An Ichneumonid wasp exit hole in the chrysalis of a spicebush swallowtail (Papilio troilus). Ichneumonid wasps are parasitoids. A parasitoid differs from a parasite in that it eventually kills its host. The wasp lays an egg in a caterpillar and the developing wasp larva then feeds on the caterpillar host. Eventually, as seen in the picture, the larval wasp matures and leaves the chrysalis of the caterpillar that it has devoured.