HARVARD UNIVERSITY -^ Library of the Museum of Comparative Zoology Bulletin of the Museum of Comparative Zoology AT HARVARD COLLEGE Vol. 104 THE ANTS OF NORTH AMERICA By William Steel Creighton With Fifty-Seven Plates CAMBRIDGE, MASS., U. S. A. PRINTED FOR THE MUSEUM April, 1950 Reprinted, 1966 The Ants of North America By William Steel Creighton College of the City of New York CONTENTS Page Introduction 8 The Present Status of Ant Taxonomy and Nomenclature 12 The History of Ant Taxonomy in North America 16 Family Formicidae 27 Key to the Subfamilies 29 Subfamily Ponerinae 29 Key to the Genera of the Subfamily Ponerinae 30 Genus Stigmatomma Roger 31 Key to the Subspecies of Stigmatomma pallipes Haldeman 32 Genus Platythyrea Roger 34 Genus Ectatomma F. Smith 35 Subgenus Parectatomma Emery 35 Genus Proceratium Roger 36 Key to the Species of Proceratium 39 Genus Sysphincta Roger 40 Key to the Species of Sysphincta 41 Genus Neoponera Emery 42 Genus Pachycondyla F. Smith 43 Genus Euponera Forel 44 Key to the Species of Euponera 45 Subgenus Brachyponera Emery 45 Subgenus Trachymesopus Emery 46 Genus Ponera Latreille 46 Key to the Species of Ponera 47 Genus Leptogenys Roger 50 Subgenus Lobopelta Mayr 50 Key to the Subspecies of L. (Lobopelta) elongata Buckley 51 Genus Odontomachus Latreille 52 Key to the Subspecies of Odontomachus haematoda Linn6 55 Subfamily Cerapachyinae 56 Key to the Genera of the Subfamily Cerapachyinae 57 Genus Cerapachys F. Smith 57 Subgenus Parasyscia Emery 57 Genus Acanthostichus Mayr 58 Subgenus Ctenopyga Ashmead 58 Subfamily Dorylinae 59 Genus Eciton Latreille 61 Key to the Subgenera of Eciton 61 4 bulletin: museum of comparative zoology Page Subgenus Labidus Jurine 61 Key to the Species of Labidus (workers) 62 Key to the Species of Labidus (males) 64 Subgenus Neivamyrmex Borgmeier 64 Key to the Major Workers of Neivamyrmex 66 Key to the Females of Neivamyrmex 68 Key to the Males of Neivamyrmex 68 Subfamily Pseudomyrminae 77 Genus Pseudomyrma Latreille 77 Key to the Species of Pseudomyrma 79 Subfamily Myrmicinae 82 Key to the Genera of the Subfamily Myrmicinae 83 Genus Myrmica Latreille 87 Key to the Species of Myrmica 92 Genus Manica Jurine 105 Key to the Species of Manica 108 Genus Pogonomyrmex Mayr 110 Key to the Species of Pogonomyrmex 113 Subgenus Pogonomyrmex Mayr 115 Subgenus Ephebomyrmex Wheeler 132 Genus Stenamma Westwood 133 Ke}^ to the Species of Stenamriia 135 Genus Aphaenogaster Mayr 138 Subgenus Attomyrma Emery 138 Key to the Species of Attomyrma , 140 Genus Novomessor P^mery 155 Key to the Species of Novomessor 155 Genus Veromessor Forel 157 Key to the Species of Veromessor 158 Genus Pheidole Westwood 161 Key to the Species of Pheidole 163 Subgenus Macropheidole Emery 168 Subgenus Pheidole Westwood 169 Genus Epipheidole Wheeler 192 Genus Sympheidole Wheeler 194 Genus Cardiocondyla Emery 195 Key to the Species of Cardiocondyla 197 Genus Crematogaster Lund 199 Key to the Species of Crematogaster 203 Subgenus Orthocrema Santschi 205 Subgenus Acrocoelia Mayr 206 Genus Monomorium Mayr 217 Key to the Species of Monomorium 217 Subgenus Monomorium Mayr 218 Subgenus Parholcomyrmex Emery 224 Genus Xenomyrmex Forel 224 creighton: ants of north America 5 Page Genus Solenopsis Westwood 226 Key to the Species of Solenopsis 228 Subgenus Solenopsis Westwood 230 Subgenus Euophthalma Creighton 233 Subgenus Diplorhoptrum Mayr 233 Genus Epoecus Emery 239 Genus Anergates Forel 241 Genus Erebomyrma Wheeler 245 Genus Myrmecina Curtis 246 Key to the Subspecies of Myrmecina americana Emery 248 Genus Macromischa Roger 250 Key to the Species of Macromischa 251 Genus Leptothorax Mayr 252 Key to the Species of Leptothorax 256 Subgenus Goniothorax Emery 259 Subgenus Dichothorax Emery 259 Subgenus Leptothorax Mayr 261 Subgenus Mychothorax Ruzsky 274 Genus Symmyrmica Wheeler 280 Genus Harpagoxenus Forel 281 Key to the Species of Harpagoxenus 284 Genus Triglyphothrix Forel 285 Genus Tetramorium Mayr 286 Key to the Species of Tetramorium 290 Genus Xiphomyrmex Forel 293 Key to the Subspecies of Xiphomyrmex spinosus Pergande 293 Genus Wasmannia Forel 294 Genus Cryptocerus Fabricius 295 Key to the Species of Cryptocerus 296 Subgenus Cryptocerus Fabricius 297 Subgenus Cyathomyrmex Creighton 298 Genus Struraigenys F. Smith 298 Key to the Species of Strumigenys 301 Subgenus Strumigenys F. Smith 303 Subgenus Trichoscapa Emery 304 Genus Cyphomyrmex Mayr 310 Key to the Species of Cyphomyrmex 316 Genus Mycetosoritis Wheeler 317 Genus Trachymyrmex Forel ? 319 Key to the Species of Trachymyrmex 320 Genus Acromyrmex Mayr 325 Subgenus Moellerius Forel 325 Key to the Subspecies of A. {Moellerius) versicolor Pergande . . 326 Genus Atta Fabricius 327 Subfamily Dolichoderinae 330 Key to the Genera of the Subfamily Dolichoderinae 330 bulletin: museum of comparative zoology Page Genus Dolichoderus Lund 331 Subgenus Hypoclinea Mayr 331 Key to the Species of Hypoclinea 333 Genus Liometopum Mayr 337 Key to the Species of Liometopum 338 Genus Iridomyrmex Mayr 340 Key to the Species of Iridomyrmex 341 Genus Forelius Emery 343 Genus Dorymyrmex Forel 346 Key to the Subspecies of Dorymyrmex pyramicus Roger 348 Genus Tapinoma Forster 350 Key to the Species of Tapinoma 352 Subfamily Formicinae 353 Key to the Genera of the Subfamily Formicinae 355 Genus Brachymyrmex Mayr 356 Genus Camponotus Mayr 359 Key to the Subgenera of Camponotus 362 Subgenus Camponotus Mayr 363 Key to the Species of Camponotus 364 Subgenus Tanaemyrmex Ashmead 371 Key to the Species of Tanaemyrmex 374 Subgenus Myrmentoma Forel 382 Key to the Species of Myrmentoma 384 Subgenus Colobopsis Mayr 390 Key to the Species of Colobopsis 392 Subgenus Myrmothrix Forel 395 Key to the Subspecies of C. (Myrmothrix) abdominalis Fabricius 395 Subgenus Myrmobrachys Forel 396 Key to the Species of Myrmobrachys 398 Subgenus Myrmaphaenus Emery 399 Key to the Species of Myrmaphaenus 401 Subgenus Manniella Wheeler 402 Genus Paratrechina Motschoulsky 402 Key to the Species of Paratrechina ; 404 Subgenus Paratrechina Motschoulsky 404 Subgenus Nylanderia Emery 405 Genus Prenolepis Mayr 410 Key to the Subspecies of Prenolepis imparis Say 413 Genus Lasius Fabricius 415 Key to the Species of Lasius 418 Subgenus Lasius Fabricius 419 Subgenus Chthonolasius Ruzsky 421 Genus Acanthomyops Mayr 426 Key to the Species of Acanthomyops 428 Genus Myrmecocystus Wesmael 434 Key to the Species of Myrmecocystus 440 creighton: ants of north America / Page Genus Formica Linn6 450 Key to the Subgenera and Groups of Formica 456 Subgenus Proformica Ruzsky 457 Key to the Species of Proformica 457 Subgenus Raptiformica Forel 460 Key to the Species of Raptiformica 462 Subgenus Formica Linn6 472 Species Belonging to the rufa Group 472 Key to the Species Belonging to the rufa Group 480 Species Belonging to the microgyria Group 496 Key to the Species Belonging to the microgyna Group 498 Species Belonging to the exseda Group 510 Key to the Species Belonging to the exsecta Group 513 Species Belonging to the fusca Group 515 Key to the Species Belonging to the fusca Group 528 Subgenus Neoformica Wheeler 543 Key to the Species of Neoformica 548 Genus Polyergus Latreille 552 Key to the Species of Polyergus 556 Literature Cited 561 Index 569 8 bulletin: museum of comparative zoology INTRODUCTION During the years that the writer spent on the preparation of this volume its character changed completely from what was originally intended. When Dr. W. M. Wheeler proposed, in the fall of 1936, that we collaborate on a field book of North American ants, his idea was to prepare a keyed catalogue similar to that which Emery pub- lished on the ants of Italy in 1916. No revisionary work was con- templated and the publication was to include keys and distributional data which would aid in field studies of our ants. This seemed an excellent idea, for many summers spent collecting ants in all parts of the United States had convinced me of the need for a single, concise volume which could be carried into the field. I gladly acceded to Dr. Wheeler's proposal and began work on the book. Dr. Wheeler's death occurred in the following spring, before he had made any active contribution to the volume. This left its preparation entirely in my hands. As I worked over the material in the Wheeler Collection, the need for revision became apparent. At that time current concepts relating, to speciation were beginning to take shape and there seemed to be abundant opportunity to apply these concepts to ant taxonomy. With this in mind I undertook not only to prepare the necessary keys and to collate the vast amount of distributional data in the Wheeler Collection, but also to revise the two infraspecific categories employed in ant taxonomy. The complexities of ant nomenclature have been considered in the section which follows this introduction. They need not be discussed here, but it seems advisable to state that, as a result of the revisionary work presented in this volume, it has been necessary to treat a large number of forms as synonyms. In 1947 Dr. M. R. Smith listed 742 species, subspecies and varieties of ants which have been taken in the United States. In the present work only 585 of these are recognized as valid taxonomic entities. Despite this reduction, the number of species has been increased, for it has been necessary to accord full specific status to many forms previously regarded as subspecies. Moreover, there has been surprisingly little need to synonymize previously recognized species. Hence, the great majority of the 157 forms which have gone into the synonymy have been subspecies or varieties. The end result has been to eliminate the variety as an infraspecific rank. For all the varieties which have been retained as valid show the characteristics of geographical races and have, for this reason, been given subspecific rank. In the case of some species which originally possessed a large number of subspecies and varieties, revision has radically altered the character creighton: ants of north America 9 of the assemblage. Under such cu-cumstances it has seemed advisable to present a single account of the changes involved. This discussion is placed immediately after the name of the species but ahead of the bibliographic citations and other data relating to it. Although this represents a departure from the customary treatment, it is believed that the method will be of substantial aid to the reader. It permits a comprehensive view of the revision within the species. It also avoids repetition, since the same revisionary considerations can often be applied to several of the variants simultaneously. The bibliographic citations carried for each species and subspecies have been extensively edited. It is no longer practical to present full bibliographies for many of our species. In recent years many regional studies dealing with the distribution of our ants have been published. Much use has been made of such studies in preparing the ranges pre- sented herein. But I cannot feel that this type of publication should be listed in the bibliography of each species which it covers. It has been assumed that if the reader of this book finds it necessary to look up references given under the various species, it will be because he wishes to secure a fuller knowledge of the structure of the insects than can be obtained from the keys. Considerable effort has been made to see that all such references apply to descriptive material or to points which elucidate the taxonomy of the species involved. Papers which carry only distributional records have been placed in the general bibliography at the end of the volume. Since much stress has been placed on the importance of distribution in this work, I wished to present the ranges of the species and sub- species in a way which would be both accurate and concise. After considerable experimentation with various methods I doubt that there is any entirely satisfactory way by which this can be done. If all known records are cited the result is an accurate but clumsy list,which requires analysis by the reader before it conveys any impression of the range. At the other extreme are those over-simplified statements which announce that a species occurs in the northeastern United States or in Sonoran areas of the southwest. Such statements leave nothing to be desired as far as brevity is concerned, but they are as vague as the first method is cumbersome. The plan followed in this volume represents a compromise between these extremes. I believe that it is accurate enough to give the reader a satisfactory picture of the range without overwhelming him with a mass of details. Another point related to distribution involves the question as to whether the territory covered in this book warrants the title chosen for it. I make no excuse for the title employed, or for the fact that I have excluded those species in Mexico