Key to the world species of Palpostilpnus, modified from Reshchikov et al. (2019)

1. Fore wing with infuscate transverse band.................................................................. 2

-. Fore wing lacking infuscate transverse band................................................................ 5

2. Fore wing with one infuscate transverse band; antenna without median white band; T2 with coarse punctures; propodeum sloping gradually..................................................................................... 3

-. Fore wing with two infuscate transverse bands; antenna with median white band; T2 with fine punctures; Propodeum sloping steeply.............................................................................................. 4

3. Mesosoma mostly reddish; infuscate transverse band of fore wing rather distal; hind tarsus brown, with white basitarsus; body shallowly and sparsely punctate; ovipositor as long as hind basitarsus; T1 about 3.0× as long as apical broad............................................................................................. P. rufinator (Aubert, 1961)

-. Mesosoma black; infuscate transverse band of fore wing on distal 0.6; hind tarsus white; body coarsely and densely punctate; ovipositor 1.4× as long as hind basitarsus; T1 1.8× as long as apical broad................................................................................................. P. mangrovi Reshchikov, Santos, Liu, Barthélémy, 2019

4. Frons, mesonotum and mesosternum transversally striated, shiny; ovipositor 1.5× as long as hind tarsus.................................................................................................. P. striator (Aubert, 1961)

-. Frons, mesonotum and mesosternum finely punctate, entirely dull; ovipositor 2.1× as long as hind tarsus............................................................................................... P. papuator (Aubert, 1961)

5. Occipital carina broadly absent dorsally; T1 short and stout, 1.5× as long as apical width............................. 6

-. Occipital carina complete dorsally; T1 longer, at least 1.7× as long as apical width.................................. 9

6. Combined area of propodeum (area superomedia and area petiolaris) open anteriorly (Figs 11G, 14E).................. 7

-. Combined area of propodeum present (Figs 6G, 12G).........................................................8

7. Body black with reddish markings (Figs 2E, 11); basal half of scutellum with arched wrinkles (Fig. 11F)................................................................. P. ngoclinhensis Pham, Sheng, Park, Tran & Reshchikov, sp. nov

-. Body reddish yellow with black markings (Figs 2G, 14); scutellum punctate, with setae (Fig. 14C)..................................................................... P. taynguyenensis Pham, Sheng, Park, Tran & Reshchikov, sp. nov

8. Body reddish with black markings (Fig. 3B); [mesosoma entirely reddish or with reddish marking basally on propodeum]; mesoscutum shorter than its maximum width (Fig. 12C)....... P. pterodactylus Reshchikov, Santos, Liu, Barthélémy, 2019

-. Body ferruginous with black markings (Fig. 2D); mesoscutum as long as its maximum width (Fig. 6F)................................................................... P. incompletus Pham, Sheng, Park, Tran & Reshchikov, sp. nov

9. Combined area of propodeum absent or, if present anteriorly open.............................................. 10

-. Combined area of propodeum present and anteriorly closed................................................... 22

10. T2–T4 with a pair of small black sports laterally or T2 with a transverse black band and T3–T4 with a pair of small black sports or sometimes T2–T4 entirely reddish, without black markings................................................. 11

-. T2–T4 with a transverse black band or entirely black........................................................ 12

11. Mesosoma black with yellow marks (Figs 7C, 7F); mesoscutum with coarse granulose texture and distinct fine punctures............................................................................. P. maculatus Sheng & Sun, 2013

-. Mesosoma yellow, with lower part of mesopleuron and prescutellar groove black; mesoscutum with fine leathery texture and indistinct.............................................. P. hainanensis Reshchikov, Santos, Liu, Barthélémy, 2019

12. Mesoscutum black, with or without yellow markings........................................................ 13

-. Mesoscutum mostly yellow or brown, with or without black markings........................................... 17

13. Mesoscutum entirely black (Fig. 5C); propodeum without any carinae (Fig. 5G).................................................................................. P. hoanglienensis Pham, Sheng, Park, Tran & Reshchikov, sp. nov.

