352 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



final word, nevertheless, cannot be spoken until incontrovertible 

 evidence has been gleaned from further experimental work. 



Summary of Data and Results 



General Summary 



1. In a city, the built-up portion of which was about one and one- 

 half miles square, 387,877 marked flies were liberated from four 

 release points. The release points were so located as to give an idea 

 of the possible spread of flies from breeding areas variously situated in 

 relation to the city as a whole and each representing different condi- 

 tions. 



2. A total of 1,056 flies were recaptured at seventy-eight stations 

 which varied from 50 to 3,500 yards from the point of release. This 

 was the greatest distance at which recaptures were attempted. 



3. The results indicated that under conditions which are favorable 

 flies may spread from any given breeding ground to all parts of a city, 

 even one of considerable size. Also that they may not only cross 

 a city offering abundant feeding and breeding areas, but may even leave 

 it and cross open country to points considerable distances beyond its 

 hmits. 



4. The full possibilities of dispersion were not determined due to the 

 relatively small size of the city, but the fact that flies spread from 

 release points on one border to points on the opposite side indicates a 

 possible radius of 2,333 yards (one and one-third miles) and that 

 flies even traversed the entire city and crossed open country to points 

 beyond justifies the belief in a still greater radius. The actual 

 territory over which flies were recovered in the city was about two 

 square miles, but possible dispersion over a territory of from five to 

 more than twelve square miles was indicated. 



5. While the results of this investigation are of general application 

 to Montana cities and towns, it is problematical to attempt to apply 

 them to more thickly populated areas where sanitary measures are 

 more easily and more generally applied. Control measures mean 

 fewer flies and fewer feeding and breeding areas, but does this mean 

 a larger or a smaller radius of dispersion for what flies there may be? 



Summary of Deductive Results 



1. House-fly dispersion (the spread of house-flies from their breeding 

 grounds and the factors controlling it) may be considered as a problem 

 concerning short periods of time or as one of seasonal significance. 



2. The factors which control dispersion are mainly, if not entirely, 

 external stimuli. As regards their effect on the radius of distribution,, 

 these stimuli may be termed, inciting {e. g., odors from feeding and 



