56 BULLETIIT 780, U. S. DEPARTMENT OF AGRICULTURE. 



SUMMARY AND CONCLUSIONS. 



The following statements concerning Nosema-disease seem to 

 be justified from the facts recorded in the present paper: 



(1) Nosema-disease is an infectious disorder of adult bees caused 

 by Nosema apis. 



(2) The disease is not particularly malignant in character, being 

 in this respect more like sacbrood than the foulbroods. 



(3) Adult workers, drones, and queens are susceptible to infec- 

 tJon, but the brood is not. 



(4) The infecting agent Nosema apis is a protozoan that attacks 

 the walls of the stomach and occasionally those of the Malpighian 

 tubules, 



(5) A colony can be inoculated by feeding it sirup containing 

 the crushed stomachs of infected bees. 



(6) One-tenth of the germs present in a single stomach are sufficient 

 to produce marked infection in a colony. 



(7) Withm a week following the inoculation the parasite can be 

 found within the walls of the stomach. 



(8) Before the close of the second week infection can be determined 

 by the gross appearance of the organ. 



(9) The disease can be produced at any season of the year by feed- 

 ing inoculations. 



(10) Infected bees may be found at all seasons of the year, the 

 highest percentage of infection occurring in the spring. 



(11) Nosema infection among bees occurs at least in Australia, 

 Switzerland, Germany, Denmark, England, Canada, and the United 

 States. This distribution shows that the occurrence of the disease 

 is not dependent altogether upon climatic conditions. 



(12) The course of the disease is not affected directly by the 

 character or quantity of food obtained and used by the bees. 



(13) A sluggish body of water, if near an apiary and used by bees 

 as a water supply, and the robbing of diseased colonies, must be 

 considered for the present as two probable sources of infection. 



(14) The transmission of the disease through the medium of flowers 

 is not to be feared. 



(15) The hands and clothing of the apiarist, the tools used about 

 an apiary, and winds need not be feared as means by which the 

 disease is spread. 



(16) Hives which have housed infected colonies need not be dis- 

 infected and combs from such colonies are not a likely means for the 

 transmission of the disease. 



(17) Bees dead of the disease about the apiary are not likely to 

 cause infection unless they serve to contaminate the water supply. 



(18) Nosema apis suspended in water is destroyed by heating for 10 

 minutes at about 136° F. (58° C). 



