THE FLIGHT ACTIVITIES OF THE HONEYBEE 25 



days the gathering may not be so great. A comparison of the amounts 

 of nectar gathered on certain days is not always absolutely indica- 

 tive of the amount of nectar available to the bees on these particular 

 days. This will be seen clearly from an inspection of Table 1, in 

 which are tabulated the total number of returning bees on each 

 day (except when the weight records were disturbed by rain), the 

 daily increase in weight of the hive, and the minimum limits of the 

 average load carried by each bee on these respective days. The 

 average load as given in this table is obtained by dividing the day's 

 gain in weight hy the total number of returns for the day. Since 

 consumption of stores, evaporation of excess water in the nectar, 

 and other sources of loss in weight of the hive as a whole are going 

 on throughout the day, it is evident that the average loads here com- 

 puted are actually the minimum limits for the average loads carried. 

 Other observers have noted that bees sometimes carry larger loads 

 of nectar than have been indicated for the best day, judging by the 

 total gain of the colony for the day (May 11, 24.1 milligrams), so 

 that the figures given in Table 1 are evidently very conservative. 

 Throughout the following discussion the expression " average load " 

 refers to these minimum limits. On May 15 slightly less nectar (20 

 grams) was gathered than on May 16, yet the average load was 

 greater by 1.2 milligrams. The total day's gain was minimized by 

 a threatening storm which reduced the number of possible flights. 



Again, on May 22 the load per bee is high (25.3 milligrams), yet 

 the total day's gathering is less than on May 20, when the average load 

 was 17.5 milligrams. This can be accounted for only by the fact 

 that on May 22 some factors were influencing the flights and length- 

 ening the average duration of each flight by about 9 minutes (Table 

 2), which would in turn reduce the total exits for the day and the 

 amount of nectar gathered. 



Without a knowledge of the number of flights which occur, a 

 study of the daily gains on May 9 and 24 would indicate that May 

 24 was a day of heavier secretion, since more nectar was brought in on 

 this day; but a comparison of the total returns and the average 

 load per bee shows that the reverse was the case. 



In general, Table 1 shows that although there is a close relation 

 between the average load carried by each bee and the daily total, 

 the amount of nectar gathered is not necessarily indicative of the 

 quantity of nectar available to the bees. The average load per bee 

 is the true indicant. 



On six days only — one in April, three in May, one in June, and 

 one in July— did the frequency of the flights drop during the hours 

 12 m. to 2 p. m., as would be required by the weight curve described 

 by Dufour (1) as typical of the spring conditions. On these days 

 the drop did not last more than half an hour, and varied in magni- 

 tude from 15 to 40 per cent of the average number of exits or returns 

 during the main flight for the day. 



THE EFFECT OF HEAVY FLIGHT NEAR BY 



Another colony about 36 feet from the one under experimentation 

 was, on May 11, at 2.30 p. m., much disturbed by manipulation, so 

 that the air in the vicinity was full of flying bees, almost as many 



