Saturday, September 29, 2012

Black Blister Beetle

This matte black beetle is a Black Blister Beetle (say that fast three times). These beetles are in the family Meloidae. They are quite common around here, especially in the fall. I find them frequently on the goldenrod around our farm. Some plants will have dozens of these beetles on them.Many of them are mating and creating mirror images of themselves for the next generation. With nearly 7500 species of blister beetles found throughout the world there is no shortage of these noxious bugs to be found. 

(This particular beetle seems to have an injury. Not sure what caused it. I can't imagine that anything would chose to feed on these beetles, but perhaps some predators don't mind the nasty taste. Or maybe the predator discovered the noxious taste after biting a wing off and decided that was enough)

 They have an elongated body with a very narrow thorax. This cylindrical shape is very typical of blister beetles. They are commonly found in  vegetable and flower gardens. Look for them near croplands, especially forage crops. The adults feed on a wide variety of foods like clover, alfalfa, soybean, radish, carrot, beans, cabbage. In the wild they will feed on pigweed. They also will feed on ornamental plants like Hostas. The black variety is especially fond of goldenrod. After mating, the females will lay eggs in clusters in the soil. After the larvae hatches it will seek out grasshopper eggs and young grasshopper nymphs that are beginning to surface from underground. Sometimes they will also feed on bee larva. This makes them an important natural control measure for these often time invasive insects. Blister Beetles aren't always the "good guy" however. They have a dark side. Blister beetles contain a chemical in their legs called cantharidin. This chemical is extremely toxic, especially to horses. The horses come in contact with the beetles in their feed. The beetles feed on alfalfa, then the horses also feed on the alfalfa. As few as 550 beetles can kill a young horse weighing 275 pounds. This chemical is also found in the controversial drug called "date rape drug". 

I myself have had a run-in with these beetles. Several summers ago we had 100's of these beetles all over our farm. They were in the gardens, in the flowers beds. They were feeding in large numbers on my hostas, and had nearly defoliated the hostas before the summer was over. At night they were around the pole lights. I also spent a lot of time near the pole lights, looking for bugs to photograph, or capture for my collection. One night I felt one of these beetles land on my neck, as I went to brush it off me it released some of this awful chemical and blistered my skin. This blister hurt for days and left a welt for over a week. These beetles mean business, this is chemical warfare at its finest.

These beetles are best looked at and not touched. They are common and easily found, some years there seems to be more of them, than other years. In the past two years I've not seen populations of them anywhere near like what I had several summers ago


  1. I'm always wary that that might happen when they are flying around the black lighting sheet and landing on me, getting caught in my hair...but 2012 wasn't a great year for any Epicauta sp. where I black light, though I saw them congregating on plants during the day. Never had any blisters, yet