December, '19] LARRIMER AND FORD: HARMOLITA MIGRATION 



421 



different places in the same row. Only the culms which had "shot" and 

 were jointed were counted, as it is in these that the adults of the second 

 generation oviposit. ^ 



The following table shows the location of the second generation infesta- 

 tion, the percentages being an average of the eight fields: 



Table II. Second Generation Infestations on the Same Eight Fields that the First Gen- 

 eration Counts Were Made 



On examining the data obtained from these counts it can be seen that 

 although the heaviest infestation remained in those parts of the fields 

 nearest the standing stubble, comparatively high infestations were found 

 even at 150 yards, which is approximately the middle of most of the fields 

 used in the counts. On the other hand the infestation caused by the 

 first generation stopped at about 30 yards. This shows that the strong 

 flying adults of the second generation will infest an entire field even 

 though they come from a narrow infested strip or a small plot of volun- 

 teer wheat in or near standing stubble. 



Since it has been shown that the second generation can infest an entire 

 field next to standing stubble, the question now arises, are these second 

 generation individuals able to infest wheat fields which are isolated from 

 standing stubble areas. It has already been stated that practically none 

 of the first generation could be found in last year's wheat which had been 

 piopci-ly plowed. It was decided to make second generation counts in 

 fields which were not adjacent to standing stubble. Also to determine 

 the efficiency of plowing under the stubble of the previous year's crop, 

 two types of these fields were taken; those in wheat last year, the stubble 

 having been plowed under, and those in a crop other than wheat the 

 previous year. Since all other conditions in these two classes of fields 

 were practically' identical, any marked variation in the percentages of in- 

 festation could be undoubtedly due to the fact that it came from the 

 plowed-under stubble in the form of early wingless generation, and 

 iience, on to the second generation infestation. 



The counts were made in the following manner: Three Uncar feet of 

 drill row were taken at five-yard intervals in the same row, these samples 

 being taken at foui' jilacos in each field, at the edge, fiO yards, 100 yards 

 and 150 yards from the edge. The samples were taken to the hiljoratory 

 and each culm carefully dissected and infestations recorded. 



