Key to the species of Stenothemus from Southeast China

1. Elytra red, with moderately indicated longitudinal costae on disc...................................................... ............................................................................................ S. chinensis (Wittmer, 1982) comb. nov.

– Elytra black, yellow or light brown, with weakly or hardly indicated longitudinal costae on disc... 2

2. Pronotum subrounded, with lateral margins obviously sinuate, posterior angles distinctly protruding .......................................................................................................................................... 3

– Pronotum subquadrate, with lateral margins nearly parallel or feebly sinuate, posterior angles hardly protruding .......................................................................................................................................... 5

3. Elytra light brown, with irregular dark markings; aedeagus: dorsal plate of each paramere rounded at apex, layered but without protuberance at inner margin................... S.kuatunensis Wittmer, 1979

– Elytra yellow or black, without markings; aedeagus: dorsal plate of each paramere acute at apex, not layered, with a wide triangular protuberance at inner margin ........................................................... 4

4. Elytra uniformly yellow...................................................... S. biimpressiceps (Pic, 1930) comb. nov.

– Elytra black, with light yellow margins................................................ S. fukienensis Wittmer, 1974

5. Antennae extending beyond elytral apices, antennomeres III‒XI obviously widened and flattened in male..................................................................................... S. longicornis Y. Yang & H. Liu sp. nov.

– Antennae unlike above, at most reaching apical one-third length of elytra ...................................... 6

6. Elytra yellow, black at apices; aedeagus: basal piece with a triangular protuberance but without middle nodule on ventral side, laterophyses hooked at apices ........ S. nigriceps (Wittmer, 1955) comb. nov.

– Elytra unlike above, without apical macula; aedeagus: basal piece with a middle nodule on ventral side, laterophyses acute, never hooked.............................................................................................. 7

7. Elytra black, at most light brown at margins; antennae with smooth longitudinal grooves on antennomeres III‒XI in male ............................. S. limbatipennis (Pic, 1926) stat. rev. et comb. nov.

– Elytra yellow or light brown, at most with brown markings; antennae without smooth longitudinal grooves on antennomeres III‒XI in male ..........................................................................................8

8. Elytra uniformly yellow; aedeagus: dorsal plate of each paramere abruptly narrowed in middle ...... ................................................................................................... S. flavus Y. Yang & X. Yang sp. nov.

– Elytra light brown, with brown markings; aedeagus: dorsal plate of each paramere nearly parallelsided.................................................................................... S. pallicolor (Wittmer, 1951) comb. nov.