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. Blister beetles overwinter as larvae in the soil and emerge as adults in the spring. Females deposit from 50 to several hundred eggs in the soil crevices. After hatching, larvae feed on grasshopper and cricket eggs.
Adults fly into fields, where they feed on foliage.
The beetles are usually found in late spring and summer. Blister beetles are often worse in fields adjacent to weedy grassy areas that contain an abundance of grasshopper eggs. Before treating a field, ascertain whether the beetles contain cantharidin by having the beetles identified by a trained entomologist. Treating blister beetle species that do not is probably unnecessary. Managing blister beetles is difficult.