Thursday, 31 October 2013

Pantala flavescens

For this Thursday evening I have one of the commonest dragonflies of the world, Pantala flavescens. I have seen this species in South Africa, in Japan, in the US and in Brazil, but it is even more widespread than that. It is absent from Europe, which is strange given its highly migratory nature and the temperatures in Southern Europe.
The larvae apparently cannot survive in water of less than 19 centigrade, so that sets the limit to the area where they are really indigenous. Other places they can only migrate to, to multiply to large numbers, but to disappear again in colder periods. They are normally seen cruising in small to large flocks over fields and in clearings, and because the larvae develop so rapidly, can make good use even of temporary, rain related puddles and ponds.
In Vietnam it is a very common species.

Pantala flaverscens, male

Ischnura senegalensis

IUCN lists Ischnura senegalensis as extremely widespread and with high tolerance for disturbance and pollution. It occurs from South-Africa to Japan. Vietnam is no exception. This is a common species, nowhere really abundant, but always present, in rice fields, ditches, verges of ponds, wet grassland and so on. It is rather similar to various other Ischnura species, but in Vietnam it is easily set aside from the orange species. The female is also readily recognizable, with the dark dorsum of the synthorax, a pattern also found in the much smaller Agriocnemis species like A. femina, but size readily sets them apart.

Ischnura senegalensis, male

Ischnura senegalensis, female

Wednesday, 30 October 2013

Agriomorpha fusca

There is a very common forest damselfly that you can encounter under almost any weather conditions, apart from heavy rain, around seeps and small trickles in forested areas, where they sit inside patches of vegetation, or mutter about in slow flight. This is Agriomorpha fusca. But although common all through the summer season, I have not seen them since September 14. But the time has come to tidy up lose ends and this is one of them. It is not a colorful damsel, apart from the yellow snout. Indeed, it is a dark creature and the name 'fusca' is well chosen.

Agriomorpha fusca, male

And another male

Agriomorpha fusca, female

Tuesday, 29 October 2013

Dysphaea basitincta

It seems like ages ago, but late July we visited Ba Be National Park. This was a great place to be for dragonflies, but because it was our first experience in the country, we did not really realize just how interesting it was. Quite a few of the species observed I have not yet seen elsewhere. One of these is a large Euphaeidae with a striking wing pattern. It is one of at least two species of Dysphaea occurring in Vietnam, the other being D. gloriosa, with unicolored reddish wings. The present species is Dysphaea basitincta, a beautiful species indeed. By the way, this is genus 62 for this blog. I have lost track of the number of proper species involved, also because of a few undescribed or possible undescribed species.

Dysphaea basitincta, male

Female Boyeria karubei and Orthetrum glaucum

Saturday at Xuan Son brought me two females that I want to introduce here. Boyeria karubei was present like last weekend, swarming in the evening by the bridge and during the day with several females ovipositing left and right. This female was caught temporarily at the bridge before released again. It is very much like the male in pattern, but of course the abdomen is not constricted at S3.

Boyeria karubei, female, a very large dragonfly
The other female of note was Orthetrum glaucum. It is interesting in that it has a basically unmarked dorsum to the synthorax, but two clear whitish lines on the flanks. This makes it easy to distinguish from female O. pruinosum, which is basically unmarked, and O. luzonicum, which has a marked dorsum.

Orthetrum glaucum, female

The same female at a slightly different angle

Monday, 28 October 2013

Matrona taoi revisited

This Saturday we visited Xuan Son National Park once more, to look for a few more goodies. Matrona taoi was encountered repeatedly, although in small numbers. We could observe a few females too, one of which was ovipositing on floating and submerged plant material while a male was either dancing nearby, or sitting close by signaling with its wings. The female has the white pterostigma also seen in the females of M. basilaris and Calopteryx coomani, but the wings are reddish brown as in the male and do not have translucent areas or lighter bases.

