Fh dP ad Om », ste ms . rae Feo <& 0%. mctyeayes 25 Preeti noe oe Nal ed or or a eran the oa eae Se hat gees Geet rake 94 Fe PS. Rar geee bo a o5*; anaes Ie oS es ae Se r 4.4545 PuSh es) teres ate os ~ ae 4 + o :o4 “ * « at - oe ‘ Cot eae oe Pe HITS SES mteteS pd oot? +e wee * 24 be: 3 Mee eer re ease pond ae ETS EN tke cer ay "ae rate Le PoP ek me ies “e ‘ heat St te Poet. 4 Ft ne oe et Te PE Ot : oa. * a . +O &, & a ao ? ¢ceT2TOO TOEO oO WPM 0 HM/1Ei (3u01S *S ‘QO ‘Iq pur preqqny °D *f “IN Aq ydvisojoyd ) 'z xX ‘SNUDILIIUD SNJoUoGluDD JO pooiq PU S1oyIOM AOU pue tofelU ‘soy “o[BWIy GOLGMBUARUINIV ER SLE MO BUOEOGICALE SL RALS.- IX ANTS THeELR stTRUGIURE, DEVELOEMENT AND BEHAVIOR BY WILLIAM MORTON WHEELER, Pu.D. PROFESSOR OF ECONOMIC ENTOMOLOGY, HARVARD UNIVERSITY; HONORARY CURATOR OF SOCIAL INSECTS, AMERICAN MUSEUM OF NATURAL HISTORY “Odws 6€ mepi Tos Bliovs TOANA ay Hewpnbein plpnuwata TOY dd\Awy (Swv THS avOpwrivys Cwhs, kai uGddov eri THY €EaTTOVWY 7 perCovwy tor Tis Gv THY THS diavolas axpiPeav. —ARISTOTLE Wew York THE COLUMBIA WNIVERSITY PRESS Ig1O All rights reserved Pe : came f THE COLUMBIA Une TY PRESS "% é oe o> "*y a “be PRESS OF « THE NEW ERA PRINTING COMPANY LANCASTER, PA ad “ TO MY WIFE DORA BAY EMERSON “mn L he Subject indeed is small, but not inglorious, The Ant, as the Pr.nce of Wisdom is pleased to inform us, is exceeding wise. In this Light it may, without Vanity, boast of its being related to you, and therefore by right of Kindred merits your Protection.”’ z —Wit.iam GouLp, ‘‘ An Account of English Ants,” 1747. iat PREERACE: This volume had its inception in a series of eight lectures delivered at Columbia University during the spring of 1905, and represents, in a much condensed form, the results of a decade of uninterrupted study of the Formicide, and of the works that have been written on these insects. If an excuse were required for its publication, one might be found in the fact that for many years no comprehensive treatise on the ants has appeared in the English language. This may be regarded as a reproach to English and American zoologists, since during all this time almost the only active contributors to myrmecology were to be found on the European continent. It must be admitted, however, that the methods of publication adopted by continental writers have not been such as to attract the attention of English-speaking students, since their works have not only been issued in a variety of languages—French, German, Swedish, Italian, Russian, etc.—but also in a great number -of often very obscure, local or inaccessible journals and proceedings of learned societies. Moreover, most of the continental observers within recent years have been too busy with special lines of investi- gation to publish compendia on myrmecology. It thus happens that although ants are our most abundant and most conspicuously active insects, they have not, till very recently, received any serious attention from American systematists, and the descriptions of most of our species must still be sought in a lot of more or less fragmentary foreign contributions. My work began in an endeavor to increase our systematic knowl- edge of the North American ants, but I was fascinated by the activities of these insects and soon saw the advantage of studying their taxonomy and ethology conjointly. This method, which was, indeed, unavoid- able, has greatly retarded the appearance of the present work, for it was impossible to write about the behavior of many of our most inter- esting forms till their taxonomic status had been definitely settled. On the other hand, I could find no satisfaction in devoting all my energies to collecting and labelling specimens without stopping to observe the many surprising ethological facts that were at the same time thrusting themselves upon my attention. My observations have now covered so much of our fauna that I shall soon be able to publish a systematic vii Viil PREFACE. monograph, which will, | hope, enable the student to form a rapid acquaintance with our ants, without recourse to the scattered and often very meager descriptions that have hitherto served as the taxonomy of the North American species. I frankly admit that in writing the following pages I have endeav- ored to appeal to several classes of readers—to the general reader, who is always more or less interested in ants; to the zodlogist, who cannot afford to ignore their polymorphism or their symbiotic and parasitic relationships; to the entomologist, who should study the ants if only for the purpose of modifying his views on the limits of genera and species, and to the comparative psychologist, who is sure to find in them the most intricate instincts and the closest approach to intelligence among invertebrate animals. Of course, the desire to interest so many must result in a work containing much that will be dull or incompre- hensible to any one class of readers; thus the technical terms and descriptions, which are full of significance to the entomologist, are merely so much dead verbiage to the general reader, and the laboratory zoologist, who shrinks at the mention of psychological matters, will care little about ant behavior beyond its physiological implications. With the exception of the appendices and the first chapter, which serves as an introduction, my account of the ants falls naturally. into two parts: a first, which is largely morphological, and comprises Chap- ters II to X; and a second, devoted to ethological considerations and embracing the remaining chapters. Tosome it may seem that too much space has been devoted to the relations of ants to other organisms and to other ants (Chapters XVI-XXVIJ1), but I justify my procedure on the ground that this subject is the one in which I have been most inter- ested, the one in which most advancement has been made within recent ‘ years, and the one that has been fraught with the greatest differences of interpretation. The series of appendices has been added largely as an aid to the beginner in the study of myrmecology. The tables for the identifica- tion of our North American ants are very incomplete, but could not have been extended to embrace the species, subspecies and varieties, and the different castes, as well as the genera, without unduly increas- ing the size of the book. I hope to make good this defect in the mono- graph to which I have alluded. In the meantime, I shall be glad to identify ants for anyone who is interested in their study, especially if the specimens are collected in America north of Mexico. The identi- fication of such material serves a double purpose: that of increasing our knowledge of the geographical distribution of our species, and of spreading throughout the country collections of correctly identified PREFACE ix specimens. The dearth of such collections, both of ants and of all other groups of insects, excepting, perhaps, the Coleoptera and Lepi- doptera, has not ceased to be a great drawback to the study of ento- mology in America. The bibliography (Appendix FE), which has been carried down to the close of the year 1908, is unfortunately very voluminous and includes many titles of unimportant works. Like all such compilations, it is necessarily incomplete, and undoubtedly contains positive errors. | A serious attempt has been made, however, to reduce these to a minimuiri, and I shall be glad to receive any additions or corrections. For portions of the text and many of the figures I have drawn rather freely on my previously published papers. A few entire chap- ters, in fact, such as those on polymorphism, have been reproduced with only slight verbal alterations. Others, like Chapters XVIII and XX, are abridgments of longer accounts of the fungus-growing and honey ants recently published in the Bulletin of the American Museum of Natural History. I am under lasting obligations to Professor H. C. Bumpus for the interest he has shown in the progress of my work, and the aid which I received in its prosecution while [ was Curator of Invertebrate Zoology in the American Museum of Natural History. To Mr. Roy W. Miner, Assistant Curator of Invertebrate Zoology in that institu- tion, I am deeply indebted for much assistance in making out the table ~ of contents, and especially in arranging and verifying the bibliography. Many of the illustrations have been made by Miss Ruth Bb. Howe. My friend, Professor Oliver S. Strong, of Columbia University, has most generously permitted me to use a number of the remarkable photographs which he and Mr. J. G. Hubbard took of living colonies of various ants in the possession of Miss Adele M. Fielde. Three of my former pupils, Messrs. A. L. Melander, C. T. Brues and-C. G. Hartman, have also contributed several interesting figures, and Mr. Brues has aided me in reading the proof. Bussey INSTITUTION, Forest Hitis, Boston, MASss., October 30, 1909. TABLE, OF CONTENTS. CHAP TE Rese ANTS AS DoMINANT INSECTS. PAGE 1 The Seeial Insects; and Their Intesest-for Man.. sci)... .: « I {I. The Dominance of Ants, as shown by— 1. Unusual Variability. 2. Wide Distribution. 3. Numerical Ascendancy. 4. Longevity. 5. Abandonment of Detrimental Specialization. 6. Versatility of Their Relations with Plants ande@thervAiirmials 4.0 (3.0 «i428 Sane ee ete eee En a 2 Ii) Probable Cause. of the Dominangespt Asits. 7 20.422. : 3 EY: Correlativelndications:ot. Vhis» Dominance: -. ee) 42. V2 Companson of Etumanyand Ant Societies: .5.5+ os eee ee. 5 1. Striking Character of the Resemblances and Their Signifi- cance. 2. Parallelism in Development. 3. Differences in Organization. VI. Analogy between the Ant Colony and the Cellular Organism = 7 plies comomics Importance, of Ants...) o 2024/04. cine ee ee te 8 , I. Their Beneficial Activities. 2. Their Noxious Habits. Wii Antseass@bfectsroer biolocical Study. <2 02 .¢ waseeeme snes « II CHAPTER: ft. THE EXTERNAL STRUCTURE OF ANTS. iy Generale Mistineuishine Characters, ©. secs anemic ce 13 Lee Scomentation. of the: Body. ones seep eee ee ee 14 TSI evn ee OMA EMIG! =o, 26 1. The Various Subfamilies Compared. 2. The Visible Seg- ments. 3. The Terminal Segments of Female and Worker. 4. The Terminal Segments of the Male. CHAPTER iT; THE INTERNAL STRUCTURE OF ANTS. athe Alimentary Uracthwec. 2 ue cis pa ceo eee eee ee 31 ~The Glandular Systema se hoe ae Oe ee ee 37 . The Reproductive Organs, Poison Apparatus and Repug- natorial ‘Oreansyarts neste os 1m te ek pecans See aere 39 . The Circulatory System, Fat-body, CEnocytes, etc........ 40 fy The ‘Respiratorye systema nroo ork cee ce eae 49 . The MiecularlSysteniaenwaat sae steaks ee ae 49 GEA PT ER: sive THE INTERNAL STRUCTURE OF ANTS (CONCLUDED). The Nervousgssystemin: Generals) sriesr pace seep toe 51 Quest ainiot man cae eee Pee OnE HE FIA Rc ty cee Te Raa, 52 1. Its Segmentation. 2. Its Finer Structure and the Signifi- cance of the Pedunculate Bodies. 2 ThesVentral Nerre=condat <2. stews seen ns ie ee ee ee 57 The Sympathetic Nervous=Systemene oar... ee eee 58 Ehe Sense=or pans oon aioe euler cies ee erate taeee sneer 59 1. Tactile Sensilla. 2. Olfactory and Gustatory Sensille. 3. Chordotonal Organs. 4. The Johnstonian Organ. 5. The Campaniform Sensillz. 6. The Lateral Eyes. 7. The Median Eyes, Stemmata, or Ocelli. CHAPTER Vi THE DEVELOPMENT OF ANTS. Behavior of Ants toward Their Young Contrasted with ‘That-of ‘Other Hymenoptera ete ee ee ae ae 67 The Nursing ofthe, Broocteie 7s 2 pacct ome mege habe ate 69 TABLE OF CONTENTS: xiii PAGE Tbs ADE Brats 3 eG oo Occ 6 Se oO a 70 1. Description. 2. Fertilization and Its Relation to Sex. 3. Development. IN lnc HEY: i ee anh Bio Fy ts ta ee aan 72 1. Description. 2. Feeding. 3. Internal Structure. RR ALIOM: cin). 455 ai 5 <2 s.4 oie aogier eRe RC ote aes See ec Sos 76 wale Coloration -of the -Callows' 2 /....24 eee eee ek ce 79 Wale siceneth of Developmental Periods sae ee a te 80 ralble eongevity of Adult Ants: 4%. x2 0 1y.cq eee eeetee a tere tac ews 81 EX. Resistance of Ants to: Noxious Influences=. 222-4 2... . 83 CHAPTER Vie POLYMORPHISM. fea Dehinition of the: Teri 25.02 somes oe os ae ee 86 I]. Extent and Character of Polymorphism among Insects.... 87 III. The Phylogenetic Origin and Development of Polymor- : plisnnen Eijyimenopteraa...).ciccacs. eae eee ee go 1. The Views of Various Authors. 2. Phylogeny of the Phases Known among Ants. IV. The Development of the Worker the Real Problem of Poly- HMOs iia CITI ATES. ips cmois Sites: cee eee ae ee ae gr 1. Weismann’s Theory of Predetermining Units. 2. Spencer’s Theory of Trophic Epigenesis. 3. Emery’s Theory of Pre- disposition. Neasbie. hee oAsnects ofthe Problem) se aaa epee te 102 1. The Physiological and Ontogenic. 2. The Ethological and Phylogenetic. 3. The Psychological. VI. The Physiological and Ontogenic Method of Explaining the Development or thet Worker sos aes ee te 103 wv 1. The Advantage of the Physiological over the Embryological Method. 2. The Two General Objections to the Physiolog- ical Explanation. 3. Inferences which tend to show that Qualitative Feeding is not Responsible for the Worker Type. 4. The Relation of Underfeeding to the Ontogeny of the Worker and Related Types. 5. Conclusion. X1V TABLE OF CONTENTS. PAGE CHAPTERS Sauer POLYMORPHISM (CONCLUDED). VII. The Ethological and Phylogenetic Method of Explaining the evelopment of the Workers eae e...cht.! 110 1. The Probable Solitary Wasp-like Origin of the Social "Habits of Ants. 2. The Origin of Division of Labor and Its Influence on Somatic Characters. 3. Application of the Biogenetic Law to the Sociogeny of Ants. 4. Correspond- ence in Rate of Development between Polymorphism and Social Organization. 5. The Nine Phylogenetic Stages in the Development of Stature. 6. Adaptive Character of These Stature Differences. 7. Objections to Weismann’s Theory of Non-inheritance of Acquired Characters as Applied to Ants. 8. The Four Stages Recognized by Plate in the Phylogeny of Ants. 9. Plate’s View Compared with Spencer’s and with That of the Author. VITL The Psychological View of the Problent = 5.- - 2 ues. 12 1. The Three Castes. 2. The Variability of Ants. Vite. the Anatomical Basis of Classticationyg. stcse-:-:. 2.7. . 131 exe @nadtinomial Nomenclature ix sje iets + -s0 aes «= -: 131 x Conspectus of the GlaSsifcationsoimamtsw s,s 52's. << 134 CHAPTER be Tue DIstrRiBuTION OF ANTS. ie@Ntodes of: Dissemination i... .3 5 ct ee She sere oe 145 II. Two Methods of Studying Ant-distribution .............. 146 me Che Paumistic Distributionof-Ants 20% 4 eee cee ae 147 1. Geological Parallelism in the .Origin and Distribution of Ants and Mammals. 2. History and Distribution of the Principal Groups. 3. The North American Ant-fauna. (a) The Preglacial Fauna. (b) The Four Postglacial Waves of Northward Migration. (c) The Four Centers of Redis- tribution. (d) Adventitious Tropical and Subtropical Forms. (e) Ants Imported by Commerce. (f) Conclusions. iy the Ethelogical Distribution og Ants”. 5. .255.~-eeen- 156 CHAPTER IX: Fosstt ANTS. f. Paleontological History of the Hymenoptera-aee. . 3.20 - 160 iieithe: lettiary Ants isl. oe clots 1 ae os ee et eee are 161 1. Relations of the Extinct to the Living Genera. 2. Localities Yielding Tertiary Ant Fossils. 3. Comparison of Lacustrine with Amber Ants. 4. Inadequacy of Past Researches on the Oeningen and Radoboj Ants. 5. Numerical Proportion of Known Fossil Ant Specimens to Those of Other Hymen- optera. 6. Relative Proportion of Fossil Ants in the Various Subfamilies and Conclusions Based Thereon. 7. The Known Genera of Amber Ants. 8. Causes of the Intermingling of Arctic and Tropical Forms. 9. Remarks on Interesting Genera and Species. 10. The Tertiary Ants of North America. xvi TABLE OF CONTENTS. PAGE [ii ities @itaternary, or Pleistocenem@uitearers as: .. vss. 173 IV. Similarity of Baltic Amber Ants to Living Baltic Species.. 174 V. Absence of Polymorphism among the Workers of Tertiary /:\\0) ine eS Sar SS Oe eee 174 CHAPBE R= oak Tue Hasits OF ANTS IN GENERAL. ies The Three-fold Activities of Ants in General) Sar e 176 II. Nutritive Activities of Ants——Six General Sources of Ants’ POOG S212. 2p ete ae ee Se Or etre Atala tide at. renee 177 Pil ProtéectivesElabits.OfeAmts . selee se ers eter e eee 178 I. Care of the Young. 2. Care of One Another. 3. Care of the Nest. 4. Methods of Defence and Attack. 5. Means of Preventing Mixture of Alien Colonies. LV. Reproduction amone- Ants’ .e.3 ose Re ee ae 182 1. Terrestrial Mating. 2. The Nuptial Flight. 3. The Found- ing of the New Colony. 4. Social Parasitism. 5. The Num- ber of Individuals in a Colony. GHAAPTER XII. AnT-NESTS. Ll. ‘Genemalearchitectural Characteristics sin. 2 cass. atk dente 192 Thy piethioderotConstrtictionn.:.5 aks otek eee 194 LL G@hianig esot oA bod Creer opcia shies tes cna ao eee 195 IV... Classification sof Amt=nestsiovn, 2c. at nt ete eee 198 V2. INests anthte* Sotl (> eat acte ne epee eee re 199 1. Small Crater Nests. 2. Large Crater Nests. 3. Mound, or Dome and Masonry Nests. 4. Nests under Stones, Boards, 2CCE CHAPTER XGua: ANT-NESTS (CONCLUDED). Wi. Nests in thesGavitiesobelblantsaeee eer a eee 207 1. In Preformed Cavities. 2. In Woody Plant-tissues (a) Carpenter Ants; (b) Gall Ants. VIL. Wale IX. TABLE OF CONTENTS. Xvi PAGE SUSMEMMC MMV ESES vic 2.5... ee ayiey ee ee ns So's es we Ze 1. Earthen Nests. 2. Carton Nests. 3. Silken Nests (a) Description; (b) Manufacture. INestamine Unitsial: Sittations=aeeeeierettiiee a oiehe sc oe ees 221 INGCESSOL Var SUTUCULITES: ya.o er tee EN Sr fale care.) 222 1. Paths, Clearings, and Covered Runways. 2. Succursal Nests. 3. Tents, or Pavilions. CHAPTER. THE PONERINE ANTS. Necessity of the Elistorical’ Method ot Study, 2.2... «22. 225 “General Significance of the, Ponerinz: asia, Group" .-..:,..'. ..!- 226 . The Genus Myrmecia as the Prototype of all Ants ....... 227) writhie Castes Ofte) Rome tints: ett os wie aseicpa lek pees ns cuca Rano 230 caNestine and i cedingeblabitsiest. cee Sor enaa ae aes er 232 Ther three Dypes-ot.-onerine Larvces eee ee itary 223 Observations on the Methods of Feeding the Larve ...... 234 CEI) GOV Neral BAO LOFe | Urea aig eye ue eects boli Beso at 237 > Dhesblatchingso ttherC allow s\ mr. sate oc -ta'e elaterereayepe 238 -Deportation and) Hunting Gabits “5.276. .- =e ye 240 . Usurpation of Queen Function by Gynecoid Workers .... 242 penylogeny,.of the Group: <) sty: c- r. ieaiers io alienioge © ca 243 CHAP TE Re XV Tue DriveR AND LEGIONARY ANTS. Seer Dory lincasia. Group... pase eee eee eae 2 au)7.. 240 AWescripiionvot tie Castesi yk i..: emeritus telat rt sera ek= 1) 248 eDithcultiesy ot. Nomenclatunec, swe eaters oie so eine cso 248 Eel Bl olers( Cxesan else Be) A) Roepam Mee ctaih cir on eee, or coon Aran ee ee ee 249 Re MMCRG CHATS 8A! I CLUS | rors auedeees mene getale o ee tactile of ot sy, Hs 2 25: . The Genera Eciton and Chehomyrmex .......,---+2-.+0++ 255 Melee rOplems-OF the MOLT ylimesun) semen meet kote yon oct ie ch 265 1. Domestic Economy. 2. Dichthadiigynes. XVIli TABLE OF CONTENTS. CHAPTERS THE HARVESTING ANTS. I. The Origin and Development of the Harvesting Habit .... Moat AO DSErVAtIONS. . .. ..-d .aste ee eee aetmers toot III. Observations of European Harvesters by Moggridge, Forel. Andre, Emery and? Otmersus ere tee re ee IV. The North African Harvester Oryopomyrmex santschii. . V. The Asiatic Harvesters Pheidole, Holcomyrme.x and Phei- DOlOGELOW 6 iia yee eee eee ee ee VI. The Australian Harvesters Pheidole longiceps and Mera- WO PLWS SF anieas Seana ame Sonata ae eaters athe eee VII. The American Harvesters (Solenopsidii and Myrmicii)... 1. Solenopsis gemunata, the “ fire ant.” 2. The Genus Pheidole. 3. The Genus Messor. 4. Ischnomyrmex cockerelli and albisetosus. 4. The Genus Pogonomyrmex. (a) Char- acterization, Range, and Classification. (b) Pogonomyrmex imbericulus, etc. (c) The Florida Harvester, etc. (d) The Texan Harvester and the “Ant-rice” Theory. (e) The Marriage Flight of the Texan Harvester. (f) The Founding of Colonies by P. molefaciens. (g) The Occident Harvester. (h) The Stinging Habits of Pogonomyrme.x. CHAPTER Savin THE RELATIONS OF ANTS TO VASCULAR PLANTS. I. The Hypothesis of Mutualism between Ants and Plants . II. Plant Adaptations Apparently Indicating Symbiosis ...... I. Dwelling-places for Ants. (a) Cavities in Stems. (0) Tubers, Bulbs, Pseudobulbs, Rootstocks, ete. (c) Ascidiz or Burse of Leaves and Petioles. (d) Spaces between or under Leaves. (e) Thorns. (f) Seed-pods. (g) Galls. 2. Food-supplies for Ants. (a) Floral Nectaries. (b) Extrafloral Nectaries. (c) Food-bodies. (d) Bead-glands (“Perldrtisen”). (e) Pith and Other Vegetable Tissues. Il: ‘The. Ants" Dwelling oa Plants eas tac eee ee rota 1. The Arboreal Genera. 2. The Habits and Structural Adaptations of Azteca and Pseudomyrma, and their Rela- tions to the Problem. 3. The Relations of Asteca muelleri to Cecropia adenopus. 4. The Relations of Ants to Myrme- codia, Hydnophytum and Myrmephytum. 5. The Relations . 294 295 302 TABLE OF CONTENTS. of Pseudomyrma bicolor to Acacia spherocephala. 6. Other Acacias Inhabited by Ants. 7. Other Examples Found in South America. iheereOthwer Relations of Ants to PlantSmepierim otis cnr ccs 1. Ants as Seed Distributors. 2. Ant-Gardens. 3. Plants P Injurious to Ants. CHAPTER Javier THE FuNGUS-GROWING ANTS. I. The Symbiotic Relation between the Fungus-growing Ants andr (Ehret Hung! \\ 5.5 cn) sacra ee eee att ecors, Per oe ME Characteristics of the “iribe Atti 2 1 eer act ie neview or the literature, : Gata hee ec iyesBelts Observations.on Atta cephalotes 2 .s. 5-2 eeu Neaoclleris Observations 2.608 ose ges aire eee ees ene 1. The Genus Acromyrmex. 2. The Systematic Position of the Fungus. 3. The Genus Apfterostigma. 4. The Genus Cyphomyrmex. VI. The Source and Nourishment of the Fungus in the Colony. (Observations of Sampaio, von Ihering, Goeldi and RUIDS Iya ete Se ae, here oe peas 3a) 5 Oak corta aga enae oe Vil. The Fungus-growing Ants of the United States......... (a) Personal Observations on—1. Cyphomyrmex. 2. Myceto- soritis. 3. Trachymyrmex. 4. Mellerius. 5. Atta s. str. (b) General Considerations. 1. Advance in the Fungus- growing Habit. 2. Condition of our Knowledge as to the Origin of the Habit. CHAPTER: Xie xix PAGE 315 318 319 320 321 324 329 333 THe RELATIONS OF ANTS TO PLANT-LICE, SCALE-INSECTS, TREE- HOPPERS AND CATERPILLARS. I. The Liquid- -excreting Insects Attended by es Bev ore ieee’ ile Relations.ot Ants .with Aphidsiemy.t.o407 cca ae asta 1. Habits of Aphids. 2. Behavior of Aphidicolous Ants. 3. The Abdominal Siphons of Aphids. XX TABLE OF ‘CONDENTS. Paci LL }ketemenstot Ants with CoccidSviimee aes nt.oo es Sones... 347 IV. Relations of Ants with Jumping Plant-lice ..........2... 349 Vpxelanons:of Ants with Treé=hoppemgemnoo a. os ee: 350 VI. Evidences for ‘‘ Mutualism” in the Relations of Ants with Elomoptera in: General 202 eae ee ee eee me 351 1. Adaptations of Aphids. 2. Adaptations of Ants. WaiieetChe Fulgoridi,. €te.es -2! S20. ee a ee eee 350 ViIT Relations of Ants with Lycznid, Caterpillars = ee 357 Ix.“ Trophobiosiss’ > isang. 622-2 ce et es eee 300 GHAR TERS OX. Honey ANTS. I. Desenption of the) Eloney-storine Habit)... 361 i... The Species of: Honey 2Atts: 5 552i eae aaa ee ee 363 1. Melophorus bagoti and cowlei. 2. Leptomyrmex rufipes. 3. Plagiolepis trimeni. 4. Camponotus inflatus. 5. Myrime- cocystus melliger, mexicanus and horti-deorum. (a) Early Observations. (b) McCook’s Observations on M. horti- deorum. (c) Forel’s Observations. (d) Personal Obser- vations. 6. Cremastogaster inflata and difformis. PLT. hes Catises. of Reépletiogon sat sot ee ee a ee 374 IV. Relations of Nest Structure and Situation to the Develop- ment ‘of Wepletes: 2s. se. ae. ee 375 V. Adaptations of Diet in Ants Living in Desert Regions.... 376 CHAR DER. Xoab PERSECUTED AND TOLERATED GUESTS. I) Extranidal and: Intranidal’ Symbiosis 40.0... joe eee ee 378 Il. Myrimecophiles in (Genetals ia5 Jen ce 5S ee eee ee 379 1. History of Investigations. 2. Number and Diversity. 3. Causes of the Myrmecophilous Habit. 4. Ethological Classi- fication. 5. Progressive Adaptation in the Four Groups. IIT. The>Synechithrans 27 pec gees <1 eee weer eee 382 IV. The SynceketeS nities cee toe ree ee a ee eee 383 1. Neutral Synceketes. 2. Mimetic, Loricate, and Symphyloid Syneeketes. 3. The Myrmecocleptics. 4. The Strigilators. Pew Tif. VII. i, TABLE OF CONDENTES. CHAPTER eer TrRuE GuEstTs, Ecro- AND ENTOPARASITES. . General Characteristics of the Relations of the True Guests and. earasites. £0. the Adiusuye memebers cece re occ. s cera) a The Symphiles—Structural Adaptations, 25.2... s+. 1. Symphilic Coloration. 2. Trichomes. 3. Mouth-parts. 4. ~ Antenne. fey pical woymnphiles: .. 5.1... sates eeeepeen ae wy be ati otro Sp = 1. The Pausside. 2. The Gnostide, Ectrephide, and Cossy- phodide. 3. The Clavigeride and Pselaphide. 4. The Lomechusine. (a) Summary of Life History. (b) Pseudogynes. 5. Critique of Wasmann’s Theories of ‘“ Amical Selection” and ‘* Special Symphylic Instincts.” Pop CEOPALASILES)y —2'S)., aye ik See hey cto CPR aR ae aed ree ee ore 1. The Phorid Metopina. 2. The Gamasid Antennophorus, etc. 3. The Sarcoptid Tyroglyphus. 4. The Thorictide. 5. The Chalcidide. REPILOPATABILCS Efe es sce icc tote Ses cia net eee a 1. Coleoptera. 2. Diptera. 3. Hymenoptera. 4. Nematodes. . Comparison of Modifications of Hosts Induced by the Three @lassesv of sParasites, oer. es eh he cma athe orc eee Miemecopnags ands Ny ri ecOld Sgr c1cuneye se ee ee ee CHAPTER XO: THE CoMPOUND NESTS. EP Sy efcie DGSh 1010) (0,) eee Reena Ae En Se Bien Par 1. Definition. 2. Classification. (a) Compound Nests. (b) Mixed Colonies. Types of Social Symbiosis in Compound Nests .......... 1. Plesiobiosis. 2. Parabiosis. 3. Cleptobiosis. 4. Lesto- biosis. (a) Pheidole calens. (b) Solenopsis fugax. (c) Diplomorium longipenne. (d) Carebara vidua, etc. (ce) Other Lestobiotic Ants. 5. Phylacobiosis. 6. Xenobiosis. (a) Formicoxenus nitidulus. (b) Formicoxenus ravouxt and corsicus. (c) Xenomyrmex — stolli. (d) Phacota sicheli and noualhiert. (e) Myrmoxenus gordiagin._ (f) XX] PAGE 398 398 A412 419 423 424 XXil TABLE OF CONTENTS. PAGE Sifolinia laure. (g) Myrmica myrmoxena. (h) Symmyr- mica chamberlini. (i) Lepthorax emersoni. (j) Lepto- thorax glacialis. , CHAPTER SExly. THE TEMPORARY SOCIAL PARASITES. ieeAnt Parasitism in dGemekal mais oct since bee ae ee 437 1. History of the Subject. 2. Establishment of the Normal Colony. 3. Redundant and Defective Types of Colony Formation. 4. Three Forms of Effecting Adoption of Queens in Alien Colonies, and Their Phylogeny. Il. Definition and Extent of Temporary Social Parasitism ... 440 III. The Known and Hypothetical Cases of Temporary Social PAF ASTESIN ered ce hott eeingy EA eae cae ee 441 1. Microgynous Formice of the rufa Group. 2. Macrogynous Fornuce of the rufa Group. 3. The Formice of the exsecta Group. 4. Bothriomyrmex. 5. Aphenogaster. 6. Oxygyne. EV... AGeneral ‘Gonclusionsoye- ni cones the Soe eee oe ee 449 CHAPFERAXCXV:. THE SANGUINARY ANTS, OR FACULTATIVE SLAVE-MAKERS. I. Definition and General Description of the Dulotic Instincts 452 IT. Distribution and Species of Slave-making Ants .......... 454 Hits The: facultative ‘Slavesmakers. 2. 5.5 soc ce eee ook 454 1. The European sanguinea. (a) Description of the Species. (b) Ratio of Slave-holding to Slaveless Colonies of san- guinea. (c) The Tactics of the Foray. (d) The Purpose of the Foray. (e) Comparison with the Rapacious Dorylines. 2. The American sanguinea. (a) The Variety. of North American Forms. (b) Comparison with the European Type. (c) Personal Observations of sanguinea Forays. 3. The Founding of the sanguinea Colony. (a) Experi- ments and Conclusions. (b) Comparison with the Colonies of Temporary Parasites. (c) Solution of the Problem of the Dulotic Instincts. TABLE OF CONPENTS. XXill CHAPTER: 2eav i. THE AMAZONS, OR OBLIGATORY SLAVE-MAKERS. PAGE PUT TOUIELORY . ....... «2c, Gey eee store cea e ase 471 Il. The European Amazons (Polyergus rufescens) ......... 471 1. Description and General Habits. 2. Expeditions. 3. In- fluence of Dulotic Relation on Behavior of Slaves of Polyergus rufescens. Pipetite. American Amazons :<. 2 See ees ok ee ee 474 1. Polyergus breviceps. 2. Polyergus bicolor. 3. Polyergus lucidus. iV. The Founding, oi Amazon Coloniesa- 4. .4.see: Me a baer 486 CHAPTER XXVIL- THE DEGENERATE SLAVE-MAKERS AND PERMANENT SOCIAL PARASITES. I. Introduction—Comparison with Preceding Types—Classi- fication and Definition (a) The Genus Strongylognathus. 1. Strongylognathus huberi. 2. Strongylognathus afer. 3. Strongylognathus christophi. 4. Strongylognathus rehbindent. 5. Strongylognathus cecilia. 6. Strongylognathus testaceus. (b) The Genus Harpagoxenus. 1. Harpagoxenus sublevis. 2. Harpagoxenus americanus. Ei sbhesbermanent-Social Parasites 21. ee eee sees 495 1. Wheeleriella santschii. 2. Epixenus andrei and creticus. 3. Sympheidole elecebra. 4. Epipheidole inquilina. 5. Epa- cus pergandei. 6. Anergates atratulus. (a) Description and Habits. (b) Experiments of Adlerz and Wasmann. (c) Personal Experiments. (d) Conclusions. 6. Ethical and Sociological Analogies. CHAPTER® XXVIIE THE SENSATIONS OF ANTS. I. Introductory. Intellectual and Intuitional Methods of Study- ing Animal Behavior. Different Types of Behavior. ithe Senses asia Basis tomitseswucdyess 8c. sin. se : : 505 XX1V TABLE OF CONTENTS. PAGE Li-SSensemecuceptionsin Ants... |. cee aay). oh eee ee 508 1. Tactile. 2. Olfactory. 3. Gustatory Sensations. 4. Per- ception of Vibrations. Stridulation as a Means of Com- munication. 5. Vision and Phototropism. Reactions to the Ultra-violet and Réntgen Rays. III. The Great Importance of the Perceptions of Odor, Touch, and Wibrations in theives Ongauibs tern eo ee ee - ae 5i7 CHA PIER Sexe THE INSTINCTIVE BEHAVIOR OF ANTS. I. Introductory. Definition of Instinct. Its Ethological, Physio- logical, Psychological and Metaphysical Aspects .... 518 Lie instinct trom-the Objective Pomtroreview: 2-20 epee. 519 Lit: The Correlation of Instincts sand -Stuuctines. neers 521 1. Instincts as Compound Reflexes. 2. The Centering of In- stinct in Reproduction. 3. Differentiation of Instincts in the Castes. 4. Deferred Instincts. 5. Vestigial and De- cadent Instincts. 6. Diseases of Instinct. The Decay of Ant Colonies Due to Disturbance of their Trophic Balance. 7. Regulation in Instinct. IV. Instinct Stimuli. Simple and Individualized Stimuli..... ery) V. Instinct from the Subjective Point of View. Instinct as Divinatony {Sympatico yes Oe ees ica ere 529 CHAPDER® Saxe THE Priastic BEHAVIOR OF ANTS. I. Introductory. Instinct and Intelligence Distinguished. The typeset Vammrochiz-cey which are employed in re- moving the dust, etc., from the surfaces of the fore-legs. The colors of ants are, as a rule, testaceous, yellow, brown, red, or black, but a few genera (Rhytidoponera, Calomyrmex, Macromischa, Iridomyrmex ) and a few North American species of Pheidole (metal- lescens and splendidula) have metallic colors. The non-metallic tints are often highly variable, even within the limits of single species. Color patterns are rarely developed and are usually found only on the upper surface of the gaster, a region which often differs in color from the head and thorax. The appendages, as in other insects, are apt to be paler than the trunk. The coloration of the hairs and pubescence, like that of the surface, may be extremely variable in the same species. To the integument belong also a number of glands, but these will be described in connection with the glands of the internal organs. The Head.—A fter this very general review of the segmentation and integument we may take up the different parts of the body in somewhat greater detail. The head varies enormously in shape. It may be cir- cular, elliptical, rectangular or triangular, and all its parts may show an extraordinary diversity of adaptive characters (Fig. 3). It consists of the cranium proper, which is very much constricted behind at its THEE XTERNAL STRUGEE OF ANTS. 17 articulation with the thorax, the eyes, the clypeus, or epistoma, a plate of very variable outline and immovably articulated with and set into the anterior portion of the cranium, the antennz, and the mouth-parts, Fic. 3. Heads of various ants. (Original.) A, Mystrium rogeri, worker; B, Myrmecia gulosa, worker; C, Eciton hamatum, soldier; D, Harpegnathus cruentatus, -.female; E, Daceton armigerum, worker; F, Leptomyrmex erythrocephalus, worker ; G, Cheliomyrmex nertoni, soldier; H, Pheidole lamia, soldier; I, Thaumatomyrmex mutilatus, worker; K, Odontomachus hematodes, worker; L. Cryptocerus clypeatus, soldier; M, Cryptocerus varians, soldier; N, Opisthopsis respiciens, worker; O, Lep- togenys maxillosus, worker; P, Azteca sericea, soldier; QO, Acromyrmex octospinosus, worker; R, Dolichoderus attelaboides, worker; S, Colobopsis impressa, soldier; T, Camponotus cognatus, soldier; U, Camponotus mirabilis, female. 3} 15 ANTS. comprising an unpaired upper lip, or labrum, the mandibles, maxillz and labium, or lower lip. In the last the originally separate and paired embryonic appendages are fused in the median line so that they form a continuous floor for the mouth or buccal cavity. In the cranium the following regions may be distinguished: the front, a region bounded anteriorly by the posterior edge of the clypeus and laterally by a pair of ridges, the frontal carinz or lamine, just mesial to the inser- tions of the antenne. A small, usually triangular, median region, the frontal area, can be easily seen in the middle line just back of the clypeus, and often there is an impressed line, the frontal groove, extending back from this area over the middle of the front. The frontal region passes with- out definite boundary into the vertex and temples, the former extending posteriorly, the latter lying above and behind the eyes. The short region between the vertex and the narrow opening, or foramen through which the alimentary tract and nervous system pass into the thorax, may be Scalled .the: occiput. ~ ie cheeks, or genz, comprise the portions of the cranium anterior to the eyes and lateral to the frontal carine. The ventral por- tion of the head, bounded in External structure of head in Myrmica rubra worker. (Janet.) A, Fic, 4. Dorsal aspect of head; B, anterior front by the labium, on the sides aspect; a, mandible; b, clypeus; c, g frontal area; d, frontal groove; e, by the cheeks and extending to frontal carina; f, vertex; g, occiput; the occipital foramen, is the h, temple; i, base of antennal scape; ; ; It is well-de- k, cheek; J, eye; m, lateral ocellus; n, median ocellus; o, tentorial pit; », labrum; g, labium; r, maxilla; s, max- illary palp; t, labial palp; wu, gula. throat, or gula. veloped in the ants and is usually divided into two equal halves by a longitudinal suture. The mandibles, being the parts with which the ant comes into most effective relations with its environment, present, like the beaks of birds and the teeth of mammals, a bewildering variety of structure (Fig. 3). THE BXTERNAL STRUCRGRE OF ANTS. 19 They are used for excavating soil or wood, cutting up the food, fighting, carrying the prey, their young or one another, and in some species, even in leaping by closing them rapidly against hard bodies. remarkable in being able to open and close their mandibles indepen- dently of the maxilla and labium. These organs, which lie underneath the small and vestigial labrum and close the mouth completely except when the insect is feeding, have a complicated and interesting structure. The maxill (Fig. 5, B,D) are paired and each consists of the following pieces, or sclerites: the hinge (cardo), the stem (stipes), the maxillary palp, which may be from 1—6-jointed, inner blade (lacinia) and an outer blade, the galea. The galea bears a row of gustatory papille and a row of bristles which Ants are an are used in cleaning the The membraneous legs and antenne. lacinia is and toothless and shows that the ant feeds on liquid substances only. This is also proved by the structure of the labiim (Fig 5;° C),; which consists of the following sclerites: the hind chin (submentum ), the chin (mentum) and the tongue (glossa), all unpaired, and the labial palpi, of from one to four joints, PiGe55 Mouthparts of Myrmica rubra. A, Seen from the lower, or ventral side, in situ; B and D, maxille; C, labium, seen from the upper, or (Janet.) consisting dorsal side, detached; a, mandible; b, maxilla; c, mentum; d, maxillary palp; e, labial palp; f, glossa, the paraglossee and hy- popharynx, which are paired. we the tongue, with which the ant rasps off or laps up its liquid or tongue; g, adductor muscle of mandible; h, abduc- tor muscle of mandible; 7, labium; k, gustatory organs; J, duct of salivary glands; m, maxillary comb; n, gular apodeme. or semi-liquid food, and cleans itself and its fellows, is a protrusible, elliptical pad, covered with fine trans- verse ridges. At its base lies the opening of the salivary duct. paraglosse are small sclerites beset with rows of. bristles. The The hypopharynx, which is less developed than in some of the other 20 ANTS: [lymenoptera, such as the wasps, covers the mentum and paraglosse. Its upper portion is somewhat lobed and bears two rows of backwardly directed bristles, which form a V and seem to be used for holding the food fast in the mouth. The upper lip, or labrum, forms the roof of the mouth. It is poorly developed and consists of a bilobed plate hidden beneath the anterior border of the clypeus (Fig. 4, Bp). The antenne are far and away the most important sense organs of. the ant. They are inserted in sockets on each side of the frontal carine, and consist of a series of joints of variable number and length. The lowest number, four, is found in the genus Epitritus (Fig. 75) ; the _ greatest, thirteen, in the males of many of our common ants. Usually the males have one more joint than the females and workers. The first joint, known as the scape, is always considerably elongated, except in the males of some species. The remainder of the antenna, the funiculus, consists of very much shorter joints, the articulations between which are less movable than that between the scape and funiculus. This latter articulation is of such a nature that the funiculus can be folded up against the scape producing the peculiar Formicid elbow in the antenna, and both this and the socket articulation at the insertion of the scape permit extraordinary freedom in the movements of the appendage. The funiculus may be of nearly uniform diameter through- out, with very similar joints, or from one to four of the terminal joints may be thickened and elongated and thus constitute a club. Ants have two kinds of eyes: the compound, lateral eyes, two in number and placed on the sides of the head (Fig. 4, /), and the simple, median eyes, ocelli, or stemmata, of which there are three on the vertex (Fig. 4, m,n). Both kinds are best developed in the males, less in the females and least in the workers, which often lack the stemmata altogether. In addition to these great differences, which are constant in the three phases of nearly all species, there are considerable differ- ences in the development of the eyes in the different genera. A more detailed account of these organs and the antennal sense organs is given in Chapter IV. The Thorax.—Owing to the fusion of the first abdominal segment of the embryo and larva with the hindermost portion of the thorax during pupation, the thorax of the adult ant may be said to consist of four segments, a pro-, meso- and meta-thoracic and a mediary segment, or epinotum. In our description we may follow Emery (1900d) who has carefully studied the external morphology and reviewed the nomen- clature of these four segments in the male, female and worker. The primitive condition of the thoracic region may be readily traced through the ergatoid females and workers of these forms to the much reduced TRE EXTERNAL, STRUCHORE "OF ANTS. 21 and specialized condition in the workers of more highly developed ants like the Camponotine. Emery starts with a primitive form like the male Streblognathus ethiopicus (Eig..6). In this in- sect’ the elements or sclerites of which the thorax is composed are clearly delimited by sutures. The prothorax is very small and consists dorsally and laterally almost entirely of the un- ‘paired pronotum, with a slender ventral element, the prosternum, to which the coxa of the fore-leg is articulated. Owing to the de- various Inve, (6 Thorax of a male Ponerine velopment of the wings, the meso- and metathorax are much larger. The former is especially well-de- veloped, in correlation with the larger size of the fore wings, and comprises dorsally a large un- paired, convex plate, the mesono- tum; ventrally on each side, and articulated below with the coxa of the middle leg, is the meso- sternum, which also forms much of the pleural wall of the thorax. ant, Streblognathus ethiopicus in profile. (Emery.) a’ and a*, Anterior and pos- terior wings; em and em’, meso- and metathoracic epimera; es and es’, epis- ternites of the same segments; epi, epi- notum; g, metasternal gland; mtn, meta- notum; pet, petiole; ppet, postpetiole; pun, pronotum; ppt, parapteron; sc, scu- tum of mesonotum; sct, scutellum; sf and st’, meso- and metathoracic ster- nites ; stg’, stg’, stg® and stg‘, stigmata of meso- and metathorax, epinotum and petiole. The parts of the prothorax are shaded with broken lines, those of the mesothorax, epinotum and petiole are unshaded, those of the metathorax are shaded with unbroken lines; the wing articulations are dotted. The space on each side between the mesonotum and the mesosternum is occupied by a pair of elements, one of which, the mesepisternum, is ventral; the other, the mesepi- meron,dorsal. The fore-wing is articulated just above the mesepimeron and below a small sclerite, which is behind the mesonotum and may be called the mesoparapteron, or prescutellum. The insertion of the fore- wing is covered by a small chitinous scale, the tegula. Viewed from above the large mesonotum in some male ants presents a Y-shaped groove, known as the Mayrian furrow (Fig. 7, sM).- Each side of the mesonotum is marked off for some distance from the median portion of the segment by a distinct suture, which may be called the parapsidal suture. The area thus cut off on each side is the parapsis. The sides and the ventral portions of the metathoracic segment are similar to those of the mesothorax, but smaller. It is possible to dis- tinguish a metasternum, to which the coxa of the hind-leg is articulated, a metepisternum and a metepimeron. Dorsally, however, the metano- a 22 ANTS. tum, which, of course, is serially homologous with the mesonotum, is very narrow antero-posteriorly and separated from the mesonotum by a large, unpaired, semi-circular element, the scutellum. Between the scutellum and metanotum, a small piece, the metaparapteron, or post- scutellum, is intercalated on each side. The hind-wing is inserted between this metaparapteron and the metepimeron. The epinotum, which, as we have seen, is morphologically the first abdominal segment, is large and convex and in many ants furnished with a pair of stout spines or teeth. It is closely applied to the metathorax from the posterior edge of the mesonotum above to the ventral edge of the meta- thorax below. The thorax has on each side three openings, or stigmata, to the respiratory tubes, or tracheze. The first, belonging morphologically to the mesothorax,. lies Fic. 7. Dorsal aspect of beneath a small flap-like expansion of thorax of male Ponerine ant, 5 Pordbonera clavdia. (Emery), “tHe *pLonebumae where (it. abuts (on Sthe a and a’, Anterior and posterior mesepimeron. The second or meta- ENE eee geet ar eo AH OTAGIC stigmata lies beneath the inser- of mesonotum; sM, Mayrian furrow; pss, parapsidal furrow; tion of the hind-wing and near the pos- ee Fe ee ao Les _terior end of the mesepimeron. The metathorax ; sct, scutellum; mtn, third stigma, belonging to the first ab- metanotum; ep, epinotum; pef, : 5 devi aeacie dominal segment, is distinctly seen on the side of the epinotum. In the female ant (Fig. 8, 4) the thorax is constructed on the same plan as that of the male, but is more robust and lacks the Mayrian furrow, which is also absent in the males of many genera. The males and females of most species, however, exhibit a greater simplification of the pleural region of the thorax, owing to the fusion of the epimera and episterna with each other and often also with the sterna in the meso- and metathorax, and a very intimate fusion of the epinotum with the latter segment. Turning to the workers, which are wingless, there is noticeable a great reduction in the size of the meso- and metathorax plus the epi- notum, so that the three divisions of the thorax are more nearly of uniform size (Fig. 8, C, Fig. 9, a). In certain species, and especially in the ergatoid females (Fig. 8, B) and soldiers of a few genera, the various dorsal elements, such as the paraptera, scutellum and meta- “ PHETEXTERNAL STRUGCRURE OP ANTS. 23 notum may still be recognized as very small sclerites, but in the workers of the highest and most specialized ants of the genera Formica and Camponotus the thorax appears to consist of three similar segments, x, XN ae et sto* eS‘iend Fic. 8. Thorax of female, ergatoid and worker Ponerine ants in profile. (Emery.) A, Myrmecia pyriformis, dealated female; B, M. spadicea, ergatoid female; C, M. pyriformis, worker ; msn, mesonotum; the remaining letters the same as in Figs. 6 and 7. owing to the disappearance of the scutellum, paraptera and metanotum as separate sclerites and to the fusion of the various elements in the pleural region of each segment. The legs of the ant show much less variation in structure than the Fic. 9. Median sagittal sections to show difference of development of thoracic segments in the worker and female Myrmica rubra. (Janet.) A, Worker; B, female; a, posterior portion of head; b, prothorax; c, mesothorax; d, metathorax; e, epino- tum (first abdominal segment) ; f, petiole (second abdominal segment). 24 ANTS. thorax and are, therefore, of less taxonomic value. Each of these appendages consists of the same fixed number of joints, the coxa, tro- chanter, femur, tibia, and five tarsal joints. The first tarsal joint, often called the metatarsus, is much elongated, especially . on the middle- and hind-legs, where it functions as a kind of secondary tibia, while the terminal tarsal joint bears a pair of usually simple, but sometimes toothed, or pectinated claws. All of the tibize may be provided at their distal ends with spurs. These are always large and pectinated on the fore-legs, Ab but may be simple on the middle and hind pairs. The finely and regularly pectinated spur of the fore tibia (Fig. 10, b) is of special interest on account of its beautiful structure and its function as a strigil. It is movable and curved and its concavity is oppo- site a similar concavity, fringed with bristles, on the base of the metatarsus. The ant draws its antenne and posterior legs between the two opposed, pecti- nated surfaces and thus wipes off any adhering foreign matter. The wings have not been used to as great an extent in descriptive works on ants as in those on other families of Hymenoptera, owing to their frequent absence in female specimens and to the Fic. ro. Strigi]) Permanently apterous condition of the workers, of Texas harvester which have hitherto formed the basis of our sys- ee eee tematic study. The venation of the fore wings, inal.) a, Distalend however, often exhibits important generic or even ee eee specific characters and its study, especially in fossil spur: c, first tarsal ants, is indispensable. It is sometimes highly vari- (metatarsal) joint. able in detail,evenin males and females reared from Fic. 11. Anterior wings of ants. (Original.) A, Ichnomyrmex cockerelli, female; B, Camponotus sansabeanus, female; C, Eciton schmitti, male; D, Strumigenys per- gandei, female; E, Lasius claviger, female; F, Dolichoderus marie, female; G, Sole- nopsis molesta, female; H, Forelius maccooki, female; I, Myrmica scabrinodis, female ; K, Pachycondyla harpax, male; L, Pogonomyrmex molefaciens, female; M, Tetra- — morium cespitum, female; N, Aphenogaster fulva, female; O, Trachymyrmex septen- trionalis, female. The following are the veins of the wing: a, costal; b, subcostal ; c, externomedian; d, anal; s, apterostigma; c, and g, cubital; h, discoidal and sub- discoidal; f, marginal, or radius; z,- transverso-median; n, basal; m, recurrent; 0, first section of radius in A, B, C, E and O, transverse cubitus in F, J and N. The following are the cells: u, first discoidal; wv, costal; 71, median; +, submedian; y, second discoidal; w, first cubital; w’, second cubital. (These terms are used in myrmecography. Some authors, like Handlirsch, regard what is here called the “ sub- costal’ as the radius + median, and the “ subdiscoidal”’ as a branch of the median.) Pee ved -_ 20 ANTS. the same mother. Several of the different types of venation which have been recognized are represented in the accompanying illustrations (Fig. 11), to which the reader is referred for the names and disposition of the various veins and cells. The Abdomen.— This region in ants is very highly specialized in all three sexual phases. In some of the most primitive tribes, like the Amblyoponii and Cerapachysi, there is no sharp separation of the seg- ments into a pedicel and gaster; the basal, though somewhat nar- rower and more accentuated, preserving essentially the same structure as the more distal segments. In most ants, however, there is a well- defined pedicel which may consist of either one or two segments, very movably articulated with each other and with the thorax and gaster. In the subfamilies Dolichoderinze and Camponotinz the pedicel always consists of but a single segment, the petiole, which is morphologically the second abdominal segment. The same condition prevails in most Ponerinz, except that there is a constriction behind the following or third segment, foreshadowing the development of a postpetiole. This segment is clearly separated off in all Myrmicinz, so that in the ants of this subfamily the pedicel consists of two highly specialized, nodi- form segments, and the first gastric is the fourth instead of the third abdominal segment, as in the Camponotinz, Dolichoderine and Poner- ine. In the Doryline the genera Eciton and A:nictus have a distinct petiole and postpetiole in the worker, but only a single segment, the petiole, in the male and female. In Dorylus and Cheliomyrmex the base of the abdomen of the-worker is more primitive and more like that of certain Ponerine ants (Amblyopone and Cerapachys ). The base of the abdomen is the seat of an interesting sound- producing, or stidulatory, organ. Landois, in a book called “ Thier- stimmen,’ published in 1874, was the first to find this organ in a Ponerine ant (“‘Ponera quadridentata,’ probably Ectatomma quaa- ridens). He believed that he had seen a similar structure in the Cam- ponotine Lasius fuliginosus, and a few years later Lubbock (1877) figured what he took to be a stridulatory organ in L. flavus. Sharp (1893) and Janet (1893), 1894) ) have since carefully investigated these organs in several different ants. The former succeeded in finding them only in the Ponerinze and Myrmicine (excepting the Cryptocerii) and believed them to be absent in the Dorylinz, Dolichoderinze and Cam- ponotine. The organ (Fig. 12) is best described as a file made of extremely fine, transverse and parallel ridges on a small area in the mid-dorsal, chitinous integument at the very base of the first gastric segment, where it is covered by the overlapping portion of the preced- ing segment. The edge of this segment (Fig. 12, Bp) is sharp and THESEXPTERNAL SPRUCTERESOL ANTS. 27 turned slightly downward or inward so that it may scrape back and forth over the file (str) when the two segments are moved on each other and thereby produce a sound of very high pitch. The file is, in all probability, merely a local specialization of the fine, polygonal elevations or asperities which cover the adjacent portions of the segment and are so characteristic of the chitinous invest- ment of many parts of the body. Each of these minute elevations is evidently secreted by one of the hypodermal chitinogenous cells. Sharp found great diversity in the structure of the stridulatory organ both among the different species and in the castes of the same species. Fic. 12. Stridulatory organ of Myrmica levinodis. (Janet.) A, Surface view of right half of the organ; str, stridulatory surface; /, lateral, reticulate surface; so, sense-organs; m, tendon of muscle; ap, lateral apophysis; r, radiating ruge at base of first gastric segment. B, Median sagittal section of organ; str, stridulatory surface at extreme anterior border of first gastric segment; p, edge of postpetiole which scratches the stridulatory file str. An interesting modification was found in an Australian Myrmicine ant of the genus Sima, which has the file divided into two parts, one con- sisting of coarse, the other of fine, ridges, and Sharp remarks that “a stridulatory performance by this insect might produce very extraor- dinary effects.” Janet, in his studies of Myrimica rubra, calls attention to the fact that there are accumulations of chitinous asperities at various widely separated regions of the ant’s body, especially on articulations which might, by their movements, produce sounds. But the true stridulatory organs he finds to be situated where they were seen by 25 ANTS, Landois and Sharp, 7. ¢., at the base of the first gastric segment, and also on the corresponding part of the postpetiole. These two segments certainly admit of the greatest amplitude and freedom of movement and are, therefore, the most favorable spots for the development of organs like those under discussion. In Myrmica rubra there are more than 50 ridges to the postpetiolar file, but in the organ at the base of the gaster there are more than 130 and these are much finer. The ridges, however, are twice as broad in the anterior as they are in the posterior portion of the gastric file. It appears, therefore, that the most highly developed stridulatory surfaces of the Myrmicine and Ponerine are not strictly homologous, since in the former subfamily the principal organ is situated on the third abdominal, whereas the only stridulatory file of the latter is on the second abdominal segment. In both cases, however, the main organ is at the base of the first gastric segment. What seem to be incipient stages in the development of the organ from ordinary polygonal asperities of the chitinous integument, are seen in the Doryline. Of the first gastric segment in one genus of this subfamily Sharp says: “ I have examined workers of several species of Eciton, and find that they have no stridulatory organ, the sculpture being uniform all over the dorsum of the neck of the segment.” My own observations on the workers of several species of Eciton, A:nictus, Dorylus and Cheliomyrmex confirm this statement. In all these genera the neck of the postpetiole and that of the first gastric segment are covered with polygonal asperities, but these are much more conspicuous than on other portions of the segments, and in one species (Eciton opacithorax ) they are transversely lengthened in the mid-dorsal region so that they foreshadow the file ridges of the Ponerinze and Myrmicine. Although the number of segments in the gaster is morphologically eight, when the pedicel consists of a single segment, and seven when it consists of two, only four segments are externally visible in the worker and female and five in the male. The remaining segments are very small and telescoped into the larger ones in front of them. Tracheal stigmata are present on the eight basal abdominal segments, 7. ¢., on the epinotum, pedicel and the five or six basal gastric segments. The terminal segments in the female and worker may bear a sting, which is of considerable interest, because it can be traced back to its primitive homologue, the ovipositor. In many Orthoptera, like the katydids and crickets, this organ consists of three pairs of appendages, which, as I have shown (1893), are the modified embryonic legs of the eighth, ninth and tenth abdominal segments. Owing to a very early embryonic fusion of their corresponding segments the pair belonging to the tenth segment moves up and comes to lie between the ninth pair, so TAEREMIERNAL STRUC Tie OF ANTS. 29 that the ninth segment appears to bear two pairs of appendages. In the Hymenoptera the ovipositor is still retained with its Orthopteroid function in certain families like the ichneumons and gall-flies, which Oviposit in the tissues of insects and plants. In the bees, wasps and ants, however, the organ has lost this primitive function and has become an organ of defence. Its embryological origin in these forms, however, is the same as in the Orthoptera. Dissections of the sting of the pupal and adult ant show that the pairs of appendages become closely applied to one another so that they appear as a single organ. The appendages of the tenth segment actually fuse to form a single, pointed, grooved piece, the gorgeret (Stachelrinne) which encloses the pair of appendages belonging to the eighth segment. These are very slender and pointed and are known as the stylets, or prickles (Stech- borsten). The appendages of the ninth segment become somewhat lamelliform and, without fusing with each other, enclose the gorgeret as the sting-sheath (Stachelschiede). In stinging, the pointed gorgeret is thrust into the skin and then the stylets are alternately pushed deeper into the wound beyond the tip of the gorgeret which they do not sur- pass when the sting is at rest. The duct of the gland that supplies the poison, which produces the burning sensation, enters the base of the gorgeret. The stylets are smooth and not barbed on their sides as they are in the bee; hence the ant is able to withdraw its sting from the wound. While the sting is very large and well-developed in the Ponerinz, Dorylinze and most Myrmicine, it is vestigial or absent in the other subfamilies. At the tip of the male gaster there are three pairs of rather com- plicated appendages forming the genital armature. They are devel- oped on the ninth abdominal segment, 7. ¢., the segment which in the female gives rise to the sting sheath. The sternal plate of this segment, which in the male lies in front of the appendages, is known as the annular lamina (Fig. 19, Ja). The three pairs of appendages enclose one another, so that we may distinguish an outermost, a median and an innermost pair. The outermost pair has been called the stipites (st). The median pair is sometimes more or less completely divided into two pairs, known as the volsellz (v) and laciniz respectively ; and the whole group of appendages comprising the stipites, volsellae and laciniz are known as the external paramera (Verhoff and Emery). The innermost pair alone is known as the internal paramera. They are closely applied to each other in the median sagittal plane of the body and function as a penis (f). During copulation the stipites, which are large, robust and often covered with hairs, function as claspers. The volselle and laciniz, which are smaller and less heavily 30 ANTS. chitinized and furnished with numerous tactile sense organs, in all probability also have a clasping function. The inner paramera are very delicate. In some ants they have serrated edges which probably serve to hold them in place in the vagina of the female. In addition to the genital valves there is a pair of small, hairy appendages, the penicilli, attached to the tergite, or dorsal plate of the tenth abdominal segment. There can be little doubt that these represent the cerci of Blattoid and other primitive insects and must therefore belong to the anal or eleventh abdominal segment. The presence or absence of the penicilli and the conformation, permanent retraction or protrusion of the different paramera are used in classification as valuable diagnostic characters. Although we may be tempted to homologize the three pairs of male genital appendages with the three pairs of appendages which go to form the sting in the female, it is very doubtful whether more than one of these pairs, the stipites, develop from rudiments of the embryonic walking limbs. If this is true, the stipites correspond with the pair of appendages of the ninth segment in the female, which give rise to the sting sheath, and the volsellz, laciniz and penis are merely differentiations of the median portion of the ninth sternite. CHA PTERSARE THE INTERNAL STRUCTURESOEANTS: “In his tam parvis, atque tam nullis, que ratio, quanta vis, que inextricabilis perfectio! "—Pliny, “ Historia Animalium,”’ XI, 2. The Alimentary Tract.—This extends the entire length of the body from the mouth to the anus as a tube with but a slight tendency to convolution in the gaster. The walls of this tube are curiously modified in different portions of its length, so that we can recognize a number of regions known as the infrabuccal chamber, buccal tube, pharynx, cesoph- agus, crop, proventriculus, stomach, small intestine and rectum. The shape and extent of these regions are indicated in the accompanying diagram taken from Janet (Fig. 13). Owing to the volume of the brain and cephalic glands, to the narrowness of the thorax and pedicel in the worker, and the great development of the wing muscles and glands in Fic. 13. Sagittal section of worker Myrmica rubra. (Janet.) t, Tongue; /br, labrum; clp, clypeus; sg, opening of salivary gland; bo, mouth opening; hp, infra- buccal chamber; ph, pharynx; phg, pharyngeal glands; oe, esophagus; cr, crop; gz, gizzard; st, stomach; lin, large intestine; mp, Malpighian vessels; rc, rectum; rcg, rectal gland; an, anus; fgl, frontal ganglion; rec, recurrent nerve; br, brain; mdg, mandibular ganglion; mg, maxillary ganglion; /g, labial ganglion; soe, subcesophageal ganglion; cho, prothoracic chordotonal organ; thg’, thg*, thg*, pro-meso- and meta- thoracic ganglia; ag’-ag*, ag, 8-11, first to eleventh abdominal ganglia; sym, sympa- thetic connective, running along cesophagus to prestomachal ganglion (stg); st, sting; vg, vagina; ten, tentorium in section. the thorax of the male and female, the alimentary canal is cramped for space and hence very tenuous, except in the gaster, where its most important parts are situated. The mouth opening, which, as we have Bi 32 ANTS. seen, is bounded above by the labrum and ciypeus, on the sides by the maxilla, and below by the protrusible tongue, leads into a short, com- pressed buccal tube, dilated ventrally to forma spheroidal sac, the infra- buccal cavity or chamber (ip). This chamber is of great importance to the ant as a receptacle both for the fine particles of solid and semi- solid food rasped off or licked up by the tongue, and for the foreign matter scraped from the surfaces of the body by this organ and the strigils. Any juices that may be contained in the substance are sucked back through the pharynx into the crop and the useless solid residuum is eventually thrown out as a little body which preserves the form of the chamber in which it was moulded. Such bodies, called by Janet “corpuscles de nettoyage,” are often seen scattered about the floors of artificial nests after the ants have been fed on starchy substances or after their bodies have been dusted 7. -with=plaster> of sparisie( Pigs. 14): Phe, snore Fie.14. Pelletsor buccal cavity is continued back into the muscular castings from the in- - : frabuccal chamber of Pharynx which narrows still further to form the ee rufa, enlarged. Jong cesophagus traversing as a slender tube the pee: head, thorax and pedicel (Fig. 13, oe). The buccal tube, which, according to Janet, “ has a protractor and a retractor muscle, is provided with soft lips that can be applied to the surface of the substances previously rasped off by means of the tongue for the purpose of obtaining any liquid they may contain. Transverse scale-like folds with their points turned outward line the walls of the buccal tube and serve to retain any solid particles not sufficiently minute.” “The pharynx is a flattened cavity the dorsal and ventral walls of which are moved by powerful dilator muscles. Behind it is furnished with two expansions arising laterally and united at their tips by a transverse constrictor muscle. During aspiration the pharynx, through the action of its dilators and a kind of posterior sphincter, opens in front and closes behind. In swallowing there is first produced a steel- yard-like movement of the dorsal wall, whereupon the pharynx is opened behind, while the buccal tube is closed in front. Then, owing to the action of the transverse constrictor, the dorsal approaches the ventral wall from before backward. The two walls thus come in con- tact with each other and the liquid which was contained in the pharynx is pushed into the cesophagus.” Immediately behind the pharynx two groups of finger-shaped post-pharyngeal glands open by a pair of orifices into the alimentary tract (Fig. 13, phg). THESINTERNAL STRUGTGRE OF ANTS. 33 The thin chitinous lining of the cesophagus is covered with delicate hairs which point backwards. At the base of the gaster the cesophagus begins to dilate to form the ingluvies, or crop (Fig. 15, cr), a thin-walled, pyriform bag, whose walls, like those of the cesophagus, consist of a layer of longitudinal and one of transverse or ring-shaped muscle fibers and a delicate chitinous lining. In the cesophagus the chitinous lining is beset with fine hairs pointing backwards. There are no glands in the crop and the chitinous walls completely resist the absorption of food, so that this organ serves merely as a reservoir for the liquid that has been imbibed or lapped up directly or sucked out of the more solid Fic. 15. Gaster of female Myrmica rubra in sagittal section. (Janet.) ppt, Post- petiole; str, stridulatory organ; gs’-gs*, first to sixth gastric segments; ht, heart; v, cardiac valve; pc, pericardial cells; u, urate cell; f, adipocyte; on, cenocyte; ot, ovarian tubules; od, oviduct; ut, uterus; rs, receptaculum seminis; bc, bursa copu- latrix; vg, vagina; vv, vulva; st, stylets of sting; gt, gorgeret; pg, poison gland; ag, accessory gland. Remaining letters as in Fig. 13. substances moulded in the infrabuccal chamber. Forel aptly calls the crop “the social stomach,” because the food it contains is at least in great part fed by regurgitation to the other ants of the colony or to the brood. The crop is remarkably distensible, especially in certain Camponotine, like the honey-ants, so that its replete or deplete condition determines the volume, and in a measure also the shape of the gaster in the worker. The crop is succeeded by a remarkable structure, the proventriculus, or pumping stomach, which has been carefully studied by Forel (1878) ) 4 OF, ANTS. and Emery (1888c), who have found it to vary greatly and to afford valuable characters for the delimitation of genera and even of sub- families. The proventriculus of our common carpenter ants (Cam- ponotus ) may be described as a paradigm (Fig. 16,4). Itisanarrowed or constricted portion of the alimentary tract and consists of several successive sections. The most anterior of these is the calyx (c). As the name implies, this is a cup-shaped section with chitinous walls dif- ferentiated into eight bands, four greatly thickened, and very convex towards the lumen, alternating with four thinner chitinous bands which are more or less concave towards the lumen. The thickened bands have been called the sepals. At the posterior narrow end of the calyx Fic. 16. The gizzard, or proventriculus, of various ants. (Emery.) A, Campo- notus ligniperdus; B, Liometopum microcephalum; C, Attia sexdens; D, Cryptocerus atratus; E, Technomyrmex strenuus, seen from the anterior end; F, sagittal section of same; a, cesophagus; b, crop; c, sepal; d, membrane between sepals; e, valve; f, bulb of calyx (pumping stomach proper) ; g, cavity of bulb; h, cylindrical portion; 1, knob-shaped valve; k, stomach, or ventriculus. these can be applied so closely to one another as to shut off the lumen and thus assume the function of a valve at this point. Posterior to this valve, the walls of the organ again dilate suddenly to form a globose section, the bulb (f), which repeats the structure of the calyx with some WHE INTERNAL STRUCTUREMOFP ANTS. 3 aT modification. This is the pumping stomach proper. It is succeeded by a slender, thin-walled tube, the cylindrical section (1), opening behind into the much more voluminous stomach on the summit of a knob, which is also valvular in structure (7). At this point the chitinous lining of the alimentary tract stops abruptly. The walls of the proventriculus, especially of its bulb, are furnished with powerful transverse and feebler longitudinal muscles. The function of the proventriculus as a pump has been explained by Emery. It is clear from the shape of the chitinous folds in the bulb and the arrangement of the musculature that the contraction of the latter must bring the folds close together and occlude the lumen, whereas the relaxation of the muscles permits the chitinous folds to flatten out through their own elasticity and thus enlarge the cavity and suck the liquid back out of the crop. Hence the organ functions like a rubber bulb with a tube and an appropriately constructed valve at each end. When the bulb is squeezed its liquid contents are forced into one tube, and when it is permitted to expand, it draws the liquid out of the other tube. The proventriculus has an important function, not only in passing the liquid food back from the crop to the true stomach, but also in filling the crop in the first place. The proventriculus of Camponotus may be regarded as representing a structure from which we can pass on the one hand through greater simplification to the Myrmicine and Ponerine proventriculus, and on the other through greater complication to that of the other Camponotinz (Plagiolepis, Prenolepis, etc.) and Doltchoderine. This complication consists, in great part, in a shortening of the calyx and a spreading and recurving of its lips till they form a bell-shaped structure more or less completely enclosing the remainder of the proventriculus. Extreme forms of this kind are seen in Jridomyrmex and Technomyrmex (Fig. 16, E, F). In these ants it is possible to see how the proventriculus may play an important role in regurgitation as well as in ingurgitation, for the contraction of the walls of the crop, especially of the ring- muscles at the posterior end, and the pressure of its liquid contents must tend to close the openings between the sepals, thus preventing the liquid from moving backward and determining its flow in the oppo- site direction. As the musculature of the crop is poorly developed, some authors, like Janet, regard the pharynx as the organ which by its peristaltic contractions probably initiates regurgitation and may even be of great importance in filling the crop during ingurgitation. All of the above-described regions of the alimentary tract arise in the embryo as a tubular infolding of the outside skin, or ectoderm, the so-called stomodeum. This is indicated in the adult by the almost 30 ANTS. complete absence of glands and the presence of a chitinous lining which is continuous at the mouth with the chitinous investment of the body and appendages. The true or individual stomach (ventriculus ) which succeeds the proventriculus, represents a sudden departure in structure and function (Figs. 13 and 15, st). It is a small, elliptical sac, hardly capable of dilatation, with very glandular walls devoid of a chitinous lining. This region alone arises from the inner germ-layer of the embryo, in which it is called the mesenteron. Its structure shows very clearly that it is adapted to digesting and absorbing the liquid food that may be permitted to pass the valve at the posterior end of the proventriculus. Though of relatively large size in the embryo and larva, the stomach in the adult ant forms but a small portion of the alimentary tract. The portion lying between the stomach. and anus, and comprising the small intestine (Fig. 15, lin), Malpighian vessels (mp) and the rectum (rc), arises in the embryo like the stomodeum from a tubular infolding of the ectoderm, the proctodzeum, and, like the stomodeum, has a chitinous lining, which in this case is continuous with the integument at the anus and ends abruptly at the junction with the posterior end of the stomach. The small intestine is a narrow tube usually more or less wrinkled by the action of its transverse musculature. Its histological structure is similar to that of the cylindrical section of the proventriculus. Near its insertion into the stomach, where it forms a valve, it receives the Malpighian, or urinary, vessels, which are merely so many long, tubular evaginations of its walls. These vessels seem to vary considerably in number in different ants. Thus, according to Adlerz (1886) there are 6 in Leptothorax, Formicoxenus and Harpagoxenus, 8 in Anergates, 8-10 in Lasius, 12 in Tapinoma, 14 in Polyergus and 20 in Formica and Camponotus. According to Meinert (1860) the number may vary in the different castes of the same species. Thus the female of Lasius flavus is said to have 7-14, the male 6-16 and the worker 7-8. Accord- ing to Janet there are 6 in all three phases of Myrmica rubra. The rectum consists of an ampulliform enlargement which narrows posteriorly to its termination in the anus. Its thin walls are furnished with a single dorsal and a pair of lateral lentiform glands. The feces and the urinary excretions from the Malpighian vessels accumulate in the rectal ampulla and are expelled by a contraction of the thin muscle- layer in its walls. The anus (Fig. 15, am) is provided with a sphincter muscle and is situated on a papilla, which, in a state of repose, is con- cealed within the small, telescoped terminal segments of the gaster. In the Camponotinz the anal orifice is fringed with a regular row of deli- cate hairs, or cilia. THE ANTERNAL STRUGPURELOF ANTS. 37 The Glandular System.—Glands are well-developed in ants, and, owing to their importance in the ethological relations of these insects, deserve particular notice. They have been studied by Meckel (1846), Leydig (1859), Meinert (1860), Forel (1874, 1878), Lubbock (1882), Nassonow (1889) and Janet (1894, 1898). The following groups may be distinguished : 1. Integumentary glands, arising in the embryo, larva or pupa as invaginations of the ectodermal cell-layer (hypodermis), and including the antennary, mandibular, maxillary, labial and metasternal glands, those of the sixth abdominal (third or fourth gastric) segment, and of the fore metatarsus. Here, too, may be included the unicellular glands connected with the olfactory and tactile organs, to be considered in the next chapter. All the integumentary glands are present in the male as well as in the worker and female ant. 2. Reproductive glands, including the penial glands of the male, and in the worker and female the homologous glands of the sting-sheath, belonging to the ninth abdominal (sixth or seventh gastric) segment ; the poison, accessory and repug- natorial, or anal glands of the worker and female, and the glands. of the seminal vesicle of the male. 3. Glands of the alimentary canal. These comprise the post- pharyngeal, ventricular and rec- tal glands and the Malpighian vessels. 4. Glands of the circulatory system, including the cenocytes, pericardial cells and adipocytes, or fat body. These, unlike the three other categories of glands, are ductless. Fic, 17. Frontal section of head of The glands of the alimentarv Myrmica levinodis worker. (Janet.) cc, : : z Central body of brain; cp, pedunculate tract have been briefly described, bodies ; ol, optic lobe ; on, optic HEELVE we. and those of the circulatory and Ye: lo, olfactory lobe with glomeruli; mg, : iS mandibular gland; rs, reservoir; cr, cri- reproductive systems will be petlum:; d, ducts from gland cells: ¢r, Pacer up later. so that here onlv ° trachee ; mx, maxillary gland; /br, labrum; Pie i mc, buccal cavity. the integumentary glands will be considered. The antennary glands consist of a few isolated cells with slender ducts opening on a small area in a depression at the base of each antenna. The mandibular glands (Fig. 17, mg) are well-de- 39 ANTS. veloped and comprise a large cluster of cells in each side of the head just in front of the optic ganglia. Their ducts, grouped in bundles, but not uniting, open separately on a cribellum, or sieve-like plate on the thin wall of a larger cavity, which narrows anteriorly and opens as a small slit at the base and near the upper surface of the mandible. The maxillary glands (m1) consist of two groups of cells near the median sagittal plane of the head, above the buccal tube and near the infrabuccal pocket. Their separate ducts open on each side on a cribellum in the lateral wall of the buccal tube. The labial, usually called the salivary glands, are paired, like the preceding, but are situated in the thorax. Their duct, however, is unpaired and opens on the labium. These glands are derived from the spinning glands, or sericteries of the larva. In Formica rufa, according to Meinert, each of the lateral ducts, before uniting with its fellow to form the unpaired terminal duct, becomes inflated and functions as a receptaculum for the glandular secretion. The metasternal glands (Fig. 18), which were first seen by Meinert and Lubbock, have been carefully investigated by Janet. He regards them as belonging to the epi- notum and calls them “glands de l’anneau mediaire,” but Emery asserts positively that they belong to the meta- sternal or ventral pieces of the third thoracic in- stead of to the epinotal, or first abdominal seg- : ment. In Myrmica Fic. 18. Section of metasternal gland of La- rubra, according to Janet, sius flavus. (Janet.) a, Orifice of episternal cham- ‘i ber; b, hairs guarding orifice; c, cribellum; d, gland- the fine ducts of the cells ; e, ducts of same; f, trichodes projecting into numerous gland cells episternal chamber; g, ganglion. unite in a large bundle and open separately ona depressed cribellum, situated on the ceiling of a large chamber formed by an invagination of the chitinous exoskeleton. From near the surface perforated by the orifices of the secretory ducts, seven or eight little chitinous folds arise and extend laterally along the walls of the chamber. These folds, which form small projecting ridges, soon unite in two groups which border a small gutter on a slight eminence. Towards the ventral region all traces of the ridges dis- RHE RINDERNAL STRUCTURE SOF ANTS. 39 * appear, but the gutter, reduced to a simple depression of the wall, is continued very distinctly to the slit which forms the opening of the chamber. This latter is always filled with air.” In Lasius flavus “ the chamber is widely open to the exterior and the grooves of its walls are absent and replaced by hairs.”’ In one of his preparations Janet found that ‘‘ these hairs are inserted inside the chamber around the cribellum and converge in such a way as to appear like a pointed, hollow brush, i, €., one reduced to the hairs that form its external surface. This pencil recalls the trichodes of myrmecophilous beetles (see Chapter XXII). In Formica rufa the chamber is much reduced and opens more widely to the exterior than in Lasius flavus. The cribellum is beset with hairs which form a brush long enough to project outside the chamber. The glands of the sixth abdominal segment consist of two small clusters of cells whose ducts open on the dorsal interseg- mental membrane just in front of the rigid chitinous border of the seventh segment. The metatarsal gland is situated in the fore-leg at the base of the tarsal comb of the strigil. The Reproductive Organs.—In the female, or queen ant, the repro- ductive organs comprise the two ovaries, each of which consists of a number of tubes, or ovarioles, in which the elliptical eggs are formed in a single series, very small at the distal or anterior and gradually increasing in size towards the proximal or posterior end of the tube. Each egg is surrounded by a follicular epithelium, which secretes from its inner surface the thin, transparent chorion enveloping the ripe egg, and is accompanied by a cluster of nurse cells. The ovarioles, which are bound together in a fascicle by richly ramifying trachez, are attached at their tapering anterior ends to the pericardium in the antero-dorsal region of the gaster ( Fig.15,0¢). The number of ovarioles in each ovary varies considerably in the queens cf different ants. Miss Bickford (1895 ) gives the following numbers for several European species: Formica rufa 45, F. rufibarbis 18-20, Lasius niger 30-40, L. flavus 24, L. brunneus 9-11, Camponotus 39-40, Myrmica ruginodis 8, M. levinodis 12, M. scabrinodis 8-9, M. sulcinodis 9-11, Anergates atratulus 12, Plagiole pis pygmea 4-5; and Miss Holliday (1903) finds the following numbers in several American ants: Pachycondyla harpax 5-7, Odontomachus clarus 5, Eciton schmitt about 250, Leptothorax emersoni 2, Cremasto- gaster minutissima 2, Colobopsis etiolata 6-7, Camponotus decipiens 12, C. festinatus 15-18, C. sansabeanus 6-17, Pogonomyrmex mole- faciens 25-30. The ovarioles of each ovary unite at their posterior ends to form a short oviduct, and the two oviducts in turn unite to form the uterus, which bears on its dorsal surface a small subspherical pocket, the seminal receptacle, which is filled with sperm by the male during 40 ANTS. the nuptial flight. The sperm is kept alive in the receptacle for years, apparently by a nutritive fluid secreted into the cavity of the organ near its orifice by a pair of appendicular glands. The eggs are fertil- ized as they pass through the uterus by sperm which is permitted to escape in small quantities from the orifice of the receptacle. The uterus opens behind into the short vagina, which bears on its dorsal surface a rather thin-walled sac, the copulatory pouch (Fig. 15, bc). The vagina (vg) opens to the exterior by means of a transverse slit (vv) just in front of the sting or its vestige on the sternal articular membrane of the seventh abdominal (fourth gastric) segment. In the worker the ovaries are also present, but, as a rule, with a greatly reduced and often highly variable number of ovarioles. Adlerz (1887) gives the following numbers for each ovary in the work- ers which he examined: Formica sanguinea 3-6, Camponotus herculeanus 1-5, Polyergus rufescens 3, Lasius flavus 1, Tapinoma erraticum 1, Har- pagoxenus sublevis 3-6, and Miss Bickford gives the following data: F. pratensis 2-6, F. rufa 4-10, L. fuliginosus 1-2, Myrmica levinodis, ruginodis, scabrinodis, Aphenogaster subterranea and Crem- astogaster scutellaris 1. The numbers observed by Miss Holliday are: Leptogenys elongata 2-3, Pachycondyla harpax 2-9, Odontomachus clarus 2-8, Leptothorax emersont 2-4, Colobopsis etiolata 1, Camponotus decipiens 1-4, C. festinatus 1-11, C. sansabeanus 1, Pogonomyrme.x molefaciens 1-7. Fic. 19. Male Lespez (1863), Adlerz and Miss Bickford failed to reproductive organs tind any tubules in the worker Tetramorium ces- oe oer ete pitum, and Miss Holliday had no better success sp, spermatozoa;vd, with the worker of Eciton schmitti. It is very CSE OE re ose doubtful, however, that the ovaries have completely seminal vesicle; de, ejaculatory duct;/a, disappeared in the workers of any of the Formi- annular lamina; og, ad A ll-d 1 1 al 1 7 penitall eeinceeac -ocleae: well-developed seminal receptacle was stipes; v, volsella; found in the workers of quite a number of species , penis. F : : Z oe by Miss Holliday, but copulation of workers with males has not been observed. In the male ant each testis (Fig. 19, ts) consists of a number of com- pact lobules (according to Adlerz 17 in Camponotus ligniperdus, 21 in Formica sanguinea, 3 in Leptothorax acervorum and Anergates atra- tulus; according to Janet 4 in Myrmica), occupying a position in the gaster like that of the ovaries in the female. The lobules, which are PHE INTERNAL STRUGTORE, OF ANTS. 4i2 crowded with cysts containing mature sperm, or testicular cells in various stages of spermatogenesis (sp), unite in each testis to form a nO a bated spe nhse, HORRA perro Fic. 20. Poison apparatus of Formica. A, Lateral and slightly dorsal aspect of apparatus in Formica rufibarbis. (Forel.) a, Duct of poison vesicle, or reservoir; Db, cushion formed by the long convoluted portion of the duct from the two free glandular tubes (c) ; d, trachee ; e, ring-muscles of vesicle wall; f, nerves; g, intima of vesicle; h, accessory gland; i, its orifice; m, gland-cells of its walls; n, muscles; 0, sting- sheath; , vestigial sting-groove; r, somewhat dislocated, vestigial right sting-stylet ; s, piece of the cloacal membrane which has been almost entirely removed. 8B, Trans- verse section through poison apparatus of Formica rufa. (Beyer.) w, Dorsal wall of vesicle; x, sections of convoluted duct forming the cushion-shaped mass; y, opening of duct into the vesicle, the lining of which is represented by the more heavily shaded layer (2). f= ANTS. long deferent duct (vd). ach duct is enlarged near its posterior end to form a thick-walled seminal vesicle (vs). The two deferent ducts unite to form a slender ejaculatory duct (de) which opens on the ninth abdominal (sixth gastric) segment at the base of the paired penis (p). The poison apparatus belongs morphologically to the sting, and is, therefore, absent in all male ants. It appears under two different forms, which Forel (1878) distinguishes as the pulvinate and the bourreleted. The former is confined to the ants of the subfamily Camponotinz (Formica, Lasius, Camponotus, etc.), a group in which the parts. of the sting have all but completely disappeared, the latter occurs in all the other subfamilies, which have the sting either highly developed or very small. In Formica the poison apparatus consists of a large, elongated, thin-walled but muscular sac or vesicle and a glandular portion ( Fig. 20). The former opens by means of a rather large orifice between the scarcely recognizable sclerites of the highly vestigial sting. To the inside of the dorsal wall of this vesicle is applied an elongate, elliptical, flattened cushion made up of a delicate, much convoluted and somewhat branched glandular tubule, which is fully 20 cm. in length when uncoiled. One end of this tubule opens into the vesicle at the middle of the ventral surface of the cushion, the other leaves the posterior end of the vesicle in the mid-dorsal line and bifurcates to form a pair of glandular tubules which terminate blindly and lie freely in the body cavity. The walls of these tubules consist of polygonal cells, each of which has a minute duct starting within its cytoplasm and opening into the axial duct, or lumen of the tubules. The second, or bourreleted type of poison apparatus is of a much simpler structure. It, too, consists of a vesicular and a glandular por- tion, with the former opening into the groove of the sting. The vesicle is smaller, however, and more pyriform or globular, and its duct to the exterior is more slender than in the pulvinate type. The glands are a pair of tubules which unite and enter, and in Myrmuica (Fig. 21, B) and many other genera, form an unpaired and somewhat convoluted tubule within the vesicular cavity. This tubule is enlarged or button- shaped at the free end where its opening is situated. In Bothriomyr- mex (Fig. 21, 4) Forel found the unpaired tubule reduced to a smal! sub-globular structure with the opening on its summit. As the bour- releted gland is usually associated with a well-developed sting, except in the Dolichoderine, and, moreover, closely resembles the poison gland of the wasp and bee, it must be regarded as the more primitive of the two types. The pulvinate gland secretes a more copious amount of liquid, which is stored in the vesicle whence it can be either ejected by some ants (/ormica rufa and its allies) in a fine spray to a distance TAERINTERNAL STRUOCGRUREMOF ANTS. 43 of 20-50 cm., or injected into wounds inflicted with the mandibles. Beyer (1890), who has made a comparative study of the development of the poison apparatus in the honey-bee, wasp, Myrmica and Formica, finds that it is smallest in the forms with the largest sting (bee) and largest in forms with only a functionless vestige of this organ. The enlargement and extraordinary convolution of the gland in the Campo- notine is therefore correlated with a degeneration of the sting as an organ of defence and the development of a novel method of using the poison in conflicts with hostile ants and other animals. Apart from a recent paper by Melander and Brues (1906), little has been published on the chemical constitution of the poison of ants in general. These authors find appreciable traces of formic acid, as a Fic. 21. Poison apparatus of a Dolichoderine and a Myrmicine ant. (Forel.) A, Bothriomyrmex meridionalis; B, Myrmica levinodis. a, Sting; b, sting-groove ; c, sting-sheath; d, accessory gland; e, duct of poison vesicle; f, poison vesicle; g, bourrelet-like termination of poison glands; h, poison glands; 7, unpaired, convoluted portion of poison gland; k, film of secretion(?) surrounding bourrelet. rule, only in the Camponotine, that is, in the forms with the pulvinate glands. In this group, as would be expected, the species of Formica head the list with more than twice as much acid relatively to their size as the species of Camponotus. In the Doryline ants (various species of Eciton) the secretion has a very strong and nauseating, fecal odor like that of the lace-wings (Chrysopa). Melander and Brues believe this to be due to leucine, and they state that “these ants are totally blind, and migratory in their habits, so that they must depend almost entirely upon a sense of smell to follow one another about. Thus it 44 | ANTS. can easily be seen how such a strong odor might be developed through the action of natural selection, from the small trace of leucine that is usually present in insect feces.” As I have found a secretion precisely like that of Eciton in certain carnivorous Pheidole (Ph. ecitonodora and antillensis), I infer that its chemical constitution may, perhaps, depend on the diet of the insects. In all ants, both in those with the pulvinate and those with the bour- releted glands, there is present a so-called accessory, or Dufour’s gland (Fig. 20, h, Fig. 21, d), which opens into the duct of the poison vesicle very near its termination. This gland is ventral to the poison apparatus and though of variable form (pyriform, cylindrical or bilobed) is rather uniform in structure throughout the family Formicide. It is a small, elongated sac, with rather thin walls composed of polygonal gland cells enveloped by delicate muscles and tracheze. Several authors have regarded its rather thick, yellowish secretion as a lubricant for the parts of the sting, but Janet has shown that no such lubricant is J necessary. Moreover, the gland is often best devel- oped in virtually stingless ants like the Camponotine. Others have surmised that the secretion is added as a necessary ingredient to the poison. Janet finds that it is alkaline and conjectures that its chief use is to neu- tralize any of the highly acid poison which may happen to adhere to the ant’s own body or remain on the parts of the sting or on the anal circlet after the gland has been dis- charged. He also finds Fic, 22. Repugnatorial glands and vesicles that all the other integu- of worker Bothriomyrmex meridionalis. (Forel.) 2 A, Whole structure seen from above; a, vesicles; mentary glands, except , 9, common orifice of same; g, clusters of unicel- those of the poison appa- lular glands; d, duct; i, intima; m, muscles in é wall of vesicle. B, Single gland cell (c) contain- Tatus, have an alkaline re- ing the convoluted termination of the ductlet (e) action, and believes that in its cytoplasm; d, main duct; t, trachea. K Sah 9’ = a this is important in pre- venting the nest chambers from becoming acid, for the secretions of the poison glands, if allowed to accumulate in a closed cavity, soon THE INTERNAL STRUCTURE OF ANTS. 45 become fatal to the ants. This is easily demonstrated when Campo- notinee are confined in a vial and irritated till they discharge their secretions. But as there seems to be little or no acid in the poison of any species except those belonging to this subfamily, Janet’s con- jecture, at least so far as the accessory gland is concerned, is far from being applicable to all ants. The repugnatorial, or anal glands (Figs. 22 and 23), were dis- covered by Forel. They are present only in the female and worker Dolichoderinzee and coexist with well-developed poison glands of the bourreleted type. They consist of grape-like clusters of large, spher- ical gland-cells, the fine intracytoplasmic ducts of which unite to form a pair of much larger ducts that open into the posterior portions of two large, thin-walled sacs, dorsal to the poison gland and closely applied to each other in the medium sagittal plane of the ant’s body. These sacs have muscular walls and serve as reservoirs for the gland- ular secretion. They have a common opening just dorsal to the anus. Their secretion is quite unlike that of the poison glands described above, being more sticky and having in nearly all Dolichoderine a characteristic odor, which Forel calls the “ Tapinoma odor’’ because it is very noticeabie in the common species of this genus in Europe and North America (7. errati- Others aptly describe very cum and sessile ). the odor as that of ‘‘ rotten cocoanuts.”’ Melander and Brues have studied the oe Fic. 23. through tip worker Bothriomyrmex meri- Sagittal section of gaster of dionalis. (Forel.) — a, Orifice secretion in Jridomyrmex analis (Fore- lius foctidus) and find that ‘when dis- tilled with steam the odor passes over and remains dissolved in the aqueous distillate. Thus freed it retains the very of repugnatorial vesicles; }, anus; c, orifice of poison vesicle; d, orifice of acces- sory gland; e, vaginal orifice ; f, terminal ganglion of ven- tral cord; g, repugnatorial gland of right side. evident odor of rancid cocoanuts. By saponification with potassium hydroxide solution it loses all odor, but on adding dilute sulphuric acid to excess an odor closely re- sembling that of fresh cocoanuts is developed. From this it is quite evident that the odorous principle is an ether of some sort.” During conflicts with other ants the Dolichoderinz smear the secretion of their repugnatorial glands on the bodies of their enemies, and from the behavior of the latter it is evident that the liquid is fatal, or, at any rate, very irritating, and that it constitutes a most efficient protection 46 ANTS. even for the most diminutive and soft-bodied species of /ridomyrme.x, Tapinoma, Azteca, etc. The Circulatory System.—Janet (1902) has studied this system in Myrmica. It comprises, as in other insects, the heart, aorta, hamo- lymph, or blood plasma, amcebocytes, or blood-corpuscles, and several ductless glands of very simple structure. The heart (Fig. 15, ht, Fig. 24, c) is a tube lying in the mid-dorsal region of the gaster and pre- senting five dilatations corresponding with the first to fifth gastric (fourth to eighth abdominal) segments, and each of these metameric regions is pierced by a pair of osteoles provided with valves. The wall of the tube is only a single cell-layer in thickness and the cells of its two halves are in pairs, indicating that they arise from the pairs of embryonic cells which I have called cardioblasts (1893}. There is no layer of muscles enveloping the tube, but very contractile muscle fibrilla are differentiated in the cytoplasm of the cells themselves. The tube is held in place by numerous suspensory filaments and five pairs of so-called aliform muscles, belonging to the first to fifth gastric seg- ments. These muscles are fan-shaped, with their broad ends meeting and uniting in the middle line below the cardiac tube and their pointed ends inserted on the supero-lateral walls of the gaster. Anteriorly the heart is continued through the slender abdominal pedicel and into the thorax as the ‘aorta, a slender non-contractile tube which opens into the head cavity. The blood, as in other insects, is a colorless liquid filling the body cavity or spaces between all the internal organs and containing very small, colorless, amoeboid and nucleated corpuscles. Circulation is effected by the systole and diastole of the heart, the pulsations of which proceed in a wave from its posterior to its anterior end. These move- ments are described as follows by Janet, with the aid of the accompany- ing diagram (Fig. 24, B): “ During systole the aliform muscles (am), the suspensory filaments (sf) and the heart (c) occupy the positions represented by the unbroken lines. In contracting, the aliform muscles shorten, and owing to this shortening, they recede in the middle region from the dorsal integument and take the position represented by the dotted lines. This movement draws down the suspensory filaments attached to the muscles and changes the direction of those attached to the dorsal integument. As these filaments can be but slightly elongated, the changes of position here described are produced, so to speak, entirely at the expense of the elasticity of the cardiac wall, which dilates consid- erably. With this dilatation the valvules move away from the points to which they were applied and the blood streams through the osteoles and fills the heart. The blood, propelled by the contracting heart, pours FHESINTERNAL STRUGCRUGRESOF ANTS. 47 into the head, bathes all the organs and then leaves it through the neck to traverse the whole thoracic cavity in an antero-posterior direction. After having passed through the much constricted peduncle of the petiole and postpetiole, it enters the gaster and flows through two passages, separated by a diaphragm that divides the body cavity into a ventral, or neural, and a dorsal, or visceral, sinus. One current descends through the dorsal, another through the ventral sinus, following the latter to the tip of the gaster. The dorsal sinus, which is very large and supplies the heart with the blood it propels into the head, is thus Fic. 24. Transverse section through heart of Myrmicarubra. (Janet.) A, Through region of rectum; c, heart; sf, suspensory filaments; am, aliform muscle; pce, peri- cardial cells; f, fat-cells; «u, urate-cell; oe, cenocyte; ch, dorsal integument; r, dorsal wall of rectum. 8, Diagram to illustrate position of heart, suspensory filaments and aliform muscle during systole (continuous lines) and diastole (dotted lines). supplied simultaneously by the posterior portion of the postpetiole and the posterior portion of the ventral sinus of the gaster.” Connected with the circulatory system are some four different kinds of cells, which are suspended either singly or in clusters in the blood current. These are the pericardial cells (Fig. 24, pc), the cenocytes (oe), the adipocytes (f), forming the fat body, or corpus adiposum and the urate cells (a2). The pericardial cells are of small size and are 45 ANTS. attached to the suspensory filaments and aliform muscles. In the living insect these cells have an acid reaction. They probably function as ductless glands, taking certain substances from the blood, transforming them and returning them to the circulation in such a form that they can be absorbed and excreted by the Malpighian vessels (Cuénot). Some authors are of the opinion that these pericardial cells also give rise to the amcebocytes, that they constitute, in other words, a hzmato- poetic organ. The cenocytes are glandular cells which arise in seg- mental clusters from the ectoderm of the embryo just behind the tracheal invaginations. In the ants these cells are very small and in the adult scattered about among the fat cells. They are very conspicuous in the young larva and still occupy their embryonic position, but in aged ants, according to Janet, they disappear. Like the pericardial cells they are probably ductless glands, producing some unknown but physiologically important internal secretion. The fat cells form large masses or packets, often filling out all the spaces of the body cavity between the viscera, especially during the larval and pupal stages. As the name indicates, Fic. 25. Longitudinal sections to show valve and method of closing the trachee in Myrmica rubra. (Janet.) A, Last abdominal trachea open; B, closed; o, stigmatic orifice; a, anterior stigmatic chamber; 6b, occluding chamber; c, fixed insertion of occluding muscle; d, mobile insertion of same; e, mobile insertion of opening muscle ; f, occluding muscle; g, opening muscle; h, stiffened portion of trachea; 7, stigmatic or main tracheal trunk. these cells have their cytoplasm filled with fat globules, which are often so numerous that the nucleus is reduced to a stellate or irregular body. Unlike the cenocytes, the fat cells are of mesodermal origin. The urate cells are found singly or in clusters among the fat cells. They are large and opaque, owing to a mass of urate crystals stored in their cytoplasm. They are most easily seen in larve and pupz and may be regarded as a very primitive form of kidney adapted for storing instead of excreting the products of tissue metabolism. THE INTERNAL STRUGHURE.OF ANTS. 49 The Respiratory System.—The trachee of ants are not unlike those of many other insects, as shown by Janet’s studies (1902) of Myrmica and other genera. In all ant-larve there are ten pairs of stigmata or tracheal orifices occurring on the meso- and metathoracic and first to eighth abdominal segments. These stigmata also persist in the adult ant as small, round openings. According to Janet the meta- thoracic pair is closed in the Myrmicine (M/yrmica), but remains open in the Camponotine (Formica) and Dolichoderine (Tapinoma). Each stigmatic orifice leads into a short stigmatic trunk which is furnished with a very interesting valve by means of which it can be closed (Fig. 25). The stigmatic trunks of the thorax and gaster bifurcate in an anterior and posterior direction and the two branches fuse on each side of the body to form a continuous longitudinal trunk. This is very large in the gaster, but much more tenuous in the thorax, where a second pair of more dorsal longitudinal trunks is formed, which, in the queens and males, supplies the wing muscles with air. The gastric trunks dilate and contract with the so-called respiratory movements of the external skeleton and in this manner the air is pumped into and out of the finest ramifications of the trachee. The gastric trunks are united by ventral, transverse, anastomosing tracheze and also give off segmental dorsal branches which break up into finer and finer ramifi- cations to supply the various viscera. The Muscular System.—For an account of this system in ants the reader must be referred to the articles of Janet, Nassonow, Berlese and Lubbock, as the subject is one of too great complexity and detail to be treated within the limits of this work. Still there is an ontogenetic change in the muscular system of the adult queen ants, which cannot be passed over, as it is of no little ethological importance. I have often observed that aged, dealated queens will float when placed in water or alcohol, and that when the thorax of immersed specimens is pierced with a needle, large bubbles of air escape, showing that the wing mus- cles must have atrophied. Janet (1906, 1907a, 1907D). has studied the histological changes, which lead up to this peculiar condition in Lasius niger, and finds that the muscles, which in the virgin queen fill up most of the thoracic cavity and are well-developed and beautifully striated till the marriage flight occurs, are completely broken down within a few weeks after dealation (Fig. 26). He maintains that this sarcolysis is not due to phagocytes devouring the muscles piece-meal, but that the blood corpuscles (amcebocytes) which creep in among the fibrille take up spontaneously the dissolving muscle substances and convert these within the cytoplasm into fat globules and albuminoid granules. Thus the amcebocytes become adipocytes and replace the muscle fibrillze ( Fig. 5 50 ANTS. % 26, B). Somewhat later the amcebocytes discharge the fat globules and albuminoid granules from their cytoplasm into the blood plasma, which from being a limpid liquid assumes a more granular appearance as it becomes charged with more and more of the metabolized products of sarcolysis. Eventually nothing remains of the muscles but their sheaths, and the thoracic tracheze become greatly enlarged, which accounts for the floating of the insect in liquid and the emission of air bubbles when the thorax is pricked under water (lig. 26,D). The fatty and albuminoid substances derived from the histolyzed wing-muscles are carried in the blood to the abdomen, where they are taken up by the Fic. 26. Wing muscles of Lasius niger queen, to show their degeneration after nuptial flight. (Janet.) A, Sagittal section of thorax and petiole of queen immedi- ately after nuptial flight; B, ten months later; C, transverse section through meso- + thorax on day of nuptial flight; D, same five weeks later; m, longitudinal vibratory . muscles; 7, transverse vibratory muscles; b, blood coagulated and charged with the products of muscle dissolution ; t, trachee. ; a ovaries and, no doubt, contribute greatly to the growth of the eggs. The queen ant thus resembles the salmon, in which, according to ~ Miescher, there is at the time of sexual maturity a conversion of part of the trunk musculature into substances that are appropriated by the reproductive cells and further their growth and maturation. CHAPTER Ie fH INTERNAL STRUCTURE OF ANTS= (CONCLUDED: ) “Tt is certain that there may be extraordinary activity with an extremely small absolute mass of nervous matter; thus the wonderfully diversified instincts, mental powers, and affections of ants are notorious, yet their cerebral ganglia are not so large as the quarter of a small pin’s head. Under this point of view, the brain of an ant is one of the most marvellous atoms of matter in the world, perhaps more so than the brain of man.’—Charles Darwin, “ The Descent of Man.” The Nervous System.