BEES IN COLONIES AFFECTED BY EUROPEAN FOULBROOD 



13 



Colony H (fig. 4) was treated as a double experiment. The infec- 

 tion of this colony was not started until after the honey flow had come 

 on quite heavily. Also, instead of freshly diseased larvae, old brown 

 rubbery scales were used that showed Bacillus pluton present micro- 

 scopically, but were heavily overgrown by Bacillus alvei. It was de- 

 sired to learn whether these scales were still infectious, so that nurse 

 bees working on them, cleaning them out, might get infective material 

 on their feet and mouth parts which could be carried to healthy larvae. 

 This was noted later in the observation hive, where, under the magni- 

 fying glass, bees were seen trying to remove some of these rubbery 

 scales, first moistening them with their tongues and then pulling at 

 them with the mandibles and front feet. 



This colony, which was marked hybrid and weak, was slow in 

 developing the disease, partly because of the diluting effect of the 





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Fig. 4. — The course of European foulbrood in colony H. 



heavy honey flow and probably partly because there was a smaller 

 number of infectious organisms present in the scales than in fresh 

 larvae. This is explained by the fact that the secondary putrefactive 

 invading organisms would tend to kill off the primary organism, be- 

 cause of the accumulation of the products of the putrefactive action. 



On the seventh day before the disease was first noted, a second 

 infection of scales macerated in sugar sirup was given this colony 

 to counteract the effect of these retarding factors. However, later on 

 the seventh day, diseased larvae were found, and from then on the 

 disease started to spread and increase irrespective of the heavy honey 

 flow, exhibiting all the symptoms and tendencies shown in colony G, 

 of which this colony was a division before infection. 



On the seventeenth day it was necessary to remove the queen and 

 start treatment, but what was taking place was evident. This removal 

 of the queen did not seem to have a very marked effect on the house 



