Continental Asian Mnais taxa are still poorly known and are notoriously difficult to elucidate. Mnais taxonomy remain a major puzzle because of the considerable variation within the species. Hämäläinen (2004) even wrote : “There is scarcely any odonate genus more difficult to work with taxonomically than Mnais”.
It is difficult to impossible to identify Mnais species from photos, even from “in hand” shots, and I certainly wouldn’t dare try to do it here. A too perilous exercice! The structure of penile organ is one of the most important key features.
Mnais species are spring insects. I discovered that in mid-March 2013, when I bumped into some immature individuals in Hoa Binh Province, during a birding trip, at a place previously visited many times. Two monts later, at Tam Dao, I was happy to see a lone fully mature male.
I did not collect any specimens, so the specific identification is impossible. I am even not certain that the Mnais of these 2 localities belong to the same species. I will try to resolve this identification problem in 2014.
With its beautiful orange coloured wings, this is one of the most stunning damselflies I have seen.
Photos taken at Hoa Binh Province
(alt. c. 500m a.s.l., 16th March 2013)
These young males haven't yet developed the pruinescence on the thorax and head. I saw 2 types of males : hyaline-winged and orange-winged, the latter more abundant. I only managed to photograph the orange-winged form.
Photos taken at Tam Dao, Vinh Phuc Province
(alt. c. 150m a.s.l., 10th May 2013)
This is a mature male. It is densely powdered with white on the frons, dorsum of synthorax, metepimeron, basal parts of legs, sides of the first 2 segments as well as the last 3 segments of abdomen.
The general wing shape seems different than that of the young males observed at Hoa Binh : broader, more roundly tipped.
To my knowledge, only two Mnais species were recognized in Vietnam, viz. M. mneme Ris, 1916 and M. andersoni McLachlan, 1873.
A careful check of the penile organe will separate them readily. The terminal divided process of penile organ, narrowly petiolated, is T-shaped in mneme, Y-shaped in andersoni.
Remarks : In 1974-1976 Asahina published a series of papers titled "A revisional study of the genus Mnais". This study, split into eight parts published in two journals, is, at least for the continental Asian taxa, an introduction to the immense problems of Mnais taxonomy rather than a definitive revision of the genus (Hämäläinen, 2004).
