Arge potanini Jakowlew, 1891

22. Arge potanini Jakowlew, 1891

( Fig. 31 View FIGURE 31 )

Arge potanini Jakowlew, 1891: 18–19 , ♀; Taeger et al. 2010: 137.

Current status. Arge potanini Jakowlew, 1891 .

Type locality. China, Gansu, “Kheikho”.

Holotype: ♀, <golden circle> // Хейхо [Kheikho] [ China, Gansu], потанин [G.N. Potanin], 21.07.[18]85. // arge // Hylotoma Potanini Yak [owlew] // к[оллекциЯ]. А. Яковлева [Collection of A.I. Jakowlew] // Arge potanini ( Jakowlew, 1891) , Det. M.C. Wei, 2014 // DEI-GISHym 89418 // HOLOTYPUS Arge potanini Jakowlew, 1891 , teste A. Taeger 2018 // Zoological Institute, St. Petersburg INS_HYM_0001928 [ ZISP].

Description. Female ( Fig. 31 View FIGURE 31 ). Body length 7.7 mm; fore wing length 7.0 mm.

Colour. Body black with weak blue-violet metallic lustre (also see remarks); tibiae and tarsi dark brown, on hind tibiae basal half yellowish white; apical half of flagellum, mouthparts brown. Pubescence silvery-white. Wing hyaline with dark transverse band below pterostigma; veins and stigma brown.

Head. Head behind eyes slightly constricted. Distance between eyes 1.3 × vertical diameter of eye; eye with vertical diameter 1.6 × its horizontal diameter. Postocellar area not convex, with weak lateral furrows. POL: OCL: OOL as 1.2: 1.0: 1.7. Medial fovea broad, flat in lower part, with weak rounded pit in upper part, open towards frontal area. Lateral carinae sharp, converging downwards, joining in sharp median carina. Supraclypeal area weakly convex, densely punctuated and wrinkled. Malar space equal to diameter of frontal ocellus. Clypeus smooth, shiny, sparsely punctate, slightly notched on ventral margin. Labrum with weakly notched on ventral margin.

Antennae. Antennal length 1.2 × maximum head width; flagellum weakly curved at base, widened towards apex, apex narrowly rounded; its setae short, dense, closely adherent.

Thorax. Mesopleuron in lower part with glabrous band; scutellum flat, narrowly rounded at apex.

Legs. Middle and hind tibia with preapical spurs; tibial spurs simple. Basal tarsomeres of hind tarsus longer than next three combined.

Wings. In fore wing, cell 3Rs with anterior margin slightly longer than posterior margin, expanded to external margin. Vein 3r-m angularly curved. Veins B and M of fore wing join up at same point on vein R. Membrane of cell 1Rs densely covered with short setae.

Abdomen. Abdomen oval (in dorsal view). Tergites in basal half smooth; in apical part densely pubescent. Saw sheath 1.5 × long as wide, simple, parallel-sided, broadly rounded at apex (ventral view), on inner surface with small, blunt spines; in lateral view triangular, narrowly rounded at apex, slightly convex on ventral margin.

Lance in lateral view convex, strongly tapered towards apex, with clearly visible annuli. Maximum width of lance equal to lancet width. Carina of apical part of dorsal margin with small indistinct denticles, remaining part of dorsal margin with longitudinal shallow fossa. Lancet with straight dorsal and ventral margin, almost blunt at apex. Annuli almost straight and perpendicular, weakly curved basally. Annular spines (ctenidia) short, simple, several times shorter than width of annulus. Ventral margin only in basal half with distinguishable 10 serrulae, rest with small denticles. Serrulae triangular narrowly rounded at apex, with small indistinct denticles along anterior margin. Between serrulae two unequal straight pore canals of marginal sensilla.

Remark. The original description is given on a single specimen ( holotype). Holotype is considerably discoloured and wing membrane partially destroyed. The males are unknown.

In the original description, there are a number of features that are not detected in the present condition of the specimen and even contradictory. Jakowlew (1891) indicates “green-bronze, abdomen yellow, legs greenish-bronze”, although the studied holotype has a distinct blue-violet metallic lustre, and the abdomen, though discoloured, is distinctly black. This is probably an error, as the other characters correspond exactly to the description. From the description, it follows that there is a transverse band on the wing, which is now practically indistinguishable.