Silkworm: interesting facts and photos. Silkworm - obtaining silk Domestication of the silkworm

The history of breeding of this butterfly, which belongs to the family of true silkworms (Bombycidae), is associated with ancient China, a country that for many years kept the secret of making an amazing fabric - silk. In ancient Chinese manuscripts, the silkworm was first mentioned in 2600 BC, and when archaeological excavations In the southwest of Shanxi province, silkworm cocoons were found dating back to 2000 BC. The Chinese knew how to keep their secrets - any attempt to export butterflies, caterpillars or silkworm eggs was punishable by death.

But all secrets are revealed someday. This happened with silk production. First, a certain selfless Chinese princess in the 4th century. AD, having married the king of Little Bukhara, she brought him eggs as a gift silkworm, hiding them in her hair. About 200 years later, in 552, two monks came to the Byzantine emperor Justinian, who offered to deliver silkworm eggs from distant China for a good reward. Justinian agreed. The monks set out on a dangerous journey and returned the same year, bringing silkworm eggs in their hollow staves. Justinian was fully aware of the importance of his purchase and by a special decree ordered the breeding of silkworms in the eastern regions of the empire. However, sericulture soon fell into decline and only after the Arab conquests it flourished again in Asia Minor, and later throughout North Africa, in Spain.

After IV crusade(1203-1204), silkworm eggs came from Constantinople to Venice, and since then silkworms have been quite successfully bred in the Po Valley. In the XIV century. Sericulture began in the south of France. And in 1596, silkworms began to be bred for the first time in Russia - first near Moscow, in the village of Izmailovo, and over time - in the southern provinces of the empire that were more suitable for this.

However, even after Europeans learned to breed silkworms and unwind cocoons, most of the silk continued to be delivered from China. For a long time, this material was worth its weight in gold and was available exclusively to the rich. Only in the twentieth century did artificial silk somewhat replace natural silk on the market, and even then, I think, not for long - after all, the properties natural silk truly unique.
Silk fabrics are incredibly durable and last a very long time. Silk is lightweight and retains heat well. Finally, natural silk very beautiful and lends itself to uniform coloring.

Silkworm caterpillars hatch from eggs (greens) at a temperature of 23-25 ​​degrees Celsius. In large sericulture farms, grenades are placed in special incubators for this purpose, where the required temperature and humidity are maintained. It takes 8-10 days for the eggs to develop, after which small larvae, only about 3 mm long, are born. They are dark brown in color and covered with tufts long hair. The hatched caterpillars are transferred to a special food shelf in a well-ventilated room with a temperature of 24-25 degrees Celsius. Each bookcase consists of several shelves covered with a fine mesh.

There are fresh mulberry leaves on the shelves. The caterpillars eat them with such appetite that Pasteur compared the loud crunching sound coming from the aft shelf with “the sound of rain falling on trees during a thunderstorm.”

The caterpillars' appetite is growing by leaps and bounds. Already on the second day after hatching, they eat twice as much food as on the first day, etc. On the fifth day, the caterpillars begin molting - they stop feeding and freeze, clasping a leaf with their hind legs and raising the front part of their body high. In this position they sleep for about a day, and then the larva straightens up strongly, the old skin bursts, and the caterpillar, grown and covered with delicate new skin, crawls out of its tight clothes. Then she rests for several hours and then starts eating again. Four days later the caterpillar falls asleep again before the next molt...

During its life, the silkworm caterpillar molts 4 times, and then builds a cocoon and turns into a pupa. At 20-25 degrees Celsius, the development of the larvae is completed in about a month, at higher temperatures - faster. After the fourth molt, the caterpillar already looks very impressive: its body length is about 8 cm, its thickness is about 1 cm, and its weight is 3-5 g. Its body is now almost naked and colored whitish, pearl or ivory. At the end of the body there is a blunt curved horn. The caterpillar's head is large with two pairs of jaws, of which the upper one (mandibles) is especially well developed. But the main thing that makes the silkworm so attractive to humans is a small tubercle under the lower lip, from which a sticky substance oozes, which, upon contact with air, immediately hardens and turns into a silk thread.

