A 3 hours walk in Koh Phangan

[Psyche]

You do have a point there, Sunny. The alecto colony you observed seems to have all members with the 'barb' pattern on the hindwing.
However the 'barb' pattern is not unique to J. alecto.
The elpis pics here in the blog also have the same pattern.
http://butterflycircle.blogspot.com/...8_archive.html

There are many alecto without the 'barb', eg. C&P4 pl. 36/45, Fleming L113 & here.
http://upload.wikimedia.org/wikipedi...aMFUpUnAC1.jpg

Scrutinising the valid pics (mounted specimens, pl.36/38, Fleming L112, & L122 above) I noted a couple of features that may be useful.
J. elpis : forewing discal band striae in spaces 1b & 2 generally thinner than the striae on the submarginal band; hindwing inner 3 white striae remains thin & only thickened noticeably from the 4th stria onwards.
J. alecto : forewing discal band striae often as thick as the submarginal band striae; hindwing inner 2 striae thin, but thickens from the 3rd stria onwards (sometimes from the 2nd.)
These features are not precise and varies a little bit.

I will be lying if I say I can differentiate these 2 with confidence. However, in Antonio' case I am helped by the fact it is a male.
The wingshape and the flat marginal spots on the forewing IDed it as a male.
Only the male of J. alecto have the black submarginal spot shown by its upperside.

TL Seow

[Silverstreak]

Thank you Dr. Seow for the insightful notes on the 2 species!

These discussions are very useful as a continuing learning process for me and the forum.