Cultivation of silk from domestic silkworms is called “sericulture.”
The first stage of the silkworm life cycle, and hence the first stage of the sericulture process, is the laying of eggs. This is typically done in an aluminum box or other container. Each egg is as tiny as a pinhead. An adult female silkworm (that is, one that is in the moth stage of its life cycle) typically lays 300-400 eggs at a time. It dies almost immediately upon laying its eggs, and the adult males die shortly thereafter. In fact, the adult stage of the life cycle is very brief; the adults possess only a rudimentary mouth and do not even eat.
The eggs are examined carefully for any sign of disease. If no such problems are detected, they are incubated for about ten days.
When the eggs hatch, this commences the larva stage. The caterpillars are only about a quarter inch long when they emerge from the egg, but they grow rapidly to a size of about three inches as they do little more than eat constantly during this stage. The caterpillar will ultimately eat about 50,000 times its initial weight.
A fine layer of gauze is placed over the caterpillars when the eggs hatch. They are fed primarily chopped white mulberry leaves, hence the alternate name of mulberry silk moth. Lettuce, Osage orange, and other plant material is also sometimes used as feed. The caterpillars eat and grow for about six weeks, shedding their skin four times along the way.
At this point, the caterpillars are ready to spin their cocoons, which takes three to eight days. This is when the silk is produced.
The silkworm climbs up onto some sort of frame that has been provided for that purpose in its container. A pair of salivary glands in the silkworm called “sericteries” produce a clear, viscous fluid called “fibroin,” while another pair of glands produce a gummy fluid called “sericin.” The silkworm forces these substances through openings—spinnerets—in its mouthpart. The fibroin secretions harden immediately when exposed to the air, forming twin filaments. These filaments are then immediately bonded together by the sericin.
This is the silk of the silkworm.
For the next several days, the silkworm meticulously builds its cocoon with this silk, following a figure-8 path hundreds of thousands of times. Over the course of this time it produces approximately one kilometer of silk.