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In the United States, the hobo spider has been considered to be a dangerous species based on a toxicology study on [[rabbit]]s where [[lesion]]s appeared after spiders were induced to bite the rabbits,<ref>Vest, D. K. (1987). Envenomation by ''Tegenaria
In the United States, the hobo spider has been considered to be a dangerous species based on a toxicology study on [[rabbit]]s where [[lesion]]s appeared after spiders were induced to bite the rabbits,<ref>Vest, D. K. (1987). Envenomation by ''Tegenaria
agrestis'' (Walckenaer) spiders in rabbits. ''Toxicon'' 25(2):221-4.</ref> although attempts to replicate the study (by injecting venom to ensure envenomation) have failed to produce [[necrosis|necrotic lesions]], and there is even question as to whether the lesions observed in the original study were necrotic.<ref name = "VetterIsbister">Vetter, R. S. and G. K. Isbister. (2004). Do hobo spider bites cause dermonecrotic injuries? ''Annals of Emergency Medicine'' 44:605-607.</ref> This laboratory study has led to the proposal that in some parts of the U.S. nearly all bites imputed to the [[brown recluse spider]] are in reality the hobo spider's bite.<ref>Vest, D. K. (1987). Necrotic arachnidism in the northwest United States and its probable relationship to ''Tegenaria agrestis'' (Walckenaer) spiders. ''Toxicon'' 25(2):175-84.</ref> The [[Centers for Disease Control and Prevention|CDC]] and other U.S. government agencies (e.g. [http://www.fs.fed.us/r1/fire/nrcg/Committees/Operations/ims/ims_web_site/Hobo%20Spider.htm]) have also used this same study as the basis for a report claiming that the hobo spider bite causes [[necrosis]] in humans,<ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/00042059.htm] Centers for Disease Control and Prevention (CDC). Necrotic arachnidism-Pacific Northwest, 1988-1996. MMWR Morb Mortal Wkly Rep 1996;45:433-6.</ref> despite the absence of any confirmed cases. In Canada, there are scientists who claim that no hobo spider bites lead to dermal necrosis.<ref>Bennett, R. G. and R. S. Vetter. (2004). An approach to spider bites: erroneous attribution of dermonecrotic lesions to brown recluse and hobo spider bites in Canada. ''Canadian Fam. Physician'' 50: 1098-1101.</ref> Hobo spiders are common in Europe, though bites are relatively unknown, and there are no confirmed reports of them causing necrosis despite hundreds of years of coexistence there. The only documented case of a verified hobo spider bite leading to necrotic skin lesions involves a person who had a pre-existing medical condition ([[phlebitis]]) that can also cause the appearance of skin lesions.<ref name = "VetterIsbister"/>
agrestis'' (Walckenaer) spiders in rabbits. ''Toxicon'' 25(2):221-4.</ref> although attempts to replicate the study (by injecting venom to ensure envenomation) have failed to produce [[necrosis|necrotic lesions]], and there is even question as to whether the lesions observed in the original study were necrotic.<ref name = "VetterIsbister">Vetter, R. S. and G. K. Isbister. (2004). Do hobo spider bites cause dermonecrotic injuries? ''Annals of Emergency Medicine'' 44:605-607.</ref> This laboratory study has led to the proposal that in some parts of the U.S. nearly all bites imputed to the [[brown recluse spider]] are in reality the hobo spider's bite.<ref>Vest, D. K. (1987). Necrotic arachnidism in the northwest United States and its probable relationship to ''Tegenaria agrestis'' (Walckenaer) spiders. ''Toxicon'' 25(2):175-84.</ref> The [[Centers for Disease Control and Prevention|CDC]] and other U.S. government agencies (e.g. [http://www.fs.fed.us/r1/fire/nrcg/Committees/Operations/ims/ims_web_site/Hobo%20Spider.htm]) have also used this same study as the basis for a report claiming that the hobo spider bite causes [[necrosis]] in humans,<ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/00042059.htm] Centers for Disease Control and Prevention (CDC). Necrotic arachnidism-Pacific Northwest, 1988-1996. MMWR Morb Mortal Wkly Rep 1996;45:433-6.</ref> despite the absence of any confirmed cases. In Canada, there are scientists who claim that no hobo spider bites lead to dermal necrosis.<ref>Bennett, R. G. and R. S. Vetter. (2004). An approach to spider bites: erroneous attribution of dermonecrotic lesions to brown recluse and hobo spider bites in Canada. ''Canadian Fam. Physician'' 50: 1098-1101.</ref> Hobo spiders are common in Europe, though bites are relatively unknown, and there are no confirmed reports of them causing necrosis despite hundreds of years of coexistence there. The only documented case of a verified hobo spider bite leading to necrotic skin lesions involves a person who had a pre-existing medical condition ([[phlebitis]]) that can also cause the appearance of skin lesions.<ref name = "VetterIsbister"/> WOW


