February, '17j 



McCOLLOCH: HESSIAN FLY SPREAD 



167 



being made to place it in direct line with infested fields. On April 

 12, the first observations were made on the hills north of Manhattan. 

 The nearest infested field to the places where the screen was operated 

 was a volunteer field to the southwest. Table II gives the results of 

 this day's observations. 



Table U — Showing the Number of Flies Taken in Flight at Distances Ranging from One-fourth to Two 

 Miles from Wheat on April 12, 1916 



On April 16, the screen was run from three to four p. m. at two 

 miles from the volunteer wheat and one female was caught. In this 

 case, the wind was slightly south of southwest and the female came 

 from the volunteer wheat or else from the wheat plots on the College 

 campus three miles away. The day was cool and partly cloudy and 

 there was little activity of flies even in the wheat fields. The wind 

 velocity was twenty-two miles per hour. 



On April 18, the screen was placed on the Manhattan country club 

 grounds from 10 to 11.30 a. m. and during that time one female was 

 caught. The wind was very strong from the southwest, the velocity 

 being from 24 to 27 miles per hour. The nearest wheat from this loca- 

 tion was five miles southwest. From 12.30 p. m. to 2 p. m., the screen 

 was run at two miles from the volunteer field mentioned above. Dur- 

 ing this time one female was caught. The wind velocity was 24 miles 

 per hour. On April 19, the screen was again run at two miles from the 

 volunteer wheat from 11 a. m. to 12.15 p. m. and five females were 

 caught. The wind velocity was 19 miles per hour during this time. 



General Notes 



It is interesting to note that of the 146 flies taken in flight, 135 

 are females and that no males have been taken at a greater distance 

 than 100 feet from wheat. As far as the writer has been able to ascer- 

 tain, flies that have been carried two miles by the wind are not injured. 

 A large number of the females taken at this distance have been placed 

 on wheat where they began to oviposit at once. Fertilization had 

 apparently taken place before flight, as all the eggs thus obtained were 

 fertile. 



