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FIGS. 1-5. ALTERNATING GENERATIONS

An eastern American species, Cynips (Acraspis) erinacei. Figures 1, 2, 5 = bisexual form ; 3, 4 = agamic form.

Indiana University Studies Vol. XVI

June, September, December, 1929

Studies Nos. 84, 85, 86

The Gall Wasp Genus Cynips A Study in the Origin of Species

By Alfred C. Kinsey, Professor of Zoology and Waterman Research Associate, Indiana University

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Waterman Institute for Scientific Research Publication No. U2; Contribution from the Department of Zoology, Indiana University, No. 220 (Entomological Series No. 7)

Actual date of publication, February 27, 1930

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SUMMARY

This investigation was undertaken with the conviction that an intensive study of any group of species should contribute to the elucidation of biologic problems of general concern. Ninety-three species represented by more than 17,000 insects and 54,000 galls have been available for this analysis of the genus Cynips and these have offered an opportunity for study- ing the nature of species, individual variation, mutation and hybridization in nature, and the factors affecting the origin of species.

Species are defined as populations with common heredity. The thesis is maintained that species, in this sense, are more than mental concepts — that species are realities which pre- serve a morphologic and physiologic identity under varying conditions, over vast areas, and thru periods of time that may extend beyond the present geologic epoch. Within these popu- lations individuals are found to vary, mutations to occur, and Mendelian races to develop as they are observed to develop in the laboratory. It appears that in Cynips, at least, these mutations have been the chief source of new species, but only when they are isolated from close relatives with which they might have interbred. Altho hybrid individuals prove com- mon, and local colonies which have arisen by hybridization between related species are not unknown, the isolation of such hybrid populations to form species seems to have occurred in only a few instances in this genus.

The data on which these conclusions are based constitute a taxonomic revision of the genus Cynips. The group as re- defined is a homogeneous unit delimited by insect morphology, gall characters, host relationships, life histories, and geo- graphic distribution. Published records are coordinated with a large body of new data on these several aspects of the group. Of the 93 species placed in this genus, 45 have previously been described (only 26 of which have heretofore been recognized in Cynips) and 48 are new to science. To the 5 instances of alternation of generations which have previously been pub- lished for the group, 6 additional cases are added.

It should be of some moment to correlate these conclusions, concerning the nature and the origin of the species of Cynips, with the studies that have been made or remain to be made on the evolution of other groups of organisms.

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TABLE OF CONTENTS

Page

Part I. The Origin of Species 7

The Taxonomic Method 8

Basis of Present Study 11

The Species Concept 17

Mutations 25

Physiologic Species 37

The Isolation of Species 49

Hybridization 55

Phylogenetic History 61

Part II. Systematic Data

Subgenus Cynips 87

Sub genus Antron 180

Sub genus Besbicus 222

Subgenus Philom.c 242

Sub genus A trusca 276

Subgenus Acraspis 306

Appendices

Acknowledgments 431

Names Pre-occupied in Cynips 433

Excluded Species 446

Nomenclatorial Data 456

General Bibliography 457

Bibliography on Cynips 460

Key to Described Cynips 482

Checklist 496

Plates 502

Index 573

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The Gall Wasp Genus Cynips

PART I. THE ORIGIN OF SPECIES

Among the diverse aspects of the so-called species problem, there is none that has received more unsatisfactory treatment than the study of species. The data of morphology and pa- leontology have given us information on the origin of orders and classes and phyla, and the geneticists and cytologists have contributed a brilliant interpretation of the mechanism which accounts for the similarities and, ipso facto, for the differences between individuals of successive generations; but compara- tive studies of species, first-hand contacts in the field with thousands of individuals of hundreds of related species, the careful examination of these individuals with modern labora- tory facilities, and the correlation of such studies with the findings of genetics, cytology, and the other sciences — in short, the thoro taxonomic study of species has only occa- sionally been accomplished.

