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XXIX. 



(3) Isle of Wight Disease in Hive Bees — Experiments on Infection with Tarsonemus 

 woodi, n. sp. By Elsie J. Harvey. Communicated by Dr John Rennie. 



(Read November 1, 1920. MS. received November 27, 1920. Issued separately Marcli 25, 1921.) 



Introductory. 



The following experiments and observations have been undertaken with a view 

 to discovering the means by which Tarsonemus is transmitted from one bee to 

 another. It is obvious that a stage of the parasite exists outside the bee, and that 

 there are also several possibilities (which may occur). One is the passage from bee 

 to bee within the hive either directly or through the medium of frames or combs. 

 Another, also within the hive, where the mites may in wandering upon the frames 

 enter the cells and invade the body of the developing larvae or pupae, and in this way 

 be present in the bee when it hatches. A third possibility is that whereby foraging 

 infected bees may leave the mite upon flowers, vegetation generally, drinking 

 grounds, or other situations, to be picked up later by other bees chancing to 

 visit these. Crawling or dead bees may in a similar manner prove to be a source 

 of infection through the contamination of the ground about the hive or of the 

 actual hive itself. 



Exhaustive investigation of this last possibility is a somewhat diflicult matter, 

 for which no opportunity has yet been found, and owing to the short time at my 

 disposal it has been set aside in favour of the more promising one of infection by 

 direct contact between bee and bee. 



Review of Former Experiments. 



The conclusions arrived at from former experiments published before the organism 

 was discovered, pointed to the probability of the disease being of an infectious 

 character. This was shown when, e.g., a frame of infected bees, say of a black colour, 

 were placed in a healthy stock of Italians, and in due course the disease became 

 evident in the yellow bees. It is admitted, of course, that only a probability is 

 indicated in such an experiment. 



What evidence we have from experiments with brood, in which frames of sealed 

 brood of bees of one colour from an infected hive have been placed in the hive of a 

 healthy stock of a different colour, points to the disease being an affection of adult 

 bees only. Many experiments of this nature have been tried, and the results have 

 been oii the whole uniformly in favour of the view that brood hatched out under 

 such circumstances was free from disease. 



