fit i K&flUUtMHWl «i MARINE BIOLOGICAL LABORATORY, Received *** No book or pamphlet is to be removed from the Lab- oratory without the permission of the Trustees. ru m Di l! a a o m a f ' : INTRODUCTION TO ZOOLOGY INTRODUCTION TO ZOOLOGY^/ A GUIDE TO THE STUDY OF ANIMALS FOR THE USE OF SECONDARY SCHOOLS BY CHARLES BENEDICT DAVENPORT, PH.D. ASSISTANT PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF CHICAGO DIRECTOR OF THE BIOLOGICAL LABORATORY OF THE BROOKLYN INSTITUTE OF ARTS AND SCIENCES, LOCATED AT COLD SPRING HARBOR, LONG ISLAND AND GERTRUDE CROTTY DAVENPORT, B.S. FORMERLY INSTRUCTOR IN ZOOLOGY AT THE UNIVERSITY OF KANSAS WITH THREE HUNDRED AND ELEVEN ILLUSTRATIONS ^® ^ — LIBRA ao gork THE MACMILLAN COMPANY, -vA LONDON: MACMILLAN & CO., LTD. 1900 All rights reserved COPYRIGHT, 1900, BY THE MACMILLAN COMPANY. Nortoooti J. S. Cushing & Co. — Berwick & Smith Norwood Mass. U.S.A. PREFACE THE general plan of this text-book is at the same time both old and new. Old, because it attempts to restore the old-time instruction in Natural History ; new, because "Natural History" is not to-day what it was a genera- tion ago. The treatment will seem new also in contrast with modern text-books of zoology, since they are devoted primarily to comparative anatomy, a field upon which we lay little stress. This departure is the outcome of a conviction that the needs of the secondary student are not best met by a course in comparative anatomy. That conviction is not altered by the circumstance that anatomy is fundamental for advanced work in zoology and physiology, for only a sixth of the secondary students go to college, and proba- bly less than four per cent of them continue their zoologi- cal work there. The vast majority of secondary students, then, are not to be zoologists, but rather men of affairs. What the ordinary citizen needs is an acquaintance with the common animals that may be the companions of his country walks, and that may even stray into Wall Street, Dearborn Street, or Commonwealth Avenue. He wants to know where else over the world the common animals of his State are to be found and, as a legislator or as a taxpayer, he wants to know how animals affect man. It is more important for him to know these matters than to know the location of the pedal ganglion of the snail, or vi PREFACE to be able to recite the various ingenious hypotheses of the ancestry of echinoderms. Our conviction is, we feel sure, the common conviction of college teachers of zoology, who have often occasion to deplore the ignorance that their students show about common animals. It is the conviction of many other thoughtful men also who have recognized that an interest in nature is a powerful agent in making men more moral, more capable of appre- ciating the world they live in, and of finding satisfaction in living. The aim of the book is indicated by its title. It is not a treatise on the modern science of zoology. It is a guide to the study of animals, which it is hoped may introduce many students to the sciences of comparative anatomy, comparative embryology, cytology, general physiology, variation and inheritance, and the others that are grouped under "zoology." This book is like a " Synoptic Room ' in the vestibule of a vast museum, containing the most essential things for those who can go in but a little way, but also fundamental for those who can penetrate farther. The illustrations of this book have received especial at- tention. An attempt has been made to give a lifelike figure of a representative of almost every family mentioned in the text. For courteous permission to reproduce the copied figures we are deeply indebted to many publishers and authors. We have to thank the authorities of the Field Columbian Museum for original photographs, Figs. 301, 302, and 305. Mr. H. W. Menke, of the same institution, kindly gave us permission to use his interesting photo- graphs of live rattlesnakes, Figs. 261, 262. To Mr. V. H. Lowe, Entomologist of the New York State Agricultural Station at Geneva, N.Y., we are indebted for the photo- PREFACE Vll graphs marked V. H. L. ; these are published by permis- sion of the Director of the Station. The majority of the original photographs, designated by the initials W.H.C.P., were made by Mr. William H. C. Pynchon, Instructor in Biology at Trinity College, Hartford. All of these, ex- cepting Figs. 183, 184, 188, and 203, are photographs of animals occurring around the Biological Laboratory at Cold Spring Harbor, Long Island. They have thus a cer- tain scientific value as indicating the fauna of that region. As many of these figures are from living animals, probably never before photographed in their natural attitudes, their publication may be considered as something of a contribu- tion to science. Of the other photographs, Figs. 31 a, 122, 276, 281, and 288, marked D. and S., were contributed by Professor N. F. Davis of Bucknell University, Lewisburg, Penn., and Mr. Ernest A. Sterling of the same institu- tion; and Figs. 127, 251, and 259 were contributed by Mr. E. R. Downing, graduate student at the University of Chicago. The figures of birds by Louis Agassiz Fuertes have been reproduced from " Citizen Bird," by Mrs. Wright and Dr. Coues, published by the Macmillan Company. Figures of the types used in the outline of laboratory work have been purposely avoided. Finally, the authors have to thank several secondary teachers who have kindly made suggestions and helpful criticisms on the outline of laboratory work and the main text. AVe solicit a continuance of these favors to the end that this book may become as perfectly adapted as pos- sible to the needs of secondary instruction in zoology. C. B. DAVENPORT. GERTRUDE C. DAVENPORT. CHICAGO, May 19, 1900. CONTENTS CHAPTER I PAGE THE GRASSHOPPER AND ITS ALLIES . . 1 Key to the four principal families of Acrididre . . 2 APPENDIX : Key to the principal families of the Orthoptera . 14 CHAPTER II THE BUTTERFLY AND ITS ALLIES ... 15 APPENDICES : Key to the principal families of Lepidoptera 41 Key to the principal families of Hymenoptera ... 42 CHAPTER III THE BEETLE AND ITS ALLIES ...... 44 APPENDIX : Key to the principal families of the Coleoptera . 58 CHAPTER IV THE FLY AND ITS ALLIES ...... 62 APPENDIX : Key to the suborders of Diptera .... 02 CHAPTER V LlTHOBIUS AND ITS ALLIES .... 74 APPENDIX : Key to the principal families of the Myriapoda . 78 Key to the commoner species of the genus Lithobius . . 79 CHAPTER VI THE SPIDER AND ITS ALLIES ... 80 APPENDIX : Key to the seven suborders of the Araueina . .95 ix 29390 CONTENTS CHAPTER VII PAGE THE CRAYFISH AND ITS ALLIES 97 APPENDICES : Key to the six chief orders of Malacostraca » 122 Key to the principal families of Podopthalinata . . . 122 CHAPTER VIII THE DAPHNIA AND ITS ALLIES 125 APPENDICES : Key to the five orders of Entomostraca . . 131 Key to the principal families of Cladocera .... 131 CHAPTER IX THE EARTHWORM AND ITS ALLIES . 133 APPENDICES : Key to the principal species of Earthworms of the United States 143 Key to the principal families of aquatic OligocliEeta . . 144 CHAPTER X NEREIS AND ITS ALLIES 145 APPENDIX : Key to the more important families of Polychseta . 159 CHAPTER XI THE SLUG AND ITS ALLIES 160 Key to the three orders of Gastropoda 160 Key to the principal families of American Pulmonata . . 161 APPENDIX : Key to the principal families of marine shelled Gastropods of the Atlantic coast of the United States . .174 CHAPTER XII THE FRESH-WATER CLAM AND ITS ALLIES 178 APPENDIX: Key to the principal families of marine Lamelli- branchiata of the east coast of the United States . . .188 CHAPTER XIII THE STARFISH AND ITS ALLIES . 192 APPENDIX : Key to the principal classes of Echinodermata . 203 CONTENTS xi CHAPTER XIV PAGE HYDRA AND ITS ALLIES ......... 205 APPENDICES : Key to the principal subdivisions of the Cnidaria 220 Key to the families of the Hydromedusae .... 220 CHAPTER XV THE PARAMECIUM AND ITS ALLIES 222 APPENDICES : Key to the four classes of Protozoa . . . 229 Key to the subclasses and orders of Infusoria . . . 229 CHAPTER XVI THE SMELT AND ITS ALLIES ........ 230 APPENDICES : Key to the principal orders of fishes . . . 252 Key to the six suborders of Teleostei 252 CHAPTER XVII THE NEWT AND ITS ALLIES ........ 254 APPENDICES : Key to the orders of Amphibia .... 266 Key to the families of Urodela 266 CHAPTER XVIII THE LIZARD AND ITS ALLIES 268 APPENDIX : Key to the four orders of Reptiles .... 280 CHAPTER XIX THE ENGLISH SPARROW AND ITS ALLIES 281 APPENDICES : Key to the orders of Birds 314 Key to the families of Passeres of northern United States . 315 CHAPTER XX THE MOUSE AND ITS ALLIES 318 APPENDIX : Key to the orders of Mammalia .... 331 CHAPTER XXI THE DEVELOPMENT OF THE FROG'S EGG . . . 332 xil CONTENTS APPENDIX I PAGE OUTLINE OF LABORATORY WORK IN ZOOLOGY .... 337 INTRODUCTION .......... 337 EXERCISES 342 I. Grasshopper 342 II. Butterfly . . 343 III. Beetle 344 IV. Housefly or Bluebottle Fly 345 V. Lithobius 347 VI. Spider 348 VII. Crayfish 349 VIII. Daphnia 351 IX. Earthworm . . 352 X. Nereis 353 XI. Slug 354 XII. Fresh-water Clam 356 XIII. Starfish 357 XIV. Hydra 358 XV. Paramecium . . . . . . . . 359 XVI. Smelt 361 XVII. Newt 362 XVIII. Lizard 363 XIX. " English " Sparrow 364 XX. Mouse 365 XXI. Development of the frog's egg 366 METHODS OF EXAMINATION 367 APPENDIX II A LIST ov BOOKS DEALING CHIEFLY WITH THE ECOLOGICAL AND SYSTEMATIC ZOOLOGY OF AMERICAN ANIMALS .... 369 APPENDIX III SYNOPSIS OF THE ANIMAL KINGDOM ...... 383 GLOSSARY . 391 I^NDEX .,»,».••>••> out INTEODUCTION TO ZOOLOGY INTRODUCTION TO ZOOLOGY CHAPTER I THE GRASSHOPPER AND ITS ALLIES Relationships. — The grasshopper belongs to an order of insects called Orthoptera.1 In this group of insects2 there is an incomplete metamorphosis during development, so that the general form of the young resembles that of the adult. The anterior and posterior pairs of wings are unequal. The jaws are adapted for biting. The name " grasshopper ' is applied to two families of insects; namely, the Acridida^8 and the Loeustidse. Both of these families have long hind legs, used in jumping, an elongated body flattened from side to side, and a wedge- shaped head directed downward ; they differ in the length of the antennae. Habits.- -The Acrididae, or short-horned grasshoppers, are found in both hemispheres. They live, for the most part, on the ground in very diverse conditions, such as in low, damp meadows or in dry uplands, arid deserts, and rocky mountain sides. They are all herbivorous, and may s, with straight (lying straight out) wings. 2 The principal families of Orthoptera may be distinguished by the key in the Appendix to this Chapter, p. 14. 3 a.Kpi5i.ov, a small grasshopper of Dioscorides. B 1 2 ZOOLOGY feed upon almost any green part of plants. Some of tLu species are gregarious (i.e. go in swarms) and may be very destructive.1 Melanoplus 2 is the prevailing genus of North America and covers nearly all of the continent. While in the East certain species of the genus Melanoplus may become destructive to vegetation, the injury done is not so great as was formerly done by the Rocky Mountain locust. At various times for some cause, probably drought, this locust has migrated eastward from its mountain home in countless millions and devastated our Western States as far as the Mississippi River. In 1873 to 1877 the Rocky Mountain locust was so destructive to vegetation in the trans- Mississippi region that Congress appointed a commission to investigate the species. In describing its effect the commission reports : - " Falling upon a cornfield, the insects convert in a few hours the green and promising acres into a desolate stretch of bare, spindling 1 The following key will aid in determining the four principal Ameri- can subfamilies of the Acrididse : — • a\. Feet without a claw-pad. Pronotum covering all the body. Fore wings lobe-like .... Tettigidce (Tettix Shorthorns) a*. Feet with a claw-pad ; antennse longer than an- terior femora. 61. Prosternum without a spine. GI. The plane of the vertex of the head meet- ing the plane of the front of head at an angle, the face looking down . . . Tryxalidce (Angle-headed Shorthorns) C2. The planes of the vertex and head round over into each other .... CEdipodce 62- Prosternum with prominent spine . . . Mehtnoplidce (Thorn-throated Shorthorns) s, black ; oir\a, armor. THE GRASSHOPPER AND ITS ALLIES 3 stalks and stubs. . . . Their flight may be likened to an immense snow-storm, extending from the ground to a height at which our visual organs perceive them only as minute, darting scintillations, , leaving the imagination to picture them indefinite distances bej^ond. ... In alighting, they circle in myriads about you, beating against everything animate or inanimate ; driving into open doors and win- dows; heaping about your feet and around your buildings, their jaws constantly at work, biting and testing all things in seeking what they can devour." The locusts of the Old World are likewise frequently very destructive. The species that lives in southern Europe, North Africa, Asia Minor, Syria, Java, and Japan is doubtless the locust of the Bible. The description given by the prophet Joel is very vivid and accurate : - " A day of darkness and of gloominess, a day of clouds and of thick darkness, as the morning spread upon the mountains ; a great people and a strong ; there hath not been ever the like, neither shall be any more after it, even to the years of many generations. A fire devoureth before them, and behind them a flame burneth : the land is as the garden of Eden before them, and behind them a desolate wilder- ness; yea, and nothing shall escape them. The appearance of them is as the appearance of horses ; and as horsemen, so shall they run. Like the noise of chariots on the tops of mountains shall they leap, like the noise of a flame of fire that devoureth the stubble, as a strong people set in battle array. Before their face the people shall be much pained ; all faces shall gather blackness. They shall run like mighty men ; they shall climb the wall like men of war ; and they shall march every one on his ways, and they shall not break their ranks. . . . They shall run to and fro in the city; they shall run upon the wall; they shall climb up upon the houses; they shall enter in at the windows like a thief." General Development of the Grasshopper. - The common red-legged grasshopper lays its eggs during the fall in holes in the ground which the female drills by means of 4 ZOOLOGY the horny plates at the tip of the abdomen. The eg thirty to one hundred in number, are laid in a mass and covered with a gelatinous secretion. In these holes, an inch or so below the surface of the ground, the eggs pass the winter and hatch out in early summer into young grasshoppers, looking like adults except for their small size and the absence of wings. As they grow larger they moult several times, i.e. cast off their cuticular coverings. After each moult the body is left soft and colorless, but being freed of its hard, tight casement, it is in a condition to grow rapidly. After each moult also the rudimentary wings (wing-pads) become larger, and the relative sizes of the parts of the body change. Just before the last moult the pupa crawls up some vertical object, clutches it firmly with the hind feet, and remains motionless in this position for several hours. Then the cuticula splits along the middle of the back, the head and body inside the cuticula swell, the head emerges from the case, and gradually the entire body works forward out of the old cuticula ; not easily, indeed, but with violent contortions and pullings. The legs and antennae are especially difficult to free ; they can pass out of the joints of the old skin only because they are soft and flabby ; but as soon as they become exposed to the air their surface secretion hardens into a firm covering. The wings are at first rolled up ; they now expand broadly, dry, and then fold up in the way we see them in the adult. Allies of the Grasshopper. - The Gryllidae,1 or crickets (Fig. 1), include cosmopolitan insects that have short, cylindrical bodies and live chiefly in hidden places, such as beneath stones or in holes Avhich they make in the 1 Name derived from sound made by crickets. THE GRASSHOPPER AND ITS ALLIES ground. Their eggs are laid loosely in these retreats. They feed on plants and, if numerous, may be decidedly injurious to vegetation. They make a familiar chirping noise, the blended sounds of which, as heard on a sum- mer evening, rise and fall in a distinct rhythm. The rate of chirp seems to be entirely determined by temperature, so that one may compute the temperature by means of the formula ^-40 FIG. 1.— Gryllus, — , , cricket. Nat. size. Photo, by W. H. in which T stands for temperature, and N the number of chirps per minute. The mechanism by which the chirp is produced is as follows : Near the mid- dle of each of the upper wings of the male cricket is a vein so modi- fied as to form a sort of file, and near the margin of the wing is a thickened scraper. When the up- per wings are brought in contact above the body, and the scraper of one is rubbed across the file of the other, the wings are set in vibration, producing the call. An aberrant form of Gryllidee is the mole cricket (Fig. 2), whose FIG. 2.--Grii!iuta?pa bore- f°re feet have become much modi- alis, mole cricket. Nat. ne(j f()r burrowing, size. Photo, by W. H. C p 1 he Locustidae,1 or long-horned 1 From the Latin name for the locust and grasshopper, as well as the lobster. 6 ZOOLOGY grasshoppers and katydids, are close allies of the short- horned grasshoppers already defined. Next to the numer- FIG. 3. — Orchelimum, meadow grasshopper. Nat. size. Photo. by W. H. C. P. ous meadow grasshoppers (Fig. 3) belonging to this group, the katydids are the best known of its representatives. The katydids have their whole body green, like the foliage they FIG. 4. — Ceuthophilus, cricket-grasshopper. Two-thirds nat. size. Photo, by W. H. C. P. inhabit. The wings are large; and when the upper wings are rubbed together, they vibrate, and cause the familiar THE GRASSHOPPER AND ITS ALLIES 7 note. Other members of this group are the cricket-grass- hoppers (Fig. 4), wingless forms, of a brown color and arched profile, which live under stones and rubbish, and also the cave " crickets," which are colorless and blind. The Phasmidae^or walking-sticks and leaf-insects, display, to a mar- vellous degree, a protective resem- blance to the twigs and leaves among which they live. The most remark- able forms live in the tropics. They have large wings, which strikingly resemble, in form, color, and vena- tion, either living or dry leaves. Upon those species which resemble dried leaves, blotches looking like fungous patches are found. Even the legs may be thin and expanded, resembling foliage. In our country only the twig-like, wingless forms, or walking-sticks, occur. These in- sects are furthermore protected by changes in color, corresponding with the seasonal color changes in twio-s; o o for the young walking-sticks, which appear in the spring, are green like the twigs, but in the autumn they become gray or brown. Figure 5 shows our only common northern species, Diapheromera femorata. It feeds on leaves, especially those of the oak, and occasionally does much damage to trees. FIG. 5.— Diapheromera, walk- ing-stick of northern U. S. Nat. size. Copied from Packard. appearance, spectre. 8 ZOOLOGY The Mantidae l are popularly called praying-mantis, on account of the devotional attitude in which the greatly en- larged front legs are held. Unlike other Orthoptera, they FIG. (i. — Phasmomantis niroUim. Praying-mantis of southern U. S. Nat. size. Copied from Packard. are carnivorous. They hunt and devour other insects some- times larger than themselves, and even prey upon each other. \Yhile most of the species are tropical, one species, Phasmo- mantis Carolina (Fig- 0), is abundant in our Southern States, and another occurs in the Missouri valley. The Blattidae,2 or cockroaches, are especially creatures of the tropics; and those which live in colder cli- mates frequent warm as well as dark places. The two which are our household pests have been imported from Europe,- -both the small brown " ( 'roton bug," which is found among water-pipes in the kitchen, and the large black species commonest in sugar-refineries, slaughter- houses, and bakeshops. They are omnivorous, eating, 7. - • Wingless cock- roach. Xat.size. Photo, l.v AY. H. C. P. seer, prophet. 2 blatta, roach of Pliny. THE GRASSHOPPER AND ITS ALLIES 9 among other things, breadstuffs, clothing, book-bindings, bedbugs, and other insects. We have also a number of native cockroaches, which live chiefly in fields and woods, under stones and logs. Some of these are wingless (Fig. 7). The following groups are frequently excluded from the Orthoptera, but show a certain relationship with them : - The Forficulidae,1 or earwigs, are rare in the northern United States, but commoner in the Gulf and Pacific States. In general appearance they resemble rove-beetles, but differ from them in having a pair of forceps at the posterior end of the body. They hide, during the day, in the corollas of v» * « * T **f» r . /""~ <^n V c.. FIG. 8. — Two North American Odonata, belonging to the family Libelhilid: About one-half nat. size. Photo, by V. H. L. flowers, upon which they feed, and fly about at night. The name earwig seems to have arisen from an unwarranted belief that these insects penetrate into the ears of persons when asleep. They were especially dreaded on account of a fear that thev mio-ht thus penetrate into the brain. V O A The Odonata,2 or dragon-flies, have four membranous, net- veined wings, of which the front pair are never larger than the hind ones. Their large heads carry relatively enormous eyes. Two groups of dragon-flies may be distinguished according as the wings, at rest, are extended (Fig. 8) or 1 forfiwila, a small forceps. " 65ovs, tooth, from the teeth of the mandibles. 10 ZOOLOGY folded together over the back. Dragon-flies live on the wing, hovering over water and preying upon other insects, especially mosquitoes. The eggs develop in the water into aquatic larvae which are quite unlike the adult. Especially the jaws are peculiar, being jointed and capa- ble of sudden protrusion, in order to catch the animals which serve as prey. These larvee are easily reared over winter in an aquarium, where not only their ferocious habits, but also their peculiar method of breathing by means of water taken in at the anus, may be observed (Fig. 9). The Ephemeridae,1 or May-flies. The FIG. 9. - - JEschna, adult May-fly possesses finely veined fore old larva, or pupa. . 1-1 ^ ^ , i , i Nat. size. Photo, wings, winch are much larger than the by w. H. C. P. hind wings. The mouth parts are rudi- mentary and the abdomen terminates in two or three filamentous appendages. As their systematic name implies, they have a very ephemeral existence in the imago state. The imago appears in swarms early in the summer and lives but a fe\v hours, eating nothing and depositing eggs upon or under stagnant water. The larvse feed upon small aquatic plants and insects, breathe by means of gills placed on the back, and live for nearly a year, or even for two or three years, in the immature stages. After many moultings the apparent adult emerges, but, unlike other insects, undergoes an additional moult before laying its eggs. As the insect is subjected to many accidents in its long and defenceless life, each species is preserved only by an enormous fecundity. . a day, i.e. lasting but a day, short-lived. THE GRASSHOPPER AND ITS ALLIES 11 White ants, or termites (Fig. 10), while not true ants, live a very similar social or communal life. They differ from ants in the venation of the net-veined wing (when present). White ants are most abundant in the tropics, where they build great conical nests of sand cemented by their saliva ; but they are found also in temperate countries. The common eastern white ant (Termes flavipes) ranges from FIG. 10.— Termes Massachusetts southward, and lives in /«?><>. — Locanium, a scale insect. Remains of females after production FIG. 15. — Pupal case of cicada. Two- of yoiuii>' ; seen as swellings on the thirds nat. size. Photo, by W. H. C. P. bark. Nat. size. Photo, by V.H.L, 14 ZOOLOGY The Homoptera include insects of very diverse size and form. The largest are the cicadas, or "locusts" (Fig. 14), some of which have the remarkable habit of requiring thirteen or seventeen years for their development. Con- sequently these cicadas appear only at intervals of thirteen or seventeen years. The young bury themselves in the ground and live by sucking juices from the roots of trees. Eventu- ally they come to the surface, leave their lar- val skin (Fig. 15), and FIG. 17. — Schizoneura, a woolly aphis, on flvqwav iq full o-rnwn apple twig. Photo, by V. H. L. cicadas. In the case of our common species of cicada there is a brood every year. Besides the cicadas the Homoptera include the little leaf-hoppers and tree-hoppers, the very destructive scale- bugs (Fig. 16), and the mealy-bugs, most of which attack fruit trees and their fruits, and the plant-lice, or aphids (Fig. IT). APPENDIX TO CHAPTER I KEY TO THE PRINCIPAL FAMILIES OF THE ORTHOPTEKA a\. Legs similar, fitted for running .... «2- First pair of legs differentiated for grasping ; pro- thorax elongated Blattidce (Cockroaches) Mantidce (Praying-mantis) APPENDIX TO CHAPTER I 15 «3. Legs similar, much elongated, and fitted for slow walking . Phasmidce (Walking-sticks) «4. Hinder legs stouter or longer than middle pair. 61. Antennae shorter than body .... Acrididce (Locusts and Short-horned Grasshoppers) 62. Antennae longer than body. Ci. Tarsi 4-jointed Locustidce (Katydids and Long-horned Grasshoppers) c2. Tarsi 3-jointed Gryllidai (Crickets) CHAPTER II THE BUTTERFLY AND ITS ALLIES Systematic Position. — Butterflies belong to the insect order Lepidoptera,1 characterized by the possession of a long, coiled, sucking proboscis; large, membranous wings, covered with colored scales; and a complete metamorphosis. They occur over the whole globe, but become more numer- ous in species in the tropics of South America and Africa. The number of known species is about twenty-five thousand.2 The Habits and Food of Butterflies. - The idea of a butterfly should not be limited to the winged adult called the imago, for strictly we may call a caterpillar a larval butterfly, and a pupa an adolescent butterfly. Hut in its different stages the habits and food of a butterfly change. Caterpillars feed, for the most part, upon plants. A few - such as the clothes-moth and certain enemies of scale in- sects - -feed upon animal matter. Any single species of caterpillar feeds upon the foliage of a restricted number of kinds of plants. At one extreme we have forms which starve unless they can reach their own particular food plant; at the other extreme there are caterpillars which can live upon the foliage of many kinds of plants, and these are consequently called polyphagous. Certain fami- 1 \e-n-is. scale ; irrepbv, wing. 2 The principal families of Lepidoptera may be distinguished by the key in the Appendix to this Chapter, p. 41. 10 THE BUTTERFLY AN 7) TT8 ALLIED 1< lies of plants especially serve caterpillars as food. Thus of the hundred species of New England butterflies, eight feed upon oaks, eleven upon willows, thirteen upon the Rosacese, and twenty-eight upon leguminous plants. It follows from the restricted food of many caterpillars, that the range of the species must often be determined by that of its food- plant. The feeding of the butterfly is mostly done in the larval stage: the pupa can take no food. The imagos of many species touch no food, but in other cases they take small quantities of the nectar of flowers, the sap of plants, and the juice of fruits. The imagos fly in the daytime, especially in the sun- shine. Certain species are characteristic of the roadside, others of meadows, gardens, or woods, while still others are found flying everywhere. Owing to its ordinarily short life, the imago is usually found not far from the larval food-plant, upon which it lays its eggs. The Broods of Butterflies and their Polymorphism. — Butterflies winter over in various stages, some in the ego; O OiT5 stage, some as larvae, others as pup?e or as imagos. Some kinds pass the winter in either of two stages. In whatever stage they tarry, the life current runs very slow, and dur- ing this season few changes take place. In the spring, development goes on rapidly: the winter generation be- comes mature and a summer generation is started. Fre- quently there is more than one brood produced during the summer, even in the Northern States. Farther south two and even three summer broods are still commoner. Where two or three broods occur they may be and usually are quite dissimilar. This is very strikingly illustrated in the case of the Zebra Swallow-tail, Iplii<-li JaPan> Itilly> and France. The method of culture is as follows : The eggs ("grains") are laid in the autumn, kept over winter in a dry, airy, and cool place, and hatched when the mul- berry begins to send out its leaves. On these leaves the larvie are put to feed, and after a month they begin to spin. For commercial purposes the larvae are induced 1 From ap/cros, bear. 2 Bombyx-like. Aristotle called the rustling silk /36/x/3os ; hence the name Bombyx for the silkworm. 3 morus, a mulberry tree. .u in stem. Nat. size. Photo, THE BUTTERFLY AND ITS ALLIES to spin the cocoons on prepared twigs or straw. A few days after the cocoon is completed its inhabitant is killed FIG. 23. — Citheroma rcf/al!x, the Regal moth. Olive and red wings, yellow spots. Nat. size. Photo, hy W. H. C. P. in-hot water. The cocoon is made of a continuous thread about three thousand metres long, of which, however, only FIG. 21. — Larva of Citheronia regalis. Head to left. One-half nat. size. Photo, by W. H. C. P. about six hundred metres make good silk. This long thread has to be unravelled. The outer end is loosened 26 ZOOLOGY by soaking the cocoon in hot water ; then several of these ends are brought together and united to form a single fibre of raw silk. Another imported silk-moth common in parts of the United States is the Cynthia1 moth, whose larva infests Ailan- thus trees. True American forms are the brown Polyphemus 2 moth, whose larva is colored light green, with oblique yellow stripes; the Promethea3 moth, whose cocoon is formed in a folded leaf which is securely fastened by silk threads to its twig ; the Nat. size. Pho- to, by V. H. L. FIG. 25. --Adult female of Cll- siocampa clis- stria. From life. Cecropia moth, expanding six inches, whose coarse tegumen- tary cocoon is bound along its whole length to a twig ; and the nearly equally large Regal moth (^Citheronia regalls, Fig. 23), whose larva is oar largest cater- male of ciisio- pillar (Fig. 24). All of these species are easily reared from the larvae or cocoons. Closely allied to the Bombycidre are the Tent-caterpillars, which arc never of great size. These are campa. From life. Nat. size. Photo, by V. H. L. FIG. 27. — Egg masses of forest Tent-caterpillar, laid on branch. Photo, by V. H. L. 1 A poetic name of Diana, from the mountain Cynthus. 