Key to species of Amplicephalus (Nanctasus) Linnavuori

1 Female sternite VII distinctly emarginate medially............................................................ 2

- Female sternite VII truncate or slightly produced medially...................................................... 3

2 Forewing with several supernumerary crossveins in clavus and along costal margin; pronotum with five pale longitudinal stripes................................................................................. A. (N.) auranticus

- Forewing without supernumerary crossveins; pronotum with a single broad median longitudinal band....... A. (N.) insularis

3 Forewing without extra crossveins; female sternite VII with small median notch and two larger pairs of sublateral notches posteriorly................................................................................... A. (N.) pallidus

- Forewing with extra crossveins; female sternite VII slightly produced or truncate without notch........................ 4

4 Aedeagus with branches of bifid apex widely separated in ventral view, sinuate in lateral view (Fig. 2D–E)................................................................................................... A. (N.) anayensis sp. n

- Aedeagus with branches of bifid apex very narrowly separated in ventral view, straight or curved dorsad in lateral view..... 5

5 Aedeagus broadened then narrowed preapically in ventral view, straight in lateral view................... A. (N.) bolivicus

- Aedeagus narrowed through most of length in ventral view, curved dorsad in lateral view (Fig. 4F–G).................................................................................................. A. (N.) paralbivenosus sp. n.