SILK-WORMS. 



347 



FIG. 310. 



worms appear in five or six days. The rearing occupies 

 about a month ; although this time may be shortened 

 by keeping the temperature high and furnishing more 

 food, the results are not satisfactory. During their 

 short lives the worms 

 cast their skins several 

 times usually four 

 and the time between 

 each casting is called an 

 age. At each age there 

 is a moment when the 

 appetite of the worms 

 appears insatiable. The 

 worms hatched from an 

 ounce of eggs consume 

 nearly a ton of mulberry 

 leaves before they reach 

 maturity ; they then 

 quit the nests filled with 

 leaves in which they are 

 kept, and crawl on to 

 bundles of branches ar- 

 ranged for them, and 

 there begin to spin. 

 This work lasts three 

 days, after which the 

 cocoons may be de- 

 tached. An ounce of 



eggs produces a hundred or a hundred and fifty pounds 

 of cocoons. 



When the cocoons have been collected, the best speci- 

 mens are set aside for future rearings, and from these 

 the moths are liberated in two or three weeks ; they 



SILK-SECRETING APPARATUS. A, organs 

 that secrete the silky matter in the silk- 

 worm : a, posterior part of the head ; 

 6, canals for the exit of the silky matter ; 

 c, reservoir and silk gland ; B, nipple 

 on the lower lip from the tip of which 

 the silk-fibre issues. 



