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H. S. Barber,

U. 5. NatiottaJ Museum,
Washington, 0, C.

THE HOUSE FLY— DISEASE CARRIER

THE HOUSE FLY - DISEASE CARRIER

™E

HOUSE FLYteVK'

DISEASE CARRIER

AN ACCOUNT OF ITS DANGEROUS
ACTIVITIES AND OF THE MEANS
OF DESTROYING IT

L. O. HOWARD, Ph.D.

NEW YORK

FREDERICK A. STOKES COMPANY
PUBLISHERS

CONTENTS

PAGE

Introduction . xv

CHAPTER I

Zoological Position, Life History, and Habits i

Life History . 6

The Egg . 1 8

The Larva . 19

The Pupa and Puparium . 23

Emergence of the Adult . 25

Structure of the Adult . 27

Difference in Size of Adults . 32

Summary of Duration of Life Round . . 35

Number of Generations . 36

Possibilities in the Way of Numbers . . 37

Number by Actual Count in Relation to

Quantity of Food . 39

Hibernation . 41

Habits of the Adult Fly . 44

Do Flies have a Color Preference? ... 47

Fly-Specks . 48

Distance of Flight . 51

Marking Flies for Experiment .... 56

Length of Life of the Adult . 58

Time Elapsing between the Issuing of the
Adult and the Period of Sexual Maturity 60

vi CONTENTS

CHAPTER II

PAGE

The Natural Enemies of the Typhoid Fly . 62

Fungous Diseases . 62

Protozoan Enemies of the House Fly . . 70

Nematode Parasites of the Typhoid Fly . . 72

The Mite Enemies of Musca Domestica . . 75

Spiders as Fly Enemies . 78

False Scorpions on Flies . 80

The House Centipede . 82

Insect Enemies of the House Fly .... 84

Predatory Enemies . . 84

Parasitic Enemies . 88

Vertebrate House Fly Enemies . 95

Fly-Catching Rats . 97

CHAPTER III

The Carriage of Disease by Flies .... 100

Exact Experiments . 102

Typhoid or Enteric Fever . 112

Suspicions of the Carriage of Typhoid by

Flies . 1 14

Inferential Proof . 116

Exact Proof . 125

Chronic Carriers . 128

Influence of Flies in the Carriage of Typhoid

in Cities . 138

Other Points . 148

Cholera . 15°

Dysentery . 155

Diarrhea in Infants . 156

Tuberculosis . . 162

CONTENTS

vii

PAGE

Anthrax . 164

Yaws ( Frambcesia tropica ) . 165

Ophthalmia . 167

Diphtheria . 170

Small-pox . 170

Plague . 171

Tropical Sore . 172

Parasitic Worms . 173

CHAPTER IV

Remedies and Preventive Measures . . . . 175

Screening . 177

Fly Traps and Fly Poisons . 178

Formalin . 185

Py rethrum and Carbolic Acid . 188

Repellents . 189

Search for Breeding Places . 190

The Treatment of Horse Manure .... 193

Removal of Manure and Receptacles for Its

Temporary Storage . 201

The Sanitary Privy . 203

A Compulsory Sanitary Privy Law . . . 210

The Capture of Adult Flies Outside of Houses 212

Special Considerations for Towns and Cities . 217

Organization . 218

Interesting the Children . 224

Boards of Health . 230

Army Camps . 233

CHAPTER V

Other Flies Frequenting Houses . . . . 23“

The Cluster Fly ( Pollenia rudis Fabr.) . . 236

CONTENTS

viii

The Biting House Fly (Stomoxys calcitrans L.)
The Little House Fly ( Fannia [ Homalomyia \

canicularis L.) . .

The Stable Fly ( Muscina siabulans Fall.)

The Cheese Fly ( Piophila casei L.)

The Fruit Flies ( Drosophila ampclophila Loew.)
The Bluebottle or Greenbottle Flies
The Blow Flies ( Calliphora erythrocephala
Meig., Lucilia c cesar L., Phormia terrano-

vce Desv. ) .

The Flesh Flies ( Sarcophaga assidua Walk.)
The Dung Flies ( Sepsis violacea Meig., Sca-

tophaga furcata Say.) .

The Moth Flies ( Psychoda minuta Banks.)

The Humpback Flies .

The Window Flies ( Scenopimis fenestralis L.)

Bibliographical List .

Appendix I .

Appendix II .

Appendix III .

Appendix IV .

Appendix V .

PAGE

240

246

248

249

251

252

254

255

256

257

258

261

273

281

285

293

305

ILLUSTRATIONS

The house fly — Disease carrier . . . Frontispiece

FIG. PAGE

1. Eggs, approximately natural size; photographed

on surface of manure pile (from New-
stead) . facing 18

2. Eggs, approximately natural size (from New¬

stead) . facing 18

3. Eggs, greatly enlarged (from Newstead) facing 20

4. Eggs, greatly enlarged — another view (from

Newstead) . facing 20

5. Egg of house fly; greatly enlarged .... 19

6. Egg hatching; greatly enlarged . . facing 22

7. Full grown larva of house fly; greatly en¬

larged . facing 22

8. Larvae in horse manure(from Newstead) facing 24

9. Larvae and puparia (from Newstead) . facing 24

10. Puparia on a bit of old rotting cloth from an

ash barrel (from Newstead) . . facing 26

11. House fly puparium and pupa; greatly enlarged 24

12. Adult house fly from above; greatly en¬

larged . facing 28

13. Adult house fly from below; greatly en¬

larged . facing 28

14. Head of adult house fly ; greatly enlarged facing 30

15. Head of adult house fly from side; greatly en¬

larged . facing 30

LIST OF ILLUSTRATIONS

1 6. A diagrammatic figure of the alimentary canal

of the house fly; greatly enlarged ... 29

17. The house centipede ( Scutigera forceps) ; some¬

what enlarged (after Marlatt) . . facing 82

18. Colonies of bacteria on a sterilized plate, aris¬

ing from fly tracks . facing 108

19. Details of window trap (redrawn from Parrott) 181

20. Fly trap for garbage can .... facing 214

2 1. Poster issued by the Florida State Board of

Health ; greatly reduced .... facing 224

22. The cluster fly ( Pollenia rndis) ; greatly en¬

larged . facing 238

23. The biting house fly ( Stomoxys calcitrans) ;

greatly enlarged . facing 238

24. The little house fly ( Homalomyia brevis) ;

greatly enlarged . facing 246

25. The stable fly ( Mnscina stabulans) ; greatly en¬

larged . facing 246

26. The cheese fly ( Piophila casei) ; enlarged facing 250

27. The fruit fly ( Drosophila ampelophila) ; en¬

larged . facing 250

28. Lucilia ccesar; enlarged . facing 254

29. Calliphora erythrocephala; enlarged . facing 254

30. Phormia terrcenovce ; enlarged . . . facing 254

31. Sarcophaga assidua; enlarged . . . facing 256

32. Sepsis violacea; enlarged .... facing 256

33. Scatophaga furcata; enlarged . . . facing 254

34. Phora femorata; enlarged greatly .... 257

35. Scenopinus fenestralis ; enlarged . 258

36. Scantling for framework of single-seated privy

(Redrawn from Stiles) . 295

37. The framework for a single-seated privy (Re¬

drawn from Stiles) . 297

LIST OF ILLUSTRATIONS xi

FIG. PAGE

38. Front view of single-seated sanitary privy (Re¬

drawn from Stiles) . 299

39. Rear view of single-seated sanitary privy (Re¬

drawn from Stiles) . 301

40. The Lumsden, Roberts and Stiles apparatus for

the safe disposal of night-soil (Redrawn from
Lumsden, Roberts and Stiles) .... 307

INTRODUCTION

IT is only within the last twelve years that the dan¬
gerous character of the common house fly has been
known; and only within the last two years have the
people at large begun to wake up to this danger and
to inquire concerning the means by which this fly can
be kept down. The writer published some account
of its life history in a bulletin on household insects
published by the U. S. Department of Agriculture in
1896. Later he made some experiments with regard
to remedies, and in 1900 published a rather lengthy
paper on the insect fauna of human excrement with
especial reference to the carriage of typhoid fever by
flies. Within the last two years, however, articles
relating to the so-called house fly in connection with
its disease-carrying possibilities have been published
literally by the thousand, and this interest, perhaps
having its origin in the United States, has spread to
nearly all parts of the civilized world, and yet in no
one of these published articles is the whole story told.
No one can find in condensed and convenient shape
the general information he desires in regard to this
insect. The publishers of this book, realizing this fact,
have invited the author to attempt to fill this want.

This book is not intended to be a scientific mono¬
graph ; it is simply an attempt to tell in an understand¬
able way what is known about the subjects indicated
in the title.

xvi THE HOUSE FLY— DISEASE CARRIER

And mention of the title brings up the point as to
whether the writer was justified when he proposed the
name typhoid fly for the old and well-known house
fly at the meeting of the Committee of One Hundred
on Public Health at the meeting of the American As¬
sociation for the Advancement of Science, in Baltimore,
during the Christmas week in 1908. He has been crit¬
icized for making this suggestion by the Association
of Economic Entomologists’ Committee on Popular
Names and also by certain medical men. The objec¬
tions have been that this name would indicate the be¬
lief on the part of the proposer and of those who should
subsequently use it that the house fly is the sole car¬
rier of typhoid or that it is the principal carrier of ty¬
phoid ; in other words, that it is given too much prom¬
inence from the standpoint of the etiology of typhoid
fever. As a matter of fact, however, the writer never
claimed that it was the only carrier of typhoid or that
it was the principal carrier of typhoid except under
certain peculiar conditions. In fact, the suggestion
seems to him to have been quite sufficiently guarded.
It was as follows: “The name ‘typhoid fly’ is here
proposed as a substitute for the name ‘house fly’ now
in general use. People have altogether too long con¬
sidered the house fly as a harmless creature, or at the
most simply a nuisance. While scientific researches
have shown that it is a most dangerous creature from
the standpoint of disease, and while popular opinion
is rapidly being educated to the same point, the re¬
tention of the name ‘house fly’ is considered inadvis-

INTRODUCTION

xvi 1

able as perpetuating in some degree the old ideas.
Strictly speaking, the term ‘typhoid fly’ is open to some
objection as conveying the erroneous idea that this fly
is solely responsible for the spread of typhoid, but,
considering that the creature is dangerous from every
point of view and that it is an important element in
the spread of typhoid, it seems advisable to give it a
name which is almost wholly justified and which con¬
veys in itself the idea of serious disease. Another
repulsive name that might be given to it is ‘manure
fly,’ but recent researches have shown that it is not
confined to manure as a breeding place, although per¬
haps the great majority of these flies are born in horse
manure. For the end in view, ‘typhoid fly’ is consid¬
ered the best name.”

As a matter of fact this name has been adopted very
generally. The newspapers took it up with avidity,
and during the summers of 1909 and especially of
1910, many good journals conducted a constant ed¬
itorial campaign, almost every issue during the sum¬
mer months containing some reading matter calling
attention to the danger of the creature and the ne¬
cessity of fighting it. It is undoubtedly true that peo¬
ple will fear and fight an insect bearing the name “ty¬
phoid fly” when they will ignore one called the “house
fly,” which they have always considered a harmless
insect. So to gain the practical end the retention of
the name “typhoid fly” seems by all means to be ad¬
visable. The only substitute suggested in the two
years since this term has been adopted which ap-

xviii THE HOUSE FLY— DISEASE CARRIER

proaches it for suggestiveness and availability is the
name “filth fly/' proposed by Dr. C. W. Stiles, of the
U. S. Public Health and Marine-Hospital Service.
But “filth fly,” while a nauseating name associated as
it must be with the dinner tables of unscreened houses,
carries simply the noisome idea and not the dangerous
idea, and the latter is one that will induce people to
fight.

It will not be an easy fight. The species is firmly
intrenched; it multiplies with startling rapidity, and
its breeding places are everywhere. Improved sanitary
methods in cities and the gradual disappearance in
cities of horse stables, due to the rapid increase in the
number of motor vehicles, are bringing about a de¬
cided lessening of the myriads of flies in the cities.
In small towns, however, and in the country and at
army posts, and especially in concentration camps, and
wherever large bodies of men are brought together
for temporary purposes in construction work, there is
great need of intimate practical knowledge of the ty¬
phoid fly and of the measures to be taken against it.
The residents of cities must also have this knowledge,
but they need it less than the others.

Acknowledgments of assistance from others will
be made in the text from time to time. The writer
wishes especially, however, to thank Prof. S. A. Forbes,
Dr. C. W. Stiles, and Dr. B. H. Ransom for allowing
him to use their very valuable but as yet unpublished
notes on several aspects of the fly question. He wishes
also to thank Mr. R. B. Watrous, Secretary of the

INTRODUCTION

xix

American Civic Association, for access to his large
correspondence on the fly crusade. He is also indebted
to Mr. Gilbert H. Grosvenor, editor of the National
Geographic Magazine, and to Mr. Robert Newstead,
for permission to use certain illustrations which will
be found properly accredited in the text.

The House Fly— Disease Carrier

ZOOLOGICAL POSITION, LIFE HISTORY, AND

HABITS

Zoological Position

OOLOGICALLY speaking, this insect belongs to

the order Diptera, or two-winged flies. In this
order it is the type of a superfamily known as the Mus-
coidea, of a family known as the Muscidse and of the
genus Musca, the specific name given to it originally
by Linnaeus being domestica; and among zoologists it
is referred to as Musca domestica L.

The superfamily Muscoidea, to which it belongs and
of which it is the type, is a very large group contain¬
ing a number of families and many species which so
closely resemble the house fly that to the untrained eye
they cannot be distinguished. Dr. David' Sharp, in
the Cambridge Natural History, writing of the house
fly, states that “it sometimes occurs in large numbers
away from the dwellings of man/’ and the writer is
often asked to explain why parties camping in the
Northwest, on the prairies for example, many miles
away from human habitations, almost immediately
find their camps infested with the house fly. The an¬
swer to such questions, and possibly the answer to the

2 THE HOUSE FLY— DISEASE CARRIER

statement made by Doctor Sharp, is that the flies found
under such conditions are not house flies, but some
species closely resembling Muscci domestica. In the
family Tachinidse, a group composed almost entirely
of species which lay their eggs upon other living in¬
sects, there are many species which almost precisely
resemble the gray-and-black-striped house fly. In the
family Dexidse, of similar habits, there are also many
which closely resemble the house fly. In the family
Sarcophagidse, which includes most of the so-called
flesh flies, the species of which either live in carrion
or excreta or in dead insects or in putrid matter, and
are occasionally parasitic, as with the species which
breed in the egg-masses of grasshoppers, there are also
many species hardly to be distinguished from Musca.
There is another great family, the Anthomyidse, which
has many species which closely resemble the house
fly and give rise to many mistakes in 'identity. These
insects in their early stages feed upon decaying vege¬
table matter and also to some extent upon growing
plants, and a few prey upon the eggs of grasshoppers.
Then, too, in the family Muscidae itself there are many
genera of similar habits and similar appearance. The
writer once, as a test, selected twenty distinct species
from among these insects and carefully pinned them
into a tray, asking chance visitors for several weeks
to pick out the true house flies from among them. No
one was ever able to distinguish between the different
forms bv looking at them with the naked eye.

The habits of the different genera of Muscidae are

ZOOLOGICAL POSITION

rather uniform, except that with a few of them the
adults bite and suck blood, while the majority, like
Musca domestica, do not. The tsetse flies of Africa,
belonging to the genus Glossina, bite, as also do the
stable flies of the genus Stomoxys and the cattle flies
of the genus Hsematobia (this genus includes the so-
called horn fly of cattle). Of the other genera, Graph-
omyia, Morellia, Mesembrina, Pyrellia, Pseudopyrel-
lia, and Phormia all breed in excrementitious matter.
The genus Myospila, formerly placed in the Muscidse
but really anthomyid, is also a breeder in this material.
The flies of the genus Muscina breed in decaying vege¬
tation and in cow dung, as also do those of the genus
Pollenia. Those of the genus Cynomyia and of the
genus Calliphora and of the genus Lucilia breed in
dead animal matter, while Chrysomyia macellaria —
the famous screw-worm fly — breeds in living flesh.

Some of these flies are occasionally found in houses, •
and further consideration of them will be found in
Chapter V. For practical purposes they are all equally
dangerous, as possible disease carriers, and to the prac¬
tical person there is no especial need to distinguish
among them ; but fortunately the house fly is the only
one that comes in abundance to houses. It is the only
one which really deserves the term domestic.

