HABITS OF THE ADULT FLY 
61 
posit their eggs; that is to say, from the fourteenth 
day from the time of their emergence. The experi¬ 
mental data upon which this statement is based are not 
given in the paper in question, and the writer there¬ 
fore wrote to him for a transcript of his record, from 
which it appears that the flies under observation 
emerged between August 21st and August 28, 1907. 
They were given fresh horse manure daily, and accu¬ 
rate thermometrical readings were recorded for each 
of the following days. Not until September 4th was 
copulation observed, and on September 9th larvae were 
found in the manure. 
Doctor Griffith, in his observations at Hove, found 
that the female flies oviposited ten days after issuing 
from the puparia, and that they could lay new batches 
of eggs at intervals of from ten to fourteen days until 
four batches have been laid. 
It seems to the writer that this period between issu¬ 
ance and sexual maturity must surely be shorter, and 
perhaps much shorter, under midsummer conditions and 
in the freedom of the open air, than that indicated by 
Hewitt and by Griffith. Breeding-cage observations 
are never quite conclusive. 
So great is the practical importance of this point, 
as already shown and as will be elaborated later, that 
the most careful experimental work should be under¬ 
taken under all sorts of circumstances and in very 
many different localities. 
