Acrotaphus

Townes, 1960

Acrotaphus is a of -attacking in the , Pimplinae, tribe Ephialtini. The genus contains 27 described distributed across the New World, with particularly high diversity in the Neotropics including the Brazilian Amazon. These wasps are of -weaver spiders in the families Araneidae and Tetragnathidae. A defining characteristic of the genus is the ability to induce behavioral modification in spiders, causing them to construct specialized " webs" that support and protect the wasp .

Acrotaphus fuscipennis by no rights reserved, uploaded by Zygy. Used under a CC0 license.Acrotaphus wiltii ♀ (47371550341) by Christina Butler from Georgia, United States. Used under a CC BY 2.0 license.Parasite wasp, left 2020-08-17-18.37.43 ZS PMax UDR (50422506593) by USGS Bee Inventory and Monitoring Lab from Beltsville, Maryland, USA. Used under a Public domain license.

Pronunciation

How to pronounce Acrotaphus: //ˌæk.rəˈteɪ.fəs//

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Identification

Acrotaphus can be distinguished from related polysphinctine (such as Hymenoepimecis and Eruga) by a combination of morphological characters including and genitalic structure. The genus belongs to the Polysphincta genus group, whose members are all . Definitive identification to level requires examination of male and reference to taxonomic ; 27 species are currently recognized, many described recently (2019–2020). Field identification is complicated by the substantial intraspecific variation in size and coloration.

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Appearance

-sized with typical pimpline including elongated bodies and long . present; males and females differ in antennal structure. Male have been described taxonomically but specific external morphological characters distinguishing Acrotaphus from related require detailed examination. -level identification relies on subtle morphological differences including patterns and body proportions.

Habitat

Found in diverse across the New World, including tropical rainforests of the Amazon basin, where multiple have been described. Specific microhabitat associations are tied to distribution, primarily in vegetation supporting -weaver spider webs. No specialized habitat requirements beyond host availability have been documented.

Distribution

New World distribution ranging from the United States (recorded from Vermont, Massachusetts) through Mexico and Central America to South America, with highest in the Neotropics. The is particularly well-represented in Brazil, with multiple described from the Amazon region and the Cerrado (Bodoquena region). Specific country records include: United States, Mexico, Venezuela, Peru, Brazil, French Guiana, and likely others throughout Central and South America.

Host Associations

Life Cycle

. females locate and lay a single on the host's body. The feeds externally on the living spider, eventually killing it. Prior to host death, the larva induces behavioral modification causing the spider to construct a modified " web"—a three-dimensional structure of non-adhesive threads lacking the typical web features (spirals, , hub). The larva then pupates within a cocoon suspended in this modified web. Development time from to adult spans multiple weeks to months depending on environmental conditions.

Behavior

females exhibit -searching targeting -weaver . involves brief paralysis of the host via stinging, followed by deposition. The most notable behavior is host manipulation: chemically or neurally manipulate host spiders to construct specialized webs that differ dramatically from normal -capture webs. These cocoon webs provide superior protection and support for compared to normal orbs. The induced web architecture varies among and host combinations, ranging from modified resting-web structures to novel three-dimensional constructions without clear counterpart in unparasitized spider behavior.

Ecological Role

Acts as a regulator of -weaver in Neotropical and Nearctic . By selectively parasitizing -sized spiders, may influence size structure and of spider populations. The behavioral manipulation of host spiders represents a complex host-parasitoid interaction that alters spider web-building and potentially affects local structure through indirect effects on spider .

Human Relevance

No direct economic importance. Of scientific interest as a model system for studying manipulation by and the evolution of behavioral manipulation in the Polysphincta group. Some have been named for cultural references (A. jackiechani) or in honor of researchers (A. franklini, A. homeofranklini).

Similar Taxa

  • HymenoepimecisAlso polysphinctine that induce web construction; distinguished by morphological characters including and genitalic structure. Both share the derived trait of behavioral manipulation, suggesting this may be primitively present in their common ancestor.
  • ErugaPolysphinctine with similar associations and behavioral manipulation capabilities; Eruga ca. gutfreundi induces different web architecture on the same host (Leucauge mariana) compared to Acrotaphus tibialis, demonstrating convergent but distinct manipulation strategies.
  • Polysphincta of the Polysphincta genus group; shares lifestyle on but Acrotaphus is distinguished by specific morphological characters and range.

More Details

Taxonomic History

The was established by Townes in 1960. Prior to 2019, only 11 were recognized. Intensive taxonomic work by Pádua, Sääksjärvi, and colleagues in 2019–2020 added 15 new species, more than doubling the known diversity. This recent activity reflects improved sampling in previously underexplored Neotropical regions rather than recent speciation.

Host Manipulation Mechanism

The mechanism by which Acrotaphus induce web construction remains unknown, but is presumed to involve chemical manipulation of the . The resulting webs consistently lack adhesive spiral threads and incorporate dense tangles or three-dimensional architectures optimized for pupal survival rather than capture. This represents one of the most sophisticated examples of host behavioral manipulation among wasps.

Nesting Associations

Two (A. franklini and A. pseudoamazonicus) have been recorded from nests of the mud-dauber Trypoxylon (Trypargilum) lactitarse (Crabronidae), suggesting possible kleptoparasitic or commensal relationships with other wasps, though the ecological nature of this association requires further study.

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Sources and further reading