Photo by Paolo Mazzei

From the eggs of the mulberry silkworm (Bombyx mori), a moth from the family of true silkworms (!), caterpillars that are only about 3 mm in size hatch after about 10 days. These are fed several times daily with ever-increasing amounts of fresh mulberry leaves. The animals are very sensitive to external influences, which is why they must be protected from drafts, temperature fluctuations, and noise. Even fine smells like perfumes can hinder their development.

Photo by Paolo Mazzei

After about 30 days and four molts, they have become about 10 cm long and have increased their weight by 10,000 times. Now they begin to spin a cocoon. This takes up to five days. Shielded from the environment, the metamorphosis of the caterpillar into a moth takes place inside.

Photo by Paolo Mazzei

In the middle of the pupal stage, when the pupa is no longer a caterpillar but not yet a butterfly, the cocoons are dried with heat, killing the pupae. If the butterflies were to emerge, the cocoons would be damaged and the silk thread could no longer be unwound. However, up to 1200 meters of the noble thread can be obtained from a single cocoon.

Photo by Paolo Mazzei

The butterflies selected for breeding live only a few days after emerging without feeding. After mating, the female lays 300 to 500 eggs, barely 2 mm in size. The life cycle begins again.

The cultivation of silk began in China. The oldest silk fabric is dated to around 2750 BC. According to legend, its discovery is attributed to Xiling, the wife of Emperor Huang Di. She observed the silkworm during its development in her garden and came up with the idea of weaving an imperial fabric from the fine thread of the cocoon.

Silk production became an important industry in ancient China and the valuable fabrics found their way to the western world via the Silk Road. 

Silk was even processed by the Mongols into light armors in combination with leather and iron elements, which could hardly be penetrated by enemy arrows.

The knowledge about silk was long a strictly and successfully guarded secret of the Chinese Empire. It was only in the Middle Ages that silk production also flourished in the Mediterranean region, after it was allegedly two monks who managed to smuggle silkworm eggs and mulberry tree seeds to Byzantium in their hollowed-out walking sticks. Silk metropolises emerged in Spain, Italy, and France. Silk was even produced in Ticino for a time.

However, due to a previously unknown disease, European silkworms were practically completely wiped out in the mid-19th century.

With industrialization, the downstream silk industry quickly developed and gained importance in Switzerland, for example in the regions of Zurich and Basel (trimmings, silk ribbons). Around 1900, the silk industry was one of the most important industrial sectors in Switzerland. From the mid-20th century, the focus shifted from processing to trading. Since then, the textile industry in Switzerland has been steadily shrinking. 

For a few years now, silk has been produced again in small quantities for the domestic market under the name Swiss Silk.