Handbook of Medical Entomology

by William A. Riley; O. A. Johannsen

As their results clearly show that the substances so often recommended are inferior to borax, we shall quote in detail their directions for treating manure so as to kill fly eggs and maggots.

"Apply 0.62 pound borax or 0.75 pound calcined colemanite to every 10 cubic feet (8 bushels) of manure immediately on its removal from the barn. Apply the borax particularly around the outer edges of the pile with a flour sifter or any fine sieve, and sprinkle two or three gallons of water over the borax-treated manure.

"The reason for applying the borax to the fresh manure immediately after its removal from the stable is that the flies lay their eggs on the fresh manure, and borax, when it comes in contact with the eggs, prevents their hatching. As the maggots congregate at the outer edge of the pile, most of the borax should be applied there. The treatment should be repeated with each addition of fresh manure, but when the manure is kept in closed boxes, less frequent applications will be sufficient. When the calcined colemanite is available, it may be used at the rate of 0.75 pound per 10 cubic feet of manure, and is a cheaper means of killing the maggots. In addition to the application of borax to horse manure to kill fly larvæ, it may be applied in the same proportion to other manures, as well as to refuse and garbage. Borax may also be applied to the floors and crevices in barns, stables, markets, etc., as well as to street sweepings, and water should be added as in the treatment of horse manure. After estimating the amount of material to be treated and weighing the necessary amount of borax, a measure may be used which will hold the proper amount, thus avoiding the subsequent weighings.

"While it can be safely stated that no injurious action will follow the application of manure treated with borax at the rate of 0.62 pound for eight bushels, or even larger amounts in the case of some plants, nevertheless the borax-treated manure has not been studied in connection with the growth of all crops, nor has its cumulative effect been determined. It is therefore recommended that not more than 15 tons per acre of the borax-treated manure should be applied to the field. As truckmen use considerably more than this amount, it is suggested that all cars containing borax-treated manure be so marked, and that public-health officials stipulate in their directions for this treatment that not over 0.62 pound for eight bushels of manure be used, as it has been shown that larger amounts of borax will injure most plants. It is also recommended that all public-health officials and others, in recommending the borax treatment for killing fly eggs and maggots in manure, warn the public against the injurious effects of large amounts of borax on the growth of plants."

"The amount of manure from a horse varies with the straw or other bedding used, but 12 or 15 bushels per week represent the approximate amount obtained. As borax costs from five to six cents per pound in 100-pound lots in Washington, it will make the cost of the borax practically one cent per horse, per day. And if calcined colemanite is purchased in large shipments the cost should be considerably less."

Hodge (1910) has approached the problem of fly extermination from another viewpoint. He believes that it is practical to trap flies out of doors during the preoviposition period, when they are sexually immature, and to destroy such numbers of them that the comparatively few which survive will not be able to lay eggs in sufficient numbers to make the next generation a nuisance. To the end of capturing them in enormous numbers he has devised traps to be fitted over garbage cans, into stable windows, and connected with the kitchen window screens. Under some conditions this method of attack has proved very satisfactory.

One of the most important measures for preventing the spread of disease by flies is the abolition of the common box privy. In villages and rural districts this is today almost the only type to be found. It is the chief factor in the spread of typhoid and other intestinal diseases, as well as intestinal parasites. Open and exposed to myriads of flies which not only breed there but which feed upon the excrement, they furnish ideal conditions for spreading contamination. Even where efforts are made to cover the contents with dust, or ashes, or lime, flies may continue to breed unchecked. Stiles and Gardner have shown that house-flies buried in a screened stand-pipe forty-eight inches under sterile sand came to the surface. Other flies of undetermined species struggled up through seventy-two inches of sand.

So great is the menace of the ordinary box privy that a number of inexpensive and simple sanitary privies have been designed for use where there are not modern sewer systems. Stiles and Lumsden (1911) have given minute directions for the construction of one of the best types, and their bulletin should be obtained by those interested.

Another precaution which is of fundamental importance in preventing the spread of typhoid, is that of disinfecting all discharges from patients suffering with the disease. For this purpose, quick-lime is the cheapest and is wholly satisfactory. In chamber vessels it should be used in a quantity equal to that of the discharge to be treated. It should be allowed to act for two hours. Air-slaked lime is of no value whatever. Chloride of lime, carbolic acid, or formalin may be used, but are more expensive. Other intestinal diseases demand similar precautions.

Stomoxys calcitrans, the stable-fly—It is a popular belief that house-flies bite more viciously just before a rain. As a matter of fact, the true house-flies never bite, for their mouth-parts are not fitted for piercing. The basis of the misconception is the fact that a true biting fly, Stomoxys calcitrans ([fig. 110]), closely resembling the house-fly, is frequently found in houses and may be driven in in greater numbers by muggy weather. From its usual habitat this fly is known as the "stable-fly" or, sometimes as the "biting house-fly."