Hobo spider bites are not known to be fatal to healthy humans. The necrosis in purported cases is similar to, but milder than, that caused by the [[brown recluse spider]], and in severe cases can take months to heal. Other reported symptoms include intense headaches, vision abnormalities, and/or general feelings of [[malaise]]. These symptoms are not confirmed for the hobo spider bite specifically due to lack of positive identification of the spider by an expert, and the [[Oregon Poison Center]] (affiliated with the [[Oregon Health & Science University]]) is attempting to gather definitive evidence regarding the validity of these reports as of September 2007.<ref>{{cite news|url=http://www.portlandtribune.com/news/story.php?story_id=119032341162984200|
Hobo spider bites are not known to be fatal to healthy humans. The necrosis in purported cases is similar to, but milder than, that caused by the [[brown recluse spider]], and in severe cases can take months to heal. Other reported symptoms include intense headaches, vision abnormalities, and/or general feelings of [[malaise]]. These symptoms are not confirmed for the hobo spider bite specifically due to lack of positive identification of the spider by an expert, and the [[Oregon Poison Center]] (affiliated with the [[Oregon Health & Science University]]) is attempting to gather definitive evidence regarding the validity of these reports as of September 2007.<ref>{{cite news|url=http://www.portlandtribune.com/news/story.php?story_id=119032341162984200|

Revision as of 17:48, 26 March 2010

Hobo spider
Hobo spider
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Arachnida
Order:
Araneae
Family:
Agelenidae
Genus:
Tegenaria
Species:
T. agrestis
Binomial name
Tegenaria agrestis
(Walckenaer, 1802)
Distribution in North America in green (native European distribution not shown)

The hobo spider (Tegenaria agrestis) is a member of the genus of spiders known colloquially as funnel web spiders. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant. 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. Although this species of spider has a reputation for aggressiveness, they will normally avoid contact with humans. Most bites occur when the spider is accidentally crushed or squeezed by a human. The spider's venom is strong enough to cause considerable local pain and necrosis.

Toxicity and aggressiveness

The toxicity and aggression of the hobo spider are currently disputed by arachnologists. Its nickname "aggressive house spider" comes from a misinterpretation of the Latin name agrestis, which literally translates to "of the fields", but mistranslated as "aggressive". If a hobo spider is tending an egg sac, it may become aggressive if it perceives the egg sac to be threatened.[1] However, they generally do not bite unless forced to protect themselves, and in the majority of cases the hobo spider does not actually inject venom when it does bite.[2]

In the United States, the hobo spider has been considered to be a dangerous species based on a toxicology study on rabbits where lesions appeared after spiders were induced to bite the rabbits,[3] although attempts to replicate the study (by injecting venom to ensure envenomation) have failed to produce necrotic lesions, and there is even question as to whether the lesions observed in the original study were necrotic.[4] This laboratory study has led to the proposal that in some parts of the U.S. nearly all bites imputed to the brown recluse spider are in reality the hobo spider's bite.[5] The CDC and other U.S. government agencies (e.g. [3]) have also used this same study as the basis for a report claiming that the hobo spider bite causes necrosis in humans,[6] despite the absence of any confirmed cases. In Canada, there are scientists who claim that no hobo spider bites lead to dermal necrosis.[7] Hobo spiders are common in Europe, though bites are relatively unknown, and there are no confirmed reports of them causing necrosis despite hundreds of years of coexistence there. The only documented case of a verified hobo spider bite leading to necrotic skin lesions involves a person who had a pre-existing medical condition (phlebitis) that can also cause the appearance of skin lesions.[4] WOW

Hobo spider bites are not known to be fatal to healthy humans. The necrosis in purported cases is similar to, but milder than, that caused by the brown recluse spider, and in severe cases can take months to heal. Other reported symptoms include intense headaches, vision abnormalities, and/or general feelings of malaise. These symptoms are not confirmed for the hobo spider bite specifically due to lack of positive identification of the spider by an expert, and the Oregon Poison Center (affiliated with the Oregon Health & Science University) is attempting to gather definitive evidence regarding the validity of these reports as of September 2007.[8][9]

Notes

  1. ^ http://www.washington.edu/burkemuseum/spidermyth/myths/hobo.html
  2. ^ [1]
  3. ^ Vest, D. K. (1987). Envenomation by Tegenaria agrestis (Walckenaer) spiders in rabbits. Toxicon 25(2):221-4.
  4. ^ a b Vetter, R. S. and G. K. Isbister. (2004). Do hobo spider bites cause dermonecrotic injuries? Annals of Emergency Medicine 44:605-607.
  5. ^ Vest, D. K. (1987). Necrotic arachnidism in the northwest United States and its probable relationship to Tegenaria agrestis (Walckenaer) spiders. Toxicon 25(2):175-84.
  6. ^ [2] Centers for Disease Control and Prevention (CDC). Necrotic arachnidism-Pacific Northwest, 1988-1996. MMWR Morb Mortal Wkly Rep 1996;45:433-6.
  7. ^ Bennett, R. G. and R. S. Vetter. (2004). An approach to spider bites: erroneous attribution of dermonecrotic lesions to brown recluse and hobo spider bites in Canada. Canadian Fam. Physician 50: 1098-1101.
  8. ^ Peter Korn (2007-09-21). "Spider bite? Drop the critter in the mail". Portland Tribune. Retrieved 2007-11-02.
  9. ^ "OHSU Wants Your Spiders, Dead or Alive". Oregon Health & Science University. 2007-09-05. Retrieved 2007-11-02.

References

Wikimedia Commons has media related to Tegenaria agrestis.
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