Friday, September 16, 2011

horses beware




Margined blister beetle, Epicauta pestifera



Cantharidin. Can-thar-i-din. 

It's a poisonous chemical, a bitter crystalline compound that causes blistering of the skin and is often used medially to remove warts. Should you need to mix up a batch of the blistering agent in your basement, it's C10H12O4 or ten parts carbon, twelve parts hydrogen and four parts oxygen, hold the mayo. 

Naturally occurring, cantharidin is a toxic oily liquid secreted by blister beetles when they are threatened, picked up or forced to watch a movie like any of the Smokey and the Bandit offerings. Sally, what were you thinking?

There are approximately 7,500 known species worldwide, so there's a lot of blistering going on out there. The one I encountered and photographed was ash gray, but other species are brightly colored, announcing their toxicity to would-be predators.

The blister beetle genus Epicauta—and the one I found with Rikki Hall and a group from Ijams is perhaps Epicauta pestifera, the margined blister beetleis generally found in farm fields. Their larvae feed on the eggs of grasshoppers, which I would imagine are enormously hard to find but I'm not a blister beetle larva. I have trouble finding my keys every morning.

As adults, blister beetles are highly toxic to horses. A few consumed in a single feeding of alfalfa hay may be lethal. So if you follow this blog and are fond of eating alfalfa, beware.

1 comment:

Rikki Hall said...

Another blister beetle common locally, Epicauta vittata, is yellow-orange with longitudinal black stripes. It's a plant feeder and can be a serious garden pest. They mobbed the bush beans in my garden this year and also attacked tomato plants that had been weakened by disease.

They are especially tough for organic gardeners since hand-picking is not an option. Soap spray on the leaves does deter them.