Thursday, 26 September 2013
On August 24 we were checking a stream just outside Tam Dao National Park near Tay Thien. A blueish damsel caught the attention of Kameliya and she called me over. It was something different and still vaguely familiar. A slender damsel with rather longish abdomen. Checking it at home it had to be an Aciagrion species. That was a surprise, as I did not know these occurred in Viet Nam, although in retrospect, it was not that strange, as they are known from neighboring countries like Thailand and China. Oleg Kosterin was kind enough to give his views on it and then I knew why it had looked familiar: I knew it from Japan. It was Aciagrion migratum. Basically the bifid superior appendages indicate closely related A. tillyardi or A. migratum, but the shape of the postocular markings (more of a stripe in migratum and more two spots with a thin line between in tillyardi (thanks Oleg!) helps clinch the ID. Up to now I have only seen it once.