RACES AND CHARACTERISTICS. 



During the course of the work fifteen different silkworm races have 

 been bred pure and used in hybridization, but a few of these have been 

 used much more than the others. These various races (Bagdad, 

 Istrian, Japanese White, Japanese Green, Chinese White, Italian Yellow, 

 French Yellow, Persian Yellow, Turkish and French Yellow, etc.) are 

 distinguished from each other by characteristics of the egg, the larva, 

 the cocoon and, to some degree, of the adult. The varying egg char- 

 acters are size, shape, color and degree of adhesiveness. The larval 

 characters are size, external appearance and, chiefly, color and pattern. 

 The cocoon characters are size, shape, character of silk as to tenacity, 

 diameter, length, etc., of the thread, and, most conspicuously, color. 

 The adult characters are size, and degree and character of patterning of 

 wings. 



These characteristics are all of course affected by fluctuating varia- 

 tion and by occasional sport (reversional or mutational) variation, but 

 for cocoon colors, larval colors and patterns, adhesiveness of egg and 

 size of egg, and certain "commercial" characters of the silk, as tenacity, 

 diameter and length of the thread, the races are well separated and have 

 long been bred pure. 



The mulberry silkworm has been domesticated and ameliorated by 

 man for about fi:V€ centuries. The exact feral species from which it is 

 derived is not certainly known. It seems most probable that the home 

 of the wild progenitor was (perhaps still is) in the mountains of 

 northern India. 



As with poultry, cattle, horses, dogs, sheep, swine, pigeons, many 

 races have been established in many lands, and much careless and use- 

 less hybridization and selection has been indulged in. Out of it all 

 there has been of course, unconsciously and consciously, a steady 

 increase in the output and in the betterment in quality of the silk pro- 

 duced by the silkworm individual. Commercially valuable char- 

 acteristics of the silk, and behavior, resistance to disease, and "tame- 

 ness" of the larva have been the points striven for by breeders. But 

 along with these, other characteristics, correlated or independent, 

 have become fixed in various races and are useful to the experimental 

 student of inheritance. 



For the purposes of our studies the nature and distinctness of the 

 varying distinguishing characteristics of the races and their steadfast- 



