Key to species of the genus Diochus Erichson recorded from China

1 Left mandible with blunt teeth (Fig. 10 H); body small, not longer than 3 mm; protarsi not dilated (Fig. 10 L); distribution in China not confirmed................................................................. D. pulchellus Cameron

- Left mandible with sharp teeth; body usually longer than 3 mm; protarsi dilated (Fig. 4 M)............................ 2

2 Antennomere II obviously shorter than III (Fig. 4 G).......................................................... 3

- Antennomere II slightly shorter than (or subequal in length to) III (Fig. 5 G)....................................... 5

3 Body large, ca. 6.0 mm; head length 1.2 times longer than width; distribution in China not confirmed.. D. japonicus Cameron

- Body medium sized, ca. 5.1 mm; head length 1.3-1.4 times longer than width...................................... 4

4 Right mandible with a long and sharp tooth (Fig. 9 J); aedeagus not well-sclerotized, with paired stick-like apical sclerites (Fig. 9 E-G); distribution in China not confirmed........................................... D. conicollis (Motschulsky)

- Right mandible with a smaller and not very sharp tooth (Fig. 4 J); aedeagus well-sclerotized, with paired horn-like apical scler- ites (Fig. 4-1 E, F).................................................................... D. bicornutus sp. nov.

5 Body small sized, 3.3 mm; aedeagus with T-shaped internal sclerite (Fig. 8); distribution in China not confirmed........................................................................................ D. antennatus (Motschulsky)

- Body slightly longer than 3.4, or distinctly longer (ca. 4 mm); aedeagus without distinct sclerite....................... 6

6 Head not possessing a median elevation between eyes.................................... D. membranaceus sp. nov.

- Head possessing a median elevation between eyes (Fig. 1, medial elevation)....................................... 7

7 Gular sutures deep and confluent before base (Fig. 6 D).................................... D. bisegmentatus sp. nov.

- Gular sutures normally deep and not confluent before base (Fig. 5 D).......................... D. ampullaceus sp. nov.