There are at least 4 species of Asiagomphus in Vietnam, but the problem is species of this genus are very similar, both in outward appearance and in appendages. The easiest is arguably Asiagomphus acco, with its dorsal tooth on the superior appendages. Asiagomphus sp. novum is also relatively simple, with the epiproct V-shaped, see the entries. Asiagomphus auricolor is apparently rather variable. I also consider it a candidate for what currently is identified as A. xanthenatus in Laos. A. auricolor has sometimes two and sometimes three lateral stripes and the female more or less yellow on S1-2. A. hainanensis has longitudinal stripes on the dorsum of the abdomen, quite different from the rings of the other three. It also often has a spot on S8, which really helps the ID.
|Asiagomphus hainanensis, finally a male. Note the oval lateral spot on S8. The humeral stripe can be much clearer.|
|The same male at a different angle. Note the longitudinal markings along the dorsum of the abdomen, all the way up to S7.|
|Another shot of the same male|
|A different male, without the oval spot on S8 and with more extensive humeral stripe.|