and devote my leisure in
winter to these investigations.

The bramble-sticks are split and the cocoons taken out one by one and
methodically transferred to glass tubes, of approximately the same
diameter as the native cylinder. These cocoons are arranged one on
top of the other in exactly the same order that they occupied in the
bramble; they are separated from one another by a cotton plug, an
insuperable obstacle to the future insect. There is thus no fear that
the contents of the cells may become mixed or transposed; and I am saved
the trouble of keeping a laborious watch. Each insect can hatch at its
own time, in my presence or not: I am sure of always finding it in
its place, in its proper order, held fast fore and aft by the cotton
barrier. A cork or sorghum-pith partition would not fulfil the same
purpose: the insect would perforate it and the register of births would
be muddled by changes of position. Any reader wishing to undertake
similar investigations will excuse these practical details, which may
facilitate his work.

We do not often come upon complete series, comprising the whole laying,
from the first-born to the youngest. As a rule, we find part of a
laying, in which the number of cocoons varies greatly, sometimes falling
as low as two, or even one. The mother has not deemed it advisable to
confide her whole family to a single bramble-stump; in order to make the
exit less toilsome, or else for reasons which escape me, she has left
the first home and elected to make a second home, perhaps a third or
more.

We also find series with breaks in them. Sometimes, in cells distributed
at random, the egg has not developed and the provisions have remained
untouched, but mildewed; sometimes, the larva has died before spinning
its cocoon, or after spinning it. Lastly, there are parasites, such
as the Unarmed Zonitis (Zonitis mutica, one of the
Oil-beetles.--Translator's Note.) and the Spotted Sapyga (A
Digger-wasp.--Translator's Note.), who interrupt the series by
substituting themselves for the original occupant. All these disturbing
factors make it necessary to examine a large number of nests of the
Three-pronged Osmia, if we would obtain a definite result.

I have been studying the bramble-dwellers for seven or eight years and I
could not say how many strings of cocoons have passed through my hands.
During a recent winter, in view particularly of the distribution of the
sexes, I collected some forty of this O