roducts, being unable, for
want of an open outlet, to flow away as formed, accumulate in the
adipose tissue, which thus serves as a common store-house for the
residues of the present and the plastic material of the future organic
processes. Here something occurs analogous to what we see in the
higher animals after the removal of the kidneys; the urea at first
contained in the blood, in imperceptible quantities accumulates and
becomes manifest when the means by which it is eliminated disappear.

In the larva of the Hydrophilus, on the other hand, the excretions
enjoy a free outlet from the beginning; and the urinary products
escape as and when formed and are no longer deposited in the adipose
tissue. But during the intense labour of the metamorphosis, any
excretion becomes impossible; the uric acid must and does collect in
the adipose substance of the different larvae.

It would be out of place, despite its importance, to pursue the
problem of the uric residues any further. Our subject is coloration.
Let us return to it with the evidence supplied by the Sphex. Her
almost transparent larva has the neutral tint of fluid white of egg.
Under its fine translucid skin there is nothing coloured, save the
long digestive pouch, which is swollen a deep purple by the pulp of
the consumed Crickets. But against this indefinite, vitreous
background the opaque white uric cells stand out distinctly in their
myriads; and the effect of this stippling is a sketchy but by no means
inelegant costume. It is skimpy in the extreme, but at any rate it is
something.

With the urinary broth of which its intestine is unable to get rid,
the larva has discovered a means of making itself look a little smart.
The Anthidia have shown us how, in their cotton-wool wallets, they
manufacture a sort of jewellery with their ordure. The robe studded
with grains of alabaster is a no less ingenious invention.

To beautify themselves cheaply by using up their own refuse is a very
common method even among insects endowed with all that is wanted for
evacuating waste matter. While the larvae of the Hunting Wasps, unable
to do better, stipple themselves with uric acid, there are plenty of
industrious creatures that are able to make themselves a superb dress
by preserving their excretions in spite of their own open sewers. With
a view to self-embellishment, they collect and treasure up the dross
which others hasten to expel. They turn filth into finery.

One of