Systenus basiflavus, Lin & Zhang & Yang, 2023

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 : 156-158

2. Systenus basiflavus sp. nov.

( Figs 2 , 9–10)

Diagnosis. Antenna brownish except scape and pedicel dark yellow; postpedicel 3.3 times longer than wide, with slightly thick portion at base. Fore and hind coxae yellow, but mid coxa dark brown. Surstylus geniculate with a finger-like dorsal process near base. Male cercus apically bifurcated with dorsal lobe slightly shorter than ventral lobe.

Description. Male ( Fig. 2 ). Body length 2.58–2.7 mm, wing length 2.33–2.5 mm.

Head metallic green with pale gray pollinosity. Frons metallic green with white gray pollinosity; face dark metallic green with dense silvery white pollinosity, nearly as wide as the width of postpedicel. Hairs and bristles on head black, but postocular bristles yellowish. 2 oc, 2 vt, 2 pvt. Antenna [aristal apical segment broken] brownish except scape and pedicel dark yellow; pedicel with black apical bristles; postpedicel elongated, 3.3 times longer than wide, basally rather thick, apically distingtly narrowed, with dense dark brown pubescence (Fig. 9). Proboscis short, brownish yellow with short yellow hairs; palpus small, dark yellow with short yellow hairs.

Thorax metallic green with pale gray pollinosity, but pleura blackish to black. Hairs and bristles on thorax black; 6 dc; 8 irregularly paired acr; 2 strong npl, 1 strong sa, 2 strong pa; sc long and strong, lsc short and hair-like. Propleuron with 1 brown bristle on lower portion.

Legs [fore tarsus and hind tarsomeres 2–5 broken] mainly yellow; fore and hind coxae yellow, but mid coxa dark brown. Hairs and bristles on legs black. Fore coxa with dark yellow hairs and bristles; mid coxa with blackish hairs and bristles; hind coxa with dark yellow hairs and 1 black outer bristle at middle. Hind trochanter with 1 black bristle. Mid tibia with 1 very long ad, 3 pd (one is strong at the base, the other two are weak), and 2 apical bristles (one is strong, the other is weak). Hind tibia with 5 pd and 2 apical bristles. Mid tarsomeres 1–3 each with 1 av at middle, tarsomeres 1–4 each with 4 apical bristles. Relative length of tibiae and five tarsomeres of legs LI 3.5: distal podomeres missing; LII 4.2: 2.0: 1.5: 1.0: 0.6: 0.4; LIII 5.5: 1.2 distal podomeres missing

Wing nearly hyaline; veins dark brown; R 4+5 and M 1 widened at first, then convergent apically; CuAx ratio 0.4. Squama yellow with blackish hairs. Halter pale yellow.

Abdomen dark metallic green with pale gray pollinosity, venter dark yellow; tergum 1 brown, but dark yellow laterally; tergum 2 dark yellow at basal margin and lateral portion; tergum 3 dark yellow at anterolateral portion. Hairs and bristles on abdomen black.

Male genitalia (Fig. 10): epandrium longer than wide; epandrial lobe thick with weakly narrow tip; surstylus geniculate with a finger-like dorsal process near base and a short obtuse denticles at extreme tip. Cercus basally slightly thick, apically bifurcated with dorsal lobe slightly shorter than ventral lobe. Hypandrium long finger-like. Phallus slightly thick, but apically narrowed and bent.

Female. Unknown.

Type material. HOLOTYPE ♂, China: Yunnan, Lvchun, Yakou, Shuikuxiafang [23°3’25.2”N, 102°46’37.71”E, 1779 m], collected by Malaise trap, 2019.IV.19–V.19, Liang Wang and Xin Li ( CAU) . PARATYPE: 1 ♂, same as holotype except, 2019.III.19–IV.19 ( CAU) .

Remarks. Systenus basiflavus sp. nov. is somewhat similar to S. digitatus sp. nov. in having the postpedicel distinctly elongated and surstylus elongated with a small dorsal process near base among Asian species, but can be easily separated from the latter by the following features: antennal scape and pedicel dark yellow; surstylus geniculate with a long finger-like dorsal process near base directed backward; cercus bifurcated apically.

Distribution. China (Yunnan).

Etymology. The specific name refers to the antenna dark yellow at base.

Figures

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.