only in its external shape, but, also in its internal
physiology. It possesses locomotive hooks,
similar to those of the worm, but not so
numerous, and more developed; its cylindrical
body is divided into rings only. When it has
passed a certain time in this stage, it assumes
the pupa form, and is enclosed in a hard case,
remaining motionless and to all appearance
inanimate. Whilst in this state, the remarkable
change from one of the lowest to one of the
highest examples of the Articulate type, is going
on; first the legs and then the wings are
developed; and when the metamorphosis is
complete, the insect, bursts its prison-house and
issues forth in its perfect form.

In its ordinary flight, the common house-fly
makes with its wings about six hundred strokes
(which carry it five feet) every second; but if
alarmed, the velocity can be increased six or
seven fold, or to thirty or thirty-five feet per
second. In the same space of time a race-horse
would clear only ninety feet. Now, compare the
enormous difference in size of the two animals,
and how wonderful will the velocity of the fly
appear! A colossal fly, the size of a race-horse,
would dash through the air like a cannon-ball.
As it is, the swiftness of their flight is often
fatal to them. On sandy dunes by the
seashore there grows a rough kind of grass, called
"marram," on the sharp points of whose rigid
blades flies and beetles are often found self-
spitted. The wings of the common gnat vibrate
at a still more rapid rate than the fly's,
being computed at many thousands per second.
The computation is made, approximately, thus:
When a spring—a tuning-fork, for instance—is
made to vibrate a certain number of times in a
second, it gives out a particular note; and,
according as the number of vibrations is increased
or diminished, this note rises or falls in pitch.
The wings of an insect also emit a musical
sound. By making a spring emit the same note
as the insect's wing, and calculating the vibrations
of the spring, the number of strokes made
in a second by the organ of flight are
ascertained.

How flies walk up glass and along a ceiling,
has been guessed at, by supposing the fly's foot
a sucker, or rather two suckers, for the foot
is cloven into two pads. Each pad (which is
furnished and fringed with innumerable hairs)
was believed, until recently, to act as a sucker.
But Mr. Hepworth and the microscope show us,
at the termination of each hair that grows on
the foot, a minute expansion, which is kept moist
by a fluid exuding from the extremity. Mr.
Samuelson, therefore, adopts the belief that each
single hairlet on the fly's foot, serves as a sucking
disc, exactly like those on the under surface of the
star-fish. The tree-frog has only five suckers on
each foot; the fly has hundreds.  Men have very
imperfectly imitated flies by walking along a ceiling
with their heads downward; the feat was effected,
clumsily enough, by a sort of snow-shoe fitting
into a groove.

Flies do not breathe, like men, through the
mouth, but through a set of holes in the abdomen,
called stigmata or spiracles. By these,
the air passes into beautifully constructed tubes,
called tracheæ, or wind-pipes. The spiracles
are furnished with a curious contrivance to
prevent dust from entering. The hole is closed by
a sort of sieve or screen, which must be seen to
be appreciated. A drawing gives you some
idea of its nature, but the real thing is far
better; and as not every one is up to such minute
manipulation, recourse should be had to
microscopic preparations, which are furnished at a
reasonable rate by Amadio of Throgmorton-street,
London, and other first-rate opticians.
The fly supplies an interesting series of objects.
Besides the compound eye, the antennæ, the
foot, and the spiracles, the proboscis of a fly is a
thing to wonder at. It is more complicated
than the trunk of an elephant. A portion of
this proboscis acts as a lip; in addition to its
lancets, a fly has teeth; yes, real teeth, like
notched chisels, and as plain as pike-staves, if
you only know where to look for them.

With these claims on our interest, we can
hardly be surprised that, in countries not too
much infested with them, flies should have had
their patrons and protectors. Not to mention
the Indian hospitals for insects, a compassionate
damsel is described as delighting to

Save drowning flies that float along the stream.

A toper invites a jolly fly to take a cheerful
drop with him:

Eager, busy, curious fly,
Drink with me, and drink as I.

Uncle Toby had not the heart to retaliate
on a fly. " Go," says he, one day at dinner,
to an overgrown one which had tormented him
cruelly all dinner-time. " Go," says he, lifting
up the sash and opening his hand to let it
escape; "go, poor devil, get thee gone; why
should I hurt thee? This world surely is wide
enough to hold both thee and me."

Shandean forbearance would be very well, if
the flies would all agree to go one way and let
us go another. But they are far too tenacious
of their rights, to make any such a bargain.
As insects are the first colonists of desert
islands, so will they be their latest inhabitants,
picking the bones of the last human survivor.
Intrusiveness is the peculiar characteristic of
flies, from the flies that buzz about
the sick man's chamber, to the flies that commit
suicide by hundreds in cream-jugs, honey-pots,
and treacle-tubs. Who was it that made a
brazen fly which, when wound up, went bouncing
about the room like any other free-and-easy
fly? There was no need to make flies more
brazen than they are. They impudently intrude
themselves at the feasts of the gentry and
nobility: even of the very Pope himself, who is
supposed always to dine alone.

Flies, unfortunately, cannot be persuaded to
leave either ourselves or our domestic animals
at peace. The humming of a fly, says Pascal,
will disturb the thoughts of the gravest philosopher.
Woman's temper is especially apt to be
put out by these winged nuisances. They make