Diostracus tibetensis, Wang, Ning, Wang, Baohai & Yang, Ding, 2015

Wang, Ning, Wang, Baohai & Yang, Ding, 2015, Two new species of the genus Diostracus Loew from Tibet, with a key to the Himalayan fauna (Diptera, Dolichopodidae), ZooKeys 488, pp. 91-104 : 96-100

Taxon classification Animalia Diptera Dolichopodidae

Diostracus tibetensis sp. n. Figs 7-8, 9-10

Diagnosis.

vt rather short and weak, 0.4 times as long as oc. First flagellomere somewhat quadrate, 1.3 times longer than wide; arista subapical (Fig. 9). Wing (Fig. 8) hyaline; crossvein m-cu medially distinctly bent with small round black nodule located at middle of crossvein. Fore coxa with bundle of short dense black anterior hairs bristle-like at extreme tip. Mid and hind femora with very long pale ventral hairs (longest ones about 3 times as long as femur thickness). Abdominal tergites 4-5 with lateral portion slightly extended downwards, only tergite 4 with very long lateral hairs.

Description.

Male. Body length 6.4 mm; wing length 7.6 mm.

Head metallic green with pale gray pollen. Eyes widely separated; face widened towards clypeus. Hairs and bristles on head black; lower postocular bristles including posteroventral hairs pale, mostly very long. Ocellar tubercle distinct, with pair of strong oc, without posterior hairs; vt rather short and weak, 0.4 times as long as oc, 0.7 times as long as pvt. Antenna (Fig. 9) black; scape without any dorsal hairs; first flagellomere short, somewhat quadrate, 1.3 times longer than wide; arista subapical, 3.9 times as long as first flagellomere, nearly bare. Proboscis blackish with pale hairs; palpus lobate, smoky black with black hairs.

Thorax metallic green with pale gray pollen; mesoscutum with two pairs of dark brown longitudinal spots (middle pair strip-like). Hairs and bristles on thorax black; 6 slightly long dc, posteriormost dc longest; acr bristles absent; 1 h and 1 short bristle, 1 ph, 2 npl, 1 sa, 1 psa; scutellum with pair of long sc and 4 very short marginal hairs (2 hairs between 2 sc). Propleuron with short pale hairs on upper portion and mostly long pale hairs on lower portion. Legs entirely black; claws well developed, empodium and pulvilli distinct. Hairs and bristles on legs black except those on coxae pale; fore coxa with bundle of short dense black anterior hairs bristle-like at extreme tip; hind coxa apically with 4 long blackish anterior hairs bristle-like. Mid and hind femora with some pale ventral hairs. Fore femur with two rows of black ventral bristles (longest ones slightly shorter than femur thickness), and with 3 long posterior bristles at extreme base. Mid femur basally with nearly two close rows of long pale ventral hairs (longest ones about 3 times as long as femur thickness), subbasally with 4 black short thick av. Hind femur with about two close rows of long pale ventral hairs (longest ones about 3 times as long as femur thickness) and with 5 black short thick av. Fore tibia with 4 ad and 4 pv on apical half; apically with 3 bristles. Mid tibia with 3 ad and 2 pd; apically with 3 bristles. Hind tibia with 4 ad, 5 pd, 3 av and 6 pv; apically with 3 bristles. Fore tarsomere 1 with row of short dense erect av spines and one row of dense thin pv (longer than av). Relative lengths of tibia and five tarsomeres: LI 3.3: 1.6: 1.6: 0.8: 0.55: 0.7; LII 5.8: 2.9: 1.1: 0.75: 0.5: 0.75; LIII 7.1: 3.2: 1.9: 1.2: 0.6: 0.8. Wing (Fig. 8) hyaline; veins dark brown, R4+5 and M convergent apically; crossvein m-cu medially distinctly bent with small round black nodule located at middle of crossvein. Squama brown with pale hairs. Halter brown to dark brown.

Abdomen rather short, nearly as long as head and thorax combined, metallic green with pale gray pollen. Abdomen with pale pubescence except dorsum with some black hairs at middle. Tergites 4 distinctly and tergite 5 weakly with lateral portion extended downward; lateral portion of tergite 4 with very long hairs apically bent, slightly shorter than those on sternite 3, but lateral portion of tergite 5 only with short hairs.

Male genitalia (Fig. 10): Epandrium relatively short, slightly longer than wide. Epandrial lobe weak, with 2 long bristles. Surstylus enlarged, with three acute denticles at apical margin. Hypandrium narrowed, bent; apically with a shallow, V-shaped apical incision and lateral lobe curled; basally with a hook-like process. Cercus straight, long finger-like, with long yellow hairs.

Female. Unknown.

Type material.

Holotype: male, China: Tibet, Nyingchi (N29°38'18", E94°21'46"), Sejilashan Mountain, Zhongshan Station, 4200 m, 20.VI.-10.VII. 2014, Malaise trap, leg. Baohai Wang and Zhaohui Pan (CAU).

Distribution.

China (Tibet).

Remarks.

The new species belongs to the unipunctatus -group. It is somewhat similar to Diostracus parvipunctatus Saigusa from Nepal in the shape of the first flagellomere and fore and mid femora with long ventral hairs, but may be separated from the latter in the following points: vt is shorter and weaker than pvt; the first flagellomere is shorter, 1.3 times longer than wide, and the abdominal tergite 5 has the short lateral hairs. In Diostracus parvipunctatus , vt is as strong as pvt or stronger; the first flagellomere is 1.5 times longer than wide ( Saigusa 1984, fig. 35), and the abdominal tergites 4-5 has the long yellow lateral hairs ( Saigusa 1984).

Etymology.

The specific name refers to the type locality Tibet.