This oil beetle (tsuchihanmyou) was sitting on my doorstep when I came home last night. As you can see in the first photo, it played dead when I first picked it up.
Oil beetles are fascinating insects, and not just because of their unusual appearance (short elytra exposing most of the abdomen). They contain a poison (cantharin) in their hemolymph, which exudes from their leg joints when they are handled, and this substance causes skin blistering in humans (link to image), so these insects are also known as blister beetles. The same chemical (but extracted from other species) has been used for centuries as an aphrodisiac (spanish fly ointment) and is contained in wart removal products.
Another interesting point about the oil beetle is that it is parasitic on small solitary bees (hanabachi). The very active beetle larva (known as a tringulin) waits in a flower for a bee to visit, then clings onto the bee’s leg and gets carried to the nest, where it feeds on the bee’s eggs and store of pollen. For more information on the oil beetle’s fascinating life cycle, please read this. For information in Japanese, please look here.
Coleoptera: Meloidae: Meloe coarctatus (hime tsuchihanmyou)
(I hope this identification is correct)
This is a male (see the pronounced bulge in the antenna)