Silkworm Lifecycle: From Eggs to Moths

History of Silk

Silk dates back to its discovery in China around 3500 BC. It was a valuable commodity traded worldwide. Advancements in technology allowed for the production of different silk types from various silkworm species. The mulberry silk moth became the primary source for silk production. Rearing silkworms for silk production is known as sericulture. We will discuss about Lifecycle of silkworm in detail in this article.

Scientific classification of Silkworm

  • Kingdom: Animalia 
  • Phylum: Arthropoda 
  • Class: Insecta 
  • Order: Lepidoptera 
  • Family: Bombycidae 
  • Genus: Bombyx 
  • Species: Bombyx mori

The Life Cycle of Silkworm

The life cycle of a silk moth begins when a female silk moth lays eggs. These eggs hatch into caterpillars or larvae, which are commonly known as silkworms. The silkworms feed on mulberry leaves and go through several stages of growth. During the pupa stage, the silkworm spins a protective cocoon around itself. Inside the cocoon, the silkworm swings its head and spins a fiber made of protein, forming the silk fiber. The cocoon acts as a protective covering for the pupa. Silk threads, also known as yarn, are obtained from the cocoon of the silk moth. The life cycle of a silkworm is explained in detail below:

Silkworm Lifecycle
Silkworm Lifecycle

1. Egg Stage:

  • Female silk moths lay eggs, usually in clusters on surfaces such as leaves or twigs.
  • The eggs are tiny, ranging in size from 1 to 2 millimeters, and have a yellowish or whitish color.
  • They are covered with a protective coating called sericin, which helps keep them safe until conditions are favorable for hatching.
  • The incubation period for the eggs lasts about 10 to 14 days, depending on the temperature and humidity.
  • During this stage, the eggs remain dormant and undergo little to no visible development.

2. Larva Stage:

  • Once the eggs hatch, tiny silkworm larvae or caterpillars emerge.
  • These larvae have a characteristic appearance with a small head, soft body, and numerous tiny hairs covering their skin.
  • At this stage, the silkworms have a strong appetite and start feeding voraciously on mulberry leaves, their primary food source.
  • The larvae undergo several molting stages, shedding their skin to accommodate their growing bodies.
  • Each molting stage is referred to as an instar, and the silkworms usually go through five instars before reaching the next stage.

3. Pupa Stage:

  • After completing their final instar, the silkworms enter the pupa stage.
  • The pupa is the resting or transitional stage of development.
  • Inside the pupa, major changes occur as the silkworm undergoes metamorphosis to transform into an adult silk moth.
  • During this stage, the silkworm spins a protective cocoon around itself using silk threads produced from special glands in its head.
  • The cocoon serves as a shield and provides a safe environment for the pupa to undergo its transformation.

4. Cocoon Stage:

  • The silkworm completes the construction of its cocoon within a few days.
  • The cocoon is oval-shaped and consists of a single continuous silk filament, which can measure up to 900 meters long.
  • The silk filament is made up of two proteins: fibroin, which gives the thread its strength, and sericin, a gummy substance that holds the fibers together.
  • The silk fibers produced by the silkworm serve as the raw material for silk production.
  • The cocoon provides protection to the developing pupa from predators and external conditions.

5. Moth Stage:

  • Inside the cocoon, the pupa undergoes complete metamorphosis, transforming into an adult silk moth.
  • When the transformation is complete, the adult moth secretes a special enzyme to dissolve a portion of the cocoon, creating an exit hole.
  • The silk moth emerges from the cocoon through this hole, usually during the night.
  • The adult silk moth has a short lifespan, ranging from about 5 to 10 days.
  • The primary purpose of the adult silk moth is to reproduce, and it does not possess functional mouthparts or a digestive system.

These stages encompass the remarkable lifecycle of a silkworm, showcasing their ability to produce silk and undergo metamorphosis.

Processing of Silk

The process of obtaining silk from the cocoon is known as the processing of silk. First, the silk is separated from the cocoon by exposing it to sunlight. After that, the silk is reeled and unwound from the cocoon. The silk thread is then bleached and spun into silk threads. Silk is an animal fiber obtained from the secretions of the silk moth and is derived from the cocoon of silkworms. Silkworms are insects that feed on the leaves of mulberry plants.

Silkworm FAQs

Q1: What is the silkworm lifecycle? 

A1: The silkworm lifecycle comprises four stages: egg, larva, pupa, and moth.

Q2: How long does it take for silkworm eggs to hatch? 

A2: Silkworm eggs typically hatch in 10 to 14 days, depending on temperature and humidity.

Q3: What do silkworms eat during their larva stage? 

A3: Silkworm larvae primarily feed on mulberry leaves, their main food source.

Q4: How many molting stages do silkworms go through? 

A4: Silkworms usually go through five molting stages, known as instars, during their larva stage.

Q5: What is the purpose of the silkworm’s cocoon? 

A5: The silkworm’s cocoon acts as a protective shelter during its transformation into an adult silk moth.

Q6: How long does it take for a silkworm to spin its cocoon?

A6: Silkworms typically take a few days to spin their cocoons, continuously producing silk threads.

Q7: What is the silk filament in a silkworm’s cocoon made of? 

A7: The silk filament in a silkworm’s cocoon consists of fibroin, providing strength, and sericin, which holds the fibers together.

Q8: Can the silk moth break out of its cocoon on its own? 

A8: The silk moth secretes an enzyme to create an exit hole in the cocoon, allowing it to emerge.

Q9: How long does the adult silk moth live? 

A9: The adult silk moth has a short lifespan of about 5 to 10 days.

Q10: What is the primary purpose of the adult silk moth? 

A10: The primary purpose of the adult silk moth is reproduction, as it lacks functional mouthparts or a digestive system.

Q11: Can silkworms go through multiple lifecycles? 

A11: Silkworms complete one lifecycle, after which adult silk moths lay eggs to begin the process again.

Q12: How is silk extracted from the cocoon without damaging the filament? 

A12: Silk extraction involves carefully unravelling the cocoon to obtain the continuous silk filament intact.

Q13: What is sericulture? 

A13: Sericulture is the practice of rearing silkworms for silk production, including cultivating mulberry trees and harvesting silk cocoons.

Q14: Are all silkworms the same species? 

A14: The most commonly cultivated silkworm species is Bombyx mori, but different wild silk moth species produce varying types of silk.

Q15: How has sericulture influenced human history? 

A15: Sericulture has a significant historical impact on trade, culture, and economic development, especially in countries like China and India.

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Binod G C

I'm Binod G C (MSc), a PhD candidate in cell and molecular biology who works as a biology educator and enjoys scientific blogging. My proclivity for blogging is intended to make notes and study materials more accessible to students.

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