CHAPTER VII 

 DISTRIBUTION AND CONCENTRATION OF FLIES 



It might be supposed that a strongly developed house 

 haunting proclivity would not be consistent with a 

 disposition to roam far afield from the locality of birth. 

 Many clever experiments have been made with marked 

 flies released and recaptured within measured distances 

 and times. After an immensity of pains taken, very 

 little profitable knowledge has been arrived at thereby. 

 Little of what we really want to know is indicated by 

 such a fact as that, out of hundreds or of thousands of 

 marked flies released, one per cent was recaptured at 

 spots as remote as a mile within two or three days, of 

 by such a fact as that a large percentage should be 

 observed to remain within a more limited home circuit. 

 The variable factors of temperature, wind, sunshine 

 and rain inevitably tend to discredit the reliability of 

 the observed results following any such experiments. 



Close observations of the habits of the house-fly re- 

 veal the very appurtenant fact that the movements of 

 newly-hatched flies, for their first six or seven days' 

 active life, differ from those of a more mature age, when 

 the breeding instinct has grown strong. The latter 

 are disposed to locate themselves for the rest of their 

 lives in and about one attractive spot, and they are' in- 

 disposed to fly high above ground or to travel far, 



