DESTRUCTION OF LARVAE WITH INSECTICIDES 321 



securing for the horses the rest they need and usually deserve, the 

 value of which rest is evident. 



I am informed by chemists that it is doubtful whether the 

 admixture of a small (|uantity of chloride of lime would seriously 

 affect the manurial properties of the stable-manure. Exact 

 information on this point, however, has not yet been secured. 



Howard (1911) records the results of experiments with 

 kerosene as an insecticide. While it was found that on a small 

 scale if eight quarts of horse-manure were sprayed with one pint 

 of kerosene which was afterwards washed down with a quart of 

 water all the larvae were killed ; on a larger scale it was not 

 wholly successful; "a considerable proportion of the larvae escaped 

 injury." Even had all the larvae been destroyed the cost of the 

 treatment wM)uld be prohibitive. 



Herms (1911) suggests that " w^ hen the manure pile can be 

 spread out to a depth of about half a foot it may be drenched 

 with a distillate petroleum, which possesses a high flash point, 

 i.e. does not ignite easily, and has the necessary insecticidal pro- 

 perty. The petroleum oils, sold as proprietary compounds on the 

 market as 'miscible oils,' 'spray emulsions,' and the like, should 

 be applied at the rate of one part of the oil to ten parts of water. 

 U kerosene oils of a low flash point are used about stables and 

 out-buildings the danger from fire must be considered." 



On account of the danger incident to its use and the cost of 

 the treatment, apart from the tact that its employment is not 

 supported by our experimental results, one is compelled to hesitate 

 in recommending the general use of kerosene or paraffin oil for 

 the destruction of fly larvae. 



Forbes had a series of experiments carried out in Illinois, U.S.A., 

 on the destruction of the larvae in manure heaps. These are 

 recorded by Howard (1911). In one series hydrated high calcium 

 lime was used. When three pounds of this lime were mixed with 

 fifteen pounds of horse-manure, ninety-four per cent, of the larvae 

 were killed; two pounds of lime mixed with twelve pounds of 

 manure killed sixty-nine and one-tenth per cent, of the larvae : 

 four pounds mixed with twelve pounds of the manure killed sixty- 

 one and three-tenths per cent. The diminished percentage in the 

 last two experiments was accounted for by the fact that the larvae 



H. H.-F. 21 