For the two following paragraphs, which indicate
the easiest method of distinguishing the house fly from
any of its allies, I am indebted to Mr. D. W. Coquil-
lett, an authority on the order Diptera :

“From nearly all the other kinds of flies that resem-

4 THE HOUSE FLY— DISEASE CARRIER

ble it, the house fly can be distinguished by having no
bristles on the sides of the thorax above the attach¬
ment of the last pair of legs and by having the vein
that ends near the tip of the wing distinctly elbowed,
a short distance before its apex. Several different
kinds of Tachinidse, Dexidse and Sarcophagidse have
a superficial resemblance to the house fly, and, like it,
have the elbowed vein, but all of them differ from the
house fly in possessing a row of bristles above the
point of attachment of the last pair of legs. The only
other family containing species that might be mis¬
taken for the house fly is the Anthomyidse, but none
of these has an elbowed vein.

“In the foregoing paragraph I stated that the house
fly can be distinguished from nearly all of the other
kinds of flies that resemble it by the two characters
mentioned. We have, in this country, a species agree¬
ing with it even in regard to the two characters given.
Indeed the resemblance is so close that only an ex¬
amination under a lens or microscope will reveal the
principal difference existing between these two spe¬
cies. I refer to Mnsca antumnalis DeGeer.* In the
male of this form the eyes are in contact on the upper
part of the head, whereas in the male of the house fly
the eyes are widely separated and the black stripe be¬
tween them is of nearly the same width throughout its
length. In the female of antumnalis the dark stripe
between the eyes is only as wide as the added breadth
of the narrowest part of the two gray stripes which

*The Musca corvina Fabricius, 1781.

ZOOLOGICAL POSITION

border it, while in the female of the house fly this
dark stripe almost touches the eyes. Autumnalis, like
its near relative, is almost cosmopolitan, but appears
to have been rarely met with in this country/’

Possibly a simpler way of putting it would be as
follows :

Mnsca domestica has four black lines on the back
of its thorax. All Sarcophagidse have three such black
lines. Most Tachinidse have four such black lines,
but the Tachinidze have the bristle of the antennae
smooth, whereas in Musca domestica this bristle is
feathered. From all Anthomyidae, Musca domestica
is at once separated by the bent vein near the tip of
the wing. Moreover, Musca domestica has no bristles
on the abdomen except at the tip which separates it
from all others except some Tachinids and many An-
thomyids, but from these it is separated by the char¬
acters given above.

Musca domestica is not alone in its genus. There
are fifteen species of the genus Musca according to
Bezzi and Stein in their Catalogue of the Palearctic
Diptera. In North America there are thirteen species
of Musca, according to Aldrich. Of none of these
other species of Musca do the habits appear to be
known. There is, however, an Indian species, Musca
cntccniata, which breeds in the same fecal masses with
the typhoid fly.

6 THE HOUSE FLY— DISEASE CARRIER

Life History

A long experience with the study of insects has in¬
dicated the somewhat remarkable fact that it is about
the commonest things in general that we know the
least. When Mr. C. L. Marlatt and the writer began
in 1895 to work on the subject of household insects,
we discovered that very few of the species found so
abundantly in households were included in the museum
collections. There would be a large series of a rare
beetle from Brazil, but no specimens of the common
house cockroach, for example; and when we began to
look into the literature of their life histories we learned
that published accounts of their transformations were
even more scarce than the specimens in the collections.
Doctor Hewitt (1910) calls attention to the vision of
Sir James Crichton Browne of the aged person show¬
ing the wondering child the only existing specimen of
the house fly, in the British Museum. This was in¬
tended as a prophecy, but it would not be surprising
if before the recent house fly crusade began there-
really was only one specimen of the house fly in the
British Museum.

With this condition of affairs existing in general,
it is perhaps not so surprising that an exhaustive study
of the conditions which produce house flies in numbers
has really never been made. The life history of the
insect was, down to 1873, mentioned in only a few old
European works and one more modern one (Taschen-

LIFE HISTORY

berg).* In 1873. Dr. A. S. Packard (1874), then of
Salem, Mass., studied the transformations of the in¬
sect and gave descriptions of all the stages, showing
that the growth of a generation from the egg to the
adult state occupies from ten to fourteen days. In
1895, the writer traced the fly’s life history, discover¬
ing that 120 eggs are laid by a single female at a time
and that in Washington in midsummer a generation is
produced in ten days.

Substances in Which This Fly Passes Its Early Life

It is safe to say that the typhoid fly will breed in
almost any fermenting organic matter, and it is also
probably safe to say that if given its preference it will
lay its eggs on a pile of horse manure. The writer
once estimated that under ordinary city and town con¬
ditions more than ninety per cent, of the flies present
in houses have come from horse stables or their vi¬
cinity, and he is still inclined to think that this esti¬
mate is probably correct. But the eggs will also be
laid upon the excreta of almost any animal. Cow
manure drying rapidly in a dry season and forming a
hardened caked surface is not a favorable nidus, yet this
fly is reared from cow manure at times. Many other
species of flies prefer cow manure, and a long list of

*The best of these old papers is little known. It was published
at Nurenberg in 1764, and is entitled “Geschichte der gemeinen
Stubenfliege, Herausgeben von J. C. Keller” and covers thirty-
four pages of text and four plates. The real author is said by
Hagen to be Freiherr Friedrich Wilhelm von Gleichen (genannt
Russworm).

8 THE HOUSE FLY— DISEASE CARRIER

species reared from this substance has been published
by the writer (1901).

The typhoid fly is, possibly next to horse manure,
attracted to human excreta, and not only visits it wher¬
ever possible for food, but lays its eggs upon it and
lives during its larval life within it. It will not only
do this in the latrines of army camps, in the open box
privies of rural districts and small villages, but also
upon chance droppings in the field or in the back alley-
ways of cities, as has been repeatedly shown experi¬
mentally in Washington.

It may very readily happen that the flies of any given
neighborhood have come from a single source, and
that the substances in which they breed differ accord¬
ing to locality and according to the supply of breed¬
ing substance. Under ordinary city conditions, un¬
doubtedly the most frequent nidus is in the horse
manure of stables, but when the conditions in a com¬
munity of a radically different nature are studied the
result is sometimes surprising. In the course of his
investigations of conditions in small towns with espe¬
cial reference to the hookworm disease, Stiles has found
that in cotton-mill towns, for example, the privies may
be a much more important breeding place of flies than
the manure piles, not only more important since flies
breeding in this substance are more likely to carry
disease germs, but also numerically more important;
for you may have 250 uncared-for privies and perhaps
only one or even no manure pile. And there are com¬
munities also where horses are scarce and pigs are

LIFE HISTORY

numerous. Stiles has seen great accumulations of pig
manure fairly swarming with fly larvae.

With regard to ordinary kitchen refuse, such as is
found in the garbage pail, it is the opinion of Prof.
J. S. Hine, of the Ohio State University, who has paid
much attention to the subject, that, while house flies
visit garbage in numbers, they appear in most cases
to be after food only, as only a few specimens of this
species were reared from such material during the sea¬
son when he was at work.

With fermenting vegetable refuse from the kitchen,
he found that the very common fly which bred in it
was not the typhoid fly, but Mnscina stabulans, the so-
called stable fly. Hundreds of these flies were reared
and their larvae were exceedingly abundant in all of
the samples of garbage examined. Musca domestica
was also reared, as was also another species known as
Phormia regina, but it seems from these observations,
although they were limited to a single locality in Cen¬
tral Ohio, that the recently acquired general opinion
to the effect that the typhoid fly breeds abundantly in
vegetable refuse when it has reached the proper fer¬
menting stage is due many times to the mistake of
considering the stable fly and its larvae as those of M.
domestica. And this is an important point, since the
stable fly is rather rarely found in houses and on food
and therefore is not an important carrier of disease.

The substances in which flies will breed were care¬
fully investigated in the city of Liverpool by Mr. Rob¬
ert Newstead, lecturer in economic entomology and

10 THE HOUSE FLY— DISEASE CARRIER

parasitology in the School of Tropical Medicine of the
University of Liverpool in 1907. Mr. Newstead is of
the opinion that the chief breeding places of the house
fly in Liverpool should be classified under the follow¬
ing heads: (1) Middensteads (places where dung is
stored) containing horse manure only; (2) Midden¬
steads containing spent hops; (3) Ash pits containing
fermenting materials. He found, as has been the ex¬
perience of observers in this country and India, that
the dung heaps of stables containing horse manure
only were the chief breeding places. Where horse and
cow manures were mixed the flies bred less numer¬
ously, and in barnyards where fowls were kept and al¬
lowed freedom comparatively few flies were found.
Only one midden containing warm spent hops was in¬
spected, and this was found to be as badly infested as
any of the stable middens. A great deal of time was
given to the inspection of ash pits, and it was found
that wherever fermentation had taken place and arti¬
ficial heat had been thus produced such places were
infested with house fly larvse and pupae, often to the
same extent as in stable manure. Such ash pits as
these almost invariably contained large quantities of
old bedding or straw and paper, paper mixed with hu¬
man excrement, or old rags, manure from rabbit
hutches, etc., or a mixture of all of these. About
twenty-five per cent, of the ash pits examined were
thus infested, and house flies were found breeding in
smaller numbers in ash pits in which no heat had been
engendered by fermentation. The typhoid fly was also

LIFE HISTORY

found breeding by Mr. Newstead in certain temporary
breeding places, such as collections of fermenting vege¬
table refuse, accumulations of manure at the wharves
and in bedding in poultry pens. Mr. F. V. Theobald
states that swarms of flies are reported to breed in the
huge masses of dust-bin refuse in certain London sub¬
urbs. It does not appear to be certain, however, that
these are Muse a domestic a.

In India, according to the observations of Surgeon
Major F. Smith, of the Royal Army Medical Corps,
horse manure is the most abundant breeding place for the
house fly around military stations. He also reared this
fly from cow dung in company with Musca entaniata.

DeGeer states that the larvae of this species live in
dung, but only in that which is warm and moist, or,
stated better, which is in a condition of perfect fermen¬
tation. The importance of the factor of fermentation
has already been referred to in the account of Mr.
Newstead’s observations and is insisted upon by Dr.
C. Gordon Hewitt in Part II of his important paper
on the Structure, Development and Bionomics of the
House Fly. He points out that Keller, writing of this
fly in 1790, reared the larvae of the typhoid fly in de¬
caying grain, where no doubt fermentation was taking
place; also in small portions of meat, slices of melon,
and in old broth. Doctor Hewitt also found that horse
manure is preferred to all other substances by the fe¬
male flies for egg-laying. He also found that the lar¬
vae will feed upon paper and textile fabrics, such as
woolen and cotton garments and sacking which were

12 THE HOUSE FLY— DISEASE CARRIER

foul with excremental products, if they were kept moist
and at a suitable temperature. He also reared adult
flies from decaying vegetables thrown away as kitchen
refuse, and on such fruits as bananas, apricots, cherries,
plums, and peaches, .which were mixed when in a rot¬
ting condition with earth to make a more solid mass.
He succeeded in rearing them in bread soaked in milk
and boiled egg and kept at a temperature of 25 0 C.,
but he was unable to rear them to maturity in cheese.

The preference which the typhoid fly has for horse
manure as a breeding nidus has been clearly shown
by a multitude of observations. One of the early ex¬
periences of the writer consisted in an effort to keep
the stables of the U. S. Department of Agriculture at
Washington in a strictly sanitary condition. The ma¬
nure was swept up and placed each day in a screened
closet. As a result there was a notable diminution of
flies in all of the buildings for hundreds of yards
around for several weeks; whereas up to the time when
the experiment began they had been a nuisance through¬
out that portion of the city. One of the many letters
received which bear upon this point may be quoted :

Washington, D. C, February 10, 1908.
“Dr. L. O. Howard,

Department of Agriculture,

Washington, D. C.

“Dear Dr. Howard :

“For the greater part of the last two years I have oc¬
cupied a room on the third floor of the Faculty Club on
the Campus of the University of California at Berkeley,
Calif. During most of the time the number of flies in

LIFE HISTORY

the Club House has been notably small, considering the
fact that the Club maintains a dining-room and its win¬
dows and doors are not screened. A year ago last fall
there was a sudden incursion of flies, so that they created
much annoyance in all parts of the Club House; and they
were specially abundant in my room. I protected my
windows by screens, and then captured the flies on sticky
fly paper, securing in that way more than 2,000. The
nuisance in other rooms continued several weeks longer,
and then gradually abated. There was no recurrence at
the corresponding season last fall.

“Recalling some statements of yours with reference to
the life history of the house fly, I noted that the epidemic
was coincident with the grading of the University ath¬
letic field, about 200 yards from the Faculty Club, and
that in that grading many horses were employed, probably
as many as fifty. So far as I am aware there are no
horses stabled on the University campus, and I do not
recall having seen any horse stables at a less distance than
two blocks, or, say, three times the distance of the athletic
field. These various relations of time and space serve to
connect the local fly epidemic in a fairly definite way with
the temporary proximity of a large number of horses.

“Yours very truly,

“G. K. Gilbert.”

In an article entitled “Experiments on Transmission
of Bacteria by Flies with Especial Relation to an Epi¬
demic of Bacillary Dysentery at the Worcester State
Hospital,” Dr. Samuel T. Orton (1910), after describ¬
ing a series of very interesting experiments indicating
the spread of a species of bacillus throughout the in¬
stitution by the agency of flies, describes a search made
to discover the breeding places of the unusual number
of flies infesting the hospital. Searching first for horse

14 THE HOUSE FLY— DISEASE CARRIER

manure, he found that there were only two such ac¬
cumulations on the hospital grounds. The one at the
stable was in a large masonry pit drained below and
covered so that while not fly-proof it was dark and dry.
No larvae or puparia were found in the pit. The ma¬
nure was molding and heating rapidly. Two other
piles where the manure was kept dry and in the dark
showed the same condition of rapid heating and mold¬
ing and no larvae were found. At the farm barn the
manure was dropped through four traps where a pile
accumulated, and was then taken to the part of the
barn where the cow manure is collected and the two
were mixed together. Here a considerable number
of larvae and puparia were found, but not in sufficiently
great numbers to account for the swarms around the
buildings. They were more abundant in the part of
the pile which consisted of pure horse manure and
grew noticeably less until the cow manure was reached,
when they were very few. Examination of the pig
pen showed piles of pig manure mixed with the straw
bedding exposed to air and rain. This was badly in¬
fested ; one ounce of material taken from a point a few
inches below the surface displayed 868 puparia. An¬
other prolific source was found in piles of spent hops
and barley malt — brewery waste which had been hauled
in as a fertilizer. The hops showed a tendency to mold
rapidly, and the flies did not breed in it as abundantly
as in the looser barley malt. In parts of the malt where
there was plenty of moisture the maggots were ex¬
tremely numerous; one ounce contained 1,018 mag-

LIFE HISTORY

gots. There had been considerable rain and the piles
were damp throughout. At one place there was a layer
of six or eight inches of soggy barley over the ground,
which was simply crawling with larvae. After six days
of continued dry weather, however, they had practically
all disappeared.

An interesting experiment was made. One pound
of material from each of the breeding places was taken
to the laboratory and kept in screen-covered glass jars
for ten days, with the following result:

Stable manure . o adult flies issued

Farm barn, horse end. .. . 77 “ “ “

Farm barn, mixed . 19 “ “ “

Farm barn, cow end . 1 “ fly “

Piggery manure pile . 361 “ flies “

Spent hops . 129 “ “ “

Barley malt . 539 “ “ “

These results as recorded are very interesting and
are probably in the main correct, although Doctor Or¬
ton states that the identification of species was by no
means thorough and the determination of the house
fly was made simply by observation of its size and gen¬
eral appearance and the characters of the mouth parts.
It is possible that the stable fly ( Muscina stabulans )
may have formed a portion at least of the flies bred
from the spent hops and the barley malt.

There is a statement in Taschenberg’s Praktische
Insektenkunde to the effect that the female house fly
lays its eggs not only upon spoiled and moist food¬
stuffs, decaying meat, meat broth, cut melons, dead
animals, manure pits, manure heaps, but even in cus-

16 THE HOUSE FLY— DISEASE CARRIER

pidors and open snuff-boxes. The entomological world
has accepted the statement, with, however, some doubt
as to the snuff-boxes. Prof. S. A. Forbes, however,
informs the writer that August 22, 1889, he received
from an old friend, T. A. E. Holcomb, then a druggist
at Kensington, Ill., a box of snuff containing dipterous
larvae. From these dipterous larvae Professor Forbes
bred the true house fly. His recollection of the matter
is very clear, and he has now in his collection a very
under-sized specimen labeled Masca domestica and
bearing an old pencil label in his handwriting, “Snuff,
August 26th.”

He afterwards called upon Mr. Holcomb in his drug
store and learned that among his constant customers
were some old foreigners who came so frequently to
have their snuff-boxes filled that for convenience in
serving them he was accustomed to keep an open box
of snuff upon one of his show-cases, and from this box
the specimens came.

