Melanostoma, Schiner, 1860

Ramage, Thibault, Charlat, Sylvain & Mengual, Ximo, 2018, Flower flies (Diptera, Syrphidae) of French Polynesia, with the description of two new species, European Journal of Taxonomy 448, pp. 1-37 : 27-29

Key to Australasian and Oceanian species of Melanostoma

1. Face with a distinct tubercle ( Fig. 7C, E); male genitalia small ( Fig. 7A, C)..........................4

– Face with only a trace of a tubercle, almost straight ( Figs 4D, 7D, 9A); male genitalia greatly enlarged, usually visible externally ( Figs 6G, 7B, D, 9B).............................................................2

2. Abdominal terga entirely black ( Figs 4A, 6 F–G); legs partly black in both male and female ( Figs 4C, 6 F–G). Male genitalia: surstylus curved towards dorsal part ( Fig. 9D) ( French Polynesia) ................................................................................................... M. polynesiotes sp. nov.

– Abdominal terga with large orange or yellow abdominal markings; male abdomen almost entirely orange with apical margins narrowly black and genitalic segments black ( Figs 7B, D, 9B); female abdomen with pairs of large, narrowly separated pale maculae ( Figs 7F, 8A); legs all orange, rarely metatibia with an indistinct medial brown band ( Fig. 7B, E). Male genitalia: surstylus curved towards ventral part ( Fig. 9G, I).........................................................3

3. Male surstylus club-shaped apically ( Fig. 9I). Female: frons extensively pollinose, with two small shiny areas above lunule and ventrad to anterior ocellus; shiny areas do not reach eye margin ( Fig. 8B) ( India, Sri Lanka, Thailand, Taiwan, Philippines, Borneo, Java, Central Moluccas: Buru) .................................................. M. univittatum (Wiedemann, 1824)

– Male surstylus tapers to slender acute apex ( Fig. 9G). Female: frons mainly shiny with two large lateral pollinose maculae; shiny areas reach eye margin ( Fig. 8C) (New Guinea, Australia, New Caledonia, Solomons, Fiji, Tonga, Samoa) ....................................... M. apicale Bigot, 1884

4. Abdominal terga with yellow maculae on terga 2–4, sometimes very large, but always with a medial continuous black vitta ( Fig. 7A) ( New Zealand) .................... M. fasciatum (Macquart, 1850)

– Abdominal terga entirely black, sometimes extensively dark pollinose (New Guinea) ................. ....................................................................................................... M. fumivenosum Doesburg, 1966