t
the insult in a mortal duel. The whole thing is confined to hostile
demonstrations and a few insignificant cuffs.

Nevertheless, the real proprietress seems to derive double courage and
double strength from the feeling that she is in her rights. She takes up
a permanent position on the nest and receives the other, each time
that she ventures to approach, with an angry quiver of her wings, an
unmistakable sign of her righteous indignation. The stranger, at last
discouraged, retires from the field. Forthwith the Mason resumes her
work, as actively as though she had not just undergone the hardships of
a long journey.

One more word on these quarrels about property. It is not unusual,
when one Mason-bee is away on an expedition, for another, some homeless
vagabond, to call at the nest, take a fancy to it and set to work on it,
sometimes at the same cell, sometimes at the next, if there are
several vacant, which is generally the case in the old nests. The first
occupier, on her return, never fails to drive away the intruder, who
always ends by being turned out, so keen and invincible is the mistress'
sense of ownership. Reversing the savage Prussian maxim, 'Might is
right,' among the Mason-bees right is might, for there is no other
explanation of the invariable retreat of the usurper, whose strength is
not a whit inferior to that of the real owner. If she is less bold, this
is because she has not the tremendous moral support of knowing herself
in the right, which makes itself respected, among equals, even in the
brute creation.

The second of my travellers does not reappear, either on the day when
the first arrived or on the following days. I decide upon another
experiment, on this occasion with five subjects. The starting-place is
the same; and the place of arrival, the distance, the time of day, all
remain unchanged. Of the five with whom I experiment, I find three at
their nests next day; the two others are missing.

It is therefore fully established that the Mason-bee of the Walls,
carried to a distance of two and a half miles and released at a place
which she has certainly never seen before, is able to return to the
nest. But why do first one out of two and then two out of five fail
to join their fellows? What one can do cannot another do? Is there a
difference in the faculty that guides them over unknown ground? Or is it
not rather a difference in flying-power? I remember that my Bees did not
all start off with