Bombyx mori

Bombyx mori

The silkworm (Bombyx mori Linnaeus, 1758) is a butterfly species of the Bombycidae family, with origins in Central and Eastern Asia.

Systematics –
From a systematic point of view it belongs to the Eukaryota Domain, Kingdom Animalia, Eumetazoa Sub-estate, Superphylum Protostomia, Phylum Arthropoda, Subphylum Tracheata, Superclass Hexapoda, Class Insecta, Subclass Pterygota, Coop Endopterygota, Superorder Oligoneoptera, Section Panorpoidea, Order Lepidoptera, Suborder Glossata, Infraorder Heteroneura, Ditrysia Division, Bombycoidea Superfamily, Bombycidae Family, Bombycynae Subfamily and therefore Bombyx Genus and B. mori Species.

Geographic Distribution and Habitat –
Bombyx mori is a moth native to northern China; its larva, known as silkworm, feeds exclusively on mulberry leaves.

Morphology –
The silkworm is characterized by a head which is the smallest part of the larva. The mouth has serrated, sharp and very robust jaws. On the upper lip has a cut where he puts the leaf to eat it. On the head there are bristles, which have the function of perceiving temperature and humidity. Under the lower lip is the supply chain, which produces the silk that produces nourishment of leaves and which preserves in silk bags until the moment of the construction of the cocoon. The eyes of the silkworm are composed of six ommatidia.
When the worm has not completed the first molt the head is shiny black; with the passing of the mute becomes more and more clear but not white.
The head of the butterfly is white except for the antennae and the eyes; it differs from that of the worm because the butterfly, not having to feed, does not need the robust apparatus of the larva. On the head it has black and brown comb antennae.

Attitude and biological cycle –
Bombyx mori has a life cycle characterized by four mutes and five ages.
Its cycle can be summarized as follows:
– 1st age: lasts about 5 days and ends with the first change;
– 2nd age: lasts 4 days and ends with the second moult;
– 3rd age: lasts 5 days and ends with the third change;
– 4th age: lasts 6 days and ends with the fourth dumb;
– 5th age: lasts 8-10 days and goes from the fourth mute to the formation of the cocoon.
In favorable conditions of breeding there is a total duration of the larval life of about one month (little food and low temperatures elongate the cilclo). The flicker occurs on average after 15 days from the beginning of the formation of the cocoon. The metamorphosis from adult larva to butterfly happens about the 5th day from the formation of the cocoon.
The larva of Bombyx mori produces silk in two glands that are placed parallel within the body. Silk is collected in the glands, from which the worm extrudes it from two openings located at the sides of the mouth, the seritteri. This in contact with the air solidifies and, guided by the movements of the head, is arranged in layers forming the rough silk cocoon. This consists of a single continuous silk thread ranging between 300 and 900 meters. The silk is made up of two proteins: two parallel fibrin threads covered with sericin.

Ecological role –
The larva of Bombyx mori, known as silkworm, has considerable economic importance as it is used in silk production; unfortunately, the introduction of synthetic fibers, in addition to having weighed down the ecological footprint of the manufacturing industry has decreased its breeding. The economic importance of the silkworm was such that in ancient times silk traveled, along with other goods, from China to the Mediterranean countries along the way that was called, for its trade, “silk road”.
According to one of the Chinese silkworm legends, the discovery of the usefulness of this insect is due to an ancient empress named Xi Ling-Shi who lived in the XXVIII century BC. The empress, while walking, noticed a caterpillar; he touched it with a finger and a silk thread appeared from the caterpillar. As the thread emerged from the worm, the empress wrapped it around her finger, creating a sensation of warmth. Finally, he saw a small cocoon, and suddenly understood the link between the silkworm and the silk. He taught what he had discovered to the people, and the news spread.
In Italy the first silkworm cultivation was in Sicily, because of the Saracens that introduced it. Subsequently, the practice spread outside the island but Sicily maintained for several centuries an advantageous position in the production of silk that contributed greatly to the wealth of the island.
The peak of Italian silk production occurred around the eighteenth century, especially in northern Italy; then began its decline between the two wars to completely disappear in the fifties. Today, China is the world’s largest producer.
However, the larva of Bombix mori has other applications. It is used by traditional Chinese medicine in the form of bombyx batryticatus or “rigid silkworm”. It is the calcified body of the larva of the fourth or fifth age and dead of calcine, a disease due to infection by the Beauveria bassiana fungus. This calcified larva is used to solve problems in the belly and digestion, such as aerophagia, abdominal pain, and drowsiness.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.




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