2 BULLETIN 988, IT. S. DEPT. OF AGRICULTURE. 



they are called upon to do. When there is a heavy honey flow and the 

 bees are at their greatest activity their lives are limited to about 6 

 weeks, while during the winter season, if every condition is favor- 

 able, they may live 6 months. On the other hand, it is clear from 

 the experience of beekeepers and from the investigations previously 

 mentioned that if the conditions in wintering are unfavorable the 

 bees are aroused to great activity.^ Under these conditions they are 

 greatly reduced in strength, and even though they may live through 

 the actual period of winter, they are so depleted in vitality that they 

 are unable to do the heavy work incident to building up the colony 

 to full summer strength, and they die off faster than their places 

 are taken by the emerging bees of the brood reared in the spring. 

 In the honeybee organism either the power of constructive metab- 

 olism is entirely lacking or it is far less effective than that of de- 

 structive metabolism, and the rate of the latter is apparently accel- 

 erated by the activity of the bees, thus bringing on more rapidly the 

 impairment of functional capacity which ends in death. The physio- 

 logical changes which occur in worker bees during this process of 

 aging are not well understood, but certain facts have been observed 

 which are significant, Mr. Goodrich-Pixell 3 has found that the 

 nerve cells in bees dying of exhaustion are highly vacuolated and the 

 cytoplasm greatly depleted, thus substantiating the work of Hodge 4 

 and of Smallwood and Phillips. 5 



Chief among the factors that influence the activity and consequent 

 welfare of a colony of bees in winter are the condition of the colony 

 at the beginning of winter (physiological age of the individuals) , ex- 

 ternal temperature, quality of the food used during confinement, 

 ventilation, humidity, and various causes of irritation. The experi- 

 ment here recorded was undertaken to study the responses of bees to 

 some of these stimuli, as measured by heat production, being a con- 

 tinuation of the work of Phillips and Demuth (loc. cit.) on the be- 

 havior of bees in winter, in which work the temperature responses 

 were of greater significance. It was carried out in December, 1915, 

 and the intention was to continue with similar experiments in other 

 seasons under a wider variety of conditions than was maintained in 

 this instance. Such investigations can be conducted only after brood 

 rearing has normally stopped, and they must be concluded before the 

 bees are filled with feces, in order that the data may not be com- 

 plicated by activity due to this disturbing factor. It is therefore 



3 Quart. Jour. Micros. Sci. [London], n. ser., 04 (1920), No. 254, Ft. 2, pp. 191-206. 

 ill. Determination of age in honeybees. 



4 Jour. Physiol, 17 (1894) Changes in ganglion cells from birth to senile death; 

 observations on man and honeybees. 



5 Jour. Comp. Neur., 27 (1916). Nuclear size in the nerve-cells of the bee during the 

 life-cycle. 



