Narrator: This is Science Today. The tobacco hornworm, a major agricultural pest, is an insect Goliath -- a fat bug three inches long.

Beckage: Because these are very large caterpillars, a single caterpillar can destroy many tomato leaves within a single day due to their large size. They're like eating machines.

Narrator: Entomologist Nancy Beckage of the University of California, Riverside is studying the David that brings the hornworm down -- a tiny parasitic wasp that injects its eggs into the caterpillar. The eggs hatch and the larvae feed on the caterpillar from within, killing it.

Beckage: How this happens is that many parasites are injected into a single host. So in this case it's called a gregarious parasite, meaning that it likes to have its buddies along, and so we have several hundred parasites developing within a single host.

Narrator: In the process, the caterpillar stops eating. Beckage is studying how and why, in hopes that the wasp will offer a natural, pesticide-free method for controlling a major pest. For Science Today, I'm Steve Tokar.