—The structure of the central nervous system is best considered in connection with the primitive segmentation as this is revealed in the embryonic ant. As stated in a previous chapter, the body of the ant, like that of all other true insects ( Pterygogenea), consists of a series of twenty metameres, or segments. The first and last of these are peculiar in certain respects and have been called the acron and telson respectively. In the embryo the ectoderm of the mid-ventral portion of each segment (except the telson) thickens and gives rise to a pair of ganglia that soon split off from a thin surface layer of cells which then become the ventral integument. The ganglia of each segment are closely approximated and connected with each other by a pair of commissures, while the ganglia of successive segments are united by pairs of connectives which therefore run longitudinally. Later these connectives lengthen, and as the body grows more rapidly than the ganglia, we find the latter forming a chain extending through the ventral region of the head, thorax and abdomen. Not only do many of the ganglia thus become rather widely separated from one another, but there is also a tendency for some of them to fuse together and make larger masses. Thus the ganglia of the first (acron), second (antennary) and third (intercalary) segments, known respectively as the proto-, deuto- and tritocerebrum of Viallanes, fuse to form the brain, or supracesophageal ganglion. As the latter term indicates, this mass is dorsal to the cesophagus, and therefore preoral. This is true, however, only of the protocerebrum of the embryo, the two other pairs of ganglia being postoral at first, but moving forward and becoming preoral before the hatching of the larva. The ganglia of the mandi bular, maxillary and labial segments also unite to form a single mass, the subeesophageal ganglion, which, as its name implies, lies behind the gullet. This ganglion is united to the brain by means of a pair of circumcesophageal connectives. The pro- and mesothoracic ganglia 51 52 ANTS. remain distinct and lie in their respective segments even in the adult ant. The first (mediary) and second abdominal ganglia, however, are drawn up into the metathorax and fused with the metathoracic ganglion, and the ganglion of the third abdominal segment comes to lie in the petiole (second abdominal segment) (Fig. 13,ag*). The fourth, fifth, sixth and seventh abdominal ganglia retain their independence, but the latter two are close together and are immediately succeeded by the fused, eighth to tenth, which constitute a single ellipsoidal mass, terminating the chain and in the adult ant lying some distance in front of the pos- terior end of the gaster (Fig. 13,ag*""!). The central nervous system of the adult ant therefore presents only eleven ganglionic masses, formed by condensation of the primitive nineteen. [For convenience in descrip- tion, this system may be divided into the brain and ventral cord, and these, with their ganglia and peripheral nerves, may be briefly consid- ered before we take up the sympathetic nervous system and the sense organs. The Brain.—I agree with those authors, who, following Rabl- Ruckard (1875), restrict the term “ brain” to the supracesophageal gan- glion, although it must be admitted that in ants and other Hymenoptera the circumcesophageal connectives are so short and robust that the supra- and subcesophageal ganglia seem to form but a single mass per- forated by the gullet. Leydig called this whole mass the brain; Janet suggests for it the term ‘“‘ encephalon.” The three primitive pairs of ganglia, constituting the proto-, deuto- and tritocerebrum, though inti- mately fused, can still be recognized in the adult brain, at least by their innervations, but the three apparent segments indicated by the outline of the organ do not correspond to the primitive segments. The proto- cerebrum is the largest single pair of ganglia in the central nervous systems and differs markedly from all the others in form and com- plexity of structure. It is broadest in the middle where it is continued on each side into the optic nerves (Figs. 28-30, on) to the compound eyes. The portion between the optic nerves may be called the mid- protocerebrum. It is flanked on each side by an optic ganglion (0g) of complicated structure and projects anteriorly as a pair of rounded frontal lobes (pb). From the notch between these, nerves are given off to the three stemmata, or ocelli (oc), when these organs are present. As the median stemma has two nerves, it must have been a paired struc- ture originally. The deutocerebrum is represented by a pair of rounded protuberances known as the olfactory lobes (ol), which are morpho- logically behind, though apparently somewhat in front of the other brain segments. According to Janet, each antenna is supplied with six nerves which arise close together from each olfactory lobe (Fig. 27). These THE INTERNAL STRUCTURE OF ANTS. 55 are: first, the infero-internal sensory nerve (nani), second, the supero- external sensory (ans), third, the chordotonal (to acho), fourth, the nerve to the anterior (adductor) muscles of the scape, fifth, the nerve to the posterior (abductor) muscles of the scape (msc), and sixth, a nerve which supplies the little muscles in the funicular joints (mf). The tritocerebrum is so much reduced that it is represented only by a pair of small bodies, concealed under the olfactory lobes and connected with each other by a slender commissure, which, however, passes under the cesophagus, thus indicating the originally postoral position of this portion of the brain. Each tritocerebral lobe gives off a nerve which soon subdivides into two branches, one (Fig. 27, cnf) going to the Fic. 27. Sagittal section of head of worker Myrmica rubra. (Janet.) acho, Antennary chordotonal organ; cnf, connective of frontal ganglion; art, antennary articulation; mans, superior antennary nerve; nani, inferior antennary nerve; nf, funicular nerve; nsc, nerve to scape; nir, labral nerve; soph, sense-organs of pharynx; mph, inferior dilator muscle of pharynx; no, nerves to ocelli; hcs, hypocerebral gang- lion; mam, adductor muscle of mandible; /g, labial sympathetic ganglion; Jn, labial sympathetic nerve; m/l, labial nerve; sol, labial sense-organs; nm, maxillary nerve; nm, mandibular nerve; s, portions of salivary gland; cn, connective between sub- esophageal and prothoracic ganglion; mal, adductor muscle of labium. Remaining letters as in Fig. 13. frontal ganglion (to be described below in connection with the sympa- thetic nervous system) the other again subdividing to innervate the labrum and the wall of the pharynx (nlr). The minute structure of the brain, with its ganglion cells and fibers, the former comprising the deeply-staining, the latter the more achro- matic portions, or “ Punktsubstanz” of authors, is too intricate to be considered in the present work. For these details the reader must be referred to the papers of Dujardin (1850), Leydig (1864), Rabl- On oh ANAS? Ruckard (1875), Brandt (1876), Dietl (1876), Flogel (1878) and INenyon (1896). I cannot, however, omit consideration of two regions of the ant brain, namely, the frontal and olfactory lobes, which have fre- quently been compared with the cerebrum and olfactory lobes of verte- brates. The frontal lobes contain two pairs of extraordinary structures, the pedunculate, or mushroom bodies ( Figs. 28-30, pb), each consisting of a cup-shaped mass of nerve-fibers, the calyx, with a stem formed of a stout bundle of similar fibers which run back into the mid-protocere- brum. The calyces are embedded in a dense accumulation of minute, deeply-staining ganglion cells, which form the bulk of the frontal lobes and evidently give rise to the fibers of the calyces and their stems. Each olfactory lobe consists of a central fibrous portion containing peripherally a large number of round bodies of still denser fibrous struc- ture and a cortical portion made up of larger ganglion cells. The round bodies have been called glomeruli from their resemblance to the well- known structures in the olfactory lobes of vertebrates. Since the antenne of ants are mainly organs of smell, the occurrence in the deuto- cerebrum of structures so much like those in the olfactory organs of vertebrates is not without interest. Fic. 28. Heads of worker (4), female (B), and male (C), Lasius brevicornis, drawn under same magnification, with brain, eyes and ocelli viewed as transparent objects. (Original.) oc, Median ocellus; pb, pedunculate bodies; og, optic ganglion ; on, optic nerve; ol, olfactory lobe; an, antennary nerve. It has been customary since the time of Dujardin to compare the pedunculate bodies with the cerebrum of vertebrates and to regard them as an organ of intelligence. Dujardin based his opinion on the fact that these bodies are largest and most elaborately developed in the social Hymenoptera. Leydig and Rabl-Rtickard expressed a similar opinion. TAZ INTERNAL STRUGLUBE OF ANTS. 55 Forel (1874) first observed that these bodies are largest in worker ants, smaller in the queens and vestigial in the males, and as the worker was supposed to be the most, and the male the least, intelligent, this was regarded as additional evidence in favor of Dujardin’s opinion. The condition described by Forel for the ants was affirmed by Brandt (1876) for the social Hymenoptera in general.. More recently Kenyon (1896), after an elaborate study of the bee’s brain, has reached a similar conclu- sion. Hesays:‘Allthat I am able at present to offer is the evidence from the minute structure and the relationships of the fibers of these bodies. This seems to be of no inconsiderable weight in support of the general idea started by Dujardin. For in connection with what was made known by Flogel and those before him and has since been confirmed - and extended by other writers, one is able to see that the cells of the bodies in question are much more specialized in structure and isolated from the general mass of nerve fibers in those insects where it is gener- ally admitted complexity of action or intelligence is greatest.” He also cites experiments of Binet (1894) which tend to show that in insects “when connections between the dorso- and ventro-cerebron are de- stroyed, the phenomena afterwards observed are similar to those seen in a pigeon or mammal when its cerebral hemispheres are removed.” In support of Dujardin’s hypothesis, Forel has published a series Fic. 29. Heads of worker (A), female (B), and male (C), Formica fusca, drawn under the same magnification, with brain, eyes and ocelli viewed as transparent objects. (Original.) Letters as in Fig. 28. of figures of the brain of the worker, female and male of the European Lasius fuliginosus, drawn to the same scale (1904). I here introduce a similar series of the American L. brevicornis (Fig. 28). Comparison of these figures shows that the pedunculate bodies do, indeed, vary quite independently of other portions of the brain and in the manner 50 ANTS. noticed by Forel. In a similar series of Formica glacialis (Fig. 29), however, there are no such striking differences in the three phases. The pedunculate bodies (pb) are as highly developed in the female as they are in the worker, and they can hardly be said to be vestigial in the male. In Pheidole instabilis (Fig. 30), too, the female and soldier have well-developed pedunculate bodies, though these seem to be insig- nificant in the male. While, therefore, the male brain in all these species, apart from the huge development of its optic ganglia and stem- matal nerves, is manifestly deficient, I doubt whether we are justified in regarding the brain of the female as being inferior to that of the worker. It is true that the worker brain is relatively larger, notwith- standing the smaller eyes and stemmata, or the complete absence of the latter, but I would interpret this greater volume as an embryonic char- Fic. 30. Heads of soldier (A), worker (B), female (C), and male (D) of Pheidole instabilis, drawn under the same magnification, with brain, eyes and ocelli viewed as transparent objects. (Original.) Letters as in Figs. 28 and ao. acter. The worker is, in a sense, an arrested, neotenic or more imma- ture form of the female, and it is well known that the volume of the brain and of the central nervous system in general is much greater in proportion to that of the body in embryonic and juvenile than in adult animals. Forel was probably influenced in his interpretation by the view, so long accepted, but now abandoned by myrmecologists, that the LAE INEERNAL STRUCTURE MOr ANTS. 57 queen ant is a degenerate creature like the queen bee. In future chap- ters of this work I shall have occasion to show the untenability of this supposition in the light of recent observations." The foregoing considerations do not, of course, invalidate Dujardin’s hypothesis. It is also true that the conditions. throughout the insect class point to a direct correlation between the development of the pedunculate bodies and the instinctive activities, but a study of these structures in other Arthropods is not so unequivocal. Turner, ina contribution from my laboratory (Zool. Bull., 11, 1899, pp. 155-160), showed that the pedunculate bodies not only occur in Crustacea ( Cam- barus) and the king crab (Limulus), but also in annelids (Nereis, Lepidonotus, Polynoé), and that they reach their greatest development in the king crab. In this animal they are a much-branched mass, which forms the bulk of the brain, and as Turner says, “ simulates in struc- ture the vertebrate cerebellum.” On Dujardin’s hypothesis we should therefore expect the king crab to be the most intelligent of arthropods. 3ut although no one will deny that this animal has had ages in which to acquire a high psychical endowment, it shows no signs of having profited by its opportunities. It would seem, therefore, that the pedun- culate bodies must be subjected to a more critical morphological and physiological study before they can be accepted as the insectean ana- logue of the human fore-brain. The Ventral Nerve-Cord.—Although the subcesophageal ganglion, like the brain, consists of three fused ganglia, these have become less modified and are clearly discernible in sagittal sections (Fig. 27). The rule that each ganglion of the central nervous system innervates only the segment in which it originated in the embryo also holds good of the suboesophageal ganglion. We find that it sends off three pairs of nerves, containing both motor and sensory fibers. The first pair (17), which is stouter than the two others, innervates the sense organs and muscles of the mandibles, and the second (mmx) and third (nl) the corresponding parts of the maxille and labium respectively. The three thoracic ganglia, owing to the voluminous and complicated leg and wing muscles which they innervate, are much larger than the abdominal ganglia. Each gives off a pair of crural nerves to the legs and, the prothoracic ganglion also supplies a chordotonal organ near its antero-ventral end (cho). From "Comparison of my figures of L. brevicornis with Forel’s of L. fuliginosus reveals the fact that the female brain of the latter species is no larger than that of the worker, whereas in brevicornis there is a slight difference in size in the corresponding phases. It appears from recent observations of De Lannoy (1008) and Emery (1908) that the queens of L. fuliginosus are but little larger than the workers and are probably temporary parasites (see Chapter XXIV). This may at least partially account for Forel’s finding the brain of the female ant inferior in organization to that of the worker. 55 ANTS, the mesothoracic ganglion arises a pair of so-called alar nerves, which innervate the great longitudinal and transverse vibratory muscles of the wings. The musculature of the epinotum, petiole and postpetiole is supplied by the first to third abdominal ganglia, the two first of which are fused with the metathoracic ganglion. The fourth abdominal (first gastric in the Myrmicide) remains in the segment to which it belongs, but lies at its extreme anterior edge. As both this and the succeeding gastric ganglia have been secondarily drawn forward, the pairs of nerves which they give off run obliquely backward, to their innerva- tions. Janet (1902) has found that each of the two nerves arising from each of the four anterior gastric ganglia divides into a dorsal and a ventral trunk. The former sends off a sensory nerve to the corre- sponding dorsal quadrant of the segment and three motor nerves to its three muscles, the latter a sensory nerve to the ventral quadrant and six motor nerves to as many muscles. The sensory nerves go to the sense-hairs of the integument. The terminal (fifth gastric) ganglion, formed, as we have seen, by a fusion of the eighth to tenth abdominal ganglia, sends off four pairs of nerves, the first to the sense organs and muscles of the stylets of the sting, the second to the sense organs and muscles of the gorgeret, the third to the anal sphincter and papilla. and the fourth to the walls of the hind gut. The Sympathetic.—This consists of several minute ganglia and nerves connected with the central nervous system and supplying the musculature of the alimentary tract. It is, to judge from Janet’s account of Myrmica (1902), well developed in ants and not unlike that of other insects. It may be said to embrace two systems, one supraintestinal and supplying the dorsal and lateral portions of the digestive tract, the other subintestinal and lying beneath the intestine and above the ventral nerve-cord. The supraintestinal system may be divided into an unpaired and a paired portion. The former begins in the small frontal ganglion (Fig. 27, fgl), which lies anterior to the brain, to which it is joined by a pair of connectives. According to Janet, these connectives arise in the protocerebrum, but other authors believe that they are of tritocerebral origin. The frontal ganglion sends a pair of coalesced nerves to the supero-anterior wall of the pharynx and a much stouter unpaired nerve, known as the recurrens (ren), downward and backward along the dorsal wall of the pharynx, to a ganglion (the hypocerebral, ics), which lies on the cesophagus just beneath the protocerebrum. Besides innervating the cesophagus this ganglion sends back a pair of long, slender connectives (sym) along the sides of the cesophagus and crop to the point where the latter contracts to form the gizzard. Here each connective termi- THE ANTERNAL STRUCTOURESOP ANTS. 59 nates in a so-called pre-stomachal ganglion, which innervates the sur- rounding wall of the crop and gizzard. The paired supraintestinal sympathetic has an anterior and a posterior portion. The former con- sists of the cesophageal ganglia, which lie on each side of the hypo- cerebral ganglion. They are united with this by commissures and with the tritocerebrum by connectives, and innervate the sides of the cesoph- agus and crop. The posterior portion of the paired system is very imperfectly known. Janet maintains that the fourth pair of nerves from the terminal ganglion of the ventral cord turns forward and innervates the posterior portion of the digestive tract in somewhat the same manner as the anterior portion is innervated by the brain through the frontal and cesophageal ganglia. He, therefore, calls these the proctodeal recurrent nerves. The subintestinal sympathetic system of Myrmica comprises a series of minute, unpaired, metameric ganglia connected with several of the ganglia of the ventral cord. This system, too, both in ants and in other insects, is imperfectly known. The Sense-Organs.—The sense-organs of ants, like those of insects in general, are modifications of the integument and the terminations of sensory nerves. Hence there can be no sense-organs in the interior of the body unless they have been carried in secondarily on infoldings of the integument. As there are no openings anywhere in the chitinous investment of the insect’s body, except those at the anterior and pos- terior ends of the midgut, the nerve terminations are never freely exposed on the surface, but always covered with at least a very delicate layer of chitin. The number and diversity of sense-organs in insects is very great, but nevertheless, attempts have been made to trace them all back to a common primitive type. One of the most recent of these attempts is that of Berlese (1907) who finds that nearly all these organs admit of hypothetical derivation from a “ proteesthesis,”” a sensilla, or sense-bud, consisting of one or a few chitin-secreting hypodermal cells, a gland cell and a nerve cell. It is possible to show that this type of structure keeps recurring in the various sense-organs of even such highly-specialized insects as the ants. Tactile (Trichodeal) Sensilla.—As stated in a previous chapter, ants are usually covered with hairs, which are coarse and long on the body and shorter and denser on the legs and especially on the antenne. As all of these hairs are movably articulated to the general chitinous integument and are provided with fine nerve terminations, they are universally regarded as tactile sensilla, although they also aid in the removal of the larval or pupal skin during ecdysis, for they are at first bent at their bases and applied to the chitinous layer to which they belong, but later, in becoming erect, loosen and push the overlying 60 ANTS. exuvia away from the surface of the body. In section each hair is seen to be a hollow chitinous tube, closed at its apex and open at its base, which is bulbously swollen and fits into a ring-shaped thickening Fic. 31. Trichodeal and campaniform sensille of ants. (Janet.) A, Trichodeal sensilla from proximal border of fore coxa of female Lasius niger, X 1,000; B, single sensilla from the group represented in A, X 2,000; C, longitudinal section through tip of middle coxa, trochanter and base of femur of Myrmica rubra worker, * 100; D, cross-section of tip of hind tibia of M. rubra, X 200; E, F and G, sections of cam- paniform’ sensillz from tip of mandibles of M. rubra; H, campaniform sensille near articulation of wing of female Camponotus herculeanus, X 500; t, chitinous hair; c, chitinous integument; h, hypodermis; n, nerve-termination; w, bell, or umbrella, in the center of which the nerve terminates; x, groups of campaniform sense-organs; 1, fossa or pit in the chitinous integument; p, pore in same. a, of the chitinous integument (Fig. 31, 4, B, Fig. 32, b). This tube is secreted by one or more large hypodermal cells, and a delicate nerve fiber extends up into its base. When the tip of the hair touches an LE AINTERNAL. STRUCLORESOP ANTS. 61 object the tactile impulse is evidently transmitted to the nerve through the movement of the bulbous base in its cup-shaped socket. There is, therefore, no essential difference between the tactile function of the hairs of ants and the analogous structure in mammals. Olfactory and Gustatory Sensilla.—It seems to be impossible to distinguish between these organs in insects, although it may be asserted that the organs of smell are situated mainly or exclusively on the antennze, whereas, those of taste are found on the mouth-parts, espe- cially on the maxille and labium and their paipi. The antennary sensille of ants have been studied by Hicks (1859), Leydig (1860), Forel (1874, 1884), Lubbock (1877), Kraepelin (1883), and more recently by Krause (1907). From the researches of these authors it appears that in addition to numerous tactile hairs like those described above, there are four more modified types of sensillae which have been more or less definitely connected with an olfactory function. These do My SOY /B pa Ly Up HAZ oto (—s - Z Z = = oa oA ee eenace=as. Fic. 32. Subdiagrammatic section of the antennal sense-organs of an ant. (Kraepelin.) a, Basiconic sensilla; b, trichodeal sensilla, or tactile hair; c, cceloconic sensilla; d, ampullaceous sensilla; f, flask-shaped sensilla; g and h, openings of same on surface of antenna; i, gland cells; k, chitinous integument. not occur on the scape and first funicular joint of the antennz, but only on the remaining joints and especially on the enlarged terminal joint, which possesses by far the greatest number of all the various sensille. The following is a very brief description of these extra- ordinary structures: (a) Clubs of Forel (now called basiconic sensilla by Berlese).— These resemble the tactile hairs, but are conical and immovable at the base and their chitinous investment is exceedingly thin (Fig. 32, a). What corresponds to the cavity of the hair contains a dense bundle of delicate protoplasmic threads, which are prolongations from as many 62 ANTS. large elliptical cells situated in the hypodermis. These cells form a compact mass, formerly supposed to be a ganglion, but now interpreted as a cluster of unicellular glands that secrete a liquid through the thin chitinous cap of the organ onto the surface of the antenne. It is, indeed, difficult to conceive such sensilla as having an olfactory function unless their exposed surfaces are moist like the olfactory organs in the mucous membranes of vertebrates. The nerve termina- tion to the basiconic sensilla applies itself to the cluster of gland cells and then breaks up into delicate branches that pass around and between the latter and up into the conical portion of the organ. (b) Clubs Lying in Elliptical Pits (cceloconic sensillee of Berlese ). —These may be derived from the preceding type by supposing that the conical hair has come to lie horizontally and to be enclosed in an elon- gated cavity in the chitinous integument (Fig. 32, c). The cellular structure of the organ is essentially the same as that of the basiconic sensillze. Champagne-cork Organs of Forel (ampullaceous sensille of Berlese).—These evidently represent a further modification of the cceloconic type, on the supposition that the hair becomes smaller and more erect and the pit in which it is enclosed becomes circular, much deeper and opens on the surface of the body by means of a small pore (Bigs 22 .00))8 (d) Flask-shaped Organs of Lubbock and Forel.—Hicks (1859) was the first to describe these extraordinary organs in M/yrinica, but Forel and Kraepelin have given a more detailed account of their struc- ture. They are really an extreme form of the ampullaceous sensilla, and may be derived from this by supposing that the chitinous ampulla has become enormously lengthened and attenuated till it forms a narrow sac enclosing the conical hair and connected with the pore in the integu- ment by means of a slender tube running more or less parallel with the surface of the antenna (Fig. 32, g,h). That these sensilla have devel- oped from those of the preceding type (c) is shown by the existence of transitional forms both in ants and in other Hymenoptera. The cellular portions of all these forms of ampullaceous sensillz are essen- tially the same as those of types a and b. The gustatory sensillz, situated on the mouth-parts ad including those in the terminal joints of the palpi, though resembling the anten- nary sensillz, in general reproduce only the more primitive of the above-mentioned types, that is, those most like the typical tactile and basiconic sensilla. The more specialized ampullaceous types are found only in the antenne. The Chordotonal Organs.—Recent studies have shown that these FHETINTERNAL .STRUCTURE OF ANTS. 63 structures, which are present in a great many insects, even in the larval stages, are typically compact, spindle-shaped bundles of sensille, each consisting of a chitin-secreting gland and a nerve cell. These cells are arranged in a series at an angle to the integument and are stretched, like a tendon, across a cavity between opposite points in the cuticle, or between a point in the cuticle and some internal organ. The gland cell secretes and retains within its cytoplasm a peculiar cone or rod, known as the scolopal body. The chordotonal organs are supposed to be auditory in function, because they are most elaborately developed in the stridulating Orthoptera (crickets and katydids), and because their structure would seem to be adapted to respond- ing like the chords of a musical instrument to delicate vibrations. In ants the development of these sense-organs is greatly inferior to that of the Orthoptera just mentioned, but they are nevertheless very easily seen when one knows exactly where to look for them. They were first detected by Lub- DockseC13877,)) “it? the proximal portion of the fore tibie of Lasius flavus, Myrmica rugi- nodis and Pheidole me- gacephala. He pointed Fic. 33. Chordotonal organs in tibie of Myrmica out their resemblance to "2" worker. (Janet.) A, Longitudinal section of fore tibia; B, cross-section of same; C, cross-section the subgenual chordo- of middle tibia; D, cross-section of hind tibia; a. tonal organs of Orthop- chordotonal organ; 6, internal fossa; ¢, small; d, large trachea; e, nerve; f, muscle; g, septum; h, scolopal bodies; i, ganglion cells; k, distal nuclei. tera, discovered by von Siebold in 1844, but al- though he fancied he could discern some of their minute structure, his account and figure are very primitive. The matter was re-investi- gated by Graber (1882), who found the organs in Solenopsis, Myrme- cina and Tetramorium, and showed that they occur not only in the fore but also in the middle and hind tibiz, that they contain scolopa! bodies and are also in other respects typical chordotonal organs. 64 ANTS. Janet (1904) has recently studied their structure with great care, and has not only added many details to those seen by his pre- decessors, but has also discovered a number of less conspicuous chordotonal organs in other parts of the ant’s body. He finds a pair in the head at the base of the antenne (Fig. 27, acho), one in the prosternum, just under the prothoracic ganglion (cho), with which it is connected by short nerves, a similar pair in the metasternum and two pairs, one in the petiole and another in the postpetiole, which lie near the tracheal stigmata and are innervated by the ganglia of their respective segments. Eight pairs of chordotonal organs have, therefore, been seen in the ant’s body, but it is not improbable, as Janet suggests, that others exist, for such minute and recondite objects are very easily overlooked even in well-prepared sections. I find that the tibial organs (Fig. 33) are very easily seen in light-colored ants that have been simply mounted in alcohol, and that they are clearer in males than in workers or females. In clove oil, or Canada balsam, however, the structures are seen only with difficulty and after they have been located in alcoholic specimens. The Johnstonian Organ.—This peculiar structure, first described by Johnston in 1855, and since carefully investigated by Child (1894), is very similar to the chordotonal organs. It is found only in the second antennal joint of insects and seems to reach its highest development in certain Orthorrhaphous Diptera (gnats). Child found it also in the Hymenoptera (Formica, Vespa, Bombus) and Berlese has published some good figures of it in the hornet. I find that it is decidedly larger in male than in worker and female ants, especially in those genera like Pheidole and Solenopsis, in which the males have an unusually swollen or globular second antennal (first funicular) joint. Janet seems to have overlooked the Johnstonian organs in the Myrmuica, which he has studied so exhaustively. In section the organ is seen to consist of a variable but considerable number of sensille differing but slightly from those of the chordotonal organs, and also containing scolopal bodies. These sensille are stretched more or less parallel with the long axis of the funiculus, through the cavity of the second joint. Their distal or hypodermal ends are attached to the articular membrane between the second and third joints, while their proximal ends are innervated by a portion of the antennal nerve. They form a compact cylinder enclos- ing the remainder of the nerve which passes on into the more distal antennal joints. Both Johnston and Child are inclined to regard the sense-organs under discussion as auditory, although the latter believes that their more primitive function is tactile. As will be shown in —— THE-INTERNAL STRUCTURE OF ANTS. 65 Chapter XXVIII, the auditory and tactile sensations of insects are not sharply distinguishable. The Campaniform Sensill#.—These problematic organs have a very simple structure, consisting of a thin, bell- or umbrella-shaped piece of the chitinous cuticle forming the floor of a cavity in the much thicker, undifferentiated chitinous layer of the integument (Fig. 31, C-H). This cavity is narrowed externally and usually, but not always, opens on the surface by means of a small pore (Ep). ” 3 her: (Photograph by J. G. Hubbard and O. S. Strong.) a, Mother queen of colony b, male. BEE DEV ELOPMENTAGEGSANT S:. $3 as long or even longer in many species of Camponotus and Prenolepis, whose sexual forms do not mate till the following spring. The lon- gevity of the workers is certainly much greater than that of the males. Lubbock (1894, p. 12) had workers of Formica cinerea that lived nearly five years, workers of I’. sanguinea that had lived at least five years, and some individuals of F. fusca and Lasius niger that attained an age of more than six years. That the workers of the Myrmicine are almost or quite as long-lived may be inferred from the fact that Miss Fielde has kept those of 4. fu/va under observation for a period of three years. But even greater than the longevity of the worker is that of the female, as would be expected from the larger size and vigor of this caste. Janet (1904, p. 42-45) records the age of a female Lasius alienus as fully ten years, and Lubbock kept a female F. fusca alive from December, 1874, till August, 1888, ““ when she must have been nearly fifteen years old, and, of course, may have been more. She attained, therefore, by far the greatest age of any insect on record.” F Closely related to the longevity of adult ants is the question of their resistance to adverse conditions. On this subject, which is of considerable importance in connection with the economic treatment of these insects, Miss Fielde has published (1901 to 1905) a number of interesting and painstaking observations. Although the optimum temperature for our northern ants lies between 70° and 80° F., the minimum and maximum to which they can be subjected and still sur- vive, are very widely separated. Miss Fielde froze females, workers and a brood of Aphenogaster fulva for twenty-four hours at —5° C. (23° F.). The insects were then gradually thawed and all survived. ven the frozen eggs, larve and pupz subsequently developed in a normal manner. When the temperature was raised to 30° C. (86° F.) the ants began to- show signs of discomfort, at 35° C. (96° F.) the smallest individuals swooned, and even the most vigorous ants with which she experimented succumbed after two minutes’ exposure to 50° C. (122° F.). It has been known for some time that female ants can go without food for the greater part of the year while they are founding their colonies. Miss [Fielde has demonstrated that large workers can fast for almost equally long periods. She succeeded in keeping F. subsericea and Camponotus americanus workers alive with- out food for from 7 to 9 months. Ants are also able to endure long submergence in cool or cold water. Miss Fielde found that Lasius latipes survived 27 hours of this treatment; C. pennsylvanicus, 70 hours, and Aphenogaster fulva eight days! This explains how ants that sometimes nest in the beds of streams, like the Texan Pogonomyr- \dult worker larve, semipupz, and nude and covered pupze in various entation of Formica < 2. (Photograph by J. G. Hubbard THE DEVELOPMENT OF -ANTS. 8 Nn mex barbatus, can survive a flood of several days’ duration. She did not test the resistance of ants to drought, but that this is considerable in many species is shown by the rich ant-fauna of many deserts like the Sahara and the deserts of the Southwestern States and northern Mexico. Miss Fielde also found that ants exhibit considerable resist- ance to the action of very violent poisons such as corrosive subli- mate, potassium cyanide and carbolic acid. Their tenacity is best shown, however, in the number of days they are able to live after severe maiming, like decapitation. Janet (18989, p. 130) kept a be- headed F. rufa alive for 19 days, and Miss Fielde kept a beheaded worker of C. pennsylvanicus alive for 41 days. And this ant walked about to within two days of its death! In their experiments Janet and ‘Miss Fielde found that the males are least, the females most resistant to adverse conditions, and that the vitality of the workers varies directly as their size. These facts, with others to be produced in the sequel, show that ants are made of remarkably tenacious protoplasm. Chained to the earth as they are, they have come to adapt themselves perfectly to its great thermal vicissitudes, its droughts and floods, and its precarious and fluctuating food-supply. CHAPTER VE POLYMORPHISM. “Ce peuple de Pygmées, de Troglodytes, est, en effet, digne de toute notre admiration. Peut-on voir une société dont les membres qui la composent aient plus d'amour public? qui soient plus désintéressés? qui aient pour la travail une ardeur plus opiniatre et plus soutenue? Quel singulier phénoméne! Je ne vois dans la trés-grande majorité de ce peuple que des étres sourds a la voix de l’amour, incapables méme de se reproduire, et qui gottent néanmoins le senti- ment le plus exquis de la maternité, qui en ont toute la tendresse, qui ne pensent, n’agissent, ne vivent en un mot que pour des pupilles dont la Nature les fit tuteurs et nourriciers. Cette république n’est pas sujette a ces vicissitudes de formes, a cette mobilité dans les pouvoirs, a ces fluctuations perpétuelles qui agitent nos républiques, et font le tourment des citoyens. Depuis que la fourmi est fourmi, elle a toujours vécu de méme; elle n’a eu qu'une seule volonté, qu'une seule loi, et cette volonté, cette loi ont constamment pour base Vamour de ses semblables.”—Latreille, “ Histoire Naturelle des Fourmis,” 1802. There is a sense in which the term polymorphism is applicable to all living organisms, since no two of these are ever exactly alike. But when employed in this sense, the term is merely a synonym of “ varia- tion,” which is the more apt, since polymorphism has an essentially morphological tinge, whereas variation embraces also the psychological, physiological and ethological differences between organisms. In zoology the term polymorphism is progressively restricted, first, to cases in which individuals of the same species may be recognized as constituting two or more groups, or castes, each of which has its own definite characters or complexion. Second, the term is applied only to animals in which these intraspecific groups coexist in space and do not arise through metamorphosis or constitute successive generations. Cases of the latter description are referred to “ alternation of genera- tions’? and “seasonal polymorphism.” And third, the intraspecific groups of reproductive individuals existing in all gonochoristic, or separate-sexed Metazoa are placed in the category of “sex” or ‘sexual dimorphism.” There remain, therefore, as properly represent- ing the phenomena of polymorphism only those animals in which characteristic intraspecific and intrasexual groups of individuals may be recognized, or, in simpler language, those species in which one or both of the sexes appear under two or more distinct forms. As thus restricted polymorphism is of rare occurrence in the animal kingdom and may be said to occur only in colonial or social species where its existence is commonly attributed to a physiological division 86 POLY MORPHISM. $7 of labor. It attains its clearest expression in the social insects, in some of which, like the termites, we find both sexes equally polymor- phic, while in others, like the ants, social bees, and wasps, the female alone, with rare exceptions, is differentiated into distinct castes. This restriction of polymorphism to the female in the social Hymenoptera, with which we are here especially concerned, is easily intelligible 1f it be traceable, as is usually supposed, to a physiological division .of labor, for the colonies of ants, bees and wasps are essentially more or less permanent families of females, the male representing merely a fertilizing agency temporarily intruding itself on the activities of the community at the moment it becomes necessary to start other colonies. Fic. 50. Males of Aphicnogaster picea. (Photograph by J. G. Hubbard and Dr. O. S. Strong.) We may say, therefore, that polymorphism among social [lymenoptera is a physical expression of the high degree of social plasticity and efficiency of the female sex among these insects. This is shown more specifically in two characteristics of the female, namely the extra- ordinary intricacy and amplitude of her instincts, which are thoroughly representative of the species, and her ability to reproduce partheno- genetically. This, of course, means a considerable degree of autonomy even in the reproductive sphere. But parthenogenesis, while un- doubtedly contributing to the social efficiency of the female, must be regarded and treated as an independent phenomenon, without closer connection with polymorphism, for the ability to develop from = un- fertilized eggs is an ancient characteristic of the Hymenoptera and Fic. 51. Colony of Acanthomyops claviger, showing workers, dealated and vir- gin females, males, worker, male and female cocoons, X 2. (Photograph by J. G. Hubbard and Dr. O. S. Strong). POLY MORPHISM. 59 many other insects, which made its appearance among the solitary species, like the Tenthredinidz and Cynipide, long before the develop- ment of social life. Moreover, polymorphism may occur in male in- sects which, of course, are not parthenogenetic. That parthenogenesis is intimately connected with sexual dimorphism, at least among the Fic. 52. Pheidole instabilis. (Original.) a, Soldier; b-e, f, typical worker (micrergate); g, dealated female: h, male. intermediate workers go ANTS. social Hymenoptera, seems to be evident from the fact that the males usually if not always develop from unfertilized, the females from fertilized eggs. While the bumble-bees and wasps show us the ancient stages in the development of polymorphism, the ants as a group, with the ex- ception of a few parasitic genera that have secondarily lost this character, are all completely polymorphic. It is conceivable that the Fic. 53. Cryptocerus varians. (Original.) a, Soldier; b, same in profile; c, head of same from above; d, worker; e, female; f, male. development of different castes in the female may have arisen inde- pendently in each of the three groups of the social Hymenoptera, al- though it is equally probable that they may have inherited a tendency to polymorphism from a common extinct ancestry. On either hypoth- esis, however, we must admit that the ants have carried the develop- ment of the female castes much further than the social bees and wasps, . POLY MORPHISM. Ds since they have not only produced a wingless form of the worker, in addition to the winged female, or queen, but in many cases also two distinct castes of workers known as the worker proper and the soldier. Different authors have framed very different conceptions of the phylogenetic beginnings of social life among the Hymenoptera and consequently also of the phylogenetic origin and development of poly- morphism. Thus Herbert Spencer. (1893) evidently conceived the colony as having arisen from consociation of adult individuals, and although he unfortunately selected a parasitic ant, the amazon (Poly- ergus rufescens), on which to hang his hypothesis, there are a few facts which at first sight seem to make his view applicable to other social Hymenoptera. Fabre (1894) once found some hundreds of specimens of a solitary wasp (Ammophila hirsuta) huddled together under a stone on the summit of Mt. Ventoux in the Provence, at an altitude of about 5,500 feet, and Forel (1874) found more than fifty dealated females of Formica rufa under similar conditions on the Simplon. I have myself seen collections of a large red and yellow Amblyteles under stones on Pike’s Peak at an altitude of more than 13,000 feet, and a mass of about seventy dealated females of Formica gnava apparently hibernating after the nuptial flight under a stone near Austin, Texas. |] am convinced, however, that such congrega- tions are either entirely fortuitous, especially where the insects of one species are very abundant and there are few available stones, or, that they are, as in the case of F. rufa and gnava, merely a manifestation of highly developed social proclivities and not of such proclivities in process of development. A very different view from that of Spencer is adopted by most au- thors, who regard the insect colony as having arisen, not from a chance concourse of adult individuals, but from a natural affiliation of mother and offspring. This view, which has been elaborated by Marshall (1889) among others, presents. many advantages over that of Spencer, not the least of which is its agreement with what actually occurs in the founding of the existing colonies of wasps, bumble-bees and ants. These colonies pass through an ontogenetic stage which has all the appearance of repeating the conditions under which colonial life first made its appearance in the phylogenetic history of the species—the solitary mother insect rearing and affiliating her offspring under condi- tions which would seem to arise naturally from the breeding habits of the nonsocial Hymenoptera. The exceptional methods of colony for- mation seen in the swarming of the honey bee and in the temporary and permanent parasitism of certain ants, are too obviously secondary and of too recent a development to require extended comment. The g2 ANTS. bond which held mother and daughters together as a community was from the first no other than that which binds human societies to- gether—the bond of hunger and affection. The daughter insects in the primitive colony became dependent organisms as a result of two factors: inadequate nourishment and the ability to pupate very pre- maturely. But this very ability seems to have entailed an incomplete- ness of adult structure and instincts, which in turn must have con- firmed the division of labor and thus tended to perfect the social organization. , Before further discussing the problems suggested by this view of the origin of the colony and the general subject of polymorphism, it will be advisable to pass in review the series of different phases known to occur among ants. This review will be facilitated by consulting the accompanying diagram, in which I have endeavored to arrange Micraner Macranér — 3 a7 MALE (Aner) _ Philisaner< — Dorylanér , ‘ Ergatanér Gynzecaneér 7 L \ LErgatandromorph Gynandromorph Pterergate S71 Ergatogyne Micrergate 8 Le Mermithergate = Macrogyne “S WORKER _ Pseudogynex<~ FEMALE => Plerergate : ge Ereetes) Microgynex™ (Gyne) Phthisergate~~ Macrergate ze “™ 8-Female eee s SS ‘ Phthisogyne a Gynzcoid Desmergate © SN SS Dichthadiigyne Dinergate the various phases so as to bring out their morphological relations to one another. The phases may be divided into two main groups, the normal and the pathological. In the diagram the names of the latter-are printed in italics. The normal phases may be again divided into primary or typical, and secondary pr atypical, the former com- prising only the three original phases, male, female and worker, the latter the remaining phases, which, however, are far from having the POLYMORPHISM. 93 same dignity or frequency. The three typical phases are placed at the angles of an isosceles triangle, the excess developments being placed to the right, the defect developments to the left, of a vertical line passing through the middle of the diagram. The arrows indicate the directions of the affinities of the secondary phases and suggest that those on the sides of the triangle are annectant, whereas those which radiate outward from its angles represent the new departures with excess and defect characters. 1. The male (anér) is far and away the most stable of the three typical phases which are found in all but a few monotypic and para- sitic genera of ants. This is best shown in the general uni- formity of structure and col- oration which characterize this sex in genera whose female forms (workers and queens) are widely different; e. g., in such a series of cases as Myr- mecia, Odontomachus, Cryp- tocerus (Fig. 53), Formica, Pheidole (Fig. 52),etc. Inall of these genera the males are very similar, at least super- ficially, whereas the workers and females are very diverse. The body of the male ant ts graceful in form, one might almost say emaciated (Fig. 50). Its sense-organs (espe-. cially the eyes and antenne), wings and genitalia are highly developed; its mandibles are Fie. 4. eMslese ton Peete (Ge ecd) more or less imperfectly devel- A, Winged male of Ponera: coarctata; B, . . 26 winged male of P. eduardi; C, ergatomorphic oped, and in correlation with male (ergatanér) of P. eduardi; D, ergatanér them the head is proportionally of P. punctatissima. shorter, smaller and rounder than in the females and workers of the same species. Even when the latter phases have brilliant or metallic colors, as in certain species of Macromischa and Rhytidoponera, the males are uniformly red, yellow, brown or black. Yet notwithstanding this monotony of structure and coloration, the male type may present 1 Weerestmne modifications. 94 ANTS. 2. The macranér is an unusually large form of male which occa- sionally occurs in populous colonies. 3. The micranér or dwarf male, differs from the typical form merely in its smaller stature. Such forms often arise in artificial nests. 4. The dorylanér is an unusually large form peculiar to the driver Fic. 55. Acanthomyops claviger and A. latipes. (Original.) A, Dealated female of A. claviger; B, a-female of A. latipes; C. B-female of same. and legionary ants of the subfamily Doryline (Dorylus and Eciton). It is characterized by its large and peculiarly modified mandibles, long cylindrical gaster and singular genitalia (Figs. 141, FE, and 142). It may be regarded as an aberrant macranér that has come to be the typical male of the Doryline. 5. The ergatanér, ergatomorphic, or ergatoid male resembles the worker in having no wings and in the structure of the antenne. It occurs in the genera Ponera, Formicoxenus, Symmyrmuca, Techno- myrmex and Cardiocondyla. In certain species of Ponera (P. puncta- tissima and ergatandria) and in Formicoxenus nitidulus the head and thorax are surprisingly worker-like, in other forms like Symmyrmica chamberlini these parts are more like those of the ordinary ant, while P. eduardi shows a more intermediate development of the head with a Nid POLYMORPHISM. 95 worker-like thorax. Forel (1904/) has recently shown that the erga- tanér may coexist with the aner, at least in one species of Ponera (P. eduardi Forel). In other words, this ant has dimorphic males ( Fig. Bae Db anda@s)e 6. The gynecanér, or gyneecomorphic male occurs in certain para- sitic and workerless genera (Aner- gates and Epacus) and resembles a female rather than a worker form. The male of Anergates is wing- less, but has the same number of antennal joints as the female (Fig. 279). In Epacus (Fig. 278) both sexes are very much alike and both have I1—12-jointed antenne (Em- ery, 1906d ). 7. The phthisanér is a pupal male which in its larval or semipupal state has its juices partially ex- tracted by an Orasema larva. This male is too much depleted to pass on to the imaginal stage. The wings are suppressed and the legs, head, Hues cés | Monomorum: aaforecta thorax and antenne remain abortive. (Original.) a, Worker; b, apterous fe- male (ergatogyne) ; c, same seen from &. Uhetfemale (gyne), or queen, «i... sae. is the more highly specialized sex among ants and is characterized, as a rule, by a larger stature and the more uniform development of her organs (Figs. 52,g,ete.). The head is well developed and provided with moderately large eyes, ocelli and mandibles; the thorax is large (macronotal) and presents all the sclerites of the typical female Hymenopteron; the gaster 1s voluminous and provided with well-developed reproductive organs. The latter possess a receptaculum seminis. The wings and legs are often propor- tionally shorter and stouter than in the male. g. The macrogyne is a female of unusually large stature. to. The microgyne, or dwarf female, is an unusually small female which in certain ants, like Formica microgyna and its allies, is the only female of the species and may be actually smaller than the largest workers (Fig. 262). In other ants, like certain species of Leptothorax and Myrmica, microgynes may sometimes be found in the same nest as the typical females. 11. The B-female is an aberrant form of female such as occurs in Lasius latipes (Fig. 55, C), either as the only form or coéxisting with 96 ANTS. the normal female which is then called the a-female.’ In this case, therefore, the female is dimorphic. The 8-female is characterized by excess developments in the legs and antenne and in the pilosity of the body or by defective development of the wings. 12. The ergatogyne, ergatomorphic, or ergatoid female, is a worker- like form, with ocelli, large eyes and a thorax more or less like that of the female, but without wings. Such females occur in a number of species of ants. They have been seen in Myrmecia, Odontomachus, Anochetus, Ponera, Polyergus, Leptothorax, Monomorium and Cre- mastogaster. There is nothing to prove that they are pathological in Fic. 57. Formica incerta. (Original. a, Normal worker; b, pseudogyne drawn to the same scale. origin. In fact, in Wonomorium floricola (Fig. 56), and certain spe- cies of Anochetus they appear to be the only existing females. In other cases, like Ponera eduardi, as Forel has shown, they occur with more or less regularity in nests with normal workers. They also occur under similar conditions in colonies of the circumpolar P. coarctata, and among other species of the genus. 13. The pseudogyne (Fig. 57,6) 1s a worker-like form with enlarged mesonotum and sometimes traces of other thoracic sclerites of the female, but without wings or very rarely with wing vestiges. This form, when it occurs among species of Formica, is produced by the presence of Lomechusine beetles in the colony (see p. 407 et seq.). POLYMORPHISM. 97 14. The phthisogyne arises from a female larva under the same conditions as the phthisaner, and differs from the typical female in the same characters, namely absence of wings, stenonoty, microcephaly and microphthalmy. It is unable to attain to the imaginal instar. 15. The worker (ergates) is characterized by the complete absence of wings anda very small (stenonotal) thorax, much simplified in the struc- Lure01 its Sclerites, (GRie SG, ete): p The eyes are small and the ocelli are aN ve tremely small. The gaster is small, owing to the undeveloped condition of the ovaries. A-receptaculum seminis is usually lacking, and the number of usually absent or, when present, ex- \ the ovarian tubules is greatly dimin- ished. The antenne, legs and man- dibles are well developed. f 16. The gynecoid is an egg-laying worker. It is a physiological rather than a morphological phase, since it is probable that all the worker ants when f ; é) is abundantly fed become able to lay ; eggs. Wasmann (1904a) observed in Fie. 58. Pseudogyne of Myr- ; . k ; mica sulcinodoides, with vestige of colonies of Formica rufibarbis that one . fore wing on left side. (Original.) or a few workers became gynecoid and functioned as substitution queens. In colonies of the Ponerine genus Leptogenys (including the subgenus Lobopelta (Fig. 137), and probably also in Diacamma and Champsomyrmex), the queen phase has disappeared and has been replaced by the gynzecoid worker. 17. The dichthadiigyne, or dichthadiiform female is peculiar to the ants of the subfamily Doryline and probably represent a further devel- opment of the gynecoid. It is wingless and stenonotal, destitute of eyes or ocelli, or with these organs very feebly developed, and with a huge elongated gaster and extraordinary, voluminous ovaries (Figs. 141, 4, and 147, b and c). 18. The macrergate is an unusually large worker form which in some species is produced only in populous or affluent colonies (For- mica, Lasius ). 19. The muicrergate, or dwarf worker, is a worker of unusually small stature. It appears as a normal or constant form in the first brood of all colonies that are founded by isolated females. 20. The dinergate, or soldier (Figs. 52, A ; 60, a), is characterized b) 8 gs ANTS. a huge head and mandibles, often adapted to particular functions ( fight- ing and guarding the nest, crushing seeds or hard parts of insects), and a thoracic structure sometimes approaching that of the female in size or in the development of its sclerites (Pheidole ). 21. The desmergate is a form intermediate between the typical worker and dinergate, such as we find in more or less isolated genera Fic. 59. Aphenogaster picea, an ant with monomorphic workers. (Photograph by J. G. Hubbard and Dr. O. S. Strong.) of all the subfamilies except the Ponerine, e. g., in Camponotus (Fig. 45, a), some species of Pheidole (Fig. 52, b-e), Solenopsis and Pogo- nomyrmex, Azteca, Dorylus (Fig. 62, b), Eciton, etc. The term might also be employed to designate the intermediate forms between the small and large workers in such genera as Monomorium, Formica, etc. POLYMORPHISM. 99 22. The plerergate, “replete,” or “rotund,” is a worker, which in its callow stage has acquired the peculiar habit of distending the gaster with stored liquid food (“honey”) till it becomes a large spherical sac and locomotion is rendered difficult or even impossible (Figs. 218 and 219). Thisoccurs in the honey ants (some North American species of Myrmecocystus, some Australian Melophorus and Camponotus, and to a less striking extent in certain species of Prenolepis and Plagiolepis ). 23. The pterergate is a worker or soldier with ves- tiges of wings on a thorax of the typical ergate or dinergate form, such as occurs in certain species of Myrmica and Cryptocerus (Fig. 63). 24. The mermithergate is an enlarged worker, pro- duced by Mermis parasit- ism and often presenting dinergate characters in the thorax and minute ocelli in the head (Fig. 254, B, C). 25. The phthisergate, which corresponds to the phthisogyne and phthisaner, is a pupal worker, which in its late larval or semipupal stage has been attacked and partially exhausted of its Fic. 60. Pheidole borinquenensis of Porto juices by an Orasema larva =p Ree ; y : Z s ‘i Rico. (Original.) a, Soldier; b, same in profile ; Pniemaaemeandac) alt isc worker, characterized by extreme stenonoty, microcephaly and microphthalmy, and is unable to pass on to the imaginal stage. It is in reality an infra-ergatoid form. 26. The gynandromorph is an anomalous individual in which male and female characters are combined in a blended or more often in a mosaic manner (Figs. 64 and 65). 27. The ergatandromorph ( Fig.66) is an anomaly similar to the last but having worker instead of female characters combined with those of the male (Wheeler, 19030). It is usually conceded that the fertilization or non-fertilization of the egg of the social Hymenopteron determines whether it shall give 100 ANTS. rise to a male or a female. And as the queen represents the typical female form of the species, the problem of polymorphism is to account for the various worker forms, and those like the soldiers, pseudogynes and ergatoid females which are intermediate between the worker and the queen. The ergatomorphic males are usually regarded as inheriting worker characters. Thus the problem of polymorphism centers in the development of the worker. It must suffice in this place to give the briefest possible state- ment of the views of the various authors who have endeavored to account for the development of this caste. These authors may be divided into three groups: 1. Those who believe with Weismann that the various castes are represented in the egg by corresponding units (determi- nants). Fertilization is then regarded as the stimulus which calls the female deter- minants into activity and meagre feeding the stimulus which arouses the worker- producing determinants in young larve arising from fertilized eggs. Such an explanation is obviously little more than a restatement or “photograph” of the Fic. -6nw) Workeres: major Problem... (Wt pseeks: “to -account vtor the and minor of Camponotus ameri- adaptive characters of the worker forms Rees ae eee ene by natural selection acting on fortuitous congenital variations. 2. Those who believe with Herbert Spencer that there is no such predetermination of the various female castes, but that these are pro- duced epigenetically by differences in the feeding of the larve. The workers simply arise from larve that are inadequately fed but are nevertheless able to pupate and hatch when only a part of their growth has been completed. This is not, like the preceding view, a restatement of the problem, since the modifications produced by inadequate feeding are conceived as somatic and not as germinal, but it fails to explain how the worker caste acquires its adaptive characters, unless this caste is supposed to reproduce with sufficient frequency to transmit acquired somatic modifications to the germ-plasm of the species. 3. A third group of investigators believes with Emery that the germ-plasm of the social Hymenopteron is indeed implicated in the problem, not as possessing separate sets of determinants, but as being POLYMORPHISM. 101 in a labile or sensitive condition and therefore capable of being de- flected by differences in the trophic stimuli acting on the larva. Ac- cording to Emery: ** The peculiarities in which the workers differ from the corresponding — sexual forms are, therefore, not in- nate or blastogenic, but ac- quired, that is somatogenic. Nor are they transmitted as such, but in the form of a peculiarity of the germ-plasm that enables this substance to take different developmental paths during the ontogeny. Such a peculiarity of the germ may be compared with the hereditary predisposition to certain diseases, which like hereditary myopia, develop only under certain conditions. The eye of the congenitally myopic individual is blastogenetically predisposed to short-sighted- ness, but only becomes short- sighted when the accommoda- Fic. 62. Heads of workers of Dorylus 5 affinis drawn to same scale to show differ- tion apparatus of the eye haS ences in size «and in number of antennal been overtaxed by continual joints. (Emery.) a, Soldier, or worker max- 4 ari eee R ima, 11 mm. long; b, worker major 5 mm. exertion. Myopia arises, like long; c, worker minima with 11-jointed an- the peculiarities of the worker tenne; d, worker minima with 1o-jointed an- tenne; e, with 9-jointed antenne, f, with 8- jointed antenne ; f’, antenna of same enlarged. ants, aS a somatic affection on a blastogenic foundation. “With this assumption the problem of the development of workers seems to me to become more intelligible and to be brought a step nearer its solution. The peculiarities of the Hymenopteran workers are laid down in every female egg; those of the termite workers in every egg of either sex, but they can only manifest themselves in the presence of specific vital conditions. In the phylogeny of the various species of ants the worker peculiarities are not transmitted but merely the faculty of all fertilized eggs to be reared as a single or several kinds of workers. The peculiar instinct of rearing workers is also transmitted, since it must be exercised by the fertile females in establishing their colonies.” The views above cited show very clearly that authors have 102 ANTS. been impressed by very different aspects of the complicated phenomena of polymorphism, and that each has emphasized the aspect which seemed the most promising from the standpoint of the general evolu- tionary theory he happened to be defending. Escherich (1906) has recently called attention to two very different ways of envisaging the problem; one of these is physiological and ontogenic, the other etho- logical and phylogenetic. As these furnish convenient captions under which to continue the discussion of the subject, ] shall adopt them, and conclude with a third, the psychological aspect, which is certainly of sufficient importance to deserve consideration. While the ontogeny of nearly all animals is a repetition or repro- duction of the parent, this is usually not the case in the social Hymen- optera, since the majority of the fertilized eggs do not give rise to Fic. 63. Vestigial wings in worker ants. (Original.) A, Myrmica scabrinedis var., with spatulate wing vestiges on mesothorax; B, and C, Thoraces of two other individuals from the same colony, showing a more vestigial development of the wings; D, Soldier of Cryptocerus aztecus with mesothoracic wing vestiges. queens but to more or less aberrant organisms, the workers. And as these do not, as a rule, reproduce, the whole phenomenon 1s calcu- lated to arouse the interest of both the physiologist and the embry- ologist. The former, concentrating his attention on the reactions of the animal to the stimuli proceeding from its environment, is inclined to study its later stages as determined by the reactions to such stimuli, without regard to any internal or hereditary predetermination or dis- position, while the embryologist seeks out the earliest moment at which the organism may be shown to deviate from the ontogenetic pattern POLYMORPHISM. Ne) of its parent. If this moment can be detected very early in the devel- opment he will be inclined to project the morphological differentiation back into the germ-plasm and to regard the efforts of the physiologist as relatively unimportant if not altogether futile. Now in his study of the social insects the embryologist is at a serious disadvantage, since he has hitherto been unable to distinguish any prospective worker or queen characters in the eggs or even in the young larve. Compelled, therefore, to confine his attention to the older larve, whose develop- ment as mere processes of histogenesis and metamorphosis throws little or no light on the meaning of polymorphism, he is bound to leave the physiologist in possession of the problem. The physiologist, in seeking to determine whether there is in the environment of the developing social Hymenopteron any normal Fic. 64. Gynandromorph of Epipheidole inquilina; male on the left, female on the right side. (Original. ) stimulus that may account for the deviation towards the worker or queen type, can hardly overlook one of the most important of all stimuli, the food of the larva. At first sight this bids fair greatly to simplify the problem of polymorphism, for the mere size of the adult insect would seem to be attributable to the quantity, its morphological deviations to the quality of the food administered to it during its larval life. Closer examination of the subject, however, cannot fail to show that larval alimentation among such highly specialized animals as the social insects, and especially in the honey-bees and ants, where the differences between the queens and workers are most salient, is a matter of considerable complexity. In the first place, it is evident that it is not the food administered that acts as a stimulus but the portion 104 ANTS. .of it that is assimilated by the living tissues of the larva. In other words, the larva is not altogether a passive organism, compelled to utilize all the food that is forced upon it, but an active agent, at least to a considerable extent, in determining its own development. And the physiologist might have difficulty in meeting the assertion that the larva utilizes only those portions of the proffered food that are most conducive to the specific, prede- termined trend of its development. In the second place, while experi- ments on many organisms have shown that the quantity of as- similated food may produce great changes in size and stature, there is practically nothing to show that even very great differences in the quality of the food can bring about morphological differ- ences of such magnitude as those which separate the queens and workers of many ants. Fic. 6s. Gynandromorph of Formica These more general consider- microgyna; head almost purely female, ations are reinforced by the fol- gaster male, thorax, petiole and legs male : : : on left, female on right side. (Original.) lowing inferences from the known facts of larval feeding: 1. There seems to be no valid reason for supposing that the mor- phogeny of the queens among the social Hymenoptera depends on a particular diet, since with the possible exception of the honey- and sting- less bees, to be considered presently, they differ in no essential respect from the corresponding sexual phase of the solitary species. In both cases they are the normal females of the species and bear the same morphological relations to their males quite irrespective of the nature of their larval food. Hence, with the above mentioned exception of the honey- and stingless bees, the question of the morphogenic value of the larval food may be restricted to the worker forms. 2. Observations show that although the nature of the food admin- istered to the larvee of the various social insects is often very different, even in closely related species, the structure of the workers may be extremely uniform and exhibit only slight specific differences. Among ants, as we have seen (p. 74), the larvz are fed with a great variety of substances. The quality of the food itself cannot, therefore, be supposed to have a morphogenic value. And even if we admit what seems to be very probable, namely, that a salivary secretion—possibly POLY MORPHISM. 105 containing an enzyme—may be administered by some ants, at least to their younger larve, the case against the morphogenic effects of quali- tative feeding is not materially altered, as we see from the following considerations : 3. In incipient ant-colonies the queen mother takes no food often for as long a period as eight or nine months, and during all this time is compelled to feed her first brood of larvee exclusively on the secre- tions of her salivary glands. This diet, which is purely qualitative, though very limited in quantity, produces only workers and these of an unusually small size (micrergates ). 4. In the honey-bees, on the other hand, qualitative feeding, namely with a secretion, the so-called ‘“ royal jelly,’ which according to some authors (Schiemenz) is derived from the salivary glands, according to others (Planta) from the chylific stomach of the nurses, does not pro- duce workers, but queens. In this case, however, the food 1s adminis- tered in considerable quantity, and is not provided by a single starving mother, as in the case of the ants, but by a host of vigorous and well- fed nurses. Although it has been taken for granted that the fertilized honey-bee becomes a queen as the result of this peculiar diet, the matter appears in a different light when it is considered in connection with von Ihering’s recent observations on the stingless bees ( Meliponide ) of South America (1903). He has shown that in the species of Melipona the cells in which the males, queens and workers are reared are all of the same size. These cells are provisioned with the same kind of food (honey and pollen) and an egg is laid in each of them. Thereupon they are sealed up, and although the larve are not fed from day to day, as in the honey-bees, but like those of the solitary bees subsist on stored provisions, this uniform treatment nevertheless re- sults in the production of three sharply differentiated castes. On hatching the queen Melipona has very small ovaries with immature eggs, but in the allied genus Trigona, the species of which differ from the Melipona in constructing large queen cells and in storing them with a greater quantity of honey and pollen, the queen hatches with her ovaries full of ripe eggs. These facts indicate that the large size of the queen cell and its greater store of provisions are merely adaptations for accelerating the development of the ovaries. Now on reverting to the honey-bee we may adopt a similar explanation for the feeding of the queen larva with a special secretion like the “royal jelly.” As is well known, the queen honey-bee hatches in about sixteen days from the time the egg is laid, while the worker, though a smaller insect and possessing imperfect ovaries, requires four or five days more to complete her development. That the special feeding of the 106 ANTS. queen larva is merely an adaptation for accelerating the development of the ovaries is also indicated by the fact that this insect is able to lay within ten days from the date of hatching. If this interpretation is correct, the qualitative feeding of the queen larva is not primarily a morphogenic but a growth stimulus. 5. The grossly mechanical withdrawal, by parasites like Orasema (see p. 418), of food substances already assimilated by the larva, pro- duces changes of the same kind as those which distinguish the worker ant from the queen, 1. e., microcephaly, microphthalmy, stenonoty and aptery. This case is of unusual interest because the semipupa, after the detachment of the para- site, seems to undergo a kind of regeneration and produces a small but harmonious whole out of the depleted formative substances at its dis- posal. What is certainly a female or soldier semi- pupa takes on worker characters while the worker semipupa may be said to become infra- ergatoid as the result of the sudden loss of the formative substances. These observations clearly indicate that the normal worker traits may be the result of starvation or withholding of food rather than the administration of a particular diet. 6. The pseudogynes of Formica admit of a similar interpretation if it be true, as I am in- clined to believe (see p. 408), that they arise from starved female larve. Here too, the organism Pee hace eae undergoes a kind of regeneration or regulation nogaster picea:maleon and assumes the worker aspect owing to a dearth left, worker on right of sufficient formative substances with which to side. (Original.) ee complete the development as originally planned. 7. In the preceding cases the ants take on peculiar structural modifications as the result of tolerating parasites that bring about un- usual perturbations in the trophic status of the colony. When ants themselves become parasitic on other ants a similar perturbation ensues, but in these cases the morphological effects are confined to the parasitic species and do not extend to their hosts. This must be attributed to the fact that the parasitic species live in affluence and are no longer required to take part in the arduous and exacting labors of the colony. Under such circumstances the inhibitory effects of nutricial castration on the development of the ovaries of the workers are re- moved and there is a tendency for this caste to be replaced by egg- laying gynzecoid individuals or by ergatogynes, or for it to disappear POLYMORPHISM. 107 completely. These effects are clearly visible in nearly all parasitic ants. In the European Harpagoxenus sublevis, for example, the only known females in certain localities are gynecoid workers. In the American Leptothorax emersoni, as I have shown (1903f ), gynecoid workers and ergatogynes are unusually abundant, while the true females seem to be on the verge of disappearing. Among the typical amazon ants (Polyergus rufescens) of Europe, ergatogynes are not uncommon. In Strongylognathus testaceus the worker caste seems to be dwindling, while in several permanently parasitic genera (Anergates, Wheeleriella, Epacus, Epipheidole and Sympheidole) it has completely disappeared. Only one cause can be assigned to these remarkable effects—the abundance of food with which the parasites are provided by their hosts. 8. In the Ponerinze and certain Myrmicine, like Phetdole, Pogono- myrmex and Aphenogaster, the larve are fed on pieces of insects or seeds, the exact assimilative value of which as food can neither be determined nor controlled by the nurses. And while they may perhaps regulate the quantity of food administered, it is more probable that this must fluctuate within limits so wide and indefinite as to fail alto- gether to account for the uniform and precise morphological results that we witness in the personnel of the various colonies (Fig. 51). More- over, accurate determination of the food supply by the workers must be quite impossible in cases like that of the Pachycondyla larva bearing the commensal M/etopina (see p. 412). g. The dependence of the different castes of the social insects on the seasons may also be adduced as evidence of the direct effects of the food supply in producing workers and queens. The latter are reared only when the trophic condition of the colony is most favorable, and this coincides with the summer months; in the great majority of species only workers and males are produced at other seasons. Here, too, the cause 1s to be sought in the deficient quantity of food rather than in its quality, which is in all probability the same throughout the year, especially in such ants as the fungus-growing Attii. While these «considerations tend to invalidate the supposition that qualitative feeding is responsible for the morphological peculiarities of the worker type, they are less equivocal in regard to the morpho- genic effects of quantitative feeding. Indeed several of the observa- tions above cited show very clearly that diminution in stature and, in pathological cases, even reversion to the worker form may be the direct effect of underfeeding. To the same cause we may confidently assign several of the atypical phases among ants, such as the micrergates, microgynes, and micranérs, just as we may regard the macrergates, 105 ANTS. macrogynes, and macranérs as due to overfeeding. These are, of course, cases of nanism and giantism, variations in stature, not in form. Similarly, all cases in which, as in certain species of Formica, Campo- notus, Pheidole, etc., the workers or desmergates vary in size, must be regarded as the result of variable quantitative feeding in the larval stage. Here we are confronted with the same conditions as Weismann observed in prematurely pupating blow-flies, and entomologists have noticed in many other insects. Such variations are of the fluctuating type and are therefore attributable to the direct effects of the environ- ment. The soldier and worker, however, differ from the queen in the absence of certain characters, like the wings, wing-muscles, sperma- theca, some of the ovarian tubules, etc., and the presence of other characters, like the peculiar shape of the head and mandibles. In these respects the sterile castes may be regarded as mutants, and Weis- mann’s contention that such characters cannot be produced by external conditions, such as feeding, is in full accord with de Vries’s hypothesis. His further contention, however, that they must therefore be produced by natural selection need not detain us, since it is daily becoming more and more evident that this is not a creative but an eliminative prin- ciple. It is certain that very plastic insects, like the ants, have devel- oped a type of ontogeny which enables them, not only to pupate at an extremely early period of larval life, but.also to hatch and survive as useful though highly specialized members of the colony. It is quite conceivable that this precocious pupation may be directly responsible for the complete suppression of certain organs that require for their formation more substance than the underfed larva is able to accumulate. At the same time it must be admitted that a direct causal connection between underfeeding on the one hand and the ontogenetic loss or development of characters on the other hand, has not been satis- factorily established. The conditions in the termites, which are often cited as furnishing proof of this connection, are even more complicated and obscure than those of the social Hymenoptera. While Grassi and Sandias (1893) and Silvestri (1901) agree with Spencer in regarding feeding as the direct cause of the production of the various castes, Herbst (1901), who has reviewed the work of the former authors, shows that their observations are by no means conclusive; and Heath (1902) makes the following statement in regard to his experiments on Californian termites: “For months I have fed a large number of termite colonies of all ages, with or without royal pairs, on various kinds and amounts of foods—proctodzal food dissected from the workers or in other cases from royal forms, stomadzeal food from the same sources, sawdust to which different nutritious ingredients have been added— POLYMORPHISM. 109 but in spite of all I cannot feel perfectly sure that I have influenced in any unusual way the growth of a single individual.” This rather unsatisfactory answer to the question as to whether quantity or quality of food or both, have an ergatogenic value, has led some investigators to seek a solution along more direct lines. Thus O. Hertwig and Herbst suggest that the morphogenic stimulus may be furnished by some internal secretion of the reproductive organs. This, too, is possible, but owing to our very imperfect knowl- edge of the internal secretions, even in the higher animals, we are not in a position either to accept or reject this suggestion. We may conclude, therefore, that while the conception of the worker phase as the result of imperfect nutrition is supported by a considerable volume of evidence, we are still unable to understand how this result can take on so highly adaptive a character. Such a concise effect can hardly be due to manifold and fluctuating external causes like nutrition, but must proceed from some more deeply seated cause within the organism itself. Of course, the difficulty here en- countered is by no means peculiar to polymorphism; it confronts us at every turn as the all-pervading enigma of living matter. CHAPTER VI. POLYMORPHISM. (CONCLUDED.) “La conservation de ces animaux et la prospérité de leur famille ne pou- voient done étre assurées que par |’établissement d’un ordre particulier et nom- breux d’individus qui suppléassent aux fonctions des méres et qui n’en eussent meme que les sentimens et les affections. La nature, en formant ici des neutres, s'est vue contrainte de s’écarter de ses lois ordinaires, pour que son ouvrage subsistat, et sa prévoyance a modifié ses ressources selon les circonstances ov les €tres devoient étre placés.”—Latreille, “ Considerations Nouvelles et Géné- rales sur les Insectes Vivant en Société,” 1817. An extensive study of the structure and habits of ants must inevi- tably lead to a certain amount of speculation concerning the phylo- genetic development of their colonies. That these insects have had communistic habits for ages is clearly indicated by the fact that all of the numerous existing species are eminently social. There can be little doubt, however, that they arose from forms with habits not unlike those we find to-day in some of the solitary wasps, such as the Bembe- cidze, or in the remarkable South African bees of the genus A/lodape. Unlike other solitary wasps, the females of Bembex may be said to be incipiently social, since a number of them choose a nesting site and, though each has her own burrow, cooperate with one another in driv- ing away intruders. Bembex has also taken an important step in the direction of the social wasps not only in surviving the hatching of her larvee, but also in visiting them from day to day for the purpose of providing them with fresh insect food. | At a very early period the ants and social wasps must have made a further advance when the mother insect succeeded in surviving till after her progeny had completed their development. This seems to have led naturally to a stage in which the young females remained with their mother and reared their progeny in the parental nest, thus constituting a colony of a number of similar females with a common and indiscriminate interest in the brood. This colony, after growing to a certain size, became unstable in the same way as any aggregate of like units, and must soon have shown a differentiation of its members into two classes, one comprising individuals devoted to reproduction and another devoted to alimentation and protection. In this division of labor only the latter class underwent important somatic modification and specialization, while the former retained its primitive and more I1o POLYMORPHISM. ROE generalized characters. It is more than probable, as I shall attempt to show in the sequel, that this differentiation was manifested in the sphere of instinct long before it assumed morphological expression. The social wasps and bumble-bees are still in this stage of sociogeny. The ants, however, have specialized and refined on these conditions till they have not only a single marked alimentative and protective caste without wings and lacking many other female characters, but in some species two distinct castes with a corresponding further divi- sion of labor. In the phylogeny as well as the ontogeny these charac- ters appear as a result of nutricial castration.? If the foregoing considerations be granted the biogenetic law may be said to hold good in the sociogeny of the ants, for the actual onto- genetic development of their colonies conforms not only to the purely conjectural requirements of phylogeny but also to the stages repre- sented by the various extant groups of social insects. It is clear that we cannot include the honey-bee among these groups, since this insect is demonstrably so aberrant that it is difficult to compare it with the other social insects. Comparison of the different genera and subfamilies of ants among themselves shows that some of them have retained a very primitive social organization, and with it a relatively incomplete polymorphism, whereas others have a much more highly developed social life and a greater differentiation of the castes. Such a comparison, coupled with a study of the natural relationships of the various genera as displayed in structure, shows very clearly that the advance from generalized to highly specialized societies did not follow a single upward course dur- ing the phylogeny, but occurred repeatedly and in different phyletic groups. And since the complications of polymorphism keep pace with those of social organization, we may say that the differentiation of the originally single worker caste into dinergates, or soldiers on the one -!“ Nutricial castration” (from nutrix, a nurse), as understood by Marchal, must be distinguished from “alimentary castration” (Emery, 1896k), although both are responsible for the infertility of the worker. Through alimentary castration the development of the reproductive organs is inhibited in the larva and pupa, and this inhibition is maintained in the adult by the strong nursing instincts which prevent the workers from appropriating much of the food supply of the colony to their individual use. In many of the higher animals also (birds, mammals) reproduction is inhibited by the exercise of the nutricial function. A third method of inhibiting or destroying the reproductive func- tion is known to occur in the “ parasitic castration” of certain bees and wasps (Andrena, Polistes) by Strepsiptera (Stylops, Xenos, etc.). See Pérez, “ Des Effects du Parasitisme des Stylops sur les Apiaires du Genre Andrena,” Actes Soc. Linn. Bordeaux, 1886, 40 pp., 2 pls. Westwood has also described a Strepsipteron (Myrmecolax mietneri) which, in all probability, produces this form of castration in certain Formicide (1861). 112 ANTES. hand, and micrergates, or small workers, on the other, has been several times repeated in remotely related genera. In some genera (Stenamma sens. str., Leptothorax) there are also indications of a lapsing of highly specialized into simpler conditions by a kind of social degenera- tion. In its extreme form this manifests itself as a suppression of castes and a consequent simplification of polymorphism. Beautiful examples of this condition are furnished by the parasitic species that have lost their worker caste. But there are also cases in which the queen caste has been suppressed and its functions usurped by workers. Not only have these greater changes been effected and fixed during the phylogenetic history of the Formicidz, but also many subtler differences such as those of stature, coloration, pilosity and sculpture. And although such differences belong to the class of fluctuating varia- tions and are usually supposed to have a greater ontogenetic than phylogenetic significance, they are undoubtedly of great antiquity and must therefore be regarded as more important than many of the minor morphological traits. Emery was the first to call attention to a number of peculiar phylo- genetic stages in the development of stature among ants (1894d). We find by comparison with the male, which may be regarded as a rela- tively stable and conservative form, that the cospecific females and workers may vary in stature independently of each other. The follow- ing are the stages recognized by Emery, with some additions of my own: 1. In the earliest phylogenetic condition, which is still preserved in the ants of the subfamily Ponerinz and in certain Myrmicine (Pseudo- myrma, Alyrmecina, ete.), the workers are monomorphic and about the same size as the males and females. 2. The worker becomes highly variable in stature from large forms (dinergates, or maxima workers) resembling the female, through a series of intermediate (desmergates, mediz) to very small forms (minima workers, or micrergates). This condition obtains in the Dorylinee, some Myrmicinze (some species of Pheidole, Pheidologe- ton, Atta), Camponotinee (Camponotus) and Dolichoderine (Azteca). 3. The worker becomes dimorphic through the disappearance of the desmergates, so that the originally single and highly variable caste is now represented by two, the soldier (dinergate) and worker proper. We find this condition in certain Myrmicine and Camponotine (Cryvp- tocerus, Pheidole, Acanthomyrmex, Colobopsis, etc.). 4. The soldier of the preceding stage disappears completely, so that the worker caste again becomes monomorphic but is represented by individuals very much smaller than the female. Such individuals are POLYMORPHISM. 113 really micrergates. This condition is seen in certain Myrmicine genera, especially of the tribe Solenopsidii (Carebara, Erebomyrma, Diplo- morium, most species of Solenopsis, etc.). 5. The worker form disappears completely leaving only the males and females to represent the species, which thus returns to the con- dition of sexual dimorphism seen in the great majority of insects and other Metazoa. This occurs in the parasitic ants of the genera Anergates, Wheeleriella, Epacus, Sympheidole and Epipheidole. 6. In certain species the workers remain stationary while the female increases in size. This is indicated by the fact that the worker and male have approximately the same stature. Such a condition ob- tains in certain Myrmicine (Cremastogaster), Camponotine (Lasius, Prenolepis, Brachymyrmex, North American species of M/yrmecocys- tus) and Dolichoderine (/ridomyrme., Dorymyrmex, Liometopum). 7. The worker caste remains stationary while the female diminishes in size till it may become even smaller than the large workers. This occurs in certain parasitic species of North America, like Apheno- gaster tennesseensis among the Myrmicine, and among the Campono- tine in the species of the Formica microgyna group (F. difficilis, nevadensis, impexa, dakotensis, nepticula). 8. The female phase disappears completely and is replaced by a fertile, or gynzcoid worker form. This occurs in certain Ponerine genera like Leptogenys (including the subgenus Lobopelta), and prob- ably also in Diacamma and Champsomyrmex. The conditions in Acanthostichus and certain Cerapachysit.( Parasyscia peringueyi) indi- cate that the dichthadiigynes of the Dorylinzee may have arisen from such gynecoid workers instead of from winged queens. g. The female shows a differentiation into two forms (a- and B-fe- males) characterized by differences in the structure of the legs and antenne, in pilosity and coloration (Lasius latipes), or in the length of the wings (macropterous and micropterous females of L. niger). The macrocephalic and microcephalic females of Camponotus abdomi- nalis and confusus described by Emery (1896k) may also be regarded as a- and B-forms. In this series of stages, one to five represent changes in the worker caste while the female remains relatively stationary, whereas stages six to nine represent the converse conditions. Stages one to four probably succeeded one another in the order given, but stage five may have arisen either from the first or fourth. The sixth to ninth stages must, of course, be supposed to have developed independently of one another. The stature differences described in the above paragraphs are, in 2) 114 ANTS. most, if not all cases, highly adaptive. This is clearly seen in such forms as the Indo-African Carebara, the huge, deeply colored females of which are more than a thousand times as large as the diminutive, yellow workers. ‘This ant dwells in termite nests where it occupies chambers connected by means of tenuous galleries with the spacious apartments of its host. The termites constitute a supply of food so accessible and abundant that the workers are able to rear enormous males and females, while they themselves must preserve their diminu- tive stature in adaptation to their clandestine and thievish habits. Simi- lar conditions are found in many species of the allied genus Solenopsis, which inhabit delicate galleries communicating with the nests of other ants on the larvae and pupe of which they feed. In one species of this genus (S. geminata), however, which leads an independent life and feeds on miscellaneous insects and seeds, the worker caste is still highly polymorphic. Another interesting case of adaptation in stature is seen in the ants of the Formica microgyna group. The females of these species are temporarily parasitic in the nests of other Formice and are there- fore relieved of the labor of digging nests for themselves and rearing their first brood of larve. On this account they need not store up large quantities of food, so that the nourishment which in non-para- sitic species goes to produce a comparatively few large females may be applied to the production of a large number of small females. This latter condition is necessary in parasitic species which are decimated by many vicissitudes before they can establish themselves successfully among alien hosts. I have already emphasized the adaptive significance of the disappearance of the worker caste among permanently parasitic species like Anergates, Wheeleriella, ete. There are several cases in which the worker and female differ greatly in color, pilosity or sculpture, and in such cases either caste may be conservative or aberrant according to ethological requirements. Thus in certain temporary parasites like Formica ciliata, oreas, crinita, Specularis and difficilis, the female is aberrant in one or more of the characters mentioned, while the cospecific worker retains the ancestral characters of its caste in the closely allied forms of F. rufa. The same condition is seen in a very different ant, Aphenogaster ten- nesseensis, as the result of similar parasitic habits. In all of these species the females alone have developed myrmecophilous characters, like the long yellow hairs of F. ciliata, or the mimetic coloring of F. difficilis, which enable them to foist themselves on the allied species and thus avoid the exhausting labor of excavating nests and rearing workers. POLYMORPHISM. eS) The foregoing observations indicate that in morphological charac- ters the worker and female of the same species have advanced or digressed in their phylogeny, remained stationary or retrograded, independently of each other. The same peculiarity is also observable in species with distinct worker and soldier castes. It thus becomes im- possible, even in closely related species of certain genera, like Phet- dole, to predict the characters of the worker from a study of the co- specific soldier or vice versa. And while adaptive characters in sta- ture, sculpture, pilosity and color must depend for their ontogenetic development on the nourishment of the larve, it is equally certain that they have been acquired and fixed during the phylogeny of the species. In other words, nourishment, temperature, and other environmental factors merely furnish the conditions for the attainment of characters predetermined by heredity. We are therefore compelled to agree with Weismann that the characters that enable us to differentiate the castes must be somehow represented in the egg. We may grant this, however, without accepting his conception of representative units, a conception which has been so often refuted that it is unnecessary to reconsider it in this connection. Having touched on this broader problem of heredity it will be neces- sary to say something about the inheritance or non-inheritance of acquired characters, especially as Weismann and his followers regard the social insects as demonstrating the non-transmissibility of somato- genic traits. In establishing this view and the all-sufficiency of natural selection to which it leads, Weismann seems to have slurred over the facts. While he admits that the workers may lay eggs, and that these may produce male offspring capable of fertilizing females, he never- theless insists that this is altogether too infrequent to influence the germ-plasm of the species. I venture to maintain, on the contrary, that fertile workers occur much more frequently in all groups of social insects than has been generally supposed. As this fertility is merely a physiological state it has been overlooked. Marchal has shown how readily the workers of the social wasps assume this state, and the same is true of the honey-bees, especially of certain races like the “ Egyptians’ and “ Cyprians” (Apis mellifica-fasciata and cypria). In the hives of these insects fertile workers are either always present or make their appearance within a few days after the removal of the queen. In the termites fertile soldiers have been observed by Grassi and Sandias and fertile workers by Silvestri. Among ants fertile or gynecoid workers occur so frequently as to lead to the belief that they must be present in all populous colonies. Their presence is also proved by the production of considerable numbers of males in old 116 ANTS. and queenless colonies. In artificial nests Wasmann, Miss Iielde and myself have found egg-laying workers in abundance. Now as the males that develop from worker eggs are perfectly normal, and in all probability as capable of mating as those derived from the eggs of queens, we are bound to conclude, especially if we adopt the theory of heredity advocated by Weismann himself, that the characters of the mother (in this case the worker) may secure repre- sentation in the germ-plasm of the species. Weismann is hardly con- sistent in denying the probability of such representation, for when he is bent on elaborating the imaginary structure of the germ-plasm he makes this substance singularly retentive of alteration by amphimixis, but when he is looking for facts to support the all-sufficiency of natural selection the germ-plasm becomes remarkably difficult of modification by anything except this eliminative factor. Certainly the simplest and directest method of securing a representation of the worker characters in the germ-plasm would be to get them from the worker itself that has survived in the struggle for existence, rather than through the action of natural selection on fortuitous constellations of determinants in the germ-plasm of the queen. If we grant the possibility of a periodical influx of worker germ-plasm into that of the species, the transmission of characters acquired by this caste is no more impossible than it is in other animals, and the social insects should no longer be cited as furnishing conclusive proof of Weismannism. Plate has attempted to overcome the difficulties presented by the normal sterility of the worker by supposing that the distinguishing characters of this caste arose prior to their inability to reproduce. He recognizes the following stages in the phylogeny of the social insects : “1, The presocial stage with but a single kind of male and female. “2. The social stage with but a single kind of male and female. The peculiarities in nesting, caring for the brood, and other instincts were already developed during this stage. “3. The social stage with one kind of male and two or several kinds of females, which were all fertile, but in consequence of the physiological division of labor became more and more different in the course of generations. The division of labor took place in such a manner that the sexual functions passed over primarily to a group A, while the construction of the nest, predatory expeditions and other duties devolved mainly on another group of individuals (B), which on that account used their reproductive organs less and less. “4. The present stage with one kind of male, a fertile form of POLYMORPHISM. 117 female, which arose from group A, and one or several kinds of sterile females, or workers (group B).” Plate assumes that the differentiation into sterile and fertile forms did not take place until stage 3, and if I understand him correctly, not till after ‘“‘ the races had become differentiated morphologically.” This view, as he admits, resembles Spencer’s (p. 100). The two views, in fact, differ merely in degree, for the underlying contention is the same, namely that sterility is one of the most recently developed characters among the social insects. There can be little doubt, however, that the smaller adaptive characters, for example those of the families of certain species of Formica above mentioned, must have made their appearance in the fourth stage of Plate’sscheme. The view which I have advocated differs from Plate’s in admitting that even in this stage the workers are fertile with sufficient frequency to maintain a representation of their characters in the germ-plasm of the species. Conclusive evidence of the presence or absence of such representation can be secured only by experimental breeding, and especially by hybridizing the male off- spring of workers of one species (a), with females of another (Db) that has workers of a different character. In the foregoing discussion attention has been repeatedly called to adaptation as the insurmountable obstacle to our every endeavor to explain polymorphism in current physiological terms. Of course, this is by no means a peculiarity of polymorphism, for the same difficulty confronts us in every biological inquiry. As the type of polymorphism with which we are dealing has been developed by psychically highly endowed social insects, it cannot be adequately understood as a mere morphological and physiological manifestation apart from the study of instinct. This has been more or less clearly perceived by nearly all writers on the subject. However various their explanations, Spencer, Weismann, Emery, Forel, Marchal and Plate all resort to instinct. Emery especially has seen very clearly that a worker type with its peculiar and aberrant characteristics could not have been developed except by means of a worker-producing instinct. In other words, this type is the result of a living environment consisting of the fostering queen and workers which instinctively control the development of the young in so far as this depends on external factors. Only under such conditions could a worker caste arise and repeat itself generation after generation. This caste may be regarded as a mutation comparable with some of De Vries’s Genothera mutations, but able to repeat and maintain itself for an indefinite series of generations in perfect symbiosis with its parent form, the queen, because, notwithstanding its relative infertility, it can be put to very important social use. Among ants this social 115 ' ANTS use not only pervades the activities of the adult worker but extends even to the more inert larval stages. Thus the latter represent a rich and ever-fresh supply of food that can be devoured whenever a tem- porary famine overtakes the colony. In certain species, like the East Indian CEcophylla smaragdina and the South American Camponotus senex, the larvee are more humanely employed as spinning machines for constructing the silken nest inhabited by the colony (see p. 216). These examples also illustrate the purposive manner in which an organism can satisfy definite needs by taking advantage of ever- present opportunities. In the lives of the social insects the threptic, or philoprogenitive instincts are of such transcendent importance that all the other instincts of the species, including, of course, those of alimentation and _nest- building, become merely tributary or ancillary. In ants, especially, the instincts relating to the nurture of the young bear the aspect of a dominating obsession. Their very strength and scope render the insects more susceptible to the inroads of a host of guests, commensals and parasites. Besides the parasitic larve of Chalcidids, Lomechusini and Metopina, to be described in Chapter XXII, there are many adult beetles and other insects on which the ants lavish as much attention as they do on their own brood. And when the ants themselves become parasitic on other ants, it is always either for the sake of having their own brood nurtured, as in the temporarily and permanently parasitic forms, or for the purpose of securing the brood of another species, as in the slave-making species. The philoprogenitive instincts arose and were highly developed among the solitary ancestral insects long before social life made its appearance. In fact, social life is itself merely an extension of these instincts to the adult offspring, and there can be no doubt that once developed it reacted rapidly and powerfully in perfecting these same instincts. It is not so much the fact that all these activities of the social insects converge towards and center in the reproduction of the species, for this is the case with all organisms, as the elaborate living environment developed for the nurture of the young, that gives these insects their unique position among the lower animals. A full analysis of the threptic instincts would involve a study of the entire ethology of the social insects and cannot be undertaken at the present time. Nevertheless the bearing of these activities on the subject of poly- morphism can hardly be overestimated and deserves to be emphasized in this connection. All writers agree in ascribing polymorphism to a_ physiological division of labor among originally similar organisms. This is tanta- POLYMORPHISM. EIQ mount to the assumption that the phylogenetic differentiation of the castes arose in the sphere of function before it manifested itself in structural peculiarities. Although this view implies that the female, or queen was the source from which the instincts and structures of the worker were derived, it has been obscured by an improper emphasis on the instincts of the honey-bee, in which the female is clearly a degen- erate organism, and on certain specialized instincts, supposed to belong exclusively to worker ants like those of the slave-makers (Polvergus and Formica sanguinea). We have therefore to consider first the in- stincts of the queen, and second, any evidence that may go to show that instinct-changes precede morphological differentiation in the phylogeny of the species. It is evident that the social insects may be divided into two groups according to the instinct role of the queen. In one group, embracing the social wasps, bumble-bees, ants and termites, the female is the complete prototype of her sex. Even the queen of the slave-making ants, manifests in the founding of her colonies all the threptic instincts once supposed to be the exclusive prerogative of the worker caste. These may be called the primary instincts. After the colony is estab- lished, however, and she no longer needs to manifest these instincts, she becomes a mere egg-laying machine and her instincts undergo a corresponding change and may now be designated as secondary. She thus passes through a gamut of instincts successively called into activity by a series of stimuli which in turn arise in a definite order from her changing social environment. The workers, however, are capable of repeating only a portion of the female gamut, the primary series. In gynzecoid individuals there is also a tendency to take up the secondary series, but in most workers this has been suppressed by countless generations of nutricial castration. The social insects of this type may be called gynecotelic, to indicate that the female preserves intact the full series of sexual attributes inherited from her solitary ancestors. In these the primary and secondary series are simultaneous or overlap completely, in the gynzecotelic social insects they are extended over a longer period of time and overlap only in part, as social life permits the extension of the secondary long after the primary series has lapsed into desuetude. It will be seen that the division of labor which led to the special differentiation of like females into workers and queens is clearly foreshadowed in the consecutive differentiation of instincts in the individual queen. The second group of social insects is repre- sented by the honey-bees and probably also by the stingless bees (Meli- ponide). In these only the secondary instincts are manifested in the queen, while the worker retains the primary series in full vigor and 120 ANTS. thus more clearly represents the ancestral female of the species. . This type may therefore be called ergatotelic. The suppression of the primary instincts in the queen honey-bee was undoubtedly brought about by the change in the method of colony formation. When the habit of swarming superseded the establishment of colonies by solitary queens, as still practiced by the gynzcotelic insects, the primary in- stincts of the female lapsed into abeyance or became latent. This change took place so long ago that it has had time to express itself in the structure of the queen honey-bee as compared with the worker (shorter tongue and wings, feebler sting, degenerate structure of hind TESS ELCe )): The first of the following examples, which seem to indicate the occurrence of instinctive prior to morphological differentiation, shows at the same time how the ergatotelic type of the honey-bee may have arisen from the gynzecotelic type of the social wasps and bumble-bees. 1. The queens of certain species of Formica (F. rufa, exsectoides, etc.), are no longer able to establish colonies without the cooperation of workers. The common method of colony formation among these insects is by a process of swarming like that of the honey-bees: a cer- tain portion of the colony emigrates and founds a new nest with one or more queens. When this method is impracticable the young queen seeks the assistance of an allied species of Formica (F. fusca), the workers of which are willing to take the place of her own species in rearing her brood. In F. rufa and exsectoides there is nothing in the stature or structure of the queen to indicate the presence of these parasitic instincts, but, in many of the allied species like F. ciliata, microgyna, etc., the colonies of which are smaller and no longer swarm, or do so only to a very limited extent, the queens have become more dependent on the workers of other species of Formica and have devel- oped mimetic characters or a dwarf stature to enable them to enter and exploit the colonies of their hosts. 