Rove Beetle

This is a very tiny Rove Beetle, 4 mm long, so small I wasn't even sure what it was without magnification. It is unusual in having a barrel shaped abdomen and elbowed antennae. The first pair of tibiae are somewhat enlarged and fringed with long bristles. I would love to know what they are used for! I think this might be a species of Bledius, because of its barrel shape, antennae and because the elytra are as wide as they are long. The beetle is black with reddish elytra, best seen in the second picture. Family Staphylinidae.