Systenus, Loew, 1857

Lin, Chen, Zhang, Chunmin & Yang, Ding, 2023, The genus Systenus Meigen, 1803 (Diptera: Dolichopodidae) from Yunnan, China, with descriptions of six new species, Zootaxa 5383 (2), pp. 153-166 : 154

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.

Figures

FIGURES 7–8. Systenus apicidigitatus sp. nov. (male). 7. Antenna; 8. Male genitalia, lateral view. Scale bar = 0.1mm. Abbreviations: hyp = hypandrius, ph = phallus, epl = epandrial lobe, sur = surstylus, cer = cercus. FIGURES 9–10. Systenus basiflavus sp. nov. (male). 9. Antenna; 10. Male genitalia, lateral view. Scale bar = 0.1mm.

FIGURES 1–6. 1. Systenus apicidigitatus sp. nov.; 2. Systenus basiflavus sp. nov.; 3. Systenus digitatus sp. nov.; 4. Systenus flavilateralis sp. nov.; 5. Systenus huanglianus sp. nov.; 6. Systenus latimaculatus sp. nov. All male. Scale bar =1.0mm.

FIGURES 15–16. Systenus huanglianus sp. nov. (male). 15. Antenna; 16. Male genitalia, lateral view. Scale bar = 0.1mm. FIGURES 17–18. Systenus latimaculatus sp. nov. (male). 17. Antenna; 18. Male genitalia, lateral view. Scale bar = 0.1mm.

FIGURES 11–12. Systenus digitatussp. nov. (male). 11.Antenna; 12. Male genitalia, lateral view.Scale bar = 0.1mm. FIGURES 13–14. Systenus flavilateralis sp. nov. (male). 13. Antenna; 14. Male genitalia, lateral view. Scale bar = 0.1mm.