Key to species of Nepalomyia from Taiwan (males)

1 Wing R2+3 and R4+5 with swollen bases............................... (N. trifurcata group) … N. siveci Wang & Yang

- Wing R2+3 and R4+5 normal, not swollen basally............................................................. 2

2 Hypandrium asymmetrical in ventral view (Fig. 8)................... (unknown species group) … N. xiaoyanae sp. nov.

- Hypandrium symmetrical in ventral view................................................................. 3

3 Hypandrium trifurcated, cercus without distinct basal tubercle (Fig. 5)........................ N. pallipilosa group … 4

- Hypandrium bifurcated, cercus with distinct basal tubercle(s).............................. N. henanensis group … 5

4 Hind first tarsomere strongly thickened; cercus with basal hairs................ N. nantouensis Wang, Yang & Masunaga

- Hind first tarsomere not thickened; cercus lacking basal hairs (Fig. 5)........................ N. orientalis (Yang & Li)

5 First flagellomere about 4–5 times longer than wide; hypandrium with narrow base and wide apex. N. horvati Wang & Yang

- First flagellomere wider than long; hypandrium with wide base and narrow apex................................... 6

6 Halter dark brown; cercus with weak basal and distinct middle tubercles................... N. taiwanensis Wang & Yang

- Halter yellow; cercus with distinct basal tubercle and no middle tubercles (Fig. 2)........ N. brevifurcata (Yang & Saigusa)