Ryan S. Davis, Arthropod Diagnostician, and Ricardo A ... · PDF fileRyan S. Davis, Arthropod...
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Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory January 2013 ENT-163-12PR Spiders Ryan S. Davis, Arthropod Diagnostician, and Ricardo A. Ramirez, Extension Entomologist DO YOU KNOW • Spiders are beneficial predators that feed on pest and non-pest insects. • The major spider of medical concern in Utah is the black widow. • Brown recluse spiders do not occur in Utah. • There is no strong scientific evidence that hobo spider bites cause necrotic (flesh eating) lesions. • Indoor management of spiders is best done by vacuuming, cleaning, sealing cracks and crevices around the home, and tolerance. • Pesticides are only recommended in outbreak situations or when medically important spiders (black widows) are present. Fig. 1. Banded orb-weaver spider (Argiope trifasciata). INTRODUCTION Spiders are arachnids, a group that includes other 8-legged arthropods like ticks, mites, sun spiders, scorpions, and harvestmen (daddy longlegs). There are approximately 621 species of spiders known to occur in Utah (Allred and Kaston, 1983). Spiders are beneficial predators and the majority of them are harmless to humans. Much fear of spiders results from the few species that can be dangerous to humans, such as the black widow and brown recluse spiders, and from the many false facts and myths about spiders. The majority of spiders have weak venom and are only capable of harming small prey that they subdue and consume. If bitten by one of these spiders there may be some slight irritation and swelling similar to a mosquito bite or bee sting. The major spider of medical concern in Utah is the black widow. All spiders are predatory and use different strategies for capturing prey. Some spider species ambush BIOLOGY or actively hunt their prey, while others trap their prey using silk webs. Spiders can produce up to eight different types of silk that are used for different purposes including making draglines, web frame threads, egg sacs, and sticky silk used to capture prey. Spiders inject venom into prey via the fangs, and use fangs and grinding mouthparts (chelicera) to grind prey into an unrecognizable mass. They regurgitate digestive enzymes into or onto the prey and suck the liquid back through the mouth. This regurgitation and sucking can also be done through fang bite holes as in crab spiders. Note that spiders do not suck food through their fangs; fangs are connected to the venom glands, not the stomach.
Transcript of Ryan S. Davis, Arthropod Diagnostician, and Ricardo A ... · PDF fileRyan S. Davis, Arthropod...
Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory January 2013ENT-163-12PR
SpidersRyan S. Davis, Arthropod Diagnostician, and Ricardo A. Ramirez, Extension Entomologist
DO YOU KNOW
• Spidersarebeneficialpredatorsthatfeedonpestandnon-pestinsects.
• ThemajorspiderofmedicalconcerninUtahistheblackwidow.
• Brownreclusespidersdo not occurinUtah.• Thereisnostrongscientificevidencethat
hobospiderbitescausenecrotic(flesheating)lesions.
• Indoormanagementofspidersisbestdonebyvacuuming,cleaning,sealingcracksandcrevicesaroundthehome,andtolerance.
• Pesticidesareonlyrecommendedinoutbreaksituationsorwhenmedicallyimportantspiders(blackwidows)arepresent.
Fig.1.Bandedorb-weaverspider(Argiope trifasciata).
INTRODUCTIONSpidersarearachnids,agroupthatincludesother8-leggedarthropodsliketicks,mites,sunspiders,scorpions,andharvestmen(daddylonglegs).Thereareapproximately621speciesofspidersknowntooccurinUtah(AllredandKaston,1983).Spidersarebeneficialpredatorsandthemajorityofthemareharmlesstohumans.Muchfearofspidersresultsfromthefewspeciesthatcanbedangeroustohumans,suchastheblackwidowandbrownreclusespiders,andfromthemanyfalsefactsandmythsaboutspiders.Themajorityofspidershaveweakvenomandareonlycapableofharmingsmallpreythattheysubdueandconsume.Ifbittenbyoneofthesespiderstheremaybesomeslightirritationandswellingsimilartoamosquitobiteorbeesting.ThemajorspiderofmedicalconcerninUtahistheblackwidow.
Allspidersarepredatoryandusedifferentstrategiesforcapturingprey.Somespiderspeciesambush
BIOLOGY
oractivelyhunttheirprey,whileotherstraptheirpreyusingsilkwebs.Spiderscanproduceuptoeightdifferenttypesofsilkthatareusedfordifferentpurposesincludingmakingdraglines,webframethreads,eggsacs,andstickysilkusedtocaptureprey.Spidersinjectvenomintopreyviathefangs,andusefangsandgrindingmouthparts(chelicera)togrindpreyintoanunrecognizablemass.Theyregurgitatedigestiveenzymesintoorontothepreyandsucktheliquidbackthroughthemouth.Thisregurgitationandsuckingcanalsobedonethroughfangbiteholesasincrabspiders.Notethatspidersdonotsuckfoodthroughtheirfangs;fangsareconnectedtothevenomglands,notthestomach.
