Scydmaeninae are best recognized by their habitus (Fig. 1.5.1) and small size (2.5mm or less) (Fig. 9.18.1), but some are similar to Pselaphinae and even some Omaliinae in which the elytra nearly cover the abdomen. However, pselaphines always have short elytra and those Omaliinae with elytra nearly reaching the abdominal apex are always much larger than 2.5mm and possess ocelli.

Scydmaeninae are widely distributed in North America and can be found in leaf litter, rotting logs and stumps, in treehole debris, moss, and under stones (Fig. 9.18.2). Some species are associated with ant colonies, but are probably preying upon other arthropods rather than the ants themselves (O’Keefe 2000). They are common locally (Campbell and Davies 1991) but, due to their small size, they are most often collected when deep pockets of damp litter or moss are processed in a Berlese funnel. Until recently, the Scydmaeninae were considered their own family within Staphylinoidea but are now placed within the staphylinine group of subfamilies in Staphylinidae (Grebennikov and Newton 2009). Scydmaenines are predators of orbatid mites (O’Keefe 2000), and some use their modified mandibles like a can-opener on the genital and anal plates of their prey (Schmid 1988).