I have been looking carefully at Asiagomphus species this year, after it became clear there are more species here than just beautiful Asiagomphus acco. In spring in Huu Lien I was able to collect two unknown species, one of which I now believe is the long missing, but in fact common, Asiagomphus auricolor. Asiagomphus species B likely is an as yet undescribed species. What these species share with A. acco and related A. xanthenatus is that they do not have the longitudinal arrow markings on the dorsum of the abdominal segments, but rather have transverse bands marking the borders between the segments. In A. acco these are much reduced in the male, but present in the female.
When on June 24 I caught a female Asiagomphus along an otherwise also very productive stream in northern Bac Kan Province, it was immediately clear to me that this was one of the Chinese species and not any of the species I had seen in Vietnam so far, because of exactly these longitudinal markings on the abdomen. The shape of the occipital ridge and the lateral markings on S2-4 helped clinch the ID as Asiagomphus pacificus, an addition to the Vietnamese list, but a species widespread in neighboring China.
To my shame and regret, I did not take proper photos of the dorsal view of the abdomen in the field, nor back at the room we stayed in at Ba Be National Park. Therefore the dorsal pattern is difficult to see in the accompanying photos taken of the preserved specimen.
|Asiagomphus pacificus, female, Bac Kan Province, June 24. Note the lack of transverse bands on the abdomen (apart from S7, the pattern of lateral spots on S3 (two), the humeral spot and largely yellow metepisternum.|
|Detail of S2-3|
|Longitudinal markings on the dorsum of abdominal segments|
|Facial pattern and shape of occipital ridge|