24/09/2013

Mysterious gomphids at Hanoi



Visiting repeatedly this two hectares pond  in the suburbs of Hanoi, invaded by water hyacinth (Eichhornia crassipes) and surrounding by a little wooded area, yielded a good range of common species (including Pseudothemis zonata, Rhodothemis rufa, Crocothemis servilia, Urothemis signata, Brachythemis contaminata, Brachydiplax chalybea, Ceriagrion auranticum, Onychargia atrocyana, Anax guttatus, Sinictinogomphus clavatus, Tholymis tillarga, Gynacantha subinterrupta…) or uncommon species (Aethriamantha aethra, A. brevipennis) but also, surprisingly, some enigmatic gomphids...
As with bird-watching, a great deal can be achieved by regularly covering
a "local patch".


In northern Vietnam, which gomphid one can expect to spot at a polluted pond in the suburbs of a big city? Only the boring Ictinogomphus pertinax. and Sinictinogomphus clavatus ? Not sure...

Over the past three years, I have been dealing with many problems of identification. Most of the time, the major puzzles concerned upland/stream species.
Generally, identifying species of lowland ponds rarely took me more than 30 minutes. The notable exceptions were 3 gomphids - among them at least 2 onychogomphines - found in the suburbs of Hanoi, at ONE pond, 500m from my home! During the summers of 2011 and 2012, despite unbearable temperatures, I took many lunchtime strolls around this pond, and what I found went beyond my expectations. Trying to identify these gomphids proved to be quite a convoluted process.

I will write below the synthesis of my sightings concerning these 3 “mysterious” species, which not only puzzled me, the dragonfly lover, but also experienced odonatologists. Some of the pictures displayed below are quite bad, I am sorry about that. They were taken 2 years ago with my first camera – at this time I thought is was the best camera in the world haha...
 
The story began in mid-June 2011. During a noon stroll, I bumped into a medium-sized male gomphid resting 50cm above the ground, 20 meters from the banks, hidden among the 30 meters wide wooded area surrounding the pond. At that time, I was interesting by Vietnamese Odonata for only few months – so an absolute beginner. After some shots in hand, I released it (big mistake...), convinced it was a common pond species, so easy to identify. If I had known that it was a new species for the country, the story would have been very different. Lucky gomphid! 


This specimen displayed the following characteristics: head well marked (labrum with pair of elongated yellow spots, anteclypeus, base of mandibles  yellow, top of frons with a pair of transverse yellow marks), synthorax black with a yellow dorsal stripe  connected to the yellow collar stripe to form a broad 7-shaped mark, superior yellow antehumeral spot, sides of synthorax with broad stripes across the mesepimeron, metepisternum and metepimeron, abdominal segments 4-7 all ringed completely [basal broader ring on S7], S7-9 broadly expanded, superior appendages whitish, brownish-tipped, the apical half curved downwards, slightly longer than the inferiors, the latter brownish with 2 branches parallel.


Frontal view with "the best camera in the world", showing the broad dorsal 7-shaped marks on the synthorax. 

                                                    Tip of abdomen.


One week later, 10 meters from the place I saw this male, I caught a glimpse of the female. I did manage some record shots but could not catch it. She displayed a similar colour pattern to the male (except some details e.g. postclypeus with a pair of lateral yellow spots). White cerci.

The female. 
Note the abdominal segments 4-7 all ringed completely (broader ring on S7) as the male.


Considering the particular shape of caudal appendages of the male, this species probably belongs to the genus Ophiogomphus*. But this needs to be confirmed by close examination of other structural features. The genus Ophiogomphus (sensu stricto) is found in Palearctic and Nearctic zoogeographical Regions; it has never been recorded in Vietnam. 

* (update May 2014 : species finally identified as Nychogomphus lui Zhou, Zhou & Lu, 2005 - see blog entry)

In July and the rest of the year 2011, I had no other sightings of this gomphid, despite regular visits.

 In 2012, I decided to make a particular effort on this area.

Mid-June, I vouchered a fragile teneral female, identical at the one photographed one year earlier. But my main target remained the male...

The teneral female.



One week later, things got more complicated. Indeed, I netted an another medium-sized female, but very different on various points from the previous ones, most notably the face predominantly black with broad yellow transverse stripe across frontal crest of frons, the yellow dorsal stripe on synthorax not connected to the collar stripe, the abdomen largely black with yellow dorsal spot on S3-6, a large yellow dorsal marking on S8, black caudal appendages... Females gomphids can be a major puzzle. I gave the specimen to Dô Manh Cuong. Until now, as far as I know, it remains unidentified*.

* (update May 2014 : species identified as a Stylurus sp., maybe undescribed. Members of this genus are known to breed in large rivers).



Frontal view of facial pattern.

Dorsal view. 
Note the yellow dorsal stripe on synthorax not connected to the collar stripe.