IDENTIFICATION
Spidersarenotinsectsandarerecognizedbyhavingfourpairsoflegsand2bodyregions(cephalothoraxandabdomen)(Figs.2-3).Theyhavebetween0and4pairsofeyesdependingonthespecies.Themostcommonnumberofeyesis6or8.Spiderspossessapairofpedipalpsormodifiedmouthparts,oftenmistakenforantennaewhichspidersdonothave,usedforsensing,mating,andfeeding.The“boxinggloves”attheendofpedipalpsorenlargedpalpsarepresentonallmalespiders.Forthemostpart,malesspidersaresmallerthanfemales.Newlyhatchedspidersarecalledspiderlingsandlooklikeadults,butsmaller.Theywillmoltmanytimes,continuingtogetlargerastheydeveloptoadulthood.
Spidersarethemostfrequentlysubmittedarachnid
pedipalps
fangs/chelicera
legs
cephalothorax
abdomen
spinnerets
abdomen
thorax
head
wings
legs
antennae
SPIDERS
INSECTS
Figs.4-5.(Top)Totalarachnidorders,and(bottom)mostfrequently
submittedspiderssubmittedtotheUtahPlantPestDiagnosticLabbetween
(UPPDL)1978and2010.
0 200 400 600 800 1000 1200 1400
Funnelweb Spiders
Widow Spiders
Wolf Spiders
Orb-Weaving Spiders
Ground Spiders
Sac Spiders
Woodlouse Spiders
Jumping Spiders
Cellar Spiders
Huntsman Spiders
Crab Spiders
Crevice-Weaving Spiders
Hacklemesh Spiders
Total Spiders Submitted
UTAH’S SPIDERS
totheUtahPlantPestDiagnosticLab(UPPDL),however,otherscommonlyencounteredincludemites(mostlyplant-feedingspidermites)windscorpions/camelspiders,ticks,pseudoscorpions,truescorpions,andharvestmen(Fig.4.).Thereareover600spiderspeciesinUtah,howeverpeoplenormallyencounteronlyafewofthese.Identifyingspiderstospeciesisdifficult,butspiderfamilies,orgroupsofspidersthatlooksimilarandhavesimilarhabits,canberecognizedwithsomepractice.InUtah,thereare13spiderfamiliesthatareregularlyencounteredinandaroundhomes.Seethegraphbelow(Fig.5)foralistofthecommonspiderssubmittedtotheUPPDLandtheirfrequency.Themostfrequentlyencounteredgroupisthefunnel-webspiders,whichincludesthehobospider.HobosarethemostcommonysubmittedspiderbecauseoftheirhabitofmigratingindoorsfromAugusttoOctobertofindmates.
Figs.2-3.(Top)Basicspideranatomy.(Bottom)Basicinsectanatomy.
Funnel-Web Spiders: AgelenidaeThemostcommonfunnelwebspidersincludethehobo(Fig.6)andgrassspiders(Fig.7).HobospidersareverycommoninhomesbetweenAugustandOctoberinUtah.Moreinformationonthehobospidercanbefoundonthehobospiderwebsite.Grassspidersareverycommonoutdoorsinsmallshrubs,grass,andinrockwallsandwoodpiles.Websareflatsheetswithafunnelandasmallholeinthemiddle.Grassspidersarenotofmedicalconcern.
Comb-Footed Spiders: TheridiidaeThisfamilyisnamedaftercomb-likeleghairsthatallowthespiderstowalkontheirdisorganizedcobwebs.Theytypicallyhangupsidedown,andmoverelativelyslowwhenwalkingoutsideoftheirwebs.Worldwide,comb-footedspidersinthegenusLatrodectus(widowspiders:Fig.8)aresomeofthemostvenomousspiders.Othercombfootedspiders(Figs.9-10)canresemblewidowspiders,butdonothavethesameharmfulvenom.
Wolf Spiders: LycosidaeWolfspidersareground-huntingspiders.Theyareeasilyrecognizedbytheireyepattern(Fig.11).Aftermating,femalewolfspidersattachtheeggsactothespinneretsuntilegghatch(Fig.13).Uponegghatch,tinyspiderlingscoverthemother’sbackforprotectionandremainthereabout1week(Fig.12).Wolfspidersareverycommoningardensandturfandshouldbeconsideredbeneficial.
