Key to species of Symbiopsocus

Males

1. Hypandrium with one tier of lobes (Li 2002: Fig. 1262G)..................................................... 2

- Hypandrium with two or more tiers of lobes (Li 2002: Fig. 1263E).............................................. 3

2. Phallosome ovoid, basally expanded (Li 2002: Fig. 1262E).......................................... diplocyclus Li

- Phallosome long and narrow (Li 2002: Fig. 1268E–F)............................................... ternatus (Li)

3. Hypandrium with median tongue-like structure (Yoshizawa & Mockford 2012: Fig. 2C)............................. 4

- Hypandrium without median tongue-like structure (Yoshizawa 2008: Fig. 2C).................................... 10

4. Hypandrium with median tongue-like structure divided bilaterally with narrow notch posteriorly (Yoshizawa & Mockford 2012: Fig. 2C)........................................................................................ 5

- Hypandrium with median tongue-like structure not divided bilaterally with narrow notch posteriorly (Li 2002: Fig. 1264G).. ................................................................................................... 6

5. Median tongue-like structure of hypandrium with a pair of processes extending from dorsal surface near base of tongue directed postero-laterally (Yoshizawa & Mockford 2012: Fig. 2C)........................................ hastatus Mockford

- Median tongue-like structure of hypandrium without process extending from dorsal surface near base of tongue directed posterolaterally (Li 2002: Fig. 1270G)........................................................ multimacularis (Li)

6. Forewing with short spur vein (Li 2002: Figs 1271B, 1272B).................................................. 7

- Forewing without spur vein............................................................................. 8

7. Forewing Rs and M meeting at a point; phallosome long and narrow, not curved medially................. dolichosus (Li)

- Forewing Rs and M connected by a crossvein; phallosome curved medially, nearly with angle of 90° (Li 2002: Fig. 1272E–F)..................................................................................... septangulatus (Li)

8. Hypandrium with median tongue-like structure relatively large; phallosome curved (Li 2002: Figs 1264G, 1264E–F)................................................................................................. bicruris (Li)

- Hypandrium with median tongue-like structure smalle; phallosome long and narrow, not curved....................... 9

9. Hypandrium with a pair of spines on bottom of ventral lobe (Liu et al. 2014: Fig. 5)................ yangminus Liu & Liu

- Hypandrium without spines on bottom of ventral lobe.......................................... ophiocephalus (Li)

10. Hypandrium basally with fine spines (Li 2002: Fig. 1266G)................................................... 11

- Hypandrium basally smooth, without spines............................................................... 13

11. Ventral and dorsal lobes of hypandrium covered with minute denticles (Yoshizawa 2008: Fig. 2C)... formosanus (Okamoto)

- Ventral and dorsal lobes of hypandrium smooth (Li 2002: Fig. 1266G).......................................... 12

12. Hypandrium basally with five spines (Li 2002: Fig. 1266G)........................................ chaulommaus Li

- Hypandrium basally with an area of small spines (Li 2002: Fig. 1269F).............................. subrhombeus Li

13. Epiproct proximally flat..................................................................... longicaulis (Li)

- Epiproct proximally invaginated on each side.............................................................. 14

14. Hypandrium asymmetrical (Li 2005: Fig. 15E)....................................................... yajunae Li

- Hypandrium symmetrical.............................................................................. 15

15. Forewing with Sc ending in Rs................................................................ leptocladus Li

- Forewing with Sc ending free in membrane................................................................ 16

16. Epiproct anteromedially with a short cone-shaped projection (Liu et al. 2011: Fig. 6)............................... 17

- Epiproct anteromedially without cone-shaped projection......................................... quadripartitus Li

17. Hypandrium basally with sharp sclerotized region on each side (Liu et al. 2011: Fig. 5)................ furcatus Liu & Liu

- Hypandrium basally without a sharp sclerotized region (Fig. 3D)................................ vietnamicus sp. nov.