U. S. DEPARTMENT OF AGRICULTURE

FARMERS' BULLETIN No. 1408

_The_ HOUSE FLY AND HOW TO SUPPRESS IT

[Illustration: fly]

[Illustration: USDA seal]

The presence of flies is an indication of uncleanliness, insanitaryconditions, and improper disposal of substances in which they breed. They are not only annoying; they are actually dangerous to health, because they may carry disease germs to exposed foods. 

It is therefore important to know where and how they breed, and to applysuch knowledge in combating them. This bulletin gives information onthis subject. Besides giving directions for ridding the house of fliesby the use of screens, fly papers, poisons, and flytraps, it laysespecial emphasis on the explanation of methods of eliminating breedingplaces and preventing the breeding of flies. 

This bulletin supersedes Farmers' Bulletin 851. 

Washington, D. C. Issued April, 1925; revised November, 1926

THE HOUSE FLY[1] AND HOW TO SUPPRESS IT. 

By L. O. HOWARD, _Chief of the Bureau of Entomology_, and F. C. BISHOPP, _Entomologist_. 

 * * * * *

 CONTENTS. Page. Kinds of flies found in houses 1 Where the true house fly lays its eggs 2 How the house fly passes the winter 6 Carriage of disease by the house fly 6 Excluding and capturing flies 7 The use of screens 7 Fly papers and poisons 8 Fly sprays 8 Flytraps 9 Preventing the breeding of flies 9 Construction and care of stables 9 Fly-tight manure pits 10 Frequency with which manure should be removed in cities and towns 10 Health office regulations for control of house flies in cities 10 Disposal of manure in rural and suburban districts 11 Chemical treatment of manure to destroy fly maggots 12 Maggot trap for destruction of fly larvæ from horse manure 13 Compact heaping of manure 15 Garbage disposal and treatment of miscellaneous breeding places 15 Sewage disposal in relation to the prevention of fly-borne diseases 15 What communities can do to eliminate the house fly 16

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KINDS OF FLIES FOUND IN HOUSES. 

Several species of flies are found commonly in houses. Some of them soclosely resemble the true house fly that it requires very carefulobservation to distinguish them from it. 

One of these is the biting stable fly[2] (fig. 1). It occurs frequentlyin houses and differs from the house fly in the important particularthat its mouth parts are formed for piercing the skin. This fly is sooften mistaken for the house fly that most people think that the housefly can bite. 

Another frequent visitant of houses, particularly in the spring andfall, is the cluster fly. [3] It is somewhat larger than the house fly, and is distinguished by its covering of fine yellowish hairs. Occasionally this fly occurs in houses in such numbers as to cause greatannoyance. It gets its name of "cluster fly" from its habit ofcollecting in compact groups or clusters in protected corners duringcold periods. 

Several species of metallic greenish or bluish flies also are foundoccasionally in houses. These include a blue-bottle fly, [4] the blackblowflies, [5] and the green-bottle (fig. 2) flies. [6] They breed indecaying animal matter. 

[Footnote 1: _Musca domestica_ L. ][Footnote 2: _Stomoxys calcitrans_ L. ][Footnote 3: _Pollenia rudis_ Fab. ][Footnote 4: _Calliphora erythrocephala_ Meig. ][Footnote 5: _Phormia regina_ Meig. And _P. Terrae-novae_ Desv. ][Footnote 6: _Lucilia caesar_ L. , _L. Sericata_ Meig. , and other speciesof the genus. ]

There is still another species, smaller than any of those so farmentioned, which is sometimes called the "lesser house fly. "[7] Thisinsect is distinguished from the ordinary house fly by its paler andmore pointed body. The male, which is commoner than the female, haslarge pale patches at the base of the abdomen, which are translucentwhen the fly is seen on the window pane. These little flies are not theyoung of the larger flies. Flies do not grow after the wings have onceexpanded and dried. 

[Footnote 7: _Fannia canicularis_ L. ]

[Illustration: FIG. 1. --The stable fly. Much enlarged. ]

[Illustration: FIG. 2. --One of the green-bottle flies (_Luciliacaesar_). Much enlarged. ]

In late summer and autumn many specimens of a small fruit fly, known asthe "vinegar fly, "[8] make their appearance, attracted by the odor ofoverripe fruit. 

All of these species, however, are greatly dwarfed in numbers by thecommon house fly. In 1900 the senior author made collections of theflies in dining rooms in different parts of the country, and found thatthe true house fly made up 98. 8 per cent of the whole number captured. The remainder comprised various species, including those mentionedabove. 

[Footnote 8: _Drosophila ampelophila_ Loew. ]

[Illustration: Fig. 3. --The true house fly. Enlarged. ]

WHERE THE TRUE HOUSE FLY LAYS ITS EGGS. 

