Theory:

Silk is an animal fibre that is obtained from the secretions of the silk moth. It is obtained from the cocoon of the silkworms.
Silkworms are insects that feed on the leaves of the mulberry plants.
 
The silkworms are insects that live for only two months which is a brief period. During their life period, the silkworm passes through four different development stages known as the life cycle of a silkworm.
The life cycle of silkworm:
The life cycle of a silkworm comprises \(4\) stages. They are eggs, caterpillars, cocoons and adult moths.
  • The life cycle of a silk moth starts when the female silk moth lays eggs.
  • The eggs hatch into the caterpillars or larvae that are known as silkworms.
  • These silkworms feed on the mulberry leaves give rise to pupa.
  • During this stage, a weave is netted around by the silkworm to hold itself.
  • After this, the cocoon swings its head, spinning a fibre made up of protein and developing into silk fibre.
  • The protective layer around the pupa and this covering are known as a cocoon.
  • The silk thread (yarn) is obtained from the silk moth's cocoon.
Stages in the life cycle of silkworm:
 
1. Egg:
It is the first stage in the life cycle of a silk worm. The female moth lays eggs during the springtime.
 
2. Silkworm:
This a stage during which the egg cracks and gives rise to a hairy silkworm. These worms feed on the mulberry leaves to reach the next stage.
 
3. Cocoon:
This is a stage in which the silkworms spin a protective cocoon around itself. The cocoon is a small cotton ball size and is made up of a single thread of silk.
 
4. Pupa:
It is a motionless stage in which the people kill the pupa by placing them in the boiling water so that the silk thread can be unwound.
 
5. Moth:
It is a stage in which the pupa changes into an adult moth. During this stage the female moth lays eggs and the lifecycle begins again.
 
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Lifecycle of silkworm
Reference:
https://www.vecteezy.com/vector-art/304113-silkworm-life-cycle-diagram