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Species Eratigena agrestis - Hobo Spider

Diamondback Rattle Spider? ;o) - Eratigena agrestis - female hobo spider - Eratigena agrestis Spider - Eratigena agrestis Tegenaria agrestis (hobo) - Eratigena agrestis - female Unknown Spider - Eratigena agrestis Hobo Spider - Eratigena agrestis - female Adult male - Eratigena agrestis - male Adult female - Eratigena agrestis - female
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Order Araneae (Spiders)
Infraorder Araneomorphae (True Spiders)
No Taxon (Entelegynes )
Family Agelenidae (Funnel Weavers)
Genus Eratigena
Species agrestis (Hobo Spider)
Other Common Names
Aggressive house spider (incorrect name, but commonly used). Please see below.
Synonyms and other taxonomic changes
Previously genus Tegenaria (transferred to Eratigena in August 2013). (1)
Explanation of Names
A common misconception is that agrestis means "aggressive", giving it the name "aggressive" house spider. This spider is not aggressive, and would rather flee than fight, unless it feels threatened without the option to escape. (This misconception is often used to help fuel fears about the potential hazards of this spider.) The Latin translation of agrestis is simply "rural" or "in the fields" (in their native Europe, this species is most commonly found in fields).
Size
All measurements are for only the body, and do not include the legs.
Female: 11-15 mm (1/2 - 2/3 inch);
Male: 8-11 mm (1/4 - 1/3 inch).
Identification
Very difficult to ID from photos. The actual spider (not a photo) needs to be examined by an expert for a definite identification. Often your local university extension office or agricultural office will have resources to assist you (with identification and control).

There is no dimorphism in color or markings. The appearance of hobo spiders is not unattractive, but their coloration is rather subdued, being a mixture of brown and rust earth shades. They have a herringbone pattern on the top side of their abdomens. Although most Agelenidae have very "hairy" looking legs, the legs of this spider are fairly smooth.

Female


Male


Often, it is easier to determine if the spider is not a hobo, rather than determine with certainty that it is a hobo. Please refer to the 2nd link on the Internet References section (below) for more information.
Range
Pacific Northwest, British Columbia;


The species is definitely marching eastward -- there are healthy populations throughout the western states -- I have documented locality records from Colorado, Montana, and Wyoming and I suspect they will be found in all the states between here (Colorado) and Washington. ~ Paula Cushing, October 2011.

There's a relatively new population around the Rouge River area of Pickering, Ontario; maybe specimens were transferred in landscaping mulch brought in from southwestern Canada. Several specimens have been verified from the area, though. ~ pers. comm. Robb Bennett & Tom Mason, August 2012.
Habitat
Often darker areas, such as flower beds, wood piles, and areas where it can weave a funnel-web. When it is found in homes, it often is found in the basement, in the darker recesses such as corners. It is a nocturnal spider, so generally it is discovered when the lights are turned on and the spider darts for cover (and/or its web).
Season
It can be found starting in mid-to-late spring, but is really noticed during the latter portion of the summer and into the fall. The males are very commonly found in late August through September, where they are very active in searching out a mate.
Food
Insects, possibly other spiders.
Life Cycle
The female hobo spider remains stationary in her web; therefore, the male must search for her. He bobs and taps at the funnel web’s entrance in a specific pattern that alternates with advances and retreats. If signals are not clear, she may attack or kill him. If she is responsive (no aggression), he slowly adds silk to her web and gradually approaches her. After mating, he usually leaves in search of other females.

The female produces one to four egg cases, each one holding 50-100 eggs. The female attaches the egg cases underneath objects, usually outdoors, although occasionally in crawlspaces. The egg sac always incorporates soil or other foreign matter between two layers of silk. The female dies in late fall.

Hobo spiderlings emerge from the egg sac the following spring. West of the Cascades, hobos probably live only one year, but inland hobos usually live two years. In these inland populations, juveniles over winter then reach adulthood the following summer when they are ready to mate and begin the cycle anew.
Remarks
Like its relatives, Tegenaria domestica and Eratigena atrica, this spider was imported from Europe into the shipping ports of the Pacific Northwest (Washington State) in the 1930s.

There is currently no solid scientific evidence suggesting that the venom of this species is of medical importance.

This spider is thought to have a necrotic venom, similar to the brown recluse spider (Loxosceles reclusa), however, the "jury is still out" on this fact; the research results that were used to report the necrotic effects of the venom have not been consistently reproduced. It may or may not be as dangerous as people have been led to believe... just be mindful and use caution when dealing with these spiders. [update 7/18/2011] A paper published in the Journal of Medical Entomology in March 2011 states this in its ending paragraph (full text of paper available here):
"This study confirms previous results and provides further evidence that the hobo spider, T. agrestis, is not a spider of medical concern. We have identified the bacteria associated with T. agrestis as ubiquitous environmental fauna and displayed the spider's inability to transfer a pathogenic bacteria. There is little evidence to support the claims that the hobo spider harbors or vectors microbial pathogens. The hemolytic venom assay demonstrates that the spider is incapable of causing severe cellular damage. Finally, the results from the mammalian assay strengthen the hypothesis that the hobo spider does not cause necrotic lesions. Although this introduced spider is common around homes in urban environments in the PNW and is expanding its range, we cannot substantiate its involvement in human necrotic tissue lesions as once suspected." (Gaver-Wainwright et al., 2011)
"Probably because T. duellica is big, T. agrestis has gained a nasty reputation, and both are common around homes in the Pacific Northwest, much public and considerable professional mythology and misinformation has arisen around these two species. Current research on a number of fronts should help to rectify this problem. However it is becoming apparent that T. agrestis probably is not the bad actor it is supposed to be."
      - Taken from Newsletter of the Entomological Society of British Columbia, Volume 22, Number 1 July 2002 (an article by Robb Bennett: Hyperbole and Hysteria on the Path to Enlightenment – a Review of Current Tegenaria Projects of Relevance to Canadian Arachnologists)
The actual spider (not a photo) needs to be examined by an expert for a definite identification. Often your local university extension office or agricultural office will have resources to assist you (with identification and control).
Internet References
How to Identify (and Misidentify) a Hobo Spider: A PDF of how to identify (and misidentify) the Hobo Spider; written by Rick Vetter, Entomology Dept, UC Riverside and Art Antonelli, Extension Specialist, Washington State University
Newsletter of the Entomological Society of British Columbia, Volume 22, Number 1 July 2002 (an article by Robert Bennett, Ph.D.: Hyperbole and Hysteria on the Path to Enlightenment – a Review of Current Tegenaria Projects of Relevance to Canadian Arachnologists)
An Approach to Spider Bites: Erroneous Attribution of Dermonecrotic Lesions to Brown Recluse or Hobo Spider Bites in Canada: Rick Vetter, MSc. and Robert Bennett, MSc, Ph.D. An interesting article (PDF format) about necrotic spider bites, their frequency of occurrence, and the frequency of misdiagnosis. Although this article deals with Canadian data, it is very insightful about necrotic spider bites in the US also.
Myths about Spiders: A website dedicated to dispelling myths about spiders, including the Hobo Spider. Maintained by Rod Crawford, Curator for Arachnids at The Burke Museum, Seattle Washington.
The Provincial Museum of Alberta: Article - Potentially Medically Significant Spiders of North America. Accurate and very informative; time well spent reading.
Works Cited
1.Phylogeny and taxonomy of European funnel-web spiders of the Tegenaria−Malthonica complex (Araneae: Agelenidae) based upon mor
Bolzern, Burckhardt, & Hänggi. 2013. Zoological Journal of the Linnean Society 168(4): 723-848.