MISCELLANEOUS INSECTICIDE INVESTIGATIONS. 3 



much foliage had been consumed. In other cases, where the entire 

 leaf except the midrib and larger veins was consumed, the measure- 

 ment was obtained by measuring an average-sized leaf and substi- 

 tuting it for the leaf which had been destroyed. Careful attention 

 was given to the condition of the foliage throughout the experiments 

 so as to supply the larvae with palatable food at all times. 



Experiment I. 



COMPARISON OF THE KILLING EFFECT OF DOUBTFUL STOMACH POISONS WITH VARIOUS 

 ARSENICALS ON LARVAE OF THE FALL "WEBWORM. 



In this experiment the arsenite of zinc compounds and other pro- 

 prietary insecticides were used at the strengths recommended by the 

 manufacturers. The homemade arsenical compounds, where sodium 

 arsenate was employed, were used at a rate to equal 0.8 pound 

 sodium-arsenate content to 50 gallons of water, except in the case of 

 arsenate of iron, which was used double strength. Arsenite of lime, 

 homemade, was used at the rate of 2 pints to 50 gallons of water. 

 All other compounds containing arsenic were used at a strength 

 equivalent to 2 pounds of arsenate of lead paste to 50 gallons of water. 

 These calculations were based upon a 15 percent arsenic-oxid (As 2 5 ) 

 content in arsenate of lead paste. Compounds containing no arsenic 

 were used at the rate of 6 pounds to 50 gallons of water. The larvae 

 used in this test were about 4 days old. The results are given in 

 Table I. 



