they make a rough egg-shaped cocoon of earthy materials. Environment, diet,
industry and internal structure are all similar; and yet one of these three
larvae, the Cetonia's, reveals a most singular dissimilarity from its
fellow-trenchermen: alone among the Scarabaeidae and, more than that, alone
in all the immense order of insects, it walks upon its back.

If the differences were a matter of a few petty structural details, falling
within the finical department of the classifier, we might pass them over
without hesitation; but a creature that turns itself upside down in order
to walk with its belly in the air and never adopts any other method of
locomotion, though it possesses legs and good legs at that, assuredly
deserves examination. How did the animal acquire its fantastic mode of
progress and why does it think fit to walk in a fashion the exact contrary
of that adopted by other beasts?

To these questions the science now in fashion always has a reply ready:
adaptation to environment. The Cetonia-larva lives in crumbling galleries
which it bores in the depths of the soil. Like the sweep who obtains a
purchase with his back, loins and knees to hoist himself up the narrow
passage of a chimney, it gathers itself up, applies the tip of its belly to
one wall of its gallery and its sturdy back to another; and the combined
effort of these two levers results in moving it forward. The legs, which
are used very little, indeed hardly at all, waste away and tend to
disappear, as does any organ which is left unemployed; the back, on the
other hand, the principal motive agent, grows stronger, is furrowed with
powerful folds and bristles with grappling-hooks or hairs; and gradually,
by adaptation to its environment, the creature loses the art of walking,
which it does not practise, and replaces it by that of crawling on its
back, a form of progress better suited to underground corridors.