70 THE GYPSY MOTH APPENDIX. 



EXPERIMENTS WITH INSECTICIDES. 



A. H KIRKLAND, A. F BURGESS. 



The dependence that necessarily must be placed upon 

 spraying with insecticides as a means of controlling the 

 gypsy moth in park lands and other places where more 

 heroic measures cannot be employed has led the committee 

 to encourage extensive investigations, under the direction of 

 the entomologist, of insecticides both new and old, these ex- 

 periments having for their object the discovery of poisons 

 that may be used effectively against the gypsy moth, as well 

 as the cheapening of the ones already in use. The discov- 

 ery by F. C. Moulton in 1803 of the iusecticidal value of 

 arsenate of lead, and the reduction of the cost of this poison 

 in 1897 to the extent of over one hundred dollars per ton 

 through joint investigations by the chemist and entomolo- 

 gists, are among the practical results of this work. 



In the course of these experiments a mass of facts has 

 accumulated which it now seems desirable to place on record. 

 While the field of our investigations has been a limited one, 

 the application of the results to other insects gives the mat- 

 ter a wider significance. In considering the value of the 

 insecticides here discussed in relation to insects other than 

 the gypsy moth, the remarkable resistance to arsenical 

 poison shown by this insect should be taken into consid- 

 eration. 



It will be noticed that the experiments in part cover the 

 caterpillar seasons of two years. In such cases the work of 

 1897 has been a continuation, on a larger scale, of that of 

 1896. In the indoor experiments the larvae were confined in 

 suitable cages and supplied daily with freshly poisoned food. 

 In the experiments out of doors the insects were confined in 

 large cloth bags upon branches previously sprayed with the 



