Blister beetles are phytophagous (plant-eating), feeding on a variety of plants including cultivated crops like potatoes and tomatoes. Their larvae feed on grasshopper eggs and a few such as the Nuttall Blister Beetle (Lytta nuttalli) attack bee larvae or feed on bee eggs and the food stored in the cells with the eggs.
The common name blister beetles come from the fact that these beetles can release a yellow oily liquid from the joints of the legs and this liquid (called cantharadin) can cause blisters if it contacts human skin. This defensive tactic is called reflex bleeding.
Blister beetles go through what is called hypermetamorphosis which means they change not only from a larval form into a different looking adult form but also during their live as a larva. They start as a sleek, host-seeking larvae and become a plump couch potato once they locate a host.