Megalestes distans Needham, 1930

 

A stunning Megalestes with the majority of thorax coloured bright metallic green, which is pruinosed with oily whitish deposits in mature males.

Male, without flash - more natural appearance I think.

Male, with flash - sharpness and contrast increase.

  
Abdomen of male dull reddish (blackish at intersegmental sutures) except S1-2 green metallic on dorsum and S8-10 dark brown.

Dorsal synthorax and mesepimeron metallic green (with orangey highlights when the light is right!) with humeral (mesopleural) suture black. Metepimeron and metepisternum pruinosed white, except a short horizontal dark green stripe (which does not reach the spiracle) on the latter.

 

Prothorax blackish with central lobes with metallic green reflections. Posterior lobe pale yellowish.

Dorsal view

Anal appendages blackish brown ; superiors slightly longer than S10, forcipate with basally, on the inner side, a short quadrate process. Inferior appendages much shorter, with two pairs of curved spines in lateral view.

 

Lateral view

I encountered the female on 2 occasions. The photos below of an ovipositing female were taken in September along a forested stream (< 1 m wide), at the first slopes of Tam Dao so at a very low altitude (ca 200m).

 

  

She is very similar to male and also brightly coloured with metallic green but white pruinosity on sides of synthorax is replaced by yellow and the abdomen is duller.

Megalestes distans is known from China (Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Shaanxi, Shandong, Sichuan, Yunnan, Zhejiang) and several localities in northern Vietnam.

I mostly encountered the males in August (the wettest month here in northern Vietnam), at montane and submontane well shaded streams – but one time as low as 200m a.s.l. (ovipositing female).

The closest congener of Megalestes distans is M. haui Wilson & Reels, 2003 (described from Guangxi), which has similar overall colouration and similarly shaped superior appendages. The two species can not be confidently separate without study of penile organ. 

At Ba Vi and Tam Dao, only M. distans has been recorded. In Vietnam, M. haui is known, at least, from Sa Pa (Lao Cai Province) (Dô Manh Cuong, pers. comm.).

Habitat, Ba Vi (800m a.s.l.). Small swift-flowing, rocky stream (2-3m wide) with heavy covert. Males Megalestes distans were perched low at the banks.
Other  Zygoptera species spotted there (in August): Anisopleura qingyuanensis, Cryptophaea vietnamensis, Noguchiphaea yoshikoae, Coeliccia acco, C. onoi, C. scutellum, Atrocalopteryx coomani, Protosticta satoi, Devadatta ducatrix, Agriomorpha fusca, Drepanosticta sp.

Earlier in the season (May, June), remarkable Anisoptera species were recorded there, such as Merogomphus tamdaoensis, Chlorogomphus auratus and Sinorogomphus nasutus satoi.

Protosticta satoi (Asahina, 1997)

Asahina (1997) described the subspecies Protosticta khaosoidaoensis satoi based on some differences of color pattern of thorax and abdomen compared to the nominotypical subspecies from Thailand.

Later, van Tol (2008) raised this subspecies to species rank, and described two forms of P. satoi, a normal form and a dark form. He then stated it was possible that the dark form of Protosticta beaumonti Wilson, 1997 figured by Wilson and Reels (2003) from Guangxi may be conspecific with the dark form of this taxon, and the normal form may be conspecific with prototypical beaumonti from Guangdong. If so, P. satoi is a junior synonym of P. beaumonti. This taxonomic issue is not yet clarified.

This slender and delicate Platystictid damselfly live low in the dense forest undergrowth, making very short hunting flights. It is a tame fellow which likes to pose for the pictures. Often its curiosity will bring it close to you. Many times I saw it hovering just in front of my nose!

Labium whitish. Pronotum with anterior and posterior lobes blackish, median lobe whitish.

Dorsal synthorax dark-greenish with metallic sheen. Sides with pale brown mesepimeron, dirty yellow metepisternum and metepimeron with a fine stripe over metapleural  suture.

Abdomen long and thin, but S8-9 obviously inflated. Pale blue marking on S9 in both sexes.  

