NOSEMA-DISEASE. . 47 



the parasites may be subjected to fermentation or putrefaction or 

 both. These factors would tend to destroy the germ, although its 

 resistance under these conditions is again considerable. 



It has been suggested by some writers that drops of water from 

 showers or dew on vegetation about the apiary might become con- 

 taminated by excrement present and thus be a source of infection. 

 This would seem to be a possibility. The extent, if any, to which 

 the disease is thus transmitted is not yet known. 



Should the excrement of infected bees faU on the soil, the chances, 

 ordinarily, would be slight that the contained parasite would reach 

 a bee and infect it. Should the surface water resulting from rains 

 carry the germ into a water supply used by bees, the chances of 

 infection from the soil as a source would be considerably increased 

 thereby. If the bodies of dead Nosema-infected bees were washed 

 into the water supply, contamination of it might follow. 



In estimating the probable danger of infection from the bodies of 

 bees dead of Nosema-disease, the possibility of the parasites being 

 destroyed after the death of such bees through putrefaction (p. 35), 

 drying (p. 31), or other means must be given due consideration. 



The facts which are known concerning Nosema-disease indicate 

 that th0 disease may be transmitted: (1) Erom the infected bees of 

 a colony to healthy bees of the same colony, and (2) from the infected 

 bees of a colony to healthy bees of another colony. When the infec- 

 tion is transmitted from infected bees to noninfected ones of the 

 same colony, the question arises as to whether such infection takes 

 place while the bees are within or without the hive. The fact that 

 the heaviest infection with Nosema apis occurs in the spring of the 

 year, and the further fact that only a comparatively few colonies of 

 the apiary are likely to be heavily infected, support the tentative 

 conclusion that the transmission of the germ takes place within the 

 hive rather than from a source outside of it. 



There are facts concerning the disease, however,- which indicate 

 that the infection under certain circmnstances is not readily trans- 

 mitted within the hive. For example, colonies which in the spring 

 of the year show less than 50 per cent of Nosema-infected bees are 

 likely to recover from the infection without treatment, showing that 

 under such circumstances the infection is not transmitted within the 

 hive, to any great extent at least. The fact that a colony may contain 

 a small percentage of Nosema-infected bees throughout the year 

 and not become heavily infected at any time furnishes further evi- 

 dence that Nosema infection does not always spread with rapidity 

 within the hive. It has been found that colonies becoming heavily 

 infected through experimental inoculation in June, July, or August, 

 are practically free from the infection within six weeks from the date 

 of inoculation, showing again that the infection is not always readily 

 transmitted within the hive. 



