Key to the Oligaphorura species of East Asia and adjacent areas*

Main diagnostic characters are shown in Table 2.

1 With 4+4 pso at antennal base........................................................................... 2 - With 3+3 pso at antennal base........................................................................... 7

2 Both Th. II–III with lateral ms; anal spines present; one anterior pso on head inside Ant. basis, three pso outside it........ 3

- Only Th. II with ms; anal spines absent.................... O. ambigua Babenko & Fjellberg, 2015 (Russia, Magadan)

3 Head with only 2+2 posterior pso; axial chaeta a0’ on head present............................................. 4

- Head with 3+3 posterior pso; axial chaeta a0’ on head absent.................................................. 5

4 Abdominal terga with 44454 pso........................................ O. kedroviensis sp. nov. (Russia, Far East)

- Abdominal terga with 5(6)5554 pso........................................ O. ussurica sp. nov. (Russia, Far East)

5 ABC labium........................................ O. chankaensis Su & Wu, 2012 (in: Sun & Wu 2012c) (China)

- Labial papilla B not thickened, i.e. A or AC labium.......................................................... 6

6 A labium; abdominal pso dorsally as follows 54453.......................... O. montana Weiner, 1994 (North Korea)

- AC labium; abdominal terga with 54464 pso.......... O. pseudomontana Su & Wu, 2012 (in: Sun & Wu 2012b) (China)

7 Abd. IV with only 3 dorsal pso.......................................................................... 8

- Abd. IV with 4–5 dorsal pso............................................................................ 9

8 Th. I with 1+1 dorsal pso; AIIIO with 4 papillae................................... O. palissai (Yosii, 1971) (Nepal)

- Th. I without pso; AIIIO with 5 papillae.................................... O. tottabetsuensis (Yosii, 1972) (Japan)

9 Posterior pso on head in unusual (triangular) arrangement............ O. kurtshevae (Martynova, 1981) (Russia, Far East)

- Posterior pso on head in usual (not triangular) arrangement................................................... 10

10 Th. III without ms................................................................................... 11

- Both Th. II–III with ms............................................................................... 15

11 Furcal remnant with cuticular fold and 1+1 posterior chaetae..................... O. absoloni (Börner, 1901) (Germany)

- Fr with cuticular fold and 2+2 posterior chaetae............................................................ 12

12 Th. I without pso....................................... O. nataliae (Fjellberg, 1987) (Russia, Far East, Chukotka)

- Th. I with 1+1 dorsal pso.............................................................................. 13

13 AC labium................................................. O. sabulosa Babenko, 2007 (Russia, Middle Siberia)

- A labium.......................................................................................... 14

14 Ventral psx 10/000/212201+ 1 m; psx on upper Sc 1-2(1)-2(1); 10 guards on labial palp........................................... O. ursi (Fjellberg, 1984) sensu Babenko & Fjellberg 2015 (Norway, Sweden, Greenland, Alaska, NE Siberia)

- Ventral psx 0/000/ 122200; psx on upper Sc completely absent; 11 guards on labial palp................................................................................................... O. ursi sensu Sun & Wu 2012 (China)

15 Furcal remnant with 1+1 posterior chaetae................................................................ 16

- Furcal remnant with 2+2 posterior chaetae................................................................ 21

16 Furcal remnant with cuticular fold...................................................................... 17

- Furcal remnant as finely granulated area without cuticular fold................................................ 18

17 Abdominal tergum IV with 5 pso; ABC labium........ O. changbaiensis (Sun & Wu, 2012; in: Sun & Wu 2012b) (China)

- Abdominal tergum IV with 4 pso; AC labium.............. O. shifangensis Liu & Sun, 2019 (in: Liu et al. 2019) (China)

18 Th. I without pso................................. O. sanjiangensis (Sun & Wu, 2012; in: Sun & Wu 2012a) (China)

- Th. I with 1+1 pso................................................................................... 19

19 A labium........................................ O. jingyueensis (Sun & Wu, 2012; in Sun & Wu 2012c) (China)

- AC labium......................................................................................... 20

20 Abdominal terga IV–V with 5 and 4 pso, respectively............................ O. wanglangensis sp. nov. (China)

- Abdominal terga IV–V with 4 and 3 pso, respectively.................... O. alnus (Fjellberg, 1987) (Russia, Magadan)

21 Furcal remnant without cuticular fold; upper Sc with 23(2)3 pso.................................................................................................... O. duocellata Babenko & Fjellberg, 2015 (Russia, Magadan)

- Furcal remnant with cuticular fold; upper Sc with 111 pso.................................................... 22

22 Th. I without pso.................................................................................... 23

- Th. I with 1+1 pso................................................................................... 25

23 Thoracic sterna without chaetae.................................. O. interrupta (Fjellberg, 1987) (Russia, Magadan)

- Ventral chaetae on Th. II–III present..................................................................... 24

24 Ventral psx: 10/000/222201+ 1 m; axial chaetae a0’ on head absent................ O. pingicola (Fjellberg, 1987) (Alaska)

- Ventral psx indistinct; axial chaetae a0’on head present … O. koreana (Weiner, 1994) (North Korea)

25 Th. II–III with ventral chaetae.................................. O. aborigensis (Fjellberg, 1987) (Russia, Magadan)

- Thoracic sterna without chaetae........................................................................ 26

26 Two anterior pso on head inside Ant. basis; chaetae p1 and p2 on head set in line; axial chaetae a0’ on head absent............................................................................ O. judithae (Weiner, 1994) (North Korea)

- One anterior pso on head inside Ant. basis; chaetae p 1 in front of p2 on head; axial chaetae a0’ on head present.............................................................................. O. linderae (Weiner, 1994) (North Korea)