April, ’23] 
NOLAN: TWO-YEAR BROOD CURVE 
121 
brood-rearing activity of the season may be divided into three major 
phases: (1) an abrupt rise from the beginning of brood-rearing in March 
Fig. 2.—Brood curve for 1921 shown by broken line, that for 1922 by unbroken 
line. Vertical divisions represent months from March to October inclusive; hori¬ 
zontal divisions represent 5000 cells of sealed brood each. 
until the maximum peak is reached at some time in May under normal 
conditions, (2) a pronounced summer decline extending from the * 
maximum until early August, and (3) a late summer, secondary peak 
and subsequent autumn decline. 
The first phase of the curve is all-important to the beekeeper during 
any current season, because a successful crop depends on the proportion 
