Key to the species of Ctenosciara in China (males)

1. Wing vein CuA2 with setae ........................................................................................................................................... 2

- Wing vein CuA2 bare ............................................................................................................... C. japonica Sutou & Ito

2. R1, R5, M1, and M2 with both ventral and dorsal setae (Fig. 1 D) ................................................. C. mutisetosa sp. nov.

- R1, M1, and M2 without ventral setae (Fig. 2 D, 3D, 4D)............................................................................................... 3

3. Tegmen as long as broad, quadrangular (Fig. 4 E). R5 with dorsal and ventral setae on the apical half (Fig. 4 D) ......... ..................................................................................................................................................... C. xijingensis sp. nov.

- Tegmen longer than broad, apically rounded (Fig. 2 E, 3E). R5 with dorsal and ventral setae only on the apical third or along its entire length (Fig. 2 D, 3D)......................................................................................................................... 4

4. R5 with dorsal and ventral setae only on the apical third (Fig. 2 D). Gonostylus with four subapical megasetae (Fig. 2 F) ......................................................................................................................................... C. pseudoinsolita sp. nov.

- R5 with dorsal and ventral setae along its entire length (Fig. 3 D). Gonostylus with 5–8 subapical megasetae (Fig. 3 F) ...................................................................................................................................................................................... 5

5. Apex of gonostylus attenuated (Fig. 3 E) ................................................................................... C. rufulenta (Edwards)

- Apex of gonostylus not attenuated, almost equally wide along entire length ........................ C. hyalipennis (Meigen)