38 
BULLETIN 780, U. S. DEPARTMENT OF AGRICULTURE. 
rays of the sun. The top of the dish was not on during the exposure. 
After intervals reckoned in hours inoculations were made of healthy 
colonies, the germs contained in one dish being used. 
Table XIX gives a summary of a set of experiments of this kind. 
Table XIX. — Resistance of Nosema apis suspended in water to the direct rays of the sun. 
Date ofinoculation. 
Period of 
exposure. 
Results of inoculation. 
Aug. 2, 1915.. 
July 27, 1915. 
Aug. 20, 1915. 
Do 
Aug. 26, 1915. 
Sept. 10, 1915 
Aug. 27, 1915. 
Sept. 11, 1914 
Sept. 13, 1915 
Do 
Sept. 14, 1915 
Sept. 16, 1915. 
Do 
Sept. 17, 1915, 
Hours. 
2 
10 
12 
18 
20 
20 
27 
27 
44 
37 
51 
58 
65 
72 
Nosema infection produced. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
No infection produced. 
Do. 
Do. 
Do. 
Do. 
The results in the foregoing table show that Nosema apis was de- 
stroyed by the direct rays of the sun in from 37 to 51 hours. It is 
seen, therefore, that Nosema apis when suspended in water shows a 
considerable amount of resistance. In the question of the transmis- 
sion of the disease this resistance may be of considerable importance. 
At the time these experiments were made the intensity of the rays 
was, as a rule, quite marked and, therefore, favorable for the destruc- 
tion of germs. The temperature of the aqueous suspension, however,, 
did not reach 136° F. (58° C.) and, therefore, was not sufficient to 
destroy the virus through heating. Some of the suspensions stood for 
more than a week in the Petri dishes, thereby introducing the factors 
of fermentation and putrefaction. The effect of these factors on the 
results is not known. 
DESTRUCTION IN HONEY. 
In performing the experiments crushed stomachs from about 10 
Nosema-infected bees were suspended in about 3 ounces of honey in 
Petri dishes (fig. 7). To prevent robbing by bees the dish was used 
with the top on. The suspension was exposed to the direct rays of the 
sun with the dishes resting on a wooden support. After different 
intervals healthy colonies were inoculated with germs which had 
been exposed to the sun. 
Even when resting on a wooden support it is not unusual during the 
summer for the honey of the suspension exposed to the sun to reach a 
temperature beyond the thermal death point of the parasite. To 
determine facts in regard to the effect of the sun's rays on Nosema 
apis, therefore, this point in regard to heat must be met by the 
technique employed. This could have been done quite easily but 
for the lack of time. 
