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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 12 



thus determine the distance that wheat can be sown from stubble of the 

 previous year's crop, without danger of infestation. 



The following is the method by which these data were obtained. 

 Wheat fields were selected adjacent to stubble, and samples taken at ten 

 yard intervals from the edge of the field next to the stubble up to 100 

 yards toward the center. In every case, fields were selected which 

 were in a crop other than wheat the previous year, in order to ehminate 

 possible infestation caused by adults coming from the stubble on im- 

 properly plowed soil. Each sample consisted of three Hnear feet of drill 

 row, each foot taken at an interval of five yards in the same row. These 

 samples were brought to the laboratoiy and carefully examined, the 

 percentage of culms infested by this species being recorded. In this way 

 the distance the adults migrated from the stubble was definitely deter- 

 mined, it being estabUshed by the area of infestation. In all cases the 

 infestation was heaviest adjacent to the stubble and decreased in a 

 regular manner with increasing distance from the stubble. 



Samples which were taken from eight fields were carefully examined 

 and infestation percentages recorded. In all 280 linear feet of drill row 

 representing 12,276 culms were handled, each cuhn being carefully 

 examined to detect the presence of this species. The tabulated data from 

 these examinations are found in the following table: 



Table I 



Note: Samples from field 8 consisted of five linear feet of drill row except at 90 and 100 yards out 

 which consisted of three linear feet. , 



From the above table and curve it can be seen that the greater part of 

 the infestation occurred within ten yards of the standing stubble, and 

 beyond 30 yards the infestation became practically negfigible. The 

 amount of infestation varied markedly in the eight fields, ranging from 

 20.1 per cent to 6.2 per cent at the stubble, but in every case it decreased 

 in practically the same ratio as the distance from the stubble increased. 

 These data show that under ordinary conditions very few of the wingless 



