Sericulture (silk farming)

Sericulture, also known as silk farming, is the process of raising silkworms to produce raw silk. Silkworms are usually the larvae of a type of caterpillar with the scientific name Bombyx mori, or "silkworm of the mulberry tree." The name comes from the silky cocoons that the larvae produce and their natural diet of mulberry leaves. Other moth larvae—such as the Oriental lappet moth, the moon moth of India, and the Chinese oak silkworm—are sometimes used commercially to make raw silk. Sericulture serves as a source of income for families throughout Thailand, China, India, and other Asian countries and in parts of Europe. Silk farming contributes to local economies and is primarily practiced in the rural areas of those countries. Although traditional silk farming was a difficult task that often required an entire family to pitch in and help, modern technology has made the process easier.

Brief History

Silk production first started around 2700 BCE, according to Chinese historical records. Legend has it that Empress Si Ling-Chi was drinking tea beneath a mulberry tree when a silkworm cocoon fell into her cup. She decided to try to use the material from the cocoon to sew clothes for her husband, Hoang-ti (als spelled Huangdi), the Yellow Emperor. The Chinese later named Si Ling-Chi the "goddess of silkworms." The process of silk production remained a secret among the Chinese for many centuries. Anyone who told outsiders the secret process of silk production was sentenced to death for the crime.

In 139 BCE, the Silk Road opened. The Silk Road was a route that traders and travelers used. It stretched from eastern China to the Mediterranean Sea. The road served as a means for China to export silk to other countries. Around 300 CE, the outside world discovered China's secret process, allegedly when a Chinese princess smuggled silkworm eggs and mulberry tree seeds into India under her headdress. According to legend, two centuries later, in 522 CE, monks took silkworm eggs from China to Constantinople and gave them to Byzantine emperor Justinian I. As a result, the Byzantine Empire was able to begin its own sericulture trade. During the eighth century, Chinese officials attempted to maintain control of the silk industry by stopping foreign trade of the material. Other countries were already practicing sericulture, however, and were able to halt China's silk monopoly. By the sixteenth century, silk was a major Italian commodity. In the eighteenth century, inventions in the textile industry helped England become a leader in European silk production, and the English took sericulture to Australia, which was a British colony at that time.

Attempts to establish a sericulture industry in the United States have historically been unsuccessful. When cotton became scarce in the wake of the American Civil War, the United States needed to find another type of material and tried to produce silk. Naturalist Étienne Léopold Trouvelot tried to crossbreed the silkworm moth with another type of moth to make the insects better able to withstand US climates. Some of the caterpillars found their way out of Trouvelot's home in Boston, however, and began to multiply rapidly. This led to the release of one of the most destructive insects in US forests, the gypsy moth, also called the spongy moth.

Overview

Silkworms were originally found in the forests of China but are no longer found in the wild. Now the species is kept alive through commercial sericulture. Sericulture is a several-step process that follows the life cycle of the silkworm. The process begins when an adult female Bombyx mori moth lays her eggs. Each moth can lay up to five hundred eggs. The eggs are kept warm so that they can hatch properly. This is called the incubation period, which can last from ten to fourteen days.

Once the silkworms hatch, they are fed constantly for approximately a month. The feeding helps the silkworms grow to a length of approximately 3 inches (7.62 centimeters). When they are full grown, silkworms begin the process of creating their cocoons. The silkworm's cocoon is created from a protein called fibroin, which the worm makes in two glands located underneath its mouth. The protein becomes hard and turns into silk when it is spit from an organ called the spinneret, which is also located under the silkworm's mouth, into a thread that can stretch up to 4,000 feet (1,219 meters) long.

Once the silkworm is inside its cocoon, the cocoon sets for about a week as the worm changes into a moth. In most cases, silk farmers heat the cocoons to kill the adult moths while they are inside. The process, called stifling, prevents adult moths from coming out of the cocoons, which would destroy the silk. Some of the adult moths are allowed to mature and come out of their cocoons, however, to keep the sericulture process going. Once the cocoons have been heated to a temperature hot enough to kill the moths inside, they are put into a hot-water bath, which makes the cocoons dissolve into threads. These threads are then threaded onto a spool, cleaned, and spun so that the threads do not come apart. Upon completion of this process, the threads can be woven into silk material.

During the twentieth and twenty-first centuries, sericulture became an ethical issue among animal rights activist groups because the process requires the killing of approximately three thousand silkworm moths for every pound of silk. According to People for the Ethical Treatment of Animals (PETA), silkworms are "sensate—they produce endorphins and have a physical response to pain." Therefore, silk is not considered a vegan or an animal-friendly material among animal rights activists.

Despite animal rights concerns and the mass production of human-made materials such as rayon and polyester, silk production worldwide has doubled since the 1970s. This is partly because of political and economic changes in China, which have led to less industrial regulation and more production. As a result, China has once again become the main source of silk around the world. China and Japan produce approximately half of the world's silk, while the other half is produced in India, Thailand, and parts of Europe. Although the sericulture industry never quite took hold in Australia, silkworms are still used there for genetic and scientific research.

Bibliography

Capinera, John L. "Sericulture." Encyclopedia of Entomology. Springer, 2008, pp. 3345–8.

Clay, Katie. "Bombyx mori." Animal Diversity Web, animaldiversity.org/accounts/Bombyx‗mori/. Accessed 25 Nov. 2024.

"Her-Story, Then: Si Ling-Chi." WAMC Northeast Public Radio, wamc.org/post/her-story-then-si-ling-chi. Accessed 25 Nov. 2024.

"Sericulture." Britannica, 6 Nov. 2024, https://www.britannica.com/topic/sericulture. Accessed 25 Nov. 2024.

"What's Wrong with Silk?" People for the Ethical Treatment of Animals, www.peta.org/about-peta/faq/whats-wrong-with-silk/. Accessed 25 Nov. 2024.