Labrogomphus torvus Needham,1931

Female Labrogomphus torvus at Huu Liên Nature Reserve, on December 1, 2014,  
enjoying the first rays of sunshine on a fresh winter morning

Labrogomphus is a monotypic genus erected by Needham (1931) to receive a female specimen of Labrogomphus torvus collected from Hainan. Chao (1954) described the male and larvae specimens collected from Fujian. It is allied to Macrogomphus, with which it agrees in having the 9th abdominal segment more than twice as long as the 8th.  
Labrogomphus torvus is a stunning blackish spiny-legged species, with a thorax handsomely striped, a curved abdomen spotted with bright yellow.  
I was lucky enough to spot both male and female the same day, in December 2013, at Huu Liên, as I wandered along a reservoir's banks.

One of the most impressive Gomphid species I have been privileged to see in Vietnam so far - the very long hind legs armed with extremely long strong spines have probably something to do with this.

... before grabbing few meters away her breakfast, a female Orthetrum pruinosum 

A voracious predator !

This stupid male landed on my net! (I read somewhere that white nets attracts certain groups, namely gomphids. Seems true...) 
Note S9 markedly elongate, S7-9 broadened and the large basal ring on S7.

                             

Male in hand. Hind femur and tibia with very long spines

Female in hand - same stuff on hind legs

Male, head. Note the particular shape of occipital ridge.

Compare with the female :

Male, caudal appendages, lateral, dorsal and ventral views

Labrogomphus torvus is known from southern China including Fujian, Guangdong, Guangxi, Anhui, Hainan Island, Hong Kong. In December 2013, it has been discovered at Huu Liên, first record for Vietnam. In June 2014, I also found it at Tây Thiên (foothills of Tam Dao) along a rather open rocky stream in degraded secondary forest and Tom Kompier recorded it the same month at Ba Be (Bac Kan Province).

According to literature, this Gomphid can inhabit a wide range of stream and river habitats, both in forested and open aspect environments, and even ponds/lakes created by impounding streams - it was the case at Huu Liên.

 

Nychogomphus lui Zhou, Zhou & Lu, 2005

Male Nychogomphus lui, Hanoi, on June 15, 2011

An enigma finally resolved thanks to Tom Kompier who recently sent me an email with a link to a Chinese website, with these words: “have a look at the photo with caption Nychogomphus lui”. I opened the link and immediately recognized a familiar Gomphid, one of the 3 mysterious Gomphids species I encountered 1,5 km from downtown Hanoi in 2011 and 2012. An unidentified species that not only puzzled me but also experienced odonatologists.

Just after receiving Tom’s email, I checked the original description by Zhou & al., 2005, which confirmed its identity.

But let’s go back to mid-June 2011 : during a noon stroll at Hanoi, I bumped into a medium-sized male Onychogomphine resting on leaves 50cm above the ground, in a tiny wooded area surrounding a small pond. A very polluted pond I must say, located 1,5 km from the city center and 400m from the Red River – the large river that runs along the city. At that time, I was interesting by Odonata for only few months – so a complete novice. After some shots in hand, I released it (big mistake...), convinced that in such a place it could not be something else than a very common species, easy to identify. If I had known that it was a new species for the country, the story would have been very different! 

Some of the pictures displayed here are quite bad, I apologize for that. They were taken 3 years ago with my first camera.

Some features of the male Nychogomphus lui : 

-head well marked (labrum with pair of elongated yellow spots, anteclypeus, base of mandibles  yellow, split yellow line over frons).

-synthorax black with a yellow dorsal stripe  connected to the collar stripe to form a broad 7-shaped mark, superior yellow antehumeral spot, sides of synthorax marked with broad yellow stripes.
-basal part of abdominal segments 4-7 all ringed completely [broader basal ring on S7], S7-9 broadly expanded.
-superior appendages whitish, brownish-tipped, the apical half curved downwards, slightly longer than the inferiors, the latter undulant curved, bifid almost to base, the two branches very closely apposed, curved strongly up to meet the superior appendages. 

Male, frontal view showing the broad dorsal 7-shaped marks on the synthorax. 

Tip of abdomen, lateral & ventral views, showing the superiors curved downwards, the inferiors undulant curved, bifid almost to base, the two branches very closely apposed.

I also did manage some record shots of the female. She display a similar color pattern to the male.

The female. Note the basal part of abdominal segments 4-7 all ringed 

completely (broader ring on S7) as the male.

Nychogomphus lui has been described in 2005 from Yunnan. As far as I know, this record from Hanoi is the first one outside China. According to Dr Haomiao Zhang (pers. comm.), Nychogomphus lui breed in rivers and streams. So the specimens I encountered came certainly from the Red River (about 700-800m wide at Hanoi) and it is probably the case of the 2 other unknown Gomphids found at the same polluted pond – among them a female Stylurus sp., members of this genus in Asia generally prefer broad, deep, slow flowing rivers. 

The most interesting thing in all this story, it is not really the fact that Nychogomphus lui is a new record for Vietnam. No, the most exciting - and puzzling - thing for me is that it passed unnoticed (in Vietnam but also in China – remember, it has only been described in 2005!) despite the fact it can live in the most unlikely of urban or suburban settings.
And believe me, Hanoi is far from being a “green city”!...