Gynacantha subinterrupta - like the other members of this genus - is a crespuscular dragonfly, not appearing on the wing until dusk has well set in. During the day it may be flushed from dark thickets. When so flushed it soon find a new resting place a few meters away.
According to Fraser (1933), blues and greens developing very late in life; thus the majority of descriptions depict the insects as drab brown relieved only by darker shades, whilst the full adult insects are often very beautiful in their display of blended greens and blues.
I have only spotted young adults, but I hope to see one day old ones with brighter-coloured markings...
Abdomen swollen at base, markedly constricted at segment 3, narrow and cylindrical from thence to the end, coloured blackish-brown in young adults.
The male has very long superior anal appendages, narrow but dilated at extremities (paddle-like), pointed, and coated with long hairs on the inner side.
Inferior appendage narrowly triangular, much shorter (1/3) than the superior one.
The female (photo above and below) show a less constricted segment 3 but differs from the male mainly in sexual characters. She have also very long lanceolate anal appendages.
Gynacantha subinterrupta is widely distributed in tropical and subtropical Asia (India,
Cambodia, Indonesia, Laos, Peninsular Malaysia, Myanmar, Nepal, Singapore, Thailand, ). Vietnam, China
This species is found in marshy areas and pools in a wide variety of lowland forests, including small wooded patches and extremely disturbed areas (I took those pictures in a fruit garden, in the inner suburbs of Hanoi).