Is this papilio Iswara or papilio prexaspes?

[bluefin]

Shot tis fella puddling but did not manage to get an underside shot.
Is this papilio iswara or papilio prexaspes?

https://farm9.staticflickr.com/8640/16060149384_09d71b68ec_c.jpg

[Psyche]

Without the benefit of the size, field shots of these two are very confusingly similar.
However, the presence of a red-ringed tornal HW black spot is indicative of the male Papilio iswara.
The local ssp. of P. prexaspes do not have a red ring but may be partially blue-ringed.
Additionally the male P. iswara has dark androconial scales on the FW giving the outer area a smooth dark appearance.

Images of 3 species P. helenus, iswara, & prexaspes have been confused on the web.

Examples of the Male Papilio iswara iswara.
http://1.bp.blogspot.com/-IfTJBI-ShQc/UYyoHoW5rQI/AAAAAAAAHOk/T2F9cqMkr2o/s1600/DSCN5872.JPG
http://www.pbase.com/lcgoh/image/158851253

Examples of the Male Papilio prexaspes prexaspes. Note a blue-ringed tornal black spot can be seen in 2nd pix.
http://4.bp.blogspot.com/-TDGuZev9XnE/Ueqh2On8_rI/AAAAAAAAKkk/9js4K-Wnoq8/s1600/BlueHelen-KSK2.jpg
http://2.bp.blogspot.com/-2mLBMylP0WU/UZRILfaLpTI/AAAAAAAAHf0/O5YaSETNyD8/s1600/DSCN7055.JPG

This is actually a female P. prexaspes.
http://fc03.deviantart.net/fs42/f/2009/114/f/3/Papilio_iswara_iswara_by_log1t3ch.jpg

TL Seow:cheers:
.

[Commander]

It led me to initially believe it was P. prexaspes because we have rarely seen P. iswara puddling in Singapore. But after looking at various field shots, including those from set specimens, there are two more minor and consistent (but may probably be variable) characteristics in that P. prexaspes has a broader and more distinctly spatulate tail, and also on the upperside the veins are darkened more within the white patch, whereas this is usually absent in P. iswara.

[Psyche]

It led me to initially believe it was P. prexaspes because we have rarely seen P. iswara puddling in Singapore. But after looking at various field shots, including those from set specimens, there are two more minor and consistent (but may probably be variable) characteristics in that P. prexaspes has a broader and more distinctly spatulate tail, and also on the upperside the veins are darkened more within the white patch, whereas this is usually absent in P. iswara.

Concur with that. The problem is in field shots the two features are hard to determine correctly.

I too thought it was prexaspes because of all the white shadings, but the FW did not seem right.
Luckily a blow-up shows the red tornal ring spot.

TL Seow : Cheers.

[bluefin]

Thank you , Dr Seow for confirming the ID. :D