Key to the species of Nyctimenius Gressitt

1 Gena covered with yellow or yellowish brown pubescence, pronotum with yellow longitudinal vittae................... 2

- Gena covered with white or grayish white pubescence, pronotum with white or grayish white longitudinal vittae.......... 4

2 Pronotum with two broad yellow longitudinal vittae at sides; elytra with two broad yellow longitudinal vittae at sides of the disc; antennomeres IX–X white; legs black brown........................................ N. mamutensis Hayashi

- Pronotum with three yellow longitudinal vittae.............................................................. 3

3 Scutellum densely covered with white pubescence, elytra with white pubescence along suture to apex, mesepimeron, mesaepisternum and metaepisternum covered with dense, yellow pubescence............. N. ochraceovittatus Aurivillius

- Scutellum densely covered with yellowish brown pubescence, elytra with yellowish brown pubescence along suture to apex, mesepimeron, mesanepisternum and metanepisternum covered with dense yellowish brown pubescence.................................................................................................. N. sabahensis Hayashi

4 Femora red or reddish.................................................................................. 5

- Femora not red or reddish............................................................................... 6

5 Antennomeres IX–X white; abdomen with discrete and elongate spots at sides............... N. palawanicus Aurivillius

- Antennomeres IX–X white, or VIII–X white; abdomen without discrete and elongate spots at sides...... N. tristis Fabricius

6 Antennomeres VIII–IX white; vertex unpunctured......................................... N. subsericeus Pascoe

- Antennomeres IX–X white or pale yellow; vertex punctured.................................................... 7

7 Antennomeres VIII–X pale yellow; femora, base of tibiae and tarsal segment V yellowish brown; vertex, pronotum and elytra moderately covered with dense and coarse punctures......................................... N. chiangi, sp. nov.

- Antennomeres IX, X and base of XI white or yellow; legs gray; vertex, pronotum and elytral base sparsely covered with fine punctures......................................................................... N. varicornis Fabricius