Silk, one of the oldest known fibres is a protein fibre, produced by the silkworm by spinning around its cocoon. The entire process of starting from the eggs till the worms are grown up and cocoons are formed as shown in the diagram below. The silk farmers let the caterpillars that make the largest cocoons, to turn into moths. The moths then laid eggs and the eggs hatched out more caterpillars making even bigger cocoons. Over the centuries, the size of the cocoon has increased and silkworm cocoons are now much bigger than the cocoons of other caterpillars (see picture). At least half a mile of continuous thread may come from one cocoon.
The silk threads are then dipped in colour liquid and used for preparing the colourful silk Saree. Chinese are the ones who started the manufacturing the silk sarees.Out of the numerous species of silk moths, scientists have enumerated about 70 silk moths which are of some economic value. The four commercially known varieties of natural silk are (1) Mulberry silk (2) Tasar or Oak Tasar silk (3) Muga silk and (4) Eri silk.
Although the bulk of world silk supply comes from the silk moth Bombyx Mori which is domesticated, the other varieties of silk are known as wild silk, as they are grown in remote forest trees in natural conditions.