IRLF B 3 371 7SS 'heir Life History 61 Classification E. DONI9THORPE, F.Z.S^&'o. BIOLOGY LIBRARY G BRITISH ANTS, THEIR LIFE-HISTORY AND CLASSIFICATION. BY H. ST. J. K. DONISTHORPE, F.Z.S., ETC. LATE VICE-PRESIDENT OF THE ENTOMOLOGICAL SOCIETY OF LONDON. With 18 Plates and 92 Diagrams. PLYMOUTH : WILLIAM BRENDON AND SON, LIMITED. 1915. DEDICATED AS A TOKEN OF ESTEEM AND FRIENDSHIP TO WILLIAM MOETON WHEELER PH.D., PROFESSOR OF ECONOMIC ENTOMOLOGY HARVARD UNIVERSITY, U.S.A. 334591 PREFACE. THE study of British ants has long been retarded by the want of a comprehensive work. In spite of the great and admitted fascina- tion of the subject very few books have been devoted to it, and of these not one attempts to deal with the whole subject. It is with the object of supplying this long-felt want that the present volume has been written. The Rev. W. Gould, who may justly be called the Father of British Myrmecology, published a little book — " An Account of English Ants " — in 1747. Although this is of great interest — both as a curiosity and also for the really admirable account of some habits of a few British ants — the author only knew five species, and of course a vast amount of information has accumulated since his time. Lord Avebury's well-known work on " Ants, Bees and Wasps " (1882), which includes most of his earlier papers on these insects, is, as regards ants, almost restricted to experiments on behaviour. The Rev. Farren- White's small popular book, " Ants and Their Ways " (1883), which touches on ants in general, gives a number of useful notes on British species, but it is neither very scientific nor accurate. Finally Edward Saunders in his admirable Hymenoptera Aculeata (1896), devoted some twenty-six pages to the British ants. The treatment is almost entirely systematic and naturally after the lapse of so many years requires bringing up to date. This brief list shows how great is the need for a work which will include all that is now known on our ant fauna. Such a work I have endeavoured to write, and as I have been studying the habits of ants for over twenty years, have taken all our British species, and have kept most of them in captivity, I feel in some measure justified in undertaking the task. Scattered throughout and often buried in our literature, are viii BRITISH ANTS. large numbers of notes and papers dealing with ants. It would be astonishing if this were not so, considering the deep and wide interest attached to these insects — morphologically, as well as physiologically, bionomically and psychologically. These notes and papers I have endeavoured as far as possible to collect and make available for the reader. This task has indeed been somewhat of a difficulty, and it would have been easier for me to write and possibly more interesting for the student to read, if a continuous account had been given of the habits, etc., of our species as known to me, instead of a narrative continually interrupted by references and by quotations from the records of other writers. I was at first tempted to adopt the former method, but on reflection it seemed obviously necessary in a scientific work to pay due attention to the historical aspect of the subject. The facts recorded by Continental and American Myrmecologists on British species which also form part of their fauna have been largely drawn upon in the preparation of the present work. The geographical distribution in Britain is in all cases given as fully and as carefully as I have been able to ascertain it from published records or from personal observation. It is to be hoped that our knowledge of this distribution will be greatly extended when further workers are induced to study these most interesting insects. With regard to the references quoted in the synonymy — I have mentioned every name that I have found applied to each species of ant, but have not attempted to quote every reference that has been made to them. It appeared better to restrict the synonymic references to the more important notices ; for, as has already been explained, there is also a vast mass of quotations and references in the text. Some slight conception of the vastness of the general literature on ants may be gathered from a mere perusal of the references, both synonymic and text, that are to be found in the following pages. An almost complete list of this