INSECTICIDES. 407 



was leased, and an insectary was erected for experimental 

 purposes. This building (Plate 63) is sixteen by twenty 

 feet on the ground, with a greenhouse on the south side, six 

 by eight feet, and a covered shed on the north side, seven 

 by eight feet. It contains, on the first floor, besides the 

 main laboratory with tables, closets, etc., a private labora- 

 tory and a chemical room. The second floor contains a 

 lodging-room for the employees. 



The experimental work carried on in this building, during 

 the summer of 1895, has proved far more satisfactory than 

 that in the building on Commercial Street, because of the 

 greater conveniences and more healthful conditions. 



INSECTICIDES. 

 Experiments with Substances for destroying Eggs. 



The value of egg-destruction, as an exterminative meas- 

 ure, was recognized at an early stage in the work of com- 

 bating the gypsy moth, and led to an extensive study of 

 substances which might be advantageously used for this 

 purpose. The requisites necessary in such a substance are : 

 that it shall be effective wherever applied ; that it shall 

 leave a permanent stain or color, enabling one to distinguish 

 treated from untreated egg-masses ; and that its price shall 

 be within practical limits. The substances found to be 

 of the greatest value, together with an explanation of the 

 method of applying them, have already been described in 

 Part I. 



During the year 1892, Mr. F. C. Moulton experimented 

 with the following substances on the eggs of the gypsy 

 moths, to discover something that could be readily applied 

 to the egg-clusters and effectually destroy them. To some 

 of the preparations were added substances which contain no 

 destructive power, but were used simply to change the color 

 of the egg-clusters on trees, so that those which had been 

 treated might be readily distinguished from the others. 



Ammonia. January 21. Five egg-clusters were treated 

 for five minutes with ammonia gas, made by heating strong 

 aqua-ammonia. Apparently the eggs were not affected, for, 

 by March 24, nearly all had hatched. 