Our present account of the gall wasp genus Cynips is offered as an intensive study of 93 species of a phylogenetically natu- ral group. It has been possible to translate so much of the story because the genus is a highly specialized unit of such recent (Oligocene or Miocene) origin that there are no serious gaps in the record as we find it today. The galls produced by these wasps are direct measures of one of the physiologic capacities of the insects, and thus afford an opportunity for the study of physiologic as well as morphologic variation within the group. The precise restriction of each species to particular hosts gives us an opportunity to analyze the rela- tion of isolation to the origin of species, and the relatively poor means of locomotion of most of the gall wasps accounts for considerable geographic variation with its further empha- sis on isolation. The existence of 42 sub apterous forms in the genus has afforded an unexpected opportunity to show the relation of mutation to the origin of species. All of these items contribute to the utility of these insects for the study of the general problem of evolution. Whether species in the genus Cynips present a fair picture of species in general can

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be determined only from further studies on other gall wasp genera and upon organisms of many diverse groups ; but mean- while we offer our data as illustrative of possibilities in the taxonomic method, and as a body of observations leading to what would seem to be unmistakable conclusions on the origin of species in this particular genus.

THE TAXONOMIC METHOD

The attainment of sound ends in any field of science de- pends on certain common fundamentals of scientific method. An adequate understanding of any phenomenon must await repeated observations of that phenomenon thruout a wide range of specific cases, and an interpretation of the data based upon a comparative study of the groups in which that phe- nomenon is known to appear. It is only because the nature of the material studied and the categorical rank of the unit of comparison varies considerably with the problem under observation that we assign each biologic question to some spe- cial field, recognizing that each sub-science provides the best means of handling particular materials and particular cate- gories.

To morphology, physiology, and psychology we make cer- tain assignments not only because we wish to deal with par- ticular aspects of the organic organization, but because these sciences are adapted for dealing with ordinarily few species which may be taken to stand as types of whole orders and classes or phyla of plants or animals. For this reason these sciences contribute data on such problems as the relationships of the larger groups, their appearance in the geologic record, and their value as evidence of the processes of evolution itself. In genetics, on the other hand, it is the individual which is the category chiefly concerned, and the correlations are made between individuals of experimentally proved hereditary re- lationships. In taxonomy the data are again individual or- ganisms, but the comparisons employed are between such groups of individuals as constitute what we call species, and between all of the species for which we may find evidence of close, phylogenetic affinities. The unfolding of the complete record of evolution would thus appear to depend upon the coordination of the contributions from cytology, genetics, taxonomy, comparative anatomy, embryology, paleontology,

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and still other fields less particularly concerned with the prob- lem ; and it is with this appreciation of the magnitude of the whole species problem that we hold a brief for the taxonomic method as fundamental to the elucidation of certain aspects of the subject.

I take it that the essential function of the taxonomic method is this interpretation of biologic phenomena by the compar- ison of related species. Whenever taxonomists increase their data (individuals studied) to a volume comparable with that on which the best research in other fields has been based, pursue their comparisons of related species as persistently as the geneticists have compared related generations of indi- viduals, and strive towards interpretations of their data which shall be coordinated with the findings from other fields of biology, we shall have a taxonomic science that cannot fail to command the respect of students. If taxonomy has been in ill repute, it is because we have considered as our chief func- tion the solution of something other than biologic problems. Too many systematists attain their objectives when each species is “represented” by a half-dozen specimens pinned in their cabinets. These are the systematists responsible for the definition of systematic entomology as the science of trans- ferring pins from one box to another. If taxonomists have too often made species-descriptions and catalogs and nomen- clatorial inanities the end of their efforts, it is no proof that the science cannot rise above its technic and concern itself with biologic: problems. As my good friend has remarked, our difference is not with taxonomy but with taxonomists.

It is, then, as something of a defense that I detail the sev- eral items of the taxonomic method and give a specific account- ing of the basis for the present analyses of species in the genus Cynips.

I should detail the taxonomic method in the following items :

1. The validation of data and conclusions by the utilization of large series of individuals of each species.

2. The utilization of series from wide-spread localities fairly rep- resentative of the range of each species.

3. The utilization of such material for every one of the species constituting the natural group under investigation.

4. The recognition of relationships between individuals and species by the consideration of every character which may be shown to have hereditary significance, to wit: morphologic structures of any and every

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sort; such physiologic characteristics as can be shown to be hereditary and subject only to such environmental modifications as may be meas- urable; such special physiologic characteristics as are more often classi- fied as psychologic, or as elements of “behavior”; and whatever other measure there may be of the physico-chemical organization which is the hereditary basis of the organism. This, in brief, demands a biologic as well as a structural basis for the recognition of species.

5. The special consideration of individual variation, with an at- tempt to analyze the hereditary or non-hereditary basis of the unusual characters. Many of the older workers made it a practice to throw their “exceptions” into the waste basket!

