September 29 I went to Tam Dao. Like everywhere, the number of stream dragonflies has fallen drastically and it was hard work to find something. At last I located two dark Euphaea specimen. Now, I already did an entry on Euphaea, but it is in for some revision, I am afraid. The first specimen today was rather straightforward and in the hand showed extensive blueish shine to the underwing. This is also very visible in the photos taken with flash. The second was very brownish and I could not see any blue shine, nor is this visible on the photos I took, but in hand it showed the same blue luster to the underside of the hindwing. Nevertheless, I could have sworn...
So when I got home I had a look at the one specimen I had collected earlier this year. I also took the article by Van Tol and Rozendaal (1995) and compared. Now I was in for a shock. Although I had simplified matters before, focusing on the shine to the wing and the amount of translucent tip to the hindwing, in fact Van Tol & Rozendaal give a few straightforward structural differences between E. guerini and E. masoni. Guerini has a tuft of long hairs at the base of S9 and has ridges on the lateral corners of the vesicle. Well, none of the specimens in the photos has hairs on S9 and the specimen in my collection certainly does not, nor does is have the ridges on the vesicle. So, irrespective the blueish shine, it is E. masoni. That means that for the time being both the specimens from Tam Dao and those from Ba Be have to be registered as E. masoni. Next year I will study the Ba Be specimens in hand too.
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| The brown-looking specimen, Euphaea masoni, male |
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| Different male, with flash clear blue shine |
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| Ventro-lateral view of S2, showing smooth vesicle |
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| Ventral view of vesicle, very smooth |
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| S9 without a trace of hair |
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