NOSEM A-DISE ASE . 2 7 



young bees emerging. All of the bees of the colonies were exposed, 

 therefore, to infection by the inoculation. 



It is seen from this experiment that during the autumn workers 

 infected with Nosema apis live, as a rule, for more than one month, 

 but that most of them die during the second month after infection. 

 These results led to the conclusion that heavy infection hi a colony 

 when no brood is being reared will destroy the colony, but that it 

 may live for two or three months following the infection. 



Although 100 per cent of the workers in each of the 5 colonies 

 were infected, the queens from 3 of them were free from infection at 

 the death of their respective colonies. The other 2 were found to 

 be infected. 



NOSEMA ENFECTION WEAKENS THE COLONY. 



There is good evidence at hand indicating that Nosema infection 

 weakens the colony. The fact that the epithelial layer of the stomach 

 is filled with parasites (fig. 3 ; Pis. I and II) at once suggests that the 

 functions of the organ, digestion and absorption at least, would be 

 decidedly impaired thereby. Likewise, when the Malpighian tubules 

 are invaded (Pis. II and III), it is to be expected that the bee suffers 

 impaired functions. The abnormal condition argues strongly that 

 such a bee is less efficient as a member of a colony than an uninfected 

 one. Further evidence that infection weakens a colony is seen in 

 the fact that in nature the heaviest infection is encountered in the 

 weaker colonies. Still further evidence is seen in the results obtained 

 in experiments Nos, 1, 3, and 4, just recited, and from inoculations 

 made in 1913, 1914, 1915, and 1916, now to be referred to. 



On June 4, 1913, a colony was inoculated by feeding it Nosema 

 apis in a sirup suspension. On the 13th it was found to be heavily 

 infected. At this time the inoculation was repeated. Wlien exam- 

 ined on July 12 the colony had not increased in strength as the unin- 

 oculated ones had done. On this date it was reinoculated. By the 

 middle of August it had not gained in strength. No reason could 

 be assigned for the failure of the colony to become strong other than 

 the presence in it of Nosema infection resulting from the inoculation. 



On June 9, 1914, a colony was inoculated with Nosema apis. On 

 the 22d it was found to be heavily infected. On July 8 it was 

 reinoculated, at which time it was weaker than the check colonies. 

 On August 6 the colony was stUl relatively weak and was reinocu- 

 lated. On the 17th it was still weak. The failure on the part of 

 the colony to become stronger is attributed to the Nosema infection. 



On August 6, 1914, a colony was inoculated with Nosema apis. 

 It became heavily infected and on September 9 it seemed to be 

 weakened as a result of the infection. It was reinoculated on this 

 date. On December 1 it was found to be heavily infected and on 

 January 15, 1915, it was dead. 



