Orthetrum serapia is painfully similar to Orthetrum sabina but has a much more restricted range being much more easterly, limited to northern Australia, the Philippines, Fiji, Papua New Guinea and the Solomon Islands. O. sabina, on the other hand, includes Australia but extends northwards to Japan and westwards through Asia into North Africa and enters Turkey and Greece, thus being covered by our European volumes.
[I have a comparison chart showing the distinction between O. serapia and O. sabina.]
I had not seen O. serapia until embarking on FNQ 2022 when I was very pleased to see the second of this confusing pair of species. I did not find a female but I did see a number of males in a few different locations.