-. Mesoscutum with yellow markings; propodeum with posterior part of lateromedian longitudinal carina and lateral part of posterior transverse carina present....................................................................... 14

14. Mesoscutum with anterior 0.3 yellow (Fig. 4E); scutellum entirely yellow (Fig. 4E)................................................................................... P. cattienensis Pham, Sheng, Park, Tran & Reshchikov, sp. nov

-. Mesoscutum with antero-laterally yellow (Fig. 8E); scutellum entirely black or with yellow marking.................. 15

15. Mesosoma largely black (Fig. 8D); postero-ocellar distance 3.2× ocular-ocellar distance (Fig. 8B)................................................................... P. melanothoracicus Pham, Sheng, Park, Tran & Reshchikov, sp. nov

-. Mesosoma largely reddish; postero-ocellar distance 1.5–2.4× ocular-ocellar distance............................... 16

16. Propodeum with area postero-externa complete; scutellum entirely black; ovipositor 0.9× as long as hind basitarsus................................................................ P. trifolium Reshchikov, Santos, Liu, Barthélémy, 2019

-. Propodeum with area postero-externa incomplete; scutellum laterally yellow; ovipositor 3.5× as long as hind basitarsus............................................................. P. tamasek Reshchikov, Santos, Liu, Barthélémy, 2019

17. Epicnemial carina absent; hind tibia apically ferruginous.............. P. ranui Reshchikov, Santos, Liu, Barthélémy, 2019

-. Epicnemial carina present; hind tibia apically black or entirely black........................................... 18

18. Area postero-externa open anteriorly; mesoscutum with black or brown markings................................. 19

-. Area postero-externa present; mesoscutum entirely yellowish, without black or brown markings...................... 21

19. Face wider, 1.7 times as wide as high; ovipositor sheath shorter than apical depth of metasoma...................................................................................... P. aki Reshchikov, Santos, Liu, Barthélémy, 2019

-. Face narrower, 1.2× as wide as high (Figs 9A, 10A); ovipositor sheath distinct longer than apical depth of metasoma (Figs 9D, 10G).............................................................................................. 20

20. Postero-ocellar distance 1.7× as long as ocular-ocellar distance (Fig. 9B); superomedia and area petiolaris of propodeum open anteriorly (9G); fore wing vein 1cu-a postfurcal to M&RS; juxtacoxal carina complete................................................................................ P. melinhensis Pham, Sheng, Park, Tran & Reshchikov, sp. nov.

-. Postero-ocellar distance 0.8× as long as ocular-ocellar distance (Fig. 10B); superomedia and area petiolaris of propodeum entirely absent (Fig. 10C); fore wing vein 1cu-a interstitial to M&RS; juxtacoxal carina absent......................................................................... P. meovacensis Pham, Sheng, Park, Tran & Reshchikov, sp. nov.

21. Postero-ocellar distance 2.0× as long as ocular-ocellar distance; mesosoma elongate, about 1.5×as long as high; hind part of T2 with black lens-shaped mark; T3 and T4 transversally black in the middle................................................................................................... P. angka Reshchikov, Santos, Liu, Barthélémy, 2019

-. Postero-ocellar distance 3.6× as long as ocular-ocellar distance; mesosoma short, about 1.25× as long as high; hind part of T2–T4 with a black band................................ P. singaporensis Reshchikov, Santos, Liu, Barthélémy, 2019

22. Mesosoma and metasoma entirely black.................................................................. 23

-. Mesosoma and metasoma black with yellow markings....................................................... 24

23. Antenna with 34 flagellomeres; lower side of hind femur without tubercles; ovipositor sheath shorter than apical depth of metasoma; antenna with middle flagellomeres white dorsally; hind tarsus testaceous......... P. brevis Sheng & Broad, 2011

-. Antenna with 22 flagellomeres; lower side of hind femur with tubercles; ovipositor sheath longer than apical depth of metasoma; antenna with middle flagellomeres entirely brownish; hind tarsus black...................... P. palpator (Aubert, 1961)

24. Mesoscutum with large, shallow punctures; postero-ocellar distance 3.4× as long as ocular-ocellar distance........................................................................ P. angkor Reshchikov, Santos, Liu, Barthélémy, 2019

-. Mesoscutum densely reticulate-punctate; postero-ocellar distance 1.25× as long as ocular-ocellar distance.......................................................................................... P. rotundatus Sheng& Sun, 2013