The Coleoptera are those insects generally denominated Beetles, they have four wings, the two outer of which are not used to fly with, but as cases to cover and protect the other two; they are called "elytra," are horny and firm in texture, and in some cases, as the Diamond Beetle and Musk Beetle, beautifully ornamented; the under pair of wings fold transversely so as to pack up under the outer ones, which are shorter. All Beetles live but one season, both sexes die before winter, leaving nothing but their eggs to continue the species, the larvæ which come from these are very destructive, eating most voraciously; for the most part, Beetles feed on decaying substances such as dung, &c., and are therefore useful creatures; there are between 40,000 and 50,000 species of them. Beetles have been called the scavengers of nature, and truly they are so, for they (with other insects) clear off all dead matter, whether animal or vegetable; the Geotrupes stercorarius, and others, dig holes in the ground and bury the excrement which is deposited on the surface, thus doing a great service to vegetation, taking it down to nourish the roots of the grass and other plants instead of allowing it to harden and decompose on the surface. All dead animals are at once attacked and devoured by insects, and the Beetles play their full share in this necessary operation. There are certain Beetles, called Burying Beetles (Necrophorus vespillo), which remove the earth from under the dead bodies of small animals, such as birds or mice, till they are beneath the level of the ground, when they cover them up and deposit their eggs in them; these bodies form stores of food for the future larvæ. The Stag Beetle (Lucanus cervus, fig. 22), the Dor Beetle (Geotrupes stercorarius), the Cockchaffer (Melolontha vulgaris), the Musk Beetle (Cerambyx moschatus, fig. 16), and the Lady-bird (Coccinella), are well-known members of this order. 2. ORTHOPTERA (Straight-winged). The Orthoptera are those insects whose wings fold longitudinally; they have two pairs, but the anterior pair are horny and serve as wing-cases to the posterior pair; their food is chiefly vegetable, but to many of their species any kind is acceptable, as their mouths are suitable for grinding-up hard substances. The Locusts (Locustidæ, fig. 21), Grasshoppers (Gryllidæ), Crickets (Achetidæ, fig. 16), and Cockroaches (Blattidæ), or Black-beetles, as they are sometimes incorrectly called, belong to this tribe. Their metamorphoses are not so complete as in many other insects, for they never entirely change their form; the larva as it leaves the egg has no wings, but otherwise is much like the parent; it changes its skin several times, which stage is analogous to the pupa state, after casting it five times and obtaining wings, it becomes the imago or perfect insect. The ravages of the Locusts are so well known that little need be said; the following is from Kirby and Spence's Entomology:--