Western Giant Swallowtail

Thanks, thought it might be. My mother-in-law has been raising these plants she calls ruda, a strong-scented herb. Had these black & white tinky worms that she was killing. I finally said, hang on, those might be caterpillars for something interesting. ID'ed them as Giant Swallowtails and let them live. They strip the plants but then the hatch. We have several we're waiting for and 6 - 8 caterpillars.

Yes, a Giant Swallowtail. The different appearance is most likely because it has just hatched. Must have been a great thing to witness.