SILK-PRODUCING INSECTS. 23 



A certain number of cocoons are put aside to 

 perpetuate the breed. This operation is based upon 

 the calculation that 1 Ib. of cocoons are equivalent 

 to one ounce of eggs that is, that the moths from 

 1 Ib. of cocoons can produce one ounce weight of 

 eggs. We have already seen that one ounce of eggs 

 will produce 80 Ibs. of cocoons. 



The mulberry tree (a native of China, and of 

 which there are two varieties : the black, Morus niger, 

 whose refreshing fruit is well known, and the white, 

 Morus alba, upon whose leaves the silkworms 

 breed) is easily cultivated wherever the vine grows, 

 but succeeds very well in more northern climates. 

 I have myself seen the Morus alba cultivated witL 

 success at Uccle, a pretty spot near Brussels, 

 already alluded to, and I know that experi- 

 ments of the same kind have met with success in 

 England, Switzerland, Prussia, Hungary, Austria, 

 Kussia, etc. 



As a consequence of its domestication, the silk- 

 worm, though very robust in China, is subject in 

 other countries to various maladies. The worst of 

 these is certainly that called Muscardine, which 

 attacks the larva at all periods of its life, but espe- 

 cially while making its cocoon. It is an infectious 

 disease, and can be communicated from the body 

 of a dead larva to that of a living one. This de- 

 structive pestilence, for which no efficacious remedy 



