G. S. Graham-Smith 
509 
Many deaths occurred between Nov. 7 and 16 when the minimum 
temperature recorded by a thermometer on the grass ranged between 
34° and 18° F. 
The numbers of the flies present were counted at various times, the 
largest number present on one day being 133. Two hundred flies 
probably developed in this cage and 85, or about 40 %, died of the 
disease (Chart 8). 
The flies in this cage had never come into contact with adult flies 
of any species large enough to be stopped by the mesh J inch in diameter 
of the net of the outer cage, though some of the minute diptera may 
have gained access to their cage. Consequently it is quite clear that 
Chart 8. Showing the deaths (columns) from empusa disease amongst house-flies 
confined in cages I and II out-of-doors, and amongst blow-flies in a larger cage. 
The approximate numbers of house-flies present at different times in cage I are 
indicated by a thin line. 
contact with infected adults of M. domestica is not essential for the 
transmission of the disease. We must assume, therefore, either that 
the infection took place in the larval stage before the larvae were placed 
in this cage (three cases had occurred amongst the parents), or that 
infection was carried by very small insects or mites which found their 
way into the cage, or lastly that the spores were carried by the wind. 
Amongst the adult flies, first confined in a large cage and then put 
into cage II, the disease commenced on Aug. 31, but during the next 
23 days only 3 cases occurred. After Sept. 24, however, cases occurred 
33—2 
