How Do Silkworms Produce Silk?
How Do Silkworms Produce Silk? The silkworm is the larva or caterpillar of Bombyx mori, the domesticated silk-moth, mulberry silkworm. A moth in the family Bombycidae, it is very important economically as the producer of silk. It is entirely dependent on humans for its reproduction and no longer occurs naturally in the wild.
There are different types of silk, but the variety we generally refer to when we talk about silk—the one used for stunning saris or flowy dresses—comes from the Bombyx mori. It isn’t actually a worm; it’s a mulberry-leaf-munching moth pupa. It spins silk to make the cocoon for its transformation into its adult form as a winged moth.
If the animal is allowed to survive after spinning its cocoon, it will release proteolytic enzymes to make a hole in the cocoon so that it can emerge as a moth. This would cut short the threads and ruin the silk. That silken cocoon is what silk producers are after, and they want it intact.
Once the worm has spun it, but before it’s able to break out and damage it, silk producers will treat the cocoon with hot air, steam, or boiling water, in a process called “stifling.” The heat kills the silkworms and the water makes the cocoons easier to unravel. In sunny, tropical areas, it might also be done by placing the cocoons in bright sunshine. These processes make the cocoon easier to unwind in a single, unbroken filament that can be woven into silk thread.
But when you dip the cocoon in boiling water or bake it with hot air, you’re killing the pupa inside. And huge amounts of pupa are killed in these ways to make the world’s silk. To make one pound of the lustrous, revered material requires about 2,500 or more silkworms.
There is a variety of silk called Peace Silk, or Ahimsa Silk, that doesn’t involve stifling. But animal-welfare advocates, including PETA, are skeptical of how humane this method is. There’s no certification to make sure the process meets standards.
One group in India reported female moths being stored in trays to lay eggs at one facility, while the males were “put into the refrigerator and kept in a semi-frozen condition” until they were brought out to mate. Once they could no longer mate, they were discarded.