Margined Blister Beetle

Subject: Beetles skeletonizing my hostas
Location: St. Louis, MO
July 14, 2012 5:15 pm
Hi bugman! My hostas are being skeletonized by what looks to me like a blue firefly (lightning bug, for keyword searching).
At first I thought slugs but the hostas are *covered* in these bugs and they also appear to be dropping some eggs or something on the leaves as well.
Any help would be appreciated!
Signature: baffled by beetles

Margined Blister Beetle

Dear baffled by beetles,
You are not as baffled as your signature indicates because you did deduce that this is a beetle.  More specifically, it is a Margined Blister Beetle,
Epicauta funebris, which you can verify on BugGuide.  What you believe to be “eggs or something” are the droppings of the beetles which as your letter indicates are voracious eaters.  You should exercise caution with Blister Beetles.  Though they do not bite nor sting, they do release a compound known as cantharidin from their joints that can cause blistering in human skin.

Droppings from Margined Blister Beetles

Thanks! I didn’t expect a reply so soon. I did look at quite a few
photographs and figured it had to be a beetle based on those but just
couldn’t find the right category to browse. I appreciate the very
timely response!
~baffled by beetles

2 thoughts on “Margined Blister Beetle”

  1. I have these margined blister beetles in my garden for the first time ever. I have grown tomatoes every year and never seen this pest. They are swarming my tomatoes and stripping the foliage. My tomatoes are staked with steel fence posts and banging on the posts vibrates the whole plant and they fall off. However they seem quite happy to invade the mulch below to hide. Hand picking is not achieving control as a new swarm soon arrives. What are the effective and practical control methods for these. I would like to save this year’s tomato crop and also prevent the problem in the future. That probably means two different control methods, and I need to know methods in both of those categories. So far they have not seemed to attack any of the other crops in my garden. We never found any on the potatoes which are the same “family” as potatoes and that garden plot is separate bot only 25 feet away.

    • We do not provide extermination advice. If you figure out a good method, please write back so that the information can help our readership.


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