The Gall Wasp Genus Cynips: A Study in the Origin of Species/Part II. Systematic Data
PART II. SYSTEMATIC DATA
Our conclusions on the nature and origin of the species of Cynips given in Part I of this study have been based upon the data now presented as the routine taxonomic treatment of the varieties, species, and subgenera of the gall wasp genus Cynips.
Cynips, as here defined, is a group of 93 highly specialized, oak inhabiting gall wasps, 26 of which have previously been included in this genus. Of the remaining species, 19 have been previously assigned to other genera, and 48 are here described as new.
Since we are dealing with the oldest name in the family Cynipidae, it is of moment to review the varied history of the nomenclature and of the taxonomic concept. This history begins with the Linnean adoption of the term (1758:553) to cover essentially all of the insects which he knew from plant galls. His Cynips, with 14 specific names, included species that we now place in six distinct genera distributed among the three tribes of the Cynipidae, as well as several species of chalcidoids, some of them parasites bred from galls produced by tenthredinids (Hymenoptera) and by cecidomyids (Diptera). Geoffroy, a contemporary of Linnaeus, made a better distinction (1762) between gall makers and parasites, altho calling the parasites Cynips and the gall makers Diplolepis. During the next century several attempts were made to fix the type of Cynips, but the only designation acceptable under the present International Rules was made by Westwood, in 1840, who named folii, probably the best known of all European gall wasps, as the type of the genus. Detailed discussion of this designation is given in the introduction to the European subgenus in this study. European usage largely followed Westwood's designation until Mayr, in 1871, used Förster's Dryophanta in precisely the sense defined by Westwood for Cynips, and Mayr's usage was adopted for the next half century. In 1910, however, Dalla Torre and Kieffer returned to Geoffroy's Diplolepis, and several recent authors have followed this practice, altho the usage is not approved by the findings of any of those (Morice and Durant, Rohwer and Fagan, Bradley, etc.) who have critically reviewed the question.
More unfortunate than this use of several terms for our present genus has been the European application of the term Cynips, ever since Mayr's publications, to a totally different genus which Rohwer and Fagan have re-named Adleria. It is to be regretted that our International Rules do not allow us to recognize this usage, but as long as we operate under the rules, we should apply Cynips to the phylogenetic unit which includes the species folii, and which, therefore, is strictly synonymous with Förster's Dryophanta.
The taxonomic concept of our present genus has only slowly emerged from this nomenclatorial confusion, altho in the brilliant revision of the Cynipidae by Hartig in 1840 all of the then-known (5) European species that we now recognize in this genus were brought together as numbers 2 to 6 of the Cynips there defined. The unity of the present group was further emphasized in 1881 by Mayr and we have already shown that 88 per cent of Mayr's inclusions are still acceptable. No later author has, in our judgment, had more than 48 per cent of his inclusions warranted phylogenetically (see page 62).
This widespread confusion in the interpretation of Cynips has not been wholly consequent on the difficulty of interpreting the relatively uniform structures of gall wasp species. Felt (Journ. Econ. Ent. 19:672) considers the situation due to the complex life cycle of our insects and to the failure of a sufficient number of economic entomologists to turn to cynipid taxonomy as an avocation. It is our own judgment that the poor work is the result of using book descriptions and “diagnostic characters” convenient for the manufacture of “Keys,” instead of actual specimens and adequate series of the species involved. The current chaos in the interpretation of cynipid genera dates from the publication, in 1893, of the cynipid volume of the Catalogus Hymenopterorum by C. C. de Dalla Torre, a painstaking bibliographer, but a systematist with a naïve faith in published descriptions and a supreme interest in the convenience of a classification. Later treatments of Cynips have uncritically accepted the Dalla Torre Catalog. If I depart from this tradition, it is because I believe that the study of thousands of individuals, representing all of the species of a group, are a sounder basis for phylogenetic interpretations than a catalog made by a biblographer who appears never to have seen two-thirds of the species involved.
The characters on which we base our present interpretation have been discussed in the first part of this study. We may repeat that we know no single character, morphologic, physiologic, or biologic, by which a Cynips may invariably be recognized. A hairy thorax, complete parapsidal grooves, undivided foveal groove, hypopygial spine which is broadened nearer the tip; a monothalamous, fundamentally spherical, separable leaf gall, occurring on a white oak; and the maturing of the adult early in the fall with emergence delayed until the winter—this is a combination of characters that will distinguish most of the agamic forms. The use of the dorsally produced and largely naked abdomen and the toothed tarsal claw of the genotype, folii, as diagnostic characters would lead to the inclusion of many species that do not belong and the exclusion of more species that do belong to true Cynips. The existence of both long-winged and short-winged species in the same genus is discussed in pages 25 to 36 of this study.
