Hobo spider explained

The hobo spider (Eratigena agrestis, formerly Tegenaria agrestis) is a member of the family of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. Individuals construct a funnel-shaped structure of silk sheeting and lie in wait at the small end of the funnel for prey insects to blunder onto their webs. Hobo spiders sometimes build their webs in or around human habitations. Despite past claims, there is no clear evidence that the hobo spider has venom that is dangerous to humans.

Taxonomy

The species was first described in 1802 by naturalist Charles Athanase Walckenaer as Aranea agrestis, in reference to its western European habitat in fields, woods, and under rocks.[1] In 1841, Walckenaer transferred the species to the genus Tegenaria. In 2013, Tegenaria was split up, and the hobo spider was transferred to a new genus Eratigena, an anagram of Tegenaria.[2]

Identification

Spiders, including the hobo spider, vary considerably in appearance, and identification can be difficult. The hobo spider is 7–14 mm in body length, and brownish in color.[3] Identification relies on an examination of the spider's anatomy. Like many species of spider the positive identification of Eratigena agrestis requires microscopic examination of the epigynum and palpal bulb (the female and male sex organs respectively) and is best done by an arachnologist. However, the following characteristics identify hobo spiders among other species with a similar general appearance:

Distribution and habitat

Eratigena agrestis is distributed from Europe to Central Asia, and is also found in western North America, in the Pacific Northwest and Great Basin. It is recorded in the checklist of Danish spider species,[5] and is present on the small island of Peberholm, probably having been carried there by foreign trains.

It is a resident of fields, avoiding human habitations occupied by major competitors, particularly the giant house spider (Eratigena atrica), which is a common resident of houses and other man-made structures in Europe. As a result, human contacts with the hobo spider are uncommon in Europe.[6] Hobo spiders build a horizontal, trampoline-like web near brick walls or wood piles where the spider has shelter and awaits prey.[3]

The hobo spider lays its eggs in September and they hatch during late spring. After the male hobo spider mates it dies.[7]

Bite effects

Although the toxicity and aggression of the hobo spider have long been debated, there is little evidence that the hobo spider is a dangerously venomous species.[8] The CDC reported case studies in the 1990s claiming that the hobo spider bite caused isolated cases of necrosis in people,[9] [10] but as of 2017, the CDC no longer lists the hobo spider among venomous species.[11] In Canada, there is no evidence that hobo spider bites cause skin necrosis.[12] Some bites reportedly from the closely related desert grass spider, Agelenopsis aperta, may have been inaccurately reported and may have actually been from the hobo spider.[13]

Bibliography

Notes and References

  1. Faune Parisienne, vol. 2, p. 187
  2. Angelo . Bolzern . Daniel . Burckhardt . Ambros . Hänggi . Phylogeny and taxonomy of European funnel-web spiders of the Tegenaria-Malthonica complex (Araneae: Agelenidae) based upon morphological and molecular data . Zoological Journal of the Linnean Society . 2013 . 168 . 723–848 . 10.1111/zoj.12040. free .
  3. Web site: Bites and stings of medically important venomous arthropods . Department of Entomology, University of California-Riverside. 5 February 2001 . Vetter RS, Visscher PK. https://web.archive.org/web/20010205015700/http://spiders.ucr.edu/dermatol.html . 5 February 2001 . 15 January 2019.
  4. Web site: Vetter . R. . Antonelli . A. . How to identify (or misidentify) the hobo spider. https://web.archive.org/web/20160807100617/http://pep.wsu.edu/wp-content/uploads/sites/7/2015/05/PLS116_1.pdf . 2016-08-07 .
  5. Web site: Checklist of Danish Spiders (Araneae) . 26 October 2011 . 14 March 2014 . 4 March 2016 . https://web.archive.org/web/20160304024828/http://www.zmuc.dk/EntoWeb/arachnology/dkchecklist.htm . dead .
  6. Dermatology E-Book p. 1448
  7. Web site: Davis. Ryan S . February 2016. Utah Pests Fact Sheet: Hobo Spider Eratigena agrestis . https://web.archive.org/web/20201028205049/https://utahpests.usu.edu/uppdl/files-ou/factsheet/Hobo%20Spider.pdf . 2020-10-28 . Utah State University.
  8. Web site: Rodney L . Crawford . Myths about "dangerous" spiders . 27 October 2015 . Burke Museum, University of Washington . 22 May 2007 . https://web.archive.org/web/20110606030646/http://www.washington.edu/burkemuseum/spidermyth/myths/hobo.html . 6 June 2011 .
  9. Web site: Hobo Spider: Natural History. Rodney L . Crawford. Burke Museum, University of Washington.
  10. Web site: US Centers for Disease Control and Prevention. Necrotic arachnidism- Pacific Northwest, 1988-1996. 1996.
  11. Web site: Venomous spiders. US Centers for Disease Control and Prevention. 31 May 2018. 7 May 2017.
  12. Bennett . R.G. . Vetter . R.S. . An approach to spider bites. Erroneous attribution of dermonecrotic lesions to brown recluse or hobo spider bites in Canada . Canadian Family Physician . 50 . 1098–1101 . August 2004 . 15455808 . 2214648 .
  13. Vetter. Richard S. December 1998. Envenomation by a spider, Agelenopsis aperta (Family: Agelenidae) Previously Considered Harmless. Annals of Emergency Medicine. 32. 6. 739–741. 10.1016/s0196-0644(98)70076-9. 9832673. 0196-0644.

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