Silk is one of the oldest fi bres known to man. It is an animal fi bre produced by certain insects to build their cocoons and webs. Although many insects produce silk, only the fi lament produced by the mulberry silk moth Bombyx mori and a few others in the same genus is used by the commercial silk industry (Jolly et al ., 1979 ). The silk produced by other insects, mainly spiders, is used in a small number of other commercial applications, for example weapon and telescope cross-hairs and other optical instruments (Spring and Hudson, 2002 ). Over the centuries