and Central America which 10 bulletin: museum of comparative zoology do not enter the United States. A political boundary is rarely a bio- logical terminus. As far as ants are concerned North America has no southern limit. In extreme cases the range of a species may extend from the central United States to northern Argentina. Hence for practical purposes one may as well select the political boundary which most closely approximates the natural boundaries of major faunistic groups. From this standpoint the northern border of Mexico serves best. Our extensive Nearctic ant fauna is largely confined to regions north of Mexico and the few representatives of this fauna which occur in Mexico are strictly limited to the higher mountain ranges. The reverse situation applies to the tropical element of the Mexican ant fauna. A number of genera and subgenera commonly encountered in Mexico and Central America have no representatives in the United States. In other cases Neotropical genera possess only one or two species which enter the United States, and these species rarely range more than a few miles north of the Mexican border. The large Sonoran component of our ant fauna is equally abundant on either side of the border. But portions of this fauna extend throughout much of South America, hence it must be given an arbitrary southern limit in any case. Unless otherwise noted all keys in this volume apply to the worker caste. The important part played by this caste in ant taxonomy is often misunderstood by those who contend that sound specific dis- tinction must rest upon the characteristics of the sexual forms. There is no objection to this view, but there are practical considerations which limit its application to ant taxonomy. For very obvious reasons the worker caste is far more likely to come into the hands of the collector. In most ant colonies the sexual forms leave the nest soon after they have reached the adult condition. Because of this, the period during which all three castes can be taken together is, ordi- narily, a very limited one. Moreover it is often impossible to secure the queen when a nest is discovered. At the slightest disturbance to the nest the queen will hide herself in its most obscure part and exten- sive excavation may fail to exhume her. These circumstances have greatly reduced the number of males and females taken in association with workers. As an example, there are sixty-three species and sub- species of Pheidole included in this volume. The worker caste of all of these has been described. But the female caste has been described in only twenty-six cases and the male caste in no more than eighteen cases. This proportion represents a reasonable approximation to what is found in most of the larger genera. Until a higher percentage of females and males can be associated with the workers it is not advis- able to present keys for the identification of the sexual forms. The introduction to this volume would not be complete without creighton: ants of north America 11 reference to the individuals and groups who contributed in various ways to its production. Of these the late Dr. W. M. Wheeler stands first. The writer not only benefited from a personal association with Dr. Wheeler but also from his generosity in the gift of a large number of identified specimens which he and others had described. Other myrmecologists who have generously contributed material are Dr. M. R. Smith, Dr. C. H. Kennedy, Dr. A. C. Cole, Dr. G. C. Wheeler, Dr. L. G. Wesson, Mr. W. F. Buren, Mr. W. L. Brown, Jr. and Mr. G. S. Walley. Without these specimens the work would have been seriously hampered. A very important contribution was made by the American Philo- sophical Society, which provided a grant to cover the preparation of the illustrations. With this grant the services of Mrs. Shirley Risser were secured, and it is due to her care and skill that the illustrations of this volume were produced. I am indebted to the Board of Higher Education of the City of New York for granting me leave during which most of the work on this book was done. I also wish to thank Harvard University for a research fellowship during 1938 and the Museum of Comparative Zoology for providing research facilities and for allowing me access to the Wheeler Collection. Thanks are due to the American Museum of Natural History for similar privileges. I wish to thank the Wheeler family for permission to examine Dr. Wheeler's unpublished manuscripts. The arduous task of proof-reading the original type-script was undertaken by Mr. W. L. Brown, Jr. His care and thoroughness have eliminated many minor errors which might have entered the volume. I wish to express my sincere appreciation to Mr. Brown for this valuable assistance. In conclusion, I venture to hope that, despite its revisionary char- acter, this volume may fulfill the purpose for which it was originally intended. By his unsparing efforts Dr. W. M. Wheeler built up a superb collection of North American ants and produced a large body of literature dealing with them. Both must be constantly consulted by anyone who hopes to do significant taxonomic work with our species. But Dr. Wheeler was aware that work in a library or a museum is only a part of the taxonomic picture. He never lost sight of the impor- tance of field work and it was his wish to arrange matters so that such work could be done accurately and without constant recourse to type specimens and original descriptions. If subsequent events show that field work on our North American ants can be done with more ease and accuracy because of this book, I will feel that it has fulfilled Dr. Wheeler's wish and that I have been amply repaid for the time and effort spent on its preparation. 12 bulletin: museum of comparative zoology THE PRESENT STATUS OF ANT TAXONOMY AND NOMENCLATURE The myrmecologist may count himself fortunate that he has to deal with a group in which specific characteristics are so clearly and easily discernible. Most ant colonies are composed of the offspring of a single female. This female usually mates but once and at that time she receives from the male the entire supply of spermatozoa which will subsequently fertilize her eggs. These sperm cells are all genetically identical, since the male ant is haploid and produces spermatozoa directly, without meiosis. The relationship of the workers produced by such a female is, therefore, a peculiar one. As Dr. George Snell has pointed out, they are not only sisters but half-identical sisters. From the standpoint of their genetic constitution there is every reason to believe that in those ant colonies which possess a single queen, the workers should show a much greater uniformity of structure than would be found in a population where both parents are diploid and where repeated insemination from random mating occurs. The hered- itary constitution of the worker caste in most ant colonies is as rigidly controlled as that of animals experimentally bred in a genetics labo- ratory. It is not sound judgement to apply to the population of an ant colony, the same considerations that would have to be used for a group of individuals selected from the general population of a non- social species. The two groups are not genetically comparable and, because of this difference, the ant colony is far easier for the taxono- mist to handle. It may be doubted that many myrmecologists have concerned themselves wich the reasons for this fact, but they have been fully aware of the fact itself and have profited greatly by it. When a student of ants observes that certain characters are constant throughout the entire worker population of a colony, he knows that this constancy has not been due to any attempt on his part to select or arrange the population with an eye to uniformity. The personal equation in specific delimitation is thus reduced to a minimum because the myrmecologist is blessed with material which advertises its own specific characters. When these same constant characters are repeated with an equal constancy in colony after colony, the myrmecologist need not be blamed if he feels that his specific criteria are as well founded as it is possible for such things to be. If the characteristics which occur in an ant colony are so favorable to taxonomic work why has the myrmecologist involved himself and his field in such an altogether horrendous maze of nomenclature? Why not be satisfied with the well-marked species that nature has so obligingly provided and let it go at that? The difficulty arises mainly creighton: a-nts of north America 13 from the methods which have been used to handle infraspecific varia- biUty. It is not surprising that myrmeeologists were among the first to recognize the need for infraspecific categories. About 1875 both Emery and Forel began to give names to units of less than specific rank. By this time the taxonomy of European ants had reached a condition of considerable stability. The mistakes and unavoidable duplication of the early workers had been largely corrected by the efforts of Roger and Mayr, and there was good agreement as to the definitive characteristics of most of the species. Indeed this agreement seems to have been too good. Because the species were so clearly marked, Emery and Forel felt no hesitation in attributing varieties or races to them. As I have attempted to show elsewhere (1938) the initial recognition of infraspecific units seems to have been due to Forel's exhaustive field work in Switzerland. Dr. W. M. Wheeler often expressed the opinion that no other myrmecologist ever studied a region with such thorough attention to detail. At first Forel not only traced the ranges and ecological characteristics of his subspecies but even recognized the existence of intergrades between them. To these he gave hyphenated names indicative of the two parent races. Those who feel that there is a great gulf fixed between modern taxonomy and the older classical brand would do well to remember Forel's Fourmis de la Suisse, which was first published three-quarters of a century ago. I do not mean to imply that Forel's treatment of Swiss ants would meet all the requirements which present-day concepts of speciation have laid upon classification. But it certainly cannot be said that the idea of intergrading geographical races is any novelty to ant taxonomy. It is unfortunate that neither Forel nor Emery were able to continue the type of work with which Forel began his myrmecological career. Both men became increasingly absorbed with the study of cabinet specimens from exotic sources. The distributional data which accompanied these expatriated specimens was seldom adequate for geographical analysis. As a result the recognition of a subspecies came to depend less and less on the behavior of the insect in the field and more and more on the structural characteristics which it showed. Even so, ant taxonomy would not have differed greatly from that of many other groups had not Emery begun the practice of subordinating the variety to the subspecies. Emery possessed a phenomenal acuity in dealing with structural variation and an equal ability for intricate organization. No one can claim that Emery's method of dealing with infraspecific variation lacked consistency. The differences on which he based his subspecies were less striking than specific distinctions and more apparent than varietal criteria. But, since the magnitude of the difference was the main consideration, the process was remarkably similar to grading eggs or apples for size. 14 bulletin: museum of comparative zoology By current standards Emery's system is unacceptable, but this has not been the main reason for the many objections which have been directed at it. The subordination of the variety to the subspecies has made ant taxonomy so complex that it has become unmanageable. There have been numerous proposals designed to alleviate this situa- tion. I shall speak only of the one which I made in 1938, since the remedy suggested has proven a very poor panacea indeed. I proposed to do away with the varietal rank altogether and treat all infraspecific variants in ants as subspecies. This proposal was based on the belief that most subspecies and varieties would prove to be geographical races when they were better known. If my surmise had been correct the preparation of this book would have been greatly simplified. It is always easier to suggest that a form be elevated to a higher rank than to show why it must be sunk as a synonym. The main difficulty has been with the varietal rank. I now know that I was wrong in supposing that most of our varieties can be treated as geographical races. Amaz- ingly few of them have the distributional characteristics which such races should show. This is particularly true of varieties based upon color. These color varieties almost never possess any distinction of range that