Tuesday, 26 August 2014

Coeliccia sp*

*Early 2017 this post was adjusted. The species occurring in Cat Tien is not true C. kazukoae, but a closely related species, soon to be published.

In the first week of August I was in Cat Tien National Park, and blablabla. Anyway, after some hard searching for forest damsels in the shade of the rainy rainforest, I ran into a small Coeliccia species with rather dull coloring. Once I understood where to look for it, close to the river, but inside the forest and low by the ground in the darker areas, I saw several more. Although the first few were immature, I also saw older individuals, with more whitish markings on the last abdominal segments, but they all had the same basic yellow-brown thorax markings, not a sign of blue.

Asahina described two small and structurally similar species from Thailand, C. kazukoae and C. megumii. Later some doubt was cast on whether these were not in fact the same species, with C. kazukoae the immature yellowish form of the black-and-blue C. megumii. Oleg Kosterin has shown these two species are in fact synonyms and lumped them as C. kazukoae. The species present in Cat Tien is however different from C. kazukoae. It will shortly be described.

Although mature and blackish on part of the thorax, no bright blue anywhere in sight. Male Coeliccia sp.

An immature female

And an immature male
The typical double lobed superior appendages of C. sp

Dorsal view of the same appendages

And the dorsal side of head. This is an immature, but kept to age a little

A few more damsels from Cat Tien worth mentioning

During the first week of August I was the guest of Roy Bateman at the lodge there, helping with the dragonfly list for the reserve. A terrible time as far as the weather was concerned. I sadly lost one camera to the incessant rain and my lenses were foggy for a large part. Still, a few additional record shots…
Let's start with Pseudocopera ciliata. A common species, but the interesting thing is that as far as I know this species is monotypic. However, in northern Vietnam the apical half of the inferior appendages is white, like the remainder of the appendages, whereas in Cat Tien, and as far as I could verify from photos from Thailand also elsewhere in the south the apical half is black.

Close-up of the appendages

This little lady is a fresh female Onycharga atrocyana, photo taken in the rain, sorry.

And this little fella is Agriocnemis nana, a pretty whispy thing that I saw on several occasions, one at the pond in the lodge garden. Apparently a southern species

When I saw this immature Argiocnemis rubescens my heart skipped a beat. It is so different from the pruinose pale examples I saw in Bac Kan Province that it is hard to believe it is the same species, certainly if you also take a look at the mature version from Cat Tien.

For this is the very blue mature male. I saw many, and none should any trace of pruinosity. Like: really? The same species?

The immature male along a tarmac road in inundated grass

A mature male perched at the edge of a pool

Monday, 25 August 2014

A few more libellulids from Cat Tien*

*Adjusted on December 28. Tetrathemis platyptera replaced by T. irregularis hyalina.

I saw a few more interesting Libellulids at Cat Tien in early August; interesting as I had not seen them before, or rarely, or in the case of Tetrathemis, was a new record for me.

The first is a small Neurothemis species, N. fluctuans. It differs from the quite a bit larger N. fulvia by the hyaline margin along the posterior edge of the hindwing.

An immature male Neurothemis fluctuans.

The female of Lathrecista asiatica, a common species of the south, although absent in the north. It occurs on pools and puddles in the forest

Immature male Lathrecista asiatica

Male Lathrecista asiatica with red abdomen and pruinose thorax.

Yet another stunning little male dragonfly that was common at the fishponds, Aethriamantha brevipennis. Although Sebastien has recorded it in the north, I have never seen them there and these were my first observations.

Again I apologize for the poor quality of the picture, this one taken with a very much steamed up lens.  It is the female of Tetrathemis irregularis hyalina, which I saw on several occasions on forested ponds.

Speaking of pretty bad photos, a record shot of Tramea transmarina euryale, yet again. Although not common, certainly not rare either.

Male Pseudothemis jorina, another southern species. In Northern Vietnam common P. zonata occurs. I do not know where the border between the distributions of these closely allied species is, or whether there is overlap.

Rhyothemis phyllis

During my week at Cat Tien in early August I saw 4 species of Rhyothemis. That is a treat for someone living in Northern Vietnam, where only R. variegata is regular. I did see R. plutonia in Huu Lien, but that is it. In Southern Vietnam both these species occur, but they are joined by R. phyllis, reasonably similar to R. variegata, and by R. triangularis. To my shame I saw the latter only once, at the fish ponds, fluttering between a couple of trees at the edge of a pond. When I had my camera out, it had disappeared, so not even a record shot. R. plutonia was common here too, as was R. phyllis, a species that could be seen anywhere, although not abundant. It is a nice larger species.

