Swallowtails - male & female ID?

[NickB]

http://www.facebook.com/photo.php?fbid= ... =1&theater
This Facebook link shows a Swallowtail pair; I saw that the male was more yellow than the female. She is much lighter in colour.
And I got to thinking of my own shots from Strumpshaw, and elsewhere, over the last few years. Re-examining them, I saw this accounted for,one morning, when all the individuals I saw were much yellower than others I had taken. I had taken it that the WB on the camera had adjusted the colours, but the colours were right!
So, from a limited sample, it does seem that the males are more yellow than the females I have seen, here and abroad.
I wondered if anyone has any observations or thoughts on this?
N

[Padfield]

That's a thought, Nick. I can't tell much from my own photos because it has taken me years to learn how to photograph yellow things anyway. It used to be a matter of luck whether a swallowtail turned out yellow or white. But all my recent hilltopping males certainly look very bright yellow. I'll keep my eyes peeled this summer.


(Hilltopping male last summer)

Guy

[David M]

Could this be because females are generally larger than males? An individual, say, 10% smaller with the same markings might possibly seem more intensely coloured due to the black coloration being 'squeezed' into a smaller space, thus making the lighter colour appear darker.

Probably talking nonsense, but just a thought all the same.

[NickB]

A couple of examples from Strumpshaw....on the same day.

Taken on the ..

..same day.