Key to the species of Japanese Acerocnema (male and females)

1. R 1 of wing with dorsal setulae on apical portion............................................................. 2

- R 1 of wing without dorsal setulae on apical portion........................................................... 3

2. Prescutum, scutum and scutellum mostly grey microtrichose, with a pair of shiny stripes on scutum (Fig. 1); male surstylus anterodistally dilated (Fig. 4)............................................................... A. incisa sp. nov.

- Prescutum, scutum and scutellum mostly shiny; male surstylus sinuate and tapering apically (see Iwasa (2014, figs 13, 14))........................................................................................ A. sinuata Iwasa

3. Frons yellow; scutum longitudinally with a central grey microtrichose band; male surstylus filiform (see Iwasa (2014, figs 8, 9)).................................................................................. A. flavifrons Iwasa

- Frons black; scutum wholly shining; surstylus clavate (see Iwasa (2014, figs 2, 3))................ A. kishimotoae Iwasa