mains an empty
vestibule.

To the spring Resin-bee, Anthidium septemdentatum, this less than half
occupied lodging presents no drawbacks. A contemporary of the Osmia,
often her neighbour under the same stone, the gum-worker builds her nest
at the same period as the mud-worker; but there is no fear of mutual
encroachments, for the two Bees, working next door to each other,
watch their respective properties with a jealous eye. If attempts at
usurpation were to be made, the owner of the Snail-shell would know how
to enforce her rights as the first occupant.

For the summer Resin-bee, A. bellicosum, the conditions are very
different. At the moment when the Osmia is building, she is still in the
larval, or at most in the nymphal stage. Her abode, which would not be
more absolutely silent if deserted, her shell, with its vast untenanted
porch, will not tempt the earlier Resin-bee, who herself wants
apartments right at the far end of the spiral, but it might suit the
Osmia, who knows how to fill the shell with cells up to the mouth. The
last whorl left vacant by the Anthidium is a magnificent lodging which
nothing prevents the mason from occupying. The Osmia does seize upon
it, in fact, and does so too often for the welfare of the unfortunate
late-comer. The final resin lid takes the place, for the Osmia, of
the mud stopper with which she cuts off at the back the portion of the
spiral too narrow for her labours. Upon this lid she builds her mass of
cells in so many storeys, after which she covers the whole with a
thick defensive plug. In short, the work is conducted as though the
Snail-shell contained nothing.

When July arrives, this doubly-tenanted house becomes the scene of a
tragic conflict. Those below, on attaining the adult state, burst their
swaddling-bands, demolish their resin partitions, pass through the
gravel barricade and try to release themselves; those above, larvae
still or budding pupae, prisoners in their shells until the following
spring, completely block the way. To force a passage from the far-end
of those catacombs is beyond the strength of the Resin-bee, already
weakened by the effort of breaking out of her own nest. A few of the
Osmia's partitions are damaged, a few cocoons receive slight injuries;
and then, worn out with vain struggles, the captives abandon hope and
perish behind the impregnable wall of earth. And with them perish also
certain parasites, even less fit for the prodigious work of cle