Pseudagrion australasiae Selys, 1876

A male in flight.

The first time I saw this species it was through my birding binoculars (very helpful for chasing odonata !). I was scanning the marsh of Van Long in search of some interesting birds when suddenly a quite big-sized blue-greenish Coenagrionid darted across my field of view, moving quickly 20-30cm above the water. A good flyer, with good accelerations, not the “weak style” of the other pond damselflies I had spotted before.

A male.

I said myself: “Yesss, a new species !” I edged forward and managed to get a few good snaps. Not easy because this guy - and the other ones I encountered after -, was skittish. But things got better when I cross paths with a tandem pair, so busy searching good oviposition sites that it didn’t pay much attention to the crazy big human slogging across the swamp. 

This leech didn't find the best host
(me for example...)

Superficially, males Pseudagrion australasiae looks very alike P. microcephalum and P. spencei. They are both azure blue, have a broad black band on the mid-dorsum thorax, black humeral stripe, segments 8 and 9 blue… But fortunately, there are some details which help to tell these species apart in the field - even “at distance”... if you have binoculars.

Arghh.. !!! Hard to get rid of  this pesky little bug !

 The most reliable feature discriminating the adult males is the size of the superior anal appendages: as long as S10 in microcephalum and spencei while they are only half that length in australasiae (left).

Also, in microcephalum and spencei, superior anal appendages are twice at least as long as the inferiors, while they have almost the same length in australasiae. A good close-up shot will do the trick.

A pair in copula.

How about female adults of P. australasiae and P. microcephalum? According to C.Y.Choong in his interesting website, middorsal thoraciq stripe of the female of microcephalum is thin, and the post-ocular spots are blue. In australasiae,  the middorsal thoraciq stripe is thick and the post-ocular spots are greenish (link here).

All the females I spotted didn't show a thick middorsal thoraciq stripe but rather 2-3 lines very close together.

 

A female ovipositing onto submerged vegetation.

The status of this species, its distribution and its relationship with P. microcephalum (Rambur, 1842) and P. bengalense Laidlaw, 1919 has been the subject of considerable confusion. Lieftinck (1936) clarified the situation, and showed that P. bengalense is a synonym (see link here). However Lieftincks' work on this subject appears to have gone unnoticed by some authors and the name P. bengalense has persisted in the literature.

P. australasiae is widely distributed (Cambodia; China (Hainan); India; Indonesia; Malaysia; Myanmar; Nepal; Singapore; Thailand) and moderately common species, occurring in open habitats. Although it appears to be rather local in occurrence across much of its range, it is likely to be under-recorded.

This damselfly is not in the Checklist of dragonfly from Vietnam (Dô Manh Cuong & Dang Thi Thanh Hoa, 2007). But I would be very surprised if it has not been recorded since then. To my knowledge, in Vietnam, P. australasiae is only known from Van Long.