The shot above is the best I could do with showing the appendages (rubbish, I know). Superior appendages strongly curved with complicated protuberances. With a macro lens, impossible to get detailed close-ups of so tiny parts of the body.

Female.

 Female is similar to the male in general maculation pattern, but abdomen more stout.

 

Female.

P. satoi dark form can immediately be distinguished by its almost wholly black synthorax with a triangular posterior marking on the metepimeron.

The coloration of the pronotum of the males shows significant variation, the median lobe may be either fully pale colored or heavily smudged dark.

P. satoi is only known from northern Vietnam. It is not an uncommon sight in lowland and montane forest streams at Tam Dao, Cuc Phuong, Ba Vi National Parks... Sometimes, I found it along streams in heavily degraded forest, but always with dense marginal vegetation. The dark form is rarer.
Further studies should reveal whether P. satoi is a junior synonym of P. beaumonti, or whether both represent distinct species.
More information about genus Protosticta in Vietnam here.

Chlorogomphus sachiyoae Karube, 1995

Most of birders have a special ‘patch’ or two.  A birding ‘patch’ is a place a birdwatcher visit regularly, know intimately and enjoy deeply. When I began chasing bugs in 2011, I maintained this practice.

On the lower slopes of Tam Dao, I have a dragonfly watching ‘patch’. It is a headwater stream of high quality, in secondary forest - but left unexploited for a long time. A wild and scenic stream with large boulders, small waterfalls, fallen trees… I know this place like the back of my hand - better perhaps. I come back again and again but I never get bored. There is always something new to discover.

Last June, I netted there a male Chlorogomphid making slow patrolling at a height of 0.5m to 1m above the stream. At this time its strongly protruded frons reminded me of Sinorogomphus nasutus, but the caudal appendages looked completely different.

When I returned home, a research on my documents (especially the paper “On the genus Cholorogomphus of Indochina with description of 6 new species and little known species” - Karube, 1995) revealed that it was a male Chlorogomphus sachiyoae.

Chlorogomphids are very similar and need to be examined in hand and identified using a combination of structural characters and general maculation pattern. 

 

The male :

Head black with yellow markings, with frons obviously triangularly protruded. Labrum black with a medium yellow spot. Postclypeus yellow. Eyes almost meeting.

Pterothorax black with yellow stripes, with a narrow antehumeral, a broad humeral and a broad lateral stripes. This specimen shows also 2 spots at upper part of metepimeron, absent in Karube’s drawing of the holotype. 

Abdomen black with yellow markings as follow : large spot at ventral of S1, two bands in S2, one oblique connected with the former spot and does not reach the dorsal top, the other one larger just before S3 and reach dorsal top (ring in dorsal view). Compare to the holotype’s drawing, these 2 bands in S2 are closer to each other and even - at one side of the body only - slightly connected.

 Middle of S3 with a thin ring. S3-6 with dorso-apical spots, the one of S5 not well marked, the one of S6 the largest. S7-10 wholly black.

 

Caudal appendages: Cerci curved inwards, with stout oblique ventral spine (obvious in lateral view, but also quite visible in dorsal view), apex bilobed.

Epiproct slightly longer than the cerci, yellowish in the middle, somewhat curved upwards at apex with 2 minutes spines on dorso apical area. In dorsal view, middle part of epiproct notched and apex obliquely truncate.

 

Wings, male.

The female :

Last year, few hundreds meters downstream, at about 250m a.sl., I netted a female Cholorogomphid at a 1m wide tributary. She was releasing eggs in flight over a shallow gravel section. At this time, I could not clinch the ID. But later, with the help of Karube's paper, I could confidently identify it as a female Ch. sachiyoae.

Abdominal markings similar to those of male but yellowish maculations of S2 more developed (the two bands are connected and enclose a black patch).

  
Head with coloration as in male; compare to male, frons less protruded and eyes more widely separated.

