Key to adults of the Japanese species of Strigiphilus

1 Dorsal anterior plate ratio (DAPW/DAPL> 0.8) (Figs 3, 6); antennae sexually dimorphic, first segment of male antennae thickened and elongated as in Fig. 2 ........................................................ Strigiphilus heterocerus

1’ Dorsal anterior plate ratio (DAPW/DAPL) less than 0.8 (e.g. Figs 36, 39, 41, 44); antennae not sexually dimorphic....... 2

2 Male genitalia with large mesosome, as in Figs 19, 24, 28; dorsal anterior plate length about half the length of the head................................................................................... Strigiphilus heterogenitalis

2’ Male genitalia with small mesosome, as in Fig. 9; dorsal anterior plate length less than half the length of the head......... 3

3 Abdominal segment III with postspiracular seta; basal apodeme of male genitalia without thickened central prolongation of (Figs 9, 14)............................................................................ Strigiphilus cursor

3’ Abdominal segment III without long postspiracular seta; basal apodeme of male genitalia with a forked prolongation, not fused to penis (Figs 32, 37, 42).......................................................... cursitans species-group ... 4

4 Preconal head margin convex (Figs 30, 32).............................................. Strigiphilus ceblebrachys

4’ Preconal head margin concave (Figs 35, 38, 40 43)........................................................... 5

5 Male genitalia as in Fig. 42; ratio of male genitalia length to total body length (GL/TL) more than 0.16..................................................................................................... Strigiphilus tuleskovi

5’ Male genitalia as in Fig. 37; ratio of male genitalia length to total body length (GL/TL) less than 0.16.................................................................................................. Strigiphilus stenocephalus