Here, into this tubercle, the excretory ducts of two silk-secreting glands located in the body of the caterpillar flow. Each gland is formed by a long convoluted tube, the middle part of which is expanded and turned into a reservoir in which “silk liquid” accumulates. The reservoir of each gland passes into a long thin duct, which opens with an opening on the papilla of the lower lip. When the caterpillar needs to prepare the silk, it releases a stream of liquid outward, and it hardens, turning into a pair of threads. It is very thin, only 13-14 microns in diameter, but can withstand a load of about 15 g.
Even the smallest caterpillar that has just emerged from an egg can already secrete a thin thread. Whenever the baby is in danger of falling down, she releases the silk and hangs on it, like a spider hangs on its web. But after the fourth molt, the silk-secreting glands reach a particularly large sizes- up to 2/5 of the total body volume of the larva.

Now every day the caterpillar eats less and less and finally stops eating altogether. At this time, the mulberry gland is already so filled with liquid that a long thread trails behind the larva, wherever it crawls. The caterpillar, ready for pupation, restlessly crawls along the shelf in search of a suitable place for pupation. At this time, silkworm breeders place bundles of wood twigs - cocoons - on the aft shelf along the side walls.

Having found a suitable support, the caterpillar quickly crawls onto it and immediately begins its work. Clinging tightly to one of the twigs with her abdominal legs, she throws her head now to the right, now back, now to the left and applies her lower lip with a “silk” papilla to various places in the cocoon. Soon a rather dense network of silk thread forms around it. But this is not the final construction, but only its basis. Having finished with the frame, the caterpillar crawls to its center - at this time, silk threads support it in the air and serve as the place where the real cocoon will be attached. And so his curling begins. As the caterpillar releases the thread, it quickly turns its head. Each turn requires 4 cm of silk thread, and the entire cocoon takes from 800 m to 1 km, and sometimes more! A caterpillar must shake its head as many as twenty-four thousand times to spin a cocoon.

It takes about 4 days to make a cocoon. Having finished its work, the exhausted caterpillar falls asleep in its silk cradle and turns into a chrysalis there. Some caterpillars, they are called carpet makers, do not make cocoons, but, crawling back and forth, line the surface of the food shelf as if with a carpet, while their pupa remains naked. Others, lovers of joint buildings, team up in twos or even threes and fours and weave a single, very large, up to 7 cm, cocoon. But these are all deviations from the norm. And usually caterpillars weave a single cocoon, the weight of which, together with the pupa, is from 1 to 4 g.

The cocoons produced by spinner caterpillars are very diverse in shape, size, and color. Some of them are completely round, others have an oval shape with a sharp end or a constriction in the middle. The smallest cocoons do not exceed 1.5-2 cm in length, and the largest reach 5-6 cm. In color, cocoons are completely white, lemon yellow, golden, dark yellow with a reddish tint and even greenish, depending on the breed silkworm. For example, the striped breed of silkworm spins pure white cocoons, and the stripless breed spins beautiful golden-yellow cocoons.
It is interesting that the caterpillars, from which male butterflies later emerge, are more diligent silkworms: they weave denser cocoons, which require more silk thread.

After about 20 days, a butterfly emerges from the pupa and is faced with the problem of how to get out of its silken shelter. After all, unlike a caterpillar, it does not have sharp jaws... However, the butterfly has a different adaptation. Her goiter is filled with alkaline saliva, which softens the wall of the cocoon. Then the butterfly presses its head against the weakened wall, energetically helps itself with its legs, and finally gets out. The silkworm butterfly is not particularly beautiful. The color of its plump, furry body is either white with a light cream pattern, or dark grayish-brown. Females are larger than males.

The wingspan of the silkworm is about 4.5 cm, but these butterflies cannot fly. Most likely, they lost this ability through the process of constant human selection. After all, why do we need individuals in sericulture that can fly away?
Domestic butterflies generally do not tend to bother themselves with unnecessary movements. They only move slowly on their thin legs and move their shaggy antennae. During their short (about 12 days) life, they do not even feed. After alkaline saliva is released from their mouth, softening the cocoon, it closes forever.

Male silkworms change their behavior only when they meet individuals of the opposite sex. That’s when they perk up, circle around their friend, constantly flapping their wings and actively moving their legs. During the mating season, the silkworm puts pairs of butterflies in special gauze bags. A few hours after prolonged mating, the female begins to lay eggs - approximately from 300 to 800. This process takes her 5-6 days. Silkworm eggs are small, about 1.5 mm long. In winter, the eggs are kept at a relatively low temperature, and when spring comes and the mulberry trees begin to leaf out, the eggs are gradually revived by first keeping them at a temperature of 12 degrees Celsius and then placing them in a brood incubator.

