swallowtail

@Jellis Pale Swallowtail =]

You could always just go with Papilio sp. :-) I agree that it is difficult to tell. Do you have any other images, say, with the tails in it?

I agree it's a tough call. Sometimes the pale swallowtails get to looking ghostly white. That looks kinda washed out white in color, but it could be an artifact of the camera angle, etc. http://greennature.com/article1967.html