Saturday, 13 February 2016

A new genus and a new species - Indolestes anomalus new for Vietnam

February 6 I had arrived in Cat Tien National Park for a 3 day field trip to work a bit with James Holden, who has been holed up there for half a year or so. We decided to work our way through the forest to visit two bits of streams that are running all year round, south of the grasslands. Hard work, as going off-trail means using GPS on working your way through bamboo. And those in the know are aware what that means. Our clothes were torn to shreds during the day, but we did see the two target Prodasineura species I really wanted to see. The first was P. doisuthepensis, a species that had been on my wish list for 2015, but I only saw it now. The other was the splendid P. hoffmanni, I already published on recently, with photos by James.

Anyway, while working our way through the forest I spotted a female Lestes with closed wings and took a quick swipe at it with my net. It looked different from anything we had seen before, although we considered it a possible Lestes elatus, a species we hardly ever, if at all, encounter. So forgive us if we failed to see immediately it certainly was not that.

What was striking in the specimen was not just the three separated markings on the mesepimeron, but also the very large ovipositor. The markings on the final segments were also not as expected of L. elatus. Later, at home, I took a closer look and noted the rather squarish pterostigmata. That set me onto the right course. The few photos of Indolestes anomalus (on Dennis Farrell's site for instance) were a good match and led me to the description by Fraser 1946 and reproduced in Asahina (1985). Wings match the original description (20mm), but abdomen was slightly larger (28.5 against 27mm). The original description is of a female. I am not sure whether the male is now known.

Indolestes anomalus is a rarely observed species, known from very few records of single specimens from Thailand only. It is good to see the species is more widespread, although the pattern of yet another single specimen from a relatively well researched area indicates it is indeed rare.

Female Indolestes anomalus. Note large bulging ovipositor, with brown S9. Top of head blackish green, three markings on the mesepimeron, the middle square, pattern of S1-2 and squarish pterostigma.
Close-up of the thorax, showing the pattern on the mesepimeron.


Thursday, 11 February 2016

Two cool species from Cat Tien

Last weekend I visited Cat Tien National Park to spend a few days with James looking for some of his recent discoveries. One of these was a fine female of Zyxomma obtusum. This is a widespread species, occurring from the Indonesian archipelago to the south of Japan, but it was unclear to me how often it has been recorded in Vietnam. I had never seen it, although I keep an eye open for it at dusk all the time, and I know of no other records. Cuong does not mention it in his overview of Vietnamese records. So it was an exciting find when James ran into it; a find that sadly we could not duplicate. But when checking some of his photos we made another discovery. A Ceriagrion he had taken a picture of last July was C. indochinense! This is a species recorded as widespread from Thailand and also from Vietnam, although I have never seen it, so it is maybe not that common. But last July at a grassy swamp there had been many. We went to check the place, but clearly it is not around in February anymore. I am happy to show both species here and look forward to seeing them myself sometime.

A fine male of Ceriagrion indochinense. This species shares a citrine-yellow abdomen and bright green thorax with yellow face with C. fallax, but it has no black at the abdominal tip. Photo courtesy of James Holden.

The female of Zyxomma obtusum. The males are whitish and ghostlike when patrolling as dusk, but the females are less obvious. However, note the dark wing bases and banded abdomen.

Tuesday, 9 February 2016

Exciting new Gynacantha species for Vietnam (or the world?)

Middle December last year James Holden contacted me to report a spectacular Gynacantha species from Cat Tien National Park. Apparently it was quite common at a certain stream, where it could be observed in good numbers during the day time, flying across the stream. Photos showed a very interesting species indeed. The massive epiproct are only matched in southeast Asia by those of G. khasiaca, a rare Indian species that has almost never been observed, although there is a recent record from Bangladesh. The appendages depicted in Fraser (1936) are very similar, although there are in fact, if one looks closely, also differences. This may be due to the drawing, but maybe the differences are real. What is more, G. khasiaca has a grass-green thorax with spectacular dark stripes over the sutures, quite different from most species. The specimens from Cat Tien are a more dull olive green and lack these bold stripes. There are other differences, but in fact there are more similarities, whether in relation to the amber markings at the wing bases or the exact match in size. It will go to far to discuss all here, but suffices it to say that the species from Cat Tien is in the very least a different subspecies and possibly, and that would be truly amazing, a new species of Gynacantha, closely related to, but sufficiently different from, G. khasiaca. Currently we are trying to verify the exact details of the specimens used by Fraser and deposited in the British Museum. Below photos taken in December, of relatively fresh specimens, by James, and of last weekend, of old specimens, by myself. More details will follow when the time is right!

Scan of old male, very dark. Note dark amber wing bases and long epiproct.
Old male in lateral view, showing olive-green thorax and blueish pattern on S2. Eyes blue, not green as in Fraser's description

A fresher male in December, courtesy of James Holden. Note again the dark wing bases, the long appendages and epiproct and yellow frons with blackish T-spot.