and the catkins and needles of
the brown-berried juniper predominating. Next come the dry excretions of
the Snail and a few rare little land-shells. A similar jumble of more or
less everything found near the nest forms, as we know, the barricade
of the Manicate Cotton-bee, who is also an adept at using the Snail's
stercoral droppings after these have been dried in the sun. Let us
observe finally that these dissimilar materials are heaped together
without any cementing, just as the insect has picked them up. Resin
plays no part in the mass; and we have only to pierce the lid and turn
the shell upside down for the barricade to come dribbling to the ground.
To glue the whole thing together does not enter into the Resin-bee's
scheme. Perhaps such an expenditure of gum is beyond her means; perhaps
the barricade, if hardened into a solid block, would afterwards form an
invincible obstacle to the escape of the youngsters; perhaps again the
mass of gravel is an accessory rampart, run up roughly as a work of
secondary importance.

Amid these doubtful matters, I see at least that the insect does not
look upon its barricade as indispensable. It employs it regularly in
the large shells, whose last whorl, too spacious to be used, forms an
unoccupied vestibule; it neglects it in the moderate shells, such as
Helix nemoralis, in which the resin lid is level with the orifice. My
excavations in the stone-heaps supply me with an almost equal number of
nests with and without defensive embankments. Among the Cotton-bees, the
Manicate Anthidium is not faithful either to her fort of little sticks
and stones; I know some of her nests in which cotton serves every
purpose. With both of them, the gravel rampart seems useful only in
certain circumstances, which I am unable to specify.

On the other side of the outworks of the fortification, the lid and
barricade, are the cells set more or less far down in the spiral,
according to the diameter of the shell. They are bounded back and
front by partitions of pure resin, without any encrustations of mineral
particles. Their number is exceedingly restricted and is usually limited
to two. The front room, which is larger because the width of the passage
goes on increasing, is the abode of a male, superior in size to the
other sex; the less spacious back room contains a female. I have already
drawn attention in an earlier chapter to the wonderful problem submitted
for our consideration by this breaking up