Wonder Webs

　　Spider webs are more than homes, and they are ingenious traps. And the world’s best web spinner may be the Goldern Orb Weaver spider. The female Orb Weaver spins a web of fibers thin enough to be invisible to insect prêt, yet _____1____ enough to snare a flying bird without breaking.

　　The secret of the web’s strength? A type of super-resilient ____2____ called dragline. When the female spider is ready to ____3_____ the web’s spokes and frame, she uses her legs to draw the airy thread out through a hollow nozzle in her belly. Dragline is not sticky, so the spider can race back and forth along ____4___ to spin the web’s trademark spiral.

　　Unlike some spiders that weave a new web every day, a Golden Orb Weaver _____5_____ her handiwork until it falls apart, sometimes not for two years1. The silky thread is five times stronger than steel by weight and absorbs the force of an impact three times better than Kevlar, a high-strength human-made ____6____ used in bullet-proof vests. And thanks to its high tensile strength, or the ability to resist breaking under the pulling force called tension, a single strand can stretch up to 40 percent longer than its original _____7____ and snap back as well as new. No human-made fiber even comes ____8____.

　　It is no ____9____ manufacturers are clamoring for spider silk. In the consumer pipeline: high-performance fabrics for athletes and stockings that never run2. Think parachute cords and suspension bridge cables. A steady _____10_____ of spider silk would be worth billions of dollars—but how to produce it? Harvesting silk on spider farms does not ____11_____ because the territorial arthropods have a tendency to devour their neighbors.

　　Now, scientists at the biotechnology company Nexia are spinning artificial silk modeled after Goldern Orb dragline. The ____12____ step: extract silk-making genes from the spiders. Next, implant the genes into goat egg cells. The nanny goats that grow from the eggs secrete dragline silk proteins in their ______13____ . “The young goats pass on the silk-making gene without____14____ help from us,” says Nexia president Jeffrey Turner. Nexia is still perfecting the spinning process, but they hope artificial spider silk will soon be snagging customers ____15____ the real thing snags bugs.

　　奇妙的網

　　蜘蛛網對蜘蛛來說不僅僅是家，它們還是奇妙的引蟲入網的陷阱。世界最棒的織網者可能是Goldern Orb Weaver的蜘蛛。雌性的Orb Weaver可以織出很細的絲，連被捕的昆蟲都看不見。但卻是堅韌得可以將一只飛入網中的鳥纏住而不弄斷。

　　那么蜘蛛網為何有如此強的力度呢?有一種網絲有超強的彈力，叫做蜘蛛的避敵絲。當雌性的蜘蛛準備織蛛網的輻條和框架時，它就用腿從一個空的噴嘴里勾出輕飄飄的絲線，放到肚子里面。避敵絲不粘，因此蜘蛛可以沿著它來回活動編織，從而來編織網的標志性螺旋。

　　與某些種類的蜘蛛不同，它不用每天織新網，只要網不破，就能一直用下去，有時一用就兩年。柔軟如絲的蛛絲的強度比相同重量的鋼絲大五倍，同時可以承受的力度比一種高強度的防彈衣的人工材料大三倍多。同時由于它有很強的張力，或者說一種能夠抵住被弄斷的往下的拉力。一根單線可以伸長至比原始長度長40%以上，然后重新彈回至原來的長度，還像新的一樣。沒有一種人造纖維可以與它相媲美。

　　因此，生產者們強烈要求蛛絲也就不足為奇了。在消費者這一方面，人們強烈要求的是高質量的運動服和永不脫絲的長襪。試想一下另外如降落傘繩索和吊橋上的繩索。如果有穩(wěn)定的蛛絲的供應，它將是一個價值上億的產業(yè)，但問題是怎么樣才能生產出穩(wěn)定的蛛絲呢?試圖以養(yǎng)蛛場收獲蛛絲是行不通的，因為生長在那塊地方的節(jié)肢動物有可能會吞掉它們的這些“鄰居”。

　　現在，生物工藝公司“Nexia”的科學家們正在研制一種仿制Goldern Orb避敵絲的人工絲。第一步驟：從蜘蛛身上抽取制絲的基因，然后，將這些基因植入山羊的卵細胞中。由這些卵細胞發(fā)育生的雌山羊會在羊奶中分泌一種帶絲的蛋白質。“Nexia”公司總裁吉弗利•特納說：“這些幼山羊不需我們的任何幫助就可以將制絲基因遺傳過去。”“Nexia”繼續(xù)在完善它的制絲過程，但是他們希望這種人造蜘蛛絲能盡快地吸引住顧客，就像真正的蛛絲抓住昆蟲一樣。