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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, insanitary
conditions, 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 apply
such knowledge in combating them. This bulletin gives information on
this subject. Besides giving directions for ridding the house of flies
by the use of screens, fly papers, poisons, and flytraps, it lays
especial emphasis on the explanation of methods of eliminating breeding
places 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


       *       *       *        *       *


KINDS OF FLIES FOUND IN HOUSES.


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

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

Another frequent visitant of houses, particularly in the spring and
fall, 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 great
annoyance. It gets its name of "cluster fly" from its habit of
collecting in compact groups or clusters in protected corners during
cold periods.

Several species of metallic greenish or bluish flies also are found
occasionally in houses. These include a blue-bottle fly,[4] the black
blowflies,[5] and the green-bottle (fig. 2) flies.[6] They breed in
decaying 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 species
of the genus.]

There is still another species, smaller than any of those so far
mentioned, which is sometimes called the "lesser house fly."[7] This
insect is distinguished from the ordinary house fly by its paler and
more pointed body. The male, which is commoner than the female, has
large pale patches at the base of the abdomen, which are translucent
when the fly is seen on the window pane. These little flies are not the
young of the larger flies. Flies do not grow after the wings have once
expanded and dried.

[Footnote 7: _Fannia canicularis_ L.]

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

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

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

All of these species, however, are greatly dwarfed in numbers by the
common house fly. In 1900 the senior author made collections of the
flies in dining rooms in different parts of the country, and found that
the true house fly made up 98.8 per cent of the whole number captured.
The remainder comprised various species, including those mentioned
above.

[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 the
world, is a medium-sized fly with four black stripes on the back and a
sharp elbow in one of the veins of the wings. The house fly can not
bite, its mouth parts being spread out at the tip for sucking up liquid
substances.

The eggs (figs. 4, 5) are laid upon horse manure. This substance seems
to 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 human
beings, carrying as it does the germs of intestinal diseases, such as
typhoid fever and cholera, from the excreta to food supplies. It has
also been found to breed freely in hog manure, in considerable numbers
in chicken dung, and to some extent in cow manure. Indeed, it will lay
its eggs on a great variety of decaying vegetable and animal materials,
but of the flies that infest dwelling houses, both in cities and on
farms, 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 localities
where little or no horse manure is found, and in such cases it breeds in
other manure, such as chicken manure in backyard poultry lots, or in
slops or fermenting vegetable material, such as spent hops, moist bran,
ensilage, or rotting potatoes. Accumulations of organic material on the
dumping grounds of towns and cities often produce flies in great
numbers.

[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 after
emerging, the time interval depending to a large extent upon
temperature, humidity, and character and abundance of food. The number
of eggs laid by an individual fly at one time ranges from 120 to 159 and
a single female will usually lay two and sometimes four such batches.
Dunn has recently reported that in Panama a fly may deposit as many as
2,367 eggs in 21 batches, and sometimes an interval of only 36 hours may
occur between the deposition of large batches of eggs. The enormous
numbers in which the insects occur are thus plainly accounted for,
especially when the abundance and universal occurrence of appropriate
larval food is considered. The eggs are deposited below the surface in
the cracks and interstices of the manure, several females usually
depositing in one spot, so that the eggs commonly are found in large
clusters (fig. 4) in selected places near the top of the pile, where a
high degree of heat is maintained by the fermentation below. The second
batch of eggs is laid from 8 to 10 days after the first. The eggs
usually hatch in less than 24 hours. Under the most favorable conditions
of temperature and moisture the egg state may last hardly more than 8
hours. The maggots which issue from the eggs are very small and
transparent. They grow rapidly, completing the growth of the larva stage
in three days under the most favorable conditions, although this stage
usually lasts from 4 to 7 days. The larval period may be prolonged
greatly by low temperature or by dryness or scarcity of the larval food.
As the larvæ (fig. 6) attain full size they gradually assume a creamy
white color. A few hours before pupation they become very restless and
migrate from their feeding ground in search of a favorable place in
which to pass the pupa stage. They will often congregate at the edges of
manure piles near the ground or burrow into the soil beneath, or they
may crawl considerable distances away from the pile to pupate in the
ground or in loose material under the edges of stones, boards, etc.

