horizon on every side; on the south, in the direction of the nests, a
curtain of hills rises to a height of some three hundred feet above
the spot at which I stand. The wind is not strong, but it is blowing
in the opposite direction to that which my insects will have to take
in order to reach their home. I turn my back on Serignan, so that,
when leaving my fingers, the Bees, to return to the nest, will be
obliged to fly sideways, to right and left of me; I mark the insects
and release them one by one. I begin operations at twenty minutes past
ten.

One half of the Bees seem rather indolent, flutter about for a while,
drop to the ground, appear to recover their spirits and then start
off. The other half show greater decision. Although the insects have
to fight against the soft wind that is blowing from the south, they
make straight for the nest. All go south, after describing a few
circles, a few loops, around us. There is no exception in the case of
any of those whose departure we are able to follow. The fact is noted
by myself and my colleague beyond dispute or doubt. My Mason-bees head
for the south as though some compass told them which way the wind was
blowing.

I am back at twelve o'clock. None of the strays is at the nest; but, a
few minutes later, I catch two. At two o'clock, the number has
increased to nine. But now the sky clouds over, the wind freshens and
the storm is approaching. We can no longer rely on any further
arrivals. Total: nine out of forty, or twenty-two per cent.

The proportion is smaller than in the former cases, when it varied
between thirty and forty per cent. Must we attribute this result to
the difficulties to be overcome? Can the Mason-bees have lost their