would separate them from the 'typical' form. The two occur together over a common range and there is usually a high degree of intergradation between them at all points of this range. I regret to say that numerous color varieties have been set up, although it was recognized at the time of original description that the type series consisted of intergrading material of this sort. In such cases the definitive varietal characters will apply to only a part of the type series. This peculiar situation is certainly irritating, for it shows the low regard in which the variety has been held even by those who elect to name them. The more I have studied color varieties, the more I have been surprised to discover how little justification there is for the recognition of most of them. These varieties possess no distinctive distributional features. There is no constancy in the color characters which are supposed to define them. Their recognition involves prac- tices which are completely at odds with our customary taxonomic procedure. Their naming places a heavy burden on our nomenclature. To arrive at a satisfactory solution for these difliculties it is necessary to recognize that in many species and subspecies of ants no narrow distinction for color can be laid down. Since the color varies we must expand our concept of the 'typical' condition to include all the color phases. In such species there is no justification for distinguishing between the 'typical' coloration and off-colored conditions merely because the type series happened to include only a part of the color range. We must, in short, synonymize many of our color variants CREIGHTON: ants of north AMERICA 15 with the 'typical' forms from which they should never have been separated. With this in mind I have relegated more than one hundred varieties to the synonymy in this volume. In the case of our subspecies the situation is much better. Com- paratively few of these have had to be considered as synonyms and in most cases revision has been upward. Most of the larger genera possess at least one 'protean' species to which many subspecies have been assigned. The structural differences which distinguish these subspecies usually consist of relatively minor variations in sculpture, pilosity and proportion which do not depart to any great extent from the structural criteria on which the species has been founded. The magnitude of these subspecific distinctions is usually very similar, hence if structure alone is considered, they would all have to be placed in the same category. On the basis of distributional data, however, they fall into two distinctly different groups. In many cases two or more of these 'subspecies' will occupy an identical range and preserve their distinctive structural features throughout this range without intergradation. Since this behavior is that of a species and not that of a geographical race, such variants show that they are the 'sibling species' with which modern taxonomy has been so vitally concerned. It is necessary to raise this type of subspecies to full specific rank. The subspecies in the second group (and a very few varieties) show the characteristics of geographical races. Each of them occupies a range of its own and maintains its structural identity over that range except in areas of overlap with the range of another subspecies. In these areas of overlap intermediate forms are produced. In this case all that need be done is to raise the varieties to subspecific rank, for this category is the proper one for geographical races. It seems clear that the arrangement just discussed will more nearly meet with the exacting requirements of modern taxonomy than does our older system. It would also appear that it takes care of most of the problems involved without calling for the use of distinctions which are, at present, subject to speculation. I find little sympathy for much that passes as gospel among the more esoteric disciples of speciation. The taxonomist cannot be expected to evince enthusiasm for species which can only be distinguished by a different rate of wing beat or the structure of the salivary chromosomes. Such matters are, doubtless, of great interest to the theorist who, because of his detach- ment from the practical side of taxonomy, is free to speculate as he pleases concerning specific criteria. But the taxonomist enjoys no such freedom. Unless he can furnish specific criteria which are reason- ably obvious and easy to use, his entire system falls into disrepute. It is plain, therefore, that the taxonomist will continue to pin his 16 bulletin: museum of comparative zoology faith on external structure as the major specific criterion. It may be that in the future we shall have to accept ecospecies and psycho- species as valid taxonomic entities, but at present such things seem best left to the theorists. THE HISTORY OF ANT TAXONOMY IN NORTH AMERICA To anyone familiar with the excellent history of myrmecology which formed a chapter in Wheeler's volume Ants a further discussion of this subject may seem redundant. There are, however, two good reasons for reviewing the matter here. Taxonomy often resembles the law in that opinions may be more important than the facts on which they are based. While it is easy to evaluate facts it is not so easy to judge the worth of an opinion unless one knows something about the individual who has given it. This alone would justify a brief account of the men who have built up the intricate structure of formicid taxonomy. But there is an even more compelling reason in Wheeler's own work. Since he modestly forbore to mention in his book his own unique contribution to the taxonomy of North American ants, it is not amiss to try to show how great that contribution has been. In the ensuing account I have dealt only with those myrmecologists who have undertaken descriptive taxonomy. This has made necessary the wholesale elimination of many notable specialists whose work has lain outside this rather restricted field. I have further limited this field by dealing primarily with those workers whose studies contributed to the classification of North American ants. This has excluded a number of eminent taxonomists whose contributions have been mainly or entirely based on the ants of other faunal regions. Even with these limitations the subject is far from easy to present since much of the taxonomy of our ants has been done by European specialists and this involves a parallel treatment of events on opposite sides of the Atlantic which can be very confusing. While the ant fauna of North America contains three Linnaean species, Monomorium pharaonis, Tetramorium caespitum and Formica fusca, it is only indirectly that we can regard the patron saint of the taxonomist as having begun the classification of our ants. For M. pharaonis has been introduced here and Linnaeus described it from African specimens, while the other two species occur in Europe as well as in America and the material on which they were based came from the former region. It was a student and compatriot of Linnaeus, the Baron De Geer who made the first description of an ant taken in North America. In 1773 he described a Formica pennsyhanica, which we now recognize as the widespread Camponotus pennsyhanicus. In creighton: ants of north America 17 1798 the Danish taxonomist Fabricius described a second ant endemic to North America. His Formica ferruginea {Camponotus pennsylvan- icus subsp. ferruginea) is a common and conspicuous insect and it is not surprising that it should have been among the first of our ants to receive recognition. Four years later the talented French myrmecolo- gist Latreille added three more descriptions of North American ants. All three species, Pogonomyrmex badius, Formica pallidefulva and Camponotus castaneus, occur along the eastern Gulf coast and in Florida and it may be assumed that Latreille received some of his speci- mens from a fellow-countryman in what was then French territory. In 1804 Fabricius described three Neotropical species whose range extends into this country (Pachycondyla harpax, Trachymesopus stigma and Solenopsis geminata) but here, as in the case of Linnaeus' spec- ies, the type material did not come from within our borders. With this handful of species as a start the taxonomy of North American ants lapsed into a period of quiescence which was unbroken for more than thirty years. In 1836 there appeared in the Journal of the Boston Society of Natural History, a posthumous publication of Thomas Say, describing a small collection of ants from Indiana. In view of the scope of Say's studies it is not surprising to find him the first American to publish in the field of ant taxonomy. It was not until the end of his life that Say became interested in ants and his death at the comparatively early age of forty-seven put an end to his myrmecological studies almost as soon as they were begun. Had Say lived to extend his observations the development of ant taxonomy in this country might have taken a very different course. Of the nine ants described by Say five are recognized at present and, since three of these are very abundant species. Say has left us a frequent reminder of the first ant taxonomy done on this side of the Atlantic. In the ten years following Say's publication only two new North American forms were described. One of these, Labidus esenbecki, was set up by Westwood in 1842, the other, Stigmatomma pallipes, by Haldeman in 1844. From the foregoing account it may be seen that up to the year 1845 remarkably few of our native ants had been described. The total number appears to have been twenty-three, for to those mentioned above, it is necessary to add the problematical Lasius exulans which Fabricius described in 1804. Of these twenty-three species only eight- een, as subsequent events have shown, were sufficiently well described to be recognizable. One may grant that in 1845 most of the western third of North America was virtually unknown and certainly uncol- lected. But even with this reservation the number of described ants seems pathetically small. I take 1845 as a significant date because it 18 bulletin: museum of comparative zoology marks the reawakening of interest in ant taxonomy. This renaissance was primarily a European phenomenon but its effects on the classifi- cation of our native ants were very considerable. In Europe, as in America, the first half of the nineteenth century was marked by an apathy toward taxonomic study. During that period, Losana and Westwood had each contributed a few species and Lund and Leach had swelled the total of unrecognizable forms, but in 1845 formicid taxonomy was essentially as Latreille and Fabricius had left it forty years before. Once the interest in the field was aroused, however, the pendulum swung to the opposite extreme. In the years immediately following 1845 no less than eight European workers began publishing on ant taxonomy. Of these eight men we need consider only three here: Julius Roger, a physician who held the Post of Public Health and Anatomy in the small town of Rauden in LTpper Silesia, Gustav Mayr, a professor in the University of Brunn and Frederick Smith, who for some years was an assistant in the Zoological Department of the British Museum. It is easy to fall into the error of thinking that, because there had been few ants described at that period, the "good old days" of myrme- cology were marked by a delightful simplicity which made taxonomy much easier than at present. With most of the world teeming with undescribed species and the literature limited to two or three dozen publications there is something to be said for this view. But such roseate retrospections fail to consider the difficulties which resulted from the total lack of what we now regard as the basic generic structure of ant taxonomy. Without exception the older authors had made use of collective genera as well as collective species. Instead of our well- defined present day genera they had left a number of conglomerate groups any one of which would have furnished (as most of them have) material for half a dozen modern genera. Successful work under these circumstances demanded great acumen in dealing with generic delimi- tations. Both Roger and Mayr possessed this characteristic to a high degree but it was one of the many desirable taxonomic qualifica- tions which Frederick Smith lacked. When Smith began his studies on the ants in the collection of the British Museum, he enjoyed an opportunity which has seldom if ever been equaled. Not only was the collection wonderfully rich in undescribed species and genera but it contained the Banks collection of Fabrician types. Frederick Smith was by very long odds in a posi- tion which any myrmecologist might have regarded with justifiable envy. For more than twenty years Smith published on this material, during which time