HOUSE-FLIES OR TYPHOID-FLIES
The page shown in Fig. 37 was copied from one of our old second readers
and shows something of the spirit in which we used to regard the
house-fly. A few of them were nice things to have around to make things
seem "homelike." Of course they sometimes became too friendly during the
early morning hours when we were trying to take just one more little nap
or they were sometimes too insistent for their portion of the dinner
after it had been placed on the table, but a screen over the bed would
help us out a little in the morning and a long fly-brush cut from a tree
in the yard or made of strips of paper tacked to a stick or, still more
fancy, made of long peacock plumes, would help to drive them from the
table. Those that were knocked into the coffee or the cream could be
fished out; those that went into the soup or the hash were never missed!
Not only were the flies regarded as splendid things with which to amuse
the baby, but they were thought to be very useful as scavengers as they
were often seen feeding on all kinds of refuse in the yard. Then, too,
they seemed to be cleanly little things, for almost any time some of
them could be seen brushing their heads and bodies with their legs and
evidently having a good clean-up. More than that it never occurred to us
that it would be possible to get rid of them even should it be thought
advisable, for they came from "out doors," and who could kill all the
flies "out doors"?
Fortunately, or otherwise, these halcyon days have gone by and the
common, innocent, friendly little house-fly is now an outcast convicted
of many crimes and accused of a long list of others (Fig. 38).
Its former friends have become its sworn enemies. The foremost
entomologist of the land has suggested that we even change its name and
give it one that would be more suggestive of the abhorence with which we
now look upon it.
[Illustration: FIG. 38--The house-fly (_Musca domestica_).]
And all these changes have come about because science has turned the
microscope on the house-fly and men have studied its habits. We know now
that as the fly is "tickling baby's nose" it may be spreading there
where they may be inhaled or where they may be taken into the baby's
mouth thousands of germs some of which may cause some serious disease.
We know that as they are buzzing about our faces while we are trying to
sleep they may, unwittingly, be in the same nefarious business, and we
know that as they sip from our cups with us or bathe in our coffee or
our soup or walk daintily over our beefsteak or frosted cake they are
leaving behind a trail of filth and bacteria, and we know that some of
these germs may be and often are the cause of some of our common
diseases. As the typhoid germs are very often distributed in this way,
Dr. Howard has suggested that the house-fly shall be known in the future
as the typhoid-fly, not because it is solely responsible for the spread
of typhoid, but because it is such an important factor in it and is so
dangerous from every point of view. The names "manure fly" and "privy
fly" have also been suggested and would perhaps serve just as well, as
the only object in giving it another name would be to find a more
repulsive one to remind us constantly of the filthy and dangerous habits
of the fly.
STRUCTURE
In order that we may better understand why it is that the house-fly is
capable of so much mischief, let us consider briefly a few points in
regard to its structure, its methods of feeding and its life-history.
The large compound eyes are the most conspicuous part of the head (Fig.
39). In front, between the eyes, are the three-jointed antennæ, the last
joint bearing a short, feathery bristle. From the under side of the head
arises the long, fleshy proboscis (Fig. 40). When this is fully extended
it is somewhat longer than the head; when not distended and in use it is
doubled back in the cavity on the under side of the head. About half-way
between the base and the middle is a pair of unjointed mouth-feelers
(maxillary palpi). At the tip are two membranous lobes (Fig. 41) closely
united along their middle line. These are covered with many fine
corrugated ridges, which under the microscope look like fine spirals and
are known as pseudotracheæ. Thus it will be seen that the house-fly's
mouth-parts are fitted for sucking and not for biting. Its food must be
in a liquid or semi-liquid state before it can be sucked through the
tube leading from the lobes at the tip up through the proboscis and on
into the stomach. If the fly wishes to feed on any substance such as
sugar, that is not liquid, it first pours out some saliva on it and then
begins to rasp it with the rough terminal lobes of the proboscis, thus
reducing the food to a consistency that will enable the fly to suck it
up. Many people think that house-flies can bite and will tell you that
they have been bitten by them. But a careful examination of the
offender, in such instances, will show that it was not a house-fly but
probably a stable-fly, which does have mouth-parts fitted for piercing.
