196 PERFECT SOCIETIES OF INSECTS. 
one retires, another occupies its place; so that in a hive 
well peopled there is never any interruption of the sound 
or humming occasioned by this action; by which it may 
always be known whether it be going on or not. 
This humming is observable not only during the 
heats of summer, but at all seasons of the year. It some- 
times seems even more forcible in the depth of winter 
than when the temperature of the atmosphere is higher. 
An employment so constant, which always occupies a 
certain number of bees, must produce as constant an ef- 
fect. The column of air once disturbed within, must 
give place to that without the hive; thus a current be- 
ing established, the ventilation will be perpetual and 
complete. 
To be convinced that such an effect is produced, ap- 
proach your hand to a ventilating bee, and you will find 
that she causes a very perceptible motion in the air. 
Huber tried an experiment still more satisfactory. On 
a calm day, at the time when the bees had returned to 
their habitation—having fixed a screen before the mouth 
of the hive to prevent his being misled by any sudden 
motion of the external air—he placed within the screen 
little anemometers or wind-gauges, made of bits of pa- 
per, feather, or cotton, suspended by a thread to a crotch. 
No sooner did they enter the atmosphere of the bees 
than they were put in motion, being alternately attracted 
and repelled to and from the aperture of the hive with 
considerable rapidity. These attractions and repulsions 
were proportioned to the number of bees engaged in 
ventilation, and, though sometimes less perceptible, were 
never entirely suspended. Burnens tried a similar ex- 
periment in the winter, when the thermometer stood in 