Male Rhyothemis phyllis, with clear basal markings to the inner wings, but remainder, apart from the apex, hyaline

Gynacantha basiguttata - new for Vietnam

In July James Holden, doing research in Cat Tien National Park, contacted me with photos of what appeared to be, based on the distinctive appendages, a male Gynacantha basiguttata. That would be a new record for Vietnam, although the IUCN redlist mentions it as a possible for Vietnam. It otherwise occurs from Singapore, Malaysia, Indonesia and the Philippines to Thailand.

Not surprisingly, I was hoping to see the species when I visited Cat Tien in the first week of August. James had after the first record seen several around the lodge. I did catch several Gynacantha there at dusk, but these turned out to be Gynacantha subinterrupta, a species I saw regularly also elsewhere in the park. There were some high-flying Gynacantha both at dusk and at sunrise, that may have been something else, until I finally in the early morning caught a female Gynacantha with clearly marked wings bases and minus the typical abdominal markings of G. subinterrupta. At last, Gynacantha basiguttata, my fourth Gynacantha species in Vietnam.

Not very brightly colored at all, and with unmarked thorax, but note the typical dark "flames" at the wing bases! Female Gynacantha basiguttata.

Sunday, 24 August 2014

Aciagrion approximans - no end to my problems*

*Adjusted on April 16, 2016, after communication with Oleg Kosterin. A. approximans has now been redescribed and takes precedence over A. tillyardi.

When checking for the umpteenth time the small pond next to the lodge in Cat Tien I noticed a small coenagrionid in the grass, freshly emerged. Although small and fresh damsels will not likely survive capture, it was clear this was something I had not seen before, so I decided to catch it and stick it under a glass in my room to harden. I am sort of glad I did, for when later checking the details, it became clear this was a small Aciagrion species with a concave posterior margin to the superior appendages. Sort of glad, as this is where the problems begin. As can be seen from the photos on Asia-Dragonfly and the discussion on the website of Dennis for Thailand, there are several species that are being claimed as A. tillyardi, the species that would be the species of choice for this little fellow. There are only a few Aciagrion with forked superior appendages. The larger A. migratum occurs in Vietnam too. Now, there is a purplish Aciagrion that occurs in Thailand, for instance, with elongate postocular spots connected by a bar across the occiput, so the complete feature is like one elongate bar across the dorsum of the head. And there is a blue species with rounder postocular spots. The appendages are apparently similar. Th original description of A. tillyardi in Laidlaw (1919) does not mention any purple tones, and nor does he mention blue for that matter. He speaks of narrow gray-blue ante-humeral bands (sic) and gray-olive sides. He does state that the head has "a linear gray-blue post-ocular mark on either side, joined by a fine transverse line of the same colour across the occiput." Not purple, but also no rounded postocular spots. He also states that segment 9-10 are gray-blue and S10 black, obviously a mistake. I assume he means that 8-9 are gray-blue. One wonders whether this description fits any of the species claimed to be A. tillyardi. Luckily, my specimen is teneral and therefore neither blue nor purple, but it does have elongate postocular markings. For the time being I claim this as A. tillyardi. It certainly is not any of the other species in the area.

The fresh tiny male Aciagrion approximans

Dorsal view of appendages
Dorso-lateral view of appendages
Dorsal view of head, showing elongate postocular markings, blacking prothorax (but blue frontal lobe) and blueish antehumerals, but note this is a very fresh specimen.
And we wait for some courageous researcher willing to dive into this genus and sort things out. I also hope to collect mature specimens later this year. Like the genus Heteragrion in South-America and so many other examples, it might be better to just discard all old descriptions based on a few specimens, now long turned into dust, where these descriptions do not provide enough detail or decent drawings. Sorry for the scientists of yore, who clearly did what they could under the circumstances and based on what was seen as proper scientific work. Sadly, it does not stand the test of time. Sacrilege! Yes, but sometimes it may be necessary to throw of the shackles of past inadequacies.

