;o 



FOURTEENTH ANNUAL REPORT OF THE 



inches below it. What this difference 

 might sometimes be in colder climates 

 may be imagined. Examples of this kind 

 might be multiplied indefinitely from 

 the records of these experiments. 



The source of the heat of the cluster 

 must, of course, be the oxidation of the 

 food consumed by the bees. The bee 

 is classed as a cold-blooded animal in 

 that the temperature of the individual 

 bees is practically that of the sur- 

 rounding medium. There is obviously, 

 from the records just given, no internal 

 regulation of the temperature of the 

 body such as is found in birds and 

 mammals, for the temperature of a 

 broodless cluster varies greatly. From 

 the observations made on the various 

 colonies, especially Colony C, it is clear 

 that heat for the warming of the clus- 

 ter is produced by muscular activity. 

 While, of course, some heat is doubt- 

 less liberated by other life processes, 

 this is practically negligible when bees 

 are quiet, as in Colony A when above 

 57° F. That higher temperatures may 

 be produced, greatly increased muscu- 

 lar activity is required, and in Colony C 

 in cold weather bees in the center of 

 the shell of insulating bees were seen 

 fanning vigorously and executing other 

 movements, such as shaking and rapid 

 respiration. We thus have the para- 

 doxical condition that bees fan to heat 

 the cluster in winter as well as to cool 

 the hive in summer. Observations of 

 this kind were repeated beyond num- 

 ber, and this theory of the method of 

 heat production is entirely supported 

 by the repeated observation of a hum- 

 ming noise from the cluster during cold 

 weather. 



A few details of the observation on 

 Colony C may be of interest. For ex- 

 ample, one bee was observed fanning 

 vigorously for 7 1-2 minutes (9.53 to 

 10.00 1-2 a. m., Jan. 23d) while the other 

 bees kept a space cleared for it. The 

 temperature of the nearest thermome- 

 ter rose 1-2°F. during this time. At 

 9.52 this thermometer was almost a 

 degree cooler than at the time of great- 

 est heat during the fanning. The ra- 

 pidity of fanning of the wings varied, 

 and toward the end of the time it be- 

 came so slow that the outline of the 

 wings was distinguishable. After the 

 excessive activity this bee stood in the 

 same place for a time. Rapid respira- 

 tion may play a more important part 

 in heat production than at first ap- 

 pears. One bee was observed to breathe 



21 times in 14 seconds and then cease 

 the rapid respiration. On other occa- 

 sions 50 or more bees would begin 

 shaking their bodies from side to side. 



The Effect of Changes in External 

 Temperature on the Heat Production. 



Another colony (Colony A) was used 

 during the winter of 1912-13 to deter- 

 mine the responses of a normal colony 

 to changes in outer temperature. It 

 also was located on the roof, where the 

 bees were free to fly whenever the 

 wheather permitted and where it was 

 exposed to rapid changes in tempera- 

 ture. It was in a 10 frame Langstroth_ 

 hive, the entrance being reduced to 3-8 

 inches deep and eight inches wide 

 and the colony was not packed 

 or given additional protection. In 

 this hive we placed nineteen 

 electrical thermometers, three on the 

 bottom board in a row down the cen- 

 ter, one in each upper corner and twelve 

 among the combs distributed in such 

 a way that the cluster could never get 

 away from all of them. Readings were 

 made hourly from 9 a. m. to 4 p. m. 

 through the entire period of observation 

 (Sept. 26th to March 28th), except Sun- 

 days and holidays, and at intervals ad- 

 ditional special series of readings were 

 made every 15 minutes (sometimes ev- 

 ery 30 minutes) during the night (5 p. 

 m. to 8:45 a. m.) for periods of several 

 days each. In all 41,413 records were 

 made of temperatures in Colony A. 



The reaction of the cluster in heat 

 production, as induced by changes in 

 external temperature, is well shown by 

 the records made from noon November 

 13 to 2 p. m. November 15 (1912), 

 when readings were made hourly from 

 9 a. m. to 4 p. m. and every 15 minutes 

 at night. From noon on November 13th 

 the outside temperature dropped slowly 

 until 6 a. m. November 15th, and the 

 weather was cloudy, so that the bees 

 did not fly. At noon on the 13th the 

 outside temperature was about 69.20F. 

 and all the points within the hive were 

 then cooler than the outside air, due to 

 the fact that it took some time for the 

 inside of the hive to warm up. At 

 4 p. m. the outside temperature 

 had dropped to 65.3°F., when it was 

 lower than any of the points within 

 the cluster, which had in .the mean- 

 time become warmer. From this time 

 until 6 p. m. the next day (14th) the 

 temperature within the cluster gradu- 

 ally dropped as the outer air cooled, 

 until the lowest one (No. 9) was 57°F. 



