The species M. saigonensis (Omodeo, 1956) was re-accessed based on a comparison between its original description and different variations of M. bahli and M. peguana. A total of 65 specimens of M. bahli and 69 specimens of M. peguana collected from various parts in southern Vietnam were used to examine. As a result, M. bahli has two different morphs (with and without concave male region). M. peguana has two subspecies, but rather stable in morphology. M. saigonensis is totally different from M. peguana in closer ventral distance between male pores, spermathecal pores, but it is very similar to the morph 2 of M. bahli. Therefore, it is concluded that M. saigonensis is a junior synonym of M. bahli.