Archibasis oscillans, a new species for Vietnam

Archibasis is a genus of medium-sized damsels occurring in South-East Asia and Australia, most abundant in New Guinea and Indonesia. 8 species are recognized at the moment, but information on the identification features of several species is scarce. Two species occur close to Vietnam. The first is the blueish Archibasis oscillans, that has been recorded from India to Thailand and Laos (and likely Cambodia, see Kosterin). The other is Archibasis viola, a purplish member of the genus, occurring in Indonesia, the Philippines, Malaysia and Singapore and, according to the IUCN redlist, with unpublished records in Thailand and Vietnam.
During my visit to Cat Tien in early August I saw a blue Archibasis on a regular basis, both inside the forest and outside near the fish ponds (but under a tree). I was able to collect several males.
Lieftinck (1949) published drawings of the appendages of several Archibasis species, also of Archibasis oscillans. The appendages are similar, but not identical. The inferiors miss the cleft visible in the drawings. In that respect they are more close to those of A. mimetes of Australia and New Guinea. That species however looks rather different. In appearance my males and females are similar to all published photos of A. oscillans that I have been able to find and the description otherwise also fits well. I cannot preclude that there may be an as yet undescribed species involved, but for the moment it seems best to consider this A. oscillans. Its occurrence is certainly not unexpected. It is a species of lowland forest occurring in the same climatic zone in nearby countries and thus fits the pattern of other species found in Cat Tien that occur in neighboring countries and have been found for the first time in Vietnam during recent fieldwork in Cat Tien, like Aciagrion tillyardi, Ceriagrion calamineum, Coeliccia kazukoae, Gynacantha basiguttata, Nychogomphus duaricus, Brachydiplax sobrina and others.

As field photos turned out bad due to foggy lenses, I took this picture in the lodge. A typical Archibasis.
The dorsum of head and thorax. Note large postocular spots, markings on prothorax, dents in humeral stripe and just visible, blue spot on center of dorsal side of S2.

Dorsal view of the appendages, note the "flag" at the tip of the superiors.
Dorsolateral view of the appendages
Lateral view, with inferiors 2/3rd of superiors, digiform, and in lateral view small cleft in superiors.
Ventrolateral view of appendages

Saturday, 23 August 2014

Ceriagrion calamineum, new for Vietnam

I have been lucky so far with Ceriagrion species. I really like this genus of robust and colorful damsels. In Cat Tien in the first week of August I encountered 3 orange-yellow species. Just a few C. auranticum, generally a common and certainly a widespread species, C. malaisei, which I had seen before in Bac Kan Province and in Ba Be National Park in the north, but also occurring, evidently, in the south. But the third was the price. Ceriagrion calamineum is a species known to occur eastward to central Thailand. Like Brachydiplax sobrina and quite a few other additions to Vietnam I found in Cat Tien, it belongs to a complex of southern species that occurs widely in Thailand and apparently extends further eastward. I found them in a corner of inundated grassland near the fishponds next to the guard station.

The beautiful male Ceriagrion calamineum

The paler female, hiding in the grass

A second male
Typical appendages in close-up

A third Brachydiplax for Vietnam

The genus Brachydiplax has currently 7 species. Two are known to occur widely in Vietnam. These are B. farinosa and B. chalybea. Traditionally the subspecies B. c. chalybea is said to occur in Vietnam, but in northern Vietnam the subspecies B. c. flavovittata is widespread. This is the same subspecies as in southern China. I do not know where the border between the two subspecies is, but B. c. flavovittata at least occurs south to Van Long Nature Reserve and Cuc Phuong National Park. In Cat Tien I found many of the nominate subspecies during my visit in early August. B. farinosa was also very common in Cat Tien, occurring mostly on forested pools. I had only seen it once in northern Vietnam, in Ba Be. It is certainly a lot less common than B. c. flavovittata in northern Vietnam.

Around the fish ponds in Cat Tien I noticed another Brachydiplax, stubbier and less brightly pruinose than B. farinosa and less yellow on the thorax than B. chalybea. It also missed the amber wing patches of that species. It soon became clear this was B. sobrina, a species known from India to Thailand. It had not been recorded in Vietnam to my knowledge, but was very common in Cat Tien.

I am sorry that the photos from this period are rather bad. One camera gave up completely in the constant rain and the other clouded over, as did the lenses.

A male Brachydiplax chalybea chalybea, with extensive yellow thorax

Here in hand, with deep yellow thorax and S1-3, plus amber bases to the wings

Brachydiplax sobrina, with green thorax and a tiny whitish spot on the anal triangle of the hindwing.

Dorsal view of B. sobrina, male

Male B. sobrina, showing the 7 cross veins in the front wing

Female B. sobrina

Yet another male B. sobrina

For comparison, a male B. farinosa under rainy and foggy conditions

Sunday, 17 August 2014

Anisogomphus tamdaoensis - range expansion

Anisogomphus tamdaoensis was described by Karube (as Merogomphus tamdaoensis) from Tam Dao in 2001. We have found it since in Hoa Binh province and in Cao Bang Province. Today (August 16) I caught two females on Mt Mau Son in Lang Son Province. Clearly this species occurs over a wide range in Vietnam. Although these are females, I find no differences with several other females of A. tamdaoensis in my possession.

Both females, the older one on top, scanned under a kitchen plate, explaining the patterns around them.

The younger of the two, identical to the specimens of A. tamdaoensis, although some have yellowish wing bases.

A more aged female, the other found today