[Illustration: FIG. 39--Head of house-fly showing eyes, antennæ and
mouth-parts.]
[Illustration: FIG. 40--Proboscis of house-fly, side view.]
[Illustration: FIG. 41--Lobes at end of proboscis of house-fly showing
corrugated ridges.]
[Illustration: FIG. 42--Wing of house-fly.]
The thorax bears the two rather broad, membranous wings (Fig. 42) which
have characteristic venation. Three of these veins end rather close
together just before the tip of the wing, the posterior one of the group
being bent forward rather sharply a short distance from the tip. The
stable-fly has this vein slightly curved forward but not nearly so
conspicuously (Fig. 43).
Nearly all the other flies that are apt to be mistaken for the house-fly
do not have this vein curved forward. The wings, although apparently
bare, are covered with a fine microscopic pubescence. Among these fine
hairs on the wing as well as among similar fine ones and coarser ones
all over the body, particles of dust and dirt or filth (Fig. 44) or,
what interests us more just now, thousands of germs may find a temporary
lodgment and later be scattered through the air as the insect flies. Or
they may get on our food as the fly feeds or while it rests and combs
its body with the rows of coarse hairs on its legs.
The legs are rather thickly covered with coarse hairs or bristles and
with a mat of fine, short hairs. On some of the segments the larger
hairs are arranged in rows and are used as a sort of comb with which the
fly combs the dirt from the rest of its body. The last segment (Fig. 45)
of the leg bears at its tip a pair of large curved claws and a pair of
membranous pads known as the pulvillæ. On the under side of the pulvillæ
are innumerable minute secreting hairs (Fig. 46) by means of which the
fly is able to walk on the wall or ceiling or in any position on
highly-polished surfaces.
HOW THEY CARRY BACTERIA
These same little pads, with their covering of secreting hairs, are
perhaps the most dangerous part of the insect for they cannot help but
carry much of the filth over or through which the fly walks, and as this
may be well stocked with germs the danger is at once apparent.
As the result of a series of carefully planned experiments it has been
demonstrated that the number of bacteria on a single fly may range all
the way from 550 to 6,600,000 with an average for the lot experimented
with of about one and one-fourth million bacteria to each fly. Now where
do all these bacteria come from? Necessarily from the place where the
fly breeds or where it feeds.
[Illustration: FIG. 43--Wing of Stable-fly (_Stomoxys calcitrans_).]
[Illustration: FIG. 44--Wing of house-fly showing particles of dirt
adhering to it.]
[Illustration: FIG. 45--Last three segments of leg of house-fly showing
the claws, the pulvillæ and the hairs on the legs.]
[Illustration: FIG. 46--Foot of house-fly showing claws, hairs,
pulvillæ and the minute clinging hairs on the pulvillæ.]
[Illustration: FIG. 47--Larva of house-fly.]
LIFE-HISTORY AND HABITS
The eggs of the house-fly may be laid on almost any kind of decaying or
fermenting material. If this is kept moist and a proper temperature
maintained the larvæ or maggots (Fig. 47) that hatch from the eggs may
develop. As a rule, however, these requirements are found only under
certain conditions and are ordinarily found only in manure heaps or in
privy vaults or latrines. All observers agree that the female fly
prefers to deposit her eggs in horse manure when this can be found and
when this is piled in heaps in the barn-yard (Fig. 48) or in the field
the heat caused by the decay and fermentation makes ideal conditions for
the development of the larvæ. Cow manure may serve as a breeding-place
to a limited extent. The flies are immediately attracted to human
excrement and breed freely in it when opportunity offers. Decaying
vegetables or fruit, fermenting kitchen refuse and other materials
sometimes also serve as breeding-places.
In suitable places in warm weather the eggs will hatch in from eight to
twelve hours and the larvæ will become fully developed in from eight to
fourteen days. They then change to pupæ (Fig. 50) in which stage they
may remain for another eight to twenty days when the adult flies will
emerge. These figures must necessarily be indefinite because the weather
and other conditions always vary. Under the most favorable conditions of
moisture and temperature it is probably never less than eight days from
egg to adult fly and under unfavorable conditions it may be as long as
six weeks.
