ovum
Egg color
The eggs laid by silkworm moths are generally pale yellowish-green, and after 2-3 days with the development of internal embryos, the egg color becomes light tea brown, and then gradually becomes thicker, and after 4-5 days, it becomes the inherent color of the variety. Egg color is purple, gray, brown, green, orange, yellow, red, white, etc., the most common egg color is purple gray, and its thickness also varies according to the variety.
egg shell
The outer circumference of the yolk membrane of silkworm eggs surrounds the egg shell. The egg shell is generally colorless and transparent, but there are also yellowish or pale greenish bands. The egg shell contains a large amount of glycine, cystine and other hard proteins called egg shells.
Silkworms
Newly hatched silkworm babies, called silkworms, have a dark brown and shiny head and a dark color on the body; The thorax is almost black , and the hooks and claws at the ends of the ventral feet are arranged in a single-order ring. The most prominent feature of the silkworm is that there are most nodular protrusions on the surface of the body, which are arranged in a certain position on the link, and 3-6 bristles are born on it. After the ants encroach on the mulberry leaves, they gradually grow, and the nodular protrusions disappear with the extension of the body wall, and the body color fades, which is commonly known as the "hair thinning period" at this time, and it is not bristle shedding.
molt
At the beginning of the molting process, gradually stop feeding and excrete the residue inside the digestive tube.
Grasp with the abdomen and feet on the silkworm seat with silk, so that the silkworm body is not easy to fall off during sleep, but lifts the front half of the silkworm body and stands still,
After about 3-6 hours, a light brown triangle appears at the junction of the head and thorax, where the new head is located.
The lowermost layer of the old epidermis appears in a state where substances secreted from dermal cells (molting glands) (molting fluid) are dissolved.
The upper end of the dermal cell is protruding, and the surface is covered with a thin film-like new epidermis. The periphery of the protrusion is interlayered with epidermal material secreted by dermal cells, forming a new inner and outer epidermis.
The front half of the silkworm descends, the whole body is wavy, and after 1-2 hours, a "T" shaped fissure appears on the back of the old skin at the junction of the head and thorax.
The new head quickly came out of the crack and after 56 minutes the whole body was out of the old skin.
In addition to the removal of the old skin during molting, the lining of the anterior and posterior digestive ducts, the anterior silk glands, salivary glands, a part of the Martens duct and trachea also emerge at the same time.
After molting, the silkworm lifts the front half of its body to stand still for a certain period of time and begins to eat mulberry.
Cocooning
The cocooning process of silkworm babies can be roughly divided into the following four stages:
In the first stage, after the mature silkworm is on, it crawls on the top, often swinging the front half of the body, exploring back and forth to the left and right, until it finds the appropriate cocoon place, it spits silk attached to the family, forms a cocoon stent and then emptys the contents of the digestive tube, and continues to spit silk on the stent, making a cocoon net. This is the preparatory period for cocooning, and the contours of the cocoon have not yet been formed.
In the second stage, on the inside of the cocoon net, a messy and loose silk circle is spit out, the cocoon net is thickened, and then the action of spitting silk is changed to "C-shaped, so that a layer of loose cocoon clothing is formed." With the completion of the cocoon coat, the silhouette of the cocoon begins to appear.
In the third stage, after the cocoon is formed, around the inner space (cocoon cavity) of the cocoon, the silk circle is changed from "∽" to "∞". At this time, the front and back ends of the silkworm body are bent backwards, and the abdominal foot is fixed to the inner wall of the cocoon cavity, and the head swings from side to side. Each "∞" shaped coil has a long shaft of 1-2 mm, and each spit out 15-25 "" shaped coils is a group, called a cocoon piece. After each cocoon is completed, the position is transferred to form a second cocoon, and so on continues to wow, gradually forming a cocoon layer. When the silk is spit out, the sericin is not dry, it is adhesion, and it is glued with the cocoon silk that was previously spit out, forming a glue state of the cocoon layer of silk.
In the fourth stage, due to the large amount of spitting and the consumption of energy substances, the silkworm body is significantly reduced, the swing of the head is slowed down, the amplitude is reduced, and the rhythm is lost, and a thin layer of pupae is spit into a thin layer in the innermost layer of the cocoon. Finally, the larvae head to the upper end of the cocoon, the tail down, spit out the silk material that remains in the body, forming a soft cocoon top, which completes the process of spitting out the silk cocoon, waiting for the pupa.
chrysalis
The molting skin is carried out after the finishing of the ripe silkworm spitting, the initial silkworm body is stationary, the body is shortened, the front 4 links and the back end 3 links are significantly reduced, the 5th and 9th links are slightly expanded, and the silkworm body is slightly spindle-shaped. During this period when the epidermis separates from the dermis and secretes to form a pupal epidermis, it is especially called pre-pupal. Generally after 2-3 days of pupal formation, the silkworm body begins to squirm, and soon (2-4 hours) in the cephalothorax realm and the back of the 1st-2th thoracic segment appear "T" shaped crack, about 10-20 minutes later, the pupal emerges from the old skin. The pupate of the first molt is all white, the body wall is soft and easy to break, and gradually hardens and colores with the passage of time, turning brown.
The pupal period is generally about 2 weeks.
The pupal is divided into three parts: head, chest and abdomen. The head is small, a small part of the white part of the front is called the top of the head, the slightly square part of the front is the forehead, the lower part of the forehead is the base of the lip, and the base of the lip is connected to the upper lip. On both sides of the forehead there are 1 pair of antennae that bend downwards and posteriorly, and 1 pair of compound eyes under the base of the antennae. A dark brown vestigated palate is visible on both sides of the upper lip, and the lower lip is concealed under the lower palate.
The thorax consists of 3 links, and from the back of the pupae, the 1st thoracic segment is slightly flattened and hexagonal, called the forebreast; The 2nd thoracic segment is the largest, pentagonal, called the mid-thorax; The 3rd thoracic segment is the smallest and is called the posterior chest. The ventral surface of the chest link has 1 pair of feet, called forefoot, middlefoot and hindfoot respectively. The pectoral foot is pressed against the ventral surface of the thorax, most of which is hidden under the wings, and only one part of the forefoot and the middle foot can be seen from the outside. On each side of the forecolletax, there is a valve, and there is a pair of wings on each side of the middle and hindhoraxes, and the hindwings are covered by the forewings and only the anterior edge is exposed.
Due to the healing of the 9th and 10th abdominal segments of the larval stage, only 9 links appear in appearance, with the 4th, 5th and 6th abdominal segments being the largest, and the anterior and posterior links are gradually reduced. The 4th, 5th, 6th, and 7th abdominal segments can move between them, especially called the exercise link.