to the side of the trochanter. F. Anterior coxas globular or transverse, usually projecting but little from the coxal cavity. G. Anterior coxae transverse, more or less cylindrical. H. Posterior coxae grooved for the reception of the femora. I. Legs stout, retractile; tibiae dilated, usually with a furrow near the outer end for the reception of the tarsi; tibial spurs distinct. J. Antennae inserted at the side of the head. K. Head prominent, mentum large, p. 5o8.Nosodendrid^ KK. Head retracted, mentum small, p. 5o8.Byrrhid^ JJ. Antennae inserted on the front; head retracted, p. 506. Chelonariid^ II. Tibiae slender, with small and sometimes obsolete terminal spurs, or without spurs. J. Head constricted behind; eyes smooth, p. 494.CUPESIDVE JJ. Head not constricted behind; eyes granulated. 472 ■ AN INTRODUCTION TO ENTOMOLOGY K. Anterior coxae with a distinct trochantin. p. 505. Dascillid^e KK. Anterior coxae without trochantin. L. Lacinia of the maxillae armed with a terminal hook. p. 505 EUCINETID^ LL. Lacinia not armed with a terminal hook. p. 505. Helodid^ HH, Posterior coxae flat; not grooved for the reception of the femora. I. Tarsi more or less dilated, first segment not short. J. Antennae eleven-jointed, terminated by a three-jointed club. p. 508 NlTIDULID^ JJ. Antennae ten-jointed, club two-jointed, p. 508 Rhizophagid^e II. Tarsi slender, first segment short, p. 508 . . Ostomid^ GG. Anterior coxae globular. H. Prosternum with a process which extends backward into a groove in the mesosternum. I. The first two abdominal segments grown together on the ventral side. p. 502 Buprestid^ II. Ventral segments free. J. Prothorax loosely joined to the mesothorax; front coxal cavities entirely in the prosternum. K. Posterior coxae laminate ; trochanters small. L. Antennae somewhat distant from the eyes, their in- sertion narrowing the front, p. 502 Eucnemtd^e LL.- Antennae inserted under the margin of the front. M. Antennas arising near theeyes. p. 499.Elaterid^ MM. Antennas arising at a distance in front of the eyes {Perothops). p. 502 Eucnemid^ KK. Posterior coxae not laminate; trochanters of middle and posterior legs very long. p. 499. . . .Cerophyiid^ JJ. Prothorax firmly joined to the mesothorax; front coxal cavities closed behind by the mesosternum. p. 502 Throscid^ HH. Prosternum without a process received by the mesoster- num, although it may be prolonged so as to meet the meso- sternum. I. Posterior coxae contiguous, p. 511 PHALACKiDiE II. Posterior coxae separated. J. Body depressed; middle coxal cavities not closed ex- ternally by a meeting of the mesosternum and meta- sternum. p. 509 Cucuj id^e JJ. Body more or less convex; middle coxal cavities en- tirely surrounded by the sterna. K. Prosternum not prolonged behind, p. 510. . . Mycetophagid^ KK. Prosternum prolonged, meeting the mesosternum. L. Anterior coxal cavities open behind, p. 510.... Cryptophagid^ LL. Anterior coxal cavities closed behind, p. 509 EROTYLIDyE FF. Anterior coxae conical, and projecting prominently from the coxal cavity. G. Posterior coxas dilated into plates partly protecting the femora, at least at their bases. H. Antennae serrate or flabellate. p. 499 Rhipicerid^ HH. Antennae with the last three segments forming a large club. I. Tarsi with second and third segments lobed beneath. p. 510 Byturid^e II. Tarsi simple, p. 506 , . , Dermestjd^ COLEOPTERA 473 HHH. Antennas with the last three segments somewhat larger than the preceding, but not suddenly enlarged, p. 510. Derodontid^ GG. Posterior coxas not dilated into plates partly protecting the femora. H. Posterior coxa3 flat, not prominent, covered by the femora in repose. I. Tarsi with the fourth joint of normal size. p. 493. Clerid^ II. Tarsi with the fourth joint very small, p. 493. CoR'^netid^ HH. Posterior coxae conical and prominent. I. Anterior coxae with distinct trochantins. p. 493. Melyrid^e II. Anterior coxae without trochantins. p. 493. Lymexylid^e DD. Abdomen with six or more ventral segments. E. Anterior coxee globular. F. Tibial spurs well developed, p. 499 Cebrionid/E FF. Tibial spurs very delicate and short, p. 499. . . . Pl.^stocerid^ EE. Anterior coxas conical. F. Posterior coxas not prominent, flat, covered by the femora in repose. G. Tarsi with the fourth joint of normal size. p. 493. . . CLERiDyE GG. Tarsi with the fourth joint very small, p. 493. Corynetid^ FF. Posterior coxas more or less conical and prominent at least in- ternally, not covered by the femora in repose. G. Anterior coxas long, with distinct trochantins. H. Abdomen with seven or eight ventral segments. I. Middle coxss contiguous; epipleuras distinct. J. Episterna of metathorax not sinuate on inner side, epi- pleurse usually wide at the base. K. Head more or less covered; antennae approximate or moderately distant; metathoracic epimera long. p. 491. L.^MPYRID^ KK. Head exposed; antennae distant; metathoracic epimera wide. p. 492 Phengodid^ JJ. Episterna of metathorax sinuate on the inner side; epipleurffi narrow at the base. p. 492 Canth.a.rid^ II. Middle coxae distant; epipleurae wanting, p. 491. Lycid^e HH. Abdomen with only six ventral segments, p. 493.MELYRID/E GG. Anterior coxae without trochantins. H. Elytra entire; length of body 10 mm. or more. p. 493. . Lymexylid^ HH. Elytra shorter than the abdomen; length of body less than 3 mm. p. 494 Micromalthid^ AA. Hind tarsi either only three-jointed, or four-jointed but apparently only three-jointed, the third joint being small and concealed in a notch at the end of the second joint. (See also AAA and AAAA.) B. Wings fringed with long hairs. A minute aquatic species from S. Cal. and Ariz. (Hydroscapha). p. 485 Hydrophilid^ BB. Wings not fringed with hairs. C. Tarsi with second segment dilated. D. Tarsal claws appendiculate or toothed; first ventral abdominal seg- ment with distinct curved coxal Hues. p. 51 1 Coccinellid^ DD. Ta'-sal claws simple; first ventral abdominal segment without coxal lines, p. 511 ENDOMYCHiDiE CC. Tarsi witn second segment not dilated. D. Elytra entirely covering the abdomen; ventral abdominal segments nearly equal, p. 51 1 LATHRiDiiDyE DD. Elytra truncate, the first and fifth abdominal segments longer than the others. E. Maxillae with galea distinct; anterior coxas small, rounded, p. 5C0. MONOTOMID^ EE. Galea wanting, anterior coxas subtransverse. p. 508. Nitidulid^ 474 AN INTRODUCTION TO ENTOMOLOGY AAA. All tarsi four- jointed. (See also AAAA.) B. The first four abdominal segments grown together on the ventral side. C. Tibiae dilated, armed with rows of spines, and fitted for digging, p. 505. Heterocerid^ CC. Tibiae neither dilated nor fitted for digging. D. Antennae inserted under a distinct frontal ridge; anterior coxae distant from the metasternum. p. 510 Colydiid^. DD. Antennae inserted on the front ; anterior coxae inclosed behind by the metasternum. p. 511 Murmidiid^ BB. Ventral segments of abdomen not grown together. C. Anterior coxas transverse, p. 511 Mycet^id.e CC. Anterior coxas either globose or oval. D. Anterior coxae globose. E. Tarsi slender, p. 51 1 Endomychid^ EE. Tarsi more or less dilated and spongy beneath, p. 509. Erotylid^ DD. Anterior coxae oval. E. Anterior coxae separated by the horny prosternum. F. Body depressed; head free. p. 510 Mycetophagid^ FF. Body cyHndrical; thorax prolonged over the head. p. 515. ClSID^ EE. Anterior coxas contiguous ; prosternum semimembranous, p. 505. Georyssid^ ^AAA. Hind tarsi with only four segments; the fore tarsi, and almost always the middle tarsi also, with five segments. B. Anterior coxal cavities closed behind. C. Tarsal claws simple. D. Abdomen with five ventral segments. E. Ventral abdominal segments in part grown together. F. Next to the last segment of the tarsi spongy beneath, p. 514. Lagriid^ FF. Penultimate segment of tarsi not spongy, p. 513 . Tenebrionid^ EE. Ventral abdominal segments free. F. Anterior coxal cavities confluent, p. 498 Othniid^ FF. Anterior coxal cavities separated by the prosternum. G. Elytra truncate; tip of abdomen exposed. p. 5o8.Rhizophagid^ GG. Elytra entire, p. 515 Sphindid^ DD. Abdomen with six ventral segments, p. 498 Eurystethid^ CC. Tarsal claws pectinate, p. 512 Alleculid^ BB. Anterior coxal cavities open behind. C. Head not strongly and suddenly constricted at base. D. Middle coxae not very prominent. E. Antennae received in grooves, p. 514 Monommid^ EE. Antennae free. F. Prothorax margined at the sides. G. Middle coxal cavities entirely surrounded by the sterna, p. 510. Cryptophagid^ GG. Epimera of mesothorax reaching the coxee. H. Metasternum long; epimera of metathorax visible, p. 514. Melandryid/E HH. Metasternum quadrate; epimera of metathorax covered. p. 509 CUCUJID.E FF. Prothorax not margined at the sides, p. 498 Pythid^ DD. Middle coxas very prominent, p. 494 Qi;DEMERiD^ CC. Head strongly constricted at base. D. Head prolonged behind and gradually narrowed, p. 494.Cephaloid^ DD. Head suddenly narrowed behind. E. Prothorax with the side pieces not separated from the pronotum by a suture. F. Prothorax at base narrower than the elytra. G. Hind coxae not prominent or but slightly so. H. Anterior coxae globular, not prominent, p. 509. CucujlD/T; COLEOPTERA 475 HH. Anterior coxaj conical, prominent. I. Abdomen composed of five free segments; tarsi with the penultimate joint lobed beneath. J. Neck wide; eyes large, finely faceted, and generally emarginate. p. 498 Pedilid^ JJ. Neck narrow, eyes not emarginate. K. Eyes large, oval, rather finely faceted, p. 498.Pedilid^ KK. Eyes small, rounded, generally coarsely faceted, p. 498. Anthicid^ II. Abdomen composed of four free segments, the first formed of two united, with the suture sometimes indicated; tarsi with the antepenultimate joint lobed beneath, p. 499.. EUGLENID^ GG. Hind coxee large, prominent. H. Tarsal claws simple; head horizontal. p.498.Pyrochroid^ HH. Claws cleft or toothed, front vertical. P.495.MELOID.E FF. Prothorax at base as wide as the elytra, p. .,'94. .Rhipiphorid.^ EE. Lateral suture of prothorax distinct; base of prothorax as wide as the elytra. F. Antennae filiform. G. Hind coxas plate-like. p. 494 Mordellid^ GG. Hind coxae not plate-like. p. 514 Mel.a.ndryid^ FF. Antenna flabellate in the male, subserrate in the female, p. 494. Rhipiphorid^, TABLE v.— THE FAMILIES OF THE LAMELLICORNIA A. Plates composing the club of the antennae flattened and capable of close apposition. B. Abdomen with six visible ventral segments, p. 515 Scarab^id^ BB. Abdomen with five visible ventral segments. C. Epimera of mesothorax attaining the oblique coxas. p. sis-Scarab/EId^e CC. Epimera of mesothorax not attaining the coxae, p. 522 . . Trogid^ AA. Plates composing the club of the antenna not capable of close apposition, and usually not flattened. B. Mentum deeply emarginate, ligula filling the emargination. p. 524.. PASSALIDiE BB. Mentum entire, ligula covered by the mentum or at its apex. p. 523. LUCANID^ TABLE VI.— FAMILIES OF THE PHYTOPHAGA This series includes three families, which are so connected by intermediate forms that it is not easy to separate them. The following table will aid the student in separating the more typical forms. A. Body elongate; antennae almost always long, often as long as the body or longer. The larvae are borers, p. 524 CERAMBYClDiE AA. Body short and more or less oval; antennae short. B. Front prolonged into a broad quadrate beak; elytra rather short so that the tip of the abdomen is always exposed. The larvae live in seeds, p. 535 Mylabrid^. BB. Front not prolonged into a beak; usually the tip of the abdomen is covered by the elytra. Both larvae and adults feed on the leaves of plants, p. 530 Chrysomelid.?!; TABLE VII.— THE FAMILIES OF THE RHYNCHOPHORA {Compiled from Blatchley and Leng) A. Beak rarely absent, usually longer than broad; tibice never with a series of teeth externally. 476 AN INTRODUCTION TO ENTOMOLOGY B. Antennae straight without a distinct club, though with the outer joints often more or less thickened; beak present at least in the female and pointing directly forward ; form usually very slender and elongate, p. 536..BRENTiDiE BE. Antennae straight or elbowed, always with a distinct club. C. Palpi flexible; antennal club rarely compact; beak always short and broad; labrum present; thorax with a transverse raised line which is either ante-basal or basal, p. 536 Platystomid^ CC. Palpi rigid and labrum wanting except in the subfamily Rhinomacerinas antennal club usually compact; beak variable in length, often long and curved downwards, p. 537 Curclxiomd^* AA. Beak absent or extremely short and broad ; tibiae with a series of teeth ex- ternally, or, if these are wanting, with a prominent curved spine at apex; an- tennae short, but little longer than the head, always elbowed, and with a com- pact club except in PhthorophcEliis where the club is lamellate; palpi rigid; body short, subcylindrical or rarely oval. B. Anterior tarsi with the first segment longer than the second, third and fourth together, p. 541 — Platypodid^ BB. Anterior tarsi with the first segment shorter than the second, third, and fourth together, p. 542 Scolytid^ Suborder ADEPHAGAf The name of this suborder, Adephaga, was suggested by the pre- dacious habits of its members. These beetles are distinguished from other Coleoptera by the presence of a suture on each side of the pro- thorax separating the pleurum from thenotum, and by the fact that the ventral part of the first segment of the abdomen is divided by the hind coxal cavities so that the sides are separated from the very small medial part (Fig. 553). The Adephaga differ from other Coleoptera in that the nutritive cells of the ovaries alternate with the egg- chambers. The larvag are campodeiform, and differ from all other beetle larvae in that their legs are six- jointed except in a single exotic species; this is one more segment than is found in the legs of other beetle larvee. The legs are usually whereas the legs of other coleopterous I St A Fig- 553-— Ventral aspect of part of thorax and abdomen of Galerita janus: ist A, first abdominal seg- ment ; 2d A, second abdominal seg- ment. furnished with two claws, larvag are one-clawed. This suljorder is represented in North America by seven families; these can be separated by Table II, page 469. Family CICINDELID^ The Tiger-Beetles The graceful forms and beautiful colors of the greater number of the tiger-beetles, those of the genus Cicindela, have made the *Sinc2 this table was published by Blatchley and Leng, the family Belidae has been separated from the Curculionidae. See page 537. f Adephaga: adephagous (dSTj^dYos), voracious. COLEOPTERA 477 Fig- 555- Fig- 554- family one of the favorites of students of Coleoptera. Their popular name is sug- gestive of their predacious habits, and of the stripes with which many are marked. They are usually a metallic green or bronze, banded or spotted with yellow. Some are black; and some that live on white sand are grayish white, being ex- actly like the sand in color. Figure 554 represents a common species of Cicindela. A useful character for distinguishing the members of this family is the fact that the terminal hook of the maxilla (the digitus) is united to this organ by a movable joint (Fig. 555, h). The sexes of the tiger-beetles can be distinguished, except in AmblycJieila, by the sixth abdominal segment of the males being notched so as to expose a small seventh segment; while in the females only six segments are visible. In the males, the first three segments of the anterior tarsi are usually dilated and densely clothed with hair beneath. The tiger-beetle larvse (Fig. 556) are as ugly and ungraceful as the adults are beautiful. The two have only one habit in common — their eagerness for prey. The larvae live in vertical burrows in sandy places or in beaten paths. These burrows occur also in ploughed fields that have become dry and hard. The}' often extend a foot or more in depth. The larva takes a position of watchfulness at the mouth of its burrow. Its dirt -colored head is bent at right angles to its lighter-colored body and makes a neat plug to the opening of the hole. Its rapacious jaws extend upward, wide open, ready to seize the first un- wary insect that walks over this living trap, or near it; for a larva will throw its body forward some distance in order to seize its prey. On the fifth t egment of the abdomen there is a hump, and on this hump are two hooks curved forward. This is an arrangement by which the little rascal can hold back and keep from being jerked out of its hole when it gets some large insect by the leg, and by which it can drag its struggling prey down into its lair, where it may eat it at leisure. It is interesting to thrust a straw down into one of these burrows, and then dig it out with a trowel. The chances are that you will find the indignant inhabitant at the remote end of the burrow, chewing savagely at the end of the intruding straw. One hundred and fourteen species of tiger-beetles are now listed in our fauna; these represent four genera, which can be separated as follows : A. Posterior coxae contiguous; eyes large, prominent. B. Third joint of the maxillary palpi shorter than the fourth. . .Cicindela BB. Third joint of the maxillary palpi longer than the fourth Tetracha AA. Posterior coxae separated; eyes small. Fig. 556. 478 AN INTRODUCTION TO ENTOMOLOGY B. Sides of the elytra widely inflexed ; thorax scarcely margined. Amblycheila BB. Sides of the elytra narrowly inflexed; thorax distinctly margined. ..Omus Cicindela. — -To this genus belong the greater number of our tiger- beetles; sevent3'-six species and many varieties occur in our fauna; excepting the two species of Tetracha, all of the tiger-beetles found in the East belong to the genus Cicindela. The members of this genus, unlike most other members of the famil}^ are diurnal in habit. They are found on bright, hot days in dusty roads, in beaten paths, and on the shores of streams. They are the most agile of all beetles; and they are not merely swift of foot, but are also able to fly well. When approached, they remain still until we can see them well but are still out of reach ; then like a flash they fly up and away, alighting several rods ahead of us. Before alighting they usually turn so that they face us, and can thus watch our movements. They hide by night and in cloudy or rainy weather in holes in the ground or beneath stones or rubbish. The beetles have been found hibernating, each in a separate burrow extending under a stone. I have seen them in September digging burrows in a hillside; these descended slightly and were about five inches deep. The beetles kicked the dirt out behind them as they dug, so that it lay in a heap at the opening of the hole. Tetracha. — ^Two species of this genus are widely distributed in the United vStates. They are rather large, metallic-green beetles. Figure 557 represents Tetracha Carolina, which can be distinguished by the apical portion of the elytra being yellow. Our only other species is Tetracha virginica. These beetles are nocturnal, hiding during the day and hunting by night. Amblycheila. — The best-known representative of this genus is Amblycheila cylindriformis, which is ig-557- found in Kansas, Colorado, Arizona, and New Mexico. It is a ver}^ large species, measuring 3 5 mm. in length. It is nocturnal, hiding in holes during the day and coming forth at night to capture its prey. Two other species of this genus have been described from Arizona and Utah. OmM5.— Thirty-three species of this genus have been found on the Pacific Coast, nearly all of them in California. They are nocturnal insects, hiding under rubbish during the daytime. Family CARABID^ The Grcund-Beetles The ground-beetles are so called because they are very common on the surface of the ground, lurking under stones or rabbish, where they hide by day. At night they roam about in search of their prey. Our more common species are easily recognized by their shining black color and long legs. On the Pacific Coast, however, the darkling beetles (Family Tenebrionidce) , which are also black and have long ^egs, abound under stones and fragments of wood on the ground. COLhOPTERA 479 But the two families can be easily distinguished by the fact that in the ground-beetles all the tarsi are five-jointed, while in the darkling beetles the hind tarsi are only four-jointed; and the darkling beetles do not run rapidly as do the ground-beetles. With the ground-beetles, the antennae are thread-like, tapering gradually towards the tip, and each segment is of nearly uniform thickness throughout its length ; the legs are fitted for running, and the antennas are inserted between the base of the mandibles and the eyes. Although most of the species are black, there are those that are blue, green, or brown, and a few that are spotted. The wing- covers are almost always ornamented with longitudinal ridges and rows of punctures. Most members of this family are predacious, feeding upon other insects, which they spring upon or capture by chase. A few species use vegetable food; but their depredations are rarely of economic importance. As there are more than two thousand described North American species, and as many of the species are very common, this family may be considered the most important family of the pre- dacious insects. The larvas of ground-beetles are generally long, with the body of nearly equal breadth throughout (Fig. 558). They have sharp projecting mandibles; and the caudal end of the body is usually furnished with a pair of conical bristly appendages. I'hey p-„ -1.3 live in the same obscure situations as the adult insects, but are more shy, and are consequently less frequently seen. Like the adults, they are predacious. Among the more common ground-beetles are the following. The searcher, Calosoma scrutator. — This is one of the larger and more beautiful of our ground-beetles ; it has green or violet wing-covers margined with reddish, and the rest of the body is marked with violet-blue, gold, green, and copper (Fig. 559). This beetle and the two follow- ing have been known to climb trees in search of caterpillars. Calosoma sycophanta, a common species in EurojDe, has been introduced and success- fully colonized in New England, as a means of combating the gipsy-moth and the brown-tail moth. This species is somewhat smaller than the preceding, and lacks the reddish band on the margins of the el}^ra. The fiery hunter, Calosoma calidum, is easily recognized by the rows of reddish or copper-colored pits on the wing-covers (Fig. 560). The bombardier-beetles, Brachmus. — There are many species of beetles that have at the hind end of the body little sacs in which 480 AN INTRODUCTION TO ENTOMOLOGY Fig. 560. is secreted a bad-smelling fluid, which is used as a means of defence. These beetles spurt this fluid out onto their enemies when attacked. But in the case of the bombardier-beetles this fluid changes to a gas, which looks like smoke as soon as it comes in contact with the air, and is ejected with a sound like that of a tiny pop- gun. When some larger insect tries to capture one of these insect-soldiers, and gets very near it, the latter fires its little gun into the face of its enemy. The noise astonishes the pursuer, and the smoke blinds him. By the time he has recovered from his amazement, the little bombardier is at a safe distance. These beetles have quite a store of ammunition; for we have often had one pop at us four or five times in succession, while we were taking it prisoner. The bombardier-beetles belong to the genus Brachinus, of which we have in this country twenty-seven species. They are very similar in appearance; the head, prothorax, and legs are reddish yellow, and the wing-covers are dark blue, blackish, or greenish blue (Fig. 561). There is a common beetle which resembles the bom- bardier-beetles quite closely in size and color, but which may be distinguished by the comb-like form of the tarsal claws; this is Lebia grandis (Fig. 562). It has been reported more often than any other insect as destroying the Colorado potato-beetle. Galerlta jdnns is still another species that bears some resemblance to the bombardier-beetles. But it is much larger, measuring 16 mm. in length, and has only the prothorax and legs reddish yellow, the head being black ; the prothorax is only about half as wide as the wing-covers. What is perhaps the most com- mon type of ground -beetle is illus- trated by Hdrpalus caliginosus, which is represented natural size in Figure 563. It is of a pitchy black color, and is one of the most common of our larger species. There are one hundred and thirty-six de- scribed species of Harpalus in this country. Most of them are smaller than this one, are flattened, and have the prothorax nearly square. The beetles of the genus, Diccelus are quite common ; and some of the larger species resemble Harpalus caliginosus quite closely. They can be distinguished by a prominent keel- shaped ridge which extends back upon each wing- cover from near the corner of the prothorax. Fig. 561. Fig. 563. Fig. 562. — Lebia grandis, natu- ral size and enlarged. Fig. 564. COLEOPTERA 481 The most common of all ground-beetles, in the Northeastern States at least, is Poecilus lucubldndns. In this species (Fig. 1 64) the nar- row, flat margin on each side of the prothorax is widened near the hind angle of this segment. The family AMPHIZOID,^ is represented in our fauna by two species of Amphizoa, which occur in California, Vancouver, and Alaska, clinging to logs or stones under the surface of streams. In these beetles the metastemum is truncate behind, not reaching the abdomen, and has a very short antecoxal piece. The family OAIOPHRONID^ consists of a single genus, Omophron, the members of which are remarkable for their round form and the fact that the scutellum is entirely concealed. They measure about 6 mm. in length, and are found in holes in wet sand near the margins of streams and ponds. They are found from the Atlantic to the Pacific; fourteen species have been described. Family HALIPLID^ The Crawling Water-Beetles This family includes a few species of small aquatic beetles, which are oval, more or less pointed at each end, and very convex; our larger species measure from 3.5mm. to 5 mm, in length, but some are much smaller. The wing-covers have rows of punctures, and the hind coxse are greatly expanded so as to conceal the basal half of the hind femora and from three to six of the abdominal segments. The anterior and middle tibiae and the tarsi of all of the legs are fur- nished with long, swimming hairs. These beetles are found in ponds and streams, but most frequently in spring-fed pools that do not dry^ up during the summer, and contain filamentous algs and other aquatic plants. They swim poorly but crawl over the stems of aquatic plants. Little is known regarding the feeding habits of the adults. Matheson ('12) found that several species feed on the contents of the cells of A7/e//a and the softer portions of Chara and other filamentous algas. He observed also that two species of Peltodytes attach their eggs to aquatic plants, mainly Nitella and Chara, while Haliplus ruficollis places its eggs within the dead cells of Nitella The larvae are aquatic, living in the same pools as the adults. The body is slender; each segment except the head is furnished on the back with fleshy lobes with spiny tips (Fig. 565), which vary greatly in size in different species; in the larvse of Peltodytes each of these spines bears a long, jointed filament, which is a tracheal gill. The larvae of this genus have no spiracles; but the larvae of Haliplus possess both thoracic and Fig. 565. abdominal spiracles. The larvae of the Haliplidce feed on filamentous algse; when mature, they leave the water and each makes a cell in the damp earth in which the pupa state is passed. About forty species of the Haliplidse have been found in our faima ; these represent three genera. In Brychius, which is represented i82 AN INTRODUCTION TO ENTOMOLOGY by two species in California, the prothorax is quadrate; in the other genera it is narrowed in front. In Hdliplus the last segment of the palpi is small and awl-shaped; in Peltodytes it is longer than the third segment, and conical. The last two genera are widely distribu- ted. Family DYTISCID^ The Predacious Diving-Beetles If one will approach quietly a pool of standing water, there may be seen oval, flattened beetles hanging head downward, with the tip of the abdomen at the surface of the water. Such beetles belong to this family. The predacious diving-beetles are usually brownish black and shining, but are often marked indefinitely with dull yellow They can be distinguished from the water scavenger-beetles, which they resemble in general appearance, by the thread-like form of the antennae. The hind legs are the longest and are fitted for swimming, being flattened and fringed with hair. The middle and the hind pair of legs are widely separated. This is due to the very large hind coxae which cover the greater part of the lower surface of the thorax. In the males of certain genera the first three segments of the fore tarsi are di- lated and form a circular disk, upon the under side of which are little cup- like suckers (Fig. 566); these serve as clasping organs. In a few cases the middle tarsi are dilated also. The fe- males of some species exhibit an inter- Fig. 566. Fig. 567. esting dimorphism in that some of the individuals have the elytra fur- nished with a nimiber of deep furrows (Fig 567), while others of the same species have them smooth. The diving-beetles abound in our streams and ponds, but they are more often foimd in standing water than in streams. When at rest they float in an inclined position, head downward, with the tip of the hind end of the body projecting from the water. The spiracles open on the dorsal side of the abdomen beneath the elytra. By lifting the elytra slightly a reservoir is formed for air, which the beetle can breathe as it swims through the water. When the air becomes impure the beetle rises to the surface, forces it out, and takes a fresh supply. These beetles are very voracious. They destroy not only other insects, but some of them will attack larger animals, as small fish. When kept in aquaria they can be fed upon any kind of meat, raw or cooked. They fly from pond to pond, and are often attracted to light at night. Many of the species make sounds, both under the water and in the air. In some cases this is done by rubbing the abdominal segments upon the elytra; in others, by rubbing the hind legs upon a rough spot on the lower side of the abdomen. COLEOPTERA 483 The females deposit their eggs singly in punctures in the tissues of living plants. The larvce are known as water-tigers, because iw-.s^^-"»..^^««t=.s of their blood-thirsti- ^Oife'^-^?'*rA««'»l' ness. They are elon- gated, spindle-form Fig. 568. grubs (Fig. 568). The head is large, oval or rounded, and flattened; the mandibles are large and sickle-shaped; in each there is a slit-like opening near the tip; from this opening a canal leads along the inner surface to a basal opening on the upper surface, which communicates with the corner of the mouth when the mandible is closed. The central part of the mouth, between the mandibles, is closed, the upper and lower lips being locked together by a dovetail joint. The mandibles are ad- mirably fitted for holding prey and at the same time sucking juices from its body. The thorax is furnished with six well-developed legs. The abdomen is terminated by a pair of processes ; at the tip of the abdomen there is a pair of large spiracles, wdiich the larva protrudes into the air at intervals, in order to breathe. When a larva is fully grown it leaves the water, burrows into the ground, and makes a round cell, within which it midergoes its trans- formations. The pupa state lasts about three weeks in summer; but the larvae that transfoitn in autumn remain in the pupa state all winter. This is the largest of the families of water-beetles; more than three hmidred North American species are known. The best way to obtain specimens is to sweep the vegetation grow- ing on the bottom of a quiet pool with a dip-net. The larger of our common species belong to Cybtster, Dytiscus, and allied genera. In Cyhister the little cups on the under side of the tarsal disks of the male are similar, and arranged in four rows. In Dytiscus and its allies the cups of the tarsal disks vary in size. Figure 569 represents a common species of Dytiscus. The most common of the diving-beetles which are of medium sizebelongto the genus AcUius. In this genus the elytra are densely punctured with very fine punctures, and the females usually have four furrows in each wing-cover (Fig. 567). There are also common diving-beetles which are of about the same size as the preceding, but which have the wing- covers marked with numerous very fine transverse stri«; these be- long to the genus Colymbetes. Of the smaller diving-beetles, measuring less than 6 mm. in length, many species can be fotmd in almost any pond. These represent many genera. Fig. 569. 484 AN INTRODUCTION TO ENTOMOLOGY Family GYRINID^ The Whirligig-Beetles As familiar to the country rover as the gurgling of the brook or the flecks of foam, on its "golden -braided centre," or the trailing ferns and the rustling rushes on its banks, are these whirligigs on its pools. Around and around each other they dart, tracing graceful curves on the water, which vanish almost as soon as made. They are social fellows, and are almost always fotmd in large numbers, either swimming or resting motionless near together. They rarely dive, except when pursued; but are so agile that it is extremely difficult to catch them without a net. Many of them when caught exhale a milky fluid having a very disagreeable odor. They feed upon small flies, beetles, and other insects that fall into the water, and are furnished with well-developed wings, with which they fly from one body of water to another. This is one of the most easily-recognized families of the whole order Coleoptera. The members of it are oval or elliptical in form (Fig. 570), more or less flattened, and usually of a very brilliant bluish black color above, with a bronze metallic lustre. The fore legs are very long and rather slender; the middle and hind legs are short, broad, and very much flattened. These insects are remarkable for having the eyes completely divided by the margin of the head, so that they appear to have four eyes— a pair upon the upper surface of the head with which to look into the air, and a pair upon the under side for looking into the water. The antennse are very short and peculiar in form. The third segment is enlarged, so as to resemble an ear-like appendage, and the following ones form a short spindle- shaped mass. They are inserted in little cavities in front of the eyes. The eggs of these insects are small, of cylindrical form, and are placed end to end in parallel rows upon the leaves of aquatic plants. The larvae (Fig. 571) are long, narrow, and much flattened. Each abdominal segment is furnished with a pair of tracheal gills, and there is an additional pair at the caudal end of the body. The elongated form of the body and the con- spicuous tracheal gills cause these larvse to resemble small centipedes. When a larva is full-grown it leaves the water and spins a gray, paper-like cocoon attached to some object near the water. The pupa state of those species in which it has been observed lasts about a month. Fig. 571. The family is a small one. At present only forty-one North American species are known. These represent three genera. The genus Gyretes is distinguished by having the last ventral segment of the abdomen elongated and conical. It is represented by two species. In the other two genera the last ventral segment is flattened and rounded at the tip. In Dineutus the scutellum is invisible; there are thirteen species of this genus. In C'^nwMs the scutellum is visible; of this genus we have twenty-six species. COLEOPTERA 485 Fig. 574. — Ventral aspect of part of thorax and abdomen of Enchro- ma gigantea: ist A, first abdom- inal segment. Suborder POLYPHAGA* In the suborder Polyphaga the ventral part of the first segment of the abdomen is visible for its entire breadth (Fig. 574); the first three ventral segments are im- movably united (except in the Cupesidee), and the notum of the prothorax is not separated from the pleura by distinct sutures. So far as known, the nutritive cells of the ovaries are massed to- gether in the terminal chamber of each ovarian tube in all members of this suborder. The larvae vary greatly in form ; some are campodeiform, some are scarabeiform, and others are vermi- form ; in none are the legs more than five-jointed, and in none are the legs two-clawed. This suborder includes all but the seven preceding families of the Coleoptera ; the families included in it are grouped into seven series ; see synopsis, page, 467. Family HYDROPHILID^ The Water-Scavenger Beetles The water-scavenger beetles are common in quiet pools, where they may be found swimming through the water, or crawling among the plants growing on the bottom. They can be easily taken by sweeping such plants with a dip-net. They are elongated, elliptical, black beetles, resembling the pre- dacious diving beetles in appearance; but they are usually more convex, and differ also in having club-shaped antennae and very long palpi. As the antennae are usually concealed beneath the head, it often happens that the inexperienced student mistakes the long palpi for antennae. These beetles are supposed to live chiefly upon the decaying vege- tation in the water; but a number of species have been known to catch and eat living insects. They breathe, by carrying a film of air on the lower surface of the body. This film gives them a silvery appear- ance when seen from below. They obtain the air by bringing the head to the surface of the water and pro- jecting the antennte, which they again fold back with a bubble of air when they descend. The female makes a case for her eggs out of a hardened silk-like secre- tion. Some species deposit as many as a hundred eggs in one of these water-proof packages (Fig. 572). The egg-cases in some instances are fastened beneath the Fig. 57; *Polyphaga: polyphagus, eating many kinds of food. 486 A N INTROD UCTION TO ENTOMOLOG Y leaves of aquatic plants; in others they are provided with floats and let loose in the water; and in still other species the cases are carried by the mother underneath her body and steadied with her hind legs. Frequently some of the young larvse devour their companions; in this way the size of the family is decreased before it escapes from the egg-case. Later they live upon insects that fall into the water, and upon snails. These larvse resemble somewhat those of the Dytis- cidae; but the body is much more plump, and the mandibles are of moderate size. The family Hydrophilidse is represented in North America by one hundred and ninety species. The largest of our common species is Hydrous triangularis (Fig. 573). In the genus Hydrous the metasternum is prolonged back- ward into a spine between the hind legs, and the sternum of the prothorax bears a deep Fig- 573- furrow. The beetles of the genus Tropisternus agree with Hydrous in the form of the prosternum and metasternum, but differ in size, our species measuring less than 12 mm. in length. The most common species in the East is Tropisternus glabra, and on the Pacific Coast T. calif ornicus. Next in size to Hydrous are several species of Hydrophilus. In this genus the metasternum is prolonged somewhat, but does not form a long, sharp spine as in Hydrous and Tropisternus, and the sternum of the prothorax bears a keel-shaped projection. Our most common species is Hydrophilus obtusdtus; this measures about 1 5 mm. in length. Some of the smaller species of this family are not aquatic, but live in moist earth and in the dung of cattle, where, it is said, they feed on dipterous larvas. Family PLATYPSYLLID^ The Beaver-Parasite Only a single representative of this family is known; this is Platypsylla cdstoris, which lives parasitically on the beaver. This beetle is about 2.5 mm. in length; the body is ovate, elongate, and much flattened; the wing-covers are short, about as long as the prothorax, and leave five abdominal segments exposed ; the eyes and wings are wanting. Specimens of this remarkable insect are most easily obtained by beating over a sheet of paper the dried skins of beavers, which can be found in fur-stores. The family BRATHINID^ is composed of the genus Brathinus, of which three species are described, two from the East and one from California. These beetles are somewhat elongate, with the outline COLEOPTERA 487 of the prothorax and of the elycra elliptical; they measure from 3.6 mm. to 5 mm. in length. The Califomian species was found living in wet moss, darkly overshadowed by bushes, at the margin of a mountain stream. Family LEPTINID^ The Mammal-Nest Beetles This famih' is represented by only three species in North America. One of these, Leptimis testdceus, is a European species, but is widely distributed in this country. It lives in the nests of mice and other small rodents and insectivora, and also in the nests of bumble-bees. Whether it is a parasite or merely a guest has not been definitely de- termined ; but it seems probable that it feeds upon the eggs and young of mites and other small creattires found in these nests. This beetle is oblong-oval and much depressed in form, and pale yellow in color; it measures from 2 mm. to 2.5 mm. in length. Specimens can be obtained by shaking a nest of a mouse over a sheet of paper. The other two species are Leptinlllus vdlidus, found in Hudson Bay territory, and Leptintllus aplodontice, found in California on a rodent {Aplodontia) . Family SILPHID^ The Carrion-Beetles The carrion-beetles are mostly of mediiim or large size, many species attaining the length of 35 mm. while the smaller species of the more typical genera are nearly 12 mm. in length; some members of the family, how- ever, are minute. The segments near the tip of the antennas are usually enlarged so as to form a compact club, which is neither comb- like nor composed of thin movable plates; sometimes the antennse are nearly filiform. These insects usually feed upon decaying animal matter; some, however, feed upon fungi; some on vegetables ; and a few species have been known to be predacious when pressed by hunger, destroying living snails and insects, even members of their own spe- cies ; while a few occur only in the nests of ants. It is easy to obtain specimens of these in- sects by placing pieces of meat or small dead pjg ^^^ animals in the fields and examining them daily. There are several other families of beetles the members of which can be attracted in this way. The larv£e also live upon decaying flesh and are found in the same situations as the adults. We haxe in this country more than one hundred species of this family. Our larger and more familiar species represent two genera, Necrophoriis and Silpha. The burying-beetles, Necrophorus. — To this genus belong the larger members of the family The body is very stout, almost cylin- drical (Fig. 575). Our common species have a reddish spot on each 488 AN INTRODUCTION TO ENTOMOLOGY end of each wing-cover; these spots are often so large that they appear as two transverse bands. In some species the prothorax and the head are also marked with red. These insects are called burying-beetles because they bury carrion. When a pair of these beetles discover a dead bird, mouse, or other small animal, they dig beneath it, removing the earth so as to allow the carrion to settle into the ground. This they will continue until the object is below the surface of the groimd. Then they cover it with earth, and finally the female digs down to it and lays her eggs upon it. The larvae that hatch from these eggs feed upon the food thus provided for them. There are many accoiints of exhibitions of remarkable strength and sagacity by burying-beetles. A pair of these insects have been known to roll a large dead rat several feet in order to get it upon a suitable spot for burying. The members of the genus Silpha are very much *f flattened (Fig. 576). The prothorax is rotmd in outline, with very thin edges which overlap the wing-covers \ somewhat. The body is not nearly as stout as that of \ a burying beetle, being fitted for creeping imder y dead animals instead of for performing deeds requiring great strength. Silpha bituberosa, which is 1-cnown as rig- 576- the spinach carrion-beetle, feeds on spinach, beets, and other plants, in the West. In some of the minute members of this family the body is nearly hemispherical. The family CLAMBID.^ consists of very minute species, measur- ing about I mm. in length. They live in decomposing vegetable matter. The edge of the hind wings is fringed with long hairs. For other characters, see table,' page 470. Only six species, representing three genera, occur in our fauna. The family SCYDM^ENID^ includes very small insects found under bark or stones, in ants' nests, or near water. They are small, shining, usually ovate but sometimes slender insects, of a brown color, and more or less clothed with erect hairs. Other characters are given in the preceding table of families. About one hundred seventy-five North American species are known. The family CORYLOPHID^^ includes minute beetles fomid under damp bark and in decaying fungi and other vegetable matter. The body is oval or rounded, and in many species is clothed with a grayish pubescence. The wings are wide, and fringed with long hairs. Some of our common species measure less than i mm. in length. Fifty- seven North American species have been described. Family STAPHYLINID^ The Rove-Beetles The rove-beetles are very common about decaying animal matter, and are often found upon the groimd, imder stones or other objects. COLEOPTERA 489 They are mostly very small insects; a few species, however, are of larger size, measuring 12 mm. or more in length. Their appearance is very characteristic, the body being long and slender, and the wing-covers very short (Fig. 577). The wings, however, are fully developed, often exceeding the ab- domen in length; when nob in use the wings are folded beneath the short wing-covers. The abdominal seg- ments are freely movable. It is interesting to watch one of these insects fold its wings; frequently they find it necessary to make use of the tip of the abdomen or of one of the legs in order to get the wings folded beneath the wing-covers. Fig. 577. The rove-beetles can run quite swiftly; and they have the curious habit, when disturbed, of raising the tip of the abdom.en in a threatening manner, as if they could sting. As some of the larger species resemble wasps somewhat in the form of the body, these threatening motions are often as effective as if the creatures really had a sting. William Beebe states (Atlantic Monthly, October 1919) that when some rove-beetles were attacked by ants they raised their tails and ejected a drop or two of a repellent fluid which drove the ants away. This observation indicates the probable explanation of the actions of these beetles when disturbed. As these insects feed upon decaying animal and vegetable matter, they should be classed as beneficial. The larvae resemble the adults in the form of the body and are found in similar situations, about decaying animal and vegetable matter, beneath bark and in fungi. Some species are guests in the nests of ants, and others in the nests of termites. Nearly three thousand North American species of rove-beetles have been described. The great majority are small and exceedingly difficult to determine. Among the large species that are common are the following. Creophilus maxilldsus. — This species varies from 12 mm. to nearly 25 mm. in length. It is of a shining black color, spotted with patches of fine gray hairs. There is a conspicuous band of these across the middle of the wing-covers, and another on the second and third abominal segments; this abdominal band is best marked on the lower side of the body. Staphylinus maculosus is a larger species, which often measures fully 25 mm. in length. It is densel}^ punctured, and of a dull brown color, with the scutellimi black, and a row of obscure, square, blackish spots along the middle of the abdomen. Staphylinus vulplnus resembles the preceding somewhat, but it has a pair of bright yellow spots at the base of each abdominal segment. Ontholestes cinguldtus is of about the same size as the preceding. It is brown, speckled with brownish black spots, and the tip of its abdomen is clothed with golden hairs. The family PSELAPHID.^ includes certain very small beetles, the larger ones not exceeding 3 mm. in length. They resemble rove- 490 AN INTRODUCTOIN TO ENTOMOLOGY beetles in the shortness of the wing-covers and in having the dorsal part of the abdominal segments entirely horny; but they differ from them in that the abdomen is not flexible, and in having fewer abdominal segments, there being only five or six on the ventral side. The species are chestnut-brown, dull yellow, or piceous, and are usually slightly pubescent. The antennae are usually eleven-jointed, rarely ten-jointed. The elytra and abdomen are convex and usually wider than the head and prothorax. These beetles are usually found under stones and bark, or flying in the twilight; a few species have been found in the nests of ants. There are three hundred and fifty- five described North American species. The family CLAVIGERID^^, or the ant-loving beetles, includes a small number of beetles that resemble the Pselaphidee in the char- acters given above except that the antennas are only two-jointed. These beetles live in the nests of ants. They excrete from small tufts of hairs, on the three basal abdominal segments, a fluid of which the ants are very fond. The ants caress the tufts of hairs with their antenna?, causing the exudation of the fluid, which they greedily swallow. The ants are said to feed the beetles and to allow them to ride about on their backs, when the beetles wish to do so. Only seven North American species are described. The family TRICHOPTERYGID^, or the feather-wing beetles, includes the smallest beetles that are known; most of our species are less than i mm. in length. The most striking feature of the typical forms is the shape of the wings, which are long, narrow, and fringed with long hairs, being feather-like in appearance; but in some species the wings are wanting. Some species live in rotten wood, muck, manure, and other decaying organic matter; few have been found in ants' nests. There are about eighty described species in our fauna. The family SCAPHIDIID^, or shining fungus-beetles, includes small, oval, very shining beetles, found in fungi, rotten wood, dead leaves, and beneath the bark of logs. The elytra are broadly truncate behind, not covering the tip of the conical abdomen. But little is known regarding their life-history. There are fifty described North American species. The family SPH^RITID^E is represented in our fatma by a single species, Sphcerites glabrdtus, which has been found in Alaska and California. This beetle is very similar in appearance to those of the genus Hister. For distinguishing characters, see table, page 470. The family SPH^RIID^ includes a single genus, Sphcerius, which is represented in North America by only three known species. They are very minute beetles, measuring about .5 mm. in length; they are very convex, and may be found walking on mud or under stones near water. The family HISTERID^ includes certain easily recognized beetles which are found about carrion and other decomposing sub- stances. They are mostly small, short, rounded or somewhat square- shaped beetles, of a shining black color, with the wing covers marked COLEOPTERA 491 by lines of fine punctures and truncate behind, leaving two segments of the abdomen exposed (Fig. 578). In some species the wing-covers are marked with red. There are nearly four \u I hundred described North American species. Mf The family LYCID^ includes certain 'B|\ beetles that were formerly classed in the ^ ^ fire-fly family; but they differ from the Fig. 578. Lampyrid^e in having the middle coxte distant, and in that the elytra lack epi- pleurae. The elytra are usually furnished with several longitudinal ribs and a network of fine elevated lines. The members of this family are diurnal in habits; they are found on the leaves of plants, where they seek and feed upon other insects. A common species is Calopteron reticuldtunt (Fig. 579). Family LAMPYRID^ The Firefly Family During some warm, moist evening early in our northern June we are startled to see here and there a tiny meteor shoot out of the darkness near at hand, and we suddenly realize that summer is close upon us, heralded by her mysterious messengers, the fireflies. A week or two later these little torch-bearers appear in full force, and the gloom that overhangs marshes and wet meadows, the dusk that shrouds the banks of streams and ponds, the darkness that haunts the borders of forests, are illumined with myriads of flashes as these silent, winged hosts move hither and thither under the cover of the night. The fireflies are soft-bodied beetles of medium or small size, with slender, usvially eleven-jointed, saw-like antennae. The prothorax is expanded into a thin projecting margin, which in most cases com- pletely covers the head (Fig. 580). The wing-covers are rather soft, and never strongly embrace the sides of the abdomen, as with most other beetles. The fireflies are nocturnal insects and are sluggish by day. The property of emitting light is possessed by adults of both sexes and by larvee. The latter and the wingless females of certain species are known as glow-worms. The light-organs of the winged adults are situated on the lower side of one or more .of the abdominal segments; but they '^^" ^ ^' are lacking in some genera. There have been many speculations as to the usefulness of the light-producing power of various organisms to the organisms them- vSelves ; and as regards many of these photogenic creatures no definite conclusions have been reached. But there is considerable evidence to show that in the case of adult lampyrids it serves to enable these insects to find their mates. It has been found that females enclosed in a perforated opaque box do not attract males, while those enclosed 492 AN INTRODUCTION TO ENTOMOLOGY in a glass vial do; thus showing that it is the light emitted by the female, and not its odor, that attracts the male. It has also been shown that in some cases at least there are specific differences in the method of flashing which enables the insects to distinguish at a distance their proper mates. More than fifty species of the Lampyridae have been found in this country. The faniily PHENGODID^ includes a small nimiber of species that were formerly included in the firefly family. In this family the prothorax, though rounded in front, does not cover the head, which is exposed. The antennae are usually plumose or flabellate in the males. The females of some species, at least, are glow-worms, re- sembling the larvae in form, and are photogenic. Only twenty -three American species have been described ; most of these are found in California, Texas, and Arizona, but some occur in the East. Family CANTHARID^ The Soldier-Beetles and others The family Cantharidae includes those genera that were formerly included in the family Lampyridas as the subfamily Telephorinae. For the distinctive characters separating this from the allied families, see the table, page 473. The application of the name Cantharidce to this family is the result of one of those unfortunate changes in generic names rendered necessary by our code of nomenclature. In this case the change is especially unfortunate, as the generic name Cantharis has been com- monly applied to certain blister-beetles and is used in that sense in many medical works and in most text-books of entomology. The change is sure to result in much confusion. The most common members of this family are the soldier-beetles, Chauliognathus. These are very abundant in late summer and autumn on various flowers, but especially on those of goldenrod. The most com- mon species in the East are the Penn- sylvania soldier-beetle, Chaidiognathus pennsylvdnicMS, which is yellow, with a black spot in the middle of the pro- thorax and one near the tip of each wing-cover (Fig. 581); and the mar- _. gined soldier-beetle, C. niargindtus. l^ig. 581. ^j^.g gpg^igg (pig_ ^g2) can be dis- tinguished from the former by the head and lower parts of the femora being orange. The beetles of this genus are remarkable for having an extensible, fleshy filament attached to each maxilla. These fila- ments are probably used in collecting pollen and nectar from flowers. This family is represented in our fauna by nine genera which in- clude more than one hundred and fifty species. COLEOPTERA 493 The family MELYRIDvE is composed chiefly of small or very small beetles, some of which are found on flowers, and others on the groimd in low, moist places. They are said to be carnivorous. They var}'' greatly in form, but bear a general resemblance in structure to the preceding four families, from which they can be distinguished by the presence of only six ventral abdominal segments. Some members of the family are furnished with soft, orange- colored vesicles, which they protrude from the sides of the body and which are supposed to be scent organs for defence. One of our most common representatives is Collops quadrimaculdtus, which is yellow-orange, with Fig. 583. the top of the head and four spots on the elytra bluish black (Fig. 583). This species is foimd on grasses in damp localities. The family is represented in our fauna by more than three hundred species. The family CLERID^, or the checkered beetles, includes a con- siderable nimiber of predacious species which are foimd on flowers and on the trunks of trees. Many of them are beautifully marked with strongly contrasting colors; this has suggested the common name checkered beetles for them. Frequently they are more or less ant -like in form, the prothorax being in these cases narrower than the wing-covers, and slightly narrower than the head. The abdomen has either five or six ventral segments; the anterior coxae are conical, prominent, and contiguous, or very slightly separated; the hind coxae are transverse, not prominent, and covered by the femora in repose; the legs are slender ; and the tarsi are five-jointed. In the larval state these insects are usually carnivo- rous, living under bark and in the burrows of wood-boring insects, upon which they prey; some are found in the nests of bees; and still others feed on dead animal matter. The family is represented in our fauna by nearly two hundred species. Figure 584 represents one of our more common species, Trichodes nuttalli. The family CORYNETID^ has recently been sep- arated from the Cleridae, which they closely resemble. In this family the fourth joint of the tarsi is atrophied; this character distinguishes these beetles from the Clerid^. About forty American species have been described. To this family belongs the red-legged ham-beetle, Necrobia rufipes. This is a small steel-blue beetle with reddish legs; it measures from 3.5 mm. to 6 mm. in length. It is found about dead animal matter in fields and in other situations. It sometimes invades storehouses and seriously infests hams. The family LYMEXYLID^E includes elongated, narrow beetles, with short serrate antennas. Only two species have been found in this country and these are rare. To this family belongs the ship- timber beetle, Lymexylon navdle, of northern Europe. The larva of this species was at one time a very serious pest in ship-yards, on accotmt of its habit of drilling cylindrical holes in the timber. The 494 AN INTRODUCTION TO ENTOMOLOGY method of control by immersing the timber during the time of ovi- position of the beetle was suggested by Linnaeus. The family MICROMALTHID^ includes a single species, Micromdlthus debilis. This is a small beetle, measuring only 2.2 mm. in length. It is elongate, piceous, shining, with the antennas and legs yellow. This species is of great interest on account of its remarkable life-history, only a part of which is yet known. Two papers on this subject have been published by Mr. H. S. Barber ('13a, '13b). Briefly, this author's observations indicate that eggs are produced by larvae as well as by the adult females; that there are seven or eight forms of larvae ; that the two sexes of adults are developed through two distinct lines of larvae; and that viviparous as well as oviparous paedogenesis occurs in the life-cycle. The larvae are found in decaying oak, chestnut, and pine logs, where they make burrows in the decay- ing wood, on which they feed. The family CUPESIDiE includes only four American species. These are found under the bark of decaying trees, and sometimes in houses. The body is covered with small scales; other characteristics are given in the table of families, page 471. The family CEPHALOID^E is a small family of which only eight American species have been described. See table, page 474, for dis- tinctive characters. The family CEDEMERID^ is composed of beetles of moderate size, with elongate, narrow bodies. The head and prothorax are somewhat narrower than the wing-covers; the antennae are long, nearly filiform, sometimes serrate; the anterior coxal cavities are open behind, and the middle coxae are very prominent. Less than fifty North American species have been described. They are generally found on plants, but some live on the ground near water. The larvae live for the most part in decaying wood. ^^ The family MORDELLIDiE includes a large number >l9i|( of small beetles which are easily recognized by their pe- /7U--4 culiar form (Fig. 585). The body is arched, the head Fig- 585. being bent down; and the abdomen is usually prolonged into a slender point. Our most common species are black; but many are variegated, and all are pubescent. The adults are usually found on flowers ; the larvae live in rotten wood and in the pith of various plants, upon which they are supposed to feed. Nearly one hundred fifty American species have been described. The family RHIPIPHORID^ includes a small num- ber of beetles, which are very remarkable in structure and habits. The wing-covers are usually shorter than the ab- domen, and narrowed behind (Fig. 586) ; sometimes they are very small, and in one exotic genus they are wanting p- g^ in the female, which lacks the wings also and resembles a larva in form. The antennae are pectinate or flabellate in the males, and frequently serrate in the females. The adult insects are foimd on flowers. The larvae that are known are parasites, some in the nests of wasps, and some on cockroaches. COLEOPTERA 495 Family MEhOYDM The Blister-Beetles The blister-beetles are of medium or large size. The body is com- paratively soft; the head is broad, vertical, and abruptly narrowed into a neck; the prothorax is narrower than the wing-covers, which are soft and flexible ; the legs are long and slender ; the hind tarsi are four-jointed, and the fore and middle tarsi are five-jointed. These beetles are found on foliage and on flowers, on which they feed in the adult state; some of the species are very common on goldenrod in the autumn; and several species feed on the leaves of potato. The blister-beetles are so called because they are used for making blister-plasters. The beetles are killed, dried, and pulverized, and the powder thus obtained is made into a paste, which when applied to the skin produces a blister. The species most commonly used is a European one, comm.only known as the Spanish-fl}^; but our Ameri- can species possess the same blistering property. The postembryonic development of those blister-beetles of which the complete life-history is known is a very remarkable one; for it has been found that in each of these cases there is a complicated hypermetamorphosis. The food of the larva consists, in some species, of the eggs of short-horned grasshoppers, in others of the egg and the food stored in the cell of some solitary bee. The female blister-beetle lays her eggs in the ground; a large number of eggs are laid by a single female ; this fact is doubtless correlated with the difficulties to be overcome by the lai-v^ in their search for their proper food, in which comparatively few are successful. The newly hatched larva is cimpodeiform (Fig. 587, A), and is known as the triungulin, a term applied to the first instar of blister-beetle larvee. This term was sug- gested by the fact that in this instar the tarsi appear to be three- clawed; but in reality each tarsus is armed with a single claw, on each side of which there is a claw-like seta. The triungulins are very active. In the case of those that feed on the eggs of short-homed grasshoppers, they run over the ground seeking a place where one of these insects has deposited its egg-pod; if a triungulin is successful in this search it bores its way into the egg- pod; if more than one find the same egg-pod, battles occur till only one is left. In the case of those species that develop in the nests of bees, the triimgulin, instead of hunting for a nest, merely climbs a plant, and remains near a flower till it has a chance to seize hold of a bee visiting the flower; it then clings to the bee until she goes to her nest, then, letting go of the bee, it remains in the cell and is shut up there with the egg of the bee and the store of food which she provides for her yoimg. The triungulin first devours the egg; after which it molts and undergoes a change of form, becoming a clumsy creature, which feeds upon the food stored in the cell. Several other changes in form occur before the beetle reaches the adult stage; these changes are quite similar to those undergone by the larva cfEpzVatito, described below. 496 AN INTRODUCTION TO ENTOMOLOGY The wonderful instinct by which the triunguHns of these bhster- beetles find their way to the nests of soHtary bees has not yet reached perfection ; for many of them attach themselves to flies, wasps, honey- bees, and other flower-visiting insects, and merely gain useless trans- portation thereby. The life-history of Epicauta vittdta, which was worked out by Mr. C. V. Riley ('77), wnll serve to illustrate the hypermetamorphosis of blister-beetles. The adult beetle is yellowish or reddish above, with the head and prothorax marked with black and with two black stripes on each wing-cover (Fig. 587, F). It feeds on the leaves of potato, and is sometimes a serious pest. The female lays her eggs in Fig. 587. — Hypermetamorphosis of Epicauta vittata. (From Sharp, after Riley.) the ground in loose, irregular masses of about 130 each; several such masses are laid by a single female. vShe prefers for purposes of ovi- position the very same warm, sunny locations chosen by the locusts for laying their eggs. The triungulins that hatch from the blister- beetle eggs (Fig. 587, A) are ver}' active; when one of them finds an egg-pod of a locust it penetrates it, and in the course of several days devours two of the eggs; a period of rest follows during which it molts. The second instar (Fig. 587, B) differs greatly in form from the triungulin, and is known as the carahoid larva. A second molt takes place after about a week, but it is not accompanied by any very great change of form, though the larva is now curved, less active, and in form like the larva of a scarab^eid beetle. About a week later, the third molt occurs; the change in form at this molt is not great, the fourth instar (Fig. 587, D) hke the third being scarabseoid inform; these two instars can be distinguished as the first scarabcBoid larva and the second scarabcBoid larva respectively. The second scara- COLEOPTERA 497 bceoid larva grows apace, its head being constantly bathed in the rich juices of the locust eggs, which it rapidly sucks or more or less com- pletely devours. In another week it forsakes the remnants of the locust egg-mass and forms a smooth cavity in the soil a short distance from it. The larva then molts; the skin is not shed entirely, but remains attached to the caudal end of the body (Fig. 587, C). The new skin of the larva becomes rigid and of a deeper yellow color, reminding one of a puparium of a dipterous insect; this instar, the fifth, is termed the coarctate larva. The insect has the power of re- maining in this coarctate larval condition for a long time, and gen- erally thus hibernates. At the fifth molt the larva becomes active again, and burrows about in the ground; it now resembles in form the second scarabaeoid larva except that it is smaller and whiter; this, the sixth instar, was termed by Riley the scolytoid larva. In the cases observed by Riley, the scolytoid larvae did not feed but transformed to pupse (Fig. 587, E) in the course of a few days. The pupa state lasted five or six days. More than two hundred species of blister-beetles have been found in this country; but by far the greater number of these are confined to the western half of this region. Our most com- mon species in the East belong to the genus Epicauta. These insects feed in the adult state on the leaves of various plants, but especially those of potato, and upon the pollen of goldenrod; the larv«, so far as is known, are parasitic in the egg-pods of locusts {Melanophis). In addition to Epicauta vittdta, discussed above, our more common species are the Pennsylvania blister-beetle, Epi- cauta pennsylvdnica, which is of a uniform black color (Fig. 588); and Epicauta cinerea, which is sometimes clothed throughout with an ash-colored pubescence, and sometimes the wing-covers are black, except a narrow gray margin ; the two varieties were formerly considered distinct species ; the first is commonly known as the gray blister-beetle, the last as the margined blister-beetle. Closely allied to the beetles mentioned above are those of the genus Macrohasis. The most common species of this genus found in the East is Macrohasis ttnicolor. This beetle measures from 8 mm. to 15 mm. in length; it is represented, enlarged, in Figure 589; it is black, but rather densely clothed with grayish hairs, which give an ashen hue to the upper surface; it is known as the ashy-gray blister-beetle. The beetles of the genus Meloe present an exception to the characters of the Coleootera in that the wing-covers, instead of meeting in a straight I Fig. Fig. 589. 498 AN INTRODUCTION TO ENTOMOLOGY line down the back, overlap at the base (Fig. 590). These wing- covers are short, and the hind wings are lacking. These beetles are called oil-beetles in England, on account of the yel- lowish liquid which oozes from their joints when they are handled. Our most common species is the butter- cup oil-beetle, Meloe angitsticollis. It is found in meadows and pastures feeding on the leaves of vari- ous species of buttercups. The species of the genus Nemognatha and some allied forms are remarkable for having the maxills developed into a long sucking-tube, which is some- 59°- times as long as the body, and which resembles some- what the sucking-tube of a butterfly. The family EURYSTETHID^ includes only three American species, one found in Alaska and two found in California. One of the latter, Eurystethus subopdcus, was found b}^ Professor VanDyke on the seashore, in crevices of inter-tidal rocks. The family OTHNIID^ is represented in our territory by five species of Othnius, one from the East and four from the Far West. They are small beetles, which are found running actively on the leaves of trees, and are probably predacious. In this family the anterior coxal cavities are closed behind, and none of the abdominal segTnents are grown together on the ventral side. The family PYTHID^ includes less than a score of North American species. Some of these live under bark, and are said to prey on bark-beetles; others are found under stones. See table, p. 474, for distinctive characters. The family PYROCHROIDvE includes a small number of beetles, which are from 8 mm. to 18 mm. in length. The body is elongate; the head and prothorax are narrower than the wing- covers; the antennae are serrate or subpectinate in the females and usually flabellate in the males (Fig. 591). The beetles are found about decaying trees, beneath the bark of which the larvas live. The family PEDILID^.— In this and in the fol- lowing family the abdomen is composed of five free segments, and the tarsi have the penultimate joint lobed beneath. In this family the eyes are large, finely ^'^^- ^^i- faceted, and usually emarginate. These beetles are arboreal in habits. There are about fifty described species in our fauna. The family ANTHICID^^^. — In this family, as in the preceding one, the abdomen consists of five free segments, and the penultimate joint of the tarsi is bilobed. But in this family the eyes are small, rounded, usually coarsely faceted, and emarginate. These are active ground beetles of predacious habits. Among our more corn- mon species are those of the genus Notoxus, in which the prothorax is prolonged over the head into a horn. There are nearly two hundred described species of this family in our fauna. COLEOPTERA 499 The family EUGLENID^ is composed of small or m.iriute beetles, found on leaves and flowers; many of them are less than 2 mm. in length. They resemble the members of the two preceding families ; but differ in having the antepenultimate segment of the tarsi bilobed, instead of the penultimate, and in having the abdomen composed of only four free ventral segments, of which the first is formed of two, firmly imited but with the suture sometimes evident. There are about forty described North American species. The family CEROPHYTID^E includes only two rare species of Cerophytum, one found in Calif omia and one in Pennsylvania. These were formerly included in the Elateridae; but they differ from that family in that the posterior coxas are not laminated, and the trochanters of the middle and posterior legs are very long. The family CEBRIONID^ includes a few species foimd in the South. They were fonnerly included in the Elateridae; but they differ from that family in that the abdomen consists of six or more ventral segments. This family differs from the following one in hav- ing the tibial spurs well developed. The family PLASTOCERID^ includes about a score of species found in the South and in California. It is closely allied to the pre- ceding family, but differs in having the tibial spurs short and very delicate. The family RHIPICERIDyE, or cedar-beetles, is represented in this coimtry by a very small number of species, which are most com- monly formd on cedars. The antennae are serrate in the females, frequently flabellate in the males. The anterior and middle coxae are conical and prominent, the former with large trochantins; the posterior coxae are transverse, and dilated into a small plate partly covering the femora. Family ELATERID.E The Click-Beetles or Elators There is hardly a country child that has not been entertained by the acrobatic performances of the long, tidy-appearing beetles called snapping-bugs, click-beetles, or skip-jacks (Fig. 592). Touch one of them and it at once curls up its legs, and drops as if shot; it usually lands on its back, and lies there for a time as if dead. Suddenly there is a click, and the insect pops up into the air several inches. If it comes down on its back, it tries again and again until it succeeds in striking on its feet, and then it runs off. Fig. ^92. Our common species of click-beetles are mostly small or of medium size, ranging from 2.5 mm. to 18 mm. in length. A few species are larger, some reaching the length of nearly 50 mm. The majority of the species are of a uniform brownish color; some are black or grayish, and some are conspicuously spotted I 500 AN INTRODUCTION TO ENTOMOLOGY (Fig. 593). The body is elongated, somewhat flattened, and tapers more or less toward each end ; the antennje are moderately elongated and more or less serrate; the first and second ab- dominal segments are not grown together on the xSr X^fi/' ventral side; and the hind coxae are each furnished jiv /^Wk ^"^'^^^ ^ groove for the reception of the femur. .^K /IfiPirV The ability to leap into the air when placed on their back, which is possessed by most members of this family and by a few members of the following ^ig; 59 3 • — A family, is due to two facts: first, the presternum is A^ld^r' prolonged in to a process which extends into a groove natural size and ^ the mesosternum; and second, the prothorax is enlarged. loosely joined to the mesothorax, so that it can be freely moved up and down. When preparing to leap, the beetle bends its body so as to bring the prosternal process nearly out of the groove in the mesosternum; then it suddenly straightens its body, with the result that the prosternal process descends violently into the groove; the blow thus given to the meso- thorax causes the base of the elytra to strike the supporting surface, and by their elasticity the whole body is propelled upward. Adult elaters are found on leaves and flowers, and are exclusively pn^^tophagous; the larvae live in various situations; most of them are phytophagous, but some species The larvae are long, nan-ow, pig. 594. worm -like creatures, very even in _ width, with a very hard cuticula, and are brownish or yellowish in color (Figs. 594 and 595). They are pig. 595. commonly known as wire-worms, a name suggested by the form and hardness of the body . Some wire-worms live under the bark of trees and in rotten wood ; but many of them live in the ground, and feed on seeds and the roots of grass and grain. In fact there is hardly a cultivated plant that they do not infest, and, working as they do beneath thesurf ace of the ground, it is extremely difficult to destroy them. Not only do they infest a great variety of plants, but they are very apt to attack them at the most susceptible period of their gro\^i:h, before they have attained sufficient size and strength to withstand the attack; and often seed is destroyed before it is germinated. Thus fields of com or other grain are ruined at the outset. The appearance of these insects when in the ground, as seen through the glass side of one of our root-cages, is shown in Fig. 596. There is a vast number of species of click-beetles ; more than five hundred have been described from North America alone. _ It is quite difficult to separate the closely alHed species, as there is but little variation in shape and color. The larvae also show comparatively little variation in the general form; but in this stage the shape of the parts of the head and its ap- COLEOPTERA 501 pendages, and the structure of the caudal end of the body, afforduseful characters. The value of these characters in indicating the principal divisions of the family is pointed out by Hyslop ('17). An extended series of experi- ments were con- ducted by Corn- stock and Slin- gerland ('91) in an effort to discover a practicable method of preventing the ravages of wire-worms. In those species that we bred, it required several years for the larva to complete its growth. In these species the full-grown larva changes to a pupa in the latter part of the suimner, in a little cell in the groimd; the pupa soon afterwards changes to an adult; but the adult remains in the cell formed by the larva till the following spring. Although we tried an extensive series of experiments, extending over several years, we were unable to find any satisfactory way of destroying the larvce infesting field crops. But we foimd that if the cells containing pupae or recently-transformed adults were broken, the insects perished. We conclude, therefore, that much can be done towards keeping these insects in check by fall-ploughing; for in this way many of the cells containing pupse or yormg adults would be broken. The eyed el- ater, Alaiis ocu- Idtus .- Although most of our click- beetles are of moderate size, we have a few species that are large. The most common of these is the eyed elater. This is the great pepper-and-salt-colored fellow that has two large, black, velvety, eye-like spots on the pro- thorax (Fig. 597). These are not its eyes, how- ever. The true eyes are situated one on each side of the head near the base of the antenna. This Fig. 596. — ^A corn-plant growing in a root-cage infested by wire-worms and click-beetles. (From a speci- men in the Cornell Insectarv.) 502 AN INTRODUCTION TO ENTOMOLOGV insect varies greatly in size, some individuals being not more than half as large as others. The larvas live in decaying wood, and are often found in the trunks of old apple trees. It was formerly believed that they fed on the decaying wood; but they have been found to be carnivorous. The larger larvas are about 60 mm. in length. There is an elater quite similar to the preceding that differs in having the eye-like spots less distinctly marked; this is Alaus myops. This species is not as common as the preceding one. The family EUCNEMID^E was formerly regarded as a subfamily of the Elaterid^. It differs from the Elateridae, as now restricted, in having the labrum concealed, and in that the antennas are some- what distant from the eyes, and their insertion narrowing the front. The adults are found under bark or on the leaves of plants ; most of the species are rare. "The larvee have a striking resemblance to those of the family Buprestidae, both in form and habits, being abruptly enlarged in front, and usually occurring in wood which has just begun to decav." (Blatchley '10.) The' family THROvSCID^ includes a few small species which resemble the elaters and buprestids in having the prosternum pro- longed behind into a process, which is received in the mesostemimi. They differ from the elaters in having the pro thorax firmly joined to the mesothorax, and the front coxal cavities closed behind by the meso- sternimi instead of by the prosternum; and from the buprestids in having the ventral abdominal segments all free. The adult beetles are found on flowers. Family BUPRESTIDS The Metallic Wood-Borers or Buprestids The buprestids resemble the click-beetles somewhat in form, being rather long and narrow; but they are easily recognized by their metallic coloring. Their bodies are hard and inflexible, and usually appear as if made of bronze ; but some species exhibit the brightest of metallic colors. The antennse are serrate; the first and second abdominal segments are grown together on the ventral side ; and these beetles do not have the power of springing when placed on the back. The adults are found upon flowers and upon the bark of trees, basking in the hot sunshine. Some of them fly very rapidly, with a loud buzzing noise; and some drop to the ground when disturbed, and feign death. Most of the larvae are borers, feeding beneath bark or within solid wood. In such species the body is of a very characteristic form, which is commonly designated as "flat -headed."' The flattened portion, however, is composed largely of the segments immediately following the head. The first thoracic segment is very wide and flat; the next two or three segments are also flattened, but are successively smaller; while the rest of the body is quite narrow and cylindrical. COLEOPTERA 503 Fig. 598. 599. Fig. 600. 599). The lar- These "flat -headed" lan^ee are legless, and have been compared to tadpoles on account of their form. Their burrows are flattened, corresponding with the shape of the larger part of the body. In some of the smaller species the lar\^as are cylindrical, and are furnished with three pairs of legs. These are leaf-miners; and in the adult state the body is much shorter than in the more typical species. This family is represented in our fauna by nearly three hundred species; among the more important of those that infest cultivated plants are the following. The \'irginian buprestid, Chalcophora virgmica. — This is the larg- est of our common buprestids (Fig. 598). It is copper-colored, often almost black, and has its upper surface roughened by irregular, lengthwise furrov/s. This bee- tle appears late in spring in the vicinity of pine-trees. The larvas bore in the wood of pine, and are often very injurious. Dicerca divaricata is 1 8 mm. or more in length, copper- colored or brassy above, with the wing-covers marked with square, elevated, black spots. The wing-covers taper very much behind, and are separated at the tips (Fig. va bores in peach, cherry, beech, and maple. The flat-headed apple-tree borer, Chrysohothris femordta. — This is one of the most injurious of all buprestids. The adult (Fig. 600) is about 12 mm. long, and is very dark green above, with bronze re- flections, especially in the furrows of the wing-covers. It appears during June and July, and lays its eggs upon the trunk and limbs of apple, peach, oak, and other trees. The larvae at first bore into the bark and sap-wood, and later into the solid wood. The transforma- tions are completed in one 3 ear. To prevent the ravages of this pest, the trees are rubbed with soap during June or July, or cakes of soap are placed in the forks of the trees, so that the rains will dissolve the soap and wash it down over the trunks. This is supposed to prevent the beetles from deposit- ing their eggs on the trees. After a tree is once infested, the larvae should be cut out with a gouge or a knife. Nursery stock that is infested should be promptly burned. The red-necked agrilus, Agrilus nificollis. — This beetle (Fig. 601) is about 7.5 mm. long. Its body is narrow and nearly c> lindrical. The head is of a dark bronze color, the prothorax of a beautiful coppery bronze, and the wing- covers black. The larva bores in the stems of raspberry and blackberry, causing a large swelling, known as the raspberry gouty-gall. 1 hese galls should be collected and burned in earlv spring. The famil / PSEPHENID^ includes only the genus Psephenus, of which we have four species, one found in the East and three in 504 AN INTRODUCTION TO ENTOMOLOGY Fig. 602. California. This genus was formerly included in the following family ; but it differs from the Dryopidas in having more than five ventral ab- dominal segments. Our eastern species is Psephenus lecontei. These beetles are found in the vicinity of running water, and often, in the heat of the day, collect on stones that project from the water; they fly swiftly when disturbed. The body is oval, subdepressed, nar- rowed in front, and clothed with fine, sill<:en hairs, which retain a film of air when the insect goes beneath water. The females deposit their eggs in a layer on the under side of submerged stones in shallow brooks. The beetles measure from 4.5 mm. to 6 mm. in length. The larva is found clinging to the lower surface of stones in rapid streams, and I have found it in muck near a spring. It is very flat, circular in out- line (Fig. 602), and measures about 7 mm. in length. It breathes by five pairs of branched tracheal gills on the ventral side of the abdomen. It is rarely recognized as an insect by the young collector; in fact it was originally described as a crustacean under the generic name Fluvicola. I have suggested the common name water-penny for the larva. When mature the larva leaves the water, and pupates under the last larval skin, beneath a stone or other object in a damp situation. The family DRYOPID^E as now restricted includes only the sub- family Parninae of the old family Parnidas, in which were included the preceding family and the following family. The Dryopidse differ from the Psephenidae in that the members of it have only five ventral abdominal seg- ments, and from the Elmidje in that in the Dryopidae the anterior coxae are transverse, with a distinct tro- chantin. This family includes small water-beetles in which the legs are not fitted for swimming. They are found most often in swift-running water, where they cling to stones, logs, or aquatic plants. The body is clothed with fine, silken hairs, which retain a film of air when the insect is beneath the water. They feed on decaying matter in the water. The larvae are also aquatic. The larva of Helichus lithophiliis (Fig. 603) resembles somewhat the water-penny {Psephenus), except that the body is more elongate and is deeply notched between the segments. Seventeen species of this family have been found in our fauna. The family ELMID.^ includes beetles that are closely allied to the preceding family in structure and in habits; but in this family the anterior coxae are rounded and without a trochantin, and the body is less densely pubescent than in the Dryopidae. Fig. 603. COLEOPTERA 505 The larvas of some exotic species are said to live in damp earth; but the larva of Stenelmis bicarindtus, which was described by Professor Matheson ('14) is aquatic. This larva (Fig. 604) differs greatly in form from the representatives of the two preceding families figured above, being long and slender. The family HETEROCERID^, or the variegated mud-loving beetles, includes only the genus Heterocerus, of which eleven species have been found in our faima. In this family all of the tarsi are four-jointed; the first four ab- dominal segments are growm together on the ventral side ; and the tibise are dilated, armed with rows of spines, and fitted for digging. These beetles are oblong or sub-elon- gate, oval, densely clothed with short, silky pubescence, very finely punctate, and of a brown color, with the elytra usually variegated with undulated bands or spots of yellow color. They live in galleries which they excavate in sand or mud at the margins of bodies of water, and, when dis- i | turbed, run from their galleries and take flight. ^H The family GEORYSSID^, or the minute mud-loving p. beetles, includes only the genus Georyssus, of which only ^^' two species have been found in the United States. They are very minute, roimded, convex, roughly sculptured, black insects, foimd at the margin of streams, on wet sand ; they cover themselves with a coating of mud or fine sand, so that they can be detected only when they move. The family DASCILLID^E includes certain beetles that live on plants, usually near water. The legs are short, with slender tibiae; The tarsi are five-jointed; the anterior coxae bear a distinct trochan- tin; the posterior coxae are transverse, and dilated into a plate partly covering the femora ; and the abdomen has five free, ventral segments, the fifth rounded at the tip. Sharp ('99) states that the larva of DascUlus cervmus is subterra- nean, and is beheved to live on roots; in form it is somewhat like a lainellicom larva, but is straight, and has a large head. Only twenty-one species of this family have been described from o\ir famia; but these represent fifteen genera. The family EUCINETID^ has recentty been separated from the Dascyllidae. In the Eucinetidse the anterior coxae do not bear a trochantin; the posterior coxae are dilated into immense oblique plates, concealing the hind legs in repose; and the internal lobe of the maxillse is armed with a terminal hook. Only eight species of this family occur in our fauna; seven of these belong to the genus Eucinetus. The larva of a European species of Eucinetus lives on fungoid matter on wood. The family HELODIDiE includes small beetles, less than 6 mm. in length, found on plants near water. As in the preceding family, the anterior coxae are without a trochantin; but the lacinia of the maxillae is not armed with a terminal hook; and the cuticula of the 506 AN INTRODUCTION TO ENTOMOLOGY body is usually soft and thin. Sharp ('99) states that the larvae are aquatic, and are remarkable for possessing antennae consisting of a great many joints. Our fauna includes thirty-two described species of this family. The family CHELONARIID^ is represented in our fauna by a single species, Chelondrium lecontei, found in Florida. See table, page 471, for distinguishing characters. Family DERMESTID^ The Dermestids There are several families of small beetles that feed on decaying matter, or on skins, furs, and dried animal substances. The most important of these is the Dermestidae, as several species belonging to this family destroy household stores or goods. The dermestids can be distinguished from most of the other beetles with similar habits by the fact that the wing-covers completely cover the abdomen. They are chiefly small beetles, although one of the common species measures 8 mm. in length. They are usually oval, plump beetles, with pale gray or brown markings, which are formed of minute scales, which can be rubbed off. These beetles have the habit of pretending that they are dead when they are disturbed; they will roll over on their backs with their legs meekly folded and lie still for a long period. The larvae do much more damage than the adults. They are ac- tive, and are clothed with long hairs. These hairs are covered throughout their entire length with microscopic barbs. This family is represented in our fauna by about one hundred thirty species; the following are some of the more important of these. The larder-beetle, Derniestes larddrius. — This pest of the larder is the most common of the larger members of this family. It measures from 6 mm. to 7.5 mm. in length, and is black except the basal half of its wing-covers, which are pale buff or brown- ■WT ish yellow. This lighter portion is usually crossed by a /ft^ band of black spots, three on each wing-cover (Fig. 605). vw[ The larva feeds on dead animal matter, as meat, skins, . • feathers, and cheese. It is often a serious pest where bacon Fig- 605. Qj. \^^-^ is stored. When full-grown it is about 12 mm. in length, dark brown above, whitish below, and rather thickly covered with long, brown hairs. It is said that these insects can be attracted by baits of old cheese, from which they may be gathered and destroyed. The carpet-beetle, Anthrenus scrophuldrice. — This is a well-known household pest. It is an introduced European insect, which was first recognized as a serious pest in this country about 1874. It feeds in its larval state on carpets, woollens, furs, and feathers; and for a considerable period was exceedingly destructive. In recent years its ravages have been greatly reduced by the more general use of rugs instead of carpets. As rags are taken up and cleaned frequently, the COLEOPTERA 507 insect does not have a chance to breed as it does under carpets which are tacked to the floor and taken tip only once or twice a year. The larva is well knox^Ti to many housekeepers as the buffalo-moth. It is a short, fat grub, about 5 mm. in length when fuU-g-rown, and densely clothed with dark brown hairs. It lives in the cracks of floors, near the edges of rooms, and beneath furniture, where it eats holes in the carpet. It also enters wardrobes and destroys clothing. The adult is a pretty little beetle which may be foimd in infested houses, in the spring, on the ceilings and windows. It measures from 2.2 mm. to 3.5 mm. in length and is clothed with black, white, and brick-red scales. There is a whitish spot on each side of the prothorax, and three irregular, whitish spots on the outer margia of each wing- cover; along the suture where the two wing-covers meet, there is a band of brick-red scales, which is widened in several places. It is worth while to learn to Icnow this beetle; for a lady-bug which often winters in our houses is frequently mistaken for it. The carpet-beetle in its adult state feeds on the pollen of flowers. Sometimes it aboimds on the blossoms of currant, cherry, and other fruits. The best way to avoid the ravages of this pest is to use rugs instead of carpets, and to trap the lan.^fe by placing w^ooUen cloths on the floors of closets. By shaking such cloths over a paper once a week, the larva; can be captured. The change from carpets to rugs is a very desirable one; foi' carpets that are tacked to the floor and taken up only once or twice a year are unwholesome. The change need not be a very expensive one. As carpets w^ear out they may be replaced with rugs; and good carpets can be made over into rugs. If the floors are not polished, as is usually the case where it w^as planned to cover them with carpets, they can be made presentable b}'- filling the cracks with putty and painting the boards where they are to be exposed. The museum pests, Anthrenus verhdsci and Anthrenus museorum. — There are two minute species of this family that are a constant source of annoyance to those having collections of insects. The adult beetles measure from 2 mm. to 3 mm. in length, and are very convex. They deposit their eggs on specimens in our collections; and the larvEe feed upon the specimens, often destroying them. In order to preserv^e a collection of insects it is necessary that they should be kept in tight cases, so that these pests camiot gain access to them. Specimens should not be left exposed except when in use. And the entire collection should be carefully examined at least once a month. The injury is done by the larvas, which are small, plirnip, hairy grubs. Their presence is indicated by a fine dust that falls on to the bottom of the case from the infested specimens. These larvas can be destroyed by pouring a small quantity of carbon disulphide into the case, and keeping it tightly closed for a day or two. Benzine poured on a bit of cotton in the box will cause the pests to leave the specimens, when they may be taken from the box and destroyed. But we have found carbon bisulphide the better agent for the destruction of these pests.. 508 AN INTRODUCTION TO ENTOMOLOGY The family BYRRHID^, or the pill-beetles, are short, very con- vex beetles of small or moderate size; some, however, are 12 mm. in length. The body is clothed with hair or minute scales. The legs can be folded up very compactly, the tibia usually having a furrow for the reception of the tarsus. These beetles are found upon walks and at the roots of trees and grass; a few live under the bark of trees. Nearly one hundred species have been found in this country. The family NOSODENDRID^ includes two species of Noso- dendron, one found in the East and one in California. They were formerly included in the Byrrhidas, but differ from that family in having the head prominent and the mentum large. These beetles live under the bark of trees. The family RHYSODID^ includes only four species, two from each side of the continent. They are elongate, somewhat flattened beetles, with the head and prothorax deeply furrowed with longi- tudinal grooves; and the abdomen with six ventral segments, the first broadly triangular, widely separating the coxae. They are found under bark. See footnote, page 470. The family OSTOMID^ includes oblong, somewhat flattened beetles, of a black or reddish black color. Most of them live under bark; but some are found in granaries, and have been widely dis- tributed by commerce. The lar\-a of a species found under bark has been observed to feed on the larva of the codlin-moth. One well-known species, Tenehroides mauritdnicus, infests gran- aries. It is a shining brown beetle measuring about 8 mm. in length; it is commonly known as the cadelle. Both adult beetles and larvae feed on grain, but are also predacious, feeding on other insects infest- ing grain. The larv£e when full-grown burrow into the sides of the bins, where they transform. The family NITIDULID^ comprises small, somewhat flattened beetles. With many species the prothorax has wide, thin margins, and the wing-covers are more or less tnmcate, so as to leave the tip of the abdomen exposed; but sometimes the elytra are entire. The tarsi are usually five-jointed, with the fourth segment very small; they are more or less dilated; the posterior coxse are flat, not sulcate; the anterior coxae are transverse; and the abdomen has five free ventral segments. Most species of this family feed on the juices of fruits and ferment- ing sap that exudes from trees; a few are found on flowers, and others on fungi or carrion. About one hundred thirty species are known tfrom North America. One of the most common species is Glischrochlus (I ps) fascidtus (Fig. 606). This is a shining black species, with two conspicuous, interrupted, reddish bands across the wing-covers, p. gQg The family RHIZOPH AGID.^ includes only the genus 7?/jzso;^/mgM5, of which there are fourteen North American species. These are small, slender, elongate species, which live beneath bark. This genus was formerly included in the preceding family; it differs from that family in that the antennas are only ten-jointed, and the club of the antenna is two-jointed. COLEOPTERA 509 The family MONOTOMID^ is composed of small, depressed beetles, found mostly under the bark of trees, but some species live in the nests of ants. The wing-covers are truncate behind, leaving the last abdominal segment exposed. There are nearly forty described North American species. Family CUCUJID^ The Ciicujids The insects of this family are very fiat and usually of an elongate form; most of the species are brown, but some are of a bright red color. As a rtile they are found under bark and are believed to be carnivorous both in the larval and adult states; but some feed in grain. There are nearly one hundred species in our fauna. The most conspicuous of our common species is Cucujus cldvipes (Fig. 607). This insect is about 12 mm. in length and of a bright red color, with the eyes and an- tennas black and the tibiae and tarsi dark. The most important member of this family is the corn silvanus, Silvanus surinamensis, which is one of the small beetles that infest stored grain. This species is readily distinguished from other small beetles with similar habits by its flattened form and the saw-like edges of the prothorax. Besides grain it often infests dried fruits and other stores. It measures from 2.5 mm. to 3 mm. in length. The larva as well as the adult feed on grain. It differs from the larva of the granary -weevil (Calendra) in the more elongate form of its body and in the possession of three pairs of legs. Family EROTYLID^ The Erotylids The members of this family are usually of moderate or small size; but some species are quite large, measuring 18 mm. or more in Fig. 607. Fig. 608. Fig. 609. length. Some of our more common species are conspicuously marked with shining black and red. To the genus Megaloddchne belong two common, large species, which are black, with two dull red bands extending across the 510 AN INTRODUCTION TO ENTOMOLOGY wing-covers. M. heros (Fig. 608) is 16 mm. or more in length. M. Jascidta is about 12 mm. in length. The genus Languria includes long, narrow species, which resemble click-beetles in form. Figure 609 represents Languria niozdrdu. greatly enlarged. This is a reddish species with dark blue wing- covers; the larva bores in the stalks of clover. It has not become a serious pest as the larvae are destroyed whenever clover is cut at the proper time. The larvae of some species of this family feed on fungi. The familyDERODONTID^E includes only five American species, two found in the East and three in the Far West. They are small brown or dull brownish yellow beetles, having the head deeply impressed, with a small, smooth tubercle on each side inside the eye. These beetles are found on fungi. The family CRYPTOPHAGID.E includes insects of small size, usually less than 2.5 mm. in length, and of variable form but never very flat. The thorax is nearly or quite as wide as the wing-covers, and the first ventral abdominal segment is somewhat longer than the others. They are generally of a light yellowish brown color, and live on fungi and decomposing vegetable matter. The family BYTURID^ includes only the genus Byturus, of which there are five species in our fauna. This genus was formerly included in the Dermestidse, but it differs from that family in having the second and third segments of the tarsi lobed beneath, the front coxal cavities closed behind, and the tarsal claws armed with a large basal tooth. The following is a well-known species. The raspberry fruit-worm, Bytiirus unlcolor. — The fruit of the red raspberr>^ is often infested by a small white worm, which clings to the inside of the berry after it is picked. This is the larva of an oval, pale, dull yellow beetle, which is densely clothed with short, fine, gray hairs. The beetle is repre- sented enlarged in Figure 610; it measures from 3.7 to 4.5 mm. in length. This insect is also injurious in the adult state, as it feeds on the buds and tender leaves of the raspberry and later attacks the blossoms. Fig. 610. The family MYCETOPHAGID^, or the hairy fungus-beetles, is composed of small, oval, rarely elongate, moderately convex beetles. They are densely punctured and hairy, and are usually prettily marked insects. They live on fungi and under bark. There are about thirty species in our fauna. The familv COLYDIID^ is composed of small insects which are usually of an elongate or cylindrical form, and are found under bark, in fungi, and in earth. Some of the species are known to be carniv- orous, feeding on the larvas of wood-boring beetles. The tarsi are four-jointed; the tibiae are not fitted for digging, and the first four abdominal segments are grown together on the ventral side. More than eighty North American species are known. COLEOPTERA 511 The ianiily MURMIDIIDiE includes five introduced species representing five genera. They are very small, oval beetles, differing -;rom the Colydiidas in having the antennas inserted on the front, and in having the anterior cox£e inclosed behind by the metasternum. The family LATHRIDIID^ includes very small beetles which are found chiefly under bark and stones or in vegetable debris, es- pecially decaying leaves. They are oblong; the wing-covers are usu- ally wider than the prothorax and entirely cover the abdomen. There are about one hundred species in our fauna. The family MYCET.^ID,^ includes only four American species, which have recently been separated from the following family; they differ from the Endomychidas in having the tarsi distinctly four- jointed. The family ENDOMYCHID^ includes a small number of species, whch are found chiefly in fungus, in decaying wood, or be- neath logs and bark. They are small, oval or oblong beetles. The antenna are about half as long as the body; the prothorax is nearly square, and usually has a wide, thin margin, which is slightly turned upwards at the sides. The family PHALACRID^, or the shining flower-beetles, in- cludes very small, convex, shining black beetles; they are found on flowers and sometimes under bark. The larvas live in the heads of flowers, especially in those of the Compositae. More than one hundred North American species have been described. Family COCCINELLID^ The Lady-Bugs These insects are well-known to nearly every child under the popular name given above. They are more or less nearly hemi- spherical, generally red or yellow, with black spots, or black, with tvhite, red, or yellow spots. The larvas occur runnmg about on foliage ; they are often spotted with bright colors and clothed with warts or with spines (Fig. 6ii). When ready to change to a pupa the larva fastens itself by its tail to any convenient object, and the skin splits open on the back. Sometimes the pupa state is passed within this split skin, and some- times the skin is forced back and remains in a little wad about the tail (Fig. 612). With very few exceptions, the lady-bugs are predacious, both in the larval and adult states. They feed upon small insects and upon the eggs of larger species. The larvae of certain species are known as "niggers" by hop-growers, and are greatly prized by them ; for they are very destructive to the hop-louse. On the Pacific Coast lady-bugs are well known as the most beneficial of all insects to the fruit-growers. In addition to the native species found there, several species have been introduced as a means of combating scale-insects. One of these, Kodolia cardinalis, which 512 AN INTRODUCTION TO ENTOMOLOGY has been incorrectly known as Veddlia cardindlis, has proved of very- great value in subduing the cottony-cushion scale {Icerya purchasi). This lady-bug was introduced from Australia. The larva cf Brachyacantha is found in the nests of ants. It is covered with dense tutts of delicate white wax; its food probably consists of the eggs of coccids living in the nests. A very common lady-bug in the East is Addlia bipunctdta. This species is reddish yellow above, with the middle of the prothorax black, and with a black spot on each wing-cover. It frequently passes the winter in our dwellings, and is found on the walls and windows in early spring. Under such circumstances it is often mis- taken for the carpet-beetle, and, unfortunately, destroyed. The nine-spotted lad3^-bug, Coccinella novemnotdta, has yellowish wing-covers, with four black spots on each, in addition to a common spot just back of the scutellum (Fig. 613). Although almost all of the Coccinellid^ are predacious, there are some that are herbivorous. One of these is p. found in the East. This is the squash-ladybird, Epildchna ^^' ^^' boredlis. This beetle and its larva (Fig. 614) feed on the foliage of various cucurbitaceous plants, but prefer that of the squash. The adult is yellow- ish, with large, black spots. The larva is yellow and is clothed with forked spines. A pupa is shown in the figure near the upper right-hand corner. The bean- lady bug, Epi- ldchna corrupta, which is found in the South and Southwest, is an- other herbivo- rous species. The family p. .,, ALLECULI- ^^^•'^^- D^, or the comb-clawed bark-beetles, includes brownish beetles, without spots, which are found on leaves and flowers and under bark. The body is usually elongate, elliptical, quite convex, and clothed above with minute hairs, which give a silken gloss to the surface. They are most easily distinguished from allied families by the tarsal claws being pectinate, and the anterior coxal cavities closed behind. The larvse of some of our species at least live in rotten wood and resemble wire- COLEOPTERA 513 worms in appearance. There are more than one hundred described North American species. Family TENEBRIONID^ The Darkling Beetles The darkHng beetles are nearly all of a uniform black color, although some are gray, and a few are marked with bright colors. The different species vary greatly in size and in the form of the body. The hind tarsi are four-jointed, and the fore and middle tarsi are five-jointed. For other characters, see table, p. 474. These insects occur chiefly in dry and warm regions. Thus while we have comparatively few species in the northeastern United States, there are many in the Southwest. Most of the species feed on dry vegetable matter, and often on that which is partially decomposed; some live in dung, some in dead animal matter, others in fungi, and a few prey upon larvae. More than eleven hundred species occur in this countr3\ The three following will serve to illustrate the variations in form and habits. The meal-worm, Tenebrto molitor. — This is a well-known pest in granaries and mills. The larva is a hard, waxy yellow, cylindrical worm, which measures when full-grown 25 mm. or more in length, and closely resembles a wire-worm; it feeds on floiu* and meal. The beetle is black and about 15 mm. in length, (Fig. 615). The larvae and pnpsc are used for bird-food and are grown in quantity by bird-supply houses. ThefoTkedinngus-heetle,Boletotheruscornutus, is common in the northeastern United States and ^^S- Fig- in Canada about the large toadstools {Poly poms) '^' ' ' which grow on the sides of trees. The surface of the body and wing- covers is very rough, and the prothorax bears two prominent horns (Fig. 616). The larva lives within the fungi referred to above. The pinacate-bugs. — Several species of Eleodes are abundant on the Pacific Coast, where they are found under stones and pieces of wood h'ing on the ground. They are apt to congregate in large numbers under a single shelter, and are ckunsy in their move- ments. They defend themselves when disturbed by elevating the hinder part of the body and discharging an oily fluid from it. They present an absurb appear- ance, walking off clumsily, and carr^'ing the hind end of the body as high as possible. The most common Fig. 617. species are large, smooth, club-shaped beetles (Fig, 617), and are commonly known as pinacate-bugs. These beetles and those belonging to several closely allied genera lack hind wings. yellow, cyiinaricai 514 AN INTRODUCTION TO ENTOMOLOGY ' The family LAGRIID^, or the lagriid bark-beetles, includes elongate beetles, with a narrow, subcylindrical prothorax, and a more or less brassy color. They are closely allied to the preceding family, but differ in having the next to the last segment of the tarsi spongy beneath. They are found under bark and on leaves. The larvae feed freely on foliage and are much less retiring in habits than those of the darkling beetles. Seventeen species are listed from the United States ; most of these are found in the South and Far West. Our most common species in the East is Arthromdcra cetiea (Fig. 6i8) ; this species measures from 9.5 mm. to 13.5 mm. in length. Fig. 618. The family MONOMMID^ is represented in this country by only six species, found chiefly in the Far West and in Florida. They are small, black, oval beetles, in which the anterior coxal cavities are open behind, the hind tarsi four-jointed, and the other tarsi five-jointed; and in which the antennae are received in grooves on the under side of the prothorax. Except one species found in Florida, our species belong to the genus Hyporhdgvis. The family MELANDRYID^ includes about eighty North American species. These are found under bark and in fungi. They are usually of elongate form, although some, like the one figured here, are not so. The maxillary palpi are fre- quently very long and much dilated; and the first seg- ment of the hind tarsi is always much elongated. Among our more common species are two belonging to the genus Penthe. These are rather large, oval, depressed beetles, upwards of 12 mm. in length, and of a deep Fig. 619. black color. Penthe obliqudta is distinguished by having the scutellimi clothed with rust-red hairs (Fig. 619). Penthe pimelia closely resembles this species, except that the scutellum is black. The family PTINID^ has been restricted recently to one of the subfamilies of the old family Ptinidse, which included, in addition to the insects now retained in it, those classed in the three following families. In the Ptinidae, as now restricted, the antemice are inserted upon the front of the head and rather close together, and the thorax is not margined at the sides. Only thirty-seven of our listed species are retained in this family. They are all small beetles and some of them are household pests, infesting stored provisions, clothing, and books. The best-known species is Ptmusfur. This is a reddish brown beetle; in the female the elytra are marked with two patches of white hairs. It measures from 2.8 mm. to 3.5 mm. The family ANOBIID^, or the death-watch family, includes a large part of the old family Ptinidse, there being more than two hundred species in our fauna. In this family the antennae are inserted on the sides of the head in front of the eyes; the thorax is usually margined at the sides; and the tibiae are without spurs. These beetles are small, and are generally of a cylindrical form, though some are broadly oval or nearly globular. They live chiefly on dry H COLEOPTERA 515 vegetable matter and are often found boring in the woodwork of buildings. Some are pests in drug-stores and groceries, where they infest a great variety of substances both vegetable and animal. Among the better-known species are the drug-store beetle, Sitodrepa pamcea, which not only infests many kinds of drugs but is also some- times a pest in groceries where it infests cereals ; and the cigarette- beetle, Lasioderma sen icoriie, which infests dried tobacco and destroys cigarettes and cigars by boring holes through them. To this family belongs the death-watch, Xestohium rufovillosum, which bores in the timbers of buildings and makes a ticking sound by striking its head or jaws against the walls of its burrows. This sound heard in the night by superstitious watchers by sick-beds has been supposed to portend death. The family BOSTRICHID^, or the powder-post beetles, includes beetles which are elongate in form; the head is usually deflexed, and protected by the thorax, which is then hood-like in form; and the first ventral segment of the abdomen is scarcely longer than the second. These beetles live almost exclusively in dry wood either in cylindrical burrows or beneath the bark. Sometimes they infest timbers to such an extent that the wood is largely reduced to powder, hence the common name, powder-post beetles. The adult of one species, AmpJncerus bicaiiddtiis, bores into the living twigs of fruit- trees and grape-vines for food, but it breeds in dying wood, such as prunings and dying branches. This species is known as the apple-twig borer and also as the grape-cane borer. The family LYCTIDvE is composed of a small number of beetles which resemble the powder-post beetles in habits. In this family the head is prominent and not covered by the prothorax; and the first ventral segment of the abdomen is much longer than the second. Most of our species belong to the genus Lyctus. The family SPHINDIDyE is represented in North America only by six small species, which are found in dry fungi which grow on the trunks of trees and on logs. The family CISID.^ includes very small beetles, rarely exceeding 3 mm. in length, found under the bark of trees and in the dry and woody species of fungi. The body is cylindrical; the prothorax is prolonged over the head; the abdomen has five ventral segments, of which the first is longer than the others; and the tarsi are all four- jointed. There are nearly one hundred species in our fauna. Family SCARAB^ID^ The Scarabceids or Lamellicorn Beetles This very large family is represented in our fauna by nearly one thousand species, and includes beetles that exhibit a wide range of variation in size, form, and habits. They are mostly short, stout -bodied beetles, of which the well-known June-bugs or May-beetles represent the most familiar type. Th^ most useful character for distinguishing 516 AN INTRODUCTION TO ENTOMOLOGY these insects is the lamellate form of the club of the antennas, the segments constituting it being greatly flattened, and capable of being brought close together. It is this character that suggests the name lamellicorn beetles. In the next family, the Trogidee, which has recently been separated from this family, the antenna are lamellate. The two families can be separated by the fact that in the Scarabasidae the epimera of the mesothorax extend to the coxae, while in the Trogidas they do not. According to their habits, the members of this family can be separated into two well-marked groups — the scavengers and the leaf- chafers. THE LAMELLICORN SCAVENGERS The lamellicorn scavengers in both the larval and adult states feed upon decaying vegetable matter. Nearly all the species live in dung, chiefly that of horses and cows ; but a few species feed upon fungi. The following are the more common representatives of this division. I. The tumble-bugs. — These are the most familiar of all dung- beetles, for their peculiar habits have attracted much attention from the earliest times. They are of rounded form, and the wing-covers are shortened so as to expose the tip of the abdomen. They are generally black, but some are colored with rich metallic hues. They vary greatly in size. The name tumble-bus: refers to the habit which many species exhibit of forming round balls of dung, which they roll long distances and then bury. They often work in pairs and it was formerly be- lieved that such a pair was a male and a female working together to make provision for their progeny ; but Fabre found by dissecting the beetles that the two members of a pair often proved to belong to the same sex; and concluded that the eager fellow-worker, under the deceitful pretense of lending a helping hand, niu-ses the scheme of purloining the ball at the first opportunity. According to the observations of Fabre ('79 and '11), the balls made early in the year are devoured by the beetles, which bury them- selves with them and feed upon them. Later other balls are made and buried, upon each of which an egg is laid. The larva hatching from this egg feeds upon the ball of dung, and when full-grown transforms within the cavity in which the ball was placed. This strange habit of rolling these balls has occasioned much speculation as to its object, and has been the source of many super- stitions, especially in ancient times. The only reasonable theory that we have met is that, as many predacious insects frequent the masses of dung from which the balls are obtained, in order to prey upon the larvae which live there, the more intelligent tumble-bugs remove the food for their larvae to a safe distance. The most noted member of this group of genera is the sacred beetle of the Egyptians, Ateuchus sdcer. This insect was held in .on tne miaaK m COLEOPTERA 517 high veneration by this ancient people. It was placed by them in the tombs with their dead; its picture was painted on sarcophagi, and its image was carved in stone and precious gems. These sculp- tured beetles can be found in almost any collection of Egyptian an- tiquities. From the habits and structure of this scarabajid the Egyptians evolved a remarkable symbolism. The ball, which the beetles were supposed to roll from sunrise to sunset, represented the earth; the beetle itself personified the sun, because of the sharp projections on its head, which extend out like rays of light ; while the thirty segments of its six tarsi represented the days of the month. All individuals of this species were thought to be males, and a race of males symbolized a race of warriors. This latter superstition was carried over to Rome and the Roman soldiers wore images of the sacred beetle set in rings. Our common tumble-bugs are distributed among three genera: Cdnthon, Copris, and PkancBtis. In the genus Canthon the middle and posterior tibia; are slender, and scarcely enlarged at the extremity. Canthon Icevis is our most coinmon species (Fig. 620). In Copris and Phanceus the middle and posterior tibias are dilated at the ex- tremity. In PhancBus the fore tarsi are wanting, and the others are not furnished with claws ; the species are brilliantly colored. PhancBus cdrnifex, with its rough copper-colored thorax and green elytra, is one pjg_ 530. of our most beautiful beetles, and is our best-known species. It is about 16 mm. in length, and the head of the male is furnished with a prominent horn. In Copris all the tarsi are present and furnished with claws. Copris Carolina is a large, well-known species, which measures more than 25 mm. in length. II. The aphodian dung-heetles. — These are small insects, our com- mon species measuring from 4 mm. to 8 mm. in length. The body is oblong, convex, or C3'lindrical in form, and, except in one small genus, the clypeus is expanded so as to cover the mouth-parts entirely. These insects are very abundant in pastures in the dung of horses and cattle, and immense numbers of them are often seen flying through the air during warm autumn afternoons. More than one hundred and fifty North American species have been described; of these, one hundred belong to the genus Aphddius. One of the more common species is Aphodius fimetdrius, which is about 8 mm. in length, and is easily recognized by its red wing-covers. III. The earth-boring dung-beetles. — These beetles are of a rounded convex form (Fig. 621). They differ from all other dung-beetles in having the antennae eleven-jointed, and in the labrum and mandibles being visible from above. This is a small group, only Fi 621 twenty-two North American species having been de- ^^' ■ scribed. The popular name is derived from that of the typical genus, Geotrtlpes, which signifies earth-boring. Those species the habits of which are known, live in excrement. The females bore 518 AN INTRODUCTION TO ENTOMOLOGY holes into the earth either beneath the dung or near it; into these holes they convey a quantity of the dung; this is to serve as food for the larvcc, an egg being laid in each hole. This is an approach to the peculiar habits of the tumble-bugs. Fig. 622. THE LAMELLICORN LEAF-CHAFERS The leaf-chafers are herbivorous insects which in the adult state usually feed upon the leaves of trees, but many of the species devour the pollen and petals of flowers. In the larval state some of these insects are found in rotten wood; others live in the ground, where they feed upon the roots of grass and other plants. These larvse are thick, fleshy grubs, with well-developed legs (Fig. 622). The caudal segments of the abdomen are very large, and appear black on ac- count of the large amount of dirt in the intestine. The body is strongly curved, so that the larvae can crawl only with great difficulty; when in the ground they usually lie on their backs. The following groups include the more important representatives of this division. I. The May-beetles or June-bugs. — During the warm evenings of May and June we throw open our windows so that we may feel the refreshing coolness of the night air and the inspiration of the new summer. Suddenly, as we sit working or reading, our peace is dis- turbed by a buzzing object which whirls above us. Then comes a sharp thud and silence. A little later the scratching of six pairs of tiny claws tells us the w^hereabouts of the intn.:der. But so familiar are we with his kind that we need not look to know how he appears, the mahogan^'-brown blunderer, with yellowish wings sticking out untidily from under his pohshed wing-covers. Although these insects are beetles, and attract our attention each year in May, they have received the infelicitous title of June-bugs. They are more properly termed May-beetles. The May-beetles belong to the genus Phylloph- aga, of which we have nearly one hundred species. The adults frequently do much injtiry by eating the foliage of trees. In the case of large trees this injury usually passes unnoticed; but small trees are often completely defoliated by them. When troublesome, they can be easily gathered by shaking them from trees upon sheets. Figure 623 represents a common species. The larvae of the different species of May-beetles are commonly classed together under the name "white-grubs." They are often great 623. COLEOPTERA 519 Fig. 624. pests in meadows and in cultivated fields. We have known large strawbern^ plantations to be destroyed by them, and have seen large patches of ground in pastures from which the dead sod could be rolled as one would roll a carpet from a floor, the roots having been all destroyed and the ground just beneath the surface finely pulver- ized by these larvas. No satisfactory method of fighting this pest has been discovered as yet. If swine be turned into fields infested by white- grubs they will root them up and feed upon them. We have destroyed great numbers of the beetles by the use of trap-lanterns, but many beneficial insects were destroyed at the same time. II. The rose-bugs. — -The common rose-bug, Macroddctylus sub- spinosus, is a well-known pest. It is a slender beetle, tapering before and behind, and measuring 9 mm. in length (Fig. 624). It is thickly clothed with fine, yellow, scale-like hairs, which give it a yellow color; the legs are long, slender, and of a pale red color. These beetles appear in early summer, and often do great injury to roses and other flowers, and to the foliage of various fruit-trees and shrubs. This is a very difficult pest to control. The best method now known is to use Paris green when safe to do so ; in other cases the beetles should be collected by jarring them into a large funnel which is fitted into a can. The larvcc of rose-bugs feed on the roots of plants. III. The shining leaf -chafers. — These insects resemble the May- beetles in form, but can be distinguished from them by the position of the hind pair of spiracles, which are visible on the sides below the edges of the wing-covers; and they differ from the other leaf-chafers in which the spiracles are in this position in that the tarsal claws are of unequal size, one claw of each pair being larger than the other. These beetles are usually polished, and many of them are of brilliant colors. To this group belong the most beautiful beetks known, many appearing as if made of burnished gold or silver, or other metal. The goldsmith-beetle, Cotdlpa lantgera. — This is one of our most beautiful species. It measures from 20 mm. to 26 mm. in length, and is a broad oval in shape. It is of a lemon-yellow color above, glittering like burnished gold on the top of the head and thorax ; the under side of the body is copper-colored and thickly covered with whitish wool. The spotted pelidnota, Pelidnota punctata. — This beetle is reddish brown above, with three black spots on each wing-cover and one on each side of the pro- thorax (Fig. 625). The scutellum, base of the head, and entire body beneath, are of a deep, bronzed- green color. The adult is commonly found feeding on the leaves of grape. The larva feeds upon decaying roots and stumps of various trees. The Japanese beetle, PopUlia japonica. — This is a very serious pest which feeds in the adult state on the foliage of man/ cultivated Fig. 625. 520 AN INTRODUCTION TO ENTOMOLOGY and wild plants, being practically omnivorous, and in the larval state feeds on the roots of grasses. It was first observed in this country in a limited area in Burlington County, New Jersey, in 19 16, and has since spread over other counties of this state and into Pennsylvania. The adult insect is about the size of the Colorado potato-beetle, but slightly longer. The head and thorax are shining bronze-green in color, with the wing-covers tan or brownish, tinged with green on the edges. Along the sides of the abdomen are white spots, and two very distinct white spots at the tip of the abdomen below the wing-covers. The larva resembles the larvse of May beetles. This pest is regarded as of so great importance that a special laboratory, "The Japanese Beetle Laboratory," has been established for investigations regarding it at Riverton, N. J. IV. The rhinoceros-beetles. — The name rhinoceros-beetles was suggested for this group by the fact that in many species the male bears a horn on the middle of the head. In addition to this horn there may be one or more horns on the thorax. These beetles are of medium or large size ; in ___ fact, the largest beetles known belong to this group. As with the flower-beetles, the claws of the tarsi are of equal size, but the fore coxse are transverse, and not prominent. One of the largest of our rhinoceros-beetles is Dynds- Fig- 626. f^s tttyrus. This is of a greenish gray color, with scattered black spots on the wing-covers, or, if only recently trans- formed, of a uniform dark brown. The male (Fig. 626) bears a prominent horn on the top of the head, and a large one and two small ones on the prothorax. The female has only a tubercle on the head. This insect is found in the Southern States; the larva lives in rotten wood. In the Far West there is a closely allied species, Dyndstes grdntii, in which the large horn on the thorax is twice as long as in D. tityrus. In the West Indies there occurs a species, Dyndstes hercules, which measures 150 mm. in length. Several other genera occur in this cotmtry, in some of which the males have prominent horns; in others the horns are represented by tubercles, or are wanting. The following species represents the latter type. The sugar-cane beetle, Euctheola rUgiceps .■ — This beetle is a serious pest in the cane-fields of Louisiana, and it sometimes injures com. Figure 627 represents the adult, audits method of attacking a plant. V. The flower-beetles. — The flower-beetles are so called because many of them are often seen feeding upon pollen and flying from flower to flower. These beetles are somewhat flattened, or nearly level on the back; the claws of the tarsi are of equal size and the COLEOPTERA 521 fore coxse are conical and prominent. More than one hundred species occur in this country. The hermit flower-beetle, Os- moderma eremicola. — This is one of the larger of our flower-beetles (Fig. 628). It is of a deep mahog- any-brown color, nearly smooth, and highly polished. It is supposed that the larva lives on decaying wood in forest-trees. The rough flower-beetle, Os- moderma scdbra, is closely allied to the preceding. It is not quite as large, measuring about 25 mm. in length. It is purplish black, and the wing-covers are rough- ened with irregular, coarsely punctured striae. It is nocturnal, concealing itself during the day in the crevices and hollows of trees. The larva lives in the decaying wood of apple and cherry, con- suming the wood and inducing more rapid decay. The genus Euphoria repre- sents well the form of the more typical flower-beetles, which are distinguished by the margin of each wing-cover having a large, wavy indentation near its base, which renders the side pieces of the meso- thorax visible from above. This indenta- tion makes it unnecessary for these insects to raise or expand their wing- covers when flying, as most beetles do, as they are able to pass the wings out from the sides. The bumble flower-beetle. Euphoria mda. — The most common of our flower-beetles, at least in the North, is a yellowish brown one, with the wing-covers sprinkled all over with small, irregular- black spots (Fig. 629) . It is one of the first insects to appear in the spring. It flies near the surface ot the ground with a loud humming sound, like that of a bumble-bee, for which it is often mistaken. During the summer months it is not seen ; Fig. 627. — The sugar-cane beetle. Fig. 628. 522 AN INTRODUCTION TO ENTOMOLOGY but a new brood appears about the middle of September. The adult is a general feeder occurring upon flowers, eating the pollen, upon corn-stalks and green com in the milk, sucking the juices, and upon peaches, grapes, and apples. Oc- casionally the ravages are very serious. The green June-beetle or fig-eater, Cotinus nitida. — This species extends over the Atlantic slope, and is very common in the South. It is a green, velvety insect, measuring from i6 mm. to 25 mm. in length. It is somewhat pointed in front, and usually has the sides of the thorax and elytra brownish yellow. These beetles often fly in great nimibers at night, making a loud buzzing noise similar to that of the May-beetles. In fact, in the South the terra June-hug is often applied to this insect. The larvae feed upon the vegetable mold of rich soils; sometimes they injure growing vegetables by severing the roots and growing stalks ; but the chief injury is due to the upheaval of the soil around the plants, which disturbs the roots; the larvae are also often troublesome on lawns and golf greens by making little mounds of earth on the surface. Sometimes they leave the ground and crawl from one place to another. When they do so, they, strangely enough, crawl upon their backs, making no use of their short legs. On one occasion we saw them crawl- ing over the pavements on the Capitol grounds at Washington in such numbers that bushels of them were swept up and carted away. The adults frequently attack fruit, especially figs, grapes, and peaches. Family TROGID^E The Skin-Beetles This is a small family, which is represented in this country by twenty -five species. Until recently these insects were included in the preceding family; they can be distinguished from scarabaeids by the fact that the epimera of the mesothorax do not extend to the coxae as they do in the Scarabaeidae. The members of this family are oblong, convex species, in which the surface of the body and wing- covers is usually very rough, and covered with a crust of dirt, which is removed with great difficulty. They are small or of medium size ; our most common species measure from 8 mm. to 12 mm. in length. The abdomen is covered by the elytra; the feet are hardly fitted for digging, but the femora of the front legs are greatly dilated. These beetles feed upon dried, decomposing animal matter; many species are found about the refuse of tanneries, and upon the hoofs and hair of decaying ^^- ^^• animals. Except a few species found in the Far West, all of our species belong to the genus Trox (Fig. 630). ^ COLEOPTERA Family LUCANID^ 523 The Stag-Beetles The stag-beetles are so called on account of their large mandibles which in the males of some species are branched like the antlers of a stag. They and the members of the following family are dis- tinguished by the form of the club of the antennae, which is composed of flattened plates ; but these plates are not capable of close appo- sition, as in the antennae of the lamellicorn beetles. In the stag-beetles the mentimi is not emarginate and the ligula is covered by the mentimi or is at its apex. The adult beetles are found in or beneath decaying logs and stumps. Some of them are attracted, at night, to lights. They are said to live on honeydew and the exudations of the leaves and bark of trees, for procur- ing which the brushes of their jaws and lips seem to be designed; but it seems probable that some species, at least, feed upon de- composing wood. They lay their eggs in crevices of the bark of trees, especially near the roots. The larvas feed upon juices of wood in various stages of decay. They re- semble the well-known larvae of May -beetles. The family is a small one; only thirty North American species are now known. The common stag-beetle, Lucanus dania. — The most common of our stag-beetles is this species (Fig. 631). It flies by night with a loud buzzing sound, and is often S- o3i- attracted to lights in houses. The larva is a large, whitish grub re- sembling the larvae of the lamellicorn beetles. It is found in the trunks and roots of old, partially decayed trees, especially apple, cherry, willow, and oak. The specimen figured here is a male; in the female the mandibles are shorter. The giant stag-beetle, Lucanus elaphus, is a large species foimd in the South. It measures from 35 mm. to 50 mm. in length, not including the mandibles, which in the case of the male are more than half as long as the bod}^ and branched like the antlers of a stag. The antelope-beetle, Dorcus parallelus. — This beetle is somewhat smaller than the species of Lucanus, and differs in having the wing-covers marked with longi- tudinal striae and the teeth on the outside of the fore tibiae much smaller (Fig. 632). Several species of stag-beetles that are much smaller than Dorcus are found in this country. Fig. 632. 524 AN INTRODUCTION TO ENTOMOLOGY Family PASSALID^ The members of this family resemble the stag-beetles in the form of the antennae, but differ in that the mentum is deeply emarginate, with the ligula filling the emargination. A single, widely distributed species is found in the United States; this is the horned passalus, Pdssaliis corniitus (Fig. 633). It is a large, shining, black beetle, with a short horn, bent forwards, on the top of the head. This beetle and its larva are found in decaying wood. The larva appears to have only four legs, the hind legs being shortened and modified so as to form part of a stridulating organ. See Figure loi, page 89. The beetles of this genus are common through- out the tropics of both hemispheres. According to the observations of Ohaus, which have been Fig- 633. confirmed by Prof essor Wheeler ('23), these beetles are social. They form colonies, consisting of a male and female and their progeny, and make large, rough galleries in rather damp, rotten logs. The parent beetles triturate the rotten wood and apparently treat it with some digestive secretion which makes it a proper food for the larvce, since their mouth-parts are too feebly developed to enable them to attack the wood directly are kept together by stridulatory signals. The stridulatory organ of the adult consists of patches of minute denticles on the dorsal surface of the abdomen, which may be rubbed against similar structures on the lower surface of the wings. Family CERAMBYCID^ The Long-horned Beetles or Ceramhycids All members of the colony Fi This is a very large family, there being more than eleven hundred de- scribed species in North America alone. As a rule the beetles are of medium or large size, and graceful in form ; many species are beautiful in color. The body is oblong, often cylindrical. The antennse are long, often .1 B g. 634. — Tarsi of Phytophaga: A, typical; Spondylis; C, Parandra. COLEOPTERA 525 longer than the whole body ; but except in one genus, Prionus, the}^ are only eleven-jointed, as with most beetles. The legs are also long, and the tarsi are apparently four-jointed, the fourth segment being very small and hidden; the third segment of the tarsi is strongly bilobed (Fig. 634). They are strong flyers and swift runners; but many of them have the habit of remaining motionless on the limbs of trees for long intervals, and when in this apparent trance they suffer themselves to be picked up. But, when once caught, many species make an indignant squeaking by rubbing the prothorax and meso- thorax together. The larvse are borers, living within the solid parts of trees or shrubs, or beneath bark. They are white or yel- lowish grubs. The body is soft, and tapers slightly from head to tail (Fig. 635); the jaws are powerful, enabling these insects to bore into the hardest wood. The larval state usually lasts two or three years. The pupa state is passed within the burrow made by the larva; frequently p. a chamber is made by partitioning off a section of the ^^* burrow with a plug of chips; but sometimes the larva builds a ring of chips around itself just beneath the bark before changing to a pupa. The pupal state is comparatively short, lasting only a few days or weeks. This family comprises three subfamilies, which are separated by LeConte and Horn as follows : A. Sides of the prothorax with a sharp margin, p. 525 Prionin^ AA. Prothorax not margined. B. Front tibiae not grooved ; palpinever acute at tip. p. 526.CERAMBYCIN.E BB. Front tibiae obliquely grooved on the inner side; palpi with the last segment cylindrical and pointed, p. 528 Lamiin^e Subfamily PRIONIN^ The Prionids The larger of the long-horned beetles constitute this subfamily. They are distinguished from other cerambycids by having the sides of the prothorax prolonged outwards into a thin margin, which is more or less toothed. The wing-covers are usually leathery in ap- pearance, and of a brownish or black color. The following are our best-known species. The aberrant long-horned beetles.^ — ^The beetles of the genus Pa- randra exhibit some strikingdifferences from the more typical ceramby- cids, and were formerly placed in a separate family, the SpondylidcB; but they are now included in the Cerambycids. There are only four North American species of this genus. These live under bark of pine trees. The fourth segment of the tarsus, although much reduced in size, is distinctly visible ; the first three segments are but slightly di- 526 AN INTRODUCTION TO ENTOMOLOGY Fig. 637 lated, and the third is either bilobed or not (Fig. 634, C). The seg- ments of the antennae have deep impressions, in which are situated the organs of special sense (Fig. 636). The most common species is Pardndra briinnea (Fig. 637); this insect is of a mahogany-brown color, and measures from 9 mm. to 18 mm. in length. The broad-necked prionus, Prionus laticollis. — This is the largest of our common species; but the individuals vary from 22 mm. to 50 mm. in length. It is of a pitchy-black color, and of the form shown in Figure 638. The antennse are twelve- jointed in both sexes. The larva is Fig- 636. ^ large, fleshy grub, and infests the roots of grape, apple, poplar, and other trees. The tile-homed prionus, Prionus imbricornis, is very similar to the preceding species but can be distinguished at a glance by the form of the antennse. In the antennas of the male the number of segments varies from eighteen to twenty, while in the female the number varies from sixteen to seventeen. The popular name refers to the fact that the segments of the an- tennas of the male overlap one another like the tiles on a roof. The larva infests the roots of grape and pear, and also feeds upon the roots of herbaceous plants. The straight-bodied prionid, Dero- brachns brunneus, is also a common spe- cies. The body is long, narrow, and some- what flattened; it measures from 25 mm. to 35 mm. in length, and is of a light brown color. The prothorax is short, and Fig. 638, jg armed on each side with three sharp spines. The sides of the wing-covers are very nearly parallel ; this suggests the common name. The adult flies b}^ night, and is often attracted to lights; the larva is supposed to infest pine. Subfamily CERAMBYCIN^ The Typical Cerambycids In this subfamily the prothorax is rounded on the sides, the tibiae of the fore legs arenot grooved, and thepalpiareneveracuteatthetip. There are nearly four hundred American species, representing more than one hundred genera. The few species mentioned below are those that the beginning student is most likely to meet. The ribbed pine-borer, Rhdgium linedtum. — This is a gray beetle mottled with black, and has a narrow thorax, with a spine on each COLEOPTERA 527 1-ig. 639. ;5ide (Fig. 639). It received its name because of the three ridges extending lengthwise on each wing-cover. Its larva bores in the wood of pine-trees. On one occasion the writer found many of them in a pine-tree eight inches in diameter, which they had bored through and through. When the larva is full-grown it makes a hole nearly through the thick bark of the tree, so that it may easily push its way out after its transformations; it then retreats a short distance and makes a little ring of chips around itself, between the bark and the wood, and changes to a pupa within this rude cocoon. The adult beetle re- mains in this pupal cell through the winter. The cloaked knotty-horn, Desmocerus pallidtus. — This beautiful insect is of a dark blue color, with greenish reflections. The basal part of the wing-covers is orange-yellow, giving the insect the appearance of having a yellow cape thrown over its shoulders (Fig. 640). The segments in the middle of the antennae are thickened at the outer end, so that they look like a series of knots. The adult is quite common in June and July on elder, in the pith of which the larva bores. The beautiful maple-borer, Glycohitis speciosus. — This is a handsome insect, p. marked with black and yellow, as indicated '^' ^'^' in Figure 641. It lays its eggs in midsum- mer on the trunks of sugar-maples, in the wood of which the larvae bore. If an infested tree be examined in the spring the presence of these borers can be detected by the dust that falls from the bur- rows. The larvce can be de- stroyed at this time by the use of a knife and a stiff wire. The locust-borer, Cyllene ro- btncB.- — ^To the enthusiastic ento- mologist the goldenrod is a rich mine, yielding to the collector more treasures than any other flower. It gives up its gold-dust pollen to every insect-seeker; and because of this generous attitude to all comers it is truly emblematic of the country that has chosen it as its national flower. Among the insects that revel in this golden mine in the autumn is a black beetle with numerous transverse or wavy yellow bands (Fig. 642). This beetle is also found on locust- trees, where it lays its eggs. The larvae bore under the bark and into the hard wood; they attain their growth in a little less than a 3'ear. The locust-trees have been completely destroyed in some localities by the depredations of these larvae. Fig. 642. Fig. 641. 528 AN INTRODUCTION TO ENTOMOLOGY The painted hickory-borer, Cyllene cdrycB. — This beetle resembles the preceding so closely that the same figure will represent either. But the hickory-borer not only infests a difi^erent kind of tree, but appears in the spring instead of the autimm. In this species the second segment of the hind tarsus is densely pubescent beneath, while it is glabrous in the locust -borer. The oak-pruner, Hypermallus villosus. — The work of this insect is much more lil<:ely to attract attention than the insect itself. Fre~ quently, in the autumn, the ground beneath oak-trees, and sometimes beneath apple-trees also, is strewn with small branches that have been neatly severed from the trees as if with a saw. These branches are sometimes nearly 25 mm. in diameter, and have been cut off by the larva of a beetle, which on account of this habit is called the oak- pruner. The beetle lays each of its eggs in a small twig. The larva eats out the inside of this twig, and works down into a larger branch, following the center of it towards the trunk of the tree. When full- grown the larva enlarges the burrow suddenly, so as nearly to sever the branch from the tree, leaving only the bark and a few fibers of wood. It then retreats up its burrow a short distance, and builds a plug of chips below it. The autumn winds break the branch from the tree. The larva remains in its burrow through the winter, and undergoes its transformations in the spring. No one has explained its object in severing the branch. The adult is a plain, brownish gray beetle. Whenever it becomes abundant its increase can be checked by gathering the fallen branches in the autumn and burning them before the beetles have escaped. Subfamily LAAIIIN^ The Lamiids As in the preceding subfamily, the prothorax is rounded with these beetles; but the lamiids are distingiaished by hav- ing the fore tibiae oblique- ly grooved on the inner side, and the last segment of the palpi cylindrical and pointed. The follow- ing are some of the more important species. The sawyer, Mono- chamus notdtus. — This beautiful brown and gray beetle is about 30 mm. long, with antennce aslong as the body in the case of the female and twice as -p- ^ long m the case of the ^^ "^^- male (Fig. 643). The larva bores in the sound wood of pine and of fir, making, when full- COLEOPTERA 529 grown, a hole 12 mm. in diameter. The pupa state is passed within the burrow. It sometimes occurs in such numbers as to kill the infested trees. The rounded-headed apple-tree borer, Saperda Candida. — Except- ing the codlin-moth, which infests the fruit, this is the worst enemy of the apple that we have. Its common name is used to distinguish it from the flat-headed apple-tree borer, already described, the larva of this species being nearly cylindrical in form (Fig. 635). The eggs are laid on the bark at the base of the tree late in June or July. The larva at first bores in the soft sap-wood, making a disk -shaped mine; after this it works in an upward direction in the harder wood, and at the close of its larval existence comes to the surface sev- eral inches above the place it entered. Itrequires nearly three years for this larva to attain its growth ; it changes to a pupa, near the upper end of its burrow, about the middle of May, and emerges as a beetle in June. The beetle (Fig. 644) is of a pale brown color above, with two broad white stripes extending the whole length of the body. Although the larva Fig. 644. is found chiefly in apple, it infests many other trees. The presence of the borers can be detected by the saw- dust-like castings which the larvee throw out at the entrances of their burrows. The two-spotted oberea, Oberea bimaculdta, is sometimes a serious pest, boring in the canes of blackberry and raspberry. The larva resembles that of the preceding species. The adult (Fig. 645) is T^, ____^^ about 12 mm. in length and of a s^^^ ^ deep black color, except the protho- m^ rax, which is yellow. There are usu- nmm^ ally two or three black spots on the / w^ pronotum, but frequently these are Fig. 645. Fig. 646. wanting. By cutting and burning all the canes after the crop has been picked, the borers in them can be destroyed. The red milkweed-beetles, Tetraopes. — There are several species of bright red beetles that are common on milkweeds {Asclepias). These belong to the genus Tetraopes. Our most common species (Fig. 646) is T. tetraophthdlmus. In this species there are four black spots on each wing-cover, and the antennae are black and not ringed with a lighter color. The larva bores in the roots and the lower parts of the stems of milkweeds. 530 AN INTRODUCTION TO ENTOMOLOGY Family CHRYSOMELID^ The Leaf-Beetles or Chrysomelids The leaf-beetles are so called because they feed upon the leaves of plants both as larv« and adults. They are usually short -bodied, and more or less oval in outline; the antennse are usually of moderate length ; and the front is not prolonged into a beak. The legs are usu- ally short, and are furnished with tarsi of the same type as those of the preceding family (see Fig. 634, p. 524). Although we are unable to cite any characteristic that will in- variably distinguish these beetles from the preceding family, the student will rarely have any difficulty in making the distinction. The beetles of the genus Dondcia, described below, are the only common ones that are liable to be misplaced. In other cases the more or less oval form of the body, and the comparatively short antennse, and the leaf-feeding habits, will serve to distinguish the chrysomelids. The leaf-beetles are nearly all comparatively small, the Colorado potato-beetle being one of our larger species. The eggs are usually elongated and yellowish, and are laid upon the leaves or stems of the plants upon which the larvas feed. Many of the larvas live exposed on the leaves of plants ; others that live in similar situations cover themselves with their excrement; some are leaf -miners; and a few, as the striped squash-beetle, bore in the roots or stems of plants. This is a large family, of which nearly one thousand North Ameri- can species are known. The following illustrations will serve to show the variations in form and habits. The long-horned leaf -beetles, Dondcia. — These are the common leaf -beetles that are liable to be mistaken for ceramby cids . They are of elongated form, with slender antennae (Fig. 647). They measure from 6 mm. to 1 2 mm. in length, and are of a metallic color — -either greenish, bronze, or purplish. The lower side of the body is paler and is clothed with very fine hair which serves as a water-proof coat when the insect is submerged. The larvae feed upon the roots or in the stems of aquatic plants ; and the adults are found on the leaves of the same Fig. 647. plants. We have many species, but they resemble one another so closely that it is difficult to separate them. The three-lined lema, Lema trilinedta. — This insect is common, feeding on the leaves of potato. The beetle is 6 mm. long, yellow, with three black stripes on the wing-covers. The eggs are usually laid in rows along the midrib on the lower side of the leaves. The larvae feed on the leaves, and can be easily recognized by a habit they have of covering their backs with their own excrement. They transform in the ground in earthen cells. There are two broods each year; the second hibernates in the ground as pupae. The asparagus-beetle, Crioceris aspdragi. — This is a small red, yellow, and black beetle, that gnaws holes into the heads of young COLEOPTERA 531 asparagus, and lays oval, black eggs upon them. The larvae, which are small, brown, slug-like grubs, also feed upon the young heads in the spring, and later in the season a second brood feed upon the full-grown plant. Figure 648 represents a head of asparagus bearing the eggs of this beetle, also a beetle and a larva enlarged. The beetle measures about 6 mm. in length. When this pest occurs, care should be taken to destroy all wild asparagus. This will force the beetles to lay their eggs upon the shoots that are cut for market. The larvsd hatching from such eggs will not have a chance to mature. The grape root-worm, Ftdia longipes. — This insect is the most destructive enemy of the grape occurring east of the Rocky Mountains. The adult is a small, grayish brown beetle, measuring about 6 mm. in length. It feeds on the leaves in July, eating out characteristic chain-like holes. The eggs are laid beneath the loose bark of the vines. On hatching, the larvae drop to the ground and burrow down to the roots, which they destroy, causing the death of the vine. Most of the larvffi do not transform till the following spring. The best means of fighting this pest is to poison the beetles while they are feeding on the leaves, and before they lay their eggs, by the use of a spray made by dissolving six pounds of arsenate of lead in 100 gallons of water. The Colorado potato-beetle, Leptinotdrsa decemlinedta.- — -A good many insect tramps have come to us from Europe and from Australia, and appropriated whatever pleased them of our grow- ing crops or stored grain. But two of our worst insect pests have swarmed out on us in hordes from their strongholds in the region of the Rocky Mountains. These are the Rocky Mountain locust and the Colorado potato-beetle (Fig. 649). The latter insect dwelt near the base of the Rocky Mountains, feeding upon the sand-burr (Solanum rostratum), until about the year 1859. At that time it began to be a pest in the potato-fields of the settlers in that region. Having acquired the habit of feeding upon the cultivated potato, it began its eastward march across the conti- nent, spreading from potato patch to potato patch. At first the migration took place at about the rate of fifty miles a 3- ear, but later it was more rapid; and in 1874 the insect reached the Atlantic Coast. The adult beetles hibernate in the groimd; they emerge early in April or May, and lay their eggs on the young potato plants as soon as they appear; both larvae and adult beetles feed on the foliage of the potato. The larvag enter the ground to transform. This pest is usually controlled by the use of Paris green. Lahidomera clivicollis: — ^This species is closely allied to the Colorado potato-beetle and resembles it in size and form. It is of a deep blue Fig. 649. 532 AN INTRODUCTION TO ENTOMOLOGY color, except the wing-covers, which are orange, with three dark-blue spots on each (Fig. 650). There is considerable variation in the size and shape of these spots; frequently the two near the base of the wing-covers are joined so as to make a continuous band extending across both wing-covers. The larva feeds on milkweed {Asclepias) . Fig. 650. The diahroticas . — -Several very important pests belong to the genus Diabrotica. In the East they are known as cucumber-beetles; but on the Pacific Coast, where they are more feared on account of their injuries to fruit and fruit-trees, they are commonly called the diabroticas. They are chiefly greenish yellow beetles, marked with black stripes or spots. The striped diabrotica, D.vittata,hsLS> two black stripes on each wing-cover. The adult feeds on the leaves of cucumber, squash, and melon; and the larva, which is a slender, worm-like creature, bores in the stems and roots of the same plants. , The twelve-spotted diabrotica, D. duodecimpunctdta, and Diabrotica sdror, agree in having six black spots on each wing- cover. The former is very common in the East; the latter occurs on the Pacific Coast, and is the most destructive of all of the diabroticas. Diabrotica longicornis is a green species, which feeds on the pollen and silk of corn and on the pollen of other plants. Its larva is known as the corn root-worm ; it is very destructive to corn in the Mississippi Valley. Its injuries are greatest where corn is grown on the same land year after year; hence a rotation of crops should be practised where this pest is troublesome. The other species of Diabrotica mentioned above are difficult to combat, as the leaves of cucumber, melon, and squash are very apt to be injured by the use of arsenical poisons. The most practicable way of protecting these vines is to cover them while young with frames covered wnth netting. Where they infest fruit-trees they can be fought with Paris green ; but this poison must be used with great care on such trees as prune and apricot. Squashes should not be grown in orchards, as is sometimes done in California. The flea-beetles. — There is a group of leaf-beetles, of which we have many species, in which the hind legs are fitted for leaping, the thighs being very large. These are commonly called the flea-beetles. The striped flea-beetle, Phyllotreta vittdta, is exceed- ingly common on cabbage, turnip, radish, mustard, and allied plants. It is a small, black, shining beetle, with a broad, wavy, pale, dull yellow stripe upon each wing- cover (Fig. 651); it measures about 2.5 mm. in length. These beetles eat nimierous little pits in the thicker ^^* "^'* leaves that they infest, and minute perforations in the thinner-leaved plants. The larva is a slender, white worm, about 8 mm. in length ; it feeds On the roots of the plants infested by the adult. The adult beetles can be destroyed with kerosene emulsion. COLEOPTERA 533 The cucumber flea-beetle, Epitrix cuciimeris, is a common pest of melon and cucimiber vines; it also attacks the leaves of potatoes, raspberry, turnip, cabbage, and other plants. This is a minute black spe- cies, meas- uring less than 2 mm. in length, punctured Fig. 653. The body is finely and clothed with a whitish pubescence ; there is a deep H '^/ ^ ' ^^"^ ^ transverse furrow across the hind ^ tV^:^ 'p'^V part of the prothorax; the antennas are dull yellow, and the legs are of the same hue, except the posterior femora, which are brown. The adult beetles feed on the leaves of plants in the same manner as the preced- ing species ; and the larv« on the roots of the infested plants. The grape flea-beetle, Haltica chalyhea. is a larger species than the two pre- ceding, measuring from 4 mm. to 5 mm. in length, and is of a dark, steel-blue color. It is a great pest in vincAards, eating into the buds of grape in early spring, and later gnawing holes in the leaves (Fig. 652). In May and June the brown, sluggish larvae may also be found feeding upon the surface of the leaves. The full-grown larva is chestnut brown marked with black spots (Fig. 653). It drops to the ground and makes a cell in the earth in which it transforms. The most important injury caused by this pest is the destruction of buds in early spring, which causes a great loss of foliage and fruit. This pest is most easily controlled by spraying the vines with an arsenical poison between the middle of June and the middle of July, while the larvae are feeding on the leaves. The wedge-shaped leaf -beetles . — These insects are characterized by the peculiar form of the body, which is narrow in front and broad behind. In most of the species the body is much roughened by deep pits, and usually the pits on the wing-covers are in regular rows. These insects and the tortoise-beetles differ from other leaf -beetles in having the fore part of the head prominent, so that the mouth is confined to the under surface. Some of the larvas feed externally upon the leaves and bear a parasol composed of their excrement; Fig. 652. 534 AN INTRODUCTION TO ENTOMOLOGY other species are leaf-miners. Balidsus rubra is a good representative of this group (Fig. 654). It varies in length fronii 3 mm. to 5 mm. It is of a reddish color, with the elevated portions of the elytra more or less spotted with black. The larva mines in the leaves of apple, forming a blotch -mine ; the transformations are undergone within the mine. We have also found this species mining the leaves of basswood in great nimibers. The tortoise-beetles. — Among the more beautiful Fig, 654. Coleoptera are certain bright golden, green, or irides- cent beetles found on the leaves of sweet potato, morning-glory, nettle, and other plants. In these beetles the body is flattened below and convex above ; the head is nearly or quite con- cealed beneath the prothorax; and the margins of the prothorax and elytra are broadly expanded, forming an approximate- ly circular or oval outline, and suggesting a resem- blance to the shell of a tortoise (Fig. 655). Not all of the species are iridescent ; and in the case of those that are, the brightness of the colors is said to de- pend on the emotions of the insect. What a beautiful way to express one's feelings — to be able to glow like Y\^. 655. melted gold when one is happy! Unfortunately for the beauty of our collections, these bright colors disappear after the death of the insect. The larvae of the tortoise-beetles are flattened, and have the margin of the body fringed with spines. At the caudal end of the body there is a forked appendage which serves a very strange purpose. This fork is bent forward over the back, and to it are attached the cast-off skins of the larva and its excrement; these constitute a parasol. When about to change to the pupa state these larvae fasten the caudal end of the body to the under side of a leaf; the skin then splits open, and is forced back to this end of the body, where it remains. The one-dotted or five-dotted tortoise, Physonota uniptmctdta. — The largest of our bright-colored tortoise-beetles is common in mid- summer, feeding on the leaves of wild sunflower. It measures from 9 to 12 mm. in length, and is yellow, with the margins whitish. On the prothorax there are five black dots — two close together in front, and three more widely separated behind. Sometimes all but one of these dots are wanting. It was this form that was first de- scribed, hence the name unipunctata. We have found the larA-a} abun- dant in July on the same plant with the adults. The milkweed-tortoise, Chelymorpha cassidea, is a large, brick red species, which measures from g mm. to 12 mm. in length, and has the prothorax and wing-covers marked with many black spots. This vSpecies feeds on milkweed (Asdepias) and various other plants. M' COLEOPTERA 535 Family MYLABRID^ The Pea-Weevil Family These are small beetles, the larvee of which live in the seeds of leguminous plants. The head of the adult is prolonged into a broad beak; and the wing-covers are rather short, so that the tip of the abdomen is always exposed (Fig. 656). This is a compara- tively small family; ninety-three species are listed in our fauna, of which eighty-one belong to the genus Mylahris. The pea-weevil, Mylahris pisdrum. — "Buggy peas" are /naH^ T well known in most sections of our country; but just how /^ffll\l the "bugs" find their way into the peas is not so generally understood. The eggs of the pea-weevil are laid upon the pod while the peas are quite small; when the larv£e hatch pj™ 5c6_ they bore through the pod into the young peas. Here they feed upon the substance of the seed, which ripens, however, and in some cases will germinate when planted. The larva before transforming eats a circular hole on one side of the seed, leaving only a thin scale, which is easily pushed away by the mature beetle. The adult is about 5 mm. in length; it is dark brown, with a few white spots on the wing-covers, and one on the prothorax near the middle. Sometimes the beetles leave the peas during the autumn or winter; but as a rule they remain in the seed till spring, and are often planted with it. Seed peas should be placed in water, and the infested ones, which will float, should be picked out and destroyed. This species is not known to oviposit on dry peas. This and other grain-infesting insects can be destroyed by placing the grain in a closed receptacle with a small quantity of bisulphide of carbon. The bean-weevil, Mylahris obtectus. — This species resembles the preceding quite closely; but it is a little smaller (Fig. 656), and lacks the white markings characteristic of A/, pisorum. It infests beans, and often several individuals inhabit a single bean. The eggs are laid within the pod, being pushed through a slit which the female gnaws through the pod. This species will oviposit on dry beans, peas, and other grain, and will continue to breed for many generations in stored beans and peas. SERIES VIL— THE RHYNCHOPHORA* The six families included in this series constitute a well-marked division of the order, which has long been known as the Rhynchophora or snout-beetles. These names were suggested by the fact that in many of these insects the head is prolonged so as to form a snout or beak; but it should be remembered that, while these names are very appropriate for a large part of this series, in some members of it the head is not thus prolonged. This is especially true of the last two *Rhynch6phora : rhynchos (New Latin), snout; phoros {(p6pos), bearing. 536 AN INTRODUCTION TO ENTOMOLOGY families, the bark-beetles and timber-beetles, in which the beak is either wanting or extremely short and broad. The most distinctive features characterizing this series of families are the following: the suppression of the gula, the gular sutures being confluent (Fig. 657, gs); the absence of sutures between the prostemum and the episterna and epimera; the meeting of the epimera of the pro- thorax on the middle line behind the prosternum (Fig. 657, em) ; and the palpi being usually short and rigid. A volume entitled "Rhynchophora or Weevils of North Eastern America" was published by W. S. BlatchleyandC. W. Lengin 1916. This work includes descriptions of the then known species found in this region, with analytical keys, and many figures. Family BRENTID^ The Primitive Weevils Fig. 657. This family is confined chiefly to tropical re- gions; only six species are found in the United States, and but one of these in the North. The northern brentid, EUpsalis minUta.- — In the female the head is prolonged into a slender snout ; but in the male the snout is broad and flat, and is armed with a pair of powerful jaws (Fig. 658). These are weapons of oftence, for the males fight desperately for their mates; and too, the males are generally larger than the females. In these respects these insects resemble the stag-beetles, the males of which also fight for their mates. The northern brentid is found beneath the bark of recently felled or dying oak, poplar, and beech trees, in the solid wood of which the larvas bore; and is widely distributed over the United States and Canada . Family PLATYSTOMID^* The Fungus Weevils This family includes a small number of snout-beetles in which the beak is short and broad, and the labnmi is present; the antennce are not elbowed, and the terminal segments rarely form a compact club; the palpi are flexible; and the prothorax bears a transverse elevated ridge at or near its base. The larvae of many species infest woody fungi, others breed in the smut of corn and wheat, and still others bore in dead wood. The *This family is the Anthribidae of many authors. COLEOPTERA 537 larvae of one cosmopolitan species, known as the coffee-bean weevil, ArcBocenis JasciculdtMS, attack seeds of various plants. Sixty-two species of this family are known to occur in America north of Mexico. Family BELID^ The New York Weevil The family Belidas is represented in our fauna by a single species, the New York weevil, Ithycerus noveboracensis. This is a large species, measuring from 1 2 mm. to 1 8 mm. in length. It is black, rather sparse- ly clothed with a mixture of ash-gray and pale brown prostrate hairs which give it a black-spotted appearance. The beak is short and broad. The mandibles are prominent, not very stout, and emarginate at the tip, with an inferior cusp. The antennae are not elbowed; the first segment is longer than the second; and the terminal segments form a small, oval club. This species breeds in the twigs and tender branches of oak, hick- ory', and possibly other forest trees. The adult beetles appear in early spring, and sometimes do much damage to fruit-trees by eating into buds, and gnawing the tender bark on new growth. They can be caught b}' jarring them on to sheets or by the use of a plrmi-curculio catcher. Family CURCULIONID^ The Curculios or Typical Siwut-Beetles The Curculionidae is a very large family; it is represented in America north of Mexico by more than eighteen hundred species; to it belong four-fifths of all our Rhynchophora. This family includes the typical snout -beetles, the head being prolonged into a well-defined beak, which is usually long and curved downward. The family Curculionidae is divided into thirteen subfamilies; but several of "these are very small. The seven subfamilies mentioned below will serve to illustrate the more important variations in structure and in habits, and they include the more important species from an economic standpoint. The subfamily Rhinomacerin^, or pine-flower snout-beetles, in- cludes a small mmiber of snout-beetles in which the elytra have no fold on the lower surface near the outer edge, and in which the labrum is distinct. The head is prominent, not deflexed; the snout is as long as the prothorax, rather flat, narrowest about the middle, wider at base and tip; the elytra are rounded at the tip, and entirely cover the abdomen. These beetles infest the staminate flowers of coniferous trees, in which the eggs are laid. Six species are found in our fauna. The subfamily Rhynchitin^, or toothed-nose snout-beetles, in- cludes snout-beetles in which the elytral fold is feeble, the labrum is wanting, and the mandibles are toothed on both the outer and the inner side. The mandibles can be spread widely, and when closed the outer tooth at the end of each projects forward so that two small, :icute teeth seem to project from the mouth. 