Birds seem to be drawn to the spindly sections, which may easily break off, allowing them to flee.
“Tails” on some butterfly wings may be more than just pretty decorations. According to a study, they’re also survival tools.Researchers report in the Proceedings of the Royal Society B on May 25 that the tails appear to draw the attention of attacking birds, diverting them away from the butterfly’s more critical body sections. The discovery could explain why wing tails have evolved independently several times in various moth and butterfly species.
Ariane Chotard of the National Museum of Natural History in Paris analyzes the wings of swallowtail butterflies, which belong to the Papilionidae family, which includes hundreds of species. Chotard notes that “a number of these butterflies have tails.” “And we don’t have a clue why.”
Predators attack some butterfly species with fake head or eyespot patterns on their wings more frequently in such areas. Chotard and her coworkers wondered if tails were a target as well.
The researchers collected 138 sail swallowtail butterflies (Iphiclides podalirius) from the wild in Ariege, France, in the summer of 2020. Sail swallowtails, which can be found all over Eurasia, have two prominent black tails on their hind wings with blue and orange spotting, which contrast sharply with the rest of the insects’ yellow, striped appearance.
Sixty-five percent of the swallowtails gathered had injured wings, and all of them had at least one tail damaged.
The researchers put wild-caught songbirds called great tits (Parus major) in cages to test their theory. The birds were then shown mock butterflies produced by pasting real swallowtail wings to a false body made of small pieces of black cardboard, and the researchers recorded the birds attacking the fake insects.
The hind wings were hit 43 times out of 59 times, or about 73 percent of the time. More than any other body region on the dummies, 23 percent of the strikes hit both a tail and colored spots on the upper portion of a hind wing at the same time.Chotard and her colleagues also calculated the amount of force required to tear different parts of the swallowtail wing. They discovered that the vein of the hind wing tail is the most delicate region of the wing, and that it is most likely to break off in the beak of a hungry bird.
The findings show that swallowtail tails deflect attacks away from the butterfly’s vulnerable body, redirecting them to brittle extensions that readily break off, allowing the insect to flee, according to the researchers. This tactic could be analogous to how certain lizards sacrifice their detachable tails to hungry predators.Chotard says it’s unknown if losing one or two tails has any consequences. “You made it, you evaded a predator, but there may be a cost, and your flight will be slower.”
Echolocating bats can be deflected by some moth tails . “Now we have evidence that butterfly tails provide a similar benefit against visual predators,” says Juliette Rubin, an evolutionary biologist at the University of Florida in Gainesville who was not involved in the research.