This is a crazy story that sounds more like science fiction than science. There's a species of "voodoo" wasp that lays its eggs inside a certain kind of caterpillar. The eggs turn into larvae that feed off the caterpillar for a few days. Then they burst out of the caterpillar's skin, climb a nearby twig or branch, and transform into their chrysalis stage.
Here's where it gets weird (well, weirder). After the larvae hatch, the host caterpillar becomes a zombie, compelled through some unknown process to watch over the chrysalises and protect them from predators. Then when the chrysalises open to release the new wasps, the catarpillar dies. How the catarpillar "knows" that it's time to die is also unknown.
Here's a link to the article on the New Scientist site, with video of a zombie caterpillar.
Zombie Caterpillars Controlled by Voodoo Wasps