PREVENTIVE MEASURES 
Success will also to a great degree depend upon the 
applicability of Doctor Hewitt’s isolated observations 
upon the period between issuance and sexual maturity 
to other seasons and to other parts of the world. 
Screening 
Three years ago I made an attempt to estimate the 
amount of money spent annually in screening houses 
in the United States. As close an estimate as could 
conscientiously be made seemed to indicate that more 
than $10,000,000 are spent every year for this kind 
of protection against flies and mosquitoes. In fly-rid¬ 
den localities the expense is undoubtedly justified, since 
the majority of the flies are kept out by careful screen¬ 
ing. No system of screening, however, seems to be so 
perfect as to keep them all out. They get in, one way 
or another, in spite of care; even where double doors 
are used they eventually gain entrance. In the summer 
time, in country houses having large open fireplaces 
disused during warm weather, flies undoubtedly come 
down the chimney, and it is necessary under those con¬ 
ditions to arrange a wire screen before the open fire¬ 
place in such a way that it can easily be removed on a 
cold day. 
The whole expense of screening, however, should be 
an unnecessary one, just as efforts to destroy flies in 
houses should be unnecessary. Their breeding should 
be stopped to such an extent that all these things would 
be useless. 
