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



8. Practically speaking there are no secondary invaders either 

 during the life of the infected larva or during the decay of the re- 

 mains. 



9. The incubation period is approximately 7 days. 



10. The brood is susceptible to infection at all seasons of the year. 



11. More brood dies of the disease during the second half of the 

 brood-rearing season than during the first half. 



12. The disease is present at least in Australia, New Zealand, 

 Denmark, England, Ireland, Germany, France, Switzerland, Canada, 

 Cuba, and the United States. The ropy foulbrood of all these coun- 

 tries is one and the same disease. 



13. Occurring as it does in such a wide range of climatic condi- 

 tions, it is evident that the presence of the disease can not be attribu- 

 ted alone to any particular climate. 



14. The course of the disease in the colony is not affected greatly, 

 if at all, by the quality of food used by the bees, or by the quantity 

 present. 



15. Colonies in which the disease has been produced through artificial 

 inoculation can be kept in the experimental apiary without transmit- 

 ting the disease to others. This fact is of special importance not 

 only in the technique of making studies, but also in the control of 

 the malady. 



16. The spores of American foulbrood remain alive and virulent 

 for years in the dry remains (scales) of larvae and pupae dead of the 

 disease and in cultures that have become and remain dry. 



17. The spores are very resistant to most destructive agencies. A 

 variation in resistance is noted both as to the individual spores of a 

 sample and as to the spores contained in different samples. 



18. Many of the spores are killed within 1 minute at 100° C. and 

 all of them from some samples are killed in less than 5 minutes. In 

 some instances 96° C. maintained for 10 minutes will destroy all of 

 the spores while 98° C. will often do it. The most resistant of the 

 spores studied when suspended in water have not withstood 100° C. 

 for 11 minutes. 



19. The spores withstand more heating when they are suspended 

 in honey or honey diluted with water than when suspended in water. 



20. The spores suspended in honey or diluted honey can be de- 

 stroyed by 100° C. but it may require half an hour or more to do so. 



21. American foulbrood spores when dry were destroyed by the 

 direct rays of the sun in from 28 to 41 hours. 



22. The spores when suspended in honey and exposed to the direct 

 rays of the sun were destroyed in from 4 to 6 weeks. 



23. The spores when suspended in honey and shielded from direct 

 sunlight remained alive and virulent for more than a year. It 



