When do silkworms spin silk?

Because silkworms only eat mulberry leaves all their lives, what they spit out when they are old is its soft, smooth and white silk, so there is a poem "Spring silkworms must weave until they die" to praise those who have dedication. This sentence comes from Li Shangyin's famous sentence "Spring silkworms die, and the candle is dying".

Silkworm moth belongs to LEPIDOPTERA, Silkworm moth family, and its temperament is docile. Silkworms have to change their clothes four times in infancy. When they are mature, they will sleep without eating, which is the so-called "silkworm sleep period". Soon, they will use up all the residues and waste liquid in their bodies and start to spit out white silk and weave cocoons. Silkworm larvae spit out all the silk in the cocoon, stay for a few days, shed wrinkled old skin, and become round and chubby yellow-brown pupa, which is called "baby pupa". Soon it became a winged silkworm moth, broke its cocoon and was free. Because they have long been domesticated from the wild, their real names are silkworm moths.

As we all know, silkworms can spin silk and form cocoons, but how silk is made is not always clear. It turns out that silkworm larvae have a complete and complex silk-making system called silk gland. Silk gland is connected to the spinning bubble called extruder under the machine head, and these two basic parts form a "natural textile machine". There are silk glands in the old larvae, which are composed of two rows of cells, which are five times longer than the body and communicate with the sac for storing silk fluid. The head squeezer is connected with the surrounding muscles. When silkworms spin silk, the muscles in the head expand and contract continuously, and the silk fluid in the silk gland is pumped out. When the silk liquid comes into contact with air, it forms slender silk.

When a silkworm spins silk and forms cocoons, its head always swings from side to side. If you look at it carefully with a magnifying glass, the cocoons of silkworms are arranged in a very neat "8" shape, and every 20 silk circles are called a silk column. When one end of the cocoon is woven, it will make a 1800 turn and start weaving the other end of the cocoon. Therefore, the silkworm cocoon is slightly thicker at both ends and slightly thinner in the middle, much like a peanut. Every time a silkworm completes a cocoon, it needs to change its position 250-500 times to weave about 60 thousand "8" silk circles, each of which is about 0.72 cm long. This is how silkworms weave and weave. After all the silk in their bodies is exhausted, they turn into moths, which are inoculated and handed down from generation to generation for the benefit of mankind from generation to generation.