They feed on leaves and flowers.
Blister beetles are an occasional, isolated problem.
Some species produce the toxin cantharidin, an irritant that can cause blisters on internal and external body tissues. The toxin, not beetle feeding, is extremely significant because it causes sickness in livestock and can even kill them. Even if beetles are killed, the problem may not be solved. Cantharidin remains in the bodies of dead beetles and can still cause injury if baled with the hay. Therefore do not sell blister beetle infested hay to horse owners.