1a. Eyes very small 2
1b. Eyes larger 3
2a. Tiny eyes with 5-6 omatidia; pronotum and head heavily scultpured; weakly shining; reddish-yellowish brown S. schmittii
2b. Large areas on thorax (especially on top of pronotum) clear of sculpturing and shiny in clear areas, rugae not parallel S. diecki
3a. Omatidia coarse: 4(5) facets in maximum diameter and generally < 15 omatidia total; pronotum completely covered by parallel rugae; modestly shining; small S. impar
3b. Omatidia finer: 7-8(10) facets in maximum diameter, and ~20 omatidia total; always dark brown; larger S. brevicorne
Reference: Smith, M. R. 1957. Revision of the genus Stenamma Westwood in America north of Mexico (Hymenoptera, Formicidae). American Midland Naturalist 57: 133-174.