New genetically modified silkworms produce cocoons incorporating the stretchier, stronger fibers spiders use to spin their webs, according to a new study. (See pictures: "World's Biggest, Strongest Spider Webs Found.")

"Our hope was that by embedding spider-silk protein [gene] sequences within silkworm silk [gene] sequences, we could get those proteins to co-assemble ... into composite fibers, and that is what happened," said study co-author Don Jarvis, a molecular biologist at the University of Wyoming in Laramie.

The genetically engineered silkworms produced silk that was still 96 to 98 percent silkworm, with only 2 to 4 percent of the fiber proteins coming from spiders, Jarvis said.

Even with such a small