48 BULLETIN 780, U. S. DEPARTMENT 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 little 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, will 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 will 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 different in outward appearance or behavior from bees of 
healthy colonies, if the queen is present and if stores are abundant. 
