Monday, 1 June 2015

Sarasaeschna - a tale of new species*

*Posting adjusted after publication of Sarasaeschna yoshitomii in November 2016

Sarasaeschna as a genus was established by Karube & Yeh in 2001 to differentiate a group of species from Oligoaeschna on structural characteristics. These are generally species frequenting damp areas, often without a lot of or even any open water, in forested surroundings. They are spring species and due to their habitat preferences often overlooked. For instance, only in recent years has it become clear that this is a much more diverse group, with only in Taiwan now already 5 different species identified. In Vietnam only one species was known, S. niisatoi, a little known and rare species only reported from Pia Oac Mountain from a small swampy area now destroyed (subsequently it was also reported from Hainan). Karube (pers. comm.) reported finding larvae of Sarasaeschna also in Sa Pa, but the species was unknown. This basically was the state of affairs for Vietnam until this spring.

On May 15 I was surveying the Tu Le area in Yen Bai Province when I noticed a hovering Aeshnid above a small depression in partly logged primary forest. After capture it became clear that this was a Sarasaeschna species, but not S. niisatoi. When I contacted Wen-Chi Yeh about it, it turned out this was a species currently being described and to be published in July, known only from a specimen collected in China. I observed at least two different males. For now I will publish this here as species novum, its true identity will be revealed upon publication of the paper.

Sarasaeschna species novum, Tu Le

Facial pattern of the male species novum from Tu Le
On May 17 I visited the Love Waterfall area in Sa Pa, location of the discovery of the larvae of Sarasaeschna, when I noticed a very small Sarasaeschna hovering over the marsh inside the forest. Sadly it eluded capture, although I was able to take some flight shots. It clearly was not S. niisatoi. But although I searched for it all day the next day, I could not relocate it. Therefore I revisited the area a week later (May 25) and this time noticed two different males after several hours. I was able to collect one and this showed definitely it concerned an as yet undescribed species. It was published in November 2016 as Sarasaeschna yoshitomii. It also occurs in Lao.

The Sarasaeschna yoshitomii from Sa Pa, as seen on discovery day
One week later, the male Sarasaeschna yoshitomii from Sa Pa in hand

Distinctive facial pattern with a lot of yellow
On May 20 I visited Pia Oac Mountain, where I wanted to check a swampy area that might be good for the elusive S. niisatoi. I did indeed see a male Sarasaeschna, but could not verify the species. Returning to Pia Oac on May 31 and assuming the season for the species might be over, I was lucky enough to find it at two different locations. A single male at the old French station, and at least 3 different males at the marshy area. I could verify this was indeed S. niisatoi.

Posed male of Sarasaeschna niisatoi

Male of Sarasaeschna niisatoi in hand
And its facial pattern

And finally, on May 30 I was visiting Xuan Son National Park looking for Idionyx selysi, when I noticed a rather large Aeshnid flying inside the forest. I was able to capture it. It turned out to be an old female of an unknown species. The wing venation reminded me of Planaeschna, and although it was strange to find an old specimen so early in the season, that is what I assumed it was. Until at home I had a closer look and noticed the flattened frons. Communication again with Wen-Chi confirmed this was yet another Sarasaeschna. It shares quite a few characteristics with S. chiangchinlii of Taiwan, but has different thorax pattern and it even larger, 66 mm. It appears to be a closely related, but undescribed species. Its identity will have to wait for confirmation until the male is located. A nice challenge for next year.

Female Sarasaeschna species novum from Xuan Son
And its distinctive facial pattern

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