HABITS -JJ 



Howard (191 1, p. 54) says that in the summer of 1910 Hine 

 made an effort to determine the distance flies can travel by 

 liberating 350 flies, each marked with a spot of gold enamel on 

 the thorax and on each wing. The marked flies were only 

 found about dwellings a short distance off up to the third day. 

 Howard also quotes Forbes who states that his experiments show 

 that flies can spread naturally for at least a quarter of a mile. 



Hewitt (191 2, p. 2) carried out experiments on this subject 

 at Ottawa, the flies being liberated from a small island in the 

 Rideau River, which runs through a part of the city. The flies 

 were obtained from pupae and " were marked by spraying with 

 rosolic acid in 10 per cent, alcohol, applied by means of a fine 

 spray. This method is simple and harmless and reliable as a 

 means of detection. The presence of a marked fly on a sticky 

 fly-paper is indicated by its producing a scarlet colouration when 

 the paper is dipped into water made slightly alkaline." " The 

 papers were placed in as many as possible of the houses in the 

 neighbouring districts on both sides of the river. The papers 

 were placed chiefly in the kitchens of houses and were collected 

 one or two days after being distributed. They were usually 

 collected in that portion of the district towards which the wind 

 had been blowing from the island, as it was found that the wind 

 was the chief factor in determining the direction of distribution 

 from day to day. The 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 observations which have been quoted relate to the 

 . flight of house-flies in the open away from houses and show 

 that under favourable conditions and assisted by the wind 

 they can fly about a mile and frequently travel half-a-mile. 

 It is not impossible, however, that they may travel still greater 

 distances. As Hine says: "It appears most likely that the 

 distance flies travel to reach dwellings is controlled by circum- 

 stances. Almost any reasonable distance may be covered by a 

 fly under compulsion to reach food or shelter. When these are 

 at hand the insect is not impelled to go far, and consequently 

 does not do so." 



