290 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



was putting into operation in Canada, we devised a series of cages 

 very similar to his. There was a double wall provided to prevent 

 infestation by eggs that might be deposited on the outside by flies, 

 that would be attracted by the odor of the manure. The cages were 

 supported on four legs about 6 inches high. Part of the apparatus was 

 a galvanized iron pan, in which the seepage from the deposit could be 

 collected for chemical examination. 



Doctor Hewitt referred to the fact that in most of the experiments 

 of this kind that have been performed only one of the two important 

 series of observations had been made. In some cases the manure has 

 been examined to determine the effect on the fly larvae. In such cases 

 the determination of the number of flies emerging was overlooked, and 

 in the other case the number of flies emerging would be determined, 

 and the effect on the larvse would be overlooked. Consequently, in 

 our series of experiments we took both of these factors into considera- 

 tion. On one side of these cages a small opening was provided. 

 Through that opening, from time to time, after the manure was placed 

 in the cage, small samples were extracted. A portion of the samples 

 was used by the chemist to determine the effect of the application, 

 and at the same time the exact mortality of house-flies was determined. 

 These observations were made in more or less extensive series, so that 

 the results could be averaged, and at least an approximately true index 

 of the situation obtained. The number of adult flies emerging was 

 watched in practically the same fashion as Doctor Hewitt's experi- 

 ments. Wire fly-traps were placed on top, and the exact number was 

 determined. We, therefore, had two methods of checking up the re- 

 sults; first, the actual examination of the larvse in the manure to deter- 

 mine the mortality, and, second, the actual emergence of adults. We 

 had the same difficulty that Doctor Hewitt encountered in obtaining 

 a uniform infestation. We found no very satisfactory method of 

 obivating that. We did what we could towards obviating it by 

 mixing the material very well, exposing it first, then having it shovelled 

 up, so as to approximate uniformity of infestation. I should say in 

 this connection also that liberal allowance was made for control cages, 

 that is, every time one of these series of experiments were started, 

 three or more cages were used, in which the manure was not treated. 

 In those cages the same examinations were made as to deaths and flies 

 emerging. In that way, allowance was made for the normal mor- 

 talitj' in the manure. 



We had planned to use all of the substances that had been recom- 

 mended for fly control, and any others, that might be suggested by 

 the chemist. We used salt, borax, copper sulphate, iron sulphate, a 

 number of proprietary substances, creosote, etc. The series of experi- 



