March 28, first trip to Xuan Son of the season

The weather forecast said that west of Hanoi might be sunny in the afternoon, so I decided to drive to Xuan Son today. As is often the case, the forecast was wrong, so a cloudy day. Nevertheless I encountered at least some goodies, although nothing unexpected. Euphaea masoni was already very common and E. guerini was out and about too. In the damselfly department Mnais mneme was common too, and I saw the first Pseudagrion pruinosum of the season. Orolestes selysi was also present in decent numbers at the "Gynacantha puddle".
I was really hoping to see Nihonogomphus schorri, which had been omnipresent in April last year. Cloudy circumstances made it impossible to judge whether it is already common in March, but I saw one male briefly. A first female Macromia flew by. Could not verify the species though, shame. And at the "Gynacantha puddle" a few Cratilla lineata and quite a few adult or semi-adult Gynacantha subinterrupta were huddled in the bushes. All in all not at all bad, given the time of the year and the weather.

Not the best of photos, but anyway, Nihonogomphus schorri, as soon as the sun showed itself, no matter how short.

Female Rhinocypha perforata, quite common

And the male of Rhinocypha perforata. See the lateral thorax pattern. It is the same as in the female, although the forum is very different.

Neurobasis chinensis is a common damsel, but also very pretty, especially when it displays the top side of the hindwing.

The female of Neurobasis chinensis, with the typical double white dot.

Euphaea masoni already very common. This specimen kind enough to keep its wings open, displaying the typical translucent base and tip in the forewing and the reddish brown luster to the inside of the wings.

But the outside is dark blueish

Mnais mneme male, this one already pruinose on the thorax, a feature missing in Mnais andersoni.

The female of Mnais mneme, specimen with reddish veins

Immature (and already missing a pair of legs) Mnais mneme. When there is no pruinosity on the thorax it can be separated from Mnais andersoni through the structure of the penile organ.

Gynacantha subinterrupta with its typical abdominal pattern of oblique light bands. This individual almost adult, but the thorax still not fully green and the face still whitish.

Face of the same individual, showing cream white, not yet yellow.

Different male, this one with yellow face and green thorax, fully mature

Nihonogomphus - more widespread

To my not small amazement I caught a male Nihonogomphus schorri in Bac Kan Province on June 21. This species was described from Huu Lien, where it co-occurs with Nihonogomphus thomassoni. In early spring it was also very much in evidence in Xuan Son National Park. To my knowledge, Bac Kan is the third province in which this species is verified. Clearly the species has a distribution in northern Vietnam much larger than just Huu Lien in Lang Son Province.

Male Nihonogomphus schorri from Bac Kan Province

Some proof, appendages in dorsal view

In lateral view

In ventral view

And the distinctive shape of the lobe

 The other Vietnamese Nihonogomphus species was also very much present in northern Bac Kan Province. I am still not sure whether this taxon is Nihonogomphus lieftincki or N. thomassoni. In communication with various scholars the question has been raised whether these two species are really distinct. But for now let's go with the fact that N. thomassoni is the taxon said to occur in Vietnam. There was something peculiar about the really large number of specimens I saw in northern Bac Kan Province. Although I had seen this species in at midday in Huu Lien and on other streams in Lang Son Province, I think I saw it only once in Bac Kan during the day. One stream where it was very common I visited during the day half a dozen times, not to see any. But in the last 30 minutes or so before darkness it would appear in good numbers, with at least one every 25 meters or so and often several in close proximity, flying rapidly just above the surface chasing each other, or sitting on low hanging branches and shrubs over the water. They would still be there when it was almost too dark to see them. This seems at variance with their behavior in Lang Son, although I have not spent a lot of time there at dusk. Nevertheless, very peculiar. I also caught a female. Please compare to the female of the Nihonogomphus entry from Xuan Son. The lateral pattern on S3 is different.

Nihonogomphus thomassoni, female, Bac Kan Province

A very green male perched in almost complete darkness, but photographed with flash

Another male Nihonogomphus thomassoni in hand

Differences between Nihonogomphus at Huu Lien and N. schorri at Xuan Son, a case for Nihonogomphus lieftincki

Yesterday, April 26, I visited Huu Lien. The day ended a little weird, when I was questioned by 5 guards demanding so see the insides of my car, the contents of a plastic bag (with Kameliya's rubber boots) and so on. It is of course good they keep an eye on things, so I tried to be cooperative to some extent. But the guy walking by with illegal electric fishing equipment was not even glanced at and the sound of chainsaws from various directions where people were cutting down any larger and accessible trees also did not seem to bother anyone, which made it look like a racial profiling exercise to me. But then again, ecotourism is quite an alien concept here and that anyone would want to take pictures of Odonata, well, weird…

Surprisingly, yesterday was rather sunny and I had another shot at various gomphids. I was able to catch two Nihonogomphus specimens and was struck by the differences with the Nihonogomphus schorri specimen from Xuan Son the other day. I doubt whether the differences are large enough to warrant a discussion of the species level, but it is an interesting case of geographical variation or inter population variability.

First, here is a Xuan Son specimen photographed perched and one from Huu Lien.