2. In many ants the callows, or just hatched workers, confine them- selves to caring for the larve and pupz and do not exhibit the foraging instincts till a later period. But even adult workers may perform a single duty in the colony for long periods of time, if not indefinitely. Thus Lubbock (1894) and Viehmeyer (1904) have observed in certain Formica colonies that only certain individuals forage for the com- munity. The latter has also noticed that, certain individuals, indis- tinguishable morphologically from their sister workers, stand guard at the entrances. In other genera, like Camponotus, Atta, Pheidole, etc., with species that have desmergates, the morphological differentiation between foragers and guardians is still unsettled. It becomes com- rig POLYMORPHISM. 121 pletely established, however, in certain genera and species with the suppression of the desmergates. A remarkable example of division of labor, without corresponding structural differentiation, is seen also in the Gcophylla above mentioned, an ant which inhabits nests of leaves sewn together with fine silk. According to the observations of Dodd (1902) and Doflein (1905), when the nests are torn apart the monomorphic workers separate into two companies, one of which stations itself on the outside of the nest, draws the separated leaves together and holds them in place with the claws and mandibles, while the other moves the spinning larvee back and forth within the nest till the rent is repaired with silken tissue (see p. 216). 3. An interesting case is presented by the honey-ants (J yrmecocys- tus melliger and mexicanus). All the workers of these species, though variable in size, are structurally alike. Among the callows, however, and quite independently of their stature, certain individuals take to storing liquid food, as | have found in my artificial nests of the latter species, and gradually, in the course of a month or six weeks, become repletes, or plerergates. Except for this physiological peculiarity, which gradually takes on a morphological expression, the plerergates and ordinary workers are indistinguishable. We must assume, there- fore, that the desire to store food represents an instinct specialization peculiar to a portion of the callow workers. There can be no doubt that as our knowledge of the habits of ants progresses many other cases like the foregoing will be brought to lght. It may be maintained that in these cases physiological states must precede the manifestation of the instincts, and that these states, how- ever inscrutable they may be, are to be conceived as structural differen- tiations. There is undoubted!y much to justify this point of view. The elaborate sequence of instincts in the queen ant, for example, is accompanied by a series of physiological changes so profound as to be macroscopical. After the loss of her wings, the wing muscles degen- erate and the fat-body melts away to furnish nourishment for the ovaries, which in the old queen become enormously distended with eggs as the breeding season approaches. Such changes would seem to be amply sufficient to account for the changing instincts. I have found that mere artificial dealation at once alters the instincts of the queen, probably through a stimulus analogous to that which leads to the atrophy of a muscle when its nerve is severed, and in the case under consideration leads to the degeneration of the wing-muscles and to changes in the ovaries. In the mermithergates and pseudogynes we also have peculiarities of behavior which are attributable to peculiar 122 ANTS. physiological states. Similarly, nutricial castration may be said to be a physiological state, namely that of hunger. We may conclude therefore that the worker, both in its ontogenetic and phylogenetic development, is through and through a hunger-form, inured to protracted fasting. Miss Fielde has shown (1904f) that the workers of Camponotus americanus may live nearly nine months with- out food, which is as long as the much larger and more vigorous queens are known to fast while establishing their colonies. The larvz of ants, too, are known to remain alive in the nests for months without growing. And even when food is abundant the workers appropriate very little of it to their individual maintenance, but distribute it freely among their sister workers, the brood and queen. It is not improbable, moreover, that the single instinct peculiar to workers, the instinct to leave the nest and forage, is the direct result of a chronic state of hunger. CHAPTER, VTE THE-HISTORY OF -MYRMECOLOGY , ANDETHE “CLASSIFICATION OFF ANTS: “Les meeurs des fourmis sont si variées qu’il est important de connoitre a quelle espece se rapporte chaque trait d’industrie, chaque particularité de leur histoire.’ —P. Huber, “ Recherches sur les Mceurs des Fourmis Indigénes,” 1810. 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. The reason for this fortunate circumstance is probably to be sought in the ingenium formice male habitat, the fact that ants are small, homely organisms with nothing to attract the amateur who cares only for size and beauty of form and color. This is, perhaps, regrettable as it has Fic. 67. Worker of Sima allaborans of India. (Bingham.) certainly retarded the accumulation of study materials in our museums and private collections, and has left the subject in the hands of a few devotees. But this disadvantage is not so great as might be supposed, because the species of ants, though far less numerous than those of butterflies and beetles, are nevertheless more abundant in individuals and hence more easily obtained. Undoubtedly the great difficulty of the study has had much to do with limiting the number of myrmecologists, especially in America. Here the literature of descriptive myrmecology, which is widely scattered through somewhat obscure serials and is written very largely in the German, French and Italian languages, has remained quite inaccessible to the average student. Even a knowleds 123 124 AN TS. of the literature, however, does not overcome all of the difficulties of the subject, for the species of ants often differ from one another by characters too subtle and intangible to be readily put in words. The “habitus” of a species, as every taxonomist knows, is something one may take in at a glance, but be quite unable to express without weari- some prolixity. Hence the importance of large collections, thoroughly studied and identified and accessible to every student. Such coilections have been lacking in America and those interested in ants have had to send their specimens abroad for identification. This is time-con- suming, to say nothing of the inconvenience to which it often puts the overworked specialist. Ants, like other organisms, may be studied from at least three different points of view, according as the observer is most interested in their classification, or taxonomy (including geographical distribu- tion), their morphology (anatomy and development) or their ethology, that is, their functional aspect (physiology and psychology). Even in such a small group of insects these various subjects are so extensive and intricate that very few observers have been able to cultivate them all with equal success. Fic. 68. Worker of Tri- gonogaster recurvispinosa of Western India. (Bingham. ) This has, perhaps, been accomplished only by Emery and Forel, each of whom has de- voted more than forty years of unremitting study to the ants. Other workers have been able to cultivate only one or at most two of the subjects above mentioned. Be- fore considering the classification it may be well to sketch with the utmost brevity the history of myrmecology in its various branches. The foundations of the taxonomy of ants were laid in the closing years of the eighteenth and the opening years of the nineteenth cen- tury by Linné, Fabricius and Latreille. Linné (1735) in his Nature” briefly described eighteen species, eight from Europe, oe Systema eight from South America and two from Egypt as belonging to the single genus Formica. species of animal and plants, are collective species, that is, they embrace several of what would now be regarded as distinct species. Fabricius (1804), besides describing a number of additional species, created five more genera: Lasius, Cryptocerus, Atta, Myrmecia and Dorylus. Of course, none of these corresponds fully to the genus bearing the same name at the present time. Some of these, like other well-known Linnzan He still retained the great majority of the species in the Linnzan genus Formica, but divided it into two purely artificial categories, one for the species with, and one for the species THE HISTORY “OF MYRIMBECLOGY. 125 without spines on the thorax. Neither Linné nor Fabricius seems to have paid much attention to the habits of the ants. The third and by far the most important of the pioneers in myr- mecography was Latreille (1798), 1802b). He collected the ants of Europe, studied their habits assiduously and described many species that had been overlooked by his predecessors, including a number of in- teresting forms. He produced good descriptions of nearly a hundred species which he had himself examined. All of these he placed in the single genus Formica which he divided into nine “ families”: the For- mice arcuate (corresponding to our present genera Camponotus and Polyrhachis), cameline (our Formica, Lasius, Myrmecocystus, CEco- phylla and Dolichoderus in part), atomarie (our Dolichoderus in part, Tapinoma and Acantholepis), ambigue (Polyergus), chelate (Odonto- machus), coarctate (Ponera, Pachycondyla, Neoponera, Ectatomma, Myrmecia, etce.), gibbose (Atta, Pheidole, Messor, Pogonomyrme.x, etc.), punctorie (Eciton, Myr- mica, Tetramorium, Myr- mecina, Leptothorax, Sole- nopsis, etc.) and caperate (Crvptocerus, Gecophylla). It is impossible to run over this arrangement without Fic. 69. Worker of Aphenogaster beccarii of the Indomalayan region. (Bingham.) admiring Latreille’s acu- men in so clearly forecasting the limits of many of our modern sub- families, tribes and genera. For nearly fifty years after the publication of Latreille’s work sys- tematic myrmecology stagnated, till a revival of interest in the subject began to set in about the middle of the past century with the work of Nylander and Mayr. Both of these authors devoted themselves to a careful study of the European species, Nylander to the boreal, French and Mediterranean, and Mayr to the Austrian and eventually to the whole European fauna. Both authors, but especially Mayr, defined the genera and species more accurately than any of their prede- cessors. Later Mayr extended his studies to the faunas of foreign countries and published several important works on the ants of Asia, Africa, Australia, and North and South America. Forel, in comment- ing on his work says: “ His remarkable perspicacity in creating genera, and in general in the distinction of the comparative value of zodlogical characters, and the minute exactitude of all his writings, which repre- sent a vast amount of labor, have raised myrmecology to the rank of 120 ANTS. the best known portions of entomology.” A well-known English hymenopterist of the same period, Frederick Smith, undertook a similar universal study of the ants, basing his descriptions on the numerous specimens from all parts of the world in the collections of the British Museum. Many of his species are so inadequately described that the writers of today are obliged either to discard them or to make pilgrimages to the British Museum for the sake of consulting the types from which they were drawn, and while some of his species bear appropriate or even elegant names, and have been identified after much labor with a fair degree of certainty, his generic distinctions give evidence of de- ficient classificatory sense. During the latter half of the nineteenth century a considerable number of local Euro- pean ant faunas were published and our knowl- edge of the ants of other lands grew apace. Adlerz studied the ants of Sweden; Ernest André of France, Europe and North Africa; Bos, Meinert and Wasmann of the Nether- lands; Curtis, Saunders and F. Smith of Eng- land; Forel of Switzerland; Emery of Italy; Gredler of Tyrol; Nassonow and Ruzsky of Russia; Schenck and Forster of Germany, while some accomplished entomologists like Roger, Gerstaecker, Shuckard and Westwood evinced a greater interest in the exotic genera and species. Nor was this activity confined to Fic. 70. Worker of o Cardiocondyla venustula the recent ants. Heer, Mayr, Emery, Ernest ae Rico. (Origit André and others published descriptions of nal. many fossil species preserved in the Baltic and Sicilian ambers and in the strata of Oeningen and Radobo}. Among this group of diligent investigators two are facile principes, Emery and Forel. In 1874 Forel published at a remarkably early age what must always be regarded as one of the finest natural histories of any group of insects, the ““ Fourmis de la Suisse,” a work to which the student must constantly turn both for information and encouragement. Emery and Forel, who both began to publish in 1869 and have con- tinued ever since to make important contributions to our knowledge, combine an excellent zodlogical and philosophical training with rare judgment and acumen. Building on the excellent foundations laid by Latreille, Nylander and Mayr, they have been able to make our knowledge of the ants more complete than that of any other family of the vast Hymenopteran order. Not only have they perfected the THE HISTORY OF MYKMECOLOGY. 127 system of the European species, but they have published excellent monographs and revisions of the faunas of other continents, so that the student of today finds it a comparatively easy task to continue the work. Although the ant-fauna of North America is vastly richer than that of Europe, few of our entomologists have cared to study its tax- onomy and as a rule these few have been poorly prepared to undertake the work. Species have been described by Buckley, Cresson, Fitch, Haldeman, McCook, Norton, Pergande, Provancher, Scudder, Viereck 4 and Walsh, but the really valuable work Fic. 71. Worker of Ste- on our fauna has been accomplished by (iigtant) poruyct SCevion: Mayr, Emery and Forel. The study of ant ethology has had a more continuous, though per- haps slower, development than the taxonomy. It is also much older, and may be said to date back to the seventeenth and eighteenth cen- turies, to authors like Wilder (1615) Bonnet (1779-83), Swammerdam (1682), Leuwenhoeck (1695), Gould (1747), De Geer (1778) and Christ (1791). The subject does not begin to assume definite form, however, till we reach the writings of Latreille (1802) and especially of Pierre, the son of the celebrated Francois Huber. P.Htuber’s work entitled “ Recherches sur les Mceurs des Fourmis Indigenes ”’ published in 1810, is perhaps the most remarkable of all works on the habits of ants. It has been widely quoted and has never ceased to be an inspira- tion to all subsequent workers. It covers much of the subject of the habits of ants in an attractive and luminous style and abounds in accu- rate and original observations. The most interesting portions of the work treat of the slave-making habits of the sanguinary ant (Formica sanguinea) and the amazon (Polyergus rufescens). Huber was not only the first to discover and interpret the symbiotic relations of these species but his account is so complete that even Forel could add to it little that was really new. Huber also observed the relations of the ants to the aphids and of the various castes to one another and correctly interpreted the origin of colonies. Since the publication of Huber’s work the habits of ants have been studied by an ever increasing number of investigators. The most com- prehensive contributions have been made by Forel and Emery, but important work has been done by Adlerz, Ernest André, Bates, Belt, Bethe, Brauns, von Buttel Reepen, Ebrard, Escherich, Goeldi, Heer, J. Huber, von Ihering, Janet, Karawaiew, Lameere, Lespes, Lubbock, Mayr, Moggridge, Reichenbach, Reuter, Rothney, Santschi, Sykes. 125 ANTS. Tanner, Trimen, Ule, Urich, Viehmeyer, Wasmann, Wroughton, and Yung, and in the United States by Buckley, Miss Fielde, Leidy, Lincecum, McCook, Pricer, Mrs. Treat and Turner. The study of myrmecophily, or the relations of the numerous guests. and parasites to the ants, and of the plants frequented by ants, has developed into a very interesting and important branch of ethology which must be mentioned in this connection. An extra- Fic. 72. Species of Macromischa. (Original.) A and B, Worker of M. isabelle of Porto Rico; C and D, worker of M. albispina of Culebra. ordinary number of articles has been published on animal myrme- cophily, especially by Wasmann, who since 1886 has devoted himself to this subject with great ardor, and has brought to light many curious facts which have a bearing not only on the ethology of ants but of DEE SAUS TORY OF MY IRMiECOLOG Y. 129 many other groups of insects. Other students of this subject are Casey, Donisthorpe, Escherich, von Hagens, Kraatz, Lespes, George Lewis, Lichtenstein, Lucas, Raffray, Reuter, de Saulcey, Joh. Schmidt, Sharp, Trimen, Viehmeyer, and in the United States Cockerell, Brues, Hamilton, Haldemann, King, Schwarz and Wickham. The relation of plants to ants has been studied by many botanists, notably by Del- pino, Huth, Holmgren, A. Meeller, Fritz Mueller, Schimper, Treub, von lhering, Rettig and Ule. Although the history of ant morphology also goes back to such investigators as Swammerdam and Leuwenhoek, little headway could be made with the study of struc- ture and development in such small organisms till the microscope and the technique of sectioning and staining had been perfected, and this was accom- plished only within the last quarter of a century. Forel and Emery, and more recently Janet, have done very important work on the anatomy of ants. Other authors worthy of mention in this hasty review, are Adlerz, Berlese, Bos, Dewitz, Fenger, Karawaiew, Leydig, Lubbock, Meinert, Nassonow, Pérez and Sharp. As yet American zoologists have ac- complished little in this interesting and accessible field of investigation. After Fis. 73. Worker of Pristomyr- P : . mex japonicus. (QOriginal.) this hasty sketch of the history of myr- mecology we may take up a somewhat more detailed consideration of the taxonomy of the Formicide. Inasmuch as the generic and specific characters of ants are to be derived not only from a male and female, but also from a worker caste, the classification of these insects presents certain difficulties and peculiarities not encountered in classifying most other animals. The exact status of a species can, of course, be determined only when all of its phases are known. The worker, as the most abundant, is usually first to fall into the hands of the systematist, and many years may elapse before the corresponding female and male are discovered. There are still a great many exotic and even several European species that are known only from one or at most two of the castes. Moreover, the resemblances between the different phases of the same species are often so remote that it is impossible to correlate workers and females workers and males, or males and females, unless they have been taken I9 130 ANTS. from the same nests. It is, therefore, largely a matter of convenience that the soldier or worker is selected as the paradigm of the species and takes precedence of the other forms in systematic descriptions. It is obvious that the female, as presenting more numerous and complete characters, would occupy this position, were it not that this caste is, as a rule, less easily obtainable. Except for the same reason, the male would also occupy a more important place in generic and _ specific diagnosis, since this sex is very stable and often presents important characters, especially in the structure of the genitalia. It is probable, therefore, that at some future time, when large numbers of male and Fic. 74. Worker of Myrmicaria brunnea of India. (Bingham.) female specimens have accumulated in our collections and have been carefully studied, the present classification of the Formicidz will un- dergo considerable alteration. Until this time arrives, however, it will be prudent to move slowly in establishing new genera. Mayr, Forel and Emery have all shown admirable conservatism and a laudable absence of the “ mihi-itch ” in dealing with this aspect of the subject. Another difficulty arises from the great variability of ants, both among members of the same colony and hence among the progeny of a single or a very few mothers, and among colonies of the same species in different stations or localities. In the former case we have what are known as “nest varieties,’ in the latter “local or geographical varieties.” The danger of basing species on mere nest varieties is often considerable and can be overcome only by studying large series of specimens collected from the same colony. Probably many of the “species”? of exotic ants included in our faunistic lists are nothing more than nest varieties. The local varieties are of peculiar interest. Like other animals, certain species of ants may be very stable though widely distributed, others highly variable though very restricted in their range. Some widely distributed species may be stable in some por- tions of their range and highly variable in others. And finally, some widely distributed species seem to be decidedly variable wherever THE HISTORY OF MYRMBCOLOGY. 131 they occur. Such a species is Camponotus maculatus, which occurs on every continent and many islands, and varies ad infinitum. In study- ing such species we are often presented with two sets of variable characters, one of which is adaptive and largely morphological, while the other comprises small indifferent traits of no considerable value to the organism in its struggle with its environment, such as slight peculiarities in size, sculpture, pilosity and color. These characters, which remind one of the De Vriesian “unit characters,” are relatively stable in- particular races or varieties and have a tendency to combine and recombine in endless permutation. Besides C. maculatus, many of the eee eead species of the large genera Formica and Pogo- of female Epitritus A : z : emme of the West nomyrmex are admirable examples of this phe- jiaies. (Original) nomenon. Characters of importance in classification may be drawn from all parts of the ant’s body, but the most useful are furnished by the number of palpal joints, shape of the clypeus, mandibles, shape and compara- tive length of the antennal joints, shape of the thorax, petiole, post- petiole, spurs of the middle and hind tibiz, tarsal claws, genitalia of the male, the venation of the wings of both sexes, the structure of the gizzard, larva and pupa. The tribes, genera and species are built on combinations of these characters. But as there are many minor charac- ters, especially in sculpture, pilosity and color, which though constant for all the members of a caste, may nevertheless vary in colonies in different localities, it becomes necessary to recognize smaller divisions than that of the species. These subdivisions are of different rank for the reason that slight differences in form or sculpture are more important, because less variable, than pilosity and coloration. Myrme- cologists have therefore recognized two categories within the species, one more important and called the race by Forel, the subspecies by Emery, and another less important category which has been called the variety by both of these authorities. Subspecies may be regarded as small or incipient species in the De Vriesian sense. They are much less frequently connected by transitional forms than the varieties. The recognition of these various categories necessitates the employ- ment of a quadrinomial nomenclature. Thus one of our common carpenter ants is known as Camponotus herculeanus Linn. subsp. ligni- perdus Latreille var. noveboracensis Fitch. This is a strictly North American variety, with red head and thorax, of a smooth race, or sub- species, of the dark-colored, opaque, circumpolar species herculeanus the typical form of which is confined to Europe. This method of 132 ANTS. naming ants has great advantages and some disadvantages. It shows the relationships of the different forms very clearly and this is an admirable trait in nomenclature, but it is also very cumbersome. For ordinary purposes it is sufficient to treat the varietal name as if it were specific and designate the ant mentioned above simply as Campo- notus noveboracensis Fitch. This is the more justifiable as the variety among ants is very nearly equivalent to the species among many other groups of animals, such as birds and mammals. In the present work I shall use the binomials as a rule and refer the reader for the full terminology of our North American ants to the catalogue in Appendix C. This chapter may be concluded with a conspectus of the present classification of the Formicide compiled very largely from the works Fic. 76. Worker of Fic. 77. Worker of Strumigenys obscuri- Strumigenys lewisi of Ja- ventris of Porto Rico. pan. (Original.) (Original.) of Emery and Forel. Concerning the important details of this classifi- cation these authorities are unanimous but there are certain points on which they differ, and many which they have left undecided till more material is forthcoming and profounder studies of whole groups of genera have been undertaken. They differ mainly on the limits of two of the five subfamilies, the Ponerinze and Doryline, Emery maintain- ing that the tribe Cerapachysi belongs with the Dorylinze whereas Forel assigns it to the Ponerine. The tribe in question certainly possesses peculiarities which ally it with both subfamilies, but the THE HISTORY OF MYRMECOLOGY. 133 development and habits of its species are so imperfectly known that its exact position cannot be determined at the present time. IL have followed Forel in placing it with the Ponerine though I appreciate Emery’s reasons for dissenting from this procedure. Some of the tribes, especially the Ponerii and Myrmicii still embrace very hetero- geneous groups of genera, and many of the genera, especially those which are known only from specimens of a single caste, are probably Fic. 78. Cryptocerus angulosus of Central America. (Original.) a, Soldier; b, worker; c, head of soldier from above. placed in the wrong tribes. Ashmead (1905c) recently undertook to construct a new arrangement of the genera, but as Emery has shown (1906a), it is anything but an improvement on the existing classifica- tion. What we need for the present as not a new arrangement, the erection of a lot of new genera on superficially aberrant species and the raising of every subgenus to generic rank, but a painstaking study of all the species in the existing groups. Until such studies have made appreciable headway, the existing avowedly imperfect classification should not be discarded without at least as much thought as has been devoted to its construction. ‘Since these remarks were written, Emery (Deutsch. Ent. Zeitsch., 1900. p. 355) has changed his views on the position of the Cerapachysii. He now places them under the new caption Prodoryline, but within the subfamil Ponerine. 134 ANTS. Family FORMICIDA® (Heterogyna). Subfamily I. PONERINZE Mayr. Worker always with highly developed sting. Frontal carinz verti- cal, oblique or forming horizontal lobes partly covering the antennal insertions. Antenne 12-, rarely 9-, 10- or I1-jointed. Palpal joints nearly always reduced. Clypeus well-developed. Pedicel nearly always 1-jointed; first gastric segment usually narrowed behind where it encloses the basally constricted second segment, which bears a stridu- latory organ on its dorsal surface—Female usually winged and but little larger than the worker; ergatoid, apterous or gynzcoid in some forms.—Male usually with long gaster; genitalia partially exserted or in a few tribes (Cerapachysii and Proceratii), completely retractile. Pedicel like that of the worker. Wings usually with 2 closed cubital cells. Wingless, ergatoid males occur in a few species—Pupz always enclosed in cocoons. Tribe 1. MyrMEcII. Australian—Worker and female: Pedicel distinctly 2-jointed as the second abdominal (first gastric segment of other Ponerine) is narrower than the succeeding segment and strongly constricted be- hind. Frontal carinz as in the Ectatommii. Eyes large. Mandibles narrow, with bicuspidate teeth. Palpi with the full number of joints. Females winged, barely larger than the corresponding workers.—Male pedicel like that of the workers. Genitalia bulky, of complicated struc- ture; stipes with dorsal and terminal branches, volsella with a well- developed lamina. Myrmecia (Fig. 3, B). Tribe 2. AMBLYOPONII. Cosmopolitan.—Pedicel t-jointed, articulating over its whole pos- terior surface with the first gastric segment. Mandibles usually nar- row, inserted at the corners of the head. Palpal joints reduced. Eyes of worker vestigial. Posterior tibiz with double spurs. Amblyopone, Stigmatomma (Fig. 131), Mystrium (Fig. 129), Prionopelta, Myopopone. Tribe 3. EcTATOMMIL. Cosmopolitan—Worker and female: Pedicel t-jointed, often scale- like, with slender insertion usually at half the height of the first ‘gastric THE HISTORY OF MYRMEGOLOGY. 135 segment. Palpal joints reduced in number. Frontal carinz diverging behind or feebly converging, their anterior ends rarely dilated to form narrow lobes, but then their posterior ends are widely separated. Typhlomyrmex, Paraponera, Ectatomma (with subgenera: Ectatomma, Acanthoponera, Stictoponera, Muictoponera, Rhytidoponera, Holcoponera and Gnamtogenys ), Thauma- tomyrmex (Fig. 3, 1), Alfaria, Emeryella. Tribe 4. PONERII. Cosmopolitan.—Pedicel of worker and female 1-jointed, usually scale-like, with slender articulation usually at the ventral side of the first gastric segment. Palpal joints reduced in number. Frontal carinz converging posteriorly, often closely approximated behind and usually forming a flattened plate anteriorly into which the posterior end of the Fic. 79. Worker of Dolichoderus bituberculatus of the Indomalayan region. (Bingham. ) clypeus is inserted like a wedge. (Odontoponera is transitional to Ectatomma in the structure of its frontal carine. ) Odontoponera (Fig. 136), Diacamma, Ophthalmopone, Dino- ponera (Fig. 132), Megaloponera (with subgen. Megalo- ponera and Hagensia), Paltothyreus, Plectroctena, Neo- ponera (Fig. 134; with subgen. Neoponera and Eumeco- pone), Pachycondyla (with the subgenera Pachycondyla (Fig. 133), Bothtoponera and Ectomomyrmex), Ponera (Fig. 131), Euponera (with the subgenera Euponera, Meso- ponera, Pseudoponera and Brachyponera (Fig. 135) ), Tra- pesiopelta, Cryptopone, Streblognathus, Belonopelta, Centro- myrmex, Psalidomyrmex, Platythrea, Rhopalopone, My- opias, Onychomyrmex, Prionogenys, Leptogenys (with the subgen. Leptogenys and Lobopelta, Fig. 137), Harpegnathus 136 ANTS. Tribe 5. ODONTOMACHII. Cosmopolitan.—W orker and female characterized by the peculiar configuration of the head and mandibles (Fig. 3, A). Anochetus (with the subgen. Anochetus and Stenomyrme-. ), Champsomyrmex, Odontomachus (Fig. 3, K). Tribe 6. PROCERATII. Cosmopolitan, but not yet known from the Indian and Ethiopian regions.—W orker with vestigial eyes and sutureless thorax. Tip of large first gastric segment turned downward and the succeeding seg- Fic. 80. Species of Liometopum. (Original.) a, Worker of L. apiculatum of Southwestern North America; b, petiole of same seen from behind; c, petiole of female; d, worker of L. microcephalum of Southern Europe; e, petiole of same. ments forming a cone with its tip directed anteriorly —Females winged and with well-developed eyes. Male genitalia completely retractile. Sysphincta (Fig. 128, a), Proceratium (Fig. 128, b), Dis- cothyrea. inde Tribe 7. CERAPACHYSII. Cosmopolitan.—W orkers blind or with vestigial eyes. Antennz Q-12 jointed. Frontal carinz erect. Males and females imperfectly known; in some cases the latter are apterous and dichthadiiform (Acanthostichus). Males with furcate subgenital plate. THE HISTORY OF, M¥YRMECOLOGY. 137 Subtribe (a) Acanthostichu. Acanthostichus, Ctenopyga. Subtribe (b) Cerapachysii s. str. Cerapachys (with the subgenera Cerapachys, Parasyscia (Fig. 125), Oocerea, Syscia and Cysias), Phyracaces, Lioponera, Sphinctomyrme.+ (with the subgen. Sphinctomyrmex (Fig. 126) and Eusphinctus), Probolomyrme.x. Subtribe (c) Cylindromyrmit. Cylindromyrmex (Fig. 127), Simopone. Subfamily Il. DORYLINZ Shuckard. Worker with sting, sometimes vestigial. Frontal carinz vertical or subvertical, closely approximated or even fused, usually leaving the antennal insertions completely uncovered and curved anteriorly around the antennal fovee. Clypeus usually much reduced or even fused with the frontal carinz. Pedicel 1- or 2-jointed. Stridulatory organ im- Fic. 81. Worker major of Pseudolasius familiaris of India. (Bingham.) perfectly developed.——Female apterous, much larger than the worker but like the worker blind or with vestigial eyes. Pedicel always 1- jointed—Male large, with 1-jointed pedicel; anal segment without cerc1 (penicilli) ; genitalia completely retractile——Pupze naked or en- closed in cocoons. Tribe 1. DoryLtt. Paleotropical—Worker eyeless; strongly polymorphic in Dorylus. Pedicel 1—2-jointed. Antennal joints usually reduced in number.— Female eyeless, with gaping end to the gaster and peculiarly formed hypopygium. Sting vestigial—Male with one cubital cell in wings. Genitalia with very narrow lamina annularis; subgenital plate furcate. Dorylus (with subgen. Dorylus (Fig. 141), Anomma, Typhlo- pone, Dichthadia, Alaopone, Rhogmus, Shuckardia), AEnic- tus (Fig. 143), A:nictogeton. ‘ 135 ANTS. Tribe 2. Ecrrontt. Neotropical—W orkers eyeless or usually with vestigial eyes; poly- morphic. Antennz 12-jointed. Pedicel 2-jointed ( 1-jointed in Chelio- myrmex ).—Female resembling that of Dorylus but with vestigial eyes. Gaster not gaping at the tip. Sting vestigial—Male with 2 closed cubital cells in the wings. Genitalia with strongly developed lamina annularis; subgenital plate furcate. Eciton (with subgen. Eciton (Fig. 145) and Acamatus (Fig. 147)), Chehomyrmex (Fig. 148). Tribe 3. LEPTANILLU. Paleotropical— Worker minute, monomorphic, eyeless. Antennz 12-jointed, inserted further apart than in the preceding tribes. Labial palpi 1-jointed.—Female resembling that of Dorylus, eyeless. Gaster gaping at the tip—Male minute, with small eyes, ocelli and mandibles and no veins in the wings. Leptanilla (Fig. 149). Subfamily II]. MYRMICINZ Mayr. Worker with a sting. Frontal carinz and clypeus usually as in the Ectatommii. Palpal joints commonly reduced in number. Pedicel dis- tinctly 2-jointed; very rarely the postpetiole is campanulate and as Fic. 82. Worker of Myrmoteras binghami of Tenasserim. (Bingham.) broad as the succeeding segment. A stridulatory organ is present in at least many of the genera.—Female usually winged, often very different from the worker and much larger; very rarely ergatoid—Male with cerci (absent in Anergates). Genitalia usually partly concealed, rarely completely retractile (Carebara). Gaster usually short. In some genera there are wingless, ergatoid males——Pupz always naked, with- out cocoons. THE HISTORY OF MYRMECOLOGY. 139 Tribe 1. PSEUDOMYRMI. Tropicopolitan.—Characterized by the closely approximated frontal carine in the worker and female (in Pseudomyrma even recalling the conditions in the Doryline ). Clypeus not distinctly wedged in between the frontal carinz. Sima (Fig. 67), Pseudomyrma. Tribe 2. MyrmiIclil. A cosmopolitan, negatively characterized group comprising all the genera that have the clypeus produced back between the frontal carinz and that are not at present assignable to the other tribes. Myrmecina, Pristomyrmex (Fig. 73), Acanthomyrmex, Podo- myrma, Lordomyrma, Dacryon, Odontomyrmex, Atopomyr- mex, Rogeria, Leptothorax (with the subgen. Leptothorax, Temnothorax, Goniothorar and Dichothorax), Trigono- Fic. 83. Two species of Polyrhachis of the Indomalayan region. (Bingham.) 4, P. mayri; B, P. bihamata. gaster (Fig. 68), Macromischa (Fig. 72), Harpagoxenus, Vollenhovia, Stereomyrmex (Fig. 71), Megalomyrmesx, Ocymyrmex, Sifolinia, Myrmoxenus, Monomorium (with the subgen. Monomorium, Adlerzia, Martia and Holcomyrme.x), Cardiocondyla (Fig. 70), Emerya, Xenomyrmex, Huberia, Phacota, Epacus, Anergates, Wheeleriella, Liomyrme-x, Machomyrma, Symmyrmica, Formicoxenus, Pheidole (with 140 ANTS. the subgen. Pheidole and Ceratopheidole), Epipheidole, Sympheidole, Stenamma, Aphenogaster (with the subgen. Aphenogaster and Ischnomyrmex), Messor, Oxyopomyr- mex (with the subgen. Oxryopomyrmex and Goniomma), Myrmica, Pogonomyrmex (with the subgen. Pogonomyr- mex, Janetia and Ephebomyrmex), Cratomyrmex, Tricho- myrmex. Tribe 3. CREMASTOGASTRII. Cosmopolitan.—With the characters of the single genus: Cremasto- gaster (with the subgen. Cremastogaster and Oxrygyne). Tribe 4. SOLENOPSIDII. Cosmopolitan.—Workers often highly dimorphic, or very small when monomorphic. Antennz with a reduced number of joints and Fic. 84. Worker of Polyrhachis lamellidens of Japan. (Original.) usually 2-jointed club. Male and female often very large compared with the workers, always winged. Male genitalia sometimes completely retractile. Many of the species are decidedly subterranean, or hypogeic. ° Pheidologeton (with the subgen. Pheidologeton and Ancleus), Aéromyrma, Solenopsis, Oligomyrmex, Carebara, Care- barella, Erebomyrma, Tranopelta, Rhopalomastix, Allo- RHE HISTORY OF MYRMBEGOLOGY. 141 merus, Lophomyrmex, Diplomorium, Melissotarsus (Fig. A 1 139). Tribe 5. MyRMICARII. Indo-A frican.—With the characters of the single genus : Myrmicaria (Fig. 74). Tribe 6. TETRAMORII. Cosmopolitan.—Usually characterized by the 1o-jointed antenne in the male, with 9-12-jointed antennz in the worker and female, in the latter the frontal carinze are often moved a great distance towards the sides of the head and form deep grooves for the antenne. Tetramorium (with the subgen. Tetramorium, Tetrogmus and Xiphomyrmesx), Eutetramorium, Triglyphothrix, Mayriella, Calyptomyrmex, Meranoplus, Strongylognathus, Rhoptro- myrmexr, Wasmannia, Ochetomyrmex. Tribe 7. DACETONII. Cosmopolitan.—Antennz of worker 5-12-jointed, in the male always 13-jointed. Daceton, Acanthognathus, Orectognathus, Strumigenys (Figs. 706 and 77), Epitritus (Fig. 75), Rhopalothrix, Ceratobasis. Tribe 8. ATTII. Neotropical—Antennz of worker and female 1i-jointed, with a tendency to form a 1-jointed club; 13-jointed in the male. All the known species cultivate fungi for food. Apterostigma, Myrmicocrypta, Sericomyrmex, Cyphomyr- mex, Atta (with the subgen. Atta, Acromyrmex, Mellerius, Trachymyrmex, Mycetosoritis and Mycocepurus). Tribe 9. CRYPTOCERII. Neotropical.—Characterized mainly by the peculiar mushroom- shaped gizzard. Frontal carinze in the worker and female prolonged backward above the eyes to form deep scrobes for the antennz.—Male very different from the female. Procryptocerus, Crvptocerus (Figs. 53 and 78). 'This aberrant genus, known only from the peculiar dimorphic workers, has been recently assigned to the Ponerine by Emery. 142 ANTS. Tribe 10. CATAULACII. Paleotropical.—\W/orker and female with deep antennal scrobes on the sides of the head but formed by the true frontal carinz only in front; further back they are bounded by special prolongations.— Male very similar to the female. Antenne in both sexes 11-jointed. Cataulacus (with the subgen. Catau/acus and Otomyrme.x). Subfamily IV. DOLICHODERIN 4: Forel. Gizzard with a 4-sepaled, reflected calyx, completely enclosed within the crop, or without a calyx. Pedicel 1-jointed. Poison gland of worker and female without pulvinus, invaginating the cuticle of the vesicle, becoming enclosed within this organ and terminating in a knob. Tube of gland straight throughout, and furnished with lateral Fic. 85. Worker of Hemioptica scissa of Ceylon. (Bingham.) tubules for each cell. Poison vesicle variable in form, usually small, sometimes like the gland itself, highly vestigial. Sting very small (ex- cept in Aneuretus), vestigial, but not transformed into an organ to sup- port the orifice of the vesicle. Cloacal orifice large, forming a non- ciliated, transverse slit, usually ventral to the tip of the gaster. Pygi- dium commonly vertical or oblique antero-posteriorly and concealed under the fourth gastric segment. Antennz 12-jointed. Anal glands almost always present and secreting an aromatic product of charac- teristic odor (Tapinoma odor).—Pupe naked, never enclosed in cocoons. Cosmopolitan. Aneuretus (Fig. 140), Dolichoderus (with subgen. Dolicho- derus (Fig. 79), Hypoclinea and Monacis), Leptomyrme., Liometopum (Fig. 80), Azteca, Semonius, Tapinoma (with the subgen. Tapinoma, Ecphorella and Doleromyrma), Turneria, Technomyrmex, Dorymyrmex, Forelius, [rido- myrmex (Fig. 86), Engramma, Bothriomyrmex, Linepi- thema. PAE HISTORY OF MYRMIECOLOGY. 143 Subfamily V. CAMPONOTINZ: Forel. ; Gizzard with a 4-sepaled straight, recurved or reflected calyx, which however, is always covered with circular muscles that separate it from the cavity of the crop. Pedicel 1-jointed. In the worker and female the poison gland forms a flat or oval cushion in the back of the vesicle, with a large tube but without accessory tubules for each cell. Poison vesicle large and elliptical. Sting transformed into a small vestigial apparatus which serves to support the orifice of the vesicle. All the gastric segments visible from above. Terminal segment conical, bear- ing at its apex the small, round, ciliated cloacal orifice. Anal glands lacking.—Pupz usually enclosed in cocoons, but sometimes naked. The following tribes are established mainly on peculiarities in the structure of the gizzard. Tribe 1. PLAGIOLEP MII. Cosmopolitan but mostly paleotropical. Plagiolepis (Fig. 87), Acropyga, Rhizomyrma, Acantholepis (with subgen. Acantholepis and Stigmacros), Brachymyr- mex, Myrmelachista, Melophorus (with subgen. Melophorus and Lasiophanes), Notoncus, Aphomomyrmex, Rhopalo- myrme.x. Tribe 2. DimMorPHOMYRMII. Paleotropical. Dimorphomyrmesx (Fig. 98). Tribe 3. MyRMOTERATII. Paleotropical. Myrmoteras (Fig. 82). Tribe 4. CGECoPHYLLII. Tropicopolitan. Ecophylla (Vig. 123), Gigantiops, Gesomyrmex (Fig. 100). Tribe 5. ForMICctt. Cosmopolitan. Prenolepis (with the subgen. Prenolepis, Euprenolepis and Nylanderia), Pseudolasius (Fig. 81), Lasius (with the sub- gen. Lasius, Prolasius and Acanthomyops), Polyergus, Formica (with the subgen. Formica and Proformica), 144 . ANTS. Myrmecocystus (with the subgen. Myrmecocystus and Cataglyphis). Tribe 6. CAMPONOTII. Cosmopolitan. Camponotus (with the subgen. Camponotus and Colobopsis), Rhinomyrmex, Mayria, Myrmecopsis, Calomyrmex, Myr- mecorhynchus, Dendromyrmex, Opisthopsis, Echinopla, Polyrhachis (Figs. 83 and 84), Hemioptica (Fig. 85). CHAPTERS ES THE GEOGRAPHICAL DISTRIBUTION OF ANTS. “ These craggy regions, these chaotic wilds, Does that benignity pervade, that warms The mole contented with her darksome walk In the cold ground; and to the emmet gives Her foresight, and intelligence that makes The tiny creatures strong by social league; Supports the generations, multiplies Their tribes, till we behold a spacious plain Or grassy bottom, all, with little hills— Their labour, covered, as a lake with waves; Thousands of cities, in the desert place Built up of life, and food, and means of life!” —Wordsworth, “ The Excursion,’ Book IV. Few circumscribed groups of animals have a more significant geo- graphical distribution than the ants. As colonies they are fettered to the soil or vegetation, but their winged females, though feeble flyers, may be wafted long distances by the wind and thus overcome mountain and water barriers of considerable magnitude. In these respects ants resemble plants, which, though rooted in the ground, are able never- theless greatly to extend the range of their species by means of wind- or animal-borne seeds. That ants are often carried by air currents to great distances beyond their normal range is attested by a number of facts. Annually numbers of female ants are wafted out to sea or into our great lakes to be drowned and eaten by fishes, or conveyed to deso- late mountain summits where they perish in futile attempts to found colonies. Occasionally however such widely dispersed females do suc- ceed in establishing themselves and in rearing their offspring. Accord- ing to Forel (1901m) the occident ant (Pogonomyrmex occidentalis), a species peculiar to the Great Plains, has been taken in Hawaii, and King (190ra) has found in Massachusetts a single colony of Formica neoclara, an ant restricted, so far as known, to the mountain valleys of Colorado. This method of dispersal is, of course, denied to all ants like the Dorylinz, certain Ponerine and Myrmicine, whose. females are wing- less, since these insects cannot cross bodies of water nor high moun- tain ranges. But as the Doryline are migratory ants, and, as a rule, do not inhabit permanent nests, their colonies compensate, to a certain II 145 146 ANTS. extent, for the apterous condition of their females. There is, however, a passive displacement or dissemination of whole colonies in certain species like the fire-ant (Solenopsis geminata), which often nests in low-lands subject to frequent and sudden inundations. Von [hering (1894) has made the interesting discovery that when a nest of these ants is flooded, they agglomerate to form a ball 16-25 cm. in diameter, which encloses the brood in the center. This ball is borne along on the surface of the water while its living units keep shifting their position to avoid too prolonged immersion, till the shore or some projecting rock or tree-trunk is reached, when the colony scrambles out of the uncongenial element. I am informed by a gentleman from Louisiana that this same ant resorts to the same method of saving its colonies in the flooded bayous of the Southern States. Similar observations have been made by Savage (1847) on the African driver ants (Anomma arcens) and by Ern. André (1885) on European ants. Finally, ant colonies or fertile female ants are often transported by man from land to land as stowaways in the cargoes of ships and railway trains. Every botanical garden annually receives several species of these insects from the tropics in the pseudobulbs of orchids, among the leaves of aroids or tillandsias, or in the soil and moss adher- ing to the roots of plants, and some of the smaller species thus unin- tentionally imported manage to establish themselves permanently in the hot-houses. Owing to these various means of dissemination, the species of ants have become more widely distributed than any other insects, with the possible exception of the Diptera. Some of our American forms, for example, Dorymyrmex pyramicus, range from Illinois to Argen- tina. Many species, like Eciton cecum and Solenopsis geminata, are coextensive with the tropical and subtropical portions of America, and the latter also occurs in the tropics of the Old World. The former, being a Doryline ant, does not occur in the West Indies. Still other species, like Camponotus herculeanus, Formica fusca and san- guinea, extend over the whole north temperate portion of the globe, and C. maculatus is represented by subspecies or varieties on every continent and on many of the outlying islands. The distribution of ants may be studied either from a faunistic or from an ethological point of view. In faunistic studies the emphasis is placed on the areas or ranges covered by the various species, sub- species and varieties and on the bearing of such distribution on the genesis or descent of taxonomic groups as units. And since the exist- ing fauna is unquestionably derived from previous faunas, which must have determined its character and composition, we are compelled to THE GEOGRAPHICAL DISTRIBUTION OF ANTS. 147 seek for antecedent explanatory conditions in geology and paleontology. In ethological studies, on the other hand, one turns at once to the adaptations of the living forms to their specific environment and works back from these adaptations to the geographical and geological con- ditions by which they are influenced. Of these two methods, which necessarily supplement each other, the latter leads to more detailed and positive results, since our knowledge of previous faunas is in all cases more or less vague and problematic. A résumé of what has been ascer- tained concerning fossil ants will be given in the next chapter, but owing to its fragmentary character, will be used rather as a confirma- tion than as a foundation for inferences drawn from our existing fauna. Emery (1893-94) and von Ihering (1894) have shown that there is a very significant parallelism between the distribution of mammals and that of ants. Both groups appear to have arisen simultaneously dur- ing the Triassic or possibly during some previous period, and to have spread over the earth’s surface in much the same manner, although, if we except the bats, few mammals have possessed such power of dis- persal as the ants. A study of the mammals indicates that during the Mesozoic era there were extensive land connections between the present continents of Eurasia, Africa, America and Australia, and that these various regions were inhabited by a primitive, widely-distributed but now extinct fauna. During this era New Zealand was cut off from Australia and during the following Eocene epoch Africa, South Amer- ica and Australia were in turn separated from the great continental mass. During the Oligocene a boreal and Indian fauna became differ- entiated in Eurasia and their separation was emphasized during the Miocene and Pliocene periods by an upheaval of the boundaries between the respective regions. During the early Tertiary, also, the connection between North and South America was severed and was not restored, according to some paleontologists, till the Pliocene epoch. It is highly probable, as Emery has suggested, that the Ponerine correspond to the primitive, widely-distributed mammals of the Mesozoic era, and together with certain Myrmicine, like Solenopsis, Pheidole, etc., rep- resent an ancient cosmopolitan ant-fauna. Ponerine occur even in New Zealand, which appears to have been isolated ever since the Jurassic. Since the Dorylinze are well developed in the tropics of both hemispheres, these ants must have arisen before Africa was sepa- rated from South America, probably from some primitive and wide- spread Ponerine forms like the Cerapachysii. The almost complete absence of Dolichoderine in Africa shows that this subfamily must have made its appearance after Africa had been separated from Eurasia. That the Dolichoderine came from Ponerine ancestors is indicated 145 ANTS. by the annectant genus -Jneuretus, still living in Ceylon, and the genera Protaneuretus and Paraneuretus, which I have detected in the Baltic amber. The Camponotine are a thoroughly cosmopolitan group, though represented by the greatest variety of types in the Old World. They must have arisen from the Ponerine at a very remote period during Mesozoic times. It is very probable that the separation of the Indian from the South American region preceded the development of certain peculiar tribes among the Myrmicinee and Camponotine since we find the singular Cryptoceri1 and Attii confined to the American tropics, whereas, the Indian region has the Cataulacii, Polyrhachis, and several remarkable Camponotine genera. The Tetramorii, too, are almost exclusively Indo-African, being represented in America only by a few more or less aberrant species. The north temperate regions both in Eurasia and America seem to have remained long enough in connection with the Indian region to acquire an admixture of types from this source. Purely north tem- perate elements are the genera Formica, Polyergus, Lasius, Myrmica, Stenamma s. str. and certain species of Leptothorax (acervorum) and Camponotus (herculeanus). Europe acquired its species of Mono- morium, Tetramorium, Cremastogaster, Plagiolepis, Acantholepis and Bothriomyrmex from southern Asia, and North America received its species of Monomorium and Cremastogaster irom the same source. The history of the North American ant-fauna deserves somewhat fuller treatment. This fauna, which during preglacial times was prob- ably exceedingly rich in genera and species, must have been largely exterminated when the northern portion of our continent was buried under the great ice-sheet. Further southward a few of the more warmth-loving forms managed to survive, where they have persisted as relicts, while somewhat more numerous remnants of the ancient preglacial arctic fauna survived along the edge of the ice-sheet or possibly on small non-glaciated islands farther north. South of the ice-sheet the survival of the old forms was greatest in the Sonoran province, i. e., in Northern Mexico and the Southwestern States. This seems to have been an arid region even at that time and was, therefore, warmer than the more humid southeastern portion of the continent. The recession of the ice-sheet at the close of the glacial epoch was followed by a northward migration of the ants. This appears to have taken place in much the same manner as Adams has described for other North American animals and plants: “The returning biota fol- lowed, in all probability, a definite successional relation and was com- posed of three general belts or ‘ waves,’ concentrically distributed south of the ice margin. The first one was of the barren ground type, the THE GEOGRAPHICAL DISTRIBUTION OF ANTS. 149 second was represented by distinct eastern and western coniferous forest types, and the third by the biota of the southeastern and south- western states. The first wave was of a trans-continental extent, the second while coniferous and transcontinental was composed of two distinct types, the eastern, represented by the biota of northeastern North America, and the western by that of the Rocky Mountains and the Pacific Coast. The northeastern biota overflowed to the north, to the northwest into the Mackensie basin and even a few forms into the Yukon valley and to the Rocky Mountains. The northwestern biota spread from the Rocky Mountains and Pacific Coast region in the United States north to British Columbia and Alaska. The third wave spread from the southeastern centre of dispersal northward to the conifers and west to the Great Plains. From the southwestern centre the life spread north on each side of the Rocky Mountains into Canada, and only stragglers spread eastward into the humid region.” Besides the three waves recognized by Adams it is necessary to recognize a fourth or tropical wave of species, which have been moving up into North America from South America. As this has come over two distinct routes, namely by way of the West Indies and Mexico, we may recognize an eastern and a western center as in the second and third waves. At present our knowledge of the ants of British America and Alaska is so incomplete that it is impossible to state whether there is a distinct tundral fauna, that is, a fauna living beyond the coniferous tree-belt. Observations in the mountains of Colorado, however, indi- cate that ants do not occur far above timber-line, which is there at an altitude of about 4,000 meters. Isolated females may sometimes be found under stones at a greater elevation, but these have been borne aloft by air-currents and perish without being able to establish formi- caries. This is also the case at more moderate elevations above the timber-line, as, for example, on the summit of Mt. Washington (Wheeler, 1905/). Even the non-glaciated portion of North America, however, has retained an ant-fauna composed very largely of well-known Eurasian genera and relicts of a more southerly type which have been unequally preserved in the eastern and western portions of the United States. The eastern portion retained a very small number of these ancient genera, probably on account of its much colder climate during the glacial epoch. Nevertheless, the eastern and western centers of the areas covered by Adams’s second and third waves each retained a cer- tain number of relicts, which seem to have formed as many constella- tions of species, subspecies and varieties within comparatively recent 150 ANTS. times. Although these have spread from their centers of origin and intermingled with the northern circumpolar fauna, they have not been sufficiently displaced to prevent the recognition of the four centers of dispersal which Adams calls the northeastern, northwestern, south- eastern and southwestern respectively. Of these the first has con- tributed very little, the last more considerably to our ant-fauna, and the northeastern and northwestern have more species in common than the other two centers. The former, in addition to the subboreal types above mentioned, is characterized by the following: Stigmatomma pallipes, Cremastogaster lineolata, Camponotus fallax, Prenolepis imparis, Polyergus and the species of Lasius of the subgenus Acan- thomyops. ‘These species, however, are often represented by distinct eastern and western subspecies and varieties and usually the western are more closely related to the Eurasian than to the eastern forms of the species. This difference in relationships is even more striking when distinct but allied species are compared in the two centers. Thus the western Stenamma nearcticum is more closely related to the European S. westwoodi than to the eastern S. brevicorne; the eastern Apheno- gaster fulva is represented in the west by A. occidentale which is merely a variety or subspecies of the European A. subterranea; the eastern Camponotus fallax, Formica rufa and Polyergus lucidus are represented in the western region by subspecies or varieties very much like the Eurasian forms. The northeastern center retains at least three relicts, Myrmecina graminicola, Ponera coarctata and Harpagoxenus common to the Eurasian fauna, but apparently absent from the northwestern center; whereas Myrmica mutica, which is . hardly more than a subspecies of the European WM. rubida, occurs only in the mountain valleys of the northwest. This center also has three genera, Symmyrmica, Sympheidole and Epipheidole, not known to occur elsewhere. These are, however, parasitic species and have probably developed from Lepthothorax- and Pheidole-like forms within comparatively recent times. Although several species of Acantho- myops occur in the Rocky Mountains, representatives of this sub- genus are far more abundant in the northeastern center from which they probably radiated. On the other hand, the species of Formica allied to the European F. rufa have had their center of origin and dis- persal in the northwest. The southeastern and southwestern centers contain more relicts of the southern preglacial fauna and have, moreover, received many acces- sions from the fourth, or tropical wave which started in South Amer- ica, probably in Archiguiana, and reached North America by way of Central America and Mexico on the one hand, and the Antilles on the THENGEOGRARAICAL DIS ERIBRORON VOR TANTS. 151 other. The southeastern and southwestern centers exhibit some blend- ing of forms through an eastward migration from Mexico across the Gulf States and a counter westward migration of forms from the southeastern center. The southeastern center is characterized by several species of Doli- choderus of the subgenus Hypoclinea, closely related to the Eurasian H. 4-notata. This group is not represented in the southwest. The species of Sysphincta and Proceratium have been retained as relicts. The latter genus seems not to occur in Eurasia. Several peculiar species of Aphenogaster (treate, marie and lamellidens) have evi- dently had their origin in the southeastern center, to which we must also assign Pogonomyrme.x badius, a single genus, Epacus, and a sub- genus of Lepthothorax (Dichothorar). In the arid southwestern center there are a number of relicts which seem to have been actively producing new forms since they were rele- gated to this area. Such are the genera Liometopum, Myrmecocystus, Messor and the subgenus /schnomyrme.x and the sections of the genus Camponotus which comprise the species allied to C. maculatus and fallax. These forms are closely related to Old World species of Indian origin. The admixture of adventitious tropical forms both in the south- eastern and southwestern centers is considerable. In the latter these have nearly all arrived by way of Mexico, in the former many are of Antillean provenience, but a certain number seem to be Mexican. The genus Eciton, e. g., is well represented in Texas and there are a few species in the Southeastern States. As this genus is not represented in the West Indies or even in Florida, the eastern forms must have immi- grated from the southwest. The same is true of species like Odon- tomachus clarus which is said to occur as far east as Georgia. O. hematodes, Xenomyrmex stolli, Cryptocerus varians, Pseudo- ponera stigma and Camponotus abdominalis, however, must have entered Florida directly from the West Indies. It is equally clear that Cryptocerus angustus, the species of the Ponerine genera Pachycon- dyla, Platythyrea, Neoponera, Acanthostichus and Cerapachys, the Myr- micine forms Macromischa and Xiphomyrme.x and the Attiine genera and subgenera Atta, Mellerius, Mycetosoritis, Trachymyrmex and Cy- phomyrmex (in part) reached the southwestern center from tropical Mexico. Other genera widely distributed in the American tropics, like Iridomyrmex, Dorymyrmex, Pseudomyrma, Strumigenys, certain species of Ponera (ergatandria, trigona, opaciceps) and Camponotus (maculatus and planatus) may have reached the adjacent portions of the United States both from Mexico and the West Indies. This is 152 ANTS. clearly the case with C. p/anatus, which occurs in the United States only at the southern tip of Florida and in southwestern Texas. Tt is not so easy to account for the distribution of species of a few tropical and subtropical genera like Pogonomyrmex, Erebomyrma and Pheidole within the United States. Pogonomyrmex is a peculiarly American genus ranging from Montana to Argentina. It is repre- sented in the Southwestern States by a number of species, one occurs in Florida and Georgia and at least one in the West Indies. The southi- eastern species (P. badius) differs from all the others in having poly- morphic workers, the West Indian form belongs to the subgenus Ephebomyrme.x, which is also represented in Brazil, Mexico, Texas and Arizona. Recently the number of known South American species of Po- gonomyrme.«x has been considerably augmented (Emery, 1905b). The question arises as to whether this genus had its center of origin in South America and radiated its species northward or whether it arose in the southwestern center of North America and extended thence southward to Argentina. The former supposition is supported by analogy with the ad- vent of so many South American forms in North America, the latter by the fact that Pogonomyrme. is closely related in structure, though not in habits, with the boreal genus Myrmica. Of Erebomyrma only a single species (E. longi of Texas) was known till recently, when Emery described another (£. peruviana) from Peru. This genus, too, is probably of South American origin. This may be inferred from the fact that the allied genera Tranopelta and Carebarella are exclusively neotropical. Moreover, the allied genus Solenopsis is represented by a much greater number of species in South than in North America. The genus Pheidole is widely distributed and represented by numerous species in the Southeastern and Southwestern States and a few species (Ph. vinelandica, tysoni, pilifera) have spread into the Northern States. Most of the North American species are quite distinct and may be regarded as endemic. I know of no species common to the West Indies and the southeastern center, and although many southwestern species occur in northern Mexico they seem to be for the most part quite distinct from the southern Mexican and South American species. As the genus is cosmopolitan it is not improbable that our species may be derived from relicts of Mesozoic forms that were preserved in the southeastern and southwestern centers during glacial times. Perhaps further studies of the Mexican and West Indian, and espe- cially of the Cuban and Haytian species may throw some light on the American distribution of this interesting genus. A few words must be said about the ‘ants that have been imported into North America by commerce, for although these comprise a com- THEVGBOGRAPHICAL DISTRIBUTION -OF -ANTS. 153 paratively small number of species, they have considerable economic importance. The following have been brought to our shores and have succeeded in gaining a foothold, especially in dwellings where they do Fic. 86. The Argentine ant (Jridomyrmex humilis). (Courtesy of Mr. W. Newell. drawing by Miss Charlotte M. King.) 4A, Worker; A’, head; A”, petiole of same in profile; B, dealated female; B’, head; B”, petiole of same; C, male; C’, head; C”, petiole. not come into competition with our native species: Monomorium pha- raonis, salomonis, destructor and floricola, Solenopsis rufa, Pheidoiec megacephala and flavens, Tetramorium cespitum, guineense and 154 ANTS. simillimum, Prenolepis fulva and longicornis, Plagiolepis longipes, Tapinoma melanocephalum and Iridomyrmex humilis. All of these, with the exception of the pavement ant (T. cespitum), are of tropical origin, ad nearly all of them have come from the Old World. 7. cespitum of Europe is now common about New York, Washington and Philadelphia, but it is so sporadic that we must conclude either that it is of comparatively recent importation, or is prevented from spreading by competition with our native ants.1 All of the other species cited above require considerable warmth and even Monomorium pharaonis, the tiny yellow house-ant, which is often a pest in ships or in the dwellings of sea-port towns, does not nest out of doors except in southern latitudes. Some of our tropical ants (Neoponera villosa, Camponotus floridanus and Pheidole flavens) manage to live for considerable periods of time in our northern hot- houses. At least one species from the American tropics (/ridomyrmex humilis (Fig. 86)) has acquired a much wider range, having recently made its appearance in New Orleans. In this locality, where its habits have been carefully studied by Titus (1905) and Newell (1908a), it has become a serious pest and is driving out the native ants. That it is spreading rapidly over the warmer portions of the globe is shown by the fact that I have recently received specimens from various locali- ties in California and from Cape Colony. It has also become a pest in Portugal (Martins, 1907), and, according to Stoll (1898) has been imported into Madeira where it has supplanted another previously introduced species, Pheidole megacephala, which was the house-ant of the island in the days of Heer (1852). Some idea of the abundance of this ant in the middle of the last century may be gained from the following extract from Heer’s work: “Tt occurs throughout the southern portion of the island of Madeira up to an elevation of 1,000 feet in prodigious numbers, especially in hot, sunny places, where it is to be found under eight out of every ten stones that may be overturned. In the city of Funchal there is ‘probably not a single house that is not infested with millions of these insects. They climb to the top stories, issue in swarms from the cracks in walls and floors and keep crossing the rooms in regular files in all directions. They creep up the legs of tables, along their edges and into cupboards, chests, etc.” This ant is very common in the Ber- mudas and West Indies and will probably be found in Florida. There can be little doubt that wherever it gains a foothold in tropical or * According to Marlatt (1898) this species has long been a resident of the Eastern States. He believes that it may be the species referred to by Kalm as occurring in the houses of Philadelphia as early as 1748. THE GEOGRAPHICAL DISTRIBGIMON OF ANTS. 15 on subtropical countries it is able to propagate very rapidly and to exter- minate the indigenous ant-fauna. This seems to be the case in Ber- muda, and I have recently seen a good illustration of its habits in the Virgin Islands. During March, 1906, I devoted ten days to a careful study of the ant-fauna of the little island of Culebra, off the eastern coast of Porto Rico, without seeing a single specimen of Ph. mega- cephala. This island is, however, completely overrun with a dark variety of the vicious fire-ant (Solenopsis geminata). One day, on visiting the island of Culebrita, which is separated by a shallow channel hardly a mile in width from the eastern coast of Culebra, I was aston- ished to find it completely overrun with Ph. megacephala. This ant was nesting under every stone and log, from the shifting sand of the sea- beach to the walls of the light-house on the highest point of the island. The most careful search failed to reveal the presence of any other species, though the flora and physical conditions are the same as those of Culebra. It is highly probable that Ph. megacephala, perhaps acci- dentally introduced from St. Thomas, a few miles to the east, had exterminated all the other ants which must previously have inhabited Culebrita. The absence of megacephala on Culebra is perhaps to be explained by the presence of the equally prolific and pugnacious fire-ant. The recent displacement of Ph. megacephala in Madeira and of our native ants in Louisiana by /ridomyrmex humilis is analogous to the Fic. 87. Worker of Plagiolepis longipes, now spread over the tropics of both hemi- spheres. (Bingham.) 4 well-known displacement in Europe and America of the black house- rat (Mus rattus) by the brown species (17. decumanus). Ina similar manner, according to Stoll, another ant, Plagiolepis longipes (Fig. 87), introduced into the island Reunion from its original home in Cochin China, has driven out some of the primitive autochthonous species. We may also look forward to the appearance of this same ant within the warmer portions of the United States, since it has already been recorded by Pergande (1894) from Todos Santos, in Lower California. Ke ANTS. Still another ant that has acquired a footing in tropical Florida, and probably also in other localities in the Gulf States, is Prenolepis longi- cornis. It has long been a common species in the green-houses of temperate Europe and America. In some of these, as in the Jardin des Plantes in Paris, it has been a permanent resident for more than forty years. In the city of New York it may sometimes be found even on the top floors of the great apartment buildings. Wasmann (1905¢) and Assmuth (1907) give good reasons for believing that the original home of this ant is India, and that it has been carried to all parts of the tropics in ships. They show that it has been accompanied in its wanderings by two myrmecophiles, a Lathridiid beetle (Colwocera madere) and a small cricket (A/yrmecophila acervorum var. flavo- cincta). The peregrinations of Tapinoma melanocephalum, which also occurs in northern dwellings and green-houses, are similar to those of P. longicornis. The foregoing sketch of the distribution of North American ants shows that our fauna is very rich in comparison with that of Europe. Nevertheless it must be admitted that we have few distinctive types— apparently only the specialized parasitic genera Epewcus, Symmyrmica, Sympheidole and Epipheidole, the subgenera Dichothorax and Acantho- myops and the ancient relicit Proceratium. WKobelt has been led by his studies on the distribution of other animals to the conclusion that our existing North American fauna, like that of other countries, “ apart from the introduced and feral domestic animals and the English spar- row—has shown no evidence of enrichment since the diluvial period. The present is a depauperate diluvial fauna. America, too, proves that we are not living in an incipient, but in a declining geological epoch, not at the beginning of a youthful, creative Quaternary, but at the close of the Tertiary period, whose generative power has been extinguished.” This statement may not be strictly true of dominant insect groups like the Formicide. Not only is it probable that our fauna is being slowly but continually enriched by accessions from the tropics, but a com- parison of the list of North American ants at the end of this volume with the lists of European species compiled by Mayr, Forel, Emery, Ern. André and others, shows that the related and identical species of both continents have a greater number of subspecies and varieties in North America. This would seem to force us to the conclusion that many of our ants are actually in a mutational or premutational phase. Turning from this more general, faunistic account to the etho- logical distribution of ants, we observe considerable differences in the frequency with which the colonies occur within the range of each species. When we thus concentrate our attention on a single form, THE GEOGRAPHICAL DISTRIBUTION OF ANTS. 137 we find that the colonies are not uniformly distributed over their whole range, but only in particular stations, or habitats, showing that these insects, like plants and many other animals, depend very inti- mately for their welfare on precise physical and organic environments, such as the nature of the soil and vegetation, the amount of mois- ture and the exposure to sunlight. Colonies that happen to be estab- lished in unfavorable localities take on a more or less depauperate appearance. This is indicated by their scarcity and the small size of the colonies and individuals, and is particularly noticeable at the very limits or just beyond the limits of the normal range of a particular form. Ff find that according to the station inhabited by the various species, subspecies and varieties, at least in North America, we may distinguish the following ethological groups, or associations: 1. The woodland, or silvicolous association, comprising the species that inhabit our moist, shady northern and eastern forests. With the extinction or drainage of these forests or the removal of the under- growth, this characteristic, and in many respects, very primitive fauna rapidly disappears. 2. The glade, or nemoricolous association, comprising the ants that prefer open, sunny woods, clearings or the borders of woods. A por- tion of this fauna maintains itself even in the gardens and parks of our cities. 3. The field, or cespiticolous association, comprising the ants that prefer to nest in grassy pastures and lawns, in situations exposed to the full warmth and light of the sun. 4. The meadow, or: pratincolous association, comprising the ants which inhabit low, grassy meadows or bogs. 5. The heath, or ericeticolous association, comprising the ants that inhabit rather poor, sandy or gravelly soil exposed to the sun and covered with a sparse growth of weeds or grasses. 6. The sand, or arenicolous association, comprising the ants that prefer to nest in pure sand. 7. The desert, or deserticolous association, comprising the ants that inhabit the dry, open deserts and plains. A few of our species, like Lastus americanus and Formica sub- sericea, are so adaptable that they occur more or less abundantly in all or nearly all of the above stations. Owing to intergradation of these stations in some places, there is, of course, a corresponding mingling of forms. Thus certain species, like Monomorium minimum, seem to belong indifferently either to the heath or sand fauna. In the deserts of the Southwestern States these two faunas may either mingle or be sharply separated from each other. In the Northeastern and 158 ANTS. Middle States a similar relation obtains between the glade and field faunas, which it is often impossible to separate by a hard and fast line. Formica schaufussi, for example, seems to occur indifferently in either station. With the exception of the sand and desert associations, which de- pend very largely on physical conditions, like soil, warmth and mois- ture, the above list comprises mainly adaptations to particular types of vegetation. Other associations of a similar character undoubtedly exist in other countries, especially in the tropics, where the relations between ants and plants are often more intimate than in temperate regions. A very striking ethological association, depending on rela- tions to the soil and consisting of species common to many of the above groups, is represented by the so-called hypogeic ants. These occur in all parts of the world, and, owing to their exclusively subterranean life, have acquired a peculiar adaptive facies. They are aptly de- scribed by Emery (1875a) as “the inhabitants of the most remote and obscure hiding places of the soil, dwellers in the narrow crannies beneath the heaviest rocks, in the very pores of the earth, blind and amblyopic pygmies of slow gait and strangely varied forms, micro- scopic remnants, so to speak, of extinct genera, that have found in the bosom of the earth a respite from the invasion of more robust and prolific types.” As a rule these hypogeeic ants are of small size, pale color and have no eyes or only vestiges of these sense-organs, although all of these peculiarities may be found in certain epigzeic species. We find, indeed, all gradations in habits between ants that live in exposed situations and extremely hypogeic forms, and there can be no doubt that the latter ethological group has been recruited from unrelated genera among the former. As nearly all ants live much of the time in dark subterranean galleries and chambers, the transition to a com- pletely hypogzeic habit is easily effected, especially when food is more accessible in the soil than on the surface, or when larger and more pugnacious ants make life at the surface intolerable. But no matter how hypogeic a species may become, it always retains enough of its ancestral habits to come to the surface for the nuptial flight of the males and females. At such times the blind and etiolated workers excavate a gallery to the surface and conduct the winged sexes to the opening. In North America there are hypogeic species of Eciton, Stigmatomma, Cerapachys, Sysphincta, Proceratium, Ponera, Sole- nopsis, -Erebomyrma, Strumigenys and Lasius, and in other parts of the world species of the genera Dorylus, Leptanilla, Aéromyrma, Dip- lomorium, Epitritus, Rhopalothrix, ete., have very similar habits, although these in most cases are very imperfectly known. Facts of THE GEOGRAPHICAL DISTRIBUMION OF ANTS. 159 great interest will surely be brought to light, when hymenopterists devote as much attention to these insects as the coleopterists have bestowed on hypogeic beetles. Many of the species (Eciton caecum, Stigmatomma, etc.) feed on larve and subterranean arthropods in general; others, like some of the small species of Solenopsis, Aéro- myrma, Erebomyrma, etc., live in cleptobiosis with other ants or termites and feed on their brood; still others, like our yellow species of Lasius s. str. and all the species of the subgenus Acanthomyops, pasture droves of aphids and coccids on the roots and subterranean stems of plants. In conclusion it should be noted that the habitat of a particular species, subspecies or variety is selected in the first instance by the fertile female ant when she establishes her colony. If the physical and living environment is congenial and moderately stable, the colony, in the great majority of cases, remains stationary, but if the condi- tions become unfavorable, it migrates to another site. In such cases the workers not only select the new habitat, but also determine and bring about the change of dwelling. CHAPTER 2 FOSSIL ANTS: Dum Phaéthontea formica vagatur in umbra Implicuit tenuem succina gutta feram, Sic modo que fuerat vita contempta manente Funeribus facta est nunc pretiosa suis. —Martial, “ Epigrammata,” Liber VI, 15. Before proceeding further with our account of existing ants, it will be advisable to review what is known of the extinct species. And as the Formicide are one of the most specialized families of the Hymen- optera, which are themselves a highly specialized order, this review may properly begin with a few remarks on the paleontological history of the order as a whole. The Hymenoptera first make their appearance during Mesozoic time, but concerning the families to which the few fossil remains be- long, there is considerable difference of opinion. Heer in 1865 de- scribed from the Lower Liassic of Aargau, Switzerland, a specimen which he regarded as an ant and named Paleomyrmex prodromus. This has long been regarded as the most ancient not only of known ants but also of Hymenoptera. According to Handlirsch (1906-1908), how- ever, who has recently subjected our knowledge of extinct insects to a critical revision, this fossil ** certainly does not belong to. the Hymen- optera, but presumably to the Homoptera.” In 1854 Westwood de- scribed two wing impressions from the Lower Purbecks of Durdle- stone Bay, England (Jurassic), as those of a couple of huge ants, Formicium brodiei and Myrmicium heeri. These are now shown by Handlirsch to belong to saw-flies of the genus Pseudosirex, which also comprises thirteen other species from the Solenhofen deposits of the same age. This singular genus is the most primitive of known Hymen- optera and has been assigned by-Handlirsch to a special family, the Pseudosiricide, differing from the Siricide and other recent Hymen- optera in having numerous longitudinal veins in the wings, a dis- tinctly Orthopteroid character which, like many other peculiarities of the Hymenoptera, points to a derivation of the order from Blattoid, or cockroach-like ancestors. The only other Hymenopteron known from the Mesozoic 1s Epjualtites jurassicus, based on a specimen from the Kimmeridge (Malm) of Spain. This insect is evidently a member of 160 Moe} s FOSSIL. ANTS. 161 the higher, or apocrital division of the order, but its affinities are very obscure. We are thus led to the conclusion that, although both the lower and higher divisions of the Hymenoptera are represented in the Mesozoic, no ants are included in the number. But so many genera and species of these insects appear full-fledged in the early Tertiary that we are compelled to believe that they must have existed in the Trias or even in the Lias, but belonged to so few genera and species or lived in such small communities that they left no remains. The numerous species of Tertiary ants not only belong to many different genera but often to living genera, and even the extinct types are readily referable to the recent subfamilies and to no others. The extinct genera, moreover, are of such a character that one would not be surprised to discover any of them alive today in some of the unex- plored portions of the Old World tropics. Among these Tertiary ants the male, female and worker phases were as sharply differentiated as they are today. Joseph Le Conte (“ Elements of Geology,” p. 511) is, therefore, mistaken when, from the fact that nearly all the fossil ants Fic. 88. Worker of Prionomyrmex Fic. 89. Worker of Bradoponera longiceps, a primitive Ponerine ant meieri from the Baltic Amber. (Mayr.) from the Baltic Amber. (Original.) a, From the left side; b, head from above. of Oeningen and Radoboj are males and females, he infers that “ the wingless condition, the neutral condition, the wonderful instincts and organized social habits, have been developed together since the Miocene epoch.” I shall show presently that had he consulted Heer’s work on these insects (1847), he would not have made this statement. Tertiary ants have been found in both Europe and North America in some 23 localities, representing several geological periods and forma- tions. The following are the European formations: Baltic amber, beds of Aix in the Provence and Gurnet Bay, Isle of Wight (Lower Oligo- 12 162 ANTS. cene); Schossnitz in Silesia, Krottensee in Bohemia and Rott in the Rhinelands (Upper Oligocene); Radoboj in Croatia, Falkenau and Kutschlin in Bohemia and Cape Staratschin, Spitzbergen (Lower Miocene) ; Sicilian amber and the beds of Brunnstatt in Alsacia (Mid- dle Miocene) ; Oeningen in Baden, Parschlug in Styria, Tallya and Thalheim in Hungary, Gabbro in Italy (Upper Miocene) ; Sinigallia in Italy (Pliocene). The age of the North American deposits has not been accurately determined. Ants have been seen in the amber of Nan- tucket- (Goldsmith, 1879) which is attributed to the Tertiary. Other Afr Fic. 90. Female of Lonchomyrmex Fic. 91. Worker of Rhopalo- heyeri, a Myrmicine ant from the Rado- myrmex pygmaeus from the boj formation. (Mayr.) Baltic Amber. ( Mayr.) localities are Green River, Wyoming; White River, Colorado. and Ouesnel, British Columbia, which are referred to the Oligocene, and Florissant, Colorado, which is said to belong to the Miocene. The Baltic and Sicilian ambers and the beds of Radoboj, Oeningen and Florissant have yielded far and away the greatest number of ants. The most beautiful specimens are those of the amber, which are often so perfectly preserved that they may be as readily studied as recent ants mounted in Canada balsam. Most of these specimens are workers and belong to more or less arboreal species, but there are also quite a number of males and females. As nearly all of the latter have wings they must have been caught in the liquid resin just before or after their nuptial flight. The preservation of the Oeningen, Radoboj and Floris- sant specimens is very inferior to those of the amber. The deposits in these localities are lacustrine, that is, they consist of fine sand or vol- canic ashes laid down in fresh water lakes. This accounts for the fact that nearly all the specimens are males and females, for as Heer says: “With few exceptions only winged individuals are found, because the wingless individuals, in this case the workers, were drowned less fre- quently than the others. Both males and females occur, but the former are much rarer than the latter, probably because the females, having a FOSSIL ANTS. 163 much larger and heavier abdomen, fell into the water more often than the males.”” The fossil ants of Florissant show the same peculiarities, except that the males are not much rarer than the females. Thus the condition which Le Conte interpreted as indicating an absence of the worker caste during Miocene and premiocene times, is easily and naturally explained. It is strange that he failed to see this, especially as in the paragraph immediately preceding the remark above quoted, he calls attention to the following interesting resemblance between modern Fic. 92. Male of Aéromyrma Fic. 93. Worker of sp. from the Baltic Amber. (Ori- Propodomyrma samlan- ginal.) dica sp. nov. from the Baltic Amber. (Ori- ginal.) lacustrine conditions and those which must have prevailed at Oeningen: “On Lake Superior, at Eagle Harbor, in the summer of 1844, we saw the white sands of the beach blackened with the bodies of insects of many species, but mostly beetles, cast ashore. As many species were here collected in a few days, by Dr. J. L. Le Conte, as could have been collected in as many months in any other place. The insects seem to have flown over the surface of the lake; to have been beaten down by winds and drowned, and then slowly carried shoreward and accu- mulated in this harbor, and finally cast ashore by winds and waves. Doubtless at Oeningen, in Miocene times, there was an extensive lake surrounded by dense forests; and the insects drowned in its waters, and the leaves strewed by winds on its surface, were cast ashore by its waves.” The conditions described by Le Conte for Lake Superior are com- mon to all our Great Lakes. The insects drowned in them are often buried in the sand of the beaches and might eventually fossilize, but 164 ANTS. the Tertiary lakes of Ocningen, Radoboj and Florissant must have been much smaller, shallower and calmer bodies of water, and the insects that dropped into them or were swept into them by streams, were probably imbedded in the mud under water.» Many of them were, of course, devoured by fishes. Professor Cockerell has sent me from Florissant several specimens of fossil fish excrement consisting almost entirely of the hard indigestible heads of ants. It is very unfortunate for the student that so few of the workers of the Oeningen, Radoboj and Florissant ants have been preserved, for our knowledge, as we have seen, is largely based on the worker caste and the males and females even of recent forms are so imperfectly known that fossils of these sexes are very difficult to classify, especially when the characters of most taxonomic value, such as the shape of the head, mouth-parts and abdominal pedicel are obliterated by flattening and distortion. Another great difficulty is encountered in attempting to correlate the Fic. 94. Worker of Elec- Fic. 95. Worker tromyrmex klebsi sp. nov. from of Stigmomyrmex the Baltic Amber. (Original.) venustus from the Baltic Amber. (Mayr.) males, females and workers of the same species. This is no easy task with carelessly collected recent ants, but with fossils, except those of the amber, it becomes almost impossible. The ants of Oeningen and Radoboj were first studied by Heer (1849, 1856, 1867) before the taxonomy of recent ants had been placed on a firm basis by the researches of Mayr. It is therefore im- possible to assign most of Heer’s species to their proper genera, and although Mayr (1867b) was able to examine a number of the Swiss paleontologist’s species, he did not have access to the types. Hence the whole ant-fauna of Oeningen and Radoboj must be reinvestigated by some one thoroughly acquainted with the recent ants. The species FOSSIL ANTS. 165 of the Baltic amber have been studied in a masterly manner by Mayr (1868a). A few additional species from the same formation were sub- sequently described by Ern. André (1895a) and Emery (1905e), and the latter has also described fourteen species from the Sicilian amber (1891e). According to Handlirsch’s list of fossil insects, of the 600 species of Hymenoptera that have been described from the Tertiary, 307 or more than half are ants. These insects must therefore have been very numerous in individuals, just as they are to-day. This is true alike of the Baltic amber and the shales of Radoboj, Oeningen and Florissant. Mayr examined 1,460 ants from the amber, Ern. André 698 and through the kindness of Prof. R. Klebs, of the Royal Amber Museum of Konigsberg and Prof. W. Tornquist of the Konigsberg Uni- versity, I have been able to study nearly 5,000 of these beautiful specimens. Heer says: “ The ants are among the commonest fossil animals of Oeningen and Radoboj. In the latter locality they pre- dominate even more in proportion to the other insects than they do at Oeningen. Altogether | have examined 301 specimens, representing 64 species; from Oeningen 151 specimens of 30 species, from Radoboj 143 specimens of 37 species and from Parschlug 7 specimens belonging to 4 species.” According to Scudder (1890), “the ants are the most numerous of all insects at Florissant, comprising, perhaps four-fifths of all the Hymenoptera; I have already about four thousand specimens of perhaps fifty species (very likely many more) ; they are mostly Formi- cide, but there are not a few Myrmicide and some Poneride.” I have recently made a rapid preliminary study of the 4,000 specimens of the Scudder collection belonging to the Museum of Comparative Zoology, and of nearly 3,000 more found at Florrisant by Prof. T. D. A. Cockerell, Mrs. W. P. Cockerell, S. Rohwer and myself, and am able to confirm Scudder’s statement. There are probably not more than 50 species in both collections, many of them being represented by a great number of specimens, and hardly 70, or one per cent., of the 7,000 specimens are workers. Of the described Tertiary ants that can be unmistakably assigned to their respective subfamilies, 139 species are Camponotine, 25 are Doli- choderinz, 85 Myrmicinz and 27 Ponerine. A single species (Anomma rubella) is referred to the Doryline by F. Smith (1868). I have not seen his description and figure of this insect, but his generic determi- nations of recent ants were often so erroneous that his competence to assign a fossil species to its proper genus may be doubted. The pro- portion of species in the other subfamilies is interesting because it is not unlike that obtaining at the present day. The number of indi- 166 ANTS. viduals belonging to each subfamily can be satisfactorily given only for the ants of the Baltic amber. Of the 2,158 specimens examined by Mayr and André, 704 were Camponotine, 1,310 Dolichoderine, 59 Myrmicinz and 25 Ponerine. The great preponderance of Dolicho- derine is due to two species, Bothriomyrmex gapperti (889 speci- mens) and Jridomyrmex geinitzi (248 specimens), which are repre- sented by 1,137 specimens, or more than half of the total number. The species of Myrmicinze and Ponerine are each represented by only a few individuals. From these facts Mayr concludes “ that the Ponerinz of the Tertiary exhibited the weakest development and have reached their full efflorescence in recent times.’’ He advances a similar opinion in regard to the Myrmicine. Emery, however, has shown that this infer- ence is erroneous, for the Ponerine—and the same is true of the Myrmicinee—are much less arboreal in their habits than the Dolicho- derine and Camponotine, and would therefore be much less fre- quently entrapped in the liquid exudations of succiniferous trees. Then, too, the Ponerinz probably formed small colonies as they do at the present time. I have found several undescribed Ponerinze and Myrmicine both in the Baltic amber and in the shales of Florissant, showing that these groups must have been at least as highly diversified in the Miocene and lower Oligocene as the other two subfamilies. Only in the amber species have the genera been at all satisfactorily established. Those described from other formations are very largely guesswork. This is especially true of such genera as Heer’s /mhoffia, Attopsis and Poneropsis. Other species were placed by him and Scud- der in the recent genera Lasius, Formica, Dolichoderus, Camponotus, Myrmica and Aphenogaster, but probably many of these allocations are erroneous. The only genera not represented in the amber, but occur- ring in the Tertiary strata, are Lonchomyrmex (Fig. 90) and Liometo- pum. We may divide the genera of the Baltic and Sicilian ambers into two groups, the extinct and recent, and the latter may be subdivided into those still represented by species in Europe (palearctic), which are nearly all common to the nearctic region as well (circumpolar), and those now confined to the tropics of the Old World (paleotropical ). Grouping the genera thus, we have the table on page 167. Of the 4o genera included in this table, ig sare extinct and27.<01 more than two thirds, are still living. Of the latter, a little more than half (14) are still represented in Europe and a little less than half (13) in the Old World tropics. It will also be seen that the ratio (7:4) of exclusively paleotropical to palearctic genera in the Sicilian amber is nearly twice that of the Baltic amber (11:13), although very few specimens of the former have been examined. But it should FOSSIL ANTS. 167 BALTIC AMBER. SICILIAN AMBER. I. Extinct Genera. Prionomyrmex Acrostigma Bradoponera Hypopomyrmex Propodomyrma gen. nov. Nothomyrmica gen. nov. Electromyrmex gen. nov. Stigmomyrmex Lampromyrmex Enneamerus Paraneuretus gen. nov. Protaneuretus gen. nov. Rhopalomyrmex 2. Recent Genera. (a) Palearctic. Ponera Ponera \onomorium Cremastogaster A phenogaster Tapinoma Myrmica Plagiole pis Leptothorax Dolichoderus Bothriomyrmex Tapinoma Plagiole pis Prenolepis Lasius Formica Camponotus (b) Paleotropical. Ectatomma Ectatomma ? Anomma Aéromyrma Sima Cataulacus Oligomyrmex Aéromyrma Leptomyrmex Technomyrmex Cataulacus CEcophylla Tridomyrme. Gesomyrmex (Ecophylla Dimorphomyrmex Gesomyrmex ? Polyrhachis 165 ANTS. be noted that all the palearctic genera enumerated for the Sicilian amber are also common to the paleotropical fauna of the present day. This will explain the following quotation from Emery (1893-94) : “ My studies on the ants of the Sicilian amber have demonstrated that at the beginning of the Tertiary, Europe had an ant-fauna of Indoaustralian character, still living and exclusively of this character in Sicily during the formation of the amber; while to the north of the sea which at that time extended across Europe, representatives of this fauna, mingled with Formica, Myrmuca and other recent holarctic types, lived in the forests of the Samland. After the disappearance of this sea the northern fauna pushed its way south- ward as far as the Mediterranean. Then came the Glacial epoch, which extin- guished the Indian fauna in the north and drove its feeble remnants, mingled with arctic forms to the warmer locali- ties of southern Europe. From these re- gions the present ant-fauna wandered back, with the disappearance of the ice, into the middle and northern portions of the continent. But the tropical forms had difficulty in returning, because the Fic. 96. A, Female of Hy- ; : popomyrmex bombiccii, a singsu- Mediterranean, the African deserts and lar Myrmicine ant from the the steppes to the eastward were so man Sicilian Amber. (Emery.) D, : PP y Side of head, showing eye and barriers to their progress. The Euro- antenna more enlarged. pean ant-fauna therefore remains com- paratively poor.” The mixture of arctic and tropical forms in the amber, a peculiarity which characterizes the other insects and the plants no less than the Formicide, has not been satisfactorily explained. Heer endeavored to account for it on the following assumption: “It is probable that the succiniferous forests also covered Scandinavia and that the conifers were able to grow even on the high mountains. As the amber region extended from Scandinavia to Germany, where a sea separated it from the remainder of the Germanic continent, we may see in this natural barrier the cause of the peculiar facies of the amber flora. It pre- sents to our view the Scandinavian type of the Tertiary, mixed. in all probability, with a mountain or subalpine type. It is, in, fact. con= ceivable that the plants and animals, embalmed as they were in their FOSSIL ANTS. 169 . elegant amber sarcophagi, could be carried long distances without sustaining the slightest injury and could, therefore, present this excep- tional appearance, which is seen nowhere else in the plants and animals of the ancient world. If we suppose that a river flowed down from the Sweden of that day and opened into the Tertiary sea near Dantzig, there would be nothing irrational in admitting that this stream might easily carry the amber in the resinous state from the distant localities and mountains of Sweden, so that the organic remains enclosed in the amber may have been gathered together from an extensive territory, from low as well as from mountainous countries, and may even belong Fic. 97. Worker of Cateulacus silvestrii from the Sicilian Amber. (Emery.) a, From the right side; b, from above; c, head from above. to different Tertiary periods. . . . If we admit that the amber does not belong to one and the same epoch, we can explain why in the plants and animals of this formation the mixture of northern and southern types is so much more striking than it is in the remainder of the European Tertiary, and why among these we find several types peculiar to high latitudes or even to mountains.” At first sight Heer’s assumptions are plausible and would seem to be supported by the fact that although ants of different genera are occasionally found enclosed in the same block of amber, these never, to my knowledge, belong to both arctic and tropical types. On the other hand, the fact that the tropical, like the extinct genera of tlie 170 ANTS. above table, are represented by very few specimens compared with the boreal genera, is not readily explained by assuming that a river brought down lowland and mountain forms from Tertiary Scandi- navia and deposited them together in the beds of northern Germany, for on this assumption we should expect to find the lowland or tropical greatly in excess of the boreal specimens. It seems more natural to suppose that during the Lower Oligocene both the extinct and the tropical genera were already reduced to dwindling relicts, though co- existing with the circumpolar ant-fauna which had taken possession of the amber forests. In other words, even at that time the modern genera were far and away the more vigorous and prolific in the Sam- land, which was to become their exclusive heritage after the glacial epoch had wiped out the tropical genera that were leading a precarious existence in the warmer and more sheltered spots. We may assume, therefore, that the greatest development of these southern genera in this northern region occurred during the Eocene or even during the Fic. 98. Worker of Dimorphomyrmex theryi of the Baltic Amber. (Emery.) a, From the right side; b, head from above. Mesozoic and that the adverse conditions, which culminated in the glacial epoch, were already beginning to destroy the older, tropical components of the Lower Oligocene fauna.? To this consideration of the amber ants a few remarks on some of the more interesting genera and species may be appended: 1. Ponerine.—The most conspicuous of these is the large Priono- myrmex longiceps (Fig. 88) of the Prussian amber. Mayr described this species from a single specimen and I have found several more in the collections loaned me by Professors Klebs and Tornquist. This ant is allied to the Australian Myrmecia, the most primitive of living Formicide, but is even less specialized in the structure of the mandibles and abdominal pedicel. Another interesting but much smaller species is Bradoponera meieri (Fig. 89), which foreshadows our modern species "Since these lines were written, I have found in one of the Konigsberg col- lections a single block of amber containing a tropical Dolichoderus and a speci- men of Formica flori. These ants, therefore, not only nested in the same locality, but foraged on the same tree. FOSSIL ANTS. 171 of Sysphincta, Proceratium and Discothyrea, 1 have also found in the Prussian amber two new Ponerine genera related to the Indian Dia- camma and Lioponera. Myrmicine.