Normally when I see spotted cucumber beetles (Coleoptera: Chrysomelidae: Diabrotica undecimpunctata) they’re crawling all over various crop plants here in the fields of southeast Michigan. These insects are major pests of cucumbers, squash, melons, and other cucurbits as well as soybeans and corn. The larvae are even referred to as corn rootworms. Although the larvae are responsible for much of the damage, the adults feed primarily on these plants as well.
A couple of weeks ago, however, I found the beetle above feeding on a thistle flower (Cirsium sp., Asteraceae) at Pinckney State Recreation Area near Chelsea, Michigan. It may have been lost and hungry or simply adventurous, because thistles don’t seem to be common hosts for these insects.
Unlike most other nectar-feeding insects, this beetle wasn’t feeding in the traditional manner through the opening of the flower. Instead it was chewing away at the bases of the flowers, a behavior known as nectar robbing.