2 The name of the fabled one-eyed giant blinded by Ulysses. 3 A name hi Greek mythology, THE BUTTERFLY AND ITS ALLIES 27 destructive species, which infest apple trees and even forest trees (Figs. 25 and 26). Eggs are laid in a ring-like cluster around a twig (Fig. 27). Here they pass the winter and hatch out in the spring as young larva1. The larvae are grc- FIG. 28. — Nest of Clisiocampa tl/xxtria, the forest Tent-caterpillar, showing the web and the way the larvae crowd together on it. Photo, by V. H. L. garious and spin a tent-like web, on which they live when not feeding (Fig. 28). When ready to transform, they spin a cocoon made of a yellow powder mixed with silk. The Noctuidae 1 (Owlet moths) are night fliers and are 1 From nox, night. 28 ZOOLOGY attracted by our lamplights. They are the most numer- ous of all our moths, eighteen hundred species being known from our country. Among the largest members of this group are the Catocala l moths already referred to. Here also are placed the boll-worm, which eats cotton-pods and green ears of maize ; the cotton-worm, which destroys the foliage of cotton ; the army-worm, which devours grass and young grain ; and the myriad cut- worms, of which some gnaw off young garden shoots at the level of the ground, while other kinds ascend trees and de- stroy buds. To the Noctuidse belong also the Tussock moth (Fig. 29), whose variegated larva bears dense brush-like tufts of whitish hairs on the first four abdominal segments, and is very de- structive to shade trees in our cities ; the Gypsy moth, lately imported into Massa- chusetts, where the state has attempted its annihilation ; and the Brown-tail moth, also lately imported to Boston. FIG. 29. — Notoiophus, The Geomctridae, or measuring-worms, the Tussock moth. 1-1 ,1 -yr • i The wingless female are< llke the Noctiuds, very numerous is shown below a and very destructive. They are so mass of e^ajs she has n i i ' ^i i i just laid '"""Nat size called because the larvae have a way From life. Photo. of proceeding, as it were, by inches in their locomotion. One of the most im- portant subdivisions is that of the canker-worms, which often strip fruit and shade trees of their foliage. 1 /card, below ; /caXos, beautiful. THE BUTTERFLY AND ITS ALLIES 29 The Pyralidae : include among other pests the bee-moth. The larva of this species feeds upon the wax of the hive and constructs silken galleries in the comb. The Tortricidae 2 contain numerous small, inconspicuous moths, whose larvre are, however, very destructive. The codling-moth is a pest of the fruit-grower, for the larva bores into apples and pears, causing them to fall prema- turely. Many species are called leaf-rollers, from the fact that the larva causes the leaf on which it feeds to curl. FIG. .'X). — Case-bearing insects on a twig. Phot:), from life by V. H. L. The Tineidae3 contain the smallest of the Lepidoptera. Their wings frequently bear long fringes. The larvas are so small that they often live in the interior of leaves, and form winding or blotch-like "mines" in them. The larvae of some species make a case out of pieces of leaves united by silk, and carry this about with them. They are known as " Case-bearers " (Fig. 30). Here also belong the clothes- 1 From Trvp, fire ; because the ancients believed these insects to arise from and live in fire. 2 tortor, tortrir, winder, from tonjueo, to roll or wind ; with reference to the habit of twisting up leaves. 3 tinea, moth. 30 ZOOLOGY moths, of which we have three species. These moths fly early in May, and lay their eggs on woollen cloth, furs, or feathers, upon which the larvse feed. This review of the Lepidoptera shows us that, on the whole, despite their beauty, they are great enemies of agriculture, since most of them feed on vegetable prod- ucts. Not only do we in this country have an abundance of native forms, but several exotic species have been im- ported; and being thus removed from their natural enemies, their natural fecundity has been unchecked, with the result that they have brought great devastation upon vast agri- cultural districts. The earnest attempts of a state to keep down for a while an introduced pest, even at great expense, is commendable. The Hymenoptera l include bees, wasps, ants, and certain less well-known insects. They all have four similar mem- braneous wings as the Lepidoptera do ; but unlike the Lepidoptera, their wings are not covered with scales, but are transparent. The mouth parts are formed for biting or for sucking, but the proboscis is not so long that it rolls up as in Lepidoptera. The Hymenoptera belong to one or the other of two groups, — the stinging Hymenoptera, in which the female is provided with a sting, and the boring Hymenoptera, which are provided with an ovipositor, or long tube, by which eggs can be placed at some distance below the sur- face. To the first division belong the bees, wasps, and hornets, certain digging or boring wasps, and the ants. To the second division belong certain species,- -as, for example, the ichneumon flies,- -which are parasitic on 1 v/j.r)v, skin, membrane ; Trrepov, wing. THE BUTTERFLY AND ITS ALLIES 31 other insects, the gall-flies, or gall-wasps, and the plant- eating Hymenoptera.1 The bees (Apidae2) include both social species and others which lead solitary lives. Of the latter, some dig their nests in the ground ; others are masons, and build their nests of mud ; others are carpenters, and make tunnels through pithy plants, or even solid wood ; while still others are leaf-cutters. These leaf-cutting bees carve circular disks from rose leaves, out of which they make cells for their young. Of the social bees, our native species belong to the genus Bombus, — the "bumble' bees. The bumblebees build nests in the ground. The queens only survive the winter. In the spring each queen chooses some mouse nest or other ready-formed cavity in a meadow, and places within it a ball of TT , . „ , , FIG. 31. — Bombus, the bumblebee. pollen. Jpon this iood she Nat. size. Photo, by W.H. c.i'. lays eggs, which develop into worker bees. As soon as the workers are full grown they begin the task of gathering food, and the queen then de- votes all her energy to egg-laying. Later in the season males and young queens also appear in the nest. The old and young queens dwell together in harmony until autumn, when all the members of the colony perish except- ing the young queens, which pass the winter in some sheltered spot and form new colonies in the spring. 1 A key to the principal families of the Hymenoptera is given in the Appendix to this Chapter, p. 42. 2 From apis, bee. ZOOLOGY The introduced, semi-domesticated honey-bees have quite a different social economy. In the first place, the nest is perennial ; consequently the young and old queens cannot remain in the same hive, else the nest would become overcrowded by the presence of too many families. As }roung queens mature, the old queen seeks to destroy them ; but she is usnsilly forced out of the hive by the workers, a num- ber of which accompany her. This migration is what we call "swarm- ing." 1 When several young queens mature at the same time, duels or repeated swarmings en- sue until only one queen remains. When a new colony is started in a hive or hollow tree, a comb is formed of wax secreted by the worker bees, and into this the queen deposits eggs des- tined to develop into workers. Still later, eggs destined to form drones are laid in cells larger than those in which workers develop. The de- veloping young workers and drones are fed with honey and bee-bread. Honey is derived from the nectar of flowers, which is lapped up by the workers, is stored for a time in the crop, where it undergoes certain transformations, and is then FIG. ol«. — Swarm of bees. Photo, by D. and S. 1 Fig. 31 a. THE BUTTERFLY AND ITS ALLIES 33 regurgitated into the cells. The nature of the transfor- mation of the nectar in the crop of the bee is not precisely known, but it is not great enough to prevent the character- istic flavors of the flowers of the buckwheat, orange, and so on, from being retained in the honey. The bee-bread is made from the pollen of the flowers, which is brought into the hive on the hind legs of the workers. When a new queen is needed for the colony, and the queen cells are empty, one may be produced by the workers in the fol- lowing manner : The partitions between three worker cells are destroyed and two of the embryos are killed. The enlarged cell is rilled with a special nutritive compound manufactured by the workers and known as royal jelly. The remaining embryo, fed upon this especially nutritious jelly, develops, not into a worker, but into a queen. Of the true wasps ( Vespidie !), some are solitary; others, like certain of the bees, rear their families in the nests of other species (guest-wasps) ; while still others are social. The last group includes our best-known species. The colony of social wasps contains males, females, and workers. As in the case of bumblebees, only the females survive the winter, and in the spring they build small nests and lay worker eggs. The workers, when grown, FIG. re.— Poiistcs. enlarge the nest and care for the numerous Slightly reduced. , ,, n Photo, by W. H. progeny ot the queen. Our social wasps c. P. belong either to the p-enus Polistes,2 which o o includes the ordinary black, brown, or yellow bodied wasps, which build mushroom-shaped nests behind window blinds and under boards (Fig. 32), or to the genus Vespa, 1 From vespa, wasp. 2 TroXto-r^s, founder of a city. D 34 ZOOLOGY Xat. size. H. C. P. which includes the black and spotted hornets and yellow- jackets, that build great masses of paper combs enclosed in a nearly spherical gray paper envelope (Fig. 33). These are found attached to trees or parts of buildings. The paper is made of finely masticated wood-fibre cemented b}~ a secretion. Certain yellow-jackets form nests in the ground. The hornets are well FIG. 33. -Vespa, a hornet, known as among the most vindic- Photo. by w. tive of our northern insects, and their sting is capable of produc- ing considerable pain. In all Hymenoptera the pain of the sting is due to the introduction of a poison into the body of the victim through the stinging organ. This poison is secreted by a special gland of the insect. The digger and mud wasps (Fossoria1) have the most varied habits. One of the most familiar species is Pclo- poeusf which somewhat resembles a true wasp, but may be easily distinguished from it by the long, slender attachment of the abdomen to the thorax and by the fact that the wings when closed lie flat and horizontal (Fig. 34), while in the true wasps they are folded like a fan. Other species bore into the pith of plants or make burrows in the ground. Many are predaceous, feeding on spiders, cicadas, etc. The ants (Formicidre 3) constitute a well-known group having features so marked that other insects, excepting 1 From /ossor, digger. 2 TT^AOS, slime. 3 From formica, ant. FIG. 34. — I wasp, showing po- sition of wings. Xat. size. Photo, by \V. H. C. P. THE BUTTERFLY AND ITS ALLIES 35 the termites, will hardly be confused with them. From the termites ants may be distinguished by the fact that the first segment of the abdomen forms a small knot or scale lying between the thorax and the remainder of the ab- domen (Fig. 35). The intelligence of ants is notorious. This intelligence has developed in connection with a highly organized social life. This social life is a communistic one. Homes are built, food is gathered, wars are made, and domains are defended bravely and loyally all for the sake of the entire community. The individual is little regarded, and each :'~ •• , - - . " FIG. 35. — Camponotus, the carpenter ant. Uniformly black. Shows scale behind thorax. Nat. size. Photo, by W. H. C. P. one is born to a caste from which escape is impossible. For, in addition to the distinction of sex characteristic of other species, we have here workers, and these workers may be of different kinds. Thus certain workers get food and care for the young ; others, which serve as soldiers and defend the colony or conduct war, are in some cases pro- vided with powerful jaws. In some species there are three or more classes of workers, each having its characteristic form of body. Ant Colonies.- -A colony is founded by a female. On warm days the young males and females may leave the nests and take flight in great numbers. This is the mar- riage flight of the queens. Within a few hours after 36 ZOOLOGY nightfall of the clay of this flight the males perish, while the queens settle down to the ground, tear off their wings, and each of them seeks an appropriate place to begin the formation of a new colony. If by chance a queen is dis- covered by some of her workers, she is cared for by them ; otherwise she must get on alone. She makes a small nest and lays eggs, which quickly develop into workers, which then assume the task of constructing the nest of the new colony. The nests of our ordinary species consist simply of tunnel-like passageways dug in the ground and enlarged at intervals to form small chambers. Most species dig their nests preferably under protecting stones or the roots of trees ; in other cases a hillock of earth and twigs, an "ant-hill," is constructed. These mounds may attain a diameter of from six to ten feet. Ant Language. — In connection with their communal life ants have gained a power of communication. By the agency of their antennse, with which two comrades are constantly stroking each other, they can tell each other of the whereabouts of food, of the approach of an invading army, or of the need of aid. They distinguish members of their own community from those of other communities, and recognize one of their number, even after a long ab- sence, and receive it back to the colony with demonstrations as of joy. Social Life of Ants. — To illustrate the complex social life of ants, a more detailed account is here given of certain interesting .species. Certain ants, such for instance as our Formica1 difficilis? a rust-red species often found living beneath large, flat stones, make slaves of another species of ant which (a curious coincidence) is a dark-colored species. In at least one slave-making species the jaws have become i Ant. 2 Difficult. THE BUTTERFLY AND ITS ALLIES 37 so modified to aid it in capturing slaves that it is absolutely dependent upon its slaves for food, and it would die surrounded by food were none of its slaves at hand to feed it. The Agricultural Ant. — One of our most interesting ants is the Agricultural Ant of Texas (^fyrmical molefaciens2). This ant makes a circular clearing about its mound, upon which it allows only one species of grass to grow. Indeed, some observers maintain that the seed of this grass is planted upon the clearing by the ants. Certain it is that the ripe seeds of the grass are carefully harvested by the ants and stored within the chambers of their mound. From time to time the seeds are brought out and dried to prevent sprouting. During rainy sea- sons, when the seeds germinate despite all pre- cautions, the ants are said to nip off the sprout upon its first appearance. The army ants, of which there are several species, occur in great numbers in tropical South America. Like many other species which live by hunting, they migrate from a locality after having exhausted it of their food. While on the march, the young of the species are trans- ported by some of the adults. When an army of these ants approaches a place, every living animal endeavors to escape. The breeding birds must be on the alert to pick off the advance Fie. 3G.-Ptmpfapeda- 1 . hs, a parasite on the guard to prevent them from returning to the army with news of the presence of nestlings. Insects of all sorts, young and old, fall a ready prey to these swarms. Some spiders escape by suspending themselves by their threads, and insects which resemble leaves often find safety in keeping rigidly still. When an army of these ants enters a house, the inhabitants find it wisest to leave the invaders in possession, for in a few hours the house is cleared of every living thing — moths, cockroaches, rats, mice, all have fled or been devoured. The leaf-cutting ants are another tropical American species. The caterpillar of Clisio- campa. Upper figure female, lower male. Photo, by V. H. L. , ant. 2 Mole or mound builder. 38 ZOOLOGY colony is very perfectly organized. The duties of the workers are divided among different gangs. Thus, when a tree has been selected, one gang ascends the trunk and cuts the leaves in pieces of a definite shape. The pieces flutter to the ground, are picked up by another gang and carried to the entrance of the ant-hill, where they are de- posited to be carried into the nest by a third relay. The bits of leaves are used to line certain of the passageways, and a fungus is grown upon them which serves the ants as food. The leaves are probably stored to provide this fungus food. The parasitic Hymenoptera have the habit either of lay- ing eggs in the body of another insect, — one of the plant- lice, a caterpillar, or other species, — or else they lay their eggs in the nest of some species of insect so that the larva can make its own way into the host (Figs. 36-38). The long, tail-like ovipositors of the female ichneumon are, in some cases, used to drill holes into trees occupied by insect burrows so that her eggs can be laid therein. These parasitic species are invaluable to agriculture in keeping down injurious insects. The gall-wasps, popu- larly not distinguished from the strict gall-flies, are familiar to us from thei;1 works. They lay eggs in various kinds of plants, especially in oaks and members of the rose family. An excessive growth of the plant tissue, called a gall, is caused either by a poison dropped into the plant with the FK;. -37. — Cocoons of Microgaster, a para- sitic hymenopter, on a sphinx larva. Photo, from the living object by V. H. L. THE BUTTERFLY AND ITS ALLIES 39 egg, or by the irritation of the developing embryo.1 The galls of gall-wasps are often more or less spherical masses FIG. 38. — Ophion, an Ichneumon which infests caterpillars. Nat. size. Photo. by W. H. C. P. which are closed, in consequence of which the confined insect must bore its way out. The galls made by the same FIG. ol). — Larvae of saw-tiy on grape leaf. Photo, by V. H. L. 1 Cf. Fig. 69, p. 07. 40 ZOOLOGY species of insect on one kind of tree are quite similar, but if the same insect stings another species of tree, a different kind of gall is produced. Also when different species of gall-wasps sting one and the same leaf, the galls will be unlike. Hence the characteristic form of the gall is determined both by the species of plant and by the species of insect which lives in it. It is interest- ing to collect galls, watch for the emerging Avasps, determine their species, and thus get their entire life history. The gall- wasps are, on the whole, injurious to agriculture. The plant-eating Hy- menoptera are extremely destructive pests. The young are known as "slugs," from their re- semblance to the true slugs, which are snail-like animals. They infest pear trees and rose bushes, leaving scorched, dried leaves behind them.1 Here also belong the currant-worm and the saw- flies (Figs. 39 and 40;, which eat leaves like caterpillars, but differ from them in having twelve or sixteen prolegs instead of ten. FIG. 40. — Eggs of Nematus, a saw-fly on gooseberry leaf. Photo, by V. H. L. 1 See "The Pear Slug," in Circular No. 26, 2d Series, U. S. Depart- ment of Agriculture, Division of Entomology. APPENDIX TO CHAPTER II 41 APPENDIX TO CHAPTER II KEY TO THE PRINCIPAL FAMILIES OF LEPIDOPTERA ai. Antennae club-shaped at apex ; wings when at rest held vertical (Fig. ID) «.2. Antennae usually having the form of a bristle, spin- dle, or thread, often with a comb ; wings at rest held out flat (Fig. 23), or else folded over body like a gable roof (Fig. 25). l>i. Hind wing usually with one or two dorsal veins [Macrolepidoptera, large-winged moths]. Ci. Antennae spindle-shaped or keeled, rarely club-shaped ; wings small ; dusk fliers. d\. Antennae prismatic .... do. Antennae not prismatic, but e\. attenuated at end, occasionally pectinate .... /!. Clear winged (Sesiina). f.2. Wings speckled, antennae much longer than head (Cossina). /3. Antennae hardly longer than head (Hepialina). BO. club-shaped, occasionally pec- tinate ... C2. Antennae bristle- or thread-like ; wings mostly broad, night fliers. d\. Wings when at rest placed like a gable roof over body, or envelop- ing it ; proboscis well developed. e\. Subcosta of hind wing united with radius for a considerable dis- tance ; body hairy . e». Subcosta of hind wing nearly or quite distinct from radius ; ab- domen ending conical ly . PapilionidcB (Butterflies) Sphingidce (IIa\vk-inoths) Xylotropidaz (Wood-borers) Zygamidm (Zygenids) (Tiger-moths) Noctuidce (Owlet-moths) 42 ZOOLOGY d%. Wings as in d\ ; proboscis usually weak ; abdomen rounded at apex ; antennae pectinate . . . Bombycidce (Silk-worms) ds. Wings rest horizontally ; proboscis weak Geometridce (Measuring-worms) 61. Hind wing with three dorsal veins [Microlepi- doptera, small-winged moths]. Ci. Wings not divided or parted. d\. Wings rest in gable fashion, with short fringe or none at all. e\. Anterior wings elongate-tri- angular ; palps extending be- yond head .... Pyralidce (Pyralids) 62. Anterior wings much elongated, cambered ; antennae with thick basal segment ; palps slightly protruding .... TortricidjR (Leaf-rollers) di. Wings at rest, flat or enveloping the body ; the anterior wings with long fringe ; strongly developed palps Tineidce (Leaf-miners) c2. Wings divided or parted .... Pterophoridce (Plume-moths) KEY TO THE PRINCIPAL FAMILIES OF HYMEXOPTERA a\. Trochanter simple ; female with sting. 61. First segment of the hind leg more or less compressed, at least on inner side, and often thickly hirsute Apidce (Bees) 62- First segment of hind leg more or less cylin- drical, neither markedly broadened nor hairy. APPENDIX TO CHAPTER II 43 * * Ci. Anterior wings folded once lengthwise ; antennce usually clearly bent at an angle Vespidw (Wasps) c2. Anterior wings not folded lengthwise. di. Abdomen appended or peduncu- late, oval or broadest anteriorly, gradually tapering posteriorly . Superfamily Fossoria (Digger and. Mud Wasps) d2- Abdominal stalk formed of one or two knots or scale-like rings ; an- tennae flagellum-like . . . Formic-idai (Ants) «2. Trochanter of two segments ; female with ovi- positor. 61. Abdomen not sessile, but appended or pedun- culate ; anterior rings without lancet-cells; hind wings with two root-cells . Superfamily Entomophaga (Parasitic and Gall-producing Ilymenoptera) 62= Abdomen sessile (or continuous with thorax) ; anterior wing with lancet-cell ; hinder wing with three root-cells . . Superfamily Phytophaga ^Plant-eating Hymenoptera) CHAPTER III THE BEETLE AND ITS ALLIES BEETLES (Coleoptera1) can be distinguished from otliei insects by the fact that the anterior pair of wings (elytra) are modified to form two horny shields, covering the pos- terior part of the body, while the posterior pair of wings are membranous. The mouth parts are formed for biting.2 During development, the beetles, like the Lepidoptera and Hymenoptera, undergo great changes of form. These changes may be observed in the potato-beetle. In this species the orange-colored eggs are deposited often in a very regular manner on the under side of the potato leaf. Here they develop for several days. In about a week, however, the young, reddish, black-spotted larva, or "grub," emerges. Like the adult beetle, it has three pairs of tho- racic legs. After feeding actively for two or three weeks, the larva descends into the ground, forms a naked yellow FIG. 41. — Larva of Lachnosterna, the June bug, at roots of aster. Photo, of living animals, uat. size, by V. H. L. s, sheath ; 7rrep6v, wing. 2 A key to some of the chief families of Coleoptera is given in the Appendix to this Chapter, page 58. 44 THE BEETLE AND ITS ALLIES 45 pupa, and emerges in about ten days as an imago. From two to four broods are produced during the year. The adult beetles hibernate in the ground, emerging and laying eggs the following spring. The larval habits of the different kinds of beetles are extremely varied, quite as varied as the habits of the adult. The details of these differences may be best considered when we take up the different kinds of beetles. The number of species of beetles which have been de- scribed is very great, probably over one hundred thousand. Of these, over ten thousand inhabit America, north of Mexico. Fortunately this vast number can be included within a relatively small number of families. Leaving the precise definition of these families to the table in the Appendix, we mav here consider •/ certain of the salient general characteristics. The running beetles include two principal families. The first of these is the tiger-beetles (Cicindelidse :), which are colored bright brown or green. They frequent sunny places, especially paths or sandy shores, and are extremely agile.2 The larva' are hunch-backed creatures, have a huge head armed with long jaws, and live in burrows, at the entrances to which they lie in wait for their prey. The second family of the running beetles includes the ground-beetles (Carabidae3 in narrow sense). This family 1 Derived from candda, caudle. 2 Fig. 42. 3 Kapafios, beetle. FIG. 42. — Three common species of Cicin- dela, the tiger-beetle. Left, red-copper bronze; middle, brown, with yellow mark- ings; right, bright green, cream-colored markings. From Packard. 46 ZOOLOGY is composed of about ten thousand species, of extremely varied form, size, and coloration. Most of them are of a shiny black color, usually with longitudinal ridges or rows of piinctations on the elytra.1 They live on the ground, and during the daytime they are concealed underneath boards and stones, but at night they fly and climb trees and shrubs in search of other insects. They are most abundant near watercourses, and are sometimes found on the seashore. Some species emit ill-smelling fluids, often with a popping sound. These fluids serve to defend them from their enemies. Some species are vegetable feeders, for instance one species whose larv?e are destructive in the South to young Indian corn. The next two families, Dytis- cidae2 and Gyrinidae,3 include beetles which are quite as de- structive to animal life of the water as the runners are to those of the land. The Dytiscidse are often large species, which have long, thread-like antenme. The Gyrinidce have short antennse and whirl around on the surface of the water, often in groups. Each eye is divided into an upper half, used for looking into the air, and a lower half, used for looking into the water. The larvre of both of these families have a long and spindle- shaped or flattened body and live in the water. 1 Fig. 43. 2 dvT-r)s, diver ; Sun/cos, fitted for diving. 3 From 70/30S, circle ; because this beetle swims in a circle. FIG. 4-'i. — Calosoma scrutator, the searcher, a ground-beetle. Nat. size. Photo, by AV.H.C.P. THE BEETLE AND ITS ALLIES 47 Another family of aquatic beetles includes Hydrophilus l and its allies, which are less strictly carnivorous than the last two families. Their antennae are short and club-shaped, and their bodies are plumper than that of Dytiscus, which is of about the same size and lives in similar places. The next family includes certain short-winged beetles (Staphylinidte 2), so called because the elytra cover only a small part of the abdomen (Fig. 44). These beetles (" rove -beetles") are usu- ally black and of small size. They are very common under decaying or- ganic matter, stones, and other objects lying on the ground. They run swiftly. Some species mimic ants and wasps. Not only do they resemble these FIG. 44. — A gus, a staphylinid. From Packard. FIG. 45. — A staphylinid elevating the abdomen. Photo, by W. H. C. P. Hymenoptera in the general form of the body, but also in the movements of the tip of the abdomen, which, when the 1 i>5ajp, water ; 0/Xos, loving. 2 (rTa^i/AZVos, from crra^iyXiy, a cluster, is Aristotle's name for a certain insect. 48 ZOOLOGY animal is irritated, is raised as though to sting (Fig. 45). These beetles feed upon decaying animal and plant matter; consequently they are useful scavengers. Some species in- habit the nests of ants and of termites, but their relations with their hosts are unknown. The larvae are not unlike the adults, and inhabit similar situations. The carrion or sexton beetles (Silphi- dre l) are usually of medium or large size, and are either stout-bodied, with red spots on each elytron (Necro- phorus2), or very much flattened and FIG. 46. — Silpha amer- .,,,-,/ -, -, ^ ^.,, ,,. ... icana, a carrion bee- with thin-edged elytra (Silpha, -b ig. 46). tie. From "Standard rpjie Species of NecropllOrilS are power- Natural History." * ful animals. When one or more pairs of these beetles discover a dead bird or small mammal on the ground, they dig out the earth from underneath and pile it upon the animal until eventually the car- cass is entirely buried. Then the female deposits her eggs upon the body, so that a rich supply of food is provided for the young larvre which hatch from the e^o-g. The members r IG. 4(. — Antnrenus, the niuse- of the geilUS Silpha do not bury um pest, a dermestid. Left, a carcass, but live and rear their la!'