INSECTICIDES. 489 



ill upon the twigs. The amount eaten upon each twig was 

 about equal, possibly a little more from the unpoisonecl 

 than from the poisoned twig. 



Experiment iVb. 14. — A twig of apple was sprayed with 

 arsenate of lead, in the proportion of 2 lbs. to 150 gal. of 

 water, and a similar twig left unsprayed. These twigs 

 were enclosed in a sack containing ten caterpillars of the 

 fiftli molt. The feeding w^as about equal upon the poisoned 

 and unpoisoned leaves. 



Experiment No. 15. — Alternate leaves on a small twig 

 of apple were painted with arsenate of lead, in the propor- 

 tion of 6 lbs. to 150 gal. of water, and ten caterpillars of 

 the fifth molt were sacked in upon it. The poisoned and 

 unpoisoned leaves were eaten equally. 



Summary. 



Of the four experiments where the caterpillars ate more 

 of the poisoned than of the unpoisoned leaves, Nos. 9 and 

 10 give most decided results against the choice of unpoi- 

 soned food. Of the four cases where the caterpillars ate 

 more from the unpoisoned than from the poisoned food, 

 Nos. 1, 3 and 4 give but a small margin upon which to base 

 a conclusion. The fourth, No. 8, is of somewhat doubtful 

 value, l)ecause six of the caterpillars died upon the second 

 day of the experiment. Balancing experiments Nos. 1, 3, 

 4 and 8 against Nos. 6, 9, 10 and 12, there remain sev^eu 

 experiments where there was no apparent choice of food. 



A fair conclusion from these results is that there was 

 no discrimination against foliage treated with the poisons 

 employed. 



Effect of Insecticides on Foliage. 



No. 1.— June 26, 1893. A mixture of f lb. of Paris 

 green, ^ lb. of lime and 2 quarts of glucose to 150 gal. of 

 water was applied to some quince bushes. About one- 

 fourth of the leaf surface was destroyed by burning. 



No. 2. — July 12, 1893. A In-anch of apple tree was 

 sprayed with Paris green and lime, in the proportion of 1 



