Sphecophaga vesparum

(Curtis, 1828)

Sphecophaga vesparum is an ichneumonid ectoparasitoid of vespid , primarily targeting Vespula vulgaris and Vespula germanica. The exhibits remarkable developmental plasticity with two female morphs: large winged females and small brachypterous females, each emerging from distinct cocoon types. It has been introduced to New Zealand and Australia as a agent for social wasps. The species is facultatively deuterotokous, producing mostly parthenogenetic females with occasional males.

Britishentomologyvolume3Plate198 by John Curtis
. Used under a Public domain license.

Britishentomologyvolume3Plate198 (cropped) by John Curtis
. Used under a Public domain license.

Bulletin - United States National Museum (1962) (20322713419) by United States National Museum;
Smithsonian Institution;

United States. Dept. of the Interior. Used under a No restrictions license.

Pronunciation

How to pronounce Sphecophaga vesparum: //sfɛˈkɒfəɡə ˈvɛspərəm//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other ichneumonids by its specialized association with vespid nests and the presence of two female morphs (winged and brachypterous). The three cocoon types (white, weak yellow, thick yellow) are diagnostic. identification requires color character analysis; morphological characters alone do not reliably separate S. v. vesparum from S. v. burra.

Images

Appearance

occur in two distinct female morphs. Large winged females are fully . Small brachypterous females have reduced wings. Cocoons show three color and texture variants: soft white cocoons, weak-walled yellow cocoons, and rigid thick yellow cocoons used for . S. v. vesparum and S. v. burra are morphologically indistinguishable but can be separated by color characters with >98% for females and 100% for males.

Habitat

Exclusively associated with nests of social vespid , particularly Vespula . Found within the capped of colonies where wasps are present.

Distribution

Native to Europe (Belgium, United Kingdom, Denmark, Norway, Flemish Region). Introduced to New Zealand (established at Pelorus Bridge, Marlborough and Ashley Forest, Canterbury) and Australia (released in Victoria).

Seasonality

Winged emerge from yellow cocoons after 1–4 years of dormancy and may live up to 3 weeks. Brachypterous females emerge from white cocoons within approximately 13 days. Multiple can occur within a single year in active nests.

Diet

Ectoparasitic larvae feed on , specifically newly pupated forms within capped of nests.

Host Associations

Vespula vulgaris - primary Common ; main in introduced range
Vespula germanica - primary German wasp; main in introduced range

Life Cycle

Ectoparasitic on pupae within capped . Females oviposit preferentially into cells where has most recently occurred. Three /cocoon types determine phenotype: white cocoons produce brachypterous females in ~13 days; weak yellow cocoons produce winged females (and possibly males) in ~15 days; thick yellow cocoons are , producing winged adults after 1–4 years. Many may originate from one winged female in one year.

Behavior

Females preferentially oviposit on immatures that have recently spun pupal caps. Winged may live up to 3 weeks. The exhibits partial chemical mimicry of host cuticular hydrocarbons, particularly linear alkanes, likely through passive recycling of prey hydrocarbons to avoid host detection. of at least 2.37 km per year has been documented in New Zealand.

Ecological Role

Ectoparasitoid that regulates of social vespid . Functions as a agent for Vespula in New Zealand and Australia. Has established self-sustaining populations at limited sites in New Zealand with rates averaging 8.5% of nests annually at Pelorus Bridge.

Human Relevance

Introduced as a agent for German and common in New Zealand (releases 1985–1987, 1987–ongoing) and Australia (approved 1989, released in Victoria). Establishment has been limited and localized; no significant reduction in wasp nest has been demonstrated despite increased rates over time. Further releases of S. v. vesparum not recommended; S. v. burra considered for re-release.

Similar Taxa

Sphecophaga vesparum burraNorth American morphologically indistinguishable but separable by color characters; failed to establish in New Zealand field releases
Other IchneumonidaeLack specialized vespid nest association, two female morphs, and three cocoon types

More Details

Chemical ecology

Hydrocarbon profiles differ across larval, pupal, and stages. Partial mimicry of V. vulgaris and V. germanica occurs through matching of linear alkanes, likely via recycling of prey cuticular hydrocarbons rather than active biosynthesis.

Reproductive biology

Facultative deuterotokous : females and males can be produced without , with females predominating and males rare. Mating can occur but is not required for .

Cocoon determination

Cocoon type is principally determined by age at oviposition: yellow cocoons from laid soon after pupal cap spinning; white cocoons from eggs laid on more developed pupae. Temperature indirectly influences cocoon type by affecting relative development rates of host and .

Natural enemies

In native range: Dimmockia incongrua, Melittobia acasta (Eulophidae), Dibrachys vesparum, possibly D. boarmiae (Pteromalidae), and one unidentified chalcid. In New Zealand: mice and spiders reported as field enemies; hyperparasitoids appear relatively unimportant.