Transcript:

music; ambience stridulating caterpillar

These highly amplified sounds are produced by a caterpillar. They’re meant to be heard at close range by ants. Now, why do you think an ant would respond to a call from a caterpillar? Welcome to Pulse of the Planet’s Science Diaries, a glimpse of the world of science from the inside.

“Okay, what you’re hearing right now is the caterpillar itself making sounds; it’s called stridulating.”

Grant Gentry is an ecologist at Samford University who studies caterpillars in Central America. He says that this Riodinid is one of the few kinds of caterpillars capable of producing sounds.

“It’s got some ridges on the back of its head capsule, which is hard, like your fingernail. And there’s these two rods on a collar right behind that, that lay on top of the head capsule. And it can move its head back and forth. And the rods scraping over those ridges makes a very distinctive sound. These caterpillars have evolved so that sound sounds exactly like an ant in distress. So when this caterpillar is attacked by an enemy, it makes this sound and the ants that are hanging around come to its aid. They react like it’s an ant. Now the ants are hanging around because in addition to this ability to make sound, the caterpillar also has nectar glands built in to its body. So it keeps the ants nearby by giving them little bribes. It bribes them with nectar, with food. And they kind of hang around, and then protect it if something nasty shows up, like a wasp.”

Our special thanks to Dr. Phillip de Vries.

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Pulse of the Planet’s Science Diaries are made possible by the National Science Foundation. I’m Jim Metzner.