plants, and would
make the creature more conspicuous. When, therefore, the diagonal
lines are developed, the longitudinal ones often disappear. There is
one other point in connection with these diagonal lines to which I
must call your attention.

In many species they are white, but in some cases--as, for instance,
in the beautiful green caterpillar of the Privet-Hawk-moth--the white
streak is accompanied by a colored one, in that case lilac. At first
we might think that this would be a disadvantage, as tending to make
the caterpillar more conspicuous; and in fact, if we put one in full
view--for instance, out on a table--and focus the eye on it, the
colored lines are very striking. But we must remember that the habit
of the insect is to sit on the lower side of the leaf, generally near
the middle rib, and in the subdued light of such a situation,
especially if the eye be not looking exactly at them, the colored
lines beautifully simulate a line of soft shadow, such as must always
accompany a strong rib; and I need not tell any artist that the
shadows of yellowish-green must be purplish. Moreover, any one who has
ever found one of these large caterpillars will, I am sure, agree with
me that it is surprising, when we consider their size and conspicuous
coloring, how difficult it is to see them.

But though the prevailing color of caterpillars is green, there are
numerous exceptions. In one great family of moths the prevailing color
is brown. These caterpillars, however, escape observation by their
great similarity to brown twigs--a resemblance which is heightened by
their peculiar attitudes, and in many cases by the existence of warts
or protuberances, which look like buds. Some, however, even of these
caterpillars, when very young, are green. Again, some caterpillars are
white. These feed on and burrow in wood. The Ringlet Butterfly also
has whitish caterpillars, and this may at first sight appear to
contradict the rule, since it feeds on grass. Its habit is, however,
to keep at the roots by day, and feed only at night.

In various genera we find Black caterpillars, which are of course very
conspicuous, and, so far as I know, not distasteful to birds. In such
cases, however, it will be found that they are covered with hairs or
spines, which protect them from most birds. In these species the bold
dark color may be an advantage, by rendering the hair more
conspicuous. Many caterpillars are black and hairy, but I do not