Sericulture: Rearing of Silkworm to Produce Silk – Definition, Process, Moriculture, Rearing Silkworm, Silk Reeling

When you think of summer apparel, linen, cotton, etc. are frequently the fabrics that come to mind. You might not instantly think of denim-silk. Whatever the case, this should serve as even more motivation to include this luxurious fabric in your wardrobe while the season is still in full flow.

For those of you with sensitive skin, silk is also hypoallergenic and exceedingly light and delicate. Additionally, it controls your body's temperature, allowing you to stay cool on hot days and maintain your body's heat on chilly nights.

Unexpectedly, thinking about silk makes it seem so natural that it will keep its quality for a very long time.

For this reason, it is frequently utilised in treasured and heirloom goods that are passed down from one generation to another. It is essentially a timeless material that may be used for many things, including form-fitting tights, cosy beds, nightgowns, and even appropriate clothing such as wedding dresses.

But from where do we get silk?

Silk is obtained from the silkworm. The silkworm spins a net around itself when it is in the pupa stage to keep itself contained. Then it turns its head while spinning a protein-based fibre that will eventually develop into silk fibre. The term "cocoon" refers to the protective barrier that several caterpillars form around the pupa. The cocoon of the silk moth is used to make the silk thread (yarn).

But how can we get silk out of the silkworm?

This concept page has the answer to this question. Let's learn how silk is extracted from the silkworm without further ado.

TABLE OF CONTENTS

• Sericulture
• Sericulture – Process
• Moriculture
• Silkworm Rearing
• Silk Reeling
• Dyeing
• Spinning
• Weaving
• Sericulture – Challenges Faced
• Practice Problems
• Frequently Asked Questions – FAQ

Sericulture

Natural fibres are made by both plants and animals. Jute, flax, and cotton are examples of plant fibres. A couple of examples of animal fibres include wool and silk. Silk is produced by silk moths, which are also referred to as "silkworms." Growing silkworms with the goal of creating silk are known as sericulture. Sericulture is a very old profession in India. India is the world's second-largest silk producer after China, and Karnataka is the nation's leading silk-producing state.

Raising silkworms and harvesting their silk is known as sericulture. The domestic silkmoth larvae, also known as "Bombyx Mori," are the most often used species of the silkworm in sericulture. Other types of silkworms, including Eri, Muga, and Tasar, are also kept in captivity for the production of "wild silks." Sericin and fibroin, two distinct proteins, are the building blocks of silk fibre. Fibroin makes up around 80% of silk fibre and is concentrated at the core. Sericin (which forms up the remainder of 20% of silk) is layered around this core. The sericin layer of the fibre, which contains pigments like xanthophyll, gives silk its colour. Each variety of silk has a unique colour, as tabulated below.

Sericulture – Process

Several sericulture techniques are used to create silkworm silk. The modern rotating Chandrika or montage, a specific rearing house, hybrid silkworms, etc. are all part of the current sericulture method. The traditional method is gathering silkworm cocoons on a bamboo frame that is shaped like a circle. The six steps of the sericulture process are demonstrated here.

• Moriculture
• Silkworm rearing and harvesting the cocoon
• Extracting the silk thread
• Dyeing of silk
• Spinning of silk
• Weaving of silk

The silk fibres are finally weaved together to create a thread. To create yarn, these threads are frequently spun together.

Moriculture

The cultivation of mulberry plants, whose leaves are utilised as silkworm food, is referred to as moriculture. Three distinct techniques can be used to grow these plants.

• Cultivation from seeds
• Root-grafting
• Stem grafting

The most popular technique for mulberry plantations is stem grafting. Here, stems from mature mulberry plants are cut into cuttings that are about 22 centimetres long and have at least three buds on them. These cuttings can either be planted right away or they can be stored in nurseries before being transplanted.

The following techniques can be used to harvest the mulberry leaves from the plants:

• The manual removal of each individual leaf, also known as ‘leaf picking’.
• The complete removal of the branch, also known as ‘branch cutting’.
• Removing mulberry shoot tops, also known as ‘top shoot harvesting’.

It's noteworthy to note that 50 silkworms can be fed with 1 kilogramme of mulberry leaves (from the egg stage to the cocoon stage).

Silkworm Rearing

To begin the process of rearing silkworms in sericulture, the female silk moth lays eggs. A single silk moth female can typically lay between 300 and 500 eggs. These eggs are subsequently sterilised using a 2% formalin solution (which has been put out on a paper or cardboard sheet).

A feeding bed is created on a rising tray by sprinkling chopped mulberry leaves all over it. Using a process known as brushing, the freshly born larvae are placed in this tray. To retain humidity, foam strips are placed on the tray after being moistened with water.

The silkworm larvae initially have a robust appetite. As they grow larger, their appetite steadily declines till they attain the active stage. The silkworm feeds on food energetically at this stage until its final feeding period.

Once the larvae reach adulthood, they begin hunting for friendly places to begin their pupation. The body of the silkworm is shrinking and becoming translucent. Now that they are fully formed, these larvae release saliva to encase themselves in a cocoon from two salivary glands on their heads. This saliva becomes condensed and turns into silk when it comes into contact with air.

The cocoon is usually spun in two to three days. To spin their cocoons, certain types of silkworms, however, can require up to 4 days.

Silk Reeling

Inside the cocoons, the larvae transform into pupae through metamorphosis. The removal of silk from these cocoons is the final step in sericulture. To kill the pupae inside, the cocoon is first boiled, exposed to steam, and heated dry. This approach is referred to as stifling.

