CATDOLL : CATDOLL: Understand the life of a silkworm in seconds? (What are the four stages of a silkworm's life?)

1. Understand the life of the silkworm in seconds?

The life of a silkworm goes through the stages of egg, larva, mature silkworm, cocoon and moth, which takes more than 50 days. The development of the silkworm goes through four stages: fertilized egg, larva, pupa and adult. The larva and adult have obvious differences in morphology and living habits. This development process is called complete metamorphosis. Chen Jiru of the Ming Dynasty wrote in "Records of the Family Temple of Yuan Keli, the Grand Marshal of the Imperial Court": "The ancients ate rice to worship the ancestors of the harvest, and wore silk to worship the ancestors of the silkworm."

2. What is the science knowledge point in the second semester of Grade 4: The life of a silkworm?

The silkworm goes through four different stages in its life: egg, larva, pupa and adult.

Silkworms hibernate as eggs, and hatch into larvae when mulberry trees sprout in spring. The larvae feed on mulberry leaves, molt after 4 days, and start to spin cocoons around 25 days. They finish spinning silk after two days, and then molt and pupate in the cocoon after another 2-3 days.

After about 10 days, the pupa turns into an adult, the silkworm moth. The male and female moths mate and lay eggs, then die. In order to meet the production requirements of raising silkworms multiple times a year, the silkworm seed farm adjusts the incubation period of silkworm eggs through various technical measures such as staggered seed production seasons, cold storage of silkworm seeds, and hydrochloric acid immersion, so that silkworm seeds can be supplied in different seasons of spring, summer, and autumn.

When silkworms hibernate, they do not eat or move. On the surface, they are sleeping, but in fact they are molting, that is, they are shedding their old skin and putting on new skin so that they can continue to grow.

The silkworm that has just shed its skin is called awake silkworms, which means waking up after sleep. The larvae of the silkworm are divided into five ages based on their sleep.

The larvae just hatched from the silkworm eggs are called first-instar silkworms. After eating mulberry leaves for about 3 days, they start their first sleep, which lasts about 1 day. After waking up from their first sleep, they become second-instar silkworms. After about two and a half days of the second instar, they start their second sleep, which lasts about 1 day. After their second sleep, they become third-instar silkworms.

After about 3 and a half days of the third instar, the silkworm begins its third sleep, which lasts about 1 day. The third sleep marks the fourth instar.

After about 4 days in the fourth instar, the silkworm begins to sleep for about two days. After the fourth sleep, it enters the fifth instar. The fifth instar lasts about 6-8 days. Before cocooning, it stops eating mulberry leaves. The silkworm body shrinks and becomes translucent, and is called a mature silkworm. Silkworms from the first to third instars are usually called young silkworms, and silkworms from the fourth and fifth instars are called adult silkworms.

3. What are the four stages of a silkworm’s life?

The four changes that a silkworm goes through in its life are: first, egg, second, silkworm, third, pupa, and fourth, butterfly. The four forms are different, which is really amazing! It also gives us a profound revelation: in this world, the same thing will appear in front of us in completely different forms at different times, so when we analyze and solve problems, we must pay close attention to the period and form of things.

4. What are the four stages of a silkworm’s life?

The life cycle of a silkworm consists of four stages: egg, larva, pupa and adult.

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 to 500 silkworm eggs. 1700 to 2000 silkworm eggs weigh about 1 gram and have a diameter of 0.2 cm. The color of silkworm eggs is light yellow or yellow when they are first laid, and changes to light red bean color or red bean color after 1 to 2 days, and then turns to gray-green or purple after 3 to 4 days. It no longer changes and is called a fixed color.

The outer layer of the silkworm egg is a hard eggshell, and inside is yolk and serous membrane. The embryo in the fertilized egg continuously absorbs nutrients during the development process and gradually develops into a silkworm. It crawls out of the eggshell, and the eggshell becomes white or light yellow after it is empty.

The first instar is four to five days; the second instar is three to four days; the third instar is four days; the fourth instar is six days; the fifth instar is seven to nine days; the pupal stage is fourteen to eighteen days; and the moth stage is three to five days.

larva:

When the silkworm hatches from the egg, its body is brown or black, very small, and covered with fine hairs, and it looks a bit like an ant, so it is 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 to 3 hours.

silkworm chrysalis:

After the silkworms spin cocoons on the cocoon nest, they will turn into pupae after about 4 days. The body shape of the silkworm pupa is like a spindle, with three body sections: head, thorax and abdomen. The head is very small, with compound eyes and antennae; the thorax has thoracic legs and wings; the bulging abdomen has 9 body segments. Professional workers can distinguish the sex of silkworms from the lines and brown dots on the abdomen of the silkworm pupa. When the silkworms first pupate, their body color is light yellow and the pupa body is tender and soft. Gradually, it will turn into yellow, yellow-brown or brown, and the pupa skin will also harden. After about 12 to 15 days, when the pupa body begins to soften again and the pupa skin is a little wrinkled and earthy brown, it will turn into a moth.

