360 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 15 



will not be necessary; in many cases it will not be needed at all, and in 

 others one or two applications will suffice to protect the plants until the 

 outbreak subsides. Spraying is not necessary nor profitable when leaf 

 rollers are few, but it is an effective means of combating them when they 

 rise to injurious numbers. 



HOST PLANT SELECTION BY HESSIAN FLY^ {PHYTOPHAGA 

 DESTRUCTOR SAY.) 



By W. B. Cartwright, Scientific Assistant, 

 U. S. Entomological Laboratory, West Lafayette, Ind. 



In connection with the Hessian fly investigations at Centralia, Illi- 

 nois, for the Fall of 1921, two sowings each of wheat, barley, rye, and 

 oats were made to determine the relative attractiveness of these grains 

 to the adult flies for oviposition and to obtain comparative data on 

 larval infestation. Identical preparations were made for both series 

 with respect to orientation of the plots and the date of sowings. 



I. Sowing September 1. 



Plants of this sowing appeared above ground on September 10. 

 On this date fifty plants from each plot were marked and numbered for 

 daily examination during the emergence period of the Hessian fly. The 

 eggs found on these plants were carefully removed and recorded as found. 

 The counts for the series are shown in Table I. 



Table I — D.\ily Egg Counts 



Date 



Sept. 11 

 14 

 15 

 24 

 28 

 29 

 30 

 1 

 2 

 .3 

 4 



Oct. 



10 

 11 

 12 

 15 

 16 



Total 



Per cent 



Wheat 



15 



7 



1 



1 



56 



85 



58 



11 



195 



170 



111 



124 



651 



9 



81 



68 



17 



9 



29 



38 



1736 



68.0 



10 



2550 

 100 



It was noted during the days from the first appearance of the plants 



^Published by permisssion of Secretary of Agriculture. 



