BUG, the common name for insects of the suborder Heter optera of the order Hemiptera (q.v.), also used in North America for almost any kind of insect; e.g., lady-bug (ladybird), June-bug (cockchafer). In a more restricted sense it is applied to mem bers of the hemipterous family Cimicidae of which the best known examples are the bed-bugs. These are oval, flattened, mahogany-coloured insects devoid of wings and with piercing, sectorial mouth-parts. The commonest species are the cosmo politan Cimex lectularius, the bed-bug of Europe and North America; and C. rotundatus, the bed-bug of the orient. These insects occur in dirty houses, etc., and are nocturnal, hiding by day in crevices. They are blood-sucking in habit, chiefly attacking man : pathologists have suspected them of transmitting several diseases, but further evidence is needed. Other members of the family include parasites of birds and bats.