Now, the disintegrating cocoon is reeled to release the silk threads via a process called reeling. After being in boiling water for around 15 minutes, the silk threads' stickiness diminishes, enabling the separation of individual filaments. These filaments are twisted into a thread with the assistance of several guides and pulleys. This silk is then reboiled in order to improve its lustre.

Around 50 silk filaments make up one silk thread. However, a single cocoon can produce almost 900 metres of filament. Thus, the silkworm is used to produce raw silk, and the sericulture process is finished.

Dyeing

• Prior to dyeing, sericin (a type of gum) from silk thread is cleansed.

• For the best colour and quality, silk thread is traditionally dyed over a period of days in coloured pots with a heated mixture of indigo leaves.

Spinning

• After it has been dyed, silk is spun into thread.

• Coloured silk strands are unwinded on spinning wheels.

• Since the beginning of time, spinning wheels have been employed for this purpose.

Weaving

• The weaving of silk thread comes after the silk thread has been spun.

• By interlacing threads, weaving transforms wrap into a material at the proper angle.

• This is the reason a loom is used. There are many different types of silk weaving equipment accessible nowadays.

Sericulture – Challenges Faced

Silk farmers face a lot of challenges in sericulture that could possibly ruin their harvest, in addition to being prone to health hazards. Pebrine and flacherie are two illnesses that can affect silkworms. Additional pests pose a threat to the silkworm larvae's ability to grow healthily. The following is a list of some significant difficulties experienced in sericulture.

• The eggs may become infected with the pebrine illness and perish before the larvae emerge. This sickness causes all larvae to develop dark patches and become listless.

• The larvae's bodies may contract as a result of viral infections. Additionally, they might begin to emit a disagreeable odour.

• The larvae may become inactive due to other viral diseases including cytoplasmic polyhedrosis.

• The muscardine infection, brought on by fungi, can make the larvae very weak and ultimately kill them.

• Dermestid notepad beetle larvae have the ability to dig into silkworm cocoons and consume the pupae. These injured cocoons are unable to reel out silk.

• A toxic chemical that sometimes formed kills silkworms.

Practice Problems

1. Which of the following statements is correct?
    

1. larval form of moth produces silks
2. salivary glands of the moth produce silk
3. by boiling, silk is extracted from cocoon of a moth
4. both (A) and (C)
    

Answer: D
Fibroin, a macromolecule produced by cocoons-making insect larvae, makes up the fibre of silk. The known silk is made from cocoons made by mulberry silkworm moth larvae that are raised in captivity (sericulture). Using hot air or steam to kill the moth pupa, the accessible strands of silk are removed from the cocoon for commercial usage. Therefore, the statements given in options A and C are correct.

So, option D is the correct answer.

2. The silkworm larva ceases to eat and begins spinning silk all over its body __________.
    

1. from inside to outside
2. from outside to inside
3. in a random motion
4. all of the above
    

Answer: B
After their fourth and final skin-shedding, the silkworms will eat most of the food they will eat for the rest of their lives. They will fully shed their healthy structure once they reach a basic size in order to prepare to turn their casing inside out around the body. Before stopping to eat and beginning to spin silk from the outside in, the fifth instar eats for eight days. The life cycle is finished in about 45 days or so.

So, option B is the correct answer.

3. Which of the following proteins are found in silk?
    

1. Sericin
2. Fibroin
3. Keratin
4. Both A and B
    

Answer: D
Sericin and fibroin, two distinct proteins, are the building blocks of the silk fibre. Fibroin makes up around 80% of silk fibre and is concentrated at the core. Sericin (which forms up the remainder of 20% of silk) is layered around this core. The sericin layer of the fibre, which contains pigments like xanthophyll, gives silk its colour.

So, option D is the correct answer.

4. Which of the following is a technique to grow mulberry plants?
    

1. Cultivation from seeds
2. Root-grafting
3. Stem-grafting
4. All the above
    

Answer: D
The cultivation of mulberry plants, whose leaves are utilised as silkworm food, is referred to as moriculture. Three distinct techniques can be used to grow these plants.

• Cultivation from seeds
• Root-grafting
• Stem grafting
   

The most popular technique for mulberry plantations is stem grafting. Here, stems from mature mulberry plants are cut into cuttings that are about 22 centimetres long and have at least three buds on them. These cuttings can either be planted right away or they can be stored in nurseries before being transplanted.

So, option D is the correct answer.

Frequently Asked Questions – FAQ

1. Which stage of silkworm produces silk?
A. Silkworms consume mulberry leaves as they develop into pupa. The silkworm spins a net around itself during the pupa stage to protect itself. Then, as it swings its head, it spins a protein fibre that will eventually become a silk.

2. Which city in India is famous for sericulture?
A. The four different types of silk are all famously produced in Assam. Since the beginning of time, the state has engaged in sericulture and is proud of its history of manufacturing Muga & Eri silks. Formerly known Assam is home to the Muga culture, which is also where the majority of the world's famous golden Muga silk is produced.

3. Where did silk originate from?
A. Silk manufacturing began in China in the Neolithic (Yangshao culture, 4th millennium BC). Until the Silk Road was established sometime in the latter part of the first millennium BC, silk was restricted to China. For another thousand years, China continued to have a virtual monopoly on the manufacture of silk.

4. Who invented sericulture?
A. Legend has it that Xilingji (Hsi-ling-chi), the 14-year-old wife of Huangdi, China's third emperor, made the initial discovery of silk around 2640 BC (Huang-Ti).

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