MICROBIAL DISEASES OF INSECTS 937 



are the silk-worm polyhedra. The significance of these bodies is not 

 known. However, they are believed to be reaction bodies belonging to 

 the highly differentiated albumins, the nucleoproteids. They may be 

 stages of the filtrable virus but no evidence has been brought forward 

 to substantiate this view. It has been determined however, that no 

 diagnosis of wilt is valid unless polyhedra are demonstrated 

 microscopically. 



The "Wipfelkrankheit" of the nun-moth in Germany is essentially 

 the same disease as that of the gipsy moth in the United States (Es- 

 cherich and Miyajima.) 



PEBRINE, AN INFECTIOUS DISEASE OF THE SILK- WORM, Bombyx 



mori 



Nosema bombycis 



HISTORY AND DISTRIBUTION. About the year 1853, anxious atten- 

 tion began to be given in the southern part of France to the ravages of 

 a disease among silk- worms which from its alarming progress,threatened 

 to issue in national disaster. Symptoms of this disease had been noted 

 as early as 1845. It finally became necessary to import seed (technical 

 term for eggs) for continuing the culture of the silk-worms. This was 

 procured first from Lombardy, but after one successful year the same 

 disappointments occurred. Then Italy was attacked, also Spain and 

 Austria; later seed was procured from Greece, Turkey, the Caucasus, 

 but to no avail; China itself was attacked and in 1864, healthy seed 

 could be obtained only from Japan. 



This disease, characterized by dark spots on the silk-worms, was 

 called pebrine, from the patois word pebre (pepper), the name given to 

 it by de Quatrefages on account of the resemblance of these spots to 

 pepper grains. 



SYMPTOMS. As above mentioned, one of the symptoms of pebrine 

 is the manifestation of dark spots in the skin of the larvae; some worms 

 languish on the frames in their earliest days, others in the second 

 stage only, some pass through the third and fourth molts, climb the 

 twig and spin their cocoons. The chrysalis becomes a moth, but the 

 moth shows signs of disease in its deformed antennae and withered legs; 

 the wings seem singed. Eggs from these moths are inevitably un- 

 successful the following year. Thus, in the same nursery in the course 



