Recluse spider

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iRecluse spiders

Brown recluse spider

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Family:	Sicariidae
Genus:	Loxosceles Heineken & Lowe, 1832

Diversity

100 species

Species

see article

The recluse spiders (genus Loxosceles), also known as fiddle-back or violin spiders, are a venomous genus of spiders known for their necrotic bite.

1 Habitat and appearance
2 Venom components and effects
3 Species
4 See also
5 Footnotes
6 External links

[edit] Habitat and appearance

Loxosceles is distributed nearly worldwide in warmer areas, and are often known as violin spiders or fiddlebacks. All have six eyes arranged in three groups of two (diads) and are usually brownish with a darker brown characteristic violin marking on the cephalothorax. Most Loxosceles can live for one and a half to two years. Members of both genera can live for very long times without food or water.

The recluse spider family includes about 13 species in the United States, the brown recluse spider (Loxosceles reclusa) being the best known of these. It is found in a large area of the Midwest, west to Colorado and the New Mexico state line and east to Northern Georgia. Oddly, it has been seldom collected in Florida, and then only as an incidental introduction.

Other notable members of this genus include the Chilean recluse (L. laeta) and the Mediterranean recluse (L. rufescens).

[edit] Venom components and effects

Loxosceles spiders, like their cousins in Sicarius, have potent tissue-destroying venoms containing the dermonecrotic agent, sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. This venom is highly necrotic in effect, capable of causing lesions (open sores) as large as a US quarter. The wounds take a long time to heal and may require skin grafts. If these open wounds get infected there can be serious consequences. Rarely, the venom is carried by the blood stream to internal organs causing systemic effects.

The Chilean recluse (Loxosceles laeta) supposedly has a more potent venom, which results in systemic involvement more often. This spider was accidentally introduced to the Los Angeles area (Alhambra, Sierra Madre, and Monterey Park). This spider, however, seems to be confined to a very limited area, even though it has lived there for over 30 years. Other members of the genus that have been tested have venoms similar to the Brown Recluse and all members of this genus are best avoided. However, the Brown Recluse and its relatives are not very aggressive and huge populations have been found in houses where the human inhabitants remained unbitten after years of cohabitation.<ref name="JMedEntomol2002-Vetter">Vetter R, Barger D (2002). "An infestation of 2,055 brown recluse spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas". J Med Entomol 39 (6): 948-51. PMID.</ref>

A possible problem with diagnosing a recluse spider bite is that the bite of these spiders is probably both underreported in some areas and over reported generally.<ref name="annemergmed2002-Vetter">Vetter R, Bush S (2002). "The diagnosis of brown recluse spider bite is overused for dermonecrotic wounds of uncertain etiology". Ann Emerg Med 39 (5): 544-6. PMID.</ref> Unfortunately several diseases can mimic the lesions of a recluse spider bite, including Lyme disease, various fungal and bacterial infections and the first sore of syphilis([1]). Therefore it is extremely important to associate the spider directly with the bite, if at all possible.

Generally, recluse spiders are usually found in the center of a sort of space web of fungal-like silk, which often contains the remains of their recent meals. For the Arizona recluse (Loxosceles arizonica) the most abundant food item seems to be night-active ants like carpenter ants. The Brown recluse is known to feed on whatever is available, and this is probably true of all sicariids.