Can Caterpillars Hear?

One of the High Counselors in our Stake that I was talking to recently was a science teacher at a High School nearby and is now studying bugs. One of the things he studied was whether caterpillars could hear any noises. It didn't look that caterpillars had ears, so he decided to do a test. He had a little sound generator and would test different frequencies and see if he could notice any reaction from the caterpillars. For most frequencies there wasn't any reaction, but there was a narrow band of frequencies that agitated the caterpillars quite a bit. The interesting thing is that these frequencies were very low. He thought about this and tested different things in nature that make that low frequency, and he found that that frequency is created when birds flap their wings! Makes sense, doesn't it? A caterpillar can hear when a bird is flying overhead and duck under a leaf or something.

So now he knew that they could hear -- the next part was to determine how they could hear.  One of his students or a college of his noticed that the little hairs on the caterpillar's back are perfectly spaced. They also noticed that the spacing was just the right length to be able to pick up those low frequencies. They hypothesized that the hairs on the caterpillar's back acted like the little hairs in our ear, making the caterpillar act like a walking ear drum. To test this out, they shaved the hairs off a caterpillar and noticed that it didn't react anymore to the low frequency sound. This is so cool!