NOSEMA-DISEASE. 25 



Such results, together with facts which are recorded on the foregoing 

 pages, are sufficient to demonstrate that Nosema-disease is an infec- 

 tious disease of adult bees. 



It is shown also by the results of this experiment that there is a 

 tendency for the infected colonies to become weakened. It is further 

 shown that when inoculated in September colonies do not die out 

 readily as a result of the inoculation. Furthermore the results 

 indicate that the infection is not readily transmitted from the infected 

 to the healthy colonies of the apiary. It is further shown that 

 colonies inoculated in September may die as a result of the infection 

 during the winter that follows, or they may survive the winter, gain 

 in strength during the brood-rearing season, and by the following 

 autumn present the appearance of healthy colonies. 



EXPERIMENT NO. 2. 



Beekeepers are always desirous of knowing whether combs from 

 diseased colonies can be used in healthy ones without causing a 

 spread of the infection. To obtain data relative to this point experi- 

 ment No. 2 was begun in July, 1913 (Table III). In the experiment, 

 brood combs from diseased colonies were inserted into colonies 

 comparatively free from Nosema infection and kept under observa- 

 tion for more than a year afterwards. 



Combs from the 5 colonies of experiment No. 2, which died 

 during the winter and spring following their inoculation with Nosema 

 apis in September, 1912, were inserted into the 6 colonies (Nos. 36, 

 50, 61, 66, 68, and 82, numbered by capital letters ''A" to ''F," 

 respectively) used in the present experiment, each colony receiving 

 from two to four combs. The colonies from which the inserted frames 

 were obtained had been dead for from seven weeks to five months 

 before they were given to the colonies. None of the 6 colonies were 

 strong, the bees being easily accommodated on from four to six 

 brood frames, a strength representing about an average for the apiary. 



Out of 110 bees examined from the 6 colonies of the experiment 

 prior to the insertion of the combs 10 (9 per cent) were found to be 

 infected; and out of 170 bees examined after they were inserted 26 

 (15 per cent) were found to be infected. This increase in Nosema- 

 infected bees can not be attributed to the introduction of the combs, 

 since a similar increase is. noted in the other colonies of the apiary 

 serving as checks. 



All of the colonies of the experiment lived through the winter and 

 spring except one (No. 61). This colony was dead when examined 

 in May, 1914. Dead bees taken from the bottom board of the hive 

 showed a high percentage of Nosema-infected bees. The 5 colonies 

 that survived gained in strength, behaved as healthy colonies, and 

 contained a percentage of Nosema-infected bees approximating that 

 113789°— 19— Bull. 780 i 



