The most common species of silkworm (moth larvae) used in commercial silk production has been 'cultivated' over many centuries and no longer exists in the wild. On mulberry trees in temperate and disease-controlled conditions, the female deposits annually 1 or 2 batches of 300 to 400 eggs. She secretes a sticky substance and fastens the eggs to a flat surface. The larvae hatch in about 10 days and eat 50,000 times their initial weight in plant material. The silkworm produces a fine thread from its silk glands and uses it to make a cocoon around itself consisting of around 300,000 figure of eight movements. Naturally, the pupae stage would be followed by the secretion of an alkali substance which would eat through the threads - allowing the subsequent emergence of a moth. However, the industry requires the threads to remain intact and so, upon the completion of the cocoon, the pupae are killed by immersion in boiling water, steaming, oven drying or exposure to the hot sun. The producers allow enough adult moths to emerge to ensure continuity of the cycle.

The usable silk from each cocoon is minute - around 500 silkworms (or 80kg of cocoons) and 200 kg of mulberry leaves are required to produce just 1 kg of silk.

After the pupae have been killed, they are typically composted to feed the mulberry trees.

For further information concerning the cruelties involved in the silk, wool, leather and fur trades, write to: Campaign Against Leather and Fur (CALF), BM 8889, London WC1R 3XX.

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Cross-reference: Fur, Leather, Wool and Silk