THEIR RELATION TO MAN 



93 



in the same way and without a break! Generally, 

 other caterpillars that spin cocoons do not work con- 

 tinuously; or if they do work steadily on, they make 

 a patchwork affair of it. They may spin a few yards 

 at one end, break the thread, put in a few yards at an- 



Silk-worm. cocoon and male moth. 



other point, and so on until the work is completed, 

 making a nice even job when everything is done, but 

 a cocoon that cannot be profitably unwound or reeled 

 because of the great number of breaks. 



Then, too, the particular species, Sericaria mori, 



has been domesticated so long that it has developed 



some highly desirable qualities. The adult moths are 



very sluggish, even the males flying little or not at all, 



13 



