Key to species of Medusapyga LaBonte and Maddison

Head with a declivous medial frontoclypeal prominence (Figs 1A, 7A); pronotum with sharp rectangular or acute hind angles (Fig. 8A); mesotrochanter with large, blunt, triangular tooth protruding from posterior margin (Fig. 13A); male visible abdominal ventrite 2 without medial preapical keel; aedeagus as in Figs. 11A, B .................................................. Medusapyga alsea LaBonte

Head with the frontoclypeal region gradually and shallowly convex (Figs 1B, 7B); pronotum with rounded hind angles (Fig. 8B); posterior margin of mesotrochanter more-or-less evenly arcuate (Fig. 13B); male visible abdominal ventrite 2 with a medial preapical keel which is sharply pointed and declivous at the posterior (Fig. 14); aedeagus as in Figs. 11C, D ................... Medusapyga chehalis LaBonte