Blister beetles are so named because when caught in the jaws of a bird or a lizard, or the fingers of a human, they deliberately pop blood vessels located in their leg joints. Out seep a few drops of yellow, nasty smelling blister blood that will indeed inflict a painful burn. The chemicals in the blood of blister beetles make up a compound called cantharidin. Cantharidin is a toxic poison that can be lethal if ingested. Hay eating animals such as horses, cattle and sheep are particularly vulnerable as some species of blister beetle feed on alfalfa. This virulent protection mechanism is why the ponderous beetles survive even while sporting their vivid colors.
After a marathon mating act which can last more than 24 hours, the female buzzes off to a far-flung location and lays her eggs in the soil. When master blister beetle grubs hatch they burrow through the ground in search of grasshopper eggs. Scientists believe blister beetles have a sense of smell that directs them to their prey. A mass of grasshopper eggs will provide nutrition for the beetle grub as it grows and develops through the winter. In April, just in time for the brittle bush bloom, the adult beetle digs out of the soil and flies in search of food and mates.
Thanks to John Alcock of ASU School of Life Sciences for the information on master blister beetles. His article and more pictures can be found at