1876.] The House Fly. 477 
In the first place, is the common house fly of America the same 
as that of Europe? After a careful comparison of a number of 
individuals from Switzerland with many native examples, no 
difference could be found. How long it has been living in this 
country there are no data to show, and it may have been a pas- 
senger on the Mayflower, or buzzed in the cabin of Captain John 
Smith’s vessel, or even performed its measured flight near the 
ceilings in the ancient town of Pemaquid. 
During the month of August the house fly is particularly 
abundant, and especially so in the neighborhood of stables. On 
placing a fly in a glass bottle, she laid, between six P. M., August 
12th, and eight the next morning, one hundred and twenty eggs. 
They were deposited irregularly in stacks, lying loose in two 
piles at the bottom of the bottle. At eight in the morning of 
August 14th several were found hatched out and crawling about 
the bottom of the bottle. Buta greater number of young were 
desired for purposes of study, and an abundance of food in which 
to rear them. A mass of freshly-dropped horse manure, still 
warm, was placed at an open window in the sun. This, with 
fresh masses added from time to time, attracted numbers of flies 
for three or four weeks succeeding, which laid eggs during that 
Period, so that thousands of young in different stages of develop- 
ment were obtained. 
Immediately after exposing the manure on the morning of 
August 12th, the flies appeared, and, penetrating down, often out 
of sight, deposited bunches of eggs in convenient crevices. The 
egg of the house fly is long, slender, cylindrical, and a little 
Smaller at the anterior end than at the other. It is .04-.05 of an 
Inch long and about one quarter as thick. The shell is so dense 
that the early embryonic phases could not be watched, but enough 
Was seen to enable us to determine that the mode of growth in 
the egg is nearly the same as that of the flesh fly, as observed by 
r. Weismann. 
he eggs thus laid were found to hatch twenty-four hours 
later, In confinement they required from five to ten hours more, 
and the maggots hatched in confinement were smaller than those 
"sared from eggs deposited in warm manure. Certain worms 
reared also in too dry manure were nearly one half smaller than 
those bred in more favorable circumstances. For several days 
di Worms living in this dry manure did not grow sensibly. Too 
tect warmth, but more especially the want of sufficient moist- 
and consequently of available semi-liquid food, seemed to 
