Biodiversity of hymenopteran parasitoids.

Parasitoid wasps are the most successful group of insect parasitoids, comprising more than half the known diversity of Hymenoptera and probably most of the unknown diversity. This lifestyle has enabled them to be used as pest control agents conferring substantial economic benefits to global agriculture. Major lineages of parasitoid wasps include Ichneumonoidea, Ceraphronoidea, Proctotrupomorpha, and a number of aculeate families. The parasitoid lifestyle arose only once among basal Hymenoptera, in the common ancestor of the Orussidae and Apocrita some 200+ Ma ago. The ancestral parasitoid wasp was probably an idiobiont on wood-living beetle larvae. From this comparatively simple biology, Hymenoptera radiated into an incredible diversity of hosts and parasitoid lifestyles, including hyperparasitoidism, kleptoparasitoidism, egg parasitoidism, and polyembryony, in several instances co-opting viruses to subdue their hosts. Many lineages evolved beyond the parasitoid niche, becoming secondarily herbivorous or predatory nest provisioners and eventually giving rise to most instances of insect societies.