538 AN INTRODUCTION TO ENTOMOLOGY The most common member of the family is Rhynchltes hicolor (Fig. 659). This is red above except the snout, and black below; the body, not including the snout, is about 6 mm. long, ^^»^ the snout is half that length. The adults are often abun- ..^^^^ dant on wild roses, and less frequently on cultivated roses. ' ' The larvae infest the hips of roses. Fig. 659. The subfamily Attelabin^, or leaf-rolling weevils, is composed of beetles which have neither an elytral fold nor a labrum, and in which the mandibles are fiat, pincer-shaped.and toothed on the inner side. The elytra do not entirely cover the abdomen, and each is separately rounded at the tip. Only five species are known from this country; all of these belong to ihegernxsAttelabiis. The females pro- vide for their young in a very remarkable way. They make compact thimble-shaped rolls from the leaves of trees (Fig. 660), and lay a single egg in each. The larvee feed on the inner parts of these rolls, and when full-grown enter the ground to transform. Sometimes these rolls are found hanging by a narrow piece to the leaf from which they were made, and sometimes they are found lying on the Fig. 660. ground separated from the leaf. The subfamily Cyladin^ is represented in Florida, Louisiana, and Texas by a single species, the sweet-potato root-borer, Cylas formicd- rius. This beetle is somewhat ant-like in form ; this fact suggested the specific name. It is about 6 mm. long; the color of the eltyra, head, and snout is bluish black, that of the pro thorax reddish brown. Both larvae and adults bore into the stems and tubers of the sweet potato, and sometimes do very serious damage. This species was formerly included in the Brentidae. The subfamily Otiorhynchin^, or scarred snout-beetles, is one of the larger of the subfamilies of the Curculionidae ; it is repre- sented in our fauna by more than two hundred species. The most distinctive characteristic of these insects is the presence in the pupa state, and sometimes also in recently matured adults, of an ap- pendage on each mandible, and in the adult state of a scar indicating the place from which the appendage has fallen. This scar is on the anterior face of the mandible, and frequently at the tip of a slight process. Many species of this family are beautifully ornamented with scales which resemble in a striking manner the scales on the wings of butterflies. Among J f the more important species are the following. W^^ The imbricated snout -beetle, Epiccsrus imhri- jfif^ cdtus, is usually a dull, silvery white beetle with ^^K^ brown markings; but the species is quite variable J[^HHL\ in color. It is represented, somewhat enlarged, in WSPv Figure 661. It is omnivorous, gnawing holes in va- / ^^^ rious garden vegetables, strawberry plants, and other p. , fruits. The greater part of the insect is clothed with ^^' ■ imbricated scales, which suggested the specific name. COLEOPTERA 539 Fuller's rose-beetle, Pantomorus fulleri. — This is an oval, black snout -beetle, lightl}^ covered with dark brown scales, and about 6 mm. in length. It attacks roses and many other greenhouse plants. The adults feed on the foliage, flowers, and buds, the larvae on the roots, of its food plants. The strawberry crown-girdler, Brachyrhlnns ovdtus: — -This is a dark brown, almost black, snout-beetle, about 5 mm. in length, which often invades dwellings in search of shelter, in the Northern States and Canada. The larvae feed on the roots of the strawberrs^ cutting them off near the crown. The adults feed on the foliage. In the adult, the hind wings are wanting and the elytra are grown together. The black vine-weevil, Brachyrhimis sulcdtiis. — This beetle is larger than the preceding species, measuring 9 mm. in length; it is black, with small patches of yellowish hairs on the elytra. The larvcc destroy the roots of strawberries; and both larvae and adults infest various greenhouse plants. The subfamily Curculionin^ is represented in our fauna by more than one thousand species, among which are some very destruc- tive pests. In this family there is on the lower side of each wing-cover a strong fold near the outer margin, which limits a deep groove in which the upper edge of the abdomen fits ; the mandibles have no scar; the antennae are usually elbowed, and have a ringed or solid club; the tarsi are usvially dilated, with the third segment bilobed and spongy beneath; in a few cases the tarsi are narrow, but not spinose beneath . The larvce are soft, white, maggot-like grubs destitute of feet. They feed chiefly on fruits, seeds, and nuts, but all parts of plants are subject to their attacks. In laying her eggs, the female first bores a hole with her snout, then drops an egg into this hole, and finally pushes the egg to the bottom of the hole with her snout. In many species the snout is highly developed for this purpose; sometimes it is twice as long as the remainder of the body. This is well shown in the acorn-weevils and the nut-weevils, ^m^j^ which belong to the genus Baldninus. Figure 662 ~^ represents Baldninus rectus resting on an acorn ; the specimen figured, when found, had her snout inserted in the acorn up to the antennae. Of the closely allied species Balanimis naslcus breeds in hickory-nuts, and Balanimis prohosctdens in chestnuts. The following are some of the more important Fig- 6b_. pests belonging to this subfamily: The plimi-curculio, Conotrachelus nenuphar. — This is the insect that stings plums, often destroying a large portion of the fruit ; the larva is also the well-known "worm" of "wormy" cherries. This species is the most destructive insect that infests pltims, cherries, and other stone fruits ; it also breeds in apple. Its presence in an orchard can be determined early in the season by a peculiar mark it makes when laying its eggs in the young fruit. The female beetle makes an 540 AN INTRODUCTION TO ENTOMOLOGY incision, with her snout, through the skin of the fruit. In this incision she lays a single egg, which she pushes with her snout to the bottom of the cavity that she has prepared . She then makes a crescent-shaped incision in front of the one containing the egg. This last cut under- mines the egg, leaving it in a little flap. The larvae feed within the fruit. In the case of the plums the infested fruit falls to the ground ; but not so with cherries. When full-grown the lan^ae go into the ground to transform. This species infests nectarines, apricots, and peaches, as well as phmis and cherries. This insect is fought in two ways : the beetles are jarred from the trees upon sheets in early spring, and destroyed before they have laid their eggs ; they are also poisoned by spraying the trees with arsenate of lead, either alone or combined with a fungicide before the fruit is large enough for them to oviposit in it. The adult beetle feeds upon the foliage, and can thus be poisoned. The apple-curculio, Anthonomus quadriglbhus, infests the fruit of apple, often in company with the plum-curculio. The specific name was suggested by the fact that there are two wart-like projections near the hind end of each wing-cover. _ The strawberry-weevil, Anthonomus signdtus, infests strawberry, blackberry, raspberry, and dewberry. The female beetle (Fig. 663) after laying an egg in the fiower- „. ,^ bud causes it to fall by cutting the pedicel; the larva de- ^^' ^' velops within the fallen bud. The cotton-boll weevil, Anthonomus grdndis, is one of the most serious insect pests known in the United States. It infests only cotton. The egg is deposited in a young boll, which the larva destroys. The adults also feed upon the young bolls and upon the leaves, doing as much or more damage than that done by the larvae. This species is a native of Central America. It spread through Mexico, and entered Texas about 1890. Since that time it has spread over a large part of the cotton-belt. Very extensive investigations of this pest have been made by the Federal Government and by several state govern- ments ; and much literature regarding it is available to those interested. The subfamily Calendrin^ includes the bill-bugs and the grain- weevils, some of which are among our more common snout-beetles. The larvae of the larger species feed upon the roots and bore in the stems of plants, especially grass and corn, while those of the smaller species infest grains and seeds. Most of our larger species belong to the genus Sphenoph- orus; one of these is represented in Figure 664. These are of medium or rather large size, and are often marked in a very characteristic manner by longitudinal elevated bands of darker color; frequently, when collected, they are covered with a coat of clay. They are commonly known as the bill-bugs. One species, Sphenophorus maidts, is an ^^^- ^^4- important pest of corn in the South ; it bores in the tap- root and lower part of the stalk. Most of the beetles hibernate in the corn-stubble, and can be destroyed by piilling out and burning the stubble. » COLEOPTERA 541 Among the smaller members of this subfamily are two exceedingly important pests of stored grains; these are the granary-weevil, Calandra grandria, and the rice-weevil, Caldndra oryzcs. The rice- weevil is so called because it was first found in rice in India; but it infests various kinds of stored grain; and in the South it is fully as important a granary -pest as is the granar>'-weevil. The two species are quite similar in appearance; but the granary- weevil is the larger, measuring from 3 mm. to 4 mm. in length; while the rice-weevil measures less than 3 mm. in length, and differs from the granary-weevil in having the elytra marked with four reddish spots. The thorax of the rice-weevil is closely pitted with round punctures; that of the granary-weevil, with sparse elongate punc- tures. The adult female of both of these species gnaws a tiny hole in a kernel of grain and then deposits an egg in it. The larva feeds on the grain, becomes full-grown, and transforms within the kernel. _ The adult continues the injury begun by the larva, eating out the inside of the kernel. The most effective method of destroying grain-weevils is by the use of carbon bisulphide. The grain is placed in a tight bin or other receptacle, and the carbon bisulphide is poured into a shallow tin pan placed on top of the grain, and then covered with blankets to keep in the fumes. Two or three pounds of carbon bisulphide should be used for each 1000 cubic feet of space. Care should be taken not to go near the bin with a lighted lantern or fire of any kind until after the blankets have been removed and the gas has been dissipated. Family PLATYPODID^ This is a small family, which is represented in our fauna by a single genus. Platypus, of which only five species have been found in America north of Mexico; these are found chiefly in the South and the Far West. Formerly this group was classed as a subfamily of the Scolytidse. It is distinguished from the Scolytidas by the fact that the first segment of the anterior tarsi is longer than the second, third, and fourth together. The form of the body is cylindri- cal (Fig. 665) ; and the head is large, wider than the prothorax. The species of this genus attack many kinds of conifers and deciduous trees. They bore deeply into the heart -wood, making "pin-holes" that often render lumber useless. The eggs are de- posited in the galleries; and the larvae feed on a fungus, which is cultivated by the beetles and is known as ambrosia. In this respect Platypus resembles several genera of the Scolytidas, which also bore in solid wood and feed on ambrosia; Fig. 66^.— Platypus ■wilsoni, femai^. (After Swaine.) 542 AN INTRODUCTION TO ENTOMOLOGY all of these are known as ambrosia-beetles. The galleries of ambrosia- beetles are usually blackened by the fungus. See further account of the ambrosia -beetles in the discussion of the next family. Family SCOLYTIDiE The Engraver-Beetles and the Ambrosia-Beetles Fig. 666. — Phthoro- phlceus liminaris. The members of the family Scolytidse are mostly of cylindrical form (Fig. 666) and of small or moderate size; some species measure only I mm. in length, but others are much larger, at- taining a length of 6 mm. or more. They are usually brown, sometimes black, and with many the hind end of the body is very blunt, as if cut off. The antennae are elbowed or bent in the mid- dle, and are clubbed at the tip; the tibiae are usually serrate; and the first seg- ment of the anterior tarsi is shorter than the second, third, and fourth together. A few members of this family infest herba- ceous plants ; our most important one of these is the following. The clover-root borer, Hylastinus ohscurus. — This pest was introduced from Europe and has become the most serious enemy of clover, especially red clover and mammoth clover, in New York State and in other sections of the North. It bores in the roots of plants beginning their second year of growth and destroys them (Fig. 667) . Where it is common it is practically impossible to keep fields in clover longer than the second stmuner after seeding. In these regions it is the common practice to seed with clover and timothy mixed; after the clover disappears the field becomes a timothy meadow. No practical method of control of this pest has been found. Fig. 667.— Work of clo- Most scolytid beetles infest woody plants; ver-root borer. (After among them are some of the most destructive Webster.) enemies of forest-trees, and a few attack fruit- trees. As a rule they are more liable to attack sickly trees, but their injuries are not confined to these. COLEOPTERA 543 The scolytid beetles exhibit two radically different types of habits; and from this point of view they can be grouped into two groups: first, the engraver-beetles or bark-beetles; and second, the ambrosia-beetles or timber-beetles. These two groups, however, do not represent a natural division of the family based on structural characters. The peculiar habits of the ambrosia-beetles are believed to have arisen independently in different parts of the series of scolytid beetles, and in the family Platypodidas as well. The Engraver-Beetles or Bark-Beetles If the bark be pulled from dead branches or trunks of trees, the inner layer and the sap-wood will be found, in many cases, to be ornamented with burrows of more or less regular form. The smoothly cut figures are the mines of engraver-beetles, which are also known as bark-beetles. Many kinds of these engravings can be found, each characteristic of a particular species of engraver beetles. A common pattern is shown in Figure 668. Many figures and detailed descriptions of the burrows of engraver- beetles have been published by writers on forest-insects ; among the more important papers on this subject published in America are those by Hopkins ('09) and Swaine ('18), in which can be found references to many other papers. The different species of engraver-beetles vary so greatly in the details of their habits that it is difficult to make generalizations re- Fig. 668. garding them in the space available here. In a common type, the adult beetle, after penetrating the bark, makes a tunnel in the inner layer of the bark or in the sap-wood or in both ; this is known as the egg-tunnel, and may be either simple or branched. In the sides of the tunnel, most species make niches, the egg-niches, in which the eggs are laid. The larva when hatched feeds on the bark or sap-wood or both and thus makes a lateral tunnel. These lateral tunnels made by the larvs often extend parallel in a more or less regular manner, as shown in Figure 668. While most of the engraver-beetles infest forest-trees, the two following species are well-known pests of fruit-trees. 544 AN INTRODUCTION TO ENTOMOLOGY The fruit-tree bark-beetle, Scolytus rugiilosus. — This species in- fests apple, quince, plum, peach, and other stone-fruits. It is some- times called the shot-hole borer by fruit-growers on account of the small entrance holes of its burrows. The adult beetle measures from 2 mm. to 2.5 mm. in length, and is dark brown or nearly black. It infests chiefly sickly trees. The peach-tree bark -beetle, Phthorophlceus limindris. — This spe- cies resembles the preceding in size and habits, except that its injuries are confined chiefly to peach and cherrv^ It can be distinguished from the fruit-tree bark-beetle by the fact that the club of the antennse is lamellate, an unusual feature in this family (Fig. 666). The Ambrosia-Beetles or Timber-Beetles Certain members of the family Scolytidas differ in habits from the engraver-beetles or bark-beetles in a remarkable manner; these are those known as ambrosia-beetles or timber-beetles. Thev are termed Fig. 669. — Gallery of Monarthnim malt in maple. (From Hubbard.) ambrosia-beetles because they cultivate fungi, commonly called am- brosia, upon which they feed; and timber-beetles, because they burrow in the solid wood. The galleries of the ambrosia-beetles can be distinguished from those of other wood-boring insects by the fact that in all of their ramifications they are of uniform size and free from wood-dust and other refuse, and their walls are stained black or brown by the fungus that is grown upon them. The galleries of different species differ in form; but usually there is a main gallery, which extends deeply into the solid wood and is often branched; and extending from the sides of the main gallery there are short chambers, termed cradles, in each of which an egg is laid and a larva reared (Fig. 669). In some species, the female de- posits her eggs loosely in the galleries, and the young and old live together in the same quarters. COLEOPTERA 545 The galleries are excavated by the adult beetles. In some species the gallery is started by a single female, in others the males assist the females in this work. The entrances through the bark to the galleries are similar to those made by the bark-beetles and like them are known as "shot-holes." Under favorable conditions colonies may continue their excavations during two or three generations. The fungi upon which these beetles feed are carefully cultivated by them. So far as is known, each species of ambrosia-beetle culti- vates only a single species of fungus, and only the most closely allied species have the same food-fungus. The fungus is started by the moth- er-beetle upon a carefully packed bed orlaA^er of chips. It is probable that some conidia are brought for this purpose from the gallery in which the female was developed. The excrement of the larvce is used in some and probably in all the species to form new beds for the propagation of the fungus. In those species in which the larvae are reared in separate cradles, "the mother-beetle is constantly in attendance upon heryoimg during the period of their development, and guards them with jealous care. Themouth of each cradle is closed with a plug of the food-fungus, and as fast as this is consimied it is renewed with fresh material. The larvae from time to time perforate this plug and clean out their cells, pushing out the pellets of excrement through the opening. This debris is promptly removed by the mother and the opening again sealed with ambrosia. The young transform to perfect beetles before leaving their cradles and emerging into the galleries." A detailed account of the ambrosia-beetles of the United States was published by Hubbard ('97), from which I have drawn largely in the preparation of the account given here. While the ambrosia-beetles are chiefly injurious to forest -trees, there are certain species that injure wine and beer casks; and one species, the pear-blight beetle, Anisdndrus pyri, sometimes infests the tips of pear and apple branches, causing an injury that is often mistaken for the bacterial disease known as pear-blight. Nearly four hundred species of scolytid beetles, representing many genera, have been described from America north of Mexico. CHAPTER XXIV ORDER STREPSIPTERA* The Stylopids or Twisted-winged Insects The members of this order are small, endoparasitic insects, which prey on other insects. Only the males are winged; in this sex, the fare wings are reduced to club-shaped appendages; the hind wings are large com- pared with the size of the tiny body, fan-shaped, furnished with radiating wing-veins, and folded longitudinally when at rest. The adult female is larviform and legless. The mouth-parts are vestigial or wanting; the alimentation is probably by osmosis. Both sexes undergo a hyper- metamorphosis. The order Strepsiptera comprises insects that were formerly classed as a family of the Coleoptera, the StA'lopidas ; for this reason, these insects have been known as the stylopids. Recently since the establishment of the order Strepsiptera, the name the twisted-winged insects, derived from the technical name of the order, has been pro- posed for them; biit the old name is less cumbersome, and will prob- ably continue to be used. The stylopids are small insects which live parasitically within the bodies of other insects, chiefly bees, Avasps, digger wasps, and certain Homoptera. Their small size and the fact that nearly their entire existence is passed within the bodies of their hosts result in their being rarely seen except by those who are searching for them. During the first stadium the young larvae of both sexes are free, and the adult winged male leads a free existence for a brief period; but only the most skilled collectors are likely to observe these minute creatures during these periods, the only free stages of their existence. The stylopids are most easily found by examin- ing adult individuals of the species of insects that they infest, in which may be found adult females and" male pupa? of the parasites. The presence of a stylopid is indicated by the projecting of the head end of the body from between tw^o of the abdominal segments of the host (Fig. 670). Frequently a single host will contain several parasites. A female Polistes with eleven male stylopids has been recorded. If this projecting part of the parasite is a fiat disk-like plate, it is the head end of a female; but if it is the rounded and tuberculate end of a cylindrical body, it is the head end of the puparium of a male. Adult male stylopids can be bred by keeping alive stylo- pized insects containing male pupae. *Strepsiptera : strepsis {(rrpixpis), a turning; pteron {irrepdv), (546) Fig. 670. — Abdo- men of stylo- pized insect: s, s, stylopids. STREPSIPTERA 547 Fig. 671. — Opthalmochlus dufyi. (After Pierce.) Figure 671 will serve to illustrate the appearance of an adult male stylopid. The more striking features are the flabellate antennge; the large, stalked, com- pound e^^es; the shortness of the pro- thorax and the mesotho- rax, and the great length of the meta- thorax ; the re- duction of the fore-wings to club-s h a p e d appendages; and the large size of the hind wings. The an- tennae of adult males differ greatly in form in the different families of this order. The number of antennal segments varies from four to seven; the third segment is always furnished with a lateral pro- longation, a flabel- lum, and one or more of the follow- ing segments may or may not be fla- bellate. The compound e3'^es of adult males are large and more Fig. 672.— Mouth-parts of male stylopids: a, Acros- Or less stalked. The chismus brtiesi. (After Pierce.) h, Pentozocer a austral- facets are separated ensis. (After Perkins.) ^y densely ciliate walls. The mouth-parts are greatly reduced; those of two adult males are represented in Figure 672. The mouth opening is small. The labrum and labium are wanting as distinct parts. In AcroscMsmus bruesi (Fig. 672,0) the mandibles are slender, cur^^ed, and scimitar- like; beneath the mandibles are the maxillae; these are two-jointed; the second segment is belie\'ed to be the reduced palpus. In Pento- zocera anstralensis (Fig. 672, h) the mandibles are greatly reduced, but the maxilllary palpi are quite large. The three pairs of legs are similar in form. The tarsi are five- jointed in one family (Mengeida^), and furnished with two claws; 548 AN INTRODUCTION TO ENTOMOLOGY " 2dA Fig. 673. — Wing of Paraxenos eberi. (From Pierce, after Sai^nders.) in the other families they are two- to four-jointed and without claws. The venation of the hind wings is degenerate. There is a variable number of radiating veins, which in the most generalized wings are eight in niimber. These are sup- posed, by Pierce ('09), to be the eight principal veins of the typi- cal wing, the costa, subcosta, ra- dius, media, cubitus, and the three anal veins, respectively (Fig. 673). The abdomen is composed of ten segments. The adult female is very de- generate in form. That part of the body which projects from the body of the host is the cephalo- thorax, the head and thorax being jonsolidated into a single disk- like region. The abdomen, which is within the body of the host, is a great sac filled with eggs. The body of the adult female is in- closed in the skin of the last larval instar, which is termed the puparium; but there is no pupal stage in this sex. The postembryonic development of the stylopids is very peculiar. In the adult female the eggs are free in the body cavity, where they hatch. The young larv« are campodeiform and active. As they bear some resemblance to the triungulins of the parasitic blister-beetles, they are termed triungulins by some writers ; but as they do not possess three tarsal claws, this term is inappropriate when applied to vhem. For this reason the first instar of a stylopid larva is termed z. iriun- gulinid. The stylopids are very prolific; more than 2000 triungulinids pro- duced by a single female have been counted. This fecundity is doubtless correlated with the uncertainty of any individual triun- gulinid being able to find its proper host. The triungulinids escape from the body of the female through unpaired median genital apertures on the second to fifth abdominal segments. These apertures open into the space between the venter of the female and the pupariimi, which is termed the brood chamber. The triungulinids escape from this space through a slit in the cephalo- thorax of the puparium, between the head and the prothorax, and then crawl over the body of the host. This is the beginning of the most critical period in the life of the stylopids. For the continued existence of any individual of the brood it must find a larva or a nvTnph of the particular species that is its proper host. This is doubtless accom- plished in different ways in the different species. Those that infest Homoptera and other insects that do not build nests must wander STREP SIPTERA 549 over the plants on which these insects live till they find ii n3TTiph of their host species. In the case of stylopids that infest social insects the problem is obviously not so difficult, especially if the triungulinids leave their host while it is in or near the nest. But those stylopids that infest solitary nest-building species are beset with more serious difficulties. It is believed that parasitized female bees and wasps are so weakened that they do not build nests ; hence the triungulinids issuing from them, and from males as well, must attach themselves to other females of the same species in order to be carried to a nest where they can find their appropriate victims. This transfer is probably made in the flowers visited by these insects. When a triungulinid finds a larva or a n^-mph of its host species it quickly bores into it, and begins its parasitic life. The most com- plete account of the metamorphosis of a stylopid yet published is that of Xenos vespdmm by Nassonow ('92). An abstract of this author's results is given by Pierce ('09, pp. 47-48) ; the more important features of them are the following. The campodeiform triungulinid grows rapidly after entering the body of its host ; at the first molt it loses its legs and becomes scarabsei- form ; later the body becomes cylindrical. From this point the develop- ment of the two sexes is different. In the case of the females, there are seven larval instars ; in the fifth instar the head and thorax are fused, forming a cephalothorax; the seventh instar pushes its cephalo- thorax out between two of the abdominal segments of the host; the skin of this instar becomes the "puparium," in which the adult female is inclosed, and which she never leaves ; the adult female is larviform ; there is no pupal stage in this sex. In the case of males, the head and thorax of the fifth instar are fused, forming a cephalothorax; the seventh instar is inclosed in the skin of the sixth, and has strongly de- veloped appendages; for this reason it may be termed a prepupa; during the seventh stadium the cephalothorax is exserted between two abdominal segments of the host ; the true pupa is formed within the skin of the seventh instar; the adult male thrusts off the cap of the puparium and emerges as a winged individual. The manner in which the female is fertilized, inclosed as she is in a puparium, has not been determined; it has been suggested that the seminal fluid is discharged into the space between the venter of the female and the puparium, the brood chamber. If this is true, the mobile spermatozoa probably pass from the brood chamber through the genital apertures into the abdominal cavity, where the eggs are massed free. The slit in the cephalothorax of the puparium, through which the triungulinids escape, may serve for the introduction of the seminal fluid into the brood chamber. The order Strepsiptera is well represented in this country. Leng ('20) lists ninety-seven American species, and doubtless there are many undiscovered species here. The described American species represent five families and eighteen genera. Students wishing to study the classification of these insects should consult the very complete monographs of the order by W. Dwight Pierce ('09, '11, and '18), and other papers listed in these works. CHAPTER XXV ORDER MECOPTERA* The Scorpion-Flies and Their Allies The winged members of this order have four wings; these are usually long, narrow, membranous, and furnished with a considerable number of cross-veins; the wings are wanting or vestigial in two genera. The head is prolonged into a deflexed beak, at the end of which chewing mouth-parts are situated. The metamorphosis is complete. This is a small order composed of very remarkable insects. The most striking character common to all is the shape of the head, which is prolonged into a deflexed beak (Fig. 674). The dorsal wall of this beak is composed largely of the greatly elongated clypeus (Fig. 675, A, c) ; the central portion of the ventral wall is the greatly elongated subm--nt.um (Fig. 675, B, sm) ; and on each side of the submentimi there Fig. 674. — Head Fig. 675. — Head of Panorpa: A, dorsal aspect; B, and tail of ventral aspect; af, antennal foramen; ca, cardo; Panorpa. e, eye; g, gena; /, labrum; Ip, labial palpi; m, mentum; mp, maxillary palpi; mx, maxillae; 0, ocelli; sm, submentum; si, stipes. (After JMiyake.) is a greatly elongated stipes of the maxilla, at the distal end of which is borne the maxillary palpus. The mentum and labium are com- paratively short ; and from each side of the labium there extends a labial palpus. The mandibles are rather small and slender and are articulated to the apex of the beak, and can cross freely. The antennse are long, very slender, and many-jointed. The compound eyes are moderately large. There are usually three promi- nent ocelli, but these are wanting in Merope and in Boreus. *Mec6ptera: mecos (/x^koj), length; pteron {wrepdv), a wing. (550) MECOPTERA 551 The prothorax is small ; the mesothorax and metathorax are large. The legs are long and slender; the tarsi are five-jointed; in some genera there are two tarsal claws, in others only one. The wings are membranous, and are usually long and narrow, but in two genera, Notiothauma and Merope, the representatives of which are very rare insects, the wings are comparatively broad. In the genus Boreus the wings are vestigial or wanting. The type of the venation of the wings in this order is well shown by the wings of Panorpa (Fig. 676). In the species figured here, the ^i_^. Fig. 676. — Wings of Panorpa. number and arrangement of the wing-veins in the fore wings is that of the hypothetical primitive type, with the addition of a considerable niimber of cross- veins, and an ac- cessory vein on vein R2. The same is true of the hind wings except that each of the branches of cubitus anasto- moses with the ad- jacent vein; that is, vein Cui anasto- moses with vein M, and vein'Cu2 with the first anal vein Fig. 677. — Base of hind wing of Panorpa. 552 AN INTRODUCTION TO ENTOMOLOGY Fig. 6j8.—Pan- orpa, female. m (Fig. 677). For further details regarding the venation of the wings in this order, see "The "Wings of Insects" (Comstock '18 a). The metamorphosis is complete. The larvae are caterpillar-like, with three pairs of thoracic legs and with or without abdominal pro- legs. The pupae are exarate, that is, the wings and legs are free, as in the Coleoptera and H^Tnenoptera. This order is represented in our fauna by six genera ; these can be separated by the following table : A. With well-developed wings. B. Wings long and narrow; ocelli present. C. Tarsi with a single claw, and fitted for grasping Bittacus CC. Tarsi with two claws, and not fitted for grasping. D. Tarsal claws toothed Panorpa DD. Tarsal claws simple Panorpodes BB. Wings comparatively wide, with many cross-veins extending from the subcosta to the costa; ocelli wanting Merope AA. Wings wanting or imperfectly developed. B. Without ocelli; small insects, less than 6 mm., in length BoREUS BB. Ocelli present; body about 20 mm., in length Apterobittacus Panorpa or the scorpion-flies. — The most common members of this order belong to the genus Panorpa, of which there are nearly twenty described North American species. Figure 678 represents a female of this genus. In our more common species the wings are yellowish, spot- ted with black. The males of this genus are remarkable for the peculiar form of the caudal part of the abdomxcn (Fig. 679). This at first sight reminds one of the corresponding part of a scorpion, and suggested the common name scor- pion-flies for these insects. But in reality the two are very different ; the last segment of the male Panorpa, instead of ending in a sting, lilvc that of a scorpion, is greatly enlarged and bears a pair of clasping organs. The tarsal claws are toothed (Fig. 680, a). V. The adults are found resting on the surface of foliage of rank herbage growing on the banks of shaded streams and in damp woods where there is a luxuriant undergrowth of herbaceous plants. They feed on dead or injured insects and upon fruits; it appears that they rarely if ever capture living prey. Fig. 679. — Abdomen of Panorpa rufescens. C Fig. 680. — a, fore leg of Pan- orpa; h, last two segments of tarsus of Bittacus, ap- posed; c, last three seg- ments of tarsus of Bittacus. MECOPTERA 553 The females lay their eggs in crevices in the earth. The larvae are caterpillar-like in form; they have three pairs of true legs and eight pairs of abdominal prolegs ; and the body is armed with promi- nent spines (Fig. 68 1 ) ; the larvae are carnivorous. The transformation takes place in a cell in the ground. Panorpodes. — The members of this genus resemble Panorpa in general appearance, and as in that genus the abdomen of the male is furnished with a pair of clasping organs; but in Panorpodes the tarsal claws are simple. Only two species have been described from North America. These are not common; and but little is known regarding their habits. Merope.- — -This genus includes only a single known species, Merope tuber. This is an exceedingly rare insect. In this genus the wings are comparatively wide (Fig. 682) ; and there are many cross-veins ex- tending from the subcosta to the costa. I have figured the venation of the wings in "The Wings of Insects" (Comstock '18 a). The ocelli are wanting. The abdomen of the male is terminated by a pair of long, scotit forceps. This is prob- ably a nocturnal insect as it is attracted to lights at night. Its life-history is un- known. Boreus. — This ge- nus includes small Me- coptera, ovir species pig. 681. -Larva of Fig. 682.-Mero/>e /«6.r, slightly "measuring from 2.5 PanorPamfes- &', . ,^< . ',?,■' .^.^ i- ^ r' -^-.^ i^ cens, first instar. (After Felt.) enlarged. (Photographed by J, G. Needham.) mm. to 5 mm. m length, which are of- ten found on snow in winter. The wings of the feinale are vestigial or wanting ; those of the male, imperfectly developed. The ocelli are wanting. The female has a long, protruding ovipositor, which in some species is nearly as long as the abdomen. The larva differs from that of Panorpa in lacking the abdominal prolegs. The pupa state is passed in an earthen cell in the ground. Four American species have been described, two from the East and two from the West. BUtacus. — Insects belonging to this genus have long, narrow wings, long legs, and a slender abdomen. They resemble crane-flies very closely when on the wing, but can be distinguished by the presence of two pairs of wings. They are almost as common as 554 AN INTRODUCTION TO ENTOMOLOGY Panorpa; and, like the scorpion-flies, are found among rank herbage growing on the banks of shaded streams and in damp woods where there is a luxuriant undergrowth of herbaceous plants. When at rest, they do not sit on the surface of foliage as does Panorpa, but hang suspended, by their front legs, from some support (Fig. 683). The members of this genus capture and feed upon living insects. They are enabled to capture their prey by means of their curiously modified tarsi, the last two segments of which are armed with teeth, and the last segment can be folded back against the next to the last segment. In this way there is formed an efficient grasping organ (Fig. 680, b, c). It is an interesting fact that, while in other predacious insects the fore legs are the chief organs of prehension, in Bittacus the hind legs are used for this purpose fully as often as the others, especially when the Bittacus is hanging suspended by its fore legs and captures an insect that comes within reach of it. Nine North American species of Bittacus have been described. ApteroMttacus . — This genus includes a single known species, Apterobittacus apterus, found in California. It re- sembles Bittacus except that the wings are completely wanting. A review of the species of the Mecoptera of America north of Mexico was published by James S. Hine (Hine '01). Fig. 683. — Natural position of Bitta- cus. (From Felt.) CHAPTER XXVI ORDER TRICHOPTERA* The Caddice-Flies The members of this order have four wings; these are membranous and usually more or less densely clothed with long, silky hairs. In the more generalized members of the order, the venation of the wings corre- sponds closely to that of the hypothetical primitive type with but few or no accessory veins; in some of the more specialized members of the order, the venation of the wings is reduced. The mouth-parts of adults, except the palpi, are vestigial. The metamorphosis is complete. The caddice-flies are moth-like insects, which are common in the vicinity of streams, ponds, and lakes, and are frequently attracted to lights at night (Fig. 684). The larv^ of these insects are the well-known caddice- worms; these live in the water, and most of them build cases about their bodies. In the adult insect, the body-wall is soft, being membranous or at the most parch- ment-like, and is thickly clothed with hairs. Fig- 684.— A caddice-fly. The two pairs of wings are membranous and usually more or less clothed with long, silky hair. The fore wings are denser than the hind wings and are often slightly coriaceous ; in a few forms the wings are naked. The hind wings are shorter than the fore wings; but they are usually broader; this is due to an ex- pansion of the anal area of the hind wings. In a few species the hind wings are reduced so that they are smaller than the fore wings ; in one species the female is apterous, and in another the wings of the female are vestigial. When not in use the wings are folded roof-lilce over the abdomen. The posterior lobe of the fore wings is specialized as a fibula, which is well developed in the more generalized forms, as Rhyacophila, but more or less reduced in the more specialized genera. The costal border of the hind wings is furnished with hamuli in some forms, as in the Leptocerid^ and some Hydropsychidas. In the more generalized forms the venation of the wings cor- responds quite closely with the hypothetical primitive type; this is well shown by the wings of Rhyacophila fusctda (Fig. 685). The more important modifications of this t}'pe shown by the wings of Rhyacophila are the following: in the fore wing the tips of the second anal vein and two of the branches of the third anal vein coalesce; the subcosta bears an accessory vein ; this, however, is unimportant ; accessory veins borne by the subcosta exist in only a few genera of this order; the coalescence of veins Cu and ist A at the base of the *Trich6ptera: trichos (Opl^, rpTx^s), the hair; pteron {irrepdv), a wing. (555) 556 AN INTRODUCTION TO ENTOMOLOGY wing; and the formation of a serial vein consisting of the base of media, the posterior arculus (pa), and the distal part of vein Cu. In the hind wings, media has been reduced to a three-branched condition by the coalescence of veins M3 and M4. In the more specialized members of this order the specialization of the preanal area of the wings is always by reduction. In the anal area of the hind wings the specialization is in some cases by addition, resulting in a broadly expanded anal area; in others it is by reduction. The head is small; the antennse are setaceous, and frequently several times as long as the bod}^; the compound eyes are usually 2d A I St A Cu2 <^«i Fig. 685. — -Wings of Rhyacophila fuscula. small and with small facets; the ocelli are either present or absent; when present they are three in number; the mandibles are mere tubercles at the base of the labrum ; the maxillae are small, and ordi- narily furnished with an obtuse maxillary lobe ; the maxillary palpi are well-developed, and furnish characters which are much used in classification; the labium is usually well-developed, and bears three- jointed palpi. The legs are long and usually slender; the coxas are very large; the femora are long and slender, and generally without spines; the tibiae are also long and slender; the tarsi are always five-jointed. The tibise and tarsi are often furnished with black or brown, some- times yellow, spine-like setas. In addition to the spine-like setae, the tibia} bear movable spurs either at the apex only, or also at some TRICHOPTERA 557 Fig. 686. — Two egg-masses of caddice-flies:a, Phryganea inlerrupla; b, TricEuodes sp. (From Lloyd.) distance before the apex ; these are larger than the spine-like setre and are usually differently colored. The number of these spurs is much used in classification. The eggs of caddice-flies are round or slightly oval in form. They are laid either in water or upon objects above water from which the larvag when hatched can find their way into the water. Some species that lay their eggs in water descend below the surface in order to glue their eggs to some submerged support. So far as is known, all species of caddice-flies, except some of the Rhyacophilidse, lay their eggs in a mass enveloped either in a cement, by which the mass is glued to some support, or in a gelatinous covering. In the latter case, the covering absorbs water and thus increases greatly in size. The form of the gelatinous mass and the arrangement of the eggs within it are often characteristic of the species (Fig. 686). The larv^ of most caddice-flies, the caddice-worms, are somewhat caterpillar-like (cruciform) in shape (Fig. 687) ; but some are more nearly campodei- form. Those that are cruciform build a portable case in which they live; most of the campodeiform larva? do not build port- able cases. In the eraciform larv^ the head is bent down, as in a caterpillar; in the campodeiform larv^as the head is hori- zontal, the mouth-parts projecting for- ward. Both types differ from the cater- pillars in having only one pair of prolegs, the anal prolegs. These are each furnished with a chitinous hook. The mouth-parts are fitted for chewing. The thoracic legs are well developed. In the case-building forms, the first abdominal segment often bears three tubercles, one dorsal and one on each side; these are the "spacing- humps," and serve to keep a space between the insect and its case for the free circu- lation of water for respiration. In several families the larvse possess abdominal tra- cheal gills; these are filamentous and are sometimes branched; they arise singly or in tufts. With the exception of a single European genus, Enoicyla, all caddice- worms are aquatic. Most caddice-worms build portable cases in which they live and which they drag about wherever they go, projecting only the front Fig. 687. — A cad dice-worm, Anabolia nervosa: A, larva extracted from its case; B, one of the dorsal spaces of the abdominal seg- ments more strongly mag- nified. (From Sharp.) 558 AN INTRODUCTION TO ENTOMOLOGY end of the body and the legs from the case when they traveh The cases of different species differ greatly in form and in materials used in their construction; but silk is used in building all of them. This silk, like that of caterpillars, is secreted by modified salivary glands and is emitted through an opening in the labium ; but in most cases it is not spun into a thread, but is poured forth in a glue-like sheet upon the objects to be cemented together; some species, however, build nets of silken strands. Some caddice-worms build their cases entirely of silk; but most of the case-building species use other materials also; these may be grains of sand, small stones, bits of wood, moss, or pieces of leaves; and some species fasten shells of small mollusks to their cases. The materials used are glued together with silk; and the case is lined with silk, so as to form a suitable protection for the soft abdomen. Ex- amples of different types of cases are figured later. When the caddice-worms are full-grown they do not leave the water to transform, as do nearly all other aquatic larvae, the pupae being as truly aquatic as the larvae. Some of the case-building species change the form and material of their cases at this time; and nearly all of them partly close their cases so as to keep out intruders and silt; but usually provision is made for the ingress of water for respiration. Some species merely cement a stone or grains of sand over each open- ing of the case; others build a sill-cen lid with a slit in it; and still others build a silken grating in each end of the case. Frequently caddice-worms leave the open water in which the larval life has been spent and seek some more secluded place in which to transform, such as crevices in bark or among roots, or they may burrow into wood or into the soil. The pupae are of the exarate type, that is, the wings and legs are free (Fig. 688). Some pupae have tracheal gills, others do not; this, however, is not correlated with the presence or absence of tracheal gills in the larva; tracheal gills may be present in either of these stages and absent in the other. In the case of those caddice-flies that emerge from rapidly flowing water, as the net-building species, the wings expand instantly when the in- sect reaches the surface of the water and are then fitted for flight; it is evident that if much time were required for the wings to become fit for use, as is the case with most other insects, the wave succeeding that which swept the insect from the water would sweep it back again and destroy it. The Trichoptera can be regarded as beneficial insects, as the larvae form an important element in the food of fishes, and especially of the brook trout. Sometimes in cities near rivers, the adults are annoying on account of the great nimibers of them chat are attracted to lights. Fig. 688.— A, pupa of Phryganea pi- losa. '(After Pic- tet.) B, mandi- bles of pupa of Molamia angusta- ta. (From Sharp.) TRICHOPTERA 559 This order includes thirteen famiHes, all of which are represented in North America. Nearly four hundred species have been described from this region. Among the more important works on the classification of these insects are McLachlan ('74-80), Ulmer ('07), and Ukner ('09). This last-mentioned work is especially important for its accounts of the early stages of these insects. The latest and most extended work on the life-histories of North American caddice-worms is that by Lloyd ('21). In this work there is a list of the more important papers on this subject, which, for this reason, need not be enumerated here. This monograph by ]\Ir. Lloyd has been of great assistance to me in the preparation of the following account of the habits of representatives of the different families. A monograph treating of all stages of North American Trichoptera has been prepared by T)r. Cornelius Betten and is to appear as a bulletin of the New York State Museum. The following table of families is copied from Needham ('iS). TABLE OF FAMILIES OF THE TRICHOPTERA For the Classification of Adults A. Micro-caddice-flies ; very small, moth-like, hairy, the fore wings bearing numerous erect clavate hairs; the marginal fringe of the wings longer than their greatest breadth; form of wings narrowly lanceolate; antenn£e rather stout and not longer than the fore wings, p. 561 Hydroptilid/e AA. Larger caddice-flies, with broader wings; marginal fringes never as long as the wings are broad; antennae usually longer than the fore wings. B. Maxillary palpi five- jointed. C. Last joint of the maxillary palpi simple, and not longer than the other joints. D. Ocelli present. E. Front tibiae with two or three spurs, middle tibise with four spurs. F. The first two joints of the maxillary palpi short and thick, the third joint much longer and thinner, p. 560 . . . .RhyacophiliDvE FF. The second joint of the maxillary palpi much longer than the first. Females, p. 564 Phryganeid/E EE. Front tibiae with a single spur, or with none; middle tibiae with only two or three spurs. Females, p. 568 Limnophilid^ DD. Ocelli wanting. E. A closed cell in the principal fork of the median vein in the fore wings, p. 567 Calamoceratid^ EE. No closed cell in the median fork. F. A closed cell in the first fork of the radial sector. G. Both branches of the radial sector forked. H. Veins Ri and R2 confluent apically or connected by an apical cross-vein in the fore wing. Females, p. 567..0dontocerid.'E HH. Veins Ri and R2 not connected apically. p. 569 Sericostomatid^ GG, Only the anterior branch of the radial sector forked, p. 566. LErTOCERID.E FF. No closed cell in the first fork of the radial sector, p. 566. . •. MOLANNID^ CC. _ Last joint of the maxillary palpi usually much longer than the others, twisted, and divided imperfectly into subsegments. D. Ocelli present, p. 563 Philopotamid^ DD. Ocelli wanting. E. Front tibias with three spurs, p. 563 Polycentropid^ EE. Spurs of front tibiae fewer than three. 560 AN INTRODUCTION TO ENTOMOLOGY F. Anterior branch of the radial sector in the fore wings forked. P- 562 Hydropsychid^ FF. Anterior branch of the radial sector simple, p. 564 ■ PSYCHOMYID^ BB. Maxillary palpi with fewer than five joints. C. Maxillary palpi with four joints; ocelH present. Males, p. 564... Phryganeid^ (iC. Maxillary palpi with two or three joints. D. Maxillary palpi filiform, with cylindric smooth joints; fore tibiae; with a single spur. Alales. p. 568 Limnophilid^ DD. Maxillary palpi hairy or scaly, appressed against and often covering the face; fore tibiae with two spurs. Males, p. 569. . Sericostomatid^ TABLE OF TRICHOPTEROUS LARV^ The following table will aid in the classification of caddice-worms. It is based on a more detailed table of the family characters of trichopterous larvae given by Lloyd ('21). A . Anal prolegs not fused in median line to form an apparent tenth abdominal segment. B. Abdomen much wider than the thorax, p. 561 Hydroptilid^ BB. Abdomen not much wider than the thorax. C. Dorsal surface of the ninth abdominal segment with a chitinous shield. p. 560 RHYACOPHILIDiE CC. Dorsal surface of the ninth abdominal segment without a chitinous shield. D. Tracheal gills present, branched, p. 562 Hydropsychid^ DD. Tracheal gills absent. E. Labrum entirely membranous , white, p. 563 . . Philopotamid^ EE. Labrum entirely chitinized. F. Frons long, extending back to the caudal margin of the head. p. 563 POLYCENTROPID^ FF. Frons normal, p. 564 Psychomyid^ AA. Anal prolegs fused in median line so as to form an apparent tenth segment. B. Dorsal surface of the labrum with a row of twenty or more heavy bristles. p. 567 CALAMOCERATIDiE BB. Dorsal surface of labrum normal. C. Labrum much longer than broad, p. 567 Odontocerid^ CC. Labrum broader than long. D. Metanotum with three pairs of plates, p. 568 Limnophilid^ DD. Metanotum soft. E. Mesonotum soft or with one pair of minute plates, p. 564 Phryganeid^ EE. Mesonotum chitinized. F. Femur of hind legs divided into two segments or apparently so. p. 566 Leptocerid^ FF. Femur of hind legs not divided. G. p. 569 Sericostomatid^ GG. p. 566 Molanid^ Family RHYACOPHILID^ The larvae are campodeiform ; they live in rapidly flowing streams with stony bottoms. The American species of this family represent two subfamilies. The members of one subfamily, the Rhyacophilin^, TRICHOPTERA 561 do not build cases, but crawl about naked beneath stones seeking their food ; they feed on small larvae and filamentous algas. The larva of our most common species, Rhyacophila fuscula, when full-grown enters a crev- ice between two large stones and builds a wall of pebbles about itself; this wall is ce- mented in place with silk; and the chamber thus inclosed is much larger than the insect (Fig. 689); it then spins a parchment-like cocoon about its body, within which it trans- forms. The making of a co- coon is a family characteris- „. ^„ ^ , ^ „, ,, ., , ., ,. tic of the RhvamnhiliH-P-onlv ^^^' 689-— A larva of Rhyacophila building nc 01 tne Knyacopnnidae , only ^^g ^^^^^ chamber, exposed by lifting off afewothercaddice-wormsspm the stone beneath which it was. (From cocoons. Needham and Lloyd.) The members of the subfamily Glossosmatina^ build cases out of sand or small stones. Our best- known species is Glossosdma anieri- cdna, the habits of which are de- scribed by Lloyd. Figure 690 repre- sents a dorsal and a ventral view of the case. The larvae live singly on the stones of the stream's bottom; but before pupating they congre- gate in dense colonies on the sides and bottoms of stones, with their cases placed edge to edge, sometimes one on top of another. At this time the floor of the case is cut away and the rim of the cup-like roof is glued to the supporting rock. Fig. 690. — Case of Glossosonta ameri- cana: a, dorsal view; b, ventral view. (After Lloyd.) Family HYDROPTILID^ The Micro-Caddice-Flies This family is composed of minute caddice-flies, which resemble tineid moths in appearance. The larv^ are found in both quiet water and rapid streams, and often occur in very great numbers. They build cases which differ in form in the different species, but are usually fiat; some are elliptical, some flask-like, and others kidney-shaped; all are open at both ends; they are much larger than the larvce. They are usually composed entirely of silk ; but in some species grains ni sand or minute bits of vegetable matter are used. "Agraylea 562 AN INTRODUCTION TO ENTOMOLOGY decorates the parchment with filaments of Spirogyra, arranged concentrically over the sides in a single ex- ternal layer." (Needham and Lloyd.) Wlien moving about, the larva usually drags its case on one edge. There is one species, Ithytrichia conjiisa, which cements its case firmly to rocks in flowing water. These cases are common ; they are parch- ment-like, elliptical, with a small opening at each end (Fig. 691, 2), and measure from 5 mm. to 6 mm. in length. They are incomplete, being ce- mented along the edges to the rock, with no floor below the larva. The larva is very remarkable in form (Fig. 691, i). When feeding, it protrudes the narrower part of its body from its case and gathers food from the surface of the rock; the expanded abdominal segments are much wider than the openings in the case. Family HYDROPSYCHID^ The family Hydropsychidas of the older authors Fig. 691. —Ithytrichia ^^^ ^gg^^ divided into four families by Uhner,— 2! case.' '' (After Hydropsychidcs, Philopotamid^, PolycentropidcE, Lloyd.) and Psychomyidae. It is to this group of families that the net-spinning cadd ice-worms belong. The best-known of these are species of the genus Hydropsyche, the nets of which have been described by many writers. The larvee of Hydropsyche live only in rapid streams and on the wave-beaten shores of lakes. They are campodeiform, and do not build portable cases, but live in tubes composed of silk and debris, and fastened permanently in place; sometimes they establish them- selves in old worm-holes in submerged wood. The most striking feature in their habits, however, is the fact that each one builds a net for the capture of its food. This net is built adjacent to the tube in which the larva lives; it is funnel-shaped and has at its down- stream end an opening in which is built a strainer. This is a beautiful object, consisting of two sets of regularly spaced strands of silk extending across the opening at right angles to each other (Fig. 692). These nets are often built in crevices between stones ; but fully as often they are built up from a flat surface, as on the brink of a waterfall. In this case they are in the form of semi- elliptical cups, which are kept distended by the current. Much of the coating of dirt with which rocks in such places are clothed in summer is due to its being caught in these nets. Sometimes when 692. — Net of Hydropsyche. TRICHOPTERA 563 the net is built up from a horizontal surface its sides are supported by bits of wood. Algae, larvae, and other small animals in the water that passes through the net are held by the strainer and thus made avail- able to the caddice-worm for food. When the larva is full-grown it surrounds itself with a case composed of fine sand or gravel in which to transform; this case is firmly cemented in place, and, in some species at least, is closed at each end with a silken grating. The instantaneous flight of the newly emerged adult when it reaches the surface of the water has been referred to on an earlier page. Family PHILOPOTAMID^ The larv^ of members of this family are campodeiform and live in rapid streams. Several of them were studied by Miss Alice A. Noyes, but as yet an account of only one of them, Chimarrha aterrima, has been published (Noyes '14). This larva spins a delicate silken net resem- bling in shape the finger of a glove. The average size of the net of a growing larva is about 25 mm. long and 3 mm. wide. The nets are rarely found singly, but are generally placed five or sLx in a row (Fig. 693) ; sometimes they occur in great mmi- bers, completely covering the stones with a thin, flocculent mass of dirty silk. There is a large opening at the end of the net facing the current, r,- ^ t^t . r ^, • 1 ^„ 11 • J. it, u- J ^ig- o93- — JNets or Cmmarrha atern- and a smaller openmg at the hmd ^a, natural size. (From Noyes.) end. the nets are fastened m place at the entrance; the rest of the sac floats freely, and is kept distended by the current. The net serves both as a hiding-place for the larva and as a sieve through which the flowing water is strained; the larva feeding on the organic particles that are entangled in it. The full-grown larva covers itself with an irregular dome of pebbles in which to transform, and spins about its body a delicate cocoon. Family POLYCENTROPID^ The larvce are campodeiform ; they usually live in flowing water, but some are found in standing water. They do not build portable cases, but make fixed silken tubes or nets. The nets of several European genera have been described; for an abstract of these aecounts, see Noyes ('14). The nets of American species have been described by Clark ('91), Vorhies (09), Noyes ('14), and Lloyd ('21). 564 AN INTRODUCTION TO ENTOMOLOGY "Several species of the genus Polycentropus live in still or slowly flowing water with sandy or muck bottoms. These larvae spin sub- terranean tubes of silk which sometimes reach lo centimeters in length. Often the tubes have one or more branches, and al- ways they contain a bulb- ous swelling near the middle in which the larva probably rests, and in which pupation takes place. In natural posi- tion the tubes are be- neath the ground, except about half an inch which projects upward into the water." (Lloyd.) Two quite different larv'al tubes of members of this family are described and figured by Miss Noyes. One of these is represented in Figure 694. This tube is found on the under side of stones, and is fastened along its entire length. "It is 21 mm. long and 5.5 mm. wide, with an expanded opening at either end. Connected with each opening and along either side is a mass of tangled, silken threads, about 20 mm. square and loosely attached to the stone. This tangled mass may float partially over the tube and so obscure it." "I have never observed the larvae feeding, but do not doubt that Mayfly nymphs and chironomid larvae become entangled in the meshes as they crawl about over the stones, for remains of these forms are abundant in the stomach contents." (Noyes.) Fig. 694. — Dwelling of Polycentropus sp. (From Noyes.) Family PSYCHOMYID^ The larvae are campodeiform. There is no account of the life- history of any American species published. The European species do not make portable cases; but the larvae live on stones in long, loosely-spun galleries of silk and sand grains. They are found mostly in swift water, but also inhabit ponds and lakes. Family PHRYGANEID^ The larvae are caterpillar-like, and usually live in standing water in which plants are growing, or in slowly moving streams of spring water. They make portable cases which are very regular in form. As these larvcE live in quiet water, they can be fed and reared in aquaria where their habits can be easily observed. The most extended account of the immature stages of these insects is that of Lloyd ('21), from TRICHOPTERA 565 Fig which the following brief notes are compiled. This author discusses three species of Neuronia and three species of Phryganea. Neuronia. — The larvae are found in slowly moving streams of spring water; rarely they are found along the edge of the large, warm streams where cool seepage enters. One species was found in a pond. The cases are cylindrical tubes of thin, rectangular bits of leaves arranged in a series of rings (Fig. 695, o). In the cases of old larvae the rings are neatly fitted without overlapping; young larvag sometimes leave the hind ends of the leaf-fragments pro- truding in long strips. Unlike other caddice-worms, these larvje often abandon their cases and wander naked through the water. The form of the case indicates that they are not long retained ; their uniform di- ameter proves that they are con- structed more rapidly than the di- ameter of the larva increases. When the season for pupation draws near, the larvas of Neuronia burrow into wood, or wedge themselves beneath bark, or in crevices, or, if the stream bottom be of clay, they may burrow into the soil. When entering the soil the larva stands on its head, with its case perpendicular to the bottom, and slowly enters, dragging its case with it. Phryganea. — The larvae live in ponds; they dwell, for the most part, among submerged plants above the bottom of the pond; hence they can be taken with a water net. They never abandon their cases as do the larvag of Neuronia. The case is a straight tube com- posed of narrow strips of leaf arranged in spiral form around the circumference of the case (Fig. 695, b). Young larvae often fail to cut the leaf-fragTuents used in the construction of the case into the rectangular form seen in the cases of old larvas; but the bases of the untrimmed fragments are arranged in a spiral (Fig. 695, c). In pre- paring to pupate, the larvae leave their abode among living plants and travel to some submerged log or chunk of wood and burrow into it until the last bit of the case is concealed. This operation sometimes requires several days of labor. When sufficient depth is reached, the larva spins a silken mesh across each end of the case. The larva of a species of Tricenodes of the family Leptoceridas makes a case somewhat similar to that of Phryganea; this is described in the account of that family. 695.— Cases of phryganeids : case of Neuronia postica; b, case of old larva of Phryganea vestita; c, case of young larva of Phryganea vestita. (After Lloyd.) 56G AN INTRODUCTION TO ENTOMOLOGY Family MOLANNID^ The only members of this family the larvae and cases of which have been described in this country belong to the genus Moldnna. The larvffi are found on sandy bottoms of streams and of lakes. The cases have been figured by several writers, and are very char- acteristic in form (Fig. 696). The case is made of grains of sand, and, has on each side an ex- tension, and at the head end a dorsal hood, which completely protects the larva when crawling- or feedincr. Fig. 696. — Case of Mo- lanna. (After Lloyd.) Family LEPTOCERID^ The larvffi are caterpillar-like, and make portable cases. Most species live in standing water, as in lakes, ponds, and the bays of streams; but some are found in flowing water and on wave-beaten shores of lakes. The cases made by the different species differ greatly in form and in the materials used in their con- struction. Among the better-known species are the following. Set odes grandis. — The larva of this species lives among aquatic vegeta- tion in ponds and lakes. Its case is composed en- tirely of silk, and is translucent, so that the body of the larva can be seen throvigh it. It is cylindrical, tapering, and slightly curved (Fig. 697, a). When ready to pu- pate, the larva fastens its case to th e stem of a plant with a band of silk, and closes the anterior end of the case with a silken membrane, in which there is a central slit for the ingress of water. Leptocerus dncylus. — The larva is found on stones in the riffles of streams and on the stones of wave-beaten lake shores. It makes a case of 1 Fig. 697 Setodes -Cases of leptocerids: a, case of grandis; b, case of Leptocerus ancylns; c, case of Mystacides sepulchralis; d, caso of TricBnodes. (After Lloyd.) ;rains of sand. The larvae studied b}' Lloyd TRICHOPTERA 567 at Ithaca, N. Y., made cases in the form of ciirved cornucopias (Fig. 697, b); those found in Wisconsin by Vorhies, who first described the species, make a case with decided lateral flanges and a hood that completely covers the head of the larva. Mystacides sepulchrdlis.— The larva of this species and its case were described by Lloyd. It was found in ponds and in slow deep pools of creeks; it lives among the rubbish on the bottom. The case (Fig. 697, c) consists of a slightly tapering tube of sand or of minute fragments of bark, lined with silk; it measures about 12 mm. in length. On opposite sides are fastened pine needles, or grass stems, or slender sticks, which extend beyond both ends of the case. Before pupation a sheet of silk with a minute perforation in the center is spun across each end of the case. Trianddes. — The larvae of species of this genus live in ponds and bays of creeks among branches of submerged plants. They are able to swim rapidly from place to place through the open water. The case (Fig. 697, d) is made of thread-like fragments of leaves arranged in a spiral. It resembles in form the case of Phryganea (Fig. 695, &), butis much smaller and more flexible, and the leaf-fragments are much narrower. Family ODONTOCERID^ The immature stages of only a single species belonging to this small family have been described in this country; the following notes re- garding this species are from Lloyd ('21). Psilotreta frontalis. — The larvse were found in up- land streams and were confined to the riffles and the portions of the streams with stony bottoms. The case of the mature larva (Fig. 698) is a slightly curved cyHnder made of sand ; cases of immature larv^ differ only in being tapered toward the caudal end. The case of the pupa has a flat pebble set neatly within the aperture at each end. All spaces around these stones are tightly closed with heavy silk, leaving no apertures for the circulation of water; this is an unusual feature in the case-building Trichoptera. During their early life the larvae are free-moving, crawling separately over the bottom of the stream. But in the early spring, just before pupation, the larvae develop a remarkable gregarious habit. Almost all of the larvffi within certain areas of the stream congregate on the sides of a few selected stones in such numbers that their cases are sometimes piled one on top of another to the depth of an inch or more, while other stones in the region are entirely uninhabited. The cases are always placed parallel to each other, with their cephalic ends directed toward the surface of the water. Family CALAMOCERATIDtE This is a small family of which only one American larva is known. The habits of this species have been described by Lloyd, from whose accounts I quote. 568 AN INTRODUCTION TO ENTOMOLOGY Ganonema americdna. — The larvae were found abundant in alder- bordered streams. The cases made by this species differ greatly from those of other described American caddice- worms. The case is made of a single piece of wood or bark or a twig ; this is hollowed from end to end, and lined with silk. Although common, they are most inconspicuous among the debris on the bottom of the stream. Figure 699 represents a case with the silk tube cut away, except around the larva. Family LIMNOPHILID^ The larvae of members of this family are cater- pillar-like, and are found in a great variety of aquatic situations, but especially in ponds and slow- moving streams, even in those that become dry during the droughts of summer; a few, Neophylax, are found in rapids. Many of the larvee that live in quiet water can be kept in aquaria. The cases made by different members of this family differ greatly in form and in the materials used in their construction; in some species the case made by an old larva differs greatly from that made by it when young. In several genera of this family the larvae make cylindrical cases of sticks and fragments of bark, which are very irregular in form; one of these is represented by Figure 700. To this family belong the larvae that build cases of the "log-cabin type" ; these are composed of sticks or of pieces of grass placed cross- wise of the case (Fig. 701). A case closely resembling this in plan but differing in appearance is made of bits of moss. Among the larvae that change the form of their case when full- grown is Limnophilus combindtus, which is described by Lloyd. Dur- Fig. 699.-Case of Ganonema amer icana. (After Lloyd.) Fig. 700. — Case of limnophilid larva. Fig. 701.— Log- cabin type of case. ing early life this larva frequents the grass and sedges that fringe the edges o£ streams, and makes a case of the cross-stick or log-cabin type. When the time for pupation draws near, it migrates away from the grassy area and makes a case differing entirely in appearance from TRICHOPTERA 569 the log-cabin type. Some individuals make a case composed of small chunks of bark (Fig. 702, a); others make cases composed almost entirely of shells of water snails (Fig. 702, b) . Different combinations of these types are frequently found. Some larvag of this famil}^ make cases of leaves; these are either fastened so as to form a fiat case, or arranged in three planes so as to form a tube, a cross- section of which is a triangle. Larvas of the genus Neophylax make cases of sand with large ballast stones at the sides; these are similar in form to those made by Goera calcarata of the next family, but are more slender, smaller, and made of lighter material. Family SERICOSTOAIATID^ Fig. 702 . — Case of Limnophilus combinatus. (After Lloyd.) The larvae are caterpillar-like, and are found in streams and lakes. The cases made by members of the different genera differ greatly in form; the three following are our best -known examples. Helicopsyche borealis. — The larvas of this species are found in stony streams and along the rocky shores of lakes. They make a spiral case of grains of sand (Fig. 703). This case so closely resembles that of a Fig. 703.— Case of snail in form that it has been described as the shell Hehcopsydu. ^^ ^ moUusk. When about to pupate, the larva? fasten (. rom 03 .) ^j^g-j, (.^ggg ^Q g^ submerged rock; at this time they display a gregarious instinct, large numbers of them congregating within a verv^ small area. They are more easily found at this time than in their earlier stages when they are living free among the sand and gravel of the bot- tom of the stream. 1 Goera calcarata. — ^The arvce of this species are found in the riffles of streams and on stones in wave-beaten areas of lake shores, where they crawl over the surface of bare, current-swept rocks. The Fig. 704.— Case of Goera larval case (Fig. 704) is a (After lyjQQ made of fine grains of sand on each side of which calcarata. Lloyd.) Fig. 705. — Case of Brachycentrus nigrisoma. (From Lloyd.) 570 AN INTRODUCTION TO ENTOMOLOGY are fastened heavy ballast stones, usually two on eacn side. Brachycentrus nigrisdma. — The larva of this species builds a case of the remarkable form shown in Figure 705. "It is constructed of minute twigs, root-fibers, and fragments of wood cut to the proper length to give even and straight edges, gradually diverging toward the anterior end. In cross-section the outer surface of the case is square; the interior is lined with a cylindrical tube of tough silk." "During the first six weeks of their lives the larvae are active, crawling about in quiet eddies along the banks of streams in search of food. After this period they move to the center of the stream and live sedentary lives, with one edge of the larger end of their cases firmly cemented to submerged rocks or sticks. Always they inhabit positions on the exposed surface of their support and always they assume the position shown in Figure 705, protruding their heads slightly and extending their prothoracic legs straight fon\^ard. The mesothoracic legs are held upward while the metathoracic legs are extended to the sides. From this position they eagerly seize and quickly devour small larv£e or bits of vegetation that float within their grasp." (Lloyd.) CHAPTER XXVII ORDER LEPIDOPTERA* The Moths, the Skippers, and the Butterflies The winged members of this order have Jour wings; these are mem- branous, and covered with overlapping scales. The mouth-parts are formed for sucking. The metamorphosis is complete. The members of this order, the moths, the skippers, and the butterflies, are well known to every ob- server of nature. Their most easily ob- served distinguishing characteristic is that which suggested the name of the order, the scaly covering of the wings and body. Every lad that lives in the country knows that the wings of moths and butterflies are covered with dust, which comes off upon one's fingers when these insects are handled. This dust when examined with a microscope is found to be composed of very minute scales of regular form; and when a wing is looked at in the same way, the pig. 7o6.-Part of a wing of a scales are seen arranged with more or butterfly, greatly magnified. less regularity upon it (Fig. 706). The body, the legs, and other appendages are also covered with scales. Fig. 707. — Scales of Euclea delphinii. (After Kellogg.) *Lepid6ptera: lepido {\eirh, \eirl5os), scale; pleron {Trrepdp), a wing. (571) 572 AN INTRODUCTION TO ENTOMOLOGY Fig. 708 -Scale of S er y da c onstans . (After Kel- logg.) It is well known that these scales are merely modified setae. That is, they are setae which, instead of growing long and slender as setae usually do, grow very wide as compared with their length. Every gradation in form can be found, from that of the ordinary seta, which occurs most abundantly upon the body, to the short and broad scale, which is best seen upon the wings (Fig. 707). This fact was pointed out by Reaumur nearly two hundred years ago; and in recent times the morphological iden- tity of setae and scales has been established by studies of their development. Mayer ('96) gave a complete account of the de- velopment of scales and illustrated his paper by most excellent figures of all stages of this development. The structure of scales is what would be expected from the fact that they are modified setae, the scales, like setae, being hollow; and the manner of their attachment to the cuticula of the body and its appendages is the same as that of the setae, each scale being provided with a pedicel which fits into a cup-like socket in the cuticula. A striking feature of the scales of Lepidoptera is the mark- ings that exist on their exposed surface. These may consist merely of many very fine longitudinal ridges (Fig. 707); or they may be series of transverse ridges between the longitudinal ones (Fig. 708). the the Fig. 709. — Cross-section of scales of Par- nassius sminlheus. (After Kellogg.) A cross-section of certain scales indicates that ridges are produced by foldings of the outer wall {i. e wall of the scale that is exposed when the scale is in place on the wing). Figure 709 represents cross-sections of a scale illustrating this condition. In some scales, however, the lumen of the scale has been filled to a considerable extent by chitin, and the origin of the ridges is not so obvious. The scales of the Lepidoptera were probably developed from that type of setae known as clothing hairs, and were primarily merely protective in function. This is doubtless their chief, if not only, function on most parts of the body, where they form a very perfect armor. The development of ridges on the surface of scales adds greatly to their stiffness, and thus increases their efficiency as a protective covering, as the corrugations in the sheets of iron used for covering the sides of buildings add to the stiffness of the metal. Upon the wings a covering of rigid scales would serve not merely to protect the wings but would tend to stiffen them, and thus arose a secondary function of scales which has resulted in the perfecting of their arrangement upon the wings in the more specialized members of the order as already indicated. There are great differences among the insects of this order regarding the regu- larity of the arrangement of the scales upon the wings. With some of the more generalized moths the scales are scattered irregularly over the svuface of the wings. But if a wing of one of the more specialized butterflies be examined with a microscope, the scales will be found arranged in regular overlapping rows; the arrangement being as regular as that of the scales on a fish or of the shingles on a roof. Figure 706 represents a sm.all portion of a wing of one of the more special- ized butterflies, where the arrangement of the scales is most perfect. In the upper part of the figure the membrane is represented with the scales removed. Even in those insects in which a very perfect arrangement of the scales upon the wings has been attained, great differences in the degree of perfection of this arrangement exist in the two wings of the same side and in the different parts of the same wing. The arrangement is most perfect in those wings and in those LEPIDOPTERA 573 parts of each wing that are subjected to the greater strain during flight; and is more perfect in swift-flying species than in those of slow flight. The taxonomic vakie of these differences in the arrangement of the scales of the wings of the Lepidoptera, and also of the different types of scales found in different divisions of the order, was investigated by Professor Kellogg ('94), to whose extended account the reader is referred for a discussion of this phase of the subject. A secondary use of the scales of the Lepidoptera is that of ornamentation; for the beautiful colors and markings of these insects are due entirely to the scales, and are destroyed when the scales are removed. The various colors of insects and of other animals are produced in quite different ways; and classifications of these colors have been proposed based on the methods of their production. The literature of this subject is too extensive to be referred to in detail here. A most enjoyable popular account is given by Pro- fessor Kellogg in his "American Insects" (Kellogg '08, pp. 583-614) and a de- tailed analysis of the methods of the production of color is given by Professor Tower in his "Colors and Color-Patterns of Coleoptera" (Tower '03). Following the classification of Tower, the colors of the scales of the Lepi- doptera may be either chemical, physical, or chemico-physical. The chemical colors are produced by pigments in the scales; the phj'sical colors are produced either by ftflection, refraction, or diffraction of light; and the chemico-physical colors are produced by either a reflecting, refracting, or diffracting structure overlying a layer of pigment. There are also what Tower calls combination colors due to a combination of the causes just mentioned. As the production of colors by pigments is the most obvious method in nature, it is the one to which the colors of the Lepidoptera are commonly attributed. But it is now well known that a large proportion of the most beautiful colors of these insects are either physical or chemico-physical; this is true of the various metallic and iridescent colors so commonly found in butterflies and many moths. Explanations of the methods of production of physical colors are given in text- books on physics; it is, therefore, only necessary here to point out a feature in the structure of the scales of Lepidoptera that results in the production of these colors. This feature is the presence of the fine longitudinal strice described above. When the strise are very fine and close together they act in thesame way as does a diffraction grating, producing the beautiful iridescent colors. Kellogg ('94) found that on certain scales from a species of Morpho the strise were from .0007 mm. to .00072 mm. apart, or at the rate of about 35,000 to an inch. The fact that certain colors are due to the way in which light is reflected from the scales can be shown by the following experiment. Place on the stage of a microscope the wing of a bright blue butterfly, and shade the specimen so that it is viewed only by transmitted light from the mirror of the microscope; when examined in this way the blue color w^ll be absent. This is due to the fact that the light passing directly through the scales is not broken up, and only the colors produced by pigment are visible. There is still another function of the scales of Lepidoptera; they may serve as the outlets of scent glands. As the scales that serve this purpose are found chiefly on the wings of males, they have received the special name of androconia, ?,\gmiy\ng male dust . Seepage 100. In the suborder Jugatas and in l^3i^^<^"2l— ^ -"Zs-Lrflr- Zr-^ some of the more generalized _r-I^e?r^^^^-"^^^^^ ' ^y— families of the suborder Frenata?, ^~~^ —"-^^^^^^^^^^^zl there are, in addition to the more -^^Z^^ — -"^^.^^^^^^^^^^ obvious setas and scales, many ?- ^^02—"ZI^^^~i. '~ ZL. "Z very small, hair-like structures, --^^^^^^^^^^Si.'^S'' -^ which differ from setse in being di- -Z^^^^^^^^^S_r~_r"'^^^ rectly continuous with the cu- Ij^'^^^^^^^r"^-^"^ '~^~^''~ ticula, and not connected with it „. t^ . r • r 1 ■ • , /T-v- \ J.1 rig. 710. — Part of a wmg of an aculeate by a jomt (Fig 710); these are ^^^t^, with most of the scales re- termed che fixed hairs or aculecB. moved go as to expose the acule». 574 AN INTRODUCTION TO ENTOMOLOGY They are so small that they can be seen only by the aid of a micro- scope, and being covered by the scales they can be seen only in bleached and stained or denuded wings. In the more generalized members of this order, the venation of the wings corresponds quite closely to the hypothetical primitive type. The most striking divergence from this type is the fact that vein M is only three-branched. This is probably due to a coalescence of veins M^ and Cui. If this is true, the vein that is commonly desig- nated as vein Cui is really vein M4 plus Cui; but for the sake of simplicity it seems best to designate it ordinarily as vein Cui. For a detailed discussion of this problem, see "The Wing's of Insects," pp. 334-337- Although the wings of Lepidoptera, except in certain specialized forms, are broadly expanded, there are but few cross-veins, and nor- mally no accessory veins. In the more specialized members of this order the number of the wing-veins is reduced. This reduction is due in some cases to the aLiOphy of a vein or veins, as, for example, the loss of the main stem of vein M in many families ; in other cases, it is due to the coalescence of adjacent veins, as, for example, the reduction of the mmiberof branches of radius or of media which has taken place in many members of the order. In many genera of this order the branches of radius of the fore wings anastomose so as to form one or more closed cells ; these have been termed accessory cells . There are several methods by which the fore and hind wings of Lepidoptera are held together in flight, in order to insure their synchronous action. In the suborder Jugatae the posterior lobe of the fore wing functions either as a jugum (see p. 61) or as a fibula (see p. 62). In most moths the wings of each side are united by a frenulum (see p. 61). In some moths and in the skippers and butterflies, the humeral angle of the hind wing is greatly ex- panded and projects be- neath the fore wing; this insures the synchronous action of the two wings and renders a frenulum unnecessarv' ; in these forms, which doubtless descended from frenate ancestors, the frenulimi has been lost. The frenulum when well developed consists of a bunch of bristles situated at the base of the costa of the hind wings, on the costal sclerite. As a rule these bristles are separate in females, and consolidated into a single strong, spine-like organ in males. Fig. 711. — Wings of Obrussa ochrefasciella, male. (After Braun.) LEPIDOPTERA 575 In some of the more generalized Lepidoptera there is a series of slightly curved, spine-like setae on the costa of the hind wing near the base, which aid in holding the wings together. These setae lie beyond the costal sclerite, not on it as does the frenulum; they are termed by Braun ('19) the costal spines. The frenulum and costal spines are both present in some moths (Fig. 711). In many moths, and especially in the Noc- tuidae, the fore wings are marked by transverse lines or bands, and by spots that are so uniform in position in different species that they have been given names, which are used to designate them in the descriptions of those species in which they occur. Figure 712 . . . , , is a diagram of a fore Fig. 712.— Diagram of afore wmg of a noctuid moth, wing of a noctuid moth The lettering is explained in the text. (After indicating the positions Crosby and Leonard.) of the named lines or bands and spots. Six transverse lines or bands and three spots have been named, as follows: The basal or subbasal band (Fig. 712, b). — This is a band extending halfway across the wing near its base. The transverse anterior band (Fig. 712 t. a). — This is often designated as the /. a. line; in some English books it is termed the first line. The median lifte (Fig. 712, m). The transverse posterior band (Fig. 712, /. p). — This is often designated as the /. p. line; it is the second line of English authors. The subterminal band (Fig. 712, 5. /). The terminal band (Fig. 712, /). The orbicular or round spot (Fig. 712, 0). — This is a round or oval spot situ- ated in the discal cell. The renijorm spot (Fig. 712, r). — This is a somewhat kidney-shaped spot at the end of the discal cell. The claviform spot (Fig. 712, c).- — An elongate spot extending from the /. a. line toward the /. p. line in cell Cu. The typical mouth-parts of adult Lepidoptera are fitted for suck- ing. In some families, the members of which do not take food during the adult stadium, the mouth -parts are vestigi- al; and in one family, the Micropterygidae, which is doubtfully in- cluded in this order, the mouth-parts are of the mandibular type. ^^ ^.„,„„ -^^^lAjpc ^^ those families in >W ^ '^^r^ which the typical form of the mouth-parts is well shown, the only parts of these organs that are well developed are the maxillae and the palpi, the other parts being either absent or Fig. 713. — Maxillas of the cotton-moth, and the tip of the same enlarged. 576 AN INTRODUCTION TO ENTOMOLOGY reducecl to mere vestiges. When only one pair of palpi are developed they are the labial palpi; when maxillary palpi are present they can be dis- tinguished by their at- tachment to the maxillae. If the head of a but- terfly or of a moth in which the mouth-parts are not vestigial be ex- -c,- r^ ^- r n amincd, there will be rig. 714. — Cross-section 01 maxillae. j- j 1 1 • found a long suckmg- tube which when not in use is coiled on the lower side of the head be- tween two forward -projecting appendages. This long sucking-tube is composed of the two maxillae, greatly elongated, and fastened to- gether side by side. In Figure 713 there is represented a side view of the maxillae of a moth; and in Figure 714 a cross-section of these organs. Each maxilla is furnished with a groove, and the two maxillcB are so fastened together that the two grooves form a tube through which the liquid food is sucked. As a rule the maxillae of insects of this order are merely fitted for extracting the nectar from flowers, but sometimes the tips of the maxillae are armed with spines, as shown in Figure 713. This enables the insect to lacerate the tissue of ripe fruits and thus set the juice free, which is then sucked up. Many moths do not eat in the adult state; with these the maxilla are wanting. The two forward-projecting organs between which the maxillae are coiled when present are the labial palpi. In some moths the maxillary palpi are also developed. The compound eyes are large and are composed of many small ommatidia. The ocelli, when present, are two in number; they are situated one on each side, above the compound eye and near its mar- gin; the median ocellus is lacking throughout the order; and in the butterflies, the skippers, and some families of moths, all of the ocelli are wanting. The antennae are always conspicuous ; they differ greatly in form in different divisions of the order, and, therefore, furnish characters that are much used in the classification of these insects. In some families the basal segment of the antennas is greatly enlarged and forms what has been termed the eye-cap. Theprothorax is small, being reduced to a collar between the head and the wing-bearing segments. In many of the more specialized Lepidoptera the pronotum is produced on each side into a flat lobe which in some cases is even constricted at the base so as to become a stalked plate; these lobes are the patagia. The legs are long and slender. In some families the front tibiae bear on their inner aspect a mobile pad ; this is termed the epiphysis; in some cases, at least, it is a combing organ used for cleaning the antennae. A special feature of the abdomen is the presence in the female LEPIDOPTERA 577 of a bursa copulatrix; that of the female of the milk-weed butterfly- is figured on page i6o. Close to the junction of the thorax and abdomen there is, in the majority of Lepidoptera, a pair of organs, which are known as the tympana. These are situ- ated on each side near the first abdominal spiracle. Several types of these organs have been described by Forbes ('i6) and by Eggers ('19), which are characteristic of certain families and groups cf families. The first tvpe is that of the Geometridae; it appears superficially as a hollow bulla located immediately below the spiracle, opening forward against the coxa of the hind leg. Some Pyralidas have rudimentary tympana in the same position. The second type is likewise wholly on the abdomen, but it is higher on the body, and its opening faces backward towards the second abdominal segment. It characterizes the Thyatiridje and Drepanidae. The third type presents a variety of appearances. Its essential part is a mem- branous disk, the tympanum proper, on the metathorax just below the root of the wing. In the Dioptidse, Notodontida?, Agaristidae, and a few noctuids and lithosians, the disk lies exposed or is merely sunk in a pit at the junction of the thorax and abdomen. In other moths having this type of tympana the disk is covered bv a hood formed by the side of the first segment of the abdomen; in the Arctiidse, Pericopidte, Liparidae, and the subfamily Herminiinse of the Noc- tuid^e, this hood lies subdorsally, wholly above the spiracle; while in the majority of the Noctuidae it is lower and incloses the spiracle, in som^e cases (Euteliinas, etc.) being supplemented by a second hood formed by the alula of the hind wing. The function of the tympana is probably auditory, as Eggers has described chordotonal organs in connection with them in several families. In the Lepidoptera the metamorphosis is complete. The larvae are known as caterpillars; they vary greatly in form and appearance, but are usually cy- lindrical, and pro- vided with from ten to sixteen legs, —six thoracic legs and from four to ten abdominal legs. The thoracic legs have a hard exter- nal skeleton ; and are jointed, taper- ing, and armed at the end with a little claw. The abdom- inal legs, which are shed with the last larval skin, are thick, fleshy, with- out joints, elastic or contractile, and armed at the ex- tremity with nu- merous minute hooks (Fig. 715); they are termed prolegs. When all five pairs are present they are borne by the third, fourth, fifth, sixth, and tenth abdominal segments. Larva of a hawk-moth. 578 AN INTRODUCTION TO ENTOMOLOGY from The hooks or crotchets with which the prolegs of caterpillars are armed vary in their arrangement in different families and thus afford useful characters for the classification of these larvae. These hooks are usually arranged in a circle or in rows on the tip of the proleg. When they are in a single row or series, they are said to be uniserial; when in two concentric row^s, biserial; when in several rows, multi- serial. When the hooks of a row are uniform in length throughout or shorter towards the ends of the row, they are said toheumordmal; when they are of two alternating lengths, biordinal; when of several lengths, multiordinal. The tip of a proleg on which the hooks or crochets are borne is termed the planta. In most lepidopterous larvee the clothing of setse is comparatively inconspicuous; such larvae are commonly termed naked in contra- distinction to the ^^^"^^31 --r^!;te:l7^. - hairy caterpil- ^- -^ ' iaj-s_ But in the so-called naked larvae, each seg- ment of thebody, when not too highly special- ized, is armed with a definite number of setae which occupy definite posi- tions. Each seta is borne on a small chitinous tubercle; the number of these setijerous tubercles and the positions they occupy differ in the different families, and, therefore, afford characters which are much used in the classification of Lepidoptera, The small tubercle bearing a single seta (Fig. 716, a) is evidently the primitive form of setif erous tubercle ; for it is the only form f oimd in the more generalized families. In some of the more specialized families the tubercles are larger and many -haired (Fig. 716, b)\ this type of tubercles is termed a verruca; it is characteristic of the so- called hairy caterpillars, as, for example, the larvae of most of the Arctiidae. In the larvae of the Satumioidea and of certain butterflies, some of the tubercles are spinose projections of the body-wall (Fig. 716, c)\ such a projection is termed a scolus. Some caterpillars are clothed with more or less numerous setae which are scattered and which have no constant position ; such setae are termed secondary setce, in contradistinction to those borne on setif erous tubercles which are of a definite number and occupy definite positions; these are termed primary setce. Among the setif erous tubercles that are constant in position, there are a few that are not present in the first instar of generalized groups ; although the setae borne by these tubercles are regarded as primary set£e when con- trasted with secondary setae, they are distinguished from those found in the first instar as subprimary setce. Fig. 716. — ^Types of setif erous tubercles. Dyar.) lepidoptera 579 In order to make use of the primary and subprimar}" seta3 in classification, it is necessary that each of these setse should be desig- nated by a distinctive term. The terminology most generally used is that proposed by Dyar ('94), who was the first author to "base a classification of lepidopterous larvse on the variations in the arrange- ment of the setiferous tubercles. The terminology of Dyar was based on a study of the tubercles of the abdominal segments. He recognized on each side of each ab- dominal segment, except the last two, eight tubercles, which he numbered with Roman numerals beginning with the one nearest the middle line of the back; the number VII was applied to a group of three tubercles on the outside of the proleg, or in a corres- ponding position in the legless abdominal segments. Subsequent studies, and especially those by Forbes ('10) and Fracker ('15), have revealed the presence of setiferous tubercles not num- bered by Dyar. Figure 717,6, represents the arrangement of the tubercles of a middle ab- dominal segment of a noctuid lar\'a as figured by Forbes. The tubercles are numbered ac- cording to the terminology of Dyar, with the addition of tubercles X, Ilia, and IX, not figured by Dyar.* The arrangement of the setiferous tubercles on the thoracic segments of any cater- pillar differs to a considerable extent from that on the ab- ^ig. 717— Arrangement of setiferous tu- 1 „,• 1 „ , r ,1 bercles m a noctuid larva: a, tubercles dommal segments of the same ^f ^ metathorax; b, tubercles of a msect. InFlgure7i7, arepre- middle abdominal segment. (After sents the arrangement of the Forbes.) tubercles on the metathorax and b that of the tubercles of a middle abdominal segment of a noctuid larva as figured by Forbes ('10). This writer also figures and numbers the setse on the head of a caterpillar. Fracker ('15) made an extended study of the classification of lepidopterous larvee, which was based quite largely on the variations in the ntmiber and positions of the setiferous tubercles; and his paper is illustrated by a large ntmiber of setal maps. This writer proposes a new terminology for the setae, using Greek letters instead of Roman nimierals. *In diagrams indicating the arrangement of setiferous tubercles, one side of a single segment is represented as if cut on the mid-dorsal and mid-ventral lines, and laid flat. The anterior edge is to the left, and the mid-dorsal line at the up- per edge. In Figure 717 the positions of the spiracle and of the legs are also indicated. 580 AN INTRODUCTION TO ENTOMOLOGY Schierbeck Ci6 and '17) proposes still another tenninology for the set«, applying a Latin name to each. Most caterpillars, except, as a rule, the larvae of butterflies, spin a cocoon. In some instances, as in the case of silk-worms, a great amount of silk is used in the construction of the cocoon; in others the cocoon is composed principally of the hairs of the larva, which are fastened together with a fine web of silk. The pupag of the Lepidoptera are typically of the obtected type ; that is, the developing wings, legs, mandibles, maxillse, and antennas are glued to the surface of the body (Fig. 718); but in some of the more generalized forms these appendages are free. In the Micro- jugatae, which are provisionally in- cluded in this order, these append- ages are free, the pupae resembling those of the Trichoptera ; but in the Hepialidas the appendages are glued to the surface of the body as in the specialized Frenatse. In some of the more generalized Frenatae, as the Fig. 718.— Pupa of a moth. Nepticulida?, and in the Heliozelidae, the appendages are all free ; between this condition and that of the truly obtected pupa of the more specialized Frenatae, various intergrades exist. The pupae of this order vary also in the number of segments of the body that are movable. The eighth, ninth, and tenth abdominal seg- ments are always fixed. All of the other segments are movable in the most generalized forms, and all are fixed in the most specialized forms; there are various intergrades between these two extremes. Different pupae of this order differ also in various other ways, thus affording characters that are of taxonomic importance. It is only recently that these characters have been used in an extended manner. A pioneer paper in this field is that of Miss Edna Mosher ('16). More than nine thousand species of Lepidoptera are known to occur in America north of Mexico. These represent two suborders and seventy families. In popular language the Lepidoptera includes two quite distinct groups of insects, the moths and the butterflies. Under the term moths are included all of the members of the first suborder, the Jugatas, and the larger number of the families of the second suborder, the Frenatae; under the term butterflies are included the remaining families of the suborder Frenats. These two groups are distinguished as follows. The moths. — These are the insects that are commonly called millers. Most of the species fly by night and are frequently attracted to lights. When at rest the wings are either wrapped around the body, or spread horizontally, or folded roof -like on the abdomen; except in a few cases they are not held in a vertical position above the body. The antennae of moths are of various forms ; they are usually thread- LEPIDOPTERA 581 like or feather-like ; only in rare cases are they enlarged towards the tip. The moths have been termed the Heterocera* by many ento- mological writers, in contradistinction to Rhopalocera,* a term ap- plied to the butterflies. The butterflies.- — All of our species of butterflies fly in the daytime; and, with few exceptions, they fold the wings together above the back in a vertical position when at rest. The antennse are thread-like, and usually with a club at the tip. It was this feature that suggested the term Rhopalocera, which is applied to them. The group butterflies as defined here includes the representatives of two quite distinct superfamilies, the Hesperioidea or skippers, and the Papilionoidea or true butterflies. The distinctive characters of these two superfamilies are discussed later. The division of the Lepidoptera into moths and butterflies is an artificial one, the group moths including representatives of both of the two suborders into which the order is divided, as indicated above. In the natural classification, the primary division of the order is based on differences in the method of uniting the two wings of each side, and on differences in the venation of the hind wings. In one suborder, the Jugatse, the posterior lobe of the fore wing is specialized so as to form an organ, a jugum or a fibula, which unites the fore and hind wings; and the venation of the hind wing§ is similar to that of the fore wings. In the other suborder, the Frenataj, the two wings of each side are united by a frenulimi in the more generalized forms and by a substitute for a frenulum in certain specialized forms ; and the venation of the hind wings is quite different from that of the fore wings. Hiibner's Tentameti. — At some undetermined date, but previous to 1810 and probably in 1806, Jacob Hiibner distributed a two-page work, giving a classifica- tion of the Lepidoptera. This work is commonly known as "Hubner's Tenta- men," tentamen being the first word in its long Latin title. Entomologists differ regarding the standing of this work; some believe that it was merely privately printed, while others regard it as a published work and adopt the generic names that were used in it. This difference of opinion is the cause of serious confusion in the names of certain genera and families. It seems to the writer that the evi- dence supporting the view that the "Tentamen" was published is conclusive. See "Entomologists Record and Journal of Variation," Vol. 31 (1919), Supple- ment. SYNOPSIS OF THE LEPIDOPTERA The families comprising this order are grouped in various ways by different writers; none of these groupings can be regarded as final in the present state of our knowledge. The following provisional arrangement has been adopted for use in this book. A. The Jugate Lepidoptera. — Moths in which the two wings of each side are united by a jugum or by a fibula, p. 592 Suborder JuGATiE B. The Microjugat^. C. The JMandibulate Jugates. p. 592 Family Micropterygid^ CC. The Haustellate Jugates. p. 593 Family Eriocraniid.e BB. The Macrojugat.-e. The Swifts, p. 594 Family Hepialid^ *Heterocera: hetero (^repos), other, different; ceras (f^pas), a horn. *Rhopal6cera: rhopalon {pb-KciXov), a club; ceras {jcipas), a horn. 582 AN INTRODUCTION TO ENTOMOLOGY AA. The Frenate Lepidoptera. — Moths, skippers, and butterflies in which the two wings of each side are united by a frenulum or by its substitute, a large humeral area of the hind wings, p. 596 Suborder Frenate B. The Generalized Frenat,^. — Moths that are supposed to retain more nearly than other Frcnatag the form of the primitive Frenatas, those that were the first to appear on earth. C. The Aculeate Frenate. — Moths in which the aculeag are distributed over the general surface of the wings. The Incurvariids. p. 598 Family iNCURVARiro^ The Nepticulids. p. 600 Family Nepticulid^ CC. The Non-aculeate Generalized Frenatae. — Moths in which the aculese are confined to small areas of the wings or are absent. The Carpenter Moths, p. 601 Family CossiD^ The Smoky Moths, p. 604 Family Pyromorphid^ The Dalcerids. p. 605 Family Dalcerid^ The Flannel-moths, p. 606 Family Megalopygid^ The Slug-caterpillar-moths, p. 608 Family Eucleid^ The Epipyropids. p. 610 Family Epipyropid^ BB. The Specialized Frenate. — Moths, skippers, and butterflies that de- part more widely than do the Generalized Frenatae from the primitive type of Lepidoptera, being more highly modified for special conditions of existence. An indication of the specialized condition of these insects is the modified form of the wings. In nearly all the base of vein M has been lost and the branches of this vein joined to veins R and Cu. C. The Specialized MiCROFRENAT^. — Frenulum-bearing moths which are usually of small, often of minute, size. In many of these moths the anal area of the hind wings is not reduced, having three anal veins; in some others the hind wings are very narrow and a broad fringe acts as a sub- stitute for the membrane of the anal area. The Acrolophids. p 611 Family Acrolophid^ The Tineids. p. 611 Family Tineid^ The Bag- worm Moths, p. 613 Family Psychid^e The Tischeriids. p. 615 Family Tischeriid^ The Lyonetiids. p. 616 Family Lyonetiid^ The Opostegids. p. 617 Family Opostegid^ The Oinophilids. p. 617 Family Oinophilid.^ The Gracilariids. p. 617 Family Gracilariid^ The Coleophorids. p. 620 Family Coleophorid.^ The Elachistids. p. 621 Family Elachistid^ The Heliozelids. p. 622 Family Heliozelid/E The Douglasiids. p. 623 Family Douglasiid^ The CEcophorids. p. 624 Family CEcophorid.e The Ethmiids. p. 625 Family Ethmiid^ The Stenomids. p. 625 Family Stenomid^ The Gelechiids. p. 625 Family Gelechiid.e The Blastobasids. p. 628 Family Blastobasid^e The Cosmopterygids. p. 629 Family Cosmopterygid^ The Scythridids. p. 631 Family Scythridid.'E The Yponomeutids. p. 631 Family Yponomeutid^ The Plutellids. p. 632 Family Plutellid^e The Glyphipterygids. p. 633 Family Glyphipterygid^ The Heliodinids. p. 634 Family Heliodinid/e The Clear- winged Moths, p. 634 Family ^Egeriid^ Superfamily Tortricoidea The Olethreutids. p. 639 Family Olethreutid^ The Typical Tortricids. p. 642 Family Tortricid^ The Phaloniids. p. 643 Family Phaloniid^ The Carposinids. p. 644 Family Carposinid^ CC. The Pyralids and Their Allies Superfamily Pyralidoidea The Pyralids. p. 644 Family Pyralidid^e The Plume-moths, p. 652 Family Pterophorid^ LEPIDOPTERA 583 The Many-plume Moths, p. 653 Family Orneodid^ The Window- winged Moths, p. 653 Family ThyridiD/E The Hyblasids. p. 655 Family HvBL^iDiE CCC. The Specialized Macrofrenat^.- — Speciahzed Frenatae which are usually of medium or large size. This division includes certain moths and all skippers and butterflies. In these insects the anal area of the hind wings is reduced, containing only one or two anal veins. D. The Fienulum-conservers. — Specialized Macrofrenatae in which the two wings of each side are tj^pically united by a frenulum; but in some highly specialized genera o' some families (Sphingidfe, Geometridas, and Dre- panidae) the supplanting of the frenulum by an expanded humeral angle of the hind wing is either far advanced or complete. This group of families includes only moths. The hawk-moths or sphinxes, p. 655 Family SPHlNGlDiE Superfamily Geometroidea The Geometrids. p. 663 Family Geometrid/E The Manidiids. p. 673 Family Manidiid^e The Noctuids and Their Allies The Dioptids. p. 673 Family Dioptid^ The Prominents. p. 674 Family Notodontid^ The Tussock-moths, p. 679 Family Lymantriid^ The Noctuids. p. 683 Family Noctuids The Foresters, p. 697 Family Agaristid^ The Pericopids. p. 698 Family Pericopid^ The Arctiids. p. 699 Family Arctiid^ The Euchromiids. p. 706 Family Euchromiid^ The Eupterotids. p. 707 Family Eupterotid/E The Epiplemids. p. 708 Family Epiplemid^ The Thyatirids. p. 709 Family Thyatirid^ The Drepanids. p. 710 Family Drepanid^ DD. The Frenulum-losers. — Specialized Macrofrenatae, in which the frenulum has been supplanted by a greatly extended humeral area of the hind wings. In some of the more generalized forms a vestigial frenulum persists (Bombycidse and Lacosomidas). This division in- cludes three groups of families: the Frenulum -losing moths, the skip- pers, and the butterflies. The grouping together of the families in- cluded in this division is merely provisional, as doubtless the loss of the frenulum has arisen independently several times. E. The Frenulum-losing Moihs. — In these moths the antennas are usually pectinate; they are never enlarged into a club at the tip. The Lacosomids. p. 712 Family Lacosomid.*; Superfamily Saturnioidea The Royal-moths, p. 715 Family Citheroniid^ The Giant Silk-worms, p. 719 Family Saturniid^ The Silk-worms, p. 727 Family Bombycid/e The Lasiocampids. p. 728 , Family Lasiocampid^ EE. The Skippers. — These are day-flying Lepidoptera which resemble butterflies in usually holding their wings erect when at rest, but are distinguished by the peculiar venation of the fore wings, vein R being five-branched, and all of the branches arising from the discal cell. The antennae are enlarged into a club towards the tip. Superfamily Hesperioidea The Giant Skippers, p. 733 Family Megathymid^ The Common Skippers, p. 734 Family Hesperiid^ EEE. The Butterflies. — Day-flying Lepidoptera that hold their wings erect when at rest, that have clubbed antennas, and that differ from the skippers in the venation of the fore wings, some of the branches of vein R coalescing beyond the discal cell. Superfamily Papilionoidea The Swallow-tails and the Parnassians, p. 740 Family PAPiLiONlDiE 584 AN INTRODUCTION TO ENTOMOLOGY The Pierids. p. 744 Family Pierid^ The Four-footed Butterflies, p. 750 Family Nymphalid^ The Metal-marks, p. 767 Family Riodinid^ The Gossamer-winged Butterflies, p. 768 Family Lyc^nid^ TABLES FOR DETERMINING THE FAMILIES OF LEPIDOPTERA TABLE A A. Wingless or with vestigial wings. This division includes only females. All males of Lepidoptera are winged. B. The larvae case-bearers; the adult female either remains within the case to lay her eggs, or leaves the case and sits on the outside of it. p. 613. Psychid^e BB. The larvae not case-bearers; the wingless adult not in a case. C. The adult female remains upon her cocoon to lay her eggs; the body of the adult is clothed with fine hairs, p. 679 Lymantriid/E CO. The adult female is active and lays her eggs remote from her cocoon; the body of the adult is closely scaled, or spined,or with bristling dark gray hair. p. 663 Geometrid/E CCC. In addition to the above there are some arctic species of the Noc- tuidae and of the Arctiidae in which the wings of the females are vestigial. AA. With well-developed wings. B. Fore and hind wings similar in form and venation, the radius of the hind wings being, like that of the fore wings, five-branched (Suborder Jugate). C. Minute moths resembling tineids in appearance. D. Adult moths with well-developed functional mandibles; subcosta of the fore wings forked near its middle, p. 592 Micropterygid^ DD. Mandibles of the adult vestigial; maxillae formed for sucking; subcosta of fore wings forked near its apex. p. 593 Eriocraniid.e CO. Moths of medium or large size, without functional mouth-parts, p. 594 Hepialid^ BB. Fore and hind wings differing in form and venation; the radial sector of the hind wings being unbranched, and vein Ri of the hind wings usually coalesced with vein Sc (Suborder Frenat^). C. Antennae of various forms, but rarely clubbed as in the skippers and butterflies; if the antennae are clubbed the hind wings bear a frenulum. D. The fringe on the inner angle of the hind wings as long as, or longer than, the width of the wing; the hind wings often lanceolate, but never fissured. (Microfrenatae.) Pass to Table B. DD. Hind wings much broader than their fringe, and not lanceolate. E. Wings fissured deeply. F. Each wing divided into six lobes, p. 653 Orneodid^e FF. Wings never more than four-lobed; usually the fore wings. bilobed and the hind wings trilobed. p. 652 Pterophorid^ EE. Wings not fissured or the front wings slightly fissured. F. Fore wings very narrow, the width at the middle less than one- fourth the length of the wing; a considerable part of the hind wings, and in many cases of the fore wings also, free from scales; inner margin of fore wings and costal margin of hind wings with a series of recurved and interlocking spines, p. 634 .^geriid^ FF. Wings scaled throughout, or if clear with the fore wings trian- gular in outline; wings not interlocking at middle with series of re- ctuved spines. G. With a double series of enlarged and divergent scales along vein Cu of the hind wings below; wings, body, and legs very long. (Agdistis.) p. 652 Pterophorid.e. GG. Without such scales on vein Cu of the hind wings. H. Hind wings with three anal veins. Care must be taken not to mistake a mere fold in the wing for a vein. When there is no thickening of the membrane of the wing along a fold, it {'". not counted as a vein. LEPIDOPTERA 585 I, Veins Sc + Ri and Rs of the hind wings grown together for a greater or less distance between the apex of the discal cell and the apex of the wing, or in some cases separate but very closely parallel, p. 644 Pyralidid^ II. Veins Sc + R, and Rs of the hind wings widely separate beyond the apex of the discal cell. J. The fringe on the anal angle of the hind wings con- siderably longer than elsewhere (sometimes not obviously SD in rubbed specimens) ; the spurs of the tibise more than twice as long as the width of the tibiae. (Microfrenatae.) Pass to Table B.* JJ. The fringe on the anal angle of the hind wings not longer than elsewhere or but slightly so; the spurs of the tibias about as long as the width of the tibiae. K. Veins Sc + R, and Rs of the hind wings grown to- gether to near the end of the discal cell (Fig. 734), or anastomosing beyond the middle of the cell (Fig. 730). L. Small moths, chiefly of a smoky black color, with thinly scaled wings, p. 604 Pyromorphid^ LL. Moths of medium size, and densely clothed with long, woolly hairs, which are light-colored or brown. p. 606 Megalopygid.'E KK. Veins Sc + Rx and Rs of the hind wings separate or grown together for only a short distance. L. 1st and 2d anal veins of the fore wings united by a cross-vein. M. Accessory cell present (Hypoptinae). p. 603. CossiD^ MM. Accessory cell absent, p. 613. . . Psychid/E LL. 1st and 2d anal veins not united by a cross-vein. M. Vein M, of the fore wings arising from the discal cell nearly midway between veins Mi and M3. N. Vein Mj of both fore and hind wings coalesced with vein Cui for a considerable distance beyond the end of the discal cell. p. 673. . . . Dioptid^ NN. Veins M^ and Cui not coalesced beyond the end of the discal cell. O. Veins R, and R3 coalesced at base, but separate from veins R4 and R5, which also coalesce at base. p. 712 Lacosomid^ 00. Veins R,, Rj, R4, and Rj united at base. p. 727 BOMBYCID.E MM. Vein M2 of the fore wings emerging from the discal cell nearer to cubitus than to radius, causing cubitus to appear four-branched. N. Fore wings with an accessory cell. O. Moths with heavy, spindle-shaped bodies, and narrow, strong wings, p. 601. CossiD^ 00. Moths in which the body is slender and the wings are ample. P. Wings ample (fore wings not half longer than wide) ; mouth-parts vestigial, p. 605. Dalcerid^ PP. Wings more or less oblong, usually twice as long as wide; mouth-parts usually developed with scaled tongue. (Micro- frenatae.) Pass to Table B. NN. Fore wings without an accessory cell. *A few of the Eucleidae present these characters; but with these moths the wings are broad and the base of media extends through the middle of the discal cell. 586 AN INTRODUCTION TO ENTOMOLOGY O. With some of the branches of radius of the fore wings coalesced beyond the apex of the discal cell. p. 608 Eucleid^ 00. With each of the five branches of radius of the fore wings arising from the discal cell. p. 655 Hybl^id^ HH. Hind wings with less than three anal veins. I. Fore wings with two distinct anal veins or with the anal veins partly grown together so as to appear as a branched vein. J. Anal veins of fore wings partly grown together so as to appear as a branched vein. p. 613 Psychid^ JJ. Fore wings with two distinct anal veins (Harrisina). p. 605 Pyromorphid^ II. Fore wings with a single fully preserved anal vein. This is the second anal vein; the first anal vein is absent or represented merely by a fold; and the third anal vein is short, not reaching to the margin of the wing, or is wanting; usually when the third anal vein is present it is joined to the second anal vein, so that the latter appears to be forked towards the base. J. Frenulum present. In most cases, the humeral angle of the hind wings is not greatly expanded. K. The five branches of radius and the three branches of media of the fore wings all present, and each one arising separate from the discal cell. p. 653 Thyridid.^ KK. With some of the branches of radius of the fore wings stalked, or else with some branches coalesced to the margin of the wing. L. The fringe on the anal angle of the hind wings con- siderably longer than elsewhere. M. Veins Sc and R of the hind wings seperate, but usually connected by a more or less distinct basal part of vein Ri. (Microfrenatce.) Pass to Table B. MM. Veins Sc and R of the hind wings fused for a greater or less distance. N. OceUi present, p. 683 Noctuid^ NN. Ocelli absent, p. 704 LiXHOSiiNiE LL. The fringe on the anal angle of the hind wings not considerably longer than elsewhere. M. The basal part of vein Ri of the hind wings, the part extending from radius to the subcosta, ap- pearing like a cross-vein which is as stout as the other veins; veins Sc + Ri closely parallel to the end of the discal cell or beyond, p. 655. Sphingid^ MM. The basal part of vein Ri of the hind wings rarely appearing like a stout cross-vein; when it does appear like a cross-vein, veins Sc + Ri and Rs strongly divergent from the point of union of veins Ri and Sc. N. Vein M2 of the fore wings not more closely joined to cubitus than to radius, cubitus being apparently three-branched. O. The basal part of the subcosta of the hind wings extending from the base towards the apex of the wing in a regular ciu-ve. P. Vein M2 of the hind wings arising nearer to cubitus than to radius; vein Mi of the hind wings joined to radius before the apex of the discal cell. p. 709 Thyatirid^ PP. Vein Mz of the hind wings either wanting LEPIDOPTERA 587 or present, but when present arising either midway between radius and cubitus, or nearer to radius than to cubitus; vein M, of the hind wing joined to radius at or beyond the apex of the discal cell. Q. Tongue (maxillse) wanting; fore wings with R2 + 3 and R4 + s stalked together, north- em species with hyaline dots on fore wings. p. 707 .' EUPTEROTID^ QQ. Tongue present, often weak; fore wings fully scaled; usually with accessory cell, or with veins R3 and R4 stalked together. p. 674 NOTODONTID^ 00. The basal part of the subcosta of the hind wings joined to radius for a short distance and then making a prominent bend tov/ards the costal margin (Fig. 909). (See also OOO.) P. Veins Rj and R4 of the fore wings widely separated from each other, stalked respec- tively with R2 and Rj. p. 712 Lacosomid^ PP. Veins R3 and R4 long-stalked with each other, widely separated from Rs which is stalked with Mi. p. 708 Epiplemid^ 000. The basal part of the subcosta of the hind wings making a prominent bend into the humeral area of the wing, and usually con- nected to the humeral angle by a strong cross- vein (Fig. 817). P. Antennse clubbed. p. 673 .... Manidiid^ PP. Antennas not clubbed, p. 663 Geometrid^ NN. Vein M2 of the fore wings more closely joined to cubitus than to radius; cubitus being in most cases apparently four-branched. O. Small moths, with the apex of the fore wings sickle-shaped, p. 710 Drepanid^ 00. Apex of the fore wings not sickle-shaped. P. Vein Sc of the hind wings apparently ab- sent, being fused except at the extreme base with radius. Care should be taken not to mistake vein Mi for radius (see Fig. 897). p. 706 EUCHROMIID^ PP. Veins Sc and R of the hind wings distinct and parallel to the point where vein R sepa- rates from the discal cell, and then approach- ing very close or fusing for a short distance. (See also PPP.) Q. Small moths with snow-white wings {Eudeilhiia). p. 710 Drepanid^ QQ. Moths that are not white. R. Vein R5 of the fore wings stalked with veins R3 and R4 (Chrysauginae). p. 644. Pyralidid^ RH. Vein R5 free {Meskea). p. 653 Thyridid.e PPP. Veins Sc and R of the hind wings not as described under PP above. Q. Antennas more or less thickened towards the tip. p. 697 Agaristid^ 58S AN INTRODUCTION TO ENTOMOLOGY QQ. Antennas not clubbed. R. Dorsal surface of the first abdominal segment with two prominent rounded bosses, the hoods of the tympana. These hoods are wholly above the spiracles, and separated by only about one-third of the width of the abdomen. Black moths with white or 3^ellow bands or spots on the wings and often with metallic tints. Found only in the Far West or in the Gulf States, p. 698. Pericopid^ RR. Hoods of the tympana less con- spicuous dorsally and more widely separated. S. Veins Sc and R of the hind wings extending separate, or the two joined for a short distance near the base of the wing; ocelli present. T, White or yellow species, with palpi not reaching the middle of the smooth-scaled front; vein Cu apparently four-branched in both fore and hind wings (Haploa). p. 700 Arctiid^ TT. Species with longer palpi, and vein Cu of the hind wings ap- parently three-branched, or species of a gray ground color, p. 683. NOCTUID/E SS. Veins Sc and R of the hind wings fused or closely parallel near the middle of the discal cell, or con- nected by a short - cross-vein (the free part of vein Ri); ocelli absent. (See also SSS.) p. 679. Lymantriid^ SSS. Veins Sc and R of the hind wings united for one-fifth or more of the length of the discal cell. T. Ocelli present (Arctiinas). p. 700. Arctiid^ TT. OcelU absent. U. Fore wings with raised tufts of scales (NolincE). p. 705. Arctiid^ UU. Fore wings smoothly scaled. V. Vein AI2 of the hind wings well developed and aris- ing slightly nearer to vein JMj than to vein Mj (Menopsimus). p. 683 NOCTUID^ VV. Vein M2 cf the hind wings arising much nearer to vein AI3 than to vein Mi, or wanting (Lithosiinae). p. 704. Arctiid^ J J. Frenulum absent. K. Vein Cu of both fore and hind wings apparently fotar-branched. L. Small moths with slender bodies, and with the apex of the fore wings sickle-shaped ; humeral veins absent, p. 710 Drepanid^ LEPIDOPTERA 589 LL. JVIoths of various sizes, but with robust bodies, and with the apex of the fore wings not sickle-shaped; hind wings with humeral veins, p. 728.Lasiocampid^ KK. Vein Cu of both fore and hind wings apparently three-branched. L. Robust moths of medium or la:rge size, with strong wings, p. 714 Saturnioidea LL. Small moths with slender bodies and weak wings {Dyspteris). p. 667 Geometrid^ CC. Antennas thread-like with a knob at the extremity; hind wings without a frenulum; ocelli wanting. D. Radius of the fore wings five-branched, and with all the branches arising from the discal cell; club of antennee usually terminated by a re- curved hook. The skippers, p. 732 Hesperioidea DD. With some of the branches of radius of the fore wings coalesced be- yond the apex of the discal cell; club of antennae not terminated by a re- curved hook. The Butterflies, p. 739 Papilionoidea TABLE B THE FAMILIES OF THE MICROFRENAT^ Contributed by Dr. William T. M. Forbes A. Basal segment of the antennae enlarged and concave beneath, forming an eye-cap. B. Fore wings with radius, media, and cubitus unbranched. p. 61 7.0postegid/E BB. Fore wings with more complex venation. C. Discal cell of fore wings very short and trapezoidal, or absent, p. 600. Nepticulid^. CC. Discal cell more than half as long as the wing. D. Discal cell oblique, its lower outer corner nearly touching the inner margin. (A few species only.) p. 628 Blastobasid^ DD. Discal cell central in the wing. E. Labial palpi minute and drooping, or absent. p. 616.. .Lyonetiid^ EE. Labial palpi moderate, upcurved. (Phyllocnistis in part, and one or two Florida genera.) p. 617 Gracilariid^ AA. Basal segment of antennae not forming an eye-cap. B. Palpus with the first segment relatively very large, normally upcurved to the middle of the front ; when the palpus is short the first segment is longer than the second, p. 611 Acrolophid^ BB. First segment of palpus small. C. Labial palpi bristled on the outer side of the second segment. D. Aculeae present over the general surface of the wings; female with piercing ovipositor; antennas typically smooth and velvety-looking, with fine bristles, or narrow, closely appressed scales, sometimes very long. p. 598 Incurvariid^ DD. Aculese absent, or present only in a small area at the base of the discal cell; ovipositor membranous, retractile; antennae typically rough, with an outer whorl of erect scales on each segment, rarely as in D. p. 61 1 Tineid^ CC. Labial palpi scaled or loose-hairy only. D. Maxillary palpi well developed and of the folded type. E. Fore wings with all veins present and with vein R5 running to the outer margin; hind wings narrow; vertex with a small, loose tuft only (Acrolepia). p. 632 Plutellid^ EE. Fore wings with vein R5 extending to the costa or absent. F. Head smooth; hind wings narrow-lanceolate; fore wings down- curved at apex. p. 617 Oinophihd^ FF. Vertex rough or rarely smooth in forms with ample hind wings; fore wings flat. G. Aculeae present, etc., as in D under C above, p. 598 Incurvariid^ f. 590 A N INTROD UCTlON TO ENTOMOLOC Y GG. Aculeas absent, etc., as in DD under C above, p. 6ii..Tineid^ DD. Maxillary palpi porrect or vestigial. E. Vertex and upper face at least with dense bristly hairs; third seg- ment of labial palpi fusiform and equal to the second in length. F. Aculea; present, etc., as in D under C above, p. 598 . Incurvariid^ FF. Aculeas absent, etc., as in DD under C above, p. 6ii.Tineid^ EE. Face at least smoothly and shortly scaled; third segment of labial jalpus long and pointed, or very short in forms with roughest vestiture^ Hind wings ample, with well-marked anal angle, often wider than their fringe. G. Hind wings with veins Mi and M2 both lost, only one vein being associated with the R-stem. p. 644 Carposinid^ GG. Hind wings with vein Mi preserved, associated with the R- stem. H. Vein Cu, of the fore wings arising from a point before the outer fourth of the discal cell; palpus more or less triangular, with a short, blunt, third segment, roughly scaled (short and nearly smooth in Laspeyresia, in which there is a strong fringe on base of vein Cu of the hind wings, save in L. lautana). p. 639, 642 Olethreutid^ and Tortricid^ HH. Vein Cuz of the fore wings arising from the outer fourth of the discal cell, save in a few Glyphipterygidae, which have short, smooth-scaled palpi, or second segment tufted and third long and slender, and no fringe on vein Cu. I. Vein 1st A of fore wings lost completely; hind wings with veins Rs and Mi connate, approximate, or stalked. J. Palpi with third segment long, slender, and tapering, often exceeding vertex, normally close-scaled, save in male Anarsia where veins R4 and R5 are stalked and both run to the costa. p. 625 Gelechiid^ JJ. Palpi with third segment short and blunt, roughly scaled; vein R5 normally running to outer margin, and often free from vein R4. p. 643 Phaloniid^ II. Vein 1st A preserved, at least at the margin of the wing. J. Hind wings with veins Rs and Mi widely separate at origin, more or less parallel. K. Palpi long, often exceeding vertex; tongue distinct. L. Veins R4 and R5 stalked and both running to costa, or united. M. Vein M2 of the hind wings arising nearer to vein Mi than to M3. p. 625 Ethmiid^ MM. Vein M2 of the hind wings arising nearer to vein M3 than to Mi. p. 624 CEcophoriD/E LL. Veins R4 and Rs long stalked; vein Rj running to outer margin. (See also LLL.) M. Ocelli very large and conspicuous (Allononyma.) p. 633 Glyphipterygid^ MM. Ocelli small or absent. N. Vein M2 of the hind vv^ings arising nearer to vein Mi than to M3. p. 625 Ethmiid^e NN. Vein M2 of the hind wings arising nearer to vein M3 than to Mi. p. 624. . .QJcophorid^e LLL. Veins R4 and R5 separate, vein Rj running to outer margin, p. 631 Yponomeutid^ KK. Palpi small, hardly exceeding the front, or obsolete; tongue obsolete; female with a brush-like tuft at end of abdomen (Kearfottia, Solenohia). p. 614. . . .Psychid^ JJ. Hind wings with veins Rs and Mi coalesced or stalked. K. Wings narrow; fore wings falcate; maxillary palpi well marked and porrect (Cerostoma, etc.). p. 631 Plutellid^ LEPIDOPTERA 591 KK. Wings broad, ample, not falcate; maxillary palpi of folded type, inconspicuous, invisible in Setiostoma. p. 625 SXENOMIDyE FF. Hind wings with pointed apex and excavated below, rarely bifid. (See also FFF.) p. 625 Gelechiid^ FFF. Hind wings narrow -lanceolate and pointed or linear, and much narrower than their fringe. G. Hind wings lanceolate, though sometimes very small, and with the principal vein running nearly through its center, widely separated from Sc. H. Hind wings with a discal cell. p. 621 Elachistid^ HH. Hind wings without a discal cell. I. Vein Rs of hind wings separating from media near the middle of the length of the wing. p. 623 Douglasiid^e n. Vein Rs of hind wings separating from media near the apex of the wing. p. 634 Heliozelid^ GG. Hind wings with vein R closely parallel with or fused to Sc near base. In the broad- winged Gracilariidag, veins Sc and R are fused and the base of vein ]M is preserved, simulating the con- dition in G, but the combined base of Sc and R curves strongly into the lobed basal half of costa, and then approaches or fuses with M at middle of wing, unlike the relation of Sc and R in G. H. Hind tarsi with strong spinules, usually near apices of seg- ments, as well as tibias; posterior legs displayed when at rest. p. 634 Heliodinid^ HH. Tarsi smooth-scaled, the spinules concealed in the scaling; the tibias often hairy, but rarely {Acrocercops, Epermenia) bristled. I. Fore wings with only four veins running from the discal cell to the costa, and five or six to the inner margin. p. 631, 632 Yponomeutid^ and Plutellid^ II. Fore wings with five veins running to costa, or only four to inner margin. J. Discal cell oblique in wing; vein Cuj very short, ninning directly across to inner margin. K. Antennas turned forward in repose; fore tibiae slender, with a small epiphysis at the apex or none. p. 620. Coleophorid^ KK._ Antennae tixrned back in repose; fore tibias with the epiphysis conspicuous, and often more than half as long as the tibia; the tibis rarely slender. L. Hind wings with veins Sc and R usually fused near base ; fore wings with a stigma, and with Ri arisi'ng near the base of the discal cell and R2 near the apex of the cell. p. 628 Blastobasid^ LL. _ Hind wings with veins Sc and R not fused ; fore wings with the space between the origins of veins Ri and R2 only three or foiu- times that between veins RjandRj. p. 629 Cosmopterygid^ JJ. Discal cell not set obliquely in wing; vein Cua nor- mally long and parallel to the medial veins. K. Male antennae heavily ciliate; accessory cell of fore wings extending halfway to base of wing; head with a large, loose, but of ten obscure, semierectile tuft. p. 615. TiSCHERIIDiE KK. Male antennae rarely ciliate; accessory cell small or absent. L. Palpi minute and drooping; vertex tufted; hind wings linear (Bedellia). p. 616 LyonetiiD/E LL. Palpi moderate, with fusiform third segment; maxillary palpi often well developed and porrect. (See also LLL.) p. 617 Gbacilariid.s 592 AN INTRODUCTION TO ENTOMOLOGY LLL. Palpi upturned, with acuminate third segment, often exceeding the vertex; maxillary palpi of folded type but very minute or obsolete. M. Vein Ri of the fore wings more than twice as long as vein R2 and arising before the middle of the discal cell. p. 629 Cosmopterygid^ MM. Vein Ri of the fore wings but little longer than vein R2, and arising beyond the middle of the discal cell. p. 631 SCYTHRIDID^ Suborder JUGATE This suborder includes those Lepidoptera in which the posterior lobe of the fore wing is specialized so as to form an organ which unites the fore and hind wings ; and in which the venation of the hind wings is similar to that of the fore wings. The Jugatae includes the more generalized members of the order Lepidoptera now living, those which are believed to resemble most closely the primitive in- sects from which in ancient times the Lepidoptera were evolved. In fact the first two families here included in the Jugatse may be of even more ancient origin, repre- senting one or two lines of evolution distinct from the lepidopterous stem. Several writers have called attention to indications of trichopterous afifinities of the two families in question; and a study of the wing- venation of these in- sects led me to believe that they are more closely allied to the Trichoptera than to the Lepidoptera. For this reason, in "The Wings of Insects" I classed them with the Trichoptera. Although these indications of trichopterous affinities are tmdoubted, it appears that the view now generally held is that, while they show a close community of descent of the Trichoptera and the Lepidoptera, they are not sufficient to warrant the removal of the families in question from the Lepidoptera. I, therefore, in- clude them, provisionsally, in this order in the following account. For a detailed discussion of this subject, see Braun ('19) and Crampton ('20 b). The suborder Jugate, as now more commonly limited, in- cludes several families, representatives of three of which have been found in America; these are the Micropter^^gidae, the Eriocraniidae, and the Hepialidee. The members of the first two of these families differ greatly in appearance from those of the third family, being very small moths which resemble the small tineids in size and appearance ; our largest species has a wing expanse of from 12 to 14 mm. For this reason they may be known as the Microjugatce. They have also been termed the Jugo-frenata, because, in addition to having the posterior lobe of the fore wing specialized so as to form an organ which serves in uniting the fore and hind wings, there is also a bunch of bristles borne by the hind wing near the himieral angle, which resembles a frenultmi ; these bristles, however, are not homologous with the frenulimi, but are the costal spines described on page 575. On the other hand, the members of the third family are mostly large moths ; many of them are ver>^ large ; and the smaller species have a wing-expanse of 25 mm. The members of this family may be known as the Macrojugatae. Family MICROPTERYGID^ The Mandihiilate Jugates The members of this family are small insects which resemble tineid moths in general appearance. As with other members of the LEPIDOPTERA 593- suborder Jugatas, the venation of the hind wings closely resembles that of the fore wings (Fig. 719). But these insects differ from all Fig. 719. — -Wings of Micropteryx. other Lepidoptera in having in the adult instar well-developed func- tional mandibles, and in that the females lack a bursa copulatrix. Chapman ('17) regards the presence of well-developed mandibles and the absence of a bursa copulatrix of sufficient importance to warrant the removal of these insects from the Lepidoptera and the establish- ment of a distinct order for them ; for this order he proposed the name Zeugloptera. Tillyard ('19) states that the wing-coupling apparatus in this family functions differently from that of the following family, in that in the MicropterA'gidse the jugal lobe is bent under the fore wing and acts as a retinaculimi for the bunch of costal spines, borne by the hind wings. In this family, the subcosta of the fore wings is forked near its middle (Fig. 719); the abdomen of the adult female consists of ten distinct segments; and there is no ovipositor. There is no published account of the transfoiTnations of our American species. The larvas of certain exotic species have been de- scribed; they are very delicate, have long antennas, and feed upon wet moss. The pupa state is passed in the ground; the pupa has large, crossed mandibles. The adults feed on pollen. Two American species have been described; these are Epimar- tyria auricrinella, which is found in the East, and Epimartyria par- della, found in Oregon. Family ERIOCRANIID^ The Haiistcllate J ti gates The members of this family, like those of the preceding one, are small insects which resemble tineid moths in general appearance. 594 AN INTRODUCTION TO ENTOMOLOGY In this family the mandibles of the adult are vestigial; the maxillee are formed for sucking, each maxilla forming half of a long sucking- tube, as in higher Lepidoptera. The females lack a bursa copulatrix but have a piercing ovipositor. An easily observed recognition character is the fact that the subcosta of the fore wings is forked near its apex (Fig. 720). The jugal lobe of the fore wing extends back above the base of the hind wing and is clasped over an elevated part of the hind wing, thus being of the type described as a fibula (see page 62). Our best-known representative of this family is Mnemonica auricyanea. The structure and transformations of this species have Sc, Sc, Ri 2d A 1st A Fig. 720. — Wings of Mnemonica. been described by Busck and Boving ('14). The adult has a wing- expanse of from 1 2 to 1 4 mm. The larva mines in the leaves of chestnut, oak, and chinquapin in early spring, making a large, bulgy blotch mine; it completes its growth within a week or ten days, and goes into the ground to transform, where it spins a tough cocoon; the change to pupa takes place in the following winter; the adult emerges in April. The pupa has long, arm-like toothed mandibles, with which it cuts the tough cocoon and with which it digs its way up to the surface of the ground. This species is found in the East. Family HEPIALID^ The Swifts or the MacrojugatCB The members of this family are of medium or large size. LEPIDOPTERA 595 Figure 721 represents in natural size one of the larger of the American species, but many exotic species are larger than this one. Our smaller species have a wing-expanse of at least 25 mm. Our best- known species are brown or ashy gray in color, with the wings marked with silvery white spots. It is said that these moths fly near the earth, and only in the eve- ning after sunset, hiding under some low plant, or clinging to the stalk of an herb during the day. Some of them fly with extreme rapidity, with an irregular mazy flight, and have, therefore, been named swifts by collectors. So long as either or both of the two preceding families are retained in the suborder Jugatse, the Hepialidae may be dis- tinguished as the Macrojugatas. In the Hepialidce the posterior lobe of the fore wing is a slender, finger-like organ, which is stiffened by a branch of the third anal vein, and which projects beneath the costal margin of the hind wing. As Fig. 721. — Sthenopis pur purascens . the greater part of the inner margin of the fore wing overlaps the hind wing, the hind wing is held between the two. This is the type of posterior lobe of the fore wing to which the term jugum is ap- plied. (Figs. 74 and 75.) The larvae are cruciform and furnished with sixteen legs; they feed upon wood or bark, and are found at the roots or within the stems of plants. They transform either in their burrows, or, in the case of those that feed outside of roots, within loose cocoons. The pupse have transverse rows of teeth on the abdominal segments; these aid them in emerging from their burrows. This family is represented in our fauna by two genera, Hepialus and Sthenopis. Hepialus. — This genus includes our smaller species, which range in wing-expanse from 25 to 55 mm. In Hepialus the apices of the fore wings are more rounded than in Sthenopis. Ten North American species have been described. Sthenopis. — This genus includes our larger species. In these the apices of the fore wings are more pointed than in Hepialus, and in some species are subfalcate. Four species have been found in our 596 AN INTRODUCTION TO ENTOMOLOGY fauna ; one of these, Sthenopis purpurdscens, is represented in Fi^re 721. The larva of Sthenopis argenteomaculatus bores in the stems of the speckled or hoary alder {Alnus incana) ; that of Sthenopis thule, in willow. Suborder FRENAT^ The members of the Frenatse are most easily recognized by the fact that the venation of the hind wings differs markedly from that of the fore wings, being much more reduced. In this suborder, vein Ri of the hind wings coalesces with subcosta, the two appearing as a single vein, except that, in some cases, a short section of the base of Ri is distinct, presenting the appearance of a cross-vein between Jc/^ 2d A I si A Fig. 722. — Wings of Prionoxystus robinicE. radius and subcosta (Fig. 722, Ri). After the separation of vein Ri, the radial sector continues unbranched to the margin of the wing (Fig. 722, Rs). Rarely, as in some members of the Gracilariidce and of the Cosmopterygidas, vein Ri of the hind wings is free, not co- alesced with vein Sc. The essential characteristic of the Frenatae is that they are descendants of those primitive Lepidoptera in which the two wings of each side were united by a frenulum. This fact should be clearly understood, for in many of the Frenatae the frenulum has been lost. The loss of the frenulum in these cases is due to its having been supplanted by a substitute for it, by an enlarged humeral area of the hind wings, which causes the two wings of each side to overlap to a LEPIDOPTERA 597 great extent. This overlapping of the two wings insures their syn- chronous action ; and the frenulum, being no longer needed for this purpose, is lost. Illustra- tions of different stages in the reduction and loss of the frenulum are given in the discussions of family characters given later. As a rule the frenulum of the female, when present, consists of several bristles, while that of the male con- sists of a single strong, spine-like organ. If one of the bristles of the compound frenukmi of a female be ex- amined, it will be found to be a typical seta, containing a single cavity. But if a frenulum of a male be ex- amined, it will be found to contain several parallel cav- ities. Evidently the fren- ulimi of the male is com- posed of several setae, as is that of the female, but these setae are grown together, Fig. 723.- hook. id A -Wings of a moth: f h, frenulum- This can be seen by examining a bleached wing that has been mounted in balsam; usually the cavities in the sette contain air, which renders them visible. The frenukmi-hook, which is present in the males of certain moths, is a membranous fold on the lower surface of the fore wing for receiv- ing the end of the frenulum, and thus more securely fastening the two wings together (Fig. 723, / A). As a rule the frenulum-hook arises from the membrane of the wing near the base of cell C; but in some moths (Castnia) it seems to have been pulled back so that it arises from the subcostal vein. THE GENERALIZED FRENAT^ Under this heading are grouped those families of moths that are supposed to retain more nearly than any other Frenatte the form of the primitive Frenatse, those that were "the first to appear on earth. In most of the families included here, the wings approach the typical form, except in the reduction of the nimiber of branches of radius of the hind wings, which is true of all Frenatae ; usually the base of media of one or both pairs of wings is preserved throughout a considerable part, at least, of the discal cell; and the anal veins are well preserved, there being two or three in the fore wing and three in the hind wing. The frenulum is usually well preserved. 598 AN INTRODUCTION TO ENTOMOLOGY There are also included in this group of families those families in which the fixed hairs or aculeae are retained over the general surface of the wings, even though in some cases, as in the Nepticulidce, the venation of the wings may be greatly reduced. The presence of aculeas distributed over the general surface of the wings is believed to indicate a generalized condition, as it is found elsewhere in the Lepidoptera only in the Jugatae. As this condition is also found in the Trichoptera, it was probably inherited from the stem foim from which the Lepidoptera and the Trichoptera were evolved. In the more specialized Lepidoptera the aculeas are confined to small areas of the wing surface or have been lost. Family INCURVARIID^ This family and the following one differ from all other Frenatse and agree with the Jugatae in having retained aculeae distributed over the general surface of the wing (Fig. 710). In this family the venation of the wings is but little reduced; the antennae are without an eye- cap ; and the females, so far as is known, are furnished with a piercing ovipositor. The moths are small or of moderate size. Many of the larvae are miners when young, and later are case bearers. The family Incurv^ariidae includes three subfamilies, which are not very distinct but which, however, are treated as families by some writers. Subfamily Adeline.' — These tiny moths are characterized by the unusually long and fine antennte of the males, which may be twice or more than twice as long as the wings. Some of the species are also conspicuous on account of their striking colors and markings. The larvas are elongate, cylindrical, with thoracic legs and five pairs of prolegs. They are at first miners; later they live in portable cases. They feed on the leaves of various herbs and shrubs ; but none of our species is known to be of economic importance. Nearly all of our species belong to the genus Adela. Subfamily Incurvariin^. — An interesting representative of this division of the family Incurvariidae is the following well-known species. The maple-leaf cutter, Paracleniensia acerifoliella. — The larva in- fests the leaves of maple, and occasionally is so abundant that it does serious injury. The larva is at first a leaf-miner, like other adelids; but later it is a case-bearer. The leaves of an infested tree present a strange appearance (Fig. 724). They are perforated with ntmierous elliptical holes, and marked by many, more or less perfect, ring-like patches in which the green substance of the leaf has been destro}-ed but each of which incloses an uninjured spot. These injuries are produced as follows: The larva, after living for a time as a leaf -miner, cuts an oval piece out of a leaf, places it over its back, and fastens it down with silk around the edges. This serves as a house beneath which it lives. As it grows, this house becomes too small for it. It then cuts out a larger piece which it fastens to the outer edges of the smaller one, the LEPIDOPTERA 599 Fig. 724. — Leaf infested by maple-leaf cutter. the lar\'a being between the two. Then it crawls halfway out upon the leaf, and by a dexterous lifting of the rear end of its body turns the case over so that the larger piece is over its back. When it wishes to change its location it thrusts out its head and fore legs from the case and walks off, looking like a tiny turtle. When it wishes to eat, it fastens the case to the leaf and, thrusting its head out, eats the fleshy part of the leaf as far as it can reach. This explains the circular form of the patches, the round spot in the center indicating the position of the case. The insect passes the winter in the pupa state within its case, which falls to the ground with the infested leaf. The moth is of a brilliant steel- blue or bluish green color, without spots but with an orange-colored head; it appears in early summer. Subfamily Prodoxin^.. — This subfamily includes the remarkable insects that are known as the yucca- moths and the closely allied bogus ^"ucca-moths. The }aicca-moths, Tegettcula. — Four species of this genus are now recognized; the best-known of these is Tegeticula alba. The life- history of this species w^as first described by Mr. C. V. Riley ('73), under the name Pronuha yiiccasella; and in most of the accoimts of this insect this name is used. The moth, however, was first de- scribed as Tegeticula alba. The most complete account of this and the allied species is that of Riley ('92). This species infests Yucca filamentosa, a plant not fitted for self- pollination or for pollination by insects in the ordinary ways ; in fact, it is pollinized only by moths of the genus Tegeticula, the larv'as of which feed on its seeds. This is one of the few cases in which a particular plant and a particular insect are so specialized that each is dependent upon the other for the perpetuation of the species. In the female moth, the maxillas are each furnished with a long, curled, and spinose appendage, the maxillary tentacle (Fig. 725, b), fitted for the collection of pollen. After collecting a large load of pollen, often thrice as large as the head (Fig. 725,), the female moth places her eggs, by means of her long, extensile ovipositor, into an ovary, usually of another flower than that from which the pollen was collected. After oviposition, the moth runs up to the tip of the pistil and thrusts the pollen into the stigmatic opening. Thus is insured the develop- ment of seeds, upon which the larvae hatched from the eggs placed in the ovary are to feed. As many more seeds are developed than are needed by the larvae, the perpetuation of the yuccas ir, assured. 600 AN INTRODUCTION TO ENTOMOLOGY The full-grown larva leaves the yucca pod and makes its way to the ground, where it spins a dense cocoon several inches below the surface. The adult moth has a wing-ex- panse of about 2 5 mm. The front wings are silvery white above ; the hind wings, semi- transparent. The bogus yucca- moths, Prodoxus. — The moths of this ge- nus are closely allied to the yucca-moths, but differ in the im- portant particular that the females lack maxillary tentacles; they are consequently incapable of pollinat- ing the joiccas as do the true yucca-moths. The larvae of Prodoxus Fig- 725- — Tegeticula alba: a, side view of head and neck of female denuded ; i , load of pollen ; 2, maxil- lary tentacle; 3, maxilte; 4, maxillary palpi; 5, antennae; b, maxillary tentacle and palpus; c, an enlarged spine; d, maxillary palpus of male; e, scale from front wing; /, front leg; g, labial pal- pus; h, i, venation of wings; j, last segment of abdomen of female, with ovipositor extruded. All enlarged. (From Riley.) feed in the flower-stem or in the flesh of the fruit. But as, in Yucca filamentosa at least, the flowers drop and the flower-stem withers if the flowers are not pollinated, the bogus yucca-moths are dependent on the true yucca-moths for the conditions necessary for the develop- ment of their larvee. The pupa state is passed in the burrow made by the larva. Eleven species of Prodoxus have been described. Family NEPTICULID.E In this family, as in the preceding one, fixed hairs or acuie^ are distributed over the general surface of the wings. In the Nepticulidas the venation of the wings is much reduced; the basal segment of the antennas is enlarged and concave beneath, so as to form an eye-cap; the female is without an ovipositor; the labial palpi are short; the maxillary palpi are long; and the maxillas are vestigial. This family includes the smallest of the Lepidoptera, some of the species having a wing-expanse of scarcely 3 mm. Although this family presents characteristics which indicate that it should be placed among the generalized Lepidoptera, the venation of the wings is greatly reduced. This indicates that it represents a distinct line of development which in some respects has become more highly specialized than are the other families included in this division of the Lepidoptera. The frenulum of the female consists merely of a group of small, functionless bristles; but in the male the frenulimi is a strong, spine- LEPIDOPTERA 601 like organ, which hooks into a well-developed frenulum hook (Fig. 726); in most cases the costal spines are well developed; this is shown in the accompany- ing figure; and the anal lobe of the fore wing is sometimes quite distinct. With the exception of several gall-making spe- cies oi Ectcrdemia , the lar- vae of all species of which the life-history is known are miners within the tissues of leaves (rarely in fruits) or in bark. They show a preference for trees and shrubs, but some mine in the leaves of herbaceous plants. The larva at first makes a very narrow linear mine. Thismine may continue as a linear mine, gradually broadening throughout its course, or it may at some period abruptly enlarge into a blotch . When full-grown, the larva, with few exceptions, leaves the mine and, drop- ping to the ground, spins a dense, flattened cocoon amongst rubbish or on the loose surface soil. (Braun '17.) More than seventy species have been described from our fauna, and doubtless many more are to be discovered. The Nepticulid^ of North America was monographed by Braun ('17). Fig. 726. — Wings of Ohriissa ochrefasciella, male. (After Braun.) Family COSSID^ The Carpenter-Moths This family includes moths with spindle-shaped bodies, and nar- row, strong wings, some of the species resembling hawk-moths quite closely in this respect. The larvse are borers; many of them live in the solid wood of the trunks of trees. The wood-boring habits of the larvcB suggest the popular name carpenter-moths for the insects of this family. These moths fly by night and lay their eggs on the bark of trees, or within tunnels in trees from which adult carpenter-moths have emerged. The caterpillars are nearly naked, and, although furnished with pro-legs as well as true legs, are grub-like in form. The pupa state is passed within the burrow made by the larva. When ready to change to an adult, the pupa works its way partially out from its burrow. This is accomplished by means of backward-projecting saw- like teeth, there being one or two rows of these on each abdominal segment. After the moths have emerged, the empty pupa-skins can be found projecting from the deserted burrows. 602 AN INTRODUCTION TO ENTOMOLOGY The carpenter-moths are of mediinn or large size. The antenrice of the males are mostly bipectinate; those of the females are either very slightly bipectinate or ciliate. In a few species the antenna are lamellate. The ocelli are wanting, and the maxillce are vestigial. The venation of the wings of our most common and most widely distributed species is shown in Figure 727. There are two well-preserved anal veins in the fore wing, and three in the hind wing. The base of media is preserved, and is forked within the discal cell. In the fore wing the veins R3 and R4+5 anastomose, forming an accessory cell. The frenulum is vestigial in this genus ; but in some other genera it is well developed. Authors differ greatly regarding the appropriate position of this family in the series of families. Certain characteristics of the larvas indicate that it belongs somewhere among the specialized Micro- frenatas; but I place it here at the beginning of the Non-aculeate Generalized Frenatae on account of the generalized structure of the wings. This family is represented in our fauna by thirty-four described species; it has been monographed by Barnes and McDunnough ('11). The family includes three subfamilies, which are separated as follows : LEPIDOPTERA 603 A. Anal veins of the fore wings united near the margin of the wing by a cross- vein HY POPTIN^ AA. Anal veins of the fore wings not united near the margin of the wing by a cross-vein. B. Veins Rs and Mi of the hind wings stalked or close together at the end of the discal cell ; antennae of male pectinate throughout Cossin.e BB. Veins Rs and Mi of the hind wings widely separate; antennas of male pectinate on basal half only Zeuzerin^ Subfamily Hypoptin^. — The members of this subfamily are dis- tinguished by the presence of the anal cross-vein near the margin of the front wings . Nearly one-half our species belong to this subfamily. They have been described from Florida, Texas, Colorado, and west- ward to California. I have found no ac- count of the early stages of any of them. Subfamily Cos- sin^. — This subfam- ily is represented in our feunaby six gen- Fig. 728.— Prionoxystus robinia, female, era including fourteen species ; but most of these are confined to the Far West and are known only in the adult state. Our best-known species are the following. The locust-tree carpenter-moth, PrionoxystMs rohmics. — Figure 728 represents the female, natural size. The male is but little more than half as large as the female. It is much darker than the female, from which it differs also in having a large yellow spot, which nearly covers the outer half of the hind wings. The moths fly in June and July ; the larvae bore in the trunks of locust, oak, poplar, willow, and other trees. It is supposed that the species requires three years to complete its transformations. It is found from the Atlantic Coast to California. The lesser oak carpentev-worm, Prio7toxyshis macmurtrei. — This is a slightly smaller species than the preceding. The lan^a bores in the trunks of oak in the East. The moth has thin, slightly transparent wings, which are crossed by numerous black lines. The male is much smaller than that of P. rohinice, and lacks the yellow spot on the hind wings. Subfamily Zeuzerin^. — ^Excepting three little-known species of Hamilcara, found in Texas and Arizona, the following species is the only representative of this subfamily in our fauna. The leopard-moth, Zeuzera pyrma. — This species is white, spotted with nimierous small, black spots, which suggested its common name. The adult has a wing-expanse of from 40 to 60 mm. It is a European 604 AN INTRODUCTION TO ENTOMOLOGY Species, which was first observed in the vicinity of New York City in 1882 ; since that time it has spread to other parts of the East. The larva is a very injurious borer in many species of trees and shrubs. The young larvee bore in the small twigs ; later they migrate to larger limbs or to the trunk. Family PYROMORPHID^ Fig. 729.— /I c oloithus fal sarins. Fig. 730. — Wings of Acoloithus falsarius. The Smoky Moths There are but few insects in our country pertaining to this family; only fifteen species are now recognized, but these represent six genera. These are small moths, which are chiefly of a smoky black color; some are marked with brighter colors; the wings are thinly scaled; and the maxillae are well developed. The larvas are clothed with tufted hair; they have five pairs of prolegs, which are provided with normal hooks. A tiny representative of the family which seems to be not uncommon in the East is Acoloithus falsarius. This moth (Fig. 729) expands 16 mm. It is black, with the prothorax of an orange color. The venation of the wings (Fig. 730) is peculiar, in that subcosta and radius of the hind wings coalesce for only a short distance beyond the middle of the discal cell, and a stump of radius projects towards the base of the wing, from the point of union of the two veins. The larva feeds in early summer on the leaves of grape and of Virginia creeper. It is said that the pupa state lasts fourteen days and is passed within a parchment-lilvc cocoon. The adults frequent flowers in the daytime. Another well-known species is Pyromorpha dimididta. This is foimd in the Atlantic and Western States. The entire insect is smoky black, except the basal half of the fore wings in front of the second anal vein, and the basal half of the costa of the hind wings, which are yellow. The wings are thinly scaled and expand 25 mm. or a little more. The male is larger than the female and is more active. Figure 731 represents the venation of the wings. Some spe- cies of the genus Pyromorpha are remarkable in that none of the branches of radius of the fore wings coalesce beyond the discal cell. LEPIDOPTERA 605 Figure 732 represents the venation of the wings of Pyromorpha marteni, a spe- cies found in the Rocky Mountains. The species of the genus Harrisina differ from the typical form of the famih- in that the anal area of the hind wings is greatly re- duced, there being only two short, strongly curved, anal veins. As in other mem- bers of the family, there are two well-developed anal veins preserved in the fore wings. The following is the best-known species of this genus. The grape-leaf skeleton- 3^ ^ izevMarrisinuamericdna ~ pig. 73i._wings of Pyromorpha dimidiata. i he wmgs of this moth are long and narrow (Fig. 733) ; the abdomen is long, and widened towards Fig- 733- — Harrisina americana. the caudal end. It is green- ish black in color, with the prothorax reddish orange. The larva feeds on the leaves of grape and of the Virginia creeper. An entire brood of these larvae will feed side by side on a single leaf while young. This species rarely becomes of economic im- portance. 2d A Fig. 732. — Wings of Pyromorpha marteni. Family DALCERID^ In this family the body is small; the antennas are short; and the wings are broad. In the fore wings there is a large acces- sory cell which is ist R3; and in the hind wings veins Sc and R are connected at a point. 606 AN INTRODUCTION TO ENTOMOLOGY The best-known species in our fauna is Dalcerides ingenita, found in Arizona. The expanse of the wings is about 25 mm. The wings are deep yellow, inclining to orange, without markings. The larva is unknown. Another species, Pincdnia coa, which is not uncommon in Mexico has been reported from Arizona by Holland ('03). Family MEGALOPYGID^ The Flannel-Moths, In this family the wings are heavily and loosely scaled, and mixed with the scales are long, curly hairs; these give the wings the appear- ance of bits of flannel. It is this that suggested the com- mon name of these moths. The body is stout and clothed with long hairs. The venation of the wings of our most common species, Lagda crispdta, is represented in Figure 734. There are three anal veins in both fore and hind wings; but in the fore wings the second and third anal veins are partially grown together. The basal part of media is more or less distinctly preserved and divides the dis- cal cell into two nearly equal parts. The subcosta and ra- dius of the hind wings coalesce for nearly the entire length of the discai cell. In these moths the maxillae are vestigial. The larvae are remarkable for the possession of seven pairs of prolegs ; these are borne by ab- dominal segments 2 to 7 and 10; but those of segments 2 and 7 are without hooks. The setiferous tubercles are verrucas bearing large numbers of fine setse ; so that the body is densely hairy ; and inter- spersed among the fine setce are venomous setce. There are only ten North American species of this family; these represent four genera. Our most common species are the two follow- ing. The crinkled flannel-moth, Lagda crispdta. — This moth is cream- colored, with the fore wings marked with wavy lines of crinkled black and brownish hairs. The male is represented in Figure Fig. 734. — Wings of Lagoa crispata. LEPIDOPTERA 607 Fig. 735. — Lagoa crispata, male. Fig- 736. — Old cocoon Megalopyge opercularis. 735; the female is larger expanding, 40 mm. In the female the an- tenna are ver>' narrowly pectinate. Thelar- VcB feed on many trees and shrubs, including oak, elm, apple, and raspberry. They are short, thick, and fleshy, and are covered with a dense coat of long, silky, brown hairs, which project upward and meet to form a ridge or crest along the middle of the back ; interspersed among these fine hairs are venomous setae. The cocoons are of a firm, parchment-like texture, covered with a thin web of rather coarse threads. Adixed with the silk of the cocoon are hairs of the larva. The cocoon is provided with a hinged lid. This species is found in the Atlantic States. Megalopyge opercularis. — This species is somewhat smaller than the preceding one; the male has a wing-expanse of about 25 mm., and the female of about 37 mm. The fore wings are umber brown at base, fading to pale yellow outwardly; they are marked with wavy lines of white and blackish hairs, and the fore margins are nearly black. The larvae are clothed with long, silky hairs, underneath which are venomous setas. The cocoons are firmly attached to a twig of the infested tree, and are each fur- nished with a trapdoor. The old cocoons that one sees in collec- tions present the appearance rep- resented in Figure 736. But I found in Mississippi a cocoon, which I believe to be of this species, that is of the form shown in Figure 737. From this it ap- pears that after the outer layer of the cocoon has been made, the larva constructs a hinged partition near one end of it, and adds no more silk to that part of the cocoon which is outside the partition. This part of the cocoon is quite delicate, and is destroyed when the moth emerges if not before. Fig. 72,7- opyge. -Complete cocoon of Megal- This species is found from North Carolina to Texas, is a very general feeder; it is often found on oak. The larva 808 AN INTRODUCTION TO ENTOMOLOGY Family EUCLEID^^ The Slug-Caterpillar Moths One often finds on the leaves of shrubs or trees, elliptical or oval larvce that resemble slugs in the form of the body and in their glidirjg motion. As these are the larvae of moths they have been # termed shig-cater pillars; but they present very little similarity in form to other caterpillars. The resemblance to slugs is greatly increased by the fact that the lower sur- face of the body is closely applied to the object upon which Fig. 738. the larv^a is creeping, the thoracic legs being small and the prolegs wanting. There is, however, on the ventral side of the abdomen a series of sucking-disks, which serve the purpose of prolegs. The head of the larva is small and retractile. In some species the body is naked; in others it is clothed with tufts of hairs; and in others there is an armature of branching spines. Several species bear venomous setee. The larvae when full-grown spin very dense cocoons of brown silk; these are egg-shaped or nearly spherical, and are furnished at one end with a cap which can be pushed aside by the adult when it emerges (Fig. 738). The cocoons are usu- ally spun between leaves. The moths are of me- dium or small size ; the body is stout, and the wings are heavily and loosely scaled. The maxillce are vestigial. These moths vary greatly in appearance, and many of them are very prettily col- ored. Considerable variation exists in the venation of the wings in this family (Fig. 739 and Fig. 740). The base of media may be preserved or wanting; in some species it is forked within the discal cell, in others not. There is also considerable variation in the coalescence of the branches of radius, but veins R3 and R4 coalesce to a greater extent than any other branches of this vein. There is no accessory cell. In the hind wings veins So *This family is termed the Cochlidiidae by some writers, and by others the Limacodidae. Fig. 739. — Wings of Adoneta spinuloides. LEPIDOPTERA 609 and R coalesce for a short distance at the point where vein Ri joins vein Sc. Only forty-three North American spe- cies of eucleids have been described ; but these represent twen- ty genera. The larvse are rarely abundant enough to be of eco- n o m i c importance ; they are chiefly inter- esting on account of their remarkable forms. The following are some of the bet- ter-known species: The saddle-back caterpillar, Siblne stimulea.- — This larva can be recognized by Figure 741. Its most characteristic feature is a large green patch on the back, resem- bling a saddle-cloth, while the saddle is represented by an oval purplish brown spot. The moth is dark, velvety, reddish brown, with two white dots near the apex of the fore wings. The larva feeds on oaks and oth- er forest trees. This is one of the species that are armed with ven- omous setae. The spiny oak-slug, Euclea delplnnii.— This larva (Fig. 742) is one of the most common of our slug caterpil- lars and one of those that are armed with venomous setae. It feeds on the leaves of oak, pear, willow, and other trees. The moth (Fig. 743) is cinnamon-brown, with a variable number of bright green spots on the fore wings. The hag-moth, Phobetron pithecium. — The common name hag- moth is applied to the larva of this species on account of its remark • Fig. 740. -Wings of Packardia geminata. Fig. 743- — Euclea delphinii. Fig. 742.