—Of this subfamily there are several genera which show a wide range of organization and specialization in both the Baltic and Sicilian ambers. Hypopomyrmex bombiccu (Fig. 96), a singular ant described by Emery from the latter formation, although possessing 10-jointed antennz and a well-developed venation in the wings, seems to represent a generalized type from which the modern Dacetonii may have sprung. In the Baltic amber Stigmomyrmex (Fig. 95), with 10- jointed, and Enneamerus with only 9-jointed antenne, are remarkable forms. The latter,except in the small number of antennal joints, resem- bles the paleotropical Pristomyrme.x. Several species referred by Mayr Fic. 99. CEcophylla brischket, an Fic. 100. Worker of Gesomyrmex arboreal Camponotine ant from the Baltic harnesi, a large-eyed, arboreal Campono- Amber. (Mayr.) tine ant from the Baltic Amber. (Mayr.) to the genus Macromischa, because they lack spurs on the middle and hind tibize, do not belong to this genus, which is exclusively neotropical and largely West Indian, but must be placed in a new genus, which may be called Nothomyrmica. Much more like the true Macromischa than any of Mayr’s species, especially in the structure of the thorax and petiole, is the extraordinary ant which [I shall call Electromyrmex kiebsi (Fig. 94). This and many other amber Myrmicine are as exquisitely sculptured as any of our modern species. Propodomyrima (Fig. 93) from the Baltic and Acrostigma from the Sicilian amber are related to the paleotropical Podomyrma and Atopomyrmex, but are 2S and more primitive in their structure. . Dolichoderine.—This subfamily is represented by a number of 172 ANTS. interesting forms, many of which Mayr originally assembled in the genus Hypoclinea. Among these it is now possible to recognize species of Dolichoderus, Iridomyrmex and Bothriomyrmex. I have already called attention to the great abundance of two of the species of Bothrio- myrmex and Iridomyrmex. In the material sent me by Professors Klebs and Tornquist there are single specimens of two new genera (Protaneuretus and Paraneuretus) of unusual interest. Both of these are closely allied to Aneuretus, a genus which is now repre- sented by a single species, A. simoni, described by Emery from Ceylon (Fig. 140). This ant combines both Dolichoderine and Fic. tor. Worker of Gesomyrmex corniger from the Sicilian Amber. (Emery.) a, From the right side; b, from above; c, head of same from above. Ponerine characters, having the head of the former, and the petiole and sting of the latter subfamily. In the Sicilian amber Emery has recognized a male Leptomyrmex (L. maravigne), a genus now con- fined to Australia and New Guinea, an extremely small Tapinoma (T. minutissimum) and a Technomyrmex (T. deletus). As the Doli- choderine are practically absent from the African continent, the great development of this subfamily in the two ambers shows that the complexion of the European Tertiary ant-fauna was decidedly Indo- australian. 4. Camponotine.—The amber species of GEcophylla, Gesomyrmex, Dimorphomyrmex and Rhopalomyrmex are worthy of note. Cco- phylla and Gesomyrmex occur both in the Baltic and Sicilian ambers, CE. brischkei and G. hernesi (Fig. 100) in the former and CE. sicula and G. corniger (Vig. 101) in the latter. These species of Gicophylla are Closely related to G2. smaragdina, the well known red tree ant of the FOSSIL ANTS. 173 Old World tropics. Gesomyrmex was supposed to be an extinct genus till Ern. André (1892c) described a species (G. chaperi) from Borneo. In the same paper and from the same locality he described the type of another interesting Camponotine genus, Dimorphomyrmex janeti. This has polymorphic workers with large reniform eyes and 8-jointed an- tenne. Some years later (1905¢) Emery found a species (D. theryt, lig. 98) of this same genus in the Baltic amber. Rhopalomyrmex (Fig. 91) resembles the neotropical Myrmelachista. It has 10-jointed antenne, with 4-jointed clubs. Only a few species of the recent genera Lasius, Formica and Camponotus have been described from the Baltic amber. The workers of one of the Camponoti, C. con- strictus (Fig. 102), are pecu- liar in possessing ocelli and in having a thorax like For- mica. Of this latter genus Mayr described only a single species, ize flort, which is Fic. 102. Worker of Camponotus constric- very closely related to the ‘Ss, with ocelli and sellate thorax, from the : Baltic Amber. (Mayr.) existing /’. fusca. Our knowledge of the fossil ants of North America is insignificant. Scudder (1890) described Lasius terreus and a Myrmica sp. from the Green River Oligocene, Camponotus vetus and Liometopum pingue from the White River Oligocene and Formica arcana, Dolichoderus obliteratus and Aphenogaster longeva from the Quesnel formation, but neither the descriptions nor the figures make it at all certain that these ants are assigned to their proper genera. He also described and figured (p. 606, pl. III, fig. 32) the wing of an ant as that of a Braco- nid, Calyptites antediluvianus. Cockerell (1906) has described a Ponera hendersom from the Florissant shales but the size of the speci- men shows that it cannot be a true Ponera. My own studies on the Florissant ants are not yet completed. Very few ants are known from the Quaternary, or Pleistocene. Some Camponotine and Dolichoderine are recorded by Handlirsch as having been found in the interglacial deposits of Re, Italy by Benassi (1806) and a number of unidentified species are enumerated from the copal, an amber-like fossil resin found in several tropical countries (Africa, Brazil, New Zealand, etc.). One of the earliest accounts of copal ants is that of Blochs (1776) who describes and figures specimens of what hegyalls Formica saccharivora, salomonis, nigra and Formica sp. In a firgseries of copal specimens from Zanzibar in the American Museum of Natural History, I find well-preserved specimens belong- 74 ANTS. ing to the following genera: Camponotus, Polyrhachis, Myrmicaria, Cremastogaster, Pheidole, Cataulacus, Atopomyrme., Ponera and Anomma, and to species very closely related to living forms of the same territory if not identical with them. In a specimen of copal from Demerara in the same collection there is a worker Azteca. In reviewing the Tertiary and Quaternary ants one is impressed with two facts that have not been emphasized in the preceding pages. One of these is the close similarity of some of the ants of the Baltic amber to species now living in the same region. So intimate is this similarity that it may, in a few cases at least amount to identity, e. g., in Ponera atavia, Lasius schiefferdeckeri and Formica flori which neither Mayr nor myself have been able to distinguish by any satis- factory characters from the living Ponera coarctata, Lasius niger and Formica fusca! Such cases bring home to us very forcibly the enor- mous age and stability of species which the student, dealing exclusively with living forms, would be inclined to regard as of very recent origin. The second fact is one to which attention seems not to have been called by previous authors, namely, the absence of polymorphism in the workers of the Tertiary ants. There are, indeed, differences in stature between workers of the same species, but I have seen no speci- mens with sufficient differences in the size and shape of the head to indicate the existence of soldiers and workers proper. This is the more noticeable, because there are recorded from the amber several genera whose living species have polymorphic workers, such as dnomma, Aéromyrma, Oligomyrmex, Camponotus and Dimorphomyrmex. The known specimens of 4éromyrma and Oligomyrmex are all males and females, so that nothing is known concerning the workers, which may have been monomorphic. To the former genus belongs also, accord- ing to Emery, the Pheidologeton antiquus described by Mayr from a female specimen. The occurrence of Anomma in the amber is very doubtful. There remain then only the genera Camponotus and Dimor- phomyrmex in which we might expect to find polymorphic workers. I have examined a number of specimens of the three species of Cam- ponotus (mengel, igneus and constrictus) described by Mayr, but all of them have the form of the minor workers of our existing Camponoti. Dimorphomyrmex theryi was based on a single specimen, but several others which I have seen are monomorphic and in this respect unlike the living type of the genus from Borneo. It may be objected, of course, that no conclusions as to the presence or absence of poly- morphism in the workers can be drawn from the amber material, both because it is too meager and because the soldiers do not forage like the workers and would not therefore be caught in the liquid resin. FOSSIL ANTS. 175 This is certainly true of some genera, but not of Camponotus, to judge from our modern species. The fact remains that no polymorphic workers have been seen in the amber, that the great majority of the species certainly had only monomorphic workers, and that genera like Pheidole and Pheidologeton, so prominent in the Old World tropics to-day, are conspicuous by their absence. In the Pleistocene, however, genera like Pheidole and Anomma have their worker polymorphism fully developed, as I have observed in the Zanzibar copal, so that this condition must have made its appearance during the late, if I am right in concluding that it was absent during the early Tertiary. CHARTERS cl: THE HABITS OF ANTS IN GENERAL. “La fourmi, qui n’est point dédaigneuse et accepte toute nourriture, est, pour cela méme, moins inquiete et moins égoiste. C'est bien a tort qu’on l'appelait avare. Loin de la, elle ne semble occupée qu’a multiplier dans sa ville la nombre des copartageants. Dans sa maternité généreuse pour ceux qu'elle n’a pas entantés, dans sa sollicitude pour ces petits d’hiers qui deviennent aujourd’hui de jeunes citoyens, nait un sens tout nouveau fort rare chez les insectes, celui de la fraternité.”—Michelet, “ L’Insecte,” 1857. Before proceeding to a more detailed account of the extraordinary habits and instincts exhibited by certain groups of ants, it will be advisable to say something about the activities that are more gener- ally manifested by these insects as a group. And as the ants, like all other living organisms, pursue the three-fold aim of securing food, perpetuating their species, and shielding themselves and their offspring from enemies and the inclemencies of a changing physical environ- ment, [ may properly include my remarks under the general heads of nutrition, protection and reproduction. The activities implied by these terms, which must, of course, be taken in an elastic sense, neces- sarily coimplicate and supplement one another in the most manifold and intimate manner. Permanent social life is, generally speaking, possible only for animals that have access to an abundant food supply. Species that have great difficulty in securing food or succeed in finding only a scanty and precarious amount, are compelled to lead solitary lives, or at any rate, can never form populous communities of long standing. It is evident, moreover, that only vegetable food is ever really abundant and that animal food is in the majority of cases limited in amount, difficult to obtain, or abundant only during certain seasons or in cir- cumscribed localities. Predatory animals like the mammals, birds and insects of prey, are, therefore, solitary in their habits, whereas vege- tarians, like the rodents, ruminants and many plant-eating insects, are prone to be more or less social. Ants, at first sight, would seem to be an exception to this rule, but this is only conditionally true. Although primitively carnivorous, these insects are unreservedly such only in the lower subfamilies like the Ponerinee and Doryline. The colonies of the former are usually rare, like those of the social wasps, and of small size, and the colonies of the Doryline, though often very 176 TE HELABITS OF “ANTS WNGEN ERAL. 177 populous, lead a nomadic existence, since they must continually seek fresh hunting grounds in order to obtain the requisite amount of food. The ants of the three remaining subfamilies, though often predatory, have adapted themselves to a more varied diet and many of them have come to rely almost exclusively on vegetable food. The following are the sources from which these insects as a family derive their nourishment : 1. The original food of ants consists of other insects, especially helpless larvee and other terrestrial arthropods such as spiders, myrio- pods and isopods, the dying imagines of the countless insects which fall to the earth when their life-work is completed, those which are just leaving their pupa-cases, and the fragments rejected by insec- tivorous birds and mammals. 2. The larve and pupe of ants are a favorite food of certain species of Eciton and Formica, which are sufficiently intrepid to pillage the nests of other species. And, in fact, in times of need many species will eat their own offspring, which may, therefore, be con- sidered as an ever-present and available food-supply stored up against periods of famine. 3. The excretions of plants, such as the sweet liquids exuding from the leaves and especially from the floral and extrafloral nectaries, the sap escaping from wounded stems, ete. 4. The honey-dew excreted by plant-lice (aphids), mealy bugs (coccids) and leaf-hoppers (membracids), and the secretions of the caterpillars of the butterfly family Lycznide. These liquids are, of course, plant juices that have undergone certain changes in the ali- mentary tract or glands of the insects. 5. The seeds of plants, especially of grasses and berries, drupes and fruits of all kinds, that have been injured by birds or other insects or by falling to the ground, for the ants are unable to gnaw through the tense skins or rinds of fruits. Some hypogeic species also feed on bulbs or tubers, the tender bark of roots, or the cotyledons of germinating seeds. 6. One tribe of ants, the Aftii of tropical America, lives exclusively on fungus hyphe, which they cultivate on vegetable substances carried into the nests. Probably no single species of ant is able to draw on all of these sources of nutrition, but many species are sufficiently adaptable to util- ize several of them. The fungus-growing ants are the most highly specialized in their diet and next to these some of the seed-storing, or harvesting species. Many ants, however, are more or. less omni- vorous, and many find it an easy matter to pass from one kind of food 13 175 ANTS. to another, if only it will yield to their mouth parts, that is, if it can be imbibed directly as a liquid or rasped off in minute particles from which the liquid can be expressed in the hypopharyngeal pocket. Ants with a specialized diet are described in detail in several of the chapters of this volume. The protective habits are always very complex in colonial organ- isms, and this is particularly true of ants. These embrace nidification, to which Chapters XII and XIII are devoted, the care of the young, which has already been briefly considered, their personal care, and that of one another, their methods of defending themselves against enemies, of keeping their nests clean, of preserving the colony free from admix- ture with other species, ete. The care which ants lavish on their young is the manifestation of an instinct so all-pervasive and obsessional that we are not surprised to find it embracing the adult members of the colony as well. That it extends even further and envelopes a motley multitude of alien arthro- pods, enabling them to live as guests or parasites in the ant colonies, will be shown in the chapters on myrmecophiles. Many observers, especially McCook, have dwelt on the exquisite care bestowed by ants on their own bodies and those of their comrades. Much of the time spent by these insects in the dark recesses of their nests is devoted to cleansing the surfaces of their bodies with their tongues and strigils. This process is not only necessary for removing all particles of the earth in which the ants work so much of their lives, but it also invests their bodies with a coating of slightly oleaginous saliva, which probably protects them from moisture and may be sufficiently antiseptic to prevent the growth of lethal moulds and bacteria. This care of one another, however, does not cease with mutual cleansing and feeding, but is also exhibited in their habit of deporta- tion. There can be little doubt that this peculiar habit has developed out of the instinct to carry the brood from place to place. It may be observed under certain conditions, as when a colony is moving to a new nest, or towards nightfall when inexperienced or weary workers have strayed some distance from the nest. In the former instance the workers that initiate the change of quarters carry their indifferent or recalcitrant companions bodily to the new nest. Of deportation under the latter conditions I once saw a beautiful example on the sandy deserts about Monahans, in western Texas. The straggling workers of the slow-moving harvesting ant, schnomyrme.x cockerelli, were re- turning from all directions to their nests just as the ¢old December twilight was setting in. Each worker bore in her slender jaws a fellow worker that she had picked up while on her way home. In a similar THE HABITS OF ANTS IN GENERAL. 179 manner the amazons are carried back to the nest by their slaves. In all cases the deported, on being seized by the deporting ant, assumes a quiescent attitude with her body curled and her legs drawn up as if she were dead. The position in which she is carried seems to be char- acteristic of certain species, though this matter has not been studied in any great detail. In Formica the deporting ant seizes the ant to be deported by the mandibles and holds her with back directed forward and downward and head uppermost. The deporting Texas harvester (Pogonomyrmex molefaciens), as McCook has shown (1879¢), seizes her companion by the back of the pedicel and holds her head uppermost and ventral surface facing forward. These ants also have a peculiar habit of walking “‘ tandem,” sometimes in threes, the middle ant holding the pedicel of the first with her mandibles and the hind ant doing the same with the middle individual. In this position I have occasionally seen them returning to the nest and have wondered whether this strange performance could be a manifestation of the play-instinct, which Huber and Forel believe they have detected in certain species of Formica. In Leptothorax another position is assumed by the deported ant, which is held by her mandibles and curls herself up over the head of her carrier with dorsal surface directed forward. Still another position is adopted by Leptogenys, at least by the deported males, which are held by the neck and lie stretched out under the body and between the long legs of the deporting worker. The long slender cocoons of this ant are carried in the same manner. The care of the nest is an important matter with all ants, for con- venience no less than sanitation requires that the galleries and cham- bers be kept scrupulously clean. All species, therefore, remove any refuse food, empty cocoons, pupal exuviee, meconial pellets, dead mem- bers of the colony, etc., to a proper distance from the living apart- ments. Veritable kitchen middens are established for this purpose, either in the open air or, if the colony is nesting under a large stone, in one of the deserted surface galleries. A peculiar reaction is exhibited by nearly all ants in the presence of some substance that they cannot remove, such as a strong-smelling liquid. They throw pellets of earth or any other débris on the sub- stance, sometimes in sufficient amount to bury it completely. The origin of this reaction which is often manifested in artificial nests, 1s very obscure. The fact that it is more frequently called forth by the presence of liquids would seem to indicate that it may be a normal method of staying the invasion of water into the galleries of the nest. It cer- tainly has all the characters of a pure reflex, although, curiously enough, its manifestation under certain conditions has been regarded 180 ANTS. as a demonstration of reasoning power. One observer who placed tobacco juice across the path of some ants that were attending aphids on a tree and saw the workers cast pellets of earth on the liquid, con- cluded that they were intentionally building a bridge, and therefore credited them with a high degree of intelligence, whereas they were merely exercising one of their customary reflexes and happened to use enough earth to enable them to cross the obstacle and reach their charges. When a colony is attacked by alien ants or disturbed by larger organisms, the character of the reaction varies with the species and the size of the community. The workers of large colonies are usually ag- gressive, those of small colonies are timid and resort to more passive means of defence. Usually the most immediate response, at least on the part of a considerable portion of the colony, is precipitate flight into the surrounding vegetation. This is invariably the resort of small colonies of fleet-footed ants. Others, like Myrmecina and the smaller species of the slow-footed Attii, “ feign death” after the manner of weevils or * skip-jack”’ beetles. They roll themselves up and remain motionless for a time. In this posture the opaque, rough-bodied species of Cyphomyrmex, Trachmyrmex and Mycocepurus are almost indis- tinguishable from particles of earth or sand. Several species with peculiar mandibles manage to escape from their enemies by leaping. In Odontomachus, the “ tic-ant”’ of the tropics, for example, the linear mandibles are inserted close together at their bases and provided along their inner edges with a few sense- -hairs which are nearly as long as the mandibles. When the ant is excited it opens its mandibles to their utmost extent, till they form together a straight line at right angles with the long axis of the body. Then as soon as a hard object is touched by the sense-hairs the blades are suddenly closed, striking the object with their tips with sufficient force to throw the insect backwards into the air for a distance of several inches. This habit is also exhibited by other genera and species with similar mandibles, for example by Anochetus sedilloti (Wrough- | ton, 1892), Strumigenys saliens (Mayr, 1892a, 1893a) and probably also by Daceton and Acanthognathus. According to Emery (1893h) the large-eyed Brazilian Gigantiops destructor is able “to leap from twig to twig,” and an Indian ant with extraordinary mandibles, Har- pegnathus cruentatus, is said to leap forward like a grass-hopper to a distance of eighteen inches (Wroughton). In many species the tough integument or specially developed spines are an important means of defense. The workers of the large species of Atta and Acromyrmex bristle with hard spines and tubercles, and THE HABITS ‘OF ANTS IN GENERAL. 181 many other Myrmicine have at least a single pair of spines on ther epinotum, apparently to protect the vulnerable pedicel from the mandi- bles of their enemies. Other species (Cryptocerus, Cataulacus, Stru- migenys and Meranoplus) can conceal their sensitive antennz in deep grooves or under broad projecting ridges along the sides of the head. 3ut ants do not have to rely altogether on such passive means of defence. The means of direct attack on their enemies are almost as Fic. 103. Virgin females and workers of Camponotus americanus, showing five pairs of the latter in the act of feeding by regurgitation. (Photograph by J. G. Hubbard and O. S. Strong.) varied and usually more efficacious. The mandibles are the principal weapons and these alone in the larger species of Camponotus and Atta are sometimes employed with telling effect. In the Myrmicinz and Ponerine their action is often supplemented by that of a well-devel- oped sting. Many species of Formica spray their enemies with formic acid, or inject it into their victim by moving the gaster forward and centering its tip on the wound made by their mandibles. In battles with other species or aliens of their own species they pull their op- ponents legs or antennz with their mandibles and spray the tense mem- 182 ANTS. branes between the joints. Enough of the acid is absorbed by the vic- tim’s blood to cause temporary paralysis or even death. The Dolicho- derinee and some Myrmicine (/schnomyrme.x, e. g.) smear their victims with a malodorous secretion from the anal glands, which seems to have an equally irritating and noxious effect. While in many species some or all of these aggressive measures may be adopted by the workers in general, other species have a specially protective caste in the soldiers (Camponotus, Atta, Pheidole, etc.). In the subgenus Colobopsis the soldiers guard the circular nest-entrance which they may even plug up completely with their peculiarly modified heads (see p. 210). In Poly- ergus and Leptogenys all the workers have sickle-shaped mandibles adapted to piercing the heads or bodies of their victims. Since many species of ants often live together in the same stations, means have been developed for preventing the fusion or mixture of colonies and the consequent exploitation of one species by another. The general truth of this statement is not invalidated by the existence of a small number of interesting species that have developed symbiotic or parasitic instincts. As a rule, members of different colonies, even of the same species, are so hostile to one another that they cannot meet in numbers without a pitched battle. This hostility tends to restrict the feeding grounds of certain species within very narrow limits. It is -generally admitted that this segregation of colonies is due to the pres- ence of characteristic odors which vary with the species, colony and caste, and, according to Miss Fielde, also with the developmental stages of the individual. The specific odor may be readily detected even by the blunted human olfactories. Thus the odor of Formica rufa is pungent and ethereal, of Hlypoclinea gagates and marie smoky, of Acanthomyops like the lemon geranium or oil of citronella, of the species of Eciton and some Pheidole, like mammalian excrement, of Cremastogaster lineo- lata fainter but equally unpleasant, of Tapinoma like rotten cocoa-nuts, etc. Undoubtedly ants are very quick to react to these various odors as well as to the “ nest-aura,” or odor which every colony derives from its immediate environment, brood, etc. For interesting accounts of this important subject the reader is referred to the recent papers of Bethe (1898) and Miss Fielde (1905¢ to e). While the protection of the colony centers in the activities of the workers, the reproduction both of the individual ants and of the colony as a whole centers in the males and females. The mating of the sexes differs according to whether only one or both of the sexual forms possess wings. No species are known in which both sexes are apte- rous. In forms like Anergates, Symmyrmica, Formicoxenus and some species of Cardiocondyla and Ponera the male is wingless, whereas this Ae HABITS OF ‘ANTS @INBGENERAT. 183 is the case with the female in the Doryline and in Leptogenys. In these cases mating must take place either within the nest or on the ground outside. When only the female is winged, unless it be possible for sisters and brothers of the same colony to mate,—and this is actually the case in Anergates—she must enter strange nests or meet the male while she is wandering about in the open. Observations on this subject are, unfortunately, very meager. When both sexes are winged mating nearly always takes place in the air on what is called the nuptial, or marriage flight. Even among these species however, mating or attempts to mate have been observed in artificial nests, but this is certainly exceptional and its normal oc- currence in wild colonies is rather doubtful. Apparently there are pro- visions for favoring cross fertilization between the sexes of different colonies. In the first place, it is rare to find colonies at the breeding season containing equal numbers of males and females. Usually one or the other sex greatly predominates and often only one is repre- sented in a colony. Then, too, the nuptial flight for all the colonies of a particular species in the same neighborhood usually takes place on the same day or even at the same hour, so that the males of one colony have an oppor- tunity of mating with the females from others. It is certain that the workers forcibly detain the impatient sexes in the nests till the pro- pitious hour arrives. Why this should be the same for all the colonies in a given locality is Fic. 104. Winged and : ; begs dealated female of Campon- Morseastlysaercrmined, but it is generally con Gey. aera co cien hat ceded to be due to meteorological conditions. enlarged. (Photograph by This, indeed, seems to be the most natural eR i Conte explanation of the phenomenon. When the hour for the nuptial flight draws near, a strange excite- ment pervades the ranks of the workers. At such times even the blind and etiolated workers of the hypogzic species venture out into the sunlight and accompany the males and females to the entrance of the nest. The winged forms move about in tremulous indecision, but, finally venture forth, run about on the stones or climb about on the erass-blades till they have filled their tracheze with a plentiful supply of oxygen. Then they spread their wings and are soon lost to view high in the air. Their evolutions, so far as they can be observed, re- semble those of the honey-bee so vividly described by Maeterlinck : “She, drunk with her wings, obeying the magnificent law of the 154 ANTS. race that chooses her lover, and enacts that the strongest alone shall attain her in the solitude of the ether, she rises still; and, for the first time in her life, the blue morning air rushes into her stigmata, singing its song, like the blood of heaven, in the myriad tubes of the tracheal sacs, nourished on space, that fill the center of her body. She rises still, A region must be found unhaunted by birds, else that might profane the mystery. She rises still; and already the ill-assorted troop below are dwindling and falling asunder. The feeble, infirm, the aged, unwelcome, ill-fed, who have flown from inactive or impoverished cities, these renounce the pursuit and disappear in the void. Only a small, indefatigable cluster remain, suspended in infinite opal. She summons her wings for one final effort; and now the chosen of in- comprehensible forces has reached her, has seized her, and bounding aloft with united impetus, the ascending spiral of their intertwined flight whirls for one second in the hostile madness of love.” It must be noted, however, that there are several important differ- ences between the nuptial flights of ants and honey-bees. In the case of the bees there is a single female for whom the males compete, whereas among ants there may be hundreds of females. Moreover the pairs of ants often descend to the earth in copula and always separate without the female tearing away the male genitalia. Nor does the female ant as a rule, return to the colony in which she was born. In “both cases the males die soon after mating. In the European literature there are many accounts of great nuptial swarms of ants, visible from afar like clouds of smoke. Similar swarms have also been witnessed in the United States. The species usually concerned in producing this phenomenon are the common Lasius niger and Myrmica rubra. The nuptials of our other species take place, as a rule, without attracting particular attention. On descending to the earth the fertilized female divests herself of her easily detached wings, either by pulling them off with her legs and jaws or by rubbing them off against the grass-blades, pebbles or soil. This act of dealation is the signal for important physiological and psychological changes. She is now an isolated being, henceforth re- stricted to a purely terrestrial existence, and has gone back to the ances- tral level of the solitary female Hymenopteron. During her life in the parental nest she stored her body with food in the form of masses of fat and bulky wing-muscles. With this physiological endowment and with an elaborate inherited disposition, ordinarily called instinct, she sets out alone to create a colony out of her own substance. She begins by excavating a small burrow, either in the open soil, under some stone, or in rotten wood. She enlarges the blind end of the burrow to THE HABITS OF ANTS: IN@GENERAL. 185 form a small chamber and then completely closes the opening to the outside world. The labor of excavating often wears away all her mandibular teeth, rubs the hairs from her body and mars her burnished or sculptured armor, thus producing a number of mutilations, which, though occurring generation after generation in species that nest in hard, stony soil, are, of course, never inherited. In her cloistered se- clusion the queen now passes days, weeks, or even months, waiting for the eggs to mature in her ovaries. When these eggs have reached their full volume at the expense of her fat-body and degenerating wing- muscles,.they are laid, after having been fertilized with a few of the many thousand spermatozoa stored up in her spermatheca during the nuptial flight. The queen nurses them in a little packet till they hatch as minute larve. These she feeds with a salivary secretion derived by metabolism from the same source as the eggs, namely, from her fat- body and wing-muscles. The larve grow slowly, pupate prematurely and hatch as unusually small but otherwise normal workers. In some species it takes fully ten months to bring such a brood of minim work- ers to maturity, and during all this time the queen takes no nourishment, but merely draws on her reserve tissues. | As soonas the workers mature, they break through the soil and thereby make an entrance to the nest and establish a communication with the outside world. They enlarge the original chamber and continue the excavation in the form of gal- leries. They go forth in search of food and share it with their ex- hausted mother, who now exhibits a further and final change in her behavior. She becomes so exceedingly timid and sensitive to the light that she hastens to conceal herself on the slightest disturbance to the nest. She soon becomes utterly indifferent to her progeny, leaving them entirely to the care of the workers, while she limits her activities to laying eggs and imbibing liquid food from the tongues of her attendants. This copious nourishment restores her depleted fat-body, but her disappearing wing-muscles have left her thoracic cavity hollow and filled with air which causes her to float when placed in water. With this circumscribed activity she lives on, sometimes to an age of fifteen years, aS a mere egg-laying machine. The current reputation of the ant queen is derived from such old, abraded, toothless, timorous queens found in well-established colonies. But it is neither chivalrous nor scientific to dwell exclusively on the limitations of these decrepit bel- dames without calling to mind the charms and sacrifices of their younger days, for to bring up a family of even very small children without eating anything and entirely on substances abstracted from one’s own tissues, is no trivial undertaking. Of the many thousands of ant queens annually impelled to enter on this ultra-strenuous life, 186 ANTS. very few survive to become mothers of colonies. The vast majority, after starting their shallow burrows, perish through excessive drought, moisture or cold, the attacks of parasitic fungi or subterranean in- sects, or start out with an insufhcient supply of food-tissue in the first place. Only the very best endowed individuals live to preserve the species from extinction. I know of no better example of the sur-— vival of the fittest through natural selection. : It is certain that the colonies of most species are founded in the manner here described. It is certain, moreover, that all this is rendered possible by the nutritive endowment of the queen. As the winged germ of the species she has all the advantages that a yolk-laden has over a comparatively yolkless egg. Now among the 5,000 known species of ants we should expect to find considerable differences in the quantity of nutriment stored up in the young queen. And this is un- questionably the case. In some species the queens are of enormous size, in others they are very small compared with the workers. And since the queens of average dimensions are able to start colonies by themselves alone, we should expect unusually large queens to accom- plish even more, and very small ones less. This, too, is borne out by observation. Unusually large queens are found in the genus Atta, a group of American ants that raise fungi for food, and are, so far as known, quite unable to subsist on anything else. The female Atta on leaving the parental nest is so well endowed with food-tissue that she not only can raise a brood of workers without taking nourishment, but has energy to spare for the cultivation of a kitchen garden. Very different is the condition of certain queen ants poorly endowed with food-tissue, especially of some whose bodies are actually smaller than the largest workers of their species. Such queens are quite un- able to bring up colonies unaided. They are, therefore, compelled after fertilization to associate themselves with adult workers either of their own or of a closely allied species. In the former case the queens may either remain in the parental nest and omit the nuptial flight, or return to the parental or to some other colony of the same species. In either case they add to the reproductive energy of an already estab- lished colony and thus prolong its life. If one of these poorly endowed queens, however, happens to alight from her nuptial journey far from any colony of her own species, she is obliged to associate with alien workers. And in this case, according to the species to which she be- longs, one of three courses is open to her: First, she may secure adoption in a small queenless colony of an allied species. Here she is fed, lays her eggs, and the resulting larvee THEPAABITS OF ANTS AINGGENERAT. 187 are reared by the strange workers. Eventually the alien workers die off and leave the queen and her own workers as an independent and sufficiently established colony, capable of rapid and often enormous multiplication. This I have called temporary social parasitism. Second, the poorly endowed queen may establish herself in a colony of another species, but be unable, even after the workers have matured, to survive the death of the host colony, except, perhaps, by migrating to another nest of the same species. This is permanent social parasitism. Third,. the queen may enter a small colony of alien workers, and, when attacked, massacre them, appropriate their larvee and pupe, care- fully secrete and nurse them till they hatch and thus surround herself with a colony of young and loyal workers that can bring up her brood for her without any drain on her food-tissues. This is the method of colony formation adopted by queens of Formica sanguinea. These queens thus manifest an instinct, hitherto supposed to be exclusively peculiar to the workers, namely, the instinct to rob the larve and pupze of another species and bring them up as auxiliaries, or slaves. Pierre Huber (1810) was the first to call attention to the method of colony formation adopted by the great majority of ants, but while we must still admire, in the light of our present knowledge, the ac- curacy of his statements, we must not forget that he did not actually observe the female ant bringing her firstling brood of workers to maturity. Subsequent authors have not failed to notice this important hiatus in the work of that gifted naturalist. Although Mayr in 1864 observed isolated female ants with eggs, the actual founding of a colony by a single queen was first witnessed by an American of some- what doubtful reputation as a myrmecologist, Dr. Gideon Lincecum (1866, 1874a). Essentially the same account is repeated in McCook’s larger work on the Texan agricultural ant (1879c). The first to witness the founding of a colony in an artificial nest, that is, under conditions accurately controlled, was Sir John Lubbock. His account, originally published in 1879, is reproduced in the various editions of his well-known book on ants, bees and wasps. August 14, 1876, he isolated two pairs of Myrmica ruginodis and succeeded in keeping them in a perfectly healthy condition through the winter. The males died during the following April and May. The females laid during the latter part of April. Some of the young had pupated by the first of July and the firstling workers appeared and began to care for the remainder of the brood by the end of that month and the first week in August. This demonstrated, as Lubbock said, “ that the queens of 18S ANTS. Myrmica ruginodis have the instinct of bringing up larve and the power of founding communities.” McCook (1883a) published several careful observations by Edward Potts to show that young females of Camponotus pennsylvanicus “when fertilized, go solitary, and after dispossessing themselves of their wings, begin the work of founding a new family. This work they carry on until enough workers are reared to attend to the active duties of the formicary, as tending and feeding the young, en- larging the domicile, etc. After that, the queens generally limit their duty to the laying of eggs.” To any one who has given even a little attention to the insect life of our northern woods, it must seem strange that the founding of colonies by this ant should not have been recorded till 1883. Certainly no obser- vation could be more easily made, for in many localities it is hardly possible to tear a strip of bark from an old log without finding one or more females of C. pennsylvanicus or of the allied varieties ferrugineus and noveboracensis, each in her little cell brooding over a few eggs, larvee, cocoons or minim workers. Usually the cell is carefully ex- cavated just under the loose bark in the decayed wood, but where pine logs are abundant these females often prefer to take possession of the deserted pupal cavities of a longicorn beetle (Rhagium lineatum). These cavities are surrounded by a regular wall of wood fibers ar- ranged like the twigs in a bird’s nest (Fig. 105). Within more recent years the observations of Lincecum, Lubbock, McCook, and Potts have been repeatedly confirmed by continental authors. Blochmann (1885), Forel (1902d), Janet (1904), von Buttel- Reepen (1go5a), Emery (1904d) and Mrazek (1906) have all pub- lished interesting notes on colony formation by isolated females of ants belonging to the common genera Myrmica, Cremastogaster, Formica, Lasius and Camponotus. On more than one occasion during the past ten years [ myself have been able, both in the field and in the laboratory, to test the truth of these observations. In fact, a catalogue of the North American species, in which I have seen evidence of the founding of colonies by isolated females, would comprise nearly all of our common ants. I have ob- served it in members of all the subfamilies except the Dorylinz. Even the Ponerinz, which I at one time supposed to be an exception, con- form to the general rule, for I have found isolated females of Odon- tomachus clarus and hematodes in the act of establishing their formi- caries. During May, 1895, I observed an unusually striking case of colony formation by queens of the Californian harvester (Pogonomyr- mex californicus) on the edge of the Mojave Desert. This recalls the THE HABITS OF ANTS IN GENERAL. 189 above cited observation of Lincecum on the Texan harvester. I ar- rived at Needles, California, May 23, a day or two after the nuptial flight of P. californicus. This was proved by the thousands of isolated females of this species, in the act of establishing their formicaries. The country in which I observed them was the sandy bottom on the Fic. 105. Camponotus pennsylvanicus queen with incipient colony in abandoned cocoon of Rhagtum lineatum under pine bark, slightly enlarged. (Original.) right bank of the Colorado River and the adjacent low escarpment of the desert. The latter is interrupted by numerous short “ draws,” which are more or less sandy like the river bottom into which they open. The surface of the escarpment, however, is very hard and stony, but it, too, is furrowed by very small draws, often only a few inches wide and containing sand washed from the surrounding sur- faces by the winter showers. After their nuptial flight myriads of Pogonomyrmex females had rained down over the whole hot, dry country for a distance of at least three miles to the south and as many to the west of the Needles. After losing her wings, each female sought out the regions of pure sand, avoiding the hard surfaces, and set to work digging a hole. The earth was brought out to one side of the 190 ANTS. burrow so as to form a diminutive mound, which when completed was about two inches in diameter. On May 23, during the hot morning hours the females could be seen at work everywhere in the draws and river bottom, often within a few inches of one another. Many had already completed their burrows, which extended down obliquely. to a depth of three to four inches, and had closed the opening behind them. It was an easy matter to dig a dealated female from each spot indicated by a small fan-shaped mound or to tempt her to the surface by inserting a straw into her burrow. A wind- or rain-storm would have obliterated at once all traces of the whereabouts of these insects. That they actually sought the pure sand, which is also the substance in which the adult colonies are found; was seen on the top of the escarpment. There each tiny draw was literally filled with incipient nests, although none could be found on the hard intervening spaces often hundreds of feet wide. The ants would, in fact, be quite unable to excavate the hard soil. The comparatively small number of adult colonies in the vicinity proved that but few of these isolated females ever succeed in rearing a colony. They are doomed to rigid, all but catastrophic, elimination, which only the best endowed and most favor- ably situated can survive. In the foregoing paragraphs attention has been repeatedly called to the fact that an ant colony is started by a single isolated female. This requires some qualification, since under very exceptional circum- stances a couple of females from the same maternal nest may meet after their marriage flight and together start a colony. During August, 1904, I found two dealated females of Lasius brevicornis occupying a small cavity under a clump of moss on a large boulder near Cole- brook, Conn. They had a few larve and small cocoons and a couple of small callow workers. The colony was transferred to an artificial nest and kept for several days. Both females were seen to take part in feeding and caring for the single packet of larve and freeing the re- maining callows from their cocoons. Without doubt these twin females were sisters that had accidentally met under the same bit of moss and had renewed the friendly relations in which they had lived before taking their nuptial flight. June 16, 1907, I found a very similar colony consisting of two dealated queens of L. flavus near Sion in the valley of the Rhone. They were in a small earthen cavity under a stone and had eggs and young larve, which they hastened to conceal when the nest was uncovered. ‘These cases are of considerable interest because, as a rule, sister ants seem to be averse to such postnuptial partnerships. Among certain ants the females may be retained and dealated by the workers in the parental nest, or carried in and readopted just after , DHEMAABITS OF ANTS INSGENERATL. IgI they’ have descended from the nuptial flight, for we often find more than one queen ina colony. In some species of Formica a single colony may thus accumulate more than fifty dealated queens. Certain obser- vations also show that colonies may multiply by fission, the offshoots migrating to new nests and taking with them some of the queens. These nests may remain connected with the parental colony by run- ways, but in some cases (Formica exsectoides) they probably become independent commonwealths. This whole subject, however, is in urgent need of careful investigation, as it has important bearings on some of the cases of symbiosis to be described in future chapters. The number of ants in a colony varies greatly according to the species, and evidently depends on the number and fertility of the queens and the nature and amount of the available food. In many species, like most Ponerinz, and the ants of the genera Leptothorax, Cardiocondyla, Xenomyrme., etc., among the Myrmicine, the colony, even at the apogee of its development, comprises only a few dozen, or at most, a few hundred individuals. But the average number for most species is much greater and may exceed a thousand or ten thousand. It is, however, very easy to overestimate the population of a colony. Forel (1874) estimated that a Formica pratensis mound of medium size contains 114,000 ants and that the largest formicaries may contain as many as 500,000. But Yung (i899, 1900) who has actually counted the ants in several hills of F. rufa, an ant which has larger colonies than pratensis, found the numbers to vary between 19,933 and 93,694. These numbers are not proportional to the size of the nest. He, there- fore, believes that Forel’s estimates are excessive. Pricer (1908) has recently given valuable statistics of Camponotus pennsylvanicus colo- nies from their inception to their adult stage, which is marked by the throwing off of males and virgin females. He finds that such adult colonies contain from 1,943 to 2,500 workers, and that they must be from three to six years old before they produce the sexual phases. It is very probable that the population of the adult ant colony, which is, after all, merely an enlarged family, fluctuates about a specific average or mean. With the exception of Pricer’s work, no attempts have been made to determine this mean for our various species or its relation to the ethological environment. Here is a promising field for statistical study. CHAPTER XII. ANT-NESTS. “Le premier objet qui frappe nos sens en commengant a étudier les mceurs des fourmis, c’est l’art avec lequel elles construisent leur habitation, dont la grandeur paroit souvent contraster avec leur petitesse; c’est la variété de ces batimens, tantot fabriqués avec de la terre, tantot sculptés dans le tronc. des arbres les plus durs; ou, composés simplement de feuilles et de brins d’herbe ramassés de toutes parts; c’est enfin la maniére dont ils répondent aux besoins des espéces qui les construisent.”—-P. Huber, “Les Mceurs des Fourmis Indi- genes,” 1810. Nothing is better calculated to illustrate the marvellous plasticity of ants than the study of their nesting habits. Not only may every species be said to have its own plan of nest construction, but this plan may be modified in manifold ways in order to adapt it to the particular environment in which the species takes up its abode. I¢ven the same colony may adopt very different methods of building at different periods in its growth and development. Hence the study of formicine archi- tecture becomes one of bewildering complexity and defies all attempts at rigid classification. Owing to this complexity it is impossible to form a correct conception of the general plan of architecture in a par- ticular species without studying its nesting habits throughout its whole geographical range. In such a subject recourse to laboratory methods is of little avail, whereas cateful and extensive observation in the field is all-important. One remarkable peculiarity of ant-nests impresses us at the very outset when we compare them with the nests of the social wasps and bees, namely, their extreme irregularity. The ants have abandoned, if indeed they ever acquired, the habit of constructing regular and per- manent cells for their brood. The advantages of such cells to the ants evidently do not outweigh the disadvantages of being unable to move their larvee and pupe from place to place when danger threatens or in response to the diurnal variations of warmth and moisture. In its essential features the typical nest is merely a system of intercommuni- cating cavities with one or more openings to the outside world (Fig. 106). Even these openings, or entrances, as they are called, are absent in the nests of hypogzic species, except at the time of the nuptial flight. The intercommunicating cavities may be excavated in the soil or in plants, and even preéxisting cavities often answer every purpose and 192 ANT-NESTS. 093 save labor. The irregular form of the cavities is a characteristic so uni- versal in ant-nests that it would seem to be preferred to a monotonous regularity. It may be important, in fact, in enabling the ants to orient themselves readily. The nest entrance is sometimes peculiarly modi- fied to suit the needs of the various species. It may be left permanently Fic. 106. Superficial galleries of Acanthomyops latipes as they appear on removing the stone that covers them. About ™% natural size. (Original.) open and guarded by workers or soldiers, or it may be closed at night; it may be enlarged or constricted for the purpose of regulating the ventilation of the cavities and preventing the inroads of enemies, it may be adroitly concealed or exposed to view and surrounded by con- spicuous earth-works. Even in this prevailing and opportunistic irregularity, however, there are singular differences of degree. The more primitive ants, like the Ponerinz, build with a certain irregularity devoid of character. The Dorylinee may hardly be said to build nests at all, but merely to bivouac in some convenient cavity under a stone or log, or they may temporarily occupy the nests of other ants or dig irregular runways beneath the surface of the soil. The higher ants, however, which form 14 194 ANTS. stationary and populous formicaries, devote a great deal of attention to architecture and work according to a more or less definite plan, which they skilfully modify to suit the conditions of a specific environ- ment. The nests of nearly all ants are the result of two different activities, excavation and construction. Both of these may be simultaneously pursued by the workers, or either may predominate to the complete exclusion of the other, so that some nests are entirely excavated in soil or wood, whereas others are entirely constructed of soil, paper or silk. As the nests of the latter type resemble those of the social wasps, one might be led to suppose that they represent the original ancestral form and that the excavated are degenerate types, but the prevalence of earthen nests among ants of the most diverse genera in all parts of the world, as well as the occurrence of similar nests among the solitary bees, wasps and Mutillids, would seem to indicate that even the most Fic. 107. Crater of Myrmecocystus semirufus of the Mojave Desert; 4 natural size. (Original. ) ancient ants practiced both methods of nesting. In other words, the variable architecture of ants may be an inheritance from presocial ancestors and may have been well-established before these insects came to live in communities. The methods employed by worker ants in making their nests are ANT-NESTS. 195 easily observed, and have been described in detail by Huber (1810) and Forel (1874). According to Forel, “They use their mandi- bles in two ways. When closed these organs form a kind of trowel, convex in front and above, concave beneath and behind, and pointed at the tip. This trowel is used for raking up the soft earth and also for moulding and compressing their constructions and thus rendering them more solid and continuous. This is accomplished by pushing the an- terior portion of the closed mandibles forward or upward. In the second place, the mandibles, when open, constitute a veritable pair of tongues with toothed edges, at least in all of the workers of our native ants that do any excavating. They thus serve not only for transporting but also for moulding or comminuting the earth.” The forelegs are used for scratching up the soil, in moulding pellets and patting them down after they have been placed in position by the mandibles, and are of so much assistance in this work that when they are cut off the insects are unable to excavate or build without great difficulty and soon abandon their work altogether. Ants dislike to excavate in soil that is too dry and friable. When compelled to do this in artificial nests they will sometimes moisten it with water brought from a distance, as Miss Fielde (1901) has ob- , served. She says that the workers of Aphanogaster picea, “like the Termites, are able to carry water for domestic uses. They probably lap the water into the pouch above the lower lip [the hypopharyngeal pocket | and eject it at its destination. A hundred or two of ants that I brought in and left in a heap of dry earth upon a Lubbock nest, dur- ing the ensuing night took water from the surrounding moat, moistened a full pint of earth, built therein a proper nest, and were busy deposit- ing their larve in its recesses when | saw them on the following morning.” As even the most extensively excavated nests represent little labor compared with the nests of social wasps and bees, ants are able to leave their homes and make new ones without serious inconvenience. Such changes are often necessitated by the habit of nesting in situa- tions exposed to great and sudden changes in temperature and mois- ture or to the inroads of more aggressive ants and larger terrestrial animals. Barring the intervention of such unusual conditions, how- ever, most ants cling to their nests tenaciously and with every evidence of a keen sense of proprietorship, although there are a few species, besides the nomadic Doryline, that seem to delight in an occasional change of residence. Wasmann has shown that Formica sanguinea often has summer and winter residences analogous to the city and country homes of wealthy people. The ants migrate from one to the 196 ANTS. other during March and April and again during late summer or early autumn (September). The summer nests are built in open, sunny places where food is abundant and the conditions most favorable to rearing the brood, whereas the winter nests are built under stumps and Fic. 108. Nest of Pogonomyrmex occidentalis at Las Vegas, New Mexico; showing the basal entrance on the southeastern side. (Original.) rocks usually in protected spots in the woods, and are used as hiber- nacula, or, very rarely, for protection from excessive heat during the summer. The migration of ants from one nest to another is determined upon and initiated by a few workers which are either more sensitive to adverse conditions or of a more alert and venturesome disposition than the majority of their fellows. These workers, after selecting a site, begin to deport their brood, queens, males, fellow workers and even their myrmecophiles. The deported workers are at first too strongly attached to their old quarters to remain in the new ones and therefore keep returning and carrying back the brood. The enterprising workers, however, obstinately persist in their endeavors to move the colony till their intentions are grasped and become contagious. The indecision or indifference of many of the workers may last for days or even for weeks, during all which time files of ants move back and forth between the two nests carrying their larve and pupz in both directions. But ANT-NESTS. 197 more and more workers keep joining the ranks of the radicals till the conservative individuals constitute such a helpless minority that they Height 1 meter, basal diameter 3.25 m., (Original. ) m. 2I 10. at Scotch Plains, N. J. circumference Large nest of Formica exsectoides, 100. Fic. are compelled to abandon the old nest and join the majority. I once observed a colony of agricultural ants (Pononomyrmex molefacic) 198 ANTS. which for at least two years had occupied a nest directly in front of my house in Austin, Texas. In the autumn of the third year when certain workers decided to establish a new nest in a vacant lot about seventy feet away, | observed that it required nearly three weeks to overcome the attachment of all the workers to their old home. Forel and Escherich (1906) distinguish two types of ant-nests, the temporary and the permanent, but this does not involve corresponding differences in architecture. The same is true of Forel’s convenient distinction of monodomous and polydomous colonies. The nest of a monodomous colony is a circumscribed unit, whereas a polydomous colony, as the name implies, spreads over several nests, the inhabitants of which remain in communication with one another and may visit back and forth. This may lead to the development of accessory structures, like covered runways, but in other respects the architecture is merely a repetition of that of the simple nest. For convenience we may adopt the following classification : A. Nests in the Soil. Small crater nests. Large crater nests. Mound or hill nests. Masonry domes. Nests under stones, logs, etc. ibe satel act B. Nests in the Cavities of Plants. t. Nests in preformed cavities of living plants. . In hollow stems. b. In hollow thorns. c. In tillandsias. d. In hollow bulbs. 2. Nests in woody plant-tissues, often in cavities wholly or in part excavated by other insects. a. In or under bark. b. In twigs. jst) . In tree-trunks. a d. In galls, pine-cones, seed-pods, ete. C. Suspended Nests. a. Suspended earthen nests. b. Carton nests. c. Silken nests. D. Nests in Unusual Sites (in houses, etc.). ANT-NESTS. E99 E. Accessory Structures. a. Succursal nests. b. Covered runways. c. Tents, or pavilions. Accurate delimitation of the foregoing categories is, of course, impossible, since two or more of them may be combined in the same nest. Thus some ants construct carton nests in dead logs or under stones, others extend their galleries from dead logs into the underlying soil. Then there are also transitional forms between the various cate- gories, as, for example, between the small and large crater nests, and between the latter and mound nests. And lastly, a single formicary may gradually pass through a series of these categories during its growth and development. Nests in the Soil.—These always consist of a subterranean portion comprising a number of more or less irregular excavations and may or may not have a definite superstructure surmounting the entrance or entrances (Fig. 106). The excavations, which are usually widely sepa- rated but are occasionally compactly branching or anastomosing, may be divided into chambers and galleries. The former are more spacious, with flattened floors and vaulted roofs, but of extremely variable size and outline; the latter are more tenuous, being more or less tubular con- nections between the chambers themselves and between these and the nest openings. Chambers and galleries are most sharply differentiated from each other in the fungus-growing ants, especially in the typical genus Atta. These nests will be described in greater detail in a future chapter. Suffice it to say in this place that the chambers of ants of the subgenera Trachymyrmex and \/ycetosoritis are large spherical cavi- ties, whereas the galleries are uniform, tubular passages entering and leaving the chambers at rather definite points. In several species the chambers have the appearance of being strung along a single vertical gallery like beads on a thread. The chambers in most ant-nests are used as nurseries for the brood and for the assemblage of the ants themselves. In species which store seeds several of the chambers near the surface may be set apart as granaries, and in the Attii nearly all the chambers of the nest are given up to fungus gardens. In the nests of the honey-ants the replete workers, or honey-bearers, hang from the hard, vaulted roofs of the chambers furthest removed from the surface, while the brood is reared in the, small and more superficial apartments. The incipient nests of all soil-inhabiting species are essentially alike in presenting only the subterranean excavations. Ants in this stage of colonial development are exceedingly timid and take the greatest care 200 ANTS. to conceal the situation of their nests. The excavated soil pellets are therefore carried some distance from the nest opening and scattered about irregularly, and the entrance itself is often kept closed with a few pebbles or so adroitly concealed in a tuft of grass or under a prostrate leaf that it is impossible to find the nest without carefully following some worker that happens to be returning from a foraging excursion. This habit of concealment is retained even by adult colonies of timid species (Dichothorax and Leptothorax). Sometimes the earthen pel- lets are scattered over a wide circular area so as to produce what may Fic. 110. Formica rufa nest 2.15 meters high and 9.8 meters in diameter; pine forests of Belgium. (Photograph by G. Severin.) be called a rudimental crater (MWyrmecocystus mojave and Apheno- gaster treate.) Another form of rudimental crater is seen in species like Trachymyrmex septentrionalis, which dumps all the excavated soil in an elliptical or crescentric heap at a distance of several inches from the opening, and in Pogonomyrme-x occidentalis and californicus, which. on first establishing their nests, arrange the soil in a fan-shaped sector at the opening (Fig. 165,4). In older nests of these ants the crater is completed by the gradual enlargement of the sector along its radii and arc till it becomes a circle (Fig. 165,B). The typical crater which is the commonest form of ant-nests in regions devoid of stones and is best developed in light soil or pure sand, is often constructed with exquisite ANT+NESTS. 201 care. It is at once restored or rebuilt after destruction by rain or wind. In sandy regions most ants carry out the sand-grains one by one and deftly lay them on the walls of the crater. Among the Atti, however, the excavated sand is moulded into large polygonal pellets of uniform size in which the grains are agglutinated by moisture. What I have called small craters vary from a couple of centimeters to 10 or 15 cm. in diameter. They are constructed by many of our species of Pheidole, Myrmica and Prenolepis, by Lasius americanus, Dorymyrmex pyramicus, Monomorium minimum, Camponotus ameri- canus and by the smaller species of Pogonomyrmex, Myrmecocystus (Fig. 107), etc. These craters vary greatly in size and shape, some be- ing very flat and ring-like, with a clear space between the central open- ing and the crater wall (Nylanderia arenivaga), others very high and narrow, and almost chimney- or tower-shaped, with the opening on the summit (Trachymyrmex turrifex, Mycetosoritis hartmam and Lasius americanus). In some species there are numerous craters corresponding to as many nest entrances, and the walls of these craters may be strung along in a series (Pheidole vinelandica) or more or less fused with one another (Ph. dentata and morrisi, Solenopsis geminata). Large craters, from 20-50 cm. or even more in diameter, are con- structed by several of our North American ants, notably by Atta texana, Mellerius versicolor, Ischnomyrmex cockerelli (Fig. 156), Mes- sor pergandei (Fig. 152), Poyonomyrmex badius, comanche and cali- fornicus, Myrmecocystus melliger and hortideorum, and several species of Formica (F. schaufussi, munda, subpolita, etc.). These craters, especially in Formica, may be multiple and fused with one another like the small craters, and thus form extensive flattened elevations, perforated with openings (/*. subsericea, neoclara, neocinera, etc.). It has been sug- gested that. the craters, though consisting of materials brought to the surface and rejected during excavation, may nevertheless be of use to the ants in protecting their nest entrances from the wind. Forel has observed that the walls of the craters of certain desert ants, like A/essor arenarius of the Sahara, are raised to a greater height on the windward side. Just as it is difficult to make anything more than a purely artificial distinction between small and large crater nests, so it is by no means easy to distinguish certain large craters from mound, or hill nests. The latter are usually much larger than the craters, not because they repre- sent more extensive excavation in the underlying soil, but because they represent a large amount of material collected by the workers from the territory surrounding the nest. This accumulation is perforated throughout with ga'leries and chambers and consists of earth, small 202 ANTS. pebbles and vegetable detritus such as straws, twigs, pine-needles, leaves, etc. The proportions of these various constituents differ greatly in the different species. In our eastern Formica exsectoides (Fig. 109) which constructs conical mounds sometimes a metre in height and two to three in diameter at the base, earth greatly predominates, whereas in the European /*°. rufa (Fig. 110) and our western subsp. obscuripes Fic. 111. Mound of thatching ant (Formica obscuripes) of Colorado, made of coarse twigs and grasses. (Original.) (Fig. 111) the dome-shaped nest consists of a mass of sticks or pine-needles resting on a large crateriform earthen base. In Pogonomyrmex molefaciens and occidentalis (Fig. 108) the mound consists very largely of pebbles. The number and position of the nest openings is also highly variable. In F. rufa the numerous open- ings are scattered over the whole surface of the mound, in F. exsectoides they are mostly aggregated in a broad belt around the base, in molefaciens there is a single opening at or near the summit, whereas in P. occidentalis the single entrance is situated at the base, and almost invariably on the southern or eastern side (Fig. 108). There can be little doubt that the mound nests of the species of Pogonomyrmex mentioned above have arisen from the large crater, which is the only form of nest in most species of the genus, through stages like those ANT-NESTS. 203 shown in Fig. 165. In F. rufa and exsectoides, however, the mound seems to have developed from multiple fused craters like those of F. sanguniea, neocinerea and subsericea, species which are also in the habit of accumulating a certain amount of detritus about the openings. This habit in the various mound-building ants is most easily observed when their nests are constructed near railway tracks. In such situations the Pogonomyrmex and Formica workers bring together great quantities of locomotive cinders and place them on their nests, so that the latter stand out as black hillocks in striking contrast with the surrounding soil and vegetation. In certain localities in Arizona, P. occidentalis also covers its mounds with the dung-pellets of spermophiles, and Was- mann has noticed that the European F. pratensis employs rabbit dung and the dried flower-heads of Centaurea in the same manner. Forel has shown that the mounds of F. rufa serve the important purpose of incubators for the brood. During the breeding season the leaves and sticks of which they consist tend to acquire the high tem- perature of a compost heap, and thereby accelerate the development of the larvee and pupz. Escherich has found that the temperature of the mounds is sometimes 10° C. higher than that of the surrounding air and must be much higher than that of the galleries in the subjacent soil. Undoubtedly the gravel mounds of Pogonomyrmex barbatus, mole- faciens and occidentalis are equally useful as incubators. Other mound nests, differing from the foregoing in their smaller size and compact earthen structure, have been designated by Forel as masonry domes (domes maconneés ). This authority, who in 1900 made a hurried myrmecological excursion through the Atlantic States, was surprised to find that many circumpolar ants (Lasius niger and flavus, Formica fusca and sanguinea), which construct masonry domes in Europe, fail to exhibit this peculiarity in the United States. He con- cluded that these structures, which, like the large mounds, serve as incu- bators, must be unnecessary in this country on account of its great annual extremes of climate. This inference is certainly premature, for although it is true that many of the circumpolar species do not make domes in the Atlantic States, they have this habit in the Mississippi Valley and Rocky Mountains, where the annual extremes of tempera- ture are even greater. [Formica subsericea and many species of Lasius and Acanthomyops become dome builders in Illinois and Wisconsin, although it must be admitted that the term “ masonry domes”’ is not always strictly applicable to their nests, since the earth of which they consist is not firmly compacted but carried up rather loosely around grass and plant stems. I have frequently seen such mounds of Lasius aphidicola, Acanthomyops interjectus and claviger and F. subsericea 204 AUN ICS) fully 30 cm. in height and 60 cm. to I m. in diameter. In the Rocky Mountain region large mound nests of Pogonomyrmex occidentalis, Formica obscuripes, opaciventris and argentata abound, and in these regions they are much needed for maturing the brood, as the nights are cold in the summer and the heat of the daylight hours must be utilized. Formica glacialis, one of the varieties of F. fusca, in Maine, makes Fic. 112. Nest of Formica integra in a huge pine stump, showing vegetable de- tritus accumulated by the workers in the crevices of the bark and about the roots. ( Original.) true masonry domes like the European ants, and in this region such nests must be very useful as incubators since the summers are short and comparatively cool. I am able to confirm Forel’s statement that in hilly or mountainous regions ant-nests are most abundant on the eastern and southern slopes. He says: “I have observed this repeatedly and also more re- cently here in America. Here, too, the same explanation applies: The morning sun awakens and urges the ants to work. During the after- noon it is sufficiently warm so that this stimulus is unnecessary. Hence ANT-NESTS. 205 the advantage of an eastern exposure which lengthens their daily activity. On a western slope, on the contrary, they lose the early morning hours, are too warm in the afternoon and are unable to do much after nightfall.” Those nests, therefore, have the most favor- able position which are exposed to the sun in the morning and shaded in the afternoon. Not only is this advantage apparent in the greater abundance of nests on southern and eastern slopes, but the nests them- selves may show structural adaptation to the position of the sun. I[ have already called attention to the constant position of the nest open- ing at the base of the southern or eastern slope of the mounds of Pogonomyrmex occidentalis. Huber says that the yellow ants (Lasius flavus) of Switzerland * serve as compasses to the mountaineers when they are enveloped in dense fogs or have lost their way at night; for the reason that the nests, which in the mountains are much more numerous and higher than elsewhere, take on an elongated, almost regular form. Their direction is constantly from east to west. Their summits and more precipitous slopes are turned towards the winter sunrise, their longer slopes in the opposite direction.” These remarks of Huber have been recently confirmed by Tissot (Wasmann, 1907@) and Linder (1908). The latter has shown that the elongate shape of the mounds is due to the fact that the ants keep extending them in an easterly direction in such a manner that only the extreme easterly, highest and most precipitous portions are inhabited by the insects. I have observed a similar and equally striking orientation of the mounds of Formica argentata in the subalpine meadows of Colorado. By far the greatest number of ant-nests, at least in many parts of the world are excavated in the soil under stones, logs, boards, etc. Most of our ants, including even those that construct large mounds, are very fond of nesting in such places during the younger colonial stages. In fact only two of our terricolous species—Dorymyrmex pyramicus in the Southern, and Prenolepis imparis in the Northern States—are so rarely found under stones as to indicate that they have a pronounced aversion for such sites. The advantage of nesting under stones is con- siderable, for these not only protect the entrances, galleries and cham- bers from rain and wind and enable the ants to dispense with the labor of roofing over their surface excavations, but they are of even greater service in conserving the moisture in the underlying soil while rapidly taking up the sun’s heat and thus accelerating the incubation of the brood. Nearly all ants prefer flat stones of moderate dimensions and not too deeply buried in the soil. Many Formice of the rufa and sanguinea groups (nepticula, difficilis, consocians, microgyna, obscuri- ventris, oreas, ciliata, dakotensis, integra, rubicunda, etc.) bank the 206 ANTS. edges of the stones with earth or plant detritus into which they often extend their galleries and chambers for the aération and incubation of the brood. Even the mound-building forms frequently start their nests in this way and gradually heap the detritus up over the stones till they are concealed under typical domes and the original lapidicolous habit of the colony is no longer recognizable. In the North American forests the logs and branches strewn about on the ground afford a sub- stitute for stones and cover the nests of many glade ants, such as F. rubicunda, integra, hemorrhoidalis, Aphenogaster fulva, etc., F. integra (Fig. 112) in the Eastern and hemorrhoidalis in the Western States fill out the spaces in and under logs with vegetable detritus. Ants are not fond of nesting under cow dung, but in Texas I have found Solenopsis geminata and Camponotus fumidus resorting to such nesting sites in regions where stones were scarce and moisture and protection from the intense heat of the sun nowhere else to be found. Forel has made simi- lar observations in the high mountain pastures of Switzerland (1874). CHAPTER aie ANT-NESTS. (CONCLUDED) “Je me suis assuré que chaque fourmi agit indépendamment de ses com- pagnes. La premiere qui congoit un plan d’une exécution facile en trace aussitot lesquisse; les autres n’ont plus qu’a continuer ce qu’elle a commencé: celles-ci: jugent par l’inspection des premiers travaux de ceux qu’elles doivent entre- prendre; elles savent toutes ébaucher, continuer, polir ou retoucher leur ouvrage, selon loccasion: l’eau leur fournit le ciment dont elles ont besoin; le soleil et l’air durcissent la matiere de leurs édifices; elles n’ont d’autre ciseau que leurs dents, d’autre compas que leurs antennes, et de truelle que leurs pattes de devant, dont elles se servent d’une maniére admirable pour appuyer et con- solider leur terre mouillée. “Ce sont la les moyens matériels et mécaniques qui leur sont donnés pour batir; elles auroient donc pu, en suivant un instinct purement machinal, exécuter avec exactitude un plan géométrique et invariable; construire des murs égaux, des vottes dont la courbure, calculée d’avance, n’auroit exigé qu’une obéissance servile; et nous n’aurions été que médiocrement surpris de leur industrie; mais, pour élever ces domes irréguliers, composés de tant d’étages; pour distribuer dune maniére commode et variée les appartemens qu’ils contiennent, et saisir les tems les plus favorables a leurs travaux; mais surtout pour savoir se con- duire selon les circonstances, profiter des points d’appui qui se présentent, et juger de l’avantage de telles ou telles opérations, ne falloit-il pas qu’elles fussent douées de facultés assez rapprochées de l’intelligence, et que, loin de les traiter en automates, la nature leur laissat entrevoir le but des travaux auxquels elles sont destinées?”—P. Huber, “Les Moeurs des Fourmis Indigénes,’” 18ro. Nests in the Cavities of Plants.— and slave-making Polyergus and Formica sanguinea. The ants of the genus Leptogenys (including the subgenus Lobo- pelta) are also interesting in another respect. The Texan L. elongata has no winged females, but instead a single gynecoid worker usurps this role in each colony. This individual is indistinguishable from the workers except for the more rounded petiolar node and more volumi- nous gaster. As the difference in the petiole is not always constant the question arises as to whether the gynecoids are not merely workers that have assumed the reproductive role. Conclusive evidence in favor of this supposition has been furnished by my former pupil, Miss M. Holliday (1903), who found the gynecoids to possess a well- o> THE PONERINE ANTS. 243, developed receptaculum seminis. The number of ovarian tubules is the same as in the workers, which also occasionally possess a receptaculum. Of course, there can be no nuptial flight, and the gynecoids must be fer- tilized either by the males of their own or other colonies, and either in the nest or while traveling over the ground. That the same peculiar usurpation of the queen function by gyneecoid workers obtains among other species of Leptogenys is indi- cated, first, by the fact that winged Leptogenys females have never been seen, although the genus is a very large one and widely distributed through. the tropics of both hemispheres, and second by Wroughton’s observations on the Indian L. diminuta (Forel, 1900-03). At Forel’s request Wroughton carefully excavated an enormous formicary of this species, “but looked in vain for a female among the many thousands of workers. All he could find was a worker whose abdomen was con- spicuously distended with the ovaries. This worker differed in abso- lutely no particular from the others, and there was nothing very extra- ordinary even about its abdomen.” It is probable that several other Ponerine genera are in the same condition, for example the paleotrop- ical Diacamma and Champsomyrmex, of which the winged females have never been seen. Wasmann (1904@) has recently shown that even in the highly specialized genera Formica and Polyergus single gyne- coid workers may assume the role of queens that have been removed from the colony. It seems probable, therefore, that the Ponerine _ above mentioned present a degenerate, or, at any rate, secondary stage of colonial development in which the true female form has dis- appeared and is supplanted by a worker, elected, so to speak, to the reproductive office. If this be true, we may be able, as I shall endeavor to show in the next chapter, to account for the peculiar dichthadiiform females of the Doryline. The habits of the Ponerine reviewed in the preceding paragraphs present a mingling of primitive and specialized features, both very interesting, the former because they throw light on the more intricate ethological conditions in the higher ants, the latter because they suggest the enormous antiquity of certain formicine instincts, which must have persisted with little change since Mesozoic or early Tertiary times. Several peculiarities, such as the highly entomophagous habits of the adults, the feeding of the larvee with pieces of insect food, the retention of the cocoon, the ability of the callows to hatch unaided, the small size of the colonies and the slight fecundity of the females in many species, coupled with many morphological characters, leave little doubt that the Ponerine arose from solitary wasps. Emery, who has studied this subject (1895), believes that the immediate ancestors of the ants are 244 ANTS. to be sought in the group of wasp-like forms represented by the Sco- liide, Thynnide and Mutillide. He leaves the Scoliide and Thynnidz out of consideration ort account of the un-antlike structure of their male genitalia, and regards the Mutillide, or velvet ants, as having many points of resemblance to the Ponerinz and especially to the Cera- pachysii. Existing Mutillids, however, present two highly specialized characters which would seem to eliminate them also from the hypo- thetical ancestral series: they are, so far as known, parasitic and their females are wingless. Emery does not attach much weight to these considerations, for it is not from the modern Mutillide that he would derive the ants, but from their more ancient, entomophagous and non- parasitic precursors. He __ believes, however, that the ancestral female ants were wingless and have re-ac- quired wings by inheritance from the males. For reasons to be given in the next chapter, in connection with the wingless females of the Dorylinz, I am unable to accept this view and am, therefore, inclined to regard the apterous condition of the female Mutillids as a very serious obstacle to Emery’s hypothesis. Handlirsch (1908) has shown that in seeking the ancestors of ants it is necessary to turn to forms in which both sexes are b winged. In this respect, and also in Fic. 140. Worker of Aneure- being non-parasitic and in hunting oo spines ene CE mer ye) A helt prey under ground, the Scoliidz rom above; b, from the side. : seem to present a more faithful pic- ture of the ancestral ants than the existing Mutillide. That the phylogenetic relations of the Ponerinz to the four other formicine subfamilies are capable of rather satisfactory formulation is evident from Forel’s statement (1903b) that if, as can hardly be doubted, the Ponerinz represent the living remnants of the primitive formicine stock, a stock in turn derived from the Scoliids, “the four other sub- families must all be considered as specialized and more or less parallel derivatives of the Ponerine, 7. e., as all arising from this common stock, but without connection among themselves. “The Dorylinz, artsing’ directly from the Cerapachyii (a tribe of Ponerinz ), have no direct points of relationship with the three other THE PONERINE ANTS. 245 subfamilies, notwithstanding the convergent character presented by the pedicel of certain workers (Eciton, 4inictus and the Myrmicine ). “The Myrmicine have no direct connection either with the Campo- noting or with the Dolichoderinz. This is evident. On the contrary, the connection of the Myrmicine and the Ponerine through groups like Myrmecia, the Cerapachyii, and perhaps Pseudomyrma, admits of no doubt. The structure of the Myrmicine gizzard and poison appa- ratus remains the same. “The Dolichoderine were derived directly from the Ponerine through a gradual transformation of the gizzard and a shortening and reduction of the poison apparatus, which has become rudimental and almost replaced by the anal glands. Nevertheless, the fundamental plan of the poison apparatus remains the same as in the Ponerine. . . . The discovery of the genus Aneuretus Emery (Fig. 140) has enabled us to put our finger on the direct derivation of the Dolichoderine from the subfamily Ponerine. Indeed the genus Aneuretus constitutes a true connecting link between these two subfamilies, as is shown by the fact that Emery first placed it among the Ponerinz, but later came to accept my opinion that it should be attributed to the Dolichoderinz. “ There remain the Camponotine, of which we have been speaking. The transformation of the gizzard is explained by the intermediate forms in the inferior genera of this subfamily (1/yrmoteras, Dimor- phomyrme.x, etc.). But it is very difficult to understand the complete transformation of their poison apparatus. Here the series is incom- plete. Let us hope, nevertheless, that the future discovery of some extant relict of paleontological times will give us the key to this enigma, as has been done by the genus Aneuretus for the Dolichoderine.” CHAT ii sans THE DRIVER AND LEGIONARY ANTS. “When we see these intelligent insects dwelling together in orderly com- munities of many thousands of individuals, their social instincts developed to a high degree of perfection, making their marches with the regularity of disci- plined troops, showing ingenuity in the crossing of difficult piaces, assisting each other in danger, defending their nests at the risk of their own lives, communi- cating information rapidly to a great distance, making a regular division of work, the whole community taking charge of the rearing of the young, and all imbued with the strongest sense of industry, each individual labouring not for itself alone but also for its fellows—we may imagine that Sir Thomas More’s description of Utopia might have been applied with greater justice to such a community than to any human society. ‘ But'in Utopia, where every man has a right to everything, they do all know that if care is taken to keep the public stores full, no private man can want anything; for among them there is no unequal dis- tribution, so that no man is poor, nor in any necessity, and although no man has anything, yet they are all rich; for what can make a man so rich as to lead a serene and cheerful life, free from anxieties, neither apprehending want him- self, nor vexed with the endless complaints of his wife? He is not afraid of the misery of his children, nor is he contriving how to raise a portion for his ‘daughters, but is secure in this, that both he and his wife, his children and grand- children, to as many generations as he can fancy, will all live both plentifully and happily.’”—Thomas Belt, “‘ The Naturalist in Nicaragua,” 1874. The driver and legionary ants are the Huns and Tartars of the insect world. Their vast armies of blind but exquisitely cooperating and highly polymorphic workers, filled with an insatiable carnivorous appetite and a longing for perennial migrations, accompanied by a motley host of weird myrmecophilous camp-followers and concealing the nuptials of their strange, fertile castes, and the rearing of their young, in the inaccessible penetralia of the soil—all suggest to the observer who first comes upon these insects in some tropical thicket, the existence of a subtle, relentless and uncanny agency, directing and permeating all their activities. These marvellous insects have been studied by many travellers—for they are among the most conspicuous creatures in the tropics—but although our knowledge of them has been notably increased within recent years, we still have much to learn con- cerning their habits and development. By its latest and most careful student, Professor Emery, the sub- family Dorylinee was taken in a broad sense to include not only the drivers (Dorylii) of tropical Africa and Asia, and the legionary, or visiting ants (Ecitoni) of the warmer portions of America, but also 246 THE DRIVER AND LEGIONARY ANTS. 247 the tribes Leptanillii, Cerapachysii, Proceratii and Acanthostichii. I have followed Forel in including the last three tribes among the Ponerinz, while admitting that they have close and important genetic SS ) Fic. 141. Castes of Dorylus helvolus drawn under same magnification. (Emery.) A, Female (dichthadiigyne) in dorsal view; B, profile view of same; a, vestige of eye; b and c, vestiges of wings; d, metathoracic stigma; C, worker major; D, worker minima; E, male; F, tip of gaster of female in profile; G, tip of gaster of female D. furcatus in dorsal view; H, same in profile. 248 ANTS. affinities with the Doryline. Little is known of the minute Leptanillit (Fig. 149) except that they are hypogeic and probably live in small colonies. In the present chapter I shall consider only the Dorylii and Ecitonii, treating the two groups in succession in an endeavor to bring out their similarities and differences, even at the risk of some repetition. The Dorylinze seem to have undergone much greater morphological differentiation in the Old than in the New World, for although Emery recognizes only three genera of Dorylii, Dorylus, Ainictus and A:nic- togeton, the first of these covers a number of subgenera (Anomma, Dorylus s. str. Typhlopone, Dichthadia, Alaopone, Rhogmus and Shuckardia), several of which have been regarded by other authors as distinct genera. All the species of Dorylus s. lat., some two dozen in number, are confined to Africa (excluding Madagascar), southern Fic. 142. Dorylus fimbriatus of South Africa. Male and workers of different sizes ; natural size. (Original. ) Asia and the adjacent larger islands. The workers are completely blind, without vestiges of eyes, and vary greatly in size in the same colony, from large soldiers with toothed mandibles and excised clypeus, through intermediates to small workers with small heads and mandi- bles, more convex clypeus and sometimes fewer antennal joints (Fig. 62). The females (dichthadiigynes) are huge, unwieldy creatures, blind and wingless like the workers, and with a peculiar pygidium and an enormous gaster to accommodate the voluminous ovaries. The males (dorylaners) are also very large, with great eyes and ocelli, sickle-shaped mandibles and peculiar genitalia. The wings have only one cubital cell. All three of the phases have but a single joint in the pedicel of the abdomen. Owing to the extraordinary differences between the phases, the nomenclature of the species of Dorylus has been in great confusion. At first only the male of one of the African forms, D. helvolus, was known and this was consigned by Linné to the genus Vespa (1764). THE DRIVER AND LEGIONARY ANTS. 249 Later Fabricius erected the genus Dorylus for it and a few other species (1793). The worker of this species was first described by F. Smith sixty-five years later (1858) as Typhlopone punctata. In 1880 Trimen discovered the female which proved to be similar to a couple of insects that Gerstaecker (1872) had previously placed in the genus Dichthadia. In 1887 Emery described and figured all three phases of D. helvolus (Fig. 141), and in a later paper (1895)) gave good reasons for supposing that Typhlopone levigata F. Smith, Dichthadia glaberrima Gerst., and Dorylus klugi Emery are merely the worker, female and male respectively of a single species, which should be known as D. levigatus. These forms have all been taken in Java, Sumatra and Borneo. Re- cently Ern. André (1900) and Brauns (1903) have discovered the dichthadiigynes of Dorylus (Anomma) nigricans and D, (Rhogmus ) fimbriatus respectively, two African species of which the males and workers were previously known. As nothing but males or workers of many of the other species have been described, it is probable that the discovery of the remaining phases will lead to considerable changes in the synonymy. The habits of Dorylus have been observed by Smeathman, Savage (1845), Trimen (1880), Unger, Green (1900), Forel 1890c), Perin- guey, Emery (19050), Marshall, Brauns (1901), Vossler (1905, 1906), Santschi (1908) and others. Most of the species are hypogzic in their habits, but those of the subgenus Anomima live a more exposed life, and one of these, A. arcens, a subspecies of nigricans, was made the subject of the earliest and most detailed observations by Savage near Cape Palmas, in West Africa. Smeathman, who first saw the armies of these ants, concluded that they had no fixed habitation, but wan- dered from place to place in long files. Savage confirms this suppo- sition and describes the temporary nest in which they bivouac—a shallow depression under the roots of trees, shelving rocks or in any situation that will afford shelter. They seem to construct no chambers or galleries but merely take advantage of fissures in rocks or the crev- ices under stones or in the soil. Their sorties are made only on cloudy days or in the night, preferably in the latter, for they cannot endure the direct or even the reflected rays of the sun. “If they should be detained abroad till late in the morning of a sunny day by the quantity of their prey, they will construct arches over their path, of dirt agglu- tinated by a fluid excreted from their mouth.” While running under thick grass, sticks, etc., they dispense with the arch. “In cloudy days, when on their predatory excursions, or migrating, an arch for the protection of the workers, etc., is constructed of the bodies of their largest class (soldiers). Their widely extended jaws, long slender 250 ANTS: limbs and projecting antenne intertwining, form a sort of net-work that seems to answer well for their object. Whenever an alarm is given the arch is instantly broken, and the ants, joining others of the same class on the outside of the line, who seem to be acting as com- manders, guides and scouts, run about in a furious manner in pursuit of the enemy. If the alarm should prove to be without foundation, the victory won or the danger passed, the arch is quickly renewed, and the main column marches forward as before in all the order of an intellectual military discipline.” This habit of hanging together in clusters by means of their hooked'claws and slender legs is very strik- ing. Savage saw a colony camping on a tree: “ trom the lower limbs (four feet high) were festoons or lines of the size of a man’s thumb, reaching to the plants and ground below, consisting entirely of these insects ; others were ascending and descending upon them, thus holding free and ready communication with the lower and upper portions of this dense mass. One of these festoons I saw in the act of formation; it was a good way advanced when first observed : ant after ant coming down from above, extending their long limbs and opening wide their jaws, gradually lengthened out the living chain till it touched the broad leaf of a Canna coccinea below. It now swung to and fro in the wind, the terminal ant the meanwhile endeavor- ing to attach it by his jaws and legs to the leaf; not succeeding, another ant of the same class (the very largest) was seen to ascend the plant, and, fixing his hind legs with the apex of the abdomen firmly to the leaf under the vibrating column, then reaching with his fore-legs and opening wide his jaws, closed in with his companion from above, and thus completed the most curious ladder in the world.” These living chains are also made for the purpose of bridging small streams. The peculiar cluster- ing habit was also observed by Savage during inundations when these Fic. 143. Worker of A4nictus aitkeni of India. (Bingham.) insects resort to the same means of survival as Solenopsis geminata in tropical America. ‘In such an emergency they throw themselves into a rounded mass, deposit their ° feebler folk,” pupae and eggs in the center, THE DRIVER AND LEGIONARY ANTS. 251 and thus float upon the water till a place of safety is reached, or the flood subsides.” Savage describes the predatory habits of Anomma at considerable length. “ They will soon kill the largest animal if confined. They attack lizards, guanas, snakes, etc., with complete success. We have lost several animals by them—monkeys, pigs, fowl, etc. The severity of their bite increased to great intensity by vast numbers, it is impos- sible to conceive. We may easily believe that it would prove fatal to almost any animal in confinement. They have been known to destroy the Python natalensis, our largest serpent. When gorged with prey it lies motionless for days; then, monster as it is, it easily becomes their victim. . . . Their entrance into a house is soon known by the simul- taneous and universal movement of rats, mice, lizards, Blapside, Blat- tide and of the numerous vermin that infest our dwellings. Not being agreed, they cannot dwell together, which modifies in a good measure the severity of the driver’s habits, and renders their visits sometimes (though very seldom in my view) desirable. Their ascent into our beds we sometimes prevent by placing the feet of the bedsteads into a basin of vinegar, or some other uncongenial fluid; this will generally be successful if the rooms are ceiled, or the floors overhead tight; otherwise, they will drop down upon us, bringing along with them their noxious prey in the very act of contending for victory. They move over the house with a good degree of order, ransacking one point after another, till, either having found something desirable, they collect upon it, when they may be destroyed ‘en masse’ by hot water; or, disap- pointed, they abandon the premises as a barren spot, and seek some other more promising for exploration. When they are fairly in we give up the house, and try to await with patience their pleasure, thank- ful, indeed; if permitted to remain within the narrow limits of our beds or chairs. They are decidedly carnivorous in their propensities. Fresh meat of all kinds is their favorite food; fresh oils also they love, especially that of Elais guiniensis, either in the fruit or expressed. Under my observation they pass by milk, sugar, and pastry of all kinds, also salt meat; the latter, when boiled, they have eaten, but not with the zest of fresh. It is an incorrect statement, often made, that ‘they devour everything eatable’ by us in our houses; there are many articles which form an exception. If a heap of rubbish comes within their route, they invariably explore it, when larve and insects of all orders are borne off in triumph—especially the former.” That the hypogeic species of Dorylus are very fond of foraging for larve in compost heaps has also been shown by Forel (1890c), Peringuey, Emery (19050) and Brauns (1901). 252 ANTS. Savage has also recorded some observations on the behavior of the various castes of Anomma workers. The large soldiers with falcate, unidentate mandibles defend the colony or seize and rend the prey. The latter office is also performed by the intermediates, which have multidentate jaws. The small workers, however, confine themselves to carrying the brood and other burdens. “ They carry their pupe and prey longitudinally under their bodies, held firmly between their man- dibles and legs, the latter of which are admirably calculated by their length and slenderness for this purpose.” The pupe are nude, at least in nearly all the species of Dorylii. The large males and females have been very rarely observed in the nests. Savage saw a number of dealated mates of Anomima nigricans: marching in file with the workers. He endeavored to divert some of them from their companions but they kept returning. This obser- vation is of considerable interest, because the males of all other ants show no ability to return to the colony or the nest, nor do they voluntarily accompany the workers on their foraging expeditions or migrations. It is said that the males of Dorylus leave the nests at = = night as they are often found about @ lights, but according to Marshall and Brauns the males of D. fim- briatus (Fig. 142) and brevipennis b are expelled by the workers and at once take flight. This expulsion requires several days and does not necessarily take place at night. Fic. 144. 