Silk - Natural Materials in Year 4 Science

What is silk made of ?


The silkworm is the larva or caterpillar of the domesticated silkmoth, Bombyx mori
 ( Latin : “ silkworm of the mulberry tree ”). It is an economically important insect being a primary producer of silk. A silkworm’s preferred food is white mulberry leaves, but it may also eat the leaves of any other mulberry tree as well as the Osage Orange.

Osage Orange

Mulberry leaves


The silkworm is entirely dependent on humans for its reproduction and does not occur naturally in the wild. The eggs of the silkmoth take about fourteen days to hatch into larvae, which eat continuously. Their droppings are black. After molting about four times, their bodies become slightly yellow and the skin becomes tighter. The larvae will then enter the pupa phase of their life cycle and enclose themselves in a cocoon made up of raw silk produced by the salivary glands. the cocoon provides a vital layer of protection during the vulnerable, almost motionless pupal state. The cocoon is made of a thread of raw silk from 300 to about 900 meters. The fibers are very fine and lustrous, about 10 micrometers in diameter. About 2 000 to 3 000 cocoons are required to make a pound of silk ( 0.4 kg ).

 ( adapted from : http :// )

A silkworm spinning its cocoon

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