The raw material for silk production is insect saliva from the caterpillar of the silkworm moth Bombyx mori. The insect spins the saliva into a cocoon when the insect is ready to pupate. Remember that life cycle of moths and butterflies goes egg -- larva -- pupa -- adult.

The silkworm (it's not really a worm; it's a caterpillar) is a domesticated insect that does not occur in nature. Silk cultures are believed to have originated in China approximately 4000 years ago and after these thousands of years of human rearing and care, the larvae have lost the ability to climb up their host plant to feed on the mulberry tree. Silkworm larvae must be fed and are totally dependent upon humans for survival.

An entire science called sericulture has developed in China centering on the growing of silkworms and harvesting of silk. The cocoon of the silk moth is comprised of one continuous strand of silk. This strand is carefully unwoven. Large factories are devoted to rearing the silkworm and processing plants are devoted to unwinding and processing the silk into commercial thread and cloth.