Some Xuân Son goodies in the rain

Misty mountains at Xuân Son, after the rain

Back to Xuân Son National Park on July 12th. A typical rainy season day with heat, dark clouds, sun and of course (torrential) rain. At this season, depending of the day, you can have more sun and less rain, or vice versa. A completely unpredictable weather.
The morning was quite sunny but the afternoon the heavens opened and that put paid to my day. The long way back to Hanoi was an epic motorcycle journey...
Below some shots taken during this (too short) session :

Ceriagrion azureum, copula

Found at an open pond in a village. A new species for my personal records. 

In mountain areas I usually ignore open habitats in favour of forest habitats, that's why I overlooked it. 
Under these latitudes, there are often some "bad" bugs (parasitic worms/leeches) in standing water so I always avoid to submerge my butt in ponds. But this time the temptation was too strong!

Matrona taoi, male, well hidden in the forest
A newly (2011) described species, hitherto known from Xuân Son (type locality) and a site in central Vietnam (Quang Binh Province). A Matrona species with metallic green abdomen and brown-reddish wings, lacking any milky coloured reticulation at the wing bases of the male (unlike Matrona basilaris for example).

It was the only Matrona taoi I saw during this short trip. More easy to find in autumn, after the rainy season (October, November & December).

Archineura hetaerinoides, male

That smells like the end of the season for this species, more abundant in April, May and June

Chlorogomphus sachiyoae, male (identified afer in-hand examination, of course)
A typical view of a male Chlorogomphus patrolling up and down a shallow rocky stream, with a slow flight, few dozens of centimeters above water. Found this guy some kilometers before Xuân Son, in a small, incised valley (depth of 15m or so) surrounded by... manioc fields!  Other interesting species there included Coeliccia sasamotoi and Cryptophaea vietnamensis. I have already noticed that interesting forest species can still maintain in very degraded habitats if woody riparian corridors have been conserved.

Euphaea masoni, male & female

Euphaea masoni, male
Note the coppery sheen on upper-side of hind wings (not often visible, generally wings appear all dark). Its close but less common congener E. guerini show an obvious greenish sheen there (see photo below), visible even in bad light conditions; but closed winged of both species show a blue-green metallic sheen. Anyway, the easiest way to separate the two species is by taking a look at the ventral base of S9, where E. guerini has a tuft of long hairs.

Euphaea guerini, male
Note the hairs at the ventral base of S9 

Euphaea decorata, male
A widespread and common species in northern Vietnam and southern China, occurring in both lowland and mountain streams.

A newly emerged male Euphaea decorata

Euphaea ochracea, male
Seems scarce at Xuân Son - only one male spotted. 
Three other Euphaea species are found at Xuân Son (masoni, guerini and decorata), all common.

Lamelligomphus formosanus, male 
Like its congeners, this species is a hovering champion, so it should be easy - in theory - to photograph it in flight. But this little fellow is skittish and quite difficult to approach. 

Lamelligomphus formosanus, female at an oviposition spot

Prodasineura croconota, male

Orolestes selysi McLachlan, 1895

The genus Orolestes contains some striking species. O. selysi is interesting in that the male comes in two wing forms : hyaline or marked blackish-brown with white patches near the tip.

 
Male (patch-winged form / October 2012-Cat Ba Island)

Prothorax green. Pterothorax bronzy green above (almost brownish in old individuals), not metallic ; sides with 2 or 3 stripes of different shades of green - more or less bluish in very mature males.

Abdomen bronzed green on dorsum of segments 1 and 2, bronzed black on the remainder, but segments 3 and 4 with a medial bluish area (sometimes only S3) ; margins of segments 7 to 9 minutely spined apically; segment 10 slightly notched. S8, 9 and 10 bluish.

The male comes in two wing forms : hyaline or partly opaque blackish-brown with lacteous patches near the tip. 

Females very similar to males in colour and pattern, but wings always hyaline.

Male (hyaline-winged form / July 2012-Foothills of  Tam Dao)

Male (patch-winged form / October 2012)

Note the greenish labrum and bases of mandibles. 

Anal appendages :  superiors black half as long again as segment 10, slender, regularly curved and forcipate, so that the apices meet; outer border finely spined along apical half ; internally there is a robust basal tooth on inner side and a dilatation which extends along inner border nearly to apex and ends in a triangular, acute tooth.

Dorso-lateral view
Note the margins of S7 to 9 minutely spined apically; S10 slightly notched

Lateral view

A pair at Cat Ba Island (October 2012)

Female insert eggs into tree branch. She choosed a vertically directed plant stem. 
 She performs oviposition accompanied by its mate. 
 Two or three times I spotted the male drive away other males who wanted to mate with the female.

Close-up on the wings. Note the medial bluish areas on S3, 4.

Height of oviposition : 1,70m. The tree (no idea of the species) was in a rather open, muddy area - but certainly under water during the rainy season (from June to September).

The female bent its abdomen, segments 3-4 and 4-5 forming a right angle. Before she started to insert her ovipositor in the plant, she touched the bark with the ovipositor, maybe to provide information leading to a choice of insertion site. Then ovipositor valves protruded and began to move alternately, gradually penetrating into plant tissue. 
During ovipositor insertion, the female rotated its abdomen from side to side. When its cutting valves become entirely inserted in the plant, the female stayed motionless for some seconds ; the egg (eggs?) was probably laid into the prepared hole during this time. Then she removed the cutting valves from the hole, moved a bit around the bark and carried on doing the same process.

The female was carefully guarded by the male throughout the whole procedure - a good boy !

In August 2013, newly emerged tenerals were spotted at a small pond together with their exuviae. 

After checking the area I found many larvae of O. selysi floating motionless near the surface, close to shoreline vegetation or fallen branches, and some of them even starting to climb out of the water.

I stayed there one hour and half with the hope to witness the whole larval emergence process, but without success. I think the emergence occurs at night or at dawn - I was there at 10 a.m., too late probably. 

 Exuviae.

Close-up on the labial mask.

The mouthparts of nymphs are cleverly modified to form an elongate, prehensile structure known as the mask. This structure is hinged in the middle and bears a pair of terminal claws. The whole arrangement is called the mask because when not in use and folded back under the head, it conceals the rest of the mouthparts. When food is sighted, the mask is thrown forward and the prey is impaled on the claws.

Larvae of O. selysi floating near the surface.

O. selysi larva (August 11, 2013)

A Zygoptera larva is recognizable by the three feather-like gills extending from the tip of its abdomen that the animal uses to "breathe" in its underwater environment (Anisoptera larvae breathe by means of internal rectal hills).  When it does move, it swims much like a fish by making lateral serpentine movements with their abdomens (Anisoptera larvae tend to walk though they can turn on the speed with jet propulsion by expelling water from their anal respiratory orifice).

 This larva chose the wrong support. Emergence is always a risky process...

 Another larva, just bellow the one attacked by ants…

 Newly emerged male.

The pond where these larvae were photographed. A small (less than 20m²) square-shaped, probably man-made pond at the foothills of Tam Dao (alt. 300m a.s.l.), in degraded forest. Other species breeding there include Coeliccia scutellum, Tetrathemis platyptera, Polycanthagyna erythromelas, Orthetrum triangulare, O. chrysis, Zyxomma petiolatum.

O.selysi is known to occur in India (Darjeeling), China (Guangxi, Hainan), Vietnam, Laos and Taiwan.

In Vietnam this species must be either scarce or very local. First published record : 1904, "in Tonkin" (= northern Vietnam) by Martin. Second one in 2004, at Cat Ba Island, Quang Ninh Province, by Dô Manh Cuong. O. selysi is actually known from several localities in northern Vietnam.

I bumped into this species at 4 lowland sites : a small marsh partially wooded surrounded by forest (Cat Ba NP), a small (less than 20m²) pond in heavily degraded forest (foothills of  Mount Tam Dao) and 2 tiny pools along rocky, forest brooks (foothills ot Tam Dao, Cuc Phuong NP).

Orolestes selysi is a forest dweller but certainly does not need good forest habitats.

  

In southern Vietnam occurs an another Orolestes : O. octomaculatus (Martin, 1902), a stunning Lestid characterized (the male) by 2 dark spots on each wings.