Growth process of Silkworm, Bombyx mori

Silkworm is abnormal insects, the most common is silkworm, also known as silkworm, mulberry leaves for food spinning cocoon one of the economic insects. Silkworm originated from China, its development temperature is 7~40℃, and the optimum temperature for breeding is 20~30℃. Silkworm babies live on mulberry leaves. After eating mulberry leaves continuously, their bodies become white. After a period of time, they begin to peel. When peeling, there is about a day's time, such as sleep-like do not eat and do not move, this is called "dormancy". After a molt, it is the second instar larva. The larvae shed their skin four times to become fifth-instar larvae. After eating mulberry leaves for eight days, they become mature silkworms and begin to spin silk and cocoon.

Silkworm age is also called instar, indicating that silkworm babies are at a certain stage of development. From the ant silkworm to the first molting is the first instar; after molting, it enters the second instar; after molting again, it enters the third instar; after molting for the third time, it enters the fourth instar, and the fourth molting is also called great molting. After the big dormancy, it enters the fifth instar. The fifth instar silkworm baby grows very fast, its body length can reach 6~7cm, and its weight can reach about 10,000 times the weight of the ant silkworm.

Silkworm instars are divided into four to five days for the first instar, three to four days for the second instar, four days for the third instar, six days for the fourth instar, seven to nine days for the fifth instar, fourteen to eighteen days for the pupae and three to five days for the moths.

silkworm eggs

Silkworms reproduce by laying eggs. Silkworm eggs look like fine sesame seeds, about 1 mm wide and 0.5 mm thick. A female moth can lay 400 - 500 eggs. 1700~2000 eggs weigh about 1 gram. The color of silkworm eggs, just laid when light yellow or yellow, after 1~2 days into light red bean color, red bean color, and then after 3~4 days into gray green or purple, it no longer changes, called fixed color. Silkworm egg outer layer is hard egg shell, inside is yolk and serosa, fertilized egg embryo in the development process of continuous intake of nutrients, gradually developed into ant silkworm, it climbed out of the egg shell, egg shell empty after turning white or light yellow.

ant silkworm

Silkworms hatch from silkworm eggs, the color of the body is brown or black, very small, and more fine hair, looks a bit like ants, so called ant silkworm. The ant silkworm is about 2 mm long and 0.5 mm wide. After it crawls out of the egg shell, it will eat mulberry leaves after 2~3 hours.

mature silkworm

Silkworm baby to the end of the fifth instar, gradually reflects the characteristics of maturity: first the feces discharged from hard soft, from dark green to green leaves; appetite loss, food mulberry quantity decreased; front digestive tube empty, chest transparent; then completely stopped eating, body drive shortened, abdomen also tends to transparent, silkworm body head chest raised, mouth silk thread, swing up and down to find cocoon site, such silkworm is called mature silkworm. People put the mature silkworm in a special container or on a cocooning device, and the silkworm spins silk and cocoons. The cocooning can be divided into four processes:

1. The mature silkworm first spits out the silk, bonds it on the cluster, and then spits out the silk to connect the surrounding cluster branches to form a cocooning support, that is, cocooning net. The cocoon web does not have a cocoon shape, but only some loose and messy cocoon filaments, which serve as a framework for cocooning.

2. After the silkworm cocoons, it continues to spit out messy silk rings, thicken the inner layer of the cocoon net, and then spin silk in an S-shaped manner, and begin to appear the outline of the cocoon, called cocooning. The silk fibers of cocoon coat are thin and brittle, arranged irregularly, and the sericin content is also high.

3. After the cocoon coat is formed, the cocoon cavity gradually becomes smaller, the front and rear ends of the silkworm body bend to the back side, forming a "C" shape, the silkworm continues to spit out cocoon silk, and the spinning mode changes from S shape to ∞ shape, which begins the process of cocoon layer.

4. When the silkworm greatly shrinks due to a large amount of silk spinning, the swing speed of the head and chest slows down, and there is no certain rhythm, and the silk spinning begins to appear messy, forming a loose and soft cocoon silk layer, which is called pupa lining.

silkworm Chrysalis

Silkworm cocooning after 4 days or so, will become pupae. The silkworm chrysalis is shaped like a spinning hammer, divided into three segments: chest and abdomen. The head is very small, with compound eyes and antennae; the chest has chest feet and wings; the abdomen has 9 body segments. Professional workers can tell male from female by the lines and brown dots on the abdomen of silkworm pupae. Silkworm just pupate, body color is pale yellow, pupa tender soft, gradually will become yellow, brown or brown, pupa skin is also hard up. After about 12 to 15 days, when the pupa begins to soften again, the pupa skin is slightly wrinkled and drab brown, it will become a moth.

Silkworm moth (adult)

Silkworm moth shape like a butterfly, the whole body covered with white scales, but because of the two pairs of wings smaller, has lost the ability to fly. Silkworm moth's head is small spherical, long with bulging compound eyes and antennae; chest has three pairs of chest feet and two pairs of wings; abdomen has no abdominal feet, terminal body segment evolved into external genitalia. Female moths are large and slow to crawl; male moths are small and fast to crawl, flapping their wings rapidly in search of a mate. Generally, after 3 to 4 hours of mating, female moths can lay fertilized eggs. After mating, the male dies, while the female lays about 500 eggs in one night, and then dies slowly.

Silkworm moth laid eggs → hatching → pupation → moth, and will complete a new generation cycle, into the next generation of growth process.