ouble-galleried tubes, thirty-seven cylindrical
tubes, seventy-eight Snail-shells and a few old nests of the Mason-bee
of the Shrubs. From this rich mine of material I will take what I want
to prove my case.

Every series, even when incomplete, begins with females and ends with
males. To this rule I have not yet found an exception, at least in
galleries of normal diameter. In each new abode the mother busies
herself first of all with the more important sex. Bearing this point in
mind, would it be possible for me, by manoeuvring, to obtain an
inversion of this order and make the laying begin with males? I think
so, from the results already ascertained and the irresistible
conclusions to be drawn from them. The double-galleried tubes are
installed in order to put my conjectures to the proof.

The back gallery, 5 or 6 millimetres wide (.195 to .234
inch.--Translator's Note.), is too narrow to serve as a lodging for
normally developed females. If, therefore, the Osmia, who is very
economical of her space, wishes to occupy them, she will be obliged to
establish males there. And her laying must necessarily begin here,
because this corner is the rear-most part of the tube. The foremost
gallery is wide, with an entrance-door on the front of the hive. Here,
finding the conditions to which she is accustomed, the mother will go
on with her laying in the order which she prefers.

Let us now see what has happened. Of the fifty-two double-galleried
tubes, about a third did not have their narrow passage colonized. The
Osmia closed its aperture communicating with the large passage; and the
latter alone received the eggs. This waste of space was inevitable. The
female Osmiae, though nearly always larger than the males, present
marked differences among one another: some are bigger, some are
smaller. I had to adjust the width of the narrow galleries to Bees of
average dimensions. It may happen therefore that a gallery is too small
to admit the large-sized mothers to whom chance allots it. When the
Osmia is unable to enter the tube, obviously she will not colonize it.
She then closes the entrance to this space which she cannot use and
does her laying beyond it, in the wide tube. Had I tried to avoid these
useless apparatus by choosing tubes of larger calibre, I should have
encountered another drawback: the medium-sized mothers, finding
themselves almost comfortable, would have decided to lodge females
there. I had to be prepared for it: