Gomphidia kruegeri kruegeri Martin, 1904

G. kruegeri is a large-sized, build robust gomphid, marked with bright citron-yellow.

This is a wary insect, not easy to photograph, especially when only armed with a 100mm macro lens. But I finally found an individual which allow me to approach at very close range less than one meter away, for a full-frame image.

G. kruegeri can easily be confused by beginners with other large gomphids of the genus Gomphidia, Sinictinogomphus and Ictinogomphus.

Difficult to approach, G. kruegeri can be confidently identified in the field by using binoculars - that I always carry around my neck. Very useful tool, not only for birders ! Best option for dragonfly watchers are lightweight and close-focusing binoculars.

The key feature is the antehumeral stripe :  the oblique dorsal stripes joined to an upper humeral spot create a characteristic “boomerang” shape.

A male perched on a prominent twig facing the water, head inclined downwards

and abdomen held well up.

Dorsal and lateral views of caudal abdomen :
 

Superior appendages nearly twice the length of segment 10, flattened laterally, forcipate; inferior very short.

Abdomen dilated at base, then narrow and cylindrical as far as S6, terminal segments again dilated but without leaf-like expansions as in genus Ictinogomphus. S10 with 2 lateral spots.

Right after photographing this tame male, I caught a glimpse of a female for the one and only time. She entered the territory of the male. Immediately, he flew up and grabbed her, creating a sound like paper crumpling as their wings collide in a blur of movement - dragonfly sex is often a rough and tumble affair! Then, they retired to a nearby bush to consummate their relationship.
I got a shot but they quickly separated, visibly disturbed by my presence. 

I managed to get a single - crappy - shot of the female before she flew up.

G. kruegeri is known from northern Vietnam, central Thailand, north Laos, southwest and southern China. This is a widespread species found in forested and open aspect lowland and montane streams and river habitats.

G. k. kruegeri is separated from G. k. fukienensis Chao, 1955, by the form of the second yellow lateral stripe on the metepisternum of the synthorax, which is reduced to two small yellow spots, and a black postclypeus. G. k. fukienensis has a more extensive second yellow lateral stripe and its postclypeus has two large yellow spots (cf. ZHAO, 1990: 425-428).

In my area around Hanoi, this species is common along rock-bottomed streams with moderate to swift flow.

Paragomphus capricornis (Förster, 1914)

 A male basking on a sunny gravel bank (Tam Dao)

A medium-sized gomphid, with common black and yellow generic colouration, and the shape of superior anal appendages characteristic for the genus.

The locality in Tam Dao, where these photos were taken in May 2013, can be described as an open lowland rocky stream, with some gravel banks surrounded by shrubs. Other gomphids spotted there : Gomphidia kruegeri, Lamelligomphus camelus.

Only males were seen.

Anal appendages black. Superiors long, double the length of segment 10, terminal half curved regularly downwards. Inferior appendages one third of the length of superiors, strongly curved in a upward direction.

Foliaceous outgrowths at the ventero-lateral margin of S8-9 (male only).

Lateral view

P. capricornis inhabits a variety of lowland and montane streams and rivers containing sand/gravel shoals, including open habitats and plantations.

This species is known from Arunachal Pradesh in India to China (Fujian, Guangdong, Guangxi, Hainan, Yunnan, Hong Kong), and south to Singapore.

Chlorogomphus auratus Martin, 1910

These shots were taken at Mount Ba Vi in May 2013 and 2014, along a well-shaded stream at 900m a.s.l, through dense forest. 

Male resting near a stream

Some "in hand" shots of the male to show close-up details of the thorax, the head and the anal appendages:

Caudal appendages black, superior one moderately bifurcate, the inferior widely opened with bifid apices. Cerci almost same lenght as epiproct, both curved in lateral view.

Dorsal view

Ventral view

Lateral view

Note the strong claw developed at the end of the tergite of the last segment

I also vouchered (along the same stream) the female oviposited in the shallow, slow-flowing margins.

Wings entirely smoked with apices darkened

An accumulated clump of eggs on the abdominal tip

 Another female caught in May 2014

Wings not smoked and tips much less darkened - young individual ?

Female found on a rock along a stream near Hoa Binh, half-eaten by an unknown predator. At least a new site for this scarce species.

Chlorogomphus auratus is only known from a handful of localities in northern Vietnam, central Laos and southern China. Apart Mount Ba Vi, recent other records from Vietnam are from Tam Dao (ca 900m asl), Cuc Phuong (ca 200m asl) and Mâu Son (900m).

For many years this species was known only from a single female; in 1995 Karube described both sexes from a series of 14 specimens taken on Tam Dao. Yokoi and Kano (2002) recorded a female, reared from the larva, from central Laos. It is likely to be under-collected and may be moderately common in some areas of Indochina. 

C. auratus is listed as Near Threatened with the hope that it can be downlisted to Least Concern as soon as viable populations are known.

Sinorogomphus nasutus satoi (Asahina, 1995)

Male resting vertically near a stream, Ba Vi NP, May 2013 

These shots were taken during some field trips at Ba Vi National Park in May. Males were on territory, rather slowly coursing up and down a well-shaded stream, at some dozens of centimeters above water’s surface, and sometimes were observed perching vertically on the stems of plants like cordulids. I had many sightings during sunny days and none when the weather was overcast.

The male of this species can be confidently identified by the general maculation pattern and the structure of the anal appendages. 

It is a large-sized species. Synthorax black, both sides being striped with  bright yellow markings. Wings smoked pale brown in aged insects.

Male, head from different angles. Note the frons triangularly protruded.

Caudal appendages black, superior one (=cerci) deeply bifurcate, the inferior (=epiproct) widely opened with bifid apices.

Dorsal view

Dorso-lateral view

Lateral view

 Male
The yellow pattern on the basal two segments of abdomen is characteristic of this subspecies, described based upon specimens collected at Tam Dao.

 Female

 Female, face

Left: female caught when ovipositing over a shallow gravel section. 

Right: valvula valvae broadly trapezoidal with middle part of apex sharply pointed

Wings, male

 This species is widespread in east, south and southwest China, and has only been recorded from a very few localities in Vietnam : Tam Dao and Ba Vi.

At Ba Vi, the specimens were found along shady streams and brooks with rocky substrate, through secondary forest (but unexploited, with closed canopy), at ca 900m a.s.l., together with Chlorogomphus auratus.

Fukienogomphus promineus Chao, 1954

At each site visited, my goal is to take photographs but also to identify the specimens, this frequently left me with a dilemma as to whether to use the net or the camera first.
Usually, as an avid nature photographer, I take pictures first...

The downside of this approach was that, on a good number of occasions, a potentially interesting specimen flew away before it could be photographed ; or it was photographed but not vouchered, and the photo didn't show enough details to clinch its identity.

To identify this male Gomphid, good close-ups of the caudal appendages were essential to understand the structure. I didn't take the risk to loose it and netted it immediately. Then I took "in hand"  photos from a variety of angles... and released it.
These shots are the first ones of this species available on the internet.

Dorsal view of the caudal appendages

Lateral view

Ventral view

Fukienogomphus promineus is known from southeastern China and only 2 mountain localities in Tonkin (northern Vietnam) : Mount Mau Son/Lang Son Province (first country record, in 2010), and Tam Dao National Park/Vinh Phuc Province (where these photos were taken, at ca 950m a.s.l). 
In June 2014, I also caught a male on the lower slopes of Tam Dao, at ca. 350m.