ertain that the Sitaris-grub does not leave
the fleece of the Mason-bee when the Bee is in her cell or at the
entrance to it, in order itself to make a rush for the coveted honey;
for this honey would inevitably cause its death, if it happened by
accident to touch the perilous surface merely with the tip of its
tarsi.

Since we cannot admit that the Sitaris-grub leaves the furry corselet
of its hostess to slip unseen into the cell, whose orifice is not yet
wholly walled up, at the moment when the Anthophora is building her
door, all that remains to investigate is the second at which the egg
is being laid. Remember in the first place that the young Sitaris
which we find in a closed cell is always placed on the egg of the Bee.
We shall see in a minute that this egg not merely serves as a raft for
the tiny creature floating on a very treacherous lake, but also
constitutes the first and indispensable part of its diet. To get at
this egg, situated in the centre of the lake of honey, to reach, at
all costs, this raft, which is also its first ration, the young larva
evidently possesses some means of avoiding the fatal contact of the
honey; and this means can be provided only by the actions of the Bee
herself.

In the second place, observations repeated _ad nauseam_ have shown me
that at no period do we find in each invaded cell more than a single
Sitaris, in one or other of the forms which it successively assumes.
Yet there are several young larvae established in the silky tangle of
the Bee's thorax, all eagerly watching for the propitious moment at
which to enter the dwelling in which they are to continue their
development. How then does it happen that these larvae, goaded by such
an appetite as one would expect after seven or eight months' complete
abstinence, instead of all rushing together into the first cell within
reach, on the contrary enter the various cells which the Bee is
provisioning one at a time and in perfect order? Some action must take
place here independent of the Sitares.

To satisfy those two indispensable conditions, the arrival of the
larva upon the egg without crossing the honey and the introduction of
a single larva among all those waiting in the fleece of the Bee, there
can be only one explanation, which is to suppose that, at the moment
when the Anthophora's egg is half out of the oviduct, one of the
Sitares which have hastened from the thorax to the tip of the abdomen,
one more highly favoured by