Thursday, 15 June 2017

At long last another Lestes

Considering my world Odonata list, Lestes is one of the genera with the most recorded species and that is not surprising, giving the number of described species and the fact they occur around the globe. But irrespective of that, there are not that many species around in Vietnam, apparently. Only three I had been able to find. Lestes praemorsus is the common species, found from the very north to the very south, and Lestes elatus from the southern half of Vietnam. Lastly, I recorded pretty Lestes nodalis from Huu Lien Nature Reserve, to the north of Hanoi. And that was it. Until on May 12 this year I stopped by the road in Lam Dong province, to the northwest of Bao Loc, to check a grassy inundated area in the afternoon. I noticed many Lestes praemorsus, but it dawned on me that some appeared to be larger than others and these all had a reduced pale abdomen tip. This could not be a coincidence. I took photos and collected a few. In the evening I became disappointed. It seemed the appendages were the same, so maybe just variants? But when I returned home several days later and was able to check them under the microscope, it became clear there were in fact differences. Most striking were the differences between the inferior appendages of the species, in addition to the aforementioned differences in coloration. Two species appeared to have this combination of characters, Lestes dorothea Fraser, 1924 and Lestes praecellens Lieftinck, 1937. The former is quite large, a little larger according to the description than mine, which fit better the species described by Lieftinck from Java in size. However, the female I photographed has much more extensive thoracic markings than that species, in line with what is to be expected of L. dorothea. That species is recorded from India, Thailand and Malaysia. Based on the structural characteristics and patterning of the male and patterning of the female I think it is safe to conclude this is L. dorothea as well.
By the way, based on the likeness of the appendages of L. praecellens and L. dorothea one may ask whether these are truly different species. There thoracic markings are also rather similar, if it weren't for the female.

Lester dorothea male. Note the lack of pruinosity on S9.

Male and female of L. dorothea

The female, showing the extensive dark markings on the thorax, unlike L. praemorsus

Another male showing the limited pruinosity on the abdomen tip

A Lestes praemorsus male for comparison. Smaller and with pruinosity on S9.


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