Flies as Carriers of Disease
That the common house-fly is not only a dirty insect, but distinctly injurious to health is now the opinion of most hygienists. There was a time when its services as a scavenger were highly thought of; but nowadays it is believed that whatever good it may accomplish in this capacity is more than balanced by the likelihood that it carries about with it the germs of disease. An essay on this subject, expanded from a shorter magazine article, has just been issued in pamphlet form by the author, Prof. William L. Underwood, of the Massachusetts Institute of Technology. Says Professor Underwood:— “The house-fly (Musca domestica) is particularly filthy because it has its birthplace and lays its eggs almost exclusively in horse manure, although, in the absence of this material, it will breed in the human excrement of our country outhouses, upon which excrement it also feeds. Our domestic animals, the dog and cat, though far from clean in all their habits, we like to have about us, but we keep them in their proper places. The house-fly, on the other hand, is generally tolerated everywhere. It crawls over the hands and faces, it gets into milk, it walks over sugar and salt, over bread and cake, often soiling and contaminating everything that it touches with its filthy feet. “Flies are a menace to health, because, after walking and feeding upon filth, they can and sometimes do carry upon their feet and tongues the germs, or seeds, of diseases like dysentery and typhoid fever. “Unfortunately, the house-fly does not confine itself to any particular diet; but is often attracted from its meal of filth to food that is intended for our own use, and it takes advantage of every open, unscreened door or window to visit our kitchens and dining rooms, and may contaminate everything it touches with its germ-laden feet. Every one has seen flies walking over food, but few people know that on those six small feet and on the fly’s tongue there may be thousands of the deadly microbes of disease.” Every female house-fly, Dr. Underwood goes on to tell us, lays on an average about one hundred and twenty eggs, which in a few hours hatch into larvæ, or “maggots,” and the full-grown adult flies appear ten days later. Contrary to the popular belief, flies do not grow in size after their last transformation. He goes on to say:— “When we consider how exposed is the system so generally in use for the disposal of human excrement in rural districts, is it strange that typhoid fever so often occurs in the country? Under such circumstances every opportunity is offered for the spread of this disease through the agency of flies, particularly the house-fly, which finds in the stable and the country outhouse the conditions most favorable for its development. “It is most important that flies should be kept away from all food supplies. To this end every effort should be made, first, to do away with all places that are favorable for the breeding of flies. Horse manure should be kept in a closed pit, or the place where it is stored should be screened. Metal screens that will not rust are best for this purpose, but, unfortunately, they are too high-priced to permit of their being used by the majority of people who live in the country. Cotton mosquito netting, however, is not very expensive, and, though it will not last as long as the rust-proof metal screens, it is just as effective in keeping out the flies. “In the second place, screens or cotton netting should be put upon the kitchen and dining-room doors and windows, and a sheet or two of sticky fly-paper, which can be bought at nearly every country store, should be placed in all rooms where food is prepared, exposed, or eaten. Fly traps, of which there are several varieties upon the market, are also of great use in destroying those flies which sometimes, in spite of nettings, find their way into rooms where the screen doors are frequently opened.”—Literary Digest.