Not a Bao Loc specialty - Heliogomphus chaoi

Karate (2004) described Heliogomphus chaoi from Bao Loc in Lam Dong Province in the south of Vietnam. This species is very similar in appearance to Heliogomphus selysi, a species occurring in for instance Thailand. H. chaoi differs especially in the shape of the vulvar scales of the female and the lack of prominent spines on the occipital ridge. In stead it has two small horns behind the lateral ocelli. Karube also notes that the superior appendages have a ventrolateral projection at the midpoint, to separate the male from H. selysi. Indeed, Asahina did not mention this for H. selysi, but I would love to see the holotype to verify this.

Anyway, last year I found this species to be common near Bao Loc at the type locality in early June. But a few days later I bumped into another small Heliogomphus in Gia Lai Province. Outward it was a little different in coloration. Notably, the superior appendages were more extensively white and S7 had a distinct anterior pale yellow ring. With differences between Heliogomphus species often slight, I thought it might be a different species, but checking it under the microscope I cannot but conclude the appendages and vesica spermalis are identical. If so, the slightly different coloration is likely nothing but a geographical variation. I concluded that the Gia Lai specimen is also H. chaoi. That species is therefore much more widespread than previously thought.

Heliogomphus chaoi in Bao Loc. Note it only has on S7 a pale yellow line along the dorsal carina and a lateral basal spot.

Another male at the same location

And the appendages in dorsal view

Heliogomphus chaoi at Gia Lai. Note the small yellow dorsal spot on S8 and the large anterior yellow ring on S7. But structurally it is not different.

The appendages in dorsal view, the white more extensive