SPKAYING. 55 



other matters relating to team traffic. The police outposts 

 were inspected by Professor Shaler of the committee in 

 charge of the work, by the director and by the superintend- 

 ents, and it was soon seen that the method was impracti- 

 cable. A perfect cordon could not be maintained, and the 

 results obtained were not proportionate to the expense 

 incurred. At the end of two weeks the plan was abandoned. 

 In the mean time some good had been done by destroying 

 caterpillars found on vehicles, and by gaining a knowledge 

 of the destination of the teaming between badly infested 

 localities and towns outside of the known infested district. 

 This knowledge was utilized in the fall inspection. 



Spraying. 



In April the director's office was removed to Maiden, at a 

 point near the centre of the infested region and having better 

 railway communications with the surrounding towns. More 

 commodious rooms were here secured, and experimenting 

 with insecticides was begun. Most economic entomologists 

 concurred in recommending spraying with arsenical poisons 

 for killing all leaf-eating larvae. Following such advice, ex- 

 periments with arsenites were begun. An early supply of 

 gypsy-moth larvae was obtained by artificial hatching, and 

 the experimental work was continued during the spring and 

 summer, the experiments with Paris green giving the best 

 results. In the laboratory it was found that young cater- 

 pillars, fed upon plants to which this poison had been 

 properly applied, died within a few days. In later experi- 

 ments it was noticed that a considerable proportion of the 

 larger caterpillars survived. In the experimental work in 

 the laboratory, no injury to the foliage was observed when a 

 mixture of one pound of this poison to one hundred and fifty 

 gallons of water was used. Glucose was also added to 

 retain the poison upon the leaves. 



When it became evident that Paris green was the most 

 effective of the arsenites, preparations were made for its use 

 on an extensive scale. In the first part of May teamsters 

 were employed, and twenty spraying outfits were put upon 

 the road in Medford. The number of men and teams was 

 soon found to be insufficient. Ten additional spraying out- 



