Key to species of the genus Diochus of Indonesia, Malaysia and Singapore

(Figs 1 −11)

1 Antennomeres longer: antennomere 3 more elongate, distinctly longer than antennomere 2; antennomere 4 more elongate, more than twice as long as wide.............................................................................. 2

- Antennomeres shorter: antennomere 3 less elongate, nearly equal to antennomere 2; antennomere 4 less elongate, less than twice as long as wide.................................................................................. 7

2 Tibiae partly in black color; known only from Borneo (Kalimantan, Indonesia)................................................................................................................. D. borneensis Cameron, 1933

- Tibiae not in black color................................................................................ 3

3 Body larger, longer than 6 mm; posterior margin of male sternite VIII emarginate medially, and with shallower emarginations on both sides......................................................................................... 4

- Body smaller, shorter than 5.5 mm; posterior margin of male sternite VIII only emarginate medially, or with deeper emarginations on both sides......................................................................................... 5

4 Posterior margin of male sternite VIII with medial emargination deep and rounded, posterior angles strongly sharpened..................................................................... D. paradoxus Huang, Janák & Zhou, sp. nov.

- Posterior margin of male sternite VIII with medial emargination shallow, not rounded, posterior angle slightly sharpened................................................................ D. paraparadoxus Huang, Janák & Zhou, sp. nov.

5 Posterior margin of male sternite VIII with medial emargination very deep, posterior angles strongly sharpened and projecting; known only from Borneo (Kalimantan, Indonesia)...................... D. parellipticus Huang, Janák & Zhou, sp. nov.

- Posterior margin of male sternite VIII with medial emargination shallow, not so rounded, with posterior angles not sharply projecting........................................................................................... 6

6 Head and pronotum more elongate; male sternite VIII distinctly narrowed at apex; aedeagus with parameres shorter and thicker........................................................ D. sulawesiensis Huang, Janák & Zhou, sp. nov.

- Head and pronotum less elongate; male sternite VIII not distinctly narrowed at apex; aedeagus with parameres longer and thinner................................................................. D. punctipennis (Motschulsky, 1858)

7 Elytra not in a uniform color, but in bicolor; basal transverse carina of male and female sternite VIII interrupted or absent................................................................................ D. pulchellus Cameron, 1918

- Elytra in a uniform color; basal transverse carina of male or female sternite VIII entire.............................. 8

8 Posterior margin of male sternite VIII nearly straight at middle, with slight emargination on both sides; basal margin of male sternite IX narrower than apical margin............................... D. lombokensis Huang, Janák & Zhou, sp. nov.

- Posterior margin of male sternite VIII emarginate at middle; basal margin of male sternite IX wider than apical margin..... 9

9 Posterior margin of male sternite VIII emarginate at middle and on both sides; aedeagus with parameres very short........................................................................ D. bogorensis Huang, Janák & Zhou, sp. nov.

- Posterior margin of male sternite VIII only emarginate at middle; aedeagus with parameres thin and long.............. 10

10 Pronotum more elongate; posterior margin of male sternite VIII with medial emargination deeper; basal transverse carina of male sternite VIII deeply produced at middle........................... D. uvellipticus Huang, Janák & Zhou, sp. nov.

- Pronotum not so elongate; posterior margin of male sternite VIII with medial emargination shallower; basal transverse carina of male sternite VIII shallowly produced at middle.......................................................... 11

11 Basal transverse carina of male sternite VIII sharp at middle; aedeagus with a T-shaped sclerite distally; body darker............................................................................... D. antennatus (Motschulsky, 1858)

- Basal transverse carina of male sternite VIII rounded at middle; aedeagus without T-shaped sclerite distally; body lighter.................................................................... D. acehensis Huang, Janák & Zhou, sp. nov.