Parasitoides

Parasitoides, or parasitoids, are organisms whose development depends on a single host and ultimately results in the host's death. Most parasitoids are insects, especially wasps in families such as Ichneumonidae and Braconidae, and tachinid flies, though the term can also apply to some other groups. Unlike parasites, which typically coexist with their hosts, parasitoids require the host to survive long enough for the parasitoid to develop and usually kill the host as part of their life cycle.

The typical life cycle begins when a female parasitoid lays eggs on or inside a host. The larva hatches and feeds on host tissues, often sparing some life functions until later stages. After consuming the host, the parasitoid pupates and eventually emerges as an adult. Hosts are frequently insects, and parasitoids are often highly specific, attacking one or a few related species. Some develop inside the host (endoparasitoids), others feed from the outside (ectoparasitoids). Parasitoids can be solitary, with one individual per host, or gregarious, with several developing within a single host.

Ecologically, parasitoids play a major role in regulating arthropod populations and are important agents of biological control. They are used in agriculture to suppress pest species, sometimes after deliberate releases of mass-reared strains (classical biological control). Notable examples include Trichogramma species, which parasitize eggs of pest moths, and various Cotesia and Aphidius wasps. While beneficial for pest management, parasitoids can also affect non-target species and may interact with complex food webs that include hyperparasitoids.