be enough to
make any regular hatching-sequence impossible in either direction.

These surmises accord with the facts: the chronological sequence of
the cells tells us nothing about the chronological sequence of the
hatchings, which take place without any definite order. There is,
therefore, no surrender of rights of primogeniture, as Leon Dufour
thought: each insect, regardless of the others, bursts its cocoon when
its time comes; and this time is determined by causes which escape our
notice and which, no doubt, depend upon the potentialities of the egg
itself. It is the case with the other bramble-dwellers which I have
subjected to the same test (Osmia detrita, Anthidium scapulare, Solenius
vagus, etc.); and it must also be the case with Odynerus rubicola: so
the most striking analogies inform us. Therefore the singular exception
which made such an impression on Dufour's mind is a sheer logical
illusion.

An error removed is tantamount to a truth gained; and yet, if it were
to end here, the result of my experiment would possess but slight value.
After destruction, let us turn to construction; and perhaps we shall
find the wherewithal to compensate us for an illusion lost. Let us begin
by watching the exit.

The first Osmia to leave her cocoon, no matter what place she occupies
in the series, forthwith attacks the ceiling separating her from the
floor above. She cuts a fairly clean hole in it, shaped like a truncate
cone, having its larger base on the side where the Bee is and its
smaller base opposite. This conformation of the exit-door is a
characteristic of the work. When the insect tries to attack the
diaphragm, it first digs more or less at random; then, as the boring
progresses, the action is concentrated upon an area which narrows
until it presents no more than just the necessary passage. Nor is the
cone-shaped aperture special to the Osmia: I have seen it made by the
other bramble-dwellers through my thick disks of sorghum-pith. Under
natural conditions, the partitions, which, for that matter, are very
thin, are destroyed absolutely, for the contraction of the cell at
the top leaves barely the width which the insect needs. The truncate,
cone-shaped breach has often been of great use to me. Its wide base made
it possible for me, without being present at the work, to judge which
of the two neighbouring Osmiae had pierced the partition; it told me the
direction of a nocturnal migration which I had been unable