1. Ventral cleft of metathorasic (hind) femur usually with 6 or more marginal stout spines at both or at least on one leg (Fig. 1.1). . . . . . . . . . . . . . . . . . . . . . . . . Isonychia bicolor
Ventral apical cleft of metathorasic femur usually with 5 or fewer stout marginal spines. . . . (Fig. 1.2); however, some may have 6-7 on one side (see note). . . . . . . . Isonychia rufa
Note: McCafferty, et al., 2017 state that "larvae of I. bicolor and I. rufa cannot be separated confidently." "Rearing larvae to the more reliable identifiable adults is required for the most confident species diagnosis."
Key to Ohio Isonychia Nymph Species