|Loxosceles reclusa Gertsch & Malaik
Common Name: Brown Recluse
image c 2004 D.Allard & M. Storey
Adult brown recluse spiders are soft-bodied, yellowish-tan to dark brown, about 1/4 to 1/2 inch long and have long, delicate grayish to dark brown legs covered with short, dark hairs. The leg span is about the size of a half dollar.
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Distinguishing characteristics are the presence of three pairs of eyes arranged in a semicircle on the forepart of the head and a violin-shaped, dark marking immediately behind the semicircle of eyes with the neck of the violin pointing towards the bulbous abdomen.
image c 2004 M.Storey
The eight legs and violin marking appear on the flattened-like cephalothorax (combined area of the head and thorax). Both the male and female brown recluse spiders are similar in appearance and equally toxic. The immature stages closely resemble the adults except for size and a slightly lighter color.
Misidentification is a significant problem in the healthcare industry. Click here to read Rick Veter's paper " Identifying and Misidentifying the Brown Recluse Spider" -Dermatology Online Journal 5 (2): 7.
|Life Cycle and Habits
These spiders spin small, loose, white to off-white webs with irregular strands. The female lays eggs from May through August in off-white silken cases (sacs) about 1/3-inch in diameter. Sacs containing 40 or more eggs each are found hung in the web, overwinter in sheltered, dark areas and are guarded by the female until her death. Each female may lay as many as 300 eggs during her lifetime. Spiderlings emerge in 24 to 36 days leaving the egg case with slow development (10 to 12 months), and are influenced by weather conditions and food availability. Spiders can survive long periods of time without food or water and may live as long as two years.
image c 2004 M.Storey
This spider is most active at night when it comes out in search of food consisting of cockroaches and other small insects. During the day, time is spent in quiet, undisturbed places such as bathrooms, bedrooms, closets, basements and cellars. The spiders sometimes take shelter under furniture, appliances and carpets, behind baseboards and door facings, or in corners and crevices. Some have been found in stored clothing, old shoes, on the undersides of tables and chairs, and in folded bedding and undisturbed towels stored for long periods of time. Outdoors, the spider may be found in sheltered corners among debris, in wood piles, under loose bark and stones, in old barns, storage sheds and garages. These spiders are very adaptable and may be active in temperatures ranging from 45 to 110 deg F.
image c 2004 M.Storey
Recluse Spider Populations
Pathophysiology: Brown recluse spider bites can cause significant cutaneous injury with tissue loss and necrosis. Less frequently, more severe reactions develop, including systemic hemolysis, coagulopathy, renal failure, and, rarely, death.
Brown recluse venom, like many of the other brown spider venoms, is cytotoxic and hemolytic. It contains at least 8 components, including enzymes such as hyaluronidase, deoxyribonuclease, ribonuclease, alkaline phosphatase, and lipase. Sphingomyelinase D is thought to be the protein component responsible for most of the tissue destruction and hemolysis caused by brown recluse spider envenomation. The intense inflammatory response mediated by arachidonic acid, prostaglandins, and chemotactic infiltration of neutrophils is amplified further by an intrinsic vascular cascade involving the mediator C-reactive protein and complement activation. These and other factors contribute to the local and systemic reactions of necrotic arachnidism.
Although numerous cases of cutaneous and
viscerocutaneous reactions have been attributed to spiders of the genus
Loxosceles, confirming the identity of the envenomating arachnid is difficult
and rarely accomplished.
The open wound may range from the size of an adult's thumbnail to the span of a hand. The sunken, ulcerating sore may heal slowly up to 6 to 8 weeks. Full recovery may take several months and scarring may remain. Plastic surgery and skin grafts are sometimes required.
An effective antivenom is not generally available. The physician will usually administer high doses of cortisone-type hormones to combat hemolysis and other systemic complications. A report suggests that treatment with dapsone (a drug used mainly for leprosy) may reduce the degree of tissue damage.
Bite Photos and other information available at : http://www.sabramsmd.com/brs/brsmain.html
Betten, J. and P. Garcia. 1999. "Loxosceles reclusa" (On-line), Animal Diversity Web. Accessed January 29, 2004 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Loxosceles_reclusa.html
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