178 DR JOHN RENNTE, MR PHILIP BRUCE WHITE, AND MTSS ELSIE J. HARVEY 



queen of an infected Isle of Wight diseased stock survives usually until the colony is 

 extinct. That her survival is in a measure due to the fact that she remains within 

 the hive, is supported by the knowledge we already possess that workers affected 

 with the disease may live for months after they are incapable of flight, and are thus 

 useless to the colony. 



Eegion of Infection within the Bee. 



The mite, Tarsonemus, occupies a very restricted region in that part of the 

 tracheal system which has its origin at the anterior thoracic spiracle. In a well- 

 established case of infection it will be found that, extending inward from this 

 spiracle on -either side indiff'erently, parasites in all stages of development may be 

 present in any part of this portion of the respiratory system, whilst the ill effects of 

 their presence may be seen not only in the region of occupation, but in the muscular 

 tissue to which these extend. It is not an infrequent occurrence in advanced 

 cases of the disease for these wider tracheae to be occupied with mites in closely 

 packed formation. All stages of development occur; e.g. ova, larvae, nymphs, and 

 adults may be found together (figs. 2 and 5). In the smaller branches frequently 

 these are occupied as far as their diameter will permit, when a single individual 

 may be found practically blocking the tube, and sometimes a linear succession of 

 individuals may be seen in such a position. 



The facts which have led us to the conclusion that the occurrence of this 

 organism in the position indicated is to be regarded as causally related to this 

 disease, are to be found not alone in the presence of Tarsonemus in the respiratory 

 system of the bee. There is the universal coincidence of its occurrence in diseased 

 bees. Further, we have been able to trace the development of the disfease within 

 bee colonies from the earliest stages of infection to its complete manifestation in 

 crawling and other definite symptoms. We have observed that the total effects 

 resulting from its development, feeding upon the bee and life generally within it, 

 renders it useless as a working unit, disorganises the social system and eventually 

 shortens the bee's life. Further, these vital effects are accompanied by visible 

 pathological conditions in the tissues. The most obvious of these is a browning or 

 blackening and thickening of the tracheal wall (figs. 6 and 7). The thickened 

 tracheae become progressively hardened and brittle in texture, and certain muscle 

 fibres become atrophied. This latter aspect of the problem is the subject of 

 separate detailed treatment in the paper which follows by Mr White. 



These pathological appearances in an infected bee may be present on both sides 

 of the anterior tracheal system. What we have described is the condition in a well- 

 established instance where breeding has been in progress for some time, but as has 

 been mentioned early stages of infection have been frequently witnessed in which 

 the number of parasites present have been observed to be as few as a single mite and 

 no abnormal condition apparent. 



