This is rather difficult.
The upperside with the pale dusting suggest N. berenice.
The underside suggest N. kurava.
This need further checking.
Possibly hybrid between the two.
ID is based on the upperside in the male so this is most likely a form of N. berenice.
Nacaduba beroe male.
Dark striae within bands mostly obsolete.
Always without a spot above the midcell band, at the costa.
FW postdiscal band usually broken in the middle.
Upperside deeper violet blue.
https://www.ifoundbutterflies.org/me...949da7a9-1.jpg
https://www.ifoundbutterflies.org/me...95727b2f-1.jpg
http://www.butterflycircle.com/check...lt_male_01.jpg
Nacaduba kurava. male.
Dark striae often weak in the mae.
Submarginal spots large rounded margins.
FW postdiscal band almost always straight & unbroken
Upperside deeper blue with a see-thru effect.
https://en.wikipedia.org/wiki/Nacadu...iMFUpUnAC1.jpg
http://www.butterflycircle.com/check...ue-SunnyC2.JPG
Nacaduba berenice male.
Dark striae within bands well-developed.
Submarginal spots irregular , may be narrow or broad.
FW postdiscal band typically broken in the middle or crooked.
Upperside lavende blue with a frosted appearance.
http://www.butterflycircle.com/check..._male_800x.jpg
https://2.bp.blogspot.com/-ceLml99O5...u/DSC_0187.JPG
http://www.butterflycircle.com/check...obby%20Mun.jpg
https://commons.wikimedia.org/wiki/F...e_(5)_male.jpg
TL Seow: Cheers.
Thank you, sir. I was thinking N. beroe gythion. N. berenice may not be found in east Nepal,and there seem to be pics of N. beroe on IFB with spot above midcell band. Matches with some example of N. berenice akaba which is N. beroe gythion now.
Sajan KC
The absence of the costal spot above the mid-cell band is an almost certainty in the ID of N. beroe.
There are a number of errors in IFB.
N. berenice is a common species ranging from India to Australia.
Here are examples of the male N. beroe.
N. beroe gythion.
India.
https://www.ifoundbutterflies.org/me...949da7a9-1.jpg
https://www.ifoundbutterflies.org/me...148de93d-1.jpg
Thailand.
https://thaibutterflies.com/wp-conte...duba-beroe.jpg
https://species.wikimedia.org/wiki/N...onMUpUnAC1.jpg
N. beroe neon.
P. Malaysia.
http://4.bp.blogspot.com/-yS0EBTwvFo...0/DSC_0105.JPG
Singapore.
https://wanderingbutterflyeffect.fil...f39fce860b.jpg
N. beroe asakusa. Taiwan.
https://www.tbn.org.tw/taxa/69f43c68...4-2c1e21dbfdce
TL Seow: Cheers
PS[I] . Nacaduba berenice akaba Type location Borneo. There is no change in the status of this. The Bornean ssp of N. beroe is neon the same as in Sumatra, Malaya & Singapore.
Correction.
The upperside is too dark to be N. berenice.
The only explanation is there are two butterflies.
The upperside is that of N. beroe.
The underside shot is that of N. kurava.
TL Seow: Cheers.
No, sir. It's very much a single individual. No doubt on that. Perhaps not all kurava individuals are transparent. Or perhaps it's a hybrid.
Sajan KC
Agreed. The underside is fairly typical for N. kurava.
Marked variations either as natural aberration or from gene introgression can occur.
In the old days collectors often keep dozens of specimens of a single species.
Invariably, a few would be found to be abnormally marked.
TL Seow: Cheers.
Agreed. It is a male Erionota thrax.
The two can be quite confusing, in S.E. Asia where the difference is less marked.
It is advisable to ID the sex/gender first as this helps in the ID.
Male have the antennal club about 3/4 white.
Female havs the antennal club about 1/2 white.
From the 2nd pic it is a male.
Erionota thrax.
Males.
https://www.ifoundbutterflies.org/me...c58ada48-1.jpg
https://www.ifoundbutterflies.org/me...553af268-1.jpg
Females.
https://www.ifoundbutterflies.org/me...unte_ag436.jpg
https://www.ifoundbutterflies.org/me...f763c7c9-1.jpg
Erionota torus.
Males.
https://www.ifoundbutterflies.org/me...2e3adf8f-1.jpg
https://www.ifoundbutterflies.org/me...f86b3ed0-1.jpg
Females.
https://www.ifoundbutterflies.org/me...943df378-1.jpg
https://www.ifoundbutterflies.org/me...43351446-1.jpg
TL Seow: Cheers.