68 The Isle of Wiqht Bee Disease. 



frequently than any othei- part, and weakens and destroys their 

 lining epithelium. The result is that death supervenes. 

 Possibly also toxic substances are produced which hasten the 

 bee's end. 



The disease is eminently one of the adult insect, and the 

 Nosema has been found in the workers, drones, and queen. 

 Occasionally it has been met with also in the larvae and pupse, 

 but is nevertheless not to be regarded as a brood disease. 



Experimental Infection. 



Spores obtained from the bodies of diseased bees have been 

 utilised for infection experiments proving the pathogenic 

 nature of Nosema apis. It has been demonstrated that healthy 

 bees contract the disease if fed with honey or syrup to which 

 spores have been added, or with honey which has come from 

 an infected hive. Further experiments have been conducted 

 showing that healthy bees become infected (1) by contaminating 

 their food with the excrement of diseased bees : (2) by placing 

 bees which have died from the disease among them ; (3), by 

 confining them in cages which diseased bees had previously 

 occupieil ; (4) by allowing them to feed on candy which had 

 been previously utilised by diseased bees. 



It has further been found that spores present within the 

 bodies of bees, which had died four months previously from 

 the disease, still retain their infective powers. So far as is 

 known infection can only take place through the agency of the 

 spores. If, for instance, the planonts and meronts are dis- 

 charged from the alimentary canal of the bee to the exterior 

 they perish immediately, and are incapable of inducing the 

 disease. The problem of hereditary infection is of great impor- 

 tance, but I am not aware that any evidence thereon is yet 

 forthcoming. If the queen is capable of transmitting the 

 parasite to the eggs, the young brood would thus be born 

 infected and the disease passed on from one generation to 

 another, as is known to be the case with the Nosema of pebrine. 

 Investigation along these lines is extremely difficult, but it is 

 none the less urgently needed. 



The Methods by which the Disease is spread. 



There are numerous possible ways by means of which the 

 disease might be spread. Watei' near the hives infected with 

 bee excrement containing the spores of the disease appears to 

 be a most important factor. Honey, pollen, and wax, if con- 

 taminated with excrement containing the Nosema spores, are 

 fertile sources of infection. Infection from one hive ov apiary 

 to another is effected by the sale of diseased swarms, by the 

 robbing of a diseased colony by healthy bees, and by swarms 



