them. There is, in fact, no doubt that they were setting eyes for the
first time on those osier-beds of the Aygues which I had selected as
the starting-point. Never would they have travelled so far afield of
their own accord, for everything that they want for building and
victualling under the roof of my shed is within easy reach. The path
at the foot of the wall supplies the mortar; the flowery meadows
surrounding my house furnish nectar and pollen. Economical of their
time as they are, they do not go flying two miles and a half in search
of what abounds at a few yards from the nest. Besides, I see them
daily taking their building-materials from the path and gathering
their harvest on the wild-flowers, especially on the meadow sage. To
all appearance, their expeditions do not cover more than a radius of a
hundred yards or so. Then how did my exiles return? What guided them?
It was certainly not memory, but some special faculty which we must
content ourselves with recognizing by its astonishing effects without
pretending to explain it, so greatly does it transcend our own
psychology.


CHAPTER 3. EXCHANGING THE NESTS.

Let us continue our series of tests with the Mason-bee of the Walls.
Thanks to its position on a pebble which we can move at will, the nest
of this Bee lends itself to most interesting experiments. Here is the
first: I shift a nest from its place, that is to say, I carry the
pebble which serves as its support to a spot two yards away. As the
edifice and its base form but one, the removal is performed without
the smallest disturbance of the cells. I lay the boulder in an exposed
place where it is well in view, as it was on its original site. The
Bee returning from her harvest cannot fail to see it.