274 



NATURAL HISTORY. 



Silk-worms are subject to several diseases, among which muscardine 

 and pebrine are the most prominent. Muscardine is caused by a fungus 

 " of precisely the same nature as the fungus which so frequently kills the 

 common house-fly, and which sheds a halo of spores, readily seen upon the 

 window-pane, around its victim/' Pebrine, on the other hand, is the result 

 of a parasitic protozoan, and in its action presents a strange analogy to 

 cholera in man, except that it is hereditary. 



As we have said, the silk-worm is a native of China, and for centuries 

 it was not known outside of that country. The Chinese knew its value 



Fig. 269. — Ailanthus silk-worm, moth, aud pupa {Philosamia eynthia). 



and enacted severe penalties for taking it out of the country ; death, even, 

 was the reward of the culprit, if found. At last — so the story goes — two 

 monks carried the eggs, concealed in the hollows of their canes, to Con- 

 stantinople, from whence the worm gradually spread over the whole of 

 southern Europe. To-day France and Italy are great silk countries, rival- 

 ling China and Japan. At various times the people of the United States 

 have had the silk-raising fever : mulberry-trees have been planted, eggs- 

 imported, and worms raised ; but, except with a few, the result has been a 

 total loss. Some, however, have been successful. Thev have obtained 

 from six to eight dollars an ounce for their eggs ; and in 1877 France paid 



