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



exhibits, however, totally different external symptoms and a distinct pathology in 

 the individual bee. Collateral work by G. F. White (1918) in America supports 

 this latter conclusion. The problem of the cause of Isle of Wight disease until now 

 has thus been left unsolved. 



Characteristics of the Disease as Hitherto Observed in the 



Colony as a Whole. 



The diagnosis of Isle of Wight disease from " symptoms " has always been a more 

 or less unsatisfactory procedure. Hitherto the presence of the disease in a colony 

 has not been recognised until infection has been well advanced in a high proportion 

 of the bees. At this stage of disability, the most usual features recognisable by the 

 bee-keeper are inability to fly, accompanied sometimes with imperfect folding of the 

 wings. In fine weather a proportion of the affected bees may leave the hive and 

 crawl around, climbing grasses, etc. Later, in the cooler part of the day, they 

 commonly collect in small clusters. Such bees are lost to the colony, since they do 

 not return to the hive, and in any case are useless as workers at this. stage. Some- 

 times large numbers come out and loiter on the alighting board in the sun, returning 

 to the hive when the sun has gone. Associated with the incapacity for flight there 

 is usually a congested condition of the colon. In certain circumstances dysentery 

 may be present as a complication. Most of these symptoms may be present in 

 other disorders of a more temporary kind, and we have been accustomed to regard 

 as true Isle of Wight disease only those cases where such visible conditions, once 

 commenced, continued in the stock, affecting succeeding broods of bees. There is a 

 continuous mortality from the disease. Bullamore and Malden regard no single 

 symptom as characteristic, and state that " the only essential feature is 'the death of 

 large numbers of bees." 



The association of the causative organism now to be considered will henceforth 

 afford an exact means of diagnosing the disease, which we suggest should now be 

 designated Acarine disease. 



Discovery of the Causal Agent op Isle of Wight Disease. 

 The present and following papers announce the discovery of a parasitic organism 

 invading the respiratory system of the adult bee, which after exhaustive investiga- 

 tion we now bring forward as the causal agent in this disease. This parasite is a 

 hitherto undescribed mite, identified by one of us (J. E.) as belonging to the genus 

 Tarsonemus. It was first observed by one of us (E. H.) in December 1919, when 

 a single example was found in a portion of trachea present in a preparation, per- 

 manently preserved, of the thoracic glands (fig. l).* It was significant of the fuller 

 knowledge of the disease, soon to be attained, that the bee in which it occurred was 



* This find was followed np at the time by a systematic search for mites in hives, npon frames, bees, etc, which 

 resulted in the finding of no fewer than five different species in definite association wiLh bees, dead and alive. (J. K.) 



