Vockeroth (1969) erected this subgenus for his new species dichoptica. His diagnosis was:
"Eye bare. Male broadly dichoptic, front narrowed posteriorly to just before anterior ocellus and at this point with a transverse impressed line, then very slightly broadened to vertex, at narrowest point just over 1/7 head width. Front of female narrowed almost to vertex, without impressed line, at narrowest point just over 1/6 head width. Face only very slightly broadened below, produced strongly forward on lower half, tubercle well developed and extending slightly beyond oral margin; oral opening 2.5 times as long as broad. Front and face black, shining, the latter with two broad vittae of dense silvery pollen which extend almost to the oral margin and beneath which, in some specimens, traces of reddish ground-colour may be seen. Scutum shining black or dark metallic blue with a weakly pollinose median area on about anterior 1/5 and with notopleuron densely silver pollinose. Scutellum shining black or dark metallic blue with well defined pollinose band on about anterior 1/6. Pleura black or dark metallic blue, lightly pollinose with part of mesopleuron and of sternopleuron densely pollinose. Dosal and ventral katepisternal pile patches broadly separated throughout. Metacoxa without tuft of pile at posteroventral apical angle. Abdomen elongate, parallel-sided in male, slightly oval in female, shining black or dark metallic blue above and below with narrow anterior margins of terga 2 and 3 and a transverse arcuate or triangular band on each of terga 2 to 4 opaque black."
Adapted from original description (Vockeroth 1969).
MALE.
Face weakly pollinose medially just below antenna, densely pollinose laterally. Pile of face, of front, and of extreme dorsal part of occiput black, those of rest of occiput white. Antenna black, basoflagellomere obscurely reddish below at base. Scutal pile mostly black, white only on notopleuron; scutellar pile black; pleural pile white. Wings slightly brownish; calypter and fringe white; haltere pale brown. Legs black, only extreme apices of femora, about basal 1/3, of pro- and mesotibiae, and extreme base of metatibia, reddish. Pile of legs mostly black, only those of coxae, of trochanters, and of ventral surfaces of femora, white. Abdomen with anterior shining areas, all of margins of tergum 2, and all sterna white-haired; abdomen otherwise black-haired.
Male genitalia: Extremely similar to those of Melangyna (Austrosyrphus) novaezelandiae Macquart. The only noticeable differences are in the more slender and more downcurved apex of the lingula, in the slightly more distinct angle separating the posterior and posteroventral margins of the superior lobe, in the slightly narrower posterodorsal process of the aedeagal base and in the slightly narrower base of the distal portion of the aedeagus.
FEMALE.
Extremely similar to male except for differences in front and abdominal shape mentioned above in generic description.
The single included species, with the male eyes broadly separated and the lower part of the face strongly produced, is so different from the other species of the genus Melangyna that it seemed at first necessary to erect a new genus for it within the Syrphini, or even that it might belong to the Melanostomini. However, the genitalia are so similar to those of the species of Melangyna (Austrosyrphus), especially in the detailed structure of the superior lobe and the aedeagal base, that a close relationship with that group is indisputable. The species could be included in Austrosyrphus but its separation as a fourth subgenus of Melangyna seems preferable. Treatment of Austrosyrphus and Melanosyrphus together as a genus distinct from Melangyna would also be reasonable, although the absence of distinctive characters other than those of the terminalia to separate these two groups as a unit from Melangyna and Meligramma makes this course impractical (from Vockeroth 1969).
Melangyna (Melanosyrphus) dichoptica 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]
unless otherwise stated