Tuesday, 25 November 2014

Gynacantha dohrni, an addition to the Vietnamese list

During our visit to Cat Tien National Park we saw many smallish Gynacantha of which the males would take up hover stations in the lodge garden or along shallow streams in the forest or also along the roads. I was able to catch several males and females at various locations. The were characterized by a very small and constricted epiproct, largely straight superior appendages with somewhat diverging tips and a median basal hump, a rather broad S1-2 with huge blue colored auricles and a yellow face with a dark anterior edge to the postfrons. The hindwings were 41-42 mm, the total body length around 61 mm. It took a bit of searching, but in the end I was able to identify it as Gynacantha dohrni, a species known from for instance Singapore and Malaysia, but as far as I know no closer than that to Vietnam. It had originally been described from Borneo by Krueger (1899), where another closely related species, Gynacantha demeter was also described in 1911 by Ris. Although that species has several characteristics (superiors 6 mm long, diverging tips) that fit the specimens from Cat Tien very well, there is a lot of doubt these two species are actually distinct. Many photos of G. dohrni that I was able to find show similar diverging tips, for instance. Ris also mentions some differences in the color of the wing base, but this too seems somewhat variable. For the moment I therefore will conclude that the specimens from Cat Tien are the same species as that occurring in Singapore and Malaysia.

Male of Gynacantha dohrni. Note the straight superior appendages and tiny epiproct and typical  coloration of S1-3.

Likewise, the female of Gynacantha dohrni
The appendages of the male, note the median basal notch and diverging tips
Close-up of the constricted and very small epiproct
Frons of the male with distinct dark anterior margin, but indistinct T-stem

Close-up of the pattern of S2, with very large blue auricles
The apical segments of the female, with exposed ovipositor

Sunday, 23 November 2014

Two new species for Xuan Son

23 November I drove to Xuan Son, yet again, in search of Planaeschna species. Sadly, the weather was not as good as hoped. It only become clear from 4 PM, way too late. But I did see some Planaeschna guentherpetersi and I also bumped into two species I had not seen at Xuan Son before. The first was Gynacantha japonica. I had seen that at Huu Lien, until now the only location in Vietnam, but evidently it is more widespread. I saw 3 flying around over a dried out muddy pond and was able to catch one. At the same location I had seen G. subinterrupta before, so it was a bit of a surprise to now catch a different species here. The other new species for the reserve was Anisopleura qingyuanensis. Not only a rather late observation, this was also interesting, because these are conspicuous insects and I have by now visited the area and the concerned stream so many times, it is truly a surprise to see it.

Very nice male Gynacantha japonica
And also very nice, male Anisopleura qingyuanensis. In fact more yellow than it looks in this picture.
The appendages in dorsal view

Saturday, 22 November 2014

Agrionoptera insignis - a jewel of the rainforest

On November 16 we visited the general Bird Lake area in Cat Tien. This area had been impossible to visit during the wet season, apart from some pools and ponds along the main road. Now the forest was dry and the trail to the Lake passable. The deep pools along the road had turned into shallow, but clear and vegetated ponds, and it was here that I spotted a nicely black-yellow dragonfly with brownish marked abdomen. It turned out to be a female Agrionoptera insignis. In the same general area I also saw another 4 males. Although we had not observed it in the wet season, it may have been around, just escaping detection in the dark and rainy weather. Be that is it may, this is apparently the first time this species is recorded from Vietnam. Surprising, as it is a wide-ranging species, occurring from New Caledonia all the way to the extreme south of Japan, and of course in neighboring Thailand and Laos. I guess it could be confused with Lathrecista asiatica, but that species is much less distinctly marked on the thorax and has black on the abdomen restricted to S9-10.

Female Agrionoptera insignis, still producing eggs. I let her go to continue her important work afterwards.
And the beautiful male Agrionoptera insignis
The male in situ

A whole lotta Ceriagrion! A new visit to Cat Tien National Park

12 to 18 November we were guests in the Forest Floor Lodge in Cat Tien and spent all day in the field looking for dragonflies, now under very different conditions than in the wet season. Everyday was filled with sunshine and the forest was already very much drier, with most ponds having disappeared, the Dong Nai River showing expanse of rocks in the rapids, and streams in the forest reduced to trickles. During the wet season I had seen 3 species of Ceriagrion, now we were hoping for a few more. And indeed, we encountered 6, 4 of which I had not seen before. One of the first was a species with bright red abdomen and red face, first seen at the pond in the lodge garden and later also encountered elsewhere. Using Asahina's (1967) summary of Ceriagrion I made a startling discovery. It keys out as, and otherwise also fits very well, C. chaoi. But I had already seen that species, and it was very different in coloration, as far as I knew. So I went back to that species too and checked it once more. In side view the appendages are very much the same, but in dorsolateral view the shape of the superiors is in fact different. I had misidentified the species I had seen in Xuan Son, in the north of Vietnam. That was not C. chaoi at all, but C. bellona, a species known from Sumatra and Borneo, also recorded from Malaysia (see Asia Dragonfly and IUCN). I have also found photos of it taken in Thailand, so it seems C. bellona has a more extensive range than generally known and may occur all over south-east Asia. Be that as it may, what I now consider C. chaoi is identical to specimens identified as such and published through photographs on the web from Singapore. I also found several photos identified as "much redder than usual C. praetermissum" from Thailand. These have a red face and greenish thorax sides, something not present in C. praetermissum. It would appear these too are C. chaoi and are identical to those from Singapore. Clearly this species also ranges to southern Vietnam. It was observed at two locations, but clear water ponds in forested environment with a lot of water plants.

