The four, listed in the order that they occur during the season are gray, striped, margined, and black, respectively. All these species have long, narrow, cylindrical, and soft bodies, and a pronounced neck and broad head when viewed from above. Because one of the larval stages is a heavy feeder on grasshopper eggs, knowledge of grasshoppers and their life cycles can be helpful. Black blister beetle. Margined blister beetle.
Horses are especially susceptible to blister beetle poisoning.
Consumption of 25 to 300 beetles can kill a mature horse. Cattle and sheep are much less susceptible, but blister beetles will reduce digestibility of hay and may throw cattle off feed. Because the toxin is absorbed and then excreted with the urine, intense inflammation of the urinary tract is a common sign of poisoning. Death may occur within 24 hours, and treatment with mineral oil by stomach tube is recommended but not always very effective. If blister beetle poisoning is suspected, contact a veterinarian immediately.