I first came across this miniature dragonfly in July 2011, and I have been very surprised by its size. Because I had in mind the image of Libellula depressa, a common large European species which also show a broad and flattened bluish abdomen.
The male has an iridescent blue frons, a light blue abdomen and wings decorated with conspicious inky blotching.
The female also bear spotted wings but less proeminent. Its abdomen is yellow with two lateral black stripes.
Palpopleura sexmaculata is widespread in Asia (from south China to India). In Thailand, it is considered as an "uncommon species found in few places in uplands and montane areas" (source : Noppadon Makbun, in his blog http:duenneud.blogspot.com).
I have no information concerning its status in Vietnam, except is has been recorded in many localities of the North-West and also in the highlands of Tây Nguyên (Centre) (Checklist of dragonfly from Vietnam/Dô Manh Cuong & Dang Thi Thanh Hoa, 2007).
It is a quite common sight in my area, but easy to overlook. I spotted it mostly in hilly areas, along marsh edges of ponds, inundated grassy banks of streams.