Mulberry cocoon consists of cocoon layer, cocoon layer, pupa body and molting. Cocoon coat is a loose and disorderly silk ring wrapped in the outermost layer of cocoon, which contains more sericin and the fiber is thin and weak, so it can't be reeled, and it can be used as silk spinning raw material together with the waste from silk reeling factory. Cocoon silk rings are arranged regularly, with many tiny gaps, which are breathable. It is the raw material of silk reeling and belongs to the part with the highest economic value in cocoon. Pupa is formed by degeneration of silkworm body, which contains about 50% crude protein, nearly 30% crude fat and most of the cocoon layer is water. After chemical treatment, it can be used as raw materials for chemical, food, textile, medicine and other industries. In order to avoid mildew and live pupae, it is necessary to kill the pupae and dry them. After treatment, they are often called fresh cocoons and dried cocoons. Take Dongfei× He Hua (a hybrid of Japanese silkworm and China silkworm) as an example, the total cocoon weight of fresh cocoon is about 2. 10g/ grain, and that of dry cocoon is about 0.92g/ grain. The cocoon shell rate of fresh cocoons is about 22%, and that of dry cocoons is about 5 1%. Mulberry cocoons are generally round, oval, waist-shaped and pointed. Round and oval cocoons are more suitable for reeling. Mulberry cocoons in China are mostly round and oval, Japanese species are mostly deep-waisted, and European species are mostly shallow-waisted. At present, most of them are hybrids. Most of the hybrids bred in China are hybrids, such as Dongfei× He Hua. The size of cocoon is measured by its width, which is called vertical width and banner. It can also be expressed by the number of cocoons in a certain area or volume, or by the number of dried cocoons in one kilogram. Generally, the cocoon shape is larger and the cocoon silk is thicker, and the cocoon silk thickness of the same cocoon is quite different. When reeling silk, the shape and size of cocoon are required to be consistent. The vertical width of spring cocoon in China is 28 ~ 37mm, and the banner is15 ~ 20 mm. There are 70 ~ 90 cocoons per liter and 550 ~ 650 dried cocoons per catty. Cocoons in summer and autumn are slightly smaller than those in spring. The color of mulberry cocoon is one of the evaluation indexes of cocoon. Mulberry cocoons in China are mostly white or milky white, Japanese varieties are mostly white, and European varieties are mostly reddish milky white or pale yellow. Most of the hybrids raised in China are white cocoons, and some are brown rice or light green. Most of these pigments exist in sericin and are removed after scouring. It is better to use white cocoon. Cocoon color is gray, beige or dull. Silkworm cocoons last for dozens of hours, and the outer silk thread that is vomited first is dried first, and the inner silk thread is vomited and then dried. The inner silk shrinks after drying, which affects the outer layer and makes the surface of mulberry cocoon form thick or thin folds. The cocoon filaments in the cocoon layer of silkworm varieties in China are mostly arranged in an "S" shape, and the contraction is coarse, which is beneficial to the cocoon filament dissociation. Japanese cocoon filaments are mostly arranged in the shape of "8", with many crosses and thin contraction. European species are somewhere in between. The cocoon thickness of mulberry cocoon can be identified by micrometer or touch. The thickness of cocoon layer is related to silkworm eggs, feeding conditions and colony environment. Even if it is the same cocoon, the thickness of each part is not consistent. The layer of waist cocoon is the thickest, followed by the swollen part, and the ends are the thinnest. There is no waist cocoon, and the swollen part is the thickest. Uneven thickness is not good for cocoon cooking, which increases the difficulty of reeling. The silk length of China spring cocoon is 900 ~ 1200m, summer and autumn cocoon is 650 ~ 900m, and Japanese mulberry cocoon is about 1200m. Cocoon silk quantity is the cocoon silk quantity of each cocoon, and it is an important index to reflect the economic value of cocoon. The amount of cocoon silk in China is 0.22 ~ 0.45g in spring and 0.2 ~ 0.37g in summer and autumn. The Japanese variety is 0.35 ~ 0.40g, and the size of cocoon silk is 2.4 ~ 3.4 denier. The relaxation rate of mulberry cocoons in China is about 70%, and that of Japanese cocoons is about 80%. High release rate, full use of raw cocoon, less waste and low consumption. In order to meet the needs of trade and improve the quality of cocoon, it is necessary to identify cocoon, evaluate its grade and determine its price, which is called cocoon evaluation. Different countries have different grading standards and cocoon evaluation methods. The evaluation of China Cocoon was conducted at the acquisition station. At the time of acquisition, sample cocoons are selected to evaluate the following items: ① cocoon rate; (2) The dry weight of the fresh cocoon layer from which the cocoon layer is stripped is called the dry shell quantity of the fresh cocoon layer; 3 colors; ④ Uniformity. Based on the dry shell quantity of fresh cocoon layer, the cocoon yield and color uniformity are revised to determine the grade and price. The evaluation of Japanese cocoon is to sample cocoons at various cocoon producing points (commonly known as Zhuangkou) and verify the following items under specified test conditions: ① cocoon retention ratio; (2) uniformity of cocoon; ③ cocoon silk length; ④ Relaxation rate; ⑤ cocoon filament size; ⑥ Raw silk quantity; ⑦ Cleanliness (that is, the degree of raw silk defects). Add the two scores of cocoon silk length and relaxation rate, then add and subtract the scores of cocoon silk uniformity, cocoon silk fineness and cleanliness, and finally evaluate the total score to determine the grade. The proportion of cocoons is a reward item.