only a single day in the air. A gad-fly is one
of the winged scourges which must have been
included among the divers sorts of flies which
devoured the Egyptians. Swarms of flies, in
houses and on the ground, are thus
acknowledged to be a plague. And it is not man
alone that suffers from them. In several parts of
the world, insects end the existence of cattle.
Perhaps Paraguay offers the most curious
instance of this; for neither cattle nor horses nor
dogs have ever run wild there, although they
swarm southward and northward in a feral state;
and Azara and Rengger have shown that this is
caused by the greater prevalence, in Paraguay,
of a certain fly, which lays its eggs in the navels
of those animals when first born. The increase
of these flies, numerous as they are, must still
be habitually checked by some means, probably
by birds. Hence, if insectivorous birds could
increase in Paraguay, flies would decrease, and
cattle and horses might run wild.

In the early days of classification, flies
and bats were enrolled together with birds as
Volatilia, because all were flying things. Our
word Fly, like the german Fliege, is doubtless
derived from the verb to fly. In other European
languages, the word for fly is derived from the
Latin Musca, (itself of undetermined origin),
which also bears the sense of a curious or
inquisitive person. Similarly, the French Mouche
also means a spy. Painters have superadded a
fly to relieve the flesh-tints of a naked figure;
mouche, therefore, is the term for a patch of
black plaister which has been the fashion for both
men and women to wear on the cheek. A bee
is a mouche à miel, or honey-fly. The Italian
Mosca speaks for itself. "You cannot have honey
without flies," answers to our own "No rose
without a thorn." Making an elephant out of a
fly, expresses exaggeration.

And pray, sir, where do all the flies come
from?

As you came, madame, from a father and
mother; only they are more prolific than your
honoured parents. Given a pair of flies, in early
spring, and it is calculated that, by the close of
autumn, they will produce upwards of two
million descendants—it is needless to account
for a few odd thousands over. On what they
feed, and of what their substance is formed,
there exists a slight difference. The green-bottle,
Musca Csesar, thrives best on carrion and
corpses; the blue-bottle, Musca vomitoria,
prefers meat which is not quite so high. One fly,
Musca carnaria, lays, instead of eggs, living
maggots; another fly (a French gentleman), of
unsettled species, is said to be able to shoot out his
eggs with force, like pellets from a popgun. The
house-fly, Musca domestica, is bred in dirt; and
the filthier the dirt, the better. The more dirt you
have in your neighbourhood, madam, the more
flies you will have in your mansion. This
circumstance may help to account for their extreme
abundance in the south of Europe. It is a blessing
for the inhabitants, that pestilential filth
should be thus converted into comparatively
harmless flies. By the wonderful transformability
of matter, what would breed an infection grows
into myriads of happy creatures.  Still, dirty habits,
and all unnecessary waste and exposure of dirt,
are false economy.  Every fly that is born, robs the
gardens and the fields of so much fertilising
element.  If no dirt were to be got at by mother flies,
their infant offspring must perish, and flies would
become rare.

Blood-sucking flies have no need of blood
to live on. The greater number of them,
pass their lives, propagate, and die, without
tasting it. In Patagonia, a good-sized fly
(Tabanus) is extremely numerous, and torments
travellers by its painful bite. The common
horse-fly, which is so troublesome in the shady
lanes of England, belongs to the same genus.
Mr. Darwin was puzzled—as in the case of
mosquitoes—to know on the blood of what
animals these insects commonly feed; for the
guanaco is almost the only warm-blooded
animal there, and it is found in quite
inconsiderable numbers compared with the
multitude of flies. The explanation is, that the
flies don't feed on blood; they don't require it,
and can do very well without it. But when they
can get it, they enjoy it excessively; instead of
a meal, they make an orgie. Strangely enough,
they are furnished with a formidable trunk
enabling them to indulge in their sanguinary
debauch whenever the opportunity occurs. The
blood-flies bite very sharp, but the pain is only
temporary.  They infuse no venom into the wound,
as bugs do—whether gnats do, is questioned by
Reáumur—to cause after-inflammation.

Mr. James Samuelson has written an excellent
little book, The Earthworm and The Common
House Fly. Those two apparently opposite
creatures are coupled together in the same
treatise, for a reason which you may not guess.
According to Cuvier, the Annelides (worms)
ought to be included in the section of the
Animal Kingdom which is called Articulata
(articulate races); of which section he regards
the Insects as the highest class, and the Worms
as the lowest. Under the title of Aunulosa, or
ringed animals, Professor Busk includes every
creature possessing a body composed of rings
or segments; and amongst the subdivisions of
that great class, he unites the Annelides (of
which the Earthworm is the typical representative)
to the Insecta (whereof the Fly is one
characteristic form) by means of the Centipedes,
which partake of the nature of both groups.
Mr. Samuelson consequently employs the worm
as an introduction to the more complicated
structure of the fly.

It is a law in natural history that the lowest
creatures in any particular section of the Animal
Kingdom, strongly resemble, when in their
perfect form, the early or embryonic stage of the
higher animals in the same section. By this
law, the adult worm resembles the infant stage
of the fly. Every individual fly has been itself
a sort of worm; that is, it has passed through a
wormlike stage before it becomes an actual fly.
The larva or maggot of the fly, the form in which
it leaves the egg, closely resembles a worm: not