The role of the cocoon is to protect the pupa produced by the larva as it enters the pupal stage.

As follows:

The cocoon is the cocoon of the mulberry silkworm. The sac-like protective layer of the pupal stage of the mulberry silkworm, containing the pupal body. The cocoon layer can be reeled, cocoon clothing and reeling after the waste silk can be used as silk cotton and silk spinning raw materials.

Presented in different shapes such as long oval, elliptical girdle, spherical or spindle, or slightly constricted in the middle, the cocoon has white, yellow, light green, flesh red and other colors, about 3 to 4 cm long, 1.7 to 2.1 cm in diameter, the surface of the white, with irregular wrinkles, and there are attached to the silkworm silk, in the form of fluffy.

Silkworm pupa, synonym of small bee child, original silkworm pupa, late silkworm pupa. Silkworm pupa is the silkworm spit silk cocoon in the cocoon into the chrysalis. Silkworm pupa is not only delicious, nutritious, or a valuable source of animal protein, but also the extraction of a variety of chemical raw materials.

Household silkworm moths, female and male moths are densely covered with white scales. The body length is 1.6-2.3cm, the wingspan is 3.9-4.3cm, and the wings are yellowish-white to grayish-white. The outer edge of the forewing is concave and cut inward at the back of the apex, the horizontal lines are slightly darker and less obvious, the end lines and the wing veins are gray-brown, the hindwings are lighter than the forewings, and the edges are slightly longer with scale hairs. The female moth has a plump abdomen with a bluntly rounded end; the male moth has a narrow abdomen with a slightly pointed end.

The larvae, the houseworms, are gray to white in color, with the 2nd and 3rd segments of the thorax slightly enlarged and wrinkled. The eighth abdominal section has a tail horn on the back. Silkworms spit cocoon after about 4 days, it will become a pupa. The body shape of the pupa is like a spindle, divided into head, thorax, abdomen, three body segments.

The head is very small, with compound eyes and antennae; the thorax has thoracic feet and wings; the bulging abdomen has nine body segments. The color is coffee-colored. Professional workers are able to tell the male and female from the lines and brown dots on the abdomen of the nymphs.

When the silkworm first pupates, the body color is yellowish, and the pupal body is tender and soft, and gradually it will become yellow, yellowish brown or brown, and the pupal skin is hardened. After about 12 to 15 days, when the pupal body begins to soften again, the pupal skin is a little wrinkled and earth brown cocoon color, it will become a moth.