owner, when she gets
back, sees nothing either, for she continues the victualling without
betraying the least uneasiness. A strange egg, laid on the provisions,
would not escape her. I know how clean she keeps her warehouse; I know
how scrupulously she casts out anything introduced by my agency: an egg
that is not hers, a bit of straw, a grain of dust. So, according to
my evidence and that of the Chalicodoma, which is more conclusive, the
Dioxys's egg, if it is really laid then, is not placed on the surface.

I suspect, without having yet verified my suspicion--and I reproach
myself for the neglect--I suspect that the egg is buried in the heap of
pollen-dust. When I see the Dioxys come out of a cell with her mouth
all over yellow flour, perhaps she has been surveying the ground and
preparing a hiding-place for her egg. What I take for a mere tasting
might well be a more serious act. Thus concealed, the egg escapes the
eagle eye of the Bee, whereas, if left uncovered, it would inevitably
perish, would be flung on the rubbish heap at once by the owner of
the nest. When the Spotted Sapyga lays her egg on that of the
Bramble-dwelling Osmia, she does the deed under cover of darkness,
in the gloom of a deep well to which not the least ray of light can
penetrate; and the mother, returning with her pellet of green putty
to build the closing partition, does not see the usurping germ and is
ignorant of the danger. But here everything happens in broad daylight;
and this demands more cunning in the method of installation.

Besides, it is the one favourable moment for the Dioxys. If she waits
for the Mason-bee to lay, it is too late, for the parasite is not able
to break down doors, as the Stelis does. As soon as her egg is laid, the
Mason-bee of the Sheds comes out of her cell and at once turns round and
proceeds to close it up with the pellet of mortar which she holds ready
in her mandibles. The material is employed with such method that the
actual sealing is done in a moment: the other pellets, the object of
repeated journeys, will serve merely to increase the thickness of the
lid. The chamber is inaccessible to the Dioxys from the first touch of
the trowel. Hence it is absolutely necessary for her to see to her
egg before the Mason-bee of the Sheds has disposed of hers and no less
necessary to conceal it from the Mason's watchful eye.

The difficulties are not so great in the nests of the Mason-bee of the
Pebbles. After this B