The true house fly (fig. 3), which is found in nearly all parts of theworld, is a medium-sized fly with four black stripes on the back and asharp elbow in one of the veins of the wings. The house fly can notbite, its mouth parts being spread out at the tip for sucking up liquidsubstances. 

The eggs (figs. 4, 5) are laid upon horse manure. This substance seemsto be its favorite larval food. It will breed also in human excrement, and because of this habit it is very dangerous to the health of humanbeings, carrying as it does the germs of intestinal diseases, such astyphoid fever and cholera, from the excreta to food supplies. It hasalso been found to breed freely in hog manure, in considerable numbersin chicken dung, and to some extent in cow manure. Indeed, it will layits eggs on a great variety of decaying vegetable and animal materials, but of the flies that infest dwelling houses, both in cities and onfarms, a vast proportion come from horse manure. 

[Illustration: FIG. 4. --Eggs of the house fly. About natural size. (Newstead. )]

It often happens, however, that this fly is very abundant in localitieswhere little or no horse manure is found, and in such cases it breeds inother manure, such as chicken manure in backyard poultry lots, or inslops or fermenting vegetable material, such as spent hops, moist bran, ensilage, or rotting potatoes. Accumulations of organic material on thedumping grounds of towns and cities often produce flies in greatnumbers. 

[Illustration: FIG. 5. --Eggs of the house fly. Highly magnified. (Newstead. )]

The house fly begins laying eggs in from 2 1/2 to 20 days afteremerging, the time interval depending to a large extent upontemperature, humidity, and character and abundance of food. The numberof eggs laid by an individual fly at one time ranges from 120 to 159 anda single female will usually lay two and sometimes four such batches. Dunn has recently reported that in Panama a fly may deposit as many as2, 367 eggs in 21 batches, and sometimes an interval of only 36 hours mayoccur between the deposition of large batches of eggs. The enormousnumbers in which the insects occur are thus plainly accounted for, especially when the abundance and universal occurrence of appropriatelarval food is considered. The eggs are deposited below the surface inthe cracks and interstices of the manure, several females usuallydepositing in one spot, so that the eggs commonly are found in largeclusters (fig. 4) in selected places near the top of the pile, where ahigh degree of heat is maintained by the fermentation below. The secondbatch of eggs is laid from 8 to 10 days after the first. The eggsusually hatch in less than 24 hours. Under the most favorable conditionsof temperature and moisture the egg state may last hardly more than 8hours. The maggots which issue from the eggs are very small andtransparent. They grow rapidly, completing the growth of the larva stagein three days under the most favorable conditions, although this stageusually lasts from 4 to 7 days. The larval period may be prolongedgreatly by low temperature or by dryness or scarcity of the larval food. As the larvæ (fig. 6) attain full size they gradually assume a creamywhite color. A few hours before pupation they become very restless andmigrate from their feeding ground in search of a favorable place inwhich to pass the pupa stage. They will often congregate at the edges ofmanure piles near the ground or burrow into the soil beneath, or theymay crawl considerable distances away from the pile to pupate in theground or in loose material under the edges of stones, boards, etc. 

[Illustration: FIG. 6. --Larvæ, or maggots, of the house fly. Aboutnatural size. (Newstead. )]

The pupæ (fig 7), or "sleepers, " are more or less barrel shaped and darkbrown in color. In midsummer this stage usually lasts from 3 to 6 days. The pupa stage is easily affected by temperature changes and may beprolonged during hibernation for as long as 4 or 5 months. Numerousrearing experiments in various parts of the country have shown that theshortest time between the deposition of eggs and the emergence of theadult fly is 8 days, and 10 and 12 day records were very common. 

The adult fly, upon emerging from the puparium, works its way upwardthrough the soil or manure and upon reaching the air it crawls aboutwhile its wings expand and the body hardens and assumes its normalcoloration. In from 2 1/2 to 20 days, as previously stated, the femaleis ready to deposit eggs. As in the case of other periods of its lifehistory, so the preoviposition period is prolonged considerably by thelower temperatures of spring and fall. In midsummer, with adevelopmental period of from 8 to 10 days from egg to adult, and apreoviposition period of from 3 to 4 days, a new generation would bestarted every 11 to 14 days. Thus the climate of the District ofColumbia allows abundance of time for the development of from 10 to 12generations every season. 

[Illustration: FIG. 7. --Pupæ of the house fly. About natural size. (Newstead. )]

Flies usually remain near their breeding places if they have plenty offood, but experiments recently made at Dallas, Tex. , show that they maymigrate considerable distances; in fact, house flies, so marked that theparticular individuals could be identified, have been recaptured intraps as far as 13 miles from the place where they were liberated. 

HOW THE HOUSE FLY PASSES THE WINTER. 

