For a moth, bats are the terror of the night sky. Bats eat flying insects that they detect in the dark using a kind of biological sonar. Hunting bats emit pulses of very high frequency sound, beyond the range of human hearing. If the sound pulses reflect off a flying insect, the bat can hear the returning echoes of the pulses. They can use these echoes to detect, intercept, and catch a flying insect.
Biologists have found that evolution has provided moths with a variety of ways to evade bat sonar. Some have noise-canceling wings that don’t reflect the bat’s sound pulses. Others can hear the bat’s pulses and take evasive action. Some emit their own pulses to jam the bat’s sonar, or warn that they are bad tasting or poisonous.
In 2021 a team of biologists from Great Britain reported that they had discovered a new feature that helps some large silkmoths avoid capture by bats. The forewing tips of these moths are curiously rippled and folded. The researchers found that the wingtip structures are powerful sound reflectors. When sounds such as the bat’s sonar pulses strike the moth’s wingtips from almost any angle, they are reflected back to their source. This allows the wingtips to act as acoustic decoys.
The researchers found that the sound reflections cause the bat to target the wingtips of the moth rather than its body, allowing the moth to escape the encounter with its life. Some related species have similar sound reflectors on the tips of their hindwings, which serve the same function. The research helps biologists better understand the evolution of the relationships between predators and their prey.
