Over the larvæ of this order the ichneumons reign with undisputed sway; attacking all indiscriminately, from the minute insect that forms its labyrinth within the thickness of a leaf, to the giant caterpillar of the hawk moth. The most useful of all, however, the silkworm, appears, at least with us, to be exempted from this scourge. De Geer, out of fifteen larvæ that were mining between the two cuticles of a rose-leaf, found that fourteen were destroyed by one of these insects.
THE EMPEROR MOTH WITH ITS CHRYSALIS AND CATERPILLAR.
The larva of all the lepidoptera is a Caterpillar composed of twelve ring-like segments, exclusive of the head, which is harder than the other parts, and always of a deeper colour than the body. Each Caterpillar has nine breathing-holes on each side; and each of the three segments nearest the head is furnished with a pair of short legs, ending in a kind of claw, which are the true legs of the insect. The Caterpillar has, however, eight or ten other legs on the hinder segments of its body. The head has twelve eyes, and two very short conical antennæ; and the mouth is furnished with two strong mandibles, two maxillæ, a labrum, and four palpi.
The habits of Caterpillars differ: some, which are called Geometers, or Loopers, advance by a succession of steps, first extending the body to its full length and adhering by the fore legs, then drawing up the hinder part of the body close to the forepart so as to form a loop, and then again repeating this process; these Caterpillars, when at rest, often adhere by their hinder feet, and extend the body stiffly, like a little dry twig; others, which are furnished with more prolegs, adhere by these to the branch or leaf, and raise the forepart of the body a little, an attitude which induced Linnæus to give the name of Sphinx to the moths in whose Caterpillars this habit prevails; some small species live between the upper and lower surfaces of leaves, in which they excavate mines; others dwell in small cases, which they manufacture of various materials; whilst others, dwelling in large societies, spin for themselves a sort of silken tent, in which they take their repose, and from which they issue daily in search of food in a regularly marshalled procession. Many make themselves cocoons; but others have no other covering in the pupa state than a smooth shining skin, or a dark mummy-like cerement. The chrysalis of a butterfly is generally angular, and that of a moth cylindrical.