Callirhytis clavula

Callirhytis clavula [Riley claims that Pergande found evidence that wasps identified as C clavula oviposited in leaves later bearing C quercusfutilis galls; [Kinsey believed this was incorrect](https://www.biodiversitylibrary.org/page/52079411#page/28/mode/1up)]

On April 20, 1894, my attention was called by Mr. Pergande to several specimens of Callirhytis clavula Osten Sacken ovipositing in the buds of Quercus prinus. This is a rather large, winged agamic form, which Mr. Ashmead informs me he has actually bred from the clavula gall. The same species also oviposits in the buds of Quercus alba. The flies were sitting on the buds with the head towards the tip of the bud, and were so absorbed in their work that they scarcely moved or altered their position, even when the twigs were allowed to sweep back with some force. The ovipositor was deeply inserted within the scale-like covering of the buds. On carefully removing the scaly covering of a bud that had been pricked, quite a number of eggs were found in clusters of three or four together, and a few singly, inserted in the tender, new, embryo leaves. It was further found that the eggs were inserted on both the upper and lower surfaces of the leaf and almost entirely hidden by the silvery pubescence of the newly formed leaf. They were attached by a short stout pedicel or stem which, however, upon very careful examination, was found to extend for a great length (six or seven times the length of the exposed egg-body) like a fine thread into the sub stance of the leaf. The distal or anterior end of the egg-stalk was also somewhat enlarged, looking like a bit of shrivelled skin. The exposed portion of the egg or egg-body was white, glistening, elongate-ovoid or bean-shaped in form and about .2 mm. in length. Two days later, or on the 22d, additional flies were observed ovipositing and the buds were marked. On the 27th these were examined and it was found that the pedicel had become shorter and stouter, while the anterior or buried end had greatly increased, the exposed portion being now half empty of its contents. Five days later, April 2yth, the young leaves had formed from these same marked buds and the eggs were still in position, but mostly empty, and when removed and closely examined it was found that under the epidermis and below the base of the exposed egg-shell there had formed a soft, colorless, globular body, having a yellowish streak internally. This body, probably the first larval stage, is easily detached from the leaf, but no movement could be discerned and the thread-like pedicel had separated from it and disappeared. So far, there is no trace of a gall or swelling to be seen, although the affected leaves appear more or less crumpled or distorted. May 4th the same leaves were again examined and the young galls had already formed, appearing as slight thicken ings of the leaf, but scarcely elevated or prominent. The spot where the egg had been inserted forms a minute depression or hollow in the leaf, with the colorless and shrivelled egg-shell still in position, the cavity thus formed being in an oblique direction to the surface of the leaf. The cell or cells in each gall are re moved from the egg-shells about twice the length of these last, but for which there would be little trace as to where the egg en tered ; they are ovoid or rounded, and each contains a perfect larva, semitransparent or colorless, with a brownish ventral spot. Most of the galls contain three to five cells. From now on, the formation of the gall is rapid, the substance of the young gall being very juicy and succulent and of a yellow ish color, its outer margin or edge being pale pinkish. On May nth the galls were nearly full grown and proved to be Callirhytis ftitilis O. S., but no flies were reared until the middle of June, and from this time until the last of the month flies in both sexes were continually bred. A number of interesting subsequent observations were made upon this interesting species, but have no especial bearing on this communication. I ought, however, to state that Mr. H. F. Bassett (Psyche, Vol. 5, pp. 235-8, Dec., 1889) has described what is, apparently, the same insect as Cal- lirhytis radicis, which he reared from a series of blister-like cavities in the bark of the root of Quercus alba, and identified with the fly which he had himself observed ovipositing in the buds of the same oak and producing the gall which gives forth Callirhytis futilis Osten Sacken. There is consequently some confusion as to the actual relations of this sexual generation, and either an error as to determination on the part of Mr. Bassett or else an erroneous record of rearing on the part of Mr. Ash- mead. I have adopted the former as the more probable. There is, however, a third explanation, which, if verified by future in vestigation, would prove to be another interesting discovery in connection with these oak gall-flies, viz., that the same species may indifferently produce a gall on the root or on the twig. When we remember how closely these two parts of the plant are related physiologically and how readily the one in most trees may be converted into the other, such a discovery should not sur prise us. 

On oviposition in the Cynipidae