HEAT PRODUCTION OF HONEYBEES IN WINTER, 9 
corresponding error in the measurements of the quantities for the 
two periods; but as there was free space in the small experimental 
hive for only a few liters of air, a relatively large change in the 
carbon-dioxid content of the air in the hive would introduce only 
a very small error in the quantity measured in any period. 
The determination of the carbon-dioxid production for the experi- 
ment as a whole is accurate. In footing the total the quantity for the 
first day is omitted, because the oxygen consumed was not measured 
that day. In the 10 days the bees produced 130 liters of carbon dioxid 
and consumed 138 liters of oxygen. The corresponding respiratory 
quotient is 0.94, which indicates that their metabolism was almost 
entirely that of carbohydrate. Their heat production, calculated 
from these data, was 688 calories. The quantity of heat measured by 
the calorimeter was larger than this, but it involved an error due to 
leakage of heat through the walls, owing to the wide difference be- 
tween the temperature of the air in the chamber and that in the lab- 
oratory, which the apparatus as used could not overcome. Making 
such allowance for this error as was indicated by subsequent test of 
the apparatus under somewhat similar conditions, the corrected 
amount of heat measured was but slightly different from this com- 
puted value. 
The number of bees in this colony, by actual count, was 9,635. The 
average weight of empty worker bees is about 0.075 gram ; their total 
weight, in round numbers, would be 720 grams. The heat output of, 
this colony, 688 calories, was therefore equivalent to 0.97 calorie 
per gram for the 10 days, or virtually 0.1 calorie per gram per day. 
This is equivalent to a heat output of 7,000 calories per day by a man 
weighing 70 kilograms (154 pounds), which is found only in unusual 
circumstances. The average individual of this size actively engaged 
in hard work at least 8 hours a day would give off about 4,000 cal- 
ories in 24 hours. The heat output of lumbermen working hard in 
the northern woods in a cold winter was found to be about 7,000 
calories per man per day, as indicated by their food consumption. 
During the period that they were working hardest their hourly ex- 
penditure of energy may have been double the average for the rest 
of the day, possibly as high as 600 calories per hour, although this 
seems doubtful. In certain experimental conditions a well-trained 
man engaged in muscular activity sufficient to cause a heat output of 
650 calories per hour, which was measured in the same manner as the 
heat output of the bees was measured in this experiment, but this 
was considered to be severe, exhausting work, almost at the limit of 
human endurance, and was continued only for short periods. This 
output, per unit of weight, would be larger than that of the colony 
of bees taken as a whole, but it will be recalled that the bees actually 
55663°— 21 2 
