12 BULLETIN 809, U. S. DEPARTMENT OF AGRICULTURE. 



Climate. — It is quite well known that American foulbrood is very 

 widely distributed. The writer has examined samples of the disease 

 from England, France, Germany, Switzerland, New Zealand, Canada, 

 Cuba, and various parts of the United States. This is sufficient to 

 show that the disease exists under a great variety of c lim atic condi- 

 tions. The practical import of the observation is that the presence 

 of American foulbrood in any particular locality can not be attrib- 

 uted entirely to the climatic conditions of the region. 



Season. — In general the losses from American foulbrood occur 

 later in the bee season than do losses from either sacbrood or Euro- 

 pean foulbrood. Experimental inoculations have shown that the 

 larvae of bees are susceptible at all seasons and that the disease can 

 be produced whenever brood is being reared. It would seem, there- 

 fore, that the severity of the disease is due more to environmental 

 conditions existing at the different seasons than to any difference 

 in the susceptibility of the larvae during these periods. 



Food. — Since American foulbrood occurs in such widely different 

 localities (see " Climate"), wherein the food of bees varies almost as 

 much as it is possible for it to vary, it may be concluded that the 

 quality of the food used by bees has very little, if anything, to do 

 in the causation of the disease. Furthermore, it is found experi- 

 mentally that the disease can be produced when the colony is well 

 supplied with food, when there is a moderate quantity present, or 

 when there is a scarcity. It would seem from the facts at hand that 

 the course of the disease probably is governed to some extent indi- 

 rectly by the quantity of food present and to a less degree, if at all, 

 by its quality. The value of these factors has not been determined 

 but it is certainly not great in either case. 



EXCITING CAUSE 



During the period from 1885 to 1902 (p. 2), Bacillus alvei was 

 assumed quite generally to be the exciting cause of foulbrood. From 

 1902 to 1907 much interest was manifested in the problem relating 

 to the cause of the foulbroods. This is shown by the investigations 

 of Lambotte (13) in Belgium, Burri (6, 7) in Switzerland, Bahr (2) 

 in Denmark, Maassen (14) and Erne (12) in Germany, and those of 

 the writer. 



The writer's experience with the bee diseases began in 1902 when he 

 was working under the direction of Dr. V. A. Moore. In the first studies 

 made, spores were found in very large numbers m the scales of the ropy 

 foulbrood. As these did not grow on the media commonly used in 

 a laboratory (17) it was at once recognized that they were not the 

 spores of Bacillus alvei. Furthermore, as B. alvei was not found in 

 any of the samples of the ropy disease, the conclusion was drawn 

 very naturally that this bacillus could not possibly be its cause. 



Bacillus alvei was found to be present, however, with much regu- 

 larity and in great numbers in the brood disease that is not charac- 



