Cocoons

Cocoons are protective coverings spun by the larvae of some insects, especially moths, during the pupal stage of metamorphosis. The cocoon encases the developing adult insect and provides protection from desiccation, predation, and environmental hazards while transformation takes place. In butterflies, the pupal stage is typically a chrysalis rather than a silk cocoon, and many species do not spin a cocoon at all.

Cocoons are usually made of silk produced by specialized glands in the larva. The silk proteins, mainly fibroin and sericin, are secreted and woven into layered envelopes that form a durable covering. The resulting cocoon can be smooth or layered, sometimes incorporating leaf fragments or other debris. The exact structure and appearance vary widely among species.

Lifecycle and human relevance: During pupation inside the cocoon, the larva is transformed into an adult moth or, less commonly, a butterfly. In commercially important silk moths such as Bombyx mori, cocoons are harvested to obtain silk threads; often the pupa is killed before it matures to maximize filament yield. In the wild, cocoons can serve as overwintering shelters or help protect the pupa from climate fluctuations.

Variations and ecology: Not all Lepidoptera spin cocoons; butterflies generally form a chrysalis, while many moths produce a cocoon, sometimes underground or within leaf litter. Cocoons vary in size, shape, and texture across species and habitats, reflecting adaptations to environmental conditions and life histories.