Queen of Textile - SILK

Silk is an important animal fibre which is the only continuous filament which is made up of protein. It is also called as Queen of Textiles because of its superior luster, strength and enough elasticity etc.

            Major Silk producing countries in the world today are Japan, China, India, Soviet Union, Italy, South Korea, Turkey, Iran, Brazil, Spain, France, Syria and Austria.

Sericulture - Life Cycle of Silk worm:

            There are four stages in the life cycle of a silk worm:

1.      Egg

2.      Caterpillar

3.      Chrysalis or Pupa

4.      Moth

Egg:

            Eggs that have been selected are kept in cold storage for approximately six weeks after they are laid. Then, they are placed in incubators where they remain until all are hatched after 12 to 15 days. One ounce of egg yields many as 36,000 silk worms. When the worm appears perforated paper is placed over them and supply of chopped mulberry leaves is spread on the paper. The worms climb through the holes, dirt and egg residues are left behind. 

Caterpillar:

                          

            It is a larva about ¼” in length. The larva requires careful maturing in a controlled atmosphere for approximately 20 to 30 days. During this period they are fed on finely cut mulberry leaves 5 times a day. During this period the silk worms do nothing but eat, except four periods of sleep lasting a day at a time during which they shed their skins and grow new ones(moulting). After its fourth moult, the silk worm settles down to a final feed lasting about 10 days, during which it eats 20 times its own weight of leaves. It is over 3 inches long and weight 5 gms.

            The worm is now fully grown and it stops eating and begins to spin filaments. The liquid silk (Known as FIBRON)is present in two glands in the silk worm. From these glands it flow into two channels to a common exit tube called, the spinnerate in the silk worm head. As it emerges the liquid silk hardens into very fine filaments and these are coated and cemented together by a gummy substance called Sericin which comes from two other glands nearby. As the silk emerges, the silk worm moves it head backwards and forwards. Gradually it surrounds itself with a strongly built cocoon made from a continuous silk strand. Spinning usually takes 2 to 3 days.

Chrysalis or Pupa: 

            After finishing spinning, the enclosed silk worm undergoes a remarkable transformation, passing from the form of a caterpillar into an inert chrysalis or Pup. If left undisturbed, the pupa inside the cocoon develops into a moth, within two weeks. The moth escapes from the cocoon by secreting a fluid that dissolves away a section of cocoon to make a hole through which the moth crawls out. The continuous silk filaments are thus broken up into the thousand of short pieces which are useless for reeling. So within few days of making its cocoon the pupa must be killed by steaming. Some good cocoons are kept for breeding.

Moth: 

            The moth emerge from the cocoons are small grayish white insects and lives only a few hours. They cannot fly, they have no mouth and cannot eat. The sole job of the silk worm is to mate and lay its batch of 300 – 400 eggs. After laying eggs, the moth dies.