The caterpillars live and metamorphose themselves in portable cases, which they manufacture from the membranous portions of leaves, whose flesh alone they eat. These cases are generally of a brown colour, resembling a dead leaf. They are attached perpendicularly under the leaves of many trees, but often under those of fruit trees.
Certain species of Œcophoræ have cases partly covered with loose pieces only slightly attached, formed of portions of leaves, and arranged in such a way that Réaumur compares them to the furbelows which ladies used formerly to attach to the bottom of their dresses.
ORTHOPTERA.
Among the Orthoptera [76] we meet with some of the largest of insects, and particularly those which are of strange and extraordinary shapes. The best known insects of this order are the Mantes, Cockroaches, Earwigs,[77] Locusts, Grasshoppers, Crickets, &c.
The Orthoptera have the anterior wings long, narrow, half-horny. These are elytra, which serve as cases for their second wings, as is the case with the Coleoptera. But the elytra of the Orthoptera are less solid and less complete than those of the Coleoptera. Moreover, they generally overlap each other when the insect is at rest, which is another distinctive characteristic. The second wings are membranous, very broad, and veined; and, when at rest, are folded up like a fan. The mouth is composed of free pieces. The mandibles, the jaws, and the two lips, always well developed, show them to be insects which grind their food. Their voracity, and the rapid way in which they multiply, sometimes make these insects the pest of the country. Above all, they are to be met with in hot countries, where they cause such great damage that all vegetation disappears on their passage. There are not a great variety of species of Orthoptera. They are insects whose metamorphoses are incomplete; that is, they undergo only trifling changes from the moment when the eggs are hatched to the time when the insect is fully developed.
When it leaves the egg, the young one resembles its parents; it differs only in size and in having no wings. After moulting four or five times it has almost reached its full growth, and its wings begin to appear under a sort of membrane. This is the pupa state. A final moulting sets free the wings also, and the insect, now perfect, launches itself into the air with its congeners.