5. How many stages are there in the life of a silkworm? What are the characteristics of each stage?

The following introduces the morphology of silkworm eggs, silkworm pupae, silkworm moths and the growth characteristics of silkworms.

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 silkworm eggs, 1700-2000 silkworm eggs, weighing about 1 gram. The color of silkworm eggs is light yellow or yellow when they are just laid, and turns into light red bean color or red bean color after 1-2 days, and then turns into gray-green or purple after 3-4 days. It will no longer change, which is called fixed color. The outer layer of silkworm eggs is a hard eggshell, and inside is yolk and serosal membrane. The embryo in the fertilized egg continuously absorbs nutrients during the development process and gradually develops into an ant silkworm. It crawls out of the eggshell, and the eggshell becomes white or light yellow after it is empty.

Ant silkworm: When the silkworm hatches from the egg, its body is brown or reddish brown, very small, and has many fine hairs, which looks a bit like an ant, so it is called an 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 to 3 hours.

The sleeping nature of silkworms: Silkworms eat a lot of mulberry, so they grow very fast and their body color gradually fades. But their appetite gradually decreases or even completely stops eating. They spit out a small amount of silk, fix their abdomen and feet on the silkworm seat, raise their head and chest, and stop moving, as if they are asleep. This is called "sleeping". The sleeping silkworms may seem motionless on the outside, but they are preparing to shed their skin inside. After shedding the old skin, the silkworms enter a new age. From ant silkworms to spinning silk cocoons, they shed their skin four times in total. Having the sleep nature is one of the growth characteristics of silkworms. Sleep nature is a genetic trait of silkworms and is also affected by the environment. The silkworms currently raised in my country belong to the four-sleeping varieties.

Silkworm age: also known as age period, which indicates the development stage of the silkworm. From the ant silkworm to the first molt is the first age; after waking up from sleep, it enters the second age; after molting again, it enters the third age; after the third molt, it enters the fourth age, and the fourth molt is also called the long sleep. After the long sleep, it enters the fifth age. The fifth-age silkworm grows very fast, with a body length of 6 to 7 cm and a weight of about 10,000 times the weight of the ant silkworm.

Mature silkworms: When silkworms reach the end of the fifth instar, they gradually show the characteristics of maturity: first, the feces they excrete change from hard to soft, and from dark green to leaf green; their appetite decreases, and the amount of food they eat decreases; the front digestive tract is empty, and the chest becomes transparent; then they stop eating completely, their bodies shorten, and their abdomens tend to be transparent; their head and chest are raised, they spit out silk threads from their mouths, and they swing left and right and up and down to find a place to build their cocoons. Such silkworms are called mature silkworms.

Cocooning during the adult stage: People put mature silkworms in special containers or on cocoons, and the silkworms will spin silk and make cocoons.

Cocooning can be divided into four processes: 1. The mature silkworms first spit out silk, which is bonded to the cocooning device, and then spit out silk to connect the surrounding cocoon branches to form a cocooning support, that is, a cocooning net. The cocooning net does not have a cocoon shape, but is just some soft and messy cocoon silk layers to serve as a support for cocooning. 2. After the silkworms make a cocooning net, they continue to spit out messy silk circles to thicken the inner layer of the cocoon net, and then spit out silk in an S-shaped manner, and the outline of the cocoon begins to appear, which is called a cocooning coat. The silk fibers of the cocoon coat are fine and brittle, arranged very irregularly, and have a high content of sericin. 3. After the cocoon coat is formed, the cocoon cavity gradually becomes smaller, and the front and rear ends of the silkworm body bend back to form a "C" shape. The silkworm continues to spit out cocoon silk, and the spinning method changes from S shape to ∞ shape, which begins the process of forming a cocoon layer. 4. When the silkworm's body is greatly reduced due to a large amount of silk spinning, the swing speed of the head and thorax slows down, and there is no certain rhythm. The spinning begins to appear messy, forming a loose and soft cocoon silk layer, called a pupa lining.

Silkworm pupa: After the silkworms make cocoons on the cocoon nest, they will turn into pupae about 4 days later. The body of the silkworm pupa is shaped like a spindle, with three body sections: head, thorax, and abdomen. The head is very small, with compound eyes and antennae; the thorax has thoracic legs and wings; the bulging abdomen has 9 body segments. Professional workers can distinguish the sex of silkworm pupa from the lines and brown dots on the abdomen. When the silkworm just turns into a pupae, its body color is light yellow, and the pupa body is tender and soft. Gradually, it will turn into yellow, yellow-brown or brown, and the pupa skin will also harden. After about 12 to 15 days, when the pupa body begins to soften again and the pupa skin is a little wrinkled and earthy brown, it will turn into a moth.