- delphinii, 610 AN INTRODUCTION TO ENTOMOLOGY Fig. 744. — Phobetron pithe- cium, larva. (After Dyar.) Prolimacddes hddia. — Fig. 745. — Prolima- codes badia, larva. able appearance (Fig. 744). It bears nine pairs of fleshy appendages which are covered with brown hairs. In the full-grown larva the third, fifth, and seventh pairs of appendages are longest; these are twist- ed up and back, and sug- gest the disheveled locks of a hag. This larva feeds on various low shrubs and the lower branches of trees. At the time of spinning, the larva sheds the fleshy processes, and they re- main on the outside of the cocoon. The skiff-caterpillar, This remarkable larva (Fig. 745) is not un- common on oak and other forest trees. It is pale apple-green, with a chestnut-brown patch on its back. The moth (Fig. 746) is light cinnamon-brown, with a tan-brown triangular spot on each fore wing. Family EPIPYROPID^ Fig. ^G.-Prohma- codes badia. This family is represented in our fauna by a single rare species which was found in New Mexico. Our species is Eptpyrops harheridna. Another species, Eptpyrops anomala, has been described from China; and larvse that are believed to belong to this genus have been found in Central America. These insects are remarkable on account of the extraordinary habits of the larvae, which are found firmly attached to living insects of the family Fulgoridae. They are usually attached to the dorsal surface of the abdomen beneath the wings of their host. The body of the larva is covered with a cottony coat, causing it to resemble a Coccus. It is supposed that these larvs feed on waxy matter excreted by the fulgorids. For a detailed account of our species, see Dyar ('02). THE SPECIALIZED MICROFRENAT^ In the "Synopsis of the Lepidoptera" given on pages 581 to 584 I have grouped together under the heading "Specialized Microfren- atas" twenty-six families of moths, which are more highly specialized than are the preceding families, and which as a rule are composed of small insects. This group of families includes most of those families that were formerly classed together as the Microlepidoptera ; but later studies have resulted in the removal from the old group Microlepidoptera of LEPIDOPTERA 611 several families of small moths, hence this name is no longer distinc- tive. Among the families of small moths removed from theMicro- lepidoptera are theMicropterygidse and theEriocraniidse, now placed in the suborder Jugatee; the Incurvariidas and the Nepticulid^, placed at the beginning of the Prenatal; and the group of families now known as the Pyralids, which are believed to be genetically quite distinct from the other families of small moths. On the other hand, in ad- dition to the families here placed in this series some authors include the Cossidae. The families of the A-Iicrofrenatag are grouped into superfamilies in various ways by different writers; but none of these groupings is sufficiently well established to be adopted here. Family ACROLOPHID^ These are large, stout, noctuid-like moths; some of the species have a wing-expanse of 30 mm. or more. The eyes are usually hairy, in which respect they differ from other "Micros." The antennae are without an eye-cap. The labial palpi are large, and usually upcurved to the middle of the front; in the males of some species they are thrown back on the dorsum of the thorax, which they equal in length. The first segment is relatively very large; when the palpus is short it is longer than the second segment ; the thorax is tufted. The vena- tion of the wings is quite generalized ; the base of media is more or less preserved, and all the branches of the branched veins are present ; there are three anal veins in both fore and hind wings; in the fore wings the tip of the third anal vein coalesces with the second anal vein. Forty-two species have been described from our fauna; these were formerly classed in several genera ; but recent writers refer them all to the genus Acrolophus. The burrowing web-worms, A. arcanellus, A. mortipennellus , and A. popeanellus.— The habits of these three species were described by Professor Forbes in his Twelfth Illinois Report (1905). The larvae normally live in the ground feeding on the roots of grass. Each larva makes "a tubular web opening at the surface and leading down into a vertical cylindrical burrow about the diameter of a lead-pencil, and six inches to two feet, or even more in depth." The larva measures about 25 mm in length. Sometimes the larvas injure young com when planted on sod. They surround the base of each plant with a fine web mixed with earth and pellets, building this up in the lower blades, which they slowly eat away. As they get larger they eat the stripped plant to the ground. When disturbed they retreat into their web-lined burrows. Family TINEIDiE The head is usually clothed with erect hair-like scales. The antenuce are shorter than the front wings. The maxillse are usually small or vestigial. The maxillary palpi are usually large and folded. 612 AN INTRODUCTION TO ENTOMOLOGY ^d^ Fig. 747.- Spuler.) Wings of Tinea parasitella. (After The labial palpi are short and clothed with but three or four bristles. In the typical genera the venation of the wings is quite generaHzed (Fig. 747), the base of media being pre- ^^ /P^ y^ served in both fore ^ and hind wings and all of the veins char- acteristic of the Frenatse being pres- ent ; but in other gen- era the venation is somewhat reduced. Many of the larvae are case-bearers; many are scavengers or feed on fungi ; some feed on fabrics, espe- cially those that con- tain much wool; few if any feed on leaves. This is a large family. More than one hundred twenty-five North American species are already known; fifty of these belong to the genus Tinea. To this family belong the well-known clothes-moths. The naked clothes-moth, Tineola hisselliella. — This is our most common clothes-moth. Although the larva spins some silk wherever it goes, it makes neither a case nor a gallery; it is, therefore, named the naked clothes-moth. But when the larva is full-grown it makes a cocoon, which is composed of fragments of its food-material fas- tened together with silk. The adult is a tiny moth with a wing- expanse of from 12 to 16 mm. ; it is of a delicate straw-color, without dark spots on its wings. The case-bearing clothes-moth, Tmea pellionella. — The larva of this species is a true case-bearer, making a case out of bits of its food-material fastened together with silk. The case is a nearly cylin- drical tube open at both ends. The pupa state is passed within the case. The adult is a small, silky, brown moth, with three dark spots on each fore wing. It expands from 11 to 17 mm. The tube-building clothes-moth or the tapestry-moth, Trichoph- aga tapetiella. — The larva of this species makes a gallery composed of silk mixed with fragments of cloth. This gallery is long and wind- ing and can be easily distinguished from the case of the preceding species. The pupa state is passed within the gallery. The moth differs greatly in appearance from the other two species, the fore wings being black from the base to near the middle, and white be- yond. It expands from 12 to 24 mm. LEPIDOPTERA Family PSYCHID^ 613 The -Worm Moths The bag-worm moths are so caUed on account of the silken sacs made by the larvas, in which they hve and in which they change to pupae. In our more conspicuous and best -known species the sac is covered either with httle twigs (Fig. 748) or, in the case of a species that feeds on cedar or arbor-vitas, with bits of leaves of these plants. When the larva is full-grown it fastens its sac to a twig or other object and transforms within it. In the adult state the two sexes differ greatly. The female is wingless, and in some genera the eyes, an- tennse, mouth-parts, and legs are vestigial or wanting, the body being quite maggot-like. At the caudal end . of the body there is a tuft of hair-like scales which are mixed with the eggs. In most species the female does not leave the sac before oviposition but deposits her eggs within it. The male moths are winged; they are small or of Fig- 748-— I moderate size. The wings are thinly scaled and in oiOikettcus some species nearly naked ; when clothed with scales " °^' they are usually of a smoky color without markings. The venation of the wings varies ■J' Jil greatly within the ^'-"'^^^ ^ - family. Figure 749 represents the vena- tion of our most com- mon species. Only about twenty species are known from our fauna, of which the following are most likely to be observed. Abbot's bag-worm, OiketicMS ahboti. — This species occurs in the more southern part of our country. The lar- va makes a bag with sticks attached to it crosswise (Fig. 748). The adult male is sable brown, with a vitreous bar at the ex- tremity of the discal cell of the fore wings ; the narrow external edging of the wings is pale ; the expanse of the wings is 33 mm. id A Fig. 749. — Wings of Thyridoptery:: formis. zbhemercz- 614 AN INTRODUCTION TO ENTOMOLOGY The evergreen bag-worm or the bag-worm, Thyridopteryx ephe- mercBJormis. — This species prefers red cedar and arbor-vitae, and for this reason has been named the evergreen bag-worm; but it also feeds on many other kinds of trees, and as it is the species that is mosthkelyto attract attention, and is sometimes a serious pest, it is often called the bag-worm. It is our best-known species, and iis life-history will serve as an illustration of the habits of the members of the family Psychidas. The bag of this species is about the same size as that of Abbot's bag-worm (Fig. 748); but it differs in being covered with bits of leaves when it feeds on cedar or arbor-vitse, or with twigs attached lengthwise when it feeds on other trees. When full-grown the larva fastens the bag to a twig with a band of silk, and then changes to a pupa. When the male is ready to emerge, the pupa works its way to the lower end of the bag and halfway out of the opening at the extremity. Then its skin bursts and the adult emerges. The male moth has a black, hairy body and nearly naked wings (Fig. 750). The adult female partly emerges from the pupa skin and pushes her way to the lower end of the bag, where she awaits the approach of Fig. 750.— Thyridop- the male. She is entirely destitute of wings and \orZl '^^''^"'''' legs. The genitalia_ of the male can be greatly extended, making possible the pairing while the female is still in the bag. After pairing, the female works her way back into the pupa skin, where she deposits her eggs mixed with the hair-like scales from the end of her body. She then works her shrunken body out of the bag, drops to the ground, and perishes. The eggs remain in the pupa skin in the sac till the following spring. Where this insect is a pest, two methods of control are practiced, first, the bags are collected and destroyed in the winter, while they still contain the eggs; second, when impracticable to collect the bags: on account of the height of the infested trees, a spray of arsenate of lead is used in the spring as soon as possible after the larvee appear. Eurycyttarus confederdta. — This is a smaller species than the two preceding ones. Figure 751 represents the sac of a male with the empty pupa-skin projecting from the lower end, and Figure 752 the fully developed male. Fig. 752. Solenobia walshella. — This is a small Fig. 751. tineid-like species; the male has a wing-expanse of about 13 mm. and the hind wings have a quite wide fringe. The fore wings are light gray speckled with brown. The bag of the larva is about 8 mm. long, made of silk, and covered with fine grains of sand or with particles of lichens and excrement of the larva. Cham- bers states that he has sometimes found small molluscan shells ad- hering to it. The larvse are found on the trunks of trees and feed w|w LEPIDOPTERA 615 Fig. 753. — Wings of Solenohia. ler.) (After Spu- upon lichens. Figure 753 represents the venation of the wings of a European species of this genus. Family TISCHERIID.E The vertex of the head is clothed with erect, broad, and short scales. The an- tennse are long, with the first segment small. The maxillae are longer than the head and thorax. The max- illary palpi are small or ab- sent. The labial palpi are short, porrect, and without bristles on the outer side of the second segment. In the front wings (Fig. 754), the costal margin is strongly arched, the apex is pro- longed into a sharp point, the discal cell is long and narrow, the accessory cell is very long, and the base of media is preserved. The hind wings are long and narrow and with greatly reduced venation. (Fig. 754). The hind tibias are very hairy. Nearly all of our spe- cies belong to the genus Tischeria. The larvae lack thoracic legs; most of them make blotch mines in the leaves of oak; but the following one infests apple; and some other species infest blackberry and rasp- berry. The trumpet-leaf miner of apple, Tischeria malifoliella. — This spe- cies infests the leaves of apple over the Eastern half of the United States and Canada, and sometimes does serious injury. The larva makes a trumpet-shaped mine just beneath the epidermis on the upper side of the leaf; the first half of the mine is usually crossed by crescent-shaped stripes of white. There are two generations annually in the North, and several in the South. The larvae pupate in their mines. The larvse of the last generation line their mmes with silk and pass the winter in them. They transform 2d A Fig. 754. — Wings of Tischeria marginea. Spuler.) (After 61C AN INTRODUCTION TO ENTOMOLOGY to pupcE in the spring and emerge as adults eight or ten days later. The adult moth expands about 6 mm. ; it has shining dark brown front wings, tinged with purplish and dusted with pale yellowish scales. To control this pest, plow the orchard after the leaves have fallen, or rake and burn the fallen leaves. Family LYONETIID^ Fig. 755. — Wings of Bedellia somnulentella. Clemens.) (After Moths with the head smooth, at least on the front. The scape of the antennae usually forms an eye-cap. The ocelli and the maxillary palpi are wanting. The 9^ labial palpi are usually very small. The wings are very narrow (Fig. 755); the hind wings are often linear, with the radial sector ex- tending through the axis of the wing. The apices of the fore wings are usually warped up or down. The larvse are leaf-miners or live in webs between leaves. The following species will serve as examples of this family. The morning-glory leaf -miner, Bedellia somnu- lentella.— The young larva makes a serpentine mine with a central line of frass; later it leaves this mine and makes a blotch mine. The pupa is naked, and fixed by the caudal end to some cross- threads on the under side of the leaf. The adult is yellow and expands about 10 mm. The apple bucculatrix, Bucculdtrix pomifoli- ella. — The larva of this species infests the leaves of apple, and when full-grown it makes a small white cocoon which is attached to the lower sur- face of a twig. These cocoons sometimes occur in great nimibers, side by side, on the twigs of an infested tree (Fig. 756). They are easily recog- nized by their shape, being slender and ribbed lengthwise. It is these cocoons that usually first I'eveal the presence of the pest in an orchard. They are very conspicuous diu-ing the winter, when the leaves are off the trees. At this time each cocoon contains a pupa. The adult moth emerges in early spring. The eggs are laid on the lower sur- face of the leaves. Each larva when it hatches bores directly from the egg to the upper surface of the leaf, where it makes a brown serpentine mine Fig. 756. — Cocoons of Bucculatrix pomifoliella. When these LEPIDOPTERA 617 mines are abundant in a leaf, it turns yellow and dies. When the larva has made a mine from 12 to 1 8 mm. in length, which it does in from four to five days, it eats its way out through the upper surface. Then somewhere on the upper surface of the leaf it weaves a circular silken covering about 2.5 mm. in diameter. Stretched out on this network, the larva, which is now about 2.5 mm. long, makes a small hole in it near the edge, then, as one would turn a somersault, it puts its head into this hole and disappears beneath the silken covering, where it undergoes a change of skin. It remains in the molting cocoon usually less than 24 hours. After leaving this cocoon it feeds upon the leaves without making a mine ; and in a few days makes a second molting cocoon which differs from the first only in being about 3 mm. in diameter. After leaving this it again feeds for a few days, and then migrates to a twig where it makes the long ribbed cocoon within which the pupa state is passed. The adult is a tiny, light brown moth, with the fore wings whitish, tinged with pale yellowish, freely dusted with brown; on the middle of the inner margin there is a dark brown oval patch. The genus Bucculatrix, to which the above species belongs, is placed by some writers in a separate family, the Bucculatrigidcs. The family Opostegid^ has been established for the genus Opostega, of which only three species have been found in this country. These are moths with folded maxillary palpi, with the scape of the antennas forming a large eye-cap, and with radius, media, and cubitus of the fore wings unbranched. The hind wings are linear. The combination of the eye-cap and the unbranched veins of the fore wings is a distinctive feature of this family. The larvae are very slender, cylindrical, without legs, and are bast- miners. Family OINOPHILID^ This family includes "strongly flattened moths, with flat coxse closely appressed to the body, usually with smooth heads, rising to a rounded ridge between the antennae, but often with a loose tuft on the vertex, and rather small maxillary^ palpi of the folded type. The' labial palpi have a well-set-off, fusiform, terminal joint as in the Tineidae, and are normally without bristles. The venation in the known genera is more or less reduced." (Forbes.) Only one species representing this family has been found in our fauna. This is PhcBoses sabinella, described by Forbes ('22), from Louisiana and Mississippi. It is a shining gray-brown (mouse gray) moth, with a wing-expanse of 9 mm. The known larvee of this family feed on decaying vegetable matter and fungi. Family GRACILARIID^ The vestiture of the head varies greatly; the vertex is clothed with prominent scales in some forms, in others it is smooth. The 618 AN INTRODUCTION TO ENTOMOLOGY Fig. 757. — Wings of Gracilaria. (After Spuler.) antennge are long; the scape forms an eye-cap in some species and not in others. The fore wings are lanceolate, normal or with some- what reduced vena- tion (Fig. 757) ; usu- ally without an ac- cessory cell, but sometimes one is pi-esent in the genus Far or nix. i li-j nnid wings are lanceolate or linear; in many members of the family they are ex- panded near the base, formingamore or less prominent hump in the costal margin, and in some species vein Ri is free, not coalesced with vein Sc. The adult moths when at rest elevate the front part of the body, the fore legs being held vertically so that the tips of the wings touch the surface on which the insect rests. The larvas are extraordinary; when young they are very much flattened and have thin, blade-like mandibles and vestigial maxillse and labium ; they merely slash open the cells of the leaf and suck up the cell-sap ; later they usually have normal mouth-parts and eat the parench}Tna. The young larvs always make a flat blotch mine; later they make a blotch mine in which the epidermis of one side of the leaf is thrown into a fold by the growth of the leaf, i. e., a tenti- formmine, or they roll a leaf. The larvse have only fourteen legs or none, never any on the sixth segment of the abdomen. This is a large f amly ; about two hundred North American species have been described, and doubtless many more are to be discovered. About one-half of our described species belong to the genus which is commonly known as Lithocolletis, but which is termed Phyllonoryc- ter by those who recognize the names in the "Tentamen" of Hubner. The following species will serve as an example of this genus. The white-blotch oak-leaf miner, Phyllonorycter hamadryadella. — This little miner infests the leaves of many different species of oaks, and is very common throughout the Atlantic States. The mine is a whitish blotch mine in the upper side of the leaf, and contains a single larva; but often a single leaf contains many of these mines (Fig. 758^ Theyoimg larva is remarkable in resembling more the larva of a beef,:^ than the ordinary type of lepidopterous larvas (Fig. 758, b). It is nearly flat; the first thoracic segment is much larger than any of the others; the body tapers towards the hind end; and there are only the faintest ruaiments of legs discernible. The larvas molt seven times. At the seventh molt the form of the body undergoes a striking change. LEPIDOPTERA 619 It now becomes cylindrical in form, there is a great change in the shape of the mouth-parts, and the fourteen feet are well developed. The full-grown cylindrical larva measures about 5 mm. in length. It spins a cocoon, which is simply a delicate, semi-transparent, circular sheet of white silk, stretched over a part of the floor of the mine. The pupa is dark brown in color, and bears a toothed crest upon its head (Fig. 758, n, o), which enables it doubtless to pierce or Saw its way out from the cocoon. The moth is a delicate little crea- ture, whose wings expand a little more than 6 mm. The fore wings NICHOLS. ENS Fig. 758. — Phyllonorycter hamadryadella: a, mine; b, young larva; c, full-grown, flat-form larva; d, head of same, enlarged; e, antenna of same, enlarged; /, round-form larva from above; g, same from below; h, head of same, enlarged; i, antenna of same, enlarged; k, maxilla and palpus of same, enlarged; /, labium, labial palpi, and spinnerets of same; m, pupa; 11, side view of pupal crest; o, front view of same; q, cocoon; Q, moth. (From the author's Report for 1879.) are white, with three, broad, irregular, bronze bands across each, and each band is bordered with black on the inner side. The hind wings are silve^!>^ As this insect passes the winter as a larva within the dry leaves, the best way to check its ravages when it becomes a pest is to rake up and bum such leaves. Another common oak-leaf miner in the East is Phyllonorycter cincinnatiella. The larv« form large blotch mines on the upper surface of leaves. In this species the larvae are social, one mine often containing from several to a dozen larvee. The loosened epidermis is brownish yellow, somewhat puckered, and often covers nearly the 620 AN INTRODUCTION TO ENTOMOLOGY entire leaf. This species like most other gracilariids passes the winter as pupae. A common miner in the leaves of locust is Parectopa robiniella. The larv^a makes on the upper surface of the leaf what has been termed a digitate mine, that is a blotch mine with a number of lateral galleries running out from it on each side. Several members of this family make tentiform mines in the leaves of apple and other fruit trees; but these species are rarely of economic importance. Family COLEOPHORID^* Moths with a smooth head, without ocelli, and without maxillary palpi. The labial palpi are of moderate size. The antennas are held extended forward in repose. The wings are very narrow. The discal Fig- 759- — Wings of Coleophora laricella. cell of the fore wing extends obliquely ; vein Cui and vein Cuo when present are ver>^ short (Fig. 759). The larvas are usually leaf-miners when young or feed within seeds; later, with few exceptions, they are case-bearers. Nearly all of our species belong to the genus Coleophora, of which about ninety species have been found in this country. The two follow- ing species are those that have attracted most attention on account of their economic importance. The pistol case-bearer, Coleophora malivorella. — The larva of this species infests apple especially but is also found on quince, plum, and cherry. The larvse hatch in mid-summer from eggs laid on the leaves and eat little holes in the leaves. They soon construct little pistol- *The typical genus of this family is commonly known as Coleophora, the name used for it by Hiibner in his "Tentamen." But those writers who do not recognize the "Tentamen" as a published work use the later name Haploptilia for the genus, and name the family the Haploptiliid^. LEPIDOPTERA 621 shaped cases composed of silk, the pubescence of leaves, and excre- ment. The larva projects itself out from the case far enough to get a foothold and eats irregular holes in the leaf, holding the case at a considerable angle with the leaf. About Sep- tember first the larvas migrate to the twigs where they fasten the cases to the bark (Fig. 760) and hibernate till April, spending about seven months in hiber- nation. They then pass to the swelling buds, expanding leaves and flowers, where they continue feeding. They become full-grown in the latter part of May, and then fasten their cases to the smaller branches. After the case is fastened to the branch the larva turns around in it, and changes to a pupa; conse- quently the moth emerges from the curved end of the case. The cigar case-bearer, Coleo- phora fletcherella. — This species, like the preceding one, is a pest of apple and other fruit trees, and resembles that species to a con- siderable extent in habits. In this species the young larvse are miners in the leaves for two or three weeks before making their cases. The case (Fig. 761) is com.- posed of fragments of leaves fastened together by silk. Fig. 760. — Coleophora malivorella: a, apple twig showing larval cases and work on leaves; b, larva; c, pupa; d, moth; b, c, d, enlarged. (After Riley.) Fig. 7C1. — Cases of the cigar case bearer. (After Hammar.) Family ELACHISTID^ The head is smooth. The scape of the antenna3 does not form an ej^e-cap. The venation is but slightly reduced (Fig. 762). The hind wings are lanceolate, with a well formed discal cell. The larvse have sixteen legs. Most of the known species make blotch mines in grasses. And some at least when full-grown leave 622 AN INTRODUCTION TO ENTOMOLOGY Fig. 762. — Wings of ElacJiista guadrella. (After Spuler.) the mine and weave a slight web from which the pupa hangs sus- pended, Hke the pupa of a butterfly. This is a small family ; most of our species belong to the genus ElacJnsta. Family HELIOZELID^ The antennae are from one-half to two-thirds as long as the front wings; the scape is short and not enlarged so as to form an eye-cap. The wings (Fig. 763) are lan- ceolate; in the hind wings there is no discal cell, owing to the coales- cence of the radial sector and media for nearly the entire length of the wing, vein Rs sep- arating near the apex of the wing. The habits of " the larvae are well- illustrated by the following species. The resplendent shield -bearer, Cop- todisca splendorif- erella. — This spe- cies infests the leaves of apple, pear, quince, thom- apple, and wild cherry. The larva is both a miner and a case-bearer. It at first makes a linear Fig mine; but later this is enlarged into a blotch mine. When full-grown the larva makes an oval case cut from the walls of its mine and lined with silk. It then seeks a safe place in which to fasten this case. This is usually on the trunk or on a branch of the infested tree (Fig. 764, d). There are two genera- tions annually. The second generation pass the winter as larvae ^^ 763- ler.) Wings of Antispila pfeifferella. (After Spu- LEPIDOPTERA 623 within their cases. The adult (Fig. 764, g), is a brilHantly colored, golden-headed moth. The basal half of the front wings is leaden- gray with a resplendent luster and the remainder golden with silvery and dark brown streaks. It expands about 5 mm. Fig. 764. — Coptodisca splendoriferella: a, leaf of apple showing work; b, summer larva: c, larva in case travelling; d, cases tied up for winter; e, hibernating larva; /, pupa; g, moth, h, parasite. (From the Author's report for 1879.) The sour gum case-cutter, AntispUa nysscefoUella. — This species infests the leaves of Nyssa syhatica. Its habits are similar to those of the preceding species. Family DOUGLASIID^ The scape of the antennge is small and does not form an eye-cap. The first segment of the labial palpi is small. The ocelli are large. The hind wings are lanceolate and without a discal cell, owing to the coalescence of the radial sector and media. Vein Rg sep- arates from media near the middle of the length of the wing (Fig. 765). 624 AN INTRODUCTION TO ENTOMOLOGY This family is represented in this country by a single species, Tindgma obscuro- fasciella, the larva of which is a leaf- miner in Rosaceae. Family CECOPHORID^ The head is usu- ally smooth, with appressed scales; sometimes with loose scales and spreading side tufts. The antennae usu- The labial palpi are well- (After Fig. 765. — Wings of Tinag7na obscurofasciella. Chambers.) ally have a comb of bristles on the scape. developed, generally curved upward ; the terminal segment is acute- ly pointed. The maxillary palpi are vestigial. The wings are fairly broad, sometimes ample Sc /? Fig. 766. — Wings of Depressaria herachana. (Fig. 766). The venation is but little reduced. In the fore wings veins R4 and R5 are stalked or co- alesce throughout; veins R2 and Cu2 arise well back from the end of the discal cell; and vein ist A is preserved. In the hind wings veins Rs and Ml are well separated and extend parallel. The posterior tibiae are cloth- ed with rough hairs above. The larvae have sixteen legs ; they are often prettily marked with dark tubercles on whitish or yellowish ground. The different species vary in their habits; the majority of them either live in webbed- together leaves or blossoms or feed in decayed wood; one species, Endrosis lacteella, is a stored-food pest in California and in Europe. About one hundred species have been described from our fauna; many of them are common. A generic revision of the American species was published by Busck ('09 a). The following one is a well- known pest. The parsnip webworm, Depressaria heraclidna. — The larvae of this species web together and devour the unfolding blossom-heads of parsnip, celery, and wild carrot. After the larvee have consumed the flowers and unripe seeds and become nearly full-grown, they burrow LEPIDOPTERA 625 into the hollow stems and feed upon the soft lining of the interior. Here inside the hollow stem they change to pupas. The moths appear in late July and early August, and soon go into hibernation in sheltered places. Family ETHMIID^ This family includes a small number of moths, which were former- ly included in the family CEcophoridas. The family Ethmiidae was established by Busck ('09b), who states that the main structural character of the imago by which this family can be distinguished from the CEcophoridae is the proximity of vein M2 in the hind wings to vein Ml instead of to vein M3 as in the CEcophoridae, it being radial not cubital. Fracker ('15) describes larv^al characters distinctive of the typical genus Ethmia. The members of this family have broad wings. The fore wings are usually bright colored, with striking patterns, often black and white. The larvae, as a rule, are social, living in a light web. They feed chiefly on plants of the family Borraginaceae. ^ Most of the species belong to the genus Ethmia of which about thirty are now known. Family STENOMID^ This family includes large moths as compared with most "micros." The wings are broad, especially the hind wings. In the fore wings all of the branches of the branched veins are typically present. In the hind wings vein Mi is joined at its base to vein Rg. The larvae live in webs on leaves, especially of oak. There are about twenty North American species, most of which belong to the genus Stenoma. A common species in the Atlantic States is Stenoma schlcegeri. This is one of our larger species, having a wing-expanse of 30 mm. The moth is of a dirty white color with the fore wings mottled with darker bands and spots, and with a conspicuous patch of brown scales near the base of the inner margin. When at rest on a leaf the insect folds its wings closely about its body, and resembles in a striking manner the excrement of a bird. Family GELECHIID^ The head is smooth or at most slightly ruffled. The labial palpi are long, curved, ascending, and usually with the terminal seg- ment acutely pointed. The maxillary palpi are vestigial or wanting. The venation of the wings (Fig. 767) is more or less reduced; the stem of vein M is wanting; vein ist A is wanting in the fore wings; and sometimes in the hind wings also. In the fore wings the second anal vein is forked at the base, i. e., the tip of the third anal vein 62G AN INTRODUCTION TO ENTOMOLOGY Fig. 767. — Wings of Pectinophom gossypiella. (After Busck.) unites with it ; and in some forms, veins R4 and R5 coalesce through- out their length , but they are usually stalked. The hind wings are usually more or less trape- zoidal; and the outer margin is usually sinuate or emarginate below the apex. The larv^ae vary greatly in habits ; some are leaf-min- ers; but more feed in rolled or spun to- gether leaves or in stems or seed heads; and one is a serious pest of stored grain. This is the larg- est family of the Microf renatac ; more than four hundred species have been described from our fauna. A revision of the American moths of this family was published by Busck ('03). The Angou- mois grain-moth , Sitotroga cerealel- la. — The larva of this moth feeds upon seeds, and especially upon stored grain. It occurs through- out our country; but it is especial- ly destructive in the Southern States. In that part of the coun- try it is extreme- ly difficult to keep grain long on account of this pest and cer- Fig. 768. — Paraleckia pinifoliella: larva, pupa, adult, and leaves mined by the larva. (From the Author's Report for 1879.) LEPIDOPTERA 627 tain beetles that also feed on stored grain. The adult moth is of a very light grayish-brown color, more or less spotted with black; it expands about 1 2 mm. The common name is derived from the fact that it has been very destructive in the province of Angoumois, France. The most effective method of destroying this pest is by the use of carbon bisulphide in the manner in which it is used against the grain-weevils, already described. The pine-leaf miner, Paralechia pinifoliella. — It often happens that the ends of the leaves of pine present a dead and brown appear- ance that is due to the interior of the leaf having been eaten out. This is the work of the pine-leaf miner (Fig. 768). At the right season it is easy to see the long, slender larva in its snug retreat by holding a leaf up to the light and looking through it ; and later the pupa can be seen in the same way. Near the lower end of the tunnel in each leaf there is a round hole through which the larva entered the leaf and from which the adult emerges. We have found this insect in several of the stouter-leaved species of pine, but never in the slender leaves of the white pine. In the North it is most abundant in the leaves of pitch-pine. The peach twig-borer, Anarsia line- atella. — This pest is generally distribut- ed throughout the United States and Canada, and sometimes it destroys a large part of the crop in some localities. The young larvee hibernate in small cavities which they excavate in the bark of young twigs. In the spring the larvae burrow into the tender shoots; the leaves of the buds unfold and then wither. There are several generations annually. The summer generations attack both twigs and fruit. The solidago gall-moth, Gnorimo- schema gallcBsolidaginis . — There are two kinds of conspicuous galls which are enlargements of the stems of golden-rod; one of these is a ball-like enlargement of the stem and is caused by the larva of a fly, Eurosta solidaginis, described in the next chapter ; the other is spindle-shaped (Fig. 769) and is caused by the moth named above. The eggs are laid on the old plants in the fall and hatch in spring. The young larva crawls to a new shoot and boring down into it causes the growth of the gall. The larva becomes full-grown about the middle of July; then before changing to a pupa it eats a passage-way through the wall of the gall at its upper end, and closes the opening Fig. 769. — Gall of the solidago gall-moth. (After Riley.) 628 AN INTRODUCTION TO ENTOMOLOGY with a plug of silk, which is so formed that it can be pushed out by the adult moth when it is ready to emerge. Some members of the family are leaf-rollers. Figure 770 represents aj°nf rol^M by a gelechiid larva, probably Anacampsis innocuella. This species infests poplar. The pink bollworm, Pectinophora gossypiella. — This species is regarded as one of the most destructive cotton insects known and ranks among the half-dozen most important insect pests of the world. It often reduces the yield of lint fifty per cent, or more and materially lessens the amount of oil obtained from the seeds. The adult is a small dark-brown moth, with a wing- expanse of from 15 to 20 mm. Figure 767 represents the shape and the venation of the wings. The larva eats the seeds and tunnels and soils the lint, causing the arrest of growth and the rotting or premature and imperfect opening of the boll (Busck). A detailed account of this pest, illustrated by many figures was published by Busck ('17). Family BLASTOBASID^ Fig. 770-— Leaf rolled by a gele- chiid larva. The scape of the antennae is armed with a fringe of strong bristles, or pecten. The labial palpi are slender and upturned or vestigial. The discal cell of the fore wings (Fig. 771) is long compared with the lengths of the apical veins (R2 to CU2); and these veins arise from the extreme end of the cell. As vein Ri arises near the base of the wing it is unusually distant from vein R2 ; to make up for the resulting weakening of the wing, the membrane is more or less thickened along the costa; this thickening is the so-called stigma. The hind wings are lanceolate, and rather narrower than the fore wings. Veins Rs and Mi are well separated at the end of the discal cell. Veins M2, AI3 and Cui are close together or coincident. About one himdred species have been described from our fauna; among them are the following. The acom-moth, Valentmia glandulella. — The larva of this species lives as a scavenger in acorns that have been destroyed by acorn- weevils Balaninus. The moth lays an egg in the destro3^ed acorn after the beetle has left it, and the larva hatching from this egg feeds upon the cnrnibs left by the former occupant. The larva passes the winter within the acorn. The moths emerge at various times throughout the simimer. LEPIDOPTERA 629 The oak-coccid blastobasid, Zenoddchitim coccivorella. — The larva is an internal parasite in the gall-like females of the coccid genus Kermes. I found it common at Cedar Keys, Fla. ^"^^ J si A 0<2 Cu, Ah Fig. 771. — Wings of Holcocera. (After Forbes.) Family COSMOPTERYGID^ The moths grouped together in this family vary greatly in structure. The fore wings are lanceolate, sometimes caudate, i. e. with the apex greatly prolonged. Vein ist A arises out of vein 2d A or is lost. The hind wings are lanceolate or linear. Vein Ri is occasionally separate from vein Sc. Veins Rs and Mi are close together. The following species will serve as examples of members of this famih'. The palmetto-leaf miner, Homaledra sabalella. — ^This species oc- curs only in the South where the saw-palmetto grows; but it is of general interest as illustrating a peculiar type of larval habit. The larvae can hardly be said to be leaf -miners; for they feed upon the upper surface of the leaf, destroying the skin as well as the fleshy part of the leaf. They are social, working together in small comi^anies, and make a nest consisting of a delicate sheet of silk covering that part of the leaf upon which they are feeding; this sheet is covered with what appears like sawdust, but which is really a mass of the droppings of the larvee (Fig. 772). The full-grown larva attains a length of 12 mm. The pupa state is passed within the nest made by the larvce. The moth expands 1 5 mm. Its general color is a delicate silvery gray, with a tinge of lavender in some individuals. The cat-tail moth, LymncBcia phragmitella. — The larva of this species feeds in the heads of cat-tail, Typha. It winters in the head, which presents a tattered and frayed appearance. The larv^ spin an abundance of silk, thereby tying the down or pappus together and 630 AN INTRODUCTION TO ENTOMOLOGY keeping it from blowing away. The overwintering larvae are half- grown. When full-grown some transform in the heads, but many go down and bore in the stems and transform there. Cosmopteryx. — "The little moths belonging to the genus Cos- mopteryx are probably familiar to anyone who has collected and ob- served insects in nature. Who has not occasionally on a warm mid- simimer day met with a slender little streak of gold and silver sitting in the sunshine on a leaf in a protected comer and twirling its long white-tipped antennas in graceful motions If, when examined more closely, it is found to be a smooth shining little moth, brown with silvery lines on palpi and antennae, and with a striking broad golden / . ll.(UUBHOl.a.EKti Fig. 772. — Homaledra sabalella: larva, pupa, adult, and part of injured leaf. (From the Author's Report for 1879.) or orange fascia across the outer half of the wing, bordered on both sides by bright metallic scales, then you have a Cosmopteryx." "The larvee are leaf-miners, and the mines are easily distinguished from most others by the scrupulous cleanliness with which the larva ejects all its frass through a hole, so that the mine remains clear and white. At maturity the larva changes its color from green to a vivid purple or wine-red, leaves the mine, and spins a matted flattened cocoon of silk." (Busck '06). Among the better-known members of this family are the following : Stagmatophora gleditschiceella. — The larva burrows in the thorns of locust. Monipha ehisella. — There are several species of Mompha that infest the fruit and pith of the evening primrose. The best-known of these is this one. Psacdphora terminella. — The larva is a miner in willow-herb, Epilobium. LEPIDOPTERA 631 Family SCYTHRIDID^ This family includes a group of genera that are closely allied to the Yponomeutidse and are included in that family by some writers. I do not find that any tangible characters of the adult insects separat- ing the two families have been pointed out ; but there appear to be diifferences in the setal characters of the larvae (see Fracker '15). The family is represented in our fauna by only two genera, Scythris and Epermenia, including twenty-two species. None of these species has attracted attention on account of its economic importance. The larva? of Scythris magnatella feed on Epilobium. They are solitary when small, folding over half of the leaf to the midrib in the central part of its length, attached with web. Later they form con- siderable web among the leaves. The pupa is formed in a delicate, flossv web. (D3^ar). The larva of Epermenia pimpinella feeds by forming a puffy mine on Pimpinella integerrima. The pupa is inclosed in a frail, open- meshed cocoon on the under side of a leaf or in angles of leaf-stalks. (Murtfeldt.) One of the more common representatives of this family is Scythris eboracensis. The adult is a small black moth tinged with violet, with a wing-expanse of about 10 mm. It is found on flowers. Family YPONOMEUTID^* In this family the ocelli are small or absent. In the more typical forms the wings are comparatively broad, with the venation but little reduced. In the fore wings all of the branches of the branched veins are usually separate, and vein R5 extends to the outer margin. In the hind wings veins Rs and Mi are well-separated. The first anal vein is distinct in both fore and hind wings. Writers differ greatly as to the limits of this family ; some include in it certain genera or groups of genera that by others are regarded as distinct families. In its restricted sense the family Yponomeutidas includes about fifty North American species; among these are the following. The cedar tineid, Argyresthia thuiella. — This is a small narrow- winged moth, which expands about 8 mm. Its ground color is pearly- white, with the fore wings dotted and marked with brown, especially on the outer half of the wing. The larva feeds on the leaves of cedar, and when full-grown spins a small, conspicuous white cocoon attached to a leaf. The apple fruit-miner, Argyresthia conjugella. — The larva of this species is a serious pest in the apple orchards of western Canada. It is pinkish white in color and about 9 mm. in length. It burrows in all directions through the fruit, causing it to deca3^ The winter is passed in the pupal state. The cocoons are made under the bark on the trunk of the tree or under leaves on the ground ; they are white, *An emended form of this family name, Hyponomeutidae, is used by some writers. 632 AN INTRODUCTION TO ENTOMOLOGY and the outer layers have the threads arranged so as to form a beautiful openwork pattern. The adult moth has a wing-expanse of about 12 mm. It is figured by Slingerland and Crosby ('14). _ The suspended lace-cocoon, Urodus pdrvnla. — This beautiful cocoon (Fig. 773) is not uncommon in Florida. It is found in various situations. I found the specimen figured here attached to an orange leaf. The adult is a brownish moth without markings and with a wing-expanse of 28 mm. The ailanthus webworm, Atteva aurea.- — The lar- vas live in communities within a slight sillcen web on the Ailanthus; they feed on the leaves and also gnaw the leaf-stalks in two. When the larva is full- grown it suspends itself in the middle of a loose web and transforms there. The adults appear in Sep- tember and October and pass the winter in this state. The adult is very striking in appearance. The fore wings are bright marigold -yellow with four bands of round pale sulphur-yellow spots upon a brilliant steel-blue ground. The hind wings are transparent, with a dusky margin and blackish veins. The wing- expanse is about 25 mm. The ermine-moths, Yponomeuta.- — There are several species of the typical genus of this family that have received the common name ermine-moths, because of the color of their fore wings, which are snowy white dotted with black. One of these, Yponomeuta padella, is an introduced species which is an apple and cherry pest. The larv£e live in a common web, and in this they spin their cocoons. The name ermine-moths is applied also, especially in England, to some of the Arctiidae that are white spotted with black. Fig. 77.-^ -—Co- coon of Uro- dus panmla Family PLUTELLID^ This family is closely allied to the Yponomeutids and is regarded by many writers as a subfamily of that family. These moths differ from the Yponomeutidfe in that they hold the antennae extended forward in repose; in this respect they resemble the Coleophoridae. The larvae differ from those cf the Yponomeutidffi and the Scythrididffi in that their prolegs are longer than wide. About fifty North American species have been described; these represent nine genera. The most important species from an economic standpoint is the following one. The diamond-back moth, Plutella maculipennis .■ — -The larva of this species infests cabbage and other cruciferous plants, eating holes of variable size and irregular form in the leaves. It is sometimes also a pest in greenhouses, infesting stocks, wall-flowers, sweet alyssum, and candytuft. The larva when full-grown spins a lace-like cocoon attached to a leaf. The moth expands about 15 mm. The fore wing.s LEPIDOPTERA 633 Fig. 774. — Wings of Glvphiptervx thrasonella. (After Spuler.) of the male are ash-colored, with a yellow stripe outlined by a wavy dark line extending along the inner margin. When the wings are closed, the united yellow stripes form a row of three diamond-shaped markings. These sug- gested the common name of the species. In the female the front wings are a nearly uniform gray . The hind wings in both sexes are a dull gray. Family GLYPHIPTERYGID^ The ocelli are usualh* large. The maxillae are strong and clothed with scales. The maxillary palpi are vestigial or wanting. The labial pal- pi are upturned to the middle of the front or beyond, often beyond the vertex. In the fore wings veins R4 and R5 are usually separate and vein Cu2 arises close to the angle of the discal cell. In the hind wings the second anal vein is strongly forked at the base. Nearly forty North American species are now known. These represent two subfamilies. Subfamily Glyphipterygi- N^. — This subfamily is composed chiefly of the species of the genus Glyplnpteryx. In this genus the wings are moderately broad (Fig. 774) and the fore wings have a lobe-like prolongation between veins R4 and R5. Ten species are now listed from our fauna. Subfamily Choreutin^. — In this subfamily the wings are broad and triangular (Fig. 775), and usually with narrow fringes. The moths bear a stril-cing re- semblance to tortricids. The lar- vae live under webs on leaves or Fig. 775. — Wings of Simcethis fabriciana. (After Spuler.) between leaves that are fastened together. 634 AN INRTODUCTION TO ENTOMOLOGY Family HELIODINID^ The hind wings are narrow-lanceolate and pointed or linear and much narrower than their fringe. The maxillary palpi are minute and porrect. The labial palpi are very short and drooping. The maxillae are strong. The tarsi are armed with more or less distinct whorls of bristles; the tibiee are also often armed with stiff bristles. Usually when at rest the imago holds the posterior pair of legs ele- vated at the sides above the wings. The larvae are not well-known; those that have been described are of various habits. Cycloplasis panicijoliella. — The larva of this species mines in grass, Panicum clandestinum. Its mine is at first a long thread-like line; towards the latter part of the life of the larva it is enlarged into a blotch. When the larva has reached maturity, it cuts a perfectly circular disk from the upper cuticle of the leaf, folds it along its di- ameter and unites the edges of the circumference, so as to make a semicircle. When completed the larva, enclosed in its semicircular cocoon, lets itself fall to the ground, where it attaches the cocoon to some adjacent object. (Clemens). Schreckensteinia erythriella. — The larva feeds on sumac bobs. It is common; the body is uniform dark green, but the frass is scarlet. When full-grown it makes a lace-like cocoon on the outside of the bob. Schreckensteinia Jestaliella. — ^The larva of this species is an external feeder on Rubus; it is spiny, and when full- grown makes a lace- like cocoon. Euclemensia basset- tella. — The larva is an internal parasite in the gall-like females of the coccid genus Kernies. The adult is a beauti- ful greenish-black moth, which has its fore wings marked Fig. 776. — Euclemensia bassettella. with reddish orange (Fig. 776). The genus Euclemensia is placed in this family provisionally. Family ^GERIID^ The Clear-winged Moths The clear-winged moths constitute a very remarK- able family, many of them resembling bees or wasps in appearance more than they do ordinary moths, a resemblance due to their clear wings and in some cases to their bright colors (Fig. 777). There are a few moths in other families, as the Fig. 777. LEPIDOPTERA 635 clear-winged sphinxes and certain euchromiids, that have a greater or less part of the wings devoid of scales; but they are exceptions. Plere it is the rule that the greater part of one or both pairs of wings are free from scales; hence the common name, clear-winged moths. In a small nimiber of members of this family the wings are scaled throughout. These insects are of moderate size; as a rule they have spindle- shaped antennae, which are terminated by a small silky tuft; some- times the antennas are pectinate; the margins of the wings and the veins of even the clear-winged species are clothed with scales; and at the end of the abdomen there is a fan-like tuft of scales. 2d A Fig. 778. — Wings of Synanthedon exitiosa. The fore wings are remarkable for their extreme narrowness and the great reduction of the anal area (Fig. 778) ; while the hind wings have a widely expanded anal area. The number of anal veins in the hind wings varies greatly within the family, the number ranging from two to four; where there are four anal veins, it is probably the third anal vein that is forked. Another remarkable feature of the wings of these insects is that in the female the bristles composing the frenulvmi are consolidated as in the male; this condition exists in the females of a few members of other families. The females of the ^geriidae possess a frenulimi hook; but this is not so highly specialized as that of the male. In addition to the presence of a highly specialiied frenulum and a frenulum-hook, there is a unique provision for holding the fore and hind wings together. The inner margin of the fore wing is 636 AN INTRODUCTION TO ENTOMOLOGY folded under; and the radius of the hind wing is armed with setae, which hook into this fold. The adults fly very swiftly and during the hotter part of the day. They frequent flowers thus increasing their resemblance to bees or to wasps. The larvag are borers, living within the more solid parts of plants. Some species cause serious injury to cultivated plants. More than one hundred species have been found in America north of Mexico. Among the better known species are the following. The blackberr}^ crown-borer or the raspberry root-borer, Bembecia margindta. — The larva of this species burrows in the roots and lower part of the canes of blackberries and raspberries, sometimes completely girdling the cane at the crown. The peach-tree borer, Synanthedon exitidsa. — This is the most important enemy of the peach-tree,except perhaps the San Jose scale in the North and the plum curculio in the South. In some parts of the country it is difficult to find a peach-tree that is not infested by it. The eggs are laid on the bark of the tree near the ground. The larvae bore downward in the bark of the trunk just below the surface of the ground. Their bun^ows become filled by a gummy secretion of the tree. As this oozes out in large masses the presence of the borer is easily detected by it. The insect always passes the winter in the larval state. When full-grown the larva comes to the surface of the ground and makes a cocoon of borings fastened together with silk. The perfect insects appear from May till October; -^ ^ the date at which most of them appear varies in ^j^^y^-^^^^^^ different sections of the country. There is a ^^^StAt^^^ single generation each year. The adults differ ^^^^jH^^^^ greatly in appearance. The general color of |W| both sexes is a glassy steel-blue. In the female ' V ' (Fig- 779) the fore wings are covered with scales, pjg_ jyg-Svtianthedon ^^^ there is a bright orange-colored band on the exitiosa , female. abdomen. In the male both pairs of wings are nearly free from scales. The usual method of fighting this pest is to carefully watch the trees and remove the larvas with a knife as soon as discovered. Recently the use of a toxic gas, paradichlorobenzene, has been found available on trees six years of age and older; and experiments are now being made to determine the practicability of its use on younger trees. See U. S. Dept. of Agr. Bull. 1 1 69, and later bulletins when pubHshed. The Pacific peach-tree borer, Synanthedon opalescens. — On the Pacific Coast there is a peach-tree boier that is distinct from the above, and appears to be an even more serious pest. The larva is more difficult to remove from the tree, as it bores into the solid wood. The female of this species lacks the orange-colored band on the abdomen. _ The lesser peach-tree borer, Synanthedon ptctipes. — ^The larvce of this species infest peach, plum, cherry, june-berry, beach-plum, and chestnut. They do not confine their attacks to the crown but more LEPIDOPTERA 637 often occur on the trunk and larger branches. This borer rarely attacks perfectly sound, uninjured trees and is not a serious pest in orchards that receive good care. Both sexes of the adult resemble the male of the peach-tree borer, having both fore and hind wings transparent. The imported currant borer, Chamxsphecia tipulijormis. — This is a small species, the adult having a wing-expanse of only about i8 mm. There are but few scales on either pair of wings except on the tip and discal vein of the fore wings and the outer margin of the hind wings. The eggs are laid on the twigs of currant. The larvae penetrate the stem, and devour the pith ; in this way they make a burrow in which they live and undergo their transformations. The perfect insects appear in June. Before this time the leaves of the infested plant turn yellow. If such plants be cut and burned in May the pest will be destroyed. The squash-vine borer, MelUtia satyriniformis . — The larva of this species (Fig. 780) does great damage by eating the interior of squash- vines; it also sometimes in- fests pump- kin-vines and those of cu- cumber and melon. It is most destruc- tive to late squash es . When full- grown the lar- vae leave the vines and enter the ground, where they make tough silken cocoons, a short distance below the surface, in which the winter is passed. The adults appear soon after their food-plants start growth. The fore wings of the adult are covered with scales and the hind legs are fringed with long, orange-colored scales. To check the ravages of this pest, the vines should be collected and destroyed as soon as the crop is harvested in order to destroy the larvae that are still in them; the land should be harrowed in the fall to expose the cocoons and then plowed deeply the following spring in order to bury them so deeply that the moths can not emerge. If the vine is covered with earth two or three feet from its base it will produce a new root system which will sustain the plant in case the main stem is injured at the base. Where late squashes are grown early squashes can be used as trap plants. Borers can be removed from the vines with a knife; when this is done the vine should be cut lengthwise, and, after the larva is removed, the vine covered with earth; if this is done carefully the wound will soon heal. The pine clear-wing moth, Parharmonia plni. — Frequently there may be seen on the trunks of pine-trees large masses of resinous gum -jSo.—Mclittia ifiiformis, squash-vine 638 AN INTRODUCTION TO ENTOMOLOGY mingled with sawdust-like matter. These are the results of the work of the larvee of this insect, which bore under the bark and into the superficial layers of the wood. The adult resembles the female of the peach-tree borer, but the abdomen is more extensively marked with orange beneath. Sc R^_R, R. /?. SUPERFAMILY TORTRICOIDEA The Tortricids The tortricids are generally small moths ; but as a rule they are larger than the mem- bers of most of the families of the Micro- frenatas. They have broad front wings, which usually end squarely. The costa of the front wings curves forward strong- ly near the base of the wing. When at rest the broad front wings fold above the body like a roof. The moths are variegated in color, but are usually brown, gray, or golden rather than of brighter hues. As a rule the hind wings are of the color of the body and without markings. The venation of the wings of a common species is represented by Figure 781. The larvEe vary greatly in habits. Many of them are leaf-rolleis. It was this habit that suggested the name Tortrix for the typical genus, from which the names of one family and of the superfamily are derived. A large portion of the rolled leaves found upon shrubs and trees are homes of tortricid larvse ; but it should be remembered that the leaf-roUing habit is not confined to this family. While many are leaf-rollers probably a larger number are borers in stems, buds, or fruits. About eight hundred North American species of the Tortricoidea have been decribed. This superfamily includes four families, which, can be separated by the following table. A. Both veins IMi and M2 of the hind wings lost. p. 644 Carposinid^ AA. Vein Wi of the hind wings present , vein M2 either present or lost. B. With a fringe of long hairs on the basal part of vein Cu of the hind wings, on the upper side of the wing. Do not mistake a bunch of long hairs arising from the wing back of vein Cu for this fringe. S^^ 2d A Fig. 781. — Wings of Ar chips cerasivorana. LEPIDOPTERA 639 C. Fore wings with veins R4 and R; stalked or united, veins M2, M.,, and Cui diverging or parallel. (A few species only), p. 642 ..... TortriciDvE CC. Fore wings with veins R4 and Rj separate, or with veins AL, M3, and Cui converging strongly toward the margin of the wing. p. 639 Olethreutid.^ BB. Without a fringe of long hairs on the basal part of vein Cu of the hind wings. C. Fore wings with the distal part at least of vein istA preserved. Vein Cu3 of the fore wings arising from a point before the outer fourth of the discal cell. D. Veins AIi and M2 of the fore wings somewhat approximate at the margin of the wing {Laspeyresia lautana) p. 639 Olethreutid^ DD. Veins Mi and M2 of the fore wings divergent or parallel, p. 642 TORTRICID^ CC. Both fore and hind wings with vein istA lost, vein Cu, of the fore wings arising from the outer fourth of the discal cell. p. 643 Phaloniid^ Family OLETHREUTID^* As a rule the members of this family are easily distinguished from all other tortricids by the presence of a fringe of long hairs on the basal part of cubitus of the hind wings, on the upper side of the wing. This fringe is lacking in a few members of this family and is present in a few members of the next family. This is the largest of the famihes of tortricids; more than four hundred North American species have been described. The following species are among those most likely to be observed, and will serve to illustrate the differences in habits of the different species. The codlin-moth, Carpocapsa pomoijella.— This is the best known and probably the most important insect enemy of the apple. The larva is the worm found feeding near the core of wormy apples. The adult (Fig. 782) is a beautiful little creature with finely mottled pale gray or rosy fore wings. There is a large brownish spot near the end of the fore wing, and upon this spot irregular, golden bands. The moth issues from the pupa state Fig. 782.— Car- in late spring and lays its eggs singly on the surface tnTlla'^ "' of the frtiit or on adjacent leaves. As soon as the larva hatches it burrows into the apple and eats its way to the core, usually causing the fruit to fall prematurely. When full grown the larva burrows out through the side of the fruit, and undergoes its transformations within a cocoon, under the rough bark of the tree, or in some other protected place. The number of generations annually varies in different parts of the country. As a rule there is in the North one full generation and usually a partial second ; where the season is longer there are two or three generations. The larvffi winter in their cocoons transforming to pupas during early spring. The method of combating this pest that is most commonly em- ployed now is to spray the trees with a solution of arsenate of lead, four to six pounds of arsenate of lead in one hundred gallons of water, just after the petals fall and before the young apples are heavy *This family is the Eucosmidse of some writers, and the Epiblemidas of others. 640 AN INTRODUCTION TO ENTOMOLOGY enough to droop. The fahing spray lodges in the blossom end of the young apple, and many of the larvas which attempt to enter at this point, the usual place of entrance, get a dose of poison with their first meal. The pine-twig moths, Evetria.- — -The genus Eve- rtia includes many spe- cies that infest the twigs and smaller branches of various species of pine. Some of our best known species were described under the generic name Retiuia but now the old- er name Evetria is applied to them. The following species are well-known. Evetria comstockidna. — This species (Fig. 783) illustrates well the hab- its of the boring species. The larva inf eststhe small branches of pitch-pine. It is a yellowish-brown caterpillar, which makes a burrow along the cen- tre of the branch. Its presence may be detect- ed by the resin that flows out of the wound in the twig and hardens into a lump. Two of these lumps are shown in the figure, one of them split lengthwise, and the oth- er with a pupa-skin pro- jecting from it. The lar- va, pupa, and adult are also figured. The moth Fig. 783. — Evetria. coinstockiana: larva, pupa, adult, and work. (From the Author's Report for 1879.) is represented natural size; the darker shades are dark rust-color, and the lighter, light-gray. The insect winters as a lar\^a; the adult emerges in May and June. Evetria frustr ana: — This species infests the new growth of several species of pine, spinning a delicate web around the terminal bud, and mining both the twig and the bases of the leaves. The larva, pupa, and adult are represented somewhat enlarged in the figure. An in- fested twig is also shown (Fig. 784). The grape-berry moth, Polychrosis vttedna.— The most common cause of wormy grapes is the larva of this moth. The moth emerges LEPIDOPTERA 641 in the spring from its cocoon on a fallen leaf where it has passed the winter in the pupa state. The first generation of larvas make a slight web among the blossom buds into which they eat destroying many embryo grapes. When full-grown the larva passes to a leaf and makes a very peculiar cocoon. It cuts a semicircular incision in the leaf, bends over the flap thus made, fastens its free edge to the leaf, and lines the cavity thus enclosed with silk; here it trans- forms to a pupa. The moths of the second and later generations lay their eggs on the berries, and the larvag bore into them and feed on the pulp and seeds. The most efficient method of control of this pest is by spraying with a solution of arsenate of lead, six pounds of the poison in one hun- dred gallons of water. The first applica- tion should be made shortly after the fruit sets, and one or two more at intervals of ten days. The bud-moth, Tmetocera ocelldna. — The larva of this insect is a pest infesting apple-trees. It works in opening fruit-buds and leaf-buds, often eating into them, especially the terminal ones, so that all new growth is stopped. It also ties the young leaves at the end of a shoot to- gether and lives within the cluster thus formed, adding other leaves when more food is needed. Sometimes so large a proportion of the fruit-buds are destroyed as to seriously reduce the amount of the crop. The pupa state is passed within the cluster of tied leaves or within a tube formed by rolling up one side of a leaf, and lasts about ten days. The moth expands about 1 5 mm. ; it is of a dark ashen gray, with a large, irregular, whitish band on the fore wing. The clover-seed caterpillar, Laspeyresia interstinctdna. — This is a common pest which feeds in the heads of clover, especially red clover, destroying many of the unopened buds and some of the tender green seeds, and spoiling the head as a whole. It sometimes greatly dimin- ishes the crop of seed. There are three generations annually. The last generation passes the winter in the pupa state as a rule; but some larvce hibernate under rubbish. The adult is a pretty brown moth, with a series of silvery marks along the costal margin of the fore wings, and two on the inner margin, which form a double crescent when the wings are closed on the back. This moth expands 10 mm. If the hay is cut early and stored the larvae will be destroyed while still in the heads. Fig. 784. — Evetria frustrana: larva, pupa, adult, and work. (From the Au- thor's Report for 1879.) Nest of Ar chips rosana. Fig. -j^e.—Ar ch- ips rosana. Q42, AN INTRODUCTION TO ENTOMOLOGY Family TORTRICID^ The Typical Tortricids The tortricidae differ, as a rule, from the preceding family in lacking a fringe of long hairs on the basal part of the cubitus of the hind wings. In the fore wings the distal part of the first anal vein is preserved, and vein Cu2 arises from a point before the outer fourth of the discal cell In a recent list 165 North American species are entimerated; these represent 15 genera. Several of our better-known^ members of this family belong to the genus Archips. This is the genus Caccecia of those writers who do not recognize the names proposed by Hiibner in his "Tentamen." These insects have been named the ugly-nest tortricids; ugly dwelling being the meaning of Caccecia, and also descrip- tive of the nests of the larvag of these insects. The four following species are common. The rose ugly-nest tortricid, Archips rosana. — The larva of this species feeds within the webbed-together leaves of rose and a number of other plants. Figure 785 represents the nest of a lar^-a in a currant leaf; and Figure 786 the adult of this species. This moth expands about 20 mm. The fore wings are olive-brown, crossed by bands of darker color; the hind wings are dusky. This species differs from the two following in that each larv^a makes a nest for itself. The cherry-tree ugly-nest tortricid, Archips cerasivordna. — This species lives upon the choke-cherry and sometimes upon the culti- vated cherry. The larvae, which are yellow, active creatures, fasten together all the leaves and twigs of a branch and feed upon them (Fig. 787), an entire brood occupying a single nest. The larvae change to pupae within the nest ; and the pupae, when about to transform, work their way out and hang suspended from the outer portion of the nest, clinging to it only by bo^k" v;<- the tail end of the body Fig.' 787. — Nest of Archips cerasivor- ana. Here they transform. LEPIDOPTERA 645 leaving the empty pupa skins projecting from the nest, as shown in the figure. The moths vary in size, the wing ex- panse of those we have bred ranging from 20 mm. to nearly 30 mm. The wings are bright ochre- yellow; the front pair marked with iiTegular brownish spots and numerous transverse bands of leaden blue (Fig. 7 88, male; Fig. 789, female). 00 _ 1 7 • The oak ugly-nest tortricid, Archips fervidana. '^ 'f ; Jl]-- , ,/J\li\ — The nests of this species are common on our male, oak-trees in late summer. They are merely a wad of leaves fastened together. Each nest contains several larvae; later the empty pupa-skins may be found clinging to the outside of the nest as in the preceding species. ^^<, J The fruit-tree ugly-nest tortricid, Archips ^^^^^^^^Bk cirgyrospUa: — This is one of the most destructive '^^^^HJkHBF of the leaf -rollers infesting fruit trees. It is a very WSpE^B^ general feeder attacking both fruit and forest trees. ^ The eggs are laid on the bark of the twigs in June. Fig. -j^^.— Archips The larvae hatch about May ist of the following female * ^ '"' ^ ^ '^' year and enter the opening buds, where they roll and fasten the leaves loosely together with silken threads. After the fruits set, they are often included in the nests and ruined by the caterpillars eating large irregular holes in them. The pine-leaf tube-builder, Eidia pinatuhdna.- — One of the most interesting of tortricid nests occurs commonly on white pine. Each nest consists of from six to fifteen leaves drawn together so as to form a tube, and is lined with silk. This tube serves as a protection to the larva, which comes out from it to feed upon the ends of the leaves of which the tube is composed; in this way the tube is shortened. I bred the moth from nests collected at Ithaca, N. Y.; and have found similar nests as far south as Florida. The moth expands 12 mm. Its head, thorax, and fore wings are of a dull rust-red color, with two oblique paler bands crossing the fore wings, one a little before the middle, the other a little beyond and parallel with it. Family PHALONIID^ In this family and in the following one the first anal vein is lost in both fore and hind wings and vein Cu2 arises from the outer fourth of the discal cell.' In this family vein Mi of the hind wings is pre- served, usually stalked with vein Rg. The palpi of the two sexes are alike. More than one hundred North American species have been de- scribed, and constantly others are being found. Comparatively little is known about the habits of our species; but most of theEuropean species whose habits are known are borers, chiefly in herbaceous plants. The juniper web-worm, Phalonia rutildna. — This is an imported species which has attracted attention by its injuries to junipers, the 644 AN INTRODUCTION TO ENTOMOLOGY leaves of which it fastens together with silk. In this way it makes a more or less perfect tube within which it lives, but from which it issues to feed. Themoth expandsabout 12 mm. andhas bright, glossy, orange fore wings, crossed by four reddish brown bands. Family CARPOSINID^ This family is distinguished from the preceding one by the fact that in the hind wings both vein Mi and vein M2 are completely lost, and the palpi of the male are short while those of the female are long. This is a small family, only five North American species are now listed, and very little is known regarding the habits of these. The currant-fruit-worm, Carposina fernalddna.- — In the unpub- lished notes of the late Professor M. V. Slingerland, I find an account of this insect. The larva feeds within the fruit of the currant, eating both the pulp and the seeds. The infested fruit soon drops. When full-grown the larva leaves the berry and goes into the ground to transform. The adult emerges in the following spring about the time the currants are turning red. SuPERFAMiLY PYRALIDOIDEA The Pyralids and their Allies This group of families includes a very large number of small or moderate-sized moths, of fragile structure, normally with firmly and finely scaled wings, and with the anal area of the hind wings broad. The first anal vein of the fore wings is almost always lost, and there is no accessory cell. In the hind wings, there are usually three anal veins; and veins Sc and R are separate along the discal cell, but grown together or closely parallel for a short distance beyond the cell. The maxillag are scaled at their base ; and the maxillary palpi when present are of the porrect type. The labial palpi often project beak-like. The larvse are characterized by the presence of only two set« on the prespiracular wart of the prothorax, and by setse IV and V of the abdomen being close together. This superfamily includes the five following families, which can be separated by the characters given in Table A, page 584. Family PYRALIDID^ The Pyralids The members of this family found in our fauna are mostly small moths, but a few are of moderate size; some tropical species, however, are quite large. So large a portion of the species are small that the famil}' has been commonly classed with the preceding families as Microlepidoptera. LEPIDOPTERA 645 The members of the different subfamilies of this family differ so greatly in appearance that it is not possible to give a general descrip- tion that will serve to distinguish it ; a very large portion of the species have a special look, due to their thin and ample hind wings with large anal areas; it is necessar}^ however, to study structural characters to find evidences of a common bond. The body is slender ; the head is prominent ; the ocelli are usually present; the antennas are almost always simple, but frequently the antennae of the male have a process on the scape or a notch and tuft on the clavola; and the palpi are usually moderate in size or long; but very often they project beak-like; for this reason the name snout-moths is often applied to this family. Fig. 790. — Wings of Nomophila noctuella. Fig. 791. — Wings of Tlascala reductella. As a rule there are three anal veins in the hind wings and one in the fore wings. The discal cell is always well-formed, but there is no accessory cell. In most cases the pyralids can be recognized by the fact that the subcosta and radius of the hind wings are separate along the discal cell, but grown together for a short distance beyond the cell, after which they are again separate (Fig. 790). In some genera these two veins do not actually coalesce, but extend very near to- gether for a short distance (Fig. 791). The two types, however, are essentially the same. This is one of the larger families of the Lepidoptera; nearly one thousand species have been described from America north of Mexico alone. The family is divided into many subfamilies, representatives of fifteen of which are found in our fauna. The best known species, those that have attracted attention on account of their economic importance, belong to the subfamilies discussed below. 646 ^.V INTRODUCTION TO ENTOMOLOGY This Fig. 792. mta fu. vein Cu Des- SUBFAMILY PYRAUSTIN^ TJie Pyraustids is one of the larger of the subfamilies of the Pyralididas; about three hundred species have been described from America north of Mexico. This subfamily in- cludes many small moths; but it contains also the majority of the larger species of pyralids; some of the species are very striking in appearance. The members of this subfamily differ from other ■era. is. pyYoXidQ by the following combination of characters. There is no fringe of long hairs on the basal part of of the hind wings; veins Ro and R5 of the fore wings arise from the discal cell distinct from vein R4 (Fig. 790); and the maxillary palpi are never ver}^ large and triangular. Among our better known species are the following. The grape leaf- folder, Desmia fun- erdlis. — ^This is a common species throughout the United States, the larva of which feeds on the leaves of grape. The larva folds the leaf by fastening two portions to- gether by silken threads. When full grown it changes to a pupa within the folded leaf. The moth is black with shining white spots. The male (Fig. 792) differs from the female in having a knot-like enlargement near the middle of each antenna. There is some vari- ation in the size and shape of the white spots on the wings. In some females the white spot of the hind wings is sep- arated into two or three spots. There are two generations of this species in the North and three or more in the South. The basswood leaf -roller, Pantogra- pha limdta. — Our basswood trees often present a strange appearance in late summer from the fact that nearly every leaf is cut more than half way across the middle, and the end rolled into a tube (Fig. 793) . Within this tube there Pig. 793. — Nest of larva of Pan- tographa limata. LEPIDOPTERA 647 Pantographa lives a bright green larva, with the head and thoracic shield black. When full grown the lar\^a leaves this nest and makes a smaller and more simple nest, which is merely a fold of one edge of the leaf, or sometimes an incision is made in the leaf extending around about two-thirds of a circle and the free part bent over and fastened ; in each case the nest is lined with silk, thus forming a delicate co- coon. Here the larvae pass the winter in fallen leaves. At Ithaca, N. Y., Professor Slingerland found that the larva; did not pupate till the following July, and that adults emerged in August. The adult moth expands about ^t, mm. ; it is straw-colored with many elaborate markings of olive with a purplish iridescence (Fig. 794). The melon-worm, Diaphdnia hyalindta. — This beautiful moth (Fig. 795) is often a serious pest in our Southern States, where the larva is very destructive to melons and other allied plants. The young larvas feed on the foliage; the older ones mine into the stems and fruit. The insect passes the winter as a pupa in loose sillvcn cocoons in dead leaves or under rubbish. The moth is a superb C'' / creature, with glistening '-" i white wings bordered ' - -^^ with black, and with a spreading brush of long scales at the end of the abdomen. This species appears to be injurious only in the Gulf States, but the moths have been taken as far north as Canada. The most practicable method of protecting cantaloupes and cucirni- bers from this pest is by planting summer squash- es among them as a trap crop at intervals of about two weeks so as to fur- nish an abundance of buds and blossoms dur- ing July and August. The earlier squash vines should be removed and destroyed before many worms have reached maturity on them; and after the crop is harvested the vines and waste fruits should be gathered and destroyed. Fig. 795. — Diaphania hyalinata: larvae, cocoon, and ad'ilts. (From the Author's Report for 1879.) 648 AN INTRODUCTION TO ENTOMOLOGY The pickle-worm, Diaphdnia nitiddlis. — This species is closely allied to the preceding one. The wings of the moth are yellowish brown with a purplish metallic reflection; a large irregular spot on the front wings and the basal two-thirds of the hind wings are semi- transparent 3'ellow. The tip of the abdomen is ornamented with a brush of long scales, as in the preceding species. The range and habits of this species are quite similar to those of the melon-worm; and it should be fought in the same way. The Webwornis. — The larvas of many pyralids have the habit of spinning a silken web beneath which they retreat when not feeding, and on this account have been termed webworms. Several species of these webworms belong to this family; among them are the follow- ing. The cabbage webworm, Hellula undalis. — This species infests various cruciferas in the Gulf and South Atlantic States. The larva is about 12 mm. in length, of a grayish yellow color, striped with five brownish-purple bands. The garden webworm, Loxostege simildlis. — This species is most injurious in the Southern States and in the Mississippi Valley. It infests various garden crops and com and cotton. The larva varies in color from pale and greenish yellow to dark yellow and is marked with numerous black tubercles. The European corn-borer, Pyrausta nubildlis. — This is a greatly feared pest which has recently appeared in this country. It is a borer in the stems of plants, in which it winters as a partly grown larva. Its favorite food appears to be com and especially sweet corn ; but it infests other cultivated plants, as dahlias and gladiolus, and many large-stemmed weeds. The full-grown larva measures about 20 mm. in length; the adult moth has a wing-expanse of from 25 to 30 mm. As this is written, efforts are being made by the National Government and by several State Governments to prevent the spread of this pest; and many circulars and bulletins are being published regarding it. Subfamily NYMPHULIN^ The Aquatic Pyralids This subfamily is of especial interest as the larvae are nearly all aquatic, differing in this respect from nearly all other Lepidoptera. The larvae of most of the species live upon plants, like water lilies and pond weeds, that are not wholly submerged; but in some species the larva has a true aquatic respiration, being furnished with tracheal gills. In our best known species, these tracheal gills are numerous and form a fringe on each side of the body of long slender filaments, which are simple in some species and branched in others. The larvas vary greatly in habits ; some species live free upon the plants they infest; in some species, each lar\^a makes a case of two leaf fragments fastened together at the edges; most of the described larvce live in quiet waters, lakes, ponds, or pools, but the larva of LEPIDOPTERA 649 Eldphila Julicdlis was found by Lloyd ('14) to live beneath sheets of silk spun over exposed surfaces of current-swept rocks, in a rapid stream. In the case of several species whose life-history has been deter- mined the pupal stadium is passed in a cocoon beneath the surface of the water. An exception to the usual habits of larvae of this subfamily is presented by Eurrhypara urticdta, introduced from Europe to Nova Scotia; this species is not aquatic, but feeds on nettle. Subfamily PYRALIDIN^ The Typical Pyralids This is a small subfamily ; only twenty-four species are now enu- merated in our lists, and these are mainly from the far Southwest. The best-known species are the two following : The meal snout-moth, Pyralisfarindlis. — The larva of this species feeds on meal, flour, stored grain, and old clover hay. It makes little tubes composed partly of silk and partly of the fragments of its food. It rarely occurs in sufficient numbers to do serious injury; and its ravages can be checked by a thorough cleaning of the infested places, or when practicable by the use of carbon bisulphide. The moth is commonly found near the food of the larva, but is often seen on ceilings of rooms sitting with its tail curved over its back. It expands about 25 mm.; the fore wings are light-brown, crossed by two curved white lines, and with a dark chocolate-brown spot on the base and tip of each. The clover-hay worm, Hypsopygia costdlis. — The larva of this species sometimes abounds in old stacks of clover-hay, and especially near the bottom of such stacks. As the infested hay becomes covered with a silken web spun by the larva, and by its gunpowder-like excrement, much more is spoiled than is eaten by the insect. Such hay is useless and should be burned, in order to destroy the insects. The moth expands about 20 nun. It is pig_ yge.—Hy- a beautiful lilac color, with golden bands and fringes % s 0 p y gi a (Fig. 796). c 0 s talis . Subfamily CRAMBIN^ The Close-wings Although this is not a large subfamily, there being only about one hundred and thirty species known in our fauna, the members of it are more often seen than any other pyralids. The larvae of most of the species feed on grass; and the adults fly up before us whenever we walk through meadows or pastures. When at rest, the moths wrap their wings closely about the body ; this has suggested the name close- 650 AN INTRODUCTION TO ENTOMOLOGY wings for the insects of this family. When one of these moths alights on a stalk of grazs it quickly places its body parallel with the stalk, which renders it less conspicuous (Fig. 797). Many of the species are silvery white or are marked with stripes of that color. About seventy of our species belong to the genus Crambus. The moths of this genus are often seen ; but the larvse usually escape observation. They occur chiefly at or a little below the surface of the ground, where they live in tubular nests, constructed of bits of earth or vegetable matter fastened together with silk. They feed upon the lower parts of grass plants; and sometimes on other crops planted on sod land infested by these insects. Thus Crambus caliginosellus is known as the corn-root webworm on account of its injury to young corn plants which it bores into and destroys; it is also known as the tobacco stalk-worm, on account of similar injury to young tobacco plants. Another species of this genus, Crambus hortuellus, is known as the cranbern/ girdler. This sometimes does considerable injury in cranberry bogs by destroying the bark of the prostrate stems of the vines. To this subfamily belong the larger com stalk-borer, Diatrcsa zeacolella, which sometimes bores into the stalks of young corn in the Southern States, and the sugar-cane borer, Diatrcea sacchardlis, which bores into the stalks of sugar-cane. Fig. 797-— Crambus. Subfamily GALLERIIN^ The Bee-moth Subfamily This is a small subfamily, of which only seven species have been found in our fauna. The best known of these is the bee-moth, Galleria mellonella. The larva of this species is a well-known pest in apiaries. It feeds upon wax; and makes silk -lined galleries in the honey-comb, thus destroying it. When full grown the larva is about 25 mm. in length. It lies hidden in its gallery during the day, and feeds only at night, when the tired-out bees are sleeping the sleep of the just. When ready to pupate the caterpillar spins a tough cocoon against the side of the hive. The moth has purplish-brown front wings, and brown or faded yellow hind wings. The fore wings of the male are deeply notched at the end, while those of the female (Fig. 798) are but slightly so. The female moth creeps into the hive at night to lay her eggs. This pest is found most often in weak colonies of bees, which it frequently destroys. The best preventive of its injuries is to keep Galleria LEPIDOPTERA 651 th£ colonies of bees strong. Of course the moths and larvae should be destroyed whenever found. Subfamily PHYCITIN^ The Phycitids Our most common members of this subfamily are small moths vitn rather narrow but long fore wings, which are banded or mottled with shades of gray or brown. The subfamily is, however, a large one and other types of coloration occur. In this subfamily there is a fringe of long hairs on the basal part of vein Cu of the hind wings ; the radius of the fore wings is only four-branched (Fig. 791) ; and the frenulum of the female is simple. This is a very large subfamily; more than three hundred species have been described from our fauna, and there are doubtless many undescribed species in this country. The larvae of the different species vary greatly in habits. Some live in flowers, some fold or roll leaves within which they live and feed; some are borers; others feed upon dried fruits, or flour and meal; and one, at least, is predacious, feeding on coccids. Usually the larva lives in a silken tube or case, lying concealed by day and feeding by night. The case made by certain of the leaf-eating species is very characteristic in form (Fig. 799), being strongly tapering and much curved ; in this instance the case is composed largely of the excrement of the larva. The following species are those that have at- tracted most attention on account of their economic importance. Fig. 799- The Indian-meal moth, Plodia inter punctella. — This is the best- known of the species that infest stored provisions. The larva is the small whitish worm, with a brownish-yellow head, that spins thin silken tubes through meal or among yeast-cakes, or in bags or boxes of dried fruits. The moth expands about 1 5 mm. The basal two- fifths of the fore wing is dull olive or cream colored; the outer part reddish brown, with irregular bands of blackish scales. The Mediterranean flour-moth, Ephestia kvhniella, is an e"en more serious pest than the preceding species, which it resembles in habits. It has become very troublesome in recent years in flouring- mills. The moth expands about 25 mm. and is grayish in color. When this pest or the Indian-meal moth infests a limited stock of flour, meal, or other cereal, the most economical way to combat it is to feed the infested product to stock, and then thoroughly clean the storage bin or pantry. In mills, where an entire building must be treated, fumigation with hydrocyanic acid gas is probably the best method of destro3ang the pest. This should be done under the direction of an expert. 652 AN INTRODUCTION TO ENTOMOLOGY Zimmermann's pine-pest, Pinipestis zimmermdnni, is a common species, the larva of which is a borer. It infests the trLinks of pine, causing large masses of glim to exude. The moths appear in mid- summer. The coccid-eating pyralid, LcBtUia cocci- divora, differs from the other members of this family in being preda- cious. It feeds on the eggs and young of va- rious scale-insects {Pulvinaria, Dactylop- ius, and Lecanium). Figure 800 represents the different stages of this insect enlarged, and the moths natural size resting on egg- sacs of Pulvinaria. Like other members of this family the larva spins a silken tube, within which it lives. On a thickly-infested branch these tubes may be found extend- ing from the remains of one coccid to an- other. To this subfamily belong also the goose- berry fruit worm, Zo- phddia grossuldricB, which feeds within the fruit of the gooseberry and currant, and the cranberry fruit -worm, Mineola vaccmii, which bores into cranberry fruit. Fig. 800.— LcBtilia coccidivora: a, egg; h, larva; c, pupa ; d, adult ; e, e, moths natural size, resting on egg sacs of Pulvinaria. Family PTEROPHORIDyE The Plume-moths The plume-moths are so called on account of the remarkable form of the wings in most species; the wings being split by longitudinal fissures into more or less plume-lil<:e divisions. In most species each fore wing is separated into two parts, by a fissure extending about one- half the length of the wing; while each hind wing is divided into LEPIDOPTERA 653 three parts by fissures extending farther towards the base of the wing. In a species found in CaHfomia, Agdistis adactyla, the wings are not divided. One hundred species belonging to this family have been found in America north of Mexico. One of our most common species is the gartered pkune, Oxyptilus perisceliddctylus. This is a small moth, expanding about 15 mm. It is of a yellowish brown color marked with dull whitish streaks and spots (Fig. 801). The larvse hatch early in the spring and feed upon the newly- expanded leaves of the grape. They fasten together several of them, usually those at the end of a shoot, with fine white silk; between the leaves thus folded the caterpillars live either singly or two or three together. They become full-grown and change to pupag early in June. The pupa is not enclosed in a cocoon, but is fastened to the lower side of a leaf by its tail by means of a few silken threads, in nearly the same way the as chrysalids of certain butterflies are suspended. The pupa state lasts about eight days. Fig. 801. — Oxy- ptilus peris- celidact vhis. Family ORNEODID^ The Many-plimie Moths These insects resemble the pkmie-moths in having the wings fissured; but here the fissuring is carried to a much greater extent than in that family, each wing being divided into six plumes (Fig. 802). As yet only a single species of this family has been found in North America. This is Orneodes huhneri. It is an introduced species. European authors state that the larva feeds on the flowers of Lonicera, Centaurea, and Scabiosa arvensis. It transforms either in the flower-head or in the ground. This species has been mistaken for another European species, Orneodes hexadactyla, and is commonly known under this name. Orneodes Family THYRIDID^ The Window-winged Moths Excepting some subtropical species found in the Gulf States and California our members of this family can be easily recognized by the presence of curious white or yellowish translucent spots upon the wings ; it is these spots that suggest the name window-winged moths for the family. 654 AN INTRODUCTION TO ENTOMOLOGY In this family the antennas are either strictly filiform or slightly thickened in the middle; the ocelli are wanting; the palpi project horizontally, and are somewhat longer than the head; and the max- illag are strongly de- veloped. The venation of the wings of Thyris is represented by Figure 803. Here all of the branches of radius of the fore wings are present and each arises from the discal cell. This is a rather unusual condition, but it occurs in the next family, in certain genera of other families of moths, and in the skippers. In one of our thyridids, Meskea, which is found in the Gulf States, veins R3 and R4 are stalked. This family is poorly represented in our fauna, only eleven species, rep- resenting six genera have been described from the United States. The spotted thyris, Thyris maculdta. — This is the most common representative of this family in the Eastern and Middle States and it occurs also in the West. This species (Fig. 804) is brownish black, sprinkled with rust-yellow dots; the outer margin of the wings, es- pecially of the hind wings, is deeply scalloped, with the edges of the indentations white. There is on each wing a translucent white spot, that of the hind wing is larger, kidney-shaped, and almost divided in two. The mournful thyris, Thyris lugHbris. — This is a larger species found in the Southern States and as far north as New York. It can be recognized by Figure 805. It is brownish black, marked with yellow, and with the translucent spots yellowish. The larva is said to infest grape. Dysodia oculatdna. —This is a yellow and brown species, with a single translucent spot in each wing; those of the hind wings are crescentic. The larvs'; infest various flowers and seeds, and beans. Fig. 803. — Wings of Thyris maculata. Fig. 804.- Thyris mtc ulata. Fig. 805.- lugubris. -Thyris LEPIDOPTERA 655 Family HYBL^ID^ This family is represented in our fauna by a single species, HyhlcBa puera, which is found in Florida. This moth has a wing- expanse of about 35 mm. The fore wings are brown mottled with indistinct spots of a darker shade; the hind wings are brown, with a median band of three bright yellow spots margined with orange, and a similar terminal spot. This is probably an introduced species. In India the larva is a leaf -roller on teak. This species has been placed in the family Noctuidse in our lists of Lepidoptera; but it is much more closely related to the Thyrididas. The venation of the wings is quite similar to that of Thyris; but the maxillary palpi are large and triangular and the first anal vein of the hind wings is present although weak ; while in the Thyrididas the maxillary palpi are minute and the first anal vein is lost. THE SPECIALIZED MACROFRENAT^ In the families included under this heading the insects are usually of medium or large size. This division includes certain moths and all skippers and butterfiies. In these insects the anal area of the hind wings is reduced, containing only one or two anal veins. In some the frenulimi is well-preserved, in others it is replaced by a broadly ex- panded anal area of the hind wing. Family SPHINGID^ The Hawk-moths or Sphinxes Hawk-moths are easily recognized by the form of the body, wings and antennas. The body is very stout and spindle-shaped ; the wings are long, narrow and very strong; the antennas are more or less thickened in the middle or towards the tip, which is frequently curved back in the form of a hook; rarely the antennae are pectinated. The sucking-tube (maxillae) is usually very long, being in some instances twice as long as the body; but in one subfamily it is short and mem- branous. When not in use it is closely coiled like a watch-spring be- neath the head. None of the species has ocelli. The venation of the wings (Fig. 806) is quite characteristic; the most distinctive feature is the prominence of the basal part of vein Ri of the hind wing, the part that extends from the stem of radius to the subcosta. This free part of vein Ri has the appearance of a cross-vein and is as stout as the other veins. In the comparatively few cases in other families where the free part of the vein Ri has the appearance of a cross-vein it is rarely as strong as the other veins. In the hawk-moths the frenulimi is usually well-preserved, but in a few it is wanting or vestigial. In many genera veins R2 and R3 of the fore wings coalesce throughout their length, which results in the radius being only four-branched. 656 AN INTRODUCTION TO ENTOMOLOGY Some of the hawk-moths are small or of medium size; but most of them are large. They have the most powerful wings of all Lepi- doptera in our fauna. As a rule they fly in the twilight, and have the habit of remaining poised over a flower while extracting the nectar, holdmg them- selves in this position by a rapid motion of the wings. This atti- tude and the whir of the vibrating wings give them a strong resemblance to hum- ming-birds, hence they are sometimes called humming-bird moths; but they are more often called hawk- moths, on account of their long, narrow wings and strong flight. Of all the beauti- fully arrayed Lepidop- tera some of the hawk- moths are the most truly elegant. There is a high-bjed tailor- made air about their clear-cut wings, their closely fitted scales and their quiet but exquisite colors. The harmony of the combined hues of olive and tan, ochre and brown, black and yellow, and greys of every con- ceivable shade, with touches here and there of rose color, is a perpetual joy to the artistic eye. They seldom have vivid colors except touches of yellow or pink on the abdomen or hind wings, as if their fastidious tastes allowed petticoats only of brilliant colors always to be worn beneath quiet-colored overdresses. The larvce of the Sphingidse feed upon leaves of various plants and trees and are often large and quite remarkable in appearance (Fig. 807). The body is cylindrical and naked and usually has a horn on the eighth abdominal segment. Sometimes instead of the horn there is a shiny tubercle or knob. We cannot even guess the use of this horn, unless it is ornamental, for it is never provided with a sting. These caterpillars when resting rear the front end of the body up in the air, curl the head down in the most majestic manner, and remain thus rigid and motionless for hours. When in this attitude Fig. 806. — Wings of Protoparce quinquemacidata. LEPIDOPTERA 657 they arc supposed to resemble the Egyptian Sphinx, and so the typical genus was named Sphinx and the family the Sphingidce. Most species pass the pupa state in the ground in simple cells made in the eaith; some, however, transform on the surface of the ground in imperfect cocoons composed of leaves fastened together with silk. One hundred species of hawk-moths occur in this country. The following are some of the more common ones. The modest sphinx, Pa- chysphinx modesta. — It was probably the quiet olive tints in which the moth is chiefly clothed that suggest- ed the name modesta for it, but it is one of the most beautiful of our hawk-moths. The bod^^ and basal third of the fore third of the fore color; while the Fi?. 807. larva. -Sphinx chersis, s are pale olive; the outer wings is a darker shade of the same middle third is still darker (Fig. 808) . The hind wings are dull carmine red in the middle or, in the eastern race, a deeper crimson; there is a bluish-gray patch with a curved black streak over it near the anal angle. The larva feeds en poplar and cotton-wood. \Arhen full-grown it is 75 mm. long, of a pale-green Fig. 808. — Pachysphinx modesta. color, and coarsely granulated, the granules studded with fine white points, giving the skin a frosted appearance; these are wanting in the western race. The twin-spotted sphinx, Smertnthus gemindtus. — This exquisite- ly-colored moth expands about 60 mm. The thorax is gray with a 658 AN INTRODUCTION TO ENTOMOLOGY velvety dark brown spot in the middle. The fore wings are gray, with a faint rosy tint in some specimens, and tipped and banded with brown as shown in Fig- ure 809. The hind wings are deep carmine at the middle, and are bordered with pale tan or gray. Near the anal angle there is a large black spot in which there is a pair of blue spots, which sug- „ . , . gested the name gemin- Fig. Sog.-Smennthus gefmnatus. ^^^^^_ ^j^^ larva feeds Upon the leaves of apple, plum, elm, ash, and willow. Harris's sphinx, Ldpara homhycoides. — This sphinx has interested us chiefly on account of the habits and mark- ings of its larva (Fig. 810). It feeds upon the foliage of pine, and is colored with alternating green and white longitudinal stripes ; the dorsal stripe is green spotted with red. It has a way of hanging head downward in a pine tassel that conceals it entirely from the sight of all but very sharp eyes, its stripes giving it a close resemblance to a bunch of pine leaves. The moth expands about 50 mm.; it is gray with the fore wings marked by several series of small brown spots. The pen-marked sphinx. Sphinx chersis. — This moth is of an almost evenly distributed ashy-gray color. This sombre color is relieved somewhat by a black band on each side of the abdomen, marked with four or five white trans- verse bars; by two dark brown, smoky bands which cross the hind wings; and by a series of black dashes on the fore wings, one in each cell between the apex of the wing and the anal vein. These dashes appear as if drawn casually with a pen. The larva (Fig. 807) is not un- common upon ash and lilac; it is greenish or bluish white above, and darker below; there are seven oblique yellow bands on the sides of the body, each edged above with dark green. When disturbed it assimies the threatening at- titude shown in the figure. The tomato-worm, Protopdrce quinquemaculdta. — This larva is the best known of all our sphinxes, as it may be found feeding on the leaves of tomato, tobacco, or potato wherever these plants are grown in our country. It resembles in its general appearance the larva of Sphinx chersis (Fig. 807); but is stouter and has a series of pale Fig. 810 . — L a par a bombycoides, larva. LEPIDOPTERA 659 longitudinal stripes low down on each side, in addition to the oblique stripes; and its favorite attitude is with the fore end of the body slightly raised. It is usually green, but individuals are often found that are brown, or even black. There appear at frequent intervals in the newspapers accounts of people being injured by a poison ex- creted by the caudal horn of this larva; but there is abso- lutely no foundation whatever for such stories. The p: pa (Fig. 8i i) is often ploughed up in gardens, and attracts at- tention on account of its cur- rious tongue-case a part of Fig. 8ii. — Protoparce qimiguemaculata, which is free resembling the handle of a pitcher. The moth is a superb creature, expanding four or five inches. It is of many delicate shades of ash-gray, m.arked with black or very dark gray ; there are a few short black dashes on the fore part of the thorax, and some irregular black spots edged with white on the posterior part; the abdomen is gray with a black middle line, and five yellow, almost square spots along each side. Each of these spots is bordered with black, and has a white spot above and below, on the edge of the segment. The hind wings are crossed by four blackish lines, of which the two intermediate are zigzag. The most practicable method of control of this pest in a small garden or in a larger field where the larvae are not numerous is by hand-picking; when they are numerous they can be destroyed by spraying with arsenate of lead; use two or three pounds of the paste dissolved in fifty gallons of water. Paris green is liable to bum the foliage of tomato. The tobacco-worm, Protoparce sexta. — This species closely re- sembles the preceding and the two are often mistaken the one for the other. The larvee have similar habits, feeding on the same plants; but in this species the larva lacks the series of longitudinal stripes characteristic of the tomato worm. The moths are easily distin- guished; this species is brownish gray instead of ashy gray; at the end of the discal cell of the fore wings there is a distinct white spot; and the two dark bands crossing the middle of the hind wings are not zigzag, and are less distinctly separate; often they are united into a single broad band. The hog-caterpillar of the vine, Ampelceca myron. — There is a group of hawk-moths the larvae of which have the head and first two thoracic segments small, while the two following segments are greatly swollen. These larvas from a fancied resemblance to fat swine have been termed hog-caterpillars; and the present species, which is com- mon on grape, has been named the hog-caterpillar of the vine. It is a comparatively small species, the full-grown larva being but little more than 50 mm. long. There is a row of seven spots varying in color from red to pale lilac, each set in a patch of pale yellow, along 660 AN INTRODUCTION TO ENTOMOLOGY the middle of the back. A white stripe with dark green margins extends along the side from the head to the caudal horn, and below this are seven oblique stripes. This larv^a is often infested by braconid parasites; and it is a common oc- currence to find one of them with the cocoons of the parasites attached to it (Fig. 812). The pupa state is passed on the surface of the ground Fig. 812. — Ampelceca myron, larva within a rude cocoon made bv with cocoons of parasites. fastening leaves together with loose silken threads. The adult expands about 55 mm. The fore wings are olive gray, with a curved, olive-green, oblique band crossing the basal third, a discal point of the same color, and beyond this a large triangular spot with its apex on the costa and its base on the inner margin. The pandorus Sphinx, Pholus pandorus. — This magnificent moth expands from 100 to 112 mm. The ground color of its wings is pale olive, verging in some places into gray ; the markings consist of patches and stripes of dark, rich velvety olive, sometimes almost black (Fig. 813). Near the inner margins of both pairs of wings the lighter color shades out into pale yellow, which is tinged in places with delicate rose-color. These markings show a harmony of contrasting shades J?:^^. Fig. 813. — Pholus pandorus. rarely equalled elsewhere by nature or art. The larva is one of the hog-caterpillars. It feeds upon the leav-es of Virginia-creeper. When young it is pinkish in color, and has a long caudal horn; as it matures it changes to a reddish brown, and the horn shortens and curls up like a dog's tail and finally disappears, leaving an eye-like tubercle. The caterpillar has on each side five or six cream-colored oval spots, enveloping the spiracles. The white-lined sphinx, Celerio linedta. — This moth can be easily recognized by Figure 814. Its body and fore wings are olive-brown; there are three parallel white stripes along each side of the thorax; LEPIDOPTERA 661 the outer one of these extends forward over the eyes to the base of the palpi; on the fore wings there is a buff stripe extending from near the base of the inner margin to the apex, and veins R5 to 2d A are lined with white; the hind wings are black with a central reddish Fig. 814.- — Celerio lineata. band. The larva is extremely variable in color and markings. It feeds on many plants, among which are apple, grape, plimi, and currant. The thysbe clear-wing, Hmnorrhdgia thysbe.- — There is a group of hawk-moths that have the middle portion of the wings transparent, resembling in this respect the ^geri- idas and certain of the EuchromiidK; but they are easily recognized as hawk-moths by the form of the body, wings, and antennee. One of the more common of these is the thysbe clear-wing (Fig. 815). The scaled portions of the wings are of a dark reddish brown ; but this species is most easily distinguished from all our other species by a line of scales Fig. 815. — Hcemorrhagia thysbe. dividing the discal cell lengthwise and representing the position of the base of vein M. The larva of this species feeds on the different species of Viburnum, the snow-berry, and hawthorn. The bumblebee hawk-moth, Hmnorrhdgia diffinis. — This clear- wing appears to be about as common as the preceding, and resembles it somewhat. It lacks, however, the line of scales in the discal cell, and the body is more nearly yellow in southern specimens. This color probably suggested the name bumblebee hawk-moth, given to this insect nearly one hundred years ago by Smith and Abbott. The larva feeds on the bush honeysuckle (Diervilla) and the snow- berry (Symphoricarpus) . 662 AN INTRODUCTION TO ENTOMOLOGY Fisf. 8 1 6. — A measuring-worm. SuPERFAMiLY GEOMETROIDEA The Geometrids or the Measuring-worms The superfamily Geometroidea is composed of those moths the larvae of which are known as measuring-worms, span-worms, or loopers. These larvae are very famihar objects, attracting attention by their pecuhar manner of locomotion. They progress by a series of looping movements. They first cling to the supporting twig or leaf by their thoracic legs ; then arch up the back v/hile they bring forward the hinder part of the body and seize the support, at a point near the thoracic legs, by the prolegs at the caudal end of the body; then, letting loose the thor- acic legs (Fig. 8 1 6), they stretch the body forward, thus making a step; this process is then repeated. It was this peculiar man- ner of locomotion that sug- /^ gested the name of the typic- al genus, Geometra, from the Greek word meaning a land-measurer. Correlated with this mode of walking there has been a loss in nearly all members of the family of the first three pairs of pro- legs. Frequently measuring- worms when resting cling by their caudal prolegs and hold the body out straight, stiff, andmotionless, appear- ing like a twig ; this is doubt- less a protective resem- blance. The geometrid larvae are leaf-feeders, and some spe- cies occur in such large niun- bers as to be serious pests. The pupae are slender, and some species are green or mottled in this state. Fig. 817. — Wings of Caripeta angusliorata. The pupa state is passed in a ven,- flimsy cocoon or in a cell in the ground. The moths are of mediimi size, sometimes small, but only rarely very large. Usually the body is slender, and the wings broad nnd LEPIDOPTERA 663 delicate in appearance. This appearance is due both to the thinness of the membrane and to the fineness of the scales with which the wings are clothed. These moths occur on the borders of woods and in forests, rarely in meadows and pastures. Their flight is neither strong nor long sustained. Many species when at rest hold the wings horizontally and scarcely overlapping ; but other species assume other positions. In the geometrids the frenulum is visually well-preserved, but in a few it is wanting or vestigial. A striking feature of the wing-venation is the fact that the basal part of the subcosta of the hind wings makes a prominent bend into the himieral area of the wing and is usually connected to the humeral angle by a strong cross-vein (Fig. 817). A monograph of the geometrid moths found in the United States was published by Packard ('76). The superfamily Geometroidea includes two families; but one of these, the Manidiidae is represented in our fauna by a single rare species. Family GEOMETRIDS In this family the antennae are not clubbed, as in the next family. The other distinctive features of the Geometridas are those given above in the characterization of the superfamily Geometroidea. There occur in our fauna representatives of six subfamilies of the Geometridae ; these can be separated by the following table : — A. Eyes small and oval. p. 664 BREPHiNiE AA. Eyes round and usually large. B. Vein M2 of the hind wings vestigial, being represented merely by a fold in the wing or by a non-tubular thickening (Fig. 817). p. 670. . Geometrin^ BB. Vein M2 of the hind wings well-preserved. C. Vein JSL of the hind wings arising much nearer to vein Mi than to vein M3 (Fig. 820). Wings usually green, p. 665 Hemithein^ CC. Vein M2 of the hind wings arising nearly midway between veins Mi and Mj or nearer to vein M3 than to vein Mi. Wings rarely green. D. Veins Sc -\- Ri and Rs of the hind wings extending distinctly separate I from each other, except that they are connected by the free part of vein Ri near the middle of the discal cell (Fig. 821). p. 666. . ..Larentiin^ DD. Veins Sc -f- Ri and Rs of the hind wings approximated or coalesced for a greater or less distance. E. Veins Sc -|- Ri and Rs of the hind wings closely approximated but not coalesced along the second fourth (more or less) of the discal cell. With transverse rows of spines on abdominal segments. {Pal- (Eacrita). p. 670 Geometrin^ EE. Veins Sc -f Ri and Rs of the hind wings coalesced for a greater or less distance. Abdomen without transverse rows of spines. F. Veins Sc -{■ Ri and Rs of the hind wings coalesced for a short distance near the beginning of the second fourth of the discal cell, thence rapidly diverging (Fig. 821). p. 666 Acidaliin^ FF. Veins Sc -+- Ri and Rs of the hind wings coalesced to or beyond the middle of the discal cell (Fig. 823), or with a short fusion near the end of the discal cell. G. Fore wings with one or two accessory cells, p. 666. . LARENTiiNiE GG. Fore wings without an accessory cell. p. 664..ai;NOCHROMiN/f; 664 AN INTRODUCTION TO ENTOMOLOGY Subfamily BREPHIN^ The members of this subfamily are most easily distinguished from other geometrids by the fact that their eyes are small and oval. It is represented in our fauna by only five species, of which the follow- ing one is the best-known. Brephos mfans. — This interesting species has been found only in the northeastern part of our country ; its range is from Labrador to New York. It is a blackish-brown moth with the fore wings marked with pinkish white and the hind wings with reddish orange (Fig. 8 1 8). The specimen figured is a male. In the female the black border on the outer margin of the hind wings is narrower, and the subterminal, light band on the fore wings is more distinctly marked. In the larva the -Brephos infans. prolegs are all present; but the first three pairs are stunted. The full-grown larva measures 30 mm. in length. The color of the larva on the dorsum varies from apple-green to blue-green according to age. The food- plant is white birch. Subfamily CENOCHROMIN^ This subfamily is represented in our fauna by only three species of which only the following one is well known. The fall canl<:er-worm, Alsophila pometdria. — The canker-worms are well-laiown pests, which are often very destructive to the foliage of fruit-trees and shade-trees. Although they attack many kinds of trees, the apple and the elm are their favorite food-plants. There are two species of canker-worms which resemble each other to such an extent that they were long confounded; but they differ structurally, being members of different subfamilies; and they differ also in habits. The two species agree in being loopers or measuring- worms in the larval state, in the possession of ample wings by the adult male, and in the adult female being wingless. They are easily distinguished however, in all stages, the eggs, larvae, and adults differing markedly. The fall canker-worm is so called because the greater number of the moths mature in the autumn and emerge from the ground at this season; but a considerable number come out of the ground in the winter during warm weather, and in the spring. As the females are wingless they are forced to climb up the trunl<:s of trees in order to lay their eggs in a place from which the larv^ae can easily find their food. The eggs appear as if cut oft" at the top, and have a central puncture and a brown circle near the border of the disk. They are laid side by side in regular rows and compact batches, and arc generally exposed. They hatch in the spring at the time the leaves appear; and the larvse mature in about three weeks. In this species LEPIDOPTERA 665 there is a pair of vestigial prolegs on the fifth abdominal segment. The pupa state is passed beneath the ground in a perfect cocoon of fine densely spun silk. The adult male is represented by Figure 819. There is a dis- tinct whitish spot near the apex of the fore wings. The moths of both sexes lack the abdominal spines characteristic of the spring canker-worm. In the fall canker-worm veins Sc -f- Ri and Rg of the hind wings coalesce for a considerable distance along the second fourth of the discal cell ; and veins Rs and Mi of the hind wings separate at the apex of the Fig. 8ig.—Alsophila pom discal cell. Control of canker-worms. — The two spe- cies of canker-worms are sufficiently alike in habits to warrant our combating them by similar methods. The fact that in each the female is wingless and is thus forced to climb up the trunks of trees in order to place her eggs in a suitable place has suggested the method of defence that has been most generally used in the past. This is to place something about the trunks of the trees which will make it impossible for the wingless female to ascend them. Some viscid sub- stance, as tar, printers' ink, or melted rubber, either painted on the trunk of the tree or upon a paper band which is tacked closely about the tree, is the means usually adopted. Many other devices have been recommended. In the use of this method of prevention, operations should be begun in the autumn, even when it is the spring canker- worm that is to be combated; for in this species some of the moths emerge in the fall or during the winter. Although the method just described is still the most available one when tall shade-trees are to be protected, it is now rarely used in orchards. Here the spraying of the trees with Paris-green or arsenate of lead soon after the leaves appear is found more practicable. This method has also the advantage of enabling the fruit-grower to reach other important pests, as the codlin-moth, at the same time. Subfamily HEMITHEIN^ The Green Geometrids As a rule the members of this subfamily are bright green in color; and as we have but few other geometrids of this color, the subfamily may be well termed the green geometrids. The distinctive structure that characterizes this subfamly is the fact that vein M2 of the hind wings arises much nearer to vein Mi than to vein M3 (Fig. 820). This is a comparatively small subfamily, including 1 7 genera and 64 species. The following species will serve as an example. The raspberry geometer, Synchlora cErdta. — The larva of this spe- cies feeds on the fruit and foliage of raspberry, but chiefly on the fruit. It, like some other members of this subfamily, has the curious habit GGG AN INTRODUCTION TO ENTOMOLOGY of covering its body by attaching to it bits of vegetable matter, so that it is masked beneath a tiny heap of rubbish. The wings of the adult are of a delicate pale green color crossed by two lines of a lighter shade ; the face is green; and the ab- domen is not marked with pink and white ocellate spots, as is the case in cer- tain allied species. Subfamily ACIDALIIN^ The members of this sub- family are most easily rec- ognized by the venation of the hind wings (Fig. 821). In these veins Sc+Ri and Rs coalesce for a short dis- tance near the beginning of the second fourth of the discal cell and then diverge rapidly. The greater num- ber of our common species are of mediimi size, with whitish wings crossed by from two to four indistinct lines, and with the head black in front ; some are pure white, and others are brown marked with reddish lines. Eighty-six species are now listed from this country. The chickweed geometer, HcBmdtopis gratdria. — This little moth (Fig. 822) is very common in our meadows and gardens during the summer and autumn months. Its wings are reddish yellow, with the fringes and two transverse bands pink. It is found from Maine tc Texas. The larva feeds on the common chickweed, Alsine media. The sweet-fern geometer, Cosymhia lumendria. — This moth is grayish white, with three rows of black dots extending across the wings, one marginal, one submarginal, and one near the base of the wings; near the center of each wing there is a small reddish ring. The moth has a wing expanse of from 20 to 25 mm. The larva is common on sweet-fern, Comptonia; it also feeds on birch. Fip. 820. — Wings of Dichorda iridaria. Subfamily LARENTIIN^ In this subfamily the branches of radius of the fore-wings anasto- mose so as to form one or two accessory cells, this anastomosis involv- LEPIDOPTERA 667 ing veinRi (Figs. 823 and 824). In the hind wings in most of the genera veins Sc+Ri and Rg coalesce to or beyond the middle of the discal cell or with a short fusion near the end of the discal cell (Fig. 823); but in certain genera, where the costal area of the hind wings is greatly expanded, these veins extend distinctly separate from each other, except that the}^ are connected by the free part of vein Ri near the middle of the discal cell (Fig. 824). In a few genera belonging to other subfamilies veins Sc+Ri and Rs of the hind wings coalesce to the middle of the discal cell, but these genera lack the ac- cessory cell in the fore wings characteristic of this subfamily. This subfamily ranks sec- ond in size among the geom- etrid subfamilies, including 365 North American species; these represent 58 genera. Many of the species are very common of Acidalia enucleata. Fig. 822. — Hcema- topis grataria. black, Trichodezia al- b o V ittdta. — This beautiful little moth, which occurs from the Atlantic to the Pacific, is the most easily recognized member of the family. It expands about 22 mm. and is of a uniform black color, with a single, very broad white band extending across the fore wing from the middle of the costa to the inner angle, where it is usually forked. The fringe of the wings is white at the apical and inner angles of both pairs; sometimes the white is lacking on the inner angle of the hind wings. The early stages are un- known. The bad-wing, Dyspteris abortivdria. — It is easy to recognize this moth (Fig. 82.";) by the peculiar shape of its wings, among them are the following The white-striped Fig. 823. — Wings mendica. of Eudule 668 AN INTRODUCTION TO ENTOMOLOGY the hind wings being greatly reduced in size. It is of a beautiful pea- green color, with two white bands on the fore wings and one on the hind wings. In color it re- /?.^, sembles members of the He- mitheinae; but the structure of its wings (Fig. 824) shows that it belongs in the Laren- tiinae. The larva feeds on the leaves of grape, which it rolls. The scallop-shell moth, Calocalpe unduldta.- — This is a pretty moth, with its yel- low wings crossed by so many fine, zigzag, dark brown lines that it is hard to tell which of the two is the ground-color (Fig. 826). It lays its eggs in a cluster on a leaf near the tip of a twig of cherry, usually wild cherry. The \avvse make a snug nest by fastening to- gether the leaves at the end of the twig; and within this nest (Fig. 827) they live, add- ing new leaves to the outside as more food is needed. The leaves die and become brown, and thus render the nest con- spicuous. There are two gen- erations in the year. The lar- vae of the fall brood are black above, with four white or green stripes, and flesh-colored below; the larvae of the summer brood are black only on the sides. When full-grown they descend to the ground to transform, and pass the winter in the pupa state. The diverse-line moth, Lygris diver silinedta. — This moth has pale ochre-yellow wings, with a brownish shade near the outer margin, and crossed by many diverging brown lines (Fig. 828). It varies from 37 to 50 mm. in expanse. We have oft- en found this moth on the side of our room, resting on the wall, head downward, and with its abdomen hanging down over its head in a curious manner. The larva feeds on the leaves of grape. There Wings of Dyspleris ahortivaria. Fig. 825. — Dyspleris aborti varia. Calocalpe un- LEPIDOPTERA 669 are two broods ; the first brood infests the vines during June ; the second, in the autumn and early spring, wintering as larvce. The spear-marked black, Rheuni- dptera hastdta.- — This is a black-and- white species, which is found from the Atlantic to the Pacific. It is much larger than the white-striped black described above, expanding 35 mm. It is black, striped and spotted with white ; It varies greatly as to the num- ber and extent of the white markings . The most constant mark is a broad white band crossing the middle of the fore wings, and often continued across the hind wings. Near the middle of its course on the fore wing this band makes a sharp angle pointing outward; and just beyond the apex of this angle there is usually a white spot. This spot and angular band together form a mark shaped something like the head of a spear. In some individuals the white predominates, other individuals are al- most entirely black, excepting the spear mark. In the East, there is more white on the fore wings than on the hind wings; this form is the variety gothi- cdta; in some parts of the West and in Europe there is more white on the hind wings than on the fore wings. Accord- ing to European authorities the larva is brown or blackish brown, with a darker line along the middle of the back, and a row of horse-shoe-shaped spots on the sides. It feeds on birch and sweet gale. It is gregarious, a colony of larvae spinning together the leaves of the food-plant, and thus forming a nest within which they live and feed. The larva has not yet been observed in this country. The beg- Fig. 828. — Lygris diversilineala. One of the most delicate- winged moths that we have in the northern Atlantic States is this Fig. 827. — Eggs and nest of Calo- calpe undidata. Fig. 829. — Eudule mendica. 670 AN INTRODUCTION TO ENTOMOLOGY species (Fig. 829). Although the wings are yellowish white in color they are almost transparent. On the fore wings there are two trans- verse rows of pale gray spots, and a single spot near the outer margin between veins M3 and Cui. (This spot was indistinct in the specimen figured.) The moth is common in midsummer. The larva feeds on violet. Subfamily GEOMETRIN.E Nearly all of the members of this subfamly can be easily recognized as such by the fact that vein M2 of the hind wings is wanting, being represented merely by a fold. This is by far the largest of the subfamilies of the Geometridce; it includes more than 500 North American species; these represent 124 genera. The following are some of the more common species. The currant span-worm, Cymatophora rihedria. — There are several species of insects that are popularly known as currant -worms. The most common of these are larvse of saw-flies, which can be easily recognized by the large nimiber of prolegs with which the abdomen Fig. 830. — Cymatophora ribearia. Fig. 831. — Cingilia catenaria. is furnished. In addition to the saw-flies there is a yellow looper spotted with black, which often appears in such great numbers on currant and gooseberry bushes as to suddenly strip them of their foliage. This larva has been named the currant or gooseberry span-worm. When full-grown it measures about 2 5 mm. in length, and is of a bright yellow color, with white lines on the sides and with numerous black spots and round dots. It has only four prolegs. There is only one generation a year; the lar\'a matures in May or June; the pupa state lasts about a fortnight; the moth flies during the summer month sand oviposits on the twigs of the plants; and the eggs remain unhatched till the following spring. The moth (Fig. 830) is pale yellow, with the wings marked by irregular dusky spots, which sometimes form one or two indefinite bands across them. The chain-dotted geometer, CingUia catenaria. — This moth has snow-white wings marked with zigzag lines and with dots of black as shown in Figure 83 1 . The head is ochreous-yellow in front ; and the thorax is yellowish at the base of the patagia. The moth flies during LEPIDOPTERA 671 September and October. The larva feeds on various shrubs and trees. The pupa state is passed in a shght but well-formed web of yellow threads, which is formed between twigs or leaves, and through which the pupa can be seen. The evergreen nepytia, Nepytia semiclusdria. — This beautiful moth (Fig. 832) is common in the vicinity of pines, spruce, fir, and hemlock during August and September. It varies from a smoky-ash color to almost snow- white; the wings are marked with black. The larva feeds on the leaves of Conifers. It is reddish yellow above, with lateral yellow bands below, while on each side are two pairs of black hair-lines. There are black spots above on the segments . When full-grown it is a little more than 25 mm. long and spins a loose cocoon among the ^. S32.-Nepytia semiclusa- leaves. The chrysahd is green with white ria. stripes and is very pretty. The spring canker-worm, Paledcrita verndta. — The eggs are o^'oid in shape, and are secreted in irregular masses, usually under loose scales of bark or between the leaflets of the expanding buds. The larvae hatch about the time the leaves expand, and become full-grown in from three to four weeks. They vary greatly in color, and are marked on the back with eight narrow, pale, longitudinal lines which are barely discernible ; the two lateral lines of each side are much farther apart than the others; and there are no prolegs on the fifth abdominal segment as in the fall canker-worm. The pupa state is passed below the surface of the ground in a simple earthen cell, which is lined with very few silken threads. The adult moths usually emerge early in the spring before the leaves expand; but they sometimes appear late in the fall, or on warm days during the winter when the ground is thawed. In both sexes the adult of this species is dis- tinguished by the presence of two transverse rows of stiff reddish spines, pointing backwards, on each of the first seven abdominal seg- ments. Regarding the control of canker-worms see page 665. The lime-tree winter-moth, Erdnnis tilidria. — This species (Fig. 833) resembles the canker-worms in many particulars. The larva is a looper which infests both fruit and forest trees; and in the adult state the male has well-developed wings, while the female is wingless. The eggs are oval, of a pale yellow color, and covered with a net- work of raised lines. They are thrust by the female under loose bark and in crevices on the trunk and large limbs. They hatch in May, and the larvae attain their full growth in the latter part of June. The larva is yellow, marked with ten crinkled black lines along the top of the back; the head is rust-colored, and the venter yellowish white. There is a second form of the larva which is brown above with slate color towards the sides. When full-grown the lan^a measures about 30 mm. in length. The pupa state is passed in the ground. The 672 AN INTRODUCTION TO ENTOMOLOGY moths issue in October or November; and then the wingjless females ascend the trees to oviposit as do the females of the canker-worms. The female is represented in the lower left-hand part of the figure. ^^-N^-^ Fig- 833. — Erannis tiliaria. (From The Author's Report for 1879.) She is grayish in color, with two black spots on the back of each segment except the last, which has only one. The male has pale yellow and brown or buff fore wings, with a central spot and a band beyond the middle, while the hind wings are much lighter. This insect can be combated by the same meth- lOds as are used against canker worms. The notched-wing geometer, En- nomos magndrins. — This is one of the larger of our geometrids. The larva is a common looper upon maple, chestnut, and birch trees, and meas- ures about 58 mm. in length when full-grown. It spins a rather dense, spindle-shaped cocoon within a clus- ter of leaves. The moth (Fig. 834) is ochre-yellow with reddish tinge. The wings are shaded towards the outer margin with brown, and are thickly spotted with small brown dots. Fig. 834. — Ennomos magnarius. LEPIDOPTERA 673 The pepper-and-salt currant-moth, Amphtdasts cognaidria. — This moth (Fig. 835) differs remarkalDly in appearance from most geometrids, the body being stouter, and the wings appearing heavier. Fig. 835. — Amphidasis cogna- tarta. Fig. 836. — Phryganidia calif ornica. R. K. It can be easily recognized by its evenly distributed pepper-and-salt markings. The larva feeds on various plants, but is found most often on currant. Family MANIDIIDiE This family is repre- sented in our fauna by a single, recently discov- ered species, Annrapteryx cremddta, found in Ari- zona. In the genus ylwM- rapteryx the antennae are gradually enlarged toward the tip forming a well-marked club ; the maxillae are well-devel- oped ; the eyes are hairy and overhung by long cilia; and the frenulum is well-developed. Our species was de- scribed by Barnes and Lindsey in "Entomo- logical News," vol. 30, p. 245. Family DIOPTID^ The Dioptids The only member of this family that is well known in this country is Phryganidia calij ornica, which occurs in California. This is a pale- brown insect, with nearly transparent wings (Fig. 836). The veins of the wings are dark, which renders them prominent. In the males there is a yellowish spot just beyond the discal cell. The venation Fig. 837. — Wings of Phryganidia. 674 AN INTRODUCTION TO ENTOMOLOGY of the wings (Fig. 837) is very different from that of any other insect that occurs in this country. The larvae feed upon the leaves of live-oaks, and sometimes occur so abundantly as to almost strip the trees of their foliage. They are said to feed singly, and appear to make little if any use of the anal feet as a means of loco- motion, generally carry- ing the last segment of the body elevated in the air. Family NOTODONTID^ The Prominents This family includes moths of moderate size, only a few of the larger ones expanding more than 50 mm. The body is rather stout and dense- ly clothed with hair, and the legs, especially the femora, are clothed with long hairs. The wings are strong, and not very broad, the anal angle of the hind wings rarely reaching the end of the abdomen. In their gen- eral appearance many of these moths bear a strong resemblance to noctuids ; but they can be easily distinguished from the Noctuidas by the position of vein M2 of the fore wings, which does not arise nearer to vein Cu than to vein R, as it does in that family ; and the fact that in this family veins Sc+Ri and Rs of the hind wings do not coalesce (Fig. 838). The first anal vein is wanting in both fore and hind wings ; and in some _ species an accessory cell is present in the fore wings. In some species the front wings have a prominence or backward projecting lobe on the inner margin, which suggested the common name of prominents for these insects (Fig. 839). The name is more generally appropriate, however, for the larvae, as a much larger pro- portion of them than of the adults bear striking prominences. Fig. zdA -Wings of HypercEschra stragula. Fig. 839. — Pheosia rimosa. LEPIDOPTERA 07^ The larvae feed tipon the leaves of shrubs and trees. Our most common species live exposed; but some species live in folded leaves. They are either naked or clothed with hairs. Many species have only well-developed prolegs, the anal pair being rudimentary, or trans- formed into elongated spikes. vSome species are hump-backed; and spines or fleshy tubercles are often present. The transformations occur in slight cocoons or in the ground. The family Notodontidas is represented in this country by about one hundred species. A monograph of the family was published by Packard ('95) in which there are many colored figures of larvas. The following are some of the more common species. The handmaid moths, Datana. — Among the more common repre- sentatives of the Notodontidae are certain brown moths that have the fore wings crossed with bars of a different shade (Fig. 840) and that bear on the fore part of the thorax a conspicuous patch of darker color. In most of our species the fore wings are also marked with a dot near the center of the discal cell and a bar on the discal vein. These moths be- long to the genus Datana. The com- mon name, handmaid, is a translation of the specific name of our most com- mon species, D. mimstra. But as this species is now generally known as the yellow-necked apple-tree worm, and as all of our species are dressed in sober attire as becomes modest servants, we have applied the term hand- maid moths to the entire genus. The larvae of the handmaid moths are easily recognized by their peculiar habits. They are common on various fruit and forest trees, but especially on apple, oak, and hickory. Fig. 840. — Datana. Fig. 841. — Datana, larva. They feed in colonies ; and have the habit of assimiing the curious attitude shown in Figure 841. The body is black or reddish, marked 676 AN INTRODUCTION TO ENTOMOLOGY Fig. 842a. — Symmerista albifrons. with lines or stripes of yellow or white. Owing to the gregarious habits of these larvag they can be easily collected from the trees they infest. All the species that we have studied agree in being single-brooded, the moths appearing in midsimimer; the eggs are laid in a cluster on a leaf; the larvse are conspicuous in August and September. In some of the species the larvae have the curious habit of leaving the branch upon which they are feeding when the time to molt arrives, the whole colony gathering in a large mass on the trunl<: of the tree, where the molt takes place. The pupa state is passed in the ground, in a very light cocoon or in none at all, and lasts about nine months ill the species that we have bred. The white-tipped moth, Symmertsta albifrons. — This oeautiful moth, which is quite common, can be easily recognized by the ac- companying figure (Fig. 842, a) ; the white patch, which extends along the costa of the fore wing for half the length from the tip, being very char- acteristic. The larva (Fig. 842, b) is quite common in the auttmin on leaves of oak. It is known as the red- humped oak-caterpillar; it is smooth and shining, with no hairs; along each side of the back there is a yellow stripe, and between these, on the back, fine black lines on a pale lilac ground; on each side below the yellow stripes there are three black lines, the lowest one just above the spiracles. The head is orange-red ; and there is an orange-red hump on the eighth abdominal seg- ment. The two-lined prominent, Heterocdmpa bilinedta. — The larva of this species(Fig.843) is much more apt to be observed Fig. 8A2b.— Symmerista albifrons, larva. f^^^ ^^^ ^^^l.t- It IS common m the latter part of the summer and in early autimm, feeding on the leaves of elm, beech, and bass wood. It measures when full-grown about 3 7 mm. in length. Its ground-color is usually green, but sometimes claret-red. There is a pale yellow stripe along the middle of the back, and on each side a stripe of the same color. The course of these side stripes is very characteristic; passing back from the head, they converge on the prothorax; on the mesothorax and metathorax they are separated from the dorsal line only by a narrowband of red or purple; on the first abdominal segment they diverge to the lateral margin of Fig. 843. lineata, —Heterocampa larva. bi- LEPIDOPTERA 677 the back, but converge again on the seventh and eighth abdominal segments. This yellow subdorsal line is bordered without by a milk- white stripe; and extending from this stripe over the side of the bod\^ there is a whitish shade which fades out below. The moth is ash colored, with the fore wings crossed by two wavy lines between which the wing is darker ; between the outer wavy line and the outer margin of the wing there is a faint band. Antler ed larvcs: — Among the remarkable forms exhibited by no- todontian larvae are those of the freshly-hatched larvae of the species of Heterocampa. Figure 844 repre- sents the first instar of Heterocampa vdria, which has on the first thoracic segment a pair of large antler-like horns, and other horns on several of the abdominal segments. In the second instar all of these horns are wanting except small vestiges of the first pair. This species feeds on oak. The freshly hatched larva of Heterocampa guttivitta is also ant- lered. The horns borne b}" the pro- thorax are four-branched and there are eight-pairs of horns on the abdomen. As in the preceding species all of these horns are wanting in the second instar except vestiges of the first pair. This species feeds especially on maple, but has been found on other trees. Fig. 844. — Heterocampa varia, larva. (After Packard.) Fig. 845. — Schiziira concinna, larva. The red-humped apple-worm, Schiziira concinna: — -The larva of this species (Fig. 845) is common on apple and alhed plants. The head is coral-red, and there is a hump of the same color on the back of the first abdominal segment; the body is striped with slender black, yellow, and white lines, and has two rows of black spines along the back, and other shorter ones upon the sides. When not eating, the larvae remain close together, sometimes completely covering the branch upon which they rest. This species passes the winter in the pupa state. The adults appear in June and July. 678 AN INTRODUCTION TO ENTOMOLOGY The Mocha-stone moths, Meldlopha. — To the germs Melalophahe- long several species of brownish-gray moths, whose fore wings are crossed by irregular whitish lines. It was these peculiar markings, resembling somewhat those of a moss-agate, that suggested the popular name given above. The larvae feed on poplar and willow, and conceal themselves within nests made by fastening leaves to- gether. Our most common species is the following. Meldlopha incliisa. — The adult (Fig. 846) is a brownish-gray moth with the fore wings crossed by three irregular whitish lines. The basal line is broken near the middle of the wing ; and the intermediate one forms an inverted Y, the main stem of which joins the third line near the inner margin of the wing, making with it a prominent V. These lines are bordered without by rust-red; there is a chocolate-colored spot near the apex of the fore wings, and an irregular row of blackish j^ ^g^ dots near the outer margin. The hairs of ^||^^^Sy<^gj^^a the thorax form a prominent crest, the fore ^^H^H^K^^^ side of which is a rich dark brown. The ^SH^hEHSb hind wings are crossed by a wavy band, ^B^BB^Il^ which is light without and dark within. w The eggs are nearly spherical and smooth ; Thev are deposited in a cluster a single layer fi«if ■" "" ^^^P °^ ^ 1^^^ (^^g- ^47)- ^^^^ ^^^ 1^^^^ hatch they make a nest either by fastening several leaves together or, as is the case when they infest poplar, by folding the two halves of a single leaf together; frequently in the latter case the tip of the leaf is folded in as shown in the figure. Within this nest the entire colony lives, feeding on the parench\Tiia, and causing the leaf to turn brown. Later other leaves are added to this nest or additional nests are made among adjoining leaves. All of these infested leaves are securely fastened to the twig by bands of silk. When the larvae become large they leave their nests at night to feed upon other leaves. These they entirely consume excepting the petioles, midribs, and larger veins. We have seen on poplar a nest composed of only three leaves which contained one hundred and twenty-five half-grown larvae; all of the leaves, about thirty in number, arising from the end of the ^, .^ branch bearing this ^^^ v nest had been con- sumed. The full-grown larv^a measures 3S-c>-c t? 1 ^ ^ c ht 1 1 1 ■ ■, • 1 ^u t:: Fig. 847. — Eggs, larva, and nest of Melalopha tncliisa. is striped with pale yellow and brownish black, and bears a pair of black tubercles close together on the first abdominal segment, and a similar pair on the eighth abdominal segment. The cocoon is an LEPIDOPTERA 679 irregular thin web ; it is made under leaves or other rubbish on the ground. The insect remains in the pupa state during the win- ter, and emerges as a Xsn/ moth in the latter part ^ of June or later. In ^ the South this species infests willow as well as poplar, and is ^'^- H^-Schizura tpomea; larva. double-brooded. Among the more grotesque larvae belonging to this family are those of the genus Schiziira, of which we have several species. Figure 848 represents the larva of Schizura ipomecB. At the left in the figure is shown a front view of the longest tubercle. This species feeds on oak, maple, and many other plants. In the Gulf States it feeds on Ipomea coccinea, which fact suggested its specific name. Family LYMANTRIID^ The family Liparidce of some writers The Tussock-moths The larvcC of these moths are among the most beautiful of our caterpillars, being clothed with brightly-colored tufts of hairs; and it is to this characteristic clothing of the larvae that the popular name tussock-moths refers. The adult moths are much plainer in appearance than the larvae ; and in the genera Hemerocampa and Notolophus, to which our most common species belong, the females are practically wingless, the wings being at most short pads, of no use as organs of flight. The tussock-moths are of medium size, with the antennae of both sexes when winged pectinated, those of the males very broadly so; the wingless females have serrate or narrowly pectinate antennae. The ocelli are wanting. The legs are clothed with woolly hairs; when the insect is at rest the fore legs are usually stretched forward, and are very conspicuous on account of these long hairs. The venation of the wings is quite similar to that of the Noctuidae, but in the Lymantriid^ the point at which veins Sc + Ri and Rs of the hind wings anastomose is farther from the base of the wing (Fig. 849). In some genera these two veins are separate being connected only by the free part of vein Ri. The tussock-moths are chiefly nocturnal; but the males of some of them fly in the daytime. The larvae of our native species are very characteristic in appear- ance. The body is hairy ; there are several conspicuous tufts of hairs on the dorsal aspect of the abdomen, and at each end of the body there are long pencils of hairs; on the sixth and seventh abdominal seg- 680 AN INTRODUCTION TO ENTOMOLOGY ments there is on the middle of the back of each an eversible gland supposed to be a scent-organ similar to the osmateria in the larvee of Papilio, and it is stated that a fine spray of liquid is sometimes thrown from them. -Wings of Hemerocampa leucos Pig. 849. tigma. mon representative of the family. numbers that it seriously injures the foliage of shade-trees and or- chards. The male (Fig. 850) is of an ashy gray color; the fore wings are crossed by undulated bands of darker shade and bear a conspicu- Fig. 850. — Hemerocam- pa leucostigma. Excepting a few rare forms our native species pertain to the genera. Hemerocampa, Noto- lophus, and Olene. In the first two of these genera the males are winged and the females are nearly wingless. In Olene both sexes are winged. Our best known of the native members of this family are the follow- ing. The white-marked tussock- moth, Hemerocampa leucostig- ma.— This is our most com- It frequently occurs in such great Fig. 851. — He Die rotuDi pa leucostigma, larva. ous white spot near the anal angle. The female is white and resembles a hairy grub more than a moth. She emerges from her cocoon and after pairing lays her eggs upon it, covering them with a frothy mass. The larva (Fig. 851) is one of the most beautiful of our caterpillars. LEPIDOPTERA 681 The head and the glands on the sixth and seventh abdominal seg- ments are bright vermilion red. There is a velvety black dorsal band, bordered with yellow subdorsal stripes; and there is another yellow band on each side just below the spiracles. The prothorax bears on each side a pencil of long black hairs with plume-like tips; a similar brush is borne on the back of the eighth abdominal segment, and the first four abdominal segments bear dense brush-like tufts of cream- colored or white hairs. When this insect becomes a pest the larvae can be destroyed by spraying the infested trees with Paris-green water; or the egg-bear- ing cocoons can be collected during the winter and destroyed. These cocoons are attached to the trunks of the trees and to neighboring objects, or to twigs. In the latter case they are usually partially enclosed in a leaf. Cocoons not bearing eggs should not be destroyed, as many of them contain parasites. Owing to the wingless condition of the female this pest spreads slowly. The well-marked tussock-moth, Hemerocampa plagiata. — The male, like that of the preceding species, is of an ashy gray color; but the markings of the fore wings are much more distinct. The female is light brown. She lays her eggs in a mass on her cocoon, covering them with hair from her body. The larva closely resembles the pre- ceding species in the form and arrangement of its tiifts of hair, but differs markedly in color, being almost entirely light yellow. There is a dusky dorsal stripe and a velvety black spot behind each of the tufts of the first four abdominal segments. The head and the glands on the sixth and seventh abdominal segments are, like the body, light yellow. The California tussock-moth, Hemerocampa vetusta. — The two species of Hemerocampa described above are found only in the East; this species is found in California, where it is common on live oak and yellow lupin trees, and has injuriously infested apple and cherry orchards. The larvae have black heads, crimson hair-bearing warts and prolegs, and the four tussocks or brush-like tufts of hairs on the back are often dark gray with brownish crests. In general the life- history of this species is similar to that of the two eastern species. The old tussock-moth, Notolophus anttqua. — ^The male is of a rust- brown color; the fore wings are crossed by two deeper brown bands and have a conspicuous white spot near the anal angle. The body of the grub-like female is black, clothed with yellowish white hairs ; she lays her eggs on her cocoon, but, unlilce the three preceding species, does not cover them with anything. The larva differs from either of the preceding in having an extra pair of pencils of plume-lilvC hairs arising from the sides of the second abdominal segment; the head is jet-black; the glands on the sixth and seventh abdominal segments are vermilion-red or sometimes bright orange; and the tubercles on the sides of the back of the second and third thoracic and the sixth and seventh abdominal segments are orange-red or yellow margined with pale yellow. 682 AN INTRODUCTION TO ENTOMOLOGY The gypsy moth, Porthetria dhpar. — ^This is a European species which was introduced into Massachusetts in 1866 by a French naturahst who was conducting experiments with silk-worms. Some of the insects escaped from him into a neighboring woodland and be- came established there; but they did not attract particular attention till about twenty j-ears later. It was then realized that this species is a serious pest . Since then millions of dollars have been expended by the State of Massachusetts and the Federal Government in an un- successful effort to exterminate it. It has spread over a large part of New England, and isolated colonies have been found in New York. The larva has a wide range of food- plants, feeding on the foliage of most forest and fruit trees. The male moth is yellowish brown; the female white (Fig. 852). In each the fore wings are crossed by many dark lines and bear a black lunule on the discal vein. The specimen figured is unusually small. The eggs Fig. 852— Porthetria dispar. are laid in a mass on any convenient object and are covered with hair from the abdomen of the female. The larva differs greatly in appear- ance from those of the preceding genera, lacking the peculiar pencils and tufts of hair; but the characteristic glands of the sixth and seventh abdominal segments are present and are red. The body is dark brown or black, finely reticulated with pale yellow, and with narrow yellow dorsal and subdorsal lines. On the dorsal aspect of each segment there is a pair of prominent, rounded tubercles bearing spiny black hairs. The first five pairs of these tubercles are bluish, the others dark crimson-red. There are also two rows of tubercles on each side of the body which bear longer hairs. The brown-tail moth, Euproctis chrysorrhcsa. — The brown-tail moth is another European pest, which was introduced into Massa- chusetts at some unknown date. It first attracted attention by its ravages in 1897, and since then has spread over a considerable part of New England and has extended into New Brunswick and Nova Scotia. The wings of the female moth are white; and the tip of the abdomen bears a tuft of yellowish brown hairs, hence the popular name of the insect. The female expands about 37 mm. The male is a little smaller than the female; and the brownish tuft at the end of the abdomen is not so conspicuous as in the female. The larva feeds on the foliage of fruit-trees and of almost all kinds of shade-trees except conifers. The eggs are laid in an elongate mass on the underside of a leaf, during July. The egg-mass is covered with brownish hairs from the tip of the abdomen of the female. The eggs hatch in two or three weeks. The larvae hatching from an egg-mass feed together on adjoining leaves at the tip of a branch. These they web together with silk, making a nest within which they pass the winter in a partially grown condition. In early spring the larvse leave their winter quar- LEPIDOPTERA 683 ters and feed on the expanding foliage. They become full grown in five or six weeks ; and then spin thin cocoons of white silk in curled leaves, crevices in bark of trees, or under any convenient shelter. About three weeks later the moths emerge. The full-grown larva of the brown-tail moth measures about 37 mm. in length. It is nearly black in ground color, clothed with tufts of brownish barbed hairs, and has a row of nearly white tufts on each side of the body. In the center of the sixth and seventh abdominal segments are small, red, retractile tubercles. The barbed hairs borne by the subdorsal and lateral tubercles are venomous and produce an inflamation of the skin of man much like that caused by poison ivy. As the cast skins of the larvae are blown about by the wind, people are frequently badly poisoned where this pest is common. To control this pest the nests in which the larvae hibernate should be collected during the winter and burned. Family NOCTUID^ The Noctuids or the Owlet-Moths If only our fauna be considered, this is the largest of all of the families of the Lepidoptera; more than 2500 species of noctuids are now know to exist in America north of Mexico. The great majority of the moths that fly into our houses at night, attracted by lights, are members of this family. The nocturnal habits of these insects, and the fact that often when they are in obscurity their eyes shine brightly suggested the name of the typical genus, Nociua, from the Latin for owl, as well as the popular name owlet -moths, by which they are known. Similar popular names have been given them in several other languages. Although there exist within the limits of the family great differences in size, form, and coloring, most of the species are dull-colored moths of medium size. In the typical noctuids, the body is large in proportion to the size of the wings; the front wings are strong, somewhat narrow, and elongated, the outer margin being shorter than the inner margin; and when at rest, the wings are folded upon the abdomen, giving the insect a triangular outline. The antennae are thread-like, or fringed with hairs, or brush-like, often pectinate in the males. Two ocelli are almost always present. The labial palpi are well developed, and in some species quite prominent. The maxilla are quite long and stout in most species. The thorax is heavy and stout. In the majority of the species the scales or the dorsal surface of the thorax are turned up more or less, foiTning tufts. The abdomen is conical and extends beyond the anal angle of the hind wings when these are spread. The venation of the wings of a member of this family is represented by Figure 853. Vein M2 of the fore wings arises much nearer to vein M3 than to vein Mr, there is usually an accessory cell; the first anal vein is wanting, and the third anal vein may be present 684 AN INTRODUCTION TO ENTOMOLOGY with its tip joined to the second anal vein near its base. On the hind wings veins Sc+ Ri and vein Rg coalesce for a short distance near the base of the wing ; vein AI2 may be either well preserved or much weak- er than the other veins, or in a few cases lost ; and there is considerable variation in the point of origin of this vein. Fig. 853. — Wings of Catocala fraxim. The majorit}^ of the larvas are naked, of dull colors, and provided with five pairs of prolegs. As a rule they feed on the leaves of plants, but some are borers and some gnaw into fruits. Among them are some of the more important insects injurious to agriculture. The family Noctuidas has been divided into many subfamilies. In the following pages the more important of those represented in our fauna are briefly discussed, in order to show, as well as possible in a limited space, the variations in form included in this family, and to indicate the position of our more important species LEPIDOPTERA 685 Fig. 854.- scabra. -Plathypenc There is a group of moths, the deltoids, which are placed at the foot of this family on account of their apparent relationship to the geometrids and to the pyralids. These moths are usually of dull colors and of medium size. The name deltoids was suggested by the triangular outline of the wings when at rest, which is well represented by the Greek letter delta. When in this position the wings slope much less than with other noctuids, the attitude being more like that assumed by the geometrids; but the hind wings are more nearly covered than with the geometrids. IVIany of the deltoids have very long palpi, resembling in their size those of the pyralids. The del- toids include the two following subfamilies. The subfamily Hypenin^. — A representative of this subfamily is the following species. The green clover-worm, Plathypena scdbra. — This is a common deltoid. The usual food-plant of the larva is clover, but it occasion- ally defoliates peas, beans, and lima beans. It is a slender green worm measuring when full-grown 16 mm. in length and only about 2.5 mm. in width in its widest part; it has a narrow subdorsal whitish line and a lateral one of the same color. When ready to trans- form it webs together several leaves and passes the pupa state in the nest thus made. The adult (Fig. 854) isa blackish brownmoth, with an irregular grayish shade on the outer half of the fore wings, and with very broad hind wings. The palpi, which are not well shown in the figure, are long, wide, and flattened; they project horizontally like a snout. The hop-vine deltoid, Hypena humuli.' — This species is closely allied to the preceding and has often been confounded with it. The larva feeds on the leaves of hop, and is sometimes a serious pest. The subfamily Herminiin^. — The following species will serve as an example of this subfamily. Epizcuxis luhricalis: — This is one of the most abundant of our deltoids. In this species (Fig. 855) the fore wings are chocolate-brown, crossed with A'ellowish lines; the hind wings are much lighter. The palpi are long; but they are curved over the head, so that they appear short when seen from above, as represented in the figure. The larva feeds on dead leaves. The subfamily Erebin^.— More than 120 species belonging to this subfamily are now The three following will serve as examples. The black witch, Erebus oddra.— This is the most magnificent in size of all of the noctuids found in this country (Fig. 856). There is much variation in the depth of coloring. The individual figured is a female; in the male the fore wings are more pointed at the apex and the median band is indistinct. It is a native of the West Indies; but it is believed that it breeds in the extreme southern portion of ^'^S- 855. — Epizeiixis luhri- calis. listed from our fauna. 686 AN INTRODUCTION TO ENTOMOLOGY the United States. Isolated individuals are found in the North in Fig. 857. — ScoUopteryx libatrix. Fig. 856. — Erebus odora. late summer or autumn. These are found as far north as Canada and west to Colorado, and even in California. These have doubtless flown north from their southern breeding places, possibly from Cuba or Mexico. The larva feeds on certain tropic- al legiuninous trees, Cassia fistula, Pithecolobhtm, and Saman. The scalloped owlet, ScoUop- teryx libatrix. — This moth is easily recognized by the shape of its wings, the outer margins of which are deeply cut and scalloped (Fig. 857). The color of the fore wings is soft brownish gray, slightly powdered with rust-red, and frosted with white along the costa. There is an irregular patch of rust-red reach- ing from the base to the middle of the wing, a single, white, transverse line before the middle, and a double one beyond the middle. The larva feeds on willow. This species is found in all parts of the United States and in Europe. The cotton-worm, Alabama argilldcea. — Excepting perhaps the cotton-boll weevil, this is the most important insect pest in the cotton-growing states. The adult insect (Fig. 858) is a brownish moth with its fore wings crossed with wavy lines of darker color and marked with a bluish discal spot and two white dots as shown in the figure. This moth is found in the Northern States and even in LEPIDOPTERA 687 ilabaina argilla- Fig. 859. — AtitograpJia fal- cifera. Canada in the latter part of the summer and in the autimm. But this occurrence in the North is due to migrations from the South, as the insect can not survive the winter north of the Gulf States. The larva feeds on the foliage of cotton; and as there are five or six generations in a year, the mul- tiplication of in- dividuals is very rapid, and the injury to the cotton great. The best-known way of combating this pest is by the use of Paris green. Dusting machines drawn by horses are in common use. The subfamily Plusiin^ includes nearly seventy North American species. In a large number of these the fore wings are marked with metallic-colored scales. The most common form of this marking is a silvery spot, shaped something like a comma, near the center of the wing (Fig. 859). In some of the species the metallic markings cover a large portion of the fore wings, in others they are want- ing. 'Most larvae have only three pairs of prolegs, the first two pairs being wanting; due to this fact they walk with a looping motion (Fig. 860) resem- bling somewhat that of the geometrids. The two following species have attracted at- tention by their injuries to cultivated plants ; the celery looper, Autographa faktfera, and the cabbage looper, Autographa brds- siccz. The subfamily Cato- CALiN^. — To this sub- family belong the "under- ■wifigs" and their allies. Here belong nearly two hundred North American species, most likely to attract attention. Fig. 86c. — The cabbage-looper, Autographa brassi- cce: a, male moth; b, egg; c, full-grown larva; d, pupa in cocoon. (After Howard and Chitten- den.) The following are some of those 688 AN INTRODUCTION TO ENTOMOLOGY The underwings or catocalas, Catocala. — The mosi; striking in appearance of thenoctuids, if we except the black witch and one or two alhed species, are the moths belong- ing to the genus Catocala. These moths are of large size, often expand- ing 7 5 mm. or more The fore wings are usually brown or gray, marked with wavy or zigzag lines. The ground- color of the hind Fig. 86i.— Catocala tlia. wings is black ; but in many species these wings are conspicuously banded with red, yellow, or white. This peculiarity has suggested the name underwings by which these insects are commonly known in England. The genus is a very large one; more than loo species are now known from this country; and many of these are extremely variable, so that nearly twice that number of named forms are now recognized. The ilia underwing, Catocala tlia, will serve as an example (Fig. 86 1). The larvee of the underwings feed on the leaves of various forest -trees. Many species infest oak and hickory. By careful search both the adults and larvae can be found resting on the trunks of these trees ; but it needs sharp eyes to do it, as the colors of these insects are usually protective, the bright-colored hind wings of the moths being covered by the fore wings when the insect is at rest. The clover-looping-owlets, Ccenurgia. — Among the more common noctuids that occur in our meadows and pastures, and that fly up before us as we wallc through them, are two species belonging to the genus Ccenurgia. These may be called the clover-looping owlets ; for the larvse feed on clover, and, as they have only three pairs of prolegs they walk in a looping manner. One of these species is Ccenurgia erechtea. This moth (Fig. 862) has dark or light drab-gray fore wings, which are marked by two large dark bands, as shown in the figure. These bands are always separate, distinct, and well defined towards the inner margin in the male; in the female the markings are much less distinct, the bands usually in- visible. The other common species of this genus is Ccenurgia crassiUscula. In this species the fore wings have either a distinct violaceous brown or a red or buffy shade, with the Fig. 862. — Ccenurgia erecUcc LEPIDOPTERA 689 two large dark bands very variable, often shading into the ground- color on the outer edge or coalescing near the inner margin ; all the markings are equally distinct in both sexes. Parallelia histrlaris. — This moth (Fig. 863) is brownish in color, and has the fore wings crossed by two parallel lines. The larva feeds on the leaves of maple. Zale lundta. — This is a brownish moth with marbled wings. It varies greatly in its markings. Figure 864 represents the female Fig. 863 . — Parallelia bistriaris. Fig. 864. — Zale lunata. which was once called edusa, and which does not show well the lunate mark on the hind wings that probably suggested the name of the species. The larva feeds on the leaves of rose, willow, maple, plimi, and other plants. The subfamily Erastriin^. — In this subfamily the moths are of small or moderate size ; and some of them bear a strong resemblance to tortricids. Many of the species are marked with bright colors, and especially with white. The two following spe- cies will serve to illustrate this group. Chdmyris cerintha. — This moth (Fig. 865) is white, with the fore wings marked with shades of olive, brown, and blue. The hind wings have a narrow border of dark scales, within which there may be a cloudy shade as shown in the figure, or this shade may be wanting. The larva feeds on the leaves of apple. Tarachtdia candefdcta. — This species (Fig. 866) is also largely white, with the fore wings marked with shades of olive, brown, and yellow. The amount of yellow varies greatly in different individuals. The larva feeds on the leaves of Ambrosia artemisicBJolia. The subfamily Apatelin^. — This is a large subfamily, including more than 600 North Amer- ican species. The various species grouped to- gether here exhibit great differences in appear- ance. Among those that are most likely to attract attention are the following. The typical genus, ApateJa, includes nearly 100 North American species. This genus is named Acronycta by those authors who do not recognize the names pioposed by Hubner Fig. 86^.— Chamyris cer- intha. Fig. 866.— Tara- chtdia cande- facta. 690 AN INTRODUCTION TO ENTOMOLOGY ■Apatela morula. in his "Tentamen," of which Apatela is one. The fore wings of these moths are generally light gray with dark spots, and in many species have a dagger-lilce mark near the anal angle. On this account they have received the name of daggers. The larv^ae exliibit much diversity in appearance; those of some species are hairy like the larv^te of arctiids, while others are nearly naked. The ochre dagger, Apatela moru- la.—This moth (Fig. 867) is pale gray with a yellowish tinge. Besides the black line forming part of the dagger near the anal angle of the fore wing, there is a similar black line near the base of the wing, and a third near the outer margin between veins Mi and M2. The larv^a feeds on elm and basswood. When full-grown it is mottled brown and greenish like bark; it is clothed with but few scattered hairs, and has a himip on the first, fourth, and eighth abdominal seg- ments. The American dagger, Apatela americdna: — This is -^ gray moth resembling in its general appearance the preceding, but with the black lines on the fore wings much less distinct. Its larva,_ however, is very different (Fig. 868). This larva looks like an arctiid, being densely clothed with yellow hairs. But these hairs are scattered over the sirrface of the body instead of growing from tubercles as with the larvae of arctiids. Along the sides of the body and at each end are a few scattered hairs that are longer than the gen- eral clothing, and there are two pairs of long black pencils borne by first and third abdominal segments, and a single pencil on the eighth ab- dominal segment. When at rest the larva remains curled sidewise on a leaf, as shown in the figure. It feeds on maple, elm, and other forest trees. The witch-hazel dagger, Apatela hamanielis.- — In the latter part of summer and in autimin what is be- lieved to be the larva of this species is common on the leaves of witch-h azel , oak, and other forest trees. It differs greatly in appearance from the pre- ceding species, being nearly naked (Fig. 869). Wlien at rest it usually lies curled as shown in the figure. It varies in color from light yellow to reddish brown. Apatela americana, larva. Its most char- LEPIDOPTERA 691 -Apatela hama- larva. acteristic feature is a double row of milk-white spots along the middle of the back. The copper hindwing, AmpMpyra pyramidoides . — The fore wings of this moth (Fig. 870) are dark brown, shaded with paler brown, and with dots and wavy lines of a glassy gray or dull whitish hue. The hind wings, except the costal third, are reddish with more or less of a coppery luster. This suggests the popular name. The larva feeds on the leaves of grape and of Virginia-creeper. The many-dotted apple-worm. Balsa maldna. In June, and again in August or September, there is sometimes found on apple-trees, in considerable ninnbers, a rather thick, cylindrical, light-green worm, an inch or more in length, with fine, white, longitudinal lines and numerous whitish dots. These are the larvce of the little moth represented by Fignire 871. The fore wings of this moth are ash-gray, marked by ir- regular, blackish lines. The larvae feed on the leaves of many other trees beside apple. The moth has been found throughout the eastern half of our country. The hop-plant borer, Gortyna immdnis .