A very important series of observations was carried
on under the direction of Professor Forbes in the sum¬
mers of 1908-1909 by his assistants, Mr. A. A. Girault,
at Urbana, and Mr. J. J. Davis, in Chicago, for the pur¬
pose of ascertaining exactly what other substances
aside from horse manure will serve as breeding places
for house flies. The results of these observations, not
previously published, have been placed at the writer’s
disposal by Professor Forbes. They constitute a very
valuable addition to our knowledge on this subject. It
was a surprise to find that nearly a thousand flies had

LIFE HISTORY

been reared from cow dung. This dung was in a stable,
and it is to be presumed that the conditions were such
that the dung did not dry readily and that there was
no preferred food in the immediate vicinity. Precon¬
ceived notions are also somewhat upset by the rearing
of 267 flies from carrion found in the street. The list
as a whole is of the greatest practical interest and is

as follows. Number house

Date Media dies bred

Sept. 1-3 .

.Rotten water-melon and muskmelon

Aug. 18 and

Sept. 8- 1 1 _

.Rotten carrots and cucumbers .

Sept. 7 . .

, Rotten cabbage stump .

Sept. 7 .

. Banana peelings .

Aug. 30 . .

.Rotten potato peelings .

Sept. 25 . .

. Cooked peas .

Oct. 1 . .

.Ashes mixed with vegetable wastes.

Sept. 7-14 .

. Rotten bread or cake .

Aug. 22 . .

.Kitchen slops and offal .

193

Sept. 10-26 .

. Mixed sawdust and rotting vege¬

tables .

Aug. 30-Sept. 4.

.Old garbage, city dump .

Aug. 14 and 18. ,

.Rotten meat, slaughter houses .

Aug. 30-Sept. 11

.Carrion in street .

267

Sept. 7 .

. Seepage from garbage pile .

Aug. 17-20 _

.Hogs’ hair, slaughter house waste..

Aug. 23-28 -

. Sawdust sweepings, Stock Yards

slaughter house .

Aug. 23 .

.Sawdust sweepings, meat market...

Aug. 16-28 _

.Animal refuse, Stock Yards .

Aug. 14 .

. Contents of paunches of slaugh-

tered cattle .

168

Sept. 2-1 1 .

.Rotten chicken feathers .

258

Aug. 16 .

. Chicken manure, stock-car dump. . . .

Aug. 31-Sept. 7.

.Cow-dung, stable, Urbana .

997

Sept. 7-10 .

. Cow-dung, outdoor yard .

Sept. 6 .

. Cow-dung, pasture .

Aug. 24- Sept. 16. Human excrement .

196

18 THE HOUSE FLY— DISEASE CARRIER

The Egg

The eggs are minute and glistening white, and they
are all long ovoid in shape. In length they vary from
one-sixth of an inch to a little longer. They are laid
in clusters of small size and irregular shape, either on
their ends or on their sides. Seen under a high power of
the microscope, the polished surface appears to be cov¬
ered with minute hexagonal markings such as is seen
in what the histologist calls pavement epithelium. Each
female fly lays on the average 120 eggs, or perhaps
more, at a time and may lay several times. Forbes’s
assistants in Illinois found that eggs from a single fly
vary from 120 to 150 in each deposit and that as many
as four deposits may be made, or say, 600 eggs by a
single fly (in lit.). One hundred and twenty was the
number observed by the writer to be the average num¬
ber, but Doctor Hewitt has counted as many as 150.

The duration of the egg stage, as observed in Wash¬
ington, was usually eight hours; that is to say, eight
hours after it was laid the egg hatched. These ob¬
servations were made in midsummer and have not been
repeated at other times of the year. Mr. Newstead in
Liverpool found that the eggs hatched in periods vary¬
ing from eight hours to three or four days, the average
time being about twelve hours. But he noted that when
laid in fermenting materials the incubation period was
reduced to a minimum of eight to twelve hours. In
a temperature of from 75 0 F. to 8o° F. they hatched
in from eight to twelve hours ; in a temperature of 6o°

Fig. i.— Eggs, approximately natural size; photographed on surface of
manure pile. (From Newstead.)

Fig. 2. — Eggs, approximately natural size. (From Newstead.)

LIFE HISTORY

F., in twelve hours, but at 45 ° F. they did not hatch
until the third day, and then only when placed in a
warmer temperature for the purpose of studying them
under the microscope.

Doctor Hewitt has carefully observed the hatching
of the eggs, and this is a process which has now be¬
come familiar to many Americans through the excel¬
lent moving-picture exhibitions given under the auspices
of the American Civic Association from films prepared
in England at the expense of Mr. Daniel Hatch, Jr.,

Chairman of the Fly-fighting Committee of the Asso¬
ciation. Doctor Hewitt’s description follows :

“A minute split appeared at the anterior end of the
dorsal side to the outside of one of the ribs [refer¬
ring to two distinct curved rib-like thickenings along
the dorsal side of the egg] ; this split was continued
posteriorly and the larva crawled out, the walls of the
chorion [the eggshell] collapsing after its emergence.

The Larva

We have just described how the egg hatches. The
young larva as it issues from the egg is a slender

20 THE HOUSE FLY— DISEASE CARRIER

creature tapering from the blunt, round, hinder end
to the pointed head end. It is glistening white in
color and only about two mm. in length. It is ex¬
tremely active and burrows at once into the substance
upon which the egg from which it hatched had been
laid, rapidly disappearing from sight. In the course
of its growth it casts its skin twice, and therefore
passes through three distinct stages of growth. In the
first one the anal spiracles, or breathing holes, on the
last segment, are contained in a heart-shaped aperture.
After the first molt these spiracles issue in two slits, and
after the second molt there are three winding slits.

In the third and last stage the larva is still white,
sometimes appearing yellowish. It is slender and taper¬
ing in front, large and truncate behind. The head has
a tiny papilla on each side. There is one great hook
above the mouth orifice. On each side of the pro¬
thorax there are spiracles which show six or seven
lobes. On the ventral base of the sixth and following
segments there is a transverse fusiform, swollen area
provided with minute teeth. The anal area is only
slightly prominent, and shows two processes close to¬
gether. The anal spiracles are prominent, less than
their diameter apart, and each with three sinuous slits
and a button at the base. In some cases two of the
winding slits are apparently connected together. With¬
in the head, or rather the anterior part of the body,
is a chitinous framework consisting of several articu¬
lated parts called the cephalopharyngeal skeleton, which
is indicated in figure 7.

Fig- 3- — Eggs, greatly enlarged. (From Newstead.)

Fig. 4. — Eggs, greatly enlarged — another view. (From Newstead.)

LIFE HISTORY

The rate of growth of the house fly larva varies ac¬
cording to temperature in much the same way as does
the period of duration of the egg stage. In the writ¬
er’s original observations in midsummer in Washing¬
ton he found that the time from the hatching to the
first molt was twenty-four hours ; from the first molt to
the second molt twenty-four hours; from the second
molt to transformation to pupa seventy-two hours ; mak¬
ing the duration of larval life five days. The larvae are
very active and migrate from place to place in a ma¬
nure pile with facility. Mr. Newstead in Liverpool ob¬
served that they mature in the shortest period in fer¬
menting materials in a temperature of between 90°
and 98° F., but that they usually leave the hotter por¬
tions of the stable manure when it reaches a temper¬
ature of from ioo° to no° F. At 540 F. the larval
stage was considerably prolonged, and larvae kept at
that temperature had not matured at the end of eight
weeks.

Doctor Hewitt at Manchester, England, showed that
larvae of the first stage might molt as early as twenty
hours after hatching, but that from twenty-four to
thirty-six hours usually elapsed before the first molt.
Under favorable conditions of temperature larvae in
this stage remained three days without molting. In
molting he noted that the skin was shed from the head
and posteriorly, and that not only the skin was shed,
but also the cephalopharyngeal sclerites, as well as the
chitinous lining of the fore portion of the alimentary
tract. He observed that the second stage of the larvae

22 THE HOUSE FLY— DISEASE CARRIER

might last only twenty-four hours, but at a lower tem¬
perature or with a deficiency of moisture the period
was prolonged and might take several days. The third
stage occupied as a rule between three and four days.

At all times the larvae are very active. When their
breeding place is disturbed they wriggle actively about
in the endeavor to conceal themselves, and so rapidly
do they accomplish this purpose that it is difficult to
take a satisfactory moving picture of them, or indeed
a photograph of any kind. When full-grown and
ready to transform, the yellowish color becomes more
pronounced, owing to the proliferation of fat cells in
great numbers in anticipation of the resting, non-feed¬
ing pupal condition. The transformation to pupa may
take place almost anywhere, but as a rule there is an
effort on the part of the larvae to descend deeper into
the manure pile or other substance in which they may
be living, and sometimes, when the substance upon
which they have fed is moist and the earth below it is
also moist and easy of entrance, they may descend two
or three inches below the surface of the ground.

The only good word that can be' said for this fly is
the fact that its larvae destroy enormous quantities of
excrementitious and waste material, greatly assisting
the bacteria of putrefaction. E. Guyenot (1907)
shows, first, that the liquefaction of albuminoid sub¬
stances is the result of a true process of digestion un¬
der the influence of certain germs of putrefaction;
second, that fly larvae, absorbing exclusively liquid
substances, easily assimilable, have the digestive tract

Fig. 6. — Egg hatching; greatly enlarged. (Original.)

Fig. 7. — Full grown larva of house fly ; greatly enlarged : a, anal spiracle ;
b, side view of larva ; c, cephalo-pharyngeal skeleton ; d, same ;
e, anal spiracle still more enlarged. (Original.)

LIFE HISTORY

reduced to the minimum and do not produce soluble
ferments in appreciable quantity ; third, that the larvae
accelerate putrefaction of bodies by assisting in the
increase of microbes; fourth, that the larvae nourish
themselves at the expense of the products of germ
chemistry — the germs can develop rapidly and spread
in all directions only by the assistance of the larvae;
there exists between these two agents of putrefaction
a true symbiosis. These conclusions, although reached
by a study of two species of the genus Lucilia, are un¬
doubtedly applicable to the larvae of other flies feeding
in animal material.

The Pupa and Puparium

Before beginning its transformation to the pupa,
the full-grown larva empties its alimentary canal, con¬
tracts from its own skin, the skin itself forming a
nearly cylindrical pupal case, the posterior portion be¬
ing slightly larger in diameter than the anterior and
both ends being equally rounded. It is then about six
mm. in length and of the shape shown at figure n.
At first this pupal skin remains pale yellowish, but
rapidly changes to red and finally to a dark chestnut
color. The insect inside loses its tracheal system, which
is withdrawn by the surrounding skin and eventually
remains inside of the skin or pupa shell but outside of
the insect itself. The insect rapidly assumes a true pupal
shape, and at the end of thirty hours, according to
Doctor Hewitt, most of the parts of the future fly can
be distinguished, although they are sheathed in a pro-

24 THE HOUSE FLY— DISEASE CARRIER

tecting nymphal membrane. A fully formed pupa
taken from the pupal sheath, or puparium as it is called,
is shown in figure n.

In this stage in Washington in midsummer the
writer has shown the normal duration to be about five
days. Mr. Newstead gives the period as from five to

Fig. n. — House fly puparium (at left) and pupa (at right) ;
greatly enlarged. (Original.)

seven days in cases where there is heat produced by
fermentation, but where there is no such heat the stage
may last from fourteen to twenty-eight days, or even
considerably longer. Doctor Hewitt states that with
a constant temperature the adult flies may emerge be¬
tween the third and fourth day after pupation, but that
the period is more usually four or five days, since the
larvae when ready to pupate as a rule leave the hotter

Fig. 8.— Larvae in horse manure. (From Newstead.)

Fig. 9. — Larvae and puparia. (From Newstead.)

LIFE HISTORY

portions of the substance in which they have been feed¬
ing and transform in the cooler portions. He sug¬
gests the idea that this migration outward may be a
provision for the more easy emergence of the fly when
the time should come. In some cases he found that the
pupal stage lasted through several weeks, but he was
never successful in keeping pupie through the winter.
Mr. Newstead found that in stable middens the puparia
occur chiefly at the sides or at the top of the wall or
framework of the receptacle where the temperature is
lowest. He found them in such situations often packed
together in large masses numbering many hundreds.
In ash pits he found the same conditions.

Where the manure is in small piles, or is partly spread
out, the full-grown larvae almost ready for transforma¬
tion are apt to migrate into the loose ground under the
pile or from the edges of the pile outwards, to trans¬
form under nearby rubbish. This habit may have a
very important practical value, since municipal regu¬
lations of individual stable practice in regard to the
removal of manure should take into consideration that
such removal at intervals longer than those required
for the larva to reach full growth may result in the
leaving of many puparia, except of course in cases
where especial receptacles for manure are in use.

Emergence of the Adult

This has been well described by Doctor Hewitt as
follows :

“When about to emerge, the fly pushes off the an-

26 THE HOUSE FLY— DISEASE CARRIER

terior end of the pupal case in dorsal and ventral por¬
tions by means of the inflated frontal sac, which may
be seen extruded in front of the head above the bases
of the antennae. The splitting of the anterior end of
the pupal case is quite regular, a circular split is formed
in the sixth segment and two lateral splits are formed
in a line below the remains of the anterior spiracular
processes of the larva. The fly levers itself up out of
the barrel-like pupa [puparium] and leaves the nymphal
sheath. With the help of the frontal sac, which it al¬
ternately inflates and deflates, it makes its way to the
exterior of the heap and crawls about while its wings
unfold and attain their ultimate texture, the chitinous
exoskeleton hardening at the same time; when these
processes are complete the perfect insect sets out on its
career.”

The frontal sac just mentioned is the distended mem¬
branous portion of the front of the head. This is con¬
stantly distending as the fly walks rapidly about after
issuing. When it is contracted at this early time, it
forms a dull area, soft and fleshy-looking, and free
from hairs. The fly possesses the power of distending
it into a bladder-like expansion, trapezoidal in outline
and almost as big as the rest of the head, pushing the
antennae down out of sight. This membrane is evi¬
dently distended with air, and, as pointed out by Pack¬
ard, its connection with the tracheae and the mechanism
of its movements would form a very interesting sub¬
ject of inquiry. Lowne, in his Anatomy of the Blow¬
fly, has described a similar structure with that insect,

Fig. io. — Puparia on a bit of old rotting cloth from an ash barrel.
(From Newstead.)

LIFE HISTORY

and he is obviously correct in supposing it to be a pro¬
vision for the pushing away of the end of the puparium
when the pupa emerges from its case. This frontal
sac has been noticed by many observers, and was well
described as long ago as 1764 by Count von Gleichen.

Structure of the Adult

In the section on zoological position, a description
has been given of the characters which separate the
adult typhoid fly or house fly from other allied or sim¬
ilar flies. The excellent illustrations given here (fig¬
ures 12 and 13) show in more or less detail its exact
structure. Especial attention should be called, how¬
ever, to the character of the mouth parts and of the
feet. The whole insect is more or less bristly and well
capable of carrying micro-organisms from putrescent
or semi-liquid substances, but the mouth parts and the
feet are especially adapted to this purpose. In addition
to two claws, each of the six feet is supplied with two
sticky pads of a light color. These are called pulvilli.
On the walking surface these pads are closely covered
with hairs which secrete a sticky fluid, and it is by
their help that flies are able to walk in any position
upon highly polished surfaces.

The mouth parts are very complicated, but form in
the main a proboscis which is not fitted for piercing
but for sucking and is illustrated so well in figure 15
that detailed description will be unnecessary. This
organ can be retracted and expanded to a certain extent.
It is somewhat complicated in structure and consists

28 THE HOUSE FLY— DISEASE CARRIER

of an upper and a lower portion, the upper portion
bearing two curved bristly lobes. The lower portion
or true haustellum expands at the tip into two lobes
which are called the oral lobes. On their under sur¬
face they have transverse chitinous bars which are
called false tracheae (pseudotracheae). The presence
of these hard ridges under the oral lobes fit it to a
certain extent for rasping solid food. The orifice to
the haustellum occurs between the lobes.

In feeding upon fluid or semi-fluid substances, the
oral lobes are simply applied to the surface and the
fluid is sucked up. When, however, they feed upon
soluble solids the process is somewhat different. Doc¬
tor Graham-Smith has carefully watched them feeding
upon crystals of brown sugar, and has done this
through the Zeiss binocular microscope. He states that
the oral lobes of the proboscis are very widely opened
and closely applied to the sugar. Fluid (saliva) seems
to be first deposited on the sugar and then strong suck¬
ing movements are made. Doctor Graham-Smith
watched a fly sucking an apparently quite dry layer
of sputum. It put out large quantities of saliva from
its proboscis and seemed to suck the fluid in and out
until a fairly large area of the dry layer of sputum
was quite moist; then as much as possible was sucked
up and the fly moved away to another spot. The same
observer noticed that flies which had the opportunity
of feeding either on fluid or partly dried milk often
chose the drier portions, and states that under natural
conditions they can often be seen sucking the dried

Fig. 12. — Adult house fly from above; greatly enlarged. ( Photograph by
N. A. Cobb. Copyright by National Geographic
Society of Washington, D. C.)

