144 THE GYPSY MOTH. 



lead sufficiently for it to pass through the strainers of the 

 pump. When arsenate of lead has been applied in pro- 

 portions of from twenty-five to thirty pounds to one hun- 

 dred and fifty gallons of water, occasional burning has been 

 noticed. This was due to the fact that the lead was not 

 thoroughly dissolved, for in such cases there was a lack 

 instead of an excess of acetate of lead in the mixture as it 

 came from the nozzle. When applied in this strength it 

 is a question whether it is safe to use it in pastures where 

 cattle are feeding or near where poultry are quartered. 



It is evident that spraying with arsenate of lead should be 

 used as an exterminative method only in exceptional cases 

 where there is no danger to animals and where more drastic 

 measures, such as fire, cannot be used. While it will un- 

 doubtedly be useful with many other insects, we would not 

 recommend that implicit reliance be placed upon it unless 

 used early in the season and at a strength of at least three 

 pounds to one hundred and fifty gallons of water. However, 

 it will probably not be necessary to use it at this strength 

 for all leaf-eating insects though some may require a greater 

 strength. Many experimenters have made trials of this ma- 

 terial since the formula was first published in the annual 

 report of the State Board of Agriculture in 1894, but we 

 are not aware that it has yet come into general use in practi- 

 cal out-door work. Professor Fernald's experiments with 

 arsenate of lead on the tent caterpillar indicate that it would 

 be effective with this species in the field when used at a 

 strength of one pound to one hundred and fifty gallons of 

 water. It has given good results when used by him at the 

 same strength for the Colorado potato beetle (Doryphora 

 decemlineata, Say) . Larger quantities have been required for 

 some other insects. 



At first sight it would seem that if it were necessary to use 

 three pounds of arsenate of lead to one hundred and fifty 

 gallons of water, the expense would be prohibitory. Yet it 

 should be borne in mind that when mixed with glucose and 

 properly applied to dry foliage, much of the solution will 

 remain throughout most, or all, of the feeding season. Its 

 application is not, therefore, as expensive as that of poisons 

 which have to be applied three or more times during the season. 