—This, is a well-known pest in the hop-growing regions. The moths deposit their eggs on the tips of the hop-vines just as they begin to climb. The young larva burrows into the vine just below the tip and spends the early part of its life in the vine at this point, causing the injury called by growers "mufflehead." Later the larva burrows to the base of the vine, where it feeds upon the stems. In this stage it is known as the hop-grub. The pupa stage is passed in the ground near the infested roots. The moths emerge in the autumn or in the follow- ing spring. To check the ravages of this pest the muffleheads should be picked off and destroyed while the larvae are still in them. The divers, Bellura.— The genus Bellura contains three North American species, i?. melanopyga,B. diffusa, and B. gortynoides. The first two of these species were bred by the writer from the leaf-stalks of the yellow pond-lily, the habits of the third species are as yet undescribed. The larv^as of the first two species are able to de- scend into water and remain there for a long time ; for this reason the common name the divers is proposed for them. The black-tailed diver, Bellura melanopyga. — Only the female of this species has been described. Fig. 870. — Amphipyra pyramidoi- des. Balsa mat- in this sex the 692 AN INTRODUCTION TO ENTOMOLOGY thick tuft of hair at the caudal end of the body is black or blackish. The larva of this species was first observed in Florida (Comstock '8i). A detailed account of its habits was later published by Welch ('14), who studied it at Douglas Lake, Michigan. It is at first a leaf-miner in the leaves of the yellow pond-lily, later it is a borer in the leaf- stallcs. Its habits are similar to those of the following species. The brown-tailed diver, Bellura diffusa. — Shortly after the dis- covery of the preceding species in Florida, the writer studied larva? with similar habits at Ithaca, N. Y. From these larvae were bred moths which proved to be Bellura diffusa. In this species the anal tuft of the female is dark brown. In the male there is a series of dark tufts on the basal abdominal segments. The young larvae of this species were not observed ; doubtless they are leaf-miners like those of the preceding species. The older larvae live in the leaf-stalks of the pond-lily, a single larva in a leaf-stalk. The larva bores a hole from the upper side of the leaf into the petiole, which it tunnels in some instances to the depth of two feet or more below the surface of the water. This necessitates its remaining below the surface of the water while feeding. The writer has seen one of these larvsi remain under water voluntarily for the space of a half- hour. The tracheae of these larvae are unusually large, and we believe that they serve as reservoirs of air for the use of the insect while under water. The form of the hind end of the larva has also been modified, so as to fit it for the peculiar life of the insect. The last segment appears as if the dorsal half had been cut away ; and in the dorsal part of the hind end of the next to the last segment, which, on account of the peculiar shape of the last segment, is free, there open a pair of spiracles much larger than those on the other segments. When not feeding the larva rests at the upper end of its burrow, with the segment bearing these large spiracles projecting from the water. The white-tailed Bellura, Bellura gortynoides. — In this species the anal tuft of the adult female is white. The habits of the larva have not been described. The cat-tail noctuids, Arzama and Archanara. — Two or more species of noctuids infest the cat-tail plant, Typha, in this country. The larvas of both are at first leaf -miners, later they bore in the stalks. Our most common species is Arzama obltqtta. According to the observations of Claassen ('21) the full-grown larva overwinters in its burrow in the cat-tail plant and transforms in the spring. But the late Professor D. S. Kellicott, who made a special study of this species, informed me in a letter written in 1882, that the larva leaves the cat-tail plant in the fall and conceals itself under bark, in old wood and even in the ground until spring when it pupates, and emerges as a moth in May. It is evident, therefore, that individuals of this species differ as to the location in which they pass the winter. Figure 872 represents either a variety of this species or a closely allied species. It was determined for me by Grote in 1882 as Arzama obliqua. I collected larvae of this form in winter from under bark of fence-posts near water. LEPIDOPTERA 69c Aiazama obligua. Fig. 873. - PsyLhom- orplia epimenis. The grape-vine epimenis, Psychomorpha epimenis.- — This is a vel- vety-black species with a large white patch on the outer third of the front wings and a brick-red patch on the hind wings (Fig. 873). The larva re- sembles somewhat that of Alypia figured on a later page, but it is bluish and has only four light and four dark stripes on each segment. It feeds upon the ter- minal shoots of grape and Virginia-creeper in spring, drawing the leaves together by a weak silken thread and destroying them. When ready to transform, which is us- ually towards the end of May, it either enters the ground or bores into soft wood to form a cell. Within this it remains until the following spring. The beautiful wood-n^Tnph, Eidhisandtia grd- fl^yi^ CO ff^^ /a.— This moth (Fig. 874) well deserv^es the popu- ^I^M^Mj^^^ lar name that has been applied to it. Its front ^^npwd|^| wings are creamy white, with a glassy surface; a ^^f M ^p^ wide brownish purple stripe extends along the costal margin, reaching from the base to a little be^-ond the middle of the wing, and on the outer margin is a band of the same hue, which has a wavy white line running through it, and is margined internally with a narrow olive-green band. On the inner margin is a yellowish olive-green cloud. The hind wings are pale ochre- yellow, with a brown band on the outer margin. The wing expanse is about 40 mm. The moth appears during the latter part of June or early in July. The larva of this species is pale bluish, crossed by bands of orange and many fine black lines. It also bears a resemblance to that of Alypia, but may be distinguished by having on- ly six transverse black lines on each seg- ment. It has the same food-plants as the species described above. It trans- forms in a cell in the ground or in soft wood. The pearl wood-njrmph, Euthisanotia Unio. — This moth closely resembles the species just described, but is smaller, expanding a little less than 37 mm. The outer border of the front wings is paler and mottled; and the band on the hind wings extends from the anal angle to the apex. The larva resembles that of E. grata; it feeds upon the leaves of Epilobium color atum, and perhaps on grape also. The subfamily Cuculliin^. — This subfamily is of considerable size, 264 North American species are now listed. Among them are the following. Fie- Euthisanotia grala. 694 AN INTRODUCTION TO ENTOMOLOGY Fig. 875. — Cucidlia speyeri. The hooded owlets, Cucullia. — We have several common grayish moths, in which the fore wings are marked with niimerous irregular dashes of dark color, and in which the thorax is furnished with a prominent tuft of scales. These moths belong to the genus Cucullia. Figure 875 repre- sents Cucullia speyeri. — These insects evidently have the power of moving this tuft of scales; for sometimes it projects forward over the head as shown in the figure, while in other speci- mens of the same species it may be di- rected backward; in this case it is much less conspicuous. The larva) of the hooded owlets feed upon the flowers of goldenrod and other Compositae. The subfamily Hadenin^. — About 370 North American species are included in this subfamily; among them are the following. The army-worm, Chphis MnipHncta. — The army-worm is so called because it frequently appears in great numbers, and, after destroying the vegetation in the field where the eggs are laid, marches like an army to other fields. This insect occurs throughout the United States east of the Rocky Mountains and is present every year; but it attracts attention only when it appears in great num- bers. The larva is from 40 to 50mm. long when full-grown, and is striped with black, 3^ellow, and green. The adult is of a dull brown color, marked in the center of each fore wing with a distinct white spot (Fig. 876). In seasons of serious outbreak of this pest it usually appears first in limit- ed areas, in meadows or pastures. If it is discovered before it has spread from these places it can be confined by surrounding the field with a ditch, or it may be destroyed by spraying the grass with Paris green water. Ordinaril}^ however, the worms are not observed imtil after they have begun to march and are wide spread. In such cases it is customary to protect fields of grain in their path by suirounding them with ditches with vertical sides ; it is well to dig holes like post- holes at intervals of a few rods in the bottom of such ditches. The worms falling into the ditch are unable to get out, and crawl along on the bottom and fall into these deeper holes. We have seen these insects collected by the bushel in this way. The zebra-caterpillar, Ceramlca picta. — Cabbage and other, garden vegetables are often subject to the attacks of a naked caterpillar, Fig. 876. — Cirphis unipuncta. LEPIDOPTERA 695 Fig. 877. — Ceramica picta, larva. which is of a Hght yellov^ color, with three broad, longitudinal black stripes, one on each side and the top o i the back. The stripes on the sides are broken by numerous pure white lines (Fig. 877). When full-grown the larva enters the ground where it makes a slight silken cocoon in which to trans- form. There are two generations a year. The adult (Fig. 878) has dark chestnut -brown fore wings and pale yellowish hind wings. Certain members of this sub- family have attracted attention on account of their ravages as cut- worms. Several of these belong to the genus Polia, the Mamestra of some authors, which includes more than 100 North American spe- cies. The majority of our described cutworms pertain to the next sub- family. The subfamily Agrotin^. — This is one of the larger of the subfamilies of noctuids, including more than 550 described North American species. Here belong the larger number of those noctuids that are known as cutworms; but other members of this subfamily exhibit quite different habits. The com ear-worm or the cotton boll-worm, Heliothis ohsoleta. — ■ This is a widely distributed pest, the larva of which infests many different plants. It is often found feeding on the tips of ears of growing corn, especially of sugar-corn; in fact it is the worst insect pest of sugar-corn. And it is also one of the more important of the pests of cotton, ranking next to the boll-weevil and the cotton-worm; the larva bores into the pods or bolls of the cotton, destroying them. It frequently infests tomatoes, eating both the ripe and the green fruit. Occasionally it is found within the pods of peas and of beans, eating the immature seeds. It also bores into the buds, seed-pods, and flower-stalks of tobacco. The full-grown larva measures from 30 to 40 mm. in length. It varies greatly in color and markings. The pupa state is passed in the ground. The number of generations annually varies according to latitude; there is probably only one in Canada, but in the Gulf States there are from four to six. Like the larva, the moth is extremely variable in color and markings. The evening primrose moth, Rhodophora fiorida. — This is a very beautiful moth with most interesting habits. It is quite common, flying at night about evening primroses, both wild and cultivated, and hiding during the day in the partially closed flowers. It expands about 30 mm. The fore wings are bright pink or rosy red from the base to the subterminal line, beyond which they are pale yellow, like Ceramica picta. 696 AN INTRODUCTION TO ENTOMOLOGY the flowers of the evening primrose. The hind wings are white. The fading petals of the primrose turn pinkish, and the pink color of the closed fore wings renders the moth invisible when in old flowers, while the yellow tips of the fore wings protruding from a flower still fresh and yellow, forms an equally perfect protection from observa- tion. This moth in its passage from flower to flower transports pollen and is the special means of insuring the cross-fertilization of the even- ing primrose. It attaches its eggs to the stalks of the flower buds or near them. The larvag feed on the petals of the flowers and bore into the buds and seed-vessels. They are bright green, covered with numerous, elevated, white granules; when full-grown they measure 30 mm. in length. Their color is protective. There is a single genera- tion each year. Cttt worms.- — ^Few pests are more annoying than the rascally little harvesters that nightly, in the spring, cut off our com and other plants before they are fairly started. There are many species of these cut-worms, but they are all the larvae of owlet-moths. In general their habits are as follows: The moths lay their eggs during mid- summer. The larvae soon hatch, and feed upon the roots and tender shoots of herbaceous plants. At this time, as the larvae are small and their food is abundant, they are rarely observed. On the approach of cold weather they bury themselves in the ground and here pass the winter. In the spring they renew their attacks on vegetation; but now, as they are larger and in cultivated fields the plants are smaller, their ravages quickly attract attention. It would not be so bad if they merely destroyed what they eat; but they have the un- fortunate habit of cutting off the young plants at the surface of the ground, and thus destroy much more than they consume. They do their work at night, remaining concealed in the ground during the daytime. When full-grown they form oval chambers in the ground in which they pass the pupa state. The moths appear during the months of June, July, and August. There are some exceptions to these generalizations : some species of cut -worms ascend trees during the night and destroy the young buds ; many pass through two generations in the course of a year ; and a few pass the winter in the pupa state. Cut -worms can be destroyed by poisoned baits of fresh clover or other green vegetation, or with poisoned dough made of bran. Much can be done by making holes in the ground with a sharpened stick, as a broom-handle. The holes should be vertical, a foot deep, and wnth smooth sides. On the approach of day the cut- woims will crawd into such holes to hide and will be unable to crawl out again. Fig. 87g.-~Agrotis c-nigrinn. One of our cut-worms, which is known as the spotted cut-worm, is the larva of the black-c owlet, A gratis c-nigrum. This moth (Fig. 879) is one of the most common species attracted to lights. It occurs throughout our country and in Europe. LEPIDOPTERA 697 Family AGARISTID^ The Foresters The validity of this family is in doubt. Some of the best -known genera that were formerly included in it have been transferred to the Noctuidse ; and it is an open question whether or not the remaining genera should be similarly transferred. The character that is used to distinguish these moths from the Noctuidse is that the antennas are more or less thickened towards the tip, while in the Noctu- idas the shaft of the antennae tapers regularly. The ve- nation of the wings (Fig. 880) is very similar to that of some noctuids. The larvae are but slight- ly clothed and live exposed on the leaves of plants. They are distinguished from those of the Noctuidee only in color, nearly all of the species being transversely striped. Our more common species feed chiefly on grape and Virginia-creeper, which they sometimes injure to a serious extent. In such cases they can be destroyed by the use of arsenical poisons, even in vineyards in the East, as the application would have to be made early in the season and the simmier rains would wash the poison from the vines. The pupa state is passed either in an earthen cell or in a very slight cocoon. The family as now restricted is one of limited extent, only sixteen North- American species are known. The larger nimiber of these occur in the Far West or in the Gulf States. The following are the best- known species. The eight-spotted forester, Alypia octomaculdta. — This species is of a deep velvety-black color. The front wings have two large sulphur- yellow spots; and the hind wings, two white spots. The tegulse are sulphur-yellow. In markings both sexes of this species closely re- semble the male of the following species represented in Figure 88 2. The larva (Fig. 881) feeds upon the leaves of grape and Virginia- creeper, and sometimes occurs in such large numbers as to do serious injury. The ground-color of the larva is white, with eight black stripes on each segment, and a broader orange band, bounded by th'i two 2dA Fig. 880. — -Wings of Copidryas gloveri. AN INTRODUCTION TO ENTOMOLOGY middle stripes; the orange bands are marked by black, conical, elevated spots. There are usually two broods each year, the moths appearing on the wing in ^CK- C^W^^'^^^ ^"^ August, the WM'^'^^i^^^^ "^ I caterpillars in June and July, and in September. The pupa state is passed in an earthen cell in the ground. Fig. SSi.—Alypia octomacidata, larva. This Species is found in the Atlantic States from Massachusetts to Texas. Langton's forester, Alypia langtdnii. — This species resembles the preceding in general appearance, but the females can be readily distinguished by the hind wings bearing only a single spot, which is yellow. The males are dimorphic; in one form the males re- semble the females in having a single spot on the hind wings, in the other form there are two spots (Fig. 882). This species is found in northern New York, the mountains of New Hampshire, Canada to the Pacific Coast, and the mountains of Cali- fornia. The larva feeds on fireweed, Epilobium angustifolium. Fig. %%2.— Alypia langtonii. Fig. 883. — Wings of Gnophcela latipennis. Family PERICOPID^ The Pericopids These beautiful in- sects occur within the limits of our country only in the far West and in the Gulf States. They resemble the wood- n>Tnph moths in their strongly contrasting colors; but can be dis- tinguished from them by the position of the origin of vein M2 of the hind wings, which appears to be a branch of cubitus (Fig. 883). This family is repre- sented in our fauna by only four species; but these represent three gen- era. Our most common species is Gnophcsla LEPIDOPTERA 699 latipennis, which is found in the Rocky Mountains and in the Pacific States, in the foot-hills of the Sierra Nevadas. The wings of this species are black spotted with yellow. There is some varia- tion in the ni,imber and size of the spots on the wings. Figure 884 represents a specimen tak- en in Colorado. This is the variety known as vermiculdta. The larva feeds on Merten- sia; when full-grown it meas- ures about 30 mm. in length. The body is blackwith sulphur- yellow interrupted bands and steel-blue tubercles. There are three pairs of the blue tubercles on each side of each segment ; each tubercle bears some short whitish hairs. Fig. 884. — GnophcBla latipennis. Family ARCTIID^ The Tiger-Moths and Footman-Moths or Arctiids The Arctiida3 includes stout-bodied moths, with moderately broad wings, which in the majority of cases are conspicuously striped or spotted, suggest- ing the popular name tiger- moths; some of the species, how- ever, are unspot- ted. A large pro- portion of the species are ex- ceedingly beauti- ful ; this renders the famly a fa- vorite one with collectors. As a rule, when at rest, the wings are folded, roof- like upon the body. Most of the moths fly at night, and are at- tracted to lights. The ocelli are present in the first subfamily, absent in the Wings of Halisidota sp. other two. The 700 AN INTRODUCTION TO ENTOMOLOGY palpi are short .usually but little developed . Themaxillge are present, but they are often weak. The most important features in the venation of the wings are the following; first, the union of veins AI2 and M3 of the fore wings with cubitus, making it apparently four-branched, in a few lithosiids these branches of media are wanting; and second, the coalescence of the subcosta and radius of the hind wings for a considerable distance (Fig. 885). The extent of the union of these two veins varies greatly in the different genera; it is for at least a fifth, usually a half of the length of the discal cell, but not beyond the end of the cell. The lai-\'ae of the tiger-moths, except that of Utetheisa, are clothed with dense clusters of hairs. In fact a large proportion of our common hairy caterpillars are members of this family. In some species, certain of the clusters of hairs are much larger than the others, re- sembling in this respect the clothing of the tussock-moths. Most larvae of the arctiids feed upon herbaceous plants, and many species seem to have but little choice of food-plant; but certain common species feed upon leaves of forest -trees. The family Arctiidae is divided into three subfamilies, each of which is regarded as a distinct family by some writers. These sub- families can be separated as follows : A. Ocelli present, p. 700 Arctiin^ AA. Ocelli absent. B. Fore wings with raised scale-tufts, p. 705 Nolin^ BB. Fore-wings smoothly scaled, p. 704 Lithoshn.e Subfamily ARCTIIN^ The Tiger-Moihs The presence of ocelli distinguishes the members of this subfamily from those of the other two. It is the largest of the three subfamilies, including about 125 North American species. The follow- ing are some of the more com- mon representatives. The genus Haploa.' — Among ^ _, , ^^^^ the more beautiful of the tiger- ''^J^/'^^j^^Mkk ^ ' ^ji^^^HI ™oths is a genus the species of ^^■^' ' ' which are snow-white or light yellow with the fore wings T?- oo/r -r *.7 ,■ banded with brown. In most Fig. 886. — Haploa contigiia. . , 1 1 • i Species the hmd wmgs are un- spotted and are snow-white, but in some the hind wings are yellow. These moths constitute the genus Hap- loa. A species common iti the Atlantic States and represented by Figure 886 is ^ .^^^t^ Haploa contigua. The insects of this ^M^*B»^>w >i ^/"^^-f^JM* genus vary greatly in their markings. %^&i%';^^?i^^^55**'^ The Bella-moth, Utetheisa bella. — ^^^^^^^^^^"^^ This is a whitish moth with lemon-yel- ^l^mM/ %^ 4<\i^^W low or orange-colored fore v/ings, cross- ^^iJfe^ ^/ > M* ed by six transverse white bands, each Fig. 887. — Utetheisa bella. LEPIDOPTERA 701 Fig. 888. — EuchcEtias egle, larva. containing a series of black dots (Fig. 8S7) ; the hind wings are pink, with a black outer margin, which is bordered within by a narrow white line. The species occurs in the Atlantic States and west to Texas. The harlequin milk- weed caterpillar, Euchce- tias egle. — This larva is the most common cater- pillar found on milkweed. It is clothed with tufts of orange, black, and white; those at each end of the body are longer than the others and are arranged radiately (Fig. 888). When full grown the lar- va makes a felt-like co- coon composed largely of its hairs. The adult has mouse-gray wings ; the abdomen is yellow, with a row of black spots along the middle of the back. The genus Apantesis. — A very large munber of species of tiger- moths belong to the genus Apantesis. These are perhaps the most striking in appearance of all members of the family. The fore wings are velvety black marked with yellowish or pink bands; in some species the lighter color predomin- ates, so that the fore wings appear to be yellow or pink, spotted with black. The hind wings are red, pink, or yellow, and are margined or spotted with black. The thorax is usually marked with three black stripes, of which the lateral ones are bonie by the patagia and tegulse. There is also a black line or a row of black spots along the middle of the back of the abdomen, and a similar row of spots on each side. Our most common species of this genus is virgo (Fig. 889). The larva of this species feeds on pigweed and other un- cultivated plants, and winters in the larval state. The salt-marsh caterpillar, Estigmene acrcea. — The popular name of this insect was given to it by Harris, nearly a century ago, and was suggested by the fact that the salt-marsh meadows near Boston, where is now the Back Bay quarter of the city, were overrun and laid waste in his time by swarms of the larvee. But the name is misleading, as the species is widely distributed throughout the Apantesis virgo. 702 AN INTRODUCTION TO ENTOMOLOGY United States, and infests a great variety of grasses and garden crops. The moth (Fig. 890) is white, marked with yellow and black. There are many black dots on the wings, a row of black spots on the back of the abdomen, an- other row on the venter, and two rows on each side. The sexes differ greatly in the ground-color of the wings; in the female, this is white throughout ; in the male. Fig. 890. — Estigmene acrcza. only the Upper surface of the fore wings is white, the lower surface of the fore wings and the hind wings above and below being yellow. The number and size of the black spots on the wings vary greatly. There are usually more submarginal spots on the hind wings than represented in our figure. The fall web worms, Hyphdntria cunea and Hyphdntria textor. — A very common sight in autumn in the North and in midsummer in the South is large ugly webs enclosing branches of fruit or forest trees. These webs are especially common on apple and on ash; but the insects that make them infest more than one hundred kinds of trees. These webs differ from those made by the apple-tree tent-caterpillar in being much lighter in texture and in being extended over all of the leaves fed upon by the colony; and they are also made later in the year. Each web is the residence of a colony of larvae which have hatched from a cluster of eggs laid on a leaf by the parent moth. It is a disputed point whether there are one or two species of fall webworms. In the North the adults are all snow-white in color and there is only a single generation annually. This form is the Hyphan- tria textor of those who believe that there are two species. In the South, some of the moths have the fore wings thickly studded with dark brown points, some are pure white, and every gradation exists between these two types. Of this southern form there are two generations annually. This form is known as Hyphantria cunea; which name should be applied to both the northern and southern forms if they prove to be specifically identical, cuneaheing the older specific name. Both forms winter in the _ pupa state. The Isabella tiger-moth, Isia Isabella. — "Hurrying along like a caterpillar in the fall" is a common saying among country people in New England, and probably had its origin in observations made upon the larva of the Isabella tiger-moth. This is the evenly clipped, furry caterpillar reddish brown in the mid- dle and black at either end, which is ..,,,, seen so commonly in the autumn ^'^- ^9i.-Ista ^sabella, larva. and early spring (Fig. 891). The extent of the black color varies in different individuals; rarely, es- pecially on the West Coast the body is all brown. In the spring after LEPIDOPTERA 703 feeding for a time the larva makes a blackish-brown cocoon composed largely of its hair. The adult is of a dull grayish tawny -yellow, with a few black dots on the wings, and frequently with the hinder pair tinged with orange-red. On the middle of the back of the abdomen there is a row of about six black dots, and on each side of the body a similar row of dots. The yellow-bear, Diacnst'a virglnica. — The larva of this species is one of the most common hairy caterpillars found feeding on herba- ceous plants. It was named by Harris the yellow-bear on account of the long yellow hairs with which the body is clothed. These hairs are uneven in length, some scattered ones being twice as long as the greater nimiber of hairs. The long hairs are more numerous near the caudal end than elsewhere, but are nowhere gathered into pencils as with the tussock-caterpillars. This larva varies greatly in color. The body is most often of a pale yellow or straw color, with a black, more or less interrupted, longitudinal line along each side, and a more oi* less distinct transverse line of the same color between each of the segments. Sometimes the hairs are foxy red or light brown, and the body brownish or even dark brown. The head and the ends of the feet and forelegs are yellowish, and the venter is dusky. The larva feeds on almost any plant. The cocoon is light, and is composed almost entirely of the hairs of the caterpillar. This insect passes the winter in the pupa state; and it is probable that there are usually two or more broods each year; but these are not well marked. The moth (Fig. 892) is snowy white, with the wings marked by a few black dots; these vary in number, but there are rarely more than three on either wing. There is a row of Diacrisia virginica. Fig. 893.- -Halisidota caryce, larva. black spots on the back of the abdomen, and another on each side, and between these a longitudinal deep yellow stripe. 704 AN INTRODUCTION TO ENTOMOLOGY The hickory tiger-moth, Halisidota cdrycB. — One of the most abun- dant of caterpillars in the Atlantic States and westward during the months of August and September is one clothed with dense tufts of finely barbed white hairs. (Fig. 893) ; there is a ridge or crest of black hairs on the middle of the back of the abdominal segments, a few long white hairs projecting over the head from the thorax, and others pro- jecting back from the last segment; there are also two pairs of pencils of black hairs, one on the first and one on the seventh abdominal segment, and a similar pair of pencils of white hairs on the eighth abdominal segment. This larva feeds on hickor}^ butternut, and other forest-trees. Its grayish cocoons, composed almost entirely of the hair of the larva, are often found under stones, fences, and other similar places. The fore wings of the adult (Fig. 894) are dark brown spotted with white. Fig, 894, — Halisidota caryce. Subfamily LITHOSIIN.E The Footman-Moths The Lithosiinse include small moths with rather slender bodies, filiform antennas, and usually narrow front wings and broad hind wings. As a rule they are closely scaled insects of sombre colors, a fact that has won for them the title of footman-moths; but in case of some 06 the species their livery is very gay. Some species fly by day, while others are attracted to lights at night. The Lithosiinag differ from the preceding subfamily and agree with the following one in lacking ocelli. They differ from the following subfamily in having the fore wings smoothly scaled. The venation of the wings differs greatly in the different genera. In some genera veins M2 and M3 of the fore wings are wanting. The larvae are cylindrical and covered with short, stiff hairs. The majority of the species whose transformations are known feed upon lichens. They transform in very delicate cocoons or have naked pupas. This subfamily includes about fifty North American species, of which the following are some of the more common ones. The striped footman, Hypoprepia minidta. — This beautiful moth is of a deep scarlet color, with three broad lead colored stripes on the front wings. Two of the stripes extend the entire length of the wings ; while the third is between these and extends from the end of the discal cell to the outer margin (Fig. 895). The outer half of the hind wings is also slate-colored. Vein M2 of the fore wings is Fig. 895. — Hypoprepia miniata. LEPIDOPTERA 705 present ; but Vein M2 of the hind wings is wanting. The larva feeds upon Hchens, and may be found under loose stones or on the trunks of trees. It is dusky, and thinly covered with stiff, sharp, and barbed black bristles, which grow singly from small warts. The cocoon is thin and silky. The painted footman, Hypoprepia fucosa. — This species is very similar to the preceding one and has been confounded with it. With the painted footman the ground-color of the fore wings is partly yellow and partly pink. The clothed-in-white footman, Clemensia albdta.- — The specific name of this insect is somewhat misleading; for although the general color of the moth is white, there are so many ashen and gray scales, and dark spots, that the general effect is gray. On the front wings the more prominent black spots are six or seven on the costa, one on the discal vein, and a row of small ones on the outer margin. The hind wings are white, but finely dusted with gray scales. With this species Vein M2 is present in both fore and hind wings. The banded footman, Illice unifascidta. — This little beauty (Fig. 896) occurs in the Atlantic States from New York to Texas. The fore wings are lead-colored, and crossed by a yellow band, which extends also along the inner margin to the base of the wings. The hind wings are pink except the apex, which is lead-colored. There is much varia- tion in the width of the yellow band. Fig- S96.— Illice There are several closely allied species which are umfasciata. difticult to distinguish from this one. The pale footman, Cramhidia pallida. — This moth is of a uniform drab color with the abdomen and the inner part of the hind wings paler; it expands 22 mm. The moths of the genus Cramhidia can be recognized by the fact that veins M2 and M3 of the fore wings are both wanting, leaving cubitus only two-branched. The two-colored footman, Tigrioides bl color. —This, is larger than the preceding species, expanding from 25 to 37 mm. It is slate-colored, with the palpi, the prothorax, the costa of the fore wings and the tip of the abdomen yellow. Vein M2 of the fore wings is wanting, leaving cubitus apparently three-branched. Subfamily NOLIN^ The Nolinas are small arctiids in which the ocelli are wanting and in which there are tufts of raised scales on the fore wings. It is a small subfamily including only fifteen North American species. Our most common species is the following. Celama triquetrdna.- — This is a gray moth with a wing-expanse of 17 to 20 mm. On the fore wings there is a short black or dark brown stripe at the base of the costa, and beyond this two spots of the same color, the outer one is near the middle of the length of the costa. The larva infests the foliage of apple, but not in sufficient numbers to be a pest. 706 AN INTRODUCTION TO ENTOMOLGOY Family EUCHROMIID^ The family SyntomidcB of various lists. These moths are most easily distinguished from the alHed famiHes that are represented in this country by the structure of the hind wings (Fig. 897); in these the subcosta is apparently absent except at the base of the wing, where it is sepa- rate from radius for a short distance. Occasionally forms are found in which the tip of subcosta is sepa- rated from radius. In some of the more specialized forms, the hind wings are greatly reduced in size and the venation is reduced. Among the better- known representatives of this family are a small num- ber of bluish-black or brown moths which have more or less vermilion or yellow on the head, prothorax, and patagia. These moths are of mediiim size, expanding from 30 to 50 mm. The dull color of the wings is usually Fig. 897. — Wings of Ctenucha virginica. relieved by the bright color of the head and patagia; and by a layer of blue scales covering the thorax and abdomen ; but in some species these are wanting. The larv« feed on grasses. Some of them strongly Fig. 898. — Ctenucha virginica. Fig. 899. — Scepsis julvicoUis. resemble those of the Arctiidas in appearance as well as in habits, being thickly clothed with hair; they also spin cocoons similar to those of arctiids. Our common forms of this group represent two genera, Ctenucha and Scepsis. In the East we have only a single species of LEPIDOPTERA 707 each of these genera, Ctenucha virginica, which is represented by Figure 898, and Scepsis Julvicollis, represented by Figure 899. The larvcB of both of these species feed on grasses. Closely allied to these is another species, which is common in the East, Lycomorpha pholus. This is black with the basal half of the fore wings and the basal third of the hind wings yellow (Fig 900). A variety of this Yig.^oo.-Lvcomorpha species occurs m Cahiomia and other parts phohis. of the West in which the lighter parts of the wings are pinkish instead of yellow. These moths occur in stony places, where the larvae feed on lichens growing on rocks. In the extreme southern part of this country and in the regions south of that, there occur highly specialized members of this family, in which the hind wings are greatly reduced in size, and the veins of the hind wings coalesce to a remarkable degree. In some of these forms the discal portion of the wings bears but few if any Cosmosoma myro- ^^^^^^ Cosmosoma myrodora from Flori- da (Fig. 901) will serve as an example of these. In this species the body and legs are bright red, with the head end of abdomen, and a dorsal band blue-black; the veins and borders, of ths wings are also black. Family EUPTEROTID^ This family is represented in North America by a single genus, Apatelodes, of which only three species occur in our fauna. These moths bear a striking resemblance to the Notodontid^, but differ in lacking maxilla. The moths usually have hyaline dots on the fore wings near the apex. The venation of the wings is very similar to that of the Notodontidae. Vein Cu of the hind wings is apparently three-branched, and in our species the frenulum is normal. The egg is flat, wafer-like, unlike that of the Notodontidae which is spherical with the micropyle at the top. The larvs are cylindrical and are covered with numerous secondary setas, some short, others much longer; there are no fleshy protuberances or verrucas present. The mediodorsal setas are usually grouped into a distinct tuft on each segment, sometimes forming long pencils. The pupa state is passed in the ground. Our two best -known species are the following. Apatelodes torrefdcta. — The moth is soft velvety ashen. The fore wings are falcate and are crossed by four wavy, brown lines; there is a hyaline dot near the apex, margined externally with reddish brown; there is a double reddish brown spot near the base of the inner margin. The wings expand from 45 to 50 mm. The larva is a yellowish or whitish, long-haired caterpillar, about 50 mm. long. There are conspicuous pencils of dark hairs on the 708 AN INTRODUCTION TO ENTOMOLOGY dorsimeson of the last two thoracic segments and the eighth abdominal segment. It occurs in midsummer on various shrubs and trees. Apatelodes angelica.- — The moth (Fig. 902) is of a pale soft steel- gray, with the outer margins of the wings toothed. The fore wings are crossed by two bands of a darker shade. The hyaline spot near the apex of the wings is usually doubled ; and there is no brown spot near the base of the inner margin as in vl. torrefacta. The wings ex- pand from 47 to 50 mm. '"^^^- *nj^. Fig. 902. — Apatelodes angelica. (From Packard.) The larva (Fig. 902) feeds on ash and on lilac. It is g^-ayish brown : the setae of the dorsimeson are comparatively short, bus are grouped in a small tuft on each body segment; no pencils are present. Family EPIPLEMIDtE This family includes moths in which the body is slender and the wings ample. In their general appearance, these moths resemble geometrids; but can be distinguished from them by the venation of LEPIDOPTERA 709 the hind wings in which veins Sc+Ri and Rg separate near the base of the wing and are strongly divergent, resembling in this respect the Lacosomidas. In the fore wings, vein Cu is apparently three-branched and veins R5 and Mi are stalked and are well separated from vein R4. The frenulum is present in our species. The moths rest with the fore wings spread and the hind wings separated from them and partly rolled about the body. Only five North American species of this family have been de- scribed, but these represent four genera. Two of these genera, Philagraula and Schidax, are each represented by a single species found in Florida. Calltzzia amordta. — This is the best -known of our species; it is found both in Canada and the United States. The moth expands about 20 mm. It is pearly-ash colored. Both pairs of wings are crossed near the middle of their length by two wavy dark lines, which are connected by a bar of the same color near the inner margin of the fore wings. On the fore w4ngs there is a third similar line near the outer margin. The larva feeds on the leaves of Lonicera dioica. The pupa state is passed at the surface of the ground. Calleddpteryx dryopterata. — This species is found in the Atlantic States. The moth is pale ochreous in color, sometimes of a pale wood-brown. Both pairs of wings are crossed by two transverse dark lines. The wing expanse is 20 mm. The larva feeds on Vi- burnum nudum. The pupa state is passed between the leaves. Family THYATIRID^ The Thyatirids The family Thyatiridse includes moths of medium size with elon- gated wings. The front wings are usually slightly widened at the anal angle (Fig. 903), and in our more common species are conspicu- ously marked with wavy or zigzag lines. The antennas are filiform and more or less velvety or pubescent in the male, and the maxillae are well developed. The moths fly by day, and when at rest fold their wings roof -like upon the abdomen. The venation of the wings is illustrated by Figure 894. The important features to be noted are the following: In the front wing vein M2 arises midway between veins Ml and M3. In the hind wing vein Sc-f Ri ^ig,go2,.-Habrosynescripta. and vein Rs are closely parallel for a space beyond the end of the discal cell and vein Mi is jointed to vein Rs by a comparatively long cross-vein (Fig. 904, c.v.), so that the two appear to separate before the end of the discal cell. In the males the tip of the frenulum is knobbed. The larvae are naked, and live upon the leaves of shrubs and trees. They often conceal themselves in a case, made by loosely fastening together leaves, or by folding a single leaf. 710 AN INTRODUCTION TO ENTOMOLOGY Only twelve species are known in our fauna; these represent five genera. One of the more common species is Habrosyne scnpta. This has fawn-colored front wings, conspicuously marked with light bands and zigzag lines (Fig. 903). According to Thaxter, it lays its eggs late in July, in chains of five or six, on the leaves of rasp- berr>% upon which the larvae feed. The ma- ture larva is rich yel- low-brown, often al- most black, with a distinct dorsal black line. The lateral por- tions are more A^ellow with blackish mott- lings. When at rest the larva either elevates the cephalic and cau- dal ends of the body, like the notodontids, so that the head rests upon the caudal seg- ments, or conceals it- self in a case formed by curling down the edge of a leaf. It makes a ver>^ slight cocoon late in August. Another common species is Psettdothya- tira cymatophoroides . This species is slightly larger than the preceding one, expanding nearly 50 mm. The front wings are silky gray tinted with rose. They are marked with a black spot at the base, a double or triple line, forming a black band at the end of the basal third of the wing, two black spots on the outer half of the costa, a black spot at the anal angle, and a row of black points on the outer margin. There is a variety, expultrix, which lacks the black band and the four black spots. The larva of this species has been foimd on red oak; it is of a rich yellow-brown, mottled with fine dark lines, and lives in a case made by fastening leaves together; some specimens have several cream-white spots. It makes a slight cocoon late in September; the adult emerges in June. Family DREPANID^ The Drepanids The typical members of this family are small, slender-bodied moths, which can be easily recognized by the sickle-shaped apex of Wings of Habrosyne scripta. LEPIDOPTERA 711 the front wings (Fig. 905). An approach to this form of wing is represented by some saturnians and by certain geometrids; but the former are larger, stout-bodied moths, and both differ in wing-venation, cubitus of the fore wings appearing only three-branched with them, whereas it appears to be four-branched with the drepanids. In addition to the more typical members of this family, which are known as the hook-tip moths, there occurs in our fauna a single species, Eudeilmia herminidta, in which the fore v ings are not falcate (Fig. 906) . In this family veins Sc-f-Ri and vein Rs of the hind wings are closely parallel or coalesced for a space beyond the end of the discal cell, resembling in this respect the Thyatiridse. But the Thyatiridse Fig. 905. — Drepana ar- cuala. r:Rz^§iR R.^^ 2d A 2d A Fig. 906. — Wings of Eudeilinia hermimata. Fig. 907. — Wings ol Drepana arcuata. are true frenulum-conservers, while the Drepanidas exhibit a very anomalous condition as regards the preservation or loss of the frenulum. While the form of the humeral angle of the hind wings in the DrepanidcB is that characteristic of the frenulum-losers, some of these moths retain the frenulum and in others it is lost (Fig. 907 and 90S). When the frenulum is present it is borne at the end of a long costal sclerite. 712 AN INTRODUCTION TO ENTOMOLOGY /?./?, The larvee are remarkable in having the anal prolegs vestigial, and the caudal segment prolonged into a more or less lizard-like tail. They live upon the foliage of shrubs and trees, and transform in a web between leaves, or in a case in a rolled leaf. Only six species belong- ing to this family occur in our fauna. These represent three genera; the venation of the wings of a species of each of these genera is figured here. Our most common hook-tip moth is Drepana arcudta. The t^^pical form of this species is of a dirty white color marked with dark brownish lines, and bands as shown in Figure 905. A summer form of this species differs in being of a light ochre-yellow color and in the course of the wavy lines on the front wings; this was described as a distinct species under the specific name gemcula. These two forms are found in the Atlantic States. A third form of this species occurs in California ; this was described under the specific name siculijer. Our single representative of this family that is not a hook-tip moth is EudeiUnia herminidta. This is a small moth with delicate snow- white wings, which expands from 18 to 25 mm. The venation of the wings is shown in Figure 906. The larva lives on cornel; the caudal prolongation of the body is very short. This species is found in the Atlantic States. Fig. 908. — Wings of Oreta rosea. Family LACOSOMID^ This family is of special interest on account of the structure of the wings of its members. While these moths clearly belong to the series of frenuliim-losing moths, having the humeral angle of the hind wings greatly expanded so that a frenulum is not needed to insure the synchronous action of the fore and hind wings, they retain a vestige of a frenulum (Fig. 909). This vestige, however, is very small and is probably no longer of any use. It was the presence of this vestige that first suggested to the writer that those families of the LEPIDOPTERA ■13 Lepidoptera which he termed Frenulum-losers were descended from frenulum-bearing ancestors (Comstock '93). The Lacosomidas seem to be the sole sur- vivors of a very distinct line of descent . In many- respects they appear to be closely allied to the Bombycidce and to the Satumioidea ; but they differ markedly both in the structure and in the habits of the larvae ; and, too, the wings of the adult, although at first sight resembling those of the silk-worm, are really quite different. In the coalescence of the branches of radius of the fore wings veins R3 and R4 remain widely sepa- rate, while in the Bomby- cidse and in the Satumi- oidea these are the first branches to coalesce. This is a small New World family. Members of it are distributed over a large part of the West- ern Hemisphere; but so far as is now known only three species occur in the United States. Two of our species are found in the East ; the third one, Lacosdma arizonicum, was described from Arizona. Melsheimer's sac-bearer, Ciclnnus melsheimeri.- — The larva feeds on the leaves of various species of oak. The habits of the young larvae have not been described. The older larvae make cases of leaves in which they live and which they carry about (Fig. 910). The adult moth (Fig. 911) is of a reddish gray color, finely sprinkled all over with minute black dots ; there is a small black Fig. 909. — Wings of Cicimius melsheimeri. Fig. 910. — Case of larva of Cicinmis. spot at the end p- of the discal cell Cicinmis melshei- of the fore wings ; and both pairs of wings are crossed by a narrow blackish band. 714 AN INTRODUCTION TO ENTOMOLOGY Lacosoma chiridota.- — Although this is the rarer of our two eastern species its complete life-history has been published by Dyar ('oo). He found the larvae common on scrub oaks on Long Island. The eggs are laid on the edge of the leaf or on one of its points. The first three instars live under a net of silken threads on the upper surface of a leaf. At the end of the third stadium the larva begins to make a case; but the larva does not leave its net and construct a complete case until during the fifth stadiiun. At the end of the sixth stadii.mi "the larva spins up one end of the case and hibernates. Pupation in the spring. A single brood in the year. " The moth is somewhat smaller than the preceding species, and darker yellowish brown in color; the outer margins of the fore wings are more scalloped. SuPERFAMiLY SATURNIOIDEA The Saturniaiis The superfamily Satumioidea includes the largest of our native moths; in fact nearly all of our very large moths belong to it, but it also includes a considerable number of species of moderate size. These moths are most easily distinguished from other moths by the structure of their wings. Here, as with the skippers and the butter- flies, the frenulum is lost and its place is taken by a greatly expanded humeral angle of the hind wing (Fig. 912), which, projecting un- der the fore wing, insures the acting together of the two in flight without the aid of a frenulimi. This losing of the frenulimi is also char- acteristic of the Lasiocam- pidas and of some members of the Drepanidse; but the saturnians difi:er from these moths in that vein M2 arises midway between radius and cubitus or is more closely united to radius than to cu- bitus, leaving the latter ap- parently three-branched while in the Lasiocampidas and in the Drepanidas cubi- tus appears to be four- '"^ branched. In the Lacoso- Fig. 912. — Wings of atheroma regalis. midse and in the Bombyci- dae the humeral angle of the hing wings is greatly expanded, but in each of these families a vestige of a frenulimi is retained. LEPIDOPTERA 715 In the Saturnioidea the branches of radius of the fore wing^s are crowded closely together and at least one of them is lost. In all of our species the antennae are naked or bear very few scattered scales. This superfamily includes two families, the North American forms of which can be separated as follows. A. Vein Mi of the fore wings coalesced with radius to a point beyond the apex of the discal cell; vein Mi of the hind wings joined to radius by the cross-vein r-m (Fig. 912), Antennae of males pectinated but little more than half way to the apex. p. 715 Citheroniid^ AA. Vein Mi of both fore and hind wings joined to radius by the cross-vein r-m (Fig. 919) or rarely (Coloradia) coalesced at its base with radius in both fore and hind wings. Antennas of males pectinated to the apex. p. 719. . . Saturniidte Family CITHERONIID^ The Royal-Moths The royal-moths are stout -bodied and hairy, with sunken heads and strong wings. The species are of medium or large size, some of them being nearly as large as the largest of our moths. There are two anal veins in the hind wings; vein Ml of the fore wings separates from radius beyond the apex of the discal cell (Fig. 912 and 913); veins Mi and M2 of the hind wings are joined to radius by vein r-m. The anten- nae of the males are broadly pecti- nated, but for only little more than half their length. The palpi and the maxillae are very small. The larvffi are armed with horns or spines, of which those on the second thoracic segment, and some- times also those on the third, are long and curved. These caterpillars eat the leaves of forest -trees, and go into the ground to transform, which they do without making cocoons. The rings of the pupa bear little notched ridges, the teeth of which, together with some strong piickles at the hinder end of the body, assist it in forcing its way upwards out of the earth. A monograph of this family including many colored figures of moths and larv^ was published by Packard ('05). This is a small family; it is not represented in Europe, and less than twenty species are known to occur in this country. The more common ones are the following. \~-- , ^^^^T" ^M, ^X X^Js/^""^ -Cu. •^p 20^ A k 'ig- 913- -Wings of Anisota virgin- lensts. 716 AN INTRODUCTION TO ENTOMOLOGY I LEPIDOPTERA 717 The regal-moth, Citherdnia regalis. — This is the largest and most magnificent of the royal-moths (Fig. 914)- The fore wings are olive- colored, spotted with yellow, and with the veins heavily bordered with red scales. The hind wings are orange-red, spotted with yellow, and with a more or less distinctly marked olive band outside the middle. The wings expand from 100 to 150 mm. When fully grown the larva measures from 100 to 125 mm. in length. It is our largest caterpillar, and can be readily recognized by the very long spiny horns with which it is armed. Those of the mesothorax and metathorax are much longer than the others.' Of these there are four on each segment ; the intermediate ones measure about 1 5 mm. in length This larva feeds on various trees and shrubs. It is known in some regions as the hickory harried devil. The imperial-moth, Basilona imperidlis. — This moth rivals the preceding species in size, expanding from 100 to 137 mm. It is sul- phur-yellow, banded and speckled with purplish brown. The full grown larva (Fig. 915) measures from 75 to 100 mm. in length. It is thinly clothed wth long hairs, and bears prominent spiny horns on the second and third thoracic segments. In the early larval stages Fig. 915. — Basilona tmpcrialis, larva. these thoracic horns are very long and spiny, resembling those of the larva of the regal-moth . The larva feeds on hickory , pine, oak, butter- nut, and other forest -trees. The two-colored royal-moth, Adelocephala htcolor: — In this species the upper side of the fore wings and the under side of the hind wings are yellowish brown, speckled with black. The under side of the fore wings and the upper side of the hind wings are to a considerable extent pink. There is usually a dark discal spot on the fore wings, upon which, especially in the males, there may be two white dots. This species is more common in the Southern States than in the North. The expanse of wings in the male is 50 mm.; in the female, 60 mm. The larva feeds on the leaves of the honey-locust and of the Kentucky coffee-tree. Anisota. — The genus Anisota contains four species of moths found in the Northeastern United States. These moths are dark yellow, 718 AN INTRODUCTION TO ENTOMOLOGY Fig. 916. — Anisota male. virgtmensis, purplish red, or brownish in color, and agree in having the fore wings marked with a white discal dot. The larvae feed on the leaves of oak; they are more or less striped and are armed with spines. These in- sects hibernate as pupae. In determining these moths, the student should remember that the two sexes of the same species may differ more in appearance than do individuals of different species but of the same sex. The sexes can be distinguished, as already indicated, by the antennas. The three species can be separated as follows. The rosy-striped oak-worm, Anisdta virginiensis.- — -The wings of the female are purplish red, blended with ochre-yellow; they are very thinly scaled, and consequent- ly almost transparent; and are not speckled with small dark spots (Fig. 916). The wings of the male are purplish brown, with a large transparent space on the middle (Fig. 917). The larva is of an ob- scure gray or greenish color, with dull brownish yellow or rosy stripes, and with its skin rough with small white warts. There is a row of short spines on each segment, and two long spines on the mesothorax. The orange-striped oak-worm, Anisdta senatoria. — The wings of the female are more thickly scaled than in the preceding species and are sprinkled with niimerous blackish dots; in other respects the two are quite similar in coloring. The male differs from that of A. virginiensis in lacking the large transparent space on the middle of the wings. The larva is black, with four orange-yellow stripes on the back and two along each side; its spines are similar to those of the preceding species. The spiny oak-worm, Anisota stigma. — The female closely resembles that of A. senatoria; and as both species are variable it is sometimes difficult to determine to which a given specimen belongs. In A. stigma the wings are rather darker and have a greater number of blackish spots, and the hind wings are furnished with a middle band which is heavier and more distinct than in A. senatoria. The male differs from that of the other two species in quite closely resembling the female in color- ing, and in having the wings speckled. The larva differs from the other species of Anisota in having long spines on the dorsal aspect of the third thoracic and each abdominal segment in addition to the much longer spines on the mesothorax. It is of a bright tawny or orange color, with a dusky stripe along its back and dusky bands along its sides. Fig. 917. — Anisota virgin- iensis, male. LEPIDOPTERA 719 The rosy Anisota, Anisota rubicunda. — The wings of this moth (Fig. 918) are pale yellow, banded with rose-color. The distribution of the color varies greatly in different specimens. In some the pink of the fore wings pre- dominates, the yellow being re- duced to a broad discal band, while in one variety the ground- color is yellowish white and the pink is reduced to a shade at the the base and a narrow stripe out- side the middle. The hind wings may be entirely yellow, or may " "Z- ^,0 . -"^^^^^"^ , -^ • 1 u J 1 -J 4.1, Fig. 918. — Amsota rubicunda. have a pmk band outside the middle. The expanse of wings in the male is 35 to 43 mm. in the female 50 mm. or more. The larva of this species is known as the green-striped maple- worm, and is sometimes a serious pest on soft-maple shade-trees. It measures when full grown about 37 mm. It is pale yellowish green, striped above with eight very light, yellowish green lines, alternating with seven of a darker green, inclining to black. There are two prominent horns on the second thoracic segment, and two rows of spines on each side of the body, one above and one below the spiracles. And on the eighth and ninth abominal segments there are four prominent dorsal spines. The species is one- or two-brooded, and winters in the pupa state. Family SATURNIID.E The Giant Silk-Worms The large size of members of this family and the ease with which cocoons of some of the species can be collected render them well known to every beginner in the study of entomology. They are stout-bodied, hairy moths with more or less sunken heads and strong wide wings. The palpi are small, and the maxillae but little developed, often vestigial. The sexes of these moths can be ditinguished by the fact that the antennse of the males are more broadly pectinated than are those of the females. The family includes our largest lepidopterous insects and all of our species are above miedium size. They can be distinguished from the Citheroniidae, some of which rival them in size, by the form of the antennae of the males, which are pectinated to the apex; and in all of our genera, except Colorddia, which is found in the Rocky Mountains, vein Ml of both fore and hind wings is joined to radius by the cross- vein r-w (Fig. 919). The wings are often furnished with transparent, window-like spots. The frenulum is completely lost. The humeral angle of the hind wings is largely developed, and is usually strengthened b}^ a deep 720 AN INTRODUCTION TO ENTOMOLOGY furrow, the bottom of which is sometimes thickened so as to ap- pear Hke a humeral vein (Fig. 919). The larvae of most of our species live ex- posed on the leaves of trees and shrubs ; but some of them, as the New Mexico range- caterpillar, feed on grass. They are more or less armed with tubercles and spines and are very conspicu- ous on account of their large size. Most of them transform within silken cocoons, which are usually very dense, and in some cases have been utiliz- ed by man. These co- coons are often at- tached to trees and shrubs, and are some- times inclosed in a leaf. They can be easily collected during the winter months, and the adults bred from them. The lar- va3 of some members of the family, as Hemi- leuca mdia, enter the ground to transform. The family Satumiidee as now recognized includes what were formerly regarded as two distinct families, the Hemileucidee and the Satumiid^. Our latest list includes only 34 species, of which the following are the better known. The Maia-moth, Hemilenca niaia. — The genus Hemileuca is represented in our fauna by elev- en species, but only one of these is found in the East. In this species (Fig. 920) the wings are thinly Fig. ^20.— Hemileuca maia. Fig. 919. — Wings of Samia cecropia LEPIDOPTERA 721 scaled, sometimes semi-transparent; they are black with a common white band near their middle; and the discal veins are usually white and broadly bordered with black. There are great variations in the width of the white band on the wings. The larva feeds on the leaves of oak ; it is brownish black, with a lateral yellow stripe ; and is armed on each segment with large, branching, venomous spines. The larva almost always enters the ground to transform. The New Alexico range-caterpillar, Hemileiica oUvics. — Of the ten western species of Hemileuca this is doubtless of the greatest economic importance. It is a grass-feeding species, which has been very de- structive in certain sections of the cattle-range in northeastern New Mexico. It was estimated that in 1909 the total infested area was at least 15,000 square miles, and that there were an average of 10 caterpillars to the square rod over this region. For a full account see U. S. Dept. Agr. Bull. No. 85, Part V. Fig. 921. — Pscudohazis hcra. Pseudohdzis. — In the West there occur two species of Pseudohazis. These are P. hera in which the ground-color of the wings is white (Fig, 921), and P. eglantenna, in which the ground-color is buff or salmon. Both species are spotted and striped with black as shown in the figure. Colorddia pandora. — This is a brownish gray species found in the Rocky Mountains. The wings are only moderately broad, and each is marked with a small black spot at the end of the discal cell. The hind wings are semi-transparent. The expanse of the wings is from 75 to r22 AN INTRODUCTION TO ENTOMOLOGY loo mm. This genus is easily recognized by the fact that vein Mj of both fore and hind wings is coalesced at its base with radius. The larvas live in the tops of pines and are abundant in alternate years; they are dried and eaten by Indians. The lo-moth, Automeris io. — This is a com- mon species in the East. The female is repre- sented by Figure 922. In this sex the ground-color of the fore wings -S purplish red. Fig. <)22.— Automeris io. The male differs greatly in ap- pearance from the female, being somewhat smaller and of a deeper yellow color, but it can be easily recognized by its general resemblance to the female in other respects. The larva is one that the student should learn to recognize in order that he may avoid handling it; for it is armed with spines the prick of which is venomous (Fig. 923) The same is true of the larva , of the Maia-moth, but that is much less common. The larva of the lo-moth is green, with a broad brown or reddish stripe, edged below with white, on each side of the abdomen. The spines are tipped with black. This larva feeds on various trees and shrubs. The poly ph emus-moth, Telea polyphetmis. — This is a yellowish or brownish moth with a window-like spot in each wing. There is a gray band on the costal margin of the fore wings ; and near the outer margin of both pairs of wings there is a dusky band, edged without with pink ; the fore wings are crossed by a broken dusky or reddish line near the base, edged within with white or pink. The transparent spot on each wing is divided by the discal vein, and encircled by yellow and black rings. On the hind wings the black surrounding the trans- parent spot is much widened, especially toward the base of the wing, and is sprinkled with blue scales. The wings expand from 125 to 150 mm. The larva (Fig. 924) feeds on oak, butternut, basswood, elm, maple, apple, plum and other trees. When full grown it measures 75 mm. or more in length. It is of a light green color with an oblique yellow line on each side of each abdominal segment except the first Fig. 923. — Automeris io, larva. LEPIDOPTERA 723 and last ; the last segment is bordered by a purplish-brown V-shaped mark. The tubercles on the body are small, of an orange color with metallic reflections. The cocoon (Fig. 925) is dense and usually en- closed in a leaf; it can be utilized for the manufacture of silk. When Fig. 924. — Telea polyphemus, larva. the adult is ready to emerge, it secretes a fluid which softens the cocoon at one end, and breaking the threads by means of a pair of stout spines, one on each side of the thorax at the base of the fore wings, it makes its exit through a large round hole. The Luna-moth, Tropcea luna. — This magnificent moth (Fig. 926) is a great favorite with amateur collectors. Its wings are of a delicate light green color, with a purple- brown band on the costa of the fore wings ; there is an eye- like spot with a transparent center on the discal vein of each wing ; and the anal angle of the hind wings is greatly prolonged. The larva feeds on the leaves of walnut, hickory, and other forest-trees. It measures when full Fig. 925. — Cocoon of Telea polyphemus. 724 AN INTRODUCTION TO ENTOMOLOGY Fig. 926. — Tropcea lima. I'lg. g2j .—Callosamia promethea, lemaie. LEPIDOPTERA 725 grown about 75 mm. in length. It is pale bluish green with a pearl- colored head. It has a pale yellow stripe along each side of the body, and a transverse yellow line on the back between each two abdominal segments. The cocoon resembles that of the preceding species in form, but is ver>^ thin, containing but little silk. The Promethea-moth, Callosdmia promethea. — This is the most common of the giant silk-worms. The wings of the female (Fig. 927) are light reddish brown; the transverse line crossing the middle of the wings is whitish, bordered within with black; the outer margin of the wings is clay-colored, and each wing bears an angular discal spot. The discal spots vary in size and distinctness in different specimens. The male differs so greatly from the female that it is liable to be mistaken for a distinct species. It is blackish, with the transverse lines very faint, and with the discal spots wanting or very faintly indicated. The fore wings also differ markedly in shape from those of the female, the apex being much more distinctly sickle shaped. The males fly by day . The larva when full grown measures 50 mm. or more in length. It is of a clear pale bluish- green color; the legs and anal shield are yellowish ; and the body is armed with longitudinal rows of tubercles. The tubercles are black, polished, wart-like ~ elevations, excepting two each on the second and third thoracic segments, which are larger and rich coral-red, and one similar in size to these but of a yellow color on the eighth abdominal segment. This lar- va feeds on the leaves of a large pro- portion of our common fruit and forest trees ; but we have found it more fre- quently on wild cherry, lilac, tulip- tree, and ash than on others. The co- coons can be easily collected during the winter from these trees. This is the best way to obtain fresh specimens of the moths, which will emerge from the cocoons in the spring or early summer. The cocoon (Fig. 928) is interesting in structure. It is greatly pjg g28.—Callosamia promethea, elongated and is enclosed in a leaf, cocoon, the petiole of which is securel}* fas- tened to the branch by a band of silk extending from the cocoon; thus the leaf and enclosed cocoon hang upon the tree throughout the 726 AN INTRODUCTION TO ENTOMOLOGY winter. At the upper end of the cocoon there is a conical valve-like arrangement which allows the adult to emerge without the necessity of making a hole through the cocoon. This structure is characteristic of the cocoons of the moths of this and the following genus. See Figure 211, page 189. The angulif era -moth, Callosdmia angidifera. — This is a somewhat rare insect which closely resembles the Promethea-moth. Specimens of it are usually a little larger than those of C. promethea, and the trans- verse line and discal spots are more angular. The most important differences, however, are presented by the male, which quite closely resembles the female of the Promethea-moth in color and markings, and thus differs decidedly from the male of that species. The male of this species is nocturnal, differing in this respect from C. promethea. The larva feeds on the leaves of the tulip-tree and of Magnolia. It make its cocoon within a leaf or it crawls down the trunk of the tree and spins its cocoon in the grass or fastens it to some object on the ground. The cocoon usually has no stem and when made in a leaf falls to the ground in it when the leaf falls. The Cecropia-moth, Sdmia cecrdpia. — This is the largest of our giant silk-worais, the wings of the adult expanding from 125 to 160 mm. The ground color of the wings is a grizzled dusky brown, es- pecially on the central area. The wings are crossed beyond the middle by a white band, which is broadly margined without with red, and there is a red spot near the apex of the fore wing just outside of a zigzag line. Each wing bears near its center a crescent-shaped white spot bordered with red. The outer margin of the wings is clay-colored. The larva is known to feed on at least fifty species of plants, including apple, plimi, and the more common forest trees. When full grown it measures from 75 mm. to 100 mm. in length and is dull bluish green in color. The body is armed with six rows of tubercles, extending nearly its entire length, and there is an additional short row on each side of the ventral aspect of the first five segments following the head. The tubercles on the second and third thoracic segments are larger than the others, and are coral-red. The other dorsal tubercles are yellow, excepting those of the first thoracic and last abdominal seg- ments, which with the lateral tubercles are blue; all are armed with black bristles. The pupa is represented by Figure 929 and the cocoon by Figure 930. The Cecropia-moth occurs from the Atlantic Coast to the Rocky Moun- tains. In the North Atlantic States there is another species which resembles it in general appearance but is much smaller, expanding from 75 to 100 mm. and is much less common ; this is Sdmia -Sarma cccropia, pupa. Columbia. In the Far West the place of the Cecropia-moth is taken by two very closely allied species. In these the ground -color of the wings is usually reddish or dusk}- brown. Sdmia gloveri is found in the Rocky LEPIDOPTERA 727 Mountain region and in Arizona; and Samia rubra in the Pacific States. In Samia rubra the crescent-shaped white spot near the center of the hind wings is more elongate and pointed than in the other species. The Ailanthus-worm, Philosdmia Walkeri. — This is an Asiatic species which has been introduced into this country. It has become Fig. 930. — Samia cecropia, cocoon. a pest in the vicinity of New York City, where it infests the Ailanthus shade trees. The moth differs from all our native species of this family in having rows of tufts of white hairs on the abdomen. Its cocoon resembles that of the Promethea-moth. The specific identity of this species is in doubt. Family BOMBYCID.^ The Silk-Worm The family Bombycidas is not represented in our fauna; but a single species, the silk-worm, is frequently bred in this country, and is usually present in collections of Lepidoptera. The silk-worm, Bombyx niori. — The moth (Fig. 931) is of a cream- color with two or three more or less distinct brownish lines across the fore wings and sometimes a faint double bar at the end of the discal cell. The head is small ; the antennse are pectinated broadly in both sexes; and the ocelli, palpi, and maxillas are wanting. A striking feature of the venation of the wings (Fig. 932) is the obvious presence of the base of vein Ri in the hind wings. The usual food of the silk- worms is the leaf of the mulberry. Our native species, however, are not suitable. The species that are most used are the white mulberry Bombyx mori. 728 AN INTRODUCTION TO ENTOMOLOGY {Moms alba), of which there are several varieties, and the black mulberry {Morus nigra) ; the former is the better. The leaves of osage orange {Madura n aiirantiaca) have also „ ^<^^^~~P='^ been used as silk-worm "^"^ '"'^^ ^ food to a considerable extent. In case silk- worms hatch in the spring before either mulberry or osage- orange leaves can be obtained, they may be quite successfully fed, for a few days, upon lettuce-leaves. The newly-hatched lar\^a is black or dark- gray, and is covered with long stiff hairs, which spring from pale- colored tubercles. The hairs and tubercles are not noticeable after the first molt, and the worm becomes lighter and lighter, until in the last larval period it is of a cream-white color. There is a prominent tubercle on the back of the eighth abdominal segment, resembling those borne by certain lar- vae of the Sphingidae. There are many special treatises on this insect, some of which should be consulted by any one intending to raise silk-worms. Fig. 932. 2dA -Wings of Bombyx mori. Family LASIOCAMPID.E The Lasiocampids The best-known representatives of this family are the tent-cater- pillars and the lappet-caterpillars. The adults are stout-bodied, hairy moths of medium size. The antennae are pectinated in both sexes, and from one-fourth to one-half as long as the front wings; the teeth of the antennas of the male are usualh^much longer than those of the female. The ocelli and the maxillae are wanting ; and the palpi are us- ually short and woolly. But the most distinct characteristic is found LEPIDOPTERA 729 in the wings. The frenulum is wanting, there being instead, as in the Saturnioidea, a largely expanded humeral angle of the hind wings. But these moths differ from the Saturnioidea in having cubitus apparently four- branched and in having the humeral angle of the hind wings strengthened by the de- velopment of some extra veins, the humeral veins (Fig. 933 h. v.). The larv£e of the Lasio- campidas feed upon the foliage of trees, and are frequently very destructive. The family is a small one, less than thirty North Ameri- can species are known; but these represent eleven genera. Our more common species represent three genera : Mala- cosoma, which includes the tent-caterpillars, and Tolype and Epicnaptera, which in- clude the lappet-caterpillars. There are several species of tent -caterpillars in this coun- try. Most of them belong to the Pacific coast; but two are common in the East. Of these the most common one is the apple- tree tent-caterpillar, Malacosoma americdna. — This is the insect that builds large webs in apple and wild cherry trees in early spring. Figure 934 represents its transformations. The moth is dull reddish brown, with two transverse whitish or pale yellowish lines on the fore wing. The figure represents a male; the female is somewhat larger. These moths appear early in the simmier. The eggs are soon laid , each female laying all her eggs in a single ring-like cluster about a twig; and here they remain unhatched for about nine months. This cluster is covered with a substance which protects it during the winter. The eggs hatch in early spring, at the time or just before the leaves appear. The larvae that hatch early feed upon the un- opened buds till the leaves expand. The larvae are social, the entire brood that hatch from a cluster of eggs keeping together and building a tent in which they live when not feeding. The figure represents a specimen in our collection. In this case the tent was begun near the cluster of eggs. But usually the larvae soon after hatching migrate down the branch towards the trunk of the tree until a fork of consider- able size is reached before they begin their tent. This is necessary, as the completed tent often measures nearly two feet in length. Fig. 933- id^ 2d A -Wings of Malacosma americana. 730 AN INTRODUCTION TO ENTOMOLOGY The larvae leave the nest daily in order to feed; and spin a sill-zen thread wherever they go. The larvEe become full grown early in June; one of them is represented on a partially-eaten leaf in the figure. When ready to transform they leave the trees and make their cocoons in some sheltered place. These cocoons are quite peculiar in appearance, having a yellowish white powder mixed with the silk. The pupa state lasts about three weeks. The easiest way to fight this pest is to destroy the webs containing the larvae as soon as they appear in the spring. This should be done early in the morning, or late in the afternoon, or on a cold day, when the larvae are not scattered over the tree feeding. Fig. 934. — Malacosma americana, eggs, tent, larva, cocoons, and adult. Another species of the genus Malacosdnia found in the East is the so-called forest tent-caterpillar, Malacosdnia dtsstria. The range of this species extends throughout the United States and Canada. It differs from the preceding species in that the larvas do not construct a true tent. It feeds on the leaves of many forest and fruit trees, but maple is its favorite food-plant. In other respects its life history is quite similar to that of the apple-tree tent-caterpillar. The moth differs from M. americana in having the oblique lines on the wings dark instead of light ; the larva differs in having a row of spots along the back instead of a continuous narrow line; the egg-masses differ LEPIDOPTERA 731 in ending squarely instead of being rounded at each end; and the cocoon is more fragile, with less powder, and distinctly double. The Great Basin tent-caterpillar, Malacosoma Jrdgilis . — This spe- cies is found throughout the northern portions of the Great Basin, extending from the Rocky Mountains to the Cascades and. Sierra Nevadas, and has been found in California. It feeds on Ceanothus and many other wild shrubs. The California tent-caterpillar, Malacosoma calif ornica, feeds nomially on oak but also attacks fruit trees. The caterpillars are orange-colored and about 25 mm. long. Malacosoma constncta. — The larva is somewhat larger than the preceding species, and may be readily recognized by the distinct blue lines along the sides. It feeds on oaks. Malacosdma pluvidlis. — This is another Pacific Coast species. The lavvse are buff-colored and usually feed upon alder, but occasionally become quite injurious to apple trees. The lappet-caterpillars. — The larvae of the species of Tolype and of Epicnaptcra are remarkable for having on each side of each segment a little lappet or flat lobe; from these many long hairs are given out, forming a fringe to the body. When at rest the body of the larva is flattened, and the fringes on the sides are closely applied to the surface of the limb on which the insect is. Thus all appearance of an abrupt elevation is obliterated; the colors of these larvse are also protective, resembling those of the bark. The following are our better-known species. The Velleda lappet, Tolype velleda. — The body of the moth is milk-white, with a large blackish spot on the middle of its back (Fig. 935). That part of this spot which is on the thorax is composed of erect scales, the caudal part of recumbent hairs. The wings are dusky gray, crossed by white lines as shown in the figure. The figure represents the male; the female is much larger. The moths are found in August and September. The larva feeds upon the leaves of apple, poplar, and svringa. Its body is bluish grav, with „. ^^ , ^ „ , ^r ■ ^. -x J- IT j Fig- 935- — Tolype velleda. many famt longitudmal hnes ; and across the back of the last thoracic segment there is a narrow velvety-black band. The larva reaches maturity during July, The cocoon is brownish gray, and is usually attached to one of the branches of the tree on which the larva has fed. The larch lappet, Tolype Idricis. — This is a smaller species, the females being about the size of the male of the preceding species, and the males expanding only about 30 mm. The wings of the females are marked much like those of T. velleda, except that the basal two- thirds of the front wings are much lighter, and the dark band on the outer third is narrower and much darker than the other dark bands. 732 A N INTROD UCTION TO ENTOMOLOG Y The males are bluish black, with the markings indistinct. The larva feeds upon the larch. When mature it is of a dull brown color and less than 40 mm. in length. When extended, the front of the first thoracic segment is pale green, and the incision between the second and third is shining black. The larva matures during July. The cocoon is ash-gray, flattened and moulded to the limb to which it is attached, and partially surrounding it. The moths appear in August or September. The winter is passed in the egg state. The American lappet, Epicnaptera americdna — This species is found from the Atlantic to the Pacific. It is somewhat variable, and the dift'erent varieties were formerly regarded as distinct species. The moth (Fig. 936) is reddish brown, with the inner angle of the front wings and the costal margin of the hind wings deeply notched. Beyond the middle of each wing there is a pale band edged with zigzag, dark brown lines. The larva lives upon apple, cherry, oak, birch, maple and ash. When full grown it measures 60 mm. in length and 12 mm. in breadth. The upper side is slate-gray, mottled with black, with two transverse pig_ ()T^e.— Epicnaptera scarlet bands, one on the second and one on americayia. the third thoracic segments. There is a black spot on each end and in the middle of each of these bands. The larva is found during July and August. It is said that the cocoons are attached to limbs like those of Tolype; but the larvae of this species that we have bred made their cocoons between leaves, or in the folds of the muslin bag enclosing the limb upon which they were feeding. The species passes the winter in the pupa state; and the moth appears in June, when it lays its eggs upon the leaves of the trees it infests. SUPERFAMILY HESPERIOIDEA The Skippers The skippers are so-called on account of their peculiar mode of flight. They fly in the daytime and dart suddenly from place to place. When at rest most species hold the wings erect in a vertical position like butterflies ; in many the fore wings are thus held while the hind wings are extended horizontally; and a few extend both pairs of wings horizontally. The head is wide; the antennas are widely separated; they are thread-like, and enlarged toward the tip; and in most cases the extreme tip is pointed and recurved, forming a hook. The abdomen is usually stout, resembling that of a moth rather than that of a butterfly. The skippers are most easily distinguished by the peculiar venation of the wings, vein R of the fore wings being five-branched, and all of the branches arise from the discal cell (Fig. 937). In some butterflies all of the branches of vein R appear to arise from the discal cell; but this is because two of the branches LEPIDOPTERA 733 coalesce to the margin of the wing. to be only four-branched. The North American skip- pers represent two families. In Australia there is a skipper- like insect, Eiischemon rafflesicB, which has a distinct frenulum. If this belongs to the Hesperi- oidea, it represents a third family, the Euschemonidae. Our two families can be sepa- rated as follows. A. Head of moderate size; club of antenna large, neither drawn ont at the tip nor recurved. Large skippers, with wing expanse o^" 40 mm. or more. p. 733 Megathymid^ AA. Head very large; club of an- tenna usually drawn out at the tip, and with a distinct recurved apical crook. In a few forms the crook of the antennas is wanting; such forms can be distinguished from the Alegathymidse by their smaller size, the wing expanse be- ing less than 30 mm. p. 734. . . Hesperiid^ Family MEGATHYMID^ In such butterflies vein R appears The Giant Skippers Fig. 937. — Wings of Epargyreus tityrus. This family includes a small number of large skippers, which are found in the South and far West. In the adult insect the head is of moderate size, the width, including the eyes, being much less than that of the metathorax. The club of the antennae is large; and, although the tip is turned slightly to one side, it is neither drawn out to a point nor reciu-ved. The body is very robust, even more so than in the Hesperiidae. These insects fly in the daytime and with a rapid darting, flight. When at rest they fold their wings in a vertical position. So far as is known the larvae in the later stages of their growth are borers in the stems and roots of various species of Yucca and Agave and the young larvas spin silken tubes between the 3^oung and tender shoots of these plants. A monograph of the family was published by Barnes and Mc- Dunnough ('12). It is represented in the United States by a single genus, Megathymus, of which eight species have been found in the United States. Megathymus streckeri (Fig. 938) will serve as an example of the giant skippers. The specimen figured is a female of the variety 734 AN INTRODUCTION TO ENTOMOLOGY known as texana. A much better known species is the yucca-borer, Megathymns yucccB. The female of this species differs from that of the preceding in having much darker wings, all of the spots being smaller, and in having onl}^ one or two white spots on the lower surface of the hind wings. The male lacks the erect hairs on the hind wings. The larva bores in the stem and root of the Yucca or Spanish bayonet. It differs greatly in appearance from the larvse of the Hesperiidae, having a small head. This species is widely distributed through the southern part of our country. Fig. 938. — Megatliyii!ii\ i'rt Family HESPERIID^ The Common Skippers This family includes all of our skippers except the very small number that belong to the preceding family, the giant skippers. The two families can be separated ■V^K^«fh^r.^ Fig. 939. — Epargyreus tityriis, larva. by the table given above. The larvce of the common skippers present a ver}^ char- acteristic appearance, having large heads and strongly con- stricted necks (Fig. 939). They usually live concealed in a folded leaf or in a nest made of several leaves fastened together. The pupse are rounded, not angular, resembling those of moths more than those of butterflies. The pupa state is passed in a slight cocoon, which is generally com- posed of leaves fastened together with silk, and thinly lined with the same substance. A monograph of the North American species was published by Lindsey ('21); and the species of the Eastern United States are de- scribed and figured in natural colors by Comstock and Comstock ('04). The family Hesperiidffi includes four subfamilies ; but only three of them are represented in this country, the fourth being confined to the Old World. Our forms can be separated as follows. A. Club of antennae large; the entire club reflexed. p. 735 Pyrrhopygin^ AA. Club of antennas variable, but never with the entire club reflexed. B. Vein Mj of the fore wings arising nearer to vein Mi than to vein M3. p. 735. Hesperiin—Etiryi}ms philodice. instead of yellow. This butterfly often occurs in large niimbers in muddy places_ in country roads, for this reason it may be known as the roadside butterfly. It is also known as the clouded sulphur. Its range extends from the mouth of the St. Lawrence to South Carolina and west- ward to the Rocky Mountains. Its larva feeds upon clover and other Leguminosse. The orange sulphur, Eurymus eurytheme. — This species closely_ re- sembles the preceding one in size, shape and markings. The typical form differs from E. philodice in being of an orange color above instead of yellow. This butterfly is found chiefly in the Mississippi Valley and west to the Pacific Ocean ; it is also found in the Southwestern LEPIDOPTERA 749 States, and occurs occasionally north to Maine. It is one of the most polymorphic of all butterflies ; the forms differ so much in appearance that four or five of them have been described as distinct species. The larva feeds on clover and allied plants, and is sometimes a pest in alfalfa fields. The dog's head, Zerene ccesonia.- — The wings are lemon-yellow above bordered on the outer margin with black. On the hind wings the border is narrow, but on the fore wings it is broad. The outline of the yellow of the fore wings suggests a head of a dog or of a duck, a prominent black spot on the discal vein serving as the eye. This is an abundant species in the Southeastern and Southwestern States, extending from the Atlantic to the Pacific. The larva feeds on clover. The sleepy yellow, Eurema niclppe.- — ^The wings above are bright orange, marked with blackish brown as follows : on the fore wings a narrow bar at the apex of the discal cell, the apical portion of the wings, and the outer margin; on the hind wings, the outer margin. In the female the outer marginal band is intemipted at the anal angle of each wing, and on the hind wings it may be reduced to an apical patch. The expanse of the wings is from 40 to 47 mm. The common name, sleepy yellow, w^as suggested by the fact that the black spot near the middle of each fore wing is reduced to a narrow transverse line, which looks like an e^-e almost closed. This species occurs from southern New England to Florida and west to Lower California. The larva feeds on several species of Cassia. The little sulphur, Eurema euterpe. — Although this species is larger than the following one it is considerable below the average size of our yellows, the larger individuals expanding less than t,-/ mm. The wings are canary -yellow above, with the apex of the fore wings and the outer margin of both fore and hind wings blackish brown. The border of the hind wings is narrow and sometimes wanting. There is a red-brown splash on the apex of the hind wings below. The distribution of this species is similar to that of the preceding one. The larva feeds on Cassia. The dainty sulphur, Nathalis lole. — This little butterfl> can be distinguished from all others described here by its small size, as it expands only from less than 2 5 mm. to 30 mm. It is of a pale canary- yellow color, with dark brown markings. There is a large apical patch on the fore wings, and a broad band parallel with the inner margin; on the hind wings there is a stripe on the basal two-thirds of the costa, and spots on the ends of the veins; these are more or less connected on the margin of the wing, especially in the female. This species also is found from Southern New England to Florida and west to Lower California. It, too, feeds on Cassia. The cloudless sulphur, CatopsUia euhule. — This large butterfly differs greatly in appearance from those described above. It expands 62 mm. The wings above are of uniform bright canary-yellow. In the male they are without spots, except frequently an inconspicuous brown dot at the tip of each vein, and a lilac-brown edging of the costal border. In the female there is a discal dot on the fore wings and a marginal row of brown spots at the ends of the veins. 750 AN INTRODUCTION TO ENTOMOLOGY This is a southern species which occasionally extends as far north on the coast as New York City, and in the Mississippi Valley as far as Southern Wisconsin. The larva feeds on Cassia. Family NYMPHALID^ The Four-footed Butterflies The family Nymphalida}, includes chiefly butterflies of medium or large size, but a few of the species are small. With a single exception, Hypatus, these butterflies differ from all others in our fauna in having the fore legs very greatly reduced in size in both sexes. So great is the reduction that these legs cannot be used for walking, but are folded on the breast like a tippet. Dr. W. T. M. Forbes has observed mem- bers of this family use their reduced fore legs for cleaning their an- tennae, and in case of Basilarchia to make a sound. More or less reduction in the size of the fore legs occurs in the Lycasnidse and Riodinidse, but there it occurs only in the males, and to a much less degree than in this family. The N\Tiiphaliclae differ from these two families in retaining all of the branches of radius of the fore wings, this vein being five-branched, except in the genus Ancea. This is the largest of the families of butterflies. It not only sur- passes the other families in number of species, but it contains a greater number and variety of striking forms, and also a larger proportion of the species of butterflies familiar to every observer of insects. There may be in any locality one or two species of yellows or of whites more abundant, but the larger ninnber of species commonly observed are four-footed butterflies. Five subfamilies of the N\Ttnphalida3 are represented in our fauna. These can be separated by the following table. Each of these sub- families is regarded as a distinct family by some writers. A. Palpi much longer than the thorax, p. 766 Libythein^ AA. Palpi not as long as the thorax. B. Vein 3d A of the fore wings preserved; antennas apparently naked, p. 765. Danain^ BB. Vein 3d A of the fore wings wanting; antennas abundantly clothed with scales, at least above. C. Discal cell of the hind wings closed by a well-preserved vein. D. With some of the veins of the fore wings greatly swollen at the base (Fig. 972). p. 761 SatyriNvE DD. With none of the veins of the fore wings unusually swollen at base. p. 764 Heliconin^ CC. Discal cell of the hind wings either open or closed by a mere vestige of a vein. p. 750 Nymphalin^ Subfamily NYMPHALIN^ The Nymphs The nymphs can be distinguished from the other four-footed butterflies as follows: the palpi are not longer than the thorax as in LEPIDOPTERA 751 the long-beaks; the veins of the fore wings are not greatly swollen at the base as in the meadow-browns, except in the genera Mestra and Eunica, which are found only in the extreme South; the discal cell of the hind wings is not closed as in the heliconians; and the antennae do not appear to be naked as in the milkweed butterflies. The larvae are nearly or quite c\"lindrical, and are clothed to a , greater or less extent with hairs and sometimes with branching spines. The chrysalids are usually angular, and often bear large projecting prominences; sometimes they are rounded. They always hang head downwards, supported only by the tail which is fastened to a button of silk. Our genera of nymphs represent six quite distinct groups, as follows. I. THE FRITILLARIES The fritillaries are butterflies varying from a little below to some- what above mediimi size. The color of the wings is fulvous, bordered and checkered with black, but not so heavily bordered as in the next subgroups. The lower surface of the wings is often marked with curv- ing rows of silvery spots. The common name fritillary is from the Latin fritillus, a dice box, and was suggested by the spotted coloration of these butterflies. In the larvae there is an even number of rows of spines on the abdomen, due to the fact that there are none on the middle of the back. The larvae feed upon the leaves of violets. There are many species of fritillaries, about fifty occur in America north of Mexico, and it is difficult to separate the closely allied species. The great spangled fritillai-y, Argynnis cybele. — This species (Fig. 957) will serve to illustrate the appearance of the larger members of this group, those belonging to the genus Argynnis. In this genus vein R2 of the fore wings arises before the apex of the discal cell. There are a num- ber of common fritil- laries which resemble the preceding in color and markings but which are much small- er, the wings expand- ing considerable less than 50 mm. These belong to the genus Brenthis. In this gen- us vein R2 of the fore wings arises beyond the apex of the discal cell. The variegated ivitiWaxy , Euptoieta claudia. — This butterfiy agrees Fig- 957. — Argynnis cybele. 752 AN INTRODUCTION TO ENTOMOLOGY with the smaller fritillaries {Brenthis) in the origin of vein R2 of the fore wing beyond the apex of the discal cell, but differs from them in the shape of the fore wing, the apex of which is much more produced (Fig. 958) and the outer margin, except at the apex, concave; it is also considerably larger. This species occurs through- out the United States east of Fig. gcs.—Euptoieta claudia. the Rocky Mountains; but is very rare in the northern half of this region. The larva feeds on the passion-flowers. II. THE CRESCENT-SPOTS This group includes some of the smaller members of the Nymph- alidas. The color of the wings is sometimes black, with red and yellow spots; but it is usually fulvous, with the fore wings broadly margined, especially at the apex, with black, and crossed by many irregular lines of black. In the larva there is an odd number of rows of spines on the abdomen, due to the presence of spines on the middle of the back of some of the abdominal segments. Sixty-three species of crescent-spots have been described from America north of Mexico; but nearly all of these are restricted to the Far West. The Baltimore, Euphydryas phaeton. — The wings are black above, with an outer marginal row of dark reddish-orange spots, and two parallel rows of very pale yellow spots; on the fore wings a third row is more or less represented. The wings expand 50 mm. or more. The larv£e feed on a species of snakehead, Chelone glabra; they are gregarious in the fall and build a common nest in which they pass the winter; but separate after hibernation. They are very striking in appearance. The head and first two thoracic segments are shming black and the last three abdominal segments are black with two orange bands around each. All the other segments have a ground color of orange with various narrow trans- verse lines of black. This species occurs in Ontario and the northern half of the United States east of the Rocky Moun- tains. It is very local, the butterflies re- maining near the bogs or moist meadows where the food-plant of the larva is found. The butterflies of the genus Phyciodes pj„ Qj-g and the allied genera abound throughout our country. They are of small size, and of a fulvous color, heavily marked with black. Each species varies considerably in markings, and -Phyciodes Uiaros. Fig 960—1, Lycxna argiolus; 2, Polygonia mpiwn, 5, Euvanessa antiopa; 6, Mitoura ^54 AN INTRODUCTION TO ENTOMOLOGY different species resemble each other closely, making this a difficult group for the beginning student. Figure 959 represents a common species. The larvse feed on asters and other Compositas. III. THE ANGLE-WINGS To this group belong many of our best-known butterflies ; there are twenty-five species in our fauna. With these the outer margin of the fore wings is usually decidedly angular or notched as if a part had been cut away. A large proportion of the species hibernate in the adult state, and some of them are the first butterflies to appear in the spring. Some of the hibernating species, however, remain in concealment till quite late in the season. The red admiral, Vanessa aialdnta. — The wings are purplish black above. On the fore wing there is a bright orange-colored band begin- ning near the middle of the costa, and extending nearly to the inner angle ; between this and the apex of the wing are several white spots as shown in Figure 961 ; on the hind wing there is an orange band on the outer margin inclosing a row of black spots. The larva feeds chiefly on elm, nettle, and hop. When first hatched it folds together a half -opened leaf at the simimit of the plant ; when larger it makes its nest of a lower expanded leaf. There are two broods ; both butterflies and chrysalids hibernate. This butterfly occurs over nearly the whole of the European and North American continents. The painted beauty, Va- nessa virginiensis. — Figure 962 represents the upper side of this butterfly. The darker parts of the wings are very dark brownish black, the light- er parts a golden orange, some- times with a pinkish tinge. In the apical portion of the fore wings there are several white spots as shown in the figure; the largest of these, the proximal one, is salmon or flesh-colored in the female. A characteristic feature of this species is the presence of two submarginal eye-like spots on the lower side Fig. 961. — Vanessa atalanta. Fig. 962. — Vanessa virginiensis LEPIDOPTERA 755 of the hind wings. The larva feeds on everlasting (Antennaria) and allied plants. This species occurs in Ontario and nearly the whole of the United States, also in South America and the Canary Islands. The painted beauty has been commonly known in this country as Vanessa huntcra; but Vanessa virginiensis is the older name. The cosmoplite, Vanessa cdrdui. — The Butterfly resembles the preceding very closely in color and markings. There is however, a smaller proportion of orange markings ; and on the lower surface of the hind wings there is a submarginal row oifour or five eye-like spots. The larva feeds upon Compositos, especially thistles. This species is very remarkable for its wide distribution. Mr. Scudder states "with the exception of the arctic regions and South America it is distributed over the entire extent of every continent." The American tortoise-shell, Aglais milberti. — The wings above are brownish black, with a broad orange-fulvous band between the middle and the outer margin. There are two fulvous spots in the discal cell of the front wings (Fig. 963). The larvaj feed on nettle (Urtica) and are gregarious in habits. This species occurs in the north- ern portions of the United States and in Canada. The mourning-cloak, Euva- nessa anUopa. — The wings above are purplish brown, with a broad yellow border on the outer mar- gin sprinkled with brown, and a submarginal row of blue spots. The upper surface is represented by Figure 964, the lower by Figure 960, 5. The larvae live on willow, elm, poplar and Celtis; they are gregarious, and often strip large branches of their leaves. The spe- cies is usually two-brooded. "This buttei-fly is apparently dis- tributed over the entire breadth of the Northern Hemisphere be- Fig. g64.—Euvanessa antiopa. low the Arctic Circle as far as the thirtieth parallel of latitude." (Scudder.) Fig. 963. — Aglais milberti. 756 AN INTRODUCTION TO ENTOMOLOGY The Compton tortoise, Eugonia j -album. — This butterfly (Fig. 965) resembles in its general appearance those of the gennsPolygonia, but it is sharply distin- guished from them by the inner margin of the fore wings being nearly straight, by the heavier markings of the fore wings, and by the pres- ence of a whitish spot on both fore and hind wings, near the apex, and be- tween two larger black patches. On the lower surface of the hind wings there is a small L-shaped -Eugonia j-albim. silvery bar. This species occurs throughout Cana- da and the northern portion of the United States east of the Rocky Mountains. It is double-brooded. Polygonia.- — The butterflies of this genus resemble the preceding species in having a metallic spot on the lower surface of the hind wings, but differ in having the inner margin of the fore wings roundly notched beyond the middle. Ten species occur in this count^}^ These differ principally in the coloring and markings of the under surface of the hind wings. The following are some of the more common ones. The green comma, Polygdnia f annus. — The silvery mark of the hind wings is usually in the form of a C or a G, the ends being more or less expanded (Fig. 960, 2) but sometimes it is reduced to the form of an L. The lower surface of the wings is more greatly variegated than in any other species of this genus; and there is a larger amount of green on this surface than in any other of the eastern species, there being two nearly complete rows of green spots on the outer third of each wing. The larva feeds upon black birch, willow, currant, and wild goose- berry. This is a Canadian species ; iDut it is also found in the Moun- tains of New England and of New York, and in the northern portions of the Western States, extending as far south as Iowa. It is single- brooded. The hop-merchant, Polygonia comma.- — As in the preceding species, the silvery mark of the hind wings is in the form of a C or a G (Fig. 960, 3) but the general color of the lower surface of the hind wings is very different, being marbled with light and dark brown; and the green spots so characteristic oifaunus are represented here by a few lilaceous scales on a submarginal row of black spots. Two forms of this species occur. In one, P. comma dryas, the hind wings above are suffused with black on the outer half, so that the submarginal row of fulvous spots is obsured, and on the lower side the LEPIDOPTERA 757 wings are more yellowish than in the other form. The latter is the typical form of P. comma comma. The larva feeds upon hop, elm, nettle, and false-nettle. It is often abundant in hop-yards, and the chrysalids are commonly known as hop-merchants, from a saying that the golden or silvery color of the metallic spots on the back of the chrysalis indicates whether the price of hops is to be high or low. This species is found in Canada and the northern part of the eastern half of the United States ; its range extends south to North Carolina, Tennessee, Arkansas and Indian Territory. It is double-brooded in the North, and at least three- brooded in the South. The gray comma, Polygdnia progne. — In its general appearance this butterfly closely resembles P. comma, but it can be readily dis- tinguished by the form of the silvery mark, which is L-shaped and tapers towards the ends. It is much grayer below with a finer striate pattern in the male. The larva feeds on currant, wild gooseberry, and rarely elm. This species occurs in Canada and in the northern portion of the United States except in the extreme West. The violet tip, Polygdnia inter rogatidnis. — This butterfly (Fig. 960, 8.) is somewhat larger than the preceding species of Polygonia and differs in the form of the silvery mark, which consists of a dot and a crescent resembling a semicolon. It received its scientific name from the Greek note of interrogation, which is identical with our semicolon. On the upper side, the outer margins of the wings and the tails of the hind wings are tinged with violet, this fact suggested its common name. This species is dimorphic ; and the two forms differ so constantly and in such marked manner that they were described as distinct species. In P. interrogationis interrogationis the upper surface of the hind wings is not much darker than that of the fore wings, and there is a submarginal row of fulvous spots in the broad ferruginous brown border. In P. interrogationis umbrosa the outer two-thirds of the upper surface of the hind wings is blackish, and the submarginal fulvous spots are obliterated, except sometimes faint traces near the costal margin. This species is found in Canada and throughout the United States east of the Rocky Mountains. IV. THE SOVEREIGNS The members of this group differ from other Nymphalid^ in that the first three veins of the hind wings separate at the same point (Fig. 966) ; in the other nymphs the humeral vein arises beyond this point. The club of the antennas is very long, and increases in size so gradually that it is difficult to determine where it begins. In its thickest part it is hardly more than twice as broad as the stalk. The palpi are slender, and the wings are rounded. The larvae present a ver\^ grotesque appearance, being ver}^ ir- regular in form, and strongly mottled or spotted in color. 758 AN INTRODUCTION TO ENTOMOLOG: The following are our best-known species. The banded ptirple, Basilarchia arthemis. — The upper surface oi the wings is velvety choco- late-black, marked with a conspicuous white bow (Fig, 967). This is a Canadian spe- cies which extends a short distance into the northern part of the United States; the larva feeds on birch, willow, poplar, and many- other plants. The red spotted purple, Basilarchia astyanax. — The upper sui face of the wings is velvety indigo-black, tinged with blue or green. There are three rows of blue or green spots on the outer third of the hind wings; the spots of the inner row vary greatly in width in different individuals. On the lower surface there is a reddish orange spot in the discal cell of the fore wings, and one on the discal vein; on the hind wings there are two orange spots similarly situated, a third at the base of cell Ri and a row of seven spots just within a double row of submarginal blue or green spots. This species occurs throughout nearly the whole of the Eastern United States south of the 43rd parallel of lati- tude. The larva feeds on many plants ; among them are plum, apple, pear, and gooseberry. The hybrid purple, Basilarchia proserpina. — There is a form of Basil- archia which was de- scribed as a distinct spe- cies under the name pro- serpina, but which is believed to be a hybrid between B. astyanax Fig. 966. — Wings of Basilarchia astyanax. Fig. 967. — Basilarchia arthemis. LEPIDOPTERA r59 Basilarchia archihpus. and B. arthemis. See Field ('lo). This butterfly has the coloring of B. astyanax, with a portion of the white bow of B. arthemis. It occurs in a narrow belt of country extending from southern Wis- consin and north- em Illinois east- ward to the Atlan- tic coast of New England. This is the region which forms the southern limit of the range of B. arthemis and the northern limit of the range of B. astyanax, the place where the two spe- cies meet. The hy- brids var}' greatly in the extent of the white band and the red spots. The viceroy, Basilarchia archtppus.- — The wings vary in color from a dull yellow orange tinged slightly with brown to a dark cin- namon color; they are bordered with black, and all the veins are edged with the same color (Fig. 968). The fringe of the wings is spotted with white, and the black border on the outer margin contains a row of white spots. This species is remarkable for its resemblance to the monarch Danaus archippus (Fig. 974). But aside from the structural charac- ters separating the two subfamilies which these butterflies represent, the viceroy ■ can be easily distinguished from the species it mimics by its smaller size, and by the pres- ence of a transverse black band on the hind wings. As Da- naus archipppus has been termed the mon- arch, this species is aptly called the vice- roy. The larva (Fig. 969, a) when full- grown is about 30 mm. in length. The body is himiped and naked, with many tubercles. In color it is dark brownish yellow or olive green, with a pale buff or Fig. 969. — Basilarchia archippus: a, larva, ft, pupa, c, nest; d, partly eaten leaf before rolled to form nest. (From Riley.) 760 AN INTRODUCTION TO ENTOMOLOGY whitish saddle on the middle segment of the abdomen. The tubercles on the second thoracic segment are club-shaped and spiny. The larva of the viceroy feeds upon willow, poplar, balm of gilead, aspen, and cottonwood. The species is two- or three-brooded and hibernates as a partially grown larva in a nest made of a rolled leaf. (Fig. 969, c). This nest is lined with silk, and the leaf is fastened to the twig with silk so that it cannot fall during the winter. So far as is known all of the species of the sovereigns hibernate as larvas in nests of this kind. It is worthy of note that only the autumn brood of caterpillars make these nests; so that the nest -building instinct appears only in alternate generations, or even less frequently when the species is more than two-brooded. B. archippus is found over nearly the whole of the United S-'ates as far west as the Sierra Nevada Mountains, and has been found sparingly even to the Pacific coast near our northern boundaries. The vice-reine, Basildrchia archippus floridensis . — ^This is a variety of Basilarchia archipptts that is much darker than the typical form; the ground color of the wings resembling that of the queen, Danaus berenice. As it is found in the same region as the queen it is supposed to mimic that species, hence the popular name suggested above. V. THE EMPERORS This group is poorly represented in our fauna; our best-known species are the two following, which occur in the South. The tawny emperor, Chlonppe clyton. — In this and the following species the apex of the front wings and the anal angle of the hind wings are considerably produced in the males, but more rounded in the females. The male is represented in Figure 970 and the dotted line at the left indicates the contour of the wings of the female. This excellent fig- ure is from the sixth Missouri report by C. V. Riley, where a detailed accoimt of the life-history of the species is given. The wings of this butterfly are more or less ob- scure tawny, mark- ed with blackish brown, and with pale spots. Thers is a submargi nal row of six eyelike spots on the hind wings. Fig. 970. — Chlorippe clyton: a, eggs; b, larva; c, pupa; d, upper surface of rriale butterfly; the dotted line at left indicates the contour of the wings of the female. (From Riley.) LEPIDOPTERA 761 The species is dimorphic; the dimorphism affects both sexes and is independent, so far as is known, of season, as there is onh' one brood each year. It is the typical form Chlorippeclyton dyton that is figured here. The socond form, Chlorippe dyton proserpina, differs in having the hind wings darker and the submarginal row of eyelike spots wanting. The larva (Fig. 970, b) feeds on hackberry. The gray emperor, Chlonppe celtis. — In this species the wings are russety brown marked with blackish brown. In addition to the sub- marginal row of six eye-like spots on the hind wings, there is one in cell Cui of the fore wings. The larva of this species also feeds on hackberry. VI. THE AN^AS The butterflies of the genus Ancea are quite distinct from any of the preceding divisions of the N>Tiiphalin«, although they have been classed with the em- perors. There are three species found in theUnited States, A . pdrtia from Flor- ida, A. morrisonii from Arizona, and the following one. The goat-weed butterfly, Ancea an- dria. — The female of this species can be easily recognized by Figure 971. The male is smaller, with wings of a rich dark orange, margined with brown, and without the light-colored band characteristic of the female. This species is found in the Mississippi Valley from Illinois to Texas. Fig. 971. — Anaa andria. Subfamily SATYRIN^ The Meadow-browns This subfamily includes chiefly brown butterflies whose markings consist almost entirely of eyelike spots. Some western species, how- ever, are bright-colored. In our species some of the veins of the fore wings are greatly swollen at the base (Fig. 972). This character is not quite distinctive; for in some species of the Nymphalinaj that are found in southern Florida and in Texas near the Mexican border some of the veins of the fore wings are swollen at the base. The larvEe are cylindrical, tapering more or less towards each end. The caudal segment is bifurcated, a character that distinguishes 762 AN INTRODUCTION TO ENTOMOLOGY them from all other American butterfly larvae excepting those of the emperors, Cblorippe. The pupae are rounded; in some cases the transfor- mation takes place beneath rubbish on the ground with- out any preparation of cell or suspension of the body. Nearly sixty species be- longing to this subfamily have been described from America north of Mexico. The eyed brown, Saty- rodes cdnthiis. — The upper surface of the wings is soft mouse-brown on the basal half and paler beyond, con- siderably so in the female; each wing bears a row of four or five small black eye- like spots (Fig. 973). This species is found in Ontario, and throughout the eastern half of the United States in wet places. The larva feeds on swamp grasses ; its head and caudal segment are each adorned with a pair of red cone-shaped tubercles. The grayling, Cercyonis dlope.- — ^This species is found from the Atlantic to the Pacific; it occurs under several forms, some of which have been described as distinct spe- cies. The most common forms found East of the Rocky Mountains are the first two described below and intergrades between these. The ex- panse of the wings is from 50 to 62 mm. The larva feeds on grass. (i) The blue-eyed grayling, Cercyonis alope alope. — The upper surface of the wings is dark brown ; on the outer half of the fore wings there is a distinct yellow band, which extends from vein R5 to the anal vein ; spots with a white or bluish center, small spot in cell Cui, which is narrowly rimmed with ^^ellow and has a minute white pupil. The lower surface of the hind wings is either with or without eye-like spots, usually with six of them. Fig. 972. — Wings of Cercyonis alot>e. Fig- 973- — Satyrodes canthus. in this band there are two dark The hind wings usually bear a LEPIDOPTERA 763 This is a Southern form, which extends into the southern portions of New England, New York, Michigan, Wisconsin, Iowa, and Ne- braska; and into the northern portions of TlHnois, Indiana, and Ohio. (2) The dull-eyed grayling, Cercyonis alope nephele. — In this form the yellow band of the fore wings is either absent or represented by a faint pallid cloud. In other respects it closely resembles the blue- eyed grayling. This is a Northern form; the southern limits of its range overlap the northern limits of the range of the blue-eyed grayling as given above. (3) The hybrid gra^dings. — In that narrow belt where the ranges of the two forms of Cercyonis alope described above overlap, all variations between the two types occur. In most of these intergrades the eye-spots of the upper side of the fore wings are surrounded by yellowish rings, or each of them is on a yellowish patch. (4) The sea-coast grayling, Cercyonis alope maritima. — In a nar- row belt along the Atlantic coast there occurs a form which is smaller than those described above, and of a dark color; this form is easily recognized by the color of the band bearing the eye-spots, it being reddish }'ellow. The White Mountain butterfly, CEneis semtdea. — The genus GEneis is composed of cold-loving arctic species whose natural habitat is the Far North; but some members of this genus are found within the limits of the United States. Their presence h ere and their distribution are extremely interesting. The best -known of these forms is the White Mountain butterfly. This butterfly is found only on the higher parts (above 5,000 feet) of the White Mountains in New Hampshire, and on the highest peaks of the Rocky Mountains of Colorado, above 12,000 feet. These two widely separated colonies of this butterfly are believed to be the remnants of an arctic fauna which was forced southward during the Ice Age. At the close of this period, as the arctic animals followed the retreating ice northward, the tops of these mountains became colonized by the cold-loving forms. Here they found a congenial resting place, while the main body of their congeners, which occupied the intervening region, was driven northward by the increas- ing heat of the lower land. Here they remain, clinging to these islands of cold projecting above the fatal sea of warmth that fills the valleys below. The White Mountain butterfly is a delicate-winged species. The upper surface of the wings is grayish brown, without spots, except sometimes a minute one in cell Mi of the fore wings; the fringe of the wings is brownish white interrupted with blackish brown at the ends of the veins. On the hind wings the marbling of the lower surface shows through som.ewhat. On the lower surface, the tip of the fore wings and the greater part of the hind wings are beautifully marbled with blackish brown and grayish white. The expanse of the wings is 43 mm. 764 AN INTRODUCTION TO ENTOMOLOGY The larva feeds on Car ex. The species is either single-brooded or requires two years for the development of a brood. A closely allied species, CEneis katahdin, is found on Mount Katahdin, A'laine. This is called the Katahdin butterfly. Subfamily HELICONIIN^ The Heliconians This subfamily consists chiefly of tropical butterflies. They are of medium or rather large size, and are easily recognized by their narrow and elongated fore wings, which are usually more than twice as long as broad. Most of the species are striking in appearance, being black banded with yellow or crimson, and sometimes with blue. The discal cell of the hind wings is closed by a well-preserved vein. The following species is the only one found in our fauna that un- questionably belongs to this subfamily. The zebra, Heliconius charitdnius. — This is a black butterfly with its wings banded with lemon yellow. There are three bands on the fore wings ; on the hind wings there is a broad band parallel with the front wings when they are spread, a submarginal row of about fifteen spots, and a row of dots on the outer margin near the anal angle. The wings expand from 62 mm. to 100 mm. The larva feeds upon the passion-flower. This species is found in the hotter portions of the Gulf States. There are two other species found in the United States that are placed in this subfamily by some writers; but in each of these the discal cell of the hind wings is open as in the Nymphalina^. These are the following. The Julia butterfly, ColcBnis julia. — This butterfly resembles the true heliconians in having very long and narrow fore wings, these being more than twice as long as broad. The upper side of the wings is dark reddish orange, with the margins of the wings black, and with a more or less distinct black band cutting off the outer third of the fore wings. On the lower surface the wings are pale rusty- red, mottled with a darker shade. The wings expand about 85 mm. This is a very common species in the tropics of America and is found in the extreme southern part of the United States. The gulf fritillary, Dione vanlllco. — In this species the front wings are about twice as long as broad, but the markings of the wings re- semble those of a fritillary more than those of an heliconian. The wings are reddish fulvous above; the veins of the front wings are black on the outer two-thirds of the wing; the black expands into spots at the ends of veins M3 to anal ; there are two white spots in the discal cell and one at the apex of it, each of these spots is sur- rounded with black; cells M3, Cu], and Cu2 each contains a round black spot. The outer margin of the hind wings has a broad black border, which contains a fulvous spot in each cell. The wings expand from 55 mm. to 75 mm. The larva feeds on the passion-flower. In addition to the six rows of thorny spines, which characterize the caterpillars of many LEPIDOPTBRA 765 other fritillaries, this one has on the head a pair of backward bending spines branched hke the others. This species occurs from New Jersey and Pennsylvania southward also in Arizona and California. Subfamily DANAIN^ The Milkweed Btitterflies These butterflies are of large size, with rounded and somewhat elongate wings, the apical portion of the fore wings being much produced. The discal cells of the wings are closed; the third anal vein of the fore wings is preserved ; and the antenna are apparently without scales. Only a very few species of this family occur in our fauna. The two following are the best-known; the others are found only in the extreme South or in California. The monarch, Ddnaus archippus.- — The upper surface of the wings is light ruddy brown, with the borders and veins black, and with two rows of white spots on the costal and outer borders as shown in Figure Fig. 974. — Danaus archippus. 974. The figure represents a female; in the male the veins of the wings are more narrowly margined with black, and there is a black pouch next to vein Cu2 of the hind wings, containing scent-scales or androconia. The larva feeds upon different species of milk-weed, Asclepias. When full grown it is lemon or greenish yellow, broadly banded with shining black. It is remarkable for bearing a pair of long fleshy fila- ments on the second thoracic segment, and a similar pair on the seventh abdominal segment (Fig. 975). The chrysalis is a beautiful object; it is bright green dotted with golden spots, and about 25mm. in length (Fig. 976). 786 AN INTRODUCTION TO ENTOMOLOGY This species occurs throughout the greater part of the United States, and is distributed far beyond our borders. It is beHeved, however, that the species dies out each year in a large part pf the Northern States, and that those butterflies which appear first in this Fig. 976. — Danaus Fig- 975.— Danaus archippus, larva. (From Riley.) archippus, chrys- alis. (From Ri- ley.) region, in June or July, have flown hither from the South, where they hibernate in the adult state. In the extreme South they fly all winter. Great swarms, including many thousands of individuals of this species, are sometimes seen, late in the year; and these swarms appear to be migrating southward. The queen, Danaus herenice. — This species is found in the Southern States. The upper surface of the wings is reddish chocolate-brown with the costal margin of the front wings and the outer margins of both pairs bordered with black. There are two partial rows of white dots near the costal and outer margins of the front wings ; and there is a larger white spot in each of the cells R5 to Cu. The male possesses a black pouch containing androconia next to vein Cu of the hind wings as in the preceding species. The wings expand from 60 to 88 mm. There is a well-marked vsxiety, Danaus berenice strigosa, in which on the upper surface of the hind wings the veins are narrowly edged with grayish white. The larva of this species feeds on milkweed. This larv^a bears three pairs of long, brown, whiplash filaments ; these are on the second thoracic and the second and eighth abdominal segments. Subfamily LIBYTHEIN^ The Long-beaks The long-beaks can be easily recog- nized by their excessively long, beak- like palpi, which are from one-fourth to one-half as long as the body and pro- ject straight forward (Fig. 977). The outer margin of the fore wings is deeply notched ; the males have only four well- developed legs, while the females have six. Fig. 977. — Hypatus bachmanni. LEPIDOPTERA 767 Only two species are listed from the United States, one from Texas and one from the East; and these may be merely varieties of one species. The snout butterfly, Hypatus bachmanni. — The wings are blackish brown above, marked with orange and white spots. This species occurs throughout the Eastern United States, excepting the northern part of New England and the southern part of Florida. The larva feeds on hackberry, and in the West where hackberry does not occur, it feeds on wolfberry. Family RIODINID^ The Metal-marks TI.e metal-marks are small butterflies, which bear some resem- blance to the gossamer winged butterflies. They are distinguished from the gossamer-winged but- /?4+5 terflies by the presence of a humeral vein in the hind wings, and from them and all other butterflies by the fact that the costa of the hind wings is thick- ened out to the himieral angle (Fig. 978). The fore legs are re- duced and brush lilvc in the males, normal in females. Only twelve species have been found in our fauna, and nearly all of these are from the Far West or Southwest. The two following species occur in the East. The small metal-mark, Cal- ephelis virginiensis. — The upper surface of the wings is rust- colored, and is crossed by four or five more or less sinuous blackish lines on the basal two-thirds, and on the outer third by two lines of shining scales, that look like cut steel, and an intermediate row of black spots. The under surface is of a brighter rust color and marked as above. The expanse of the wings is 20 mm. This species occurs in the Southern States. The large metal-mark, Calephelis boredlis. — The upper surface of the wings is dull brownish yellow, crossed by obscure transverse stripes; on the outer half of the wings are two lead-colored lines, with ix row of black dots between them. The under surface is of a rather Fig. 978. — Wings of Ernests zela. 768 AN INTRODUCTION TO ENTOMOLOGY dark and a pale orange; paler and duller next the base, marked with transverse black lines and dots, and transverse series of steel-colored spots. The wings expand from 25 to 30 mm. This is a rare butterfly; it has been taken in New York, New Jersey, West Virginia, Michigan, and Illinois. Family LYC^NID^ The Gossamer-ivinged Butterflies /?4-^5 The family Lycaenidce includes butterflies which are of small size and delicate structure. In size they resemble the smaller Hesperiidas; but they can be distinguished at a glance from the skippers, as they present an entirely different appear- ance. The body is slender, the wings delicate and often brightly colored, and the club of the antenna straight. The antennse are nearly always ringed with white; each is situated very closely to the edge of an eye, often flattening it; they are not in pits; and a conspicuous rim of white scales encircles the eyes. An easily-observed combination of characters by which the members of this family can be distinguished is the absence of one or two of the branches of radius of the fore wings, this vein being only three- or four- branched, and the origin of vein Mi of the fore wings at or near the apex of the discal cell (Fig. 979). In all other butterflies occurring in our fauna in which radius is only three- or four-branched (except Parnas- sius),vem Mi of the fore wings coal- esces with radius for a considerable distance beyond the apex of the discal cell. An exception to the characters of the Lycasnida) is presented by Feniseca, as indicated in the table of families, p. 739. A characteristic of this family is that while in the female the front legs are like the other legs, in the male they are shorter, without tarsal claws, and with the tarsi more or less aborted. The caterpillars of the Lyctenida? present a very unusual form, being more or less slug-like, reminding one of the larvasof the Eucle- idae. The body is short and broad; the legs and prolegs are short and small, allowing the body to be closely pressed to the object upon which the insect is moving — in fact some of the species glide rather Fig- 979- — Wings of Heodes thoe. LEPIDOPTERA 769 than creep; and the head is small, and can be retracted more or less within the prothorax. The body is armed with no conspicuous ap- pendages ; but some of the species are remarkable for having osmeteria which can be pushed out from the seventh and eighth abdominal segments, and through which honeydew is excreted for the use of ants. Certain other species are remarkable in being carnivorous; one American species feeds exclusively upon plant-lice. The chrysalids are short, broad, ovate, and without angulations. They are attached by the caudal extremity, and by a loop passing over the body near its middle. The ventral aspect of the body is straight and often closely pressed to the object to which the chrysalis is attached. The family Lyca^nidae is represented in our fauna by three well- marked groups of genera, which are hardly distinct enough to be ranked as subfamilies; these are known as the hair-streaks, the cop- pers, and the blues respectively. In addition to these there is a single species, the wanderer, the relationship of which is uncertain. I. THE HAIR-STREAKS The hair-streaks are usually dark brown, with delicate striped markings, which suggested their common name; but some species are brilliantly marked with metallic blue, green, or purple. The hind wings are commonly furnished with delicate tail-like prolongations (Fig. 980), and the eyes are hairy. The fore _ wings of the male often bear a small dull oval spot near the middle of the costal part of the wings, the discal stigma, which is filled with the peculiar scent-scales known as androconia. The males are also distinguished by having a tuft of hair-like scales, the beard, on the front; this is wanting or very thin in the females. More than sixty species occur in America north of Mexico ; of these nearly twenty occur in the eastern half of the United States. The banded hair-streak, Thecla calanus. — -p\z. qSo.^Theda cal- In the northeastern United States the most common of the hair-streaks is this species (Fig. 980) . The upper surface of the wings is dark bro'vn or blackish brown. The under surface is blackish slate-brown nearly ai dark as the upper surface, and marked as shown in the figure. The larva feeds on oak and hickon\ Excepting the southern por- tion of the Gulf States, the species is found throughout our territory east of the Rocky Alountains, and in the southern part of Canada. The olive hair-streak, Mitoura ddmon. — ^The upper surface of the wings is dark brown, with the disk more or less deeply suffused with brassy yellow in the male or tawny in the female; the hind wing has two tails, one much longer than the other, both black tipped with white. The lower surface of the hind wings is deep green; both fore and hind wings are marked with white bars bordered with brown. (Fig. 960, 6). 770 AN INTRODUCTION TO ENTOMOLOGY Southern individuals have much longer tails than the one shown ill the figure; and there is a variety, patersonia, in which the upper surface of the wings is all dark brown. The larva feeds on red cedar and smilax. This species occurs from Massachusetts to Florida and westward to Dakota and Texas. The banded elfin, Incisdlia ntphcn.- — In the butterflies of the genus Incisalia the fringe of the outer margin of the hind wings is slightly prolonged at the end of each vein, giving the wings a scalloped out- line ; they also lack tail-like prolongations of the hind wings. There are several species occurring on both sides of the continent. One of these, the banded elfin, is represented in Figure 960, 4. In this species there is a distinct white or whitish edging near the base of the under side of the hind wing which limits a darker band that occupies the outer two-thirds of the basal half of the wing. This species occurs in the Eastern and Middle States. The larva feeds on pine. The hair-streaks desci ibed above are of moderate size and modest colors. The two following will serve to illustrate a somewhat differ- ent type. The great purple hair-streak, Atlides halesus. — This is the largest of our eastern hair-streaks, the larger individuals expanding 50 mm. In the male the greater part of the upper surface of the wings is bright blue; the discal stigma, the outer fourth of the fore wings, the apex of the inner margin of the hind wings, and the tails are black. In the female the outer half of the wings is black. This species occurs in the southern half of the United States and southward. It has been found as far north as Illinois. The larva is said to feed on oak. The white-m hair-streak, Thecla m-alottm. — This is a smaller species, expanding about 37 mm. The upper surface of the disk of the wings is a rich, glossy dark blue, with green reflections; a broad outer border and costal margin are black. The hind wing has two tails, and a bright dark orange spot preceded by white at the anal angle. The under surface is brownish gray, and on this surface both wings are crossed by a common, narrow white stripe which forms a large W or reversed M on the hind wings. This species occurs in the southern half of the United States. The lar\^a feeds on oak and on milk- vetch. II. THE COPPERS The coppers, as a rule, are easily distinguished from other gos- samer-winged butterflies by their orange-red and brown colors, each with a coppery tinge, and conspicuous black markings. Ihey are the stoutest of the Lycaenidae. Among the exceptions to the more common coloring of these insects are the following: In the male of Heodes epixanthe, a small species which frequents cranberry bogs, the wings have a purple tinge; and in Heodes heteronea, a species found from California to Colorado, the male is blue. Eighteen species of the group are now listed in our fauna ; the two following will serve as examples: LEPIDOPTERA 771 The American copper, Heddes hypophlcBas.- — This is the most common of our coppers in the Northeastern States and in Canada. Its range extends also along the boundary between the United States and Canada to the Pacific Ocean, and southward into California; and in the east along the Alleghany Mountains south to Georgia. The fore wings are orange-red above, spotted with black, and with a blackish brown outer border; the hind wings are coppery brown, with a broad orange-red band on the outer margin; this band is indented b}^ four black spots. The larva feeds on the common sorrel (Rtimex acetosella). The bronze copper, Heodes thoe.- — This is larger than the preceding species, thewings expanding 3 7 mm. or more. In the male the wings are coppery brown above, spotted with black, and with a broad orange-red band on the outer margin of the hind wings. The female differs in having the fore wings orange-red above, with prominent black spots. This species occurs in the Middle and Western States from the Connecticut Valley to Nebraska. The larva feeds on curled dock (Rumex crispus). III. THE BLUES The blues can be distinguished from the other gossamer-winged butterflies by the slender form of the body, and the blue color of the upper surface of the wings of the males at least ; in many species the upper surface of the wings of the female is much darker than that of the male. Thirty -eight North American species have been described; but most of these occur only in the Far West. This is a rather difficult group to study owing to the fact that in several cases a single species exists under two or more distinct forms, and also that the two sexes of the same species may differ greatly. It often happens that two individuals of the same sex but of different species resemble each other more closely in the coloring of the upper surface than do the two sexes of either of the species. The spring azure, Lyccsna arglolus.- — ^In this species the hind wings are without tails, the e} es are hairy, and the lower surface of the wings is pale ash-gray. This combination of characters will distin- guish it from all other blues occurring in the Eastern United States. But the species is not confined to this region, as it occurs in nearly all parts of the United States, in a large part of Canada, and most of the Old World. This butterfly exhibits polymorphism to the greatest degree of any known species. In this country alone there are thirteen or more named forms. Some of these are geographical races ; some are seasonal forms; and some are distinct forms that exist at the same time and place as the more typical form. In the Old World many other forms of this species have been described. Two forms are represented in Figure 960, i and 7. The larva feeds on the buds and flowers of various plants, es- pecially those of Cornus, Cimicifuga, and Actinomeris. They are frequently attended by ants for the sake of the honey-dew which 772 AN INTRODUCTION TO ENTOMOLOGY they excrete from osmeteria which they push out from the seventh and eighth abdominal segments. The tailed blue, Everes comyntas. — The butterflies of the genus Everes can be distinguished from our other blues by the presence of a small tail-like prolongation of the hind wing. This is borne at the end of vein eu2. Our common species (E. comyntas) is distributed over nearly all parts of North America. The male is dark purplish violet above, bordered with brown; the female is dark brown, some- times flecked with bluish scales. In the Eastern United States this is the only species of the genus. The larva feeds upon clover and other leguminous plants. IV. GENUS FENISECA Fig. 981. — Feniseca tarquinins. The wanderer, Feniseca tarquinius. — This is the only known mem- ber of the genus Feniseca, the affinities of which have not been deter- mined . It does not seem to belong to either of the three groups of genera mentioned above. A distinctive featvire of this genus is the fact that vein Mi of the fore wings coalesces with a branch of radius for a considerable distance beyond the apex of the discal cell; in this re- spect it differs from all other members of the Lycasnidae found in our fauna. The upper surface of the wings of this but- terfly (Fig. 981) is dark brown, with a large irregular, orange-yellow patch on the disk of the fore wing, and one of the same color next the anal angle of the hind wing. This species is of unusual interest, as the larva is carnivorous in its habits. It feeds on plant-lice ; and, so far as observed, it feeds only on the woolly aphids. It is found more often in colonies of the alder blight (Schizoneura tessellata) than in those of the allied species. It is found from Maine to Northern Florida and westward to Kansas. It is a very local insect, being found only in the neighbor- hood of water where alder grows. I do not know why the name the wanderer was applied to this butterfly, it may have been on ac- count of its local appearance in widely separated places, or because in habits the larva deviates far from the more usual habits of caterpillars. The name is also appropriate as its nearest relatives are found in Africa and in Asia. The chrysalis of Feniseca presents a remarkable appearance (Fig. 982); the anterior half when viewed from above bears a curious re- semblance to a monkey's face; and it differs from all other lycasnid pupae in our fauna in having on each side a row of small rounded tubercles. Fig. 982. — Chrysa- lis of Feniseca. Enlarged. CHAPTER XXVIII ORDER DIPTERA* The winged members of this order have only two wings; these are home by the mesothorax. The second pair of wings is represented by a pair of knobbed, thread-like organs, the halteres, these are present in nearly all flies, even when the mesothoracic wings are wanting. The mouth-parts are formed for sucking. The metamorphosis is complete. To the order Diptera belong all insects that are properly termed flies, and only these. The word fly forms a part of many compound names of insects of other orders, as butterfly, May -fly, and chalcis-fly ; but when used alone, it is correctly applied only to dipterous insects. To some flies other common names have been applied, as mosquito, gnat, and midge. The presence of a single pair of wings and of a pair of halteres is siifhcient to distinguish members of this order from those of all other orders, except in the case of a few wingless forms. This is a large order both in ninnber of species and of individuals. Aldrich ('05) gives a list of about eight-thousand North American species, distributed in more than a thousand genera. Different species differ greatly in habits. Some are very annoying to man. Familiar examples are the mosquitoes, which attack his person, the flesh-flies, which infest his food, the botflies and the gad- flies that torment his cattle, and the gallgnats that destroy his crops. Some species are extremely noxious, being disease carriers, as for example the mosquitoes that transmit malaria and yellow fever. Other species are beneficial. Those belonging to the Syrphidee and the Tachinidffi destroy many noxious insects ; and very many species, while in the larval state, feed upon decaying animal and vegetable matter, thus acting as scavengers. There are certain structural features of flies that are used in the classification of these insects and to which special terms have been applied. The more important of these terms are defined below ; others are defined later in the discussion of chaetotaxy. The head and its appendages. — The head is very mobile, being con- nected to the thorax by a slender neck. It is variable in shape and in its relative size. The compound eyes are usually large, sometimes occupying a large part of the surface of the head. When the eyes are contiguous on the upper side of the head they are termed holoptic; when they are sep- arated more or less broadly they are termed dichoptic. In "some flies each compound eye is divided into two parts, one of which is a day- eye and the other a night-eye. See page 144. The ocelli are usually three in number. *Diptera: dis (5ts), two; pteron (irrepdv), a wing. (773) 774 AN INTRODUCTION TO ENTOMOLOGY The antenncs vary greatly in form in the different families. In Fig. 983. Fig. 984. Fig. 985. Fig. Fig. 987. the more generalized families the antennas consist of many segments, which, except the basal two, are, similar in form (Fig. 983). Frequently such antennse bear whorls of long hairs (Fig. 984). In the more specialized families there is a reduction in the nimiber of segments of the anten- nae. This is brought about either by a more or less complete consolidation of the segments beyond the second into a single segment (Figs. 985 and 986), or by a dwindling of the terminal segments, so that they form merely a slender style (Fig. 987) or bristle (Fig. 988). Such a bristle is termed the arista. In most cases where a style or arista exists it is borne by the third segment, and this segment is then usually greatly enlarged. When the enlargement of this segment has taken place evenly the style or arista is terminal; but frequently one part of the third segment- is expanded so that it projects beyond the insertion of the arista (Fig. 989) ; then the arista is said to be dorsal. The month-parts of flies are formed for sucking, and sometimes also for piercing. Their structure differs greatly in different families; and in some cases it is exceedingly difficult to determine the homologies of the different parts. In the more typical forms the mouth-parts consist of six bristle-lilce or lance-like organs enclosed in a sheath and a pair of jointed palpi. There are differences of opinion as to the homologies of these parts, but according to the most generally accepted view they are as indicated below. The mouth-parts of a mosquito will serve as an example of a comparatively generalized type. Fig. 989. DJPTERA 775 Figure 990 represents a side view of the head of Anopheles with the bristle-like organs removed from the sheath. The parts are as follows : Fig. 9QO.— Head of Anopheles. explained in the text. (After Nuttall and Shipley.) The lettering is the antennse (a) ; the labnmi or labnmi-epipharynx (Ir-e) ; the hypo- pharynx (h) ; the two mandibles (m) ; the two maxilla:^ (mx) ; the labiinn (/) ; and the maxillary palpi (mp). The labium is the sheath in which the six bristle- like organs are normally enclosed ; the maxillary palpi are not en- closed in the sheath. At the tip of the labium there is on each side a lobe-like appendage; these are termed the labella. The lab- ella are believed by some writers to be the labial palpi ; but it seems more probable that they are the paraglossae. The labella of certain flies are quite large ; in the house- fly, for example, they are ex- panded into broad plates, which are fitted for rasping. The frontal liinule (Fig. 991, /. I) is a small crescent-shaped sclerite immediately above the antennas, which is characteristic of the second suborder, the Cyclorraoha. In most members of this suborder there is a s^.ture Fig 991. — Head of a fly: A, antennse; ar, arista, E, eye; /. /., frontal lun- ule; J.S., frontal suture. 776 AN INTRODUCTION TO ENTOMOLOG Y separating the frontal lunule from that part of the head (vbove it; this is termed the frontal suture. Frequently the frontal suture extends down on each side to near the mouth (Fig. 991,/. s). The ptUinum is a large bladder-like organ which exists in those flies that have a frontal suture. The ptilinum is pushed out through this suture when the adult is about to emerge from the pupariimi. In this way the head end of the pupariimi is forced off, making a large opening through which the adult escapes; afterwards the ptilinum is withdrawn into the head. If a specimen is captured soon ^r->, after its emergence / Y from the pupar ium , ^ ^^;?=:Ca^ // there may be seen /y'ZT~Sc^--.L "\J: // insteadofthe // /^^---A >^^^^ f"^ frontal suture the / \ /^'^77,: =c^^^p^p^^-iNi I /fWr 7 \ bladder-lilve ptili- W^^yi ^ ^iJT^ \ ^/~Vy ^A) ^ / J^ numprojecting r^^^^ ^^^^'^^\ rxh^v /— — ( from the head, im- \~^^^^^^ . ^J^\. \^-^^^<^^^_^ mediately above ^ ^^'^^>^L^.--^^\.'tiw^^^^^^^^'^^^ ^^® antennas. \j_,^<-^~( ^v. - Aes^ V^*" M ^ -^^^^ thorax and ^"""^ X^x'' Nn X"'^''^<1^ a ^'^-^ appendages. — \^J^'^" — '^x.'^'' v^""^^^^^ '^^^ thoracic region ^J \^ ^ of the body con- \cp sists chiefly of the mesothorax, both T X 1 ^ cu t T, 1 T -e the prothorax and Fig. 992.— Lateral aspect of thorax of P achy r Jnna f err u- , rne^fa-thnrax bp ginea. (After Young). The thoracic segments to P® metatliorax De- which the sclerites belong are indicated by the num- mg greatly reduced bers I, 2, and 3. A, A, A, first abdominal segment; in size. The thorax ae?n, anepimerum, the upper part of the epimerum; q£ ^ crane-fly (Fig aes, anepisternum, the upper part of the episternum; , .,, ^ " ex, coxa; em, epimerum of the metathorax; h, halter; 992;, Will serve to kem, katepimerum, the upper part of the epimerum; illustrate the StrUC- kes, katepisternum, the lower part of the episternum; ture of this part in me, meron; psc, prescutum; psl, postscutellum ; sc, ^j^g more general- scutum; si, scutellum; sp, spiracle; tr, trachantin. .^^^ members of this order, and will also serve as a type with which to compare the thorax of the more specialized forms. There are differences of opinion among writers on this order re- garding the homologies of certain thoracic sclerities. The most ex- tended investigation of this subject is that of Young ('2 1) who studied and figured the thorax of representatives of fifty-five of the fifty-nine families found in our fauna. I have adopted this writer's conclusions regarding the homologies of the sclerites in question. The most distinctive feature of the wings of the Diptera is the fact that only the first pair are developed as organs of flight ; the second DIPTERA 111 pair being greatly reduced in size. The second pair of wings are known as the halteres, they are thread-Hke, enlarged at the end, and bear organs of special sense, the function of which has not been definitely determined. They are present in nearly all mem- bers of the order, even when the front wings are wanting; they can be easily seen in a crane-fly (Fig- 993)- The fore wings are thin, mem- branous, and usually either naked or clothed with microscopic setee; but with mosquitoes the wings bear a fringe of scale-like setse on the margin and usually also on each of the wing-veins, and in the moth-like flies (Psychodidae) and in some others the clothing of sets is very conspicuous. In the more generalized members of this order the venation of the mesothoracic wings corresponds quite closely to the h^^pothetical primitive type. Neither accessory nor intercalary veins are ever de- veloped, and only the principal cross-veins are present. The most Fig. 993. — ^A crane-fly, and halteres. showing wings /?, R., idA Fig. 994. — Wing of A Jiisopus. striking divergence from this type is the fact that vein M is only three-branched. The wing of Anisopus (Fig. 994) is a good example of a generalized dipterous wing except that the branches of radius have been reduced. In the more specialized forms the typical arrange- ment of the veins has been greatly modified by the approaching and coalescing of the tips of adjacent veins, as shown later. 778 AN INTRODUCTION TO ENTOMOLOGY In many families there is a notch in the inner margin of the wing near its base (Fig. 995, a. e) ; this is the axillary excision; that part of the wing lying between the axillary excision when it exists, and the axillary membrane is the ;/?05^m or io6^ (Fig. 995, /). In certain fami- lies the axillary membrane, the membrane of the wing base, is ex- panded so as to form a lobe or lobes which fold beneath the base of the wing when the wings are closed; this part of the wing is the alula or alulet. The alulaj are termed the squamcs by some writers and the calypteres by others. The alulse are well developed in the common /?, /?,+j 2d A+Cu2 Fig. 995. — Wing of Conops. House-fly. Each alula, in those species where the alulae are well de- veloped, consists of two lobes which fold over each other when the wings are closed. These two lobes are designated as the upper squama or squamula alaris and the lower squama or squamula thoracalis re- spectively. The alulae are called the tegulas by many writers on Dip- tera ; but the term tegula was first used in insect anatomy for the cup- like scale which covers the base of the wing in certain insects, as most Hymenoptera, and should be restricted to that use. The terms alula and alulet are also often misapplied, being used to designate the pos- terior lobe of the wing. The legs vary greatly in length and in stoutness. The coxse are usually long, and in most of the fungus-gnats (Mycetophilidas) they are very long. When pulvilli are developed they are membranous pads, one beneath each tarsal claw. A third appendage, the empodium, often exists be- tween the two pulvilli of each tarsus. The empodia may be bristle-like or tapering (Fig. 996) or membranous, resembling the pulvilli in form (Fig. 997) in the last case they are described as pulvilliform. In descriptions of flies the number of tibial spurs borne by the different pairs of legs is often indicated by a brief formula, as, for example; "Tibial spurs i :2:2" indicates that the fore tibiae bear each one spur; the middle tibiae, two; and the hind tibas two. Fig. 996. Fig. 997. DIPTERA 779 CH^TOTAXY OR THE ARRANGEMENT OF THE CHARACTERISTIC BRISTLES OF DIPTERA In certain families of the Diptera some of the setas with which the body is clothed are stout bristles, termed macrochcEtcE. In the classification of these families much use is made of the number, position, and arrangement of these bri&tles. This has made necessary the establishment of a set of terms by which the different bristles or sets of bristles can be designated. Such a terminology was proposed by Osten-Sacken in 1881, and is still in use with additions. In the choice of terms Osten-Sacken and later writers have used those that in- dicate the places of insertion of the bristles. But owing to the fact that the homol- ogies of the sclcrites of the head and thorax had not been definitely determined at the time Osten-Sacken wrote he proposed a "purely conventional terminology" for the areas upon which the bristles are inserted ; and in this he has been followed to the present time. The result is that some of the terms are misleading; as for example, the so-called frontal bristles are not inserted on what is really the front but on the vertex. But the use of these terms is so firmly established that it is not probable that they will be changed. In the following account I have endeavored to indicate the homologies of the parts named in those cases where the terms applied to them differ from those used in accounts of other orders of insects, and which are defined in Chapter II. In defining the special terms used by writers on chsetotaxy I have made free use of the definitions given by Osten-Sacken ('81), Hough ('98), Williston, ('08) and Walton ('09). THE PARTS OF THE HEAD The homologies of the areas of the head were determined b}'' Peterson ('16) who studied and figured the heads of representatives of nearly all of the families of Diptera found in our fauna, and who gives a diagram representing a hypothetical type of the head-capsule of Diptera (Fig. 998). The conclusions of Peterson are based on comparisons of heads of the more generalized Diptera with those of the more generalized members of other orders of insects; for descriptions of the latter see above, pages 37-40 and 96-97. The more important landmarks for determining the homologies of the areas of the cephalic aspect of the head, the region in which the greatest confusion exists, are the stem of the epicranial suture (Fig. 998, .y. e. s); the arms of the epicranial suture (Fig. 998, a. e. s); and the positions of the invaginations of the dorsal arms of the tentorium (Fig. 998, i. d.); and of the anterior arms of the tentorium (Fig. 998, i. a.) In Figure 999 is given a diagram illustrating the terms applied by writers on chastotaxy to the areas of the head. These terms are defined below. The antennal fossa, fovea, or groove. — Depressed areas of the fronto-clypeus in which the antennas rest (Fig. 999, a.f.) The Bucca.^Th.a.t part of the wall of the head on each side that is ventrad of the transverse impression, and ventrad of the eye, extending ventrad to the edge of the mouth opening, cephalad to the vibrissal ridge and continuing caudad on the gena to the caudal margin of the head (Fig. 999, b.) The cheeks. — This term is used differently by different systematists; by some is applied to the space on each side of the head that is between the lower border of the eye and the oral margin, differing from the bucca only in that it does not extend over the caudal aspect of the head; by others it is applied to this space and the so-called gena of writers on chaetotaxj'^ ; and by others to the so-called gena alone. The cheek- grooves. — A more or less distinct depression on each side below the eye. The clypeus. — See fronto-clypeus. The epistoma. — The oral margin and an indefinite space immediately con- tiguous thereto. The face. — That part of the cephalic aspect of the head lying below an imag- inary horizontal line passing through the base of the antennas. (Fig. 999, Fa.). 780 AN INTRODUCTION TO ENTOMOLOGY The facial depression. — See antennal fossa. The facialia or facial ridges. — -See vibrissal ridges. The front.— (a) The true front (Fig. 998, fr.) is the first of the unpaired sclerites be- tween the arms of the epicranial suture. See above pages 37 and 38. This term has been generally applied to this sclerite since it was proposed by Kirby (Kirby and Spence) nearly a century ago. {b) The so-called front of writers on chsetotaxy is that part of the vertex that extends from the base of the antennas to the upper margin of the head (Fie. 999, Fr.). The frontalia. — See frontal vitta. The frontal orbits. — See genovertical plates. The frontal triangle. — In holoptic flies, those in which the eyes are contiguous on the upper side of the head, the triangle between the eyes and the antennae, the apex of which is above, is termed the frontal triangle. Some times this term is applied to a triangle indi- cated by color or a depression in the corre- sponding position in flies with dichoptic eyes. The frontal lunule. — See page 775. The frontal suture. — See page 776. The frontal vitta. The median portion of the so-called front, extending from the base of the antennte to the ocelli (Fig. 999, f. v.). The fronto-clypeus. — This term is applied to the combined front and clypeus when the suture between them is obsolete, as is usually the case in Diptera. It is the part bounded above by the arms of the epicranial suture (Fig. 998, a. e. s) and below by the clypeo- labial suture (Fig. 998, c. I. s.). The gencB. — (a) The true genas (Fig. 48, G, page 39). The term genae was introduced into entomology nearly a century ago by Kirby (Kirby and Spence) and was applied to the lateral portions of the epicranium, that part on each side of the head lying beneath and behind the eye; and has been generally used by writers on insect morphology in this sense, {b) The so-called genas of writers on ch£Btotaxy are portions of the cephalic aspect of the head, that part on each side which is dorsad of the transverse impression, laterad of the arm of the frontal suture and mesad of the eye (Fig. 999, g). This region is "the sides of the face" of older descriptions and the parafacialia of some later writers. The genovertical plates. — The so-called front of writers on chsetotaxy (see above) is usually distinctly divided into three parts, a median, the frontal vitta or frontalia, and two lateral, the genovertical plates or parafrontalia. (Fig. 999, g-P-)- The interfrontalia. — Specialized stripes on the middle of the so-called front, formed from the enlarged ocellar triangle. The occiput. — The term occiput is applied by writers on the classification of the Diptera to the caudal aspect of the head, this includes the gen« and post- genas described on page 39. The ocellar plate or ocellar triangle. — ^A triangle indicated by grooves or de- pressions on which the ocelli are situated. The orbits. — That pa^-t of the epicranium on each side immediately contiguous to the compound eye. The orbit is sometimes indicated by structural characters, at other times it is indefinite. The parafacials. — The so-called genae of writers on chastotaxy. The parafrontals.- — The genovertical plates. The peristome. — The region around the mouth. (e ps^ gl md Fig. 998. — Hypothetical type of head-capsule of Diptera; a. e. s, arms of epicranial suture; a, f, antennal fossa; ant, antenna; a. s, antennal sclerite; c, cly- peus; c. e, compound eye; c. I. s. clypeo-labial suture; /2, f ur- ea; /3, furca; g, galea, ge, gena; gl, glossa; i. a. and i. d, invagi- nations of the tentorium; /, lab- rum; le, labella; m, membrane; md, mandible; mx. pi, maxilla- ry palpus; oc, ocelli; 0. /, oral lobe; pgl, paraglossa; 5. e. s, stem of epicranial suture; v, vertex. (From Peterson.) DIPT ERA 781 The poslgencB. — See page 39 . The plilinum. — See page 776. The transverse impression. — See cheek-groves. The tormcB. — A sclerite situated between the clypeus and the labrum in the more speciahzed Diptera. It is composed of two sclerites which belong to the lateral portions of the epipharynx and are internal in the more generalized in- sects; but they become exposed and united on the middle line in the more special- ized Diptera. In such cases the tormae are sometimes incorrectly termed the clypeus. See Peterson ('16 p. 19). The vertex. — (a) The term vertex, as defined by Kirby (Kirby and Spence» 1 815- 1 826), is the dorsal portion of the epicranium; or, more specifically, that portion which is next the front and between the compound eyes (Fig. 998, v. v. v.) (h) This term is often applied merely to the top of the head. Fig- 999- — Diagram illustrating the terms applied by writers on chastotaxy to the areas of the head: a. f. antennal fossa; b, bucca; E, eye; Fa, face; Fr, the so- Fig. 1000. — Cephalic bristles: fa, fa- called front; f.v, frontal vitta; g, the so- cial, fr, frontal; /. 0., fronto-orbital; called gena; g.p, genovertical plate; v, g. 0, greater ocellar; /. 0, lesser ocel- vibrissa; v. r, vibrissal ridge. lar; ve, vertical; vi, vibrissas. The vertical triangle. — See the ocellar plate. The vibrissal angles. — Two prominences at the lower ends of the vibrissal ridges upon which are borne the vibrissas. The vibrissal ridges. — Two ridges, one on each side, inside the arms of the frontal suture, constituting the lateral boundaries of the antennal fossa, and bearing the vibrissas (Fig. 999, v. r). These are also termed the facialia or facial ridges. THE CEPHALIC BRISTLES The ascending frontal bristles.^See frontal bristles. The beard. — A clothing of hair borne by the lower part of the so-called occiput and on the buccae. The cilia of the posterior orbit. — A row of bristles along the posterior orbit of the eye. 782 AN INTRODUCTION TO ENTOMOLOGY The cruciate bristles. — A pair of bristles on the lower part of the frontal \'itta, directed inward and forward. The facial bristles. — A series of bristles on either side borne by the vibrissa! ridge, above the vibrissa (Fig. looo, fa.). The facio-orbital bristles. — Bristles borne on that portion of the face on each side next to the orbit, the so-called gena. The frontal bristles. — A row of bristles on each side on the boundary line be- tween the frontal vitta and the genovertical plate. (Fig. lOoo, fr.) the uppermost of these, from one to four in number, are termed the ascending frontal bristles; the lower ones, which are often directed across the frontal vitta, are termed the transfrontral bristles. The fronto-orbital bristles. — A bristle or bristles on the genovertical plate, immediately below the vertical bristles. (Fig. lOOO, fo.). So named because they are on that part of the so-called front next to the orbit. The lateral facial bristles. — One or two bristles sometimes present on the sides of the face below, towards the eye. The lower fronto-orbital bristles. — These are situated on the lower part of the genovertical plates near the eyes and are not quite in line with the fronto-orbitals. They are not of fiequent occurrence. The ocellar bristles. — (a) The greater ocellars or the ocellar pair, a pair of bristles on the ocellar triangle ]ust back of the median ocellus (Fig. lOOO, g. o.). (b) The lesser ocellar bristles, from three to twelve pairs of bristles, usually inserted in two parallel lines, sometimes in four, which begin very close to the insertion of the greater ocellar bristles and extend backward a variable distance (Fig. looo, /. o.). The occipito-central bristles. — A pair of bristles on the upper part of the occipu^: just below and almost in line with the inner vertical pair. The occipito-lateral bristles. — ^A pair of bristles borne, one on each side, a little back of the outer vertical bristles. The orbital bristles. — See fronto-orbital bristles. The postorbital bristles. — See cilia of the posterior orbit. The postverfical bristles. — The hinder pair of the lesser ocellar bristles. The preocellar bristles. — ^A pair of small bristles sometimes found below the median ocellus. The transfrontal bristles. — See frontal bristles. The vertical bristles. — Two pairs of bristles, an inner and outer pair, inserted more or less behind the upper and inner corners of the eyes (Fig. lOOO, ve.). The vibrissce. — A pair of stout bristles, one on each side of the face, near or a little above the oral margin (Fig. lOoo, vi). These are the longest or strongest cf the bristles borne on the vibrissa! ridges. THE THORACIC SUTURES The transverse suture. — The suture between the prescutum and the scutum of the mesothorax. The notopleural or dorsopteural su'ure. — The suture on each side separating the mesonotum from the pleurum of the mesothorax. The mesopleural suture. — The suture on each side separating the episternum and the epimerum of the mesothorax. The sternopleural suture. — The suture on each side separating the mesopleurum and the sternopleurum. THE PLEURAL DIVISIONS The propleura. — The pleura of the prothorax (Fig. looi, pr.). The notopleura. — A sclerite on each side at the end of the transverse suture in DIPTERA 783 the presutural depression. (Fig. looi, np.). The mesopleura. — The upper part of the episterna (anepis- terna) of the mesothorax (Fig. looi r:es.). The s'ernopleura. — The lower part of the episterna (katepi- sterna) of the mesothorax (Fig. lOOI, s'.). The pteropleura. — The upper part of the epimera (anepimera) of the mesothorax, (Fig. looi, Pt.). The hypopleura. — The lower part of the epimera (katepimera) of the mesothorax (Fig. looi, hy.). The metapleura. — The pleixra of the metathorax. OTHER TERMS FOR PARTS OF THE THORAX Fig. looi. — Diagram of the thorax of a fly illustrating the terms applied by writers on chffitotaxy to the areas of the thorax. The positions of the more important bristles are indicated by dots: ex, ex, ex, coxce; h. c, humeral callus; h, halter; hy, hypo- pleui'a; mes, mesopleura; np, notopleura or presutural depression; po. e, postalar callus; pr, propleura; pt, pteropleura; s, scutellum; sq, sq, squamae or calypteres; st,_ sternopleura; w. b. wing-base. (After Riley and Johannsen.) The alar frenum. — ^A little ligament dividing the supraalar cavity into an anterior and a posterior part. The humeral callus. — Each of the anterior lateral angles of the prescutum of the mesothorax, usually a more or less rounded tubercle. (Fig. looi, h. e.). The prealar callus. — A not very prominent projection, situ- ated before the root of the wing, on each side of the mesonotum, just back of the outer end of the transverse suture. The postalar callus. — A more or less distinct rounded swelling on each side, situated between the root of the wing and the scutellum. (Fig. lOoi, ^o. c). The presutural depression. — A depression, usually triangular in shape, at the outer end of the transverse suture, near the notopleural suture (Fig. lOOi, np). The supraalar groove or cavity. — A groove on the mesothorax immediately above the root of the wing. The scutcllar bridge. — A small ridge on either side of the scutellum connecting it with the scutum, crossing the intervening suture. THE THORACIC BRISTLES The acrostichal bristles. — Two rows of bristles, one on each side of the mediaii line of the mesonotum, the two rows nearest to the median line (Fig. 1002, a). Those in front of the transverse suture are termed the anterior acrostichals or preacroslichals ; those behind this suture, the posterior acrostichals or pos'acrosti- chals. The anterior acrostichals. — See the acrostichal bristles. The discal scutellar bristles. — See the scutellar bristles. The dorsocentral bristles. — A row of bristles on each side next to and parallel with the acrostichals bristles (Fig. 1002, dc). Those before the transverse suture are termed the anterior, those behind, the posterior, or postsutural dorsocentrals. The humeral bristles. — One or more bristles inserted on the humeral callus. (Fig. 1002, // m). 784 AN INTRODUCTION TO ENTOMOLOGY ■ :rr~~>..