he described several hundred species and not a few genera. It is safe to say that not more than a third of these could creighton: ants of north America 19 be recognized from his descriptions. For Smith possessed what Wheeler has called a "deficient classificatory sense" and few of the species which he described had a structure sufficiently distinct to show through the verbal camouflage with which he obscured them. In addition, Smith had little regard for what other workers in the field had done, hence he frequently made synonyms. It may be said that he showed no partiality here for as often as not he redescribed his own species under new specific names. The effect of these faulty practices on Smith's contemporaries may be easily imagined. I happen to know that Julius Roger found them intolerable, for I own the copy of the 1858 Catalogue which Smith inscribed and sent to Roger in the following year. This volume is interleaved and copiously annotated in Roger's microscopic script. On almost every page Roger has noted one or more corrections and some of these are made with obvious acerbity. It must have been particularly annoying to Roger, who was striving to modernize the genera of Latreille and Fabricius, to watch Smith's placid disregard of Fabrician species. Smith rede- scribed most of them under new names and in one instance {Solenopsis geminata) repeated the error four times. A good deal of Roger's taxonomic work was taken up correcting Smith's mistakes and he thus became the first of several investigators who were forced to labor at this uncongenial task. Forel, with his characteristic impetuosity, once published a statement that neither Smith's descriptions nor his types could be depended upon. But while Forel's annoyance is understandable, he obviously overshot the mark. It is only because of Smith's types, or rather because of the fact that many of them were preserved in the collection of the British Museum, that Smith's work was saved from oblivion. In 1894 Mayr visited the British Museum and examined Smith's material. He was able to rectify many errors and later, through the efforts of Emery, others were eliminated. In such circuitous ways many of Smith's species have been made recog- nizable to other workers in the field but there still remains a large residue whose exact nature will probably never be known. In contrast to the reprehensible work of Smith, that of Mayr is the cornerstone on which our present day taxonomy has been reared. Mayr began his studies of ants at an early age, publishing his first paper when only twenty-one years old. Thereafter he continued to publish on myrmecological topics for more than fifty years. Thus it happened that while in his youth Mayr worked with Nylander, Roger and Smith, he later became a contemporary of Emery and Forel and lived to see the advent of two other notable myrmecologists, W. M. Wheeler and F. Santschi. It is seldom that one man can claim a contemporary acquaintance with so many of the major figures in 20 bulletin: museum of comparative zoology a field. It is even less seldom that the work of one man has such a profound effect in shaping a field. At a time when most myrme- cologists were content with the few genera which they had inherited from their predecessors of the eighteenth century, Mayr embarked on a course of generic delimitation which gave us many of our most important present day groups. It is significant that Mayr's name is attached to such well known genera as Camponotus, Pogonomyrmex, Aphaenogaster, Tetramorium and many others. In addition Mayr was the first formicid taxonomist to make extensive use of dichot- omous keys. These keys were often presented in connection with work that amounted to a generic revision although, since the papers carried other material as well, they were not so designated. Other workers in the field of ant taxonomy have produced far more descrip- tive work than Mayr but it is certain that no one has made a more timely or far reaching contribution than he did. Mayr's first myrme- cological interests lay almost entirely within the confines of his native Austria, Later he extended his work to include the entire European ant fauna and about 1862 turned his attention to exotic species. In this work he was joined by Roger and, since Smith had been occupied with exotics for several years, most of the development of our North American ant taxonomy at the middle of the last century lay in the hands of these three men. The death of Roger in 1865 and that of Smith ten years later would have left Mayr in possession of the field if it had not been for the entrance of two very able young myrme- cologists, Emery and Forel. Both these men matched Mayr's youthful start in the field of myrmecology for each published his first paper dealing with ants at the age of twenty-one. Like Mayr the newcomers began their studies on local faunas and for some time their interest in exotic species was slight. About 1880, however, both Emery and Forel began to publish on exotic ants. As Mayr was already well embarked on this work, it may be seen that the period from 1880 to 1900 was one of rapid expansion in ant taxonomy. Each paper of any size carried descrip- tions of dozens of new species and it is a tribute to the skill of all three men that comparatively few synonyms were made. I wish at this point to discuss the parallelism which is said to have marked the lives of Emery and Forel. This concept was developed by Forel who, on the occasion of Emery's death in 1925, published an account of the similarities between Emery and himself. Most of these are of little consequence and Forel's preoccupation with them may be considered the foible of a failing septuagenarian who was approaching the end of his own life. But recurring throughout the recital is the theme of parallel activity or identical practice in the creighton: ants of north America 21 field of myrmecology. It is this part of Ford's statement that needs elucidation, since it does not follow that because two men work together in the same field their methods or attitudes must be the same. Actually there was a highly significant difference in the way in which the two men treated ant taxonomy. Forel received his formal training in medicine. Thereafter he did postgraduate work in neural anatomy and psychiatry. In 1879 he was appointed as the Director and physician in charge of the Cantonal Asylum at Burgholzi, Switzerland. Few people would deny that he was a genius. Not only was he an acknowledged authority in myrme- cology and psychiatry but he was equally at home when practicing hypnotism or proselyting for prohibition. He possessed an abounding and infectious enthusiasm which even his severest critics found hard to resist. In his work with ants he was a superb observer in the field and keenly aware of the importance of ecological data as an aid to the structural distinctions of taxonomy. He clearly derived great pleasure from describing new species and genera of ants and did so with ability and distinction. His knowledge of what other taxono- mists had done was excellent and among the great number of new ants which he described comparatively few were synonyms. But Forel clearly felt that the important function of taxonomy was the description of new forms. The character of his publications leaves no room for doubt on this point. Although he could turn out beauti- fully coordinated faunal studies and had many excellent opportunities to do so, he rarely produced this type of work. Despite their titles, many of his faunal studies, for example his formicid section of the Histoire physique, naturelle et politique de Madagascar, or that of the Biologia Centrali- Americana, are little more than vehicles for carrying the descriptions of new species. In both these large and important papers previously described species are listed with bibliographic citations only and neither work makes any attempt to furnish keys which would aid in a faunal study. Their value in such work is, therefore, limited almost entirely to those species which were first described in the two publications. It must not be thought that Forel was unaware of the characteristics of the species which he neglected. He knew them well, but he clearly regarded the organizational aspects of taxonomy as boring routine. It appears that he never published a generic monograph, certainly not one of any size. He was fond of publishing miscellanies in which a single paper carried descriptions of new ants from widely scattered parts of the world, a circumstance which made coordination impossible. Forel was proud of his species and genera and bitterly resented criticism of them. For the person who called one of these species in question struck at what Forel felt 22 bulletin: museum of comparative zoology was the heart of his work. And this work was of truly heroic propor- tions, since during his life Forel described three thousand new ants. But it is correct to state that this enormous mass of description was his major contribution to ant taxonomy. In contrast to Forel, Carlo Emery was far less spectacular. In 1881 he was appointed Professor of Zoology in the University of Bologna and held this position until his retirement many years later. In his work on ant taxonomy Emery was thorough and methodical to a fault. He published many faunal studies, most of which are exten- sively keyed and provided with data on the previously described species as well as the new ones. He monographed several large and diiKcult g'^nera with exceptional care. His view of taxonomy was always inclusive. A new species was of little significance unless it could be seen in relation to the others in the genus. His ability for specific and generic description was equal to that of Forel and the care that he put into the organization of his taxonomy was incom- parably greater. Emery's work was so exact that he made even fewer synonyms than Forel, but he always welcomed the opportunity to correct such errors, and more often than not was the first to call attention to the mistake. He never lost sight of the fact that the description of a new species is only the beginning of taxonomy and no amount of comparison or difficulty in keying was too arduous for Emery if it permitted an easier recognition of the species involved. During his life Emery described almost as many new species as did Forel, but it is clear that he regarded this feat as less important than the taxonomic organization which accompanied it. We may count ourselves fortunate that it was Emery rather than Forel who undertook the first inclusive account of North American ants. In the three-cornered competition that developed between Mayr, Emery and Forel in the closing years of the last century, Emery had the better of it as far as material from North America was con- cerned. This was due in part to his association with Pergande, who sent Emery much of the material on which his classic Beitrdge zur nordamerikanischen Avieisenfauna was based. With these and other specimens Emery was able to describe, by the year 1900, more North American ants than had been recognized by all other European myrmecologists combined. By that time he had set up about one hundred and eight forms coming from our region. Of the ninety or so remaining forms Mayr had described thirty-two, Roger twenty, Forel sixteen, F. Smith ten and the older authors about a dozen. It may be seen that by the year 1900 the contributions of European myrme- cologists to our ant fauna numbered about two hundred forms. Let us now see how our own myrmecologists fared during the period creighton: ants of north America 23 from 1845 to 1900. The record is scarcely an inspiring one for there is no American counterpart with which to match the activity in Europe during that period. In defense of our early myrmecologists it may be said that they worked with considerable odds against them. There were few adequate libraries, type material was nowhere avail- able and specimens sent to Europe for comparison all too frequently appeared as new species under the name of some European specialist. In 1852 Haldeman re-entered the myrmecological field with the de- scriptions of two new species belonging to the genus Eciton. Three years later Asa Fitch described six North American ants of which three were new forms. In 1862 Walsh described two forms of Lasius and in 1865 the elder Cresson gave us the description of Pogonomyrviex occidentalis. During the next two years there appeared from the pen of S. B. Buckley the descriptions of sixty-seven North American ants which he regarded as new species. The numerical magnitude of this contribution is apparent when it is considered that prior to Buckley's effort there had been less than half that many species described on this side of the Atlantic. Buckley's collection was not only much larger than any previously