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

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

The adult fly, upon emerging from the puparium, works its way upward
through the soil or manure and upon reaching the air it crawls about
while its wings expand and the body hardens and assumes its normal
coloration. In from 2 1/2 to 20 days, as previously stated, the female
is ready to deposit eggs. As in the case of other periods of its life
history, so the preoviposition period is prolonged considerably by the
lower temperatures of spring and fall. In midsummer, with a
developmental period of from 8 to 10 days from egg to adult, and a
preoviposition period of from 3 to 4 days, a new generation would be
started every 11 to 14 days. Thus the climate of the District of
Columbia allows abundance of time for the development of from 10 to 12
generations 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 of
food, but experiments recently made at Dallas, Tex., show that they may
migrate considerable distances; in fact, house flies, so marked that the
particular individuals could be identified, have been recaptured in
traps 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 an
adult, hiding in cracks and crevices of buildings, etc., appears to be
erroneous. Under outdoor conditions house flies are killed during the
first really cold nights, that is, when the temperature falls to about
15° or 10° F. In rooms and similar places protected from winds and
partially heated during the winter flies have been kept alive in cages
for long periods, but they never lived through the entire winter. In
longevity experiments one record of 70 days and another of 91 days was
obtained. 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 other
species, which may be easily mistaken for the house fly, is responsible
for the prevailing belief as to the way the house fly overwinters. There
is therefore no reliable evidence whatever that adult house flies
emerging during October and November pass the winter and are able to
deposit their eggs the following spring, although they may continue
active in heated buildings until nearly the end of January. On the other
hand, there is evidence that house flies pass the winter as larvæ and
pupæ, and that they sometimes breed continuously throughout the winter.
In experiments at both Dallas, Tex., and Bethesda, Md., house flies have
been found emerging during April from heavily infested manure heaps
which had been set out and covered with cages during the preceding
autumn. In the Southern States, during warm periods in midwinter, house
flies may emerge and become somewhat troublesome; they frequently lay
eggs on warm days.

The second way in which the house fly may pass the winter is by
continuous breeding. House flies congregate in heated rooms with the
approach of the winter season. If no food or breeding materials are
present they eventually die. However, where they have access to both
food and suitable substances for egg laying they will continue breeding
just as they do outdoors during the summer. Even in very cold climates
there are undoubtedly many places, especially in cities, where house
flies 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 of
varying lengths, and this is especially true of the legs. Thus, when it
crawls over infected material it readily becomes loaded with germs, and
subsequent visits to human foods result in their contamination. Even
more dangerous than the transference of germs on the legs and body of
the fly is the fact that bacteria are found in greater numbers and live
longer in its alimentary canal. These germs are voided, not only in the
excrement of the fly, but also in small droplets of regurgitated matter
which have been called "vomit spots." When we realize that flies
frequent and feed upon the most filthy substances (it may be the excreta
of typhoid or dysentery patients or the discharges of one suffering from
tuberculosis), and that subsequently they may contaminate human foods
with their feet or excreta or vomit spots, the necessity and importance
of house-fly control is clear.

In army camps, in mining camps, and in great public works, where large
numbers of men are brought together for a longer or shorter time, there
is seldom the proper care of excreta, and the carriage of typhoid germs
from the latrines and privies to food by flies is common and often
results in epidemics of typhoid fever.

And such carriage of typhoid is by no means confined to great temporary
camps. In farmhouses in small communities, and even in badly cared for
portions of large cities, typhoid germs are carried from excrement to
food by flies, and the proper supervision and treatment of the breeding
places of the house fly become most important elements in the prevention
of typhoid.

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




EXCLUDING AND CAPTURING FLIES.


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

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


THE USE OF INSECT SCREENS.

A careful screening of windows and doors during the summer months, with
the supplementary use of sticky fly papers, is a protective measure
against house flies known to everyone. As regards screening, it is only
necessary here to emphasize the importance of keeping food supplies
screened or otherwise covered so that flies can gain no access to them.
This applies not only to homes but also to stores, restaurants, milk
shops, and the like. Screening, of course, will have no effect in
decreasing the number of flies, but at least it has the virtue of
lessening the danger of contamination of food.

Insect screens for doors and windows should be well made and must fit
tightly, otherwise they will not keep insects out. It is equally
important that they be made of good and durable screen cloth. Copper
insect screen cloth, although a little higher in price, will prove more
economical in the long run, as it lasts many years. If, however, the
cost of copper screen cloth is objectionable, steel screen cloth, either
painted or galvanized, can be used. Painted steel screen cloth will last
one or more years without repainting, its durability depending upon the
climate. In humid regions, of course, it will rust more quickly than it
will where the climate is dry. The same may be said of galvanized steel
insect screen cloth.

