Key to Ptygomastax species

1. Antennae 14 segments, antennal organ on the tenth segment................................................... 2

1’ Antennae 13 or 15 segments, antennal organ on the tenth or twelfth segment...................................... 5

2. Body size larger, hind tibiae longer....................................................................... 3

2’ Body size smaller, hind femur shorter..................................................................... 4

3. body size larger in male, hind tibiae longer. Male hind tibia with 14~16 spines on outer side and 12-14 on inner side; female hind femur with 18~21 spines on outer side and 13-15spines on inner side.......... Ptygomastax sinica Bey-Bienko, 1959 .

3’ body size larger, pronotum without transverse sulci, hind tibia with 15~17 spines on outer side and 11~13 spines on inner side...................................................................... Ptygomastax nihilsulcus sp. nov.

4. Body smaller, hind femur shorter, male hind tibia with 11~12 spines on inner side and 14 spines on outer side; female hind tibia with 10 spines on inner side and 12 spines on outer side.......................... Ptygomastax longifemora Yin, 1984 .

5. Antennae 13 segmented, with antennal organ on the tenth segment; female hind tibia with 10~14 spines on outer side................................................................... Ptygomastax heimahoensis Zheng et Hang, 1974 .

5’ Antennae 15 segments, antennal organ on the twelfth segment; female hind tibia with 15~17 spines on outer side......................................................................... Ptygomastax abaensis Zheng, Ye et Yin, 2012 .