4 BULLETIN 1349, U. S. DEPARTMENT OF AGRICULTURE 



similar curves, representing the daily egg-laying rate of various 

 individual queens. Brtinnich's work, unlike Dufour's, is based, not 

 on an actual count of each cell containing brood, but on a mathe- 

 matical calculation of the number of such cells derived from linear 

 measurements of the brood area on each frame throughout the 

 season. From data thus obtained daily egg-laying rates are cal- 

 culated for the whole season. Although the claim can not be made 

 that Brimnich's work is as nearly accurate as Dufour's, the Swiss 

 investigator has adopted a method which is fairly speedy and readily 

 utilized, and which gives results reliable enough for most purposes. 



METHOD 



In 1920 work on this problem at the Bee Culture Laboratory was 

 first begun when Lloyd R. Watson, formerly apicultural assistant, 

 made actual counts weekly of all eggs, larva?., and sealed brood in 

 five colonies for the entire season. Any such method of counting 

 brood on each comb is necessarily slow. In cool weather it involves 

 the possibility of brood becoming chilled before the operation is 

 completed; at other times there is danger of robbing, and in any 

 event there is too long a disturbance of the colony. Accordingly, 

 when the writer took over the work at the beginning of the season of 

 1921, a photographic method was determined upon, whereby photo- 

 graphs are taken weekly of every frame containing sealed brood, and 

 counts are made later from the negatives. Only sealed brood is 

 counted, because of its greater clearness on the negatives. As a 

 result of the use of this method, photographic records of 16 colonies 

 were obtained in 1921, and of 32 colonies in 1922. Adding to these 

 the counts from the five colonies in 1920, the equivalent of a total of 

 53 individual seasonal brood-rearing records has been obtained 

 already from the work now in progress. 



A small building adjacent to the apiary not only houses the camera 

 permanently but also affords protection from robber bees while 

 taking the pictures. During exposures two 500-watt electric lamps 

 furnish light sufficient to obtain good negatives at all times within 

 the building, regardless of conditions of light outdoors. The camera 

 itself is fastened securely to one end of a base made of 2-inch plank. 

 To maintain the brood frames firmly in position during exposures 

 and yet to have in the negative an image of every cell on the exposed 

 side of each comb, a substantial holder (Plate I, A) is used which 

 consists of a base with two uprights at each end, the uprights being 

 joined by a top piece. The width of the holder is such that the lower 

 half of each end bar of a Langstroth frame just fits into a groove extend- 

 ing upward from the base on the inner surface of each upright. A 

 super spring fastened to the rear edge of each groove presses the end 

 bar firmly against the front edge, and thus, the brood frame is held 

 rigidly in a definite position, although it may easily be slipped in 

 and out of the holder. The holder itself is fastened securely to the 

 same base as is the camera, but at such a distance from the lens as to 

 give a reduction to a scale two-thirds that of the original. Because 

 of the uniform focal distance and the uniform illumination, all 

 negatives are made on an identical scale and under the same light 

 conditions. By the aid of a suitable device attached to the frame 

 holder there is photographed with each frame of brood a record 

 showing the date, the hive and hive body from which the frame came, 



