Definition:

Parasitoids are insects that feed on the body of another insect or arthropod during the larval stage of the their life cycle. The host organism will die as a result. When the parasitoid completes its life cycle, it becomes a free-living insect, no longer dependent on the host.

Parasitoids may comprise up to 25% of all insects (Parasitoids, Nick Mills, University of California, Berkeley).


Most parasitoids belong to the Hymenopteran or Dipteran orders.

Examples:

Probably the best known example of a parasitoid is the braconid wasp Cotesia congregatus. This wasp uses a piercing ovipositor to lay her eggs in the body of a tomato or tobacco hornworm. When the larvae emerge from the eggs, they feed on the hornworm's body. The larvae eventually chew their way through the caterpillar's skin, and pupate on its body. A hornworm infested with braconid wasps will be covered in tiny, white cocoons. The adult braconid wasps emerge from the cocoons, leaving a dead hornworm behind.