As Chlorogomphus albomarginatus and Ch. takakuwai, Ch. sachiyoae is, for instance, only known from Tam Dao* - pretty amazing! Apparently, it has never been recorded since its description in 1995. 

*update June 2014 : this is no longer the case. Ch. sachiyoae has been recorded this year at different other sites in northern Vietnam.

I spotted the male at this 10m wide boulder river in forest at 300m a.s.l., fast-flowing in the steeper sections, with dense marginal vegetation. Other species encountered there include, amongst others, Archineura hetaerinoides, Atrocalopteryx coomani, Coeliccia onoi, C. scutellum, C. acco, Euphaea guerini, E. decorata, Philoganga vetusta, Rhinocypha orea (June 2014), Indocnemis orang, Devadatta ducatrix, Protosticta satoi, Agriomorpha fusca, Macromia pinratani vietnamica, Idionyx thailandica, Leptogomphus perforatus, Asiagomphus acco, Heliogomphus scorpio, Zygonyx iris… A pretty good ‘patch’ I think !

Chlorogomphus albomarginatus Karube, 1995

June 2013, Mount Tam Dao, 1100m a.s.l, along a rocky, shaded stream. 
For one hour or longer, I have been trying to get good shots of skittish males Caliphaea thailandica. As I was approaching carefully my 4^th or 5^th male, a large, black UFC (“unidentified flying creature”) appeared suddenly 15 meters away, close to the ground. I put my camera back in the bag, grabbed quickly my net and ran like crazy on slippery rocks. It was a large, black female dragonfly with striking black wings. She was flying slowly above shallow water, seeking a place to oviposit. An easy prey, even for a clumsy dragonfly hunter like me.

I captured the beast and was more than happy to discover inside my net a gorgeous female Chlorogomphus. A this time, the heavily-marked wings and the completely black abdomen remind me of the female of Ch. nakamurai. I snapped photos from every angle for further identification, and released her.

 Vertex swollen (in the female Ch. nakamurai, the vertex shows an obvious pair of long protuberances). Antehumeral stripe almost disappeared and humeral stripe quite broad (broader than those of Ch. nakamurai).

One month later, Dô Manh Cuong sent me a paper of Karube about the genus Chlorogomphus in Indochina with description of 6 new species. Haruki Karube is THE specialist of Asian Chlorogomphids and Tam Dao is one of his preferred hunting ground in Vietnam. He described three new species from Tam Dao (Chlorogomphus takakuwai, Ch. sachiyoae, Ch. albomarginatus), which have never been recorded elsewhere* !

*update June 2014 : this is no longer the case. Ch. sachiyoae has been recorded this year at different other sites in northern Vietnam.

With this document, I confidently identified my guy as Ch. albomarginatus. This species has been described from Tam Dao in 1995, but has not been recorded since then - except maybe by Karube himself.

 Abdomen almost wholly black, robust, especially in basal 3 segments.

Wings are broad, covered with deep black markings (Ch. nakamurai : dark-brown). Hind wings show a milky white band at the margin of this mark. Black mark of fore wings with a hyaline hole in the middle. No obvious blackish area at wings tips (unlike Ch. nakamurai).

Female Ch. albomarginatus resembles superficially to Ch. nakamurai, but can be easily separated by the head, the colour pattern of the wings, the pterothorax, ...

For a good comparison of the wings, have a look at this photo of a female Ch. nakamurai.

I think it really is a stunning dragonfly (and for once, the female is more beautiful than the male) and one I hope to bump into again. I will return at this stream next year and hopefully spot the male!

As I said above, Chlorogomphus albomarginatus is only known from Tam Dao. I spotted this female at a heavily shaded, rocky stream in steep terrain, in bamboo forest. Other interesting species noted there include Caliphaea thailandica, Coeliccia onoi, C. scutellum, C. acco, Indocnemis ambigua, I. orang, Rhipidolestes owadai, Devadatta ducatrix, Megalestes distans, Protosticta satoi, Agriomorpha fusca…

Many thanks to Dô Manh Cuong and Noppadon Makbun for providing documents!