^^ / ^c* ''" ...a. , , a ^ — . U'- ^ ds-: The hypopleural roiv. — A row of bristles extending in a more or less vertical direction on the hypopleura, usually directly above the hind coxae. They are sometimes grouped into a tuft. (Fig. looi). The inner dorsocentral bristles. — These are the acrostichal bristles. The intraalar bristles. — A row of two of three bristles between the supraalar group and the dorsocentral bristles (Fig. 1002, i. a). The intrahumeral bristles. — These are the same as the presutural bristles. The marginal sciitellar bristles. — See the scutellar bristles. The mesopleural roiv. — A row of bristles inserted on the mesopleurum, near its dorso- caudal angle, or along its caudal margin. (Fig. lOOi). The metapleural bristles. — • A fan like row on the meta- pleurum conspicuous in some families but not found in the Calypteratae. The notopleural bristles. — Usually two bristles, inserted immediately above the dorso- pleural suture, between the humeral callus and the root of the wing, on the noto- pleura. (Fig. 1002, n p I), The postacrostichals. — See the acrostichal bristles. The postalar bristles. — - Bristles on the postalar callus back of the supraalar bris- tles. (Fig. 1002, pa). The posthnmeral bristles. — One or more bristles situated on the prescutum near the inner margin of the humeral callus. (Fig. 1002, ph.) The preacrostichals. — See acrostichal bristles. The prealar bristle. — A bristle found in the Anthomyiidae inserted just back of the transverse suture in line with the supraalar bristles. (Fig. 1002, pra). The prescutellar row. — A row of bristles in front of the scutellum consisting of the hindermost dorsocentral and the acrostichal bristles. The presutural bristles. — One or more bristles situated immediately in front of the transverse suture, above the presutural depression. (Fig. 1002, pr.). The propleural bristles. — A bristle or bristles inserted on the lower part of the pleurum of the prothorax, immediately above the front coxa. The prothoracic bristle. — The same as the propleural bristle. The pteropleiiral bristles. — Bristles inserted on the pteropleura. The scutellar bristles. — (a). The dorso-scutellar bristles., usually a single pair of bristles, borne on the dorsal portion of the scutellum, one on each side of the median line, slightly behind its middle. (Fig. 1002, ds). (b) The marginal scu- tellar bristles, usually a distinct row of large bristles borne on the margin of the scutellum (Fig. 1002, ni-s). The sternopleural bristles. — One or several bristles on each sternopleurum below the sternopleural suture and near it. The supraalar bristles. — Usually one to four bristles above the root of the wing, between the notopleural and the postalar bristles. (Fig. 1002, sa). The trichosticnal bristles. — The same as the metapleural bristles. n/>l pre Fig. 1002. — Thoracic bristles: a, acrostichal; dc, dorsocentral; ds. dorsoscutellar; hm, hum- eral; in, intraalar; ms, marginal scutellar; npl, notopleural; pa, postalar; ph, posthum- eral; pr. presutural; sa, supraalar; /. sq., lower squama or calypter; u. sq. upper squama or calypter; w. b, wing-base. (After Riley and Johannsen.) DIPTERA 785 THE BRISTLES OF THE LEGS The extensor row. — ^A row of bristles on the upper surface of femur. The flexor roic. — One or more rows of bristles placed along the lower surface of the femur. The preapical bristle. — A large bristle found on the extensor side on the distaJ third of the tibia in some families of the Acalyptratae; it is quite distinct from the tibial spurs. This term is sometimes used for a bristle on the femur. The tibial spurs. — One or more bristly spurs placed at the distal end of the tibia. THE ABDOMINAL BRISTLES The discal brtsUes. — Usually one or more pairs of bristles inserted near the middle of the dorsal wall of the abdominal segments before the hind margin. The lateral bristles. — One or more bristles situated on or near the lateral margins of the abdominal segments, above. The marginal bristles. — Bristles inserted on the posterior margin of the ab- dominal segments, above. Flies undergo a complete metamorphosis. The larvee are com- monly called maggots. These are usually cylindrical and are footless. In the more generalized families the larvas possess a distinct head ; but in the more specialized Diptera there is an anomalous retarding of the development of the head; with these the rudiments of the head are invaginated within the body of the larva and the head does not be- come exposed until the pupal stage is reached. The development of the head in thsse insects is described in Chapter IV. The pupas are usually either naked or enclosed in the last or the next to the last larval skin. A few are enclosed in cocoons. When the pupa state is passed within the last larval skin the body of the pupa separates from the larval skin more or less completely; but the larval skin is not broken till the adult fly is ready to emerge. . In this case the larval skin, which serves as a cocoon, is termed a pupariiim. In some fam- ilies the puparium retains the form of the larva; in others the body of the larva shortens, assuming a more or less barrel-shaped form before the change to a pupa takes place. SYNOPSIS OF THE DIPTERA Suborder Orthorrhapha. The Straight-seamed Flies, p. 794. Series I. — Nemocera. The Long-horned Orthorrhapha. p. 795. Subseries A. — The True Nemocera. The Crane-flies, p. 795. Superfamily Tipuloidea The Primitive Crane-flies, p. 796. Family Tanyderid^ The Phantom Crane-fly Family, p. 796. Family Ptychopterif.* The So-called False Crane-flies, p. ■ji.^y. Family Anisopid.e The Typical Crane-flies, p. 798. Family Tipulid^ The Dixa midges, p. 800. Family DlxiD^ The Aloth-like' Flies, p. 801. Family Psychodid^ The Midges, p. 802. Family Chikonomid^ The Mosquitoes, p. 804. Family Cclicid/E The Fung'AE-gnats. p. 810. Family Mycetophilid^ The Gar ;nats. p. 813. Family Cecidomyiid^ Subseries B.— fhe Anomalous Nemocera. The March-flies, p. 820. Family Bibionid^ The Scatopsids. p. 821. Family Scatopsid^ 786 ^A^ INTRODUCTION TO ENTOMOLOGY The Black-flies, p. 821. Family Simuliid^e The Net-winged Midges, p. 824. Family Bleph.arocerid.^ The Solitary-midge, p. 828. Family Thaumaleid.e Series II. — Brachycer.'V. The Short-horned Orthorrhapha. p. 828. Subseries A. — The Anomalous Brachycera. The Horse-flies, p. 829. Family Tabanid^ The vSoldier- flies, p. 830. Family SxRATiOMYiiDiE The Xylomyiids. p. 832. Family Xylomyiid^ The Xylophagids. p. 833. Family Xylophagid^ The Coenomyiids. p. 834. Family Ccenomyiid/E Subseries B. — The True Brachycera. The Snipe-flies, p. 834. Family Rhagioxid.=e The Tangle- veined Flies, p. 836. Family Nemestrinid/E The Small-headed Flies, p. 837. Family Acrocerid^e The Bee-flies, p. 838. Family Bombyliid.f The Stiletto-flies, p. 839. Family Therevid^ The Window-flies, p. 839. Family Scenopinid^ The Robber-flies, p. 840. Family Asilid^ The Mydas-flies. p. 842. Family Mydaid^ The Apiocerids. p. 842. Family Apiocerid^ The Long-legged Flies, p. 843. Family Dolichopodid,^ The Dance-flies, p. 845. Family Empidid.e The Spear-winged Flies, p. 84O. Family Lonchopterid.e Suborder Cyclorrhapha. The Circular- seamed Flies. Series I.- — Aschiza. Cyclorrhapha without a frontal sutm"e. The Humpbacked Flies, p. 847. Family Phorid^ The Flat-footed Flies, p. 848. Family Platypezid^ The Big-eyed Flies, n. 849. Family Pipunculid^ The vSyrphus-flies. p. 850. Family Syrphid^ Series II. — Schizophora. Cyclorrhapha with a frontal suture. Section I.— Myodaria. The Muscids. Subsection I. — Acalyptrat/E. The Acalyptrate Muscids. The Thick-headed Flies, p. 853. Family Conopid.e The Dung-flies, p. 854. Family Cordylurid^ The Clusiids. p. 854. Family Clusiid^ The Helomyzids. p. 854. Family Helomyzid^ The Borborids. p. 855. Family Borborid^ The Phycodromids. p. 855. Family PhycodroMID/E The Sciomyzids. p. 855. Family Sciomyzid/E The Sapromyzids. p. 856. Family Sapromyzid^ The Lonchasids. p. 856. Family Lonch^id^ The Ortalids. p. 856. Family Ortalid^ The Trypetids. p. 858. Family Trypetid^ The Tanypezids. p. 858. Family Tanypezid^ The Micropezids. p. 858. Family Micropezid^ The Seosids. p. 858. Family Sepsid^ The Piophilids. p. 858. Family Piophilid^ The Psihds. p. 859. Family Psilid^ The Diopsids. p. 859. Family Diopsid^ The Canaceids. p. 859. Family Canaceid^ The Ephydrids. p. 859. Family Ephydrid^ The Chloropids. p. 860. Family Chloropid^ The Asteiids. p. 860. Family Asteiid^ The Drosophilids. p. 860. Family Drosophilid^ The Geomyzids. p. 861. Family Geomyzid^ The Agromyzids. p 861. Family Agromyzid^ The MiHchiids. o. 862. Family Milichiid^ The Ochthiphilids. p. 862. Family Ochthiphilid^ Subsection II. Calyptrat.i;. The Calyptrate Muscids. Superfamily Anthomyioidea The Anthomyiids. p. 863. Family Anthomyiid.'e DIPTERA 787 Superfamily Muscoidea. The Bot-flies of Horses, p. 864. Family Gastrophilid^ The CEstrids. p. 866. Family (Estrid^ The Phasiids. p. 868. Family Phasiid^ The Alegaprosopids. p. 869. Family Megaprosopid^ The Blow-fly Family p. 869. Family Calliphorid^ The Sarcophagids. p. 870. Family Sarcophagid^ The Tachina-flies. p. 871. Family Tachinid.^ The Typical Muscids. p. 872. Family MusciD^ Section II. Pupipara. The Louse-flies, p. 874. Family Hippoboscid^ The Bat-ticks in part. p. 875. Family Streblid^ The Bat-ticks in part. p. 875. Family Nycteribiid^ The Bee-lice. p. 876. Family Braulid^e TABLES FOR DETERMINING THE FAMILIES OF THE DIPTERA Table A.— DIPTERA WITH WELL DEVELOPED WINGS. A. Flies in which the abdomen is distinctly segmented, and the two legs of each thoracic segment are not widely separated. Habits various, but the adults do not live parasitically upon either birds or mammals. B. Antennae consisting of more than three segments. (Note that a style or arista borne by the third segment is not counted as a segment.) C. Antenna consisting of more than five distinct segments, the segments beyond the second not consolidated; cell ist A of the wings but slightly narrowed at the margin of the wing, if at all; palpi usually elongate, and composed of from three to five segments. D. Small moth-like flies, w^ith the body and wings densely clothed with hairs and scales. Wings with from nine to eleven longitudinal veins but with no cross-veins except sometimes near the base of the wings. (Fig. IOI4). p. 801 PSYCHODID^ DD. Flies that do not resemble moths in appearance. E. Mesonotum with a distinct V-shaped transverse suture. F. The radial sector four-branched, p. 796 Tanyderid^ FF. The radial sector with less than four branches. G. W^ith only one anal vein. p. 796 Ptychopterid^ GG. With two anal veins, p. 798 Tipulid/E EE. Mesonotum without a distinct V-shaped suture. F. Media three-branched {Anisopus and Trichocera). p. 797.. Anisopid^ FF. Media simple, two-branched, or wanting; cell M2 is not divided by a cross-vein. G. Wings with a network of fine lines near the outer and inner margins in addition to the veins (Fig. 1048). p. 824 ■ Blepharocerid^ GG. Wings without a network of fine lines. H. The margin of the wings and each of the wing-veins fringed with scales (Fig. 1019). p. 804 Culicid^ HH. The wing-veins with or without a fringe of hairs, but without a fringe of flat scales. I. Anal veins entirely wanting; vein M wanting or at most represented by a single unbranched fold. p. 813 Cecidomyiid^ II. Anal veins usually present or represented by folds ; vein M present or at least represented by a fold which is usually branched. J. Ocelli present. K. Antennae shorter than the thorax; coxae not un- usually long. 788 AN INTRODUCTION TO ENTOMOLOGY L. Cross- vein m-cu present, p. 820. . .Bibionid^ LL. Cross- vein m-cu wanting, p. 821 . Scatopsid^. KK. Antennae usually longer than the thorax; legs slender and usually with greatly elongate coxae. L. Vein m-cu present, the first branch of the radial sector, vein R2 + 3, arising slightly proximad of vein m-cu. {Mycelobia) p. 797 ANisopiDiE LL. Vein m-cu present or absent, when present the forking of the radial sector is distad of it. M. Eyes rounded or oval. p. Sio.Mycetofhilid^ MM. Each eye with a narrow expansion, the two expansions extending behind the antennae and in front of the ocelli, and meeting on the middle line of the head or nearly so. N. With tibial spurs; larvs with well-developed head (Sciarinae) p. 812 Mycetophilid^ NN. Without tibial sptus, larvae with a poorly developed head (Lestremiinae). p. 816 CECIDOMYIIDyE JJ. Ocelli absent. K. Antennae short, not clothed with long hairs, and with most of the segments wider than long; wings very broad, p. 82 1 Simuliid^ KK. Antennae either bushy, being densely clothed with long hairs, or slender with narrow segments; wings nanow or moderately broad. L. Wing-veins well-developed on all parts of the wing M. Vein Ri ending at or near the end of the second third of the costal margin, p. 828.Thaumaleid^ MM. Vein Ri ending on the outer margin of the wing. p. 800 DixiD^ LL. Wing veins much stouter near the costal margin of the wing than elsewhere, p. 8o2.Chironomid^ CC. Antennae either consisting of four or five distinct segments or consisting of five or more segments, with those beyond the second more or less closely consolidated so as to appear as a single segment consisting of several sub- segments. (Figs. 985, 986); cell 1st A closed by the coalescence of the tips of veins Cuj and 2nd A, or greatly narrowed at the margin of the wing ; palpi rarely elongate, and composed of from one to three segments. D. Antennae consisting of four or five distinct segments, empodia wanting or bristle-like. E. The first branch of media terminating at or before the apex of the wing. p. 842 MvDAib^ EE. The first branch of media terminating on the outer border of the wing. F. The vertex of the head sunken, the eyes bulging and never con- tiguous, p. 840 ASII.ID^. FF. The vertex of the head plane or convex, the eyes not bulging; eyes of males often contiguous, p. 838 Bombyliid/e. DD. Antennae consisting of five or more segments but with those beyond the second more or less closely consolidated; empodia resembling pulvilli in form. E. The alulets large, p. 829 Tabanid^ EE. The alulets small or vestigial. F. The branches of radius crowded together near the costal margin; tibiae without spurs, p. 830 Stratiomyiid^ FF. The branches of radius not crowded together near the costal margin; at least some of the tibiae with spurs. G. Cell M3 closed, p. 832 Xylomyiid^ GG. Cell M3 open. DIPTERA 789 H. Scutellum without spinous protuberances, p. 835 Xylophagid^ HH. Scutellum with two spinous protuberances, p. 834. . . COENOMYIID^ BB. Antennas consisting of not more than three segments; the third segment either with or without a style or an arista, but not divided into subsegments. C. Antennte consisting apparently of a single globular segment bearing a long, arista ; wings with some stout veins near the costal margin and other weaker veins extending across the wing unconnected by cross-veins (Fig. 1099). p. 847 Phorid^ CC. Flies that do not present the type of wing- venation represented by Figure 1099. p 847. D. Cells M and ist M2 not separated. (See Figures 1094 and 1095, p. 844 for examples of this type of wing- venation). E. Vein R with a knot-shaped swelling at the point of separation of veins R2 4- 3 and R4 4- s; the cross-vein r-m at or near this swelling when present; frontal suture absent, p. 843 Dolichopodid^ EE. Vein R with or without a swelling at the point of separation of veins R2 4- 3 and R4 4- 5; the cross-vein r-m more remote from the base of the wing; the frontal suture present. (Muscoidea). Pass to Table B. DD. Cells M (or 2d M) and ist M2 separate. E. Radial sector three-branched. F. Venation intricate due to an unusual anastomosing of the veins (Fig. 1077) p. 836 Nemestrinid^ FF. Venation not of the type represented by Figure 1077. G. Vertex of the head distinctly hollowed out between the eyes; eyes never contiguous, p. 840 Asilid^ GG. Vertex of the head not hollowed out between the eyes; eyes often contiguous in males. H. Alulets very large, p. 837 Acrocerid^ HH. Alulets small or rudimentary. I. Cell Mj present. J. Vein Rs ending before the apex of the wing. p. 842.. Apiocerid^ JJ. Vein Rs not ending before the apex of the wing. K. Empodia pulvilliform. p. 834 Rhagionid^ KK. Empodia wanting, p. 839 Therevid^ II. Cell Mj obliterated by the coalescence of veins M3 and Cuj. J. Third segment of the antennae without a style or an arista; vein Ali ending at or before the apex of the wing. p. 839 SCENOPINID/E JJ. Third segment of the antennae usually with a style or an arista; vein Mi ending beyond the apex of the wing. K. Vein Cu2 extending free to the margin of the wing or coalesced with vein 2d A for a short distance at the margin of the wing. p. 838 Bombylid^ KK. Vein Cu2 joining vein 2d A far from the margin of the wing, often extending towards the base of the wing p. 845 Empidid^ EE. Radial sector with not more than two branches. F. Wings lanceolate and with no cross-veins except at the base. (Fig. 1097) p. 846 Lonchopterid^ FF. Wings not of the type represented by Figure 1097. G. Empodia pulvilliform. p. 837 Acrocerid.e GG. Empodia not pulvilliform. H. Vein Cu2 not coalesced with vein 2d A to such an extent as to cause the free part to appear like a cross- vein. I. Antennas with a terminal style or arista. J. Antennae with a terminal arista, p. 848 . Platypezid^ JJ. Antennae with a terminal style. 790 A N INTROD UCTION TO ENTOMOLOG Y K. Front with grooves or a depression beneath the antennae, p. 853 Conopid^ KK. Front convex beneath the antenna;, p. 850.... Syrphid^ II. Antenna; v.-ith a dorsal arista. J. Head extremely large, and with nearly the entire surface occupied by the eyes. (Fig. 1103). p. 849. Pipunculid^ JJ. Head not of the type represented by Figure 1103. K. Wings with a vein-like thickening, the spurious vein, between veins R and M. p. 850 Syrphid.e KK. Wings without a spurious vein. L. Front with grooves or a depression beneath the antennae, p. 853 Conopid.« LL. Front convex beneath the antennte. p. 850. . vSyrphid^ HH. Vein Cuz appearing as a cross- vein or curved back towards the base of the wing (Figs. 1096 and 1 1 15). I. Antennae with a terminal style or arista, p. 845. Empidid.^; II. Antennae with a dorsal arista. J. Proboscis vestigial; mouth opening small; palpi wanting (Botflies) Pass to Table B. JJ. Proboscis not vestigial; palpi present in most cases. K. Frontal suture present (Myodaria). Pass to Table B. KK. Frontal suture absent, p. 845 Empidid-E AA. Flies in which the abdomen is indistinctly segmented, and the two legs of each thoracic segment are widely separated by the broad sternum. The adults live parasitically upon birds, or mammals. B. Head sunk' in an emargination of the thorax; eyes round or oval; palpi forming a sheath for the proboscis, not projecting in front of the head. p. 874. HlPPOBOSCID^ BB. Head with a fleshy movable neck; eyes wanting or vestigial; palpi pro- jecting leaf -like in front of the head. p. 875 Streblid/E TABLE B.— THE FAMILIES OF THE MYODARIA A. The alulae or calypteres small or rudimentary; the subcostal vein often in- distinct or vestigial, but sometimes well-preserved; vein Ri shortened and often very short; thorax without a complete transverse suture; postalar callus usually absent. (Subsection i — Acalyptratas). B. Subcosta distinctly separated from vein Ri and ending in the costa notice- ably before Ri, the latter ending near or beyond the middle of the wing in most cases. C. Oral vibrissas present and distinctly differentiated from the hairs of the peristome. D. A distinct costal break or scar proximad of the tip of Ri near the apex of Sc. E. The postvertical bristles are divergent or parallel or wanting. F. The frontals are convergent (lacking in Hydromyza) and stand nearer the median line than the fronto-orbitals. Abdominal spiracles in most cases in the chitin. p. 854 Cordylurid^ FF. The frontals absent, or if present and convergent stand in line or laterad of the line of the fronto-orbitals; transverse suture in- terrupted in the middle; anal vein does not reach the wing-margin; cross veins in most cases approximated; abdominal spiracles in the conjunctivas, p. 854 Clusiid^ EE. Postvertical bristles convergent, costa of wing in nearly all cases with a row of spines projecting beyond the ciliation. p. 854 Helomyzid.^; DD. Costa without a sign of a break; palpi vestigial in most species. E. Palpi vestigial; "front" never bristly near the antennae; anal vein not produced to the wing margin, p. 858 Sepsid/-, DIPTERA 791 EE. Palpi well-developed; "front" and face bristly; anal vein pro- duced to the wing-margin. Seashore flies, p. 855. . . Phycodromid^ CC. Oral vibrissas not differentiated from the peristomal hairs. D. Legs very long and stilt-like; tibiae usually without preapical bristle; cell R5 constricted at the wing-margin. E. Proboscis greatly elongate and folding near its middle; arista terminal; ovipositor very long (Stylogaster) p. 853. . .Conopid^* EE. Proboscis short ; arista dorsal; ovipositor not lengthened. F. Buccffi and posterior orbits narrow, p. 858 .... Tanypezid^e FF. Buccs broad, p. 858 Micropezid^ DD. Legs not long and stilt-like. E. Preapical tibial bristles present; "ovipositor" membranous and re- tractile. F. Postvertical bristles well -developed and converging. G. Anal' vein produced to the wing margin; last tarsal segment enlarged and flat. p. 855 Phycodromid^ GG. Anal vein not produced to the wing margin; last tarsal segment normal, p. 856 Sapromyzid^ FF. Postvertical bristles parallel or diverging, rarely lacking, p. 855. SCIOMYZID^ EE. Preapical tibial bristles absent, if present in exceptional cases, the ovipositor horny and not wholly retractible, or the cell ist A of the wing drawn out into a lobe, or vein Ri bristly above. F. Ovipositor membranous, retractile; vein Ri bare above; cell ist A without acute process or lobe. G. Palpi well developed; postvertical bristles converging or wanting, p. 862 Ochthiphilid^ GG. Palpi vestigial; postvertical bristles divergent; the "front" not bristly except at the vertex, p. 858 Sepsid^ FF. Ovipositor horny, not wholly retractible; postvertical bristles not converging; palpi present. G. The costal break or scar is located just proximad of the tip of vein Sc; cell M and the cell ist A small, the latter with rounded apex; only one fronto-orbital bristle, p. 856 Lonch^id^ GG. Costa either unbroken or if broken there is also a trace of a break basally, indicated by a dark or light scar or constriction; cell M and cell 1st A large, the latter in many cases with a sharp angle or prolonged into a lobe; or the costa with a strongly marked stigma due to an abrupt double curve in vein Ri near its tip and the secon i tergite of the abdomen with at least one long bristle on each side. p. 856 Ortalid^ BB. Subcosta absent, or vestigial, or running very close to vein Ri and ending with it in the costa before the middle of the wing, or evanescent at the tip. C. Head produced on each side into a lateral process bearing the eye. p. 859. DlOPSID^ CC. The eyes not stalked. D. First segment of hind tarsi swollen and in most cases shorter than the second segment; oral vibrissas present, p. 855 BoRBORiDiE DD. First segment of hind tarsi normal. E. Subcostal vein evanescent at the tip, where it turns sharply forward at some distance before the tip of vein Ri; wings nearly always pic- tured; cell 1st A angular or drawn out into an acute lobe; no pre- apical tibial bristle, p. 856 Trypetid^ EE. The subcosta runs very close to Ri or is fused with it either wholly or in part but only in a few cases suddenly interrupted at the tip, in which case the wing with a fold extending across from the costal fracture to the tip of cell M. F. Cell 1st A wanting. *See Table A for distinctive characters of those Conopidae in which the free part of vein Cuj does not appear like a cross-vine. 792 AN INTRODUCTION TO ENTOMOLOGY G. Subcosta vestigial or only basally indicated as a fold; costa fractured but once; cell M and anal vein wanting; ocellar tri- angle large and conspicuous; head bristles but feebly developed. p. 860 ChLOROPIDvE GG. Subcosta developed basally at least; ocellar triangle in most cases not conspicuous; head bristles well-developed. H. Costa twice fractured, basally and near the tip of Ri; arista never feathered below, p. 859 Ephydrid^ HH. Basal fracture of the costa indistinct; cell Rj very long, the bounding veins converging, p. 860 Asteiid^ FF. Cell 1st A present though in some cases quite small. G. Basal cells M and ist A large; wings with a fold extending across from the costal fracture to the tip of cell M; frontal triangle conspicuous, p. 859 Psilid^ GG. Basal cells JVI and ist A small; wings without a fold. H. Arista plumose, in rare cases pectinate; wing with two costal fractures; vibrissae present, p. 860 DrosophiliD'E HH. Arista bare or pubescent ; if in a few cases plumose then costa of wing with but one fracture which is situated dis- tinctly before the tip of Ri. I. Tormae large and distinctly projecting; vein So distinctly isolated at its extremity ; ocellar triangle large nearly attain- ing the base of the antennEe; costal fracture close to the tip of Ri. p. 859 Canaceid^ II. Tormae small and not projecting, or differing in other characters. J. Anterior part of the "front" not bristly; postvertical bristles not converging; cells M and 1st M2 not confluent; Sc distinct to the tip; arista bare. p. 858. . .Piophilid^ JJ. Not such flies. K. Costa broken twice; proboscis in most cases genicu- late; postvertical bristles converging, rarely parallel or wanting; anal vein in most cases vestigial or wanting. p. 862 MlLICHIID^ KK. Costa broken but once or proboscis not geniculate. L. Postvertical bristles divergent, in exceptional cases wanting; basal segment of the arista minute, shorter than broad; the so-called genae narrower than the buccae, except in Phytomyza in which cell ist Mj is open distally. p. 861 Agromyzid^ LL. Postvertical bristles converging, or if wanting Cell Rs long and narrowed in the margin of the wing; or cells ]M and ist M2 confluent, or proboscis genicu- late, or arista plumose; basal segment of arista longer than wide; the so-called genas as broad as or broader than the buccse. p. 861 . . . .Geomyzid^ AA. At least the lower lobe of the alulae or calypteres well-developed; the sub- costal vein distinct in its whole course; vein Rj never very short; thorax with a complete transverse suture; and the postalar callus present. (Sub- section II. — Calyptratffi). B. Proboscis usually much reduced or vestigial, not functional; mouth-open- ing small. (Bot-flies). C. Costa ends at or slightly beyond the tip of vein R4 -j- 5; vein Mi + 2 extends in a nearly straight line toward the outer margin of the wing p. 864 Gastrophilid^ CC. Costa extends to the tip of vein Mi + 2] vein Mi -f- 2 with a bend so that cell Rs is much narrowed or closed at the margin of the wing. p. 866. (I^STRID^ ^B. Mouth-opening normal; mouth-parts functional. DIPTERA 793 C. Hypopleural bristles absent. Cell R s very slightly or not at all narrowed at the margin of the wing. (Anthomyioidea). p.' 863 Anthomyiid^ CC. Either the hypopleural or the pteropleural bristles or both present. Cell R,s narrowed or closed. (Muscoidea). D. Both hypopleural and pteropleural bristles present. E. Clypeus more or less produced below the vibrissal angles. Like the bridge of a nose. Abdomen not armed with stout bristles. The con- junctivae of the ventral sclerites of the abdomen present, p. 868. Ph.\siid^ EE. Clypeus flattened, at most slightly produced. Abdomen bearing some stout bristles. The conjunctiva; of the ventral sclerites of the ab- domen not visible. F. Clypeus receding and short; the cheeks very broad; vibrissjE located near the middle of the face; antenna short, p. 869. . . . Megaprosopid^ FF. Clypeus long and never conspicuously receding; the oral margin more or less prominent; vibrissal angles near the oral margin; antennae usually long. G. Second ventral sclerite of the abdomen lying with its edges either upon or in contact with the ventral edges of the corre- sponding dorsal sclerite. H. Hindermost posthumeral bristle almost always lower (more ventrad) in position than the presutural bristle; body color very frequently metallic green or blue, or yellow; arista plumose. p. 869 Callipiiorid^ HH. Hindermost posthumeral bristle on a level with or higher (more dorsad) than the presutural bristle; arista bare, pubes- cent, or plumose only on the basal two-thirds; body coloring gray or silvery, tessellated or changeable pollinose. I. Fifth ventral abdominal sclerite of the male either wanting or with the caudal margin straight, presutural intraalar bristle rarely present, p. 870 Sarcophagid^ II. Fifth ventral abdominal sclerite of the male cleft to beyond the middle. p. 871 Tachinid^ GG. Second ventral abdominal sclerite, as well as the others, more or less covered, sometimes wholly, by the edges of the dorsal sclerites. p. 871 Tachinid/E DD. Either the hypopleural or the pteropleural bristles present; basal bristles of the abdomen reduced; arista plumose to the tip. p. 872. . . . MUSCID^ TABLE C— DIPTERA IN WHICH THE WINGS ARE WANTING OR VESTIGIAL A. Mesonotum with a complete V-shaped transverse suture (Chionea) p. 798. Family Tipulid^ AA. Mesonotum without a V-shaped transverse suture. B. Flies in which the abdomen is distinctly segmented and the two ]ezs, of each thoracic segment are not widely separated. The adults do not live parasitic- ally upon either birds, mammals or the honey-bee. C. Nematocerous flies; antenna more or less thread-like and consisting of six or more segments. D. Wings short, strap-like, thickened, and without distinct venation {Eretmoptera). p. 802 Chironomid^ DD. Wings and halteres wholly wanting (Pnyxa, female) p. 810 Mycetophilid^ CC. Brachycerous flies. D. Antennae consisting apparently of a single segment, which bears a long, three-jointed arista, p. 847 Phorid^ 794 AN INTRODUCTION TO ENTOMOLOGY DD. Antennae three-jointed, third joint with an arista. E. Hind metatarsi shorter than the second segment and more or less thickened, p. 855 Borborid^ EE. Hind metatarsi longer than the second segment and slender. p. S59 Ephydrid^ BB. Flies in which the abdomen is indistinctly segmented (except Braula), and the two legs of each thoracic segment are widely separated by the broad sternum. The adults are parasites. C. Flies parasitic upon birds or mammals. D. Head folded back on the dorsum of the thorax, p. 875 . . . Nycteribiid^ DD. Head not folded back on the thorax. EE. Head sunk in an emargination of the thorax; eyes round or oval; palpi forming a sheath for the proboscis, not projecting in front of the head. p. 874 Hippoboscid^ EE. Head with a fleshy movable neck; eyes wanting or vestigial; palpi projecting leaf -like in front of the head. p. 875. Streblid^ CC. Flies parasitic upon the honey-bee. p. 876 Braulid^ MEIGEN'S FIRST PAPER ON DIPTERA In the year 1800, J. A. Meigen published a paper on the classifi- cation of the Diptera, in which many generic names were proposed. This was followed by a second paper published in 1803, in which nearly all of the generic names used in his first paper were discarded and new names proposed. The first paper was evidently not widely distributed for it was practically unknown for more than one hundred years. Attention was called to it by Mr. Fr. Hendel in 1908, and since then an eft'ort has been made to substitute the generic names proposed by Meigen in 1800 for those used by him in 1803. If this were done, not only would these generic names be changed but the well-known names of many families based on these generic names would need to be changed also. Fortunately this revolution in nomen- clature is not necessary, even according to the law of priority; for the names published by Meigen in 1 800 were not adequately defined and no type species were indicated. Suborder ORTHORRHAPHA.- The Straight-seamed Flies This suborder includes those flies in which the pupa escapes from the larval skin through a T-shaped opening, which is formed by a lengthwise split on the back near the head and a crosswise split at the front end of this (Fig. 1003), or rarely through a crosswise split between the seventh and eighth abdominal segments. The adults do not have a frontal lunule. ^'T-sha^ed"o"cnin"" ''''^^' The families included in this suborder ^ ^^^ opcnmg. are commonl}' grouped in two series : the Nemocera and the Brachy- cera. *Orthorrhapha ; orthos {op^^), straight; rhaphe {pai))^ a seam. DIPTERA 795 Series I.— NEMOCERA* The Long-horned Orihorrhapha This series of families is termed the Nemocera from the fact that in the more typical forms the antennas are elongate and slender; but in some families placed at the end of the series, the Anomalous Nemo- cera, the antenna are shorter and less thread-like than in the more typical forms. The antennae are composed of from six to thirty-nine segments, usually from eight to sixteen. The palpi are pendulous and consist of from one to five segments, usually of four. Except in a few genera, cell ist A is not narrowed towards the margin of the wing. In those cases where the radial sector is three-branched, it is veins R4 and R5 that have coalesced ; in the Brachycera veins R2 and R3 are the first to coalesce. SUBSERIES A. — THE TRUE NEMOCERA In this subseries the antennae are usually long and frequently bear whorls of long hairs, especially in the males. The legs are long and slender, and the abdomen is usually long and slender. SUPERFAMILY TIPULOIDEA The Crane-flies The crane-flies are mosquito- like in form ; but they are usually very much larger than mosqui- toes. The body is long and slender, the wings narrow, and the legs very long (Fig. 1004). This family includes the larger members of that series of families in which the antenuce are thread- like, the Nemocera; but it also ^ig. 1004.-A crane-fly. includes some species that are not larger than certain mosquitoes. Most crane-flies differ from all other Nemocera in that the trans- verse suture of the mesonotum is V-shaped; but one small family the Anisopidffi, lack the V-shaped suture. This superfamily includes the four following families ; these can be separated by the characters indicated in the table of families page 787. *Nem6cera: nema {vrjfia), thread; ceras {nipas), horn. 796 AN INTRODUCTION TO ENTOMOLOGY Family TANYDERID^ The Primitive Crane-flies This family is of especial interest as it includes the most general- ized of living crane-flies. It is a small family, only ten species repre- senting three genera being known. Of these a single genus, Proto- plasa, represented by three species, has been found in North America. Protoplasa vtpio and Protoplasa vanduzeei are found in the West and Protoplasa fUchii, in the East. The life-history of no member of this family is known. Alexander ('20) described what is probably the larva of Protoplasa fitchii. It was found in a much decayed maple log in Fairfax County, Virginia. Fig. 1005. — Wing of Protoplasa fitchii. The venation of a wing of Protoplasa fitchii is represented by figure 1005. The generalized condition of this wing is shown by the following features ; both branches of vein vSc are preserved ; the forking of the other branched veins is nearer the base of the wing than in the typical crane-flies; and all of the branches of vein R are distinct. Family PTYCHOPTERID^ The Phantom Crane-fly Family This is a small family of which only six or seven species have been found in our fauna; and of these only three are found in the East. These flies differ from the typical crane-flies in having only one anal vein preserved, and the transverse suture of the mesonotum is rather poorly defined. The larvae are found in decaying vegetable matter rich in organic mud, usually in swamps, swales, or wet meadows, but sometimes in shaded woods. They feed on decaying vegetable matter, diatoms, and the organic mud in which they live. DIPTERA 797 The phantom crane-fly, Bittacomorpha davipes. — This remarkable insect is the member of this family that is most likely to attract atten- tion. Its long legs are banded with black and white and the metatarsi are conspicuously enlarged and swollen. In its progress through the air the legs are held outspread like the spokes of a wheel with the metatarsi hanging vertically. It uses its wings but little in flight but is borne along by currents in the air. The black and white banding of its legs makes it a very conspicuous object as it drifts phantom- like through the air. Family ANISOPID^* The So-called False Crane-Flies The family Anisopidse has not been classed with the crane-flies till recently ; the presence of ocilli and the lack of a V-shaped trans- verse mesonotal suture in this family having been regarded as charac- ters excluding it from the Tipuloidea. On the other hand the members of this family resemble crane-flies in certain features of the venation of the wings; for this reason they have been known as false crane-flies. But a study of the larvffi and pupae of members of this family has shown that it should be regarded as one of the families of the Tipu- loidea. This family is represented in our fauna by three genera, Anisopus Trichocera, and Mycetohia; of these the last two have been commonly classed in other families ; but the immature stages of the three genera are very similar. Anisopus. — The adults are mosquito-like insects with spotted wings, which often enter houses, where they are found on windows. I R,., Fig. 1006. — Wing of Anisopus. have also observed them in considerable numbers just at nightfall, feeding on sugar which had been placed on trees to attract moths. *This family has been known as the Rhyphidae. 798 AN INTRODUCTION TO ENTOMOLOGY Fig. 1007. They feed on over-ripe fruit, the exuding sap of trees, and upon the nectar of flowers. Figure 1006 represents the venation of the wings and Figure 1007 the form of the antennae. Only four species of this genus are recorded from the United States. The larvae are found in decaying vegetable matter, in manure, in sewage, and in similar material. Trichocera. — The members of this genus often at- tract attention by appearing in swarms in the autumn and early spring, and sometimes on warm, sunny days in winter. The swarms vary greatly in size, sometimes one includes thousands of individuals. They are usually from five to twenty-five feet above ground; and all members of a swarm face the wind. These flies are often found during the winter months in cellars, resting on the windows. , Nine species have been described from our fauna. In this genus the radial sector is three-branched and there are two distinct anal veins. The larvse are found in decaying vegetable matter, beneath dead or decaying leaves, and in fungi. They have also been found in stored roots and tubers, especially potatoes. Mycetobia.- — A single species of these genus, M. divergens is found in North America. This is a small fly measuring from three to four millimeters in length and resembling superficially a fungus-gnat more than a crane-fly. For this reason it has been commonly classed in the Mycetophilidae. In this genus cell ist M2 is lacking, the radial sector and media are each two-branched, and there is only one distinct anal vein. The larvce are common in wounds on trees from which sap is exuding, and in decaying wood. Family TIPULID^ The Typical Crane-Flies To this family belong the far greater number of the crane-flies, the other three families of the Tipuloidea including but few species. The typical crane-flies difter from the Anisopidse in having a V-shaped transverse mesonotal suture (Fig. 1008), from the Tanyderidge in that the radial sector has less than four branches, and from the Ptychopteridas in having two distinct anal veins. Figure 1009 represents the venation of a wing of a member of this family. The most striking feature of this venation is the fact that the forking of the branched veins is near the distal end of the wing. This gives the wing a very distinctive appearance. Crane-flies are seen most often in damp localities, especially where there is a rank growth of vegetation; but sometimes they occur in DIPTERA 799 great numbers flying over meadows and pastures. In most cases their power of flight does not seem to be well developed for they fly slowly, and only a short distance at a time. Some species, however, sustain themselves in the air for long periods. This is especially true of some of the smaller species; which often collect in swarms at twi- 1009. — Wing of Tipula abdominalus. light, forming a small cloud, and dancing up and down like some of the midges. Their ability to walk is also poor, for they use their long legs awkwardly, as if they were in the way. Little is known regarding the feeding habits of the adult crane-flies; but some species have been observed to feed on the nectar of flowers. Many species are attracted to lights. The larvae of crane-flies vary greatly in habits both as to the situations in which they live and as to the nature of their food. Some are aquatic; Antocha lives in silken cases on rocks in swiftly flowing streams; and members of several other genera live on svibmerged plants. Some live in or beneath damp cushions of moss. Many live in mud or sand along the margins of streams, in swamps, or in shaded woods, while others are strictly terrestrial, burrowing in the soil of meadows and pastures. The larvffi of most species are scavengers feeding on decaying vegetable matter, but some feed on living vegetable tissue, and still others are carnivorous. For a detailed account of the life-histories and the structural characteristics of the early stages of the different groups of crane-flies see Alexander ('20). The Tipulidas is a large family; nearly 3000 species are known and about 500 species have been described from North Ameiica alone. Among those that are of especial interest are the following : The snow-flies, Chionea. — To the genus Chionea belong several species of crane-flies in which the wings are vestigial, being reduced to mere knobs, much smaller than the halteres. These flies are most often seen in winter crawling about on the snow; but they are occa- sionally found in the spring and fall in leaf -mold. The meadow-maggots or leather-jackets. — The larvee of some species of crane-flies, most of which belong to the genus Tipula, often do considerable damage in meadows, pastures, and grain fields by devouring the roots of the plants. The full-grown larvas are about 25 mm. long and of a dirty-grayish color. As the body-wall is of a tough leatherv^ texture these larvas are commonly known as leather- 800 AN INTRODUCTION TO ENTOMOLOGY jackets. Serious outbreaks of these pests have occurred at various times in Ohio, Indiana, Ilhnois, and Cahfornia. In the case of the species infesting ranges, pastures, and grain and alfalfa fields in California it was found that the larvse usually come out upon the surface of the ground during the night and could be destroyed by the use of poisoned-bran bait, made by mixing one pound of Paris green, twenty-five pounds of bran, and sufficient water to make a flaky mash. The bait is applied with a broadcast grain seeder. Family DIXID^ The Dixa-Midges These midges closely resemble mosquitoes in size and lorm; but they are easily distinguished by the venation of their wings, loio). (Fig. Fig. loio. — Wing of Dixa. The wing-veins are not furnished with scales, and are distinct over the entire surface of the wing; the costa is prolonged into an ambient vein, the subcosta is well de- veloped, but is short, ending in the margin of the wingnearitsmiddle,and before the first fork of the radius; the radius is four-branched, the vein Ri extends par- allel to the margin of the wing to a point on the outer end of the wing; the media is two-branch- ed; and themedial cross- vein is wanting. The an- tennas (Fig. I on) are sixteen-jointed, and dif- fer but slightly in the two sexes; the legs are long and slender; and the cau- dal end of the abdomen Fig. ioi2.-Larva of Dixa, ot the male is enlarged. (After Needham and Lloyd.) Fig. loii. DIPTERA 801 The family includes only a single genus, Dixa, of which eight species have been found in North America. The adult midges occur in the vicinity of streams and in swam- py places. The larvEe are aquatic, living in ponds or slowly running water; they resemble somewhat those of Anopheles but the body is almost always bent so that the head and tail come close together. They progress by alternate thrusts of the two ends of the body the bent portion traveling foremost (Fig. 1012). The first and second ab- donimal segments each bear a pair of pseudopods on the ventral surface. These larvas feed on algae. Family PSYCHODIDyg? The Moth-like FUes There may be found frequently upon windows and on the lower surface of the foliage of trees small flies which have the body and wings densely clothed with hair and which resemble tiny moths in appearance. The wings are broad, and when at rest slope at the sides in a roof -like manner or are held horizontally in such a way as to give the insect a triangular outline (Fig. 10 13). The moth-like appearance of these insects is siiffi- cient to distinguish them from allotherflies. The ven- ation of the wings, (Fig. 10 14) is also very peculiar. All of the longitudinal veins separate near the base of the wing except veins R2 and R3 and veins Mi and M2. In some forms veins R4 and R5 are distinct, as shown in the figure, in others they coalesce complete- ly, so that radius is only four-branched. Cross-veins are wanting in most cases. The antenna? are long and slender, and are clothed with whorls of Fig. 1013.— A m o t h -1 i k e fly. C.V., Fig. 1014. — ^Wing of a moth-like fly, hairs (Fig. 1015). Those of the male are longer; and in the species figured the two basal segments are clothed with scales like those of theLepidoptera. Scales of this form occur also on the wings, palpi, and legs of certain species. 802 AN INTRODUCTION TO ENTOMOLOGY The moth-like flies are often very minute and rarely exceed 4 mm. in length. Most of the species, so far as is known, feed on nectar or other fluid matter other than blood ; but the species of the genus Phlebotomus are blood-suckers, feeding upon the blood of various rep- tiles, amphibians and mammals, including man ;and it has been found that some exotic species transmit certain diseases of man, as the Euro- pean pappatici fever, or three day fever, and the Peruvian veruga (Riley and Johannsen '15). A single species of this genus, Phlebotomus vexdtor, has been found in the United States; this is a minute species, measuring 1.5 mm. in length. It was taken on Plummer's Island, Maryland. The larvas of members of this family are found in various situ- ations; in decaying vegetable matter, in sewage, in cow dung, in exuding sap on tree- trunks, and in streams. About thirty species have been de- scribed from the United States. Family CHIRONOMID^ The Midges Fig. 1015. — Antennae of Psychoda: m, antenna of male and the second seg- ment of the same more enlarged; /, antenna of female and the tip en- larged. The members of this family are more or less mosquito-like in foi-m, but are usually more delicate than mosquitoes. The ab- domen is usually long and slender; the wings narrow; the legs long and delicate; and the antennas, especially in the males, strongly plumose (Fig. 1016). In fact many of these insects are commonly mistaken for mosquitoes; but only a few of them can bite, the greater number being harmless. The midges are most easily distinguished from mosquitoes by the structure of the wings (Fig. 1017). These are furnished with fewer and usually less distinct veins; and the veins, although some- times hairy, are not fringed with scale-like hairs. There is a marked contrast between the stouter and darker colored veins near th'^ costal border of the v/ing and those on the other parts of the wing, which seem to be fading out. The costal vein is not prolonged into an ambient vein, beyond the apex of the wing. In several genera of this family the wings are either absent or vestigial; of these a single species has been found in our fauna. This is Eretmoptera browni, a species described by Pro- fessor Kellogg from tide-pools on the Pacific Coast. In this species the wings are short, strap-like, thickened, and without distinct ve- nation. The name midge has been used in an indefinite way, some writers applying it to any minute fly. It is much better, however, to restrict Fig. 1016. — Antennfe of Chironomus. f, fe- male; m, male. DIPTERA s:-3 3t to members of this family except where it has become firmly estab- lished as a part of a specific name. The wheat-midge and the clover- seed midge are examples of names of this kind; it would not be wise to attempt to change these names, although the insects they represent belong to the gall-gnat family, and hence are not true midges. /?, /?.+- Fig. 1017. — Wing of Chironomtis. Midges often appear in large swarms, dancing in the air, especially towards the close of day. Professor Williston states that, over mead- ows in the Rocky Mountains, he has seen them rise at nightfall in most incredible numbers, producing a buzzing or humming noise like that of a distant waterfall, and audible for a considerable distance. Most larvae of midges are aquatic; but some live either in manure, in decaying vegetable matter, under bark, or in the ground. Some of the pupas are free and active, others are quiescent; some of the latter remain partly enclosed in the split larval skin. The larvae and pupae of the aquatic species are of much importance as fish-food. Many of the aquatic larvae live in tubes which they build of bits of dead leaves and particles of sand fastened together with viscid threads. These tubes are frequently seen upon the surface of dead leaves, stones, and sticks; and they are often made in the mud of the bottom of a pool, in which case they open at the surface of the mud. Many of the species are blood-red in color, and hence are frequently known as blood-ivornis. The aquatic larvae feed on algae, decaying vegetable matter, di- atoms, and small Crustacea; the terrestrial species, on manure or de- caying vegetable matter. There are a few cases reported of the larv« of midges infesting living plants . To the genus Culicoides belong the small midges commonly known as sandflies or punkies. Certain minute species are sometimes ver>^ abundant, and extremely annoying on account of their bites. They are exceedingly troublesome in the Adirondack Mountains, in the White Mountains, and along mountain streams generally; they are also abundant in some places at the seashore. More than 200 species of the Chironomidae have been described from our fauna. The family was monographed by Professor Johannsen ('05 and '08). 804 AN INTRODUCTION TO ENTOMOLOGY Family CULICID^ The Mosquitoes The form of mosquitoes is so well known that it would be un- necessary to characterize the Culicidce were it not that there are certain mosquito-like insects that are liable to be mistaken for mem- bers of this family. The mosquitoes are small flies, with the ab- domen long and slender, the wings narrow, the antennae plimiose in the males, (Fig. 1018), and usually with a long, slender, but firm proboscis. The thorax lacks the transverse V-shaped suture characteristic of the crane-flies ; and vein M of the wings is only two-branched. But the most dis- tinctive feature of mosquitoes is the fringe of scale-like setae on the margin of the wings and also „. Z k / . ■, r u.\ • • /T7- \ Fig. 1018. — Antennee mmost casesoneachof thewmg-vems (Fig.1019). %^ mosquitoes, m, The eyes are large, occupying a large part of male; /, female! the surface of the head. The ocelli are wanting. The antenna? are composed of fifteen segments, of which the first segment, the scape, is concealed by the large globular pedicel (Fig. 173. p. 153) and has been over-looked by many describ- ers of mosquitoes. The pedicel contains the Johnston's organ de- scribed on pages 152 to 154. The form of the mouth-parts differs in the two subfamilies; those of Anopheles are represented by Figure Fig. 1019. — Wing of a mosquito. 990 on page 775 ; in the Corethrin£e they are short and not adapted for piercing. The larvce of mosquitoes are all aquatic. They are well known and are commonly called "wigglers," a name suggested by their wriggling motion as they swim through the water. They vary in details of structure but the larva of Culex will serve to illustrate the general form of the body (Fig. 1020). The head and thorax are large and the abdomen is slender. The next to the last abdominal segment, the eighth, bears a breathing-tube; and when the larva is at rest it hangs head downward in the water, with the opening of this DIPTERA 805 tube at the surface. (Fig. 102 1). At the end of this tube there is a rosette of plate-like lobes (Fig. 1022, a) which resting on the surface WuFfFi/jnTJI^ ■ Luteral ccmi '^ Qirtu2>e Fig. 1020. — Larva of Culex showing details of external structure. (From Riley and Johannsen.) Fig. 1 02 1. — A glass of water containing eggs, larvae, and pupas of mosquitoes. film, keeps the larva in position. At the end of the last abdominal segment there are one or two pairs of tracheal gills. About the mouth, on the antenna, and on the caudal segments of the abdomen are tufts of setae that afford characters much used in the classification of mosquito larvae. These various tufts have received special names as indicated in Figure 1020. The food of mosquito larvae varies with the different species, with most of them it consists of organic matter in suspension in the water, or floating upon the surface, or settled or growing upon the bottom. Some mosquito larv£E are can- nibalistic; those of the Corethinse are all preda- cious and seize their prey with the antennas. So far as is known, there are four larval instars in all species of mosquitoes, with the fourth molt the larva becomes a pupa. The pupje of mosquitoes like the larv« are aquatic, but they differ greatly in form from the larvae. (Fig. 1023). The head and thorax Fig. 1022. — a, end of breathing tube of larva; 6, breathing tube of pupa. 806 AN INTRODUCTION TO ENTOMOLOGY are greatly enlarged and are not distinctly separated, while the abdomen is slender and flexible. With the change to the pupa state a remarkable change takes place in the re- spirator}^ system. There are now two breath- ing tubes, and these are borne on the thorax. One of these is represented greatly enlarged by Figure 1022, 6. At the tail-end of the body there is a pair of leaf-like appendages, with which the insect swims, for the pupae of mosquitoes, and also of certain midges, differ from the pupae of most other insects in being active; but the pupse take no food. The duration of the pupal stage is brief, usually larva~f°^'^nT^' ^°^ ^°^^ ^^^" ^^^'° ^^ ^^^^® ^^^'^' ^^^f^ *^® "' • > P pa. gj^i^ splits down the back, and the winged mosquito carefully works itself out and cautiously balances itself on the cast skin, using it as a raft, until its wings are hardened so that it can fly away. All adult mosquitoes are commonly regarded as blood-sucking insects and are feared on that account; but there are many species that never suck blood at all, and of the blood-sucking species many attack by choice birds and mammals other than man. It is only the females that suck blood ; the mouth-parts of males are not fitted for piercing the skin of animals. The males feed on nectar, the juices of ripe fruits, and other sweet substances; this is also true to a certain extent of females. The different species of mosquitoes differ greatly in their manner of oviposition. Those most often observed about water-barrels, Culex, lay their long, slender eggs side by side in a boat-shaped mass, on the surface of the water (Fig. 102 1) ; species of Anopheles deposit their eggs separately upon the surface of the water; and many Aedes lay their eggs on the ground after the pools in which they were de- veloped have dried out. In this case the eggs remain unhatched until later rains or melting snow refill the pools. The eggs of some mosqui- toes hatch very soon after they are laid; but with the majority of species the winter is passed in the egg state ; and in the case of certain species it is believed that the eggs may remain on dry ground several years awaiting rain and then hatch. The famih^ CulicidcB is divided into two subfamilies, the Coreth- TvcicC and the Cuhcince. Subfamily CORETHRIN^E This is a small group of mosquitoes including but few species. It is distinguished from the Culicina) by the comparative shortness of the proboscis, which is not much longer than the head and is not fitted for sucking blood. The larvag of members of this subfamily are transparent; they are predacious and capture their prey with their antennas; they feed on infusoria, small Crustacea, and small larvae, including those DIPTERA 807 of mosquitoes; they are free-swimming and are foimd most abun- dantly beyond the line of shore vegetation. The pupai are also trans- parent at first but become darker colored just before transforming. The females of Corethra phmiicdrnis . as observed by Professor Need- ham, deposit their eggs on the surface of the water, laying them down flatwise, in a spiral held together by scanty gelatine. A monograph of this subfamily was published by Johannsen ('03). Subfamily CULICIN.^ To this subfamily belong by far the greater number of mosquitoes. With these the proboscis is longer than the head and thorax taken together; this character is sufficient to distinguish them from the Corethrinae. The Culicina^ have received much attention in recent }'ears. Since the discovery that certain species are carriers of diseases of man many investigators have studied mosquitoes, and thousands of papers have been published regarding them. Fortunately the more important results of these investigations have been summarized by several writers and published in easily available books. The most important contribution to this subject is the monograph by Howard, Dyar, and Knab (' 1 2-' 1 7) . This is a large work in four volumes. A more avail- able and more recent monograph is that of Dyar published in 1922. It has been demonstrated that malaria, yellow fever, filariasis, and dengue are each caused by a parasitic organism, which has a complex life-cycle, part of which is passed in man and part in certain mosquitoes; and that it is only by being bitten by an infected mosquito that one contracts any of these diseases. There are also diseases of other mammals and of birds that are transmitted in a similar way. In each case the parasitic organism is restricted in host relations, infecting in turn only certain species of Vertebrates and certain species of mosqui- toes. Representatives of eleven genera of the Culicinae have been found in the United States. Some of these occur only in the extreme South and others are either rare or rarely attack man. The species that are our most serious pests are included in the genera Culex, Anopheles, and Aedes. Culex. — To this genus belong our common house mosquitoes that have unspotted wings and short palpi in the females and which when at rest on a vertical wall hold the body parallel with the wall or with the tip of the abdomen inclined toward it (Fig. 1024) . These are very annoying pests ; but although many of the species of this genus transmit blood diseases of birds and animals they do not play an important role in human diseases. Fig. 1024. — Nor- mal position of Cnlex and Anopheles on a wall; Culex above, Ano- pheles below, (From Ri]ey and Johann- sen.) 808 AN INTRODUCTION TO ENTOMOLOGY The eggs are laid in boat-shaped masses or "rafts" on the surface of the water of ponds of a permanent nature and on water of artificial containers, as water-barrels. A larva of Culex is described and figured above (Fig. 1020). AnopJieles: — To this genus belong those mosquitoes that have been found to be the carriers of malaria. Nine species oi Anopheles have been found in the United States, of which four are known to be carriers of this disease. In this genus the palpi of both sexes are nearly or quite as long as the proboscis and the wings are frequently spotted. When at rest on a vertical wall the body is usually held at an angle with the vertical (Fig. 1024). Some species often enter houses. They hibernate in the adult state and can be found during the winter in cellars. The eggs are laid singly in small numbers upon the sur- face of water. The larva when at rest floats in a hori- zontal position beneath the surface film (Fig. 1025). There is no respiratory tube but in- stead a flattened area on the Fig- 1025.— Normal position of the larvas eighth abdominal segment into of Culex and Anopheles when at rest. ^Viirh thp two c^niraHpc; onpn Culex, left, Anopheles, middle; Culex ^^^^^ ^^^ ^^^? Spirac es open, pupa, right hand figure. Malaria IS a well-known and widely distributed disease. It is most common in the vicinity of swamps, and is more virulent in the South than in the cooler parts of the country. It is caused by unicellular parasites in the blood which feed upon the red blood corpuscles. These parasites belong to the genus Plasmodium of the Protozoa. Three species of these malarial parasites are now recognized, each of which causes a distinct type of malaria. The life-cycle of the malarial parasites is an exceedingly com- plicated one. Our knowledge of it is the result of extended investi- gations by several workers. The history of these investigations is a most interesting one; butlspace can not be taken to narrate it here. Accounts of these investigations, with details of the results obtained are given by Howard, Dyar, and Knab ('12) and Riley and Johannsen ('15). The following summary of the life-cycle is condensed from the accounts by these writers. The malarial infection is introduced into the blood circulation of man by the bite of a mosquito that has previously bitten a person having this disease. It is only certain species of mosquitoes of the genus Anopheles that transmit this disease to man. The infecting organism, which in that stage of its development is known as a sporozoi'.e, penetrates a red blood corpuscle and becomes an amoeboid schizont. This lives at the expense of the blood corpuscle and as it develops there are deposited in its body scattered black or reddish black particles. These are generally called melanin granules, but are much better referred to as hcemozoin, as they are not related to melanin. The haemozoin is the most conspicuous part of the parasite, a feature of advantage in diagnosing from unstained preprations. As the schizont matures, its nucleus breaks up into a number of daughter nuclei, DIPTERA 809 each with a rounded mass of protoplasm about it, and finally the corpuscles are broken down and these rounded bodies are liberated in the plasma as spores which are known as merozoits. These spores infect new corpuscles, where they again go through the stages of schizonts and merozoits, and thus the asexual cycle is continued. The malarial paroxysm is coincident with sporulation. Parallel with the asexual cycle sexual elements or gametes are produced by schizonts. These sexual elements, however, can not copulate within the human organism on account of the unfavorable temperature. To enable them to carry out this function, and to develop further they must be transferred to the aliment- ary canal of an Anopheles, which is done when one of these mosquitoes sucks the blood in which they are. Here the union of the male and female gametes takes place and there results a stage known as the migratory ookinete. The ookinete penetrates the wall of the midintestine of the mosquito and there transforms to the oocyst. In the process of growth of the oocyst further stages occur, first by its division the sporoblasts, and from these, by further division, the sporozoits, when the oocyst is mature it bursts, liberating the sporozoits which thus pass into the general body cavity of the host. The sporozoits now find their way into the sali- vary glands of the host and there remain until the mosquito, in biting, forces them along with the saliva, through its proboscis into a human being. Then the asexual cycle begins in the blood of a new host. Aedes. — This is a very large genus of world-wide distribution Dyar ('22) describes 73 species that have been found in the United States. The species vary greatly in habits; but with most of them the larvag develop from over-wintering eggs in early spring pools. Some species, however, breed in water-barrels, and other artificial containers ; one of these is the carrier of yellow fever. The yellow-fever mosquito, Aedes csgypti, is distributed through- out all tropical regions of the world and is often carried by commerce into temperate regions. But as it is destroyed by frost it can not become established where frosts occur. Hence outbreaks of yellow fever in the North are checked naturally as winter approaches, and with our present knowledge of the methods of control of this disease it is not probable that it will be permitted to become epidemic again in the United States. When yellow fever appears the patients should be kept in mosqui- to-proof rooms, so that they may not serve as centers of distribution of the disease ; and the breeding places of mosquitoes should be drained or screened, or oiled. The yellow fever mosquito breeds in cisterns, water-barrels, flower-vases, and in the various water receptacles about houses. The life-cycle under favorable conditions is completed in from twelve to fifteen days. This is essentially a domesticated species. It is rarely found far from the habitations of man. The fact that yellow fever is transmitted by this mosquito has been definitely established; but it is not certain that the causative organism is known, although some investigators claim to have found it. The yellow fever mosquito was first described by Linnaeus in 1762 under the name Culex cegypti. But the Linnasan genus Culex has been divided and this species pertains to the genus Aedes established by Meigen in 1818; hence its correct name is Aedes cegypti. Unfortunately a score of other names have been applied to it; those most commonly found are Aedes calopiis, Stegomyia fascidta, and Stegomyia calopus. 810 AN INTRODUCTION TO ENTOMOLOGY Other mosqviito-borne diseases of man. — In tropical :ountries there are, in addition to malaria and yellow fever, two other diseases of man that have been found to be transmitted by mosquitoes ; these are dengue and filariasis. The causative organism of dengue has not been discovered ; but it is believed to be a protozoan of ultra -microscopic size. Filariasis is due to the presence in the blood, the hnnphatics, the mesentery, and subcutaneous connective tissue of nemotode worms belonging to the family Filariidas, and which pass part of their life-cycle in the bodies of mosquitoes. One of these parasites, Filaria bancrofti, is the cause of the extraordinary deformities of different parts of the human body known as elephantiasis. Mansdnia.—ln this genus "the larvse are peculiar in having the air tube adapted for piercing the vascular roots of certain aquatic plants, from which they get their supply of air. The eggs are de- posited in rafts in swamps where suitable plants grow, and the young larvae descend to the roots, never coming to the surface again." (Dyar, '22). Mansonia pertHrhans is widely distributed in the United States and Canada. Its larva lives attached to the roots of a species of Carex growing in marshes or the edges of ponds. The winter is passed as half-grown larva. Wyeomyia smlthii: — This species is remarkable on account of its habits. "The larA'se live in the water in the leaves of pitcher plants (Sarracenia piirptirea), passing the winter frozen up in the ice cores. The eggs are laid on the still, dry, newly opened leaves and hatch when water collects in them" (Dyar Fig. 1026. — Mycelophila punctata. (Aftt Johannsen.) '22). The adult can be distin- guished from all other Culi- cinse found north of Southern Florida by the presence of a tuft of sets on the metonotum. Family MYCETOPHILID^ The Fungus-Gnats These flies are of medium or sma 11 size and more or less mos- quito-like in form. They are most easily recog- nized by the length of the cox£e (Fig. 1026). The ncelli are DIPTERA 811 present; the antennas, as a rule, lack whorls of hairs (Fig. 1027) and all the tibiae are furnished with spurs. At first sight considerable variation seems to exist in the venation of the wings as shown in the three wnngs represented in Figure 1028; but in realit}^ the variations are comparatively slight. The costa extends along the margin of the wing to the end of the radial sector. Radius preserves three branches in the more generalized forms (Fig. 1028, a); in some genera veins Ri and R2+3 coalesce from the apex of the wing backward for a greater or less distance so that the basal part of vein R2+3 appears like a cross-vein (Fig. 1028, b); in some genera _^ r Sc. b 3 Cu, _ ^ ~ r^ ^^^ c«. C«. ^...^, /?.+= /M+, Fig. 1028. — Wings of fungus-gnats. (The drawings are after Winnertz; the lettering is original.) radius is only two-branched, this condition may have been brought about by the complete coalescence of veins Ri and R2-f3 or by the coalescence of veins R2-1-3 and R4+5, whichever may be the case the two branches are cornmonlv designated as Ri and Rg respectivelv (Fig. 1028, c). ' . The fungus gnats are exceedingly numerous both in nimiber of individuals and in number of species. They are often found in great numbers on fungi and in damp places where there is decaying vege- table matter. They are active and leap as well as fly. A monograph of the known species of the world, not including the Sciarinse, was published by Professor Johannsen ('09a) ; and in a later 812 AN INTRODUCTION TO ENTOMOLOGY series of papers he published a synopsis of the species of North Amer- ica, including the Sciarince (Johannsen '09-' 12). The larvffi of most species hve upon and destroy mushrooms, usually the wild plants, but sometimes they are pests in mushroom cellars; other species are found in decaying wood; and certain species of the subfamily Sciarinag are sometimes pests of cultivated plants, destroying seed corn, seed potatoes, and the roots of other plants. In this family the larva is more or less cylindrical, smooth, soft, whitish in color, and with a small strongly chiti- nized head, which is usually brown or black, and is provided with mandibles and maxillae. There are usually eight pairs of spiracles. The pupa is not enclosed in the skin of the larva; but in some genera the transformations are undergone in a delicate cocoon. The subfamily Sciarince. — The family Mycetophilidas is divided into nine subfamilies, eight of which are represented in our fauna. One of these subfamilies, the Sciarinae, rnerits special mention in this place. The members of this subfamily differ from the more typical fungus-gnats as follows; the coxae are not so greatly elongated; the eyes differ in shape, there being a narrow ex- Fig. I029.--Eyes of Sciara. Fig. 1030.— Wing of Sciara. (After Enderlein.) pansion of each eye extending above the base of the antennee and meeting or nearly meeting the expansion of the other eye, (Fig. 1029), while in other fungus-gnats the eyes are either round, oval, or kidney- shaped, but not markedly narrowed above; and the cross-vein r-m is in the same right line with the second section of the radial sector (Fig. 1030). DIPTERA 813 The larvas of some species of the genus Sclara often attract atten- tion on account of a strange habit they have of sticking together in dense patches. Such assemblages of larvce are frequently found under the bark of trees. But what is more remarkable is the fact that when the larvse are about to change to pupse an assemblage of this kind will march over the surface of the ground, presenting the appearance of a serpent-like animal. Such a congregation is commonly spoken of as a Sciara-army-worm. Examples have been described that were four or five inches wide and ten or twelve feet long, and in which the larvas were piled up from four to six deep. The larvae crawl over each other so that the column advances about an inch a minute. THE FAMILY SCIARID^ OF ENDERLEIN The establishment of a family to be known as the Sciaridae was proposed by Enderlein ('ii & '12 a). The proposed family includes the subfamily Sciarinee of the MycetophilidcB and the subfamily Lestremiinae of the Cecidomyiidee and is characterized by the form of the eyes; the two subfamilies agreeing in having the type of eyes described above (Fig. 1029) and differing in this respect from other fungus-gnats and gall-gnats. This proposed, grouping of these two subfamilies has not been generally ac- cepted. While they agree in the shape of their eyes, they differ in the presence of tibial spurs in the Sciarinae and the absence of these spurs in the Lestreniiinae; and they differ markedly in the form of their larvae. The larvce of the Lestremiinae have, like those of other Cecidomyiidas, an undeveloped head, indistinct mouth- parts, and a well-developed sternal spatula; the larvae of the Scarinae have, on the contrary like other Mycetophilidae, a well-developed head which is strongly chitinized, and strong, toothed mandibles, and do not have a sternal spatula. Family CECIDOMYIID^* The Gall-Gnats The gall-gnats are minute flies which are ex- tremely delicate in structure. The body and wings are clothed with long hairs, which are easily rubbed off. The antennae are usually long and clothed with whorls of hairs (Fig. 103 1) ; but they vary greatly in length, in the number of their segments, in the form of the segments of the flagellum, and in the nature of their clothing. Except in the first subfamily, the ocelli are wanting. The legs are slender and quite long, but the coxae are not greatly elongated and the tibiee are without spurs. Except in the first sub- family, the wing-veins are greatly reduced in nimi- ber (Fig. 1032), the anal veins being entirely want- Fig. 1031. — An- ing, and the media wanting or merelv represented bv tennas of gall- a slight, unbranched fold ; in the first subfamily, the f, female, en- Lestremiin^e, vein M is well preserved. Varged more A striking feature of this family is the presence than that of in most species (z. e. in all except the first two small the male, subfamilies) of what have been generally known as arched filaments *This family is named the Itonididag by some writers, those who recognize the names published by Meigen in 1800; seepage 794 for a discussion of these names. 814 AN INTRODUCTION TO ENTOMOLOGY on the antenna (Fig. 1033). These filaments occur in series, and there may be one, two or three of these series on each segment of the flagellum. As each of these series has the appearance of a looped Fie. 1032. — Wing of a eall-enat. thread extending around the segment of the antenna they are termed circumfili by Dr. Felt, who has described and figured many forms of them in his series of papers on this family. fifth segment of antenna of Fig. 1033. — Antennal segments with circumfiH: a, nttn segment ot antenna ot Karschomyia viburni, male; b, fifth antennal segment of a Rhopalomyia, female; c, sixth antennal segment of Winnertzia calciequina, female. (From Felt.) To this family belong the smallest of the midge-like flies. On account of their minute size the adult flies are not apt to attract the DIPTERA 815 attention cf cbe young student. But the larvae of many species cause the growth of galls on plants, some of which are sure to be found by any close observer. Other species arrest the growth of the plants they infest, and cause very serious injury. The larvse are small maggots, with nine pairs #'"'^^ "^'"^ of spiracles. The head is small, poorly developed, %^ . 3, and without mandibles ; between the head and the first thoracic segment there is a large neck-seg- Fig- i •^34- Head ment, which gives these larvae the appearance of fJJ^ the^Sla°T- having an extra segment. Many species are bone. brightly colored, being red, pink, yellow, or orange, and many species possess in the last larval instar a peculiar chitinous organ on the ventral aspect of the prothorax; this organ is known as the breast-hone or sternal spatula, or anchor process (Fig. 1034). It varies in form in different species; different views are held regarding its function, none of which seems well established. The larv^al mouth-parts are fitted only for taking liquid food ; but the nature of this food differs greatly in different members of the family. Some species are parasitic in the bodies of aphids and other Homoptera; some are predacious feeding on either aphids, coccids, mites, or larvae and pupae of other Diptera, especially those of other species of gall-gnats; some feed on the excrement of other larvae or that of cattle and of birds; but most species are vegetable feeders. Among those that feed on plants many species produce galls. The larvffi of several genera of the second subfamily, the Heteropezinse give birth to living young, as described later. Different modes of pupation have been observed among the gall- gnats; in some the pupa is naked; in others the change to the pupa state takes place within a puparium, but this puparium differs from that of most Diptera in being formed by the next to the last larval skin, the last larval molt taking place within it ; in some species as the wheat-midge, the puparitrm consists only of the peunltimate larval skin, in others as the Hessian fly, it is lined with a delicate silken layer (Marchal '97); and in still others the pupa is enclosed in a delicate cocoon instead of in a puparium. The literature regarding this family is very extensive; hundreds of articles have been written about those species that are of economic importance, and very many papers have been published on the classi- fication of these insects ; A monograph of the species of the world was published by Kieffer in 18 13 and a review of the American species is being published by Dr. Felt in his annual reports as State Ento- mologist of N e w York . See also Felt (' 1 8 ) for descriptions and figures of the galls produced by members of this family. The family Cecidomyiidce is separated into three subfamilies, which can be separated by the following table : A. Ocelli present; veinM, preserved either simple or forked, p. 816. LESXREMnN^E AA. Ocelli wanting; vein M wanting or represented merely by a fold. B. Antennae without either circumfili or horseshoelike appendages; the first segment of the tarsi usually longer than the second p. 8i6.Heteropezin^ 816 AN INTRODUCTION TO ENTOMOLOGY BB. AntenriEe with circumfili or {Winnertzia) with horseshoelike appendages; the first segment of the tarsi shorter than the second p. Si/.Cecidomyiin^ Subfamily LESTREMIIN^ The members of this subfamily differ from other gall-gnats in having ocelli, in the shape of their eyes, these resembling those of Sciara (Fig. 1029), and in the less reduced venation of their wings, vein M being preserved ; in some genera this vein is forked (Fig. 1035) in others it is unbranched. yl/i+2 Fig. 1035. — Wing of Lestremia. (After Kiefifer.) Most of the known larvae of this subfamily live in decaying vege- table matter, especially in rotten wood under bark. Subfamily HETEROPEZIN^ This subfamily includes comparatively few species, none of which is known to be of economic importance. The known larva live in the decaying bark of trees. Some of them are remarkable for the fact that they give birth to living young. This type o^ reproduction is termed paedogenesis (See page 192). It was first discovered by Nicholas Wagner in 1862 and has been in- vestigated by several other Europeans. It has also been studied in this country by Dr. Felt ('11) who gives an extended account of it as observed by him. in Midstor americdna, and by Professor Hegner ('12 and '14) who gives the history of the germ cells in the psedogenetic larva of this species. The larva of Miastor americdna possesses two ovaries, one on either side of the body in the tenth or eleventh segments. Each ovary consists of typically thirty-two oocytes, each of which is accompanied by a group of nurse-cells, and with them is surrounded by a folicular epithelium. The nuise-cells furnish nutrition to the growing oocytes, gradually becoming reduced as the oocytes increase in size. Finally the oocyte with accompanying nurse-cells, still surrounded by the follicular epithelium, becomes separated from the rest of the ovary and DIPTERA 817 Is forced by the movements of the larva into some other part of its body. Here it continues its growth and development at the expense of the tissues of the mother-larva. Not all of the oocytes com.plete their development, since usually only from five to seventeen young are produced by a single mother-larva (Hegner) . When the tissues of the mother-larva are consumed, the young larvae break forth from the skin of their parent and continue their growth. These larvee may in turn produce another generation of larvffi in the same manner. It is believed that this asexual, pasdo- genetic reproduction may continue through many generations cover- ing a period of two or three years. Finally a generation of larvas are produced which do not reproduce in this manner, but which when full grown transform first to pupse and then to adults, which repro- duce sexually. According to the observations of Kieffer ('13) the adult females of those species in which pjedogenesis occurs produce each only four or five eggs, while other gall-gnats produce a large number of eggs Subfamily CECIDOMYIIN^ This subfamily includes the larger number of the gall-gnats ; to it belong those _ species that have attracted attention on account of their economic importance, and others that are well known on ac- count of the conspicuous galls produced by them. Much has been published regarding some of these species; but unfortunately they are discussed under different generic names by different writers. For this reason the common names will be found more useful when one is attempting to learn what has been published regarding these species. The pine-cone willow-gall. — One of the most common and conspicuous of the galls made by gall-gnats is the pine- cone willow-gall (Fig 1036). This often occurs in great abundance on the tips of twigs of the heart-leaved willow, Salix cor data. The gnat that causes the growth of this gall is Rhabdophaga strobiloides. The larva remains in the heart of the gall throughout the summer and winter, changing to a pupa early in the spring. The adult emerges soon after- ward, and lays its eggs in the newly-started buds of the willow. The pine-cone willow-gall guest, Cecidomyia albovittdta. — This species breeds in large numbers between the leaves composing the Fig. 1036. — The pine-cone willow-gall. 818 AN INTROD UCTION TO ENTOMOLOGY pine-cone willow-gall. The larvseof this gnat do not seem to interfere in any way with the development of their host, there being abundant food in the gall both for the owner of the gall and for its numerous guests. The clover-leaf midge, Dasyneura trijolii. — The leaflets of white clover are sometimes infested by white or orange-colored maggots which fold the two halves of the leaflet together. From one to twenty of these larvse may be found in a single leaflet. When full grown the larvag make cocoons, and undergo their transforma- tions within the folded leaflet. In Figure 1037 an infested leaf containing cocoons is repre- sented natural size, also a larva and an adult gnat, greatly enlarged. The clover-flower midge, T,, 1 , f ., Dasyneura lesuminicola. — This -Ine clover-leai midge. . -^ *. . *t^i IS a very serious pest. The larvse live in the heads of clover and destroy the immature seed. Different kinds of clover are infested by this pest; but red clover is its chief food plant; and in some parts of this country it has seemed impossible to raise clover- seed on account of this insect. The larva of the clover-flower midge passes the winter on or slightly below the surface of the ground, usually but not always, in a cocoon; it changes to a pupa early in the spring, and emerges an adult in late April or early May. The eggs are laid in the small green clover heads, many eggs in a single head, as each larva infests a single floret. The larvas mature in about four weeks, and then drop to the ground to transform. Two or three weeks later a second gen- eration of midges appear and lay their eggs. The most efflcient method of combating this pest is to make the first cutting of clover early, before the first generation of midges have matured, that is, early in June; the drying of the clover heads will result in the destruction of the larvse in them ; and thus the second crop of clover will not be infested. Care should be taken to cut at the same time any clover that may be growing wild in fence-corners by roadsides, or elsewhere. The Hessian-fly, Phytophaga destructor. — ^This is the most serious pest infesting wheat in this country. The larvse live at the base of a leaf between it and the main stalk, where they draw their nourish- ment from the plant. There are two or three broods of this insect in the course of the year. The larvse of the fall brood infest the young wheat-plants near the surface of the ground. When full-grown each changes to a pupa within a brown puparium, which resembles a flax- seed. Here they remain throughout the winter. In the spring the adult gnats emerge and lay their eggs in the sheaths of leaves some distance above the ground. The irifested plants are so weakened by DIPTERA 819 the larvae that they produce but little if any seed, and often bend or even break off at the weakened spot. There is no method by which a crop of wheat can be saved from the ravages of this pest after it is infested by it ; the only means of control are those that prevent infestation. Wliere practicable all in- fested stubble should be plowed under immediately after harvest and the soil rolled or lightly harrowed , thus preventing the emergence of the fall brood of gnats; but this can not be done where clover or grasses are sown with the wheat. The most available means of con- trol is to sow wheat moderately late, that is, after the fall generation of gnats has disappeared, but early enough to secure the maximum yield of grain. This safe date varies with the latitude, longitude, and elevation above sea level. This date has been carefully determined for the different parts of the country and can be ascertained for any locality by application to a State or Federal Entomologist. Dr. A. D. Hopkins, who has made a very extended investigation of this subject states that the first general coloring of the foliage, especially on the hickories, dogwood, birch, ash, etc., is, as a rule, coincident with the safest and best time to begin sowing wheat on any farm within the range of winter wheat culture. The wheat-midge, Thecodiplosis moselldna. — This gnat is also a very serious enemy of wheat. It deposits its eggs in the opening flowers of wheat. The larv« feed on the pollen and the milky juice of the immature seeds, causing them to shrivel up and become com- paratively worthless. When full-grown the larva? drop to the ground, where the transformations are undergone near the surface. The adults appear in May or June. No effective method of control of this pest has been devised. Until recently our common wheat-midge was supposed to be the same as the European species the specific name of which is tritici, and which has been placed successively in the following genera; Tipula, Cectdomyia, Diplosis, and Contarinia. But it has been found to be another European species the Thecodiplosis moselldna. The resin-gnat, Re- tinodipldsis resimcola. — This species infests the branches of various species of pine. I have found it throughout the Atlantic region from New York to Florida. The larvcB live together in _. _ considerable numbers Fig. I038.-The resin-gnat. ^i^^i^^ ^ j^p ^f ^.^g^^^ They derive their nourishment from the abraded bark of the twig; and the resin exuding from the wound completely surrounds and 820 AN INTROD UCTION TO ENTOMOLOG Y protects them. The transformations are undergone within the Itimp of resin. After the gnats emerge the empty pupa-skins project from the lump of resin as shown at the right in Figure 1038. In this figure the gnat, a single wing, and a part of the antenna of each sex are represented, all greatly enlarged. The pear-midge, Contarlnia pynvora. — The female of this species deposits her eggs by means of her long ovipositor, in the interior of the unopened blossoms of pear. The young fruit is destroyed by the larvae. There is a single annual generation. The winter is passed in the ground, usually as pupse but sometimes as larvae. This is an intro- duced European species, which has not yet become a serious pest in this country. The chrysanthemiim gall-midge, Diarthronomyia hypogcsa. — This species causes the growth of galls on the leaf, stem, and flower-head of the chr^^santhemvmi plant, and is sometimes a serious pest in green- houses. A detailed accoimt of it is given in Bulletin No. 833 of the U. S. Department of Agriculture. SUBSERIES B. THE ANOMOLOUS NEMOCERA In this subseries the antennas are composed of many segments, but are shorter than the head and thorax, and are without whorls of long hairs. The segments of the flagellum of the antennae are short and broad and are closely pressed together. The abdomen is com- paratively stout, and the legs are shorter and stouter than in the True Nemocera. Family BIBIONIDiE The March-Flies In this family the abdomen is often comparatively robust, and the legs shorter and stouter than in most of the families with thread- like antenna (Fig. 1039). The antennas are rarely longer than the head and thorax, and composed of short, broad, and closely-pressed- together segments (Fig. 1040). These insects resemble the fungus- gnats in having ocelli ; but they differ from them in the shortness of . - ^ the antennae, in the fact that the \ ^/ % . idi^J coxas are not greatly elongate, ^^^^fe^^^ B \y^'^W ^^^ ^^^'^ tibial spurs of any f^T) M \S^^^ magnitude are confined to the /W\ W ■■-^"^ front tibiae. The venation of the -p- TOAo —A wings of the tvpical genus is Wig. ioz9-—Bihio. tlnna oi Bibio^' represented by Figure 104 1. The cross-vein m-cu is present, and vein Cu forks at a considerable distance from the base of the wing. The adult flies are generally black and red, sometimes yellow. They are most common in early spring; which has suggested the name March-flies ; but some occur later in the season, and even in the au- tumn. DIPTERA 821 The larvae vary in habits ; some species feed on decaying matter, while others attack the roots of growing plants, especially of grass. M,+, Fig. I 04 I. Wing of Bibio. Afi+1 They have ten pairs of spiracles, which is a rather large number, al- though there are other insects with as many. The pupae are usually free. For descriptions of our species of bibionid flies see McAfee ('21). Family SCATOPSID^ This family includes minute black flies ; our known species measure in length from less than one millimeter to three millimeters. Formerly these flies were included in the Bibionidae; but they differ markedly in the venation of their wings from members of that family. In the Scatopsidas vein Cu forks at or very near the base /?, of the wing (Fig. 1042) and the cross-vein m-cu is wanting. In some species there is a vestige of an anal vein but usually there is none. This is a small family, only about a score of species are known from our fauna; these are de- scribed by MelanderC 1 6) . Most of the known larvae live in excrement. One species, Cobol- diaformicdrimn, is believed to be myrmecophilous, for the adult was taken as it crawled from a populous nest of the carpenter ant. In this species the wings are vestigial. F.\MiLY SIMULIIDAE The Black-Flies The common name, black-flies given to the members of this family is not distinctive, for there are many species of other families that are of this color; but like many other names that are descriptive in form, Fig. 1042. — Winj Melander.) of Reichertella collaris. (After 822 AN INTRODUCTION TO ENTOMOLOGY it has come to have a specific meaning distinct from its original one It is like the word blackbern^; some blackberries are white, and not all berries that are black are blackberries. In this family the body is short and stout; the thorax is much arched, giving the fly a humpbacked appearance (Fig. 1043) ; and the legs are comparatively short. The antennse are scarcely longer than the head and are eleven jointed; the segments of the flagellum are short and closely pressed together (Fig. 1044), they are clothed with fine hairs, but do not bear whorls of long hairs. The ocelli are absent. In the male the eyes are very large and contiguous, and divided; the upper half of each has the facets very much larger than the Fig. 1044. lower, from which they are distinctly divided by a horizontal line. The upper half of each is doubtless a night-eye, while the lower half is a day-eye. In the female, the eye facets are of almost uniform size ; and the two eyes are widely separated. The pro- boscis is not elongated, the small labella are homy, and the palpi are 2d A Fig. 1045. — Wing of Simulium. four-jointed. The wings are broad, iridescent, and not clothed with hairs. The veins near the costal border are stout; those on the other parts of the wing are vestigial (Fig. 1045), and are usually represented merely by folds.* The females of many species suck blood and are well-known pests. Unlike mosquitoes and midges, the black-flies like heat and strong light. They are often seen in large numbers disporting them- selves in the brightest sunshine. *The forked fold that I believe to be a vestige of vein Cu is not so regarded by some writers, who refer to it as the fold between media and cubitus and label two folds of the anal area as cubitus. I can see no reason for this conclusion; in no other flies that 1 have studied is there a fold between media and cubitus. i DIPTERA 823 The lar\^£e are aquatic ; and usually live in swiftly-flowing streams, clinging to the surface of rocks in rapids or on the brinks of falls. They sometimes occur in such large numbers as to form a moss-like coating over the rocks. There is a disk-like sucker fringed with little hooks at the caudal end of the body by means of which the larva clings to the rocks ; and just back of the head there is a fleshy proleg which ends in a similar sucker fringed with hooks (Fig. 1046). By means of these two organs the larva is able to walk with a looping gait similar to that of a measuring-worm. It has also the power of spinning silk from its mouth, which it uses in locomotion. The hooks on the caudal sucker and at the end of the proleg are well adapted to clinging to a thread or to a film of silk spun upon the rock to which the larva is clinging. Respiration is accomplished by means of blood-gills, which appear on the dorsal side of the last abdominal segment, but are evaginations of the ventral wall of the rec- tum, and lie, when retracted completely within the Fig. 10 46.— rectal cavity (Headlee '06). The head bears two Head of larva large fan-shaped organs, which aid in procuring food. The food consists chiefly of algae and diatoms. When full-grown the larva spins a boot-shaped cocoon within which the pupal state is passed (Fig. 1047). This cocoon is firmly fastened to the rock upon which the larva has lived or to other co- coons, for they occur in dense masses, forming a carpet-like covering on the rocks. The pupa breathes by tracheal gills which are borne on the prothorax. The adult fly, on emerging from the pupa-skin, rises to the surface of the water and takes flight at once. Soon after this the eggs are laid, I have often watched Simillium pictipes hovering over the brink of a fall where there M was a thin sheet of swiftly-flowing water, and m^ have seen the flies dart into the water and out WL again. At such times I have always found the ^Wk surface of the rock more or less thickly coated ^^L with eggs, and have no doubt that an egg is g| fastened to the rock each time a fly darts into 9 the water. Malloch ('14) states that the eggs ^ are deposited in many cases on blades of grass, Fig. 1047.— Cocoon twigs, or leaves of trees which are dipping in and larva. running water. Until recently all members of this family were included in the genus Simulium; consequently in nearly all of the published accounts of these insects the various species are placed in this genus. But later writers have divided the old genus Simulium into several genera, Enderlein ('21) now recognizes fifteen genera of which seven are represented in North America. Monographic papers on the North American species of this family have been published by Coquillett ('98), Johannsen ('03) and Malloch ('14). 824 A N I NT ROD UCTION TO ENTOMOLOG Y This is a comparatively small family. Malloch ('14) in his "Catalogue of North American and Central American Simuliidce" lists 3 8 species. The species that have attracted most attention in the United States are the following. The Adirondack black-fly Prosimulium hlrtipes. — This is a widely distributed species but it has attracted most attention in the moun- tains of the Northeastern States, where fishermen find it to be a scourge in May and June. In this species the radial sector is dis- tinctly forked. The southern buffalo-gnat, Cnephia pecudrum. — This is the "Buffalo-gnat" of the Mississippi Valley, which in the past has been a terrible pest of mules and other domestic animals, sometimes caus- ing their death- but it seems to be much less common now than in former years. In this species the radial sector is very indistinctly forked at the apex. The popular name of this insect refers to a fancied resemblance in the shape of the insect when viewed from one side to that of a buffalo. The turkey-gnat, Simulium meridiondle. — This species closely resembles the preceding in habits, infesting all kinds of domestic animals, especially in the Mississippi Valley. As it appears at the time that turkeys are setting and causes great injury to this fowl, it is commonly known as the turkey-gnat. In this species the radial sector is not forked. The white-stockinged black-fly, Simulium veniistum. — ^This species is widely distributed and is one of the more common species of the genus. It can be distinguished from the other species men- tioned here by the fact that the tibiae are silvery^ white above. In the Adirondacks it appears later than Prosimulium hirtipes and is not so serious a pest. Professor Needham writes: "Guides have a saying, that, when the black-flies put on their white stockings in June, the trouble is about over. This species has the white stockings". The innoxious black-fly, Simulium pictipes. — This black-fly is very widely distributed and at Ithaca it is our most common species. Although it may abound where during many summers I have taken my classes for study of aquatic insects, I have never known it to bite. Family BLEPHAROCERID.E The Net-winged Midges The net-winged midges are extremely remarkable insects; for in certain respects the structure of the adults is very peculiar, and the larvae appear much more like crustaceans than like insects. The adults are mosquito-like in form; but they differ from all other insects in having the wings marked by a net-work of fine lines which extend in various directions and are not influenced at all by the veins of the wing (Fig. 1048). They are, however, quite constant in their position in the species that I have studied. When a wing is examined with a microscope, the fine lines are seen to be slender thickenings extending along the courses of slight DIPTERA 825 folds in the wing. The significance of these folds is evident when a net-winged midge is observed in the act of issuing from its pupa-skin Fig. 1048. — Wing of Blepharocera tenuipes. When the wing is first pulled out of the wing-sheath of the pupa, that part of it which is crossed by the fine lines is plaited somewhat like a fan and folded over the other portion. By this means the \ying, which is fully developed before the adult emerges, is packed within the wing-sheath of the pupa, which is much shorter and narrower than the wing. When the wing is finally unfolded, it does not become perfectly flat, but slight, alternating elevations and depressions remain, showing the positions of the former folds, a permanent record of the unique history of the wings of these insects. Ordinarily the wings of insects, while still in the wing-sheaths of the pupa, are neither longer nor wider than the wing-sheaths, but expand after the adult emerges from the pupa skin. Usually it takes considerable time for the wings to expand and become fit for flight and during this interval the insect is in an almost helpless condition. In certain caddice-flies that emerge from swiftly-flowing water, the time required for the expansion of the wings has been re- duced to the mini- mum. In the net- ' winged midges, which also emerge from swiftly-flowing water the difficulty is met by the wings reaching theirfull develop- ment before the adult leaves the pupa-skin. It is only necessary when the adult emerges from the water that it should unfold its wings to be ready for flight. The members of this family have three ocelli. The compound ^1 ~^l Fig. 1050 Fig. 1049. — Section of head through the eyes of Blepharocera tenuipes: 0, ocelH; br, brain; /./, large facets; 5./, smah facets, 0. I, optic lobes. (From Kellogg.) 826 AN INTRODUCTION TO ENTOMOLOGY eyes are usually divided in both sexes; the upper part of each eye being composed of large facets, characteristic of night-eyes, and the lower part, of smaller facets, characteristic of day-eyes, in a few- species the eyes are divided only in the males. Figure 1049 repre- sents a section of the head of the Blepharocera tenuipes through the eyes. The antennse are thread- like, but are not furnished with whorls of long hairs (Fig. 1050). The mouth parts are elongate; the females have slender flat- tened elongate mandibles (Fig. 105 1 ) the males are without mandibles. The legs are very long. On the dorsum of the mesothorax there is on each side, beginning just in front of the base of the wing, a well-marked suture like that of the crane-flies; but the two do not meet so as to form a continuous V-shaped suture as in the Tipulidae. In some species at least there are two kinds of females, which differ somewhat in the shape of the head. These two forms also differ in habits, one being blood- sucking, the other feeding upon nectar. The adults may be found resting on the foliage of shrubs or trees on the margins of mountain-brooks, or dancing in the spray of waterfalls. The immature forms of these in- sects are even more wonderful than are the adults. The larvae live in water, in swiftly-flowing streams, where the water flows swiftest. I have observed the transformations of Blepharocera tenuipes, which is abundant in some of the ravines near Ithaca, N. Y. The larvae of this species are readily seen on account of their black color, and are apt to attract attention on account of their strange form. (Fig. 1052, a). At first sight the body ap- pears to consist of only seven segments, but careful examination reveals the presence of smaller segments alterna- ting with these. Each of the larger segments except the last bears a Fig. 105 1. — Mouth-parts of female of Bibiocephala doanei: I. ep, labrum- epipharynx; md, mandibles; mx. I, maxillary lobe; mx. p, maxillary pal pus; hyp. hypopharynx; li, labium; pg, paraglossa. (From Kellogg.) 1052. — Blepharocera: a, larva, dorsal view; b, larva, ventral view; c, puparium, side view. DIPTERA 827 pair of conical, leg-like appendages. On the ventral side of the body (Fig. 1052, b) each of the seven larger segments except the last bears a sucker, the cavity of which extends far into the body, and each of these segments except the first bears two tufts of tracheal gills; but those of the last segment are united. The head, which forms the front end of the first of the seven larger divisions, bears a pair of slender antenna?, each of these consists of a very short basal seoment and two long segments; at the tip of the last of these there is a pair of minute appendages and a bristle. The suture between the head and the remaining parts of the first division is best seen on the ventral side of the body. On the dorsal side a suture may be seen dividing the last division into two segments. The pupa-stage is passed in the same place as the larval. Like the larvae the pupse are very conspicuous on account of their black color, and are apt to occur like the larvae closely clustered together. The pupa is not enclosed in the larval skin, and differs greatly in form from the larva. On the dorsal side the skin is hard, forming a convex scale over the body (Fig. 1052, c); and the thorax bears a pair of breathing organs, each composed of four flattened leaves, two of them delicate tracheal gills, and the other two protecting chitinized plates; on the ventral side the skin is very delicate, soft, and trans- parent; so that the developing legs and wings may be easily seen when the insect is removed from the rock. The pupae cling to the rock by means of six suckers, three on each side near the edge of the lower surface of the abdomen; and so firmly do they cling that it is difficult to remove specimens without breaking them. I have watched the midges emerge from their pupa-skins and escape from the water. The pup^ occurred in groups so as to form black patches on the rocks. Each one was resting with its head down stream. Each midge on emerging forced its way out through a trans- verse rent between the thorax and abdomen. It then worked its body out slowly and in spite of the swift current held it vertical. The water covering the patch of pupae varied from 6 mm. to 25 mm. in depth. In the shallower parts the adult had no trouble in working its way to the surface still clinging to the pupa-skin by its very long hind legs. While still anchored by its legs the midge rests on the surface of the water for one or two seconds and unfolds its wings; then freeing its legs it takes flight. The adults emerging from the deeper water were swept away by the current before they had a chance to take wing. The time required for a midge to work its way out of the pupa- skin and take flight varied from three to five minutes. The larvae of the net-winged midges live only in swift -flowing streams; they are found, therefore, only in mountainous or at least hilly regions. It is believed that they feed chiefly on algae and di- atoms. It does not seem probable that these delicate midges can deposit their eggs on the rocks in the swift-running water where the larvae live, as do the females of Simulium. It is more likely that the eggs are deposited on the wet rocks at the margins of the stream and that the larvae migrate to the center of the stream. 828 AN INTRODUCTION TO ENTOMOLOGY This family is a small one; but it is world-wide in distribution. Representatives of it have been found in both North and South America, in Europe, and in Australia and New Zealand. A mono- graph of the North American species was published by Kellogg ('03) and one of those of the world by the same author (07), a table of the North American species is given by Kellogg in Williston ('08). Family THAUMALEID^ The Solitary-Midge Only a single species of this family is known to occur in North America; this is Thaimidlea americdna. It is a small fly measuring about 8 mm. in length, and is found on the banks of streams. The antennee are short, about as long as the head, and nearly of the same structure in the two sexes ; the segments of the antennae ex- cept those at the base are slender and are clothed with a few short hairs. The ocelli are wanting. The eyes are largeand meet in front in both sexes. The venation of the wings is illustrated by Fig. 1053 vein Ri ends at or near the end of the second third of the costal margin; the radial sector is two-branched; media is simple; and there are no anal veins. The larvae live in streams and resemble those of Chironomidee. This family has been commonly known as the Orphnephilidae; but it has been shown by Bezzi ('13) that the typical genus was first described under the name Thaumalea. Fig. 1053. — Wing of Thaumalea americana. Series II— BRACHYCERA* The Short-horned Orthorrhapha In most of the families included in this division of the Orthorrhapha the antennae are short and three-jointed, the flagellum being reduced to a single segment, with or without a style or arista; but in the first subseries, the Anomalous Biach^xera, the flagellum is more or less distinctly segmented. In all of the Brachycera the palpi are porrect and one- or two-jointed; and the first anal cell is either closed or narrowed towards the margin of the wing. *Brachycera : brachy, short ; ceras {icepat) , a horn. DIPTERA 829 SUBSERIES A — THE ANOMALOUS BRACHYCERA In the families constituting this subseries the antennae consist of five or more segments; but those beyond the second, the fiagelkim, are usuahy more or less consolidated. In some cases the antennae do not differ markedly in form from those of certain Anomalous Ne- mocera; but the Brachycera are sharply distinguished from the Ne- moceraby the palpi being porrect and only one or two-jointed and by the fact that the anal cell is either closed or narrowed towards the margin of the wing. In this subseries the head and thorax are not furnished with strong bristles and the empodia are pulvilli-form. Family TABANID^ The Horse-Flies The horse-flies are well-known pests of stock, and are often extremely annoying to man. They appear in summer, are common in woods, and are most abundant in the hottest weather. In this family the flagellum of the antennae ■^^^•^^f^54-— is composed of from four to eight, more or less of^rola^ closely consolidated segments and is never Fig. 1055.- nus. furnished with a distinct Style or arista (Figs. Antenna 1054, 1055). The wing-veins (Fig. 1056) are otChry- evenly distributed over the wing, as the branches of vein R are not crowded together as in the following familv ; the costal vein is continued as an ambient vein which extends Fig. 1056. — Wing of Tabanus. completely around the wing; the alulets are large, in other Anomalous Brachycera they are small or vestigial. The flight of these flies is very powerful, they are able to outstrip the swiftest horse. The males feed on the nectar of flowers and on sweet sap. The mouth-parts of the female are fitted for piercing the, 830 AN INTRODUCTION TO ENTOMOLOGY Fig. 1057. — Taba- niis atratns. skin and sucking the blood of men and quadrupeds; the females, however, also feed on sweets of plants when they cannot obtain blood. The larger species, as well as some ■S. v^' ^ of moderate size, belong to the genus I^H^I Tahdnus of which nearly two hundred ^''\JBmL^r^ species are listed from North America. ^^^^Bp^ One of the most common of these is ^^3^^ the mourning horse-fly, Tahdnus ai- ^^^^^ rdtus. This insect is of uniform black . ^^^^^KL color throughout, except that the ^^^BP^^H body may have a bluish tinge (Fig. ^Pr ^H 1057). The species of this genus attack ^ ^^ cattle and other farm animals almost exclusively. To the genus Chrysops belong the smaller and more common horse-flies with banded wings (Fig. 1058). The species of this genus attack man as well as other animals. To this genus belong the well-known deer-flies familiar to fishermen and hunters. Sixty- three North American species of this genus are listed by Aldrich. The eggs are deposited in large masses on plants or on exposed stones in the bed of a stream. The larvse are aquatic or semi-aquatic. As far as known, they are predacious, feeding on various small animals, some upon snails, others upon the larvae of insects. In most cases they have a single pair of spiracles, which is situated at the hind end of the body; some have a pair of spiracles at each end of the body. Figure 1059 represents a larva of Tab- aims. The pupa is not enclosed in the skin of the larva. Hine ('03) redescribes all Ohio Species and gives a table of the North American Family STRATIOMYIID^ The Soldier-Flies Fig. 1059. — Larva of Tabanus. The soldier-fiies are so called on ac- (Photo. by M. V. Slinger- count of the bright-colored stripes with ^^^^•) which some of the species are marked. In the more typical members of this family the abdomen is broad and greatly flattened (Fig. 1060) and the wings when at rest lie parallel upon each other over the abdomen. But in some genera the abdomen is narrow and considerably elongate. DIPTERA 831 The antennce vary greatly in form, in some genera the flagellum s long and consists of several quite distinct segments (Fig. 1061) in others it is short with but few indis- #tinctly separated segments and with an arista (Fig. 1062) as in the True Brachycera. The most distinctive characteris- tic is the peculiar venation of the wings (Fig. 1063). The branches of vein R are crowded together near the costal border of the wing ; and the first omyta. cell M2 is unusually short and broad; the branches of vein M and vein Cui are comparatively weak, and the tibiae are with- out spurs. These flies are found on flowers and leaves, especially in the vi- cinity of water, and in bogs and marshes, but some species are found far from water. The larvas occur in various situations; some are aquatic and feed upon algse, decaying vegetable matter, and small Crus- tacea; some live in privies, in cow-dung, and in other decaying Fig. io6o.- Strati Fig. 1062. Fig. 1063. — Wing of Stratiomyia. matter; some are found under bark of trees that has become slightly loosened and feed upon sap and upon insect larvse; and some have been found in nests of H^Tnenoptera and in those of rodents, where they act as scavengers. The larvffi are spindle-form or elliptical and flattened, and with the surface of the body finely shagreened. The posterior pair of spiracles is situated in a cleft or chamber at the end or near the end of the body. In the aquatic forms the apical respiratory chamber is furnished along its margins with long plumose hairs. When the larva is at rest hanging from the surface of the water these hairs are spread radiatingly upon the surface film; they thus form a means of support and prevent the water from enter- ing the respiratory chamber. Fig. 1064.— Pupariura of The aquatic species leave the water to Odontomyia. 832 AN INTRODUCTION TO ENTOMOLOGY transform. The pupag of the Stratiomyiidse are enclosed within the last larval skin, differing in this respect from other Brachycera (Fig. 1064) . This is a large family ; more than three hundred species, represent- ing more than forty genera, have been described from North America Family XYLOAIYIID^ I group together here, provisionally, two genera, as representing CH2+2dA Fig. 1065. — Wing of Xylomyia. (After Verrall.) a separate family, that have been placed by some writers in the Stratiomyiid^ and by others in the Rhagionidce. These genera Q.veXylomyia and Rhachicerus. Both differ from the Rhagionidse, as restricted here, in the form of the antennee, they clearly belong with the Anomalous Brachycera. They differ from the Stratiomyiidae in that the branches of radius are not crowded together near the costal border of the wing and in the possession of tibial spurs. They agree with each other and differ from all other Anomalous Brachycera found in our fauna in that cell M3 is closed (Fig. 1065). Xylomia. — This genus includes rather elongate flies, somewhat Ichnenmon-like in appearance, which are mainly of black coloration with more or less yellow markings. The fiagellum of the antennae consists of eight closely con- solidated segments, the last of which usually bears a tiny style (Fig. 1066). Six species have been described from our fauna. ■t'lg- lobb.-- The larvae of Xylo- ^lyZ myta palhpes have been m y i a . found under the bark of (After fallen trees and are pre- Verrall.) dacious. Rhachicerus. — The members of this genus resemble Xylomyia in the form of the body but differ mark- edly in the structure of the antennee. In Rhachicerus the fiagellum of the antennas consists of from twenty to thirty-five segments. The seg- ments of the fiagellum are more or less cup-shaped ; and in some species Fig. 1067. — Antenna of Rhachicerus (From Williston.) DIPTERA 833 one edge of each segment is prolonged so that the antennae are pecti- nate (Fig. 1067). Four species of this genus have been found in America north of Mexico. The larva of Rhachicerus mtidus has been found in a decayed log. Family XYLOPHAGID^ This family, like the preceding one, includes slender flies, which are Ichneumon-like in appearance. It is distinguished from other Anomalous Brachycera as follows: from the Stratomyiidse in that the branches of radius are not crowded together near the costal border of the wing (Fig. 1068) and in the possession of tibial spurs; from the Fig. 1069.- Cu,+2dA - • Antenna of Xylo- Fie. 1068.— Wine of Xylophagus. phagus and, p, palpus. Xylomyiidee in that cell M3 is open; and from the Coenomyiidae in the absence of spinous protuberances on the scutellum. The flagelliim of the antenna consists of several closely consolidated segments; the antenna of a member of the typical genus is represented in Figure (069. This family is represented in our fauna by the following genera: Fig. 1070. — Wing oi Ccetwmyia ferruginea. (After Verrall.) Xylophagus, Glutops, Arthoceras, Arthropeas, and Misgoniyia. These genera include sixteen species described from our fauna. 834 AN INTROD UCTION TO ENTOMOLOGY The larvae that are known Hve in earth or under the bark of rotten trees and feed upon the larvas of other insects. Family CCENOMYIID^ The members of this family differ from the Stratiomyiidas in that the branches of radius are not crowded together near the costal border of the wing (Fig. 1070) and in the possession of tibial spurs; and they differ from all other Anomalous Brachycera in that the scutellum is armed with two spinous protuberances. The eyes are pubescent ; the flagellum of the antenna consists of eight closely consolidated seg- ments (Fig. 1071); veins M3 and Cui anastomose for a considerable distance; and the tips of veins Cu2 and 2nd A are narrowly separated or, rarely, united for a short distance. This family is represented in our fauna by a single species, CcEuoniyia ferrugtnea. This is a large thick- bodied fl}% often measuring 25 mm. in length; but it varies greatly in size. It is of a pale yellowish brown color. The larvae are usually found in the ground, but they are ofCceno- sometimes found in decaying wood ; they are predacious, myia. feeding upon insect larvae. SUBSERIES B- — THE TRUE BRACHYCERA In the families constituting this subseries the antennae are usually three-jointed, but in some cases they are four- or five-jointed; the third segment is not ringed, but usually bears a style or an arista. A similar type of antenna is possessed by the Cyclorrhapa, which were formerly on this account included in the Brachycera; but this term is now restricted to the Short -horned Orthorrapha. In the first three families the head and thorax are not furnished with strong bristles and the empodia are pulvilliform. Family RHAGIONID^* The Snipe-Flies These trim-appearing flies have rather long legs, a cone-shaped abdomen tapering towards the hind end (Fig. 1072) and sometimes a downward-projecting proboscis, which with the form of the body and legs has suggested the name snipe-flies. The body is naked or hairy, but it is not clothed with strong bristles. Frequently the hairy covering, though short, is very dense and is of strongly-contrasting Fig. 1072.— Chr y s 0- pila tho- racica. *This family has been commonly known is the older name and is now coming into use. the Leptidce, but Rhagionidae DIPTERA 835 colors. Three ocelli are present. The antennas are only three- jointed and the third segment bears a style or an arista (Fig. 1073). The proboscis is usually short, only a few members of the family having it long like the bill of a snipe. The wings are broad, and when at rest are held half open. The empodia are pulvilliform (Fig. 1074). The venation of the wings is compara- tively generalized . Figure 1075 represen ts the venation of a wing of the typical genus. The flies are usually of moderate size. They may be found about low bushes and on tall grass. They are sometimes slug- gish and, therefore, easily caught. They are sometimes predacious upon other Fig. 1073.- A n t enn; of Chryso pila. insects, and the species of Symphoromyia suck blood as do horseflies. The females of the genus Atherix have the remarkable habit of clustering in large numbers on branches or rocks overhanging water, where they deposit their eggs in common, and dying as they do so, add their bodies to the common mass, which may contain thousands R> R,^, Fig. 1075. — Wing of Rhagio. of individuals. Figure 1076, copied from Sharp ('99) represents a European species, Atherix ibis, natural size, and a mass of dead flies, much reduced. It is said that the larv« feed upon the bodies of the dead mothers until the mass is loosened and falls into the water, where the larvae complete their growth. Other writers state that the larvae drop into the water when hatched. Large masses of these flies have been observed in various parts of this country; and formerly, in the Far West, they were collected by the Indians and used for food after being cooked. It is said that as many as a hundred bushels of flies could be collected in a single day. For an account of the methods of collecting the flies and of preparing them for food practiced by the Indians see Aldrich ('12). 836 AN INTRODUCTION TO ENTOMOLOGY The larvae of this family are found in various situations; some as those of Atherix live in water, but a larger number live in earth, in decaying wood, or in sand. The larvas of Vermileo resemble ant-lions in habits, digging pit- falls in sand for trapping their prey. Only one species, Vermileo comstocki, has been found in America; this lives in the moun- tains of California ; other species are well-known in Europe. I pro- pose the common name ant-tigers for the larvae of this genus. Family NEMESTRINID^ The Tangle-veined Flies Fig. 1076. — Antherix ibis: A. The fly, natural size; B, mass of dead flies overhanging water, much reduced. (From Sharp.) The members of this family are of meditmi size ; some of them resemble horse-flies, and others bee-flies. They can be recognized by the peculiar venation of the wings, there being an unusual amount of anastomosing of the veins (Fig. 1077), which gives the wings a very characteristic appearance. The antennas are small and short; the third segment is simple and furnished with a slender, jointed, terminal style. The proboscis is usually long, sometimes very long and fitted for sucking nectar Fig. 1077. — Wing of Parasymmidus clausa. from flowers. The head and thorax are not armed with strong bristles, and the empodia are pulvilliform. But little is known regarding the habits of the larvae; one species has been found to be an internal parasite of coleopterous larvae. Only six species have been found in America north of Mexico. DIPTERA 837 Family ACROCERID^'' The Small-headed Flies These flies are easily recognized by the unusually small head, the ^arge humpbacked thorax, the inflated abdomen, and the very large alulets (Fig. 1078). The body is devoid of bristles and the empodia are pulvilliform. The head is composed almost entirely of eyes, and in some genera is minute. The eyes are contig- uous in both sexes or nearly so. The antennae are three-jointed, and are furnished with a style or an arista in some genera, in others not. Sometimes the antennse are apparently two-jointed, the first seg- ment being sunken in the head. The venation of the wings varies greatly in the different genera. The accompanying figure (Fig. 1079) represents a single genus rather than the family. The flies are generally slow and feeble in their movements. In some species that feed upon flowers the proboscis is very long, some- Fig. 1078.— Pterodontia misella. Fig. 1079. — Wing of Eulonchus. times exceeding the body in length. Other species take no nourish- ment in the adult state, and have no proboscis. The larvag of only a few members of this family have been ob- served; these are parasitic in the egg-sacs or in the bodies of spiders. The life-history of an American species, Pterodontia flavipes has been described by King ('16). The females of this species deposit their eggs on the bark of trees ; they produce a large number of eggs ; in one of the cases observed these numbered 3,977. This production of many eggs is doubtless an adaptation made necessary by the fact that many of the young larvae will fail to find spiders to attack and will conse- quently perish. A larva that succeeds in finding a spider bores into its body and there lives till fully grown ; it leaves the body of its host to transform. ''This is the family Cyrtidae of some authors ; but Acroceridae is the older name. 838 AN INTRODUCTION TO ENTOMOLOGY A monograph of the North American species of this family was pubhshed by Cole ('19). Family BOMBYLIID^ The Bee-Flies These flies are mostly of mediiim size, some are small, others are rather large. In some the body is short and broad and densely clothed with long, delicate hair (Fig. 1080). Other species resemble the horse-flies somewhat in appearance, especially in the dark color or markings of the wings; but these can be dis- tinguished from the horse-flies bv the form of the antennae and the venation of the wings. The antennee are usually short; they are three-jointed with or without a style; in some genera the style is so large that it may be con- sidered a fourth segment. The ocelli are pres- ent. The proboscis is sometimes very long and slender, and some- times short and furnished with fleshy lips at the extremity. The radial sector is three-branched ; cell R3 is sometimes divided by a sectorial cross-vein (Fig. 1081, s); cell M3 is obliterated by the coalescence of veins M3 and Cui;in a few genera cell Mi is also oblit- erated by the coalescence of veins Mi and M2; cell ist A is narrowly Fig. 1080. — Bombylius. Fig. 1 08 1. — Wing of Pantarbes capita. open, or is closed at or near the border of the wing. The alulets are small or of moderate size. The empodia are pulvilliform. The adult flies feed on pollen and nectar, and are found hovering over blossoms, or resting on sunny paths, sticks or stones; they rarely alight on leaves. The larvse are parasitic, infesting hymenopterous and lepidopter- ous larvffi and pupae and the egg-sacs of Orthoptera. The pupae are free. The family is a large one ; more than four hundred and fifty North American species, representing forty-one genera are listed by Aldrich ('05). DIPTERA 839 Family THEREVID^ The Stiletto-Flies With the flies of this family the head is transverse, being nearly as wide as the thorax; and the abdomen is long and tapering, suggest- ing the name stiletto-flies. These flies are small or of meditmi size; they are hairy or bristly. The antennse are three-jointed; the third segment is simple, and usually bears a terminal style ; but this is some- times wanting. Three ocelli are present. The legs are slender and bristly ; the empodia are wanting. The radial sector is three-branched, (Fig. 1082) and the last branch, vein R5, terminates beyond the apex of the wing; the three branches of media are separate ; the cross-vein m-cu is present ; and the first anal cell is usually closed. 2d A + Cu, Fig. 1082. — Wing of Thereva. The adult flies are predacious; they conceal themselves among the leaves of low bushes or settle on the ground in sandy spots, wait- ing for other insects, chiefly Diptera, upon which they prey. The larvce are long and slender, and the body is apparently com- posed of nineteen segments. They are found in earth, fungi, and de- caying wood. They feed on decaying animal and vegetable matter and are said to be predacious also. The pupae are free. The family is a comparatively small one, including but few genera and species. Family SCENOPINID^ The Window-Flies The window-flies are so-called because the best-known species are found almost exclusively on windows; but the conclusion that these are the most common flies found on windows should not be drawn from this name; for such is not the case. 840 AN INTRODUCTION TO ENTOMOLOGY These flies are of medium size, our most common species measuring 6 mm. in length. They are usually black, and are not clothed with bristles. The thorax is prominent, and the abdo- men is flattened and somewhat bent down, so '^SBto W\ ^^^^ ^^^ body when viewed from the side presents (^^ W% a hump-backed appearance (Fig. 1083). When at '^ mm rest, the wings lie parallel, one over the other, on the abdomen; when in this position they are very inconspicuous. There are three ocelli. The an- tennae are three-jointed; the first and second seg- ments ai e short, the third is long and bears neither a style nor an arista (Fig. 1084). The venation of the wings is represented by Figure 1085. The radial sector is three-branched; cells Mi and M3 are both obliterated by the coalescence of the veins that bound them ; the first anal cell is closed at a considerable distance before the margin ; and cell R is much longer than cell 2d M. The larvae, which are sometimes found in dwellings under carpets or in furniture, are very slender, and are remarkable for the appar- ently large number of the segments of the body, each of the abdom- Fig. 1083.— Scenopi- ^. nus. Fig- 1084 Fig. 1085. — Wing of Scenopinus. inal segments except the last being divided by a strong constriction. They are also found in decaying wood, and are supposed to be carniv- orous. The family is a very small one. The most common species is Scenopinus Jenestrdlis. Family ASILID^ The Robher-Flies These t^re mostly large flies, and some of them are very large. The body is usually elongate, with a very long, slender abdomen (Fig. 1086); but some species are quite stout, resembling bumblebees in DIPTERA 841 form. This resemblance is often increased by a dense clothing of black and yellow hairs. In this and the following family the vertex of the head is hollowed out between the eyes (Fig. 1087). In this family the proboscis is pointed and does not bear fleshy lips at the tip. The antennae project forward in a prominent manner. They are three-jointed, and with or Fig. 1086. — Erax api- calis destroying a cotton worm. Fig. 1088. Fig. 1087. — Head of a robber-flv. without a terminal style. The style when present sometimes appears like one or two additional segments (Fig. 1088). Vein Ml (Fig. 1089) does not terminate at or before the apex of the wing as in the following family. Cell M3 is present, but is usually closed by the coalescence of the tips of veins M3 and Cui. The tips of veins Cu2 and 2d A may or may not coalesce for a short distance. The robber-flies are extremely predacious. They not only destroy other flies, but powerful insects, as bumblebees, tiger-beetles, and dragon-flies, fall prey to them; they will also feed upon larvae. They are common in open fields and are as apt to alight on the ground as on elevated objects. Fig. i( -Wing of Erax. The larvce live chiefly in the ground or in decaying wood, where they prey upon the larvae of beetles; some, however, are supposed to teed upon the roots of plants. The pupae are free. More than five hundred North American species of this family, representing seventy-five genera, have been described. 842 AN INTRODUCTION TO ENTOMOLOGY Family MYDAID^ The Mydas-Flies The Mydas-flies rival the robber-flies in size, and quite closely resemble them in appearance. As in that family, the vertex of the head is hollowed out between the eyes; but these flies can be distinguished by the form of the proboscis, which bears a pair of fleshy lobes at the tip, by the form of the antennae, which are four-jointed, long and more or less clubbed at the tip (Fig. 1090), and by the peculiar venation of the wings (Fig. 109 1), vein Ml terminating at or before the apex of the wing, and the branches of vein R coalescing near the apex of the wing in an unusual way. The adults are said to be predacious. The larvffi of some species, at least, live in decaying wood, and some are known ^1090! t*^ P^^y upon the larvag of beetles. The family is a small one, there being only about one hundred known species, of these nearly fifty have been found in M + : Fig. 1091. — Wing of Mydas. North America, but most of these occur south of the United States. The family includes the largest known Diptera. Family APIOCERID^ The Apiocerids This family includes only a small number of species, which are rare and occur in the Far West. The}' are rather large and elongate, and are found upon flowers. The head is not hollowed out between the eyes; the ocelli are present; the antennee are three-jointed, with or without a short simple style; the proboscis is not adapted for piercing. The radial sector is usually three-branched, but sometimes it is only two-branched; all of the branches of vein R end before the apex of the wing (Fig. 1092) ; DIPTERA 843 cell M3 is present but closed by the coalescence of veins M3 and Cui 7?. M^+Cu, Fig. 1092. — Wing of Apiocera. at the margin of the wing; and the medial cross-vein is present, empodia are wanting. The larvee are unknown. The Fig. 1093. — Do- lichopus lo- batus . Family DOLICHOPODID^ The Long-legged Flies These flies are of small or mediimi size and usually bright metallic green or blue in color. The legs are much longer than is usual in the families belonging to the series of short-horned flies (Fig. 1093). This suggested the name Doltchopus, which means long-footed, for the typical genus; and from this the family name is derived. It should be remembered however, that these flies are long-legged in comparison with the allied families, and not in comparison with crane-flies and midges. The members of this family are easily distin- guished as such by the peculiar venation of the wings, the most characteristic features of which are the following: cells M and ist M2 are rarely if ever separated by a com- plete vein; the basal part of vein M3 being either atrophied Fig. 1094) or represented by a short spur (Fig. 1095) ; veins R2+3 andR4+5 separate near the base of the wing, and there is usually at the point of separation a more or less knot-shaped swelling; the cross-vein r-m, when present, is near this swelling, so that cell R is very short. The members of this family have three ocelli; the antennae are three-jointed; the second segment of the antennas is sometimes ves- tigial and the third segment bears an arista; the palpi are one-jointed; and the empodia are not pulvilliform. The adults are predacious and hunt for smaller flies and other soft-bodied insects. They are usually found in damp places, covered with rank vegetation. Some species occur chiefly on the leaves of aquatic plants, and about dams and waterfalls ; and some are able to run over the surface of water. Others occur in dry places. 844 AN INTRODUCTION TO ENTOMOLOGY In the genus Melanderia, of which two species have been found on the Pacific Coast, the outer lobe of the labella is mandible-Hke, Mi+Ctii Fig. 1094. — Wing of Dolichopiis coquilletli. and doubtless functions as a mandible. For descriptions of these remarkable flies see Aldrich ('22). The males of some species have the fore tarsi exceedingly elon- gated and slender, with the last segment in the shape of a compara- tively large, oval, black disk, as shown in Figure 1093 ; in others the front tarsi are plain but the middle ones are elongated, thickened, and very black; and in still others the first two segments of the antennse are ornamented with coarse black hair and the arista covered with a black pubescence. In several cases the males have been observed to display these ornaments before the female when courting. Detailed accounts of these observations are given by Professor Aldrich in the monograph of Dolichopus by Van Duzee, Cole, and Aldrich ('21). The larv£e live in a variety of situations, some in earth or decom- posing vegetable matter, some in the burrows of wood-boring larvas Fig. 1095. — Wing of Psilopodiiis sipho. and also under bark; some in the stems of plants; and some ar° aquatic. But little is known regarding the habits of the larvae; it is said that some species feed on decaying vegetation, while others are believed to be predacious. DIPTERA 845 This is a ven,- large family ; and representatives of it are common everywhere in the United States and Canada. Family EMPIDID^ The Dance-Flies The dance-flies are of medium or small size; they are often seen in swarms flying with an up and down movement under trees or near shrubs and over the surface of water. These flies are predacious, like the robber-flies, but they also frequent flowers. The family is a rather difficult one to characterize owing to great variations in the form of the antennse and in the venation of the wings. The branches of vein Cu coalesce with the adjacent veins (vein Cui with vein M3 and vein Cu2 with vein 2d A) from the margin of the wing towards the base for a considerable distance (Fig. 1096). In most genera this coalescence is carried so far that the free parts of the branches of vein Cu appear like cross-veins. The only other Fig. 1096. — Wing of Rhamphomyia. families of the suborder Orthorrhapha in which this occurs are the Dolichopodidce and the Lonchopteridce, and the venation of the wings in each of these is very different from that of the Empididas. The antennas are three-jointed, the flrst and second segments are often very small, and then appear like a single segment, the third segment may or may not bear a style or an arista. The mouth -parts are in many cases long, and extend at right angles to the body or are bent back upon the breast. The larvce live in various situations, some in the ground or in decaying wood, and some species are aquatic; they are believed to be either predacious or scavengers. The pupaj are free. This family is a large one. It was monographed by Coquillett ('96) and by Melander ('02). 846 AN INTRODUCTION TO ENTOMOLOGY Family LONCHOPTERID^ The Spear-winged Flies These are minute flies, which measure from 2 mm. to 4 mm. in length, and are usually brownish or yellowish but never green nor metallic in color. When at rest the wings are folded flat, one over the other, on the abdomen. The apex of the wing is pointed, and the wing as a whole is shaped somewhat like the head of a spear (Fig. 1097). This suggested the family name. The venation of the wings is very characteristic, and is sufficient to distinguish these flies from all others. The cross-veins r-m and m-cu are oblique, and near the base of the wing. Vein Cu2 is very short, and extends towards the base of the wing. In the females Fig. 1097. — Wing oi Lonchoptera, female. vein Cuj coalesces with vein M3 as shown in the figure, but in the males the tip of vein Cui is free. The posterior lobe is wanting. Three ocelli are present. The antennse are three-jointed; the third segment is globular, and bears a long arista. These flies are common from spring till autumn, in damp grassy places. They frequent the shores of shady brooks, where the atmos- phere is moist. The males are very rare in this country. Professor Aldrich examined over 2,000 specimens and found only two males among them. "The larvae live under leaves and decomposed vegetable matter. The larva transforms into a sort of semipupa within the last larval skin, and later into a true pupa" (Williston '08). The family includes a single genus, Lonchoptera, of which only three North American species are known. Suborder CYCLORRHAPHA* The Circtdar-seamed Flies To this suborder belong those families of flies in which the pupa is always enclosed in a puparium from which the adult escapes through *Cycl6rrhapha : cyclos. (k^kXos), a circle; rhaphe, (pa(piq), a seam. DIPTERA 84"; a round opening made by pushing off the head-end ot 1098) , the cap thus pushed off is often split lengthwise, as shown in the figure. The adult flies possess a frontal lunule and except in the first four families a frontal suture, through which the ptilinum is pushed out. w^hen the adult is about to emerge from the puparitmi. The antennas are three-jointed, with a terminal or dorsal arista, rarely with a terminal style; in the Pupipara the antennas are apparently only one- or two-jointed and sometimes lack the arista. The radius is not more than three-branched; cells Mi and M3 are wanting. The empodia are never pulvilliform. SERIES I— ASCHIZA* Cyclonhapha without a frontal suture In most of the Cyclorrhapha the head end of the puparium is forced off by the expansion of the bladder-like ptilinum, which is pushed out through the frontal suture when the adult is ready to emerge; but in four families this is not the case, there being no frontal suture present. These families are grouped together as the Series Aschiza. They are the Phorid^, Platypezidas, Pipunculidae, and Syrphidae. Family PHORID^ The Hump-hacked Flies These are minute, dark-colored, usually black flies, which can be easily recognized by their himipbacked form, their peculiar an- tennae, and the peculiar venation of the wings. Certain species are often found lunning about rapidly on windows, others on fallen leaves. Sometimes they are seen in swarms dancing up and down in the air. Many species measure less than 2 mm. in length, and some less than i mm. The head is small ; the thorax large and humped ; and the abdomen rather short. The antennse are three-jointed; but the first segment is exceedingly small, and the second is enclosed in the third, so that they appear as single-jointed. The third segment bears an arista, composed of two short basal segments and a long, usually more or less plimiose third segment. The legs are large and strong and well adapted to jimiping. The femora, especially of the hind legs are often very stout and flattened. The wings (Fig. 1099) are large, and are furnished with a series of strong veins near the costal border, which extend but a short distance beyond the middle of the wing. From these strong veins from three to five weak ones extend across the wing. In the females of some species that live in the nests of ants and termites the wings are absent or very much reduced in size. *Aschiza: a (a), without; schizo (ax^^'^), a cleft. 848 AN INTRODUCTION TO ENTOMOLOGY The laivffi of the different species differ greatly in habits, some feed on decaying vegetable matter, dead insects, snails, etc. ; somear^ common in mushrooms, and are sometimes a pest in mushroom eel- lars; some are internal parasites of other insects, as bees, wasps, ants, saw-flies, etc. ; several species are known to live in the nests of ants, some as parasites and others as commensals. One of these Metopina M+, Fig. 1099. — Wing of Phora. pachycondyle lives curled about the neck of its host ant-larva, par- taking of the food given the latter by the attendant worker ants; and one has been bred from an egg-sac of a spider. A monograph of the North American species of this family was published by Brues ('03) and one by Malloch ('13). i\bout 150 species have been described from this region. The Phoridae are classed among the Brachycera by some writers and among the Cyclorrhapha by others. Morris ('22) states that when the adult fly of a species studied by him, Hypocera incrassdta, emerges from the puparium a circular cap, consisting of the skin of the cephalic region and thoracic segments of the larva, is split off by means of a fissure passing round the body between the third thoracic and first abdominal segments. This confirms the opinion that this family should be placed in the Cyclorrhapha. Family PLATYPEZID^ The Flat-footed Flies These flies resemble the house-fly somewhat in appearance but are very much smaller. They hover in the air in shady places and alight frequently on the leaves of low plants, where they run about in circles with great rapidity. The head is hemispherical or spherical, and as broad as or broader than the thorax. The antennae are three-jointed with a termiral arista. The legs are short and stout, and the tarsi of the hinder pair are often very broad and fiat (Fig. 11 00); but they vary greatly in form in different gen&ra. The wings are rather large, and when at DIPTERA 849 rest lie parallel upon the abdomen ; the axillary excision is prominent, but the posterior lobe of the wing is small (Fig. iioi); the alulets are minute. The radial sector is two-branched; veins Ml and M2 either coalesce throughout or sep- arate near the margin of the wing ; the medial cross vein is present in some members of the family and absent in others; cells 2d R, M, and ist A are short. This family is represented in North Amer- ica by about twenty-five species, and these are usually rare. The larvae live in mushrooms, the puparia are not very different from the larvas in form. Fig. 1 1 00.— Leg of P/d- typeza, a, forked hairs of leg greatly- enlarged. IIOI. — Wing of Platypeza. Family PIPUNCULID^ The Big-eyed Flies The members of this family are small flies with very large heads composed almost entirely of eyes (Fig. 1102). The head is nearly spherical and broader than the thorax. The antennse are small, short, three-jointed, with a dorsalarista. The ocelli are present. Theabdomenis somewhat elongate with the sides nearly parallel. The body is thinly clothed with hair or nearly naked. The wings are much longer than the abdomen, and when at rest they lie parallel to each other upon it. The venation of the wings (Fig. 11 03) closely re- sembles that of the Conopid^. The radial sector is two-branched. Veins R4+5 and Mi +2 approach each other at their tips. Vein M3 coalesces with vein Cui for nearly its Fig. II 02.- punctdus. -Pi- 850 AN INTRODUCTION TO ENTOMOLOGY entire length. Veins Cu2 and 2d A coalesce at their tips, except in Chalarus. In this genus vein Mi +2 is atrophied and the medial cross- vein absent. Cells R and M are long. The flies hover in shady places. They are sometimes found on flowers, and may be swept from low plants ; our most common species Fig. 1 103. — Wing oi Pipunculus. measure about 3 mm. in length, not including the wings. The larvae so far as known are parasitic upon bugs. This small family is represented in North America by about thirty species, nearly all of which belong to the genus Pipunculus. Family SYRPHID^ The Syrphus-Flies The family Syrphidas includes many of our common flies ; but the different species vary so much in form that no general description of their appearance can be given. Many of them mimic h^Tnenopterous insects, thus some species resemble bumblebees, others the honey- bee, and still others wasps ; while some present but little resemblance to any of these. The most distinctive characteristic of the family is the presence of a thickening of the membrance of the wing, which appears like a longitudinal vein between veins R and M. This is termed the spu- rious vein, and is lacking in only a few members of the family; it is represented in Figure 1104 by a band of stippling. Vein R4+5 is never forked; the tips of vein R4+5 and Mi +2 coalesce; and the first anal cell is closed. The antennse are three-jointed; the third segment usually bears a dorsal arista, but sometimes it is furnished with a thickened style. The face is not furnished with longitudinal furrows to receive the antennae as in the Muscidae. The frontal lunule is present, but the frontal suture is wanting. The adults frequent flowers and feed upon nectar and pollen. Some fly with a loud himiming sound like that of a bee, others hover motionless except as to their wings for a time, and then dart away suddenly for a short distance, and then resume their hovering. DIPTERA 851 The larvae vary greatly in form and habits. Some prey upon plant lice, and are often found in the midst of colonies of these insects ; some feed in the stems of plants and in bulbs ; others feed on decaying vege- table matter, and live in rotten wood, in mud and in water; and others live in ordure or in decomposing animal remains. Some are found in the nests of ants ; and some in the nests of bimiblebees and wasps. Among the common representatives of this family there is one that so closely resembles a male honey-bee as to be often mistaken for it. This is the Drone-fly, Enstalis tenax. It is common about /?. + 3 Fig. 1 104. — WmgolEristaUs. flowers. The larva lives in foul water, where it feeds on decaying vegetable matter; it is of the form known as "rat-tailed," which is described below. The larvcB of the genus Volucella live as scavengers in the nests of bimiblebees and of wasps {Vespa). Some of the species in the adult state very closely resemble bimiblebees. The larvae of the genus Mtcrodon are hemispherical, slug-like creatures (Fig. 1105), which resemble mollusks more than ordinary maggots; they are common in ants' nests. The larvae of several species that live in water as well as some that live in rotten wood are known as rat-tailed maggots on account of the long, tail-like, appendage, with which the hind end of the body is furnished. This is a tube, like that of a diver, which enables the insect to obtain air when its body is submerged beneath several inches of water or decaying matter. This tube being telescopic can be length- ened or shortened as the insect may need it ; and at its tip there is a ros- -'i^ m^l ette of hairs, which, floating on the surface of the water, keeps the tip Vig.iio^.-Microdo^t, adult from being submerged. The larva and larva. has on the ventral side of its body Fig. 11 06.-. several pairs of tubercles armed with SyrpMis. spines, which serve as prolegs. Among the more common members of this family are the yellow- banded species belonging to the genus Syrphus (Fig. 1 1 06) . The larvae 852 ^^V INTRODUCTION TO ENTOMOLOGY of these live in colonies of aphids, and do much good by destroying these pests. This family is a very large one; more than 300 species represent- ing about 60 genera have been described from America north of Mexico. Williston ('86) published an extended monograph of our species. SERIES II— SCHIZOPHORA* Cydorrhapha with a frontal suture This series of families includes all of the Cydorrhapha except the four preceding families in which the frontal suture is wanting. In this series, the Schizophora, there is a frontal suture through which the ptilinum is extruded in order to force off the head end of the pu- pariimi when the adult is ready to emerge. This series is divided into two quite distinct sections, the Myodaria and the Pupipara. SECTION I— MYODARIA The Muscids This section of the order Diptera is a very large group, including many families and probably more than half of all the living species of this order. As many of the species are very common, it usually happens that a large portion of the flies in a collection belong to the families included in this section. Excepting the first family, the Conopidas, the families included in the Myodaria differ from all of the preceding families in that vein Cu2 coalesces with vein 2d A to such an extent that it appears like a cross-vein or is curved back towards the base of the wing; and they differ from the following families, the Pupipara, in having the ab- domen distinctly segmented and the two legs of each thoracic seg- ment not widely separated. The antennae are three-jointed; the third segment bears an arista which is almost always dorsal in position. The radial sector is not more than two-branched ; cells Mi and M3 are wanting ; and the two branches of cubitus coalesce with the adjacent veins (Vein Cui with M3 and Cu2 with 2d A) for nearly their entire length, except in the Conopidse. The families included in this section are grouped in two subsec- tions, the Acalyptratas and the Calyptratae. *Schiz6phora: schizo (<^x'f«), a cleft; phoros {(pop6s), bearing. DIPTERA 853 Subsection I— THE ACALYPTRAT^* The Acalyptrate Muscids In the families included in this subsection of the Myodaria the alulae or calypteres are always small or rudimentary; the subcostal vein is often indistinct or vestigial, but well preserved in some forms; vein Ri is shortened and is often very short; the thorax is without a complete transverse suture; the posterior callus is usually absent; and the abdominal spiracles, with some exceptions, are in the con- junctiva?. The flies are usually small or very small, they are never large. The subsection Acalyptratae includes many families, twenty- three of which are represented in our fauna. Some of these families include well-known species that have attracted attention on account of their economic importance or for other reasons; but most of the families have been studied comparatively little in this country. Family CONOPID^ The Thick-headed Flies With the members of this family the head is large, being broader than the thorax. The body is more or less elongate ; it may be naked or thinly clothed with fine hair, but it is rarely bristly. The ocelli may be either present or absent. The antennse are prominent and project forward; they are three-jointed; and the third Fig. 1 107. — Wing of Physocephala affinis. segment bears either a dorsal arista or a terminal style. The radial sector is only two-branched (Fig. 1107); veins R4+5 and Mi -1-2 end near together or coalesce at their tips. The medial cross-vein is present. Vein M3 coalesces with vein Cui for nearly its entire length. Veins Cuj and 2d A coalesce at their tips, and sometimes for nearly the entire length of vein Cu2. *Acalyptratse: a (d); without; calypter (koKvitti^p), a sheath. 854 AN INTRODUCTION TO ENTOMOLOGY The adult flies are found on flowers. In some genera the abdomen is long, with a slender, wasp-like pedicel (Fig. \ ^ / 1 1 08). In others the abdomen is of the more usual VjSy form. The larvae are parasitic, chiefly upon ^^^^^^^^ bumblebees and wasps, but some species infest y^TV locusts. The eggs are deposited by the female, // m\K in some cases at least, directly upon the bodies of ' * the bees or wasps during flight. The newly Fig. 1108.— CoMo^5. hatched larvse burrow within the abdominal cavity of their host. Nearly one hundred North American species have been described. Family CORDYLURID^ The Dung-Flies The members of this family are often of considerable size for Acalyptratce, they are never very small. The subcostal vein is dis- tinctly separated from vein Ri and ends in the costa; vein Ri is nearly half as long as the wing, cell M is not minute; the frontal vitta is usually well differentiated from the orbits; and the vibrissas are present. Although members of several families of flies frequent excrement certain species of this family and of the Borboridas are so commonly observed about dung and refuse that they have received the common names of dung-flies. Among these are those of the genus Scatophaga; these are rather slender flies, which have the body clothed with yellowish hair, and which are often abundant especially about fresh cow-dung. Other members of this family are foimd in meadows and in moist places; some feed on other insects which they capture. The larvce of some species have been bred from excrement ; some live in the stems of plants ; and some are said to be parasitic in cater- pillars. This family is named the Scatophagidae by some writers, and by some it is classed with the Calyptratse. The family CLUSIIDiE is a small family of rather small flies; only a few representatives of which are found in our fauna. In this family the subcostal vein is distinctly separated from vein Ri and ends in the costa; vein Ri is less than one-third as long as the wing; the so- called front is broad and bristly to or nearly to the base of the an- tennae; the frontal vitta is not differentiated from the orbits; the ocellar bristles are usually present; the post vertical bristles are di- vergent; and the vibrissas are present. Larvae of this family have been found in decaying wood and under the bark of trees. This family is named the Heteroneuridas by some writers. Family HELOMYZID^ The members of the Helomyzidse can be recognized by the follow- ing combination of characters; the wings are armed with a row of DIPTERA 855 spines along the costa (Fig. 1109); the subcostal vein is distinct; the oral vibrissas are present ; the postvertical bristles, which are located on the back of the head somewhat behind the ocelli, are convergent; and the tibiae are armed with spurs and with preapical bristles. The flies are found in shady and damp places; many of them have been found in caves; and some species on windows. Fig. 1 109. — Wing of Leria. (After WilHston.) "The larvae of Leria have been bred from bat and rabbit dung; those of Helomyza from truffles, decaying wood, etc." (WilHston) The family was monographed by Aldrich and Darlington ('08) ; they recognized ten genera and about two score species found in the United States. The family BORBORID^ is composed of rather small or very small black, brown or obscurely yellowish flies, having a quick short flight. Some of the species are very common, occurring in great num- bers about excrement or near water. These "dung-flies" differ from those of the Cordyluridas in that the subcostal vein of the wings is wanting or indistinct and in having the hind metatarsi dilated and usually shorter than the following segment. The larvce of some of the species, at least, live in excrement. The family PHYCODROMID.^ includes only a few species of flies that are found among sea-weeds along the sea-shore. Two species are listed from Alaska and one from California. This family is named the Coelopidse by Hendel ('22). Family SCIOMYZID^ The members of this family are usually brown or brownish yellow in color; and in many species the wings are spotted or infumated. They are usually found in moist situations, as along the banks of streams. The larvae are aquatic. These flies lack vibrissee. The face in profile forms a sharp often very acute angle with that of the oral margin. The postvertical bristles are divergent when present. This family is represented in this country by more than twenty genera and by nearly one hundred described species. It has been 856 AN INTRODUCTION TO ENTOMOLOGY monographed by Cresson ('20) and also by Melander ('20a) under the name Tetanoceridas. Family SAPROMYZID^ The head is as broad as or a httle broader than the thorax; the legs are of moderate length ; the hind tibi« bear a preapical bristle ; the abdomen is short ; the ovipositor is neither flat nor drawn out ; the subcostal vein is distinctly separated from vein Ri and ends in the costa; vein 2d A does not reach the margin of the wing; the oral vi- brissas are absent; the second antennal segment bears a dorsal bristle ; the postvertical bristles are convergent ; and one or more stemopleural and a mesopleural bristle are present. This family is composed of small flies, which are seldom more than 7 m_m. in length. Nearly one hundred species have been described from America north of Mexico. A synopsis of the family was pub- lished by Melander ('13 a). The larvffi of Sapromyza live in decaying vegetable matter. This family is named the Lauxanidae by some writers. The family LONCH^ID^ includes the genera Lonchcsa and Palloptera, which are included in the Sapromyzid^ by some writers. These genera differ from the Sapromyzidas in that the hind tibias are without a preapical bristle; and the ovipositor is flattened and more or less projecting. A svnopsis of our species is included in Melander ('13a). Lonchcca pollta has been reared from a decaying fungus {Polyporus) and from human excrement. Family ORTALID^ This family like the Trypetidse is a large one and contains many common species which have the wings beautifully marked with dark spots or bands. The members of this family differ from the Tr\^petidas in that the subcostal vein extends to the margin of the wing in the usual way and in that the lower fronto-orbital bristles are wanting. Comparatively few species of the Ortalidae have been bred and these differ greatly in habits. The larvse of some have been found under bark of dead trees, others in excrement, some are parasitic on lepidopterous larv£e, and several infest growing plants. Among the latter are ChcEtopsis miea and Tritoxa flexa which sometimes infest onions; but the most important onion maggot is Hylemyia antiqua of the family Anthomyiidae. The family includes six subfamilies each of which is given family rank by Hendel ('22). Family TRYPETID.^ This is a very large family including many common species with pictured wings, in which it resembles the preceding family, the DIPTERA 857 Ortalidffi. These two families can be separated by differences in the subcostal vein; in the Trypetida the distal part of the subcostal vein is abruptly turned forward and usually becomes very weak. In this family the vibrissas are wanting; the fronto-orbital bristles are nimierous and extend down to the antennae; cells M and ist M2 are separated by a cross-vein ; the legs are moderately long; the tibiae lack preapical bristles; and the ovipositor is flattened and more or less projecting. The larvae of the species that have been bred infest living plants. Some are leaf-miners, some live in the stems of plants, some make galls, and some are pests that infest fniit. Among the better-known species are the following. The apple-maggot, Rhagoletis pomonella. — The adult is blackish with the head and legs yellowish ; the abdomen is crossed by three or four white bands (Fig. mo) and the wings are crossed by four dark confluent bands. The fe- male punctures the skin of the apple with her ovipositor and lays her eggs in the pulp. The larvae bores tunnels in all direc- tions through the fruit. Early maturing varieties of apples are especially attacked. When full-grown the larva goes into the ground to transform where it hibernates in a brownish puparium. This is a serious pest in the Eastern States and in Canada. This is a native species, originalh^ feeding in the fruit of wild thorn. It has been found that most of the flies can be destroyed before they lay their eggs by appljang a spray of arsenate of lead, four pounds in one hun- dred gallons of water, during the first week of July. The flies lap up drops of moisture from the fruit and foliage and are thus poisoned. The fallen apples should be collected or hogs allowed to iTin in the orchard. The cherry fruit-flies, Rhagoletis cinguldta and Rhagoletis fausta. These two species, which are closely allied to the apple-maggot, infest cherries, but not so commonly as does the plum curculio. The cherry fruit-flies can be destroyed by the use of the arsenate of lead spray early in June. Fig mo. — The apple-maggot: j, lar- va; 2, puparium; j, adult; la. head of larva from side showing the oral hooks and spiracle; ib, head of lar- va from below; ic, caudal spiracle of larva. 858 • AN INTRODUCTION TO ENTOMOLOGY The currant fruit-fly, Epdchra canadensis. — The larva of this species is a small white maggot which feeds within currants and goose- berries. The infested fruit colors prema- turely and usually falls to the ground. No practicable method of controlling this pest has been suggested. The round goldenrod gall. — One of the most familiar of abnormal growths on plants is a ball-like enlargement of the stem of goldenrod (Fig. mi). This is caused by Fig. II II. — The round a maggot, which lives within it, and which goldenrod gall. develops into a pretty fly with banded wings ; this is Eurosta solidaginis. The larva hibernates in the gall; the adult emerges in May. The gall of this species is easily distinguished from that of the solidago gall-moth, described in the preceding chapter, by its rounded form The family MICROPEZID^ is represented in America north of Mexico by a few species; most of the species of this family occur in vSouth America. In our representatives of the family, the subcostal vein is distinctly separated from vein Ri ; cell R5 is closed or narrowed at the margin; the head is subspherical; the buccas are broad; the face is retreating; the vibrissae are wanting; and the proboscis is short. The family TANYPEZID^ includes the genus Tanypeza, which differs from the preceding family in that the buccce and the posterior orbits are narrow. The described species are chiefly from South and Central America. These flies are rare in the United States. The family SEPSID^ includes only a few species. These are small slender flies, which are principally scavengers, feeding and breeding in decaying organic matter. They are not rare, and can be obtained by sweeping grass in meadows and pastures, especially where there are droppings of horses and cattle. "Species of Sepsis are particularly abundant and can be found on fresh dung, where they run about with vibrating wings pirouetting in a unique and pretty dance." The family has been monographed by Melander and Spuler ('17). Family PIOPHILID^ This family includes only a few species of small flies, rarely ex- ceeding 5 mm. in length . They are usually glistening black or slightly bluish metallic in luster. They are found about either decaying organic matter, preserved meats, or cheese. The best known species is the following. The cheese-maggot, Piophila cdsei. — This fly lays its eggs on cheese, ham, and bacon. The larvag live in these substances and are often serious pests. They are commonly known as "skippers" on account of the remarkable leaps they can make. This is accomplished by first bringing the head and tail ends together and then suddenly straightening the body; in this way they can leap several inches. DIPTERA 859 The members of this family were formerly included in the Sepsidce. The family Piophilidee was monographed by Melander and Spu- ler ('17). Family PSILID^ The flies of this family are of moderate size and slender. In many of the species the antennje are very long and decumbent, but in others they are of moderate length. The vibrissas are wanting; the costa is interrupted near the end of vein Ri; and cells ist A and M are com- plete and relatively large. Five genera including thirty-three species have been described from our fauna. For a synopsis of the family see Melander ('20 b). The following is our best-known species. The carrot rust-fly, Psila rosce. — The larva of this species infests carrots, celery, parsnips, and parsley. In the case of carrots and pars- nips the larvas perforate the roots in all directions ; their burrows are of a rusty color, hence the common name of the insect. When celery is attacked the fibrous roots are eaten off and destroyed. The family DIOPSID^E is represented in North America only by the following species. The stem-eyed fly, Sphyracephala brevicornis. — This is a very singular fly, which is "found on the leaves of skunk-cabbage and the foliage of other plants in shady glens. On each side of the head there is a lateral process, upon which the eye is situated. The life-history of the species is unknown. The family CANACEID^ is represented in our fauna by a single described species, Cdnace snodgrassi, recorded from New Jersey. Family EPHYDRID^ These are small or very small, black or dark-colored flies, that live in wet places. The subcostal vein is coalescent for the greater part of the length with vein Ri, being distinct only at its proximal end; cells M and ist M2 are not separated by a cross- vein; the hind metatarsi are not thickened and are longer than the following seg- ment ; the vibrissas are wanting; and in some species the mouth cavity is very large. Most of the species live about fresh water; but to this family belong the "Brine-flies" the larvse of which live in salt or strongly alkaline waters. These are common in pools about salt-works ; and in the far West and in Mexico these larvae occur in the alkaline lakes in countless numbers, and are washed ashore in such quantities that bushels of them can be collected. They are gathered by the Indians, who dry them and use them for food, which they call koo-tsabe, accented on the first syllable. The best-known "brine-flies" belong to the genus Ephydra. Still more remarkable are the habits of the larva of the petroleum- riv. Psilopa petrolei, which lives, feeds, and swims about in the pools of crude petroleum, which are numerous in the various oil-fields of 860 AN INTRODUCTION TO ENTOMOLOGY California. For an account of the structure and habits of this larva see Crawford ('12). Family CHLOROPID^ This family includes a considerable number of species that are common in meadows and other places where there is rank growing grass, in such situations they can be collected in large numbers by a sweep-net. The members of this family are small bare species; with moder- ately short or very short wings; the subcostal vein is vestigial cells M and I St M2 are not separated by a cross- vein ; the antenna; are usually short and with the third joint rounded ; the vibriss£c are rarely present ; and the postvertical bristles are convergent. The larva:' of the different species differ in their habits; many species infest the stems of wheat, oats, rye, clover, and grasses; some live in burrows or cavities in plants made by other insects; a few feed upon the egg-shells and cast-off skins of insects; some live in excre- ment; and species of Caurax develop in the egg-sacs of spiders. Among the more important members of this family is the following species. The European frit-fiy, Oscinis frit. — This is a minute black species, measuring from i . i to 2 mm. in length. It was first described by Linnaeus in vSweden, where it was a very serious pest of barley, the larvae feeding upon the immature kernels. The light and worthless kernels resulting from this the Swedes called "frits", hence the com- mon name of the species. There are several generations annually. The larvae of the late fall generation winter as stem miners in winter grain; and spring grain is attacked in the same way by the spring generation. In this country the commonest fr;rm of injury is to the stems of wheat close to the ground. The larva of this species can be easily distinguished from the larva of the hessian fly by the fact that it works in the center of the stem and crawls actively when removed. For a detailed account of this species see Aldrich ('20). This family is named the Oscinida; by some writers. The family ASTEIID^E includes a few genera, mostly exotic, that were formerly classed in the Drosophilidae by some writers and in the Chloropidac (Oscinidae) by others; it can be separated from these families by the characters given in Table B. The best-known representative of the family in our fauna is Sigaloessa Jlaveola, which is widely distributed in the Atlantic states. Family DROSOPHILID^ The Pomace-flies and their Allies. There are certain small yellowish flies from three to four milli- meters in length which are very common about the refuse of cider- mills, decaying fruit, and fermenting vats of grape pomace; these are the pomace-flies (Fig. 1112); their larvae live in the decaying fruit. DIPTERA 861 f Fig. 1 1 12. — A poniacc-fly. The pomace-flies and tlicir allies constitute the family Drosophil- idoc. In tliis family the costa is microscopically broken twice, once just beyond the humeral cross-vein and again just before the end of vein Ri ; the subcostal vein is vestigial ; the arista arc ahuost invariably plu- mose; the vibrissas are present; the postvertical bristles are convergent; and the foremost fronto-orbital bristles are proclinate. The larvcC of most species of this family, so far as is known, live in deca>'ing fruit or in fungi ; a few are leaf-miners; and some exotic species have been fovmd feeding on other insects, Alciirodcs and Clastoptcra. One of the pomace-flies, Drosophila tnelanogastcr, which is easily bred and which has a short life-cycle, is widely used in laboratories in the study of heredity. This species has been commonly known as Drosophila anipelophila; but tnelanogastcr is the older specific name. A monograph of this family was published by Sturtevant ('21). The family GEOMYZID^ is a group of small flies of which nearly fifty species have been described from our fauna. In these flies the postvertical bristles are convergent when present; the clypeus is large, the foremost fronto-orbital bristles are directed backward; and the fringe of the calyi)teres is not dense. The larvre of the few species of which the habits are known live in the stems of plants or mine in leaves. The family was monographed by Melander ('13 b). Family AGROMYZIDvE of Phylomyza aquil- sites of the cottony-cushion scale This family includes small or minute flies in which the costa is broken only at the end of the subcostal vein; the oral vibrissae are present, the arista of the an- tennae is closely short-pubescent, the post-vertical bristles are di- vergent, and the lower fronto- orbital bristles are convergent. The genus Cryptochcctmn dif- fers from the typical members of this family in having the costa twice broken and in that the an- tennaj lack the arista. One or two species of this genus have been introduced into California from Australia, as they are para- 862 AN INTRODUCTION TO ENTOMOLOGY About one hundred species of the Agromyzidce as restricted here have been described from our fauna. See monograph of the family by Melander ('13 b). So far as is known the larvse of most members of this famil}^ feed on Hving plants by forming burrows or mines in various parts of them, but principally in the leaves. A common species, Phyiomyza aquilegice, makes serpentine mines in the leaves of wild columbine. Aquilegia canadensis. (Fig. 11 13). The family MILICHIID^ is a small group of flies that is often classed with the Agromyzidee. The members of this family differ from the agromyzids in that the costa is broken twice, once be- yond the humeral cross-vein at which place there is usually a stronger costal bristle, and again just before the end of vein Ri, and the post vertical bristles are convergent. See monograph of this family by Melander ('13 6). The family OCHTHIPHILID^ is also a small group of flies which is often classed with the Agromyzidse. In this family the oral vibrissas are wanting or not differentiated; the postvertical bristles convergent, the subcostal vein ends in the costa; and the clypeus is small. See monograph of the family by Melander ('13 b). Only thirteen species, representing three genera, are recognized by Melander from our fauna. Larvae of species of Leucopis prey upon aphids and upon coccids. This family is named the Chamsyidae by Hendel ('22). SUBSECTION II.