Silkworm spinning and cocoon formation can be divided into four processes:
(1) Mature silkworms spit out the silk first, then stick it on the cocoon feeder, and then connect it with the surrounding branches to form a cocoon net. The cocoon net has no cocoon shape, just some soft and messy cocoon silk layers as the support for cocoon formation.
(2) After the silkworm completes the cocoon web, it continues to spit out messy silk loops, thickens the inner layer of the cocoon web, and then spins in an S shape, and the outline of the cocoon begins to appear, which is called cocoon clothing. The silk fibers in cocoon shell are thin and brittle, with extremely irregular arrangement and high sericin content.
(3) After the cocoon layer is formed, the cocoon cavity gradually becomes smaller, and the front and rear ends of the silkworm body bend backward to form a C-shape. Silkworms continue to spit out cocoon silk, and the way of spinning silk is transformed from s to infinity, and the process of cocoon formation begins.
(4) When the silkworm's body is greatly reduced due to a large amount of spinning, the head and chest swing slowly, and there is no certain rhythm, and the spinning begins to appear messy, forming a loose and soft cocoon silk layer called pupa lining. Finally, the silkworm's head is up and its tail is down, and the silk material remaining in the body is spit out to form a soft cocoon top, and the process of spinning and cocooning is over.
The content of this article comes from: China Agricultural Development Report by China Agricultural Publishing House.