After 6 instars of development, larvae become a 7th instar pseudo-pupa for overwintering. Though they are voracious feeders, blister beetles are of major concern due to their toxicity to livestock. Blister beetles produce the highly toxic chemical cantharidin. This poison is highly stable, and persists even after a beetle is killed. So beetles crushed during the harvesting process are still toxic to livestock.
Horses are particularly sensitive to cantharidin poisoning.
Cantharidin poisoning effects the urogenital and gastrointestinal systems. Symptoms include colic, abdominal pain, depression and anorexia Pollakiuria and frequent urination. Blister beetle hemolymph will on contact cause blistering of human skin. Sampling Methods Blister beetles tend to form large groups in small areas of a field, thereby making them difficult to sample. The high toxicity level of these beetles coupled with their congregation behavior makes detection critical before feeding the hay to livestock.