sect is a very ingenious and
beautiful adaptation of the principles of mechanism to the purposes of
life.

But in the insect organisation, a still more surprising display of
mechanical skill is made. A comparatively heavy body is not only
carried rapidly and conveniently along the surface of the ground, it
is also raised entirely up from it at pleasure, and transported
through lengthened distances, while resting upon nothing but the thin
transparent air. From the top of the central piece--technically termed
thoracic--of the insect's body, from which the legs descend, two or
more membraneous sails arise, which are able to beat the air by
repeated strokes, and to make it, consequently, uphold their own
weight, as well as that of the burden connected with them. These
lifting and sustaining sails are the insect's wings.

The wings of the insect are, however, of a nature altogether different
from the apparently analogous organs which the bird uses in flight.
The wings of the bird are merely altered fore-legs. Lift up the front
extremities of a quadruped, keep them asunder at their origins by bony
props, fit them with freer motions and stronger muscles, and cover
them with feathers, and they become wings in every essential
particular. In the insect, however, the case is altogether different.
The wings are not altered legs; they are superadded to the legs. The
insect has its fore-legs as well as its wings. The legs all descend
from the under surface of the thoracic piece, while the wings arise
from its upper surface. As the wings are flapping above during flight,
the unchanged legs are dangling below, in full complement. The wings
are, therefore, independent and additional organs. They have no
relation whatever to limbs, properly so called. But there are some
other portions of the animal economy with which they do connect
themselves, both by structure and function. The reader will hardly
guess what those wing-allied organs are.

There is a little fly, called the May-fly, which usually makes its
appearance in the month of August, and which visits the districts
watered by the Seine and the Marne in such abundance, that the
fishermen of these rivers believe it is showered down from heaven, and
accordingly call its living clouds, manna. Reaumur once saw the
May-flies descend in this region like thick snow-flakes, and so fast,
that the step on which he stood by the river's bank was covered by a
layer four inches thick in a few