418 THE GYPSY MOTH. 



practical and effective method of destroying the caterpillars 

 of the gypsy moth would be provided if a poison could be 

 found which would meet the exigencies of the case. It will 

 be seen by the records which follow that we have experi- 

 mented with insecticides in general use, which are adapted 

 to our work, and also with many new insecticides which 

 were prepared for this purpose by our former chemist, 

 Mr. F. C. Moulton. 



All of the insecticide experiments here recorded were 

 performed under my immediate supervision, by Messrs. 

 Reid and Schrader in 1893, Messrs. Minott, Mosher and 

 Kirkland in 1894, and by Mr. Kirkland and his assistants 

 in 1895. 



Details of the Experiments. 



The caterpillars used in the field or out-door experiments 

 were taken from infested trees near the place of experi- 

 mentation. Those used in the in-door experiments were, 

 as a rule, from eggs hatched early in the season by means 

 of artificial heat. 



In the in-door experiments on young caterpillars lettuce 

 was the food plant generally used, leaves of elm, apple or 

 willow being substituted as soon as such foliage could be 

 obtained. In the field experiments the caterpillars were 

 confined upon branches of trees on which they were known 

 to feed readily. 



All poisons used in the experiments of 1893, and the 

 greater part of those used in 1894, were carefully weighed 

 out in the insectary at Amherst. During the latter part 

 of 1894, and throughout the season of 1895, they were 

 weighed on a very accurate set of balances at the Maiden 

 office. 



The poison was applied to the foliage used in the in-door 

 experiments both by dipping the leaves in the poison mixt- 

 ures and by spraying with small hand bellows. In the 

 field experiments the poison was always applied by use of 

 the spraying bellows. After heavy rains the branches on 

 which the caterpillars were confined were resprayed in the 

 same manner as would be adopted in spraying operations 

 in the field. In nearly all cases a small amount of glucose 



