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B第九篇：Wonder WebsSpider webs are more than homes, and they are ingenious traps. And the world’s best web spinner may be the Golden Orb Weaver spider. The female Orb Weaver spins a web of fibers thin enough to be invisible to insect prey, yet___tough____?enough to snare a flying bird without breaking. The secret of the web’s strength? A type of super-resilient___silk____?called dragline. When the female spider is ready to___weave___?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___it___?to spin the web’s trademark spiral. Unlike some spiders that weave a new web every day, a Golden Orb Weaver____reuses___?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___material____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_length and snap back as well as new. No human-made fiber even comes____close___. It is no___wonder___?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____supply___?of spider silk would be worth billions of dollars — but how to produce it? Harvesting silk on spider farms does not_work_?because the territorial arthropods have a tendency to devour their neighbors. Now, scientists at the biotechnology company Nexia are spinning artificial silk modeled after Golden Orb dragline. The_first?step: extract silk-making genes from the spiders. Next, implant trie genes into goat egg cells. The nanny goats that grow from the eggs secrete dragline silk proteins