^: "lkldl£ f1^' ri-ht' adult. From Packard. young beneath it. While the families of beetles hitherto considered are in general useful to man by acting as scavengers or by destroying insects injurious to vegetation, we have now 1 eKp6s, a dead body ; <£f/ocj, to bear. THE BEETLE ANT) ITS ALLIES 49 name from the resemblance of their long, often to consider a family, that of the Dermestidae,1 which is economically directly injurious in a variety of ways. The species of this family include small, oval, or elongated beetles with gray or brown markings, which are due to scales and can be rubbed off. The larvae are fuzzy, and are more injurious than the imagos. They feed on wool, leather, fur of all sorts, as well as on dried and salted meats. Our most destructive species have been imported from Europe. One of them is the carpet-beetle or "buf- falo-bug," which lives upon carpets and clothing. The museum pest is a closely related species which works sad havoc with insect collections, unless these are subjected several times a year to the poisonous fumes of carbon disulphide (Fig. 47). The stag beetles (Lucanidee 2) have received their com- mon branched mandibles to the antlers of a stag. The plates of the club-shaped antenna cannot be brought compactly together, as in the next family. The adult beetles live on the sap of trees, and the larvre bore into the wood of the roots and trunk. The common large stag-beetle, which is often attracted into our houses by lamplight, is Lucanus dama. In the South the giant stag-beetle {Lucanus elepJians) is found, with mandibles which, in the case of the male, are more than three-fourths the length of the body. Closely allied to the last is the great family of lamelli- corn3 beetles, in which the ends of the antennae bear flat, 1 Sep/j.r), to gnaw), a worm which destroys pelts. 2 From lucus, grove. 3 lamella, a small plate or leaf ; cornu, horn. E FIG. 48.— Dorcus, a stag - beetle. Nat. size. Photo. by W. H. C. P. 50 ZOOLOGY • closely applied plates. This family includes many very large insects. We can separate it into two groups, - - the scavengers and the leaf-chafers. The scavenger lamellicorns, commonly known as tumble- bugs, live in the dung of horses and cows, which they form into balls and roll long distances (Fig. 49). The dung-rolling habit has long excited interest ; indeed, among the Egyptians it was a source of superstition. So high was the veneration of this people for this their sacred beetle, that they reproduced it in their paint- ings and sculpture. The ball of dung is really intended for the dep- osition of an egg, and it is rolled by both males and females to a hole in the ground which has been dug in a safe place for its reception. The leaf-eating lamellicorns include the May-beetles or "June-bugs' (Lachnosterna1) which are attracted by lamplight at night. They enter with a busy humming sound, soon come in violent contact with the wall or a piece of furni- ture, and fall heavily to the floor. They feed at night upon the foliage of trees and shrubs. Another common species is the rose-bug,2 which bears the name Macro- dactylus 3 subspinosus. It is destructive to the blossoms and young fruit of grapes, FIG. 49. — Copris, a tumble- bug. Nat. size. Photo, by W.^H. C.P. n sheep's wool ; arepvov, the chest. 2 Fig. 50. 3 /^a/epos, large ; finger. FIG. 50. — Macro- dactylus, the rose-bug. Nat. size. Photo, by W. H. C. P. THE BEETLE AND ITS ALLIES 51 FIG. 51. — rujlpes, a metallic wood-borer. From "Standard Natural History." roses, and other members of the plant family Rosaceae. The larvae of the May-beetles are the fat, whitish, bowed grubs which are often found in the spring in the soil where they have passed the winter. They are very destructive, for they feed on roots of grass, herbs, and shrubs (Fig. 41). Another family of beetles very destruc- tive to trees is that of the metallic wood- borers or Buprestidae.1 The adults are found upon flowers and the bark of trees, where their metallic colors glitter in the sunshine (Fig. 51). The larvae, which have relatively enormous heads, bore beneath the bark of trees or into the wood. This family reaches its highest development in the tropics. Closely allied to the foregoing is the family of click beetles or Elateridae.2 These have the power, when placed on their backs, of leaping into the air by means of a special device on the under side of the animal (Fig. 52). The larvae, called "wire-worms' because of their round, hard bodies, live under the bark of trees and in rotten wood or upon vegeta- tion in the ground. They are most de- structive to germinating grain, especially maize. It requires several years for them to mature. The fireflies (Lampyridae3) make up ?, among the ancients a poisonous beetle, living in grass by swallowing which oxen (/SoOs) swell out (trp^d^ . 2 eXariyp, driver. 3 Xd^Trw, to shine ; oupd, tail. FIG. 52.— One of the click beetles. Nat. size. Photo, by W. H. C. P. 52 ZOOLOGY a another and a well-known family. They are distinguished by soft wing-like elytra and by the great expanse of the thoracic shield, which partly or wholly covers the head. Certain non- luminous species live on flowers, especially the golden-rod ; the lumi- nous species are noctur- nal. The light-giving or- gan lies in the abdomen. The larv?e also are lumi- nous and are known as glow-worms (Fig. 53). A family of consider- FIG. 53. -- Photuris, a firefly. «, larva; - . b, adult. The lines to the left of figures able economic import- represent actual lengths of animals. From £ince js that of the TenC- Packard. . briomdae, so called from the principal genus Tenebrio,1 the larva of which, known as the meal- worm, occurs in flour and cereals and looks much like a wire-worm.2 The adult beetle is black and about one-half an inch long (Fig. 54). The family is not abundant in the northeastern part of the United States. 0 i i • i f i i^ i ,1 FiG.54. — Tenehrio, the meal- Several kinds Ot adult beetles worm Left, larva; right, can be found under the bark of adult. From Leunis. 1 Miller, because it lives in flour. 2 These larvse are reared by bird-fanciers for bird food, and may be obtained in bird stores. THE BEETLE AND ITS ALLIES 53 trees, but these are mostly carnivorous and are seeking their prey there. The minute bark-borers or engraver beetles (Scolytidie1), however, feed on the innermost layer of bark. As they eat in lines, a pattern is formed which is characteristic for each species. Along these lines, niches are made in which eggs are laid and larva? hatch. The borings are injurious to the trees, often causing their death. Herbaceous plants also are infested by certain spe- cies. An example is the destructive Pine Borer (Fig. 55), which is common throughout the United States and Canada. One of the most injurious of all the families of beetles is that of the weevils (Cur- culionidse2). These beetles are small, and their heads are drawn out into a long snout by which they bore holes in plant tissue to receive their eggs (Fig. 56). The dull colors of the beetles render them in- conspicuous to insect-feeding birds. The number of species is reckoned at over ten thousand, and the family is of world- wide distribution, its dispersion having been aided by com- merce. Grain-weevils are great pests in stored wheat, rice, or maize. They also oviposit in the planted seeds. Buds are attacked, and nuts, stone fruit, and fleshy fruits are made " wormy ' by them. Extremely destructive also is the great family of long- FIG. 55. - - Den- droctonus, an engraver bee- tle. Magnified 2. 5 times. From " Standard Nat- ural History." FIG. 56. - - Balani- nus, a weevil, of brown color. From Packard. 1 From o-KoXuTTTw, to mutilate. 2 curculio, a grain-weevil. ZOOLOGY horned beetles, "buck-beetles," (or Cerambycidse1), of which about six hundred species are known in North America alone. The an- tennae and legs of these beetles are very long.2 The larvae bore into even the hardest woods, and live in the wood for two or three years. Timber and shade trees are thus greatly dam- aged. A favorite collect- ing ground for Ceramby- cidre is the golden -rod, where the black, yellow- banded locust borer, Cyllene robince (Fig. 59), is pretty sure to be found. Still another destructive family is that of the leaf-eating beetles, — the Chrysomelidre,3 to which the potato-beetle belongs. These beetles are thick and round in shape. They lay their eggs upon the leaves of plants. The larv?e feed on the leaves or burrow in the stem. Usually the larva is conspicu- ously colored and exposed, and relies for protection upon its dis- agreeable odor and taste. The most destructive species to agri- culture in the northern United FIG. bl. — Prlonus laticollis, a long- horn. Black. Nat. size. Photo, by W.H.C.P. FKJ. 5 gold, and /^Xoy, apple. THE BEETLE AND ITS ALLIES 55 States is the ten-lined Colorado potato-beetle, Doryplwra1 decemlineata. Until about 1859 this species fed upon the sand-bur {Solatium rostratmiri), at the eastern base of the Rocky Mountains and south into Mexico. With the advent of settlers and the plant- ing of the cultivated potato (Solanum tuberosum, a native of Mexico), this more thrifty, cultivated species was adopted as its food-plant, and the potato-beetle began its eastern migration. It spread slowly at first, but within fifteen years had reached the Atlantic coast. The little red, yellow, and black asparagus-beetle, the yellow, black-striped cucumber and melon beetle, the tortoise-beetle, whose broad, iridescent, translucent elytra are conspicuous on the leaves of the morning-glory, nettle, and other plants, all belong to this family. So long has become our list of destructive beetles that it is with satisfaction that we turn at the end to a family which is almost wholly beneficial to the vegetable kingdom, as well as to most vegetable-feeders, includ- ing man. This is the ladybird family, FIG. 59. — Coccinellidce. These beetles are preda- ceous, both in the larval and adult stages, feeding upon small insects and insect eggs (Figs. 60 and 61). They are especially active in freeing plants from scale-insects and plant-lice. So rapidly do the latter multiply that were it not for the voracious larvse of the ladybird most plants would be 1 5opv6pos, spear-bearing. robin&, the locust borer, found on the golden - rod. Photo, by W. H. C. P. 56 ZOOLOGY destroyed in a single season. The larvte of the ladybirds are dark, spotted, and hirsute. One of the commonest of our eastern ladybirds is a red- backed, two-spotted one (Adalia i>'' pun data). The food of beetles is, as we have seen, extremely varied, pIG. <;i. more varied, indeed, than that of Anbtisocel- FIG. CO.— Pupa of ,, if-- lata. Adult. Aiiatisvcellutaon anJ Other Order Ot insects ; WOOd- Nat. size. a leaf. Nat. size, fibre, bark of living or dead trees, Photo- b^ Photo, by V.H.L. . , V.H.L. leat and stem tissue, nuts, truits, grains, insects, adult and larval and dead animals of vari- ous sorts, are all utilized by them as food. Those beetles which destroy living plants, or which feed on fruits and grains utilized by man, those which burrow in tim- ber, devour meat or articles of human industry and collections prized by man, may be ranked as economically injuri- ous. One species, indeed, is injurious as a parasite of a useful animal ; this is a curious beaver parasite, Platypsylla 1 castoria,2 In so far as certain predaceous beetles feed upon other carnivorous species of insects, as do certain tiger carrion beetles, or upon small fish, FIG. fi2. — Platypsylla castoria, the beaver as do some of the Dytiscidse, or upon parasite. From -• j. • i TI • -IT P.I Packard. domestic bees, like certain allies ot the weevils, they may be indirectly injur- ing man. Of all the families of beetles, probably the leaf- eaters cause greatest destruction ; next to them come the weevils, followed by the Cerambycidse and the others. s, broad ; \j/v\\a, a flea. 2 Fte. 62. THE BEETLE AND ITS ALLIES 57 Every part of the plant has its coleopterous enemy. As Le Conte and Horn have said: "As the function of the Cerarabycidse is to hold the vegetable world in check by destroying woody fibre, the Brnchidiu (weevils) effect a similar result by attacking the seeds, and the Chrysome- lidte by destroying the leaves.-" The list of beetles directly or indirectly useful to man is small. The carrion-beetles, tumble-bugs, and rove- beetles, which feed upon decaying animal and vegetable matter, are useful as scavengers. Of those which serve us by killing other insects injurious to vegetation, the lady- bird beetle stands first. The economic importance to us of this one family can hardly be estimated. Different kinds of ladybirds feed on different species of insects. At one time it seemed that the orange industry, if not that of fruits in general, was doomed in California on account of the destruction wrought by the introduction of a scale-insect. As the insect had been imported, we had no native beetle which attacked it. Search was made abroad, and a lady- bird beetle was found in Australia which feeds on this particular scale-insect. The Australian beetle was intro- duced into California, and now the scale-insect is subdued. The larva; of some of the checkered beetles l feed upon the larvas of boring beetles, while the larva} of tiger-beetles watch at the mouth of their burrows for other insects upon which they feed. Carabid beetles are said to ascend trees in search of canker-worms. Larva} of ground-beetles prey upon the pupating plum Curculios. Other beetles eat cut- worms, and infest the common wasps. One beetle, the blister-beetle, known in the markets as 1 A family of rather small beetles, living in flowers and on trees, and often with, contrasting colors. 58 ZOOLOGY the Spanish fly, has been for ages used as a drug. When disturbed, there exudes from the joints of this insect a liquid serving as a protection, since it burns or blisters the disturber. This property is retained in the extracted or dried substance. The article sold in drug stores is ob- tained from crushing the dried beetle. The larvse of vari- ous beetles have been prized as food by certain peoples from the Romans of Pliny's time down to the present, for they are eaten with relish by certain tribes of South American Indians. Fireflies sewn in lace are sometimes worn by the Spanish and Cuban women as adornments for evening dresses, while other beetles with particularly hard and beautifully colored and iridescent wing-covers are used as settings in hat ornaments and buckles, as well as in jewels. APPENDIX TO CHAPTER III KEY TO THE PRINCIPAL FAMILIES OF THE COLEOPTERA (The terminology of the key may be understood by reference to the figures on page 59.) a\. Hind tarsi with five segments, as likewise also usually the other tarsi, certain aquatic families excepted [Pentamera] . T>I. Elytra, short, exposing nearly whole of abdo- men . Staphylinidce (Rove-beetles) &o. Elytra, nearly or quite covering abdomen. GI. Antennae bent, first segment long, ter- minating in a club made of applied lamella?. di. Lamellae closely applied and flat- tened . LnmrtUcornia (Lamellicoras) dz- LamelUe not closely applied ; man- dibles very large .... Lucanidce (Stag-beetles) APPENDIX TO CHAPTER III 59 FIG. 62o. — Under surface of Harpalus, a ground-beetle. After Le Conte. a, lignla ; b, paraglossse ; c, supports of labial palp1 ; d, labial palp ; e, men- turn ; f, inner lobe of maxilla ; y, outer lobe of maxilla; h, maxillary palp ; i, mandible ; k, buccal open- ing; I, gula or throat; mm, buccal sutures; o, prosternum ; p', epister- num of prothorax ; p, epimeron of protborax; q, qf, qff, coxre; r, r' , >", trochauters ; s, •••', s", femora or thighs; t, t', t", tibiae ; v, V2, Vs, etc., ventral abdominal segments ; w, episterna of mesothorax (the epim- eron just behind it) ; x, meso- sternum : ?/, episternum of meta- thorax ; yf, epimeron of metathorax ; z, mctasternum. 1 1 ho leader should run to base of hibial palp, d. FIG. 626. --Upper surface of Necro- phorus, a carrion beetle. After Le Conte. a, mandible: 6, maxillary palp; c, labrum1; d, epistome ; e, antenna ; y. vertex of head ; /;, back of head; •/, neck; /.prothorax; m, elytron; n, wing or hind wing ; o, scntel- lum (of mesothorax) ; p, dor- sal surface of metathorax; q, femur or thigh ; r, r'2, r3, etc., dorsal abdominal segments; s, s'2, .s3, etc., spiracle openings or stigmata; t, t', t', tibiae; v, tibial spurs; iv, tarsi. 1 The leader should run to the V-shaped piece in front of d. 60 ZOOLOGY Antennae straight, or, if bent, not ter- minating in lamellate club. di. Maxillary palp as long as or longer than antennae . HydrophilidoB ( Water-scavengers ) dz- Maxillary palp clearly shorter than antennae. d. Six to seven ventral segments, or if only five, the first 3 or 4 are grown together, /i. Anterior coxse spherical or transverse, projecting little from the coxal cavity. <7i. All legs used in run- ning or walking . Carabidce (Eunners) g.2. At least the hinder legs used for swim- ming /2. Anterior coxse conical or tooth-like, projecting prominently from coxal cavities. gi. Anterior coxse coni- cal ; abdomen com- posed of six rings . ~] DytiscidoB (Divers) i Gyrinidw } (Whirligigs) Silphidas (Carrion-beetles) ffz- Anterior coxas ap- proximately cylin- drical ; c u t i c u 1 a soft, leathery Abdomen composed of five rings. /i. Anterior coxas spherical ; prothorax with a pro- cess resting in a depres- sion of the mesothorax. gi. Not capable of leaping into the air Lampyridce (Fireflies) Buprestidce (Metallic Wood-borers) APPENDIX TO CHAPTER III 61 gr2. Capable of leaping into the air . . Elateridai (Click-beetles) /2. Anterior coxae conical, pro- truding from coxal cavi- ties .... Dermestidai (Dermesticls) Hinder tarsi 4-jointed ; anterior and posterior tarsi, 5-jointed [Heteromera]. &i. Fore coxse separated, more or less enclosed in coxal cavity Tenebrionidcv (Meal-beetles) b-2- Fore coxae near together, protruding ; neck evident ; elytra broader than attachment to thorax ....... Meloidce (Blister-beetles) Tarsi apparently 4-jointed, really 5-jointed, with very small, hidden, penultimate segment [Cryp- topentamera] . 61. Head drawn out into proboscis . . . Curculionidcv (Snout-beetles) 62. Head not drawn out into proboscis. Ci. Head prominent ; antennae usually as long as or longer than body . . Ccrambycida.' (Long-horns) c2. Head short, sunk in thorax. d\. Antennae short, bent, with thick terminal knob .... Svolytidm (Engravers) es ^ insects mucll Hy. Nat. size. Photo, by AV. H. larger than themselves, such as bumble- f P bees and dragon-flies. The horse-flies (Tabauiclse4) include the large mourning horse-fly, Tabanus astratus, which is of a uniform black color, the white-lined Tabanus, T. lineola (Fig. 66), and the smaller golden-headed horse and ox flies with banded crvp6s or o-ep0os, a small winged insect. - Fig. 04. 3 From asihts, a gadfly. From tabanus, the gadfly of Pliny. THE FLY AND ITS ALLTES 67 wings (Fig. 67). Only the female sucks blood, while the male feeds in flowers. They are powerful and rapid fliers. The larvae are carnivorous and live in the earth or water. FIG. 66.--Tdbanus Ihieola, white- lined horse -fly. X 1.2. Photo, by W. H. C. P. FIG. <>7. — Chrysops, handed horse- fly. X 1.5. Photo, by W. H. C. P. The black-flies (Simuliidse r) are representatives of the long-horned flies (Nematocera). They are familiar pests in the forests of our Northern country. The females, which alone suck blood, occur in such num- bers and are so active that they render certain places almost uninhabitable to man. Their bite often produces wide- spreading and painful inflammation, accompanied by swelling (Fig. 68). The larvse are aquatic. The Southern black-fly or " buffalo gnat ' sometimes causes the death of domestic animals. The gall-gnats (Cecidomyidse 2) are minute flies which lay eggs on plants. The larva? make their way into the plant tissue, and cause the further de- velopment of the tissue to be abnormal, so that excrescences FIG. (J8. — Simulium, the black-fly. En- larged. From Packard. 1 From shmtl, together ; or simultas, a hostile encounter. 2 KTJKI'S, gall-apple ; /xi»?a, fly. 68 ZOOLOGY or galls are produced. The galls are formed only in grow- ing tissue such as the tips of branches, buds of flowers or growing leaves, and are less striking on the whole than the galls of Hemiptera (Fig. 69). A certain kind of gall-fly, called Hessian-fly (Fig. TO), is extremely injurious to wheat FIG. (>'-.). -- Plant galls produced by Hemiptera and Diptera. 1. Pine-apple on twigs of the spruce fir produced by the spruce-gall Aphis (U/iennes abretis, one of the Hemiptera). 2. Covering gall on the petiole of the pyra- midal poplar (Populus pyramidalis), produced by Pemphigus burxarius, one of the Hemiptera. :>. Covering galls on an ash leaf (Fraxinus excelsior) , produced by Diploxi-t bnftdaria (Diptera). 4. Covering gall on Pistacia (Pisfacia lentiscu.fi}, produced by PenipJiif/ii* rornii'tdarhifi. 5. Solid galls ou the cortex of Dnvana lonyifolifi, produced by Cecidoxes eremite (Hemip- tera) . (>. Longitudinal section of one of these galls. 7. Capsule galls on the leaf of the turkey oak (Quercus cerris, Hemiptera), produced by Cecidomyia cerri*. 8. One of these galls cut through, with the operculum still firmly attached. 9. The same, with the operculum falling away ; X 3. The remain- ing figures natural size. From Kerner, " Pflanzen Leben." THE FLY AND ITS ALLIES 69 because it infests wheat seedlings and so weakens them that they produce no grain. Other minute gnats or midges are destructive to clover in the United States, either by binding the leaves together and sucking the sap of the plant or by destroying the young seed. The mosquitoes, or Culicidse,1 are so well known that it is hardly necessary to describe them. They can always be F - identified by the feathery an- tennae, by the presence of a fringe of hairs on the hind margin of the wing, and by the fact that the marginal vein runs all around the periphery of the wing. The larvae are usually aquatic, but some species which are abun- dant on our Western arid plains must breed in the earth. The eggs of the aquatic species are laid in a boat-shaped mass, which floats on the surface of the — Cecidomyia, the Hessian- fly. . Never less than 30 pairs of legs ; antennae 14-jointed . Most of the segments with 2 pairs of legs ; an- tennae with 5 to 8 segments ; 1 pair of maxillae [Diplopoda]. l>\. Anus in penultimate segment ; body covered with bunches of hairs .... 1 Diminutive of Scolopendra. Scutigeridce (Ex. Scutigera) Lithobiidce (Ex. Lithobius) Scolopemlridw (Ex. Scolopemlni) Greophilidce (Ex. Geophilus) Polyxenidce. APPENDIX TO CHAP TEE V 70 Anus in ultimate segment ; body without bunches of hairs, d. Mandibles not rudimentary ; mouth parts not suctorial. d\. Segments 80 or more. e\. Anal segment produced into a spine .... Julidce (Ex. Julus) e2. Anal segments produced into 2 slender papilhe, or uni- dentate .... Craspedosomidce d-2. Segments 19 or 20 ... Polydesmidce (Ex. Polydesmus) Co. Mandibles rudimentary, mouth parts reduced Polyzoniidw KEY TO COMMONER SPECIES OF THE GENUS LITHOBIUS a\. Posterior angles of none of dorsal plates pro- duced ; pores on coxae uniseriate. b\. Anal feet armed with 1 spine ; posterior coxae unarmed ; spines of first pair of feet, 2, 2, 2-2, 3, 2 (Central States) . . . bilabiatits b-2. Anal feet armed with 3 spines ; coxse with indistinct spine ; spines of first pair feet, 2, 3, 2 (Central States) .... cardinalis «2. Posterior angle of the 9, 11, 13 dorsal plates pro- duced ; antennae, 33-43 joints (eastern U.S.) forficatus «3. Posterior angle of the 7, 9, 11, 13 dorsal plates produced ; 31-38 joints of antennae (southern U.S.) . . . . . . . . spinipes «4. Posterior angle of the 6, 7, 9, 11, 13 dorsal plates produced ; joints of antennae, 14.-23 (eastern U.S.) multidentatus CHAPTER VI THE SPIDER AND ITS ALLIES SPIDERS constitute a well-defined group called Araneina,1 characterized by an unsegmented cephalothorax and abdo- men, of which the latter is stalked, and bears spinning tubercles or spinnerets upon its hinder end. Antennae are absent. The first pair of mouth appendages are called chelicerse and end in claws, at whose apices the poison- glands open to the exterior. The second pair of mouth parts, called pedipalps, are long, and seem to take the place of antennae. Near the stalk of the abdomen on the ventral side is a pair of slits which open into two lung sacks (hence Dipneumones). In a few spiders there is a second pair of slits; these spiders have four lung sacs (hence Tetrapne union es).2 The best known of our spiders are the orb web-spinning garden spiders, belonging chiefly to the genera Epiera3 or Argiope 4 and the house cobweb spinning spider Theridium.5 Argiope spins webs of very geometric form between stems of weeds, Branches of shrubs, or along fences in our meadows.6 Its web belongs to the full-orb type in fa, spider. 2 A key to the seven subdivisions of the Araneina will be found at the end of this Chapter, page 95. 3 e/uLireipos, skilful, experienced. 4 Name of a nymph. '° eypidiov, a little wild animal. 6 Fig. 78. 80 THE SPIDER AND ITS ALLIES 81 contrast to the condition in other orb-spinners, in which a sector of the circle is omitted or in which a sector only is formed. At the centre of the web of Argiope there is an oval, closely woven shield of silk. The spider, when at rest, is usually found upon or under this shield. Another frequent character of the web is a zigzag ribbon, extending FIG. 78. — Web of Argiope, placed horizontally over a fish-way. by W. H. C. P. Photo. downward from the central shield, and sometimes upward also, and attached to two or more radii. This zigzag, which is doubtless the "winding1 stair' referred to in O the rhyme, " The Spider and the Fly," is formed, as Fig. 79 shows, by preventing the fusion of the strands as they emerge from the spinnerets. G 82 ZOOLOGY The genus Theridium and its allied genera constitute the most extensive family found in the United States. The spiders belonging to the family are small, with relatively large, rounded abdomens. They have eight eyes, arranged in the manner shown in the diagram, Fig. 80. Their webs show no attempt at geometric arrangement, such as is seen in the web of Argiope and other orb-weavers, but the threads cross in every direction, forming a sort of intricate trestle- work. The species Theridium tepidario ni ui is the common little cobweb-spinner of our houses and barns ; it also spins about fences. Its color varies from a livid white to a livid brown or plumbeous color. In the south this species FIG. <9. — Argiope spinning the "winding stair." The numbers 1, 2, 3, 4, indicate IS much preyed upon points successively formed in the order of b mud-daubillff wasps these numerals. From McCook. ° (Sphex1), which put twenty to thirty of them in each cell of the nest as food for the young. Probably this enemy is one of the causes that has driven this species to the homes of man. Food. — Both Argiope and Theridium feed upon insects. Flies, bees, grasshoppers, etc., are caught in the web and wasp. THE SPIDER AND ITS ALLIES 83 bound up, either for immediate or future consumption. A few authentic instances have been recorded of the capture of mice by ordinary spiders, and some tropical 0 0 0 0 spiders are said to capture occasionally small 0 0 birds within their webs. All spiders eat FIG. so. — Dia- , , ,. ., 1-1 gram of posi- voraciously, and ordinarily drink a great tkmof eyes in deal of water; yet they may survive, in Theridium. J The four cen- tne absence 01 rood ana water, tor many trai eyes are months. the largest. Distribution. — Argiope occurs over all of North America. A. cophinaria, the basket Argiope, is the large black and yellow spider well known to all frequenters of Melds. It occurs from Massachusetts to Texas, and west to the Pacific coast. A. argent at a, distinguished by the serrated form of the abdomen, is found in the Southern States, the West Indies, and northern South America. Theridium occurs all over the world. T. tepidariorum is found, outside of the United States, in South America, Europe, and Australia. Twelve other species of this genus are found in New England alone. Some of these spin webs in trees or bushes, others in stone walls or among rocks. Spinning Habits. - - Spiders spin for a variety of purposes. Cocoons are made of silk, for the protection of eggs ; under- ground nests, like that of the trap-door spider, are lined with silk ; and, especially, nets are made of it to ensnare insects. The silky threads may serve also to suspend the spider while it drops from a tree, or they may, by their friction with the air, serve to suspend certain spiders in aerial migrations.1 This latter use is especially noteworthy. 1 The ballooning habit of spiders has been noticed since early times, but it was formerly misinterpreted. Thus Pliny speaks of wool being rained. The poet Spenser wrote : — 84 ZOOLOGY A small spider, when desirous of taking flight, climbs up some high object, such as a fence post, elevates the spin- nerets, and spins loose silk into the air (Fig. 81). After enough of it has been thus formed, the spider lets go, and is supported by the currents in the air while it is wafted great distances. Thus Darwin, on his voyage in the Beagle, saw cobwebs bearing up spiders floating in the air over his vessel more than sixty miles from shore. The method of spinning deserves careful attention. The spinning-organs consist of a set of glands lying in the hinder part of the abdomen, and opening to the exterior through a number — - often several hundred --of spin- ning "spools." These spools are the modified mouths of glands, and are grouped upon and between tubercles called spinnerets. The secretions of the glands, as they are poured out into the air, fuse together and harden into a thread. The thickness of the thread is determined by the number of glands secreting together. " More subtle web Arachne cannot spin ; Nor the fine nets, which oft we woven see, Of scorched dew, do not in th' ayre more lightly flee." Thompson writes : — " How still the breeze ! save what the filmy threads Of dew evaporate brushes from the plain." THE SPIDKU AND ITS ALLIED 85 Classification. - -Spiders are separated, according as they spin webs or do not do so, into two main groups, sedentary and wandering spiders. The sedentary spiders are sub- divided into four sub-orders, which we shall consider in turn : — FIG. 82. — Mygale, a Tunnel-weaver, allied to the " trap-door spider." Nat. size. From Emerton. 1. Tunnel- weavers (Territelarite 1). These spiders make tubes in the earth, and line them with silk. The repre- sentatives of this group in the Southwestern States are 1 terra, earth ; tela, tissue or web. 86 ZOOLOGY commonly known as trap-door spiders. The lid of the nest is covered with hardened dirt, and when closed, looks exactly like the ground around FG it. Some of these spiders gain a great size and capture birds (Fig. 82). 