The prevailing opinion that the house fly lives through the winter as anadult, hiding in cracks and crevices of buildings, etc. , appears to beerroneous. Under outdoor conditions house flies are killed during thefirst really cold nights, that is, when the temperature falls to about15° or 10° F. In rooms and similar places protected from winds andpartially heated during the winter flies have been kept alive in cagesfor long periods, but they never lived through the entire winter. Inlongevity experiments one record of 70 days and another of 91 days wasobtained. No uncaged house flies were found during three seasons'observations in unheated and only partially heated attics, stables, unused rooms, etc. , where favorable temperature conditions prevailed. The common occurrence in such places of the cluster fly and a few otherspecies, which may be easily mistaken for the house fly, is responsiblefor the prevailing belief as to the way the house fly overwinters. Thereis therefore no reliable evidence whatever that adult house fliesemerging during October and November pass the winter and are able todeposit their eggs the following spring, although they may continueactive in heated buildings until nearly the end of January. On the otherhand, there is evidence that house flies pass the winter as larvæ andpupæ, and that they sometimes breed continuously throughout the winter. In experiments at both Dallas, Tex. , and Bethesda, Md. , house flies havebeen found emerging during April from heavily infested manure heapswhich had been set out and covered with cages during the precedingautumn. In the Southern States, during warm periods in midwinter, houseflies may emerge and become somewhat troublesome; they frequently layeggs on warm days. 

The second way in which the house fly may pass the winter is bycontinuous breeding. House flies congregate in heated rooms with theapproach of the winter season. If no food or breeding materials arepresent they eventually die. However, where they have access to bothfood and suitable substances for egg laying they will continue breedingjust as they do outdoors during the summer. Even in very cold climatesthere are undoubtedly many places, especially in cities, where houseflies would have opportunity to pass the winter in this manner. 

CARRIAGE OF DISEASE BY THE HOUSE FLY. 

The body of the house fly is covered thickly with hairs and bristles ofvarying lengths, and this is especially true of the legs. Thus, when itcrawls over infected material it readily becomes loaded with germs, andsubsequent visits to human foods result in their contamination. Evenmore dangerous than the transference of germs on the legs and body ofthe fly is the fact that bacteria are found in greater numbers and livelonger in its alimentary canal. These germs are voided, not only in theexcrement of the fly, but also in small droplets of regurgitated matterwhich have been called "vomit spots. " When we realize that fliesfrequent and feed upon the most filthy substances (it may be the excretaof typhoid or dysentery patients or the discharges of one suffering fromtuberculosis), and that subsequently they may contaminate human foodswith their feet or excreta or vomit spots, the necessity and importanceof house-fly control is clear. 

In army camps, in mining camps, and in great public works, where largenumbers of men are brought together for a longer or shorter time, thereis seldom the proper care of excreta, and the carriage of typhoid germsfrom the latrines and privies to food by flies is common and oftenresults in epidemics of typhoid fever. 

And such carriage of typhoid is by no means confined to great temporarycamps. In farmhouses in small communities, and even in badly cared forportions of large cities, typhoid germs are carried from excrement tofood by flies, and the proper supervision and treatment of the breedingplaces of the house fly become most important elements in the preventionof typhoid. 

In the same way other intestinal germ diseases, such as Asiatic cholera, dysentery, enteritis (inflammation of the intestine), and infantilediarrhea, are all so carried. There is strong circumstantial evidencealso that tuberculosis, anthrax, yaws, ophthalmia, smallpox, tropicalsore, and the eggs of parasitic worms may be and are carried in thisway. In the case of over 30 different disease organisms and parasiticworms, actual laboratory proof exists, and where lacking is replaced bycircumstantial evidence amounting almost to certainty. 

EXCLUDING AND CAPTURING FLIES. 

The principal effort to control this dangerous insect must be made atthe source of supply--its breeding places. Absolute cleanliness and theremoval or destruction of anything in which flies may breed areessential; and this is something that can be done even in cities. Perhaps it can be done more easily in the cities than in villages, onaccount of their greater police power and the lesser insistence on therights of the individual. Once people are educated to the danger andlearn to find the breeding places, the rest will be easy. 

In spite of what has just been said, it is often necessary to catch orotherwise destroy adult flies, or to protect food materials fromcontamination and persons from annoyance or danger; hence the value offly papers and poisons, flytraps, and insect screens. 

THE USE OF INSECT SCREENS. 

A careful screening of windows and doors during the summer months, withthe supplementary use of sticky fly papers, is a protective measureagainst house flies known to everyone. As regards screening, it is onlynecessary here to emphasize the importance of keeping food suppliesscreened or otherwise covered so that flies can gain no access to them. This applies not only to homes but also to stores, restaurants, milkshops, and the like. Screening, of course, will have no effect indecreasing the number of flies, but at least it has the virtue oflessening the danger of contamination of food. 