— CALYPTRAT^ The Calyptrate Muscids To this subsection belong our most familiar representatives of the muscid flies, of which the house-fly and the flesh-flies are good illus- trations. In the families included here the alulas or clypteres are well developed or of moderate size, not rudimentary ; the subcostal vein is always distinct in its whole course ; vein Ri is never very short ; there is a complete transverse suture on the thorax; the postalar callus is present and separated by a distinct suture from the dorsum of the thorax; and the abdominal spiracles, with but few exceptions, are in the chitin. The flies are usually of moderate or considerable size, never very small. The subsection Calyptratae includes a series of families that are exceedingly difficult to differentiate. In fact no two of the author- ities on this group of flies agree either as to the number of families that should be recognized or as to the limits of certain families that are generally recognized. This is believed to be due to the fact that this group of flies is of recent origin and the different types included in it have not become segregated by the dropping out of intermediate forms. It is the dominant group of flies, including an immense num- ber of species. DIPTERA 863 Family ANTHOMYIID^ The Anthomyiids The anthomyiids are very common flies of which about five hun- dred species have been described from North America. They are somewhat similar to the house-fly in appearance but structurally distinct. In this family cell R5 of the wings is very slightly or not at all narrowed, vein Mn-2 extending in a nearly straight line to the margin of the wing (Fig.1114) and not bent in its outer part towards the tip of the vein R4+5 as in the house-fly. The hypopleural and often the pteropleural bristles are absent ; and the proboscis is never adapted Fig. 1 1 14. — Wing of Lispa. for bloodsucking. The adult flies are found on leaves and flowers, and are also often found on windows in our dwellings. The larval habits are variable. Most species live in decaying vegetable matter; many live in excrement, and doubtless are convey- ers of typhoid fever, like the house-fly or typhoid-fly. Several species have been found to be the cause of internal myiasis, having been taken into the alimentary canal with vegetables and continuing to live there. A few species are parasitic within living insects. And some attack growing plants. Among the latter are certain well- known pests of garden crops. The more important of these are the following. The cabbage-root maggot, Hylemyia brdssiccB. — This insect in its larval state feeds on the roots of cabbage, radish, turnip, and cauli- flower; it also attacks the roots of various weeds belonging to the same family of plants. There are two or more generations of this pest each year. The first generation infests the young plants; the eggs of the second generation are laid late in June or in July; later generations, if they occur, do but little harm. The most practicable methods of control of this pest are to protect the seed-beds with a covering of cheesecloth in order to exclude the 864 AN INTRODUCTION TO ENTOMOLOGY flies; to protect the plants when they are set out by fitting around the stem of each next to the ground a tarred paper card, these cards can be obtained from seedsmen and dealers in garden supplies; and by the use of a solution of corrosive sublimate crystals, one ounce dis solved in ten gallons of water. Two applications of one-half cupful to a plant are made, one, three or four days after the plants are set, and another eight or ten days later. The solution is poured on the stem and at the base of the plant. Great care should be taken to keep the supply of this poison where children or animals can not get it. The onion maggot, if j'/^nj/a antlqua.— The larva of this species is often exceedingly destructive to onions, destroying young plants in the spring, and when the plants are older, burrowing into the bulb and causing decay. This species is difficult to control. As the flies require from ten days to two weeks after emergence in which to mature their eggs, many of them can be destroyed before they are ready to oviposit by a poisoned bait spray composed of one-fifth ounce sodium arsenite, one pint molasses, and one gallon water. There are two or three generations annually of this pest. The raspberry-cane maggot, Hylemyia rubtvora. — The larva of this species burrows in the new canes of black and red raspberries and blackberries and kills them. The eggs are laid on the young shoots in the spring. The larva bores into the pith of the shoot, and tunnels downward; when about half way to the groimd it girdles the wood beneath the bark. The part of the shoot above the girdle soon wilts, shrinks in size and droops over. The larva continues its burrow downward in the pith to the surface of the ground, transforms to a pupa without leaving its burrow in late June or early July; but the adult does not emerge till the following April. To check the ravages of this pest, cut off and bum the wilting canes as soon as observed. The beet or spinach leaf-miner, Pegomyia hyoscyami. — This leaf miner infests the leaves of beets, sugar-beets, spinach, orach, mangels, and chard. The mine at first is thread-like but is soon enlarged to form a blotch. Several larvae usually occupy the same leaf and their mines usually coalesce. There are several generations each year, and the winter is passed in the pupal state under fallen leaves in the soil. Where practicable the infested leaves should be picked and burned. By plowing the field deeply as soon as the crop is removed the over- wintering pupae can be buried . The kelp-flies, Fucellia.- — -The larvae of these flies live in brown sea-weeds, cast up by waves along ocean beaches. The adults can be found all summer long on the masses of these weeds often in immense nrmibers. The North American species, of which thirteen are known, were monographed by Aldrich ('i8). Family GASTROPHILID^ The Bot-flies of Horses This family includes the well-known pests the larvae of which infest the alimentary canal of horses and which are commonly known DIPTERA 865 as bots. These insects constitute the genus Gastrophilus, three species of which are now well established in the United States and Canada. In the adult flies the oral opening is small and the proboscis vestigial. The members of this genus can be distinguished from those of the following family by the venation of the wings ; the most striking fea- ture of which is that vein Ml +2 extends in a nearly straight line towards the margin of the wing (Fig. 1115). Fig. 1 1 15. — -Wing of Gastrophilus. The genus Gastrophilus has been commonly included in the family CEstridccbut it is now believed to represent a distinct line of develop- ment. The three species that are established in this country are the following. The common bot-fly or the stomach bot, Gastrophilus intestindlis. — The adult fly closely resembles the honey-bee in form except that the female (Fig. 11 16) has the end of the abdomen elongate and bent forward under the body. The wings are transparent with dark spots, those near the center form an irregular, transverse band. This fly is most often seen flying about horses, which have an instinctive fear of it. The eggs are laid on different parts of the host, but preferabh^ on the long hairs investing the inside of the forelegs. The eggs rarely hatch when left untouched; but the horse by scratching the forelegs with the teeth removes the small cap of the egg-shell and inadvert- ently takes the larva into its mouth. The larvae thus taken into the mouth are carried with the food or water to the stomach. When the larvae reach the stomach they fasten themselves to the inner coat of it, and remain there until full-grown. Then they pass from the animal with the dung, and crawl into some protected place, where they transform within a puparium. The adult fly measures about 18 mm. in length. This species is found throughout the United States and Canada where horses are present. It has been commonly known as Gastrophilus equi, but intestinalis is the older specific name. Fig. 1 1 16. 86G A N I NT ROD UCTION TO ENTOMOLOG Y The chin-fly or the throat-bot, Gastrophilus nasdlis. — This species is smaller than the common bot-fly and the wings are not marked with dark spots as in that species. The female usually deposits its eggs upon hairs under the jaws, and for this reason is commonly known as the chin-fly ; but sometimes the eggs are laid upon the flanks or forelegs of the host. The manner in which the larvae reach the mouth of the horse has not been definitely determined; but having reached the mouth they are carried down the alimentary canal. In some cases the larvae attach themselves to the pharynx, and as this is the only species that is known to do this, the larva is known as the throat-bot. But this species is sometimes found in the stomach, and it attaches by preference in the duodenum. When the larvae are matured they pass out from the horse and burrow in the manure or soil to transform. This species is widely distributed in the United States and Canada. The red-tailed bot-fly or the nose-fly, Gastrophilus hcemorrhoiddlis . — The adult fly is easily distinguished by the bright orange-red tip of the abdomen. The wings are unspotted as in the chin-fly but differ from those of both of the preceding species in that the cross-vein m-cu is much farther from the base of the wing than is cross- vein r-m. The female oviposits on the lips of the horse; the flight of the fly about the nose of the horse when attempting to oviposit on its lips, suggested the common name, the nose-fly. The larvae of this species attach themselves during their early stages within the stomach ; but later loosen themselves and reattach in the rectum, from which they gradually move to the anus, where they remain for a short time before dropping to the ground to transform. This species is found in the North-Central and Northern Rocky Mountain States and in the western provinces of Canada. Family CESTRIDyE Bot-Flies {except Gastrophilus) and Warble-Flies This family includes flies that are large or of medium size ; most of the species resemble bees in appearance; some, the honey-bee, others, bumblebees. The mouth-opening is small, and the mouth- parts are usually vestigial. The venation of the wings differs from that of the preceding family in that vein M, +2 is bent so that cell R5 is much narrowed or closed at the margin of the wing. The larvae are parasitic upon mammals ; some develop in tumors under the skin and others, in the pharyngeal and nasal cavities of their hosts. As a rule each species infests a single species of mammal ; and closely allied oestrids are parasitic, in a similar manner, upon closely allied mammals. In addition to the species that infest our domestic animals, other species infest rabbits, squirrels, deer, and reindeer. One that lives beneath the skin of the neck of rabbits is very common in the South. DIPTERA 867 The sheep bot-fly, CEstrus ovis. — This species is viviparous; the female fly deposits larvae, which have hatched within her body, in the nostrils of sheep. The larv^ pass up into the frontal sinuses and into the horns when they are present. Here they feed upon the mucus. They are very injurious to sheep, causing vertigo or the disease known as "staggers." When full-grown they pass out through the nostrils and undergo their transformations beneath the surface of the ground. The ox-warble-flies, Hypoderma hovis and Hypoderma linedtum. — If during the later winter months the backs of cattle be examined by rubbing the hand over them, there will be found present in many cases small lumps or swellings in each of which there is an opening through the skin; these swellings are known as warbles, and each contains a maggot, which when full grown measures nearly or quite 25 mm. in length. The maggots that produce these warbles are the larvas of flies, which for this reason are known as warble-flies. Two species of warble-flies both of which were introduced from Europe, infest cat- tle in this countr}% and are very serious pests. The warble-flies when attempting to oviposit anno\" cattle, which have an instinctive fear of them and run about in an eftort to escape them; this leads to decreased milk yield. The larvae as para- sites injuriously affect the health of the cattle. And the holes in the skin through which the larvce escape from the warbles very seriously reduce the value of the hide when made into leather. A careful estimate made by the Department of Agriculture of Canada showed that the annual loss in value of hides in Canada due to warbles is between 25 and 30 per cent, of the total value of the hides. Our two species of warble -flies have much in common. The adults measure from 12 to 14 mm. in length and are bumblebee-like in appearance. They attach their eggs to hairs of cattle, usually on the hind legs, more rarely on the flanks. The newly hatched larva crawls down to the hair follicle where it penetrates the skin. Later the second instar of the larva is found in the wall of the oesophagus. The exact course of the migration from the hind legs to the oesophagus has not been determined; but it is believed that the larv® travel in the loose connective tissues under the skin to the region of the throat and into the oesophagus where the muscles bifurcate. This part of their migration occupies about four months. They remain in the oesophagus about three months, and then migrate to the lumbar region. This part of the migrations of the larvae is better- known than the earlier part. Hadwen ('19) states as follows: "The last larvae to leave the oesophagus are at the pai'nch end. They pass out under the pleura and go to the neural canal, either up the crura of the diaphragm, or up the posterior border of the ribs entering the canal by the posterior foreamen. The lar\"a evidently makes use of the canal as an easy means of access to the limibar region, the part of of theanimal which is best suited for passing its last stages within the host. The larvce follow connective tissue exclusively , no larvee have been discovered in muscular tissue." 868 AN INTRODUCTION TO ENTOMOLOGY The larvae complete their growth in the lumbar region, causing as they increase in size the formation of the warbles. The hole through the skin into the cavity of the warble serves as a breathing hole for the larva and as a means of escape when it is full-grown. The mature larvse leave the warbles and drop to the ground to transform. This takes place during the first half of the year. The average pupal period is about one month. The adults live only a short time as they are unable to feed. The above account refers to both of our species of warble-flies; the following details chiefly compiled from Hadwen ('19) will serve to distinguish the two. The bomb-fly, Hypoderma bovis. — The adult fly measures 14 mm. in length ; there is yellow hair on the anterior part of the thorax ; the alute are bordered with reddish brown; and the tail end of the abdomen is orange-yellow. As a rule the flies lay their eggs while the cattle are running; the eggs are laid singly at the roots of the hairs ; the flies are clumsy insects and strike at the animals blunder- ingly. The presence of one of these flies in a herd of cattle causes them to scatter and stampede just as a crowd of people would do if a bomb were thrown in their midst. For this reason Mr. R. C. Shan- non ('22) has suggested "bomb-fly" as a common name for this species. The name "European warble-fly" that is often applied to it is not distinctive, as both of our species are of European origin. The eggs are laid mostly on the outside of the hind quarters and on the legs above the fetlocks ; they are laid during June and July. In the larva the segment in front of the spiracular segment is unarmed. The heel-fly, Hypoderma linedtum.- — The adult fly is 12.7 mm. in length ; the anterior part of the thorax is black and shining; the alulae are uniformly white; and the tail end of the abdomen is reddish- orange. The eggs are laid mostly when the animals are recimibent and on all parts which the fly can reach when it is resting on the ground. Even when the animals are standing the fly is able to lay eggs on those hairs which are close to the ground, namely on the heels. The frequency with which this species lays its eggs in this place has caused it to be known as the heel-fly. This species irritates the cattle much less than does Hypoderma bovis, and consequently is able to lay several eggs on a single hair. The eggs are usually laid during May. In the larva the segment in front of the spiracular seg- ment is spinose. Family PHASIID^ The Phasiids This is a comparatively small family, which is composed of certain genera that were formerly included in the Tachinidae but which are now regarded as representatives of a distinct branch of the Muscoidea. In this family the clypeus is more or less produced below the vibrissal angles, like the bridge of a nose. The conjunctivae of the DIPTEFA 869 ventral sclerites of the abdomen are present, and frequently well- developed, surrounding the sclerites. Vein M1+2 is bent so that cell R5 is narrowed or closed at the margin of the wing; in some genera vein Mi+2 joins R44-5 at a considerable distance before the margin of the wing. The abdomen is not armed with macrochaetse. There are only a few records regarding the habits of members of this family. Some species are parasitic on adult Coleoptera, and other on n^-mphs and adults of Hemiptera. Family MEGAPROSOPID^ This is a small group of flies the rank of which is in question ; some authorities regard it as a distinct family and others, as a subfamily of the TachinidcC. With these flies the clypeus is receding and short ; the cheeks are very broad; the vibrissse are located near the middle of the face; and the antennce are short. This family is represented in our fauna by two genera, Mega- prosoptis and Microphthalma. Microphthalma disjuncta has been bred from the larva of Phyllophaga arciiata. Family CALLIPHORID^ The Blow -fly Family Certain members of this family are very familiar objects and are commonly known as blow-flies, bluebottle-flies, or greenbottle-flies. With these, and with most other members of the family as well, the body, especially the abdomen, is metallic blue or green in color. This fact has suggested the common names bluebottle-flies and greenbottle-flies, that have been applied to certain species. These names, however, merely indicate in each case the more usual color of the species; for in all of the metallic colored species of this family the color varies; it may be either violet, green, blue, or copper color. In this family the arista of the antenncC is plumose ; both the hypo- pleural and the pteropleural bristles are present; the hindermost posthumeral bristle is almost always more ventrad in position than the presutural bristle; and the second ventral sclerite of the abdomen lies with its edges upon or in contact with the ventral edges of the corresponding dorsal sclerites. The larvae of the different species vary in habits ; some have been bred from cow-dung; some feed on fresh or decaying meat and on the bodies of dead animals; one frequently infests w^ounds on animals, and two are blood-sucking parasites of nestling birds. The following are our best-known species. The blow-flies Calltphora: — The blow-flies normally live out-of- doors, but they often enter houses in search of material upon which to deposit their eggs. They then attract attention by their large size, much larger than that of the house-fly, and by the buzzing noise that they make. They lay their eggs upon meat, cheese, and other 870 A N INTROD UCTION TO ENTOMOLOG Y provisions. The eggs soon hatch and the larvae develop rapidly. There are several species of this genus in our fauna ; all of them have reddish palpi; bluish black, opaque thorax; metallic blue or green, more or less whitish pollinose abdomen; two or three posthumeral bristles; and black legs. There are two common species CalUpkora erythrocephala, in which the bucca is reddish brown and the beard black ; and CalUphora vomitoria, in which the bucca is black and the beard reddish. The large bluebottle-fly, Cynomyia cadaverma. — This is a com- mon species which resembles the blow-flies in size and in habits; it differs from them in that the abdomen is without silvery pruinosity, and there is only one posthumeral bristle on each side. The greenbottle-fly, LucUia ccesar. — This also is a common species, which resembles the blow-flies in habits; but it is smaller and its cheeks are bare. The abdomen is sometimes bluish but more often greenish. The screw-worm fly, Chrysomyia macellaria. — This is a bright metallic-green fly, with three black stripes on the thorax, and a yellow face. It measures from 8 to lo mm. in length. It lays its eggs on decaying animal matter and also in wounds, sores, and the nostrils and ears of men and cattle. The larvse living in these situations often cause serious sickness, and sometimes even death. This is a widely distributed species ; but it has attracted most attention in the South- western States where it is a serious pest of stock. The cluster-fly, Pollenia rudis. — The cluster-fly is so-called be- cause of its habit of entering houses in the autumn and hiding away in protected nooks in large groups or clusters. It is a dark colored, slow-moving species, slightly larger than the house-fly. The thorax is thickly beset with soft woolly hair in addition to the bristles ; the abdomen is brown with white pollinose spots. The calliphorid parasites of nestling birds, ProtocalUphora. — Two species at least are found in our fauna, P. avium and P. splendida. Both of these have been found to be external blood-sucking parasites of nestling birds, often causing the death of the nestlings. Plath ('19) found that of 63 nests of five species of birds studied by him 39 were infested. Family SARCOPHAGID^ The Sarcophagids This family has been commonly known as the flesh-flies because some of them lay their eggs in bodies of dead animals, resembling in habits the blow-fly, which belongs to the family Calliphoridce ; but a wider knowledge of the habits of various members of this family shows that this name is misleading. The Sarcophagidse as limited by Aldrich ('16) in his monograph of the North American species includes all of the Muscoidea that agree in having the following characteristics : The coloration is gray DIPTERA 871 or silvery, tessellated or changeable pollinose ; vein Mi +2 has an almost angular bend and ends considerably before the apex of the wing; the sides of the face are hairy ; and the arista of the antennas is plumose above and below for nearly half its length or a little more. None of the species has discal machrochgetae on the abdominal segments, hairy eyes, long proboscis, rudimentary palpi, or more than a single pair of discal scutellar bristles. So far as is known all species of this family are larviparous. The different species show a wide range in larval habits; but by far the greater number of the species that have been bred are parasitic in other arthropods. They have been bred from various insects, from scorpions, and from the egg-sacs of spiders. Several species have been bred from dead fish ; and a considerable number from the excre- ment of mammals. Five or six species live only in the tubular cups of pitcher-plants (Sarracenia) , feeding on the dead insects found there. It has been found that Sarcophaga hcBmorrhoiddlis is some- times the source of intestinal myiasis in man, and several cases of cutaneous myiasis caused by larvae of Wohlfdhrtia vigil have been described by Walker ('22 a). For the determination of species of this family one should consult the moEC9Taph by Aldrich ('16). Family TACHINID^ The Tachina-Flies The tachina-fiies are often found about flowers and rank vege- tation. They are usually short, stout and bristly (Fig. 11 17). They differ from the following family, the Mus- cidae, in that with the tachina-flies both the hypopleural and the pteropleural bristles are present; and they differ from the two preceding families, the Calliphor- idae and the Sarcophagidas, in that in this family the second ventral abdominal sclerite, as well as the others, is more or less covered, sometimes wholly, by the edges of the dorsal sclerites. This is a very large family, more than ". ^ ^ u- a £ ^ 1 J J • 1- ^ J r Fig. 1 1 17. — A tachina-fly. fourteen hundred species are listed from f^arva, adult, puparium. North America alone; and from the and eggs upon the fore standpoint of the agriculturist it is the part of an army-worm, most beneficial family of the Diptera. This family includes two subfamilies; the Dexiinae, and the Tachininas, each of which is regarded as a separate family by some v/riters. The larvse are parasitic, chiefly within caterpillars, but they have been bred from members of several other orders of insects. An ex- tended list of tachinid parasites and their hosts is given by Coquillett 872 AN INTRODUCTION TO ENTOMOLOGY ('97). The manner in which the larva finds its way into the body of its host differs greatly in different species of tachinids. Many obser- vations on this have been made at the Gipsy Moth Laboratory and re- ported by Townsend ('08 b). In many species the female fastens her eggs to the skin of the caterpillar (Fig. 11 17); when the larvae hatch they bore their way into their host and live there till they are full-grown. In some of the viviparous species the female punctures the skin of the caterpillar with the sheath of her ovipositor and de- posits the larva within the body of the host. Some species deposit their eggs on the leaves of the food-plant of their host ; these eggs are swallowed when the leaves are eaten. But most remarkable of all is the method practiced by Eupeleteria magnicornis ; this is a viviparous species which infests the larva of the brown-tail moth. It attaches its larvae to the surface of stems and leaves by a thin membranous case, which is cup-shaped and surrounds the anal end of the larva. Attached to the stem or leaf by this base, the maggot is able to reach out in all directions as far as its length will permit. As the maggot is deposited on the silken thread with which the caterpillar marks its trail as it leaves its nest, it is in a position where it can attach itself to the caterpillar when it is on its way back to the nest. Family MUSCID^ The Typical Muscids To this family belong the house-fly and many other well-known members of the Muscoidea. In this family either the hypopleural or the pteropleural bristles are present, the basal bristles of the ab- domen are reduced, and the arista of the antennae are plumose to the tip. Among the more important species are the following. The house-fly or typhoid-fly, Musca domestica. — This is the most familiar representative of the order Diptera, as it abounds in our dwelHngs. The flies lay their eggs preferably on horse-manure, but will oviposit on other decaying vegetable matter, when horse-manure is not available. • A single female may deposit from 120 to 160 eggs at one laying, and they have been observed to make as many as four layings: The larvae become full-grown in from five to seven days; the pupa state lasts from five to seven days; and in about fourteen days after the flies emerge they are ready to oviposit. Hence there may be at least a generation a month during the warm season ; and from a few overwintering flies an immense number may be developed. The house-fly is not only an exceedingly annoying pest in our dwel- lings, but as it will breed in human excrement, especially where there are open closets, it is doubtless often a carrier of the germs of typhoid fever, dysentery, and other enteric diseases. For these reasons Dr. Howard has suggested that this species be known as the typhoid-fly and the "Swat-the-fly" crusades have been urged. Various means of protection from this pest, as window-screens and different kinds of traps, are well-known; but as Howard has so well put it, "the truest DIPTERA 873 and simplest way of attacking the fly problem is to prevent them from breeding, by the treatment or abolition of all places in which they can breed." Garbage cans should be kept tightly closed and emptied at least once a week. Manure should be stored in tight receptacles or treated with borax, one-half pound of borax to eight bushels of manure. The borax should be applied immediately after the removal of the manure from the barn. Apply the borax particularly around the edges of the pile with a flour sifter or any fine sieve, and sprinkle two or three gallons of water over the borax treated manure. It is estimated that the cost of the borax will be about one cent per horse per day, (Cook, Hutchison, and Scales '14). The stable-fly, Stomoxys calcitrans: — This species resembles the house-fly in appearance, but it is a trifle larger and has its mouth- parts fitted for piercing and for sucking blood. It annoys cattle greatly; and before storms and in the autumn it enters our dwellings and attacks us. The popular belief that the house-fly bites more viciously just before a rain is due to invasions of this species at such times. The mouth-parts of the true house-fly are not fitted for pierc- ing. The stable-fly is especially common in barns. It breeds in vegetable refuse, manure and excrement. The horn-fly, Hcematdbia trritans. — This is an exceedingly annoy- ing pest of homed cattle. It resembles the house-fly in appearance, but is less than half as large. These flies cluster in great nimibers around the base of the horns; they also settle upon the back. The larvse live in fresh cow-manure. The flies can be killed by spraying the cattle with kerosene emulsion or with crude petroleum. The tsetse-fly, Glossma morsitans. — This species, which is closely allied to the stable-fly, is widely distributed in Africa and is the carrier of the blood parasite that causes the disease of cattle known as nagana and the sleeping sickness of man. SECTION II— PUPIPARA Under this head are classed several families of flies that are para- sitic in the adult state. In most cases the adults live like lice on the bodies of birds or of mammals ; but two species are parasites of the honey-bee. The name Pupipara was suggested by the fact that in the best -known forms the larvse attain their full growth within the body of the female fly, where they are nourished by the product of glands specialized for this purpose. It was formerly believed that the young are born as pupae ; but it is now known that the change to the pupa state does not take place until after the larva is born. It is also known that this remarkable manner of development is not re- stricted to this group of families as it is characteristic also of the tsetse-fly. But the name Pupipara has been so generally used for this group of families that it seems best to retain it. In the Pupipara the eyes are never large and in some forms they are either vestigial or wanting ; the ocelli are present in some genera in others they are wanting. The antennas are apparently only one- or 874 AN INTRODUCTION TO ENTOMOLOGY two-jointed, and in some genera lack the arista; the mouth-parts are short and not at all retractile ; the wings are well developed in some forms, in others they are vestigial or wanting ; the abdomen is indis- tinctly segmented in most cases and leathery in appearance. Family HIPPOBOSCID^ The Louse-Flies The louse-flies are very abnormal flies that, in the adult state, live like lice, parasitically, upon the bodies of birds and mammals. Some species are winged, others are wingless, and still others are winged for a time and then lose their wings. The body is depressed ; the head is closely attached to the thorax which is notched to receive it. The antennas are apparently one- jointed, with a terminal arista or style; they are situated in depres- 2dyl Fig. 1118. — Wing of Lynchia. sions near the mouth. The legs are broadly separated by the sternum ; they are comparatively short and stout; the tarsal claws are strong and are often furnished with teeth. The winged forms vary greatly in the venation of the wings. The veins near the costal border are usually strong while the others are weak. Figure 1 1 18 represents the venation of Lynchia. The sheep-tick, Melophagns ovhius. — This well-known pest of sheep is the most common member of the Hippoboscidas found in this country. It is wingless and its halteres are vestigial (Fig. 1 1 19). It is about 6 mm. in length, of a reddish or gray-brown color, and with the entire body covered with long bristly hairs. This pest is often very injurious, especially to lambs after shearing time, as it tends to migrate from the old sheep to the lambs at this period. The life-history of this species illustrates well that type of development which suggested the name Pupi- para for the Hippoboscidas and allied flies. The struc- ture of the female genital tract is described by Pratt ('99). A striking feature of it is the presence of two pairs of much branched glands, Fig. 1 1 19. DIPTERA 875 the "milk-glands", which secrete a fluid for the nourishment of the larva. The larv^ become full-grown in the uterus of the female and are bom one at a time at intervals of several weeks. In about twelve hours after the larva is born the pupariimi is completed; and the adult emerges in from nineteen to twenty-four da}'S later. To control this pest the sheep should be dipped twice after shear- ing, in some good "dip" of which several kinds are on the market (See Farmers' Bull. 798, U. S. Dept. Agr.) Among the more common representatives of this family, besides the sheep-tick, found in this country are the following. Lynchia americdna. — This is a yellowish winged species rather common on owls and other raptorial birds, and on the partridge or ruffed grouse. Lipoptena depressa. — This species is found on deer. The young adults are winged and probably fly about in search of their host ; but later after becoming established on a deer they shed their wings. Family STREBLID^ The Bat-Ticks in part This family and the following one include small flies that are parasitic upon bats. In this family the head is of moderate size, with a freely movable neck, but is not bent back upon the dorsum of the thorax, as in the following family. The eyes are vestigial or wanting; the ocelli are wanting; the palpi are broad and project leaf- like in front of the head ; the wings are sometimes wanting or vestigial. In this family, as in the Hippoboscidce, the larva becomes fully grown within the body of the parent female. For figures and descriptions of some of our species of this family see Ferris ('16). The genus Ascodipteron, species of which are found in the AustraHan region and in other parts of the Eastern Hemisphere, is of great interest, because the females become endoparasites. The adults of both sexes are winged at first. Later the female, probably after copulation, cuts a hole through the skin of a bat and after shedding her wings and legs nearly completely imbeds herself in her host. The insect then increases greatly in size and becomes a flask-shaped creature, both head and thorax becoming invaginated so that they are not visible. The caudal end of the body projects from the cavity in which the insect lies. The larvs, which become full-grown one at a time, are ejected from the uterus and fall to the ground, where they pupate. For a more detailed account see Muir ('12). Family NYCTERIBIID^ The Bat-Ticks in part This family includes small, spider-like, wingless flies, which are parasitic upon bats. The head is narrow, and when at rest is folded back in a groove on the dorsimi of the thorax. The e}"es and ocelli are vestigial; the antennas are short and only two-jointed; the legs are long, and the tarsal claws of ordinary form; although these insects are wingless, the halteres are present, but sometimes vestigial. 876 AN INTRODUCTION TO ENTOMOLOGY The reproduction of these flies is of the pupiparous type. When the mature larva is born it is fastened in some cases to the host, (Muir, '12) and in others the female leaves the host for a short time and fastens the larva to the perch to which the bats cling (Scott, '17). In each case the larva is pressed against the supporting object to which it adheres firmly. Only a few species have been found in this country, for figures and descriptions of these see Ferris ('16 and '24). Family BRAULID^ The Bee-Lice This family includes only a single genus, is only one well-known species, Braula cceca. Braula, of which there This is a minute insect, 1.5 mm. in length, which is parasitic up- on the honey-bee (Fig. 1 120). It is found clinging to the thorax of queens and drones. It is wingless and also lacks halteres; the head is large ; the ocelli are wanting; the eyes are vestigial; the legs are comparatively short; and the last segment of the tarsi is furnished with a pair of comb-like ap- pendages. The bee-louse was described by Reaimiur nearly two hundred years ago and remained the only known species of this family till 1914, when another species, Braula kohli, was described from the Belgian Kongo; this species is parasitic on an African honey-bee, Apis mellifica var. adamsoni. The affinities of this family are in doubt. Until recently Braula has been supposed to be similar in its mode of development to the sheep tick, and for this reason the family classed with the Pupipara. But it is now known that Braula lays eggs; and the developmental stages have been found in tunnels under the capping of sealed honey (See "Monthly Letter" of the U. S. Bureau of Entomology, Number 113, September 1923). It is maintained by both Bomer and Bezzi that Braula should be classed near the Phoridas. But Muggenburg ('92) has shown that there is a ptilinum in this genus. It, therefore, does not belong to the series Aschiza. Fig. 1 120. — Braula ccBCca. (From Starp after Mein- ert.) CHAPTER XXIX ORDER SIPHONAPTERA* The Fleas The members of this order are small, wingless insects, in which the body is laterally compressed, so that the transverse diameter is small, the vertical one great. The mouth-parts are formed for piercing and suck- ing. The metamorphosis is complete. The name of this order refers to the form of the mouth-parts and to the wingless condition of these insects. These tiny tormentors are best known to us in the adult state; for it is only "the adults that annoy us and our household pets. The larv^as and pupae are rarely observed except by students who search for them. The body of the adult is oval and greatly compressed, which allows the insect to glide through the narrow spaces between the hairs of its host. The integtmient is smooth, quite hard, and armed with bristles, which are arranged with great regularity (Fig. 1 1 2 1 ) and thus afford good characters for distinguishing the different species. The smoothness and firmness of the body make it easy for the insect to escape when caught between the fingers of man or the teeth of lower animals. When once out of the clutch of an enemy it quickly leaps away. _ Fig. 1121.— The dog-flea and The head is broadly joined to the thor- ax. There are no compomid eyes; but on each side of the head there is usually an unfaceted eye; these, however, are sometimes wanting. Each antenna lies in a groove somewhat behind and above the e^^e (Fig. 1122). The antennae are three-jointed; the third joint, the flagellum, often called the club, may be unsegmented, segmented on the posterior border only, or completely segmented into several, usually nine, more or less separate pseudo-segments (Fig. 11237!). There is usually an internal thicken- ing of the body-wall extending over the vertex from one antennal groove to the other (Fig. 1122, /), this is known as the falx or sickle- shaped process. That part of the dorsal wall of the head in front of the antennal groove and this thickening is termed, by writers on the Siphonaptera, the/row5; the part behind them, the occiput; and the lateral aspects of the head, below and behind the eyes, the gencB or cheeks. A remarkable feature of the head of the Siphonaptera is the fact that in the more generalized forms it is divided into two distinct *Siphonaptera : siphon (a-i), wmg. (884) HYMENOPTERA 885 The membranous nature of the wings, which suggested the name of the order, is not a distinctive characteristic, for it is possessed by the wings of many other insects. The two pairs of wings are similar in texture. The wings of each side are held together by a row of hooks, the hamuli, on the front mar- Fig. 1 1 26. — The veins of a typical hymenopterous wing. gin of the hind wing (Fig. 11 25); these hooks fasten to a fold in the hind margin of the front wing, so that the two wings present a continuous surface. The hind wings are smaller than the fore wings and have a more reduced venation. Some forms are apterous. This is one of the orders in which in the specialization of the wings the wing-venation is reduced. In the more generalized members of the order this reduction of the wing-venation is slight, but in the more specialized forms it is extreme. Even in the more generalized forms, where nearly all of the veins are preserved, the courses of the branches of the forked veins have been greatly modified. This has been brought about by the coalescence of veins from the margin of Pig. 1 127. — The cells of a typical hymenopterous wing. the wing inward. To understand this one should study a series? of wings of Diptera in which all stages of the modification of the venation in this way are illustrated, for in the H}Tnenoptera only the later stages are shown. The series of figures illustrating the coalescence of veins Cu2 and 2d A in the Diptera will aid in understanding what has happened in the Hymenoptera. Figures 1126 and 11 27 represent what may be regarded as a AN INTRODUCTION TO ENTOMOLOGY typical hymenopterous wing; in the former the veins are lettered, in the latter, the cells. These are figures of a fore wing of Pamphilius (Fig. 1135) except that vein R2, which is lacking in this genus, is added. This vein is well preserved in Macroxyela (Fig. 1134); but in Macroxyela vein Cu2 is lost ; the position of the last forking of the cubitus is indicated, however, by a bend in this vein. In these figures of the typical hjinenopterous wing the lines indicating the course of the free part of media, after it separates from radius, are crossed by short lines. The cells marked m, ni, m, in Figure 11 27 are termed the marginal cells; and those marked sm, sm, sm, sm, the suhmarginal cells; the three cells, M4, ist M2, and M3 are termed the discal cells. The working out of the various ways in which the wing-venation has been reduced in the more specialized families is an exceedingly difficult problem, one that is beyond the scope of this book. A general discussion of it has been published by the writer (Comstock '18); a special paper on the venation of the Chalastogastra has been pub- lished by Professor A. D. AlacGillivray ('06); and a very detailed account of the modifications of the wing-venation in the Clistogastra has been prepared by Professor J. C. Bradley and will probably soon be published. The mouth-parts are formed for chewing in all Hymenoptera, and in the more specialized members of the order they are fitted for both chewing and for sucking or lapping liquid food. In the saw-flies, for example, the mouth-parts resemble quite closely the orthopterous type, while in the bees they differ markedly from this type; and intermediate forms exhibit intermediate degrees of modification of the mouth-parts. In the long-tongued bees the labrum and man- dibles retain the form characteristic of chewing in- sects and the mandibles function as organs for crush- ing or cutting; but the labium and maxilla; are elon- gated , the maxilte form a sheath to the labium , the three organs thus constituting a suctorial apparatus (Fig. 1 1 28). In this figure the maxillse are repre- sented separated from the labium. The legs of the H\Tnenoptera present characters that are much used in the classification of these in- sects. Among the more striking of these are the fol- lowing ; the trochanter may consist of two segments (Fig. 67, B) or of only one; the metatarsus of thehind legs is greatly enlarged in bees (Fig. 67, C); and in several families the fore legs are fitted with an organ which is used in cleaning the antennae, the antenna cleaner or strigilis. This consists of a curved, Fig. 1 1 28. —Head of a honey-bee: a, antenna; c, clypeus; u, lab- rum; m, man- dible; mx, max- illa; p, labial palpus, /, la- bium. HYMENOPTERA 887 Fig. 1 129. — Leg of an ant, and strigilis enlarged. (From A. B. Comstock, Hand- book of Nature Study.) comb-like, movable spur on the distal end of the fore tibia (Fig. 1 1 29) and opposite this, on the base of the metatarsus, a concavity fringed with hairs. In cleaning an antenna it is drawn through the space be- tween these two parts of the strigilis. In addition to the terms defined above the following are used in descriptions of Hy- menoptera. The malar space. — The area on each side of the head includ- ed between the proximal end of the mandible and the ventral end of the compound eye. The propodeum. — The first abdominal segment when it forms a part of the alitrunk or wing-bearing region of the body. See characterization of the suborder Clistogastra. This is often called the epinotiim by writers on ants. The parapsides or scdpid<£: — In many H^-menoptera the prescutimi of the mesothorax is prolonged backward to a greater or less extent ; in some it extends a considerable distance toward the scutellum but does not reach it (Fig. 1130, B) ; in others it reaches the scu- tellum dividing the scutimi into two parts (Fig. 1130, A); these separated halves of the scutum are commonly called the parap- sides or scapulcB. (Fig. 1130, par) The pardpsidal Jurrows or no- tauli. — The sutures separating the prescuttun from the parapsides. (Fig. 1 130, p.f). The posterior lobes of the pro- notum. — A distinctly differenti- ated rounded lobe, on each side covering the spiracle, which forms the lateral extension of the pro- notum of Sphecoidea. The prepectus. — An area along the cephalic margin of the epi- stemimi of the mesothorax which in some Hymenoptera is separated by a suture-like furrow. The epicnemium.— This is the same part as the prepectus. The cenchri. — A pair of membranous lobes or areas on the meta- notum of all Chalastogastra. Fig. 1 130. — A. Mesonotum of Eury- toma. B. Mesonotum of Cimbex. (After Snodgrass.) psc, prescutum, set, scutum, par, parapsides; p.f, parapsidal furrows. 888 AN INTRODUCTION TO ENTOMOLOGY The gaster. — The swollen portion of the abdomen behind the pedi- cel in the suborder Clistogastra. The pygidial area. — In many of the aculeate or stinging Hymen- opetra there is an area on the pygidivim which is bounded on each side by a carina, the two carinas meeting posteriorly on the middle line of the segment ; this area is known as the pygidial area. The anal lobe. — The posterior lobe of the wings, which is defined on page 6i (Fig. 71, /) is also called the anal lobe. In the suborder Clistogastra the presence or absence of an anal lobe in the hind wings is an important taxonomic character. The preaxillary excision. — In the hind wings of some H^-menoptera there is in addition to the axillary excision, defined on page 61, an- other notch, the preaxillary excision. In the hind wings of the Hymenoptera the axillary excision, when present, is at the apex of ae pae Fig. 1 13 1. — Wings of Elis: ae, axillary excision; pae, preaxillary excision. the second anal furrow, which lies between the second and the third anal veins (Fig. 1131, ae); the notch may be present in forms in which' both the furrow and the veins are lacking. The preaxillary excision is situated at the apex of the first anal fold, which is just cephalad of the first anal vein (Fig. 1131, pae). The preanal lobe.— That portion of the anal area of the hind wings that lies between the axillary excision and the preaxillary excision constitutes the preanal lobe. In the Hymenoptera the metamorphosis is complete. The larvae of the Chalastogastra are caterpillar-like in form and are furnished with thoracic legs and usually with abdominal prolegs ; but in some, mostly borers or internal feeders, the prolegs are wanting. In all H YMENOP TERA 889 Clistogastra the larvas are maggot-like in form and have no legs. The pupae are of the exarate type, that is, the legs and wings are free, as in the Coleoptera. With many species the larva, before changing to a pupa, spins a cocoon about its body. With some this cocoon is composed of comparatively loose silk, and resembles somewhat the cocoon of a moth. In others the cocoon is of a dense parchment-like texture, and in still others it resembles a very delicate foil. Parthenogenesis. — The production of young by females that have not mated is known to occur in members of several families of this order. In some species the young thus produced are all males; in others they are all females; and in still others both males and females are developed from unfertilized ej"gs. Among the well-known examples of parthenogenetic reproduction are the following. Some- times a queen honey-bee produces eggs before she has mated; from such eggs only males are developed. The eggs produced by fertile worker bees and fertile worker ants, neither of which mate, develop only into males. In certain gall- flies there is an alternation of a generation consisting of males and females and a generation consisting only of females, which reproduce parthenogenetically; the young of the latter are males and females. In some species of the Tenthred- inidce the reproduction is believed to be entirely parthenogenetic, males of these species being unknown. Polyembryony. — In several genera of minute parasitic Hymenoptera the number of young produced is not dependent upon the number of eggs laid, for with these insects many embryos are developed from a single egg. This type of development is termed polyembryony; and has been investigated by several workers. A recent paper on this subject is that of Dr. R. W. Leiby {'22), in which there is a list of the earlier papers. Dr. Leiby traced the development of Copidosoma gelechice, a parasite of the solidago gall-moth, the insect that makes the spindle-shaped gall on golden-rod (Fig. 769). The parasite oviposits in the eggs of the moth which it finds on leaves or stems of goldenrod in early fall. By the arrival of cold weather the developing egg or parasite body is found as a polynuclear mass within the completely formed host embryo, which has developed synchronously. When the host larva hatches in the spring the parasite body is found lodged in the fat-body of the host. As the host larva grows the polygermal mass becomes a mass of embryos, which are later set free into the body-cavity of the host larva as parasitic larvae. These larvae feed upon the body content of the host devouring the blood, muscles, fatty tissue, and in fact everything except the chitinous parts. An average of 163 adult-parasites is developed from a single egg. The details of this development are described at length by Dr. Leiby and are illus- trated by many figures. In a later paper Dr. Leiby and C. C. Hill ('23) described the development of Platygaster heimales, a parasite of the Hessian fly. From some of the eggs of this parasite a single larva is developed; but from others two larvae are produced. This species is of great interest as illustrating the beginning of polyembryony. Aquatic Hymenoptera. — It has long been known that the adults of certain parasitic Hymenoptera descend beneath the surface of water in order to ovi- posit. One of these is a parasite of caddice-worms, the others whose hosts are known lay their eggs in the eggs of various aquatic insects. Most of the observa- tions on these insects have been made in Europe but recently Professors Mathe- son and Crosby ('12) have described the habits of three minute species which have been reared at Ithaca, N. Y.; they also give a list of the known aquatic Hymenoptera. The classification of the Hymenoptera. — The classification of the Hymenoptera, i. e., the sequence of the families and the groupings of these families into superfamilies, adopted in this chapter is that recently worked out by Messrs. J. C. Bradley, S. A. Rohwer, and J. Bequaert. Authorities are not in agreement as to the proper application of certain generic family and other group names in the order Hymenoptera. The matter is a 890 AN INTRODUCTION TO ENTOMOLOGY technical one, and is before the International Commission on Zoological Nomen- clature for a definite decision. Until such a decision is rendered, we prefer to re- tain tne long established usage of these names, as indicated below, where is also shown the equivalent name used by some recent authors. Argidae instead of Cryptida) for a family of sawflies. CimbicidtE instead of Crabronid^ for a family of sawflies. Proctotrupidee instead of Serphidas for a family of parasitic wasps. Proctotrupoidea instead of Serphoidca for a superfamily of parasitic wasps. Ceraphronidae instead of CalliceratidEe for a family of parasitic wasps. Toryminae instead of ailimominae for a subfamily of chalcid-flies. Lasius instead of Acanthornyops or Donisthorpea for a genus of ants. Pompilidae instead of Psammocharidse for the family of spider-wasps. Bethylidae instead of Psilidae for a family of parasitic wasps. Prosopidas instead of Hylasidaj for a family of bees. Prosopis instead of Hylteus for a genus of bees. Bombidaj instead of Bremidae for the family of bumblebees. Bombus instead of Bremus for a genus of bees. Anthophora instead of Lasius or Podalirius for a genus of bees. Ammophila instead of Sphex for a genus of thread-waisted wasps. SYNOPSIS OF THE HYMENOPTERA Suborder CHALASTOGASTRA. The sawflies and horn-tails, p. 891. The Xyelid sawflies. p. 896 Family Xyelid^e The Web-spinning and the leaf-rolling Sawflies. p. 897. .Family Pamphiilid^ The Horn-tails, p. 898 Family Siricid^ The Xiphydriid sawflies. p. 899 Family Xiphydriid^ The Stem Sawflies. p. 900 Family Cephid^ The Cimbicid Sawflies. p. 902 Family Cimbicid^ The Typical Sawflies. p. 902 Family Tenthredinid^ The Argid Sawflies. p. 904 Family Argid^ The Oryssids. p. 905 Family OryssiDvE Suborder Clistogastr.v or Apocrita. Superfamily Ichneumonoidea The Stephanids. p. 919 Family Stephanid^ The Braconids. p. 919 Family Braconid.^ The Ichneumon-flies, p. 922 Family Ichneumonid.^ The TrigonaUds. p. 929 Family Trigonalid/E The Aulacids. p. 929 Family Aulacid^ The Gasteruptiids. p. 930 Family GASTERUPTiiDyE Superfamily Proctotrupoidea. The Roproniids. p. 931 Family ROPRONIID^ The Helorids. p. 931 Family Helorid^ The Vanhorniids. p. 931 Family Vanhorniid^ The Proctotrupids. p. 931 Family Proctotrupid^ The Belytids. p. 932 Family Belytid^ The Ceraphronids. p. 932 Family Ceraphronid^ The Pelecinids. p. 932 Family Pelecinid^ The Scelionids. p. 933 Family Scelionid^ The Platygasterids. p. 933 Family Platygasterid^ Superfamily Cynipoidea. The Cynipids. The Gall-flics or Gall-wasps and their Allies, p. 934 Family Cynipids Superfamily Chalcidoide.\. The Chalcid-flies. p. 941 Family Chalcidid^ Superfamily Evanioidea. The Ensign-flies, p. 949 Family EvANilD^ Superfamily Vespoidea. The Vespoid-wasps. The vSpider-wasps. p. 950 Family Pompilidae The Embolemids. p. 951 Family Embolemid^ The Cleptids. p. 951 Family Cleptid^ HYMENOPTERA 891 The Cuckoo- wasps, p. 951 Family Chrysidid^ The Anthoboscids. p. 952 Family ANTHOBOSCiDyE The Sapygids. p. 952 Family Sapygid^ The Thynnids. p. 952 Family Thynnid^ The Tiphiids. p. 953 Family Tiphiid^ The Velvet-ants. p. 953 Family Mutillid^ The Scoliids. p. 954 Family Scoliid/E The Ants. p. 954 Family Formicid^ The BethyHds. p. 965 Family Bethylid^ The Rhopalosomids. p. 965 Family Rhopalosomid/E The Typical Wasps or Diploptera. p. 965 Family Vespid^ Superfamily Sphecoidea. The Sphecoid-wasp and the Bees. I. The vSphecoid-Wasps. The AmpuHcids. p. 978 Family Ampulicid^ The Dryinids. p. 978 Family Dryinid^ The Typical Sphecoid- wasps, p. 979 Family Sphecid^ II. The Bees. p. 989 The Bifid-tongued Bees. p. 993 Family PROSopiDyE The Andrenids. p. 995 Family Andrenid/E The Leaf-cutter Bees and their Allies, p. 999 Family Megachilid^ The Bumblebees, p. looi Family Bombid^ The Honey-bees. p. 1005 Family Apid^ KEY TO THE SUBORDERS OF HYMENOPTERA A. Base of abdomen not slender but broadly joined to the thorax by a more or less immovable joint; subanal vein of the fore wing present (except in the genus Acordulecera) ; wings always present, p. 894. Suborder Chalastogastra AA. Base of the abdomen constricted to a slender pedicel and joined to the thorax (alitrunk) by a narrow movable joint; subanal vein of the fore wings absent; wings often absent, p. 907 Suborder Clistogastra KEY TO THE FAMILIES OF CHALASTOGASTRA By Dr. H. K. Townes A. Front tibia with two apical spurs; body usually rather short and broad. B. Third antennal segment very long, about as long as or longer than all of the following segments together; fore wing usually with vein Ro. p. 896. Xyelid^ BB. Third segment of antenna not remarkably long or the antenna consisting of three segments only; fore wing without vein R2. C. Subcostal vein present and distinct; antenna with thirteen or more segments, filiform, p. 897 Pamphiliid^ CC. Subcostal vein absent or present as a trace; antenna either with less than thirteen segments or pectinate or serrate. D. Antenna ending in a knob; abdomen with the lateral margin sharp. p. 902 ClMBICID^ DD. Antenna not ending in a knob, filiform, somewhat enlarged toward the tip, or of other form; abdomen with the lateral margin rounded. E. Antenna with three, six, or thirteen or more segments, p. 904. Argid^ EE. Antenna with seven to twelve segments, p. 902 . TENTHREDiNiDiE AA. Front tibia with one apical spur; body usually more elongate. B. Antenna attached under a ridge just above the mouth, apparently arising from the mouth, p. 905 Oryssid^ BB. Antenna attached normally, near the middle of the face. C. Abdomen terminating in a hard spike-like or triangular point (in females, above the ovipositor), p. 898 SiRlciDiE CC. Abdomen not terminating in a hard point. D. Pronotum rectangular, saddle-shaped, with lateral and dorsal surfaces; abdomen compressed, p. 900 Cephid^e DD. Pronotum a narrow collar extending around the front of the thorax, presenting a lateral and cephalic but no dorsal surfaces ; abdomen cylin- drical, p. 899 XiPHVDRIIDiE 892 AN INTRODUCTION TO ENTOMOLOGY KEY TO THE FAMILIES OF THE COMMONER CLISTOGASTRA* Bv Dr. H. K. Townes A. Wings present. B. Either the antenna with more than thirteen segments or the hind wing without closed cells ( = cells completely surrounded by veins) ; legs usually with two trochanters (parasitic Hymenoptera). C. Antenna with seventeen or more segments, rarely as few as fifteen; costal cell of front wing obliterated by the fusion or close approximation of the costal and R + M veins; hind wing nearly always with closed cells. D. Fore wing with vein M2 so that cells Mi and i st M2 are separate, p . 922 ICHNEUMONID^ DD. Fore wing lacking vein M2, cells Mi and ist M2 confluent, p. 919 Braconid^ CC. Antenna with sixteen or fewer segments; costal cell of fore wing present though usually very narrow, or rarely completely absent. D. Abdomen attached high on the thorax (alitrunk) so that there is quite a distance between its base and the bases of the hind coxse. E. First abdominal segment cylindrical, set off from the rest of the abdomen which is small and oval ; anallobe present, p. 949.Evaniid^ EE. First abdominal segment gradually enlarged toward the apex, not set off from the rest of the abdomen; anal lobe absent. F. Hind tibia strongly swollen toward the tip; fore wing can be folded lengthwise, p. 930 Gasteruptiid^ FF. Hind tibia not swollen toward the tip; fore wing can not be folded, p. 929 AuLACiD^ DD. Abdomen attached low on the thorax so that its base is next to those of the hind coxag. E. Hind margin of hind wing with a deep notch which sets off an "anal lobe." F. Body metallic greenish or bluish; abdomen with three or rarely four exposed tergites and concave beneath, p. 951. .CHRYsmiDiE FF. Body not greenish or bluish; abdomen with more than four ex- posed tergites and convex beneath. G. Antenna with ten segments; front tarsus of female usually chelate, p. 978 Drvinid^ GG. Antenna with twelve or thirteen segments; front tarsus of female simple, p. 965 Bethylid^ EE. Hind margin of hind wing without a notch. F. Hind corner of pronotum not reaching the tegula, separated from it by a more or less distinct sclerite, the prepectus; middle tibia with one apical spur or rarely none; fore wing with only a single distinct vein which is usually forked at the tip; antenna elbowed. p. 941 Chalcidid^ FF. Hind corner of pronotum reaching the tegula, the prepectus absent ; middle tibia usually with two apical spurs ; antenna usually not elbowed. G. Abdomen more or less compressed, polished, and most of it covered by a single tergite; costal vein absent; cell 2d Ri + R2 large, p. 934 Cvnipid^ GG. Abdomen cylindrical or depressed; costal vein present or cell 2d Ri + Ro small or absent. (Proctotrupoidea) H. First segment of hind tarsus one fourth as long as the second; second to fourth abdominal segments of female each as long as the head and thorax together; abdomen of male shorter and clavate; large species, p. 932 Pelecinid^ HH. First segment of hind tarsus longer than the second; second to fourth segments of abdomen not exceedingly long; mostly very small species, (other families of Proctotrupoidea) ^_ See other key at II on page 909. *A complete key to the Clistogastra including the uncommon and aberrant forms will be found on page 908. HYMENOPTERA 893 BB. Antenna with thirteen or fewer segments; hind wing with closed cells; legs each with a single trochanter (aculeate or stinging Hymenoptera). C. Hind corner of pronotum not in the form of a rounded lobe and always extending back to touch the tegula (Fig. 1195, A). D. An erect scale or one or two knot-like swellings on the stalk between the main body of the abdomen and the thorax (alitrunk); front wing without vein M2 . . . (ants), p. 954 Formicid.^ DD. No scale or node between the abdomen and the thorax; front wing with vein M2; antenna usually with twelve segments in the female and thirteen in the male. E. Cell M4 of fore wing longer than cell Cu + Cui (Fig. 1182); wings can usually be folded lengthwise, p. 965 Vespid^ EE. Cell M4 of fore wing shorter than cell Cu + Cui; wings can not be folded. F. Mesopleurum divided by a transverse groove into an upper and a lower half; legs unusually long, the hind femur reaching approxi- mately to the tip of the abdomen, p. 950 P0MPILID.E FF. Mesopleurum not divided by a transverse groove; legs shorter. G. Hind coxae widely separated by the broad plate-like metaster- num which overlaps their bases; apical part of wing membrane with fine parallel ridges; eye margin strongly notched opposite the antenna, p. 954 Scoliid^ GG . Hind coxae not widely separated and not overlapped at the base. H. Antenna with twelve segments (females), p. 953.Tiphiid^ HH. Antenna with thirteen segments (males). I. Abdomen without any or with two visible terminal spines. p. 953 '. MUTILLID^E II. Abdomen with a single upcurved terminal spine, p. 953. TlPHIID^ CC. Hind corner of pronotum in the form of a rounded lobe and not touching the tegula (Fig. 1195, B). If the thorax is so hairy that the pronotum is invisible, the specimen is a bee and belongs here. D. First segment of hind tarsus not dilated; hairs not plumose; abdomen often petiolate. p. 979 Sphecid^ DD. First segment of hind tarsus enlarged and flattened; some of the hairs plumose, especially those on top of the thorax . . . (bees). E. Hind tibia without apical spurs . . . (honey-bee), p. 1005. Apid^ EE. Hind tibia with apical spurs. F. Cell below the stigma of fore wing with a hair-like line extending downward from the base of the stigma; anal lobe absent; hind tibia of females and workers with a corbicula except in Psithyrus . . . (bumblebees), p. looi Bombid^e FF. Cell below the stigma of fore wing without a hair-like line or the hind wing with an anal lobe; hind tibia without a corbicula. G. Tongue short, its apex divided (bifid), p. 993. . . . Prosopid^ GG. Tongue long or short but its apex never divided and fre- quently pointed. H. Front wing with three cells beneath the stigma and the cell beyond the stigma, p. 995 Andrenid^ HH. Front wing with two cells beneath the stigma and the cell beyond the stigma. I. Labrum not large and free, usually entirely concealed by the clypeus, if visible then strongly inflexed; most females with a ventral abdominal pollen-collecting brush; pygidial area absent, p. 999 Megachilid^ II. Labrum large, free, and uncovered; female without a ventral abdominal pollen-collecting brush; pygidial area usually present, p. 995 Andrenid^e AA. Wings absent or reduced so that they are useless for flight and the normal venation is disturbed. B. An erect scale or one or two knot-like swellings on the stalk between the mainbody of the abdomen and the thorax (alitrunk); antenna elbowed . . . (ants), p. 954 FoRMiciD^ 894 AN INTRODUCTION TO ENTOMOLOGY BB. No scale or nodes between the abdomen and thorax. C. Pronotum not movable, fused with the rest of the thorax; very hairy ant-like insects, usually red and black, p. 953 Mutillid^ CC. Pronotum movable, jointed to the rest of the thorax; less hairy insects. D. Antenna elbowed; hind corner of pronotum not reaching the tegula, separated from it by a special sclerite, the prepectus. p. 941 . Chalcidid^ DD. Antenna not ellDowed ; hind corner of pronotum reaching the tegula. E. Second and third abdominal sternites membranous, in dried speci- mens with a longitudinal fold; ovipositor always exposed beyond the tip of the abdomen, p. 922 Ichneumonid^ EE. Second and third abdominal sternites sclerotized, without a longi- tudinal fold; ovipositor usually retracted into the abdomen. F. Front tarsus chelate; antenna with ten segments, p. 978 . Dryinid.^: FF. Front tarsus normal. G. Abdomen compressed, covered mostly by a single tergite. p. 934 Cynipid^ GG. Abdomen depressed or cylindrical. H. Head elongate with the antenna inserted close to the anterior end. p. 965 Bethylid^ HH. Head of normal shape, not elongate; antenna with twelve segments, p. 953 Tiphiid^ Suborder CHALASTOGASTRA or SYMPHYTA* The Sawflies and Horn-tails This suborder includes the more generalized members of the Hymenoptera, those in which the form of the body is less modified and the venation of the wings less reduced than is the case with other members of the order. The basal segments of the abdomen are similar in form and the abdomen is broadly joined to the thorax as in the more generalized orders of insects. The first abdominal segment is not closely anchy- losed to the thorax, forming a propodeum, as is the case in the Clisto- gastra, and its tergum is usually longitudinally divided on its middle line. The adult forms of the Chalastogastra have never developed the highly specialized habits and instincts exhibited by many members of the suborder Clistogastra, especially by the wasps, ants and bees. There are no parasitic forms in this suborder except in the single genus Oryssus, p. 907. There are no wingless forms of the Chalastogastra. In the more generalized members of the suborder nearly all of the wing-veins are preserved, although the courses of the branches of the forked veins have been greatly modified, as indicated on an earlier page, and as is shown in the figures of wings given later. The ovipositor of the females is well developed and complicated in structure. It is fitted for making incisions in the leaves or stems of plants and is more or less saw-like in form. It is this fact that *The name Chalastogastra is the one most commonly applied to this sub- order and for that reason is used in this work; but some authors use Symphyta, which is really the older name. The etymology of these names is as follows: — Chalastogastra; chalastos (xaXaaros), loose; gastros {yaarpos), the belly. Symphyta: sym {abv), with; phyton {(j>vt6v), plant. HYMENOPTERA 895 suggested the common name sawflies which is applied to members of this order. The ovipositor and its sheath consists of three pairs of appendages or gonapophyses ; one pair arising from the sternum of the eighth abdominal segment and two pairs from the sternum of the ninth abdominal segment. The outer pair of the ninth abdominal segment constitute the sheath of the ovipositor, so called because when the ovipositor is not in use it is enclosed between the two members of this pair of gonapophyses. The ovipositor is a double organ, con- sisting of two similar blades situated side by side. Each blade con- sists of two gonapophyses, an upper or posterior one, known as the support or lance, and a lower or anterior one, the so-called saw or lancet. The supports are the inner gonapophyses of the ninth ab- dominal segment, and the saws are the gonapophyses of the eighth abdominal segment. Although each of the saws is closely joined to its support it can be moved backward and forward along it. Figure 1132 represents one of the blades of the ovipositor of Cimhex amer- icana. The ovipositor of this saw- fly is fitted for cutting slits in Fig. I i32.-Blade of ovipositor of Cimbex ig^ves in which the eggs are de- amencana; a, support; b, lancet. ^^^^^^^^ j^ ^^^^^^ members of this suborder that deposit their eggs in the stems of plants or the trunks of trees, as the Siricidfe, the ovipositor is slender and long. After a slit has been cut or a hole drilled in the trunk of a tree, as the case may be, an egg is forced down between the blades of the ovipositor to the nidus prepared for it. The larvje of the Chalastogastra are all plant-feeders. With the exception of those that are leaf -miners they are caterpillar-like in form. Prolegs are present in the Xyelida?, Cimbicidae, Tenthredinidae and Argidce; but these are not provided with hooks as are the prolegs of caterpillars. A striking feature of the lar\^ae of this suborder is the possession of a pair of ocelli, one on each side, which in their position and in their structure agree with the ocelli of adult insects, that is, they are primary ocelli. This characteristic distinguishes these larvae from the larvce of Lepidoptera, which have only adaptive ocelli, usually several on each side (see page 136). A classification of the larvse of this suborder was published by Yuasa ('22). 896 AN INTRODUCTION TO ENTOMOLOGY Family XYELID^ The Xyelid Saw flies The members of this family can be recognized by the form of the antenna^ and the venation of the wings. The basal segments of the fiagellimi are consolidated, thus forming what appears to be a very long third segment of the antenna and the remaining segments of the flagellum are small (Fig. 1 133). Except in Neoxyela alberta, a species recently described from Banff, Alberta, the members of this family differ from all other H^Tnenoptera in that the free part of vein R2 of the fore wings is present (Fig. 1134)- The posterior margin of the pronotum is straight or nearly so. The mesonotum is short and never extends much beyond the anterior margins of the tegulas. The anterior tibiae are armed with two apical spurs. In some species the ovipositor is very long, in others it is of moderate length . The described larv^ feed on the foliage of hickory, butternut, pecan, elm, and the staminate flowers of pine. In the larvas each of the ten abdominal segments bears a pair of prolegs, although in some species those of the first and ninth segments are smaller than the others. Fig. 1 134. — Wings of Macroxyela. The cells are lettered. HYMENOPTERA 897 Family PAMPHILIID^ The Web-spinning and the Leaf-rolling Sawflies The common names given above were suggested by the fact that the larvce of some species build nests by tying the leaves of their food plants together with a web of silk, and others build nests by rolling the edge of a leaf and live inside the tube so formed. The larvce of some species are gregarious. The \arvse of members of this family have long, seven-jointed antennse, well-developed thoracic legs, but lack abdominal prolegs. In the fore wings of the adult (Fig. 1135) vein Sc is preserved as a distinct vein ; the free part of vein R2 is wanting ; and vein Cu2 is usually preserved, at least as a short spur. In the hind wings vein Sc is more or less distinctly preserved. The body of the adult is robust. The posterior margin of the pronotum is straight or nearly so. The mesonotum is short and never extends much beyond the anterior margins of the tegul«. The anterior tibi^ are armed with two apical spurs. The ovipositor of the female is short. More than fifty species have been described from America north of Mexico; but the larv^ of onh' a few of these are known; among these are the following. The plum web-spinning sawfiy, Neurotoma inconspicua. — The lar- vae of this species feed on the foliage of plum and cherry; they are gregarious and form unsightly nests by spinning webs over the leaves ; frequently these webs cover an entire tree. The injury is done in early siunmer. When full-grown the larvae find their way to the ground, where they pass the remainder of the simimer and winter in earthen cells, they transform to pupse in the spring, and the adults emerge in May or June. This pest is controlled by spraying or dusting the infested trees, with lead arsenate. The peach sawfiy, Pamphllius persiciis. — This pest of the peach is one of the leaf-rolling species. The adults emerge from the ground late in May or early in June and lay their eggs on the leaves; the eggs soon hatch ; each larva cuts a slit in a leaf and then rolls over a portion of the leaf, making a case within which it sta^^s during the daytime, feeding chiefly at night. There is a single generation a year. The larva passes the winter in the ground. The same method of control is used as with the preceding species. AN INTRODUCTION TO ENTOMOLOGY Fig- 1 135- — Wings oi Pamphilus. The veins are lettered. Family SIRICID^ The Horn-tails The common name horn-tails is appHed to members of this family because the last abdominal segment bears a more or less horn-like prolongation. This is short and triangular in the males, and is a prolongation of the last ven- tral segment; in the females it is long and often spear-shaped, and is a prolongation of the last dorsal segment. The body is cylindrical (Fig. 1 136); the head large and widened behind the eyes; the pronottim is right-angled, so that it presents both a strictly dorsal and a cephalic as- pect, the latter concave; vein Sci of the front wings is absent (Fig. 1 13 7) ; the propodeum is divided longitu- dinally ; the anterior tibias each with only one apical spur; the sheath of the ovipositor is very long and exserted beyond the end of the ab- domen; the ovipositor is fitted for boring. Fig. 1 136. — Tremex columha. HYMENOPTERA 899 The wSiricid^ is a small family ; only about fifty species represent- ing five genera are known. The North American species, of which there are twenty, have been monographed by Bradley ('13). The larvse bore in the trunks of trees; our best-known species is the following one. The pigeon horn-tail, Tremex columba.- — The larva of this species infests maple, elm, apple, pear, beech, oak, and sycamore. The female (Fig. 1 136) in order to oviposit pierces the wood of a tree to the depth of 10 to 12 mm; the eggs are laid singly; sometimes her ovipositor gets wedged in the wood and holds her a prisoner until she dies. The larva is cylindrical and attains a length of 40 mm. It transforms within its burrow, in a cocoon made of silk and fine chips. C+Sc^ Sc, Fig. 1 137. — Wings oi Sirex juve7tcus. (From Bradley.) The adults of this species vary in color and marking; based on these variations, three fairly distinct races have been recognized, which to a considerable extent are geographical, although their ranges overlap. In the typical form, race columba, the abdomen is black, with ochre-yellow bands and spots along the sides; this is the common form in Quebec, Ontario, and the northeastern United States. In the race aureus the ground color of the abdomen is yellow and the markings black; this is the common form in the Rocky Mountains and is found on the Pacific Coast. In the race sericeus the entire body is fulvous, the legs beyond the femora yellow, and the wings dark reddish brown ; this race is found in the southeastern United States and as far north as Pennsylvania and West to Utah. Family XIPHYDRIID.-E The Xiphydriid Sawflies This family is composed of a small number of species which are closely allied to the Siricidce but which differ from them in several 900 AN INTRODUCTION TO ENTOMOLOGY important particulars. As with the horn-tails the body is cylindrical but the last abominal segment is not terminated by a triangular or lanceolate process. The back of the head is separated from the pro- notum by an elongate neck; the pronotum is ver\' short medially and not angulate laterally; vein Sci is present in the front wings as a transverse vein (Fig. 1 138) and the sheath of the ovipositor is seldom longer than the last tergite. '^n,.,^^' Fig. 1 138. — Wings of Xiphydria maculata. (From JMacGillivray.) The members of this family are of moderate size. Less than a dozen species have been described from North America. The known Idirvss, bore in dead and decaying wood of deciduous trees. Family CEPHID^ The Stem Saw flies The stem sawflies are so-called because the larvse bore into the stems of plants or in the tender shoots of trees and shrubs. The adults are slender, elongate insects of moderate size. The pronotum is more or less quadrate and longer than is usual in theH^Tnenoptera. The front wings are without a distinct cell between the costa and vein Sc+R+M, and with cross-vein m-cu joined to vein M at or near its separation from vein R (Fig. 1139). The anterior tibiae are armed with one terminal spur. This family is of moderate size; less than a score of species have been found in our fauna; but these represent nine genera. Some of the species are of economic importance. Several species bore in the stems of grains and grasses, the following species illustrate the habits of these. HYMENOPTERA 901 The wheat-sawfly-borer, CepJms pygmcBus.- — The larvas of this species bore in the stems of wheat, a single larva in a stem, dwarfing and stunting the growth of the plant. As the grain becomes ripe the larva works its way toward the ground ; and at the time of harvest the greater mmiber of them have penetrated the root. Here, in the lowest part of the cavity of the straw, they make preparations for passing the winter, and even for their escape from the straw, as adults, the following year. This is done by cutting the straw circularly on the inside, nearly severing it a short distance from the ground, so that a strong wind will cause it to break off at this point. After the circular cut has been made, the larva fills the cavity of the straw just below it for a short distance with a plug of borings. Between this stn. Fig. 1 139. — Wings of Cephiis pygmcEus. The cells are lettered. (From Mac- Gillivray.) plug and the lower end of the cavity, the wall of the cavity is lined with silk forming a cocoon within which the larva passes the winter and changes to a pupa in March or April. The adult insects emerge early in May. The currant-stem girdler, Janus integer. — The larva of this species bores in the upper portion of the canes of currant. Its presence is indicated by the wilting and drooping, in late spring, of the new growth at the tip of the infested cane. This is due to the fact that the parent sawfly after depositing her egg in the cane moves up a short distance above where the egg is deposited and with her ovipositor girdles the cane, sometimes nearly severing it. This killing of the tip, and thus checking the growth of the cane, seems to be necessary for the development of the egg and larva. The larva bores in the pith of the cane. In the fall it eats a hole through the woody wall of the cane to the outer bark, thus making provision for the escape of the adult, and then spins a cocoon in which it hibernates. The 902 AN INTRODUCTION TO ENTOMOLOGY change to the pupa state takes place in April and the adult emerges in May. The obvious method of control of this pest is to remove and bum the infested portion of the canes while the larvae are in them. Fig. 1 140. — Cimbex americana. Abdomen except first segment: 7, 8, g, pleurites; T, T, T, tergites; S, S, S, sternites; cr, cercus; sp, SDiracle. (After Snodgrass.) Family CIMBICID^ The Cimhicid Sawflies This is a small family, which is represented in our fauna by a few genera and a limited ntmiber of species. In this family the body is stout and often very large; there are distinct pleural scler- ites in the abdomen (Fig. 1 140) and the antennse are clavate. The anterior tibise and meta- tarsi bear ribbon-shaped or spatulate hairs ; the pul villi are large, broadly sessile on the last tarsal segment, and are not retractile. The sheath of the ovipositor extends but lit- tle if at all beyond the end of the abdomen. The body of the larvae is cylindrical, stout, and covered with a waxy bloom when living; the thoracic legs are well-developed and five-jointed; and the abdomen bears eight pairs of prolegs. The lar- vae live free upon foliage upon which they feed. The American sawfiy, Cimbex americana.- — This is the largest of our common sawflies. The female is about 1 8 mm. in length and has a black head and thorax, a steel-blue or purplish abdomen, with four yel- lowish spots on each side, smoky brown wings, and black legs, while her feet and short, knobbed antennae are pale yellow. The male is longer and slenderer and differs somewhat in color. Several varieties of this species, differing in color, have been described. The eggs are laid in June in crescent-shaped slits made in leaves. The food plants are elm, birch, linden, and willow. The larva is greenish yellow, with black spiracles and a black stripe down its back. When disturbed it spurts forth a fluid from glands just above the spiracles. It clings to the upper surface of a leaf and feeds on the edge of the leaf. When not feeding it rests on one side with the body curled up in a spiral form. There is but one generation each year. When the larva is full-grown it burrows in the ground, makes an oval, brownish cocoon, and there spends the winter, not changing to a pupa until spring. The adults appear in May or June. Family TENTHREDINIDyE The Typical Sawflies This is a very large family, including more than seven-eighths of all of the members of the suborder Chalastogastra. To this family HYMENOPTERA 903 belong all of the Chalastogastra in which the radial cross-vein of the fore wings is opposite cell R4, or cell R3, or is wanting, except, the small family Cimbicidse. The typical sawflies differ from the Cimbi- cidas in lacking pleural sclerites in the abdomen and in that the antennas are not clavate. The anterior tibiae and tarsi do not bear ribbon-shaped or spatulate hairs, as in the Cimbicidae ; and the pulvilli are inserted on the end of the last tarsal segment and are retractile, like the finger of a glove. The sheath of the ovipositor extends but little if at all beyond the end of the abdomen. The larvas are caterpillar-like; the thoracic legs are always present and are usually well developed, but are vestigial in some species. Prolegs are usually present; these are borne on abdominal segments 2-7 and ID or 2-8 and 10, rarely the prclegs are vestigial. The larvae of the different species differ greatly in size, varying from 10-40 mm. in length. The larvae of the majori- ty of the species live free on the foliage of plants, upon which they feed (Fig. 1 1 4 1 ) . The plants infested by the different species include trees, both deciduous and conifers, shrubs, herbs, grasses, and ferns. The lar- vae of some species are leaf- miners; others fold the edges of leaves ; some make galls on leaves, especially of willow and poplar; others make galls in the stems of these plants; and one spe- cies, Caulocampa acericau- lis, bores in the petioles of maple leaves. Among the species that have attracted attention on account of their economic importance are the following. The imported currant- worm, Pteronidea ribesi: — This is the commonest and best-known of the garden pests. The adult sawflies appear early in the spring and the females lay their eggs in rows along the principal veins on the underside of the leaves of currants and gooseberries. The eggs are glued to the leaf -veins and not inserted in slits, as is usually the case with sawflies, and they increase considerably in size before hatching. They hatch in a week or ten daj^s; and the larvae begin at once to feed upon the leaves. Often by the time the larvae Fig. 1 1 41. — The locust saw-fly, Pteronidea trilineata: a, egg; b, young larva; c, full- grown larva; d, anal segment of full-grown larva; e, cocoon;/, adult. 904 ^A^ INTRODUCTION TO ENTOMOLOGY become full-grown the infested bush is completely stripped of its foliage. The larvas are at first whitish, as they increase in size the color changes to green ; after the first molt the body becomes covered with many black spots and the head is black; at "the last molt they lose their black spots and assimie a uniform green color tinged with yellow at the ends. When full-grown the larvs descend to the ground and spin their cocoons, either just below the surface of the ground or beneath rubbish; sometimes the cocoons are attached to the stems or leaves some distance from the ground. A second genera- tion of the sawflies appears late in June or early in July; and some- times a third generation is developed; this makes it necessary to fight this pest throughout the spring and summer. The larvae can be easily destroyed in the spring by spraying the bushes with Paris green or with arsenate of lead; later when the fruit is near maturity fresh hellebore should be used at the rate of four ounces in two or three gallons of water, or as a dry application, one pound in five pounds of flour or air-slacked lime. The pear-slug, Calnoa cerasi. — This is a well-known pest of pear, cherry, and plum. It causes the leaves of the infested tree to turn brown. When such leaves are examined it is found that the injury is due to small, slimy, slug-like larvs, which have eaten off the upper surface of the leaves, leaving the skeleton of veins and the lower epidermis to turn brown, wither and fall; sometimes trees are entirely defoliated in this way by midsummer. When full-grown the larvce descend and burrow into the ground a short distance, where each constructs an earthen cell in which it transforms. A second genera- tion of the sawflies appear and lay their eggs about three weeks later. The larvce can be destroyed by the use of arsenate of lead spray or by dusting the leaves with freshly slaked lime. The rose-slug, Clddius isonienis. — Often in the summer our rose- gardens look as if fire had swept over them, so scorched and brown are the leaves. The cause of this apparent conflagration is a trans- parent jelly-like slug, greenish above and yellowish below, which eats the upper surface of the leaves, leaving patches of the lower surface and the veins. These slugs usually feed by night and remain hidden on the lower surface of the leaves by day. When ready to pupate they crawl down or drop to the ground and burrow beneath the surface ; here each makes a little cell and then transforms. The adult fly is shining black with smoky wings and with the fore and middle legs grayish or dirty-white. The female is 5 to 6 mm. in length. There are two broods a year, one in June and one in August. The last brood passes the winter in the ground.. This pest can be destroyed with a solution of whale-oil soap, or with kerosene emulsion. Family ARGID^ The Argid Saw-flies This family has been recently separated from the Tenthredinidas, from which it is distinguished by the absence of a post-tergite. This is a distinct apical plate borne by the scutellum, which is present in all of the Tenthredinidffi and absent in this family. HYMENOPTERA 905 The family Argidse consists chiefly of tropical insects, but a few representatives of the family are found in this country. Among these are two species of Stericttphora, the larvae of which occasionally infest sweet potatoes to an injurious extent. Family ORYSSIDAE The Oryssids In former editions of this book the oryssids were given the rank of a suborder, Idiogastra. The adults resemble those of the Chalas- togastra in the shape of the abdomen but the form and habits of the larvcC are those characteristic of the Clistogastra. However, there does not seem to be sufficient justification for giving the family the rank of a suborder and it has therefore been referred back to the suborder Chalastogastra in which it was originally placed. In sequence of relationships the family should probably precede the Cimbicidas and Tenthredinidas and stand in closer relation to the Cephidas. The Oryssidse is a small family of rare insects, only a single species of larva being known in this country. In the shape of the body (Fig. 1 142, A) the members of this family strongly resemble the Siri- cidas. They are easily distin- guished from all of the other Chalastogastra by the anomalous position of the antennae, which are inserted far below the eyes, im- mediately above the mandibles, under a transverse ridge (Fig. 1 142, B); by the more reduced venation of the wings; and by the remarkable form of the ovi- positor. In the fore wings (Fig. 1143) the transverse part of vein M2 is wanting; and in the hind wings R4 is wanting; therefore, there are no closed submarginal cells in the hind wings. This combina- tion of characters distinguishes the Oryssidas from all of the Chal- astogastra. In the Oryssidas the first anal cell of the fore wings is preserved, in which respect the members of this family differ from all of the Clistogastra. Fi g. 1 142. — Oryssus sayi; A, female; B, head seen from in front. (From Sharp.) 906 AN INTRODUCTION TO ENTOMOLOGY In the form of the ovipositor and in its position when at rest the 3L 4+5 ^M, Fig. 1 143. J/2 -Wings of Oryssus ahietimis. (From MacGillivray.) Oryssidaj differ from all other H}Tnenoptera. The following account of this organ is that of Rohwer and Cushman ('17). Lying below and on each side of the eighth tergite in the female is a large heavily chitinized plate, the two together forming ventrally a channel for the re- ception of the ovi- positor, and each bearing at its tip a small triangular ap- pendage. These plates apparently represent the fused ninth and tenth ter- gites which are lon- gitudinally divided dorsally (Fig. 1 144, 9T and loT), and the appendages are apparently the cer- ci (Fig. 1 1 44, c); the eighth sternite is in- ternal and lies above and some- what behind the ninth, and is rep- resented by two triangular plates, from the upper angle of which or- iginate the lancets (fi r s t gonopophy- ses) (Fig. 1 145, //); Fig. 1 144. — Lateral aspect of abdomen of the female of Oryssus. (After Rohwer and Cushman.) Fig. 1 145. — Details of the ovipositor of Oryssus: 9 T, 10 T, ninth and tenth tergites; 8 S, eighth sternite; 9 S, ninth sternite; //, lancet; /, lance; sh, sheath; 0, ovipositor ; c, cerci. (After Rohwer and Cushman.) the ninth sternite is also internal, lying below and in front of the eighth and represented by two more or less triangular plates which extend postero- ventral; the lance (second gonopophyses) originates from the inner ends of these plates and becomes fused a short distance cephalad of its origin (Fig. 1145, /); HYMENOPTERA 90'i the two parts of the sheath (third gonopophyses) arise from the apices (Fig. 1 145, Sh). Shortly cephalad of the origin of the lance and lancets the latter en- ter the groove of the former, the complete ovipositor as thus formed extending cephalad in an inverted position enclosed within a membranous sac, probably in- vaginated intersegmental skin, into the mesothorax, where it is coiled, and re- turning upon itself continues caudad in its normal position and enters the base of the sheath (Fig. 1145J. The Oryssid^ is a widely distributed family, members of it having been found in all of the major geographical regions of the world. But it is a small family, including only a few genera and species. A single genus, Oryssus, is found in North America, of which about a dozen species have been described from this region. The adults are very active and are found run- ning over the trunks of trees and on timber. The larvEe were formerly supposed to be borers in the trunks of trees; but it has been shown by Burke ('17) that they are parasitic on the larvse of Bnprestis and probably on other wood-boring larvae. The larva of only a single species, Oryssus occi- dentalis, is known. This is white, subcylindrical, about one-third as thick as long, and legless ; but the positions of the legs are indicated by chitinized disks. The mouth-parts are very simple, the labrum, la- bium, and maxilla being merely fleshy lobes, but the mandibles are heavily chitinized; the antennae are tubercle-like and set at the summits of rounded elevations. In the pupa of the female (Fig. 1146) the termi- nal portion of the ovipositor is external and ex- tends over the back the entire length of the body. Referring to this, Rohwer and Cushman ('17) state as follows: The reason for the formation in the pupa of the long external ovipositor is in- explicable, and its reduction to the form existirg in the adult is equally inex- plicable. This is rendered all the more difficult to understand by the fact that in the prepupa the ovipositor is coiled as it is in the adult, while in the pupa it forms a simple loop in the thorax. Fig. 1 146.— Pupa of Orys- sus, female. (After Roh- wer and Cush- man.) Suborder CLISTOGASTRA or APOCRITA* Parasitic Hymenoptera, ants, wasps and bees This most striking characteristic of this suborder is the fact that what appears to be the first abdominal segment, but which is really the second, is greatly constricted forming a slender petiole or waist between the larger portion of the abdomen and the alitrunk or wing- bearing region of the body (Fig. 1147). *The name Clistogastra is the one most commonly applied to this suborder and for that reason is used in this work; but some authors use Apocrita, which is really the older name. The etymology of these names is as follows: Clistogastra: clistos (xXeto-ros), closed; gaster (yasT-qp), the belly. Apocrita: apocritos (dTTOKptTos), separated; apo (otto), from, crino {kpIvu), to separate. 908 AN INTRODUCTION TO ENTOMOLOGY In this subor :ler the intermediate region of the body is not merely the thorax but includes also the first abdominal segment, only the tergum of which is preserved in the adult. This is known as the median segment, or the propodeum and can be identified by its spiracles, the third pair of this region of the body. It should be re- Fig 114- membered that the thorax bears only two pairs of spiracles (see page 115). From the above it follows that what appears to be the first abdominal segment in the Clistogastra, and which is usually so-called, is really the second. In the Clistogastra the ovipositor and its sheath are composed of the same morphological elements as are those of the sawflies described on an earlier page ; but these parts differ greatly in form in different members of this suborder. In some the ovipositor is a boring instru- ment by means of which deep holes are made into trees and eggs placed in these holes; in others it is used for thrusting the eggs into the bodies of other insects; and in still others it is modified so as to form a sting with which poison glands are connected. AN INCLUSIVE TABLE OF FAMILIES OF THE CLISTOGASTRA FOR ADVANCED STUDENTS By Dr. J. C. Bradley A. With well-developed wings.' B. Hind wings without an anal lobe.* C. No erect scale or node between the gaster and the propodeum. D. The costal cell of the fore wings eliminated by the coalescence of the costal and subcostal veins, except in the case of two or three rare genera. The venter is membranous and has in dried specimens a longitudinal fold. E. The transverse part of vein M2 of the fore wings wanting, causing the union of cells Mi and ist M2 (Fig. 1148). F. The abdomen not very long and slender and strongly com- pressed, p. 919 BRACONID.E FF. The abdomen very long, slender, and strongly compressed. (The genus Hymenopharsalia) p. 922 Ichneumonid^ EE. Cells Ml and ist M2 separated by the transverse part of vein M2 (Fig. 1 152). p. 922 ICHNEUMONID^ DD. The costal cell of the fore wings present. The venter chitinized. E. Abdomen borne on the dorsal surface of the propodeum far above the hind coxae. F. The transverse part of vein Mo present in the front wings, which have at least two closed submarginal cells, p. 929 Aulacid^e FF. The transverse part of vein Me wanting in the front wings, which do not have two closed submarginal cells, p. 930 GASTERUPTIIDyE EE. Abdomen borne between the hind coxae, or on the end of the pro- podeum slightly above them. F. The transverse part of vein M present and situated close to the stigma. *In the hind wings of the insects belonging under this category neither the second anal furrow nor the axillary excision is present, but there is sometimes present a weak preaxillary excision, more rarely (some genera of Braconidag) a pronounced notch, but never forming a deep slit. See also footnote on page 911. HYMENOPTERA 909 G. Antennae in both sexes of more than fifteen segments; tro- chanters clearly two-segmented. H. Two or three closed submarginal cells in the forewings. p. 929 Trigonalid^ HH. Only one closed submarginal cell in the forewings. p. 919 Stephanid^ GG. Antennas of thirteen segments in the male and twelve in the female; trochanters one-segmented. H. Pronotum without posterior lobes (see Fig. 1195) its lateral extensions reaching the tegulse. I. Cell M4 of the forewings shorter than cell Cu + Cui or absent (Mutillins). p. 953 Mutillid^ II. Cell M4 of the forewings present and longer than cell Cu + Cui (Fig. 1 182). (Vespince.) p. 965 Vespid^ HH. Pronotum with posterior lobes terminating at a distance from the tegute (Fig. 1195). (This distance is short in the Ampulicinae.) I. Abdomen of male with only six exposed segments, the fourth and following scarcely exposed; that of the female with compressed apex. Prothorax elongate, usually with a median longitudinal groove. Nude insects, often brilliantly metalhc. (Ampulicinae.) p. 978 Ampulicid^ II. Abdomen of male with seven exposed segments; that of the female not compressed at apex. Prothorax short with- out median longitudinal groove. Usually hairy insects, some of the hairs plumose. (A few genera in the various families of bees. Pass to EE on page 914.) FF. The transverse part of vein M situated about two-thirds of the way from the wing base to the end of the costal cell (C + Sci) or wanting. G. Wings not longitudinally plaited in repose. Ovipositor not carried along the mid-dorsal line. H. The pronotum laterally reaching the tegulae. No prepectus present. I. Hind metatarsi one-fourth the length of the following segment. Large insects; the abdomen of the female filiform and several times the length of the head and thorax together; that of the male shorter and clavate. p. 932 .... Pelecinid^ II. Hind metatarsi at least as long as the following segment. J. Mandibles in a reversed position, their apices directed outwardly, away from the mouth-opening, p. 93 1 Vanhorniid^ JJ. Mandibles in a normal position. K. Cells Cu + Cui and M3 of the forewings fully en- closed and separated from each other by perfect veins. L. Cell M4 of the forewings triangular; antennas com- posed of sixteen segments, p. 931 HeloriDjE LL. Cell M4 of the forewings irregularly six-sided; antennas composed of fourteen segments, p. 931 ... . ROPRONIID^ KK. Cells Cu + Cui and M3 partly enclosed by brown lines, or altogether wanting. Claws not pectinate. L. Abdomen sharply margined by a carina along the sides; antennae arising near the clypeus. M. Antenna of never more than ten segments, rarely with only eight or nine. Front wings with- out vein C or "stigmal" vein (Sc2 -f Ri), often without any venation, p. 933. . . . PlatygasteriDyE MM. Antennae usually of twelve segments, more rarely of eleven segments, or if of seven or eight segments the club is unsegmented. p. 933 Scelionid^ 910 AN INTRODUCTION TO ENTOMOLOGY LL. Abdomen immargined laterally (acute in Tele- nominae but without a carina). M. Forewings with a distinct stigma. N. A closed, usually very short, marginal cell (2d Ri + R2) present. Antennas of thirteen segments. Abdomen with a short cylindrical petiole, the second segment much longer and larger than the others, p. 931 . .Proctotrupid^ NN. No closed marginal cell (2d Ri + R2) but the basal part of the marginal vein (vein r) often present in the forewings. O. Antennae of eleven segments. (Megas- pilinse.) p. 932 Ceraphronid^ 00. Antennae of twelve or more segments (a few genera of Diapriinas). p. 932 . . . Belytid^ MM. Forewings without a distinct stigma. N. Costal cell (C + Sci) either closed along the margin, or if open very narrow; the marginal cell (2d Ri + R2) if present narrowly triangular, its proximal margin a straight line: Abdomen not compressed nor dorsally keeled. Hypo- pygium of the female not divided, but closely applied to the pygidium, the ovipositor issuing from between them at the tip of the abdomen. O. Hind wings with a closed median cell (M). Forewings almost invariably with a closed marginal cell (2d Ri + R2). Antennae of four- teen or fifteen segments. (Belytinae.) p. 932 Belytid^ 00. Hind wings without any closed cells; forewings without a closed marginal cell (2d Ri + R2). P. Abdomen margined laterally, the margin acute but not sharply carinate. Antennae arising from near the clypeus and composed of ten to twelve segments. Scutellum not divided into three lobes. (Telenominae.) p. 933 SCELIONID.^ PP. Abdomen not at all margined laterally. Scutellum divided by two oblique curved impressed lines into three lobes. (Calli- ceratinae.) p. 932 Ceraphronid.^ NN. Costal cell (C + Sci) open along the costal margin and abnormally wide. The marginal cell (2d Ri + R2) present; often closed; often open along the costal margin, sometimes at tip; it is always four-sided, acute at apex and at its base. Abdomen more or less strongly com- pressed and with a mid-dorsal keel, if rarely but little compressed and without a keel, it is more or less swollen dorsally. Hypopygium of the female divided, the ovipositor issuing from the cleft thus formed, anterior to the apex of the ab- do*men. p. 934 Cynipid^ HH. The pronotum not reaching the tegulae, separated there- from by a chitinized sclerite, the prepectus. Antennae el- bowed, never more than thirteen-segmented. Fore wings with a short, narrow costal cell open along its anterior margin (Fig. 1 166); its apex remote from the stigmal vein (Fig. 1166, d); a more or less elongate marginal vein (Fig. 1166, b)\ postmarginal and a stigmal spur (Fig. 1166, d). An occasional HYMENOPTERA 911 trace of the transverse part of vein M is the only additional vein present, there being never any closed cells, p. 941 Ch.a.lcidid^ GG. Wings longitudinally plaited in repose, ovipositor carried along the mid-dorsal line. Pronotum reaching the tegulae, the prepectus not being distinctly set off. {Leucospis.) p. 941 Ch.vlcidid^ CC. An erect scale or one or two nodes between the propodeum and the gaster. p. 954 Formicid^ BB. Hind wings with an anal lobe.* If there are any closed cells in the hind wings the antennae are thirteen-segmented in the male, twelve- in the fe- male, except in a few instances where the number is reduced by fusion, but then the apical segments always form a club, or are abruptly recurved or otherwise strikingly modified (except that in some species of Crabro both sexes have twelve-segmented, otherwise normal antennee). C. Hind wings without closed cells. Number of antennal segments variable, but never thirteen in the male and twelve in the female, nor are the apical segments in the male either formed into a distinct club, or strongly re- flexed or otherwise peculiarly modified. Vein dissolution extensive. D. Abdomen attached to the dorsal surface of the propodeum. p. 949. . . EV.\NIID^ DD. Abdomen attached normally, at the apex of the propodeum between or slightly above the hind coxae. E. AntenncB composed of ten segments, or if of thirteen in the female {Ampulicomorpha) then the pronotum is elongate and has a median longitudinal sulcus. F. Antennae inserted on a frontal prominence distant from the clyp- eus; mouth ventral. Fore tarsi simple, p. 951 Embolemid^e FF. Antennae inserted close to the clypeus. Fore tarsi of the female usually chelate, p. 978 Drvinid^e EE. Antenna usually composed of thirteen segments, more rarely of twelve or eleven segments, or multiarticulate. F. Abdomen with six exposed segments or less. Forewings always with cells M and Cu + Cui closed. Ovipositor an extensile jointed tube. G. Venter convex; abdomen with six exposed segments, p. 951 . . Cleptid^ GG. Venter strongly concave; abdomen with at most five usually three or four exposed segments. Brilliantly metallic, p. 951 ... . Chrysidid^ FF. Abdomen with eight exposed segments, the petiolar segment very short and scarcely perceptible. Ovipositor a true sting, p. 965. Bethylid^ CC. Hind wings with at least a closed median cell (cell M). Males with thirteen, females with twelve antennal segments, except in rare instances, where they have been reduced slightly below that number in the males, in which case they usually either end in a jointed club or the last segments are recurved or hooked or otherwise modified. Venation usually well pre- served. *If there is a very deep or slit-like incision on the margin of the hind wing, the insect is certain to come under this heading. There are some genera of Sphecidae (of the tribes Larrini, Astatini and the subfamily Sphecinae) in which the axillary excision or both axillary and preaxillary excisions are reduced to small and incon- spicuous notches, close to one another, and in some cases the axillary excision is altogether lacking. But in all such cases the second anal furrow is distinct, its apex close to that of the first anal furrow, and it delimits a large anal area behind it, which therefore lacks only the notch itself in order to become a distinct anai lobe. In all insects falling under grouping B this furrow is wanting, due to there- duction or entire absence of the area which in a more primitive condition exists behind it and forms the anal or posterior lobe of the wing. 912 ^A^ INTRODUCTION TO ENTOMOLOGY D. The pronotum extending laterally directly to the tegulae, where its lateral prolongations do not terminate in the form of a rounded "pos- terior lobe" covering the spiracles. E. Cell M4 of the forewings longer than cell Cu + Cui. Lateral pro- longations of pronotum forming a posterior angle which lies above the tegulas. Wings usually longitudinally plaited, p. 965 Vespid^ EE. Cell M4 of the forewings shorter than cell Cu + Cui or absent. Lateral prolongations of pronotum bluntly rounded, not lying dorsad of the tegulse. Wings never longitudinally plaited. F. Mesopleura divided by a transverse suture into an upper and lower plate. First and second abdominal sternites imbricate. Coxae very large and long; the legs long and usually distinctly spinose. p. 950 Pompilid^e FF. Mesopleura not divided by a transverse suture. Coxae and legs not unusually long. G. First abdominal segment united by a ball and socket joint to the second, and itself forming an almost completely separated "scale" or "node." Hypopygium of male unciform. Females winged; a worker caste present. (Some more primitive genera of ants.) p. 954 FoRMiciD^ GG. First abdominal stemite attached to the second by a suturi- form articulation or more or less imbricate, the first segment not forming a "scale" or "node" between the propodeum and the gaster.* H. Mesosternum not forming with the metastemum a con- tinuous plate overlying the bases of the hind and middle coxae Axillary excision of the hind wings in normal position, apex of male abdomen without three retractile spurs between the last tergite and its stemite. L Vein M4 + Cui of the forewings opposite vein m-cu or nearly so. Second and third tarsal segments of the female not dilated. J. Mesosternum with two laminae which overlie the bases of the middle coxae. K. Little or no constriction between the first and second abdominal sternites, which are almost or somewhat imbricate. A trace of a vein (base of Rs) often divides the first submarginal cell (R + ist Ri). Hypopygium of male not unciform. Apex of the marginal cell (2d Ri + Rs) distant from the wing apex by not more than the length of the cell. Both sexes winged, p. 952 Anthoboscid^ KK. First and second abdominal sternites separated by a strong and distinct suturiform articulation and either the hypopygium of the male is unciform, or the females are wingless and carried about by the males in mating. L. Hypopygium of the male not unciform; but some- times it is tridentate at apex with the middle tooth long and spiniform. Females apterous and carried about by the males in mating. First submarginal cell usually divided by a weak vein (base of the radial sector), p. 952 Thynnid^ LL. Hypopygium of male unciform, known American females winged. First submarginal cell not divided (base of Rs wanting). M. Diurnal insects with normal eyes and ocelli. Females winged. (Tiphiinas.) p. 953 . Tiphiid^ *Some genera of Mutillidae in which the first or first and second abdominal segments are more or less nodose may be recognized as falling in this category by the unciform hypopygium of the males, the apterous females, and the absence of a neuter caste. HYMENOPTERA 913 MM. Nocturnal insects with enlarged eyes and ocelli. The marginal cell (2d Ri + R2) removed from the apex of the wing by several times its length. Fe- males unknown but presumably apterous. (Brachy- cistinae.) p. 953 Mutillid^ JJ. Mesosternum simple or with two minute erect teeth between the bases of the coxas. K. Marginal cell (2d Ri + R2) removed by less than its length from the wing apex; the fourth submarginal cell (R3) not traversed by an adventitious vein. Abdomen never petiolate. > L. No constrictions between the abdominal segments (except between the first and the second), all tergites and all but the first and second sternites loosely im- bricated plates. The last tergite of the male a small simple lamina. Edges of the hypopygium of the fe- male turned upwards and meeting on the mid-dorsal line, often fused, enclosing the sting in a cone. Both sexes winged. Vein m and M2 of the hind wings wanting. Mesosternum unarmed, upper surface of hind coxae simple, p. 952 Sapvgid^ LL. Strong constrictions between each of the ab- dominal segments, the tergites and sternites all heavily chitinized and not loosely imbricate; the last tergite modified and hood-like. Female apterous. Upper surface of the hind coxae, at least in the male, with a lamella. (Methocinseand Myrmosinae.) p. 953- TlPHIID^ KK. Marginal cell (2d Ri + Ro) removed by two or more times its length from the apex of the wing; cell R.3 when present usually traversed by a longitudinal adventitious vein. Often nocturnal insects with large eyes and ocelli. Females apterous. (Several subfamilies.) p. 953. MUTILLID.^ II. Vein M4 + Cui of the forewings more than two-thirds its length apicad of vein m-cu. Second and third tarsal seg- ments of the female dilated, deeply excised, and filled with membrane between the lobes. Nocturnal insects with very large eves and ocelli. Petiole long and slender. Hypopygium unarmed, p. 965 Rhopalosomid^ HH. Mesosternum and metasternum together forming a con- tinuous plate overlying the bases of the hind and middle coxae, separated from each other by a transverse suture. Axillary excision of the hind wings almost opposite the apex of cell Ms -f Cui + Cu. Abdomen of male with three spines, retractile between the last sternite and tergite. Tongue elon- gate. Wings with membrane striolate. p. 954 Scoliid/E DD. Pronotum terminating behind laterally in the form of two clearly differentiated rounded "posterior lobes," covering the spiracles. These lobes reach the tegulas in North American forms only in the extremely rare genus Dolichurus. E. Posterior metatarsus not dilated. No plumose hairs. Females without pollen- collecting apparatus, but often with a comb on the an- terior tarsi. Maxillae rarely elongate; if so, either the ocelli are distorted, or the abdomen has a petiole composed only of the first sternite. F. Abdomen of the male with only three or four exposed tergites. Last sternite of the female enclosing the sting, its edges fused in the mid-dorsal line. (Dolichurinae.) p. 978 Ampulicid^ FF. Abdomen of the male with seven exposed tergites. Stmg not en- closed by the hypopygium. p. 979 Sphecid/E 914 AN INTRODUCTION TO ENTOMOLOGY EE. Posterior metatarsi elongate and dilated. Some of the hairs, especially of the thorax, plumose. A pollen-collecting brush or a corbicula present in the majority of females. Maxillae usually with either the stipes or the lacinia elongate; the latter often very long and covering the tongue; the ocelH never distorted; the abdomen rarely petiolate, and never with a petiole composed only of the first sternite. F. Hind tibiae with apical spurs. If the marginal cell {26. Ri + R2) is long and slender, reaching nearly to the wing apex, the anal lobe is short and fully separated. Cell M4 usually as large as cell ist M2. G. Females without a corbicula. First submarginal cell (R + 1st Ri) rarely divided (by the base of Rs) in which case there is a large anal lobe present. In case the marginal cell (2d Ri + R2) is longer than the three submarginals, taken together, there is usually a well-marked anal lobe in the hind wings. H. Wings with two submarginal cells (very rarely less). I. Tongue short and the basal segments "of the labial palpi not sheath-like; or the labrum is large and free and uncovered. Females without a ventral pollen-collecting brush; often with a pygidial area. J. Tongue short, its apex bifid; labial palpi normal. Fe- male only rarely with a pygidial area. Mesepisternal suture present. Labrum hidden (Prosopinae). p. 993 Prosopid^ JJ. Tongue long or short, but its apex acute; the labial palpi normal or their basal segments sheath-like. Mes- episternal suture wanting. (Many.) p. 995 . . Andrenid^ II. Tongue elongate, the basal segments of the labial palpi sheath-like. Labrum not large and free, usually entirely covered by the clypeus, or if somewhat visible, then strongly inflexed. Females without a pygidial area; those of the non-parasitic species with a ventral pollen-collecting brush. p. 999 Megachilid^e HH. Wings with three submarginal cells. Females without a ventral pollen-collecting brush; often with a pygidial area. I. Tongue short, its apex bifid. Labial palpi normal. Fe- males rarely with a pygidial area. Mesepisternal furrow present. Labrum hidden. (Colletinse.) p. 993 . . Prosopid^ II. Tongue long or short, but its apex acute. The labial palpi normal, or the basal segments sheath-like. Mes- episternal suture rarely present. (Most.) p. 995 . Andrenid^ GG. Females and workers with corbiculae (except Psithyrns). First submarginal cell divided by a transverse, hair-like chitinized streak (base of Rs), rarely indistinct. Marginal cell (2d Ri + R2) rather long and pointed or appendiculate, usually as long as the three submarginal cells taken together, and extending far beyond the apex of the third (R4) . Malar space large and distinct. Hind wings stalked, the anal lobe absent. Tongue very long; the two basal segments of the labial palpi and the laciniae elon- gate, and forming a sheath. Social insects with normally a worker caste (except in Psithyrus). p. looi Bombid^ FF. Hind tibiae without apical spurs. Social insects with a worker caste. Workers with corbiculae; females without functionally de- veloped ones. Marginal cell (2d Ri + R2) long and slender reaching nearly to the wing apex. Anal lobe of the hind wing long and scarcely separated." Cell ist M2 much larger than cell M4. Eyes hairy, p. 1005 Apid^ AA. Apterous or subapterous (the wings so reduced as to interfere with the normal venation). B. The ventral segments membranous, more or less concave with a longi- tudinal fold in dried specimens. HYMENOPTERA 915 C. Second and third abdominal tergites connate.* D. Abdomen sessile, or if petiolate, the petiole not curved, or expanded at apex. (A few genera.) p. 919 Braconid^ DD. Abdomen with an elongate petiole, which is strongly decurved and expanded at apex. {Thaumatotypidea in Stilpnini.) p. 922 Ichneumonid^e CC. Second and third abdominal tergites not connate. D. Abdomen petiolate, the first segment elbowed and enlarged posteriorly (Cryptin£e in part), p. 922 ICHNEUMONiDiE DD. Abdomen sessile (Aphidiins in part), p. 919 BraconiD/E BB. The ventral segments chitinized, convex and without a longitudinal fold. C. Pronotum separated from the tegulae laterally by the interposition of a chitinized sclerite, the prepectus. Antennae elbowed. Hypopygium of the female divided, the ovipositor issuing from anterior to the tip of the ab- domen. (A few genera.) p. 941 Chalcidid^ CC. Pronotum reaching the tegulas laterally or the latter altogether ab- sent; no prepectus present. D . First abdominal segment not forming a ' ' scale " or " node ' ' between the propodeum and the gaster. Thorax sometimes with sutures largely obliterated. E. Fore tarsi chelate. (Females of Anteoninae.) p. 978. . . . Dryinid.^ EE. Fore tarsi normal. F. Hypopygium of the female divided, the ovipositor issuing from before the tip of the abdomen, which is more or less strongly com- pressed and with a mid- dorsal keel. Second abdominal tergite the longest. Petiole very short, cylindrical, scarcely visible. Wingless or subapterous forms are usually agamic females. (Mostly Cynipinas.) p. 934 Cynipid^ FF. Hypopygium of the female not divided, but closely applied to the pygidium, the ovipositor or sting issuing from between the two, at the tip of the abdomen. Abdomen rarely or never strongly com- pressed, without a mid-dorsal ridge. G. Mesopleura not divided by a transverse sutiue. Coxse and legs not unusually long. H. Abdomen margined laterally, the sides sometimes only acute, but usually with a blade-like carina. I. Antennae composed of ten segments, rarely less, but in that case without an unsegmented club. p. 933 . Platygasterid^e n. Antennae composed of eleven or twelve segments, or if of seven or eight they have an unsegmented club. p. 933 SCELIONID^ HH. Abdomen neither acute nor margined laterally. I. Males. J. Antennae of ten segments (Myrmecomorphus) . p. 951 . . . Embolemid^ JJ. Antennae of thirteen segments, p. 953 Mutillid/E JJJ. Antennas of fifteen segments. (Belytinae.) p. 932.... Belytid/e II. Females. J. Antennas of ten or eleven segments. K. Antennas of eleven segments. (Six genera.) p. 932 CERAPHRONIDyE KK. Antennae of ten segments. L. Antennae inserted close to the mouth. (Several genera.) p. 932 Ceraphronid^ LL. Antennae inserted on a frontal prominence in the middle of the face {Myrmecomorphus). p. 951 Embolemid/E JJ. Antennas of twelve segments. (See also JJJ.) *If the suture is entirely obliterated, the presence of two pairs of spiracles will indicate that the apparent second segment consists really of the second and third. 916 AN INTRODUCTION TO ENTOMOLOGY K. Prothorax, mesothorax, and propodeum more or less intimately fused into a chitinous box; usually with little or no trace of sutures, more rarely with the sutures visible but connate; still more rarely the prothorax is fully separated. L. First tergite not reaching the base of the petiole, but forming an apical gibbous cap thereto. Pro- thorax separated. (Apterogyninae and Chyphotinse.) p. 953 MUTILLID^ LL. First tergite reaching the base of the petiolar segment. M. Upper surface of posterior coxae with an erect inner lamella at base. Pronotum separated from mesothorax by a movable suture. (Myrmosina;.) p. 953 TiPHiiD.« MM. Posterior coxae simple. Pronotum and pro- podeum fused to the thorax, the sutures lacking. Ocelli wanting, p. 953 Mutillid^ KK. Prothorax, mesothorax, and propodeum fully separated. L. Hind edge of mesosternum with two horizontal lamellae between the middle coxae, which they partly overlap, p. 952 Thynnid^ LL. Mesosternum without such lamellce overlapping the bases of the coxae. M. Mesosternum with two minute, erect teeth between the middle coxae. Mesothorax elongate. Moderately large ant -like insects. (Methocinae.) p. 953 TiPHiiD^ MM. Mesosternum unarmed. Mesothorax rarely elongate. N. Head oblong, porrect; antennae inserted close to the mouth, never geniculate. Femora, es- pecially of the fore-legs, usually strongly thick- ened in the middle. Scutellum without pits. p. 965 Bethylid.^ NN. Head usually globular or transverse. An- tennae inserted in the middle of the face. Fem- ora not medially strongly thickened. Scutellum usually foveolate. O. Antennae geniculate. Scutellum with deep an- terior iovese; or if these are absent it is not distinctly separated from the mesonotum. (Sixteen genera.) p. 932 Belytid^ 00. Antennae not geniculate. Scutellum dis- tinct, without fovese. (New genus in Myr- mosinae.) p. 953 Tiphiid^ JJJ. Antennae of from thirteen to fifteen segments. K. Antennae inserted close to the mouth. Head oblong, porrect. Anterior femora spindle-shaped, p. 965 Bethylid.e KK. Antennae inserted on the middle of the face. Head globular or transverse. L. Abdomen produced behind into a pointed tube. Spur of the anterior tibiae without a ventral blade-like lamella. (Three genera.) p. 931 . . . Proctotrupid^ LL. Abdomen not produced behind into a tube. Spur of the anterior tibiae with two prongs and no ventral lamina. Anterior femora clavate. p. 932 . Bely'Tid^ HYMENOPTERA 917 GG. Mesopleura divided by a transverse suture into an upper and lower plate. Coxae very large and long; the legs long and usually distinctly spinose. p. 950 Pompilid^ DD. First abdominal segment forming a "scale" or "node" between the propodeum and the gaster. Thorax with its sutures distinct, but the mesothorax usually much reduced in size. p. 954 Formicid^ SuPERFAMiLY ICHNEUMONOIDEA The Larger Parasitic Hymenoptera Often after a great outbreak of insects people are astonished that the hordes of pests have disappeared so quickly and completely. Few of them realize that the subjugation of the pests was probably due either to the weather or to the activities of parasitic insects. In this superfamily are included some of the parasites most often re- sponsible for the control of insect outbreaks. They perform also the less noticeable but more important role of keeping most species of herbivorous insects below the level of economic importance. Entomologists have made many attempts to supplement the activities of native parasites with introduced species. Usually this has been a matter of going to the native home of an introduced pest for the purpose of bringing in the insects found to attack it there. Some introduced parasites have found conditions in their new home favorable for rapid and continued reproduction and have effected spectacular control. Pests of major importance have been reduced to insignificant numbers in a few years. Most attempts to introduce beneficial insects have met with failure or with very moderate success due to the inability of the parasite to establish itself or to build up sufficient numbers. A single success in this field of work, however, more than compensates for many failures. In the parasitic superfamily Ichneumonoidea are included the Stephanida?, Braconidas, Ichneumonid^, Trigonalidse, Aulacid-e, and Gasteruptiid^. In these families are most of the larger species of parasitic Hymenoptera. They have rather complete venation in the fore wing, no anal lobe in the hind wing, and an indefinitely large number of antennal segments, usually seventeen to sixty or more. The multi-segmented antenna is the only distinctive character of the superfamily and this is subject to the exception that the Aulacidse and Gasteruptiidse have only fourteen antennal segments. This obvious lack of cohesion makes one doubt the naturalness of the group. Correlated with its parasitic habits the larva of ichneumonoids is degenerate, legless, and maggot-like. Except for the mandibles the head appendages are more or less vestigial. The body has thirteen segments and in the mature larva nine pairs of spiracles. Ichneu- monoid larvse differ from those of parasitic Diptera in lacking the mouth hooks and pharyngeal skeleton so characteristic of the latter. They differ from chalcidoid larvae in having the labium and maxilla present or represented by sensory areas. These organs are not de- tectable in the chalcidoids. The ichneumonoids are all parasites upon other arthropods. 918 AN INTRODUCTION TO ENTOMOLOGY Lan^ce and pupse of holometabolous insects are the usual hosts. Some braconids parasitize plant lice and a very few attack adult Coleoptera. A few genera of ichneumonids are parasites in the eggs, cocoons or on the bodies of spiders. In a typical life history of an ichneumonoid, the adult female locates the host larva by searching in a likely spot, identifies it with a few gentle taps on her antenna, and then quickly deposits an egg inside the larva by inserting her sting-like ovipositor. The larva writhes and thrashes about but is usually not able to drive away the parasite before the deed is done. The parasite's egg soon hatches and the tiny maggot-like larva that issues from it lies in the body cavity of its host. It grows gradually by feeding on the blood and fat body, avoiding the vital organs. The host larva develops in a normal manner but perhaps is unusually lethargic. When the host is nearly ready for pupation the parasite begins more rapid feeding and growth. Soon it begins to gorge itself with the vital organs of its host which rapidly sickens and dies, leaving a limp and shrivelled carcass of which the parasite makes short work. The cocoon is spun by the mature parasite larva either in the remains of its host or a short distance away. Throughout its feeding life the parasite has not excreted any visible wastes. Just before pupation it discharges the accumulated wastes in its intestine in a mass called the meconium. This dries to a hard pellet in the posterior end of the cocoon. Pupa- tion takes place and a few days or weeks later the adult parasite gnaws a hole in one end of its cocoon and escapes fully hardened and colored. This is usually at a time when a new generation of the host is ready for parasitism. Some species are obligatory secondary parasites and will feed only on some other parasite. Others are either primary or secondary parasites according to whether or not other parasites are in the hosts in which they develop. Instead of living in the inside of their hosts, the larvae of some species are external feeders. In these cases the parasite egg is placed on the host or near it and the larva feeds through cuts in the host's skin. External parasites are liable to be dislodged and therefore are seldom found on exposed and active hosts. The usual victims are larvae or pupae in tunnels, nests, or cocoons. The externally parasitic species usually permanently paralyze the host by a sting from the ovipositor before depositing the egg. This immobilization of the host gives further protection to an externally feeding larv^a. An ichneumonoid larva feeding externally upon a paralyzed host in its burrow has habits which differ but little from those of tiphiid wasps whose larvae feed upon scarabseid beetle grubs permanently paralyzed in their burrows by a sting from the parent wasp. It is a short step from this type of life history to that so common among the wasps usually called predators. In these the female provisions a nest lor her offspring with one or several paralyzed insects. The difference is in the amount of care given to her offspring's food by the adult wasp rather than in the habits of the larva itself. It is thus difficult to distinguish between the parasitic and the predacious habit among the Hymenoptera. Recently some authors have been using the term HYMENOPTERA 919 parasitoid for the economy of the parasitic Hymenoptera (see Wheeler (23), page 26), for although the host is kept alive and usually de- veloping while it is being consumed the parasite eventually devours its prey completely as does a true predator. With the infinite variation in types of parasitism and the frequent intergradation with other modes of life it seems useless to try to restrict the term "parasite " too closely. Adult ichneumonoids feed upon the honey-dew secreted by Homoptera and at flowers such as Umbelliferae whose nectar can be reached by the insect's usually short mouth parts. For water, of which they need a good supply, they lap up dew or rain drops from leaves. The females frequently feed upon the host juices that exude from punctures made by the ovipositor. Some species will attack a larva or a pupa just for this purpose, puncturing it again and again to lap up the juices, but never depositing an egg. Since only the larva is parasitic, adult ichneumonoids show none of the degenerative specializations for a parasitic habit that would otherwise be expected. Polyembryony, or the development of several larvse from a single egg, is known to occur among the ichneumonoids only in the braconid genus Macrocentrus. Parthenogenesis is possible in most species. Unmated females usually produce only males. In a few cases females are produced. In these species the male is usually either extremely rare or entirely unknown. Family STEPHANID^ The Stephanids The stephanids are among the strangest of the Hymenoptera. The spherical head is on a long neck and has a crown of teeth. The very slender antennse arise just above the mouth. The hind femur is enlarged and has a series of teeth beneath. These insects are rare outside of the tropics and even there are not common. Their life history is unknown although they are supposed to be parasitic on the larvae of wood-boring beetles or in the nests of solitary bees or wasps. Family BRACONID^* The Braconids The Braconidas have a close superficial resemblance to the Ich- neumonidas. They differ from this family in always lacking vein M2 so that cells Mi and ist M2 are confluent (Fig. 11 48) and, except in the subfamilies Aphidiinae and Paxylommatinas, in having the second *Ashmead ('00) has given a key to the genera of Braconidae, but unfortunately this is difficult to use and contains many errors. Some recent revisions of North American species and genera are as follows: Aphidiinee, Bull. Md. Agr. Exp. Sta. 191 1, 152 : 147-200; Opiinee, Proc. U. S. Nat. Mus. 1915, 49 : 63-95; Bracon, Proc. U. S. Nal. Mus. 1917, 52 : 305-343; Apanteles, Proc. U. S. Nat. Mus. 1920, 58 : 483-576; Neoneurinse and Microgasterinae, Proc. U. S. Nat. Mus. 1922, 61 : 1-76; Meteorus, Proc. U. S. Nat. Mus. 1923, 63 : 1-44; Microbracon, Proc. U. S. Nat. Mus. 1925, vol. 67, art. 8, 85 pages; Braconinae, Proc. U. S. Nat. Mus. 1927, vol. 69, art. 16, 73 pages; Macrocentrus, Proc. U. S. Nat. Mus. 1932, vol. 80, art. 23, 55 pages; and Euphorinae, Misc. Pub. U. S. Dept. Agr. 1936, no. 241, 36 pages. 920 AN INTRODUCTION TO ENTOMOLOGY Wings of a braconid. and third abdominal segments inflexibly joined together. There is usually also a vein crossing the large cell situated below the stigma. This is wanting in the Ichneumonidse. The braconids as a rule are smaller than the ichneumonids. Many of the North American braconids large enough to be confused with ichneumonids have black wings and a red and black body, a color combination rare in the latter group. In this family are included proba- bly over two thou- sand North Ameri- can species. The great majority are parasitic upon caterpillars. The rest attack mainly thelarv^ae of weevils, leaf-beetles, borer beetles, and cyclorrhaphous Diptera. The subfamily Aphidiinse attacks plant lice, the subfamily Ichneutinae sawfly larvae, and the rare subfamilies Paxylommatinse and Neoneurinae are ant parasites. A few Alysiinae are secondary parasites. Because of the excellent characters offered by their venation, the braconids are easier to classify than the ichneumonids, yet because of their small size they have escaped the attention of the average entomologist so that many facts about them are still to be learned. About eighteen subfamilies are now recognized, of which the Alysiins, Aphidiina?, and Paxylommatinae are sometimes treated as separate families. Some of the larger and more interesting groups are discussed below. The subfamilies Vipiinas (= Braconinae), Spathiinae, HecabolinEe, Doryctina?, Hormiinae, and Aleiodinae are all closely related and per- haps should be made a single subfamily. In these the clypeus is arched upwards and the labrum is very concave so that there is a circular opening above the mandibles, hence the name Cyclostomi which is applied to this group. Members of the Cyclostomi usually parasitize caterpillars or beetle larv^ae living in tunnels or nests. The female permanently paralyzes the host larva by stinging it with her ovipositor, then deposits one or several eggs on its body. She may stop to lap up the juices exuding from the ovipositor wound. The eggs hatch into lar^^ae which feed through holes cut in the skin of the host. When mature, they spin cocoons near the host remains. The subfamily Cheloninse has the abdomen in the shape of an oval shield which looks like an inverted bath tub or a turtle shell. In some genera there are evident sutures separating the three tergites which make up the dorsal shield. In this subfamily the parasite inserts its egg into the egg of the host. The parasitized host larva, HYMENOPTERA 921 except for being somewhat stunted, develops normally to maturity, when the nearly grown parasite larva emerges from its body and finishes it off in one big meal. Ascogdster quadridentdtus was intro- duced into this country from Europe to control the codlin moth. Its life history is typical of the subfamily. In midsummer about thirty-five days are required for a generation. Although its activities are helpful, this species does not effectively control the codlin moth. The Microgasterinas includes species with hairy eyes and with the abdomen so short that it is surpassed by the hind femur. Except in the genus Apdnteles there is a tiny cell near the center of the fore wing. Most of our species have eighteen antennal segments. Microgdster, Microplltis, and Apdnteles are the genera of importance. All are parasitic on caterpillars. The genus Apdnteles contains nearly two hundred North American species and is probably the most beneficial among the braconids. Each species attacks a particular type of caterpillar — leaf miners, or cutworms, or larvsi of Sphingida;, etc. Many are gregarious parasites, often a hundred or more developing from a single host. The female may insert ten to thirty eggs at a single thrust of her ovipositor and may make several thrusts into a single caterpillar. The parasite larvae all mature at exactly the same time and bore to the outside simul- taneously. Often they spin their yellow or white cocoons at the point on the caterpillar from which they emerged, when they look superfi- cially more like eggs than cocoons (Fig. 1 1 49) . Other species may spin a mass of cocoons bound together by more or less loose silk near the body of the caterpillar (Fig. 11 50). The parasitized caterpillar lingers on for a few days after the parasites have left it and finally dies. The species commonly attacking sphingid larvae is Apdnteles congregdtus. Apdnteles glomerdtus attacks larvee of the cabbage butterfly. Through the efforts of Dr. C. V. Riley this European species was intro- duced and it is now widely distributed in North America. Other species of Apdnteles have been introduced to control the gypsy moth and the European corn borer. The Braconinae ( = AgathidincB) includes species with the cell next to the stigma extending less than half-way beyond the end of the stigma to the wing tip. There is a very small cell in the center of the wing below the stigma. These are the bra- conids most frequently collected on flowers. Many of the species have black wings and the abdomen or pj entire body red. Some species have elongate mouth parts for reaching nectar and the head prolonged below into a sort of beak. Edrinus limitdris is a black species about nine millimeters Fig. 1 149. — Caterpillar \\ith co- coons of a braconid. 022 AN INTRODUCTION TO ENTOMOLOGY long, common in the early spring. Most Braconinse parasitize cater- pillars. The Macrocentrinse includes the genus Macrocentnis with about forty species in North America. They are yellowish brown or more or less black in color. They are slender with long legs and with an ovipositor as long as the body. Caterpillars living in nests or in tunnels are the usual hosts. Macrocentrus ancylkorus is a native species first discovered parasitizing the strawberry leaf -roller {An- cylis comptdna) in New Jersey. It has been found the most effective control of the oriental fruit moth, a notorious pest of peaches, and has now been colonized in peach orchards all over the eastern United States and in some foreign countries. In some localities it parasitizes more than eighty per cent of the fruit moth larvae. Macrocentrus gifuensis is a polyembryonic species from the Old World introduced a few years ago to help control the European corn borer. It is one of the most effective parasites of this pest. The Alysiinae includes species with the teeth of the mandibles pointing outward instead of inward toward the mouth. The only other Hymenoptera with this type of mandible are the Vanhomiidce and the ichneumonid genus Lysiognatha, very rare insects. The Alysiinae are parasites of fly maggots, and the paddle-like mandibles are used by some for digging in filth in search of hosts. The Aphidiinae includes delicate little species with a movable joint between the second and third abdominal segments and with reduced wing venation. All are parasites of plant lice. The female aphidiine approaches an aphid and identifies it with a few taps of her antennae. She then stands high and ducks her abdomen down between her legs and forward in front of her head to plunge her ovipositor into the plant louse. In a few days the developing parasite larva has eaten out the inside of the aphid. It cuts a hole in the bottom of the aphid's empty skin and through this glues the carcass to the substratum. Then it makes its cocoon in the aphid's ab- domen. The adult braconid emerges by cutting a circular lid (Fig. 1151). In the genus Praon, the cocoon is spun beneath instead of inside the host and the dead aphid is used as a roof for the cocoon. Plant lice with braconid cocoons inside have an inflated appearance and brownish color that makes them conspicuous among a colony of living aphids. These ig- 1151- parasites are of prime importance in reducing the numbers of aphids and were it not for them, the lady beetles, the lace-wing flies, and the syrphids, plant lice would be serious pests. Family ICHNEUMONID^* The Ichneumon Flies The Ichneumonidae includes most of the larger parasitic Hy- menoptera. They are similar to the Braconidas and differ from most *The following papers should be consulted for identification of species: HYMENOPTERA 923 other Hymenoptera in having the narrow cell just behind the costal vein obliterated by the fusion or close approximation of the costal vein and the vein behind it and usually by having some of the ab- dominal sterna membranous. They differ from braconids in having cells Ml and ist M2 of the fore wing separ- ated by a vein (Fig. 1 152) and the second and third abdominal tergites movable. There are a very few exceptions to one or the other of these char- acters. Except for the frequent absence of the areolet, a small cell near the middle of the wing (Fig. 1 152), ich- neumonids have a very constant and distinctive venation in the fore wing. Many species are wasp-like in appearance but may at once be recognized as ich- neumonids by the long many-segmented antenna. Except perhaps for the Chalcididae this is the largest family of the Hymenoptera. Probably about six thousand species occur in the United States. All are parasitic and many are important enemies of destructive insects. The taxonomy of the family is difficult because the subfamilies and tribes are not easily characterized and must be learned by experience. Five subfamilies are usually recognized, but these are admittedly unnatural in some degree and any definition of them is subject to exceptions. The student, however, can place most of the common species by means of the key below. Some of the more important tribes of ichneumon flies are discussed under the different subfamilies, but space will not permit all of them to be mentioned. Fig. 1 1 52. — Wings of an Ichneumon fly. Tribes of Pimplinae, Proc. U. S. Nat. Mus. 1921, vol. 60, art. 4, pages 1-7; Labe- nini, Rhyssini, Xoridini, Odontomerini, and Phytodietus, Proc. U. S. Nat. Mtis. 1920, 57 : 405-474; Acoenitini, Proc. U. S. Nat. Mus. 1920, 57 : 502-523; Ly- corini, Polysphinctini, and Theronia, Proc. U. S. Nat. Mus. 1920, 58 : 7-48; Pimplini (except Theronia), Proc. U. S. Nat. Mus. 1920, 58 : 327-362; Odon- tomerus, Proc. U. S. Nat. Mus. 1930, vol. 77, art. 3, 15 pages; Cremastini, Proc. U. S. Nat. Mus. 1917, 53 : 503-551 and Proc. U. S. Nat. Mus. 1920, 58 : 268-288; Cryptini with a very small areolet, Proc. U. S. Nat. Mus. 1929, vol. 74, art. 16, 58 pages; Exetastes, Proc. U. S. Nat. Mus. 1937, 84 : 243-312; Netelia, Lloydia 1938 (1939), I : 168-231; Trogini, Trans. Amer. Ent. Soc. 1939, 65 1307-346; Ichneumoninae, Travis. Amer. Ent. Soc. 1877, 6 : 129-212; Diplazonini, Trans. Amer. Ent. Soc. 1895, 22 : 17-30; Tryphoninse (except Diplazonini), Trans. Amer. Ent. Soc. 1897, 24 : 193-348; Glypta and Lissonota (= " Lampronota"), Trans. Amer. Ent. Soc. 1870, 3 : 151-166. The last four papers cited are out of date and somewhat unreliable, but are the best available. Ashmead ('00) has given a key to all the genera, but the student will find this unreliable. 924 AN INTRODUCTION TO ENTOMOLOGY KEY TO THE SUBFAMILIES OF ICHNEUMONID^ By Dr. H. K. Townes A. Spiracles of first abdominal segment situated definitely behind the middle of the segment; sternite of first abdominal segment immovably fused with the tergite or if rarely free, then the abdomen strongly compressed. B. Abdomen more or less compressed; areolet (= a small cell near the center of the wing) more or less triangular or absent, p. 927 Ophionin^ BB. Abdomen depressed or cylindrical; areolet more or less pentagonal, quadrangular, or occasionally absent. C. Sternaulus (a horizontal groove in lower part of mesopleurum) sharp and usually more than half as long as the mesopleurum; ovipositor usually surpassing tip of abdomen, p. 927 Cryptin^ CC. Sternaulus absent or poorly defined and short; ovipositor not or but slightly surpassing tip of abdomen, p. 928 Ichneumonin^ AA. Spiracles of first abdominal segment situated near or in front of the middle of the segment; sternite of first abdominal segment usually more or less free from the tergite. B. Face and clypeus forming an even undivided surface; male claspers drawn out into a pair of long spines; ovipositor sheaths slightly shorter than the first abdominal segment, rather broad, flat, and somewhat polished; areolet large and rhomboidal. p. 927 (tribe Mesochorini) Ophionin^ BB. Face more or less separated from clypeus by a groove, or insect otherwise not entirely agreeing with the above. C. Ovipositor surpassing tip of abdomen; abdomen often with definite elevations and depressions above and usually elongate, p. 924. . Pimplin^ CC. Ovipositor not or but slightly surpassing tip of abdomen; abdomen without definite elevations and depressions above and not elongate unless also petiolate. p. 926 Tryphonin^ Subfamily PIMPLIN^ Most species of Pimplinae are black with femiginous or banded legs. They are parasites mainly of caterpillars and wood-boring beetle larvae. Their long ovipositors are adapted to reaching hosts in tunnels in wood or in weed stems. Megarhyssa ( = Thalessa) is our largest ichneumon fly (Fig. 11 53). It is a parasite of the wood-boring larva of the pigeon horn-tail, Treniex cclmnha. When a female finds a tree infested by this borer she selects a place which she judges to be opposite a Tremex burrow and making a derrick out of her body proceeds with great skill and precision to drill a hole in the tree. At the beginning of the process the excess length of the ovipositor is coiled into a sack formed by the very elastic membrane between the sixth and seventh abdominal segments. When most of the ovipositor is deep in the wood the ovipositor sheaths which do not enter with it form a loop over her back (Fig. 11 53). After the Tremex burrow is reached, a long egg flows down the tube in the slender ovipositor and is left on or near the host. The larva which hatches from the egg feeds upon the Tremex larva by sucking its blood and eventually destroys it entirely. When full grown it pupates in the Tremex burrow. The adult gnaws a hole through the bark to emerge. If the adult is a female, there are males waiting just outside and she is mated just after emergence or even before she can extricate herself from the hole. Females of the HYMENOPTERA 925 Fig. 1 1 53. — Megarhyssa lunator. four North American species are easy to distinguish. Megarhyssa atrdta has a black body and yellow head. The northern species M. nortoni has yellow circular spots on the sides of the abdomen. M. hmdtor and M. greenei have brownish abdomens with angulate yellow stripes on the sides (Fig. 1 1 53). M. lunator has an ovi- positor twice as long as its body while that of M. greenei is about one and a half times as long as its body. The tribe Polysphinctini comprises small species usually without an areolet in the fore wing and with a rather short ovipositor. They are parasites of spiders. The female tempo- rarily paralyzes a spider by stinging it and then glues an egg to its abdomen . The spider recovers and resumes its nor- mal activities. The maggot- like parasite larva hatches and keeps its tail end attached to the egg shell to maintain its position on the spider's abdo- men. It feeds through the skin of the spider and finally kills it and then spins a cocoon and soon emerges as an adult. The tribe Pimplini includes robust species with stout ovipositors about half as long as the abdomens. In the genus Theroiiia are species that are almost entirely fulvous in color. The other three genera, Pinipla, Apechthis, and Itoplectis are black and can usually be dis- tinguished from other Pimplinas by the hind tibia which is white at the middle and has the apex and base (including the extreme base) black. Members of this tribe are parasitic upon pupae of Lepidoptera. Each species parasitizes a great variety of hosts differing considerably both in size and relationships. Due to the varying sizes of the hosts the adult parasites have a remarkable variation in size. Usually males develop in the smaller hosts and females in the larger so that males average smaller than females. This is a frequent phenomenon among parasitic Hymenoptera but no satisfactory explanation for it has been advanced. Itoplectis conqnisitor is a common parasite on tent caterpillars and Theronia atalantce is a common hyperparasite of Itoplectis conquisitor. Sometimes Itoplectis is itself a secondary parasite. Species of Pinipla and Apechthis give off a strong pungent odor when captured. The tribe Lissonotini includes species with a tiny notch near the tip of the ovipositor and a single bulla or weak place in vein M2. The propodeum usually has a single semicircular carina. The larvae are internal rather than external parasites, a biological characteristic 026 AN INTRODUCTION TO ENTOMOLOGY found in the present subfamily only in this tribe and in the Pimplini. Caterpillars boring in twigs or weeds are the usual hosts of those with long ovipositors. The rest attack cutworms and similar caterpillars. Gljpta rufiscutelldris is a common parasite of the oriental fruit moth. In some localities it gives a moderately effective control of this pest. The genus Ceratogdstra contains wasp-like species with conical pointed abdomens. They are commonly found on goldenrod flowers. Subfamily TRYPHONIN^ The Tryphoninse includes most of the ichneumon flies that attack sawfiies, and the group is most abundant in our northern forests. In the tropics, where sawfiies are scarce, few species occur. Some Try- phoninas are slender, pale brown in color, and have large eyes. They fly at night and are often confused with the superficially similar Ophioninas but may be at once distinguished from these by their possession of an areolet and by the characters given in the key to subfamilies. The tribe Tryphonini contains short stocky species with the propodeum divided into many areas by cross and longitudinal carinse. Most of the species are black with the abdomen and legs largely reddish. The life history is quite characteristic of this and related groups. The egg is large and oval with a slender stalk. The female inserts the stalk of the egg into the skin of a sawfly larva near its head where the larva cannot turn to reach it with its mandi- bles. The stalk stays embedded in the larva's skin, anchoring the egg in place. After the sawily spins its cocoon the egg hatches into a small larva which feeds on the host until it is consumed. The parasite pupates to emerge as an adult the following spring to para- sitize the next generation of sawfiies. A female may often be seen with an egg ready for deposition attached by its stalk to her ovipositor, and in the genus Polyhldstus a dozen or more eggs may be carried on the ovipositor at once. The older eggs, those near the tip of the ovipositor, contain fully developed larvae. It is said that if a host is not found soon enough the oldest eggs are discarded. The tribes Mesoleiini and Mesoleptideini contain species usually more slender than the Tryphonini and with the propodeum not divided into numerous areas by carinae. These tribes also parasitize sawfiies, but the egg does not have a stalk and is inserted into the host larva. The tribe Metopiini contains species that are usually black, with a very protuberant face, and short stout legs. Most of the species are small, though the genus Met dp his contains fairly large individuals. The Metopiini are parasites in lepidopterous pupse. The genus Metacaliis contains two cosmopolitan parasites of clothes moths. The tribe Diplazonini contains small stocky bright-colored species with the upper tooth of the mandible broad and chisel-shaped. All are internal parasites of aphid-eating syrphid larvae. The adult emerges from the host puparium. Dipldzon IcEtatdrius is a species that is common all over the world. It may be recognized by its black-, white-, and red-banded hind tibia, HYMENOPTERA 927 Subfamily OPHIONIN^ This subfamily may usually be recognized by its compressed abdomen, though a few species have the abdomen indistinctly com- pressed. All are internal parasites, usually solitary. The majority parasitize caterpillars. The tribe Mesochorini is characterized in the key to subfamilies. The species are mostly small. All are secondary parasites. The female of Mesochdrns finds a host that is already parasitized and probes with her ovipositor until the parasite larva is reached, where- upon she oviposits within the body of the parasite. The braconid genus Apdnteles is frequently attacked by Mesochorus. The tribe Campoplegini includes a great number of species. The face is evenly convex, not separated from the clypeus by a groove, and is covered by short, thick silvery -white hair. The head and thorax are usually entirely black and the abdomen more or less reddish. Many species are important enemies of injurious caterpillars. A colony of Anisota larvse is sometimes found with many dead individuals stuck to the leaves and twigs. They are swollen at the middle and shrivelled at both ends. These have been parasitized by Hyposoter fugitivus whose cocoon makes a swelling in the middle of the dead caterpillar. Many Campoplegini spin exposed cocoons. These are closely woven, oval in shape, and often whitish encircled with irregular dark bands. The tribe Ophionini includes species with an unusual venation in the fore wing. The large cell just above cell ist M2 (Fig. 1154) extends further distad than does cell ist. M2. Most are night-flying species about eighteen to twenty millimeters long, yellowish brown in color, and with large eyes. These belong to the genera Ophion and Enicosplliis (Fig. 1 1 54) . They parasitize cutworms and similar caterpillars. One very large species of Enicospllus infests the cater- pillars of the polyphemus moth and its rela- tives. The caterpillar lives until it spins a cocoon, but does not change to a pupa. The Fig. 1154.— Ophion. ichneumonid lar^^a, when full grown, spins a dense brownish cocoon within the cocoon of the caterpillar. Thyreo- don atricolor is a large coal-black species with bright orange antennas. It is often seen flying along the edges of woods in search of its hosts, sphingid larvas. This species and other large ichneumonids will sting with the ovipositor if not handled carefully. The tribe Therionini includes relatively large species with very slender abdomens and the hind tarsi more or less swollen. They are parasites of various caterpillars. Subfamily CRYPTIN^ The Cryptinse can usually be recognized by the exserted ovipositor somewhat shorter than the uncompressed abdomen and by the fact that the first abdominal segment is narrow at the base, decurved 928 AN INTRODUCTION TO ENTOMOLOGY and broadened at the apex and with the spiracles much nearer the apex than the base. The species are external parasites of pupas and prepupse in cocoons. A few parasitize wood-boring beetle larvse or are internal parasites of dipterous larvse. The tribe Hemitelini includes small species with the outer vein of the areolet lacking so that the areolet is incompletely formed. Hemiieles parasitizes a variety of pupas enclosed in cocoons and often attacks cocoons of other ichneumonids and of braconids, thus be- coming a secondary parasite. Gelis is very similar to Hemiteles in appearance and habits except that the females are always wingless. The males may be either with or without wings, even in the same species. The wingless forms have a superficial resemblance to ants. Besides attacking various small insect cocoons, Gelis often parasitizes the egg cocoons of spiders. The tribe Phygadeuonini has the areolet complete and the pro- podeum with both longitudinal and transverse carinas. It includes a large number of rather small species parasitic on Lepidoptera and Diptera. The tribe Cryptini differs from the two preceding tribes by having two transverse and no longitudinal carinas on the propodeum. The larger species of the subfamily belong here. Agrothereutes extremdtis infests the cocoons of the cecropia moth. The odor of fresh silk draws the female parasite to the newly spun cocoon of the host. About thirty parasites develop in each cocoon. Agrothereutes nuncius parasitizes the promethea moth, and a third species of the genus at- tacks the polyphemus. Subfamily ICHNEUMONIN^ Members of this subfamily resemble the Cryptinas in general ap- pearance but lack a definite stemaulus, have a short ovipositor, and are more stocky in build. They are all parasitic upon lepidopterous pupas. The female oviposits into either the host larv^a or the pupa, but the adult emerges from the pupa in both cases. In the tribe Phccogenini the propodeal spiracles are round. Other members of the subfamily have these spiracles long and oval. The Phccoginini are small species parasitic upon Microlepidoptera. The tribe Ichneumonini comprises many species about thirteen millimeters long and somewhat wasp-like in appearance. It may be distinguished from the preceding tribe by the long oval propodeal spiracles and from the following tribe by the fact that the scutellum is usually fiat or convex, and not subconically elevated. In this tribe the females are usually of a more stocky build than the males and often so differently colored that it is difficult to decide which males belong with the various females. The sexes also differ in habits, the males being entirely free-living and the females of many species spending much of their time searching for hosts in grass tufts and under dead leaves and debris. Females may be found overwintering in rotten logs, under bark, and in tufts of grass. Some species enter hibernating quarters in August, long before the first signs of cold weather. Each kind occurs in a particular type of shelter and is not HYMENOPTERA 929 to be found elsewhere. Species hibernating in logs often congregate in groups of three to twenty in old beetle burrows and other cavities. It is strange that Ichneimion idtimus and /. mendax, two of the com- monest species collected in hibernation, have never in the author's knowledge been found during the growing season, and their males are apparently unknown. The genus Hoplismenus, with a conical scutellum, is parasitic on nymphalid butterflies. The other species, most of which have been included in the genera Ichneimion and Anihlytcles, parasitize largely Noctuidae and Geometridae. The tribe Trogini includes large species about twenty millimeters long with subconical scutella. Tragus vulplnus is a common red species with black wings. The female oviposits into caterpillars of swallowtail butterflies, and the adult parasite emerges through a hole cut in the side of the chrysalid. Most of the other Trogini are parasitic on hawk moths. Family TRIGONALID^ The Trigonalids The family Trigonalidas includes a small number of rare species. The adults look very much like sawflies. They differ from other ichneumonoids in having a distinct costal cell in the fore wing and more than fourteen antennal segments. Female trigonalids lay their minute flattened eggs, about ten thousand in number, on the under- side of leaves just back of the margin. In some species they are in- serted into the leaf tissue. The eggs hatch when eaten with the leaves by caterpillars or sawfly lar\^ae, provided that the shell is broken in the process. The young larva enters the body cavity of the cater- pillar and develops either as a primary parasite or as a secondary parasite on some other parasite of its host. Some species are parasitic in vespid nests. It is not known how these reach their hosts. One species found parasitic in vespid nests has been observed to insert its eggs into the margins of leaves. For a classification of the family see Schulz, Genera Insectorum 1907, fasc. 61, 24 pp., 3 pis. Family AULACID^ The Aidacids The aulacids have the abdomen attached high on the propodeum far above the bases of the hind coxae as in the Gasteruptiidae and the Evaniidae. They may be distinguished from these families by the venation (Fig. 1155), the linear hind tibia, and the lack of a separate petiolar segment to the abdomen. The ovipositor is somewhat longer than the abdomen. There are three Nearctic genera: Pristdiilacus with three or more teeth on the tarsal claws; Odqntdulacus with one or two rather blunt teeth on the claws; and Aulacus (= Pamme- gischia) with the claws apparently simple but each with a tooth at the extreme base. Aulacus parasitizes the larvae of Xiphydria, a wood- boring sawfly. The other two genera attack larvce of wood-boring 930 .l.V INTRODUCTION TO ENTOMOLOGY Wings of an aulacid. Coleoptera. All may be collected on the trunks of dead or dying trees but are seldom common. Female aul- acids have the inner side of each hind coxa notched to form a channel for the guid- ance of the ovi- positor when the coxae are brought to- gether over it. It is interesting to note that the braconid genus Capitonius and the ichneumonid genera Labena and Apechoneura have the hind coxas notched for the same purpose. These genera further resemble the Aulacidae in having the abdomen attached high on the propodeum and in being parasitic on wood-boring Coleoptera. Apparently the habit of supporting the ovi- positor between the hind coxae when it is in use has some causal con- nection with the high attachment of the abdomen. Revisions of this family were included in their papers on Evaniidae by Bradley ('08) and Kieffer ('12). Family GASTERUPTIID.^ The Gasteruptiids The family Gasteruptiidae, often spelled incorrectly Gasterup- tionidae, resembles the Aulacidae and the Evaniidae in having the abdomen attached high on the propodeum. It differs from these families in having the hind tibia bulbously swollen toward the tip and in having venation like Figure 1157. The front wing can be folded lengthwise. Figure 1156 represents a species of Gas- teriiption, in which genus are included nearly all of the twenty-odd North American members of the family. Fig. 1 1 57. — Wings of Gastertiption incertus. HYMENOPTERA 931 Except that some have long ovipositors and some short, the various species look much alike. They are parasitic in the nests of solitary bees and wasps. The adults are common on umbelliferous flowers and around logs in which their hosts are nesting. A monograph of this family was included by Kieffer ('12) in his paper on Evaniidae. SuPERFAMiLY PROCTOTRUPOIDEA The Proctotr lipoids The Proctotrupoidea includes mostly very small species super- ficially resembling chalcids or braconids. Most of them are black with the legs and antenna often brownish or reddish. The first three families listed have a fairly complete venation in the front wing. In the other families it is more or less reduced. The hind wing has never more than one closed cell and lacks an anal lobe. The ovi- positor issues from between dorsal and ventral plates at the tip of the abdomen. In most other parasitic hymenoptera it issues from a subterminal cleft on the ventral side of the abdomen. These insects may be distinguished from chalcids by the fact that the pronotum extends back to the tegula. They dift'er from the braconids and ich- neumonids in having never more than fifteen antennal segments. A few proctotrupoids are inquilines. The rest are internal parasites of other insects or their eggs. The North American Proctotrupoidea were monographed by Ashmead ('93). Note that the first three subfamilies of Ashmead's classification, those in which the hind wings possess an "anal lobe," are now included in the Vespoidea and Sphecoidea. The family ROPRONIID/E includes the single genus Ropronia with a few rare species in North America. The adults are about eight millimeters long and have a subcircular compressed abdomen on a petiole. They may be collected among rank herbage in moist woods. The immature stages are unknown. The family HELORIDtE includes the genus Helorus with the single species H. paradoxus in North America. It is a black species, about four millimeters long with fifteen -segmented antenna and a petiolate abdomen. The adults may be collected on umbelliferous flowers. The larvae are parasitic in the cocoons of Chrysopa. The family VANHORNIID.'E includes the single rare species Vanhoriiia eucnemiddrum occurring in eastern North America from Massachusetts to Virginia. It is a parasite of Isorhipis ritficdrnis, a beetle working in dead wood that is fairly sound. The adult Van- lidrnia has very broad mandibles with the teeth pointing outwards. The abdomen is covered almost entirely by single dorsal and ventral sclerites. See Crawford ('09). The family PROCTOTRUPID^,* also called Serphida?, con- tains several closely related genera and about two score North American species ranging from about three to six millimeters in *For a monograph of the family see Kieflfer ('14) and for a recent revision of our species see Brues, Jour. New York Ent. Sac. 1919, 27 : 1-19. 932 ^A' INTRODUCTION TO ENTOMOLOGY length. They may be recognized by the large stigma in the fore wing just beyond which is a short but well-defined cell smaller than the stigma. The abdomen is circular in cross-section and tapers to a coni- cal point. In the male there is a pair of pointed claspers and in the female a heavy tubular ovipositor sheath. The species of Procto- trupes have a red abdomen. The proctotrupids whose habits are known are all solitary or gregarious internal parasites of beetle larvae. The family PELECINID.E is represented by a single species, Pele- clnus polyturdtor (Fig. 1 1 58). The females are often confused with ich- neumon flies but maybe easily recog- Fig, 1 158. nized by the long cylindrical abdo- men. The abdomen of the male is much shorter, with about the same length and shape as that of a Sphex wasp. This sex is very rare in the United States, but is common in some parts of South America. The species is a solitary internal parasite on the larvas of June-beetles. The adult females are common in August and September. This family and the Proctotrupidse have many structural resemblances. They are doubtless closely related. The family BELYTID^* differs from the following procto- trupoid families in that the antennae arise from an elevated portion of the face at some distance above the clypeus. It differs from the preceding families in that the fore wing lacks a stigma. There are two subfamiHes: the Belytinae with a closed cell in the hind wing, and the Diapriinse without a closed cell in the hind wing. The subfamily Belytinae contains several common genera whose species resemble Figure 11 59. Some species are known to parasitize larvag of My- cetophilidae and other Diptera breeding in fungi. The subfamily Diapriinse contains, among others, the remarkable genus Gdlesus. This has an oblong head with a turret of teeth on top. The face slopes sharply back- wards to the mandibles which are long and Fig. 1159. Proctotrupid point backwards. The wings can be folded lengthwise. Gdlesus and other Diapriinae are parasites in dipterous puparia. In the family CERAPHRONID^, often called Calhceratida?, the nine to eleven-segmented antennae are inserted next to the clypeus, but unlike the Scelionidae and Platygasteridae the lateral margin of *For a monograph of the family see Kieflfer ('16). H YMENOP TERA 933 the abdomen is rounded. In the subfamily Megaspilinas the fore wing has a large stigma. This is absent in the other subfamily, Cera- phroninae. The ceraphronids attack a variety of hosts, including Cecidomyiidas and other Diptera. Certain species of Lygocerus are secondary parasites of braconids which attack aphids. The family SCELIONID^ have the usually twelve-segmented antennas attached near the clypeus. The abdomen is more or less depressed and has an acute, usually carinate, lateral margin. Except possibly for the Platygasterida?, this is the largest family of the Proctotrupoidea. The species are all parasitic in insect or spider eggs. Bmis parasitizes the eggs of spiders, Trissolcus and Hadroiidtiis parasitize eggs of Hemiptera, and Telenomus attacks eggs of Lepi- doptera and Hemiptera. Scelio attacks the eggs of locusts. A species of Scelio has been observed to penetrate the loose soil above a locust's egg pod and with her very extensible ovipositor reach every egg in the pod for oviposition. Sometimes she first chews a hole in the pod and backs into it for oviposition. A few scelionids exhibit the interesting phenomenon called phoresy — they attach to another insect for transportation. Phanuriis benejiciens is a common parasite of the eggs of pyralidid moths in the Oriental Region. The adult Phanurus attaches to a female moth, and when the latter oviposits the parasite leaves the body of the moth to parasitize the freshly laid eggs. The European Rielia manticlda has comparable habits. The female takes up a position on the body of an adult Mantis, usually a female. The wings are then discarded and the scelionid lives as a true external parasite. The usual position is under the wings of the host, but other more or less protected areas are inhabited also. When the Mantis lays her egg mass the Rielia enters the frothy, not yet hardened, covering of the egg pod to parasitize the eggs. After oviposition the parasite returns to the Mantis. Scelionid first stage larv« are like those of certain other hymenop- terous egg parasites in being of a bizarre yet undifferentiated form which is often termed cyclopoid from its general resemblance to Cyclops, the water flea. The body is sack-like and unsegmented. At the anterior end is a pair of long mandibles, and posteriorly is a long ventrally curved tail that is often forked. Near the middle of the body are bands or tufts of long spines. The long mandibles and whip-like tail serve for locomotion and for disorganizing the contents of the egg. The second stage lar\^a is of more normal form. The family PLATYGASTERIDyE includes many minute black species. The usually ten-segmented antenna are attached next to the clypeus, the abdomen is depressed with a sharp lateral margin, and the wings are veinless (Platygasterinse) or with a single short vein (Inostemminse). Most of the species parasitize the larvae of Cecidomyiidae. The egg is inserted into that of the host, but develop- ment of the parasite is retarded until the host egg has hatched. Sometimes young cecidomyiid larvae are attacked. There are a few records of platygasterids being reared from mealy bugs, white flies. 934 AN INTRODUCTION TO ENTOMOLOGY and other insects. Some species of Platygaster are poly embryonic. For a revision of the Platygasterinse see Fonts, Proc. U. S. Nat. Mus. 1924, vol. 64, art. 15, 145 pages. SUPERFAMILY CYNIPOIDEA The Cynipids Most members of this superfamily are small insects and many of them are minute; for this reason they are not commonly observed; but the galls produced by some species, especially those that are found on oaks and roses, are very familiar objects. Not all cynipids, however, produce galls ; some are parasites and others are inquilines, living in galls produced by other species. The antennae of the cynipids are not elbowed and only rarely composed of more than sixteen segments ; the pronotimi is produced on each side so as to reach the tegula or is separated from it only by a membranous area ; the wings lack a stigma and have at most five closed cells ; the wings are rarely wanting ; the abdomen is strongly compressed. In most genera the tergites of the basal abdominal segments differ greatly in length ; in some the sec- ond is half as long as the entire ab- domen (Fig. 1 1 60). For papers on the classification of the Cynipoidea see Ashmead ('03) Fig. 1160.