Isonychia, Eaton, 1871

Muthukatturaja, M., Balasubramanian, C., Rathinakumar, T. & Sivaramakrishnan, K. G., 2021, A new species of Isonychia Eaton, 1871 (Ephemeroptera: Isonychiidae) from Kapila River, Central Western Ghats, India, Zootaxa 4908 (2), pp. 283-291 : 289

Key to the known male imagoes of Oriental Isonychia (excludes I. khyberensis)

1. Wings light brown, shiny, with dark brown veins ( Ulmer, 1912)................................ Isonychia formosana

- Wings transparent.................................................................................... 2

2. Abdomen red, the postsegmental margins of all tergites and those of the first five sternites pitch black; the following sternites somewhat lighter ( Ulmer, 1913)............................................................ Isonychia grandis

- Abdomen reddish brown; postsegmental margins of terga V–VI pitch black; sterna pale yellow....................... 3

3. Peneal lobe distinctly separated.......................................................................... 5

- Peneal lobe not distinctly separated....................................................................... 4

4. Penes without serrations or large spines and with distal angles rounded, length relatively equal to gonostyli pedestals ( Vasanth et al., 2019)......................................................................... Isonychia moyarensis

- Anterolateral margins of penes rounded with scattered barbs on dorsal surface; penes relatively short, reaching ½ of gonostyli pedestals.......................................................................... Isonychia radhae n. sp.

5. Pterostigma dark brown ( Ulmer, 1939)...................................................... Isonychia winkleri

- Stigmatic area dull white (Hsu, 1936).................................................. Isonychia kiangsinensis