Hypselosyrphus trigonus Hull, 1937

Reemer, Menno, 2013, Taxonomic exploration of Neotropical Microdontinae (Diptera: Syrphidae) mimicking stingless bees, Zootaxa 3697 (1), pp. 1-88 : 35-37

Hypselosyrphus trigonus Hull, 1937

Figs 96–99 .

Hypselosyrphus trigonus Hull, 1937: 21 .

Studied type specimens. HOLOTYPE. PANAMA. Female. Label 1: "Canal Zone: Barro, Colorado. 16-VII-1924. N. Banks."; label 2 (red.): "M.C.Z. Type 31169"; label 3 (large, red-bordered): " Hypselosyrphus trigoniformis Hull, F.M.H. ". Coll. MCZ.

Additionally studied specimens. BELIZE. Female. No further data. Coll. RMNH. PANAMA: 1 female, Chiriqui, 15 km NW Hato del Volcan, 1200 m, 24-31.V.1977, Peck & Howden, coll. CNC.

Note on holotype: The holotype is labelled as Hypselosyrphus trigoniformis Hull , but this must be a mistake, because Hull has not described a species under that name. He did, however, describe Hypselosyrphus trigonus , the description of which agrees well with this specimen.

Redescription (based on holotype)

Adult female Body size: 7 mm.

Head. Face occupying 1/5 of head width in frontal view; shining blackish brown; with long white pilosity on lateral 1/3; with white pollinosity on lateral 1/5. Gena hardly developed. Oral cavity directly bordering eye margins; with lateral margins not produced. Frons shining dark brown, dark pilose, except white pilose directly along eye margin. Vertex convexly produced, shining dark brown; black pilose; ocellar triangle not elevated compared to rest of vertex. Occiput black; narrow; with anterior row of dorsally orientated short black pile on dorsal 1/2; with posterior row of posteriorly orientated pale pile over entire length; black pollinose on dorsal half, white pollinose on ventral half. Eye entirely with short, pale pile, about as long as ommati diameter. Antennal fossa about as wide as high. Antenna pale brown; antennal ratio 4:1:4. Basflagellomere with acute apex; with small sensory pit at half of the segment, situated in a wide groove from base of arista to near apex. Arista pale, about as long as basoflagellomere.

Thorax. Dark brown. Scutum densely black pilose, except for transverse fasciae of pale pile along suture and along posterior margin. Postpronotum black pilose, postalar callus white pilose. Scutellum apicomedially sulcate, with convex posterior margin, without calcars; directed upward, making an angle with the scutum of about 45°; long white pilose anteriorly, long black pilose posteriorly, long white pilose posteroventrally. Anepisternum a little convex, no clear division between anterior and posterior part; anterior part black pilose, posterior part with a few black pile along posterior margin. Anepimeron entirely black pilose. Katepisternum black pilose dorsally; with a few pile ventrally. Katatergum long microtrichose. Anatergum short microtrichose. Other pleurae bare. Calypter grey, halter brown.

Wing: hyaline, vaguely darkened around stigmal crossvein, and vaguely yellowishly tinged around and posteriad of pterostigma (best seen before a dark background); microtrichose, except on 1st costal cell, basal 2/5 of 2nd costal cell, basal 1/10 of cell r1, basal 2/5 of cell br, posterobasal 2/5 of cell bm, basal 2/5 of cell cup.

Legs: Brown, except fore- and middle-tarsi yellow and apical four tarsomeres of hindleg yellow; black pilose, except yellow pilose on apical three tarsomeres. Metatibiae strongly widened, with greatest width slightly apically of middle, about 1.5 times as wide as posterior femur at largest width; with strong excavation at cicatrice (lateral view); pilosity about half as long as width of tibia. Hind-basitarsus enlarged; about 1.5 times as wide as apex of metatibia in dorsal view. Coxae and trochanters brown, with black pile.

Abdomen. Oval, wider than thorax, with largest width at posterior margin of tergite 2. Colours hard to assess in type specimen because of partial folding and darkening of the segments. Hull (1937) states: "Abdomen short, oval, flat, vitreous, dark reddish brown on first, second and narrowly on base of third segment. Remainder bright orange." Sternite 1 black and black pilose. Other sternites yellow and yellow pilose.

Male. Unknown.

Diagnosis. Recognized by the following combination of characters: scutellum sulcate, alula entirely microtrichose, hind tibia brown and black pilose, abdomen orange to reddish brown.

Distribution. Known from Belize and Panama.

Figures

FIGURES 96 – 99. 96 – 99. Hypselosyrphus trigonus female (holotype). 96. habitus dorsal; 97. habitus lateral; 98. head frontal; 99. head lateral. 100 – 104. Hypselosyrphus ulopodus male (holotype). 100. habitus dorsal; 101. habitus lateral; 102. head frontal; 103. head lateral; 104. wing. 105 – 106. Hypselosyrphus vexillipennis female (holotype). 105. habitus dorsal; 106. habitus lateral.