Asiagomphus acco - a great species

Asiagomphus xanthenatus acco was described as a subspecies of A. xanthenatus by Asahina, but the rather different appendages prompted its elevation to specific status (Do Manh Cuong, and see also Karube). I saw it once last year, in Ba Be, towards the end of July. I was very happy to renew my acquaintance with it, when on May 18 I did not see one, not two, but many at about 300m asl in Tay Thien (Tam Dao). Here a few shots.

The male of Asiagomphus acco, with extensive yellow S1-2 and black S3-8.

Dorsal view of appendages

And lateral, note the tooth halfway on the venter of the superior appendage

And in ventral view