Diostracus strenus, 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 strenus sp. nov.

Figs 21 , 22 , 23 , 24

Type material.

Holotype: China • ♂, Tibet, Shigatse, Yatung County (27°48'N, 88°90'E), 2700-3200 m, 2018. VII. 13, leg. Yajun Zhu. Paratype: • 1 ♂, same data as for holotype but Pamaimang, 3350 m, 2018. VII. 14.

Diagnosis.

MSSC: dark and robust fly; FI and TI distinctly thickened; posterior ventral margin of It1 and anterior ventral margin of It2 expanded into auriform lobes; crossvein m-cu acutely and deeply arched to vein M1, forming a ‘h’ -shaped curve, with a jet-black mark inside curve.

Description.

Male (Fig. 21 ). Body length 6.0 mm; wing length 8.0 mm.

Head (Fig. 22A ) dark metallic green with pale brown 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 short, 0.7 × as long as oc, nearly as long as pvt. Antenna black; scape with a weak dorsal bristle at basal 1/3; first flagellomere subtriangular, 1.5 × longer than wide; arista apicodorsal, 3 × as long as first flagellomere, nearly bare. Proboscis blackish with pale hairs; palpus lobate, 3.5 × as long as broad, blackish with a purple luster, without distinctive bristle.

Thorax dark metallic green with pale brown pollinosity. Hairs and bristles on thorax black; six mostly hair-like dc except 1st and 6thdc long and thick; acr absent; one h, one ph, two npl, one sa, one psa; scutellum with pair of 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 and mid trochanters 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, pale, anterior hairs on apical 1/4; CII with cluster of black bristles at extreme apex; CIII nearly bare. Fore trochanter elongated, with lobate posterior process. FI distinctly thickened, with group of pale hairs on apical 1/5 (less than FI depth) (Fig. 22D, E ); TI distinctly thickened, curved, with three ad on basal half, two pd on apical 1/3, row of five long pv on apical 1/3, apically with comb of short pale av spines (Fig. 22D, E ); It1 shortened, concave ventrally, posterior ventral margin expanded into a auriform lobe (Fig. 22D, E ); It2 thickened and recurved, somewhat flattened dorsoventrally, with anterior ventral margin at extreme base expanded into an auriform lobe, corresponding to the auriform lobe of It1, a spine-like lobe at basal 1/4, and two rows of short pv spines (Fig. 22D, E ). FII with rows of pale postoventral hairs (as long as FII depth), and one ad at apical 1/8; TII with rows of curved ventral hairs on basal 2/3 (longest ones 2 × longer than TII depth), three weak ad, two weak pd, apically with two long bristles. FIII with two ad on apical 1/6, rows of sparse pale ventral hairs on basal half (less than FIII depth); TIII with five ad, three pd, without outstanding ventral bristle, apically with two bristles. Relative lengths of tibia and five tarsomeres: LI 5.7: 0.6: 2.8: 2.1: 1.0: 1.0; LII 8.8: 5.2: 2.2: 1.3: 0.8: 1.0; LIII 10.3: 4.7: 3.0: 1.4: 0.7: 1.0.

Wing (Fig. 22C ) hyaline, indistinctly tinged grayish; veins dark brown; crossvein m-cu acutely and deeply arched to vein M1, forming a ‘h’ -shaped curve, with a jet-black mark inside curve. Squama brown with brown hairs. Haltere blackish with pale knob.

Abdomen (Fig. 22B ) nearly as long as head and thorax combined, dark metallic green with pale gray pollinosity. Abdomen with pale pubescence. Sternite IV medially with an obtuse process, and one tubercle bearing bundle of brown bristles, latero-posterior corner with brown bristles (Figs 23A , 24A ). Sternite V split into pair of sclerites, each sclerite ginkgo leaf-like (Figs 23A , 24A ).

Male genitalia (Figs 23B, C , 24B, C ): Epandrium slightly longer than wide. Epandrial lobe elongated, lamellated, apically with two short bristles. Surstylus thick, apex dark, bending inwards, with a finger-like inner process. Hypandrium thick, apically with a shallow, V-shaped incision. Cercus straight and clavated, inner surface somewhat hollow, with long pale hairs along margin, apical half with dense, erect, dark yellow bristles on inner surface.

Female. Unknown.

Distribution.

China (Tibet).

Remarks.

The new species belongs to D. fenestratus group. It looks like D. flexus , but can be separated from the latter by the following features of males: the weak acute ventral process near extreme base of It2, the swollen apex of It2, the row of erect dense strong long posterior, and the anterior ventral bristles on apex of TII.

Etymology.

The name of new species refers to the strongly thickened legs.

Figures

Figure 21. D. strenus, male; lateral view. Scale bar: 1 mm.

Figure 22. D. strenus male A head, lateral view B abdomen, lateral view C wing D TI and It, anterior view E TI and It, posterior view. Scale bars: 1 mm.

Figure 23. D. strenus male A abdominal Sternite IV and V, male genitalia removed, ventral view B male genitalia, lateral view C male genitalia, ventral view. Scale bar: 1 mm.

Figure 24. D. strenus male A abdominal Sternite IV and V, male genitalia removed, ventral view B male genitalia, lateral view C male genitalia, ventral view. Scale bar: 1 mm.