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1、Unit4Web(II)JohnWyndhamFurtherInformationonText-relatedDetailsinsecticide:amaterialusedtokillinsectsinalldevelopmentalforms.Insecticidesareusedinagriculture,medicine,industryandthehousehold.Theuseofinsecticidesisbelievedtobeoneofthemajorfactorsbehindtheincreaseinagriculturalproduc
2、tivityinthe20thcentury.Nearlyallinsecticideshavethepotentialtosignificantlyalterecosystems;manyaretoxic(有毒的)tohumans;andothersareconcentratedinthefoodchain.Itisnecessarytobalanceagriculturalneedswithenvironmentalandhealthissueswhenusingthem.spiderbites:Spidersarewidelyknown,andfea
3、redbysome,fortheircapabilityofbitinghumanbeings.Whilemostspidersarebelievedtobeharmlesstopeople,somespidershavebiteswhichareknowntobemedicallysignificant,andwhichcanproducenoticeablesymptomsinhumans.Forapproximately200speciesin20genera,moderateoseveresymptomscanresult,includingnec
4、roticwounds,systemictoxicity,andinsomecases,death.Fourgeneraarepositivelyknowntohavepotentiallylethal（致命的）bites.spiderweb:Mostspidersproducesilkenthreadtobuildwebs,andsomespidersilkstrandsarestrongerthansteelstrandsofthesamethickness.Thespider,afterspinningitsweb,willthenwaiton,or
5、near,thewebforapreyanimaltobecometrapped.Thespidercansensetheimpactandstruggleofapreyanimalbyvibrations(震动)transmittedalongtheweblines.insectintelligence:Scientificresearchesshowthatsocialinsects,thosewhoshareresourcesandreproducecooperatively,suchasbees,ants,andwasps(黄峰)arecapabl
6、eofcertainintelligentbehavior.Individually,oneinsectmaynotbecapableofmuch;collectively,socialinsectsarecapableofachievinggreatthings:buildinganddefendinganest,foraging（搜查）forfood,takingcareofthebrood(昆虫等)一次产出的卵),allocatinglabor,formingbridges,andmuchmore.thetotem:Oneoftheislanders
7、hadaspiderdesignonhischest.Itisthetotem（图腾）oftheislandersonTanakuatua.Totemisananimal,aplant,oranaturalobjectservingamongcertaintribalortraditionalpeoplesasthesignofaclanorfamilyandsometimesworshipedasitsfounder,ancestor,orguardian.II.DifficultpointsoftheText“Thentheblackmenwesawt
8、odaymusthavebeendifferentones,”…(