studied by an American taxonomist but it was made up of material coming from widely separated parts of the country. As State Geologist of Texas Buckley had collected a number of ants from the central portion of that state. These Texas specimens made up slightly more than half the collection. The remaining speci- mens had been taken by Buckley at Washington, D. C. and Naples, N. Y., or had been given him by Norton. Most of Norton's material came from Connecticut but there were also specimens from Florida and California. In addition Norton had turned over to Buckley a series of identified European ants for purposes of comparison. Buckley worked up his ant collection in Philadelphia, where he had the refer- ence facilities to be found in the personal library of Dr. Le Conte as well as those in the libraries of the Philadelphia Academy of Natural Sciences and the Philadelphia Entomological Society. I mention these details because it is easy to get the impression from some of Buckley's critics that his work was done in complete ignorance of the subject he was investigating. On the contrary, Buckley seems to have been fortunate in having at his disposal considerably more facilities for research than were usually available at that time. Indeed it is hard to see how his situation could have been materially improved unless he had undertaken a trip to Europe to consult type specimens. His chances for producing what might have been a monumental contribu- tion to our ant taxonomy were excellent. W^hat he actually did was to write a treatise that is best regarded as a myrmecological curiosity. It seems scarcely believable that with his obvious interest in the 24 bulletin: museum of comparative zoology insects which he was describing, an interest that his severest critics have never denied, Buckley should have failed to produce a single description which permits the positive recognition of any of his species. In the majority of cases it is quite impossible to determine to what genera the insects belong, for Buckley's descriptive ineptitude was equalled by his extraordinary lack of regard for generic distinction. It should be borne in mind that by 1867 Mayr and Roger had de- limited most of our common genera, but even if we excuse Buckley's disregard of these men's work it is impossible to condone a neglect of previous authors which extends to Linnaeus. Buckley actually de- scribed as new, a species which he called Myrmica rubra. Since Linnaeus' species is described and figured in Latreille's Histoire Naturelle des Fourmis, a volume which Buckley had borrowed from LeConte's library, it seems reasonably clear that this same volume must have been gathering dust while Buckley penned the description of his homonym. Buckley's shortcomings have been variously attrib- uted to lack of training, the difficulties of the subject and innate perverseness. I believe that there is a much simpler explanation. Buckley modeled his descriptions upon those of Frederick Smith. This much would be obvious from a comparison of the works of the two men even if we did not have Buckley's published statement that he was strongly influenced by hb English contemporary. Buckley's choice of a mentor was a fatal one for his work. Unlike Smith he left no types by which his species might have been checked. Thus the sole factor which saved Smith's species was lacking in Buckley's case. That all of Buckley's species have not been thrown into the discard is due to the fact that in a few instances he included field data with his descriptions, which identified the insect well enough to permit Mayr, Emery and Wheeler to surmise what it was. Even so only ten of his forms survive. In this ignominious fashion ended the first major attempt at formicid taxonomy on this side of the Atlantic. Very little additional work was done in this country in the years immediately following Buckley's fiasco. In 1868 Norton published the description of Eciton sumichrasti and four years later Cresson described two other species in the same genus. Between the years 1879 and 1881 McCook added a handful of new forms, while Pro- vancher, in 1887, published several descriptions of Canadian ants. About 1893 Pergande began a series of studies dealing with North American ants. Much of Pergande's material was from Mexico but he described at least nine forms from areas in the United States. Pergande was a competent worker who knew the literature and en- joyed the respect and cooperation of his European contemporaries. When Forel vbited the United States in 1899 he made a special trip cbeighton: ants of north America 25 to Washington to make Pergande's acquaintance. The quality of Pergande's descriptions was superior, but his most important con- tribution to ant taxonomy in this country was indirectly made. As has already been mentioned he sent numerous specimens to Emery. It was Pergande's practice to divide each series sent into two halves, one of which he retained. When Emery made his half the basis for a new species, Pergande had authentic material, if not type material, of that same species in his possession. There was thus built up a valuable nucleus of specimens whose authenticity could not be ques- tioned. These, with Pergande's own types, constituted the first sig- nificant ant collection in this country. It is to be regretted that Pergande's work with ants was of such short duration. He published little after 1895, in which year the second and final portion of Emery's Beitriige appeared. To summ'arize the above, it is apparent that at the close of the last century the great preponderance of work on the taxonomy of North American ants had been done by Europeans. Their descriptions out- numbered those of our native myrmecologists more than two to one. The disparity was made much greater by the fact that of the hundred or so descriptions contributed by our workers more than sixty were wholly worthless. Authentic material was extremely scarce, and the majority of it was confined to the small collection made by Pergande. Despite Pergande's valuable work the taxonomy of North American ants was largely a European monopoly. I have stressed the year 1900 because it marks the appearance in the field of myrmecology of the man who was to bring about profound changes in this situation. In the fall of 1899 W. M. Wheeler accepted a professorship in the Department of Biology at the University of Texas. Wheeler's name has come to be so intimately connected with myrmecology that it seems strange to contemplate his novitiate in this field. The early hold which the science laid upon Wheeler's European contemporaries had not marked the initial years of his career. Wheeler's earlier scientific publications had embraced a con- siderable variety of subjects with the major stress, perhaps, on insect embryology. He had published studies in entomological taxonomy but these had dealt with dolichopodid and empid files. Certainly there was little to indicate that, during the next thirty-seven years of his life Wheeler would devote himself largely to the study of ants. Wheeler has stated that his initial interest in ants was occasioned when he happened to notice a number of workers of Atia iexana carrying leaf fragments into their nest. Seven years later this chance observation had come to fruition as an elaborately documented mono- graph of more than a hundred pages which is still, after forty years, 26 bulletin: museum of comparative zoology one of the best accounts of the attine ants ever pubhshed. From the outset of his work with ants Wheeler refused to be discouraged by the difficulties involved in studies of their taxonomy. Where a less ener- getic individual might have despaired, Wheeler persisted in his efforts to build up a working collection of authentically determined species. He corresponded extensively with Forel, Emery and Pergande, each of whom sent him identified specimens. The success of his work was such that by the end of three years he had amassed enough material to publish his first generic monograph, the Revision of the Ants of the Genus Leptothorax. This paper must have come as a profound surprise to Emery, Forel and Mayr, for in it they could clearly see the end of the supremacy which they had enjoyed in the field of North American ant taxonomy. The same year in which this paper appeared (1903) Wheeler left the University of Texas to accept a curatorship in the American Museum of Natural History. While there he extended his interest in ant taxonomy to include various exotic groups but the majority of the taxonomic papers published during his curatorship dealt with the classification of our native species. W'hile at Texas Wheeler had spent much time in the field, and in that state and in other parts of the southwest which he subsequently visited he col- lected assiduously. From this material came a large number of new species. In 1907 Wheeler visited Forel and was able to secure a splendid series of cotypes and identified specimens which greatly facilitated his studies. In 1908 Wheeler accepted a professorship at Harvard. During the first eight years that he was there he published a number of important papers dealing with the classification of North American ants. But he was busying himself more and more with exotic material and the Mountain Ants of Western North America, which was published in January 1917, was the last large paper on our ants. Thereafter he published few articles dealing with North American species, although his work on exotic ants increased in volume until his death in 1937. The significant period of his work with our species lies, therefore, between 1900 and 1916. In these sixteen years he described more than two hundred and seventy forms, a contribution which so far surpasses that of any other myrmecologist as to make comparisons futile. Yet it may be stated that the most valuable contribution which W'heeler made to the taxonomy of our ants was not in the large number of new species which he described. It was rather that Wheeler carried his taxonomy into the field and amplified structural distinc- tions with others relating to habits, distribution and ecology. For no amount of study of expatriated specimens can furnish these vital details and until the taxonomy of our ants was brought back to this creighton: ants of north America 27 country it perforce remained as lifeless as the preserved specimens on which it was based. It is Wheeler's singular distinction that by his indefatigable efforts he made our ant taxonomy the living thing it is today. Family FORMICIDAE The family Formicidae is often defined as a group of social Hymen- optera in which the worker is apterous, the antennae are geniculate and the abdominal pedicel consists of one or two segments. Whatever faults this definition may have, it points to one significant fact. The structure of the abdominal pedicel plays a very important part in the taxonomy of this group. It is used not only as one of the family characteristics, but also as a means for distinguishing the subfamilies. If the situation were always exactly as described above there would be little difficulty in this latter regard. Unfortunately the case is by no means so simple. In the subfamily Ponerinae the structure of the pedicel is subject to wide variation. A considerable number of the representatives of this subfamily have a pedicel of an intermediate character. It may be regarded as consisting of one segment or of two depending upon the view taken by the observer. In all such cases the first segment of the pedicel is well-marked but the second is not clearly distinct from the rest of the gaster. Its size is often as great as, or even greater than, the following gastric segment, from which it is usually separated by a distinct groove or impression. I have men- tioned this point because there is no good agreement among myrme- cologists as to how this situation is to be handled. Some follow Emery and treat this poorly defined 'node' as the postpetiole. Others make no attempt to recognize a postpetiole in such cases. Since there is no agreement as to what terminology should be employed considerable confusion has resulted. It is regrettable that some authorities treat the Ponerinae as having two petiolar segments and others regard them as having only one. But it is even more unfortunate when these two methods of treatment are combined in a single key. In the generic and subgeneric key which Wheeler published in 1922 the subfamily Ponerinae is separated on the basis of a single segment in the abdomi- nal pedicel. Yet there are repeated references to the postpetiole in the key to the ponerine genera. Much of this confusion could be avoided if the stress were placed on the gaster rather than on the petiolar segments. Except in the case of a few African Dorylinae and some Australian Cerapachyinae there is little doubt about the limit of