Silkworm cocoon

Silkworm cocoon

　　Generally refers to the silkworm cocoon of the mulberry silkworm. It is a capsule-like protective layer formed during the pupal stage of the silkworm, enclosing the pupa inside. The protective layer consists of the cocoon floss, cocoon shell, and pupal lining, among other parts. The cocoon shell can be reeled into silk, while the cocoon floss and waste silk after reeling can be used as materials for silk wadding and spun silk. The pupa is rich in protein and vitamin B, and can be used in pharmaceuticals, extracted for pupal oil, or served as feed for fish and livestock.

Formation and Morphological Structure After the mature silkworm climbs onto the mountage, it first spins loose silk to form the cocoon floss. Then, the head and thorax begin to move rhythmically, spinning out silk loops shaped like ~ or ∞. About 15–25 such loops accumulate to form a silk sheet. Many such sheets, bonded together by sericin, constitute the cocoon shell. The silk threads on the cocoon shell are called cocoon filaments. Once the cocoon shell is completed from the outside inward, the pupal lining forms within the inner cavity of the shell, completing the process of spinning and cocooning. Silkworm cocoons come in various shapes such as oval, oval-waisted, spherical, or spindle-shaped. They appear in white, yellow, light green, flesh-red, and other colors, though white cocoons are predominantly used in production.