10 



Circular 218, U:S. Dept. of Agriculture. 



anywhere within this territory lead to the conclusion that the efforts 

 to ascribe serious results to this organism are misleading. That a 

 colony of bees may be weakened by heavy artificial infection of the 

 organism is by no means proof that the organism under usual con- 

 ditions of the apiary ever leads to the death of a colony. In fact, so 

 far as can be determined from the present evidence, it is doubtful 

 whether a colony of bees free to fly is seriously affected by this 

 parasite. Petersen (13) observed many bees infected with Nosema 

 spores, but observed no pathogenic symptoms. 



The effects of food containing material which the bees are unable 

 to digest (15) , leading to the ordinary conditions of dysentery, and of 

 various other environmental factors in permitting or encouraging the 

 growth of the organism have not been adequately studied. Zander 

 (22, 23) attributed an infectious dysentery to this organism, as dis- 

 tinguished from the ordinary dysentery with which beekeepers have 

 long been familiar when the bees are wintered badly. It remains to 

 be established whether conditions of ordinary dysentery are favorable 

 to the growth of the organism, and whether it in turn causes certain 

 additional conditions favorable to the death of the bees. Without 

 wishing to underestimate the damage from Nosema apis alone, it is 

 exceedingly doubtful whether it is the cause of a serious disease 

 of bees. 



Various names have been given to the disease caused by this 

 organism, such as Nosema disease (a translation of Zander's name 

 Nosemaseuche) , Microsporidiosis (actually suggested as a substitute 

 for the name Isle of Wight disease) , nosemosis, infectious dysentery, 

 and Nosemakrankheit. 



Distribution by years. — During the years 1912, 1913, and 1921 

 special requests were sent out to beekeepers asking for samples of 

 adult bees that appeared to be suffering from some disorder. This 

 fact accounts for the larger numbers of samples received during these 

 years. Table 2 shows the results of the examinations of samples 

 received, so far as the presence of Nosema apis is concerned : 



Table 2. — Samples of Nosema disease, by years. 



Year. 



Nosema 

 present. 



Nosema 

 doubt- 

 ful. 



Nosema 

 absent. 



No diag- 

 nosis lor Total. 

 Nosema. ' 



1910 





 1 



35 



11 

 

 5 

 6 



20 

 8 

 5 

 9 



15 





 

 

 

 

 1 

 •i 



2 

 1 

 

 

 2 



6 

 7 

 19 

 52 

 14 

 16 

 31 

 21 

 20 



13 

 21 

 16 

 15 

 9 

 21 

 4 

 5 

 1 



19 

 29 



100 

 78 

 23 

 43 

 43 

 48 

 30 

 38 

 32 



202 



1911... 



L912 



L913 



lull 



©15 



L916 



1917 



L918 



L919 



27 fl 

 22 1 

 14') 6 



1920 



1921... . 



Total 



145 



V 



414 IIS 



685 



