Description
The life history of the silkworm (Bombyx mori) is a classic example of complete metamorphosis, involving four main stages: egg, larva (caterpillar), pupa (within cocoon), and adult moth. This cycle forms the basis for sericulture and silk production.
Stages of Silkworm Life History
Egg: Female moths lay between 350–400 tiny, pinhead-sized eggs, usually once a year on mulberry leaves. Eggs hatch in spring under warm conditions after about 10–14 days.
Larva (Caterpillar/Silkworm): The hatching larva is a small, hairy creature that immediately starts feeding voraciously on mulberry leaves. This stage, lasting about 24–30 days, involves several molts as the larva grows and can increase in size by many thousand times.
Cocoon (Pupa within Cocoon): Mature silkworms stop eating and start spinning a protective cocoon around themselves by secreting a long, proteinaceous silk thread, forming the “cotton ball”–like cocoon. This spinning process takes about 2–3 days, and each cocoon can yield up to a kilometer of silk thread. Inside the cocoon, the larva transforms into a pupa (chrysalis), remaining immobile.
Adult Moth: After 10–14 days within the cocoon, the adult silk moth emerges. Its primary role is reproduction—the moth mates, lays eggs, and thereby begins the cycle anew. Domesticated moths are unable to fly and depend entirely on humans for survival and propagation.
Additional Details
The silkworm’s lifecycle, from egg to adult, typically lasts 6–8 weeks, though it may vary with temperature and species.
Most commercial silk is harvested by boiling the cocoon before the moth emerges, ensuring the silk thread remains continuous.
The silkworm exhibits various “instar” (larval) stages, each separated by molting.
The life cycle of the silkworm is crucial for understanding silk production and the biological principles of metamorphosis.