84 



the moat certain evidence of the presence of Nosema apis is afforded by 

 finding the characteristic spores. Unfortunately these are not always 

 present. . . . Our observations show that during the warmer months the 

 parasites often do not reach the spore stage, but seem to kill the affected 

 bees before this stage is reached " (p. 48 of 1913 report). 



Our evidence is unfortunately rather contradictory, as we have been 

 able to find abundance of spores in the months of May, June, July, August 

 and September as readily as in other months. Our illustration of a section 

 of a chyle-stomach in which every visible cell is heavily infected with 

 spores (PI. I. fig. 2) is from a summer bee. And we are a little doubtful 

 of any heavy mortality resulting entirely from infection in the period of 

 the bees' maximum vigour, at an early stage of the parasites' growth. This is 

 especially so since we have found, throughout the summer, living bees 

 without any obvious signs of disease, which proved to be very heavily 

 infected with spores. Further it is claimed that the chyle-stomach of the 

 bee is, even under normal conditions, constantly shedding and renewing 

 its secreting epithelium. 



Pulping Expekiments. 



The routine of examining individual bees for Nosema diagnosis, although! 

 valuable and most reliable as regards the single bee in question, has several 

 serious disadvantages. The first of these is due to the amount of time 

 required to examine thoroughly even one bee, and the second, which 

 depends upon this fact, is that one is led to base conclusions regarding 

 a whole stock upon the results obtained from the examination of relatively 

 insignificant numbers. A small sample of bees taken at random from a 

 stock does not correspond, say, to a sample of a homogeneous fluid or solid 

 substance. 



This difficulty has been largely overcome in our later work by the 

 introduction of the method of pulping collections of bees designed for 

 examination for the presence of Nosema spores. Our method is simply to 

 cut off the abdomens of the bees, letting them drop into an ordinary mortar. 

 They are then gently pulped in sufficient water to render the contents fluid. 

 Sometimes we have removed the alimentary canals from behind the honey 

 sac and teased these collectively in a little water in a large watch-glass. 

 Samples of the resulting fluid in either case are taken up with a pipette, and 

 if Nosema spores are present in the pulped preparation, they are usually found 

 in the first drop examined. Our first experiment of this nature was as 

 follows. ' • 