But, of course, not every caterpillar that weaves a cocoon is given the opportunity to turn into a butterfly. Most of cocoons are used to obtain raw silk. The pupae are killed with steam, and the cocoons are soaked and unwound on special machines. From 100 kg of cocoons you can get approximately 9 kg of silk thread.
The silkworm spins the most beautiful yarn, but the caterpillars of some other butterflies are also capable of creating silk thread, although it is coarser. Thus, fagar silk is obtained from the cocoons of the East Asian atlas (Attacus attacus), and silk is obtained from the cocoons of the Chinese oak peacock eye (genus Antheraea), which is used for the production of scallop.

China - amazing country, filled with myths and legends. According to one of the ancient legends, the wife of the mythical Yellow Emperor taught her people to weave and extract silk from the silkworm. How much you can believe this legend is unknown, but to this day China is breeding this butterfly.

What does it look like

This is a fairly large butterfly with a wingspan of up to 60 mm, which has unique individual characteristics. For example, in the process of evolution and domestication, it lost its ability to feed and acquired.

After emergence, she mates, lays larvae and dies. Its ancestors ate the leaves of the mulberry tree; it was in its crown that they lived, which is why the name of this insect came about.

Lifestyle

It has been noted that males, when spinning a cocoon from a single silk thread, spend a little more vital resource and time on this. As a result, the male’s cocoon turns out to be 25% heavier than that of the female. The process of creating a silk cocoon is very labor-intensive and troublesome, releasing two strong, but at the same time thin threads from the lower lip, the caterpillar weaves its house for 18-25 days to transform into a butterfly.

An important point in the life of a silkworm is the arrangement of a place for forging: thin rods must be installed in it, and it is in them that the silkworm will weave its house. The size of the cocoon reaches 38 mm, it is very dense with closed edges.

Reproduction

The life cycle of an insect is simple and primitive, and over many years of work with it by humans, it has been refined into a mechanism.
After mating, the female spends 2-3 days laying eggs; she produces about 600 eggs per clutch. After the appearance of a tiny caterpillar and with proper maintenance, it will grow and develop for about 25 days until it reaches maturity. And only then will preparations begin for transformation into a butterfly.

The pupa becomes a pupa on the 10th day, and only then can silk cocoons be used to produce silk thread.

Economic importance

Today you can go to silkworm breeding factories, see and learn the entire production process, but several centuries ago for the Chinese, everything related to the production of silk from silkworms was a closely guarded secret, the disclosure of which was punishable by death. But there are no secrets that cannot be revealed. The same thing happened in this case. Gradually, cunning traders revealed this secret, and it became the property of many nations. Silk production began to develop in India, Europe, Russia, and Kazakhstan.

The silkworm is a worker in the textile industry.

The second country where they began to engage in this profitable business, based on the reproduction of butterfly larvae, was India. Today it occupies a leading position in the production of natural silk.

The silkworm is no longer found in wildlife, and the whole life cycle takes place under human supervision.

Modern developments make it possible to select the silkworm to such an extent that the cocoon itself has whitest color. Cocoons of gray, green or yellow color are not suitable for producing high-quality silk, so breeders do not use them in large-scale production.

The silkworm is very interesting insect, which has been known to man since ancient times as silk source. According to some data mentioned in Chinese chronicles, the insect became known as early as 2600 BC. The process of obtaining silk was a state secret for centuries in China, and silk became one of the clear trade advantages.

Starting from the 13th century, other countries, including Spain, Italy, and North African countries, mastered the technology of silk production. In the 16th century, technology reached Russia.

Nowadays, the silkworm is actively bred in many countries, and in Korea and China it is used not only to produce silk, but also for food. The exotic dishes that are prepared from it are distinguished by their originality, and silkworm larvae are used for the needs of traditional medicine.

India and China are leaders in silk production and it is in these countries that the number of silkworms is greatest.

What does a silkworm look like?

This insect earned its unusual name thanks to the tree it feeds on. Mulberry, a tree also called mulberry, is the only source of food for the silkworm.

Silkworm caterpillar eats a tree day and night, which can even lead to its death if the caterpillars occupy such trees on the farm. To produce silk on an industrial scale, these trees are grown specifically to feed insects.

