Papilio multicaudata [pusillus]
Populations of this swallowtail were assigned to the new subspecies pusillus in the Systematics publication in 1998. But research by Michael Fisher in a 2012 book on Colorado butterflies called this into question, and James Scott in 2014 argued Fisher was right, and that smaller pusillus was in fact a form and not a subspecies. The idea is that the "form" is the result of a smaller pupa due to larvae that simply aren't feeding as well as the larger populations.
At any rate, I've seen multicaudata flying in Tehachapi Mountain Park, but have only been able to get photos in Arizona.