In late September I found this strikingly-colored rove beetle (Coleoptera: Staphylinidae: Paederus sp.) in an old field/prairie environment here in southeast Michigan. Rove beetles can be identified in part thanks to their notably short elytra. In beetles, these modified forewings look like hard shells that cover their hind wings, which are used for flight. In the photo above the elytra are the large black anatomical structures on the middle of the animal.
Several species of beetles in this particular genus contain a toxic chemical in their hemolymph (“blood”) called paederin. If a person crushes one of these beetles on their skin, this chemical can cause a condition known as paederus dermatitis.