Moths are a mainstay food source for bats, which use echolocation to hunt their prey. Scientists are studying how moths have evolved passive defenses over millions of years to resist their primary predators. While some moths have evolved ears that detect the ultrasonic calls of bats, many types of moths remain deaf. In those moths, researchers have found that the insects developed types of ‘stealth coating’ that serve as acoustic camouflage to evade hungry bats.