Burmagomphus vermicularis - I presume

When in July checking some of the streams in Ba Be National Park that were both not very fast flowing, and with muddy substrate, in open terrain bordered by forested hills, I regularly flushed freshly emerged smallish gomphids with quite interesting markings, like the oblique lines on the dorsum of the synthorax. Although I did not see any mature individuals, clearly this was a Burmagomphus species. Only two Burmagomphus species have been recorded from Vietnam, of which one and is the widespread Burmagomphus vermicularis, known from Southern China, Hainan, Taiwan, Laos and Vietnam. This species inhabits muddy streams in agricultural areas bordered by forested hills. (The other is recently described B. schneideri from southern Vietnam.) Now, it is of course possible that other species of this genus share the preference for this habitat and it is not impossible that more of the at least 24 known species occur in Vietnam, so until I catch a male the identification remains tentative, but it is likely that what I encountered is in fact this rather common species.

Freshly emerged female Burmagomphus vermicularis, presumably

The same individual, at a slightly different angle