s of the cross-section vary: the
horizontal measures twenty-five to thirty millimetres;[8] the vertical
measures only fifteen.[9] This greater dimension of the cell, where
the thickness of the perfect insect is concerned, leaves a certain
scope for the action of its legs when the time comes for forcing the
barricade, which is more than a close-fitting mummy-case would do.

[Footnote 7: 3 to 4 inches.--_Translator's Note_.]

[Footnote 8: .975 to 1.17 inch.--_Translator's Note_.]

[Footnote 9: .585 inch.--_Translator's Note_.]

The barricade in question, a door which the larva builds to exclude
the dangers from without, is two- and even three-fold. Outside, it is
a stack of woody refuse, of particles of chopped timber; inside, a
mineral hatch, a concave cover, all in one piece, of a chalky white.
Pretty often, but not always, there is added to these two layers an
inner casing of shavings. Behind this compound door, the larva makes
its arrangements for the metamorphosis. The sides of the chamber are
rasped, thus providing a sort of down formed of ravelled woody fibres,
broken into minute shreds. The velvety matter, as and when obtained,
is applied to the wall in a continuous felt at least a millimetre
thick.[10] The chamber is thus padded throughout with a fine
swan's-down, a delicate precaution taken by the rough worm on behalf
of the tender pupa.

[Footnote 10: .039 inch.--_Translator's Note_.]

Let us hark back to the most curious part of the furnishing, the
mineral hatch or inner door of the entrance. It is an elliptical
skull-cap, white and hard as chalk, smooth within and knotted without,
resembling more or less closely an acorn-cup. The knots show that the
matter is supplied in small, pasty mouthfuls, solidifying outside in
slight projections which the animal does not remove, being unable to
get at them, and polished on the inside surface, which is within the
worm's reach. What can be the nature of that singular lid whereof the
Cerambyx furnishes me with the first specimen? It is as hard and
brittle as a flake of lime-stone. It can be dissolved cold in nitric
acid, discharging little gaseous bubbles. The process of solution is a
slow one, requiring several hours for a tiny fragment. Everything is
dissolved, except a few yellowish flocks, which appear to be of an
organic nature. As a matter of fact, a piece of the lid, when
subjected to heat, blackens, which proves the presence of an organic
glue cementing the