LEPIDOPTEEA. 



237 



The cocoons spun on these branches of heather ought to be 

 large, heavy, and well-shaped. The good cocoons are regular; 

 their ends are rounded and not pierced; and they are hard] 



Fig. 214 Spherical cocoon Fig. 215. Cocoon of Bombyx mori, 



of the Bombyx mori. drawn in towards the middle. 



especially at their extremities, and have a fine grain. These are 

 cylindrical. The best are drawn in towards the middle, or have a 

 concavity on either side of it (Fig. 215). Every one knows that 

 there are white and yellow cocoons. They are the produce of 

 different races of worms. 



Commerce recognises two kinds of white silk : the first white 

 and the second white. The silk of the first white is produced by 

 the race Sina, the cocoons of which are of a perfect and azured 

 white. They produce the most beautiful and most precious silk, 

 and serve for the fabrication of light and delicate coloured tissues. 

 The silk of the second white is furnished by two races : the 

 Espagnolet and the Roquemaure. 



The races that produce yellow cocoons are more numerous than 

 the white ones. The yellow races are divided into three groups : 

 those that have small, middle-sized, or large cocoons. The first 

 and second are stronger, and more esteemed than the last. 



The greatest number of the races of silkworms have, let us here 

 mention, white and yellow cocoons ; there are some, however, of 

 those whose cocoon is of a greenish white, or even quite green, or 