Fig. 13. — Adult house fly from below; greatly enlarged. (Photograph by
N. A. Cobb. Copyright by National Geographic
Society of Washington, D. C.)

LIFE HISTORY

remains near the top of a milk jug. They constantly
apply ttieir mouth parts to the surface over which they
are walking, attempting to suck up some nutrition,
and under certain conditions the imprints of their oral
lobes can afterwards be made out under the lens.

In order to understand the digestive processes of a
fly and to comprehend fully just what a disease germ

Fig. 16.— A diagrammatic figure of the alimentary canal of the
house fly ; greatly enlarged. Pit., Pharynx ; Oes., Esophagus ;

P. Ven., Proventriculus ; Veil., Stomach; F. Int., Fore
intestine; H. Int., Hind Intestine; Cr., Crop;

Rect., Rectum.

passes through after it is sucked up by one of these
creatures, it is necessary to know something of the
structure of the alimentary canal. This is simpler with
the house fly than with many other flies, more so in
fact than that of the blow fly, whose anatomy was so
carefully worked out by the famous English micro-
scopist, Lowne. It consists of a pharynx, a rather
narrow esophagus, a proventriculus or chyle stomach,
a crop, a ventriculus or true stomach, a fore and a hind

30 THE HOUSE FLY— DISEASE CARRIER

intestine. The proventriculus is a nodular structure
with muscular walls and probably acts also as a pump¬
ing stomach. The food, passing through the esophagus
into the proventriculus, immediately goes by an almost
continuous route into the crop. The tube leading into
the crop leads out from the proventriculus on the under
side backwards and ends in the crop itself, which is a
double organ situated in the lower part of the abdomen
of the fly. This crop is really a temporary storehouse
for the fly’s food, and in this storehouse it remains
practically unchanged, as has been proved by exact
experimentation. Returning from the crop, possibly
pumped back by the muscular walls of the proventricu¬
lus, it recedes again into the true stomach or ventricu-
lus, which is a somewhat expanded tubular organ run¬
ning fore and aft and situated above the tube leading
to the crop. The stomach proper extends back through
the thorax under the big muscles of the back and into
the abdomen, where it ends just over the point where
the crop begins to dilate. It runs into the rather nar¬
row fore intestine, which con volutes upon itself four
or five times, and ends in the hind intestine, which in
turn ends in the rectum. The intestine is called the
hind intestine from the point where the Malpighian or
urinary tubules enter.

Naturally the structure and function of the crop
and the proventriculus are matters of considerable in¬
terest in considering the distribution of disease germs
by flies. As Graham-Smith points out, the crop is first
distended with liquid food at the beginning of a meal,

Fig. 14. — Head of adult house fly; greatly enlarged. (Photograph by
N. A. Cobb. Copyright by National Geographic Society
of Washington, D. C.)

Fig- 15- — Head of adult house fly from side; greatly enlarged. (Photo¬
graph by N. A. Cobb. Copyright by National Geographic
Society of Washington, D. C.)

LIFE HISTORY

and, if after this the fly continues to feed, the food
may pass directly into the true stomach through the
chyle stomach. If the fly is disturbed before any of
the food has entered the stomach, the food which has
been sucked into the crop is gradually passed into the
stomach. Eventually the contents of the crop get into
the intestine. The proventriculus seems to act also as
a valve and be capable of closing the orifice into the
stomach so that the food shall all pass into the crop.
When the crop is fully distended it opens so that food
can pass directly into the stomach, and naturally also
opens later to allow the food to pass from the crop
forward and back.

Careful observations made by this author indicated
the rate at which. food passes from the crop into the
intestine, in which he showed that, using colored fluid,
after three minutes the crop was full of red fluid, but
none was found in the stomach or intestine. After ten
minutes the fluid was just beginning to pass into the
stomach. After fifteen minutes the crop was still full
and the upper third of the stomach was full. After
two hours in one case the crop was still full and the
upper three-fourths of the intestine was full. Other
observations indicated that the crop may remain full,
after a single feeding, for as long as four days, thus
acting as a storage reservoir against any possible scar¬
city of food.

Some interesting observations were also made by the
same author on the habits of flies after feeding on dif¬
ferent fluids. These observations were made in cages,

32 THE HOUSE FLY— DISEASE CARRIER

and he found that after gorging themselves they usually
climbed up the sides of the cage and moved from place
to place, often stopping to rub one leg against another
or to clean themselves by passing the legs over their
heads and wings. At intervals he noticed that they
sat still and regurgitated large drops of liquid from
the tips of their beaks. He showed that the drops
gradually enlarged until they were about equal in size
to the head of the fly. Sometimes the drop was de¬
posited, sometimes slowly withdrawn, and this occurred
several times. When disturbed, the drops were de¬
posited or withdrawn with great rapidity. Flies were
often seen to suck up the drops deposited by other flies.
It is these regurgitated drops which make the larger
stains upon a window covered with fly-specks.

Attention should be called to the shape of the com¬
pound eyes of the fly, and it will be noticed that they
are so situated that a fly can see in all directions at the
same time.

Difference in Size of Adults

There is a considerable difference in the size of the
adult winged flies, but this by no means signifies that
small adult flies grow into large ones. This is a wide¬
spread popular fallacy. The writer once in his younger
days attended a meeting of the Philosophical Society
of Washington to listen to a paper by the late C. V.
Riley on some phases of insect life, in the course of
which the house fly was incidentally mentioned. With
his entomological training, he was amazed in the dis-

LIFE HISTORY

cussion which followed to hear one of the most emi¬
nent of America’s scientific men (an astronomer, by
the way) ask Professor Riley, “It is true, of course, is
it not, that the little flies one occasionally sees on the
window-pane grow and become the large flies that are
so numerous?”

No fly, after it issues from the puparium, grows at
all ; no insects grow after the last molt ; in fact, insects
can grow only by casting their skins, and none of the
insects having what is called a perfect metamorphosis
casts the skin after reaching the imago or winged
stage.

But some typhoid flies are larger than others, and
the explanation is a different one from that of the
growth of the winged form. The same thing is seen
with other insects, and it results as a rule from the
amount of larval food; certain larvae stinted in their
supply of food transform to pupae when small and nat¬
urally become small adults. There is a distinct con¬
nection with them, as with human beings, in stint and
stunt, aside from the similarity of the words and their
origin.

With the house fly, however, some exact observa¬
tions have been made on this point by Griffith (1908)
and Packard (1874). Griffith found that when the
larvae were kept cool and the pupae warm all the flies
that came out were small. In fact, he found that it
was a rule that cold surroundings, even with plenty
of food, produced small flies. And he further states
that such small flies are incapable of reproduction. He

34 THE HOUSE FLY— DISEASE CARRIER

points out that small flies are found at the end of sum¬
mer when it has become cooler, and also in the early
spring, the latter having hatched late the previous au¬
tumn. The question of the hibernation of flies will be
considered in a later paragraph, but in this connection it
should be stated that Doctor Griffith secured repro¬
duction in the late autumn and winter, but that all of
the resulting flies were of small size, though their lar¬
vae were kept at a warm temperature. The flies from
only one of these batches were of normal size, while
those in one set were “extremely small, quite pigmies ;
and these died from no apparent cause, probably from
marasmus, after a month.” He further states that
from the same batch of eggs he has reared large, me¬
dium and small flies. Packard ( 1874) found that those
larvae which were reared in too dry manure were
nearly one-half smaller than those taken from the ma¬
nure heap. No direct warmth and the absence of mois¬
ture seemed to cause them to become dwarfed.

The error of deduction made by the famous astron¬
omer was by no means an error of observation, as ap¬
pears from what precedes, but there are found in houses
other flies of entirely different species from the house
fly, as will be shown in another chapter. Some of
these are considerably smaller, and one of them, the
little fly often seen on window-panes ( Homalomyia
canicularis) , is very much smaller. In fact, as though
to perpetuate the error, the Germans call this last spe¬
cies “die kleine Stubenfliege” — the little room fly or
house fly.

LIFE HISTORY

Summary of Duration of Life Round

In summarizing- the duration of the life round, we
find that the writer’s Washington observations made
the total life round approximately ten days, as indi¬
cated in an earlier paragraph. These were midsummer
observations made in August, 1895, on the Depart¬
ment of Agriculture grounds in the city of Washing¬
ton, but in a warmer climate they may be hastened
even beyond this minimum. Thus, in India Surgeon
Major F. Smith, of the Royal Army Medical Corps,
found at Benares that from a collection of one day’s
fresh droppings of three horses the adult Musca domes-
tica was obtained on the eighth day after the laying of
the eggs, thus shortening the period considerably.
Moreover, Doctor Hewitt’s minimum rate of growth
was : egg, eight hours ; first-stage larva, twenty hours ;
second-stage larva, twenty-four hours; third-stage
larva, three days; pupa, three days — a total of eight
days and four hours, surely a much shorter period
than often happens in England, although the occa¬
sionally high summer temperature combined with the
moist climate of that country may occasionally bring
about this shortening. Mr. Newstead’s observations
in Liverpool, on the other hand, show a minimum
period of from ten to fourteen days and a maximum
of from four to five weeks or longer.

Dr. A. Griffith, Medical Officer of Hove, England
(a seaport on the English Channel), experimented with
house flies during 1904-7. He gives as the minimum

36 THE HOUSE FLY— DISEASE CARRIER

time in any of his sets of rearings, which he tabulates
in Public Health, May, 1908, four and one-half to six
days from egg to pupa, and three and one-half days
from pupa to adult fly, a minimum for the life round
of eight days. He found great variations in this
period, according to the prevailing temperature.

Number of Generations

Taking the minimum duration of a generation in
Washington so far as observed (and this must not be
taken as the scientific minimum, since it depends upon
observations taken only during midsummer of a single
year), or we will say perhaps a midsummer average
under Washington conditions, and accepting Doctor
Hewitt’s observations as to the time elapsing between
the issuing of the adult flies and their sexual maturity
as being, perhaps under American conditions, ten days,
we see that there is time for the development of seven
generations between April 15th and September 10th.
Flies, it is true, continue to emerge from manure piles
and other breeding places much later than September
1 oth, and in fact during the season of 1910 active lar¬
vae were found as late as the 30th of November, while
on the occasional warm days of that period adult flies
were still active and laid eggs. The generations of
springtime and of autumn, however, are of much slower
development than those of midsummer, so that it is
probably safe to say that there are seldom more than
nine generations a year under outdoor conditions in
places comparable in climate to Washington.

LIFE HISTORY

Farther south, however, where the summer is longer,
and particularly where the climate is moist, there may
be more generations than this. In India, for example,
where Surgeon Major Smith made his observations
showing a minimum rate of eight days to a generation
and where the warm spell is very long, an extraordi¬
nary abundance of flies in the autumn, with proper
conditions of moisture, is a certainty. No wonder
that the punkah was invented in India ! In the same
way, as one goes north the number of generations per
year is naturally smaller and the autumnal abundance
of flies becomes greatly lessened in consequence.
Forbes’s assistants in Illinois found the life round in
midsummer to vary from nine to fourteen days.

Possibilities in the Way of Numbers

This number of generations has a direct bearing
upon the number of flies, not only at different periods
during the summer, but also in the early autumn, since
there is, barring accidents, a constant and definite and
enormous increase. Of course some summers are
warmer than others and some are moister than others,
and upon these two factors, taken in connection with
that of available places for breeding, the number of
flies must depend.

Take, for example, the possibilities in Washington,
and let us estimate — on the basis of the survival of all
eggs and all individual flies — upon plenty of places for
the insect to develop and for the larvie to feed, upon
an average of ten days to a generation in midsummer

38 THE HOUSE FLY— DISEASE CARRIER

(this period increasing in the autumn and being greater
also in the springtime), and also upon a period of ten
days after emerging of the adult flies before sexual
maturity is gained (this point of the duration of the
existence of the adult fly before the attainment of sex¬
ual maturity has been the weak element in other cal¬
culations that have been made of house fly abundance)
— let us start, then, on April 15th with a single over¬
wintering fly which on that day lays 120 eggs, and we
will have the following table:

April 15th, the over-wintering female fly lays 120 eggs.
May 1st, 120 adults issue, of which 60 are females.

May 10th, 60 females lay 120 eggs each.

May 28th, 7,200 adults issue, of which 3,600 are females.
June 8th, 3,600 females lay 120 eggs each.

June 20th, 432,000 adults issue, of which 216,000 are
females.

June 30th, 216,000 females lay 120 eggs each.

July 10th, 25,920,000 adults issue, of which 12,960,000
are females.

July 19th, 12,960,000 females lay 120 eggs each.

July 29th, 1,555,200,000 adults issue, of which 777,600,000
are females.

August 8th, 777,600,000 females lay 120 eggs each.
August 18th, 93,312,000,000 adults issue, of which 46,-
656,000,000 are females.

August 28th, 46,656,000,000 females lay 120 eggs each.
September 10th, 5,598,720,000,000 adults issue, of which
one-half are females.

Such figures as these stagger the imagination. They
are apt to make one feel hopeless at the thought of at¬
tempting to exterminate or to hold in check a creature

LIFE HISTORY

with such possibilities of multiplication ; but it must be
remembered that in the supposed instance upon which
we have figured, all of the eggs hatched and all of the
progeny have survived, whereas in nature a fly has
many chances of death, not only between the egg and
the adult, but as an adult before the period of sexual
maturity has been reached. And it is upon this period
which must elapse between the issuing of a fly and the
time when it shall lay eggs that one of the several ex¬
cellent plans for the warfare against this species has
been based. It must be remembered, on the other hand,
that in the table we have assumed that each female
has laid only 120 eggs, that is one batch, while in
reality she may lay four such batches. The task of
estimating the possibilities on the larger basis is left
to some reader who likes to multiply. Does not a con¬
templation of these possibilities, even with all the pos¬
sible accidents of nature to limit them, indicate in the
strongest possible way, even if the carriage of disease
by these pernicious creatures were not considered, the
necessity of an effort on the part of people to assist
nature in limiting a nuisance to humanity?

Number by Actual Count in Relation to
Quantity of Food

On August 9th in Washington a quarter of a pound
of rather well -infested horse manure was taken from a
manure pile, and in it were counted 160 larvae and 146
puparia. This would make about 1,200 house flies to
the pound of manure. This, however, cannot be taken

40 THE HOUSE FLY— DISEASE CARRIER

as an average, since no larvae are found in perhaps the
greater part of ordinary horse manure piles. Neither,
however, does it show the limit of what can be found,
since on the same date about 200 puparia were found
in less than one cubic inch of manure taken from a spot
two inches below the surface of the pile where the lar¬
vae had congregated in very great numbers. This, as
stated, was in August and the height of the fly season
had not yet been reached. Major N. Faichnie, of the
Royal Medical Corps, in the Journal of the Royal Med¬
ical Corps for November, 1909, gives the result of cer¬
tain experiments with flies, indicating that in India he
reared 4,000 flies from one-sixth of a cubic foot of
trench ground. He also states that he reared 500
flies from one dropping of human excreta.

Further counts have been made by Dr. W. B. Herms,
of the University of California ( 1910) . Doctor Herms
took four samples from different parts of an average
horse manure pile in Berkeley, Cal. (not near a livery
stable). The four samples weighed fifteen pounds in
all and contained by actual count 10,282 larvae, nearly
all of which were nearly or quite full grown. The
weight of the entire manure pile was estimated at
1,000 pounds, and, at the rate counted, estimating that
possibly one-third of the pile was uninfested, the pile
contained 455,000 and more larvae. Is it any wonder
that flies swarm near the average stable?

LIFE HISTORY

Hibernation

The typhoid fly apparently suddenly disappears with
the first sharp frost. It will reappear later on the
warmest days. With a great reduction of the tem¬
perature of their breeding places, many larvae are killed,
and eggs as well. Whether the pupae in their tight
puparia are destroyed by a certain degree of cold does
not seem to be known. The adult flies undoubtedly
linger in warmed houses throughout the winter, but
that enough of them remain in active condition in such
locations to perpetuate the species and to start the rap¬
idly multiplying generations of the following summer
seems doubtful. The adult flies undoubtedly remain
dormant even in warmed dwellings, and it is altogether
likely that some of them remain dormant throughout
the winter months in sheltered but cold situations.
Many adult insects pass the winter in this way, and
observations have been made which indicate that this
is the case with the house fly, although as a matter of
fact sufficient attention has not been paid in the obser¬
vations on record of the exact specific identity of the
flies in question. As has been pointed out before, there
are so many species of flies which so exactly resemble
the typhoid fly to the macroscopic eye that any one
may be pardoned for stating that house flies have been
seen tucked away carefully in cracks, when a micro¬
scopic examination would have shown that some other
species was concerned.

