Sericulture

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Sericulture is the rearing of silkworms for the production of raw silk. Although there are several commercial species of silkworms, Bombyx mori is the most widely used and intensively studied. According to Chinese records, the discovery of silk production from B. mori occurred about 2700 BC. Today, China and Japan are the two main producers, together manufacturing more than 50% of the world production each year.

[edit] Production

Silkworm larvae are fed cut-up mulberry leaves, and, after the fourth molt, climb a twig placed near them and spin their silken cocoons. The silk is a continuous-filament fiber consisting of fibroin protein, secreted from two salivary glands in the head of each larva, and a gum called sericin, which cements the two filaments together. The sericin is removed by placing the cocoons in hot water, which frees silk filaments and readies them for reeling. The immersion in hot water also kills the silkworm larvae.

Single filaments are combined to form yarn. This yarn is drawn under tension through several guides and wound onto reels. Finally, the yarn is dried, and the now raw silk is packed according to quality.

The stages of production are as follows:

The silk moth lays eggs.
When the eggs hatch, the caterpillars are fed mulberry leaves.
When the silkworms are about 35 days old, they are 10,000 times heavier than when they hatched. They are now ready to spin a silk cocoon.
The silk is produced in two glands in the silkworm's head and then forced out in liquid form through openings called spinnerets.
The silk solidifies when it comes in contact with the air.
The silkworm spins approximately 1 mile of filament and completely encloses itself in a cocoon in about two or three days but due to quality restrictions, the amount of usable silk in each cocoon is small. As a result, 5500 silkworms are required to produce 1 kg of silk.
The silkworm then metamorphoses and changes into a moth; however, the silkworm is usually killed with heat before it reaches this stage. The silkworms are killed, because once they reach the moth stage, the moth secretes a fluid to dissolve the silk so it can emerge from the cocoon. This damages the cocoon and the silk then becomes a lower quality. Some silkworms are allowed to live to be used for breeding.
The silk is obtained from the undamaged cocoons by brushing the cocoon to find the outside ends of the filament.
The silk filaments are then wound on a reel. One cocoon contains approximately 1,000 yards of silk filament. The silk at this stage is known as raw silk. Just one thread consists of 48 individual silk filaments.
A yarn can now be formed by combining several threads of silk.