The larvæ thrive best when the manure is kept quite wet. I have often
found them in almost incredible numbers in stables that had not been
cleaned for some time. The horses standing there at night added fresh
material and kept it just wet enough to make conditions almost ideal
(Fig. 49).
The pupæ are usually found where the manure is a little dryer, but it
must not be too dry. When the flies issue from the pupæ they push their
way up to the surface where they remain for a short time and allow the
body to harden and the wings to dry before they fly away to other manure
or, as too often happens, to some near-by kitchen or restaurant or
market place.
[Illustration: FIG. 48--Barn-yard filled with manure. Millions of flies
were breeding here and infesting all the near-by houses.]
[Illustration: FIG. 49--Dirty stalls; the manure had not been removed
for some days and the floor was covered with maggots.]
Of course it is impossible for them to issue from this filth without
more or less of it clinging to their bodies. Now if these flies would
breed only in barn-yard manure and fly directly from the stable to the
house there would be comparatively little reason to complain, at least
from a sanitary standpoint, for the amount of barn-yard filth that they
carried to our food would be of little consequence. But when they breed
in privy vaults or similar places, or visit such places before coming
into the house or dairy or market place the results may be much more
serious.
FLIES AND TYPHOID
It has been abundantly demonstrated that the excrement or the urine of a
typhoid patient may contain virulent germs for some time before he is
aware that he has the disease, and it has been shown that the germs may
be present for weeks or months, and in some cases even years after the
patient has recovered. If a fly breeds in such infected material, or
feeds or walks on it, it is very apt to get some of the germs on its
body where they may retain their virulence for some time, and should it
visit our food while covered with these germs some of them would
probably be left there where they might produce serious results. More
than that. If the fly should feed on such infected material the typhoid
germs would go on developing in the intestine of the fly and would be
passed out with the feces in which they retain their virulence for some
days. In other words, the too familiar "fly-specks" are not only
disgusting, but may be a very grave source of danger. It will be seen
that in this way several members of a community might become infected
with the typhoid germs before anyone was aware that there was a case of
typhoid or a "bacillus carrier" in the neighborhood.
One more example out of the scores that might be cited to show how the
fly may carry typhoid germs. They may enter the sick chamber in the home
or in the hospital and there gain access to the typhoid germs. These
they may carry to other parts of the house or to near-by houses, or the
flies may light on passing carriages or cars and be carried perhaps for
miles before they enter another house and contaminate the food there.
These are hypothetical cases, but they illustrate what is taking place
hundreds of times every season all over the world wherever typhoid fever
and flies occur, and no country or race is known to be immune from
typhoid, and the fly is found "wherever man is found."
In the summer of 1898 a commission was appointed to investigate the
prevalence of typhoid fever in the United States Army Concentration
Camps. The following are some of the conclusions as reported by Dr.
Vaughan:
"FLIES UNDOUBTEDLY SERVED AS CARRIERS OF THE INFECTION
"My reasons for believing that flies were active in the
dissemination of typhoid may be stated as follows:
"_a._ Flies swarmed over infected fecal matter in the pits and then
visited and fed upon the food prepared for the soldiers at the mess
tents. In some instances where lime had recently been sprinkled
over the contents of the pits, flies with their feet whitened with
lime were seen walking over the food.
"_b._ Officers whose mess tents were protected by means of screens
suffered proportionately less from typhoid fever than did those
whose tents were not so protected.
"_c._ Typhoid fever gradually disappeared in the fall of 1898, with
the approach of cold weather, and the consequent disabling of the
fly.
"It is possible for the fly to carry the typhoid bacillus in two
ways. In the first place, fecal matter containing the typhoid germ
may adhere to the fly and be mechanically transported. In the
second place, it is possible that the typhoid bacillus may be
carried in the digestive organs of the fly and may be deposited
with its excrement."
