Hobo spider

The hobo spider (Eratigena agrestis, formerly Tegenaria agrestis) is a member of the genus 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. The hobo spider lays its eggs in September and they hatch during late spring. After the male hobo spider mates it dies.[2]

Hobo spider
Female hobo spider
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Agelenidae
Genus: Eratigena
Species:
E. agrestis
Binomial name
Eratigena agrestis
Distribution in North America in green
Synonyms[1]
  • Aranea agrestis Walckenaer, 1802
  • Tegenaria agrestis (Walckenaer, 1841)
  • Philoica agrestis (Karsch, 1873)
  • Tegenaria rhaetica Thorell, 1875
  • Tegenaria magnacava Exline, 1936
  • Tegenaria osellai Brignoli, 1971
  • Tegenaria trinacriae Brignoli, 1971

Taxonomy

The species was first described in 1802 by naturalist Charles Athanase Walckenaer as Aranea agrestis,[1] in reference to its western European habitat in fields, woods, and under rocks.[3] In 1841, Walckenaer transferred the species to the genus Tegenaria.[1] In 2013, Tegenaria was split up, and the hobo spider was transferred to a new genus Eratigena, an anagram of Tegenaria.[1][4]

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.[5] 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:

  • Hobo spiders lack the colored bands found on many spiders of the family Agelenidae where the leg joints meet.[6]
  • The abdomen has chevron (V-shaped) patterns (possibly many of them) down the middle, with the chevrons pointing towards the head.[5]
  • Hobo spiders have a light stripe running down the middle of the sternum. If the spider instead has three or four pairs of light spots on the lateral portions of the sternum, then it is one of the other two related Eratigena species. However absence of spots is not conclusive proof that the spider is a hobo spider, since the spots on other Eratigena species may be extremely faint and not readily visible.[6]
  • Hobo spiders do not have two distinct longitudinal dark stripes on the top side of the cephalothorax, instead showing indistinct or diffused patterns. Washington spiders with distinct dark stripes include spiders from the genera Agelenopsis and Hololena and possibly some wolf spiders.[6]

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.[1] It is recorded in the checklist of Danish spider species,[7] 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.[8] Hobo spiders build a horizontal, trampoline-like web near brick walls or wood piles where the spider has shelter and awaits prey.[5]

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.[9] The CDC reported case studies in the 1990s claiming that the hobo spider bite caused isolated cases of necrosis in people,[10][11] but as of 2017, the CDC no longer lists the hobo spider among venomous species.[12] In Canada, there is no evidence that hobo spider bites cause skin necrosis.[13] 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.[14]

References
  1. "Taxon details Eratigena agrestis (Walckenaer, 1802)", World Spider Catalog, Natural History Museum Bern, retrieved 2016-01-03
  2. Davis, Ryan (February 2016). "Utah Pests Fact sheet" (PDF). Hobo Spider Eratigena agrstis – via Utah University.
  3. Faune Parisienne, vol. 2, p. 187
  4. Bolzern, Angelo; Burckhardt, Daniel; Hänggi, Ambros (2013). "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. 168: 723–848. doi:10.1111/zoj.12040.
  5. Vetter RS, Visscher PK (5 February 2001). "Bites and stings of medically important venomous arthropods". Department of Entomology, University of California-Riverside. Archived from the original on 5 February 2001. Retrieved 15 January 2019.
  6. Vetter, R.; Antonelli, A. "How to identify (or misidentify) the hobo spider" (PDF). Archived from the original (PDF) on 2016-08-07.
  7. "Checklist of Danish Spiders (Araneae)". 26 October 2011.
  8. Dermatology E-Book ISBN 978-0-723-43571-6 p. 1448
  9. Crawford, Rodney L (27 October 2015). "Myths about "dangerous" spiders". Burke Museum, University of Washington. Archived from the original on 6 June 2011. Retrieved 22 May 2007.
  10. Crawford, Rodney L. "Hobo Spider: Natural History". Burke Museum, University of Washington.
  11. "Necrotic arachnidism- Pacific Northwest, 1988-1996". US Centers for Disease Control and Prevention. 1996.
  12. "Venomous spiders". US Centers for Disease Control and Prevention. 31 May 2018. Retrieved 7 May 2017.
  13. Bennett, R.G.; Vetter, R.S. (August 2004). "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. PMC 2214648. PMID 15455808.
  14. Vetter, Richard S (December 1998). "Envenomation by a spider, Agelenopsis aperta (Family: Agelenidae) Previously Considered Harmless". Annals of Emergency Medicine. 32 (6): 739–741. doi:10.1016/s0196-0644(98)70076-9. ISSN 0196-0644.

Bibliography
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