— Amphibolips. and Dalla Torre and Kieffer ('02 and '10). Dalla Torre and Kieffer recognize only a single family of cynipids, the Cynipidae; this they divide into ten subfamilies, seven of which are represented in our fauna. These are the Ibaliina^, Anacharitinae, Aspicerinas, Figitinas, Euco- ilinae, Charipinae, and Cynipiuce. The first six of these subfamilies include comparatively few species. These are parasitic, infesting chiefly dipterous larvag and aphids. The last subfamily, the Cyni- pinas merits a more detailed discussion. Subfamily CYNIPIN^ This subfamily is composed of the gall-flies or gall-wasps as they are termed by some writers. Most of the species cause the growth of galls on plants, but some species, the guest gall-flies, are inquilines living in galls produced by other species. Although these insects are known as the gall-flies it should be remembered that galls are produced by many insects that do not belong to this subfamily. Galls made by plant -lice, flies, and moths HYMENOPTERA 935 have been described in the preceding pages, and galls are also produced by beetles and certain other insects; but the great majority of tliese strange growths are made either b\' gall-midges, mites, plant-lice, or true gall-flies (Cynipin^) . The galls made by mites and plant-lice have open mouths, from '.vhich the young of the original dweller escape. But in the case of the gall-flies the gall is closed, and a hole must be made by the insect in order to emerge. Moreover, there is no reproduction of insects within the galls of gall-flies, as there is within the galls of mites and plant-lice. It is a remarkable fact that each species of gall-insects infests a special part of one or more particular species of plants, and the gall produced by each species of insect is of a definite form. Hence when an entomologist who has studied these insects sees a familiar gall, he knows at once what species of insect produced it. Naturalists have speculated much as to the way galls are made to grow. It has been supposed that at the time the egg is laid there is deposited in the tissue of the plant with it a drop of poison, which causes the abnormal growth. I3y this theory the difi'erences between the galls of different insects was explained by supposing that the fluid produced by each species of insect had peculiar properties. There are certain kinds of galls which may be produced in this way. Thus it is said that the wound made by a certain saw-fly in the leaves of willow causes an abundant formation of plant-cells, and the gall thus formed attains its full growth at the end of a few days, and before the larva has escaped from the egg. But with the gall-flies the gall does not begin to grow until the larv^a is hatched ; but as soon as the larva begins to feed, the abnormal growth of the plant commences. In this case, therefore, if the gall is produced by a poison, this poison must be excreted by the larva. Galls produced by the different species of cynipids differ greatly in form and are found on all parts of plants. A most useful manual for the identification of galls is the "Key to American Insect Galls" by Dr. Felt ('i8) in which, are figures of the galls of many of our gall-making insects, including those of all orders. There are two terms that are frequently used in the descriptions of galls ; these are monothalamotis, indicating that the gall contains a single larval cell, and polythalamous indicating that the gall is com- pound, containing more than one larval cell. Certain insect-galls have been found valuable for various purposes; they have been used in medicine, in the manufacture of ink, for tan- ning, and for dyeing. A sirmmary of the literature dealing with the uses of insect -galls was published by Fagan ('i8). There exists in many species ot gall-flies an alternation of generations; that is, the individuals of one generation do not re- semble their parents, but are like their grandparents. In many cases the two succeeding generations of a species differ so greatly that they have been considered as distinct species until by careful studies of the life-cycle one has been found to be the offspring of the other. 938 AN INTRODUCTION TO ENTOMOLOGY In those species where an alternation of generations exists, one generation consists only of agamic females while the other consists of both males and females, which reproduce sexually. In some cases the galls produced by the two generations are quite similar; but in others they are very different and are found on different parts of the host plant. For an example of this see the account of the hedgehog gall-fly, Andricus erinacei, given below. The guest gall-flies or inqtiilines: — Some species of this subfamily do not form galls but lay their eggs in the galls made by other species. The larvae of these inquilines feed upon the galls produced by their hosts and in some cases do not discommode the owners of the galls in the least. But some guest gall-flies are parasites as well as guests. For example, Triggerson in his study of the hedgehog gall-fly ('14) found that the larva of Synergus erindcei, a guest in the hedgehog gall, mines from cavity to cavity of the gall and feeds on the occupant of each in turn. Among the more conspicuous of our cynipid galls are the following. The oak hedgehog gall, Andricus erindcei.- — A common gall on the leaves of white oak is one known as the oak hedgehog gall. This gall is rounded or oblong, with the surface finely netted with fissures, and more or less densely covered with spines (Fig. 1161, a). It varies in length from 10 mm. to 15 mm., and occurs on both sides of the leaves. The point of at- tachment is generally on the midrib, though it is often found on the lateral veins. When young the gall is yellowish green, but in autumn it becomes yellowish brown. This gall is poly- thalamous, containing from two to eight larval cells (Fig. 1161, b). Within the hedgehog galls is developed one generation, the agamic one, oi Andricus erinacei. The alternating generation, the sexual one, is developed in very different galls made on the terminal growing points of buds and bud-scales. These are small, thin-walled, elongate, egg- to 3 mm. in length, and are monothalamous. The life-cycle of this species was very carefully worked out by Triggerson ('14), from whose account the data given here are com- piled. The two generations are distinguished by the use of trinominal names, as follows. . Andricus erinacei erinacei.- — This is the agamic form, which is de- veloped in the oak hedgehog galls. In this form the wings are vestigial not twice the length of thescutellum. The adults emerge in November and deposit their eggs in the leaf- and flower-buds. Andricus erinacei bicolens.- — -This is the sexual form, which is de- veloped in the galls formed in the buds. The larvcc hatch in May, from eggs laid by the agamic form the previous autimm and produce the galls known as the soft oak-bud galls. The adults, male and female, emerge early in June, and the females lay their eggs in the Fig. 1 1 61. — The oak hedgehog gall: a, gall on leaf; b, sec- tion of gall. shaped galls, from HYMENOPTERA 937 leaf-veins ; from these eggs hatch the larv^ that cause the growth of the oak hedgehog galls. In the sexual form the wings are well- developed. The name bicolens was proposed for this form bv Kinsey ('20). The oak-apples. — There are various kinds of galls found on the leaves and stems of oaks that are commonly known as oak-apples, a name suggested by the spherical form and large size of some of them. Sev- eral of these are quite similar in ex- ternal appearance but are markedly different in internal structure. In all there is a firm outer wall and a small, central larval cell (Fig. 1 162). The part of the gall be- tween the larval cell and the outer wall differs in struc- ture in the galls of different species of gall-flies; in some it is filled with a spongy mass of tis- sue, in others the larval cell is held in place by a small number of filaments that radiate from it to the outer wall. The large oak-apple, Amphtholips conflilens. — This is the largest of our common oak-apples, measuring from 18 to 50 mm. in diameter. It occurs on several species of oak and is usually attached to a vein or the petiole of a leaf. The space between the larval cell and the outer wall of the gall is filled with a spongy mass of tissue, in which in some of the galls there are many radiating fibers, as shown in the figure above, but in other galls these fibers are indistinct, the space being filled with an amorphous mass of tissue. In spite of the fact that these galls are common and conspicuous the life-cycle of the species that produces them has not been fully worked out. What is known of it is based chiefly on the observations of Walsh (1864), little has been added during the long interval since this publication. The oviposition has not been observed. The galls appear on the leaves early in the spring; from some of them there emerges in June a generation of gall-flies consisting of both males and females; and from other galls there emerges in the autumn a generation of gall-flies which consists only of females. An oak-apple. 938 AN INTRODUCTION TO ENTOMOLOGY Fig. 1 1 63. — The large empty oak-apple. The large empty oak-apple, Amphtholips indnis. — There are two oak-apples which are very similar in structure, and which may be termed the empty oak-apples. In these the space between the central larval cell and the outer shell contains only a few, very slender, silky filaments, which hold the larval cell in place (Fig. 11 63). The larger of these two galls, measures from 25 to 35 mm. in diameter, and is found on the leaves of the scarlet oak and red oak. Externally this gall resembles that of the preceding species but is easily dis- tinguished by its internal structure. The adult gall-flies emerge in June and early in July; they are male and female; an agamic form of this species is not known. The smaller empty oak-apple, Diplo- lepis centncola. — This gall is found on the lower side of leaves of the post-oak and measures from 1 5 to 20 mm. in diameter. It is sometimes tinged with pink and covered with a white bloom. The adult gall-flies emerge in October and are all females. A sexual generation of this species is not known. The oak-bullet- gall, Disholcaspis globulus. — One of the most common galls on white oak, chestnut oak, and scrub chestnut oak is a bullet-shaped gall w^hich is at- tached to the small twigs of these trees. This gall measures from 8 to 16 mm. in diameter and oc- curs singly or in clusters of two, three, or more. In- ternally it is of a compact, rather hard, corky texture, and contains a free, oval, larval cell, re- sembling an egg. The adult gall-flies emerge during October and November ; these are all females; a sexual generation of this species has not been identified. The giant oak-gall, Andricus calif ornicus. — This is the most com- mon oak-gall of the Pacific Coast. It is very abundant on the twigs Fig. 1 1 64. — The mossy rose-gall. HYMENOPTERA 030 and branches of the CaHfomia white oaks, and during the winter, when the trees are bare, it is a very conspicuous object, on account of its abundance and large size. It varies in shape from globose to reniform and also varies greatly in size; some of the larger ones measure more than loo mm. in their greatest diameter. The outer surface of the gall is white and usually smooth; the interior is more or less filled with a compact soft material, and contains from one to a dozen larval cells. Several varieties of the gall-fly that produces this gall are described by Kinsey ('22). The mossy rose-gall, RJwdltes roses. — This is a very common poly- thalamous gall, which is fonned on the stems of rose bushes, especially of the sweetbrier. The gall consists of a large mass of moss-like filaments surrounding a cluster of hard kernels (Fig. 11 64). In each of these kernels a gall-fly is developed. The galls appear early in the summer, but the adults do not emerge till the following spring. These are male and female; there is no alternation of generations in this species. SuPERFAMiLY CHALCIDOIDEA The Chalcid-flies This superfamily is the most highly evolved of the Hymenop- tera. It includes the family Chal- cididse with a very large number of genera and species. A few species are as large as honey-bees, but the vast majority are minute. Most are black or metallic green- ish in color, but some are brown or yellow. The most distinctive feature of the group is the pres- ence of a separate sclerite, the prepectus, in front of the meso- pleurum. This sclerite is inter- posed between the pronotum and the tegula so that the two are not in contact as in most other Hy- menoptera. In a few chalcids the prepectus is very small or entirely absent. Chalcids have the an- tenna elbowed and never with more than thirteen segments. The ovipositor usually does not extend beyond the tip of the ab- domen but may be quite long. Each wing has only a single vein. In some genera a few other indistinct veins can be traced. Fig. 1 165. — A chalcid-fly, Aphycus emptor. Fore wing of a chalcid-fly, 940 AN INTRODUCTION TO ENTOMOLOGY The vein that persists in the wings of chalcid-flies consists probably of the coalesced subcosta, radius, media, the stigma, the radial cross- vein, and the base of vein R3. Writers on the Chalcidoidea make use of a special set of terms in describing the different parts of this com- pound vein. These are the suhmarginal vein or subcostal vein (Fig. 1 166, a), the marginal vein (Fig. 1166, h), the postmarginal vein (Fig. 1 166, c), and the stigmal vein (Fig. 1166, d). The chalcid-flies constitute an exceedingly im.portant group of in- sects from an economic standpoint ; and nearly all of them are bene- ficial, being parasites that do much to keep in check noxious insects. A few species, however, are ph}i;ophagous ; among these are those of the genus Isosonia that infest the stalks of growing grain, and species of several genera that infest the seeds of various plants. While these are noxious, the fig-insects, forming the subfamily Agaoninte, although phytophagous are very beneficial to man. Insects in all stages of their development suffer from the attacks of chalcid-flies, eggs, larvae, pup^e, and even adults in a few cases being attacked by them. The larvag of chalcid-flies usually feed within the body of their host, but some species are external parasites of other larvce. While the development of most species of chalcid-flies is a normal one, in certain species remarkable modifications of the usual course exists. The phe- nomenon of polyembryony which has been observed in several species is dis- cussed on an earlier page. Another modification of the usual course of develop- ment is the existence of a hypermetamorphosis that occitrs in some genera. Fig. 1 167. — Planidium of Perilampus. From left to right, dorsal, lateral, and ventral views. (After Ford.) Fig. 1168.— Peril- ampus hyalinus. Mature larva, greatly enlarged. (From Smith.) In these cases the larvae when they leave the egg differ greatly in form from ordinary chalcid-larvae (Fig. 1167). and are active, moving about in search of their prey. This active instar was termed by Professor Wheeler, who first de- // YMENOP TERA 941 scribed it, the planidiuni, from the Greek meaning diminutive wanderer. The planidea of the species of several genera have been described. Two of these, Orasema viridis, described by Wheeler ('07a) and Psilogaster Jasciiventris de- scribed by Brues ('19) are parasites of ants, and Perilampus hyalmus described by H. S. Smith ('12) is a secondary parasite of the tachinid and ichneumonid para- sites of the fall webworm. The planidium figured above was found by Miss Norma Ford within the bodies of dissected specimens of one of the meadow- grasshoppers, Conocephalns fasciatus; it is probably a secondary parasite of some parasite of the grasshopper (Ford '22). The development of Perilampus hyalinus will serve as an illustration of the life-cycle of these remarkable parasites. The egg has not been observed, but it seems probable that it is deposited upon the food plant of the fall webworm in the vicinity of a colony of this insect. The planidia, which measure less than 0.3 mm. in length and are therefore almost invisible to the unaided eye, were found first on the exterior of the caterpillars; later within their bodies, having bored through the cuticula of the caterpillar by means of their well-developed mandibles; still later the planidia were endoparasitic within the larvas of parasites of the caterpillars. After feeding for a time the planidium molts; the second instar is ovate in shape, with the head bent underneath. After another short period of feeding the larva molts a second time and becomes greatly changed in form (Fig. 1168). Finally after the primary parasite has left the caterpillar and pupated the larva of Peri- lampus becomes an ectoparasite. It then soon completes its growth and pupates. Family CHALCIDID/E Many authors regard as distinct families the groups treated here as subfamiUes. Since there is much difference of opinion regarding the extent of the various groups and since the definition of many of them is difficult, it seems unwise to call them families. The classi- fication adopted is that of Ashmead ('04), except that the Leucospi- dinas are separated from the Chalcidinse and that Ashmead 's families are reduced to subfamilies. Some authors recognize additional groups, among them the following: Eupelmidae, Tanaostigmatida;, and Signiphoridae here included in the Encyrtinse; Leptofoenidas ( = Pelecinellida') here included in the Cleonyminse ; Tridymidaj included in the Miscogasterinfe; Spalangidae included in the Ptero- malinae; and Aphelinidae, Elachertidag, Entedontidae, and Tetra- stichidffi here included in the Eulophinaj. A thorough revision of the genera and higher groups is greatly needed. Such a work would do much to help the study of this difficult yet most interesting and important family. The key to the subfamilies will serve for most species, though the diversity of form in many groups and the present state of our knowl- edge makes the construction of a reasonably perfect key quite difficult. KEY TO THE SUBFAMILIES OF CHALCIDID.^ By Dr. H. K. Townes A. Tarsi with three segments; wing hairs usually arranged in lines; very small species, p. 949 Trichogrammatin^ AA. Tarsi with four or five segments. B. Hind wing linear; tarsus with four or five segments; minute species, p. 948 Mymarin/E BB. Hind wing not linear, wider near the middle. C. Tarsi with four segments, or sometimes five-segmented; axilla of fore wing produced on to mesonotum, its anterior margin on or in advance of 942 AN INTRODUCTION TO ENTOMOLOGY an imaginary line drawn from tegula to tegula; anterior tibial spur small and weak D. Hind coxa extremely large and disc-like; hind tarsus very long. p. 948 Elasmin^ DD. Hind coxa of approximately normal size, more or less cylindrical; hind tarsus of normal length, p. 947 Eulophin^ CC. Tarsi with five segments; axilla normal, not produced on mesonotum forward of the tegula; anterior tibial spur larger and strong. D. Hind femur much enlarged and with a row of teeth beneath. E. Hind tibia ending in a long spine beyond the insertion of the tarsus and with a single weak apical spur. F. Prepectus a large triangular sclerite; thorax metallic green (genus Podagrion). p. 943 Ormyrin^ FF. Prepectus a small almost completely hidden sclerite; thorax never metallic green, p. 944 Chalcidin.-e EE. Hind tibia rather squarely truncate and with two apical spurs. F. Wings folded longitudinally in repose; ovipositor recurved over dorsum of abdomen, p. 947 Leucospidin^ FF. Wings never folded ; ovipositor not recurved, p. 946 Cleonymin^ DD. Hind femur of more normal size and with not more than two teeth beneath. E. Alesopleurum large and evenly convex, without a groove for the femur; apical spur of middle tibia long and stout, p. 946 Encyrtin^ EE. Mesopleurum with a groove for the reception of the femur; apical spur of middle tibia not stout. F. Pronotum above with only an anterior face, not visible from the dorsal aspect; mandible sickle-shaped, p. 944 Eucharin^ FF. Pronotum above with a dorsal face so that it is easily visible from above. G. Thorax very robust and short; abdomen small, oval, polished, and entirely or largely enclosed by the second or the fused second and third tergites. p. 944 Perilampin^ GG. Thorax and abdomen not as above, of more normal propor- tions. H. Head of female long, oblong, and with a deep longitudinal groove above; front and hind femora and tibiae stout, the middle ones slender; male wingless with three- to nine-seg- mented antenna, p. 943 Agaontin^ HH. Not as above. I. Hind tibia with one apical spur; head often large, in front often wide and flat with a reticulate surface and strias converging to the mouth, p. 947 Pteromalin^e II. Hind tibia with two apical spurs, one of which may be quite small; head usually not as above. J. Hind coxa usually large and with more or less of a ridge above; abdomen usually compressed and the ovipositor usually long. p. 943 Ormyrin^ JJ. Hind coxa not enlarged, rather cylindrical in cross section; ovipositor not or slightly surpassing the tip of the abdomen. K. Pronotum large, quadrate and as wide as the meso- notum; color black or brown, never metallic; abdomen usually compressed, p. 945 Eurytomin.'E KK. Pronotum short transverse, conical or conically produced anteriorly and narrower than the mesonotum; color often metallic greenish; abdomen usually de- pressed. L. Mesepisternum large; front or hind femur often enlarged, p. 946 Cleonymin.« LL. Mesepisternum not unusually large; neither front nor hind femur enlarged; species resembling the Pteromalinag. p. 947 Miscogasterin^ HYMENOPTERA 943 Subfamily ORMYRIN^ The subfamily Omiyrinre has gone also under the names Tory- minae and Callimominae. Most species are more or less metallic green with compressed abdomens and long ovipositors. They are parasitic largely on cynipid and cecidomyiid gall insects. The com- monest genus is Callimome (= Torymus). Although most of its species are parasites of gall insects, Callimome drupdrum infests the seeds of apple. For a revision of the genus see Huber, Proc. U. S. Nat. Mus. 1927, vol. 70, art. 14, 144 pages. Monodontomerus is para- sitic upon a great variety of hosts. Megastigmus includes brownish species with a large black stigma in the fore wing. The larvae develop in seeds. Some are common in rose hips, and others destroy the seeds of coniferous forest trees. See Crosby ('09). Podagrion is a parasite in the eggs of Mantidae. The genus Ormyrus is parasitic on gall in- sects. It has the abdomen tapering to a conical tip and peculiar bands of large punctures on the tergites. The ovipositor is not ex- serted. Subfamily AGAONTIN^ The Fig Insects This subfamily is composed of those remarkable insects that live within figs and fertilize them. It is represented in the United States by a single species, Blastophaga psenes, that was introduced into Cali- fornia in order to make possible the production of the Smyrna fig in that state. The fruit of the fig tree consists of a hollow receptacle on the Hning of which the flowers are borne. At the apex of the fig there is a more or less distinct opening leading into the interior. It is through this opening that the female fig insect leaves the fig in which she was developed and enters a young fig in order to oviposit. The eggs are laid at the base of a modified form of pistillate flower, known as gall-flower, that is found in wild figs, and the larvae produce little galls in which they develop. The female fig insect when leaving the fig in which she was developed becomes covered with pollen which is carried into the young fig which she enters to oviposit, and thus the flowers in this fig are fertilized. The male fig insect is wingless. It crawls about over the galls in the fig in which it was developed, and when it finds a gall containing a female it gnaws a hole in it and then thrusting the tip of its abdomen through the puncture fertilizes the female. It is only in the wild figs that the gall-flowers are developed. For this reason only the wild figs are suitable for the development of the fig insects. But the female insect will enter the cultivated figs seeking a place to oviposit and will thus fertilize them. Although the numerous varieties of common cultivated figs do not require the stimulus of pollination and the resulting fertilization of the ovary to make the fruit set, in the case of the Smyrna fig, which 944 AN INTRODUCTION TO ENTOMOLOGY is the most desirable variety grown, without this stimulation the young figs soon turn yellow and drop. It is the oily kernel of the fertile seed that gives the Smyrna figs their superior quality. The fertilization of the edible figs is termed caprification. It is brought about by placing in the fig trees fruit of the wild figs contain- ing the fig insects. In order to produce the Smyrna figs it is necessary to grow also the wild figs, or caprifigs as they are termed. There are many species of fig insects living in the wild figs of tropical and semi-tropical countries. Subfamily PERILAMPIN^ The members of this subfamily are short species with large heads, robust thoraces, and short oval abdomens. Some are metallic green and thus resemble cuckoo wasps. Others are black. Most of our species belong to the genus Perildmpus. Perildmpus lays its eggs on leaves partially inserted into incisions made by the ovipositor. The first stage lan.^a is a tiny active animal with chitinous armor and series of spines beneath (Fig. 1167). The name planidium has been given to this type of larva. The planidium attaches to a passing caterpillar and bores into its body. There it locates and penetrates the larva of a tachinid, ichneumonid, or other parasite of the caterpillar. After the primary parasite of the caterpillar has completed its growth and pupated, the Perildmpus larva emerges from its body and finishes development as an external parasite of the parasite pupa. The other larval instars lose the specializations of the planidium stage and look more like normal parasite larv'ae (Fig. 11 68). Most species of Perildmptis are secondary parasites, but P. chrysopcE is a primary parasite of lacewing-flies. Subfamily EUCHARIN^ The subfamily Eucharinas includes a few uncommon or local species parasitic on ants. In the tropics species and individuals are more numerous. Some genera have a bizarre pair of spines extending backwards from the scutellum. The eggs are laid in the leaves or buds of plants. The first stage larva is a planidium resembling that of the Perilampinee. Probably the planidia attach to worker ants and are thus carried to the ant larvae and pupae which they parasitize. Subfamily CHALCIDIN^ This subfamily is easily recognized by its very swollen hind femur, though certain members of other groups have this character also (see the key to subfamilies). The peculiar hind legs appear to be suited for grasping prey. Females occasionally grasp host larvae with thein for oviposition. The Chalcidince includes most of the large species of the family. Some of our species of Spilochdlcis are as large as yellow jacket wasps and on account of their similar black and yellow color HYMENOPTERA 945 are easily confused with them while on the wing. Common genera are Spilochdlcis, with the abdomen on a noticeable stalk and with an apical spur on the middle tibia; and Chdlcis with an oval unstalked abdomen. Spilochdlcis mar ice is a common parasite in the cocoons of the large silk moths. Some species of Chdlcis are parasites of lepi- dopterous pupae and others of fly maggots. Some oviposit into tachinid maggots while they are still inside the bodies of their cater- pillar hosts. The tachinid larvae complete their development and pupate before succumbing to the Chdlcis hyperparasites. Subfamily EURYTOMIN^ This subfamily is remarkable on account of the diversity of its habits. Primary and secondary parasites of a variety of insects, egg parasites, and phytophagous species are included. Members of the genus HarnioHta ( = Isosoma) infest the stems of growing grasses, either forming gall-like swellings or living in the center of the stems. The two following species are of economic importance. The wheat joint-worm, Harmollta tritici, is a well-known pest that infests the stalks of growing wheat and certain grasses. It causes a woody growth which fills up the cavity of the stalk, and sometimes also causes a joint to swell and the stalk to bend and lop down. The presence of this insect is often indicated by pieces of hardened straw coming from the threshing machine with the grain. There is but a single generation of this species in a year. The insect remains in the straw and stubble during the winter, the adults emerg- ing in the spring. The methods of control of this pest are rotation of crops, burning or deep ploughing under of stubble when practicable, or harvesting of stubble in spring with a horserake and burning it before the adults emerge. The wheat straw-worm, Harmollta grdndis, is often a serious pest of wheat west of the Mississippi River. In the East it is less injurious than the wheat joint-worm. There is a summer generation which consists only of winged females and a winter and spring generation which consists of both males and females. These are smaller than the summer form and are frequently wingless. The adults of the winter and spring generations emerge in April, and the females deposit their eggs in the young wheat plants ; the larvae eat out and totally destroy the forming heads of wheat. The adults of the second generation deposit their eggs about the time the wheat is heading, just above the youngest and most succulent joints which are not so covered by the enfolding leaf-sheaths as to be inaccessible to them. The larvse pupate by October, and the winter is passed in the straw or stubble. Evoxysoma vUis infests the seeds of wild grapes and occasionally attacks cultivated varieties. Bruchophagiis funebris infests the seeds of red and crimson clovers and alfalfa. The genus Decdtoma attacks gall-making insects. Rlleya parasitized Cecidomyiidae. Macrorlleya parasitizes the eggs of tree crickets. Axima lives as a parasite in the 946 AN INTRODUCTION TO ENTOMOLOGY nests of Ceratlna dupla, the little carpenter bee. Eurytoma is a large genus parasitic on many types of insects. A few species infest seeds. Recent revisions of United States species are : Harmolita, Proc. U. S. Nat. Mus. 1919, 55:433-471; Decatoma, Proc. U. S. Nat. Mus. 1932, vol. 79, art. 28, 95 pages. For an account of the seed-infesting species see Crosby ('09). Subfamily ENCYRTIN^ This is a large and diverse group parasitic on many kinds of insects. It can be recognized by the broad mesopleurum without the usual groove for the femur and by the large heavy spur on the middle tibia. This spur is used in jumping. Many parasitize Coccidce, Aphidse, and Aleyrodidse. At least four highly successful cases of biological control are due to the introduction of these insects to para- sitize scale insects or mealy bugs. Polyembryony is a common phenomenon in the Encyrtinse and reaches its highest development in this group. The eggs of the poly- embryonic species are inserted into those of Lepidoptera. The para- site larvae mature in the host caterpillar just before it pupates. Copidosoma truncatellum is a common parasite of Autographa hrassiccB, the cabbage looper. The female lays one or two eggs into the egg of Autographa. Usually the second egg deposited is without a sperm and is therefore unfertilized. Each egg develops inside the growing host caterpillar into hundreds of parasite larvae. The fertilized egg produces female larvas and the unfertilized egg produces male larvae. Beside these sexual larvae which mature into adults, there are many sexless larvae in which the reproductive and respiratory systems are not developed. These die without maturing. The host larva is usually much larger than an unparasitized caterpillar and somewhat more sluggish. Just before pupation it is killed by its parasites which by that time practically fill its body. The parasite lar\^ae pupate in the skin of their host and emerge as adults through holes cut to the outside. Twelve hundred to three thousand may develop in a host. A single egg usually gives rise to about one thousand adults. Some Encyrtinae have the body rather long and narrow, the disc of the mesonotum more or less concave, and notauli present. These are often put in a separate subfamily, the Eupelminae. The species are mostly egg parasites or secondary parasites. They are good jumpers, and their peculiar ability to turn both the head and abdomen back over the thorax seems to be used to help them leap much as the click beetles use the movable prothorax for this purpose. Many have short wings with a joint at the middle so that they can be folded upwards when the abdomen is raised. Subfamily CLEONYMIN^ This is a relatively small heterogeneous group that is probably polyphyletic. The species that have been reared are mostly from Coleoptera. HYMENOPTERA 947 Subfamily LEUCOSPIDIN^ This subfamily includes the single genus Leucospis in the Nearctic Region. Our only widespread species is L. afflinis, a large black and yellow chalcid frequently found on flowers. It has been bred from nests of a leaf-cutter bee, Megachlle. For a revision of the species see Weld: Proc. U. S. Nat. Mus. 1922, vol. 61, art. 6, 43 pages. Subfamily MISCOGASTERIN^ This group is related to the Pteromalinae. It differs in having two instead of one spur on the hind tibia. Species have been bred from gall insects, dipterous larva?, and other hosts. Subfamily PTEROMALIN^ This is one of the larger subfamilies of the Chalcididse. Many of the species are of economic importance either as beneficial primary parasites of common pests or as harmful secondary parasites. Pteromalus pupanmi is a common parasite of the cabbage butter- fly. Oviposition is into the pupa. It is said that if a female Ptero- malus finds a caterpillar of this species preparing to pupate, she will wait patiently until the pupa is formed and will then oviposit into it. Many Pteromalus larvae develop in a single host. In a few weeks they become adults and emerge from a hole chewed in the pupal shell. Dibrachys bouchednus is a widespread species attacking many kinds of insects. The principal requirement for a host seems to be that it be enclosed in a cocoon. Since braconid and ichneumonid cocoons are the ones most commonly attacked, the species is usually a secondary parasite and therefore harmful. It is often reared from Apanteles cocoons. After a host cocoon is located and identified with the antennee, the female inserts her ovipositor and stings the enclosed larva or pupa once to several times until it is paralyzed. If the host is lying against the wall of the cocoon the female laps the juices that flow through the ovipositor puncture. If the host is away from the cocoon wall a feeding tube is constructed. To do this the female parasite pushes the tip of her ovipositor just through the cocoon wall. A mucilaginous substance then exudes from the tip of the ovipositor. Additional quantities of this substance are occasionally added as the ovipositor is slowly advanced toward the pupa. Eventually there is a mucilaginous tube enclosing the ovipositor from the cocoon wall to the paralyzed host. The ovipositor is withdrawn and the parasite then sucks the juices of the host through the tube. When she has finished feeding she seals the tube with a drop of the same material and then lays several eggs on the host. The habit of making a feeding tube is a common one among the Pteromalinae. Subfamily EULOPHIN^ Species of this subfamily are very numerous and mostly quite small in size. They are diverse in habits and in host selection. 948 ^A^ INTRODUCTION TO ENTOMOLOGY Euplectnis platyhypence is a common parasite of army worms. It is unusual in being an external parasite of an exposed host. The eggs are deposited on the caterpillar's skin in groups of about twenty to thirty. The larvse form a compact mass with the heads attached to feeding holes in the skin of the host. The caterpillar does not die until they become mature and detach from their feeding holes. The parasites pupate under the dead host. Melittdhia is common in the nests of solitary bees and wasps. The female gains access to the larval cell, stings the enclosed larva or pupa to paralyze it and then deposits her eggs on it. The parasite larvtc develop externally. Several generations develop on the same host before it is completely consumed. The males are short-winged and have the antenna modified into a pincher-like structure for hold- ing the female's antenna during courtship. They are very pug- nacious and often kill each other in battle. The females are either short- or long-winged. Tetrastich us is a large important genus parasitic on many kinds of insects. T. aspdragi oviposits in the eggs of the asparagus beetle. The beetle egg hatches and the larva lives to maturity but is killed in its pupal cell by its parasites. About a half dozen parasite larvae develop in each host. A large and important group of Eulophin^, sometimes put in the separate subfamily Aphelininse, are parasites of scale insects. A few attack aphids and aleyrodids. Several species of this group have been introduced into various countries to control certain species of scale insects and have proved remarkably efficient. In some species of Coccophagus and related genera the male and female larvae are strikingly different in morphology and in habits. The male and female eggs also are different. The female larva develops as a primary parasite of a scale insect while the male larva is a secondary parasite in the scale, either upon a female larva of its own species or on some other chalcid. For a revision of Coccophagus see Compere: Proc. U. S. Nat. Mus. 1931, vol. 78, art. 7, 132 pages. Subfamily ELASMIN^ Eldsmus is the only North American genus of the Elasminas. It contains small black or brown species somewhat triangular in cross section. Most species are solitary or gregarious external parasites of caterpillars. Subfamily MYMARIN^ The Fairy-flies The Mymarinas includes exceedingly minute species parasitic in the eggs of other insects. They may be recognized by the linear hind wings pedunculate at the base (Fig. 11 69). Species of the genus Al- Idptus are some of the smallest insects known. One has a body length of only 0.21 millimeters. The entire development of the Mymarinai is in the host egg. There are two larval instars of which the first is HYMENOPTERA 949 cyclopoid, resembling that of the SceHonidce. As many as fifty para- sites have been reared from a single egg, although one is the usual Fig. 1 169. — Cosmocoma elegans. Subfamily TRICHOGRAMMATIN^ This subfamily comprises minute egg parasites with three-seg- mented tarsi. Trichogramma evanescens ( = minuttmi) is an ubiquitous species parasitizing almost any insect egg that can be pierced with its ovipositor. It is an important parasite of many economic pests and has frequently been reared in insectaries for liberation in fields and orchards to control various insects. The success of these at- tempts has not been encouraging. Several other forms of Tricho- gramma resemble T. evanescens very closely, differing somewhat in color and in length of the life cycle when reared at a constant tem- perature. Since they will not interbreed with T. evanescens they are now regarded as distinct species. Hydrophylax aquivolans is an aquatic species parasitic probably upon damsel fly eggs. It has narrow wings and uses them as oars for "flying" through the water. Some species of Trichogrammatinae have two larval instars, the first of cyclopoid form as in the Mymarinse and Scelionidas. Others have a single instar, a bag of cells with a mouth. This larva gets the egg contents on the inside of its body and then pupates. SUPERFAMILY EVANIOIDEA Family EVANIIDiE The Ensign-flies The family Evaniidae is so distinctly separated from all other famihes of the Hymenoptera that it is regarded as constituting a separate superfamily. We have in this case a superfamily represented by a single family. The family Evaniidae dift'ers from all of the preceding families in the presence of a well-marked anal lobe in the hind wings (Fig. 1 170) and it differs from all of the following families in that the petiole of 950 AN INTRODUCTION TO ENTOMOLOGY Fig. 1 17 1. — Evania ap- pendigaster the abdomen is attached to the dorsal surface of the propodeum (Fig. 1 1 7 i) in- stead of at the hind end of it, as it is in the following families. Theab- domen is short and carried aloft — like a flag; this fact sug- gested the common name ensign-flies for these in- sects. The venation of the wings is greatly reduced, and in the hind wings there are no closed cells; the trochanters are two-segmented; and the ovipositor is not at all or but little exserted. All of the species are parasitic in the eggs of cockroaches. This family was monographed by Bradley ('08) and Kieffer ('12) It is represented in our fauna by two genera, Evania and Hyptia. SUPERFAMILY VESPOIDEA Fig. 1 1 70. — Wings of Evania appendigaster;!, anal lobe. The Vespoid-Wasps This superfamily is one of three superfamilies, the Evanioidea, the Vespoidea, and the Sphecoidea, in which the hind wings are typically furnished with an anal lobe; but in some of the more specialized members of the Vespoidea and of the Sphecoidea the anal lobe has been lost. This is the case in certain genera of the Formi- cidcc, Mutillidas, and Vespidas; these exceptional forms can be placed by the table of families on pages 906 to 915. The members of Vespoidea differ from the Evanioidea in that the petiole of the abdomen is attached to the hind end of the propodeum; and they differ from the Sphecoidea in that the lateral extensions of the pronotum, which reach the tegulas (except in the Cleptidae and Chrysididas) , are not in the form of well-differentiated rounded lohes, as is the case in the Sphecoidea. See Figure 1195 on a later page. The Vespoidea is represented in our fauna by fourteen fnmilics ; these can be separated by the table of families referred to above Family POMPILID^ The Spider-Wasps The members of this family are commonly called spider-wasps, because they provision their nests with spiders ; this habit, however, is not distinctive as certain other wasps use spiders for this purpose. HYMENOPTERA 951 The members of this family are slender in form, with long spin}^ legs, (Fig. 1 1 72). The pronotimi extends back on each side to the tegula; and the abdomen is sessile. Many of the species are of medium size, but some are ver\^ large; in fact, the largest of our H^Tiienoptera belong to this family. Most of the Pompilidffi make their nests in the ground. The wasp first finds a spider and stings it until it is paralyzed, and then digs a burrow, which spider-wasp^ is enlarged at the lower end, forming a cell for the reception of the spider; the spider is then dragged down into the cell and an egg attached to it; then the passage leading to the cell is filled with earth. Detailed accounts of the actions of these spider-wasps when making and provisioning their nests are given bv Peckham and Peckham ('98) and bv Rau andRau ('18). " Among the giants of this family are the well-known tarantula- hawks of the genus Pepsis of the Southwest, which store their bur- rows with tarantulas. Many a hard-fought battle do these spider- wasps have with these enormous spiders, and sometimes they are conquered and ignominiously eaten. Not all members of this family are digger-wasps, for some are mason-wasps. The species of the genus Pseudagenia make thimble- shaped cells, of mud, attached to the lower surface of stones, in chinks of walls, under bark and in various other situations; and at least one species oiCeropales is said to be parasitic in the nests of Pseudagenia. More than one hundred species belonging to this family have been described from our fauna. A classification of the family was pub- lished by Banks ('11). The family EMBOLEMID.^ includes only a few rare species the habits of which are unknown. Family CLEPTID^ Cleptes This family includes only the genus Cleptes, which was formerly included in the following family. But the genus Cleptes differs from the Chr}^sididae in that there are six exposed segments in the abdomen and the venter is convex. It is believed that these wasps are parasitic in the cocoons of saw-flies ; as one of them infests the currant -worm in Europe. Several native species are found in the Far West. Family CHRYSIDID^ The Cuckoo-Wasps The cuckoo-wasps are wonderfully beautiful creatures, being usu- ally a brilliant metallic green in color. The species are of moderate 952 AN INTRODUCTION TO ENTOMOLOGY size, the largest being only about 12 mm. in length. They can be distinguished from other H>TTienoptera by the form of the abdomen, in which there are at most five and usually only three or four exposed segments (Fig. 1 1 73), and which is strongly concave below, so that it can be readily turned under the thorax and closely applied to it. In this way a cuckoo-wasp rolls itself into a ball when attacked leaving only its wings ex- posed. In this family and in the preceding one ' 1 17 -i —Chrysis the antennae are 13 -segmented in both sexes; nitidula. the pronotum does not reach the tegulae; there are no closed cells in the hind wings; and the ovipositor is an extensile jointed tube. The cuckoo-wasps are so-called because they are parasitic in the nests of solitary wasps and solitary bees. A cuckoo-wasp seeks until it finds a wasp or bee, building its nest, and when the owner of the nest is off collecting provisions steals in and lays its egg, which the unconscious owner walls in with her own egg. Sometimes the cuckoo- wasp larva eats the rightful occupant of the nest, and sometimes starves it by eating up the food provided for it. The bees and wasps know this foe very well, and tender it so warm a reception that the brilliant-coated little rascal has reason enough to double itself up so the righteous sting of its assailant can find no hole in its armor. There is one instance on record where an outraged wasp, unable to sting one of the cuckoo-flies to death, gnawed off her wings and pitched her out on the ground. But the undaunted invader waited until the wasp departed for provisions, and then crawled up the post and laid her egg in the nest before she died. A monograph of the North American species was published by Aaron ('85), one of the species of the world by Mocsary ('89), and another by Bischoff ('12). The family ANTHOBOSCID^ is represented in North America by a single species, Sierolomorpha amhigtia. This is shining black, with an oval abdomen, the first segment of which is constricted off from the rest. It measures 4.5 to 6 mm. in length. Family SAPYGID^ The Sapygids This is a small family including only three North American genera, and but little more than twenty species. These insects are of moderate size, with short legs, and are usually black, spotted or banded with yellow, rarely entirely black. So far as their habits are known, they are inquilines in the nests of solitary wasps and solitary bees, The family THYNNIDyE is represented in our fauna by a single rare species of the genus Glyptometopa, found in California. HYMENOPTERA 953 Family TIPHIID.E The Tiphiids The tiphiids are quite closeh' related to the followinj^ family, the velvet-ants. In fact, some of the genera now included in the Tiphiidag have been classed in the Mutillidaj. The characters separating these two families are indicated in the table of families of the H\Tnenoptera given above. The family Tiphiida3 includes three subfamilies. The subfamily TIPHIIN^ is represented in our fauna by five genera; these are Pterombtis, Epotnidtopteron, Elis (Myzine), Tiphia, and Paratiphia. One of the most common species is Tiphia inorndta (Fig. 1174). This is a shining black species ; the male measures from 7 to 1 1 mm. in length and has an upward projecting spine near the tip of the abdomen. The female measures p. "^ T'bi ' from 12 to 14 mm. in length. The accompanying ^morncUa. figure represents a female; in this sex the anten- nae are curled much more than is indicated in the figure. This species is parasitic upon white-grubs, the larvae of the Mav-beetles. For descriptions of species of Tiphia see Malloch ('18). The subfamily METHOCIN^ includes forms in which the two sexes are very dissimilar; the males are winged, the females are wing- less and resemble ants. Our only species is Methoca stygia. The subfamily MYRMOSIN^ includes two genera, Myrmdsa and Myrnwsida. The males are winged and the females are wingless. Our most common species is Myrmosa unicolor. The subfamily has been monographed by Bradley ('17). Family MUTILLID^ The Velvet-ants These handsome insects resemble ants in the general form of the body, but lack the scale-like knot of the pedicel of the abdomen characteristic of the true ants, although there is sometimes a constriction between the first and second abdominal segments (Fig. 11 75). The body is often densely clothed with hair, which gives the insects the appearance of being clothed in velvet; and as the Fig. 1175. body is usually ringed or spotted with two or more strongly contrasting colors, they are very conspicuous. But in many species the body is naked. The colors most commonly worn by the velvet-ants are black and scarlet. The males are winged and frequent flowers. The females are wingless, but they run very rapidly and they sting severely. In the western states there are many straw yellow species, which are nocturnal. These insects are abundant in the warmer portions of our country, and several species occur in the North. A large species, Dasymuttlla 954 AN INTRODUCTION TO ENTOMOLOGY occidentalis, which measures from 1 6 to 30 mm. or more in length, is known in the South as the "cow-killer ant" because of the popular superstition that its sting is very dangerous to live stock. Andre ('03) states that the mutillids of which the habits have been observed are parasites of nest-buildine Hymenoptera in the cells of which they deposit their eggs. The larvee attack those of the owners of the nest without touching the provisions which the cell may contain. In this country a species has been reared from the cells of the solitary bee, Nomia pattern, and one from the nests of the mud- dauber, Chalyhion cceruleum. In Europe several species are parasitic in the nests of bumblebees; and in Africa several species have been found to be parasitic on the tsetse fly. The Mutillidas of North America have been monographed by Fox ('99) and those of the Eastern United States by Bradley ('16). Family SCOLIID^ The Scoliids The scoliids are quite closely related to the preceding family but differ in their general appearance, resembling wasps rather than ants. They are parasitic on white grubs, the larva? of Scarabseidas. In their habits they do not exhibit as much intelligence as do most digger wasps; for they do not build nests and transport prey to them for their carnivorous larvae. Instead of this they dig in the ground where the white grubs are, and finding one they sting it in order to paralyze it, work out a crude cell about it, and attach an egg to a ventral abdominal segment of the grub. The larva of the scoliid con- sumes the grub and then spins a cocoon and completes its development in this place. The members of this family are very striking in appearance, being of large size and with the abdomen marked with conspicuous spots. Two genera are represented in our fauna, Scolia and Campsomeris {Elis) . In Scolia the transverse part of vein M2 of the fore wings is wanting, in Campsomeris it is present. Family FORMICID^ The Ants The great number of ants and their wide distribution render them the most familiar of all insects except perhaps the house-fly. As has been said by Professor Wheeler, an indefatigable investigator of these insects, "Ants are to be found everywhere, from the arctic regions to the tropics, from timiberline on the loftiest mountains to the shifting sands of dunes and seashores, and from the dampest forests to the driest deserts. Not only do they outnumber in individuals all other terrestrial animals, but their colonies even in very circumscribed HYMENOPTERA 955 localities often defy entuneration." The present time has been termed the "age of insects" and of all insects the Formicidse is the dominant family. The habits of ants have attracted the attention of students of animal behavior from very early times and many volimies have been written on this subject. Among those most often quoted and to be found in most public libraries are those of Gould (1747), P. Huber (1810), and Lubbock (1894). The most comprehensive contributions have been made by Forel and Emory, each of whom has published more than one hundred papers in various European journals, and by Wheeler in this country. Among the other American writers who have made important contributions to our knowledge of the ways of ants are Buckley, Miss Fielde, Leidy, Lincecimi, McCook. Pricer, Mrs. Treat, and Turner. But the most important work on this sub- ject is Professor Wheeler's "Ants, their Structure, Development and Behavior" Cio). In the following pages there is space for only the more important generalizations that can be made regarding this family. Ants are easily recognized by the well-known form of the body. The most distinctive feature is the form of the pedicel of the abdomen; this consists of either one or two segments, and these segments are either nodiform or bear an erect or inclined scale (Fig. 11 76). Fig. 1 176. When the pedicel of the abdomen consists of a single segment it is known as the petiole; when it consists of two segments the first segment is termed the petiole and the second segment the postpetiole. The swollen portion of the ab- domen behind the pedicel is known as the gaster. Another striking characteristic of ants is that in the antenna of females and workers and of the males of some species the basal joint, the scape, is long and the antennse are abruptly elbowed at the extremity of this joint. The ants are all social insects, there being no solitary species. Each colony consists of three castes, the males, the female or queen, and the workers. As with the social bees and the social wasps, and unlike the termites, the workers are all modified females. With most ants the males and the queens are winged and the workers wingless; the wings of queens, however, are deciduous. In certain genera that live as parasites in the nests of other ants the worker caste is wanting, and in some species the females are wingless. With many ants the poljonorphism is not restricted to the presence of three uniform castes for one or more of the castes may be represented by more than one form. Of the males there may be either an unusually large form, or dwarfs, or ergatoid males, that is, males that resemble workers in having no wings and in the structure of the antennae. The queens exhibit a similar series of forms; those of unusually large stature ; dwarfs which are sometimes smaller than the largest workers; and ergatoid queens, which are a worker-like form, with ocelli, large eyes, and a thorax more or less like that of the normal queens, but without wings. The workers are even more 956 AN INTRODUCTION TO ENTOMOLOGY polymorphic than the sexual forms. In many species the workers are of two distinct sizes, the worker majors and the worker minors. In colonies that are founded by an isolated female the first brood of workers is of the worker minor form. With many species a worker form exists in which the head and the mandibles are very large, the soldier caste. And with the honey-ants in some of the workers, the repletes, the gaster is a large spherical sac, being distended by the crop which is used as a reseivoir for storing honey-dew to be used later by the colony. Although all ants are social, great differences exist among them as to the size of their colonies. In the more primitive species the fully developed colony consists of only a few dozen individuals with comparatively feeble caste development; while in the more highly specialized forms a colony may consist of hundreds of thousands of individuals and exhibit an elaborate polymorphism. The different species of ants differ also in their nesting habits. By far the greater number of species excavate their nests in the ground. Certain species are often seen burrowing in paths or other open places ; but many more are to be found under small flat stones or other objects lying on the ground. Some species, especially those in which the colonies become large, build large mounds of the exca- vated material. These mounds are very familiar objects in many parts of our country. A striking difference between the nests of ants and those of wasps and bees is that the ants do not construct premanent cells for their brood. The eggs, larvae and pupae are stored in chambers of the nest and are moved from one to another in order to take advantage of the changes in temperature and moisture. Thus the brood may be brought near the surface of the nest during the warmer portion of the day and removed to deeper chambers at nightfall. While most species of ants nest in the soil, there are many that build their nests in wood, in timbers, in the trunks of decaying trees, in or under bark, or in hollow stems. Others, especially certain tropical species, build in cavities of living plants; and still others, as Cremasto gaster, build carton nests. Large swarms of winged ants are often seen. These are composed of recently matured males and females that have emerged at the same time from many different nests, probably from all of the nests of the particular species involved that exist in the immediate region, and in which young queens and males have been developed. The object of these flights is mating, and they render probable the pairing of males and females from different nests, thus preventing too close inter- breeding. The factors that determine the occurrence of the nuptial flights from all the nests of a species in one locality at the same time are not understood. In the case of those species in which the female is wingless the mating must take place either in the nest or on the ground outside. HYMENOPTERA 957 After the pairing of the sexes the males soon die and each female proceeds to found a new colony if she is not captured by workers and taken into a colony already established or finds her own way into one. Except among the parasitic ants the method of founding a colony is as follows: The female breaks off her wings; then seeks out a small cavity under a stone or under bark or makes one in the ground. She closes the entrance to this cavity and remains isolated without food for weeks or months while the eggs in her ovaries are developing. During this period there is a histolysis of the large wing-muscles the products of which are used as food . When the eggs are mature they are laid and the larvag that hatch from them are fed by the female, or queen as she is termed, with her saliva till they are ready to pupate. As the young queen takes no food during this period, that fed the larvae must be derived from the fat stored in her body and the dissolved wing-muscles. The adults that are developed from this first brood or larv« are workers, but owing to the limited amount of food that they have received they are abnormally small ; that is, of the form known as worker minors. These open the chamber in which they were developed and go forth to collect food for them- selves and for the queen, and they take charge of the second brood of larvae, which being supplied with abundant food develop into larger workers. The nest is now enlarged by the addition of new chambers and the growth of the colony continues. A few years later numerous males and females are developed, which at the proper time leave the nest for their nuptial flight. The method of founding colonies described above is the usual one. But in some species the females have lost the power of establishing a colony unaided and must be adopted by workers of her own species or by workers of an alien species. The adoption of a queen by workers of an alien species explains the existence of some of the mixed colonies which are sometimes observed. The practice of slave-making de- scribed later, is the explanation of others. In certain highly parasitic species the worker class is wanting and the queens must become established in the nest of an alien species. The worker ants are so-called because upon this caste devolve all the labors of the colony after they appear on the scene in the founda- tion chamber. As a rule workers are sterile; but sometimes, as with bees, and wasps, fertile workers occur. It is believed that on!}' males are developed from eggs laid by workers. The feeding habits of ants differ greatly in different members of the family. Some of the more primitive forms are strictly carnivo- rous, feeding on insects and other small animals that they can destroy ; while others add vegetable substances to their diet. Many feed on sweet fluids, as sap exuding from wounded stems, the nectar excreted by extrafloral nectar glands, and honey-dew produced by aphids, membracids, the larvee of certain butterflies, and other insects, and the leaf-cutting ants cultivate fungi upon which they feed. Ants also lick their larvae in order to feed on the exudates excreted by them. This exchange of nourishment between the workers and 958 AN INTRODUCTION TO ENTOMOLOGY their wards, which is known as trophallaxis, is discussed in the chapter on Isoptera (pp. 279-280). The study of the habits of ants in the field is often supplemented by observations on colonies kept in artificial nests. Several types cf such nests are in use; for descriptions of them see Wheeler ('10). The family Formicidae includes seven subfamilies, all of which are represented in the United States; but two of these subfamilies, the Cerapachyinae and the Pseudomyrminae, are confined to tropical and subtropical regions and their range extends only into the southern part of our territory, where they are represented by only a very small number of species. The workers of the other subfamilies can be separated by the following table, which is based on one published by Professor Wheeler in "The Hymenoptera or Wasp-like Insects of Connecticut" (Vierick '16). This work includes also tables of the genera and subgenera of ants found in America north of Mexico. For keys to the subfamilies, genera, and subgenera of the world see Wheeler ('22). KEY TO THE SUBFAMILIES OF ANTS (Includes only the workers) A. Anal orifice round, terminal, surrounded by a fringe of hairs; abdominal pedicel consisting of a single segment; no constriction between the first and second segments of the gaster; pupae rarely naked, most frequently in a co- coon, p. 963 FORMICIN^ AA. Anal orifice ventral, in the shape of a slit; pedicel of the abdomen con- sisting of one or two segments. B. Pedicel of the abdomen consisting of a single segment; no constriction between the first and second segments of the gaster; sting vestigial; pupas naked, p. 962 Dolichoderin/e BB. Pedicel of the abdomen consisting of one or two segments, when only of one, a distinct constriction between the first and second segments of the gaster, sting developed, sometimes very small but capable, nevertheless, of being exserted from the abdomen. C. Pedicel of the abdomen consisting of a single segment; gaster with a distinct constriction between its first and second segments; frontal carinae separated or close together, when close together, dilated to form oblique or horizontal laminge partly covering the insertions of the antennae; pupae always enclosed in cocoons, p. 959 Cerap.\chyin.« and Ponerin^ CC. Abdominal pedicel consisting of two segments; pupae naked. D. Frontal carinae very close together, almost vertical, not at all covering insertions of antennae; eyes always very small or absent; tropical and subtropical, p. 958 Dorylin^ DD. Frontal carinae of a different conformation and covering the antennal insertions; eyes rarely vestigial or absent; cosmopolitan, p. 959, 960 PsEUDOMYRMiN^ and Myrmicin^ Subfamily DOHYLIN^ The Legionary or Visiting Ants The members of this subfamily are largely confined to Equatorial Africa and tropical America. The colonies are nomadic, wandering from place to place in search of prey, and forming only temporary nests. Some of the species travel in vast armies and often overrun HYMENOPTERA 959 houses in the tropics, clear out the vermin with which they may be infested, and compel the human inhabitants to leave for a time. The subfamily is represented in ovir fauna by a single genus, Eciton, species of which occur from North Carolina and Colorado sotithward. Our species, however, do not form large armies, though they hunt in files like the tropical species, and the colonies of some of the species may consist of thousands of individuals. Some of the species are fond of kidnapping the brood of other ants. The females are wingless and much larger than the workers. The workers are pol^Tiiorphic. The subfamily CERAPACHYIN^ is represented in our fauna by two genera, Cerdpachys and Acanthostichns , species of which occur in Texas. These genera were formerly included in the subfamily Ponerinae. Subfamily PONERIN^ The Ponerme Ants In the ants of this subfamily the pedicel of the abdomen consists of a single segment and there is a distinct constriction between the first and second segments of the gaster (Fig. 1 177). The constriction between the first and second segments of the gaster distinguishes these ants from those other ants in which the Fig. 1177. A ponerid. pedicel of the abdomen consists of a single seg- ment. Our representatives of this subfamily are rare or of local occurrence in the North, where they form small colonies, often of a few dozen individuals. They make their nests in the soil or in old logs. As a rule the queens are but little larger and the males but little smaller than the workers, and there is only a single foiin of worker in a species. The pupa stage is passed within a cocoon. These ants are carnivorous, feeding on other insects and do not collect honey-dew. In the South Odontomachus is common, forming large colonies of active ants of large size, under old logs. The subfamily PSEUDOMYRMIN^ includes four genera only one of which, Pseudomyrma, is represented in North America. This is a neotropical genus, species of which are found from Florida to Texas, and in southern California. They are very slender ants and make their nests in hollow twigs or other cavities of plants. The larvae are of a remarkable form; the body is long, the head large and ventrally placed, and the thoracic and first abdominal segments are furnished with peculiar exudatory papillas, which form a cluster about the mouth. These ants were formerly included in the sub- family Mynnicinas. 960 AN INTRODUCTION TO ENTOMOLOGY Subfamily MYRMICIN^ The Myrmicine Ants In this subfamily the pedicel of the abdomen consists of two segments (Fig. 1178) and the frontal carinEe cover the antennal in- sertions. This is a large subfamily; more than half of the species of ants found in America north of Mexico belong to it. The following species will serve to illustrate the re- markable differences in habits of its different Fig. 1178.— A myrmicid. members. The little yellow house-ant, Monomorium pharadnis. — This is the species commonly known as the "little red ant" although it is light yellow in color. It is the most troublesome of all ants that invade our dwellings. When these ants build their nests within the walls or beneath the foundations of a house it is almost impossible to dis- lodge them. By trapping and destroying the workers their numbers can be lessened somewhat ; but so long as the queens are undisturbed in their nests the supply of workers will continue. Sometimes the nests can be reached by pouring carbon bisulphid into the crevices from which the workers come. The thief ant, Solenopsis molestus. — This is a species with minute yellow workers and much larger brown females and blackish males, which is common in open grassy places, where it may have independent nests under stones. But they often make burrows in the walls of . nests of other and much larger ants, from which they emerge to prey upon the larvae and pupse of the larger ants, which are unable to follow them into their tenuous burrows. The harvesting ants. — Several genera of myrmicine ants feed on seeds, and as they collect these seeds and store them in their nests they are known as harvesting ants. It was to these ants that vSolomon referred. They have also been known as agricultural ants ; for it was formerly believed that they sow around their nests seeds of the plants from which they collect the grain that they use. But this has been disproved. Most of our harvesting ants are confined to the warm and arid regions of the Southwest, where insect prey is scarce and the ants are compelled to feed on seeds. A single species, Pheidole pilifera, which is a southern species, occurs along the coastal plain as far north as Massachusetts. The shed-builder ant, Cremastogaster lineoldta. — In the tropics ants belonging to several genera build carton nests attached to branches of trees. One of these genera is Cremastogaster of which we have a common species, C. lineoldta, in the Northern States and Canada. This is a small ant, the workers measuring from 3 to 4. 5 mm. in length. HYMENOPTERA 961 It is usually yellowish brown, with a black abdomen; but it varies greatly in color. Its favorite nesting-place is under stones or under- neath and within the decayed matter of old logs and stimips. Out of this material the ants sometimes make a paper-lilce pulp with which they build a nest attached to the side of a log, or even to the branches of a shrub at some distance from the ground. While such nests are uncommon these ants often build small sheds at some dis- tance from the nest, over the herds of aphids or coccids from which they obtain honey-dew (Fig. 1179). In these cases the aphids or Fig. 1 179. — A "cow-shed" built by ants. (From A. B. Comstock, Handbook of Nature Study.) coccids are huddled together on a branch, from which they are de- riving their nourishment, and are completely covered by the "cow- shed" built by the ants. An inquiline or guest ant, Leptothorax enter soni. — This ant, the habits of which are described in detail by Wheeler, lives only associ- ated with another species, Myrmtcdbrevinodis, The Myrmica "builds its nest in the soil of bogs, in clumps of moss {Polytrichimi) or under logs and stones, and the Leptothorax excavates small cavities near the surface and communicating by means of short, tenuous galleries with those of its host. The broods of both species are brought up separately. The Leptothorax, though consorting freely with the Myrmica workers in their galleries, resents any intrusion of these ants into its own chambers. The inquilines do not leave the nest to forage but obtain all their food in a very interesting manner, from their hosts. Both in the natural and artificial nests the Leptothorax are seen to mount the backs of the Myrmicas and to lick or shampoo 962 AN INTRODUCTION TO ENTOMOLOGY their surfaces in a kind of feverish excitement. This shampooing has a two-fold object: to obtain the oleaginous salivary secretion with which the Myrmicas cover their bodies when they clean one another, and to induce these ants to regurgitate the liquid food stored in their crops." The fungus-growing ants.- — Among the many remarkable examples of insect behavior none is more marvellous than the habits of the fungus-growing ants, although analogous habits are exhibited by certain termites and by the ambrosia beetles, discussed in earlier chapters of this book. The fungus-growing ants constitute one of the tribes, the Attii, of the Myrmicin^, of which about loo species, subspecies, and varieties have been described. They are confined almost exclusively to tropical and subtropical America; but one species is found as' far north as New Jersey. Many accounts have been published re- garding these insects, which have been commonly known as the leaf- cutting ants or the parasol ants. These names were suggested by the fact that these ants cut pieces from the leaves of trees and carry them, like parasols, into their nests. The use that the ants make of the leaves that they carry into their nests was long a mysterv\ But it is now known that the leaves are used as a culture medium upon which they cultivate a fungus, which they eat and feed to their lar^^as, and which is their only food. Professor Wheeler ('07 b) has published a monograph of the fungus-growing ants of North America in which is given a resume of the writings of previous students of the Attii; and a chapter is de- voted to these insects in his volume on "Ants" ('10). Subfamily DOLICHODERIN^ In this subfamily, as in the following one, the pedicel of the ab- domen consists of a single segment and there is no constriction between the first and second segments of the gaster ; but these ants can be dis- tinguished from the Formicinse by the fact that the anal orifice is in the form of a slit. These ants, also, often possess in addition to the poison glands, anal glands which excrete a foul smelling, sticky fluid, which is used as a means of defense in their combats with other ants. Only about a dozen species have been described from our fauna and most of these are southern. Certain tropical species build carton nests attached to trees and some of our species make carton nests under stones. The members of this subfamily are especially fond of honey-dew and attend aphids and coccids to secure it. Some of the species, "establish their nests on or near the nests of larger ants and either feed on the refuse food or waylay the workers when they return home and compel them to give up their booty" (Wheeler). The most important species of the subfamily in our fauna is the following. The Argentine ant, Iridomyrmex humilis. — This is an introduced species, which has become an exceedingly serious pest in the Gulf States and in Southern California. Its injuries are of two kinds: H YME NOP TERA 963 first, as a household pest, entering and overrunning dwelHngs; and second, as an orchard pest. Its injuries in orchards are due to the fact that it protects aphids and coccids in order to secure the honey- dew that they excrete. The ants drive away the insect enemies of the aphids and coccids, which as a result multiply to an abnormal extent. It has been found that this ant can be exterminated in houses and orchards by the use of an arsenical poisoned syrup. Detailed directions for the preparation and use of this syrup are given in bulletins published by the U. S. Department of Agriculture. Subfamily FORMICIN^ The Typical Ants This subfamily is characterized by the form of the anal orifice, which is round, terminal, and surrounded by a fringe of hairs. The pedicel of the abdomen consists of a single segment and there is no constriction between the first and second segments of the gaster (Fig. 1 1 80). The following are some of our more common species. The carpenter ant, Campo- notus herculeanus pennsylvdmcus . Fig. 1 180.-A formicid ant. —This is one of the largest of our common ants. It is the large black species that builds its nests in the timbers of buildings, in logs and in the trunks of trees. Frequently it builds in the dead interior of a living tree, excavating a complicated series of chambers. The mound-building ant, Formica exsectoides. — This species is the builder of our largest ant-hills; these are often one meter in height and two meters across, and sometimes they are much larger than this. New colonies are often formed by fission, a portion of the colony emigrating and founding a new colony with one or more queens. In this way many colonies are often established in a limited area. The head and thorax of this ant are rust-red, while the legs and abdomen are blackish brown. The blood-red slave-maker, Formica sanguhiea. — More than a century ago Pierre Huber called attention to the fact that this species which is common in both Europe and America, keeps in its nests the workers of other species of Formica, which aid in performing the labors of the colony. The relations of the two species thus associated have been commonly regarded as that of slaveholders and slaves. The slaveholders obtain their slaves by making periodical forays on the colonies of the common black Formica fusca, and of other species of Formica, and bringing to their own nest the worker larvae and pup^. Some of these are eaten, but others are reared, and these knowing no other home take their place as active members of the colony. 964 AN INTRODUCTION TO ENTOMOLOGY In the blood-red slave-maker the gaster is black or brown and there is a notch in the margin of the clypeus. The nests of this species are low obscure mounds of earth or are excavated under stones or logs or around sttmips. Alany subspecies and varieties of this species are recognized, some of which do not keep slaves. The shining amazon, Polyergvis hlcidus. — The species of the genus Polyergus were named amazons by Pierre Huber on account of their warring habits. Species of this genus occur in this country as well as in Europe. The shining amazon is a beautiful, brilliant red species widely distributed in the Eastern and Middle states. The species of this genus are slave-makers that have become absolutely dependent' on their slaves. They cannot build their own nests or feed themselves or care for their young, but have only retained the power of fighting to get more slaves. Their mandibles are sickle-shaped and fitted only as weapons of offence. Like Formica sanguinea, these ants make periodical forays on the colonies of other species of Formica and carry home the worker larvae and pupae. The workers developed from these perform all of the labors of the colony except that of the making of forays on the colonies of other ants, in which they take no part. The young queens of Polyergus, being unable to work, establish new colonies of their species by securing adoption in some small weak colony of another species of Formica after killing its queen by piercing her head. The corn-field ant, Ldsius niger americdnus. — To the genus Lasius belong several common species of small brown ants that make small mounds in various situations. These ants are fond of honey-dew and not only care for the aphids from which they obtain it but collect the eggs of the aphids and store them in their nests through the winter, and in the spring place the recently hatched plant-lice on the stems and roots of the plants on which they feed. A well-known species of this genus is the corn-field ant, the habits of which are discussed in the account of the corn-root aphis, p. 419. The honey -ants, Myrmecocystus. — The ants of this genus are found in the arid regions of the Southwest, from the city of Mexico to Southern California and to Denver, Colorado. They have received the name of honey-ants from the remarkable fact that with them some of the workers function as honey-pots or reservoirs for storing the honey-dew collected by other workers, from nectar excreting galls on trees and from aphids and coccids. The individuals in which the honey-dew is stored are known as repletes. The workers that collect the honey-dew swallow it and carry it in their crop to the nest. There they regurgitate it and feed it to a replete, which in turn swallows it and retains it in its crop. The crop of the replete becomes so greatly distended that the gaster becomes a translucent sphere, as Fig. 1181. large as a pea, on the surface of which the sclerites appear as isolated patches separated by the tense, pelucid, yellowish, intersegmental membrane (Fig. 1 181). The repletes are unable to go HYMENOPTERA 965 about but remain quiet clinging to the roof of a chamber of the nest. When the season for obtaining honey-dew is passed, these Hving cells disgorge their supply through their mouths, for the use of the colony. There are several species and subspecies of Myrmecocysttts in some of which the replete form has not been found. Family BETHYLID^ The Bethylids This is a large family of parasitic wasps, including many genera and species. The family is widely distributed, representatives of it being found in all parts of the world. Our species are of small or moderate size. Those whose habits are known prey upon either coleopterous or lepidopterous larvae, and before pupating most of them spin cocoons. In this family there are eight exposed segments in the abdomen, the petiolar segment is ver^^ short and scarcely perceptible, and the ovipositor is a true sting. The majority of genera comprise species that are winged in both sexes; but in a few genera the males alone are winged. Some of the wingless females are ant -like in appearance. Among those species that prey upon important insect pests are Neoscleroderma tarsalis, which is parasitic on the beetle, Silvdnus surinamensis, and an undescribed species of Goniozus, which is parasitic on the codlin-moth in Kansas. A detailed account of the life-history of LcbUhs trogodermatis, which is an external parasite of dermestid larvae, is given by Howard ('oi). This family was mono- graphed by Kieffer ('14). The family RHOPALOSOMID^ although widely distributed is a very small family. It is represented in our fauna by Rhopalosoma poeyi, the larva of which was found by Hood ('13) to be an external parasite of a bush-cricket, Orochans saltdtor, in Maryland. The adult is nocturnal; it has very large eyes and ocelli, and the petiole of the abdomen is long and slender. Family VESPID^ The Typical Wasps or Diploptera The family Vespida^ includes our most familiar wasps, the hornets, and the yellow -jackets, and their near allies. All members of this family are winged and nearly all of them when at rest fold their wings lengthwise like a fan ; for this reason they are often termed the Diplop- tera or the diplopterous wasps. In the habit of folding their wings when at rest, the typical wasps differ from all other Hymenoptera except the Gasteruptiidae, the chalcid genus Leucospis and the genus Galesus of the family Belytidae. In this family the lateral ex- tensions of the pronotum are angular extensions behind and above the 966 AN INTRODUCTION TO ENTOMOLOGY tegulce; cell M4 of the fore wings is longer than cell Cu+Cuj (Fig. 1 182); and there are closed cells in the hind wings. The typical wasps found in America north of Mexico represent seven subfamilies of the family Vespidas. These can be separated pr.I. Fig. 1 1 82. — Wings of Vespa diabolica: pr. I, preanal lobe; pr. exc, preaxillary excision. (From Bradley.) by the following table, for which I am indebted to Professor J. C. Bradley. A. Fore wings with two submarginal cells; antennas clavate. p. 967 . . Masarin^ AA. Fore wings with three submarginal cells. B. Vein M4 + Cui of the fore wings elongate (Fig. 1183); cell M3 four-sided; wings not plaited, p. 967 EuPARAGiiNiE BB. Vein M4 + Cui of the fore wings exceedingly short (Fig. 11 89); cell M3 a scalene triangle (Fig. 1189); wings longitudinally plaited when at rest. C. Hind wings with an anal lobe (Fig. 1189). D. Tarsal claws bifid; middle tibiae with one apical spur; solitary wasps without a worker caste. E. Mandibles short, obliquely truncate and toothed at the apex, folding above each other beneath the clypeus or very slightly crossing; head quadrate; abdomen petiolate, the apex of the petiole globose and strongly constricted before the second segment, p. 968.Zethin^ EE. Mandibles elongate, crossing each other or placed parallel in a long sharp beak; if the abdomen is petiolate the head is transverse. p. 969 EUMENIN^ DD. Tarsal claws simple; middle tibiae with two apical spurs; social wasps building open or closed paper nests. E. Extensory muscle of the abdomen fixed on the thorax in an oval slit between the apical scales of the propodeum; the slit always broadly rounded at its upper angles, p. 973 Epiponin^e EE. Extensory muscle of the abdomen fixed on the thorax in a narrow and much compressed slit between the apical scales of the propodeum. p. 974 POLISTIN.^ CC. Hind wings without an anal lobe, somewhat stalked (Fig. 1182); ab- domen conical; social wasps with a worker caste, building closed paper nests; tarsal claws simple; middle tibiae with two apical spurs, p. 975 Vespin^ If we take into account only the habits of these insects the sub- families of the typical wasps can be separated into two groups, the solitary Diploptera, those in which a single female makes a nest for her young, and the social Diploptera or social wasps, in which many individuals work together to make a nest. This grouping of the HYMENOPTERA 967 subfamilies, however, is not regarded as a natural division of the family Vespidas, as each of the two groups is believed to be poly- phyletic, and too, F. X. Williams ('19) has shown that in the genus Stenogaster, found in the Oriental and Australian regions, some species are solitary and others are social; but this grouping is useful in a discussion of the habits of these insects THE SOLITARY DIPLOPTERA Fig. 1 1 83 .—Wings of Euparagia scutellaris. Bradley.) (After The subfamily EUPARAGIIN^ includes the ^quus Euparagia, two species of which are found in the Southwest. These wasps differ from other Vespidas in that cell M3 of the fore wings is four-sid- ed (Fig. 1 183). Very little is known regard- ing the habits of these insects. For figures and descriptions of the species see Brad- ley ('22). The subfamily MASARIN^isavery widely distributed group but it is repre- sented in our fauna only by the genus Pseudomdsaris, of which thirteen species have been described; these are found in the Far West and Southwest. In these wasps there are only two sub- marginal cells in the fore wings and the antennae are clavate. The North American species were monographed by Bradley ('22). There are but few accounts of the nest-building habits of masarid wasps. Giraud ('71) describes the habits of Ceramius lusitdniciis, a species found in France. This is a mining wasp, which digs a burrow in the ground, leading to a cell, in which the larva lives. The larva is fed by the mother, who brings to it from time to time a supply of a paste, described as being somewhat like dried honey. When the larva is full-grown it lines its cell with a layer of silk, otherwise the pupa is naked. Ferton ('10) describes the habits of Celonltes abbrevidtus, another species found in France. This is a mason wasp, which makes earthen cells attached to the sides of rocks or to stems of plants. A figure of one of these nests is given by Sharp ('99) page 89. In this figure the cells are represented as opening downward. This species also provisions its nest with a paste made of pollen and honey ; and the full-grown larva lines its cell with silk. The most remarkable feature in the habits of these two species is that they provision their nests with a paste made of pollen and 968 AN INTRODUCTION TO ENTOMOLOGY honey. In this respect they differ from other solitary wasps in the same way that the solitary bees differ from other sphecoid wasps. But this difference in habits is not true of all masarid wasps as is shown by the habits of the following species, which provisions its nests with larvae. The only published account of the nest -building habits of an American masarid is that by Dr. Anstruther Davidson ('13) who described the nest of Pseudomdsaris vespoides. This is our largest and most handsome species; it measures from 15 to 22 mm. in length, is black marked with yellow, and is widely distributed in the Far West; but is not common. Dr. Davidson's account of the nest follows. Their nests, a combination of cells as shown in the accompanying illustration, are built after the manner of the common mud dauber wasp and when completed are plastered over with a further layer of clay. They are usually attached to a twig in a low bush, the one in the illustration being found on a Audibertia shrub. When the cell is completed the opening is closed by a stopper of clay which is, however, always depressed below the rim of the cell so that the top shows as a series of miniature cups. The clay used is that common to the neighborhood, but in the process of building it is mixed with some secretion that makes the whole of such stony hardness, that it seems impossible any insect could possibly cut its way through it. Perhaps the cup shaped depression on top may be a device to conserve the rain necessary to soften the stopper and render the exit of the wasp possible. That rain or excessive moisture is necessary before the insect can successfully emerge is suggested by the results attained in indoor hatching. In those nests kept indoors in dry receptacles while the wasp usually attains the mature state, it only exceptionally cuts its way out. Kept under these conditions the larvae do not always matiu-e in the following spring as the following record makes evident. Of a cluster of cells gathered in June, 1902; in April, 1903, I opened two of them to find one had pupated while the other was still in the larval state. It remained in this state till March, 1905, when it died. The other cells were then opened, one contained a live larva, the other four or five contained perfect insects all dead, apparently unable to emerge. The capability of insects to survive for more than one season in the larval stage is probably an evolutionary acquirement, and a necessity to those insects living on a food supply that is wholly dependent on climatic conditions. As the writer has shown elsewhere in re- cording a similar experience with Anthidium corisimile, this is a very necessary acquirement in a country where, as sometimes happens, no rain at all may fall, and no food supply would in those seasons be available. The cells are stored with small larvae of what species I am unable to determine. As in the nests of the European species, the cells are lined with a layer of silk. Figiu-e 1 184, a represents a nest given me by Professor Doane of Stanford University; this is an incomplete nest in which the cells have not been plastered over with an additional layer of clay; Fig. 1184, b is a diagram of a longitudinal section of a single cell showing the cup at the upper end; Figure 1184, c represents a completed nest ; this was given me by Dr. Davidson. The subfamily ZETHIN.^^ is represented in our fauna by a single genus Zethus. of which there are two species, Zethus spmipes and Zethus slossoncB, common in the southeastern part of the United States. Ashmead ('94) states that our Zethus spmipes builds globular cells of clay or sand and mud mixed, which are attached by a small pedicel HYMENOPTERA 969 to some shrub or tree. I find no other account of the habits of this species, and the other species of Zethus the habits of which have been described build nests of a very different type. Saussure ('75) states that Zethiis romandiniis, found in Cayenne, "constructs with woody fibres and gummy materials several rounded cells, with thick walls toward the bottom and irregularly united, recalling a little those of Bombtts." Ducke ('14) describes and figures the nest of a Brazilian species, Zethus lohuldtiis. This nest consists of a long mass of cells, suspended from a twig and is composed of fragments of leaves cement- Fig. 1184. — Nests of Pesudomasaris vespoides: a, incomplete nest; b, diagram of a cell showing the cup at the upper end; c, completed nest. ed together by a resinous substance. Williams ('19) describes the nest of Zethus cyanopterus, which he observed in the Philippines; this nest is made of bits of leaves which "are chewed along one or more of their edges which makes them adhere the more firmly to the nest." This author says nothing about the use of a gummy material for cementing together the fragments of leaves. Subfamily EUMENIN^ The Eumemds This subfamily includes b}^ far the greater number of our species of the solitary Diploptera ; and is represented in our fauna by about eight genera. The distinguishing features of these wasps are indicated in the table of subfamilies given above. 970 AN INTRODUCTION TO ENTOMOLOGY The different species of etmienids differ greatly in habits; many are miners digging burrows in the earth leading to cells in which pro- visions are placed for their young; some make burrows in wood, which they divide into cells by partitions of mud; some build their nests in the stems of pithy plants or make use of any suitable cavity that they find; and others are mason or potter-wasps, making cells of earth, which are built in holes, or on the surface of the ground, or attached to twigs. Although the adult eumenids do not confine themselves to a carnivorous diet but often visit flowers to obtain nectar, they all provision their nests with insects, which they have paralyzed with their sting ; usually only a single species of caterpillar is used for this purpose by each wasp. A remarkable feature that has been observed in the nesting habit of many eumenids and perhaps is true of all, is that after the cell is prepared the egg is suspended by a slender thread from the ceiling or side of the cell. In some cases, at least, this is done before the pro- visioning of the nest is begun. An African species, Odynerus tropicdlis, the habits of which are described by Roubaud (' i6) does not provision its cell with prey amassed in advance, but feeds its larva from day to day with small, entire, paralyzed caterpillars, and does not close the cell until the larva has completed its growth. The following examples will serve as illustrations of the habits of members of the subfamily. Among the more detailed accounts of the .Activities of some of our species are those of Peckham and Pecldiam ('05), Hartman ('05), Isley ('13) and Rau and Rau ('18). For a general account of the habits of these insects see Roubaud ('16). Odynerus.- — The greater nimiber of our species of eumenids belong to the genus Odynerus. In this genus the abdomen is sessile. The shape of the body and frequently the coloration resemble those of the social wasps known as yellow-jackets, although usually the body is more slender and smaller. The common species are quite neighbor- ly; and, owing to this resemblance to the yellow-jackets they inspire us'with a fear that is out of all proportion to their will or ability to inflict pain. -^^S^ Many species of Odynerus are miners. ^^^^i Their burrows are to be found both in level ^^^^ ground and in the sides of cliffs. Branch- — — .^^--^^^m^g^a-;^.-^ ing from these burrows are short passages, "^^rf^^^J^^ — "~ each leading to a cell, from the ceiling of ~ZIEirzpz,..zj^.r^ which an egg is suspended by a slender thread ; and in which food is stored for the Fig. 1 185.— Turret over the larva. In the species that have been stud- burrow of Odynerus gem- ied, this food consists of small, paralyzed ^""^- ^^fter Rau and Rau.) caterpillars. Some of the mining species while digging the burrow build a turret over the entrance of it, made of pellets of mud removed from the burrow; one of these turrets is figured by the Raus (Fig. 1 185). The material of which the turret is composed is used to fill up the burrow after the cells are finished. HYMENOPTERA 971 In digging the burrow and in tearing down the turret the earth is softened with water, which the wasp brings in her mouth from some pool or stream - Not all species of Odynerus mine in the ground; many burrow in the stems of pithy plants, making a series of cells separated by parti- tions of mud ; other species will avail themselves of any convenient cavity in which to make their nest, frequently utilizing the deserted nests of the sphecoid-wasps known as mud-daubers. In this case a Fig. ii86.—Eumenes fraterntis and its nests. single cell of a mud-dauber is divided by a transverse partition, mak- ing two cells for the smaller Odynerus . One year these wasps plastered up many of the keyholes in our house, including those in bureaus. Some species of Odynerus are masons constructing nests entirely of mud. One of our species, Odynertts birenimaculdtus, makes a nest about the size of a hen's egg. This is composed of hard clay, fastened to a twig of a bush, and contains many cells. The jug-builders, Eumenes. — The wasps of the typical genus of this sub- family are potter-wasps which build nests that appear like miniature water-jugs. The nests of our common species, Eumenes fraterntis, are often found attached to twigs (Fig. 1 1 86). In this genus the ab- domen of the adult is petiolate. These wasps provision their nests with cater- pillars and frequently with cankerworms. Fabre, who studied the habits of a European species of Eumenes observed what goes on within the nest by making a window in the side of it. The egg is suspended from the ceiling of the nest by a slender thread; Fig. 1 187. ridens. -Monobia quad- 972 AN INTRODUCTION TO ENTOMOLOGY when the larva hatches it at first makes use of the egg-shell as its habitation and stretches down to feed on the caterpillar below it; if disturbed it retreats up its support. Later when the larva has increased "^ '" in size and strength it descends to the mass of food. Monohia quddridens. — This species (Fig. 1187) is common in most of the states east of the Missis- sippi. It is larger than the jug-builders, and the abdomen of the adult is sessile. Figure 1 1 88 repre- sents a nest of this species, now in the Cornell University collection, which was made in a board in the side of a barn. The partitions are made of mud. Each cell contained a pupa when the nest was opened, hence it was not evident what the food of the larvce had been ; but several observers state that this species stores its nests with large cutworms; and it is doubted that this species is a carpenter-wasp. It seems probable that the nest figured here w^as made in a deserted burrow of the large carpenter-bee, Xylocopa virginica. It differs from a nest of this bee only in that the partitions are made of mud. THE SOCIAL WASPS Since the social Diploptera are the only wasps that are social they are commonly referred to as the social wasps instead of the more technical name. As with the ants the colonies of social wasps consist of three castes, the female or queen, the workers, and during the later part of the season, the males. The workers are females in which the reproductive organs are imperfectly developed. In the genus Belonogaster a worker caste is be- lieved to be lacking. In Polistes it is very difficult to make a distinction between females and work- ers, for they can apparently all become fertile. In the temperate regions the colonies exist for only one season; the males and the workers die in the autirmn ; the females hibernate and each starts a new colony in the spring. At first the fe- male performs the functions of both worker and queen, starting the building of the nest and laying the eggs. In the early part of the season only workers are developed; after they appear they carry on the labors of the colony, expanding the nest and procuring the food for the larv£e; the only function of the Fig. II.S8 — Xest of Motiobia quadri- dens. HYMENOPTERA 973 queen then is to produce the eggs. In the later part of the season males and females are developed. The social wasps are predacious, and they feed their larvae upon insects which they have malaxated. The wasps are also fond of the sweets of flowers, the juices of fniits, and of noney-dew. They also feed upon a liquid which the wasp larva emits from its mouth. This exchange of nourishment between the larvee and the adults, termed trophallaxis, is discussed in the Chapter on Isoptera, page 279. In the temperate regions the multiplication of colonies is brought about by the production of many males and females in the nest in the later part of the season; these pair, the females hibernate, and each female founds a new colony in the spring. But in the Tropics many of the Epiponinffi form large perennial colonies, which from tmie to time give off swarms, in a way quite similar to the well-known swarming of the honey-bee. Representatives of three of the subfamilies of social wasps are found in America north of Mexico. The distinguishing characters of these are indicated in the table of stibfamilies of the Vespidas given above. Subfamily EPIPONIN^ This is a large group of wasps including a great variety of forms, which exhibit great differences in the architecture of their nests. «+2d4 Fig. 1 189. — Wings of Misclwcyttarus lahiatus: pi, posterior or anal lobe; ax. exc, axillary excision. (From Bradley.) The species are mostly confined to tropical America; but three are found in the southern portions of the United States. Figure 1 1 89 represents the venation of the wings of Mischocyttams lahiatus. Brachygastra lechegitdna.- — This species is found within the limits of our territory only along the Mexican border. Its nest resembles in form externally those of hornets {Vespa) but the combs are attached 974 AN INTRODUCTION TO ENTOMOLOGY to the envelope. This wasp is especially interesting from the fact that it frequently stores honey in the combs of its nest; but the honey is probably not an exclusive or essential constituent of the larval food. Mischocyttarus .■ — This tropical genus is represented in our fauna by two species, one, Mischocyttarus cuhensis, found in Florida and in Southern Georgia, one, Mischocyttarus flavitdrsis, found in the South- west, Colorado, and California. These wasps make small, few-celled paper nests, without an en- velope like those of Polistes; but the wasps are easily distinguished from Polistes by the form of the first segment of the abdomen which is slender and elongate, forming a pedicel. The nests of M. cubensis are found on palmetto leaves. Subfamily POLISTINiE Polistes The wasps of the genus Polistes and their nests are very familiar objects. The nests consist each of a single comb suspended by a peduncle, and the comb is not enclosed in an envelope (Fig. 1190). These nests are often built under the eaves of buildings, in garrets, and in sheds and barns ; they are also often made under flat stones in fields, and sometimes attached to bushes. The combs of our species of Polistes are horizontal; but the nests of Polistes linedtus, which I Fig. 1 190. — N est oi Polistes. Fig. 1191. — Polistes. found hanging from the ceiling of a cave in Cuba, are long, narrow, vertical combs, from one to two inches in width and from twelve to eighteen inches in length. The nests are made of a grayish paper-like material, composed of fibers of weather-worn wood, which the wasps collect from the sides of unpainted buildings, fences, and other places, and convert into a paste by the action of the jaws and the addition of some fluid, prob- ably an oral secretion. The nests of Polistes are usually comparatively small ; but some have been found in Texas that measured more than a foot in diameter. In this genus the abdomen is long and spindle-shaped (Fig. 1 191). HYMENOPTERA 975 Several of the species are known to store small quantities of honey in their combs. These wasps are often infested by stylopids. Subfamily VESPIN^ The Hornets and the Yellow- Jackets This subfamily includes those wasps that are commonly known as hornets and the yellow- jackets. With these insects the body is Fig. 1 1 92. — Vespa. comparatively short and rather stout (Fig. 1 192); the abdomen is at- tached to the thor- ax by a very short pedicel; and the color is black, spot- ted and banded with yellow or yel- lowish white. The membersofthissub- family differ from other vespoid wasps in that the hind wings are without an anal lobe (Fig. 1182). These wasps make their nests of paper, which in some cases is com- posed of fibers of weather-worn wood, like that of Polistes described above, in other cases of fragments of more or less decayed wood. These nests consist of a series of horizontal combs suspended one below another and all enclosed in a paper envelope (Fig. 1193). When the wasps wish to enlarge their nest they remove the inner layers of the envelope, and add to the sides of the combs, build addi- tional combs below, and put on new layers on the outside of the Fig. 1 193. — Nest of Vespa, with side removed. (From A. B. Comstock, Handbook of Nature Study.) 976 ^A^ INTRODUCTION TO ENTOMOLOGY Fig. 1 194. — Early stage of nest of Vespa. envelope. By these additions the nest may become of large size by the end of the season. Very small empty nests consisting of a single comb with but few cells and enclosed in an envelope of only one or two layers of paper are often found (Fig. 1194)- Such a nest is evidence of a trag- edy. A queen wasp, in the spring, had started to found a colony. It was necessary for her to go back and forth in the fields collecting material for her nest and food for her larvae; and be- fore a brood of workers were de- veloped to relieve her of this dangerous occupation she became the prey of some bird and the de- velopment of the colony was wrecked. Two quite different types of nests are made by different spe- cies of these wasps, and these are made in quite diif erent situations. One kind is built above ground; these are attached to bushes or trees, or beneath the eaves of buildings; they are made of a grayish paper composed of fibers of Vv^eather-wom but not decayed wood. This paper is comparatively strong, so that the envelope of the nest is composed of sheets of paper of considerable size, a single sheet often completely enveloping the nest. The other kind of nest is built in a hole in the ground, which is enlarged by the wasps as they need more room for the expansion of the nest. The paper of which these nests are made is brownish in color and is made out of partially decayed wood; it is very fragile and would not be suitable, therefore, for use in nests built in exposed places. Even though the nest is built in a protected place, the use of this fragile material necessitates a different style of architecture. The enveloping layers of the nest, instead of being composed of sheets of considerable size, are made up of small, overlapping, shell-like portions, each firmly joined by its edges to the underlying parts. If a completed hornet's or yellow-jacket's nest be examined it will be found that some of the later-built combs consist wholly or in part of cells that are larger than those in the first -made combs ; the smaller cells are those in which workers were developed; the larger ones those in which the sexual forms were reared. It has been found that at least two species of this subfamily are social parasites. In these species the worker caste has been lost, there being only males and females. The female enters the nest of another species of Vespa and lays her eggs, and her larvae are reared HYMENOPTERA 977 by the rightful owners of the nest. The species that are known co be parasites are Vespa drctica, which infests the nests of Vespa diaholica, and Vespa austriaca, v^hich. infests the nests of Vespa riifa in Europe. Vespa austriaca fias been found in this country but Vespa nifa is not known to occur here. The American host of Vespa austriaca has not been definitely ascertained, but is thought to be Vespa consobrina. See Wheeler and Taylor ('21). The members of the subfamily Vespinse found within the limits of our territory are commonly included in a single genus, Vespa; but some writers place all of our species except Vespa crabro in a separate genus Vespula; Only a few of our species can be mentioned here. The giant hornet, Vespa crabro. — This is our largest species, measuring from 18 to 22 mm. in length. It is brown and yellow in color and is found around New York City, on Long Island, and in Connecticut. It builds its nests in hollow trees and within buildings suspended from the roof. The white-faced hornet, Vespa maciddta. — This is the common, large black and white hornet. It is widely distributed in the United States and Canada. The nest, which is sometimes very large is usually attached to the limb of a tree. The yellow-jackets.- — This common name is applied to several small, black and yellow species of Vespa, which are so closely related that it is difficult to distinguish them. Most of the species build their nests in the ground ; these are the brownish paper nests described above. Sometimes the nest is built in a stump or under some object lying on the ground. On one occasion I found a fine large nest under the base-board of one of my bee-hives, and into which I inadvertantly thrust my toes, with sad results, while examining the hive. The nest is now in the Cornell collection. SUPERFAMILY SPHECOIDEA The Sphecoid-wasps and the Bees The superfamily Sphecoidea resembles the two preceding super- families in the presence of an anal lobe in the hind wings, except in ig- _ _ _ Head and thorax of a sphecoid-wasp, p, pronotum, p. I., posterior lobe of the pronotum; /, tegula. some specialized genera of the Ampulicidae and some bees; it differs 978 AN INTRODUCTION TO ENTOMOLOGY from the Evanioidea in that the petiole of the abdomen is attached to the hind end of the propodeum ; and it differs from the Vespoidea in that there is on each side a lateral extension of the pronotum in the form of a distinctly differentiated rounded lobe, which covers the spiracle (Fig. 1195, B); these lobes are known as the posterior lobes of the pronotum ; they do not reach the tegulae except in some Drsnnidae and Ampulicidas. These exceptional forms can be placed in their families by the table on pages 906 to 914. The families constituting the superfamily Sphecoidea, which can be separated by the table referred to above, represent two quite dis- tinct groups of families, known respectively as the sphecoid-wasps and the bees. These two groups of families are distinguished as follows. A. First segment of the posterior tarsi cylindrical and naked; or with but little hair; hairs clothing the thorax simple; nests provisioned with animal food. p. 978 The Sphecoid- Wasps AA. First segment of the posterior tarsi elongate and dilated; some of the hairs, especially of the thorax, plumose; nests provisioned with honey and pollen. p.989 The Bees THE SPHECOID-WASPS The group known as the Sphecoid-wasps includes three families, the Ampulicid£e,the Dryinidse, and the Sphecidaj. These three fam- ilies and certain families of the Vespoidea were formerly classed to- gether as the Fossores or digger-wasps ; which names were suggested by the fact that most of the species belonging to these families make nests for their young by digging burrows in the ground or in wood. But this group is no longer regarded as a natural one notwithstanding the striking similarity in habits exhibited by its members. The family AMPULICID^ is represented in our fauna by only two genera, Rhindpsis and Dolichtirus, the species of which are very rare. So far as is known the members of this family prey on cock- roaches, with which they store their nests. Family DRYINID^ The Dryinids This family is composed of small parasitic wasps; it is widely distributed over the world and is represented in our fauna by many genera. The fore wings have a lanceolate or ovate stigma ; the hind wings are without closed cells; the antennas consist of ten segments, the anterior tarsi of the female are usually chelate; and either the pro- notimi has a longitudinal sulcus or the antennas are borne close to the clypeus. The females of the genus Gondtopus are wingless, ant- like, and are without a scutellum. These parasites confine their attacks to the homopterous insects belonging principally to the families Fulgoridse, Membracids, and Cicadellidas. HYMENOPTERA 979 The femals dndnid seizes her victim with her raptorial fore legs; one pair of pincers usually grips the neck of the prey, the other pair grips the abdomen towards the apex or the hind legs. The wasp then inserts her egg into the body of the bug. A few days later the immature lar\'a of the parasite appears outside the body of its host enclosed in a sac composed of molted skins. Here it remains, with its head in the opening in the body-wall of its host, until it has com- pleted its growth. It then leaves its host and spins a silken cocoon, which in some cases is furnished with an outer covering formed of the larval sac or of round patches of epidermis stripped off from the leaf surface. A detailed account of the habits of these remarkable insects is given by Perkins ('05) and the family Dryinidas was monographed by Kieffer ('07), and Kieffer ('14) in a paper on the Bethylidee. Family SPHECID^ The Typical Sphecoid ll'a^^^ In this family the hind wings have an anal lobe and some closed cells; the abdomen of the male has seven exposed tergites; the sting of the female is not enclosed by the hypopygitmi ; the posterior meta- tarsi are not dilated as in the bees and there are no plumose hairs. All members of the Sphecidas are winged. To this family belong all of our common nest-building sphecoid wasps. These differ from the bees in that they provision their nests with animal food, insects or spiders, which they have paralyzed by stinging them. Different members of the family differ greatly in their nesting habits; some are mason-wasps, building cells of earth; many burrow in the ground ; and others burrow in the stalks of pithy plants or make use of cavities that they find. Alost members of the Sphecidje, after preparing their nest, rapidly accumiilate an amount of prey sufficient to enable the young to develop to maturity, lay an egg with it, and then close the cell before the egg has hatched. This method is termed mass provisioning. But certain members of the family, Bemhex and some others, feed their young from day to day as long as they remain in the larval state. This method is termed progressive provisioning. As each larva re- quires constant attention for a considerable time only a few young can be reared by a single female in this way. Many of these wasps after stinging their prey and before placing it in their nest malaxate {i. e. chew) its neck or some other part of the body and lap up the exuding juices. The family Sphecid® is divided into six subfamilies, some of which include two or more quite distinct groups of genera or tribes. As many of these tribes are given subfamily rank by some writers each of those represented in our fauna is defined below. These tribes can be separated by the following key, which has been kindly prepared for me by Professor J. Chester Bradley. 980 AN INTRODUCTION TO ENTOMOLOGY A KEY TO THE TRIBES OF SPHECID^ OCCURRING IN THE UNITED STATES A. Postscutellum with squamae which project backward, and base of propodeuiti with a median spine, p. 989 Oxybelini AA. Postscutellum and propodeum simple. B. Only I submarginal cell. Inner margins of eyes emarginate or strongly converging toward the clypeus (except in Anacrabro, which may be recog- nized by its flat venter). C. Inner margins of eyes entire, p. 989 Crabronini CC. Inner margins of eyes deeply emarginate. p. 982 Trypoxylonini BB. Usually 3 submarginal cells, sometimes two, rarely only one, in which case the inner margins of the eyes are neither emarginate nor strongly convergent toward the clypeus. C. Anal lobe large, reaching to opposite or beyond the apex of the cell M3 + Cu, + Cu. D. The marginal cell not appendiculate. Abdomen with a cylindrical petiole. Middle tibiae with two apical spurs, p. 983 Sphecini DD. The marginal cell appendiculate. Abdomen not petiolate. E. Ocelli normal. Middle tibiae with two apical spurs, p. 981 ASTATINI EE. Ocelli distorted. Middle tibiae with one apical spur. p. 981 Larrini CC. Anal lobe small, not reaching to opposite the apex of the cell M3 + Cui + Cu. D. Ocelli normal, circular and convex. E. Antennae inserted low on the face, near the base of the eyes. F. No epicnemium. G. First abdominal segment sessile or with a cylindrical petiole which is composed only of the stemite. Middle tibiae with a single apical spur. H. An appendiculate cell present, or the mandibles with an external notch, usually both. p. 982 Dinetini HH. No appendiculate cell. Mandibles without an external notch, p. 985 Pemphredonini GG. First abdominal segment, petioliform, the petiole consisting however of both sternite and tergite, nodose at apex. Middle tibiae with two apical spurs, p. 986 Melliniis in Nyssonini FF. An epicnemium present. Middle tibiae with two apical spurs. p. 986 Nyssonini EE. Antennae inserted near the middle of the face above the bases of the eyes. F. Abdomen without a cylindrical petiole which is composed only of the sternite. G. Transverse part of vein M distant from the stigma by less, usually much less, than twice the distance between the apex of the cell 2d Ri + R2 and the apex of the wing. Labrum rarely exserted. H. Hind femora without a transversely expanded reniform apical plate. I. Upper margin of clypeus extending across in a straight line or arch, without a median lobe. Cell R5 usually small and triangular, or if not, the middle tibiae have two apical spurs, p. 986 Nyssonini II. Upper margin of clypeus with a median lobe extending up- ward toward the antennae. Cell Rs four-sided. Middle tibiae with one apical spur. p. 986 Philanthini HH. Hind femora broadened at apex, there forming a transverse reniform plate, p. 986 Cercerini hymenoptera 981 GG. Transverse part of vein M distant from the stigma by two or more times the distance between the apex of cell 2d Ri + Rj and the apex of the wing. Labrum exserted. p. 987. , StizinI FF. Abdomen with a cylindrical petiole which is composed only of the sternite. p. 985 Psenini DD. OcelU distorted, p. 988 Bembicini Subfamily LARRIN^ Tribe ASTATINI The members of this tribe are rather small, seldom more than 12 mm. in length. They are usually black or black and red. As in the following tribe the anal lobe of the hind wings is large, the marginal cell of the fore wings is appendiculate, and the abdomen is not petio- late; but these wasps differ from the Larrini in that the ocelli are normal and the middle tibiaa are armed Mdth two apical spurs. The habits of Astata unkolor and of Astata bicolor are described by the Peckhams ('98; ; tnese species burrow in the ground and pro- vision their nests with bugs. Tribe LARRINI Most members of the Larrini are of moderate size, but our species range from 3 mm. to about 23 mm. in length. They are usually rather stoutly built insects (Fig. 1196). The anal lobe of the hind wings is long and scarcely sepa- rated from the preanal lobe (Fig. 1197); the marginal cell of the fore wings is appendiculate; the ocelli are distorted; and the middle tibise are armed with one apical spur. Nearly all of the species burrow in sandy places and provision their nests with orthopterous insects or with bugs ; but ap Fig. 1 197. — Wings of Tachysphex terminatus. Williams ('13) states that a few of the smaller species make their nests in brambles. 982 AN INTRODUCTION TO ENTOMOLOGY Some members of the Larrini (Tachyspkex) dig short burrows in the ground at the bottom of which the prey is placed with an egg, and then the burrow is closed with loose sand, there being no well- formed cell ; several of these burrows are often made and stored in a single day. Other members of the Larrini make deeper bur-ows which contain from a few to many cells. For a monograph of this tribe see Fox ('93). Tribe DINETINI In this tribe the anal lobe of the hind wings is small, not reaching to opposite the apex of cell Ms+Cui+Cu; the ocelli are normal, circular and convex. The tribe is composed chiefly of small and little known insects except the genus Lyroda. A common species of this genus, Lyroda subita, practises progressive provisioning, feeding its young from day to day with crickets of the genus Nemohius; its nest is made in the ground. The small wasps of the genus Miscophus pre) on spiders. For a monograph of this tribe see Fox ('93). Subfamily TRYPOXYLONIN^ This subfamily includes a single tribe, the Trypoxy- lonini. In these wasps the inner margin of the eyes is deeply incised, the ocelli are normal, the marginal cell of the fore wings is not appendiculate, and there is only one submarginal cell. The body is black, slender, and of medium size. I have found, in New York, the nests of Trypoxylou fngidum very common in branches of sumac (Fig. 1 198), more common than those of any other insect except the little carpenter-bee, Cerattna. The cells of the nests of Trypoxylon are separated by partitions of mud and are stored with spiders. The larva of Try- poxylon frigidimi when full-grown makes a very slender cocoon, with the upper end rounded and sometimes slightly swollen, and the lower end blunt and of denser texture than the remainder of the cocoon. An extended account of the habits of two other species of Trypoxylon, T. albopilosum and T. rubro- cmctum, is given by the Peckhams ^'89), who studied these species in Wisconsin. Of special interest are the observations made by these writers on the cooperation of the males and females during the nest-building i\est of Tr\ period. They state as follows. poxylonjng "With both species when the preliminary work of ^dum. clearing the nest and erecting the inner partition has been performed by the female, the male takes up his station inside HYMENOPTERA 983 the cell, facing outward, his little head just filling the opening. Here he stands on guard for the greater part of the time until the nest is provisioned and sealed up, occasionally varying the monotony of his task by a short flight." "V\'e have frequently seen him drive away the brilliant green Chrysis fly which is always waiting about for a chance to enter an unguarded nest." "In one instance, with nthrocinctum w^here the work of storing the nest had been delated by rainy weather, we saw the male assisting by taking the spiders from the female as she brought thein and packing them into the nest, leaving her free to hunt for more." Some species of Trypoxylon are mud-daubers. Trypoxylon albi- tarsis, a shiny black species with white tarsi, builds large nests of mud, which consist of several parallel tubes, often three inches or more in length, placed side by side. These nests are known as pipe-organ nests. Each tube is divided by transverse partitions into several cells, which are provisioned with spiders. The tubes when completed are not covered with an extra layer of mud as is commonly the case in the nests of other mud-daubers. When an adult is ready to emerge from the cell in which it was developed, it mkes a hole through the exposed side of the tube. For a monograph of Trypoxylon see Fox ('93). Subfamily SPHECIN^ The Thread-waisted Wasps These insects are termed the thread-waisted wasps on account of the great length of the petiole of the abdomen (Fig. 1199). With these wasps the marginal cell of the fore wings (2d R1+R2) is not appendiculate; the anal lobe of the hind wings is large, extending to the apex of cell M3+CU1+CU2 or beyond (Fig. 1200); and the middle tibise bear two apical spurs. These are the most commonly observed of all of our sphecoid wasps, as certain species build their mud nests in the attics of our houses; and, too, the ^ Fig. iigg.Sceliphron cementarium . Fig. 1200. -Wings of Sceliphron cementarium 984 AN INTRODUCTION TO ENTOMOLOGY peculiar shape of the body makes them very conspicuous. Most of the species burrow in the ground and store their nests either with caterpillars or with Orthoptera. But those best known to us are the mud-daubers. The mud-daubers make nests of mud attached to the lower surface of fiat stones or to the ceilings or walls of buildings. These nests usually consist of several tubes about twenty-five millimeters in length placed side by side (Fig. 1201) and are provisioned with spiders. The mud-daubers may be seen in damp places collecting mud for their nests, or exploring build- ings in search of a place to build. They have a curious habit of jerking their wings frequently in , a nervous manner. There ^' "* ' are in this country two ^ig- 1 201. -Nest of a mud-dauber removed from ■ ■, ■. J- 4. -u + jf J a wall exposmg the cells: o, larva full-grown; 0, Wiaely aiStriDUtea ana cocoon, c, young larva feeding on its spider- common species of mud- meat ; d, an empty cell. (From A. B. Comstock, daubers; these are the Handbook of Nature Study.) blue mud-dauber, Chaly- bion ccerulium, which is steel blue with blue wings, and the yellow mud-dauber, Sceliphron cementdrium, which is black or brown with yellow spots and legs. The latter of these species has been commonly described under the generic name Pelopcsus. The tool-using wasps, Ammophila.- — Among the members of the Sphecinse, that burrow in the ground and store their nest with cater- pillars are certain species of the genus Ammophila. These are of especial interest on account of the habit, first observed by the Peckhams, of pounding down the earth with which they close their burrow by taking a stone or some other object in their mandibles and using it as a hammer. The genus Chldrion, formerly known as Sphex, includes species which are among the most common of flower visitors in the warmer parts of our country, and are among the largest and most handsome, and therefore most often observed of our wasps. In the West the common, very large, all metallic green Chldrion cydneum is a very striking insect; and in the East Chlorion ichneumdneum, which is brownish red with the end of the abdomen black is the most noticeable. Subfamily PSENIN^ This subfamily includes two tribes, the Psenini and thePemphre- donini; each of these has been regarded as a separate subfamily or family. HYMENOPTERA Tribe PSENINI The Psenini are small sphecoid-wasps in which the base of the abdomen is slender, forming a petiole much like that of the Sphecinge, but differing in being flattened and usually furrowed above (Fig. 1202), and these wasps are much smaller than the true thread-waisted wasps. The antennae are inserted at the level of the middle of the eyes; and there are three complete submarginal cells in the fore wings. These wasps make their burrows either in sand or in the pith of brambles, and pro- vision them with aphids or other small Homoptera. Fig. 1202.— A Tribe PEAIPHREDONINI psenid. In this tribe the antennas are inserted low on the face, near the level of the base of the eyes; and there are at most two submarginal cells present, sometimes a trace of vein r-\-tn and Rs Fig. 1203. — Wings of Stigmus podagricus. (From Bradley). incompletely indicates a third (Fig. 1203). The ab- domen is sometimes sessile. The pemphredonids usually burrow in the pith of dry branches and provision their burrows with plant- lice. A very common species in the East is Stigmus fraternus. This insect measures 5 mm. in length, and makes tortuous burrows in the pith of sumac (Fig. 1 204) . Other common members of the tribe are larger. Some species of Xylocelia (Diodontus) have been found to burrow in the ground. This tribe was monographed by Fox ('92). Fig. 1204.— Nest of Stig- mus fraternus. 986 AN INTRODUCTION TO ENTOMOLOGY Subfamily BEMBICIN^ Tribe PHILANTHINI In this tribe the upper margin of the clypeus is suddenly expanded into a broad median lobe, usually rhomboidal, extending upward toward the antennae (Fig. 1205). These wasps bur- row in the ground; some species provision their nests with ants others with bees. Tribe CERCERINI Fig. i205.-Face of a I^ the Cercerini philanthid; c, clypeus. the hmd femora are 1206— Hind leg broadened at the apex, Cerceris 'dypeata. there forming a trans- verse reniform plate (Fig. 1206); in both male and female there is a distinct pygidial area; the transverse part of vein M is distant from the stigma by less than twice the distance between the apex of the cell 2dRi+R3 and the apex of the wing (Fig. 1207); and the anal lobe of the hind wings is large. Wings of Cerceris. The species of Cerceris usually burrow in the ground and provision their nests with beetles; but some provision their nests with bees {Halictus) Tribe NYSSONINI In the Nyssonini the ocelli are never distorted and the upper margin of the clypeus extends directly across in a straight line or an HYMENOPTERA 98^ arch without a median lobe. In most genera the middle tibia have a single apical spur and the second submarginal cell (R5) is small and triangular; but in V the middle tibiae two apical spurs Sphecius speciosus. some have and cell R5 is four-sided. These wasps burrow in the ground ; some spe- cies store their nests with Homoptera, others with Orthoptera. Our best-known rep- resentative of this tribe is the Cicada-Killer, Sphecius speciosus. This is a formidable insect, measuring about 30 mm. in length (Fig. 1208). It is black, sometimes of a rusty color, and has the abdomen banded with yellow. It digs deep burrows in the earth and provisions each with a Cicada. Figure 1209 represents its wings. Fig. 1209. — Wings of Sphecius speciosu: Tribe STIZINI In the Stizini the transverse part of vein M is distant from the stigma by two or more times the distance between the apex of cell 2dR]+R2 and the apex of the wing; the labrum is usually transverse, rarely long and pointed; the ocelli are normal; and the middle tibiag are armed with two apical spurs. The species of the genus Stizus are gregarious, many individuals building their burrows near together. The common and' conspicuous western Stizus unicinctus is believed to lay eggs in nests of Chlorion {Priononyx) atratrum. 988 AN INTRODUCTION TO ENTOMOLOGY Tribe BEMBICINI With these wasps the ocelli are distorted, the middle tibice are armed with only one evident apical spur; and the labrum is elongate, pointed, rostriform (Fig. 1210). Our best-known representatives of this tribe belong to the genus Bembix; these are stout-bodied wasps, usually black with greenish or greenish-yellow bands. They burrow in the sand and provision their nests with flies. Some species at least practise progressive provisioning. After excavating its burrow and making a cell, the wasp captures a fly and stings it to death, then places it on the floor of the cell and attaches an egg to it. After the larva has hatched, the mother collects flies from day to day, feeding the larva till it is ready to change to a pupa, closing Fig- 1210.— Faceof the nest behind her each time she leaves it. Bembex: I, lab- A common and well-known member of this ^^™" tribe in the South is Sticta Carolina, which is called the "horse guard." This is a large species which hunts about horses in order to capture flies. Microhemhex monodonta is one of the most abundant of wasps along the seashore everywhere on the Atlantic, Gulf, and Pacific coasts. This species is black with greenish -white markings; the pleuras and mesoscutum are black and the wings are slightly dusky. The North American Bembicini were monographed by Parker ('17)- Subfamily CRABRONIN^ This subfamily differs from all other Sphecids except the Try- poxylonini in having only one submarginal cell (Fig. 121 1), and it Fig. 121 1. — Wings of Crabro singularis; ap, appendiculate cell, differs from the Trypoxylonini in that the inner margin of the eyes is not emarginate. It includes two tribes, each of which is classed as a subfamily by some writers. HYMENOPTERA 989 Tribe CRABRONINI In the Crabronini the postscutellum and the base of the prcpodeum are unarmed; the eyes are usually much widened below, their inner margins strongly converging towards the clypeus; and the longitudinal free part of vein M of the fore wings is complete. The head is generally large and square when viewed from above, and sometimes broader than the thorax (Fig. 12 12). The different members of this tribe vary greatly in their nesting habits. Some mine in the pith of such plants as sirmac and elder; some bore in more solid wood; some dig burrows in the ground; and others make use of any suitable hole they can find, often the deserted burrow of some other insect. These insects usually provision their nests with flies. The North American Crabronini was monographed by Fox ('95). Tribe OXYBELINI The Oxybelini are easily distinguished from all other sphecoid wasps by the two squamae projecting back from the metanotum and by a median spine borne by the base of the propodeimi (Fig. 12 13). The inner margin of the eyes is convex, not converg- ing toward the clypeus; and the longi- tudinal free part of vein A I is lost or present as a trace. These wasps nest in sand and provision their nests with flies. Fig. 1213. — Metanotum and 'PTTT? ■RTTTTc: propodeum of Oxybelus: ^ ^^ £.ilil^ sq., squama; sp., spine. Superfamily Apoidea of Authors The bees constitute a very large group of insects, including besides the well-known honey-bee and the bumblebees thousands of other species, many of which can be observed visiting flowers on any pleasant simmier day. Friese ('23) statesthat 12,000 species ofbees havebeen described, of which 2,500 are from North America and estimates that there are 20,000 living species in the world. The bees differ from all other Hymenoptera, except some members of a small subfamily of vespoid wasps, the Masarinae, in that they provision their nest with pollen and honey instead of with animal food, as do other nest-building Hymenoptera. The honey is obtained from flowers in the form of nectar, which is swallowed and trans- ported to the nest in the crop. While in the crop the nectar undergoes a chemical change, which is probably di:e to a mixture with it of a ferment derived from the salivary glands, and becomes what is known as honey. 900 AN INTRODUCTION TO ENTOMOLOGY The distinctive characteristics of bees that have been recognized are chiefly those that are correlated with the habit of collecting pollen and nectar for provisioning their nests. These consist in specializa- tions of the form and arrangement of some of the hairs, fitting them for collecting and carrying pollen ; in the dilation of the metatarsus of the hind legs, which forms a part of the pollen-collecting apparatus; and in varying degrees of specialization of the maxillas and labium to form a proboscis fitted for extracting nectar from flowers. ■ These characteristics are easily recognized in the higher bees, but in the most generalized bees (Prosopis) they are feebly developed, and too as male bees do not collect and carry pollen to nests they do not possess organs for this purpose; this is also true of both sexes of the parasitic bees, the females of which have acquired the habit II k I Fig. 1214. — Hairs of various bees: a-f, of bumblebees; g-j, of Melissodes sp.; k-n, of Megachile sp. (After John B. Smith.) of laying their eggs in the nests of other bees, and consequently, have become degenerate so far as their pollen-collecting apparatus is con- cerned. A characteristic of bees found in onl}^ a few other Hymenoptera is the presence, especially on the thorax, of plumose hairs. Many forms of these hairs exist; some of them are represented in Figure 12 14. In this figure there is also represented (Fig. 12 14, n) another type of hair which is spirally grooved ; this type is found in the pollen brush of leaf-cutter bees, Megachilidag. It has been suggested that the plumose hairs serve to hold the grains of pollen that become en- tangled among them when a bee visits a flower; but they occur in males and in parasitic bees neither of which gathers pollen; they are lacking, however, in some parasitic bees. HYMENOPTERA 991 Female bees, excepting those of the genus Prosopis and of the parasitic bees, are furnished with pollen-brushes or scopce, for collect- ing and transporting pollen. In most bees these consist of brushes of hairs borne by the hind legs, but in the Megachilidae the brush is on the ventral side of the abdomen. In some bees the pollen brushes are restricted to the tibia and the metatarsus of the hind legs, in others they are borne on these two segments and on the femur, trochanter and coxa as well (Fig. 12 15). With the queens and workers of the nest-building bumblebees and with the workers of the honey-bee the pollen carrying apparatus is Fig. 1215. — Hind leg of female of Colletes. (From Brane.) Fig. 1 2 16. — A. Inner surface of the left hind leg of a worker honey-bee; B. Outer surface of the same. (After D. B. Casteel.) very highly specialized (Fig. 12 16). On the outir surface of the tibia of the hind legs there is a smooth area which is imargined on each side by a fringe of long ciu'ved hairs; this structure is known as the pollen basket or corhicula; and on the inner surface of the metatarsus, termed planta by some writers, there is a brush of stiff hairs by means of which the bee gathers the pollen from its body. In the honey-bee the hairs composing this brush are arranged in transverse rows and are termed the pollen combs. The mouth-parts differ greatly in form in the different groups of bees; this is especially true of the maxillae and labitmi, which together constitute the proboscis, used for extracting nectar from flowers. The mandibles are, fitted for chewing and do not vary so much in form. 992 AN INTRODUCTION TO ENTOMOLOGY In the most generalized bees, the Prosopidae, the proboscis is com- paratively short and the labiimi is either notched at the tip {Prosopis; Fig. 12 1 7) or is quite deeply bifid (Colletes, Fig. 12 18). In all other bees the labium is pointed at the tip. Among the bees with a pointed labium the proboscis varies greatly in length; in some (Sphecodes, Fig. 1 2 19) it is comparatively short, while in the more specialized forms, as in Apis (Fig. 1220) it is greatly elongate. Fig. 12 1 7. — Pro- boscis of Pro- sopis. (After Saunders.) Fig. 1 2 19. — Probos- cis of Sphecodes. (After Saunders.) Fig. 12 18. — Probos- cis of Colletes. (After Saunders.) Fig. 1220. — La- bium of the honey-bee. (Af- ter Saunders.) The two sexes of bees differ in the number of abdominal tergites exposed to view; in the male there are seven, in the female, only six. The different species of bees exhibit great differences in habits; some are solitary; each female providing a nest for her young; some are parasitic, the females laying their eggs in the nests of other bees and the larvas feeding on the provisions stored by their hosts; and some are social, living in colonies consisting of many individuals. The social bees are the honey-bees, the bumblebees, and the stingless honey-bees of the Tropics. In all of these, as with the social HYMENOPTERA 993 wasps and the ants, there is in addition to the males and the egg- laying females a worker caste ; with all other bees there are only two forms, the males and the females. The parasitic bees do not constitute a natural division of the group of bees, as was formerly supposed, instead of that it isevident that members of several of the families of bees have acquired the parasitic habit. The bees of the genus Psithyrus, which are parasitic in the nests of btmiblebees, are closely allied to the bumblebees and should be placed with them in the family Bombida?; the parasitic genera Stelis and Ccelioxys are evidently members of the leaf-cutter- bee family, the Megachilida?; and there are many parasitic genera belonging to the family Andrenidas. The nests of solitary bees, like those of the digger-wasps, are of many forms. The mining-bees dig tunnels in the ground ; the mason- bees build nests of mortar-like material; the carpenter-bees make tunnels in the stems of pithy plants or bore in solid wood ; and some bees make nests of comminuted vegetable matter. The distinctive characteristic of the nests of bees is the fact that they are always provisioned with honey and pollen. In many cases closely allied spe- cies of bees differ in their nesting habits; for example, different spe- cies of the genus Osmia build very different kinds of nests. Although many entomologists have studied the bees intensively, no classification of them has been proposed that is generally ac- cepted. Some writers regard them as constituting a single family, the Apidffi; other writers recognize several families and restrict the term Apidag to the honey-bee family ; but these writers differ among themselves as to the number of families that should be recognized. When several families of bees are recognized thev are commonly grouped together as the superfamily Apoidea; but the writers whose classifications I have adopted believe that the bees are a group of sphecoid wasps that have acquired the habit of provisioning their nests with honey and pollen, and should not, merely for this reason, be placed in a separate superfamily. An analogous case is that of the subfamily Masarinse some members of which differ from other Vespidas in nest-provisioning habits in the same way that bees differ from other sphecoid wasps. Family PROSOPID^ The Bi fid-ton gued Bees The members of this family differ from all other bees in having the tip of the labiimi either shallowly emarginate at the apex or deeply bifid. Inallof them the labium is comparatively short. This family has been commonly known as the wasp-like bees. It includes two quite distinct subfamilies. Subfamily PROSOPIN^ This subfamily is represented in our fauna by a single genus, Prosopis. The members of this genus, of which there are many 994 ^iV INTRODUCTION TO ENTOMOLOGY species, are small black bees, with pale, usually yellow, marks. They are the least specialized of the bees. The body is almost bare, but an examination with a microscope will reveal the presence on the thorax of a few of the plumose hairs characteristic of bees; the labium is short and broad and shallowly emarginate at the apex (Fig. 12 17) and the hind legs of the females are not furnished with pollen brushes. The nimierous species of this genus build nests in the stems of pithy plants, or in burrows in the ground, or in crevices in walls. I have found them in dead branches of sumac. In some cases, at least, the burrow used was an old burrow made by some other pith- mining bee or wasp. After the burrow is made or selected, the walls of it are coated with a glistening substance, probably silk, which is sometimes dense enough to form a distinct membrane. Then a cell is formed at the bottom of the burrow of the same material ; and at the bottom of the cell a denser circular disk is spun, which makes a quite firm partition, the edges of which extend slightly up the sides of the cell. The cell is provisioned with a semi-liquid paste consisting largely of honey but containing also some pollen. It is said that when collect- ing provisions for its nest the bee swallows both pollen and nectar, brushing the pollen to the mouth by aid of the front legs. Usually several cells are made, one above another, in the burrow; although the walls of the cells are quite delicate, the cells are firmly separated by the dense silken partition at the bottom of each. Subfamily COLLETIN.E In this subfamily the labium is short, and deeply emarginate at the apex; (Fig. 12 18). The body, especially the head and thorax, is more or less densely clothed with hair; and in the female the hind legs are furnished with pollen -brushes. Our most common repre- sentatives belong to the genus Colletes. Colletes. — In most species of this genus the abdomen is marked with pubsecent white bands. All of the species, the habits of which have been described, burrow in soil, either that which is level or in banks, or sometimes in the interstices of walls. In favorable situ- ations, some of the species are gregarious, many individuals digging their tunnels in a limited area. Sharp ('99) in writing of Colletes states: "They have a manner of nesting peculiar to themselves; they dig cylindrical burrows in the earth, line them with a sort of slime, that dries to a substance like gold-beater's skin, and then by partitions arrange the burrow as six to ten separate cells, each of which is filled with food that is more liquid than usual in bees." Professor J. B. Smith ('01) in his account of Colletes compdcta states that this species digs a burrow which extends from 18 to 28 inches down; from this, lateral branches from two to six inches in length are made, at the end of each of which a cell is formed. The bee begins making cells from the bottom of the burrow and works up, never making more than four and rarely more than two cell-bearing HYMENOPTERA 995 laterals from one upright. How many such burrows an individual female may make was not determined. Family ANDRENID^ The Andrenids The family includes those solitary nest-building bees and their parasitic allies in which the tongue is either short or long but is pointed at the apex, and in which the pollen-brushes of the nest- building females are borne by the hind legs. To this family belong a large portion of the species and genera of our bees. Space can be taken here to discuss only a few of these. HalictMs. — Among the more common of our mining bees are those of the genus Halictus. This is a large genus including very many species, among which are the smallest of our bees. The nests of some % % fl^- 1 *\ % a^^ -i >% -fcj3««. ># Fig. 1 22 1. — Diagram of part of a nest of Halictus. species are excavated in level ground; other species dig tunnels in the vertical sides of banks. These bees are often gregarious, hundreds of nests being built near together in the side of a bank. If these nests be studied in midsummer, each will be found to consist of a burrow extending into the bank (Fig. 1221) and, along the sides of this main burrow or corridor, smaller short burrows each leading to a cell, the sides of which are lined with a thin coating of firm clay. In each of these cells that is closed will be found either a mass of pollen and nectar with an egg upon it or a larv^a feeding on the food stored for it. The most striking feature of these nests is the fact that several bees use the corridor as a passage way to the cells they are building and provisioning. But this corridor is not a public one; it is con- stricted at its outer end and is guarded by a sentinel whose head nearly fills the opening. When a bee comes that has a right to enter the sentinel backs into the wider part of the corridor and allows it 996 ^A^ INTRODUCTION TO ENTOMOLOGY to pass and immediately thereafter resumes its guarding position with its head closing the opening of the corridor. The explanation of this association of several bees, in a single nest was worked out by Fabre. He found that in the spring each female Halictus that has survived the winter mxakes a nest and rears a brood. Then the old bee and the young ones together clean out the nest, enlarge it, and use it as a carefully guarded apartment house, each bee having her own group of cells. Halictus (Augochldra) . — A detailed account of the habits of one species of this subgenus, A. humerdlis, was given by Professor J. B. Smith ('oi). This species is a mining bee which digs very deep burrows. Certain other species of this genus have very different nesting habits. These burrow in decomposing sap-wood beneath the bark of trees and make their cells of bits of decayed wood agglu- tinated together. Anthophora. — The genus Anthophora is widely distributed and includes many species, more than eighty have been described from North America alone; but the habits of only a few of these have been described. The nests of those American species the habits of which are well known are usually built in steeply inclined or perpendicular banks of earth, preferably in those of compact clay; they are also excavated in the clumps of clay held between the roots of stumps in stump- fences. In the West a favorite nesting place of these bees is in the walls of sun-dried bricks of the adobe houses. Like Halictus and Andrena, the bees of this genus are gregarious, hundreds of individuals building their nests close together in the same bank of earth. A striking feature of these nests is the presence of a cylindrical tube of clay extending outward and downward from the entrance of the tunnel (Fig. 1222). This tube is rough on the outside but smooth within. It is composed of small pellets of earth compacted together. These pellets when brought out from the tunnel are wet and easily molded into the desired form, but soon become dry and firm. The wetness of the pellets of clay brought out from the tunnel in a hard dry bank is explained by the fact that these bees when nest-building go to some place where water can be had and after lapping up a supply of it fly to their nest. This water is obviously used for softening the hard clay (Frison '22). The tunnel extends into the bank a variable distance and leads to a cluster of oval cells. The layer of earth forming the wall of a cell is made firm by some cementing substance; this is shown by che fact that when a liimp of earth containing nests is broken apart the cells retain their form and may be readily separated from the earth sur- rounding them. Nininger ('20) in his notes on the life-history of Anthophora stanf or didna state: "At the bottom of a tunnel five to seven inches deep, the bee excavated an oval chamber about three- fourths inch in diameter by one inch deep, and then built up within this a nest-cell to fit, made of pellets of clay and worked smooth on the inner side, after which it was coated with a thin layer of water- proofing which seemed to be a salivary secretion." HYMENOPTERA 997 The water-proofing of the wall of the cell is an essential feature for without it the semi-fluid mass of pollen and nectar with which the cell is provisioned would be partially absorbed by the wall of the cell. Fig. 1222. — Section of a bank with nests of Anthophora, (Photographed by Miss P. B. Fletcher.) The larvas remain in their cells throughout the winter, and trans- form to pups in the spring. The duration of the pupa state is short, the adult bees appearing early in the summer. The parasitic beetles Hornia are often found in the nests of Anthophora. Andrena. — Among the larger of our common mining bees are certain species of the genus Andrena; some of these nearly or quite equal in size the workers of the honey-bee. They build their nests in road sides and in fields that support a scanty vegetation. They sink a vertical shaft with broad cells branching from it. These bees, though strictly solitary, each female building her own nest, frequently build their nests near together, forming large villages. I once re- ceived from a correspondent a description of a collection of nests of this kind which was fifteen feet in diameter, and in the destruction of which about two thousand bees were killed ; what a terrible slaughter of innocent creatures ! The small carpenter-bee, Cerdtina dupla. — The nests of this bee are built in dead twigs or sumac and in the hollows of brambles and other plants. They are more common than those of any other of our solitary bees that build in these situations. This is a dainty little bee. 998 AN INTRODUCTION TO ENTOMOLOGY about 6 mm. in length , and of a metallic bl ue color. She always selects a twig with a soft pith which she excavates with her mandibles, and so makes a long tunnel. Then she gathers pollen and nectar and puts it in the bottom of the nest, lays an egg on it, and then makes a parti- tion out of pith-chips, which serves as a roof to this cell and a floor to the one above it. This process she repeats until the tunnel is nearly full (Fig. 1123), then she rests in the space above the last cell, and waits for her young to grow up. The lower one hatches first ; and after it has attained its growth, it tears down the partition above it, and then waits patiently for the one above to do the same. Finally after the last one in the top cell has matured, the mother leads forth her full-fledged family in a flight in the sunshine. After the last of the brood has emerged from its cell, the substance of which the partitions were made, and which has been forced to the bottom of the nest by the young bees when making their escape, is cleaned out by the family, the old bee and the young ones all working together. Then the nest is used again by one of the bees. I have collected hundreds of these nests and by opening different nests at different seasons, have gained an idea of what goes on in a single nest. There are Fig- 1223. — two broods each year. The mature bees of the fall ^.^^^'^j^^V brood wmter m the nests. The large carpenter-bee, Xylocopavirgmica. — This is a large insect, measuring from 22 to 24 mm. in length and resembling a bumblebee in size, and somewhat in appearance. But it can be easily distin- guished from a bimiblebee, as the female has a dense brush of hairs on the hind leg, instead of a basket for carrying pollen. This bee builds its nest in solid wood, and sometimes excavates a tunnel a foot in length, which it divides into several cells. The partitions between the cells are made of chips of wood, securely cemented together, and arranged in a closely-wound spiral. This arrangement of chips is easily seen when the lower side of a partition is examined; buttheuppersideof a partition which forms the floor of the cell above it is made concave and very smooth, so that the arrangement of the chips is not visible. The nest of Monobia quadridens described on an earher page (Fig. 11 88) was probably made in a deserted tunnel of Xylocopa. Mowo^m, however, maker the partitions of its nest of mud. This species is distributed generally throughout the United States and is the only species of Xylocopa found in the Northeastern part of this country. Eight other species have been described from the South and the West. A monograph of the species of Xylocopa of the United States was published by Ackerman ('16). HYMENOPTERA 999 Family MEGACHILID^ The Leaf -cutter Bees and their Allies To this family belong those bees in which the pollen brush of the female is borne on the ventral side of the abdomen and the parasitic bees that are allied to them. In this family the tongue is long and there are only two submarginal cells of approximately equal size in the fore wings. Among the better-known representatives of the family are the following. The leaf -cutter bees, Megachlle. — The bees of the genus Megachile have a curious habit of making cells for their young out of neatly-cut pieces of leaves. These cells are packed away in such secure places that one does not often find them ; but it is a very easy thing to find ., / % M Fig. 1224. — A leaf-cutter bee, Megachila latimanus, its nest, and rose-leaves cut by the bee. fragments of leaves from which the pieces have been cut by bees. The leaves of various plants are used for this purpose, but rose-leaves are used more frequently than any other kind. In Figure 1224 there are represented one of these bees, its nest, and a spray of rose-leaves from which pieces have been cut by the bee. The nests are made in various situations. The specimen figured was taken from a piece of hemlock timber in which many of these bees had bored tunnels to receive their cells. I have also found nests of these bees in a tunnel in the ground under a stone, between shingles 1000 AN INTRODUCTION TO ENTOMOLOGY on a roof, in the cavity of a large branch of sumac, in the cavity of a lead pipe, and in Florida in the tubular leaves of a pitcher-plant. When a suitable tunnel has been made or found the bee proceeds to build a thimble-shaped tube at the bottom of it. For this purpose it cuts from leaves oblong pieces, each of which forms a part of a side and the bottom of the thimble-shaped tube. Two such pieces had been cut from the lower leaf on the left side of the spray figured here. When the thimble-shaped tube is completed, the bee partially fills it with a paste of pollen and honey, and then places an egg upon the supply of food. She then cuts several circular pieces of leaves, the diameter of which is a little greater than the diameter of the tube, and forces them into the open end of it, thus making a tightly fitting plug; three of these circular pieces have been cut from the spray figured. Usually several cells of this kind are placed end to end in a burrow; and sometimes many bees will build their nests near to- gether in the same piece of wood. Alciddmea producta. — Among the more common members of the Megachilidas is this species which builds its nests in branches of sumac and other pithy plants. I have collected many of the nests during winter, from which the bees emerged the following spring. A dis- tinctive feature of the nest is the fact that the partitions between the cells are composed of comminuted plant fibers. The larva when full-grown spins a silken cocoon, which fills the cell. The adult is a black bee, 7 mm. long, with white marginal bands on the abdominal segments; these are often interrupted on the middle line. Trachusa lateralis. — This is a parasitic species which is very com- mon in the nests of Alcidamea producta. This bee is somewhat smallerthan its host and has on each side of the three basal abdominal segments a rather small ovate yellowish-white spot. The cocoons of this species are denser than those of Alcidamea producta, do not fill the cell, and bear at the apex a tiny nipple. Other illustrations of the habits of members of this family can be referred to here only briefly. The petals of various flowers and especially those of Pelargonium often have pieces cut from them shaped like those cut from the leaves of rose by the leaf-cutter bees. This is probably the work of some species of Osmia, as certain European species of this genus are known to build in their burrows thimble-shaped tubes resembling those of the leaf -cutter bees, except that they are composed of pieces of petals. Other species of Osmia make their cells of comminuted vegetable fibers. These are placed in various situations. There are in our collection several old cells of mud-wasps in each of which are several cells of this kind, from which were bred a small species of Osmia. Some species of Osmia make use of empty shells of snails, Helix, in which to build their cells, and some European species are known to cover the snail shell thus used with a mound of fragments of grass or of pine needles. HYMENOPTERA 1001 Many bees make their cells of a cement-like substance made of a mixture of earth and some fluid which is believed to be secreted by the salivary glands. These bees are commonly known as the mason- bees. The fimi-cement-like nature of the nests of some of the mason- bees leads to the belief that the earth of which they are made is mixed with some other fluid than water. They are much firmer than are the tubes built by Anthophora, which are made of a mixture of earth and water. A remarkable accumulation of the nests of an Old World species of mason-bee, known as the wall-bee, Chalicodoma murdria, was ob- ^^H^^^^^^^^^^9 ^^^^^^^^1 ^^^^^^HHHHte ^^ 9 ^^^^^^^^^^^1 ^^^^^^^^^ll^^^l^^^*^\''lr^H H^^^^H ^^^^^^BrrT^^^^H PPRHI ^^^^^^^^^^^^^^KBg^^- t ' j^fijJnJI^S Wk^ '^?^^^^^ jT^^^^^^ff -*>>s^:^. "^ ', 4-fS?^^'* Si,.-f < < w Fig. 1225. — Nests of the wall-bee on the Temple of Dendera. served by the writer on the walls of the Temple of Dendera in Egypt. This temple, which was buried by drifting sands long ago has been excavated by modern archaeologists; but the inscriptions on the walls of the temple are being rapidly buried again beneath a layer of the cement-like nests of the wall-bee (Fig. 1225). Family BOMBID^ The Bumblebees The family Bombidas includes the well-known nest-building bimiblebees and certain parasitic biraiblebees, Pstthyrus, that infest ilie nests of the nest-building species. The members of this family 1002 ^.V INTRODUCTION TO ENTOMOLOGY are large bees or of medium size , they are robust with oblong bodies and a rather dense covering of hair. They are common, and are conspicuous on account of their noisy flight and striking coloration, which is usually yellow and black. They are called bumblebees on account of the sound they make in flight; in England 'they are commonly known as bumblebees. The distinctive characters of this family are given in the table of the Clistogastra on page 912. Most writers recognize only two genera in the Bombidse, Bombus and Psithynis; but some have sepa- rated certain species from Bombus and placed them in a separate genus, Bombias. As there is considerable doubt regarding the validity of this genus it will not be discussed here. The nest-building bimiblebees, Bombus. — The members of this genus are social insects, each species consisting as in other social in- sects of three castes, the queens, the workers, and the males. In this genus the queens as well as the workers possess pollen-baskets or corbiculae on the hind legs; as the queen when founding a colony must collect pollen. With the bumblebees the queens are larger than either the workers or the males and, in temperate regions, are the only ones that live through the winter; as in these regions the colonies, like those of our northern species of social wasps, break up in the autimin and all of the bees, except the young queens perish. These crawl away into some protected place and pass the winter. In the spring each queen that has survived the winter founds a new colony, performing, until a brood of workers has been developed, both the duties of queen and of worker. In South America, where according to von Ihering, bumblebee colonies are perennial, new nests are formed by swarming as among the social wasps of the same region. In selecting a place for her nest the queen usually chooses a deserted mouse-nest, within which she builds her nest; sometimes an old bird's nest is used for this purpose. In certain European species the queen, sometimes at least, constructs her nest entirely without making use of a nest of another animal. This she does by making use of moss or soft dead grass, which she combs together with her mandibles and legs, for this reason these species are often known as "carder-bees." Many observers have studied the founding and development of colonies of bumblebees; among these is Sladen ('12) who has made very detailed studies of the species found in England. The following condensed summary is based on the statements of this author. Having found a suitable nest the queen spends a good deal of time in it, the heat of her body gradually making its interior perfectly dry. She then gathers the finest and softest material she can find into a heap and in the center of this makes a cavity with an entrance at the side just large enough for her to pass in and out. In the center of the floor of this cavity she forms a lump of paste made of pollen moistened with honey. Upon the top of this lump she builds with her jaws a circular wall of wax, and in the little cell so formed she lays HYMENOPTERA loos her first batch of eggs, and seals it over with wax. The queen now sits on her eggs day and night to keep them warm, only leaving them to collect food when necessary. In order to maintain animation and heat through the night and in bad weather when food cannot be obtained, it is necessary for her to lay in a store of honey. She there- fore sets to work to construct a large waxen pot to hold the honey. This pot is built in the entrance passage of the nest (Fig. 1226). The eggs hatch four days after they are laid. The larvce devour the paste which forms their bed and also fresh food furnished by the queen. To feed the larvae the queen makes a small hole with her mandibles in the skin of wax that covers them. While the larvae remain small they are fed collectiveh% but when they grow large they are fed individually. As the larvae grow the queen adds wax to their covering, so that they remain hidden. When the larvae are full- grown, each one spins around itself an oval cocoon, which is thin and oney-pot Fig. honeypol pollen and eqrjs 1226. — Honey-pot. (From Sladen.) papery but very tough. The queen now clears away most of the brown wax covering, revealing the cocoons, which are pale yellow. These first cocoons number from seven to sixteen, according to the species and the prolificness of the queen . These cocoons are incubated by the queen, who spends much time sitting on them, with her abdomen stretched to about double its usual length so that it will cover as many cocoons as possible. The bees that are developed during the early part of the summer are all workers ; these relieve the queen of all duties except laying the eggs. They feed the larva, construct honey-pots and special recep- tacles for pollen or store these substances in cocoons from which workers have emerged. The appearance of a nest in mid-summer is represented by Figure 1227. Later in the simimer males and queens are developed; and in the autumn the colony breaks up. The bumblebees play a very important role in the fertilization of certain flowers, as those of red clover, in which the tubular corolla is so long that the nectar can not be reached by bees with shorter tongues. A monograph of the Bombidas of the New World was published by Franklin ('12-13). 1004 AN INTRODUCTION TO ENTOMOLOGY The parasitic bumblebees, PsUhyrns. — To this genus belong those parasitic bees that infest the nests of bumblebees. They closely re- semble bumblebees in appearance and in structure, except that, as in other parasitic bees, the females do not possess organs for collecting and carr}dng pollen. Although the females of Psithyrns are easily distinguished from those of Bomhus by the absence of the pollen- baskets or corbiculaj in the former, the males of the two genera are very similar. In Psithyrus there is no worker caste. The conclusions of different observers as to the extent of the parasitism of Psithyrus differ widely. Sladen ('12) from his studies of English species regards them as the deadliest enemies of the bunch cf hcTK U-pot-'i cluster's cf ccccr n t bh hoTvey Fig. 1227. — Nest in mid- summer. (Prom Sladen.) birmblebees whose nests they infest. He found "That it is the practice of the Psithyrus female to enter the nest of the Bomhus, to sting the queen to death, and then get the poor workers to rear her young instead of their own brothers and sisters." This conclusion is not in accord, however, with those of other European writers ; and the American species of Psithryus whose habits have been studied, rarely, if ever, kill the host queen. For a detailed account of the relations of these parasites and their hosts and for references to the literature of this subject see Plath ('22). For descriptions of the New World species see Franklin ('i2-'i3). HYMENOPTERA 1005 Family APID^ The Honey-bees The family Apid«, as restricted here, includes only a single genus Apis, of which only four species are known, and one of these is doubtfully distinct. In this country a single introduced species, the honey-bee, Apis mellifica, is found. This species has been widely distributed over the world by man. The other species are restricted to the Indomalyan region; these are A. dorsdta, A. fldrea, and A. indica. The last named species is probably a variety of Apis mellifica. The colonies of A . dorsata and A . florea build a single pendent comb from the lower sides of a branch, and are not available for cultivation. A . mellifica and A . indica nest in cavities, as hollow tree-trunks and caverns, and will make use of hives prepared for them. This family consists of social bees in which the hind tibias are without apical spurs; the workers are furnished with pollen-baskets or corbiculfe on the hind legs, but the queens are without functionally developed ones. Unlike the queen of the nest-building bumblebees the queen of the honey-bee is unable to found a colony or even to exist apart from workers of her own species. The honey-bee was introduced into America more than three centuries ago, and escaping swarms have stocked our forests with it; for when free, swarms almost invariably build their nests in hollow trees. These nests include a variable number of vertical combs, which have cells on both sides, instead of a single series as is the case in the combs of our native social wasps. The cells of which the comb is composed are used both for storing the food of the colony and for rearing the brood. The three castes of bees of which a colony is composed are easily distinguished. The workers are the well-known form that we see collecting pollen and nectar from flowers and entering and leaving the hive in large ntimbers. They constitute the greater part of the colony; an average strong colony will include from 35,000 to 50,000 workers. They are females in which the reproductive organs are imperfectly developed; they do not ordinarily lay eggs, and when they do the eggs develop only into males. The workers do not pair with males, consequently their eggs are unfertilized, and unfertilized eggs of the honey-bee produce only males. The workers are so-called because they perform all the labors of the colony. Young workers attend to the inside work of the hive; they take care of the young brood, and for this reason are termed nurse-bees, they build combs^^ and protect the entrance of the hive against robbers. The older workers go into the field to collect pollen, nectar and propolis. The drones are larger than the workers, and are reared in larger cells. If honeycombs be examined, some sheets will be seen to be composed of larger cells than those of the more common type. It is in cells of this kind that the eggs are laid which are to develop into males. In shape the drones are broader and blunter than the workers. 1006 AN INTRODUCTION TO ENTOMOLOGY They are few in number and are only present in the hive during tha early summer. After the swarming season is over, these gentlemen of leisure are driven out of the hive by the workers or are killed by them. The queen is larger than a worker, and has a long pointed body. She is developed in a cell which differs greatly from the ordinary hexagonal cell of honey- comb. This cell is large, cylindrical, and extends vertically. In Figure 1228 the beginnings of two queen cells are represented on the lower edge of the comb, and a completed cell extends over the face of the comb near the left side. From the lower end of this cell hangs a lid, which was cut away by the workers to al- low the queen to emerge, pig. 1228.— Comb of honey-bee with queen- The queen larva is fed with a substance called royal jelly. This is a substance which resembles blanc-mange in color and consistency. It is excreted from the mouth by the nurse-bees, and is very nutritious food. The origin of this food, whether it is a secretion from special glands of the nurse-bees, or is regurgitated from their stomachs is not at present known. During the first three days of the larval stage of worker bees they are also fed with royal jelly after which they are fed with honey and bee-bread. It has been demonstrated that in the egg state there is no differ- ence between a worker and a queen. When the workers wish to develop a queen they tear down the partitions between three adjacent cells containing eggs that under ordinary conditions would develop into workers. Then they destroy two of the eggs, and build a queen- cell over the third. When the egg hatches they feed the larva with royal jelly, and it develops into a queen. In early summer several queen-cells are provided in each colony. As soon as a queen is developed from one of these the old queen at- tempts to destroy her. But the young queen is guarded by the work- ers, and then the old queen with a goodly portion of her subjects swarm out, and they go to start a new colony. The swarming of the honey-bee is essential to the continued exist- ence of the species; for in social insects it is as necessary for the colonies to be multiplied as it is that there should be a reproduction of individuals. Otherwise, as the colonies were destroyed the species would become extinct. With the social wasps and with the bumble- bees the old queen and the young ones remain together peacefully in the nest; but at the close of the season the nest is abandoned by all as an unfit place for passing the winter, and in the following spring HYMENOPTERA 1007 each 3'oung queen founds a new colony. Thus there is a tendency towards a great multipHcation of colonies. But with the honey-bee the habit of storing food for the winter, and the nature of the habita- tions render it possible for the colonies to exist indefinitely. And thus if the old and young queens remained together peacefully there would be no multiplication of colonies, and the species would surely die out in time. We see, therefore that what appears to be merely jealousy on the part of the queen honey-bee is an instinct necessary to the continuance of the species. The sting of a queen-bee is no ignoble weapon, but it is rarely used except against a rival queen. When several young queens mature at the same time there is a pitched battle for supremacy, and the last left living on the field becomes the head of the colony. One morning we found the lifeless bodies of fifteen young queens cast forth from a single hive — a montrment to the powers of the surviving Amazon in triumphant possession within. The materials used by bees are wax and propolis, which serve as materials for construction; and honey and bee-bread used for food. The comb is made of wax, which is an excretion of the bees. When a colony needs wax, many of the workers gorge themselves with honey and then hang quieth^ in a curtain-like mass, the upper bees clinging to the roof of the hive, and the lower ones to the bees above them. After about twenty-foirr hours there appear on the lower surface of the abdomen of each bee little plates of wax that are forced out from openings between the ventral abdominal seg- ments called wax-pockets. Other workers attend to this curtain and collect the wax as fast as it appears, and use it at once in constructing comb. Propolis is a cement used for cementing up crevices, and is made of a resin which the bees collect from the buds of various trees, but especially of the poplar. Honey is made from the nectar of flowers and is taken into the crop of the bee, and there changed into honey, and then regurgitated into the cells of the comb. Bee-bread is made from the pollen of flowers, which the bees bring in on the plates fringed with hairs on the hind legs, thecorbiculs. Very many books have been written regarding the habits of the honey-bee; some of these are to be found in most public libraries. There are also many manuals for the use of those who wish to keep bees ; among these is a small one for beginners by Mrs. A. B . Comstock ('20) and a cyclopedia by A. I. and E. R. Root ('17). The U.S. De- partment of Agriculture has published many bullletins on this subject ; one of a general nature is "Farmers Bulletin 447." BIBLIOGRAPHY The following list includes only the titles of the books and papers to which references have been made in the preceding pages. Aaron, S. F. ('85). "The North American Chrysididae." Trans. Am. Ent. Soc. Vol. 12, pp. 209-248. AcKERMAN, A. J. ('16). "The carpenter-bees of the United States of the genus Xylocopa." Jour. N. Y. Ent. Soc. Vol. 24, pp. 196-232. Adelung, N. von ('92). "Beitrage zur Kenntnis des tibialen Gehorapparates der Locustiden." Zeit. wiss. Zool. Vol. 54, pp. 316-385. Aldrich, J. M. ('05). "A catalogue of North American Diptera." Smithsonian Misc. Coll. Part of Vol. 46. Aldrich, J. M. ('12). "Flies of the leptid genus Atherix used as food by Cali- fornia Indians (Dipt.)