The best observations on this general subject which

42 THE HOUSE FLY— DISEASE CARRIER

have been published are those made by Mr. F. P. Jep-
son, research student in medical entomology, Cam¬
bridge University, England. According to Mr. Jepson
(1909), when the frosts come and the cold weather
begins in earnest, unprotected flies are probably killed.
Those which have found the shelter of some place like
a kitchen or a restaurant or a bake house, where the arti¬
ficial temperature is sufficient unto their needs, continue
to live actively ; and will even breed when conditions
are favorable. He states that some flies possibly exist
in dormant condition in such protected localities as be¬
hind pictures and loose wallpaper. He found sluggish
specimens behind books on a bookshelf in December
and January and observed them for some time, find¬
ing them in the same positions and still living a month
later. His observations ceased at the end of January,
but he saw no reason why they should not live on until
spring and then begin to breed. In the course of his
experiments he found that the flies occurring at the
close of the year are much more hardy than those oc¬
curring in summer. This fact was experimentally
proved, as will be shown later. He further states that
one of his friends found flies, presumably typhoid flies,
to issue in large numbers from the empty frame of an
old window which was removed during the winter.

Jepson experimented with the early stages, and,
knowing the idea that possibly the puparia hibernate,
he attempted to carry 200 pupae through the winter,
but without success.

The most interesting part of his experimental work,

LIFE HISTORY

however, was with 200 flies captured in February fly¬
ing about in the sculleries and kitchens of one of the
colleges at Cambridge. They were quite as active as
in the summer. The kitchens are underground, and
the fires are kept up continuously. The temperature
varied from 65° F. in the mornings to 8o° F. in the
evenings, and the flies, although somewhat sluggish
in the morning, became active when the fires were
poked up. The 200 flies under experimentation were
transferred to a greenhouse, which was kept in a sim¬
ilar temperature to the kitchens where they were cap¬
tured, and were kept in closed vessels with a supply
of moist bread beginning to ferment. It is worthy of
note, by the way, that he found that on several occa¬
sions the flies would not lay their eggs upon bread
which had not begun to ferment. After the flies had
been confined twenty-four hours they laid their eggs,
and on the following day all of the eggs hatched. As
the bread became moldy the larvae avoided it, and were
transferred to other enclosures and fed upon stale bread
slightly moistened. They fed until full grown, then
crawled away from the moisture and transformed to
pupae under pieces of newspaper. At a temperature
ranging between 65° F. and 75 0 F. in February, the
entire duration of the life round occupied three weeks.

It thus appears that under artificial heat conditions
the typhoid fly, given food for its larvae, will continue
to breed almost as rapidly as during the summer time.

Mr. Jepson’s observations on the length of life of
the adult flies in the winter time further support the

44 THE HOUSE FLY— DISEASE CARRIER

idea that the species constantly hibernates in this con¬
dition. Upon the emergence of the adults which he
reared in confinement in February, they were trans¬
ferred to a large net cage and were kept alive success¬
fully for eleven and one-half weeks. The original flies
caught in the kitchens in February were kept in cap¬
tivity for ten weeks. How long they had lived before
capture, of course, was unknown, but presumably since
the previous autumn. The question of the length of
life of the adult fly under all conditions will be con¬
sidered in a later paragraph.

Habits of the Adult Fly

On issuing from its pupal sheath, the first impulse
of the adult fly is to feed. After its rest in the pupal
condition, during which time it has taken no food and
has subsisted by the physiological consumption of the
fat cells stored up during the last larval period, it has
naturally become hungry, and it flies immediately to the
first point offering sustenance. The sense of smell of
the typhoid fly must be very keen, although its selec¬
tion of attractive odors undoubtedly differs from our
own. It is very catholic in its choice of food — the milk
jug and the freshly baked custard pie are apparently
equally in favor with the slop bucket, the garbage pan,
and all sorts of unmentionable filth. It knows the odor
of cooking, and it flies unerringly towards the nearest
kitchen, although here the temperature of the kitchen
stove may attract it almost as much as the possibility
of something good to eat. As has been shown in our

HABITS OF THE ADULT FLY

brief discussion of the mouth parts of the adult fly, its
food must be liquid, and when it alights upon a solid
a plentiful flow of a salivary liquid enables it to make
some slight impression and to gain sustenance. Thus it
drinks as well as eats, and liquids apparently contain¬
ing little that will help it to exist are sought by it, but
it especially prefers semi-liquid mixtures. Every one
who reads this book knows how in the old days, and
even now in some places, the typhoid fly swarmed or
swarms in a certain class of public restaurants and in
poorly cared-for eating places. The story of the man
who entered a dimly lighted railway restaurant and
asked for “a piece of that huckleberry pie” and was in¬
formed that it was not huckleberry but custard, is lit¬
erally true. Dr. Theobald Smith phrased it very hap¬
pily in a paper written a few years ago in the following
words : “When we go into a public restaurant in mid¬
summer, we are compelled to fight for our food with
the myriads of house flies which we find there alert,
persistent and invincible.” Doctor Smith has been very
fortunate in the choice of the word “persistent.” The
typhoid fly does not seem to have any common sense.
At one time he is alert, to use Doctor Smith’s word,
and it is impossible to catch him, but his persistence
even in the face of imminent danger is one of his char¬
acteristics which is most impressive. When one lies
drowsily in bed of a summer morning with but one fly
in the room, “persistence” is the only word to apply
to its annoying return again and again and again to
the face of the sleeper in spite of repeated slaps. Here

46 THE HOUSE FLY— DISEASE CARRIER

it is the perspiration which attracts the fly. It is
hungry and thirsty and wants food and drink.

The typhoid fly is a diurnal species. It rests during
the night. It is not especially fond of the bright sun¬
shine, and if one stays in direct sunlight he is not often
troubled by it. But it revels on the shaded porch and
in the lighted house away from the sun’s direct rays.
It flies into the dimly lighted stable in search of places
to lay its eggs, but in absolute darkness and even in
darkness which is not absolute it rests immovable. Its
resting position seems to be a matter of indifference
to it ; it can sleep equally well on the ceiling or on the
side wall. It does seem to have some preference for
anything hanging perpendicularly, such as an old-fash¬
ioned rod supporting a candelabrum or a central gas
fixture or a window-curtain string, and this observed
preference has been taken advantage of by the inventors
of certain fly traps which consist of a suspended strip
of sticky paper.

Reverting once more to the feeding of the adult fly,
a correspondent whose name the writer has unfortu¬
nately forgotten described an instance where he had
left a blood-stain on a slide at which a house fly sub¬
sequently sucked. On examining it afterwards under
the microscope, the fly, he found, had taken up all of
the red blood corpuscles and had left all of the white.

Flies are great feeders. Where food is abundant
they will suck at it almost continuously or at very brief
intervals. As indicated elsewhere, the alimentary canal
is comparatively simple, the digestive processes seem

HABITS OF THE ADULT FLY 47

of the simplest and the food passes through the body
with the greatest facility.

Do Flies Have a Color Preference?

Galli- Valerio (1910) states that the French agri¬
cultural journals have published a statement that Fe,
having observed that flies do not rest upon walls cov¬
ered with blue paper, blue-washed the walls of his milk
stables and that the flies then disappeared, and asks
the question whether a similar method could be used
to keep flies out of houses. He himself conducted ex¬
periments with a box having glass walls, 35 X 35 X 35
cm. in size, and pasted on the walls bits of paper all
the same size but of different colors, and afterwards
introduced a certain number of house flies. For sev¬
eral days, after turning the cage in different positions
so as to avoid error from other causes, he counted the
flies which were standing on the different colors. The
results were as follows :

Clear green . 18

Rose . 17

Clear yellow . 14

Azure . 13

Clear red . 10

Dark gray . 9

White . 9

Dark red . 8

Black . 7

Pale gray . 5

Dark yellow . 5

Dark green . 5

Red . 4

Orange . 3

Clear brown . 3

Pale rose . 3

Very clear green. ... 2

Blue . 1

Pale violet . 1

Dark brown . 1

Lemon yellow . 1

The observer noted that eighty-seven flies stood on
the clear light colors, and fifty-two on the dark. Blue

4-8 THE HOUSE FLY— DISEASE CARRIER

was surely one of the colors least visited, but on the
contrary azure was one of those most frequented. He
thinks that possibly after all it was only a chance, but
is of the opinion that Fe’s observation should be the
basis of an experiment on a large scale with the same
ultramarine blue which he employed. It seems doubt¬
ful, however, that a cold, hungry fly will be kept from
a warm, odoriferous kitchen by the bluest of blue col¬
ors.

Fly-specks

Since, on account possibly of the simplicity of the
digestive processes just referred to, pathogenic bacteria
and other micro-organisms pass unchanged through
the alimentary canal of the typhoid fly, the question of
fly-specks becomes one of great importance. Every
casual observer knows that they are laid with great
frequency, and that when flies are abundant their
specks are to be found everywhere. Curiously enough,
few exact observations have been made upon the fre¬
quency with which the fly deposits its excreta. Major
N. Faichnie, previously referred to, working in India,
found that when a fly is put in a clean paper box it passes
its excrement fifty times in twenty-four hours; that is
to say, about once every half hour ; but he neglects to
state whether there was food in the box. Presumably
there was some food, and also presumably there was
not much of a semi-liquid character. Cobb (1910)
gives a table of the intervals between defecation of a
well- fed fly, together with notes on the spores in the
excreta. One naturally infers, from the title of the

HABITS OF THE ADULT FLY

article, that the fly in question was a house fly, but
upon consulting an important paper by the same author
(1906), entitled “Fungous Maladies of the Sugar
Cane,” the same table is found printed on page 64
and the fly in question is said to be a Sarcophagid,
and therefore not Musca domestica. In his opening
paragraph in the 1910 article, Doctor Cobb explains,
“In some of these paragraphs, however, the statements
are inferences fully justified by experiments with very
similar species,” and this table is evidently one of these
inferential statements. It is not safe to state that be¬
cause, as shown in the table, a well-fed Sarcophagid
fly will defecate on the average once every four and
one-half minutes, from half past nine until half past
eleven, a true Musca will do the same. It is by no
means impossible that it will do so, but unfortunately
we have not the proof. Still with this explanation it
will be interesting to state that in the interval between
9:35 and 11:26 the fly observed by Doctor Cobb (it
had been fed at 9: 23) made twenty-three fly-specks at
intervals varying from one to fifteen minutes, an av¬
erage of about four and one-half minutes ; and in ten
of these twenty-three specks Doctor Cobb found spores.
Herein lies one very great danger from flies. Certain
authors believe that the danger from disease germs
that pass through the fly’s body in this way is greater
than from those that are supposed to be carried from
foul substances on its feet.

With the abundance of flies in the late summer, the
number of fly-specks becomes almost unlimited. Doc-

50 THE HOUSE FLY— DISEASE CARRIER

tor Cobb states that he possesses actual counts made
by the use of a little counter of his own invention, but
that he does not publish these records for fear that he
will be accused of sensationalism. He says that win¬
dow-panes with from 1,000 to 10,000 fly-specks per
square foot are not at all uncommon, and that from
ten to fifty per square foot is a common number in what
are considered well-kept homes. And this is only in
places where the dirt can be readily seen. He states
that on neutral-tinted objects which are not cleaned so
frequently fly-specks occur in millions. “On wallpaper,
chandeliers, outside veranda posts, on cornices, ceil¬
ings, and window blinds, the numbers are almost past
computation/’ He further shows that examination of
the excreta of flies captured in the open shows that
they contain a great variety of spores in living con¬
dition. He finds that the digestion of the fly consists
simply in the absorption of those substances readily
soluble in its weak digestive fluids and the evacuation
of all others; therefore the fly is an enormous feeder.
Doctor Cobb states that in a single meal it frequently
swallows nearly half of its own weight of food. This
accounts for the frequency of the fly-specks, and, con¬
sidering the number of flies, for the enormous num¬
ber of specks.

Doctor Graham-Smith, elsewhere quoted, made a
few studies of the number of deposits left by flies. He
found that the rate at which the deposits are produced
depends upon temperature and the form of food, flies
being most lively in hot weather or when placed in a

HABITS OF THE ADULT FLY

warm incubator. He fed three lots of flies on syrup,
milk, and sputum, respectively, for several days, and
noted that those fed on syrup produced an average of
four and seven-tenths deposits per fly per day, those
on milk eight and three-tenths and those fed on sputum
twenty-seven. In the latter case he states that the feces
were much more abundant and liquid than usual, and
that in fact the flies seemed to suffer from diarrhea.
In another series of experiments ten flies were given
a single feed of milk and then transferred to fresh
cages. They deposited either by regurgitation or as
excrement forty-one spots in the first hour, sixteen in
the second and third, twenty-four in the fourth, twenty-
four in the fifth, and fifty-nine in the prolonged inter¬
val between the sixth and twenty-second hour. With
another series of eleven flies, milk was always present
in the cage so that the flies could feed as often as they
wished, and here thirty-two spots were made in the
first hour, forty in the second and third, ten in the
fourth, eighteen in the fifth, and 134 in the sixth to
the twenty-second hour; making a total of 164 spots
from the ten flies that had had but one feeding and
224 from the eleven flies which had the milk contin¬
uously in their cage.

Distance of Flight

Prof. S. P. Langley, the late Secretary of the Smith¬
sonian Institution, was, as every one knows, greatly
interested in the problem of aeronautics, and his ex¬
periments with flying machines heavier than air prac-

52 THE HOUSE FLY— DISEASE CARRIER

tically made him the first successful investigator in this
direction, since the Wright brothers acknowledge that
they owe very much to Langley’s scientific papers on
this subject. From his interest in this direction, Pro¬
fessor Langley devoted certain grants from the so-
called Hodgkins fund* to the study of the mechanism
of flight of various birds and insects. Some of the
results of these studies have already been published in
the Smithsonian Miscellaneous Collections. During the
past ten years a series of these investigations have been
carried on under Prof. Robert von Lendenfeld of the
University of Prague, and from a report received from
Professor von Lendenfeld by the present Secretary of
the Smithsonian Institution, Doctor Walcott, which the
writer has been permitted to see. it appears that, after
a study of the organs of flight in the Lepidoptera,
Hymenoptera, and Diptera by Messrs. Hauptmann,
Groschl, Ritter, and Professor von Lendenfeld, the
latter became convinced that of all the forms of insects,
and indeed of all flying animals, the Diptera would
furnish the best models for flying machines. He thinks
that a model built according to this pattern should be
made and experimented with. Certain studies by Mr.
Ritter on the blow fly, which are at the time of this
writing in the hands of the Smithsonian Institution
for publication, indicate that this insect and its flight
would form the best basis for a model.

This is an interesting and important statement, since

*A bequest to the Smithsonian Institution for the investigation
of the properties of the upper air.

HABITS OF THE ADULT FLY

it has been made after a long series of comparative
studies, and its truth will readily be admitted by any
one who has paid much attention to the flight of Dip-
tera. Cobb, in his paper on the Fungous Maladies of
the Sugar Cane, records a number of observations on
the flight of flies in connection with the distribution by
the flies of the spores of a fungous disease of sugar
cane. He states that he never succeeded in tiring his
flies very perceptibly if they had a free space to move
around in. When confined in a room they were kept
on the wing for hours without showing much fatigue.
By dissection he showed that with certain of the Sar-
cophagid flies the thoracic or wing muscles constituted
twenty-six and two-tenths per cent, of the weight of the
fly, and that the mass of the great thoracic muscles is
proportional to the apparent power of flight among dif¬
ferent flies. He records also a remarkable example of
the power of flight of one of the larger flies. On a
voyage across the Mediterranean from Algiers to Mar¬
seilles, he observed a Dipterous insect keeping pace with
the steamer “so accurately that it almost seemed as
if it were joined to the boat by some invisible rigid
connection. The boat left Algiers at noon and as long
as there was any light left by which to observe, the
insect kept its place steadily. This was in midsummer.
The insect never made any attempt to come aboard.
The boat was not particularly fast, her speed being
about thirteen knots.”

Every one who has driven a fast team of horses over
a road through pine timber must have noticed the ex-

54 THE HOUSE FLY— DISEASE CARRIER

traordinary flight of the gadflies of the family Taban-
idse, which for hours will circle about the horses, fly¬
ing with ease much more rapidly than the speed of the
vehicle, alighting only occasionally. It is not intended
to convey by these instances the impression that it is
known that the house fly is at all extraordinary as a
flier among the Diptera — in fact, when the truth is
fully known it may be shown to be comparatively a
weak flier among its relatives; but it darts here and
there through the air with great speed, and if it were
obliged to fly great distances the writer has little doubt
of its ability to do so.