The silkworm goes through the following life cycles:

The silkworm butterfly is a large insect, and its wingspan reaches 6 centimeters. She has white color with black spots, on the wings, in the front part of them, there are notches. Pronounced comb mustache distinguish males from females, in whom this effect is almost invisible.

The butterfly has practically lost the ability to fly and modern individuals spend their entire lives without rising into the sky. This was caused by their very long detention in unnatural living conditions. Moreover, according to available facts, insects stop eating food after turning into butterflies.

The silkworm acquired such strange features because it was kept at home for many centuries. This has now led to the insect cannot survive without human guardianship.

Over the years of its breeding, the silkworm has managed to degenerate into two main species: monovoltine and multivoltine. The first species lays larvae once a year, and the second - up to several times a year.

Hybrid silkworms can have many differences in characteristics such as:

• body shape;
• wing color;
• dimensions and general shape of the butterfly;
• dimensions of the pupa;
• color and shape of caterpillars.

The larvae or eggs of this butterfly are scientifically called grena. They have a laterally flattened oval shape, with elastic transparent film. The dimensions of one egg are so small that per gram of weight their number can reach two thousand.

Immediately after the butterfly lays its eggs, they have a light milky or yellowish color. As time passes, changes occur, leading to the appearance of a pink tint in the larvae, and then to complete change colors to purple. If the color of the eggs does not change over time, it means the larvae have died.

Silkworm eggs have a fairly long maturation period. He puts them in summer months: in July and August, and then they hibernate until spring. The processes occurring in them at this time slow down significantly in order to survive the effects of low winter temperatures.

If the grena overwinters at temperatures not lower than +15 degrees, then there is a risk of poor development in future caterpillars, so in winter it is necessary provide for grains optimal temperature regime. Caterpillars appear before leaves have time to grow on the trees, so grena is stored in refrigeration units at temperatures from 0 to -2 degrees throughout this period.

The caterpillars of this butterfly are also called silkworms, which cannot be considered a scientific name. Externally, silkworm caterpillars look like this:

Immediately after birth, the caterpillar has a very small size and a weight not exceeding half of one milligram. Despite this size, all biological processes in the caterpillar proceed normally, and it begins to actively develop and grow.

The caterpillar has very developed jaws, pharynx and esophagus, due to which all consumed food is absorbed very quickly and well. Each of these little caterpillars has more than 8,000 muscles, allowing them to bend into intricate poses.

In forty days the caterpillar grows to a size of thirty s one more time exceeding its original dimensions. During the period of growth, she sheds her skin, which for natural reasons becomes small for her. This is called molting.

During molting, the silkworm caterpillar stops eating tree leaves and finds a separate place for itself, usually under the leaves, where it tightly attaches itself to them with its legs and freezes for some period. I also call this period the caterpillar's sleep.

As time passes, the head of a renewed caterpillar begins to emerge from the old skin, and then it comes out entirely. At this time you cannot touch them. This can lead to the fact that the caterpillar simply does not have time to shed its old skin and dies. During its life, the caterpillar molts four times.

The intermediate stage in the transformation of a caterpillar into a butterfly is the cocoon. Caterpillar creates a cocoon around itself and inside it turns into a butterfly. These cocoons are of greatest interest to humans.

The moment when a butterfly should be born and leave its cocoon is very easy to determine - it begins to move literally a day before, and you can hear light tapping sounds inside. This knocking appears because at this time the already mature butterfly is trying to free itself from the skin of the caterpillar. A curious fact is that the time of birth of the silkworm butterfly is always the same - from five to six in the morning.

A special liquid, similar in consistency to glue, which is secreted by butterflies, helps them free themselves from the cocoon by splitting it.

The lifespan of a moth is limited to only twenty days, and sometimes they do not even live up to 18 days. In this case it is possible meet long-livers among them who live for 25 and even 30 days.

Due to the fact that the jaws and mouth of butterflies are not sufficiently developed, they cannot feed. The main task of the butterfly is to procreate and for its short life they manage to lay many eggs. In one clutch, a female silkworm can lay up to a thousand of them.

It is noteworthy that even if an insect loses its head, egg laying process will not be interrupted. The butterfly body has several nervous systems, which allows her to continue laying and live for a long time, even in the absence of such a significant part of the body as the head.

These butterflies are used by humans to produce silk; in general, the silkworm is a very long-standing inhabitant of our planet. Some argue that people began to use it five thousand years BC.

