The flush of light blue on the hind wings, denote this as being a female, I think.

The males have no blue markings, from what I have read . It was quite windy when this shot was taken but the butterfly seemed quite content, for a while at least, as I slowly approached from behind for this shot. I did not notice it until I downloaded the images that I took of this butterfly, about three or four, this is the best of...but one of its antennae seems to be missing.

Then again, it may be that it is just laid back/foreward or laid possibly to one side out of eye view, as not to be to conspicuous, don't know.
Eastern Tiger Swallowtail, Papilio glaucus ♀
EOS 20D
1/250 sec. @ f/9 ISO 400
Canon EF-S 60mm f/2.8 Macro
Midday, plenty of sun, no flash