INSECTICIDES. 455 



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

 proportion of | lb. 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 ])ranch 

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

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

 caterpillars placed upon it. All died without pupating. 



Xo. 37 (field experiment). — June 27, 1893. A branch 

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

 proportion of | lb. 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 lb. Arsenate of Lead to loO gal. Water. 



Xo. 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 lb. to 150 gal. 

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

 seventh day ; and five were lost. 



Xo. 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 lb. to 150 gal. of 

 water. All lived through the experiment and molted. 



Check experiment : none dead. 



Xo. 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 lb. to 150 gal. 

 of w-ater. 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. 



X'o. 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 lb. to 150 gal. 



