fit of her
early enthusiasm: theirs is the well-spread table, theirs the spacious
apartments. The work has begun to pall by the time that the last eggs
are laid; and the last-comers have to put up with a scurvy portion of
food and a tiny corner.

The difference shows itself in another way after the cocoons are spun.
The large cells, those at the back, receive the bulky cocoons; the small
ones, those in front, have cocoons only a half or a third as big. Before
opening them and ascertaining the sex of the Osmia inside, let us wait
for the transformation into the perfect insect, which will take place
towards the end of summer. If impatience gets the better of us, we can
open them at the end of July or in August. The insect is then in the
nymphal stage; and it is easy, under this form, to distinguish the two
sexes by the length of the antennae, which are larger in the males,
and by the glassy protuberances on the forehead, the sign of the future
armour of the females. Well, the small cocoons, those in the narrow
front cells, with their scanty store of provisions, all belong to males;
the big cocoons, those in the spacious and well-stocked cells at the
back, all belong to females.

The conclusion is definite: the laying of the Three-horned Osmia
consists of two distinct groups, first a group of females and then a
group of males.

With my pan-pipe apparatus displayed on the walls of my enclosure and
with old hurdle-reeds left lying flat out of doors, I obtained the
Horned Osmia in fair quantities. I persuaded Latreille's Osmia to
build her nest in reeds, which she did with a zeal which I was far from
expecting. All that I had to do was to lay some reed-stumps horizontally
within her reach, in the immediate neighbourhood of her usual haunts,
namely, the nests of the Mason-bee of the Sheds. Lastly, I succeeded
without difficulty in making her build her nests in the privacy of my
study, with glass tubes for a house. The result surpassed my hopes.

With both these Osmiae, the division of the gallery is the same as
with the Three-horned Osmia. At the back are large cells with plentiful
provisions and widely-spaced partitions; in front, small cells, with
scanty provisions and partitions close together. Also, the larger cells
supplied me with big cocoons and females; the smaller cells gave me
little cocoons and males. The conclusion therefore is exactly the same
in the case of all three Osmiae.

Before dismissing the Osmiae, l