Aptesis

Förster, 1850

Species Guides

1

Aptesis is a of in the Ichneumonidae, first described by Arnold Förster in 1850. The genus contains approximately 74 described with an almost distribution. Species within this genus are primarily ectoparasitoids of and cocoons, with some species serving as important agents. Well-studied species include Aptesis nigrocincta, a ectoparasitoid of apple sawfly cocoons, and Aptesis basizona, a parasitoid of pine sawflies used in programs.

Aptesis nigrocincta by (c) Owen Strickland, some rights reserved (CC BY), uploaded by Owen Strickland. Used under a CC-BY license.Aptesis (Pezoporus) tsugae by the Smithsonian. Used under a CC0 license.Aptesis (Pezoporus) tsugae by the Smithsonian. Used under a CC0 license.

Pronunciation

How to pronounce Aptesis: //æpˈtiː.sɪs//

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Habitat

in this are associated with where their occur. Aptesis nigrocincta has been observed in organically managed apple orchards in Switzerland, where females locate host cocoons at depths of 10–25 cm in the soil. Aptesis basizona is associated with pine forests in Europe where its diprionid sawfly hosts feed on pine trees.

Distribution

Almost distribution. Native to Europe, with Aptesis basizona documented from central, western, and northern Europe including Czechoslovakia, Hungary, and Sweden. Introduced established through programs, including propagation facilities in Belleville, Ontario, Canada. GBIF records confirm presence in Denmark, Norway, and Sweden.

Seasonality

Aptesis nigrocincta is , producing two per year. Field studies in Switzerland documented rates ranging from 12.1 to 39.7% within single generations, indicating discrete seasonal activity periods.

Diet

food requirements have been documented for Aptesis basizona; is reduced approximately 80% and longevity drastically shortened when mated females are deprived of food and provided only water. For Aptesis nigrocincta, food deprivation drastically reduces both longevity and lifetime fecundity.

Host Associations

Life Cycle

Aptesis nigrocincta: Development from to takes 39.6 days for females and 38.0 days for males at 20°C. Females are nearly wingless and significantly smaller than males. Females mate immediately after ; copulation averages 21.7 seconds. Pre-oviposition period averages 5.8 days. Aptesis basizona: Development continues until feeding is completed and cocoons are spun; stages can be held in cold storage to retard development pending shipment to release areas. Temperature during immature stages affects adult reproductive capacity.

Behavior

Females of Aptesis nigrocincta exhibit , ovipositing on already parasitized by conspecifics despite being a solitary where only one offspring develops per host. Superparasitism decisions are condition-dependent: females with higher loads and lower host encounter rates are more likely to superparasitize. At 20°C, females require 29.3 minutes to deposit an egg on a host; at 25°C, 19.9 minutes. Females can discriminate between parasitized and unparasitized hosts but may still choose to superparasitize based on internal state and environmental conditions.

Ecological Role

Important mortality factor for . Aptesis nigrocincta constitutes the most important mortality factor of apple sawfly cocoons in studied Swiss orchards. Aptesis basizona rates vary from 3 to 90% on different diprionid and in different areas, demonstrating significant of pine sawflies.

Human Relevance

Used as a agent. Aptesis basizona was propagated at Belleville, Ontario for release against the European spruce sawfly (Diprion hercyniae), European pine sawfly (Neodiprion sertifer), and other Diprionidae. Laboratory rearing techniques were developed to allow propagation, cold storage for development retardation, and shipment to release areas.

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