jority of cases is that of the
Common Snail, Helix aspersa. It is sometimes of full size, sometimes
half-developed. Helix nemoralis and H. caespitum, which are much
smaller, also supply suitable lodgings; and this would as surely apply
to any shell of sufficient capacity, if the places which I explore
possessed others, as witness a nest which my son Emile has sent me from
somewhere near Marseilles. This time, the Resin-bee is settled in Helix
algira, the most remarkable of our land-shells because of the width and
regularity of its spiral, which is copied from that of the Ammonites.
This magnificent nest, a perfect specimen of both the Snail's work and
the Bee's, deserves description before any other.

For a distance of three centimetres (1.17 inches.--Translator's
Note.) from the mouth, the last spiral whorl contains nothing. At this
inconsiderable depth, a partition is clearly seen. The moderate diameter
of the passage accounts for the Anthidium's choice of this site to which
our eye can penetrate. In the common Snail-shell, whose cavity widens
rapidly, the insect establishes itself much farther back, so that, in
order to see the terminal partition, we must, as I have said, make a
lateral inlet. The position of this boundary-ceiling, which may come
farther forward or farther back, depends on the variable diameter of the
passage. The cells of the cocoons require a certain length and a certain
breadth, which the mother finds by going higher up or lower down in
the spiral, according to the shape of the shell. When the diameter is
suitable, the last whorl is occupied up to the orifice, where the final
lid appears, absolutely exposed to view. This is the case with the adult
Helix nemoralis and H. caespitum, and also with the young Common Snail.
We will not linger at present over this peculiarity, the importance of
which will become manifest shortly.

Whether in the front or at the back of the spiral slope, the insect's
work ends in a facade of coarse mosaic, formed of small, angular bits
of gravel, firmly cemented with a gum the nature of which has to
be ascertained. It is an amber-coloured material, semi-transparent,
brittle, soluble in spirits of wine and burning with a sooty flame and a
strong smell of resin. From these characteristics it is evident that the
Bee prepares her gum with the resinous drops exuded by the Coniferae.

I think that I am even able to name the particular plant, though I have
never caught the ins