Eruga

Townes & Townes, 1960

Species Guides

1

Eruga is a of ichneumon wasps in the tribe Ephialtini, comprising approximately 15 distributed across the Afrotropical, Nearctic, and Neotropical regions. Members of this genus are ectoparasitoids of spiders, specifically targeting species in the Linyphiidae and Tetragnathidae. The genus is notable for behavioral manipulation of spiders, inducing them to construct modified 'cocoon webs' that support and protect the 's pupal cocoon.

Eruga rufa by the Smithsonian. Used under a CC0 license.Eruga rufa by the Smithsonian. Used under a CC0 license.Eruga rufa by the Smithsonian. Used under a CC0 license.

Pronunciation

How to pronounce Eruga: /ˈɛ.ruː.ɡə/

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Identification

As a within the polysphinctine group of ichneumonids, Eruga likely share the general characteristics of this clade: slender bodies, long , and adaptations for spider . Specific diagnostic features for the genus are not documented in the provided sources. Species-level identification requires examination of morphological characters described in original species descriptions.

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Distribution

Afrotropical, Nearctic, and Neotropical regions.

Host Associations

Life Cycle

Ectoparasitoid development on spider . The is deposited as a white mass on the region of the spider's . First instar larvae partially emerge from the egg . Second instar larvae induce spiders to build modified cocoon webs. Third instar larvae possess eight pairs of retractable with tiny hooks that facilitate hanging and movement on web threads after host death. occurs within a cocoon constructed on the modified web.

Behavior

Induces spiders to abandon normal webs and construct specialized cocoon webs from scratch—a rarely observed in unparasitized individuals. The cocoon webs are structurally distinct from normal webs, typically featuring reduced sheet areas, shorter interception threads, and three-dimensional tangle structures with non-sticky radial lines converging at the cocoon site. In Eruga unilabiana, larvae move to hang on web threads before killing the host, a strategy not previously recorded in the polysphinctine group. Cocoons are constructed horizontally, differing from the vertical orientation typical of most polysphinctine .

Ecological Role

of sheet-weaving and orb-weaving spiders, regulating spider . The behavioral manipulation of represents a complex host-parasitoid interaction that may influence spider web architecture evolution.

Similar Taxa

  • AcrotaphusBoth are polysphinctine ichneumonids that induce cocoon webs in spiders; Acrotaphus tibialis induces protective barrier tangles in Argiope trifasciata webs
  • HymenoepimecisBoth are polysphinctine ichneumonids that manipulate Leucauge mariana to build different cocoon web structures; Hymenoepimecis tedfordi induces planar radial organization with tangles below

More Details

Web Manipulation Specificity

Different Eruga induce distinct cocoon web architectures in the same species. Eruga cf. gutfreundi induces a three-dimensional radially arranged cocoon web in Leucauge mariana that has no clear counterpart in unparasitized spider webs, while Hymenoepimecis tedfordi induces a different structure in the same host species.

Host Size Selection

Eruga unilabiana preferentially parasitizes intermediate-sized female spiders, likely because they provide sufficient resources for larval development while being less vulnerable to attack than larger individuals.

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Sources and further reading