nature is awful

The parasitoid wasp Glyptapanteles lays its eggs, about 80 at a time, in young geometrid caterpillars. The eggs hatch and the larvae feed on the caterpillar's body fluids. When they are fully developed, they eat through the caterpillar's skin, attach themselves to a nearby branch or leaf and wrap themselves up in a cocoon.

The caterpillar, still alive, behaves as though controlled by the cocooned larvae. Instead of going about its usual daily business, it stands arched over the cocoons without moving away or feeding.

The caterpillar – now effectively a zombie – stays alive until the adult wasps hatch.

Janssen and colleagues at the Brazilian Federal University of Viçosa noticed that when they moved a paintbrush towards parasitised caterpillars, the insects would thrash about, apparently in an attempt to protect the cocoons.