INSECTICIDES. 477 



Experiments with London Purple and Acetate of 



Lead. 



No. 1. — July 7, 1893. London purple and acetate of 

 lead, in the proportion of f lb. each to 150 gal. of water, 

 were thoroughly mixed and allowed to stand and settle for 

 one hour and a half. It was tlien stirred and allowed to 

 stand one-half hour longer, at the end of which time it was 

 strained through two thicknesses of cheese cloth, a small 

 amount of glucose added, and an oak branch sprayed with 

 the mixture. Ten caterpillars, of the fifth molt, were then 

 placed upon the branch. July 22, for lack of food, they 

 were transferred to a freshly sprayed branch. None of these 

 caterpillars died for nearly two weeks after the branch was 

 first sprayed, but after they were transferred to the second 

 sprayed branch they died more rapidly. Three began pu- 

 pating, but none emerged. The foliage of the first branch 

 was slightly burned, while that of the second was in good 

 condition. 



No. 2. — July 6, 1893. A branch of a small oak tree 

 was sprayed with London purple and acetate of lead, in the 

 proportion of | lb. each to 150 gal. of water. The London 

 purple and acetate of lead were mixed in a little water, glu- 

 cose added and thoroughly stirred ; the rest of the water was 

 then added and the mixture thoroughly stirred again. Ten 

 fifth-molt caterpillars, five very large and five small, were 

 then placed on the branch. July 25, the branch was re- 

 sprayed, on account of rain. Two of these caterpillars 

 began to pupate, but none emerged. They died gradually, 

 the last one living nearly a month. Foliage considerably 

 burned. 



No. 3. — July 6, 1893. A branch of oak was sprayed 

 with London purple and acetate of lead, in the proportion 

 of 1 lb. each to 150 gal. of water. The London purple and 

 acetate of lead were thoroughly mixed with water in a 

 beaker, a teaspoonful of glucose was added and the mixture 

 thoroughly stirred. Eleven fifth-molt caterpillars were 

 placed on the branch. July 20, the branch was res[)rayed, 

 on account of rain. Of the eleven caterpillars, only two 



