740 DR JOHN RENNIE, MR PHILIP BRUCE WHITE, AND MISS 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. 
Region 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 indifferently, 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 disease within 
bee colonies from the earliest stages of infection to its complete manifestation in 
crawding and other definite symptoms. We have observed that the total effects 
resulting from its development, feeding upon the bee Jnd 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. 
