The Ozark Swallowtail ("Papilio joanae") and the Black Swallowtail were once thought to be the same species. Felix Sperling did an analysis of the Ozark Swallowtail's DNA. He suggested that even though the Ozark Swallowtail looks exactly like the Black Swallowtail, it is actually more closely related to the Old World Swallowtail ("Papilio machaon").