Just prior to their metamorphosis into moths, Bombyx mori pupae spin silk fibers to weave their cocoons. In nature, the moth chews his or her way out of the cocoon once the transformation is complete. But in the fabric industry, silk is mass produced through the breeding and domestication of silkworms on what are essentially moth factory farms. When the caterpillars enter the pupa stage of their development, their cocoons are plunged into boiling water. This kills the silkworms and begins to unravel the longer fibers.
Approximately 15 silkworms are killed to produce a single gram of silk. Although it is very occasionally harvested after the moth has broken free, the strands are considerably shorter and the finished product is not commercially viable on a large scale.
There are other methods of producing silk that do not result in the death of the insect; however, there are still ethical issues to be considered. “Ahimsa silk,” for example, is made from the cocoon of the Bombyx mori moth after the moth has chewed through and discarded it. The silkworms used in this method of production are still domesticated and, just like other domesticated farmed animals, are bred for the purposes of production at the cost of their own health and well-being. The adult moths cannot fly because their bodies are too large and the adult males cannot eat due to underdeveloped mouth parts. The same would be true of moths in large commercial operations, but they are killed before reaching adulthood.