Insect screens for doors and windows should be well made and must fittightly, otherwise they will not keep insects out. It is equallyimportant that they be made of good and durable screen cloth. Copperinsect screen cloth, although a little higher in price, will prove moreeconomical in the long run, as it lasts many years. If, however, thecost of copper screen cloth is objectionable, steel screen cloth, eitherpainted or galvanized, can be used. Painted steel screen cloth will lastone or more years without repainting, its durability depending upon theclimate. In humid regions, of course, it will rust more quickly than itwill where the climate is dry. The same may be said of galvanized steelinsect screen cloth. 

Insect screen cloth made with 16 meshes to the inch is recommended, for16-mesh screen cloth will keep out flies and most mosquitoes[9] andother small insects which at times are found almost everywhere. 

[Footnote 9: Where the yellow fever or dengue fever mosquito occurs, 18-mesh screen cloth (or 16-mesh screen cloth made from extra heavywire) should be used. ]

FLY PAPERS AND POISONS. 

[Illustration: FIG. 8. --Conical hoop flytrap side view. _A_, Hoopsforming frame at bottom. _B_, Hoops forming frame at top. _C_, Top oftrap made of barrel head. _D_, Strips around door. _E_, Door frame. _F_, Screen on door. _G_, Buttons holding door. _H_, Screen on outside oftrap. _I_, Strips on side of trap between hoops. _J_, Tips of thesestrips projecting to form legs. _K_, Cone. _L_, United edges of screenforming cone. _M_, Aperture at apex of cone. (Bishopp. )]

The use of sticky fly papers to destroy flies that have gained access tohouses is well known. Fly-poison preparations also are common. Many ofthe commercial fly poisons contain arsenic, and their use in thehousehold is attended with considerable danger, especially to children. This danger is less with the use of a weak solution of formalin. A veryeffective fly poison is made by adding 3 teaspoonfuls of the commercialformalin to a pint of milk or water sweetened with a little brown sugar. A convenient way of exposing this poison is by partly filling anordinary drinking glass with the solution. A saucer or plate is thenlined with white blotting paper cut the size of the dish and placedbottom up over the glass. The whole is then quickly inverted and a smallmatch stick placed under the edge of the glass. As the solutionevaporates from the paper more flows out from the glass and thus thesupply is automatically renewed. 

FLY SPRAYS. 

Sprays designed to destroy or repel house flies fill a certain need inconnection with the house-fly problem. No very satisfactory repellentsubstances for this insect have been found which are at the same timeadaptable to general use about the home, or places where foods arehandled. Extracts of pyrethrum flowers are now generally availablecommercially, and these give fairly good results in the destruction ofhouse flies in buildings. Most of the sprays of pyrethrum extractcontain kerosene oil as a carrier, and undoubtedly the kerosene has muchto do with the toxicity of the spray. Such materials are most applicableto buildings which become infested with flies and which can be readilyclosed up at night and the air within thoroughly saturated with thespray by means of an atomizer. Under such conditions the flies arerather quickly overcome by the spray and if a sufficient quantity isused they will not revive. 

FLYTRAPS. 

Flytraps may be used to advantage in decreasing the number of flies. Their use has been advocated not only because of the immediate results, but because of the chances that the flies may be caught before they layeggs, and the number of future generations will be reduced greatly. 

Many types of flytraps are on the market. As a rule the larger ones arethe more effective. Anyone with a few tools can construct flytraps for asmall part of the price of the ready-made ones. A trap (fig. 8) which isvery effective in catching flies and is easily made, durable, and cheap, may be made of four barrel hoops, four laths, a few strips of boxing, and 8 1/2 lineal feet of screening, 24 inches wide. (For greater detailssee Farmers' Bulletin 734. )

The effectiveness of the traps will depend on the selection of baits. Agood bait for catching house flies is 1 part of blackstrap molasses to 3parts of water, after the mixture has been allowed to ferment for a dayor two. Overripe or fermenting bananas crushed and placed in the baitpans give good results, especially with milk added to them. A mixture ofequal parts brown sugar and curd of sour milk, thoroughly moistened, gives good results after it has been allowed to stand for three or fourdays. 

PREVENTING THE BREEDING OF FLIES. 

As previously stated, fly papers, poisons, and traps are at best onlytemporary expedients. The most logical method of abating the flynuisance is the elimination or treatment of all breeding places. Itwould appear from what is known of the life history and habits of thecommon house fly that it is perfectly feasible for cities and towns toreduce the numbers of this annoying and dangerous insect so greatly asto render it of comparatively slight account. On farms also, in dairies, and under rural conditions generally, much can and should be done tocontrol the fly, which here, as elsewhere, constitutes a very seriousmenace to health. 

CONSTRUCTION AND CARE OF STABLES. 

In formulating rules for the construction and care of stables and thedisposal of manure the following points must be taken intoconsideration. In the first place, the ground of soil-floor stables mayoffer a suitable place for the development of fly larvæ. The larvæ willmigrate from the manure to the soil and continue their growth in themoist ground. This takes place to some extent even when the manure isremoved from the stables every day. Even wooden floors are not entirelysatisfactory unless they are perfectly water-tight, since larvæ willcrawl through the cracks and continue their development in the moistground below. Water-tight floors of concrete or masonry, therefore, aredesirable. Flies have been found to breed in surprising numbers in smallaccumulations of material in the corners of feed troughs and mangers, and it is important that such places be kept clean. 

FLY-TIGHT MANURE PITS. 

The Bureau of Entomology for a number of years has advised that manurefrom horse stables be kept in fly-tight pits or bins. Such pits can bebuilt in or attached to the stable so that manure can be easily thrownin at the time of cleaning and so constructed that the manure can bereadily removed. It is desirable that the manure be placed in thesefly-proof receptacles as soon as possible after it is voided. Theessential point is that flies be prevented from reaching the manure, andfor this reason the pit or bin must be tightly constructed, preferablyof concrete, and the lid kept closed except when the manure is beingthrown in or removed. The difficulty has been that manure often becomesinfested before it is put into the container, and flies frequently breedout before it is emptied and often escape through the cracks. To obviatethese difficulties a manure box or pit with a modified tent trap or conetrap attached is desirable. 

In order to retain the fertilizing value of manure to the greatestextent it is advisable that air be excluded from it as much as possibleand that it be protected from the leaching action of rains. This beingthe case, there is really no necessity for covering a large portion ofthe top of the box with a trap, but merely to have holes large enough toattract flies to the light, and to cover these holes with ordinaryconical traps, with the legs cut off, so, that the bottoms of the trapswill fit closely to the box. The same arrangement can be made wheremanure is kept in a pit. If manure boxes or pits are kept fly tight theyare satisfactory under farm or dairy conditions for the storage ofmanure during the busy season when it can not be hauled out daily. 

FREQUENCY WITH WHICH MANURE SHOULD BE REMOVED IN CITIES AND TOWNS. 

In deciding the question as to how often manure should be removed incities and towns, it should be borne in mind that when the larvæ havefinished feeding they will often leave the manure and pupate in theground below or crawl some distance away to pupate in débris underboards or stones and the like. Hence the manure should be removed beforethe larvæ reach the migratory stage; that is to say, removal isnecessary every three days, and certainly not less frequently than twicea week during the summer months. A series of orders issued in 1906 bythe health department of the District of Columbia, on the authority ofthe Commissioners of the District, covers most of these points, andthese orders, which may well serve as a model to other communitiesdesiring to undertake similar measures, may be briefly condensed asfollows:

 HEALTH OFFICE REGULATIONS FOR CONTROL OF HOUSE FLIES IN CITIES. 

 All stalls in which animals are kept shall have the surface of the ground covered with a water-tight floor. Every person occupying a building where domestic animals are kept shall maintain in connection therewith a bin or pit for the reception of manure and, pending the removal from the premises of the manure from the animal or animals, shall place such manure in said bin or pit. This bin shall be so constructed as to exclude rain water and shall in all other respects be water-tight, except as it may be connected with the public sewer. It shall be provided with a suitable cover and constructed so as to prevent the ingress and egress of flies. No person owning a stable shall keep any manure or permit any manure to be kept in or upon any portion of the premises other than the bin or pit described, nor shall he allow any such bin or pit to be overfilled or needlessly uncovered. Horse manure may be kept tightly rammed into well-covered barrels for the purpose of removal in such barrels. Every person keeping manure in the more densely populated parts of the District shall cause all such manure to be removed from the premises at least twice every week between June 1 and October 31, and at least once every week between November 1 and May 31 of the following year. No person shall remove or transport any manure over any public highway in any of the more densely populated parts of the District except in a tight vehicle, which, if not inclosed, must be effectually covered with canvas, so as to prevent the manure from being dropped. No person shall deposit manure removed from the bins or pits within any of the more densely populated parts of the District without a permit from the health officer. Any person violating any of the provisions shall, upon conviction thereof, be punished by a fine of not more than $40 for each offense. 

Not only must horse stables be cared for, but chicken yards, piggeries, and garbage receptacles as well. In cities, with better methods ofdisposal of garbage and with the lessening of the number of horses andhorse stables consequent upon electric street railways, bicycles, andautomobiles, the time may come, and before very long, when windowscreens may be discarded. 

DISPOSAL OF MANURE IN RURAL AND SUBURBAN DISTRICTS. 

The control of flies in rural and suburban districts offers a much moredifficult problem. Here it is often out of the question to remove allmanure from the premises twice a week, and the problem is to find somemethod of disposal or storage which will conserve the fertilizing valueof the manure and at the same time prevent all flies from breeding, ordestroy such as do breed there. 

