an's fist, in
which case I have no doubt that it is the work of several. Those bulky
nests, comprising more than fifty cells, can tell us nothing exact, as a
number of workers must certainly have collaborated to produce them.

The walnut-sized nests are more trustworthy, for everything seems to
indicate that they were built by a single Bee. Here females are found
in the centre of the group and males at the circumference, in somewhat
smaller cells, thus repeating what the Mason-bee of the Pebbles has told
us.

One clear and simple rule stands out from this collection of facts.
Apart from the strange exception of the Three-pronged Osmia, who mixes
the sexes without any order, the Bees whom I studied and probably a
crowd of others produce first a continuous series of females and then a
continuous series of males, the latter with less provisions and smaller
cells. This distribution of the sexes agrees with what we have long
known of the Hive-bee, who begins her laying with a long sequence of
workers, or sterile females, and ends it with a long sequence of
males. The analogy continues down to the capacity of the cells and the
quantities of provisions. The real females, the Queen-bees, have wax
cells incomparably more spacious than the cells of the males and receive
a much larger amount of food. Everything therefore demonstrates that we
are here in the presence of a general rule.

But does this rule express the whole truth? Is there nothing beyond a
laying in two series? Are the Osmiae, the Chalicodomae and the rest of
them fatally bound by this distribution of the sexes into two distinct
groups, the male group following upon the female group, without any
mixing of the two? Is the mother absolutely powerless to make a change
in this arrangement, should circumstances require it?

The Three-pronged Osmia already shows us that the problem is far from
being solved. In the same bramble-stump, the two sexes occur very
irregularly, as though at random. Why this mixture in the series
of cocoons of a Bee closely related to the Horned Osmia and the
Three-horned Osmia, who stack theirs methodically by separate sexes
in the hollow of a reed? What the Bee of the brambles does cannot her
kinswomen of the reeds do too? Nothing, so far as I know, can explain
this difference in a physiological act of primary importance. The three
Bees belong to the same genus; they resemble one another in general
outline, internal structure and habits; an