Pseudagrion microcephalum (Rambur, 1842)

The male of Pseudagrion microcephalum is often confused with P. australasiae. However, it has much longer superior anal appendages (visible from up to one meter distance if you have good eyes) and is - noticeably in my opinion - smaller  in size. 

And compare to its bigger cousin, it is a weaker flyer,... but that's just a birder's remark !

A male.

Anal appendages, lateral view                                                 Dorsal view

Superiors anal appendages black, blue within, as long as segment 10, deeply cupped within,  bifid at apex as seen in profile, with small  spines at the base on inner side; inferiors less than half the length of superiors, white, small cone-like.
According to Fraser (1933), microcephalum show considerable variation in appendages shape throughout its range, especially the superiors. 

The superior anal appendages is as long as S10 in microcephalum while they are only half that length in australasiae (for more details, see the post of this species). This is definitely the best feature to examine for a secure male identification. 

In Vietnam, other species more likely to be confused with it are, at least, Pseudagrion spencei and a Pseudagrion sp. nov. not yet described, both with males marked quite similarly on the thorax. These 2 species have been found in 2013 in northern Vietnam by Tom Kompier. The former is likely quite common (largely overlooked) ; the latter has been discovered in November at Huu Liên Natural Reserve (110 km north from Hanoi).

The males of these 3 species are very similar and need to be examined in hand and identified using a combination of structural characters (caudal appendages) and general maculation pattern. For more details, please consult Tom’s blog (odonatavietnam.blogspot.com).

A pair in copula. 

The female differs in several respects from the male, especially the thorax : bluish-green , richly suffused with golden orange on dorsum, especially in the humeral area, azure blue laterally.

A supposed immature female.

Pseudagrion microcephalum has a wide distribution from both Orient and Australasia. Recorded from western, northern and eastern Australia , China, including Guangxi, Guangdong, Hainan, Jiangxi  and Taiwan, India, Burma and Sri Lanka, Ryukyus in Japan, Bangladesh, Indonesia, Laos, East Malaysia, Peninsula Malaysia, Thailand and Vietnam. 

I bumped into this damselfly from time to time in ponds or along grassy banks of slow moving streams.