INSECTICIDES. 417 



Six cirg.s-clii.sters re-commenced hatching, and a few cater- 

 pillars emerged. 



Crude Castor Oil and Turpentine. — January 5. Five 

 egg-clusters, treated with the above mixture, hatched April 

 30. 



Paraffine Gas or Residuum Oil. — Thinking this oil might 

 be of some value for treatinsj eo'g-clusters, a number of 

 experiments were made which gave very satisfactory re- 

 sults. January 5. Twelve egg-clusters were treated with 

 paraffine gas oil, none of which hatched. During the winter 

 and spring of 1895, from one hundred to two hundred egg- 

 clusters were treated with paraffine gas oil, with the result 

 that none of them hatched. 



Raupenleim. — April 27. Five egg-clusters were care- 

 fully covered with Raupenleim, the layer being about one- 

 eighth of an inch thick. None of the eo'o^s hatched. 



The experiments in treating egg-clusters with various 

 gases were made with a view to finding some practical way 

 of dealing with stone walls, hollow trees and other more or 

 less inaccessible places, in which eggs had been laid in 

 large quantities. The substances which were found to give 

 the most satisfactory results, i. e., chlorine and bromine 

 vapors, were tested on a large scale in the field, but here 

 their use was found to be, at best, only partially effective. 



Insecticides for Destroying the Caterpillars. 

 Spraying with the common arsenical jioisons, such as 

 Paris green, London purple, etc., was one of the first 

 methods employed for the destruction of the caterpillars 

 of the gypsy moth, and the failure of these poisons to do 

 effective work in the field has already been stated. When 

 it became evident that the caterpillars were not being de- 

 stroyed in any great numliers by tliese poisons, an effort 

 was made to discover a more effective poison, and much 

 time and labor were spent in this undertaking. The most 

 careful attention was given to this prol)lem ; for, with 

 modern spraying machinery, the thorough application of 

 a poison to trees is easily accomplished, and thus a cheap, 



