The first description of the nymph of Potamanthodes macrophthalmus You, 1984 and reinstatements of the genera Potamanthodes Ulmer, 1920 and Stygifloris Bae, McCafferty, and Edmunds, 1990 (Ephemeroptera: Potamanthidae)

The Chinese endemic mayfly Potamanthodes macrophthalmus You, 1984 is the single species relating the taxon Potamanthodes Ulmer, 1920 to other generic taxa of the family Potamanthidae because it has larger compound eyes and longer penes than congeners. However, its nymphs remained unknown and its detailed imaginal morphology is incomplete until now. Upon newly collected materials and type specimens, the main diagnostic characters of its nymph, which is described for the first time here, are revealed. This includes relatively large eyes, tiny mandibular tusks and remarkable body colour pattern. In imaginal stage, besides longer penes and larger eyes, the blunt apex of penis and shape of bent R-1 vein of hindwing are additional recognisable characters. Taxonomically, Potamanthodes presents unique characters, such as MP2 originating at base of CuA in forewing, partially pigmented forewings, acute costal projection on hindwings of imagoes and bristle-like setae row on nymphal forefemora. Therefore, Potamanthodes and Stygifloris Bae, McCafferty, and Edmunds, 1990 stat. rev. are reinstated as genera in this study.