eave
the victualler entire liberty of action; but the former do not exceed
the width of a cell, a width agreeing with the bulk of the future
cocoon, whereas the latter, with their excessive diameter, require more
than one chamber on the same floor.

When free to choose, the Osmia settles by preference in the small reeds.
Here, the work of building is reduced to its simplest expression and
consists in dividing the tube by means of earthen partitions into a
straight row of cells. Against the partition forming the back wall of
the preceding cell the mother places first a heap of honey and pollen;
next, when the portion is seen to be enough, she lays an egg in the
centre of it. Then and then only she resumes her plasterer's work
and marks out the length of the new cell with a mud partition. This
partition in its turn serves as the rear-wall of another chamber, which
is first victualled and then closed; and so on until the cylinder is
sufficiently colonized and receives a thick terminal stopper at
its orifice. In a word, the chief characteristic of this method of
nest-building, the roughest of all, is that the partition in front is
not undertaken so long as the victualling is still incomplete, or, in
other words, that the provisions and the egg are deposited before the
Bee sets to work on the partition.

At first sight, this latter detail hardly deserves attention: is it
not right to fill the pot before we put a lid on? The Osmia who owns a
medium-sized reed is not at all of this opinion; and other plasterers
share her views, as we shall see when we watch the Odynerus building
her nest. (A genus of Mason-wasps, the essays on which have not yet been
translated into English.--Translator's Note.) Here we have an excellent
illustration of one of those latent powers held in reserve for
exceptional occasions and suddenly brought into play, although often
very far removed from the insect's regular methods. If the reed, without
being of inordinate width from the point of view of the cocoon, is
nevertheless too spacious to afford the Bee a suitable purchase against
the wall at the moment when she is disgorging honey and brushing off her
load of pollen; the Osmia altogether changes the order of her work; she
sets up the partition first and then does the victualling.

All round the inside of the tube she places a ring of mud, which, as the
result of her constant visits to the mortar, ends by becoming a complete
diaphragm minus an or