Tuesday, 20 May 2014

The Heliogomphus enigma

When exploring around Nam Bung earlier this month I saw quite a few Heliogomphids that I identified as Heliogomphus scorpio based on the shape of the (all black) appendages. In fact, Sebastien Delonglee also had identified this species as such (see also his blog). However, when checking streams low on the Tam Dao range last weekend I noticed that the appendages of the Heliogomphids there seemed different. Interestingly, Sebastien during his visit to Xuan Son noticed the same. I asked Dr. Karube and he told me he was aware of two different types of Heliogomphus, but that apart from the appendages the species were very much alike. Nevertheless, we all agree that these actually are two different species. The identity of the Yen Bai type, in fact that also occurs around Tam Dao, is unknown for the moment. The species I encountered at Tam Dao now (and Sebastien at Xuan Son) is the real Heliogomphus scorpio.

The Yen Bai Heliogomphus, very yellow and long appendages
The Tam Dao Heliogomphus scorpio, much paler and different appendages
The appendages in dorsal view of the unidentified species

Those of the Tam Dao Heliogomphus scorpio. Both superior and inferior appendages are differently shaped

The unidentified species, note the double tooth on the basal process

The same for Heliogomphus scorpio, a much longer process, but no double tooth

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