Key to the species of the sinuatus group

1 Elytra twice as long as pronotum or slightly longer. Median lobe with small subacute apex; parameres extending slightly beyond apex of median lobe (Fig. 45). Body black. Body length: 5.0– 6.5 mm. Japan (Hokkaido, Honshu)..... G. sinuatus

- Elytra slightly less than twice as long as pronotum. Median lobe with blunt obtuse apex; parameres extending significantly beyond apex of median lobe (Fig. 47). Body reddish brown to black. Body length: 4.9–6.0 mm. Japan (Honshu).................................................................................................... G. suensoni