Requesting for help to ID butterfly

[Samuel T]

24566
Would like to ask for help to ID this butterfly taken at the Upper Seletar Reservoir. Appreciate guidance on the identification of this butterfly. Thanks in advance.

Regards
Samuel

[Psyche]

Female Nacaduba beroe neon.
FW without costal spot 12.

In the past the 6-line Blues posed a lot of problems because of wide variability in markings.
The angled shot caused the wingshape to be distorted in perspective.
Female 1. strongly convex FW; 2. Abdominal tip pointed ; 3. Palpi are longer in female but not noticeable because of the angle.

Nacaduba beroe.
1. Black striae or lines within bands poor or obsolete in the male, variable in the female.
2. FW postdiscal band usually broken in the middle.
3. FW costal spot 12 (lowest spot on the forward margin) ABSENT in male & female( rarely vestigial).
4. Male with wingbases darkened.
Males.
http://4.bp.blogspot.com/-yS0EBTwvFoQ/VP75FBXA8sI/AAAAAAAAUbE/3fW3Rbxdoxo/s1600/DSC_0105.JPG
https://wanderingbutterflyeffect.files.wordpress.com/2010/03/6a0100a801ee89000e0123ddf39fce860b.jpg
female (with broad markings & dark striae prominent)
http://www.butterflycircle.com/checklist/mugshots/Nacaduba%20beroe%20neon/Sunny-Chir---EOS-1D-Mark-III--13_08_2011--0115_1-copy-4.jpg

Nacaduba kurava
1. Black striae within bands poor in the male, strong in the female.
2. FW band usually intact & submarginals often large forming a regular band.
3. FW costal spot 12 always present.
Male & female.
https://c2.staticflickr.com/2/1202/1048289265_090421b1cc.jpg
https://wanderingbutterflyeffect.files.wordpress.com/2008/10/6a0100a801ee89000e00fad6b787da0005.jpg

Nacaduba berenice.
1. Dark striae within bands strong.
2. FW band usually broken in the middle.
3. FW submarginals irregularly arranged.
4. FW costal spot 12 always present.
Two males & three females.
http://2.bp.blogspot.com/-JiwYoYOjqZY/U4Hk2bI2aXI/AAAAAAAAOCQ/Zl7eiooIvDM/s1600/HFH2224+Nacaduba++berenice+icena.jpg
http://www.butterflycircle.com/checklist/mugshots/Nacaduba%20berenice%20icena/Rounded%206%20Line%20Blue%20-%20Fedrick%20Ho.jpg
http://1.bp.blogspot.com/-xFQx2YUBf8c/U5xj17_wpnI/AAAAAAAAONY/I69gkZT-jvk/s1600/HFH_2642-Nacaduba+berenice+icena.jpg
https://www.thaibutterflies.com/wp-content/uploads/2016/07/Nacaduba-calauria-400x284.jpg
http://photobucket.com/gallery/user/digimania/media/cGF0aDovbmFjdWR1YmEuanBn/?ref=

Nacaduba calauria.
1. Dark striaes within bands strong (as in berenice)
2. FW postdiscal band almost always straight & unbroken.
3. FW submarginal spots 4 & 5 sharply pointed.
4. FW costal spot 12 always present.

Pair (female on the right) & single female.
http://www.butterflycircle.com/checklist/mugshots/Nacaduba%20berenice%20icena/june%2014%20mating%20nacaduba%20berenic%20-%20Ellen%20Tan.JPG
http://www.butterflycircle.com/checklist/mugshots/Nacaduba%20calauria%20malayica/Nacaduba-calauria-malayica---2--.jpg

Note only Ionolyce helicon resembles N. beroe in having FW costal spot 12 absent in both sexes, but FW band serially broken at every vein.
Male & female.
http://www.butterflycircle.com/checklist/mugshots/Ionolyce%20helicon%20merguiana/Ionolyce-helicon-merguiana-(Pointed-Line-Blue).jpg
http://3.bp.blogspot.com/-_tCoAYTboNg/UKjT1dUbUHI/AAAAAAAAHS4/um95Y_-F404/s1600/HFH0261+Pointed+Line+Blue+(female).jpg

TL Seow: Cheers.

[Samuel T]

Thanks Dr Seow for the ID. 😍

Regards
Samuel

[atronox]

Yes, the absence of the lowest costal spot on the forewing is a diagnostic feature for this species