Wednesday, 6 January 2016

Mortonagrion falcatum - an addition to the Vietnamese list

On January 2 I revisited the area around Lake Duong Dong, located centrally on Phu Quoc. The previous day had been quite productive and I was hoping to find a few more additional species for the holiday list. We had found a trail into the forest that after a bit of a hike crossed a stream and it was there that I noticed perched at the tip of a small stick over dead leaves just above the ground by the side of the stream a tiny damsel. Because of its drab basic coloration I thought it was a female and also it did not have obvious appendages in dorsal view. But just as I was getting ready to take better shots my foot slipped a bit and it darted off. Because it was both drab and tiny I immediately lost it. I searched for a long time for additional specimens, but could not find any. Disillusioned, I continued the hike for a while, but on the way back revisited the place and again searched high and low, to no avail. Before leaving even more disillusioned I rechecked the place of the original sighting and there it was! Tiny and inconspicuous, back at its stick. I crawled down next to it and took some photos. But when I wanted to pounce on it, it again darted off into another dimension. The thing was: when I checked the photos (in the middle of shooting) it was a male! I did my best to get as good a close-up of the appendages and this saved the day.

I knew I had seen something like it on some website somewhere and just started leafing through Coenagrionidae. Yes, of course, Mortonagrion! But the first logical suspect, with a sort of similar abdominal pattern, M. arthuri, has rather different appendages. But eventually I found it in Lieftinck (1934): Mortonagrion falcatum. Recognizable by its strange, quite distinctive, appendages. Records are scarce, but it is a widely distributed species, occurring in Indonesia, Singapore, Malaysia, Myanmar, Thailand and with a record from Lao PDR. On the IUCN Red List it is hypothesized that it occurs in Cambodia and Vietnam. Well, it does (in Vietnam, but given the location of Phu Quoc it is highly likely it also occurs in Cambodia. See the pictures below of this interesting midget.

Not a very conspicuous little insect at all, when it perches over brown leaves, but actually rather pretty: Mortonagrion falcatum

The distinctive appendages, the superiors broad and up slanting.


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