2. Orb-weavers (Orbite- lariee 1). These, which are typically represented by Argiope, are well known ; yet few persons have studied the almost mathematical precision with which the webs are built. Foundation lines (Fig. 83) of unusual strength are first laid down, to form the periph- ery or frame of the web. Then radii are spun from a central little ball of floss to the frame. The radii are, often at least, laid down alternately on opposite sides of the centre. The number of radii formed by a species of spider is not perfectly constant, but varies within limits. It would be an interesting occupation to sketch a number of webs of Argiope showing the variations in the number of radii and the other details of form. After the radii are placed, the spiral lines are laid down. In the completed web four regions are distinguishable, as follows, passing from the centre outward : (1) the notched zone, consist- ing of four to eight turns of a spiral at the centre ; (2) the free zone in which no spiral is laid down ; (3) the spiral space, the main part of the spiral framework ; (4) the 1 orbis, circle ; tela, web. rs FIG. 83. — Diagram on nomencla- ture of parts of an orb-web. FS, foundation space ; SS, spiral space; CS, central space ; FZ, free zone ; NZ, notched zone ; H, centre. From McCook. THE SPIDER AXD ITS ALLIES 87 foundation space, without the spiral lines, and at the outer margin of the web. No study is more interesting than that of the details of construction of these parts of the spider web, while they are being made out of doors or in large glass jars. FIG. 84. — Orb-web of Epeira. a, first spiral line ; b, second spiral line ; c, line to nest. From Emerton. 3. Line-weavers (Retitelarise1).- -Of this group The- ridium is a type. The web consists of a fine irregular mesh with strands running above and below in various direc- tions.2 The spider stands below the main part of the net, back downward. 1 rete, net ; tela, web. 2 Fig. 85. 88 ZOOLOGY 4. Tube- weavers (Tubitelarue 1). Here belong the spiders that spin webs in the grass, which are so conspicuous in the morning when laden with dew (Fig. 86). At one side of the web a tube leads down among the grass stems. At the opening of this tube the spider stands ready to FIG. 85. —Web of Theridium, a " cobweb." From Emerton. dart out after prey, or to retreat as occasion demands (Fig. 87). The wandering spiders do not spin webs of any kind. They are classified into three groups as follows : — 1 tubus, tube ; tela, web. THE 8PIDER AND ITS ALLIES 89 (1) Crab spiders (Laterigradse *) are so called because they run sideways. They make nests by fastening together leaves by threads of silk. Their young are reared in these nests, and watched over by the mother (Fig. 88). ('2) Running spiders (Citigradre2). - These are for the most part large and powerful species which wander over FIG. 86. — Web of a tube-weaver; looking down upon the web, which is in a corner between two vertical walls. The tube is in the angle. Photo, by W. H. C. P. fields or along watercourses in search of prey. Our Northern species belong chiefly to the genus Lycosa3 (Fig. 89). They live in holes in the ground, making a ring of silk at the orifice. The female carries her eggs about in a special cocoon attached to the end of the abdomen. The j side ; gradus, locomotion. 2 citus, rapid, + yradus. 3 Xtkoj, wolf. 90 ZOOLOGY FIG. 87. — Agalena, the common grass spider. Nat. size. Photo, by W. H. C. P. young are borne on the back of the mother. The great size, black color, and hairiness of some of these spiders have given them an apparently unjustified reputation of being very poison- ous. Naturalists who have al- lowed these spiders to bite the hand report that the bite is rarely more poisonous than that of the mosquito. (3) Jumping spiders (Salti- gradse 1). - This family includes many familiar, active species of high intelligence. Some of these of grayish color live in houses, and are recognized as members of this family by their half -running, half- jumping gait (Fig. 90). The cocoon is attached to some object and enclosed in a sort of tent, in which the mother also lives to guard the young. The economic impor- tance of spider webs is con- siderable. First of all, they are of the greatest importance in capturing many destructive insects, such as flies, mosquitoes, and moths. Another use 1 saltus, jumping, + yradus. o o o o O O o o FIG. 88. — Thomisus, a crab spider. Dia- gram showing arrangement of eyes at bottom of figure. From Emertou. THE SPIDER AND ITS ALLIES 91 to which they have been put is in making silk cloth. The silk of the spider is smoother and glossier than that of the silk-worm, but it is much harder to collect in quantity. A spool is passed against the spinnerets of an individual spider and slowly revolved, winding the silk upon it. The difficulty comes in rearing the spiders, for they are extremely voracious and if the supply of flies is insufficient FIG. 89. — Lycosa, a running spicier. Ocelli formula below. From Emer- ton. FIG. 90. — Attus, a jumping spider. From Emerton. they attack and devour one another. Consequently they must be kept isolated and fed individually, and yet yield in the end only an ounce or so (about 30 grammes) of silk. Other uses of spiders' silk are : in the construction of cross-hairs in telescopes, and in medicine as a narcotic in case of fevers, - - a temporary fad. Poisonous Spiders. — Spiders are feared by many people from a belief that they are very poisonous, even fatally so. Spiders have, indeed, biting jaws provided with poison- 92 ZOOLOGY glands, and their bite is often fatal to insects, and even to small birds and mammals. But most spiders cannot spread the chelicene sufficiently to make a bite in the human skin, and even the largest forms seem to inflict but a slight wound, scarcely ever greater than that of a mosquito. The stories of the severe effects of the bite of the Taran- tula, one of the Lycosidse, are entirely fabulous. Spiders show a marked sexual dimorphism. Particularly among the orb-weavers the males are much smaller than the females of the same species, but the legs of the male are relatively the longer and stronger. The male is usually shorter lived than the female, for the latter has often to watch the egg-cocoons, or carry them about with her until the young hatch out. The male also builds less perfect webs than the female. The relation existing between mated pairs is often peculiar. The male is frequently killed and eaten by the female; but if the male can over- come the female, she may fall his victim. Among wander- ing spiders there is often a selection by the female from among several rivals, which engage in severe battles with each other. Allies of the spider must be briefly mentioned. The spider belongs to the class Arachnoidea,1 characterized as follows : Air-breathing, wingless arthropods, whose head and thorax are usually united to form a cephalothorax, which bears two pairs of jaws and four pairs of legs ; the ab- domen, which is not always separated from the cephalo- thorax, possesses no legs. The principal subdivisions of the Arachnoidea are as follows : - The Arthrogastra,2 including the scorpions and their allies, are characterized by the fact that the abdomen is j, spider ; eUos, form. - dpdpov, joint ; yarnf/p, abdomen. THE SPIDER AND ITS ALLIES 93 palp. segmented and intimately joined with the cephalothorax.1 Here belong the true scorpions, in which the posterior six segments of the abdomen are much smaller in diameter than the seven anterior segments, and form a sort of tail (post-abdomen ) . Nearly twenty species of scor- pions occur in the warmer parts of North America. Centrums in- famatus ranges from the * O southern Atlantic States, through Texas, and north into southern Kan- sas. The tip of the tail bears a sting, which con- nects with a poison-sac. The largest scorpions of the tropical countries are the most dangerous, but the wounds even of these are rarely fatal. The Phalangina,2 the extremely common "Daddy-long-legs," or harvest-men, in which the legs are very long, FlG oi.__Buthus, a European scorpion. and the abdomen short Dorsal view. MX., maxillary; Cephth., , . . , rp. cephalothorax; Troch., trochanter ; Tor.s'., and tlllCK. hey OCCUr tarsus; AbO., abdomen ; Bla., poison blad- aboilt houses, in woods, der; St., sting. From Kraepelin in "Das Tierreich.' and in fields. They feed on small insects and are highly beneficial animals to 2 0aAd77ioj>, a spider, especially a poisonous species. Dorsal ridge*--- Lateral ridge-' 1 Fig. 91. 94 ZOOLOGY FIG. 92. — Liobunum dorsatum, one of the harvestmen. The long legs are apt to be thrown off in handling the living animal. The second left leg is accordingly absent in this specimen. Nat. size. Photo, by W. H. C. P. FIG. 93. — Psoroptes, the sheep scab, female. Right figure, dorsal view; left figure, ventral. Industry. Much enlarged. After Salmon, Bulletin 21, Bureau Animal THE SPIDER AND ITS ALLIES 95 man. Liolmnum dorsatum is a common grayish species with a darker dorsal band, which emits a clear fluid when handled (Fig. 92). The Areneina, or spiders, already considered. The Acarina,1 or mites and ticks, in which, as in spiders, the abdomen is unsegmented, but is fused with the cephalo- thorax. Mites have typically a round body. They exhibit great diversity of form and habits. All are terrestrial, excepting one group of aquatic mites, and are often of a bright red color (A tax). The free-living species prey on smaller animals, as well as dead organic substances. Others are parasitic in animals , . . • f p J.T 9 i FIG. 94. — Pal- or plants, living in fur or leathers/ and even Ien6) a sea_ penetrating into the skin, as the small red spider. : 1.5. ,, , . ,, r. 0 ,, Photo, living "jigger or " c nigger ' or our bouthern byW.H.c. P. States does. Finally, there lives in the sea an aberrant family of spiders which crawl on the sea-bottom or over hydroids, and thus have forsaken a terrestrial life for a completely aquatic one (Fig. 94). APPENDIX TO CHAPTER VI KEY TO THE SEVEN SUBORDERS OF THE ARANEIISTA «i. With 4 slits into lung sac [Tetrapneumones]. Che- lifer claw directed downward ; 8 closely grouped eyes Territelar!«' (Tunnel-weavers) a*. 2 slits into lung sac [Dipneum ones]. Chelifer claw directed inward. i a/cct/n, mite. 2 Fig. 93. 96 ZOOLOGY b\. Eyes in 2 transverse rows ; most species spin webs [Sedentarise]. Ci. Legs not spread flat out. d\. Spinnerets short and inclined together, and on under side of abdomen, which is usually round. e\. Anterior row of eyes near margin of head e-2. Anterior row of eyes remote from , margin of head .... d\. Spinnerets at end of abdomen, which is elongated ..... Ci . Legs spread flat out ..... 61. Eyes in 3 transverse rows ; spin no webs, but hunt prey [Vagabundse]. Ci. Anterior eyes smallest .... c2. The anterior eyes largest . OrbitelaricB (Orb-weavers) Retiielarice (Line-weavers) Tubitelarice (Tube-weavers) Laterigradce (Crab spiders) CitigraddB (Running spiders) Saltigradce (Jumping spiders) CHAPTER VII THE CRAYFISH AND ITS ALLIES THE crayfish belongs to the class of Crustacea, since it breathes by means of gills, possesses two pairs of antennae, a pair of mandibles bearing palps, and a pair of append- ages on all body segments excepting the last. The Crustacea are divided into two subclasses,- - Entomostraca, of which Daphnia is an example, and Malacostraca, to which the crayfish belongs. All the Malacostraca 1 have 19 pairs of appendages.2 The crayfish,3 which is closely related to the marine lobster,4 is an inhabitant of fresh-water lakes, rivers, and pools. It thrives in diverse surroundings; for some species prefer cool mountain streams and others muddy pools, while certain species, both in Europe and America, are found in brackish as well as fresh water. Indeed, the European Astacus fluviatilus is said to be frequently s, soft ; 'ocrrpaKov, shell (since the shell is less hard than that of mollusks). 2 Keys to the six chief orders of Malacostraca and to families of the stalk-eyed Crustacea will be found in the Appendix to this Chapter, p. 122. 3 The old English spelling of this word was ''crevis'' or "crevice." The ere came to be spelled phonetically cm//, while vis became changed to fisli in accordance with the popular nomenclature of all aquatic animals. 4 The English word " lobster " is from the old English lopystre, which is probably corrupted from the Latin locusta, by which term Pliny refers to the lobster. H 97 98 ZOOLOGY caught off the Livoniaii coast, even some distance out at sea. Individuals of an American species have been taken from a mineral spring impregnated with sulphur and magnesia at a temperature of 70° Fahr. (21° Cent.), while several kinds of the American "burrowing' or " chimney "-forming species have been found in meadows and clay bottoms, often at great distances from streams. Certain species that are blind inhabit caves only. In England, according to Huxley, "in granite districts, and others in which the soil yields little or no calcareous ty matters to the water which flows over it, crayfishes do not occur. They are intolerant of great heat or of much sun- shine ; hence they are most abundant in those parts of rivers which flow east and west, and thus yield the most shade from the midday sun." The food of the crayfish is very varied ; it may be living or dead, animal or plant. On account of the need of calcareous matters in the food, crayfishes are especially fond of the stoneworts (Chara) and various succulent roots, like the carrot. It is said that crayfishes sometimes make excursions inland in search of plant food. They likewise devour shells of snails, their own cast-off skins, and occasionally each other, shell and all. There are two great groups or subfamilies of cray- fishes. One, restricted to the Northern Hemisphere, is found in Europe, Asia, and North America. The other is found in the Southern Hemisphere, in Australia, Tasmania, New Zealand, Fiji Islands, Madagascar, and South America. No crayfishes have been found on the continent of Africa, or in the rivers of northern Asia that flow into the Arctic Ocean, or in those of southern Asia. These Asiatic rivers are populated by fluviatile crabs, to which the cray- THE cnAYFixrr AND ITS ALLIES 99 fishes of the region have probably succumbed. All the islands now inhabited by crayfishes, such as England. Japan, and Cuba,1 were probably once connected with the mainland. The northern subfamily of crayfishes contains, accord- ing to Faxon, two genera- -Astacus and Cambarus- -of which the latter can be subdivided into the subgenera Cambarus and Cambaroides. These groups occupy dis- tinct geographical areas. The genus Astacus is found, in the Old World, in Europe and western Asia as far south as the Aral and Caspian seas, and in America in the region west of the Rocky Mountains, draining into the Great Salt Lake and the Pacific Ocean. It is thus seen to occupy the western sides of the two northern continents. Likewise Cambarus and Cambaroides occupy the two eastern coasts of the northern continents; for Cambarus is found in North America east of the Rocky Mountains in the region bounded on the north by Lake Winnipeg and New Bruns- wick and on the south by Guatemala and Cuba, while Cambaroides is limited to the Amoor River basin in Asia, and to Japan. We thus find among the crayfishes what is known as discontinuous genera; that is, genera which now occupy widely separated areas, such as Astacus in Europe and Pacific North America, but which once ranged over the intervening regions as well. From some cause, the struggle for existence became too severe in the intervening regions, so that Astacus and Cambarus were annihilated on the eastern and western sides of the continents respectively. In southern Asia we find that the struggle was doubtless with the successful river-crab. It is interesting to note 1 It is doubtful whether Cuba has been connected with the mainland. 100 ZOOLOGY that, probably on account of the preserving influence of climate, the other animals and the plants of the eastern sides of the two continents and those of the western sides are more alike than those from opposite sides of the same continent. One of the best pieces of evidence for the con- clusion of a former hemispherical distribution of the two genera of crayfishes is that there occur in the caves of Carniola in southern Austria crayfishes l belonging to the genus Cambarus - - the only known living representatives of this type in Europe. The mere fact that it lives in a cave is not sufficient to make the Carniola crayfish a Cam- barus, for in North America the genus has certainly not originated under the influence of subterranean life ; it is more likely that the caves of Carniola have protected these crayfish from the widespread destruction which has over- whelmed their fellows outside. Only one crayfish, Cambarus Bartonii, is found in New England., and here, with two or three local exceptions, only in the rivers of Maine. This C. Bartonii has the widest geographical distribution of all the northern species. C. Blanding'd is the most widely distributed of the southern species. C. pellucides is the blind species found in Mammoth and Wyandotte caves. The lobster (Homarus) is, as we have already seen, the nearest living salt-water relative of the crayfish. There are only two species of the genus Homarus. One, Homarus americanus, occurs on our Atlantic coast, the other, H. vulyaris, is the lobster of Europe. On our Pacific coast there is the "spiny lobster," but this is not closely related to the eastern lobster (Fig. 95). The national gov- 1 These crayfishes are blind, like the cave-inhabiting Cambarus of America. THE CRAYFISH AND ITS ALLIES 101 eminent has transplanted the Atlantic lobster to several localities on the Pacific coast, but it is not yet known whether it will thrive there. The American lobster ranges from Labrador to Delaware Bay, and from near shore to a FIG. 95. — Palinurus, the spiny lobster. One-fourth nat . size. From Rathbun ; drawn by H. L. Todd. depth of 100 fathoms. It attains its greatest size on the rocky shores in the cooler waters from Maine to Labrador. It migrates but little along the coast ; in the fall, however, it moves out into deep water, and in the spring back again 102 ZOOLOGY into the shallower bays ; the time of migration depending upon the length of the season. It is said to be a nocturnal animal, searching most actively for its food at night. The sense which probably aids it most in this search is that of smell, as the attraction of the bait in the traps - - the so- called lobster-pots — testifies. In respect to food it is, like the crayfish, omnivorous. Protection of the Lobster. — There has been much differ- ence of opinion in regard to the size at which a lobster becomes mature and before which, therefore, it cannot be caught without danger of extermination. The legislation on the matter has accordingly been very varied. In Con- necticut the law makes the limit six inches, while in Massachusetts and New York it is placed at ten and one- half inches. Herrick has carefully investigated the relation of length to maturity, and concludes that, on the Massa- chusetts coast at least, the lobster becomes mature between the limits of eight and twelve inches, and hence that all present legislative protection is insufficient. The increasing rarity of large lobsters in our markets testifies to the correctness of this conclusion. Enemies of the Lobster. — Besides its worst enemy, man, both the adult (particularly the egg-bearing female, called by fishermen the " berry lobster," or "berry hen") and young lobsters are attacked by many kinds of fish. Two or three internal parasites are known to infest the lobster, while sometimes it is greatly hampered in its movements by the number of messmates it; carries about attached to its shell. Barnacles, mussels, tube-forming worms, and various seaweeds are all found at times attached to the shell of the lobster. Upon moulting, however, the animal is enabled to rid itself of all these hangers-on ; but this very process of THE ('HAY FISH AND ITS ALLIES 103 moulting, or casting off the entire shell at intervals, is attended with great dangers to the lobster, since the animal is so soft bodied as to be able to offer little resistance to its enemies. The moulting process in the lobster, crayfish, and other Crustacea is made necessary from the fact that these animals are enclosed in a chitinous covering which is impregnated with salts of lime. It is evident that an animal cannot increase in size while so encased ; hence special provision for growth has to be made by the moulting or casting off of the hard shell. This process is accomplished in the following manner: previous to the throwing off of the old skin a new soft one is formed inside, the lime is absorbed from the old shell in a dorsal line along the carapace, reaching from the rostrum to its posterior margin. Ab- sorption also takes place at the joints of the limbs. AVhen the lobster has attained this stage it is dark in color, and known by fishermen as the " black lobster." The carapace now splits along this dorsal median line of absorption, the blood leaves the limbs, which are thus made flabbier, and by involuntary muscular movements they are drawn, large claw and all, through the joints of the old shell. The anterior portion of the body is first drawn out through the dorsal rent, and lastly the tail. Not only is the entire outer covering cast off, but the lining of the oesophagus, stomach, and intestine as well, since these organs are formed by an infolding of the skin. By means of the return of the blood to the limbs and rapid absorption of water, the body of the lobster soon swells to a size far beyond that of the old shell. There remains in the stomach, after moulting, a calcareous nodule which has long been known by the name of "crab's- eyes." These " crab's-eyes ' were formerly much sought 104 ZOOLOGY after and prized on account of their supposed medicinal qualities. The function of these gastroliths or " craVs- eyes ' was for a long time rather obscure. It is now believed that during the time of absorption of lime from the shell, previous to moulting, the blood becomes strongly impregnated with lime. If all the lime that must be re- moved were to remain in the blood, it would probably be fatal to the animal ; hence it is taken up by secreting cells located in the wall of the stomach, and there deposited. After the old skin is cast, the gastrolith is soon absorbed, FIG. 90. — Palasmonetes vulyaris, a common shrimp. Nat. sizo. Photo. 'by W. H. C. P. probably to aid in strengthening the new shell. Bits of water-worn shells, entire gastropod shells, parts of lobster coverings, spines of sea-urchins, etc., have been found in the stomachs of lobsters and crayfish, which likewise would probably have been dissolved and used in hardening the shell. Shrimps and prawns l belong to a thin-skinned, long-tailed family of Crustacea.2 They are extremely common in bays 1 These are common names of small Crustacea applied chiefly to the decapod family Carididse,* although also applied to certain Schizopods. The term shrimp is applied to the smaller species, and prawns to the larger. 2 Fig. 90. * (capis, a small marine crustacean. THE CRAYFISH AND ITS ALLIES 105 along our coast, and even penetrate into rivers. Two river shrimps l are found in the United States east of the Missis- sippi River. These Crustacea are able to maintain their enormous numbers only by virtue of their great repro- ductive capacity, necessitated by the circumstance that they furnish almost the entire food supply for many kinds of fishes and other foes. Even in the principal shrimping grounds of the United States- -such as San Francisco and FIG. 97. — Gebla affinis, right side. Two-thirds natural size. ' Photo, by W. H. C. P. New Orleans — there is said to be no diminution in the numbers of shrimps. The Thalassinidae 2 include certain crayfish-like species which live on our coast, burrowing in mud-flats, where they live concealed during the day. On account of their being of only medium size and difficult to obtain, they are commonly little known. Our Eastern species are Grebia affinis (Fig. 97) and Callianassa stimpsoui. The hermit crabs (Pagurida33) occupy a position inter- mediate between the long and short tailed Decapods in 1 Palwmon Ohionis and Pal eomonetes exilipes. 2 0a\d(Tcrivos, color of the sea. 3 irdyovpos, a kind of crab. 106 ZOOLOGY respect to the length of their abdomen. The abdomen is soft, and the animal protects it by inserting it within the coiled shell of some gastropod. Moreover, the abdomen is asymmetrical, being coiled to one side to correspond with the shape of the borrowed house (Fig. 99). The abdominal feet become degenerate, with the exception of the posterior pair, which are modified into a hook-like process, by means of which the crab maintains itself securely in the shell. FIG. OS. Eupagunis longicarpus. Two individuals in shells. Photo, while alive by W. H. C. P. When one shell becomes too small, it is abandoned for a larger one. Numerous species of hermit-crabs occur on our coast, ranging from the shore line to a depth of several hundred fathoms. Eupagurus longicarpus is the little active hermit found in almost any tide-pool from Massa- chusetts Bay to the Gulf of Mexico. Hydroids, polyps, sponges, often attach themselves to these borrowed shells (Fig. 98) ; indeed, a Chinese hermit-crab always bears an anemone on its large claw, with which it plugs up the aperture when obliged to retreat within its shell. One of THE CRAYFISH AX.D IT* ALLIED 10' the East Indian hermit-crabs, the so-called palm-crab, feeds upon cocoanuts, Avhich it opens by inserting its claws into the eyes and then breaking the shell upon the rocks. The Hippidae include certain oval animals, which bur- row, like a mole, head first, in sandy beaches. The name of our common eastern species, Hip pa J talpoides? indicates this resemblance ('Fig. 100). FIG. 99. — Eupayurus lonylcurpus removed from shell, x' Ifc. Photo, by W. H. C. P. FIG. 100. — Hippa Nat. size. Photo, by W. H. C. P. The Brachyura are represented on our shores by three principal families, which may be designated as triangular crabs, arched crabs, and square crabs. The spider-crabs, or sea-spiders, as they are sometimes called, belong to the triangular crabs. As their name implies, their legs are very long and slender.3 These crabs frequent oyster-beds and sea-bottoms in general. When 1 From i'TTTTos, horse ; used by Aristotle as the name of a kind of crab. 2 Like talpa, the mole. 3 Fig. 101. 108 ZOOLOGY seen stalking over such uneven surfaces, the advantage of these stilt-like legs is at once evident. The surface of the body of some species of spider-crabs is hairy, entangling inorganic matter, while hydroids, barnacles, and algae attach themselves to the shell. Libinia emarginata and dubia^ the former ranging from Maine south, and the latter from Cape Cod to the Gulf of Mexico, are our two species which FIG. Wl. — IJliitiin dubia. One-third nat. size. Photo, hy W. H. C. P. undergo such concealment. The great Japanese spider- crab is said to be the largest of all the Crustacea, some individuals measuring, from tip to tip of the first pair of legs, 18 to 20 feet. The edible crab is a typical arched crab. It is so called because the carapace is arched in front. The carapace is also broader than long, and narrower behind than in front. THE CRAYFISH AND ITS ALLIES 109 The legs of this family are short and broad, and in some species the posterior pair is especially broad - - an adapta- tion for swimming. These crabs may be divided into two groups — the burrowing crabs and swim- ming crabs. To the burrowing crabs belongs the genus Cancer (Fig. 102), which includes the edible crab of Europe, especially prized in England, together with several American species; while our common edible, soft-shelled or blue crab, Callinectes hastatus (Fig. 103), and the beautiful "lady crab" (Fig. 104) belong to the swimming group. Representatives of other families of crabs are, however, eaten in various localities and by various peoples. For example, our little Pinnotheres FK;. 102. - - Panopeus sayi, allied to Cancer. The mud- crab. One-half nat. size. Photo, by W.H.C.P. FIG. 103. — Callinectes hastatus, blue crab. Reduced to one-third. Photo. by W. H. C. P. 110 ZOOLOGY ostreum (Fig. 105), found in the mantle chamber of the oyster, is eaten by us together with the oyster or separately. FIG. 104. — Platyonichus ocellatus, lady oral). Reduced to one-third. Photo, by W. H. C. P. The fiddler crabs are representative of the square crabs. These are the familiar animals which crowd salt marshes and run sideways to and from their burrows. One claw is much larger than the other. When the crab is disturbed, the large claw is brandished in a manner which has been likened to the movements of a riddle as one plays upon it. Crelasimus pugnax is the most abundant species, and ranges from Cape Cod to the Gulf of Mexico. Together with Cambarus it does much damage by burrowing in the levees of the Mississippi River (Fig. 100). FIG. 105. — Pinnotheres oxtreum. X 4 From Rathbui). THE CRAYFISH AND ITS ALLIES 111 The economic im- portance of the Deca- poda may be inferred from the fact that the receipts for the lobster alone, taken and sold by United States fishermen, is Fie, 106. - Gelasimus pugnax. Nat. size. estimated for 1892 Fronto-dorsal view. Photo. l>y W. H. C. P. at one million dollars. The yield to Canadian fishermen was in ad- dition worth half a million dollars. From the United States Fish Com- mission Bulletin for 1890-91 we find that the bine-crab fisheries on the Atlantic and Gnlf coasts re- turned almost half a million dol- lars, while the shrimp catch in the same waters brought nearly a quarter of a million dollars more. The latter industry on the Cali- fornia coast is much greater, for the shrimp trade of San Francisco Bay alone is valued at a quarter of a million dollars yearly. The remaining orders of Mala- costraca maybe briefly mentioned. The Stomatopoda1 include only FIG. 107. — Squt/la empusa, the Sqililla,2 the mantis shrimp, SO mantis shrimp. Dorsal aspect. From Bigelow. 1 (rr6/xa, mouth ; TTOUS, foot. 2 <7/d\Aa, classic name for a marine crustacean. 112 ZOOLOGY called because of a certain resemblance to the mantis insect (Fig. 107). This animal is found on our east coast, where it burrows in the sand. It is a little longer than a crayfish. Being hard to catch, it is not much used as food. The Cumacea include a few small marine Crustacea, not ordinarily seen. They are of interest be- cause of the reduced carapace which is transitional to the condition found in the lower Crustacea. The Isopoda l include FIG. 108. - - Oiiis'.