THE HOUSE-FLY 



377 



Photo by N. A. Cobb 



Copyright, igio, by the Xational Geographic Magazine 



SIDE VIEW OF THE HEAD OF A HOUSE-FLY 



The same head is shown front view on the opposite page. The end of the proboscis car- 

 ries a sieve through which all the food is strained. The meshes of this sieve allow germs 

 and all btit the largest spores to pass. The house-fly takes in only liquid food. When the 

 fl\ eats solid food, it first spues saliva on it so as to dissolve it. 



