Hypselosyrphus Hull

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 30-31

Hypselosyrphus Hull stat. n. Figs 97-102

Hypselosyrphus Hull, 1937a: 21. Type species Hypselosyrphus trigonus Hull, 1937: 21, by original designation.

Description.

Body length: 7-10 mm. Stingless bee mimicking flies with short to moderately long antennae and oval to triangular abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex narrow, in most species convexly produced and shining, flat in some species. Occiput narrow over entire length, except ventrally strongly widened in Hypselosyrphus ulopodus . Eye with short, sparse pile. Eye margins in male strongly converging at level of frons, with mutual distance smaller than width of antennal fossa, except 3 times as wide in Hypselosyrphus ulopodus . Antennal fossa about as wide as high. Antenna as long as or shorter than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular, triangular or apicomedially sulcate; without calcars. Anepisternum without or with weak sulcus; pilose anterodorsally and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/8 to 1/4 of cell dm. Abdomen oval or kite-shaped, 1.2 to 2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus furcate near apex, with dorsal process in some species a little longer than ventral process; epandrium with or without ventrolateral ridge.

Diagnosis.

Vein R4+5 without posterior appendix. Crossvein r-m located between basal 1/8 and 1/4 of cell dm. Subcostal vein joins costal vein after level of crossvein r-m. Postpronotum pilose. Abdomen oval or kite-shaped (tergite 2 wide, subsequent tergites triangularly narrowing). Antenna as long as or shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere not furcate. Occiput narrow in dorsal half (usually also in ventral half, except in Hypselosyrphus ulopodus Hull, 1944).

Discussion.

When Hull (1937a) erected the genus Hypselosyrphus for his species trigonus, he mentioned its similarity to Ubristes Walker, 1852 species, without clearly stating the differences. In his key to the groups of Microdontinae , Hull (1949) separated these taxa by the absence ( Hypselosyrphus ) or presence ( Ubristes ) of an appendix on vein R4+5. This character serves well to separate Hypselosyrphus from Ubristes s.s. as defined in the present paper, and almost always for Stipomorpha (appendix on vein R4+5 seldomly missing), which was included in Ubristes until now. In later keys and catalogues, Hypselosyrphus was treated as a junior synonym of Ubristes ( Thompson 1969, Thompson et al. 1976). Cheng and Thompson (2008) also considered Hypselosyrphus (and Stipomorpha Hull, 1945) synonymous with Ubristes , but nevertheless differentiated the groups in their key. They consider abdominal shape to be diagnostic: oval or rectangular in Ubristes , short, almost equilaterally triangular in Hypselosyrphus , much longer, isosceles triangular in Stipomorpha . As there are many varieties in abdominal shape among the the taxa involved, it is hard to decide where to draw the line. Other characters are necessary to distinguish these taxa satisfyingly (see key and diagnoses).

Diversity and distribution.

Described species: 11. Descriptions of five additional species are in preparation by the first author. Hypselosyrphus is known from Panama, the Amazon region and southern Brazil. Considering the small number of specimens known, it seems likely that the genus is widespread in tropical South America.