The practical question involved in the distance of
flight, however, is the one of protection of food sup¬
plies at a distance from fly breeding places which can¬
not be controlled. Will the proper care of the stables
and houses in a given city square relieve the houses in
this square from the fly pest to a measurable degree,
provided stables and houses one square or two squares
away remain uncared for? The situation must be
much as it is with mosquitoes, although the house fly
is a much stronger flier than any mosquito. The house
fly will seldom travel very much farther than it has to
fly for food and a proper nidus for its eggs, but as a
matter of fact it is very difficult to prove this. Fur¬
ther experimental work should be carried on in this di¬
rection.

J. S. Hine {in lit.) states that in the summer of 1910
he made an effort to determine the distance that flies
travel. At a barn where he was carrying on some work

HABITS OF THE ADULT FLY

he captured some 350 flies and marked each one’s wing
or thorax with a small spot of gold enamel. Flies so
marked were repeatedly observed about dwellings from
twenty to forty rods from the barn up to the third day,
but in a dwelling house a half mile away none of the
marked specimens was detected. This, however, was a
very unsatisfactory experiment, because it does not in
the least show that if the dwellings twenty to forty
rods from the barn had not existed flies would not have
been found in the dwelling half a mile away. As Hine
himself states, “It appears most likely that the dis¬
tance flies may travel to reach dwellings is controlled
by circumstances. Almost any reasonable distance may
be covered by a fly under compulsion to reach food or
shelter. Where these are close at hand the insect is
not compelled to go far, and consequently does not
do so.”

Hewitt is of the opinion that normally house flies
do not fly great distances, and compares them to do¬
mestic pigeons which hover about a house in the im¬
mediate neighborhood. He states that they are able
to fly, however, for a considerable distance and can be
carried by the wind. At one time when he was vis¬
iting the Channel Islands he found the house fly from
one and one-half to two miles from any house or any
likely breeding place that he was able to find. He
mentions some exact experifnents made by Dr. M. B.
Arnold at the Monsall Fever Hospital, Manchester,
where 300 flies were captured alive and marked with a
spot of white enamel on the back of the thorax. They

56 THE HOUSE FLY— DISEASE CARRIER

were liberated in fine weather, and out of the 300 five
were recovered in fly traps at distances of from thirty
to 190 yards from the place of liberation, and all within
five days. He further states that he had found them
at an altitude of eighty feet above the ground, -and
calls attention to the fact that such a height would fa¬
cilitate their carriage by the wind.

An experiment made under the direction of Prof.
S. A. Forbes, of which he has sent me a written ac¬
count, indicates that house flies may spread naturally
for at least a quarter of a mile, going, in one significant
instance, from the tuberculosis hospital to the general
hospital of Cook County, Illinois. House flies trapped
at one point were sprayed with a chemical solution and
liberated. Then flies caught on fly paper elsewhere
were sprayed with another solution, the result being
that those which had previously been sprayed were
turned dark blue in color by the second solution.

Marking Flies for Experiment

Professor Hine found that it was a very difficult
matter to mark flies so that they might be recognized
from others, since they are very sensitive to anything
unusual, and any foreign substance on their bodies or
wings causes them to act abnormally. They contin¬
ually try to remove the foreign substance and seem to
tire themselves out. He found that many specimens
marked with the greatest care would hardly fly after
they were marked, so that it was easy in many cases to
approach them and pick them up with the fingers. He

HABITS OF THE ADULT FLY

is of the opinion, therefore, that marked flies are likely
to be abnormal and are not fit for purposes of exact
experimentation. He found that it was impossible to
clip off the wing extremity and not inconvenience the
flight.

On this subject of marking, Mr. J. P. Jepson, of
Cambridge, England, conducted some interesting ex¬
periments during July and August, 1908, under the di¬
rection of Professor Nuttall. He first tried ordinary
household flour, but the flies soon rid themselves of it.
This substance was used on account of the observation
that flies seen in mills often seem quite white in color.
Rice starch powder was next tried, with no success.
They were finally marked with ordinary colored black¬
board chalks which were finely ground up in a mortar
and dusted on the flies until they were completely cov¬
ered. They tried to clean themselves, beginning with
the eyes, but never succeeded in removing the chalk
from the upper portion of the thorax or from the base
of the wings. Further experiments were tried with
aniline dyes either made in the form of a powder with
rice starch or mixed with alcohol in the form of a
spray. Then again shellac was mixed with the alcohol
in order to make the color sticky. In his summary
he found that the use of various aniline dyes did not
prove satisfactory; with fuchsine the mortality was
very large. He found that dusting with rice starch
powder and then spraying with shellac and alcohol give
an excellent color, but decided that the flies must be
allowed to clean their eyes before spraying and that

58 THE HOUSE FLY— DISEASE CARRIER

the spray must be thinly applied. The best result
reached by this method was ten days. The reverse,
namely, spraying with alcohol and shellac and then
dusting with rice powder, was satisfactory where the
shellac was not applied too thickly. Colored chalks
gave very satisfactory results, yellow and brick red
being the best ; the yellow lasting for nine days and the
brick red for twenty days.

Length of Life of the Adult

It seems that in midsummer the adult flies do not
live long, and it is extremely difficult to keep them
for any length of time in an enclosure, which, of course,
is the only true way of ascertaining exact age. At this
time of the year, flies die rapidly in confinement. In
June, 1898, the writer was unable to keep alive flies
collected at large and placed under a gauze enclosure
three feet cube for more than three days, but of course
this experiment meant nothing, since the age of the
flies collected was not known. Mr. Hine is convinced
that flies do not live a great many days in warm sum¬
mer weather. Marked flies in his experiments in Au¬
gust were not to be found after the third day, and in
his experiments with individuals, in confinement with
all necessary food, he was unable to keep them alive for
more than twelve days. He mentions an instance where
on a farm at Ira, Ohio, a pile of infested manure at
the barn was hauled up and spread in a field a quarter
of a mile away on August 15th; the occupants of the
house stated that there was a notable reduction in the

HABITS OF THE ADULT FLY

number of flies by August 20th. Major N. Faichnie,
referred to above, in experimenting with flies in India
in the summer, found that they lived eleven days only.
Mr. Jepson, in his notes on the breeding of the com¬
mon house fly during the winter months, incidentally
mentions the fact that during the summer of the pre¬
vious year (1908) in no case was he able to keep flies
alive for more than three weeks, and then only with a
few individuals; whereas, as previously stated, flies
reared during the winter were kept alive for eleven and
one-half weeks, and flies caught in kitchens in Febru¬
ary were kept alive for ten weeks and had presumably
been living since the previous autumn.

If we take Jepson’s statement of three weeks as be¬
ing the probable limit of the life of the adult fly in
midsummer, and if we conclude, as we must, that the
average life at that period is much shorter than this,
it becomes evident from what will be stated in the fol¬
lowing paragraph that after the female fly has laid her
eggs in summer she has not much longer to live. The
plain inference from this will naturally be that the hi¬
bernating flies in the winter time are probably for the
most part females which have not laid their eggs. Un¬
fortunately for the conclusions just stated. Doctor
Hewitt records the fact that he has kept flies in cap¬
tivity in the summer time for seven weeks, while Grif¬
fith (1908) was able to keep a male sixteen weeks.

Ficker (1903), in an account of experiments carried
on between June and October, states that he kept flies
alive in confinement for four weeks, feeding them on

60 THE HOUSE FLY— DISEASE CARRIER

sugar, bread, water, or milk. Unfortunately he does
not give the exact dates of this particular observation,
and it may have been on an October generation, which
would have hibernated.

Time Elapsing Betzveen the Issuing of the Adult and
the Period of Sexual Maturity

The practical value of the determination of this
period is very great. If an adult female fly can be
destroyed before she lays her eggs, we will have killed
not only the actual fly, but 120 to 600 potential flies
due in a very short time, and if this female fly can be
caught in the early spring the table on an earlier page
will indicate that instead of performing a very simple
act we have apparently saved the world from almost
a calamity. From this can be seen the value of fly
traps. Of course the destruction of breeding places
is very important, but traps for adult flies are by no
means to be despised when we have this idea in view ;
and the use of fly traps in the early part of the season
becomes obviously all-important. The destruction of
hibernating flies is equally of value; but these subjects
will be considered in the chapter on remedies.

So far as the writer knows, the only observers who
have paid any attention to this very important point
of the period elapsing before sexual maturity are
Hewitt (1910) and Griffith (1908). Hewitt states
that he found flies become sexually mature in ten to
fourteen days after emergence from the pupal state,
and that four days after copulation they begin to de-

HABITS OF THE ADULT FLY

posit their eggs; that is to say, from the fourteenth
day from the time of their emergence. The experi¬
mental data upon which this statement is based are not
given in the paper in question, and the writer there¬
fore wrote to him for a transcript of his record, from
which it appears that the flies under observation
emerged between August 21st and August 28, 1907.
They were given fresh horse manure daily, and accu¬
rate thermometrical readings were recorded for each
of the following days. Not until September 4th was
copulation observed, and on September 9th larvae were
found in the manure.

Doctor Griffith, in his observations at Hove, found
that the female flies oviposited ten days after issuing
from the puparia, and that they could lay new batches
of eggs at intervals of from ten to fourteen days until
four batches have been laid.

It seems to the writer that this period between issu¬
ance and sexual maturity must surely be shorter, and
perhaps much shorter, under midsummer conditions and
in the freedom of the open air, than that indicated by
Hewitt and by Griffith. Breeding-cage observations
are never quite conclusive.

So great is the practical importance of this point,
as already shown and as will be elaborated later, that
the most careful experimental work should be under¬
taken under all sorts of circumstances and in very
many different localities.

THE NATURAL ENEMIES OF THE TYPHOID

FLY

S with every other living creature, nature makes

i \ its own effort to limit the abundance of the fly
under consideration, and the extraordinary facility for
multiplication which the fly possesses is in turn the re¬
sult of the instinctive effort of the organism to main¬
tain its status in spite of the numerous enemies which
confront it. The natural enemies of the house fly be¬
gin with the acme of the vertebrate series (man him¬
self) and end with the lower forms of plant life, and we
will begin our consideration of these agencies with
the latter forms.

Fungous Diseases

In the autumn it is a matter of common observation
that many flies in houses and on the windows become
sluggish and frequently die in such positions. The
sluggishness may be accounted for in a measure by. the
advent of cold weather, and as a matter of fact cold
weather frequently drives indoors other species of flies
of a more sluggish nature than the house fly. In this
way the so-called cluster fly ( Pollenia rudis), a rather
sluggish species, which will be referred to in another
chapter, is frequently found in houses in the autumn.

NATURAL ENEMIES

But the principal cause of the sluggishness on the part
of the house fly in the autumn is the attack of fungous
diseases. Sometimes they are found to be dead without
any evidence of the cause of death. Later they are
seen to be surrounded by a white fungus growth.

There is a group of fungi belonging to the En-
tomophthoreae, many of which are parasitic upon in¬
sects. There are several genera in this group, but the
only one which need be considered at present is the
genus Empusa. The fungi of this group have been
studied by Dr. Roland Thaxter of Harvard University,
and it is from his writings that the following state¬
ments have been drawn.

The infection of insects by these fungi results from
contact with a spore which, adhering to the insect, en¬
ters its body by means of a fungous thread known as
a hypha. The exact method of the entrance of the
hypha is not known, but it must be through the thin¬
ner membrane connecting the body segments and the
leg joints, or through the breathing pores. It has been
suggested that the spores may be eaten, but Thaxter
thinks that this is not the usual means of introduction,
since experiments that he has made contradict it, and
he finds that as a rule the digestive tract during life
does not seem to be penetrated by the fungus. After
one of these hyphse has entered the body of the insect
it develops with some rapidity at the expense of the
softer tissues. It multiplies, not by branching or by
continuing to grow, but by the formation of short,
thick fragments of various sizes and shapes that are

64 THE HOUSE FLY— DISEASE CARRIER

continually reproduced by budding or division until
the insect is more or less completely filled with them.
These fragments are called hyphal bodies. They con¬
tain a highly concentrated, fatty protoplasm and are
capable of subsequent and often very extended develop¬
ment.

When the mass of these bodies has been completed
and the death of the insect attacked has occurred, the
fungus may proceed at once to the completion of its
development under proper conditions of temperature
and moisture, but if these conditions are absent a rest¬
ing stage ensues in which the contents of each hyphal
body becomes surrounded by a single wall which in¬
creases in thickness as the resting stage continues. The
fungus may remain dormant in this condition for a
considerable period. Doctor Thaxter has observed the
hyphal bodies germinating after several weeks, and
thinks that they probably retain their vitality for a
much longer period, and may perhaps hibernate under
certain circumstances.

When a moist atmosphere and a sufficiently high
temperature come they germinate with great rapidity.
With the common house fly fungus ( Enipusa tmiscce )
a slight change in the amount of atmospheric moisture
is sufficient to bring about germination. This, accord¬
ing to Thaxter, is very noticeable on the seashore,
where slight changes of the wind from the water or
from the shore bring about a very rapid and noticeable
effect upon the flies thus parasitized when watched in
the ordinary atmosphere of the house. With other

NATURAL ENEMIES

species of Empusa attacking other insects, a much
greater degree of moisture is necessary, and certain
forms occur only in very moist situations.

In germinating, each hyphal body or resting spore
sends out one or more hyphse, which grow with great
rapidity, but the manner of this germination, together
with the subsequent development of the resulting hy-
phae, varies considerably with different species and un¬
der different conditions. In the simplest case a single
hypha thus produced may grow directly to the outer
air and then produce a single conidium or set of con-
idia. In other cases a single hypha may branch indefi¬
nitely, each final branch bearing a conidium or conidia.
This usually happens where the conditions of growth
have been very favorable, and the complex may be
found side by side with the more simple form.

The conidium or spore is formed by budding from
one of these hyphse, which in this case is called a con-
idiophore. This bud increases in size and becomes
separated from the conidiophore by a cross-partition.
Within the mother cell thus formed is developed a
single spore. When this cell increases in size by the
absorption of water, the wall of the mother cell be¬
comes separated from that of the conidium and some¬
times to such an extent that the conidium is seen float¬
ing free in the large spherical mother cell. Finally by
a rupture the conidium is discharged violently into the
air, often for a considerable distance. With Empusa
muscce, the conidia are bel'l-shaped or nearly spherical,
with a broad base and a measurably pointed apex,

66 THE HOUSE FLY— DISEASE CARRIER

They contain usually a large oil globule and are sur¬
rounded after discharge by a mass of protoplasm.

If the conidium when discharged has come in con¬
tact with a suitable host insect, it adheres to it and sends
out a hypha of germination which enters its body as
just described. Secondary conidia are formed as a
provision for further dissemination in case the primary
spore has fallen on a substance unsuited to its proper
development. With Empusa muscco the secondary con¬
idia are like the primary, or more commonly they are
sub-ovoid, small, round at the apex, and formed by
direct budding from the primary form. These also are
discharged, but are apparently better suited to resist
unfavorable conditions than the primary ones, and
probably retain their power of germination much
longer.

There is also another morphological character of
these fungi — the formation of simple hyphae which pro¬
ject out beyond the conidiophores. When they reach
in the direction of the material upon which the de¬
stroyed insect stands they attach the body to it, and
are then called rhizoids. W'hen they stick out in any
other direction, however, they seem to be functionless
and are called cystidia or paraphyses. The hyphae of
attachment or rhizoids may be simple or variously
branched, and their germination may be variously
modified into an extended sucker. They do not seem
to enter into soft substances, and their adhesion is ap¬
parently due to the presence of a viscous secretion.
They are produced with great rapidity, appearing often

NATURAL ENEMIES 67

before the host is dead, and increase greatly in number
with the appearance of the conidiophores.

This will suffice perhaps for a general account of the
development of these curious parasitic fungi. Empusa
niiisca Cohn., one of the most abundant of them, at¬
tacks the house fly, and also certain other large flies,
such as the blow flies and many flower flies. It was
first described by DeGeer in 1782, and has since been
carefully studied by many observers. It is almost as
universal as the house fly itself, and is the only Em¬
pusa known south of the Equator. As a rule, accord¬
ing to Thaxter, the species is found about houses, usu¬
ally within them, and occurs in great abundance from
late June until late in the autumn. It seems altogether
likely that the majority of the deaths of flies in the late
autumn are caused by this species. In England, ac¬
cording to Hewitt, it is found from about the begin¬
ning of July to the end of October, usually indoors.
In Washington the epidemic ceases in December.

It is not yet known how this fungus lasts over from
one year to another. Mycologists have never grown it
in artificial cultures, and there is evidently much yet
to be learned about many important points in its life
history. Much experimental work has been done with
the fungus diseases of other injurious insects, particu¬
larly with those of forms injuring cultivated crops,
but no striking large-scale results of value have
been obtained. It is possible that something practical
can be gained from a close and prolonged study of this
disease of the house fly, and it is interesting to note

68 THE HOUSE FLY— DISEASE CARRIER

that the city of London local government board on
public health and medical subjects is now aiding Dr.
Julius Bernstein in a detailed investigation of the life
history of Empusa muscaz and in an attempt to cultivate
it in artificial media, with the object, if possible, of em¬
ploying these cultures to destroy flies on a large scale.

