Spider silk is a protein fiber spun by spiders. Spiders use their silk to make webs or other structures, which function as nets to catch other animals, or as nests or cocoons to protect their offspring. They can also use their silk to suspend themselves. All spiders produce silks, and a single spider can produce up to seven different types of silk for different uses. Consisting of mainly protein, silks are about a sixth of the density of steel (1.31 g/cm3). As a result, a strand long enough to circle the Earth would weigh less than 500 grams (18 oz).
Many small spiders use silk threads for ballooning. They extrude several threads into the air and let themselves be carried away by winds. Although most rides will end a few yards later, it seems to be a common 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. The extremely fine silk that spiders use for ballooning is known as gossamer. The threads of spider silk made of protein molecules are stronger than steel of the same size. Also spider webs can stretch and absorb water.
Spider spotted near Pune