Aciagrion borneense - another cool little damsel

Wednesday September 10 I was for work in the city of Danang, visiting some communities on the outskirts. While traversing some former rice fields now covered in grass and puddles I noticed a small and slender blue damsel. A little later I saw several more, interacting in little territorial disputes amongst themselves and with Agriocnemis femina. I could catch one with my fingers and put it in an empty water bottle. In the evening, back at home in Hanoi, I could take some photos and identify it as Aciagrion borneese, a very common and widespread species, that has been recorded before in Vietnam, according to the IUCN information, but apparently recorded only rarely, although given the fact it is common and widely distributed from Indonesia to Thailand and Cambodia in disturbed habitats, it may be also widespread in the south of Vietnam. It is a distinctive species because of the reduced blue on S8 and S10, with blue dorsum to S9. The appendages are a close match with the drawings in Ris (1911), although slightly larger (abdomen 22 mm against 19 mm in the description).

Caught in a trap: Male Aciagrion borneense inside its plastic cage

The scanned insect

Close-up of the thorax and head

Dorsal view of S8-10 and appendages

The same in lateral view