Monday, 25 April 2016

Two new Rhyothemis species from Phu Quoc

On April 12 to 15 we visited Phu Quoc Island to see a few of the dry season specialties. This year is exceptionally dry and the island suffers from break-neck speed development and ground water abuse, but I was able to locate many of the goodies that I hoped for, although not all. Amongst these were two Rhyothemis species that I had not recorded before. One of these is known to occur in the island and although numbers are low, I bumped into it at a handful of widely separated locations. This is the smallish and wonderful Rhyothemis obsolescens.

The other I did not recognize. At a pond in the forest on several days I observed a male Rhyothemis perched that looked a lot like R. plutonia, but the greenish iridescence on the wings seemed more extensive and the remarkable purple of that species was missing. The wings seemed to have a reddish ground colour and towards the tip the greenish colour was visible as dots too. I tried to catch it, but I could not. In the end it dawned on me that this is Rhyothemis aterrima. This species has been recorded in Vietnam before. Cuong & Hoa list a record by Asahina from Binh Duong Province from 1962. But I know of no other records. Supposedly it is not uncommon in for instance Malaysia, but it is difficult to find photos on the web, so maybe it is actually not that common. I am very happy with it.
This is the wonderful male of Rhyothemis obsolescens. The pale borders to the wings give them a sort of out of focus aspect.
From below the golden shine is missing, but the brown and paler areas form a beautiful pattern. It excels at holding its wings at different angles.
Although this specimen takes a more conservative pose.

This is the difficult Rhyothemis aterrima male. This photo is a little too dark and therefore it looks quite a bit like R. plutonia. But note the relative slender hinds wings, extensive green and lack of purple.

Much more apparent in this photo is the reddish ground colour of the wings and it can be clearly seen that the green on the outer wings forms distinct dots.

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