"Underside of hind wing brilliant metallic blue with orange and black spots" [1]. More precisely, the spots, usually seven of them, have orange centers with predominantly black circumference. However, the surroundings of an orange spot rarely amount to a fully black annulus, and are typically dappled with a white obstruction. On the fifth spot from anterior to posterior, you will often find not just one, but two dabs of white. This description can be checked against numerous digital photographs, and even against video evidence [2-3], but the most fun is to go out in nature and find one yourself [4]! Or if you haven't any in your region, maybe check the history books going back as far as the late 1700s [5]. Most of the more recent articles I could find were more about chemical defence, than chemical morphogenesis. The later was an interest of Alan Turing in the years before his untimely death. These days, not only can we take more and more data integrals, it should also be easier to work out the theory using all sorts of computer algorithms. Any thoughts? Cheers --Brad [1] https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=3106&context=jaas [2] https://www.butterfliesandmoths.org/species/Battus-philenor [3] https://www.youtube.com/watch?v=u2cE86AA1q0&app=desktop [4] https://0x0.st/zO7w.JPG [5] http://entnemdept.ufl.edu/creatures/bfly/pipevine_swallowtail.htm