12 HOUSE FLIES. 
Experiments were therefore carried on with kerosene. It was 
found that 8 quarts of fresh horse manure sprayed with 1 pint of 
kerosene, which was afterwards washed down with 1 quart of water, 
was thoroughly rid of living maggots. Every individual was killed 
by the treatment. This experiment and others of a similar nature on 
a small scale were so satisfactory that it was considered at the close of 
the season that a practical conclusion had been reached, and that it 
was perfectly possible to treat any manure pile pconlamaialilse and in 
such a way as to prevent the breeding of flies. 
Practical work in the summer of 1898, however, demonstrated that 
this was simply another case where an experiment on a small scale 
has failed to develop points which in practical work would vitiate the 
results. 
The stable of the United States Department of Agriculture, in 
which about 12 horses were kept, was situated about 100 yards 
behind the main building of the department and about 90 yards from 
the building in which the Bureau of Entomology is situated. This 
stable was always very carefully kept. The manure was thor; 
oughly swept up every morning, carried outside of the stable, and 
deposited in a pile behind the building. This pile, after accumulating 
for a week or 10 days, or sometimes 2 weeks, was carried off by the 
gardeners and spread upon distant portions of the grounds. At all 
times in the summer this manure pile swarmed with the maggots of 
the house fly. It is safe to say that on an average many thousands of 
perfect flies issued from it every day, and that at least a large share of 
the flies which constantly bothered the employees in the two buildings 
mentioned came from this source. 
On the basis of the experiments of 1897, an attempt was niadee 
beginning early in April, 1898, to prevent the breeding of house flies 
about the department by the treatment of this manure pile with kero- 
sene. The attempt was begun early in April and was carried on for 
some weeks. While undoubtedly hundreds of thousands of flies were 
destroyed in the course of this work, it was found by the end of May 
that it was far from perfect, since if used at an economical rate the 
kerosene could not be made to penetrate throughout the whole pile of 
manure, even when copiously washed down with water. A consider- 
able proportion of house-fly larves escaped injury from this treatment, 
which at the same time was found, even at an economical cost, to be 
laborious, and such a measure, in fact, as almost no one could be 
induced to adopt. 
There remained, however, another measure which had been sug- 
gested by the writer in an article on the house fly published in 1895, 
namely, the preparation of an especial receptacle for the manure; and 
this was very readily accomplished. A closet 6 by 8 feet had been 
459 
