10 BULLETIN" 1328, IT. S. DEPAETMENT OF AGEICTJLTUEE 



On any particular day the magnitude of the experimental error 

 depends upon the combination of factors operating on that day. 

 On 89 of the 105 days on which records were taken, omitting records 

 accidentally falsified by various causes, it appears that out of every 

 100 of the 2,434,666 contacts formed by outgoing bees, 96.84 re- 

 turns were registered. On 37 of these days the records show more 

 bees coming back than were recorded as going out, and these so- 

 called gains in the returns give an obvious error of at least 1.86 

 per cent for the days recorded in Table 1. These 37 days were dis- 

 tributed as follows, and showed for every 100 exits daily the fol- 

 lowing average returns for each group : April, 4 days, 111.99 ; May, 

 10 days, 104.50; June, 7 days, 104.87; July, 16 days, 104.29. These 

 data give some idea of the magnitude of the daily experimental error 

 which may take place. The percentage returns on these days varied 

 from 100.08 to the maximum, one day in April, when they were as 

 high as 127.81. 



If the days are selected on which the apparatus worked well, and 

 the daily percentage of error which occurred, so far as it could be 

 determined, is kept in mind, the general utility of the curves ob- 

 tained from these data for such purposes as a study of the effect of 

 external environmental factors is little affected by this error. For 

 a study of the average duration of each flight, where a greater 

 degree of accuracy is essential, a closer selection of data is necessary. 

 Referring, therefore, to the outline of the problems on which it is 

 hoped that such an apparatus may give some information, it is found 

 that this apparatus is performing its function as regards four of 

 them, one of which has been rated as the most important in this in- 

 vestigation. 



FACTORS INFLUENCING THE FLIGHT 



The various activities of the colony population are so interrelated 

 that in a study of any one factor, influencing any particular activity 

 such as flight, it sometimes becomes exceedingly difficult to gauge 

 its exact influence, or even to give the right factor the credit -for the 

 behavior observed. Since it is possible not only to observe the varia- 

 tions in flight produced by changes in the intensity of any single 

 factor throughout the course of a day, but also to gauge to a certain 

 extent the gross influence of this factor on the day's flight as a whole, 

 it is necessary in a study of any factor to make use of both of these 

 sources of information. To ascertain the gross influence of any 

 factor, a general survey of the whole period in which records were 

 made is necessary. 



THE SEASONAL SURVEY 



In order to obtain a comprehensive picture of the daily flight 

 activities throughout the season, it is necessary to plot a curve (fig. 

 2) of the total daily exits from the hive (Table 1). As might be 

 expected, this curve has several high points, representing the data 

 for those days when the conditions for flight were at an optimum for 

 the period of the season in which they occur. A day that is consid- 

 ered an optimum for April would very naturally be a bad flight day 

 for June or July ; therefore in a study of any particular day a com- 

 parison must be made between this day and another in close prox- 

 imity to it, when, presumably, or as far as can be ascertained, the 

 field conditions, internal conditions of the colony, and the number of 



