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 an 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 
