24 BULLETIN 780, IT. S. DEPARTMENT 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. 