Orb-Weaving Spiders: AraneidaeOrbweaversbuildtheclassiccircular/spiralweb.InUtah,thecat-facespider(Figs.14-15)andbandedgardenspider(Fig.1)arethemostcommon.Thecatfacespiderisusuallyfoundmakingwebsnearlightswhereitcapturesinsects.Thebandedgardenspider(Fig.1)mayencounterhumanactivityinthefallwhenthefemalesearchesforaplacetolayitseggsac.Thesespiderscanhelpreducethenumberofflyinginsectsaroundthehomeandshouldbeleftalone.
Ground Spiders: GnaphosidaeGroundspiders(Figs.16-17)aremostlynocturnal,ground-dwelling,wanderinghuntersfoundinleaflitter,beneathrocks,andwithinandunderdecomposingwood.Silkisusedprimarilyformakingsheltersandforenclosingeggsacs--nothunting.Thesespiderscanoccasionallybefoundindoorsontheground,orclimbingonwallsorceilings.
Sac Spiders: ClubionidaeTheyellowsacspider(Figs.18-19)isacommonhouseholdspiderthatcanbeseenwalkingonwallsandceilings.Duringtheday,itmakesawhitesilkenretreatwheretheceilingandwallsmeet,orincorners.Thevenomisnotharmfultohumans;however,bitescanbepainfulandleavearedbump.Theyaremoreaggressivethanmostspidersandcanbitemultipletimesifmishandledorifcaughtinclothesorbedding.Similarsacspiderscanbefoundoutsideinrolledplantleaves.
Fig.6
Fig.8
Fig.7
Fig.9
Fig.10
Fig.12
Fig.15Fig.14
Fig.16 Fig.17
Fig.18 Fig.19
Fig.11
Fig.13
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Jumping Spiders: SalticidaeJumpingspiders(Figs.22-23)areverycommonbothinsideandoutsidethehouse.Thesesmall,“furry”spidershavegoodvision(Fig.22)andhuntpreyinacatlikefashion.Theyareactiveduringthedaytimeandcanfrequentlybeseenaroundwindowsandbrightareaswherethelighthelpsthemlocateprey.Duringrainyorcloudydays,theycanbefoundhidinginasmallwebretreat.Retreatsarealsousedforprotectionduringmolting,egglaying,andhibernation.
Cellar Spiders: PholcidaeCellarspiders(Figs.24-25)generallyhavelong,slenderlegsandonly6eyes(Fig.24).Theyareoftenfoundindoorsindark,secludedplaceswheretheycanfillunusedareaswiththeclassic“creepy”cobwebs.CertainspeciesofPholcidaecanbeeasilymistakenforbrownreclusespiders(Loxosceles);however,theyarenotharmfultopeople.
Huntsman Spiders: SparassidaeOccasionally,large,goldenspiderswithblack“socks”onthelegs(Fig.26)aresubmittedtotheUPPDLinthefallforidentification.ThegoldenHuntsmanspideristhemostcommonHuntsman,orgiantcrabspider,inUtah,andcangrowupto2-3inchesacross!Theirflatshapeallowsthemtohideeasilyincracks,behindcurtains,andinthecrevicesoftreebark(Fig.27).
Crab Spiders: ThomisidaeCrabspidersgettheirnamefromtheirabilitytowalksideways.Asambushhunters,theywaitmotionlessforpreytocomeintorange.Manyarecoloredtomatchflowers(Fig.28),plants,androcks(Fig.29)whichhelpsthemcaptureprey.Afterenvenomatingprey,crabspiderssucktheprey’sliquefiedinsidesoutofthesmallbiteholes.Whenfeedingisfinished,thepreyappearsintact.
Crevice-weaving Spiders: FilistatidaeMostcommonlyoccrringinUtah’ssoutherncounties,thecrevice-weavingspider(Figs.30-31)canmakeitswebsaroundtheoutsidesofhomeswherecrevicesorgapsprovideprimehabitat.Thisisanotherspiderthatisoftenmistakenforthebrownreclusespider(Loxosceles reclusa),butisnotharmfultohumans.
