at the insect distinguishes
between two kinds of materials, without being an absolute purist and
sternly excluding any sort of blending. The very much indented leaves,
whose projections can be completely removed with a dexterous snip of
the scissors, generally furnish the various layers of the barricade; the
little robinia-leaves, with their fine texture and their unbroken edges,
are better suited to the more delicate work of the cells.

A rampart at the back of the Earth-worm's shaft is a wise precaution and
the Leaf-cutter deserves all credit for it; only it is a pity for the
Megachiles' reputation that this protective barrier often protects
nothing at all. Here we see, under a new guise, that aberration of
instinct of which I gave some examples in an earlier chapter. My notes
contain memoranda of various galleries crammed with pieces of leaves
right up to the orifice, which is on a level with the ground, and
entirely devoid of cells, even of an unfinished one. These were
ridiculous fortifications, of no use whatever; and yet the Bee treated
the matter with the utmost seriousness and took infinite pains over her
futile task. One of these uselessly barricaded galleries furnished me
with some hundred pieces of leaves arranged like a stack of wafers;
another gave me as many as a hundred and fifty. For the defence of a
tenanted nest, two dozen and even fewer are ample. Then what was the
object of the Leaf-cutter's ridiculous pile?

I wish I could believe that, seeing that the place was dangerous, she
made her heap bigger so that the rampart might be in proportion to
the danger. Then, perhaps, at the moment of starting on the cells, she
disappeared, the victim of an accident, blown out of her course by
a gust of wind. But this line of defence is not admissible in the
Megachile's case. The proof is palpable: the galleries aforesaid are
barricaded up to the level of the ground; there is no room, absolutely
none, to lodge even a single egg. What was her object, I ask again, when
she persisted in obstinately piling up her wafers? Has she really an
object?

I do not hesitate to say no. And my answer is based upon what the Osmiae
taught me. I have described above how the Three-horned Osmia, towards
the end of her life, when her ovaries are depleted, expends on useless
operations such energy as remains to her. Born a worker, she is bored by
the inactivity of retirement; her leisure requires an occupation. Having
nothing better