The long, trailing structures on some moths’ wings play a crucial role in protecting them from bat predation, a point supported by research from the Florida Museum of Natural History.
Many moths and some nocturnal butterflies sport unusually shaped wings, with slender tails extending along their backs. While their beauty is evident to onlookers, scientists have long sought to understand what practical advantage these features confer. Recent work points to a functional use: the tails act like ultrasonic reflectors. When bats, relying on echolocation, target these moths, the tails deflect the sonar signal, causing the predator to zero in on a bright, reflectively amplified area and sometimes tear away a portion of the wing. In turn, the butterfly or moth can survive such encounters while the wing damage is sustained.
In a series of controlled tests, Juliet Rubin and her colleagues explored whether this tail design is always advantageous or if other explanations might exist. The Saturnia moon moth, also known as the moon moth, featured in the experiments. Researchers observed notable growth at the wing tips, suggesting additional functional dynamics beyond simple intimidation or signaling. The team aimed to determine whether the tailed wings might influence mating outcomes. In an aviary study, it appeared that females did not show a strong preference for males with altered tails; roughly equal numbers of females chose males with normal wings and those with rear portions removed. This finding challenges the hypothesis that the tails primarily evolved to improve mating success for insemination.
Further investigations considered whether the tail structures might affect daytime survival when predators like birds, which lack echolocation, hunt. To simulate real prey while controlling variables, scientists used mealworm models fashioned to resemble moon moth bodies and fitted some with intact rear tails while others were tail-less. These puppet moths were placed among branches and leaves, and Carolina wrens were introduced to observe predation patterns. The birds fed on both tail-bearing and tail-less models at similar rates, indicating that the tail feature does not significantly alter daytime predation risk for these moths.
Collectively, these results undermine competing theories about the evolutionary origin of the tail-like wing extensions. The findings do not support the idea that the tails arose to court or inseminate mates, nor do they reveal obvious adverse side effects under natural predation. The tail structures appear to function in a way that minimizes risk from echolocating bats while not imposing a clear cost in other ecological contexts. In short, the empirical studies help clarify the adaptive value of this striking wing morphology and point to a complex, multi from function rather than a single, simple purpose [Citations: Florida Museum of Natural History].