Saturday, 19 April 2014

Nihonogomphus schorri

On April 13 I was birding in Xuan Son National Park. Xuan Son is a dragonfly paradise, but it was still early in the season. When the sun came out for a bit in the late morning I noticed to my excitement several gomphids along the concrete road in the forest. I was able to first catch a female ovipositing on the wet concrete and later a male patrolling to same place. Several other males and females were observed (at least 10) and one male was photographed as it sat on a plant by the side of the main stream where a small stream runs into it, close to the first stone bridge.

Because of the thorax pattern of the males, with greenish-yellow humeral stripes, and the yellow-orange appendages, I thought these might be Amphigomphus nakamurai (see my blog entry on that species), but in hand the lower appendages of the male were clearly different. At home the general structure of the appendages pointed straight to Nihonogomphus, a genus with 19 species distributed in eastern Asia. The most recently described species is Nihonogomphus schorri, Do & Karube 2011. Luckily I had access to that paper, as the pattern (with broad lateral black stripe separating metepisternum from metepimeron) on the synthorax did not fit most species. Close inspection of distal segment of penile organ and of the appendages helped to clinch the ID. In fact Nihonogomphus schorri is until now only known from Huu Lien Nature Reserve in Lang Son Province, where it was collected in May and June (2009 and 2008 respectively). This is 160 km from Xuan Son National Park in Phu Tho Province as the crow flies.

Male Nihonogomphus schorri perched by stream
Different male N. schorri

Showing the greenish antehumeral stripes

The female N. schorri

Nihonogomphus schorri, female top and male bottom. The male is 60 mm.

Facial pattern of live female
Facial pattern of male after preservation

Characteristic penile organ of male, separated only one third of length of segment and with long flagellar processes

Male appendages in dorsal view
Male appendages in lateral view
Male appendages in ventral view

Female appendages in dorsal view

Female appendages in (almost) lateral view

Lateral view of male apparatus S1-2

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