A key to Microleon, Butler, 1885, based on male genitalia characters

1 Gnathos present...................................................................................... 2

- Gnathos absent....................................................................... M. dianensis sp. nov.

2 Gnathos triangular or spatulate................................................................. M. yoshimotoi

- Gnathos T-shaped..................................................................................... 3

3 The left dorsal arm longer than the right one in sacculus............................................. M. decolatus

- The right dorsal arm slightly longer than the left one in sacculus................................................ 4

4 Aedeagus apex with a delicately dentate sclerotized band........................................... M. longipalpis

- Aedeagus apex without a sclerotized band................................................ M. simingensis sp. nov.