Key to species of the genus Nipponophloeostiba (modified from Shavrin 2020)

1 Postocular portions of head distinctly widened lateroposteriad, with short posterior carina not reaching posterior margin of eye. Aedeagus as in Figs. 86–87 in Watanabe (1990). Head and pronotum reddish-brown, elytra and abdomen yellow-brown. Body length: 2.30–2.70 mm. South Japan .............................................. N. verrucifera Watanabe, 1962

- Postocular portions of head not or indistinctly widened lateroposteriad, with longer posterior carina reaching posterior margin of eye or basal margin of ptonotum. Coloration different...................................................... 2

2 Head as broad as pronotum. Elytra moderately long, significantly longer than pronotum. Median lobe and parameres narrow as in Fig. 2 in Shavrin (2020). Head and abdomen brown, pronotum reddish-brown. Body length: 1.75–2.22 mm. Malaysia .................................................................................... N. thayeri Shavrin, 2020

- Head slightly narrower or broader than pronotum. Elytra shorter, slightly broader than pronotum. Median lobes and parameres different. Coloration different........................................................................... 3

3 Head slightly narrower than pronotum.Aedeagus as in Fig. 39 in Shavrin (2020). Head, pronotum and abdomen reddish-brown, elytra yellow-brown, with darker parascutellar portion. Body length: 2.07 mm. Laos, Indonesia (Sulawesi)............................................................................................ N. longilobata Shavrin, 2020

- Head slightly broader than pronotum. Aedeagus and coloration different. Body larger............................... 4

4 Temples slightly shorter than longitudinal length of eyes. Elytra as broad as long. Body reddish-brown. Median lobe narrow; parameres strongly broadened in apical portions as in Fig. 3 in Shavrin (2023a). Habitus as in Fig. 1 in Shavrin (2023a). Body length: 2.33 mm. Indonesia (Bali)................................................... N. explanata Shavrin, 2023

- Temples three times shorter than longitudinal length of eyes. Elytra slightly longer than broad. Head, pronotum and abdomen reddish-brown; elytra yellow-brown, with reddish apical portion. Median lobe wide; parameres slightly broadened in apical portions (Fig. 7). Habitus as in Fig. 1. Body length: 2.34 mm. Papua New Guinea ................. N. hornabrooki sp. n.