4inictus grandis of Marshall succeeded in finding a Lower Burma. (Bingham.) a, Male; . sini Pea. AF cane nest of fimbriatus containing a female and several males. It con- sisted of a broad, spheroidal cavity in the earth, about 70 cm. in diameter and completely filled with a damp, friable mass of earth perfo- rated throughout with tenuous galleries. The cavity was connected with the surface by means of five or six galleries 15 to 25 mm. in diameter. Brauns believes that such nests are excavated and occupied only during the breeding season. There seems to be only a single female to each Dorylus colony and she is dragged along by the workers when they migrate. Evidences of this habit are seen in the scratched ventral : THE DRIVER AND LEGIONARY ANTS. 253 surface and the absence of some of the tarsal joints in all the various dichthadiigynes of this genus that have come under the observation of myrmecologists. Some recent observations indicate that certain species of Eciton and Dorylus may have permanent nests and that their expeditions are of two kinds, predatory and migratory. According to Vosseler (1905 ) Anomma molestum of German East Africa occupies the same nest till it has destroyed all the available prey in a locality. This requires some eight or ten days. Then the colony migrates to a new nest. He observed one of these migrations which continued without interruption for twenty-four hours. Santschi (1908) recently discovered under an oven in a dye-shop in Tunis, a large Typhlopone fulvus nest from which hundreds of males took flight about four o'clock in the afternoon of six consecutive days. The dyer stated that he had observed this flight at the same season for four years. “ This indicates,” as Santschi remarks, “ that even if the migrations of Dorylus are of general occur- rence, they are not obligatory and that under certain circumstances these ants may inhabit the same nest for long periods of time.” The majority of species of Dorylus are undoubtedly carnivorous or entomophagous, but Green (1900b) has shown that at least one species, D. orientalis of India, is herbivorous, that is, feeds on the bark of trees and the tubers of plants such as the potato. The genus 4nictus comprises more than thirty species, the majority of which are south Asiatic, whereas most of the species of Dorylus are African. The workers of Znictus (Fig. 143) have two joints in the abdominal pedicel although the males and females have only one. Wroughton and Forel (1890e) first identified the males of Ainictus (Fig. 144) as belonging to workers that had been placed in the genus Typhlatta, so that this latter name had to be abandoned. More recently Emery (to01h) has described and figured the female of . abeillei. It differs from the dichthadiigynes of Dorylus in its smaller stature and in having a very small, pointed pygidium. The genus 4:nictogeton is known only from a single male specimen from the Congo, on which Emery (tooth) founded the species fossiceps. The habits of ZEnictus have been observed by Wroughton (1892) and Brauns (1901). It is much less hypogeic than Dorylus. Of an undetermined Indian species Wroughton says: “This is the only spe- cies of worker I have ever met; but it is far from uncommon in the Dekhan. Notwithstanding the possession by the A:nictus worker of two knots in the pedicel like the Myrmicide, she is distinctly ponerine in character and carries her booty exactly as do the Poneridz. She has brought the military organization to perfection. Perhaps on 254 ANTS. account of her small size (single-handed she does not seem to be able to cope with a Pheidolc, as small as or smaller than herself), she cannot afford to relax discipline, like Lobopelta, even in the moment of victory. Whatever the reason, a column of Ainictus (five or six abreast), so long as it is above ground, never shows the slightest irregularity. The destination of the column is not fixed before hand by scouts, as is apparently the case with Lobopelta. It starts, and proceeds at a long slinging trot, until-a likely hole, crevice or ant’s nest is met with, when it pours in, until enough having entered, the remainder of the column goes on, in search of another hole. Moreover, at times, when on the march, the column at a certain point in its length, turns off at an angle, striking out a new line, and, though this menceuvre is often repeated, so far as I have seen, it never happens a few files from the head of the column, but always so that each column shall be strong enough to cope with any ant com- munity likely to be met with. In- deed, this manoeuvre seems often to be of the nature of a flanking movement. I have seen a strong column, marching on a white ant heap, detach in this way, columns right and left, and the several de- tached columns enter the heap from different points of the compass. The notion irresistibly forced on Fic. 145. Workers and soldier of anyone, watching these manceuvres, es ee drawn to the same scale. jg that they are either the result of Tin Ot preconcerted arrangement, or are carried out by word of command.” Brauns makes a similar observation on the South African species: “Enictus is not as sensitive to sunlight as Dorylus and therefore moves over ground for considerable distances, especially after rain and when twilight is setting in, or even in the bright sunshine. The files resemble those of Anomma, in miniature, of course, and are narrow, regular columns. Of several expeditions of dinictus eugenti which I have witnessed in the Orange Free State, one was noteworthy. In this instance the ants carried their brood on the under side of their bodies, just as it is borne by the Ponerinae, especially by Leptogenys, according to my observations.” THE DRIVER AND’ LEGIONARY -ANTS. 25 WwW Wroughton has seen the workers of the Indian 4. wroughtoni expelling the males from the nest. These males escaped on two consecutive days from “a small hole in the floor of a mudwashed verandah, and it did not appear to be a hole used for the regular traffic of the nest.” It is an interesting fact that the males of the Doryli have nearly always been found escaping from holes in the floor or foundations of human dwellings. In tropical and subtropical America the Doryline are represented by two genera, Eciton and Cheliomyrmex. Of the former about sev- enty species are known, of the latter but one, C. nortoni. The genus Eciton is so homogeneous that it has been split into only two subgenera, Acamatus and Eciton s. str. It resembles the Old World 4nictus in having the pedicel two-jointed in the worker, and in the structure and smaller size of the female. Both worker and female usually have vestiges of eyes, consisting of a single ommatidium on each side of the head, but not connected with the brain by means of optic nerves, so that they must be useless as visual organs. In some species (E. hama- tum (Fig. 3C and 145), /ucanoides and foreli) the largest workers, or soldiers, have peculiarly elongated and hooked jaws of unknown func- tion. The males of Eciton resemble those of Dorylus (Figs. 146 and 147d), but they are smaller, have two complete cubital cells in the wings, and their mandibles are usually longer and more falcate. As in the case of Dorylus, the three phases of Eciton have been placed in as many different genera, the worker in Ec/ton, the female in Pseudodichthadia and the male in Labidus. Hetchko, Mayr (1886b) and W. Miller (1886) first showed that the insects which entomologists had been in the habit of calling Labidus were the males of Eciton, and Ern. André has recently found that the insect which he described as Pseudodichthadia incerta is the female of E.cwcum. Although the males of several species are known, few have been taken with their workers, and are described in the literature under independent names. In addi- tion to that of E. cecum the females of only three species are known, that of E. opacithorax, discovered by Schmitt in North Carolina, that of E. carolinense taken by Forel in the same state, and that of E. schmitti (Fig. 147c) taken by myself in Texas. All the phases are known only of E. cawcum, opacithorax and schnutti. The genus Cheliomyrme-. is confined to the warmest parts of America and appears to be rare except in certain localities. I have recently received a number of specimens of C. nortoni (Fig. 148) from British Honduras, but it is recorded also from Colombia and Mexico. Only the worker form is known, and that is remarkable for the hooked and bidentate mandibles of the soldier form, and in having only a single > 6 ANTS. mn joint in the pedicel like the Old World Dorylus. Eciton has a much wider distribution, ranging from North Carolina and Colorado to Patagonia, but the largest and most numerous species are found only within the tropics. According to von Ihering (1894) the prominent species do not extend southward beyond the Cebus-line in Brazil, and in Mexico they probably cease with the northern limit of the terra caliente on the eastern coast. No species are known from the West Indies. Observations on the habits of Eciton are more numerous than those on Dorylus. They have been made in Brazil by Lund (1831), W. Muller (1886), Hetchko, Bates (1892) and von Ihering (1894), in Trinidad by Urich (1893-94), in Guiana by Bar, in Colombia by Forel (1901 ),in Nicaragua by Belt (1874),in Mexico by Sumichrast (1868 ) and myself (1901a), in North Carolina by Schmitt and Forel (1899c ), in Texas, New Mexico and Colorado by Long and myself (19002, 1go1). All residents in the American tropics are familiar with these ants, which are variously designated as ‘ padicours,” “ tuocas,” “ tepe- guas,” “soldados” army, foraging, legionary, or visiting ants. Their habits are similar to those of Dorylus and Ainictus, but there are inter- esting differences among the various species. Some, like the widely dis- tributed, eyeless E. cecum, are completely hypogzic, or subterranean, others like E. crassicorne, are subhypogeic, or creep along under cover of the dead leaves and other vegetable detritus on the surface of the soil. Most species, however, carry out their expeditions in full view and often exposed to the sunlight (E. predator, hamatum, pilosum, schmitti, etc.). Bates has described differences in the methods of making forays in the various Brazilian species, and some of these same species have been studied by Belt. His description of a foray of E. predator may be re- garded as typical of all the epigzeic forms: “ One of the smaller species (Eciton predator) used occasionally to visit our house, swarm over the floors and walls, searching every cranny, and driving out the cock- roaches and spiders, many of which were caught, pulled, or bitten to pieces and carried off. ... I saw many large armies of this, or a closely allied species, in the forest. My attention was generally first called to them by the twittering of some small birds, belonging to several different species, that followed the ants in the woods. On approaching to ascertain the cause of the disturbance, a dense body of the ants, three or four yards wide, and so numerous as to blacken the ground, would be seen moving rapidly in one direction, examining every cranny, and underneath every fallen leaf. On the flanks, and in advance of the main body, smaller columns would be pushed out. These smaller columns would generally first flush the cockroaches, THBeOKIVER, AND LEGIONS CAN TS. i) cn ol grasshoppers and spiders. The pursued insects would rapidly make off, but many, in their confusion and terror, would bound right into the midst of the main body of ants. ... The greatest catch of the ants was, however, when they got amongst some fallen brushwood. The cockroaches, spiders and other™nsects, instead of running right away, would ascend the fallen branches and remain there, whilst the host of ants were occupying all the ground below. By and by up would come some of the ants, following every branch, and driving before them their prey to the ends of the small twigs, when noth- ing remained for them but to leap, and they would alight in the very midst of their foes, with the result of being cer- tainly caught and pulled to pieces. Many of the spiders would escape by hanging sus- pended by a thread of silk from the branches, safe from the foes that swarmed both above and below.” In regard to another spe- cies, EH. hamatum, which has large, light-colored — soldiers with very Jong hook-shaped jaws (Fig. 3C), Belt says: “I think Eciton hamata does not stay more than four or five days in one place. I have sometimes come across the a a aes Fic. 146. Eciton esenbecki. (Original.) a, migratory columns. Male in profile; b, dorsal aspect of head. may easily be known by al! the common workers moving in one direction, many of them carrying the larve and pupz carefully in their jaws. Here and there one of the light-colored officers moves backwards and forwards directing the columns. Such a column is of enormous length, and contains many thousands, if not millions, of individuals. I have sometimes followed them up for two or three hundred yards without getting to the end.” Belt succeeded in finding the temporary nest of an army of thes« 18 258 ANTS. ants: “ They make their temporary habitation in hollow trees, and sometimes underneath large fallen trunks that offer suitable hollows. A nest that I came across in the latter situation was open at one side. The ants were clustered together in a dense mass, like a great swarm of bees, hanging from the roof, but reaching to the ground below. Fic. 147. Castes of Acamatus schmitti; drawn under the same magnification. (Original.) a, Worker; b, young female (dichthadiigyne) ; c, old female with enlarged ovaries, in the act of ovipositing; the anterior portion of the body is covered with mites (Cillibano hirticoma) ; d, male. Their innumerable long legs looked like brown threads binding together the mass, which must have been at least a cubic yard in bulk, and con- tained hundreds of thousands of individuals, although many columns were outside, some bringing in the pupz of ants, others the legs and THE DRIVER AND LEGIONARY ANTS. 259 dissected bodies of insects. I was surprised to see in this living nest tubular passages leading down to the center of the mass, kept open just as if it had been formed of inorganic material Down these holes the ants who were bringing in booty passed with their prey. I thrust a long stick down to the center of the cluster and brought out clinging to it many ants holding larve and pupz which were probably kept warm by the crowding together of the ants. Besides the common dark- colored workers and light-colored officers, I saw there many still larger individuals with enormous jaws. These they go about holding wide open in. a threatening manner, and I found, contrary to my expectation, that they could give a severe bite with them, and that it was difficult to withdraw the jaws from the skin.” These observations recall the clustering habit of the African Anomma as described by Savage, a habit which seems to be common to a number of Ecitons. I have seen it in E. sumichrasti, schmitti and opacithorax. Excellent observations on the Mexican species were made by Sumi- chrast (1868) from whom I quote the following: “ The most charac- teristic trait of the ants of this genus consists in the inroads or migrations which they undertake at undetermined epochs, but in rela- tion, it appears to me, with the atmospheric changes. What traveller, passing over the tierra caliente, has not encountered the phalanxes of tepeguas upon the path of the primitive forests? What inhabitant of these countries has not, at least once, been unpleasantly torn from the arms of sleep by the invasion of his domicile by a black army of soldados? “The purpose of these expeditions of Eciton is, without doubt, multiple, for the circumstances that these sorties, as one may call them, coincide more often with a change of season, hardly permits one to consider them exclusively as simple razzias undertaken at the expense of other insects. One can believe them to be sometimes expeditions of pillage, sometimes changes of domicile, veritable migrations. I believe that the following facts, which passed under my observation at the hacienda of Potrero, near Cordova, at the end of September of the past year, show proof of this. During about three months, a colony of soldados |E. predator| had been domiciled under a little bridge formed by some rough trunks of trees bound together by a heap of vegetable mould. The continued excavation which engaged the ants on the under side of the bridge, threatened to cause the disappearance of all the earth which covered the flooring. Every day I watched these labors in the hope of discovering at last the interior of the formicary, but this hope was disappointed, for on the thirtieth of September, in the morning, I found the nest completely abandoned. Its inhabitants 260 ANTS: did not return until about four months later, and this reappearance, which was of short duration, was followed almost immediately by a visit which these insects made to my habitation, on the. twelfth of February, in the night. I have similar observations in regard to another species [/. foreli] and I think I can conclude that the Eciton, at least the two species in question, are in the habit of forming tem- porary nests or habitations for themselves, which they abandon from time to time, distinct from those where are found the reproducing sexes, and where is the place of the growth of the larve and their metamorphoses. “The nests are found in cool, shady places in great woods or woe Pray) ba ; A k \ e Wend y ir See ee py) FO nee J xi goa Y ) f A if ye Fic. 148. Cheliomyrmex nortoni of Central America. (Original.) a, Soldier; b, head of same from above; c, worker media; d, head of same; e, worker minima ; f, tarsus to show toothed claws. among rocks and are tunneled more often at the foot of, and among the roots of, old trees. The earth or the fragments of wood, which the ants cast out, sometimes form a dome above, but at times only an irregular opening indicates the existence of a colony. “The extraction of one such nest, beside the difficulty of pene- trating to the center through the entangled roots of the tree, is not an easy thing, for at the first alarm, the soldados sally forth in myriads and attack the aggressor with fury. THE DRIVER AND LEGIONARY ANTS. 261 ‘“ Besides the changes of domicile, which are so generally in relation with the atmospheric variation as to serve as a rule to the inhabitants of the country, the Eciton devotes itself every season to excursions for pillage, destined to supply the larve with nourishment. Nothing is more curious than these battwes executed by an entire population. Over an extent of many square meters, the soil literally disappears under the agglomeration of their little black bodies. No apparent order reigns in the mass of the army, but behind this many lines or columns of laggards press on to rejoin it. The insects concealed under the dry leaves and the trunks of fallen trees fly on all sides before this phalanx of pitiless hunters, but, blinded by fright, they fall back among their persecutors and are seized and despatched in the twinkling of an eye. Grasshoppers, in spite of the advantage given them by their power of leaping, hardly escape any more easily. As soon as they are taken, the Eciton tears off the hinder feet and all resistance becomes useless. “If some heap of dry leaves, some tree or bush presents itself upon the path of the columns, a party of hunters separates itself from the mass of the army, and, after having ransacked it in every part, retakes its place in the advance guard. I have observed, sometimes, that little flies, of the family Syrphides, follow, flying above them, the column of Eciton, but cannot give any account of the evolution of these Diptera." “Tt is probable that the Ecitons attack the larve and pupz of other ants to make them serve as food for the nourishment of their own larve or for sustaining themselves. I surprised, one day, in the first hours of a sombre and rainy morning, a considerable assemblage of tepeguas [E. foreli| fastened one upon another like a swarm of bees and entirely still. Having dispersed them I perceived in the place which they covered with their bodies a quantity of little white larve, brought away doubtless, from the nests of some Myrmicide. At another time I witnessed the pillage of a nursery of other ants by a quite enormous band of workers minores [E. hamatum]; alarmed by the reprisals which I made on their account, they took to flight, some of them carrying between their mandibles as many as three larve at once. Among the Mexican species of the genus Eciton, that to which they apply more specially the name of soldados |E. predator], may be noticed for the habit which it has of invading the habitations of the country. These visits ordinarily take place at the beginning of the ‘These “Syrphids” probably belong to the Conopid genus Stylogaster, of which Townsend (1897) found three species hovering over troops of Ecifon in the lowlands of the Rio Naubla, in the state of Vera Cruz, Mexico. 262 AN TS: rainy season, and almost always during the night. The expeditionary army penetrates the habitation which it proposes to visit at many points at once, and for this purpose divides itself into many columns of attack. One is apprised very soon of their arrival by the household commotion among the parasitic animals. The rats (Mus tectorum), the spiders, the cockroaches (Periplaneta australasie Fab.), abandon their retreats and seek to escape from the attacks of the ants by flight. Fic. 149. Castes of Leptanilla. a, L. minuscula, male; b, head; c, copulatory organs of same. (Santschi.) d, L. revelieri, dichthadiiform female, dorsal view; e, same in profile; f, worker. (Emery.) Alimentary substances the soldados hold in no esteem, and they disdain even sugary things, to which the ants in general are so partial. Dead insects even do not seem to invite their covetousness. It has often happened to me to be obliged to abandon my abode, without having time to carry away my collection, to which they have never done the least injury. The trouble occasioned by these insects in entering houses is more than compensated by the expeditious manner in which they purge them of vermin, and in this view their visit is an actual benefit.” THE DRIVER AND LEGIONARY ANTS. 263 Bates appears to have been the first to observe the habits of the hypogeic E. cacum. The armies of this ant move “ wholly under covered roads, the ants constructing them gradually but rapidly as they advance. The column of foragers pushes forward step by step under the protection of these covered passages, through the thickets, and on reaching a rotting log, or other promising hunting ground, pour into the crevices in search of booty. I have traced their arcades, occa- sionally for a distance of one or two hundred yards; the grains of earth are taken from the soil over which the column is passing, and are fitted together without cement. It is this last mentioned feature that distinguishes them from the similar covered roads made by Ter- mites, who use their glutinous saliva to cement the grains together. The blind Ecitons, working in numbers, build up simultaneously the sides of their convex arcades, and contrive in a surprising manner, to approximate them and fit in the keystones without letting the loose, uncemented structure fall to pieces.” To the foregoing observations of other authors I may add some of my own on the Texan species, dwelling on certain points not noticed in the above descriptions. The workers of all the Ecitons I have seen have a peculiar nauseating, fecal odor, which is also found in a few carnivorous species of Pheidole (Ph. antillensis and ecitonodora). The males and females, however, have a sweet and pleasant odor, which probably accounts for the strong attraction they have for the workers, for in the living colonies the latter always form a mass enveloping the sexual phases. The males are produced in great numbers. Towards nightfall on one occasion I witnessed the escape of the males of FE. schmitti from a nest in the dry limestone soil near Austin. Throughout the spring and summer months these insects fly to the lights at night in great numbers. There is cnly a single mother queen to a colony, but the workers readily adopt queens from other colonies of the same species. I have never seen these females dragged along during the expeditions, but it is probable that this is the case. Owing to their smaller size they are undoubtedly more easily moved from place to place than the huge Dorylus queens, and this may account for the fact that none of the numerous females of E. schmitti and opacithorax which I have seen was mutilated or abraded. The eggs are very small and exceedingly numerous. The -worker larve are slender, and the pupz are never enclosed in cocoons. None of the Texan Ecitons forms very large or conspicuous armies though they hunt in files like the large tropical species. Their food consists very largely of the larve and pupz of other ants. On many occasions I have seen FE. schmutti, opacithorax and crassicorne plunder- 204 ANTS. ing formicai1ies and carrying the brood to their temporary nests. This habit is also well-known in the tropical species and is expressly men- tioned by nearly all the authors above cited. The kidnapped larvz and pupe are stored for a time and then eaten like any other insect prey. All the species I have seen, with the exception of E. cacum, are exclu- sively entomophagous. E. cecum is, as Bates observed, exclusively hypogeic in its habits and never appears in the open, but tunnels along just beneath the surface of the soil or under clusters of stones. I have never been able to find even its temporary nests, although it is one of the most abundant ants in central Texas. It may often be found ferreting out larve in or under old logs, under cow-dung, or the dead bodies of cats and dogs. Sometimes on these subterranean forays, it chances to enter the galleries of other ants and then a fierce battle ensues. On one occasion I found a number of dead E. cacum workers on the refuse heap of a large nest of the Texan harvester (Pogonomyrmex molefaciens) and on examining the workers of this colony, which were running about on the denuded nest area, I found each of them carrying the head of an E. cecum immovably attached by the closed mandibles to the anten- nal scape. This told the story of a fierce subterranean conflict in which the harvesters had come off victorious, though compelled to carry about the detached heads of their assailants. E. c@cum is also very fond of certain vegetable substance, especially of nuts. I have sometimes attracted and trapped great numbers of workers by burying a few walnut or pecan kernels in the lawns near Austin. The Ecitons carry their larve and pupz under their bodies like the Dorylii and the Ponerine. They move very rapidly and orient them- selves with surprising alacrity for animals that are quite blind and have to rely entirely on their contact-odor sense. This was observed by Forel (1899c ) in E. carolinense and I have noticed it in a number of spe- cies. Torel says: ‘“ Throw a handful of Ecitons with their larve on a spot with which they are absolutely unacquainted. In such circumstances other ants scatter about in disorder and require an hour or more (sometimes less) to assemble and bring their brood together and espe- cially to become acquainted with their environment, but the Ecitons do this at once. In five minutes they have formed distinct files which no longer disintegrate. They carry their larve and pup, marching in a straight path, palpating the ground with their antennz and exploring all the holes and crevices till they find a suitable retreat and enter it with surprising order and promptitude. The workers follow one another as if at word of command, and in a very short time all are in safety.” THE DRIVER AND LEGIONARY ANTS. 205 In cavity Ecitons are remarkably restless, at least at certain times during the day. Part of a fine colony of E. schmitti which I kept some years ago, exhibited this restlessness in a striking and ludi- crous manner. The colony was at first confined in a tall glass jar on a square board surrounded by a water moat. The ants kept going up and down the inside of the jar in files for many hours. Finally I removed the lid. The file at once advanced over the rim and descended on the outer surface till it reached the circular base of the jar where it turned to the left at a right angle and proceeded completely around the base till it met the column at the turning point. To my surprise it kept right on over the same circumference which was long enough to accommodate all the individuals. They continued going round and round the circular base of the jar, following one another like so many sheep, without the slightest inkling that they were perpetually travers- ing the same path. They behaved exactly as they do on one of their predatory expeditions. They kept up this gyration for forty-six hours before the column broke and spread over the board to the water’s edge and clustered in the manner so characteristic of this and the allied species (E. opacithorax, sumichrasti, etc.). I have never seen a more astonishing exhibition of the limitations of instinct. For nearly two whole days these blind creatures, so dependent on the contact-odor sense of their antenne, kept palpating their uniformly smooth, odoriferous trail and the advancing bodies of the ants imme- diately preceding them, without perceiving that they were making no progress but only wasting their energies, till the spell was finally broken by some more venturesome members of the colony.! In conclusion attention may be called to certain problems that are suggested by our present meager knowledge of the Dorylinz. Besides the investigation of the species with a view to obtaining all the phases and thus clearing up the taxonomy, we are in great need of a fuller insight into the domestic economy of these singular insects. As yet no one has been able to observe the methods of rearing the brood and the mating of the sexual forms, which must, of course, take place without a true marriage flight. Nor has it been possible to plot the *T have found a remarkable observation of the same kind recorded by Fabre in the sixth volume of his incomparable “Souvenirs Entomologiques.” He describes an army of caterpillars of the “processionaire du pin” (Cnethocampa pityocampa) going round and round the outside of a large vase 1.35 m. in circumference for seven days! During this period the caterpillars were on the march 84 hours altogether, stopping to rest on their path only when overtaken by the cold of the night, and not actually deviating till the eighth day. Fabre estimates that the caterpillars crawled around the vase 335 times. In this case the insects were not guided by contact-odor like the Ecitons, but by the silken thread spun by each individual over the surface traversed. 266 ANTS. territory covered by the annual migrations of any of the species, to de- termine the time spent in the bivouacs or in the presumably more per- manent breeding nests, or the precise relations which these nomadic ants bear to their myrmecophiles. Curiously enough, these seem to be more numerous both in species and in individuals than the myrmecophiles of the non-migratory ants of other subfamilies. Another problem of more theoretical interest is presented by the dichthadiigynes, which are so unlike typical female ants. To Emery these forms seemed to indicate that the females of ancestral ants were wingless and that the alate condition represented a secondary inheri- tance from the male sex within comparatively recent times. He was confirmed in this opinion by his discovery of apterous dichthadiiform females in the very primitive species of Acanthostichus and Parasyscia. There is, however, another possibility, which seems not to have been considered. The occurrence in certain Ponerine (Leptogenys and probably also in Diacamma and Champsomyrme.x ) of gynzcoid work- ers that have supplanted the winged females, suggests that the dichtha- diigynes may also be highly modified gynecoids. It must be admitted that this view is beset with serious difficulties. First, we must suppose, on such a hypothesis, that the gynzecoids are phylogenetically fixed forms of very ancient origin, since in 4:nictus and Eciton they are quite unlike the existing workers in having only a single joint in the pedicel. Hence they cannot be compared directly with the gynzcoids of Formica, which are merely workers that usurp the queen’s place and function during the ontogenetic development of the colony. Second, Emery has figured in the female Dorylus helvolus minute “ rudiments of wings” and a conformation of the thoracic sclerites suggestive of the typical winged form. If he has correctly interpreted these various structures we are bound to suppose that the dichthadiigyne is a highly degenerate, alate female and both his hypothesis and the one I have suggested must be abandoned. The females of Eciton and A:nictus, however, certainly have a much simpler and more worker-like thorax, and | am by no means certain that Emery has correctly interpreted the conditions in Dorylus. Too few female Doryline are known at the present time to enable us to decide this question, which must he left to future students. CHAPTER Vir THE HARVESTING ANTS: “Verrit tetra boum gratos formica labores Et caveis fruges turba nigella locat, Quamlibet exiguo videatur pectore, sollers, Quo legat hiberne commoda grana fami. Hane juste famulam nigri jam dixeris Orci, Quam color et factum composuit domino. Namque ut Plutonis rapta est Proserpina curru, Sic formicarum verritur ore Ceres.” — Anthologia Latina,” - 104. The two preceding chapters contain an account of the primitive and carnivorous species which represent the savage and hunting stages in the development of ant societies. In this and the following chapter I shall endeavor to sketch the habits of certain ants that have largely abandoned entomophagy and have taken to a benigner, vegetarian diet. I have called attention (p. 176) to the fact that abundance of food is necessary to the maintenance of social life and that the fullest expan- sion and development of such life is possible only to animals that have learned to draw on the vegetable kingdom for a large part of their sustenance. Hence we are not surprised to find that in warm, arid countries, where, during many months of the year, insect food is either very scarce, or where the competition for food among ants and other animals is very keen, a number of the former have become confirmed vegetarians as their last resource in the struggle for existence. Under such circumstances the seeds of herbaceous plants obviously furnish the most accessible and nutritious food. The harvesting habit thus developed is only one of many indications of an ever-increasing depen- dence of ants on the vegetation, a subject which will occupy us in several of the succeeding chapters. Even a few of the eminently ter- restrial and carnivorous Ponerinze and Dorylinz, as we have seen, show indications of vegetarianism. The three higher subfamilies, however, have a much more varied and unstable diet, with an increasing ten- dency to imbibe plant-juices, either directly from the floral and extra- floral nectaries, or indirectly after they have passed through the bodies of aphids and other Homoptera, or to feed on fungi; seeds or fruit. Among these subfamilies certain tribes and genera have become so addicted to specialized diets as to be of unusual interest. It is easy to conceive of the origin and development of the graniy- 267 2608 ANTS. orous habit, for a carnivorous ant, used to collecting insects and crush- ing their hard integuments with its powerful mandibles, is already fully equipped with the apparatus necessary for dealing with seeds. And although many harvesting ants have more convex mandibles and blunter teeth than carnivorous species, it is impossible merely from examina- tion of the mouthparts to ascertain whether an ant is granivorous or not. It may be doubted, furthermore, whether there is such a thing as a purely granivorous ant. There is clearly no advantage in an ant’s losing its taste for the succulent tissues of other insects, although there is an obvious advantage in its supplementing this diet with seeds during certain seasons of the year. Indeed, many, if not all, of the species mentioned in the following pages are quite as eager to secure insect food as seeds, especially while they are raising their brood, and unquestionably many ants that are supposed to be exclusively ; redaceous will, on closer Fic. 150. Worker of the Indian harvester, P d Holcomyrmex scabriceps. (Bingham.) study, be found to be more or less granivorous. If the foregoing considerations are correct, we should expect to find the harvesting ants arising sporadically and often in distantly related genera and species. ‘This appears to be the case, for although these insects belong to a single subfamily, the Myrmicinae, they occur in at least three of the tribes, the Solenopsidii, the Tetramorii and the Myrmicii. Among the Solenopsidii, however, only a single species of Solenopsis (S. geminata) is known to be granivorous, and only a por- tion of the enormous genus Pheidole comprises such species. The small genus Pheidologeton is also granivorous. Among the Tetramorii, Tetramorium cespitum is only rarely and sporadically granivorous, and this is perhaps true of a certain number of species of Meranoplus. Among the Myrmicii, Messor and Ischnomyrmex comprise harvesting species, whereas the species of the allied Stenamma and A phenogaster are predaceous. Flolcomyrmex, now regarded as a subgenus of MJono- morium, Pogonomyrmex, Oxyopomyrmex (with its subgenus Goni- omma), which are closely related to Messor, and probably also Ocy- myrmex, are highly granivorous. The earliest of all recorded myrmecological observations undoubt- edly relate to two harvesting ants, Messor barbarus and structor. The former occurs throughout the Mediterranean littoral of Europe, Asia THE HARVESTING ANTS. 269 and Africa and presents in the warmer portions of its range, which is now known to extend southward to the Cape of Good Hope, a bewil- dering complex of subspecies and varieties. M. structor seems to be absent in Africa, but ranges through southern Europe and Asia as far as Java. The ancient peoples were undoubtedly familiar with the granivorous habits of these ants and probably also with those of a third species, M. arenarius, inhabiting the deserts of North Africa. To them. refer the many allusions in the writings of Solomon and the Mischna, and of the classic writers Hesiod, sop, lian, Plutarch, Orus Apollo, Plautus, Horace, Virgil, Ovid and Pliny. Medieval authers, like Aldrovandus and Bacon, merely repeated the accounts of the ancients. The entomologists of the early portion of the last cen- tury, however, failing to find any harvesters among the ants of temperate Europe, began to doubt, or even to deny their existence. This skepticism is much in evidence in the works of Gould (1747), Latreille (1802), Huber (1810), Gené (1845), Kirby and Spence (1846),and Blanchard( 1871). The sub- ject was taken up, however, by Sykes (1820) and Jerdon (1851) in India, by Moggridge (1873) in southern France and by Buckley (1861a), Lincecum (1862), McCook (18774, 1879c), Morris (1880) and Mrs. Treat (1878) in the United States. These authors suc- ceeded in showing that the ancient accounts were correct. For a detailed history of the subject and for extracts from the various authors of antiquity, the reader is referred to Bochart’s ‘‘ Hierozoicon”’ and to the works of Moggridge and McCook. Here I shall confine Fie. 151. Diagram ; ; : of nest of Oxyopomyr- myself to the recent observations, considering mer santschii. (Sant- first, in all brevity, the Old World harvesters schi-) Explanation in text. and concluding with a somewhat fuller ac- count of our American species. Sykes was the first of modern observers to describe the storing of seeds by ants. He saw Pheidole providens at Poona, India, bringing grass seeds, which had been moistened by the rains, out of the nests and exposing them to the sun to dry. Jerdon confirmed these observa- tions on Ph. providens, Ph. diffusa and Solenopsis rufa, a subspecies of the tropicopolitan S. geminata. He saw the ants not only drying their piles of seeds but also collecting them from different plants and storing 270 ANTS. them in the nests, although he was unable to ascertain the purpose of these activities. All doubt was removed, however, by Moggridge’s excellent work, which was carried out at Mentone in 1871 and 1872 on Messor barbarus and structor, the very species that had been observed by the ancients. [le opened the nests of these ants and studied their granaries, which are flat chambers connected by galleries and irregu- larly scattered over an area sometimes nearly 2 m. in diameter and to a depth of about 35 cm. in the soil. He saw the workers collect the seeds from the ground or even pluck them from the plants, remove Fic. 152. Nest of Messor pergandei in Arizona desert, in a spot where the alkali prevents the growth of nearly all plants except Suw@da. The dark material at the border of the crater is seeds and chaff rejected by the ants. In more favor- able spots in the desert the seeds produce the ring of plants seen in Fig. 154. ( Original.) their envelopes and cast the chaff and empty capsules on the kitchen middens outside the nest. During the winter a nest of the average size may contain as much as a quarter of a liter of seeds. Among the stores in the granaries he was able to recognize seeds belonging to at least eighteen different families of plants. In confirmation of Pliny and Plutarch he maintains that the ants bite off the radicle to prevent the seeds from germinating, a process which is also arrested by bring- TEE ARV ESTING TiN gS. 27% ing them when damp with the rain to the surface, spreading them in the sun and then carrying them back to the granaries. Some of the seeds sprout, nevertheless, either in the nests or on the kitchen middens. “As the ants often travel some distance from their nest in search of food, they may certainly be said to be, in a limited sense, agents in the Fic, 153. Nest of Messor pergandei in the Arizona desert, showing circle of chaff. (Original. ) dispersal of seeds, for they not unfrequently drop seeds by the way, which they fail to find again, and also among the refuse matter which forms the kitchen midden in front of their entrances, a few sound seeds are often present, and these in many instances grow up and form a little colony of strange plants. This presence of seedlings foreign to the wild grounds in which the nest is usually placed, is quite a fea- ture where there are old established colonies of Atta barbara, where young plants of fumitory, chickweed, cranesbill, drabis Thaleana, etc., may be seen on or near the rubbish heap. . . . One can imagine cases in which the ants during the lapse of long periods of time might pass the seeds of plants from colony to colony, until after a journey of many stages, the descendants of the ant-borne seedlings might find them to “I te ANTS. selves transported to places far removed from the original home of their immediate ancestors.” \loggridge also observed that not only Pheidole pallidula but also Ph. megacephala, an Old World ant which now over- runs the warm portions of both hemispheres, are harvesting ants. The more recent investigations of Forel (1894a), Ern. André (1881e), Emery (1899a), Lameere (1902), Escherich (1906), and others have confirmed Moggridge’s observations. Forel and Lameere have studied the habits of /. barbarus and arenarius in the deserts of North Africa. According to Forel, the latter species, which is the most powerful insect of that region, excavates enormous nests over an area 7-10 m. in diameter and to a depth of 2 m., with several openings, Fic. 154. Crater of Messor pergandei in the Arizona desert, showing ring of herbaceous plants that have sprung up from discarded seeds in the chaff circle. (See Figs. 152 and 153.) (Original.) each surmounted by a crescentic crater sometimes 50 cm. broad and made of coarse sand pellets. The granaries are flat chambers about 15 cm. in diameter and 1.5 cm. high, connected by galleries with one another and with the surface. Lameere believes that the area occupied by single colonies of this ant is even greater than that given by Forel. He also describes the harvesting habits of another Messor (M. caviceps) THE HARVESTING ANTS. 273 and of two species of Holcomyrmex (H. lameerei and chobauti) pecu- liar to the sandy and extremely barren portions of the desert. H. chobauti resembles M. caviceps in having a pronounced cavity on the under side of the head. Of the former species he says: ‘‘I saw the long files of workers carrying seeds of the ‘drin’ (Aristida pungens ) to their nests. The seed of this plant has the form of a slender spindle surmounted by a long, trifid and plumose spine. The ant rides this grain as a witch rides her broom; she carries it beneath her, hold- ing it firmly by the small end in her mandibles with the end of the grain fitting into the notch under her head. This interesting character, which this ant shares with J/. caviceps, may be regarded as an adapta- Fic. 155. Dealated female, male, and workers of Ischnomyrmex cockerelli, * 2. ; (Original. ) tion to the method of carrying the drin seed. It should be noted that I found MW. caviceps in a region of the Eolian desert where the drin is almost the only plant that can subsist. On the other hand there is no drin in the region of Hamada where I first. found H. lameerei, which has the under side of the head but little excavated.” Still another interesting ant of the North African desert has been recently discovered in Tunis by Santschi. This is a small black species, Oxyopomyrmex santschii. Its habits are described as follows by its discoverer in a letter published by Forel (1904a): The nests are “so characteristic that when one has once seen one of them. nothing 19 274 ANTS. easier than to find others. I am surprised to learn that they have not attracted the attention of other observers. Especially remarkable is the tiny crater, which has the form of a cone [Fig. 151] hardly more than 4-5 cm. in diameter and 2.5-3 cm. high. The circumference of its funnel-shaped top is 3-4 cm. across and its margin is always per- fectly circular and entire, except in nests in process of construction, Fig. 156. Crater of Ischnomyrmex cockerelli in Arizona desert, showing the large rough entrance. (Original.) when it is at first semilunar like the very small nests of Messor are- narius. At the bottom of the funnel the small entrance is found at a depth of 2-3 cm. It is horizontal, attaining a length of 5 cm.,a breadth of 1 cm. anda height of 5 cm. In this first chamber the pupz are kept for the purpose of enjoying the warmth, and here I have found a number of workers and winged females. Thence the gallery continues to descend to a depth of 15-20 cm. and finally opens into two or three chambers of the same dimensions as the first. These contain pupz and an ample provision of very small seeds. This ant is therefore granivorous. I surprised a few of the workers entering the nest with seeds in their mandibles, but they go out foraging singly and not in files like Messor and other genera. They are very slow in their move- THE HARVESTING ANTS. 275 ments and are very apt to stop motionless at the least alarm. Day or night one or two of the workers may be seen on the outer surface of the crater, scarcely moving unless molested, but when disturbed they hurriedly retreat into the nest to spread the alarm. Their habits are rather nocturnal. If a light is brought near the nest when a worker is on the point of leaving it with a grain of sand, she hurriedly backs into the entrance and there stops, closing it perfectly with her burden. If the observer remains very quiet, she eventually comes forth and deposits her load on the slope of the crater. There are scarcely more than thirty individuals in a nest. I have found this species only in a very circumscribed area, south of Kairouan, on compact, sandy soil in Fic. 157. Male, virgin female, and worker of the Texan harvester, Pogonomyrmex molefaciens, nearly twice natural size. (Original.) which the chambers are easily excavated.’ I quote this description at length and reproduce Santschi’s figure on account of the remarkable resemblance of the Oxyopomyrme.x nest to those of the fungus-growing Trachymyrme.x to be described in the next chapter. The genus O.ryo- pomyrme.x is represented by several species, some of which have been placed in a subgenus, Goniomma. One of these, G. hispanica of south- western Europe, is also a harvesting ant, according to Ern. André (1881e). To the old observations of Sykes and Jerdon on harvesting ants in India,’ Wroughton (1892) has added accounts of the habits of Hol- comyrmexr scabriceps (Fig. 150) and Pheidologeton ocellifer. Of the former he says: “ In a community of this genus there are workers of all sizes. Holcomyrmex is, as a rule, a most industrious harvester, and 276 ANTS. sets about her work in a most methodical way. The workers never forage individually for grain, but all take the same road and all return by the same road; the result being that every nest is the starting point of one, or often of several, well-beaten tracks, cleared of vegetation and obstacles, and extending sometimes 100 feet and more in length. How these tracks are engineered I have never discovered, but am pretty cer- tain that they are made gradually ; a commencement at hazard is made, and then, as the country immediately adjoining the road is exploited, the road itself is carried forward. Where one of these roads crosses a sheet of bare rock, it is there marked in white; I can only presume that this is the result of some chemical action, set up by the formic acid exuding from the ants; this acid, though too small in quantity in a single ant to cause any appreciable effect, might easily become sufficient when thousands of ants are continually passing, backwards and _ for- wards, all day long. Holcomyrmex brings home the grain unthreshed, and, in this form, it is taken into the nest, from whence the chaff is brought out and deposited around the entrance, or, where the force of a prevalent wind is felt, on a heap to leeward.” Wroughton does not believe that H. scabriceps, which Rothney regards as the harvester par excellence of India, compares with Pheidole as a harvester. The following note on Pheidologeton ocellifer, an ant with highly polymorphic workers, was communicated to Wroughton by Aitken: “The entrance (of the nest) which is strewn with chaff, is large, but the passage soon splits up, and I failed to follow it. I turned up a lot of pupz, however, close to the surface. The community is enormous and industrious, collecting large seeds of trees or plants, which it takes a dozen to carry; these are taken in and the husks are thrown out after- wards. If P. ocellifer meets a white ant or any other insect, she col- lects it in the same way. The smaller soldiers often laid a jaw to a burden, but the giants appear to do nothing.” Wroughton confirms this observation on the carnivorous tastes of Pheidologeton. He found also that the huge soldiers neither dig nor defend the nest and that they are less pugnacious than the smaller workers. It is probable that they function as seed crushers like the soldiers of the allied genus Pheidole. Armit (1878), Roth (1885) and Tryon (1900) have published a few observations on harvesting ants in another arid or semiarid region, Australia. These are Pheidole longiceps, Meranoplus dimidiatus and M. diversus. Tryon calls attention to the seed-distributing habits of the Pheidole in the following passages: “‘ That this Brisbane harvesting ant, also, is an important agent in the local dispersion of plants—espe- cially weeds—and is connected with their sudden appearance on heaps of soil excavated from a depth, is sufficiently demonstrated in the fol- THE HARVESTING ANTS. 277 lowing observations: The ants of one nest were noticed to be harvesting the seeds of Portulacca oleracea Linn. and of Amaranthus viridis Linn.—both common weeds—and growing at a comparative distance from the nest. These seeds had remained stored up in their nest for some time, when rain suddenly came on, and under its influence the seeds—especially those of the latter plant—commenced to germinate. Of those which had already thrown out a radical, this was bitten off and brought to the surface; some of these seeds were also gnawn into, and the ruptured black perisperm—containing more or less food sub- stance—in like manner rejected. Other seeds, which had swollen in response to moisture, were carried up for the purpose of being dried and re-stored. In the midst of these operations, however, rain came on again, and the ants retired, leaving seeds on the surface. These immediately germinated, and a small patch of Amaranthus grew up, making the site of what was before a nest of harvesting ants, quite isolated among plants of different character. On a second occasion Fic. 158. Large mound nest (modified crater) of Pogonomyrmex molefaciens with entrance in depression at summit. (Original.) a nest, in which much seed of Eleusine indica was known to have been harvested some months since, was dug up. Some of the grass seed selected from the nest was afterwards sown; also some of the earth from the nest which was known to contain both seeds of this plant and of another species of Amaranthus. In both cases the sowings were made in situations remote from such places in which any of these plants were already growing, and, as a result, in the course of time, numerous 278 ANTS. plants of both Eleusine indica and this second Amaranthus sprang up in these new localities, where they continued to flourish.” The genus Meranoplus, to which some of the observations of the Australian naturalists mentioned above refer, is related to Tetra- morium, the type of which is the pavement ant, 7. cespitum, of Europe and of our Atlantic States. It is, therefore, interesting to note that this ant occasionally stores seeds in the chambers of its nests. This has been observed by Janet in Europe, and I have also seen the cham- bers of a colony of this ant near Mamaroneck, N. Y., filled with grass seeds. In this case we have apparently either an evanescent or an incipient habit. Turning to America we find a goodly array of harvesting ants, nearly all members of genera we have already considered and nearly all inhabitants, like the Old World harvesters, of warm and exception- ally arid regions. Our species are the following: 1. Solenopsidii: Solenopsis geminata, represented by the typical form of the species and several varieties; and probably no less than twenty species of Pheidole. 2. Myrmicii: Five species of Messor, two of Ischomyrmex and some thirty species of Pogonomyrmex, which are about equally divided between North and South America. This last genus may be regarded, perhaps, as the New World representative of the African Ocymyrme.v. Solenopsis geminata, the “ fire-ant,” is armed, as its popular name indicates, with a formidable sting which it uses on the slightest provo- cation. Its colonies are populous and so numerous that it may be said to be in possession of a large portion of the soil of the American tropics. The nests are made under stones or consist of numerous untidy craters, fused and scattered about irregularly. It is difficult to say whether this ant is more granivorous than entomophagous, for it attacks and eats almost everything that comes in its way. It will even attend coccids on the roots of grasses and occasionally do some damage to soft fruits, like strawberries or germinating garden seeds. During the summer and autumn months its shallow nest-chambers contain quantities of carefully husked seeds, which usually belong to species of Euphorbia, Croton, Plantago and other herbaceous plants. It seems to be less fond of grass seeds. I have already called attention to the preference of this ant for nesting in loamy soil along streams and to its remarkable habit of floating about in balls when its nests are inundated (p. 146). Of the numerous harvesting species of Pheidole, only one, Ph. pili- fera, is common in the Northern States. It has been studied by Morris, McCook and Mrs. Treat. Ph. vinelandica and tysom, which range as THE HARVESTING ANTS. 279 far north as New Jersey and New York, have similar habits. I have found a considerable number of harvesters among the species of the dry deserts of Colorado, Texas, New Mexico, Arizona and Mexico (Ph. coloradensis, instabilis, ceres, sitarches, soritis, vaslitti, carbonaria, ete.). Though far more peaceable, these ants often resemble S. gemui- nata in their nesting habits. Some of them at least (Ph. instabilis, sitarches) are certainly unable to prevent the germination of seeds in their granaries during the wet weather. I infer, therefore, that they do not bite off the radicle as has been claimed for the European Messor and the Australian Pheidole. The large-headed soldiers of the numer- Fic. 159. Disk of Pogonomyrmex rugosus in the Arizona desert. (Original.) ous carnivorous species of Pheidole function as trenchers and carve the tough insects brought into the nest by the small, feeble workers, and thus make the soft tissues accessible to the community. Among the seed-storing species, however, the soldiers have become the official nut- crackers of the colony. I have seen the workers of some of the species (instabilis and sitarches) feeding the larve directly with pieces of crushed seeds. More striking are the habits of our largest harvesters belonging to the genera Messor, Ischnomyrmex and Pogonomyrmex. With the 280 w ANTS. y = , single exception of the [lorida harvester (P. badius), all of these _ ants are confined to the dry plains and ‘ec ail of the Western and Southwestern States, where, just as in the deserts of the Old World, insect food is scarce, at least during many months of the year. | Of the five species of Messor, M. pergandei, carbonarius, andrei, julianus and stoddardi, which are confined to the extreme southwéstern portion of the United States and northwestern Mexico, I have been able to study only the first in a living condition. It is a shining, jet- black ant of moderate size, very common in the deserts of southern Arizona and the Mojave Desert of California. The workers, which form populous colonies, vary much in the size of the body and the head, like the Mediterranean M. barbarus. The nests (Figs. 152-154) are single or more rarely multiple craters, much flattened, with rounded slopes, 50 cm. or more in diameter, and with one to three large and very irregular central openings. Sometimes these are slit-shaped and as much as 5 or 6 cm. long. The rough galleries and granaries are ex- cavated to a depth of at least 60 cm. in the hardest and most sunbaked portions of the desert soil. Late in the afternoon long files of workers may be seen in the full activity of harvesting. Sometimes these files may be followed for a distance of 20 or 30 m. from the nest before the ants disperse among the scant vegetation in search of seeds. They seem to have no preferences, but eagerly seize all the mature seeds they find and carry them to the nest, where they carefully remove the husks and store the edible kernels in the granaries. The chaff and seed-pods are then™ carried out and dumped on the kitchen midden which forms a crescen- tric or circular zone at the periphery of the crater. Sound seeds are often thrown out with the chaff and eventually germinate, so that old nests are often marked by a circlet of growing plants, just as Moggridge has described for the European species. There can be little doubt that the other North American species of Messor have very similar habits. A number of alcoholic specimens of one of these, 1/7. andrei, sent me by Professor H. Heath from California, still bear grass-seeds in their clenched mandibles. One of our two species of [schnomyrme.x, I. cockerelli (Fig. 155) is widely distributed over the deserts of western Texas, southern New Mexico and Arizona and northern Mexico from an altitude of 2,500 feet in the northern portion of its range (at Monahans, Texas) to 7,000 feet on the Mexican plateau. The other species, /. albisetosus, seems. to be a rarer ant of more circumscribed distribution. At Fort Davis, Texas, both species were found nesting side by side, so that I was able to compare their habits. /. cockerelli is a large, very slender, long-legged ant of a deep cherry-red color, with jet black gaster adorned with a 2 a HARI "ESTING ANTS. ; 281 ot . At its base. It stalks about very slowly and is quite, : ut i astead endeavors to defend itself with the ‘milk-_ white, fainiiamedorod ‘secretion of its anal glands. Though the colo- nies are rather populous, the workers forage singly. They carry one _ another like the species of Leptothorax, the deported ant being held by the mandibles while ‘curling her body up over the head of her carrier. Then nests (Fig. 156) are so large and made of such rough materials that one can hardly believe that they can be the work of such frail insects. pret 4 Be A © — Fic. 160. Disk of Pogonomyrmex rugosus, showing one of the paths extending off towards the upper right-hand corner of the figure. A partial ring of chaff and rejected seeds is seen to the left of the entrance. (Original.) They are huge craters from 60 cm. to 2 m. in diameter and from .20-.50 em. in height, built of coarse desert soil intermingled with large pebbles sometimes 2cm. in diameter. The center of the crater is funnel-shaped. with 2 great entrance of irregular outline frequently as much as 5-8 cm. across. The galleries and chambers are proportionally large and excavated in such hard soil and to such a depth that I have never been able to explore them satisfactorily. Although these nests bear a cer- tain resemblance, on a large scale, to those of Messor pergandei, they seem even more like the work of some desert rodent or reptile. /. albisetosus is a smaller and more opaque species, covered with abun- dant, very coarse, white, hairs. Its nests resemble those of cockerelli. 282 ANTS. but are usually smaller and more often situated under large stones. Both species are omnivorous, with an evident preference for fruits and seeds. At Monahans, | found the craters of cockerelli covered with the disjointed pods of the mesquite (Prosopis juliflora) which had been carried into the nest, deprived of the sweet pulp enclosing the hard seeds and then rejected. On the kitchen middens I also recog- nized the legs and elytra of three species of Eleodes and of several other beetles. At Fort Davis, the workers of albisetosus were seen carrying in the dried seeds of umbelliferous plants, grasses and cotton- wood (Populus fremonti), and occasionally stopping to collect pieces of insects (shards of Podophylla and Coccinella) and bits of cow-dung, or even bird-droppings. None of these substances, however, is stored in the nests, but merely carried in and then rejected. These ants are not, therefore, highly developed harvesters like those of the allied sub- genus Messor, but resemble more closely the northern species of A phe- nogaster. In Connecticut I have often seen A. picea collecting and temporarily storing in its nests small flowers, green seeds or the pulp- covered akenes of raspberries, and Emery long ago made a similar observation on an Italian variety of A. testaceopilosa. Of this ant he says: “It is not predaceous but collects soft vegetable substances, such as petals of flowers and green seeds, which it carries into the nest and then rejects, after having extracted from them any utilizable sub- stances,’ and he adds in a foot-note: “ In a courtyard of the University of Palermo I saw this ant daily collecting the petals of roses that were somewhat dried but still of the natural tint, and later rejecting them, soiled and crumpled, and of a yellow color, as if they had been tritu- rated. The typical A. testaceopilosa, which I have observed in Sar- dinia, has intermediate habits and lives partly on prey, partly on vegetable substances.” During the summer of 1907 I was able to confirm Emery’s observations on several colonies of A. testaceopilosa in the Alameda at Gibraltar. These observations are of considerable interest in connection with the habits of the fungus-growing ants to be considered in the next chapter. The most characteristic American harvesters are the large or medium-sized, black or red ants of the genus Pogonomyrme.x, which is closely related to Wyrmica of the temperate and boreal portions of the Northern hemisphere. In most of the species of Pogonomyrmex the head of the workers and females bears on its under side a conspicuous beard of long, curved hairs (ammochete), a character to which the generic name (‘bearded ant”) refers and one which occurs also in many species of Messor, in Holcomyrmex and in other desert ants (see p. 16). The genus ranges from British America to Patagonia, THE HARVESTING ANES: 283 but the species are almost exclusively confined to the dry moun- tainous deserts and plains, where some of them ascend to an altitude of 5,000-8,000 feet. Most of them are aggregated in two groups, one of which inhabits Argentina and Chile; the other the South- western States and northern Mexico, and few are known to occur in the long intermediate region. The subgenus Ephebomyrme., which comprises small, beardless species, with coarse, reticulate sculp- ture is represented by a single form (£. schmitti) in Hayti, another (E. negelii) in Brazil, and a few in Mexico, Texas and Arizona (E. wnberbiculus, pima and townsendi). Another subgenus, Janetia, is represented by a single species (J. mayri) in Colombia. Only one of the species of Pogonomyrmex s. str., the Florida harvester (P. badius), is known to occur east of the Mississippi River. According to Forel (1901m), P. occidentalis has been taken in Hawaii. Little is known of the habits of the South American Pogonomyrme.x. Berg (1890) has published a few notes on P. cunicularis and five other species occurring in Argentina, Chile and Uruguay, but no mention is made of their harvesting habits. Their nests seem to be insignificant, with the exception of those of cunicularts, which are described as surmounted Fic. 161. Incipient nest of Po- by craters 50 cm. in diameter erected gonomyrmex molefaciens, a small pile ens =p : ; of pebbles hiding the nest entrance; in sandy soil. Janetia, according to natural size. (Original.) Forel, does not harvest seeds, but this statement is open to doubt. All of the North American Pogonomyrmex (including those of the subgenus Ephebomyrmex) are unquestionably harvesting ants, although none of them disdains insect food whenever it can be procured. They all excavate their nests in soil fully exposed to the rays of the sun and are able to endure prolonged droughts. According to my observations our species may be divided into four groups, as follows: 1. P. subdentatus, apache, sancti-hyacinthi and desertorum, and Ephebomyrmex imberbiculus, townsendi and pima. These are small species confined to the deserts of Texas, New Mexico, Arizona, Cali- fornia and northern Mexico. Their colonies are always insignificant and widely scattered, comprising only a few dozen individuals. The nests are small, obscure craters, 10-20 cm. in diameter and a few centi- meters high. The workers make no attempt to cut down the surround- ing vegetation, which often grows on the crater immediately around the entrance. 284 ANTS. 2. P. californicus, comanche and badius. Larger than the preced- ing and living in colonies of one to a few hundred individuals. They nest exclusively or by preference in sand, and construct flat, single or multiple craters from 30-60 cm. in diameter and 3-5 cm. high with rounded slopes and oblique, central entrances. The workers make no attempt to clear away the vegetation around the nest. 3. P. barbatus and its numerous subspecies and varieties: mole- faciens, rugosus, fuscatus, marfensis, nigrescens, etc. This is the largest and most powerful of our species, the celebrated “ Texan har- vester ” or “agricultural ant.” It forms extensive colonies of several hundred individuals and shows great variability in the construction of its nests. In their simplest form, e. g., in rugosus, these present a bare, circular disk, or area I-2 m. in diameter, produced by cutting down and removing all the vegetation around the central opening (Figs. 159 and 160). In other cases, e. g., in molefaciens, the opening is at the sum- mit of a conical crater of pebbles, partly or wholly covering the disk and sometimes as much as 50 cm. high (Fig. 158). This crater, as well as the underlying soil, to a considerable depth (5 m. according to one account!) is perforated with flat chambers connected by galleries. 4. P. occidentalis, which, like barbatus, forms large colonies and clears away the vegetation from great circular areas, which vary from 2-5 m. in diameter. In the center of the area it always con- structs an elegant gravel cone (modified crater) 60 cm. to I m. in diameter and 20-30 cm. high, with an oblique, excentric opening near the base and nearly always on the eastern or southern slope. The cone and underlying soil, sometimes to a depth of 3 m., are riddled with flat chambers, which, as in barbatus, are denser and more numer- ous in the cone and more scattered and connected by longer galleries in the soil (Fig. 164). Some years ago I published a few observations on E. imberbiculus and P. subdentatus (1902b). These and the other species of the first of the above groups, like all ants that form small colonies, are very timid and inoffensive. Workers of imberbiculus kept in an artificial nest were seen to feed their larvae on pieces of house-flies and crushed seeds. Of the species of the second group, only one, the Florida harvester (P. badius) has come under the observation of previous authors. Mrs. Mary Treat (1878) studied this ant in Florida, and McCook (1879¢ ) made a few observations on workers kept in confinement. It harvests the seeds of many plants (Euphorbia, Croton, Aristida, etc.), and stores them in the flat granaries of its nests. It not only collects seeds that | THE HARVESTING ANTS. 285 have fallen to the ground but plucks them directly from the plants, husks them and deposits the chaff on the kitchen middens at the periphery of its low, rounded craters. My own observations, made in the sandy grounds about Jacksonville, Florida, confirm those of Mrs. Treat, who failed to find any tendency on the part of this ant to cut down the vegetation or to clear areas around its nests. P. badius differs from all the other known species of the genus in having highly polymorphic workers. The huge-headed soldiers are not abundant in the colonies and seem to be no more aggressive or pugnacious than the intermediate and small workers. P. comanche, which is common in the sandy post-oak woods about Austin and Milano, Texas, and in the Fic. 162. Incipient crater of Pogonomyrmex rugosus in patch of Astragalus which the ants are beginning to cut down and clear away. 3 natural size. (Original. ) alluvial bottoms of the Colorado River in the same region, and P. cali- fornicus, which is abundant in sandy portions of the deserts of Texas, New Mexico, Arizona and California, have very similar habits. The latter is represented by several local varieties and subspecies. Both species carefully close their nest entrances at night. The incipient nests are crescentic or semilunar with the very oblique entrance o: 2586 ANTS. one side, but as the crater grows, it becomes circular and eventually surrounds the entrance. The marriage flight of californicus and its method of establishing colonies are described in a former chapter (p. 189 et seq.). P. molefaciens (Fig. 157), the common Texan variety of the Mexi- can barbatus, was first studied by Buckley (1861, 1866, 1867) and Lincecum (1862, 1866, 1874) and later by McCook (1879c) and myself (1902). The papers of Buckley and Lincecum contain some of the earliest modern observations on harvesting ants. P. molefaciens ranges from the seashore at Galveston and Corpus Christi to an alti- tude of 5,000 ft. in western Texas and over 8,000 ft. in Mexico, where it often inhabits the same stations as the typical barbatus. The latter is readily distinguished by its black head and thorax and red gaster, whereas molefaciens is ferruginous red throughout. The Texan harvester has attracted no little attention on account of Lincecum’s statement that it actually sows the seeds of the “ ant-rice”’ (Aristida stricta and oligantha) around the periphery of its disks or mounds, and cultivates the crop in addition to harvesting and storing it in its granaries. This notion, which even the Texan schoolboy has come to regard as a joke, has been widely cited, largely because Darwin stood sponsor for its publication in the Journal of the Linnean Society. McCook, after spending a few weeks in Texas observing P. molefactens and recording his observations in a book of 310 pages (1879c); failed to obtain any evidence either for or against the Lincecum myth. He merely succeeded in extending its vogue by admitting its plausibility. Four years of nearly continuous observations of molefaciens and its nests enable me to suggest the probable source of Lincecum’s miscon- ception. If the nests of this ant can be studied during the cool winter months—and this is the only time to study them leisurely, as the cold subdues the fiery stings of their inhabitants—the seeds, which the ants have garnered in many of their chambers will often be found to have sprouted. Sometimes, in fact, the chambers, are literally stuffed with dense wads of seedling grasses and other plants. On sunny days the ants may often be seen removing these seeds when they have sprouted too far to be fit for food and carrying them to the refuse heap, which is always at the periphery of the crater or cleared earthen disk. Here the seeds, thus rejected as inedible, often take root and in the spring form an arc or a complete circle of growing plants around the nest. Since the Pogonomyrme.x feeds largely, though by no means exclu- sively, on grass seeds, and since, moreover, the seeds of Aristida are a very common and favorite article of food, it is easy to see why this grass should predominate in the circle. In reality, however, only a THE HARRY ESTING ANS. 287 small percentage of the nests, and only those situated in grassy locali- ties, present such circles. Now to state that the molefaciens, like a provident farmer, sows this cereal and guards and weeds it for the sake of garnering its grain, is as absurd as to say that the family cook is planting and maintaining an orchard when some of the peach stones, which she has carelessly thrown into the backyard with the other kitchen refuse, chance to grow into peach trees. There are several other facts that go to show that the circle of grass about the molefaciens nests is an unintentional and inconstant by-product of the activities of the ant-colony. First, the Aristida often grows in flourishing patches far from the nests of molefaciens. Second, Fic. 163. Mound of Pogonomyrmex occidentalis at Las Vegas, New Mexico, show- ing large cleared area around cone. (Original.) one often finds very flourishing ant colonies that have existed for years in the midst of much travelled roads or in stone side-walks thirty meters or more from any vegetation whatsoever. In these cases the ants simply resort for their supply of seeds to the nearest field or lawn, or pilfer the oat-bin of the nearest stable. Third, it is evident that even a complete circle of grass like that described by Lincecum and McCook would be entirely inadequate to supply more than a very small fraction of the grain necessary for the support of a flourishing colony of these ants. Hence they are always obliged to make long trips into the surrounding vegetation, and thereby wear out regular 285 AN Tae paths which radiate from the cleared disk in different directions, often to a distance of 10-20 m. from the nest. These paths, in the case of the typical Mexican barbatus, remind one of human footpaths, as they may be as much as 10-15 cm. wide. The existence of these well- beaten paths, which are often found in connection with grass-encircled nests, is alone sufficient to disprove Lincecum’s statements. The reader may be referred to McCook’s work (1879c) for an account of many interesting details in the habits of molefaciens. 1 shall stop to record only a few observations on the marriage flight, the method of establishing formicaries, the development of the nests, etc., matters which have been either overlooked or inadequately described by previous authors. During three successive years (1901-1903) at Austin, Texas, the nuptial flight of molefaciens took place on one of the last days of June (28 and 29) or the first in July. On one of these occasions (July 4, 1903) the flight was of exceptional magnitude and beauty. A few days previous the country had been deluged with heavy rains, but Independence Day was clear and sunny, the mesquite trees were in full bloom and the air resounded with the hum of insects. For several days. I had seen a few males and winged females stealthily creep out of the nest entrances as if for an airing, but hurry back at the slightest alarm. From 1.30 to 3 o’clock, however, on the after- noon of July 4, all the numerous colonies which I could visit during a long walk through the fields and woods west of the town, gave forth their males and females as if by a common impulse. The number issuing from a single large nest was often sufficient to have filled a half liter measure. Soon every mound and disk was covered with the bright red females and darker males, intermingled with workers, many of whom kept on bringing seeds and dead insects into the nest as unconcernedly as if nothing unusual were happening. The males and females, quivering with excitement, mounted the stones or pebbles of the nest or hurriedly climbed onto the surrounding leaves and grass and rocked to and fro in the breeze. Then, raising themselves on their feet and spreading their opalescent wings, they mounted obliquely one by one into the air. I could follow them only for a distance of 10 or 20 m. when their rapidly diminishing bodies melted away against the brilliant, cloudless sky. Many pairs, hesitating to take flight, chased one another about on the surface of the nest. The amorous males seized many of the females before they could leave the ground. Lizards crept forth in great numbers and gulped down quantities of the fat females, while others were borne off into the air by large robber flies (Asilide). By a little after three o’clock the males and females had left the nest and only the workers were seen pursuing the quiet THE HARVESTING ANTS. 289 routine business of bringing in seeds. Later in the afternoon innum- erable fertilized and dealated females which had descended from their flight, were running hither and thither over the ground in search of suitable places in which to establish their formicaries. At nightfall a terrific shower, amounting almost to a cloud-burst, descended on the country. When I arose the following morning the weather was clear Fic. 164. Section of nest of Pogonomyrmex occidentalis, showing arrange- ment of chambers and of some of the connecting galleries. (Photograph by G. A. Dean.) again, but I was unable to find a single female on the rain-scoured soil. One and all had been swept into the streams that were booming through ‘the gullies and cafions on their way to the Colorado River. At 12 M. I saw about the entrance of a nest a few males and virgin females and on digging into it detected several others. An examination of 20 290 ANTS. other colonies, which had celebrated their nuptial flight the day before, revealed the same conditions. It is certain, therefore, that the molefaciens colonies do not throw off all their males and females during the nuptial flight, and are thus able to avoid a com- plete destruction of the annual sexual generation. This conclusion is also borne out by the observations of Mr. W. H. Long, Miss A. Rucker and Miss M. Holliday, who witnessed several minor nuptial flights during the latter part of the summer (August 6-10). I have also seen mature males and winged females in the nests in March and April, so that there are probably small flights also during the spring months. But unlike many other ants, molefaciens does not dealate and permanently detain in the nest a number of females in addition to the mother-queen that originally established the formicary. At any rate, I have never been able to find more than one dealated queen in a colony, which, therefore, occupies only a single nest. This 1s also true of the other species of Pogonomyrmex that have come under my observation. The formicaries of molefaciens are founded in the same manner as those of P. californicus described in a former chapter. As Lincecum was the first to observe, the recently fertilized female digs down into the soil to a depth of about 15 cm., closes the opening after her and gradually brings to maturity a brood of about a dozen very small and timid workers. During the following spring the workers open the nest to the surface, but are always careful to keep the entrance hidden under a few sticks or pebbles, which have the appearance, as Lincecum says, of having been drifted together by the wind (Fig. 161). It is not till the second year, when a number of large workers have been pro- duced, that the ants begin to cut down the vegetation around the nest entrance, now left fully exposed, and to establish their circular disk, which is continually enlarged as the number of workers increases. On the deserts east of Alberquerque, New Mexico, I saw a number of incipient colonies. of P. rugosus in the act of cutting down young Astragalus plants and clearing disks about 30 cm. in diameter (Fig. 162). The further development of the nest differs with the character of the soil. Where this is an even adobe or sandy loam, no crater is constructed, but the disk is merely enlarged. In localities where there are many pebbles scattered over the soil, these are assiduously collected and built into a crater (Fig. 158). The cleared disk is obviously an adaptation for securing the maximum amount of dryness for the granaries in the soil, and although seeds are often stored in the crater chambers, the latter seem to be of even greater utility in incubating the brood. The larve, as in E. imberbiculus, are fed with pieces of THE HARVESTING ANTS. 291 crushed or broken seeds. In my artificial nests these pieces were coated with saliva by the workers before being administered to the brood, a precaution which may insure the conversion of the starch into sugar and facilitate its assimilation by the larve. The occident harvester (P. occidentalis) which ranges over the Great Plains from Montzna to northern Texas, New Mexico and Ari- zona, rarely descending below 5,000 feet and thriving best at an altitude “of 6,000 to 8,000 feet, has been studied by Leidy (1877) and McCook (1882) and more recently by Headlee and Dean (1908) and myself. Fic. 165. Diagrams of three stages in the development of the modified masonry dome of Pogonomyrmex occidentalis. (Original.) A, Small mound of earth thrown up by queen when starting her formicary; x, entrance, 2, first chamber; A’, same nest in section; B, crater nest (second year) formed by incipient colony; B’ section of same; C, mound, or dome of adult colony; C’ section of same showing galleries and chambers. It is a smaller ant than P. barbatus and much more precise and uniform in its nesting habits. Its constructions are, in fact, the most elegant and extensive of any of the known species of the genus. As in the case of barbatus, the edge of the carefully cleared disk on which the fine gravel cone rests is sometimes surrounded by a circle of grass or other plants which grow from the refuse heap (Fig. 163). P. occi- dentalis is not in the habit of foraging in files, so that no paths radiate from the cleared disk. This absence of paths is attributed by McCook to the sparse and tufted character of the vegetation of the Great Plains, which makes beaten roads unnecessary. During July, 1903, I witnessed the nuptial flight of this insect near 292 ANTS. Colorado Springs. It took place on a clear afternoon and resembled in nearly all respects the nuptial flight of molefaciens described above. During the summer months of 1906 I saw dealated females founding their colonies in the rocky plains about Buena Vista, Colorado. The female enters the soil obliquely, throwing the earth backward with her legs or carrying it out with her mandibles till it accumulates in the form of a small fan-shaped mound as in molefaciens and californicus. 1 have inferred the manner of growth of the crater from examination of many nests of different sizes and ages, and represent the process in the accompanying diagram (Fig. 165). A and A’ show in surface view and section respectively the nest as dug by the dealated queen, + being the opening and z the cell in which she brings up her first brood of small workers after closing the entrance. The moundlet of excavated earth is soon disintegrated by the wind or rain. When, during the following spring, the young brood break out to the. surface, they construct a crater like B and B’. This corresponds to the permanent nests of such forms as P. comanche, californicus and badius. Gradually, however, the wall of the crater back of the slanting entrance is built up more rapidly than the wall in front, till a cone is produced with the opening near the base on one side (C and C’), and as it grows the chambers are extended up into it from the underlying soil. This is the adult form of the nest and is not represented in the sand-inhabiting species men- tioned above. P. molefaciens also presents a stage like B and B’, but the opening is perpendicular and the crater rim grows uniformly around its whole periphery and often to a much greater height. B and B’ may also be taken to represent on a large scale the permanent nest-form of the small species of the genus, P. desertorum, Ephebomyrmex imber- biculus, ete. A good account of the distribution and nesting habits of P. occi- dentalis in the higher, western portion of Kansas has been published by Headlee and Dean. These authors give measurements of the nests and interesting figures of their architecture. One of these figures is here reproduced with Mr. Dean’s permission (Fig. 164). In conclusion, attention may be called to the stinging habits of Pogonomyrmex. In this respect the smaller and more timid species are no more formidable than other Myrmicine ants of the same size dwelling in small colonies. But this is not the case with P. occidentalis, P. barbatus and the allied varieties and subspecies. The sting of these ants is remarkably severe, and the fiery, numbing pain which it pro- duces may last for hours. On several occasions when my hands and legs had been stung by several of these insects while I was excavating their nests, | grew faint and almost unable to stand. The pain appears THE HARVESTING ANTS: 8) to extend along the limbs for some distance and to settle in the lym- phatics of the groin and axille. If it be true, as has been reported, that the ancient Mexicans tortured or even killed their enemies by binding them to ant-nests, P. barbatus was certainly the species em- ployed in this atrocious practice. It is commonly supposed that the poison responsible for the pain inflicted by these and other ants is formic acid, but chemical analysis of P. molefaciens by Melander and Brues (1906) failed to reveal any traces of this substance. Hence the poison of this insect must be some unknown substance, possibly a nucleoalbumin. This confirms the opinion of other authors, who, like Furth (1903), deny that the general physiological effects of the sting, even in the European ants, are due to formic acid. CHAPTER: XVII. THE RELATIONS OF ANTS TO VASCULAR PLANTS: “Plantas itaque norunt formice.”’—Michael Gehlerus, 1610. “Die Ergriindung der interessanten Gemeinschaft zwischen Pflanzen und Ameisen wurde bisher als ein rein botanisches Problem aufgefasst. Aber gerade hierin liegt—wenn mir ein Urteil in dieser Frage zugestanden werden sollte— die Ursache der geringen Erfolge, um nicht zu sagen der Misserfolge. Man war stets allzusehr geneigt, die Anpassungsfahigkeit der Pflanzen an plotzlich ein- tretende, sie beruhrende Verhaltnisse, als erheblich hinzustellen, umgekehrt aber glaubte man diejenige von lebenden Wesen mit so achtungsgebietender Begabung, wie solche den Ameisen eigen ist, wbergehen zu mussen; der Instinkt dieser findigen Tiere tauschte eben tber den nur héchst schwerfallig arbeitenden An- passungsmechanismus der Pflanze hinweg.” — Rettig, “Ameisenpflanzen und Pflanzenameisen,” 1904. The hypothesis of intimate mutualistic relations between ants and the higher plants is one of those fascinating constructions in which certain gifted and imaginative botanists have rivalled the inventors of the mimicry hypothesis in the zoological field. Both of these construc- tions have been treated as facts of the utmost value in supporting a still more general hypothesis—that of natural selection, and both, after having been carried to extremes by their respective adherents, are now facing the reaction that is overtaking Neodarwinism. Authors like Fritz Muller, Schimper, Huth, Delpino, Beccari and Heim have mar- shalled a formidable array of observations in favor of the view that many plants develop elaborate structures to be used as lodgings by certain pugnacious ants or even furnish these insects with exquisite food substances, and in return for these services are protected by their tenants from the leaf-cutting ants or from other leaf-destroying ani- mals. These observations are now being subjected to critical revision by authors like Rettig and H. von Ihering, whose attitude towards the whole subject is avowedly skeptical and reactionary. It behooves us therefore to examine both sides of the argument and, if possible, to adopt a position which will favor and not forestall further investigations. We may divide our subject into two parts and consider, first, the plant adaptations that are said to indicate symbiosis, and second, the ants that are associated with plants. The supposed adaptations may be considered under two heads: the dwelling places and the food ‘provided for the ants. The former consist either of preformed cavities or of structures from which the pith or loose tissue can be easily removed 294 RELATIONS OF ANTS TO VASCULAR PLANTS. 29 eat and thus converted into habitable tenements. In both cases the cavity is entered through a small orifice which either preexists or is made by the ants. This orifice then constitutes the nest opening, or entrance. These simple requirements are fulfilled by a great many plant structures which therefore make admirable domiciles for small ants that live per- manently in small colonies or for incipient colonies of larger ants that later form populous communities. The rigid vegetable tissues are an excellent protection against enemies, and the cavities are moist, dark and free from moulds, so that they make perfect nurseries for the larve and pup. Cavities of this description are especially utilized by ants in the tropics, probably because there these insects are more abundant and the struggle for existence is keener. The following paragraphs will show how numerous and variable are the plant organs that may be tenanted by ants: 1. Cavities in Stems.—Almost any hollow or pithy stem, with resistant walls sufficiently thin to be pierced by ants, may be entered and occupied by these insects. Some plants, how- ever, are especially well-suited to these purposes, for example, those of the Old World genera Randia, Myristica, Cleroden- dron, Kibara and Bambusa, with preformed cavities, and Endospermum and Juglans with pithy stems; among the New World genera: Cecropia, Triplaris, Tachigalea, Hum- boldtia, Tachia, Ficus, Cordia, Duroia, Coussapoa, Ptero- cladon, Pterocarpon, Bom- bax, Cladium, etc., with Fic. 166. Stems of ‘ myrmecophilous ” Z on plants. (Escherich, after Schimper.) 4, preformed cavities, and Coc- Ficus inequalis; B, Triplaris americanus ; . . C, same, older stem; D, Humboldtia coloba uvifer 2AM ees age Ue ifera, Sap LES laurifolia; x, entrance to cavity of stem. Schwartzia, Platymyschium and Sambucus with pithy stems. The entrances to the cavities are actually foreshadowed as pits in the internodes in Cecropia and Clerodendron. 2. Tubers, Bulbs, Pseudobulbs, Rootstocks, etc.—Many examples could be cited under this head. The most celebrated are the Malayan Rubiaceous epiphytes of the genera Myrmecodia and Hydnophytuin, 246 ANTS. which have large pseudobulbs full of preformed cavities, nearly always tenanted by ants. Certain ferns of the genus Lecanopteris from the same region, and certain orchids of the genera Grammatophyllum and PLANTS OF BOLIVIA COLKECTEO BY 8. §. WILLIAMS, 1201-1902 ae ) ae, { oblar~r'’ Dr we fone) Fic. 167. The “ Palo Santo” (Triplaris boliviana) in fruit, from a specimen in the herbarium of the New York Botanical Garden. (Original.) Schomburgckia are also cited as providing accommodations for ants in their pseudobulbs. 3. Ascidiz or Burse of Leaves and Petioles.—The straight or con- voluted leaf-petioles of certain pitcher plants (Nepenthes bicalcarata) RELATIONS OF ANTS TO VASGUEAR PLANTS. 297 are often hollowed out and inhabited by ants (Heim), and the curious ascidia of Dischidia rafflesiana are similarly utilized. In North America various species of ants inhabit the old, dry pitchers of Sarracenia. In Fic. 168 Stem and leaf of Endospermum formicarum, the former inhabited by colonies of Camponotus quadriceps. (Dahl.) Two nest openings are seen in upper part of stem. Where the petiole joins the leaf there are two nectaries. South America several genera of plants (Tococa, Majeta, Microphys- cla, Calophyscia, Myrmedone, Hirtella) have bladder-like dilatations of 295 ANTS. the petiole or base of the leaf which are regularly inhabited by colonies of small ants. 4. Spaces Between or Under Leaves.—In four species of East Indian palms belonging to the genus Korthalsia the spiny ochrea, or leaf-sheath, is enlarged and boat-shaped and applied to the stem in such a way as to enclose a cavity, which, according to Heim, is often ten- anted by ants. Many plants with equitant or clasping leaves furnish similar lodgings (Calamus amplectens, the banana, etc.). In tropical America certain epiphytic Tillandsias are very generally inhabited by ants, as I have repeatedly observed in Mexico, Florida and the West Indies. Sometimes a single bud-like Tillandsia will contain colonies of three or four species in the spaces between its overlapping leaves. 5. Thorns.— Several species of Acacia, both in Africa (A. fistulosa) and tropical America (4. spa- dicigera, spherocephala, hinds), bear pairs of thorns which are enor- mously enlarged or inflated and filled with loose tissue. The ants gnaw round holes near the pointed tips of the thorns, remove the tissue and take possession of them as nests. 6. Seed-pods.— Dried Fic. 169. Rootstock of fern (Lecanopteris carnosa) inhabited by ants, from Central Luzon. From a specimen in the New York Botanical seed-pods of plants, after Garden. (Original.) the seeds have escaped or decayed, are sometimes converted into ant lodgings. Professor C. H. Kigenmann sent me from Cuba several colonies of Camponotus inequalis which he found nesting in the pods of a leguminous vine. 7. Galls.—These may also be cited in this connection, though they have been considered in a previous chapter (p. 208). A survey of these various cases shows very clearly that ants may take possession of any vegetable cavity which suits their convenience, and that in the great majority of cases at least, the plants show no adaptations to the insects. But the plants are not limited to this letting of apartments rent-free ; they are said to offer the more alluring induce- ment of a free supply of food, both solid and liquid. 1. Floral Nectaries—Like other Hymenoptera and insects in gen- eral, ants are fond of visiting flowers and imbibing their nectar. The REEAIMONS OF ANTS TO VASCUEAR PLANTS. 299 floral nectaries are regarded as alluring organs and volumes have been written on the insects and birds that visit them. In these works, how- ever, the ants are not seriously considered, probably because they treat the flowers very cavalierly, for, unlike the bees, they do not concentrate their attention on particular plants and make cross-fertilization one of their main avocations. 2. Extrafloral, or Extranuptial Nectaries—These organs which, like the floral nectaries, secrete a saccharine liquid, are situated on the most diverse portions of the plant body, and occur in hundreds of species, both among ferns and flowering plants.'| While there can be no doubt that in many of these plants the extrafloral nectaries are assiduously visited by ants, it by no means follows that these organs have been developed for the purpose of attracting these insects. Indeed, it must be admitted that the significance of the nectaries of this type is far from clear. Some botanists, like Bonnier, Johow, and Lloyd, believe that they may be excretory organs and that the excretion is carried off in small quantities dissolved in the liquid nectar. It has been noticed that the organs in question are sometimes developed only on young leaves, as in the poplar and brake fern, and that the formation of sugar is in all probability the result of more active metabolism in the surrounding tissues or due to other unusual physiological conditions of rapid growth. The excretion thus formed is then utilized by ants and many other insects (wasps, flies, beetles, etc.). This sober physiological explanation is rejected by Schimper (1888) and others on the ground that the excretory function of these nectaries has never been proved. They are therefore interpreted as alluring organs devised especially for ants and scattered over the sur- face of the plant for the purpose of extending the surveillance of these insects. Their development on the young leaves is said to be only what we should expect, for such parts would be in greatest need of protection from injury or defoliation. Even Schimper, however, is compelled to admit that this view of the extrafloral nectaries can be accepted only if it can be proved, “first, that the visitations of the ants confer protec- tion on the plants with extranuptial nectaries and that in the absence of the insects a much greater number would perish or fail to produce flowers or set seeds, than when the insects are present, and second, that * The following is a list of some of the genera that comprise species with extra- floral nectaries: Pteris, Polypodium, Acrostichum, Populus, Quercus, P@onia, Rhipsalis, Sarracenia, Darlingtonia, Gossypium, Psidium, Balsamina, Vicia, Pha- seolus, Dolichos, Lablab, Cassia, Acacia, Erythrina, Canavalia, Ailanthus, Rosa, Crategus, Prunus, Syringa, Passiflora, Sambucus, Viburnum, Luffa, Impatiens, Melampyrum, Turnera, Crozophora, Marcgravia, Stillingia, Alchorea, Ricinus, Centaurea, Helianthus. 300 ANTS. the nectaries have no other function in the life of the plant and cannot be regarded as having arisen for some other function.” Neither of these propositions has been established, although there is a little evi- dence to show that the ants actually protect certain plants whose nec- taries they are in the habit of visiting. But Schimper, who studied this subject in Brazil, admits that plants with extrafloral nectaries differ greatly in the extent to which they are visited by ants, and | have reached a similar conclusion from observing species of Cassia, Stil- lingia, Ricinus, Atlanthus and Populus. Schimper endeavored to ascertain whether the extrafloral nectaries had any such function as that attributed to them by Johow and Bonnier. He extirpated all the nectaries of Cassia, and finding no visible changes in the well-being of the plant, concluded that the organs have little importance in metabo- lism and that their main function is to attract ants. This does not follow from the experiment, however, for it is quite possible that with extirpation of the organs under discussion their function might be transferred to other parts of the plant. 3. Food-bodies.— These structures are known to occur in only a few Fic. 170. Base of leaf with as- cidia, of Tococa lancifolia. (Escherich, after Schumann.) a, Lower; b, upper surface of leaf; +x, openings of ascidia. plants peculiar to the American tropics. ‘In Cecropia and Porouma they are called ‘“ Mullerian bodies,” and are yellow or red, elliptical cor- puscles about the size of a millet seed. They are found embedded in a dense mat of hairs forming a large cushion, or “ trichilium” at the base of the leaf-petiole. In Cecropia these bodies, which Schimper found to contain oily and albuminous substances, are easily detached and are carried away and eaten by the ants. Whether this is also the case in Porouma has not been ascertained. Acacia sphero- cephala possesses similar corpuscles, known as “ Beltian bodies,’ but these are borne singly on the tips of the leaflets (Fig. 178, C). 4. Bead-glands (“ Perldriisen ”).—These are modified trichomes or elevations, which sometimes appear as transparent bead-like bodies, scattered in great numbers over the surfaces of green plants. Accord- ing to Rettig (1904), they are characteristic of certain Vitacez, Piper- acee, Melastomacez and Urticacez, rarer in Moracez, Bigoniacez RELATIONS OF ANTS TO VASCULAR PLANTS. 301 and Sterculiaceze. This author has detected them on the leaves of Cecropia, where they had been overlooked by previous observers. Like the Miillerian and Beltian corpuscles, the bead-glands are rich in fatty oils, proteins and sugar. In Bunchosia gaudichaudiana they are visited by ants (Cremastogaster and Cryptocerus), according to Fritz Miller. Other species, however, belonging to the genera Gnetum, Fic. 171. Tococa formicaria, from a specimen in the herbarium of the New York Botanical Garden. (Original.) Leea and Pterospermum, which possess these glands, are described as “free from ants.” Both the food bodies and the “ Perldrtisen”’ ar: obviously modifred glands, and differ from the nectaries much as certain animal structures, like the milk glands, in which the cells them- 302 ANTS. selves break down to form the secretion, differ from the salivary glands which secrete a liquid without undergoing disintegration. 5. Pith and Other Vegetable Tissues.—Dahl (1901) describes cer- tain ants of the Bismarck archipelago and their larve as feeding on Fic. 172. Cecropia adenopus (Schimper.) A, Tip of branch with leaves cut off ; t, trichilia at base of leaf petioles; +, prostoma or depression in internode; +’, stoma or opening to hollow internode made by Azteca muelleri at the prostoma. £6, Lon- gitudinal section of stem showing the hollow internodes and at (y) the septa per- forated by the ants. the pith in the twigs of Clerodendron, and von Ihering (1907) finds that Azteca muelleri eats the tissue that grows over the perforation through which it enters the hollow twigs of the Cecropia. There 1s, of course, no myrmecophilous adaptation on the part of the plants in these cases. Turning now to the ants which are supposed to take advantage of the inducements offered by the plants, we find in both hemispheres many species that are very fond of wandering over the vegetation and visiting the nectaries, food-bodies, etc. In the tropics whole genera have become largely or exclusively arboreal, but this does not mean RELATIONS OF ANTS TO VASCULAR PLANTS. 303 that the food of the insects is obtained exclusively or even in great part directly from the plants, for, as will be shown in a future chapter, many ants visit plants mainly for the purpose of feeding on the excre- ment of the aphids, coccids, etc. In the Old World the exclusively, or at any rate, very largely arboreal genera are Gecophylla, Cataulacus, Sima and Polyrhachis, in the New World Azteca, Pseudomyrma, Cryptocerus, Myrmelachista and Allomerus, and in both hemispheres Dolichoderus, Camponotus, Cremastogaster and Iridomyrmex. The only forms, however, which are so exclusively arboreal as to show unquestionable structural adaptations to this habit, belong to the genera Azteca, Pseudomyrma, Sima and to Colobopsis, a aubeetes < of Campo- notus. Concerning the habits of Asteca and Pseudomyrma Forel (1904) says: “The species of Azteca show very disparate condi- tions in the castes of the same species. Some- times the head of the female is elongated, sometimes greatly broadened; and in like man- ner vary the proportions of the large and small workers. Emery was the first to call attention to this fact in his excellent monograph of the genus Azteca [1894k]. I believe that these differences are correlated with differences in habit. Just as the Species: of Eciton are the ea Regs re PON robbers of the soi! in the primeval forest and leaf petiole of Cecropia the Atta species are the destroyers of the foliage ie ace ean of the neotropical woods, so the species of cushion in which the Azteca and Pseudomyrma are the true monarchs Miullerian bodies (m) are formed. of the trees. To my knowledge, none of the species of Azteca and only one Pseudomyrma (P. elegans) nest in the ground. But what a varied arboreal existence is led by these little monkeys among the ants as they climb and scurry about everywhere on the trees! Some of them build carton nests on the trunks and ee others nest in great cavities in the trunks; others (A. hypophylla) nest under the leaves of certain vines with these organs closely “ter to the trunks, and close up any openings at the edges of the leaves with carton. Others, again, make use of the cavi- ties of dead branches, while still others nest in the natural medullary cavities of living Cecropia trees or any hollow swellings or spaces in all kinds of plants. Finally Mr. Ule has discovered and described ant- gardens in which grow certain epiphytes that are sown by species of Azteca. Now I believe that the long, narrow head of the female and of the large workers of many members of this genus, as well as that 304 ANTS. of many species of Pseudomyrma point to a life in very narrow, tubular branches and twigs. {he small Azteca worker is small enough to enter and leave such openings without the great elongation of the head, which in the much larger queen is necessary for the accommodation of the powerful mandibular muscles. ect) ee ar Poy ERS 7 Fic. leri in the main trunk of Cecropia adenopus ; 174. Carton nest of Azteca muel- Santa Catharina, Brazil. the American ( Original.) From a specimen in Museum of Natural History. The nearly brainless and jawless male does not require this adapta- tion. A broad, depressed head points to a life in much flattened cavities (A. hypo- phylla),etc. There are,to be sure, other differences in the form of the head (trigona and aurita, both carton- builders) that cannot be ac- counted for in this way.” At least one species of Azteca (A. viridis) is green, a very un- usual color in ants and evi- dently an adaptation to life among living leaves. In Pseu- domyrma species the whole body is greatly elongated. These are, in fact, the most slender of ants and anyone who has seen colonies of them filling narrow twigs and stems like so many sardines packed in a box, will be sure to regard the lengthening of the to life in small tubular cavities. The species of the Old World genus Sima resemble the spe- body as an adaptation cies of Pseudomyrma_ very closely in structure and habits. The soldiers of Colobopsis, as I have shown in a former chapter (p. 211) have singularly truncated heads, adapted to fitting into and closing the perfectly circular entrances to the galleries of the nests which are always in wood or m the hollow culms of sedges. Perhaps the soldiers of many species of Cryptocerus and Cataulacus use their wonderful heads for the same or similar purposes. RELATIONS “OF ANTS TO: VASG@OBAR PLANTS. 395 The foregoing facts, it must be confessed, do not furnish a very solid foundation for the myrmecophily hypothesis that has been built upon them. At most they disclose considerable adaptability on the part of the ants, and a rather dubious or clumsy counter adaptation on the part of the plants. But the authors who would convince us that there is a definite symbiosis between such very different organisms, advance as their chevau.x de bataille a few cases in which certain exqui- sitely arboreal ants live in a definite association with certain plants that present unusual structural characters. . Such are the association of the Brazilian Azteca muelleri with Cecropia adenopus, that of the Malayan Iridomyrmex myrmecodie with Myrmecodia and Hydnophytum and that of Pseudomyrma with Acacia in Central and with 7riplaris in South America. We must therefore consider these cases in somewhat greater detail. The relations of Azteca muelleri to Cecropia adenopus have been studied by Fritz Miller (1876, 1880), Schimper (1888), and von Ihering (1891, 1907). The -..tree known as the “imbauba” or “im- bauva”’ belongs to the Urticace and is very slender and candelabra- shaped, growing to a height of 12- 15 m. It is most abundant along the Brazilian littoral. The trunk and branches are hollow except at the nodes, where there are thin transverse septa (Fig. 172). The sap is colorless, not milky nor rub- ber-containing, as stated by some authors. The crown of foliage is meagre and consists of large, paim- ately lobed leaves. At some time of its life each node bears a leaf, the long petiole of which has at its base & a hairy cushion, known as the Fic. 75s Hydnophytum montanum trichilium (Figs. 172¢, 173), sr Cod pseudobulb in sec- which the yellow Millerian bodies . (m) are imbedded. The cavities of older and larger trees are almost without exception tenanted by Asteca muelleri, which per- forates the septa and thus causes all the internodal cavities to communicate with one another, both in the trunk and _ branches. The ants do not, however, live in the smallest, still actively growing twigs. The just-fecundated queen enters the branches while the tree 21 306 ANTS. x ~ eS = Fic. 176. Myrmecodia pentasperma of Bismarck Archipelago, with pseudobulb opened to show ants (Iridomyrmex cordatus) inhabiting the cavities. (Dahl.) REEATIONS OF ANTS TO. VASCUEAR PLANTS. 