2 BULLETIN 988, TJ. 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 
Avelfare 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., 64 (1920), No. 254, Pt. 2, pp. 191-206. 
ill. Determination of age in honeybees. 
* Jour. Physiol, 17 (1S94) 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. 
