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Tuesday, May 11, 2010

Beware the Wandering and Recluse

Chilean recluse displaying violin markings © Jim Kalisch Department of Entomology, University of Nebraska-Lincoln

One potent issue in our trip to Chile is the highly toxic Chilean recluse spider Loxosceles laeta. This triggered a medical journey into some of the most toxic species on planet Earth.

See also our page: Sexual Paradox in Spiders

In Spanish, the Chilean recluse is known as araña de rincón, or "spider of the corner"; in Portuguese, as Aranha-marrom or "brown spider". It is one of the larger species of recluse, generally ranging from 8–40 mm in size (including legs). Like most recluses, it is brown and usually has markings on the dorsal side of its thorax, with a black line coming from it that looks like a violin with the neck of the violin pointing to the rear of the spider resulting in the nickname "fiddleback spider" or "violin spider" in English-speaking areas.

This spider is considered by many to be the most dangerous of the recluse spiders , and its bite is known to frequently result in severe systemic reactions, including death. Some bites are minor with no necrosis, but a small number produce severe necrotic lesions or even systemic conditions sometimes resulting in renal failure and in 3-4% of cases death. The serious bites form a necrotising ulcer that destroys soft tissue and may take months, and very rarely, years to heal, leaving deep scars. The damaged tissue will become gangrenous and eventually slough away. Initially there may be no pain from a bite, but over time the wound may grow to as large as 10 inches (25 cm) in extreme cases. An anti-toxin is currently under development.

It's a good measure to buy some potent fly-spray and spray it around your bed area and window cracks and check your bedding carefully before getting into bed. People get bitten when they unintentionally squeeze them in clothing and bedding. These spiders frequently build their webs in woodpiles and sheds, closets, garages, and other places that are dry and generally undisturbed. The spider frequently is found in human dwellings. It can be found in nine out of ten houses from springtime and onwards, but is not commonly known to attack humans or to be particularly aggressive. Still, as any other spider, it will bite if it comes in contact with human skin and feels threatened.

Brazilian wandering spider

However while researching the recluse we came upon an even more deadly spider which is reputedly one of the 3 -5 -10 most deadly species on Earth, when a girl was stung in Australia by a species of box jellyfish reputedly THE most toxic species and the most painful. This is the Brazilian wandering spider, Phoneutria spp., more than earning its Greek name of murderess.

These spiders are really creepy for several reasons. One, it’s fierce. This is not some wimpy spider that will run away at the first sign of a human, allowing careless hikers to escape a painful death without even knowing they’re in danger. No, these spiders will attack anyone and anything they see as threatening. They’re both deadly and aggressive. Second, they’re not incredibly easy to avoid. They get the “wandering” part of their name from the fact that they roam around, rather than live in a particular web or tree. In densely populated areas, you can imagine how many people get bitten by an aggressive spider that wanders all over the place. They’re responsible for more cases of venom intoxication in Brazil than any other animals. Thankfully, even if the spider bites you it might not inject venom. Only about a third of it’s victims receive venomous bites. But if you do get any venom, you’re really going to regret it. It’s reportedly one of the most painful venoms in existence, thanks in large part to a high concentration of serotonin in the venom. While the venom is potentially fatal, the worst thing the Brazilian spider can cause would probably only make you die of embarrassment. The venom can cause priapism, an erection that won’t go away and might actually cause impotence. There is an antidote to the venom, but since it is so fast acting you’d better be carrying it on you if you’re out in the South American jungle. You’re not getting to a hospital in time.

White tail and daddy long legs

This brings me back to the white tail spider which has gained an odd reputation for precipitating Necrotizing fasciitis in our own country New Zealand. This may be more mythology than fact because although personal accounts of severe infections abound at least one research study has contradicated the claims, but woven into the story is another tale of carnivorous spiders. The daddy long legs spider Pholcus phalangioides has toxic venom but is harmless to humans because it cannot bite through thick human skin, however the idea is that the white tail, which is a carnivorous spider which hunts other spiders might become very toxic if it has just eaten a daddy long legs. Pholcids are natural predators of the Tegenaria species of house spiders, and are known to attack and eat redback spiders and huntsman spiders. Redbacks are considered one of the most dangerous spiders in Australia with neurotoxic venom. The irony of this is that the daddy long legs also eats other spiders, so might in turn eat a white tail!

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