Oil beetle (female)

The blister beetle genus Meloe is a large, widespread group commonly referred to as oil beetles. They are known as "oil beetles" because they release oily droplets of hemolymph from their joints when disturbed; this contains cantharidin, a poisonous chemical causing blistering of the skin and painful swelling. Members of this genus are typically flightless, without functional wings, and shortened elytra.
As in other members of the family, they are hypermetamorphic, going through several larval stages, the first of which is typically a mobile triungulin that finds and attaches to a host in order to gain access to the host's offspring. In this genus, the host is a bee, and each species of Meloe may attack only a single species or genus of bees; while sometimes considered parasitoids, it appears that in general, the Meloe larva consumes the bee larva along with its provisions, and can often survive on the provisions alone, thus they do not truly qualify. (information from Wikipedia)