Produced by the Larva of a species of moth ( Bombix mori) commonly called the silkworm. It is native to china and has been cultivated successfully in a number of countries including Iran, Turkey, India. The finest silk for the rug-making traditionally comes from China and an area around the caspian Sea. In Azerbijian region produces a type referred to as rasht silk, which is generally regarded as the best in the world. Silk is used either on its own or in combination with wool by a number of individual groups in all the major rug-making countries. Silk has a number of limitations. It is reasonably hardwearing but it lacks the springiness and suppleness of wool. Silk rugs tend to retain any creases or scuffing in the pile, and far greater care is needed to protect them from damage. It is also extremely expensive. However, its physical beauty is unsurpassed.