Silkworm Cocoon

Cocoon, Silkworm

 

the casing formed by the caterpillars of silkworms before metamorphosis into a pupa; the raw material for obtaining natural silk.

The cocoons of the mulberry silkworm have the greatest commercial value, but cocoons of the Chinese oak silkworm, the ailanthus silkworm, and other silkworms are also used. The caterpillars of these silkworms secrete a double silk thread consisting of the protein fibroin, the sticky substance sericin, pigment, and other substances. In winding its cocoon on a cocoon support the caterpillar lays the thread around its body in the form of the figure eight, and these loops constitute the basic, reelable part of the casing. A continuous silk thread can reach a length of 1,200 m and a thickness of 20–30 micrometers. The cocoons of the mulberry silkworm are oval, spindle-shaped, or cylindrical; cocoons of the oak silkworm are less regular in shape. The cocoons selected for reeling are treated with hot air or steam to kill the pupa and prevent its metamorphosis into a moth, which damages the cocoon as it emerges. The cocoons are then dried so that they will not spoil during storage. The weight of a live cocoon ranges from 1.5 to 3.5 g, and the weight of the reelable casing is 350–550 mg. The cocoon of females is on the average 20 percent heavier than that of males.

REFERENCES

Mikhailov, E. N. Shelkovodstvo. Moscow, 1950.
Uchebnaia kniga shelkovoda. Moscow, 1966.

E. N. MIKHAILOV

References in periodicals archive ?
The process of degumming of fibers was performed to extract sericin proteins that make up the glue, which constitutes the internal structure of the fibers of the silkworm cocoon (Bombyx mori); this was carried out by a thermochemical process that involves washing the silk fibers three times with water at 83[grados]C for 5 hours and drying at room temperature for 2 hours.
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A silkworm cocoon fell into her cup, and when she grabbed the bundle, it unwound into a single strand of silk.
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The roundish shape of the new sporty minicar was designed to project the protective image of a silkworm cocoon as well as the image of a nimble rabbit, company officials say.
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