Thanks for the comment - I know this one is confusing (part of the reason I posted it). However, this is not P. zelicaon. It is similar visually, but it is an insect from the desert in New Mexico where no Anise Swallowtails fly (I have personally seen no Anise Swallowtails closer than about 120 miles, but they may be in some of the higher mountains nearer). However, P. polyxenes is abundant here, and yellow form adults are rare but reliably present in the population. They tend to fly mostly among the earliest individuals to emerge (typically April and May), before the majority of individuals emerge (usually in June). These differ in wing shape, and the pattern and coloration are subtly different from P. zelicaon. However, if you compare it with P. polyxenes coloro (yellow form), you will see that it is an exact match, although that supspecies is not supposed to fly in central New Mexico either (I think we actually are at the east edge of a blend zone between asterias and coloro here). Yellow form P. polyxenes are rare in most regions but become more common as you move into the southwestern deserts and southward beyond the US (in Central and South America the Black form individuals are rare). Anise Swallowtails have a black form as well, so it can be confusing. Some would have Anise and Black Swallowtails as variants of one species, but I have seen them flying together yet distinct in many places and consider them to be separate species that occasionally hybridize.
Compare here: 'Butterflies of America'

I get so confused sometimes it isn't funny. Just when I think I'm getting proficient at this identification thing, someone like you comes along and throws me a curve ball! I appreciate it though! I am so fascinated by taxonomy and how two species can resemble each other so closely. I live in WV and spend a great deal of time tracking down our swallowtails. I have had fun learning the difference between the many dark swallowtails here that all mimic the beautiful Pipevine. I am blown away by the way two species can bear the same colors in subtly different patterns, such that you have to really look closely to see that they are not the same. I had a debate with a close friend who is an ecologist, and about to earn her PHD, over a butterfly I photographed last year. I only discovered this past month that I was correct and she was not. Fortunately, she was super humble about it and excited for me. Now I'm busted again, though. Great shots. I hope to get out west with my camera some day, so i can photograph all the incredible birds and butterflies you have that we in the East do not! Thanks!

The first time I saw one of these in my yard here (only a few years ago actually), I was pretty blown away, I never expected to see one like this here, in fact, we supposedly should NEVER see a yellow form of any of these "dill-worm" swallowtails here - but we do. In theory our only yellow swallowtails are Two-tailed Tigers and (up high in the mountains) Western Tigers, though Giants might qualify since they are yellow below. We have both Baird's and Blacks, some of the "Blacks" I rear from eggs look more like Baird's (that shouldn't happen), so I'm still pretty confused by some of these myself. Ironically, I'm hoping to take some trips east to see some of the incredible things you have there that we don't!