In Dr. Daniel D. Jackson's report to the Merchants' Association of New
York on the "Pollution of New York Harbor as a Menace to the Health by
the Dissemination of Intestinal Diseases Through the Agency of the
Common House-fly," he shows graphically that the prevalence of typhoid
and other intestinal diseases is coincident with the prevalence of
flies, and that the greatest number of deaths from such diseases occurs
near the river front where the open or poorly constructed sewers scatter
the filth where the flies can feed on it, or along the wharves with
their inadequate accommodations and the resulting accumulation of filth.
FLIES AND OTHER DISEASES
Not only is the house-fly an important factor in the dissemination of
typhoid fever, but it has been definitely shown that it is capable of
transmitting several other serious diseases.
The evidence that flies carry and spread the deadly germs of cholera is
most conclusive. The germs may be carried on the body where they will
live but a short time, or they may be carried in the alimentary canal
where they will live for a much longer period and are finally deposited
in the fly-specks where they retain their virulence for some time. Flies
that had been allowed to contaminate themselves with cholera germs were
allowed access to milk and meat. In both cases hundreds of colonies of
the germs could later be recovered from the food. As with the typhoid
germs milk seems to be a particularly good medium for the development of
the cholera germs. In several of the experiments that have been made
along this line the milk has been readily infected by the flies visiting
it.
Of course an outbreak of cholera is of rare occurrence in our country,
but unfortunately this is not so in regard to some other intestinal
diseases such as diarrhea and enteritis which annually cause the death
of many children, especially bottle-fed babies. Those who have made
close studies of the way in which these diseases are disseminated are
convinced that the flies are one of the most important factors in their
spread.
It has long been observed that flies are particularly fond of sputum and
will feed on it on the sidewalk, in the gutter, the cuspidor or wherever
opportunity offers. It is well known, too, that the sputum of a
consumptive contains myriads of virulent tubercular germs. A fly feeding
and crawling over such material must necessarily get some of it on its
body, and as it dries and the insect flies about the germs will be
distributed through the air, possibly over our food. It has been shown
that the excretion from a fly that has fed on tubercular sputum contains
tubercular bacilli that may remain virulent for at least fifteen days.
Thus we see again the danger that may lurk in the too familiar
"fly-specks."
Although it is generally supposed that the flea is solely responsible
for the spread of the bubonic plague and no doubt is the principal
distributing agent, the fact must not be overlooked that the house-fly
may also be of considerable importance in this connection. Carefully
planned experiments have shown that flies that have become infected by
being fed on plague-infected material may carry the germs for several
days and that they may die of the disease. During plague epidemics flies
may become infected by visiting the sores on human or rat victims or by
feeding on dead rats or on the excreta of sick patients, and an infected
fly is always a menace should it visit our food or open wounds or sores.
Anthrax bacilli are carried about and deposited by flies showing the
possibility of the disease being spread in this way.
Some believe that leprosy, smallpox and many other diseases are carried
by the house-fly, so it is little wonder that it is fast losing its
standing as a household companion and that we are beginning to regard it
not only as a nuisance but as a source of danger which should no longer
be tolerated in any community.
Of course only a small per cent of the flies that visit our food in the
dairies or market places or kitchens actually carry dangerous diseases,
but they are all bred in filth and it is not possible without careful
experiments or laboratory analysis to determine whether any of the germs
among the millions that are on their bodies are dangerous or not. The
chances that they may be are too great. The only safe way is to banish
them all or to see that all of our food is protected from them.
FIGHTING FLIES
Screens and sticky fly-paper have their places and give some little
relief in a well-kept house. But of what use is it to protect your food
after it has entered your home if in the stores, in the market place, in
the dairy barn, or dairy wagon, in the grocers' and butchers' cart, it
has been exposed to contamination by hundreds of flies that have visited
it.
