Chrysotus trapezinus, Wei, Lianmeng & Zhang, Lili, 2010

Wei, Lianmeng & Zhang, Lili, 2010, A taxonomic study on Chrysotus Meigen (Diptera: Dolichopodidae) from southwest China: descriptions of eleven new species belonging to the redefined C. laesus - group, Zootaxa 2683, pp. 1-22 : 18-20

10. Chrysotus trapezinus sp. nov.

( Fig. 10 )

Diagnosis. Eyes separated on face. Postocular setae black. Proboscis blackish brown, palpus blackish brown. All coxae black, femora black, base of tibiae brown. Squama pale with brown setulae. Halter pale. Male terminalia with cercus ax-like. Hypandrium with a ventral process bearing ridges.

Description. Male: Body length 2.2 mm, wing length 2.0 mm. Head: Metallic green with pale gray pollinosity; eyes contiguous on face. Setulae and setae on head black, postocular setae black. Antenna black; first flagellomere nearly trapezoidal ( Fig. 10 B). Proboscis blackish brown with black setulae; palpus blackish brown with 1 black apical seta. Thorax: Dark metallic blue green with pale gray pollinosity. Setulae and setae on thorax black; 6 strong dc, 8 irregularly paired acr short and setula-like; scutellum with 2 pairs of setae, basal pair short and setula-like; propleuron with 1 black setula and 1 black seta on lower part. Legs: Yellow, all coxae black, femora black; base of tibiae brown; fore and mid tarsi from tip of tarsomere 1 onwards brown to blackish brown, hind tarsus blackish brown, tarsomere 1 dark yellow basally. Setulae and setae on legs black. Mid and hind coxae each with 1 outer seta. Fore femur with 2 pv apically, hind femur with 3 av apically. Fore tibia with 1 ad, apically with 3 short setae; mid tibia with 2 ad, apically with 4 setae; hind tibia with 2 ad and 4 pd, apically with 4 setae. Relative lengths of tibia and 5 tarsomeres of legs LI 62: 32: 16: 12: 9: 8; LII 80: 40: 20: 15: 10: 9; LIII 85: 27: 22: 15: 10: 8. Wing: Hyaline, veins brown; R4+5 and M1+2 parallel apically, CuAx ratio 0.25. Squama pale with brown setulae. Halter pale. Abdomen: Dark metallic green with pale gray pollinosity; setulae and setae on abdomen black. Male terminalia ( Fig. 10 A). Epandrium with angular projection posteriorly. Ventral projection of epandrium with end pointed, clearly withdrawn back from level of distal margin of lateral epandrial lobe. Lateral epandrial lobe wide and short, arched apically, bearing 2 setae. Surstylus distinctly curved. Cercus ax-like, small, with setae. Hypandrium with ventral process bearing ridges. Proximal portion of hypandrium with projection. Postgonite with two strip-like arms and anterior process, about as long as arms length, and projections slightly beyond epandrium. Female: Unknown.

Type material. HOLOTYPE ɗ, Guizhou: Zhenning, Bahe, 1100 m, 28.VI.2008, LM Wei, SG Jiang, WP Chao, MH Liu and QL Xiao. PARATYPE: 1 ɗ, same as holotype.

Etymology. From the Latin trapeza “trapeze”, meaning shape of first flagellomere is nearly trapezoidal.

Remarks. Based on the male terminalia, the new species is very similar to C. xinanus sp. nov., but the first flagellomere of C. trapezinus is nearly trapezoidal, end of ventral projection of epandrium not extending beyond the level of the apical margin of the lateral epandrial lobe, cercus ax-like and the apical ventral process of the hypandrium with ridges.

According to the key of Negrobov et al. (2000), the new species will run to C. nudisetus Negrobov et Maslova, 1995 , but can be separated from the latter by ventral projection of epandrium clearly withdrawn from level of distal margin of lateral epandrial lobe; hypandrium with only a ventral process bearing ridges.

Based on the key of Becker (1922), the new species will run to couplet 3, but differs from all species under the couplet by blackish brown femora and yellowish brown tibiae.

Figures

FIGURE 10. Chrysotus trapezinus sp. nov. (A) male terminalia, left lateral view; (B) male first flagellomere, lateral view.