workers equipped with tools for cutting clay as hard as granite to cut
a piece of gauze does not strike me as a happy inspiration; you cannot
expect a navvy's pick-axe to do the same work as a dressmaker's
scissors. Secondly, the transparent glass prison seems to me ill-
chosen. As soon as the insect has made a passage through the thickness
of its earthen dome, it finds itself in broad daylight; and to it
daylight means the final deliverance, means liberty. It strikes
against an invisible obstacle, the glass; and to it glass is nothing
at all and yet an obstruction. On the far side, it sees free space,
bathed in sunshine. It wears itself out in efforts to fly there,
unable to understand the futile nature of its attempts against that
strange barrier which it cannot see. It perishes, at last, of
exhaustion, without, in its obstinacy, giving a glance at the gauze
closing the conical chimney. The experiment must be renewed under
better conditions.

The obstacle which I select is ordinary brown paper, stout enough to
keep the insect in the dark and thin enough not to offer serious
resistance to the prisoner's efforts. As there is a great difference,
in so far as the actual nature of the barrier is concerned, between a
paper partition and a clay ceiling, let us begin by enquiring if the
Mason-bee of the Walls knows how or rather is able to make her way
through one of these partitions. The mandibles are pickaxes suitable
for breaking through hard mortar: are they also scissors capable of
cutting a thin membrane? This is the point to look into first of all.

In February, by which time the insect is in its perfect state, I take
a certain number of cocoons, without damaging them, from their cells
and insert them each in a separate stump of reed, closed at one end by
the natural wall of the node and open at the other. These pieces of