Blister beetles produce cantharidin, a highly toxic chemical that irritates the gastrointestinal and urinary tracts and may lead to death, especially in horses. The larvae prey on subterranean grasshopper and bee eggs. Blister beetles or oil beetles are members of the family Meloidae. This family includes over 300 species in the United States and more than 2,500 worldwide. The genus Epicauta is the largest and contains many species that concern forage producers in semi-arid regions of the western United States.
Blister beetles produce cantharidin, which is toxic to people and animals.
For centuries, cantharidin was prescribed as a cure for a variety of ailments. Spanishfly or cantharis, a preparation of dried meloid beetles, was thought to cure gout, carbuncles, rheumatism and many other medical disorders, in addition to its use as an aphrodisiac. Today, the toxic properties of cantharidin are more widely recognized and its use is largely restricted to veterinarians, who employ it as a counterirritant and blistering agent. Blister beetles commonly found in Colorado alfalfa fields. Biology and Habits Most species of blister beetles have one generation per year.