BEETLES (Coleoptera). Beetles form one of the most extensive orders of insects, there being upwards of 3000 known British species. They vary much in appearance, but a Beetle is readily recognised by its front wings, or elytra; these form a tough horny sheath or case, which lies over the real wings, and protects them when the insect is not flying. Sometimes, the elytra are very short the mouth is fitted with jaws for cutting. The metamorphosis is complete, i.e., the larva or grub is very unlike either the quiescent pupa or the perfect insect. The period that elapses before Beetles arrive at their perfect state varies from a few weeks to two or three years, but is usually rather longer than in Butterflies or Bees. Various Beetles attack growing plants and roots. Thus, Otiorhynchus sulcatus and O. picipes attack Vines, Roses, and other plants, gnawing off the bark. Some species of Beetles attack Mushrooms, while others bore into the wood of old trees, or eat leaves (e.g. Turnip Fly), or burrow in the leaves, or form galls on roots (Cabbagegall Weevil). Of some kinds, the beetles are hurtful; of others, the larvae. Many kinds, however, are beneficial, such, for instance, as the common Ground Beetle (Carabus, Fig. 224), and the Devil's Coach Horse (Ocypusolens, Fig. 225). These live upon other insects and snails. One kind of Beetle--the Ladybird--is very beneficial in a garden, as it preys upon the aphides, or plant lice. For instructions in dealing with the noxious kinds, see Asparagus Beetle, Bean Beetle, Beet Carrion Beetle, Click Beetle, Cockchafer, Lily Beetle, Rosechafer, and Turnip Fly.