The protein fiber of silk is composed mainly of fibroin and is produced by larvae to form cocoons. larvae spin the silk cocoon and turn into mites while inside. After hatching from the egg, the worms take one month to grow large enough to spine the silk. They spend three weeks in the cocoon, then they emerge as mites to lay eggs. Eggs hatch into worms in a few weeks, then the cycle continues.
Silkworms go through four stages of development egg, larva, pupa, and adult. The adult stage is the silkworm moth. The larva is the silkworm caterpillar. Since the silkworm grows so much, it must shed its skin four times while it is growing. This stages-within-a-stage are called instars. The Latin name for the silkworm is bombyx Mori, which means "silkworm of the black mulberry tree".
Silkworm produces silk fiber which used in the manufacture of shirts, ties, blouses, high-fashion, underwear, pajamas, and robes. Fabrics made of silk include charmeuse, shantung, crepe de chine, dupioni, noil, tussah, taffeta, and chiffons. The silk fiber is used in many industries such as parachutes, bicycle tires, and artillery gunpowder bags as well as non-absorbable surgical sutures.