20 



BULLETIN 1328, U. S. DEPARTMENT OF AGRICULTURE 



the wind velocity was as high as 14 to 17 miles per hour. Again, 

 on May 19 (fig. 6), a day when the morning's weight was all but 

 regained at the end of the day, a wind of 9 to 10 miles per hour, 

 from 8 a. m. to 4 p. m., apparently scarcely affected the flight, which 

 was greater by 54 returns than on the following day when the wind 

 velocity was only 1 to 4 miles per hour. On these two days the 

 wind velocity was taken from an anemometer about 5 feet from the 

 ground and about 20 feet from the hive. 



The only other windy day of any consequence — June 22, a day in 

 the dearth — during which from 9 a. m. to 6 p. m. the wind varied 

 from 16 to 21 miles per hour shows a reduction of 28.53 per cent in 



Pig. 8. — Flight, temperature, and hive-weight data for May 20, 1922^ a day in. 

 a time of honey flow 



the total day's flight, when compared with June 23, a day with 

 little or no wind. The wind velocity on the former day is taken 

 from the data obtained by the Weather Bureau in Washington at a 

 higher elevation from the ground. 



THE EFFECT OF TEMPERATURE 



It is only when all the factors influencing flight but one are at 

 least at an intensity favorable for flight, and this last factor is 

 increasing in intensity toward this condition, that its minimum in- 

 tensity can be determined. Any one factor can become the lagging 

 factor at one time or another. In the early part of the season tem- 

 perature is this factor more often than any other. 



