INSECTICIDES. 419 



"was added to the poison mixtures, in order to increase the 

 adhesive qualities. In the experiments conducted at the 

 insectary the caterpillars were confined in glass jars or in 

 lantern globes. In the field experiments the caterpillars 

 were sacked in (enclosed by means of a thin cloth bag of 

 proper dimensions) upon the branches of trees. In the case 

 of the in-door experiments the poisoned food Mas renewed 

 and the jars cleaned daily. For the field experiments 

 branches of sufficient size to allow the caterpillars to feed 

 till reaching maturity were chosen, and thus, as a rule, no 

 change was necessary. 



Each jar or sack used in the experiments was given a 

 number, which was recorded in a book, in which the records 

 of the ten caterpillars used in each experiment were carefully 

 noted. In many of the experiments a "check" was em- 

 ployed, to determine the normal death rate of caterpillars 

 feeding on unpoisoned food. This check consisted of the 

 same number of caterpillars confined in a jar or bag in the 

 same manner as those in the experiment, with the exception 

 that they were kept supplied with fresh, unpoisoned food. 



Daily observations were made both ui)on caterpillars feed- 

 ing on the poisoned and unpoisoned food, and the results 

 recorded. Many of the experiments on young caterpillars 

 were discontinued at the end of about a fortnight, or after 

 they had entered the succeeding molt. 



The following pages contain the records of the experi- 

 ments which have been conducted with the dift'erent insecti- 

 cides : — 



Experiments with Paris Green. 

 i lb. Paris Green to 150 gal. Water. 



No. 1. — March 7, 1894. Ten caterpillars, three days 

 old, were placed on lettuce leaves which had been treated 

 with Paris green, in the proportion of ^ lb. to 150 gal. of 

 water. Two died on the third, three the fourth, one the 

 fifth, three the sixth and one the seventh day. 



Check experiment : none dead. 



No. 2. —April 26, 1894. Ten caterpillars, six days old, 

 were placed on lettuce leaves which had ])een ti-eated with 

 Paris green, in the proportion of ^ 11). to ir)0 gal. of water. 



