XXI. ANIMAL FIBERS 



THE principal animal fibers, silk and wool, are of such great im- 

 portance that some mention must be made of them in connection 

 with our study of sources of fibers. The value of the silk manu- 

 factured annually in this country is about $125,000,000 and that 

 of woolen manufactures is about $400,000,000. 



Silk. Our supply of silk in the raw or unfinished state comes 

 from France, Italy, Japan, and China. The raw silk is derived 



from the cocoon of 

 the silkworm which 

 feeds on the leaves 

 of the mulberry tree. 

 Any one who has 

 seen the American 

 silkworm moth and 

 its larva will have a 

 fair idea of the Chi- 

 nese silkworm, but 

 the latter is more delicate and requires very careful handling. 

 The American silkworm may be found during part of the summer 

 on the under side of the leaves of the oak or elm, but unlike the 

 Chinese silkworm it has no commercial value. 



The Chinese silkworms are produced from tiny eggs about the 

 size of a mustard seed and are of a pale ash color. These eggs 

 are laid by female silk moths, each moth laying, usually in June, 

 three to five hundred eggs. During the hatching season, the 

 following April, these eggs are kept in a room of a warm, even 

 temperature. The eggs hatch into little black threadlike worms 

 which require constant attention on the part of their owners. For 

 the first few days mulberry leaves are cut up into small pieces and 

 fed to the silkworms every half hour both day and night. This pe- 

 riod is gradually extended to an hour, and finally when they have 



120 



American silkworm moth (Polyphemus). 



