Key to the Asian species of Trigastrotheca

1. Occiput, mesopleuron, mesosternum and propodeum ocheous yellow (Figs 1 A, C, 2B); metasomal tergites 3 and 4 at least with posteriorly and laterally whitish or ochreous yellow (Figs 2 B, 3C); dark mark (brown or black) on middle part of mesoscutum absent, or if present, only on anterior half (Figs 4 A, 5C, E).....................................................2

-. Occiput, much of mesopleuron and mesosternum, propodeum and metasomal tergites 3 and 4 (except anterolateral areas) black (Fig. 9); dark (black) mark on middle part of mesoscutum extending to scutellar sulcus........... T. tridentata (Enderlein)

2. Metasomal tergites 2–5 broadly dark brown or black medially surrounded by paler marks (Figs 3 A, 8C) [only males known]......................................................................................................3

- Metasomal tergites 2–5 ochreous yellow medially, some tergites with brown or black sublateral spots (Figs 2 A, 6C) [only females known]...................................................................................... 4

3. Median area of metanotum with a distinct midlongitudinal carina (Fig. 8 B); base of hind wing with a well-developed glabrous area distal to vein cu-a (Fig. 8 B); antenna with 49–53 flagellomeres; fore wing length> 4.5 [4.9–5.1] mm................................................................................................... T. sureeratae sp. nov.

-. Median area of metanotum without midlongitudinal carina (Fig. 4 A, C); base of hind wing with reduced setosity but this extending to vein cu-a anteriorly and with only a small glabrous area posteriorly (Fig. 4 C); antennae with 45–47 flagellomeres; fore wing length <4.0 [3.6] mm............................................................ T. maetoi sp. nov.

4. Body length c. 6.5 mm; metasomal tergites tricoloured, white laterally, ochreous medially and metasomal tergites 3 and 4 with black sublateral spots (Figs 5 C, 6B,C); postero-medial prominence of 5th metasomal tergite blunt and bordered by more or less evenly curved emarginations (Fig. 6 B)................................................ T. pariyanonthae sp. nov.

- Body length c. 4.1 mm; metasomal tergites ochreous brown without white markings, metasomal tergites 2 and 3 somewhat darker sublaterally, and 4th metasomal tergite with an ill-defined brown sublateral spot (Figs 1 A, 2A); posteromedial prominence of 5th metasomal tergite acute and emarginations more or less straight (Fig. 2).............. .. T. luzonensis sp. nov.