12 BULLETIN 780, U. S. DEPAKTMENT OF AGKICULTUEE. 



In experiments recorded in the present paper the bees used have 

 been largely hybrids, being for the most part grade Italians. Two 

 each of tested Carniolans and Caucasians and a few common blacks 

 have been among the colonies used. The bees were found to be sus- 

 ceptible to Nosema infection in all instances. It is not unlikely that 

 future studies will show a difference among the races as to their 

 relative immunity to the disease, but sufficient data are yet wanting 

 to justify a definite statement in regard to the point. 



Nosema infection has been reported from Australia (Price and 

 Beuhne, 1910), Brazil (Zander, 1911), Canada (White, 1914), Eng- 

 land (Fantham and Porter, 1911), Germany (Zander, 1909), and 

 Switzerland (Nussbaumer, 1912). Studies have not yet been made in 

 Denmark on the disease (Bahr, 1916). The writer (1914) has found 

 it in samples of bees received from 27 different States of the United 

 States. Out of 120 samples examined 40 contained the parasite. 

 Samples showing infection were received from the coast plains and 

 mountains of the East, from the plains of the Mississippi Valley, 

 from the plateaus and plains of the West, and from the South and 

 the North. 



The infection was found in bees received from Florida and southern 

 California, but in 15 samples received from Texas it was not found. 

 The data thus far obtained indicate that less infection occurs in the 

 southern portion of the United States than farther north. Whether 

 it is found in the Tropics or in the coldest climate in which bees are 

 kept is not yet known. 



Laidlow (1911) reports that heavier infection was encountered in 

 some parts of Australia than in others. Nussbaumer (1912) reported 

 the infection from 14 of the cantons of Switzerland. 



The practical import of these observations in connection with the 

 climate, to the beekeepers of the United States at least, is that the 

 presence of the disease in a region can not be attributed entirely to 

 the climatic conditions present. It is possible, however, that the 

 climate of a particular region may affect somewhat the occurrence 

 and the course of the disease in that locality. 



Infection in apiaries hap been found to occur at all seasons of the 

 year, but is greatest during the spring. In the studies reported in 

 the present paper (p. 20) infection was greatest in April and May, 

 being greater in these months than in March. Very little of a 

 definite character is known of the infection as it occurs in nature 

 during the winter. Experimentally it has been found that bees are 

 susceptible to infection with Nosema apis at all seasons of the year. 



