Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their toxicity to would-be predators.
Cantharidin is a poisonous chemical that causes blistering of the skin. It is used medically to remove warts and is collected for this purpose from species of the genera Mylabris.