Eruga

Townes & Townes, 1960

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

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 , Eruga likely share the general characteristics of this clade: slender bodies, long , and for . 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.

Images

Distribution

Afrotropical, Nearctic, and Neotropical regions.

Host Associations

Sphecozone sp. - Linyphiidae ; of Eruga unilabiana
Eurymorion sp. - Linyphiidae ; of Eruga unilabiana
Dubiaranea sp. - Linyphiidae ; of Eruga unilabiana
Leucauge mariana - Tetragnathidae ; of Eruga cf. gutfreundi
Argiope trifasciata - Tetragnathidae ; of related polysphinctine , not confirmed for Eruga

Life Cycle

development on . The is deposited as a mass on the region of the spider's . First partially emerge from the egg . Second instar larvae induce spiders to build modified 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 to abandon normal webs and construct specialized 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 converging at the cocoon site. In Eruga unilabiana, 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 -weaving , regulating spider . The behavioral manipulation of represents a complex host-parasitoid interaction that may influence spider web architecture evolution.

Similar Taxa

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

More Details

Web Manipulation Specificity

Different Eruga induce distinct 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 webs, while Hymenoepimecis tedfordi induces a different structure in the same host species.

Host Size Selection

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