What characters are used to determine species in this genus?

Overall appearance: Small size (abt. 6-9mm), dark color (often shiny black or dark brown in Nearctic species, w/black, brown, or yellowish legs), forewings with rounded apex (and often a pale hashmark at arculus).

Generic: 5-segmented maxillary palp with long 5th segment, forewing apical forks F1, F2, F3, and F5 present (F4 missing), discoidal cell short and wide with thickening of anterior tip (this usually causes conspicuous reflections in that area), spur formula 1,4,4 (though the short single spur on the front tibia is often not visible in many lateral photos).

Specific: Mostly characters of male terminalia (shape of claspers, aedeagus, and AB9 sternal projections). Characters for a few common species (obscura, socia, feria, atterima) can be found here.