t; this movement causes a current of air which can be
felt by holding the hand before the opening of the hive. When the
workers of the corps are fatigued, comrades who have been resting come
to take their place. These acts are not the result of a stupid
instinct which the Hymenoptera obey without understanding. If we place
a swarm, as Huber did, in a roomy position where there is plenty of
air, they do not devote themselves to an aimless exercise. This only
takes place in the narrow dwellings which Man grants to his winged
guests.

The attention of Ants to public hygiene is more than equalled by their
attention to personal hygiene. Without going into the question of
their athletic exercises, which have attracted considerable attention,
it is sufficient to quote one observer as to their habits of
cleanliness. McCook remarks:--"The Agricultural Ants--and the remark
applies to all other Ants of which I have knowledge--is one of the
neatest of creatures in her personal habits. I think I have never seen
one of my imprisoned harvesters, either _Barbatus_ or _Crudelis_, in
an untidy condition. They issue from their burrows, after the most
active digging, even when the earth is damp, without being perceptibly
soiled. Such minute particles of dust as cling to the body are
carefully removed. Indeed, the whole body is frequently and thoroughly
cleansed, a duty which is habitually, I might almost venture to say
invariably, attended to after eating and after sleep. In this process
the Ants assist one another; and it is an exceedingly interesting
sight which is presented to the observer when this general 'washing
up' is in progress."[112]

[112] H. C. McCook, _Agricultural Ants of Texas_, 1879,
chapter on "Toilet, Sleeping, and Funeral Habits," p. 125.

_Prudence of Bees._--Certain species exhibit very great prudence,
especially the _Melipona geniculata_, which lives in a wild state in
South America. They place their combs in the hollow of a tree or the
cleft of a rock; they fill up all the crevices and only leave a round
hole for entry. And even this they are accustomed to close every
evening by a small partition, which they remove in the morning. This
door is shut with various materials, such as resin or even clay, which
the bees bring on their legs as those of our own country bring pollen.

All these facts were observed with great exactness in a swarm given in
1874 by M. Drory (who during a long period of years studi