AMERICAN FOULBROOD. 39 



belief that occasionally it does. Experimental evidence indicates 

 that it probably does. Colonies in the experimental apiary, with a 

 larva or pupa dead of the disease here and there only, certainly did 

 not become badly diseased for more than a year and apparently 

 recovered. To have proved conclusively, however, that such colonies 

 were completely free from possible infection from within would have 

 necessitated observations over a much longer period. 



It is known that worker, drone, and queen larvse die of the disease. 

 Theoretically it is possible that a colony might become queenless as 

 a direct result of American foulbrood but care must be taken in 

 attributing this condition to the disease, for very often queens are 

 reared in diseased colonies, and to all appearances are healthy. 

 Whether a larva once infected ever recovers from the disease is not 

 known. 



From the facts at hand it may be concluded, therefore, that the 

 prognosis in American foulbrood in an untreated colony is especially 

 grave. From the practical viewpoint, at least, complete recovery 

 from the disease without treatment, if it occur at all, should be con- 

 sidered for the present to be the exception. While an infected colony 

 may live for a long time and 3rield a profitable surplus for a considera- 

 ble period, this is not the rule; more often the course of the disease 

 is comparatively short, and the destruction of the colony the outcome. 



SUMMARY AND CONCLUSIONS 



A brief summary of facts known about American foulbrood together 

 with a few conclusions drawn from them are given here. Some of 

 the facts have been known for many years, others are of more recent 

 origin, and still others are new. All of them are supported by experi- 

 mental studies recorded in the present paper. 



1. American foulbrood is an infectious disease of the brood of bees 

 caused by Bacillus larvae, 



2. All larvse — ^worker, drone, and queen — are susceptible to the 

 infection; adult bees are not. 



3. Man evidently is not susceptible to infection with the organism 

 nor are the experimental animals. 



4. So far the disease has not been encountered or produced in 

 other insects than honeybees. 



5. The brood of bees can be infected through feeding the spores 

 of the bacillus to a colony. 



6. The spores contained in a single scale are more than enough to 

 produce considerable disease in the colony. 



7. The portal of entry of the infecting agent is somewhere along the 

 alimentary tract of the larva, most likely the stomach (mid -intestine). 



