Zygonyx iris Selys, 1869

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 India to southern China and south to Borneo. It is a common species over much of its range.

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

4 commentaires:

  1. Superbe reportage et magnifiques photos. Je serai dans quelques semaines à HCM pour un an... Si tu descend par là, je ne serai pas contre quelques spots/conseils, etc ;)

    1. Merci pour les compliments! Il y a peu de chance que l`on se rencontre à HCM-Ville car je suis ``cantonné`` à Hanoi. Mais si tu montes au Nord fais moi signe. Et je peux toujours te renseigner par email sur les bons coins (sebastiendlngl40@gmail.com)

  2. Superb photos and information all round ... you make me want to go out and photograph everything again! And you are so right ... they tend to hover above waterfalls, seemingly forever. However, though the males are difficult to get close too, the females are very approachable once landed and I was even able to pick one out of the branches with my fingers! Keep up this wonderful work and I'm sure you'll reach your target of 50 for the year, very soon! Dennis

  3. Thanks Dennis I will try to reach... 50 posts this year, the half of the species I have spotted. But maybe you want to say : 50 new species for this year! Uii, this is an impossible challenge, unless I devote all my time to it - and not only spare time !