Silkworm. Cocoons of the silkworm

Extremely interesting is the history of breeding such an insect, as a silkworm. The technology was developed a long time ago, in ancient China. The first mention of this production in the Chinese chronicles dates from 2600 BC, and the cocoons of the silkworm found by archaeologists date back to the year 2000 BC. E. The Chinese made silk production a state secret, and for many centuries this was an obvious priority for the country.

Much later, in the 13th century, the cultivation of such worms and the production of silk fabrics began to deal with Italy, Spain, the countries of North Africa, and in the 16th century - and Russia. What kind of insect is a silkworm?

Butterfly silkworm and her offspring

A domesticated butterfly mulberry silkworm today does not occur in the wild and is bred at special plants to produce a natural thread. An adult is a large enough insect of light color, reaching 6 cm in length with a wingspan of up to 5-6 cm. Breeders of many countries are engaged in breeding various breeds of this interesting butterfly. After all, optimal adaptation to the peculiarities of different localities is the basis for profitable production and obtaining maximum income. Many silkworm breeds were discovered. Some give one generation per year, others - two, and there are species that give several broods a year.

Despite the size, butterfly mulberry silkworm does not fly, since it has long lost this ability. She lives only 12 days and during this time does not even eat, having an undeveloped oral cavity. With the onset of the nuptial period, silkworms are planted in separate pouches. After mating, the female during 3-4 days is engaged in the laying of eggs in an amount of 300-800 pieces in the oval, which has an oval shape with significantly varying sizes that are directly dependent on the breed of the insect. From the same kind of depends and the period of deducing the worm - it may be in the same year, and maybe - in the next.

Caterpillar - the next stage of development

The caterpillar of the silkworm is removed from eggs at a temperature of 23-25 ° C. In the factory, this occurs in incubators at a certain humidity and temperature. Eggs develop for 8-10 days, then a brown small up to 3 mm long larva of the silkworm, which is pubescent with hairs, appears from the grenade. 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, tightened with a net and having a specific purpose - here the caterpillars eat incessantly. They feed exclusively on fresh leaves of mulberry, and the proverb "appetite comes with eating" is absolutely accurate for determining the gluttony of caterpillars. The need for food grows in them in a geometric progression, on the second day they are eaten twice as much food as in the first.

Moulting

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 the leaf, then with a sharp straightening she bursts the skin, releasing the caterpillar and giving her the opportunity to rest and re-engage in satisfying hunger. For the next four days, she absorbs the leaves with an enviable appetite until the next molt sets in.

Transformations of the caterpillar

For the entire period of development (about a month) the caterpillar molts four times. The last moult turns it into a fairly large specimen of a magnificent light pearl shade: the body length reaches 8 cm, the width is up to 1 cm, and the mass is 3-5 g. A large head with two pairs of well-developed jaws, especially the upper jaws, "Zhvalami." But the most important quality, which is important for the production of silk, is the presence of a tubercle under the lip in the adult caterpillar, from which a special substance that solidifies upon contact with the air and turns into a silk thread.

Formation of silk thread

This tubercle ends two silk glands, which are long tubes with the middle part, turned into the body of the caterpillar into a kind of reservoir, accumulating a sticky substance, which subsequently forms a silk thread. If necessary, the caterpillar, through the opening under the lower lip, releases a trickle of liquid outward, which solidifies and turns into a thin, but strong enough thread. The last in the life of an insect plays a large role 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 adult caterpillars, silk glands occupy 2/5 of the total body weight.

Stages of cocoon construction

Having reached the adult state after the 4th moult, the caterpillar begins to lose its appetite and gradually ceases to eat. The silk glands are filled with liquid by this time so that a long thread constantly extends behind the larva. This means that the caterpillar is ready for pupation. She begins to search for a suitable place and finds it on the rods-kokonniki, placed in time by the silkworms along the side walls of the stern "floors".

Having settled on the twig, the caterpillar begins to work intensively: it alternately rotates the head, applying a tubercle with a hole for the silkworm to various places on the hawk, thereby forming a very strong network of silk thread. It turns out a kind of skeleton for future construction. Then the caterpillar crawls to the center of its frame, holding in the air by means of threads, and begins to twist the cocoon itself.

Cocoon and Pupation

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

The weight of the cocoon together with the pupa does not exceed 3-4 g. The cocoons of the silkworm are of a variety (from 1 to 6 cm) in shape, round (oval, with lintels) and in color (from snow-white to golden and lilac). Specialists noted that the males of silkworms are more diligent in the part of weaving cocoon. Their dwellings for pupae differ by the density of the winding of the thread and its length.

And again the butterfly

After a lapse of three weeks, a butterfly emerges from the chrysalis, which needs to get out of the cocoon. This is difficult, since it is completely devoid of jaws adorning the caterpillar. But the wise nature has solved this problem: the butterfly is supplied with a special gland that produces alkaline saliva, the application of which softens the cocoon wall and promotes the release of the newly formed butterfly. So the silkworm closes the circle of its own transformations.

However, the industrial breeding of the silkworm interrupts the reproduction of butterflies. The bulk of cocoons are used to produce raw silk. After all, this is a ready product, it remains only to unwind the cocoons on special machines, after killing the pupae and treating the cocoons with steam and water.

So, the silkworm, whose breeding on an industrial scale, will probably never lose its relevance, is a magnificent example of a domesticated insect that brings a very considerable income.