Very small slender species with male broadly dichoptic, face produced strongly forward below, scutellum black and abdomen black or with small lateral yellow triangles (from Vockeroth 1969).
Adapted from original description (Vockeroth 1969).
Head: Eye bare. Front broad in both sexes, sometimes with impressed median line on lower half which curves laterad just above the antennae, slightly and uniformly narrowed from anterior to posterior margin, at level of anterior ocellus about 2/7 head width in male, 1/3 head width in female. Face yellow laterally or entirely black, produced strongly forward below, with strong tubercle which does not project quite as far forward as oral margin. Oral opening 2.5 to 3 times as long as broad. Arista short, distinctly thickened on basal half.
Thorax: Scutum moderately shining, entirely black or with postpronotum and presutural margin bright yellow. Scutellum black. Pleura black or extensively yellow on upper half. Subscutellar fringe sparse. Dorsal and ventral katepisternal pile patches broadly separated throughout. Metasternum bare. Wing with black swelling at extreme base of costa; cell R2+3 rather broadened apically and apical crossvein distinctly angulate; anal lobe slightly reduced; alula very narrow.
Abdomen slender, unmargined, in male tapering very slightly from base of segment 2 to end of tergum 4, in female tapering rather strongly from apex of tergum 2 to apex of abdomen. Terga black or with triangular lateral yellow markings; sterna entirely black or with extreme apices yellowish. Male genitalia: Tergum 9 very slightly asymmetrical, with left side slightly smaller than right. Left surstylus small, almost flat, sub quadrate, with posteroventral angle slightly produced and bluntly rounded; right surstylus moderately or greatly enlarged, either its posterior margin curved slightly mediad or entire surstylus inflated and hood-like. Sternum 9 only very slightly asymmetrical, with a deep broad posteroventral emargination extending about halfway to anterior margin; apicolateral process of sternite broad, with large subquadrate medial projection extending along most of its length. Superior lobe elongate, projecting posterodorsad, the posterolateral margin usually compressed and blade-like, the dorsal portion broadened or tapering apically. Aedeagal base in the form of a very short cylinder with apex broadly open, the posterodorsal margin produced as a triangular plate with broadened base and subacute apex. Distal portion of aedeagus very short, subcylindrical or slightly expanded toward apex, entirely membranous, with or without minute setulae posteriorly and posterolaterally at apex.
Giluwea Vockeroth, 1969.
Vockeroth, J.R. (1969) A revision of the genera of the Syrphini (Diptera: Syrphidae). Memoirs of the Entomological Society of Canada 62, 176 pp. [1969.07.15]
This very peculiar genus appears to have no close relatives. Only three other groups have dichoptic males but there is no indication of any relationship among the four. One of these, Melangyna (Melanosyrphus), also occurs at high altitudes in New Guinea, and like Giluwea has the face produced below, but it has symmetrical genitalia and lacks the swelling at the base of the costa found in both species of Giluwea. A second group, Eosphaerophoria, is widespread in the Oriental region; it too lacks the costal swelling, has the scutellum acute or subacute apically, has aberrant wing venation, and has the male genitalia with sternite 9, the superior lobes and the aedeagus strongly asymmetrical but the surstyli symmetrical. The third group, a single species of Allograpta from New Zealand, is undoubtedly not related to Giluwea. It is tempting to speculate that the species of Giluwea may have dichoptic males because of their occurrence in high open montane areas and a subsequent change in flight and mating habits. However, the other groups with dichoptic males occur at lower altitudes, so this attempted explanation would not apply to them (from Vockeroth 1969).
unless otherwise stated