Blister beetles are long or cylindrical, soft-bodied or leathery, with broad, round or rectangular heads. The pronotum (just behind the head) is narrower than the head and the rest of the body. The wing covers are rounded curved around the body (not flattened). The antennae are threadlike or beaded.
Many species are black, brown, or other drab colors, sometimes with iridescent blues or bronzes or with yellow, orange, or red head, legs, or markings. Others are mostly yellow, orange, or red, sometimes with dark spots or stripes. When squeezed, blister beetles exude an irritating, oily chemical that can blister one’s skin.
The larvae go through several stages that look very different from each other. The grublike stages that parasitize underground bee nests are unlikely to be seen. The earliest stage, though tiny, is active; at this point, they have large heads and slender bodies, with functioning legs.