THE BROOD-BEARING CYCLE OE THE HONEYBEE 5 



the location of the frame in the hive body, and the particular side 

 of the frame. A net of wires forming 1-inch squares is permanently 

 fixed to the holder at such a point as barely to clear the surface of 

 any brood frame in the holder and still be in focus. The squares, 

 showing clearly in the negative (Plate I, B), divide the brood area 

 into such small sections as to render possible an extremely accurate, 

 direct count. 



For recording the counts from each negative, a card is ruled into 

 squares identical in size and number with those in the picture itself. 

 All squares corresponding to areas containing only sealed worker 

 cells may be credited with the number of cells contained in 1 square 

 inch; but in squares containing unsealed as well as sealed cells, the 

 number of unsealed cells must be deducted first. There are many 

 contradictory statements as to the number of cells per square inch, due 

 in part to attemps to derive it mathematically from the dimensions 

 of some single cell instead of counting the actual numbers in areas 

 large enough to get a trustworthy average. Watson, by making 

 such counts, found the average number per square inch to be slightly 

 in excess of 26. This number has been used in the results presented 

 here. Some variation exists between individual combs, however, 

 possibly due to the foundation used. Thus, in combs from certain 

 foundation the writer has found 26.3 worker cells per inch, and in 

 combs from foundation bought after the results for 1921 were ob- 

 tained he has found approximately 27 worker ceils per square inch. 

 Much of this latter type of foundation has been used since that date, 

 and subsequent results are therefore being calculated on this basis. 

 It is very evident that the general relations of a curve based on the 

 amount of brood counted will remain the same, regardless of whether 

 in the counts the number of cells per square inch is taken to be 26, 

 27, or some other figure of nearly the same size. As a matter of fact, 

 the difference between 26 and 27 is less than 4 per cent, or less than 

 40 in every 1,000. 



In areas containing 50 per cent or more of unsealed cells it has been 

 found preferable to count each individual sealed cell. Sealed drone 

 cells also are counted individually. They have little influence on 

 the totals, however, because by proper selection of brood combs it 

 has been possible to keep the total of sealed drone cells well below 

 000 on any one count. Since in counting individual cells, either 

 scaled or unsealed, some arbitrary rule must be followed in crediting 

 them to a particular square; all such cells are credited to, or deducted 

 from, the total of the square immediately to the left of the vertical 

 dividing line, or below the horizontal dividing line, as the case may 

 be. Totals for each card and colony are calculated on an adding 

 machine. The photographic record once obtained, the actual count- 

 ing may be delayed until any convenient time, so long as the nega- 

 tive docs not deteriorate. A series of such records permits making 

 ;i year-by-year comparison of any portion of the sealed-brood area. 

 Cut films, 5 by 7 inches in size, are used exclusively in this work. 



Before photographing, all of the frames containing sealed brood 

 in any given hive body are shaken or brushed free of adhering bees, 

 placed in an empty hive body, and immediately carried to the build- 

 ing where the photographs are made. The exposures can be made 

 in 10 seconds, i bus keeping the frames out of the hive for an exceed- 

 ingly short time. Danger of chilling the brood is thus reduced to a 