6. The accumulation of data with due scientific caution, and the further preservation of data in the form of labelled specimens, with the detailed citation of all such data in publication. In this admirable item of technic, taxonomy has been in advance of other fields of biology.

7. The classification of the species of the group to show every recognizable degree of phylogenetic affinities, the interpretation to be based on the above criteria for the recognition of relationships, upon host affinities (if available), the facts and known factors of geographic distribution, and correlation with the known geologic history of the area involved and the paleontologic history (if available) of the group and all closely related groups.

8. The interpretation of biologic phenomena within the group by an appeal to this phylogenetically established classification, to show the occasion and the order of evolutionary origin and the conditions of ex- tension of the phenomena exhibited within the group.

9. The careful consideration and utilization of findings from other fields of scientific research at every step of the taxonomic investigation.

The above program is an ideal not always obtainable even with the best of modern facilities, albeit a standard by which the merit of a piece of taxonomic work may be adjudged. It demands the intensive treatment of such small groups of spe- cies as genera or families in contrast to the wider fields of interest of the older systematists. It calls for the so-called revisional treatment of genera instead of the miscellaneous species descriptions of long repute. It demands that phylo- genetic units, instead of local faunas or floras, be the basis of taxonomic consideration. It demands that the taxonomist’s role as the diagnostician of specimens emanating from en- thusiastic collectors and hard-pressed economic entomologists be subordinated to the phylogenetic interpretation of biologic phenomena.

BASIS OF PRESENT STUDY

The present study is based upon more than 17,000 insects and an estimated 54,000 galls — a total of over 71,000 speci- mens representing the 93 species known in the genus Cynips. Every one of the insects has been examined under the higher powers of a binocular microscope. Thousands of the speci- mens have been repeatedly re-examined in direct comparison with every specimen whose affinities might in any way throw light on the interpretation of the characters under observa- tion. Exactly 16,899 of the insects and nearly all of the 54,000 galls of the genus are in our own collections where they have been available for all the comparisons and endless re-comparisons that have been necessary during the four years of intensive study given to this group of species. There are 96 Schmitt boxes of the mounted material of Cynips which constitute the permanent validation of our conclusions on this group, and this collection will be available at all times to fu- ture students. Part of our material is being distributed among museums and other workers on Cynipidae. Outside our own collections, I have studied the Cynips material in the American, U.S. National, Philadelphia Academy, Harvard (Museum of Comparative Zoology), Field, Illinois Natural History, and Stanford Museums.

The specific distribution of the material used in the present study is as follows :

Species

Agama (1 var.)

Arida (1 var.)

Bella (3 var.)

Cava (1 var.) .........

Centricola (4 var.)

Conica (1 var.)

Cornifex (1 var.)

Divisa (2 var.)

Disticha (1 var.) .......

Dugesi (4 var.)

Echinus (6 var.)

Folii (4 var.)

Fulvicollis (7 var.)

Gemmula (4 var.)

Guadaloupensis (3 var.) Hirta (7 var.)

Insects	Galls
Examined	Examined
57	177
24	406

56 1,182

118	245
3 ..... .	38
4	12
. . 1,090	1,092
13	5
110	360
589	6,460
646	935
. . 5,170	14,581
746	547
18	67
. . 1,457	5,240

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FIG 6. AMERICAN COLLECTIONS OF CYNIPS

Sources of material on which this study is based.

Kinsey: Gall Wasp Genus Cynips

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	Insects	Galls
Species	Examined	Examined
Longiventris (2 var.)	129	... 355
Mirab'ilis (2 var.)	26	... 393
Maculosa (2 var.)	29	70
Mellea (11 var.)	431	. . . 1,010
Multipunctata (4 var.)	175	... 1,189
Nubila (3 var.)	64	... 186
Pezomachoides (8 var.)	5,890	. . .18,135
Plumbea (1 var.)	30	38
Teres (3 var.)	55	... 180
Villosa (7 var.)	367	... 1,400
Totals — 93 varieties	17,351 insects	54,460 galls

We should have had thousands of specimens of every one of these insects. Failing that, our conclusions on certain mat- ters have been based to a large degree upon the more avail- able species, and the intensive study of those species has of- fered interpretations of our smaller bodies of data which would not otherwise have been possible.