Today the worms of this butterfly are bred for silk, Interesting Facts, that in China and Korea, silkworm dolls are used as food, they are fried and such a dish is considered exotic, and these larvae are also used in folk medicine.

In our world, the most important countries that produce silk (60 percent of the total market) are India and China, where the largest number of silkworms live.

Today, people know much more about the production and types of silk than about the insect that gave us this magnificent silk thread. This is what we will talk about in this article. Let's find out what the silkworm looks like, what it eats, how it is bred, as well as its reproductive characteristics.

Appearance

Silkworms get their name from their diet. They recognize only one tree - this is the mulberry, in scientific language this tree is called mulberry. Silkworm caterpillars eat non-stop day and night. Therefore, some farm owners experience inconvenience if the tree is occupied by caterpillars of this breed. In the silk industry Mulberry tree specially grown to provide food for silkworms.

This insect goes through a standard development process, which can be seen in the video. Like all insects, the wild silkworm goes through four life cycles, namely:

• egg (larva) formation;
• appearance of a caterpillar;
• pupal formation (mulberry cocoons);
• butterfly.

The butterfly is quite large in size. The wingspan is about 60 millimeters. To the main characteristics appearance The following indicators can be included:

• color white with dirty spots;
• there are clear brown bandages on the wings;
• the front part of the wing is processed with a notch;
• males have combed mustaches, while in females this effect is weakly expressed;

Externally, the wild silkworm is very beautiful. In the photo and video you can see what this breed of butterfly looks like in life.

Today, this species practically does not fly, due to being kept in unnatural conditions. There are also interesting facts that state that these insects do not eat when they become butterflies. This breed has obvious distinctive features from all other species. The fact is that for many centuries, people kept silkworms at home and therefore, today these butterflies cannot survive without his care and tutelage. For example, caterpillars will not look for food, even if they are very hungry, they will wait for a person to feed them. To date, scientists cannot give an exact answer about the origin of this species.

In modern sericulture there are many varieties of silkworms. Most often, hybrid individuals are used. In general, this breed can be divided into two types:

• the first is univoltine, this species can produce offspring no more than once a year;
• the second is a polyvoltine one, which produces larvae several times a year.

Hybrids are also different external signs, which include:

• wing color;
• body shape;
• the size that characterizes the pupa;
• shapes and sizes of butterflies;
• size and color of the caterpillars (there is a breed of silkworm with striped or single-colored caterpillars).

You can see what all possible types of silkworms look like in a photo or video.

Silkworm productivity indicators include the following characteristics:

• the amount of dry cocoons produced and their overall yield;
• how far the cocoon shells can unwind;
• silk yield;
• technical properties and quality of the resulting silk.

What characteristics do silkworm eggs have?

In the scientific field, silkworm eggs are called grena. The features are as follows:

• oval shape;
• slightly flattened sides;
• elastic and translucent shell.

The egg size is incredibly small; one gram can contain up to two thousand eggs. Once the butterflies have laid the egg, it has a light yellow or milky color, and over time the color of the eggs gradually changes, first turning a little pink and finally becoming dark purple. And when the color of the eggs does not change, this indicates that their vital capacity has been completely lost.

The ripening period for grena is long. Butterfly larvae lay in July and August. They then hibernate until spring. During this period, all metabolic processes in the egg slow down significantly. This is necessary so that grena can transfer low temperatures, and the appearance of caterpillars was regulated. For example, if in winter the eggs were kept at a temperature not lower than +15 degrees, then the future caterpillars develop very poorly. This is due to the fact that they hatch very early, even before the mulberry leaves appear (this main source food for silkworms). Therefore, during this period, the eggs are placed in the refrigerator, where a constant temperature regime is maintained from 0 to -2 degrees.

Life cycle of caterpillars

The appearance of caterpillars refers to the larval stages of silkworm development. They used to be called silkworms, but based on scientific terms, this name is incorrect. TO external characteristics caterpillars include the following indicators:

• the body has a slightly elongated shape;
• there is a head, abdomen and chest;
• there are horny appendages on the head;
• on the inside of the body there are three pairs of pectoral and five abdominal legs;
• Caterpillars have chitinous coverings that perform a protective function and at the same time act as their muscles.

You can see the external data of the caterpillars in the photo, and also see their life cycle in the video.

