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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 10 



brood was on the wing, the prevaihng wind was from the southwest. 

 Field C and the northwest part of field D were in a direct line to catch 

 any fly that might be carried from field B. A line drawn due north- 

 east through D from the southeast corner of field B marked the extent 

 of serious infestation in field D. The fact that the east side of field 

 D was uninjured, together with the non-infestation of fields A and F, 

 is a strong point in favor of wind distribution. 



Screen Experiments 



In order to gather more definite data on wind dispersal of adult flies 

 and the distance they are carried, it was planned to carry on some 

 screen experiments about Manhattan. In order to do this it was 

 necessary to select areas far removed from wheat fields and erect 

 screens for catching the flies. 



Two localities were chosen for this work, one for data on short dis- 

 tance flights, and the other for data on long distance flights. The 

 first one was located near a small plot of wheat where migration 

 could be studied for a range of 600 feet and the other locality was on 

 the hills north of Manhattan where migration of from one to three 

 miles could be studied. 



At the first locality, three permanent screens were used, namely, 

 the field insectary having a screen area of 60 square feet, located 100 

 feet from the infested wheat, and two smaller screens, each having an 

 area of 6 square feet placed at 400 feet and 450 feet, respectively, 

 from the wheat. A portable screen was used for longer distances. 

 Table I gives the results obtained at these screens. 



Table I — Showing the Number of Flie.s Taken in Flight at Short Distances from Wheat 



For studying the long distance flights, a portable screen four feet 

 square was used. This screen was moved from place to place, efforts 



