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Heres a program from our archives.Several species of caterpillars found mostly in Central and South America were recently discovered to be able to produce sounds. How and why they do this might surprise you. I'm Jim Metzner and this is the Pulse of the Planet.ambience, caterpillarsWe're listening to highly amplified sounds of the Riodinid Caterpillar. The recordings were made by Philip DeVries, a Tropical Field Ecologist at the University of Texas. He began his research watching the caterpillars interact with certain species of ants.DeVries: After observing Riodinid caterpillar and ant interactions for some time, you cannot fail to notice that these caterpillars have little rods that beat up and down on the head. I became convinced, that these caterpillars were producing some sort of a sound, even though I couldn't hear it, that was somehow attracting ants. What I did was I looked at the caterpillar heads and these little rods under a scanning electron microscope, and these rods reminded me of a Latin American percussion instrument which is a long gourd with concentric grooves on it and played with a stick. I then found a very sensitive microphone and amplifier and was able to indeed show that these things did produce a call, and make recordings of them.Dr. DeVries has found that ants can protect a caterpillar from predators, and the sounds are a caterpillar's means of attracting ants to it.DeVries: The caterpillar calls are very similar to the kinds of calls that are produced by ants. When an ant produces a call, it's nest mates will come to it. In effect, the caterpillar calls are exploiting this communication system.This archival program is part of our thirtieth anniversary celebration. If you want hear more, check out our podcast.