Most are elongate-oval, soft-bodied beetles 10 mm long or less. Many are brightly patterned in black and brown, yellow, or red. Some melyrids (Malachiinae) have peculiar orange structures along the sides of the abdomen, which may be everted and saclike or withdrawn into the body and inconspicuous. Some melyrids have the two basal antennomeres greatly enlarged. Most adults and larvae are predaceous, but many are common on flowers. The most common North American species belong to the genus Collops (Malachiinae); C. quadrimaculatus is reddish, with two bluish black spots on each elytron.
Four New Guinean species of Choresine (the more abundant C. pulchra, the less abundant C. semiopaca and the two infrequent C. rugiceps and C. sp. A, the latter as yet unnamed) have been found to contain batrachotoxins, which may account for the toxicity of some birds such as the Blue-capped ifrit which eat them. The hypothesis that Phyllobates frogs in South America obtain batrachotoxins from related genera of the Melyridae (Choresine does not occur there) has not been tested due to the difficulty of field-work in Colombia.
The family Melyridae contains 520 species in 58 genera in North America. In Europe 16 genera are present; however, the largest diversity is in tropical rainforests.