ICHNEUMON, a Linnxan genus of insects, now a family or tribe, ichneamonida, of the order hymenoptera, section terebrantia. 'the ichneumonidce are extremely numerous. Gravenhorst's Ichneumonologia Europea describes nearly 1650 European. species, and they are equally abundant in other parts of the world. Many of them are minute, others are large insects; a few of the tropical species are amongst the largest of insects. They have the abdomen united to the thorax by a pedicel. which is often very slender. The abdomen itself is slender, and the whole form attenuated. The antenna are generally thread-like, composed of a great number of joints, and are kept in very constant vibration. The ovipositor in some is short; in some it is very long, much longer than the body of the insect, and inclosed in a kind of sheath formed of two parts, concave on their inner surface, from which it is disen gaged when about to be used, the whole then often seeming as three threads proceed ing from the extremity of the abdomen. All the ichneumon ida3 deposit their eggs either in or on—generally in—the bodies, eggs, or larvN of insects, or in spiders. Some of
them deposit their eggs in aphides. They are thus extremely useful to the farmer and gardener. Particular species of ichneumonidm, are the natural enemies of particular kinds of other insects. Thus, microgaster glomeratus and pimple instigator lay their eggs in the caterpillars of the cabbage butterfly. Some species deposit only one egg in the egg or larva which is destined to afford food to their own larva; others deposit a number of eggs together. Those which have a long ovipositor use it to reach eggs or larva under the hark of trees, in holes of wood, etc. The ichneumon larvm gen erally consume only the fat of the larva on which they feed, which continues to subsist and so to sustain them till they are. ready for transformation into pupa. In their perfect state, the ichneumonidce feed only on the juices of flowers. They are very often to be seen flying about umbelliferous flowers. The ichneumon larvm are without feet. The pupae of many are inclosed in silken cocoons.