Key to males of species of Condylostylus from Vietnam

1 At least mid and hind coxae brown or black (Figs. 1-3, 5-6); cercus not geniculate in shape (Figs. 13–15, 17)............ 2

- All coxae yellow (Fig. 4); cercus geniculate in shape (Fig. 16)................................... C. geniculatus Yang

2 Fore coxa yellow (Figs. 2, 6)............................................................................ 3

- Fore coxa black (Figs. 1, 3, 5)........................................................................... 4

3 Wing dark brown with distinct white opaque window (Fig. 8); fore coxa with numerous short setae on inner surface; cercus much elongated (7–8 times as long as epandrium), and without setose ventral process (Fig. 14)............................................................................................... C. damingshanus Wang, Zhu et Yang

- Wing brown to dark brown but without distinct white window (Fig. 12); fore coxa without such setae on inner surface; cercus rather short (little longer than epandrium), with short ventral process bearing long setae (Fig. 18)... C. vietnamensis sp. nov.

4 Cercus wide band-like or nearly finger-like (Figs. 13, 15); fore tarsomere 1 not flattened basally; all femora entirely black (Fig. 3), or at most with extreme tips of femora brownish yellow or brown (Fig. 1)...................................... 5

- Cercus expanded and hatchet-shaped (Fig. 17); fore tarsomere 1 basally flattened; all femora black with yellow apices (Fig. 5)..................................................................................... C. latipennis Parent

5 Cercus wide band-like, slightly shorter than epandrium, not extending much beyond apex of surstylus, without setose ventral mound (Fig. 13)...................................................................... C. conspectus Becker

- Cercus thin finger-like, slightly longer than epandrium, much extending beyond apex of surstylus, with distinctive setose ventral mound (Fig. 15)................................................................... C. fenestratus (Wulp)