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BULLETIN 780, U. S. DEPARTMENT OF AGRICULTURE. 



constrictions are less marked, and the transparency is diminislied. 

 In late stages of the disease, however, the stomach approaches the 

 normal in size and the constrictions are again well marked. The 

 organ is then white and opaque and the tissues are friable and easily- 

 crushed. When crushed the mass presents a milky appearance. 



Upon microscopic examination Nosema apis is found in very large 

 numbers in the crushed tissues. The presence of the parasite is 

 almost invariably recognized by its spore form. The presence of 

 Nosema-infected bees in a colony is the one constant colony symptom 

 of the disease. 



METHODS EMPLOYED IN EXPERIMENTAL STUDIES. 



As Nosema apis has not been grown in the laboratory by artificial 

 methods, in carrying out these investigations it has been necessary 



to inoculate a large number of 

 colonies of bees. The use of a 

 few bees in cages was found to 

 be inadequate for experimental 

 purposes. A 4 to 6 frame nu- 

 cleus in a 10-frame hive body 

 (fig. 5) serves well the purposes 

 of an experimental colony. 

 The experimental apiary (PL 

 IV) , consisting usually of about 

 50 colonies, was the same one 

 that was used in the sacbrood 

 studies. During the bee sea- 

 son the colonies were inocu- 

 lated and kept in the apiary 

 in the open under conditions 

 similar to those occurring in 

 nature. Precautions similar 

 to those observed in the sac- 

 brood studies were followed in 

 the present studies. During the winter colonies to be inoculated 

 were removed to and kept in the laboratory. The top of the hive 

 body was screened and the bees given free opportunity for flight 

 through a hole in the window. 



The manner of obtaining the parasite Nosema apis from diseased 

 bees for use in the inoculations is described under "Diagnosis" 

 (p. 48). The stomachs of from 5 to 10 infected bees are amply suffi- 

 cient for each inoculation. After their removal from the bees they 

 are crushed, suspended in sirup, and fed to a colony free or practically 

 free from Nosema infection. The methods throughout are similar 



Fig. 5.— Experimental hive, having four Hoffman 

 frames, a division board, Petri dishes as feeders, the 

 entrance nearly closed with wire cloth, and the open- 

 ing on the side of the hive body occupied by the 

 frames. (Original.) 



