INSECTICIDES. 451 



of oak was sprayed with arseuate of lead, in tlie proportion 

 of ^ lb. to 150 gal. of water, and ten caterpillars, of the 

 fourth molt, were placed upon it. Three of these died before 

 pupating, the last one dying thirty-seven days after the first 

 spraying. Of the seven that pupated, all emerged. Foliage 

 uninjured. 



No. 13 (field experiment).— June 29, 1893. A branch 

 of a small oak was sprayed with arsenate of lead, in the 

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

 caterpillars placed upon it. July 20, the branch was re- 

 sprayed on account of the rain on the 18th. Only one cater- 

 pillar died before pupating, and seven were able to complete 

 the process of pupation and emerge. Another one fed on 

 the leaves for nine days after the spraying and pupated, but 

 was injured in removing, and therefore not counted in the 

 above summary. Foliage uninjured. 



No. 14 (field experiment). — June 29, 1893. A branch 

 of a small oak tree was sprayed with arsenate of lead, in the 

 proportion of \ lb. to 150 gal. of water, and nine fifth-molt 

 caterpillars were placed upon it. July 20, the branch was 

 resprayed on account of rain. Only one caterpillar died 

 before pupating, and that on the forty-first day after the first 

 spraying. Of the eight that pupated, two died without 

 emerging. Foliage uninjured. 



^ lb. Arsenate of Lead to 150 gal. Water. 



No. 15. — 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 \ lb. to 150 gal. 

 of water. On the eighth day all were dead. 



No. 16. — 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 ^ lb. to 150 gal. of 

 water. One died the fifth day ; the remainder lived through 

 the experiment and molted. 



Check experiment : none dead. 



No. 17.— 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 \ lb. to 150 gal. 

 of water. One died the third, one the fourth, two the fifth, 