Insect screen cloth made with 16 meshes to the inch is recommended, for
16-mesh screen cloth will keep out flies and most mosquitoes[9] and
other 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 heavy
wire) should be used.]


FLY PAPERS AND POISONS.

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

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


FLY SPRAYS.

Sprays designed to destroy or repel house flies fill a certain need in
connection with the house-fly problem. No very satisfactory repellent
substances for this insect have been found which are at the same time
adaptable to general use about the home, or places where foods are
handled. Extracts of pyrethrum flowers are now generally available
commercially, and these give fairly good results in the destruction of
house flies in buildings. Most of the sprays of pyrethrum extract
contain kerosene oil as a carrier, and undoubtedly the kerosene has much
to do with the toxicity of the spray. Such materials are most applicable
to buildings which become infested with flies and which can be readily
closed up at night and the air within thoroughly saturated with the
spray by means of an atomizer. Under such conditions the flies are
rather quickly overcome by the spray and if a sufficient quantity is
used 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 lay
eggs, and the number of future generations will be reduced greatly.

Many types of flytraps are on the market. As a rule the larger ones are
the more effective. Anyone with a few tools can construct flytraps for a
small part of the price of the ready-made ones. A trap (fig. 8) which is
very 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 details
see Farmers' Bulletin 734.)

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




PREVENTING THE BREEDING OF FLIES.


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


CONSTRUCTION AND CARE OF STABLES.

In formulating rules for the construction and care of stables and the
disposal of manure the following points must be taken into
consideration. In the first place, the ground of soil-floor stables may
offer a suitable place for the development of fly larvæ. The larvæ will
migrate from the manure to the soil and continue their growth in the
moist ground. This takes place to some extent even when the manure is
removed from the stables every day. Even wooden floors are not entirely
satisfactory unless they are perfectly water-tight, since larvæ will
crawl through the cracks and continue their development in the moist
ground below. Water-tight floors of concrete or masonry, therefore, are
desirable. Flies have been found to breed in surprising numbers in small
accumulations 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 manure
from horse stables be kept in fly-tight pits or bins. Such pits can be
built in or attached to the stable so that manure can be easily thrown
in at the time of cleaning and so constructed that the manure can be
readily removed. It is desirable that the manure be placed in these
fly-proof receptacles as soon as possible after it is voided. The
essential point is that flies be prevented from reaching the manure, and
for this reason the pit or bin must be tightly constructed, preferably
of concrete, and the lid kept closed except when the manure is being
thrown in or removed. The difficulty has been that manure often becomes
infested before it is put into the container, and flies frequently breed
out before it is emptied and often escape through the cracks. To obviate
these difficulties a manure box or pit with a modified tent trap or cone
trap attached is desirable.

In order to retain the fertilizing value of manure to the greatest
extent it is advisable that air be excluded from it as much as possible
and that it be protected from the leaching action of rains. This being
the case, there is really no necessity for covering a large portion of
the top of the box with a trap, but merely to have holes large enough to
attract flies to the light, and to cover these holes with ordinary
conical traps, with the legs cut off, so, that the bottoms of the traps
will fit closely to the box. The same arrangement can be made where
manure is kept in a pit. If manure boxes or pits are kept fly tight they
are satisfactory under farm or dairy conditions for the storage of
manure 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 in
cities and towns, it should be borne in mind that when the larvæ have
finished feeding they will often leave the manure and pupate in the
ground below or crawl some distance away to pupate in débris under
boards or stones and the like. Hence the manure should be removed before
the larvæ reach the migratory stage; that is to say, removal is
necessary every three days, and certainly not less frequently than twice
a week during the summer months. A series of orders issued in 1906 by
the health department of the District of Columbia, on the authority of
the Commissioners of the District, covers most of these points, and
these orders, which may well serve as a model to other communities
desiring to undertake similar measures, may be briefly condensed as
follows:


   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 of
disposal of garbage and with the lessening of the number of horses and
horse stables consequent upon electric street railways, bicycles, and
automobiles, the time may come, and before very long, when window
screens may be discarded.


DISPOSAL OF MANURE IN RURAL AND SUBURBAN DISTRICTS.

