Kong Posh: Silk the queen of Textiles

Sham S.Misri

Silkworms were domesticated in China thousands of years ago. Stories have been told through the generations based on fact and partly on legend. The tale which persists is that about 2,640 B.C. A Chinese empress was watching the cocoons that little worms were spinning in the mulberry trees in her palace gardens. She unwound one of the threads on a cocoon and found that it was one, very long strand of shiny material. Fascinated, she pulled strands from several cocoons through her ring to form a thicker thread. Eventually, with the help of her ladies of the court, she spun the threads into a beautiful piece of cloth to make a robe for the emperor, Huang-Ti. This magnificent material, silk, became known at the "cloth of kings".

For thousand of years the royal family of China had silk. The Chinese kept the secret of how silk was made for 2500 years. Silk cloth was sold to the West, but the source of the shiny thread that made the material was not revealed. The penalty in China for telling that the silk came from the cocoons of the little silkworms was death! Some very strange ideas were formulated by Westerners to explain the origin of silk. Here are a few: Silk came from the colored petals of flowers in the Chinese desert, silk came from a spider-like animal that ate until it burst open and the silk threads were found inside its body.

Legend has it that the Japanese carries off four Chinese maidens, who knew the secret of silk, along with mulberry shoots and silk moth eggs. Today Japan is the leading producer of silk! Another story is that a Chinese princess married an Indian prince. She carried silkworm eggs and mulberry shoots to India in her headdress and the secret of raising silkworms in her head.

Two Christian monks told Emperor Justinian of Constantinople that they had learned the secret of silk. Emperor send them back to China to get eggs and mulberry shoots for him. They returned many years later with the eggs and shoots hidden inside their hollowed-out walking sticks. Since Justinian was the emperor of Constantinople, a crossroads city, the secret soon spread throughout Europe.

After hatching from an egg, the silkworms eat mulberry leaves and grow larger. When they are finger-sized, they spin a cocoon, pupate inside the cocoon, and then emerge as a moth to mate and female lays nearly 400 -500 eggs. Silkworms go through four stages of development, as do most other insects: egg, larva, pupa and adult. The larva is the silkworm caterpillar. The adult stage is the silkworm moth.

If the silk moths are allowed to emerge from the cocoons, they would make holes in the silk thread. Silkworm farmers kill the pupas inside the cocoons by baking them in a hot oven or sun drying. Then the cocoons are soaked in boiling water to loosen the threads. A person finds the end of the thread and places it on a winding bobbin. Then a machine unrolls the cocoon, winding the silk from five to six cocoons together to make one silk thread. Then the thread is woven into cloth.

Silkworms are insects. All insects have six legs in the adult stage. Silkworm caterpillars have six real legs, plus five pairs of false legs on the rear of the body used for grasping twigs and leaves. Silkworms shed their skins four times while growing. Silkworms are cold-blooded, as are all insects. A warm-blooded animal always has the interior of its body at the same temperature (98.6°F or 37°C for a human) unless it is sick. If their interior temperature gets too high or too low, it will die. A cold-blooded animal's interior temperature is usually within a few degrees of the air around it.

Mostly the smallest caterpillars, which make the smallest cocoons, turn into male moths. The big caterpillars turn into female moths. The medium-sized worm’s ones can go either way.

Silkworm moths don't eat or drink anything. They mate, the female lays eggs, and then they die within 3-6 days. Silkworms operate entirely on instinct.

In order to unwind the cocoon, we kill the pupa inside. Place the cocoons in a 200°F (90°C) oven for 30 minutes. Then drop the cocoons in boiling water. After five minutes, one can begin to unwind the cocoon. Unwinding five at a time will make a fine, strong, thread.

Raising silkworms needs space and access to fresh mulberry leaves, and silkworm eggs.

Caterpillars eat for about 26 days before spinning silk. It takes about 3 days to fully spin a cocoon and turn into a pupa. The moth emerges from the cocoon after about 21 days.

The female moth lays eggs about 2 days after emerging from the cocoon.

