Monday, 28 October 2013

Pseudagrion enigma*

I already posted earlier on my suspicion that there is another species of blue Pseudagrion besides P. microcephalum and P. australasiae. Today on the way to Cuc Phuong we stopped just outside the park at a pond where I knew in summer the possible third species had been present. We were lucky, because there were two male P. microcephalum sitting on the vegetation in the middle of the pond (which is part of a small stream). I collected one male. Then our attention was drawn to two other males in the grass by the side of the pond. Indeed, the enigma Pseudagrion! Due to the morning cold the colors were not vivid, but it did seem the right species and I collected also one of these. A female, the strange brownish female I published before, turned up with the two males, heightening the excitement! Under the microscope there is no room for doubt. This is a different species, with different, but long appendages, smaller size, much shorter lower appendages, and different ocular spots. For comparison I scanned the male with two P. microcephalum (we saw several more inside Cuc Phuong National Park at Ho Mac) and P. australasiae that I had on file from Van Long. For the moment, I treat the enigma species as Pseudagrion, but I am open to any suggestions.*

* Subsequent literature research pointed out that this species is P. spencei, a widely distributed species, but not known from Vietnam.

P. australasiae, top, P. microcephalum (two specimens center) and P. spencei, bottom
I took some photos both in the field and in the hand of the two species with long appendages, M. microcephalum and M. spencei.

Pseudagrion microcephalum, male

Pseudagrion spencei, same as in scan, so actually more vivid when warm

A second male Pseudagrion spencei, also cool

Same male as in previous picture
In hand they look like this:

Pseudagrion microcephalum, male

Pseudagrion spencei, see appendages

The appendages in close-up:

P. microcephalum, dorsolateral

P. microcephalum, dorsal

Pseudagrion spencei, dorsolateral

Pseudagrion spencei, dorsal
And the post-ocular spots

P. microcephalum, male

P. spencei, male

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