Xuan Son, Nihonogomphus schorri, male, April 13

Huu Lien, Nihonogomphus species, male, April 26

Apart from some differences in the coloration, the difference in shape is striking. I only saw one perched in Xuan Son, so it is difficult to generalize. But the difference is born out also by structural differences between the specimens caught. HW shorter and body longer in Huu Lien (BL 47mm against 44mm, HW 34mm against 35mm). (Measurements given by Do & Karube for N. schorri BL 45mm, HW 32.5mm)

The Huu Lien specimen in hand, different from the one perched in the photo

Xuan Son specimen in hand, also different from one perched in photo

An interesting difference, apart from the body shape also evident here, is the black line over the metapleural suture. The Huu Lien specimens all have a thin branch, sharply defined, which is much more diffuse in Xuan Son, giving the impression of a continuous broad black stripe rather than a branch. In the drawings by Do & Karube this branch is completely lacking and the stripe narrows dorsally.

What can already be seen here is the difference in shape of the first segment of the penile organ. Let's pull that close:

Huu Lien Specimen 1, look at the hook directed posteriorly

Huu Lien Specimen 2, identical hook

Xuan Son Specimen, no hook, just pointed straight down

What is interesting is that the shape of the first segment of the penile organ of the Xuan Son specimen is closest to the drawing in Do & Karube, which was of course based on Huu Lien specimens of N. schorri.

Huu Lien Specimen 1, appendages in ventral view. Note the inferior appendage is not spread and although bent upwards, reaches the shoulder of the superiors.

The Xuan Son specimen, spread in a V and falling short clearly off the shoulder  of the superiors

Second Huu Lien specimen, identical to the first specimen

Interestingly again is that the Xuan Son specimen fits well the drawings in Do & Karube, in which the inferior appendage is spread in a V and falls clearly short of the shoulder.

Dorsal view Huu Lien specimen 1

Dorsal view Huu Lien specimen 2

Dorsal view Xuan Son specimen

Note that the shapes and color are consistently different (in the small sample), also given the two in situ photos of life specimens. Both Xuan Son specimens (including the perched specimen) have half of S10 yellow, which is obscured in the Huu Lien specimens, but again clearly illustrated in Do & Karube.

The lamina of the anterior lamina is also drastically different. It is, in short, a completely different structure. And the anterior hamule, with a shoulder in the Xuan Son specimen, as to be expected for N. schorri, only broadens somewhat, without a clear shoulder, in the Huu Lien specimens.

This is a Huu Lien specimen, note the rectangular, but almost square,  lamina at the bottom of the structure

This is the Xuan Son N. schorri. Note the narrow and clearly excavated lamina, which also almost disappears under the adjacent structure. It is very different.

It is clear that the specimens from Huu Lien, the type locality of Nihonogomphus schorri, are a different species. As a matter of fact, shape of appendages and penile organ first segment, shape of anterior and posterior hamuli, measurements, black labrum, all fit very well Nihonogomphus lieftinck, a species from Fujian, Hunan, Hubei and also Guangdong in China. See the drawings in Chao (1954), and in Wilson & Xu (2009), including. The differences in coloration could be geographical variation. With a more thorough study of the type material of N. lieftincki structural differences might become apparent, but for the time being I call this Nihonogomphus cf. lieftincki.

Nihonogomphus schorri

On April 13 I was birding in Xuan Son National Park. Xuan Son is a dragonfly paradise, but it was still early in the season. When the sun came out for a bit in the late morning I noticed to my excitement several gomphids along the concrete road in the forest. I was able to first catch a female ovipositing on the wet concrete and later a male patrolling to same place. Several other males and females were observed (at least 10) and one male was photographed as it sat on a plant by the side of the main stream where a small stream runs into it, close to the first stone bridge.

Because of the thorax pattern of the males, with greenish-yellow humeral stripes, and the yellow-orange appendages, I thought these might be Amphigomphus nakamurai (see my blog entry on that species), but in hand the lower appendages of the male were clearly different. At home the general structure of the appendages pointed straight to Nihonogomphus, a genus with 19 species distributed in eastern Asia. The most recently described species is Nihonogomphus schorri, Do & Karube 2011. Luckily I had access to that paper, as the pattern (with broad lateral black stripe separating metepisternum from metepimeron) on the synthorax did not fit most species. Close inspection of distal segment of penile organ and of the appendages helped to clinch the ID. In fact Nihonogomphus schorri is until now only known from Huu Lien Nature Reserve in Lang Son Province, where it was collected in May and June (2009 and 2008 respectively). This is 160 km from Xuan Son National Park in Phu Tho Province as the crow flies.

Male Nihonogomphus schorri perched by stream

Different male N. schorri

Showing the greenish antehumeral stripes

The female N. schorri

Nihonogomphus schorri, female top and male bottom. The male is 60 mm.

Facial pattern of live female

Facial pattern of male after preservation

Characteristic penile organ of male, separated only one third of length of segment and with long flagellar processes

Male appendages in dorsal view

Male appendages in lateral view

Male appendages in ventral view

Female appendages in dorsal view

Female appendages in (almost) lateral view

Lateral view of male apparatus S1-2