Matrona taoi, female

The male of Matrona taoi

Displaying to the female ovipositing nearby (or to potential competitors?), by opening and closing of the wings and raising the abdomen

Pseudagrion spencei, new to Vietnam (but likely common)

Some research into the literature on Pseudagrion lead me to Fraser 1933 and his treatment of the Odonate Fauna of British India, after some pictures from southern China already pointed me to widespread P. spencei, known from Bangladesh, Pakistan, India, Nepal, Southern China and Hong Kong. Not from Vietnam, but we can change that now. For my species is a perfect match with the description from Fraser. So, I have changed the captions to the earlier entries on this species and added a post script.

Pseudagrion enigma*

I already posted earlier on my suspicion that there is another species of blue Pseudagrion besides P. microcephalum and P. australasiae. Today on the way to Cuc Phuong we stopped just outside the park at a pond where I knew in summer the possible third species had been present. We were lucky, because there were two male P. microcephalum sitting on the vegetation in the middle of the pond (which is part of a small stream). I collected one male. Then our attention was drawn to two other males in the grass by the side of the pond. Indeed, the enigma Pseudagrion! Due to the morning cold the colors were not vivid, but it did seem the right species and I collected also one of these. A female, the strange brownish female I published before, turned up with the two males, heightening the excitement! Under the microscope there is no room for doubt. This is a different species, with different, but long appendages, smaller size, much shorter lower appendages, and different ocular spots. For comparison I scanned the male with two P. microcephalum (we saw several more inside Cuc Phuong National Park at Ho Mac) and P. australasiae that I had on file from Van Long. For the moment, I treat the enigma species as Pseudagrion, but I am open to any suggestions.*

* Subsequent literature research pointed out that this species is P. spencei, a widely distributed species, but not known from Vietnam.

P. australasiae, top, P. microcephalum (two specimens center) and P. spencei, bottom
I took some photos both in the field and in the hand of the two species with long appendages, M. microcephalum and M. spencei.

Pseudagrion microcephalum, male

Pseudagrion spencei, same as in scan, so actually more vivid when warm

A second male Pseudagrion spencei, also cool

Same male as in previous picture
In hand they look like this:

Pseudagrion microcephalum, male

Pseudagrion spencei, see appendages

The appendages in close-up:

P. microcephalum, dorsolateral

P. microcephalum, dorsal

Pseudagrion spencei, dorsolateral

Pseudagrion spencei, dorsal
And the post-ocular spots

P. microcephalum, male

P. spencei, male

Sunday, 27 October 2013

Mortonagrion aborense in Cuc Phuong

Sebastien Delonglee recently recorded Mortonagrion aborense for the first time in Vietnam, from the suburbs of Hanoi (see also his blog and my own entry on the species). It was surprising that this species had not been recorded elsewhere in Vietnam, given the unlikely location of its discovery. I was therefore happily surprised when I bumped into about 6 males and a female in a small muddy pond with emergent vegetation under tree cover in Cuc Phuong National Park. Yet another species that may not be as rare as the scarceness of records suggests.

Mortonagrion aborense, male

Another male

And yet another

Mortonagrion aborense, female

Saturday, 26 October 2013

Noguchiphaea yoshikoae and Vestalaria miao

This weekend provided excellent opportunity to compare two similar species, even if in fact they belong to different genera. Noguchiphaea yoshikoae, named in 1976 by Asahina, and Vestalaria miao, named by Wilson and Reels in 2001. In Xuan Son National Park they can be seen side by side almost, at least in close proximity and on the same small stream. Interestingly in the morning only V. miao was present, but later in the afternoon there were as many N. yoshikoae as there were V. miao.
Although both species have a green head, green prothorax, green and yellow synthorax and green abdomen with whitish S8-10 dorsum and otherwise also a similar shape, there are clear structural differences in the shape of the appendages and in the typical horns that Noguchiphaea sports on the posterior lobe of the prothorax. These are more apparent in the female than in the male, but are well visible in hand. However, there are some clear characteristics that can be seen with binoculars to separate these two species. Although V. miao has a brownish edge along the wingtips, N. yoshikoae has very clear black "stigmata" (although technically not the same as pterostigmata, it is a pigmented area, black and well demarcated. Also, the lower half of the eyes is, just as in the females, blueish grey in Noguchiphaea, but green in Vestalaria.

