Page:Jardine Naturalist's library Entomology.djvu/320

314 JOPPA PICTA. XXXI. Fig. 3. and the species delineated on the following plate, afford examples of the very extensive family of the Ichneumonidæ, whose economy is so remarkable. They deposit their eggs in the bodies of other insects, particularly caterpillars, which are there hatched, and the young feed on the entrails of the unfortunate victim. To enable them to convey their eggs into holes and fissures where caterpillars or pupæ often lurk, they are generally provided with a long ovipositor, which is usually very slender, and too weak to pierce the skin of the hand, although the insects often make the attempt when seized. As this weapon generally appears tripartite, these insects were formerly named Muscæ tripiles, and, from their habit of vibrating their antennæ, Muscæ vibrantes. They may, in general, be known by their narrow elongated form, attenuated, and, in most cases, petiolated abdomen, with its hair-like appendages behind, and long many-jointed antennæ, which are often recurved and annulated. The Ichneumonidæ are a very numerous tribe, no fewer than 1300 European species having been described by Gravenhorst in his monograph of this family, and of these a large proportion occur in Britain. Our British species, however, have not yet been carefully investigated, and it is much to be desired that some competent observer would undertake the task. These insects perform an essential service by destroying so