24 BULLETIN 1328, U. S. DEPARTMENT OF AGEICULTURE 
numbers of outgoing bees decrease, followed later by a corresponding 
decrease in the number of returns until flight ceases for the day. 
The characteristic differences typical of the flights during a honey 
flow and dearth are respectively : 
1. During the honey flow, as on May 20 (fig. 8), there is a very 
steep ascent of the outgoing curve on the advent of the optimum 
conditions for flight, with a corresponding abrupt descent in the 
curve on the approach of sundown. In a dearth, as on May 19 
{Q.g. 6) or July 12 (fig. 10), these ascents are more gradual. Instead 
of the peak of the flight being reached within three-quarters of an 
hour or an hour after the main flight to the field begins, as in the 
honey flow, it is not attained until about four or even five hours later. 
2. In the honey flow the portion of the curve lying between the 
morning peak and the time when, at the close of flight, the number 
of exits begins to drop, approximates a horizontal straight line, 
showing that the rate of flight is fairly constant, there being almost 
as many bees departing as arriving. In the dearth, on the other 
hand, as on July 12 (fig. 10) , this portion of the curve is not horizon- 
tal but tapers away gradually to zero, indicating that on the dis- 
cover}' of the dearth the bees conserve their energies by reduced 
activity. 
3. The horizontal distance (indicating length of flight) between the 
curves representing the outgoing and incoming bees in a heavy honey 
flow is always shorter and sometimes very much shorter than it is 
in a dearth. This is specially apparent when in the morning the 
flights are on the increase and again in the evening when they are 
on the decrease. This distance, which is indicative of the average 
duration of each voj^age, can not be followed precisely on a curve 
plotted in this manner. This will be dealt with separately in a dis- 
cussion of the average duration of the trips (p. 26). 
4. A study of the changes in weight of the hive, indicated in 
Figures 4 to 10, shows that as the successive number of departing 
bees increases the weight correspondingly decreases; then, again, 
as the number of nectar-laden returning bees increases the hive be- 
gins to regain its early morning weight. During the first days of 
the honey flow the time at which this regaining of the original weiglit 
occurs is well on in the afternoon or even at the end of the day. As 
nectar conditions improve, the time at which the original weight is 
regained comes earlier in the day. Then, as the honey flow wanes, 
this time again occurs toward the latter part of the day. In the 
dearth proper the drop in weight of the hive is considerable. This 
is due more to the long trips, with the majority of the flying force 
absent from the hive at one time, than to the small loads that they 
bring back. Since little or no nectar comes in, the morning Aveight 
is frequently never regained, a loss in weight being continually re- 
corded for the entire day. This loss indicates the amount of stores 
consumed to maintain this flight activity in a main search for nectar, 
and to maintain other colony activity. 
The amount of nectar gathered on any particular day depends 
not only upon the factors governing nectar secretion, but also on the 
factors governing the flights for that day. The secretion may be 
equally good on two selected days,, but on account of a relatively ad- 
verse condition for flight of shorter or longer duration on one of these 
