The Caterpillar and the Parasitic Wasp: James Cameron's "Aliens" comes to life

This is one of the most outrageous and bizarre examples of parasitism out there.  The wasp lays it's eggs inside the body of the caterpillar.  After the wasp larvae spend time maturing in the body of the caterpillar, the eat their way out, like something out of Aliens.  After the wasp larvae hatch, they begin to form a cocoon with the help of the caterpillar.  Assuming the caterpillar survives the wounds sustained by the larvae hatching, the caterpillar uses it's silk to build the wasps' cocoon.  The caterpillar then will defend the cocoon until it starves to death.

A caterpillar covered in wasp larvae.