Two new Stylogomphus species for science and for Vietnam

Today my paper on two new Stylogomphus species was published in Tombo. And with it two species I had found last year have received a name. The first I found along the Ho Chi Minh Highway just south of Phong Nha - Ke Bang National Park in May 2016 (and again this year) and also a little north of Khe Sanh. The other, a tiny species, I found perched in bright sunlight on a rock in a stream near Bao Loc in Lam Dong Province. Stylogomphus species are notoriously similar in their outward appearance, but have obviously different caudal appendages. That means that it is virtually impossible to separate them by observation or even photos, much like Leptogomphus species. Here are photos of both species.

Stylogomphus delicatus, a species with long and deeply cleft inferiors

Stylogomphus annamensis, a species with short and rounded inferiors

Macrogomphus albardae in Cat Tien*

*This entry was adjusted on December 31, 2019, following the publication in Zootaxa of a paper by Oleg Kosterin, which I had the pleasure of reviewing, on 12 June 2019. The paper addressed the considerable confusion surrounding a group of similar Macrogomphus species, showing, amongst others that Macrogomphus matsukii is a doubtful species and that records of Macrogomphus species identified as such from Cat Tien actually refer to Macrogomphus albardae. M. guilinensis from central and northern Vietnam actually is a junior synonym of the same M. albardae and occurs in a variety of distinct forms. Turns out that the 'matsukii' type gomphids I had been chasing for some time after first seeing them hover in the distance above a river in central Vietnam were conspecific with the species that I knew well from the north, but that based on previous misidentification and confusing literature had identified as M. guilinensis. Anyway, thanks to the careful work by Oleg the situation is now much clearer.

Original text:
James Holden had been reporting Macrogomphus matsukii from Cat Tien NP for a while and I decided to pay him a visit to get to see it in May. Last year I had seen Macrogomphus hovering over a large river at dusk (a habit shared by many gomphids, and certainly M. guilinensis) in Quang Binh Province, but had failed to ascertain beyond reasonable doubt that it was this species. Photos by James from last year had us initially discuss whether it was M. borikhanensis or M. matsukii, because the lateral pattern on the thorax had only two clear stripes. Facial pattern is very much like M. matsukii though. There seems to be some doubt whether these two species may in fact be conspecific anyway.

Commentary December 31, 2019:
Kosterin (2019) shows that the records of M. matsukii on which I based the above knowledge were in fact misidentifications of M. albardae, while M. matsukii remains a sort of phantom species. And he also showed that M. borikhanensis is another junior synonym of M. albardae. So the whole discussion on whether the Cat Tien specimens were one or the other was non-sensical in retrospect.

Below text with portions adjusted on December 31, 2019, in bold:
Just before I went to Cat Tien the rains picked up and the riverbed filled up quickly, so that circumstances had changes considerably when I got there on May 12. Indeed, we saw none, but on the 13th the waters had receded a little and the circumstances the species seems to favor (small trickles over the rocks by the side of the main stream) were restored. And towards dusk: there they were. 3 males hovering over the streams, for a short period joined by a Orientogomphus naninus. That distracted us and therefore I failed to get the stunning pictures I was hoping for. The different individuals had some variability in the extent of the middle lateral stripe, which was absent or represented by a small mark at the dorsal end. Otherwise they seemed perfect for M. albardae.
This is a widespread species, occurring widely in SE Asia. It includes at least the following junior synonyms: M. guilinensis, M. rivularis and M. borikhanensis.

Male Macrogomphus albardae, hovering at dusk over stream

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.