I40 



twenty-seven different states in the U.S.A., and in two samples of 

 adult bees from Canada." 



M'Cray and White, 1918 (6), report with reference to United 

 States that "the disease weakens and even kills colonies. . . . The 

 exact losses from it are not known, but in America they are less 

 than has been attributed to it in some other countries." 



Considerable doubt has hitherto existed as to what degree, and 

 under what conditions, Nosema apis is pathogenic in bee colonics. 

 In the accounts of the occurrence of Nosema given by Zander, he 

 associates as a common feature the presence of dysentery in the 

 affected bees accompanied by a high mortality. The bees die in 

 large numbers within the hive, and also in many cases they leave 

 the hive, dying outside. He attributes the condition known as 

 " May sickness " to Nosema apis, but claims also that there may be 

 a mortality from its presence at any time of the year. In April 

 and May it is mainly young bees which are affected. 



White, in the communication quoted, mentions that in spring 

 especially " manv 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 

 percent, of the bees in samples taken from thtm were found to be 

 infected with the para-ite. It is an interesting and important fact 

 that a very large number of colonies which are strong and 

 apparently doi'g well are found upon examination to contain at 

 least a small percentage of Nosema infected bees." Anderson and 

 Rennie (i) "found it to be present over prolonged periods in 

 healihy stocks," and we have in recent years amply confirmed the 

 observations upon which this conclusion was based. 



Beuhne, 1916(2) records a series of important experiments with 

 stocks harbouring Nosema, the result of which showed that in 

 Victoria, Australia, the parasite had not the virulent character 

 described by Zander. Nosema apis in Australia is described as 

 comparatively harmless during normal seasons. It was found to 

 be present in almost every apiary in Victoria, and even wild bees 

 in trees were affected. 



With a view to obtaining further light upon the conditions 

 under which Nosema apis is pathogenic to hive bees, to what 

 extent and under what conditions the parasite is distributed, we 

 have during a series of years made many systematic observations 

 and experiments.* Typical examples of these are here recorded. 



The Course of Nosema Infection in Observed Cases. 



No. I. History of a Stock Artificially Infected with Nosema 

 apis. — On 4th May 1917,3 stock of Dutch bees (No. 31)^ was placed 

 in a new hive upon a site not previously occupied by bees. This 

 stock covered five frames, and there was a good supply of brood. 

 Five additional new frames with new foundation were placed in 

 the hive. On the same day thirty-two bees were caged and fed on 

 candy contaminated with fresh Nosema spores. Two of these 



' These researches are being conducted with the aid of grants provided 

 by the Development Commissioners through the Board of Agriculture for 

 Scotland. 



' The numbers are apiary references only. 



