Melanostoma Schiner 1860

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