Silkworms (incorrectly spelled silk worms) are the larval form of the domesticated silk moth, Bombyx mori. The silk moth was domesticated in its native habitat of northern China from its wild cousin Bombyx mandarina, a cousin which still survives today. Archaeological evidence suggests that occurred about 3500 BCE.
Key Takeaways: Silk Worms
- Silkworms are the larvae from silk moths (Bombyx mori).
- They produce silk fibers—water-insoluble filament from glands—to create cocoons; humans simply unravel the cocoons back into strings.
- Domesticated silkworms tolerate human handling and massive crowding and are totally dependent on humans for survival.
- Silk fibers were used to make clothing by the Longshan period (3500–2000 BCE).
The fabric we call silk is made from the long thin fibers produced by the silkworm during its larval stage. The insect’s intent is to create a cocoon for its transformation into the moth form. Silkworm workers simply unravel the cocoons, each cocoon producing between 325–1,000 feet (100–300 meters) of fine, very strong thread.
What is Silk?
Silk fibers are water-insoluble filaments that animals (chiefly the larval version of moths and butterflies, but also spiders) secrete from specialized glands. Animals store the chemicals fibroin and sericin—silkworm cultivation is often called sericulture—as gels in the insects’ glands. As the gels are excreted, they are converted into fibers. Spiders and at least 18 different orders of insects make silk. Some use them to construct nests and burrows, but butterflies and moths use the excretions to spin cocoons. That ability that began at least 250 million years ago.
The silkworm caterpillar feeds exclusively on the leaves from several species of mulberry (Morus), which contain a latex with very high concentrations of alkaloid sugars. Those sugars are toxic to other caterpillars and herbivores; silkworms have evolved to tolerate those toxins.
Silkworms are today completely dependent on humans for survival, a direct result of artificial selection. Other characteristics bred into the domestic silkworm caterpillar are a tolerance for human proximity and handling as well as for excessive crowding.
Archaeological evidence indicates that the use of cocoons of the silkworm species Bombyx to produce cloth began at least as early as the Longshan period (3500–2000 BCE), and perhaps earlier. Evidence of silk from this period is known from a few remnant textile fragments recovered from well-preserved tombs. Chinese historical records such as the Shi Ji report silk production and depict garments.
The Western Zhou Dynasty (11th–8th centuries BCE) saw the development of early silk brocades. Many silk textile examples have been recovered from archaeological excavations of Mashan and Baoshan sites, dated to the Chu Kingdom (7th century BCE) of the later Warring States period.
Silk products and silkworm-rearing technologies came to play a critical role in Chinese trade networks and in the interaction of cultures among different countries. By the Han Dynasty (206 BCE–9 CE), silk production was so important to international trade that the camel caravan trails used to connect Chang’An with Europe were named the Silk Road.
Silkworm technology spread to Korea and Japan about 200 BCE. Europe was introduced to silk products through the Silk Road network, but the secret of silk fiber production remained unknown outside of eastern Asia until the 3rd century CE. Legend has it that the bride of a king of the Khotan oasis in far western China on the Silk Road smuggled silkworms and mulberry seeds to her new home and husband. By the 6th century, Khotan had a thriving silk production business.
The Divine Insect
In addition to the tale of the bride, there are myriad of myths associated with silkworms and weaving. For example, a study on 7th century CE rituals in Nara, Japan by Shinto religion scholar Michael Como found that silk weaving was tied to kingship and courtly romance. The legends appear to have arisen in mainland China, and are likely related to the silkworm’s lifecycle in which it exhibits an ability to die and be reborn into a totally different form.
The ritual calendar at Nara included festivals tied to the deities known as the Weaver Maiden and other goddesses, shamans, and female immortals represented as weaving maidens. In the 8th century CE, a miraculous omen is said to have occurred, a silkworm cocoon with a message—16 jeweled characters—woven into its surface, prophesying long life for the empress and peace in the realm. In the Nara museum, a benevolent silk moth deity is illustrated, one who works to expel plague demons in the 12th century CE.