MICROBIAL DISEASES OF INSECTS 939 



race of worms free from corpuscles can soon be obtained. This has 

 been found to be the most effective method of combating pebrine 

 Excessive heat saps the vitality of the silk-worm and makes it ready 

 prey to disease. Open air cages result in much hardier, more active 

 worms, 



NoSEMA-DlSEASE OF BEES 



Nosema apis Zander 



HISTORY AND DISTRIBUTION. This disease was apparently first 

 noticed about sixty years ago by Donhoff (1857) who discovered, 

 microscopically, small oval bodies in the stomachs of adult bees which 

 he supposed had died of exposure. He sent some of the bees to Leuck- 

 hart who after examining them -microscopically expressed the belief 

 that the oval bodies were the spores of a fungus. So Donhoff referred 

 to this bee disorder as "Pilzsucht" (fungous disease). In 1909 Zander 

 found similar small oval bodies in the walls of stomachs taken from 

 affected bees and to these organisms he gave the name, "Nosema apis" 

 and for the disease he (1911) used the name "Nosemaseuche." This 

 disease is known in Europe under similar names, " Nosemakrankheit" 

 in Switzerland (Nussbaumer, 1912; Angst, 1913), "Nosemasygdommen" 

 in Denmark (Bahr, 1915). Nosema infection has been reported also 

 from Australia (1910), Brazil (1911), Canada (1914), England (1911), 

 and Germany (1909). White* has found Nosema-disease in samples 

 of bees received from 27 different states of the United States. The 

 distribution in the United States, however, has been hard to determine 

 as beekeepers have not learned to recognize the disease produced by 

 Nosema apis by any one name. " Spring dwindling" and "weakened 

 colonies" were descriptive terms applied by beekeepers to colonies in 

 which Nosema apis was found. The highest percentage of Nosema- 

 infected bees occurred in weak colonies. 



SYMPTOMS. Nosema-disease is an infectious disease of adult honey- 

 bees. It is not particularly malignant in character, being more in this 

 respect like sacbrood than the foulbroods. So far as is known, all races 

 of honey-bees are susceptible. This disease presents only a few symp- 

 toms. These White described as characteristic of the colony rather 

 than of the individual as a unit, since it is the colony as a whole that is 

 of primary interest to beekeepers. 



*White, G. F. Nosema-disease, Bui. 780, U. S. D. A. 1919, pp. 59. 