Fig.20 Fig.21
Fig.22
Fig.25Fig.24
Fig.23
Fig.26 Fig.27
Fig.28 Fig.29
Fig.30 Fig.31
Woodlouse Spiders: DysderidaeWoodlousespiders(Figs.20-21)lookvisciousbecausetheirmountpartsandfangsprojectoutwardfromthebody.Theirpresenceandabundancecanbeassociatedwiththatof“potatobugs”(isopods:Fig.20),theirprimaryprey.Theyarecommonlyfoundoutdoorsingardensandlandscapes,butoccasionallycomeindoors.Woodlouse
OfUtah’sspiders,theblackwidowisthemajorspiderofconcernandshouldbecontrolled.Allotherspidersshouldbetoleratedoutdoors,andminimalmanagementpracticescanreducetheirpresenceindoors.Ideally,theyshouldbecapturedandreleasedwhenfoundinside.Ifadditionalcontroltechniquesaredesiredpleaseuseoneoracombinationofthetechniquesbelow.
Mechanical/Physical: Exclusion• Sealallcracksandcrevicesleadingintothe
homewithsiliconecaulk,expandablefoam,orscreen.
• Installweatherstrippingarounddoorsandwindows,especiallyalldoorsleadingtotheoutside,includingthegaragedoor.
CleaningandHabitatModification• Vacuumregularly.Spiders,webs,andegg
sacscanbesuckedup,directlyeliminatingtheproblem.
• Minimizeclutter.Spiderslovesecludedplacestohideandlayeggsacs.Simplifytheenvironmentinsidebycleaningregularlyandstoringclutterinsealablestoragebins.Outside,moveoreliminaterockandwoodpiles,oranythingthatcreatesspiderhabitat.
• Replaceexteriorlightingwithsodiumvaporlights(yellowbulbs)whicharelessattractivetoinsects.Insectsareattractedto“normal”exteriorlightsatnight.Theincreaseininsects(spiderfood)willalsoattractanincreasednumberofspiderslookingforfood.
MonitoringSpiderstickytrapsthataresoldinlawnandgardencenterscanbeplacedalongbaseboardstoprovideanindicationofwhattypeofspidersarepresent,wherehteyarecomingfrom,andcanprovidesomecontrol.TrapscontaininghobospiderattractantsarenotrecommendedforindoorusebetweenAugustandOctober,asthismayleadtoanincreaseinhobospidersinthehome.
Chemical: Insecticidesshouldonlybeusedforspidersifthereisaseriousinfestation.Avoidcalendar-basedspraysforspidersthatput“barriers”aroundstructures.Ifchemicalsarenecessaryforspiders,theyshouldbetargetedandtimedwithspideractivityandlifecycles,andatmakingdirectcontactwiththespider.Insecticidaldustscanprovidesome
CONTROL controlofspidersinvoidsandsecludedplaces,andcanevenbepuffeddirectlyontospiderwebs.Aerosolformulationscanbeeffectivewhendirectlysprayedataspider,buthaveminimalresidualeffectagainstspiders.Thereareover900insecticidesregisteredforcontrolofspidersinUtah.Themostcommonactiveingredientsare:deltamethrin,lambda-cyhalothrin,permethrin,pyrethrin,andtetramethrin.Whenusingsprays,microencapsulatedformulationsofinsecticidesaremosteffectiveagainstspidersoutdoors.Followingaretipsonchemicalcontrolofspiders.
• Insecludedareas,crawlspaces,cracksandcrevices,orwallvoids(areaswherepeoplewon’tbecomingincontactwithchemicals),useadustformulationofaninsecticidelikeTriDiepurchasedatthelocalhomeandgardenstore.Donotusethisproductasabroadcasttreatment,wherepeoplemaycomeincontactwithit.
• Liquidordustinsecticidesmaybeapplieddirectlytowebs(thisworksespeciallywellforblackwidowspiders).
• Aerosolsprayscanbeusedtodirectlysprayspiders;spidersnotdirectlycontactedwiththistreatmentwillnotdie.
• Ifanoutsidetreatmentisdesired,insecticidespraysarebesttimedwhenhoboeggsacsarehatching.Thiswilldependlargelyontemperature,butyoucanexpecteggstohatchfrommidMaytomidJuneinnorthernUtah.
Bite Prevention Tips• Tokeepwanderingspidersoutofyourbed,
removethebedskirtandpullthebedoutfromthewallabout8inchesfromAugusttoOctober.
• Takecautionwhenpickingclothesupoffthefloororinlaundrybaskets.Spidershidingintheseclothescanbemistakenlygrabbed,resultinginabite.
• Shakeoutclothingbeforeputtingiton,especiallyiftheclothingwasonthefloor.
• Storechildren’stoysoffofthefloorsospiderscan’tcanhideunderthem.
• Wearalongsleeveshirtwithsleevestuckedintogloveswhenworkingoutdoors,especiallyaroundrockorwoodpiles.
