204 MISS ELSIE J. HARVEY ON 



Experiments. \ 



1. To Discover ivhether Bees hecome infected before Emergence froti y^ QqUs, 



Early iu the spring of this year a few frames of brood from a badly affect, g^ stock 

 were placed in an incubator ; 155 of the bees which hatched out were examine^tij -^ith 

 the result that only the tube on one side in one bee was found infected withv^ ^j^g 

 parasite. This evidence, as far as it goes, therefore, does not exclude the possibiK'^^y 

 that mites may enter the cells and invade a bee's body before it emerges from ti\-^g 

 cells, but its rarity, as shown here, would seem to suggest that at best it is only^^ 

 an incidental occurrence, and is not one of the regular ways in which infection' 

 is conveyed. 



2. To Discover the Stage or Stages which occur normally outside the Bee. 



{a) By examination of the individuals in the tubes, in cases where the infection 

 had only newly commenced, it is often found that an ovigerous female with a few 

 eggs in different stages of development are the only parasites present. This would 

 suggest that the migratory stage of the parasite is the fertilised female. In such a 

 case migration of the male does not seem to be necessary, although, as is seen from 

 the results of the experiments recorded, they leave the body of the dead bee. 



(6) Equal numbers of living and of dead bees were placed in separate petri 

 dishes, and these were kept as nearly as possible at the temperature of the hive. 

 The dishes were examined microscopically at intervals of from two to forty-eight 

 hours. Fifteen such experiments were carried out, with the result that only 10 

 mites, all of which were females, were recovered from tlie living bees : one of these 

 was alive and active. As many as 75 (62 female and 13 male) were found in the 

 dishes containing the dead bees. Of the 62 female mites, 8 were alive and active, 

 while all the 13 males appeared dead. None of the females seen outside the bee 

 were carrying fully developed ova. It would appear from these experiments that 

 migration of both sexes takes place from the dead bee. 



3. An Endeavour to produce Infection artificially. 



{a) By contact with living sick bees. 



These experiments were carried out in small queen cages. The bees were fed 

 with soft candy and kept as far as possible at the temperature of the hive. The 

 infective bees were in five cases crawlers picked up from in front of the hive ; in two 

 cases the bees were caught on entering the hive of a stock which was known to have 

 a high per cent, of infection, and in the remaining three, the bees were taken from 

 the frames of a sick stock. Virgin queens headed six of the experiments. 



In these experiments the healthy bees were maintained iu contact with sick bees 

 for periods extending from four to seventeen days. In only one case was a positive 



