A type of Blister beetle. When threatened or squeezed under pressure, they emit a chemical called cantharidin that creates blisters and irritates human skin. These wounds will heal, but they are painful. This chemical defense can ward off predators and give the beetle time to escape.
American Oil Beetles have a soft, yet stout abdomen with a shell covering that looks like a series of overlapping plates. The insect can appear as a dull black or, in some cases, a shiny black or dark blue. The surface texture is slightly bumpy, not slick and smooth. Antennae are visible on the head.
These particular beetles do not fly and are slow movers. Adults can be found gingerly walking around plants they eat, such as buttercups, and in grass. They are active all year, but more so in the spring, when they are more likely to be seen. The larvae are somewhat devious. One will sit on flowers, waiting for a bee to land. It will latch onto the bee for a free ride back to the hive. Once there, the beetle larva feeds on the same food as the bee larvae. It will pupate safely inside and emerge in the spring.