Thressa bimaculata, Liu, Xiao-Yan, Yang, Ding & Nartshuk, Emilia P., 2011

Liu, Xiao-Yan, Yang, Ding & Nartshuk, Emilia P., 2011, Species of the genus Thressa Walker, 1860 from China (Diptera, Chloropidae), ZooKeys 129, pp. 29-48 : 31-32

Thressa bimaculata sp. n. Figs 311

Diagnosis.

Scutum with 2 small yellow spots on both sides anterior to scutellum. Dorsal portion of katepisternum with a small band-like yellow spot. Legs yellow except tarsomere 5 brown. Abdomen black except tergite 5 medially black and laterally yellow.

Description.

Male. Body length 2.0 mm, wing length1.8 mm.

Head (Figs 3, 4) black without microtomentum, about 0.75 times as long as high, wider than thorax; face sometimes concave in lateral view, bright brown; epistoma yellow; frons black, about as long as wide, projecting only slightly in front of eye, almost entirely occupied by broad ocellar triangle; gena linear; vibrissal angle obtuse; parafacial black, narrow; postgena black; clypeus light black. Ocellar triangle very large and broad, smooth, black, shiny, reaching to anterior margin of frons with broad apex; ocellar tubercle black. Occiput black. Cephalic setae and setulae black, weakly developed; if extremely short, in 1 row on the surface of the triangle; orb very minute, upright; oc extremely small; pvt small hair-like, upright, convergent; vte shorter than pvt and vti indistinct. Antenna dark brown, with thick grayish microtomentum, but postpedicel missing in holotype. Proboscis and palpus black with blackish setulae.

Thorax (Figs 5, 6) shiny black without microtomentum, evenly covered with short setulae. Scutum strongly convex, almost as long as wide, with 2 slightly impressed short and shallow depressions on dorsocentral lines, and 2 small yellow spots on both sides of scutum anterior to scutellum. Thoracic pleuron darkish brown except for katepimeron and anepimeron with some pale gray microtomentum; dorsal portion of katepisternum with a small band-like yellow spot. Scutellum about 0.7 times as long as wide; ap sc short, distinctly shorter than scutellum. Setae and setulae on thorax black. Legs yellow except tarsomere 5 brown. Setulae on legs yellow, but apical portion of tarsi with some brown setulae. Tibial organ distinct, oblong. Wing (Fig. 7) about 2.7 times as long as wide, hyaline without brown spot near wing apex, costal cell somewhat tinged with brown; veins brown. Relative lengths of 2nd: 3rd: 4th costal sections = 5: 3: 1; discal cell narrow and long; crossveins r-m and m-m not approximate, r-m at basal 1/3 of discal cell. Halter pale yellow on knob, brown on stem.

Abdomen shiny black except for tergite 5 medially black and laterally yellow; venter yellow. Setulae on abdomen black. Male genitalia (Figs 8-11): Epandrium short tubular, weakly sclerotized, yellow with yellow long setulae, with 2 band-like sclerites along posterodorsal notch; surstylus basally broad with short spinous setulae, distally narrowed, attached to epandrium anteroventrally. Cercus small, semicircular in dorsal view. Gonites arranged in a row; postgonite slightly incurved distally with pointed apex, with some sensory setulae, basally gradually narrowed; pregonite shorter than postgonite, basally broad and round, distally narrowed; basiphallus longer than wide, cylindrical; distiphallus cylindrical, longer than basiphallus, extended to basal 1/4 of pregonite, largely membranous but weakly sclerotized on apical end; phallapodeme long, extended near base of basiphallus, with basal stalk broad in lateral view. Hypandrium narrow.

Female. Unknown.

Type material.

Holotype ♂, Yunnan: Mengla (21°29'N, 101°33'E, 780m), 9. V. 2009, Guoquan Wang. Male type specimen dry mounted on label laterally on right thorax; postpedicel is missing.

Distribution.

China: Yunnan.

Remarks.

The new species is somewhat similar to Thressa cyanescens (Becker) in the scutum with the slightly impressed short and shallow depressions on dorsocentral lines and the abdomen shiny black except tergite 5 medially black and laterally yellow. But it can be separated from the latter by the scutum with 2 small yellow spots on both sides anterior to the scutellum; the dorsal portion of the katepisternum with one small band-like yellow spot; the cercus semicircular in dorsal view. In Thressa cyanescens , the scutum is entirely shiny black; the thoracic pleuron is entirely shiny black except for the microtomentose katepimeron; the cercus has a concavity on the ventral margin ( Becker 1916; Kanmiya 1983; Nartshuk 1993).

Etymology.

The specific name is from the Latin bi- ( “two”) and maculatus ( “maculate”), refers to the scutum with 2 small yellow spots.