Key to the world species of the genus Erythropompilus Shimizu & Pitts, 2021

Female

1 Frons, in profile, strongly convex (Fig. 2C); in dorsal view, gena slightly thickened (Fig. 2B); clypeus narrower than LID (Fig. 2D); OOD larger than 0.85 × POD........................................................................ 2

- Frons, in profile, gently convex; in dorsal view, gena thin; clypeus as broad as LID; OOD shorter than 0.75 × POD........ 3

2 Mesosoma mostly orange-red (Fig. 2A); vertex, in frontal view, distinctly convex (Fig. 2D); lateral margin of pronotal dorsum, in dorsal view, slightly narrowing anteriorly (Fig. 2E)......................... E. macroplacoideus Wu & Ma, sp. nov.

- Mesosoma entirely black; vertex, in frontal view, almost transversely straight (Fig. 3A in Shimizu et al. 2021); lateral margin of pronotal dorsum, in dorsal view, not narrowing anteriorly........................... E. taiwanensis Pitts & Shimizu

3 Gena, in dorsal view, very thin, abruptly receding posteriorly; lateral margin of pronotal dorsum, in dorsal view, slightly narrowing anteriorly (Fig. 1 B in Shimizu et al. 2021)............................... E. malaysiensis Pitts & Shimizu

- Gena, in dorsal view, not very thin, roundly receding posteriorly; lateral margin of pronotal dorsum, in dorsal view, concave and scarcely narrowing anteriorly (Fig. 5B)........................................ E. thailandensis Pitts & Shimizu

Male

1 Clypeus less than LID (Fig. 3D); mid and hind femora without small spines set in pits apicodorsally; OOD larger than 0.85 × POD............................................................................................... 2

- Clypeus as broad as LID (Fig. 1D); mid and hind femora with small spines set in pits apicodorsally; OOD shorter than 0.8 × POD............................................................................................... 3

2 Placoids small, shorter than 1/2 of each flagellomere; mesosoma dark rufous; SGP triangular; aedeagus not extending beyond apex of parapenial lobe, and apical margin slightly emarginated medially................. E. taiwanensis Pitts & Shimizu

- Placoids large, longer than 3/4 of each flagellomere (Fig. 3H); mesosoma partly orange-red (Fig. 3A); SGP arrowhead-shaped (Fig. 3K); aedeagus extending beyond apex of parapenial lobe, and apical margin strongly concave medially (Fig. 4E).......................................................................... E. macroplacoideus Wu & Ma, sp. nov.

3 Frons, in profile, spherically convex (Fig. 1C); side of S4 and S5, each with tuft of dense and erect black bristles (Fig. 1J); SGP broad, almost parallel-sided, and with rounded apex, slightly thickened basal medially (Fig. 1K); S6 with slightly arcuate emargination posteriorly (Fig. 1I)............................................ E. venterisetalis Wu & Ma, sp. nov.

- Frons, in profile, gently convex; side of S4 and S5 without tuft of dense and erect black bristles; SGP not parallel-sided, if parallel-sided, it narrow and long; S6 with inverted-V-shaped emargination posteriorly.............................. 4

4 Mesosoma mostly orange-red; placiods large, much longer than 1/2 of each flagellomere; SGP long, parallel-sided for most part....................................................................... E. thailandensis Pitts & Shimizu

- Mesosoma usually dark rufous; placiods small, shorter than 1/2 of each flagellomere; SGP arrowhead-shaped....................................................................................... E. malaysiensis Pitts & Shimizu