Ceriagrion fallax and Ceriagrion chaoi*

*Identity of Ceriagrion chaoi was confirmed by Rory Dow and this entry adjusted on January 21, 2020.

When checking a small very clear man-made pond at Xuan Son National Park first a large yellow Ceriagrion flew into my vision. Reminiscent of C. melanurum, which I know from Japan, it is a bit like a small flame moving about. Voracious as I remember C. melanurum too. A large splendid Ceriagrion, not uncommon, apparently, but I had not seen it before. Then when scanning some of the floating water plants I also noticed a smaller reddish Ceriagrion. Unlike C. auranticum the thorax was not greenish, and it looked a bit like C. malaisei. However, clearly it had darker dorsal S8-10, something not apparent in that species. There were quite a few about, in copula ovipositing. Nevertheless, it was not easy to catch one and one I did I let it escape again. But eventually I could make some close-ups and confirm it was Ceriagrion chaoi. I know of no records from Vietnam before. It is smaller than the rather similar C. malaisei, with very different appendages, a darker dorsal side of the synthorax and rather apparent darker dorsum to S8-10. For reference I include below the appendages of C. malaisei.

Ceriagrion fallax, male

A large species, bright yellow, with blackish dorsum to S7-10

Three copula of Ceriagrion chaoi

Ceriagrion chaoi, male, with characteristic darker S8-10

Appendages of C. chaoi, male

And for comparison, the very differently shaped appendages of C. malaisei