AMERICAN FOULBROOD. 35 



usually spreads more or less rapidly within an infected colony, tlie 

 fact remains that it frequently does not. 



It was observed that many diseased colonies could be present 

 in the experimental apiary without causing the infection to be 

 transmitted to other colonies in the apiary. This fact is naturally 

 very significant. On account of it certain views concerning the 

 manner of transmission of the disease, which might otherwise be 

 regarded as probable, are rendered untenable. If flowers visited 

 by bees from infected colonies, and later by bees from healthy ones, 

 are a likely source of infection, or if the water supply is such a source, 

 or if drones are a means by which the disease is likely to be trans- 

 mitted, there woiild have been a different observation to report. 



In a few instances in the experimental apiary colonies near heavily 

 infected ones became infected. That the disease may have been 

 transmitted through the drifting or accidental straying of bees is 

 one of the possible explanations for the disease in these cases. That 

 a slow form of robbing might have taken place should be considered 

 also as a possible explanation in these cases. 



Brood comb containing brood dead of American foulbrood will 

 transmit the disease when placed in a hive containing a healthy 

 colony. The likelihood that the disease will be transmitted by 

 combs from diseased colonies, which contain honey but no brood, 

 probably is frequently overestimated. It would seem that a spread 

 of the disease in this way would depend considerably upon the amount 

 of infection that was present in the colony from which the combs 

 were removed. This would depend also somewhat upon the presence 

 or absence of brood in the colony to which the combs were given. 

 Sufficient facts are wanting to make definite statements in regard to 

 the probability of infection in such cases. Robbing material con- 

 taining the spores of American foulbrood from any source is likely to 

 transmit the disease although it does not necessarily do so. 



How often the disease would be transmitted through the medium 

 of hives which have housed infected colonies, if used without flaming, 

 has not been definitely determined. Experimental colonies have 

 been placed in such hives and kept in them for a year with the result 

 that no disease appeared.^ It probably will be found that in many 

 cases the treatment of the hive bodies is not necessary to insure that 

 the disease will not be transmitted by them. From the results 

 obtained by practical apiarists and by observation made in the exper- 

 imental apiary during these studies the fact has been well established, 



1 An experiment in whichf our colonies were used, was made as follows: The insides of the top and bottom 

 board of each of two hive bodies were washed with an aqueous suspension of spore-containing material and 

 allowed to dry, and the inside of the walls of each of two others were similarly washed and allowed to dry. 

 Colonies were transferred to these four hives during the summer. American foulbrood appeared in the 

 two colonies housed in hives of which the tops and bottoms had been contaminated with disease material 

 but did not appear in the other two. These results, naturally, are not conclusive but they are suggestive. 



