Black Blister Beetles

On Saturday I was at Fairview Farm in Somerset County to look for odonates and butterflies. As I passed through one of the meadows, I noticed that the goldenrod plants were covered with black beetles. Upon closer examination, they turned out to be blister beetles, most likely Black Blister Beetles (Epicauta pennsylvanica), which are common on goldenrod in the late summer.

Blister beetles are so-called because they secrete a toxin called cantharidin as a defensive mechanism when they are threatened. Contact with cantharidin can cause blistering of the skin; ingestion can cause renal damage or even death. For this reason, it is best to avoid touching blister beetles directly. If you must move one, capture it in a container and move it that way. Fortunately, their distinctive shape makes blister beetles easy to recognize.