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Carabidae (ground beetles; class Insecta, order Coleoptera) Major family of generally black, brown, or metallic beetles, whose size ranges widely, from 2 to 35 mm long. They are often flightless, with fused elytra. The legs are long and slender, and adapted for running; in some species they are specialized for digging. The mandibles are prominent. Most ground beetles are carnivorous, but some species feed on plant material. Many species are nocturnal hiding under stones during the day. Tiger beetles (Cicindela species, which some authorities classify as a family, Cicindellidae) are thought to be the fastest-running land beetles, with speeds of almost 2.4 km per hour. Bombardier beetles (Brachinus species) deter attackers with puffs of caustic chemicals, dispelled audibly from the abdomen. There are 25 000 species, distributed world-wide.