beetle

Common name of insects in the order Coleoptera (Greek ‘sheath-winged’) with leathery forewings folding down in a protective sheath over the membranous hindwings, which are those used for flight. They pass through a complete metamorphosis. They include some of the largest and smallest of all insects: the largest is the Hercules beetle Dynastes hercules of the South American rainforests, 15 cm/6 in long; the smallest is only 0.05 cm/0.02 in long. Comprising more than 50% of the animal kingdom, beetles number some 370,000 named species, with many not yet described.

Beetles are found in almost every land and freshwater habitat, and feed on almost anything edible. Examples include click beetle or skipjack species of the family Elateridae, so called because if they fall on their backs they right themselves with a jump and a loud click; the larvae, known as wireworms, feed on the roots of crops. In some tropical species of Elateridae the beetles have luminous organs between the head and abdomen and are known as fireflies. The potato pest Colorado beetle Leptinotarsa decemlineata is striped in black and yellow. The blister beetle Lytta vesicatoriaf, a shiny green species from southern Europe, was once sold pulverized as an aphrodisiac and contains the toxin cantharidin. The larvae of the furniture beetle Anobium punctatum and the deathwatch beetle Xestobium rufovillosum and their relatives are serious pests of structural timbers and furniture (see woodworm).