Blister beetles are an interesting bunch of beetles. There are about 300 species in the US primarily found in the Southwest, and they vary in color from brown, black, to gray, and may have yellow, reddish orange, black, or white stripes or spots. They’re about an inch to an inch and a half in length, have elongated, pliable bodies, long legs, compound eyes, a bowed head, and a distinctivethread-like antenna.
The master blister beetle, or Lytta magister, is a mix of deep black and bright red orange in color. You may find these beetles by the swarm in Phoenix during springtime, dangling from flowering brittlebushes.
When threatened, these beetles pop a blood vessel on their leg joints which secretes a bad smelling, yellowish substance that contains cantharidin, a burn agent (or a poison in large doses) that is colorless and odorless. When in contact with human skin, it causes painful blisters, hence why the beetle is called a blister beetle. It’s this same secretion that deters birds and mice to feed on these beetles, and leaves them to propagate their species in peace.
A male beetle courts a female by climbing on her back and sweeping his antennae across her head. If the male beetle is smaller than the female beetle, she refuses. When they do mate, they can stay attached to each other for hours, with some couples being observed to be attached for more than 24 hours. During this time, the female beetle goes about her business feeding from flower to flower with the male attached to her back.
Once they finish mating and separate, the female flies off to find a place where she can lay her eggs in the ground and she then promptly leaves them to their fate. Once these eggs hatch and turn into beetle grubs, they then burrow into the soil in search of food, which come in the form of grasshopper eggs. Sounds harsh for the little grasshopper babies, but bees may have it worse.
Other species of blister beetles have newborn larvae called triungulin. These triungulin pack themselves together by the hundreds to mimic the look of a female bee (they even smell like a female bee). When a male bee comes along to try to mate with fake bee, the triungulin then latch on to the male bee’s body and some of them get off when the male bee comes into contact with other actual female bees. Eventually these triungulin find their way to the bee’s nest where they feast on bee larva and their food. Other choice snacks include eggs of wasps and locusts.
If you find an infestation of these beetles on your property, call a professional exterminator to take care of them for you so you can remain blister free!