literature, up to 1908, will be found in Wheeler's charming book, " Ants, Their Structure, Development and Behavior " (New York, 1910). In the present work the native genera and species are almost in- variably described from a long series of British specimens — my own captures. To this account the full original description is always added in the language of the describer. PREFACE. ix It has been, of course, impossible to describe the introduced species, or to quote many of the references to them ; for other- wise this book would have become inordinately long. For the same reason I have for the most part contented myself with a list of the myrmecophiles (other insects, etc.) found with each species of ant. At some future date I hope to write a companion volume entirely devoted to the British myrmecophilous fauna. A list — as complete as I have been able to make it — of the literature dealing with British ants is printed at the end of the book. This list also includes papers on myrmecophiles, as from these latter I have largely obtained information on the distribu- tion of their ant-hosts. Other notes on ants contained in papers on Hymenoptera, and Entomology generally, will be found in the references under each species. It may be stated that I have personally verified every reference given in this book. In catalogues, such as Dalla Torre's, etc., dealing with vast accumulations of literature, it is impossible to guard against occasional errors, which are unfortunately copied again and again, and sometimes increased by mistakes in the copying. I can only hope that by much pains I myself have erred as little as possible in this direction. I must thank most of our Entomologists for kindly sending me ants to name, and allowing me to see their captures. I am deeply indebted to Mr. J. H. Durrant, the Rev. F. D. Morice, and Pro- fessor E. B. Poulton for kind encouragement and assistance, Professor E. A. Minchin for dissections of the internal structure, Mr. E. A. Elliott for translations from the Danish and Swedish, and Mrs. Mellor for her kindness in collating and type- writing the Pilot-files, card-indexes, etc., in connection with my extensive myrmecological library. The following account of twenty years of labour and experience has been brought to a conclusion during the opening months of a supreme national crisis — wellnigh within sound of the guns. At such a time it is too much to hope or even to wish that the problems of biological science should receive their due meed of attention. But later on, when the success of which we cannot be doubtful shall have attended our efforts and those of our Allies, when in- tellectual pursuits have resumed their sway, it is hoped that the x BRITISH ANTS. present volume will serve both as an inducement and an aid to the study of the most fascinating of all insects. The figures inserted in the text (except Figs. 45-50) were drawn by the late T. Carreras. Nearly all are from nature ; but a few are copies, and in such cases reference is made to the sources from which they were taken. The drawings for Figs. 45-50, and also the beautiful paintings reproduced on Plate IV, are the work of the accomplished Belgian entomologist and artist, J. Bondroit. The photographs of eggs, larvae, pupae, and perfect insects are from negatives taken by A. W. Dennis from specimens of my own collecting : those representing nests and their surroundings are from negatives taken by myself, except where otherwise stated. HORACE DONISTHORPE. December Slat, 1914. CONTENTS. PREFACE .... CONTENTS LIST OF ILLUSTRATIONS INTRODUCTORY . EXTERNAL STRUCTURE THE HEAD . THE THORAX THE WINGS . THE ABDOMEN THE GENITALIA INTERNAL STRUCTURE THE GLANDS GLANDS IN THE HEAD THORACIC GLANDS ABDOMINAL GLANDS . REPRODUCTIVE ORGANS . THE CIRCULATORY SYSTEM THE RESPIRATORY SYSTEM THE MUSCULAR SYSTEM THE NERVOUS SYSTEM . LIFE HISTORY . PROPAGATION COLONY FOUNDING METAMORPHOSIS PARTHENOGENESIS . LARVAE PUPAE .... POLYMORPHISM PAGE vii-x xi-xii xiii-xv 3-64 3-15 3-6 7-9 9-11 9-13 13-15 17-26 18-22 18-19 19 19-24 22-24 24 25 25 25-26 26-43 26-27 27-29 29-30 30 30-32 32-34 34-43 xii BRITISH ANTS. PAGE PSYCHOLOGY ....... 43-52 How ANTS KNOW EACH OTHER . . . . 47-48 How ANTS COMMUNICATE WITH EACH OTHER . 48-49 How ANTS FIND THEIR WAY .... 49-52 ^GEOGRAPHICAL DISTRIBUTION ..... 52 GEOLOGICAL RECORD . . . . . 