In the following treatment, each variety is handled under the following heads:
Synonymical Bibliography.
Comparative Descriptions: female, male, gall.
Range.
Types: data upon and location of type specimens.
Original Descriptions: quoted only if types have not been available for this study.
Inquilines.
Parasites.
Biologic and Phylogenetic Discussion.
All data presented in this study are original unless accredited (“acc.”) to other sources in the literature or to friends who have provided insects and galls for my use. All locality records apply to both insect and gall material examined unless specifically given for galls only or upon the basis of published authority.
The nomenclature follows the International Rules with one exception: Names originally published with a quercus or Q. between the generic and specific term are considered polynomials and without nomenclatorial standing under Opinion 50 of the Code, but accepted in this study as binomials—dropping the inserted host term—dating from the original publication. From Linnaeus to present students of the group, nearly everyone except the International Commission on Nomenclature has considered such names binomial and my present usage is in accord with practically all current practice among cynipid workers. Under date of October 16, 1923, the attention of the International Commission was directed to the impracticability of changing more than a hundred names affected by Opinion 50 in the relatively small family Cynipidae alone; but to date (six years later) we have only the formal acknowledgement of the communication by the Secretary of the Commission.
The species now accepted as true Cynips have been discovered as follows:
| In 1770, 1 variety, 1 species was known | ||||
| By 1790, | 0 | varieties, | 0 | species were added |
| By 1810, | 0 | varieties, | 0 | species were added |
| By 1830, | 0 | varieties, | 0 | species were added |
| By 1850, | 5 | varieties, | 5 | species were added |
| By 1870, | 6 | varieties, | 5 | species were added |
| By 1890, | 11 | varieties, | 6 | species were added |
| By 1910, | 6 | varieties, | 0 | species were added |
| By 1930, | 64 | varieties, | 9 | species were added |
| — | — | |||
| Totalling | 93 | varieties, | 26 | species |
Nearly two-thirds of the varieties have been described since the beginning of the World War. There are almost as many varieties now known in this genus as Riley (in Bassett 1882:330) predicted in the American fauna of the entire family Cynipidae.
The great increase in known forms within the last twenty years would suggest that now we must have exhausted the ready opportunity to print “new species” after a Cynips; but to one acquainted with the number of unexplored faunas in the highly varied biologic areas of the United States, with our almost complete lack of knowledge of the Cynipidae of the two largest oak floras in the world—in Mexico and southeastern Asia, or even with the scant work done on the gall wasps of more northern and Mediterranean Europe, it may appear that we are only laying a foundation for extensive discoveries yet to be made in this very genus of insects. It is astounding that any one had a fair concept of species a generation ago, when the mere fact of the existent species was hardly conceived. It becomes evident that the complexity of many a group may still be far beyond anything of which we are yet cognizant. Surely, taxonomic research is but on the threshold of data from which we may ultimately proceed to sound conclusions on matters of prime concern in the science of biology.
CYNIPS Linnaeus
Details of synonomy and type fixation are given under the several subgenera. As here defined the genus includes:
Cynips Linnaeus, 1758 (in part), Syst. Nat. Ed. 10, 1:553.
Philonix Fitch, 1859, 5th Rpt., Nox. Ins. N.Y.: 783.
Dryophanta Förster, 1869, Verh. zoo.-bot. Ges. Wien 19:335.
Acraspis Mayr, 1881, Gen. gallenbew. Cynip.: 2, 29.
Sphaeroteras Ashmead, 1897, Psyche 8:67.
Antron Kinsey, new subgenus.
Besbicus Kinsey, new subgenus.
Atrusca Kinsey, new subgenus.
AGAMIC AND BISEXUAL FEMALE.—In the agamic form generally rufous, rufous brown, and piceous in color, less often light brownish rufous or black, the abdomen usually darker than the thorax; the body of the bisexual female almost entirely black.
