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Silkworm Life Cycle Stages

 
By María Luz Thurman, Biologist/ornithologist. Updated: February 11, 2024
Silkworm Life Cycle Stages

The silkworm moth (Bombyx mori) is a biological marvel which is integral to the world of sericulture, also known as silk making. The name can be a little confusing since it is not actually a worm, but an insect with a larval stage that resembles a worm. They are of the order Lepidoptera, the order that makes up moths and butterflies. Although they are flying insects in their adult stage, during their larval stage they are known as caterpillars. It is during this period they expel a filament from special glands which are used to make their cocoons.

Understanding the silkworm life cycle stages will help you to know how silk is made. This is only one aspect of these fascinating insects, so let AnimalWised explain more about the silkworm moth life cycle.

Silkworm egg stage

As the diagram above depicts, the silkworm moth life cycle begins with the egg stage. This crucial stage lays the foundation for subsequent development, holding within its genes the building blocks for the adult insect. Although there are other species of silkworm, they all have very similar characteristics throughout their developmental stages. In this article, we focus on the silkworm moth (Bombyx mori) which is the most widely cultivated.

Other types of silkworm include:

  • Muga silkworm (Antheraea assamensis)
  • Oak silkworm (Antheraea pernyi)
  • Eri silkworm (Samia ricini)

For all of these silkworms, egg laying takes place in groups on the leaves of some plants. In the case of Bombyx mori, they do so exclusively on the leaves of the mulberry tree, the main food source of these worms. It is for this reason they are often referred to as mulberry silkworms, although there are various breeds. A female can lay between 300 and 500 eggs during her adult life.

The eggs are initially white and over time acquire a characteristic yellow hue before hatching. This stage spans approximately 10 to 12 days and involves the development of the embryo within the egg. This is when the fundamental genetic characteristics that will shape the future silkworm are established.

This incubation period not only lays the biological foundation for subsequent development, but also exhibits notable adaptations. The eggs show resistance to adverse conditions, such as changes in temperature, ensuring the survival of the species in various environments.

Silkworm Life Cycle Stages - Silkworm egg stage

Silkworm moth larval stage (caterpillar)

The larval stage of the silkworm moth is when they are a caterpillar. They are also insatiably voracious, leading to the rapid development necessary for this life cycle stage. Silkworm moths are caterpillars for approximately 20 to 30 days, beginning with the hatching of the egg and the birth of the larvae. From their first days, they experience accelerated growth, acquiring the essential characteristics that will define their appearance and function later on.

A distinctive feature of the larval phase in the silkworm life cycle is the process of molting, not shown in diagram. This is when the larva sheds its rigid exoskeleton to accommodate its rapid increase in size. These successive molts mark transitions in development, allowing the larva to adjust its body structure for the next stages of the cycle.

The voracity of the larva is manifested in its diet of mulberry leaves (in the case of Bombyx mori), which constitutes its main food source. During this phase, the silk glands are activated, secreting silk fluid that will be crucial for the production of the cocoon.

The accumulation of significant energy reserves by the larva during this phase of the silkworm life cycle is essential. These reserves will be used later during metamorphosis in the pupa phase and the construction of the cocoon.

The larval phase is not only crucial for the individual development of the silkworm, but also plays a determining role in silk production. The quality and quantity of silk produced is directly linked to the health and nutrition of the larva during this period.

Silkworm Life Cycle Stages - Silkworm moth larval stage (caterpillar)

Silkworm moth pupa phase (cocoon construction)

As mentioned above, the silkworm moth's characteristic cocoon construction occurs during the pupal phase. It is this process which marks the beginning of metamorphosis. The silkworm pupal stage lasts approximately 8 to 10 days, during which the larva transforms into a pupa, beginning an intricate process of weaving a protective cocoon.

During cocoon construction, the pupa uses sericogenic glands to secrete silk fluid. Upon contact with air, these fluids solidifiy to create a filament. This silk filament is then intricately woven to create the cocoon. Composed primarily of fibroin proteins, this cocoon offers strength and durability thanks to the hardened silk thread. The protective role of the cocoon is essential, as it provides security to the pupa while it undergoes internal transformations.

The quality and quantity of silk produced are directly linked to the activity of the sericogenic glands during this process. At the end of the pupal phase in the silkworm moth life cycle, the adult moth is fully formed inside the cocoon, ready to emerge into its adult form.

