202 THE CANADIAN ENTOMOLOGIST. 



ingredient in this compound, is present in very variable proportions, which 

 is just what one might expect in a waste product. Sometimes it forms 

 less than twenty per cent, of the mixture, while other samples will contain 

 more than forty per cent. It is associated chiefly with lime and coloring 

 matter. The arsenic present is in a very fine state of division, and inti- 

 mately mixed with the lime and other ingredients, forming a very fine 

 powder. It is much more soluble than Paris Green, and hence more liable 

 to scorch the foliage, while its very variable strength makes it uncertain in 

 its effects. For these reasons London Purple is not likely to take the 

 place of Paris Green as an insecticide, which, when unadulterated, is 

 nearly uniform in its composition and effects. An artificial mixture of 

 arsenic and lime of uniform strength and colored could be supplied at 

 about the same price, and would be more reliable than London Purple ; 

 but owing to the more ready solubility of the arsenic in this form and its 

 caustic character, it is apt, unless used with much care, to destroy portions 

 of the tissues of the leaves on the plants to which it is applied, making 

 them appear as if scorched or burnt. 



Experiments have been carried on for the past two seasons at the 

 Agricultural College at Lansing, Michigan, by Prof. A. J. Cook, on the 

 use of London Purple as a remedy for the Codling Worm. Early in the 

 summer, while the fruit was quite small, some crab apple trees were 

 syringed thoroughly with London Purple mixed with water, and it is 

 claimed that the poison, which, when the water has evaporated, forms a 

 thin coating on the fruit, either prevents the Codling Moth from depositing 

 her eggs or else poisons the young larvEe as soon as they are hatched, the 

 result being the saving of a very large proportion of the crop from injury, 

 while other trees near by not similarly treated bore very wormy fruit. It 

 is also said that, as the fruit approaches maturity, the most delicate 

 chemical tests fail to show a trace of the poison. I scarcely think that 

 the experiments yet tried in this direction have been sufficiently extended 

 to warrant any general conclusions being based on them, and provided it 

 were proven that this remedy was a certain and safe one, the popular 

 prejudice against applying such virulent poisons directly to the fruit we 

 are to eat would be so strong as to prevent the general use of any such 

 means. Indeed, were it generally known that the apple growers of any 

 district were in the habit of applying arsenic in any form directly to their 

 fruit, it would interfere very seriously with their sales, and it is doubtful if 

 apples so treated would find a ready market anywhere. 



