Tuesday, 25 November 2014

Gynacantha dohrni, an addition to the Vietnamese list

During our visit to Cat Tien National Park we saw many smallish Gynacantha of which the males would take up hover stations in the lodge garden or along shallow streams in the forest or also along the roads. I was able to catch several males and females at various locations. The were characterized by a very small and constricted epiproct, largely straight superior appendages with somewhat diverging tips and a median basal hump, a rather broad S1-2 with huge blue colored auricles and a yellow face with a dark anterior edge to the postfrons. The hindwings were 41-42 mm, the total body length around 61 mm. It took a bit of searching, but in the end I was able to identify it as Gynacantha dohrni, a species known from for instance Singapore and Malaysia, but as far as I know no closer than that to Vietnam. It had originally been described from Borneo by Krueger (1899), where another closely related species, Gynacantha demeter was also described in 1911 by Ris. Although that species has several characteristics (superiors 6 mm long, diverging tips) that fit the specimens from Cat Tien very well, there is a lot of doubt these two species are actually distinct. Many photos of G. dohrni that I was able to find show similar diverging tips, for instance. Ris also mentions some differences in the color of the wing base, but this too seems somewhat variable. For the moment I therefore will conclude that the specimens from Cat Tien are the same species as that occurring in Singapore and Malaysia.

Male of Gynacantha dohrni. Note the straight superior appendages and tiny epiproct and typical  coloration of S1-3.

Likewise, the female of Gynacantha dohrni
The appendages of the male, note the median basal notch and diverging tips
Close-up of the constricted and very small epiproct
Frons of the male with distinct dark anterior margin, but indistinct T-stem

Close-up of the pattern of S2, with very large blue auricles
The apical segments of the female, with exposed ovipositor

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