52-53 COLLECTING AND OBSERVATION ..... 54-64 MOUNTING AND PRESERVING . . . . . 56-57 OBSERVATION NESTS ...... 57-64 INDIGENOUS GENERA AND SPECIES . . . . 65-334 PONERINAE . .;v . .. >• * . 65-74 PONERA . . . . . . . , . 66-74 MYRMICINAE . . . . . ., \ • . . . 74-178 MYRMECINA . . . ... . . . . 75-81 FORMICOXENUS . . ... . . .. 82-87 ANERGATES . . . . . . > . 87-95 MONOMORIUM . T . ., . . . , . 95-101 SOLENOPSIS . Tv . . . * . . 101-107 MYRMICA ... . . . . . 107-138 STENAMMA . . -. . ,. . . 138-144 LEPTOTHORAX . . . . . .+ , . . 144-169 TETRAMORIUM . 169-178 DOLICHODERINAE . . . . . 178-184 TAPINOMA . . . . ... . . . 178-184 CAMPONOTINAE . . . . . . . 184-334 DONISTHORPEA . . . . . . 184-241 FORMICA . 241-334 COSMOPOLITAN AND INTRODUCED SPECIES . . . 334-350 PONERINAE 335-336 MYRMICINAE 336-342 DOLICHODERINAE ....... 342-343 ^CAMPONOTINAE ....... 343-350 BIBLIOGRAPHY 351-365 SYSTEMATIC INDEX : ANTS AND MYRMECOPHILES . 367-373 LIST OF SUBSCRIBERS 375-379 LIST OF ILLUSTRATIONS. PLATES SEPARATELY PRINTED. PLATE FACING PAGK I. Eggs, larvae, and pupae of Ponera coarctata, Myrmecina gramini- cola, Solenopsis fugax, and Myrmica ruginodis ... 29 II. Eggs, larvae and pupae of Anergates atratulus, Monomorium pharaonis, Leptothorax interruptus, and Tetramorium caespitum 31 III. Eggs, larvae, and pupae of Tapinoma erraticum, Donisthorpea nigra, and Formica rufa ....... 32 IV. Ergatandromorph of Formica mfibarbis, and Gynandromorph of Formica sanguinea ........ 34 V. Male, female, and worker of Ponera coarctata, P. punctatissima, and Myrmecina graminicola . . . . . .78 VI. Male and female of Anergates atratulus, and male, female, and worker of Formicoxenus nitidulus and Monomorium pharaonis . 87 VII. Male, female, and worker of Solenopsis jugax and Myrmica sul- cinodis . . . .... . . . . 106 VIII. Male, female, and worker of Leptothorax interruptus, L. acervorum, and Stenamma westwoodi ....... 144 IX. Male, female, and worker of Tetramorium caespitum and Tapinoma erraticum ......... 178 X. Male, female, and worker of Donisthorpea fuliginosa and D. aliena. 184 XI. Carton nest of Donisthorpea fuliginosa and mounds of D. flava . 193 XII. Nest of Donisthorpea umbrata ..... . . . . 228 XIII. Nests of Formica rufa 250 XIV. Nests of Formica rufa v. alpina and F. pratensis .... 266 XV. Male, female, and worker of Formica pratensis .... 268 XVI. Nests of Formica pratensis and F. exsecta . . ... . 273 XVII. Male, female, and worker of Formica ruftbarbis .... 320 XVIII. Nests of Formica exsecta and F. picea 333 FIGURES PRINTED IN THE TEXT. FIO. 1. 2. 3. 4. 5. Worker of Formica pratensis . Underside of head of Formica pratensis Mandible of Formica pratensis ^ Maxilla of Formica pratensis ^ Labium of Formica pratensis ^ Thorax of Streblognathus aethiopicus <$ PAGE 2 4 5 5 6 7 xiv BRITISH ANTS. PIG. PAGE 7. Thorax of Formica pratensis $ ....... 8 8. Fore-wing of Formica (rufa L.) ..... .10 9. Fore-wing of Ponera (coarctata Latr.) . . . . . .11 10. Fore- wing of Myrmecina (graminicola Latr.) . . . „ .11 11. Fore- wing of Formicoxenus (nitidulus Nyl.) . . . .11 12. Fore- wing of Anergates (atratulus Schenck) . . . . .11 13. Fore-wing of Monomorium (pharaonis L.) . . . . .11 14. Fore- wing of Solenopsis (fugax Latr.) . . . . . .11 15. Fore- wing of Myrmica (ruginodis Nyl.) .... .11 16. Fore- wing of Stenamma (westwoodi West.) . . . .11 17. Fore- wing of Leptothorax (interruptus Schenok) . . . . 11 18. Fore-wing of Tetramorium (caespitum L.) . . . . .11 19. Fore- wing of Tapinoma (erraticum Latr.) . . . . .11 20. Fore- wing of Donisthorpea (aliena Forst.) . . ... . 11 21. Abdomen of Ponera coarctata $ .12 22. Abdomen of Myrmica ruginodis £ . . . . . . .12 23. Abdomen of Tapinoma erraticum $ . . . ... . 12 24. Abdomen of Formica pratensis £ . . . . . .13 25. Abdomen of Formica pratensis <$ . . . * .13 26. (J genitalia of Formica rufibarbis (dorsal) . . . .14 27. c? genitalia of Formica rufibarbis (ventral) . . . .. . 14 28. Stipes, volsella, and sagitta of Formica rufibarbis (dissected out) . 15 29. $ genitalia of Ponera punctatissima . . . . . . .15 30. $ genitalia of Myrmica scabrinodis . . . .- . . . 15 31. Internal structure of Myrmica rubra ^ . . . . .16 32. Gizzard of Formica pratensis $ 17 33. Gizzard of Tapinoma erraticum Q (anterior view) . . . .18 34. Poison apparatus of Formica rufibarbis ty . , . . . . 