Spider silk

Spider silk is a fibre secreted by spiders. Spider silk is a remarkably physically powerful material. Its tensile strength is similar to that of high-grade steel — according to Nature , spider silk has a tensile strength of approximately 1.3 GPa, while one source lists a tensile strength for one form of steel at 1.65 GPa. However, spider silk is much less dense than steel; its ratio of tensile strength to density is perhaps 5 times better than steel — as strong as Aramid filaments, such as Twaron or Kevlar. In fact, a strand of spider silk long sufficient to circle the earth would weigh less than 16 ounces (less than 460 grams).
Spiders usually use their silk to make structures, either for protection for their offspring, or for predation on other creatures. They can also suspend themselves using their silk, in general for the same reasons.
The Trapdoor spider will burrow into the ground and weave a trapdoor-like structure with spindles around so it can tell when prey arrives and take it by surprise.
Many small spiders use silk threads for ballooning. They extrude several threads into the air and let themselves become carried away with upward winds. Although most rides will end a few meters later, it seems to be a ordinary way for spiders to invade islands. Many sailors have reported that spiders have been caught in their ship's sails, even when far from land.