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Over 100 species of insects spin cocoons. It is believed that the Chinese discovered how thread could be taken from wild silkworm cocoons around 3000 B.C. Eventually, silkworms were domesticated through numerous attempts at selective breeding. Silkworm breeding techniques were introduced to Japan around the second century A.D., and it was during the Heian Period (794–1192) that experts were invited to Japan from the Korean Peninsula and the practice spread nationwide.
"The history of silk can be described as the history of the ‘domestication' of silkworms. Domesticated silkworms, whose larvae do not escape from the nest and adult moths cannot fly, are the result of ingenious selective breeding. This is indeed the history of selective breeding techniques," says Hajime Inoue, Entomorogical research coordinator, National Institute of Sericultural and Entomological Science, Ministry of Agriculture, Forestry and Fisheries. |
Selective breeding of silkworms is like biotechnology in that new races are breeded by the cross-breeding of parental silkworms with desirable characteristics and breeding from mutants, aiming for silkworms that produce strong thread, large cocoons that enable production of longer thread, and worms that are resistant to disease.
Silk had to contend with the invention of nylon, which could be mass-produced in far strong quantity than silk, and from the transition in Japanese apparel from kimono, which was traditionally made from silk, to Western clothes. These factors provided the motivation for Japan, which plays a significant role in contemporary silk development, to take up the challenge of discovering new, unconventional uses of silk, as well as to improve silk as a product.
One of the representative results of this work is the recent creation of breeds with high productivity by races improvement applying biotechnology. Take food for silkworms, for example. Silkworms usually just eat mulberry leaves, but through races improvement, new polyphagous breeds have been developed that eat feed that does not contain mulberry, and even some that eat apples and carrots. Other new breeds include silkworms that make large cocoons and produce thread more than 2,000m in length, and ones that females produce yellow colored cocoons and males produce white cocoons. Progress of silkworm technology continues apace.
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| From cocoon to silk: first, cocoons are boiled, then stands of raw silk are reeled off the cocoons and spun into silk thread, which is finally worked into silk products. |
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