July 23. 1917 Toxic Values and Killing Efficiency of Arsenates 201 



EXPERIMENTAL WORK 



SERIES A. — VERY SMALL CATERPILLARS 



The caterpillars employed in series A were the very small ones and 

 varied in size from those just hatched to forms about 5 to 7 days old 

 (approximately 10 mm. in length). Both wild-rose and apple foliage 

 was used. As the caterpillars were collected mostly on the rose, it was 

 considered possible that for a time they might refuse to eat apple foliage 

 and then feed to excess when they did begin. Since lead arsenate and 

 water alone failed to stick well or spread evenly on the rose foliage, 

 flour paste (i pound of flour to i gallon of water) was prepared. This 

 gallon of paste was diluted with 3 gallons of water and used at the rate 

 of 20 c. c. to the 1,000 c. c. of lead-arsenate solution. No flour paste 

 was added to the lead-arsenate solution on the apple foliage. 



The strength of solutions used, date of application, and daily drop 

 are recorded in Table I. 



Table I. — Effect 0/ arsenates on very small caterpillars 



" Very few; 13 to 20 yet on foliage show feeble signs of life. 

 * New foliage prepared and added. 

 <: Discontinued. 



98975°— 17- 



