Brown recluse spider

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Brown recluse spider
A male brown recluse spider
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Sicariidae
Genus: Loxosceles
Species: L. reclusa
Binomial name
Loxosceles reclusa
Gertsch & Mulaik, 1940
The brown recluse has six eyes (three pairs), unlike most spiders.

The brown recluse spider (Loxosceles reclusa) is a timid but dangerous spider that lives in the United States.

Description[change | change source]

Name[change | change source]

The scientific name of the spider Loxosceles reclusa comes from words that mean "slanted leg recluse". The "slanted leg" part comes from the fact that these spiders have their legs touching the ground at an angle instead of straight up and down. The "recluse" part is because this spider is very shy and runs away from humans.

Appearance[change | change source]

The brown recluse spider can be light brown, dark brown, or even gray. Sometimes it is called the violin spider since its head has a darker mark on it that looks like a violin. Not including its legs, it can grow to about 2 cm (0.79 in) long. They have six eyes, which is an unusual number of eyes for a spider.

Male and female brown recluses can be identified once the spider has molted several times. Spiders have a set of appendages on their faces called pedipalps. The pedipalps on the male have much larger ends than the ones on females. These fattened pedipalps serve as the sex organs for the male. The female has her sex organs on the underside of her body. This is perhaps the only way to easily tell a male from a female. Scientists who study brown recluses and their relatives can even identify relatives of the brown recluse by studying the shapes of the sex organs.

Habitat[change | change source]

Brown recluse spiders only live in the United States.[1][2][3] Spiders living in the south west part of the USA live in the woods, and spiders in the north east part live inside houses. Brown recluse spiders like dry, dark areas that have good hiding places. Wild brown recluse spiders live in hollowed rotting tree trunks and logs. Brown recluses that live in houses usually like garages, basements, and attics. These are places where people are less likely to bother them, and they have lots of good hiding places, like cardboard boxes.

Sometimes, people mail boxes without checking them first for spiders. Brown recluses can hide inside these boxes and might make their home wherever the package is opened. However, spider experts have found brown recluses sent through the mail rarely start a new colony in their new home, partly because there are no other brown recluses for them to mate with.[4][5] Sometimes brown recluses sent through the mail set up colonies in warehouses. However, they do not move very far from their colony, which is usually not well-established in the new place.[6][7]

Food[change | change source]

Brown recluse spiders are insectivores. They eat soft-bodied insects (like moths or flies) and other spiders. They are cannibals and will not hesitate to eat each other. When mating, a female brown recluse will try to eat the male.

When preying, the brown recluse slowly creeps toward its prey. Once it is close enough, it pounces on the prey and sinks its fangs into the prey. Its fangs contain a deadly venom that kills the prey very quickly.

Brown recluses can go without food or water for a very long time. Some brown recluses can go for five seasons with no food or water.[8][9]

Behavior[change | change source]

Brown recluse spiders are hunting spiders, so they spend most of the time on the ground. They hide during the daytime and sleep, and at night they come out to hunt. They usually do not climb unless they are running from something. They can walk upside-down, but most brown recluses walking on ceilings have probably come from the upstairs floor. The blood cannot flow through their legs while they walk, so they must stop every few seconds to allow the blood to flow.

Brown recluses are very good at survival. They can go without food or water for more than a year.[8][9] They are also very good at surviving in people's homes during cold winters.[10] If they get their leg caught in something, such as a crack or a predator's mouth, they can drop the leg. The spider can still walk around with only four legs, as long as there is still one leg on each side.[9]

Because these spiders are so good at surviving in hard times, it is very hard to get rid of them. Bug sprays and pest killers usually are not good for killing them, except for some kinds that are against the law to use.[9] A spider that has been sprayed might even become vicious.[9]

Brown recluse spiders are afraid of people, and usually if they see one they stand still. If the person chases the brown recluse, it will most often run and hide. Even though brown recluse spiders are scared of people, it is a bad idea to try to touch one, because their bite can be very dangerous.

