Gynacantha demeter, an addition to the Vietnamese list*

* This entry was published originally as Gynacantha dohrni. After discussion with Oleg Kosterin, I agreed that this should be rectified and published here as G. demeter. It took a while to get round to doing so. The below text is adjusted (on December 24, 2019) in places in line with this new insight.

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. They 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 demeter Riss, 1911, a species known from for instance Singapore, Thailand and Cambodia, but as yet not from Vietnam. This species is very close in appearance to Gynacantha dohrni Krueger, 1899. The characteristics of my specimens (superiors 6 mm long, diverging tips) fit G. demeter very well, and S2 is also less wide than expected for G. dohrni. With G. demeter also recorded from Thailand and nearby Cambodia, it is not a surprise to find it at Cat Tien.

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

Likewise, the female of Gynacantha demeter

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