Diostracus acutatus Wang, Wang & Yang, 2015

Figs 1, 2, 31A, B, 32A, B

Diostracus acutatus Wang, Wang & Yang, 2015: 96, figs 1-6.

Material examined.

China • 3 ♂♂ 6 ♀♀, Tibet, Shigatse, Yatung County; 27°48'N, 88°90'E; 13 VII. 2018; 2700-3200 m; leg. Yajun Zhu ; • 2 ♂♂ 1♀, same data as for preceding; Pamaimang; 14 VII. 2018; ca 3350 m .

Diagnosis.

The species belongs to the Diostracus fenestratus group, characterized by specialized It1 and It2 (MSSC). It1 distinctly shortened, with a nearly acute apicoventral process; It2 basally bent with a short finger-like ventral process near extreme base. Females of D. acutatus are characterized by the apical or subapical antenna, oblique crossvein, m-cu oblique, and brownish trochanters.

Male (Fig. 1A). Same as description of Wang et al. (2015).

Female (Fig. 1B). Body length 6.0-6.4 mm; wing length 6.9-7.8 mm. Antennal scape with two short dorsal bristles, first flagellomere somewhat prolonged, 1.2 × longer than width, arista apical or subapical, 4.6 × longer than first flagellomere (Fig. 31A, B). Proboscis yellowish brown with blackish edge; palpus relatively smaller than males, not reaching apex of proboscis. six dc, anterior four short and weak, 5th long and weak. Propleuron with a single pale hair on upper portion, and group of 5-7 long pale hairs on lower portion. Legs black, except trochanters yellowish brown. CI without distinctive bristle or hair, but with short pale anterior hairs on lower portion; FI without distinct bristles; TI with an ad at basal 1/4, four pd, apically with one bristle and comb of anterior bristles; FII with two anterior bristles on apical 1/3; TII with three ad, two pd, apically with five bristles; FIII with three anterior bristles on apical 1/3; TIII with four ad, two pd, 4-6 weak v, apically with two bristles. Wing (Fig. 32A, B): m-cu somewhat curved, forming right angle with CuA1. Halter yellow.

Female terminalia (Fig. 2): Abdominal tergite VIII split into pair of sclerites; epiproct split into pair of triangular hemitergites, apically with row of seven strong curved spines; dorsal lobes of cercus rounded in lateral view, with yellow bristles; ventral lobes of cercus membranous.

Remarks.

Diostracus acutatus is similar to D. nishidai Saigusa, in that they both have acute apico-ventral corners of It1 and It2 and the shapes of wings and the appendages on abdominal sternite IV are nearly identical. But for males, they are different in the shapes of the main lobe of surstylus, and the apicoventral corner of It1 in D. acutatus is sharper.