Chrysotus laxifacialus, 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 : 15-16

8. Chrysotus laxifacialus sp. nov.

( Fig. 8 )

Diagnosis. Face “X-shaped”, the narrowest portion at below middle, which is about as wide as width of tarsomere 5 (MSSC). Middle and lower postocular setae (including postero-ventral setulae) black. Antenna with first flagellomere subtriangular, nearly as long as wide. Proboscis dark, palpus dark tinged with brownish. Legs black, fore and mid tibiae brownish yellow but dark basally; hind tibia slightly brownish. Squama brown with black setulae. Halter pale, but black basally. Male terminalia with proximal portion of hypandrium without projections. Postgonite with strip-like arms and spearhead-like anterior process.

Description. Male: Body length 2.5 mm, wing length 2.3 mm. Head: Metallic green with pale gray pollinosity. Face widened both above and below, narrowest portion at below middle, about as wide as width of tarsomere 5. Setulae and setae on head black, middle and lower postocular setae (including postero-ventral setulae) black. Antenna with semicircular first flagellomere, nearly half as long as wide; arista black, short pubescence. Proboscis dark, palpus dark tinged with brown, with 1 black apical seta. Thorax: Dark metallic green with pale gray pollinosity. Setulae and setae on thorax black; 6 strong dc, 5–6 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: Black, fore and mid tibiae brownish yellow but dark basally; hind tibia slightly brownish; fore and mid tarsi from tip of tarsomere 1 onwards brownish black to black, hind tarsus black. Setulae and setae on legs black. Mid and hind coxae each with 1 outer seta. Fore femur with 3 pv apically; mid femur with 2 av and 2 pv apically; hind femur with 4 av apically. Fore tibia with 1 ad, apically with 3 short setae; mid tibia with 3 ad and 1 ventral, upper one short and weak, without pd, apically with 4 setae, hind tibia with no longer setulae on anterior face and with 2 ad and 4 pd, apically with 4 setae. Relative lengths of tibia and 5 tarsomeres of legs LI 73: 36: 20: 10: 10: 10; LII 90: 45: 25: 15: 10: 10; LIII 110: 30:25: 20:10: 10. Wing: Hyaline, veins brown; R4+5 and M1+2 parallel apically, CuAx ratio 0.3. Squama brown with black setulae. Halter pale, but with base black. Abdomen: Dark metallic green with pale gray pollinosity; setulae and setae on abdomen black. Male terminalia ( Fig. 8 ). Epandrium with angular projection posteriorly. Ventral projection of epandrium with angular end beyond level of distal margin of lateral epandrial lobe. Lateral epandrial lobe with concave distal margin, bearing 2 setae. Surstylus almost straight and pointed apically. Cercus gingko leaf-like, with pointed end; phallus slender. Hypandrium with ventral process, acute apically. Proximal portion of hypandrium without projection, with narrow portion. Postgonite with strip-like arms and spearhead-like anterior process, within epandrium. Female: Unknown.

Type material. HOLOTYPE ɗ, Guizhou: Chishui, Dagangou, 100 m, 28º32’N, 105º40.5’E, 27.III.2010, WP Cao.

Etymology. From the Latin lax “wide” and faci “facial”, meaning face is wider.

Remarks. Based on characters of the terminalia, the new species is closely related to C. xinanus , sp. nov., but differs as outlined in the diagnosis.

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 the lateral epandrial lobe with distal margin concave; hypandrium with only a ventral process acute apically.

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 8. Chrysotus laxifacialus sp. nov., male terminalia, left lateral view.