24 BULLETIN 780, U. S. DEPARTMEISTT OF AGRICULTURE. 



during the period from October 5 to October 16, inclusive, 132 

 (70 per cent) were found infected. These colonies when examined 

 on October 28 showed that, out of 100 bees examined, 78 (78 per 

 cent) were infected. It will be noted, therefore, that following the 

 feeding inoculations there was a marked increase in the percentage 

 of Nosema-infected bees in each of the 10 colonies inoculated. 



In the experiment sufficient precautions were not taken to prevent 

 robbing at the time the inoculations were made. This resulted in an 

 increase also of Nosema-infected bees in some of the uninoculated 

 colonies (Table II) of the apiary — the checks. The increase in the 

 number of infected bees disappeared more readily from the check 

 colonies, however, than from the inoculated ones, suggesting that 

 probably, a comparatively small amount of the contaminated sirup 

 was obtained by the robbing bees. 



On December 17, out of 100 bees taken from the 10 inoculated 

 colonies 49 (49 per cent) were found to be Nosema infected, showing 

 that the percentage of infected bees had decreased. 



From comparison of the inoculated colonies in October and in 

 December, it was observed that their strength had decreased and that 

 they were relatively weaker than the checks. Toward the last of 

 December one of the 10 inoculated colonies died. During the last 

 week of the year the remaining 9 were packed for the winter as were 

 also the check colonies. Some of the weaker check colonies were 

 united, giving them a slight advantage in strength over the inoculated 

 ones. 



The winter 1912-13 being a favorable one for bees, the winter 

 losses were low. In March, 1913, when the first examination of the 

 apiary was made, 4 of the 10 colonies that had been inoculated had 

 died out. Four of the six inoculated colonies that were still alive 

 showed 4, 6, 2, and 2 Nosema-infected bees respectively in samples 

 of 10 bees examined. Neither of the other two inoculated ones 

 showed at the time the presence of Nosema infection. All of the 19 

 uninoculated colonies packed in December were alive in March, 1913. 

 Out of 190 bees caught from the entrance of these check colonies 

 during March only 6 (3 per cent) were Nosema infected. 



By the middle of May another of the inoculated colonies (No. 12) 

 had died, making 5 in all. Of the 10 colonies that had been inoculated 

 in September, 1912, the 5 that lived through the winter and the 

 following spring continued to gain in strength during the summer of 

 1913 and by autumn were apparently as strong and healthy as any in 

 the apiary. 



By experiment No. 1 it is shown that when colonies are inoculated 

 with Nosema apis a high percentage of adult bees of each colony 

 becomes Nosema infected — results which confirm similar ones 

 previously obtained by Donhoff (1857), Zander (1909), and others. 



