free space above the series,
a space showing that the laying is ended, for, if the mother had any
more eggs available, she would have lodged them in the room which she
leaves unoccupied. This string of fifteen appears to be rare; it was the
only one that I found. My attempts at indoor rearing, pursued during two
years with glass tubes or reeds, taught me that the Three-horned
Osmia is not much addicted to long series. As though to decrease the
difficulties of the coming deliverance, she prefers short galleries, in
which only a part of the laying is stacked. We must then follow the same
mother in her migration from one dwelling to the next if we would obtain
a complete census of her family. A spot of colour, dropped on the Bee's
thorax with a paint-brush while she is absorbed in closing up the mouth
of the tunnel, enables us to recognize the Osmia in her various homes.

In this way, the swarm that resided in my study furnished me, in the
first year, with an average of twelve cells. Next year, the summer
appeared to be more favourable and the average became rather higher,
reaching fifteen. The most numerous laying performed under my eyes, not
in a tube, but in a succession of Snail-shells, reached the figure of
twenty-six. On the other hand, layings of between eight and ten are not
uncommon. Lastly, taking all my records together, the result is that the
family of the Osmia fluctuates round about fifteen in number.

I have already spoken of the great differences in size apparent in
the cells of one and the same series. The partitions, at first widely
spaced, draw gradually nearer to one another as they come closer to
the aperture, which implies roomy cells at the back and narrow cells in
front. The contents of these compartments are no less uneven between one
portion and another of the string. Without any exception known to me,
the large cells, those with which the series starts, have more abundant
provisions than the straitened cells with which the series ends. The
heap of honey and pollen in the first is twice or even thrice as large
as that in the second. In the last cells, the most recent in date,
the victuals are but a pinch of pollen, so niggardly in amount that we
wonder what will become of the larva with that meagre ration.

One would think that the Osmia, when nearing the end of the laying,
attaches no importance to her last-born, to whom she doles out space
and food so sparingly. The first-born receive the bene