1 Lateral prescutal stripe straight (Fig. 2).................................................................... 2
- Lateral prescutal stripe curved outward (Figs. 5, 13, 16, 32, 40)................................................ 3
2 Isolated spot beneath anterior end of lateral prescutal stripe present; sternite 8 apically with a spiky middle projection; lobe of gonostylus short and partly sclerotized (Figs. 1, 2) (Oosterbroek 1978: p. 63, figs. 89, 92, 96A).... N. aculeata (Loew, 1871)
- Isolated spot beneath anterior end of lateral prescutal stripe absent; sternite 8 apically widely V-shaped at middle, with tuft of long golden hairs; lobe of gonostylus slender and fleshy (Oosterbroek 1979b: p. 169, figs. 10, 12)................................................................................................ N. quadristriata (Schummel, 1833)
3 Sternite 8 with a middle appendage (Figs. 35, 43) (Yang & Yang 1987: p. 244, Fig. 3A).............................. 4
- Sternite 8 without middle appendage (Figs. 8, 19) (Tangelder 1984: p. 28, Fig. 17)................................. 8
4 Projection of sternite 8 acute at apex; wing tip with numerous small macrotrichiae (Fig. 41) (Oosterbroek 1978: p. 70, fig. 10 3)................................................................................ N. tenuipes (Riedel, 1910)
- Projection of sternite 8 blunt at apex; wing tip with some small macrotrichiae...................................... 5
5 Tergite 9 darkened with a sickle-shaped pale yellow spot in front of posterior projection; mid-posterior margin of sternite 8 sunken (Figs. 35, 36) (Oosterbroek 1979b: p.175, figs. 59–61, 65–59)............. N. lundbecki lundbecki (Nielsen, 1907)
- Tergite 9 without spot; mid-posterior margin of sternite 8 flattened or convex (Fig. 14) (Yang & Yang 1987: p. 244, Fig. 3A; Oosterbroek 1978: p. 103, figs. 160A, 160B; Alexander 1925: p. 403)........................................... 6
6 Posterior extension of tergite 9 shallowly incised, without lateral projection; mid-posterior margin of sternite 8 with small projection (Yang & Yang 1987: p. 244, Figs. 3A, 3B)............................. N. xinjiangensis Yang and Yang, 1987
- Posterior extension of tergite 9 deeply incised, with lateral projections; mid-posterior margin of sternite 8 with relatively long projection (Oosterbroek 1978: p. 103, figs. 157, 160A, 160B; Alexander 1925: p. 403).............................. 7
7 Occipital marking extending up to top of vertex; median projection of sternite 8 knob-like at tip (fig. 13) (Oosterbroek 1978: p.103, figs. 156A, 156B, 160A, 160B)...................................... N. cornicina cornicina (Linnaeus, 1758)
- Occipital marking not extending to top of vertex; median projection of sternite 8 subtruncate at tip (Alexander 1925: p. 403)................................................................................ N. ligulata Alexander, 1925
8 Wing without distinct shades; caudo-ventral surface of sternite 9 with broad lateral plates and a ventrally directed medisternal appendage (Tangelder 1984: p. 28–29, Fig. 16).......................................... N. pjotri Tangelder, 1984
- Wing with shade at basal part of vein R4+5 and cross vein r-m; medisternal appendage of sternite 9 absent (Figs. 6, 8, 17, 19)..................................................................................................... 9
9 Posterior extension of tergite 9 deeply depressed with two conical projections bearing short tines; sternite 8 clothed with long golden hairs (Figs. 6, 8, 9) (Oosterbroek 1979b: p. 140, figs. 8A).......................... N. analis (Schummel, 1833)
- Posterior extension of tergite 9 slightly depressed with four projections bearing tiny black spines; sternite 8 clothed with small hairs (Figs. 17, 19, 20)................................................................. N. kanasensis sp. nov.