Key to Chinese species of subgenus Blacus Nees

1 Parastigma of ♀ medium-sized to large and comparatively wide, distinctly differentiated from vein C+SC+ R (Figs 26E, 28H) and first discal cell acute anteriorly....................................................................... 2

- Parastigma of ♀ small and narrow, less differentiated from vein C+SC+ R, and first discal cell acute anteriorly (Figs 2I, 4J, 12F, 20H, 24G); if parastigma of ♀ medium-sized to large and distinctly differentiated from vein C+SC+ R, then first discal cell truncate anteriorly (Figs 6H, 8J, 10I, 16I, 18I, 22E, 30I)....................................................... 4

2 Length of ovipositor sheath 0.22 × length of fore wing, 0.9 × length of hind femur, 0.6 × length of hind tibia; 1-CU1: 2-CU1 ≈ 1: 2 (Fig. 14I); length of malar space 1.6 × basal width of mandible; body and fore wing comparatively short; length of hind femur 4.6 × its width..................................................... Blacus (Blacus) longicornis sp. nov.

- Length of ovipositor sheath 1.5–2.4 × length of fore wing, 5.0–7.9 × length of hind femur, 3.5–5.5 × length of hind tibia (Figs 26I, 28I); 1-CU1: 2-CU1 = 1: 4 to 1: 6 (Figs 26E, 28H); length of malar space 2.0–2.4 × basal width of mandible; body and fore wing comparatively long; length of hind femur 5.5 × its width.................................................. 3

3 Length of ovipositor sheath 1.5 × length of fore wing, 5.0 × length of hind femur, 3.5 × length of hind tibia and approx. as long as body; length of malar space 2.0 × basal width of mandible; length of first metasomal tergite 1.7 × its apical width (Fig. 26H); metasomal tergites slightly punctate; body black................................ Blacus (Blacus) rugifacialis sp. nov.

- Length of ovipositor sheath 2.4 × length of fore wing, 7.9 × length of hind femur, 5.45 × length of hind tibia and approx. twice as long as body; length of malar space 2.4 × basal width of mandible; length of first metasomal tergite 1.9–2.1 × its apical width (Fig. 28G); metasomal tergites partly distinctly rugose; body brown............ Blacus (Blacus) tianmushanensis sp. nov.

4 Parastigma of fore wing less differentiated from vein C+SC+R and first discal cell acute anteriorly (Figs 2I, 24G)......... 5

- Parastigma of fore wing distinctly differentiated from vein C+SC+R and first discal cell truncate anteriorly (Figs18I, 30I).. 9

5 Vein CUla of fore wing nearly at same level as vein 2-CU1 (Figs 2I, 24G); vein 2-M absent (Figs 2I, 24G); malar space distinctly longer than basal width of mandible (Figs 2B, 24B).................................................. 6

- Vein CUla of fore wing distinctly bent basally, distinctly below level of vein 2-CU1 (Figs 7H, 12F); vein 2-M and ratio of length of malar space to basal width of mandible variable........................................................... 7

6 Antenna more robust (Fig. 2C); frontal suture present; vein 2-1A of fore wing short (Fig. 2I); length of first metasomal tergite 1.7 × its apical width (Fig. 2G); length of ovipositor sheath 0.21–0.22 × length of fore wing; basal half of metasoma brown ventrally (Fig. 1); hind coxa and hind trochanter yellow (Fig. 2H)............. Blacus (Blacus) adustiabdominus sp. nov.

- Antenna slender (Fig. 24C); frontal suture absent; vein 2-1A of fore wing long (Fig. 24G); length of first metasomal tergite 2.1 × its apical width (Fig. 24E); length of ovipositor sheath 0.30 × length of fore wing; basal half of metasoma reddish ventrally (Fig. 23); hind coxa and hind trochanter yellowish-red (Fig. 24H)............... Blacus (Blacus) rufiabdominus sp. nov.

7 Marginal cell of fore wing comparatively large (Fig. 20H); vein 3-SR+SR1 of fore wing straight, and reaching apex of fore wing; vein 2-M of fore wing present (Fig. 20H); propodeal tubercles distinct and large............................................................................................. Blacus (Blacus) pappianus Haeselbarth, 1973

- Marginal cell of fore wing comparatively small (Figs 4J, 12F); vein 3-SR+SR1 of fore wing curved basally, and not reaching apex of fore wing; vein 2-M of fore wing absent or indistinct (Figs 4J, 12F); propodeal tubercles absent................. 8

