The Brown Recluse Spider - UT Extension

Agricultural Extension ServiceThe University of TennesseePB1191TheBrownRecluseSpider1

2

ContentsIntroduction -------------------------- 4Description ---------------------------- 5Biology ---------------------------------- 6Habitat ----------------------------- 6Web ---------------------------------- 6Feeding ----------------------------- 7Life Cycle ------------------------- 7Distribution --------------------------- 7Venomous Bites --------------------- 8Avoiding Bites ---------------------- 10Control -------------------------------- 11Sanitation ----------------------- 11Monitoring --------------------- 11Insecticide Applications -- 12Cracks And Voids ------------ 12Spot Treatments -------------- 12Space Treatments ------------ 13Exterior Treatments -------- 13Literature ---------------------------- 14CreditsDistribution records of the brownrecluse spider in Tennessee wereprovided by Mike Cooper, TennesseeDepartment of Agriculture.The Tennessee Pest ControlAssociation provided a grant to helpsupport the first preparation of thispublication.Originally produced by HarryWilliams, Professor; Robert Greene,Graduate Assistant, Entomology andPlant Pathology; and Riley S. Rees,M.D., Vanderbilt University.3

TheBrownRecluseSpiderKaren M. Vail, Associate ProfessorHarry Williams, Professor EmeritusEntomology and Plant PathologyJohn A. Watson, M.D.Chief Resident, Division of DermatologyVanderbilt University Medical CenterIntroductionFew things cause as much fear and anxiety in people asthe thought of poisonous spiders. Araneophobia, irrationalfear of spiders, is widespread in the United States. Thebrown recluse spider is one of the feared poisonous spidersoccurring in Tennessee. This spider is often visualized as anaggressive, bad-tempered monster, just waiting for an opportunity to ambush people. In reality, the brown recluse spideris a shy, retiring spider that does not attack people andusually only bites in response to being injured. Most reported bites occur when putting on old clothing in which thespider is hiding or rolling over on a spider in bed. The brownrecluse spider lives up to its name. Most people living inproximity to the spider will never see it, nor be bitten by it.4

DescriptionThe brown recluse Loxosceles reclusa Gertsch and Mulaikis a medium-sized spider belonging to the Order Aranea(spiders) and the Family Loxoscelidae (the brown spiders).The adult body ranges from 7mm to 12mm in length (1/4 toinch) and 3mm to 5mm wide (1/8 to under 1/4 inch). The legsspan an area roughly the size of a quarter to a half-dollar.The color of the brown recluse varies from a light yellowish brown to a dark, reddish or chocolate brown, butmost are light to medium brown. Their body is denselycovered by short hairs, and the male abdomen is generallysmaller than that of the female. The second pair of legs arelonger than the remaining pairs in both sexes. Three pairs ofeyes are arranged in a semicircle (Figure 1). Since mostother spiders have eight eyes, this feature alone caneliminate many specimens suspected of being a brownrecluse spider.The most distinguishing characteristic is the violinshaped marking on the carapace (the top of the body directlyThree pairsof eyesFigure 1.Carapace showing the six eyes and violin-shaped markings.5

above the legs). Although variable, the violin-shaped markingis usually much darker than surrounding areas and mayappear longitudinally lined. In some individuals, the size ofthis violin-shaped marking may be considerably reduced.Other spiders may have a violin-shaped marking. The bestidentification feature for the brown recluse is the semicircular arrangement of the three pairs of eyes. Contact yourcounty Extension agent to identify a suspected brown reclusespider.BiologyHabitat:Brown recluse spiders prefer sheltered areas with lowmoisture levels. They have been found under loose bark, inhollow logs and under stones. People have created many newhabitats which these spiders have successfully exploited.They have been found in all types of buildings. In homes,they tend to prefer darkened storage areas in closets, garages,basements, attics and cupboards. The following list includesmany of their preferred hiding places. They have been foundin utility boxes, under bridges, inside barn walls, under haybales, in drainage passages under roads, among feed sacks,under inner tubes, under houses, under furniture, behindpicture frames, in underground pump houses and coldstorage cellars, under and in boxes, among papers, in clothinghanging on walls, under boards, in firewood stacks, in demolished houses, under piled bricks, in kitchen cabinets andother seldom disturbed and sheltered places.Web:The brown recluse spider builds irregular, patternlesswebs in poorly-lighted areas. There is usually a thickerportion of web (sometimes almost tubular) built in a protected area such as in a crevice or between two rocks. Thespider will retreat to this area of the web when threatened.The silk web is sticky when new, but loses this feature withtime, primarily due to dust accumulation. Silk webs are laid6

