her. To
compile a register of births is absolutely impossible here. Fortunately
there are a few species in which we do not find this difficulty: these
are the Bees who keep to one gallery and build their cells in storeys.
Among the number are the different inhabitants of the bramble-stumps,
notably the Three-pronged Osmiae, who form an excellent subject for
observation, partly because they are of imposing-size--bigger than any
other bramble-dwellers in my neighbourhood--partly because they are so
plentiful.

Let us briefly recall the Osmia's habits. Amid the tangle of a hedge, a
bramble-stalk is selected, still standing, but a mere withered stump. In
this the insect digs a more or less deep tunnel, an easy piece of work
owing to the abundance of soft pith. Provisions are heaped up right at
the bottom of the tunnel and an egg is laid on the surface of the
food: that is the first-born of the family. At a height of some twelve
millimetres (About half an inch.--Translator's Note.), a partition
is fixed, formed of bramble saw-dust and of a green paste obtained by
masticating particles of the leaves of some plant that has not yet
been identified. This gives a second storey, which in its turn receives
provisions and an egg, the second in order of primogeniture. And so it
goes on, storey by storey, until the cylinder is full. Then a thick plug
of the same green material of which the partitions are formed closes the
home and keeps out marauders.

In this common cradle, the chronological order of births is perfectly
clear. The first-born of the family is at the bottom of the series; the
last-born is at the top, near the closed door. The others follow from
bottom to top in the same order in which they followed in point of
time. The laying is numbered automatically; each cocoon tells us its
respective age by the place which it occupies.

To know the sexes, we must wait for the month of June. But it would be
unwise to postpone our investigations until that period. Osmia-nests are
not so common that we can hope to pick one up each time that we go out
with that object; besides, if we wait for the hatching-period before
examining the brambles, it may happen that the order has been disturbed
through some insects' having tried to make their escape as soon as
possible after bursting their cocoons; it may happen that the male
Osmiae, who are more forward than the females, are already gone. I
therefore set to work a long time beforehand