From Wikipedia, the free encyclopedia
The Chilean recluse spider is a venomous spider, Loxosceles laeta, of the family Sicariidae (formerly of the family Loxoscelidae). In Spanish, it (and other South American recluse spiders) is known as araña de rincón, or "corner spider"; in Portuguese, as Aranha-marrom or "brown spider". 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.
|Chilean recluse spider|
Description and habitatThe Chilean recluse is one of the larger species of recluse spiders, 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. Coloring varies from light tan to brown and the violin marking may not be visible. Since the "violin pattern" is not diagnostic, it is far more important, for purposes of identification, to examine the eyes. Contrary to most spiders, which have 8 eyes, recluse spiders have 6 eyes arranged in pairs (dyads) with one median pair and 2 lateral pairs.
The Chilean recluse spider is native to South America (it is common in Chile, and can be found throughout South America), and can now be found worldwide, including in North and Central America, Finland, and Australia. The spider is known to have established itself in the Los Angeles area, and infestations have been reported in Vancouver, British Columbia, Cambridge, Massachusetts, and Florida.
Like other recluse spiders, the Chilean recluse builds irregular webs that frequently include a shelter consisting of disorderly threads. Unlike most web weavers, they leave these webs at night to hunt. 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. The spiders can last a long time without food or water , a fact that encourages their worldwide spread.
Medical significanceAs indicated by its name, this spider is not aggressive and usually bites only when pressed against human skin, such as when putting on an article of clothing. Like all sicariid spiders, the venom of the Chilean recluse contains the dermonecrotic agent, sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. According to one study, the venom of the Chilean recluse (along with the six-eyed sand spider), contains an order of magnitude more of this substance than that of other sicariid spiders such as the brown recluse.
Some bites are minor with no necrosis, but a small number produce severe dermonecrotic lesions (cutaneous loxoscelism) or even systemic conditions (viscerocutaneous loxoscelism); sometimes resulting in renal failure and in 3-4% of cases in a clinical study in Chile, death. (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)
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. Bites may take up to seven hours to cause visible damage; more serious systemic effects may occur before this time, as venom of any kind spreads throughout the body in minutes. Deaths have been reported for the related South American species.
First aid involves the application of an ice pack to control inflammation, the application of aloe vera to soothe and help control the pain, and prompt medical care. If it can be captured, the spider should be brought with the patient in a clear, tightly closed container for identification. However, by the time the bite is noticed any spider found nearby is not likely to be the culprit.
Ohio State University Fact Sheet
1991 Kenny Road, Columbus, Ohio 43210
not actual size
brown recluse spider Scientific Name
Brown Recluse Spider
Susan C. Jones, Ph.D.
Assistant Professor of Entomology
Extension Specialist, Household & Structural Pests
The brown recluse spider is uncommon in Ohio. Nonetheless, OSU Extension receives numerous spider specimens that homeowners mistakenly suspect to be the brown recluse. Media attention and public fear contribute to these misdiagnoses.
The brown recluse belongs to a group of spiders that is officially known as the "recluse spiders" in the genus Loxosceles (pronounced lox-sos-a-leez). These spiders are also commonly referred to as "fiddleback" spiders or "violin" spiders because of the violin-shaped marking on the top surface of the cephalothorax (fused head and thorax). However, this feature can be very faint depending on the species of recluse spider, particularly those in the southwestern U.S., or how recently the spider has molted.
The common name, brown recluse spider, pertains to only one species, Loxosceles reclusa. The name refers to its color and habits. It is a reclusive creature that seeks and prefers seclusion.
The brown recluse spider and ten additional species of Loxosceles are native to the United States. In addition, a few non-native species have become established in limited areas of the country. The brown recluse spider is found mainly in the central Midwestern states southward to the Gulf of Mexico (see map). Isolated cases in Ohio are likely attributable to this spider occasionally being transported in materials from other states. Although uncommon, there are more confirmed reports of Loxosceles rufescens (Mediterranean recluse) than the brown recluse in Ohio. It, too, is a human-associated species with similar habits and probably similar venom risks (unverified).
not actual size
Recluse spiders have six eyes that are arranged in pairs.