With this idea in mind, it has been recommended that stable manure becollected every morning and hauled out at once and spread rather thinlyon the fields. This procedure is advisable from the point of view ofgetting the maximum fertilizing value from the manure. Immediatespreading on the fields is said largely to prevent the loss of plantfood which occurs when manure is allowed to stand in heaps for a longtime. This method will be effective in preventing the breeding of fliesonly if the manure is hauled out promptly every morning and spreadthinly so that it will dry, since it is unfavorable for fly developmentin desiccated condition. The proper scattering of the manure on thefields is best and most easily and quickly accomplished by the use of amanure spreader, and many dairies, and even farms, are practicing thedaily distribution of manure in this way. Removal every three or fourdays will not be sufficient. Observations have shown that if manurebecomes flyblown and the maggots attain a fairly good size before themanure is scattered on the fields, they can continue their developmentand will pupate in the ground. 

CHEMICAL TREATMENT OF MANURE TO DESTROY FLY MAGGOTS. 

During the summer months, when fly breeding is going on most actively, the farmer is also busy and often can not spare the time to removemanure regularly. The general practice, therefore, has been to keep themanure in heaps located, as a rule, very near the stables. How can flybreeding be prevented in such accumulations? As a result of recentinvestigations, it is now possible to point out two methods which arepractical and effective. 

The first is the treatment of the manure pile with chemical substanceswhich will kill the eggs and maggots of the house fly. The Bureau ofEntomology, in cooperation with the Bureau of Chemistry and the Bureauof Plant Industry, has conducted a series of experiments in which alarge number of chemicals were applied to infested manure andobservations made, not only on their efficiency in killing the maggotsbut also as to their effect on the chemical composition and bacterialflora of the manure. The object was to find some cheap chemical whichwould be effective in destroying the fly larvæ and at the same timewould not reduce the fertilizing value of the manure. 

TREATMENT WITH HELLEBORE. 

Of the numerous substances tried, the one which seems best to fulfillthese conditions is powdered hellebore. [10] For the treatment of manure awater extract of the hellebore is prepared by adding 1/2 pound of thepowder to every 10 gallons of water, and after stirring it is allowed tostand 24 hours. The mixture thus prepared is sprinkled over the manureat the rate of 10 gallons to every 8 bushels (10 cubic feet) of manure. From the result of 12 experiments with manure piles treated undernatural conditions it appears that such treatment results in thedestruction of from 88 to 99 per cent of the fly larvæ. 

Studies of treated manure indicated that its composition and rottingwere not interfered with. Furthermore, several field tests showed thatthere was no apparent injury to growing crops when fertilized withtreated manure. 

Since the solution is somewhat poisonous it should not be left exposedwhere it might be drunk by livestock. It is quite safe to say thatchickens will not be injured by pecking at hellebore-treated manure. This has been tested carefully. Hellebore can be obtained both in groundand powdered form, but the powder gives the best results in thedestruction of fly larvæ. 

[Footnote 10: _Veratrum viride_ or _V. Aloum_. ]

TREATMENT WITH POWDERED BORAX. 

Another chemical found to be even more effective as a larvicide ispowdered borax. This substance is available in commercial form in allparts of the country. It has the advantage of being comparativelynonpoisonous and noninflammable and is easily transported and handled. The minimum amount necessary to kill fly larvæ was found to be 0. 62pound per 8 bushels of manure, or about 1 pound per 16 cubic feet. Bestresults were obtained when the borax was applied in solution, or whenwater was sprinkled on after the borax had been scattered evenly overthe pile. Borax is not only effective in killing the larvæ, but when itcomes in contact with the eggs it prevents them from hatching. Whenapplied at the rate of 1 pound to 16 cubic feet it was found to killabout 90 per cent of the larvæ, heavier applications killing from 98 to99 per cent. 

Borax has no injurious effect on the chemical composition or rotting ofthe manure. However, when added in large quantities with manure to thesoil it will cause considerable injury to growing plants. A number ofexperiments have been conducted to determine the effect on crops of theuse of manure treated with borax as herein recommended. When applied atthe rate of 15 tons per acre it appears that no injury as a rule willfollow. Some crops are more sensitive to borax than others, and also thetendency to injury appears to vary on different soils. It is necessary, therefore, to repeat the warning issued in connection with a previousbulletin[11] on this subject, that great care be exercised, in theapplication of borax, that the manure does not receive more than 1 poundfor every 16 cubic feet, and that not more than 15 tons of manure sotreated are applied to the acre. 

In view of the possible injury from the borax treatment as a result ofcarelessness in applying it, or from other unforeseen conditions, it isrecommended that horse manure and other farmyard manures which are to beused as fertilizer be treated with hellebore. Borax, on the other hand, is such a good larvicide that it call be used with advantage on theground of soil-floor stables, in privies, on refuse piles, and on anyaccumulations of fermenting organic matter which are not to be used forfertilizing purposes. 

[Footnote 11: Department Bulletin 118, U. S. Department of Agriculture, p. 25. ]

TREATMENT WITH CALCIUM CYANAMID AND ACID PHOSPHATE. 

