60 THE HOUSE FLY—DISEASE CARRIER 
sugar, bread, water, or milk. Unfortunately he does 
not give the exact dates of this particular observation, 
and it may have been on an October generation, which 
would have hibernated. 
Time Elapsing Betzveen the Issuing of the Adult and 
the Period of Sexual Maturity 
The practical value of the determination of this 
period is very great. If an adult female fly can be 
destroyed before she lays her eggs, we will have killed 
not only the actual fly, but 120 to 600 potential flies 
due in a very short time, and if this female fly can be 
caught in the early spring the table on an earlier page 
will indicate that instead of performing a very simple 
act we have apparently saved the world from almost 
a calamity. From this can be seen the value of fly 
traps. Of course the destruction of breeding places 
is very important, but traps for adult flies are by no 
means to be despised when we have this idea in view; 
and the use of fly traps in the early part of the season 
becomes obviously all-important. The destruction of 
hibernating flies is equally of value; but these subjects 
will be considered in the chapter on remedies. 
So far as the writer knows, the only observers who 
have paid any attention to this very important point 
of the period elapsing before sexual maturity are 
Hewitt (1910) and Griffith (1908). Hewitt states 
that he found flies become sexually mature in ten to 
fourteen days after emergence from the pupal state, 
and that four days after copulation they begin to de- 