307 is still young (50 cm. to 2 m. high) at a particular point, a small depression at the upper end of a furrow at the top of the internode, where, as Schimper has shown, the wall lacks the fibro-vascular bun- dles and is most easily perforated. Von Ihering calls the depression the ‘‘prostoma,”’ the perforation which is formed in it the “stoma.” The queen thus enters an internode by making a stoma and feeds on the tissue (“stomatome”) which, according to von Ihering, soon pro- liferates over and closes the opening from the inside. In the small internodal cavity the first workers, six to eight in number, are reared, and these restore communication with the outside world by again open- ing the stoma. Von Ihering says that as many as five to ten queens may each start a colony in one of the internodes of the oe same tree, that these colonies forsake the internodes in which they were reared and migrate to more distal internodes and that they eventually engage with one another in conflicts that terminate in the death of all except one of the queens and a fusion of the worker personnel of the different colo- nies to form one larger com- MliiMiveave Sch gia! Tusions olf hostile colonies is so contrary to what is known to occur in other ants that it may well be doubted. I[t is more probable that only one of the original Fic. 177. Hollow thorns of Acacia sp. ; : : inhabited by Pseudomyrmax fulvescens; Ja- colonies together with its queen lapa, Mexico. (Original.) The entrances survives and that all the others 2" "ea the tips of the thorns. are either massacred, or driven away from the tree. After this single colony has grown and perforated the septa it starts a spindle-shaped carton nest in the bole, a little distance above the ground. This so-called “metropolitan” nest (Fig. 174), which was discovered by von Ihering, resembles the carton nests built by other species of the genus on the branches of Cecropia and other trees. Where the nest occurs the bole of the Cecropia presents a spindle- shaped enlargement, which von Ihering regards as a gall—* the largest known gall,” but his figures and several of these nests recently acquired 303% ANTS. by the American Museum of Natural History prove conclusively that such an interpretation is erroneous. The wall of the hollow trunk, where it encloses the nest, shows no structural modification except a bending outward of the woody fibers. About half the thickness of this wall is gnawed away by the ants from the inside, leaving a thin zone encircling the trunk, which naturally bulges out under the weight of the superposed trunk and crown of foliage. As there is no hyper- trophy of the tissues in the spindle-shaped deformation, the term gall, as applied to a structure of such simple mechanical origin, is a mis- nomer. When the metropolitan nest is established the ants make a large entrance in the adjacent wall of the trunk and through this and the other openings in the branches pass to and from the foliage. They collect the Mullerian bodies and store them in the nest where they can be eaten at leisure. So dependent is the Azteca colony on the Cecropia for this food that it perishes when the tree dies or is cut down. Those who have seen the living imbauba and its occupants are unanimous in describing the insects as rushing out and fiercely attack- ing any one who ventures to touch the foliage. Alien ants, especially, are vigorously assailed and either killed or driven from the tree. Von Ihering, however, calls attention to the fact that various Chrysomelid larvee, caterpillars and the sloth (Bradypus tridactylus) are permitted to feed on the leaves unmolested. Fritz Muller and Schimper believed that the Azteca protects the tree from defoliation by the large leaf- cutting ants of the genus Atta, but von Ihering has shown that the plant, even when entirely free from its so-called protectors, is rarely or never visited by Atta. It thus appears that the Cecropia is not known to have any enemies against which the Azteca could avail. The ani- mosity of these ants is probably greatest against alien colonies of their own species, and is directed to retaining possession of the feeding grounds and neighborhood of their nest. This is, of course, a well- known trait of ant-colonies in general. Although von Ihering says that “‘in order to thrive the imbauba no more requires the Azteca than a dog does fleas,” he nevertheless believes that the Mullerian bodies and the prostome are myrmecophilous adaptations. In this, he seems to me, to concede too much, for if the ants are of no use to the Cecropia, why should the latter develop structures for the purpose of attracting and retaining this superfluous bodyguard? And of the three Cecro- pian structures, which might be regarded as indicating myrmecophily, namely, the cavities of the trunk and branches, the prostomes and the Mullerian bodies, the first can hardly be an adaptation to harboring ants, the second are produced, or at any rate, started, as Schimper admits, by the pressure of the axillary buds against the surface of the RELATIONS OF ANTS TO VASCUEAR’ PLANTS. ' 309 internodes, while the Mullerian bodies, though continually formed anew as they drop off or are carried away by the ants, may have an excre- tory or some other nonmyrmecophilous function, for aught that is known to the contrary. The adaptation, therefore, has every appear- ance of being on the side of the ant rather than on that of the tree. This is also indicated by two other considerations: first, by the habits Fic. 178. Acacia sphaerocephala. (Schimper.) A, End of branch showing pairs of hollow thorns which are inhabited by ants (Pseudomyrma); x, openings of nests; B, leaf of same plant; y, nectary on upper surface of petiole; C, tip of leaf- let enlarged showing Beltian body. of the Azteca, which seems to have taken up its abode in the Cecropia within comparatively recent times, since it has not abandoned the con- struction of large fusiform carton nests like those produced on the branches of trees by many other species, although the cavities of the Cecropia seem to be better adapted to long cylindrical nests or would 310 ANTS. seem to render the construction of carton nests altogether superfluous. In the second place, certain species of Cecropia, having essentially the same structure as (. adenopus, are nevertheless free from ants. This is true, for example, of C. peltata, as I have observed in Porto Rico (1907d). Here no species of Azteca occurs and the tree is almost never tenanted by ants of any description, although it has well-developed prostomes and distinct Mullerian bodies. It thrives on the mountains of the island, even when its foliage is much eroded and perforated by insects. Of the Brazilian species, C. lyratiloba, according to von Ihering, resembles adenopus in having Mullerian bodies and in being regularly inhabited by Azteca. The same is true of C. sciadophylla, which is peopled with A. emeryi according to Forel. Both Schimper and von Ihering, however, found C. hololewca without trichilia and without ants. The former author also describes and figures this tree as lacking the prostomes. The allied genus Porowma is imperfectly known. Rettig says that it has Miillerian bodies like Cecropia, and Forel (19047) mentions Asteca duroi@ as occurring in its twigs. The * myrmecophilous’ Rubiaceee, embracing the genera Myrme- codia (Vig. 176), Hydnophytum (Fig. 175) and Myrmephytum, with about sixty species, confined to the Austromalayan region, have been studied by Rumphius (1750), Gaudichaud (1826), Caruel (1872), H. O. Forbes (1880, 1886), Beccari (1884, 1885), Treub (1883, 1888) Burck (1892), Haberlandt (1893), Karsten (1895), Dahl (1901) and Rettig (1904). These plants are epiphytes on trees or rocks in hot, sunny places and grow from large, bulbous stems full of cavities that communicate with the outside by means of small holes. These bulb- like structures are nearly always occupied by ants. Treub found that the cavities arise in the very young plant and are not started, though they may be subsequently enlarged, by the insects. /ridomyrmex myrmecodic, a subspecies of J. cordatus, is the ant most frequently found nesting in these plants, but species of the same or other genera have also been recorded (Camponotus maculatus, Cremasto- gaster difformis and Pheidole javana). In some species of Myrme- codia the bulb bristles with spines, as if for protection, but notwith- standing the presence of these structures and the ants, no one has been able to detect the existence of any enemy that might injure or devour the plants. Treub observed that specimens grown in localities inac- ‘In a very recent study (“Cecropia peltata und ihr Verhaltnis zu Azteca Alfari, zu Atta sexdens und anderen Insekten,” etc., Biol. Centralbl., 29, 1900, pp. 1-16, 33-55, 65-77, pls. 1-5), Fiebrig is even less inclined than von Ihering to accept the theory of myrmecophily among plants. He shows that Cecropia pel- tata of Paraguay (apparently not the C. peltata of the Antilles!) is not protected from its great number of insect and other enemies by the Azteca alfari, though this ant constantly occupies its cavities and feeds on its Miillerian bodies. ey » RELATIONS OF ANTS TO VASCUEAR PLANTS. 31t cessible to the ants throve as well as those filled with the insects. And he, Karsten, Rettig and others, after a careful study, found that the walls of the cavities are provided with lenticelli and that the cavi- ties themselves probably have a twofold function: to contain air and thus prevent the tissues of the plant from becoming overheated during hot, dry spells, and to take up and to store water for purposes of growth at other seasons of the year. It would seem, therefore, that the ants merely take advantage of the cavities without either bene- fiting or injuring the plant. This case of Myrmecodia and the allied Rubiacee is very interesting as epitomizing the change of opinion which will eventually extend to other instances of so- called symbiosis between ants and plants. Rum- phius in 1750 declared Myrmecodia to be a zoo- phyte, believing that the ants brought together twigs and built a nest out of which the Myr- mecodia germinated. He therefore called the plant “nidus germinans formicarum rubrarum et nigrarum.” Now we have a physiological ex- planation, which some may regard as a sordid anticlimax to this and other fanciful views concerning the relations of the Myrmecodia to its tenants. But to the Fic. 179. Ant gardens of the Amazon. (Ule.) thinking naturalist Rum- A, Large spherical ant garden covered with seed- 2 ling plants; B, small garden on Cordia. phius’s explanation is merely a childish absurdity, while that of the recent botanists is infinitely more stimulating to the scientific imagination, disclosing as it does, on the one hand, the age-long struggles of a plant to live on the atmosphere and its moisture while exposed on hot cliffs and tree- trunks, and, on the other hand, the no less persistent endeavors of the plastic ant to find new domiciles for its pullulating commonwealths. The classical account of the relations of Acacia spherocephala ( Fig. 312 ANTS. 177 and 178) and a species allied to Pseudomyrma bicolor is given by Belt in “ The Naturalist in Nicaragua” (1874). He describes the large paired thorns tenanted by the ants, the extranuptial nectaries on the leaf- petioles and the yellow food-bodies at the tips of the leaflets, and puts these various structures down as so many symbiotic adaptations. He says that ‘“ hundreds of ants are to be seen running about, especially over the young leaves. If one of these be touched, or a branch shaken, the little ants (Psewdomyrma bicolor Guér.) swarm out from the hollow thorns and attack the aggressor with jaws and sting. . . . These ants form a most efficient standing army for the plant, which prevents not only the mammalia from browsing on the leaves, but delivers it from the attacks of a much more dangerous enemy, the leaf-cutting ants.” 3elt sowed the seeds of Acacia in his garden and reared some of the young plants. “Ants of many kinds were numerous; but none of them took to the thorns for shelter, nor the glands and fruit-like bodies for food. ... The leaf-cutting ants attacked the young plants and defoliated them, but I have never seen any of the trees out on the savannahs that are guarded by the Pseudomyrima touched by them, and have no doubt the Acacia is protected from them by its little warriors.” There are several other thorn-inhabiting Pseudomyrme (belti, fulves- cens, spinicola) that nest in this and other species of Acacia in Central America and Mexico, and a Cremastogaster is also mentioned by Belt in this connection. Concerning the development of.the thorns he says: “ The thorns, when they are first developed, are soft, and filled with a sweetish pulpy substance; so that the ant, when it makes an entrance into them, finds its new house-full of food. It hollows this out, leaving only the hardened shell of the thorn. Strange to say this treatment seems to favor the development of the thorn, as it increases its size, bulging out towards the base; whilst in my plants that were not touched by the ants, the thorns turned yellow and dried up into dead but per- sistent prickles. I am not sure, however, that this may not have been due to the habitat of the plant not suiting it.” According to Rettig (1904) this latter statement is based on insufficient observation, for the enlargement of the thorns is not produced by the ants, although it does not make its appearance till the plant has grown considerably. It has been known for some time that the Old World also has its acacias with enlarged thorns tenanted by ants. Gerstaecker (1871), Schweinfurth (1867-68) and more recently Keller (1892) have called attention to the East African ‘‘ uwadi” acacia (4. fistulosa), the greatly inflated thorns of which are white at first but when old become brown or black. According to Keller these thorns are nearly always inhabited by species of Cremastogaster (chiarinii, ruspolu or acaci@). He main- RELATIONS OF ANTS TO VASCULAR PLANTS. 313 tains that 4. fistulosa, which furnishes a gum of commercial value, is never eaten by cattle and he attributes this immunity to the protecting ants. Concerning the growth of the thorns he says: “ Of the manner in which the young inflations arise | am unable to form any satisfactory conception. They are produced in great num- bers at the beginning of the rainy season, when the vegetation awakens, and are then green and soft. I never saw a hole in one of them. They are completely closed on all sides, and it is not till later that they are opened by the ants. I have seen no injuries, wounds, nor anything that could indicate that the deformation is due to insects, and I cannot therefore regard the infla- tions of the thorns as gall-formations. With this conclusion also harmonizes the fact com- municated to me by Schweinfurth, that acacias grown from seed in Cairo also developed the inflations. The only explanation I can suggest is that in this plant an originally abnormal growth has become perfectly normal, under the influence of natural selection, through adaptation to sym- biosis with ants.” Keller calls attention to the Fic. 180. Broken & ee the 1 eae f 4] twig of sunflower (He- singular fact that only a small number of the jjanthus annuus) show- thorns on a plant become inflated. This sug- ing ants (Myrmica brevinodis) caught and ; . : killed by the exuding may be responsible for the deformation, which sap. (Original.) is then put to good use by the ants. gests that bacteria or other pathogenic organisms A few words may be added on certain South American plants of the genera Cordia, Humboldtia, Ficus (e. g., inequalis), Tococa (Figs. 170 and 171) and Triplaris (Figs. 166, B and 167) and the East Indian Clerodendron fistulosum. All of these have preformed cavi- ties either in the stems or in burse on the leaves and _ petioles. Clerodendron is said to have in the internodes preformed thin spots, or prostomata, which are selected as entrances by the ants (Colo- bopsis clerodendri). The leaves of this plant are furnished with innumerable nectaries along the midrib on the lower surface. In Cordia nodosa the flower-bearing stem is dilated above and contains a short, conical cavity which, according to Schimper, is not homologous with the medullary cavity of other plants, as its walls are formed by a fusion of a number of stems. The chamber, which is furnished with a small preformed opening above, is commonly tenanted by ants. Schu- mann (1888) and Metz (1890) have noted the remarkable fact that 314 ANTS. this plant, when growing in the Antilles, fails to develop the hollow swellings in the stems. The hollow twigs of the Polygonaceous Tri- plaris, or “ palo santo,’ of which some twenty species are known, are said to be invariably occupied by Pseudomyrma. Of these ants Forel (19041) says: “ Through the investigations of Mr. Ule the fact becomes more and more firmly established that a definite group of Pseudomyrma species (arboris-sancte, dendroica and triplaridis) lives symbiotically in the natural medullary cavities of Triplaris. In 1896 I myself Fic. 181. Mound of Formica exsectoides .70 meters high and 2.46 meters in diameter, almost completely covered with a moss (Polytrichum commune) which eventually envelops the summit of the nest and extinguishes the colony. (Original.) observed in Colombia how P. arborts-sancte var. symbiotica fiercely attacked anyone who touched the tree. Their brood filled the whole living tree from the trunk to the smallest green branches. They seemed to have entered this secure and ramifying domicile through a small dead and broken branch on the lower part of the trunk.” No doubt the various cases cited in the preceding pages are of great interest, both to the botanist and myrmecologist, but it is equally certain that none of them has been studied with suificient care to warrant the conclusions advocated by Belt, Schimper and others. The relation- ships under discussion are all compatible with the view that the ants have adapted themselves to the plants—plantas itaque norunt formice —but the converse of this proposition is in most, if not in all instances, open to doubt. Travelers and naturalists who observe for a short RELATIONS OF ANTS TO VASCULAR PLANTS. 31 nr time in the tropics, where all of these wonderful cases occur, are very apt to jump to conclusions, and carefully devised experiments, which alone can throw the necessary light on the subject, are still wanting. The opinion here maintained is indirectly supported by what is known concerning some of the other relations that may obtain between plants and ants. These relations may be considered under the follow- ing heads: 1. Ants as Seed Distributors.—In the preceding chapter Mog- gridge’s observations on the distribution of seeds by Messor barbarus were mentioned, together with other facts which indicate that ants are important agents in scattering seeds. This habit is not confined to granivorous species. Lubbock (1894) saw Lasius niger carrying violet seeds into its nest. More recently Sernander (1903) and some other botazists have come to believe that the ants eat the caruncles and that these structures are developed as lures, like the extrafloral nectaries and food-bodies, to induce the ants to carry the seeds to a distance and thus increase the chances of their survival. Dr. E. B. Southwick tells me that he has seen the ants in Centra] Park, N. Y., carry away the seeds of the blood-root (Sanguinaria canadensis) and feed on their caruncles. 2. Ant-gardens.—This name is given by Ule (1902) to certain sponge-like ant-nests (Fig. 179) which he found built on the branches of trees in the forests of the Amazon. These nests consist of soil carried up by the ants (4steca olithrix, ulei and traili and Camponotus femoratus) and held together by the roots of numerous epiphytes, which grow out of it on all sides, making it resemble the head of a Medusa. The ants not only perforate the soil with their galleries but, according to Ule, actually plant the epiphytes. This he infers from seeing the insects in the act of carrying the seeds. Perhaps these are brought into the nest for the sake of their caruncles and then germinate in the rich soil, but it 1s quite as probable that they are sown by the wind. 3. Plants Injurious to Ants.—If it be true that some plants deserve to be called “ myrmecophilous,” because they are helpful to ants in the struggle for existence, it is equally true that there are other plants that might with even greater justice be called “ myrmecophobic,” or “ myr- mecechthric,” because they are injurious or even deadly to these insects. Such are, for example, certain moulds and bacteria. Queen ants while founding their colonies in damp cavities in soil or decaying wood often succumb to the incursions of these organisms, which under certain conditions may even exterminate the brood of larger colonies. Miss Fielde (1901b) says: “ Penicillium crustaceum grows to ripeness, in 316 ANTS. either darkness or light, upon eggs, larve or pupe, if left for a few days unattended in the humid atmosphere required by the ants, and its sprouting spores may be seen on their surfaces under a magnification of about five hundred diameters. If the spores are left undisturbed they cover the young with a delicate dense white coat that becomes sage-green with the ripening of the new spores. ... This delicate mould does not grow upon the bodies of dead ants, but is there replaced by Rhyzopus nigricans, with long and spreading hyphe, and in this a hag em: te. wi Nohiiy Fic. 182. Old mound of Formica exsectoides covered with vegetation and with only a few lingering remnants of the colony in its summit. (Original.) may lie the cause for the carrying off and casting away of all ants that die or are killed in the nest.” Botanists have described several peculiar arrangements in higher plants, such as excessive hairness, slipperiness or stickiness of the stems, or special palisades of hairs about the floral nectaries (nectarostegia ) as means of preventing ants and other desultory arthropods from plun- dering the secretions intended for bees and other cross-fertilizing agents. But these arrangements, if really developed for this purpose, are often inefficacious. Vosseler (1906) has recently described an African ant which manages to get around the woolly hairs protecting the nectaries RELATIONS OF ANTS TO VASCULAR PLANTS. Say, in Cobea scandens and gains access to these organs by biting a hole through the base of the petal, a habit which has also been observed in bees that are confronted with flowers whose nectaries they are unable to reach in any other way. But there are graver maladjustments between plants and ants, maladjustments that may lead to the death of the insects in great numbers or even to the extinction of their colonies. I have described a number of such cases in a recent paper (1906/). The abundant and sticky juices of Silene, Lactuca and Helianthus exuding onto the stems or petioles often entrap and kill numbers of ants (Fig. 180). We owe to a similar property of the resiniferous conifers of the Tertiary the preservation of the ants in the Baltic and Sicilian ambers. Our North American pitcher plants (Sarra- cenia) also entrap, kill and digest enormous numbers of ants in the liquid at the bottoms of their ascidia. The ants most frequently found in these modified leaves are Cremastogaster pilosa, a species which will sometimes even nest in the dead pitchers of a plant whose active green leaves are busy killing them off in great numbers—a singular commen- tary on the “ intelligence’’ of these insects, especially when we stop to consider that C. pilosa is one of the ants that constructs such beautiful sheds over aphids and coccids. Another hostile relationship between plants and ants has been described in detail by Holmgren (1904). He observed that the mound nests of Formica exsecta in the bogs of Lapland are gradually invaded and eventually so completely covered with a dense carpet of moss (Polytrichum strictum) that the ants are either driven away or de- stroyed. This moss is in turn replaced by a carpet of Sphagnum, in which many plants eventually take root, so that the ants are instru- mental in forming the hummocks of moss and hence facilitate the growth of peat-forming vegetation. In the bogs of Prussia, according to Kuhlgatz (1902), the 1/yrmica nests are invaded in a similar manner by P. strictwm, and I have been able to observe various stages in the extinction of colonies of our North American F. exsectoides by an allied moss, P. commune (1906/]). This moss starts in the form of a narrow zone around the base of the huge mound nests (Fig. 181) and gradually grows upward till it completely envelopes their summits with a dense mat and either smothers the colony outright or compels it to emigrate (Fig. 182). CHAPTER (Savi: THE FUNGUS-GROWING ANTS. “Quoique dans l'immense série des étres, la fourmi ne soit qu’un point qui sans sa mobilité échapperoit presque a nos regards, il n’en est pas moins vrai que cet atome animé est digne d’etre l’objet de nos méditations. C'est ici qu’il convient de dire que Auteur de la nature n’est jamais plus lui-meme que dans ce qu'il y a de plus petit.”"—Latreille, “ Histoire Naturelle des Fourmis,” 1802. Although our examination, in the last chapter, of the relations between ants and vascular plants has led us to doubt the existence of a true symbiosis between these organisms and to interpret their rela- tions as the result of a direct adaptation on the part of the ants, we are compelled to admit that there is what may be called a true symbiosis Fic. 183. Worker Fic. 184. Worker of Serico- of Myrmicocrypta brit- myrmex opacus of South Amer- tont of Porto Rico. ica. (Original.) ( Original. ) between ants and some of the lower plants. These ants all belong to the Myrmicine tribe Attii, which is peculiar to tropical and subtropical America, and the plants with which they are so intimately associated are fungi. The association is symbiotic, because the fungi are provided 318 THE FUNGUS-GROWING ANTS. 319 with their substratum, or nutriment by the ants, and in turn supply these insects with their only food. The Attii, of which about one hundred species, subspecies and varieties have been described, are all fungus-growers and -eaters. The tribe ranges from about 40° S. to 40° N. of the equator, but is best rep- resented in the tropics. The species have been assigned to five genera. which, beginning with the most primitive, are /yrmicocrypta, Cypho- myrmex, Apterostigma, Sericomyrmex and Atta. The last of these is divided into six subgenera: Mycocepurus, Mycetosoritis, Trachymyr- mex, Mellerius, Acromyrmex and Atta s. str. Vhe subgenus Atta i \ : Fic. 185. © Worker of Fic. 186. Two species of Cyphomyr- Apterostigma pilosum of mex occurring in the United States. (Orig- Brazil. (Original.) inal.) a, C. rimosus; b, C. wheeleri. comprises the leaf-cutting, or parasol ants, the largest and most pow- erful species of the tribe, living in great colonies and inhabiting the territory between 30° north and 30° south of the equator. The workers are highly polymorphic and much smaller than the males and females. The colonies of the species of Mallerius and Acromyrmex are much less populous, and the workers, though variable in size, do not exhibit such marked polymorphism as those of Atta s. str. In Trachymyrmex and the remaining subgenera the workers are monomorphic and but little smaller than the males and females, and the colonies are even feebler than those of Acromyrmex. Mycetosoritis and Mycocepurus 320 ANTS. are in certain respects transitional to the genera Cyphomyrmex and Myrmicocrypta (Fig. 183), and species of the last show affinities with Sericomyrmex (Fig. 184). Apterostigma (Fig. 185) is very aberrant, resembling in form certain Myrmicines of the subgenera Apheno- gaster and Ischnomyrmex. The workers of Atta are covered with stiff, erect or suberect, hooked or curved hairs, and the surface of the body is tuberculate or spinose. In Cyphomyrme.x the body is smoother and covered with short, appressed, scale-like hairs. In Sericomyrmex and Apterostigma the hairs are soft, flexuous and very abundant. With few exceptions all the Attii have the sur- face of the body opaque and of a ferruginous, brown or blackish color. All the species, moreover, though very powerful and able to make surprisingly extensive excavations in the soil, are very slow and sedate in their movements. The sting of the workers is vestigial, but Fic. 187. Fungus (Tyridiomyces Fic. 188. Worker of formicarum) cultivated by Cypho- Mycocepurus smithi of myrmex rimosus on insect excrement. the American tropics. (Original.) a, Bromatia, or food ( Original.) bodies; b, yeast-like cells of which these consist. in the larger species the sharp jaws may be used as most efficient organs of defence. The smaller species are extremely timid and when roughly handled “ feign death” like many beetles. In all the species the hard, rough or spinose integument must afford efficient protection from alien ants and other enemies. The Attii are such conspicuous, abundant and destructive insects in tropical America that we are not surprised to find an extensive litera- ture on their taxonomy and habits. The latter have been described by Buckley (1860), Bates (1863), Lincecum (1867), Norton (1868), B. R. Townsend (1870), Belt (1874), McCook (1879a, 1879b), Morris THE FUNGUS-GROWING ANTS. 321 (1880), Brent (1886), Tanner (1892), Moeller (1893), von Ihering (1894, 1898), Urich (1895a, 18950), Swingle (1896), Forel (1896a-c, 1897, 1899-1900, 1901), Sampaio (1894), Goeldi (1905a and b, Forel 1905) and J. Huber (1905). I have recently reviewed these authors in a paper on the North American Attii (1907c), to which the reader is referred for many details that cannot be given in this chapter. The first important observations on these insects were published by Belt in his interesting volume, “ The Naturalist in Nicaragua.” He Fic. 189. Mycetosoritis hartmani of Texas. (Original.) a, Worker, dorsal view ; b, same in profile; c, male. was the first to surmise the use to which the leaves, ete., are put by Atta cephalotes, concerning which he writes: “ Notwithstanding that these ants are so common throughout tropical America, and have excited the attention of nearly every traveller, there still remains much doubt as to the use to which the leaves are put. Some naturalists have supposed that they used them directly as food; others, that they roof their underground nests with them. I believe the real use they make of them is as a manure, on which grows a minute species of fungus, on which they feed ;—that they are, in reality, mushroom growers and eaters. This explanation is so extraordinary and unexpected, that I may be permitted to enter somewhat at length on the facts that led me to adopt it. When I first began my warfare against the ants that attacked my garden, I dug down deeply into some of their nests. In our mining operations we also, on two occasions, carried our excava- 22 322 ANTS. tions from below up through very large formicariums so that all their underground workings were exposed to observation. I found their nests below to consist of numerous rounded chambers, about as large as a man’s head, connected together by tunnelled passages leading from one chamber to another. Notwithstanding that many columns of the Fic. t90. Section of Mycetosoritis hartmani nest in pure sand; about % natural 9 4 size. Two of the chambers contain pendent fungus gardens. (Photograph by C. G. Hartman.) ants were continually carrying in the cut leaves, I could never find any quantity of these in the burrows, and it was evident that they were used up in some way immediately they were brought in. The chambers were always about three parts filled with a speckled, brown, flocculent, spongy-looking mass of a light and loosely connected substance. THE FUNGUS-GROWING ANTS. ei Throughout these masses were numerous ants belonging to the smallest division of the workers, which do not engage in leaf-cutting. Along with them were pupe and larve, not gathered together, but dispersed, apparently irregularly, throughout the flocculent mass. This mass, which I have called the ant-food, proved, on examination to be com- posed of minutely subdivided pieces of leaves, withered to a brown color, and overgrown and lightly connected together by a minute white fungus that ramified in every direction throughout it. I not only found this fungus in every chamber I opened, but also in the chambers Fic. ror. Fungus garden of the Mycetosoritis nest shown in Fig. 190 enlarged about %4. (Photograph by C. G. Hartman.) of the nest of a distinct species that generally comes out only in the night-time, often entering houses and carrying off various farinaceous substances, and does not make mounds above its nests, but long wind- ing passages, terminating in chambers similar to the common species and always, like them, three parts filled with flocculent masses of fungus-covered vegetable matter, amongst which are the ant-nurses and immature ants. When a nest is disturbed, and the masses of ant- food spread about, the ants are in great concern to carry away every morsel of it under shelter again; and sometimes, when I dug into the nest, I found the next day all the earth thrown out filled with little 324 ANTS. pits that the ants had dug into it to get out the covered up food. When they migrate from one part to another, they also carry with them all the ant-food from their old habitations. That they do not eat the leaves themselves | convinced myself, for I found near the tenanted chambers, deserted ones filled with the refuse particles of leaves that had been exhausted as manure for the fungus, and were now left, and served as food for larve of Staphylinide and other beetles. “These ants do not confine themselves to leaves, but also carry off Fic. 192. Two North American species of Trachymyrmex. (Original.) a, T. turrifex; b, T. septentrionalis. any vegetable substance that they find suitable for growing fungus on. They are very partial to the inside white rind of oranges, and I have also seen them cutting up and carrying off the flowers of certain shrubs, the leaves of which they have neglected. They are very particular about the ventilation of their underground chambers, and have numer- ous holes leading up to the surface from them. These they open out or close up, apparently to keep up a regular degree of temperature below.” Observations on A. cephalotes were resumed in 1892 in Trinidad by Tanner, who was the first to study these insects in artificial nests and to prove that not only the adult Atte but also the larve feed on the fungus described by Belt. A year later, Alfred Moeller published the most important of existing works on these ants and their relations to the fungi which they cultivate. He studied several Brazilian species of Atta belonging to the subgenus Acromyrmex (discigera, coronata, octospinosa, meileri) and to the genera Apterostigma ( pilosum, melleri, wasmanni, and an undetermined species) and Cyphomyrmex (auritus, strigatus). A. octospinosa and discigera, which nest in the woods, THE FUNGUS-GROWING ANTS. 325 form truncated cones of dead leaves and twigs, beneath which they excavate a single chamber containing a large fungus garden sometimes 1.5 meters long. 4. melleri has similar habits, but coronata resembles the species of the subgenus 4Afta s. str. in forming several chambers, each with its own fungus garden. In all of these species the garden is built up on the floor of the chamber in the form of a loose sponge-work of triturated leaf-fragments, permeated with fungus hyphze which he Fic. 193. Tower-shaped nest crater of Trachymyrmex turrifex in Texan cedar brake; natural size. (Photograph by A. L. Melander.) describes as follows: “ Over all portions of the surface of the garden are seen round, white corpuscles about .25 mm. in diameter on an average, although some of them are fully .5 mm., and sometimes adja- cent corpuscles fuse to form masses I mm. across and of irregular form. After a little experience one learns to detect these corpuscles with the naked eye as pale, white points which are everywhere abundant in all nests. Under the lens they sometimes have a glistening appear- ance like drops of water. They are absent from the youngest, most recently established portions of the garden, but elsewhere uniformly distributed, so that it is impossible to remove with the fingers a particle too small to contain some of the white bodies. I call these the ‘ koh!- rabi clusters’ of the ants’ nests. They constitute the principal, if not 326 ANTS. the only food of the species of 4tta.” These clusters are made up of the “heads of kohlrabi which are small terminal dilatations of the hyphz of a spherical or oval form.” Moeller confirmed Belt’s observations on the solicitude of the ants for their gardens, and showed that these insects in artificial nests will completely rebuild these structures within twelve hours after they have been disintegrated or scattered. He saw the ants eating the fungus and was able to satisfy himself that the different species of Atta will eat the kohlrabi from one another’s colo- nies, but not that of Apterostigma or Cyphomyrmex. Belt supposed that the smallest workers, or minims comminute the leaves and build up the fungus gardens. According to Moeller, however, this is the office of the mediz, as the leaves are too thick to be manipulated by the smallest workers. The latter have another function, namely, that of weeding the garden and keeping down the growth of spores belonging to alien fungi. Moeller emphasizes the remarkable fact that the gardens are pure cultures although the hairy, rough- bodied workers must be continually bringing into the nests all sorts of spores and bacteria. It is probable, also, that the minims are instrumental in producing the “ kohlrabi heads,” as these are not developed when the mycelium is grown in artificial culture media apart from the influence of the ants. He summarizes the results of this portion of his studies in the following words: “All the fungus-gardens of the Atta species I have investigated, are pervaded with the same kind of mycelium, which produces the ‘ kohlrabi Fic. 194. Diagram clusters’ as long as the ants are cultivating the of nest of Trachymyr- = : 4 mex turrifex with five gardens. ~ Under the influence*of the amis neither chambers. The right free aérial hyphe nor any form of fruit are half of the figure is a ‘s é ; continuation of the ever ‘developed: 99 Dike “miycelumeiprolererares lower portion of the through the garden to the complete exclusion of left half. (Original.) any alien fungus, and the fungus garden of a nest represents in its entirety a pure culture of a single fungus. The fungus has two different forms of conidia which arise in the garden when it is removed from the influence of the ants. The hyphe have a very pronounced tendency to produce swellings or diverticula, which show several more or less peculiar and clearly differ- entiated variations. One of these, which has presumably reached its present form through the influence of cultivation and selection on the part of the ants, is represented by the ‘ kohlrabi heads.’ ”’ THE FUNGUS-GROWING ANTS. 327 Moeller undertook to determine-the systematic position of the fun- gus. He naturally supposed that the discovery of the fruiting form would show it to be an Asco- or Basidiomycete. Although he failed to raise either of these forms from his mycelial cultures, he succeeded on four occasions in finding an undescribed Agaricine mushroom with wine-red stem and pileus growing in extinct or abandoned Acromyrmex nests. From the basidiospores of this plant, which he called Rhozites gongylophora, he succeeded in raising a mycelium resembling in all respects that of the ant gardens. Three of the species of dcromyrme.v did not hesitate to eat portions of this mycelium and of the pileus and Fic. 195. Vestigial nest crater of Trachymyrmex septentrionalis. (Original.) The nest entrance is at +, the pile of sand pellets shown in the lower right-hand corner represents the crater of Atta terana and Meallerius versicolor, stem of the Rhozites. He believed, therefore, that he had definitively established the specific identity of the fungus cultivated by the ants. A careful perusal of Moeller’s observations shows an important lacuna at this point. That his Atte ate portions of the pileus and stem of the Rhozites does not prove that it is the fruiting form belonging to the fungus they habitually cultivate and eat. Nor is Moeller on much surer ground when he assumes that the mycelia cultivated by different 328 ANTS. genera of Attii belong to different species of fungi, for it is very prob: able that the ants of one species would avoid fungus taken from the nest of another on account of the alien nest-aura. Certainly, to the human olfactories, the fungus gardens of Atta texrana have a very striking odor which is al- together lacking in the gar- dens of Trachymyrme., and it would be strange if these differences did not affect the appetites of such sensitive insects as the ants. In my opinion, it is not improbable that the fungi cultivated by the ants may be more closely re- lated to the moulds (As- comycetes) than to the mushrooms _ ( Basidiomy- cetes). Moeller does, in fact, call attention to cer- tain Ascomycete peculiari- ties in the mycelium culti- vated by Acromyrmex discigera. This is a mat- Fic. 196. Diagram of a large nest of a ter, however, to be settled southern variety of Trachymyrmex septentrio~- by the mycologist, and I nalis, showing near the surface the small original 1 Bs : 2 chamber of the queen, five chambers with pen- merely call attention to it dent fungus gardens, and a newly excavated jn this connection, be- chamber in which the garden has not yet been ’ started: an OnemaL) cause Moeller’s somewhat s : g : guarded statements have assumed an unduly positive form in subsequent reviews of his work. The species of A pterostigma investigated by Moeller usually nest in cavities in rotten wood which is often also inhabited by other insects. The fine wood castings and excrement of these insects are used by the ants as material with which to construct their fungus-gardens. 4. wasmanni constructs the largest nests, and it is only in the gardens of this species that the mycelium produces structures analogous to the “kohlrabi heads” and “clusters” of Acromyrmex. The “heads,” however, are club-shaped instead of spherical dilations of the hyphe. The gardens of pilosum, malleri and of another undetermined A pterostigma, which live in feeble colonies of only twelve to twenty individuals, are suspended from the roofs of the small cavities, 3 to 4 THE FUNGUS-GROWING ANTS. oe cm. in diameter, in the rotten wood and exhibit a peculiar structure not seen in other Attii. “ The garden is often completely, or at least nearly always in great part, enclosed in a white cobweb-like membrane. It was often possible to obtain a view of uninjured nests of A. pilosum that had been excavated in clefts of the rotten wood. In such cases the envelope enclosed the whole fungus gar- den like a bag, with only a single orifice or entrance. The envelope is attached in a pendent position to the surrounding wood, roots or particles of earth by means of \ radiating fibers, and this explains why the gardens are so easily torn asunder while the Ye TET nest is being uncovered.’’ Even in cap- tivity these ants persisted in hanging their gardens to the sides of the glass dishes in which they were kept. The two species of Cyphomyrmex ob- served by Moeller were found nesting under bark or in rotten wood lke Apterostigma. The largest gardens of C. strigatus are only 8 cm. long, whereas those of C. auritus may attain a length of 15 cm. and a breadth and height of 5 cm. These gardens are never pendent and never enclosed in a mycelial Fic. 197. Worker of envelope. In other respects they resemble Wee eee LEA can those of Apterostigma and are grown on the — (Original.) same substrata. Moeller’s studies were confined to the adult colonies of the Attii. The question as to how these ants came by their fungi in the first place, was subsequently answered by the researches of Sampaio (1894), von Ihering (1898), Goeldi (1905a and 6) and Huber (1905, 1907, 1908). Sampaio found fungus gardens in very young formicaries of the Brazilian Atta serdens, and von Jhering showed that the virgin female of this species, on leaving the nest for her marriage flight, carries in her infrabuccal pocket a pellet of hyphz taken from the fungus garden of the maternal formicary. This pellet is the unex- pelled refuse of her last meal. After fecundation she digs a cavity in the soil, closes its opening to the outside world and sets to work to found a colony. She spits out the pellet of hyphz and cultivates it, while she is at the same time laying eggs and rearing the larve. Von Ihering and Goeldi maintain that she crushes some of her eggs and uses them as a substratum for the incipient fungus garden. J. Huber | : O ANTS. © Gs describes the behavior of the young queen in greater detail and is able to trace the:development of the colony up to the hatching of the first brood of workers. He finds that the female expels the pellet from her buccal pocket the day following the nuptial flight. It is a little mass .5 mm. in diameter, white, yellowish or even black in color, and con- sists of fungus hyphz imbedded in the substances collected from the ant’s body by means of the strigils on her fore feet and thence depos- ited in her mouth. By the third day six to ten eggs are laid. At this time also the pellet begins to send out hyphe in all directions. The female separates the pellet into two masses on this or the following day. For the next ten to twelve days she lays about ten eggs daily, while the fungus flocculi grow larger and more numerous. At first ’ in the deserts of Fic. 198. Nest craters of Mellerius versicolor in a sandy “ draw’ Arizona. (Original.) the eggs and flocculi are kept separate, but they are soon brought together and at least a part of the eggs are placed on or among the Hocculi. Eight or ten days later the flocculi have become so numerous that they form when brought together a round or elliptical disk about Icm. in diameter. This disk is converted into a dish-shaped mass with central depression in which the eggs and larvee are thenceforth kept. The first larvee appear about fourteen to sixteen days after the Atta THE FUNGUS-GROWING ANTS. 33! female has completed her burrow, and the first pupe appear about a month after the inception of the colony. At this time the fungus garden has a diameter of only 2 cm. There are no “ kohlrabi”’ cor- puscles in the earlier stages, and when first seen they are at the periphery of the disk. A week later the pup begin to turn brown and in a few days the first workers hatch. Hence the time required for the estab- lishment of a colony under the most favorable conditions is about forty days. After this rapid survey of the matter, Huber asks the impor- tant question: How does the Atta female manage to keep the fungus alive and growing? Obviously the small amount of substance in the original pellet must soon be exhausted and the growing hyphe must Fic. 199. Male, dealated female, soldier and series of workers of Atta terana; natural size. (Photograph by A. L. Melander and C. T. Brues.) be supplied with nutriment from some other source. His interesting answer to this question may be given in his own words: “ After care- fully watching the ant for hours she will be seen suddenly to tear a little piece of the fungus from the garden with her mandibles and hold it against the tip of her gaster, which is bent forward for this purpose. At the same time she emits from her vent a clear yellowish or brownish droplet which is at once absorbed by the tuft of hyphz. Hereupon the tuft is again inserted, amid much feeling about with the antennz, in the garden, but usually not in the same spot from which it was taken, and is then patted in place by means of the fore feet. The fungus then sucks up the droplet more or less quickly. Often several of these 332 ANTS. drops may be clearly seen scattered over the young fungus garden. According to my observations, this performance is repeated usually once or twice an hour, and sometimes, to be sure, even more frequently. It can almost always be observed a number of times in succession when a mother ant that has no fungus, as sometimes happens in the cultures, is given a piece of fungus belonging to another Atta female or from an older colony. ‘The mother ant is visibly excited while she explores the gift with her antenne, and usually in a few minutes begins to divide it up and rebuild it. At such times she first applies each piece to her vent in the manner above described and drenches it with a fecal droplet.” Irom these observations Huber concludes that the droplet must be liquid excrement and that the fungus owes its growth to this method of. manuring. » asa “et - ‘ 5 “iss P: mS Senin h rs rede Fic. 228. Mimetic Staphylinids that live with ave been bre rom ant- Doryline ants. (Wasmann.) Facultative Adoption of queen (Most Formicidz) by workers of same species ' Obligatory Adoption of queen by workers of same species Obligatory Adoption of queen by workers of another species Temporary Social Parasitism y Slavery, or Dulosis ( Tutelary Parasitism) (Pupillary Parasitism ) Permanent Social Parasitism In the cases of temporary social parasitism the initiative of the queen ant is shown with great clearness. She actively seeks adoption in the colony of another species and permits the alien workers to bring up her first brood of young. The full benefits of this form of para- sitism, however, can be secured only by the elimination of the queen of the host species, for if this insect remained in the colony she would continue to produce young and the nurture bestowed on these by the workers would seriously interfere with the development of the para- site’s own progeny. As will be shown presently, different species seem to have developed different methods of getting rid of the host queen. RHE LEMPORARY SOCIAL@EAKASITES. 441 In the course of a year or two, the workers of these host species, being unable to reproduce, gradually die off and leave the parasitic queen and her offspring in possession of their nest, as a pure colony, and requiring no further assistance in its growth and development. ‘The colony becomes populous and aggressive, with nothing to indicate that it began life as a parasitic community. This method of colony forma- tion is adopted by some of the most powerful ants of temperate regions, and some of the most remarkable temporary parasites are members of the circumpolar genus Formica. Two groups of species in this genus, one embracing F. rufa and its allies, the other F. exsecta and its allies, ate especially interesting in this connection. The workers of these various species are very similar. They have red heads and thoraces and black or brown gasters, but the cospecific females may exhibit extraordinary differences in size, sculpture, pilosity and colora- tion. According to size they may be divided into microgynous species, in which the female is little larger and sometimes even smaller than the worker, and macrogynous species, with the female considerably larger than the worker as in the members of other Formica groups. It is a singular fact that although the species in both of these subgroups are widely distributed and often very common in certain localities, no one has ever seen one of the females founding a colony independently. It is known, however, that in some of the species the colonies are often enlarged by adoption of females of the same species or even of a dif- ferent subspecies. The microgynous species are most abundantly rep- resented in North America. It was a study of these which first led me to the discovery of temporary parasitism as a regular or normal occurrence and to make the prediction (1904/) that it would be found to occur very generally in the rufa and exsecta groups on both conti- nents. I will present the grounds for this prediction as succinctly as possible. 1. Microgynous Formice of the Rufa Group.—The commonest ants with minute females in the mountains of the Atlantic States are F. difficilis and its variety, consocians. The females of these are almost as small as the large workers and are fulvous yellow in color. In the Litchfield Hills of Connecticut I found that as a rule consocians lives in populous, independent formicaries under stones which it banks with plant débris. Like other members of the rufa group, it is a very pug- nacious ant. During the course of several summers a number of small, incipient colonies were found, containing a consocians queen associated with workers of F. incerta, a variety of schaufussi, and sometimes also with a few consocians workers. F. incerta is a cowardly ant which forms numerous rather small formicaries in the same locality. {le 442 ANT workers are reddish-yellow and of about the same size as the consocians queen. I naturally inferred that the mixed colonies must owe their origin to the adoption of consocians queens by incerta workers. A number of experiments were performed, which left no doubt concern- ing the correctness of this inference. The account of one of these experiments may be repeated here: July 21, 4.30 P. M., an artificially dealated consocians female was placed in a nest with twenty imcerta workers and several worker Fic. 262. Formica microgyna. (Original.) a, Dealated female; b, large worker drawn to same scale; c, head of worker; d, petiole of same from behind; e, petiole of female. cocoons taken from one of the most vigorous colonies found during the entire summer. The workers were unusually large and more like the workers of pure schaufussi, but with the coloration and pilosity of incerta. The female seemed disinclined to approach the workers, which were brooding over their cocoons, but she moved towards them when the illumination of the chamber was reversed. She was at once seized by a worker and showered with formic acid. She escaped to a THE EEMPRORARY SOCIAESRARASITES. 443 corner of the nest. By 5.15 P. M. she had returned, mounted the pile of cocoons and was licking the workers, who were submitting to this treatment as if it were a matter of course. A few moments later she fed one of the workers and then kept alternating between feeding and caressing them with comical rapidity and perseverance. The colony was watched till 7.45 P. M., but no hostilities were seen. July 22, 7 A. M.: The previous night had been cold and the female seemed to have passed it hanging from the roof pane in a corner of the nest. Later, as it grew warmer, she returned to the incerta and their brood, caressed and fed the workers and took food from their lips. Only once during the day was a worker seen to tug for a few moments at one of her antenne. On the four following days (July 23 to 26) no hostilities were observed. The consocians female had been definitively adopted. Numerous observations in the field have convinced me that the queen soon after her adoption lays eggs, the larve hatching from which are reared by the incerta workers. In this manner a mixed colony arises. While the queen keeps on laying eggs and producing more workers, the incerta gradually die of old age. Then, of course, a pure colony remains, and the consocians workers have become sufficiently numerous to enlarge and defend the nest and care for their queen and successive broods of their own species. The purpose of adoption and the signification of the small size and yellow color of the female are apparent. The queen pursues the same tactics as some of the myrme- cophilous beetles (Lomechusa, Atemeles, etc.) described in a previous chapter. She ingratiates herself with the workers by means of her mimetic resemblance to them, by her conciliatory and passive demeanor and by her neutral or soothing odor, and is thus able to exploit their blind philoprogenitive instincts for her own advantage and that of her offspring. Since she is thereby relieved of the necessity of nourishing her young with substances elaborated from her own tissues, she can be of diminutive stature, and this, in turn, represents a saving to her parental colony, for it is thus enabled to rear on a given amount of food a much greater number of queens than the macrogynous species. As a matter of fact, the adult consocians colony produces an enormous number of these dwarf females. One important problem in the parasitism of consocians remains to be elucidated: What becomes of the mother queen of the incerta colony ? Several possible answers suggest themselves. The consocians queen may succeed in obtaining adoption only in moribund and queenless colonies, or if she enters colonies provided with a queen, this insect may voluntarily forsake the nest, or she may be driven away or killed 444 ANTS. by her own workers or by the intrusive queen. Observations on arti- ficial colonies show that the consocians queen treats the host queen with indifference, even after she has been confined in the same nest for Over a year, or as if she were one of the workers. Moreover, the incerta queen displays no inclination to forsake her colony, and no hostilities develop between her and her own workers. I deem it prob- able, therefore, that the parasite instinctively seeks out some impov- erished or queenless colony of the host species. We shall see, however, that this custom is by no means universal among the temporary parasites. Other North American Formice of the rufa group known to have diminutive females as small as those of consocians or even smaller are: microgyna (Fig. 262), rasilis, nevadensis, impe.xa, nepticula and dako- tensis. As the nesting habit of these is very similar to that of con- socians, and as I have found in Colorado two small mixed nests of dakotensis and incerta, I believe that there is little doubt that all these species are temporary social parasites. 2. Macrogynous Formice of the Rufa Group.—The forms included here are the typical European rufa, with its subspecies, pratensis and truncicola, and in America the subspecies obscuriventris, obscuripes and integra, with several varieties, and the species ciliata, crinita, oreas, comata and specularis. In several of these forms the stature of the female is somewhat diminished and in ciliata (Fig. 263), crinita, etc., her color, pilosity or sculpturing are aberrant. Small mixed colonies of F. truncicola and fusca have been known for some years. Forel (1874) described one which he found near Loco, Switzerland; one was found by Zur Strassen in Saxony, and Was- mann (1901-02, 1905d) has recently found three others in Luxem- burg. These mixed colonies were originally regarded as accidental or abnormal occurrences, but my observations (1904h, 1906c) indi- cated very clearly that they are merely incipient and transitory stages in the normal life of the truncicola colony and that the queen of this species is a temporary parasite. After observing two of the mixed colonies in artificial nests Wasmann reached the same con- clusion. Recently (1908) Viehmeyer has shown that truncicola females are readily adopted by fusca workers. Now as the North American integra and its varieties, hemorrhoidalis and coloradensis, closely resemble the European truncicola in structure and nesting habit, and as I have succeeded in causing a female integra to be adopted by work- ers of subsericea, there can be little doubt that the huge formicaries of all these rufa forms have their beginnings in temporary parasitism. Finally, the species with rich red or yellow, very glabrous or unusually LAE BEMPORARY SOCIAL EAacAsITES. 445 hairy females, like ciliata, crinita, dakotensis and specularis, probably have similar habits. Muckermann, in fact, discovered in Wisconsin some five colonies of specularis mixed with subsericea, and with females of the former species only. Although Wasmann has endeay- ored to make out that these nests represented cases of incipient slavery, there can be no doubt that the observations, as they stand, will bear no such interpretation, but point rather to temporary social parasitism. Fic. 263. Formica ciliata. (Original.) a, Dedlated female; b, large worker drawn to same scale; c, head of worker; d, petiole of same seen from behind; e, petiole of female. There are no published observations on the origin of rufa and pratensis colonies. It is not improbable, however, that these ants in the early stages of colony formation are parasitic on fusca. In Switzerland, during the summer of 1907, I found on two or three occasions a recently killed, but not mutilated, pratensis queen in the recesses of a fusce nest, and Professor Escherich showed me a typical rufa queen which 446 ANTS: he found near Strasburg living with a small number of fusca workers.? These -facts, taken singly are rather insignificant, but conjointly they point very decidedly to the conclusion that most, if not all, the ants of the rufa group are temporary parasites. 3. The Formice of the Exsecta Group.—This group, which is char- acterized by having the head of the worker and female deeply excised behind, is represented in Europe by the typical F’. exsecta, its subspecies pressilabris and F. suecica, a species recently discovered in Sweden by Adlerz; in North America by F. exsectoides, its subspecies opaciventris and F. ulkei. These ants build mound nests, often several to a colony, and sometimes of large size, especially in America (Figs. 109 and 181). The females are large in our forms, but smaller in exsecta and pressilabris, and scarcely larger than the workers in suecica. There is indirect evidence that all of these ants, except ulkei, which has not yet been observed in nature, are temporary parasites. In his ‘““Fourmis de la Suisse” Forel described two small mixed colonies of evsecta-fusca and two of exsectopressilabris-fusca. During the sum- mer of 1907 I also found a mixed colony of the latter composition, occupying a single small mound, on the slopes of Monte Generoso. Similar mixed colonies of exsectoides and subsericea have been repeatedly observed in the Eastern States. Forel observed one at Hartford, Conn., and the late Rev. P. J. Schmitt found five near Beatty, Pa. These invariably contained queens of esectoides only, and all were obviously incipient, since they comprised not more than fifty workers, both species included. I have found two of these mixed colonies at Colebrook, Conn., and have observed the behavior of an exsectoides queen when she is introduced into a colony of subsericea workers. She is very passive and conciliatory and in one of my experi- ments was readily adopted by the alien colony. Considering the close taxonomic affinities of F. ulkei to exsectoides and the diminutive stature of the female swecica, we may assume that these species can hardly differ in their habits from the other members of the e.rsecta group. 4. Bothriomyrmex.—Among the mixed colonies recorded by Forel (1874) there was one composed of two species of Dolichoderine ants, Bothriomyrmex meridionalis and Tapinoma erraticum, which he found on the Borromean Islands in the Lago Maggiore. This colony, like the colonies of truncicola-fusca and exsecta-fusca above mentioned, had * During the past summer (1909) I found three mixed colonies of F. rufa and fusca, which show very clearly that the former is a temporary parasite like consocians. Two of these, discovered in the Turtman Valley, in Switzer- land, each consisted of a rufa queen and several fusca workers, the third, found at Zermatt, contained besides a rufa queen a few workers of the same species. PHESEEMPORARY SOCIAESPARASITES. 447 been regarded as an exceptional or abnormal occurrence till very recently, when Santschi (1906, Forel, 1906d) discovered several mixed colonies of varieties of these species (B. atlantis and T. nigerrimum ) in the Tunisian desert, and showed by a series of surprising observa- tions that they were cases of temporary parasitism. The Bothrio- myrmex queen, on descending from her nuptial flight, wanders about on the ground till she finds a Tapinoma nest and then permits herself to be seized and “arrested” by the Tapinoma workers. These then proceed to drag her into their burrow by her legs and antenne. After entering the nest the parasite may be attacked from time to time by the workers, but she takes refuge on the brood or on the back of the Tapi- noma queen. In either of these positions she seems to be quite immune from attack. This observation throws light on certain peculiarities in the behavior of F. consocians, for this insect also mounts the brood pile as soon as she enters the incerta nest and when in this position is never molested by the alien workers. Santschi observed that the Bothriomyrme.x queen often spends long hours on the back of the large Tapinoma queen and that while she is in this position she busies herself with sawing off the head of her host! By the time she has succeeded in accomplishing this cruel feat, she has acquired the nest odor and is adopted by the Tapinoma workers in the place of their unfortunate mother. The parasite thereupon proceeds to keep them busy bringing up her brood. They eventually die of old age and the nest then becomes the property of a thriving, pure colony of Bothriomyrmex atlantis. The queen of this species, as Santschi has shown, is mimetic like that of consocians, being but little larger than the Tapinoma workers and provided with an odor like that of the host species, though this odor is lacking in her own workers. Santschi has thus been able actually to witness the elimination of the host queen. But the method employed by Bothriomyrme.x in accomplishing this is not universal among parasitic species, as we shall see when we come to his interesting observations on the permanent social parasite Wheeleriella. 5. Aphaznogaster.— The female of the Myrmicine ant 4 phenogaster tennesseensis (Fig. 264), in being deep red and of very small size, with a glabrous body and huge, flattened epinotal spines protecting the vul- nerable abdominal pedicel, is so unlike the females of any other members of the genus Aphenogaster that she was originally described by Mayr as the type of a distinct species (4. Jevis). These peculiarities suggest temporary parasitism and this is borne out by the observations of Schmitt and myself (1901c). Schmitt found near Beatty, Pa., a small mixed colony of A. tennesseensis and A. picea, a variety of fulva and one of the commonest ants in the Northern States. He was impressed 448 ANTS. with the fact that the nest of this colony was under a stone, because tennesseensis normally nests only in rotting wood. During the summer of 1902 I found near Rockford, Ill., two mixed colonies like that observed by Schmitt, except that the variety picea was represented by the variety rudis. Both colonies were of small size and situated under stones. In one of them a tennesseensis queen was unearthed. There can be little doubt, therefore, that the glabrous queens seek out small nests of some variety of fulva and start their colonies in them just as consocians does in the nest of incerta. This habit is also indicated by the sporadic distribution of tennesseensis and its occurrence only in Fic. 264. In the first vertical row: virgin and dealated female of Aphenogaster tennesseensis ; in the second vertical row: male and two workers of the same spe- cles; remaining figures: virgin female, male and workers of Aphenogaster fulva. 1%. (Original.) localities where some form of fulva is abundant. After the extinction of the host workers the pure tennesseensis colony evidently migrates into old logs and stumps and there attains its full development. A single adult colony of this species, like that of consocians, produces a great number of small females, whereas the non-parasitic Apheno- gaster have all they can do to bring up a few of their large queens. Another A phenogaster (A. marie), which is a rare species taken only in the Atlantic States and structurally closely related to tennesseensis, also has very small females (4.5 mm. long), with large epinotal spines. It is, in all probability, like this species, a temporary parasite in nests of A. fulva. 6. Oxygyne.—lorel has assigned to a special subgenus, Orygyne, a series of Cremastogaster species (emme, ebenina, soror, travancoren- PAE PEMPORARY .SOCTAESPARASITES. 449 sis, dalyi, aberrans, ranavolone, agnetis, daisyt, marthe and depressa) from Madagascar, India and the Malayan region, because they have unusually small, glabrous females, with falcate, pointed or very oblique mandibles, abbreviated frontal carine and sometimes very. strong epinotal spines and a robust abdominal pedicel. The workers of these various forms are much like those of the ordinary species of Cremas- togaster with large queens. In one species of Oxrygyne (ranavalone, Fig. 265), according to Emery (1897a), the aged female has the gaster enormously enlarged and subspherical like that of the mother queens of the permanently parasitic dAnergates (Fig. 279, b). Forel has sug- gested that the structural peculiarities of the Orygyne queens are prob- ably correlated with peculiarities of habit. Comparison of a series of these insects, kindly given me by the eminent myrmecologist, with the microgynes of Formica and Aphenogaster, convinces me that they must be temp- orary parasites on other species of Cremastogaster. Their sickle-shaped mandi- bles, so much like those of Polyergus and Strongylo- gnathus (Figs. 271, 273) point to a method of assas- sinating the host queen similar to that employed by Bothriomyrmex. The sug- gestion here advanced would, at any rate, consti- tute a good working hy- : 3 ‘ Fic. 265. Female of Oxygyne ranavalone. pothesis in carrying on (Emery.) a, Virgin female, showing falcate mandibles; b, fertile female with enlarged ova- further researches on the Bestand caster! species of Oxygyne. While studying the foregoing known and hypothetical cases of tem- porary parasitism, one’s attention is arrested by the following consid- erations of general interest : t. Temporary social parasitism occurs in several unrelated species belonging to three of the five subfamilies of Formicidz, and must therefore have originated independently on more than one occasion in. the past history of the family. 2. Parasite and host are always members of the same genus or of closely allied genera. This seems to be necessary, because such inti- 30 450 ANTS. mate symbiotic relations would be impossible between species of very diverse habits. 3. The host, being in all cases a very widely distributed and abun- dant species, forms an omnipresent substratum, so to speak, on which the sporadic parasitic forms manage to graft themselves. That the latter are either rare ants or abundant only in circumscribed localities, suggests that the adoption of their queens by alien workers is beset with many obstacles. The colonies of some of these ants, like those of F. rufa and exsectoides, when once established, may, indeed, grow to enormous dimensions and extend themselves over a number of nests by repeatedly adopting fertile queens of their own species, but the geo- graphical distribution of these forms is never as continuous and uniform as that of the host. 4. The hosts of the temporary parasites are, as a rule, cowardly and prolific species. Both of these peculiarities fit them for being exploited, not only by these parasites, but also by the slave-making ants. And as ant colonies are the more timid and conciliatory the smaller they are, we find that the parasites prefer incipient or moribund colonies to the larger and more aggressive communities of the host species. 5. Temporary parasitism, being transitory, has not, as a rule, pro- foundly affected the morphological characters of the species. The workers, in fact, have remained unaffected, though the female, in whom the peculiar habit centers, certainly shows structural and instinc- tive peculiarities that can be interpreted only as adaptations to a para- sitic life. Such are the dwarf stature, the mimetic coloration, the long yellow hairs of F. ciliata and crinita, so like the trichomes of many myrmecophilous beetles, and the conciliatory and insinuating behavior. 6. The production of a great number of dwarf females by pure adult colonies of F. consocians and A. tennesseensis bears a very inter- esting and suggestive resemblance to the production of a vast number of minute eggs by many nonsocial parasites like the ascarids, cestodes, Sacculina, etc. This has been universally regarded as an adaptation to the great destruction of individuals incident to the complicated and arduous efforts of the parasite to get a foothold on or in its host. The exception to this rule furnished by the macrogynous Formice of the rufa and exsecta groups may be due to the fact that in these species the queens are so often adopted by workers of their own opulent colo- nies, and the occasions on which they actually need to found colonies with the aid of alien species so infrequent, that they have not become. dwarfed in stature and have not developed pronounced mimetic or myrmecophilous characters. THE MIEMPORARY SOCIAESPARASITES. 451 _7. The elimination of the host queen in colonies invaded by the temporary parasites destroys the reproductive powers of the host colony. Hence this form of parasitism is strictly comparable to the castration induced in their hosts by many nonsocial parasites like Sacculina and Stylops. We may therefore designate cases like that of Bothriomyrmex and Tapinoma as examples of social castration. This term, as will be shown in the sequel, will apply also to most of the ~ mixed colonies formed by dulosis and permanent social parasitism. 8. The future development of the temporary parasites may be sup- posed to lead most naturally in the direction of permanent parasitism. This, however, can eventuate only if the species limits and accelerates the growth of its colonies or foists itself only on well-developed colonies of the host. Contrariwise the parasite would outgrow the host colony, or the latter would die off prematurely unless its queen were retained in the nest. We shall see that such Malthusian practices are actually carried out by the permanent social parasites and have resulted in the complete extinction of the unnecessary worker caste. CHAP TER ee ws THE SANGUINARY ANTS, OR FACULTATIVE SLAVE-MAKERS. “TY shall next bring forward a scene still more astonishing, which at first, perhaps, you will be disposed to regard as the mere illusion of a lively imagina- tion. What will you say when I tell you that certain ants are affirmed to sally forth from their nests on predatory expeditions, for the singular purpose of pro- curing slaves to employ in their domestic business; and that these ants are usually a ruddy race, while their slaves themselves are black.”—Kirby & Spence, “ Entomology,” 6th ed., 1846. “Ce fait choquant et hideux, tachons du moins de le comprendre. II est propre a quelques espéces; il est un incident particulier, un cas exceptionnel, mais rentrant au total dans une loi générale de la vie des fourmis.”—Michelet, “L’Insecte,’” 1884. The mixed colonies described in the last chapter are transitory consociations of two species merely formed as a means of establishing colonies, which, in their adult stages, are able to hold their own unaided in the struggle for existence. The cases to be described in this and the following chapters are more permanent symbiotic alliances, though they differ so much among themselves that it is difficult to include them in a single definition. With one or two exceptions, to be described in their proper places, these mixed colonies may be said to be formed by dulosis, or slavery, and this peculiar phenomenon may be defined as the habit of making periodical raids on particular alien species, seizing their worker larve and pupe and rearing and adopting a portion of these. But neither the periodical raid nor the rearing of the alien ants alone constitutes slavery. Many of the species of Eciton make such raids on other ants and pillage their nests, but they attack any terrestrial ants indiscriminately and the young are all devoured. And even if some of these were permitted to hatch, a mixed colony would not result, because the Ecitons have no fixed home, but wander from place to place. Moreover, although the mixed dulotic colony certainly owes its origin to the rearing and adopting of the alien young, many nondulotic ants will do this if such young are placed in or near their nests. Forel (1874) long ago formed mixed colonies in this way, and more recently Miss Fielde (1903c) has shown the extreme to which this experiment can be carried. She succeeded in making triple and quadruple mixed colonies of ants belonging not only to different genera, but also to different subfamilies (Fig. 266). One 452 THE SANGUINARY ANTS. 453 of her experiments resulted in the formation of a colony com- prising workers of Stigmatomma pallipes (Ponerine), Formica sub- sericea (Camponotine), and Aphenogaster fulva (Myrmicine) ; another was made up of such heterogeneous components as Cai- ponotus pennsylvanicus, Formica sanguinea, A. fulva and Cremasto- gaster lineolata. In these artificial mixed colonies she found that Fic. 266. Mixed colony consisting of workers of Camponotus pennsylvanicus, Formica subsericea and Aphenogaster picea reared by Miss A. M. Fielde. Photo- graph by J. G. Hubbard and Dr. O. S. Strong.) “there is a close affiliation of ants of different species. Those of dif- ferent subfamilies sometimes lick one another. Introduced young 1s carried about and taken care of without regard to its origin. Ants of one genus accept regurgitated food from those of another genus.” She gives the following recipe for producing such colonies: “If one or more individuals, of each species that is to be represented in thi future mixed nest, be sequestered within twelve hours after hatching, 454 ANTS. and each ant so sequestered touch all the others with its antenne during the three ensuing days, these ants will live amicably together there- after, although they be of different colonies, varieties, species, genera or subfamilies.” Such experiments are of the greatest interest as showing the importance of the philoprogenitive instincts and the uni- formity of their development in the workers of the most diverse species of Formicidz, and adequately account for the presence of slaves in the mixed colonies, but they cannot be said to throw any light on the other essential peculiarities of slavery, namely, the raiding habit and its con- centration on particular species. These peculiarities, as we shall see, must be referred to a different source. Like the temporary parasites, with the possible exception of Owvy- gyne, the slave-making ants are confined to the north temperate zone and extend far up into boreal and alpine regions. Indeed, it is not improbable that the development of the slave-making habit is connected in some way with the long winters, short summers and small amount of food in the subarctic belt. All the known slave-makers are members of four genera: Formica (the species of the sanguinea group), Poly- ergus, Strongylognathus and Harpagoxenus, the first two comprising Camponotine, the last two Myrmicine ants. The habits of Harpa- govenus are imperfectly known, but the other genera form an inter- esting series, in which Formica sanguinea represents the slave-making habit in process of development, Polyergus its most specialized and Strongylognathus its involutionary or degenerate development. F. san- guinea and Polyergus have been studied by many observers. As Huber’s and Forel’s brilliant accounts of these ants have been exten- sively quoted in many accessible works, it will not be necessary to repeat them here. I shall therefore confine myself to a brief enumeration of the known slave-makers and to some observations of my own on the American forms. This will be the more advisable, since there are few published observations on our sanguinea and almost none on the expe- ditions of our Polyergus. 1. The European Sanguinea.—The typical form of this, the san- guinary, or blood-red slave-maker, which is easily distinguished by the median notch in the anterior border of its clypeus, is common through- out temperate Europe and probably also in northern Asia (Fig. 267). In Japan, the easternmost portion of its range, it has developed at least one variety, fusciceps. In Europe it lives under stones, in logs and stumps, or about the roots of plants and often accumulates considerable vegetable débris about its nest entrances. Those who have studied its habits are unanimous in regarding it as one of the most gifted and versatile of ants. It is certainly one of the most belligerent, and, at THE SANGUINARY ANTS. 45 Wr least when living in large colonies, assails any intruder with its mandibles, simultaneously turning the tip of its gaster forward and injecting formic acid into the wound. F. sanguinea is, to use Was- mann’s expression, a facultative slave-holder, for it sometimes lives in independent, slaveless colonies. As it has lost none of its essential formicine instincts, it is able to excavate a nest, secure its own food and bring up its own young without the aid of slaves. But even when these auxiliaries are present, much, if not most, of the labor of the Fic. 267. The typical Formica sanguinea of Europe. (Original.) a, Dealated fe- male; b, pseudogyne; c, worker; d, head of same, showing the notched clypeus. colony devolves on the sanguinea, and there is nothing to show that the slaves contribute anything more to the communal activities than would be contributed by an equal number of small sanguinea workers. The normal slaves of . sanguinea are members of the F. fusca group, namely, fusca, glebaria, rubescens, gagates, rufibarbis and cinerea, but it occasionally enslaves members of the rufa group (rufa, pratensis and their varieties). Wasmann (1902a) has published sta- tistics of 410 sanguinea colonies found nesting within an area of 4 sq. kilom. in Holland. In this region the ratio of slave-containing to slaveless colonies was as 40:1; that of colonies containing the normal slaves (fusca, rufibarbis) to those with pratensis and rufopratensis as 78.6:1; and that of the nests containing fusca only, rufibarbis only or both of these forms as 70.5:3. There can be no doubt that the typical fusca is the form most frequently enslaved in northern Europe and at 450 ANTS. higher elevations in the Alps, but in the valleys of Switzerland the varieties glebaria and rubescens and F. cinerea are the commonest slaves. In other words, sanguinea usually enslaves the common fusca form of its environment, and the ability of the slave-maker to live in a variety of different environments accounts for the diversity of its slaves. Wasmann’s statistics therefore apply only to certain regions, as he himself admits, for he calls attention to the fact that in the vicinity of Luxemburg rufibarbis furnishes a greater number of slaves than in Holland. Forel (1874) mentions a number of slaveless colonies of sanguinea which he found at Maloja at the end of the Engadin, and near the same place (at Samaden and St. Moritz) I found two large areas in which the proportion of slaveless to slave-containing colonies must have been fully as 40:1, or the reverse of Wasmann’s ratio. But even the slave-holding colonies of the European sanguinea con- tain comparatively few slaves, the average ratio of the sanguinea workers to that of the auxiliaries in 100 nests near Limburg being, according to Wasmann (1891) 3-5:1. He maintains that the youngest colonies, as a rule, have the greatest number of slaves and that it is usually the oldest colonies that are slaveless. In this respect the san- guinea colonies bear an interesting resemblance to those of the tem- porary parasites. The tactics of F. sanguinea in procyring its slaves have been vividly described by Huber (1810), Forel (1874) and Wasmann (1891/1). The sorties occur in July and August after the marriage flight of the slave species has been celebrated and when only workers and mother queens are left in their formicaries. According to Forel the expedi- tions are infrequent—‘ scarcely more than two or three a year to a colony.”” The army of workers usually starts out in the morning and returns in the afternoon, but this depends on the distance of the san- guinea nest from the nest to be plundered. Sometimes the slave- makers postpone their sorties till three or four o’clock in the afternoon. On rare occasions they may pillage two different colonies in succession before going home. The sanguinea army leaves its nest in a straggling, open phalanx sometimes a few meters broad and often in several com- panies or detachments. These move to the nest to be pillaged over the directest route permitted by the often numerous obstacles in their path. As the forefront of the army is not headed by one or a few workers that might serve as guides, but is continually changing, some dropping back while others move forward to take their places, it is not easy to understand how the whole body is able to go so directly to the nest of the slave species, especially when this nest is situated, as is often the case, at a distance of 50 or 100 m. We must suppose THE SANGUINARY ANTS. 457 that the colony has acquired a knowledge of the precise location of the various nests of the slave species within an area of a hundred meters or more of its own nest. This knowledge is probably acquired by scouts leaving the nest singly and from time to time for a period of several weeks, and these scouts must be sufficiently numerous to deter- mine the movements of the whole worker body when it leaves the nest. This presupposes not only a high development of memory, but some form of communication, for the nest attacked is usually one of many lying in different directions from the sanguinea nest. When the first workers arrive at the nest to be pillaged, they do not enter it at once, but surround it and wait till the other detachments arrive. In the meantime the fusca or rufibarbis scent their approach- ing foes and either prepare to defend their nest or seize their young and try to break through the cordon of sanguinea and escape. They scramble up the grass-blades with their larvee and pupz in their jaws or make off over the ground. The sanguinary ants, however, intercept them, snatch away their charges and begin to pour into the entrances of the nest. Soon they issue forth one by one with the remaining larve and pupz and start for home. They turn and kill the workers of the slave-species only when these offer hostile resistance. The troop of cocoon-laden sanguinea straggle back to their nest, while the bereft ants slowly enter their pillaged formicary and take up the nurture of the few remaining young or await the appearance of future broods. Forel is of the opinion that many of the young brought home by the sanguinea are eaten, for the number of those which eventually hatch and become auxiliaries is very small compared with the number pillaged during the course of the summer. Wasmann believes, however, that the forays take place for the specific purpose of obtaining young to rear. This seems to be disproved by the fact that even small sanguinea colo- nies are quite able to get along without slaves and by the insignificant number of these individuals in many nests. Darwin has interpreted the surviving and adopted workers as a kind of by-product, or as rep- resenting food which the ants failed to eat at the proper time, and such they would appear to be in the adult colony, though, as we shall see, they have an additional significance as the result of an instinct inherited by the sanguinea workers from their queen. That the foray is, to some extent at least, due to the promptings of hunger, seems to be shown by the fact that sanguinea sometimes plunders the nests of ants which it could not adopt as slaves. Thus Forel and others have described forays of sanguinea on Lasius niger and flavus. Not only are the forays of sanguinea very similar to those of the nest-pillaging Ecitons, but the former ant also resembles the rapacious 455 ANTS. Dorylines in its frequent change of dwelling. I have already mentioned the summer and winter nests of sanguinea, but this ant is also fond of changing its habitation in the same wood or field and of moving into nests which it has pillaged. Hence one often encounters sanguinea workers: in the act of moving their young or sexual forms to new quarters. On such occasions they also carry their slaves in the same manner as they carry small workers of their own species; the ant carried being held by the mandibles while she coils herself up and remains motionless under the head and thorax of her carrier. It is not always easy at first sight to distinguish these changes of dwelling from dulotic expeditions. 2. The American Sanguinea.—The typical sanguinea does not occur in North America, but in its stead we have no less than six subspecies and varieties: aserva, rubicunda, subnuda, subintegra (Fig. 268), pube- rula and obtusopilosa, and two species: pergandei and munda, which, however, might be regarded merely as extreme subspecies. All of these forms have the clypeal border notched, a character which serves to distinguish them from our numerous other Formice of the rufa, exsecta, fusca and pallide-fulva groups. F. munda is confined to the Rocky Mountains, where it lives in rather small colonies and never makes slaves. fF. pergandei is a more widely distributed species, but seems to be very rare, as only a few of its colonies have been seen. The one from which the types of the species were taken near Wash- ington, D. C., contained also workers of F. pallide-fulva, and one which I found near Colorado Springs contained several workers of subpolita. The sanguinea subspecies and varieties cited above present a maze extremely difficult to disentangle taxonomically, and although I have made many observations on dozens of colonies in different parts of the country, I am quite unable to define their ethological peculiarities. I have no doubt that such peculiarities exist, but their accurate definition will require years of observation overa great area.’ Some of the forms, such as rubicunda, aserva and subnuda are preeminently boreal or alpine, others, like subintegra and puberula prefer warmer latitudes and lower altitudes. In this general account I shall not endeavor to distin- guish further between the habits of the various forms, but compare them as a whole with the single European type. This comparison will show that the American forms are peculiar in more than one particular. The colonies of our sanguinea are quite as frequently slaveless as *I have recently found (1908f) that the Workers of one of our subspecies, aserva, are not slave-makers. The queens of this form of sanguinea establish their colonies by kidnapping the pupe of F. glacialis, but the workers do not inherit this instinct. Hence the old colonies of aserva are pure, as Forel has observed (1900¢). THE SANGUINARY ANTS: 459 Fic. 268. Dealated queens, workers and cocoons of Formica subintegra, neat twice the natural size. (Photograph by J. G. Hubbard and Dr. O. S. Strong. 460 ANTS. those of the typical form. In the Ute Pass and Florissant Canyon of Colorado I have found localities abounding in slaveless colonies like the localities in Maloja, Samaden and St. Moritz in the Engadin. As a rule, however, the colonies contain slaves and the ratio of these to the sanguinea is usually much greater than it is in Europe. The aver- age ratio in seventy colonies on which I have made notes is 1.5 sanguinea to 4.5 slaves, which is practically the opposite of the ratio given by Wasmann for the European form. I have been unable to confirm his statement that the number of slaves decreases with the size of the colony, as I have seen many large colonies with numerous slaves and many small ones with few or none at all. As the typical forms of the fusca group of Formice ,are confined to Europe, our sanguinea is found to enslave our peculiarly American varieties of the same group. Of these we have an extensive series, some of which are very local in their distribution. But still another group of Formice, that of pallide-fulva, not represented in Europe, is compelled to contribute slaves to our sanguinea. This group, including the typical pallide-fulva, schaufussi, incerta, nitidiventris, fuscata, etc., occurs only east of the Rocky Mountains. The following list includes the names of the fusca and pallide-fulva forms (cited in the order of their frequency) which I have taken as auxiliaries in the nests of our ‘various sanguinea: 1. F. aserva—slaves: F. subsericea, F. glacialis. 2. F. rubicunda—slaves: F. subsericea, neorufibarbis, subenescens, fuscata, neogagates. 3. F. subnuda—slaves: F. subsericea, argentata. 4. F. subintegra—slaves: F. subsericea, glacialis, subpolita, sub- @enescens, nitidiventris, schaufussi, incerta, fuscata, neogagates. 5. Ff. puberula—slaves: F. subsericea, argentata, subpolita, neoci- nerea, neoclara, neogagates. 6. F. obtusopilosa—slave: F. argentata. 7. F. pergandei—slaves: F. pallide-fulva, subpolita. It will be seen that of the fourteen different slave forms in this list F. subsericea (Fig. 269) is far and away the most common. This, F. glacialis and argentata are also the most closely allied to the European fusca. The predominance of subsericea as a slave is due to its being the most abundant and widely distributed ant of its group in North America. The other forms are local: F. cinerea, e. g., occurring only in sunny meadows from Colorado to Illinois; neoru- fibarbis and glacialis in alpine and boreal regions; neoclara along the sandy water-courses of the Rocky Mountains; subenescens in the shady, deciduous woods of Wisconsin and the neighboring states, THE SANGUINARY ANTS. 401 etc. These forms are enslaved only when sanguinea happens to be living in the particular regions where they are the dominant fusca forms. But as these regions are usually inhabited by subsericea to some extent, this ant never enjoys complete immunity if there are any slave-makers in the neighborhood. Occasionally sanguinea colonies are found to contain slaves of two or even three fusca or pallide-fulva forms. One small colony observed at the edge of a meadow in Colo- rado contained neoclara, neocinerea and nitidiventris workers in nearly equal proportions. According to my observations, our sanguinea makes many more raids during the course of the summer than her European prototype. On Fic. 269. Deadlated females, workers, larve, nude and covered pupe of Formica subsericea, nearly twice the natural size. (Photograph by J. G. Hubbard and DraO: S. Strong.) several occasions I have seen a colony plunder a subsericea nest nearly every day for a week or a fortnight. Provided Forel’s statement in regard to the typical sanguinea is correct, this peculiarity of the Amer- ican forms would account for its having so many more slaves. This, however, is not the only reason: though individually smaller as a rule, less pugnacious and living in smaller and obscurer formicaries, our sanguinea enslaves fusca forms which are much more cowardly and 462 ANTS. gv tes » a4 7 : He; docile than the typical /-uropean fusca and rufibarbis. This latter is, © indeed, very far from being a gentle and tractable ant. | ‘i The slave-making tactics of our sanguinary ants are in the main very similar to those of the European form. They usually start on their raids in the morning and may return laden with booty before noon, or their expeditions may drag along for the remainder of the day or even over the following day if the colony to be pillaged is at some distance, of large size and belligerent, or contains a great number of larve and pupe. Sometimes, however, the sortie is postponed till the afternoon. This was the case in the following instance which I take from a number of similar expeditions of which Ihave kept notes: Rockford, Ill., July 14. At 4 P. M. I located a large colony of F; fuscata which was nesting under a piece of wood in a loose hazel thicket. On removing the wood I found a large, flat chamber, from the bottom of which a single opening 2 cm. in diameter led down into the subterranean galleries of the nest. The chamber was full of fus- cata workers, winged females, larve and naked pupz and the whole assemblage hastily poured down the opening out of sight. Looking up I saw a scattered army of rubicunda rapidly approaching the nest. When they reached the circle of grass immediately surrounding the earth just exposed by the removal of the wood, they stopped and com- ‘pletely surrounded the spot. They waited or kept advancing and retreating, but never entered the hole until the rear detachment had arrived. Even after the whole army, numbering at least 400 rubicunda, had assembled, they kept up this advancing and retreating movement for fully fifteen minutes, as if fearing the fuscata, which in the meantime were hiding in their nest. Now and then a rubicunda, bolder than her sisters, would enter the hole, but dart out again immediately. After twenty minutes more of this manceuvring, however, the slave-makers grew bolder and began to pour into the opening. [For some time longer and at intervals of three to five minutes a rubicunda would emerge from the nest with a larva or pupa and start for home. As soon as one of these lucky individuals appeared, four or five of the workers on the outside of the nest would try to wrest away her booty. Sometimes one of them was successful and at once started off for her nest. Finally, at 4.35 P. M., thirty-five minutes after the nest had been sur- rounded, a winged fuscata female shot out of the opening, immediately followed by fully fifty others and a flood of fuscata workers carrying larve and pupe in their jaws. » They scattered at once in all directions, breaking through the rubicunda cordon and making for the grass beyond. The rubicunda instantly fell upon both females and workers and tore the larve and pupz from the jaws of the latter. The long- Fie THE SANGUINARY ANTS. 463 a legged fuscata, however, all managed to escape unscathed and with a few of their young. The wildest excitement prevailed till all the fuscata were out of the nest, but not one of them remained on the premises ten minutes after the first winged female had emerged from the opening. The rubicunda then proceeded to pillage the nest at their leisure, bring- ing out the deserted larve and pupz and making for home. I followed them as they hurried off over a very tortuous path under the hazel bushes to their formicary, which was covered by a pile of twigs and dead leaves, some 40 meters from the nest they had pillaged. Loitering about the rubicunda nest were a number of slaves, large subsericea and an occasional small fuscata. These seemed to show great interest in the larvee and pupe with which the rubicunda were constantly arriving. I returned to the fuscata nest. It was now 5.25 P. M. and the last straggling rubicunda were just starting home with the last of the pupe. In the meantime the fuscata had established themselves under a bunch of dead leaves around the roots of a hazel bush about two meters from their old quarters. They had transported thither the rescued larvee and pupz and were very busy carrying in the workers and females that had strayed about in the grass. This was done with marvellous dis- patch and precision. The whole raid had been accomplished in an hour and a half, without the death or injury of a single ant, showing that the rubicunda, like her European congener, accomplishes her purpose by surprising and terrorizing rather than by killing the colonies on which she preys. The unharmed fuscata could at once set to work to raise another large brood to be pillaged in turn at a later date, and this is as it should be—from the rubicunda point of view. F. fuscata, like the other members of the pallide-fulva- group, is even more cowardly than subsericea, so that the raid above described is not typical in all respects. Large swbsericea or neoclara colonies offer a much more hostile resistance to the invading slave-makers, and the battle may continue for hours or even days before the latter succeed in pillaging the nest. At such times the sanguinea will not hesitate to use her mandibles and the ground may be strewn with the corpses of both species. Colonies that have been attacked and_ plundered repeatedly season after season seem to submit to the affliction more passively than those attacked for the first time. Owing to the great differences in the size and condition of the colonies of both the slaves and the slave-makers, the forays of the latter present an enormous range of variability, and it would be desirable to record many more observations on them, both in Europe and North America. Like the typical sanguinea, our American forms may also pillage the nests of ants belonging to strange genera. I once witnessed a 404 ANTS. ridiculous foray of a large rubicunda colony on a woodland variety of Myrmica scabrinodis near Rockford, Ill. The foray was carried out exactly as if it had been directed against one of the normal auxiliary species. After killing or putting to flight the scabrinodis, the rubicunda returned to their nest with the small larve and pupe of an ant belong- ing to an entirely different subfamily. In another rubicunda nest in the same wood, | found two of the flat chambers full of uninjured pup of scabrinodis. Vhese had evidently been set apart from the rubicunda young and from those of the normal auxiliaries (in this case F. subenescens). Forel (1874) made a similar observation on a san- guinea nest in which Lasius niger and L. flavus cocoons had been stacked up in a chamber by themselves. Near Rockford, IIl., a large number of subintegra workers were seen one morning to make a normal assault on a Lasius americanus colony and to return with a number of cocoons in their jaws and many Lasius workers hanging to their legs and antennz. ‘These forays, which are probably not at all infrequent and are, moreover, undoubtedly undertaken by colonies of considerable size and of some experience in capturing the normal auxiliaries, point to hunger as one of the impulses which compels them to undertake their expeditions. We can hardly suppose that sanguinea workers, even after some practice in making slaves, have any definite ideal asso- ciation between the kidnapped pupz and the slaves that hatch from them or they would not make forays on such unsuitable species. 3. The Founding of the Sanguinea Colony.—How do the mixed colonies of the facultative slave-makers arise? As no one had been able to observe the behavior of the sanguinea queen just after descend- ing from her nuptial flight and while establishing her colony, Forel and Wasmann supposed that she must either be adopted by some colony of the slave species or bring up unaided a brood of her own which could then by dulosis make the mixed colony. During the summer of 1905 I performed a number of experiments on young, artificially dealated queens, introducing them into nests containing several sub- sericea workers with their brood. I here transcribe the account of one of these experiments from my paper ‘On the Founding of Colonies by Queen Ants” (1906c): July 8,9 A. M. A rubicunda female was placed in a nest contain- ing 33 subsericea workers, small and large, 150 cocoons, and a few larve. The workers at once seized their cocoons and fled into the light chamber. One or two of them attacked the female, but she shook them off and killed one of them. In the meantime some of the workers kept stealing into the dark chamber for the purpose of securing cocoons and carried them to the remotest corner of the light chamber. As the THE SANGUINARY ANTS. 405 morning wore away the female gradually became more and more excited. By 1 P. M. she had killed five more workers and was busy © carrying the cocoons back from the illuminated into the dark chamber, where she had already stored most of them in a corner. In a few minutes she had secured all the cocoons in the light chamber, 36 in number. She interrupted this task twice, each time for the purpose of killing a worker that came within her reach. Finally she retired to the dark chamber and began to collect the cocoons into a more compact pile. Two of the workers persisted in stealing in and hurrying back with a cocoon taken from the edge of the pile. The female soon per- ceived this, however, and dispatched both of them. The whole per- formance resembled a dulotic expedition in miniature, carried out by a single virgin queen instead of by an army of rubicunda workers. In killing the subsericea workers she was quite as ruthless as the workers of her own species, but more sure on account of her larger size and. greater strength. She exhibited very beautifully what may be called the ‘ prancing» movement, so characteristic of the females in this stage of their activities. She moved in a jerky fashion, taking a few steps in one direction, then turning her body and taking a few steps more. July 9, 8 A. M., only two of the workers survived. They had regained possession of 30 of their cocoons, however, and were guarding them in a remote corner of the light chamber, while the female was watching over the great bulk of the brood in a corner of the dark chamber. By 10.30 she had entered the light chamber, recaptured all but 6 of the cocoons, carried them into the dark chamber and placed them on her pile. The two workers were wandering about in a state of “ abulic dejection.” At 11.30 one of them was seen to enter the dark chamber and approach the female, but the latter opened her mandibles and the worker fled. The female had stacked her cocoons in a compact heap and was bent on defending them. Apparently she had not forgotten the 6 cocoons still remaining in the light chamber. At any rate, she secured 4 of them by 12 M. She took up her position on the pile of cocoons, and whenever light was admitted into the dark chamber, opened her mandibles and went to prancing about as if looking for an enemy. By 1.15 P. M. she had secured one of the remaining cocoons in the light chamber. July 10,6 A. M. In the night the female had killed the two remaining workers and had taken their last cocoon. Throughout the day she kept closely to the brood, prancing whenever the light was admitted into the chamber and fiercely seizing a straw or my finger whenever either was held near her. She seemed to dis- play a much greater interest in the pupe than in the larve. July 11 fo 15 she remained in statu quo. Whenever the nest was uncovered sie Be 40 6 ANTS. hastily took up a cocoon and tried to conceal it. July 16,7 A. M., five callow workers had hatched during the night. One larva had been partially eaten by the female. At 1.40 she was surprised in the act of opening’a cocoon. She used her fore and middle feet to hold the cocoon while she tore a large, elliptical hole with her mandibles in the portion of its wall overlying the concave ventral surface of the pupa. Through this hole the worker was later drawn after it had thrust out its antenne and legs. Whenever the nest was uncovered throughout this and the following of the first days, the female could nearly always be detected in the act of either opening a cocoon or removing the pupal envelope from a callow just released. By the afternoon of July 16 some of the callows began to assist the female in releasing their sister workers so that the number of callows now began to increase rapidly. On the morning of July 17 there were 19 altogether, by 5 P. M. 24, by 7.30 A. M., July 16-30; and by 7.30 A.