Head distinctly narrower than the thorax if the thorax is distinctly robust, nearly as wide as the thorax if the thorax is more slender as it is with most forms, distinctly wider than the thorax if the wings are short and the thorax consequently reduced; the cheeks more or less protruding beyond the eyes (in the agamic female) or the eyes larger and extending as far as or slightly beyond the cheeks (in the bisexual female); malar space between one-third and one-half the length of the compound eyes, quite without a malar furrow or at most with a faint indication of a furrow; with a low, broad, more or less indefinite median ridge; head irregularly coriaceous to finely rugose, scatteringly hairy, the hairs light yellowish, longest on the face and about the edges of the head, the vertex more naked. Antennae rufous to dark brown or black, often brighter basally, finely hairy (less so in the bisexual female), of moderate length or long, always slender, hardly enlarged terminally; with 13 to 15 segments, the first of moderate length, swollen, vase-shaped, the second no longer than wide, the third a third or more longer than the fourth, the penultimate segment a little longer than wide, the last one-quarter to one-half again as long as the preceding, the last two segments sometimes incompletely separated.
Thorax moderately large to very large and heavy (in long-winged varieties), or much reduced in size (in short-winged varieties), usually a little longer than high (as high as long in short-winged varieties), three-quarters again as long as wide in short-winged varieties, nearly twice as long as wide in the bisexual form. Mesonotum of the agamic forms more or less closely but shallowly punctate, with scattering, moderately long, yellow hairs, in part smooth, in part coriaceous to finely rugose between the punctation; the mesonotum of the bisexual females finely or sparingly roughened and sparsely hairy if not entirely smooth and naked; parapsidal grooves continuous or (in a few long-winged forms and several short-winged forms) more or less obliterated anteriorly, not wide, of moderate depth, smooth at bottom (except anteriorly in a few cases), gradually convergent but still not close together posteriorly, gradually divergent anteriorly (or sharply divergent if the thorax is very large and robust); median groove usually lacking (but some varieties have an indication of some median groove, especially posteriorly); anterior parallel lines (in most long-winged agamic forms) narrow to broad, moderately separated, wholly or in part finely punctate, or (especially in short-winged varieties and bisexual forms) not well defined, more obscure or obliterated anteriorly, slightly broadened and more or less divergent posteriorly; lateral lines (in long-winged agamic forms) mostly smooth, naked, rather broad, approaching the scutellum posteriorly but not extending to the parapsidal grooves anteriorly, these lines more or less obliterated in some long-winged varieties and in most short-winged varieties and bisexual forms. Scutellum of normal size, of moderate width, distinctly longer than wide (in long-winged varieties) or small and not much longer than wide (in the forms with the shortest wings), hardly broadened posteriorly, well rounded at the tip (more pointed in some short-winged varieties); flattened to cushion-shaped, often (not always) with a slight flattening, depression, or elevation along the median, longitudinal line; punctate and finely or more heavily rugose; scatteringly hairy, the hairs densest along the edges; with a shallow, arcuate foveal groove (which often grades into the anterior depression of the scutellar disk, especially in short-winged varieties), this groove undivided or at least with not more than a very fine, indefinite division into foveae; a well-defined foveal ridge separating the scutellum from the rest of the mesonotum (the ridge indefinite in some short-winged and bisexual forms); pronotum very narrow anteriorly (in long-winged forms), or broadened and distinctly visible dorsally (in many short-winged forms); laterally rugose and punctate, with not long, not dense, yellowish hairs. Mesopleura (of agamic forms) at least in part and sometimes wholly punctate and scatteringly hairy, smooth and shining between the punctations; the mesopleura of bisexual forms more nearly smooth and naked.
Abdomen of moderate size (in long-winged forms) or larger (in short-winged forms), one-third to three-quarters again as long as high; in some varieties not produced dorsally or ventrally, with the second segment not tongue-shaped; in other varieties (and in all bisexual forms) more or less produced dorsally with the second segment tongue-shaped; the second segment covering one-half to two-thirds of the whole abdomen (less than a half in some short-winged forms); the abdomen usually smooth, shining, and naked except for sparse patches of hairs latero-basally (with even these hairs reduced in bisexual forms), or sometimes the entire abdomen has a not dense coating of hairs, or (in the agamic forms of the subgenus Besbicus and in still other agamic forms) the sides of all the abdominal segments are well coated with appressed hairs. Hypopygial spine of agamic forms large but not extending much further than the lateral lobes of the hypopygium; the spine distinctly broad, in some instances very broad, a broadened area usually nearer the tip than the base of the spine (in most wingless forms of the subgenus Acraspis the spine is of uniform width for its whole length); sometimes the dorsal point, sometimes the ventral point of the spine extends furthest; much of the spine punctate and hairy, the tip bearing a tuft of long, yellowish hairs; the whole spine a little smaller in short-winged forms and still smaller, narrower, and less hairy in bisexual forms. Ventral valves not prominent.
