Diostracus fasciculatus, 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 fasciculatus sp. nov.

Figs 7 , 8 , 9 , 10 , 11 , 31C , 32C

Type material.

Holotype: China • ♂, China: Tibet, Shigatse, Yatung County (27°48'N, 88°90'E), 2700-3200 m, 2018. VII. 13, leg. Yajun Zhu. Paratypes: • 3 ♂♂ 2 ♀♀, same data as for holotype; 11 ♂♂, 4 ♀♀, same data as for preceding, but Pamaimang, 3350 m, 2018. VII. 14.

Diagnosis.

MSSC: posterior margin of wing somewhat prolonged along vein CuA1. TII and TIII prolonged; apex of TII swollen with two rows of narrow, flat, willow leaf-like ventral bristles, row of long av and pale curve ventral hairs, row of erect pv along whole length, apically with three long bristles; It1 swollen at extreme base, with rows of long curved posterior bristles.

Description.

Male (Fig. 7A ). Body length 5.0-5.4 mm; wing length 5.8-6.2 mm.

Head (Fig. 8A ) 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 pale. Ocellar tubercle distinct, with pair of strong oc, without posterior hairs; vt rather short, 0.5 × as long as oc, nearly as long as pvt. Antenna black; scape without dorsal bristle; first flagellomere subtriangular, 1.5 × longer than wide; arista apicodorsal, 4.5 × as long as first flagellomere, nearly bare. Proboscis blackish with pale hairs; palpus lobate, 4 × as long as broad, blackish with a purple luster, without distinctive bristle.

Thorax (Fig. 8B ) dark metallic green with pale gray pollinosity. Hairs and bristles on thorax black; six mostly hair-like dc except posterior most one dc longest and thick; acr absent; one h, one ph, two npl, one sa, one psa; scutellum with pair of long sc. Propleuron with two or three sparse short pale hairs on upper portion and one or two short pale hairs on lower portion.

Legs nearly entirely black except fore trochanter dark yellow; claws well developed, empodium and pulvilli reduced. Hairs and bristles on legs black except those on coxae pale. CI without distinctive bristle, but with dense erect anterior pale hairs on apical 1/4; CII nearly bare; CIII with blackish bristle at extreme apex. Fore trochanter elongated, with hook-like posterior process (Fig. 8D ). FI distinctly thickened (Fig. 8D ); TI slightly thickened, weakly curved, with one ad at basal 1/3, two pd (one at apical 1/3 outstanding), row of weak pv along whole length; It1 shortened, concave ventrally, anterior ventral margin expanded into a lobe and recurved, with short bristles apically (Fig. 8D ); It2 with a finger-like lobe at extreme base, corresponding to the cavity of It1, apical half thickened with short dense pv. FII somewhat flattened laterally, with three ad on apical half; apex of TII swollen with two rows of narrow flat willow leaf-like ventral bristles, row of long av (anterior ones somewhat curved), rows of pale long ventral hairs (2-3 × longer than TII depth, curved), row of erect pv along whole length (as long as TII depth), apically with three long bristles (Fig. 8E ); It1 swollen at extreme base, with rows of long curved posterior bristles (Fig. 8E ). FIII with two av on apical 1/3, rows of sparse pale ventral hairs along whole length (less than FIII depth); TIII with four ad, three pd, without outstanding ventral bristle, apically with two strong long bristles. Relative lengths of tibia and five tarsomeres: LI 5.3: 0.8: 1.5: 1.8: 0.7: 0.75; LII 7.3: 2.9: 1.4: 0.85: 0.45: 0.75; LIII 8.9: 3.3: 2.3: 1.2: 0.65: 0.85.

Wing (Fig. 8C ) hyaline, indistinctly tinged grayish; veins dark brown, R4+5 curved at apical 1/3; crossvein m-cu acutely and deeply arched to vein M1, forming a hairpin curve, with a slender jet-black brand inside hairpin curve; posterior margin somewhat prolonged along vein CuA1. Squama brown with brown hairs. Halter brown.

Abdomen (Fig. 9A ) nearly as long as head and thorax combined, dark metallic green with pale gray pollinosity. Abdomen with pale pubescence. Sternite IV medially with pair of obtuse anterior process (very close), bearing bundle of brown hairs (Fig. 10A ). Sternite V split into pair of sclerites, each sclerite ginkgo leaf-like (Fig. 10A ).

Male genitalia (Figs 9B, C , 10B, C ): Epandrium slightly longer than wide. Epandrial lobe pale and lamellated, band-like, elongated, apically with short hairs. Surstylus thick, bent inwards, apically furcated. Hypandrium thick, apically with a deep, U-shaped incision in ventral view. Cercus broad, leaf-like, nearly as long as epandrium, with long dark yellow hairs along margins.

Female (Fig. 7B ). Body length 4.9-6.7 mm; wing length 6.1-7.9 mm. Nearly as same as male, but: antenna (Fig. 31C ) scape with two short dorsal bristles, first flagellomere somewhat prolonged, 1.2 × longer than width, arista apicobasal, 4.6 × longer than first flagellomere. Proboscis yellowish brown with blackish edge; palpus relatively smaller than males, not reaching apex of proboscis. Six weak dc, except posterior most dc longest and thicken. Propleuron with one or two pale curved hairs on lower portion. Legs black, except trochanters yellowish brown. CI without distinctive bristle or hair, but with short pale anterior hairs on lower position; FI without distinct bristles; TI with one ad at basal 1/4, four pd, apically with a 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. 32C ): m-cu straight, forming acute angle with CuA1. Halter yellow.

Female terminalia (Fig. 11 ): Abdominal tergite VIII divided into two sclerites; epiproct split into pair of triangular hemitergites, apically with row of nine strong curved spines; dorsal lobes of cercus triangulated, with dark yellow bristles; ventral lobes of cercus short, apex rounded, with long yellow hairs.

Distribution.

China (Tibet).

Remarks.

The new species belongs to the flex subgroup D. fenestratus group. The species is unique for the shape of wings and It1-2, and the prolonged TII and TIII which have relatively short IIt1 and IIIt1. Females are characterized by an arched crossvein m-cu, and the crossvein vertical adjunct to vein CuA1; the trochanters are black.

Etymology.

The new species name refers to the cluster of bristles on apex of TII of males.

Figures

Figure 7. D. fasciculatus A male; lateral view B female, lateral view. Scale bars: 1 mm.

Figure 8. D. fasciculatus male A head, lateral view B thorax, lateral view, show the bristles C wing D FI, anterior view E part of TII and IIt 1, anterior view. Scale bars: 1 mm.

Figure 9. D. fasciculatus male A abdomen, lateral view B male genitalia, lateral view C male genitalia, ventral view. Scale bars: 1 mm.

Figure 10. D. fasciculatus male A abdominal Sternite IV and V, male genitalia removed, ventral view B male genitalia, lateral view C male genitalia, ventral view D surstylus, ventral view. Scale bars: 0.2 mm.

Figure 11. D. fasciculatus 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.