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.