Silkworms and silk

Production of silk from silkworms is called Sericulture. The lifecycle of any moth goes through many stages. Initial form is that of an egg. The eggs hatch into caterpillars which eat, grow and molt several times. The caterpillar or larva changes into a pupa. From the pupa emerges the adult insect.

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Silkworms are not worms but the caterpillars of the Asian silkworm moths. A moth may produce about thousands of eggs. Their silk glands may form more than a quarter of their weight. Many caterpillars are silk makers, the most common species being ‘bombyx mori’. These silkworm moths are domesticated like the honey bee.
 
Most important period in silk production comes during the silkworm’s brief life span of about 20-24 days. The new born worms are fed with mulberry leaves several times a day. By four weeks time, they are more than 5 cms. They are fed regularly and they molt repeatedly. After several molts, they get ready to stop eating and start to spin a cocoon. Cocoons are nothing but a pupal casing made by the caterpillar.

The silk spinning organ of the caterpillar is called spinneret. Silk glands open into spinneret on the caterpillar’s lip. When secretions passing through the spinneret come in contact with air, they harden, forming a two-part thread. First the caterpillar weaves a net to hold itself. Then it swings its head from side to side in the shape of number ‘8’ spinning approximately 1 mile of filament and encloses itself in a cocoon in two or three days. Caterpillars feeding on different foods may spin silk of different colors. The worms get sealed inside the cocoon within 2 days. They transform themselves into a pupa and then an adult moth. 

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The silk is obtained from undamaged cocoons are wound on a reel. During this process, some of the silk worm gets killed. A silk sari is actually got as a result of death of thousands of silkworms.  One cocoon may contain approximately 1000 yards of silk filament. Silk at this stage is what is called raw silk. To obtain about 1kg of silk, there is a need of about 5500 silkworms.

India is the second largest producer of silk after the Chinese who are the pioneers.

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