Epeorus, Eaton, 1881, Eaton, 1881

Key to mature View in CoL nymphs in Sapporo City and adjacent areas

1 Gill I anteriorly enlarged ( Figs 16e View FIGURE 16 , 17e View FIGURE 17 , 24d View FIGURE 24 , 25e View FIGURE 25 ); gill VII with longitudinal fold ( Figs 17g View FIGURE 17 , 25g View FIGURE 25 ); pronotum slightly projecting laterally ( Figs 29b, d View FIGURE 29 )................................................................................. 2

- Gill I not anteriorly enlarged ( Figs 6d View FIGURE 6 , 7e View FIGURE 7 , 11d View FIGURE 11 , 21d View FIGURE 21 , 22e View FIGURE 22 ); gill VII without longitudinal fold ( Figs 7h View FIGURE 7 , 22g View FIGURE 22 ); pronotum roundly projecting laterally ( Figs 29a, c View FIGURE 29 )......................................................................... 3

2 Gill I strongly enlarged and meet at beneath mesothorax ( Figs 15b, e View FIGURE 15 , 16e View FIGURE 16 , 17e View FIGURE 17 ); posterior margin of abdominal terga with sharp denticles ( Figs 17j View FIGURE 17 , 31c View FIGURE 31 ).................................................................. E. ( C.) curvatulus

- Gill I slightly enlarged and not meet at beneath mesothorax ( Figs 23b, e View FIGURE 23 , 24d View FIGURE 24 , 25e View FIGURE 25 ); posterior margin of abdominal terga with blunt denticles ( Figs 25j View FIGURE 25 , 31e View FIGURE 31 )................................................................ E. ( I.) aesculus

3 Gills with dark-violet spots ( Figs 6d View FIGURE 6 , 11d View FIGURE 11 ); gills II–VII with anal proximal projections ( Figs 6d View FIGURE 6 , 11d View FIGURE 11 ); posterior margin of abdominal terga with sharp denticles ( Figs 7k View FIGURE 7 , 12g View FIGURE 12 , 31a, b View FIGURE 31 ).................................................... 4

- Gills without dark-violet spots ( Fig. 21d View FIGURE 21 ); gills II–VII with anal ribs ( Fig. 21d View FIGURE 21 ); posterior margin of abdominal terga with blunt denticles ( Figs 22j View FIGURE 22 , 31d View FIGURE 31 ).................................................................. E. ( P.) nipponicus

4 Outer margin of inner incisor of the left mandible with sharp serration ( Fig. 7c View FIGURE 7 )....................... E. ( B.) latifolium

- Outer margin of inner incisor of the left mandible without sharp serration ( Figs 12c, f View FIGURE 12 ).................. E. ( B.) L-nigrum

Key to male imagines in Sapporo City and adjacent areas

1 Black markings on the base of veins of the forewing ( Figs 8e View FIGURE 8 , 13e View FIGURE 13 , 18e View FIGURE 18 ).......................................... 2

- No markings on the base of veins of the forewing ( Fig. 26e View FIGURE 26 )................................................... 3

2 Penis with titillators ( Figs 13f View FIGURE 13 , 18f View FIGURE 18 )....................................................................... 4

- Penis without titillators ( Fig. 8f View FIGURE 8 )............................................................. E. ( B.) latifolium

3 Forceps base without projection, penis laterally expanded with spines ( Fig. 26f View FIGURE 26 )........................ E. ( I.) aesculus

- Forceps base with projection, penis laterally expanded without spines (following Ma et al. 2021: p. 1149, figs 12c, 13c).......................................................................................... E. ( P.) nipponicus

4 Posterior margin of styliger plate triangular edged ( Fig. 13f View FIGURE 13 )....................................... E. ( B.) L-nigrum

- Posterior margin of styliger plate rounded ( Fig. 18f View FIGURE 18 )............................................ E. ( C.) curvatulus