16 BULLETIN 780, U. S. DEPARTMENT OF AGRICULTURE. 
From Table II it will be noted that in April there were 24 colonies 
in the apiary. Out of 240 bees examined from them during the 
month, 72 (30 per cent) were Nosema infected. The number of bees 
out of each sample of 10 was found to vary from to 10. 
During May, out of 410 bees examined 96 (23 per cent) were found 
to be Nosema infected. 1 
During June, out of 130 bees taken from 13 colonies 19 (15 per 
cent) were found to be Nosema infected. 
During July, out of 130 bees examined 21 (16 per cent) were 
found infected. 
During September, out of 170 bees examined 14 (8 per cent) proved 
to be Nosema infected. 
Out of a total of 1,140 bees examined in 1912, from April to Sep- 
tember, inclusive, 236 (20 per cent) Nosema infected bees were found. 
The number of infected bees found in the different colonies varied 
from 5 to 100 per cent. 2 
Five of the 24 colonies died. These were dead by the end of May. 
It was found that the number of infected bees present in them varied 
from 50 to 100 per cent. The number of infected bees in the colo- 
nies that lived varied from 5 to 33 per cent. 
All of the colonies that died were weak when first examined in the 
spring and dwindled until they disappeared. The colonies that 
lived gained in strength and behaved as healthy ones. 
The colonies that died had sufficient stores. The queen in each 
of them was apparently in good condition and brood was being 
reared. At times, indeed, the brood was in excess of the amount 
that could properly be cared for by the diminishing number of bees 
present. These and other facts which have been observed justify 
the belief that the immediate cause of death in each of the five colo- 
nies that died was the Nosema infection that was present. These 
colonies, therefore, may be said to have died of Nosema-disease. 
The number of colonies in the spring was increased during the bee 
season through swarming and by division. 
In September an experiment was begun in the apiary in which 10 
colonies were inoculated with Nosema apis. The results of these 
inoculations will be referred to later under experiment No. 1 (p. 23). 
Examinations were made in 1913 for the prevalence and persist- 
ence of Nosema infection in the apiary studied in 1912. Naturally 
the colonies present were not altogether the same as those of the 
previous year. Some of them had been lost and some represented 
the increase. The results obtained are summarized in Table III. 
1 Fractions are omitted in this paper, as a rule. 
2 As the younger bees and the older ones were avoided in selecting samples for examination, the results 
recorded in this paper show a higher percentage of Nosema-infected bees in the colonies than actually 
existed. 