To obtain data on geographic distribution and the relation of geographic isolation to the origin of species, I have at- tempted to secure representative series of each Cynips from as many and as widely distributed localities as possible. It was in the fall of 1917 that I made my first collections of the genus, and in the twelve years that have intervened I have travelled over thirty-two thousand miles in the pursuance of the distributional data originating from my own collections. In 1919 and 1920 I went as a Sheldon Travelling Fellow of Harvard University to the South and to the Far West. For a number of years I have been relieved from part of my teach- ing to pursue research under a grant of the Waterman Insti- tute of Indiana University, and in this connection I have en- gaged in extensive field work thruout the northern Middle West and in the southeastern quarter of the United States. In the course of these contacts with gall wasps in the field, as well as thru the longer hours spent over the microscope, I have gradually developed my present concept of species.

My own cross-country field work has been supplemented with collections made thru every season and in some cases for sev- eral years by collectors working in their native areas. Over a hundred such collectors have contributed data, sending mate- rial from localities in nearly every one of the United States

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and from England, France, Germany, Denmark, Italy, Hun- gary, Austria, Czech o -S 1 ovaki a , Finland, and Russia among European countries. This cooperation has been indispensa- ble, and specific acknowledgment of my indebtedness to each collector is made with each item in the systematic portion of this paper. The accompanying map (Fig. 6) will show the extensive — albeit still inadequate — sources of our American material of Cynipidae.

The accumulation of these geographic data has received some impetus from repeated analyses we have made of our held technic. By using the automobile we reach twice as much territory in a given time as we were formerly able to reach by railroad transportation. We find that the densest popula- tions of Cynipidae are, for some reason not yet apparent to us, located on isolated oak trees or at edges of woodlands, and it is there that we now concentrate most of our efforts while in the field. It was some years before we learned that the distribution of most species of gall wasps is very local, and that it is a waste of time to attempt to make collections of populations that are sparsely scattered over the country- side. If large populations are not readily available at the first stopping place, we take a sample and move a hundred yards to a half-mile across country, continuing the procedure until we have discovered some tree or thicket heavily laden with galls. Many a rural community will bear witness to the peculiarities of our conduct in their countryside, but our cabi- nets of insects and galls bear more eloquent testimony to the effectiveness of this method.

Because of the peculiar host relations of the higher Cynipi- dae, it is necessary to collect from every species of oak in each locality in order to obtain a satisfactory set of specimens. To avoid being misled, in our interpretations of species, by such local populations as might segregate into Mendelian races, we make it a point to secure material from separated trees of each host wherever possible. Our returns are more than doubled when two of us work together in the held. We have given from a few hours to several days to the exploration of each locality, but upon careful accounting we find that, with two or more of us working together, we can take a fair sample of a region in four or hve hours.

In order to secure approximate data on the furthest exten- sion of the range of each species, we do not make our col-

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lecting stations too near each other. Usually they are not less than fifty miles apart. In some instances it has been possi- ble to revisit important regions and make further collections which would more precisely establish the limits of ranges, or give more extended data on the variation of species in transi- tion areas. As already noted, this cross-country field work has been supplemented by year-round collections from many localities.

Since the coordination of taxonomic studies depends upon an accurate understanding of the Latin binomials that have been used for previously described species, I have made a thoro study of the holotypes — the single specimens which are absolute criteria of the correct application of each published name — for 76 out of the 78 American species of the genus. Practically all of these holotypes were studied after this study had advanced toward completion and when it was possible to make critical comparisons with my own material. Of the 15 European forms in this genus, I have seen types of four. The types of seven are not in existence, and the remaining five are established by types which I have not seen. Wherever I have not seen the types, the original descriptions are quoted in full in the systematic portion of this study.

Finally, among the material resources available for the present study mention should be made of the technical assist- ance and museum equipment that has been available for sev- eral years chiefly thru the interest of the Zoology Faculty and the Administration of Indiana University and grants else- where acknowledged from the Waterman Institute of Indi- ana University, from the Elizabeth Thompson Science Fund, and from the Bache Fund of the National Academy of Sci- ences.

These are the bases of the present study of the genus Cynips. This is our warrant for undertaking an interpretation of spe- cies in this group of insects. We offer no further extenua- tion of the fact that our conclusions are not in accord with systematic work that has been based on more meager mate- rial. We believe it no coincidence that our conclusions more nearly accord with those of Dunn who studied 12,600 speci- mens of the 86 forms of the salamanders of the family Plethodontidae, or of Mickel who studied approximately 10,000 specimens of the genus Dasymutilla. In handling even such large numbers of individuals of a limited group of spe-

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cies, one becomes convinced that accurate information on the variability or constancy of species over wide areas, the ex- tent of host and geographic isolation between related species, the correlation of biologic and structural facts, and the at- tainment of sound conclusions as to the affinities of species within any group and consequent interpretations of species and biologic phenomena cannot emanate from anything short of the most extensive data that modern facilities can provide.

