Beetle, an insect with specialized forewings, or outer wings, that form an extremely durable covering called an elytra. There are more species of beetle—more than 300,000 in all—than of any other kind of insect. More than 30,000 species live in North America.

Rhinoceros beetlesRhinoceros beetles reach two inches in length.

Many beetles are incorrectly called bugs. The wings of beetles are different from those of bugs. The forewings of most bugs have gauzy tips that overlap at the back. The forewings of most beetles are heavy and horny throughout, meeting in a straight line along the back.

In most species, the beetle's forewings encase and protect the hindwings, or inner wings, which are thin and membranous. To fly, the beetle raises its forewings and unfolds the hindwings. The beating wings typically make a whirring or humming sound. Some species of beetles are poor fliers or do not fly at all. Such beetles are usually swift runners. They may lack hindwings or have ones that are quite small. The forewings of some ground beetles are fused together along the midline of the back.

True bugs have sucking beaks, while most beetles have strong mouths adapted to biting. (The word beetle is derived from the Anglo-Saxon bitan, "to bite.") Depending on the species, the jaws are used for grasping and killing prey, or for gnawing, boring, or chewing The jaws of certain species are large and resemble pincers.

Beetles have three pairs of legs. Some beetles have long, slender legs adapted for running. Others have legs suited for swimming or digging.

Beetles vary greatly in size. Some species are less than 1/16 of an inch (1 mm) long, others grow five to six inches (13 to 15 cm) long. The goliath beetle, a scarab native to Africa, is the heaviest insect known; it can weigh more than two pounds (900 g).