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A Hearing Test for Moths

Despite the fact that they don't communicate through sound, some moths have ears. Find out why on this Moment of Science.

Moths aren’t the noisiest of creatures. They actually don’t make sounds at all – unless you count thudding against a screen on a summer night. But despite the fact that they don’t communicate through sound, some moths have ears.

Why would a moth have ears, if not to converse with other moths? Ears allow moths to listen for the approach of one of their greatest predators – moth-eating bats.

Sound Waves

When bats hunt at night, they use sonar, or sound waves, to find their prey. The sound waves bats send out are too high-pitched for us to hear, but they’re heard loud and clear by moths with ears.

Bats are incredibly adept at avoiding even tiny obstacles like twigs – and at honing in on prey – by listening to the echoes that bounce back from these solid objects. Moths with ears can detect this skillful predator even from a distance – and try to get away. Moths without ears, on the other hand, are more likely to become dinner.

Hunting

Here’s how you can conduct a test to see whether moths in your neighborhood have ears. The only equipment you’ll need is a set of keys. After you’ve spotted some moths fluttering around a light or screen, jangle the keys nearby. In addition to the jangling, the keys will emit high-pitched sound you can’t hear – much like the sounds predator bats make when they’re hunting.

Moths with ears will dive away from the sound, as if to escape a hungry bat. Moths without ears won’t react at all. But at least this time, they won’t be dinner.

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