In the mature brown recluse spider as well as some other species of recluse spiders, the dark violin marking is well defined, with the neck of the violin pointing toward the bulbous abdomen. The abdomen is uniformly colored, although the coloration can range from light tan to dark brown, and is covered with numerous fine hairs that provide a velvety appearance. The long, thin, brown legs also are covered with fine hairs, but not spines. Adult brown recluse spiders have a leg span about the size of a quarter. Their body is about 3/8 inches long and about 3/16 inches wide. Males are slightly smaller in body length than females, but males have proportionally longer legs. Both sexes are venomous. The immature stages closely resemble the adults except for size and a slightly lighter color. Whereas most spiders have eight eyes, recluse spiders have six eyes that are arranged in pairs in a semicircle on the forepart of the cephalothorax (see close-up view). A 10X hand lens or microscope is needed to see this diagnostic feature. In order to determine the exact species of Loxosceles, the spider's genitalia need to be examined under a high-power microscope. This requires the skills of a spider expert.
Life Cycle and Habits
Egg laying primarily occurs from May through July. The female lays about 50 eggs that are encased in an off-white silken sac that is about 2/3-inch diameter. Each female may produce several egg sacs over a period of several months. Spiderlings emerge from the egg sac in about a month or less. Their development is slow and is influenced by weather conditions and food availability. It takes an average of one year to reach the adult stage from time of egg deposit. Adult brown recluse spiders often live about one to two years. They can survive long periods of time (about 6 months) without food or water.
The brown recluse spider spins a loose, irregular web of very sticky, off-white to grayish threads. This web serves as the spider's daytime retreat, and it often is constructed in an undisturbed corner. This spider roams at night searching for insect prey. Recent research at the University of Kansas indicates that the brown recluse spider is largely a scavenger, preferring dead insects. Mature males also roam in search of females.
Brown recluse spiders generally occupy dark, undisturbed sites, and they can occur indoors or outdoors. In favorable habitats, their populations are usually dense. They thrive in human-altered environments. Indoors, they may be found in attics, basements, crawl spaces, cellars, closets, and ductwork or registers. They may seek shelter in storage boxes, shoes, clothing, folded linens, and behind furniture. They also may be found in outbuildings such as barns, storage sheds, and garages. Outdoors, brown recluse spiders may be found underneath logs, loose stones in rock piles, and stacks of lumber.
The brown recluse spider is not aggressive, and it normally bites only when crushed, handled or disturbed. Some people have been bitten in bed after inadvertently rolling over onto the spider. Others have been bitten after accidentally touching the spider when cleaning storage areas. Some bites occur when people put on seldom used clothing or shoes inhabited by a brown recluse.
The physical reaction to a brown recluse spider bite depends on the amount of venom injected and an individual's sensitivity to it. Some people are unaffected by a bite, whereas others experience immediate or delayed effects as the venom kills the tissues (necrosis) at the site of the bite. Many brown recluse bites cause just a little red mark that heals without event. The vast majority of brown recluse bites heal without severe scarring (http://spiders.ucr.edu/avoidbites.html).
Initially, the bite may feel like a pinprick or go unnoticed. Some may not be aware of the bite for 2 to 8 hours. Others feel a stinging sensation followed by intense pain. Infrequently, some victims experience general systemic reactions that may include restlessness, generalized itching, fever, chills, nausea, vomiting, or shock. A small white blister usually initially rises at the bite site surrounded by a swollen area. The affected area enlarges and becomes red, and the tissue is hard to the touch for some time. The lesion from a brown recluse spider bite is a dry, blue-gray or blue-white, irregular sinking patch with ragged edges and surrounding redness--termed the "red, white, and blue sign." The lesion usually is 1½ inches by 2¾ inches or smaller. Characteristics of a bite are further discussed at http://www.amednews.com/free/hlsa0805.
The bite of the brown recluse spider can result in a painful, deep wound that takes a long time to heal. Fatalities are extremely rare, but bites are most dangerous to young children, the elderly, and those in poor physical condition. When there is a severe reaction to the bite, the site can erupt into a "volcano lesion" (a hole in the flesh due to damaged, gangrenous tissue). The open wound may range from the size of an adult's thumbnail to the span of a hand. The dead tissue gradually sloughs away, exposing underlying tissues. The sunken, ulcerating sore may heal slowly up to 6 to 8 weeks. Full recovery may take several months and scarring may remain.