19 35. Poison apparatus of Bothriomyrmex meridionalis $ . . .20 36. Poison apparatus of Myrmica laevinodis Q ..... 20 37. Repugnatorial glands of Tapinoma erraticum ^ . . . .21 38. Sketch to show position of repugnatorial glands of Tapinoma erra- ticum ^ ........... 22 39. Reproductive organs of Myrmica rubra ? 23 40. Ovaries of pseudogyne of Formica rufa ...... 23 41. Reproductive organs of Myrmica rubra <$ ..... 24 42. Brain, etc., of Donisthorpea fuliginosa $ 25 43. Head of larva of Myrmica scabrinodis 31 44. Hairs on Myrmica larva 32 45. Ergatandromorph of Myrmica scabrinodis 36 46. Ergatandromorph of Formica sanguinea .37 47. Mermithogyne of Donisthorpea flava 38 48. Pseudogyne of Formica sanguinea 39 49. Pseudogyne of Formica rufa var. rufo-pratensis . . . .40 50. Pterergate of Myrmica scabrinodis 41 51. Stand for " Lubbock " nests 58 52. Four-chambered " Janet " plaster nest ...... 59 53. " Santschi " observation nests 61 54. " Crawley-Lubbock " observation nest 61 LIST OF ILLUSTRATIONS. xv FIG FACE 55. " Donisthorpe " observation nest ....... 63 56. Head of Ponera coarctata ? and P. punctatissima $ . . . .67 57. Epinotum and pedicel of Myrmecina graminicola ^ . . . .77 58. Pedicel of Formicoxenus nitidulus ^ ...... 83 59. Head and thorax of Formicoxenus nitidulus $ . . . . .83 60. Monomorium pharaonis ^ ........ 97 61. Antenna of Solenopsis fugax Q . « . . . .102 62. Antenna of Solenopsis fugax £ . . . . ... .102 63. Epinotum, spines, and pedicel of Myrmica laevinodis £ . . . Ill 64. Epinotum, spines, and pedicel of Myrmica ruginodis ^ . . .116 65. Antenna of Myrmica ruginodis Q . . . . .. .116 66. Antenna of Myrmica ruginodis $ . . . . . . 116 67. Antenna of Myrmica sulcinodis ^ . . . • • .« • • 122 68. Antenna of Myrmica scdbrinodis ^ . . . . V . . 126 69. Antenna of Myrmica scabrinodis $ . . . ... . 126 70. Antenna of Myrmica scabrinodis v. sabuleti £ . . . . . 132 71. Antenna of Myrmica scabrinodis v. sabuleti $ . . . . .132 72. Antenna of Myrmica lobicornis ^ . . . . . . • 134 73. Antenna of M yrmica lobicornis $ . . „ ; . . . . 135 74. Head of Stenamma westwoodi £ ...... . • . . 140 75. Stenamma westwoodi ^ . . . . » . . . . 140 76. Pedicel of Leptothorax nylanderi <$ . . . . . . . . . 156 77. Scutellum and epinotum of Leptothorax tuberum $ . . . . . . 163 78. Pedicel of Leptothorax tuberum $ . , . . . . 163 79. Scutellum and epinotum of Leptothorax interruptus $ . . .166 80. Pedicel of Leptothorax interruptus $ 166 81. Head and shoulders of Tetramorium caespitum $ . . . .171 82. Donisthorpea fuliginosa $ with gaster distended with eggs . . .189 83. Donisthorpea nigra $ . . . . . . . .201 84. Scales of Donisthorpea flava £, D. umbrata ^, and D. mixta £ . . 217 85. Donisthorpea umbrata $ . . . -.v « . . . . 224 86. D. mixto-umbrata ^ with patches of algae on body and legs . . 235 87. Scale of Formica rufa $ . . . y 246 88. Head of Formica rufa ^ and F. rufa v. alpina ^ 265 89. Head of Formica exsecta $ . 274 90. Clypeus of Formica sanguinea $ ... • . « • • .281 91. Side view of thorax of Formica rufibarbis ^ . • • • .321 92. Thorax and scale of Formica gagates ^ and Formica picea ^ . . 329 " To him who is satisfied with amassing collections of curious objects, simply for the pleasure of possessing them, such objects can afford, at best, but a childish gratification, faint and fleeting ; while he who extends his view beyond the narrow field of nomenclature, beholds a boundless expanse, the exploring of which is worthy of the philosopher, and of the best talents of a reasonable being." — BURCHELL, "Southern Africa " 1, 505 (1822). " Field study of the Formicidae is certainly becoming much more interest- ing and precise through our increasing knowledge of dulosis and temporary social parasitism, since every ant colony examined no longer represents to the observer merely a meaningless aggregate of individuals, but a definite stage in the life-cycle of a colonial organism. Thus the myrmecologist is prompted to attack a host of fascinating problems suggested by the origin, development and decline, both onto- and phylogenetic, of a living com- munity and the instinctive processes involved in the numerical regulation of its polymorphic components." — WHEELER, "Bull. Amer. Mus. Nat. Hist." 24, 645 (1908). " Myrmecology has been more fortunate than many other branches of entomology in the men who have