510 IOWA DEPARTMENT OF AGRICULTURE 



on warm days (if free to fly), and therefore the problem, so far as it is 

 under the control of the beekeeper, is primarily to obviate the necessity 

 for the production of heat. If brood is reared the work of the bees is 

 necessarily enormously increased, and their vitality is correspondingly de- 

 creased. So far as evidence is available in our work, the colony is not 

 fully recompensed for this expenditure of energy by an increase in the 

 strength of the colony by bees thus reared. 



The colonies to be discussed under this heading (Nos. 1 and 3) were 

 wintered in a constant-temperature room at the University of Pennsyl- 

 vania, Philadelphia, Pennsylvania, in special 6-frame hives (to economize 

 space and concentrate the colony so that fewer thermometers would be 

 required) with full entrances and were not propolized or sealed at the top. 

 During the regular series of readings the room was kept at a temperature 

 which rarely dropped below 40° F. or went above 45° F., and the average 

 temperature from October 14 to March 6 was 42.67° F. This temperature 

 was chosen as being nearly the one usually considered best by beekeepers. 

 The foods given these colonies were stored in the combs, just as placed 

 by the bees. There was some pollen available in colony No. 1. On this 

 colony, 24,077 temperature readings were taken. 



According to what has been said in the previous section, we should 

 expect bees at such a temperature to maintain a compact cluster and to 

 generate some heat at all times. This was actually the case, the tempera- 

 ture of the interior of the clusters dropping below 64° F. only a few 

 times in either colony. 



Colony No. 1, on honey stores, was in the constant-temperature room 

 from October 12, 1912, to March 24, 1913, or 163 days. It was then re- 

 moved for a flight and put back the same evening, where it remained 

 until March 28. From March 7 at 9 a. m. until March 28 at 4 p. m. 

 readings were made on this colony every 15 minutes night and day, with 

 the exception of the period between 9 a. m. and 7 p. m. on the 24th, 

 when it was out of doors. During this period of three weeks the temper- 

 ature of the room was changed slowly, being raised as high as 64° F. 

 and cooled to 13° F. 



When this colony was first placed in the room for the regular series 

 of readings, after a preliminary confinement, October 12 (the readings 

 were begun Monday, October 14), it maintained a cluster temperature 

 which usually lay between 64° and 68° F., the daily average tempera- 

 ture departing from these rather narrow limits only four times up to 

 November 22. The average temperature is 66.5° F. During the first five 

 weeks the temperature of the room was less regular than later (due to 

 faulty working of the regulating apparatus), and this doubtless accounts 

 for some irregularities in the cluster temperature. At first the three ther- 

 mometers in the cluster (1, 2, and 5) gave temperature readings quite 

 close together, while thermometer 6, which was near the cluster, gave 

 readings intermediate between the three thermometers of the cluster and 

 the four others in the hive, farther from the cluster. After November 22 

 the records of the thermometers in the cluster were more widely sep- 

 arated and the temperature of the center of the cluster (shown on ther- 