Once the caterpillar hatches from the egg, it is very small, weighing only half a milligram. But with such small size and weight, the caterpillars’ body has all the necessary biological processes for full life activity, so they grow intensively. The caterpillar's body has very powerful jaws, an esophagus, a developed pharynx, intestines, circulatory and excretory system. Thanks to such a developed organism, all food consumed is very well absorbed. Imagine that these babies have more than four thousand muscles, which is eight times more than in humans. Associated with this are the acrobatic acts that the caterpillars can perform.

The life cycle of a caterpillar lasts about forty days, during which time it increases in size by more than thirty times. Due to this growth rate, the shell with which the caterpillars are born becomes small, so they need to shed their old skin. This process is called molting. During this period, individuals stop feeding and find a place to molt. Tightly attaching their legs to the leaves, or holding onto a tree, they freeze. Popularly this period is called sleep. This spectacle can be seen in detail in the photo. Then the caterpillar seems to hatch anew from the old skin. First, the head appears, which has increased several times in size, and then the rest of the body. The caterpillars must not be touched during sleep, otherwise they will not be able to shed their old cover, as a result of which they die.

During their entire life span, caterpillars go through the molting process four times. And each time they have a different color. In the photo and video you can see the colors of the caterpillars.

The main part of the caterpillar's body for humans is the silk gland. This organ is the best developed, thanks to artificial maintenance for many centuries. The silk we need is formed in this organ.

The final stage of development: the silkworm pupa

Silkworm cocoons do not form for long (you can see them in the photo). This is an intermediate stage of development. The caterpillar forms a chrysalis around itself and remains there until it transforms into a butterfly. Such silkworm cocoons are the most valuable for humans. Many amazing processes take place inside, inside the cocoon the caterpillar goes through the stage of the last molt and turns into a pupa, and then it becomes a butterfly.

The appearance of a butterfly and its flight can be easily determined. The day before emergence, the cocoons begin to move. If you lean against the cocoon at this time, you can hear a slight noise, like tapping. This is a butterfly shedding its chrysalis skin. Interestingly, butterflies appear strictly at the allotted time. This is the period from five to six o'clock in the morning.

In order to get out of the cocoon, the mucous membranes of the butterfly secrete a specialized glue that splits the cocoon and makes it possible to fly out (newborn butterflies can be seen in the photo).

Butterflies live very short lives, no more than 18-20 days, but there are also long-livers that can reach an age of 25-30 days. Butterflies have undeveloped jaws and mouths, so they cannot eat. During such a short life, their main purpose is to mate and lay eggs. One female can lay more than one thousand eggs per clutch. The laying process does not stop, even if the female does not have a head, because her body has several nervous systems. In order to ensure good survival rates for future offspring, females attach the grena very tightly to the surface of a leaf or tree. That's all! This is where the life cycle of silkworms ends.

Then the process begins again, and all the above stages go through again, supplying humanity with silk thread.

The history of breeding such an insect as the silkworm is extremely interesting. The technology was developed a long time ago, in Ancient China. The first mention of this production in Chinese chronicles dates back to 2600 BC, and silkworm cocoons found by archaeologists date back to 2000 BC. e. The Chinese elevated silk production to the status of a state secret, and for many centuries it was a clear priority for the country.

Much later, in the 13th century, Italy, Spain, and other countries began to breed and produce such worms North Africa, and in the 16th century - Russia. What kind of insect is this - the silkworm?

Silkworm butterfly and its offspring

The domesticated silkworm butterfly is not found in the wild today and is bred in special factories to produce natural thread. An adult is enough large insect light in color, reaching 6 cm in length with a wingspan of up to 5-6 cm. By breeding various breeds of this interesting butterfly Breeders from many countries are engaged in this. After all, optimal adaptation to the characteristics of different areas is the basis for profitable production and maximum income. Many breeds of silkworm have been developed. Some produce one generation per year, others two, and there are also species that produce several broods per year.

Despite its size, the silkworm butterfly has long ago lost this ability. She lives only 12 days and during this time she does not even eat, having an undeveloped oral cavity. With the coming mating season silkworm breeders deposit pairs in separate bags. After mating, the female spends 3-4 days laying eggs in the amount of 300-800 pieces in a grain, which has an oval shape with significantly varying sizes, which are directly dependent on the breed of the insect. The breeding period of the worm also depends on the species - it could be in the same year, or maybe next year.

