46 THE HOUSE FLY— DISEASE CARRIER 



it is the perspiration which attracts the fly. It is 

 hungry and thirsty and wants food and drink. 



The typhoid fly is a diurnal species. It rests during 

 the night. It is not especially fond of the bright sun- 

 shine, and if one stays in direct sunlight he is not often 

 troubled by it. But it revels on the shaded porch and 

 in the lighted house away from the sun's direct rays. 

 It flies into the dimly lighted stable in search of places 

 to lay its eggs, but in absolute darkness and even in 

 darkness which is not absolute it rests immovable. Its 

 resting position seems to be a matter of indifference 

 to it ; it can sleep equally well on the ceiling or on the 

 side wall. It does seem to have some preference for 

 anything hanging perpendicularly, such as an old-fash- 

 ioned rod supporting a candelabrum or a central gas 

 fixture or a window-curtain string, and this observed 

 preference has been taken advantage of by the inventors 

 of certain fly traps which consist of a suspended strip 

 of sticky paper. 



Reverting once more to the feeding of the adult fly, 

 a correspondent whose name the writer has unfortu- 

 nately forgotten described ah instance where he had 

 left a blood-stain on a slide at which a house fly sub- 

 sequently sucked. On examining it afterwards under 

 the microscope, the fly, he found, had taken up all of 

 the red blood corpuscles and had left all of the white. 



Flies are great feeders. Where food is abundant 

 they will suck at it almost continuously or at very brief 

 intervals. As indicated elsewhere, the alimentary canal 

 is comparatively simple, the digestive processes seem 



