recognized as common property without dispute. The sisters come and go
peacefully through the same door, attend to their business, pass and
let the others pass. Down at the bottom of the pit, each has her little
demesne, her group of cells dug at the cost of fresh toil, when the old
ones, now insufficient in number, are occupied. In these recesses,
which are private estates, each mother works by herself, jealous of her
property and of her privacy. Every elsewhere, traffic is free to all.

The exits and entrances in the working fortress provide a spectacle
of the highest interest. A harvester arrives from the fields, the
feather-brushes of her legs powdered with pollen. If the door be open,
the Bee at once dives underground. To tarry on the threshold would mean
waste of time; and the business is urgent. Sometimes, several appear
upon the scene at almost the same moment. The passage is too narrow for
two, especially when they have to avoid any untimely contact that would
make the floury burden fall to the floor. The nearest to the opening
enters quickly. The others, drawn up on the threshold in order of their
arrival, respectful of one another's rights, await their turn. As soon
as the first disappears, the second follows after her and is herself
swiftly followed by the third and then the others, one by one.

Sometimes, again, there is a meeting between a Bee about to come out and
a Bee about to go in. Then the latter draws back a little and makes way
for the former. The politeness is reciprocal. I see some who, when on
the point of emerging from the pit, go down again and leave the passage
free for the one who has just arrived. Thanks to this mutual spirit of
accommodation, the business of the house proceeds without impediment.

Let us keep our eyes open. There is something better than the
well-preserved order of the entrances. When an Halictus appears,
returning from her round of the flowers, we see a sort of trap-door,
which closed the house, suddenly fall and give a free passage. As soon
as the new arrival has entered, the trap rises back into its place,
almost level with the ground, and closes the entrance anew. The same
thing happens when the insects go out. At a request from within, the
trap descends, the door opens and the Bee flies away. The outlet is
closed forthwith.

What can this valve be which, descending or ascending in the cylinder
of the pit, after the fashion of a piston, opens and closes the house
at