Dryocosmus quercuspalustris (sexgen)

Dryocosmus quercusnotha (sexgen)

New Observations on the Gall of CYNIPS QUERCUS PALUSTRIS, 0. S. 

Among the oak galls described in my previous articles, one of the most singular is the gall I named Cynips quercus palustris, from its frequent occurrence on Q. palustris, the pin-oak, although it is also occasionally found on other oaks of the red-oak group. This gall is especially remarkable on account of a small, cocoon-like body, containing the pupa, which rolls freely about in a comparatively large cavity, without being connected in any way with the walls of this cavity, or, in other words, with the substance of the plant upon which the gall is growing. An examination of the shell of this cocoon-like body (which, for brevity's sake, I will call ovule) proves that it does not consist of animal, but of vegetable matter, in other words, that the ovule is not a cocoon, although it contains the larva and afterwards the pupa. The growth of these galls is so sudden that, although I have seen thousands of them, I do not remember having seen one which was not full grown as far as the size is concerned. Once or twice only I discovered specimens arrested in their growth by some unknown agency and withered in that state; and in such specimens I observed the ovule still connected, by a short stem, with the leaf or branch upon which the gall was growing. It would seem, therefore, that the ovule is nothing but the usual kernel, existing in many other galls, but which here, during the growth of the gall, becomes disconnected from its shell. 

During my rambles in the Central Park, in New York, in May, 1869, among numberless galls of this kind on the pin-oak, I observed a good many which were double, that is, consisted of two galls soldered together. Such galls instead of globular were oblong, sometimes slightly narrowed in the middle. Usually, there was no partition on the inside between the two galls ; in the cavity thus formed was the likewise double ovule. The coarctation in the middle of the ovule was generally much more marked, than that of the gall. The double ovule contained two well-formed pupae without any partition between them, and hence almost in contact with each other. 

Such double galls showed different degrees of coalescence, and the coalescence of their ovules was always in exact proportion to the coalescence of the outer shells of the galls. Sometimes the galls, although coalescent externally, were still separated by a partition internally; then each gall contained its own ovule. But whenever there was no inner wall between the galls, the ovules were also coalescent. In one case I observed the inner wall only partially removed, the cavities communicating by a rather small opening ; the ovules were in this case coalescent by a small portion of their surface, otherwise retaining their rounded shape and thus almost representing the figure eight. 

In one of the galls I observed a small green caterpillar with yellow stripes, which had taken its abode in it and eaten up a part of the ovule, and perhaps also sucked out the larva. 

Cynips quercus notha, n. sp.

Still more remarkable, perhaps, than the preceding observation, is the discovery, among large numbers of the gall of C. q. palustris, of another gall, constructed on the same principle, that is, with a moveable ovule on the inside, but entirely different in the details of its organization. This gall, growing on the same trees and in exactly the same situation with that of C q. palustris, often alongside with it, is, however, much more rare. Its shell is not globular but oblong, much thinner and hence less succulent than that of C. q. palustris. Its green surface shows some longitudinal, semitransparent veins, of which there is no trace in the other gall. The ovule likewise is different; instead of round it is elongated, rounded at one end, pointed at the other, resembling a seed very much; its outer shell is much harder, smooth and shining. One of these galls had coalesced with a gall of C. q. palustris, just in the same manner as the above mentioned double galls of the latter kind. And, singular enough, the ovule of this double gall showed, by its unsymmetrical shape, that it was the compound of the ovules of the two different kinds. (I have preserved the specimen in my collection.) I obtained several specimens, male and female, from these galls, which showed no perceptible difference from C. q. palustris. What the different shape of the gall means, is a mystery to me. Until this is solved, I propose to call the gall Quercus notha, in order to distinguish it from the other. It may be that the flies themselves, upon , closer examination, would show some specific differences. Both galls excluded their flies between the 20th and the 30th of May. 

Contributions to the Natural History of the CYNIPIDAE of the United States and of their Galls. Article 5th.