the gaster regardless of whether 28 bulletin: museum op comparative zoology there are two petiolar nodes or one. It is significant in this connection that Emery, despite the fact that he regarded the first gastric segment of most ponerines as the postpetiole, always included this segment when he spoke of the gaster of these insects. Since there is such excellent agreement as to what the term gaster implies in the case of ants, this fact may be put to good use in dealing with the above diflBculty. In the overwhelming majority of the ponerines the gaster is different from that of most other ants; thus the subfamily may be separated on the basis of gastric structure without any chance for confusion since under this plan it is not necessary to mention the pedicel at all. This plan has been followed in the key below and I have also used this same character to bring out our representatives of the Cerapachyinae. I am aware that this distinction will not apply uniformly in that subfamily nor will the characters which have been used to separate the Cerapachyinae from the Ponerinae. But, since the Cerapachyinae are transitional in so many respects it seemed best to avoid doubtful generalizations and treat our few represen- tatives in a way which puts certainty of recognition in first place. The key which follows will apply only to the worker and female. In it, as in other keys presented elsewhere in this volume, no attempt has been made to deal with the male caste. There is reason to believe that at present there is no altogether satisfactory method for handling male ants if they are dissociated from the worker and female. Dr. M. R. Smith, who recently published an exhaustive monograph (1943) dealing with generic and subgeneric characters of male ants, was at pains to point out certain difficulties inherent in such an attempt. The structure of the male is often remarkably inconstant and this variability requires extensive qualification in the case of key char- acters. By the time these have been whittled down to care for all the possible exceptions there is usually not much left of them. If I understand Dr. Smith correctly, the generic habitus of most male ants is an extremely subtle matter and one which 'often defies accurate description'. It seems plain enough that the ordinary dichotomous key is not sufficiently fiexible to handle these subtleties and that one might do as well or better with unkeyed illustrations as a guide to generic habitus in the male. At least this is the method followed in the present volume. The majority of the plates which have been prepared to show generic characteristics carry a figure of the male. Those who prefer to work with keys are referred to Dr. Smith's 1943 monograph, which is by far the best presentation of this subject that has yet appeared. CREIGHTON: ants op north AMERICA 29 Key to the Svhfamilies 1. Gaster with a distinct constriction between the first and second segments or, if this constriction is faint, the mandibles are linear and the petiole is produced into a conical dorsal spine 2 Gaster without any constriction between the first and second segments . . 3 2. Antennal scape short and very stout, even at the base, the scape flattened throughout or with a greatly enlarged tip which bears a prominent lateral furrow for the reception of the funiculus Cerapachyinae Antennal scape not as above, usually long and slender, but if short and enlarged at the tip, at least the basal third of the scale is slender. . Ponerinae 3. Abdominal pedicel consisting of two segments 4 Abdominal pedicel consisting of one segment 6 4. Frontal carinae narrow and not expanded laterally so that the antennal insertions are fully exposed when the head ia viewed from above 5 Frontal carinae expanded laterally so that they partially or wholly cover the antennal insertions when the head is viewed from above . . Myrmicinae 5. Eyes very large, suboval or reniform and consisting of several hundred fine ommatidia Pseudomyrminae Eyes vestigial or absent, if present consisting of a single ocellus-like structure Dorylinae 6. Cloacal orifice distinctly circular and usually surrounded by a fringe of hairs Formicinae Cloacal orifice slit-like, the hairs, when present, not forming an encircling fringe Dolichoderinae Subfamily PONERINAE The subfamily Ponerinae is regarded as a very primitive group of ants. This is apparent both in their structure and habits. Although there are ponerine genera in which certain features are highly special- ized, their general structure has undergone very little evolutionary advance. Throughout most of the subfamily the worker caste shows a condition of primary monomorphism. The worker closely approaches the female in size and there is no tendency toward the production of medias or minors in the worker caste. The habits of these ants show a comparable lack of specialization. The group is uniformly carnivor- ous. The workers collect other insects or small arthropods and these are cut to pieces and fed directly to the larvae. Regurgitation seems to play a much smaller part in the life of the colony than is the case in the higher subfamilies. The nest-founding reactions of the ponerine female are also primitive. During the rearing of the first brood she leaves the nest t3 forage for food and it is presumed that she does not utilize salivary secretions to feed the larvae. There would seem to be no morphological reason why she might not do so, for Haskins and 30 bulletin: museum of comparative zoology Enzmann have shown (1938) that in many ponerine genera the wing muscles of the female degenerate after dealation as is the case in the higher subfamilies. While the representatives of some ponerine genera are very aggressive and pugnacious none of the species which occur in the United States show these traits. In general they are inoffensive or even timid ants which form small colonies and exhibit few spectacular characteristics. Except for Stigmatomma, which is more abundant in the northern part of the country than in the south, all the other genera clearly belong to the southern component of our ant fauna. This is true even in the case of Ponera for, although one species of this genus has a range which reaches New England and southern Canada, its primary representation is in areas further south. The only part of the United States in which ponerine ants are found in any degree of abundance is the region bordering the Gulf of Mexico and the Mexican boundary. Even in this region the incidence notably increases from north to south. The two areas which support the greatest ponerine population are southern Florida and the Brownsville region in southwestern Texas. In the northern half of the United States these insects make up a very minor and inconspicuous part of our ant fauna. Key to the Genera of the Subfamily Ponerinae 1. Gaster without a distinct constriction between the first and second segments; node of the petiole forming a conical spine above; mandibles linear and inserted near the midline of the head; antennal fossae bounded in the rear by a rounded ridge which runs diagonally inward from the eye Odontomachus Gaster with a distinct constriction or groove between the first and second segments; node of the petiole blunt or rounded above; mandibles inserted at the sides of the head; antennal fossae not bounded in the rear by a diagonal ridge 2 2. Anterior border of the clypeus denticulate; mandibles with a row of coarse, bidenticulate teeth Stigmatomma Anterior border of the clypeus variously shaped but never denticulate; mandibular teeth, when present, single 3 3. Thoracic dorsum without sutures, at most a shallow impression at the point at which the suture should be, usually not even an impression present 4 Thoracic dorsum with at least the promesonotal suture present, and usually the mesoepinotal suture present as well 6 4. Apex of the gaster directed ventrally or anteroventrally when the major axis of the gaster is in line with that of the thorax; head and thorax punctato-granulose or punctato-rugose, gaster smooth with numerous pUigerous punctures 5 creighton: ants of north America 31 Apex of the gaster directed to the rear when the major axis of the gaster is in Une with that of the thorax; head, thorax and gaster covered with even, straight, longitudinal rugae Ectatomma 5. Petiole scalelike, the front and rear faces flattened; anterior border of the clypeus not projecting in the middle Proceratium Petiole nodiform, low and much rounded above; clypeus with a narrow median lobe which projects strongly beyond the rest of the anterior border Sysphincta 6. Tarsal claws distinctly pectinate; mandibles without distinct teeth Leptogenys Tarsal claws simple; mandibular teeth usually distinct 7 7. Cheek with a distinct carina extending from the eye to the clypeus Neoponera Cheek without a carina 8 8. Pronotum marginate on either side Pachycondyla Pronotum not marginate on either side 9 9. Thoracic dorsum with only the promesonotal suture present; clypeus flat, the suture which separates it from the front of the head indistinct Platythyrea Thoracic dorsum with both the promesonotal and mesoepinotal sutures present; clypeus with a projecting median lobe, the suture which separates the clypeus from the front of the head clearly distinct 10 10. Tibia of the middle and hind legs with a single spur Ponera Tibia of the middle and hind legs with two spurs, the smaller lateral spur often obscure Euponera The difference in the tibial spurs used to separate Ponera and Euponera is often difficult to utilize because of the small size of the lateral spur. For practical purposes the three groups involved are more easily separated as follows : 1. Middle tibiae with stiff hairs on the extensor surfaces; eyes small, the facets indistinct Euponera Subgenus Trachymesopus 2. Middle tibiae without stiff hairs on their extensor surfaces; eyes of moderate size, their facets very distinct Euponera Subgenus Brachy ponera 3. Middle tibiae without stiff hairs on their extensor surfaces; eyes small, their facets indistinct Ponera Genus StiGMATOMMA Roger (Plate 1, figures 1-5) The primitive and wide-spread genus Stigmatomma is represented in North America by a single species, S. pallipes. The habits of this interesting insect have been repeatedly studied, the latest and most inclusive account being that of Haskins (1928 et seq.). Haskins has 32 bulletin: museum of comparative zoOlogt been able to show that the female of palUpes forages for food during the period of nest-founding. This trait, also found in other archaic Ponerine genera, is regarded as primitive and ancestral to the closed type of nest-founding practiced by most ants. Haskins' observations are of much interest since they prove that the nesting behavior of pallipes is in accord with its strikingly primitive structural features. According to the above author the main diet of pallipes consists of small geophilid centipedes. Fragments of small insects are also fre- quently used as food. These are fed directly to the larvae, again a primitive habit, without recourse to regurgitation. The great majority of records for pallipes and its several subspecies come from regions characterized by heavy cover and considerable precipitation. This has led to the belief that the range of this insect is coincidental with such areas. From a statistical standpoint the records are overwhelmingly in favor of such an interpretation. Indeed, the only contrary one appears to be that of the insect which I took at Elmo, Kansas and later described as the subspecies subterranea. In discussing the peculiar situation of the nest of subterranea, I pointed out that if this subspecies is able to lead a hypogaeic existence on the dry and open plains of Kansas, there is a possibility that the range of pallipes may blanket much of the United States and southern Canada. If this ant becomes epigaeic only in moist, wooded areas it will not be easy to implement our present knowledge of its range. It is only by accident that a hypogaeic ant which lives well below the surface is apt to be discovered. Nevertheless I believe that in the future records of pallipes will be forthcoming from areas where it is not known to occur at present. Key to the subspecies of Stigmatomma pallipes Haldeman 1. Inner border of the mandible strongly sinuate, the portion bearing the double teeth forming a marked convexity 2 Inner border of the mandible not sinuate, the portion bearing the double teeth straight or nearly so -pallipes subsp. oregonense 2. Funicular joints 2-5 at least twice as broad as long; largest worker 5 mm. in length pallipes subsp. monligena Funicular joints 2-5 about as long as broad or longer than broad; largest worker 6.5 mm. in length 3 3. Occiput slightly but distinctly concave; median teeth of the clypeus smaller and finer than the flanking teeth; color ferrugineous, the head