Key to species of Nipponeurorthus

1. Forewing with a brown stripe along distal margin............................................................ 2

- Forewing without any marking along distal margin........................................................... 5

2. Male gonocoxite 9 bifurcated (Fig. 9)....................................................... N. furcatus sp. nov.

- Male gonocoxite 9 not bifurcated......................................................................... 3

3. Male ectoproct with posterolateral corners strongly protruding into a pair of digitiform processes (Fig. 4); distal parts of male gonocoxite+gonostylus+gonapophysis 10 blade-like and crossing each other at mid-length (Fig. 4)..................................................................................................... N. damingshanicus sp. nov.

- Male ectoproct with posterolateral corners feebly produced; distal parts of male gonocoxite+gonostylus+gonapophysis 10 not crossing each other.................................................................................... 4

4. Forewing with brownish markings distal to outer series of gradate crossveins (Nakahara 1958: Plate 8-2); male gonocoxite+gonostylus+gonapophysis 10 proximally sinuate (Nakahara 1958: Fig. 7 B).................... N. fasciatus Nakahara

- Forewing without brownish markings distal to outer series of gradate crossveins (Yang & Gao 2001: Fig. 1); male gonocoxite+gonostylus+gonapophysis 10 straight (Yang & Gao 2001: Fig. 5)...................... N. tianmushanus Yang & Gao

5. Male gonocoxite 9 distally bifurcated or trifurcated........................................................... 6

- Male gonocoxite 9 distally simple........................................................................9

6. Forewing with dark markings............................................................................ 7

- Forewing without any dark marking....................................................................... 8

7. Forewing only with brown markings on most crossveins and branching points of most longitudinal veins (Nakahara 1958: Plate 2-1); male gonocoxite+gonostylus+gonapophysis 10 with distal parts crossing each other (Nakahara 1958: Fig. 6 B).................................................................................... .. N. punctatus (Nakahara)

- Forewing with blackish brown markings along most longitudinal veins on distal half and costal crossveins on proximal half (Nakahara 1966: Plate 4-2); male gonocoxite+gonostylus+gonapophysis 10 presents as a pair of long spinous projections but not crossing each other (Nakahara 1966: Fig. 22)........................................ N. multilineatus Nakahara

8. Male gonocoxite 9 distally bifurcated into a slender, acutely pointed gonostylus 9 and an obtuse ventral lobe (Aspöck & Aspöck 2008b: Fig. 3)............................................................. N. flinti Aspöck & Aspöck

- Male gonocoxite 9 distally trifurcated into a slender, acutely pointed gonostylus 9 and two obtuse lobes (Nakahara 1958: Fig. 4 a).............................................................................. N. fuscinervis (Nakahara)

9. Male gonocoxite 9 with apex strongly incurved (see figure in Chen 1998: P. 104); Chinese species......... N. qinicus Yang

- Male gonocoxite 9 with apex not incurved; Japanese species.................................................. 10

10. Forewing with longitudinal veins almost yellow (Nakahara 1958: Plate 9-2); male gonocoxite+gonostylus+gonapophysis 10 with each distal lobe inflated and bearing three large claw-like projections (Nakahara 1958: Fig. 3 B)................................................................................................... .. N. pallidinervis Nakahara

- Forewing with longitudinal veins entirely brown (Nakahara 1958: Plate 9-2); male gonocoxite+gonostylus+gonapophysis 10 with each distal lobe inflated laterally and bearing two small claw-like projections (Nakahara 1958: Fig. 5 B)............................................................................................... N. tinctipennis Nakahara