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Heres a program from our archives.ambience, Caterpillars In a tropical rainforest, there's not only an incredible variety of living things, but complex networks of species which depend upon each other for their survival. I'm Jim Metzner and this is the Pulse of the Planet.Right now we're listening to an example of this interdependence. It's the highly amplified sounds of a Licenid Caterpillar of Central and South America. The caterpillar produces these sounds to attract ants, and that's where the symbiotic, or mutually beneficial relationship begins. Telling us more about it is Philip DeVries, a Tropical Field Ecologist at the University of Texas.DeVries: The symbioses between Licenid caterpillars and ants is simply that the caterpillars produce a secretion which is often high in amino acids or sugars, which is eaten by the ants and they produce this in exchange for protection against predators.So the caterpillars attract the ants with sounds, the ants ward off wasps which prey on the caterpillars, and in return, the ants get to feed on the caterpillars' secretions.DeVries: It shows you just how many symbiotic interactions are potentially out there because, if you consider one species of ant and one caterpillar, well you also have to consider the plant the caterpillar's feeding on. So you then have a plant/ant/caterpillar symbiosis. You put in wasps, predators of a variety of species, and then all the various plants that are found in the tropics. And very, very quickly on a small geographic scale, you find that the number of symbiotic interactions, the potential ones that are out there are simply staggering. So if you consider how many possible symbiotic, interdependent relationships there are in the tropics that we will never see simply because they are being cut down at a rapid rate, is really a very depressing thought.This archival program is part of our thirtieth anniversary celebration. If you want hear more, check out our podcast.