"blister beetle:any of various soft-bodied beetles of the family Meloidae, such as the cantharis, that secrete a substance capable of blistering the skin."
So there's lots of speculated reasons, but we still don't have definitive answers as to for one particular species of beetle why it's this way versus another species.
On Wednesdays, I waxed the lobby floors with a substance that smelled like beetle dung, which shined up those floors like nothing else I had ever seen.