Diostracus acutatus, 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

Taxon classification Animalia Diptera Dolichopodidae

Diostracus acutatus sp. n. Figs 1-3, 4-6

Diagnosis.

vt rather short, 0.5 times as long as oc. First flagellomere somewhat triangular, 1.5 times longer than wide; arista apical (Fig. 4). Fore tarsomere 1 distinctly shortened, thickened, concave ventrally, and with a nearly acute apicoventral process; tarsomere 2 basally bent, concave ventrally, and with a short finger-like ventral process near extreme base (Figs 2, 5). Crossvein m-cu much elongated, strongly bent (Fig. 3).

Description.

Male. Body length 8.0 mm; wing length 8.5 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 long strong oc, without posterior hairs; vt rather short, 0.5 times as long as oc, nearly as long as pvt. Antenna (Fig. 4) black; scape without any dorsal hairs; first flagellomere subtriangular, 1.5 times longer than wide; arista apical, 4 times as long as first flagellomere, nearly bare. Proboscis blackish with pale hairs; palpus lobate, 3.5 times as long as broad, produced far beyond apex of proboscis, blackish with a purple luster, and 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 mostly hair-like dc except posteriormost 1 dc longest and thick; acr absent; 1 h and 1 very short hair, 1 ph, 2 npl, 1 sa, 1 psa; scutellum with pair of long sc. Propleuron with short pale hairs on upper portion and long pale hairs on lower portion. Legs nearly entirely black except fore trochanter dark yellow; claws well developed, empodium and pulvilli reduced. Fore trochanter elongated, with hook-like posterior process (Fig. 2). Fore femur distinctly thickened (Fig. 2). Mid femur slightly bent, somewhat flattened dorsoventrally. Fore tibia slightly thickened, weakly curved (Fig. 2). Fore tarsomere 1 distinctly shortened, thickened, concave ventrally, and with a nearly acute apicoventral process; tarsomere 2 basally bent, concave ventrally, and with a short finger-like ventral process near extreme base (Figs 2, 5). Hairs and bristles on legs black except those on coxae pale; fore coxa with group of long pale anterior hairs at base; hind coxa apically with 2 brownish anterior bristles. All femora somewhat bare ventrally, with only very short, sparse pale ventral hairs, except fore femur with 3 distinct pale av hairs basally. Mid femur with 3 anterior bristles on apical 1/3. Fore tibia with 4-5 ad and 1 posterior bristle at apical 1/3. Mid tibia with 3 pd, and with very long posterior hairs on apical 1/5 somewhat curved; apically with 1 short spine-like av. Hind tibia with 5 ad and 4 pd; apically with 1 ad. Relative lengths of tibia and five tarsomeres: LI 3.7: 0.7: 2.2: 1.35: 0.7: 0.75; LII 7.1: 3.7: 1.4: 0.9: 0.45: 0.65; LIII 7.6: 3.6: 2.1: 1.1: 0.5: 0.7. Wing (Fig. 3) hyaline, indistinctly tinged grayish; veins dark brown, R4+5 and M convergent apically; crossvein m-cu much elongated, strongly bent, margined with black on long anterior portion, and with blackish spot at short posterior portion. Squama brown with pale hairs. Halter brown.

Abdomen distinctly longer than head and thorax combined, metallic green with pale gray pollen. Abdomen with pale pubescence. Tergite 5 with lateral portion slightly extended downward. Sternite 1 with a nearly acute process at middle; sternite 4 medially with an obtuse anterior process and 2 short thin, contiguous posterior processes bearing bundle of brown hairs. Hypandrium not distinctly swollen.

Male genitalia (Fig. 6): Epandrium slightly longer than wide. Epandrial lobe short thick, finger-like, weakly bent, with an acute basal process; 1 slightly long bristle present at middle and 1 short thick bristle at tip. Surstylus short thick, apically furcated, with 1 very short apical denticle bearing 1 very short spine-like bristle. Hypandrium short thick, apically with a shallow, V-shaped apical incision, subapically with 2 small acute processes. Cercus slightly bent, nearly finger-like in lateral view, with long dark 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 flexus -subgroup of the fenestratus -group. It may be separated from Diostracus flexus Takagi and Diostracus nishidai Saigusa from Nepal by the fore tarsomere 1 with a nearly acute apicoventral process and fore tarsomere 2 with a short finger-like ventral process near the extreme base (Figs 2, 5). In Diostracus flexus and Diostracus nishidai , the fore tarsomere 1 has an obtuse apicoventral corner, and the fore tarsomere 2 has no finger-like process near the extreme base ( Saigusa 1984, figs 7-8).

Etymology.

The specific name refers to the fore tarsomere 1 with a nearly acute apicoventral process.