Battus philenor (Pipevine Swallowtail)

I finally lucked out and found a late instar Battus philenor. This guy was walking along a trail, presumably looking for a good spot to pupate. I persuaded it to walk on a stick for a brief period to pose for a couple of portraits and then left it where I found it.

The orange and black coloration exhibited by Battus philenor are considered aposematic coloration, warning would-be predators of their distasteful nature. This distastefulness is due to the sequestering of aristolochic acids that are found in their host plants of the Aristolochia genus.
A wee bit of gentle prodding coaxed the cat to evert its osmeterium, a defensive organ that is used to dissuade predators and/or parasitoids.