Key to the species of the genus Microlithosia in Laos based on the male genitalia

1 Distal saccular processes asymmetrically branched; aedeagus with field of short spines.............................. 2

- Distal saccular processes symmetrically branched; aedeagus with a bundle of slender spines and field of short spines............................................................................................... M. laosana n. sp.

2 Apex of valvae strongly angled; left distal saccular process with three short, asymmetric divaricates processes..................................................................................................... M. umbripuncta

- Apex of valvae roundly angled; left distal saccular process with three short, symmetric divaricates processes... M. nanlingica