32 THE HOUSE FLY—DISEASE CARRIER 
and he found that after gorging themselves they usually 
climbed up the sides of the cage and moved from place 
to place, often stopping to rub one leg against another 
or to clean themselves by passing the legs over their 
heads and wings. At intervals he noticed that they 
sat still and regurgitated large drops of liquid from 
the tips of their beaks. He showed that the drops 
gradually enlarged until they were about equal in size 
to the head of the fly. Sometimes the drop was de¬ 
posited, sometimes slowly withdrawn, and this occurred 
several times. When disturbed, the drops were de¬ 
posited or withdrawn with great rapidity. Flies were 
often seen to suck up the drops deposited by other flies. 
It is these regurgitated drops which make the larger 
stains upon a window covered with fly-specks. 
Attention should be called to the shape of the com¬ 
pound eyes of the fly, and it will be noticed that they 
are so situated that a fly can see in all directions at the 
same time. 
Difference in Size of Adults 
There is a considerable difference in the size of the 
adult winged flies, but this by no means signifies that 
small adult flies grow into large ones. This is a wide¬ 
spread popular fallacy. The writer once in his younger 
days attended a meeting of the Philosophical Society 
of Washington to listen to a paper by the late C. V. 
Riley on some phases of insect life, in the course of 
which the house fly was incidentally mentioned. With 
his entomological training, he was amazed in the dis- 