Two other species of Empusa are recorded by Thax-
ter as developing in the typhoid fly. These are E.
sphcurosperma (Fres.) Thaxter and E. arnericana
Thaxter. E. sphcrrosperma is peculiar for the great
diversity of its hosts, since it destroys insects of all or¬
ders except that to which the grasshoppers belong. It
is a very common form and often produces very con¬
siderable epidemics among insects. It is recorded as
destroying the clover weevil in great numbers on one
occasion near Geneva, N. Y., by Dr. J. C. Arthur, and
in 1909 produced an extraordinary epidemic in the
same insect in the vicinity of Washington, D. C.

As it happens, an allied insect, probably accidentally
imported from Europe, is causing great damage at the
present time in the alfalfa fields in Northeastern Idaho.
Prof. F. M. Webster of the Bureau of Entomology at
Washington immediately conceived the idea of attempt¬
ing to introduce this fungus from Washington into
Idaho, in the hope that it would attack the alfalfa
weevil. Owing to the dry climate out there, however,
the experiment failed; the conidia would not develop,
and it would seem very difficult if not impossible to
produce, artificially, moisture conditions which will en¬
able alfalfa growers to handle this disease practically.

NATURAL ENEMIES

The only record of the attack of this species on
Musca domestica is by Brefeld. Empusa americana
seems confined to large flies, like the house fly, the
blow flies and the like. Doctor Thaxter states that it
is frequently met with from June to October on the
borders of woods near brooks or in shrubbery about
houses. The fly is generally found fixed to the under,
or rarely the upper, sides of leaves or bare twigs a few
feet above the ground. It occurs in New England and
North Carolina. The rhizoids or attaching hyphse, in¬
stead of growing out in the form of numerous scat¬
tered threads, are developed in an even layer around the
insect’s body, forming with the conidiophores a con¬
tinuous mat-like covering, which often becomes dark
rust colored on exposure to the weather.

These are, so far as known, the only true botanical
enemies of the house fly. Of course, breeding as it
does in fermenting organic matter and in the dirtiest
and filthiest locations, and frequenting such situations
as it does in search of food, it carries upon its body,
and within its alimentary canal for the brief period
which it takes for its food to pass through, any num¬
ber of spores of fungi and of bacteria, but it is prob¬
able that nearly all of these are carried accidentally
by the fly and do it no harm. Many species of many
genera of fungi and bacteria have been cultivated upon
sterilized plates upon which flies caught haphazard
have been allowed to walk and which they have been
allowed to speck, but as just stated these are probably
innoxious to the fly itself. From the observations of

70 THE HOUSE FLY— DISEASE CARRIER

Mr. H. T. Giissow, Dominion Botanist of Canada,
quoted by Hewitt, the fungi reared in this way have
numbered seven species, while the bacteria have num¬
bered eleven species.

Protozoan Enemies of the House Fly

Certain microscopic protozoa of the group Flagel-
lata have been found in the alimentary canals of vari¬
ous insects, and one species known as Herpetomonas
muscce domestica? has been found in the intestine of
the house fly. The genus to which it belongs is said
by Calkins to be the most primitive and least changed
from the free-living forms of the flagellated intestinal
parasites. It is a general parasite of flies of very wide
distribution. It was carefully studied by Prowazek in
1904 and by Captain W. S. Patton of the Indian Med¬
ical Service in 1908 and 1909.

Patton found that in Madras, India, about one hun¬
dred per cent, of the flies caught in the bazaar meat
shops are infected with this parasite, and he made an
exhaustive study of its life history which continued
for more than a year. He found that it exists in three
stages which he calls the preflagellate, the flagellate
and the postflagellate. The first stage is usually found
in the midgut, the parasites lying in masses within the
peritracheal membrane. They are round or slightly
oval bodies of very minute size, which multiply by
simple longitudinal division or by multiple segmenta¬
tion so that a large number is formed in a short time.
The flagellate stage is characterized by the projection

NATURAL ENEMIES

of a single stout filament. In this stage it elongates
and divides later by simple longitudinal division. In
the postflagellate stage the organism shortens in length
and eventually loses its filament.

Whether the presence of these intestinal parasites
affects the vitality of the fly is not mentioned, nor is it
understood whether they can be transmitted to any
other animal.

Since the typhoid fly does not bite, it seems likely
that such a transfer does not take place. It is inter¬
esting to note, however, that a parasitic flagellate of
the same genus, namely, Herpetomonas donovani, is
the causative organism of the tropical disease known
as kala azar, characterized by an enlargement of the
spleen, by irregularly recurrent fevers, anaemia and
emaciation, usually resulting in death, and that Cap¬
tain Patton has discovered that the same parasite un¬
dergoes a transformation in the intestine of a bedbug
( Cimex rotundatus ) in India, confirming a suggestion
made with reasons by L. Rogers, who had previously
discovered the flagellated stage of the parasite. When
the blood of a kala azar patient is sucked into the ali¬
mentary canal of the bedbug the parasites are liberated
by the digestive process and begin to develop from
the second to the fifth day. There is no evidence that
the bedbugs are infected except from human beings,
and there is no scientific proof that human victims ac¬
quire the disease from the bugs.

Another flagellate genus, Crithidia, is found in the
intestinal tract of certain flies, and one of them has

72 THE HOUSE FLY— DISEASE CARRIER

also been given the specific name Muscat domestic at by
H. Werner.

Nematode Parasites of the Typhoid Fly

The nematodes, or thread-worms, have long been
subjects of observation. They are greatly elongated,
thread-like organisms, frequently of considerable size;
for the most part laying eggs, but in rare cases bearing
living young. The younger stages or larvae of most
of them have a different habitat from that of the adult
worm. Some of them develop in damp, muddy earth,
migrating finally to lead a parasitic life within some
animal ; some are parasitic in plants. The old time super¬
stition that a horse-hair when left in water for a suffi¬
cient length of time becomes a living worm arises from
observations upon some of the largest nematodes. Very
many insects are parasitized by the worms of this group.

H. J. Carter, in Bombay, in November, 1859, while
examining the head of a common house fly, noticed
that two nematode worms came out of it. Later, in
July, i860, he discovered that on the average about
every third fly in Bombay contained from two to
twenty or more of these worms, which were chiefly
to be found in the proboscis, though occasionally oc¬
curring among the soft tissues of the head and hinder
part of the abdomen. He described them as bisexual,
mature, and nearly all of the same size. He placed
them in the genus Filaria, and described them as Filaria
tnuscce in the Annals and Magazine of Natural History,
Vol. VII, pages 30-31.

NATURAL ENEMIES

Other observers have studied this parasitic worm,
which is now placed in the genus Habronema. Hewitt,
in England, after dissecting many hundreds of flies,
found only two specimens of this parasite. He feels
certain that the one found in England is the same as
the one found by Carter in India.

The same species occurs in the United States and
has received some attention from Dr. B. H. Ransom,
of the Bureau of Animal Industry of the U. S. De¬
partment of Agriculture at Washington. Doctor Ran¬
som has very kindly given the writer the following
note, hitherto unpublished, which is sufficiently interest¬
ing to print in full :

“Referring to Habronema musccc, this parasite seems
to be very common in the house fly. Out of thirty-four
flies examined between June ioth and July nth, most
of them caught in the laboratory of the Zoological Di¬
vision, the remainder bred from horse manure obtained
at the Experiment Station of the Bureau of Animal
Industry, Bethesda, Md., nine were infested. The
number and distribution of the parasites in these nine
flies were as follows :

1. Five in the proboscis.

2. Six in the head and proboscis, one in the thorax.

3. One in the head.

4. Two in the head.

5. Five in the head.

6. Two in the head.

7. One in the head.

8. One in the abdomen.

9. Two in the thorax.

74 THE HOUSE FLY— DISEASE CARRIER

“Twenty-six dipterous larvae (species not deter¬
mined) from horse manure which were examined for
the presence of nematodes were all free from infection
with H. musca;. Thirteen larvae of Musca domestica
and several pupae were examined with negative results.
These were bred from house flies confined in a dish
with horse manure which had previously been boiled
to destroy any fly larvae or nematodes which might
have been present. That some of the flies were infested
with Habronema was determined by examining a num¬
ber after oviposition had occurred. An undersized
male which developed in the culture just referred to,
the only adult that was obtained in this culture, was
examined with negative results.

“That infection with Habronema muscce is acquired
during some stage prior to the imago was proved by
the discovery of the parasites in a fly caught just as it
was emerging from the pupa (No. 9, referred to
above). Beyond this fact the observations made by
me (made incidentally in the course of another in¬
vestigation) have proved little as to the life history of
the parasite. On several occasions I have placed the
worms taken from flies in water and in horse manure,
but in no case was it observed that any further develop¬
ment occurred. The worms invariably died within a
few days. It would seem, however, that the larval
stage of the parasite which is found in the fly must in
some way escape from its host, reach sexual maturity
either as a free living form or in another host, and
produce young which find their way into other flies

NATURAL ENEMIES

during an early stage in the development of the insects.
It is improbable that the worms develop to maturity
in the fly, since they have been found only in the larval
stage in that host. It might be noted in this connec¬
tion that Carter erred in identifying certain structures
as reproductive organs.”

Other nematodes have been found in the typhoid
fly, but it is not as yet determined that they are surely
distinct from the one just mentioned.

The Mite Enemies of Musca Domestica

Many flies of different species are often noticed to
have small red mites attached to their bodies. This
has been found to be the case with small flies as well
as with large ones — even mosquitoes have enemies of
this kind. Some of these mites probably exert a dele¬
terious effect upon their host and are true parasites,
but with others the flies simply act as aeroplanes to
carry the mites from one place to another. (A free ride
seems to be the only object for which they have at¬
tached themselves to the fly.)

Attention was called to these mites in the first place
by DeGeer in 1735. Linnaeus wrote of one of them in
1758, and other writers have made mention of them
and have described several species. Mr. Nathan Banks,
an authority upon this group of creatures (Arachnids),
has given the writer the following information :

“Latreille based a new genus and species on mites
from the house fly, and he called it Atomus parasiticum.
This is the young of one of the harvest mites of the

76 THE HOUSE FLY— DISEASE CARRIER

family Trombidiidae, but the adult has not been reared
and is still unrecognized in Europe. Riley found these
harvest mites on house flies in Missouri, in some years
so abundantly, he says, that scarcely a fly could be
caught that was not infested with some of them cling¬
ing tenaciously at the base of the wings. Later he suc¬
ceeded in rearing the adult, and described it as Trom-
bidiutn muscarum. In recent years Oudemans has de¬
scribed Trombidium niuscce from larval mites found
on house flies in Holland.

“All these forms are minute, six-legged, red mites,
which cling to the body of the fly and with their thread¬
like mandibles suck up the juices of the host. They are
nearly related to the so-called ‘red-bugs,’ or ‘chig-
gers,’ of the Southern United States. When ready to
transform, they leave the fly and cast their skins, the
mature mite being a free-living, hairy, scarlet creature
about one and five-tenths mm. long. The adults are
usually found in the spring and early summer, while
the larvae are usually found in the autumn on house
flies and other insects.

Mites of the genus Pigmeophorus, of the family
Tarsonemidae, have also been taken on house flies.
They cling to the abdomen of the fly, but it is not cer¬
tain whether they feed on the insect or use it simply
as a means of transportation. The hypopus, or mi-
gratorial nymphal stage of several species of Tyro-
glyphus, has been found on house flies. This hypopus
attaches itself by means of suckers to the body of any
insect that may be convenient. The mites do not feed

NATURAL ENEMIES

on the fly, but when the fly reaches a place similar to
that inhabited by the mites the latter drop off, cast
their skins, and start new colonies. DeGeer observed
large numbers of these tiny mites on the back and neck
of the house fly. Linnaeus named one of them Acariis
muscarnm. Berlese has reared from stable flies what
he considers as this Acariis mtiscarum of Linnaeus, and
finds that the adult belongs to the genus Histiostoma.

The hypopi most commonly found on the house fly are
those of the common household cheese- ham- and flour-
mites. All through the summer months, and in warm
houses during the winter months, these creatures breed
with astonishing rapidity and fecundity. The females
bring forth their young alive, and these in turn reach
full growth and reproduce until a cheese, once infested
by a few, swarms with the crawling multitude which
causes its solid mass to crumble and become mixed with
excremental pellets and cast-off skins.

During the summer months the mites are soft-bodied
and have comparatively feeble powers of locomotion,
and, as they become numerous enough to devour
the whole of a cheese with no other food at hand, it
was for a long time a puzzle to know what became of
them and to understand how a cheese could become in¬
fested without coming in contact with another infested
cheese or without being placed in an infested room. It
has been learned, however, that when necessity requires
it and when the insects happen to be in the proper stage
of growth, they have the power not only of almost in¬
definitely prolonging existence but of undergoing a

78 THE HOUSE FLY— DISEASE CARRIER

complete change of form, acquiring hard, brown, pro¬
tective coverings into which all of the legs can be drawn
in repose. In this hard shell, or hypopus state, it may
remain for many months without food.

In the majority of cases, however, where a given
cheese is completely destroyed, all of the young and
old mites perish, and only those of middle age, which
are ready to take on the hypopus condition, survive.
These fortunate survivors, possessing their souls in
patience, retire into their shells and fast and wait, and,
as everything comes to him who waits, some lucky day
a house fly comes that way and *the little mite clings
to it and is carried away to some spot where another
cheese or food in some other form is at hand.

Spiders as Fly Enemies

In spite of the well-remembered poem beginning
“‘Will you walk into my parlor?’ said the spider to
the fly,” it is a curious psychological fact that the writer
had practically completed the writing of this chapter
on the natural enemies of the house fly before he dis¬
covered that he had forgotten to say anything about
spiders. That was not because he is getting old and
forgetful, but because in the rooms which he has had
the good fortune habitually to frequent during later
years he has rarely seen a spider. Although, if given
the opportunity, they would kill an unlimited number
of flies, they are not permitted to build their webs and
increase in localities where the flies are the greatest
nuisances; that is to say, in houses, shops, and hos-

NATURAL ENEMIES

pitals. It will not be necessary, therefore, to give
spiders any extended consideration here. Mr. Nathan
Banks, the well-known writer on these interesting crea¬
tures, has jotted down for the writer the following
brief notes on the subject:

“The most common spider in houses is Theridium
tepidariorum Koch. It occurs throughout the civilized
world. It builds an irregular web in the upper corners
of rooms, and if the housewife is not too tidy, one may
often see flies in its webs. Steatoda borealis and T entana
triangulosa are related spiders, occurring in this coun¬
try and in- Europe ; their webs are commonly under or
behind furniture, in darker places than those of the
Theridium. They do not catch as many flies, but their
webs are safer from the housekeeper’s broom.

“Agalena ncevia, a common field spider, is frequently
found in houses, especially outhouses, outside kitchens,
etc. ; sometimes they live in these double screens ; they
need some crack or hole in which to retire; the web
spreading fan-like from this hole, which they line with
silk.

“ Salticus scenicas is a common jumping spider about
houses, usually on the outer side of houses, but often
seen on windows, where one may watch with much in¬
terest their method of stalking and suddenly leaping
on unsuspecting flies.

“In cellars, packing boxes, and other dark places,
other spiders occur; Tegenaria derliami and Amauro-
bins ferox being common in the United States and in
Europe.

80 THE HOUSE FLY— DISEASE CARRIER

“Several of the orb-weaving spiders are often found
on porches, where their snares will intercept many
flies. Epeira sericcitci nearly always occurs near or on
buildings.”

False Scorpions on Flies

There is a group of Arachnids, known as the false
scorpions or pseudoscorpions, which are much smaller
and simpler in structure than the true scorpions. They
have no poison gland and no spine at the end of the
body. They bear much the same relation to the true
scorpions that the mites do to the true spiders. • They live
beneath the bark of trees, in moss, between the leaves
of old books, etc. They run sidewise and backwards,
and live on mites and small insects. Two or three
species of the false scorpions are sometimes found
clinging by their claw-like pedipalps to the legs of the
house fly and other kinds of flies. It is not known
why they attach themselves to these insects, but it is
hardly probable that they feed on them, and it seems
altogether likely that they simply attach themselves in
the same way as does the hypopus of the Tyroglyphid
mite, in order to be carried to some better feeding
ground. Much has been written upon this subject,
and many different views are held about this attach¬
ment, but there is no sound evidence on the one side
or on the other. The suggestion has been made that
the false scorpion seizes the legs of the flies without
realizing their size, and that they remain attached until
the fly dies and then they feed upon the body. Doctor

NATURAL ENEMIES

Hewitt has reviewed the habits of one of the species
known as C hemes nodosus Schrank, which, he states,
is more abundant in England in some years than in
others. He quotes Godfrey (1909): “The ordinary
habitat of Cherries nodosus, as Mr. Wallace Kew has
pointed out to me, appears to be among refuse, that is,
accumulations of decaying vegetation, manure heaps,
frames and hotbeds in gardens. He refers to its occur¬
rence in a manure heap in the open air at Lille, and
draws my attention to its abundance in a melon frame
near Hastings in 1898, where it was found by Mr.
W. R. Butterfield.” Doctor Hewitt very justly calls
attention to the fact that it is not difficult to under¬
stand the frequent occurrence of this false scorpion
on the legs of flies, in view of the facts just quoted
from Mr. Godfrey, since flies frequent such rubbish
heaps for the purpose of laying eggs, or he suggests
that when they have recently emerged from puparia
in such places and are crawling about while their wings
are drying their legs are readily to be seized by the
Chernes. In closing his account of this species he
writes, “It is obvious that the association [between
the Chernes and the fly] will result in the distribution
of the pseudoscorpionid, but whether this is merely
incidental and the real meaning lies in a parasitic or
predaceous intention on the part of the Arachnid, as
some of the observations appear to indicate, further
experiments alone will show.”

