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Papilio troilus
The underside of the wing is missing an orange spot, which would actually identify this as a Spicebush Swallowtail. They are almost identical on the underside. Here are images to help compare:
Black Swallowtail: http://bugguide.net/node/view/30995
Spicebush Swallowtail: http://bugguide.net/node/view/29412