procession has marched by, there remains, as a record of its
passing, a narrow white ribbon whose dazzling whiteness shimmers in the
sun. Very much more sumptuous than ours, their system of road-making
consists in upholstering with silk instead of macadamizing. We sprinkle
our roads with broken stones and level them by the pressure of a heavy
steam-roller; they lay over their paths a soft satin rail, a work of
general interest to which each contributes his thread.

What is the use of all this luxury? Could they not, like other
caterpillars, walk about without these costly preparations? I see two
reasons for their mode of progression. It is night when the
Processionaries sally forth to browse upon the pine-leaves. They leave
their nest, situated at the top of a bough, in profound darkness; they
go down the denuded pole till they come to the nearest branch that has
not yet been gnawed, a branch which becomes lower and lower by degrees
as the consumers finish stripping the upper storeys; they climb up this
untouched branch and spread over the green needles.

When they have had their suppers and begin to feel the keen night air,
the next thing is to return to the shelter of the house. Measured in a
straight line, the distance is not great, hardly an arm's length; but
it cannot be covered in this way on foot. The caterpillars have to
climb down from one crossing to the next, from the needle to the twig,
from the twig to the branch, from the branch to the bough and from the
bough, by a no less angular path, to go back home. It is useless to
rely upon sight as a guide on this long and erratic journey. The
Processionary, it is true, has five ocular specks on either side of his
head, but they are so infinitesimal, so difficult to make out through
the magnifying-glass, that we cannot attribute to them any great power
of vision. Besides, what good would those short-sighted lenses be in
the absence of light, in black darkness?

It is equally useless to think of the sense of smell. Has the
Processional any olfactory powers or has he not? I do not know. Without
giving a positive answer to the question, I can at least declare that
his sense of smell is exceedingly dull and in no way suited to help him
find his way. This is proved, in my experiments, by a number of hungry
caterpillars that, after a long fast, pass close beside a pine-branch
without betraying any eagerness of showing a sign of stopping. It is
the sense of touch that