A full-grown brown recluse compared to a U.S. penny, which is 0.75 inches across (19.05mm)

Brown recluses will normally only bite a person if the person is touching the spider or if the spider is stuck between the person and something else. Most brown recluse bites happen when someone puts on clothes that have a brown recluse spider living inside of them. For people who have brown recluses living in their house, it is a good idea to shake out any clothes that have been on the floor for a few days before putting them on. These people should also be careful when walking around in attics, basements, or dark parts of the house with no shoes on.[11] Wearing socks or gloves helps, because the spiders have very short fangs.[12] It is very common for people living with brown recluses to never see the spiders and never be bitten, and good habits can help make sure no one is bitten.[11]

Danger and myth[change | change source]

A brown recluse bite that has healed. It has left a scar behind.

Brown recluse spiders have been feared since they were discovered in 1940, and people will often take drastic approaches to rid their homes of these spiders. Spider experts noticed that the bite of a brown recluse could sometimes lead to a terrible infection called necrosis.[13] Sometimes the necrosis becomes fatal, but these fatal bites are actually very rare, and most bites from brown recluses are no more harmful than a normal spider bite.[14][15] The spider's bite is most dangerous for people who are young or overweight.[16]

It is very common for people bitten by spiders to arrive in a doctor's office without bringing the spider that bit them. When this happens, a doctor must guess what sort of spider could have bitten the person. The brown recluse spider is a very common spider to blame, since its name is so well-known, but it is very seldom that the brown recluse spider was involved.[15][17][18] Doctors' guesswork has led many people to believe brown recluses exist outside their native area, such as in California, even though this is not true. In most cases, either a disease was the cause of the symptoms, or a different kind of spider bit the person and the doctor makes a mistake when he or she guesses it was a brown recluse.[19][2][20][21][22]

Very little is known about the venom of the brown recluse, and spider venom experts have been looking for a long time for ways to effectively tell whether a brown recluse has bitten a patient as well as an antidote for its venom.[23][24][25][26][27][28][29][30][31][32]

References[change | change source]

