


LEPIDOPTERA. 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, 
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Fig. 215.—Cocoon of Bombyx mori, 
Fig. 214 —Spherical cocoon 
drawn in towards the middle. 
of the Bombyx mori. 
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 Roguemaure. 
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 

