Key to species (males) of Systenus from China

1 Antenna with very long postpedicel, 5–6 times longer than wide and very long arista (Yang et al. 2011, fig. 271a; Lin & Yang 2022, fig. 1B)........................................................................................ 2

- Antenna rather short with short, thick postpedicel, at most 4 times longer than wide and rather short arista (Figs 7, 9, 11, 13, 15, 17)................................................................................................. 3

2 Arista with terminal flag (Yang et al. 2011, fig. 271a); R 4+5 and M 1 weakly convergent apically (Yang et al. 2011, fig. 271b); cercus simple, finger-like (Yang et al. 2011, fig. 271c).................................. S. sinensis Yang et Gaimari

- Arista simple (Lin & Yang 2022, fig. 1B); R 4+5 and M 1 strongly convergent apically (Lin & Yang 2022, fig. 1A); cercus basally short and thick with long finger-like apical process (Lin & Yang 2022, fig. 1E)................ S. jinxiuensis Lin et Yang

3 Wing hyaline, without dark apical band; R 4+5 and M 1 convergent apically; abdominal segment 7 not petiolate............ 4

- Wing with wide grayish brown apical band (Fig. 6); R 4+5 and M 1 parallel apically; abdominal segment 7 petiolate.......................................................................................... S. latimaculatus sp. nov.

4 Postpedicel 4.0 times longer than wide; cercus strongly bent (Figs 7, 15)......................................... 5

- Postpedicel at most 3.3 times longer than wide (Figs 9, 11, 13, 17); cercus more or less straight....................... 6

5 Antenna wholly dark brown; R 4+5 and M 1 weakly convergent apically; cercus basally slightly thick, apically with long thick ventral process (Fig. 16).............................................................. S. huanglianus sp. nov.

- Antennal two basal segments dark brownish yellow; R 4+5 and M 1 strongly convergent apically; cercus basally very thick, apically with short thin ventral process (Fig. 8)........................................... S. apicidigitatus sp. nov.

6 Postpedicel distinctly elongated, 3.0–3.3 times longer than wide, arista apical (Figs 9. 11); thoracic pleura wholly metallic green; surstylus elongated with a small dorsal process near base................................................ 7

- Postpedicel short and wide, 2.0 times longer than wide, arista subapical (Fig. 13); thoracic pleura mostly dark yellow (Fig. 4); surstylus short and thick without dorsal process near base................................... S. flavilateralis sp. nov.

7 Antennal scape and pedicel dark yellow; postpedicel 3.3 times longer than wide, basally slightly thickened (Fig. 9); surstylus geniculate with long finger-like dorsal process near base directed backward (Fig. 10); cercus bifurcated apically.............................................................................................. S. basiflavus sp. nov.

- Antenna wholly blackish; postpedicel 3.0 times longer than wide, basally rather thickened, apically finger-like (Fig. 11); surstylus nearly straight with very short dorsal process directed forward (Fig. 12); cercus not furcated apically................................................................................................ S. digitatus sp. nov.