Now we're looking at the amazing structural properties of spider silk. The stuff is stronger than steel, yet it can stretch to 140 percent of its length. A fly, caught in a web, cannot trampoline back off the web. The silk also stays tough at low temperatures. But its properties vary.
Spiders have six spigots for spinning silk, and they mix their fluids to regulate the composition.
They can make one kind of silk for catching flies and another to shape a parachute that'll carry them away on the wind. A spider might spend an hour weaving a web to trap bugs. A day later the gossamer cross members will be broken while the main guy lines stay intact. The spider eats the protein-rich broken strands. Then he spins new silk from the recycled strands.