Wednesday, 2 July 2014

Sympetrum

On June 24 and 29, and again on July 9 I saw several Sympetrum dragonflies in Pia Oac, Cao Bang Province, both immatures and adults. Only one species had been recorded in Vietnam, S. hypomelas (see blog Sebastien). I presumed it was this species, although it had more extensive yellow markings in the wing and was much redder. However, on July 2 in Sa Pa I saw very fresh S. hypomelas and luckily also a mature male. It is actually rather different. For instance it displays almost no yellow in the wing. Later that afternoon in a different location, I found 4-5 males of Sympetrum of the same type I had seen in Pia Oac: all red and with more yellow in the wing. They also behaved differently. While the earlier male hypomelas had been sitting on leaves at a favorable spot, these males all hovered and patrolled over a small pond. Under the microscope many differences are apparent. Not only the appendages, the hamulus and the penis are different, but also as indicated the wing pattern, markings on thorax and abdomen and the frons is adorned by a black mustache absent in hypomelas. Once you know it, it is easy, as often. Now I also know that some internet photos of hypomelas that are all red, are not hypomelas at all. This species is Sympetrum speciosum, known from China, but new to Vietnam. It would be, based on the reduced yellow in the wing, S. speciosum taiwanum, but Wilson already indicated that these subspecies should be lumped and as you can see on the photos, the amount of yellow in the wing is variable. Nevertheless, it seems a higher altitude species here, both at the summit of Pia Oac and here above Sa Pa town at around 1700m asl.

Adult male Sympetrum hypomelas, showing clear contrast between yellow and red parts of thorax

Fully mature male Sympetrum speciosum, complete lack of yellow
S. hypomelas, note the thick black line along the lateral carina of the abdomen and the clear yellow tones

S. speciosum, note the lack of yellow on the body and the reduced amount of black on the abdomen, but the large amber basal patch and the reddish veins.


Photo of both species, speciosum above and hypomelas below. Note the reduced amount of yellow  in the wing of hypomelas and the reddish veins in the basal half of the wings of speciosum.

This is a possible pitfall. Immature male speciosum, but with large amounts of amber in the wing

Appendages of S. hypomelas in dorsal view. Note differences in color, amount of black and shape.

The same for Sympetrum speciosum.

Appendages of Sympetrum hypomelas in lateral view

The same for Sympetrum speciosum

The differences in hamule and genital lobe. Here the pointed hamule of S. hypomelas, with minor hook

More rounded hamule of S. speciosum, with large hook.

Frons of S. hypomelas in dorsal view, no mustache

The same for S. speciosum, frons bordered by black line

Face of S. hypomelas, with extensive yellow on postclypeus and labrum.

Bright red face of S. speciosum.

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