Key to species of genus Malayepipona (modified from the key of Nguyen 2020)

1. S2 strongly convex in basal half................................................... M. assamensis Giordani Soika

- S2 nearly flat or slightly convex at base, then slightly and gradually convex toward apical margin..................... 2

2. T2 without apical lamella............................................................................... 3

- T2 with apical lamella................................................................................. 7

3. Upper part of propodeum usually with a pair of relatively blunt teeth just behind metanotum (Figs. 48, 71).............. 4

- Upper part of propodeum normal, without a pair of teeth just behind metanotum................................... 5

4. Wings dark brown, strongly infuscate, making apical dark spot of forewing marginal cell inconspicous (Fig. 68); female clypeus with separated spots (Fig. 69); area between cephalic foveae on vertex punctate (Fig. 70).............................................................................................. M. clypeata Nguyen & Carpenter, 2012

- Wings brown, slightly infuscate, apical dark spot of forewing marginal cell conspicuous (Figs 40–41); female clypeus wholly ferruginous and male clypeus yellow (Figs 42–43); area between cephalic foveae on female vertex smooth, shiny................................................................................ M. nigricans Bai, Chen & Li, sp. nov.

5. Area surrounding foveae distinctly depressed, smooth and shiny, making foveae obvious (Fig. 3); head and mesosoma largely brown mixed with ferruginous and yellow (Fig. 1)............................... M. brunnea Bai, Chen & Li, sp. nov.

- Area surrounding foveae not depressed, smooth and shiny, making foveae inconspicuous (fig. 9 in Nguyen, 2020)); head and mesosoma obviously different from above................................................................. 6

6. Punctures on head and mesosoma smaller and weaker, interspaces between punctures not carinate; pronotal carina not produced at humeral angle, round; metasomal terga shiny, T 1 in dorsal view less than 1.5 times as wide as long, T2 with weaker sparser punctures.................................................................. M. pagdeni Giordani Soika, 1993

- Punctures on head and mesosoma large and coarse, interspaces between punctures reticulate; pronotal carina strongly produced at humeral angle; metasomal terga dull, T 1 in dorsal view more than twice as wide as long, T2 with strong dense punctures.................................................................................. M. fincta Nguyen, 2020

7. S2 nearly flat at base, then slightly convex to apical margin (Fig. 39)............................................ 8

- S2 concave or slightly convex at base, then slightly convex to apical margin....................................... 9

8. Clypeus sparsely punctate (Fig. 33); T2 with short apical lamella, T3 without apical lamella (Fig. 38).......................................................................................... M. maculosa Bai, Chen & Li, sp. nov.

- Clypeus densely punctate and coarser (Fig. 2 in Nguyen & Carpenter 2013); T2 with longer apical lamella, T3 with short apical lamella (Fig. 5 in Nguyen & Carpenter 2013)...................................... M. malickyi (Gusenleitner, 2010)

9. T2 with short apical lamella, T3–T5 without apical lamella................................................... 10

- T2 with longer apical lamella, T3 with short apical lamella................................................... 13

10. Female head with long dense setae (Fig. 5 in Gusenleitner 2012)......................... M. visenda Gusenleitner, 2012

- Female head with shorter setae (Figs 61–62, 12–15, 33–34)................................................... 11

11. Wings dark brown, strongly infuscate (Figs 10–11); T2 with inconspicuous apical lamella, just visible in lateral view (Fig. 19)................................................................... M. flaviclypeata Bai, Chen & Li, sp. nov.

- Wings brown, not infuscate (Figs 22–23, 51, 60); T2 with obvious apical lamella (Figs. 30, 58, 66)................... 12

12. Clypeus densely coarsely punctate; apical tooth of mandible pointed (fig. 1 in Nguyen 2020); pronotal carina strongly produced at humeral angle; female head and mesosoma wholly black (Figs 1–4 in Nguyen 2020); forewing with dark spot at apex of marginal cell...................................................................... M. bidoup Nguyen, 2020

- Clypeus sparsely punctate; apical tooth of mandible rounded (Fig. 61); pronotal carina not produced at humeral angle, round (Fig. 64); female head and mesosoma with yellow marks (Figs, 60–61, 64); forewing without dark spot at apex of marginal cell................................................................... M. triangula Bai, Chen & Li, sp. nov.

13. Border between anterior and dorsal surfaces of T1 slightly raised, with faint edge (Fig. 30).......................... 14

- Border between anterior and dorsal surfaces of T1 bluntly angulate, with obvious edge (Fig. 58)...................... 15

14. Female clypeus black, laterally with two thick longitudinal yellow strips, T4 without apical lamella.......................................................................................... M. seomyty Nguyen & Carpenter, 2013

- Female clypeus entirely brownish yellow or with one basal transverse yellow band and two connected yellow spots at apex (Figs 24–25), T4 with short apical lamella..................................... M. lamellata Bai, Chen & Li, sp. nov.

15. Clypeus densely coarsely punctate; posterior surface of propodeum with scattered shallow punctures; female clypeus entirely black; T1–T2 with apical yellow bands, T3–T5 without bands...................... M. furva Nguyen & Carpenter, 2013

- Clypeus with sparser punctures medially; posterior surface of propodeum with dense thin striae, mixed with minute punctures (Fig. 54); female clypeus black with two yellow lateral spots at base (Fig. 52); T1–T5 with apical yellow bands (widest on T2 and narrowest on T5) (Fig. 58)........................................... M. sparsipuncta Bai, Chen & Li, sp. nov.