26/07/2012

Tetrathemis platyptera (Selys, 1878)



Tetrathemis platyptera is a very attractive libellulid that I have spotted on a few occasions above stagnant waters, often very small forest pools.


With its emerald-green eyes, bronze-green reflection on thorax, it is a very “photogenic” dragonfly.


The adult male has stunning blue eyes and a metallic green thorax marked broadly with yellowish stripes. 


The wings are hyaline, but the hindwings are faintly tinted with yellow. According to Fraser in The Fauna of British India, including Ceylon and Burma – Odonata (1933), the depth of the colour depends partly on the age of the specimen and partly on the locality, some showing a very intense amber tint, others with no colouring at all, especially teneral specimens.


The abdomen is black, marked with spots (lateral ones from S1 to S4-S5, which decrease in size and length from segment to segment; dorsal basal spot(s) on S7; remaining segments unmarked).



Wings, male. 

 A male caught by a wolf spider.


Female (2 photos below) almost similar in markings to the male, but the abdomen spots are larger, the wings show a much richer and deeper tint of amber.


Her abdomen is also much stouter.
I saw the female briefly, mating and ovipositing immediately after.

Copula.

The female deposits her eggs on branches or leaves overhanging water, from whence the newly hatched larvae drop into their future habitat. One day, I have seen a mass of eggs deposited on a dead branch, 30 cm above the water (watch this scene of oviposition in the video below).

A female on the branch where she will soon begin to oviposit. The male is hovering in close proximity (blue spot in background) to guard the oviposition site and prevent harassment by other males.

                                                                                       Oviposition in action.

Tetrathemis platyptera is widely distributed in tropical and sub-tropical Asia, with records from India, Myanmar, Thailand, Laos, Vietnam, China, Peninsular Malaysia, Java and Sumatra (+Cambodia, Bangladesh?).
According to some authors, this is a rather local species over much of its range, but probably under-recorded.

The place were all these photos were taken : a small pond in degraded forest, at the lower slopes of Tam Dao. Other species breeding there include Coeliccia scutellum, Orolestes selysi, Polycanthagyna erythromelas, Orthetrum triangulare, O. chrysis, Zyxomma petiolatum.

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