Saturday, 23 August 2014

A third Brachydiplax for Vietnam

The genus Brachydiplax has currently 7 species. Two are known to occur widely in Vietnam. These are B. farinosa and B. chalybea. Traditionally the subspecies B. c. chalybea is said to occur in Vietnam, but in northern Vietnam the subspecies B. c. flavovittata is widespread. This is the same subspecies as in southern China. I do not know where the border between the two subspecies is, but B. c. flavovittata at least occurs south to Van Long Nature Reserve and Cuc Phuong National Park. In Cat Tien I found many of the nominate subspecies during my visit in early August. B. farinosa was also very common in Cat Tien, occurring mostly on forested pools. I had only seen it once in northern Vietnam, in Ba Be. It is certainly a lot less common than B. c. flavovittata in northern Vietnam.

Around the fish ponds in Cat Tien I noticed another Brachydiplax, stubbier and less brightly pruinose than B. farinosa and less yellow on the thorax than B. chalybea. It also missed the amber wing patches of that species. It soon became clear this was B. sobrina, a species known from India to Thailand. It had not been recorded in Vietnam to my knowledge, but was very common in Cat Tien.

I am sorry that the photos from this period are rather bad. One camera gave up completely in the constant rain and the other clouded over, as did the lenses.

A male Brachydiplax chalybea chalybea, with extensive yellow thorax

Here in hand, with deep yellow thorax and S1-3, plus amber bases to the wings

Brachydiplax sobrina, with green thorax and a tiny whitish spot on the anal triangle of the hindwing.

Dorsal view of B. sobrina, male

Male B. sobrina, showing the 7 cross veins in the front wing

Female B. sobrina

Yet another male B. sobrina

For comparison, a male B. farinosa under rainy and foggy conditions

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