Mesochorus

Gravenhorst, 1829

Species Guides

4

Mesochorus is a large of ichneumonid wasps containing approximately 690-900 described worldwide. Members are obligate hyperparasitoids that attack the larvae of primary , typically ichneumonid or braconid wasps, and occasionally tachinid flies. These primary parasitoids are themselves endoparasitoids of larval Lepidoptera and Coleoptera, placing Mesochorus at the fourth in complex . The genus has been extensively studied in agricultural contexts due to its interactions with agents.

Mesochorus orcae by the Smithsonian. Used under a CC0 license.Mesochorus flavimaculatus by the Smithsonian. Used under a CC0 license.Mesochorus flavimaculatus by the Smithsonian. Used under a CC0 license.

Pronunciation

How to pronounce Mesochorus: /mɛsˈoʊˌkɔrəs/

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Habitat

Occurs in diverse terrestrial including forests, agricultural systems, and grasslands. have been documented in alfalfa fields, oak woodlands, and tropical conservation areas. Presence is dictated by availability of complexes involving primary and their herbivorous hosts.

Distribution

Worldwide distribution with records from North America, Central America ( Rica), South America (Brazil), Europe (Denmark, Norway, Sweden), and Australia. The is particularly diverse in the Neotropics, with 158 new described from Área de Conservación Guanacaste, Costa Rica alone.

Host Associations

Life Cycle

Females locate primary larvae or pupae developing within herbivore and oviposit directly into these secondary hosts. Development occurs entirely within the primary parasitoid, with the hyperparasitoid consuming the host from within. Specific developmental rates and stage requirements vary among ; some species show preferences for particular developmental stages of their primary parasitoid hosts.

Behavior

Females exhibit active -finding , capturing lepidopteran larvae to access primary within. Mesochorus discitergus shows variable success against host defensive tactics: caterpillars using vigorous responses are captured approximately 68% of the time, while those dropping on silken threads are captured 39% of the time, and those dropping unattached are captured roughly 26% of the time. Females use from primary parasitoids such as Cotesia marginiventris to locate suitable hosts.

Ecological Role

Functions as a fourth-trophic-level hyperparasitoid in complex , potentially disrupting of herbivorous pests by attacking their natural enemies. In agricultural systems, of Mesochorus may reduce the effectiveness of -based pest management. Conversely, they may contribute to of parasitoid and prevent hyperabundance of any single primary parasitoid .

Human Relevance

Significant relevance to programs, where hyperparasitism by Mesochorus can undermine pest management efforts targeting agricultural pests such as the alfalfa weevil and various noctuid caterpillars. The has been studied extensively to understand factors affecting capture and location, with implications for improving . Citizen science projects have contributed to discovery of new , including Mesochorus baccanellonyah described from a specimen collected by primary school students in South Australia.

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