Chamberss Edinburgh Journal, No. 437 | Page 8

a fire
kindled with his old broom, and sipped sparingly to the melody of a
good old song about the good old times, when crossing-sweepers grew
rich, and bequeathed fortunes to their patrons.

INSECT WINGS.
Animals possess the power of feeling, and of effecting certain
movements, by the exercise of a muscular apparatus with which their
bodies are furnished. They are distinguished from the organisations of
the vegetable kingdom by the presence of these attributes. Every one is

aware, that when the child sees some strange and unknown object he is
observing start suddenly into motion, he will exclaim: 'It is alive!' By
this exclamation, he means to express his conviction that the object is
endowed with animal life. Power of voluntary and independent motion
and animal organisation are associated together, as inseparable and
essentially connected ideas, by even the earliest experience in the
economy and ways of nature.
The animal faculty of voluntary motion, in almost every case, confers
upon the creature the ability to transfer its body from place to place. In
some animals, the weight of the body is sustained by immersion in a
fluid as dense as itself. It is then carried about with very little
expenditure of effort, either by the waving action of vibratile cilia
scattered over its external surface, or by the oar-like movement of
certain portions of its frame especially adapted to the purpose. In other
animals, the weight of the body rests directly upon the ground, and has,
therefore, to be lifted from place to place by more powerful mechanical
contrivances.
In the lowest forms of air-living animals, the body rests upon the
ground by numerous points of support; and when it moves, is wriggled
along piecemeal, one portion being pushed forward while the rest
remains stationary. The mode of progression which the little earthworm
adopts, is a familiar illustration of this style of proceeding. In the higher
forms of air-living animals, a freer and more commodious kind of
movement is provided for. The body itself is raised up from the ground
upon pointed columns, which are made to act as levers as well as props.
Observe, for instance, the tiger-beetle, as it runs swiftly over the
uneven surface of the path in search of its dinner, with its eager
antennæ thrust out in advance. Those six long and slender legs that bear
up the body of the insect, and still keep advancing in regular alternate
order, are steadied and worked by cords laid along on the hollows and
grooves of their own substance. While some of them uphold the weight
of the superincumbent body, the rest are thrown forwards, as fresh and
more advanced points of support on to which it may be pulled. The
running of the insect 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