  1. Jone SC. "Ohio State University Fact Sheet: Brown Recluse Spider. url=".
  3. Vetter, Rick. "Myth of the Brown Recluse: Fact, Fear, and Loathing". Retrieved 2008-05-02.
  4. [1] University of Florida Fact Sheet
  5. Palmer, Diane. "Brown recluse spiders blamed for more wounds than they inflict, study suggests". Clemson University Public Service Activities. Retrieved 12 September 2007.
  6. Vetter, R.S.; Edwards, G.B.; James, L.F. (2004). "Reports of envenomation by brown recluse spiders (Araneae: Sicariidae) outnumber verifications of Loxosceles spiders in Florida". J. Med. Entomol 41 (4): 593–597. ISSN 0022-2585.
  7. Edwards, G.B. 2001. The present status and a review of the Brown Recluse and related spiders, Loxosceles spp. (Araneae: Sicariidae), in Florida. Entomology Circular #406, Fla. Dept. Agric. & Consumer Services Division of Plant Industry. 6 pp.
  8. 8.0 8.1 Horner, N.V. & Stewart, K.W. (1967). "Life history of the brown spider, Loxosceles reclusa, Gertsch and Muliak". Texas Journal of Science 19: 333.
  9. 9.0 9.1 9.2 9.3 9.4 Sandidge J.S. and Hopwood J.L. (2005). "Brown Recluse Spiders: a review of biology, life history and pest management". Transactions of the Kansas Academy of Science 108 (3/4): 99–108. doi:10.1660/0022-8443(2005)108[0099:BRSARO]2.0.CO;2.
  10. Elzinga R.J. (1977). "Observations on the longevity of the Brown Recluse Spider, Loxosceles reclusa Gertsch & Mulaik". Journal of the Kansas Entomological Society 50 (2): 187–8.
  11. 11.0 11.1 "An Infestation of 2,055 Brown Recluse Spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas" by Richard S. Vetter and Diane K. Barger, J. Med. Entomol. 39(6): 948Ð951(2002); available online at
  12. Sandidge, J.S. (2009). Brown recluse spiders: a knowledge based guide to control and elimination. McLouth, Kansas: BRS Pest Control.
  14. Anderson P (1998). "Missouri brown recluse spider: a review and update". Mo Med 95 (7): 318–22. PMID 9666677.
  15. 15.0 15.1 Leach J, Bassichis B, Itani K (July 2004). "Brown recluse spider bites to the head: three cases and a review". Ear Nose Throat J 83 (7): 465–70. PMID 15372917., in turn citing: Wright SW, Wrenn KD, Murray L, Seger D. Clinical presentation and outcome of brown recluse spider bite. Ann Emerg Med 1997;30: 28–32.
  16. Wasserman G (2005). "Bites of the brown recluse spider.". N Engl J Med 352 (19): 2029–30; author reply 2029–30. doi:10.1056/NEJM200505123521922. PMID 15892198.
  17. Gomez H, Krywko D, Stoecker W (2002). "A new assay for the detection of Loxosceles species (brown recluse) spider venom". Ann Emerg Med 39 (5): 469–74. doi:10.1067/mem.2002.122914. PMID 11973553.
  18. Vetter, R.S. (2009). "Arachnids misidentified as brown recluse spiders by medical personnel and other authorities in North America". Toxicon 54 (4): 545–547. doi:10.1016/j.toxicon.2009.04.021. PMID 19446575.
  19. Vetter, R.S. (2005). "Arachnids submitted as suspected brown recluse spiders (Araneae: Sicariidae): Loxosceles species are virtually restricted to their known distributions but public perception is that they exist throughout the United States". J. Med. Entomol 42 (4): 512–521. doi:10.1603/0022-2585(2005)042[0512:ASASBR]2.0.CO;2. ISSN 0022-2585. PMID 16119538.
  20. Osterhoudt KC, Zaoutis T, Zorc JJ (2002). "Lyme disease masquerading as brown recluse spider bite". Annals of emergency medicine 39 (5): 558–61. doi:10.1067/mem.2002.119509. PMID 11973566.
  21. Moran GJ, et al. 2006. Methicillin-resistant S. aureus infections among patients in the emergency department. New England J. Med. 355: 666–74
  23. Isbister GK, Gray MR (August 2003). "White-tail spider bite: a prospective study of 130 definite bites by Lampona species". The Medical journal of Australia 179 (4): 199–202. PMID 12914510.
  25. Maynor ML, Moon RE, Klitzman B, Fracica PJ, Canada A (March 1997). "Brown recluse spider envenomation: a prospective trial of hyperbaric oxygen therapy". Acad Emerg Med 4 (3): 184–92. doi:10.1111/j.1553-2712.1997.tb03738.x. PMID 9063544.
  26. Maynor ML, Abt JL, Osborne PD (19892). "Brown Recluse Spider Bites: Beneficial Effects of Hyperbaric Oxygen". J. Hyperbaric Med 7 (2): 89–102. ISSN 0884-1225. Retrieved 2008-07-22.
  27. Elston DM, Miller SD, Young RJ 3rd, Eggers J, McGlasson D, Schmidt WH, Bush A. Comparison of colchicine, dapsone, triamcinolone, and diphenhydramine therapy for the treatment of brown recluse spider envenomation: a double-blind, controlled study in a rabbit model. Arch Dermatol 2005; 141(5):595–7.
  30. Burton K. "The Brown Recluse Spider: Finally stopped in its tracks". Archived from the original on 2006-04-20. Retrieved 2006-09-02.
  31. Lowry B, Bradfield J, Carroll R, Brewer K, Meggs W (2001). "A controlled trial of topical nitroglycerin in a New Zealand white rabbit model of brown recluse spider envenomation". Ann Emerg Med 37 (2): 161–5. doi:10.1067/mem.2001.113031. PMID 11174233.