OTHER ARACHNIDS
UtahStateUniversityiscommittedtoprovidinganenvironmentfreefromharassmentandotherformsofillegaldiscriminationbasedonrace,color,religion,sex,nationalorigin,age(40andolder),dis-ability,andveteran’sstatus.USU’spolicyalsoprohibitsdiscriminationonthebasisofsexualorientationinemploymentandacademicrelatedpracticesanddecisions.UtahStateUniversityemployeesandstudentscannot,becauseofrace,color,religion,sex,nationalorigin,age,disability,orveteran’sstatus,refusetohire;discharge;promote;demote;terminate;discriminateincompensation;ordiscriminateregardingterms,privileges,orconditionsofemployment,againstanypersonotherwisequalified.Employeesandstudentsalsocannotdiscriminateintheclassroom,residencehalls,orinon/offcampus,USU-sponsoredeventsandactivities.ThispublicationisissuedinfurtheranceofCooperativeExtensionwork,actsofMay8andJune30,1914,incooperationwiththeU.S.Dept.ofAg.,NoelleE.Cockett,VicePresidentforExtensionandAgriculture,UtahStateUniversity.
Page6UPPDL,5305OldMainHill,LoganUT84322,utahpests.usu.edu T:435.797.2435
Precautionary Statement:UtahStateUniversityExtensionanditsemployeesarenotresponsiblefortheuse,misuse,ordamagecausedbyapplicationormisapplicationofproductsorinformationmentionedinthisdocument.Allpesticidesarelabeledwithingredients,instructions,andrisks,andnotallareregisteredforediblecrops.“Registereduse”pesticidesmayonlybeappliedbyalicensedapplicator.Thepesticideapplicatorislegallyresponsibleforproperuse.USUmakesnoendorsementoftheproductslistedherein.
IMAGES & REFERENCESFigures: 1,4-6,12-13,26RyanS.Davis,UtahStateUniversityExtension. Figures: 31 EdwardL.Manigault,ClemsonUniversityDonatedCollection,Bugwood.org.Figures: 2-3ErinHodgson,IowaStateUniversity. Figures: 33RichardL.Coviello,UCDavisIPMProgram.
Figures: 7,9,16-25,29 JosephBurger,Bugwood.org. Figures: 34 GaryAlpert,HarvardUniversity,Bugwood.org. Figures: 8,14-15,32WhitneyCranshaw,ColoradoStateUniversity,Bugwood.org. Figures: 35 UniversityofIdaho.Figures: 10 UniversityofWisconsin,DepartmentofEntomology,Bugwood.org. Figures: 36 DavidCappaert,MichiganStateUniversity,Bugwood.org.Figures: 11 JoelSmith,UtahStateUniversity. Figures: 27MarieKnight,UniversityofFlorida,Bugwood.org. Allred,D.M.,andKaston,B.J.1983.AlistofUtahspiders,withtheirlocalities.GreatBasinFigures: 28JonYuschock,,Bugwood.org. Naturalist,April.Vol.43,No.3:pp.494-522.Figures: 30,37SturgisMckeever,GeorgiaSouthernUniversity,Bugwood.org.
ADDITIONAL RESOURCES1.Utah’sTop20Arachnids 4.SpiderMyths:UniversityofWashingtonBurkeMuseum
2.ColoradoStateUniversityFactSheet 5.SpidersofNorthAmerica(Book)
3.UniversityofCaliforniaDavisFactSheet 6.TheBiologyofSpiders(Book)
Spider Bites • Ifyouseeaspiderbite,youshouldcatchthespiderforidentification.Findingarandomspiderinthehouse
afteramysteryskinirritationoccursdoesnotimplicatethespider.• Cleananddisinfectthebiteusingatopicalaniseptic,andcoverwithasterilebandage.• Monitorthebiteandvisityourdoctorifsymptomsprogress.• Secondarybacterialinfectionsarepossibleafteranyspiderorinsectbite,andcanbecomeseriousifleft
untreated.
Figs.32-37.OthercommonarachnidsinUtah.Thepicturesarenottoscale.Ingeneral,ticks,mites,andpseudoscorpionsaresmall,whileharvestmen,sunspiders,andscorpionsarelarger.(Toplefttoright)harvestman(daddylonglegs);camelspiderorsunspider;RockyMt.woodtickfemaleandmale.(Bottomlefttoright)pseudoscorpion;two-spottedspidermites;scorpion.
Fig.32 Fig.33 Fig.34
Fig.35Fig.37
Fig.36
FactSheetSeries:Insects—Beneficial;Structural;Nuisance;Biting,Stinging,HealthRelated
