Watch: The Zombie Caterpillar

This is a sneak peak from our documentary  Invasion of the Brain Snatchers.

The white creatures you're looking at are parasitic wasp larvae that have brainwashed this tobacco hornworm.

"Somehow these wasps, while living inside the caterpillar, have managed to hijack some of the regulatory mechanisms to turn off feeding. They basically managed to manipulate the brain of the caterpillar so that it no longer eats. And that's very impressive because that is the major behaviour of this animal," says Dalhousie University's Dr. Shelley Adamo.

But there's even more mind manipulation going on inside this caterpillar.

"It's been transformed into a wasp bodyguard. And what it's going to do, this caterpillar, is to whip around and protect those wasps from anything that's going to come and potentially damage those cocoons. Its whole existence now revolves around protecting those parasites that are sitting on its back," says Dr. Adamo.

As the adult parasitic wasps emerge from their cocoons and leave their dying host behind, Dr. Adamo suggests that we get over the ick factor. "When you see these wasp larvae wiggling out of their host it just looks so disgusting. But you have to appreciate, first of all - this is how the wasp make their living. But also it's just a marvel of evolution. When you think about how these two species have co-existed for a very, very long time and the wasps have learned tricks on how to exploit the physiology of its host to its own advantage and that is amazing and a wonderful example of how animals can co-evolve."

To learn more about parasites that manipulate their hosts, watch Invasion of the Brain Snatchers on CBC's The Nature of Things with David Suzuki.