know
any large caterpillar which is black and smooth.

Brown caterpillars, also, are frequently protected by hairs or spines
in the same way; but, unlike black ones, they are frequently naked.
These fall into two principal categories: firstly, those which, like
the Geometridae, put themselves into peculiar and stiff attitudes, so
that in form, color, and position they closely resemble bits of dry
stick; and, secondly, those which feed on low plants, concealing
themselves on the ground by day, and only coming out in the dark.

Yellow and yellowish-green caterpillars are abundant, and their color
is a protection. Red and blue, on the contrary, are much less common
colors, and are generally present as spots.

Moreover, caterpillars with red lines or spots are generally hairy,
and this for the reason given above. Such species, therefore, would be
avoided by birds. There are, no doubt, some apparent exceptions. The
Swallow-tail Butterfly, for instance, has red spots and still is
smooth; but as it emits a strongly-scented liquid when alarmed, it is
probably distasteful to birds. I cannot recall any other case of a
British caterpillar which has conspicuous red spots or lines, and yet
is smooth.

Blue is, among caterpillars, even a rarer color than red. Indeed,
among our larger larvae, the only cases I can recall are the Lappets,
which have two conspicuous blue bands, the Death's-head Moth, which
has broad diagonal bands, and two of the Hawk-moths, which have two
bright blue oval patches on the third segment. The Lappets are
protected by being hairy, but why they have the blue bands I have no
idea. It is interesting, that both the other species frequent plants
which have blue flowers. The peculiar hues of the Death's-head
caterpillar, which feeds on the potato, unite so beautifully the brown
of the earth, the yellow and green of the leaves, and the blue of the
flowers, that, in spite of its size, it can scarcely be perceived
unless the eye be focussed exactly upon it.

The Oleander Hawk-moth is also an interesting case. Many of the
Hawk-moth caterpillars have eye-like spots, to which I shall have to
allude again presently. These are generally reddish or yellowish, but
in this species, which feeds on the periwinkle, they are bright blue,
and in form as well as color closely resemble the blue petals of that
flower. One other species, the Sharp-winged Hawk-moth, also has two
smaller blue spots, with reference to which I can