contributed to its development. These have been actuated, almost without exception, not by a mania for endless multiplication of genera and species, but by a temperate and philosophical interest in the increase of our knowledge." — WHEELER, "Ants," 1910, p. 123. Mandible Clypeus Frontal area Frontal carina Frontal furrow Eye Median ocellus Lateral ocellus Vertex Prothorax Mesothorax Epinotum Scale Gaster Funiculus Scape Metatarsus Tarsus Fig. 1. Worker of Formica pratensis. BRITISH ANTS. INTRODUCTORY. EXTERNAL STRUCTURE. ANTS can be distinguished from all the other members of the order Hymenoptera by the construction of the abdomen, which is divided into two very distinct regions, a slender very movable pedicel of one or two joints (the petiole and post-petiole — the petiole with a scale or node on the upper surface), and a larger posterior portion, the gaster. In certain low forms in the Ponerinae the construction of the abdomen comes nearer to that of some of the Fossores, but such forms, not occurring in Britain, do not concern us here. The con- sistency of the chitinous integument of the body is very variable, being thicker, harder, and more brittle in species of the more primitive groups, Ponerinae and Myrmicinae, and thinner, softer, and more flexible in the more recently developed groups, Dolich- oderinae, Camponotinae, etc. Some species are glabrous, and shining ; others pilose and pubescent, opaque, rugose, punctured, striate, etc. The hairy covering, when present, consists of (1) pilosity, viz. longer hairs, erect or sub-erect; and (2) pubescence, viz. short closely applied hairs which cover parts, or the whole of the body. The Head. The head varies considerably in shape, it may be three-cornered, four-cornered, round, oval, elongate, transverse, etc. The organs attached to it are the mandibles and other parts of the mouth, the eyes and the antennae. The head above terminates anteriorly with the clypeus, an immovable plate varying in shape. The genae, or cheeks, are situ- ated on either side of the clypeus extending between the eyes and the mandibles. Posterior to the clypeus in nearly all cases is a BRITISH ANTS. small space, usually triangular in shape, which is called the frontal area ; and behind this an impressed longitudinal line, the frontal furrow, is often present, which runs back towards the base of the head. The front is the region lying between the frontal carinae (a pair of ridges, situated on the inner side of the insertion of the antennae), and is bounded anteriorly by the clypeus. Posteriorly it passes indefinitely into the vertex of the head and the temples ; the latter lie above and behind the eyes. The occiput is the short region between the vertex of the head and the narrow opening (the foramen) beneath at its junction with the thorax. The ventral surface of the head between the labium and the above-mentioned opening is the gula or throat, it is generally divided by a longitudinal suture. Mandible Maxillary palpus Tongue Maxilla Labial palpus Foramen Fig. 2. Underside of head of Formica pratensis ^. The compound or lateral eyes are situated on either side of the head ; the simple or median eyes, stemmata, or ocelli, when present, are three in number, and are placed triangularly on the front of the head. Both kinds of eyes are most highly developed in the males, and least in the workers, the ocelli being wanting in the latter of some species. The facets of the compound eyes vary greatly in size and number in different species. It has been estimated that the lateral eye in the worker of Ponera punctatissima only consists of one facet ; in the worker of Solenopsis fugax from 6-9, in the female 200, and in the male 400 ; Tapinoma erraticum — worker 100, female 260, male 400 ; Formica pratensis — worker 600, female 830, male 1200. The mandibles are very variable in structure, being sometimes long, narrow and pointed, but often broad and massive, having three borders, an external, an internal, and a terminal, the latter EXTERNAL STRUCTURE. being often more or less strongly toothed. The mandibles can be opened and closed independently of the other parts of the mouth. The maxillae and labium are situated beneath the very small Internal border Fig. 3. Mandible of Formica pratensis Q labrum and keep the mouth completely closed except when the ant is feeding. The maxillae