I was actually thinking of buying some parasitic wasps for my greenhouse.
If you hate aphids like me you'll love this description
During part of their reproductive cycle, aphid wasps capture and lay eggs within the bodies of live aphids. When aphid wasp larvae hatch from the eggs, they parasitize the aphid hosts for food. As the aphid wasp larvae develop into adults, the aphids die slowly as they are consumed from the inside out. Eventually, the adult aphid wasps leave the dead aphids, leaving hollow aphid mummies behind.
http://www.astrographics.com/GalleryPrintsIndex/GP2013.html
If you hate aphids like me you'll love this description
During part of their reproductive cycle, aphid wasps capture and lay eggs within the bodies of live aphids. When aphid wasp larvae hatch from the eggs, they parasitize the aphid hosts for food. As the aphid wasp larvae develop into adults, the aphids die slowly as they are consumed from the inside out. Eventually, the adult aphid wasps leave the dead aphids, leaving hollow aphid mummies behind.
http://www.astrographics.com/GalleryPrintsIndex/GP2013.html