Vestalaria miao, male

Another male. Note green eyes and diffuse brownish wingtips.

Noguchiphaea yoshikoae, male. Note blueish grey lower halves to eyes (and dark reddish brown upper) and very sharply demarcated stigmata of the front wings.
In close up the horns on the pronotum are also visible in the males of Noguchiphaea.

Note the lack of horns in Vestalaria and the color of the eyes
Note the horns on the posterior lobe of the prothorax and the color of the eyes of Noguchiphaea

Noguchiphaea yoshikoae, male in hand, compare shape with V. miao
V. miao, male in hand, compare with N. yoshikoae for instance shape of appendages

Friday, 25 October 2013

Diplacodes trivialis

There are a few species here in Vietnam that are very common and apparently resistant to pollution so that they can be found almost anywhere, like Brachymesia contaminata and Orthetrum sabina. One dragonfly quite resistant, it seems, is Diplacodes trivialis. It is not found readily at the same dirty ponds, but present even in the most insect-devoid paddies. It is a small dragonfly, the adult males easily identified by their blueish-grey appearance and white appendages. In the south of Vietnam there is another species, of which the female is quite similar, although males are easily distinguished on the basis of their dark wingtips. This is D. nebulosa, but it is apparently absent around Hanoi. Exactly because D. trivialis is so common, I did not take many photographs of it. Here are a few, by means of which I introduce it to the audience. Please applaud.

Diplacodes trivialis, male

Another male, slightly less pruinose, still showing yellow on the thorax

And an immature male, colored as a female would be, but recognizable as male by for instance the appendages

Thursday, 24 October 2013

Tidying up the last bits of Xuan Son

Just before the weekend starts with new adventures time to tidy up the remainder of records from Xuan Son. I will start with another new species for me, Vestalaria miao. And to be honest, I cannot be a 100% sure of the ID. Noguchiphaea yoshikoae occurs also in the area, but has characteristic horns on the prothorax, not present in Vestelaria. And Vestalaria miao was recorded right there in Xuan Son, but who knows, maybe another species is present too. So the search for more evidence continues. Here she is:
Vestalaria miao, female, with slightly tinted wings

The same female in hand, note the absence of horns on the posterior lobe of the prothorax

For comparison female Noguchiphaea yoshikoae of Tam Dao in September, very similar although wings slightly different in shape and clear, eyes of different color

Note the horns on the posterior lobe of the prothorax
The second species to publish here is Cratilla lineata, of which I encountered a female in the rain. Cool as addition to the earlier male. She is very similar in markings, but of course with a differently shaped abdomen.

Cratilla lineata, female
What else was worth to mention? How about a teneral male Pseudagrion pruinosum? Here he is, as a possible stumbling block for the unwary.

Pseudagrion pruinosum, immature male. The appendages are a give-away. The neck looks rather bull-like, due to a rain drop that has lodged itself there.

Close-up of the neck and the rain drop. Soon after it would remove it by brushing.
The last to enter for today was an array of Calopteryds. The first is Calopteryx coomani, a species I have seen regualrly at Tam Dao National Park and that also frequents Xuan Son. Especially the female is superficially similar to the female of Matrona basilaris, but that species has, just like the male, a milky shine to the bases of the wings due to the fine maze of veins there, absent in C. coomani. Both are large species, but C. coomani is even more robust.

Atrocalopteryx coomani, male, with blueish shine to abdomen and visibly here translucent areas in the wings.

Male showing the largely translucent front wings and bases to the hind wings.

Atrocalopteryx coomani, female
Matrona basilaris was already introduced in an another entry, but not the female. Compare here to the female of Atrocalopteryx coomani, to which it is rather similar when perched and the milky bases to the wings are not visible. The color of the wings is more greenish and the wings are more slender.
Matrona basilaris, female. I saved this one from the water, where it had become entangled in cobwebs when ovipositing. It did not linger when I released it and perched far away, which explains the grainy picture.

Matrona basilaris, male, for completeness sake
And finally, because it is such a special species, another Matrona taoi male. I find this species much more like A. coomani than like M. basilaris, when it comes to size and shape of the wings.

Matrona taoi, male