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

With this idea in mind, it has been recommended that stable manure be
collected every morning and hauled out at once and spread rather thinly
on the fields. This procedure is advisable from the point of view of
getting the maximum fertilizing value from the manure. Immediate
spreading on the fields is said largely to prevent the loss of plant
food which occurs when manure is allowed to stand in heaps for a long
time. This method will be effective in preventing the breeding of flies
only if the manure is hauled out promptly every morning and spread
thinly so that it will dry, since it is unfavorable for fly development
in desiccated condition. The proper scattering of the manure on the
fields is best and most easily and quickly accomplished by the use of a
manure spreader, and many dairies, and even farms, are practicing the
daily distribution of manure in this way. Removal every three or four
days will not be sufficient. Observations have shown that if manure
becomes flyblown and the maggots attain a fairly good size before the
manure is scattered on the fields, they can continue their development
and 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 remove
manure regularly. The general practice, therefore, has been to keep the
manure in heaps located, as a rule, very near the stables. How can fly
breeding be prevented in such accumulations? As a result of recent
investigations, it is now possible to point out two methods which are
practical and effective.

The first is the treatment of the manure pile with chemical substances
which will kill the eggs and maggots of the house fly. The Bureau of
Entomology, in cooperation with the Bureau of Chemistry and the Bureau
of Plant Industry, has conducted a series of experiments in which a
large number of chemicals were applied to infested manure and
observations made, not only on their efficiency in killing the maggots
but also as to their effect on the chemical composition and bacterial
flora of the manure. The object was to find some cheap chemical which
would be effective in destroying the fly larvæ and at the same time
would not reduce the fertilizing value of the manure.


TREATMENT WITH HELLEBORE.

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

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

Since the solution is somewhat poisonous it should not be left exposed
where it might be drunk by livestock. It is quite safe to say that
chickens will not be injured by pecking at hellebore-treated manure.
This has been tested carefully. Hellebore can be obtained both in ground
and powdered form, but the powder gives the best results in the
destruction 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 is
powdered borax. This substance is available in commercial form in all
parts of the country. It has the advantage of being comparatively
nonpoisonous and noninflammable and is easily transported and handled.
The minimum amount necessary to kill fly larvæ was found to be 0.62
pound per 8 bushels of manure, or about 1 pound per 16 cubic feet. Best
results were obtained when the borax was applied in solution, or when
water was sprinkled on after the borax had been scattered evenly over
the pile. Borax is not only effective in killing the larvæ, but when it
comes in contact with the eggs it prevents them from hatching. When
applied at the rate of 1 pound to 16 cubic feet it was found to kill
about 90 per cent of the larvæ, heavier applications killing from 98 to
99 per cent.

Borax has no injurious effect on the chemical composition or rotting of
the manure. However, when added in large quantities with manure to the
soil it will cause considerable injury to growing plants. A number of
experiments have been conducted to determine the effect on crops of the
use of manure treated with borax as herein recommended. When applied at
the rate of 15 tons per acre it appears that no injury as a rule will
follow. Some crops are more sensitive to borax than others, and also the
tendency to injury appears to vary on different soils. It is necessary,
therefore, to repeat the warning issued in connection with a previous
bulletin[11] on this subject, that great care be exercised, in the
application of borax, that the manure does not receive more than 1 pound
for every 16 cubic feet, and that not more than 15 tons of manure so
treated are applied to the acre.

In view of the possible injury from the borax treatment as a result of
carelessness in applying it, or from other unforeseen conditions, it is
recommended that horse manure and other farmyard manures which are to be
used as fertilizer be treated with hellebore. Borax, on the other hand,
is such a good larvicide that it call be used with advantage on the
ground of soil-floor stables, in privies, on refuse piles, and on any
accumulations of fermenting organic matter which are not to be used for
fertilizing 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 to
determine whether fly larvæ would be killed by any substance the
addition of which would increase the fertilizing value of the manure. A
mixture of calcium cyanamid and acid phosphate was found to possess
considerable larvicidal action. Several experiments showed that 1/2
pound of calcium cyanamid plus 1/2 pound of acid phosphate to each
bushel of manure give an apparent larvicidal action of 98 per cent. The
mixture in the form of a powder was scattered evenly over the surface
and then wet down with water. The use of this mixture adds to the manure
two 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 the
application 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 to
pupate, show a strong tendency to migrate. This migration takes place
mostly at night, and the larvæ sometimes crawl considerable distances
from the manure pile. Now it is possible by means of a very simple
arrangement called a maggot trap to destroy fully 99 per cent of all
maggots breeding in a given lot of manure. A successful maggot trap
which the Maryland Agricultural College constructed at the college barn
is shown in Figure 9. The trap was designed by R. H. Hutchison and
constructed under his supervision. The manure, instead of being thrown
on the ground, is heaped carefully on a slatted platform, which stands
about 1 foot high. This particular platform measures 10 by 20 feet.
There are six 2 by 4 pieces running lengthwise 2 feet apart. Across
these 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 of
concrete 4 inches high surrounds the floor. The floor slopes a little
toward 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 floor
is filled with water to a depth of 1 inch in the shallowest part. Flies
will lay their eggs on the manure as usual, but the maggots, when they
have finished feeding and begin to migrate, crawl out of the manure,
drop into the water below, and are drowned. Each week the plug is
removed from the pipe, and all the maggots are washed into the cistern.
The floor is then cleaned of any solid particles by means of a
long-handled stable broom or by a strong stream of water from a hose.
The pipe being again plugged, the floor is again partly filled with
water and the trap is ready for another week's catch. A platform of this
size will hold the manure accumulating from four horses during the
period of four months, or about 20 days' accumulation from 25 horses, if
the heap is well built and made at least 5 feet high.

