Key to the Eastern Palaearctic Synergus species

1 Radial cell of fore wing closed (Fig. 14).................................................................... 3

- Radial cell of fore wing partially or entirely open (Fig. 88)..................................................... 2

2 Radial cell of fore wing entirely open, R1 and Rs do not reach wing margin.............................. S. castaneus

- Radial cell partially open, R1partially running along wing margin........................... S. kawakamii, new species

3 Posterior band of micropunctures on syntergite extending to ventral edge (Figs 15, 42, 105–106)..................... 4

- Small posterodorsal patch of micropunctures on syntergite never extending laterally (Figs 29, 57, 73–74, 121 –122)..... 10

4 Lateral frontal carina indistinct, visible only near torulus; female F1 curved medially and expanded apically; male F1 strongly expanded apically and basally, 3.0 times as long as pedicel......................................... S. deqingensis

- Lateral frontal carina present, distinct (Figs 1–2, 16–17, 91–92, 107–108); female F1 not curved medially and not expanded apically (Figs 7, 22, 97); male F1 expanded only apically, if expanded basally than wider apically than basally (Figs 8, 23, 98).................................................................................................... 5

5 Syntergite without anterolateral row of setae; female lower face yellow, female F2 slightly incised medially..... S. jezoensis

- Syntergite with anterolateral row of setae, female lower face black, dark brown or reddish brown, female F2 not incised medially (Figs 7, 22, 97)................................................................................... 6

6 Female F1 3.0–3.3 times as long as pedicel, 1.25 times as long as F2 (Figs 7, 35, 97); male F1 expanded only apically, if expanded basally than broader apically than basally (Figs 8, 36, 98)............................................. 7

- Female F1 about 2.0 times as long as pedicel, subequal with F2; male F1 expanded apically and basally and as broad apically as basally............................................................................................ 9

7 Posterior band of micropunctures on syntergite broad, dorsally extending to 1/3 of its length (Figs 42, 105–106); male F1 expanded only apically (Figs 36, 98)..................................................................... 8

- Posterior band of micropunctures on syntergite narrow, dorsally extending to 1/5–1/7 of its length (Fig. 15); male F1 expanded apically and basally (Fig. 8).............................................................. S. abei, new species

8 Female head quadrangular in frontal view (Fig. 91); frontal carinae uniformly strong, reaching lateral ocellus (Figs 91–92), male F1 strongly expanded apically (Fig. 98).............................................. S. khazani, new species

- Female head rounded in frontal view (Fig. 30); frontal carinae weak, not reaching lateral ocellus (Figs 30–31); male F1 weakly expanded apically (Fig. 36)........................................................ S. changtitangi, new species

9 Head ovate in frontal view; lower face with strong median carina raised above striae; pedicel in female longer than broad; median mesoscutal impression short, reaching to mid length of mesoscutum and sometimes abruptly broadened posteriorly; scutelar foveae rugose; female syntergite slightly incised dorsoapically.................................. S. gifuensis

- Head triangular in frontal view; lower face with weak median carina not raised above striae; female pedicel as long as broad; median mesoscutal impression long; scutellar foveae alutaceous; female syntergite strongly incised dorsoapically..................................................................................................... S. japonicus

10 Lower face, frons and genae partially or entirely black or very dark brown (Figs 16–21, 58–65); mesosoma black or dark brown (Figs 24–28, 68–72)............................................................................. 11

- Lower face, frons and genae partially or entirely light brown to yellowish; mesosoma reddish brown................. 13

11 Head coriaceous, without striae and deep punctures on frons, vertex and interocellar area; mesoscutum uniformly alutaceous or very delicately coriaceous, without distinct transverse rugae between notauli........................... S. hakonensis

- Head rugose, with distinct deep punctures on frons, vertex and interocellar area, with striae on frons; mesoscutum coriaceous or rugose, with distinct elevated transverse rugae between notauli.............................................. 12

12 Female and male head in frontal view trapezoid, height of eye 1.8–1.9 times as long as length of malar space (Figs 58, 62); female POL:OOL:LOL=2.1:1:1.2 (Fig. 59); length of lateral ocellus in male nearly equal to POL (fig. 63); female F1 1.3–1.4 times as long as F2 (Fig. 66)........................................................... S. ishikarii, new species

- Female and male head in frontal view rounded or ovate, height of eye only 1.45 times as long as length of malar space (Figs 16, 20), female POL:OOL:LOL=2.8:1:1.2 (Fig. 17); length of lateral ocellus in male 0.6 timeslength of POL (Fig. 21); female F1 almost as long as F2 (Fig. 22).................................................... S. belizinellus, new species

13 Head of female and male in frontal view triangulate, higher than broad; gena narrow, straight and not rounded aside head in frontal view(Figs 134, 137).................................................................. S. xialongmeni

- Head of female and males in frontal view always rounded, always broader than high; gena convex, visible behind eye in frontal view (Figs 43, 47, 107, 111, 123, 126) ……………………………………………………………………….……………….. 14

14 Head and mesosoma reddish brown (Figs 123–127, 130–132)......................................... S. chinensis

- Head reddish brown, mesosoma black (Figs 118–120)....................................................... 15

15 Postgena without setae (Fig. 45); male F1 not expanded apically (Fig. 51); median mesoscutal line strongly impressed only in posterior half, extending to 2/3 of mesoscutum length, never complete (Fig. 54); mesoscutellum about as long as broad (Fig. 55)............................................................................ S. formosanus, new species

- Postgena with dense white setae along hypostoma (Fig. 109, 113); male F1 expanded apically (Fig. 115); median mesoscutal line strongly impressed, complete, reaches anterior margin of mesoscutum (Fig.119); mesoscutellum 1.4 times as long as broad (Fig. 120)..................................................................... S. symbioticus, new species