202 



Journal of Agricultural Research 



Vol. X. No. 4 



SERIES B. — NEARLY MATURE CATERPILIvARS 



Series B was similar in every way to series A except that the cater- 

 pillars used were from half -grown to nearly mature larvae and only apple 

 foliage was used. The results are given in Table II. 



Table II. — Effect of arsenate on nearly mature larvce 



<» New foliage prepared and added. 



^ Two parasitized. 



DISCUSSION OF RESULTS 



The results of the tests to determine the relative killing efficiency of 

 the hydrogen and basic lead arsenate as shown by data contained in the 

 above tables (I and II) and summarized in Table IV approximate very 

 closely those obtained by Tartar and Wilson^ in 1915 and substantiate 

 in general the work of previous investigators, in that the acid arsenate 

 has a decidedly higher killing efficiency at a given dilution than does the 

 neutral arsenate. It will be noted that the figures in the tables do not 

 emphasize the differences in killing efficiency of these arsenates, par- 

 ticularly with the more concentrated solutions, but observation during 

 the actual tests showed the differences clearly. Had the drop been 

 recorded more frequently than every 24 hours, this difference, as indi- 

 cated in the tables, would probably have been more marked. From 

 Tables II and IV it is seen that until the fourth day no caterpillars died 

 on the twigs sprayed with neutral lead arsenate, while both the acid lead 



I Tartar, H. V.. and Wii,son, H. F. Op. cit. 



