I spotted many times this large libellulid along swift rocky streams, including those in open and agricultural land, in lowland and montane. The adult males hawk over a limited beat over rivers, generally over a rapid or below a waterfall. But they almost never land! And when they finally perch, they do not tolerate close approach…
Getting a good shot of this species is really difficult; but one day, you will probably bump into a tame individual that will accept what all the other ones have always refused : to be approached less than 1 meter. It happened to me.
The adult male has broad dark metallic greenish-blue stripes on thorax. Abdomen black, with mid-dorsaI carina finely yellow. Tips of wings enfumed.
Close-up on wings.
Head : frons dark metallic blue
Female (photo below) resembles the male but the lateral yellow markings on abdomen (segments 1 to 3) are more extensive, and the thorax has broad yellow stripes (the immature male also).
Male and female pair over water and travel in tandem for great distances up-stream seeking suitable situations to deposit the eggs. The larvae are adapted, by a flat limpet-like abdomen, to cling to rocks.
A female ovipositing by dipping her abdomen tip quickly into shallow water. To get some good close-ups of the female, no other solution than to capture her with a net during mating or oviposition. The rest of the time, she is invisible.
A female perched - a rare sight!
Zygonyx iris is a widely distributed species, occurring from northeast
Remarks: Another Zygonyx species occurs in Vietnam . Z. asahinai Matsuki & Saito, 1995
This species is known from southern and eastern China (Fujian, Guangdong, Guangxi, Zhejiang) and has been recorded in very few localities in northern Vietnam (Mau Son mountain in Lang Son Prov., Tam Dao NP in Vinh Phuc Prov., at least).
Z. asahinai resembles Z. iris in general appearance but can be readily distinguished from the latter by the following characteristics (from Matsuki & Saito, 1995) :
1. Labium entirely black in aged stage
2. Antehumeral yellow stripe very narrow and short, both infraepisterna darkened entirely
3 ♀wings yellowish orange tinted in the basal one-fourth
4. Different configuration of male accessory genitalia and caudal appendages
5. Different configuration of valvula vulvae