Yellow sac spider

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Yellow sac spider

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Family:	Miturgidae
Genus:	Cheiracanthium
Species:	C. inclusum

Binomial name

Cheiracanthium inclusum
Hentz, 1847

The Yellow sac spider (Cheiracanthium inclusum and Chiracanthium mildei), alternately known as the black-footed spider, is not a true sac spider (of the family Clubionidae), but a long-legged sac spider, that is, a member of the family Miturgidae that was formerly classified in that group. It is one of a handful of spiders in North America whose bites are generally considered to be medically significant.

It is a rather small pale yellow spider, found in most of North, Central and South America. It takes shelter in flattened silk tubes during the day and moves about to hunt during the night. It often lives in houses and can frequently be found crawling upon walls or other vertical surfaces.

Ventral view of Cheiracanthium sp. This specimen has lost several legs.

[edit] Medical significance

The bite of these spiders is believed to be toxic to humans but rarely produce more than local symptoms. They are believed to produce a high percentage of the spider bites suffered by people, possibly because they wander about when people cannot see well or are asleep, and so they may get squeezed and bite to protect themselves. Bites that occur to farm laborers may occur because spiders hiding in their shelters on leaves may get squeezed.

It has been noted that a large number of bites attributed to the brown recluse spider may actually be the result of yellow sac spider bites, which possess a cytotoxic venom known to contain several proteolytic enzymes including alkaline phosphatase, deoxyribonuclease, esterase, hyaluronidase, lipase, and ribonuclease.^[1] These enzymes can cause localized tissue necrosis (which may be similar to that caused by a recluse bite), though the symptoms are less severe and do not result in the systemic effects occasionally seen with recluse envenomations.

However, the view that this spider is dangerous to humans has been questioned. A recent study of 20 confirmed yellow sac spider bites revealed no evidence of necrosis; further review of international literature on confirmed bites revealed only a single bite with mild necrotic symptoms. ^[2]

[edit] Notes

^ http://www.ajtmh.org/cgi/content/full/71/2/239 Diaz, James H. "The global epidemiology, syndromic classification, management, and prevention of spider bites", American Journal of Tropical Medicine and Hygiene 71(2), 2004, pp. 239-250
^ http://www.ajtmh.org/cgi/content/abstract/74/6/1043 Richard S. Vetter, Geoffrey K. Ibister, Sean P. Bush, and Lisa J. Boutin, "Verified bites by yellow sac spiders (genus Cheiracanthium) in the United States and Australia: Where is the necrosis?", American Journal of Tropical Medicine and Hygiene, 74(6), 2006, pp. 1043-1048