Silkworm is a caterpillar of the mullberry tree butterfly, Bombyx Mori, which comes from north of China. Silkworm is the only domesticated butterfly (that means it does not exist anymore in wild). It's breeded to produce silk.
Each female lays about 300-400 eggs, called « seeds ». Those seeds, placed in a tempered room (23-24 °C) for about two weeks, will give birth to 2 mm caterpillars. Those caterpillars live for about a month in which they eat night and day, growing to 9 cm and having their birth weight multiplied by 10 000 !
Silkworms eat only white mullberry tree leaves. Those leaves must be fresh and so have to be harvested manually each day.
This growth goes along with 4 sloughings which establish the 5 ages of a silkworm. The 5th age, which squares the last breeding week, is the most important. It's during this last week that a silkworm eats the 75% of its total food. It's also during this stage that serigen glands of the caterpillar are getting filled with a sticky slime, which once dried becomes a raw silk thread. Once the serigen glands are full, silkworms stop feeding and seek for places to settle their cocoons. The breeders provide racks or brushes in which the worms will settle. The cocoon, made of a single wisp, is finished within 4 days.
The cocoon wisp length can vary from 300 meters to 2000 meters long.
A few figures :
The breeding period is from may to october, that equals two full breeding cycles (from seeds to thread) per year on our weather.
A production unit, or a breeding time, is about 30 grams of seeds (60 000 eggs).
To feed those 60 000 worms, a total amount of 2 tons of fresh mullberry tree leaves is needed, of which 75% for the last 10 days of breeding.
At least 90% of worms build a cocoon.
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