752 DR JOHN RENNIE, MR PHILIP BRUCE WHITE, AND MISS ELSIE J. HARVEY 



W. No. 2. — Tarsonemus has been known to be present in this stock since the 

 beginning of August. It is now wintering, and no signs of disease have ever been 

 observed. 



No. 24. — Infection from near the end of June to the beginning of September and 

 not found later. Stock has not prospered. 



Re. No. 1. — Slow progress of infection. No signs of disease ; stock wintering. 



Re. No. 2. — Infection took place within three months, and the progress very slow. 



R. No. 2. — Proximity to two heavily infected stocks is a feature of this case. 

 Infection probable within a month, rose in two months about 97 per cent., and the 

 stock has dwindled to very small dimensions. 



W. No. 3. — Known to be infected for two months before any suspicious signs 

 appeared, and these only slight in character. The stock has done well, but its 

 possible survival till spring is doubtful. 



Table III. 



The bees referred to in the foregoing table were all obtained from stocks 

 recognised as suffering from the disease. The bees had been preserved on the dates 

 mentioned. The results confirm the presence of Tarsonemus in diseased bees over 

 the four years 1916-20, and also make clear the important fact borne out by the 1920 

 examinations that the breeding of Tarsonemus goes on throughout the whole year. 



General Considerations. 



For a sound appreciation of the foregoing records, and particularly of their 

 diversity in detail, it is necessary that the various factors likely to be present 

 affecting the course and culmination of the epizootic within the bee colony 

 should be clearly set forth. 



A colony of bees consists normally of a population which particularly in summer 

 is undergoing a continuous and relatively rapid change, both as regards its con- 

 stituent members and also as regards the total numbers. Daily during the working 

 season there is both a steady mortality and a steady increase. This latter depends 



