Tramea transmarina vs Tramea phaeoneura

Tramea transmarina can be found in Peninsular Malaysia and Borneo while T. phaeoneura is confined to Borneo. Even in Borneo, T. phaeoneura is much less common compared to T. transmarina. Both the species are hard to be identified when they are high in flight. One may use the extensiveness of dark patch of hind wings to tell them apart - T. transmarina has more extensive dark patch of hind wings compared to T. phaeoneura. However, this character is sometime variable. The best way to verify these two species is to look into their anal appendages and genitalia.