Legs long, wholly punctate and hairy; tarsal claws usually of moderate weight, heavy in the subgenera Besbicus and Philonix; usually strongly toothed, less strongly toothed in bisexual forms, in a few agamic females only weakly toothed.
Wings usually long, extending fully one-half of their length beyond the tip of the abdomen; or wings reduced to three-quarters or to half the normal length; or wings reduced still further, being in many cases mere stubs; the shortened wings with reduced venation. If long, the wings are clear or slightly tinged with yellow, set with short, dark hairs which form a short fringe about the entire margin, the fringe longest on the hind margin; veins moderately heavy to very heavy, the subcosta, radius, and basalis always the heaviest, dark brown, and more or less limitedly infuscated; the subcosta not reaching the margin, colorless at a point near the origin of the radius; the first abscissa of the radius arcuate-angulate to distinctly angulate at a little more than 90°, more or less infuscated, without a point or with a short point projecting from the apex of the angle into the radial cell; the second abscissa nearly straight or slightly curved or, usually, more curved especially toward the tip, the vein ending distinctly back of the margin of the wing, the tip in many species triangularly expanded; the radial cell moderately broad, sometimes short, sometimes long, always open; areolet always present; cubitus fine, continuous, reaching the basalis near the mid-point, slightly infuscated at the basalis; all of the cells clear, or the cubital and (less often) the discoidal and (rarely) the radial cells with irregular, dark spots or larger, more indefinite, more smoky patches.
Length 1.2 to 5.0 mm., the agamic forms averaging nearer 3.0 mm., the bisexual forms nearer 2.0 mm., the agamic insects in general moderately large and robust, the bisexual forms usually more slender but not always shorter than the corresponding agamic generations.
MALE.—Differs from the bisexual female of the same species in having the compound eyes a little larger, protruding further beyond the cheeks; the antennae almost uniformly dark or at least darker on the basal segments, with one more segment than in the female, the third segment a little longer than in the female and with a suggestion of a curve; the abdomen small, elongate triangulate, moderately long petiolate; the legs often darker in some small part; the wings at least relatively longer than in the female; the spotting in the cubital cell lighter or heavier than in the female; length slightly greater than in the female, the legs apparently longer than in the female.
GALL OF AGAMIC FORMS.—Usually monothalamous (polythalamous in pezomachoides). Fundamentally spherical tho often much distorted in surface outline. The thin lining of the larval cell constitutes the nutritive layer; the cell wall (lacking in most of Acraspis) constitutes the protective layer; the bulk of the gall (except in Acraspis) is made up of a thinly or densely fibrous or a more compact parenchyma layer which holds the larval cell centrally and, in a few species (including all of Antron), contains a second, unoccupied cavity; an outermost hardened layer (constituting the bulk of the gall in Acraspis) is the collenchyma layer; and the epidermal layer is usually naked or finely pubescent, in Acraspis becoming contorted into a faceted surface sometimes coated with long spines or wool-like processes. Attached by only a small point (and therefore easily separable) on a main vein, usually on the under surface (less often on the upper surface, rarely on the petioles or young twigs) of leaves of white oaks; known from every group of white oaks that occurs in the regions inhabited by these insects.
GALL OF BISEXUAL FORM.—Monothalamous. A small, thin-walled, hard-shelled, largely naked, roughly egg-shaped or simple seed-like cell; or a larger thin-walled, more succulent, irregularly bladdery capsule; in either case without well differentiated layers of tissue or unusual epidermal development and without a differentiated larval cell except the central cavity of the gall; always within young buds, often completely enclosed by the unopened bud; closely connected to the young or older twigs or (in adventitious buds) on the bark of the older trunks; on white oaks of the same species which harbor the agamic generation of the insect.
RANGE.—Known from North America from southern Canada to central Mexico, from Europe wherever oaks occur, and from the borders of Asia and Africa on the Mediterranean Sea; not known, but to be expected from the rest of Asia wherever oaks occur. Figure 7.
GENOTYPE.—Cynips folii Linnaeus. Designated by Westwood, 1840, Generic Synop.: 56. See the discussion under the European subgenus Cynips.
The genus is here divided into six subgenera, Cynips, Antron, Besbicus, Philonix, Atrusca, and Acraspis, under each of which the systematic and biologic data are presented.