consist of a car do or hinge, a stipes or stem, a lacinia or inner -blade, a galea or outer -blade, and a palpus which may consist of from one to six joints. Galea Maxillary palpus Gustatory papillae Lacinia Stipes Cardo Fig. 4. Maxilla of Formica pratensis ty. The outer-blade is furnished with gustatory papillae, and a row of bristles used in cleaning the legs, etc. The labium consists of a submentum or hind-chin, a mentum or chin, the hypopharynx and paraglossae which are double, the glossa 6 BRITISH ANTS. or tongue, and the labial palpi which may consist of from one to four joints. The tongue is covered with fine transverse ridges ; it can be protruded, and with it the ant rasps and licks up its food, and cleans itself and its companions. The opening of the salivary duct is situated at the base of the tongue. The hypopharynx covers the mentum and paraglossae, and possesses two rows of bristles directed backwards, which are Tongue Hypopharynx Labial palpi Salivary duct Para- Salivary glossa duct Mentum Submentum Fig. 5. Labium of Formica pratensis $. used for firmly holding the food. The roof of the mouth is formed by the labrum, which is bilobed, and is concealed by the clypeus. The antennae, which are elbowed, are inserted on either side of the frontal carinae ; the first joint is the scape, which is usually long, except in the males of a few species, and the remaining joints form the funiculus, which is sometimes clubbed. The number of joints in the antennae of ants varies from four to thirteen — the male usually possessing one more joint than the female or worker. No British ant has less than ten joints to its antennae. Table showing the number of joints to the antennae of the male, female and worker in British genera. Ponera Myrmecina Formicoxenus Anergates Monomorium Solenopsis Myrmica Stenamma Leptothorax Tetramorium Tapinoma Donisthorpea Formica . 12-13 12 12 13 12 12 12 11 11 11 11 — 13 11-12 11-12 12 11 10 13 12 12 13 12 12 12-13 11-12 11-12 10 12 12 13 12 12 13 12 12 13 12 12 EXTERNAL STRUCTURE. The Thorax. The thorax is divided into four segments, the prothorax, meso- thorax, metathorax, and epinotum. The epinotum (which is the metanotum of some earlier writers and the propodeum of others) was the first abdominal segment of the larva, which has been fused to the thorax during pupation. In the primitive form, all the component parts of the thorax of the male ant are distinctly separated by sutures. The prothorax is small and is divided into the pronotum and prosternum ; the former comprises both dorsally and laterally the greater part of the prothorax, while the latter is small and narrow, and to it the coxa of the fore leg is articulated. Scutum of Fore Prae- Tegula mesonotum wing scutellum Hind wing Scutellum Metanotum Epimeron of metathorax Epinotum Episternite of mesothorax Sternite of Episternite of mesothorax metathorax Fig. 6. Thorax of Streblognathus aethiopicus <£. (Emery.) 1, 2, 3, and 4 stigmata of meso- and metathorax, epinotum, and petiole. The mesothorax is large and bears the fore-wings ; its anterior dorsal portion, the scutum of the mesonotum, often spoken of as the mesonotum, bears in many male ants a Y-shaped furrow, called the Mayrian furrow, and on either side is a longitudinal suture, the parapsidal furrow, which separates off the area known as the parapsis. The prae- scutellum ( =paraptera of Emery) of the meso- thorax, is situated at the posterior end of the scutum behind the articulation of the fore -wings. Covering the insertion of the fore- wing a chitinous scale, the tegula, occurs. The scutellum, a large semi-circular plate, is situated between the prae-scutellum and the metanotum. The coxa of the intermediate leg is articulated to the mesosternum ; between this and the pronotum is the episternite of the mesothorax, and above the latter is the epimeron of the mesothorax. The metanotum, the dorsal part of the metathorax, consists of a narrow band between the scutellum and the epinotum, and on either BRITISH ANTS. side between the scutellum and the metanotum lies the post- scutellum, or paraptera of the metathorax. The coxa of the hind- leg is articulated to the metasternum, and the ventral portion of the metathorax is divided into areas as in the mesothorax, viz. the epimeron, the episternite and the sternite. The hind-wing is inserted between the