Diostracus polytrichus, Zhu & Tang & Yang, 2023

Zhu, Yajun, Tang, Chufei & Yang, Ding, 2023, Six new species of Diostracus Loew (Diptera, Dolichopodidae) from Tibet, ZooKeys 1163, pp. 1-46 : 1

Diostracus polytrichus sp. nov.

Figs 16 , 17 , 18 , 19 , 20 , 31D , 32E

Type material.

Holotype: China • ♂, China: Tibet, Shigatse, Yatung County (27°48'N, 88°90'E), Pamaimang, 3350 m, 2018. VII. 14, leg. Yajun Zhu. Paratypes: • 2 ♂♂ 2 ♀♀, same data as for holotype.

Diagnosis.

MSSC: palpus black; wing crossvein m-cu nearly straight, with jet-black nodule; halter yellow, with blackish apex. Abdomen with dense ventral hairs.

Description.

Male (Fig. 16A ). Body length 6.6-7.0 mm; wing length 9.4-9.8 mm.

Head (Fig. 17A ) dark metallic green with pale gray pollinosity. Eyes separated; face widened towards clypeus. Hairs and bristles on head black; lower postocular bristles including posteroventral hairs brownish. Ocellar tubercle distinct, with pair of strong oc, without posterior hairs; vt rather short, 0.3 × as long as oc, sometimes hair-like; pvt slight shorter than oc. Antenna black; scape bare, or with three or four dorsal bristles; first flagellomere semicircular to subtriangular, 1.2-1.6 × longer than wide; arista apico-dorsal, 4.2-7.5 × as long as first flagellomere, nearly bare. Proboscis blackish with pale hairs; palpus lobate, 2.2-2.5 × as long as broad, blackish with a purple luster, without distinctive bristle.

Thorax dark metallic green with pale gray pollinosity; mesoscutum with two dark brown longitudinal stripes. Hairs and bristles on thorax black; six weak dc except posterior most one dc longest and thick, occasionally with excess dc; acr absent; one weak and one strong h, one ph, two npl, one sa, one psa; scutellum with pair of long sc. Propleuron with one or two sparse long pale hairs on upper portion and group of long pale hairs on lower portion.

Legs nearly entirely black except fore trochanter dark brown; claws well developed, empodium and pulvilli reduced. Hairs and bristles on legs black except those on coxae pale. CI with group of pale curved anterior hairs on basal 1/3, upper ones long, and cluster of erect bristles on apical 1/4; CII nearly bare; CIII with blackish bristle at extreme apex. FI thickened, with two rows of ventral hairs (as long as FI depth), basal ones pale, and one posterior bristle at extreme base; TI with two pd, three d, row of six or seven long pv on apical half, apically with two bristles and comb of anterior bristles; It1-2 with rows of pd and pv, ventral surface with short dense fine hairs, It1 with row of av spines, extending to It2 (Fig. 17D ); FII with two rows of av on basal half, one distinct v at middle, row of short av on apical 1/3, row of pale long pv on basal 2/3 (longest ones 2.5 × longer than FII depth); TII with two ad, two pd, apically with four bristles. FIII with four av on middle 1/3, apically with one av; TIII with four ad, four pd, four short ventral bristles, apically with three long bristles and comb of short anterior bristles. Relative lengths of tibia and five tarsomeres: LI 6.9: 3.1: 3.2: 1.7: 1.1: 1.0; LII 5.8: 3.2: 1.4: 0.9: 0.5: 0.8; LIII 7.8: 3.4: 2.5: 1.5: 0.8: 0.9.

Wing (Fig. 17C ) hyaline, indistinctly tinged grayish; veins dark brown; crossvein m-cu nearly straight, curved around nodule, with a jet-black nodule. Squama brown with brown hairs. Halter yellow with blackish apex.

Abdomen (Fig. 17B ) nearly as long as thorax, dark metallic green with pale gray pollinosity, bent upwards medially. Abdomen with dense long pale pubescence. Sternite V split into pair of sclerites (Figs 18A , 19A, B ).

Male genitalia (Figs 18B, C , 19C, D ): Epandrium swollen, slightly longer than wide. Epandrial lobe tiny and pale, lamellate, apically with two pale bristles. Surstylus bifurcated, dorsal lobe broad and lamellated, inner surface with dense dentiform bristles, ventral lobe elongated, broad and leaf-like, apical margin pale, with one long inner bristle at middle. Hypandrium relatively small, apically with a deep U-shaped incision in ventral view. Cercus band-like, apical 1/3 becoming narrower, with long yellow hairs along margins.

Female (Fig. 16B ). Body length 5.4-6.0 mm; wing length 6.8-7.9 mm. Nearly as same as male, but: ocellar tubercle without posterior hairs, antenna (Fig. 31D ) scape with two short dorsal bristles, first flagellomere semicircular, nearly as long as width, arista apicobasal, 5.6 × longer than first flagellomere. Proboscis blackish; palpus relatively smaller than males, not reaching apex of proboscis. Seven weak dc, except posterior most dc longest and thicken. Propleuron with two or three sparse short pale curved hairs on upper portion and group of five or six sparse long pale curved hairs on lower portion. Legs black. CI with erect pale hairs on anterior surface, ones on lower portion black and thick; FI with one preapical pv; TI with four pd, two pv, apically with three bristles and comb of short anterior bristles; FII with one strong preapical av and one weak preapical pv; TII with three ad, two pd, apically with four strong bristles; FIII with one strong preapical av and one weak preapical pv; TIII with three ad, apically with three bristles. Wing (Fig. 32E ): m-cu straight, forming obtuse angle with CuA1; area around m-cu tingled with blackish ash. Halter yellow with blackish apex.

Female terminalia (Fig. 20 ): Abdominal segments VII and VIII slender; tergite VIII divided into two sclerites; epiproct split into pair of hemitergites, apically with row of five strong curved spines; dorsal lobes of cercus finger-like, somewhat elongated, with dark yellow bristles; ventral lobes of cercus short, apex rounded.

Distribution.

China (Tibet).

Remarks.

The new species is quite similar to D. tibetensis , but the cerci of new species are lamellate with broad base. Females of the new species are characterized by the semicircular first flagellomere of antenna, the straight crossvein m-cu, and the blackish apex of halter.

Etymology.

The name of the new species refers to the dense abdominal ventral hairs.

Figures

Figure 16. D. polytrichus A male; lateral view B female, lateral view. Scale bars: 1 mm.

Figure 17. D. polytrichus male A head, lateral view B abdomen, lateral view C wing D It 1, anterior view. Scale bars: 1 mm.

Figure 18. D. polytrichus male A abdominal Sternite IV and V, male genitalia removed, ventral view B male genitalia, lateral view C male genitalia, ventral view. Scale bars: 1 mm.

Figure 19. D. polytrichus male A abdominal Sternite IV and V, male genitalia removed, ventral view B abdominal Sternite IV and V, male genitalia removed, lateral view with some angles C male genitalia, lateral view D male genitalia, ventral view. Scale bars: 1 mm.

Figure 20. D. polytrichus female, abdomen A dorsal view B lateral view C ventral view. Scale bar: 1 mm.

Figure 31. Female antenna, lateral view A D. acutatus, show apical arista B D. acutatus, show subapical arista C D. fasciculatus D D. polytrichus E D. translucidus. Scale bars: 1 mm.

Figure 32. Apex of female wing A, B D. acutatus C D. fasciculatus D D. translucidus E D. polytrichus. Scale bar: 1 mm.