PREVENTIVE MEASURES 195 



was killed by the treatment. This experiment and 

 others of a similar nature on a small scale were satis- 

 factory. Practical work during the summer of 1898, 

 however, demonstrated that on a large scale this sub- 

 stance cannot be used to good effect. A large manure 

 pile containing the accumulations of a week or ten days 

 or two weeks and coming from a stable in which four 

 horses were kept was sprinkled thoroughly with kero- 

 sene and an attempt was made to wash the kerosene 

 down to a certain extent with water. The experiment 

 was begun early in April and was carried on for some 

 weeks. While undoubtedly hundreds of flies were de- 

 stroyed 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 through the whole pile of manure. A con- 

 siderable proportion of larvae escaped injury from this 

 treatment, which at the same time was found to be very 

 laborious. It was a measure, in fact, which almost no 

 one could be induced to adopt practically. 



The actual experiments indicated the following facts : 



Eight quarts of fresh horse manure alive with mag- 

 gots were mixed August 5th with two quarts of air- 

 slaked lime. August 7th no larvse were dead, and on 

 August 9th very many had hardened into puparia. 



August 6th, eight quarts of horse manure were thor- 

 oughly mixed with two quarts of gypsum or land plas- 

 ter. No larvae were dead three days later. 



August 7th, eight quarts of horse manure alive with 

 larvae were thoroughly mixed with two quarts of gas 