-us, the sow-bug. Dorsal view. Nat. size. Photo, by \V. H. C. P. FIG. 10<». - • Talorchestia lonf/ieornis, the beach flea. Nat. size. Photo, by W. H. C. P. the sow-bugs or wood-lice (Fig- 108), noteworthy for forming the largest group of land Crustacea, and certain marine and fresh-water groups. The Amphipoda2 are exclusively aquatic creatures, found under decaying vegetation on beaches of lakes or the sea (Fig. 109), and crawling amidst marine hydroids. Being laterally com- pressed, the Amphipods tend to lie on one side when at rest. 1 tVos, equal ; TTOVS, foot. 2 d/x0i, both ; Trotfs, foot. THE CRAYFISH AND IT 8 ALLIES 113 Edible Lobsters. — The American lobster, Homarus Ameri- canus, differs little in appearance from the European lob- ster, If. vulgaris. Formerly the American lobster attained the greater size, but the excessive catches of our species in the last few years are rapidly doing away with this differ- ence. The so-called Norwegian lobster finds its way into European markets, while on our California!! coast the so- called spiny lobster or sea-crayfish takes the place of our true Atlantic lobster, and, like the latter, is said to be in danger of extermination on account of overfishiiief. c5 O Edible Crayfish. - The nearest fresh- water ally to the lobster - - the crayfish — has not yet attained the pop- ularity in our markets which it possesses in Europe, particularly in" France. So much is the crayfish esteemed in Paris that the enormous crayfish farms throughout France are unable to supply that city, consequently cray- fishes are imported in considerable quantities from Ger- many. In America, it is our French population mainly that makes a market for the crayfish. Astacus nu/res- cens is the crayfish sold in San Francisco markets. ( )n the Atlantic coast, New York and New Orleans are the main centres of consumption. Cambarus affims, taken from the Potomac River, is the crayfish found in the spring in the New York markets. Later in the season this market is supplied by C. virilis and immunis, which are shipped from Montreal, Milwaukee, and other Western cities. Edible Crabs. --Of the crabs which reach our market the most important is the blue crab. These crabs are kept moored in floating boxes until they have moulted, and then they are sent to market as soft-shelled crabs. i 114 ZOOLOGY The shore crabs, Cancer, are little eaten in the United States.1 Edible Carididae. - The shrimps and prawns have within recent years begun to appear in large numbers in the Eastern markets. For many years the Pacific species P J? :.*% X" : A A^ ^ .«£ \,:: lawv- FIG. 110. — Lhniihts 2)o!i/i>Ji"iiiux, the king-crab or horseshoe-crab. have been dried and shipped by the Chinese in large quantities to China. 1 Very unfortunate is the destruction of the "king-crab," Limulus, which is only distantly related to the Decapoda. In Delaware Bay they are caught in great numbers and ground up as fertilizer. As they are taken only during the breeding season, they are being rapidly extermi- nated. The American Limulus belongs to an order entirely unrepresented 011 the European coast (Fig. 110). THE CRAYFISH AND ITS ALLIED 115 Development of Lobsters. — Lobsters lay eggs in July and August. In the fall they migrate to deep water, and pass the winter there. In the spring they migrate back to the shore — the females tarrying behind the males until the eggs of last summer, which she still carries attached to her swimmerets, shall be further advanced. In June the young hatch out, moult, and swim to the surface. The FIG. 111. — An early stage of develop- ment of egg. Appendages becom- ing bifid. Paired dotted areas above indicate eyes ; these are fol- lowed by the first three paired ap- pendages : aiitennules, antennae, and mandibles. Below in the mid- dle line is the forming tail; above is the mouth. After Herrick. FIG. 112. - - Surface view of egg nauphius. Antennae show begin- ning of segmentation; mandibles and maxillae seen on each side of the abdomen. Embryo 10-18 days old. X 25. From Herrick. female now moults, 1m t does not spawn again for a whole year ; that is, she spawns in alternate years. The number of eggs carried varies with the age of the female ; middle- aged lobsters may carry up to one hundred thousand eggs, but the old or young ones as few as three thousand. The egg as freshly laid is about 1.5 millimetres in diameter and is stored with food material, called yolk, much as in the case of the hen's egg. As in the chick, the development 116 ZOOLOGY takes place, as it were, on top of the egg (Figs. Ill, 112). Eyes and mouth appendages early make their appearance; then the other appendages, and the tail (Fig. 113). For a long time the back of the thorax is greatly distended by the yolk stored there, and the eyes are huge (Fig. 114). Immediately after hatching, the young lobster is about one-third of an inch long. The eyes are still abnormally large, the telson is spatulate, and the abdomen is without FIG. 113. — Surface view of embryo FIG. 111. — Lobster embryo. 01 days with all of thoracic appendages old ; eyes have developed pigment, formed. The forked telson partly X 15. From Herrick. overlies the brain. Note the large eyes, which are yet without pig- ment. Embryo about 21 days old. X 25. From Herrick. swimmerets. On account of its resemblance to the Schizop- oda, the larva at this stage is known as the " Schizopod larva' (Fig. 115). In moulting for the fourth time, the exopods are lost from the future walking appendages, and the animal resembles a lobster except for its small size (Fig. 115a). During these early moultings the young lobsters undergo a terrible mortality, so that out of ten thousand embryos hardly two, on the average, survive. After the THE CRAYFISH AND ITS ALLIES 117 fifth or sixth moult the little lobsters sink to the bottom, and then begin their journey shoreward. From this time until they are about four inches long, only very few indi- viduals have ever been seen. This is due, it is said, to the fact that they hide deep down among the rocks, where they cannot be dredged. When they are four inches long or so, they become bolder, leave the rocks, and, like the FIG. 115. — Larval view of lobster, extracted from an egg which was about ready to hatch. The concretions in the intestine are destined to go into the newcuticula after moulting, x 25. From Herrick. adults, make burrows for themselves in the sand or under stones. Development of Crayfish. — The crayfish develops simi- larly to the lobster, — from a large egg filled with yolk. The early stages are much like those of the lobster ; but those changes which in the lobster take place during the first three stages of free life are in the crayfish passed in the egg. Consequently at the time the crayfish hatches it 118 ZOOLOGY is almost, but not exactly, like an adult crayfish except in size. The telson of the just-hatched crayfish has, to be precise, a somewhat more oval form, and the first pair of swimmerets are undeveloped; but these differences soon disappear. FiG.lloa. — Third larval stage, lateral view. Note the dif- ference between this and the adult. X 11. From Herrick. Regeneration of Lost Parts. - -If you attempt to pick up a crab by one of its claws, you frequently find yourself in possession of a portion of the leg only, while the crustacean has made good its escape. Moreover, it will be seen that the leg always separates at a certain place ; namel}r, be- tween the second and third segments. This is the place where a fusion occurs between two segments which are free TIIE CRAYFISH AND ITS ALLIES 119 in the first larval stage. This power of defensive mutila- tion occurs in those appendages which are most apt to be seized, — namely, the five thoracic legs, — and is wholly under the control of the reflex nervous system, for it may occur when the entire voluntary nervous system has been removed. The leg of a dead crustacean shows no such capacity. If the leg of a lobster is cut off at some point distal to that of normal rupture, the limb will later be found cast off up to this point. Here a sort of double membrane or diaphragm exists, with a central opening only large enough to admit the passage of nerves and blood-vessels. Upon rupture this passage is soon plugged up by coagulated blood — • clearly a device to prevent ex- cessive hemorrhages. Soon after a leg is cut off a papilla- like body grows out from the stump of the limb, develops into the shape of a small limb, and grows larger, with each successive moult, until the normal size is reached. The antennse, too, are much exposed to injury, but with them autotomy is not practised. The}^ begin to grow out at the place of injury, and at least one moult is necessary for their complete restoration. Abnormalities in the claws of the lobster are not un- common. The thumb-like protuberances of the next to the last of the joints of the great claw is sometimes bifid, or carries a large wart. The finger which opposes the thumb is also sometimes forked (Fig. 116). Many of these abnormalities are probably due to injury of the claw; but others cannot be explained in this way. For instance, cases have been observed of lobsters having crushing claws of equal size on the two sides of the body. An antenna has been seen replacing an eye, and this result may be obtained by cutting off an eyestalk near its base 120 ZOOLOGY when an antenna will regenerate (Fig. 117), one or two extra oviducts may occur, or double monsters — sort of Siamese twins - - may be hatched out. Similar monstrosities are found in other arthropods. Physiological Division of Labor. The difference between a " highly developed " animal and a lowly organized one is not first of all a difference of size nor a difference in the number of parts, - just as a large population or numerous cities are not the pri- mary characteristics of a highly civilized state. But just as a complex civilization is one in which each of the different citizens has his own special task to per- form for the commonwealth, so a highly developed organism is one in which each different o reran o has its special role to play. The worm Nereis has more segments o to the body than the crayfish, but these segments are very nearly alike — the parapodia especially FIG. lib. — Two abnormal claws. J Upper figure shows a double are quite similar. In the crayfish, CrCe°ther^TextS °" the other hand, the append- finger. From Herrk-k. ages are dissimilar. Each pair has a special function to perform and is specially adapted, often complexly fashioned, to meet this need. What is true of the appendages is like- 777 K CRAYFISH AND ITS ALLIES 121 wise true, to an equal degree, of the internal organs. The internal organs of Nereis are repeated in each segment; but in the crayfish the egg-ducts lie in one segment, the heart in another part of the body, and so on. Some of the seg- ments have given up one or more functions to perfect a Fiu. 117. — Eyestalks of a Decapod dissected out. Oil the right an antenna has regenerated in place of the amputated eye. opt., optic nerve. After Herbst. single one in which it lias specialized. There has been a division of labor between the different parts of the body, and in consequence a greater perfection in the performance of each function. More perfect fulfilment of function is the result of physiological division of labor, just as a higher civilization is the result of individual division of labor. 122 ZOOLOGY APPENDIX TO CHAPTER YII KEY TO THE SIX CHIEF ORDERS OF MALACOSTRACA Body segments, 20 ; abdomen with 7 segments ; at least 1 pair of maxillipeds. 61. Cephalothorax with carapace, at least 2 pairs of maxillipeds [Thoracostraca]. Ci. Eyes stalked. d\. No uncovered thoracic segments ; 3 or 2 pairs of maxillipeds, and 5 or 6 pairs of legs .... <72. 3 free thoracic segments ; 5 pairs of maxillipeds ; 3 pairs of legs c2. Eyes not stalked ; 4 to 5 thoracic seg- ments not covered by carapace ; 2 pairs of maxillipeds ; 6 pairs of thoracic legs b'2- Cephalothorax without marked carapace ; usually 7 free thoracic segments ; only 1 pair of maxillipeds ; eyes not stalked [Arthrostraca]. d. Body usually broad ; abdomen with short, often-fused segments, and with gills on legs c2. Body laterally compressed ; abdomen mostly elongated, with 3 pairs of swim- ming legs, and behind them 3 pairs of springing legs ..... «o. Body segments, 21, enclosed in bilobed shell, abdomen with 8 segments ; the last 2 without appendages ; no maxillipeds [Leptostraca] Podopthalmata (Ex. Crayfish) Stomatopoda o Cnmacea Isopoda Amphipoda Neb ali 2. Squarne large ; antennas usually under antennules ; first pair of thoracic legs with small chehe ; cephalothorax without cross-suture, gills laminate ThalassimdcB Astacidcb (Ex. Craylish) C arid idee (Shrimps and Prawns) n-2. 2 pairs of maxillipeds resembling the 6 following pairs in being bifid [suborder Schizopoda]. CHAPTER VIII THE DAPHNIA AND ITS ALLIES Relationships. — Daplmia1 belongs to the division of Crustacea called Entomostraca.2 The Entomostraca 3 are distinguished from the higher Crustacea — the Malacos- O <— ' traca - -by the negative character that the number of segments and appendages in the body is variable, instead of there being constantly 10 pairs of appendages. The group of Entomostraca to which Daphnia belongs comprises the more primitive of living Crustacea. They occur in both fresh and salt water and, excepting Protozoa, are the most abundant aquatic animals. They are of great economic importance, since they constitute the main food supply "of fish. On the coast of Norway and Scotland the fishermen prepare for a catch of herring or mackerel when the sea becomes red with Entomostraca. Whalers like- wise seek their booty where these Crustacea are abundant on the open seas, for even the whalebone whales devour the small animals in great quantity, straining them out of the sea-water by means of their whalebone strainers. De- spite all their enemies, the numbers of Entomostraca are maintained by virtue of an enormous fertility. The 1 From Aa0i/77, daughter of the river-god Peneus ; she was transformed into a laurel tree. - efTo.i'.oi', cut into, segmented ; oarpaKov, shell. 3 The live orders of Kntomostrara may be distinguished by means of the key given at the end of this Chapter, page 131. 125 126 ZOOLOGY Entomostraca are rich in species also, partly because they occur in such diverse environments. Thus they live in fresh water, in the sea, and even in the Great Salt Lake and in vats where salt is crystallized out. They live in little pools, such as dry up in summer. They are found also as parasites on the gills or in the skin of fishes. Habitat and Food. - - Daphnia 1 lives in ponds, lakes, and slow-running streams over all the globe. During the fall in northern latitudes the Daphnias, of at least certain species, lay fertilized eggs, called winter eggs, which may lie dormant, however, not merely for the winter but throughout an entire year. During most of the year females alone occur and unfertilized "summer eggs" are alone produced. The abundance of Daphnia in any pond is determined by a number of causes. One of the most important of these is food. The food of Daphnia consists chiefly of fresh-water algre, such as nostocs and diatoms ; and it has been shown that the abundance of Daphnia in a pond is closely determined by the abundance of the kind of alga 1 Key to the principal genera of the family Daphnidse : — a i. Head rounded, not beaked. &i. Antennules long ; abdomen not wholly cov- ered by shell Moina b-2. Antennules short ; whole body enclosed in shell Ceriodaphnia a-2- Head beaked below. bi. Beak slight ; shell angled below or extending in long spines from lower angle ; pigment spot roundish Scapholeberis ft2. Shell rounded below, with a blunt spine above ; pigment spot elongate .... Simocephalus 63. Shell extending in sharp spine at upper pos- terior angle ; pigment spot small . . Daphnia THE DAPHNIA AND ITS ALLIES 127 ant.i ant.Z abd.f which forms its principal food. Another factor upon which the number of Daphnia in a pond depends is tem- perature. A high temperature seems to be unfavorable to Daphnia, so that not the summer, but the spring and autumn are its periods of maximum reproductive activ- ity. This activity is like- wise checked in winter even though there is plenty of food. The family Branchiopoda 1 is closely allied to the Clado- cera. The common repre- sentative of this family, Branchipus, has an elongated, distinctly segmented body whicli carries eleven pairs of lobed, leaf-like feet, func- tioning both as respiratory and locomotor organs. Like Daphnia, Branchipus pro- - • FIG. 118.--Apus glacialis, ventral dlices Winter eggs Which Can aspect, abd.f., abdominal feet; Withstand desiccation even «nt' f > antennule ; ant. 2, antenna ; lor., labrum ; ma., mandible ; mx., for years ; indeed, in Some cases, a certain amount of desiccation is a prerequisite of hatching. Apus differs from Branchipus in having a broad shield (Fig. 118). The family Ostracoda2 comprises some very abundant, 1 j3pdyxia-> gills ; Totfs, foot. 2 HxrrpaKov, shell of a testacean ; eI5os, like. first maxilla; ov., aperture of ovi- duct: .s. /. pi., sub-frontal plate; •s7f. f/l., shell-gland; tli.f., thoracic feet; th.f. 1, first thoracic foot. After Bernard. 128 ZOOLOGY minute, bean -shaped little crustaceans, which have to move their appendages very vigorously to support their heavy bodies in the water. The Ostracods are found in almost all pools and streams,, especially in the early spring. Many of them seem to be exclusively parthenogenetic. / V FIG. 119. — Acartia, a marine Copopod. Greatly magnified. Photo, by W. H. C. P. Of the Copepoda1 the commonest fresh-water genus is Cyclops, which occurs in a similar habitat witli Daphnia and is sometimes found even in pure drinking water. The female carries a conspicuous egg-sac on each side of the abdomen, and reproduction occurs with such rapidity that oar ; Trews, foot. THE DAPJfNTA AND TTS ALL1KS 129 one Cyclops might, under the most favorable conditions, have 5,000,000,000 descendants in one year. It is conse- quently easy to understand how Cyclops often becomes the most abundant eiitomostracan in our waters, and how in some lakes it has been found that there are over one million of them to each square metre of water surface. Large numbers of the Copepoda are marine. One of the most common is Acartia (Fig. 119), which swarms to such FIG. 120. — Mussel-shell bearing barnacles (Balauus). Photo, by W. H. C. P. an extent on the surface of the water as to make great phosphorescent areas. Barnacles are the only attached non-parasitic Crustacea. Certain species of them are found fastened to rocks on the seashore at low-tide mark. If you watch barnacles in rock pools, you can see them open the valves of their shells, protrude their elongated appendages, which together form a sort of rake, and pull in particles which happen to be float- ing about them. Other species of barnacles attach them- selves to floating seaweed, ship bottoms, and whales ; under these circumstances, despite their sessile habit, they enjoy a constant change of locality. Barnacles doubtless gain great protection from the circumstance that they are K 130 ZOOLOGY sessile and enclosed in shells ; but their peculiar habits have given rise to certain peculiarities in reproduction. They are hermaphroditic; i.e. both male and female germ- cells occur in the same individual. Despite this fact, dwarf male individuals are occasionally found inside the shell of the barnacle ; these are known as " complemental males." The general form of the barnacles has also be- come greatly modified by their sessile habit, so that they were long regarded as mol- lusks, until it was shown that the larvje are almost exactly i/ like those of other Ento- mostraca. Trilobites1 are extinct giant Entomostraca, closely allied to Branchipus. They were immensely abundant in early geologic times, and their re- mains form a large part of certain rocks. They had a segmented body, with bifid appendages and long antemue, T ,1 T - 101 . , ,. and their compound eyes were FIG. 121. — A restoration of the J borne on the great frontal ""eld. Some of them were Beecher. nearly half a metre long. ventral aspect of a Triiobite. 1 Having three lobes. APPENDIX TO CHAPTER VIII 131 APPENDIX TO CHAPTER VIII KEY TO THE FIVE ORDERS OF ENTOMOSTR A.CA a\. Free-living or parasitic inhabitants of the sea or of fresh water. ?>i. 2 pairs of maxillae. t'i Mandible without palp ; 4 or more pairs of foliate swimming legs behind maxillae [Phyllopoda]. di. With 10 to 40 pairs of legs . . Sranchiopoda (Ex. Branchipus) (Z2. With 4 to 6 pairs of legs . . . Cladocera (Ex. Daphnia) Co. Mandible with leg-like palp ; only 2 pairs of appendages behind maxillae . . Oatramiltt 60. Only 1 pair of maxillae, followed by 4-5 pairs of bifid, oar-like feet ; often deformed as a result of parasitism Copepnda (Water-fleas) «o. Sessile marine animals, whose body is surrounded by a usually calcified mantle ; 6 pairs of tendril- like feet Cirripedia (Barnacles) Key to the principal families of Cladocera, to which group Daphnia belongs : — a\. Body enclosed in a bivalve shell ; mandibles trun- cate below ; maxillae distinct, spiny. 61. 6 pairs of similar, foliaceous, distinctly branchiate feet ; swimming antennae with 2 unequal ranii ; intestine straight . . SididcK b-2. 5 (or 6) pairs of feet, the anterior pair more or less prehensile and destitute of branchiae. Ci- Ranii of antennae 3- and 4-jointed ; 5 pairs of feet, the last with a curved appendage guarding the branchial sac ; antennules of the female sort, 1 -jointed Daph nidus 132 ZOOLOGY Co. 0 pairs of feet ; an ten miles elongated, many-jointed . . . . Cg. Antennae with both ranii o-jointed ; in- testine convolute ..... Body wholly or nearly destitute of a bivalve shell ; feet not branchiate, spiny ; abdomen curved, ending in two long stylets Bosminidce Lynceuhe Polyphemidce CHAPTER IX THE EARTHWORM AND ITS ALLIES Relationships.- -Earthworms1 belong to an order of Annelids known as Oligocheeta.2 This group is distin- guished by a prevailingly non-marine life, by the absence of parapodia, by few bristles, and by the absence of tenta- cles, palps, cirri, and gills.3 Habits. — Earthworms, as the name implies, are inhabit- ants of the ground, through which they burrow and in FIG. 122. — Flash-light photograph of earthworm and slug crawling on a pave- ment at night. Photo, by D. and S. 1 There are not very many kinds of terrestrial Oligochseta. The prin- cipal American species may be distinguished with the aid of the key given in the Appendix to this Chapter. - 6X1705, few ; XCU'TT?, hair. 3 The Oligochfeta exhibit two principal subdivisions ; the first of which includes terrestrial species of the single family Lumbricidse, and the second various aquatic families, — a key to which is given on page 144, ] 33 134 ZOOLOGY which they gain their food. They sometimes come to the surface at night in search of companions and food (Fig. 122). Even during the day in rainy weather they extend the anterior end of the body out of their burrows. Earth- worms, found on the surface at other times, have, for the most part, been parasitized by a fly, and are in consequence weak or dying. During the daytime, if the surface mois- ture permits, they lie near the mouth of their burrows, probably for the sake of the sun's warmth. In this posi- tion they can be seen by looking down into the holes. At such times they are often caught by birds. In dry weather, or when the ground is freezing, earthworms burrow deep to a moist stratum, or to below the frost line, and hiber- nate there. Food. — EartliAvorms are omnivorous. As they burrow through the ground, the earth is taken into the alimentary tract, and the digestible particles are dissolved out and absorbed as food. Earthworms can, however, be fed upon green and dead leaves, decajdng wood, seedlings, bits of flesh, and even filter paper. Earthworms have the habit of dragging into their burrows leaves which they intend to devour. There the leaves are moistened with a fluid excreted by the worm. This fluid partially digests the food. After being taken into the alimentary tract, the food reaches an organ of the canal known as the gizzard. This part has thick muscular walls, and contains in its cavity small stones ; by the action of both the muscular gizzard and the small stones, the food is ground up in much the same way as are the grains of corn by the aid of stones in the gizzard of a hen. Resistance and Regeneration. - -The capacity which earth- worms possess of resisting certain untoward conditions is THE EARTHWORM ANT) ITS ALLIES 135 very great. Thus they may be kept for months in a moist vessel without food, or with only filter paper, with- out starving. On the other hand, they die in a dry atmos- phere in a few hours, whereas they may be submerged in water for several days without injury. Very remarkable is their power of healing after injury. If an earthworm be cut in two near the middle, and the halves be kept under favorable conditions, each half may develop its missing organs so that two complete worms will result. The anterior half of one worm may be attached to the hinder end of a second worm by the cut edges, owing to the fact that the cut edges grow together. This operation is called grafting. Economics. - - Earthworms are, to a certain extent, in- jurious to vegetation, since they eat tender seedlings and roots, but, on the other hand, they are almost indispensable to agriculture. Their burrows permit rain to percolate deep into the ground, instead of running off on the sur- face. They keep the soil loose, facilitating the penetration of the roots of plants. The earth that passes through their bodies is ejected on the surface of the ground near the openings of their burrows, and is called a " casting." By means of castings the deeper-lying earth is brought to the surface, and the surface layer of rich earth, called " vegetable mould,'1 is in this way increased in thickness by additions to its upper surface. The thickness of the layer of mould which the castings of one year, if uniformly spread out, would make has been estimated by Darwin to be in England about two-tenths of an inch. Most of these castings are merely taken from the deeper-lying mould, but they are enriched by the intestinal secretions in pass- ing through the body of the worm. These intestinal secre- 136 ZOOLOGY tions are said to have the power of slowly dissolving sand and thus of turning it into soiL Darwin says, " It is a marvellous reflection that the whole of the superficial mould over any smooth expanse has passed, and will again pass, every few years, through the bodies of worms. The plough is one of the most ancient and most valuable of man's inventions, but long before he existed the land was, in fact, regularly ploughed, and still continues to be thus ploughed, by earthworms." The group to which earthworms belong is closely related to that which includes Nereis of the seashore. They are both ringed worms or Annelids.1 But whereas Nereis and O its allies have parapodia provided with numerous bristles, the earthworm has 110 parapodia, and only a few bristles on each segment. The group to which Nereis and its allies belong is called (see Chapter X) Polychseta, and the group to which the earthworm belongs is appropriately named Oligocliceta. The aquatic Oligochaeta2 are among the commonest inhabitants of ponds and ditches, living sometimes in the mud and sometimes at the surface of the water. Tubifex3 is common in slow-running brooks, and lives in the mud of the bottom, forming tubes in it. The thread-like bodies of the worm are stretched up beyond the surface of the mud and wave in the water in graceful undulations. Often the worms are so numerous that their reddish color gives a decided tinge to the bottom. They thrive well in fresh- water aquaria. 1 Annulus, a little ring. 2 A key for the determination of the principal families of aquatic Oligo- chseta is given in the Appendix to this Chapter, page 144. 3 tubus, tube ; face re, to make. THE EARTHWORM AND ITS ALLIED 137 Dero 1 is very common on the surface of ponds, particu- larly in the midst of duck-weed (Lemna), the leaves of which it cements together to form a floating tube in which it lives, and by which it is accompanied in all its migra- Fm. 12o. — Dero, the duck-weed worm. Enlarged. After Reighard. The lettering is as follows : or., mouth ; phx., pharynx ; oe., oesophagus; ftff. <>., segmental organ ; in., intestine; pav., pavilion or tunnel; dg. app., finger- like appendages. From Reighard. tions. Dero can also be told by the sort of funnel at the hinder end of the transparent body, from the margins of which finger-like filaments arise which aid in respiration (Fig. 123). Nais2 does not construct tubes, and it has no respiratory , to skin (= flay). 2 PCUS, a water-nymph. 138 ZOOLOGY filament at the hinder end of the body (Fig. 124). It also has eyes ; while Dero has none. Both Dero and Nais have the interesting habit of reproducing by dividing the body transversely. In the middle of the body tentacles begin to arise, a new mouth is formed, and the worm constricts into two. I n d e e d, sometimes several new heads may be forming in the midst of a single worm. This habit is of advantage not only in multiplying the number of individuals of the species, but also as a means of protection. For if, by chance, the larva of the water-beetle Dytiscus seizes a Nais and bites it in two, the part which escapes can go on developing new^ individuals. The slow-moving, burrowing habit of the earthworm has led to a nearly complete absence of such appendages as Nereis possesses. There are other ringed worms i • T , i i . i -i •, FIG. 125. — Phasci)- in which the burrowing habits have led to iosoma, a Gephy- a loss even of the segments in the adult. rean- One-fourth r™ • • , i ,-, ,. nat. size. From 11 us is the case in the group Gephyrea.1 Leunis. 