74 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



this mixture in ten Imperial (13^^ wine or U. S. A.) gallons of water, 

 and in this suspend a sack containing ten pounds of crystal copper 

 sulphate. vStir occasionally until the copper sulphate is dissolved. 

 This poisoned stock solution of copper sulphate is used in the same 

 manner as a straight solution of copper sulphate, diluted and added to a 

 lime solution that is equally diluted. This formula in the 4-4-40 and 

 5-5-40 used on the potato and in the 3-10-40 used on the apple, has 

 given satisfaction wherever used in the prouer amounts per acre. In 

 certain cases where only one-half as much spray as should be applied 

 was used or where the application was delayed until the potato beetle 

 larvae were more than half grown, some complaints were made, but where 

 instructions were followed excellent results were obtained. 



The mixture of equal parts of super-fine quick re-acting white arsenic 

 and hydrated lime is now on the market in Nova Scotia, in two pound 

 packages. 



We have recently developed a method of using white arsenic in one 

 of the copper arsenic dusts. Following the success of the dust made up 

 of dehydrated copper sulphate, hydrated lime and arsenate of lime 

 both in pest control and low cost, an opportunity developed of still 

 further reducing the cost by using burned lump lime in place of hydrated, 

 finely crv^stalized copper sulphate in place of the dehydrated, and white 

 arsenic in place of arsenate of lime. This formula reduces the already 

 low cost of copper arsenic dust by around two dollars per hundred 

 rounds. 



During the past season, we made around one ton of the white arsenic, 

 lump lime, crystal copper sulphate dust and the results from it were so 

 satisfactory that the Cooperative Fruit Companies intend manu- 

 facturing an experimental batch of fifty tons, for their members testing 

 in 1922. Whether the manufacture of this dust gravitates to insecti- 

 cide concerns, cooperative companies or large growers, the saving will 

 be the same since the method allows them to use the white arsenic 

 direct, the reactions that go to make it safe being obtained by only a 

 trifling manipulation. 



We have found it most important to get white arsenic that is adapted 

 to our needs. There is, as we have already stated the widest difference 

 in quickness in reacting, fineness and texture in different lots of material. 

 Fineness does not alwa\^s indicate speed in reacting. For all of the 

 purposes that I have outlined, a quick reacting material is superior; 

 it must also be of even fineness and capable of passing a screen of 200 

 meshes to the inch or finer. Some of our most satisfactory samples 

 have, independent of fineness, shown a fine texture or fluffiness that is 

 usually an indication of a quick reacting material. So far as our work 