THE SPECIES CONCEPT

The earliest work of the systematists emphasized the simi- larities of individuals within species and the sharp distinc- tions between individuals of diverse species. This view was an inheritance from man’s primitive knowledge of plants and animals, and one which, bolstered by a widespread misinter- pretation of the doctrine of the uniformity of nature, is still widely held outside of scientific circles today.

As the facilities for the more careful examination of indi- viduals were developed early in the last century, scientific emphasis was shifted to the fact that no two individuals are exactly alike, and the species problem resolved itself into a search for the factors of evolution. As a direct result of those investigations there has developed a growing conviction that individuals are the only realities in nature, and an agree- ment that species are only convenient concepts originating and ending in the minds of scientists. This is the basis of recent demands that we return to what is, curiously, called the Linnean species, it being argued that that was as near reality as any present-day concept, and an article far more ready for the use of those who are not taxonomic specialists. Taxon- omists have contributed little to the resolution of this con- fusion, for many of them are bewildered at the array of geographic variants and transition zone hybrids which have recently become available particularly from our own continent, and species are frankly defined in the codes as concepts that may be standardized and established by quasi-legal verbiage.

One wonders to what extent this confusion as to the nature of species has delayed our understanding of the origin of species. Perhaps it is this confusion which leaves us without a convincing reply for the fundamentalists who insist that data from the evolution of domesticated plants and animals and from laboratory genetics may explain the origin of varieties but not of species. There is a peculiarly hollow ring to our statement that varieties are incipient species and that the evolution of species is too slow a process for human observation. Moreover, the illogical sequence in most of our texts, where the evolution materials are followed by the data of heredity, is some evidence that the geneticists do not per- ceive the application of their laboratory findings to species

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in nature; and such students as Bateson and Morgan have suggested that that application must be made by the taxon- omists if (it is implied) the taxonomists ever become con- vinced that there are realities in nature that deserve to be called species.

Now, with these imputations of the unreality of species, I find myself no longer in accord. In the data that follow, evidence is presented that species are realities in nature more nearly satisfying the geneticist’s concepts than the conven- tions of current taxonomy, and that the origins of such species are more satisfactorily explained on hereditary bases than by philosophic theories that may be invoked in extenuation of the fact and the factors of organic evolution.

We may begin our analysis of species by an examination of a few individuals taken in the field. We then become im- pressed with the truth of the assertion that no two individuals are exactly alike. And if we extend our investigations to several dozen individuals, we shall be confused by the varying characters that enter into any population which ordinarily passes as a species.

But if, on the other hand, we extend our examination to several hundred such individuals, we shall become impressed with another opinion, namely that there are many more points of uniformity than of variation among individuals taken from a given locality and habitat. Perhaps a half-dozen characters will show appreciable variation, while the hundreds of other characters that go to make up an organism are remarkably constant. One may believe that if larger series were more often utilized in taxonomic work the current bewilderment over variation would give way to a renewed respect for a certain uniformity that exists thruout such groups of indi- viduals.

Again, the variation that may be observed in characters that do vary occurs within narrow limits. Thus, the antennal count in species of Cynips often varies by one, but among many thousands of individuals none has shown two segments more or less than any other individual in that species. The length of the wings in relation to the length of the body of any cynipid is not altogether an invariable item, but among the many measurements I have made this wing-body ratio is always within three or four per cent of the mean for the

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species. In one species which constitutes an exception to this generalization, mutations are involved, and these will be treated in a later section of this paper.

Finally, the limits of variation of any character prove to be strikingly uniform thruout the great populations which we propose to call species. Whenever we have taken a reasonably large sample from any point over the usually considerable range of a species, the biometric data have not proved funda- mentally different from data for any other fair sample from any other point in the range. The case of Cynips erinacei will serve to illustrate our experience. Erinacei is not only the most variable Cynips but one of the most variable cynipids I have examined. Reference to the descriptions in the sys- tematic portion of this study will show that every one of the few characters which distinguish these insects from the most closely related species vary between limits approached by some one or another of the related species. The galls present more apparent variation, showing every gradation from smooth, naked, spherical, monothalamous structures (fig. 312) to densely spiny, ellipsoidal, polythalamous galls (fig. 315) which may have as many as eight larval cells. An initial experience with these extreme types of galls would lead one to believe they represented distinct species, and so they have always been classified heretofore. Increased material, however, has shown that every extreme and every one of the intermediate characters occurs thruout the range of erinacei.

