I have myself examined in all, at various times, some in the closet and some in the field, about a thousand specimens bred from or taken out of the gall of Cynips quercus aciculata--a species described by Osten Sacken from two specimens furnished by myself--and they were all beyond a doubt female. There can be no mistake here, because in this genus the male is distinguishable at a glance by its differently shaped and very much smaller abdomen; but to prevent the possibility of error, in most cases I ascertained the presence of the ovipositor.
The trees from which I obtained the galls, or "oak-apples" as they are commonly called, on which I experimented, were an isolated and scattering group of 50 or 60 black oaks (Quercus tinctoria [velutina]), situated on a blue-grass prairie and without any other kind of forest-trees inter-mixed with them. The distance from this group to the nearest timber-land is about 150 yards. For many years I have procured from this source just as many Cynips q aciculata as I wanted, the galls occurring in prodigious exuberance there; and I had noticed three years ago that upon 6 or 7 of the largest black oaks in this group, on which the Cynips had hitherto been almost exclusively found, being cut down for fuel, the insect shifted its quarters to some other large trees which stood at the other end of the group, passing over a number of much smaller and younger trees lying in the intermediate space. One of these last large trees in particular was so badly infested by Cynips in 1863, that it must have borne from 400 to 500 galls. I have, however, occasionally found these galls elsewhere on quite young trees and even on saplings.
These same galls occur on the black oak in two or three other localities near Rock Island, IL, but by no means so abundantly. They are, however, exceedingly local, and if all the black oaks within two miles of Rock Island were divided into groups of the same size as the one above described, I am confident that for one such group where the galls exist, certainly fifty and perhaps one hundred will be entirely destitute of them. I speak the more confidently on this point, because one of my favorite modes of collecting is by "beating," and because it is scarcely possible to "beat" an oak, where these large and conspicuous galls or "oak-apples" exist, without becoming aware of their presence. Another fact leads to the same conclusion. Every spring in the locality above referred to dozens and dozens of oak-apples of last year's growth may still be seen hanging on the trees, being almost invariably those from which the Cynips or its parasites have made their exit. In the winter of 1863-4 I have carefully looked for such oak-apples in many black oak patches where I had failed to find them in the summer, and could not discover a single one. Yet the trees being mostly leafless a single specimen would have been easily seen. On the same prairie mentioned above there is another group of black oaks, similar and similarly situated to the one that swarms with oak-apples, and distant from it about .25 mile. Yet a careful search in the winter failed to discover a single oak-apple hanging on the boughs. On the other hand I had no difficulty finding on the same occasion many of these galls still hanging on the trees in the two or three localities where I commonly find them in small numbers in the summer; nor in finding numerous galls of Cynips quercus inanis OS on the red oak still hanging on the tree. Yet that gall is not one-twentieth part so abundant as the one which produces aciculata.
There are found near Rock Island the following species of oak, named in the order of their relative abundance, and on none of them, except the black oak, have I ever found the kind of gall which produces aciculata:--Quercus tinctoria [velutina], (black oak, by far the most abundant of any,) alba (white oak), rubra (red oak), macrocarpa (burr oak), imbricaria (laurel oak), and prinus variety discolor (swamp white oak.) Q coccinea (the scarlet oak) is believed by my friend Dr Fred Brendel, to be a mere variety of Q tinctoria, but it does not, so far as I am aware, occur in this vicinity. The identity of Q tinctoria and Q coccinea is an important fact, because Osten Sacken allows that his Cynips quercus coccineae, bred by him from Q coccinea, is scarcely distinguishable from C q spongifica, bred by him from Q tinctoria [velutina], and only separates them on account of the supposed distinctness of the galls from which the two insects were bred, and the supposed distinctness of these two so-called species of oak.
On May 17th, 1863, I visited the above described group of black oaks, and although their leaves were only about .75 grown, I noticed, in addition to several of last year's dry and brown oak apples, a very great number of green and freshly formed ones, many of which had attained their full size. On cutting a few of them open, I found the larva of the Cynips about .5 grown. Some of these galls had the terminal nipple attributed to the gall of spongifica by Osten Sack, some were smoothly spherical as the gall of aciculata was described by the same author, many had several nipples scattered irregularly over their surface, and 2 or 3 had as many as 12 or 14. The few I cut into had a rind or skin as thick as that of the normal gall of aciculata. I noticed a single specimen which was irregularly lobed like a common tomato.
On May 24th some of the galls contained full-grown larvae, and on May 25th I found in several of them female pupae. On June 4th I opened several galls gathered May 24-5, and found in them some larvae and pupae, and one male and two female imagos of C q spongifica OS. Shortly afterwards I collected about 100 galls, as they were beginning to get ripe, and bred from them in all during the month of June, 6 male and about 20 female of spongifica, besides a great number of the Cynipidous inquiline or guest gall-fly, Synophrus laeviventris OS, and of two distinct species of parasitic Chalcididae belonging apparently to Callimome and Decatoma, and a single Bracon very near mellitor Say. Up to June 14 all the galls that produced spongifica flies were thin-shelled and of the type of the q coccineae. Such galls were then brown and ripe, whereas the more hard-shelled and thick-shelled ones were then more or less green and succulent. On June 14th, however, I bred a male spongifica from one of the latter description of galls, and many female afterwards from such galls; and I found that all the intermediate grades between the two types occurred in the galls that produced spongifica, some having a shell no thicker than writing-paper which wrinkled and collapsed and shrivelled up in drying, and some a shell as thick as ordinary cardboard, so as to retain their plump, apple-like appearance under the roughest usage; some again having a terminal nipple, some many nipples, and some none at all or next to none. The last spongifica (a male) came out June 18, and after that date no more made their appearance, nor after the last day of June any more inquilines or parasites except a single female Callimome(?) on July 23d. Of the whole number of galls somewhere about 1/2 remained on hand imperforated by any insect, those that were perforated having been from day to day picked out and thrown away. About the last of June, the thicker shelled galls having now become partially ripe and dry, I gathered 2 or 3 hundred more from the same locality, selecting of course those which had not been perforated by any insect.
