Evolution

Hyperparasitism has evolved in only three insect orders: in Hymenoptera (in 17 families) and in a few species of Diptera and Coleoptera. Its evolution was preceded by that of primary parasitism that evolved in the Hymenoptera during the Jurassic, about 135 mya. In the primary parasitoids, ectophagous feeding probably evolved before endophagous, with the parasitoid egg deposited near or on the host rather than in it. Hence, ectophagous parasitoids usually attacked concealed hosts, often within galleries in wood or plant galls. The use of venom by primary parasitoids apparently developed very early and produced physiological changes in the host. Although the venom of the more ancestral ectophagous parasitoids resulted in idiobiosis (permanent paralysis or death), the venom of the specialized endophagous species tended toward koinobiosis (temporary or nonlethal paralysis).

Facultative hyperparasitism probably evolved from primary ectophagous parasitoids because few special adaptations are needed to oviposit and feed externally on a primary parasitoid as well as on the primary's phytophagous host. Obligate hyperparasitism has a wider taxonomic distribution and may have evolved via facultative hyperparasitism as an opportunistic behavior to specialize only in attacking readily available primary parasitoid hosts—especially if they share similar physiological and/or ecological attributes. Hence, it is not surprising that hyperparasitoid species can be either ecto- or endophagous, whereas some are idiobionts and others are koinobionts.

The host spectrum of hyperparasitoids is broader at the species level than that of primary parasitoids, but hyperparasitism is usually restricted to immature stages of hymenopteran hosts (larvae and/or pupae) that are natural enemies mainly of phytophagous insects in the Hemiptera (mainly suborder Sternorrhyncha), Lepidoptera, and the hymenopteran suborder Symphyta. Hyperparasitoids rarely attack the egg and adult stages of primary parasitoids. Also interesting is that some families of Hymenoptera that are well known for their species of primary parasitoids (Braconidae, Trichogrammatidae, Aphidiidae, Mymaridae, and almost the entire superfamily Proctotrupoidea) do not seem to have evolved any hyperparasitoids. Similarly, in the order Diptera, hyperparasitoids are absent in some important parasitic groups such as the family Tachinidae.

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