Polycanthagyna erythromelas (McLachlan, 1895)

Polycanthagyna erythromelas is one of the 4 Aeshnids I encountered the most in the Hanoi area (sensu lato, i.e. within a 60-70 km radius)- with Tetracanthagyna waterhousei, Gynacantha subinterrupta and Anax guttatus. If the two latter species are commonly spotted in agricultural landscapes, along ponds, the two former ones are strict stream forest-dwellers.

A resting male, photographed at a tiny pond in secondary forest (foothills of Tam Dao)

P. erythromelas is a dragonfly of very large size (wingspan of about 120 mm), with striking colours: male dark, female coppery red, both yellow striped.
The strongly contrasted sexes and their powerful build make a pair of magnificent insects.

According to literature, P. erythromelas is quite common in suitable habitat across much of its range. But for me it is an uncommon sight (4-5 sightings in 3 years) - like other jungle Aeshnids I could say, due to their inconspicuous nature.

Male and female were observed at forest ponds or streams, the latter as she was coming to oviposit in soil in steep banks or wet mossy rocks. 

Male :

Face greenish, upper surface of frons, vesicle, occiput black.

Thorax dark, broadly marked with bright yellow as follows : moderately broad antehumeral stripes, two broad bands on each side, one on middle of mesepimeron, the second, much broader, covering nearly the whole of metepimeron.

Wings, male.

Wings hyaline, very long and rather pointed at apices.

Abdomen black with yellow markings, tumid at base, markedly constricted at S3, then very gradually dilating to S7.

Anal appendages:  superiors black, coated with long thick hair on upper surface; inferiors simple, triangular, curled upward.

Tip of abdomen, dorsal.

 Dorso-lateral.

Lateral.

Female :

She differs rather broadly from the male, especially in shape and colouring of abdomen. 

Thorax dark reddish, marked as the male.

Abdomen bright coppery red, yellow striped, with the intersegmental sutures and whole of terminal three segments black.

Simply beautiful. That's all I really have to say.

Large robust ovipositor, extending nearly to end of abdomen; dentigerous plate produced and furnished with a number of variably sized robust spines, longer and more robust at apical border. Like Tetracanthagyna, the female oviposits in dry soil, the powerful ovipositor and pitchfork-like dentigerous plate being adapted for this purpose (Fraser, 1933).

End of abdomen of an ovipositing female, covered with soil. 

P. erythromelas is a widespread species, known from India and Pakistan, Nepal, Thailand, Myanmar, China, Thailand, Laos and Vietnam.

I found it in both primary (Cuc Phuong NP) and secondary forests, sometimes in intermediate-aged secondary forests (<30 years).

Macromidia rapida Martin, 1907

Macromidia rapida, male, Huu Liên, June 2014

Martin (1907) erected the genus Macromidia to include the type species M. rapida Martin (from “Tonkin”, i.e. North Vietnam).

Another male, from Tam Dao

(remark: this photo has been taken after quite a long examination in hand, 
that’s why position of the wings looks unnatural - they should lie flat)

In 3 years, I bumped into M. rapida only 3 times, at rocky streams of Ba Vi and Tam Dao’s foothills, running through secondary forests. It is certainly not scarce but just inconspicuous - spend the great part of the day hiding in the vegetation.  

Two times, I found M. rapida resting at eye level amongst bushes, along moderate to fast flowing open/partially shaded rocky streams - one time inside willow-like shrubs in the middle of the stream.

The third time, an individual was netted as it was zigzagging low over a tiny, shallow pool at the margin of a stream, just before rain. Cat-like reflexes are needed to catch this little fellow!

(same remark as photo above)

Abdomen black, yellowish striped on the middorsal line.

Head largely dark reddish brown; frons dark metallic green, labium pale brownish. Narrow yellow stripe on the anteclypeus.
Synthorax shining metallic green and yellow laterally; dorsum (mesepisternum) metallic green with lower portion reddish brown.

 "Oh my god what happen to me !"

Tip of abdomen, dorsal.

Caudal appendages of typical Macromidia type, the superior yellowish with dark base and apex.

Tip of abdomen, lateral.

I didn’t spot the female, but according to Asahina (1988), head and thorax patterned as those of the male insect. Cerci yellowish with black type.

M. rapida is found in southern China, Thailand, Cambodia and Vietnam. This species inhabits streams of lowland/mid-elevation forests, even degraded ones (young secondary forest for example, as I saw at Ba Vi).

Macromidia genialis shanensis (Fraser, 1927)

Last May, during a field trip in the foothills of Mount Ba Vi, I bumped into a cordulid dragonfly tucked away deep in the bushes. After some shots, I caught it for closer examination of caudal appendages, and identified a male Macromidia. I first thought it was M. rapida, a species I had seen along the same stream, but I noticed some obvious differences: cerci black (pale yellowish and black-tipped in rapida), face largely dark green, large yellow spot dorsally on S6. 

Later, with the help of some documents (Fraser, Asahina), I confidently identified it as Macromidia genialis shanensis.

Macromidia species are crepuscular in nature and rest in dense vegetation near streams during day. They become active as rain threatens or dusk approaches, circling and zigzagging low over streams.

Head metallic dark green, except yellow labium and yellow anteclypeus.

Synthorax marked on sides with 2 broad, green metallic stripes, enclosing a citron-yellow area; beneath (lower part of metepimeron) also citron-yellow. 
Wings hyaline tinged with yellow at the base. 
Abdomen black, with S7-9 inflated; S2 with a dorsal spot; S3-5 with a middorsal yellow longitudinal line; S6 with a large oval-shaped dorsal spot. 

Anal appendages wholly black, of nearly the same shape as in M. rapida.

Tip of abdomen, dorsal

Male basal abdomen with secondary genitalia, lateral (M. rapida on the right for comparison). Note the shape of genital lobe: triangular in M. g. shanensis and rounded in rapida 

               Male head (right, M. rapida)

                      Male abdomen, dorsal (right, M. rapida)

The genus Macromidia is purely oriental in distribution and contains a dozen of species, among them 2 has been recorded in Vietnam: M. genialis and M. rapida.

A number of subspecies of M. genialis have been described. Macromidia g. genialis is known from Peninsular Malaysia, M. g. erratica from Java, Sumatra and Sarawak, M. g. shanensis from Myanmar, Thailand, Laos, Vietnam (+China?).

The first record of M. g. shanensis in Vietnam is recent (in 2011, by Karube). Its inconspicuous nature may at least in part account for the paucity of records. 

I found this male at a partially shaded, 3 meters wide rocky stream with well vegetated banks, but running through an open, heavily logged forest at the foothills of Mount Ba Vi. This suggests that this species do not require high quality habitats and therefore should be more common.

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.