The Great Insect Pest by Margaret Ross Evans, M. D.

Review and Herald Publishing Association · Takoma Park, Washington, D. C. · Jun 6, 1912

The Great Insect Pest

By Margaret Ross Evans, M. D.

MARGARET ROSS EVANS, M. D.

THERE are a number of species of flies commonly found in houses, but the house-fly proper (Musca domestica) composes more than ninety-eight per cent of them all. This insect is gray in color with streaks of blackish gray. Fine hair covers its body, but especially its feet and legs. The mouth parts are arranged for lapping. The fly which bites is not the true house-fly, but the stable-fly, which is identical in shape and color with the house-fly, but whose mouth has a piercing proboscis enabling it to bite severely.

The cluster-fly is another species frequenting houses, but it is slightly larger than the house-fly, and is more sluggish. In the fall it is very liable to attacks of an epidemic fungous disease, which causes it to die on the windowpane or elsewhere.

The so-called blue-bottle fly, or blow-fly, sometimes makes its appearance in houses. This fly breeds in decaying meat.

A small fly quite similar to the house-fly is responsible for the erroneous idea that a fly grows, this species being looked upon as the young of the larger fly, which is not the case.

A still smaller, jet-black fly known as the window-fly breeds in the dust under the carpets and in the curtain hangings.

The fruit-fly is a little fly that finds its way into the kitchen and dining-room during the fruit season.

The true house-fly, however, as we have before stated, far outnumbers all other species. Its distribution is worldwide. No more important insect pest is known to man. The farther south we go, the more numerous and troublesome this fly becomes. More than ten million dollars every year is expended in the United States alone for screening purposes.

The enormous numbers in which flies occur can readily be accounted for when we study into their life history. At the approach of winter the adult fly hibernates, hiding in crevices and out-of-the-way places. As the warm spring advances, it comes out from its hiding-place, and begins to lay its tiny white eggs. The average number of eggs laid by an individual fly is one hundred twenty. The egg hatches in about eight hours. It then remains in the larval state for four or five days, at the end of which it becomes a pupa. In another five days there issues forth from the pupa a full-grown adult fly, ready to lay its quota of eggs.

The average life of a fly is still a question, but there is plenty of time during the ordinary summer season for the development of more than a dozen generations.

The eggs are laid on a great variety of substances, particularly on spoiled foodstuffs, meat broths, dead animals, manure heaps, and human ejecta. In the larval stage the fly thrives on all kinds of filth. Horse-stables form the principal breeding-places. A single stable where a horse is kept will supply house-flies for a neighborhood.

The writer has attended camp-meetings where unprotected closets were daily breeding house-flies by the thousands. Many of these selfsame flies, after swarming over the pits and feeding upon the infected material, proceeded to the kitchen- and dining-tent to crawl on the food prepared to be eaten. Not only the entire camp, but the surrounding neighborhood as well was subjected to this vast multitude of disgusting creatures.

The fly is not merely an annoying inhabitant of the home; it is a dangerous

disseminator of disease germs. It is a deadly enemy to human beings. The feet and body of the fly are particularly adapted to carrying germs. Experiments have shown that the number of bacteria clinging to a single fly may range all the way from a few hundred to several million. These microscopic organisms adhere to food over which the fly walks.

Moreover, investigators have shown us that the fly feeds on typhoid bacilli, and that during a period of two weeks after eating them these virulent germs may be found in fly-specks. Milk, water, foodstuffs, and store products are often contaminated in this way. Cholera germs also pass uninjured through the intestinal tract of the fly.

Eggs of tapeworms are eaten by the fly. The eggs are not destroyed, but may be excreted days later.

Flies feed on sputum, and when the tubercular sputum is eaten by the fly, active tubercular bacilli have been found in fly-specks dropped on food fifteen days later.

Epidemics of intestinal disorders of children are most frequently caused by flies. The milk is infected somewhere during its transportation from the cow-stable to the baby's bottle.

Abating the fly nuisance is a matter well worthy of more serious attention than is usually given it. All possible means should be employed to exclude flies from the kitchen and milk-room. Doors and windows should be carefully screened during the summer months. Proper disposal of garbage and dooryard rubbish is of the utmost importance. A prompt gathering of horse manure, which may be treated in various ways or may be collected in an especially prepared fly-proof bin, will do much to lessen the number of flies in a given neighborhood.

At our camp-meetings closet vaults should be so constructed as to prevent the ingress and egress of flies and the hatching of eggs. When the pit is dug, wooden frames with wire nettings may be erected. An arrangement of lids or double doors is necessary to render it fly proof. Aside from these rigid precautions the vault should be daily treated with a thin layer of chlorid of lime.

Lime can be purchased by the barrel for two or three cents a pound. While this may seem expensive, it is well worth while. Every city, every community, and every health officer should conduct a campaign against this insect pest and its breeding-places.

Eternal vigilance should mark our efforts in eradicating it from the land. A flyless home should be our aim.

Washington, D. C.