16 BULLETIN 780, U. S. DEPAKTMENT OF AGEICULTURE. 



From Table II it will be noted that in April there were 24 colonies 

 in the apiary. Out of 240 bees examined from them durmg 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. 



Durmg May, out of 410 bees exammed 96 (23 per cent) were found 



to be Nosema infected.^ , • , rv /■. c 



During June, out of 130 bees taken from 13 colonies 19 (15 per 

 cent) were found to be Nosema infected. 



Durmg 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.^ 



Five of the 24 colonies died. These were dead by the end of May. 

 It was fotmd that the number of infected bees present in them varied 

 from 50 to 100 per cent. The nuniber of infected bees in the colo- 

 nies that lived varied from 5 to 33 pfer 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 diiring 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 imder 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. 



' As the younger bees and the older ones were avoided in selecting samples for examination, the results 

 recorded in this paper ^ow a higher percentage of Nosema-infected bees in the colonies than actually 

 existed. 