1 ytfivpa, bridge ; because they were once considered to bridge the gap between holothurians and worms. FIG. 124. — Nais: a, mouth; b, anus; c, intes- tine. From Leunis. THE EARTHWORM AND ITS ALLIES 139 This group contains several rather rare animals. One of the commonest is Phascolosoma,1 which is a tough but smooth-skinned, cigar-shaped worm, which one can dig up on our sandy beaches (Fig. 125). One end is pointed ; from the other a great proboscis terminating in tentacles surround- ing a mouth can be extruded. Another species found on our beaches after a storm, something like a small cucumber in shape and size, has a row of bristles at each end, indicating its relationship with the bristle-bearing worms. This species, Echiurus,2 is seg- mented when young like Nereis, but eventually it loses its seg- mentation (Fig. 12(>). Several species of Sipimculus are edible, and are held in esteem by the Chinese. To the account of the Oli- gochreta above given may be postset added some statements concern- Fm' one-half nat. size. About prob., proboscis ; ant. set., anterior seta;; post, set., posterior setjB. After Greef, from Par- ker and Haswell's " Text- book." ing a group of annelids of very different appearance. The leeches, or " blood-suckers," are flattened Avorms, Avhich, like the earthworm, show metamerism ; that is, there is a repetition of the in- ternal organs. They are also segmented ; that is, the body has external rings, although they may be obscure. One segment' does not, hoAvever, as in the earthworm, 1 0d(TKa;\oj, sac ; adder ; ot)/>d, tail. 140 ZOOLOGY correspond with one metamere, but there are three, four, or five segments to a metamere. Leeches have no para- podia and no bristles ; but they have a sucking disk at the posterior end of the body for the purpose of adhesion (Fig. 127). They usually have a smaller, anterior sucking disk around the mouth, which may or may not be provided Avith teeth, for the purpose of cutting through the skin. When there are no teeth, the pharynx is protrusible, forming a proboscis. With a few exceptions, all leeches FIG. 127. — Clepsine, the flat blood-sucker. Ventral view. Posterior sucker at left. Nat. size. From life. Photo, by E. R. D. live in water ; but in Ceylon there is a land leech which lives in foliage and attacks man and other animals. ( Hlier leeches may live in damp places at a considerable distance from water. Leeches suck the blood of fishes and other aquatic animals. Certain kinds devour worms, insects, and other small creatures. The commonest of the larger blood-suckers of our waters is Nephelis,1 which is not distinctly segmented. It" varies from black to slate color, and is sometimes striped or spotted. It lives in running water, in ditches, and ponds. 7, wife of Atliamas. THE EARTHWORM AND 7TN ALLIES 141 Clepsine1 is a very flat and broad leech, which is common under floating wood. It feeds on snails and creeps like the inch -worm. The female carries its young attached to its under surface (Fig. 127). FIG. 128. — Pedicellina americana, an encloproctous bryozoan. A colony, magnified 15 diams. Photo- of living animals by W. H. C. P. Possibly allied to the Gephyrea is the group of Bryozoa,2 or moss-animals. These are noteworthy from the fact that they are compound, many individuals budding off from one another, as in plants. They are found abundantly both in the sea and in fresh water. Two main groups are dis- 1 From K-XeVTw, to steal. 2 fipvov. moss ; faov, animal. FIG. 129. — Buyula turrita, a marine ectoproct. A colony, magnified 1.5 diams. Photo, of living animals by W. H. C. P. FIG. l.'it'. — PlumateUa polymorpha, a fresh-water ectoproct, magnified 1.5 diams. Photo, of living animal by W. H. C. P. 142 APPENDIX TO CHAPTER IX 14° o tiiiguislied, the Endoprocta (Fig. 128), in which the individual consists of a long stalk and a " head ' or body proper ; and the Ectoprocta (Figs. 129-131), usually without such a stalk. The Ectoprocta are the prevailing type. The marine species form lace-like mats on sea- weed or stand up as branching, bushy colonies (Fig. 129). Some of the fresh-water forms make loose, antler- like colonies (Fig. 130), while others lie on the surface of a more or less spherical mass of jelly which they have themselves secreted (Fig. 131). FIG. -131. -- Pectinatella maf/nijica,a, dense complex of colonies, growing upon a stick. Each star-shaped group represents a single colony. One-half uat. size. Photo, of living mass by W. H. C. P. APPENDIX TO CHAPTER IX KEY TO THE PRINCIPAL SPECIES OF EARTHWORMS OF THE UNITED STATES ffi. Clitellum begins on segment xiii or xiv ; $ pore on segment xviii or xix ; 2 gizzards in segments v and vi. 61. 2 dorsal vessels ; lives in soil of prairies 62- 1 dorsal vessel ; lives in river-bottom land Clitellum does not begin in front of segment xviii ; $ pore on segments xii and xiii, or (usually) xv. 61. Prostomium incompletely divides buccal lobe [genus Allolobophora], ( Diplocardia \ commit nis D. riparia 144 ZOOLOGY ci. Tubercles on segments xxviii-xxxi ; ill- smelling ; purple-banded ... A. fcetida Co. Tubercles on segments, xxxi and xxxiii . A. caliyosa r3. Tubercles 011 segments xxvii, xxviii ; color reddish brown .... A. tumid a r4. Tubercles on segments xxiv-xxx ; about 100 segments ..... A. parva 05. Tubercles on segments xxviii-xxx . A. subrubicunda c$. Tubercles on segments xxix-xxxi (occa- sionally xxix, xxx); number of seg- ments, 150 A. rose a 62- Prostomium completely divides buccal lobe [genus Lumbricus] . Ci. Tubercles on segments xxviii-xxxi ; red- brown or purple ; about 120 segments. L. ntbellus Co. Tubercles on segments xxxiii-xxxvi ; number of segments, 180 L. hercnleus KEY TO THE PRINCIPAL FAMILIES OF AQUATIC OLIGOCH^ETA a\. Dorsal blood-vessels visible only in the anterior part of the body ; farther back, as intestinal sinus, disappearing underneath the intestinal glands EnchytneMas rto. Dorsal blood-vessels running on top of food canal and visible throughout its entire length. &i. In each segment, except the first, contractile lateral blood-vessels Lumbriculidas bo. Lateral vessels contractile only in anterior segments. Ci. Dorsal and ventral vessels united in each segment, except in the first 5, by 2 lateral vessels Tubificidce (Ex. Tubifex) Co. Dorsal and ventral vessels united in each segment by a lateral vessel . . . Naidce (Exs. Nais, Dero) CHAPTER X ,-* NEREIS AND ITS ALLIES NEREIS1 is one of the commonest worms found on our seacoast. It occurs in sandy or muddy beaches, at or below low-water mark, especially where tidal currents flow swiftly. It inhabits burrows, which it makes in the sand and lines with a mucilaginous secretion to bind together the walls of sand or mud. At certain seasons of the year, during the breeding season, these worms may be found swimming near the surface of the sea. Nereis lives on both plant and animal food. To capture its prey it thrusts out a long proboscis, provided with two powerful jaws. The thrusting out consists essentially of a rolling inside out, — just as the finger of a glove may be rolled inside out. When the proboscis is rolled in again, the jaws, retaining their grip on the food, carry it into the food canal. While many kinds of small animals serve Nereis as food, it is itself devoured by various fishes which dig it out of the sand or capture it when it swims free at night or during the breeding season. Such a favorite with fishes naturally makes excellent bait, and is well known to fishermen under the name " clam-worm " or "sand-worm." Nereis is distinguished by the fact that its segments are numerous and nearly all alike, and bear appendages of similar form. The single pair of jaws on the proboscis is ts, daughter of Nereus, one of the Nereids, or sea-nymphs. L 145 146 ZOOLOGY characteristic ; and the four eyes on top of the head, com- bined with two antennae and two palps, serve to determine its family with precision. The parapodia have a dorsal and a ventral cirrus. The commonest species on the coast of New England and in Long Island Sound is Nereis virens,1 which grows to a length of thirty centimetres. Its color is dull green to bluish green, and iridescent. The gills on the parapodia are green at the head end, but farther back they become bright red, owing to the blood which flows through them. This species lives in northern seas, and is found on the coasts of Great Britain, Norway, Labrador, and south FIG. 132. — Euglycera. One-half natural size. Photo, by W. H. C. P. to Long Island Sound. South of Long Island Sound the commonest species is Nereis limbata? which grows to a length of, at most, only fifteen centimetres, and is of a dull brown or bronze color. This species is found as far south as South Carolina. Often associated with Nereis in sandy beaches is a large, strong, flesh-colored worm, pointed at both ends, so that the head is not nearly as evident as in Nereis, and having small appendages, so that it looks smooth like an earthworm. This 1 Green. 2 Bordered or edged. NEllEIfi AND TT8 ALLIES 147 is Euglycera.1 Its proboscis has four jaws, situated at the corners of a square, instead of two as in Nereis. The pointed head and powerful writhing muscles enable the animal to burrow with great rapidity (Fig. 132). A second kind, Autolytus,2 is a small animal which lives in little tubes attached to algre or hydroids (Fig. 133). The parapodia at the anterior half of the animal are different from those at the posterior half, for the latter are large and fitted for swim- ming. Eventually one of the middle segments of the body becomes trans- formed into a head, with eyes and tentacles, then the whole of the hinder half breaks off spontaneously. The newly formed head is now the head end of the new individual. This individual leads a different kind of life from the half which remains in the tube, for it swims freely in the water. The separated individuals are either male or female, whereas the part which lives in the tube never pro- FIG 133. -1 Autolytus duces eggs, but merely forms a new tail every time the old tail is cut off to form a sexual individual. A third kind, Lepidonotus 3 is characterized by the possession of a representative of a fam- ily of Polychreta in which the animal bin Is off male or female in- dividuals from its hinder end. bud, head of the budded individual. After A. Aijassiz. 1 e5, typical ; rAikepa, a woman's name, also applied to a family of Polychseta. Euglycera means typical of the family GlyceridaB. 2 auros, self ; AIAJ, to separate ; hence, self-separating. s, scale ; ^WTOJ, back. 148 ZOOLOGY a double row of scales covering over the back (Fig. 134). These scales are outgrowths of the dorsal part of the parapodia, and serve for respiration. In allied genera the scales are covered with bristles, which may be so very long and abundant as to hide the scales. They produce a brilliant iridescence. One of these worms with the great bristles may be several inches long and relatively broad, and is commonly known as the "sea-mouse" (Fig. 135). Both Lepido- notus and the sea-mouse occur in out-of-the- way places, - - crevices of rocks at low tide or fairly deep water, - - so that they are not com- monly seen at the seashore. The sedentary Polychaeta are mostly smaller and less familiar animals than the free-living Polychseta, but they have an interest for us in showing how greatly modified an organism becomes when it takes on a sedentary life. Its swimming appendages become rudimen- tary ; its eyes are usually lack- ing ; there is no protrusible proboscis armed with powerful jaws ; the gills become grouped almost exclusively about the FIG. iai.— Lep- idonotus, the scaled worm. Nat. size. Photo, by W. H. C. P." FIG. 135. — Aphrodite, a sea-mouse. r. i.).». — r\imn>uiit5, A, Neil-mouse. i c ±1 i ^ i Nat. size. From Johnston. uPPer end of the bod7> wnere X Eli Kit* AND ITS ALLIES 140 they can be thrust out of the tube ; the mouth comes to lie at the bottom of a funnel, which receives as food small parti- cles floating in the water ; even the segmentation of the body becomes lost at the hinder end of the animal ; in a word, all those organs which are useful for active carnivo- o rous life have become re- duced to the bare needs of a quiet herbivorous life. FIG. 1 ;>(.). — Amphitrite, removed from its Fi<;. 137. — Polycirrus, the blood tube. Nat. size. Photo, by W. H. C. P. spot. Nat. size. Photo, by W. H. C. P. The first of these sedentary worms that we have to con- sider is not completely modified from the type found in free-living species. Cirratulus 1 lives in tubes in mud or sand. It is yellow 1 From cirrus, curl, ringlet. 150 ZOOLOGY or orange in color, and has long cirri, which, arising from nearly every segment, reach out in all directions. These function as gills, and when broken off may remain alive for days. Clymenella,1 which looks like a reddish, jointed straw, builds tubes of agglutinated sand, and has a serrated, funnel- shaped tail end. Its parapodia are very small (Fig. 139). FIG. 138. — Tube of Cistenides. Nat. size. Photo, by W. H. C. P. Fid. 139. — Clymenella, straw- worm. The anterior seg- ments only are shown. After M. Lewis. Amphitrite2 (Fig. 136) builds firm tubes of sand. From the head spring numerous tentacles and three pairs of blood- red gill-tufts. The body is large anteriorly but becomes slender behind, where there are no bristles. Allied to Amphitrite are a large number of common worms found on our coast. Polycirrus, or the blood-spot (Fig. 137), is somewhat smaller than Amphitrite and characterized by a 1 Diminutive of K\vfj.evr}, daughter of Oceanus. 2 ' A.fjuj>tTplTij, wife of Neptune, goddess of the sea. NEREIS AND ITS ALLIES 151 uniform crimson color and a large number of cirri massed at the head. The tubes made by some of the Terebellidee are very beautiful. The tube of Cistenides (Fig. 138) is found in the sand under stones and is composed of grains of sand cemented together and regularly arranged so as to form a firm wall. Finally, Serpula1 secretes crooked, round calcareous tubes, which may be found adhering to stones near low water (Fig. 140). From the mouth of the tube the head, with its tentacles, may be protruded, but it quickly re- tracts from danger and closes the open- ing of the tube as a marine snail does its shell, by means of an operculum or lid. Some worms have gained a parasitic habit, and in con- sequence have become much modified in form and struc- ture. Such is the case with some of the round- worms. Some of these are thread-like, live in springs or pools, and are regarded by the uninitiated as animated horse-hairs. Others are spindle-shaped, as for example the "vinegar eel" and the round- worms that are common in stagnant water. Others live in the food canal, as for example the stomach worm (Ascaris) of the horse and the 1 Diminutive of serpens, serpent. FIG. 140. — Serpula tube on a bit of oyster shell that is perforated by the boring sponge. The tube lies in the centre of the figure. Nat. size. Photo, by W. H. C. P. 152 ZOOLOGY B FIG. 141. — Trichina. A, encysted form in muscle of pork; B, female; (', male; bh, envelope of cyst; cy, cyst; de, male duct; e, embryos; /, fat globules; h, testis ; mf, muscle fibre; oe, pharynx; ov, ovary; no, opening to egg duct; zh, cell masses in intestines. After Clans. NEREIS AND ITS ALLIES 153 T) pin-worm of man. Others still penetrate into the mus- cles, and cause great pain and often death. Such is the pork-worm, Trichina,1 which gets into man through un- cooked pork, multiplies in the food canal, migrates in great numbers into the muscles and encysts itself there (Fig. 141). Another group which is largely parasitic is that of the flatworms. Some flatworms live free in ponds. They will be found abundantly among plants taken from small ponds in the summer and autumn, and are commonly known as Pla- naria2 (Fig. 142). They may be recognized not only by their flattened form, but also by a curious proboscis which pro- trudes from the middle of the under side of the body and bears «/ mouth at its tip. These a FIG. 142. — Species of fresh-water Plaiiaria. 1, Dendrocoelum lacteum, cream color; -, Pla- naria maculata ; 3, head end of same to show light streak. After Woodworth. creatures have a marvellous power of regeneration, so that every piece into which a worm is cut will reproduce an entire one (Fig. 143). If the worm is mutilated but not wholly cut in two, bizarre forms may result by a modified tendency to regenerate (Fig. 144). Other flatworms are parasitic, such as the liver-fluke of the sheep (Fig. 145). This destructive parasite has a hair. 2 planus, flat. 154 ZOOLOGY complicated series of stages to go through before it be- comes adult. Thus the flukes in the liver of the sheep produce eggs which develop into embryos. These em- bryos get out of the liver into the food canal, and thence -ij: V ec.10. \J \J ~Mixrch13.Apr.4-. Jan.25. FA.5. Fe~b,17 \ V § | J)&c.10. V Jan. 2 5.' FIG. 143. — Showing results of cutting Planarians into two pieces ; the pieces develop into entire animals. After Morgan. to the exterior. If they are deposited near a pool of water, they may develop further, otherwise they must die. In the water a ciliated larva l hatches from each egg, swims about for a time until it finds a fresh-water snail, bores into it, and encysts itself there. In this 1 Fig. 146, A. NEREIS AND ITS ALLIES 155 FIG. 144. — Showing abnormal forms resulting from mutilation of Plu- narians. After Van Duyue. encysted stage the worm is known as a "sporocyst," because it is full of germs (spores) of a new genera- tion.1 The spores develop in the snail into curious organisms, a sort of second- o ary larvae known as redia.2 The redise may produce, by a kind of internal budding, new redise, and so on re- peatedly, until at last, on the death of the snail, or from some other cause, the last generation of redia} produces liver- flukes.3 The young liver-flukes wriggle out of the snail, attach them- selves to damp grass, lose their tails, and encyst them- selves. If these cysts be eaten by a sheep, they develop in the sheep's body into an adult liver-fluke (Fig. 145). Thus the stages which we can recognize in the liver-fluke are : - First generation : egg from liver-fluke, larva, and adult sporocyst. Second generation : redia (this may be several times repeated). Third generation : " cercaria " larva, encysted larva, and adult liver-fluke. 1 Fig. 140, B. 2 Fig. 140, C. 3 These, while young, have tails, and are called " cercaria." ever FIG. 145. - Distomum, the liver-fluke. Nat. size. Excr., excretory pore; mo., mouth; rep?'., reproductive aperture ; -srA1/*., posterior sucker. From Parker and Has- well. 156 ZOOLOGY Another flat worm is such an abject parasite that it has lost most of the organs usually possessed by worms. This is the tapeworm (Fig. 147). When the eggs of the tape- worm are taken into the body of an herbivorous animal, the embryos develop there for a way and then stop. When flesh containing these embryos is eaten by a carnivorous eye . (fast. or.su c&s B FIG. 146. — Development of Distomum. A, ciliated larva ; /?. sporocyst con- taining developing rediae ; C, redia, containing a daughter redia and embryo liver-flukes; D, free-swimming, tailed larva of liver-fluke;- b. op, birth opening; etit, food canal of redia; eye, eyespots ; gast, young redia; r/erni, mor, early stages in formation of the embryo liver-fluke; int, intestine of larval liver-fluke; o?s, oesophagus; or. SK, oral sucker; pap, head papilla of ciliated larva, A: ph, pharynx; proc, processes of redia; vent, su, ventral sucker. After Thomas. animal, the embryos attach themselves to the food canal of •> their host and form, by rapid growth, a long chain of seg- ments, each of which is full of germs. The chain, or NEREIS AND ITS ALLIES 157 FIG. 147.— Tsenia solium, the human tapeworm. Entire specimen, about natural size. Cap, head. After Leuckart. 158 ZOOLOGY " tape," absorbs fluid food, which soaks through its body wall. As the segments at the older end of the animal mature, they are set free and pass out of the alimentary tract, to be picked up, perchance, in the food of an herb- ivorous animal or else to perish. The economic importance of parasitic worms is very great. Thus, although no great epidemics of the flukes have occurred in this coun- try, a million sheep are annually lost by this para- site in Great Britain ; and in 1879 and 1880 it was estimated that three million sheep died annually in England alone of this parasite. In Buenos Ayres, during 1882, a million sheep died of fluke disease. By great care in prevent- ing infection, especially during damp seasons, we may be able to prevent FiT A is allied to the flat worms. It includes chiefly marine animals, of somewhat flattened form and great length, even as great as thirty metres. They protrude a long, slender proboscis. These worms are especially abundant in the sand of the seashore, although land nemerteans occur. Cerebratulus (Fig. 148) is a common form from the east coast. APPENDIX TO CHAPTER 159 APPENDIX TO CHAPTEPv X KEY TO THE MORE IMPORTANT FAMILIES OF POLYCH.^TA a\. Head distinct from trunk ; proboscis protrusible [wandering Polychseta]. bi. With broad dorsal scales .... b-2. No scales ; only one mouth-segment. Ci. Cirri not leaf-like ; body long and not flattened. d\. Head not segmented. e\. Jaws composed of many pieces . e-2- Two powerful jaws . d». Head with its lobes segmented . c2. Small worms, body flattened, cirri evident «o. Head not distinctly separated from trunk ; pro- boscis short, not protrusible ; no jaws [seden- tary Polychseta]. bi. Gills, when present, arise either from almost all, or else the middle segments. GI. Body not separated into various regions ; distinct head ; no antenna ; gills in form of elongated, thread-like cirri C2. Body divided into 2 or 3 different regions ; no antennal cirri ; proboscis present ; no gills &2- Gills almost always present and limited to the anterior end of the body ; no cirri ; body divided into an anterior and a posterior part. Ci. Gills confined to the anterior segments ; head lobe small ; numerous antenna in 2 bunches ; no antennal cirri c2. Gills confined to head ; 2 inrolled leaves standing at the sides of the mouth Aphroditidce (Ex. Lepidonotus) Eunicidce Nereidu' (Ex. Nerds) Glycerida* (Ex. Ki (Ex. Antolytus) Cirratulidce (Ex. C'irratulus) Maldanidaz (Ex. ClymeiH'llu) Terebellidce (Ex. Amphitrite) SerpulidoK (Ex. Serpula) CHAPTER XI THE SLUG AND ITS ALLIES THE slug belongs to the group of Mollusca.1 This group contains animals which possess two distinctive organs — the foot^ by means of which locomotion is effected, and the mantle, a fold of skin covering over or enclosing a greater or less part of the body. The mantle usually secretes on its outer surface a calcareous shell. Exceptionally, both shell and mantle may be entirely absent in the adult. Among the Mollusca, the slug occupies the class Gastrop- oda,2 characterized by the possession of a head, which bears feelers and eyes, and an unpaired foot, situated on the ventral surface of the body and used to crawl upon.3 Gastropods are either with or without an external shell. When the shell is present, it is made of one piece, that is, it is univalve^ 1 mollis, soft. - -yao-Trjp, belly, stomach ; TTOUS, foot. 3 A key to the principal families of gastropod shells of the Atlantic coast of the United States is given in the Appendix, p. 174. 4 The three orders of Gastropoda may be distinguished by aid of the following key : — «!. Breathing by means of lungs ; no operculnm ; living on land and in fresh water . . . Puhnonnta a2. Breathing by gills ; chiefly marine. 160 THE SLUG AND ITS ALLIES 161 Slugs belong to the group of air-breathing, land-inhabit- ing gastropods, or Pulmonata.1 They may be found in the spring, summer, and autumn, under wet, decaying pieces of wood, under stones or fruit, in the grass, on the shady side of fences ; in a word, in moist, dark situations. They especially shun sand, ashes, and sawdust, because these substances tend to dry up the mucus which they secrete over their body to retain its internal fluids. Slugs are nocturnal (Fig. 122), hence they have the reputa- tion of being rather rare. During the winter they live in the ground encased in their own slime, but some species frequent greenhouses in cold weather, and in consequence of this habit mav remain active all the year round. *j «/ The food of slugs consists chiefly of the green leaves of succulent plants, and also of ripe fruit, such as apples. Our largest slug, Lim«.r2 maximus? is easily maintained ?>i. Gills in front of heart ; mantle-complex on anterior side of intestinal sac ; operculum constantly present Prosobranchiata b-2- Gills behind heart ; if shelled, without oper- cnlum Opisthobranchiata Key to the principal families of the American Pulmonata :- t(i. Eyes at apex of (usually retractile) tentacles. l>i. With external shell ; 4 tentacles . . . Helicidce (Ex. Helix) &2. Without external shell Lhnacidce (Ex. Limax) «2- Eyes on inner side or at base of the (non- retractile) tentacles. bi. Thick shell, with thick, often-toothed outer edge ........ Auriculidce (Ex. Melumpus) 6.2. Thin shell, with sharp margin . . . Limmndce (Ex. Pbysa) 1 Provided with lungs ; from pulmo, lung. 2 Aet/xa£, naked snail. 3 Largest. M 162 ZOOLOGY in captivity by keeping in a dark box and feeding on the blanched leaves of cabbage. In captivity one individual will sometimes devour another. Of our three principal species of slugs there may be first mentioned Limax maximus, which gains a length of about 10 centimetres and has a light brown color, marked with longitudinal rows of black spots along the back and sides. This species was almost un- known in this country until the middle of the sixties, but it is now widespread through- out the East. It has doubt- less been introduced from the continent of Europe, where it is very abundant. Second, Limax ay rest is1 is usually about 2.5 centimetres long ; it varies in color from whitish through gray to black. It is now common in the eastern United States, but is believed to have been introduced from Europe. Third, Limax cam- genera figured are: A, Actaeon ; pestris? a native species, is B, Aplustrum; C, Cylicbna; D, , , Atys; E, Phiiine ; F, Doiabeiia; smaller than agrestis, and its tuberosities are not so much flattened or plate-like. It occurs widely distributed east of the Rocky Mountains. Economically, slugs are of importance because at times in some localities they cause much destruction in gardens 1 Living in the field. 2 Living in open fields. FIG. 149. — Illustrating the transi- tion of form in the shell of certain Opisthobranchs, from the pointed spiral to the almost tiat plate. The G, Aplysia ; //, Pleurobranchus. Drawn to various scales. From Cooke, " Mollusca." THE SLUG AND I'M ALLIED 168 .c.d ep- and greenhouses. Particularly in Europe, Limax agrestis has often devastated fields of young shoots ; this species is especially fond of bulbous plants. In the apparent absence of a shell the slug seems to be an aberrant gastropod. Other land gastropods — the snails — have an evident shell. In Limax the shell is reduced to a thin, horny ^ J plate, embedded in the mantle. Between the con- dition seen in the snail and that in Limax there are intermediate condi- tions, in which the large shell is partly covered by the mantle, and others in which the shell has become reduced in size. In allies of Limax - in a genus called Ario'ti — FIG. 149a. — Illustrating the gradual covering of the shell (*7t) in certain Opisthobranchs by the epipodia (ep] and mantle ; c. d, cephalic disc. Drawn to various scales. A, Haminea; /:>, Sca- phander; C, Aplustrum ; I), Aphysia ; E, Philine. From Cooke, "Mollusca." the shell is reduced to a few calcareous grains. An exactly similar series in the degeneration of the shell is found in certain Opistho- branchs, illustrated in Fig. 149. The beginnings of this process of covering the shell are seen in many gastropods in which the mantle edges may protrude beyond the lips of the aperture, and are folded back over the outer surface of the shell. A more developed condition is seen in species like Aplysia, in which the mantle is permanently reflected.1 In Limax the reflected edges of the mantle Fig. 149rt. 164 ZOOLOGY have permanently grown together. The reflection of tl it- man tie seems to be of advantage by affording additional protection to the visceral mass. But after the complete over- growth of the mantle the shell seems to be useless, and con- sequently degenerates. The Pulmonata are either terrestrial, like the slug, or aquatic. Of the terrestrial Fis. ir,o.- shell of Helix, alboia- pulmoiiates other than the 6m, a common forest snail. Nat. slua- the most important are size. Photo, by W. H. C. P. the snails 01 the genus Helix.1 Helix 2 is noteworthy, because it is richer in species than any other molluscan genus, since it contains over three thousand species. The distribution of the genus is world- wide. In North America the snails are most abundant in limestone regions, consequently they are more numerous in individuals in the South and West than in granitic New England. One of the most interesting species is Helix nemoralis, a European form, which has been intro- duced into our country at Burlington, New Jersey, and Lexington, Virginia. At these places it has multiplied so rapidly, and varied to such a degree, that three hundred and eighty-five varieties have been enumerated from an area, at Lexington, not over one thousand feet in extent in its greatest diameter3 (Fig. 151). Any species of Helix collected in large numbers is apt to show abnor- malities in the number of tentacles and of eyes upon the 1 e'\i£, a turning round, as in spire of snail shell. 2 Fig. 150. 3 See paper by Professor J. L. Howe, in American Naturalist, Decem- ber, 1898, THE A NT) TTS ALLIES 165 tentacles. Besides Helix, a very abundant cosmopolitan land pulmonate is Pupa.1 Being of small size, it is, how- Fi 162) _ Thig ^ ^Photo. by animal has a sort of coat of mail, since its shell is made up of eight pieces, lying one behind the other, along its back. When removed from the rock or shell on which it rests, it coils up like a pill-bug or armadillo. Coordinate with the Gastropoda is the group of Cepha- lopoda.3 In this group belong the squids and cuttlefishes. They have a large, distinct head, a circle of arms about the mouth, a funnel-shaped foot, and huge eyes on each side of the head (Fig. 163). The squids are the best-known cephal- opods, since they travel in schools in our harbors and are often cast upon the shore after a storm. They can also be obtained in the markets of our coastwise cities, since their flesh is used to a certain extent as food. Cuttlefishes, 1 Eolis, daughter of Eolus, the god of the winds. ~ xircji', coat, case, covering. 3 Ke(pa\r), head ; TTOI/S, foot ; because the arms or foot are placed around the mouth. 