Pound for pound, spider silk is the toughest fiber in the world—rivaling even steel. A single spider can produce up to seven different varieties. Some are stiff and strong, acting like girders to hold up a web. Others are extremely elastic or sticky to entangle prey. "What makes spider silk amazing," says biologist Jessica Garb of the University of California at Riverside, "is its strength in combination with elasticity."
Some things about spider silk are difficult to understand. But Garb and her colleague Cheryl Hayashi have unraveled the genetic code for one of the more perplexing types of silk—the strands spiders use to weave their egg cases. Each case must be tough enough to keep out parasites, impermeable to rain and fungus, and breathable while insulating eggs from temperature extremes. These qualities alone would make an impressive fabric, but Garb and Hayashi speculate that egg cases may even block ultraviolet light and, unlike certain kinds of spider silk, resist shrinkage.
The two biologists studied the silk gene to shed light on hundreds of millions of years of spider evolution. But their work opens the way for materials scientists to try to duplicate the fiber. "It could be thought of as a blueprint, a recipe for a superior material based on one of the strongest natural fibers," says Garb. "There has even been talk of bullet-proof finery."
"Unraveling Spider Silk." "Modular Evolution of Egg Case Silk Genes Across Orb-Weaving Spider Superfamilies." Jessica E. Garb and Cheryl Y. Hayashi in Proceedings of the National Academy of Sciences, Vol. 102, No. 32, pages 11379–11384; August 9, 2005. www.pnas.org