6 BULLETIN 804, IT. S. DEPAETMEITT OF AGRICULTURE 



flow as jDossible in order not to have the influence of a heavy honey 

 flow until other factors had been studied. At Ithaca the main honey 

 flow is generally from buckwheat, coming from the 1st to the mid- 

 dle of August. Eather unfortunately for the best results from the 

 experiments, however, the summer of 1918 was unusual in this sec- 

 tion, for the abnormally heavy honey flow from clover necessitated 

 finishing the work earlier than had been planned, owing to the great 

 difficulty of artificially infecting colonies during the heavy honey 

 flow. 



There were seven colonies in the original experimental apiary. 

 At first it was intended to work on a larger scale, but the trend of 

 the observations soon led to the plan of working in more detail and 

 on a smaller scale. These colonies were moved some distance apart 

 to prevent drifting and robbing. Some were divided and some were 

 strengthened in an efl'ort to make a series of experiments on colonies 

 of different strengths. The colonies were designated by letter and 

 the combs of each colony by number. From time to time some of 

 these colonies were artificially infected with diseased European foul- 

 brood larvae from samples sent to the laboratory for diagnosis. 

 Similar colonies were held intact and uninfected for controls. The 

 infection was made by feeding diseased larvae macerated in sugar 

 solution (about 50 per cent). For the preliminary experiments 10 

 larvae were fed in about 250 c. c. of sirup. Later, after the heavy 

 honey flow had begun, it was necessary greatlj^ to increase this dose in 

 order to start the infection. The infected sirup was fed to the bees 

 in sterilized glass petri dishes, placed on top of the frames and pro- 

 tected by an empty comb-honey super placed on the regular hive 

 body with the cover on top. 



At the time of inoculation, the condition of each colony was noted 

 as to age, race, condition and appearance of the queen, proportion 

 of mirse bees to old field bees, the number of frames of brood with 

 the amount in each, its age, sealed or unsealed; in other words, the 

 condition of the colony with regard to factors known to be signifi- 

 cant in resisting disease. In two colonies the infected sirup was 

 slightly colored with harmless eosin dye to determine where the fresh 

 sirup was placed and its ultimate disposition. At first daily obser- 

 vations were made to determine the earliest appearance of disease, 

 the period of incubation, the symptoms exhibited, and the rate of 

 increase. 



By holding up each comb in bright sunlight so that the light shone 

 directly on the larvae, it was easy to detect the first symptoms of the 

 disease. All the healthy larvae had the characteristic firm, well- 

 rounded, pearly-white, glistening appearance. The first effect of 

 the disease, besides an abnormal uneasy movement, was a loss of the 