down as the spider walks, and the web becomes thicker.Webs can eventually become sheet-like if located in an areaof abundant prey.Feeding:Brown recluse spiders feed on a variety of insects, otherarthropods and occasionally a spider. Their bite quicklyparalyzes prey, which may remain alive for a few days untilthe spider decides to feed on it. The spider is alerted to thepresence of prey by web vibrations caused by passing prey.However, there is some evidence that the brown reclusespider might forage short distances from the web at night.Prey is located and bitten, but not wrapped in silk.Life Cycle:The brown recluse spider has been known to live up totwo years in captivity. It is quite possible that they may gothrough two winters in outdoor conditions. Some scientistsbelieve brown recluse spiders may live five to 10 years underideal conditions. These spiders develop egg sacs betweenFebruary and September, with most development from Maythrough July. Each egg sac normally contains between 20 and50 eggs. The female usually constructs up to five egg sacs.Spiderlings emerge from the egg sac within three to fiveweeks and stay in the web with the mother for one or twomolts (shedding of skins) before migrating to other suitablehabitats. The spiderlings molt six or seven times beforebecoming an adult in the following year.DistributionThe brown recluse spider is found in every county inTennessee with the possible exception of a few extremeeastern counties. They are far more common in the westernhalf of the state. Their major range extends from centralTexas to Alabama, north to southern Ohio and west to southeastern Nebraska, Kansas and Oklahoma.7

Venomous BitesThere are 13 different species of Loxosceles in the UnitedStates and four of them, L. reclusa, L. deserta, L. laeta and L.refescens, have been associated with human reactions. Thebrown recluse spider, Loxosceles reclusa, typifies the species,and is widely distributed throughout the midwest, southwestand particularly throughout Tennessee. Often called theviolin or fiddle back spider because of the violin-shapedfigure on its dorsal cephalothorax, it varies in size dependingon diet and habitat.Since most brown recluse spiders hibernate in the winter(except those which live indoors), most bites occur betweenMarch and October when humans accidentally disturb theirhabitat: closets, out-buildings or woodpiles. Despite theirusual timid nature, these spiders are inherently more dangerous than other spiders because they have adapted theirhabitat to live in close association with people.Often initially painless, the bite wound starts with acentral pimple and produces an irregular red reaction in 6-12hours, followed by blister formation and/or skin death (Figure 2). The resultant skin ulcer heals slowly and may requireskin grafts or flaps to reconstruct the defect. Tissue examination of the lesions demonstrate acute blood vessel injury andwhite cell infiltration. The initial bite is often asymptomaticand may be difficult to diagnose clinically unless the patientsaw the spider. Often these bites are confused with wasp orbee stings, tick bites, allergic reactions or skin abscesses. Theresulting lesion often becomes painful and/or itchy. Casereports of blood abnormalities, kidney failure or death havebeen recorded.The venom of the brown recluse spider contains at leastnine protein fractions identifiable by molecular weight on gelelectrophoresis. One major protein is a phospholipase enzyme.This venom fraction aggregates platelets, induces white bloodcells to enter the wound, liberates inflammatory mediatorsand produces skin lesions when injected into rabbits.The treatment of brown recluse spider bites remainscontroversial. Rest, Ice, Compressions and Elevation8

Figure 2. The bite wound starts with a central pimple and produces anirregular red reaction in 6-12 hours which precedes blister formation orskin death.(RICE) have been useful in reducing redness and swelling.Antihistamines can be used for itching and analgesics, asappropriate, for pain control. Antibiotics used systemicallyseem to reduce the incidence of secondary infections. A babyaspirin taken the first day of the bite, if there are nocontraindications, is helpful to reduce clotting within theblood vessels. Tetanus toxoid should be given as for a dirtywound. A drug called dapsone can be used in severe orprogressing bites. Steroids should be reserved for patientswith significant generalized symptoms such as rash andblood hemolysis. Excising the bite site acutely should beavoided since the inflammatory reaction produced by thevenom will inhibit wound healing and produce inferiorclinical results (Figure 3). Plastic surgical procedures can behelpful for reconstructing the wound site after the activephase of tissue damage has been completed. This may takeup to 20 weeks.9

Figure 3. Excising the bite wound acutely should be avoided since theinflammatory reaction produced by the venom will inhibit wound healing.Avoiding BitesMost bites occur when the spider is pressed against theskin inside clothing or when rolled on in bed. To minimizebites in homes where brown recluse is present:1.2.3.4.5.6.store clothing in sealed plastic bags or storage boxes,store shoes in plastic shoe boxes,shake clothing and shoes before wearing,move beds away from walls or curtains,remove bed skirts from box springs,do not use bedspreads that touch or come close tothe floor,7. inspect bedding before climbing into bed, and8. place glueboards under each bedpost.10