Saturday, 10 October 2015

A few hours in Vientiane, Laos and a new species for the Laotian list.

This Thursday I had a few hours to spare in Vientiane and took a cab to the outskirts of the town. Thank God the surroundings are not close to being as polluted as around Hanoi and I was able to find 38 species in a short time. Vientiane is about as far south as Ha Tinh in Vietnam, which is about the southern edge of my general research area (northern Vietnam). But its species are quite different, much more southern. There was a lot of overlap with the commoner species in Cat Tien National Park, for instance. I was happy to catch a Epophthalmia frontalis male. Yokoi & Souphanthong actually list 31 Macromiidae, 28 of them Macromia. Which is rather astounding. But anyway, I was happy with my frontalis. And I was able to take pictures of male Lestes elatus and female Ceriagrion cerinorubellum. I had seen both these species in Cat Tien, but had not seen these sexes. Below a few pictures. And another very common species in some inundated and apparently deserted rice fields was an Aciagrion. I had to go back to Ris (1911) and Fraser (1933) to find out what may be the differences between Aciagrion occidentale and A. borneese. The appendages look rather similar and the A. borneese I had from Da Nang had been eaten by vermin. But in the end the description of Fraser pointing out that S8 is blue with a black triangle on it in A. occidentale, whereas A. borneese has a broad dorsal black stripe over the whole segment, provided the clue. Photos from India confirm the pattern on A. occidentale, and I therefore conclude that the specimens I saw were A. borneese, on the premise that the pattern is consistent over the complete range of these species. Interestlingly Yokoi & Souphanthong do not list either of these species for Laos. A. borneese is a very common species in Thailand and that country is of course right opposite the river at Vientiane.

Let's start with the addition to the Laotian list, Aciagrion borneese. Note dorsally black S8 and S10, whereas S9 is marked by a thin blackish dorsal line.
Another male with the distinctive pattern

Female Ceriagrion cerinorubellum. Possible to confuse with C. auranticum because of the green eyes and orange-brown cranium. However, S3-7 are blackish above and blue-green laterally, not orange, and S9 misses the clear darker marking.

Lestes elatus female

And the male, which I had failed to find in Cat Tien.

And finally a fine male Epophthalmia frontalis

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