W. V. Cooper and \Y. a. 15. Walling I7l> 



Tabic VI is a summary of the results of a further series of experiments 

 which were a duplicate of those recorded in Table V, except that sawdust 

 was substituted for sand. 



The figures given for the controls in the experiments on the old and 

 young larvae represent the average mortality in seven control experi- 

 ments, each on 25 larvae. There was, however, a very marked variation 

 in the mortality of the controls themselves, and, as this had not been 

 observed to any great degree before the advent of the Chalcid fly, is 

 to be attributed to the ravages of the latter. The very frequent 

 discrepancies, obtained in this series, in which the mortality in the 

 experiment is markedly lower than in the control, may also in many 

 cases be caused by the Chalcid fly. Comparing the results on sawdust 

 with those on sand, it is at once evident that the toxic agents are not 

 nearly so effective in the case of the former. This is merely a confirma- 

 tion of a result obtained in an earlier series of experiments, but it is 

 of importance as indicating that the high toxic values, which various 

 substances show with sand, would in all probability be reduced in 

 actual practice, owing to the relatively higher adsorptive powers of 

 the fleece. 



The highly poisonous nature of arsenic sulphide, nitrobenzene and 

 creosote is again confirmed in this series of experiment. 



(6) Experiments with emulsions. 



The experiments with emulsions include most of the compounds 

 which previous series of experiments have shown to be fairly efficient, 

 together with some new preparations. 



The actual experiments were carried out as follows: 



40 gms. of sawdust were taken and sprayed with an emulsion con- 

 taining 1 % of the active constituent. Sufficient liquid was used to 

 make the sawdust just damp, the sawdust being well mixed during the 

 spraying. Fifty larvae were then placed in the sawdust, in a glass 

 jar, the mouth of which was covered with a piece of muslin. The 

 results are given in Table VII. 



Satisfactory results have only been given by two of the preparations, 

 namely those containing safrol, and /3-naphthol and sulphur. The 

 general results are not nearly so good as those given by the powders 

 and the series was therefore not extended further, except that some of 

 the same poisons were tried at a higher concentration. The whole 

 of these experiments were, however, so badly infested with the Chalcid 

 fly that the results were useless. 



12—2 



