Mulberry silk is the most common kind of silk in the world . It makes up 90% of the silk supply in the world. Mulberry Silk is produced by the silkworms which are fed from the mulberry leaves (hence its name).
Mulberry silkworm is a silk-secreting insect that was domesticated by the ancient wild mulberry silkworm. It feeds on mulberry leaves, so it is also called the silkworm. Due to the long-term selection and cultivation of the silkworm, the silk glands in the silkworm body are very developed, and the silk secretion ability is far stronger than that of the wild silkworm with its homology. The silk quality is good, and it has extremely high economic value. The quantity and yield of cocoon silk are far more than other silkworms. The position of silkworm in animal taxonomy is as follows: Arthropoda — Insecta — Lepidoptera — Heterocera — Bombysidae — Bombyx — Bombyx mori.
The scientific name of the silkworm is Bombyx mori. Silkworms can be divided into different types according to their chemical properties, dormancy, cocoon color, and place of origin.
Bombyx mori is a completely metamorphic insect. In its lifetime, it has to go through four developmental stages of egg, larva, pupa, and adult (moth) that are completely different in morphology and function in order to complete a generation.
The silkworm reproduces with eggs, which are the stage of embryogenesis, development and formation of larvae. Because of the different silkworm species, there are diapause (yuenian) eggs and non-diapause (nonyuenian) eggs.
After the non-diapause eggs are laid, they gradually form embryos through cleavage, and develop continuously, forming larvae and hatching in about 1 day.
Approximately 7 days after the fertile eggs (diapause eggs) are laid, after the embryo has developed to a certain degree, it enters a temporarily stopped diapause period. During the diapause period, the embryo morphology rarely changes, and even if the temperature and other conditions are suitable, it will not develop forward. It must be released under certain conditions after the diapause or artificial incubation treatment (such as soaking) is applied before the diapause period. Acid, etc.) stop its diapause process before it will continue to develop and hatch. For example, when hatching in late April, the diapause eggs laid in early June will not hatch until the spring of the following year under natural conditions, which lasts about 10 months; even the diapause eggs laid in the autumn period generally have to go through 5 to 7 Diapause can be lifted by one month and the incubation function can be obtained.
The larval stage is the growth stage where food is ingested and nutrients are accumulated. The newly hatched larvae are brown or russet and resemble ants, so they are called ant silkworms. Ant silkworms grow rapidly by feeding on mulberry leaves, and their body color gradually fades to white. When the larvae (commonly known as the silkworm) grow to a certain extent, they need to shed their old skins, and then continue to feed on the new ones that grow wider, which is called molting. During the moulting period, the larvae spin silk to fix their feet on the silkworm seat, without eating or moving, which is called sleep. Sleeping is the process of molting, during which new skin is formed and old skin is shed. Silkworms that have just shed their skins are called silkworms. Sleeping is the boundary of the silkworm age. Bombyx mori larvae generally go through the 4th and 5th instar, the 1st to 3rd instars are called the juvenile silkworm (commonly known as small silkworm) stage, the 4th to 5th instars are called the strong silkworm (commonly known as large silkworm) stage, and they develop to the last instar (5th instar). At the end of the period, mulberry eating is gradually stopped, and the body of the silkworm shrinks and becomes transparent. At this time, it is called the mature silkworm (commonly known as the old silkworm). After the mature silkworm finds a suitable cocoon site, it spins silk and forms a cocoon and pupates in it, and the larval stage ends here.
The silkworm grows and grows rapidly only during the larval stage of eating mulberry. When the ant silkworm grows extremely to the 5th instar, the weight increases from 0.41 ~ 0.51 mg at hatching to 5 ~ 6 grams, an increase of about 10,000 times; the volume increases from 0.008cm 3 at hatching to 4.847cm3, which increases About 6,000 times; the growth of silk glands is more significant than the increase in body weight and volume. Compared with ant silkworms, the weight of silk glands increases by 16,000 times when they reach the 5th instar mature silkworm. Under suitable temperature conditions, the larvae of the bimorphic four-sleeping silkworm species usually develop for 3~4 days for the first instar, 3 days for the 2nd instar, 4~5 days for the 3rd instar, 7~8 days for the 5th instar, and the whole instar passes around 25 days.
Pupa is the transitional stage from larva to adult metamorphosis. The mature silkworm takes about 2 days from the start of silking to the completion of cocooning. At this time, the body is significantly shortened into a spindle shape, which is called pre-pupa (latent pupa). After 2 to 3 days, the pupal skin is formed, that is, the larval epidermis is shed and pupated. The body is white and extremely soft when the pupae are just formed. As time progresses, it gradually turns brown, and finally becomes dark brown, and the skin hardens day by day. The pupal stage is the transitional period from the larvae to the adult development metamorphosis, which does not eat or move in appearance and has no morphological changes. However, the body is undergoing violent metamorphosis. The dissociation and transformation of larval organs and the occurrence and formation of adult organs are all completed in the pupal stage. When the pupa completes its development, it sheds its pupa skin and emerges as an adult (moth). The elapsed time of pupal stage varies with species and temperature, and is 10 – 15 days under suitable temperature.
Adults (moths) are the reproductive stage of mating, laying eggs and reproducing offspring. At the end of the pupal stage, the adult worms have formed in the pupal skin, and when they emerge, they first split from the back of the chest of the pupa. The adult worms shed the pupa shell from the crack and spit out alkaline gastric juice to the cocoon end to moisten the cocoon layer and dissolve it. Sericin is then used to separate the silk strands with the chest and feet to form a cocoon and crawl out. The silkworm moth crawling out of the cocoon has a moist body surface, its wings curled up, and it stands still. After about 10-15 minutes, the scales are dry, the moth wings are stretched, and the moth body is fully mature. The male moth looks for the female moth to mate, and then the female moth lays eggs to start a new generation.
Silkworm moths undergo a series of rapid life activities such as emergence, mating, and laying eggs, and the nutrients in their bodies are consumed in large quantities. Because they do not ingest food during the adult stage, after the male moths mate and the female moths lay eggs, approximately 6 to 10 days will pass. When the energy necessary for life activities is exhausted and cannot be maintained, it will naturally die. This is the end of a generation of silkworm.
Eggs, larvae, pupae, and adults are the four developmental stages of the silkworm in one generation, and each stage has a different meaning in its life history. The elapsed time of each developmental stage varies with silkworm species and breeding environment conditions.
1. Silkworms eggs
2. Larva (Catepillar) Stages
3. Cocoons
Once the worms start pupating in their cocoons, individual long fibres are extracted from cocoons and fed into the spinning reel to make silk threads, and then, various types of silk fabric.
In nature, silkworm cocoon colours vary from white, yellow, straw, salmon, pink to green. The colours in the silk are from natural pigments absorbed when the silkworms eat mulberry leaves.
4. Silk Moths
If we leave the cocoons as they are, we should be able to see the final stage.
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