28 BULLETIN 1328, 17. S. DEPARTMENT OP AGRICULTURE 



It will be noted that the average duration of the voyages was 

 determined with a probable error ranging from less than one-half 

 of 1 per cent to about 7 per cent, the average probable error being 

 2.45 per cent. 



The number of days in the honey flow on which the average dura- 

 tion of the voyages could be determined with full confidence in the 

 figures was small, owing not only to the fact that the honey flow in 

 1922 was short but also to the fact that it occurred very early in the 

 season, when relatively more difficulties in connection with the appa- 

 ratus had yet to be overcome. With changing weather conditions the 

 duration of the voyages can be determined more conveniently by the 

 graphic method, which, although not so accurate, is correct to about 

 3 minutes for the scale used in studying the data. 



A survey of a few days (Table 2) shows that the average duration 

 of the voyages varies considerably. The shortest average flight over 

 a considerable period of time is that which occurred on April 20, 

 8.92 minutes, and the longest that of July 10, 103.92 minutes. Every 

 gradation between these limits occurred. It will be noted that during 

 the dearth of July the average duration of each flight is much longer 

 than during the honey flow ; and yet there are days in July when the 

 duration corresponds very closely with such honey flow days as 

 May 8 and 9. 



It will be noted also that the duration of the voyages on May 8 

 and 9 was from two to three times as long as it was on May 15 

 and 17, and yet all four days (Table 1) were days of fairly good to 

 good honey flow. This great difference can be attributed only to the 

 nature and distribution of the honey plants. On May 8 and 9 the 

 bees are working on the black locust (Eobinia pseudacacia) en- 

 tirely. The tuliptree {Liriodendron tulipifera) was not yet secret- 

 ing nectar. On the 15th and 17th only the tuliptree was secreting, 

 the black-locust blooms having been destroyed by a heavy rain on 

 the 14th. The distribution of the trees of these two species in the 

 immediate vicinity of the hive shows roughly that the black-locust 

 trees most accessible are on the average about three times as far 

 away as the nearest available tuliptrees. The structure of the flower 

 of the black locust undoubtedly also contributes to lengthening the 

 average duration of the voyages by requiring a greater exertion from 

 the bee in securing its load of nectar. 



The data for May 15, June 6, and July 25 (Table 2) show that 

 the duration of the flights may sometimes vary considerably within 

 the same day. Under uniform conditions, however, it is usually very 

 constant for the greater part of the day's flight. 



Graphs (figs. 11, 12, and 13) have been drawn to show in greater 

 detail these variations in the duration of the trips for May 15, a 

 day of good honey flow from tuliptree; for July 10, a day in 

 the dearth; and for May 9, a honey-flow day with locust secretion, 

 with flights of intermediate length. Owing to the heavy flight 

 which occurred on May 15, it has been necessary to cut the graph 

 into three sections in order to draw it to the same scale as the graph 

 for July 10. These sections should be joined so as to give a con- 

 tinually ascending curve such as is shown in Figure 12 for July 10. 

 These curves show that at the commencement of flight the duration 

 of the trips is relatively short, soon to be followed by the balanced 