and thorax scarcely or not at all darker than the gaster. . . . pallipes subsp. subterranea Occiput flat; median teeth of the clypeus as large as the flanking teeth; color (in mature specimens) dull brown to piceous brown, the head and thorax usually darker than the gaster pallipes creighton: ants of north America 33 1. Stigmatomma pallipes (Haldeman) Typhlopone pallipes Haldeman, Proc. Acad. Nat. Sci. Phila., Vol. 2, p. 54 (1844) 9. S. pallipes Emery, Zool. Jahrb. Syst., Vol. 8, p. 261 (1895) 9 9 cT; Wheeler, Biol. Bull., Vol. 2, p. 65, figs. 5, 6, 7 (1900) 9 9 d'; Creighton, Amer. Mus. Novitates, No. 1079, p. 3 (1940) 9 9 ; M. R. Smith, Amer. Mid. Naturalist, Vol. 37, No. 3, p. 532, pi. 2, fig. 5 (1947) 9 . S. pallipes subsp. arizon'ense Wheeler, Bull. Amer. Mus. Nat. Hist., Vol. 34, p. 389 (1915) 9 . S. pallipes var. wheeleri Santschi, Ann. See. Eng. Belg., Vol. 57, p. 429 (1913) 9 9 d^. S. serratum Roger, Berl. Ent. Zeitschr., Vol. 3, p. 251 (1895) 9 . Arotropus binodosus Provancher, Canadian Nat., Vol. 12, p. 207 (1881) 9 . Type locality: none given. Types: None known to exist. Autotypes in the collection of the Boston Society of Nat. Hist. Range: southern Ontario and Quebec south to the Gulf coast with a sporadic distribution in Texas and the southern Arizona mountains. In the Appalachian highlands the insect occurs at elevations below 3000 feet. In my publication dealing with S. pallipes I presented reasons for synonymizing arizojiense and wheeleri with the typical pallipes. Since that time I have received, from Dr. L. G. Wesson, additional informa- tion concerning the first of these two forms. It may be recalled that I discussed the possibility that the single specimen on which arizonense was based might have been a mislabelled representative of our eastern subspecies. I was prepared to believe that the insect does not occur in Arizona. This view has since been nullified by the discovery of two additional Arizona specimens of pallipes by R. G. Wesson. I have not examined the specimens but Dr. Wesson, who has compared them with the eastern form, writes me that the differences "are not particu- larly impressive". Thus, while there seems to be no reason to re- establish the subspecies arizonense, it will be necessary to recognize a considerable addition to the range of the typical pallipes. 2. Stigmatomma pallipes montigena Creighton Stigmatomma pallipes subsp. montigena Creighton, Amer. Mus. Novitates, No. 1079, p. 7 (1940) 9 9. Type locality: Little Switzerland (3400') near Spruce Pines, N. C. Type: A.M.N.H. Paratypes: M.C.Z., Coll. W. S. Creighton. Range: this subspecies replaces the typical pallipes at higher elevations in the mountains of the southeastern United States. It intergrades with pallipes to produce the form which Santschi has called wheeleri. 34 bulletin: museum of comparative zoology 3. Stigmatomma pallipes oregonense Wheeler Stigmatomma pallipes subsp. oregonense Wheeler, Bull. Amer. Mus. Nat. Hist., Vol. 34, p. 389 (1915) 9 9 ; Creighton, Amer. Mus. Novitates, No. 1079, p. 7 (1940) 9 9 . TjT^e loc: worker, Marion County, Oregon; female, Olympia, Washington. Types: A.M.N.H., M.C.Z. Range: low elevations in the coastal mountains of Oregon, Washington and British Columbia. 4. Stigmatomma pallipes subterranea Creighton Stigmatomma pallipes subsp. subterranea Creighton, Amer. Mus. Novitates, No. 1079, p. 8 (1940) 9 9 . Type loc: Elmo, Kansas. Type: A.M.N.H. Paratypes: M.C.Z., Coll. W. S. Creighton. Range: known only from type material. Genus PlATYTHYREA Roger (Plate 2, figures 1-3) The tropicopolitan genus Platythyrea has a single representative, P. punctata, which occurs in the southern United States. The records for this species indicate that it is confined to the southern tip of Florida and the area immediately around Brownsville, Texas. P. punc- tata is not likely to be confused with any of our other ponerines. In addition to its characteristic thoracic structure (see key) it has, when fully mature, a peculiar greyish black color and a dull, mattelike surface which give it a very distinctive appearance. The habits of punctata have been observed by Forel in Barbados (1899), Wheeler in the Bahamas (1905) and M. R. Smith in Puerto Rico (1936). The insect prefers to nest in old stumps or logs or under the bark of trees in shady situations. The workers are active and forage singly. The colonies are small consisting of from fifty to two hundred individuals. It is both carnivorous and predatory. 1. Platythyrea punctata (F. Smith) Pachycondyla punctata F. Smith, Cat. Hym. Brit. Mus., Vol. 6, p. 108 (1858) cf. Platythyrea punctata Roger, Berl. Ent. Zeitschr., Vol. 7, p. 173 (1863); Forel, Rev. Suisse Zool., Vol. 9, p. 335 (1901); M. R. Smith, Amer. Mid. Natu- rahst. Vol. 37, No. 3, p. 533, pi. 3, fig. 9 (1947) 9 . Platythyrea inconspicua Mayr, Verh. Zool-bot. Ges. Wien, Vol. 20, p. 961 (1870) 9 ; Emery, Ann. Soc. Ent. Fr. (6), Vol. 10, p. 56 (1890) 9 . creighton: ants of north America 35 Type loc: San Domingo. Type: British Museum. Range: southern Florida and southwestern Texas and southward through the Antilles and Central America. Genus ECTATOMMA F. Smith The genus Ectatomraa is represented in America north of Mexico by a single species, E. (Parectatomma) hartmani. This insect is very imperfectly known. It was described by Wheeler in 1915 from one worker which was taken at Huntsville, Texas. There are no additional records to show that it has been found again. In contrast to our lack of knowledge concerning hartmani there is a large and entertaining body of literature dealing with the behaviour of E. tuberculatum in Texas. This is the famous "kelep", whose introduction into the United States was attempted in the hope that the ant would control the ravages of the cotton-boll weevil. The introduction of tuberculatum into Victoria County, Texas in 1904 was given a great deal of pub- licity. It is not surprising that when Wheeler expressed doubts as to the ability of the insect to acclimatize itself he was taken to task for his views. The most vociferous champion of the "kelep" was Dr. 0. F. Cook, who published several reports dealing with the habits of tuberculatum (1904 et seq.). The zeal which Dr. Cook exhibited in defense of the "kelep" appears to have been considerably greater than his knowledge of myrmecology. He was very soon in serious difficulty with Wheeler. The latter had little patience with Cook's "Corybantic enthusiasm" and less for his peculiar interpretation of facts. The exchange of opinion between the two men was continued over a period of two years. Dr. Cook held up manfully under a very heavy fire but was presently faced with the uncomfortable realization that tuberculatum was not becoming acclimatized, precisely as Wheeler had predicted. This put an end to Cook's publications on the "kelep" and terminated an unusually bizarre episode in myrmecological literature. Subgenus ParECTATOMMA Emery 1 . EcTATOMMA (Parectatomma) HARTMANI Wheeler Ectatomma (Parectatomma) hartmani Wheeler, Bull. Amer. Mus. Nat. Hist., Vol. 34, p. 390 (1915) 9 ; M. R. Smith, Amer. Mid. Naturalist, Vol. 37, No. 3, p. 535 (1947) 9 . Type loc: Huntsville, Texas. Type: M.C.Z. Range: known only from the single type. 36 bulletin: museum of comparative zoology There has been considerable confusion in regard to this species and much of this is undoubtedly due to the fact that it is known only from a single type specimen. I have ventured to propose an altogether different method of treatment for hartmani from that employed by Dr. M. R. Smith in 1947. Dr. Smith utilized the presence of bifid tarsal claws as the separatory character for the genus Ectatomma, I believe that he is mistaken in supposing that this character holds throughout the genus. I have not examined the type of hartmani since Dr. Smith's 1947 generic monograph appeared, hence I cannot state that the claws of hartmani are simple. I feel sure, however, that this is the case for this condition is regularly encountered in the closely related subgenus Gnamptogenys. While I have utilized the lack of distinct sutures on the thoracic dorsum of hartmani as a means for separation, there is an even simpler method of recognition. The beautifully regular longitudinal rugae which cover all parts of this insect distinguish it clearly from any other North American species. Genus PrOCERATIUM Roger (Plate 3, figures 1-4) Up to the present time only five representatives of the genus Proceratium have been described from North America. With so few forms involved the chance for taxonomic confusion ought to be slight. It is somewhat disconcerting, therefore, to discover that only one of these five forms, P. croceum, is easily and certainly recognizable. The remaining four have become involved in an intricate taxonomic tangle, for which there seems to be no altogether satisfactory solution at present. In 1863 Roger set up the genus Proceratium to include his new North American species silaceum as well as his older croceum, which he had earlier placed in the genus Ponera. The differences which separate these two species are very distinct and little difficulty would have resulted if Roger's plan had been followed. But the matter was put in a very different light when Emery described a third species, crassicorne, thirty years later. In preparing his Beitrdge Emery studied specimens of croceum and silaceum which Roger had sent to him. Whether these were types is not clear. Emery speaks of them as 'original examples'. But at least it is certain that Roger had iden- tified these specimens and if they were not types they had been com- pared with type material. The specimen of silaceum was imperfect, the abdomen and petiole having been broken off, but Emery was able to remedy this defect, since he had three workers referable to creighton: ants of north America 37 silaceum. These specimens, which Pergande had sent him, came from Beatty, Pennsylvania. Emery also had a single female of silaceum which had been loaned him by Mayr. On the basis of these five specimens Emery redescribed silaceum and confirmed the wide differences which separate that species from croceum. But Emery was not content to let the matter rest, for he had two additional specimens which he was not willing to fit into Roger's scheme. Both these specimens had been taken by Pergande in or near Washington, D. C. According to Emery, these two speci- mens were slightly smaller than silaceum (2.33 mm. against 2.75 mm. for silaceum) and had a lower petiolar node and thicker antennae, with the joints of the scape, except the last, all much wider than those of silaceum. As a result Emery considered these specimens as repre- senting a new species, which he called crassicorne and, since one of his specimens was a little more hairy than the other, he made the hairier one the type of the variety vestitum. Before he did so, however, Emery secured a statement from Pergande that all of the specimens which he had collected in the type locality of vestitum (Charlton Heights, Md.) were also hairy. This was the situation in 1915 when Wheeler, on the basis of five specimens, added the subspecies rugulosum to silaceum. In making his comparison Wheeler had what appears to be a part of the nest series from Beatty, Pennsylvania, which Emery had used in his redescription of silaceum. Wheeler regarded these four specimens from Beatty as cotypes of silaceum (which they cer- tainly are not) and marked them with a cotype label. As far as I know, they are still so marked, although when I examined them in 1938 they had been placed with material identified as vestitum. I have no wish to seem unduly harsh in evaluating the above work. P. silaceum is never an abundant ant and other myrmecologists as well as Emery and Wheeler have been forced to deal with limited amounts of material. Yet it is not unreasonable to claim that neither Emery nor Wheeler exercised the caution which the circumstances demanded. Emery had seen only seven specimens, Wheeler only nine. Neither man had a field acquaintance with the insects they were studying. It is not surprising, therefore, to find that each of the three new forms which they set up is highly suspect. In my opinion, crassicorne, rugulosum and vestitum are all synonyms of silaceum. In the following paragraphs I have presented the reasons on which this opinion is based. In past years I have taken many colonies of Proceratium in various stations in the southeastern United States. In the majority of these colonies there were workers whose golden yellow color marked them as callows. While they had not attained the rich, chestnut brown 38 bulletin: museum of comparative zoology color of the mature worker these callows were active in the colony, since their integument had become hard. It is evident that the worker of Proceratium colors slowly, even for a ponerine, and that most colonies will