Saturday, 23 July 2016

Aciagrion - some additional species*

*Adjusted after email conversation with Oleg. A. pallidum changed into A. hisopa.

Aciagrion is quite a speciose and difficult genus, not in the least because many of its members are tiny and thus vulnerable. Thank God that Kosterin et al. (2014) at least sorted the problem of Aciagrion approximans. I had already recorded this species from Cat Tien National Park (a teneral male), but could only ID it properly after the mess surrounding A. tillyardi had been resolved. And I recorded A. borneense and A. migratum already. But there are other species in the area and there were historical records of A. hisopa, A. occidentale, and A. pallidum (Do & Dang).

This spring turned out to be quite productive. Aciagrion approximans turns out to be in fact quite common in Lam Dong Province, where I saw large numbers, but I also recorded it from Quang Tri and Thua Thien - Hue Provinces. It stands out with its typical purplish violet color and in hand has deeply cleft superior appendages in lateral view, but with the dorsal and ventral edges parallel.

On June 11, 12 and 18 I observed Aciagrion hisopa at the same locations as where I recorded Platylestes platystylus (see previous post). All observed specimens were blue and the females did not have reddish abdomens, like A. pallidum would. A. pallidum and A. hisopa have very similar appendages and blue specimens can be confusing. In both species  the lines on the thorax can be diffuse, although they only become truly black in A. hisopa.

On June 18, again at the same site in Dak Lak Province, I noticed another small species with triangular black mark on the dorsum of S8. Otherwise it was similar to A. borneense, which also occurred there, but I thought it might be A. occidentale. The appendages in lateral and dorsal view are virtually identical, but there is one important additional clue and that is that the internal surface of the superior appendages and the complete inferiors are ivory white in A. borneense.

The last species to mention is a blue-and-black species from Thua Thien - Hue Province. I discussed these specimens with Oleg Kosterin and we concluded that it cannot be separated from A. migratum on the basis of its appendages, even if it has a different hue. More research would be necessary to separate it (for instance through DNA analysis), but for now it seems better to treat it as a variant of A. migratum.

Aciagrion occidentale male, note the triangular mark on S8.
Probably the same male in flight
Aciagrion occidentale, female
Male Aciagrion hisopa, June 12, Lam Dong Province. Note the lack of black on the thorax
Female Aciagrion hisopa, June 18, Dak Lak Province

Another male, June 18, Dak Lak Province
A typical Aciagrion approximans, a study in violet, May 2016, Lam Dong Province
And finally Aciagrion migratum, Thua Thien - Hue Province, June 21. If you look carefully you can see the deeply incised superior appendages, but unlike in A. approximans the dorsal and ventral edges diverge.

Friday, 22 July 2016

Platylestes platystylus - also in Vietnam

May 28 I received an email from James Holden. Platylestes platystylus had been found at the fish ponds in Cat Tien National Park. Thrilling, because this is a little known and elusive species, according to the IUCN website. Dennis Farrell has reported it from Thailand, where it was known to occur, and it has also been recorded from Lao DPR. It ranges all the way west to India, although there is some doubt whether this really all concerns the same species.

Anyway, it was great to hear it occurred in Vietnam, because Lestidae are quite uncommon here, with just a few species compared to for instance Thailand. I was also rather envious, because it is a beautiful species and because I want to see every species known in Vietnam. Frustrating, because it is of course impossible to see everything.

On June 11 I was crossing the provincial border from Gia Lai Province into Dak Lak Province when I noticed an inundated depression in the open landscape. Until recently the area had been parched, but now the rains had started and water had accumulated there. It turned out it was probably the remnant of what once was a swamp. It was late in the afternoon, but I did see a few interesting damsels and decided to have a closer look. And there it was: a male Platylestes platystylus! It moved away quickly, but I had no doubt, but also no picture. While dusk settled I had to leave, but decided to return on my way back from my destination (Bao Loc).

The next morning I drove further south and into Lam Dong Province when I noticed a small shallow and grassy pond that looked promising. And there I found my second male Platylestes platystylus. Maybe not that uncommon after all, just occurring in not often researched temporary habitat?

On the way back north a week later (June 18) I revisited the depression in Dak Lak, but now in the morning. It was really crowded will all sorts of exiting species. Amongst the 35 species or so I found on the 1.5 hectare several species of Aciagrion, several Lestidae, several Ceriagrion, but also Indothemis limbata and I. carnicata side by side, and lots of other goodies. And at least 10 Platylestes platystylus. Now I had my photos sorted.

The first Platylestes platystylus male on photo, June 12 in Lam Dong Province
The same male in dorsal view

This is the female, June 18 in Dak Lak Province

Another male on June 18

Male appendages in lateral view

And male appendages in dorsal view