38 



BULLETIN 780, XJ. S. DEPABTMENT 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 Jdnd. 



Table XIX. — Resistance of Nosema apis suspended in water to the direct rays of the sun. 



Date of inoculation. 



Period ol 

 exposure. 



Kesults 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. 



Bouts. 

 2 

 10 

 12 

 '18 

 20 

 20 

 27 

 27 

 44 

 37 

 61 

 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 Nosevm 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 sim. 



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 pomt of the parasite. To 

 determine facts in regard to the effect of the sun's rays on Nosma 

 apis, therefore this point in regard to heat must be met by the 

 technique em^poyed. This could have been done quite easUy but 

 for the lack of tune. 



