any of numerous small, round, often brightly colored and spotted beetles of the family Coccinellidae, feeding chiefly on aphids and other small insects, but including several forms that feed on plants.
1690s, from lady + bug (n.). The "lady" is the Virgin Mary (cf. German cognate Marienkäfer). In Britain, now usually ladybird beetle (1704), through aversion to the word bug, which there has overtones of sodomy.