Key to the brachypterous Paederus species of mainland China

1 Male mandibles with dorsal tooth....................................................................... 2

- Male mandibles without dorsal tooth...................................................................... 7

2 Internal sac of aedeagus with two spines................................................................... 3

- Internal sac of aedeagus with one spine.................................................................... 4

3 HL/PL ≥ 1.00. Male right mandible with small dorsal tooth; internal sac of aedeagus with one long curved spine and one short spine. Posterior margin of female tergite VIII truncate.................. P. (Gnathopaederus) szechuanus (Chapin, 1927)

- HL/PL ≤ 0.95. Male right mandible with large dorsal tooth; internal sac of aedeagus with two short spines. Posterior margin of female tergite VIII convex.......................................... P. (Gnathopaederus) bursavacua Willers, 2001

4 Length of antenna no more than 3.0 mm; length of pronotum no more than 1.3 mm ............................................................................................... P. (Gnathopaederus) jilongensis Li & Zhou, 2009

- Length of antenna more than 3.3 mm; length of pronotum more than 1.6 mm ..................................... 5

5 Dorsal plate of aedeagus straight in lateral view and internal sac with one short spine. Female sternite IX slender............................................................................ P. (Gnathopaederus) cheni Peng & Li, 2015

- Dorsal plate of aedeagus weakly curved in lateral view and internal sac with one long spine. Female sternite IX stout...... 6

6 Smaller species, length of body: 8.3–10.5 mm. Male right mandible with small dorsal tooth; small aedeagus with more slender parameres...................................................... P. (Gnathopaederus) yunnanensis Willers, 2001

- Larger species, length of body 11.6–12.4 mm. Male right mandible with large dorsal tooth; large aedeagus with stouter parameres......................................................... P. (Gnathopaederus) xuei Peng & Li, 2015

7 Coloration of abdomen black............................................................................ 8

- Abdomen bicoloured (usually segments III–VI reddish and segments VII–X black)............................... 14

8 Coloration of head brown. Dorsal plate of aedeagus longer and extending far beyond apices of parameres.................................................................................. P. lateralis Li, Solodovnikov & Zhou, 2014

- Coloration of head black. Dorsal plate of aedeagus shorter and not reaching apices of parameres...................... 9

9 Small species, length of body no more than 8.5 mm .................. P. sinisterobliquus Li, Zhou & Solodovnikov, 2013

- Large species, length of body larger than 9.0 mm.......................................................... 10

10 Internal sac of aedeagus with two spines................................................................. 11

- Internal sac of aedeagus with three spines................................................................ 13

11 Maximum width of abdomen more than 2.1 mm. Parameres of aedeagus slender. Female sternite IX longer.......................................................................... P. parvidenticulatus Li, Zhou & Solodovnikov, 2013

- Maximum width of abdomen no more than 2.0 mm. Parameres of aedeagus stout. Female sternite IX shorter............ 1 2

12 HL/HW ≥ 0.95. aedeagus with apically hooked dorsal plate in dorsal view and two long sclerotized spines in the internal sac. Female sternite VIII with elliptic depression posteriorly................. P. volutobliquus Li, Zhou & Solodovnikov, 2013

- HL/HW ≤ 0.90. aedeagus with apically acute dorsal plate in dorsal view and two short sclerotized spines in the internal sac. Female sternite VIII without depression..................................... P. nanlingensis Peng & Li, new species

13 Length of antenna no more than 3.0 mm. Aedeagus with apically acute dorsal plate in dorsal view. Posterior margin of female tergite VIII convex.............................................................. P. jianyueae Peng & Li, 2014

- Length of antenna more than 3.2 mm. Aedeagus with apically hooked dorsal plate in dorsal view. Female tergite VIII with pro- nounced median process posteriorly.................................... P. biacutus Li, Zhou & Solodovnikov, 2013

14 Aedeagus stout, with short and stout dorsal plate in dorsal view............................................... 15

- Aedeagus slender, with long and slender dorsal plate in dorsal view............................................ 17

15 Legs reddish with infuscate apical portion of femora. Aedeagus with apically acute dorsal plate in dorsal view........................................................................................... P. tibetanus Cameron, 1928

- Legs yellowish brown. Aedeagus with apically convex dorsal plate in dorsal view................................ 16