contain a considerable number of light-colored workers during the spring and summer months. While Proceratium shows a certain flexibility in nest sites, it clearly prefers to nest in 'red rotten' logs. In such situations the color of the punky wood blends remarkably with that of the fully colored workers. The golden yellow workers, on the other hand are very conspicuous. For this reason they are sometimes the only specimens secured. This circum- stance has undoubtedly contributed to the confusion which surrounds silaceum. When such golden yellow individuals are examined under a micro- scope much more light is reflected than is the case with the fully colored workers. This glare largely obliterates certain details of surface sculpture. This is particularly true of the rugose-reticulate sculpture on the head which may, in strong lights, be scarcely visible. I believe that this is due to the fact that the rugae are nearly transparent in the yellow specimens and that they do not cast shadows as they do when they become darker. It may further be noted that the extent to which the body hairs are erected usually bears a close correlation to the degree of coloration in the worker. In the golden yellow speci- mens many of the body hairs are reclinate or appressed. As the color deepens more and more hairs become erect. Since the hairs also darken with age, it is easy to get the impression that the fully colored worker is much more pilose than the callow. In my opinion, the above facts will explain the recognition of the variety vestitum and the subspecies rugulosum. The first was said to be a more hairy and more coarsely punctured version of crassicorne. The second differed from silaceum only in its darker color and heavier sculpture. But Emery's recognition of crassicorne cannot be explained on this basis. As already noted, crassicorne was supposedly distin- guished from silaceum by its slightly smaller size, its lower and thicker petiolar node and its thicker funicular joints. There is very little reason to put much faith in the matter of size difference. Since Emery had only one specimen of crassicorne and four workers of silaceum, he could scarcely have been expected to realize that the size range in most nest series of silaceum embraces the size of crassicorne also. The difference in the width of the funicular joints is also of less significance than might be supposed. According to Emery the last funicular joint of silaceum is the same length as the preceding four joints taken together, while that of crassicorne is distinctly longer than the pre- ceding four joints taken together. Emery's figures do not bear this creighton: ants of north America 39 out for, if allowance is made for the fact that the funiculus of silaceum is figured as strongly curved, the proportion of the terminal joint to the preceding four is almost identical in both species. The same consideration applies to the structure of the petiolar nodes. Emery's figure of silaceum is drawn with the node of the petiole close to the declivious face of the epinotum. In his figure of crassicorne the node is sloped away from the declivious face of the epinotum. This gives the impression that the node of crassicorne is lower than that of silaceum. If the figure of crassicorne is enlarged to the size of that of silaceum and the angle of the petiole altered to conform with that of the latter insect, the two figures are practically identical when super- imposed. In this case Emery seems to have been the victim of an optical delusion which resulted from the position in which he drew the petiole of crassicorne. It is interesting to note that most myrmecologists have avoided any mention of crassicorne unless it was absolutely necessary to do so. The only attempt to deal with this species in any detail appears to be that published by the Wessons in 1940. According to these investi- gators the nests of crassicorne show a contrast to those of silaceum, since crassicorne nests both in rotten wood and in the soil while silaceum nests only in rotten wood. I cannot attach much significance to this distinction for, if I understand the matter correctly, the speci- mens which the Wessons discovered in soil seem to have been strays. The only clearly established nest of crassicorne which they mention was in all respects comparable to those of silaceum. Key to the species of Proceratium 1. Length 3.75-4 mm.; node of the petiole seen in profile thick and blunt above, the base very little thicker than the crest; epinotal teeth prominent croceum Length 2.75 mm. or less; node of the petiole in profile slender, the base notably thicker than the crest; epinotal teeth very short, scarcely more than angles silaceum 1 . Proceratium croceum (Roger) Ponera crocea Roger, Berl. Ent. Zeitschr., Vol. 4, p. 288 (1860) 9 . Sysphingta crocea Mayr, Sitzungsb. Akad. Wiss. Wien., Vol. 53, p. 501 (1866) 9 . Proceratium croceum, Mayr, Verb. Zool- bot. Ges. Wien, Vol. 36, p. 437 (1886); Emery, Zool. Jahrb. Syst., Vol. 8, p. 264, pi. 8, figs. 5, 6 (1895) 9 9 ; M. R. Smith, Ann. Ent. Soc. Amer., Vol. 23, p. 390, figs. 1-3 (1930) cf; M. R. Smith, Amer. Mid. Naturalist, Vol. 37, No. 3, p. 532, pi. 2, fig. 6 (1947) 9. 40 bulletin: museum of comparative zoology Type loc: 'the state of Carolina'. Types: none in this country. Range: Gulf Coast region from eastern Texas to Florida and sporadically north to latitude 38°. 2. Proceratium silaceum Roger Proceratium silaceum Roger, Berl. Ent. Zeitschr., Vol. 7, p. 172 (1863) 9 ; Emery, Zool. Jahrb. Syst., Vol. 8, p. 265, pi. 8, figs. 7, 8 (1895) 9 9 ; Emery, Bull. Soc. Ent. Fr., p. 101, fig. 2 (1896) 9 ; Kennedy & Talbot, Proc. Indiana Acad. Sci., Vol. 48, p. 202, figs. 1-7 (1939) 9 9 cf . P. silaceum subsp. rugulosum Wheeler, Bull. Amer. Mus. Nat. Hist., Vol. 34, p. 390 (1915) 9 9 . P. crassicorne Emery, Zool. Jahrb. Syst., Vol. 8, p. 265, pi. 8, figs. 9, 9a (1895) 9 , P. crassicorne var. vestitum Emery, Ibid., p. 266 (1895) 9 . Type loc: 'North America'. Types: none in this country. Range: most of the United States east of the Mississippi River except southern Florida, northern New York and New England. This insect has also been taken in southern Ontario by Dr. Kennedy. These Canadian records (Pelee Island and vicinity) are, however, no further north than others from Pennsylvania and southern New York. Genus SySPHINCTA Roger (Plate 4, figures 1-2) For most students of North American Formicidae the genus Sys- phineta is exempUfied by the extraordinary gastric configuration found in S. pergandei. In this species the dorsum of the first gastric segment is greatly expanded and strongly curved. As a result the posterior edge of this segment actually lies at the middle of the lower surface of the gaster. The whole posterior half of the gaster consists of the rounded dorsum of the first segment. The remaining gastric segments form a conical projection which points forward and downward from the middle of the gaster. While all the members of the genus Sysphincta possess a gaster in which the tip is reflected, the degree of curvature is seldom so extreme. In some of the species, among them melina, the reflected gastric tip appears to be tucked under the posterior end of the gaster, a condition very similar to that which occurs in the related genus Proceratium. For this reason Sysphincta is best separated from Proceratium by using Emery's criteria of the angular, projecting median lobe of the clypeus and the feebly incrassate antennal scapes. In Proceratium the clypeus lacks the angular, projecting, median lobe and the antennal scapes are notably thickened at the tips. The rarity of the two species which represent the genus Sysphincta in North America has become a myrmecological by-word. In the case creighton: ants of north America 41 of S. melina there is nothing to controvert such a view. During more than eighty years since its description by Roger it has been taken once. A different situation marks our knowledge of pergandei. While the number of specimens in collections is small the locality records of this handful of material present a rather surprising picture. S. pergandei has now been taken in nine eastern states and its known range extends from southern New York to northern Alabama and Mississippi. At present the recorded western limit of the range is central Ohio. In view of this rather extensive range it seems clear that the rarity of pergandei is not an outcome of restricted distribution. Perhaps it would be more correct to say that pergandei is a very elusive ant rather than a very rare one. The data concerning the nesting habits of pergandei is fragmentary and contradictory. In 1905 Wheeler cited the fieldwork of Schmitt who found this insect under large stones in damp meadows. This observation has been repeated by people whose own findings negate it. There is equally good, if not better, evidence to show that pergandei nests on rocky hillsides where the cover is dense. There is reason for believing that the insect is subterranean in habit but its feeding re- sponses have not been ascertained with certainty. A very suggestive approach to this last problem has been made by L. G. and R. G. Wesson (1940), who had the good fortune to secure a single colony of pergandei and keep it under observation. This nest consisted of a queen, eleven workers and eight males. Since it was found in close proximity to a nest of Camponotus castaneus the artificial nest was made to include both colonies. The castaneus workers were excluded from the chamber housing the pergandei colony but the latter could enter the chamber containing the castaneus workers and brood. The results failed to show any special relationship between the two species. On the other hand the members of the pergandei colony soon began to attack and kill each other. As this is usually an index of faulty environmental conditions one is tempted to wonder if the enforced proximity to the castaneus colony may not have produced this result. Attempts to feed the pergandei colony with various sorts of living and dead insects also gave negative results for the most part. The only insect food which the workers were observed to accept consisted of the gasters of formicine ants. On the basis of these studies the W^essons suggest that pergandei may feed upon dead or dying ants. Key to the species of Sysphincta 1. Anterior portion of the petiole depressed, the posterior portion forming a low but distinct scale; reflected dorsum of the gastric segment not strongly projecting to the rear and forming an even curve with the reflected tip; 42 bulletin: museum of comparative zoology length 3.5 mm melina Petiole evenly convex above, the anterior portion not depressed; reflected dorsum of the gastric segment strongly projecting to the rear so that the reflected tip appears to arise from the mid-ventral surface of the gaster; length 4.0 mm. pergandei 1 . Sysphincta melina (Roger) Ponera melina Roger, Berl. Ent. Zeitschr., Vol. 4, p. 291 (1860) 9 9 cf . Proceratium melinum Mayr, Verh. Zool-bot. Ges. Wien, Vol. 36, p. 438 (1886). 5. melina Emery, Zool. Jahrb. Syst., Vol. 8, p. 263, pi. 8, figs. 1-3 (1895) 9 9 d'. Type loc: "Carolina". Types: none in this country. Range: known only from the type material and a few other specimens taken by Schmitt in Pennsylvania. 2. Sysphincta pergandei Emery Sysphincta pergandei Emery, Zool. Jahrb. Syst., Vol. 8, p. 264, pi. 8, fig. 4 (1895) 9 ; Emery, BuU. Soc. Ent. Fr., p. 101, fig. 1 (1896) 9 ; Emery, Genera Insectorum, Fasc. 118, pi. 2, fig. 6 (1911) 9 ; M. R. Smith, Ent. News, Vol. 39, p. 242 (1928) d", M. R. Smith, Amer. Mid. Naturalist, Vol. 37, No. 3, p. 532, pi. 2, fig. 7 (1947) 9 . Type loc: "Pennsylvania and District of Columbia". Types: none in this country. Range: eastern United States. Southern New York to northern Alabama and Mississippi and west to Ohio. Most of the records appear to come from hilly or mountainous areas. Genus NeOPONERA Emery (Plate 5, figures 1^) Neoponera is a New World genus with most of the species occurring in Central America and tropical South America. The number of species which range northward into Mexico is small and of these only one, N. villosa, reaches southwestern Texas. The insect which Forel described in 1901 as Neoponera agilis was said to have been taken in California but this has been generally regarded as an error in the locality. It is possible that the locality referred to some region in Lower California but it is very unlikely that agilis occurs within our borders. These insects frequently reach our ports in shipments of tropical fruit, etc., but they do not appear to be able to establish themselves after introduction. The endemic N. villosa is, therefore, the only member of the genus which need be considered. CREIGHTOX: ANTS OF NORTH AMERICA 43 1. Neoponera villosa (Fabricius) Formica villosa Fabricius, Syst. Piez., p. 409 (1804)