Thressa flavior (Duda, 1934)

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 : 38-40

Thressa flavior (Duda, 1934) Figs 3744

Chalcidomyia flavior Duda, 1934: 124. Type locality: Sumatra. (Holotypes deposited in Museum für Naturkunde, Berlin).

Thressa flavior (Duda): Sabrosky 1977: 319; Nartshuk 1993: 114.

Diagnosis.

Scutum with a yellow transverse stripe anterior to scutellum, about 1/7 times as long as scutum. Paratergite and anepisternum with one oblique, wide, yellow stripe; dorsal portion of katepisternum with a small triangular yellow spot. Surstylus pipe-like. Cercus long, oblong in dorsal view.

Description.

Male.Body length3.0-3.5 mm, wing length2.4-2.9 mm.

Head (Figs 37, 38) black without microtomentum, about 0.8 times as long as high, wider than thorax; face sometimes concave in lateral view, bright brown with a yellow transverse stripe below antenna; epistoma yellow; frons black except for anterior 1/8 yellow, about 0.75 times as long as wide, projecting only slightly in front of eye, almost entirely occupied by broad ocellar triangle; gena black, narrow, about 1/10 times as high as postpedicel; vibrissal angle obtuse; parafacial black, linear; postgena black; clypeus light black. Ocellar triangle very large and broad, shiny black, smooth, 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 black with thick grayish microtomentum, but postpedicel with yellowish brown ventral surface; postpedicel 2 times as long as wide, parallel-sided; arista pectinate with 4 branches dorsally and 3 ventrally, apically with some short setulae, black except for basal segment yellow. Proboscis and palpus light blackish brown with blackish setulae.

Thorax (Figs 39, 40) black without microtomentum, with granulated microsculpture, evenly covered with short setulae. Scutum strongly convex, almost as long as wide, with a yellow transverse stripe anterior to scutellum, about 1/7 times as long as scutum. Thoracic pleuron black except for paratergite and anepisternum with one oblique, wide, yellow stripe; dorsal portion of katepisternum with a small triangular 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 for tarsomere 5 brown. Setulae on legs yellow, but apical portion of tarsi with some brown setulae. Tibial organ distinct, oblong. Wing 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: 2: 1; discal cell narrow and long; crossveins r-m and m-m not approximate, r-m at basal 0.4 of discal cell. Halter pale yellow on knob, brown on stem.

Abdomen mainly yellow, tergite 2 posteriorly with two narrow black lateral stripes, basal 1/2 of tergite 3 with a transverse black stripe, rest of tergite 3 and following tergites with a mid-longitudinal black stripe; venter yellow. Setulae on abdomen black. Male genitalia (Figs 41-44): Epandrium short tubular, weakly sclerotized, yellow with long yellow setulae, with 2 band-like sclerites along posterodorsal notch; surstylus pipe-like, basally broad with short spinous setulae, distally narrowed, attaching to epandrium anteroventrally. Cercus long, oblong in ventral view. Gonites arranged in a row; postgonite long with some sensory setulae; pregonite slightly shorter than postgonite, basally broad, distally narrowed; basiphallus longer than wide, cylindrical; distiphallus cylindrical, longer than basiphallus, reaching to dorsal margin of hypandrium, 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.

Specimens examined.

Holotype ♂, Sumatra, 1924, E. Jacobson; 1 ♂, Yunnan: Menglun (21°55'N, 101°13'E, 630m), 10. III. 1999, Ding Yang; 1 ♂, Hainan: Wuzhishan (18°50'N, 109°42'E, 600m), 16. V. 2007, Kuiyan Zhang. Type specimen pinned thoracic pleuron, other specimens dry mounted on label laterally on right thorax.

Distribution.

China: Yunnan, Hainan; Indonesia; Malaysia.

Remarks.

The species is somewhat similar to Thressa polita (de Meijere) in the scutum with a yellow transverse stripe anterior to the scutellum. But it can be separated from the latter by the abdomen being mainly yellow, tergite 2 posteriorly with two narrow black lateral stripes, basal 1/2 of tergite 3 with a transverse black stripe, rest of tergite 3 and following tergites with a mid-longitudinal black stripe; the legs entirely yellow. In Thressa polita , the abdomen is mostly black except for the basal portion and posterior margin yellow; the legs are yellow except the femora partly black ( de Meijere 1910; Nartshuk 1993).