GALL-FLY, Cynips, a Linmean genus of insects, now forming the (Let. gall-inhabiting) of entomologists, and belonging to the order hymenoptera (q.v.), section terebrantia (Lat. boring), which section is characterized by the females being furnished with an ovipositor. Gall-flies arc nearly allied to ichneumons, but principally differ from them in depositing their eggs not in the bodies of the larvae of other insects, nor in their nests, but in plants, on the juices of which their larvae are nourished. The ovipositor of the female is long, slender, in part spirally rolled up when not in use, and lodged in a groove on the under-side of the abdomen, near the origin of which it is attached; it has at its extremity lateral teeth forming a kind of saw. By means of this organ, the insect makes a minute puncture where she is to deposit her egg, which is sometimes in a leaf; and then generally in one of the ribs of the leaf, sometimes in a young shoot or twig, sometimes in a bud, or in some other part of a plant, not excepting the roots; each species of gall-fly choosing some particular plant, and some particular part of the plant, to which it confines its attackS. An irritant fluid is supposed to be lodged in the punc
ture along with the minute egg, as a tumor immediately begins to form, becoming an excrescence known as a gall. The egg itself increases in size before it is hatched; the gall very rapidly attains its full dimensions; and within it the larva of the gall-fly feeds on the juices of the plant in their most concentrated form; for galls are found to contain the peculiar principles of the plants on which they grow in greater abundance than the adjoining or other parts. It is not until the larva has undergone its transformations, first into the pupa, and then into the perfect insect, that it eats its way out of the gall in which it has previously existed. See GALLS.