Silkworm Life Cycle Stages - Silkworm moth pupa phase (cocoon construction)

Silkworm pupal metamorphosis

Pupal metamorphosis in silkworm moths is another crucial phase spanning approximately 16 days in the life cycle of the silkworm. It is an extraordinary process that takes the individual from pupal form to emergence as a silk butterfly. Metamorphosis in animals is one of the most fascinating developments in nature since it they go through a complete morphological change, despite being the same animal.

During the first days of silkworm metamorphosis, the pupa undergoes internal reorganization at the cellular and tissue level. Fundamental body structures are redefined, a process that involves the selective decomposition of larval tissues and the reconstruction of new tissues. It is these new tissues that will configure the adult anatomy of the butterfly.

The transformation of organs and limbs is a key aspect of this phase of the silkworm life cycle, adapting the anatomy of the larva to become the adult structure of the butterfly. The energy reserves accumulated during the larval phase, mainly in the form of fat which fuels this fundamental metamorphic process.

Upon completion of pupal metamorphosis, the silkworm moth emerges from the cocoon. This process includes the opening of the cocoon and the emergence of the winged adult. Unlike some other mother or butterflies, the silk moth's wings are underdeveloped, rendering it incapable of flight.

Pupal metamorphosis, or silkworm metamorphosis, highlights the amazing adaptability of the silkworm and its ability to radically transform to meet the demands of its next life phase.

Silkworm Life Cycle Stages - Silkworm pupal metamorphosis

Adult silkworm emergence (moth)

The final phase of the silkworm life cycle manifests itself with the emergence of the adult, the silkworm moth. Occurring after pupal metamorphosis, this represents the complete transition from the pupa to the winged form. It is a relatively brief period, with adult silkworm moths only living around 5 to 10 days on average. This means the total life expectancy of a silkworm moth is 49 to 66 days from egg to death of the adult.

Emergence begins with the opening of the cocoon, a critical process that frees the adult silkworm moth. Once out of the cocoon, the wings unfold to reveal a delicate anatomy with wings covered in tiny scales. Although the wings are smaller and underdeveloped compared to other butterfly species, this deployment is essential for adult function.

As stated above, unlike most types of moths or butterflies, the silkworm moth is unable to fly due to its smaller wings and more robust body. This feature is an adaptation to focus on reproduction rather than flight. The adult life of the silk butterfly is brief, with a primary focus on reproduction. After mating, the female lays eggs to start a new life cycle.

Although they share many similarities, you can discover the differences between moths and butterflies in our comparison guide.

Silkworm Life Cycle Stages - Adult silkworm emergence (moth)

Reproduction

In the silkworm, reproduction is a vital process that ensures generational continuity and plays an essential role in silk production. The process begins with identifying suitable partners.

Communication between the sexes involves the release of pheromones, chemicals that act as signals to attract mates. Elaborate courtship precedes mating, where the male performs specific movements and releases additional pheromones. After mating, the female deposits eggs in groups on mulberry leaves in the case of Bombyx or other plants in other silkworm species. This marks the beginning of the life cycle of a new generation.

Reproduction in the silkworm not only ensures the continuity of the species, but also plays a crucial role in silk production. You can see the full silkworm life cycle stages in the diagram above or learn more about a similar developmental process with our article on the how long is the life cycle of butterflies?

If you want to read similar articles to Silkworm Life Cycle Stages, we recommend you visit our Facts about the animal kingdom category.

Bibliography
  • Ashraf, H., & Qamar, A. (2023). Silkworm Bombyx mori as a model organism: A review. Physiological Entomology, 48(4), 107-121.

  • Borah, S. D., & Boro, P. (2020). A review of nutrition and its impact on silkworm. Journal of Entomology and Zoology Studies, 8(3), 1921-1925.

  • Hsueh, T. Y., & Tang, P. S. (1944). Physiology of the silkworm. I. Growth and respiration of Bombyx mori during its entire life-cycle. Physiological zoology, 17(1), 71-78.

  • Meng, X., Zhu, F., & Chen, K. (2017). Silkworm: a promising model organism in life science. Journal of Insect Science, 17(5), 97.

  • Nurkomar, I., Trisnawati, D. W., & Arrasyid, F. (2022). Life cycle and survival of eri silkworm, Samia cynthia ricini Biosduval (Lepidoptera: Saturniidae) on three different cassava leaves diet.

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