Many experiments with mixtures of commercial fertilizers were tried todetermine whether fly larvæ would be killed by any substance theaddition of which would increase the fertilizing value of the manure. Amixture of calcium cyanamid and acid phosphate was found to possessconsiderable larvicidal action. Several experiments showed that 1/2pound of calcium cyanamid plus 1/2 pound of acid phosphate to eachbushel of manure give an apparent larvicidal action of 98 per cent. Themixture in the form of a powder was scattered evenly over the surfaceand then wet down with water. The use of this mixture adds to the manuretwo important elements, nitrogen and phosphorus. 

MAGGOT TRAP FOR DESTRUCTION OF FLY LARVÆ FROM HORSE MANURE. 

The second method of handling manure is one which does not require theapplication of chemicals. It is based on the fact, mentioned on page 4, that the larvæ of the house fly, a few hours before they are ready topupate, show a strong tendency to migrate. This migration takes placemostly at night, and the larvæ sometimes crawl considerable distancesfrom the manure pile. Now it is possible by means of a very simplearrangement called a maggot trap to destroy fully 99 per cent of allmaggots breeding in a given lot of manure. A successful maggot trapwhich the Maryland Agricultural College constructed at the college barnis shown in Figure 9. The trap was designed by R. H. Hutchison andconstructed under his supervision. The manure, instead of being thrownon the ground, is heaped carefully on a slatted platform, which standsabout 1 foot high. This particular platform measures 10 by 20 feet. There are six 2 by 4 pieces running lengthwise 2 feet apart. Acrossthese are nailed 1-inch strips with 1/2 to 1 inch spaces between them. The wooden platform stands on a concrete floor, and a rim or wall ofconcrete 4 inches high surrounds the floor. The floor slopes a littletoward one corner from which a pipe leads to a small cistern near by. This pipe is plugged with a stopper of soft wood, and the concrete flooris filled with water to a depth of 1 inch in the shallowest part. Flieswill lay their eggs on the manure as usual, but the maggots, when theyhave finished feeding and begin to migrate, crawl out of the manure, drop into the water below, and are drowned. Each week the plug isremoved from the pipe, and all the maggots are washed into the cistern. The floor is then cleaned of any solid particles by means of along-handled stable broom or by a strong stream of water from a hose. The pipe being again plugged, the floor is again partly filled withwater and the trap is ready for another week's catch. A platform of thissize will hold the manure accumulating from four horses during theperiod of four months, or about 20 days' accumulation from 25 horses, ifthe heap is well built and made at least 5 feet high. 

[Illustration: FIG. 9. A maggot trap for house-fly control. View showingthe concrete basin containing water in which larvæ are drowned, and thewooden platform on which manure is heaped. (Hutchison. )]

Experience with this maggot trap clearly indicates that best results canbe secured if the manure is compactly heaped on the platform and keptthoroughly moistened. It is best to apply a small amount of water eachmorning after the stable cleanings have been added to the pile. Itshould be borne in mind that in order to make this trap a success theplatform beneath the pile must be kept comparatively free ofaccumulations of manure, and moisture applied regularly to drive themaggots out. 

COMPACT HEAPING OF MANURE. 

Another method of disposing of manure has been recommended by Englishwriters. The manure is built up in a compact rectangular heap, the sidesof which are beaten hard with shovels. The ground around the edges ofthe heap is made smooth and hard and loose straw is placed in smallwindrows around the manure pile about 1 foot from the edge. Theexclusion of the air, together with the high temperature and gasesformed by fermentation, tends to make the heap unfavorable for thedevelopment of fly larvæ. Those which do happen to develop in thesurface layers will migrate and pupate in the ring of straw around theheap, where they are destroyed by burning. 

GARBAGE DISPOSAL AND TREATMENT OF MISCELLANEOUS BREEDING PLACES. 

It is just as true under farm conditions as in cities that breedingplaces other than horse manure must be attended to. Garbage must bedisposed of, hog and poultry manure must be cared for, and especially ondairy farms it is extremely important that every precaution be taken toprevent the contamination of milk by flies. 

It is very desirable that all refuse possible, accumulated from citiesand towns, be burned. Incineration has been practiced successfully by anumber of towns and cities with populations of from 10, 000 to 15, 000 andover. In larger cities provision should be made for burning carcasses aswell as garbage and other refuse. If city and town garbage is sold tohog feeders the municipal authorities should have control of thesanitary conditions about the feeding yards, as there is great dangerfrom fly breeding in such places if not kept clean. 

SEWAGE DISPOSAL IN RELATION TO THE PREVENTION OF FLY-BORNE DISEASES. 

