Asiagomphus acco (Asahina, 1996)

In 1996, Asahina described the subspecies Asiagomphus xanthenatus acco from Cuc Phuong, Ninh Binh province, Vietnam. 
Wilson (2005) subsequently recorded this latter taxon from southern China (Guangxi), but considered it unlikely that A. x. acco belonged to the nominate A. xanthenatus xanthenatus described by Williamson (in 1907, from 4 males collected in Myanmar).

In 2011, considering the fact that the anal appendages of A. xanthenatus acco are very different in style with Williamson’s original description and drawings of A. xanthenatus xanthenatus (superior appendages of X. x. acco shows a ventral spine in lateral view, inferiors are more stout and inner margin makes a “V” – and not “U” - shape, + wing venation different), Do Manh Cuong elevated acco to species status.

Here some pictures of A. xanthenatus xanthenatus from Thailand (Noppadon Makbun).

A male.

In lateral view, the synthorax bears 3 stripes : a L-shaped stripe on dorsum (mesepisternum) and 2 other broad ones on the sides.
The male abdomen is mainly black, but the basal two segments are  yellowish, and there is also an obvious yellowish spot on the top of the 9th one.

Different views of the male anal appendages :

- Dorsal view:

- Lateral view : the superior appendages shows a ventral teeth ; this is not the case of A. xanthenatus xanthenatus. One of the main reasons to elevate A. xanthenatus acco to full species rank.

- Ventral view : 
A male hovering. Blurred photo, but I like it ! It was raining, the light was poor, so the shutter speed was too low to freeze the dragonfly's motion.

I don't like very much photos "in hand", but this kind of stunning view is almost impossible in natural conditions !

The female is similar to male in colour and pattern, but abdominal segments 4 to 7 with a basal pair of yellow spots (larger on S7) - S3-8 wholly black in male.

 This female was caught in July 2103 while ovipositing along a brook in forest (at the lower slopes of Tam Dao).

Asiagomphus acco is known from northern Vietnam (Huu Lien, Lang Son, Cuc Phuong, Tam Dao…), Lak Sao in Laos and southern China, in “primary” or secondary forest streams, in lowland and sub-montane areas.

These photos were taken on the lower slopes of the Ba Vi and Tam Dao mountains, along well-shaded streams or brooks, in degraded forest.

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