No. 4.] GYPSY MOTH — APPENDIX. 355 



insecticide is prepared. In the proceedings of the same 

 society for 1897, p. 4G, Mr. Kirklaud gave a full account of 

 the use of arsenate of lead against the gypsy moth. 



This insecticide is easily prepared by putting 11 ounces 

 of acetate of lead in 4 quarts of water in a wooden pail, and 

 4 ounces of arsenate of soda (50 per cent.) in 2 quarts of 

 water in another wooden pail, and when entirely dissolved 

 mixing them in a hogshead containing 150 gallons of water, 

 when a chemical reaction will take place, forming arsenate 

 of lead as a fine white powder in suspension in the water. 

 If cold water be used, the solution of the acetate of lead 

 will require a little time ; but, however, if the water be hot, 

 it will dissolve very quickly. It is customary to add from 

 2 to 4 quarts of glucose to the above amount of water. 

 If it is desired to use larger proportions of the arsenate of 

 lead, it is only necessary to use more acetate of lead and 

 arsenate of soda, but in the proportions given above. A 

 more detailed and exact explanation is given in a following 

 paper by Mr. F. J. Smith. 



Arsenate of lead has already proved to be the most val- 

 uable insecticide known for the destruction of the gypsy 

 moth. It does not injure the foliage of the most delicate 

 plants, even when used in as large a proportion as 25 pounds, 

 or even more, to 150 gallons of water ; in fact, there is no 

 known arsenical insecticide so harmless to vegetation as arse- 

 nate of lead. This substance remains in suspension in water 

 much longer than Paris green, because of its very low spe- 

 cific gravity, which is 1.00668, while that of Paris green is 

 3.42225. In spraying, the low specific gravity of arsenate 

 of lead and its consequent suspension in water for a consider- 

 able length of time make it possible to distribute it more 

 evenly over vegetation. The white color is also a decided 

 advantage, for one is able to see at a glance whether a tree 

 or shrub has been sprayed ; and it is a noteworthy fact that 

 this insecticide adheres to the foliage far longer than any 

 similar substance now in use. 



What has been said with regard to the value of this insec- 

 ticide for the destruction of the gypsy moth is also true in 

 the case of other leaf-eating insects. In every case where 

 we ourselves have performed experiments on these insects, 

 and in all cases reported by others who appear to understand 



