December, '19] larrimer and ford: harmolita migration 



423 



Data were taken from seven fields which were in wheat last year but 

 not next to standing stubble. The results are found in the table fol- 

 lowing: 



Table III. Second Gener.\.tion Counts on Seven Fields in Wheat L.vst Year but Not Next 



TO Standing Stubble 



The above table shows that the infestation, although markedly lighter 

 than in fields adjacent to standing stubble, was fairly uniform throughout 

 the fields. 



Similar data were taken from eight fields which were in a crop other 

 than wheat last year and at the same time not next to standing wheat 

 stubble. The results from these eight fields are found in the following 

 table : 



Table IV. 



Second Generation Counts on Eight Fields Not in Wheat Last Year and Not 

 Next to Standing Stubble 



Again the infestation was fairly uniform throughout the field. 

 Although these fields were not in wheat last year nor next to standing 

 stubble, the infestation from this species was practically the same (veiy 

 slightly less) as fields on plowed wheat stubble. This is shown in the 

 accompanying graph. 



The fact that there was no great difference in the infestation in fields 

 which were and were not in wheat the previous year, that is in fields not 

 adjacent to stubble, tends to show that the plowing under of stubble is 

 fairly efficient in the control of this species. If the first generation adults 

 were able to emerge from plowed under stul)blc, surely there would be a 

 much greater infestation in those fields which were in wheat last year. 



Since we find the ordinary infestation in fields isolated from standing 

 stubble which were not in wheat last year, the (luestion arises "where is 

 the source of infestation in these isolated fields? " This can be an.swered 

 in only one way. The second generation must come from the firet and 

 since practically all of the fii"st generation is fouinl near the etlge of the 



