48 BULLETIN 780, U. S. DEPAETMENT OF AGRICULTURE. 



Colonies may die out, or they may only become weakened by the 

 disease. Each of these conditions invites robbing, which in a certain 

 number of cases probably results in the transmission of the disease. 

 The likelihood of the transmission of the disease through robbing, 

 however, seems to be not nearly as great as in the case of the foul- 

 broods. 



Uninoculated colonies in the experimental apiary have always 

 remained practically free from infection, although colonies heavily 

 infected as the result of experimental inoculations were present. 

 This fact suggests that very httle infection, if any, results either 

 from the visit of healthy bees to flowers previously visited by infected 

 ones, or, furthermore, from the straying or drifting of bees from 

 infected to healthy colonies. 



The possibility that the queen may be infected and that infection 

 will be transmitted by her to the other bees of the colony need give the 

 apiarist no uneasiness, and no concern need be felt that drones will 

 spread the disease in the apiary. 



Fear that Nosema-infection might be transmitted by hives which 

 have housed infected colonies need not be entertained; neither is it to 

 be feared that the hands or clothing of the beekeepers, or the tools used 

 about an apiary, wiU serve as means for the transmission of the 

 disease. Furthermore, the spread of the disease is not to be attrib- 

 uted directly to winds. 



Theoretically it would seem that combs from Nosema-diseased 

 colonies, if inserted into a healthy colony, would be the means of 

 transmitting the disease and that the danger would extend over a 

 period of a few weeks or months (p. 39). Experimentally it is 

 shown, however, that such combs can be inserted immediately without 

 transmitting the disorder, at least appreciably (p. 43). 



Evidence is yet to be obtained to prove that insects other than 

 honeybees are susceptible to infection with Nosema apis. A few 

 experiments made in which silkworms, maggots, and ants were 

 inoculated with this parasite gave negative results. At the present 

 time, therefore, there is no cause for fear that Nosema-disease wiU be 

 transmitted as the result of a similar infection in other insects. 



DIAGNOSIS OF NOSEMA-DISEASE, 



Nosema-disease usually can be diagnosed from the colony symptoms 

 present together with the gross appearance of stomachs removed from 

 adult bees of the colony. 



Weakness, especially in the spring of the 'year, should cause a sus- 

 picion that the disease is present. The suspicion is strengthened if in 

 such a colony the brood in general is normal, if the adult bees are not 

 noticeably difiPerent in outward appearance or behavior from bees of 

 healthy colonies, if the queen is present and if stores are abundant. 



