Diostracus concavus, 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 concavus sp. nov.

Figs 3 , 4 , 5 , 6

Type material.

Holotype: China • ♂, Tibet, Nyingchi, Bomi, Gagela Mountain, 3026 m, 2013. VII. 13, leg. Xiaoyan Liu.

Diagnosis.

MSSC: first flagellomere 1.5 × longer than wide; propleuron with group of seven long pale hairs on upper portion and group of ~ 20 long pale hairs on lower portion; It1 shortened and expanded, concave ventrally, forming a hollow with an expanded It2. Wing (Fig. 4B ) hyaline, m-cu acutely and deeply arched to vein M1, forming an ‘h’ -shaped hairpin with a slender jet-black mark inside.

Description.

Male (Fig. 3 ). Body length 5.7 mm; wing length 6.8 mm.

Head (Fig. 4A ) 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 short, 0.7 × as long as oc, nearly as long as pvt. Antenna black; scape without dorsal bristle; first flagellomere subtriangular, 1.5 × longer than wide; arista subapical, 5.2 × as long as first flagellomere, nearly bare. Proboscis blackish with pale hairs; palpus lobate, 3 × as long as broad, blackish with a purple luster, without distinctive bristle.

Thorax 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; two h, one ph, two npl, one sa, one psa; scutellum with pair of long sc. Propleuron with group of seven long pale hairs on upper portion and group of nearly 20 long 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 with cluster of anterior dense, erect, long, pale hairs on apical 1/4 (nearly as long as CI) and comb of pale hairs along anterior margin; CII and CIII nearly bare. Fore trochanter with rows of tiny ventral spines and a hook-like posterior process. FI distinctly thickened, with cluster of four or five erect ventral bristles at extreme base; TI distinctly thickened, weakly curved, with 3 ad, two pd, row of six long pv on apical 1/4; It1 shortened and expanded, concave ventrally, forming a hollow with expanded It2, anterior margin expanded into two dentiform lobes with row of four or five bristles, ventral margin expanded into a lobe at base (corresponding to the lobe of It2), with a subapical pv (Fig. 4C, D ); basal half of It2 expanded and concave ventrally, anterior margin expanded into a pale dentiform lobate and a rectangular lobate, posterior ventral margin expanded into a finger-like lobe at extreme base, apical half with rows of erect ventral bristles, apical half of It2, It3-5 with a ventral suture. FII somewhat flattened laterally, with three ad on apical 1/3; TII with three weak ad, three weak pd, apical 1/5 with two rows of long pale anteroventral hairs (longest ones nearly as long as 1/4 of TII) and row of erect short pv (nearly as long as TII depth), and row of long pale posteroventral hairs along whole length (nearly as long as FII depth), apically with three long bristles. FIII with an anterior bristle and two curved av subapically; TIII with four ad and four pd, apically with two strong long bristles. Relative lengths of tibia and five tarsomeres: LI 5.0: 0.7: 2.5: 2.0: 1.0: 1.3; LII 9.0: 6.1: 2.2: 1.3: 0.7: 1.0; LIII 10.3: 5.2: 3.0: 1.5: 0.7: 1.0.

Wing (Fig. 4B ) hyaline, indistinctly tinged grayish; veins dark brown; crossvein m-cu not elongated, acutely and deeply arched to vein M1, forming a ‘h’ -shaped curve with M1, with a slender jet-black brand inside hairpin curve; posterior margin somewhat prolonged along vein CuA1. Squama brown with brown hairs. Halter pale (somewhat faded).

Abdomen 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 anterior process and a tubercle bearing bundle of brown bristles, each latero-posterior corner with a tubercle bearing bundle of brown bristles (Figs 5A , 6A ). Sternite V split into pair of sclerites, each sclerite ginkgo leaf-like in shape (Figs 5A , 6A ).

Male genitalia (Figs 5B, C , 6B, C ): Epandrium slightly longer than wide. Epandrial lobe long, wavy, band-like, with an acute basal process, a short bristle at tip. Surstylus thick, lamellated, with two short spines. Hypandrium short thick, apically with a shallow, V-shaped apical incision. Cercus rather short (1/3 as long as epandrium), spoon-shaped, with dark yellow hairs on outer surface, apical one long (nearly as long as cercus), and subapically with group of dense erect dark yellow bristles on inner surface.

Female. Unknown.

Distribution.

China (Tibet).

Remarks.

The new species belongs to the Diostracus flexus subgroup of D. fenestratus group. This new species has wing characteristics similar to that of D. strenus sp. nov., but the latter can be separated from D. concavus by It3-5, which is normal and has no ventral suture (MSSC).

Etymology.

New species name refers to the concave It1 of males.

Figures

Figure 3. D. concavus, male; lateral view. Scale bar: 1 mm.

Figure 4. D. concavus male A head, lateral view B apex of wing C apex of TI and It 1 - 2, posterior view D apex of FITI and It 1 - 2, anterior view. Scale bars: 1 mm.

Figure 5. D. concavus 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 6. D. concavus 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.