Ichneumonid wasps are parasitoids. A parasitoid differs from a parasite in that it eventually kills its host. The wasps lay an egg in a caterpillar. The developing wasp larva then feeds on the caterpillar host. Eventually, as seen in the spicebush swallowtail chrysalis photo PR# BF2419 showing the wasp exit hole, the larval wasp matures and leaves the chrysalis of the caterpillar that it has devoured.