Silkworms only eat fresh mulberry leaves which are available in most temperate climates in the spring and summer. Silkworms will not eat any other food.

Once eggs are out of the refrigerator they will hatch. Fresh leaves are fed and growth starts.

Hygienic conditions, maintenance of proper temperature and humidity gives good results.

Sometimes the tiny silkworms will eat their shed skin. The larger ones don't. Each stage the silkworm goes through is called an "instar". First instar caterpillars are black. The second and third instars are grayish-white with black heads. The fifth and final instar has a white head. In between each instar is a time of resting and molting. We say the silkworm is "sleeping".

The silkworm does 80% of its eating during the fifth instar. The silk glands now make up 25% of its body weight. The larva has increased its size 10,000 times since birth. The final instar of the larval stage is 2-3/4 inches long.

In each instar, the caterpillar has six real legs (as do all insects). It also has five pairs of false legs on the rear of its body. The body is made up of thirteen segments, each of which has a black dot on the side. These dots are called spiracles, and the silkworm breathes through them.

The silkworm eats continuously for twenty-six days. Then it stops eating and spins its cocoon. The silk thread from a single cocoon is about one-and-a-half kilometers (one mile) long. The caterpillars like to spin cocoons in dry grass where it forms cocoons.

The cocoon-spinning process takes about three days. While spinning, try not to disturb their threads or they will have to start over again. Once the cocoons are all spun, remove dried-up leaves to prevent mold from forming. The silk is actually hardened silkworm saliva. When the silkworm ate leaves, they were digested and nutrients were sent into the bloodstream. The silk glands absorbed these nutrients. The larva has a small spinneret on its lip, through which the silk emerges. The single strand of silk that forms the cocoon is about one mile long!

The silkworm moves its head in figure 8 patterns as it spins the cocoon. When the cocoon is partially made, you can see the head moving around inside if you hold it up to the light.

Pupa and moth

Inside the cocoon, the silkworm sheds its skin one last time and becomes a brown-shelled pupa. Inside this shell, the pupa takes three weeks to change into the adult silk moth. When the transformation is complete, the moth emerges from the cocoon. The adult moth has a special secretion which is used to dissolve the silk so it can push its way out of the cocoon.

When the silk moths emerge, their wings are crumpled, but they get pumped full of fluid and harden it about an hour. The moths cannot fly since their bodies are large and their wings are small. The moths do not eat or drink.

Females silk moths are significantly larger than males. Females periodically extrude a scent gland through the hole in their abdomen. Males have a flap of skin at the end of their abdomen and flutter their wings frequently. Each moth will expel a reddish-brown fluid shortly after emerging from the cocoon. This fluid is like the moth's "urine" that it retained since it couldn't "urinate" while it was in the cocoon.

The silkworm moth mates with another moth within hours of emerging from the cocoon. The moths remain mated for one day, then separate. The female lays eggs immediately afterward. The moths do not eat, and die naturally after one week.

The moths stay mated for about a day. After separation, the female lays eggs and the male looks for another female. Sometimes another male mates with the female before she can lay eggs. Each female will lay between 200 - 500 eggs! Put paper on the bottom of the container and remove empty cocoons as the moths emerge. The moths will lay eggs on the paper. When the moths are dead, save the dead moths and cocoons to make display cases.

It is interesting to note that one ounce of silkworm eggs contains 40000 eggs (1500 eggs per gram). These worms will eat 1500 kilograms of mulberry leaves, and will spin cocoons. The yields may vary. On an average 50 kilograms of silk cocoons may be harvested.

When first laid, all eggs are yellow. After three days, they will turn white if they are infertile, or turn black if they are fertile.

Care to be taken while rearing;

Change mulberry leaves at least three times a day. Silkworms will not eat dried-up leaves.

Do not disturb the silkworms once they start to spin. If the framework for the cocoon is disturbed, then they will not make a cocoon. They will turn brown, then black, and die.

Avoid overcrowd the silkworms. Remove old leaves and droppings before mold starts to form.