16 Male labrum with sinuate anterior margin. Aedeagus with short parameres. Female sternite VIII with truncate median process posteriorly..................................................................... P. describendus Willers, 2001

- Male labrum with deeply excavate anterior margin. Aedeagus with long parameres. Posterior margin of female sternite VIII convex.............................................................. P. daicongchaoi Peng & Li, new species

17 Dorsal plate of aedeagus not reaching apices of parameres.................................................... 18

- Dorsal plate of aedeagus extending beyond apices of parameres............................................... 21

18 Segments III-VI of abdomen reddish and with black patch in middle; elytra with pronounced impression.................................................................................... P. (Harpopaederus) gottschei Kolbe, 1886

- Segments III-VI of abdomen pale-reddish and without black patch in middle; elytra without impression............... 19

19 Body length no more than 10.0 mm. Dorsal plate of aedeagus without denticles................................................................................................... P. (Harpopaederus) antennocinctus Willers, 2001

- Body length more than 11.0 mm. Dorsal plate of aedeagus with claw-like denticles............................... 20

20 Length of aedeagus: 2.4 mm; dorsal plate with five denticles. Female tergite VIII apically narrower....................................................................................... P. (Harpopaederus) deplectens Assing, 2015

- Length of aedeagus: 2.7 mm; dorsal plate with two denticles. Female tergite VIII apically broader...................................................................................... P. (Harpopaederus) chinensis Bernhauer, 1931

21 Dorsal plate of aedeagus without denticles................................................................ 22

- Dorsal plate of aedeagus with denticles.................................................................. 23

22 Length of aedeagus: 1.4 mm; internal sac without sclerotized basal structures...... P. (Harpopaederus) xui Peng & Li, 2015

- Length of aedeagus: 2.0 mm; internal sac with one clip-shaped weakly sclerotized basal structure........................................................................................ P. (Harpopaederus) edentulus Assing, 2015

23 Legs with blackish metatibiae.......................................................................... 24

- Coloration of metatibiae much paler (usually yellowish)..................................................... 25

24 Length of aedeagus: 2.4–2.7 mm, with apically stouter dorsal plate. Female sternite VIII with short median process posteriorly................................................................. P. (Harpopaederus) apfelsinicus Willers, 2001

- Length of aedeagus: 2.9 mm, with apically more slender dorsal plate. Female sternite VIII with long median process posteri- orly.................................................... P. (Harpopaederus) lineodenticulatus Li & Zhou, 2007

25 Forebody longer than 5.8 mm. Aedeagus long.............................. P. (Harpopaederus) minicus Assing, 2015

- Forebody no more than 5.5 mm. Aedeagus short........................................................... 26

26 Internal sac of aedeagus with one long, apically acute, and sclerotized apical structure............................. 27

- Internal sac of aedeagus without distinctly sclerotized apical structure......................................... 29

27 Length of aedeagus: 2.4 mm, with long apical portion of the dorsal plate....... P. (Harpopaederus) cultellatus Assing, 2015

- Length of aedeagus: 1.9–2.1 mm, with short apical portion of the dorsal plate.................................... 28

28 Coloration of tibiae pale; mandibles and shape of head without sexual dimorphisms. Aedeagus with moderately sclerotized apical internal structure............................................ P. (Harpopaederus) agnatus Eppelsheim, 1889

- Coloration of tibiae dark; mandibles and shape of head with pronounced sexual dimorphisms. Aedeagus with strongly sclerotized apical internal structure..................................... P. (Harpopaederus) konfuzius Willers, 2001

29 Femora brown. Dorsal plate of aedeagus with 20 small denticles; parameres apically weakly curved in larteal view...................................................... P. (Harpopaederus) multidenticulatus Li, Zhou & Solodovnikov, 2014

- Femora bicoloured. Dorsal plate of aedeagus with several large denticles; parameres apically hooked in larteal view...... 3 0

30 Head transverse (HL/HW: 0.9). Dorsal plate of aedeagus with short apical portion. Female sternite VIII with strongly convex posterior margin....................................... P. (Harpopaederus) brevior Li, Zhou & Solodovnikov, 2014

- Head weakly transverse (HL/HW: 0.99). Dorsal plate of aedeagus with long apical portion. Female sternite VIII with long median process posteriorly...................................... P. (Harpopaederus) gracilacutus Li & Zhou, 2007