Silkworm moth (adult): Silkworm moths are shaped like butterflies, with white scales all over their bodies, but because their two pairs of wings are small, they have lost the ability to fly. The head of the silkworm moth is spherical, with bulging compound eyes and antennae; the chest has three pairs of thoracic legs and two pairs of wings; the abdomen has no ventral legs, and the terminal body segment has evolved into external genitalia. The female moth is large and crawls slowly; the male moth is small and crawls faster, with its wings vibrating rapidly, looking for a mate. Generally, the female moth can lay fertilized eggs 3 to 4 hours after mating. The male dies after mating, and the female moth can lay about 500 eggs in one night, and then slowly dies.

The silkworm lays eggs, hatches into silkworms, turns into pupae, and then turns into moths, completing the cycle of a new generation. This is the life history of the silkworm.

6. How many stages does a silkworm go through in its life and how long does each stage last?

In order to master the production rules of silkworm breeding, it is necessary to understand the general knowledge of silkworms, such as their morphology and living habits. Silkworms have four development stages in their life: egg, larva (silkworm), pupa (cocoon), and adult (moth). Silkworms are beneficial insects that can spin silk and make cocoons.

Eggs: They are oval in shape, slightly smaller than millet grains, gray-green or gray-purple in color, and there are about 1,700 to 1,800 eggs per square centimeter.

Larvae (silkworm): The appearance of silkworms is divided into head, thorax and abdomen. The head is what we usually call the mouth, the thorax has three segments, with three pairs of thoracic legs, and the abdomen has ten segments, with four pairs of abdominal legs. There are about 2100 to 2300 silkworms per square centimeter.

Pupa (cocoon): The mature silkworm will pupate on the 5th day after it goes to the cocoon. The pupa is spindle-shaped and yellowish brown.

Adult (moth): has a pair of white scaly wings, but cannot fly. Mating and laying eggs

The moth dies after 2-3 days.

400 to 600 pills.

Age distinction: During the development process, silkworms generally go through four sleeps and five instars from hatching to cocooning. The length of the silkworm period varies depending on the species, feeding season and feeding conditions. In the spring, silkworms can form cocoons after 25 to 28 days. When silkworms grow to a certain age, they will shed their old skin and grow new skin. During the period of molting, they do not eat or move, which is called sleep. The period between sleeps is called instar.

Generally, the first to third instars are called the young silkworm stage, and the fourth to fifth instars are called the adult silkworm stage.

First instar: From hatching to the first molting, it is called the first instar. The dormancy period is called the first sleep. The instar lasts three to three and a half days. In the early stage, the silkworm body is small, covered with bristles, and its body color is dark brown like an ant, so it is called ant silkworm.

Second instar: The period from the first molting to the second molting is called the second instar, and the dormancy period is called the second sleep. The instar period lasts about three days. The second instar period is shorter than the other instars.

The third instar: From the second molting to the third molting, it is called the third instar. The dormancy period is called the third sleep. The instar lasts about four to four and a half days. At this time, the spots on the silkworm body can be identified.

Fourth instar: From the third molting to the fourth molting is called the fourth instar. The dormancy period is called the fourth sleep. Commonly known as the big sleep. After about five to six days of the instar, the markings on the silkworm body become clearer.

The fifth instar: from the fourth molting to the tufting, it is called the fifth instar, which takes about 7 to 8 days. The silkworm body is enlarged with clear spots. From the ant larva to the fifth instar, the weight increases by about 10,000 times.

Differentiation of developmental periods in each age group: During the developmental process of silkworms at the same age, due to changes in appetite, body color, etc., it can be divided into five periods. Correctly grasping these five periods is of great help in the reasonable management of mulberry and dormancy.

Less feeding period: After molting, the skin and mouthparts of silkworms are very tender and soft, and it takes some time for them to start eating mulberry. The first day after molting, they eat less mulberry, which is called the less feeding period.

Middle feeding period: the body color gradually turns green, the body becomes slender, the wrinkles on the skin spread out, and the amount of mulberry eaten is between the small feeding period and the large feeding period.

The amount of mulberry given should be appropriately controlled during the period of low food intake and medium food intake.

Peak feeding period: The body color is glossy and bluish white, gradually changing from bluish to white. The appetite is strong, the feeding period is long, and the growth has reached the maximum limit at this age.

Hypnotic period: The body color changes from bluish white to fried beige (white with yellow), and the skin becomes tight and shiny. The appetite decreases, silk threads are spit out, and the silkworm gradually falls asleep. At this time, it is called a sleeping silkworm. After the fifth instar, the silkworm is called a mature silkworm.

The last feeding of silkworms before they sleep is called "stop feeding". The fourth feeding of silkworms after they wake up is called "feeding". The period from feeding to stopping feeding is called "feeding during mulberry season". The period from stopping feeding to feeding is called "feeding period", also called "sleeping period". The period from silkworm hatching to cocooning is called the whole process.