1, 4 - Pipevine Swallowtail (Battus philenor)
2, 3, 5 - Black Swallowtail (Papilio polyxenes)
As can be seen here, the black swallowtail is very similar to the toxic and bad-tasting pipevine swallowtail. It is also nearly identical to the Ozark swallowtail, and was once considered synonymous with it. However, molecular genetics have proven that the Ozark swallowtail is actually descended from a completely different line of Old World butterflies.
The similarities between the black swallowtail and the pipevine swallowtail are known as Mullerian mimicry. This form of mimicry is when two species share the same warning signals to predators and both share genuine anti-predation attributes. Both butterflies are unpalatable to predators, and if a predator eats one member of either species, it learns to avoid both of them (as they look very similar). This can also be considered a form of mutualism, as both mimic and original model benefit from this “interaction”.
Illustrations of Exotic Entomology. J. O. Westwood, from illustrations by the late Dru Drury, 1837.