204 



THE BEE-KEEPERS' REVIEW 



mentioned external temperature 

 food, ventilation, humidity, the con- 

 dition of the colony at the begin- 

 ning of winter, and various forms 

 of irritation. In the present paper 

 special emphasis is placed on heat 

 production, by which is meant the 

 responses of the bees of the cluster 

 to the outer temperature and to 

 changes in the outer temperature as 

 manifested in the generation of 

 heat by the bees. 



A special reason for this empha- 

 sis in a premiminary paper is that 

 all previous work on the tempera- 

 ture of the cluster in winter, of 

 which there has been considerable 

 has failed to show definitely what 

 the normal responses are. The data 

 are often those of abnormal con- 

 ditions and are therefore mislead- 

 ing, making them almost valueless 

 for purposes of application. One 

 source of error which is to be 

 found in all the records known to 

 authors is the use of the mercury 

 thermometer, for, when such a 

 thermometer is used, it is almost 

 impossible to avoid disturbing the 

 cluster at each reading so that it 

 reacts abnormally. Furthermore, as 

 the authors will attempt to show 

 at a later time, disturbances of 

 the colony may influence the tem- 

 perature of the cluster for a consid- 

 erable period, often more than one 

 day. Usually no account has been 

 taken of the necessary corrections 

 to be made for the mercury ther- 

 mometer. 



Because of the errors in other 

 work on the subject, due to the 

 use of mercury thermometers chosen 

 tor the work here recorded are of 

 another kind. Electrical thermom- 

 eters are used, by means of which 

 readings can be made without ap- 

 proaching the hive, and the ther- 

 rrometers (couples) are of course 

 permanently fastened in place. 

 These are of the type known as 

 thermocouples or thermal junctions 

 and the readings are made by 

 means of a potentiometer indicator 

 and a sensitive galvanometer of 

 the d'Arsonval type. The wires 

 used in the thermocouples are cop- 

 per and constantin (a copper-nickel 

 ailoy), giving an electromotive force 

 of about 40 u V per degree centi- 

 grade. A detailed description of 

 the apparatus is impossible here, 

 and it need only be stated that the 

 method as used gives readings to 



an accuracy of 0.09° F. (0.05° C); 

 the thermometers are practically 

 instantaneous in their action — that 

 is, show changes in temperature 

 without a "lag;" the readings of 

 many thermometers can be made 

 consecutively on one carefully cal- 

 ibrated instrument, insuring uni- 

 formity which is impossible in us- 

 ing many mercury thermometers; 

 and, a point of importance in such 

 work, the readings can be made at 

 the rate of two a minute, which 

 would be impossible with widely 

 scattered instruments. In all, 161, 

 617 temperature readings were made 

 during the winter 1912-13, and the 

 work is being continued. 



Part of the colonies are kept in 

 a well-insulated room (used as a 

 "bee cellar") in the zoological la- 

 boratory of the University of Penn- 

 sylvania, Philadelphia, Pa., which 

 can be kept at a temperature us- 

 ually varying not over 2° F., far 

 more uniform than the ordinary 

 bee cellar. Abundant ventilation is 

 provided, and the room is complete- 

 ly darkened to avoid possible dis- 

 turbance by light. The tempera- 

 tures of the indoor colonies are 

 read from an adjoining laboratory 

 to eliminate the possible errors due 

 to disturbance, and the room is 

 entered rarely (about once a week 

 on an average and, if possible only 

 after the day's records are made) 

 and only when absolutely neces- 

 sary. It is found that entering 

 the constant-temperature room 

 may under some conditions influ- 

 ence the behavior of the bees in a 

 marked manner. 



Other colonies are kept on the 

 roof of the same laboratory, where 

 they are left untouched from the 

 beginning to the end of a series 

 of readings. The Avires of the ther- 

 mometers are led to the room be- 

 low through rubber tubes, and all 

 the temperature readings are made 

 at a distance, as is absolutely nec- 

 essary to eliminate disturbance. 

 Disturbances of outside colonies 

 have also been found to influence 

 their behavior in a pronounced 

 manner, especially in cold weather. 



By studying the temperature of 

 various fixed points within each 

 hive it has been found possible to 

 use the temperature readings as a 

 substitute for direct obsrevations. 

 After becoming familiar with the 

 (Continued on page 225) 



