the different
inhabitants, each of whom had his own storey, his own closed cell.

When the accommodation consisted of no more than a simple cylinder,
with no state-bedroom at the end of it--a bedroom always reserved for
a female--the contents varied with the diameter of the cylinder. The
series, of which the longest were series of four, included, with a
wider diameter, first one or two females, then one or two males. It also
happened, though rarely, that the series was reversed, that is to say,
it began with males and ended with females. Lastly, there were a good
many isolated cocoons, of one sex or the other. When the cocoon was
alone and occupied the Anthophora's cell, it invariably belonged to a
female.

I have observed the same thing in the nests of the Mason-bee of the
Sheds, but not so easily. The series are shorter here, because the
Mason-bee does not bore galleries but builds cell upon cell. The work
of the whole swarm thus forms a stratum of cells that grows thicker from
year to year. The corridors occupied by the Osmia are the holes which
the Mason-bee dug in order to reach daylight from the deep layers.
In these short series, both sexes are usually present; and, if the
Mason-bee's chamber is at the end of the passage, it is inhabited by a
female Osmia.

We come back to what the short tubes and the old nests of the Mason-bee
of the Pebbles have already taught us. The Osmia who, in tubes of
sufficient length, divides her whole laying into a continuous sequence
of females and a continuous sequence of males, now breaks it up into
short series in which both sexes are present. She adapts her sectional
layings to the exigencies of a chance lodging; she always places a
female in the sumptuous chamber which the Mason-bee or the Anthophora
occupied originally.

Facts even more striking are supplied by the old nests of the Masked
Anthophora (A. personata, ILLIG.), old nests which I have seen utilized
by the Horned Osmia and the Three-horned Osmia at the same time. Less
frequently, the same nests serve for Latreille's Osmia. Let us first
describe the Masked Anthophora's nests.

In a steep bank of sandy clay, we find a set of round, wide-open holes.
There are generally only a few of them, each about half an inch in
diameter. They are the entrance-doors leading to the Anthophora's abode,
doors always left open, even after the building is finished. Each of
them gives access to a short passage, sometimes straight, som