-M. «July 209,50.) Onierhe following days the numbers ran thus: July 20, about 60; July 21, about 75; July 22, about 100; July 23 and 24, about 130. This completed the callow brood, as some of the cocoons failed to hatch. The female took the greatest interest in her black family, and they bestowed on her every attention. Soon after they had begun to feed and clean her another marked change supervened in her instincts. Instead of defending herself and brood when the nest was uncovered she slunk away, or at any rate attempted to conceal herself among the mass of workers. She had become highly photophobic and behaved exactly like the old queens, that invariably make for the galleries whenever the nest is disturbed or illuminated. This experiment was concluded and the ants were liberated in the garden on July 20. The above experiment shows very clearly that the female rubicunda, when placed with a small number of subsericea workers and their pupe, displays a chain of instincts that result in her gaining possession of the latter. To all appearances she is quite ready to be amicably adopted by the subsericea, but when received with marked hostility, as is probably almost invariably the case, her animosity is very quickly kindled, and she slays the subsericea with all possible dispatch, thus manifesting instincts very similar to those of her own workers when engaged in a dulotic raid. Owing to her powerful mandibles and closely knit frame she is always a match for several workers and may kill as many as twenty-one of these in a very short time. Before she has killed them all, however, she becomes much interested in their brood, eagerly col- lects and secretes it in some favorable corner and guards it with open mandibles till the callows are ready to hatch. These she skilfully divests of their cocoons and pupal envelopes. Their advent in consid- THE SANGUINARY ANTS. 467 erable numbers appears to be the signal for another marked change in the instincts of the female. She now becomes very timid, fleeing whenever the nest is disturbed and taking refuge in the darkest and remotest corner of the nest. In this instinct phase the female remains throughout the remainder of her life. The reactions displayed in the foregoing experiment are, moreover, so definite, uniform and purpose- ful even in artificial nests that one can hardly doubt that they are similarly manifested in a state of nature. It is evident that, especially in timid, incipient, wild colonies of F. subsericea, the females may meet with less opposition and therefore with greater and more immediate success. Still the fact that rubicunda is a local ant and by no means one of our most abundant species shows that the successful establish- ment of colonies in a state of nature must be attended with considerable difficulties. The search of the rubicunda female for weak or incipient subsericea colonies, even in regions where the latter ant is very abun- dant, must often be vain or illusory. This is tantamount to saying that the element of chance must enter very largely into the life of the rubi- cunda queen, just as it does into the lives of most parasitic animals. If it should happen that the rubicunda queen enters a subsericea nest with a queen of its own, the latter must be eliminated. In one of my artificial nests there was a queen cocoon among the worker cocoons of subsericea appropriated by the rubicunda. She eventually hatched and lived unmolested for a time. In the course of some weeks, how- ever, the subsericea workers began to pull their sister about by the legs and antenne in a vicious manner. One morning, probably as a result of this treatment, she was found dead in the nest. This assassi- nation of a queen by her sister workers acquires a new significance in the light of Santschi’s observations on Wheeleriella and Monomorium salomomts to be described in Chapter XX VII. Perhaps in many cases the subsericea queen is simply driven out of the nest or killed by the intrusive rubicunda queen. Which of these two methods is commonly adopted can be determined only by further observations and experi- ments. It is certain, however, that queens of the slave species are not permitted to live in mixed dulotic colonies of the sanguinea and Pol- vergus type. In this respect these colonies resemble the mixed colonies of the temporary and permanent social parasites. My experiments and conclusions were received with skepticism by Wasmann (1906!) and Escherich, because they had been performed on unfertilized queens. These authors argued that fecundated queens in their natural environment would probably behave differently. Was- mann performed several experiments with such queens and found that they were adopted by the slave species without hostility. Viehmeyer, 468 ANTS. however, has recently (1908) found that the fecundated European sanguinea behaves in precisely the same manner as rubicunda, and still more recently (1908)) Wasmann has repeated his experiments with this same result. A number of experiments which I performed during the summer of i907 with queens of F. aserva and subintegra showed that these insects behave precisely like rubicunda (Wheeler, 1908f ). Although the young colony of sanguinea resembles that of the tem- porary parasites like F. consocians and tuncicola, it differs in one important respect: the alien workers which it contains are younger, whereas in the incipient colony of the temporary parasite, they are older than the queen. Santschi (1906) therefore calls the former a “pupillary,” the latter a “ tutelary”” parasite. Wasmann and Santschi believe that slavery has arisen from temporary parasitism, but although I was the first to advance this opinion, I have been compelled to aban- don it. Wasmann found that a colony of F. truncicola, which he has shown to be a temporary social parasite in all essential particulars like F’. consocians, accepted and reared fusca pupe placed in its nest. This, however, is not dulosis. In order to establish his case he would have to prove that the truncicola workers can also make periodical forays on fusca for the sake of capturing their young, and there is no more evidence that truncicola can do this than there is of similar behavior on the part of consocians. Santschi, if I understand him correctly, believes that the sanguinea colony restricts its forays to the scattered fragments of the original fusca colony from which the queen secured her first supply of auxiliaries, and that the slave-making expeditions cease when these fragments are exhausted. This assumption seems to explain the fact that old sanguinea colonies are sometimes slaveless and pure, like the adult colonies of consocians, truncicola, ete. It is, how- ever, rendered highly improbable by the fact that both in Europe and in North America sanguinea colonies not infrequently contain slaves of two or more different species or varieties. There is also some evi- dence that the same colony may have slaves of different species at different times (see p. 472). The similarity between old sanguinea colonies and adult colonies of temporary parasites like F. consocians may be due to various causes: in the. slave-makers to a dearth of suit- able nests to pillage, or adaptation to an independent life owing to sufficiency of other food (dead insects, honey-dew, etc.), or to a lapsing of the predaceous instincts with age; in the temporary parasites the purity of the colony is brought about, as has been shown, by a gradual extinction of the tutelary workers. In my opinion both temporary parasitism and dulosis have arisen independently from the practice of F. rufa and F. sanguinea of adopting fertilized queens of their own THE SANGUINARY ANTS. 469 species, and to this extent my views coincide with those of \Vasmann and Santschi. Great difficulty was formerly experienced in accounting for the various dulotic instincts, because these were supposed to be the exclu- sive property of the sterile workers. On this assumption they could be transmitted only through the queen and she was supposed not to manifest them. The discovery in the queen of a type of behavior essentially like that of the workers solves this problem, for these instincts are seen to be primarily important in the establishment of the colony. They are naturally inherited by the workers, but in this caste they have been modified and intensified by fusion with the foraging instincts. Thus instincts which in the reproductive caste are useful in establishing the colony are useful in the sterile caste in procuring food and incidentally, perhaps, in adding to the working personnel of the colony. The differences in the display of the instinct by the two castes is due to the fact that the workers make their forays in concert and on populous colonies of the slave species, which the female could probably not enter. The discriminative character of dulosis, that is, its concentration on particular slave species, may be readily explained by the fact that both worker and queen sanguinea have been reared by the slave-workers, or at any rate have become familiar with them in the parental nest. What is more natural, therefore, than that both san- guinea queens and workers should seek out colonies of the familiar species, the queens for the purpose of nidification, the workers for the purpose of obtaining food? If we adopt Wasmann’s view that the young of the slave species are pillaged for the purpose of being reared instead of eaten, we may suppose that the pure colonies of these species in the vicinity of the sanguinea nests appear to these ants as so many detached and refractory portions of their own colony and therefore to be brought together in the one nest. I have already given my reasons for dissenting from Wasmann’s view, although I admit that the san- guinea workers of the same or different colonies may inherit in very different intensities their mother’s instinct to pillage larvae and cocoons for the sake of rearing them, and that the number of slaves in a colony may represent the degree to which this instinct on the part of the work- ers preponderates over that of hunger. Hunger and affection are such closely linked emotions in all animals that we cannot doubt that queens and workers alike possess them. They are, moreover, displayed by all ants in their tendency to eat their own larve and pupe. It is certain, however, that a rational explanation of slavery can be formed only by recognizing it as a form of parasitism in which the slaves are the host. +72 ANTS. — x . : ae, i But as the slaves are brought together from different colonies, the host is really synthetic. Santschi expresses this conception when he says: “In fine, slavery reduces itself to a form of pupillary parasitism that perpetuates and extends itself beyond the confines of the nest.’ The dulotic raid and synthetic character of the host sharply distinguish the slave-makers from the temporary parasites. CHAPTER: Xeavae THE AMAZONS, OR OBLIGATORY SLAVE-MAKERS. “ L’histoire des fourmis amazones et de leurs auxiliaires, nous prouve encore, que si l’éducation peut effacer la haine qui existe entre des espéces différentes, et par conséquent ennemies, elle ne sauroit changer leur instinct et leur caractere, puisque les amazones et leurs esclaves, élevées avec les mémes soins et par les memes nourrices, vivent dans la fourmiliére mixte sous des lois enti¢rement opposées.”—P. Huber, “Recherches sur les Moeurs des Fourmis Indigénes,” 1810. The observations recorded in the last chapter show that the Euro- pean and American sanguinary ants represent two different stages in the development of slavery, and suggest the question as to which is the more advanced or specialized. The greater variation and usually smaller size of the New World forms indicate a more primitive or inchoate condition, but, on the other hand, the greater number of slaves and more frequent expeditions, except in F. aserva, indicate a higher and more specialized development of the dulotic instincts. A very similar problem confronts us in the obligatory slave-makers of the genus Polyergus, the amazons, whose distribution parallels in an interesting manner that of F. sanguinea. Polyergus, too, is circum- polar, with only a single representative in Europe, the typical P. rufescens, whereas North America has at least four subspecies and a few undescribed varieties. The subspecies are: P. breviceps, ranging from the Rocky Mountains eastward to Illinois and Kansas; me.i- canus in Mexico; bicolor, known only from Wisconsin and Illinois, and Jucidus, ranging from the Atlantic seaboard, north of the Caro- linas, to the eastern slopes of the Rocky Mountains. The genus is therefore represented by the greatest number of different forms in the Middle West. 1. The European Amazons.—P. rufescens was the first slave-making ant to be described by P. Huber (1810). His splendid observations were confirmed and extended by Forel in 1874 and little of importance has since been added. Unlike sanguinea, rufescens is, on the whole, a rare ant, especially in northern Europe. In Switzerland, however, along the shores of Lake Leman, where Huber and Forel carried on their investigations, one may be sure of finding a number of its colonies without difficulty. It is one of the most beautiful of ants, the worker and female being of.a rich brownish-red color, slightly tinged with 47 4720 « ANTS. ae purplish, while the male is coal-black with white wings. The worker is extremely pugnacious, and, like the female, may be readily distin- guished from the other Camponotine ants by its sickle-shaped, toothless, but very minutely denticulate mandibles. Such mandibles are not adapted for digging in the earth or for handling thin-skinned larvee or pupe and moving them about in the narrow chambers of the nest, but are admirably fitted for piercing the armor of adult ants. We find therefore that the amazons never excavate nests nor care for their own young. ‘They are even incapable of obtaining their own food, although they may lap up water or liquid food when this happens to come in contact with their short tongues. For the essentials of food, lodging and education they are wholly dependent on the slaves hatched from the worker cocoons that they have pillaged from alien colonies. Apart from these slaves they are quite unable to live, and hence are always found in mixed colonies inhabiting nests whose architecture throughout is that of the slave species. Thus the amazons display two contrasting sets of instincts. While in the home nest they sit about in stolid idleness or pass the long hours begging the slaves for food or cleaning themselves and burnishing their ruddy armor, but when outside the nest on one of their predatory expeditions they display a dazzling courage and capacity for concerted action compared with which the raids of san- guinea resemble the clumsy efforts of a lot of untrained militia. The amazons may, therefore, be said to represent a more specialized and perfected stage of dulosis than that of the sanguinary ants. In attain- ing to this stage, however, they have become irrevocably dependent and parasitic. Wasmann believes that Polyergus is actually descerfded from F, sanguinea, but it is more probable that both of these ants arose in pretertiary times from some common but now extinct ancestor. The normal slaves of the European amazons are the same as those reared by sanguinea, viz: F. fusca, glebaria, rubescens, cinerea and rufibarbis; and of these fusca is the most frequent. But the ratio of the different components in the mixed nests is the reverse of that in sanguinea colo- nies, there being usually five to seven times as many slaves as amazon workers. The simultaneous occurrence of two kinds of slaves in a single nest is extremely rare, even when the same amazon colony pil- lages the nests of different forms of fusca during the same season. This is very probably the result of the slaves’ having a decided prefer- ence for rearing only the pupe of their own species or variety and eating any others that are brought in. Two slave forms may, however, appear in succession in the same nest. Near Morges, Switzerland, Professor Forel showed me an amazon colony which during the summer THE AMAZONS. 473 of 1904 contained only rufibarbis slaves, but during 1907 contained only glebaria. Unlike sanguinea, rufescens makes many expeditions during July and August, but these expeditions are made only during the afternoon hours. One colony observed by Forel (1874) made 44 sorties on thirty after- noons between June 29 and August 18. It undoubtedly made many more which were not observed, as Forel was unable to visit the colony daily. He gives the following statistics on these 44 expeditions: “ On 4 of them the army separated into two columns, from 6 it returned without having found a nest to plunder (through fatigue or losing the trail), on 3 the amazons found only formicaries containing neither larvee nor cocoons, from 6 they brought back only a meager supply of these, from 25 a great number. Of the 44 attacks, 19 were on fusca colonies and 19 on rufibarbis. Three of the latter were unsuccessful because they yielded no booty. The same formicary was visited repeat- edly: the ants visited altogether 7 colonies of fusca (one 6 times, one 4 times, one 3 times, two twice and two once), and 8 rufibarbis colonies (one 5 times, two 4 times, one twice and four once).” Forel estimated the number of amazons in the colony at more than 1,000 and the total number of pup captured at 29,300 (14,000 fusca, 13,000 rufibarbis and 2,300 of unknown provenience, but probably fusca). The total number for the summer (1873) was estimated at 40,000. This number is certainly above the average, as the amazon colony was an unusually large one. Colonies with only 300 to 500 amazons are more frequent, but a third or half of the above number of pillaged cocoons shows what an influence the presence of a few colonies of these ants must have on the Formica colonies of their neighborhood. Of course, only a small proportion of the cocoons are reared. Many of them are undoubtedly injured by the sharp mandibles of the amazons and many are destroyed and eaten after they have been brought home. The tactics of Polyergus, as I have said, are very different from those of sanguinea. Theants leave the nest very suddenly and assemble about the entrance if they are not, as sometimes happens, pulled back and restrained by their slaves. Then they move out in a compact column with feverish haste, sometimes, according to Forel, at the rate of a meter in 334 seconds or 3 cm. per second. On reaching the nest to be pillaged, they do not hesitate like sanguinea but pour into it at once in a body, seize the brood, rush out again and make for home. When attacked by the slave species they pierce the heads or thoraces of their opponents and often kill them in considerable numbers, The return to the nest with the booty is usually made more leisurely and in less serried ranks. 474 ANTS. The observer of one of these forays cannot fail to be impressed with the marvellous precision of its execution. Although the ants may occasionally lose their way and have to retrace their steps or start off in a different direction, they usually make straight for the nest to be plundered. They must, therefore, like sanguinea, possess a keen sense and memory of locality. There can be little doubt that they often leave the nest singly and make a careful reconnoissance of the slave colonies in the vicinity. “This year [1873],” says Forel, “I kept seeing ‘the amazons of my colony leaving the nest one by one and going great distances (as much as fifty paces from the nest), marching a short distance at a time. I saw some in little squads of four or five inspect- ing the nests of /. fusca situated at more than thirty paces from their own. They hunted out the openings and carefully scrutinized the sur- roundings. These facts prove more and more that each amazon worker studies the slave-nests around its own and on its own account, and this permits the army as a whole to direct itself in a mass and to reach a decision at a given moment.” It is an interesting fact that the slaves take on certain peculiarities, apparently by imitation, from the amazons with which they are living. The timid fusca, e. g., becomes fierce and aggressive, a peculiarity which it also acquires when dwelling with sanguinea. In rufibarbis the change in behavior is less apparent, because this ant, even when living alone, is very belligerent. The behavior of the amazons seems also to be influenced by their slaves. According to Forel, those with rufibarbis slaves leave their nests more frequently and earlier and later in the day and move in denser armies and more rapidly than amazons with fusca slaves. It is rather difficult to account for these colonial idiosyncrasies. Perhaps only the more vigorous Polyergus succeed in enslaving rufibarbis, while feebler or more languid colonies have to content themselves with the more tractable fusca. While in its nest rufescens is under the tutelage of its slaves. These sometimes prevent the warriors from making a foray or go out and meet them, when they have gone astray and carry them home. When the colony moves to a new nest the slaves take charge of matters and carry the amazons. We have seen that when the sanguinea colony changes its headquarters, it is the slaves that are carried. 2. The American Amazons.—I have been able to observe all our American subspecies of rufescens in a living condition, except me.i- canus, which is known only from a few cabinet specimens. Even the precise locality from which these came is unknown, but it must have been either in the northern portion of Mexico, or if further south, at a considerable altitude. The worker of this subspecies resembles that of THE AMAZOWNS: 475 breviceps very closely, judging from Forel’s description (1899a) and a couple of type specimens which he has generously given me. The Mexican form differs only in having very few or no hairs on the dorsal surface of the body, and is hardly more than a variety of breviceps. Its slaves are unknown but are in all probability some form of fusca. I take from my note books the following observations on our other amazons : (a) Polyergus breviceps.—This subspecies, which I shall call the occidental amazon, is not uncommon in several localities in the moun- tains of Colorado and New Mexico at altitudes between 2,000 and 2,500 m. I have also seen a few specimens that were taken at much lower elevations in Illinois and Kansas. Of all our subspecies breviceps resembles the European type most closely. Its color, pilosity and sculpture are practically the same, it forms rather large formicaries and its slaves are much like those of rufescens. These comprise F. argentata, subsericea and neocinerea, ants so similar in size and color that they would be regarded as identical by any one but a myrmecolo- gist. F. neocinerea occurs only in rich meadows, the two others on dryer ground. ‘The ratio of slaves to breviceps workers is the same as that of fusca to rufescens in Switzerland. During the summer of 1903 and 1906 I witnessed several forays of breviceps in Cheyenne Canyon near Colorado Springs and in Florissant Canyon, west of Pikes Peak. One of the most typical of these forays was seen in the former locality. An unusually large colony, containing fully 1,000 breviceps workers, was found nesting under some large stones near the top of the steep bank of Cheyenne Creek. The formicary extended out under the stones and must have covered an area of fully 2.5 sq. m. Under the edge of one of the stones was the single entrance, about 2 cm. in diame- ter. July 20 at 1 P. M., after seeing a few breviceps and their slaves (subsericea) loitering about the entrance, I stationed myself at the nest in the hope of witnessing a foray. After waiting nearly an hour (at 1.55 P. M.) I saw the beautiful red ants boil up, so to speak, in the opening. In a few moments they came rushing out in great numbers and kept running about just outside the entrance till 2.15, when they started in a compact army up the embankment and obliquely in a south- westerly direction. Soon, however, they returned to the nest as if changing their minds and again started out due south and straight up the bank. The procession formed with great alacrity and then pushed ahead at the rate of one m. in forty seconds, over smooth ground, but requiring about one minute to make the same distance over the dead oak leaves. There was no leader, the army being headed by a few workers which were continually being passed by workers overtaking 476 ANTS. them from the rear. They neither hesitated nor stopped till they reached a large subsericea nest about 25 m. from their own, on the top of the embankment. This nest was under and around a couple of large, flat stones, and had two entrances a short distance apart. There were a few subscricea sauntering about the entrance, but as soon as they scented the approaching army they scampered into their nest. The amazons arrived at 2.40 P. M. and at once poured into the two entrances in a mass like wine being poured into a couple of funnels. Two minutes later the first breviceps emerged with a cocoon in her jaws and was at once followed by a file of others similarly laden. They started for home in great precipitation. One that was timed made the entire distance of 25 m. in a little more than four minutes. As the army must have comprised fully 1,000 workers, there was soon a long file, each carrying a larva, nude pupa or cocoon. I returned to the subsericea nest in time to see a few workers of this species rush out of the opening with larve, run the gauntlet of the amazons and make off to the open ground beyond. From time to time a breviceps would emerge from the nest carrying a subsericea worker, take it a few centimeters from the opening and put it down. To my surprise the black ant scrambled to her feet and ran away uninjured. I saw this performance repeated more than a dozen time by different amazons. Not a single subsericea was killed or even maimed! The plundering of the nest continued, the breviceps returning repeatedly from their own nest to get more pupe. By 2.55 the number of these brought out of the nest had dwindled considerably and at 3.06 the supply ceased altogether. Nevertheless the breviceps kept entering the nest and coming out with empty jaws till 3.15 when they began to straggle home. The last ones left the pillaged formicary at 3.30 and moved away slowly or sauntered about as if reluctant to return home without booty. The feverish excitement so apparent in these insects a few moments before had suddenly subsided. At the entrance of their own formicary the slaves were running about in considerable numbers and seemed to be greatly excited over the quantities of booty that were being brought in. Soon, however, both slaves and breviceps entered their nest and all was quiet. I again went back and found the subsericea cautiously returning to their pillaged nest. On raising the stones I found a great many unharmed workers in the galleries but not a single larva or pupa. These ants must have remained in their nest during the whole time that the rape of their brood was in progress! The foray was remark- able on account of the behavior of both species, for the subsericea, though abundant, had made no attempt to protect the young which they had for weeks been rearing with infinite solicitude, and the breviceps THE AMAZONS. 477 had been more courteous and considerate than their vocation of pro- fessional kidnappers would seem to permit. In the neighborhood of Colorado Spring breviceps is rare and sporadic, but in the subalpine meadows about Florissant it is as common as the typical rufescens in the meadows on the shores of Lake Leman. The nests of neocinerea in which breviceps lives at Florissant are grass- covered mounds like those of the European glebaria and rubescens, but larger (sometimes nearly a meter in diameter and 2-3 dem. high). On the slopes surrounding the meadows, however, the western amazon also lives in the nests of argentata, which are usually found under stones or logs. The abundance of these slave-makers at such an alti- tude (2,500 m.) indicates that they belong to the Canadian zone and that they will also be found in the southern portions of British America. This distribution is significant in connection with their close structural and ethological relationship to the European and probably also Asiatic rufescens. (b) Polyergus bicolor—This subspecies was simultaneously dis- covered by Father Muckermann at Prarie-du-Chien, Wis., and myself at Rockford, Ill., and has not been recorded from any other localities. It is closely related to breviceps, but differs in its smaller size and in having the gaster of the worker and female black, instead of red, like the remainder of the body. We may therefore call it the black and red amazon. Like breviceps it often forms rather large colonies and its slave (F. subenescens) is closely allied to the typical European fusca and gagates. F. subenescens, according to my observations, occurs only in rich, shady woods, and prefers to nest in logs or stumps so rotten as to be easily broken apart. The six colonies of bicolor which I have found in widely separated localities near Rockford, were all in such logs or stumps in shady spots where the undergrowth had - been removed. The average ratio of bicolor to subenescens workers in the mixed colonies was at 1:3. The following notes were made on a single colony of these ants late in July and early in August, 1902: July 24, 2 P. M., I came upon a troop of about 300 bicolor in the act of pillaging a rather large subenescens colony that was nesting in a small rotten stump under some hickory trees. The stump was cau- tiously broken open and the bicolor were seen rushing about the gal- leries, biting the shining, black swhenescens, or even the bits of wood in a kind of insensate ‘‘ Mordlust.” The subenescens seemed to be more dismayed than injured. The bicolor seized the larve and pup with tremulous eagerness and began to leave the nest. Soon the whole troop, laden with booty, was under way, in an open phalanx, threading 478 «ANTS. the grass and pattering over the dead leaves. By 2.20 they had reached their own nest, which was in a dead branch only 8 cm. in diameter, concealed under a pile of old oak leaves. Some of the ants made one or two journeys back to the swbenescens nest, which was some 20 m. from their own, for the purpose of bringing the remaining pupe. The subenescens workers were left wandering about their stump disconso- lately and by 2.30 all the bicolor had entered their branch under the leaves. July 26, I again visited the bicolor nest, but a shower came up, so that no observations could be made. July 27, the rain continued and although it cleared off in the afternoon the amazons remained in their nest. July 29 was warm and sunny. I reached the nest at 1.35 P. M., just as the straggling rear of the army was issuing from under the leaves covering the dead branch. The main body had advanced only 2.5 m. from the nest and was soon joined by the stragglers. The ants moved rapidly at a rate of 1.3 m. per minute in a rather compact body 2.3 m. long and 5-15 cm. broad. They seemed to be greatly excited and hastened on in frenzied eagerness. When about 10 m. from the nest they halted as if they had lost their way and scurried about wildly in all directions over and under the dead leaves. This lasted nearly fifteen minutes. Then the troop again formed and advanced even more rapidly than before in the direction of the stump where I first saw it July 24 in the act of pillaging a subenescens nest. But when the ants had come within about 1.5 m. of the stump they veered off to the left to a pile of dead leaves. At this point a few subenescens workers were running about and it seemed as if there must be a nest of these ants in the immediate vicinity. Such was evidently also the impression of the amazons, for the troop halted and began to scurry about under the leaves. The few subenescens did not desert the premises, but fell upon the amazons and pulled them ‘about by the legs and antenne. Fully fifteen minutes were consumed in this feverish search. Then the amazons seemed to have gained the impression that there was no nest at this spot. The column turned back slowly, with movements indicative of disappointment or fatigue. After retreating about 2 m. in the direction of their own nest, an offshoot of the troop suddenly started to the right and after covering about 60 cm. came upon a nest. I raised the leaves slightly and found a small hollow in the vegetable mould containing several hundred subenescens workers huddled about some twenty larvee and pupe. This undoubtedly represented a colony that had been previously pillaged, probably the one I had seen attacked July 24. The poor ants had moved first to the spot where the bicolor THE AMAZONS. : 479 had first scented them, but had again decamped and were now detected. The amazons pounced upon the disheartened band, part of which scat- tered in all directions with a few of the larvae. Many, however, stood their ground resolutely and attacked the invaders. These lashed them- selves into a kind of fury, pierced the heads and thoraces of the suwbe- nescens with their sickle-shaped jaws and strewed the leaves with their jet-black corpses. There were very few larve and pupe to take home, but many of the amazons seized uninjured subenescens and joined the ranks of the homeward bound procession. They moved back in a long, loose file, very unlike the compact troop on its outward journey, and over’a different path. They arrived at their nest by 2.35 P. M. The whole foray had taken little more than an hour and only a quarter of this time had been spent in pillaging the temporary subenescens nest. July 30. I remained in the vicinity of the bicolor nest from 1.10 to 4.30 P. M., but there was no sortie, although the weather was propitious. July 31. There was no sortie, but I stayed near the nest and made the following observations: At 2 P. M. a single amazon left the branch and by her apparent determination arrested my attention. She hurried on in a southeasterly direction over a rather irregular course, making short excursions to the right and left, and exploring every hole and cavity in the ground and under the dead leaves. I followed her for a distance of nearly 25 m. to a pile of dead leaves heaped about the base of an old stump. Here she slipped out of sight. After waiting some minutes for her to reappear, I removed the leaves and found, a few cm. from the spot where I had lost sight of her, a large subenescens nest containing many larve and pupe. The galleries ran under the dead leaves and up into the stump. This nest had evidently not been pillaged during the course of the summer, and I inferred that the amazon was a scout that had succeeded in locating a treasure. She failed to reappear and must have returned to her nest unnoticed. About half an hour later another amazon left the nest in the branch and made off in a direction at a right angle to the first. She went about 2 m. in one direction, then turned abruptly and continued 2.3 m. in another direction to a large rotten stump surrounded by dead leaves. Like the first scout she slipped under the leaves and failed to reappear. As several subenescens were running about on the stump, there must have been a nest in the immediate neighborhood, but I failed to find it. After watching the amazon nest for some time longer without observing any further developments, I went home. August I. On reaching the bicolor nest at 1.10 P. M. I noticed no unusual activity. A few of the amazons and slaves emerged from time 480 ANTS. to time from the mass of oak leaves covering the branch and anon reéntered the nest. At 1.15 a bicolor scout emerged and went in the direction taken by one of the scouts on July 31. I followed her for about 6 m. when she disappeared under the dead leaves. I returned to the nest in time to see another scout start out and move away in the opposite direction. When about 4 m. from the nest she also dis- appeared under the leaves, At 1.35 the bicolor, about 300 strong, came pouring out of the nest as if in response to some sudden signal. They were not restrained by the slaves loitering about the entrance, but moved around rather leisurely for some minutes like a crowd assem- bling Then at 1.40 P. M. they started and soon detached themselves completely from the nest. I expected to see them make for one of the stumps that had been reconnoitered by the scouts July 31, but they took the opposite direction. They moved very rapidly, in a more crowded body than they had presented on previous occasions, and four to six abreast. They soon reached the spot where some twenty minutes before I had seen the first scout disappear. Here they halted for a few moments and assembled, then they turned at a right angle and pro- ceeded about half a meter and forthwith began to disappear under the leaves. Two subenescens suddenly darted out with larve in their jaws and fled. I raised the leaves and found in a depression of the soil about 500 subenescens workers and two dealated queens all hud- dled together with only six or eight pupz in their midst. This was certainly a temporary nest in which the ants had taken refuge after being plundered by the amazons on some previous afternoon. The bicolor fell upon them, tore away their few remaining pup and by 1.50 P. M. were starting home. At first the subenescens did not flee, but hung about as if thoroughly disheartened or indifferent. Some of them attacked the amazons, but these for some reason showed very little animosity. Finally the swbenescens dispersed and the amazons filed home, many of them carrying uninjured subenescens, apparently because they did not wish to leave the nest with empty jaws. By a few minutes past two the slave-makers were all in their branch under the oak leaves and all was quiet in the neighborhood. August 2. Arriving at the bicolor nest at 1.20 P. M. I saw the last members of the troop just leaving the dead oak leaves. I followed the stragglers and found that the army had assembled at the spot to which I had traced the first scout August 1. The ants were ferreting in some galleries in the vegetable mould under the leaves, but there were no subenescens to be seen. They seemed to be very reluctant to leave the spot, but they finally spread apart and began to investigate the oak leaves in the vicinity. They soon reached the stump that had con- THE AMAZONS. 481 tained the flourishing subenescens colony reconnoitered by the scout, climbed about on it and thrust their heads into every cranny. It was all to no purpose—the subenescens had moved away with their fine lot of young. Slowly and in what seemed to be a crestfallen and dis- appointed spirit the amazons assembled and returned with empty jaws to their nest. They had all entered the dead branch before 2 P M. August 5. At 1.45 P. M.I visited the bicolor nest for the last time. Carefully removing the dead oak leaves I broke open the branch, but it was empty. The colony had moved to some other spot and I searched for it in vain in the neighborhood. These observations are recorded in detail because they illustrate so many of the interesting peculiarities of the amazons. The behavior of Fic. 270. Polyergus lucidus and its slave, somewhat enlarged. (Original.) In the upper row: worker of P. lucidus, head of same and head of Formica schau- fussi; in the middle row, male, virgin female and worker of P. Jucidus; in the lower row workers of F. schaufussi. the scouts confirms Forel’s opinion of the way in which the location of slave nests is ascertained, and the behavior of the amazon troup and of the harassed subenescens colonies on successive days shows how complicated are the environmental conditions which these insects have to meet and the intricacy of the problems with which the observer has to deal. The slave colonies are repeatedly plundered and driven from pillar to post, till they probably emigrate to other localities in sheer desperation. Then the Polyergus, too, finding no nests to pillage, are compelled to seek a new field for their persistent and pernicious activities. Surely Fabre is right in maintaining that the life of a preda- 32 452 ANTS. tory parasite is not a bed of roses. The amazons have indeed acquired brilliant military instincts, but if these ants were capable of reflection they might occasionally regret having abandoned the quiet pastoral life which their ancestors probably led. (c) Polyergus lucidus (Figs. 270 and 271).—This is the largest, handsomest and most graceful of our amazons, and even surpasses the European form in its brilliant red coloring and gleaming surface. It may be called the shining amazon. Owing to its wide distribution in the Eastern States it has been known for some time. Mrs. Treat (1877) and McCook (1880b) saw its colonies, but Burrill (1908) is the only author who has described one of its forays. In the Atlantic States it is very rare and sporadic. During the past five years I have seen only four of its colonies in New York and New Jersey, and these were at great distances from one another. It is more frequently met with on the warm eastern slopes of the Rocky Mountains in Colo- rado, where, unlike breviceps, it occurs only at lower elevations. It is the furthest removed of all of our subspecies from the European type in its smooth surface, in the coloring of its queens, which, in eastern colonies, at least, have the head and thorax nearly black, in the small size of its communities and the character of its slaves. These are not members of the fusca, but of the pallide-fulva group of Formice, and are represented by schaufussi, or the closely allied incerta or nitidi- ventris. The very small size of the colonies of these ants may account for the same peculiarity in /ucidus. The slave species makes obscure crater nests in sunny, open pastures and such places are therefore also the home of the shining amazons. The ratio of these to slaves in the mixed colonies is about 1:5 or 6. It is an interesting fact that Jucidus resembles its slaves in having a smooth, shining sur- face, a slender, elegant stature and long legs, whereas breviceps and bicolor resemble the fusca forms which they enslave, in having a more pilose and pubescent surface, more thickset stature and shorter legs. These resemblances may therefore be regarded as mimetic. Near my former home in Bronxville, N. Y., there was an unusually fine lucidus-incerta colony, which I had under observation for five years. During four years this colony produced numbers of males and females, both winged and ergatoid, and the winged females lingered for weeks in the nest without dealation. The first week of April 1908, I found the whole community with its larvae and mother queen enjoying the spring warmth in the superficial galleries just under the large flat stone with which I covered the nest in September 1903. I captured the queen and part of the colony and transferred them to an artificial nest. August 9 I again visited the nest, and to my THE AMAZONS. 453 surprise, found it teeming with several hundred males clinging to the lower surface of the stone, but with no winged or dealated females. Besides the males I found only a single large ergatoid female, several dozen workers and slaves, and half a dozen cocoons enclosing nearly mature male pupe. Without doubt, the ergatoid had usurped the role of the mother queen and, being unfertilized, had produced only male offspring. The comparatively small number of slaves had been able to rear an enormous number of these little creatures, although the absence of incerta pupe in the nest indicated that the Polyergus Fic. 271. Polyergus lucidus. (Original.) a, Worker in profile; b, head from above. workers had made no forays during the summer of 1908. The fol- lowing is a description of one of the forays made by this colony July 31, 1904, while it was still in a normal condition: On reaching the nest at 2.20 P. M. I found the lucidus pouring out of it in numbers. They ran about on the stones and surrounding soil till 2.37, when a troop of nearly 200 had congregated and began to move away from the nest, slowiy‘at first and then with feverish paces. At 2.45 they reached, by a direct path through the grass, an obscure crater nest of incerta, situated some fifteen meters from their own. They at once poured into the opening, slaughtering or putting to flight the icerta that were loitering about or issuing from the galleries. One minute later (at 2.46) the first Juwcidus emerged with a cocoon. Then followed a stream of these ants, each similarly laden, and started for -home. Several were unable to secure sound pup, but grabbed up empty cocoons and pupal exuviz and fell in line. Some also brought out recently hatched and callow incerta and slaughtered them on the nest crater. The last cocoon was brought out at 3.13 and a few moments later the last amazon left the nest and joined the returning troop. During the pillage some of the incerta endeavored to defend their nest, 454 ANTS. but were promptly dispatched by the Jucidus. The corpses were dragged away by a lot of \/yrmica sabuleti that had their nest about the roots of a plant within 30 cm. of the incerta nest. By 3 P. M. the last lucidus had disappeared into her nest. The whole expedition there- fore consumed only forty minutes. During the summer of 1902 I found near Rockford, IIl., a fine lucidus-nitidiventris colony. . Thirty of the amazons were transferred to an artificial nest furnished with a wet sponge and a dish of honey, for the purpose of studying their behavior when isolated from their slaves. In the course of a few days the ants were famished and kept vainly begging one another for food. They often licked the water from the surface of the sponge and two that had accidentally stumbled into the honey head foremost, so that their tongues were brought in contact with it, lapped it up with avidity. They soon began to die of hunger and when only sixteen of them survived I wished to see whether they would adopt alien workers of subsericea and nitidiventris taken from a garden far removed from any /ucidus colony. At two o’clock one afternoon three of the former (A’, B’, C’) and three of the latter (A, B, C) were placed in the nest. They began to run about in great dismay, especially when they happened to touch one of the amazons with their antenne. From the first, however, the subsericea seemed to be much more frightened and to irritate the amazons more than did the nitidiventris. One large lucidus that had lost her right antenna and right tarsus seemed to be in a particularly vicious frame of mind, pos- sibly because she had been spending much of the day trying to ‘comb an imaginary antenna with an imaginary strigil and had repeatedly tumbled over while attempting this feat. This ant pounced on A’ and B’ like a cat and killed them in quick succession. She pierced the gaster of A’ with her sharp jaws till its contents flowed out on the floor of the nest. B’ she pierced through the thorax. For some time the surviving subsericea (C’) succeeded in evading the amazons, which in the meantime had worked themselves up into such a fury that they even attacked one another. I saw one of them grab a sister worker by the neck and hold on for three quarters of an hour. The amazons, though visibly irritated by the nitidiventris, did not seize them by the body, but only by the legs and antenne. The smallest individual (4) lost its left middle leg in such an encounter. At this point the observations were interrupted. At 9 P. M. both 4 and B were found dead{ and C and C’ were run- ning about. C”’ skulked in the corners of the nest, but C was seen to walk up to one of the amazons, protrude her tongue, and feed the THE AMAZONS. 485 famished creature for several minutes, then go to the food chamber, take a draught of honey, return and feed a number of them in succes- sion. For an hour she thus moved back and forth between the amazons and the honey till all had been fed. At 8 A. M. on the follow- ing morning the amazons were huddled together on the sponge, as if asleep, and in their midst was the nitidiventris, C, also resting peace- fully. The subsericea, C’, still alive but distrustful, was lurking in the furthest corner. I tapped the nest gently to arouse its inmates. C immediately ran into the food chamber, imbibed a lot of honey, returned and began to feed the Jucidus, like a solicitous mother who wakens early and sets about getting breakfast for a large family. The friendly relations between C and the amazons continued throughout the day. Early the following morning C’ was found dead in a corner and C was ministering to the amazons. Before noon, however, I found her lan- Fic. 272. Queen of Polyergus rufescens and her incipient colony of Formica fusca workers. (Photograph by Prof. C. Emery.) guidly dragging her body about the food chamber. Her head had been pierced by one of the stupid and ungrateful lucidus. She died in a few hours. At 3 P. M. twenty large subsericea workers, with a number of larve and pupz, were placed in the light chamber. The sixteen amazons entered the chamber and began to attack the black intruders in a per- fect frenzy of valor. To my surprise the subsericea stood their ground, took the offensive and were soon driving the amazons around the nest like a herd of sheep. They seized the /ucidus by the legs and antennz, 486 ANTS. showered them with formic acid, mauled them about, gnawed off their legs and left them in a pitiable plight. This victory for the subsericea was not only a surprise, but coming so soon after the death of the self- sacrificing nitidiventris, made me feel much as I felt when a boy on reading of the death of the suitors in the Odyssey. These observations on /ucidus, with many others which space forbids relating, show that this subspecies is much more belligerent and of a more vicious disposition than breviceps or bicolor. This is the more surprising because the ants which it enslaves are more cowardly and docile than the slaves of the other subspecies. The behavior of the ministering nitidiventris also shows that this form and not subsericea is the natural slave of lucidus. 3. The Founding of Amazon Colonies.— Most authors have inferred from the absence of the domestic instincts in the amazons that the queens of these ants would be unable to establish a formicary without the aid of alien workers. Forel and Wasmann have therefore insisted that the rufescens queen must be adopted by a band of fusca, and they have published several observations which go to show that such an adoption can be rather easily brought about in artificial nests. These observations have been recently confirmed and extended by Viehmeyer (1908). In this respect Polyergus rufescens resembles the temporary parasites. Several experiments in which I introduced artificially dealated queens of /ucidus into nests containing incerta workers with their brood gave rather conflicting results. In some cases the /ucidus queens behaved like sanguinea queens under similar conditions, to the extent of killing the alien workers, but they paid absolutely no attention to the brood. In other cases they were more passive and conciliatory, but equally indifferent to the imcerta cocoons. It will be necessary, there- fore to study this question further before making definite statements in regard to the method employed by our American amazons in estab- lishing colonies. But even if the method of rufescens should be found to obtain also in our subspecies, we should not be justified in deriving it from that of the temporary social parasites, for we might conceive it to have arisen secondarily by involution or degeneration from that employed by sanguinea.' "Professor Emery, in a paper just received (Nuove Osservazioni ed Esperimenti sulla Formica Amazzone. Rend. Sess. R. Accad. Sci. Inst. Bologna, 1909, pp. 31-36), records an experiment which goes a long way towards solving the problem here considered. July 13 he placed a dealated P. rufescens queen in a Janet nest containing a F. fusca queen, fourteen workers and a few pupe. The rufescens, on being attacked by the workers, offered no resistence, but showed great interest in the fusca queen, who received her amicably. By July THE AMAZONS. 487 The dulotic instincts reach the apogee of their development in Polyergus. This ant is, however, at the same time a permanent social parasite on its host, the slaves, and replete with degenerate tendencies. These, in the further course of evolution, may be expected to gain the upper hand, and, overwhelming and supplanting the predatory instincts, lead to the peculiar conditions to be described in the next chapter. 20 the attacks had ceased and both queens were living on friendly terms with two of the workers. On the morning of July 22 the fusca queen was found dead in the nest. Her head had been perforated by the mandibles of the Polyergus, who was now adopted and courted by all the workers. Fig. 272 is taken from a photograph of the diminutive colony that arose in this manner. This experiment indicates that P. rufescens founds its colonies in the same manner as Bothriomyrmex (vide supra, p. 447). CHAPTER XXVII. THE DEGENERATE SLAVE-MAKERS AND PERMANENT SOCIAL PARASELES: “Concluons done que le parasitisme n’est inoffensif qu’accidentellement et que son effet normal est de nuire. Il faut par conséquent considérer comme aussi éloigné que possible de l’union sociale tout étre qui se nourrit de la sub- stance d’un autre. Au point de vue physiologique sa fonction est en opposition avec celles de sa victime; au point de vue psychologique il n’entre dans la sphére de sa conscience que pour y causer de la douleur, autre signe non moins manifeste d’opposition. I] appartient a un optimisme plus courageux que clair- voyant de chercher une harmonie au sein de la plus apre concurrence. Mais le parasitisme ne nuit pas seulement a la victime, il nuit au parasite lui-meme, sinon immédiatement dans l’individu, du moins par accumulation dans l’espéce.” —Espinas, ‘“ Des Societés Animales,” 1877. The true slave-making ants, both facultative: and obligatory, are closely allied members of the Camponotine subfamily. The ants to be considered in the present chapter, however, are all Myrmicine and cannot, therefore, have arisen from such forms as sanguinea and Poly- ergus. Considered by themselves they represent a heterogeneous assem- blage of remotely related genera, which may be described in the order of increasing degeneration. Several of these ants resemble their respec- tive hosts so closely that it is from these that some authors suppose them to have been derived. But this supposition, though plausible, 1s, nevertheless, open to doubt, for the resemblance between host and parasite may be due to mimicry and therefore to convergence rather than to true morphological relationship. We have seen that many myrmecophiles, some of the temporary parasites, like Formica conso- cians, and some of the amazons simulate their hosts, and it is con- ceivable that parasites as extreme as those we are about to consider, might show even more striking resemblances as the result of a long process of adaptation and association. Very similar resemblances are also known to obtain between many parasitic bees of various genera and their respective hosts. The symbiotic ants with which we are here concerned, fall naturally into two groups. Those which I shall call the degenerate slave- makers, resemble Polyergus in certain respects, but differ in permitting the queens of the host species to survive and reproduce in the mixed colonies. The permanent social parasites, on the contrary, live in host colonies whose queens have been eliminated, and differ, moreover, from 488 THE DEGENERATE SLAVE-MAKERS. 489 all the other social parasites in lacking the worker caste. The ants of both groups are throughout life dependent on their hosts and are, there- fore, permanent social parasites, but | would restrict this term to the workerless species, since they represent the most extreme type. A. The Degenerate Slave-makers.—This group embraces only two genera, Strongylognathus and Harpagoxenus, formerly known as Tomognathus. Strongylognathus is a strictly palearctic genus, con- fined, so far as known, to Europe, western Siberia, Asia Minor and the southern shores of the Mediterranean. It contains only two spe- cies, testaceus and hubert, but the latter has several subspecies and varieties (christophi, rehbinderi, afer and cecilie). These ants are very small, measuring only 2.5-4.5 mm. in length, and of a yellowish or dark brown color. The head of the worker and female is more or less excised behind, with very prominent posterior corners and sub- parallel sides. The mandibles are toothless, narrow, pointed and sickle-shaped, like those of Polyergus, but without denticles. All of the forms occur only in nests of Tetramorium cespitum (Fig. 273, d), a very common ant which they closely resemble in size and appear- ance. 1. Strongylognathus huberi (Fig. 273, c).—This species was origi- Fic. 273. a, Strongylognathus testaceus worker. (Original.) b, head of female of same; c, S. huberi, head of worker; d, Tetramorium cespitum L. host of S. tes- taceus and huberi. nally described by Forel (1874) from specimens taken in Canton Vallais, Switzerland, on a warm slope near Fully, in the valley of the Rhone. More recently (1900d ) he has published additional obser- vations on a colony from the same locality. He found that the workers of huberi are very numerous, that they will go forth in a closed phalanx, much like that of the amazons, and pierce the heads strange Tetramorium workers placed near their nests and that they 490 ANTS. will also take up the pupze of the strange ants and carry them home. In his more recent observations Forel found that the strange pup thus brought in were carried out by the host workers and cast away. This behavior and the fact that no one has witnessed a spontaneous foray of huberi, seem to indicate that these ants never voluntarily leave the nest and pillage the Tetramorium colonies in their neighborhood. It is probable, therefore, that the habits observed by Forel are vestigial. In other respects, however, huberi is less degenerate than the amazons, for it occasionally excavates the soil.? 2. Strongylognathus afer.—This is merely a variety of huberi from Spain and Algiers. It was originally described by Emery (1880) from the female only. Forel discovered its colonies in Algiers and found that they resemble those of the typical huberi in having numerous workers. 3. Strongylognathus christophi—Emery (1889a) described this subspecies from female specimens collected at Sarepta on the Volga. Ruzsky (1905) has recently taken the workers at Turgai in western Siberia and Astrachan. 4. Strongylognathus rehbinderi.—This robust variety of christophi was found by Rehbinder (Forel, 1904a) in a convent garden at New Athos near the foot of the Caucasus. The workers were running along a path, apparently carrying pupz in their jaws. Forel believes that they must have been on a foray. If this is true, we should have to admit that Strongylognathus is still able to make forays on Tetra- morium like those of the amazons on F, fusca, but we must await further observations before accepting this inference. 5. Strongylognathus cecilie—Only the male and female of this form are known. It was based by Forel on specimens taken in Spain. 6. Strongylognathus testaceus (Fig. 273, a and b).—This species is widely distributed in Europe and is not uncommon in certain por- tions of Germany and Switzerland. Its habits have been studied by Schenck (1852), von Hagens (1866), Forel (1874), Wasmann (1891h), Viehmeyer (1906, 1908) and others. It is of a yellowish color and distinctly smaller and feebler than huberi and its varie- ties. Moreover, the workers are so much reduced in numbers as to represent a mere vestige of their caste. [Forel is, therefore, of the opinion that they are on the verge of disappearing and leading to a condition in which the species is represented by males and females only. It is certain that these workers no longer make spontaneous * During July, 1900, | found near Zermatt, in the valley of the Visp, seven colonies of S. huberi. Some experiments, performed on the largest of these, confirmed Forel’s conclusions, THE DEGENERATE SLAVE-MAKERS. 491 forays on alien colonies of Tetramorium. When the latter are brought near a mixed colony and a conflict ensues, the testaceus endeavor to kill the strange workers, but are too feeble to pierce their armor, and, if the mixed colony is victorious, this is due to the efforts of the host workers. The testaceus, though able to excavate and to feed independently, contribute little or nothing to the structure of the nest and probably obtain most of their food from the tongues of the Tetramorium. The broods of both species are cared for by the host, since the parasites have ceased to interest themselves in the educa- tion of their own young. Unlike many parasitic ants, S. testaceus is often found in vigorous and populous colonies of the host species. The flourishing condition of such colonies, a number of which were shown me by Mr. Viehmeyer in the heaths near Dresden, must be due either to the retention of the Tetramorium queen or to the adoption of the Strong\lognathus queen at a very late stage in the development of the colony. That we must accept the former alternative is proved by the following observations: In Bohemia, Wasmann found a large mixed colony which contained 15,000—-20,000 Tetramorium, some thousand Strongylognathus and pupz of both species. About 70 per cent. of the pupze were males and females of the parasitic species, the remainder were worker pup, and there were two large male pupe of the host. This nest contained a fertile queen of Tetramorium and one of Strongy- lognathus, living side by side. During June, 1907, Professor Forel and I were able to confirm this discovery. We found a similar testaceus- Strongylognathus colony on the Petit Saléve, near Geneva. This colony, though much smaller than the one described by Wasmann, contained a fertile Tetramorium queen. The diminutive Strongylognathus queen was not found, but must have been present, as there were in the nest young worker pupz in addition to the imagines of this species. Was- mann is inclined to believe that these mixed colonies arise through the alliance of a testaceus and a Tetramorium queen, but it is more probable that the former enters a colony of the latter after it has been estab- lished and become rather populous, since the founding of colonies even by pairs of queens of the same species is an extremely rare occurrence (see p. 190). Although the host and parasitic queens come to live side by side in the mixed colonies, the offspring of the latter are exclusively workers, the two male pupze found by Wasmann being the only known exception to this rule. Forel (1900d) explains this absence of the male and female offspring of the host queen as the result of a regulatory instinct: ‘“ The females and males of Strongylognathus are smaller and less troublesome to nourish. This is evidently sufficient to induce the Tetramorium workers to rear them in the place of their own enormous 492 ANTS. queens and males, the larve of which they therefore undoubtedly devour or neglect, as they do in the case of all that seems to be super- fluous.”” The absence of the conspicuous males and females of the host species in nests infested with testaceus aids the investigator in search- ing for the parasites, especially during late June and early July, when the host species is rearing the sexual brood, for nests containing male or female larvee or pupe of the Tetramorium may be quickly passed over and attention concentrated on the nests in which these are absent. Wasmann has shown that testaceus is more resistant to unfavorable conditions than its host. This suggests the feasibility of introducing it into America, where T. cespitum has become thoroughly acclimated and rather abundant, especially in some parts of the Atlantic States. Il. Harpagoxenus (Tomognathus)—The two known species of this genus are rare and very local ants, allied to Leptothoraxv, the genus to which their hosts belong. The workers are small, dark-brown, with short legs and hairy bodies and are easily recognizable by their broad, toothless mandibles and their peculiarly elongated frontal carinz, which extend back to the vertex and there bend outward, forming scrobe-like depressions for the short antenne. 1. Harpagoxenus sublevis (Fig. 274).—The habits of this ant have been studied by Adlerz (1886, 1896) and Viehmeyer (1906, 1908). It Fic. 274. Harpagoxenus sublevis. (Adlerz.) a, Male; b, ergatoid female. was formerly supposed to be confined to boreal Europe, having been discovered in Finland by Nylander (1848) and taken in Denmark by Meinert (1860), and in Sweden by Stolpe (1882) and Adlerz (1886, 1887, 1896), but Viehmeyer has recently shown that it also inhabits the heaths near Dresden. In the locality last mentioned it is always found in the nests of Leptothorax acervorum, and although this is its common host in northern Europe, Alderz has observed it also in the THE DEGENERATE SLAVE-MAKERS. 493 nests of L. muscorum and L. tuberum. The mixed colonies may con- tain males and females as well as workers of both the host and parasitic species. The males of sublevis are so much like those of Leptothorax that Adlerz failed to distinguish them till he published his final paper (1896). All the females which he found were wingless and ergatoid, with a thorax like that of the worker, but with ocelli and a receptaculum seminis. He naturally took these ergatoids to be the only females of the species, but in addition to these Viehmeyer has discovered winged females in some of the colonies in Saxony. Adlerz’s observations seem to show that sublevis secures its auxiliaries by attacking Lepto- thorax colonies, driving away the adult ants and taking possession of their nests and young. The latter are then reared as auxiliaries, or hosts. It is not impossible, however, that sublevis may recruit the number of its auxiliaries by making occasional sorties like Polyergus, for Adlerz succeeded in finding one nest in which the parasites were living with two species of Leptothorax (acervorum and muscorum). The domestic instincts of sublevis are very much blunted or obsoles- cent. It rarely or never excavates, and although it is able to feed itself 1f food is within reach, it does not go in quest of it, but leaves this to its host. A number of sublevis which Adlerz isolated with a number of larve and some food managed to live for 135 days, but the larve shriveled up or died. It seems probable, therefore, that this ant depends on its slaves for the nurture of its young. When the mixed colony moves to a new nest the sublevis are carried by the Leptothorax; very rarely are the roles reversed. Sometimes when the sublevis endeavor to leave the nest they are restrained by their slaves in much the same manner as Polyergus. Adlerz observed the males mating with the ergatoid females, but this occurred only between individuals belonging to different colonies. The larve of sublevis are so much like those of their hosts that he could not distinguish them. They are nourished both with regurgitated liquid food and with pieces of insects, a method of larval feeding which was also observed by Viehmeyer. This author believes that sublevis was originally lestobiotic like Sole- nopsis, that is, that it once robbed and devoured the young of an ant in whose neighborhood it nested without forming a mixed colony. The following are his views on the phylogeny of sublevis and its method of establishing colonies: “* The starting point of the development was rep- resented by an ant allied to Leptothorax, with males and females, both winged, and, like many other ants, with a predilection for eating the larve and pupz of allied species. This habit, practiced only occa- sionally at first, became established and the ants took to nesting near other ants, which at first tolerated these thieves unwillingly (compound 494 ANTS. nest). The thief ants then gradually became marauders (mixed colony). With increasing dependence on their auxiliaries, which showed itself in the dwindling of the worker instincts and the disap- pearance of the mandibular teeth, the difficulty, of founding colonies by means of winged females increased and led to the development of the ergatoid forms. In these the ancient lestobiotic and predatory instincts united with the newly acquired female instincts, so that the ergatoids became incomparably better fitted for founding colonies than the winged forms, which therefore tended to extinction. We must still, however, endeavor to explain why the winged females have never been found in the colonies of northern Europe. This may be accounted for in two ways. We may regard the winged female either as a rever- sion or as the lingering vestige of a not yet completely eliminated winged form. The latter alternative seems to be indicated by the remoteness of the locality in which this form occurs from the true Fic. 275. A, Harpagoxenus americanus worker and B, its host, Leptothorax curvi- spinosus worker. (Original.) geographical range of the species. The development of this sex would probably be unequally advanced in two regions differing so much in climate and other conditions. But we must wait to see whether this ant does not occur also in other regions, perhaps in northern Germany.” 2. Harpagoxenus americanus (Fig. 275, 4).—This species, which is smaller and of a darker brown color than sublevis, seems to be extremely rare. To my knowledge it has been taken on only three occasions. The type specimens, describe by Emery (1893-94), were found by Pergande at Washington, D. C., in a nest of Leptothorax curvispinosus (Fig. 275, B), but no observations on the relations THE DEGENERATE SLAVE-MAKERS. 495 of the two species were recorded. Schmitt found a few specimens while sifting vegetable mould for beetles near Beatty, Pa., and I found it during the summer of 1905, in a rich, boggy wood near Bronxville, N. Y. Here there were several fine L. curvispinosus colonies nesting in the hollow twigs of elder bushes, and in three of these colonies there were specimens of H. americanus. One con- tained only a single worker, another six, and a third eight workers and a queen of the parasitic ant. The latter insect was not ergatoid, but decidedly larger than the workers, with well-developed ocelli and a typical, though small, female thorax, showing distinct traces of having borne wings. All three colonies contained larve and pupz, presumably of the parasitic species, but no Leptothorax queens. When confined in artificial nests the americanus were very inactive and paid no attention to the brood. All the colonies were too small to admit of the suppo- sition that they had been formed by repeated forays on the part of Harpagoxenus. This ant, in fact, has every appearance of having reached a more abject stage of parasitism than its European congener. In the same locality I found a mixed queenless colony of the yellow L. curvispinosus and the black L. longispinosus inhabiting a hollow ‘ elder twig. If a dealated queen of H. americanus happened to estab- lish her colony in such a nest as this, we should havea case like Adlerz’s sublevis living with both L. acervorum and muscorum, but the inference that this indicated repeated slave-making forays on the part of ameri+ canus would be erroneous. B. The Permanent Social Parasites——The ants included in this group are all small and nearly all of them belong to monotypic genera. The absence of workers makes it difficult to assign definite positions to these genera in our classifications, which are based very largely on the worker forms. 1. Wheeleriella santschu (Fig. 276).—This is a small, dark-brown species, the female of which measures 4-4.7 mm. in length, the male only 3.5-3.8 mm. It was discovered by Santschi in the cactus fields near Kairouan, Tunis, and lives in the nests of the most abundant of all the North African ants, Monomorium salomonis and its varie- ties. The female Wheeleriella resembles Strongylognathus testaceus in having the posterior border of the head deeply excised and its posterior corners projecting as blunt horns. Santschi’s interesting observations have been published by Forel (tg06d) and may be briefly summarized. Although both sexes have well-developed wings, mating seems to take place, at least as a rule, in the outer galleries of the nest and between brothers and sisters (adelphogamy). After fecundation the dealated female roams about over the surface of 490 ANTS. the soil in search of J/onomorium nests. When near the entrance of one of these, she is “arrested,” to use Santschi’s expression, by a number of J/onomorium workers, which tug at her legs and antennz and sometimes draw her into the galleries. At other times she may be seen to dart into the nest entrance suddenly, so that she is arrested within the nest itself. There are no signs of anger on the part of the \/onomorium and she is soon able to move about in the galleries without restraint. The workers forthwith feed and adopt her. In the course of a few days she begins to lay eggs which are received and cared for by the Zonomorium workers. Santschi observed that the colonies infested with Wheeleriella were usually of small size, had an impoverished appearance and lacked queens of the host species, and he was able to account for these peculiar conditions. The Wheel- eriella queen pays no at- tention to the much larger Monomorium queen, but this insect is ‘assassinated by her own workers and the parasitic queen is adopted in her place. - Forel believes that this singular perversion of in- stinct is due to the prefer- ence of the workers for a smaller fertile indivi- dual, just as the Tetra- morium workers prefer to rear the small males and females of Strongy- lognathus instead of their own bulky sexual phases. This explanation is not Fic. 276. Wheeleriella santschii of Tunis; female; very satisfactory, how- (Original.) é ever, .for, .as “we have seen, the huge mother Tetramorium is retained in the nest, whereas it is precisely this individual that is destroyed in the infested Mono- morium colonies. Hence there must be some other reason for the assassination of the host queen by her own progeny. , 2. Epivenus andrei and creticus——These ants have been recently described by Emery (1908a), the former from females taken between Jaffa and Jerusalem in a nest of Monomorium venustum, and originally referred to this species by Ern. André (18810), the latter from a single THE DEGENERATE SLAVE-MAKERS. 497 male taken in Crete. As both species are related to Wheeleriella santschii, Emery believes that they lack the worker caste. 3. Sympheidole elecebra (Fig. 277, A).—This species, which is much smaller than Wheeleriella (female 2.75-3 mm.; male 2.5—2.75 mm. ), lives in the nests of Pheidole ceres, a common ant in the moun- tains of Colorado and New Mexico at altitudes between 2,500 and 3,000 m. The parasites and host are very similar, but the female of the former is much smaller, has a more rounded head and a very broad post-petiole. I have seen only two females: one taken by Schmitt in a ceres nest at Boulder, Colo., the other with eighteen males, taken by myself August 17, 1903, in the Ute Pass, near Manitou in the same state. The ceres colony in which I found these ants was carefully examined, but contained only workers and soldiers of the host species, and besides the adult parasites, a number of their pupe. No workers of the latter species could be detected, though from what we know of other ants, they should have been in the nest, if they exist at all, at the time of maturity of the males. When the nest, which was under a stone, was first disturbed, the Pheidole workers seized the para- sites and their pupz and quickly carried them into the galleries. As there are usually from one to five dealated queens in the un- infested colonies of ceres, their absence in this nest shows that they must have been eliminated. And as the elecebra queens are very small and feeble com- pared with the ceres queens Fic. 277. Parasites of Phictdole. (Origi- (which cancun cag cars nal.) A, Dealated female of Sympheidole ele- mm.), ig is probable that cebra; B, deadlated female of Epipheidole in- the latter are killed bv their quilina. 7 \ own workers and soldiers. 4. Epipheidole inquilina (Fig. 277, B).—Like the Sympheidole, this ant resembles its host, which is also a common Pheidole (P. pili- fera). Emery (1893-04) saw the small queen of Epipheidole (length 3-3.3 mm.) among some soldiers and workers of pilifera collected in Nebraska, but he regarded the insect as an unusually microgynic Pheidole. During late July and early August, 1903, I found near Colorado Springs three colonies of Ph. coloradensis, a subspecies of 33 495 ANTS. pilifera, containing males and females of the Epipheidole. In these colonies the coloradensis queens were absent, as in the case of the ceres and Sympheidole. It is probable, therefore, that they are elimi- nated by their own workers after the intrusion of the parasite. 5. Epacus pergandei ( Fig.278).—This species is known only from the types, a number of small black males and females taken by Pergande in a nest of Monomorium minimum near Washington, D. C., and described by Emery (1893-04). According to Pergande’s statement, the nest contained the winged sexes of the host in addition to those of the para- site, but as he also found that when both species were put in the same vial the Epacus queens attacked and killed some of the Monomorium males, I am inclined to believe that there is some confusion in his observations. He may have mixed two Monomorium colonies that were nesting very close together, one of which may have been pure and have contained the winged sexes, whereas the other consisted of male and female Epawcus and Monomorium workers. During the past eight years I have examined hundreds of M. imini- mum nests, but have never suc- ; ceeded in finding Epewcus. This Fic. 278. Ep@cus pergandei. (Emery.) : apn ae Meek Beiidesiacediareceate is not surprising, however, as all the workerless parasites are rare and very local in their distribution. 6. Anergates atratulus (Fig. 279).—This extraordinary ant, like the preceding, is far from common, though it is widely distributed in conti- nental Europe. For this reason it is better known than any of the other workerless parasites. Its host is Tetramorium cespitum. Studies on its habits have been published by Schenck (1852), von Hagens (1867), Forel (1874), Adlerz (1886), Wasmann (1891/) and Janet (1897¢e). Both male and female are peculiarly modified. The former is 2.7—3 mm. long, of a pale, sordid yellow color, wingless and pupa-like, with the gaster strongly curved downward at the tip. Although its legs are rather well developed, it moves very slowly and with a dawdling gait. The fore legs are furnished with strigils which are pecfiniform in specimens from certain localities (Switzerland), but in those from other localities (Sweden, Holland, France) the teeth are lacking and the strigils may be vestigial or absent. Janet has shown that the man- dibular glands are well developed, though the mandibles are very small and feeble. The black, winged female is of the same size as the male THE DEGENERATE SLAVE-MAKERS. 499 and has the gaster of normal dimensions, but with a longitudinal dorsal groove before fecundation. After entering the Tetramoriuim nest, however, the ovaries become greatly enlarged and the gaster expands till it becomes a flattened sphere 4 mm. in diameter, on which are seen, in the form of little plates, isolated by the enormous distention of the articular membranes, the strongly chitinized rings, which, in the virgin, constitute the whole external surface of the gaster. Both male and female have 11-jointed antennz and large ocelli, but the eyes are rather poorly developed. Owing to the apterous condition and sluggish move- ments of the male, mating takes place in the nest among the offspring Fic. 279. Anergates atratulus. (Original.) a, Virgin female; b, old queen; c, head of same; d, pupoid male; e, head of same. of the same mother (adelphogamy). This can be readily observed both in natural and artificial nests. The couples are so firmly united that they can be killed, without separating, in warm alcohol. After fecundation the females fly out of the nests, so that the nuptial flight, though vestigial and unisexual in this ant, still subserves the important function of disseminating the species. Tetramorium colonies infested with Anergates contain only the workers of the host species. Adlerz and Wasmann have shown that these pay very little attention to the virgin Anergates, but carry the males about and lick them assiduously, and that during these operations the latter assume a characteristic, motionless attitude. Both the male and female parasites are, of course, fed by their hosts, as they are quite unable to eat independently. 528 ANTS. Adlerz and Wasmann have made some experiments with a view to ascertaining the method whereby the female dAnergates becomes asso- ciated with the Tetramorium. Adlerz in Sweden placed several unfer- tilized Anergates queens in a strange nest of the host species. They moved about among the workers as if unperceived. Nearly the same results were obtained on placing unfertilized Anergates in a normal colony containing a 7etramorium queen. He also placed several larve, pup and male and female imagines of Anergates in a normal Tetra- morium colony which was living in an artificial nest. In every case the strangers were almost at once amicably received. Similar observa- tions were made by Wasmann in Holland. He found that strange Tetramorium workers did not in the least injure the male and female Anergates, whereas they killed without mercy a number of Strongylo- gnathus testaceus males and females which he placed in the nest. The experiments of Adlerz and Wasmann were not carried far enough to throw any light on the permanent adoption of the Anergates and the fate of the Tetramorium queen. It now seems probable that the latter insect is killed by her own workers soon after the colony is invaded by the parasitic queen. Since the publication of Santschi’s notes on IVheeleriella, renewed observations on young Anergates queens in the presence of alien Tetramorium colonies, and under natural con- ditions, have become a desideratum. June 6, 1907, at 2 P. M., while collecting ants near Vaud, in the very meadow in which Forel as a very young man made many of his classical observations on Formica sanguinea, Polyergus, Strongylognathus testaceus and other species of his ‘‘ Fourmis de la Suisse,” I discovered a medium-sized Tetramorium colony from which female Anergates were escaping in considerable numbers. The nest was around the roots of a plantain, and the females issued one by one from the entrances, climbed the leaves to their tips and flew away in all directions over the sun-lit grass. At 3.30 P. M. Professor Forel joined me and we excavated the nest with great care. It contained, besides the obese mother queen of Anergates and several thousand Tetramorium workers, more than a thousand winged queens, a few hundred of the pupa-like males, several pupz and a few larve of the parasitic species. In the galleries of the nest dozens of couples were united in the act of mating. The Tetramorium workers picked up the single males and hurried away with them, but they paid little attention to the females. The colony was placed in a bag and on the following day used for experiments on Tetramorium colonies in Pro- fessor Forel’s garden at Chigny. On opening the bag I found several of the Anergates in copuld, but most of the females had either lost their wings or were ready to drop them at the slightest touch. Eight Tetra- THE DEGENERATE SLAVE-MAKERS. 501 morium colonies that had large nests with multiple craters in the paths of the garden were selected and the females were placed near them one at a time on the ground. In all cases when they were placed within a few centimeters of the openings, they entered the nests almost imme- diately ; when placed at a greater distance they wandered about demurely till they found an opening and then at once crept into it. Seven of the nests were thus entered by numbers of the queens without creating the slightest excitement among the Tetramorium workers. These merely stopped when they happened to meet a female, seized her by the wings, thorax or pedicel, but at once dropped her and went about their work. In no case was one of the queens injured. In three of these colonies they were seized by single workers and carried into the nest as fast as I could set them on the craters. Both males and females were placed near the openings of one of these nests. The males were seized with signs of keen interest and some animosity, to judge from the way in which the workers bent their gasters forward and tried to sting the helpless creatures. They were not killed, however, but carried a few decimeters from the nest and then thrown away, sometimes from the top of a pebble or lump of earth. This was being done while other workers were carrying the females into the nest. One vigorous colony exhibited a different behavior: All the parasites, both male and female, were at once seized, pulled about by the legs, wings and antenne, and then carried away and dumped on the ground at some distance from the nest. In this instance several of the parasites of both sexes were injured so that they could not walk. Strange Tetramorium workers placed on any of the nests above mentioned were suddenly pounced upon and killed. These observations show that the dAnergates queens are, as a rule, treated with great lenity and even carried into the nests, but that the males are rejected. They also show that certain colonies are positively hostile to both sexes of the parasites. In all cases, how- ever, the behavior of the Anergates queens was very uniform: they sought and entered the Tetramorium nests as if these belonged to them, offered no resistance when seized, and, when roughly handled, merely curled up and feigned death. The experiments were continued through- out the morning. With. the gradually increasing temperature towards noon the Tetramorium became more numerous and active outside their nests, but their treatment of the Anergates, which I was continually giving them, remained the same. Late in the afternoon the experi- ments were repeated on two of the colonies, which, during the morn- ing, had been entered without protest by a number of the parasitic queens. The workers were out in a multitude, excavating and dragging in insect food. When male, female or pupal Anergates were placed 502 ANTS. on these nests, the males and pupz were promptly seized and thrown away and the females were also seized, but less promptly, and also rejected. Some of the latter that had managed to enter the nests were soon brought out and dumped at a distance of several decimeters. from the entrances. | watched the nests for some time and although a few of the females were not brought out, I am, of course, unable to state whether they were subsequently adopted, killed in the galleries, or ejected. It appears, therefore, that the acceptance of the parasites by the Tetramorium under natural conditions is not as immediate and simple as the observations of Adlerz and Wasmann on artificial nests would lead one to suppose. The fact that Anergates is so rare an ant, notwithstanding its sporadic colonies produce enormous numbers of females in regions inhabited by myriads of Tetramorium colonies, shows that permanent adoption is not easily effected. Were the contrary the case, Tetramorium cespitum would itself become a rare, if not extinct, species. There can be no doubt that of the seven permanent social parasites above enumerated, Anergates is the most specialized and degenerate. This 1s clearly shown in the ergatoid and nymphoid structure of the male and the structure of the head in both sexes. All the other species agree in being in a less advanced stage, although they, too, have lost the worker caste. This loss may be said to be due to disuse, but it followed necessarily upon the reduction in size of the male and female, and this condition in turn was probably initiated by the same causes that have led to the dwarfing of the queens among the temporary parasites. Forel, Lubbock and Wasmann are inclined to believe that Anergates represents a form that was once dulotic. Lubbock says: “Tn Anergates, finally, we come to the last scene of this sad history. We may safely conclude that in distant times their ancestors lived, as many ants do now, partly by hunting, partly on honey; that by degrees they became bold marauders and gradually took to keeping slaves; that for a time they maintained their strength and agility, though losing by degrees their real independence, their arts, and even many of their instincts; that gradually even their bodily force dwindled away under the enervating influence to which they had subjected themselves, until they sank to their present degraded condition—weak in body and mind, few in numbers, and apparently nearly extinct, the miserable repre- sentatives of far superior ancestors, maintaining a precarious existence as contemptible parasites of their former slaves.’ This interpretation of Anergates as a very degenerate dulotic ant seems to have been sug- gested by the obvious dwindling of the worker caste in Strongylog- THE DEGENERATE SEAVE-MAKERS. 593 nathus testaceus, but there is nothing in the structure of Anergates or of any of the other workerless ants to prove that they are descended from slave-making species. More probable is the supposition that they have been derived from temporary parasites or xenobiotic forms with habits like those of Leptothorax emerson. The Anergates or Wheel- eriella colony differs from those of species like Formica consocians in reaching its complete development, that is, the stage in which the sexual offspring of the mother queen mature, in a much shorter period of time. This period must fall within the lifetime of the Tetramorium or Mono- morium workers and can therefore hardly exceed three or four years. This acceleration of colonial development is made possible by a sup- pression of the useless worker caste and a dwarfing of the sexual individuals, although there is a concomitant increase in their numbers. And all of these interesting compensatory developments are necessi- tated in turn by the castration of the host colony, for this is what the elimination of the host queen amounts to. As this is a mortal injury to the host colony and a serious injury to the host species, it is not surprising that the intrusion of the parasites is resisted and that the latter, as Lubbock says, are “ few in number and apparently nearly extinct.’ In other words, extreme parasitism in ants, as in other organisms, tends continually to defeat its own ends and to undermine its own existence. The zoologist, as such, is not concerned with the ethical and socio- logical aspects of parasitism, but the series of ants we have been con- sidering in this and the four preceding chapters cannot fail to arrest the attention of those to whom a knowledge of the paragon of social animals is after all one of the chief aims of existence. He who without prejudice studies the history of mankind will note that many organiza- tions that thrive on the capital accumulated by other members of the community, without an adequate return in productive labor, bear a significant resemblance to many of the social parasites among ants. This resemblance has been studied by sociologists, who have also been able to point to detailed coincidences and analogies between human and animal parasitism in general.t| Space and the character of this work, of course, forbid a consideration of the various parasitic or semi- parasitic institutions and organizations—social, political, ecclesiastical and criminal—that have at their inception timidly struggled for adop- tion and support, and, after having obtained these, have grown great and insolent, only to degenerate into nuisances from which the sane *Cf., e. g., Massart and Vandervelde’s interesting paper: “ Parasitisme Organique et Parasitisme Social,” Bull. Sci. France et Belg., XXV, 1803. 304, AN Ts and productive members of the community have the greatest diff- culty in freeing themselves.* * Besides the mixed- colonies of ants considered in this and the two pre- ceding chapters, there are a few cases of a very exceptional and problematic character These are: 1. A mixed colony comprising workers of Lasius niger and L. flavus found by Adlerz (1896) in Sweden. 2. Two small mixed colonies comprising workers of L. nearcticus and L. americanus found near Rockford, Ill. (Wheeler, 19057). 3. Four small mixed colonies comprising workers of L. latipes and L. amer- icanus found near Colebrook, Conn. (Wheeler, 19057). 4. The small mixed colony of Leptothorax curvispinosus and L. longispinosus mentioned on p. 495. 5. A colony consisting of a male, two winged females and several workers of Pseudomyrma flavidula and several workers of Ps. elongata, found in a hollow Cladium culm in the Bahamas (Wheeler, 1905b). Adlerz believed that his mixed Lasius colony had been formed by dulosis, but Wasmann suggested that it was probably the result of an accidental alliance between fertilized queens of different species. I am inclined to believe that neither this nor the other colonies above enumerated arose in either of these ways, but by the accidental irruption of one colony into the contiguous brood galleries of another, followed by the pillaging and rearing of a number of alien worker larve or pupe. This is not dulosis, but as I have shown (p. 452), merely one of its conditions. CHAPTER. 2O@ViITIe THE SENSATIONS? OF Satins: “Tl faut donc, bon gré mal gré, étudier la psychologie et la physiologie en rapport l’une’ avec l’autre, en comparant leurs résultats, en tachant de trouver les relations les plus exactes possibles, entre leurs notions et les termes qui sy rapportent, méme au risque de retomber souvent dans l’anthropomorphisme sans le vouloir. Si nous connaisons ce dernier danger, et si nous le combattons sans relache, le corrigeant sans cesse, nous marcherons, d’erreur corrigée en erreur corrigée, lentement mais surement vers la vérité relative que seule nous pouvons connaitre. Si pas contre, ne voyant qu'un coté de la question, nous nous obstinons a vouloir d’un coup faire de la mécanique soi disant objective la ou toutes les. bases nous manquent pour le faire, nous tomberons dans l’absurde et n’arriverons a rien.”—Forel, ‘Sensations des Insectes,” V, 1901. To close our survey of the ants without a more coherent treatment of the subject of their behavior than is represented by the scattered references to “ reactions,” “habits” and “instincts”? in the preceding chapters, would be to turn aside from the very fons et origo of our interest in these insects. For structure and development, distribution in time and space, and the multifarious ethological relationships we have been considering are merely the more obvious aspects of an intricate and subtle behavior that enables these creatures to lead their balanced, but nevertheless plastic, social life amid an environment made up of refractory matter and more or less indifferent or hostile organisms. In endeavoring to gain an insight into the behavior of any animal, two courses are open to us. These may be designated as the intel- lectual and the intuitional, and it depends on the temperament and training of the observer which he will follow, or whether he will be inclined to follow both. The intellectual course is the one usually pursued by the scientist pure and simple, and is especially exalted by those most thoroughly embued with the spirit of our laboratories, where living organisms are best loved when they are dead, or, at any rate, when they can be subjected to the methods of investigation that have yielded such valuable results to the development of physics and chem- istry. In this environment the intellect proceeds on her clean path, according to her peculiar method, first cutting up the indiscerptible, flowing process, which is the life of every organism, into stationary concepts, and then combining these congealed and partial abstractions into a system that will have “explanatory’’ value—in obedience to Goethe’s well-known dictum: 505 500 ANTS. “Wer will was Lebendig’s erkennen und beschreiben Sucht erst den Geist herauszutreiben ; Dann hat er die Theile in seiner Hand, Fehlt leider nur das geistige Band.” Nor is the intellect able to proceed in any other manner, and that her ways are right and justifiable is shown by her triumphs. To extoll these in this place is unnecessary, but it should be remarked that the intellect, as Bergson has so beautifully shown, was evolved as an instru- ment of action and fabrication, and not for the purpose of under- standing or explaining an inorganic flux or movement, much less a durational and creative flux, like that which we call life. The intuitionist, in dealing with the behavior of animals, proceeds along the path of esthetic insight, sympathy and introspective knowl- edge of our own internal processes. His method is, therefore, essen- tially psychological and metaphysical. He does not deal with things or quantities, but with the living creative movement as immediately experienced in his own consciousness. He attempts to place himself en rapport with the organism and to move in the stream of its vital current. Being an animal organism himself, he may, therefore, be said to feel something of what must be taking place in other animals. This experience cannot be expressed, or can be expressed only through indirect or artistic channels, because language is essentially a work of the intellect. Thus the intellectual course is definite and concise, but its prime object is to eventuate in action or practice, whereas the intuitional course is vague, contemplative and ineffable, but is nearer reality. To the narrow scientific mind the intuitional method of contem- plating animal behavior has always been as great an abomination as is the self-sufficient, geometrical and mechanical method of the scientist to the nature lover. Both methods, when carried to extremes, lead to false or inane, or, at best, very partial interpretations—the scientific to a kind of animal phoronomy, like the reflex-theories of Bethe and *“ Modern science, no less than ancient science, proceeds according to the cinematographic method. It cannot do otherwise; all science is subject to this law. It is, in fact, of the essence of science, to manipulate signs, which it substitutes for the objects themselves. These signs undoubtedly differ from those of languages in their greater precision and higher efficacity, but they are none the less subject to the general condition of the sign, which is to denote a fixed aspect of reality under an arrested form. In order to think movement, an incessantly renewed effort of the mind is necessary. Signs are made for the purpose of dispensing with this effort by substituting for the moving continuity of things an artificial recomposition which is their equivalent in practice and has the advantage of being easily manipulated.”—Henri Bergson, “ L’Evolution Créatrice,” 4th ed., Paris, Félix Alcan, 1908, p. 356. See also the other works of this remarkable philosopher: “Essai sur les Données Immédiates de la Conscience,” 6th ed., 1908, and “ Matiére et Mémoire,” 5th ed., 1908. THE SENSATIONS OF ANS, 5oF Jexkull, the intuitional to the humanizing of animals and all the per- versities of the American “nature-fakers.” It is generally easy to class a particular observer according to his temperament and training. The scientist is prone to follow the intellectual method till he ends in rank atomic materialism, but he deserves admiration and sympathy for his consistency and his whole-souled confidence in his method. The intuitionist tends to become a panpsychist and though he may humanize the brute, we must remember that this is not a penal offence and that it does credit to his heart if not to his head. The scholastic will naturally adopt the intellectual method because he is used to work- ing among concepts and abstractions as if they were realities, but if he be a member of some religious body, he will not be averse to using the intuitional method, though in his hands it will be curbed and more or less perverted in the interests of dogma. He who enters on the study of animal behavior in the right spirit will strive to avoid both the nar- rowness of the laboratory worker and the superficial emotionalism of the nature-lover. That he will always adopt the proper attitude between these extremes is not to be expected of human nature, but it is possible to cultivate a critical and catholic spirit. If I decline to join the ranks of those whose only ambition is to describe and measure the visible movements of animals, and am willing to resort to a comparative psy- chology in which inferences from analogy with our own mental proc- esses shall have a place, I do this, not because I believe that the former course would be altogether unfruitful or uninteresting, but because the latter seems to me to promise a deeper and more satisfactory insight into the animal mind. In attempting to give a comprehensible account of such complicated phenomena as those of animal behavior, it is necessary to follow the course of the intellect and classify the various processes involved according to certain salient characters. Some authors have dwelt on the simplicity of certain processes, the complexity of others, while other authors have laid greater stress on automaticity and plasticity as differentiz. It is, indeed, convenient to distinguish first, simple responses to sensory stimuli, 7. e., reflex behavior; second, instinctive behavior, which has been referred by some to chains or series of such reactions—melodies, so to speak, of which the reflexes are but single notes or chords—and third, plastic or modifiable behavior, that is, behavior which is not stereotyped and automatic like the typical reflexes and instincts, but varies adaptively in response to the exigencies of the environment, and is more or less influenced by the previous expe- rience of the individual organism. By many this modifiable activity is supposed to be essentially intelligent. While such a treatment of 50S ; ANTS. the subject is convenient and will be followed in this and the two suc- ceeding chapters, it must be borne in mind that it is very artificial and schematic, as is clear from the fact that the psychical process in animals, the source of its visible activities, is neither a unity nor a multiplicity. Whatever views may be entertained concerning the nature of this process and the best method of studying it, all authors agree in regarding the simple sensory reactions as the basis of any scientific study of behavior and that this should be supported in turn by a mor- phological study of the sense organs. I shall, therefore, follow this course in our study of the ants, referring the reader to Chapter IV for the necessary data on the structure of the sense organs. For many interesting details, which lack of space compels me to omit, the reader must also be referred to the works of the following authors, who have contributed to our knowledge of sensation in ants: Huber (1810), Forel (1874, 1878d, 1886, 1900-01), Lubbock (1881), Bethe (1898, 1900, 1902), Janet (1893b, 1894), Wasmann (18999), von Buttel-Reepen (1900), Miss Fielde (1901a, 1901b, 1902, 1903a, 1903), 1904, 1905), Miss Fielde and Parker (1904), Viehmeyer (1900), Piéron (1904, 1905, 1906, 1907), and Turner (19070). The study of the sensory responses of ants is beset with grave difficulties, first, because these responses are more numerous, complex and obscure than in many lower animals; second, because several senses may be coimplicated in what appears as a single response, and third, because the sense organs of ants are merely analogous and by no means homologous with our own. These conditions prevent the observer and experimenter from isolating a single sense. Both the structure of the sense organs and experiment show, moreover, that ants respond to stimuli to which our own senses are irresponsive. It has, therefore, been suggested by Bethe and others that we abandon the terminology of human sensation with its subjective connotations and adopt a new one of purely objective import, that we speak of photorecepting instead of seeing, chemorecepting instead of smelling, tasting, etc. The reasons given for adopting these terms are not very cogent. Strictly speaking, we should have to use them for the higher animals and our fellow-men. As Forel remarks: “One ought not to say, ‘My wife has a headache.’ One should say, ‘This animal machine which I believe to be my wife exhibits certain facial cortortions and emits certain articulate sounds that correspond with those emitted by myself when I have a headache, but I have no right to say that she has a headache.’” The difficulties above mentioned are not to be avoided by adopting a new nomenclature, but by further and more persistent THE SENSATIONS OF ANTS. 509 experimentation and observation. I have emphasized them because they seem to have been ignored by some investigators. Although touch is one of the most important senses of ants, it has not been thoroughly studied in these insects. Its great delicacy is attested by the number, distribution and structure of the tactile hairs or sensilla. As these are extremely fine and abundant on the antennal funiculi, we are justified in concluding that the latter are the principal organs of touch and as the moving ant continually palpates and explores the surfaces over which she travels, it is not improbable that she gleans perceptions of the forms of objects. But it is impossible to dissociate this mechanical sense from the chemical or olfactory sense, since the organs of both are not only situated in the same antennal joints, but are intermingled with one another. It is probable that ants also per- ceive tactile stimuli to the general chitinous integument where it is not furnished with hairs. That these insects have a very delicate tempera- ture sense, although the location and nature of its organs are quite unknown, is shown by many of their habits, notably by the way they regulate their hours of activity and the way they place their brood in the best situations for utilizing the warmth of the earth and stones. That ants are capable of feeling pain hardly admits of doubt, for, as Forel says: “ They often exhibit unequivocal signs of discomfort, espe- cially when their antennz are pinched, or when their nerve terminations come in contact with certain corrosive or strongly irritating substances.” But the quiet manner in which an ant, that has just had an antenna, a leg or even her abdomen cut off, will gorge herself with honey, shows that her sensation of pain must differ profoundly, both in quality and intensity, from that which we should suffer from similar operations. Much more attention has been devoted to the study of the sense of smell than to that of touch. Forel (1874, 1878d), the pioneer in this field of investigation and the one who has established all the impor- tant facts, found that many ants, when deprived of their antennz, not only do not attack alien ants, but even lick them, that they cannot care for the young or excavate the nest, and are able to eat only when they stumble on their food by accident. Such ants also make unusual move- ments with their legs and palpi in attempting to substitute these organs for their missing antenne. Forel believes that the pros- trate, club-shaped sensilla (see Chapter IV, p. 62) are the principal olfactory organs, because they are the ones best developed in insects with the keenest sense of smell (e. g., in Ichneumon flies). Ants are able to perceive odors diffused in the air as well as those dissolved in liquids; for even the blind species often stop and wave their funiculi about in a peculiar manner when within a short distance of an odorous 510 ANTS. body. It is probable, however, that the odor stimulates the delicate end organs only when it is dissolved in the thin film of glandular secre- tion covering the antennal club. When the antennz actually touch the surface of a body, however, the ant, in all probability, receives both tactile and olfactory stimuli, and these probably fuse to produce a single sensation, which Forel calls the topo-chemical, or contact-odor sensation. He believes, therefore, that the ant has a sense of odor- shape. To make this clear he suggests that we fancy ourselves to be blind or in total darkness and in possession of delicate olfactory organs in our finger-tips. Then, if we moved about, touching objects to the right and left along our path, our environment would appear to us to be made up of shaped odors, and we should speak of smells that are spherical, triangular, pointed, etc. Our mental processes would be largely determined by a world of chemical configurations, as they are now by a world of visual (7. e., color) shapes. Blind ants are, of course, permanently in the condition here described, and as all other ants spend most of their time in the dark recesses of the nest, and, with the exception of very few species, rely but little on their eyesight, we can see how different must be our own mental processes from those of these insects. In order to understand many of the commonest reactions of ants, such as the recognition of friends and foes, the homing instincts of the worker and the development of certain peculiarities of myrmecophiles, we must suppose that ants have not only extremely acute powers of odor-discrimination, but no less extraordinary powers of odor-associa- tion. Even the degenerate human olfactories can detect the different species and in some cases even the different castes of ants (Eciton) by their odors, but these insects carry the discrimination much further. They not only differentiate the innate odors peculiar to the species, sex, caste and individual and the adventitious or “ incurred” odors of the nest and environment, but, according to Miss Fielde, they can detect “ progres- sive odors,’ due to change of physiological condition with the age of the individual. She believes that “as worker ants advance in age their progressive odor intensifies or changes to such a degree that they may be said to attain a new odor every two or three months.” Miss Fielde is also convinced that different antennal joints are specialized for the perception of different odors. This conclusion was reached by cutting off the joints one at a time and studying the subsequent behavior of the ant. She says: “ The organ discerning the nest-aura, and probably other local odors, lies in the final joint of the antenna, and such odors are discerned through the air; the progressive odor or the incurred odor is discerned by contact, through the penultimate joint; the scent » THE SENSATIONS OF ANTS. 511 of the track by the antepenultimate joint, through the air; the odor of the inert young, and probably that of the queen also, by contact, through the two joints above, or proximal to those last mentioned, while the next above these by contact also discerns the specific odor.” This statement not only lacks confirmation by other observers, but seems to be the only one which implies that the olfactory organs of an animal may exhibit regional differentiations. This has not even been claimed for dogs, which, nevertheless, possess extremely delicate powers of odor discrimination and association. This would be no serious objec- tion, however, if we were able to discover the slightest support for Miss Fielde’s hypothesis in the structure of the antenne. We do, indeed, find in the funiculi a variety of sensilla, as has been shown in Chapter IV, but none of these is confined to a single joint or to two joints. Miss Fielde, moreover, completely ignores the tactile organs of the antennz and makes this surprising statement: “ During five years of fairly constant study of ants I have seen no evidence that their antenne are the organs of any other sense than the chemical sense.” And still she observed that ants that had lived in a Petri dish for over a year felt perfectly at home in any new Petri dish to which they were transferred. For an interpretation of such a case of “ recognition ” one would certainly turn to a mechanical rather than to a chemical sense. Many of her interpretations of the behavior of ants with muti- lated antennz are open to the obvious objection that she tacitly denies the existence of perception where there is no visible response or where the animal inhibits certain of its activities. If we add to this objection the very limitations of the method, 7. ¢., the necessity of removing all the joints distal to the one whose function is being tested, and the con- sideration that the hypothesis is not needed in explaining the facts, it will be seen that we are not sufficiently justified in regarding the ants’ antenna as an organ made up of a series of specialized “ noses.” It is not always easy to distinguish taste from smell in our own sensory experience, and in ants, where even the structure of the sen- sill in the antennze and mouthparts are very similar, the difficulty is greatly enhanced. That the rows of sensille on the maxille and at the base and tip of the tongue are the organs of taste seems to be proved by the observations of Forel (1886-88, 1900-01). He found that ‘““ when morphine or strychnine are mixed with honey, the ants fail to detect these substances with their antennze. The odor of the honey attracts them and they begin to eat it. But as soon as their mouth- parts come in contact with it they at once turn away. It is easy to observe the preferences of ants for certain viands; they will partake of some and not of others, but they will neglect everything, sometimes 512 ANTS. even their duties and the defence of the nest, in order to partake of honey, so inordinate is their fondness for this substance.” Forel has seen ants that were attacked in their nest and in imminent danger of being overpowered by their enemies, nevertheless stop a moment and imbibe a little of the honey which he was holding out to them. The fondness of nearly all ants for sweets, such as the excreta of plant-lice, and their dislike of ill-smelling things, such as carrion and the feces of mammals, is very pronounced.? Taste is evidently the sense in which these insects approach most closely the higher animals and man. Whether or not ants are able to perceive the stimuli that we call auditory, has been much debated. In Chapter II I have shown that stridulatory organs are well developed in the Ponerinz and Myrmicinze and are present in a rudimental form also in the Doryline; and that the ants possessing these organs actually emit very shrill sounds— usually of so high a pitch as to be inaudible to us—has been observed more or less clearly by a number of investigators, notably by Swinton (1878, 1879), Wroughton (1892), Sharp (1893), Janet (18930), Emery (1893), Wasmann (1893a), Adlerz (1895) and myself (1903f). Forel (1874) and Wasmann (1893) have shown that the workers of European Camponott make sounds also by striking the walls of their nest repeatedly with their gasters, and Gounelle (1900) observed that workers of the Brazilian Camponotus mus, which nests in the twigs and dried leaves of the bamboo, produce, when disturbed, a very audible, metallic and whirring sound like that of a rattlesnake, by repeatedly striking the walls of the nest with their heads. In Chapter IV attention was called to the fact that all ants (even the Camponotinz and Dolichoderinz!) possess in all their tibia, and probably also in other parts of their bodies, structures built on the same fundamental plan as the famous chordotonal organs of the stridulating crickets and katydids. This fact renders it extremely probable that ants perceive not only the stridulatory vibrations of their fellows, but also other vibrations. All students of these insects would doubtless agree to this statement. At this point, however, opinions begin to diverge. Huber (1810) and Forel (1874) deny that ants hear sounds, and the latter, while admitting that they respond easily to grosser mechanical shocks, failed to obtain any response to sounds of a very high pitch. Lubbock (1881), on the other hand, believed that they react to such sounds, but he failed to obtain any experimental evidence for his view. Parker and Miss Fielde (1904) failed to observe any reactions to “aérial *I have seen Eciton cwcum visiting carrion, but this was evidently for the purpose of feeding on the larve of flies, Silphids, etc. A correspondent informs me that the ants of the Philippines have similar habits and are very important agents in reducing the number of flies at certain seasons of the year. THE. SENSATIONS OF ANTS. 513 sound waves from a piano, violin and Galton whistle, which collectively gave a range of from 27 to 60,000 vibrations per second.” The insects reacted, however, to vibrations reaching them through the soil and other solids. These vibrations were received through the legs, as they were perceived even when the antennz, head, abdomen and any one or two pairs of legs were removed. In contradiction to this view and that of Forel, several authors have recently maintained that ants do perceive aérial vibrations. That this is the case has been stated by Weld (1899) for Cremastogaster lineolata, Lasius americanus and Aphenogaster sp., and by Metcalf (1900) for “a small black ant.” Wasmann (18 91f, 18999) has recorded similar, rather inconclusive observations. I have also virtually expressed myself in favor of such a view in one of my papers (1903a@), in a passage which as been over- looked or misunderstood by some recent students of this subject, and may therefore be repeated in this place: * Stridulation, at least among the Myrmicinz, Ponerinze and Doryline, is an important means of com- munication, which Bethe has completely ignored and even Forel and other myrmecologists have failed to appreciate. It readily explains the rapid congregation of ants (Myrmicinz) on any particle of food which one of their number may have found, for the excitement of finding food almost invariably causes an ant to stridulate and thus attract other ants in the vicinity. It also explains the rapid spread of a desire to defend the colony when the nest is disturbed. This is especially notice- able in species of Pheidole, Myrmica and Pogonomyrmex. It 1s the secret of being able in a short time to catch ants like P. molefaciens in great numbers by simply burying a wide-mouthed bottle up to its neck in the mound of the nest. An ant approaches and falls into the bottle. It endeavors to get out, and failing, begins to stridulate. This at once attracts other ants which hurry over the rim and forthwith swell the stridulatory chorus till it is audible even to the human ear. More ants are attracted and soon the bottle is filled. If it be corked and shaken for the purpose of still further exciting its contents, and then held over another Pogonomyrmex colony whose members are peacefully sauntering about on the dome of the nest, the wildest excite- ment will suddenly prevail, as if there had been a call to arms—or to dinner. Even more remarkable is the stridulation in a colony of Atta fervens (=texana), the Texan leaf-cutting ant. Here the different ants, from the huge females through the males, large soldiers and diminishing castes of workers to the tiny minims, present a sliding scale of audibility. The rasping stridulation of the queen can be heard when the insect is held a foot or more from the ear. To be audible the male and soldier must be held somewhat closer, the largest workers 34 514 ANTS. still closer, whereas the smallest workers and minims, though stridu- lating, as may be seen from the movements of the gaster on the post- petiole, are quite inaudible to the human ear. It is not at all improb- able that all this differentiation in pitch, correlated as it is with a differentiation in the size and functions of the various members of the colony, is a very important factor in the cooperation of these insects and of ants in general. The contact-odor sense, important as it undoubtedly is, must obviously have its limitations in the dark, subter- ranean cavities in which the ants spend so much of their time, espe cially when the nests are very extensive like those of Atta. Under such conditions stridulation and hearing must be of great service in maintaining the integrity of the colony and of its excavations.” If the view of Miss Fielde and Parker be accepted, we must suppose that the Pogonomyrmex in the experiment above described, were thrown into agitation by vibrations passing from the bottle of stridulating ants through my body to the soil of the nest. It seems to me much more probable that the ants perceived the stridulation directly as aérial vibrations. More numerous experiments, however, have been recently performed by Turner (1907b). Although he worked only with Camponotine ants (Formica fusca and F. sanguinea), which are not known to stridulate, he found that they responded to vibra- tions as low as 256 and as high as 4,138 per second. “The re- sponses, in the form of zigzag movements, were usually slight for pitches higher than 3,000 vibrations per second and sometimes slight for other pitches; but, to most pitches under 3,000 vibrations per second, the ants usually responded in a pronounced manner, usually darting about as though much excited.” Turner believes that he took sufficient precautions, by resting the nest on cotton and felt, to exclude the transfer to the ants of vibrations through the floor, table and walls of the nest. It is, however, extremely difficult to prove that such vibrations were excluded, and for this reason we cannot, with the data at hand, reject the statements of Miss Fielde and Parker. As these authors say: “It has long been recognized by physiologists, if not by the scientific public, that touch and hearing in the vertebrates are very closely related. The apparent separateness of these senses in us is due to the fact that the air waves by which our senses are usually stimu- lated are too slight to affect our organs of touch. If, however, we transfer our experiments to water, we at once meet with a medium in which, as has long been known, vibrations can be both heard and felt. In dealing with a like question among the lower animals it therefore seems to us misleading to attempt to distinguish touch from hearing, and we shall be more within the bounds of accuracy if we discuss the DEAE SSENSATIONS qi PPP Grice She cn Socmbban Se oveaedaos Subgen. Lobopelta Mayr. Median spur of middle and hind legs alone developed, lateral spurs lacking; Small species, with avyestieialeyess joe misee nee oe eee Ponera Latr. Both spurs of the middle and hind legs well-developed; medium or large Species, with laneenveyes ts eect Gee eee Oe oe 10. Cheeks with: a longitudinalMcarinas-e-nee eee eee ee! Neoponera Emery. Gheeks, -withoutsancarinae set seen rae oe ee aa ee nee Vat . Clypeus flat, separated from the frontal carine by a scarcely perceptible Stituresor monerateall Bbodylopaqhe= nase quence eee ‘Platythyrea Mayr. Clypeus separated from the frontal carine by a distinct suture; body sub- Opaqtie PO Shins hae ee Nes eee aes oe are ee ee Eee ee Tes Pronotum more or less marginate on the sides; middle tibiz not abbreviated nor beset “with? promitient bristless274.2... ne Pachycondyla F. Smith. Pronotum not marginate on the sides; middle tibiz short, with prominent bristles on their extensor surfaces. Euponera Forel; subgen. Pseudoponera Emery. Subfamily DoryLin ®. 4 Clase FOOTING Cle oF eee Ses as, SN Sa, are Eciton WLatr. Clawisssimple sceecr ci ors eeen eae on neato ise cers Subgen. 551-552. Hill, J. A.. 1905. Fights between Two Species of Ants. Victorian Natur. 22: 35-30. Hilzheimer, Max, 1904. Studien uber den Hypopharynx der Hymenopteren. Jena. Zeitschr. Nat. 39: 119-150, I pl. | Hinds, W. E., 1907a. *Papers on the Cotton Boll Weevil and Related and Associated Insects. An Ant Enemy of the Cotton Boll Weevil. U. S. Dept. Agri. Div. Ent. Bull. No. 63: 45-48, 1 fig. —1907b. *Some Factors in the Natural Control of the Mexican Boll Weevil. Jbid. Bull. No. 74, 79 pp., 4 pls., 2 text-figg. Hochhuth, J. H., 1871. *Enumeration der in den russischen Gouvernements Kiew und Wolhynien bisher aufgefundenen Kafer. Bull. Soc. Imp. Nat. Moscou 3: 85 seq. Hoffer, E., 1890. *Skizzen aus dem Leben unserer heimischen Ameisen. Mitth. Nat. Ver. Steiermark 26: 149-171. Holliday, M., 1904. A Study of Some Ergatogynic Ants. Zool. Jahrb. Abt. Syst. 19: 293-328, 16 fige. Hollman, M., 1883-’84. *Nachtrag zu Briiggemanns Verzeichniss der bisher in der Gegand von Bremen aufgefundenen Kaferarten, mit besonderer Bertick- sichtigung der bei Ameisen gefundenen Kafer. Abh. Nat. Ver. Bremen 7: 477-479. Holmgren, N., 1904. *Ameisen (Formica exsecta Nyl.) als Hugelbildner in Siimpfen. Zool. Jahrb. Abt. Syst. 20: 353-370, 14 figg. Hooke, R., 1667. Micrographia or some physiological descriptions of minute bodies made by magnifying glasses, with observations and inquiries there- upon (p. 203 Formice). London 38 pls. Hope, F. W., 1837. Inquiries into the ground for the opinion that Ants lay up stores of food for the Winter. Trans. Ent. Soc. London 2 Proc.: 37.— 1840. On some doubts respecting the GEconomy of Ants. J/bid. 2: 211- 213. — 1845. *Description of some new species of Coleoptera from Adelaide in New Holland. Jbid. 4: 106 seq. Hoppe, T. C., 1755. Verschiedene Nachrichten von Ameisen. Mylius Physik. Belust. 3, 25: 1075-1087. Hopkins, A. D., 1905. Insect Injuries to Forest Products. Yearbook U. S. Dept. Agric. 1904: 381-308, 14 figg. | LITERATURE. 609 Horn, G. H., 1879. *Monographic Revision of the Species of Cremastocheilus and Synopsis of the Euphoride of the United States. Proc. Am. Phil. Soc. 18: 382-408, pl. 4.— 1886. *Concerning Cremastocheilus. Ent. Amer, 1: 187, 188. Horvath, G., 1886. Sur lintelligence des Fourmis. Suppl. contenant la revue des articles publiés dans la Rovartani Lapok, 3: XII. — 1889. Papirosbol épits hangyak. Term.-tud. Kozl. 21: 151, 2 pls. Hubbard, H. G., 1876-’78. *Notes on the Tree-nests of Termites in Jamaica. Proc. Bost. Soc. Nat. Hist. 19: 267-271. Huber, F., 1804. *Extr. Sulle Formiche, uso delle loro antenne, e loro rapporti coi pidocchi delle piante e coi gallinsetti. Nuov. Scelt. d’Opusc. Inter. 1: 206-212. Huber, P., 1810. *Recherches sur les mceurs des Fourmis indigenes. Paris et Genéve, 1 Vol.— 1861. Réimpression. Genéve. Huber, J., 1905. *Ueber die Koloniengriindung bei Atta sexdens. Biol. Centralb. 25: 606-619; 625-635, 26 figg.— 1907. *Jdem. (Transl.) Smiths. Report for 1906: 355-367, pls. 1-5.— 1908. *A origem das colonias de Sauba (Atta’ sexdens). Bol. Mus. Goeldi 5, 1: 223-241. Huepsch, 1777. Beschreibung einer Maschine die Ameisen und anderen Insekten zu vertilgen. (In Germ. and French.) Cdln, 1 pl. Hutton, F. W., 1904. Index Faune Nove Zealandie. London, Dulau & Co. (pp. 96, 97, list of Formicide). Hudson, G. V., 1890. (Swarming of Atta antarctica.) Ent. M. Mag. (2) 1: 23. Huth, E., 1886a. *Ameisen als Pflanzenschutz. Mitth. Ver. Frankfurt a. O. 4: 101, 138, 171. —1886b. *Myrmecophile und myrmekophobe Pflanzen. bid. 4: 317-337. VON IHERING, H., 1882. Ueber Schichtenbildung durch Ameisen (Atta cepha- lotes). Briefl. Mitth. aus Mundonovo, Rio Grande do Sul, Brasilien. Oct., 1881. Neues Jahr. Mineral. 1: 156, 157.— 1891. *Die Wechselbeziehungen zwischen Pflanzen und: Ameisen in den Tropen. Das Ausland 24: 474- 477. —1894- Die Ameisen von Rio Grande do Sul. Berl. Ent. Zettschr. 39: 321-446, 1 pl.— 1898. *Die Anlage neuer Colonien und Pilzgarten bei Atta sexdens. Zool. Anz. 21: 238-245, 1 fig. —1903. Zur Frage nach dem Ursprung der Staatenbildung bei den sozialen Hymenopteren. J/btd.- 27, 4. —r1905. A Formiga Cuyabana. Revista Agricola 124 (15 Nov.) : 511-522, S. Paulo. — 1907. *Die Cecropien und ihre Schutzameisen. Engler’s Botan. Jahrb. 39: 666-714, pls. 6-10, 1 text-fig. Illiger, J. C. W., 1802. Magasin ftir Insektenkunde, 1: 188. Imhoff, L., 1838. Insecten der Schweiz. Bascl. 2.— 1843. Grosse Schwarme von Formica nigra am 17 Juli 1841. Ber. tib. Verh. Naturf. Gesell. Basel 5: 164-180.— 1852. Ueber eine Art afrikanischer Ameisen. Jbid. 109: 175-177. : Istvanffi, G., 1894. *Gombatenyészto hangyak. Termes Kozl. Magyar. Tars. pp. 378-387. JACOBSON, EDWARD, 1907. Notes on Web-spinning Ants. [’ictorian Nat. 24: 36-38.—1908. Verfertigung der Gespinnstnester von Polyrhachis bicolor Sm. auf Java. (Communicated by E. Wasmann.) Notes Leyden Mus. 30: 63-67, pl. 6. Jacobson, Edw., & E. Wasmann, 1905. Beobachtung iiber Polyrhachis dives auf Java die ihre Larven zum Spinnen der Nester benutzt. Notes Leyden Mus. 20a ice =1A0) Jacquelin-Duval and Lespis, 1849. *(Observations on the Claviger testaceus found in an Ant’s nest.) Ann. Soc. Ent. France p. \xxii. 40 610 ANTS. Janet, C., 1872. *(Note on the insects living with Tetramorium cespitum.) Ibid. p. li.—1892. [Marques extérieurs correspondants aux organes Chordotonaux des Fourmis.] Jbid. 61 (Bull.): 247-248.—1893a. Nids artificiels en platre. Fondation d’une colonie par une femelle isolée. Bull. Soc. Zool, France 18: 168. Paris 183 4 p. (Note 3).—1893b. Sur la pro- duction des Sons chez les Fourmis et sur les Organes qui les produisent. Ann. Soc. Ent. France 62: 159. (10 p.) (Note I.).—1893c. Appareil pour V’Elevage et l’Observation des Fourmis. Jbid. 62: 467 (16 p.), 3 figg. (Note 2).—1893d. *Etudes sur les Fourmis. 3me note Extr. Bull. Soc. Zool. France 18: 168-171. — 1893e. *Sur les Nématodes des glandes phar- yngiennes des Fourmis (Pelodera Janeti L. D.). C. R. Hebd. Ac. Sc. Paris, Séance du 20 Noy., 1 fig. —1894a. Sur l’Anatomie du pétiole de Myrmica rubra. Mém..Soc. Zool. France 7: 185, 18 pp., 6 figg. — 1894b. Sur l’Appareil de stridulation de Myrmica rubra. Ann. Soc. Ent. France 63: 109, 9 pp., 2 figg. (Note 6).—1894c. Sur la Morphologie du squelette des segments post-thoraciques chez les Myrmicides (Myrmica rubra femelle). Além. Soc. Acad. l’Oise 15: 591. Beauvais 9 pp., 11 figg. (Note 5).—1894d. *Pelodera des glandes pharyngiennes de Formica rufa. Mém. Soc. Zool. France 7: 45 Paris 18 pp., 11 figg. (Note 4).—1894e. Sur les Nerfs de l’antenne et les organes chordotonaux chez les Fourmis. C. R. Sé. Acad. Sc. Inst. France 118: 814, 2 figg. —1894f. Sur le Systeme glandu- laire des Fourmis. J/bid. 118: 989 (Note 3).—1895a. Structures des Mem- branes articulaires des Tendons et des Muscles (Myrmica, Camponotus, | Vespa, Apis). Limoges, 26 pp., 5 figg. (Note 12).—1895b. Sur les Muscles des Fourmis, des Guépes et des Abeilles. C. R. Sé. Acad. Sc. Inst. France 121: 610, 1 fig. (Note 7).—1895c. Sur l’Organe de nettoyage tibio-tarsien de Myrmica rubra. Ann. Soc. Ent. France 63: 691 Paris 14 pp., 7 figg. (Note 8).—1896a. *Sur le Lepismina polypoda et sur ses rapports avec les Fourmis. Bull. Soc. Ent. France 65: 131.—1896b. *Sur les Rapports des Lépismides myrmécophiles avec les Fourmis. C. R. Sé. Acad. Sc. Inst. France 122: 790, 1 fig. (Note 8).—1896c. *Les fourmis. Bull. Soc. Zool. France 21: 60-93. —1897a. *Sur les rapports du Discopoma comata Berlese avec le Lasius mixtus Nylander. C. R. Acad. Paris 124, 2: 102-105, 4 figg. (Extr. Rev. Sc. (4), 7, 4: 117.) (Note 9.) —1897b. *Sur les rapports de l’Antennophorus Uhlmanni Haller avec le Lasius mixtus Nyl. /bid. 124, 9 — II: 583-585, 1 fig. (Transl. Ann. Mag. Nat. Hist. (6) 19: 620-623, 1 fig. d Ausz. von R. v. Hanstein, Nat. Rundschau 12, 33: 422-423; von S. Sch., Nat. Wochenschr. 12, 30: 357-358; von E. K[rause], Prometheus 8, 403: 620-622, ~ 1 fig. Abstr. Journ. R. Micr. Soc. London 3: 203; Amer. Nat. 31, 366: 544, 1 fig. 31, 368: 726-728.) (Note 10.) —1897c. Etudes sur les Fourmis, les Guépes et les Abeilles. Limites morphologiques des anneaux post-céphaliques et musculature des anneaux post-thoraciques chez la Myrmica rubra. Lille, 4 le Bigot fréres, 36 pp., 10 figg. (Note 16).—1897d. *Appareils pour l’'Ob- : servation des Fourmis et des Animaux myrmécophiles. Mém. Soc. Zool. France 10: 302, Paris 22 pp., 3 figg. 1 pl. (Note 15).—1897e. *Rapports des animaux myrmécophiles avec les fourmis. Limoges, Ducourtieux, 100 pp. (Abstr. Nat. Sc. 12: 323-327.) (Note 14.) —1897f. *Sur le Lasius mixtus, l’Antennophorus uhlmanni, ete. Limoges, 62 pp., 16 figg. (Note 13). —1897g. Les Fourmis. Expos. Intern. Bruxelles, Section des Sciences. Bruxelles, Haycz, 56 pp., figg. — 1898a. Sur un organe non deécrit, servant A la fermeture du réservoir du venin et sur le mode de fonctionnement de laiguillon chez les fourmis. C. R. Acad. Sc. Paris 127: 638-641, 13 figg. — 1898b. tudes sur les fourmis, les guépes et les abeilles. Anatomie du corselet de la Myrmica rubra reine. Mém. Soc. Zool. France 11: 393-449, 1 pl, 25 figg. (Note 19).—1898c. Etudes sur les Fourmis, les Guépes et les Abeilles. Aiguillon de la Myrmica rubra. Appareil de fermeture de la ee ee i ee eee LITERATURE. O11 glande a venin. Faris, G. Carré et C. Naud, 27 pp., 3 pls., 5 figg. (Note 18).—1898d. Etudes sur les Fourmis, les Guépes et les Abeilles. Systéme glandulaire tégumentaire de la Myrmica rubra. Observations diverses sur les Fourmis. Parts, Geo. Carré et C. Naud, 28 pp., 9 figg. (Note 17).— 1898e. Sur une cavité du tégument servant, chez les Myrmicine, a étaler, au contact de l’air, un produit de sécrétion. C. R. Acad. Sc. 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Maria-Laach.” 33 (1887) ].—1889b *Ueber sklavenhaltende Ameisen. Ausz. in Ent. Nachr. Karsch. 15, 4: 65-66. (Aus Natur. Offenb. 35: I-11.) — 188gc. *Neue Ecitongaste aus Siidbrasilien. Deutsch. Ent. Zeitschr. pp. 185-190, pl. 1.—1889d. “Ueber einige myrmekophile Heteropteren. Jbid. pp. I9I-192.—1889e. *Nachtragliche Bemerkungen zu Ecitochara und Ecitomorpha. Jbid. p. 414.—1889f. “Zur Lebens- und Entwicklungsge- schichte von Dinarda. Wien. Ent. Zeit. pp. 153-162. —1889g. *Zur Kennt- niss der Dinarda-Formen. J/bid. pp. 181-182;— 1890a. *Apteranillus Forelin. sp. Deutsch. Ent. Zeitschr. pp. 318-320.— 1890b. Einige neue Hermaphro- diten von Myrmica scabrinodis und M. levinodis. Stett. Ent. Zeitg. 51: 298-299. — 1890c. *Oc6chrotus unicolor Luc. Deutsch. Ent. Zeitschr. p. 206. —1890d. *Myrmecophila Salomonis n. sp. Jbid. pp. 303-304. — 18g0e. *Neue myrmekophile Staphyliniden aus Brasilien. Jbid. pp. 305-318, pl. 2. —18g90f. *Ueber die verschiedenen Zwischenformen von Weibchen und Arbeiterinnen bei Ameisen. Stett. Ent. Zeitg. 51: 300-309.— 1890g. *Ver- gleichende Studien tiber Ameisengaste u. Termitengaste. Haag. Sep. aus Tijdschr. Ent. 33: 27-97, pl. 1. 2 Nachtr. pp. 262-266.—1890h. *Verzeich- niss der von Dr. Aug. Forel in Tunesien und Ostalgerien gesammelten Amei- 640 ANTS. sengiiste. Deutsch. Ent. Zeitschr. pp. 297-302. — 18901. *Zur Lebensweise der gelbrothen Sibelameise (Strongylognathus testaceus). Natur u. Offenb, 12. 1891a. Ueber Lautausserungen von Myrmica ruginodis und Gehorsver- moégen von Formica rufa. Stimm. Maria-Laach 50: 214.—1891b. *Eine neue Clavigeride aus Madagaskar (Rhynchoclaviger cremastogastris), mit vergleichenden biologischen Bemerkungen. Stett. Ent. Zeitg. pp. 3-10, pl. 1. —1891c. Parthenogenesis bei Ameisen durch ktnstliche Temperaturver- hiltnisse. Biol. Centralb. 11: 21-23.—1891d. *Verzeichniss der Ameisen und Ameisengiiste von Hollandisch-Limburg. Haag. Sep. aus Tijdschr. Ent. 34: 30-64.—1891e. *Zur Bedeutung der Fuhler bei Myrmedonia. Biol. Centralb. 11, 1: 23-25.—1891f. Zur Frage nach dem Gehorsvermoégen der Ameisen. Jbid. 11, 1: 26.—1891g. *Vorbemerkungen zu den internation- alen Beziehungen der Ameisengaste. Jbid. 11, 11: 331-343.—1891th. *Die zusammengesetzten Nester und gemischten Kolonien der Ameisen. 262 pp., 2 pls., 16 figg. Miinster i. W. Aschendorffsche Buchdruckeret. — 18928. *Ein neuer Paussus vom Somaliland. Muitth. Schweiz. Ent. Gesell. 8, 9.— 1892b. *Die internationalen Beziehungen von Lomechusa strumosa. Bvol. Centralb. 12, 18-21; 584-5590; 638-669. — 1892c. Einiges iiber springende Amei- sen. Wien. Ent. Zeitschr. 11: 316, 317. —1892d. *Zur Biologie einiger Amei- sengaste. Deutsch. Ent. Zeitschr. pp. 347-351. — 1893a. Lautausserungen der Ameisen. Biol. Centralb. 13: 39, 40.—1893b. *Neue Myrmekophilen. Deutsch. Ent. Zeitschr. pp. 97-112, pl. 5.—1893c. *Zwei neue Staphyl- inidengattungen aus Sikkim. Jbid. pp. 206-208. —1893d. “Ueber Paussiger und Articeropsis Wasm. Wien. Ent. Zeitg. p. 257. —1893e. *Eine myrme- kophile Ceratopogon-Larve (C. Braueri n. sp.). Jbid. pp. 277-279. — 1893f. *“Centrotoma rubra Saule. in Bohmen. J/bid. p. 279.—1894a. *Zur Myrmekophilenfauna des Rheinlandes. Deutsch. Ent. Zeitschr. pp. 273 and 274. —1894b. *Die europaischen Dinarda, mit Beschreibung einer neuen deutschen Art. Ibid. pp. 275-280.— 1894c. *Zur Lebens- und Entwicklungsgeschichte yon Atemeles pubicollis, mit einem Nachtrag uber Atemeles emarginatus. Ibid. pp. 281-283.—1894d. *Ueber Atemeles excisus Thoms. Jbid. pp. 283-284. —1894e. *Ueber Xantholinus atratus Heer (picipes Thoms.). Ibid. pp. 285-287. — 1894f. *Formica exsecta Nyl. und ihre Nestgenossen. Verh. Nat. Ver. Bonn. 51, 1: 10-22.— 1894g. *Kritisches Verzeichniss der myrme-— kophilen und termitophilen Arthropoden. Mit Angabe der Lebensweise und Beschreibung neuer Arten. xvi+ 231 pp. Berlin.—1895a. *Zur Kennt- niss einiger schwieriger Thorictus-Arten. Deutsch. Ent. Zeitschr. 1: 41- 44.— 1895b. *Verzeichniss der von Prof. Aug. Forel im Fruhling 1893 in der algerischen Provinz Oran gesammelten Ameisengaste. J/bid. pp. 45-48. —1895c. *Zur Kenntniss der myrmekophilen und termitophilen Arthropo- den. Zool. Anz. 471: 111-114. —1895d. *Die Ameisen- und Termitengaste von Brasilien. 1. Verh. Zool. Bot. Gesell. Wien 4: 137-179. (Sept. 1- 45.) —1895e. *Zur Kenntniss einiger Thorictus-Arten. 2. Deutsch. Ent. Zeitschr. 2: 291-293.—1895f. *Zur Biologie von Lomechusa_ strumosa. Ibid. 2: 294. —1895g. *Die ergatogynen Formen bei den Ameisen und ihre Erklarung. Biol. Centralb. 15, 16 and 17: 606-646. — 1896a. *Eine Ameisen- kolonie durch Nematoden zerstort. Tijdschr. Ent. 41: 18-19.—1896b. *Os hospedes das formigas e dos termites (cupim) no Brazil. Bolet. Mus. Paraense 1, 3: 273-324, 2 pls. —1896c. *Kritische Bemerkungen tiber einige Myrmekophilen und Termitophilen. Vien. Ent. Zeitg. 1: 32-36. — 1896d. *Notes sur la chasse des Coléoptéres myrmécophiles et termitophiles. Rev- nes, 4 pp.—1896e. *Dinarda-Arten oder -Rassen? Wien. Ent. Zeitg. 4 and 5: 125-142. —1896f. *A revision of the genus Clidicus. Notes Levyd. Mus. 18: 14-18.— 1896g. *Die Myrmekophilen u. Termitophilen. Vortrag gehalten am 16 Sept. 1895 zu Leyden. C. R. 3 Congr. Internat. Zool. Leyde, pp. 411-440, 1 text-fig. Auss: von K. W.v. Dalla Torre. Zool. Centralb. LITERAPURE, 641 3, 18: 636-638. — 1896h. *Einige neue Paussus aus Java, mit Bemerkungen iiber die myrmekophile Lebensweise der Paussiden. Notes Leyden Mus. 18: 63-80, 1 pl. — 1896i. *Zur Kenntniss einiger Thorictus-Arten. 3. Deutsch. Ent. Zeitschr. 2: 242-243. — 1896j. *Revision der Lomechusa-Gruppe. Jbid. 2: 244-256. — 1896k. *Zoologische Ergebnisse einer von Dr. K. Escherich und Dr. L. Kathariner nach Centralkleinasien unternommenen Reise. Myrme- kophilen. Jbid. 2: 237-241. — 18974. *Selbstbiographie einer Lomechusa. Stimm. Maria-Laach. 1.—1897b. *Instinkt und Intelligenz im Thierreich. 94 pp. Freiburg i/B. — 1897¢. *Vergleichende Studien,ttber das Seelenleben der Ameisen und der héheren Thiere. 122 pp. Freiburg i.B.— 18974. *Zur Entwicklung der Instinkte (Entwicklung der Symphilie). Verh. Zool.-bot. Gesell. Wien. 3: 168-183. —1897e. *Ueber einige myrmekophile Acarinen. I. Zool. Anz. 20, 531: 170-173. — 1897f. *Bemerkungen tiber einige Ameisen von Madagaskar. Ibid. 20, 536: 249-250. (Abstr. Journ. R. Micr. Soc. London 1897: 375.) —1897g. *Eine neue Xenodusa aus Colorado, mit ‘einer Tabelle der Xenodusa-Arten. Deutschr. Ent. Zeitschr. 2: 273-274, pl. 1, fig. 9. —1897h. *Ueber ergatoide Weibchen und Pseudogynen bei Ameisen. Zool. Anz. 20, 536: 251-253. —18g97i. *Ein neuer Fustigerodes aus der Kap- kolonie. Wien. Ent. Zeitg. 7: 201.—1897j. *Ueber einige myrmekophile Acarinen. II. Zool. Ang. 541: 346-350.— 1897k. *Neue Myrmekophilen aus Madagaskar. Deutsch. Ent. Zeitschr, 2: 257-272, pls. 1 and 2. — 1897]. *Zur Biologie der Lomechusa-Gruppe. J/bid. 2: 275-277.—1897m. *Ein neuer Dorylidengast aus Siidafrika. Jbid. 2: 278, pl. 2, fig. 6.—1897n. *Ein neuer Eciton-Gast aus Nord-Carolina. Ibid. 2: 280-282, pl. 2, fig. 4.— 18970. *Ein neues myrmekophiles Silphidengenus aus Costa-Rica. Ibid. 2: 283-285, pl. 2, fig. 5.—1897p. *Zur Morphologie und Biologie der Lo- mechusa-Gruppe. Zool. Anz. 546: 463-471.—1897q. *Die Familie der Paussiden. Stimm. Maria-Laach. 9 and 10.—1898a. *Ameisenfang von Theridium triste Hahn. Zool. Anz. 21, 555: 230-232.—1898b. *Ueber Novoclaviger und Fustigerodes. Wien. Ent. Zeitg. 3: 96-99. — 1898c. *Eine neue dorylophile Tachyporinengattung aus Siidafrika. /bid. 3: 101-103, figg. I-4.—1898d. *Eine neue Philusina vom Cap. Ibid. 3: 103-104. — 1898e. *Ein neuer Claviger aus Bosnien. J/bid. 4 and 5: 135.—1898f. Die Gaste der Ameisen und Termiten. Jllustr. Zeitschr. Ent. 3, 10-16, 1 pl. — 1898g. *Erster Nachtrag zu den Ameisengasten von Hollandisch Limburg, mit bio- logischen Notizen. Haag. Tijdschr. Ent. 41: 1-18.—1898h. *Ein kleiner Beitrag zur Myrmekophilenfauna von Vorarlberg. Mitth. Schweiz. Ent. Gesell. 10:: 134-135.— 18981. *Zur Kenntniss der Myrmekophilen und Ameisen von Bosnien. JViss. Mitth. Bosn. Herz. Landesmus. 6. — 1898}. *Einige neue myrmecophile Anthiciden aus Indien. Verh. Zool.-bot. Gesell. Wien 7: 482-484.—1898k. *Ueber die Gaste von Tetramorium cespitum, sowie tiber einige andere Myrmecophilen. Versl. 53 Somerverg. Ned. Ent. Ver. (11 Jun.) pp. 60-65.— 18981. *Zur Lebensweise von Thorictus Forell. Mit einem anatomischen Anhang und einer Tafel. Natur. Offenb. 8: 466- 478.— 1898m. *Neueres tiber Paussiden. Verh. Zool.-bot. Gesell. Wien 7: 507-515. —1898n. *Die Hohlenthiere. Stimm. Maria-Laach. 6 and 7.— 18980. “Ueber Myrmecophilen. Tijdschr. Eni. 41 Versl. pp. 60-65. — 1898p. *Thorictus Foreli als Ectoparasit der Ameisenftihler. Zool. Anz. 21, 564: 435-436, 7 figg.—1898q. *Nochmals Thorictus Foreli als Ectoparasit der Ameisenfithler. Jbid. 21, 570: 536-546.—1898r. Eine neue Reflextheorie des Ameisenlebens. Biol. Centralb. 18: 578-589. — 1898s. *Eine Ameisen- kolonie durch Nematoden zerst6rt. Tijdschr. Ent. 41: 18-19. — 18g9a. *Instinct und Intelligenz im Thierreich. Freiburg i/B. Herder’sche Ver- lagshandlung. —1899b. *Lasius fuliginosus als Raubameise. Zool. Anz. 22: 85-87, 153, I fig. —1899c. *Zur Kenntniss der bosnischen Myrmekophilen 42 64 ANTS. und Ameisen. JI’iss. Mitth. Bosn. Hercegov. 6: 767-772, 3 figg. — 1899d. *Neue Termitophilen und Myrmecophilen aus Indien. Deutsch. Ent. Zcit- nd . . . bed Schr. pp. 145-109, 2 pls. —1899e. *Ein neues myrmecophiles Curculioniden- genus aus der Kapkolonie. J/bid. pp. 170-171, 1 pl.—1899f. *Eine neue dorylophile Myrmedonia aus der Kapkolonie, mit einigen anderen Notizen uber Dorylinengaste. Jbid. pp. 174-177.— 1899g. *Die psychischen Fahig- keiten der Ameisen. (95. Beitr. Kenntn. Myrmekoph. Termitoph.) Zoologica II, 26: 132 pp., 3 pls.—1g00a. *Zur Kenntniss der termitophilen und myr- mekophilen Cetoniden Sudafrikas, IJllustr. Zeitschr. Ent. 5: 65-68; 81-84, 1 pl. Nachtrag pp. 103-104.—1900b. *Neue Dorylinengaste aus dem neo- tropischen und dem athiopischen Faunengebiet. (114. Beitr. Kenntn. Myr- mekoph. Termitoph.) Zool. Jahrb. Abt. Syst. 14: 215-289, 2 pls. — 1g00c. *Zwei neue Lobopelta-Gaste aus Siidafrika. Deutsch. Ent. Zeitschr. pp. 403-404, I fig. —1g00d. *Ein neuer Gast von Eciton carolinense. Ibid. pp. 409-410. — 1g00e. *Zwei neue myrmekophile Philusina-Arten aus Siidafrika. Ibid. pp. 405-406.—1g900f. *Ueber Atemeles pubicollis und die Pseudo- gynen von Formica rufa L. Jbid. pp. 407-409.—1901a. Zum Orientier- ungsvermogen der Ameisen. Allgem. Zeitschr. Ent. 6: 19-21; 41-43, 1 fig. —r1go1b. *Zwei neue Liometopum-Gaste aus Colorado. (116. Beitr. Kenntn. Myrmekoph. Termitoph.) Wien. Ent. Zeitg. 20: 145-147. — 1gorc. *Zur Lebensweise der Ameisengrillen (Myrmecophila). Natur. Offenb. 5, 47, 3: 129-152.—1g01d. *On Some Genera of Staphylinidz, described by Thos. L. Casey. Canad. Ent. 5, 33: 249-252. —1901e. *Giebt es thatsichlich Arten, die heute noch in der Stammesentwicklung begriffen sind ? Zugleich mit allgemeinen Bemerkungen itber die Entwicklung der Myrmekophilie und Termitophilie und tber das Wesen der Symphilie. Biol. Centralb. 5, 21, 22 and 23.—1901-’o2, *Neues tiber die zusammengesetzten Nester und gemischten Kolonien der Ameisen. Allgem. Zeitschr. Ent. 6: 353-355; 360- 371; 7: 1-5; 33-37; 72-77; 100-108; 136-139; 167-173; 206-208; 235-240; 260-265 ; 293-298; 340-345; 385-390; 422-427; 441-449, 1 pl. (Ref. R. von Hanstein. Nat. Rundsch. 18: 368-370.) —1902a. *Neue Bestatigungen der Lomechusa-Pseudogynentheorie. Verh. Deutsch. Zool. Gesell. 12: 98-108. —1g02b. Noch ein Wort zu Bethe’s Reflextheorie. Biol. Centralb. 22: 573-576. — 1g02c. *Zwei neue europdische Coleopteren. Deutsch. Ent. Zeitschr. p. 16.—1g902d. *Verzeichniss der von Dr. W. Horn auf Ceylon 1899 gesammelten Termiten, Termitophilen und Myrmekophilen. /bid. pp. 79-80. — 1g02e. *Coléoptéres myrmécophiles recueillis par le prof. A. La- meere en Algérie. Ann. Soc. Ent. Belg. 46: 159.—1902f. *Biologische und phylogenetische Bemerkungen iiber die Dorylinengaste der alten und der neuen Welt, mit specieller Beriicksichtigung ihrer Convergenzerscheinungen. Verh. Deutsch. Zool. Gesell. 12: 86-89.—1902g. *Riesige Kurzfliigler als Hymenopteren-Gaste. (132. Beitr. Kenntn. Myrmekoph. Termitoph.) In- sektenborse 19: 267-268; 275-276; 282, 3 figg.—1902h. *Ein neuer myrme- kophiler Ilyobates aus dem Rheinland (Ilyobates brevicornis n. sp.). Deutsch. Ent. Zeitschr. p. 62.—1902i. Zur Ameisenfauna von Helgoland. Jbid. pp. 63-64. —1902j. *Zur Kenntnis der myrmecophilen Antennophorus und anderer auf Ameisen und Termiten reitender Acarinen. (121. Beitr. Kenntin. Myrmecoph. Termitoph.) Zool. Anz. 25: 66-76.—1902k. *Termiten, Ter- mitophilen und Myrmekophilen, gesammelt auf Ceylon von Dr. W. Horn 1899, mit anderm ostindischen Material bearbeitet. Zool. Jahrb. 5, 17, Syst.: 99-164, pls. 4, 5.—1903a. *Zur Brutpflege der blutroten Raubameise (For- mica sanguinea Ltr.). Jnsektenbérse 20: 275-276. —1903b. *Zum Mimicry- typus der Dorylinengaste. (135. Beitr. Kenntn. Myrmecoph. Termitoph.) Zool. Anz. 26: 581-590. —1903¢. *Zur naheren Kenntnis des echten Gast- verhaltnisses (Symphilie) bei den Ameisen- und Termitengasten. Biol. Centralb, 23: 63-72; 195-207; 232-248; 261-276; 298-310. —1904a. Ameisen- “ LITERATURE. 643 arbeiterinnen als Ersatzkoniginnen. Muitth. Schweiz. Ent. Gesell. 11: 67-70. —1g04b. *Zur Kenntniss der Gaste der Treiberameisen und ihrer Wirthe am obern Congo, nach den Sammlungen und Beobachtungen von P. Herm. Kohl C. SS. C. bearbeitet. (1738. Beitr. Kenntn. Myrmekoph. Termitoph.) Zool. Jahrb. Suppl. 7 Festschr. Weismann pp. 611-682, 3 pls. — 1904c. *Neue Beitrage zur Kenntniss der Paussiden mit biologischen und phylogenetischen Bemerkungen. (142. Beitr. Kenntn. Myrmekoph. Termitoph.) Notes Leyden Mus. 25: 1-82, 6 pls. —1904d. *Die moderne Biologie und die Entwicklungs- theorie. 2 Ed. 323 pp., 4 pls., 4o text-figg. Herdersche Buchh. Freiburg. i/B. —r1g05a. *Die phylogenetische Umbildung ostindischer Ameisengaste in Termitengaste. Mitth. Schweiz. Ent. Gesell. 11: 66-70. C. R. 6me. Congr. Internat. Zool. Berne pp. 436-449, 1 pl.—1905b. *Versuche mit einem brasilianischen Ameisennest in Holland. (1750. Beitr. Kenntn. Myrmekoph. Termitoph.) Tijdschr. Ent. 48: 209-213, 1 pl.—1905c. Berichtigungen zu Note I dieses Bandes. Notes Leyden Mus. 25: 110.—1905d. *Ursprung und Entwickelung der Sklaverei bei den Ameisen. (1746. Beitr. Kenntn. Myrmekoph. Termitoph.) Biol. Centralb. 25: 117-127; 129-144; 161-169; 256-270; 273-202, 2 figg. (Analyse Rev. Sc. (5) 5: 820-823.) — 1905¢e. *Some Remarks on Temporary Social Parasitism and the Phylogeny of Slavery among Ants. Biol. Centralb. 25: 637-644.—1905f. *Nochmals zur Frage uber die temporar gemischten Kolonien und den Ursprung der Sklaverei bei den Ameisen. Jbid. 25: 644-653.—1905¢. *Zur Lebensweise einiger in- und auslandischen Ameisengaste. (748. Beitr. Kenntn. Myrme- koph. Termitoph.) Zeitschr. Wiss. Insekt.-biol. 1: 329-336; 384-390; 418-428. —1g06a. *Zur Geschichte der Sklaverei beim Volke der Ameisen. Stim. Maria-Laach 70: 405-425; 517-531.—1906b. *Zur Myrmekophagie des Griinspechts. Tidschr. Ent. 48: 6-12.—1906c. *Zur Lebensweise von Atemeles pratensoides Wasm. Zeitschr. Wiss. Insekt.-biol. 2: 1-12; 37-42, 3 figg. Anhang. Ein merkwtirdiges Heizmaterial bei Formica pratensis. pp. 42-43.—1906d. *Beispiele rezenter Artenbildung bei Ameisengasten und Termitengasten. Biol. Centralb. 26: 565-580.—1906e. *Zur Kenntniss der Ameisen und Ameisengaste von Luxemburg. (1753. Beitr. Kenntn. Myrme- koph. 1 and II Teil.) Arch. Trimestr. Inst. Grand-Ducal. Sect. Sc. t and 2: 17 pp., 2 pls. —1906f. K. Escherich, Die Ameise, Schilderung ihrer Lebens- weise. Biol. Centralb, 26: 801-806.— 1906g. *Die Gaste der Ameisen und ‘der Termiten. Vortrag 77 Versamml. Deutsch. Naturf. Acrzie Meran. Verh. 1906, 2.—1g06h. *Die moderne Biologie und die Entwickelungstheorie. 3rd Ed. Freiburg 1. Breisgau.—1907a. Ameisennester “ Boussole du Mon- tagnard.” Naturwiss. Wochenschr. N. F. 6: 391, 392, fig. —1907b. Sur les Nids des Fourmis migrantes (Eciton et Anomma). Atti Pontif. Accad. Rom. Nuov. Linc. 60: 6 pp.—1907c. *Ueber einige afrikanische Paussiden. Deutsch, Ent. Zeitschr. pp. 147-153, pl. 1.—1907d. *Ueber einige Paussiden des Deutschen Entomologischen National-Museums. Jbid. pp. 561-566, 3 figg.—1908a. Zur Kastenbildung und Systematik der Termiten. Biol. Centralb, 28: 68-73. —1908b. *Weitere Beitrige zum sozialen Parasitismus und der Sklaverei bei den Ameisen. Jbid. 28: 257-271; 289-306; 321-333; 353-3823; 417-441, 3 figg. Nachtrag, Jbid. 28: 726-731.—1908c. *Ein neuer ' Paussus von Togo. Deutsch. Ent. Zeitschr. p. 576.—1908d. Die Sinne der Ameisen. Vortrag gehalten auf der Wander-Versammlung “ Luxemburger Naturfreunde” in Ettelbriick, am 3. Mai 1008. Luxemburg, P. Worré- Merkens. — 1908e. *Myrmechusa; eine neue Gattung zwischen Myrmedonia und Lomechusa. Ann. Mus. Civ. Hor. Nat. Genova (3) 4: 38-42, 5 figg. — 1908f. L’Udito nelle Formiche. Riv. Fis. Mat. Sci. Pavia 9, 108: 1-7.— 1908g. *On the Evolution of Dinarda, a genus of Coleoptera. Transl. by Horace Donisthorpe. Zoologist, pp. 68-71. 644 ANTS. Wasmann, E., and Edw. Jacobson, 1905. Beobachtungen uber Polyrhachis dives auf Java die ihre Larven zum Spinnen der Nester benutzt. Notes Leyden Mus. 25: 133-140. Waterhouse, C. 0., 1882. *|Note on Paramellon sociale Waterh.] Proc. Ent. Soc. London pp. iv-v.—1907. @ of Genus Dorylus. Trans. Ent. Soc. London p. vi, 2 figg. Webster, F. M., 1887-’88. *Ihe relation of Ants to the Corn-Aphis. Rep. Comm. Agric. Wash. pp. 148-149. Also Imsect Life 1, 5: 152.—1899. *On the Relations of a Species of Ant, Lasius americanus, to the Peach Root Louse, Aphis prunicola. Canad. Ent. 31: 15-16.—1907. *The Corn Leaf-Aphis and Corn Root-Aphis. U. S. Dept. Agric. Bureau Ent. Circ. No. 86, 13 p. Weed, C. M., 1891. *Sixth Contribution to a Knowledge of the Life History of Certain Little Known Aphidide. Bull. Ill. State Lab. Nat. Hist. 3: 207-214. von Weidenbach, C., 1859. *Verzeichniss der in der Umgegend von Augsburg vorkommenden Myrmekophilen. 12 Ber. Nat. Ver. Augsb. p. 83. Weir, J., 1898. The Ears of Worms, Crustaceans and Ants. Sci. Amer. Apr. p. 214. Weismann, Aug., 1892. Das Keimplasma. Eine Theorie der Vererbung. Jena, Gustav Fischer. pp. 494-498. — 1893a. The All-Sufficiency of Natural Selec- tion. Contemp. Rev. Sept. pp. 309-338. — 1893b. Die Allmacht der Natur- zuchtung. [Eine Erwiderung an Herbert Spencer. Jena, Gust. Fischer. 96 pp. — 1894. The Effect of External Influences upon Development. Romanes Lecture, London, Henry Frowde pp. 29-48.—1902. Vortrage iiber De- scendenz-theorie. Jena, Gustav Fischer 2: 101-118. Weld, LeRoy D., 1899. The Sense of Hearing in Ants. Science N. S. 10: 766- 768. Remarks by M. M. Metcalf, /bid. 11: 1094. Wellenius, 0.,,1904a. Ett meddelande om Tomognathus sublevis Nyl. Meddel. Soc. Faun. Flor. Fenn. 29: 70-72. — 1904b. For Finland nya eller sallsynta myror. IJbid. 29: 124. Wesmael, C., 1825. *[Observations on the habits of Claviger testaceus.] Lettre addressée a M. le comte Dejean par M. C. Wesmael. Encyc. Méth. Hist. Nat. Ent. 10: 223.— 1838. Sur une nouvelle espéce de fourmi de Mexique. Bull. Acad. Roy. Soc. Brus. Bell. Lettr. 5: 766-771, pl. 19, figg. 1-4. Westhoff, Friedrich, 1881-’82. *Die Kafer Westfalens. Suppl. Verh. Nat. Ver. Rheinl. Westf. 38. Westwood, J. 0., 1839-’40. *Introduction to the modern classification of insects. 2 Vols. London.—1840. Observations on the genus Typhlopone, with Descriptions of several exotic species of Ants. Ann. Mag. Nat. Hist. 6: 81-89, 1 pl. — 1843-’45. *Monograph of the Coleopterous Family Pausside. Arch. Ent. 2, London. —1847a. Description of a New Dorylideous insect from South Africa, belonging to the genus A€nictus. Tyrans. Ent. Soc. London 4: 237-238, fig. —1847b. Description of the Driver Ants. (Anomma arcens.) Ibid. 5: 296-300, fig. —1852. “Description of some new species of the Coleopterous family Pausside, with a synopsis of the family. Jbid. (2) 2: 84-96.— 1854. Contributions to Fossil Entomology. Quart. Journ. Geol. Soc. London pp. 378-396, pls. 14-18.— 1855. *Description of a new genus of Coleopterous Insects inhabiting the interior of Ants’-nests in Brazil. Trans. Ent. Soc. London (2) 3: 90-94.—1856. *Descriptions of various species of the Coleopterous family Pselaphide, natives of New South Wales and South America. Jbid. (2) 3: 268-280.— 1861. *Notice of the Occurrence of a Strepsipterous Insect parasite on Ants, discovered in Ceylon by J. Nietner. Jbid. (2) 5: 418-420.— 1869. *Remarks on the genus Ectrephes and descriptions of New Exotic Coleoptera. Ibid. pp. 315-320. — 1874. *Thesaurus Entomologicus Oxoniensis. Oxford. , LITERATORE 645 Wetherill, C. M., 1852. Chemical Investigation of the Mexican Honey Ant. Proc. Acad. Nat. Sc. Phila. 6: 111, 112. von Wettstein, R., 1888. *Ueber Kompositen der Gsterreich-ungarische Flora mit zuckerabscheidenden Hiullschuppen. Sitzber. Akad. Wien. — 1890. *Pflanzen und Ameisen. Schrift. Ver. Verbreit. Naturw. Kenntn. Wien 29: 307-327. Wheeler, W. M., 1900a. *The Female of Eciton sumichrasti Norton, with some Notes on the Habits of Texan Ecitons. Amer. Nat. 34: 563-574, 4 fige. —1goob. A Study of Some Texan Ponerine. Biol. Bull. Boston 2: 1-31, 10 figg.—x1g00c. *The Habits of Myrmecophila nebrascensis Bruner. Psyche 9: 111-115, 1 fig.-—1g00d. *A New Myrmecophile from the Mush- room Gardens of the Texan Leaf-Cutting Ant. Amer. Nat. 34: 851-862, 6 figg.—1g00e. The Habits of Ponera and Stigmatomma. Biol. Bull. Boston 2: 43-69, 8 figg.—1g01a. Notices biologiques sur les fourmis mexi- caines. Ann. Soc. Ent. Belg. 45: 199-205. [In English.] —1g901b. *Micro- don Larve in Pseudomyrma nests. Psyche 9: 222-224, I fig.—1go1c. *The Compound and Mixed Nests of American Ants. Amer. Nat. 35: 431-448; 513-539; 701-724; 791-818, 20 figg.—1901d. *The Parasitic Origin of Mac- roérgates Among Ants. /bid. 35: 877-886, I fig. —1901e. *An Extraordi- nary Ant-guest. /bid. 35: 1007-1016, 2 fgg. —1902a. New Agricultural ants from Texas. Psyche 9: 387-303.—1902b. A New Agricultural Ant from Texas, with Remarks on the known North-American Species. Amer. Nat. 36: 85-100, 8 figg.—1g902c. A Neglected Factor in Evolution. Science N. S. 15: 766-774.—1902d. The Occurrence of Formica cinerea Mayr and Formica rufibarbis Fabricius in America. Amer. Nat. 36: 947-952. — 1902e. An American Cerapachys, with Remarks on the Affinities of the Cerapachy- ine. Biol. Bull. 3: 181-191, 5 figg.—1902b. A Consideration of S. B. Buckley’s “ North American Formicide.” Trans. Texas Acad. Sc. 4, 2, 2: I5 pp.—1902c. Formica fusca Linn. subsp. subpolita Mayr. var. perpilosa, n. var. Mem. Soc. Cient. Ant. Alzate Mexico 17: 141-142. —1903a. The Origin of Female and Worker Ants from the Eggs of Parthenogenetic Workers. Science N. S. 18: 830-833.—1903b. Some New Gynandro- morphous Ants, with a Review of the Previously Recorded Cases. Bull. Amer. Mus. Nat. Hist. 19: 653-683, 11 figg.—1903c. *Erebomyrma, a New Genus of Hypogeic Ants from Texas. Biol. Bull. 4: 137-148, 5 fige. —1903d. *A Revision of the North American Ants of the Genus Leptothorax Mayr. Proc. Acad. Nat. Sc. Phila. 55: 215-260, 1 pl. — 1903e. Extraordinary Females in Three Species of Formica, with Remarks on Mutation in the Formicide. Bull. Amer. Mus. Nat. Hist. 19: 639-651, 3 figg. —1903f. *Ethological Observations on an American Ant (Leptothorax Emersoni: Wheeler). Arch. Psycol. Neurol. 2: 1-31, 1 fig.—1903g. A Decad of Texan Formicide. Psyche 10: 93-111, 1o figg.—1903h. The North American Ants of the Genus Stenamma (sensu stricto). Jbid. 10: 164-168. — 1903i. Some notes on the Habits of Cerapachys august. Jbid. 10: 205-209, I fig. —1g04a. A Crustacean-Eating Ant (Leptogenys elongata Buckley). Biol. Bull. 6: 251-259, 1 fig. —1904b. *Three New Genera of Inquiline Ants from Utah and Colorado. Bull. Amer. Mus. Nat. Hist. 20: I-17, 2 pls. —1904c. The American Ants of the Subgenus Colobopsis. Jbid. 20: 139-158, 7 figg.—1904d. Ants from Catalina Island, California. Ibid. 20: 269-271.— 1904e. Dr. Castle and the Dzierzon Theory. Science N. S. 19: 587-591. — 1904f. The Ants of North Carolina. Bull. Amer. Mus. Nat. Hist, 20: 299-306.—1904g. On the Pupation of Ants and the Feasibility of Establishing the Guatemalan Kelep or Cotton-weevil Ant in the United States. Science N. S. 20: 437-440. —1904h. *A New Type of Social Para- sitism among Ants. Bull. Amer. Mus. Nat. Hist. 20: 347-375.— 19041. Some Further Comments on the Guatemalan Boll-weevil Ant. Science N.S. 646 ANTS. 20: 766-768. — 1904j. Social Parasitism among Ants. Amer. Mus. Nat. Hist. Journ. 4,4 (Oct.) : 74-75. —1905a. *An Interpretation of the Slave-making Instincts in Ants. Bull. Amer. Mus. Nat. Hist. 21: 1-16.—1905b. The Ants of the Bahamas, with a List of the Known West Indian Species. J/bid. 21: 79-135, I pl., 11 figg.—x1905¢c. New Species of Formica. Jbid. 21: 267-274.—1905d. The North American Ants of the Genus Dolichoderus. Ibid. 21: 305-319, 2 pls., 3 figg.—1g05e. The North American Ants of the Genus Liometopum. J/bid, 21: 321-333, 3 figg. —1905f. An Annotated List of the Ants of New Jersey. Jbid. 21: 371-403, 4 figg.—1905g. Worker Ants with Vestiges of Wings. Jbid. 21: 405-408, 1 pl.—1g05h. Ants from the Summit of Mount Washington. Psyche 12: 111-114.—1905i. *How the Queens of the parasitic and slave-making Ants establish their Colonies. Amer, Mus. Journ. 5, 4: 144-148.—1905j. *Some Remarks on Temporary Social Parasitism and the Phylogeny of Slavery among Ants. Biol. Centralb. 25: 637-044. — 1905k. Dr. O. F. Cook’s “ Social Organization and Breeding Habits of the Cotton-protecting Kelep of Guatemala.” Science N. S. 22: 700-710.— 1906a. The Queen Ant as a Psychological Study. Pop. Sc. Month. (April): 291-290, 7 figg.; also Suppl. Scientific American (1906). —1906b. *The Habits of the Tent-building Ant (Cremastogaster lineolata Say). Bull. Amer. Mus. Nat. Hist. 22: 1-18, 4 pls., 3 text-figg. — 1906c. *On the Founding of Colonies by Queen Ants, with Special Reference to the Parasitic and Slave-making Species. Jbid. 22: 33-105, 7 pls. — 1906d. On Certain Tropical Ants Introduced into the United States. Ent. News 17: 23-26.— 1906e. New Ants from New England. Psyche 13: 38-41, I pl. —r1g906f. The Ants of Japan. Bull. Amer. Mus. Nat. Hist. 22: 301-328, I pl., 2 figg.—1g906g. The Ants of the Grand Cafion. Jbid. 22: 320-345. —1g906h. The Ants of the Bermudas. Jbid. 22: 347-352, 1 fig. — 1906i. Concerning Monomorium destructor Jerdon. Ent. News 17: 265. — 1906j. Fauna of New England. 7. List of the Formicide. Occas. Papers Bost. Soc. Nat. Hist. 7: 1-24.—1906k. The Kelep Excused. Science N. S. 220 348-350. — 19061. *An Ethological Study of Certain Maladjustments in the Relations of Ants to Plants. Bull. Amer. Mus. Nat. Hist. 22: 403-418, pls. 53-58.—1907a. *The Polymorphism of Ants, with an Account of some Singular Abnormalities due to Parasitism. Jbid. 23: 1-93, pls. 1-6. — 1907b. A Collection of Ants from British Honduras. Jbid. 23: 271-277, 2 pls. — 1g907c. *The Fungus-growing Ants of North America. Jbid. 23: 669-807, 5 pls., 31 figg.—1907d. The Ants of Porto Rico and the Virgin Islands. Ibid. 24: 117-158, pls. 11, 12,.—1907e. The Ants of Jamaica. IJbid. 24: 159-163. — 1907f. Ants of Moorea, Society Islands. Jbid. 24: 165-167. — 1g07g. Ants from the Azores. Jbid. 24: 169-170.—1907h. *Notes on a New Guest Ant, Leptothorax glacialis, and the Varieties of Myrmica brevi- nodis Emery. Bull. Wis. Nat. Hist. Soc. 5, 2 (April): 70-83.— 1907i. On Certain Modified Hairs Peculiar to the Ants of Arid Regions. Biol. Bull. 13, 4 (Sept.) : 185-202, 14 text-figg. —1907j. *The Origin of Slavery among Ants. Pop. Sc. Month. 71, 6 (Dec.): 550-559.—1908a. The Poly- morphism of Ants. (Abstract) Ann. Ent. Soc. Amer. 1, 1: 39-60, pl. 1. (Abstr. of Art. in Bull. Amer. Mus. Nat. Hist. 23: I-93, pls. 1-6.— 1908b. *Studies on Myrmecophiles. I Cremastocheilus. Jour. N. Y. Ent. Soc. 16, 2: 68-70, 3 figg.—1908c. *Studies on Myrmecophiles. II Heterius. bid. 16, 3: 135-143, 1 fig.—x1908d. *Studies on Myrmecophiles. II] Microdon. Ibid. 16, 14: 202-213, I fig.—1g08e. Honey Ants, with a Revision of the North American Myrmecocysti. Bull. Amer. Mus. Nat. Hist. 24: 345-397, 28 figg.—1908f. *The Ants of Casco Bay, Maine, with Observations on Two Races of Formica sanguinea Latreille. Jbid. 24: 619-645. — 1908g. A European Ant (Myrmica levinodis) Introduced into Massachusetts. Journ. Econ. Ent. 1,.6: 337-330. LITERATURE. | 647 Wheeler, W. M., and W. H. Long, 1901. The Males of Some Texas Ecitons. Amer. Nat. 35: 157-173, 3 figg. Wheeler, W. M., and J. F. McClendon, 1903. Dimorphic Queens in an American Ant (Lasius latipes Walsh). Biol. Bull. 4: 149-163, 3 figg. White, F. B., 1871-’72. *The Nest of Formica rufa and its inhabitants. Scott. INGE 12 AIC2AS Aste Ae White, W. F., 1883. Ants and their Ways; with illustrations, and an appendix giving a complete list of genera and species of the British Ants. London. xvi-+ 279 pp. White, 1882. [Great swarms of C*codoma in the Parana.] In “Cameos from the Silver Land.” 2: 437, 438. Wickham, H. F., 1889. *Collecting Notes. Ent. Amer. 5, 4: 77-78. — 1890. *Remarks on some western Tenebrionide. Jbid. 6, 5: 83-88.— 1892. *Notes on some myrmecophilous Coleoptera. Psyche 6: 321-323.— 1893. *Field Notes from Texas and Louisiana. Canad. Ent. 25, 6: 139-143. — 1894. *Further notes on Coleoptera found with Ants. Psyche 7: 79-81. — 1898. *On Coleoptera found with Ants. (Fourth Paper.) Jbid. 8: 219-221, I pl. —1g00. *On Coleoptera found with Ants. (Fifth Paper.) Jbid. 9: 3-5. —1g01. *Two New Blind Beetles, of the Genus Adranes, from the Pacific Coast. Canad. Ent. 33: 25-28, 3 figg. Wilde, J., 1615. De formica liberimus. Amberg@, Schonfeld, 108 pp. Wilkinson, T., 1865. *Ants’-nest Beetles at Scarborough. Ent. M. Mag. 2: 14. Will, F., 1885. Die Geschmacksorgane der Insekten. Zeitschr. Wiss. Zool. 42: 674-707, pl. 27. Wissmann, 1848. *ntomologische Notizen IX. Stett. Ent. Zeitg. p. 79. Wollaston, T. V., 1854. *Insecta Maderensia. London.—1864. “Catalogue of the Coleopterous Insects of the Canaries in the Collection of the British Museum. London. Wood, W., 1821. Illustrations of the Linnean Genera of Insects. London 2: 61. Wray, J. De acido formicarum succo. Phil. Trans. 68: 2063; Crell’s Chym. AN AGL ie, Te Ziyke Wroughton, R. C., 1892. *Our Ants. Journ. Bomb. Nat. Hist. Soc. Part 1: 48 DPee2eplss; Part ll 2onpp:. 2epls: XAMBEJU, V., 1889. *Description de deux larves de Coléoptéres. Rev. d’Ent. PP. 332-335. —1889-’90. *Paussides, Clavigérides et Scydmenides, recuellis dans le Bassin du Rhone et dans la vallée de la Tet. Fewuill. Jeun. Nat. 20: 21-22. — 1891-’93. *Mceurs et métamorphoses d’Insectes. I. Ann. Soc. Linn, Lyon. 38, 39 (Sep. Lyon. 1893).—1901-’02. Mceurs et métamor- phoses d’insectes (suite). Jbid. 48: 1-40; 49: 1-53; 95-160. YUNG, E., 1899. Dénombrement des nids de la Fourmi fauve. (F. rufa L.) Arch. Zool. Expér. (3) 7, Notes et Rev., 3: xxxili-xxxv.— 1900. Combien y a-t-il des fourmis dans une fourmiliére? (Formica rufa). Arch. Sc. Phys. Nat. Genéve (4) 10: 46-56; Rev. Sc. (4) 14: 269-273. ZAVATTARI, E., 1907a. Di alcuni Imenotteri della Somalia Italiana. Boll. Mus. Zool. Anat. Comp. Torino 22, 548: 4 pp. —1907b. Imenotteri dell’Alto Zambesi, raccolti dal Rev. L. Jalla. Ibid. 22, 550: 4 pp. Zeller, P. C., 1852. *Die Schaben mit langen Kiefertastern. Linn. Ent. 6: 81-108. Zetterstedt, J. W., 1840. Insecta Lapponica Descripta. Lipsie. von Zur Miihlen, 1888. Ueber hiesige Formiciden. Sitzb. Nat. Gesell. Dorpat. G2: 327-333: 648 ANTS. ANONYMOUS. (Blois), “H. B.”, 1833. Has anyone observed the under-described Act in the Great Black Ant? Mag. Nat. Hist. 6: 287-288. (D.), 1743. Das Lob des Flohes, der Ameisen und der Spinne. (D.), 1771 or 1781 (?). Die Saure von den Ameisen abzuscheiden. Almanach Scheidekiinstler. p. 54. (E.) Erzahlung von einem Ameisen Kriege. Hamb. Mag. 2: 317; Allerneueste Mannigfaltigk. 3: 139. (v. Ferrari, J. A.), 1845. *Zur Beurtheilung der in Ameisennestern vorkommen- den Insekten, insbesondere der Kafer, von einem suddeutschen Entomologen. Stett. Ent. Zeitg. p. 119 seq. “A. H.”, 1884. [Swarms of winged ants in New Zealand.] New Zeal. Journ. Ney 2:3 £20: (H.) Historia naturalis Formicarum. Urban’s Gentlem. Mag. 23: 363.— 1728. Historia musculorum Formice. (publ. with J. Donglin’s Histoire des Muscles). (N.) Naturgeschichte der Ameisen. Bérner’s Samml. Naturgesch, 1: 179. (N.), 1753. Nachricht von einer Ameisenschlacht. Gentlem. Mag. Aug.; Mylit. Phys. Belustig. 21: 839. (0.), 1701. Observations sur les Fourmis nommeées fourmis de visite, connues a Paramaribo; province de Surinam,:dans Amérique Méridionale. Mém. Acad. Sc. Paris. Histoire p. 16. .Ed. in 8vo. Histoire p. 19. (S.) Sur les fourmis qui a la Martinique nuisent aux cannes a sucre. Rosier Observ. Physique 8: 384. (V.) Von einem Heer fliegender Ameisen. Schreber’s Neue Cameralschriften T: 218. (J. G. W.), 1874. Bemerkungen zu F. Liebrecht’s Artikel “Ueber die gold- grabenden Ameisen.” Zeitschr. Ethnol. 6: 316-318. 1786. Von den grossen braunen Ameisen in Surinam. Lichtenberg Mag. 4: 47-48. 1885. [Note on Mounds of Pogonomyrmex occidentalis.] Amer. Nat. 19: 305. 1891-’92. *Chrysomelid Larve in Ants’-nests. IJusect Life 4: 148, 149. 1896. *L’esclavage chez les fourmis. Nat. Canad. 23: 21-26. 1897. |Ueberbriickung einer mit Wasser gefiillten Rinne durch Ameisen.] Inscktenborse 14: 51. 1897. Early Appearance of Formica rufa. Ent. M. Mag. (2) 8: 141; 158; 183. 1899. *Tropische Ameisen als Pilzziichter. Natur. 48: 135-137. 1899. Ameisen und Bienen. Diirfen wir diesen Tieren seelische Eigenschaften zuschreiben? Jbid. 48: 198-199. 1907. *[On fungi formed in ants’ nests.] Gard. Chron. (2) 18: 401, figg. INDEX A. Abdomen 26 Acacia 207, 224, 298, 299, 305, 307; A. fistulosa 298, 312, 313; A. hindsii 208; A. spadicigera 298; A. spherocephala Ais, HOOh Goo, gis Acamatus 138, 255; A. schmitti 258 Acanthognathus 141, 180 Acantholepis 125, 143, 148, 403; A. ab- dominalis 365 Acanthomyops 80, 143, 150, 156, 159, 182, 203, 342, 347, 416, 515; A. clavi- ger 80, 88, 94, 203; A. interjectus 203; A. latipes 94, 193 Acanthomyrmex 112, 139, 150 Acanthoponera 135 Acanthostichii 137 Acanthostichus 136, 137, 151, 227, 266 Acromynmes T4t, 180,\ 300, 327.) 328; 338; A. coronata 324, 325; A. disci- gera 324, 328; A. lundi 397; A. mel- lert 324, 325; A. octospinosa 17, 324 Acron 51 Acropyga 143 Acrostichum 299 Acrostigma 167, 171 Adelphogamy 439 Adipocytes 47, 48, 49 Adlerzia 139 Adranes 404; A. cecus 405; A. lecontei 400, 405 Enictogeton 137, 248 ZENIGIUS 26)..28, 665, 137, 245, 248.) 253, 255, 256, 266, 386; 4. aitkem, 250; 4G, eugenti 254; AL. grandis 252; AB. wroughtont 255 Aéromyrma 140, 158, 159, 163, 174, 429; A. nossindambo 428 Agricultural ants 187 Ailanthus 299, 300 Akermes colime 349 Alaopone 137, 248 Alchorea 299 Aleocharine 405 Alfaria 135 Alimentary Tract 31 Allodape 110 Allomerus 140, 303 Allotinus horsfieldi 360 Alpha-female 113 Alydus calcaratus 422 Amaranthus viridis 277, 278 Amazons 471 Amblyoponii 26, 134 Amblyopone 26, 134, 227. e Amblyteles ot Ambrosia beetles 338 Ammochete 16 Ammophila hirsuta 91 Ameebocytes 48, 49 Amorphocephalus 412 Amphisbenians 422 Amphotis 407 Ancleus 140 Aner 93 Anergates 36, 95, 107, 113, 114, 138, 139, 182, 183, 224, 449; A. atratulus 39, 40, 408, 499, 500, 501, 502, 503 Aneuretus 142, 148, 245; A. simoni 172, 244 Annular lamina 29 Anochetus 96, 136, 227, 230, 234; A. sedilloti 180 Anomma 137, 167, 174, 175, 248, 250; A, arcens 146, 249, 251, 252; A. mo- lestum 253; A. nigricans 252: A. rubella 165 Anommatophilus 386 Anommatoxenus 386 Anoplognathus 229 Anoplotermes ater 429; A. morio 420 Antenne 20 Antennophorus 412, 415, 416; A, foreli 413; A. grandis 413; A. pubescens 408, 413, 414; A. uhlmanni 413 Ants of North America, list of, 561 Ant-nests, architecture of, 192 Anus 36 Aorta 46 Aphenogaster 70, 74, 107, 140, 166, 167, 268, 282, 320, 391, 393, 403, 440, 513; A. beccarui 125; A. fulua 24, 81, 83, 150, 206, 389, 404, 447, 448, 453; A. lamellidens 151; A. levis 447; A. longeva 173; A. marie 151, 448; A. occidentalis 150; A. picea 82, 87, 08, 106, 195, 282, 447, 453; A. rudis 448; A, subterranea 40, 150; A. tennes- S€ENStS 113, 114, 303, 447, 448, 450: A. testaceopilosa 282, 387; A. treate I51, 200, 404 Aphidicolous ants 11 Aphids 11, 339 Aphis 347, 352; A. maidi-radicis 11, 354; A. papaveris 352 Aphneus 359; A. lohita 258 Aphomomyrmex 143 Apis 72; A. cypria fasciata 115 Apocephalus pergandei 419 115; A. mellifica- 649 650 a Apteronina schmitti 387 Apterostigma 24, 141, 319, 326, 328, 329, 237, 3303) 4. melleri 324, 328; A. pilosum 319, 324, 328, 329; A. was- mannt 324 Arabis Thaleana 271 Arachnida 379 Aristida 284, 287; A. oligantha 286; A. pungens 273; A. stricta 286 Artemisia vulgaris 340 Arthropterus 402 Association, arenicolous 157; cespiti- colous 157; deserticolous 157; eri- nemoricolous 157; pra- ceticolus 157; tincolous 157 Astragalus 290 Atelura 392, 396; A. formicaria 391, 392, A. wheeleri 392 Atemeles 404, 405, 406, 407, 443; A. emarginatus 407; A. paradoxus 407; A. pubicollis 403, 407 Atopomyrmex 139, 172, 174 Atta 10, it.) 725 einen Omi emee Seer Te 151, 180, 181, 182, 186, 199, 308, 310, 326, 330, 331, 332, 337, 338, 341, 438, ; silvicolous 157 514, 524; A. barbara 271; A. cepha- lotes 10, 321, 324, 337; A. fervens 513; A. sexdens 34, 329, 333, 337> 540) eA. ter Onas 20s 2 77m 2S ens Is 333, 1334393353) 330103375 13955 553 Attaphila 393, 397; A. bergi 3097; A. fungicola 395, 396 AtHiN7iIe TATE 77 Sea 7 Attopsis 166 Azteca 46, $8, 112, 142, 215, 303, 304, 308, 309, 310, 341, 349; A. alfari 310; A. aurita 216, 304; A. barbifex 216; A. constructor 216; A. duroie 310; A, decipiens 216; A. hypophylla 216, 303, 304; A. lallemandi 216; A. lani- ans 216; A. mathilde 216; A. muelleri 216, 302, 304, 305; A. multinida 216; A. nigriventris 216; A. olithrix 213, 315; A. schimperi 216; A. sericea 17; A, stalactitica 216; A. traili 213, 315; A, trigona 214, 216, 304; A. ulet 213 315; A. viridis 304 B. Balsamina 299 Baltic amber 162 Bambusa 295 Batrisus 404 Battles of Ants 181 Bead-glands 300 Beckia 383 Bees 13, 29; carpenter 209, 212; social WS ys Behavior, automatic 507; instinctive 518; plastic 507, 531; reflex 507, 529 Belonopelta 135 Beltian bodies 300 Bembex 110 INDEX Beneficial ants 7, 8 Beta-female 95, 96, 113 Blattide 400 Blattoidea 14 Blood 46 Bodies, 55, 56 Bombax 295; B. ceiba 216 pedunculate or mushroom 54, Bothriomyrmex 42, 142, 148, 167, 1725 449, 451, 487;. B. atlantis 447; B. gepperti 166, 349; B. meridionalis 43, 44, 45, 446 Bothroponera 135 Brachymyrmex 113, 143, 341, 361; B. heeri 349; B. termitophilus 428 Brachyponera 135; B. solitaria 236 Brachynus 403 Braconide 340, 419 Bradoponera 167; B. meieri 161, 170 Bradypus tridactylus 308 Brain 51, 52 Braunsina 392 Bromatia 334 Buccal tube 32 Bull-dog ants 227 Bumblebees 90, 91, 110 Bunchosia gaudichaudiana 301 Cc: Calamus amplectens 298 Callows, coloration of, 79 Calomyrmex 16, 144 Calophyscia 297 Calyptites antediluvianus 173 Calyptomyrmex 141 Camponotine 13, 15, 26, 143 Camponotii 144 Camponotus 11, 23, 35, 36, 39, 42, 43, 70, 83, 98, 99, 108, 112, 120, 125, 144, LS toe LOO TO74 L7 sa hi 4we eS eon moss etsy bie uA Ais, OR. Yost, BOO, SK 364, 374, 391, 420,,515, 524; C. ab- dominalis 113, 151; C. abscisus 432; C. americanus 14, 79, 83, 100, 122, 181, 183, 201; C. cognatus 17; C. con- fusus 113; C. constrictus 173, 174; C. decipiens 39, 40, 209; C. fallax 150, 208, 393; C. femoratus 213, 315; C. ferrugineus 188, 208; C. festinatus 30, 40; C. floridanus 154; C. fumidus 206; C. herculeanus 40, 60, 131, 146, 148; C. igneus 174; C, inequalis 212, 208, 426; C. inflatus 365, 366; C. lateralis 422; C. levigatus 208, 393; C. ligni- perdus 34, 40, 72; C. maculatus 131, 146, 151, 310; C. melleus 393; C. men- get 174; C. mirabilis 17; C. nearctt- cus 213; C. nigriceps 393; C. nove- boracensis 131, 132, 188, 208, 407, 418; C. pennsylvanicus 10, 83, 85, 131, 188, 189, 191, 208, 393, 407, 417, 419, 422, 453; ©. planatus 151, 152, 426; C. punctulatus 351; C. quadriceps 75, INDEX 297; C. rasilis 209; C. rubroniger 426; C. sansabeanus 24, 39, 40, 349, 393; C. senex 118, 221; C, sex-guttatus 208, 210, 211; C. termitarius 429, 430; C. Ves, 173 Canna coccinea 250 Canavalia 299 Carabide 402 Cardioblasts 46 Cardiocondyla 94, venustula 126 Cardo 19 Carebara 113, 114, 138, 140, 428, 436; C. lignata 426, 427; C. vidua 427 Carebarella 140, 152; C. bicolor 428 Careya australis 223 Carya myristicefolia 212 Cassia 299, 300 Castalius ananda 358 Castes, as mutations 117; I12 Castration, alimentary 110; nutricial 110, 122; parasitic 110 Cataglyphis 144, 376 Catapecilma 359; C. elegans 358 Cataulacii_142 Cataulacus 142, 167, 174, 181, 303, 304; C. silvestrii 169 Cecropia 207, 295, 300, 301, 307, 308, 309; C. adenopus 214, 302, 303, 305, 310; C. lyratiloba 310; C. peltata 310; C. sciadophylla 310 Cells; of wing 24; urate 48 Cemonus unicolor 353 Centaurea 203, 299 Centromyrmex 135 Centrotus 351, 355 Cephaloplectus 386 Cerapachys 26, 137, 151, 158, 227 Cerapachysii 26, 133, 136, 137 Cerapterus 402; C. quadrimaculatus 403 Ceratina dupla 212; C. nana 209 Ceratobasis 141 Ceratoconcha 385 Ceratoderus 402 Ceratopheidole 140 Ceratopogon 383 Cercopide 350 Cerebrum 54 Cetonia 391; C. floricola 384, 420 Chetopisthes 400 Chaitophorus 347 Chalcidide 419 Chalcura bedeli 418 Chalicodoma 72 Champsomyrmex 97, 113, 243, 266, 527 Characters, of taxonomic value 131; spe- cific and generic 129 Cheliomyrmex 26, 28, E75. 2555 259 Chennium 404 Chorion 39 E30) LS2sekOU se Ge stature of pericardial 47; nose (Ce nortont 651 Chrysopa 43, 340, 345, 353 Cillibano comata 410, 416; C., 258, 409, 416 Circulatory system 46 Cladium 295, 504; C. jamaicense 212 Classification, conspectus of 134 Claviger 407; C. testaceus 400, 405 Clavigeride 379, 399 Claws 24 Cleanliness of ants 177, 179 Cleared nest areas 222 Cleptobiosis 426 Clerodendron 295, 302; C. fistulosum 312 Clypeus 18 Clytanthus 422 Clythra 384 Cnethocampa pityocampa 265 Cobea scandens 317 Coccide 11 Coccids 347 Cock-roaches 14 Cocoon 77; shape and color of 79 Coccinella 282 Coccinellide 346 Coccus nanus 349 Coccoloba rugosa 223; uvifera 208, 210 295 Collecting ants 545; myrmecophiles 548 Colobopsis 78, 112, 144, 182, 208, 303, 304; C. clerodendri 313; C. culmicola Zr G. etvolata 30% 404 200.210. rent: 212; C. impressa 17; C. pylartes 212; C. truncata 212, 422 Colonies, dispersal of 146; founding of 185; formation of 120, 438; mixed 452; phylogeny of, 110 Colors of ants 16 Color patterns of ants 16 Coluocera madere 156 Cometopsylla rufa 350 Commissures, ganglionic 51 Commoptera solenopsidis 383 Communication 535 Connectives, ganglionic 51 Conopide 419 Cooperation 536 Copal ants 174 Coptosoma 357 (Cah Zo Sitit,, Susy SG. 223; C. nodosa 313 Corpus adiposum 47 Corpuscles de nettoyage 32 Corvus cornix 425; C. corone 425 Coscinoptera 384 Cossyphodes 404 Cossyphodinus 404 Cossyphodites 404; C. woodroofei 404 Costa 24 Coussapoa 295 Coxa 21 Crabronide 422, 340 Cranium 16, 18 Crategus 299 hirticoma macrophylla 652 INDEX Cratomyrmex 16, 140 Cremastocheilus 388, 390, 399; C. cana- liculatus 391; C. castanee 391; C. crinitus 391; C. harrisi 391; C. kno- chi 391; C. spinifer 391; C. wheeleri 391 Cremastogaster 11, 96, 113, 140, 148, TOF manos, 215, 223, 301, 303, 312) 341, 344, 349, 357, 358, 359, 360, 403, 404, 426, 448, 449; C. acaci@ 312; C. alegrensis 428; C. artifex 215; C. chiarinti 312; C. clara 209; C. dif- fornus 310, 371, 372, 3733 C. ebenina 215; C. inconspicua 215; C. inflata Bie 372. 373, 3705 Ga MOvaecrsse Ge kirbyi 215; C. lineolata 150, 182, 208, 213, 214, 215, 223, 341, 343, 382, 393, 426, 453, 513; C. marginata 215; C. minutior 426 C. minutissima 39; C. montezumia 215; C. mucronata 372, 373; C. opaciceps 215; C. parabiotica 425, 426; C.-peringueyi 215; C. physo- thorax, 372) (Gee pilosa aai7.e 3488 16. punctulata 349; C. quadriformis 428; C. ramulinida 215; C. ranavalone 215; C. rogenhofert 215; C. ruspolii 312; C. schencki 215; C. scutellaris 40; C. sordidula 65; C. stadelmanni 215; C. steinheili 426; C. stolli 215; C. sul- cata 215; C. tricolor 215; C. tumidula 372; C. victima 223 Cremastogastrii 140 Crop 31, 32, 33 Cross-fertilization 183 Croton 278, 284 Crozophora 299 Crustacea 379 Cryptocerii 26, 141 Cryptocerus 93, 99, I12, T2445 Re25s 4, 181, 301, 303, 304; C. angulosus 133; C. angustus 151; C.-atratus 34; C. aztecus 102, 426; C. clypeatus 17; C. varians 17, 90, 151, 426; C. wheeleri 426 Cryptopone 135 Ctenopyga 137 Curetis thetys 358 Cylindromyrmii 137 Cylindromyrmex 137; C. whymperi 228 Cynipide 89 Cyphodeira 383 Cyphomyrmex 141, 151, 180, 319, 320, BZOwNS2OuNso yin) 1G. (GUTIIUS 8327.0 320)5 C. comalensis 333; C. minutus 333; C. rimosus 319, 320, 333; C. striga- tus 324, 329; C. wheeleri 319, 333, 334 Cyrtophorus 422 Cysias 137 D. Daceton 141, 180; D. armigerum 17 Dacetonii 141 Dacryon 139 Dactylopius 349; D. adonidum 349; D. wheeleri 349 Darlingtonia 299 Dealation 184; of female 121 Death-feigning 180 Decarthron stigmosum 404 Dendromyrmex 144 Dendrophilus 388 Deportation 177, 241 Desmergate 98 Deutocerebrum 51, 52 Diacamma; 74,072 “11356 135) 17 t,.8 2335 234; 242, 243, 266, 527 Dichthadia 137, 248, 249; D. glaberrima 249 Dichthadiigyne 97, 248, 266 Dichothorax 139, 156, 200 Dimorphomyrmex 143, 167, 172, 174, 2408 srs 7 Dy) yanen 173 then £705. 173, L74 Dimorphomyrmii 143 Dinarda 387; D. dentata 379, 380, 387, 388 ; D. hagensi 387; D. merkeli 387; D. nigrita 387, 388; D. nigritoides 387; D. pygme@a 387 Dinardilla liometopi 387 Dinergate 97 Dinoponera 135; D. grandis 233, 242 Diplocotes 404 Diplomorium 113, 141, 158, 428; D. longipenne 427 Dischidia rafflesiana 297 Discopoma 410; D. comata 416 Discothyrea 136, 171 Discoxenus 386 Discrimination, color 516 Dispersal of queen ants 145 Distribution, centers of 149; ethological 156; faunistic 146; of North Ameri- can ants 148 Docility 537 Doleromyrma 142 Dolichoderine 13, 15, 26, 142 Dolichoderus 11, 15, 125, 142, 167, 172, 215, 200) 303-5 39416 341048 350s BOGLme. attelaboides 17, 216; D._ bispinosus 216; D. bituberculatus 135; D. debilis 425, 426; D. gibboso-analis 384; D. marie 24; D. obliteratus 173; OD. quadrinotatus 422; D. quadrispinosus 215 Dolichos 299 Dorylaner 94, 248 Dorylii 8, 137 Doryline 13, 28, 29, 137 Dorylobius 386 Dorylocerus 386 Dorylogaster 386 Dorylomimus 386 Dorylophila 386 Dorylopora 386 Dorylostethus wasmanni 385 . 4 + * INDEX 6 Doryloxenus 386 Dorylus 26, 28, 65, 66, 94, 98, 124, 137, 158, 248, 249, 251, 252, 253, 254, 255, 256, 263, 382, 386, 515; D. affinis 101; D. brevipennis 252; D. fimbriatus 248, 240, 252; D. furcatus 247; D. helvolus 247, 248, 240, 200; 2D. klugi 2405 D.: nigricans 249; D. orientalis 253 Dorymyrmex 113, 142, 151; D. pyrami- Cus 146, 201, 205, 425, 426 Duct, deferent 42, ejaculatory 42 Dulosis 440 Duroia 295 E. Echinomegistus wheeleri 409, 415 Echinopla 144 Ecitochara 386 Ecitodulus 387 Ecitogaster 387 Ecitomorpha 386; E. simulans 385 Ecitomyia wheeleri 383 Eciton 26, 28, 43, 44, 65, 66, 72, 94, 98, TES MLSS, thle GOs LOL 2275 245025 3F Zeb e50.) 200,eso2 410. 4525) 505 se. carolinense 255, 264, 387; E. cecum 146, 159, 255, 256, 263, 264; E. cras- Sicorne 256, 263; E. esenbecki 257; E. foreli 255, 259, 261, 419; E. hama- Hie Le 25 A wehbe 250) 257 2on Ee lucanoides 255; E. opacithorax 28, 255, 72505203, 2605; BE. piulosum 2s56i>. E: predator 256,15 250, 9261, 387: E: Schimttt 24, 39, 40, 66, 255, 256, 250, 263, 265, 387, 409, 416, 537; E. sumi- chrasti 259, 265 Ecitonidia wheeleri 387 Ecitonii 8, 138 Ecitonilla 386 Ecitonusa 386; FE. foreli 387; E. schmit- ti 387 Ecitophila 386 Ecitophya 386 Ecitopora 386 Ecitotonia 386 Ecitoxenia 386; E. brevipes 387 Ecitoxenus 387 Ecphorella 142 Ectatomma 125, 135, 167, 227, 232; E. quadridens 26; FE. tuberculatum 9, 226, Dei. ARE Rey oy iia vied Ectatommii 134 Ectomomyrmex 135 Ectoparasites 381, 412 Ectrephes 404 Egg, of ants 69, 70; fertilization of 71 Elais guiniensis 251 Elasmosoma berolinense 419; E. vigilans 420 Electromyrmex 167; E. klebsi 164, 171 Eleodes 282 Eleusine indica 277, 278 Embryo 72 * Embryonic life, length of 80 Emerya 139 Emeryella 135, 230 Encephalon 52 Enchenopa ferruginea 351 Endoparasites 381, 419 Endospermum 295; E. formicarwmn Engramma 142 Enneamerus 167, 171 297 Ephebomyrmex 140, 152, 283; E. im- berbiculus 283, 284, 290, 292; E. negeli 283; E. pima 283; E. town- sendi 283 Ephialtites jurassicus 160 Epimera 22 Epinotum 22 Epipheidole 107, 113, 140, 150, 156; E. inquilina 103, 497, 498 Episterna 22 Epitritus 20, 141, 158; E. emme 131 Epecus 065, 107, 113, 139, 156; E. per- gandei 4908 Epithelium, follicular 39 Epixenus andrei 496; E. creticus 406 Epizeuxis americalis 383 Erebomyrma 113, 140, 152, 158, 159; E, longi 152, 428; E. peruviana 152, 428 Eretmotes 388 Ergatandromorph 99 Ergataner 94 Ergates 97 Ergatogyne 96 Ergatotelic type of social insects 120 Eriococcus texanus 349 Erythrina 299 Ethology, history of, 127 Eucalyptus platyphylla laris 221 Eucharine 418 Eucharis myrmecie 418 Euderces 422 Eumecopone 135 Euphorbia 278, 284 Euphoria hirtipes 384; E. inda 384 Euponera 135 Euprenolepis 143 Eurosta solidaginis 212 Eusphinctus 137 Eutermes fulviceps 429 Eutetramorium 141 Eyes 18, 20; lateral 65; median 66 F. Female, myrmecophilous and mimetic characters of 114; stature of 114 Femur 24 Feniseca 360; F. tarquinius 359, 360 Ficus 295; F. inequalis 295, 313 Filaments, suspensory 46 Fire-ant 11 Food-bodies 300; of ants 177 Foraging BAIR IS 32 223; E. tessel- 654 Forda 347; F. formicaria 347; F. inter- jecti 347; F. kingi 347; F. lasit 3473 F. pallidula 347 Forelius 142; F. fatidus 45; F. mac- cooki 426 Formic acid 43, 181 Formica 10, 11, 23, 36, 42, 43, 49, 79; 75, 78, 79, 93, 96, 98, 106, 108, 124, Tenens, L439, 146, 166; 167, 168, 173, 179, 181, 188, 191, 243, 341, 358, 360, 393, 420, 422, 427, 449, 515, 517, 532; F. arcana 173; F. argentata 204, 205, 460, 475, 477; F. aserva 458, 460, 467, 471; F. ciliata 114, 120, 205, 351, 385, 444, 445, 450; F. cinerea 83, 357, 455, 456, 472; F. coloradensis 444; F. con- socians 205, 441, 442, 443, 444, 446, 447, 448, 450, 467, 488, 503; F. comata 444; F. crinita 114, 444, 445, 450; F. dakotensis 113, 114, 205, 444, 445; F. difficilis 113, 114, 205, 441; F. ex- secta 317, 387, 441, 446, 450, 458; F. exsectoides 120, 191, 197, 202, 203, 314, 316, 317, 333, 381, 382, 384, 385, 389, 391, 446, 450; F. exsectopressi- labris 446; F. flor 160, 173, 1745) B- URC By byl, Gy tein WAS AKO, TIGR, we 203, 204, 387, 420, 444, 445, 446, 455, 457, 458, 461, 462, 467, 472, 474; F. fuscata 460, 462, 463; F.fusciceps 454; F, fusco-rufibarbis 387; F. gagates 455; F. glacialis 56, 204, 351, 458, 460; F. glebaria 455, 456, 472, 473, 477; F. gnava 69, 91, 391, 393; F. hemorrhoi- dalis 206, 444; F. impexa 113, 444; F. incerta 96, 405, 407, 441, 442, 443, 444, 447, 448, 460, 482, 483, 484, 486; F. integra 204, 205, 206, 222, 351, 384, 391, 393, 444; F. microgyna 95, 104, 113, 114, 120, 205, 442, 444; F. munda 201, 450, 458; F. neocinerea 201, 203, 389, 460, 461, 475; F. neoclara 145, 201, 460, 461, 463; F. neogagates 460; F. neorufibarbis 393, 460; F. nepticula 113, 205, 444; F. nevadensis 113, 444; F. nigra 174; F. nitidiventris 460, 461, 482, 484, 485, 486; F. obscuripes 202, 351, 384, 444; F. obscuriventris 205; F. obtusopilosa 458, 460; F. opaciven- tris 204, 446; F. oreas 114, 205, 351, 444; F. pallide-fulva 393, 458, 460, 461; F. pergandei 458, 460; F. pra- tensis 40, 65, 191, 203, 222, 407, 430, 444, 445, 455; F. pressilabris 446; F. puberula 458, 460; F. rasilis 444; F. rubiginosa 204; F. rubescens 455, 456, 472, 477; F. rubicunda 205, 206, 458, 460, 462, 463, 464, 465, 466, 467; F. rufa 8, 32, 38, 39, 40, 41, 42, 75, 85, OL, 14s) 120s sFOsmus2s TOL, 200; 202; 203, 205, 333, 352, 353, 382, 384, 387, 391, 407, 430, 431, 432, 434, 441, 444, 445, 446, 450, 455, 458; F. rufibarbis INDEX 39, 41, 97, 407, 455, 456, 457, 462, 472, 473, 537; F. rufopratensis 455; F. saccharivora 174; F. salomonis 174; F. sanguinea 40, 83, 119, 127, 146, 195, 203, 205, 224, 242, 353, 385, 387, 388, 407, 408, 409, 410, 4II, 417, 437, 453, 454, 455, 467, 468, 471, 472, 473, 474, 488, 500, 514; F. schaufusst 158, 201, 238, 385, 386, 380, 391, 441, 442, 460, 481, 482; F. specularis 444, 445; F. subenescens 391, 460, 464, 477, 478, 479, 480, 481; F. subintegra 458, 459, 460, 467; F. subnuda 458; F, subpolita 201, 420, 460; F. sub- sericea 11, 80, 83, 84, 157, 201, 203, 351, 380, 391, 393, 444, 445, 446, 453, 460, 461, 463, 465, 466, 475, 476, 477, 484, 485, 486, 537; F. swecica 446; F. truncicola 444, 446, 467; F. ulkei 446 Formicii 143 Formicium brodiei 160 Formicoxenus 36, 94, 139, 182, 432, 434; F. corsicus 431; F. nitidulus 94, 430, 431; F. ravouxt 431 Frontal area 18; groove 18 Fulgoride 356 Fungus-growing ants 318 Funiculus 20 G. Galea 19 ‘Gall-flies 68 Ganglia 51; abdominal 52; mediary 52; mesothoracic 51; metathoracic 2 cesophageal 58; optic 52; prothoracic 51 Ganglion, frontal 53, 58, hypocerebral 58, 59; prestomachal 58; subcesopha- geal 57; supracesophageal 51 Garden ants 574 Gardens 213; of ants 315 * Gaster 26, 28 Gelechia galle-solidaginis 212 Gene 18 Geoica 347 Gesomyrmex 143, 167, 172, 515; G.- chaperi 173; G. corniger 172; G. hornest 171, 173 Gigantiops 143, 515; G. destructor 180 Glands, anal 45; antennary 37; ductless 48; Dufour’s 44; integumentary 37; lentiform 36; mandibular 37; maxil- lary 38; metasternal 38; of alimentary canal 37; of circulatory system 37; poison 45; pulvinate 42; reproductive 37; repugnatorial 45 Glandular system 37 Glomeruli 54 Glossa 19 Gnamptogenys 135 Gnetum 301 INDEX 655 Gnostus 400; G. formicola 404; G. mein- erti 404 Gongylidia 334 Goniomma 16, 140, 268, 275, 377; G. hispanica 275 Goniothorax 139 Gordius formicarum 420 Gorgeret 29 Gossyparia mannifera 347 Gossypium 299 Grammatophyllum 296 Granivorous ants 268 Gula 18 Guests, indifferently tolerated 381; true 381, 398 - Gustatory papille 19 Gynecaner 95 Gynecoid 97, 113, 242, 427 Gynezcotelic type of social insects 119 Gynandromorph 99 Gyne 95 Jal Hagensia 135 Harpagoxenus 36, 139, 150, 432, 454, 480, 492; H. americanus 494, 495; H. sublevis 40, 107, 492, 493 Harpegnathus 135, 227, 229, 230; lake cruentatus 17, 180; H. rugosus 241 Harvesting ants I1, 268, 575 Heart 46 Helianthus 299, 317; H. annuus 313 Hemerobius 340 Hemioptica 144; H. scissa 142 Heterius 388; H. blanchardi 389; H. brunneipennis 387, 389, 390; H. fer- rugineus 388, 390; H. horni 389; H. tristriatus 389 Hirtella 297 Hister 388 Histeride 379 Histoblasts 78 Holcomyrmex 16, 139, 282, 377, 426; H. chobauti 273; H. lameerei 273; H. scabriceps 268, 275, 276 Holcaspis cinerosus 208, 210; H. per- niciosus 368, 360, 375 Holcoponera 135 Homing 532 Homopterus 402 Honey ants 361 Honey-bee 105, 183 Honey-dew 11, 340 House-ants 10, 573 Huberia 139, 349 Humboldtia 295, 313; H. laurifolia 295 Hydnophytum 207, 2095, 305, 310; H. montanum 305 Hylotorus 402 Hyperaspis 360; H. reppensis 357 Hypoclinea 142, 172; H. gagates 182, 516; H. marie 182, 516; H. quadri- notata 151 Hypogeic ants 158, 515 Hypopharyngeal pocket 195 Hypopomyrmex 167; H. bombiccii 168. 171 16 Ichneumon-flies 13 Identification, table for 557 Imhoffia 166 Impatiens 299 Infrabuccal chamber 31, 33 Ingluvies 32 Ingurgitation 35 Instars of ants 14 Instinct 518 Instinct-actions 519 Instinct-feelings 519 Instincts, regulation of 527; alteration in female 121; deferred 524; of queen ants 185; pathological 426; philopro- genitive 118; vestigial 425 integument 15 Intestine 31 Intruders, inimically persecuted 380 Iridomyrmex 10, 16, 35, 46, 113, 142, [505 L675, 72303 sate manalismAy 426; I. cordatus 306, 310; I. geinitzt 78, 166; f. humilis 153, 154, 155, 223; 542; I. melleus 223; I. myrmecodie 305, 310; I. nitidus 350; I. purpureus 228, 350 : Ischnomyrmex 140, 151, 182, 268, 278, 320; I. albisetosus 280, 281, 282; I. cockerelli 24, 69, 177, 201, 273, 274, 280, 281, 282 Tsomeralia 418; I. coronata 413 Issus 356 Ve Janetia 140; J. mayri 283 Juglans 295 K. Kapala 418; K. floridana 413 Kelep 9, 226 Kermes 349 Kibara 205 Kitchen middens 179 Kohlrabi clusters 325; heads 325 Korthalsia 298 L. Labidus 255 Labium 18, 19 Lablab 299 Labor, physiological division of 87, 118 Labrum 18, 20 Lachnodiella cecropie 249 Lacinia 19, 29 Lactuca 317 Lelaps 383 Lamprinus 382 Lampromyia miki 422 656 Lampromyrmex 167 Larva 72; feeding of 104; internal struc- ture of 75 Larval life, length of 80 Lasiophanes 143 Hastuseatn,.36, 42, 74,' 75, 78, 79, 113, M245 025, 143, 148, 150, 158; 150, 166, TOFMOZG. TSS, 214, 224, 341, 349,0358) 361, 393, 405, 413, 420, 515, 532; L. alienus 83, 388; L. americanus 11, 157, 201, 354, 504, 513; L. aphidicola 203, 4090, 415; L. brevicormis 55, 57, 190, 347; L. brunneus 39; L. claviger 24; L. emarginatus 222, 533; L. flavus Ber20, 30, 30, 40; 63, 72: 190) 2038 2ost 222, 356, 405, 457, 464, 504; L. fu- liginosus 26, 40, 55, 57, 214, 216, 382; L. latipes 83, 113, 504; L. mixtus 392, 408, 410, 411, 416; L. nearcticus 347, Hog; L. niger MO, ire gos 40, So. Go, 72) 83, TLS; L7Age loan e20gn omicM BAe 345, 347, 352, 356, 357, 457, 464, 504, 533; L. schiefferdeckeri 174: L. ter- reus 173; L. umbratus 340, 356 Leaf-cutting ants 576 Leaping ants 180 Lebioderus 402; L. goryi 399 Lecanium hemisphericum 349 Lecanopsis 349 Lecanopteris 207, 296; L. carnosa 208 Leea 301 Legs 23 Lepismina 392; L. formicaria 3091 Leptanilla 138, 158; L. minuscula L. revelieri 262 Leptogenys 79, 97, 113, 135, 138, 170, Dy Ue IA A, Aa, ala, tie Salah 262; 266, 527; LL. elongata 40: L. maxil- losa 17 Leptomyrmex 142, 167, 364, 374: L. erythrocephalus 17; L. maravigne 172; L. rufipes 364 Leptothorax 36, 95, 96, 111, 125, 139, 167, 179, 191, 200, 280, 341, 430, 492; L. acervorum 40, 148, 492, 405; L. canadensis 208; L. curvispinosus 212, 494, 495, 504; L. emersoni 39, 40, 107, 393, 425, 434, 435, 436, 503; L. forti- nodis 208, 209; L. glacialis 393, 4363 EL. longispinosus 212, 222, 504; L. muscorum 493, 495; L. obturator 208, 209: L. petiolatus 426; L. schaumi 208; L. serviculus 432; L. tuberum 493; L. unifasciatus 431 Lestobiosis 427 Linepithema 142 Liometopum 113, 142, 151, 166, 223, 341; L. apiculatum 136, 214; L. microcepha- lum), Bay 136s euAe2n6, 13038 5) I. “OCci= dentale 387; L. pingue 173 Liomyrmex 139 Lioponera 137, 171 Liphyra 384; L. brassolis 359 INDEX Lobes, frontal 54; olfactory 52 Lobopelta, 7%, 72, 74, 97, 113, 135, 230, 233, 242, 254; L. aspera 242; L. bing- hamt 242; L. birmana 242: L. bis- marckensis 242; L. chinensis 241, 242; . L. diminuta 243; L. distinguenda 241; L. elongata 73, 226, 233, 235, 238, 230, { 240, 242; L. kitelli 242 . Lomechon 400, 412 Lomechusa 400, 401, 405, 406, 407, 421, 422, 426, 443; L. strumosa 380, 401, 407, 408, 409, 410, 411 Lomechusini 399 Lonchomyrmex 166; L. heyeri 162 Lophomyrmex 141 Lordomyrma 139 Luffa 290 Lycena betica 357; L. pseudargiolus 352 Lycenide 357 M. Machomyrma 139 Macraner 94 | Macrergate 97 d Macrogyne 95 Macromischa 16, 93, 139,151, 171, 215; M. albispina 127; M. isabelle 127 : Majeta 297 Male ants 93 Male, ergatomorphic 94 Malpighian vessels 36, 48 ; Mandibles 19; use of in excavating and building 195 Manna 347 Marcgravia 299 Margarodes 349 Marriage flight 183 Martia 139 Mating of ants 182 Maxille 18, 19 Mayria 144 Mayrian furrow 21, 22 Mayriella 141 Meconium 77, 78 Mediary segment 20 Megalomyrmex 139 Megaloponera 135 Megastilicus’ 382, 381, 382, 383 Melampyrum 299 Melipona 105 Melissotarsus 141, 232; M. beccarii 242 Melophorus 16, 99, 143, 364, 365, 374; M. bagoti 362, 363, 364; M. cowlei 363, 364 Membracide 11, 350 Memory 539 Mentum 109 Meranoplus 141, 181, 268, 377; M. dt- midiatus 276; M. diversus 276 Merismoderus 402 Mermis 420, 421 Mermithergates 420, 526 388; M. formicartus INDEX Mesenteron 36 Mesepimeron 21, 22 Mesepisternum 21 Mesonotum 21, 22 Mesoparapteron 21 Mesoponera 135 Mesosternum 21 Mesothorax 20, 21 Messor 16, 125, 140, 151, 268, 274, 278, 270, 282,. 377; M. andrei 280; M. arenarius 201, 269, 272, 274; M. bar- barus 65, 268, 270, 272, 280, 393, 427; M. carbonarius 280; M. caviceps 272, 273; M. julianus 280; M. pergandei NOMZOT We7On 27272) 250, 200; MM: stoddardi 280; M. structor 268, 269, 270 Metallic colors of ants 16 Metaparapteron 22 Metasternum 21 Metatarsus 24 Metathorax 20, 21 Metepisternum 21 Metepimeron 21, 22 Metopina 107, 118; 407, 412, 413 Michthysoma heterodoxum 422 Micraner 94 Micrergate 97 Microclaviger cervicornis 404 Microdon 385, 386; M. apiformis 385; M. devius 385; M. mutabilis 385; M. tristis 383, 385, 386; M. variegatus 386 Microgyne 95 Microphyscia 297 Microsiphum 347 Mictoponera 135 Mimeciton pulex 385, 387 Mimocete 386 Mellerius 141, 151, 319, 338; M. chiso- sensts 333; M. versicolor 201, 327, 329; 330, 333,337 Monacis 142 Monomorium 96, 98, 139, 148, 167, 268, 341, 349, 431, 527; M. decamerum A2SieiViw GeSimUctOoTs LO, 53,0220... floricola 96, 153, 426; M. heyeri 428; M. pachycondyle M, minimum 157, 201, 386, 498; M. pharaonis 10, 153, 154, 221; M. salo- monis 153, 467, 495, 496; M. sub- nitidum 432; M. termitobium 428; M. venustum 406 Morphology, history of 129 Mounting ants for cabinet 547 Movements, random 532 Muellerian bodies 300 Muscles, aliform 46 Muscular system 49 Mus tectorum 262 Mutation 536; of Gnothera 117 Mutilation, effect of 85 Mutillide 244 43 657 Mycetosoritis 141, 151, 199, 319, 337; hartmani 201, 321, 322, 323, 333, 334) 335, 336 Mycocepurus 320 Myopias 135 Myopopone 134 Myristica 295 Myrmecia 03,96, %24, 125, 170, 227, 230, 232) 233.2456 Ue forficata 228, 229, 418; M. gulosa 17, 229; M. nigro- cincta 229; M. ‘pyriformis 23; M. sanguinea 228; M. spadicea 23; M. tarsata 229 Myrmecti 134 Myrmecina 63, T11, 125, 139, 180; M. graminicola 150 Myrmecocheilus 391 Myrmecocleptics 391 Myrmecocela ochroceella 383 Myrmecocystus 16, 99, 113, 125, 144, 151, 201, 341, 362, 363, 364, 365, 374; M. bicolor 16; M. bombycinus 418; M. desertorum 417; M. horti-deorum 201, 363, 365, 366, 367, 368, 369, 370, 371, 373, 374, 375; M. megalocola 412, 417; M. melliger 10, 121, 201, 365, 366, 368; M. mendax 376; M. mexi- canus 121, 366; M. mojave ‘200; M. orbiceps 376; M. semirufus 194; M. testaceus 349; M. viaticus 396, 397, 418 Myrmecodia 207, 295, 305, 310, 311; M. pentasperma 306 Myrmecoids 422 Myrmecolax nietneri 419 Myrmecophags 422 Myrmecophana fallax 422 Myrmecophila 393; M. acervorum 393, 396; M. americana 393; M. austra- lis 393; M. dubia 393; M. flavocincta 156, 393; M. formicarum 393; M. ne- brascensis 393, 394, 396; M. nehawkee 393; M. ochracea 393, 396; M. ore- gonensis 393; M. pergandei 393; M. prenolepidis 393; M. salomonis 393 Myrmecophily, history of 128 Myrmecopsis 144 Myrmecorhynchus 144 Myrmecoxenes 381 Myrmedone 297 Myrmedonia 382, 383, 388; M. cremas- togastris 382; M. funesta 379, 382; M. humeralis 382; M. planifer 382; M. schwarzi 382 : Myrmelachista 143, 173, 303 Myrmeleon 422 Myrmephytum 310 Myrmetes 388 Myrmica 11, 40, 42, 43, 49, 64, 70, 75; OB 90) 125) .D40, 148,) D52,) LOOsmmo.E 168, 173, 188, 201, 214, 282, 317, 341, 358, 393, 404, 513, 515; M. alpina 141, 180, 319;'M. smith 655 436; M. brevinodis 313, 434, 436; M. canadensis 214, 425, 434, 435; M. levinodis 27, 37, 39, 49, 43, 70, 72, 432; M. mutica 80, 150, 388, 432, 433; M. myrmoxena 432, M. punctiventris 537; M. rubida 150, 434; M. rubra TS.) 23, 27, 28, 31, 33, 36; 38, 40, 47, 53; 60, 63, 81, 184, 405; M. rugi- nodis 30, 40, 63, 72, 81, 187; M. sabu- leti 484; M. scabrinodis 39, 40, 102, 464, 533; M. sulcinodis 39, 97 Myrmicaria 141, 174, M. brunnea 130 Myrmicii 133, 139, 141 Myrmicine 13, 15, 26, 28, 29, 138 Myrmicium heeri 160 Myrmicocrypta 141, brittoni 318 Myrmecia 382; Myrmoteras 143, hami 138 Myrmoteratii 143 Myrioxenus 139; M. gordiagini 432 Mystrium 134; M. camille 230; M. rogert 17 2155 B10, 320;nso7 a M. fussi 382 245, 515; M. bing- N. Nabis lativentris 422 Napochus termitophilus 400 Nectaries, extrafloral 299; floral 298 Nectarostegia 316 Neoblissus parasitaster 357 Neocerus 404 Neoponera 125, 135, 151, 232; N. in- versa 421; N. villosa 154, 226, 235 Nepenthes bicalcarata 296 Nerve-cord, ventral 57 Nerves, alar 58; antennary 52, 53; crural 57; motor 58; ocellar 52; optic 52; proctodeal recurrent 59; sensory 58 Nervous system 51; sympathetic 52, 58 Nest-aura 510 Nests, artificial 549; between or under leaves 298; carton 214; change of 196; classification of 198; compound 423; in cavities of stems 295; in galls 208; in houses 221; in plant cavities 207; in seed-pods 298; in soil 199; in stone walls 222; in thorns 298; in tubers, pseudobulbs, etc. 295; in wood 208; large crater 201; mounds 201; orien- tation of 204; silken 217; succursal 223; small crater 201; summer and winter 195; suspended 213; under stones, logs, etc. 205 Nothomyrmica 167, 171 Notoncus 143. Noxious ants 7 Nuptial flight 183 Nylanderia 143, 361; N. arenivaga 201 O. Ocelli 20, 66 INDEX % Ochetomyrmex 141 Ocymyrmex 16, 139, 268, 278 Odontomachii 136 Odontomachus 93, 96, 125, 136, 180, 227, 220;9230, 231, 234; O. chelifer 421; O. clafus 39, 40, 151, 188, 226, 233, 235; O. hematodes 17, 151, 188, 226, 233, 421 Odontomyrmex 139 Odontoponera 135; O. transversa 238 Odors of ants 182; progressive 510; specific 512 Ccophylla 78, 121, 125, 143, 167, 172, 216, 223, 237, 303, 341, 521; G. brisch- kei 171, 173; CG. smaragdina 118, 1735 2175 -2LG, 210; 220,022 w2eo mah oe 359; CG. virescens 220, 223 (Ecophyllii 143 - CEningen ants 164 GEnocytes 47, 48 (Esophagus 31, 32 # Oligomyrmex 140, 167, 174, 428 Onychomyrmex 135 Oocerea 137 Odlelaps odphilus 417 Ophthalmopone 135, 233; O. ilgi 240 Opisthopsis 144; O. respiciens 17 Orasema 95, 99, 106, 412, 418, 421, 426; O. coloradensis 418; O. wiridis 414, 415, 416, 418; O. wheeleri 418 Orectognathus 141 ; Organs, chordotonal 62, 63; Johnstonian © 64 = Orthezia 349 Orthopterus 402 Osteoles 46 Otomyrmex 142 Ovaries 39, 40 Ovarioles 39, 40 Oviduct 39 Oxygyne 140, 448, 454; O. aberrans 449; O. agnetis 449; O. daisyi 449; O. dalyi 449; O. depressa 449; O. ebenina 448; O. emme 448; O. marthe 449; O. ranavalone 449; O. soror 448; O. travancorensis 448 Oxyopomyrmex 16, 140, 268, 275, 377; O. santschii 273 Oxysoma 393; O. oberthueri 396, 397 1 Pachycondyla 74, 107, 125, 135, 151, 231, 233; P. fuscoatra 421; P. harpax 39, 40, 226, 234, 393, 407, 412, 413 Pachypodistes galdii 384 Peonia 299 Paleomyrmex prodromus 160 Paleococcus rose 349 Palpi 19 Paltothyreus 135 Parabiosis 424 Paracletus cimiciformis 347 Paraglosse 19 INDEX Paramera 29, 30 Paraneuretus 148, 167, 172 Paraponera 135; P. clavata 22, 421 Parapsidal suture 21 Parapsis 21 Parasites, permanent social 495 Parasitism, brood 405; hetercecious 405; homeecious 405; permanent social 440; pupillary 440; temporary social 440; tutelary 440 EGER Gig Gy EUS 29a HOR 125 auguste 226; P. peringueyi 113 Parmula 385 Parthenogenesis 71, of workers 116; re- lation to polymorphism 87; relation to sex 89 Passiflora 209 Pausside 379, 399, 402 Paussoides 402 Paussomorphus 402 Paussus 400, 401, 402; P. arabicus 403; P. cucullatus 402; P. dama 399; P. favieri 403; P. hova 399; P. linnei 403; P. lineatus 403; P. spiniceps 399 ; P. spherocerus 402; P. turcicus 403 Pedicel 26 Pelodera janeti 420 Pemphigus 347, 352; P. 348, 359 Pemphredon insigne 353 Penicillium crustaceum 315 Penis 29, 42 Pentaphis 352 Pentaplatarthrus 402; P. natalensis 399 Periplaneta australasie 262 Petiole 26 Phacota ~ 139; -P. sicheli 432 Phagocytes 49 Phanynx) 30) 32 Phaseolus 299 Pheidole 64, 74, 93, 98, 107, 108, 112, TS eZ OM 25 eT ON Ty Omi wl 7a 75, RG2eeZ2Ol 254 206.) 270. 279, 350, 459, 377, 403, 513; Ph. absurda 420; Ph. antillensis 44, 263; Ph, borinquenen- sis 99; Ph. calens 427; Ph. carbonaria 270 eee Geres, 270. Avs, ao7; Ph. coloradensis 279, 497; Ph. commutata 420, 421, 426; Ph. dentata 201; Ph. desertorum 391; Ph. diffusa 269; Ph. ecitonodora 44, 263; Ph. flavens 153, 154; Ph. instabilis 56, 77, 89, 279, 420, 415, 416, 418, 426; Ph. javana 310; Ph, lamia 17, 212, 428, 429; Ph. longi- ceps 276; Ph. megacephala 10, 63, 153, 154, 155, 221, 272; Ph. metallescens 16; Ph. morrisi 201; Ph. pallidula 272, 303, 403; Ph. pilifera 152, 278, 497, 498; Ph. providens 269; Ph. sitarches 279; Ph. splendidula 16; Ph. termi- tobia 428; Ph. tysoni 152, 278; Ph. tessellatus 347, noualhiert 432; P. 659 vaslitti 279; Ph. vinelandica 152, 201, 278, 418 — Pheidologeton 112, 140, 175, 268, 377, 524; Ph. antiquus 174; Ph, ocellifer 275, 276 Pheidoloxenus wheeleri 419, 420 Phenacoccus 349 Phoride 419 Phthisaner 95, 418 Phthisergate 99, 418 Phthisogyne 97, 418 Phylacobiosis 429 Phylogeny of subfamilies 244 Phyracaces 137 Physiological states 121 Pilosity of ants 15 Pinus rigida 213 Pith as food for ants 302 Plagiocheilus 391 Plagiolepidii 143 Plagiolepis 35, 78, 99, 143, 148, 167, 341, 374, 391; P. custodiens 404; P. jou- berit 365; P. longipes 10, 154, 155, 3903; P. pygmea 39; P. trimeni 364, 365 Plantago 27 Plant-lice 11 Plants injurious to ants 315; cophilous 294 Plastophora crawfordi 419 Platyarthrus hoffmanseggi 383 Platythyrea 73, 135, 151, 233; P. punc- tata 80, 226 Platymyschium 295 latyrhopalus 402 Plectroctena 135 Pleistocene ants 173 Plerergate 99, 121 Plesiobiosis 424 Pleuropterus 400, 399 Podomyrma 139, 172 Podophylla 282 myrme- 402; P. brevicornis Pogonomyrmex 16, 74, 80, 98, 107, 125, D3, L40,, W525 Sone 20m OS 278-270) Phe Alla evil, 77, asks, ust, Guizle Je» apache 283; P. badws 151, 152, 201, 280, 283, 284, 285, 292; P. barbatus NU Oh 2O3eeee 2Odee8O. 20%. 202. 203, 427, 520; P. californicus 188, 180, 200, 201, 284, 285, 290, 292; P. com- anche 201, 284, 285, 292; P. cunicu- laris 283; P. desertorum 282; P. mar- fensis 284; P. molefaciens 24, 39, 40, On FO W7OS UO Oey Os G1, 25/G, 277, 283, 284, 286, 287, 288, 290, 292, 203, 393, 304, 426, 513; P. nigrescens 284; P. occidentalis 10, 11, 145, 1096, 200, 202) 203, 204. 205, 222) 28aueene 287, 280, 291, 425, 426; P. rugosus 279, 280, 284, 285, 200; P. sancti- hyacinthi 283; P. subdentatus 283 Pogonoxenus 400, 412 660 INDEX Poison apparatus 42, 43; bourreleted type of 42; pulvinate type of 42 Polistes 72 Polybia pygmea 397 Polyergus 36, 96, 119, 125, 143, 150, 182, 224, 242, 243, 437, 449, 454, 487, 488, 493, 500, 527, 533, 534; P. bicolor 477, 478, 479, 480, 481, 486; P. breviceps Agee 70, 477, 486; -P. luctdus) iso, 481, 482, 483, 484, 485, 486; P. mexi- canus 474; P. rufescens 40, 91, 107, 127, 388, 425, 471, 472, 473, 474, 475; 485, 486, 487 Polymorphism, phylogeny of 91; causes of 100; conspectus of phases 92; defi- nition of 86 Polyplocotes 404 Polypodium 299 Polyrhachis 15, 144, 148, 167, 174, 215, 216, 223, 303, 521; P. alexandry 221 ; iP bvhamata 1393 VP dives 2075 227, 223; P. jerdont 216; P. lamellidens 140; P. mayri 139; P. muelleri 221, 222; P. spinigera 217 Polytrichum 434; P. commune 314, 3173 P. strictum 317 Ponera Wi, Gan o4a tes. 1355 5S 67, 174, 182, 231, 233, 234, 238; P. atavia 174; “PB. coarctata.93; "06, 150s, 1745 P. eduardi 93, 94, 95, 96; P. ergatan- dria 94, 151; P. hendersoni 173, P. Opaciceps 151; P. -pennsylvanica 75, 79: 226, (2325 237, 2395 a punctatts= sima 65, 93, 94; P. quadridentata 26; P. trigona 151 Ponerii 133; 135 Ponerine) 13, (155) 26,28, 20) 134) 225 Poneropsis 166 Populus 299, 300; P. fremonti 282 Porouma 300, 310 Portulacca oleracea 277 Postpetiole 26 Postscutellum 22 Pouch, copulatory 40 Prescutellum 21 Prenolepis 11, 35, 78, 83, 99, 113, 143, 167, 201, 341, 349, 358, 360, 362, 363, 364, 365, 379; P. fulva 154; P. wn- paris 11, 150, 205, 361, 376; P. longi- GOMMISMLOA E545) 150.) 221 303 ae eentes= tacea 376 Prionogenys 135, 227 ; Prionomyrmex 167; P. longiceps 161, 170 Prionopelta 134 Pristomyrmex 139; P. japonicus 129 Probolomyrmex 137 Proceratii 136 Proceratium 136; 151, 156, 158, 171, 227; P. silaceum 2209 Procryptocerus 141 Proctodeum 36 Proctotrupide 419 Proformica 143 Prolasius 143 Pronotum 21 Propodomyrma 167, 171; P. samlandica 163 Prosopis juliflora 282 Prosternum 21 Prostesthesis 59 Protaneuretus 148, 167, 172 Prothorax 20, 21 Protocerebrum 51, 52 Protopaussus 402, 403 Proventriculus 33, 34, 35; bulb of 34; sepals of 34 Prunus 299 Psalidomyrmex 135 Pselaphide 379 Pseudochalcura 418; Ps. gibbosa 418 Pseudococcus cuatalensis 349 Pseudodichthadia 255; Ps. incerta 255 Pseudogyne 96, 106, 407, 526 Pseudisobrachium mandibulare 420; Ps. montanum 420; Ps. myrmecophilum 420; Ps. rufiventre 420 Pseudolasius 143; Ps. familiaris 137 Pseudometagia 418 Pseudomyrma 73, 111, -139, 151, 245; 303; 304;:305; 309,, 314, 24%, 515. 5076 Ps. arboris-sancte 314; Ps. belti 312: Ps. bicolor 312; Ps. dendroica 314; Ps. elegans 303; Ps. elongata 426, 504; Ps. flavidula 426, 504; Ps. fulvescens 307, 312; Ps. mexicana 386; Ps. spini- cola 312; Ps. symbiotica 314; Ps. tri- plaridis 314 Pseudomyrmii 139 Pseudoponera 135, 234; Ps. stigma 151, 226, 234 Pseudosiricide 160 Pseudosirex 160 Psidium 299 Psylla pyricola 350 Psyllide 349 Ptelea trifoliata 209 Ptenidium 383 Pterergate 78, 99 Pteris 299 Pterocladon 295 Pteromalide 340 Pterospermum 301 Ptilium 383 Publilia concava 351 Pubescence of ants 15 Punktsubstanz 53 Pupa 76 Pupal life, length of 80 Pupation 76 Pygostenus 386 Pyrophorus 402 Python natalensis 251 Q. Quaternary ants 173 ee INDEX Ouedius 382 Queens, parasitic 186 Quercus 299; Q. undulata 375, 368 R. Races 131 Radoboj ants 164 Randia 295 Reactions, historical basis of 531; pho- tophobic 515; phototropic 515; to Roentgen rays 516 Reasoning 540 Receptaculum seminis 39 Recognition, of friends and foes 534 Rectum 31 Reflexes, catenary 520 Regurgitation 35 Reproductive organs 39 Respiratory system 49 Rhinomyrmex 144 Rhinopsis ruficornis 422 Rhipsalis 299 Rhizomyrma 143 Rhogmus 137, 248 Rhopalomastix 140 Rhopalomyrmex 143, 167, 172, 173; R. pygmaeus 162 Rhopalopone 135 Rhopalosiphum 352 Rhopalothrix 141, 158 Rhoptromyrmex 141 Rhozites gongylophora 327 Rhynchoclaviger 404 Rhytidoponera 16, 93, 135 Rhyzopus nigricans 316 Ricinus 299, 300 Ripersia 349 Rogeria 139 Rosa 299 Run-ways 222 510, S. Saccharomyces 334 Sacculina 450, 451 Saliva of ants 177 Salivary duct 19 Sambucus 295, 299 Sanguinaria canadensis 315 Sapium 205 Sarcolysis 49 Sarracenia 297, 299, 317 Saw-flies 13, 68 Scape 20 Schizoneura 347 Schomburgcekia 2096 Schwartzia 295 Scoliide 244 Scolytide 338 Sculpture of ants 15 Scutelligera 385 Scutellum 22 Scutigera 235 661 Seed-distribution, ants instrumental in gu5 Segmentation 14 Semonius 142 Sensations 505; auditory 512; contact- odor 514; olfactory 509; tactile 509; temperature 509; of vibrations 513, 514; visual 515 Sense-organs 59 Sensilla, ampullaceous 61; basiconic 61 ; campaniform 65; clubs of Forel 61; ceeloconic 61; flask-shaped organs of Forel 61; gustatory 61, 511; olfactory 61, 511; tactile, or trichodeal 59 Sericomyrmex 141, 318, 319, 320, 337 Shuckardia 137, 248 Sideroxylon 432 Sifolinia 139; S. laure 432 Silene 317 Silphide 399 Sima 27, 139, 167, 303, 304; S. allabor- ans 123; S. rufonigra 422 Simopone 137 Siphonophora 352 Siphons of aphids 343 Siricide 160 Slave-makers, degenerate 489; faculta- tive 452; obligatory 471 Social bees 68, 90 Social wasps 68 Soldier 97 Solenopsia imitatrix 420 Solenopsidii 140 Solenopsis, (63) 1645, 08s) Is .eerl 4a uZs5. 140, 147, 152, 158, 159, 377, 428, 429, 493, 515; S: fugax 65, 420, 427; geminata 11, 114, 146, 155, 201, 206, 250, 2085) 20051127 Oye 70 So ybetLOL aS. latro 427; S. molesta 10, 24, 221, 427; GS. orbula 4273) Se Tufia, 1535) 209) s9- texana 427; S. validiuscula 418 Solidago 212 Spalgis 360; S. epius 359 Species 130 Sperm 39, 40 Spermatogenesis 41 Sphagnum 317 Sphecophila polybiarum 397 Sphinctomyrmex 137; S. taylori 227 Spines of ants 180 Spondyliaspis eucalypti 350 Staphylinide 379 Stemmata 20, 66 Stenamma 111, 140, 148, 268; S brevti- corne 150; S. nearcticum 150; S. westwoodi 150 Stereomyrmex 136, 139; Sternum 22 Sternocelis 388 Stictoponera 135 Stigmacros 143 Stigmata 22, 28, 49 Stigmatomma 134, 158, 159, 227, S. hornt 127 231, 662 233; S. pallipes 72, 150, 226, 231, 232, 238, 239, 453 Stigmomyrmex 167, 171; S. Stilicus 386 Stillingia 299, 300 Stimuli 537; individualized 528; simple 528 Sting 28, 29, 42 Stipites 19, 29 Stomach 35 Stomachis 352 Stomodeum 35 Streblognathus 135; S. @ethiopicus 21 Stridulation 513 Stridulatory organ 26, 27, 28 Strigil 16, 24 Strigilators 393 Strongylognathus 141, 449, 454; S. afer 489, 490; S. ce@cilie 489, 490; S. chris- tophi 489, 490; S. huberit 425, 489, 490; venustus 164 S. rehbinderi 425, 489, 490; S. tes- taceus 107, 489, 490, 491, 492, 495. 500, 503 Strumigenys 141, 151, 158, 181, 428; S. lewisi 132; S. obscuriventris 132; S. pergandei (245, S. saliens 180 Stylets 205 nae Stylogaster 261, 419 Stylops 419, 451 Submentum 19 Subspecies 131 Succoring companions 536 Sugar-lerp 349 Symmyrmica 94, 139, 150, 156, 182; S. chamberlini 94, 432, 433 Sympheidole 107, 113, 140, 150, 156; S. elecebra 497, 408 Symphiles 381, 398; antenne of 4o1; color of 398; mouth-parts of 4o1 Sympolemon 386 Synageles 422 Synechthrans 380, 382 Synemosyna 422 neeketes 381; loricate 386; mimetic 386; neutral 383; symphiloid 386, 388 Syringa 299 Syrphide 340 Syscia 137 Sysphincta 136, 151, 158, 171, 227; S. pergandei 229 aE: Tachia 295 Tachigalea 295 Tactile hairs 15 Tapinoma 36, 46, 49, 125, 142, 167, 182, 357, 360, 451; 7. erraticum 40, 45, 65, 2A, S53 Sol Aco dOm en EVE Azer T. littorale 426; T. melanocephalum 154, 156; TL. minutissimum 172; T. nigerrimum 356, 447; T. sessile 45 Tapinoma-odor 45 Tarsus 24 INDEX Taxonomy, history of 124 Technomyrmex 35, 94, 142, 167; T. dele- tus 172; T. strenuus 34 Tegula 21 Telson 51 Temnothorax 139 Temperature, effect of, on adult ants 83; effects of, on growth 80, 81 Temples 18 Tenthredinide 89 Tents for aphids and coccids 223 Teratosoma 400 Termes natalensis 427 Termites 1, 2, 3, 195, 338 Termitomyia 383 Termitoxenia 383 Tertiary ants 161 Testes 40 Tetramorii 141 Tetramorium 63, 125, 141, 148, 215, 341, 393, 403, 496; T. aculeatum 216; T. africanum 216; T. cespitum 24, 40, 72, 53, 154,, 222, 208, 276) 3e45 4205 425, 489, 490, 491, 492, 498, 499, 500, 501% 502; IL. ganeense 10, 153; De simillimum 10, 154 Tetramopria aurocincta 420 Tetraporia 400 Tetrogmus 141 Tettigometra 356, 357, 360; T. B56 5, ads liqua 357 Thaumatomyrmex 135, 227,830; Th. mu- tilatus 17 Thea fornucosa 350; Th. Theridion 422 Thorictide 379, 399 Thorictus 400, 412; Th. castaneus 418; Th. foreli 412, 417, 418; Th. pauciseta costatus unpressifrons 356; T. ob- opaca 350 417, 418 Thynnide 244 Tibia 24 Tillandsia 207, 298, 432; T. bentha- miana 425 Tillomorpha 422 Tococa 207, 213, 297; T. formicaria 301 ; T. lancifolia 300 Tomognathus 492 Trachee 22 Trachymyrmex 141, 151, 180, 199, 275, 319, 3373 L. arizonensis 333, 335; f- obscurior 328, 333; T. septentrionalis 24, 200, 327, 324, 333) 230; 0. turns fex 201, 324, 325, 326, 333, 335, 336 Trama 347, 352; TI. radicis 340 Tranopelta 140, 152, 428 Trapeziopelta 135 Tree-ants 515 Tree-hoppers 11 Trial and error 532 Triballus 388; T. californicus 388 Trichilium 300 Trichodes 39, 399 . ‘ i "sche INDEX 663 Trichomyrmex 140 Trighyphothrix 141 Trigona 105 Trigonogaster 139; T. recurvispinosa 123 Trilobitidius 386 Dilan os AGI BOs siisy Sens? We americanus 295; T. boliviana 296 Tritocerebrum 51, 52 Trochanter 24 Trophobiosis 360 Turnera 299 Turneria 142 Tychea 347 Tylois 400~ Typhlatta 253 Typhlomyrmex 135 Typhlopone 137, 248; T. fulvus 253; T. levigata 249; T. punctata 249 Tyridiomyces formicarum 320, 334 Tyroglyphus wasmanni 417 ° U. Urodiscella philoctena 411, 417 Uropoda ovalis 411, 417 Vv. Vagina 40 Vanduzea arcuata 351 . Variability 130 Varieties 131; local or geographical 130; nest 130 Veins of wings 24 Velvet-ants 13 Ventral cord 52 Ventriculus 36 Vespa 248, 541; V. germanica 529 Vertex 18 Viburnum 299 Vicia 299 Vollenhovia 139 Volselle 29 W. Wasmannia 141 Wasps 135) 2o5890s00lsSocialet. 2) 110 Wheeleriella 107, 113, 114, 139, 224, 447, 467, 500, 503, 527; W. santschii 495, 496, 497 Wing muscles, degenerating 49, 50 Wings 24 Worker 97; as a hunger form 122; guarding instincts of 120; nursing in- stincts of 120; fertile 115 xe di Xanionotum hystrix 383 Xantholinus 382 Xenobiosis 430 Xenocephalus 386 Xenodusa 405, 426; X. cava 405, 407 Xenomyrmex 139, 191; X. floridanus 432; X. lucayanus 426, 432; X. stoll: 151, 431, 432 Xenos 419 Xiphomyrmex 141, 151 Z. Zezius 359; Z. chrysomallus 358 Zizyphus rugosus 358 ) MI 4Y + ¥ P 4 t+ THE COLUMBIA UNIVERSITY PRESS Columbia University in the City of New York The Press was incorporated June 8, 1893, to promote the publication of the results of original research. It is a private corporation, related di- rectly to Columbia University by the provisions that its Trustees shall be officers of the University and that the President of Columbia University shall be President of the Press. 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