This week was warm enough to go insect hunting in the yard, so the Friday beetle is back with new material.  I snapped a few shots of this little staphylinid under a brick, figuring I’d identify it later.

That turned out to be a more complicated process than I’d anticipated. It’s a member of the the subfamily Aleocharinae, the obscure rove beetles. To arrive at an identification any more specific than that is basically impossible. The late James Ashe wrote:

The seemingly endless diversity, the small size of most adults, and the virtual lack of illustrated keys and descriptions of aleocharines for most geographical regions make the Aleocharinae one of the most taxonomically difficult groups of beetles. For example, Casey (1906, 1911), who described most North American aleocharines, did not provide keys to most taxa, and recent comprehensive identification guides (Arnett 1968, Moore and Legner 1974, 1979) did not provide keys to aleocharine genera. Consequently, it is virtually impossible for a specialist in the Staphylinidae to identify the vast majority of aleocharines from most geographic regions even to genus, much less to species…

What’s particularly frustrating about this taxonomic situation is that it can’t really be avoided.  Aleocharines are common beetles, and there are more than 1,000 species of them on our continent. That is, there are more obscure rove beetle species than there are bird species, but without the array of field guides.update: Thanks to commentator Adam Brunke, we learn that this mystery rove beetle is Apocellus, in the Oxytelinae rather than the Aleocharinae.

Photo details (all): Canon MP-E 65mm 1-5x macro lens on a Canon EOS 50D
ISO 100, f13, 1/250 sec, flash diffused through tracing paper