INSECTICIDES. 455 



of hop-hornbeam was sprayed with arsenate of lead, in the 

 proportion off Ib. to 150 gal. of water, and ten caterpillars, 

 of the fourth molt, placed upon it. July 8, the foliage was 

 so badly burned that the nine remaining caterpillars were 

 transferred to a freshly sprayed branch of oak. By the 19th 

 of July all were dead. The foliage of the oak was slightly 

 burned. 



No. 36 (field experiment) . June 27, 1893. A branch 

 of hop-hornbeam was sprayed with arsenate of lead, in the 

 proportion of | Ib. to 150 gal. of water, and ten fifth-molt 

 caterpillars placed upon it. All died without pupating. 



No. 37 (field experiment). June 27, 1893. A branch 

 of hop-hornbeam was sprayed with arsenate of lead, in the 

 proportion of | Ib. to 150 gal. of water, and nine fifth-molt 

 caterpillars placed upon it. Of these, only one completed 

 the process of pupation and emerged, three having died 

 before beginning to pupate. Foliage uninjured. 



1 Ib. Arsenate of Lead to 150 gal. Water. 



No. 38. March 7, 1894. Ten caterpillars, three days 

 old, were placed on lettuce leaves which had been treated 

 with arsenate of lead, in the proportion of 1 Ib. to 150 gal. 

 of water. One died the fifth, three the sixth and one the 

 seventh day ; and five were lost. 



No. 39. May 9, 1894. Ten caterpillars, six days old, 

 were placed on lettuce leaves which had been treated with 

 arsenate of lead, in the proportion of 1 Ib. to 150 gal. of 

 water. All lived through the experiment and molted. 



Check experiment : none dead. 



No. 40. May 28, 1894. Ten caterpillars, of the first 

 molt, were placed on lettuce leaves which had been treated 

 with arsenate of lead, in the proportion of 1 Ib. to 150 gal. 

 of water. Four died the fourth, one the seventh, one the 

 eighth and one the ninth day ; the remainder lived through 

 the experiment. 



Check experiment : one died the third and one the seventh 

 day. 



No. 41. June 10, 1894. Ten caterpillars, of the second 

 molt, were placed on elm leaves which had been sprayed 

 with arsenate of lead, in the proportion of 1 Ib. to 150 gal. 



