koinobiont

A koinobiont is a type of parasitoid whose larval development occurs inside a living host that continues to grow and develop after oviposition. The term is used in parasitoid biology to distinguish this strategy from idiobiont parasitoids, which immediately arrest the host's development or kill it at the time of parasitism.

In a koinobiont interaction, the female typically lays eggs in or on a host (often immature stages of insects such as caterpillars, beetle larvae, or aphids). The larva develops progressively within the host, allowing ongoing host growth; the parasitoid often modulates host physiology and may regulate growth to optimize resources. Most koinobiont development is endoparasitic (inside the host), though some are ectoparasitic.

Because the host remains viable longer, koinobiont parasitoids can attack larger hosts and often exhibit highly specialized host ranges. They are common in several wasp families, especially Ichneumonidae and many Chalcidoidea, as well as some Braconidae. Their life cycles can be lengthy and complex, sometimes involving host metamorphosis coinciding with parasitoid maturation.

Understanding koinobiont strategies informs biological control and ecological studies of host–parasitoid dynamics. See also: parasitoid, endoparasitoid, idiobiont, host–parasitoid interaction.