Merogomphus tamdaoensis Karube, 2001

As you can probably guess, Merogomphus tamdaoensis has been discovered at Tam Dao. Until recently this species was only known from this mountain range, where it is not uncommon (at least in the last remnants of good forest), but in May 2013 I found it at Ba Vi, about 50 km from Tam Dao, approximately at the same elevation (900m).

 Male (Ba Vi)

  

Male: 

Synthorax black with markings as follows: antehumeral stripe slender and connected to the collar stripe to form a T-marking; humeral stripe slender; mesepimeron with a median stripe with dorsal part spread anteriorly (ice axe-shaped stripe); metepisternum and metepimeron also largely yellow.

Abdomen expanded in the last four segments, black with a longitudinal line running on the dorsal carina from S2 to S8.

Male (Tam Dao)

Male "in hand"

Caudal appendages black. Superior short and conical, spiny. Inferior appendages with opened divarications, roundly truncate at apex.

Dorsal view

 Lateral view

Ventral view

Female:

Pattern of markings very similar to those of the male. Yellow markings on the abdomen more developed, notably on sides of the first segments.

Female (Tam Dao)

 Female (Ba Vi)

Some "in hand" shots:

Thoracic maculation as in male, yellow markings on sides of the first abdominal segments  more developped.

Wings, male.

Habitat, Tam Dao.  

This stream, which is home to other rare forest-dwellers such as Atrocalopteryx coomani, Noguchiphaea yoshikoae..., is partly surrounded by "su su" fields (known in English as christophine or chayote). Those crops are gaining ground year after year (in conjunction with tourism development) and already adjoining the right bank of the stream. Cutting adjacent forest change the aquatic microclimate and lead to changes in Odonata diversity.

Situated downstream of the Tam Dao Hill Station, this site might also be subject to pollution discharge, especially at the peak tourist season (summer). The stream banks littered with plastic wastes are a very sad and deplorable sight, especially in a so-called "National Park".

I found M. tamdaoensis at Tam Dao (type locality) and Ba Vi National Parks (both at ca 900-1000 m a.s.l. ; but in 2013, Tom Kompier also netted a female at the foothills of Tam Dao, at 300-350m). 
In June 2014, Tom also found it at Cuu Thac - Tu Son (Hoa Binh Prov.), in submontane forest.
This Gomphid is hithertho only known from these three localities.

Indocnemis ambigua (Asahina, 1997)

Asahina (1997) described the species as Coeliccia ambigua from Tam Dao, Vinh Phuc Province in northern Vietnam, but it has been moved later to the genus Indocnemis.

In his description Asahina pointed out that the venation of ambigua was not consistent with the genus Coeliccia Kirby but with the genus Indocnemis Laidlaw.

In Indocnemis the anal crossing ends on the anal bridge vein (red circle) and not on the wing margin except in one of four specimens examined by Asahina. But, as pointed out by Wilson and Reels (2003) another characteristic of the genus Indocnemis is the presence of four cells between discoidal cell and the nervure descending from the subnode, whereas Coeliccia has just three cells. This species has three cells consistent with the genus Coeliccia. So the term "ambigua" is still appropriate!

Male : the head is mat black, prothorax and synthorax grey (in fact mat black finely pruinosed), the latter with two pale bluish stripes on each side.

The black (not pruinosed) band on the dorsal synthorax contrast with the greyish tint of the rest of the synthorax.

The abdomen is black dorsally, except segments 9-10 bluish tinted.

Caudal appendages also pale bluish ; the superiors much shorter than the inferiors (please note that the photo of appendages was also taken in the field, with the insect alive. With so tiny parts of the body, I can not expect detailed close-ups. Photographing damselflies appendages require other equipment that I don’t have!).

A mating pair

An ovipositing tandem pair

The male remain in tandem with the female while she deposits eggs, termed "contact guarding". Guarding prevents another male from inseminating the female.

This female oviposit into moss at a vertical surface of a rock

I spotted the female very few times. I am not sure that she has been described - not by Asahina at least.

Indocnemis ambigua inhabits montane forest streams. It is known from a limited number of sites in northern Vietnam (Tam Dao only, the type locality) and southern China (Guangxi).

Currently there is only two species recognised in the genus Indocnemis, the other one is I. orang (Förster in Laidlaw, 1907).

Those shots were taken at Tam Dao, along small rocky streams with heavy covert (alt. : 950-1.000 m a.s.l.). Probably the first ones of this species on the internet.

Calicnemia soccifera Yu & Chen, 2013

In May 2013, during a field trip to Ba Vi National Park, I photographed  a male Calicnemia sp. at a shady rock seeping with water (at ca 900m a.s.l.).
When I got home, I did a little research and it turns out to be C. soccifera, a recently described species from Yunnan. It was the first record from Vietnam. Subsequently, I found it in Xuan Son National Park. Tom Kompier recorded it also in different locations in northern Vietnam.

The Latin adjective soccifera [soccus + ferre] means “sock-wearing” and refers to the remarkable black colored tibiae and tarsi compared to the reddish brown femora.

Some "in hand" shots :

Calicnemia mortoni (Laidlaw, 1917)

The adult male has black thorax with pale bluish-purple stripes. The abdomen is black, segments 1 and 2 and the base of 3 brick-red.

A teneral male

A tandem pair

An ovipositing tandem pair

The female has black thorax marked with yellow-citron stripes. The abdomen is brown dorsally more or less reddish on segments 2 and 3 ; the terminal segments are reddish on ventral side.

A shady rock seeping with water, habitat of Calicnemia mortoni (Tam Dao, elevation : ca 1O50m a.s.l). The males were also perching on sunny vegetation around.
Other species spotted there (in May) : Agriomorpha fusca, Rhipidolestes owadai, Coeliccia onoi, Devadatta ducatrix, Indocnemis orang.

This montane species is known to occur in India (Sikkim, Darjeeling), Nepal, Bhutan and northern Vietnam. Those pictures were taken at Tam Dao National Park.
Many thanks to Noppadon Makbun for giving me documents about this species.