Key to the species of Noctitrella Gorochov

1 Epiphallus each side with a spine-like projection near apical margin of dorsal surface .............................................. 2

- Epiphallus without any projection near apical margin of dorsal surface...................................................................... 6

2 Ectophallus parameres cystiform at apices; epiphallus each side with a short spine-like projection near apical margin of dorsal surface ............................................................................................................................................................ 3

- Ectophallus parameres unlike above; epiphallus each side with a long spine-like projection near apical margin of dorsal surface ................................................................................................................................................................ 5

3 Epiphallus distinctly narrowed apically, each side with a distinct spine-like projection on dorsal surface; endophallus narrow at apex, with round apical margin..................................................................................................................... 4

- Epiphallus slightly narrowed apically, each side with an indistinct spine-like projection on dorsal surface; endophal- lus wide at apex, with bilobate apical margin ................................................................................... N. hirsuta Ingrisch

4 Epiphallus parameres unidentated at apex; rami without any projection on outer sides .......... N. tranquilla Gorochov

- Epiphallus parameres multidentated at apex; rami each with a projection near apical one-third of outer side ............. .................................................................................................................................................... N. denticulata sp. nov.

5 Epiphallus each side with a spine-like projection near apex of dorsal surface; endophallus with acute apex ............... ...................................................................................................................................................... N. spinosa Gorochov

- Epiphallus each side with a spine-like projection at apical one-third of dorsal surface; endophallus with broadly rounded apex ...................................................................................................................................... N. glabra Ingrisch

6 Endophallus not bifurcated at apex, ectophallus parameres short ................................................................................ 7

- Endophallus bifurcated at apex, ectophallus parameres very long............................................................................... 8

7 Epiphallus narrow at base, slightly narrowed apically; endophallus short, not reaching apex of epiphallus................. ...................................................................................................................................................... N. berezini Gorochov

- Epiphallus wide at base, distinctly narrowed apically; endophallus long, extending over apex of epiphallus ............. ................................................................................................................................................... N. plurilingua Ingrisch

8 Head slightly wider than anterior margin of pronotum ................................................................. N. devexa Gorochov

- Head not wider than anterior margin of pronotum ....................................................................................................... 9

9 Metanotal gland with large and slightly transverse concavity ......................................................... N. ardua Gorochov

- Metanotal gland with small and round concavity..................................................................... N. parardua Gorochov