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How Do Silkworms Make Silk? You'll Be Amazed to Know

How Do Silkworms Make Silk?
Have you ever wondered what goes into the making of that fine, lustrous, beautiful silk thread, which further gets transformed into a classic garment and adorns your look? This AnimalSake post gives you a detailed explanation on how silkworms make silk.
Snehal Motkar
Last Updated: Jul 31, 2017
Did You Know?
Around 50,000 silkworms are killed, while extracting silk through sericulture, for making one silk sari.
If we come down to the basics, silk is a natural protein fiber, produced by the larvae of certain specific insects, like caterpillars of moth. It is composed mainly of fibroin. Other insects also produce silk, but the aforementioned type has been used for textile manufacturing. Moreover, researchers have determined that out of the many species of silk moths, 70 are of certain economic value. Again out of these 70, there are only 4 natural silk varieties that have a commercial value -- Mulberry silk, Tasar silk, Muga silk, and Eri silk. The best type of silk comes from the mulberry silkworm Bombyx mori, which is obtained by domestication. The other silkworm species produce silk that is known as "wild silk", since the silkworms are grown in the remote forests in natural weather conditions.

We all know that silk was discovered in China, but how? Very few people know when, where, and how was it discovered. There are many legends about this strong and rich fabric; however, the following is the most popular one, and it goes like this. A Chinese Emperor named Huangdi was extremely annoyed seeing his mulberry trees getting damaged at a rapid rate and ordered his wife Xilingshi to find out the cause of this damage. The empress obeyed his command and started observing the trees very carefully for a few days. To her surprise, certain white-colored worms were constantly eating the leaves and then started spinning a shell around themselves with a shiny, white material. When the empress dropped one shell into hot water, she found a slender thread unwinding itself from the shell. Within some time, she was holding a single long, shiny thread, which is known as silk in today's world.
Nature-made Silk
Silk cocoon
A Completely Formed Silk Cocoon
Silk production is nothing but one out of the several stages through which the silkworm goes through during its life cycle, finally unraveling the most desired and loved silk thread out of a cocoon.
A cocoon is a protective case or shell that the silkworm spins around itself. A silkworm stops eating when it is ready to enter the pupal stage and spin the cocoon. The pupal stage is when the larval structures of the silkworm are broken down forming adult structures and the caterpillar gets transformed into a moth. The cocoon helps the worm to stay protected from the harsh and unfriendly weather conditions. Hence, usually the insects spin a cocoon around themselves at the start of winter, and spend the entire season inside the cocoon without the need for food and water. This stage is often referred to as the sleeping stage of the silkworm.

The cocoon is made of silk, which is spun from a pair of specially modified salivary glands known as sericteries. These sericteries are used for the production of fibroin, a creamy, soft, clear fluid that is released from the insect's mouth. The cocoon is formed or spun from a single thread of silky fluid, which solidifies after coming into contact with air. The silk thread formed out of one entire cocoon is around 300 m long, and a silkworm takes 3 to 4 days to spin the cocoon completely. The worm rotates itself in the direction that forms the number 8.
Tasar silk is produced by the silkworm, Antheraea mylitta and Antheraea paphia, and it is copperish in color. These silkworms feed on the food plants, like Sal and Arjun.
Muga silk is produced by the silkworm, Antheraea assamensis, and it is golden-yellow in color. The food of these silkworms includes the aromatic leaves of Som and Soalu plants. Muga silk is mainly used for making silk saris.
Eri silk, often referred to as Endi or Errandi silk, is produced by the silkworm Philosamia ricini, and it is creamy-white in color. As compared to other types of silk, eri silk is a little less shiny. These silkworms mostly feed on castor leaves.
Silk Quality Depends on the Silkworm's Diet
Silkworm eating mulberry
Silkworm Feeding on Mulberry Leaves
Silkworms have an amazingly large appetite, which keeps on increasing as they grow. They keep cutting and slicing the mulberry leaves (staple food) and never stop eating throughout the larval stage, which spans over 35 days. They have large, strong jaws for cutting those hard mulberry leaves and munching on them.
However, the offspring needs young leaves, which are soft and tender to cut with their developing jaws. Silkworms do not need water at all; they just need fresh and moist mulberry leaves every day, and there is tremendous increase in leaf consumption during the last three weeks. If these worms eat wilted or dead mulberry leaves, they do not produce good quality silk.

After eating for almost six weeks continuously, the silkworm grows to its maximum size of 3 inches. It stops eating and changes color. At this stage, it is 70 times larger than the original size and weighs 10,000 times more than it was when hatched. During this stage, the silkworm sheds its skin four times. When fully grown, the silkworm attaches itself to a twig for the next stage -- spinning the cocoon.
Silk Production through Sericulture
Boiled silk
Boiling Process of Silk Cocoons
China began producing silk almost 5000 years ago, and this long duration is enough to make the mulberry worm (better known as silkworm) completely dependent on humans for its life. No silkworms can now survive in the wild; they are found only in kids' cardboard boxes and in commercial silk production farms.
In natural silk production, the silkworm rests inside the cocoon for at least three weeks to let the transformation happen. Then it chews up some part of the cocoon and makes a hole for its emergence out of it. Unfortunately, in sericulture, the pupa is not allowed to escape from the cocoon, because it is put in boiling water eventually causing death of the pupa. This is done to obtain the single long thread of silk, which will otherwise break into smaller ones, decreasing the commercial value of the final product.
A New Approach to Silk Production
Silkworm cocoon
Silk Cocoon After the Emergence of Moth
The conventional method of silk production involves killing of several silkworms to make silk clothes, which isn't a very good idea. Thus, Kusuma Rajaiah (from India) found a new technique of producing silk without killing the silkworms and named it as "Ahimsa Silk".
Ahimsa stands for non-violence and respect for every living being on Earth. He says that Mahatma Gandhi, a man of non-violence, was the inspiration behind his new approach. It was Mahatma Gandhi's dream to produce silk without killing worms, but unfortunately it remained unfulfilled at that time. However, Kusuma Rajaiah carried his dream forward and became successful in fulfilling it.

According to this new method of silk production, the pupa is allowed to emerge from the cocoon and then the cocoons are steamed or boiled for extracting silk threads. The only downside to this method is that the long silk thread breaks into smaller threads, which are difficult to spin into a yarn.
It's always good to know where all our stuff comes from including the fabric used for our clothes. Now that we know how those little worms are killed before transforming into moths, we should focus on using more and more "peace silk" or "ahimsa silk". We can also lend our support to companies that sell such Eco-friendly types of silk, or recycled silk by promoting its use.