with yellow, is all that the urinary palette of
the Locustidae shows us. A caterpillar, the Spurge Hawk-moth's, will
take us a little farther. Dappled red, black, white and yellow, its
livery is the most remarkable in our part of the country. Reaumur in
fact calls it _la Belle_. The flattering title is well-deserved. On
the black background of the larva, vermillion-red, chrome-yellow and
chalk-white figure side by side in circles, spots, freckles and
stripes, as clearly marked as the glaring patches of a harlequin's
dress.

Let us dissect the caterpillar and apply the lens to its mosaic. On
the inner surface of the skin, except in the portions coloured black,
we observe a pigmentary layer, a coating here red, there yellow or
white. We will cut a strip from this coat of many colours, after
depriving it of its muscular fibres, and subject it to the action of
nitric acid. The pigment, no matter what its hue, dissolves with
effervescence and afterwards yields murexide. Here again, then, it is
to uric acid, present, however, in small quantities in the adipose
tissue, that the caterpillar's rich livery is due.

The black parts are an exception. Unassailable by nitric acid, they
retain their sombre tint after treatment as before, whereas the
portions stripped of their pigment by the reagent become almost as
transparent as glass. The skin of the handsome caterpillar thus has
two sorts of coloured patches.

Those of an intense black may be likened to dyers' products: they are
completely impregnated with the colouring matter, which is part and
parcel of the molecular constitution and cannot be isolated by the
nitric solvent. The others, red, yellow or white, are actually
painted: on a translucid sheet is a wash of urinary pigment, which is
discharged by the minute ducts issuing from the adipose layer. When
the action of the nitric acid has ceased, the transparent circles of
the latter stand out against the black background of the former.

Yet one more example taken from a different order. As regards elegance
of costume, the Banded Epeira[6] is the most highly favoured of our
Spiders. On the upper surface of her corpulent belly alternate, in
transversal bands, bright black, a vivid yellow like that of yolk of
egg and a dazzling white like that of snow. The black and yellow also
show underneath, but arranged differently. The yellow, in particular,
forms two longitudinal ribbons, ending in orange-red on either side of
the spin