A parasitoid is an organism that lives on or in a host organism and ultimately kills the host.

Most insect parasitoids are found in the Order Hymenoptera and roughly 10% of all described insect species are parasitoids. In many species eggs are laid within the bodies of other organisms (most commonly other insects) the eggs hatch and feed on the internal organs of the host. Initially the parasitoid larvae feeds on non-essential organs thus feeding without killing the host. Eventually the larvae either feeds on the vital organs killing the host or pupates within the host and then emerges as an adult killing the host.

Parasitoids are commonly used in biological control.

A photograph of a parasitic wasp, _Peristenus digoneutis_, preparing to lay an egg in a tarnished plant bug nymph.

A parasitic wasp, Peristenus digoneutis, laying an egg in a plant bug nymph.
Scott Bauer, USDA

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