The striking black-and-yellow pattern of the swallowtail butterfly serves as a survival mechanism. The bright colors act as a classic warning coloration, designed to instinctively deter potential predators such as birds. The red eye spots are also intended to confuse predators.
The black background of the wings helps the butterflies absorb heat more efficiently when they are basking in the sun. This allows them to warm their flight muscles on cooler mornings.