Habitat of Lamelligomphus camelus (Hoa Binh Province) : foothill fast flowing and open rocky stream (here surrounded by bushes and rice fields, not forest). This species was abundant here.
Male adults usually settles on rocks in mid-stream. A quite tame creature, easy to get close to.
The caudal appendages look rather gruesome, as they are large compared to the size of the dragonfly.
Note the “camel humps” (slightly hooked forward in lateral view) on S8 and (although the picture is not very sharp) the basodorsal tooth on the superior appendages, both diagnostic features.
For comparison, look at this other male Lamelligomphus photographed at Hoa Binh Province :
Superficially it looks like camelus, but it is not camelus : no pair of hump-like tubercles on S8 and no dorsal tooth on the superior appendages.
Tip of abdomen, lateral.
It is impossible to clinch identification from these 2 photos above. A specimen need to be collected.
In the the key to Chinese Lamelligomphus provided by Wilson & Xu, 2009, the shape of the male’s hamuli are important diagnostic features, among others.
The genus Lamelligomphus is very diversified in Chinese territory with 11 species known there (Wilson & Xu, 2009). On the contrary, only two species have been recorded from Vietnam : camelus and biforceps. The male above is not biforceps also, so clearly something unrecorded in the country.
Lamelligomphus camelus is known from eastern, southern and southwest China (Fujian, Guangdong, Guangxi, Hainan), Laos and Vietnam (North and Centre, common species, Dô Manh Cuong pers. comm.).
Many thanks to Dô Manh Cuong for the ID confirmation and the informations about this species