In the consideration of these measures we have not touched upon theremedies for house flies breeding in human excrement. On account of thedanger of the carriage of typhoid fever, the dropping of human excrementin the open in cities or towns, either in vacant lots or in darkalleyways, should be made a misdemeanor, and the same care should betaken by the sanitary authorities to remove or cover up such depositionsas is taken in the removal of the bodies of dead animals. For modernmethods of sewage disposal adapted for farm use one should consultDepartment of Agriculture Department Bulletin No. 57. In the absence ofmodern methods of sewage disposal, absolutely sanitary privies are primenecessities, whether in towns or on farms. Directions for building andcaring for such privies will be found in Farmers' Bulletin 463 and inYearbook Separate 712, "Sewage Disposal on the Farm. " The box privy isalways a nuisance from many points of view, and is undoubtedly dangerousas a breeder of flies which may carry the germs of intestinal diseases. The dry-earth treatment of privies is unsatisfactory. No box privyshould be permitted to exist unless it is thoroughly and regularlytreated with some effective larvicide. Since the fecal matter in suchprivies is seldom used for fertilizing purposes it may well be treatedliberally with borax. The powdered borax may be scattered two or threetimes a week over the exposed surface so as to whiten it. 

WHAT COMMUNITIES CAN DO TO ELIMINATE THE HOUSE FLY. 

Antifly crusades have been very numerous in recent years, and some havebeen noteworthy both in methods and in results. However, it will not beamiss here to emphasize the importance of concerted, organized effort onthe part of whole communities, not only cities, but suburban and ruralneighborhoods as well. By the most painstaking care one may prevent allfly breeding on his premises, but it will avail him little if hisneighbors are not equally careful. Some sort of cooperation isnecessary. One of the first and most important elements in any antiflycrusade is a vigorous and continued educational campaign. It has beenthe experience of those who have undertaken such crusades that peoplegenerally regard the fly as a somewhat harmless nuisance and that thefirst work of the campaign was to bring the people to a realization ofthe dangers from flies and the possibility of getting rid of them. Inthe educational campaign every possible means of publicity can beemployed, including newspapers, lectures, moving pictures, posters, handbills, cartoons, instruction in schools, etc. 

The antifly crusade is a matter of public interest and should besupported by the community as a whole and engineered by the healthofficers. But health officers can do little toward the necessary work ofinspection and elimination without funds, and therefore the support ofthe campaign must manifest itself in increased appropriations forpublic-health work. Very often it is lack of funds which prevents thehealth officers from taking the initiative in the antifly crusades, andthere must necessarily be much agitation and education before they canprofitably take up the work. Right here lies a field for civicassociations, women's clubs, boards of trade, etc. , to exercise theirbest energy, initiative, and leadership. 

ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THISPUBLICATION WAS LAST PRINTED

 _Secretary of Agriculture_ ARTHUR M. HYDE. 

 _Assistant Secretary_ R. W. DUNLAP. 

 _Director of Scientific Work_ A. F. WOODS. 

 _Director of Regulatory Work_ WALTER G. CAMPBELL. 

 _Director of Extension Work_ C. W. WARBURTON. 

 _Director of Personnel and Business Administration_ W. W. STOCKBERGER. 

 _Director of Information_ M. S. EISENHOWER. 

 _Solicitor_ E. L. MARSHALL. 

 _Bureau of Agricultural Economics_ NILS A. OLSEN, _Chief_. 

 _Bureau of Agricultural Engineering_ S. H. MCCRORY, _Chief_. 

 _Bureau of Animal Industry_ JOHN R. MOHLER, _Chief_. 

 _Bureau of Biological Survey_ PAUL G. REDINGTON, _Chief_. 

 _Bureau of Chemistry and Soils_ H. G. KNIGHT, _Chief_. 

 _Office of Cooperative Extension Work_ C. B. SMITH, _Chief_. 

 _Bureau of Dairy Industry_ O. E. REED, _Chief_. 

 _Bureau of Entomology_ C. L. MARLATT, _Chief_. 

 _Office of Experiment Stations_ JAMES T. JARDINE, _Chief_. 

 _Food and Drug Administration_ WALTER G. CAMPBELL, _Director_ _of Regulatory Work, in Charge. _

 _Forest Service_ R. Y. STUART, _Chief_. 

 _Grain Futures Administration_ J. W. T. DUVEL, _Chief_. 

 _Bureau of Home Economics_ LOUISE STANLEY, _Chief_. 

 _Library_ CLARIBEL R. BARNETT, _Librarian_. 

 _Bureau of Plant Industry_ WILLIAM A. TAYLOR, _Chief_. 

 _Bureau of Plant Quarantine_ LEE A. STRONG, _Chief_. 

 _Bureau of Public Roads_ THOMAS H. MACDONALD, _Chief_. 

 _Weather Bureau_ CHARLES F. MARVIN, _Chief_. 

U. S. GOVERNMENT PRINTING OFFICE: 1938

For sale by the Superintendent of Documents, Washington, D. C. Price 5 cents

[Transcriber's Note:Footnotes 10 & 11 renumbered to avoid the confusion generatedby two footnote 9's. ]