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 in 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 INFECTION 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. When 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 still 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. 
