28 THE CULTURE OE THE MULBERRY SILKWORM. 



a perforated bottom and open at the top. Arrange in this cylinder round baskets 

 three-fourths filled with cocoons; then cover the cylinder with a perforated lid. In 

 about thirty minutes the operation will be completed, after which remove the 

 cylinder, take out the baskets, and spread out the cocoons to dry before storing, to 

 prevent them from spoiling. 



Mr. T. A. Keleher of this office has adopted the following plan: 



The cocoons are placed in an air-tight box of about 24 cubic feet capacity; about 

 half an ounce of bisulphid of carbon in a small dish is placed in the box and left 

 over night. It is best to open one or two of the cocoons to find if the chrysalides 

 are dead; if not the operation must be repeated. Care should be exercised that 

 no fire of any kind be brought into the vicinity during this operation as the bisul- 

 phid of carbon is very inflammable. 



In shipping- cocoons care must be taken to pack them in baskets or 

 cases permeable to air, but sufficiently close to keep out rats and mice, 

 which are very destructive to cocoons. 



DISEASES OF SILKWORMS. 



In every successful rearing of an ounce of eggs about 40,000 worms 

 are hatched, and 30,000 succeed in spinning cocoons. The rest either 

 die from casual wounds or from diseases incidental to restricted action. 

 But sometimes whole chambers are destroyed by hereditary and con- 

 tagious diseases, and it is of supreme importance to cultivators to learn 

 how these scourges may be avoided. 



In this limited treatise only a bare mention can be made of the most 

 fatal diseases and of the necessary precautions to be taken to guard 

 against them. The general cause of disease is the domestication of 

 the worm. By using good eggs, however, and following the methods 

 which are actually employed by successful rearers, remunerative results 

 are usually obtained. To obtain good eggs it is necessary to adopt new 

 methods. These are chiefly such as involve the use of the microscope. 



Among the many diseases of silkworms, the principal ones are: 



Pebrine, flacherie or naccidity, gattine or macilenza, calcino or mus- 



cardine, and grasserie. 



PEBRINE. 



This disease was first noticed in epidemic form in France in 1845. 

 Since then it has appeared in Italy, Spain, Portugal, Turkey, Turkes- 

 tan, the Caucasus, Kashmir, China, and Japan, threatening to destroy 

 the silk industry. 



Between 1833 and 1865 the annual crop of cocoons in France was 

 reduced by pebrine from 57,200,000 pounds to 8,800,000 pounds. No 

 remedy has been found for the disease, but the Pasteur microscopical 

 selection of eggs, insuring the birth of healthy worms, is a sure prevent- 

 ive. The universal adoption of this method has made pebrine almost 

 a thing of the past; and following Pasteur's line of research, means 

 have now been discovered for avoiding every kind of silkworm disease. 



Worms affected with pebrine develop slowly, irregularly, and very 

 unequally. Black spots are the most marked outward characteristics 



