d material on the surface. The larva of the
Cigale, on the contrary, works outward from within, upward from below;
it opens the door of exit at the last moment, so that it is not free for
the discharge of excavated material until the work is done. The first
enters and raises a little rubbish-heap at the threshold of her burrow;
the second emerges, and cannot, while working, pile up its rubbish on a
threshold which as yet has no existence.

The burrow of the Cigale descends about fifteen inches. It is
cylindrical, slightly twisted, according to the exigencies of the soil,
and always approaches the vertical, or the direction of the shortest
passage. It is perfectly free along its entire length. We shall search
in vain for the rubbish which such an excavation must apparently
produce; we shall find nothing of the sort. The burrow terminates in a
cul-de-sac, in a fairly roomy chamber with unbroken walls, which shows
not the least vestige of communication with any other burrow or
prolongation of the shaft.

Taking its length and diameter into account, we find the excavation has
a total volume of about twelve cubic inches. What becomes of the earth
which is removed?

Sunk in a very dry, crumbling soil, we should expect the shaft and the
chamber at the bottom to have soft, powdery walls, subject to petty
landslips, if no work were done but that of excavation. On the contrary,
the walls are neatly daubed, plastered with a sort of clay-like mortar.
They are not precisely smooth, indeed they are distinctly rough; but
their irregularities are covered with a layer of plaster, and the
crumbling material, soaked in some glutinous liquid and dried, is held
firmly in place.

The larva can climb up and down, ascend nearly to the surface, and go
down into its chamber of refuge, without bringing down, with his claws,
the continual falls of material which would block the burrow, make
ascent a matter of difficulty, and retreat impossible. The miner shores
up his galleries with uprights and cross-timbers; the builder of
underground railways supports the sides and roofs of his tunnels with a
lining of brick or masonry or segments of iron tube; the larva of the
Cigale, no less prudent an engineer, plasters the walls of its burrow
with cement, so that the passage is always free and ready for use.

If I surprise the creature just as it is emerging from the soil in order
to gain a neighbouring bough and there undergo transformation, I see it