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

Experience with this maggot trap clearly indicates that best results can
be secured if the manure is compactly heaped on the platform and kept
thoroughly moistened. It is best to apply a small amount of water each
morning after the stable cleanings have been added to the pile. It
should be borne in mind that in order to make this trap a success the
platform beneath the pile must be kept comparatively free of
accumulations of manure, and moisture applied regularly to drive the
maggots out.


COMPACT HEAPING OF MANURE.

Another method of disposing of manure has been recommended by English
writers. The manure is built up in a compact rectangular heap, the sides
of which are beaten hard with shovels. The ground around the edges of
the heap is made smooth and hard and loose straw is placed in small
windrows around the manure pile about 1 foot from the edge. The
exclusion of the air, together with the high temperature and gases
formed by fermentation, tends to make the heap unfavorable for the
development of fly larvæ. Those which do happen to develop in the
surface layers will migrate and pupate in the ring of straw around the
heap, 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 breeding
places other than horse manure must be attended to. Garbage must be
disposed of, hog and poultry manure must be cared for, and especially on
dairy farms it is extremely important that every precaution be taken to
prevent the contamination of milk by flies.

It is very desirable that all refuse possible, accumulated from cities
and towns, be burned. Incineration has been practiced successfully by a
number of towns and cities with populations of from 10,000 to 15,000 and
over. In larger cities provision should be made for burning carcasses as
well as garbage and other refuse. If city and town garbage is sold to
hog feeders the municipal authorities should have control of the
sanitary conditions about the feeding yards, as there is great danger
from 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 the
remedies for house flies breeding in human excrement. On account of the
danger of the carriage of typhoid fever, the dropping of human excrement
in the open in cities or towns, either in vacant lots or in dark
alleyways, should be made a misdemeanor, and the same care should be
taken by the sanitary authorities to remove or cover up such depositions
as is taken in the removal of the bodies of dead animals. For modern
methods of sewage disposal adapted for farm use one should consult
Department of Agriculture Department Bulletin No. 57. In the absence of
modern methods of sewage disposal, absolutely sanitary privies are prime
necessities, whether in towns or on farms. Directions for building and
caring for such privies will be found in Farmers' Bulletin 463 and in
Yearbook Separate 712, "Sewage Disposal on the Farm." The box privy is
always a nuisance from many points of view, and is undoubtedly dangerous
as a breeder of flies which may carry the germs of intestinal diseases.
The dry-earth treatment of privies is unsatisfactory. No box privy
should be permitted to exist unless it is thoroughly and regularly
treated with some effective larvicide. Since the fecal matter in such
privies is seldom used for fertilizing purposes it may well be treated
liberally with borax. The powdered borax may be scattered two or three
times 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 have
been noteworthy both in methods and in results. However, it will not be
amiss here to emphasize the importance of concerted, organized effort on
the part of whole communities, not only cities, but suburban and rural
neighborhoods as well. By the most painstaking care one may prevent all
fly breeding on his premises, but it will avail him little if his
neighbors are not equally careful. Some sort of cooperation is
necessary. One of the first and most important elements in any antifly
crusade is a vigorous and continued educational campaign. It has been
the experience of those who have undertaken such crusades that people
generally regard the fly as a somewhat harmless nuisance and that the
first work of the campaign was to bring the people to a realization of
the dangers from flies and the possibility of getting rid of them. In
the educational campaign every possible means of publicity can be
employed, including newspapers, lectures, moving pictures, posters,
handbills, cartoons, instruction in schools, etc.

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




ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS
PUBLICATION 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 generated
by two footnote 9's.]