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1、Unit1ThePerfectSwarmNarrator:Damagefromswarmsoflocustscanreachdisastrousproportions.Asingleswarmofdesertlocustscanconsumeover70,000metrictonsofvegetationaday.Thereis,however,onecontinentthat’slocust-free:NorthAmerica.旁白：蝗虫群的破坏可以达到灾难性的程度。一堆沙漠蝗虫每天可以消耗超过70000公吨的植被。然而，有一个大陆没有蝗虫：
2、美国北部。Interestinglyenough,thiswasn’talwaystrue.Forhundredsofyears,theRockyMountainlocustwasacommonpestintheAmericanWest.Backinthemid-1800s,thousandsofpioneersjourneyedacrosstheU.S.insearchoffreelandandnewopportunities.Theysettledonthefrontierofthewesternstates,andbegantofarmt
3、helandintensively,growingcornandothercrops.有趣的是，这并不总是真的。几百年来，落基山蝗虫是美国西部常见的害虫。早在19世纪中期，成千上万的拓荒者就穿越了这座城市。美国在寻找自由的土地和新的机会。他们定居在西部各州的边境，开始集中耕种土地，种植玉米和其他作物。Then,in1875,outofnowhere,ararecombinationofaircurrents,drought,andbasicbiologyproducedtherightconditionsforanunthinkableeven
4、t,theworststormeverrecorded,the“perfectswarm.”Itcameoverthehorizonlikeastrange,darkcloud.Notmillions,notbillions,buttrillionsofinsects,sweepingthroughthelandlikealivingtornado.Thosewhosawtheincredibleeventandsurvivedneverforgotwhattheywitnessed.然后，1875年，突然间，罕见的气流、干旱和基本生物学的结合
5、为一场不可想象的事件创造了合适的条件，这是有史以来最严重的风暴“完美群”。“它像一朵奇怪的乌云般从地平线上掠过。不是几百万，不是数十亿，而是数万亿的昆虫，像活生生的龙卷风一样横扫大地。那些看到了令人难以置信的事件并幸存下来的人从来没有忘记他们见证了什么。TheswarmcametogetheroverthestateofTexas,andsoonmovedquicklyacrossthefrontierinahugedestructivecloudthatwasnearly3,000kilometerslong.Thestormspreadno
6、rthtowardsNorthDakota.ThelocustseventuallywentasfarwestastheRockyMountains,leavingapathofdevastationanddestructionwherevertheywent.这些蝗虫群聚集在德克萨斯州上空，很快就在一片巨大的破坏性云层中迅速穿越边境，这片云长达近3000公里。风暴向北扩散到美国北达科他州。蝗虫最终向西一直走到落基山脉，留下了一条毁灭和毁灭的道路。Anaccountfromonepersonwhoobservedtheswarmdescribe
7、dthelocuststorm.Thelocustscamedownfromtheskylikehail.Frightenedpeopleranscreamingintotheirhomesasthelocusts’clawsdugintotheirskinandhungupontheirclothing.Theyheardsharpcracksastheinsectscameunderfoot.Thelargelocustswereeverywhere,lookingwithhungryeyesturningthiswayandthat.Th
8、eirbodiesblockedthesun,bringingdarknessalongwiththedestruction.一位观察蝗虫群的人描述了
