6 BULLETIN 92, U. S. DEPARTMENT OF AGRICULTURE. 



presence of a disease among adult bees. From the evidence at hand 

 it seems most probable that the disorder encountered by Donhoff and 

 the one encountered by Zander are one and the same disease. 



Aside from rediscovering the disease Zander has identified the germ 

 causing it as a protozoan (a one-celled animal parasite) and has given 

 to it the name Nosema apis. For the disease he has used the name 

 "Nosema Seuche." This is an appropriate one, as it suggests some- 

 what the nature of the disease. The name "Nosema disease," which 

 the writer suggests as the common name for this disease, is, it will be 

 observed, only a translation of the German name used by Zander. 



The germ Nosema apis gains entrance to the body of the bee by way 

 of the alimentary canal. In the walls of the stomach the growth and 

 multiplication of the parasite take place to an enormous extent, 

 causing the abnormal appearance manifested by the organ. When the 

 disease reaches an advanced stage the stomach is white and fragile 

 and reveals upon a microscopic examination the presence of the para- 

 site in very large numbers. In the spring of the year, especially, 

 many weak colonies show upon examination a high percentage of 

 Nosema-infected bees. Quite often, indeed, in the examinations that 

 have been made of such colonies, 50 to 90 per cent of the bees in sam- 

 ples taken from them were found to be infected with the parasite. 

 It is an interesting and important fact that a very large number of 

 colonies which are strong and apparently doing well are found upon 

 examination to contain at least a small percentage of Nosema-infected 

 bees. 



Nosema apis has a very wide geographic distribution. It has al- 

 ready been encountered in Germany by a number of investigators; 

 it has been found in Australia, Switzerland, and England. The 

 writer has found it in samples of bees received from 27 different States 

 in the United States and in two samples of adult bees from Canada. 



From the facts gathered it would seem that many of the cases called 

 ''spring dwindling" by the beekeepers are caused, in part at least, by 

 Nosema apis. This statement is not by any means to be interpreted 

 as saying that Nosema disease and spring dwindling are always the 

 same. 



It has been demonstrated experimentally that colonies can be 

 weakened and killed by feeding to them material containing Nosema 

 apis. For this and other reasons it seems certain that the disease 

 causes a loss to apiaries, but, for want of sufficient data, the extent 

 of such loss can not now be estimated at all definitely. From the 

 facts at hand one is justified in at least drawing the conclusion that 

 Nosema infection in a colony tends to weaken the colony. Nosema 

 apis is therefore a germ in which the beekeeper is economically 

 interested. 



