Heliogomphus scorpio (Ris, 1912)

 2 males Heliogomphus scorpio on May 15, 2014, at Xuân Son  

I spotted this elegant Gomphid for the first time in May 2014, resting on leaves or rocks along forested streams. 

During 2 years, I misidentified it with another Heliogomphus, apparently undescribed, found at Tam Dao, until I bumped into the true scorpio (at Xuân Son).

Some characteristics : almost entirely dark abdomen with a pale ring at the base of the 7th segment, S7-10 broadened, face largely black with a whitish stripe on frons, synthorax with a dorsal stripe connected to the collar stripe to form a 7-shaped mark, superior antehumeral spot and.... terrifically gruesome appendages!
 

Heliogomphus scorpio male on May 23, 2014 at Tam Dao (alt. ca 300m)

Male in hand, from Tam Dao

Abdomen tip, dorsal view : superiors lyrate in shape,  convergent, curled strongly, 

with a long, strong  basolateral spine

Lateral and ventral views of caudal appendages : inferiors stout with two branches very widely divaricate, almost in line.

Compare with the appendages of a Heliogomphus sp. (yet to be described?) found at Tam Dao and Ba Vi :

Lateral spine of superior appendages much shorter, with 2 tooth at apex.

Abdomen tip of Heliogomphus sp. (left) and H. scorpio

Heliogomphus scorpio (left) and Heliogomphus sp. caught at the same stream at Tây Thiên (Tam Dao). Very similar pattern but apparently Heliogomphus sp. more yellow

The very pale female Heliogomphus below is likely to be scorpio, but without absolute certainty. Photographed at Tây Thiên (Tam Dao) where the 2 species share the same habitat.

I took these pictures at the lower slopes of Tam Dao and at Xuân Son National Parks, along forested streams. I spotted Heliogomphus scorpio and Heliogomphus sp. sharing the same portion of stream at Tây Thiên (Tam Dao) on May 2014.

Heliogomphus scorpio is known from southern and southeastern China, Laos and northern Vietnam, and found at forest streams in both lowland and montane areas.

Other Heliogomphus species known in Vietnam (that I am aware of): H. retroflexus (in the North), H. chaoi (South, type locality is Lam Dong Province) and H. selysi.