The range of this species extends about 1,300 miles east and west and 450 miles north and south. We have samples of erinacei from nearly a hundred localities fairly well dis- tributed over this tremendous area of possibly 500,000 square miles. In every large sample, erinacei is as variable as we have described it, and yet, after all, it is everywhere uniform — uniform in its constancy of variation. Even erinacei is, then, the sort of population which we would call a species.

Erinoxei may present an extreme case, but it is not funda- mentally different from the thing which one finds everywhere in nature. It is moreover, the picture of species to which our knowledge of mutation and Mendelian hybridization would lead us, and our definition of species must become genetic if we take into account the similarities and the differences which we find within a species. The essential uniformity of most

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of the characters of individuals depends, of course, on their possession of common genes, originating from the accessi- bility thru interbreeding to common stocks of genes. The uni- formity of the limits of variation within a species may be the result of similarly mutating genes, or of genes derived from hybridization with some exotic influence. Such hereditary property may become fairly well distributed in the course of time thruout any interbreeding population, and if the genes belong to groups of multiple factors controlling single char- acters in the organism, we have an explanation for the occur- rence of every degree of variation between definite limits within a population. The other possible explanation of these common limits of variability is that similar genes may have not only the same potentialities but the same lack of potenti- alities, reaching similar limits to their capacities for directing the growth of the individual organism or to withstand the effects of environmental factors. As Bateson put it, the degree of variation of an organism may be inherited as much as its degree of uniformity.

We may, then, allow for all individual variation while defin- ing species as populations with common heredity. The older definition of a species as a group of similar (implying nearly identical) individuals fails because of the amount of varia- bility actually found in nature. Definitions of species as groups of individuals distinguished by a definite number of diagnostic characters, or by certain degrees of difference from other species lead to artificial concepts that take no adequate account of individual variation, Mendelian inheritance, hy- bridization, or mutation. The definition of species on the basis of their fertility or infertility does not delimit phylo- genetic units, for while it is true that the individuals within a species must be mostly fertile inter se if they are to main- tain any sort of hereditary relationship, the failure of distinct species to interbreed may be due to geographic or seasonal occurrence or to other factors not directly concerned with reproductive physiology. But if species are defined as popula- tions with common heredity, we obtain a concept which seems genetically sound and which, we shall try to show, is a reality in nature.

An appreciation of the fact that species are great popula- tions distinct from Mendelian races, local colonies, or the

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preposterous Jordanon of botanical literature, may best be acquired by field experience with a group of related organisms. For illustration we may again utilize Cynips erinacei and some of its close relatives as they occur in the eastern portion of the United States.

We have already described erinacei as a highly variable species occurring on the leaves of the white oak, Quercus alba, over a tremendous area chiefly in the northern Middle West. On almost all of the infested trees at any locality in this area one may find a mixture of smooth and spiny galls of every extreme and intermediate type. Often all types of galls are crowded onto a single leaf, but occasionally a particular tree will have a preponderance of one type, and on several occa- sions we have found isolated trees well covered, as far as we could discover, with galls of only a single extreme type. These peculiar colonies, however, have always been on isolated trees or groups of trees, and they would appear to represent Mendelian races in which homozygosity in regard to particular characters had been affected by the isolation of the colony. Subsequent examinations of insects from such galls have failed to indicate that these local populations are homozygous in regard to any of the other characters that might vary within the species, and such colonies are passed by the taxonomist as ephemeral entities not satisfying the species concept.