." Ent. News. Vol. 23, pp. 159-163. Aldrich, J M. ('16). "Sarcophaga and allies in North America." The Thomas Say Foundation of the Ent. Soc. of Am. Aldrich, J. M. ('18). "The kelp-flies of North America (genus Fucellia, family Anthomyidas)." Proc. Cal. Acad. Sci. Vol. 8, pp. 157-179. Aldrich, J. M. ('20). "European frit fly in North America." Jour. Agr. Re- search. Vol. 18, pp. 451-473. Aldrich, J. M. ('22). "A new genus of two-winged fly with mandible-like labella." Proc. Ent. Soc. Wash. Vol. 24, pp. 145-148. Aldrich, J. M., and Darlington, P. S. ('08). "The dipterous family Helomy- zidas." Trans. Am. Ent. Soc. Vol. 34, pp. 67-100. Alexander, C. P. ('19). "The crane-flies of New York. Part I. Distribution and taxonomy of the adult flies." Cornell Univ. Agr. Exp. Sta. Memoir 25. Alexander, C. P. ('20). "The crane-flies of New York. Part II. Biology and phylogeny." Cornell Univ. Agr. Exp. Sta. Memoir 38. Andre, E. ('03). "Hymenoptera Fam. Mutillidae." Genera Insect., Fasc. 11. Anthony, Maude H. ('02). "The metamorphosis of Sisyra." The American Natm-alist. Vol. 36, pp. 615-331. Ashmead, W. H. ('93). "A monograph of the North American Proctotrypidae." Bull. U. S. Nat. Mus. No. 45. Ashmead, W. H. ('94). "The habits of the aculeate Hymenoptera." Psyche. Vol. 7, pp. 19, 39-46, 59-66, 75-79- Ashmead, W. H. ('00). "Classification of the ichneumon-flies, or the superfamily Ichneumonoidea." Proc. U. S. Nat. Mus. Vol. 23, pp. 1-220. Ashmead, W. H. ('03). "Classification of the gall-wasps and parasitic cynipoids, or the superfamily Cynipoidea." Psyche. Vol. 10, pp. 7, 59, 140, 210. Ashmead, W. H. ('04). "Classification of the chalcid flies, or the superfamily Chalcidoidea." Memoires of the Carnegie Museum, Vol. I, No. 4. Carnegie Institute, Pittsburgh, Pa. Audouin, J. V. (1824). "Recherches anatomiques sur le thorax des animaux articules." Ann. Sci. Nat. Tome I, pp. 97-135, 416-432. Baker, A. C. ('20). "Generic classification of the hemipterous family Aphidi- da;." U. S. Dept. Agr. Bull. 826. Baker, C. F. ('04). "A revision of American Siphonaptera, or fleas, together with a complete list and bibliography of the group." Proc. U. S. Nat. Mus. Vol. 27, pp. 365-469. Baker, C. F. ('05). "The classification of the American Siphonaptera." Proc. U. S. Nat. Mus. Vol. 29, pp. 1 21-170. Banks, Nathan ('05). "A revision of the nearctic Hemerobiidag." Trans. Am. Ent. Soc. Vol. 32, pp. 21-51. Banks, Nathan ('07). "A revision of the nearctic Coniopterygidae." Proc. Ent. Soc. Wash. Vol. 8, pp. 77-86. (1008) BIBLIOGRAPHY 1009 Banks, Nathan ('ii). "Psammocharidae: Classification and descriptions." Jour. N. Y. Ent. Soc. Vol. 19, pp. 219-237. Banks, N., and Snyder, T. E. ('20). "A revision of the nearctic Termites by- Nathan Banks with notes on biology and geographic distribution by Thomas E. Snyder." U. S. Nat. Mus. Bull. 108. Barber, H. S. ('13a). "Observations on the life history of Micromalthus debilis Lee." Proc. Ent. Soc. Wash. Vol. 15, pp. 31-38. Barber, H. S. ('13b). "The remarkable life-history of a new family (Micromal- thidse) of beetles." Proc. Biol. Soc. of Wash. Vol. 27, pp. 185- 190. Barnes, W., and McDunnough, J. H. ('11). "Revision of the Cossidae of North America." Contrib. Nat. Hist. Lepidoptera N. Am. Vol. i, No. I. Decatur, 111. The Review Press. Barnes, W., and McDunnough, J. H. ('12). "Revision of the Megathymidae." Contrib. Nat. Hist. Lep. N, Am. Vol. i, No. 3. Decatur, 111. The Review Press. Barnes, W., and McDunnough, J. ('17). "Check list of the Lepidoptera of boreal America." Decatur, 111. Herald Press. Bellesme, J. ('78). "Note au sujet d'un travail adresse a I'Acad. par M. Perrez sur la bourdonnement des insectes." Compt. Rend. Acad. d. Science. Vol. 87, p. 535. Berlese, Antonio ('96). "Le Cocciniglie italiane viventi sugli agrumi. Part HI. I Diaspiti." Firenze. Berlese, Antonio ('09a). "Gli Insetti." Vol. i (1909) 4to, pp. x + 1004. 1292 text figures and 10 plates. Societa Editrice Libraria, Milano. Berlese, A. ('09b). "Monografia dei Myrientomata." Redia, Firenze. Bezzi, M. ('13). "Taumaleidi (Orfnefilidi) italani." Portici. Boll. Lab. Zool. Gen. Agr. Vol. 7, pp. 227-266. BiscHOFF, H. ('13). "HymenopteraFam. Chrysididae." Genera Insect., Fasc. 151. Blanc, M. L. ('90). "La tete du Bombyx mon a I'etat larvaire." Extrait du volume des travaux du laboratoire d'^tudes de la soie. Lyons, 1889-90. Blatchley, W. S. ('10). "An illustrated catalogue of the Coleoptera or beetles (exclusive of the Rhynchophora) known to occur in Indiana." The Nature Publishing Co., Indianapolis. Blatchley, W. S. ('20). "Orthoptera of northeastern America." The Nature Publishing Co., IndianapoHs. Blatchley, W. S., and Leng, C. W. ('16). "Rhynchophora or weevils of north eastern America." The Nature Publishing Co., Indianapolis. Boise, M. P. ('90). "Note on Braula casca." Bull. Soc. Ent. France, 1890. p. cc. BoRNER, C. ('04). "Zur Systematik der Hexapoden." ZooLAnz. Vol. 27, pp. 511-533- BoRNER, C. ('08a). "Eine monographische Studie liber die Chermiden." Arb. Kais. Biol. Anstalt. Bd. VI, Heft 2, 1908, pp. 224-245. BoRNER, C. ('o8b). "Ueber Chermesiden." Zool. Anz. Vol. 33, pp. 612-616. BouviER, E. L. ('05-07). "Monographic des Onychophores." Ann. Sci. Nat. 9e serie, tome 2, p. 1-383, PL I-XIII; tome 5, p. 61-318. Bradley, J. C. ('08). "The Evaniidae, ensign-flies, an archaic family of Hymen- optera." Trans. Amer. Ent. Soc. Vol. 27, pp. 101-194, with II plates. Bradley, J. C. ('13). "The Siricidae of North America." Jour. Entom. and Zool. Vol. 5, pp. 1-30, with 5 plates. Bradley, J. C. ('16). "Contribution toward a monograph of the Mutillidas and their aUies of America north of Mexico." Trans. Am. Ent. Soc. Vol. 42, pp. 309-336. Bradley, J. C. ('17). Contributions toward a monograph of the Mutillidae and their alHes of America north of Mexico. IV. A review of the Myrmosidae." Trans. Am. Ent. Soc. Vol. 43, pp. 247-290. 1010 AN INTRODUCTION TO ENTOMOLOGY Bradley, J. C. ('22). "The taxonomy of the masarid wasps, including a mono- - graph on the North American species." Univ. Cal. Publ., Tech. Bull. Vol. I, pp. 369-464. Berkeley, Cal. Brauer, F. ('69). "Beschreibung der Verwandlungsgeschichte der Mantispa styriaca, und Betrachtung liber die sogenannte Hypermetamor- piiose Fabre's." Vsrh. d. Zool. Bot. Ges. Wien. Vol. 19. Brauer, F. ('76). "Die Neuropteren Europas." Wien. Brauer, Friedrich ('85). "Systematisch-zoologische Studien." Sitzb. der Kais. Akad. Wissensch. 1885, pp. 237-413. Braun, a. F. ('17). "Nepticulidag of North America." Trans. Am. Ent. See. Vol. 43, pp. 155-209. Braun, A. F. ('19). "Wing structure of Lepidoptera and the phylogenetic and taxonomic value of certain persistent trichopterous characters." Ann. Ent. Soc. Am. Vol. 12, pp. 349-366. Brindley, H. H. C98). "On certain characters of reproduced appendages in Arthropoda, particularly in Blatta." Proc. Zool. Soc. Lond. 1898, pp. 924^58. Brues, C. T. ('03). "A monograph of the North American Phoridse." Trans. Am. Ent. Soc. Vol. 29, pp. 331-404, with 5 plates. Brues, C. T. ('19). "A new chalcid-fly parasitic on the Australian bull-dog ant." Ann. Ent. Soc. Am. Vol. 12, pp. 13-21. Brues, C. T., and Melander, A. L. ('15). "Key to the families of North Ameri- can insects." Published by the authors. BuGNiON, E., and Popoff ('ii). "Les pieces buccales des Hemipteres." Ar- chives de Zoologie Experimentale et Generale. Series 5, Vol. 7 (191 1 ), pp. 643-675. Burges, E. ('80). "Contribution to the anatomy of the milkweed butterfly." Anniv. Mem. Bost. Soc. Nat. Hist. Burke, H. E. ('17). "Oryssus is parasitic." Proc. Ent. Soc. Wash. Vol. 19, pp. 87-88. Burr, Malcolm ('ii). "Dermaptera." Genera Insect. Fasc. 122. BuscK, August ('03). "A revision of the American moths of the family Gelechi- das, with descriptions of new species." Proc. U. S. Nat. Mus. Vol. 25, pp. 767^38. BuscK, August ('06). "A review of the American moths of the genus Cosmo- pteryx." Proc. U. S. Nat. Mus. Vol. 30, pp. 707-713. BuscK, August ('09a). '"A generic revision of American moths of the family CEcophoridae, with descriptions of new species." Proc. U. S. Nat. Mus. Vol. 35, pp. 187-207. BuscK, August ('09b). "Notes on Microlepidoptera with descriptions of new North American species. Proc. Ent. Soc. Wash. Vol. 11, pp. 91-103. BuscK, August ('14). "On the classification of the Microlepidoptera." Proc. Ent. Soc. Wash. Vol. 16 (1914), pp. 47-54. BuscK, August (,'17). "The pink bollworm, Pectinophora gossypiella." Jour. Agr. Research. Vol. 9 (1917), pp. 343-370- BuscK, A., and Boving, A. ('14). "On Mnemonica auricyanea Walsingham." Proc. Ent. Soc. Wash. Vol. 16, pp. 151-163, with 8 plates. Carlet, G. ('77). "Memoire sur I'appareil musical de la cigale." Ann. Sci. Nat. Zool. 6e serie, tome. 5. Carpenter, G. H. ('03). "On the relationships between the classes of the Arthropoda." Proc. Royal Irish Acad. Vol. 24, pp. 320-360. Carpenter, Geo. H. ('06). "Notes on the segmentation and phylogeny of the Arthropoda, with an account of the Maxillae in Polyxenus la- gurus." Quart. Jour. Micr. Sci. Vol. 49, pp. 469-491. CARRifiRE, J., and Burger, O. ('97). "Die Entwickelungsgeschichte der Mauer- biene {Chalicodoma muraria, im Ei." Nova Acta, Kais. Acad. Leop. -Carol in. Deutsch. Akad" d. Naturf. Vol. 69. Caudell, a. N. ('03). "The Phasmidae or walking-sticks of the United States." Proc. U. S. Nat. Museum. Vol. 26, pp. 863-885, with plates. Caudell, A. N. ('04). "An orthopterous leafroller." Proc. Ent. Soc. Wash. Vol. 6, No. I, pp. 46-49. BIBLIOGRAPHY 1011 Caudell, a. N. ('07). "The Decticinae (A group of Orthoptera) of North America." Proc. U. S. Nat. AIus. Vol. 32, pp. 285-410. Caudell, A. N. ('16). "The genera of the tettiginid insects of the subfamily Rhaphidophorinae fDund in America north of Mexico." Proc. U. S. Nat. Mus. Vol. 49, pp. 655-690. Caudell, A. N. ('18). "Zorofypus hubbardi, a new species of the order Zoraptera from the United States." Canad. Entom. Vol. 50, pp. 375-381. Caudell, A. N. ('20). "Zoraptera not an apterous order." Proc. Ent. Soc. Wash. Vol. 22, pp. 84-97. Chapman, T. A. ('17). "Micropteryx entitled to ordinal rank; Order Zeuglop- tera." Trans. Ent. Soc. London, 1916, pp. 310-314 (April '17). Cheshire, Frank R. ('86). "Bees and bee-keeping." London, L. Upcott Gill. Cholodkovsky, N. a. ('15). A paper on Chermes injurious to conifers, published in Russian. Petrograd, 1915. An abstract in English is given in the Review of Applied Entomolog>', Vol. 3 (1915), pp. 592-599. Child, C. M. ('94). "Beitrage zur Kenntniss der antennalen Sinnesorgane der Insekten." Zeit. wiss. Zool. Vol. 58, pp. 475-525-528, mit 2 Taf. Claassen, P. W. ('21). "Typha insects: their ecological relationships." Cornell Univ. Agr. Exp. Sta. Memoir 47. Clarke, Cora H. ('91). "Caddis-worms of Stony Brook." Psyche. Vol. 6, pp. 153-158. Cole, F. R. ('19). "The dipterous family Cyrtida; m North America." Trans. Am. Ent. Soc. Vol. 45, pp. 1-79. CoMSTOCK, Mrs. A. B. ('05). "How to keep bees. A handbook for the use of beginners." Doubleday, Page & Co, Garden City, N. Y. CoMSTOCK, J. H. ('8ia). "An aquatic noctuid larva." Papilio. Vol. I, pp. 147- 149. CoMSTOCK, J. H. ('81b). "Report of the Entomologist of the U. S. Dept. Agr.for 1880." Includes report on scale-insects. CoMSTOCK, J. H. ('82). "Report on insects for the year 1881." Ann. Rept. U. S. Dept. Agr. for the year 1881. CoMSTOCK, J. H. ('83). "Report of the Department of Entomology." Includes second report on scale insects. Second Rept. Dept. Ent., Cornell Univ. Exp. Sta. CoMSTOCK, J. H. ('93). "Evolution and taxonomy." The Wilder Quarter- Century Book, pp. 37-114, PI. I-III. CoMSTOCK, J. H. ('01). "The wings of the Sesiidae." (In Monograph of the Sesiidae by Wm. Beutenmiiller. Memoirs Amer. Mus. Nat. Hist. Vol. I, p. 220. CoMSTOCK, J. H. ('12). "The spider book." Doubleday, Page & Co., Garden City, N. Y. CoMSTOCK, J. H. ('i8a). "The wings of insects." The Comstock Publishing Company, Ithaca, N. Y. Comstock, J. H. ('i8b). "Nymphs, naiads, and larvae." Ann. Ent. Soc. Am. Vol. 2, pp. 222-224. Comstock, J. H. and A. B. ('04). "How to know the butterflies." With forty- five full-page plates in colors. The Comstock Publishing Company, Ithaca, N. Y. Comstock, J. H., and Kochi, C. ('02). "The skeleton of the head of insects" The American Naturalist. Vol. 36 (1902), pp. 13-45, with 29 text figures. Comstock, J. H., and Needham, James G. ('98-'99). "The wings of insects." A series of articles on the structure and development of the wings of insects, with special reference to the taxonomic value of the characters presented by the wings. Reprinted from The American Naturalist, with the addition of a table of contents. 124 pages, 90 figures. Ithaca, N. Y., 1899. The articles ap- peared originally in The American Naturalist, Vol. XXXII (1898), pp. 43, 81, 231, 237, 240, 243, 249, 253, 256, 335, 413, 420, 423, 561, 769, 774, 903; Vol. XXXIII (1899), pp. 118, 573, 845. 851, 853, 858. 1012 AN INTRODUCTION TO ENTOMOLOGY CoMSTOCK, J. H., AND Slingerland, M. V. ('91). "Wireworms." Cornell Univ. Agr. Exp. Sta. Bull. 33. Cook, F. C, Hutchinson, R. H., and vScales, F. M. ('14). "Experiments in the destruction of fly larvee in horse manure." U. S. Dept. Agr. Bui. 118, pp. 1-26. CoQUiLLETT, D. W. ('96). "Revision of the North American Empidae — ^A family of two-winged insects." Proc. U. S. Nat. Mus. Vol. i8, pp. 387- 440. CoQUiLLETT, D. W. ('97). "Rcvision of the Tachinidae of America north of Mexico." U. S. Dept. Agr., Div. Ent. Tech. Ser. No. 7. COQUILLETT, D. W. ('98). "The buffalo-gnats, or black-flies, of the United States." U. S. Dept. Agr., Div. Ent. Bull. No. lo, New Series, pp. 66-69. Crampton, G. C. ('09). "A contribution to the comparative morphology of the thoracic sclerites of insects." Proc. Acad. Nat. Sci. Phila., 1909, pp. 3-54- Crampton, G. C. ('14). "Notes on the thoracic sclerites of winged insects." Ent. News. Vol. 25 (1914), pp. 15-25. Crampton, G. C. ('15). "The thoracic sclerites and the systematic position of Grylloblatta campodeiformis Walker, a remarkable annectent, 'orthopteroid' insect." Ent. News. Vol. 26, pp. 337-350. Crampton, G. C. ('17). "The nattire of the veracervix or neck region in insects." Ann. Ent. Soc. Am. Vol. 10, pp. 187-197. Crampton, G. C. ('18). "A phylogenetic study of the terminal abdominal struc- tures and genitalia of male Apter>'gota, ephemerids, Odonata, Plecoptera, Neuroptera, Orthoptera, and their allies." Bull. Brooklyn Ent. Soc. Vol. 13 (191 8), pp. 49-68, pi. 2-7. Crampton, G. C. ('20a). "Some anatomical details of the remarkable winged zorapteron, Zorolypus hubardi Caudell, with notes on its rela- tionships." Proc. Ent. Soc. Wash. Vol. 22, pp. 98-106. Crampton, G. C. ('20b). "A comparison of the external anatomy of the lower Lepidoptera and Trichoptera from the standpoint of phylogeny." Psyche, Vol. 27, pp. 23-45. Crampton, G. C. ('21). "The origin and homologies of the so-called 'super- linguae' or 'paraglossae' (paragnaths) of insects and related arthropods." Psyche. Vol. 28, pp. 84-92. Crawford, D. L. ('12). "The petroleum fly in California, Psilopa petrolei." Pomona Col. Jour. Ent. Vol. 4, pp. 687-697. Crawford, David L. ('14). "A monograph of the jumping plant-lice or Psyllidae of the New World." U. S. Nat. Mus. Bull. 85, pp. ix-|-i86, with 30 plates. Crawford, J. C. ('09). "A new family of parasitic Hymenoptera." Proc. Ent. Soc. Wash. Vol. 2, pp. 63-64. Cresson, E. T. ('20). "A revision of the nearctic Sciomyzidae." Trans. Am. Ent. Soc. Vol. 46, pp. 27-89. Crosby, C. R. ('09). "On certain seed-infesting chalcis-flies." Cornell Univ. Agr. Exp. Sta. Bull. 265. Crosby, C. R. ('11). "The apple redbugs." Cornell Univ. Agr. Exp. Sta. Bull. 291. Crosby, C. R., and Leonard, M. D. ('18). "Manual of vegetable-garden in- sects." pp. XV -|- 391, many figures. The Macmillan Co., New York. Crosby and Slingerland ('14). "Manual of fruit insects." The Macmillan Co, New York. Dalla Torre, K. von ('08). "Anoplura." Genera Insect,, Fasc. 81, Dalla Torre,W. von, and Kieffer, J. J. ('02), "Hymenoptera Fam, Cynipidae." Genera Insect., Fasc. 9 and 10. Dalla Torre, K. W. von, and Kieffer, J. J. ('10). "Cynipidae." Das Tierreich. 24 Lieferung, pp. i-xxxv-t-i-891. Davidson, Anstruther ('13). "Masaria Vespoides." Bull, Southern Cal. Acad. Sci. Vol. 12, p. 17. Davis, K. C, ('03). "Sialididae of North and South America." N. Y, State Mus. Bull. 68, pp. 442-487. BIBLIOGRAPHY 1013 Dewitz, H. ('84). "Ueber die Fortbewegung der Thiere an senkrechten, glatten Flachen vermittelst eines Secretes." Pfluger's Archiv. f. d. ges. Phys. Vol.33. DoYfiRE, M. (1840). "Memoire stir les Tardigrades." Ann. des Sci. Nat. (2). Vol. 14, pp. 269-361. DucKE, A. ('14). "Ueber Phylogenie und Klassifikation der sozial Vespiden." Zool. Jahrb. Vol. 36, pp. 303-330. DuFOUR, Leon (1824). "Recherches anatomiques sur les Carabiques et sur plusieurs autres insectes Col^opteres." Ann. Sci. Nat. Vol. 2 (1824), pp. 462-498. Duncan, C. D. ('24). "Spiracles as sound producing organs." The Pan-Pacific Entomologist. Vol. I, pp. 42-43. Dyar, H. G. ('90). "The number of molts of lepidooterous larvas." Psyche, Vol. 5, pp. 420-422. Dyar, H. G. ('94). "A classification of lepidopterous larvae." Ann. N. Y. Acad. Sci. Vol. 8, pp. 194-232. Dyar, H. G. ('00). "Notes on the larval-cases of Lacosomidae (Perophoridae) and life-history of Lacosoma chiridota Grt." Jour. N. Y. Ent. Soc. Vol. 8, pp. 177-180. Dyar, H. G. ('02). "A lepidopterous larva on a leaf -hopper." Proc. Ent. Soc. Wash. Vol. 5, pp. 43-45. Dyar, H. G. ('22). "The mosquitoes of the United States." Proc. U. S. Nat. Mus. Vol. 62, Art. I, pp. 1-119. (No. 2447.) Eaton, A. E. ('83-'85). "A revisional monograph of recent Ephemeridas." London Trans. Linn. Soc. Vol. 3. Eggers, Friedrich ('19). "Das thoracal bitympanale Organ einer Gru.ppe der Lepidoptera Heterocera." Zool. Jahrb. Vol. 41, Abt. f. Anat., pp. 273-376. Enderlein, G. ('09). "Klassifikation der Plecopteren, sowie Diagnosen neuer Gattungen und Arten." Zool. Anz. Vol. 34, pp. 385-419. Enderlein, G. ('i i). "Die phyletischen Beziehimgen der Lycoriiden (Sciariden) zu den Fungivoriden (Mycetophiliden) und Itonididen (Cecido- myiiden) und ihre systematische Gliederung." Archiv. fur Naturg. 191 1. L 3. Suppl., pp. 116-208. Enderlein, G. ('12a). "Embiidinen Monographisch Bearbeitet." Coll. ZooL Selys Longchamp Tasc. IIL Enderlein, G. ('12b). "Zur Kenntnis der Zygophthalmen. Ueber die Gruppier- ung der Sciariden und Scatopsiden." Zool. Anz. Vol. 40, pp. 261-282. Enderlein, G. ('21). "Die systematische Gliederung der Simuliiden." Zool. Anz. Vol. 53, pp. 43-46. ExNER, S. {'91). "Die Physiologic der Facettirten Augen von Krebsen und Insecten." 1891, 8vo., pp. i-viii, 1-206, 7 plates. Franz Deuticke, Leipzig und Wien, 1891. Fabre, J. H. (1876-1904). "Souvenirs entomologiques ; Etudes sur I'instinct et les moeurs des insectes." 10 vol. Paris, Librairie Ch. Delagrave, 1879-1904. Fabre, J. H. ('i i ). "The life and love of the insect." Translated by Alexander Teixeira de Mattos. London: Adam and Charles Black. Fagen, M. M. ('18). "The uses of insect galls." Amer. Nat. Vol. 52, pp. 155- 176. Felt, E. P. "Studies in Cecidomyiidae "and "A study of gall midges." A series of papers published in the annual reports of the State Entomo- gist of New York. Felt, E. P. ('96). "The scorpion-flies." loth Report N. Y. State Ent. for 1894. Felt, E. P. ('05- '06). "Insects affecting park and woodland trees." N. Y. State Mus. Memoir 8, 2 vols. Felt, E. P. ('11). "Miastor americana Felt, An account of pedogenesis." 26th Report of the State Ent. of N. Y. N. Y. State Mus. Bull. 147. Felt, E. P. ('18). "Key to American galls." N. Y. State Mus. Bull. 200. Ferris, G. F. ('16). "Some ectoparasites of bats (Dipt)." Ent. News. Vol. 27, pp. 433-438. 1014 AN INTRODUCTION TO ENTOMOLOGY Ferris, G. F. ('19). "Some records of Polyctenidae (Hemiptera)." Jour. N. Y. Ent. Soc. Vol. 27, pp. 261-263, I plate. Ferris, G. F. ('24). "The New World Nycteribiidae (Diptera Pupipara). Ent. News. Vol. 35, pp. 191-199- , ^^ Ferton, Ch. ('19). "Notes detachees stir I'mstmct des Hymenopteres melliferes et ravisseurs." Ann. vSoc. Ent. France, Vol. 79, pp. 145-178. Field, W. L. W. ('id). "The offspring of a caotured female of Basilarchia Proserpina." Psyche. Vol. 17, pp. 87-89. PoLSOM, J. W. ('99). "The anatomy and physiology of the mouth-parts of the collembolan Orchesella cincta." Bull. Mus. Comp. Zool. Vol. 35, No. 2. FoLsoM, J. W. ('00). "The development of the mouth-parts of Anurida mari- Hma." Bull. Mus. Comp. Zool. Vol. 36, pp. 87-157. FoLsoM, J. W. ('13). "Entomology," pp. vii+402, 304 text figures, and 4 plates P. Blakiston's Sons & Co., Philadelphia. FoLSOM, J. W. ('16). "North American collembolous insects of the subfamilies Achorutinae, Neanurinas, and Podurinae." Proc. U. S. Nat. Mus. Vol. 50, pp. 477-525- , , Forbes, W. T. M. ('10). "A structural study of some caterpillars. Ann. Ent. Soc. Am. Vol. 3, pp. 94-143. Forbes, W. T. M. ('14). "A structural study of the caterpillars: III, The somatic muscles." Ann. Ent. Soc. Am. Vol. VII, pp. I09-I24,with9 plates. Forbes, W. T. M. ('16). "On the tympanum of certain Lepidoptera." Psyche. Vol. 23, pp. 183-192. Forbes, W. T. M. ('22a). "Five strange Lepidoptera (Oinophilidae, Noctuidae, Gelechiidse)." Ent. News. Vol. 33, pp. 97-104. Forbes, W. T. M. ('22b). "The wing-venation of the Coleoptera." Ann. Ent. Soc. Am. Vol. 15, pp. 328-345, with 7 plates. Ford, Norma ('22). "An undescribed planidium of Perilampus." Canad. Ent. Sept. 1922. Fox, W. J. ('92). "The North American Pemphredonidae." Trans. Am. Ent. Soc. Vol. 19, pp. 307-326. Fox, W. J. ('93). The North American Larridae. Proc. Acad. Nat. Sci. Phila., 1893, pp. 467-551- Fox, W. J. ('95). "The Cerabraninas of boreal America." Trans. Am. Ent. Soc. Vol. 22, pp. 129-226. Fox, W. J. ('99). "The North American Mutillidae." Trans. Am. Ent. Soc. Vol. 25, pp. 219-300. Fracker, S. B. ('12). "A systematic outline of the Reduvidae of North America." Proc. Iowa Acad. Sci. Vol. 19 (1912), pp. 217-247. Fracker, S. B. ('15). "The classification of lepidopterous larvae." Illinois Bio- logical Monographs, Vol. 2, No. i. Univ. 111., Urbana, 111. Franklin, H. J. ('12-13). "The Bombidae of the New World." Trans. Amer. Ent. Soc. Vol. 38, pp. 177-486; Vol. 39, pp. 73-200. 22 plates. Freiling, H. H. ('09). "Duftorgane der weiblichen Schmetterlinge nebst Beitragen zur Kenntnis der Sinnesorgane auf dem Schmetter- lingsfliigel und der Duftpinsel der Mannchen von Danais und Euploea." Zeit. wiss. Zool. Vol. 92, pp. 210-290, 6 plates. Friese, H. ('23). "Die europaischen Bienen (Apidae). Das Leben und Wirken unserer Blumenwespen," pp. 1-456, with 33 colored plates. Berlin und Leipzig. Prison, T. H. i'22). "Notes on :;he life-history, parasites and inquiline associates of Anthophora abrupta Say, with some comparisons with the habits of certain other Anthophorin^ (Hymenoptera) . Trans. Am. Ent. Soc. Vol. 48, pp. 137-156. Fuller, Claude ('12). "White ants in Natal." Agr. Jour. Union of S.Africa. Sept. and Oct. 191 2. Fulton, B.B. ('15). "The tree crickets of New York: life history and bionomics." N. Y. Agr. Exp. Sta. Tech. Bull. 42. FuNKHousER, W. D. ('17). "Biology of the Membracidae of the Cayuga Lak© Basin." Cornell Univ. Agr. Exp. Sta. Memoir ii. BIBLIOGRAPHY 1015 Gage, J. H. ('19). "The staining of coccids." Ent. News, 1919, pp. 142-143. Gahan, J. ('00). "Stridulating organs in Coleoptera." Trans. Ent. Sec. Lond., 1900, pp. 433-452. Ganin, M. ('69). "Beitrage zur Erkenntniss der Entwickelungsgeschichte bei den Insecten." Zeit. vviss. Zool. Vol. 19, pp. 381-451. GiRAUD, J. ('71)- "Note sur les moeurs du Ceiamiiis lusua?iicus Klug." Ann. Soc. Ent. France. Vol. 40, pp. 375-379. GoNiN, J. ('94). "Recherches svir la metamorphose des Lepidopteres." Bull, de la Soc. Vaudoise des vSciences Naturelles. Vol. 31 (1894), pp. 90- 139- Gould, Rev. W. (1747). "An account of English ants." London, Millar. Graber, V. ('76). "Die tympanalen Sinnesapparate der Orthopteren." Denks. Akad. wiss. Wien., Math.-nat. Klasse. Vol. 36 (1876). Graber, V. ('82). "Die chordotonalen Sinnesorgane und das Gehor der Insecten. I. MorphologischeTheil." Arch.Mik.Anat. Vol. 20, pp. 506-640. II. Physiologische Theil." Arch. Mik. Anat. Vol. 2 1 , pp. 65-145. Graham, S. A. {'22). "A study of the wing-venation of the Coleoptera." Ann. Ent. Soc. Am. Vol. 15, pp. 191-200. Grassi, B. ('89). "Les ancetres des myriapodes et des insectes." Arch, de Ital. Biol. Vol. II, pp. I, 291, 389. Grim, Oscar ('70). "Die ungeschlechtliche Fortpflanzung einer Chironomiis u. deren Entwicklung aus dem unbefruchteten Eie." Mem. Acad. Imp. S. Petersbourg. ye ser., tome 15. GuENTHER, K. (,'01 ). "Ueber Nervenendigungen auf dem Schmetterlingsfliigel." Zool. Jahrb. Abt. Anat. u. Ontog. Vol. 14, pp. 551-572. GuiLBEAU, B. H. ('08). "The origin and formation of the froth in spittle- insects." Amer. Nat. Vol. 42, pp. 783-789. Hadwen, S. ('19). "Warble Flies, Hypoderma lineatum Villers and Hypoderma bovis De Geer." Dept. Agr. Canada, Health of Animals Branch. Scientific Series, No. 27, Ottawa. Hagen, H. (1852). "Die Entwicklung und der inner Bau von Osmylus." Linnaja Entomologica. Vol. 7, pp. 368-418. Hammar, a. G. ('08). "On the nervous system of the larva of Corydalis corniUa." Ann. Ent. Soc. Am. Vol. i, pp. 105-127. Handlirsch, Anton ('o6-'o8). "Die Fossilen Insekten und die Phylogenie der Rezenten Fomien." Leipzig, 1906-1908, i vol. text, pp. ix-|- VI + 1430; I vol. plates, pp. xi and 51 plates. Hansen, H. J. ('90) . "Gamle og nye hovedmomenter til Cicadariernes morphologi og systematic." Ent. Tidskr. Vol. 11, pp. 19-76, with two plates. Trans, by Kirkaldy in The Entomologist, Vols. 33 to 36. Hansen, H. J. ('93). "Morphologic der Gliedmassen und Mundtheile bei Crustaceen und Insecten." Zool. Anz., 1893, pp. 193-198, 201-212. Hansen, H. J. ('94). "On the structure and habits of Hemimerus talpoides Walk." Ent. Tidskr. Vol. 15, pp. 65-93. Hansen, H. J. ('03). "The genera and species of the order Symphyla." Quart. Jour. Micr. Sci. Vol. 47, pp. i-ioi. Hartman, C. G. ('05). "On nests of Odynerus." Univ. Texas. Bull. No. 65, pp. 6-10. Hawley, Myron ('17). "The hop redbug, Paracalocoris hawleyi Knight." Jour. Econ. Ent. Vol. 10, pp. 545-552. Headlee, T. J. ('06). "Blood-gills of Simulium pictipes." Am. Nat. Vol. 40, pp. 875-889. Hebard, Morgan ('17). "The Blattidae of North America north of the Mexican boundary." Am. Ent. Soc. Mem. No. 2. Hegner, R. W. ('12). "The history of the germ cells in the psedogenetic larva of Miastor." Science. Vol. 36. Hegner, R. W. ('14). "The germ-cell c>^cle in animals." The Macmillan Co., New York. Hendel, I-'riedrich ('22). "Die palaarktischen Muscidae acalyptratae Girsch- Haplostomata Frey nach ihren Familien und Gattungen." 1016 AN INTRODUCTION TO ENTOMOLOGY "Konowia" Ztschr. f. syst. Insecktenkde. Bd. i, op. 145-160, 253-365. Henneguy, L. Felix ('04). "Les insectes," pp. xviii+804, with 622 text figures and 4 plates in colors. Masson et Cie., Paris, iqo4. Herrick, Glenn W. ('14). "Insects injurious to the houseliold and annoying to man," pp. xvii+470, eight plates, 152 text figures. The Macmillan Co., New York, 19 14. Hess, Walter N. ('17). "The chordotonal organs and pleural discs of ceramby- cidlarvae." Ann.Ent.Soc.Am. Vol. 10, pp. 63-74, with four plates. Hesse, R. ('01). "Untersuchungen liber die Organe dcr Lichtempfindung bei niederen Thieren. VII. Von den Arthropoden-Augen." Zeit. wiss. Zool. Vol. 70, pp. 347-473. Hewitt, C. Gordon ('14). "The house-fly, Musca donieslica, its structure, habits, development, relation to disease, and control." Cambridge, at the University Press, 1914. Heymons, R. ('99). "Beitrage zur Morphologic und Entwicklungsgeschichte der Rliynchoten." Nova Acta, Kais. Leop.-Carolin. Deutsch. Akad. d. Naturf. Vol. 74, No. 3. Heymons, R. ('07). "Die verschiedenen Formen der Insectenmetamorphose." Ergebnisse und Fortschritte der Zoologie. Vol. i,pp. 137-188. Hilton, W. A. ('02). "The body sense hairs of lepidopterous larvae." The America Naturalist. Vol. 36, pp. 561-578. Hinds, W. E. ('02). "Contribution to a monograph of the insects of the order Thysanoptera inhabiting North America." Proc. U. S. Nat. Mus. Vol. 26, pp. 79-242, with eleven plates. HiNE, J. S. ('01). "A review of the Panorpidae of America north of Mexico." Bull. Sci. Lab. Denison Univ. Vol. 2, pp. 241-264. HiNE, J. S. ('03). "Tabanidae of Ohio." Ohio State Acad. Sci. Special Papers No. 5. HocHREUTHER, RuDOLF ('12). "Die Hautsinncsorgane von Dytiscus marginalis L., ihr Bau und ihre Verbreitung am Korper." Zeit. f . wiss. Zool. Vol. 103, pp. 1-114. HoEK, P. P. C. ('81). "Report on the Pycnogonida." In Report on the scientific results of the voyage of H. M. S. Challenger. Zoology. Vol. 3, 1881. HOFER, B. ('87). "Untersuchungen uber den Bau der Speicheldriisen und des dazugehoreneden Nervenapparates von Blatta." Nova Acta, Kais. Leop.-Carolin. Deutsch Akad. d. Naturf. Bd. 51, No. 6. Holland, W.J. ('98). "The butterfly book." Doubleday & McClure Co., New York. Holland, W. J. ('03). "The moth book." Doubleday, Page &• Co., New York. Holmgren, Emil ('95). "Studier ofver hudens och de Kortelartade hudorganens morfologi hos skandinaviska makrolepidopterlarver." Kongl. Svenska Vetenskaps-Akademieus Handlingar. Bandet 2^, No. 4. Holmgren, N. ('09). "Termitenstudien I. Anatomische Untersuchungen." K. Svensk. Vetensk. Handl. Vol. 44 (1909), pp. 1-215. Hood, J. D. ('13). "Notes on the life history of Rhopalosoma poeyi. Proc. Ent. Soc. Wash. Vol. 15, pp. 145-148. Hopkins, A. D. ('09). "Contribution toward a monograph of the scolytid beetles." U. S. Dept. Agr. Bull. 17, Tech. Series. Horton, J. R. ('18). "The citrus thrips." U. S. Dept. Agr. Bull. No. 616. Feb. 14, 1918. Hough, Garry Den. ('98). "The Muscidae collected by Dr. A. Donaldson Smith in Somali Land." Proc. Acad. Nat. Sci. Phil. Vol. 55, pp. 165-187. Howard, L. O. ('95). "Revision of the Aphelininae of North America." U. S. Dept. Agr. Bull. No. i. Tech. Ser. Howard, L. O. ('01). "The insect book." Doubleday, Page & Co., New York. Howard, L. O. ('07). "New genera and species of the Aphelinrr.ae with a revised table of genera." U. S. Dept. Agr. Bull. No. 12, Tech. Ser. Part IV. BIBLIOGRAPHY 1017 Howard, L. O., Dyar, H. G.. and Knab, F. ('i2-'i7). "The mosquitoes of North and Cential America and the West Indies." 4 vol. Pub- lished by the Gai negie Institution of Washington. Hubbard, H. G. ('97). "The au.brcsia beetles of the United States." U. S. Dept. Agr. Bulv No. 7, new series, pp. 1-30. Huber, p. (1810). "Recherches sur les mceurs des Fourmis indigenes." Paris et Geneve. Hungerford, H. B. ('19). "The biology and ecology of aquatic and semi- aquatic Hemiptera." The Kansas Univ. Sci. Bull. Vol. 11, No. 17, pp. 3-265. Hungerford, H. B. ('22). "The Nepidse of North America." The Kansas Univ. Sci. Bull. Vol. 14, No. 18. Hungerford, H. B. ('23). "Some studies on the genus Hydrometra in America north of Mexico, with description of a new species." Canad. Entom. Vol. 55, pp. 54-58- Hungerford, H. B. ('24). "A new Mesovelia with some biological notes regarding it (Hemiptera- Mesoveliidas). Canad. Ent. Vol. 56, pp. 142-144. Huxley, T. H. ('78). "A manual of the anatomy of invertebrated animals." D. Appleton & Co., New York. Hyslop, J. A. ('17). "The phylogeny of the Elateridte based on larval charac- ters." Ann. Ent. Soc. Am. Vol. 10, pp. 241-263. Isely, Dwight ('13). "The biology of some Kansas Eumenida^." The Kansas Univ. Sci. Bull. Vol. 8, pp. 235-309. JoHANNSEN, O. A. ('03). "Aquatic nematocerous Diptera." N. Y. State Mus. Bull. 68, Ent. 18, pp. 328-441. JoHANNSEN, O. A. ('05). "Aquatic nematocerous Diptera II." N. Y. State Mus. Bull. 86, Ent. 23, pp. 76-316. JoHANNSEN, O. A. ('o8). "New North American Chironomidce." N. Y. State Mus. Bull. 124, 23d Rept. State Entomologist, pp. 264-285. JoHANNSEN, O. A. ('09a). "Mycetophilida'." Genera Insect. Fasc. 93. JoHANNSEN, O. A. ('09b). "North American Henicocephalida^." Psyche, Feb. 1909, pp. 1-4. JoHANNSEN, O. A. ('o9-'i2). "The fungus gnats of North America." Maine Agr. Exp. Sta. Bulls. 172, 180, 196, 200. Johnston, Christopher ('55). "Auditory apparatus of the Culex mosquito." Quart. Jour. Micr. Sci. Vol. 3, pp. 97-102. Jones, Paul R. ('12). "Some new California and Georgia Thj^sanoptera." U. S. Dept. Agr., Bur. Ent. Bull. No. 23, Tech. Ser. Part I, 1912. Kellogg, V. L. ('94). "The taxonomic value of the scales of the Lepidoptera." Kans. Univ. Quart. Vol. 3, pp. 45-89. Kellogg, V. L. ('99). "The mouth-parts of the nematocerous Diptera." Psyche. Jan., March, April, May, June, 1899. Kellogg, V. L. ('01). "The histoblasts (imaginal buds) of the wings and legs of the giant crane-fly {Holorusia ruhiginosa). Psyche. Vol. 9, pp. 246-250. Kellogg, V. L. ('02). "The development and homologies of the mouth parts of insects." The American Naturalist. Vol. 36 (1902), pp. 683-706. Kellogg, V. L. ('03). "The net-winged midges (Blepharocerida?) of North America." Proc. Cal. Acad. Sci., 3d ser.. Zoology. Vol. 3, pp. 187-226, with 4 plates. Kellogg, V. L. ('04). "Regeneration in larval legs of silk-worms." Jour. Exp. Zool. Vol. I (1904), pp. 593-599- Kellogg, V. L. ('07). "Diptera Fam. Blepharoceridas." Genera Insect., Fasc. 56. Kellogg, V. L. ('o8a). "American insects," pp. xiv -1- 694, with 812 text figures and 13 plates in colors. Henry Holt & Co., New York, 1908. Kellogg, V. L. (o8b). "Mallophaga." Genera Insect., Fasc. 66. i018 AN INTRODUCTION TO ENTOMOLOGY Kenyon, F. C. ('95). "The morphology and classification of the Pauropoda, with notes on the morphology of the Diplopoda." Tufts College Studies, No. 4 (1895). KiEFFER, J. J. ('07). "Hymenoptera Fam. Dryinidae." Genera Insect., Fasc. 54. KiEFFER, J. J. ('12). "Evaniidse." Das Tierreich, 30 Lieferung, pp. xix + i- 432. Includes EvaniinEe, Gasteruptioninse, and Aulacinas. KiEFFER, J. J. ('13). "Fam. Cecidomyids." Genera Insect., Fasc. 152. KiEFFER, J. J. ('14). "Serphidae (-Proctotrupidae)." Das Tierreich, 42 Lieferung, pp. xvii + 1-254. KiEFFER, J. J. ('16). "Diapriidae." Das Tierreich, 44 Lieferung, pp. i-xxx + 1-627. King, J.. L. ('16). "Observations on the life history of Pterodontia flavipes Gray (Diptera)." Ann. Ent. Soc. Am. Vol. 9, pp. 309-321. with 2 plates. Kinsey, a. C. ('20). "Life histories of American Cynipidae." Bull. Am. Mus. Nat. Hist. Vol. 42, pp. 319-357. Kinsey, A. C. ('22). "Studies of some new and described Cynipidae." Indiana Univ. Studies, No. 53, University Bookstore, Bloomington, Ind. KiRBY, W., AND Spence, W. (1815-1826). "An introduction to entomology." London (18 15-1826). KiRBY, W. F. C'o4-'io). "A synonymic catalogue of Orthoptera. Vol. I. Euplexoptera, Curioria, et Gressoria. Vol. II. Achetidas et Phasgonuridae. Vol. III. Locustidae vel Aridiidffi." London, British Mus. KiRKALDY, G. W. ('98). "An economic use of waterbugs." Ent. Mo. Mag. Vol. 34 (1898), p. 173- Kolbe, H. J. ('89). "Einfuhrung in die Kenntnis der Insekten." Berlin, 1889. KoRSCHELT, E., AND Heider, K. ('99). "Text-book of the embryology of in- vertebrates." Vol. 3. London, 1899. Kowalevsky, a. ('87). "Beitrage zur nachembryonalen Entwicklung der Musciden. Theil I." Zeit. wiss. Zool. Bd. 45. Krafka, J. ('15). "A key to the families of trichopterous larvae." Canad. Ent. Vol. 47, pp. 217-225. Krecker, F. H. ('09). "The eyes of Dactylopius." Zeit. wi.ss. Zool. Vol. 93, PP- 73-89. Landois, H. ('67). "Die Ton- und Stimmapparate der Insecten in anatomische- physiologische und akustischer Beziehung." Zeit. wiss. Zool. Vol. 17, pp. 105-184, Taf. X, XI. L.ang, Arnold ('91). "Text-book of comparative anatomy." English transla- tion, Macmillan & Co., London and New York. Latzel, R. ('80). "Die Mvriopoden der Osterreichisch-Ungareschen Monarchic." Alfred H'older, Wien, 1886. Law, James ('87). "The farmer's veterinary adviser." Published by the Author, Ithaca, N. Y., 1887. Lehr, Richard ('14). "Die Sinnesorgane der beiden Fliigelpaare von Dytiscus marginalise Zeit. wiss. Zool. Vol. no, pp. 87-150. Leiby, R. W. ('22). "The polyembryonic development of Copidosoma gelechioe, with notes on its biology." Jour. Morphologv. Vol. 37, pp. 195- 285. Leiby, R. W., and Hill, C. C. ('23). "The twinning and monoembryonic develop- ment of Platygaster hiemalis, a parasite of the Hessian fly." Jour. Agr. Research. Vol. 25, pp. 337-350. Leng, Charles W. ('20). "Catalogue of the Coleoptera of America, north of Mexico." John D. Sherman, Jr., Mt. Vernon, N. Y. Leon, N. ('97). "Beitrage zur Kenntnis des Labiums der Hydrocoren." Zool. Anz. Vol. 20, pp. 73-77. Leydig, Franz ('67). "Der Eierstock und die Samentasche der Insekten." Nova Acta, Kais. Akad. Leop.-Carolin. Vol. 33. Lienard, V. ('80). "Constitution de I'anneau oesophagien." Bull. Acad. Roy. Belg. 2 ser tome. 49, pp. 179-188, i plate. BIBLIOGRAPHY 1019 LiNDSEY, A. W. ('21). "The Hesperioidea of America north of Mexico." Univ. of Iowa Studies, Vol. 9, No. 4. Published by the University, Iowa City, Iowa. LlNN^us (Carl von Linne). "Systema naturae, sine regna tria naturae systematice proposita per classes, ordines, genera et species, etc." First edition, 1735; twelfth edition, 1768. To be obtained of dealers in second-hand books. Lloyd, J. T. ('14). "Lepidoptcrous larvae from rapid streams." Jour, N. Y. Ent. Soc. Vol. 22, pp. 145-152. Lloyd, J. T. ('15). "Notes on Ithytrichia confusa Morton." Canad. Ent. Vol. 47, pp. 117-121. Lloyd, J. T. ('21). "The biology of North American caddice-fly larvas," Cin- cinnati, Ohio. Bull. 21 of the Lloyd Library. LoziNSKi, Paul ('08). "Beitrag zur Anatomic und Histologic der Mundwerk- zeuge der Myrmeleonlarven." Zool. Anz. Vol. 33, pp. 473-484, with 9 figures. Lubbock, J. ('73)- "Monograph of the Collembola and Thysanura." London Roy. Soc, 1873. Lubbock, Sir John ('94). "Ants, bees and wasps." Revised Ed. Intemat. Sci. Ser., Appleton & Co., New York. Lugger, Otto ('98). "The Orthoptera of Minnesota." Third Ann. Report of theEntomologiftof the State Exp. Station of the Univ. of Minne- sota, for the year 1897. This is a reprint of Bull. No. 55 (Dec. 1897) of the same station. Lyonet, p. (1762). "Traite anatomique de la chenille qui ronge le bois de saule." Amsterdam, 1762. McAtee, W. L. ('08). "Notes on an orthopteron leaf-roller." Ent. News. Vol. 19, pp. 488-491. McAtee, W. L. ('21). "Notes on nearctic bibionid flies." Proc. U. S, Nat. Mus. Vol. 60, Art. II. McClendon, J. F. ('02). "The life history of Ulula hyalina." The Amer. Nat. Vol. 36, pp. 421-429. McClendon, J. F. ('06). "Notes on the true Neuroptera." Ent. News, 1906, pp. 116-121. MacGillivray, a. D. ('06). "A study of the wings of the Tentlaredinoidea, a superfamily of Hymenoptera." Proc. U. S. Nat. Mus. Vol. 39, pp. 569-654, with 24 plates. MacGillivray, Alex. D. ('21). "The Coccidje." Scarab Co., Urbana, 111., 1921. McIndoo, N. E. ('14). "The olfactory sense of the honey bee." Jour. Exp. Zool. Vol. 16, pp. 265-346. McLachlan, Robert ('74-'8o). "A monograph revision and synopsis of the Trichoptera of the European fauna." London, John Van Voorst, I 874-1 880. Malloch, J. R. ('13). "The insects of the dipterous family Phoridse in the United States National Museum." Proc. U. S. Nat. Mus. Vol. 43, pp. 411-529. Malloch, J. R. ('14). "American black flies or buffalo gnats." U. S. Dept. Agr., Bur. Ent. Bull. No. 26, Tech. Ser, Malloch, J. R. ('17). "A preliminary classification of Diptera, exclusive of Pu- pipara, based upon larval and pupal characters, with keys to im- agines in certain families. Part I." Bull, 111. State Lab. Nat. Hist. Vol. 12, Art. III. Malloch, J. R. ('18), "The North American species of the genus Tiphia (Hy- menoptera Actdeata) in the collection of the Illinois State Natural History Survey." Ill, Nat. Hist. Survey Bulletin, Vol, 13, pp. 1-24, Marchal, P, ('97). "Les Cecidomyies des cereales et leurs parasites," Ann. Soc, Ent. France. Vol. 66, pp. 1-105. Marchal, P. ('13), "Contribution a I'etude de la biologic des Chermes." Ann. Sci. Nat. 9th Series (Zoology), Vol. 18 (1913), PP- 153-385- Marlatt, C, L, ('95), "The hemipterous mouth." Proc. Ent. Soc. Wash. Vol. 3, pp. 241-249, i020 .4A^ INTRODUCTION TO ENTOMOLOGY Marlatt, C. L. ('98). "The principal enemies of the grape." U. S. Dept. Agr. Farmers' Bull. No. 70. Marlatt, C. L. ('07). "The periodical cicada." U. S. Dept. Agr., Bur. Ent. BuH. 71, 1907. Matheson, Robert ('12). "The Haliplidse of North America, north of Mexico." Jour. N. Y. Ent. Soc. Vol. 20, pp. 156-193. Matheson, Robert ('14). "Life-history notes on two Coleoptera (Pamidce)." Canad. Ent. Vol. 46, pp. 185-189. Matheson, R., and Crosby, C. R. ('12). "Aquatic Hymenoptera in America." Ann. Ent. Soc. Am. Vol. 5, pp. 65-71. Mayer, A. G. ('96). "The development of the wing scales and their pigment in butterflies and moths." Bull. Mus. Comp. Zool. Vol. 29, pp. 209-236. Mayer, A. M. ('74). "Experiments on the supposed auditory apparatus of the mosquito." The American Naturalist. Vol. 8, p. 577. Meek, W. J. ('03). "On the mouth- parts of the Hemiptera." Kansas Univ. Sci. Bull. Vol. 2, pp. 257-277, 5 plates. Meijere, J. C. H. DE Coi). "Ueber das letzte died der Beine bei den Ai-thro- poden." Zool. Jahrb. Anat. Vol. 14 (1901). Melander, A. L. ('02a). "TwonewEmbiidaj." Biol. Bull. Vol. 3, po. 16-26. Melander, a. L. ('02b). "Notes on the structure and development of Embia texana." Biol. Bull. VjI. 4, pp. 99-118. Melander, A. L. ('02c). "A monograph of the North American Empididse." Trans. Am. Ent. Soc. Vol. 28, pp. 195-367. Melander, A. L. ('03). "Notes on North American Mutillidse, with descriptions of new species." Trans. Am. Ent. Soc. Vol. 29, pp. 291-330. Melander, A. L. ('13a). "A synopsis of the Sapromyzidse." Psyche. Vol.20, pp. 57-82. Melander, A. L. ('13b). "A synopsis of the dipterous groups Agromyzinee, Milichiinas, OchthiphilinEe, and Geomyzinse." Jour. N. Y. Ent. Soc. Vol. 21, pp. 219-273, 283-300. Melander, A. L. ('16). "The dipterous family Scatopsidae." State Coll, Wash. Agr. Exp. Sta. Bull. 130. Melander, A. L. {'20a). "Review of the nearctic Tetanoceridse." Ann. Ent. Soc. Am. Vol. 13, pp. 305-332. Melander, A. L. ('20b). "Synopsis of the dipterous family Psilidse." Psyche. Vol. 27, pp. 91-101. Melander, A. L.,and Spuler, A. C'17). "The dipterous families Sepsidas and Piophilidas." State Coll. Wash. Agr. Exp. Sta. Bull. 143. Mercer, W. F. ('00). "The development of the wings in Lepidoptera." Jour. N. Y. Ent. Soc. Vol. 8, pp. 1-20. MiALL, L. C. ('95). "The natural history of aquatic insects," pp. ix+395, with 116 figures. Macmillan & Co., London and New York. MiALL, L. C, and Denny, A. ('86). "The structure and life-history of the cock- roach." London, 1886. MocsARY, A. ('89). "Monographia Chrysidarum Orbis Terrarum TJniversi." Budapestini Typis Societatis Franklinianae. 4to, pp. 1-643. Morgan, Anna Haven ('12). "Homologies in the wing-veins of May-flies." Ann. Ent. Soc. Am. Vol. 5, pp. 89-106. Morgan, Anna H. ('13). "A contribution to the biology of May-flies." Ann. Ent. Soc. Am. Vol. 6, pp. 371-413. Morgan, T. H., and Shull, A. F. ('10). "The life cycle of Hormaphis hamamely- dis." Ann. Ent. Soc. Am. Vol. 3, pp. 144-146. Morrill, A. W. ('03). "The greenhouse aleyrodes {A. vaporariorum Westw.) and the strawberry aleyrodes (A. packardi Morrill)." Hatch Exp. Sta. Mass. tech. Bull. No. i. Morrill, A. W., and Back, E. A. ('11). "White flies injurious to citrus ir Florida." U. S. Dept. Agr., Bur. Ent. Bull. No. 92. Morris, H. M. ('22). "On the larva and pupa of a parasitic phorid fly — Hypoceya incrassata." Parasitology. Vol. 14, pp. 70-74. Morse, A. P. ('20). "Manual of the Orthoptera of New England." Proc, Best. Soc. Nat. Hist. Vol. 35, No. 6. BIBLIOGRAPHY 1021 MosHER, Edna ('i6). "A classification of Lepidoptera based on characters of the pupa." Bull. 111. State Lab. Vol. 12, pp. 12-159. MouLTON, Dudley ('ii). "Synopsis, catalogue, and bibliography of North American Thysanoptera." U. S. Dept. Agr., Bur. Ent. Tech. Ser., Bull. No. 21, 1911. MuGGENBURG, F. H. ('92). "Der Russel der Diptera pupipara." Arch. f. Naturgesch. Vol. 58, pp. 287-392. MuiR, F. ('12). "Two new species of Ascodipteron." Bull. Mus. Comp. Zool. Vol. 54, pp. 351-366. MuiR, F., AND Kershaw, J. C. ('12). "The development of the mouth-parts in the Homoptera, with observations on the embryo of Siphanta." Psyche. Vol. 19, pp. 77-89. MuLLER, Johannes (1826). "Zur vergleichenden Pbysiologie des Gesichtssinnes des Menscher und der Thiere." Leipzig, 1826. MuTTKOWsKi, R. A. ('10). "Catalogue of the Odonata of North America." Bull. Pub. Mus. Milwaukee. Vol. i, Article i. Milwaukee, Wis., 1910. Needham, J. G. ('97). "The digestive epithelitxm of dragon-fly nymphs." Zool. Bull. Vol. I, pp. 103-113. NEEDH.A.M, J. G. ('01). "Aquatic insects in the Adirondacks." N. Y. State Mus. Bui. 47 ( 1 901), pp. 384-560, 573-596. Needham, J. G. ('03). "A genealogic study of dragon-fly wing- venation." Proc. U. S. Nat. Mus. Vol. 26, pp. 703-764, plates 31-54. Needham, J. G. ('05). "May-flies and Midges of New York." N. Y. State Mus. Bull. 86. Needham, J. G. ('18). "Aquatic insects," in "Freshwater biology" by Ward and Whipple, pp. 876-946. John Wiley & Sons, New York, 191 8. Needham, J. G., and Lloyd, J. T. ('16). "The life of inland waters," pp. 1-438, with 244 figures. The Comstock Publishing Co., Ithaca, N. Y., 1916. Newcomer, E. J. C18). "Some stoneflies injurious to vegetation." Jour. Agr. Research. Vol. 13, pp. 37-41. Newport, G. (1839). The article "Insecta." Todd's Cycl. of Anat. and PhysioL London, 1839. Nininger, H. H. ('20). "Notes on the life-history of Anthophora stanfordiana." Psyche. Vol. 27, pp. 1 35-137- NoYES, Miss A. A. ('14). "The biology of the net-spinning Trichoptera of Cascadilla Creek." Ann. Ent. Soc. Am. Vol. 7, pp. 251-276. Nuttall, G. H. F., and Shipley, A. E. ('01). "Studies in relation to malaria. II. The structure and biology of Anopheles." Jour. Hygiene. _Vol. I, pp. 451-483. Oestlund, O. vv. ('18). "Contribution to knowledge of the tribes and higher groups of the family Aphidid^ (Homoptera)." Seventeenth Rept. State Ent. of Minn., pp. 46-72. OsBORN, Herbert ('96). "Insects affecting domestic animals." U. S. Dept. Agr., Div. Ent. Bull. No. 5, new series, 1896. Osten-Sacken ('81). "An essay of comparative chaetotaxy, or the arrangement of characteristic bristles of Diptera." Mittheil. Miinchener Ent. Ver., 1881, pp. 121-140. OuDEMANs, A. C. ('10). "Neue Ansichten tiber die Morphologic des Flohkopfes, sowie liber die Ontogenie, Phylogene und Systematik der Flohe." Novit. Zool. Vol. 16, pp. 133-158. OuDEMANS, J. T. (.'87). "Beitrage zur Kenntniss der Thysanura und Collembola." Original in Dutch {Acad. Proefsch. Amsterdam, 1887). OuDEMANs, J. T. ('88). "Beitrage zur Kenntniss der Thysanura und Collembola." Bijdragen tot de Dierkunde. Amsterdam. Packard, A. S. ('76). "A monograph of the geometrid moths or Phalaenidae of the United States." Rept. U. S. Geol. Survey of the Territories. F. V. Hayden, Vol. 10. Packard, A. S. ('80). "On the anatomy and embryology of Limulus." Anni- versary Memoires of the Boston Soc. of Nat. Hist., 1880. 1022 AN INTRODUCTION TO ENTOMOLOGY Packard, A. S. ('95). "Monograph of the bombycine moths of America north of Mexico, including their transformations and origin of the larval markings." Mem. Nat. Acad. Sci. Vol. 7. Packard, A. S. ('98). "A text-book of entomology," pp. xvii+729, with 654 text figures. The Macmillan Co., London and New York. Packard, A. S. ('05). "Monograph of the bombycine moths of North America. Part II. Family Ceratocampidse, subfamily Ceratocampinae." Mem. Nat. Acad. Sci. Vol. 9. Pankrath, O. ('90). "Das Auge der Raupen und Phryganidenlarven." Zeit. wiss. Zool. Vol. 49, pp. 690-708. Parker, J. B. ('17). "A revision of the bembicine wasps of America north of Mexico. Proc. U. S. Nat. Mus. Vol. 52, pp. 1-155. Patch, Edith M. ('09). "Homologies of the wing veins of the Aphididas, Psylli- dcB, Aleurodidse, and Coccidae." Ann. Ent. Soc. Am. Vol. 2, pp. 101-129, with 6 plates. Patch, Edith M. ('10). "Gall aphids of the elm." Maine Agr. Exp. Sta. Bull. No. 181. Patton, W. S., and Cragg, F. W. ('13). "A textbook of medical entomology." Christian Literature Soc. for India, London, Madras, and Cal- cutta. Peckham, G. W. and E. G. ('98). "On the instincts and habits of the solitary wasps." Wis. Geol. and Nat. Hist. Survey. Bull. No. 2. Peckham, G. W. and E. G. ('05). "Warps social and solitary." Houghton, Mifflin & Co., Boston and New York. Perez, J. ('78). "Sur les causes de bourdonnement chez les insectes." Comptes Rend. Acad, des Sci. Vol. 87, p. 378. Pergande, Theo. ('01). "The life-history of two species of plant-lice, inhabiting both the witch-hazel and birch." U. S. Dept. Agr., Div. Ent. Tech. Ser., Bull. No. 9. Pergande, Theo. ('04). "North American Phylloxerinas affecting Hicoria (Carya) and other trees." Proc. Davenport Acad. Sci. Vol. 9, pp. 185-273, with 21 plates. Perkins, R. C. L. ('05). "Leaf -hoppers and their natural enemies (Pt. I. Dryin- idae)." Exp. Sta., Hawaiian Sugar Planters' Association. Bull. No. I, Part I. Peterson, Alvah ('15). "Morphological studies on the head and mouth-parts of the Thysanoptera." Ann. Ent. Soc. Am. Vol. 8, pp. 20-66. Peterson, Alvah ('16). "The head-capsule and mouth-parts of Diptera." Illinois Biol.Monogr. Vol. 3, No. 2. Univ. of 111., Urbana, 111. Pierce, W. Dwight ('09). "A monographic revision of the twisted winged insects comprising the order Strepsiptera Kirby." U. S. Nat. Mus. Bull. No. 66. Pierce, W. Dwight ('ii). "Strepsiptera." Genera Insect., Fasc. 121. Pierce, W. Dwight ('18). "The comparative morphology of the order Strepsip- tera together with records and descriptions of insects." Proc. U. S. Nat. Mus. Vol. 54, pp. 391-501. Plath, O. E. ('19). "A muscid larv'a of the San Francisco Bay region which sucks the blood of nestling birds." Univ. Cal. Pub. Zool. Vol. 19, pp. 191-200. Plath, O. E. ('22). "Notes on Psithyrus, with records of two new American hosts." Biol. Bull. Vol. 43, pp. 23-44. PococK, R. I. ('10). Article "Cetitipedt" in the eleventh edition of the Encyclo- paedia Britannica. PococK, R. I. ('11). Article "Millipedes" in the eleventh edition of the Encyclo- paedia Britannica. Pratt, H. S. ('99). "The anatomy of the female genital tract of the Pupipara as observed in Melophagiis ovinus." Zeit. wiss. Zool. Vol. 66, pp. 16-42. Quaintance, a. L., and Baker, A. C. ('13). "Classification of Aleyrodidae." U. S. Dept. Agr. Tech. Ser. Bull. No. 27, pp. 1-114. BIBLIOGRAPHY 1023 QuAiNTANCE, A. L., AND Baker, A. C. ('17). "A Contribution to our knowledge of the white flies of the subfamily Aleyrodinas (Aleyrodfdas)." Proc. U. S. Nat. Mus. Vol. 51, pp. 335-445. Rath, O. vom ('96). "Zur Kenntnis der Hautsinnesorgane und des sensiblen Nervensystems der Arthropoden." Zeit. wiss. Zool. Vol. 61, pp. 499-539. Rau, Phil., and Rau, Nellie ('18). "Wasp studies afield." Princeton Univ. Press. Redikorzew, W. ('00). "Untersuchungen tiber den Bau der Ocellen der Insek- ten." Inaugural-Dissertation, Universitat Heidelberg. Leipzig, Wilhelm Engelmann, 1900. Rees, J. VAN ('88). "Beitrage zur Kenntnis der inneren Metamorphose von Musca vomttoria." Zool. Jahrb. Abt. Anat. Bd. 3 (1888). Rehn, a. G., and Hebard, M. ('12). "A revision of the genera and species of the group Mogoplistii (Orthoptera ; Gryllidae) found in North America north of the Isthmus of Panama." Proc. Acad. N. S. Phil., June, 1912. Richardson, Harriet ('05). "A monograph of the isopods of North America." U. S. Nat. Mus. Bull. No. 54 (1905). Riley, C. V. ('69). "First annual report on the noxious, beneficial and other insects of the State of Missouri." Jefferson City, Mo., 1869. Riley, C. V. ('73)- "On a new genus in the lepidopterous family Tineidae, with remarks on the fertilization of yucca." Fifth Rept. Ins. Mo., pp. 150-160. Riley, C. V. ('77). "On the larval characters and habits of the blister-beetles belonging to the genera Macrobasis Lee. and Epicauta Fabr.; with remarks on other species of the family Melvidae." Trans. Acad. Sci. St. Louis. Vol. 3, pp. 544-565. Riley, C. V. ('79)- "Philosophy of the pupation of butterflies and particularly of the Nymphalida;." Proc. Am. Ass. Adv. Sci. Vol. 28, 1879. Riley, C. V. ('92). "The yucca moth and yucca pollination." Missouri Botanical Garden. Third Ann. Rept., St. Louis, Mo., 1892. Riley.Wm. A., andJohannsen.O. A. ('15). "Handbook of medical entomology," pp. IX +348, with 174 figures. The Comstock Publishing Co., Ithaca, N. Y., 191 5. Roger, O. ('75). "Das Fliigelgeader der Kafer." Erlangen, 1875, 90 p. Rohwer, S. a., and Cushman, R. A. ('17). "Idiogastra, a new suborder of Hymenoptera, with notes on the immature stages of Oryssus." Pioc. Ent. Soc. Wash. Vol. 19, pp. 89-98. Rolleston, George ('70). "Forms of animal life." Oxford, Clarendon Press. RooT,A. I. andE. R. ('17). "TheABCandXYZof bee culture." The A. I. Root Co., Medina, Ohio. RouBAUD, E. ('16). "Recherches biologiques sur les guepes solitaires et social d'Afrique." Ann. Sci. Nat. Zool. loe serie, Vol. i,pp. 1-157. Sanderson, E. D. ('12). "Insect pests of farm, garden and orchard," pp. XII+ 684, with 513 figures. John Wiley & Sons, New York, 1912. Saunders, E. ('91). "On the tongues of the British Hymenoptera." Proc. Linn. Soc. London. Vol. 23, pp. 410-432, with 8 plates. Saussure, Henri de ('75). "Synopsis of American wasps." Washington, Smithsonian Institution. Savigny, J. C. (1816). "Memoires sur les animaux sans vertebres." Paris, 1816. Schenk, Otto ('02). "Die antennal Hautsinnesorgane einiger Lepidopteren und Hymenopteren mit besonderer Berucksichtigung der sexual Un- terschiede." Zool. Jahrb. Anat. u. Ontogene. Vol. 17, 1902. Schierbeek, a. ('16). "On the setal pattern of caterpillars." Koninkljke Akademie van Wetenschappen te Amsterdam. Proceedings. Vol. 19, No. 1. Schierbeek, A. ('17). "On the setal pattern of caterpillars and pupae." Onder- zoekingen verricht in het Zoologisch Laboratorium der Ryksuni- versiteit Gronigen. Vi. E. J. Brill, Leiden, 191 7. Schiodte, J. C. ('6i-'83). "De metamorphosi eleutheratorum." Kjobenhaven, 1861-1883- 1024 AN INTRODUCTION TO ENTOMOLOGY ScHMiEDEKNECHT, Otto ('09). "Fam. Chalcididas." Genera Insect. Fasc. 97. ScHMiEDER, R. G. ('22). "The tracheation of the wings of early larval instars of Odonata Anisoptera, with special reference to the development of the radius." Ent. News. Vol. 33, Nos. 9-10. Schneider, Anton ('85). "Die Entwicklung der Geschlechtsorgane bei den Insekten." Zool. Beitrage, Breslau, Vol. I. ScHWABE, Josef ('06). "Beitrage zur Morphologie und Histoligie der tympanal Sinnesapparate der Orthopteren." Zoologica. Heft 50. vStuttgart, 1906. Scott, Hugh ('17). "Notes on Nycteribiidee, with descriptions of two new genera." Parasitology. Vol. 9, pp. 593-610. ScuDDER, S. H. ('93). "'The songs of our grasshoppers and crickets." Twenty- third Annual Report of the Entomological Society of Ontario, 1892, pp. 62-78. ScuDDER, S. H. ('97). "Guide to the genera and classification of the North American Orthoptera." Edward M. Wheeler, Cambridge, Mass. ScuDDER, S. H. ('00). "Catalogue of the described Orthoptera of the United States and Canada." Proc. Davenport Acad. Nat. Sci. Vol. 8, pp. i-ioi. Seaton, Frances ('03). "The compound eyes of Machilis." Amer. Naturalist. Vol. 37, pp. 319-329- . Seiler, W. ('05). "Ueberdie Ocellender Ephemeriden." Zool. Jahrb. Bd. 22, pp. 1-40. Seurat, L. G. ('99). "Contributions a I'etude des Hymenopteres entomophages. " Ann. Sci. Nat. Zool. Vol. 10 (1899), pp. 1-159. Shannon, R. C. ('22). "The bot-flies of domestic animals." The Cornell Veterinarian, July 1922. Sharp, David ('95). "Insects." Parti. The Cambridge Natural History . Vol. 5, pp. 83-584, figures 47-371. Macmillan & Co., London and New York, 1895. Sh.\rp, David ('99). "Insects." Part II. The Cambridge Natural History. Vol. 6, pp. 626, with 293 text figures. Macmillan & Co., London and New York, 1899. Shipley, A. E. ('98). "An attempt to revise the family Linguatulida;." Arcliives de Parasitoligie. Vol. i . Siebold, C. T. von ('44). "Ueber das Stimm und Gehororgane der Orthopteren." Arch. Naturg. Vol. 10, pp. 52-81, i Taf. Silvestri, F. ('96). "I Diplododi." Ann. Mus. Genova, (2). Vol.16 (1896). Silvestri, F. ('05). "Contribuzione alia conoscenza della metamorfosi e dei costumi della Lebia scapularis, con descrizione dell' apparato sericiparo della larva." Estratto dal "Redia." Vol. 2 (1904). Silvestri, F. ('07). "Descrizione di un nuovo genera di insetti apterigoti." Boll. Lab. Zool. Portici, 1907. Silvestri, F. ('13). "Descrizione di un nuovo ordine di insetti." Boll. Zool. Gen. e. Agr. Portici. Vol. 7, pp. 193-209. Sladen, F. W. L. ('12). "The humble-bee, its life-history and how to domesticate it, with descriptions of all the British species of Bombus and Psithyrus." Macmillan & Co., London. Slingerland, M, V. ('94). "The cabbage root maggot, with notes on the onion maggot and allied insects." Cornell Univ. Agr. Exp. Sta. Bull. No. 78. Slingerland, M. V., and Crosby, C. R. ('14). "Manual of fruit insects." pp. xvi + 503, with 396 figures. The Macmillan Co., New York. Smith, H. S. ('12). "Technical results from the gipsy moth parasite labora- tory." U. S. Dept. Agr., Bur. Ent. Tech. Series, Bull. No. 19. Part IV. Smith, J. B. ('92). "The structure of the hemipterous mouth , " Science. Vol. 19, No. 478. Smith, J. B. ('01). "Notes on some digger bees." Jour. N. Y. Ent. Soc. Vol. 9, pp. 29-40, 52-72. Smith, L. W. ('17). "Studies of North American Plecoptera." Trans. Am. Ent. Soc. Vol. 43, pp. 433-489. BIBLIOGRAPHY 1025 Smith, R. C. C'21). "A study of the biology of the Chrysopid^." Ann. Ent. Soc. Am. Vol. 14, pp. 27-35. Smith, R. C. ('22). "The biology of the Chrysopids." Cornell Univ. Agr. Exp. Sta. Memoir 58. Snodgrass, R. E. ('05). "A revision of the mouth-parts of the Corrodentia and the Mallophaga." Trans. Am. Ent. Soc. Vol. 31, pp. 297-30;. Snodgrass, R. E. ('09). "The thorax of insects and the articulation of the wings." Proc. U. S. Nat. Mus. Vol. 36, pp. 511-595. Snodgrass, R. E. ('loa). "The thorax of the Hymenoptera." Proc. U. S. Nat. Mus. Vol. 39, pp. 37-91, with 16 plates. Snodgrass, R. E. ( lob). "The anatomy of the honev bee." U. S. Dept. Agr., Bur. Ent. Tech. Series, Bull. No. I'S. Snyder, T. E. ('15). "Biology of the termites of the eastern United States, with preventive and remedial measures." U. S. Dept. Agr., Bur. Ent. Bull. 94, Part II, 1915. Stiles, C. W. ('91). "Bau u. Entwicklungsgeschichte v. Pentastomum prohoscide- um Bud. und Pentastomum subcylindtcum Dies." Zeit. wiss. Zool. Bd. 52, pp. 85-157. Straus-Durkheim, H. E. (1828). ' "Considerations generales sur I'anatomie comparee des animaux articules, auxquelles on a joint I'anatomie descriptive du Hanneton vulgaire." Paris, 1828. Sturtevant, a. H. ('21). "The North American species of the Drosophila." Carnegie Institution of Wa^h. Publication No. 301. Swaine, J. M. ('18). "Canadian bark-beetles, Part II." Dom. Canada. Dept. Agr., Ent. Branch. Bull. 14. Thompson, C. B. (.'17). "Origin of castes of the common termite Leucotermes flavipes Kol." Jour. Morph. Vol. 30, No. i, Dec. Thompson, C. B. ('19). "The development of the castes of nine genera and thirteen species of termites." Biol. Bull. Vol. 36, pp. 379-398. Thompson, C. B., and Snyder, T. E. ('19). "The question of the phylogenetic origin of termite castes." Biol. Bull. Vol. 36, pp. 1 15-130. Tillyard, R. J. ('16). "Studies in Australian Neuroptera. No. 3. The wing- venation of the Chrysopidae." Proc. Linn. Soc. New South Wales. Vol. 41, pp. 221-248. Tillyard, R. J. ('19). "On the morphology and systematic position of the family Micropterygidse (sens, lat.)." Proc. Linn. Soc. New South Wales. Vol. 44 (1919), pp 95-136. Tillyard, R. J. ('21). "A new classification of the order Perlaria." Canad Ent. Vol. 53, pp. 35-43. Tillyard, R. J. ('22). "New researches upon the problem of the wing-venation of Odonata." Ent. News. Vol. 33, pp. 1-7, 45-51. Tower, D. G. ('14). "The mechanism of the mouth-parts of the squash bug, Ajiasa tristis De Geer." Psyche. Vol. 21, pp. 99-108. Tower, W. L. ('03). "The development of the colors and color patterns of Coleoptera, with observations upon the development of color in other orders of insects." Decennial Publ. Univ. Chi. Vol. 10, PP- 33-70, 3 plates. Tower, W. L. ('06) . "Observations on the changes in the hypodermis and cuticula of Coleoptera during ecdysis." Biol. Bull. Vol. 10, pp. 176-192. TowNSEND, A. B. ('04). "The histology of the light organs of Photinus margi- nellus." Am. Nat. Vol. 38, pp. 127-148. TowNSEND, C. H. ('08a). "The taxonomy of the muscoidean flies, including descriptions of new genera and species." Smithsonian Misc. Coll, Vol. 51, No. 1803. TowNSEND, C. H. ('08b). "A record of results from rearings and dissections of Tachinidas." U. S. Dept. Agr., Bur. Ent. Tech. Ser., Bull. No. 12, Part VI. Triggerson, C. J. ('14). "A study of Dryophanta erinacei (Mayr) and its galL" Ann. Ent. Soc. Am. Vol. 7, pp. 1-34. Ulmer, George ('07). "Trichoptera." Genera Insect., Fasc. 60. Ulmer, G. ('09). "Trichoptera." Heft 5/6 of "Die Siisswasserfauna Deutsch- lands" herausgegeben von A. Braur. Jena. Verlag von Gustav Fischer 1026 AN INTRODUCTION TO ENTOMOLOGY Van Duzee, E. P. ('17). "Catalogue of the Hemiptera of America north of Mexico excepting the Aphididae, Coccidas, and Aleurodidae." Univ. Cal. Pub., Tech. Bull. Ent. Vol. 2, pp. i-xiv, 1-902. Van Duzee, M. C, Cole, F. R., and Aldrich, J. M. ('21). "The dipterous genus Dolichopus Latreille in North America." U. S. Nat. Mus. Bull. 116. Van Rees.— See Rees, J. van. Verhoeff, K. W. ('03). "Beitrage zur vergleichenden Morphologic des Thorax der Insekten niit Beruchsichtigun der Chilopoden." Nova Acta, Kais. Leop.-Carolin. Deut. Akad. der Naturf. Vol. 81 (1903), pp. 63-109, pis. 7-13. Verson, E. ('04). "Evoluzione postembrionale degli arti cefalici e toracali nel filugello." Atti del Reale Istituto Veneto di scienze lettere ed arti. Tomo 63 (1903-1904), pp. 49-87, with 3 plates. Verson and Bisson C'gi). "Cellule glandulari ipostigmatiche nel Bomhyx 7nori." Bull. Soc. Ital. Vol. 23, pp. 3-20. Viereck, H. L. ('16). "The Hymenoptera, or wasp-like insects of Connecticut." By H. L. Viereck, with the collaboration of A. D. MacGillivray, C. T. Brues, W. M. Wheeler, and S. A. Rohwer. State Geol. and Nat. Hist. Survey of Connecticut. Bull. 22. VoGEL, Richard ('ii). "Ueber die Innervierung der Schmetterlingsflugel und tiber den Bau und Verbreitung der Sinnesorgan auf denselben." Zeit. wiss. Zool. Vol. 98, pp. 68-134. VoRHiES, C. T. ('09). "Studies on the Trichoptera of Wisconsin." Trans. Wis- consin Acad. Sci., Arts and Letters. Vol. 16, Part I, No. 6. Wagner, Nicholas ('62). "Spontane Fortpflanzung bei Insectenlarven." Denkschrift d. kais. Kansan'schen Univers. Wagner, Nic. ('63). "Beitrage zur Lehre von Fortpflanzung der Insectenlarven." Zeit. wiss. Zool. Vol. 13, pp. 514-527, 2 Taf. Wagner, Nic. ('65). "tjber den viviparen Galknuckenlarven." Zeit. wiss. Zool. Vol. 15, pp. 106-117, I Taf. Walker, E. M. ('14). "A new species of Orthoptera, forming a new genus and family." Canad. Ent. Vol. 46, p. 93. Walker, E. M. ('19). "The terminal abdominal structures of orthopteroid insects: a phylogenetic study." Ann. Ent. Soc. Am. Vol. 12, pp. 267-316, with 9 plates. Walker, E. M. ('22a). "Some cases of cutaneous myiasis, with notes on the larvae of Wohlfahrtta vigil." Jour. Parasitology. Vol. 9, pp. 1-5. Walker, E. M. ('22b). "The terminal structures of orthopteroid insects: a phylogenetic study." Ann. Ent. Soc. Am. Vol. 15, pp. 1-76, with II plates. Walton, W. R. ('09). "An illustrated glossary of chaetotaxy and anatomical terms used in describing Diptera." Ent. News. Vol. 20, pp. 307- 319, with 4 plates. Weele, H. W. van der ('08). "Ascalaphiden monographisch Bearbeit." Coll. Zool. du Baron Edm. Longchamps. Fasc. 8, Bruxelles, 1908. Weele, H. W. van der ('10). "Megaloptera monographic revision." Coll. Zool du. Baron Edm. Longchamps. Fasc. 5, Bruxelles, 1910. Weismann, a. ('64). "Die nachembryonale Entwicklung nach Beobachtungen an Musca vomitoria und Sarcophaga carnaria." Zeit. wiss. Zool. Bd. 14 (1864). Welch, Paul S. ('14). "Habits of the larva of Bellura melanopyga Grote (Lepi- doptera)." Biol. Bull. Vol. 27, pp. 97-114. West, Tuffen ('61). "The foot of the fly; its structure and action: elucidated by comparison with the feet of other insects," etc. Part L Trans. Linn. Soc. Lond. Vol. 23 (1862), pp. 393-421, 3 plates. Wheeler, W. M. ('00). "The habits of Myrmecophila nebrascensis Brunner." Psyche. Vol. 9, pp. 111-115. Wheeler, W. M. ('07a). "The polymorphism of ants." Bull. Am. Mus. Nat. Hist. Vol. 23, Art. I. Wheeler, W. M. ('07b). "The fungus-growing ants of North America." Bull. Am. Mus. Nat. Hist. Vol. 23, pp. 669-807. BIBLIOGRAPHY 1027 Wheeler, W. IM. ('io). "Ants, their structure, development and behavior." The Columbia University Press, New York. Wheeler, W. M. ('i8). "A study of some ant larvae, with a consideration of the origin and meaning of the social habit among insects." Proc. Amer. Phil. Soc. Vol. 57, pp. 293-343. Wheeler, W. M. i'22). "Keys to the genera and subgenera of ants." Bull. Am. Mus. Nat. Hist. Vol. 45, pp. 631-710. Wheeler, W. M. ('22-'23). "Social life among the insects." Lowell Lectures. Published in The Scientific Monthly, Vols. 24-26. Wheeler, W. M. ('23). "Social life among the insects." Harcourt, Brace & Co., New York. Wheeler, W. M., and Taylor, L. H. ('21). "Vespa arctica Rohwer, a parasite of Vespa diabolica DeSaussure." Psyche. Vol. 28, pp. 135-144. WiLLEM, Victor ('00). "Recherches sur les Collemboles et les Thysanoures." Mem. cour. Mem. sav. etr. Acad. Roy. Belgique. Vol. 58, pp. 1-144. WiLLL\MS, F. X. ('13). "The Larridse of Kansas." The Kansas Univ. Sci. Bull. Vol. 8, No. 4. Williams, F. X. ('19). "Philippine wasp studies." Exp. Sta. Hawaiian Sugar Planters' Assn. Bull. 14, pp. 19-186. Williston, S. W. ('86). "Svnopsis of the North American Syrphidse." U. S. Nat. Mus. Bull. No. 31. Williston, S. W. ('96 and '08). "Manual of the families and genera of North American Diptera." Second Edition. New Haven, James T. Hathaway. Third Edition, 1908. Young, B. P. ('21). "Attachment of the abdomen to the thorax in Diptera." Cornell Univ. Agr. Exp. Sta. Memoir 44. YuASA, Hachiro ('22). "A classification of the larvae of the Tenthredinoidea." 111. Biol. Monographs. Vol. 7, No. 4. Univ. 111., Urbana, 111. ZiMMERMANN, O. ('8o). "Ueber eine eigenthiimaliche Bildung des Riickengefasses bei einigen Ephemeridenlarven." Zeit. wiss. Zool. Vol. 34, pp. 404-406. References to go with Chitin, p. 30 For definitions of the words Chitin, Chitinization, Chitinize, see the large English Dictionaries: A New English Dictionary on Historical Principles, Vol. II, Oxford, 1893, Webster's New International Dictionary of the English Lan- guage, 1924, Funk and Wagnall's New Standard Dictionary of the English Language, 1928. Newport, G. Article, Insecta, in Todd's Cyclopaedia of Anatomy and Physi- ology, Vol. II, p. 801 (1836-39). Rolleston, George. "Forms of Animal Life." Pp. civ and cxxxiii. 1870. Odier, Auguste. "Memoir sur la composition chemique des parties comee des insects." Mem. de la Soc. d'Hist. Natrl. Paris t. i pp. 29-42 (1823). Translation of the ibove with additional remarks bv J. G. Children, F. R. S. The Zoological Journal, Vol. I, pp. '101-115 (1825). Ferris and Chamberlin. "On the use of the word 'chitinized'." Entomological News, Vol. XXXIX, pp. 212-215 (1928). The authors discuss the inconsistency of the use of this word to indicate the hardening of the integument of insects when the term was introduced by Odier to indicate the soft, colorless cuticula after the hardening substances and pigment had been removed by boiling in caustic potash solution. Snodgrass, R. E. "Some further errors of body- wall nomenclature in entomol- ogy." Entomological News, Vol. XL, pp. 150-154 (1929). He emphasizes the objections of Ferris and Chamberlin for the use of chitinize, etc., for hardening the cuticula, and makes some suggestions for improvements. Campbell, F. L. Detection and estimation of insect chitin. Annals of the Entomological Soc. of America. Vol. xxii, (1929) pp. 401-426 (60 references to chitin) . INDEX Figures in boldface type refer to pages bearing illustrations. Aaron, vS. F., 952 Abedus, 367 A calks, 88 Acalyptratas, 786, 853 Acanthaclisis, 304 Acanthocephala femorata, 390 Acanthomyops, 890 Acanthostichus, 959 Accessory cells, 574 Accessory circvtlatory organs, 122 Accessory glands, 162 Accessory veins, 68 Acerentomidce, 218 Acerentomon, 218 Acerentomon doderoi, 25 Acerentulus, 218 Acetabula, 52 Achoriites armatus, 228; A. nivicola, 228; A. maritima, 229; A. socialis, 228 Acidalia enudeata, wings of, 667 Acidaliinae, 663, 666 Acilius, 483 Ackerman, A. J., 998 Acoenitini, 923 Acoloithus falsarins, wings of, 604 Acone eyes, 141 Acorn-moth, 628 Acrida turrila, 134 Acrididae, 252 Acroceridas, 786, 789, 837 Acrolophidas, 582, 589, 611 A crolophus, 611; A. arcanellus, 611; A. mortipennellus, 611; A. popea- nellus, 6 1 1 Acronycta, 689 Acroschismus brnesi, 547 Acrydiinse, 253, 259 Acrydium arenosum obscurum, 260; A. granidatum, 260 Aculeas, 573 Abdomen, 75; appendages of the, 76; segments of the, 75 Adalia bipunctata, 512 Adaptive ocelh, 135, 136 Adela, 598 Adelges, 429; A. abietis, 432; A. abietis, gall of, 432; A. green-winged, 432; A. pine-bark, 432; A. pine-leaf, 431; A. pinicorticis, 432; A. pinifolice, 431 ; gall of, 432; A. wings of, 414, 428 Adelginiae, 429 Adelinse, 598 Adelocephala bicolor, 717 Adelung, N. von., 150 Adephaga, 468, 469, 476 Adipose tissue, 123 Adirondack black-fly, 824 Adoneta spinidoides, wings of, 608 Adventitious veins, 70 Aedes, 806, 809; A. agypti, 809; A. caloptis, 809 yEgeriidse, 582, 584, 634 ^olothripidae, 344 /Eololhrips fasciatus, 344; A. nasturtii, 342 Mollis dorsalis, 500 /Escinia cyanea, hind-intestine and part of tracheal system of naiad of, 319 ^schnidse, 320 Agamic forms of aphids, 415, 416 Agaontinae, 942, 943 Agaristidse, 583, 587, 697 Agathidinse, 921 Agdistis adactyla, 653 Aglais milberti, 755 Agrilus ruficollis, 503 Agrion, 324 Agrionidse, 324 Agrionids, true, 324 Agromyzidag, 786, 792, 861 Agrothereutes extrematis, 928; A. nun- cius, 928 AgrotincE, 695 A gratis c-nignini, 696 Ailanthus webworm, 632 Ailanthus-worm, 727 Air-sacs, 118 Akers, Ehzabeth, 78 Alabama argillacea, 686, 687 Alar frenum, 783 Alans oc Hiatus, 501 Alcidamea producta, 1000 Alder blight, 421 Alder-flies, 285 Aldrich, J. M., 830, 844, 860, 864, 870 Aleiodinas, 920 Aleiirocliiton forbesii, 437, 440 Aleyrodes, 439 Aleyrodidse, 177, 400, 437 Aleyrodid, an, 437 Alenrodothrips fasciapennis, 346 Alimentary canal, 107 Alitrunk, 49 Alia plus, 948 Alleculids, 474, 512 Alsophila pometaria, 664, 665 Alternation of generations, 935 Alveolus, 32 1029 1030 AN INTRODUCTION TO ENTOMOLOGY Alula or alulct, 60, 778 Alypia langtonii, 698; A. octomacidata, 697; larva, 698 Alysiinse, 920, 922 Ambient vein, 74 Amblycera, 337 Amblycheila, 477, 478; A. cylindri- formis, 478 Amblycorypha, 237; A. oblongifolia, 236, 237; A. rotiindifolia, 237; A. nhleri, 237 Amblyteles, 929 Ambrosia-beetles, 542, 544 Ambry sus, 367 Ametabola, 174 Ametabolous development, 174 Ammophila, 890, 984 AmpelcEca myron, 659, 660 Amphibolips confluens, 937; A. inanis, 938 Amphicerns bicaudatus, 515 Amphidasis co gnat aria, 673 Amphipneustic, 115 Amphipyra pyramidoides, 691 Amphizoidae, 470, 481 Ampulicidae, 891, 909, 913, 977, 978 Anabolia nervosa, 557 Anacampsis innocuella, 628 Anacharitinse, 934 Anacrabro, 980 Anajapyx, A. vesicidosus, 224 Ancea, 761; A. andria, 761; ^. morri- sonii, 761; yl. portia, 761 Anal angle, 60 Anal area, 75; the veins of the, 65 Anal furrow, 73 Anal lobe, 888 Anal lobes, 445 Anal plates, 445 Anal ring, 445 Anal ring setae, 445 Anal setae, 445 Anamorphosis, 218 Anaphothrips siriahis, 345 Anarsia lineatella, 627 Anasa tristis, 389 Anastomosis, 326 Anastomosis of veins, 70 Anax, 317 Anaxipha, 242; A. exigua, 243, 244 Anchor process, 815 Ancylis comptana, 922 Ancyloxipha vurnitor, 738 Andre, E., 954 Andreria, 996, 997 Andrenidse, 891, 893, 914, 995 Andricits erinacei, 936; A. calif ornicus, 938 Androconia, 100, 573 Anepimerum, 51 Anepistemum, 51 Angles of wings, 60 Angle-wings, the, 754 Angoumois grain-moth, 626 Angulifera-moth, 726 Anisandrus pyri, 545 Anisolabis annulipes, 462; A. marilima, 462 Anisomorpha bnprestoides, 262 Anisopidas, 785, 787, 788, 797 Anisoptera, 316 Anisopiis, •j()'j; wing of, 797 Anisota, -ji-j, 927; A. rosy, 719; A. rubicunda, 719; A. senatoria, 718; A. stigma, 718; A. virginiensis, 718 Anobiidse, 471, 514 Anobium, 79 Anopheles, 808; head of, 775 Anoplura, 211, 214, 347 Anosia plexippiis, head of, 109 Ant, see Ants Antecoxal piece, 54 Antecubital cross-veins, 319 Antelope-beetle, 523 Antenna cleaner, 886 Antenna, 40, 41; the development of, 199 Antennal fossa, fovea, or groove, 779 Antennal sclerites, 39 Antenodal cross- veins, 319 Anteoninae, 915 Anterior arculus, 72 Anthicidae, 475, 498 Anthidium consimile, 968 Anthoboscidae, 891, 912, 952 Anthocharis genutia = Euchloe genutia, 748 Anthocoridae, 356, 358, 377 Anthomyiidas, 786, 793, 863 Anthomyioidea, 786 Anthonomus grandis, 540; A. signatus, 540; A. qiiadrigibbtis, 540 Anthony, Alaude H., 113, 282 Anthophora, 890, 996; nests of, 997; A. stanfordiana, 996 Anthrenus museorum, 507; A. scrophu- laricB, 506; A. verbasci, 507 Antispila pfeifferella, wings of, 622 Antlered larvae, 677 Ant-lion, head and mouthparts of, larva of, 282 Ant-Hons, 303 Antocha, 799 Ants, 954; Amazon, 964; carpenter, 963; corn-field, 964; fungus-growing, 962; harvesting, 960; honey, 964; in- quiline or guest, 961 ; mound-build- ing, 963; slave-maker, 963; thief, 960; typical, 963 Anuraphis maidi-radicis , 419; A. re- sells, 418 Anurapteryx, 673; A. crennlata, 673 INDEX 1031 Anurida, 47; A. manlinta, post-an- tennal organ of, 226, 229 Anus, 113 Aorta, 122 Apanteles, 921, 927, 947; A. congregatus, 921; A. glomeratus , 921 Apantesis, 701; A. virgo, 701 Apatela, 689; A. americana, 690; A. hamamelis, 690; lar\'a, 691; A. morula, 690 Apatelinje, 689 Apatelodes, 707; .1. angelica, 708; A. torrefacta, 707 Apechonetira, 930 Apechthis, 925 Apex of the wing, 60 Aphelinidae, 941 Aphelininae, 948 Aphididse, 177, 400, 415, 417; different types of individuals in, 416 Aphidiinse, 919, 920, 922 Aphidinje, bark-feeding, 418; leaf- feeding, 418; root-feeding, 419 Aphidoidea, 400, 412 Aphids, 412; giant hickory-, 418; strawberry-root, 419; typical, 415; woolly, 420 Aphis, corn-root, 419; A. forbesi, 419; A. gossypi, 413; A. melon, 413; A. pomi, 418; A. apple-leaf, 418; rosy apple-, 418; A. woolly apple, 421 Aphis-lions, 299 Aphodian dung-beetle, 517 Aphodius, 517; A. fimetariiis, 517 Aphrophora qiiadranotata, 403 Aphycus emptor, 939 Apidag, 108, 891, 893, 914, 1005 dpis, 992, 1005; A. dorsata, 1005; A. fiorea, 1005; A. indica, 1005; A. mcl- lifica, 1005; wings of, 884 Apiocera, wing of, 843 Apioceridse, 786, 789, 842 Apocrita, 907 Apodemes, 95, 98 Apoidea, 989, 993 Apoph^^ses, 31 Appendages, the development of, 1 94 Apple fruit-miner, 631 Apple-maggot, 857 Apple-worm, many-dotted, 691 Apposed image, 143 Aptera, 207 Apterobittaciis, 554; A. apterus, 554 Apterogynina;, 916 Apterygogenea, 206 Apterygota, 206, 211, 217 Apyrrothrix araxes, 735 Aquatic Hymenoptera, 889 Arachnida, 9 Aradidae, 357, 358, 359, 388 Aradus acutus, 389 Arceocems fascicidatus, 537 Archanara, 692 Archips argyrospila, 643; A. cerasi- vorana, 642; A. fervidana, 643; A. rosana, (A2 Arctiidae, 583, 588, 699 Arctiinas, 700 Arculus, 72 Areolet, 928 Argentine Ant, 962 Argidae, 891, 895, 904, 905 Argynnis cybele, 751 Argyresthia conjugella, 631; A. thuiella, Arilus cristatiis, 381 Arixenia esau, 463; A . jacobsoni, 463 Arixeniidae, 463 Armored Scales, 454 Army- worm, 694 Arolium, 58 Arthoceras, 833 Arthromacra cenea, 514 Arthropeas, 833 Arthropleona, 228 Athropoda, i Articular membrane of the setae, 32 Articular sclerites of the legs, 53; of the wings, 54, 55 Arzama, 692; A. obliqua, 692, 693 Ascalaphidse, 284, 305 Aschiza, 786, 847 Ascodipteron, 875 Ascogaster qiiadridentatus , 921 Ashmead, W. H., 921, 922, 929, 968 Asihdas, 786, 788, 840 AsparagLxs-beetle, 530 Aspicerinae, 934 Aspidiotus perniciosus, 458 Astatini, 980, 981 Astatus bicolor, 981; A. unicolor, 981 AsteiidEe, 786, 792, 860 Aster ochiton packardi, 440; A. vapora- riorum, 439 Ateuchus, 88; /I. sacer, 516 Atherix, 835; A. ibis, 835, 836 Atlanicus, 240; A. davisi, 240; A. testaceus, 240 Atropidaj, 333 A tropes divinatoria, 80; A. pulsaloria, 334 Atryone conspicua, 738 Attelabinae, 538 Attelabus, 538 Atteva aurea, 632 Attii, 962 Auditory pegs, 147 Audouin, J. V., 49 Augochlora, 996 Aulacaspis roscc, 458 Aulacid, wing of, 930 Aulacidae, 890, 892, 908, 917, 929 1032 AN INTRODUCTION TO ENTOMOLOGY Aidacus, 929 Autographa brassica, 687; A.falcifera, 687, 946 Automeris to, 722 Axillaries, 54 Axillary cord, 60; A. excision, 61, 778; A. furrow, 74; A. membrane, 60 Axima, 945 Bacillus pestis, 879 Back-swimmers, 362 Bad-wing, 667 BcEus, 933 Bag-worm Moths, 613; Abbot's, 613; evergreen, 614 Baker, A. C, 419 Baker, C. F., 880 Balaninjis, 539; B. nasicus, 539; B. prohoscideus, 539; B. rectus, 539 Baliosus rubra, 534 Balsa malana, 691 Baltimore, the, 752 Banded elfin, 770 Banded purple, 758 Banks, Nathan, 280, 296, 303, 307, 951 Barber, H. S., 494 Bark-beetles, 543; fruit-tree, 544; peach-tree, 544 Barnacle scale, 454 Barnes and Lindsay, 673 Barnes and McDunnough, 602 Basal anal area, 320 Basal anal cell, 327 Basal or subbasal band, 575 Basement membrane, 31, 109, 118 Basilarchia, 750; B. archippus, 759; B. archippusfloridensis, 760; B. arthemis, 758; B. asiyanax, 758; B. proserpina, 758 Basilona imperialis, 717 Basswood leaf-roller, 646 Bat-ticks, 875 Bean leaf-roller, 736 Bean-weevil, 535 Bear animalcules, 12 Beard, 781 Beaver-parasite, 486 Bedbug, 103, 355, 378 Bedbug, big, 382 Bedbug-hunter, masked, 381 Bedellia somnulentella, 616 ; wings of , 6 1 6 Bee-bread, 1006, 1007 Beech-tree blight, 422 Bee-flies, 838 Bee-lice, 676 Bee-moth, 650 Bees, 952, 977, 978, 989; bifid tongued, 993; hairs of various, 990; leaf-cutter, 999; three castes of, 1005 Beet or Spinach leaf-miner, 864 Beetles, 464 Beetle, ventral aspect of a, 465 Beggar, 669 Belidas, 476, 537 Bella-moth, 700 Bellesme, J., 92 Bellura, 691; B. diffusa, 691, 692; B. gortynoides, 691, 692; B. melanopyga, 691; B. white tailed, 692 Belonogaster, 972 Belostoma, 367; B. fluminea, 367 Belostomatidffi, 356, 357, 365 Belytidse, 890, 910, 915, 916, 932 Belytinae, 910, 915, 932 Bembecia marginata, 636 Bembicini, 981, 986, 988 Bembex, 979, 988 Benacus, 366; B. griseus, 367 Bequaert, J., 889 Berlese, A., 25, 106, 113, 128, 132. 133, 134, 151, 155, 398 Berothidas, 284, 298 Berotha insolita, 298 Bethylidae, 891, 892, 894, 911, 916, 965, 979 Betten, Dr. Cornelius, 559 Bezzi, M., 828, 876 Bibionidffi, 785, 788, 820 Bibio, 820; wing of, 821 Bibiocephala doanei, mouth parts of female, 826 Big-eyed Flies, 849 Bill-bugs, 540 Bird-lice, 335 Bischoff, H., 952 Bittacomorpha clavipes, 797 Bittacus, 553, 554 Blackberry crown-borer, 636 Black-dash, 738 Black-flies, 821; innoxius, 824; white- stockinged, 824 Black scale, 453 Black witch, 685 BlastobasidEe, 582, 589, 591, 628 Blastophaga, 59; B. psenes, 943 Blasturus, 312 Blatchley, W. S., 236, 502 Blatchley and Leng, 475, 536 Blatta orientalis, 266 Blattella germanica, 265, 266 Blattidse, 234, 263 Blattoidea, 263 Blepharocera, 144; B. tenuipes, 826; wing, 825; section of head, 825; larva, 826 BlepharoceridcB, 786, 787, 824 Blissus leucopterus, 387 Blister-Beetles, 495 Blood, 122 Blood-gills, 114, 120 Blow-fly family, 869 Blues, the, 771 INDEX 1033 Blue, tailed, 772 Bluebottle-fly, large, 870 Body-segments, 34 Body-wall, 29, 34 Boletotherus cornutus, 513 Bollworm, pink, 628 Bombardier-beetles, 479 Bomb-fly, 868 Bombias, 1002 Bombidas, 890, 891, 893, 914, 993, looi, 1003 Bombus, 890, 1002, 1004; nest of, 1004 Bomb^'cidse, 58^, 585, 727 Bombyliidse, 786, 788, 789, 838 Bombylius, 838 Bombyx mori, 128, 727 Book-lice, 331, 333 Book-louse, mouth-parts of, 331 Boophilus anniilatiis, 2 Eorboridce, 786, 791, 794, 855 Boreus, 550, 551, 553 Boriomyia, 297 Borner, C, 430, 432, 876 Bot-flies, 864; common, 865; of Horses, 864; red-tailed, 866; sheep, 867; stomach, 865 Bothropolys vitdtidentatus, 21 Bostrichidae, 471, 515 Brachelytra, 467, 468; families of the, 470 Brachinus, 479, 480 Brachyacantha, 512 Brachycentrus nigrisoma, 569, 570 Brachycera, 786, 828; Anomalous, 786, 829; True, 786 Brachygastra lechegiiana, 973 Brachypauropodidse, 19 Brachyrhimis ovatiis, 539; B. sulcatus, 539 Brachystola magna, 257 Bracon, 919 Braconidae, 890, 892, 908, 915, 917, 919 Braconinse, 920, 921 Bradley, Prof. J. C, 886, 889, 908, 950, 953, 954. 966, 979 Brand, 738 Brathinidae, 471, 486 Brathinus, 486 Brauer, F., 206 Braula, 876; B. cceca, 876; B. koJili, 876 Braulidae, 787, 794, 876 Braun, A. F., 575, 592, 601 Breast bone, 815 Bremidae, 890 Bremus, 890 Brenthis, 752 Brentidae, 476, 536 Brephinae, 663, 664 Brephos infans, 664 Brindley, H. H., 172 Brine-flies, 859 Bristle-tails, 219 Bristles, antipygidial, 879; the ab- dominal of Diptera, 785; the cephalic of Diptera, 781; of the legs of Dip- tera, 785; the thoracic of Diptera, 783, 784 Brown-tail moth, 682 Bruchophagus funebris, 945 Brucs, C. T., 931 Brycliius, 481 Buljonic plague, 879 Bucca, 779 Bucculae, 353 Bucculatrix, apple, 616; B. pomijoliella, 616; cocoons of, 616 Bucculatrigidas, 617 Buckley, 955 Bud-moth, 641 Buenca, 364 Buffalo-gnat, Southern, 824 Bugnion and Popoff, 398 Bugs, ambush-, 382; assassin-, 380; burrower-, 391, 392; chinch-, 386, 387; creeping water-, 367; fiat-, 388; flower-, 377; four-lined leaf-, 375; giant water-, 365; harlequin cab- bage-, 391; insidious flower-, 378; lace-, 384; leaf-, 375; many-combed, 379; negro, 391, 392; shield-backed, 392; shore, 369; squash-, 389; stilt-, 388; stink-, 390; tarnished plant-, 376; thread-legged, 382; toad-shaped, 368; true, 350; unique-headed, 383 Bulte, 74 Bumblebees, looi, 1002; parasitic, 1004 Buprestidse, 472, 502 Buprestid, Virginian, 503 Biiprestis, 907 Burges, E., 109, 160 Burke, H. E., 907 Bursa copulatrix, 159 Busck, A., 625, 628 Busck and Boving, 594 Butterflies, 571, 581, 583, 739 Buzzing of flies and bees, 91 Byrrhidas, 471, 508 Byturidae, 472, 510 Byturus, 510; B. unicolor, 510 Cabbage-butterfly, 746; development of the wings of, 196 Cabbage looper, 687 Cabbage-root maggot, 863 CaccEcia, 642 Caddice-Flies, 555; Micro-, 561 Caddice-worms, 557 Cadelle, 508 Cascum, 113 Canis, 309, 312 1034 AN INTRODUCTION TO ENTOMOLOGY Ccenomyia ferruginea, wing of, 833 CcEnurgia, 688; C. crassiuscula, 688; C. erechtea, 688 Calamoceratidae, 559, 560, 567 Calandra granaria, 541; C. oryza, 541 Calendrinse, 540 Calephelis borealis, 767; C. virginiensis, 767 Caliroa cerast, 904 Calledapteryx dryopterata, 709 CallibcEtis, 312 Calliceratidae 890, 932 Callimome drupariim, 943 Callimominae, 890, 943 Calliphora, 869; C. erythrocephala, 870; C. vomitoria, 870 Calliphoridae, 787, 793, 869 Callosamia angulifera, 726; C. />/-o- methea, 724, 725; cocoon of, 189 Callizzia amorata, 709 Calocalpe undidata, 668, 669; eggs and nest of, 669 Caloptenus italicus, 149 Calopteron reticulatiim, 491 Calopteryx, 324 Calosoma calidum, 479, 480; C 5frz<- /a/or, 479; C sycophanta, 479 Calypteratas, 786', 862 Calypteres, 778 Camel-crickets, 241 Campodea, 157, 161 ; C. staphylinus, 224 Campodeidae, 224 Campodeiform, 184 Caniponotus herculeanus pennsylvani- cus, 963 Campoplegini, 927 Campsomeris, 954 Camplonolus carolinensis, 240 Campylenchia latipes, 405 Canaceidffi, 786, 792, 859 Canace snodgrassi, 859 Candle-fly, Chinese, 409 Canker-worm, spring, 671; fall, 664; control of, 665 Cantharida;, 473, 492 Cantharis vesicatoria, larva of, 117 Canthon Icevis, 517 Capitate, 41 Capitonius, 930 Capnia, 179, 330; C. pygmcea, 326; C. wing of, 330 Capniidae, 330 Caprifi cation, 944 Caprifigs, 944 Capsidffi, 375 Carabidae, 470, 478 Carahus auratus, alimentary canal of, 110 Cardo, 44 Caripeta angustiorala, wings of, 662 Carlet, G., 89, 90 Carolina locust, 82 Carpenter, G. H., 17 Carpenter-bee, large, 972, 998; small, 997 Carpenter-moth, locust-tree, 603 Carpenter-moths, 601 Carpenter-worm, lesser oak, 603 Carpet-beettle, 506 Carpocapsa pomonella, 639 Carposina fernaldajia, 644 Carposinidae, 582, 590, 638, 644 Carriere and Burger, 103 Carrion-Beetles, 487 Carrot rust-fly, 859 Case-bearer, cigar, 621 Cat-flea, 882 Catocala, 688; C.fraxini, wings of, 684; C. ilia, 688 Catocalinae, 687 Catopsilia eiibule, 749 Cat-tail moth, 629; noctuids, 692 Caudell, A. N., 240, 241, 272 Caulocampa acericaidis, 903 Cave-crickets, 241 Cebrionidce, 473, 499 Cecidomyia albovittata, 817 Cecidomyiidas, 785, 787, 788, 813 Cecidomyiinae, 816, 817 Cecropia-moth, 726 Cedar-beetles, 499 Cedar tineid, 631 Celama triqiietrana, 705 Celerio lineala, 660, 661 Celery looper, 687 Cells of the wing, terminology of the, 72 Celonites abbreviatus, 967 Cenchri, 887 Centipedes, 20 Cephaloidae, 474, 494 Cephidas, 890, 891, 900 Cephus pygmaus, 901; wings of, 901 Cerambycidae, 475, 524 Cerambycids, typical, 526 Cerambycinae, 526 Ceramica picta, 694; larva, 695 Ceramins lusitanictis, 967 Cerapachyinge, 958, 959 Cerapachys, 959 Ceraphronidae, 890, 910, 915, 932 Ceraphroninag, 933 Cerastipsocus venosiis, 331 Ceratina dupla, 946, 997; nest of, 998 Ceratocombus, 374 Ceratogastra, 926 CeratophilHdae, 882 Ceralophyllus fasciatus, 878 ; C. muUis- pinostis, 878 Ceratopogon, 136 Ceratubas, 446 Cercerini, 980, 986 Cerceris dypeata, 986; C. wings of, 986 INDEX 1035 Cerci, 24, 77, 232 Cercopidae, 400, 402 Cercyonis alope, 762; C. alope yiephele, 763; alope maritima, 763 Ceresa bubalus, 404; C. diceros, 405 Ceropales, 951 Cerophytidce, 472, 499 Cerophytum, 499 Ceroplastes, 453; f. cirri pediformis, 454 Cerorcs, 446 Cervical sclcrites, 40 Ceuthophilus, 232, 241; C. lapidicola, 233; C. maculatus, 241; f. 7/Wfn, 241 ChcEtopsis ccnea, 856 Chain-dotted geometer, 670 Chalarus, 850 Chalastogastra, 890, 891, 894, 895 Chalcid-flies, 939 Chalcid-fly, wing of, 939 Chalcididae, 892, 894, 911, 915, 941 Chalcidinas, 941, 942, 944 Chalcidoidea, 890, 939, 940 Chalcis, 945 Chalicodoma muraria, looi; nests of, lOOI Chalcophora virginica, 503 Chalybion ccsrulium, 954, 984 ClianicEsphecia Hpidiformis, 637 Chamasyidse, 862 Chamyris cerintha, 689 Chapman, T. A., 593 Charipinee, 934 Chauliodes, 288; C. pectinicornis, 288; C. rastricornis, 288 Chauliognathus , 492; C. marginatus, 492; C. pennsylvanicus, 492 Cheeks, 779 Cheek-grooves, 779 Cheese-maggot, 858 Chelonariidas, 471, 506 Chelonarium lecontei, 506 Cheloninae, 920 Chelophores, 11 Chelymorpha cassidea, 534 Chemical sense organs, 130, 132 Chermes, 429; C. abieticolens, 432; C. viridis, 432 Chermidaj, 400, 410 Cherry-fruit-fiies, 857 Cherry-tree ugly-nest tortricid, 642, 643 Cheshire, F. R.', 102, 103 Chiasognathus, 88 Chickweed geometer, 666 Chigoe, 883 Child, C. M., 153, 154 Chilopoda, 20 Chimarrha alerrima, 563 Chinch-bug, 386 Chin-fly, 866 China wax, 102, 441 Chionaspis pinifoUce, 456, 458 CInonaspis furfura, 441, 457 Chionea, 799 Chiromeles torquatus, 463 Chironomidge, 785, 788, 793, 802 Chirononiiis, 120, 147, 148; wing of, 803 Chirotonetes albomanicatus, wing of, 309,310 Chitin, 30 Chitinized tendons, 95 Chloealtis conspersa, 259 Chlorion, 984; C. cyanenm, 984; C. ich- ueiimonetim, 984; C. atratiim, 987 Chlorippc celtis, 761; C. clyton, 760 Chloropida?, 786, 792, 860 Chordotonal ligament, 147 Chordotonal organs, 145, 146, 147, 148; of the Acridiida?, 148, 149; of the Locustidffi and of Grylhdae, 149 Choreutinas, 633 Chortophaga viridifasciala, 257 Choruses, 93 Cholodkovskv, N. A., 432 Chrvsalid, 186 Chrysalis, 186 Chrysanthemum gall-midge, 820 Chrysidida?, 891, 892, 911, 950, 951 Chrysis nitidula, 952 Chrysohothris feniorata, 503 Chrysomelidas, 475, 530 Chr\somphalns tenebricosiis, pygidium of, 448 Chrysomyia macellaria, 870 Ckrvsopa, 170, 171, 300; C. nigricortiis, wings of, 300, 301", 302 Chrysopidffi, 109, 284, 299 Chrysops, 830; C. niger, 830 Chylestomach, 11 1 ChyphotiucB, 916 Cicada, head of, 397, 398; the musical organs of a, 89, 90; tracheation of wings of, 395, 396 Cicada-killer, 987 Cicada, periodical, 402 Cicada plebia, 89 Cicadas, 177, 401 Cicadidee, 400, 401 CicadellidEe, 400, 406, 978 Cicindela, 476, 477, 478; maxilla of, 45 Cicindclidae, 469, 476 Cicinnus melsheimeri, 713 Cigarette-beetle, 515 Cimbex americana, 902; blade of ovi- positor of, 895 Cimbicidas, 890, 891, 895, 902 Cimex, 378; C. lectularius, 378, 379; C. pilosellus, 378 Cimicidae, 356, 358, 378 Cingilia catenaria, 670 Circular-seamed Flies, 846 Circulation of the blood, 122 1036 AN INTRODUCTION TO ENTOMOLOGY Circulatory system, 121 Circumfili, 814 Cirphis unipuncta, 694 Cisidaj, 474, 515 atheroma regalis, 716, 717; wings of, 714 Citheroniidse, 583, 715 Claassen, P. W., 327, 692 Cladius isomerus, 904 Clambidae, 470, 488 Clastoptera, 403; C. cbiiisa, 404; C. proteus, 403 Clavate, 41 Clavicornia, 467, 469 Claviform spot, 575 Clavigeridse, 470, 490 Clavola, 41 Qavus, 350 Clear-winged moths, 634 Clear-wing, thysbe, 661 Clemensia albata, 705 Cleonymina;, 941, 942, 946 Cleptes, 951 Cleptidffi, 890, 911, 950, 951 Cleridae, 473, 493 Click-beetles, 4Q9 Climacia dictyona, 292; cocoon and cocoon-cover of, 292 Clisiocampa americana, 1 70 Clistogastra, 890, 891, 894, 907, 908 Cloaked knotty-horn, 527 Cloeon, head of, 144; C. dipterum, 312 Close-wings, 649 Closing apparatus of the tracheae, 116 Clothes-moths, 612; case-bearing, 612; naked, 612; tube-building, 612 Clothilla pulsatoria, 80 Clothing hairs, 33 Clouded sulphur, 748 Cloudy- wing, northern, 737; southern, 737 Clover-flower midge, 818 Clover-hay worm, 649 Clover-leaf midge, 818 Clover-looping-owlets, 688 Clover-root borer, 542 Clover-seed caterpillar, 641 Clover-seed chalcid, 945 Clover-worm, green, 685 Clusiidae, 786, 790, 854 Cluster-fly, 870 Clypeus, 38, 779 Cnaphalodes strobilobiiis, 430 Cnephia pecnartim , 824 Coarctate pupae, 191 Coboldia formica rittm, 821 Coccidae, 177, 400, 401, 440 Coccid-eating pyraHd, 652 Coccids, the Cochineal, 450; the en- sign, 450; the giant, 449; metamor- phosis of, 448 ; mouth-parts of a, 443 ; the pseudogall, 454 Coccinas, 450 Coccinella novemnotata, 512 Coccinellidae, 473, 511 Cochineal, 441 Cochlidiidse, 608 Cockroach, head of a, 38; head and neck of, 39; internal anatomy of, 107; labium of a, 46; tentorium of a, 96; the base of a leg of a, 53 Cockroach, American, 266, 267; com- mon wood-, 266, 267; oriental, 266; wing of nymph of, 265 Cockroaches, 263, 950 Coccophagus, 948 Coccus cacti, 441, 450 Cocoon, 188; modes of escape from the, 188 CodUn-moth, 639 Coelioxys, 993 Coenagrionidae, 324 Canomyia ferrtiginea, 834 Ccenomyiidae, 786, 789, 834 Coffee-bean weevil, 537 Colcenis jidia, 764 Cole, F. R., 838, 844 Coleophora, 620; C. fletcherella, 621; malivorella, 620, 621 Coleophoridse, 582, 591, 620 Coleoptera, 109, 211, 213, 214, 215, 218, 464; synopsis of the, 467 Colleterial glands, 160 Colletes, 991, 992; C. com pacta, 994 Colletinae, 914, 994 Collembola, 214, 217, 225 CoUophore, 76, 227 Collops quadrimacidatiis, 493 Colonici, 434 Colopha eragrostidis, 423; C. nlmicola, 422, 423 Coloradia, 719; C. pandora, 721 Colorado potato-beetle, 531 Colors of butterflies and moths, 573 Colydiidae, 474, 510 Colymbetes, 483 Comma, gray, 757 Comma, green, 756 Commissure, 125 Complete metamorphosis, 180 Compound eyes, 134, 139; absence of, 135; dioptrics, 141 Compton tortoise, 756 Comstock, Mrs. A. B., 1007 Comstockaspis perniciosa, 458 Concave veins, 73 Coniopterygidas, 307 Conjunctiva, 34 Connectives, 123 Connexivum, 355 ConocephaHnae, 235, 238 INDEX 1037 Conocephalus, 86, 87, 233, 238; C. fascia/US, 233, 941 Conopidffi, 786, 790, 791, 853 Conops, 854; wing of, 60 Conorhinus, 382 Conotrachelus nenuphar, 539 Contarinia pyrivora, 820 Convex veins, 73 Cook, F. C, 873 Copidosoma gelechice, 889; C. trunca- telliim, 946 Copiphorina?, 235, 239 Copper, American, 771; bronze, 771 Copper hindwing, 691 Coppers, 770 Copris, 517; C. Carolina, 517 Coptodisca splendoriferella, 622, 623 Coquillett, D. W., 823, 845, 871 Corbicula, 991 Cordnlegaster, 320 Cordyluridas, 786, 790, 854 Corcidas, 357, 359, 389 Corethra, 121; C. cidiciformis, 154; C. phimicornis, 807 Corethrinas, 806 Corisa, 360 Corium, 350 Corixa, 360; C, eggs of, 362; C. mer- c en aria, 362 Corixidas, 356, 357, 360 Corn-borer, European, 648 Cornea, 138, 139 Corneagen, 138 Corneal hypodermis, 138, 139 Corn ear-worm, 695 Corneas of the compound eyes, 36; of the ocelli, 37 Corn stalk-borer, larger, 650 Corrodentia, 212, 213, 214, 217, 331 Corrugations of the wings, 73 Corydalinee, 286 Corydalus, 62, iii, 119, 125, 126, 136; head of, 39; head of a larva of, 38, 137; C, larva of, 288; C. cornntus, 287, 288; wing of pupa of, 287 Cor^dophida?, 471, 488 Corynetidae, 473, 493 Corythucha arcnaia, 384 Cosmocoma elegans, 949 Cosmoplite, 755 Cosmopterygidse, 582, 591, 592, 629 Cosmopteryx, 630 Cosmosoma myrodora, 707 Cossidae, 582, 585, 601 Cossinae, 603 Cossus ligniperda, 104, 105 Costa, 64 Costal fold, 735 Costal margin, 60 Costal spines, 575 Cosymbia lumenaria, 666 Cotalpa lanigera, 519 Coliniis nitida, 522 Cotton-boll weevil, 540 Cotton-boll worm, 695 Cotton-moth, maxillae of the, 575 Cotton-stainer, 385 Cotton-worm, 686 Cottony maple-scale, 453 Cow-killer ant, 954 "Cow-shed" built by ants, 961 Coxa, 56 Coxal cavities, 52 Coxites, 222 Crabro, 989; C. singularis, wings of, 988 Crabronidfe, 890 Crabroninac, 988 Crabronini, 980, 989 Cranihidia pallida, 705 Cramliina', 649 Crambus, 650; C. caliginosellus, 650; C. hortuelliis, 650 Crampton, G. C, 40, 43, 49, 233, 272, 592 Cranberry fruit-worm, 652 Crane-flies, 795; phantom, 797; prim- itive, 796; so-called false, 797; typ- ical, 798 Crawford, D. L., 860, 931 Cray-fishes, 6 Cremaster, 187 Cremastini, 923 Cremastogaster lineolata, 960 Creophilus maxillosjis, 489 Crescent-spots, 752 Cresson, E. T., 856 Cricetomys, 463 Cricket, head of a, 37, 40, 136; part of the tentorium of a, 96 Crickets, 242; ant-loving, 249; field-, 247; house-, 248; larger brown bush-, 244; larger field-, 248; mole-, 250; pigmy mole-, 251 ; smaller field-, 248; sword-bearing, 243; tree-, 245; wing- less bush-, 250 Crioceris asparagi, 530 Crista acustica, 152 Crochets, 578 Crop, no Crosby, C. R., 377, 459, 889, 943, 946 Crosby and Leonard, 575 Cross-veins, 64, 71 Crotch, 88 Croton-bug, 265, 266 Crumena, 444 Crura cerebri, 123 Crustacea, 6 Cryptidae. 890 Cryptinae, 924, 927 Cryptini, 923, 928 Cryptochcetum, 861 Cryptophagidae, 472, 474, 510 1038 AN INTRODUCTION TO ENTOMOLOGY Cryploptilum trigonipalpum, 250 Crystalline cone-cells, 140 Ctenidia, 879 Ctenocephalus canis, 882; C. Jelis, 878, 882 Ctenucha virginica, 706 Cuban termite, nest of, 279 Cubital area, 320 Cubito-anal fold, 73 Cubitus, 64 Cuckoo- wasps, 951, 952 Cucujidas, 472, 474. 509 Cucujo, 165 Cucujus clavipes, 509 Cucullia, 694; C. speyeri, 694 Cuculliin^, 693 Cucumber flea-beetle, 533 Culex, 153, 806, 807; larva of, 805; C. CEgypti, 809 Culicida;, 785, 787, 804 Culicinae, 807 Culic aides, 803 Cupesidae, 471, 494 Curculio, apple-, 540 Curculionidas, 476, 537 Curctdionince, 539 Curculios, 537 Curicta, 364 Currant borer, imported, 637 Currant fruit-fly, 858 Currant fruit-worm, 644 Currant moth, pepper-and-salt, 673 Currant span-worm, 670 Currant stem-girdler, 901 Currant-worm, imported, 903 Cushman, R. A., 906, 907 Cuticula, 30 Cuticular nodules, 31 Cut worms, 696 Cybister, 483 Cycloplasis panicifoliella, 634 Cyclops, 6 Cyclorrhapha, 786, 846; with a frontal suture, 852 ; without a frontal suture, 847 Cyclostomi, 920 Cydnidse, 357. 359, 39 1 Cydninae, 392 Cyladinas, 538 Cylas formicanus, 538 Cylisticus convexus, 7 Cyllene caryce, 528; C. robincr, 527 Cymatophora ribearia, 670 Cynipidse, 890, 892, 894, 915, 934 Cynipinae, 915, 934 Cynipoidea, 890, 934 Cynomyia cadaverina, 870 Cypridopsis, 6 Cyrtidae, 837 Cyrtomenus mirabilis, 392 Cyrtophyllus concavus, 93 Cyrtoxipha Columbiana, 244 Dactylopius, 28 Dactyls, 251 Dagger, American, 690; ochre, 690; witch-hazel, 690 Dalceridae, 582, 585, 605 Dalcerides ingenita, 606 Dalla Torre, 347, 934 Damsel-flies, 314, 315, 321; naiad of, 323; stalked- winged, 324; tracheal gill of a, 120, 323 Danainas, 750, 765 Danaus archippus, 759, 765; chrysalis, 766; larva, 766; D. berenice, 766; D. berenice strigosa, 766 Dance-flies, 845 Daphnia, 6 Darkling Beetles, 513 Darwin, Charles, 88, 181 DascilUdae, 472, 505 Dascillus cervinus, 505 Dasyniutilla occidentalis, 953 Dasyneiira leguminicola, 818; ZP. trifolii, 8i8 Datana, 28, 675; Z?. ministra, 675: larva, 675 Davidson, Dr. Anstruther, 968 Day-eyes, 142 Death-watch family, 514 Death-watch, 80, 515 Decatoma, 945 Decticinae, 235, 239 Decticus verrucivorus, 150, 151, 152 Definitive accessory veins, 69 Deltoids, 685 De Meijere, 58 Dendroleon, 304 Dengue, 810 Densariae, 447 Dentes, 228 Depressaria heracliana, 624; wings of, 624 Dermaptera, 212, 214, 460 Dermestes lardarius, 506 Dermestids, 472, 506 Dermis, 31 Derobrachus brunneus, 526 Derodontidae, 473, 510 Desmia funeralis, 646 Desmocerus palliatus, 464, 527 Deutocerebrum, 124 Development without metamorphosis, 174 Dewitz, H., loi Dexiinae, 871 Diabrotica, 532; D. duodecimpunctala, 532; D. longicornis, 532; D. sorer, 532; D. vitata, 532 Diacrisia virginica, 703 Dialeurodes citri, 440 INDEX 1039 Diamond-back moth, 632 Diaphania hyalinata, 647; D. nitidalis, 648 Diapheromera, 169; D. feniorala, 261 Diapriinse, 910, 932 Diarthronomyia hypogaa, 820 Diaspidinae, 454 Diatraa saccharalis, 650; D. zeacolella, 650 Dibrachys boucheanus, 947 Dicalus, 480 Dicer ca divaricata, 503 Dichorda indaria, wings of, 666 Digitate mine, 620 Digitules, 442 Digitus, 45 Dilar americanus , 297 Dilaridse, 284, 297 Dinetini, 980, 982 Dineutus, 484 Diodontus, 985 Dione vanilla, 764 Diopsidae, 786, 791, 859 Dioptidae, 583, 585, 673 Diplazoninae, 923 Diplazon latatorius, 926 Diplolepis centricola, 938 Diplopoda, 15 Diploptera, 966; The SoHtary, 967 Dipsocoridas, 356, 358, 374 Diptera, 212, 214, 215, 217, 773 Diptera, synopsis of the, 785 Discal cell, 74, 886 Discal vein, 74 Disholcaspis globulus, 938 Dissnsteira Carolina, 82, 233, 234, 258 Distal retinula cells, 140 Divers, 691 Diver, black-tailed, 691; brown-tailed, 692 Diverse-line moth, 668 Divided eyes, 144 Diving-beetles, the predacious, 482 Dixa, larva of, 800; wing of, 800 Dixidse, 785, 788, 800 Doane, Prof. R. W., 968 Dog-flea, 882, 877 Dog's head, 749 Dolichoderinae, 958, 962 Dolichopodidae, 786, 789, 843 Dolichopus coqmlletti, wing of, 844; D. lobatus, 843 Dolichurus, 978 Donacia, 530 Donisthorpea, 890 Dorcus parallelus, 523 Dorsal diaphragm, 121, 162 Doru aculeatum, 463 Doryctinae, 920 Dorylinas, 958 Douglasiidae, 582, 591, 623 Doyere, M., 12, 13 Drceculacephala, 407; D. reticulata, 407 Dragon-flies, 314, 316 Dragon-fly, exuviae of naiad of, 319 Drepana arcuata, 711, 712 Drepanidas, 583, 587, 588, 710 Drone-fly, 851 Drones, 1005 Drosophila ampelophila, 861; D. mela- 7iogaster, 861; egg of, 168 Drosophilidae, 786, 792, 860 Dr^dnidae, 891, 892, 911, 915, 978, 979 Drug-store beetle, 515 Dryopidas, 471, 504 Ducke, A., 969 Dufour, L., no Dung-beetles, earth-boring, 517 Dung-flies, 854, 855 Dusky-wing, Martial's, 737 Dyar, H. G., 33, 173, 579, 610, 807, 810 Dynastes grantii, 520; D. hercules, 26, 520; D. tityrus, 520 Dysdercus suturellus, 385, 386 Dysodia oculatana, 654 Dyspteris abortivaria, 667; wings of, 668 Dytiscidas, 470, 482 Dytiscus, 483 Earinus limitaris, 92 1 Earwig, European, 463; hind wing of an, 461; handsome, 462; little, 462; ring-legged, 462; seaside, 462; spine- tailed, 463 Earwigs, 460 Eaton, A. E., 311 Ecdysis, 171 Echidnophaga gallinacea, 883 Echidnophagidae, 882 Eciton, 959 Ectoderm, 29 Ectognatha, 222 Ectotrophi, 220 Egg, 166; -burster, 171; -calyx, 159; -folHcles, 158; -tooth, 171 Egg-masses of caddice-flies, 557 Eggers, P., 577 Ejaculatory duct, 162 Elachertidae, 941 Elachista quadrella, wings of, 622 Elachistidas, 582, 591, 621 Elasminae, 942, 948 Elasmus, 948 Elateridae, 472, 499 Eleodes, 513 Elephantiasis, 810 Elis (Myzine), 953 Ellipes, 252; E. minuta, 252 Elm-gall colopha, cockscomb, 422 Elm-gall tetraneura, cockscomb, 424 Elmidae, 471, 504 1040 AN INTRODUCTION TO ENTOMOLOGY Elophila fiilicalis, 649 Elytra, 59, 212, 464 Embia major, 340; E. sabulosa, 338; E. texana, 339 Embiidina, 209, 211, 213, 215, 338 Embolemidag, 890, 911, 912, 915, 951 Embolium, 351 Emesa brevipennis, 382 Emory, 955 Emperor, tawny, 760; gray, 761 Empididse, 786, 789, 790 Empoasca fabcc, 407 Empodium, 58, 778 Empoa roscE, 407 Enchenopa binotata, 405 Enchroma gigantea, 465 Encoptolophus sordidus, 257 Encyrtinae, 941, 942, 946 Enderlein, G., 338, 813, 823 Endomychidffi, 473, 474, 511 Endo- skeleton, 95 Endothorax, 97 Endrosis lacleella, 624 Eneopterinae, 243, 244 Engraver-beetles, 542, 543 Enicocephalidse, 356, 358, 383 Enicocephalus formicina, 383 Enicospilus, 927 Ennomos niagnarius, 672 Ensign-flies, 949 Entedontidae, 941 Entognatha, 224 Entomobryidae, 229 Eosentomidae, 218 Eosentomon, 218 Epargyreus tityrus, 734, 736 Epermenia pimpinella, 631 Ephemera, 312; E. simidans, 312; E. varia, 178, 311 Ephemerella, 312 Ephemerida, 180; ocelli of, 139, 209, 211, 212, 213, 308 Ephemeridae, 312 Ephestia kuhniella, 651 Ephydra, 859 Ephydridae, 786, 792, 794, 859 Epiblemidae, 639 Epiccerus imbricatus, 538 Epicauta, 497; E. cinerea, 497; E. pennsylvanica, 497; E. vittata, 496 Epicnaptera americana, 732 Epicnemium, 887 Epidermis, 31 Epicranial suture, 37 Epicranium, 38 Epilachna borealis, 512; E. corrtipta, 512 Epimartyria auricrinella, 593; E. par- della, 593 Epimerum, 51 Epinotum, 887 Epipharynx, 46 Epiphysis, 576 Epiplemidae, 583, 587, 708 Epipleurae, 74 Epiponinae, 966, 973 Epipyropidae, 582, 610 Epipyrops barberiana, 610; E. anomala, 610 Episternum, 51 Epistoma, 779 Epithelium, 109, 118; of mid-intestine, 112 Epitrix cucumeris, 533 Epizeuxis lubricalis, 685 Epochra canadensis, 858 Epomidiopteron, 953 Erannis tiliaria, 671, 672 Erastriinae, 68g Erax apicalis, 841 Erax, wing of, 841 Erebinae, 685 Erebus agrippina, 26 Erebus odor a, 685, 686 Eretmoptera broumi, 802 Ericerus pe-la, 441 Eriococcinae, 450 Eriococcus araucaria, 444 Eriocraniidae, 581, 584, 593 Eriosoma americana, wings of, 414 Eriosoma lanigera, 421 Eriosomatinae, 420; gall-making, 422 Eristalus, wing of, 851; E. tenax, 851 Ermine-moths, 632 Erotylidae, 472, 474, 509 Eruciform, 184 Erythroneura comes, 406, 407 Erythrothrips arizonce, fore wing of, 344 Estigmene acrcca, 701, 702 Ethmia, 625 Ethmiidae, 582, 590, 625 Euchatias egle, larva, 701 Eucharinae, 942, 944 Euchloe geniitia = Anthocharis genutia, 748 Euchromiidae, 583, 587, 706 Eucinetidas, 472, 505 Euclea delphinii, 609; scales of, 571 Eucleidae, 582, 586, 608 Euclemensia bassettella, 634 Eucnemidag, 472, 502 Eucoilinas, 934 Eucone eyes, 141 Eucosmidae, 639 Euctheola rugiceps, 520 Eudeilinia herminiata, 711, 712 Eudule mendica, 669; wings of, 667 Euglenidce, 475, 499 Eugonia j-album, 756 Eulia pinatubana, 643 Eulonchus, wing of, 837 Eulophinae, 941, 942, 947, 948 INDEX 1041 Eumenes, 971; E. fraternus, 971 EumeninEe, 966, 969 Eunica, 751 Euparagia, 967 Enj-aragiinae, 966, 967 Eupelereria magnicornis, 872 EupelmiJae, 941 Eupelminas, 946 Euphoria, 521; E. inda, 521 Euphorinas, 919 Euphydryas phaeton, 752 Euplectrus platyhypencE, 948 Eitproctis chrysorrhiva, 682 Eiipsalis minuta, 536 Eupterotidce, 583, 587, 707 Euptoieta daudia, 751, 752 Eurema eider pe, 749; £. nicippe, 749 Eurosta solidaginis, 627, 858 Eurrhypara urticata, 649 Eurycyttarus confederata, 614 Eur'ygaster alternatus, 393 Eurymus eurytheme, 748; £. philodice, 748 Enryophthalmus succindus, 386; heme- lytron of, 385 Eurypauropidae, 20 Eurypauropus ornatus, 19; £. spinosus, 19, 20 Eurystethidce, 474, 498 Eurystethus subopaciis, 498 Eurytoma, 946 Eurytomids, seed-infesting, 946 Eurytominse, 942, 945 Euscelis exitiosus, 406 Euschemon rafflesia, 733 Eusternum, 52 Euthisanotia grata, 693; £. 7on'o, 693 Euthrips citri, 345; £. fuscus, 345; £. ^y?*^', 345; -E- /rzVia, 345 Eiivanessa antiopa, 753, 755 Evania, 950; £. appendigaster, 950; wings of, 950 Evaniidte, 890, 892, 911, 949 Evanioidea, 890, 949, 950, 978 Evening primrose moth, 695 Everes comyntas, 772 Evergreen nepytia, 671 Evetria, 640; E. comstockiana, 640; £. friistrana, 640 Evoxysoma vitis, 945 Exarate pupae, 190 Exetastes, 923 Exner, S., 141, 143 Exuviae, 171 Eye-cap, 576 Eyed brown, 762 Eyes of insects, two types of, 134; with double function, 143 Fabre, J. H., 516, 954 Face, 779 Facial depression, 780 Facialia or facial ridges, 780 Fairy flies, 948 Falcicida hehardi, 244 Fall webworms, 702 Falx, 877 Felt, E. P., 814, 815, 816 Femur, 57 Fenestra, 274 Feniseca, 772; F. tarqidnius, 422, 772 Ferris, G. F., 875, 876 Ferton, Ch., 967 Fibula, 62 ; of Corydalus, 63 Fidia longpipes, 531 Fielde, Miss A., 955 Fiery hunter, 479 Fig-eater, 522 Fig-insects, 943 Figitinae, 934 Filaria bancrofti, 810 Filariasis, 810 Filiform, 41 Fiorinia fiorinic, 455, 456 Fire-brat, 223 Firefly Familv, 491 Fish-flies, 286 Fish-moth, 223 Fixed hairs, 31, 573 Flannel-moths, 606 Flannel-moth, crinkled, 606 Flat-headed apple-tree borer, 503 Flat-footed Flies, 848 Flask-like sense-organ, 131 Flea-beetles, 532 Fleas, 877; antennae of, 878; head of, 878; broken-headed, 881; unbroken- headed, 881 Fletcher, Miss P. B., 997 Flower-beetles, 520 Flower-beetle, hermit, 521; rough, 521 Fluvicola, 504 Follicular epithehum, functions of the, 159 Folsom, J. W., 43, 47, 226 Fontanel, 274 Fontanelle, 274 Footman-moths, 699, 704 Footman, banded, 705; clothed-in- white, 705; painted, 705; pale, 705; footman, striped, 704; footman, two- colored, 705 Forbes, S. A., 419, 611 Forbes, Wm. T. M., 465, 577, 579, 589, 617- 750 Ford, Norma, 941 Fore-intestine, 108, 109 Forel, 955 Forester, eight-spotted, 697 ; Langton's, 698 Foresters, 697 Forficula auricidaria, 463 1042 AN INTRODUCTION TO ENTOMOLOGY Forked fungus-beetle, 513 Formica exsectoides, 963; F. sanguinea, 963, 964; F.fusca, 963 Formicidae, 108, 891, 893, 911, 917, 954 Formicinae, 958, 963 Fossores, 978 Four-footed Butterflies, 750 Fox, W. J., 954. 982, 983. 985. 989 Fracker, S. B., 579, 625 Fracticipita, 880, 881 Franklin, H. J., 1003, 1004 Frenatae, 582, 596; Aculeate, 582; Generalized, 582, 597; Non- Aculeate Generalized, 582; Specialized, 582 Frenulum, 61 Frenulum-conservers, 583; Frenulum- losers, 583 Frenulum hood, 61 Frenulum-hook, 597 Friese, H., 989 Frison, T. H., 996 Frit-fiy, European, 860 Fritillaries, 751 Fritillary, great spangled, 751; gulf, 764; variegated, 751 Frog-hoppers, 402 Frons, 877 Front, 37, 780; so-called, 780 Frontalia, 780 Frontal lunule, 775, 780; orbits, 780; suture, 776, 780; triangle, 780; vitta, 780 Fronto-clypeus, 780 Froth-glands of spittle insects, 102 Fruit-tree ugly-nest tortricid, 643 Fucellia, 864 Fulgoria candelaria, 409 Fulgoridae, 400, 408, 978 Fungus-gnats, 810; wings of, 811 Fungus weevils, 536 Funicle, 41 Furc£e, 98 Furcce maxillares, 332 Furcula, 228 Furrows of the wing, 73 Gage, S. H., 444 Gahan, J., 88 Galerita janus, 480 Galesus, 932, 965 Galgulidse, 388 Galgulus, 368 Gall-aphid, vagabond, 424 Galleria mellonella, 650 Galleriinas, 650 Gall-flies, 936 Gall-gnats, 813; wing of, 814 Gallicolae, 434 Gametes, 809 Gamogenetic eggs, 416 Ganonema americana, 568 Garden-flea, 229 Gartered plume, 653 Gaster, 888, 955 Gasteruptiidae, 892, 908, 917, 930, 965 Gasteruption incerius, wings of, 930 Gastric caeca, 112 Gastrophilidea, 787, 792, 864 Gastrophilus, 865; G. equi, 865; G. hcEinorrhoidalis, 866; G. intestinalis, 865; G. nasalis, 866; wing of, 865 Gaurax, 860 Gelastocoridae, 356, 357, 368 Gelastocoris ocidatus, 368 Gelechiidae, 582, 590, 625 Gelis, 928 Genacerores, 447 Genae, 39, 780, 877; so-called, 780 Geniculate, 41 Genital appendages, the development of the, 201 Genital claspers, 76 Genitalia, 76 Genovertical plates, 780 Geometridae, 583, 584, 587, 589, 663 Geometrids, 662; green, 665 Geometrinae, 663, 670 Geometroidea, 583, 662 Geomyzidae, 786, 792, 861 Geophilus flavidus, 21 Georyssidae, 474, 505 Georyssiis, 505 Geotrupes, 517 Germarium, 158 Gerridae, 356, 357, 370 Gerris conformis, 371 Giraud, J., 967 Glands, 98; connected with setae, 99 Glandular hairs, 33 Glenurus, 304 Glischrochiiis (Ips) fasciatus, 508 Glossina morsitans, 194, 873 Glossosoma americana. Case of, 561 Glover's scale, 457 Glow-worms, 165 Glutops, 833 Glycobius speciosiis, 527 Glyphipterygidce, 582, 590, 633 Glyphipteryginae, 633 Glyphip'teryx, 633; G. thrasonella, wings of, 633 Glypta rufiscutellaris, 926 Glyptocombus saltator, 374 Glyptometopa, 952 Gnathochilarium, 16 Gnophrrla latipennis, 698, 699 Gnorimoschema gallcpsolidaginis, 627 Goat-weed, butterfly, 761 Goera calcarata, 569; case of, 569 Goldenrod-gall, round, 858 Golden-eyed-flies, 300 INDEX 1043 Gomphmes, 318 Gomphus descriptus, wings of, 318; wings of naiads of, 317 Gonapophyses, 76, 232, 895 Gonatopiis, 978 Gonin, J., 199 Goniodes styUfer, 336 Goniozus, 965 Goniurus proleus, 736 Gooseberry fruit worm, 652 Gortyna immanis, 691 Gossamer- winged butterflies, 768 Gould, W. R., 955 Graber, V., 146, 149, 150 Gracilaria, wings of, 618 Gracilariida?, 582, 589, 591, 617 Gradual metamorphosis, 175 Graham, S. A., 466 Grain- weevils, 540 Granary- weevil, 541 Grape-berry moth, 640 Grape flea-beetle, 533 Grape-leaf skeletonizer, 605 Grape leaf-folder, 646 Grape root-worm, 531 Grape-seed chalcid, 945 Grape-vine epimenis, 693 Grasshopper, lubber, 257; western, 254 Grasshoppers, cone-headed, 239; leaf- rolling, 240; long-horned, 234; meadow, 238; shield-backed, 239; shorthomed, 252 Grassi, B., 157, 172 Grayling, 762; blue-eyed, 762; dull- eyed, 763; hybrid, 763; sea-coast, 763 Greenbottle-fly, 870 Grimm, O., 192 Ground-beetles, 478 Gryllacrinae, 235, 240 Gryllidae, 234, 242 Gryllinse, 243 Grylloblatta campodeiformis, 268 Grylloblattidae, 215, 268 Gryllotalpa borealis, 251; chirp of, 93; G. hexadactyla, 251 Gryllotalpinse, 243, 250 Gryllus, 83, 248; ventral aspect of the meso- and metothorax of, 98; G. assimilis, 248; G. assimilis luctuostis, 248; G. assimilis pennsylvanicus, 248; G. domesticus, 248, 249 Guenther, K., 132 Guest gall-flies, 936 Guilbeau, B. H., 102, 403 Gula, 39 Gynandromorph, 156 Gypona, 408 Gyponinag, 407 Gypsy moth, 682 Gyretes, 484 Gyrinidae, 470, 484 Gyrinus, 484 Gyropidae, 337 Habrosyne scripta, 709, 710 Hadeninae, 694 Hadronolus, 9^3 Hadwen, S., 86V Hcematobia irritans, 873 Hasmatopinidse, 349 Hccmatopimis asini, 349; H. euryster- nus, 349; H. suis, 349 HcBmatopis grataria, 666, 667 Hcematosiphoji inodorus, 378 Hcemorrhagia diffinis, 661 ; H. thysbe, 661 Haemozoin, 808 Hagen, H. A., 113, 171 Hag-moth, 609 Hair-streaks, 769 Hair-streak, banded, 769; olive, 769; white-m, 770; purple, 770 Halictus, 986, 995; nest of, 995; H. humeralis, 996 Haliplidas, 470, 481 Haliplus, 481, 482 Halysidota, sp., wings of, 699 Halobates, 372; H. micans, 372; H. sericeus, 372 Haloptiliidae, 620 Halteres, 59 Haltica chalybea, 533 Halysidota caryce, 704; larva, 703 Hanianielistes spinosus, 426, 427 Ham-beetle, red-legged, 493 Hamilcara, 603 Hammar, A. G., 125, 126 Hamuli, 61, 885 Handlirsch, A., 260, 262, 263, 284, 289 Handmaid moths, 675 Hansen, H. J., 23, 24, 43 Hapithiis agitator, 245 Haploa, 700; H. contigua, 700 Haploptilia, 620 Harlequin milk-weed caterpillar, 701 Hannolita, 945; //. grandis, 945; II. tritici, 945 Harpaliis caliginosus, 480; head of, 468; labium of, 45, 52; prothorax of, 468 Ilarrisiiia americana, 605 Hartman, C. G., 970 Harvestmen, 9 Hatching of young insects, 171 Hatching spines, 171 Hautsinnesorgane, 130 Hawk-moth, bumblebee, 661 Hawk-moths, 655; larva of a, 577 Head, 36 Headlee, T. J., 823 Head measurements of larvae, 173 1044 AN INTRODUCTION TO ENTOMOLOGY Hearing, organs of, 145 Heart, 121 Hebridffi, 356, 358, 359, 372 Hebrus, 373 Hecabolinag, 920 Heel-fly, 868 Hegner, R. W., 816, 817 Helichus lithophikis, 504 Heliconiinae, 750, 764 Heliconius charitonius, 764 Helicopsyche borealis, 569 Heliocharis, base of wing of, 322 Heliodinidae, 582, 591, 634 Heliothis obsoleta, 695 Heliothrips fasciatiis, 345; H. hcemor- rhoidalis, 345 Heliozelidse, 582, 591, 622 Helix, 1000 Hellula undalis, 648 Helodidae, 472, 505 Helomyzidffi, 786, 790, 854 Heloridas, 890, 909, 931 Helorus paradoxus, 931 Hemelytra, 59, 350 HemcrobiidEe, 284, 294 Hemerobius, 301; larva of, 297; H. hnmuli, wings of, 295 Hemerocampa, 679, 680; H. leiicosligma, 680; H. plagiata, 681; H. vetusta, 681 Hemileuca maia, 720; H. olivice, 721 Hemimeridas, 269, 463 Hemimeriis boitvieri, 463; H. talpcides, 463; H. deceptus, 463; H. vicinus, 463; H. advectns, 463; //. vosseleri, 463; H. sessor, 463; //. hanseni, 269, 463 Hemimctabola, 179 Hemimetabolous, development, 178 Hemiptera, 212, 213, 214, 215, 216, 350 Hemispherical scale, 453 Hemiteles, 928 Hemitelini, 928 Hemitheinag, 663, 665 Hendel, Fr., 794, 856, 862 Henicocephalus, culicis, 384 Henneguy, L., 117, 124 Heodes epixanthe, 770; /f. heteronea, 770; H. hypophlaas, 771; H. tkoe, 771; wings of, 768 Hepialid, wings of a, 62 Hepialidffi, 581, 584, 594, 595 Hepialus, 595 Hermininae, 685 Herrick, G. W., 379 Hesperia, 737; H. iessellala, 737 Hesperiidas, 583, 734 Hesperiinse, 735 Hesperioidea, 589, 732 Hesperoctenes longiceps, 379 Hesperophylum heidemanni, 377 Hesse, R., 136, 137, 139 Hess, W. N., 146, 147, 148 Hessian-fly, 818 Hetcerina, 324; base of wing of, 323 Helerocampa bilineata, 676; larva, 676; H. guttivitta, 677; H. varia, 677 Heterocera, 581 Heteroceridas, 474, 505 Heteroceriis, 505 Heterocordylus malinus, 376 Heterogamy, 177, 415 Heteropezinse, 815, 816 Heteroptera, 209, 350 Hewitt, C. G., 202 Heymons, R., 174, 354, 398, 399 Hexagenia, 312 Hexapoda, 26 Hexapoda, sub-classes and orders of, 211; table of orders, 212 Hickory-borer, painted, 528 Hickory horned devil, 717 Hicks, B., 155 Hill, C. C, 889 Hilton, W. A., 128, 129, 132, 133 Hind-intestine, 108, 112 Hinds, W. E., 341, 342 Hine, J. S., 554, 830 Hippiscus apicnlatus, 258, 259 Hippoboscidae, 108, 787, 790, 874 Hispopria foveicollis, 88 Histeridas, 470, 490 Histoblast, 195, 205 Histogenesis, 204 Histolysis, 204 Hochreuter, R., 155 Hoeck, P. P. C., 1 1 Hofer, B., 127 Hog-caterpillar of the vine, 659 Holcocera, wings of, 629 Holland, W. J., 739 Holmgren, E., 99, 280 Holometalsola, 180 Holomctabolous development, 180 Holorusia rubiginosa, 197 Holosphyriim boreale, 250 Homaledra sabalella, 629, 630 Homochronous heredity, 181 Homologizing of the sclerites, 35 Homoptera, 209, 211, 212, 215, 394 Honey, 1007 Honey-bee, 158, 992, 1005; African, 876 Honey-bees, stingless, 992 Honey-pot, 1003 Hood, J. D., 965 Hooded owlets, 694 Hook-tip moths, 711 Hoplismenns, 929 Hoplopsyllus anomalus, 882 Hop-merchant, 756 Hop-plant borer, 691 Hop-vine deltoid, 685 Hormaphidinae, 424 INDEX 1045 Hormaphis hamamelidis, 425 Hormiinae, 920 Hornet, giant, 977; white-faced, 977 Hornets, 975 Hornia, 997 Horn-fly, 873 Horn-tails, 890, 894, 898 Horse-flies, 829 Horse-guard, 988 Horseshoe-crabs, 8 House-fly, 872; larva of the, 202 Howard, L. O., 807, 872, 965 Huber, P., 955 Hiibner, J., 620 Hubner's Tentamen, 581 Human flea, 882 Humeral, angle, 60; callus, 783; cross- vein, 71; suture, 274; veins, 74 Hump-backed Flies, 847 Hungerford, H. B., 361, 364, 365 Hutchison, R. H., 873 Huxley, T. H., 40 Hyblcea puera, 655 Hybl£Eida5, 583, 586, 655 Hybrid purj^le, 758 Hydrometra, 373; H. australis, 373; //. martini, 373; H. wileyi, 373 Hydrometridae, 356, 357, 373 Hydrophilidse, 471, 473, 485 Hydrophilus, 486; egg sac of, 170; em- bryo of, 76; maxilla of, 44; H. obtusatiis, 486 Hydrophylax aqidvolans, 949 Hydropsyche, 562; net of, 562 Hydropsychidse, 560, 562 HydroptilidjE, 559, 560, 561 Hydrous, 486; H. triangnlaris, 486 HylEeidffi, 890 Hylmis, 890 Hylastinus obsciirus, 542 Hylemyia antiqua, 864; H. brassier, 863; H. rubivora, 864 Hymenopharsalia, 908 Hymenoptera, 108, 210, 211, 213, 214, 884 Hymenopterous wing, typical, 885 Hypatus bachma^ini, 766, 767 Hypeninae, 685. Hypena humnli, 685 Hyperaschra stragula, wings of, 674 Hypermallus villosiis, 528 Hypermetamorphosis, 191 Hyphantria ciinea, 702 ; H. textor, 702 Hypocera incrassata, 848 Hypodernia bovis, 867; H. lineatum, 867, 868 Hypodermal structures, 95; glands, 98 Hypodermis, 29 Hyponomeutidas, 631 Hypopharynx, 47, 400 Hypopleura, 783 Hypoprepia fucosa, 705; H. miniata, 704 Hypoptinae, 603 Hypopygium, 75 Hyporhagus, 514 Hyposoter fugitivus, 927 Hypothetical tracheation of a wing of the primitive nymph, 63 Hypothetical type of the primitive wing-venation, 62 Hypsopygia costalis, 649 Hyptia, 950 Hyslop, J. A., 501 Ibaliinas, 934 Icerya, 449; I. piirchasi, 449, 512 Ichneumon-flies, 922 Ichneumonidae, 890, 892, 894,908,915, 917, 922 Ichneumoninffi, 923, 924, 928 Ichneumonoidea, 917 Ichneutinae, 920 Ichneumon idtimus, 929 ; /. mendax, 929 mice unifasciata, 705 Imaginal disc, 195, 205 Imago, 191 Imperforate intestines, 108 Imperial-moth, 717 Incisalia niphon, 770, 753 Incisurae, 447 Incomplete metamorphosis, 178 Incurvariidae, 582, 589, 590, 598 Incurvariinae, 598 Indian-meal moth, 651 Inner margin of wing, 60 Inocellia, 289 Inostemminae, 933 Inquilines, 936, 952 Insects, 26 Instars, 172 Integricipita, 880, 881 Intercalary veins, 69 Interfrontalia, 780 Intermediate organ, 152 Internal anatomy, 94 Internal organs, the transformations of the, 204 Internal skeleton, 95; sources of the, 95 Intersegmental plates, 40 Intima, 109, 117 Invaginations of the body-wall, 95 lo-moth, 722 Iphiclides marcellus, 743 Iridomyrmex hnmilis, 962 Isabella tiger-moth, 702 Ischnocera, 337 Ischnopsyllidae, 881 Ischnopsyllus, 878 Isia isabella, 702 Isley, D., 970 Jsogenus sp., wings of, 329 1046 AN INTRODUCTION TO ENTOMOLOGY Isometopidse, 356, 359, 374 Isometopus pulchellus, 375 Isoptera, 209, 211, 213 Isorhipis nificornis, 931 Isosoma, 940 Ithobalus, 741 Ithycerus noveboracensis, 537 Ithytrichia confusa, 562 Itonididas, 813 Itoplectis conquisitor, 925 Jahsus perclavalus, 388; /. spinosus, 388 Janet, C, 87 Janus integer, 901 Japanese beetle, 519; Laboratory, 520 Japygidae, 224 Japyx, 161, 220, 224; /. solifiigus, 220; ovary of, 222, 461 Jigger, 883 Johannsen, Oskar A., 803, 807, 811, 823 Johnston, Christopher, 152 Johnston's organ, 152 Joint- worms, grass and grain, 945; wheat, 945 Jones, P. R., 342 Judeich and Nitsche, 116 Jugatas, 581, 584, 592 Jugates, haustellate, 593 ; mandibulate, 592 Jug-builders, 971 Jugular sclerites, 40 Jugum, 61 ; of a hepialid, 63 Julia butterfly, 764 Julus, 16 June-beetle, green, 522 June-bug, 515, 518, 522 Juniper web-worm, 643 Karschomyia vihurni, 814 Katepimerum, 51 Katepistemum, 51 Katydid, chirp of the, 93; angular winged, 237; northern bush-, 237; round-winged, 237; Uhler's, 237; the false, 236 Kellicott, D. S., 692 Kellogg, Vernon L., 100, 197, 199, 200, 336, 573, 828 Kelp-flies, 864 Kenyon, F. C, 18, 19 Kermes, 454, 455, 634; K. ilicis, 441 Kermesiinae, 454 Kieffer, J. J., 815, 817, 931, 932, 934, 950, 965, 979 King-crabs, 8 Kinsey, A. C, 939 Kirby and Spence, 97 Kirkaldy, G. W., 362 Knab, F., 807 Korschelt and Heider, 203 Kowalevsky, A., 202 Krecker, F. H., 443 Lahena, 930 Labenini, 923 Labia minor, 460, 462 Labial palpi, 46 Labidomera clivicollis, 531 Labium or second maxillae, 45 Labrum, 38, 43 Lac-dye, 441 Lace-bud, hawthorn, 384 Lace-cocoon, suspended, 632 Lace-like cocoon, 188 Lacewing-fiies, 299 Lacinia, 45 Lac-insect, 440 Lacosoma arizonicum, 713; L. chiridota, 714 Lacosomidje, 583, 585, 587, 712 Lady-bugs, 511, 512; bean, 512; nine- spotted, 512 Lcelitis trogodermatis, 965 Lcertias philenor, larva, 741 LcEtilia coccidivora, 652 Lagoa crispata, 606, 607 Lagriidai, 474, 514 Lake-flies, 312 Lamellate, 41 Lamellicorn beetles, 515; leaf-chafers, 518; scavengers, 516 Lamellicornia, 468, 469; the families of the, 475 Lamiinae, 528 Lampronota, 923 Lampyridas, 473, 491 Landois, H., 91 Languria, 510; L. mozardi, 510 Lantern-fly of Brazil, great, 408 Lapara bombycoides, 658 Lappet-caterpillars, 729, 731; ameri- can, 732; larch, 731; velleda, 731 Larder-beetle, 506 Larentiinas, 663, 666 Large-intestine, 113 Larrinae, 981 Larrini, 980, 981 Larvae, adaptive characteristics of, 181 ; the different types of, 183; the term defined, 180 Lasioderma serricorne, 515 Lasiocampidag, 583, 589, 728 Lasius, 451, 964; L. americaniis, 419; L. niger americanus, 964 Laspeyresia interstinctana, 641 Lateral conjunctivae, 35 Laternaria phosphorea, 408 Lathridiidae, 473, 511 Latzel, R., 19, 21, 23, 24 Larentiinae, 663, 666 INDEX 1047 Leach, W. E., 174, 347 Leaf-beetles, 530 Leaf-beetles, long-horned, 530 Leaf-chafers, shining, 519 Leaf-hoppers, 406; apple, 407; de- structive, 406; grape-vine, 406 Leaf-insects, 260 Leaf-miner, morning-glory, 616 Leather-jackets, 709 Lebia grandis, 480 Lecaniinae, 451 Lecaniiim, 445; L. hesperidum, 451, 452 Legionary or Visiting ants, 958 Legs, 56; the development of, 197 Leiby, R. W., 889 Leidy, 955 Lema tnlineata, 530 Leng, C. W., 467 Lentigen layer, 138 Leon, N., 354 Leopard-moth, 603 Lepidoptera, 213, 214, 215, 216, 571; frenate, 582; metamorphosis of, 577 Lepidosaphes, 445; L. gloverii, 457; L. pinncBformis, 456, 457; L. ulmi, 457 Lepisma saccharina, 48, 78, 223 Lepismatidae, 223 Leptidas, 834 Leptinidae, 470, 487 Leptinillus aplodontia, 487; L. validus, 487 Leptinotarsa decenilnieata, 531 Leptinus testaceus, 487 Leptoceridae, 559, 560, 566 Leptocerus ancylns, 566; case of, 566 Leptocoris trivittatus, hemelytron of, 389 LeptofanidcE, 941 Leptophlebia, 312 Leptopsyllidae, 881 Leptothorax emersoni, 961 Leptysma margimcollis, 257 Lepyronia quadrangularis, 403 Leria, wing of, 855 Lestes rectangidaris, wing of, 321, 322 Lestremia, wing of, 816 Lestremiinffi, 813, 815, 816 Lethocertis, 366; L. americanus, 366; head of, 352 ; last segment of beak of, 354 Leucocytes, 122 Leucopis, 862 Leucospidinae, 942, 947 Leucospis affinis, 947 Lihellula luctuosa, 316 LibelluHdae, 318, 321 Libytheinse, 750, 766 Lice, true, 347; jumping plant-, 410 Lienard, V., 125 Ligament of the ovary, 159; of the testes, 162 Light-organs, 164 Limacodidae, 608 Lime-tree winter-moth, 671, 672 Limnobates, 373 Limnophilidae, 559, 560, 568 Limnophilus combinatus, 568; case of, 569 Limnoporus, 371 ; Z.. rufoscuHllatus, 371 Limulus Polyphemus, 8 Lincecum, 955 Lingula, 438 Lingua, 47 Lingiiatida, 14 Linguatulids, 14 Linnaeus, 206, 252 Linognathiis pilijerus, 349; L. vituli, 349 Liotheidffi, 337 Liparid^, 679 Lipoptena depressa, 875 Lis pa, wing of, 863 Lissonota, 923 LithocoUetis , 618 LithosiincC, 586, 704 Lloyd, J. T., 559, 564, 567, 570, 649 Lloydia, 923 Locust borer, 527 Locust, Boll's, 258; Carolina, 258; clouded, 257; coral- winged, 258; red- legged, 256; Rocky Mountain, 254; seventeen-year, 402 Lociista viridissima, 128 Locustidas, 234, 252 Locustinffi, 253, 254 Locusts, 252; band- winged, 257; north- em green-striped, 257; pigmy, 259; slant-faced, 259; spur-throated, 254 Lomamyia, 298 Lonchcea, 856; L. polita, 856 Lonchaeidas, 786, 791, 856 Lonchoptera, 846; wing of, 846 Lonchopteridae, 786, 789, 846 Long-beaks, 766 Long-horned beetles, 524 Longistigrna caryce, 418 Longitudinal veins, 64 Long-legged flies, 843 Louse, body-, 348; crab-, 349; dog-, 349; head-, 348; hog-, 349; horse-, 349; long-nosed ox-, 349; short' nosed ox-, 349 Louse-fiies, 874 Loxostege similalis, 648 Lubbock, J., 18, 48, 106, 955 Lucanidce, 475, 523 Lticanus dama, 523 Lucanus elaphiis, 523 Lncilia ccesar, 870 Luna-moth, 723 Lyccena argioliis, 753, 771 Lycaenidffi, 584, 739, 768 Lycidae, 491 1048 AN INTRODUCTION TO ENTOMOLOGY Lycomorpha pholns, 707 Lycorini, 923 Lyctidas, 471, 51 5 Lyggeidse, 357, 359, 386 Lygidea mendax, 377 Lygris diversilineata, 668, 669 Lygiis pratensis, 376 LymantriidEe, 583, 584, 588, 679 Lymexylidee, 473, 493 Lymexylon navale, 493 Lymncecia phragmitella, 629 Lynchia, wing of, 874; L. americana, 875 Lyonet, P., 104, 105, 106 Lyonetiidse, 582, 589, 591, 616 Lyreman, 401 Lyroda suhita, 982 Lysiognatha, 922 McAtee, W. L., 241 McClendon, J. F., 300 McCook, H. C, 955 MacGillivray, A. D., 446, 458, 886 Machilidae, 222 Machilis, 220; mandibles of, 220; ovary of, 222; M. alternata, 174; M. ommatidium of, 139; leg of, 57; ventral aspect of, 77; tracheae of, 116, 117 Mclndoo, N. E., 155 Macrobasis, 497; M. tmicolor, 497 Macrocentrinae, 922 Macrocentrus, 919; Macrocentrus ancy- livorus, 922; Af. gifnensis, 922 Macrocephalus, 383 Macrochaetas, 779 Macrodactyliis siihspinosus, 519 Macrofrenatae, Specialized, 583, 655 Macrojugatae, 594 Macrorileva, 945 Macrovelia harrisii, 370 Macroxyela, 886; wings of, 896 Macroxyela distincta, 896 Maia-moth, 720 Malacosoma americana, 729, 730; M. calif ornica, 731; M. consiricia, 731; M. disstria, 730; M.fragilis, 731; M. pluvialis, 731 Malar space, 887 Malarial Infection, 808 Malloch, J. R., 823, 824, 848, 953 Mallophaga, 211, 214, 335 Malpighian vessels, 113; as silk- glands, 113 Mammal-nest beetles, 487 Mandibles, 43 Mandibular sclerites, 353, 398 Manidiidae, 583, 587, 673 Mansonia, 810; M. perlurhans, 810 Mantidas, 234, 262 Mantis religiosa, 263 Mantispa, 290; hypermetamorphosis of, 290; M. styriaca, 290 Mantispidas, 289 Mantoidea, 262 Manubrium, 228 Many-plume moths, 653 Maple-borer, beautiful, 527 Maple-leaf cutter, 598 Marchal, P., 431, 815 March-flies, 820 Marey, 81 Marginal accessory veins, 69 Marginal cells, 886 Margins of wings, 59, 60 Marlatt, C. L., 398 Masarinae, 966, 967, 989, 993 Mass provisioning, 979 Mathcson, R., 481, 505 Maxillae, 43 ; cross-section of, 576 Maxillary, palpus, 44; pleurites, 40; sclerites, 353, 398; tentacle, 599 Maxillulae, 16, 43 May-beetle, heart of a, 121 ; leg of a, 106 May-beetles, 515, 518 Mayer, A. G., 572 Mayer, A. M., 154 May-flies, 308, 3*12 May-fly, metamorphosis of, 311; wings of a, 70 Meadow-browns, 761 Meadow-maggots, 799 Meal snout-mouth, 649 Meal-worm, 513 Mealy-bugs, 448, 450 Measuring-worms, 662 Mechanical sense-organs, 130 Mecoptera, 210, 211, 213, 214, 215, 550 Media, 64 Medial cross- vein, 71 Median, caudal filament, 78; furrow, 74; line, 575; plates, 55; segment, 49, 908; sutures, 35 Medio-cubital cross- vein, 71 Mediterranean flour-moth, 651 Meek, W. J., 398, 399 Megachile, 947, 999; Af. latirnanus, nest of, 999 Megachilidae, 891, 893, 914, 990, 999 Megalodachne, 509; M. heros, 510; M. fasciata, 510 Megalomus mastus, wings of, 296 Megaloptera, 284 Megalopyge opercularis, 607; cocoon of, 189 Megalopygidae, 582, 585, 606 Megamelus notula, antenna of, 409 Megaphasma dentricus, 262 Megaprosopidae, 787, 793, 869 Megaprosopus, 869 Megarhyssa lunator, 925; M. atrata, 925; M. nortoni, 925; M. greenei, 925 INDEX 1049 Megaspilinae, 909, 933 Megastigmus, 943 Megathymidae, 583, 733 Megathymus, 733; M. streckeri, 733, 734; M. yucca, 734 Meigen, J. A., 794, 813 Meinert, 347 Melalopha, 678; M. inclusa, 678 Melander, A. L., 339, 340, 845, 856, 861, 862 Melandryidae, 474, 475, 514 Melanin granules, 808 Melanoplus, 160; ental surface of the jileurites of the meso- and meta- thorax of, 96; head of, 97; tentorium of, 97 Melanoplus hivittatus, 255, 256; M. differentialis, 256; M. feinur-riibrum, 254, 256; M. spretiis, 254 Melissodes, 990 Melittia satyrinifonnis, 637 Mellinus, 980 Mellitobia, 948 Meloe, 497; M. angiisticollis, 498 Meloidse, 109, 475, 495 Melolontha vulgaris, larva of, 185 Melon-worm, 647 Melophagus ovinus, 194, 874 Melsheimer's sac-bearer, 713 Melyridae, 473, 493 Membracids, 400, 404, 978 Membrane, 350 Mentum, 46 Mercer, W. F., 196 Merian, Maria Sibylla, 408 Merope, 550, 551, 553; M. tuber, 553 Merozoits, 809 Merragata, 373 Mesenteron, 108, iii Mesochorini, 924, 927 Mesochorus, 927 Mesogenacerores, 447 Mesoleiini, 926 Mesoleptideini, 926 Mesonotum, 50 Mesophragma, 97 Mesopleura, 783 Mesothorax, 48 Mesovelia douglasensis, 372; M. mul- santi, 372 Mesoveliidae, 356, 358, 372 Mestra, 751 Metacalus, 926 Metallic wood-borers, 502 Metal-mark, large, 767; small, 767 Metameres, 34 Metamorphosis of insects, 166 Metanotum, 50 Metaphragma, 97 Metapleura, 783 Metapneustic, 115 Metathorax, 48 Meteor us, 919 Methoca stygia, 953 Methocinffi, 913, 916, 953 Metopiini, 926 Metopius, 926 Metrobates, 371; M. hesperius, 371 Miastor americana, 816 Microbembex monodonta, 988 Microbracon, gig Microcentrum, 237; M. retinerve, 2yi; M. rhombifoliiim, 236, 237 Microdon, 851 Microfrenatce, Specialized, 582, 610; families of, 589 Microgaster, 921 Microgasterinae, 921 Microlepidoptera, 610 Microplitis, 921 Micromalthidse, 473, 494 Micromalthus debilis, 494 Micromus, 297 Micropezidas, 786, 791, 858 Microphthalma, 869; M. disjuncta, 869 Micropterygida;, 575, 581, 584, 592 Microvelia, 370 Micropteryx, wings of, 593 Micropyle, 167 Midges, 802 Mid-intestine, 108, in Migrants, 435 Milichiidaj, 786, 792, 862 Milk-glands, 875 Milkweed-beetles, red, 529 Milkweed Butterflies, 765 Milkweed butterfly, reproductive or- gans of the, 160; transformations of the, 187 Millers, 580 MiUipedes, 15 Milne-Edwards, 47 Mindarinas, 419 Mindarus, 419; M. abietinus, 420 Mineola vaccinii, 652 Miridas, 356, 358, 359, 375 Mischocyttarus, 974; M. cubensis, 974; M. flavitarisis, 974; M. labiatus, wings of, 973 Miscogasterinas, 941, 942, 947 Miscophus, 982 Misgomyia, 833 Mites, 9 Mitoura damon, 753, 769 Mnemonica auricyanea, 594; M. wings of, 594 Mocha-stone moths, 678 Mocsary, A., 952 Mogoplistinse, 243, 250 Molanna angustata, 558 Molanna, case of, 566 1050 ^A^ INTRODUCTION TO ENTOMOLOGY MolannidEe, 559, 560, 566 Molting fluid, 172; glands, 99 Molting of Insects, 171 Mompha eloisella, 630 Monarch, the, 765 Monarthrum mali. Gallery of, 544 Moniliform, 41 Monobia qiiadridens, 971, 972, 998 Monochamus notatiis, 528 Monodontomerns, 943 Monommidce, 474, 514 Monothalamous, 935 Mononyx, 368 ; AI. fuscipes, 368 Monophlebinas, 449 MonotomidEe, 473, 509 Mordellidae, 475, 494 Mordwilkoja vagabiinda, 424 Morgan, Miss A. H., 70, 311 Morgan, T. H., 426 Morrill, A. W., 438 Morris, H. M., 848 Mosaic vision, theory of, 141, 142 Mosher, Miss Edna, 580 Mosquitoes, 804; antennae of, 153 Moth, pupa of a, 580 Moth-like Flies, 801 Moth-like fly, wing of, 80 Moths, 571 Mourning-cloak, 755 Mouth-parts, 42; the development of, 200 Mucrones, 228 Mud-daubers, 984 Mufflehead, 691 Muggenburg, F. H., 876 Muir and Kershaw, 398 Muller, Fritz, 181 Muller, J., 141 Muller 's organ, 149 Murgantia histricnica, 391 Murmidiidas, 474, 511 Mnsca domestica, 872 Muscidae, 787, 793, 872; development of the head in the, 202 Muscids, 852; typical, 872 Muscles, 104 Muscoidea, 787 Museum pests, 507 Music of flight, 80 Musical notation of the songs of in- sects, 92 Musical organs of insects, 78 Mutillidae, 891, 894, 909, 913, 915, 916, 950, 953, 954 Muttkowski, R. A., 320, 323 Mycetasidae, 474, 511 Mycetobia, 798 Mycetophagidae, 472, 474, 510 MycetophiHdce, 785, 788, 793, 810, 813 Mydaidas, 786, 788, 842 Mydas, wing of, 842 Myiasis in man, 871 Myiomma cixiiformis, 375 Mylabridae, 475, 535 Mylahris obtectus, 535; M. pisorum, 535 Mymarinae, 941, 948, 949 Myodaria, 786, 852 Myriapoda, 15 Myrientomata, 24 Myrmecia, wings of, 74 Myrmecocystus, 964, 965 Myrmecomorphus, 915 Myrmecophila pergandei, 249 Myrmecophilinas, 243, 249 Myrmeleon immaculatus, 304; Myr- meleon, wings of, 304 Myrmeleonidae, 284, 303 Myrmica brevinodis, 961; stridulating organ of, 87 Myrmicinas, 958, 960 Myrmosa, 953; M. unicolor, 953 Myrmosinae, 913, 916, 953 Myrmosula, 953 Mystacides sepidchralis, 567; case of, 566 Mytilaspis citricola, 456; M. pomorum, 457 Nabidag, 356, 358, 380 Nabis, 380; A^. ferus, 380; N. subco- leoptratus, 380 Nagana, 873 Naiad, the term defined, 179 Nassonow, N., 549 Nasuti, 277 Nathalis iole, 749 Naucoridse, 356, 357, 367 Naupliiform, 185 Necrobia rufipes, 493 Necrophorus, 487 Needham, J. G., 112, 178, 312, 313, 317, 807 Needham and Lloyd, 561 Neelidse, 229 Neelus, 229 Neides muticus, 388 Neididae, 357, 359, 388 Nemestrinidse, 786, 789, 836 Nemobius, 84, 242, 248, 982; A^. fas- ciatus, 249; N. palustris, 249 Nemocera, 785, 795; N. Anomalous, 785, 820; N. the true, 785, 795 Nemognatha, 498 Nemonra sp., wings of, 329 Nemouridae, 330 Neoconocephalus, 239; N. ensiger, 239 Neohermes, 288; A'', calif ornicus, 288 Neoneurinae, 920 Neophylax, 569 Neoscleroderma tarsalis, 965 Neoteinia, 194 Neoxabea, 245; A^. bipunctata, 245 Neoxyela alberta, 896 INDEX 1051 Nepa apiculata, 364, 365 Nepidag, 356, 357, 364 Nepticulidae, 582, 589, 600 Nepytia semidusaria, 671 Nerthra, 368; N. stygiea, 368 Nerves, 123 Nervous system, 123 Nestling birds, parasites of, 870 Netelia, 923 Net-winged midges, 824 Neuronia, 565; lateral aspect of the mesothorax, 57; N. postica, 565 Neuropore, 130 Neuroptera, 207, 209, 211, 213, 215, 281; N. mantis-like, 289; N. mealy- winged, 307 Neurotoma inconspicua, 897 Newcomer, E. J., 326 Newport, G., 106 New York weevil, 537 Nidi, 112 Niggers, 511 Night-eyes, 143 Nigronia, 288; TV. fasciatus, 288; N. serricornis, 288 Nininger, H. H., 996 Nitidulid£E, 470, 472, 473, 508 Noctuid moth, Diagram of a fore wing of a, 575 Noctuidae, 583, 586, 588, 683 Noctuids, 583, 683 Nodal furrow, 74 Nolinae, 705 Nomia patteni, 954 Nomophila noctuella, wings of, 645 Nosodendridas, 471, 508 Nosodendron, 508 NotauU, 887 Notched-wing geometer, 672 Notiothaiima, 551 Notodontidae, 583, 587, 674 Notolophiis, 679, 680; N. antiqua, 681 Notonecta, 363 Notonecta undidata, 362 Notonectidas, 356, 357, 362 Notopleura, 782 Notopleural suture, 782 Notostigma, 22 Notoxus, 498 Notum, 49 Noyes, Miss Alice A., 563, 564 Nurse-bees, 1006 Nurse-cells, 158 Nycteribiidae, 787, 794, 875 Nymph, the term defined, 176 Nymphalidffi, 584, 739, 750 Nymphalinas, 750 Nymphon hispidum, 11 Nymphs, 750 Nymphulinae, 648 Nyssonini, 980, 986 Oak-apples, 937; large, 937; large empty, 938; smaller empty, 938 Oak-bullet gall, 938 Oak-coccid blastobasid, 629 Oak-gall, giant, 938 Oak hedgehog gall, 936 Oak-leaf miner, white-blotch, 618 Oak-pruner, 528 Oak-slug, spiny, 609 Oak ugly-nest tortricid, 643 Oak- worm, orange-striped, 718; rosy- striped, 718; spiny, 718 Oberea bimacnlata, 529 Oblique vein, 319 Obriissa ochrefasciella, Wings of, 574, 601 Obtected pupse, 191 Occiput, 39, 780, 877 Ocellar triangle, 780; plate, 780 OcelH, 134, 135 Ochteridae, 356, 357, 368 Ochterus, 368; 0. americanns, 369 Ochthiphilidae, 786, 791, 862 Ocular sclerites, 39 Odonata, 180, 212, 213, 314 Odontaidacus, 929 Odontoceridae, 560 567 Odontomachus, 959 Odontomerini, 923 Odo?itomerus , 923 Odontomyia, puparium of, 831 Odynerus, 970, 971; 0. geminus, 970; O. tropicalis, 970; O. birenimaculatus, 971 Qicanthinas, 243 CEcanthus, 84, 85, 86, 242, 245; table of species, 246; (E. argentinus, 246; CE. calif amicus, 246; CE. nigricornis, 247; CE. niveus, 93 CEciacus vicarius, 378 CEcophoridas, 582, 590, 624 ffidemeridae, 474, 494 CEdipodinae, 253, 257 CEneis katahdin, 764; CE. semidea, 763 Qinochrominse, 663, 664 QJnocytes, 163 Oesophageal, sympathetic nervous sys- tem, 125, 127; valve, iii Oesophagus, no CEstridai, 787, 792, 866 CEstrus ovis, 867 Ohr-Wurm, 460 Oiketiciis abboti, 613 Oinophilidae, 582, 589, 617 Olene, 680 Olethreutidffi, 582, 590, 639 Olfactory pores, 131, 154; pore of Mclndoo, 155 Oligotoma saundersi, fore wing of, 339 Ommatidium, 135; structure of, 139 Omophronidae, 470, 481 1052 AN INTRODUCTION TO ENTOMOLOGY Omiis, 478 Oncometopia, 407; O. undata, 407 Onion maggot, 864 Oniscoida, 7 Ontholestes, cingulatus, 489 Onychii, 58 Onychophora, 4 Oocyst, 809 Ookinete, migratory, 809 Ootheca, 170; of a cockroach, 264 Operculum, 438 Ophion, 927 Ophioninse, 924, 927 Opostega, 617 Opostegidse, 582, 589, 617 Opthalmochlus diiryi, 547 Oral hooks, 201 Orange-tips, The, 747; falcate, 748; olympia, 748 Orasema viridis, 941 Orbicular or round spot, 575 Orbits, 780 Orchelimum, 238; O. vulgare, 238 Orchesella, 229 Oreta rosea, wings of, 712 Organs of sight, 130 Ormenis, 410; O. septentrionalis, 410 Ormyrinae, 942, 943 Ormyrus, 943 Orneodes hexadactyla, 653; 0. htthneri, 653 Orneodidse, 583, 584, 653 Orocharis sallator, 245, 965 Orphnephilidas, 828 Ortalidas, 786, 791, 856 Orthezia, 102, 448, 450 Ortheziinse, 450 Orthoptera, 212, 214, 215, 230 Orthopteroid insects of uncertain kin- ship, 267 Orthorrhapha, 785, 794; short-horned, 828 Oryssidse, 891, 905, 907 Oryssus, 894, 906; ovipositor of, 906; O. abietinus, wing of, 906; O. occiden- talis, 907; O. sayi, 905 Osborn, H., 337, 349 Oscinidae, 860 Oscinis frit, 860 Osmeteria, 101 Osmia, 993, 1000 Osmoderma eremicola, 521; O. scabra, 521 Osmyhdas, 109 Osmylus hyalinatus, wings of, 68, 69 Ostia of the heart, 121 Ostomidae, 472, 508 Othniidae, 474, 498 Othnius, 498 Otiocerus, 409; O. coqnebertii, 409 Otiorhynchinae, 538 Oudemans, J. T., 117, 880 Outer margin, 60 Ovarian tubes, 157, 158 Ovaries, 156 Oviduct, 156, 159 Ovigerous legs, II Ovipara, 416 Oviparous, 191 Ovipositor, 76 Owlet-Moths, 683 Ox-warble-flies, 867 Oxybelini, 980, 989 Oxybelus, 989 OxyptUus periscelidactylus , 653 Oyster-shell scale, 457 Pachysphinx modesta, 657 Pachypsylla celtidis-mamma, 411 Packard, A. S., 149, 189 Packardia geminata, Wings of, 609 PcEcilocapsus lineatus, 375, 376 Paedogenesis, 192, 816 Paedogenitic, larvae, 192; pupae, 192 Painted beauty, 754 Palae, 361 Palaeodictyoptera, 210, 211 Palseostracha, 8 Paleacrita vernata, 671 Palloptera, 856 Palmetto-leaf miner, 629, 630 Palpicomia, 467, 469 Palpifer, 44 Palpiger, 46 Palpognaths, 21 Pamniegischia, 929 Pamphila sassacus, wings of, 738 Pamphiliidae, 890, 891, 897 Pamphilinae, 737 Pamphilius, persicus, 897; wings of, 67, 898 Pankrath, 137 Panorpa, 552; Head of, 550; wings of, . 551 Panorpodes, 553 Pantarbes capita, wing of, 838 Paniographa limata, 646, 647 Pantomorus fulleri, 539 Papilio glaucus, 742 ; larva, 742 ; glaucus glaucus, 742; glaucus turnus, 74.2; polyxenes, 74.1 ; larva, 742; win^s of, 740; P. thoas, 173; larva of, 101; P. zolicaon, 742 Papihonidas, 583, 739, 740 Papilionoidea, 589, 739 Papilioninae, 740 Papirius, 229 Paraclemensia acerifoliella, 598, 599 Parafacials, 780 Parafrontals, 780 Paraglossae, 43 Paragnatha, 43; of Machilis, 221 INDEX 1053 Paralechia pinifolieUa, 626, 627 Parallelia bistriaris, 689 Parandra, 469, 524, 525; P. brunnea, 526 Paraphyses, 448 Paraprocts, 232 Parapsidal furrows, 887 Parapsides, 51, 887 Paraptera, 51 Parasites, Respiration of, 120 Parasitoid, 919 Parasymmiclus claiisa, wing of, 836 Paratenodera sinensis, 263 Paratiphia, 953 Parcoblatta pennsylvanica, 266 Parectopa robin iella, 620 Parharmonia pini, 637 Parker, J. B., 988 Pamassiinse, 744 Parnassius, 744; P. sminth.eiis , cross- section of scales of, 572 Parsnip web worm, 624 Parthenogenesis, 889, 919 Paraxenos eberi, Wing of, 548 Parornix, 618 Passalidse, 475, 524 Passalns cornutiis, 524; stridulating organ of a larva of, 89 Patagia, 50, 576 Patch, Dr. Edith, 422, 432 Paurometabola, 176 Paurometabolous development, 175 Pauropodidee, 20 Pauropoda, 18 Patiropus huxleyi, 18 Paxylommatinse, 919, 920 Peach sawfly, 897 Peach-tree borer, 636; lesser, 636; Pacific, 636 Peach twig-borer, 627 Pear-blight beetle, 545 Pear-midge, 820 Pear-slug, 904 Pea-weevil, 535; family, 535 Peckham and Peckham, 957, 970, 981, 982 Pecten, 628 Pectinae, 448 Pectinate, 41 Pectinophora gossvpiella, 628; wings of, 626 Pedicel, 41 PediHdce, 475, 498 Pegomyia hyoscyami, 864 Pelecinidae, 890, 892, 909, 932 Pelecinellidas, 941 Pelicinus polyturator, 932 Pediculidae, 348 Pediculns, capitis, 348; P. corporis, 348 Pe-la, 441 Pelidnota punctata, 519 Pelobius, 120 Pelocoris, 367; P. femoratus, 367 Pelogonus, 368 PelopcEus, 984 Peltodytes, 481, 482 Pemphigus acerfolii, 422 Pemphredonini, 980, 984, 985 Penis, 162 Pentastomida, 14 Pentatomidae, 103, 357, 359, 390 Penthe, 514; P. obliquata, 514; P. pimelia, 514; prothorax of, 53 Penthima americana, 408 Pentozocera auslralensis, 547 Pepsis, 951 Perceoreille, 460 Perez, J., 92 Pericardial, cells, 164; diaphragm, 163 Pericopidae, 583, 588, 698 Perilampinae, 942, 944 Perilampus hyalnius, 940, 941 ; P. chrysopce, 944 Peripatoides nova-zealandiccc, 4 Peripatus, i, 4 Peripheral sensory nervous system, 128, 129 Periplaneta americana, 266; P. orien- tal is, 107, 127 Peripneustic, 115 Peripodal, cavity, 197; membrane, 197 Peristome, 780 Peritoneal membrane, 109 Peritremes, 52 Peritrophic membrane, 111, 112 Perkins, R. C. L., 979 Perlidae, 328 Peterson, A., 341 Petiole, 955 Petroleum-flv, 859 Pettit, R. H', 365 Phaeogenini, 928 Phceoses sabinella, 617 Phagocyte, 164, 204 Phagocytic organs, 164 Phagocytosis, 164, 204 PhalacridiE, 472, 511 Phalonia rutilana, 643 Phaloniida;, 582, 590, 639, 643 Phanceus, 517; P. carnifex, 517 Phaneropterinae, 235, 236 Phanurus beneficiens, 933 Pharynx, 109 Phasgonuridae, 234 Phasiidae, 787, 793, 868 Phasma, 121 Phasmidas, 234, 260 Phasmoidea, 260 Pheidole pilifera, 960 Phengodidas, 473, 492 Pheosia rimosa, 674 1054 AN INTRODUCTION TO ENTOMOLOGY Philagraula, yog Philanthini, 980, 986 Philopotamidae, 559, 560, 563 Philopteridae, 337 Philosamia waLkeri, 727 Phlebotomus, 802; P. vexator, 802 PhloeothripidEe, 346 Phobelron pitheciiim, 609, 610; larva, 610 Pholisora, 737; P. catullus, 737 Pholus pandorns, 660 Phojiapate, 88 Phora, wing of, 848 Phoresy, 933 Phoridas, 786, 789, 793, 847 Photimis marginellus, 165 Photurus pennsylvanicus, 165 Phragmas, 97 Phryganea, 565; P. pilosa, pupa of, 558; P. veslita, 565 Phryganeidae, 559, 560, 564 Phryganeids, Cases of, 565 Phryganidia californica, 673 Phthirius pubis, 349 PhthorophlcEus liminaris, 542, 544 Phyciodes, 752; P. Iharos, 752 Phycitinaj, 651 Phycodromida;, 786, 791, 855 Phygadeuonini, 928 Phyllium, 261 ; P. scythe, 262 Phyllonorycter , 618; P. cincinnatiella, 619; P. hamadryadella, 618, 619 Phyllophaga, 518 Phylloscyrtus ptdchellus, 244 Phyllotreta vittata, 532 Phylloxera, 433; gall-inhabiting form, 436; gall of, 434; grape, 433; root- inhabiting form, 435, 436; P. vas- tatrix, 433; wings of, 429 Phylloxeridae, 400, 428 PhylloxerinEe, 433 Phymata, 383; P. erosa, 383 Phymatida^, 356, 358, 382 Physocephala affinis, wing of, 853 Physonota unipunctata, 534 Phytodietus, 923 Phytomyza aquilrgice, 861 ; mine of, 861 Phytophaga, 468, 469; families of the, 475 Phytophaga destnictor, 818 Pickle-worm, 648 Pieces jugulaires, 40 Pierce, W. Dwight, 548, 549 Pierida; 584, 739, 744 Pieris napi, 747; P. protodtce, 747; wings of, 745; rapes, 746 Piesnia cinerea, 385 Piesminae, 385 Pigeon horn-tail, 899 Pigment cells, accessory, 138, 140; iris, 140 Piliferous tubercles of larvae, 35 Pill-beetles, 508 Pimpinella integerrima, 631 Pimpla, 925 Pimplinae, 923, 924 Pimplini, 925 Pinacate-bugs, 513 Pinconia coa, 606 Pine clear-wing moth, 637 Pine-cone willow gall, 817; guest, 817 Pine-leaf, miner, 627; scale, 458; tube- builder, 643 Pine-pest, Zimmermann's, 652 Pine-twig moths, 640 Pinipestis zimmermanni, 652 Piophila casei, 858 Piophilida?, 786, 792, 858 Pipunculidae, 786, 790, 849 Pipunculiis, 849; wing of, 850 Pistol case-bearer, 620 Planidium, 941 ; of perilampus, 940 Planta, 578, 991 Plant-lice, 412; jumping, 410 Plasma, 122 Plasmodium, 808 Plastoceridae, 473, 499 Plates, 4.48 Plathemis lydia, 314 Platygaster iieimales, 889 Platygasteridae, 890, 909, 915, 933 Platygasterinae, 933 Plathypena scabra, 685 Platv'peza, wing of, 849 Platypezidae, 786, 789, 848 Platypodidae, 476, 541 Platypsyllidas, 470, 486 Platypus, wilsoni, 541 Platysomidag, 476, 536 Plea, 364 Plecoptera, 136, 209, 211, 213, 325 Pleura, 34 Pleiu-ites, 35 Pleurostigma, 21 Plodia inter punctella, 651 Plum-curculio, 539 Plume-moths, 652 Plum web-spinning sawfly, 897 Plusiinae, 687 Plutella maculipennis, 632 PlutelHdse, 582, 589, 591, 632 Pocock, R. I., 17, 21 Podagrion, 943 Podalirius, 890 Podical plates, 232 Podisus, 391; P. maculiventris , 391 Podura aquatica, 229 Poduridae, 115, 228 Polistes, 546, 972; nest of, 974; P. lineatus, 974 Polistinae, 966, 974 Pollen brushes, 991 INDEX 1055 Pollenia rudis, 870 Polyblastus, 926 Polycentropidce, 559, 560, 563 Polycentropus, 564 Polychrosis viteana, 640 Polyctenidse, 356, 379, 359 Polyembryony, 168, 889, 946 Polyrgiis, 964; P. Incidus, 964 Polyformia, 467, 469 Polygonia, 756 Polygon ia comma, 753, 756; P. comma comma, 757; P. comma dryas, 756; P.faiin::s, 753, 756; P. interrogationis, 753, 757; progne, -jzi Polymitarcys, 312 Polyphaga, 467, 468, 485 Polyphemus-moth, 722 Polysphmctini, 923, 925 Polystcechotes punctatus, 299; P. vit- tatus, 299 Polystcechotidas, 284, 298 Polythalamous, 935 Polyxenus, 16, 17 Pomace-flies, 860, 861 Pomocerus aquatica, ommalidium of, 225 PompiHdas, 890, 893, 912, 916, 950, 951 Ponerinae, 958, 959 Pontia rapcE, 195 Popillia japonica, 519 Poplar-leaf gall aphid, 424 Popoff, 398 Pore-plate, 131 Porocepkalus, P. annulatus, 14; P. proboscideus, 14, 14 Porthetria, dispar, 682 Postalar callus, 783 Postantennal organ, 227 Postcubital cross- veins, 319 Postembryonic molts, number of, 172 Posterior arculus, 72 Posterior lobe, 778; of the wing, 61 ; of the pronotum, 887 Postgenacerores, 447 Postgenffi, 39, 781 Postnodal cross- veins, 319 Postnotum, 50 Postpetiole, 955 Postphragma, 98 Postscutellum, 50 Poststernellum, 52 Powder-post beetles, 515 Praetarsus, 58 Praon, 922 Pratt, H. S., 874 Praying mantes, 262; eggs of, 170 Prealar callus, 783 Preanal area, 75 Preanal lobe, 888 Preaxillary excision, 888 Preepistemum, 51 Pregnacerores, 447 Prepectus, 887 Prephragma, 98 Prepupa, 185 Prescutum, 50 Presternum, 52 Presultural depression, 783 Pricer, 955 Primary ocelli, 135; structure of, 137, 138 Primitive weevils, 536 Primordial germ-cells, 158 Prionid, straight-bodied, 526 Prioninffi, 525 Priononyx, 987 Prionoxystus macmurtrei, 603; P. ro- binice, 603; wings of, 70, 596, 602 Prionns, broad-necked, 526; P. ini- bricornis, 526; P. laticollis, 526 Pristaulacus, 929 Prociphilus imbricator, 422; P. tessel- latus, 421, 422 Proctodseum, 108 Proctotrupes, 932 Proctotrupidae, 108, 890, 910, 916, 931 Proctotrupoidea, 890, 931 Prodoxinee, 599 Prodoxus, 600 Progrediens type, 431 Progressive provisioning, 979 Projapygidae, 224 Projapyx, 224 Prolabia pidchella, 463; P. burgessi, 462 Prolegs of larvae, 78; the development of, 182 Prolimacodes badia, 610 Promethea-moth, 725 Prominent, two-lined, 676 Prominents, 674 Pronotum, 50 Prcnuba yuccasella, 599 Prophragma, 97 Propleura, 782 Propneustic, 115 Propodeum, 49, 887, 908 Propolis, 1007 Propupa, 343 Propygidium, 75 Prosimuliiim hirtipes, 824 Prosopidse 890,891 893,914,992,993 Prosopinee, 914, 993 Prosopis, 890, 990, 991, 992, 993 Protapteron, 218 Prothorax, 48 Protocalliphora, 870; P. avium, 870; P. splendida, 870 Protocerebrum, 47, 124 Protoparce qumquemaculata, 658; pupa, 659; wings of, 656; P. sexta, 659 1056 AN INTRODUCTION TO ENTOMOLOGY Protoplasa, 796; P. fitchii, 796; P. vanduzeei, 796; P. vipio, 796 Protosialis americana, 286 Protura, 218 Proventriculus, no, 111 Psacaphora termineUa, 630 Psammocharidae, 890 Psectra, 294; P. diptera, 294 Pselaphidae, 470, 489 Pseninse, 984 Psenini. 981, 984, 985 Psephenidae, 471, 503 Psephenus, 503; P. lecontei, 504 Pseudagenia, 951 Pseudococciis citri, 451; P. (Dacty- lopius) destructor, eyes of, 443; P. longispinosiis, 451; wing of, 442 Pseudocone eyes, 141 Pseudo-cubit US-one, 301 Pseudo-halteres, 59 Pseudohazis, 721; P. eglanterma, 721; P. hera, 721 Pseudomasaris, 967, 968, 969; P. vespoides, 968; nests of, 969 Pseudo-media, 301 Psetidomyrma, 959 Pseudomyrminse, 958, 959 PseudophyllinEe, 235, 238 Pseiidothyatira cymatophoroides, 710 Pseudova, 191, 416 Psila roscE, 859 Psilidas, 786, 792, 859, 890 Psilogaster fasciiventris, 941 Psilopa petrolei, 859 Psilopodins sipho, wing of, 844 Psilotreta frontalis, 567 ; case of, 567 Psithyrus, 993, looi, 1002, 1004 Psocid, wings of, 332 Psocidas, 333 Psocids, 331 Psychida;, 582, 584, 585, 586, 613 Psychodidffi, 785, 787, 801 Psychomorpha epimenis, 693 Psychomyidae, 560, 564 Psyllia, floccosa, 410; pear-tree, 41 1 ; P. pyricola, 411 Pterodontia flavipes, 8^7; P. misella, 837 Pteromalinae, 941, 942, 947 Pteromalns puparum, 947 Pterombus, 953 Pteronarcella, 328; P. hadia, wings of, 328 Pteronarcidae, 328 Pteronarcys, 120, 328; head of, 136; P. dorsata, 325 Pteronidea rihesi, 903; P. trilineata, 903 Pterophoridae, 582, 584, 652 Pterophylla camellifolia, 237, 238 Pteropleura, 783 Pterostigma, 74, 327 Pterygogenea, 206 Pterygota, 211, 230 Ptilinum, 190, 776, 781 Ptinidas, 47 1, 514 Ptiniis fur, 514 Ptychopteridas, 785, 787, 796 Pulex irritans, 882 PulicidEE, 882 Pulsations of the heart, 122 PulviUi, 58 Pidvinaria, 453; P. acericola, 453; P. innumerahilis , 170; P. vitis, 453 Punkies, 803 Pupa, 186; of a beetle, 466 Pupae, active, 187; the different types of, 190 Puparium, 190, 815 Pupipara, 193, 873, 876 Pycnogonida, 10 Pygidial area, 888 Pygidium, 75, 445; diagram of a, 446, 447 Pyralididae, 582, 585, 587, 644 Pyralidinae, 649 Pyralidoidea, 582, 644 Pyralids, 582, 644; aquatic, 648; typ- ical, 649 Pyralis farinalis, 649 Pyrausta nubilalis, 648 Pyraustinae, 646 Pyrochroidae, 475, 498 Pyromorpha, 604; P. dimidiata, 604; wings of, 605 ; P. marteni, wings of, 605 Pyromorphidag, 582, 585, 586, 604 Pyrrhocoridee, 357, 359, 385 Pyrrhopygin£E, 735 Pythidae, 474, 498 Quadrangle, 322 Queen, the, 766, 1006 Radial cross- vein, 71 Radicicolas, 434 Radio-medial cross- vein, 71 Radius, 64 Ramphocorixa acuminata, 362 Ranatra fusca, 365 Range-caterpillar, New Mexico, 721 Raphidia, 289 Raphidiidae, 289 Raphidioidea, 289 Raspberry fruit-worm, 510; geometer, 665 ; root-borer, 636 Raspl3erry-cane maggot, 864 Rasping organs, 87 Rat-flea, Indian, 882 Rath, O. vom, 132 Rat-tailed maggots, 851 Rau and Rau, 951, 970 Reaumur, R. A. F. de, 572, 876 Rectum, 113 INDEX 1057 Red admiral, 754 Red-bug, 385; apple-, 376; false apple-, 377; hop- 377, Red-humped apple-wcrm, 677 Redikorzew, W., 137 Red-necked agrilus, 503 Red spotted purple, 758 Reduviidae, 356, 358, 380 Reduvius personatus, 381 Regal-moth, 716, 717 Regions of the body, 36 Re i chert el I a collaris, wing of, 821 Reighardia, 14 Reniform spot, 575 Repletes, 964 Reproduction of lost limbs, 173 Reproductive organs, 156; of the fe- male, 157; of the male, 160, 161 Resin-gnat, 819 Respiratory organs, the closed or apneustic types of, 119; the open or holopneustic types of, 114 Respiratory system, 113 Resplendent shield-bearer, 622, 623 Reticulitermes, 279; R. {Leucolermes) flavipes, 278 Retina, 138 Retinodiplosis resinicola, 819 Retinula, 138, 140 Rhabdom, 137 Rhabdomere, 137 Rhabdophaga strohiloides, 817 Rhachicerus, 832; R. nilidus, 833 Rhagio, wing of, 835 Rhagionidffi, 786, 789, 834 Rhagium lineatum, 526 Rhagoletis cingtdata, 857; R. fatista, 857; R. pomonella, 857 Rhagovelia, 370; R. obesa, 370 Rhamphomyia, wing of, 845 Rhaphidop'horince, 235, 241 Rheumaptera hastata, 669 Rheumat abates, 372 Rhinoceros-beetles, 520 Rhinomacerinse, 537 Rhinopsis, 978 Rhipiceridae, 472, 499 Rhipiphoridae, 475, 494 Rhizophagidas, 472, 474, 508 Rhizophagtis, 508 Rhodites rosce, 939 Rhodophora florida, 695 Rhopalocera, 581 Rhopalomyia, 814 Rhopalosoma poeyi, 965 Rhopalosomids, 891, 913, 965 Rhyacophila, 555; R. fuscida, 555, 561; wings of, 556 Rhyacophilidse, 559, 560 Rhynchites bicolor, 538 Rhynchitinae, 537 Rhynchophora, 468, 469, 535, 537; families of the, 475 Rhynchophorns, head and prothorax of, 469 Rhysodidffi, 470, 508 Ribbed pine-borer, 526 Rice- weevil, 541 Rielia manticida, 933 Rileva, 945 Riley, C. V^, 171, 177, 187, 496, 599, 921 Riley and Johannsen, 378 Ring- joints, 41 Riodinidse, 584, 739, 767 Riper sia, 451 Ripipteryx, 252 Roadside butterfly, 748 Robber-flies, 840 Rodolia cardinalis, 511 Rohwer, S. A., 906, 907 Rolleston, 107 Root, A. I., and E. R., 1007 Root-cage, 501 Ropronia, 931 Roproniidae, 890, 909, 931 Rose-beetle, Fuller's, 539 Rose-bugs, 519 Rose-gall, mossy, 938, 939 Rose-slug, 904 Rose ugly-nest tortricid, 642 Roubaud, E., 970 Round-headed apple-tree borer, 529 Rove-beetles, 488 Royal jelly, 1006 Royal-moth, two-colored, 717 Royal-moths, 715 Ruptor ovi, 171 Sabine stimulea, 609 Sacred beetle of the Egyptians, 516 Saddle-back caterpillar, 609 Saissetia hemisphcerica, 453; 5. olea 452, 453 Saldida;, 356, 358, 369 Salivary glands, 103, 104 Saltatorial orthoptera, 177 Salt-marsh caterpillar, 701 Samia cecropia, 726; pupa, 726; cocoon, 727; wings of, 720; 5. Columbia, 726; S. gloveri, 726; 5. rubra, 727 Sand-crickets, 242 Sandflies, 803 San Jose scale, 458 Saperda Candida, 529 ' Sapromyza, 856 SapromyzidcE, 786, 791, 856 Sapygidag, 913, 952 Sarcophaga hcemorrhoidalis , 871 Sarcophagidae, 787, 793, 870 Saturniidse, 583, 719 Saturnoidea, 583, 589, 714 1058 AN INTRODUCTION TO ENTOMOLOGY Satyrinffi, 750, 761 Satyr odes canthus, 762 Saussure, H. de, 969 Saw-flies, argid, 904; cimbicid, 902; leaf-rolling, 897; stem, 900; typical, 902; web-spinning, 897; xiphydriid, 899 Sawfly, American, 902; locust, 903 Sawyer, 528 Scale-insects, 440; control of, 459 Scales of butterflies and moths, 571, 572, 573 Scalloped owlet, 686 Scallop-shell moth, 668, 669 Scape, 40 Scaphidiidse, 470, 490 Scapulas, 887 Scarabseidse, 475, 515, 954 Scarabeiform, 184 Scatophaga, 854 Scatopsida;, 785, 788, 821 Scelio, 933 Scelionidae, 890, 909, 910, 915, 933, 949 Sceliphron cementarium, 983, 984; wmgs of, 983 Scenopinidae, 786, 789, 839 Scenopinus, 840; wing of, 840; 5. fenestralis, 840 Scent-glands of females, 100 Scepsis fulvicollis, 706, 707 Schierbeek, A., 580 Schidax, 709 Schiodte, J. C, 88, 185 Schistocerca americana, 256 Schizoneura americana, 421 ; 5. pinicola, 420; S. rileyi, 421; 5. ulmi, 421 Schizont, 808 Schizophora, 786, 852 Schizopteridse, 356, 358, 373 Schizura, 679; S. concinna, larva, 677; 5. ipomece, larva, 679 Schmiedknecht, O., 929 Schneider, A., 192 Schreckensteinia erythriella, 634; 5. fes- taliella, 634 Schwabe, J., 150, 151 Sciara, eyes of, 812; wing of, 812, 813 Sciara army worm, 813 Sciaridae, 813 Sciarinae, 812, 813 Sciomyzidae, 786, 791, 855 Sclerites, 35 Scolia, 954 Scoliidae, 891, 893, 913, 954 Scoliopteryx libalrix, 686 Scolopale, 146 Scolops, 409 Scolus, 578 Scolytidse, 476, 542 Scolytns rugulosus, 544 Scopas, 991 Scorpion, 9 vScorpion-flies, 550, 552 Scorpions, lateral ocelli of, 137 Screw-worm fly, 870 Scudder, S. H., 92, 235 Scudderia, 237; S. mexicana, 237; 5. septentrionalis, 237 Scurfy scale, 457 Scutellar bridge, 783 vScutellerida;, 357, 359, 392 Scutellum, 50 Scutigera forceps, 22 Scutigerella, 24 Scutum, 50 Scydmsenidae, 470, 488 Scythrididee, 582, 592, 631 Scythris eboracensis, 63 1 ; 5. magnatella, 631 Searcher, the, 479 Seaton, Frances, 139 Second antecoxal piece, 54 Secondary sexual characters, 157 Sectorial cross-vein, 71 Segmentation of the appendages, 34; of the body, 34 Segments of the head, 47, 48 Seiler, W., 139 Semidalis aleurodiformis, 306 Seminal vesicle, 162 Sense-cones, 131 Sense-domes, 154, 155 Sense-hairs, 33 Sense-organs, classification of the, 129; cuticular part of the, 130; of un- known functions, 154 Sensillum, ampuUaceum, 131; basi- conicum, 131; chceticum, 131; coelo- conicum, 131; placodeum, 131 ;■ trichodeum, 130, 132 Sepsidae, 786, 790, 791, 858, 859 Sepsis, 858 Serial veins, 67 Sericostomatidae, 559, 560, 569 Serphidag, 890 Serrate, 41 Seryda consta7ts, scale of, 572 Setae, 32 ; classification of, 33 ; primary, 578; subprimary, 578; secondary, 578 ; taxonomic value of, 33 Setiferous sense-organs, 130 Setiferous tubercles, arrangement of, 579; types of, 578 Setodes grandis, 566; case of, 566 Sexuales, 436 Sexuparae, 435 Sharp, David, 87, 88, 89, 144, 194, 301, 505, 506, 967, 994 Sheep-tick, 874 Shellac, 441 Shull, A. F., 426 INDEX 1059 Sialidae, 284 Sialis infumata, 285, 286; larva of, 286 Sibine stiniidea, 609 Siebold, C. T. von, 92, 145 Siebold's organ, 152 Sierolomorpha ambigua, 952 SigalcESsa flaveola, 860 Signiphoridse, 941 Sight, organs of, 134 Silk-glands, cephalic, 103 Silk-Worm, 114, 727; sense hairs of the, 133 Silk-Worms, giant, 719 Silpha, 488 Silphidae, 470, 471, 487 Silvanns surinamensis, 509, 965 Silverfish, 223 Silvestri, F., 16, 25, 113 Simathis fabriciana, wings of, 633 Simuliida:, 786, 788, 821 Simulium, 120; head of larva of, 200; larva of, 1 1 1 ; wing of, 822 Simulium meridionale, 824; 5. pictipes, 824; 5. venustum, 824 Siphlurus alternatus, caudal end of abdomen of, 308 Siphonaptera, 211, 214, 877 Siphunculata, 347 Sirex juvencus, wings of, 899 Siricidae, 890, 891, 898 Sistens, 431 Sisyra flavicornis , 292; 5. umbrata, 291; larva of, 292; silk-organs of, 282, 283 Sisyridae, 284, 291 Sitodrepa panicea, 515 Sitotroga cerealella, 626 Skiff-caterpillar, 610 Skimmers, 321 Skin-beetles, 522 Skipper, least, 738; silver-spotted, 736 Skippers, 571, 583, 732; common, 734; giant, 733 Skippers with a costal fold, 735 Skippers with a brand, 737 Sladen, F. W. L., 1002, 1004 Sleeping sickness of man, 873 Slingerland, M. V., 417, 459, 644, 647 Slingerland and Crosby, 459 Slug-caterpillar moths, 608 Small-headed flies, 837 Small-intestine, 113 Smell, organs of, 132 Smeriiithiis geminatus, 657, 658 SminthuridEe, 229 Sminthurus, 115, 229; S. hortensis, 229 Smith, J. B., 398, 994, 996 Smith, R. C, 300, 302 Smoky moths, 604 Snake-flies, 289 Snipe-fUes, 834 Snodgrass, R. E., 49, 50, 55, 57, 98, 205 Snout-beetles, 535; imbricated, 538; pine-flower, 537; scarred, 538; toothed-nose, 537; typical, 537 Snout-butterfly, 767 Snow-flea, 228 Snow-flies, 799 Snyder, T. E., 280 Soldier-beetles, 492 Soldier-flies, 830 Solenobia, wings of, 615; S. walshella, 614 Solenopsis molestus, 960 Solidago gall-moth, 627 Solitary-midge, 828 Solpugida, 9 Somites, 34 Soothsayers, 262 vSooty-wing, 737 Sovereigns, the, 757 Sow-bugs, 7 Spalangidae, 941 Spathiinse, 920 Spatula, sternal, 813 Spear-marked black, 669 Spear-winged flies, 846 Spermatazoa, 160 Spermatheca, 159 Spermathecal gland, 160 Spermatophores, 162 Sphajriidas, 471, 490 Sphcrrites glabratus, 490 Spha;ritida3, 470, 490 Spharagemon bolli, 258 Sphecidse, 891, 893, 913, 979 Sphecinae, 983 Sphecini, 980 Spheciiis speciosus, 987; wings of, 987 Sphecodes, 992 Sphecoidea, 891, 931, 950, 977 Sphecoid-wasp, head and thorax of, 977 Sphecoid-wasps, 977, 978, 979; typical, 962 Sphenophorus, 540; 5. maidis, 540 Sphex, 890, 984 Sphindids, 474, 515 Sphingidae, 583, 586, 655 Sphinx, 657; chersis, 657, 658; Harris's, 658; modest, 657; pandorus, 660; pen-marked, 658; twin-spotted, 657; white-lined, 660 Sphinxes, 655 Sphyracephala brevicornis, 859 Spiders, 9 Spider-wasps, 950 Spilochalcis marice, 945 Spines, 32, 445 Spiracles, 52, 113, 114; structure of, 116 Spiracular musical organs, 91 Spirostreptus , 16 Spittle-insects, 402 1060 AN INTRODUCTION TO ENTOMOLOGY Spondylidae, 525 Spondylis, 469, 524 Spongilla-flies, 291; labia of, 293 Spongophorus ballista, 404; 5. querini, 404 Sporoblasts, 809 Sporozoite, 808, 809 Spotted pelidnota, 519 Spring azure, 771 Spring of the CoUembola, 76 Spring-tails, 225 Spuler, A., 859 Spurious vein, 70 Spurs, 32 vSquama, 778 Squamge, 60 Squash-bug, egg-mass of the, 170 Squash-vine borer, 637 Stable-fiy, 873 Stadia, 172 Stag-beetles, 523 Stagmatophora gleditschiceella, 630 Stagmomantis Carolina, 263 Staphylinidae, 470, 488 Staphylinus macidosus, 489; S. vid- pinus, 489 Stegomyia caloptis, 809; S. fasciata, 809 Stelis, 993 Stem-eyed fly, 859 Stem- mother, 415 Stenelimis bicarinatus, 505 Stenohothriis, 82 Slenogaster, 967 Stenoma, 625; S. schlcEgeri, 625 Stenomida;, 582, 591, 625 Stenopelmatinae, 235, 242 Stenopelmatus, 242; ventral aspect of the metathorax, 98 Stephanid£e, 890, 909, 917, 919 Sterictiphora, 905 Sternal spatula, 815 Sternellum, 52 Sternites, 35 Stemopleura, 783 Sternum, 34, 52 Sthenopis, 595; 5. argenteomaculatus, 596; S. pupurascens, 595, 596; S. thule, 596 Sticktight flea, 883 Sticta Carolina, 988 Stigma, 74 Stigmata, 113 Stigmus fraternus, 985; S. podagriciis, wings of, 985 Stiletto-flies, 839 Stink-bugs, source of odor, 355 Stink-flies, 300 Stink-glands, 102, 462 Stipes, 44 Stizini, 981, 987 Stizus unicinctus, 987 Stomach, iii Stomodasum, 108 Stomoxus, calcitrans, 873 Stone-flies, 325 Stone-fly, naiad of, 327 Stratiomyia, 831; wing of, 831 Stratiomyiidse, 786, 788, 830 Straus Durckheim, 40, 106, 121 Strawberry crown-girdler, 539 Streblidse, 787, 790, 794, 875 Strepsiptera, 59, 194, 211, 212, 546 Stridulating organs, 81; of corixidas, 362; of the locustidae, 82; of the gryllids and the tettigoniidae, 83; of Ranatra, 365 Strigilis, 886 Striped flea-beetle, 532 Sturtevant, A. H., 861 StyH, 56, 76, 222 Stylopidse, 109, 546 Stylopids, 546, 975; mouth-parts of male, 547 Stylus, 442 vSubcosta, 64 Subcostal fold, 73 Subgalea, 44 Subimago, 312 Submarginal cells, 886 Submentum, 46 Subnodus, 319 Subcesophageal commissure 125; gan- glion, 123, 124 Subquadrangle, 323 Subterminal band, 575 Sugar-cane, beetle, 520; borer, 650 Sulphur, cloudless, 749; dainty, 749; little, 749; orange, 748 Sumac bobs, 634 Superimposed image, 143 Superlinguse, 43, 226 Supertriangle, 319 Supplements, 70 Surpa-alar groove or cavity, 783 Supra-anal plate, 231 Supra-tympanal or subgenual organ, Suspensoria of the viscera, 162 ; thread- like, 163 Sutures, 35; the thoracic of Diptera, 782, 783 Swallow-tail, black. 741; larva, 742; tiger, larva, 742; zebra, 743 Sweet-fern geometer, 666 Sweet-potato root-borer, 538 Swifts, 594, 595 Symmerista alhifrons, larva, 676 Symphasis varia, 291 Sympherobiidse, 284, 293 Sympherobius, 294; S. amicidus, wings of, 294 Symphoromyia, 835 INDEX 1061 Symphyla, 23 Symphypleona, 229 Symphyta, 894 Synanthedo7i exitiosa, 636; wings of, 635; 5. opalescens, 636; 5. pictipes, 636 Synchloe olympia, 748 Synchlora errata, 665 Synergus erinacei, 936 Synlomidse, 706 Syrphidae, 786, 790, 850 Syrphus, 851 Syrphus-flies, 850 Systelloderus biceps, 383 Tabanidae, 786, 788, 829 Tabanus, 830; atratus, 830; wing of, 66, 829 Tachardia lacca, 440 Tachina-flies, 871 Tachinidas, 787, 793, 871 Tachininas, 871 Tachvsphex ler)iii)iatus, 981; wings of, 981 TcEiiiopleryx, 326; T. pacifica, 326 Tafalisca lurida, 245 Tanaostigmatidae, 941 Tangle-veined flies, 836 Tanyderida;, 785, 787, 796 Tanvpeza, 858 Tanypezida;, 786, 791, 858 Tapestry-moth, 612 Tapetum, 144 Tarachidia candefacta, 689 Tarantula hawks, 951 Tardigrada, 12 Tarsal claws, 58 Tarsus, 57 Taste and smell, organs of, 132 Tegeticida, 599; T. alba, 599, 600 Tegmina, 59, 230 Tegula, 54 Tela mono, 405 Telea polyphemus, ^22; larva, 723 Telenomus, 933 Telson, 75 Telson-tails, 211, 218 Tenaculum, 228 Tenagogonus, 371; T. gillettei, 371 Tenebrio molitor, 466, 513 Tenebrionidae, 474, 513 Tenebroidts maiirttanicus, 508 Tenent hairs, 58, 100, 101 Tentamen, 581, 620 Tent-caterpillars, 729; apple-tree, 729, 730; California, 731; forest, 730; Great Basin, 731 Tenthredinidae, 890, 891, 895, 902 Tentorium, 96 Terebrantia, 344 Tergites, 35 Tergum, 34 Termatophylidas, 356, 359, 377 Termes gilvus, 276 Terminal band, 575 Terminal filament, 158 Termite, queen, 276 Termites, 158, 194, 273 Termitoxinia, 156 Termopsis angusticollis, wings of , 274 Testes, 160 Testicular follicle, structure of a, 161 Tetanoceridas, 856 Tetracha, 478 Tetraneura colophoides, 424; T. gra- minis, 424 Tetraopes, 529; T. tetraophthalmus, 529 Tetrastichidse, 941 Tetrastichus asparagi, 948 Tettigoniidae, 234 Thalessa, 924 Thanaos, 737; T. viartialis, 735, 737 Thaumalea americana, 828; wing of, 828 Thaumaleidae, 786, 788, 828 Thaumatotypidea, 915 Thecabius popiilicaulis, 424 Thecla calanns, 769; T. m-album, 770 Thecodiplos'is mosellana, 819 Thereva, wing of, 839 Therevidas, 786, 789, 839 Therionini, 927 Thermobia domestica, 223 Theronia atalantce, 923, 925 Thick-headed flies, 853 Thompson, C. B., 278 Thorax, 48; diagram of, 50, 51 Thorybes datinus, 737; T. pylades, 737 Thread-waisted wasps, 983 Three-lined lema, 530 Thripidas, 344 Thrips, 341; banded, 344; bean, 345; grass, 345; greenhouse, 345; imma- ture forms of citrus-, 343; onion, 345; orange, 345; pear, 345; strawberry, 345; tabaci, 345; tobacco, 345 Throat-bot, 866 Throscids, 472, 502 Thyatiridae, 583,' 586, 709 Thynnidae, 891, 912, 916, 952 Thyreocorin^, 392 Thyreocoris ater, 392; T. pulicarhis, 392 Thyreodon atricolor, 927 Thyrididae, 583, 586, 587, 653 Thyridopteryx ephemerceformis, 614; wings of, 61, 613 Thyris lugiibris, 654; T. maculata, 654; wings of, 654; T. mournful, 654; T. spotted, 654 Thysanoptera, 178, 209, 211, 212, 215, 341 Thysanura, 211, 219 1062 AN INTRODUCTION TO ENTOMOLOGY Tibia, 57. Tibicen linnet, 401 Tibicina septendecim, 402 Tiger-beetles, 476 Tiger-moths, 699, 700; tiger-moth, hickory, 704 Tigrioides bicolor, 705 Tillyard, R. J., 300, 593 Timber-beetles, 544 Tinagma obscurofasciella, 624; wings of, 624 Tinea, 612; T. parasitella, wings of, 612; T. pellionella, 612 Tineida;, 582, 589, 590, 611 Tineola biselliella, 612 Tingidae, 357, 384 Tinginae, 384 Tipftia, 953; T. inornata, 953 Tiphiidae, 891, 893, 894, 912, 913, 916, 953 Tiphiinse, 953 Tipula, 799; T. abdominalis, larva of, 2 ; wing of, 799 Tipulidae, 785, 787, 793, 798 Tipuloidea, 785, 795 Tischeria, 615; T. malifoliella, 615; T. marginea, wings of, 615 Tischeriidas, 582, 591, 615 Tlascala reductella, wings of, 645 Tmetocera ocellana, 641 Tobacco-worm, 659 Tolype laricis, 731; T. velleda, 731 Tomato-worm, 658 Tomocerus pliirnbens, 225 Tool-using wasps, 984 Tormse, 781 Tortoise-beetles, 534 ; -scales, 45 1 ; -shell , American, 755 Tortricidae, 582, 500, 639, 642 Tortricids, 638; typical, 642 Tortricoidea, 582, 638 Tortrix, 638 Toryminffi, 943 Torymiis, 943 Touch, organs of, 131 Tower, W. L., 99, 172, 354, 573 Townes, H. K., 891, 892, 941 Townsend, Miss A. B., 165 Townsend, C. H., 872 Toxicognaths, 21 Traches, 113, 116; the structure of the, 117 Tracheal gills, 119; the development of, 182 Tracheation of wing of imago of Calosoma, 466 Tracheation of wing of imago of Dytiscus verticalis, 466 Tracheoles, 113, 118 Trachiisa lateralis, 1000 Tramea, 317 Transverse, anterior band, 575; con- junctivas, 34; cord, 326; impression, 781; posterior band, 575 Treat, Mrs., 955 Tree-hoppers, 404; buffalo, 404; two- horned, 405; two-marked, 405 Tremex colnmba, 169, 898, 899, 924; T. aureus, 899; T. sericeus, 899 Trepobates, 372; T. pictus, 372 Tricenodes, 565, 567; case of, 566 Triangle, 319 Triatoma sanguisuga, 382 Trichocera, 798 Trichodectes eqiii, 336; T. latus, 336; T. scalaris, 336; T. spherocephalus, 336 Trichodectidce, 337 Trichodes niittalli, 493 Trichodezia albovittata, 667 Trichogens, 30 Trichogramma evanescens, 949; T. mi- nutum, 949 Trichogrammatinas, 941, 949 Trichophaga tapetieUa, 612 Trichopore, 32, 130 Trichoptera, 211, 213, 555 Trichopterous Larvae, table of, 559 Prichopterygidae, 471, 490 Trichostibus parvula {Urodiis parvula), 188 Tridactylinae, 243, 251 Tridactylus, 252; T. apicalis, 252 Tridymidas, 941 TrigonalidEe, 890, 909, 917, 929 Trigonidiinae, 243 Triphelps insidiosus, 378 Trissolcus, 933 Tritocerebrum, 47, 124 Tritoxa flexa, 856 Triungulin, 495 Triungulinid, 548 Triungulins, 548 Trochanter, 57 Trochantin, 53; of the mandible, 40 Trades divinatorius, 33 1 , 333 Trogidae, 475, 522 Trogini, 923, 929 Tragus vulpinus, 929 Tropcea luna, 723, 724 Trophallaxis, 280, 958, 973 Tropidacris latreillei, 26 Tropisternus, 486; T. calif amicus, 486; T. glabra, 486 Trox, 522 Trumpet-leaf miner of apple, 615 Truxalinae, 253, 259 Trypetidae, 786, 791, 856 Tryphoninae, 923, 924, 926 Tryphonini, 926 Trypoxylon, 982; T. albitarsis, 983; T albopilosum, 982; T. frigidum, 982: T. rubrocinctum, 982, 983 ; nest of, 982 INDEX 1063 Trypoxyloninae, 982 Trypoxylonini, 980. 982, 988 Tsetse-fly, 873 Tubulifera, 345 Tumble-bugs, 516 Tunga penetrans, 883 Turkey-gnat, 824 Turner, 955 Tussock-moth, 679; California, 681; old, 681; well-marked, 681 Twisted-winged insects, 546 Two-spotted oberea, 529 Tylus, 353 Tympana, 145, 577 Typhoid-fly, 872 Udamoselis, wings of, 437 Ulidodes hyalina, 305; larva of, 306; wings of, 305 Underwings, 687 Ungues, 58 Unguiculus, 227 Unguis, 227 Urodiis parvula (Trichostibus parvula), 632 Utetheisa, 700; U. Bella, 700 Vagina, 159 Valentinia glandulella, 628 ValvulcE, 232 Van der Weele, 284, 285, 306 Van Duzee, E. P., 362, 844 Van Dyke, E. C, 498 Vanessa atalanta, 754; V. cardui, 755; V. huntera, 755; V. virginiensis, 754 Vanhornia eucnemidariim , 931 Vanhorniidffi, 890, 909, 922, 931 Van Rees, 202 Vas deferens, 156, 162 Vasiform orifice, 438 Vedalia cardinalis, 512 Velia, 370 Veliidas, 356, 357, 369 Velvet-ants, 953 Venomous setas and spines, 100 Ventral diaphragm, 163; heart, 163; sacs, 222; sympathetic nervous sys- tem, 127; tube, 227 Ventriculus, iii Verhoeff, 49 Vermiform, 185 Verruca, 578 Verson, 114, 199 Vertex, 39, 781 Vertical triangle, 781 Vespa, 975; V. arctica, 977; V. austriaca, 977; V. consobrina, 977; V. crabro, 977; V. diabolica, 9TJ\ wings of, 966; V. maculata, 977; nest of, 975, 976; V. rufa, 977 Vespidse, 108, 891, 893, 909, 912, 950, 965, 993 Vespinae, 966, 975 Vespoidea, 931, 950, 978 Vespoid-wasp, head and thorax of, 977 Vespoid-wasps, 950 Vespida, 977 Viallanes, 47 Vibrissae, 782 Vibrissal angles, 781 ; ridges, 781 Vice-reine, 760 Viceroy, the, 759 Viereck, H. L., 958 Violet tip, 757 Vipiinae, 920 Visiting ants, 958 Visual cell, structure of a, 137 Vitellarium, 158 Vitreous layer, 138 Viviparity, 192, 193 Viviparous insects, 191; adult agamic females, 192 Vogel, R., 155 Volucella, 851 Wagner, Nicholas, 192, 816 Walker, E. M., 233, 252, 268 Walking-sticks, 260 Wall-bee, looi; nests of, 1001 Wanderer, the, 772 Warble-flies, 866 Wasps, social, 972; typical, 965 Water-beetles, the crawling, 481 Water-boatmen, 360, 361 Water-bugs, giant, 365 Water-measurers, 373 Water-penny, 504 Water-scavenger beetles, 485 Water-scorpions, 364 Water-striders, 370; broad-shouldered, 369 Water-tigers, 483 Wax, 1007 Wax-glands, 102; outlets of, 445 Web worms, 648; burrowing, 611; cab- bage, 648; garden, 648 Wedge-shaped leaf-beetles, 533 Weevil, black vine-, 539; strawberry-, 540 Weevils, leaf-rolling, 538 Weisman, A., 202, 203 Wheat joint-worm, 945 Wheat-midge, 819 Wheat-sawfly-borer, 901 Wheat straw-worm, 945 Wheeler, W. M., 280, 524, 940, 941, 954, 955, 958, 961, 962, 977 Whirligig-beetles, 484 White-ants, 273 White, checkered, 747 White flies, 437 1064 ^A^ INTRODUCTION TO ENTOMOLOGY White fly, citrus, 440; greenhouse, 439; maple, 440; strawberry, 440 White, gray-veined, 747 White-gn:.bs. 518 White marked tussock-moth, 680 White Mountain butterfly, 763 White-striped black, 667 Whites, the, 745 White- tipped moth, 676 Williams, F. X., 967, 969, 981 Williston, S. W., 852 Window-flies, 839 Window-winged moths, 653 Wings, 58; the development of, 182, 195; specialization of, 212 Wings of the heart, 121, 162 Wing-veins, reduction of the number of, 65; the chief branches of the, 64; the increase of the number of, 68; the principal, 64 Winnertzia calciequina, 814 Wire-worms, 500 Witch-hazel cone-gall, 425 Witch-hazel-gall, the spiny, 426 Wohlfahrlia vigil, 871 Wollaston, 88 Wood-nymph, beautiful, 693; pearl, 693 Workers, 1005 Wyeomyia smithii, 810 Xenopsylla cheopis, 882 Xenos vesparum, 549 Xestobium rufovillosum, 515 Xiphidium, 238 Xiphosura, 8 Xiphydria maculata, wings of, 900, 929 Xiphydriidse, 890, 891, 899 Xoridini, 923 Xyelids, 890, 891, 895, 896 Xylocelia (Diodontus), 985 Xylocopa virginica, <)'J2, 998 Xylomyia, 832; X. pallipes, 832 Xylomyiidas, 786, 788, 832 Xylophagidte, 786, 789, 833 Xylophagus, 833; wing of, 833 Yellow, sleepy, 749 Yellow-bear, 703 Yellow-fever mosquito, 809 Yellow-jackets, 975, 977 Yellows, the, 748 Yponometita, 632; Y. padella, 632 Yponomeutidas, 582, 590, 591, 631 Yucca-borer, 734 Yucca-moths, 599; bogus, 600 Zale lunata, 689 Zebra, the, 764 Zebra-caterpillar, 694, 695 Zenodochiiim coccivorella, 629 Zerene cccsonia, 749 Zethinae, 966, 968 Zethus, 968; Z. cyanopterus, 969; Z. lobtdatus, 969; Z. romandinus, 969; Z. slossonce, 968; Z. spinipes, 968 Zeiizera pyrina, 603 Zeuzerinas, 603 Zophodia grossularice, 652 Zoraptera, 215, 270 Zorotypidae, 270 Zorotypus, 270; Z. huhbardi, 271; Z. snyderi, 271, 272 Zygoptera, 321