
INSECTS AND DISEASE 
The danger of transmission of disease by flies increases with the 
extent to which human excreta are exposed to the access of flies and 
with the duration of the warm season, which favors fly breeding. 
Danger is not confined, however, to unsewered rural districts or to 
the South. The Association for Improving the Condition of the Poor 
in New York City made a careful study of the relation between flies 
and infant diarrhea in the summer of 1914. Nearly 1000 infants 
were carefully observed, half of them being in ordinary homes and 
half in homes where special efforts were made to protect the infant 
and his food from flies. The homes studied were classified accord- 
ing to their general cleanliness and according to their freedom from 
flies. In the homes where flies were abundant, 1.9 times as many 
infants suffered from summer diarrhea as in the homes protected from 
flies, and 1.8 times as many were attacked under dirty conditions as in 
the clean homes. Where both factors were combined, in dirty and 
fly-ridden homes, there were 2.4 times as many infants who suffered 
from diarrhea as in the clean and fly-protected tenements. 
PREVENTION OF FLY-BORNE DISEASE 
The practical methods of controlling the spread of disease by flies 
fall under four main headings: the prevention of fly breeding, the 
destruction of adult flies, the protection of human discharges from 
access of flies, and the protection of food by screening houses and 
covering the food itself. 
PREVENTION OF FLY BREEDING 
The usual methods employed in fighting the dangerous Muscidz 
are really of little avail. Sticky fly-paper, wire flytraps, and poisons 
will undoubtedly kill a large number but infinitely more are breeding 
where they came from. Screening our windows and doors will un- 
doubtedly keep many out but it is not pleasant to live in a cage. 
Furthermore, the people from whom we buy our milk and other 
food-stuffs may not beso careful. The only thoroughgoing method 
is to stop the trouble at its souree—prevent fly breeding. The 
adults we kill cannot thereafter breed, but they have probably done 
so before and many of their companions are sure to escape altogether. 
If we could do away with the breeding places, or make them unfit 
for fly larve, or keep adult flies away from them, the thing would be 
done. Nearly all the books and lecturers say that this is easy. It is 
well to be optimistic but better to recognize the whole truth. It 
cannot be done easily. 