post-scutellum and the epimeron of the metathorax. The epinotum, which is really the first abdominal segment, is bordered by the epimera of the metathorax above, and the sternites of the metathorax below. Three stigmata, or spiracles (orifices of tracheae) occur on either side of the thorax, the first close to the junction between the meso- thorax and pronotum, the second below the insertion of the hind- wing, and the third on the epinotum. Parapsis Tfigula Fore- wing Hind-wins Post-scutellum Pronotum Mayrian furrow Prae-scutellum Scutellum Metanotum Epinotum Petiole Fig. 7. Thorax of Formica pratensis <$. The thorax in the males and females of most ants is generally more simple than in this primitive form on account of the fusion of the epimera and episterna with each other, and also with meso- and inetathorax, and epinotum. The female thorax has the same divisions as the male, but is more robust and the Mayrian furrows are never present. In the workers, being wingless, the meso- and metathorax are greatly reduced, and in the higher and more recent genera, such as Formica, the thorax apparently consists of three segments only, the prono- tum, mesonotum and epinotum, owing to the disappearance of the scutellum, the paraptera and the metanotum. The legs of ants are not very variable and always consist of the same number of joints — the coxa, trochanter, femur, tibia, and a five-jointed tarsus, the first joint of which is always long, especially in the intermediate and posterior legs, and is called the metatarsus. The last joint of the tarsus carries two claws (unguiculi) which EXTERNAL STRUCTURE. 9 are generally simple, but sometimes toothed or pectinate. The apices of the tibiae are often armed with movable spurs (calcaria), which may be simple in the intermediate and posterior pairs, but if present are always large and pectinate in the anterior ones. These latter are called strigils, and are curved and fringed with bristles on their inner side. Bristles also occur on the metatarsus, opposite to those on the strigil, and the ants clean their antennae by drawing them between these bristles. The wings of ants have not been used in classification to the same extent as in other families of the Hymenoptera, chiefly because the workers, which are most often found, are wingless, and the females, which lose their wings after the marriage flight, are more frequently taken in this " deflated " condition ; moreover, the venation of the wings may vary considerably, even in males and females from the same colony. The longitudinal veins of the fore-wings have been named by Emery (1913) as follows :— Costa, subcosta, pterostigma (=stigma Linnaeus), medius, brachius, radius, and cubitus. The transverse veins : transversomedialis , basalis (or discoidalis) , first and second cubitalis, and recurrens (or medialis). The cells : costal, median, submedian, radial, cubital 1, 2, and 3, discoidal 1 and 2. Not all, however, of these cells and veins actually occur in most British genera (cf. the following figures). The Abdomen. The abdomen is highly specialized, and in most ants it is sharply divided into a pedicel and gaster. The pedicel may consist of one joint, the petiole, or two joints, the petiole and post-petiole; it is very mobile and is articulated anteriorly to the epinotum and posteriorly to the gaster. When the pedicel is one-jointed it usually consists dorsally of a more or less high scale of variable shape and thickness. The petiole is morphologically the second abdominal segment, for actually, as we have seen, the epinotum is the first, and conse- quently the first gastric segment is the third abdominal one. When the pedicel is two- jointed it consists of two nodiform segments, and the first gastric segment is therefore the fourth abdominal one. The gaster varies in shape, being round, oval, long, or cordiform, etc., and shows five segments in the worker and female, and six in the male when the pedicel is one-jointed, and four in the worker and female and five in the male, when two-jointed. Morphologic- ally the gaster consists of eight segments when the pedicel is one- jointed and seven when two -jointed ; but the terminal segments are very small and are telescoped into those in front of them. In those ants which possess the power of stridulating, the sound- ^CXJOQ \ lifPi 14^ tf0- § <»"§ '5 S a .•£> oi