Shots of the tip of abdomen showing the black caudal appendages, the saw-toothed vulvar lamina and the large yellow dorsal marking on S8.

At the end of June, I finally found a male, but not the one I expected – i.e. the one I saw one year earlier! It was smaller than the other gomphids I had spotted there previously. At distance, the most obvious feature was the yellow-orange marks on the abdomen. Carefully, I made some shots (risky!... it could have flew away!) before netting it. 

 A stunning little gomphid, with a yellow-striped synthorax and a yellow-orange abdomen (except S1-2). Note also S7-9 broadened, the yellowish caudal appendages.


Synthorax black with a quite short yellow dorsal stripe not connected to the yellow collar stripe, no superior antehumeral spots, sides of synthorax with broad stripes across the mesepimeron and metepimeron, two yellow patches not connected on the metepisternum. The extent of yellow colouration on sides of synthorax is far more developed in naninus, armatus, minor and circularis (moreover, the 3 latter show superior antehumeral spots).


 Facial pattern.


Tip of abdomen, dorsal.

The caudal appendages were particularly interesting: divergent inferior appendages, much shorter - about half length - of superior appendages, the latter long, bracket-like in dorsal view, and abruptly curved downwards apically in lateral view, with a minute peg-like process at tip. All of these features match very well with the genus Orientogomphus (see Chao, 1990; Wilson, 2008).
 
Tip of abdomen, ventral view. Note the minute peg-like process at tip of superior appendages.

In Vietnam, only one species of Orientogomphus is known : O. naninus (Foerster, 1905), from Lang Son, near the Chinese border. When I studied the Lieftinck’s drawings (1937) of O. naninus, I noticed that this specimen differs on some points, notably the pattern of the thorax (no broad middle stripe on metepisternum, just two yellow patches not connected). Moreover O. naninus is apparently a stream-dwelling species; its presence at a lowland pond would be incongruous, to say the least. 

O. armatus (Chao & Xu, 1987) from China, O. minor (laidlaw, 1931) from Thailand and Peninsular Malaysia or O. circularis (Selys, 1894) from Burma also did not fit with this male specimen.

After one year kept in my fridge (!), I finally gave this male to Dô Manh Cuong, who will be much more competent than me to discover its secrets. Unfortunately, the specimen was depressed, so Cuong could not examine the penile organ. I just hope than one day this identification issue will be solved.

The interesting thing in all this story, it is not really the fact that some of these gomphids are very probably new records for Vietnam*. No, the most exciting - and puzzling - thing for me is that they passed unnoticed despite the fact they can live in man-made habitats. Difficult to find any explanation to that. Inconspicuous or scarce species? Insufficient survey work at the lowland ponds ? I would tend towards the latter.

* (update May 2014 : Nychogomphus lui is indeed a new addition to the Odonata fauna of Vietnam. And the Stylurus sp. indet. doesn't appear to belong to any of the Stylurus already recorded in the country)

As the discovery of Mortonagrion aborense proved recently, in Vietnam, a new species (new for the country-list I mean) can be find even in the most unlikely of settings (a capital city matches well to this category!). This lends credence to my idea that, in this beautiful country, lowlands ponds remain largely under-surveyed.

Tom Kompier (a dragonfly lover based at Hanoi who recently set up a blog here) suggested that these mysterious gomphids, or at least some of them, might not breed in this pond but in the Red River (500 m away) and settle in the nearby woods during the maturation period.

I call upon the readers to give some clues as to what their identity might be, so that my lunchtime strolls in the Hanoi’s stifling heat were not in vain! 


PS : Sadly, in 2012, the pond has been drained, then dredged. And the wooded area around has been cut down. The story of “The pond and the mysterious gomphids” have ended - not a happy ending. 
But hopefully it will continue elsewhere in the capital city!

19/09/2013

Mortonagrion aborense (Laidlaw, 1914)



Hämäläinen (1989) transferred Agriocnemis aborense Laidlaw, 1914 to the genus Mortonagrion Fraser, 1920. He also demonstrated that Agriocnemis binocellata Fraser, 1922, Indagrion gautama Fraser, 1922 and Mortonagrion simile Ris, 1930 are all conspecific with Mortonagrion aborense.

Mortonagrion aborense is a tiny creature (length : 23-24mm), easy to overlook unless you are looking for it. But once you have found one, it is quite easy to lose touch with it in the darkness of shaded ponds because of its swift flight - swift compared to many other pond damselflies I mean. However, the blue end segments of the male help it to stand out. 

Habitat, Hanoi.

 Adult male.


I only spotted adults with yellow-green stripes. But they can also be blue-striped.


A mating pair... found with the help of binoculars !


Shots "in hand" :

Greater part of labrum black; anteclypeus, bases of mandibles and postclypeus greenish ; vertex and occiput black, the latter with rounded postocular spots.
 
Prothorax black on dorsum except the anterior lobe, which is yellow-green.