The problem is a larger one than keeping the house free from flies;
larger but not more difficult, for the remedy is simple, effective,
practicable and inexpensive. Destroy their breeding-places and you will
have no flies. As the flies breed principally in manure the first
remedial measure is to see that all manure is removed from the
barn-yard at least once a week and spread over the fields to dry, for
the flies cannot breed in the dry manure. If it is not practicable to
remove it this often the manure should be kept in a bin that is closed
so tight that no flies can get into it to lay their eggs. Sometimes the
manure may be treated with some substance such as kerosene, crude oil,
chlorid of lime, tobacco water or mixture of two or more of these and
thus rendered unsuitable for the flies to breed in, but in general
practice none of them has been found very satisfactory for the treatment
is either not thorough enough or is too expensive of time and material.
Outdoor privies and cesspools must be carefully attended to. The latter
can be easily covered so no flies can get in and if the filthy and in
every way dangerous pit under the privy be filled and the dry-earth
closet substituted one of the greatest sources of danger, especially in
the country and in towns with inadequate sewerage facilities, will be
done away with. After these things are done there remain only the
garbage cans and the rubbish heaps to look after.
Of course your neighbor must keep his place clean too, for his flies are
just as apt to come into your house as his, so the problem becomes one
for the whole community.
Almost all cities and many of the smaller towns have ordinances which
if enforced would afford adequate protection from flies, but they are
seldom if ever rigidly enforced and it yet remains for some enterprising
town to be able to advertise itself as a "speckless town" as well as a
"spotless town."
AN EXPERT'S OPINION
In a recent important bulletin issued by the Bureau of Entomology, Dr.
L.O. Howard discusses the economic importance of several of the insects
that carry disease. I wish to quote two or three paragraphs from the
pages in which he discusses the house-fly or typhoid fly to show the
opinion of this excellent authority in regard to this pest.
"Even if the typhoid or house fly were a creature difficult to
destroy, the general failure on the part of communities to make any
efforts whatever to reduce its numbers could properly be termed
criminal neglect; but since, as will be shown, it is comparatively
an easy matter to do away with the plague of flies, this neglect
becomes an evidence of ignorance or of a carelessness in regard to
disease-producing filth which to the informed mind constitutes a
serious blot on civilized methods of life."
On another page:
"We have thus shown that the typhoid or house fly is a general and
common carrier of pathogenic bacteria. It may carry typhoid fever,
Asiatic cholera, dysentery, cholera morbus, and other intestinal
diseases; it may carry the bacilli of tuberculosis and certain eye
diseases. It is the duty of every individual to guard so far as
possible against the occurrence of flies upon his premises. It is
the duty of every community, through its board of health, to spend
money in the warfare against this enemy of mankind. This duty is as
pronounced as though the community were attacked by bands of
ravenous wolves."
Again:
"A leading editorial in an afternoon paper of the city of
Washington, of October 20, 1908, bears the heading, 'Typhoid a
National Scourge,' arguing that it is to-day as great a scourge as
tuberculosis. The editorial writer might equally well have used the
heading 'Typhoid a National Reproach,' or perhaps even 'Typhoid a
National Crime,' since it is an absolutely preventable disease. And
as for the typhoid fly, that a creature born in indescribable filth
and absolutely swarming with disease germs should practically be
invited to multiply unchecked, even in great centers of population,
is surely nothing less than criminal."
The whole bulletin (No. 78, Bureau of Entomology) should be read and
studied by all who are interested in this subject.
OTHER FLIES
Occasionally other flies looking more or less like the house-fly are
seen in houses. Some of these have the same type of sucking mouth-parts
and have habits very similar to the house-fly, but as they are usually
much less common and as nearly all that has been said in regard to the
house-fly would apply equally well to them and as the same measures
should be adopted in fighting them they need not be discussed further
here.
I have already called attention to the fact that a fly which looks very
much like the house-fly is sometimes found in the house and will often
bite severely. It has quite a different style of beak, one that is
fitted for piercing so it may suck the blood of its victim (Fig. 51). As
these flies often seem to be more persistent before a rain the weather
prophet will tell you that "It is surely going to rain for the
house-flies are beginning to bite."
These stable-flies, as they are called, are great pests of cattle and
horses in some sections. It is thought that they are important factors
in the spread of some of the diseases of domestic animals, and their
habit of sometimes attacking human beings makes it possible for them to
carry certain disease germs from animals to man or from man to man.