Agriocnemis lacteola Selys, 1877

Adule male resting on a spikesedge (Eleocharis), above a small marshy pool.

Agriocnemis lacteola can be easily found in flooded swampy fields, marshy edges of pools. But you really have to look closely for this little bugger as it is so small. 
 

For the identification, I used the “The Fauna of British India, including Ceylon and Burma” of Fraser (1933).

With its almost completely creamy white abdomen contrasting with the black thorax/occiput, the adult male is unmistakable. The face (labium and labrum) and the crescent-shaped post-ocular spots are also white.
The prothorax is black on dorsum, whitish at the sides ; posterior lobe is margined with white ; anterior lobe is creamy white.

The thorax is black on dorsum, with two narrow white antehumeral stripes. Pterostigmas are whitish/pale blue.
The dorsal marking on S2 is shaped like a vase, expanded at base with sometimes two parallel long branches (see second photo above).
S3 has a narrow mid-dorsal stripe. S4-10 are milky white.

Sub-adult male

  The immature male is not described in “The Fauna of British India”. Compare to the adult, the main difference is the color pattern of the dorsal thorax and the humeral stripe, which are both gray-brown and not black. 

 Sub-adult male. The thorax hasn't yet its ink black color pattern.

Adult male/Below : sub-adult. 

 But depending on the level of maturation, there are intermediate individuals, from light gray to almost black.

The same with the abdomen, which turn progressively from grayish to creamy white.

Adult female

The mature female differs rather widely from the male. It is a much stouter insect, and the first time I saw it, I thought it was a different species !

Post-ocular spots are crescent-shaped like the male but show an amazing azure blue color.
Thorax is similar to the male, but white has been replaced by bluish-green.

                                     The little things below the abdomen of this adult female

                                            are water mite larvae (Hydrachnidia, Acari).

The abdomen is also bluish-green, the dorsum of all segments rather broadly black, this expanding subapically on S2-6 and again narrowing to become confluent with the apical black ring.
I saw also a completely "blue" female, but I couldn't get a decent pic...

As Agriocnemis pygmaea and A. femina, the young female of A. lacteola is reddish.

Immature female

But it is easily identified by the pinky crescent-shaped post-ocular spots, the whitish pterostigma, the plain red brick thorax and abdomen (except the last segments more brownish) and the whitish anal appendages. 

This view from above of one immature female showing well the
crescent-shaped post-ocular spots and the pale anal appendages.

Agriocnemis lacteola is often found in disturbed habitats and is likely to be under-recorded.
This species occurs in India and Bangladesh, Nepal, Thailand, China (Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Yunnan, Zhejiang, Hong Kong), Vietnam (Laos, Cambodia?).

This tiny species seems to be fairly common in the agricultural lowlands around Hanoi, but it is easy to over-look unless you undertake searches..."the nose in the grass" ! 

I often spotted it in low marshy vegetation dominated by sedges (Carex/Eleocharis sp).

The agricultural plain of the North Vietnam (Red River delta) isn't really a paradise for dragonfly lovers - for bird lovers it is much worse : a BIG misery.
Poor odonata fauna but good enough for a beginner like me !

Hand-planting rice seedlings. 
A scene which remain unchanged for thousands of years.