WEATHER AND CHANGE IN WEIGHT OF BEE COLONY 25 



NET GAIN 



The net gain is accumulated late in the day. Figure 10 shows 

 that the colony did not regain its original weight until between 4 

 and 5 o'clock in the afternoon, and since increase stops on the aver- 

 age at 6 o'clock any net gain must be accumulated between these 

 hours. Undoubtedly the nature of the nectariferous plants abound- 

 ing in any one locality will, together with the prevailing climatic 

 factors, determine the time and amount of gain in weight. An en- 

 tirely different picture may be expected in the buckwheat regions, 

 since buckwheat is known to secrete nectar only in the forenoon. 



Figure 1 well illustrates the vast differences, as shown by hourly 

 changes in the hive weight, that may exist in the interrelationship 

 of nectar-producing plants, bees, and weather factors. The two 

 curves in this figure represent these changes for May 9 (solid line) 

 and September 28 (dash line), 1922. On both of these days the net 

 gain was practically identical, but the activities of the bees in secur- 

 ing this gain were vastly different on the two occasions. On the 

 earlier day the morning loss ceased at 8 o'clock; on the other it contin- 

 ued until 11 o'clock and was more than seven times as great. On 

 May 9 the original weight was regained by 12 o'clock, whereas on 

 September 28 it was not regained until between 4 and 5 o'clock in 

 the afternoon. The comparison of these two days also serves to em- 

 phasize the statement made earlier that to be of service weight rec- 

 ords must be taken frequently and methodically. If only early 

 morning and evening records are taken nothing can be known as to 

 the time during the day when nectar is being brought into the hive, 

 and, moreover, if the last weight of the day were made an hour or 

 two earlier, one day might show a gain while the other shows a loss. 



NOCTURNAL LOSS 



The nocturnal loss during the fall is appreciably higher in com- 

 parison with the net gain than it is in the spring. For the days 

 showing a net gain in Table 3, the nocturnal loss amounts to 48.72 

 per cent of the net gain. The correlation between these two is also 

 much higher than it is in the spring, being .8568 ±.0333. A calcu- 

 lation of Dufour's (11) data likewise shows a higher correlation be- 

 tween nocturnal loss and net gain for the fall, being .8689 ± .0458, as 

 opposed to a spring correlation of .6663 ±.1002. 



A higher correlation between net gain and nocturnal loss, as well as a 

 larger per cent of loss, is naturally to be expected when net gains are 

 small. Such a condition obtains in this case, since a larger part of the 

 nocturnal loss is to be attributed to consumption for colony maintenance. 



CORRELATIONS BETWEEN EXTERNAL FACTORS AND THE CHANGES 



IN COLONY WEIGHT 



Having discussed the changes in weight of the colonies during the 

 spring and fall honey flows and the correlations for the various parts 

 of the day, it now is desirable to determine what degree of correlation 

 exists between the changes in weight and the factors of the environ- 

 ment in so far as data are available for computation. These will be 

 discussed in the following order: Temperature, relative humidity, 

 solar radiation, and hours of sunshine. Numerous coefficients of 

 correlation along these lines arc presented in Table 2, together with 

 their probable errors'. 



42201—25 4 



