The history of breeding such an insect as silkworm is extremely interesting. The technology was developed a long time ago, in ancient China. The first mention of this production in the Chinese annals dates back to 2600 BC, and silkworm cocoons found by archaeologists date back to 2000 BC. e. The Chinese elevated the manufacture of silk as a state secret, and for many centuries this was an obvious priority of the country.
Much later, in the 13th century, Italy, Spain, the countries of North Africa began to engage in the cultivation of such worms and the production of silk fabric, and in the 16th century - Russia. What kind of insect is the silkworm?
Silkworm butterfly and its offspring
Domesticated mulberry silkworm is not found in the wild today and is bred in special plants to obtain natural thread. An adult is a fairly large insect of light color, reaching 6 cm in length with a wingspan of 5-6 cm. Breeders of many countries are engaged in breeding various breeds of this interesting butterfly. After all, optimal adaptation to the characteristics of various localities is the basis for profitable production and maximum revenue. Many breeds of silkworm were bred. Some give one generation a year, others give two, and there are species that give several broods a year.
Despite its size, the silkworm butterfly 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 mating season, silkworms plant pairs in separate bags. After mating, the female for 3-4 days engages in laying eggs in the amount of 300-800 pieces in a grena, which has an oval shape with significantly varying sizes, which are directly dependent on the breed of the insect. The period of removal of the worm also depends on the species - this may be in the same year, or maybe in the next.
Caterpillar - the next stage of development
The silkworm caterpillar is hatched from eggs at a temperature of 23–25 ° С. In the factory, this occurs in incubators at a certain humidity and temperature. The eggs develop within 8-10 days, then a brown, small up to 3 mm long silkworm larva, pubescent with hairs, appears from the grains. Small caterpillars are placed in special trays and transferred to a well-ventilated warm room. These containers are a construction similar to a whatnot, consisting of several shelves, covered with a net and having a specific purpose - here the caterpillars are constantly eating. They feed exclusively on fresh mulberry leaves, and the proverb “appetite comes with food” is absolutely accurate for determining the gluttony of caterpillars. Their food demand is growing exponentially, on the second day they eat twice as much feed as on the first.
Molting
By the fifth day of life, the larva stops, freezes and begins to wait for its first molt. She sleeps for about a day, clutching the leaf with her legs, then with a sharp straightening, the skin bursts, releasing the caterpillar and giving her the opportunity to relax and again take up the hunger. For the next four days, she absorbs the leaves with an enviable appetite, until the turn of the next molt comes.
Caterpillar Transformations
Over the entire period of development (about a month), the caterpillar molts four times. The last molt turns it into a fairly large specimen of a magnificent light pearl shade: body length reaches 8 cm, width - up to 1 cm, and weight is 3-5 g. A large head stands out with two pairs of well-developed jaws, especially the upper jaws, called "stingy." But the most important quality that is important for silk production is the presence of a tubercle under the lip of an adult caterpillar, from which a special substance oozes, freezing when it comes into contact with air and turns into a silk thread.
Silk thread formation
This silk tubercle ends with two silk-separating glands, which are long tubes with the middle part turned into a kind of reservoir in the body of the caterpillar, accumulating an adhesive substance, which subsequently forms a silk thread. If necessary, the caterpillar through the hole under the lower lip releases a trickle of liquid outward, which solidifies and turns into a thin, but sufficiently strong thread. The last in the life of the 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, not afraid to fall. In an adult caterpillar, the silk glands occupy 2/5 of the total body weight.
Stages of building a cocoon
Having reached adulthood after the 4th molt, the caterpillar begins to lose its appetite and gradually stops eating. The silk glands by this time are filled with liquid so that a long thread constantly stretches behind the larva. This means that the caterpillar is ready for pupation. She begins to look for a suitable place and finds it on the cocoon bars, timely placed by silkworms along the side walls of the stern “whatnots”.
Having settled down on a twig, the caterpillar begins to work intensively: it turns its head one by one, applying a tubercle with a hole for the silk-removing gland to different places on the cocoon, thereby forming a very strong network of silk thread. It turns out a kind of frame for future construction. Further, the caterpillar creeps into the center of its frame, keeping in the air by means of threads, and begins to twist 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 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 work, the caterpillar falls asleep in a cocoon, turning into a chrysalis.
The weight of the cocoon together with the chrysalis does not exceed 3-4 g. Silkworm cocoons are the most diverse in size (from 1 to 6 cm), shape (round, oval, with jumpers) and color (from snow-white to golden and lilac). Specialists noted that males of silkworms are more diligent in the part of weaving the cocoon. Their doll houses are characterized by the density of the winding thread and its length.
