Some Chlorogomphids

It was already quite late in the Chlorogomphid season when we started traveling around northern Vietnam, thus we only recorded 6 species from this family, out of 17 mentioned by Karube (2013) as occurring in Vietnam (we now know that Sinorogomphus hiten also occurs in Vietnam, so there are at least 18 species). As Karube mentions, Pia Oac Nature Reserve in Cao Bang Province is a great place for them, with 7 recorded species. The most common species there seems to be Chlorogomphus piaoacensis. We encountered many of them all over the general Pia Oac area, very common at the end of June, but already far less by the second week of July. At the same streams this species was flying, we also caught two similar species that had not yet been recorded from Pia Oac. The first of these, surprisingly, was Chlorogomphus (Sinorogomphus) tunti. This species is known from western China and central Vietnam. It has highly distinctive appendages, the most important clue in the identification of most species. The second was Chlorogomphus (Sinorogomphus) sachiyoae. This species until recently was only known from Tam Dao, but occurs much more widely. Sebastien for in stance was the first to find it at Xuan Son and I found it also in northern Bac Kan Province and thus also at Pia Oac in Cao Bang Province.
The fourth species I was lucky enough to encounter at Pia Oac was Chlorogomphus takakuwai. This species had already been recorded from Pia Oac and is also known from Tam Dao and Lao Cai Province. I saw only one female, ovipositing under forest cover in a shallow stream. The fifth species I saw during the trip was Chlorogomphus auratus, with one female on mount Mau Son and a possible female in Cao Bang Province. Below some photos. And no, these are not all the same species! The thing fascinating about Chlorogomphid species, especially Sinorogomphids) is that they look very much alike, share the same general habitat and behavior. It is truly a mystery why and how so many different species can co-occur in such proximity.

Male Chlorogomphus (Sinorogomphus) piaoacensis, the commonest species in Pia Oac (but nowhere else?). Note the pattern on S1-2 and the highly distinctive appendages (with the tooth-brush shaped superiors, see below).

Clearly not the same species! Chlorogomphus (Sinorogomphus) tunti, male.

Obviously the same species as directly above, another Chlorogomphus (Sinorogomphus) tunti male.

Chlorogomphus (Sinorogomphus) sachiyoae. Clearly different from the two previous species. Note pattern of S1-2 and lack of apical spot on S7. This one captured in Bac Kan Province.

Another Chlorogomphus (Sinorogomphus) sachiyoae, this one captured in Pia Oac Nature Reserve on same stream as C. piaoacensis and C. tunti.

A very different specimen and not just because it is a female. Chlorogomphus (Petaliorogomphus) takakuwai. Note orange wing bases and distinctive marking on S1-2.

Highly distinctive rounded superior appendages without branches of C. piaoacensis.

And in dorsolateral view, showing distinctive toothbrush shape

And in even more detail

The same for C. sachiyoae. Rounded, but with clear branch at halfway point

Appendages of C. sachiyoae in lateral view, showing distinctive shape of apex.

Dorsal view of the deeply forked superior appendages of C. tunti

The same in lateral view, showing the downward angle in the stem of the superior appendage