Key to world species of Palpostilpnus Aubert, 1961

1. Fore wing with infuscate transverse band (Figs 11A, 12E, 23B, 24A, 27A).................................2

– Fore wing lacking infuscate transverse band (Figs 5A, 6H, 7A, 9A, 10H, 13A, 14G, 15A, 16D, 17A, 18D, 19A, 20A, 21H, 22A, 23A, 25A, 26F)..............................................................................5

2. Fore wing with one infuscate transverse band (Figs 11A, 12E, 24A). Antenna without median white band (Figs 11A, 24A). T2 with coarse punctures (Fig. 12A). Propodeum sloping gradually......3

– Fore wing with two infuscate transverse bands (Figs 23B, 27A). Antenna with median white band (Figs 23B, 27A). T2 with fine punctures. Propodeum sloping steeply.................................4

3. Mesosoma mostly reddish (Fig. 25A). 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 times as long as apically broad ..................... P. rufinator (Aubert, 1961)

– Mesosoma black (Fig. 11A, D). Infuscate transverse band of fore wing on distal 0.6 (Fig. 12E). Hind tarsus white. Body coarsely and densely punctate. Ovipositor 1.4 times as long as hind basitarsus. T1 1.8 times as long as apically broad (Fig. 11C) ................................ P. mangrovi sp. nov.

4. Frons, mesonotum and mesosternum transversally striated, shiny. Ovipositor 1.5 times as long as hind basitarsus (28A) .................................................................................. P. striator (Aubert, 1961)

– Frons, mesonotum and mesosternum finely punctate, entirely dull. Ovipositor 2.1 times as long as hind basitarsus (Fig. 24B) ................................................................... P. papuator (Aubert, 1961)

5. Occipital carina broadly absent dorsally (Fig. 14F). T1 short and stout, 1.5 times as long as apically broad (Fig. 13D) ........................................................................... P. pterodactylus sp. nov.

– Occipital carina complete dorsally (Fig. 10G). T1 longer, 1.7–2.35 times as long as apically broad (Figs 9D, 17D, 20D)..............................................................................................................6

6. Combined area of propodeum (area superomedia and area petiolaris) absent or, if present, anteriorly open (Figs 6C, 10C, 16A, 18B, 21C) .................................................................................7

– Combined area of propodeum (area superomedia and area petiolaris) present and anteriorly closed (Fig. 22D) ...........................................................................................................................14

7. T2 (or T3–T4) with a pair of small black spots laterally (Fig. 10B)..........................................8

– T2–T4 with a transverse central black band, or entirely black (Figs 18A, 21B)........................9

8. Mesosoma black, with yellow marks. 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 (Fig. 9C, E). Mesoscutum with fine leathery texture and indistinct punctures (Fig. 9E) ...... P. hainanensis sp. nov.

9. Mesoscutum black, with anterior portion laterally yellow (Figs 17C, E, 20C, E)........................10

– Mesoscutum mostly yellow or brown, with black marks (Figs 5E, 15E)....................................11

10. Propodeum with area postero-externa complete (Fig. 21C). Scutellum entirely black (Fig. 20E). Ovipositor 0.9 times as long as hind basitarsus .................................................. P. trifolium sp. nov.

– Propodeum with area postero-externa incomplete (Figs 18B, 19D). Scutellum laterally yellow (Fig. 17E). Ovipositor 3.5 times as long as hind basitarsus ................................. P. tamasek sp. nov.

11. Epicnemial carina absent (Fig. 15C). Hind tibia apically ferruginous (Fig. 15A) .... P. ranui sp. nov.

– Epicnemial carina present (Fig. 5C). Hind tibia apically black or entirely black (Figs 5A, 6D).....12

12. Mesoscutum with black marks (Fig. 5E). T1 entirely black (Fig. 6A). Area postero-externa absent (Fig. 6C) .......................................................................................................... P. aki sp. nov.

– Mesoscutum yellowish, without black marks (Figs 7E, 25E). T1 testaceous with postpetiole brown (Figs 7D, 25D). Area postero-externa present (Figs 8C, 26B)........................................................13

13. Postero-ocellar distance 2.0 times as long as ocular-ocellar distance (Fig. 8G). Mesosoma elongate, about 1.50 times as long as high (7C). Hind part of T2 coloured black as a lens, T3 and T4 transversally coloured black in their middle (Fig. 8 A–B) ...................................... P. angka sp. nov.

– Postero-ocellar distance 3.6 times as long as ocular-ocellar distance (Fig. 26E). Mesosoma short, about 1.25 times as long as high (Fig. 26C). Hind part of T2–T4 coloured black as a band (Fig. 26A) ..................................................................................... P. singaporensis sp. nov.

14. Mesosoma and metasoma entirely black (Fig. 23A).....................................................................15

– Mesosoma and metasoma black with yellow colouration (Fig. 22A)............................................16

15. Antenna with 34 flagellomeres. Lower side of hind femur without tubercles. Ovipositor sheath shorter than apical depth of metasoma. Antenna with middle flagellomeres coloured white dorsally. Hind tarsus testaceous ....................................................................... P. brevis Sheng & Broad, 2011

– Antenna with 22 flagellomeres. Lower side of hind femur with basal tubercle. Ovipositor sheath longer than apical depth of metasoma. Antenna with middle flagellomeres coloured entirely brownish (Fig. 23A). Hind tarsus black .................................................... P. palpator (Aubert, 1961)

16. Mesoscutum with large, shallow punctures (Fig. 22E). Postero-ocellar distance 3.4 times as long as ocular-ocellar distance (Fig. 22E) ...................................................................... P. angkor sp. nov.

– Mesoscutum densely reticulate-punctate. Postero-ocellar distance 1.25 times as long as ocularocellar distance ................................................................................ P. rotundatus Sheng & Sun, 2013