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.
|The brown-looking specimen, Euphaea masoni, male|
|Different male, with flash clear blue shine|
|Ventro-lateral view of S2, showing smooth vesicle|
|Ventral view of vesicle, very smooth|
|S9 without a trace of hair|