Caterpillar - the next stage of development

The silkworm caterpillar hatches from eggs at a temperature of 23-25 ​​°C. In factory conditions, this occurs in incubators at a certain humidity and temperature. The eggs develop within 8-10 days, then a small brown silkworm larva, up to 3 mm long, pubescent with hairs, appears from the grena. Small caterpillars are placed in special trays and transferred to a well-ventilated, warm room. These containers are a structure like a bookcase, consisting of several shelves covered with mesh and having a specific purpose - here the caterpillars eat constantly. They feed exclusively on fresh mulberry leaves, and the proverb “appetite comes with eating” is absolutely accurate in determining the gluttony of caterpillars. Their need for food increases and already on the second day they eat twice as much food as on the first.

Shedding

By the fifth day of life, the larva stops, freezes and begins to wait for its first molt. She sleeps for about a day, wrapping her legs around a leaf, then, when suddenly straightened, the skin bursts, freeing the caterpillar and giving it the opportunity to rest and resume satisfying its hunger. Four next days she eats leaves with an enviable appetite until the next molt comes.

Caterpillar transformations

During the entire period of development (about a month), the caterpillar molts four times. The last moult turns it into a fairly large individual of a magnificent light pearl shade: the body length reaches 8 cm, the width is up to 1 cm, and the weight is 3-5 g. It stands out on the body with two pairs of well-developed jaws, especially the upper ones, called “mandibles”. ". But the most important quality that is important for the production of silk is the presence in an adult caterpillar of a tubercle under the lip, from which a special substance oozes, which hardens when it comes into contact with air and turns into silk thread.

Silk thread formation

This tubercle ends with two silk-secreting glands, which are long tubes with a middle part transformed in the caterpillar’s ​​body into a kind of reservoir that accumulates an adhesive substance, which subsequently forms a silk thread. If necessary, the caterpillar releases a stream of liquid through a hole under the lower lip, which solidifies and turns into a thin but quite strong thread. The latter plays a big role in the life of an insect and is used, as a rule, as a safety rope, since at the slightest danger it hangs on it like a spider, without fear of falling. In an adult caterpillar, silk-secreting glands occupy 2/5 of the total body weight.

Stages of cocoon construction

Having reached adulthood after the 4th moult, the caterpillar begins to lose appetite and gradually stops eating. By this time, the silk-secreting glands are filled with liquid so that a long thread constantly trails behind the larva. This means the caterpillar is ready to pupate. She begins to look for a suitable place and finds it on the cocoon rods, timely placed by the silkworm breeders along the side walls of the aft “shelves”.

Having settled on the twig, the caterpillar begins to work intensively: it alternately turns its head, applying the tubercle with the hole for the silk-secreting gland to different places on the cocoon, thereby forming a very strong network of silk thread. It turns out to be a kind of frame for future construction. Next, the caterpillar crawls to the center of its frame, holding itself in the air by threads, and begins to spin the cocoon itself.

Cocoon and pupation

When building a cocoon, the caterpillar turns its head very quickly, releasing up to 3 cm of thread for each turn. Its length to create the entire cocoon is from 0.8 to 1.5 km, and the time spent on it takes four or more days. Having finished its work, the caterpillar falls asleep in a cocoon, turning into a pupa.

The weight of the cocoon together with the pupa does not exceed 3-4 g. Silkworm cocoons come in a wide variety of sizes (from 1 to 6 cm), shape (round, oval, with bars) and color (from snow-white to golden and purple). Experts have noticed that male silkworms are more diligent in weaving cocoons. Their pupal homes differ in the density of the thread wound and its length.

And again the butterfly

After three weeks, a butterfly emerges from the pupa and needs to get out of the cocoon. This is difficult, since it is completely devoid of the jaws that adorn the caterpillar. But wise nature solved this problem: the butterfly is equipped with a special gland that produces alkaline saliva, the use of which softens the wall of the cocoon and facilitates the release of the newly formed butterfly. This is how the silkworm completes the circle of its own transformations.

However, industrial breeding of silkworms interrupts the reproduction of butterflies. The bulk of cocoons are used to obtain raw silk. After all, this is already a finished product; all that remains is to unwind the cocoons on special machines, having previously killed the pupae and treated the cocoons with steam and water.

So, the silkworm, the breeding of which on an industrial scale will probably never lose its relevance, is an excellent example of a domesticated insect that brings in quite a lot of income.