DISPERSAL UNDER URBAN CONDITIONS 



73 



periud of cold weather which checked the Hies' activity. Never- 

 theless, they are of value as indicating the possibilities in the way 

 of the range of Might of flies under normal city conditions. There 

 is no (l(iul)t that given the necessary conditions with regard to 

 wind and elevation above the ground the range would be consider- 

 ably greater than was actually found in these experiments. The 



Map of portion of City of Ottawa showing range of flight of marked flies. 



X Point where marked flies were liberated. Shaded portions A, B, C, etc. 

 indicate breeding places of flies. Numbers in circles indicate number of 

 marked flies recovered at the various points. 



greatest range of flight obtained in these experiments, namely 700 

 yards, represents an actual flight of considerably greater distance 

 than is represented by a straight line from the place of liberation 

 to the point of capture. 



The chief breeding places of house-flies on a large scale are 

 shown on the accompanying map as shaded areas. The western 



