Cocoon usually refers to mulberry cocoon. The capsule-shaped protective layer of silkworm pupa contains pupa. The protective layer includes cocoon coat, cocoon layer and pupa lining. Cocoon layer can be used for reeling, and cocoon coat and waste silk after reeling can be used as raw materials for silk cotton and silk spinning. The cocoon is oval or slightly constricted in the middle, with a length of 3-4cm and a diameter of 1.7-2. 1cm. The surface is white or light yellow, with irregular wrinkles and attached silk, shaping fluffy. The silk on its inner wall is very regular. Light and tough, not easy to tear. It is slightly fishy and has a light taste.