380 Report of the Entomologists o'f the 



About 300 caterpillars included in 3 nests were used in these ex- 

 periments. The first application was made May 22, the second 4 

 days later and the third 7 days from the time of the second appli- 

 cation. At the time of the first application the caterpillars were 

 less than half grown. 



Paris green. — Similar experiments were made with Paris 

 green. It was applied in the same proportion and at the same 

 time as the green arsenite. 



Results. — Four days after the first application nearly all of the 

 caterpillars were sluggish. Within 3 days after the second 

 application only a few live worms could be found. The third 

 application was hardly needed. Where the Paris green was 

 evenly applied there was no apparent difference between its effects 

 and that of the green arsenite. 



Experiments in 1898. Green arsenite. — About 200 worms, 

 from 2 nests, were used and the green arsenite applied twice 

 in May at intervals of ten days. The green arsenite was 

 mixed with lime water in the same proportion as in 1897. No 

 Paris green was used. 



Arsenite of lime. — (For formula see page 388 of this report.) 

 Similar experiments were conducted with arsenite of lime, the 

 applications being made at the same time. 



Results. — The effects were practically the same in both in- 

 stances as with the poisons used the year previous. 



Conclusions. — The above indicates that the 3 arsenicals used 

 may be depended upon to kill the caterpillars if applied early 

 enough. The first application should be made before the cater- 

 pillars are half grown. 



Destroying the caterpillars in the nests. — This is done in a 

 variety of ways. Any way that is thorough and convenient and 

 does not result in injury to the tree will answer. It is only neces- 

 sary to be prompt and thorough. A common practice is to pull 

 out the nest with the gloved hands and destroy the caterpillars. 

 Others practice burning the nests with a torch or pouring kerosene 

 upon them. 



