Fly
a two-winged insect. There are in North America sixty families of flies, including 8,000 known species. The common house fly bears the appropriate scientific name of Musca domestica. The fly passes through all four stages of insect life. The common house fly lays about 150 eggs at a time, preferably in horse manure. The maggots are cylindrical and footless. In a week's time they enter the pupa state, and in another week they emerge full-grown flies. The fly does not increase in size after it acquires its wings.
The middle portion of the fly, or the thorax, bears two gauzy front wings and three pairs of legs. The second or rear pair of wings, to which an insect is entitled, is represented, in the case of the fly, by a pair of knobbed, club-shaped appendages, or balancers. No one knows just what use is made of them. It has been suggested that they serve as ears. The head is provided with a pair of inconspicuous feelers or antennae. The mouth parts are adapted to suck up water, filth, vegetable scum, blood, or any semi-fluid material. The most prominent feature is a pair of large compound eyes, composed of 125,000 facets, occupying the greater portion of the side of the head. Each facet represents the end of a tube running down to nerve endings which are sensitive to light. Most flies have, in addition, two or three small, simple eyes on the top of the head, between the compound eyes.
The abdomen, the third part of the body, is composed of several segments or rings. On the side of each segment is a small hole or spiracle, through which the fly breathes. A fly can stand with its head under water without inconvenience, but it drowns if its abdomen is under water.
The fly comes pretty near having its brain in its stomach. There is a well developed nervous system. The main enlargement or ganglion, the center of the nervous system--the brain, we may call it--lies in the floor of the body cavity. The head contains only a small portion of the nervous system. A fly having lost its head is able to walk about, though in an aimless way, with apparently as little inconvenience as though it had lost but a leg or a wing. It dies instantly if the real nervous center be injured.
The fly has a complete circulatory system,--heart, arteries, and veins. The alimentary canal is distinct. The sense of smell is located apparently in the antennae. As stated, the ears are believed to be located at the base of the balancers, although there is a theory also that certain hairs on the antennae serve as ears. When a living fly is held by the legs its wings vibrate rapidly. The apex of the wing describes a figure eight in the air. The buzz of the house fly is in "F." It is considered, therefore, that its wings vibrate 330 times per second. It is thought that the buzzing is increased by the rubbing of certain parts of the body upon each other. The fact that a fly can walk on a smooth pane of glass or upside down on a ceiling has given rise to the oft repeated explanation that the feet are furnished with surfaces that act like a boy's leather sucker. Such is not the case, however. The foot is sticky and adhesive. It is furnished also with hook-like appendages with which to cling to the slightest irregularity of surface.
The best preventive against flies is cleanliness about the premises. Flies breed in filth of all descriptions. However unwelcome they may be flies do an important work as scavengers. In untidy households they clean up and remove an immense amount of filth that might otherwise breed contagion. There is nothing in nature more repulsive than maggots; but they, too, have their work. They devour dead animals that would otherwise pollute the air. It has been said that a fly and its progeny of maggots will devour an ox or a horse in less time than would be required by a full grown lion.
The fly that fills a carcass with maggots is a buzzing blowfly with a steel-blue abdomen. The skippers that infest cheese, ham, and bacon are the maggots of a small, slender, black fly.
In spite of their manner of feeding, flies are scrupulously cleanly. They rub and brush and polish their feet and mouths with great care. The fly that bites so fiercely before a rain is not a house fly, but a stable fly. It is very similar in appearance to a fly that settles on a dog's ear. A fly that clusters on the backs of cattle in pastures is still another very similar fly that breeds in cow manure.
Flies are a source of contagion. They light in all sorts of filth to feed. They carry germs on their feet and mouth parts. It has been said that 250 American soldiers were killed by bullets during the Spanish-American War, and that 5,000 were killed by infectious diseases, the germs of which were conveyed by flies.
See Insect; Mosquito; Cranefly; Gnat; Batfly; Gadfly; Gallfly; Hessian Fly, etc.
The fact is that, regarded as a contrivance for disseminating the germs of fatal diseases, the fly is one of nature's masterpieces. A fairly large bacterium is as much smaller than a fly as a fly is smaller than an elephant. The microbes of many of our ordinary contagious disorders are a thousand times more minute than this.
The insect, moreover, is equipped with spines, hairs, folds, cavities, and projections innumerable for microbes to cling to. In addition, each of its six little feet has the sticky pad which we used to call a sucker, adhesive enough to hold the fly on a window pane, and therefore just the thing for picking up germs by the hundred. One may well credit reports of a single fly, filthy from a swill-barrel and loaded with 582,000 bacteria of one species alone. Moreover, the fly, living on infected food, takes the microbes into his own digestive tract, carries them about for days, and deposits them by thousands in the "fly-specks." There, for example, Bacillus tuberculosis may live for two weeks.
It would be bad enough if the fly merely crawled about in the sputum of a tuberculous patient or the dejecta of a case of typhoid, and then simply infected the food on the way to our mouths. It does worse than this: it starts a culture of the deadly germs in the food which we are to eat to-morrow; and by the time tomarrow arrives, the single microbe has become a thousand.
Fundamentally, the fly is in the world because there are moist and smelly things there. Flies cannot breed in dry places; they will not breed in clean ones. In general, then, whatever is damp and dirty contributes to the plague. Among other contributory negligences are stables; cow-barns; piggeries; decaying vegetables, meat, and cheese; dead animals; rotting straw, paper, and rags; old mattresses--the thousand and one decayable objects that get into the ash-barrel and the dump, when they ought to go into the fire. If we had no decaying organic matter, we should have no flies.--E. T. Brewster in September, 1909, McClure's.
I believe we can nowhere find a better type of a perfectly free creature than in the common house fly. Not free only, but brave; and irreverent to a degree which I think no human republican could by any philosophy exalt himself to. There is no courtesy in him. Strike at him with your hand, and to him the fact of the matter is, what to you it would be if an acre of red clay, ten feet thick, tore itself up from the ground in one massive field, hovered over you in the air for a second, and came crashing down with an aim. He steps out of the way of your hand and alights on the back of it.
You cannot terrify him, nor govern him, nor persuade him, nor convince him. The earth worm has his digging; the bee her gathering and building; the spider her cunning network; the ant her treasury and accounts. All these are comparatively slaves, or people of vulgar business. But your fly, free in the air, free in the chamber--a black incarnation of caprice--wandering, investigating, flitting, flirting, feasting, at his will, with rich variety of choice in feast, from the heaped sweets in the grocer's window to those of the butcher's backyard, and from the galled place on your cab-horse's back to the brown spot in the road, from which, as the hoof disturbs him, he arises with angry republican buzz--what freedom is like his?--John Ruskin.