10 BULLETIN 988, U. S. DEPT. OF AGRICULTURE. 



engaged in the excessive activity of heat production at any one time 

 are only a small part of the total colony, the rest of them being 

 crowded together in the shell of the cluster or in empty cells of the 

 honey comb or standing quietly. The amount of work done by the 

 bees that are really active is comparable with that done by the man 

 in unusual conditions, and is therefore relatively enormous; and this 

 is maintained not only for short periods but through the whole day 

 and the whole winter. 



Moreover, it will also be observed that the temperature conditions 

 during this experiment were those in which bees are the least active. 

 In fact, as mentioned previously, the temperature in the respiration 

 chamber during the experiment was about the same as that which 

 beekeepers usually maintain in cellars for wintering bees. Colonies 

 wintered outdoors, especially if unprotected, must endure in many 

 cases much more severe temperature conditions. Furthermore, this 

 experiment was conducted at a time of the year when bees are 

 naturally more nearly quiescent. Bees are usually more active dur- 

 ing the latter part of winter than during late fall and early winter. 

 The figures obtained in this experiment, therefore, represent about as 

 low an expenditure of energy as is ever found in a colony of bees, 

 except for short intervals. In a preliminary test with this colony 

 the quantities of carbon dioxid measured were decidedly larger than 

 these, owing to less favorable conditions. 



A hj^grometer suspended in the chamber was read at frequent 

 intervals. The maximum and minimum readings for each day 

 are shown in the table. During the first five days the humidity was 

 allowed to remain at a high level. This was accomplished by keep- 

 ing the air of the system in circulation only part of the time, 

 virtually every other hour. During the other five days the humidity 

 was kept much lower by maintaining a constant circulation of air 

 through the sulphuric acid. There was a very noticeable difference 

 in the quantities of water vapor removed from the chamber in the 

 several days of the two periods, owing to the fact that the relative 

 dryness of the air in the later period was causing a loss of water 

 from the wood of the hive. No difference in the activity of the bees 

 that could be ascribed to the difference in water- vapor content of the 

 air was noticeable in the temperature curves or in the carbon-dioxid 

 output of the various days. 



The barometer was read at noon each day. There were no sig- 

 nificant changes in barometric pressure during the course of the ex- 

 periment. The reading on the 13th was 755 millimeters, which rose 

 each succeeding day to 769 on the 16th, then fell to 750 on the 18th. 

 It was 767 on the 19th and for the rest of the experiment remained 

 within 4 millimeters of this pressure. 



