Semi-Gall of the Hawthorn, produced by Cecidomyia? drawn from a specimen.
A few weeks afterwards, on opening this drawer, we were surprised to see a brood of several dozens of a species of gall-fly (Cynips), similar in form and size to that whose eggs cause the bedeguar of the rose, and differing only in being of a lighter colour, tending to a yellowish brown. We have since met with a figure and description of this gall in Swammerdam. We may remark that the above is not the first instance which has occurred in our researches, of gall insects outliving the withering of the branch or leaf from which they obtain their nourishment.
Woolly Gall of the Oak, less than the natural size, caused by a Cynips, and drawn from a specimen.
The woolly substance on the branch of the oak which we have described was similarly constituted with the bedeguar of the rose, with this difference, that instead of the individual cells being diffused irregularly through the mass, they were all arranged at the off-goings of the leaf-stalks, each cell being surrounded with a covering of the vegetable wool, which the stimulus of the parent egg, or its gluten, had caused to grow, and from each cell a perfect fly had issued. We also remarked that there were several small groups of individual cells, each of which groups was contained in a species of calyx or cup of leaf-scales, as occurs also in the well-known gall called the oak-apple.
We were anxious to watch the proceedings of these flies in the deposition of their eggs, and the subsequent developments of the gall-growths; and endeavoured for that purpose to procure a small oak plant in a garden-pot; but we did not succeed in this: and though they alighted on rose and sweet-briar trees, which we placed in their way, we never observed that they deposited any eggs upon them. In a week or two the whole brood died, or disappeared. (J. R.)
There are some galls, formed on low-growing plants, which are covered with down, hair, or wool, though by no means so copiously as the one which we have just described. Among the plants so affected are the germander speedwell, wild thyme, ground-ivy, and others to which we shall afterwards advert.
Oak-apple Galls, one being cut open to show the vessels running to granules.