Key to Chinese species of the indubius group

1. Pronotum with median longitudinal furrow; elytra with surface very uneven; 4th to 6th abdominal segments with tergites and sternites distinctly separated ( Hemistenus)............................................................2

- Pronotum without median longitudinal furrow; elytra with surface weakly uneven; 4th to 6th abdominal segments with tergites and sternites completely fused without joint suture ( Hypostenus) ....................... 4

2. Abdominal punctation denser, interstices on 3rd to 7th abdominal tergites distinctly smaller than half diameter of punctures; posterior margin of 7th abdominal sternite of male without emargination. Aedeagus as in Fig. 11, spermatheca as in Fig. 13. BL: 4.0– 4.2 mm. China: Sichuan .......................................... ................................................................................................................... S. pectorifossatus Tang, sp. nov.

- Abdominal punctation sparser, interstices on 3rd to 7th abdominal tergites smaller than half diameter of punctures; posterior margin of 7th abdominal sternite of male with slight median emargination..............3

3. Body larger (BL: 3.8–4.2 mm); median longitudinal furrow and impressions on pronotum very deep. Aedeagus as in Fig. 16, spermatheca as in Fig. 18. China: Sichuan ......... S. erlangshanus Tang, sp. nov.

- Body smaller (BL: 3.0– 3.7 mm); median longitudinal furrow and impressions on pronotum relatively shallow. Aedeagus as in Fig. 6, spermatheca as in Fig. 8 .. China: Sichuan ... S. zhuxiaoyui Tang, sp. nov.

4. Body larger (BL: 4.3–4.8 mm), elytra shorter (EL: EW=43.5: 47.0). Aedeagus as in Fig. 9 (in Tang & Li 2005), spermatheca as in Fig. 10 (in Tang & Li 2005). China: Anhui ......... S. guniujiangensis Tang & Li

- Body smaller (BL: 3.3–3.5 mm), elytra longer (EL: EW=38.0: 37.5). Aedeagus as in Fig. 5 (in Tang & Li 2005), spermatheca as in Fig. 6 (in Tang & Li 2005). China: Anhui ................... S. paradecens Tang & Li