Male Ceriagrion chaoi, note red face, bright red abdomen, greenish flanks and brownish dorsum
Another male
Another male, showing the bicolored thorax and red face
Appendages of C. chaoi in lateral view. Very similar to C. bellona.
But see the triangular subapical process to the superiors in dorsolateral view, rather different
The second species I ran into was very small Ceriagrion praetermissum. The male of this species also has red abdomen and red face, but has otherwise pale brownish tones. This appears to be a dry season species, that now was very common around the larger lakes, like Crocodile Lake and Bird Lake. There were still many fresh individuals in the forest or hiding in the grass. It may well be abundant in a little while. The appendages of the male and female are quite distinctive. The female has a long ovipositor and the male has a characteristically forked inferior appendage. Apparently C. praetermissum was not yet known from Vietnam, but it is common in neighboring countries.

Male Ceriagrion praetermissum with brownish thorax, but orange-red abdomen and red eyes.
Another male
Female C. praetermissum, with long ovipositor and red eyes.
Very characteristic inferior appendages of C. praetermissum
The next new species I ran into was the long-bodied Ceriagrion olivaceum. This species is as big as C. praetermissum is minute. I only saw three fresh individuals, all males, but as this is also a dry season species, it may likely become more common a little later in the season. This species has rather pale eyes and the abdomen does not become reddish.

Long-bodied male Ceriagrion olivaceum with greenish eyes and only marginally orange-brown abdomen.
Another fresh male.
The appendages of the male
The last, and a very spectacular, new species was Ceriagrion cerinorubellum. This is a beautiful green and orange species, rather large, with characteristically long inferior appendages. Not that this plays a role in its identification, its size and coloration rule out other species at a glance. I saw only two in a drying out pond with extensive rush-fields.

Spectacular Ceriagrion cerinorubellum, striking and beautiful.
Another male, with a dark spot on the thorax.
The two other species I encountered were C. malaisei, of which I saw a single male at Crocodile Lake that I could not take a picture of, and C. aurantiacum, which too I saw at Crocodile Lake, but in somewhat larger numbers, and at the fishponds.

Green-eyed Ceriagrion aurantiacum
Another male in dorsal view
And the lateral view of the appendages, with the relatively long and straight inferiors

Sunday, 16 November 2014

Second visit to Cat Tien National Park

Kameliya and I went for a 6 day visit to Cat Tien National Park, as follow up for my earlier visit in the summer. Today is day 5 of the stay, so one more full day to go. Until now it has been very different from the earlier (rainy season) visit. The best thing is that it does not rain, or hardly. Every morning is clear blue and before it gets warm it is very pleasant. Some great birds too, with Lesser Adjutant, Painted and Woolly-necked Storks, Grey-headed Fish Eagle, Brown Fish Owl, Siamese Fireback, Wreathed Hornbill and Great Hornbill and many more. But we are here for the Odonata list. Until today the following species were added:

Gynacantha dohrni (new for Vietnam)
Agrionoptera insignis (apparently new for Vietnam, but occurs all around)
Tetrathemis hyalina (already on the list, but not yet in our survey)
Trithemis pallidinervis (to be expected)
Neurothemis intermedia (likewise)
Epophthalmia vittata (or frontalis) (already found by James)
Tramea virginia (to be expected)
Zyxomma petiolatum (to be expected)
Rhinagrion hainanense (a great addition, known of course from the north)
Ischnura aurora (to be expected)
Archibasis viola (the second Archibasis, apparently not new for Vietnam)
Copera chantaburii (already known from Vietnam)
Orolestes octomaculata (already recorded by James)
Ceriagrion chaoi (note that this is a different species than what I presumed was C. chaoi. I will need to change that species, so this is an addition to the Vietnamese list)
Ceriagrion praetermissum (new for Vietnam)
Agriocnemis femina (to be expected)
Agriocnemis minima (to be expected)
Mortonagrion aborense (to be expected)

With some luck we will add 20 species or so, although 2 of the above had been recorded by James already this summer, and one was known from historical records. So watch this space, as soon I will provide the evidence!