MICROBIOLOGY OF DISEASES 01 INSECTS 657 



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 seemed singed. Eggs from these moths were inevitably un- 

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

 of the two months that it takes a larva to become a moth, the pebrine 

 disease was alternately sudden or insidious; it burst out or disappeared, 

 it hid itself within the chrysalis and reappeared in the moth or the eggs 

 of a moth which had seemed sound. 



Causal Organism. — The causal organism for this disease is micro- 

 scopic but nothing further of its nature is known. 



In the worms suffering from pebrine, corpuscles or polyhedral 

 bodies, first noted by Pasteur, are found in all tissues and all fluids of 

 the body, even in the material from which the silk is made; naturally 

 they are also found in the dejecta of the worms. These same bodies 

 are found in and on the infected eggs, pupae and moths and in innumer- 

 able quantities in the dust of the infected nurseries; they are easily 

 recognized microscopically. 



Although these polyhedral bodies are neither known to be the etio- 

 logical factor, nor the effect of the disease, elimination of all eggs, 

 containing these bodies results in its suppression. 



It is generally accepted, however, that Nosema bomhycis is the cause of p6brine. 

 The spores find their way from the caterpillar by means of the dejecta or through the 

 disintegration of dead forms to other silk- worms. Some of the parasites find their 

 way into the ovary, produce spores, pass through the pupal and imaginal stages of 

 the host into the next feneration of silk-worms. The spores are often regarded as 

 pfibrine-corpuscles. 

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