If one will extend his collections in the first locality to a number of trees scattered over any appreciable distance — several hundred yards or a mile or two — he will leave the region with a sample that is as variable but as uniform as we have described it. If one travels to a second locality, five miles or fifty miles or a hundred and fifty miles from the first, the first collections may be duplicated. If one continues this procedure day after day, over the thousands of square miles which are the range of erinacei, one must become impressed with the fact that this is a population of inconceivably great numbers of individuals that are in certain aspects different and yet in an essential way similar over this tremendous territory. Of course, we can take only scant samples of the population, and we are reduced toi glancing at most of the trees with their thousands of galls which we have no time to gather; or we fall to wondering how many inconceivable millions of individuals of erinacei there are on all the trees

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in all the fields and woodlands and mountain forests thru which we journey at many miles an hour, for hour after hour, yesterday, today, and tomorrow. Nevertheless, our samples seem typical, for they are surprisingly uniform; and after such field experience, one comes to feel there is a reality summed up in the word “species” which is more than a few cabinet specimens or a bottle full of experimental material or a Latin binomial in a textbook. It is an existent, tremendous population of living individuals whose identities and dis- similarities, whose divergences from all other populations, whose origin in some remote past and extension thru actual generations and years of time, whose position on these par- ticular trees in these particular valleys and everywhere over these miles of actual country — it is this reality which, to us, constitutes the species problem.

But we have met erinacei everywhere across the miles of Indiana and across Ohio. This morning we found it in the stream valleys and over the hillsides of West Virginia. At noon we still found it in more rugged country in the heart of the mountains, and now, near the end of the day, our road- signs read Maryland and we know we are near the crest of the Alleghanies. We get out of the car and climb the hillside. It is thick woodland and we find only stray galls now and again. They are smooth and naked specimens, for aught we can tell like the smooth galls of erinacei. A mile down the road we find an open meadow where two isolated trees offer promise of richer collections. The farm boy helps, and we collect more smooth galls while we wonder about the varied mixture which spreads so many miles back of us. It is drizzling now, and sheets of fine snow come whirling off the mountain, but we espy a tree in the next open, and in the gathering dusk find — many naked but only two spiny galls for our collections! We return to the car, wondering what is the matter with the sample.

Before we sleep that night we shall have worked our way down into the valley of the Potomac. On the next day we shall collect across the valley of the Shenandoah, and in the days that follow out onto the sand coast of Virginia and south- ward along the shores of the Carolinas. Within a few months we shall breed the insects from the smooth galls we gather, and then we shall know that from the Maryland line to the

Kinsey : Gall Wasp Genus Cynips

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coast we were dealing with pezomachoides, which is another species. At first the population was a mixture of insects of erinacei and pezomachoides and hybrids between, and it was only near the ocean that we found pure colonies of this new species, altho the typically smooth gall of pezomachoides was dominant to the western limits of the influence of the insect. But pezomachoides, altho very similar to erinacei, varies within limits that are different from those of erinacei. We shall find pezomachoides wherever we collect, until some day we turn in from the coast toward the heart of Georgia and meet a larger form of naked gall which will be derivatus; and then when we cross the southern front of the Blue Ridge and go into the Cumberlands we shall find the insect called advena, and in Kentucky it will be ozark, and in southern Indiana it will be erinacei again. In each area we shall find a population obviously related to every other, but each will constitute a population whose limits of variation are different from those of any other. Sometimes these limits overlap, sometimes they are wholly within, sometimes they are wholly without the limits for each other species. Sometimes the populations are wholly segregated by mountain crests and divides, sometimes the populations hybridize and intergrade over broad zones of transition ; but always each population is distinct in a great area which is the heart of the range of each species. This is the picture which has gradually de- veloped over the 32,000 miles, thru the 12 years during which we have pursued species.

And now, one confusion needs explanation before we are finished with this part of our discussion. It must be pointed out that there is a biologic concept called species and a tax- onomic category called species, and that the two are not always synonymous. The concept we have developed is the biologic concept to which all except the taxonomists must refer whenever they consider the problem of species. This is the sense in which even taxonomists, including ourselves, intend the word when it is used in most biologic connections. But this biologic species is, unfortunately, the first of the tax- onomic categories, the fundamental unit with taxonomic sig- nificance. As a category taxonomists may label this a geo- graphic variant, a variety, a subspecies, or a species. There

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Indiana University Studies

is no uniformity in current practice, and the only attempts at uniformity have been based on purely artificial distinctions. The resolution of the terminology must take into account as a question of convenience that no category higher than the genus may be written into the nomenclature, and as a matter of fact that there are often three or four degrees of phylo- genetic affinities which may be recognized below what seems to be best called a genus.

The ichthyologists believe that they have the solution in calling this lowest category a species and the second category a genus, thereby making their order the equivalent of many a genus among insects. I interpret the mammalogists to mean that they call a Mendelian race a variety, and the fundamental taxonomic unit a subspecies, which they imply is an incipient “species” (their next category) . The botanists, as nearly as I can perceive, call their lowest unit either a variety or a