THE FLIGHT ACTIVITIES OF THE HONEYBEE 23 



personal equation in the taking of such intangible data, this method 

 was not wholly satisfactory, though useful for a broad interpreta- 

 tion. A better method would have been to supplement these data 

 with an actual measurement of the light intensity by means of a 

 photometer. Had this been done, when light is a lagging factor a 

 more definite intensity would have been found marking the com- 

 mencement of flight and on the approach of sunset the intensity at 

 which the number of exits begins to fall would also prove to be 

 rather definite. Whether these two intensities as affecting flight at 

 the beginning and end of the day would be identical, or whether the 

 evening intensity is lower or higher than the morning is a matter 

 yet to be determined. 



The flight curve typical of a bright, sunny day with all other fac- 

 tors at their most favorable intensity shows a sudden ascent to a 

 point where the outgoing and incoming bees begin to balance in 

 number, and continues more or less level till, at the end of the day's 

 flight, the descent of the curve is as abrupt as was its commencement. 



On dull days the ascent of the curve is more gradual, as is usual 

 when some factor is not at an optimum. 



Comparing the months of May and July, it is found that on the 

 first day of May the sun rose at 5.03 and on the last day at 4.37 a. m. 

 Although the flight commenced about 7 a. in. on most of the sunny 

 days in this month, the first quarter of an hour having exits amount- 

 ing to at least 400 bees ended at 7.45 or 8 a. m. Throughout July, on 

 the other hand, when the sun rose about the same time (4.38 to 4.59 

 a. m.), on account of the high temperature prevailing the first bees 

 were flying as early as 5.45 to 6 a. m. and yet the first quarter of an 

 hour with as many as 400 exits usually did not occur until 8.15 to 

 8.45 a. m. Though the colony was weaker in July than in May, these 

 facts reflect the nectar conditions prevailing rather than the effects 

 of temperature or light. 



THE HONEY FLOW 



A survey of the flight activities of the season as a whole (fig. 2 or 

 Table 1) shows that of all the external environmental factors which 

 influence the magnitude of the flight occurring on any normal day, 

 a heavy honey flow of nectar is the strongest. These flights during 

 the honey flow (May 3 to May 28) were on the average three to four 

 times as great as at any other period of the observations (see fig. 2). 

 In order to follow in minute detail the variations in the flight which 

 occur in the course of a day's activity, the number of bees departing 

 and the number returning to the hive each quarter of an hour have 

 been recorded, as well as the quarter-hourly change in the weight of 

 the hive. 



The flights typical of the honey flow are well illustrated by the 

 records for May 20 (fig. 8) or May 15 (fig. 4), and those of a dearth 

 are also well illustrated by the records of July 10 (fig. 9), July 12 

 (fig. 10), and May 19 (fig. 6), a day of dearth within the period of 

 the honey flow. In general it is found that at the beginning of the 

 day's flight the number of bees leaving each quarter of an hour 

 becomes larger and larger, to be followed later by a corresponding 

 increase, as on May 20 (fig. 8) or July 12 (fig. 10), in the number 

 of bees returning. At the close of the day's flight the successive 