During the month of June I had endeavored to experiment on the mode in which these galls are generated, by enclosing the boughs of different species of oak with gauze-bags and placing therein freshly-hatched specimens of male and female spongifica. Owing to the mischievous propensities of certain unknown persons, the only fact I was enabled to arrive at was, that this insect when fed on white sugar, which it appears to eat freely, lives only 6 or 8 days.
On July 16th I examined the group of black oaks, from the accessible boughs of which I had sometime before stripped all the galls. There were no new galls formed there, neither were there any subsequently formed there during the summer. Out of about 16 or 18 galls left on a particular tree, three or four of which I opened contained each a lively cynipidous larva in the central nucleus, and full one-half of the whole number were not perforated. On September 6th I opened two of the oak-apples gathered early in June, and found a black female pupa, apparently aciculata, in each. On Sept 17th and 18th I found in the same lot of oak-apples 7 female aciculata in the imago state, and during the month of October and the early part of November I bred very numerous imagos of the same, say from 50 to 60, all female. On October 25th I obtained three specimens from galls with a thinnish shell, and one from a gall with a shell as thin as paper with a distinct nipple at the tip. Of three others bred the same day from thick-shelled galls, one came from a gall with a terminal nipple, and the other two from spherical galls. On October 27, out of 11 or 12 female aciculata that came out, several came from galls with a terminal nipple and from galls covered with nipples all over, the rest from spherical galls. Other specimens continued to come out till November 16, and a single one after that date. Not a single parasite had made its appearance since July 23rd. On January 20, 1864, I cut into 30 or 40 of the remaining galls and found in them 9 aciculata female fresh and limber but dead, and 2 specimens dead and dried up, besides some dead and dried up parasites.
Besides the locality above referred to, I reared in 1862 a male spongifica and several female aciculata from a different locality, the gall of the former gathered in the spring and that of the latter in the autumn and both found on q tinctoria [velutina].
From the above facts I draw the following conclusions:--
1st. Cynips q spongifica OS is identical with C q coccineae OS, as there are confessedly no distinctive specific characters of any importance, and the galls occur on the same species of oak (q tinctoria [velutina]) and are connected by all the intermediate grades. The spongy matter of the gall of q coccineae is said to be "whiter" than that of q spongifica, but I noticed several galls of aciculata, the spongy matter of which was in January, 1864, almost pure white.
2nd C q spongifica OS occurs male female exclusively on q tinctoria [velutina], and emerges not later than June from galls that commenced their growth in the preceding month of May.
3rd C q aciculata OS is a dimorphous form of C q spongifica OS, occurs exclusively in the female sex and exclusively on q tinctoria [velutina], and emerges from the last of September to the middle of November, and many of them not till the following spring, from galls that commenced their growth in the preceding May, which are undistinguishable from those which produce C q spongifica, the same kinds of gall from the same lot of trees, gathered at the same time, producing spongifica male and female in June and aciculata female in October and November, and nothing whatever but a solitary parasite in the intervening period.
Suppose, for argument's sake, that aciculata and spongifica are distinct species. Then we are met immediately by the following difficulties:--1st. Is it likely that two distinct species of Cynips should produce, on the same species of oak, galls which are indistinguishable? I know of no such case in the whole Class Insecta. 2nd Is it likely that when spongifica, as above shown, is so local that it is only found in one station out of fifty near Rock Island, aciculata should select that particular station instead of some other one of the remaining 49? 3rd. If aciculata is a distinct species, then we are compelled to believe with Hartig in the existence of agamous species; ie of species that propagate from year to year ad infinitum without sexual intercourse with a distinct individual. I cannot believe that any species in the whole Animal Kingdom is uniformly agamous, for the simple reason that we should then have almost as many races, and finally species, as individuals. Monstrosities and remarkable variations, which with bisexual species are mostly eliminated by intercrossing with normal individuals, would then by the laws of inheritance be always intensified and exaggerated from generation to generation, and what was originally one homogeneous species would split up into an almost infinite number of distinct and sharply defined types.
That it may not be supposed that I approached this subject biased in favor of the conclusions above announced, it is proper to state that my original guess was, that there were two broods of this Cynips every year, the first a spring brood male female of the type spongifica, the second an autumnal brood, female only, of the type aciculata, generated in the ordinary course by the first brood, and in its turn generating by parthenogenesis the spring brood of spongifica in the following uear. It is scarcely necessary to add, that the facts utterly overthrow this hypothesis.
