Key to the valid species of the Otostigmus rugulosus group (Modified from Lewis, 2010)

1 With prefemoral distodorsal spine on leg 20................................................................. 2

- Without prefemoral distodorsal spine on leg 20.............................................................. 3

2 Typically with 4+4 main forcipular coxosternal teeth, tergites without spinules, sternite 21 with sides converging posteriorly.. O. spinosus

- Typically with 3+3 main forcipular coxosternal teeth, tergites typically with spinules, sternite 21 with sides ± parallel............................................................................................... O. punctiventer

3 With 3+3 main forcipular coxosternal teeth................................................................. 4

- With 4+4 main forcipular coxosternal teeth................................................................. 5

4 With a single apical coxopleural spine............................................................. O. martensi

- With two or three apical coxopleural spines................................................................. 6

5 Coxopleural process long, and curved in females, ultimate leg prefemora with four rows of spines, leg 20 with one tarsal spur................................................................................... .. O. xizangensis n. sp.

- Coxopleural process short and straight, ultimate leg prefemora with three rows of spines, leg 20 without tarsal spur.......................................................................... O. rugulosus incl. O. rugulosus striaturatus

6 Sternite paramedian sutures absent or present on anterior sternites only and very short ............................... 7

- Sternite paramedian sutures present...................................................................... 10

7 Tergites with small tubercles................................................................... O. noduliger

- Tergites without small tubercles.......................................................................... 8

8 Coxopleural process without lateral spines........................................................ O. olivaceus

- Coxopleural process with one or two lateral spines........................................................... 9

9 First 3 pairs of legs with two tarsal spurs, ultimate legs without tarsal spur................................... O. feae

- First 15 pairs of legs with two tarsal spurs, ultimate legs with tarsal spur................................. O. fossuliger

10 With (19)20–21 antennomeres and two apical and one subapical coxopleural spine................................ 11

- With 18 antennomeres and two apical coxopleural spines................................................ O. beroni

11 Sternite paramedian sutures complete in mid-body region, the basal 2.66 antennomeres glabrous. Sternite 21 narrowed posteriorly........................................................................ O. angusticeps schindleri

- Paramedian sutures occupying at most anterior 50% of each sternite in mid-body region, the basal 2.33 antennomeres glabrous. Sternite 21 with sides diverging, parallel or converging posteriorly........................................ O. astenus