77 

 The difference in the number of eggs found in the checks and in the treated 

 plots is greater hero than at Littleton (see Table IV). This difference is doubtless 

 due to the greater force witli which the spray stream is applied with a power sprayer 

 than with a compressed air sprayer. It seems clear that the difference is due to 

 the mechanical action of the spray stream in knocking eggs from the plants rather 

 than to any marked repellent qualities of the spray materials themselves. Lead 

 arsenate has not been demonstrated to be repellent to insects, and yet no more 

 eggs were found in the plot sprayed with this material than in the plots treated 

 with the nicotine sprays. In view of this fact, it is impossible to attribute definite 

 repellent qualities to the Black-leaf "40", in this connection. 



The number of larvae found compared with the number of eggs present, as 

 expressed in the last column of the table, indicates the toxic effect of the spray 

 materials. The counts in the check plots may be taken as a normal progression of 

 development of the eggs. The counts in the plot treated with lead arsenate indicate 

 a kill of about 50 per cent, while those in the plots treated with both strengths of 

 Black-leaf "40" indicate 100 per cent control. 



The final count was made on August 20 and 2L The detailed results are recorded 

 in Table VII, and are summarized below. 



Summary. 