It is difficult for a physician to accurately diagnose a "brown recluse bite" based simply on wound characteristics. It is absolutely necessary to have the spider for a positive identification. Necrotic wounds can result from a variety of agents such as bacteria (Staphylococcus, "flesh-eating" Streptococcus, etc.), viruses, fungi, and arthropods (non-recluse spiders, centipedes, mites, ticks, wasps, bedbugs, kissing bugs, biting flies, etc.). Necrotic conditions also can be caused by vascular and lymphatic disorders, drug reactions, underlying diseases states, and a variety of other agents. An annotated list of conditions that could be mistaken for a brown recluse spider bite is available at http://www.ama-assn.org/amednews/2002/08/05/hlsa0805.htm. Misdiagnosis of lesions as brown recluse bites can delay appropriate care.
If bitten, remain calm, and immediately seek medical attention (contact your physician, hospital and/or poison control center). Apply an ice pack directly to the bite area to relieve swelling and pain. Collect the spider (even a mangled specimen has diagnostic value), if possible, for positive identification by a spider expert. A plastic bag, small jar, or pill vial is useful and no preservative is necessary, but rubbing alcohol helps to preserve the spider.
An effective commercial antivenin is not available. The surgical removal of tissue was once standard procedure, but now this is thought to slow down wound healing. Some physicians administer high doses of cortisone-type hormones to combat hemolysis and other systemic complications. Treatment with oral dapsone (an antibiotic used mainly for leprosy) has been suggested to reduce the degree of tissue damage. However, an effective therapy has not yet been found in controlled studies.
Control of indoor infestations of the brown recluse spider can take a long time (6 months or more) and can be difficult because humans have a very low tolerance for this pest, it tends to be widely dispersed within infested buildings, and it seeks secluded sites. Control of spiders, including the brown recluse, is best achieved by following an integrated pest management (IPM) approach. IPM involves using multiple approaches such as preventive measures, exclusion, sanitation, trapping, and chemical treatment when necessary.
Preventing spider bites
Shake out clothing and shoes before getting dressed.
Inspect bedding and towels before use.
Wear gloves when handling firewood, lumber, and rocks (be sure to inspect the gloves for spiders before putting them on).
Remove bedskirts and storage boxes from underneath beds. Move the bed away from the wall.
Exercise care when handling cardboard boxes (recluse spiders often are found in the space under folded cardboard flaps).
Install tight-fitting screens on windows and doors; also install door sweeps.
Seal or caulk cracks and crevices where spiders can enter the house.
Install yellow or sodium vapor light bulbs outdoors since these attract fewer insects for spiders to feed upon.
Tape the edges of cardboard boxes to prevent spider entry.
Use plastic bags (sealed) to store loose items in the garage, basement, and attic.
Remove trash, old boxes, old clothing, wood piles, rock piles, and other unwanted items.
Eliminate clutter in closets, basements, attics, garages, and outbuildings.
Do not stack wood against the house.
Clean up dead insects that the brown recluse spider can feed on.
Use sticky traps or glueboards to capture spiders.
Dust and vacuum thoroughly to remove spiders, webs, and egg sacs (dispose of the vacuum bag in a container outdoors).
Use a rolled up newspaper or fly swatter to kill individual spiders.
There are many labeled pesticides for spider control. Some are labeled for homeowner use, while others are labeled only for the licensed, certified pesticide applicator. It would be prudent to enlist the services of a professional pest management company when dealing with an indoor infestation of the brown recluse spider.
Research indicates that recently developed pyrethroids (e.g., cyfluthrin, cypermethrin, etc.) are particularly effective against brown recluse spiders. Wettable powders and microencapsuled "slow-release" formulations of these chemicals provide residual activity and are preferable to using emulsion-type sprays. Insecticide treatments should be applied so that the chemical contacts as many spiders and webs as possible. Residual liquid sprays should be applied to the outside perimeter of the home (including under eaves, patios, and decks; behind window shutters), baseboards, undisturbed corners, and other suspected spider harborages. Residual dusts should be applied to voids and inaccessible areas where spiders may hide. Aerosol flushing agents such as pyrethrins, though ineffective by themselves in providing control, can cause spiders to move about so that they contact treated surfaces.
Click here for PDF version of this Fact Sheet.
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868