Agriomorpha fusca May, 1933

Agriomorpha fusca is one of the damselflies I encountered the most in the good forests around Hanoi. When the forest seems desperately empty, when nothing is flying around, there are always some valiant Agriomorpha fusca hanging around. 

May (1933) described Agriomorpha fusca from 'Fan-Chi-Schan', Guangdong. Agriomorpha is a monotypic genus.

Both sexes are quite identical in color pattern, except the face: labrum, clypeus and front of frons creamy orange in the male, yellowish in the female. There is also a slightly difference in the synthoracic pattern: the male has a wholly mat black synthorax, the female bears a short white stripe along the humeral suture, at the base of the forewing – sometimes present in the male, but less obvious. Another difference I noticed concern the protorax: sides are much paler in the female. 

According to Wilson & Reels (2001), there are geographic variations in the synthoracic pattern of this species. The Hong Kong form is the darkest with a synthorax almost completely black. The Hainan form is the most patterned with elaborate striped synthorax. 
The synthoracic pattern of the north Guangdong form, where the type was described, is intermediate between the Hainan and Hong Kong forms. There are no structural differences between these geographic forms.
At Ba Vi and Tam Dao I encountered individual with a synthorax almost completely black; but at Mâu Son, 200km further north, close to the Chinese border, specimens show a well striped synthorax - see photos below. 

A male.

A male from Tam Dao, close-up. The name “fusca” fits like a glove.

For comparison, a male from Mâu Son (Lag Son Province), near China

Close-up of another male from Tam Dao, but without flash this time. I have to use a higher ISO than I would like. A noisier, less contrasted picture, but more natural I think. In thick, dark forest, if you are not using flash, you can not reduce the aperture diameter (=increase the f-number) so the depth of field (DOF) is shallow. For me, it is important to have the entire insect sharp, so a large DOF is necessary. Actually I have only a ”scientific”/informative approach to Odonata photography - i.e. as much as possible fine details must be visible, in particular critical features necessary for proper specific identification -, maybe later I will approach my subjects from a more artsy perspective! But I am afraid I am not skilled at all in this kind of approach!

A shot showing the orange labrum, clypeus and front of frons of the male. Note also the short whitish stripe along the humeral suture, at the base of the forewing, not always present in the male, but well marked in the female.

  The male has forceps-like cerci and rudimentary paraprocts.

A female.

A female, close-up.

A bad shot of a not fully mature female - note the brownish synthorax.

I bumped a few times into pairs in copula. But it's one thing to see a mating pair, quite another to get good shots, especially in dark forest. Patience, luck and highly cooperative subjects are the most important factors to succeed.

Odonata have secondary sex organs, meaning they don't store sperm near the copulatory organ. The male must transfer some sperm from a gonopore on his 9th abdominal segment to his penis, which is located under his 2nd abdominal segment. Once he's charged his seminal vesicle with sperm, he's ready to go!

 Now let’s go for the acrobatics! The female's genital opening is near the tip of her abdomen, while the male's penis is closer to his thorax. The female must bend her abdomen forward to bring her genitalia into contact with his penis.

The famous 'wheel' formation during mating, unique to the order Odonata. 
Always a popular subject for photographing.

The female was observed ovipositing on moss growing on stream bank rock surfaces. The male perched nearby guarding his mate while she deposits eggs. 

Agriomorpha fusca is known from southern China and northern Vietnam. It is common and widespread throughout Hong Kong and Guangdong, and recorded from several sites in Hainan, Fujian.
I can safely say that northern Vietnam supports thriving populations of this species.