Thorax black on dorsum, marked with a yellow-green antehumeral stripe on each side; laterally also yellow-green – striped. 
Legs greyish (in fact only coxae, trochanter and femur) - looks like pruinosed. 
S2 with a pair of small oval spots on dorsum; S3-6 black, with lateral stripes nearly confluent across the dorsum at base and again approaching each other subapically on each segment (these markings, except at base, nearly obsolete on S6); S7 with a pair of basal dorsal spots only ; S8 pale bluish ventrolaterally, with a basal blue ring; S9 entirely blue save for an apical row of black spines; segment 10 blue, with its apical border and the mid-dorsal line narrowly black. 

Male, tip of abdomen, lateral.

 Anal appendages black, superiors rather longer than segment 10, curved a little downwards as seen from the side, broad and hollowed out on the inner side, the apex hooked inwards as seen from above ; inferiors considerably shorter, with 2 pairs of spines as seen from above.

Male, tip of abdomen, dorsal.

The female is similar to the male, but the markings on the abdomen are slightly different. 

 Adult female.

Like many species of damselflies (e.g. genus Agriocnemis), tenerals and sub-adults are reddish. 

Teneral male.


Teneral female. 

This is the first record of M. aborense in Vietnam*. I found it... in the suburbs of Hanoi (!), at some small, well shaded ponds hidden among a tiny (one hectare) wooded area – a birding patch in fact. I never expected to find any interesting odonata there, that’s why I never really searched. But one day I had the good idea to scan thoroughly the water surface with the binoculars...

M. aborense is widespread in Asia (from India to Thailand and Laos, and south to Borneo and Sumatra), but quite local in occurrence, found in forest streams, shady ponds and marshes. Although it can sometimes be found outside of forest, it is always in the vicinity of forest and probably depends on some forest cover for its survival.

Its presence in a small wooded patch surrounding by paddy fields and residential areas, in the suburbs of a bustling megacity, is quite amazing.

*In 2013, Tom Kompier found it also at Van Long NR, Cuc Phuong NP and Huu Liên NR. It was surprising that this species had not been recorded elsewhere in Vietnam, given the unlikely location of its discovery. Yet another species that may not be as rare as the scarceness of records suggests!

05/09/2013

Polycanthagyna erythromelas (McLachlan, 1895)


Polycanthagyna erythromelas is one of the 4 Aeshnids I encountered the most in the Hanoi area (sensu lato, i.e. within a 60-70 km radius)- with Tetracanthagyna waterhousei, Gynacantha subinterrupta and Anax guttatus. If the two latter species are commonly spotted in agricultural landscapes, along ponds, the two former ones are strict stream forest-dwellers.

A resting male, photographed at a tiny pond in secondary forest (foothills of Tam Dao)

P. erythromelas is a dragonfly of very large size (wingspan of about 120 mm), with striking colours: male dark, female coppery red, both yellow striped.
The strongly contrasted sexes and their powerful build make a pair of magnificent insects.

According to literature, P. erythromelas is quite common in suitable habitat across much of its range. But for me it is an uncommon sight (4-5 sightings in 3 years) - like other jungle Aeshnids I could say, due to their inconspicuous nature.

Male and female were observed at forest ponds or streams, the latter as she was coming to oviposit in soil in steep banks or wet mossy rocks. 

Male :

Face greenish, upper surface of frons, vesicle, occiput black.
Thorax dark, broadly marked with bright yellow as follows : moderately broad antehumeral stripes, two broad bands on each side, one on middle of mesepimeron, the second, much broader, covering nearly the whole of metepimeron.




Wings, male.

Wings hyaline, very long and rather pointed at apices.
Abdomen black with yellow markings, tumid at base, markedly constricted at S3, then very gradually dilating to S7.

Anal appendages:  superiors black, coated with long thick hair on upper surface; inferiors simple, triangular, curled upward.

Tip of abdomen, dorsal.

 Dorso-lateral.


Lateral.


Female :
She differs rather broadly from the male, especially in shape and colouring of abdomen. 


Thorax dark reddish, marked as the male.
Abdomen bright coppery red, yellow striped, with the intersegmental sutures and whole of terminal three segments black.


Simply beautiful. That's all I really have to say.


Large robust ovipositor, extending nearly to end of abdomen; dentigerous plate produced and furnished with a number of variably sized robust spines, longer and more robust at apical border. Like Tetracanthagyna, the female oviposits in dry soil, the powerful ovipositor and pitchfork-like dentigerous plate being adapted for this purpose (Fraser, 1933).



End of abdomen of an ovipositing female, covered with soil. 

P. erythromelas is a widespread species, known from India and Pakistan, Nepal, Thailand, Myanmar, China, Thailand, Laos and Vietnam.

I found it in both primary (Cuc Phuong NP) and secondary forests, sometimes in intermediate-aged secondary forests (<30 years).