Blister beetles are one-half to one inch long and have comparatively soft bodies. The head is broad and vertical. The section of the body between the head and the wings [prothorax] is distinctly narrower than the wings, and usually is slightly narrower than the head. It appears that the insect has a neck. The wing covers are soft and flexible, and the legs are comparatively long.
Blister beetles contain an oily, caustic substance in their body fluids called cantharidin that helps protect them from natural enemies. Cantharidin is toxic and can severely injure livestock, particularly horses. Horses that have ingested cantharidin may exhibit signs of colic, including excessive salivation, sweating, cramps, and urinary straining; a fatal dose will include fever, depression, shock, and death.