172 ZOOLOGY best known from their "bones" or rudimentary shells \j embedded in the mantle, are inhabitants of deeper waters. They have shorter bodies than the squids, and their arms are eight in number instead of ten as in the case of the squids. In both groups locomotion is effected by the reaction to a stream of water which is taken into the mantle chamber at the edges of the mantle and is forced out through the " funnel," which lies between the eyes in Fig. 1(33. The shell is rudimentary in both the squids and the cuttlefishes, and like that of the slug is embedded in the mantle. Even in Spirilla the shell, though coiled and containing a siphon, is completely covered by the skin of the animal. There are two liv- ing genera of Cephalopoda which have an external shell. One is an ally of FIG. iitt. — L Argonauta? which IS found in all tropical seas. The other is the sole survivor of a once abundant group. This is the Pearly Nautilus of the Indian and Pacific oceans. Its shell is di- vided into water-tight compartments, in the last formed of which the animal lies. It keeps its attachment to the shell by means of a central strand of tissue — the siphon (Fig. 164, s). Allied to the Nautilus is the huge a sailor in the Argo. THE SLUG AND ITS ALLIES 173 family of Ammonites, of which two thousand species are known, ranging from the Silurian up to the Cretaceous formations. FIG. 164. — Nautilus pompilius, the Pearly Nautilus. Median section, c, outer- most chamber whose bottom is formed by the septum, tie ; s, siphon travers- ing all compartments ; ?,eye; h, hood; rn, part of mantle, reflected over the shell ; /, lobes enclosing tentacles (t) ; si, incomplete funnel ; mu, shell muscle ; n, gland secreting the capsules for eggs. After Owen. 174 ZOOLOGY APPENDIX TO CHAPTER XI Spirulidw VermetidcB KEY TO THE PRINCIPAL FAMILIES OF MARIXE-SHELLED GASTROPODS OF THE ATLANTIC COAST OF THE UNITED STATES, ADAPTED FROM A. C. APGAR a i. Shell spiral, of one to many whorls. 61. Spire in a single plane, and whorls not in con- tact. [A cephalopod shell ; liable to be mistaken for a gastropod-shell, page 172] bo. Spire dextral. Ci. Operculated ; aperture not over \ area of shell. d\. Anterior margin of aperture entire. €i. Shell tubular ; spiral at apex, irregularly twisted near aper- ture ..... e>2. Shell regularly spiral, elongated ; width less than 1 length ; whorls 5 or more ; angle of spire less than 45° ; aperture less than ^ length of shell, /i. Whorls rounded , almost sepa- rated, crossed by elevated longitudinal ribs ; aperture oval ; lip continuous ; our species over 10 mm. long . /2. Whorls about 5; minute shell, less than 5 mm. long ; width about | length ; aperture about i length ; apex blunt /3. Whorls 5-10 ; shells elon- gated, conical, turreted ; aperture ^-| ; length of shell of our species 4-10 mm. long .... 63. Shell regularly spiral, shortened ; width nearly as great as or greater than length ; whorls ScalariidcB Rissoidce Pyramidellidce APPENDIX TO CHAPTER XI 175 usually few ; angle of spire always over 50°, usually over 90° ; aperture over \ length of shell. /i. Shell conical, pearly under epidermis and within aper- ture, usually brilliantly so ; umbilicus deep and large . /2. Shell globular or oval ; spire short, body whorl large ; umbilicus rounded, dis- tinct, either free or covered by a callus ; angle of spire 90° or more /a. Shell top-shaped to globular ; interior pearly, 8-30 mm. long ; umbilicus when pres- ent not rounded nor cov- ered with a callus . /4. Shell minute, nearly disk- shaped, widely umbilicated Anterior margin of aperture notched or produced into a canal. e\. Shell with canal formed by a de- cided prolongation of anterior end. /i. Large, heavy shells, over 100 mm. long, pear-shaped ; whorls angulated or nodu- lous /2. Rather thin shells, 20-80 mm. long, ovate to pear-shaped ; whorls rounded and cov- ered with 40-00 small re- volving ridges . . /s. Shells over 20 mm. long, with longitudinal, rib-like undu- lations crossed by revolving lines . Trochidcv Naticidae (Ex. Natica) Littorinidce (Ex. Littorina) Adeorbidce Fasciolariidce (Ex. Fulgur) Bwcinidce Muricidw (Ex. Urosalpinx) 176 ZOOLOGY /4. Shells less than 20 mm. long ; aperture with a notch near posterior end, formed by outer lip not squarely meet- ing body wall . fr,. Shells less than 15 mm. long ; aperture entire at posterior end ; narrow, and a little less than -J the length of the shell ; canal rather short . .* e-2. Canal short or absent ; aperture notched, /i. Shells large, 40 mm. or more long ; whorls rounded /2. Shells 20-40 mm. long; whorls rounded /3. Whorls flattened, surface usually beaded ; aperture over i length of shell Co. Non-operculated, or operculum very mi- nute ; aperture with neither a canal nor a notch at anterior end. (I i. Aperture over f area and f length of shell ; spire distinct, pointed ; shell ear-shaped ..... (?o. Aperture \ the area or more, and the full length of the shell. Ci. Shell with 1 whorl, less than 2 mm. long .... ?o. Shell with several whorls, under 4 mm. long ; spire flat . e-s. Several whorls, a pit in place of spire, over 6 mm. long . t?s. Aperture less than ^ the area of the shell. e\. Aperture | to whole length of shell ; spire distinct, usually flattened ; under lip with single fold or smooth Plwirotnmidce Columbellidce Philinidce, Scaphandridce Bull idee TornatinidoB APPENDIX TO CHAPTEE XI 177 ?2. Aperture i-f length of shell ; under lip with 2 or more teeth c3. Non-operculated ; aperture with canal at anterior end ; our species 20 mm. or less long b3. Sinistral ; whorls in contact. <"i. Shell ovate-globose, small, not over 5 mm. long, transparent ..... c.2. Shell elongated, turreted, slender, less than oO mm. long. .... GS. Shell large, over 100 mm. long, with pro- duced anterior canal . a-2. Shell flat, boat or cup shaped, if somewhat spiral, not forming a complete whorl. bi. Shell with apex somewhat spiral and an in- ternal, usually horizontal, partition or dia- phragm fto. Shell conical or cup-shaped, with apex turned forward ; no shelf or partition. GI. No perforation at apex or notch in mar- gin c-2. Apex recurved ; margin or apex perfo- rated . . > . . . Auriculidce (Kx. Mt'lunipiis) Triforidce Calyptrwidce (Ex. Crepidiila) Acmceidce (Limpets) Fissurellidce N CHAPTER XII THE FRESH-WATER CLAM AND ITS ALLIES THE fresh-water clams belong to the group of lamelli- branch mollusks, characterized by the absence of a distinct head, by the possession of leaf-like gills on the sides of the body, and by the presence of a calcareous shell composed of a right and a left valve. Economically this group is the most important to man of all Mollusca. It includes both marine and fresh-water species. About six thousand species of living lamellibranchs and over ten thousand fossil species are recognized. They all fall into two prin- cipal subdivisions. The first (Siphonata) includes species which possess a siphon and have the mantle edges grown together, while the second (Asiphonata) has no siphon and has the mantle lobes for the most part wholly separated.1 Anodonta and Unio are extremely common in the ponds, lakes, and rivers of North America. Anodonta is more apt to be found in still waters and Unio in running waters. They lie partly buried in the mud of the bottom, with the valves of the shell gaping open and the partly united edges of the mantle protruding. They do not lead wholly sedentary lives, but may burrow or plough along the bottom. Their food is gained from organic particles borne along 1 A key to the principal families of bivalve shells will be found in the Appendix, p. 188. 178 THE FRESH-WATER CLAM AND ITS ALLIES 179 in the current of the water. A part of this current is carried through the mantle chamber and forced out again, deprived of usable food and of the oxygen used in respira- tion. By devouring organic matter these clams act as useful scavengers of the water. The family of Unionidae, to which Unio and Anodontia belong, is of world-wicte distribution, but nowhere else are Unionidre so numerous as in the United States. They show in our country a most marvellous variability also, so that hundreds of kinds have been described from our waters. The extraordinary abundance of Unios in North America is due to the fact that nowhere else is there such a large area of soluble limestone as in our Mississippi valley. The clams take from the water the lime which they use in the construction of their shells, change it into an insoluble form, and thereby advantageously reduce the amount of the inorganic matter in solution, for this change in the quality of the water renders it more fit to drink and to sustain other animal and plant life. Although numerous and of large size, the Unionidae do not seem to be much used as human food. The aborigines, however, made use of them, as the great shell-heaps on the banks of rivers of the Ohio valley testify. They yield also pearls, which occasionally, especially in the Ohio valley, are of precious quality. Even the small, imperfect pearls are of value, since they are ground up to make the powder used in polishing the more valuable pearls. The spawning season of our Unioimhe is short. The eggs pass, during the latter part of October, into the gills of the parent, where they undergo their early development, protected by the parent shell and supplied richly with oxygen. The cleavage is unequal because of the larger 180 ZOOLOGY amount of yolk in some of the cells than in the others. Eventually a shell is formed, which divides into two valves united by a straight hinge. A spine is formed on the free edge of each valve, and a thread (byssus thread) is secreted from the body. The young at this stage is known as Glochidium (Fig. 165). In the spring Glochidia become free from the mother, and attach themselves to the gills or fins of a fish by means of the spines on the shells. Here they become transformed. The single adductor muscle dis- appears, and becomes replaced by the two characteristic of ' R B. J. TD. -- FIG. Ki"). — A, advanced embryo of Anodonta: B, free glochidium. /, pro- visional byssus ; s, sbell ; .s7t, books ; .sm, adductor muscle ; so, sense organs ; w, cilia. From Korschelt and Heider's " Embryology." the adult; the gills arise, the shell gains its adult char- acter, and becomes free from the fish on which it has lived temporarily as a parasite. There are other species of fresh-water lamellibranchs besides the Unionidae. These belong to the Cycladidae, allies of the marine Cardidre or Veneridre. They have much the shape of our common hard-shell clam of the sea, but are much smaller in size, rarely exceeding 15 milli- metres. Cyclas (or Sphserium) is of world-wide distribu- THE FRESH-WATER CLAM AND ITS ALLIES 181 tion, but it is especially abundant in North America. It occurs in ditches, ponds, and rivers of New England, as well as in the South and West Some species of it inhabit brackish water. Pisidium has both valves unsymmetrical. Its species are still smaller than those of Cyclas, rarely exceeding 10 milli- metres. It likewise is found in ditches, ponds, and streams all over our country. The remaining families which we shall consider come from the sea, and all occur on our Eastern coast. The Pholadidae1 and Teredidae2 include certain wood and rock- boring species, which do great damage by boring into wooden vessels and pilings (Fig. 1(3(3). In such locations they are commonly called ship-worms. The boring is done by the movements of the shell, combined with the action of the muscles and foot. The only thing which seems effectively to stop these mollusks from boring into wood is iron rust, so that piles driven full of nails are apt not to FKJ. KM;.— TV/WO ncpali*, 11-1 in a piece of timber. /'. be attacked. paUe£. SjSt siph,,lls: T, tube; V, valves of shell. 1 0oAds, Greek name for a boring mussel. From the " Cambridge 2 repe'w, to bore. Natural History." 182 ZOOLOGY The Solenidse1 include the "razor-shell" (Fig. 167). This animal, like the shell, is elongated and subcylindrical. By means of its foot, which can be protruded between the FIG. 167. — Emis direct us. Young. Nat. size. Photo, by W. H. C. P, \alves, it excavates, with great rapidity, a hole in the sand or mud, into which it draws itself. These mollusks are sometimes used for food, but it is not easy to get them in quantity. The Mactridae2 include species commonly known in the North as hen-clams and surf-clams. They are more ellip- tical and larger than the common hard-shelled clam or " quo- hog," and have a proportionately lighter shell (Fig. 168). They are not often used as food because they become very tough when cooked. The Myidae3 include the common clam of New England, Mya arenaria, abundant along our whole Eastern coast and used as food chiefly in New England. These clams occur in great numbers in every mud-flat. Their great siphon is extended at high tide to the surface of the ground, so as to take in and throw out water (Fig. 169) ; but at low tide it is retracted, and the clam lies invisible in its burrow. This clam was much prized by the Indians, as the great, ancient shell-heaps along the coast testify. In 1892 the clam com- , a channel or tube. 2 /xd/crpa, a baking-trough. 3 fj.va, Greek name for a kind of mussel. THE FRESH- \VATER CLAM AND ITS ALLIES 183 merce for New England was estimated to be worth nearly half a million dollars. FIG. Iti8. — Mactra solMisshna, the Eastern hen clam. Nat. size. From Gould-Binney. The Veneridae l include the hard-shelled clam or u fjiio- hog " of the Indians. Venus mercenaria is the commonest species, and is most abundant south of Cape Cod. It owes FIG. 1G9. — My a arenaria, the New England " clam." At the left the foot is seen ; at the right, the siphon. One-half nat. size. From Yerrill. " Inverte- brates of Vineyard Sound." 1 Venus, the goddess of love. 184 ZOOLOGY its name " mercenaria " to the fact that the purple-colored patch seen on the margin of the shell was used as money FIG. 170. — I'e/ias mei\"jiuifi to-0 times height ; epidermis polished ; um- bones not over one-quar- ter from anterior end Pholadidcc 7.eredid(e (Shipworms) Ledidce (Ex. Y old in) Solenidce (Uazor Clatus) APPENDIX TO CHAPTER Xll 189 /:>. Shell thin, rounded in front, narrowed and gaping be- hind, cartilage pit shal- low ; external ligament short .... Shells inequivalve. e\. Length and height about equal, e-2. Length decidedly greater than height. /!. Over 25 mm. long ; right valve nearly flat ; whole shell compressed to one- sixth length . /2. Over 50 mm. long ; 'slightly inequivalve ; no external ligament; internal car- tilage on spoon -shaped process of left valve f.2. Length about 3 times height ; umbones central, Psammoliidfc fs. Length less than 3 times height ; surface covered with radial ridges, chalky white, umbones near an- terior end /4. Length about 2 times height; epidermis polished, with notched border extending beyond the edge of the thin shell, /4. Shell with thick black epidermis ; external liga- ment prominent and on shorter end of the shell, e». Length less than twice height. J\. Shell somewhat triangular, with internal cartilage between deep triangular pits, similar in each valve Solrmyidw SaxicctvhUv Mactridce (1 leu Clams) Pmidoriflre 190 ZOOLOGY /3. Shell under 18 mm. ; promi- nent external ligament, «2. Shell not at all gaping bi. With not over 3 cardinal teeth in each valve. t'i. Valves equal in size, curvature, and markings. di. Anterior muscular impression very small, hinder large; shell elongated, mussel-shaped ; umbo at or near posterior end .... d». Hinge line straight, formed by ears at sides of umbo, radiating ribs, scalloped edge .... d$. Height and length nearly equal ; a decided pallial sinus (Hi d±. Height and length nearly equal ; no distinct pallial sinus, at most a mere undulation of pallial line at posterior end. f\. With a plain lunule in front of umbones; without radial ribs. fi. Over 20 mm. long, com- «/ *• O 7 pressed , ligament external /_». Shell somewhat quadrant shaped; less than 8 mm. long; surface with con- centric ridges. /s. Shell less than 5 mm. long, very much compressed ; ends rounded . e2. With no lunule and with dis- tinct radial ribs . Co. Valves unsymmetrical. (?i. 2 muscular impressions, a distinct pallial sinus. (See t?2 under «!.) d». 1 muscular impression ; height never much less than length Tellinidce Mytilidce (Mussels) Pectinidce (Scallops) Veneridce inl-shelled Clams) As t art i < he Crassatellidce ErycinidcK Oardiidce APPENDIX TO CHAPTER XII 191 €]_. Fixed mollusks with large rough shells attached by large valves, €'2- Fixed mollusks, with their pearly shells attached by smaller valve which is flat or concave and perforated or notched e*. Free mollusks ; hinge line straight, formed by ears at sides of umbo ; with radial ribs ..... With many small cardinal teeth in each valve. Ci. With distinct radiating ribs ; shell over 30 mm. long Co. Smooth, length and height equal ; under 12 mm. long c3. Elongated shells, length nearly or twice height ; a pallial sinus .... Ostreidce (Oysters) Anomiidce (Jingle shells) Pectinidce ArcidoK (Ark-shells) NucnlidcK Ledidce KEY TO THE PRINCIPAL GENERA OF FRESH-WATER LAMELLI- BRANCHIATA «i. Siphonate ; without marked muscular impression, Fain. Cycladidce bi. Valves sub-symmetrical ..... Genus Cyclas b>2- Valves unsymmetrical ; siphons united . • . Pisidium cto. Asiphonate ; with two muscular impressions . Fain. Unionidw l)\. Hinge with teeth. Ci. With short cardinal teeth and long lateral teeth ....... Unio Co. With short cardinal teeth and no lateral teeth ....... Maryaritana Hinge without teeth, or with only a small ridge, Anodonta CHAPTER XIII THE STARFISH AND ITS ALLIES Systematic Position. — The starfishes belong to the group of Echinodermata,1 characterized by a radial, usually five-rayed, structure, a more or less well-developed system of calcareous plates in the skin ; a system of water-tubes, which is used by the movable forms for locomotion; and the separation of the intestine from the body cavity. Distribution and Habitat. — The common pink starfish of the eastern United States (Asterias2 vulc/aris3) ranges from Labrador to northern Florida. A dark brown form, sometimes called Asterias Forbesii^ is recognized by some authors as a separate species inhabiting the coast from Massachusetts Bay southward. Our shore starfish extends out into fairly deep water, but is not abundant at greater depths than 60 fathoms. In Long Island Sound it is found especially on. the oyster beds, where it is very destructive. On rocky coasts starfishes will be found in crevices of the rock or in tide-pools. They love cool waters, and are often found hanging on vertical walls or ledges. Upon reaching the surface of quiet water, they may extend one or more of their arms out upon the under side of the surface film. hedgehog, sea-urchin ; Se'p/xa, skin. A key to the principal classes of Echinodermata will be found in the Appendix to this Chapter. - dcrT^p, star ; dtrrepias, starred. 3 Common. 4 Of Forbes, an English zoologist. 102 THE STARFISH AND ITS ALLIES 193 Food. - -The favorite food of the starfish is some kind of mollusk, especially bivalves, such as mussels and oysters. Their method of feeding is as follows: They crawl over the bivalve, arch the body over it, apparently pull open the valves, then turn the stomach inside out over the soft body within the shell, and gradually digest it. The star- fish probably finds its food by means of a keen chemical sense. Starfishes are of economic importance on account of their destructiveness to oysters, but since the oystermen have learned to keep the beds clear of starfishes and that tear- ing starfishes into pieces only aids in their increase, as each piece produces a whole starfish, the damage wrought by starfishes must be less than it was formerly. Development. - - Starfishes have the sexes distinct ; and the sex can usually be told by the color. The female has a more bluish tint, while the males are of a reddish brown color. Both the eggs and sperm are extruded into the water through small openings on the aboral surface at the interspace between two adjacent arms. The egg is hardly visible to the naked eye, and is enclosed in a delicate membrane. The egg undergoes cleavage ; that is to say, the single sphere breaks up into two, four, eight, sixteen spheres, and so on. Finally a hollow ball, made up of these spheres or cells, is formed, called the "blastula." Next the wall of this hollow sphere is pushed in at one side, forming a sort of cup with two walls. This is the so-called "gastrula." The cavity of this cup is the digestive cavity. At first it is a sac with only one opening, but later a second opening, the true mouth, breaks through, and the former opening persists as the anus. Pairs of arms, edged with cilia, now bud out on o 194 ZOOLOGY each side of the body, and the larva becomes bilaterally symmetrical.1 Meanwhile, inside the body, the system of water tubes of the adult starfish has begun to form, and finally, over the stomach on the left side, five main water tubes, radially arranged, make their appearance ; these are the five radial tubes, one of which runs down each future arm.2 On the right side of the stomach, calca- reous plates are laid down to form the aboral wall of the starfish.3 The young star is now found as a parasite at the hinder end of the larva. Soon all the front end of the larva, together with the long arms, becomes absorbed. Up to this stage the larva lias been free-swimming, but it now settles to the bottom. There the process of resorption is completed, the upper and lower surfaces of the star approach each other, the calcareous skeleton and sucking- feet rapidly develop. At this stage the disk is so large, and the arms so short, that the young starfish looks more like a sea-urchin than an adult starfish. The elongated arms and the pedicellarue of the adult are not gained until three years have passed. t/ -*- 1 Figs. 176 and 177. 2 Fig. 178. Fig. 179, ab>. FIG. 176-179. — Larval stages and metamorphosis of starfish. After drawings of E. B. Wilson, from Brooks, " Invertebrate Zoology." FIG. 176. — Dorsal view of starfish larva with beginnings of ciliated arms. FIG. 177. — Ventral view of same larva. FIG. 178. — Side view of an older larva in which young star is beginning to arise. FIG. 179. —Ventral view of same larva, a, anterior end ; b, posterior end; 1-4- , ciliated projections; a', preoral arms; a HI, oral surface of young star with beginning water tubes, am-am5; ab, ub', ab^, aboral surface of star; c, postoral arm ; i, intestine; m, mouth; n, lateral arm ; o,anus; ce, oesopha- gus; q, q', dorsal lateral arms; *, stomach; ww', water tubes ; am, Fig. 177. region from which water tubes arise. om FIG. 17ti. FIG. 177. FIG. 179. 195 196 ZOOLOGY Abnormalities are frequently found among starfishes, — partly on account of their capacity for regeneration, even from the disk and a single arm. Thus one may find a starfish with three or four rays, or with a small ray interpellated in be- tween normal-sized ones. Not all abnormalities seem to be the result of mutila- tion, however; for example, sometimes two arms seem FIG. 180. — Abnormal starfish (Astenas), apparently produced by fusion of two to be fused (Fig. 180). r°Thalf nat- size> Phot°* by Other Starfishes. — Aste- . \j, -T. FIG. 181. — Ct'ibrella sanguinolenta. Nat. size. From Leuuis. THE STARFISH AND ITS ALLIES 197 rias vulgaris belongs to the gionpAsteroidea.1 But there are over five hundred other species of starfishes. In some of these — as in Asterias — the skele tal plates of the skin make a net work ; in others they form a solid calcare- ous covering. To the first class belong, besides Asterias vulgaris, Aste- rias ocliraceaf which oc- curs commonly on the Pacific coast from Sitka, Alaska, to San Diego, California. This has a much thicker, more solid skin than the FIG. 182. — Solaster, a multirayed starfish. t ,-, , . . A Reduced. From Leunis. Atlantic species. A. gi- gantea^ attains a diam- eter of over two feet. Next to A. vulgaris, our commonest Eastern species is a smooth, leathery, blood-red star- fish, about 10 centi- metres in d i a m e t e r, called Oribrella 4 san- 1 APT-TIP, star ; eTSos, form. 2 o>x/>6s, pale yellow. 3 giyanteus, gigantic. This species occurs on our Pacific FIG. 183. — Archiaster, a webbed starfish. coast. Slightly reduced. Photo, by W.H.C.P. 4 cribrum, sieve, ZOOLOGY guinolenta1 (Fig. 181). Certain starfishes have many arms instead of only five, as in the case of Solaster 2 endeca 3 of the northern Atlantic (Fig. 182). In still other star- fishes the rays are partially connected by a membrane like the web of a duck's foot, so that the whole outline is nearly pentagonal (Fig. 183). The Ophiuroidea. — In the Ophiuroidea 4 the organs are not prolonged from the disk into the arms, consequently FIG. 184. — Amphlura squamata. One of the Ophiuridae. Nat. size. Photo, by W. H. C. P. the arms may be thrown off without injury to the animal ; hence the name "brittle-star." The brittle-stars fall into two groups, in one of which, the serpent-stars, the arms are uiibranched, while in the other, the "basket- fish," the arms are branched. Of the serpent-stars there are two common forms on the New England coast,- -a Avhite species, with long, slender arms, Amphiurab squamata 6 (Fig. 184), and the spotted Ophiopholis,7 which has shorter, stouter arms. The 1 Blood-red. 5 dfjL5e/ca, eleven. 7 60is, snake ; 0oXi':, scale. 4 50ts, serpent ; ovpd, tail. THE STARFISH AXD ITS ALLIES 199 animals live in crevices of the rock, and being of rather small size, are not commonly seen. At the base of the arms, on the right and left, are a pair of slits, which form the exits from pouches into which the reproductive glands open. In certain species the pouches are used for brood- ing the young. The basket-fish occur in Northeastern FKJ. 185. — Strongylocentrotus, the Eastern green sea-urchin, with tube feet extended. From " Standard Natural History." waters, from low tide to one hundred fathoms, and are often brought up by fishermen, to whose lines they have a habit of clinging. The branching of the arms enables the animal to hold its prey, which consists of shrimp and fish. The Echinoids, or sea-urchins, may be regarded as star- fishes in which the arms have shortened and the disk en- larged so as to fill up the interspaces, and make a solid, 200 ZOOLOGY nearly spherical form. The sea-urchins eat various small animals, and get food also from small bits of organic matter in the mud which they swallow. They live more concealed than the starfish, for some burrow in the mud and others -such as our green sea-urchin of the Maine coast (Fig. 185) — grind out pockets in the rocks by means of their spines. Others cover themselves with seaweed, and thus become inconspicuous. Besides the green sea-urchin, FIG. 186. — Arbacia, the Easteru black sea-urchin. Tube feet retracted. Nat. size. Photo, by W. H. C. P. which is found north of Cape Cod, we have a black sea- urchin (Arbacia, Fig. 186), which extends south as far as North Carolina. We have on the east coast also two kinds of flat sea-urchins (sand-dollars), which live in the sand from low water to one hundred fathoms. Their spines are small and silky (Fig. 187). Some sea-urchins lose their strictly radial form and become bilateral, having a ] jointed anterior end (Fig. 188). THE STARFISH AND JT-S ALLIES 201 The Holothurians l may be likened to soft-skinned sea- urchins, with the body drawn out to the form of a cucum- FIG. 187. — Echinarachnius par ma, the sand dollar. Spines removed from left side. Nat. size. Photo, by W. H. C. P. FIG. 188. — Clypeaster, a bi- lateral sea-urchin from the West Indies. Spines partially removed and surface rubbed in patches. Reduced photo. ber, or even of a worm. The calcareous skeleton is reduced to small plates embedded in the skin. The mouth is sur- rounded by a circle of tentacles. The ambulacral feet are sometimes absent. The Holothurians live in sand and mud, often deeply buried, and feed on small marine animals or the decaying particles mingled with the mud which they devour. They are of considerable economic importance. The members of one genus (Holothuria) is taken in great numbers on the coral reefs of the Pacific i v\o6ovpioi', a sort of water-polyp. FIG. 189. — Caudina, the tailed Holothuriau. a, mouth; b, anus. After Selenka. £02 ZOOLOGY J FIG. 191. — Metacrinus interruptus. After P. H. Carpenter. FIG . 15 10. — »S'// » apt a inhe re tt s. a , tentacles; b, longitudinal mus- cles; c, alimentary tract. - After Quatrefages. Ocean and the China Sea, where they are com- monly known as lk tre- pangs." They are cut open, washed, boiled, dried, and sometimes smoked. They are sold in Chinese ports, and some species are con- sidered by Chinese epi- cureans as great deli- cacies. Several species of Holothurians occur on the Maine coast. A bar- rel-shaped form with a APPENDIX TO CHAPTER XIII 203 sort of tail (Caudina,1 Fig. 189) occurs on the Massa- chusetts coast. A worm-like form, but with a beautifully transparent skin (Synapta,2 Fig. 190), is found in sandy beaches from Massachusetts to New Jersey. The Crinoids,3 or sea-lilies, are familiar as fossils to resi- dents of New York State and the Ohio and Mississippi valleys. The living animals are less often seen, for they are inhabitants of the deep sea. They have a cup-like body, with the mouth at its centre directed upward, and surrounded by tentacles (Fig. 191). The cup is either borne on the end of a long stalk or is unstalked. The former condition is more usual among the fossil species. APPENDIX TO CHAPTER XIII KKY TO THE PRINCIPAL CLASSES OF ECHINODEKMATA «i. Sessile ; mouth turned upward ; body calyx-shaped Crinnidea (Sea-lilies) a-2- Not sessile. b\. Body short ; skin hard, containing calcareous plates ; mouth directed downward ; madre- poric plate present. Ci. Body with arms which carry a longitu- dinal series of plates. di. Arms with ventral furrow . . Axtcrnidea (Starfish) d2. Arms without ventral furrow . . Ophiuroidea (Serpent stars) 1 cauda, tail. 2 awairrbs, fastened together ; from vvv, with, and ctTrrw, to fasten. 