The Defenses of Butterflies: Aposematic Signals

Another method of avoiding predation seems very opposite to hiding. Bright colors, strong aromas, and conspicuous noises are warning signals used by animals to ward away prey. By showing themselves so obviously and sometimes even calling attention to themselves, these animals show predators that it is best to avoid a meal made by something so conspicuous. Aposematic signals (from apo meaning away and sematic meaning sign or meaning) warn predators that there is something about the intended prey animal that will likely sicken the predator. Warning colors and other aposematic signals are often associated with toxicity or unpalatability. These signals are beneficial to both the predator and the prey as the predator avoids a potentially harmful meal and they prey gets to keep on keeping on.

Aposematic signals are powerful warning devices. In some areas species that are aposematic come to resemble each other in a mimicry complex known as Müllarian mimicry. This is where two species that are both noxious to predators have similar warning colors and patterns to help reinforce their unpalatability to their predators. A predator that eats a distasteful Monarch butterfly will likely avoid the similar looking and also noxious Queen butterfly when looking for a future meal.

Another type of mimicry comes from species that are afforded protection by displaying aposematic signals of noxious species but are themselves harmless. This complex is called Batsian mimicry and it involves a model species that is known to be distasteful. Mimic species that display similar aposematic signals will be passed over by predators that have already had a run-in with the noxious model species. Here in Tampa Bay the female of the Tiger Swallowtail often does not resemble its flamboyant bright yellows mate and instead has a black overall coloring with a dusting of blue scales on the lower wing. To a predator, this distinctly looks like a noxious Pipevine Swallowtail and may help the female Tiger Swallowtail to live long enough to lay eggs and ensure another generation.