8 First metasomal tergite 1.3–1.5 × longer than its apical width (Fig. 12E); marginal cell of fore wing comparatively small (Fig. 12F); apical part of pterostigma less wide; vein 3-SR+SR1 of fore wing distinctly curved basally (Fig. 12F); antenna more slender (Fig. 12C)................................................... Blacus (Blacus) leptostigma Ruthe, 1861

- Length of first metasomal tergite 1.6–1.8 × longer than its apical width (Fig. 4G); marginal cell of fore wing comparatively large (Fig. 4J); apical part of pterostigma wider; vein 3-SR+SR1 of fore wing slightly curved basally (Fig. 4J); antenna more robust (Fig. 4C).......................................................... Blacus (Blacus) exilis (Nees, 1811)

9 Length of ovipositor sheath 0.50 × length of fore wing (Fig. 29); antenna of ♀ slender (Fig. 30C); length of body 3.5 mm and length of fore wing 3.2 mm (Fig. 29)......................................... Blacus (Blacus) xizangensis sp. nov.

- Length of ovipositor sheath less than 0.40 × length of fore wing; antenna of ♀ robust (Figs 6C, 8C, 8E, 10C, 16C, 18C, 22C); length of body and fore wing variable.................................................................... 10

10 Third antennomere of ♀ very robust and dark brown (Fig. 18C); scutellar sulcus with strongly developed carinae beside medio-longitudinal carina (Fig. 18D); basal half of antenna of ♀ largely moniliform (Fig. 18C)..; [first metasomal tergite 1.4–1.9 × longer than wide apically].............................................. Blacus (Blacus) paganus Haliday, 1835

- Third antennomere of ♀ slender and often yellowish brown (Figs 8C, 10C, 16C, 22C, 6C); scutellar sulcus smooth or with some weak or indistinct rugae beside medio-longitudinal carina (Figs 6E, 8D, 22D); basal half of antenna of ♀ not moniliform (Figs 6C, 8C, 10C, 16C, 22C)............................................................................... 11

11 Third antennomere dark brown; length of first tergite 1.5 × its apical width (Fig. 10G) and propodeal tubercles indistinct (Fig. 10E); vein 1-CU1 of fore wing as long as vein 2-CU1 (Fig. 10I); [frontal suture (= medial suture of frons) absent or obsolescent (Figs 10A, B)]............................................................ Blacus (Blacus) hebeiensis sp. nov.

- Third antennomere brownish yellow or yellow; length of first tergite 1.7–2.6 × its apical width (Figs 6F, 8H, 16G, 22G), if about 1.7 × then propodeal tubercles distinct (Fig. 6E); vein 1-CU1 of fore wing much shorter than vein 2-CU1 (Figs 8J, 16I)... 12

12 Length of first tergite 1.7 × its apical width and distinctly widened apically (Fig. 6F); propodeal tubercles large (Fig. 6E); apical half of antenna of ♀ distinctly moniliform (Fig. 6C); mesoscutal lobes anteriorly darker than posteriorly (Fig. 6E).............................................................................. Blacus (Blacus) flavimaculus sp. nov.

- Length of first tergite 2.0–2.6 × its apical width and hardly widened apically or parallel-sided (Figs 8H, 16G, 22G); propodeal tubercles small (Figs 8F, 16D, 22F); apical half of antenna of ♀ hardly or not moniliform (Figs 8C, 8E, 16C, 22C); mesoscutal lobes anteriorly as dark as posteriorly (Figs 16E, 22D) or slightly darker (Fig. 8D)................................. 13

13 Head in dorsal view sparsely setose (Fig. 8A); first metasomal tergite aciculate-rugose (Fig. 8H); antenna of ♀ more slender and less conspicuously setose (Figs 8C, 8E); [mesoscutal lobes reddish-brown (Fig. 8D)]................................................................................................ Blacus (Blacus) forticornis Haeselbarth

- Head in dorsal view densely setose (Figs 16A, 22A); first metasomal tergite rugose or reticulate-rugose (Figs 16G, 22G); antenna of ♀ less slender and more conspicuously setose (Figs 16C, 22C)....................................... 14

14 Dorsal face of propodeum distinctly oblique in lateral view (Fig. 16D); vein 3-SR+SR1 of fore wing about 6.0 × longer than vein r (Fig. 16I); frontal suture (= medial suture of frons) absent or obsolescent (Fig. 16A)....................................................................................... Blacus (Blacus) longipennis (Gravenhorst, 1807)

- Dorsal face of propodeum subhorizontal in lateral view (Fig. 22F); vein 3-SR+SR1 of fore wing about 8.0 × longer than vein r (Fig. 22E); frontal suture more or less developed......................... Blacus (Blacus) radialis Haeselbarth, 1973