Key to the known pupae of Hexatoma of Mongolia

1. Cephalic crest consists of one pair of horns (Fig. 59). Sheaths of legs reach posterior margin of third abdominal segment (Fig. 58, 59).................................................... Hexatoma (Hexatoma) nubeculosa (Burmeister, 1829)

- Cephalic crest consists of two pairs of horns (Fig. 34). Sheaths of legs shorter, ending before posterior margin of third abdominal segment (Fig. 36, 46)................................................................................ 2

2. Sheaths of legs reach two thirds of third abdominal segment (Fig. 46). Antennal sheath of male very long, almost reaching to tips of the legs. Antennal sheath of female shorter, reaching tips of wings.. Hexatoma (Eriocera) ussuriensis Alexander, 1934

- Sheaths of legs shorter, reaching to the middle of third abdominal segment (Fig. 36). Antennal sheaths of male shorter, reaching to tips of wings. Female pupa unknown.......................... Hexatoma (Eriocera) stackelbergi Alexander, 1933