3 Kpivov, lily ; dSos, form. 204 ZOOLOGY c%. Body without arms ; more or less spheri- cal or cake-shaped .... Echinoidea (Sea-urchins) 62. Body elongated ; skin soft, leathery, contain- ing microscopic calcareous bodies ; madre- poric plate absent ; mouth surrounded by tentacles Holothuroidea (Sea-cucuuibers) CHAPTER XIV THE HYDRA AND ITS ALLIES HYDRA belongs to the group of Coelenterata,1 which includes sponges, and certain organisms with nettling capsules — Cnidaria.2 The Coelenterata have a more or less radial form, and a system of internal cavities serving for digestion as well as for body cavity. The sponges are all sessile, have no nettling capsules, have the body wall perforated by many fine incurrent openings, and a larger exhalant opening (Fig. 192). The Cnidaria3 have nettling organs of some sort. Hydra belongs to this group. There are two common species of Hydra ; the one is of a green color {Hydra* viridis5)^ and the other is flesh- colored {If. fuscaQ~). They are found in standing or slow- running water, attached to submerged plants, sticks, and stones. Throughout the winter they live at the bottom of ponds, below the ice. The body of Hydra is soft and highly contractile, so that, when first drawn from the water, it appears like a speck of jelly. Left undisturbed, the animal expands, and its five to eight tentacles wave s, hollow; evrepov, intestine. nettle. 3 A key to the principal subdivisions of the Cnidaria and especially of the Hydromedusse will be found in the Appendix to this Chapter. 4 vdpa, a mythological monster, capable of regenerating its head. 5 Green. 6 Brown. 205 206 ZOOLOGY slowly about in search of food. The tentacles are richly supplied with nettling cells, each of which contains a fluid-filled capsule, in which is coiled a thread-like tube. FIG. 102. — Sycon gelatinosum. A portion slightly magnified: one cylinder (that to the right) bisected longitudinally to show the central stomach cavity opening on the exterior by the osculum, and the position of the incur- rent and radial canals; the former indicated by the black bands, the latter dotted, ip marks the position of three of the groups of inhalant pores at the outer ends of the incurrent canals ; o, osculum. When stimulated by contact with some foreign body the tentacle closes around it, while from each capsule the lasso-thread rolls out as the finger of a glove is rolled inside out, and discharges the irritating poison .through THE HYDRA AND ITS ALLIES 207 the lumen of the thread. If a small animal has been the irritant, it is instantly caught in the thread, paralyzed by the poison, and soon conveyed to the Hydra's mouth. The principal food of Hydra is small worms and the smaller Crustacea, such as Daphnia and Cyclops. a \ fWo/ ') v) Ik FIG. 193. — A colony of Cordylophora lacustris, on a shell of Mytilus. For clearness, a number of the erect branches are cut off at the stolon, a, very young shoot without lateral branches; b, young stock with lateral branches but no gouophores; c, a stock with gonophores on lateral branches; d, fully grown stock with lateral stems. After Schulze. Fresh-water Cnidaria are of extremely few kinds. Hydra was once regarded as the only instance, but others are now known. One of these, called Cordylo- phora, is found chiefly in brackish water or in fresh water, near the coast. Like many of the marine hydroids, Cordy- 208 ZOOLOGY lopliora produces its young in special capsules, called gonophpres, which are rudimentary jelly-fishes (Fig. 193). The young become free when they have gained an elon- gated, cylindrical form. There are other fresh-water species which have free jelly-fishes. In this country we have a species, Microhydra l Ryderi, hitherto known only about Philadelphia, whose hydroid stage is extremely small and bears no tentacles. The jelly-fishes are set free during July. Fresh-water jelly-fishes have also been described from Lake Tanganyka, Africa, and from a tank at Regent's Park, London, to which they had doubtless been imported on plants. It is very probable that all fresh-water hydroids which produce jelly-fish have, geo- logically speaking, recently come from the sea. Hydra, however, is probably a long-established fresh-water species. The marine hydroids are, in contrast to the fresh- water ones, very numerous. The Hydrocorallidae 2 are peculiar in that they secrete a great amount of calcareous sub- stance, so that they were formerly regarded as belonging to the typical corals (Scyphozoa). They may be easily distinguished by the absence of radial septae in the cups occupied by the hydroid. Here belong the millepore corals of Florida. The Tubularidae3 include some hydroids of large size, single individuals of Tubularia becoming six inches long. Other species grow 011 gastropod shells which are occu- pied by hermit-crabs (Figs. 194 and 195). So thickly do they grow that they make a plush-like covering on the upper part of the shell, and they have the curious habit 1 Small Hydra. 2 Combining the qualities of Hydra and the corals. 3 From tubulus, a little tube. THE HYDRA AND TTN ALLIES 209 of building out the lip of the shell so as to enlarge the aperture. They do this in order that the hermit-crab, as it grows larger, shall not be forced to exchange the shell for a larger one, leaving the hydroids on the cast-off shell to roll about on the beach and perish. Of the Campanularidae,1 or bell-hydroids, one of the common representatives is Obelia,2 which may be found at low tide hanging from -i i ,1 11 FIG. 1!H. — Stylactis, a tubularian rocks beneath seaweed, and hydroid> gl.0^ugou asn:iiL Nat. looking like delicate white size. Photo, of living animal by threads (Fig. 196). Observed FIG. 195. — Hydractinia, a tubularian hydroid. a, colony growing on gastro- pod shell inhabited by a hermit-crab ; b, bit of colony enlarged ; dz, modified, tactile, individuals; s, reproductive individuals; sp, spines. From Parker and Haswell. campanula, a little bell. os, a spit. 210 ZOOLOGY under the microscope each stem appears as a series of hydranths placed in zigzag1 fashion, one beyond the other. FIG. 10(!. — Obelia ( ?) , a group of campanularian hydroid colonies. Nat. size. Photo, by W. H. C. P." Another common kind is Sertularia,1 which forms rusty brown threads (Fig. 197 ). All the hydranths of one stem occur in one plane and oppositely. Both t u 1) 11 1 a r i a 11 and c a m p a 11 u 1 a r i a 11 hy droids may give rise to jelly-fishes. These jelly-fishes are formed as buds on the hydrant] i, and after they become able to move of themselves they are ;. 1<»7. — Sertularia, a small colony. J i.r> nat, size. cut off from the parent and 1 Derived from serta, garland. THE HYDRA AND J7'N ALLIES 211 swim away. The jelly-fishes then give rise to the sexual products and discharge them into the water (Fig. 198). In other cases the jelly-fish is formed but never separated FIG. 198. — Bougainvillea ramosa. A, entire colony, natural size; B, portion of the same magnified; C, immature medusa; dr. c, circular canal; cu, cuticle or perisarc ; ent. ccw, enteric cavity ; hyd, polyp or hydranth; hyp, hypostome or manubrium ; med, medusa; mnb, manubrium ; rad. c, radial canal; t, tentacle; v, velum. From Parker's "Biology," after Allman. This is closely allied to the New England B. super cllians. 212 ZOOLOGY from the parent, and the eggs develop in the bud. In still other cases a mere bud, called gonophore, is formed, which becomes full of sexual products without ever ac- quiring resemblance to a jelly-fish. The jelly-fish is the primitive type which has undergone a reduction in some cases to a gonophore. It is an interesting fact that in certain species sometimes jelly-fishes and sometimes gono- phores will be produced. In the Campanularidae the FIG. 199. — Zygodactyla. Reduced. From a drawing by A. Ajjassiz. gonophores are encased in a cuticular capsule, but in the Tubularidse they are quite naked. There are certain hydromedusre in which the hydroid stage is unknown or known to be lacking. Here belong some jelly-fishes of large size, like Zygodactyla, one of the Trachomedusse of our coast, which may become eight to ten inches in diameter (Fig. 199). Besides these the sea contains many small species, which are easily captured in the net, and which are of extreme beauty and delicacy. Besides the Hydromedusre, the group of Hydrozoa in- cludes the Siphonophora.1 These animals are always colonial and free-swimming, and are among the most 1 0-/0WJ/, a siphon ; o/)6s, bearing. THE HYDRA AND ITS ALLIES 213 beautiful inhabitants of the sea. Those who have crossed the Atlantic are acquainted with the " Portuguese man-of- •fon. FIG. 200. — Physalia arethusa. Nat. size. After Agassiz. •net nlc FIG. 201. — Halistemma terge- stinum. The entire colony. cw, coenosarc; dz, dactylo- zooid ; hph, hydrophyllium or bract; net, nectocalyx or swimming-bell; ntc, battery of nematocysts; p, polyp; pn, pneumatophore or float; t, tentacle. After Glaus. 214 ZOOLOGY warv (Physalia,1 Fig. 192), which often swarms in the Gulf Stream. The huge float which lies on the surface of the water serves also as a sail by which the animal is transported by the wind. There are other smaller, more graceful species of more typical form (Fig. 201). The structure of a siphonophore is very complex. From the float hangs a central stem. Upon this stem are budded feeding zooids — hydranth-like forms provided with mouth and tentacles — and reproductive zooids- - gonophore-like forms which produce the germ cells. There are leaf -like expansions also, which are rudimentary medusae. All the many forms budded on the stem are modifications of the hydroid type. Contrasted with the Hydrozoa are the Scyphozoa,2 which are, on the whole, larger animals. These, too, occur both in the sessile, polyp form and in the jelly-fish form. The sea-anemones are common examples of the polyp. These are, for the most part, solitary, fleshy creatures, often brilliantly colored, and therefore appropriately called by the Germans " sea-roses," and in this country and in Eng- land " sea-anemones." They are of cylindrical form, bear a circle of tentacles around the mouth at the upper end, and have a muscular base by which they attach themselves. They vary in diameter from one-sixth of an inch to two feet. Some species live in the sand, out of which they get some organic food, and at least one species (Minyass) is free-swim m ing. Our commonest Northern sea-anemone is Metridium marginatum (Fig. 202), which occurs on rocky shores south bladder. 2 o-Kixpos, cup ; fwoz>, animal. 3 For a figure of Mnyas, see Parker and Haswell, "Text-book of Zoology," p. 189, Fig. 13U. THE HYDRA AND ITS ALLIES 215 to New Jersey, but reaches its maximum development along the coast of Maine. It varies greatly in color, some individuals being white, others salmon-colored or olive. The flat upper surface bears the slit-like opening to the internal sac. Either one or both angles of this slit have thickened edges, and corresponding to this difference is a FIG. 202. — Metridium, one of our sea-anemones. Two individuals shown expanded. Photo, of the living animals in the water, by W. H. C. P. difference in the internal structure. Inside, the central cavity is separated into compartments by radial partitions. The coral polyp does not differ essentially from Metri- clium. But it has the habit of secreting lime at its base, so that, in course of time, a high cup is built up. The top of the cup bears radial septa,1 which are laid down i Fig. 203. 216 ZOOLOGY in the interspaces between the fleshy partitions men- tioned in speaking of Metridium. Since most corals, like FIG. 203. — Coral cup of manicina. Nat. size. Photo, by W. H. C. P. hvdroicls, bud freely, and since every bud secretes coral at its base, an extensive and complicated limy mass may be produced. This is the way in which the brain corals and •6£tt***-.fi-i-^ •*.•>. ,- , FIG. 204. — Astranyla dTO>/>, a Greek at Troy, known for his loud voice. THE PAEAMECIUM AND ITS ALLIES 225 an aquarium, when the Stentors, if present, will attach themselves to the glass sides of the vessel. The attach- ment of Stentor to objects is not permanent, for it may loose its hold and swim free. When the animal is stained in hcematoxylin, the characteristic nucleus, looking like a chain of beads, becomes evident. Vorticella,1 the bell-animalcule, is found in pools or infusions, permanently attached by a long stalk. When the animal is irritated, it contracts its stalk, which twists into a close spiral. Carchesium 2 differs from Vorticella, in forming colonies, so that a number of heads are attached to a central stalk. A colony, when fully expanded, appears like a fine, white mould attached to a submerged object. In both of these types the food consists of small organic particles, which are swept into the gullet by the circlet of cilia placed around the upper end of the body. The Suctoria3 are sessile Infusoria, from whose upper surface numerous remarkable sucking-tentacles arise. By means of these tentacles the animal can hold on to Para- , mecia and other free-swimming Infusoria, from which it extracts the body fluids. Some Suctoria are stalked (e.g. Podopliora^, while others are unstalked (e.g. Aeineta'0). They are found most abundantly in standing water, either fresh or salt, and are often attached to other animals, - Bryozoa, entomostracans, and pulmonate mollusks. Of the group Flagellata,6 or lash-animalcules, Euglena7 is a common representative . It is of microscopic size, but occurs in such numbers as often to give a decided green 1 Dim. from vortex, whirlpool. 4 TTOUS, foot ; 60/>tfs, eyebrow. 2 Kapxyviov, goblet, Fig. 207. 5 d/aVr/Tos, without movement. 3 From sugere, snctum, to suck. & JlayeUum, a lash. 7 evy\r)vos, with a beautiful eye. 226 ZOOLOGY color to the pools of water it inhabits. It is spindle- shaped, and bears a flagellum at its anterior end. At the base of the flagellum is a red "eyespot." Allied to Euglena is Volvox,1 a spherical, multicellular c-.vac FIG. 2<>S. — Eiif/lena viriilis, a lash-animalcule. A-D, four views illustrating the characteristic movements ; E and //, enlarged views of adult ; F, out- line of anterior end further enlarged ; G, resting stage ; cy, cyst ; .//, liagel- huu ; m, mouth; nu, nucleus; w, gullet; pg, pigment spot; /•, reservoir. After Kent and Klebs. ~~| organism, half animal and half plant, and forming a sort of con- necting link between the Pro- tozoa (or one-celled animals) and the multicellular higher organ- isms. Volvox occurs abundantly in our ponds and gets its name from its manner of revolving in FIG. 209. -- Volvox globator. t]ie water (Fig. 209). Much magnified. Photo. Y, .'••.•••. £ of the living animal. Very different in habitat irom 1 From volvere, to roll. THE PAEAMECIUM AND ITS ALLIES 227 the foregoing are the Sporozoa,1 which are minute rod- like organisms, occurring as parasites in the body of various kinds of higher animals, especially in the food- tract. They increase by transverse division of their rod- like bodies ; but periodically they encyst, and divide into numerous "spores," which, under favorable conditions, are set free in great numbers. \ *': ;/?SiVr.Ar? '' - Jiiii; fv (^?iii^m^m0^^n ~- ^-iSSfS?;0;|Sssk FIG. 210. — Amoeba, the proteus animalcule. Greatly magnified, n, the nucleus; w. v, water vacuoles ; c. ?-', contractile vacuoles; /. v, food vacuoles. E. B. Wilson, "The Cell." Of all Protozoa, probably the simplest is Amoeba.2 This type varies greatly in size, from 0.02 mm. to about 0.3 mm. It appears as a clear, highly refractive body of changing outline. The body does not look homogeneous when viewed with a high power, but contains various granules derived from ingested food, vacuoles of water, and a trans- parent, slightly more dense, spherical or ellipsoidal body, 1 0-7T6/OOS, spore ; fwoj/, animal. 2 aioi3? alteration. 228 ZOOLOGY the nucleus, which it is often difficult to make out on the living animal. The whole substance of the Amoeba is mobile, so that the internal organs have no fixed relation to one another. Quantities of Amoeba can usually be obtained for study by gathering the mud from the edges of stagnant pools, or by scraping the green growth from flower-pots, and letting these gatherings, covered with a little water, stand in a fairly warm place for two or three weeks. Even the Protozoa bear important relations to man. One species, Amoeba coli, has long been known occasion- ally to inhabit the food canal of man, and it is now known that an amcebiform organism (probably one of the Sporo- zoa) is the cause of malarial diseases. Since in one common species 48 hours are required to complete a developmental cycle, the recurrence of the fever every alternate day is explained. It is now demonstrated that at least one of the common agents in infection with malaria is the mosquito, which carries the germs of the malaria parasite from one host to another. Other Sporozoa, of at least one species, are parasitic in the human liver, others attack fish and cause them to die in large numbers; still others cause sickness and death among domesticated animals. The Texas fever among cattle is believed to be caused by an organism l belonging to this group, the inoculation of the cattle being effected by the cattle-tick. The reproductive capacity of Protozoa is so great that their importance in the world, despite their small size, is not astonishing. One of the early students of Protozoa, Ehrenberg, computed that from one individual of Para- mecium aurelia 268,000,000 might be developed in one 1 Called Piroplasma biyauinum. APPENDIX TO CHAPTER XV 229 month by the process of division. Apparently the divi- sion cannot go on indefinitely, but from time to time the Paramecia unite temporarily in pairs and undergo an exchange of some of their nuclear matter. This is doubt- less the beginning of what is known in the higher animals as sexual reproduction. APPENDIX TO CHAPTER XV KEY TO THE FOUR CLASSES OF PROTOZOA a\. Without non-retractile appendages. bi. With retractile pseudopodia .... Rhizopoda (Ex. Amoeba) 62. Without pseudopodia ; covered with an im- perforate cuticula ; parasites . . . Sporozoa «2. With non-retractile appendages. 61. No cilia, but with one or more flagella . . Flagellata (Ex. Euglena) 62. With cilia, or sucking tentacles . . . Infusoria (Ex. Paramecium) KEY TO THE SUBCLASSES AND ORDERS OF INFUSORIA a\. With vibratile cilia and no sucking tentacles . CILIATA b\. Body everywhere closely beset with cilia. GI. No adoral zone Holotricha (Ex. Parameciuiu) C2. Adoral zone present .... Heterotricha (Ex. Stentor) 62. Body only partly ciliated. GI. Cilia limited to ventral side . . . HypotriGha c2. Cilia form a circlet around or at upper edge of animal Peritricha (Ex. Yorticella) a2. With sucking tentacles . . ... SUCTORIA CHAPTER XVI THE SMELT AND ITS ALLIES THE smelt is one of the class of fishes.1 This class com- prises vertebrates that breathe by means of gills and do not use their appendages for walking. The smelts, which belong to the salmon family, are pre- eminently inhabitants of the northern temperate zone, since all but one of the ten genera occur only there. They are small marine fishes, and although a feAv are inhabitants of the deep sea, most live near the shore, and in the spring ascend rivers to spawn. Some of them have become cut off from descending to the sea and live permanently, as tk land-locked " forms, in fresh water. Such " land-locked ' individuals are of smaller size than the marine ones. The food of smelts, like that of other Salmonidee, is chiefly animal, consisting of smaller fishes or insects, small crusta- ceans, and mollusks. Smelt are of considerable economic importance, since they share with other members of the salmon family a delicately flavored flesh. Our Atlantic form, Osmerus 2 mordaxf which ranges from Delaware Bay northward, is caught most abundantly in Maine. The total Atlantic 1 Keys to the principal orders of fishes and the six suborders of the Teleostei will be found at the end of this Chapter, page 252. 2 6o-/>o7p6s, odorous ; the Greek name is the equivalent of the English "smelt." 3 Biting. 230 THE SMELT AND ITS ALLIES 231 smelt fishery is valued at 1125,000. Smelt eggs are arti- ficially hatched and planted in rivers previously unin- habited by them. Smelt are said to return to these rivers after spending the winter in the sea. The early settlers on our Eastern coast, like the Indians before them, used smelt to fertilize the land. At present this wasteful pro- ceeding is illegal ; but the bones and scraps from the canning factories are used to make commercial fertilizers, since they are rich in phosphorus — an important plant food. The family Salmonidae includes some of our most im- portant food fishes. It is distinguished from other fami- lies of Physostomi by the circumstances that both ventral and adipose fins are present, that both premaxilla and maxilla bear teeth l and form the margin of the upper jaw, and that the head is naked, body scaly, belly rounded, and pseudobranchue present. Besides the smelt there are numerous important species. The salmon proper2 are restricted to the north temperate and arctic regions, and live either in the sea, migrating to fresh water to spawn, or exclusively in brooks and lakes. The migrations of salmon from the sea up the rivers are remarkable. Hun- dreds of miles are sometimes journeyed, rapids swum, and falls leaped, for the purpose of laying eggs in some remote lake. The females, with their burden of eggs, have be- come so exhausted at the end of the migration that most, or all of them, die immediately after laying the eggs. On the Atlantic coast the Penobscot River has the most im- portant run of salmon. The Pacific salmon passes up the Sacramento and Columbia rivers, and up many rivers of British Columbia and Alaska. In these rivers the fish 211. 2Fig. 212. 232 ZOOLOGY are caught as they ascend to breed. Such is the greedi- ness and lack of foresight of the canning fisheries on the Columbia River that very few salmon are permitted to pass the nets of the canning factories, and consequently THE SMELT ANT) ITS ALLIES 233 the apparently inexhaustible supply of this fish lias been immensely reduced, and the fishery will soon become destroyed. op FIG. 212. — Salmofario. ct. I, adipose lube of pelvic fin ; an, anus ; c./, caudal fin ; d. /. 1, first dorsal ; d.f. ?, second dorsal or adipose fin : I. /, lateral line ; op, operculum; pct.f, pectoral fin; pv.f, pelvic fin; v.f, ventral fin. After Jardine. The trout, of which there are a number of kinds on both continents, is commercially much less important than the FIG. 213. — Coregonus, the lake whitefish. Much reduced. From Goode. salmon proper. As a result of overfishing, and the pollu- tion of streams by factories and sewage, this fish is dis- appearing from Eastern waters. ZOOLOGY The whitefish (Coregonus1), of which we possess many species, is exclusively an inhabitant of fresh water.2 Its teeth are almost completely absent, or very small ; it feeds almost exclusively upon small arthropods and mollusks. It is of very great commercial importance, its fisheries being valued tit nearly three million dollars a year. Leaving now the Salmonidse, we may briefly consider some of the other more important families of bony fishes. FK;. 21-4. — Morone americana, the white perch. The fish is searching for food along the bottom of the aquarium, an instinct which it shows in nature also. About one-third nat. size. Photo, of living animal by Dr. R. W. Shufeldt, from " Bull. U. S. Fish Com.," 1899. The darters are spiny-rayed fishes of small size, from four to seventeen centimetres long, brightly colored, and with well-developed pectoral fins. They live in clear streams, half concealed under stones, and are most abundant in the Mississippi drainage basin. , the pupil of the eye ; ywvia, angle. 2Fig. 213. THE SMELT AND ITS ALLIES 235 The perches are a widespread family, represented in this country chiefly by the common yellow perch of the East, the u wall-eyed pike ' ' of the Great Lake region, and the white perch of the Atlantic coast (Fig. 214). These fish have an oblong, compressed body covered with small scales ; they are highly rapacious, and are believed to be FIG. 215. — Eupomatis yibbosus, the common sunfish. Two-thirds uat. size. Photo, of living animal by Dr. R. W. Slmfeldt, "Bull. U. 8. Fish Com.," 1899. destructive to the young of other species of fish. They are esteemed as food, although fortunately not to the extent of annihilation. The sunfishes1 have a percoid form, but have only one dorsal rln instead of two. They live in fresh water, have 1 Fio-. 215. 236 ZOOLOGY rapacious habits, are brilliantly colored, and build nests in the sand, which both male and female watch over and defend with courage. Some species living in the Great Lakes are known as black bass or rock bass. The small New England species, with the brilliant red edge to the operculum, is called pumpkin-seed. The toadfishes (Fig. 216) are represented in our faunas by a common species which lives under stones in harbors and attaches its eggs to the under side of stones. It is a vigorous fighter. The sculpin (Fig. 217) is closely related to the toadfish. Like the latter it has a broad head and nearly scaleless body. The pectorals are large, and the two dorsals extend along the greater part of the back. Allied to the foregoing is the rock eel (Fig. 218), which is sometimes brought up in the seine from a depth of 8 to 10 fathoms. FIG. 216. — Batrachus tau, the toadfish. Dorsal view. Two-thirds nat. size. Photo, by W. H. C. P. FIG. 217. — Acanthocottns, the little sculpin. Two-thirds nat. size. Photo. by AV. H. C. P. The silversides are especially abundant along our At- lantic coast. They have an elongated, somewhat com- THE SMELT AND ITS ALLIES 237 pressed body, and a broad, bright silvery band on the sides, against a greenish general body color. The dorsal x. : •" FIG. 218. — Pholis, the rock eel. Right side. Nat. size. Photo, hy W. H. C. P. spines are slender. The fish swim near shore, in dense schools. One species on the Californian coast is known as a "smelt," and is a good food fish. FIG. 219. — Gasterosteus punyitius, the nine-spined stickleback; male (above) and female near the nest in rushes. The female is about to deposit its eggs in the nest. 238 ZOOLOGY The sticklebacks are small, elongated fishes, having an extremely slender tail and a large mouth. The dorsal fin is preceded by two or more large isolated spines. The fishes live in either fresh or brackish water. In some of FIG. 220. — Gasterostea.s bispinvaux, the two-spined stickleback. Above, nest with eggs, and male entering. Below, male depositing its mil on the eggs. Figs. 219 and 220 are reproductions of water-color paintings in the Museum of Comparative Zoology at Harvard College. the species the male builds an elaborate nest from bits of aquatic plants, firmly united by a special mucilaginous secretion. The nest, which is built among the plants of the stream, consists of a short cylinder, through the hori- THE SMELT AND ITS ALLIES 239 zontal cavity of which the fish can lie while it deposits its eggs. The male is polygamous, and guards the single nest, which receives the eggs from various females (Figs. 219, 220). The codfishes, among the most important of food fishes, are characterized by having ventral fins without spines, and articulated fin-rays, well-developed caudal fin, isocercal tail, and barbel on chin. Our common codfish (Fig. 221) . 221. — Gad its morrhua, the codfish. About one-seventh nat. size. After Storer. occurs over the whole of the North Atlantic ; but the most important fishing localities are the banks near New- foundland, especially Grand Bank. The flatfishes are peculiar among fishes in that they have the habit in the adult stage of lying on one side. In consequence the under eye migrates to the upper side, so that both eyes come to lie on the same side of the body. The mouth also tends to become unsymmetrical. The flatfish, consequently, illustrates well the principles of self- adaptation to a peculiar environment. The catfishes are distinguished by the possession of four to eight long barbels around the mouth, and by the 240 ZOOLOGY absence of scales on the body. They are characteristic of South America, but there are a large number of species in the United States, mostly found in the Mississippi valley • ->>.•. X ' * .§ . * ' ;« -* V X x\ X X VV , v\V NV FIG. 222. — One of the flatfishes, seen from the upper side. Two-thirds nat. sixe. Photo, by W. H. C. P. and the Great Lakes, inhabiting deep or sluggish waters, and living in the mud. The common New England FIG. 22-"». — Anicairus iirhtilosiix, the catfish. About one-half nat. size. Photo, of living animal by Dr. R. AV. Shufehlt, " Bull. U. S. Fish Com.," 1899. THE KNELT ANT) ITS ALLIES 241 pecies is Ameiurus1 catus? the bull-head or horn-pout.3 t was with reference to this species that Thoreau wrote hat they are "a bloodthirsty and bullying race of rangers, ahabiting the river-bottoms, with ever a lance at rest and eady to do battle with their nearest neighbor." The tiff, jagged rays of the pectoral fins can make severe vounds. The great catfish of the Mississippi River, vhich may weigh up to 90 kilogrammes, is known as imeiurus lacustris.^ This, as well as most other species •f catfish, is much prized as food. FIG. 224. —The brook sucker. After Goode. The suckers are characteristic North American fish, ibundant in every creek, and consequently known to every over of woods and brooks. Characteristic is the form of ips, which are thick and drawn down at the corners.5 They ire rather sluggish fishes, and feed on small aquatic insects tnd suck up mud. They are not generally esteemed as ood, inasmuch as their flesh is coarse and very full of )ones. In the Mississippi valley, however, they are so ibundant and large that they are of some commercial mportance. not curtailed. 2 Cat. 3 Fig. 223. Living in lakes. 5 Fig. 224. R 242 ZOOLOGY The term "minnow" is applied to two distinct families of small fish. One of these is also known as " killifish." The killifish have a broad head covered with scales, and have well-developed teeth in the month. They occur in schools in shallow water on the shore, and ascend streams to their sonrce. They are carnivorous, and feed at the surface. In one species from the Southern coast, Heterandria l for- mosa,2 the male is only about two centimetres long, and is the smallest known vertebrate. Our commonest species on FIG. 225. — Fumhdus heteroclitus, a killifish or shore minnow. Xat. size. Photo, by W. H. C. P. the shore, or in brackish water, is Fiindiilm 3 heteroclitus 4 (Fig. 225). The minnows of the other family have a nar- row head without scales, and with no teeth in the mouth. They occur exclusively in fresh water, and are known as "shiners." The " goldfish" is related to this group. The pike and pickerel (Esox5) are roughly cylindrical fishes, with large mouth, elongated, depressed jaws, and strong, hooked teeth.6 They are large, voracious, fresh- water fishes, confined, with the exception of a single species, to the United States. The " muskallunge " of the Great s, different ; r)p, avdpos, man, male. 2 Comely. 3 fundus, bottom. 4 erepo/cXtros, irregular or unusual. 5 f