82 THE HOUSE FLY— DISEASE CARRIER

The House Centipede

There is a small, rather fragile-looking centipede,
known scientifically as Scutigcra forceps Raf., which
for many years has been a constant inhabitant of houses
in the Southern United States, and which seems to
have been gradually extending its northward range.
It is now occasionally found in houses as far north
as Albany. N. Y., and perhaps even farther.

It seems to be peculiarly a domestic animal ; that is
to say, it has accommodated itself perfectly to the con¬
ditions existing in human habitations. Its form and
its sudden movements have made it an object of fear,
especially to women and children. It is fond of damp
localities, and is especially abundant in bathrooms, in
basements, in cellars, and in ground-floor kitchens and
pantries, where there is more or less dampness and
warmth. It has been called the skein centipede, since
when crushed its long legs look like a mass of threads.
This creature, as has been shown by Marlatt (1896),
seems to be a normal inhabitant of the southern tier
of the United States, spreading north into Pennsyl¬
vania as early as 1849 and reaching New York and
Massachusetts twenty or twenty-five years later. It
is now common throughout New York and the New
England States and extends westward beyond the
Mississippi.

The character of its mouth parts indicates that it is
predatory and carnivorous in its habits; the jaws are
strong, and its food consists principally of other in-

Fig. 1 7. — The house centipede ( Scutigcra forceps) ; somewhat enlarged.
(After Marlatt.)

NATURAL ENEMIES

sects living in houses, such as house flies, small cock¬
roaches, and clothes moths. Years ago the writer ob¬
served its method of catching both Croton bugs and
house flies upon the wall of the kitchen of a house in
which he lived in Georgetown, D. 0. It feeds and is
especially active at night, being seen in the daytime
usually only when disturbed. On this occasion, with
the late Dr. James Fletcher, the writer went to the
pantry in the evening and saw a good-sized specimen
of the Scutigera on the wall eating something. The
light was turned as low as was consistent with fairly
clear observation. The object held in its front legs
was seen to be a small Croton bug. It was eaten with
astonishing rapidity, but in the act of eating this speci¬
men a house fly was observed by the centipede, close
to it, resting upon the wall. It instantly jumped, ap¬
parently with all of its legs at once, and covered the
fly, which was thus confined as if it had been in a hen
coop. When the Croton bug was devoured, the pair
of legs opposite the fly seized it and passed it to the
pair of legs immediately in front, and in succession
it was passed up to the front legs, by which it was held
while being devoured. So it is obvious that its great
number of legs are of use, not only in walking, but
in the capture of its prey. The same operation was
repeated several times.

The popular belief is that this little creature is very
poisonous, and indeed it belongs to the poisonous group
of centipedes. Very few cases are recorded, however,
of its having bitten a human being, and it is question-

84 THE HOUSE FLY— DISEASE CARRIER

able whether it would attack any animal or insect larger
than itself. Marlatt states that if pressed with the
bare foot or hand, or if caught between sheets in beds,
it will unquestionably bite in self-defense. He also
shows that the few such cases on record indicate that
severe swelling and pain may result from the poisonous
injection. Prompt application of ammonia, however,
will alleviate the symptoms.

No one knows much about the life history of this
creature. Full-grown specimens are found in houses
all through the year ; half-grown individuals are some¬
times found in the summer; the youngest ones known
differ from the older ones chiefly in having fewer legs.
It is interesting to note that a careful look at the hind
segments of the young will show the long posterior
legs folded up within and ready to be extended after
the next molt.

Under present conditions of house fly abundance, it
might be as well not to disturb this Scutigera when
it is found in houses, but with the conditions which
will shortly be brought about, we hope, it will be easy
to destroy the centipedes with pyrethrum powder, even
if they do not, as is likely, die of starvation.

Insect Enemies of the House Fly

Predatory enemies. — It seems rather strange that,
with the very numerous predaceous insects which de¬
rive their sustenance from soft-bodied and more or less
helpless species, there should not be more which gain
their livelihood from the larvae of the typhoid fly. It

NATURAL ENEMIES

is true that the larvae of certain Carabaeid beetles, and
especially those of the genera Harpalus, Platynus and
Agonoderus, are sometimes found frequenting manure
and feeding upon young fly larvae, and that certain
rove beetles and their larvae, of the family Staphylinidae,
are also found in the same situations, engaged in the
same task. And Packard (1874) records the finding
of a beetle pupa in'the puparium of the house fly. But
one would think that a pile of horse manure swarming
with fly larvae would attract hordes of predatory beetles
and of pirate bugs and the like. Is it that house fly
maggots are distasteful to these voracious creatures?
Or is their perception of odors keen and are the am-
moniacal odors of the manure pile repugnant? It is
difficult to say. The typhoid fly belongs plainly to a
most persistent type, and it feeds freely and abundantly
in close proximity to many insects which we would
naturally suppose to be its enemies.

But we must not forget the ants. It is true that
many ants are nuisances, and in the case of the destruc¬
tion of the typhoid fly by ants we have simply one nui¬
sance multiplying at the expense of another, but Forel
and Wheeler admit that as a group ants are beneficial
and that many species deserve our protection. Capt.
P. L. Jones of the U. S. Army Medical Corps (quoted
by Garrison, U. S. Naval Med. Bull., Oct., 1910, p.
551) made certain experiments in the Philippines to
determine whether the scarcity of flies in those islands
was due to some epidemic disease. In the course of
the experiments it was found impossible to raise flies

86 THE HOUSE FLY— DISEASE CARRIER

unless the eggs and larvae (in manure) were protected
from ants, as the latter invariably carried off both
eggs and larvae and even pupae.

In the work against the cotton boll weevil carried
on in the Southern United States by the experts of
the Bureau of Entomology of the U. S. Department
of Agriculture, it was found that the “fire ant” of the
Southern cotton fields ( Solenopsis gemminata, var.
diabola ) is an important enemy of the weevil, and
strong efforts were made to multiply the ants. It was
soon found that they were strongly attracted to horse
manure and undoubtedly destroyed all its other insect
inhabitants. Mr. W. D. Pierce of the Bureau informs
the writer that the little black ant Monomorium mini¬
mum also frequents horse manure heaps in Texas, and
he also says that several species of the ant genus Phei-
dole have this habit.

Moreover, that famous pest in Louisiana and parts
of California, known as the “Argentine ant” ( Iri -
domyrmex humulis ) nests readily in horse manure, and
its active, pugnacious and predatory habits undoubtedly
induce it to prey upon the maggots found there.

Mr. Pierce’s ant suggestion was of sufficient interest
to follow up, and therefore the writer has corresponded
with Prof. Wilmon Newell, of College Station, Texas;
Prof. J. B. Garrett of the State University of Louisiana
at Baton Rouge; and Mr. T. C. Barber, in charge of
the Audubon Park laboratory of the U. S. Bureau of
Entomology at New Orleans — all of them men who
have had intimate acquaintance with the Argentine ant,

NATURAL ENEMIES 87

and who have made special studies of its habits. The
reply from each was the same in its general tone.

Professor Newell never found the Argentine ant
nesting in pure horse manure, but has found them in
manure that contained a large amount of straw or hay.
A certain public dumping ground carrying much ma¬
nure was heavily infested with the ants, but house flies
bred from it in such enormous numbers that the health
officer was called in. The observer found colonies of
ants on the ground and also an abundance of fly larvae.
His experience has been that house flies are not notice¬
ably reduced in places where the Argentine ant swarms.

Professor Garrett writes that the mess hall in which
about 300 of the students take their meals is in a lo¬
cality where the ants are very abundant, and yet the
house flies are apparently as numerous as ever. He
thinks that the ants do destroy quite a number of lar¬
vae in manure, but that they do not use them as an
article of food to a sufficient extent to cause an appre¬
ciable decrease. Mr. Barber is of the same opinion.

Mr. F. C. Pratt, an agent of the Bureau of Entomol¬
ogy, located at Sabinal, Texas, made an especial study
of fly larvae at Dallas on one occasion. He found that
the fire ant, on one occasion when he was experiment¬
ing with cow manure in order to raise parasites of the
horn fly, took complete possession of his rearing cages
and their contents. In his opinion, they feed upon all
fly larvae.

Aside from ants, there are other predatory insect ene¬
mies of flies not yet mentioned. Wasps catch house

88 THE HOUSE FLY— DISEASE CARRIER

flies, sometimes in considerable numbers. It is not an
uncommon sight to see any one of several different
species of wasps flying about houses, capturing flies
both on the wall and on the wing. The robber flies of
the family Asilidae also catch house flies, on porches
sometimes. On the whole, however, the predatory in¬
sect enemies of the house fly are negligible, so far as
the beneficial result of their work is concerned.

Parasitic Enemies

To a certain extent the same may be said of the para¬
sitic enemies of this species, but these are perhaps more
numerous than the predatory insect enemies, and sev¬
eral of them are accustomed to frequent excreta in the
search of larvae in which to deposit their eggs. This
is especially true of cow dung, and many minute hy-
menopterous parasites may be found frequenting drop¬
pings in the pasture in order to lay their eggs in some
one of the many species of maggots which are to be
found there in a very short time.

These very minute, active, four-winged parasites be¬
long either to the subfamily Figitinae of the gall-fly
family Cynipidae or to the superfamily of true parasites
known as Chalcidoidea.

In the gall-fly family, Cynipidae, most of the species
of which produce galls upon living plants and very
numerously upon the oak, there is one subfamily of
minute forms, the Figitinae, parasitic upon other insects
and for the most part upon dipterous maggots. Those
frequenting cow dung will lay their eggs in apparently

NATURAL ENEMIES

almost any one of the many species of dipterous larvae
found there, and have been reared from the larvae of
the horn fly, from several species of true dung-flies
(family Scatophagidae) , and from others. Two spe¬
cies, however, are reared from the maggots of the ty¬
phoid fly. These are Figites anthomyiarum, reared
from the house fly in Germany by Reinhard, and
Figites scutellaris, also a European species. If careful
rearing experiments were carried out continuously in
this country with house fly larvae, it is probable that
other species of this group would be reared. Prof.
T. D. A. Cockerell, for example, caught one of them —
Eucoila impatiens Say — on horse dung at Las Cruces,
N. Mex., in 1894, and suspected its parasitism on house
fly larvae (Insect Life, VII, 209). Many similar ob¬
servations can doubtless be made very easily.

The Chalcidoid parasites of Masca domestica are
more numerous. In the family Pteromalidae there is
a genus, Spalangia, which seems practically confined to
dipterous larvae. One species, Spalangia niger, was
found by the German author Bouche to lay its eggs in
the pupae of the house fly and to issue in April and
May. The larvae of the Spalangia are spindle-formed
and white, almost translucent, and are to be found in
the autumn in the puparia of the house fly, where they
destroy the true pupae.

Several species belonging to this same genus are to
be found in the United States, and one of them at least
has similar habits. Mr. H. L. Sanford, of the Bureau
of Entomology at Washington, in opening a series of

90 THE HOUSE FLY— DISEASE CARRIER

puparia of Musca domestica in January, 1911, in order
to ascertain what proportion of the pupae were living,
was surprised when a fully formed and active adult
black Spalangia crawled immediately from the opening
made by his dissecting needle. This will be described
by Girault as Spalangia miisccc. A certain proportion
of the house fly puparia are affected by this parasite in
precisely the same way as are the puparia in Europe
by Spalangia niger as described by Bouche. Mr. San¬
ford’s observation shows that the adults may be fully
formed and ready to emerge at a very early date.

Another European Pteromalid parasite, namely, Ste-
nomalus muscarum, is recorded as being a parasite of
the house fly pupa.

Much attention has been given to the Chalcidoid
parasites of the typhoid fly by A. A. Girault and G. E.
Sanders, of the University of Illinois. In their first
paper ( Psyche , December, 1909, pp. 1 19-132) they
described an interesting form under the name Nasonia
brevicornis from a series of 640 specimens, nearly all
reared from puparia of various flies in the Office of the
State Entomologist of Illinois at Urbana during 1908.
They came from various decomposing materials, from
which several species of flies were reared, but a num¬
ber undoubtedly came from Musca domestica.

It is a minute, dark, metallic, brassy-green fly with
clear wings and rather stolid and serious temperament.
Girault and Sanders state that it heeds external influ¬
ences very slightly, and quietly and persistently gives
its whole attention to reproduction. They found that

NATURAL ENEMIES

both sexes crawled rapidly. The female is able to fly ;
but the favorite mode of locomotion appears to be
crawling. The wings of the male appear to be non¬
functional. Actual experimentation with fifty maggots
and ten puparia of the house fly showed that the para¬
sites laid their eggs in the puparia and developed rap¬
idly. The maggots and puparia were placed in a breed¬
ing jar on September 9th, and on September 26th six
males and ten females of the parasites issued from the
puparia. On September 12th, eight female parasites
were confined separately in small gelatine capsules,
each with a healthy puparium of the house fly. The
parasites appeared to lay their eggs in several cases,
but none issued afterwards and about half of the flies
came out.

Most careful observations were made by the authors
on the egg-laying process of this parasite. The female
was observed to walk carefully over a two-days’ old
puparium, examining the entire surface. After a point
was selected, the ovipositor was inserted with some dif¬
ficulty, the operation requiring one minute and a half.
The hole was then enlarged, and the ovipositor was
again pushed in for its entire length and remained for
forty-five seconds, during which time apparently an
egg was deposited. After the ovipositor was with¬
drawn the parasite examined the puncture with its
antennae and mandibles.

The parasite apparently attacks only the puparium,
and that only after it has been formed for about twenty-
four hours, and a number of them issue from the same

92 THE HOUSE FLY— DISEASE CARRIER

puparium. Observations were carried on through suc¬
ceeding months and the duration of the life cycle was
carefully studied ( Psyche , February, 1910). The life
cycle is longer in the spring and shorter in summer,
the average life cycle being twenty-two and one-
half days with usual temperature. They found that
one female was able to parasitize twenty-two puparia
and another one seventeen. The authors suspect that
the phenomenon of polyembryony, that is to say, the
development of a number of adult individuals from a
single egg, takes place with this species. Counts of
several thousand reared specimens of the parasite in¬
dicated that fifty-eight and nineteen-hundredths per
cent, of them were female and forty-one and eighty-one-
hundredths per cent, were males. They found that the
adult parasites issue from the host puparium through
from one to three circular holes of various positions,
several issuing from each hole. As to the abundance
of the parasite, the authors indicate that during Sep¬
tember and October, 1908, they reared 8,000 or more
specimens, and these were reared quite accidentally, that
is to say, without conscious effort on their part to in¬
crease the number. The local abundance of the para¬
site was indicated by the fact that in a portion of a
given experiment the percentage of parasitism was as
high as ninety per cent. This percentage of mortality
on the part of the house fly, however, was by no means
general, and the parasite had apparently concentrated
its attack on certain spots. The authors made an un¬
successful attempt to propagate the species artificially

NATURAL ENEMIES

by scattering 1,000 specimens of mixed sexes over a
garbage heap on September 23d. This, however, was
too late in the season, and weekly collections of fly
puparia thereafter gave no result.

The authors found that this parasite hibernates as
a full-grown larva in the puparia of the flies, trans¬
forming to pupa early in the spring and emerging
shortly afterwards. As examples of intensive and care¬
ful study of a given species, the papers on this form by
the authors mentioned are excellent.

The same authors have made a careful study of an¬
other house fly parasite of this group, known as Pachy-
crepoideus dubius. This species was reared in com¬
pany with the preceding species, and the experiments
of the writers indicated that it is a true primary para¬
site of the house fly. They were unable to make any
observations on the biology of the species, except to
notice that the adults in three cases emerged from the
fly puparium through a single hole with jagged edges.

Still another parasite of this group, studied by Gir-
ault and Sanders, and described in Psyche for August,
1910, is Miiscidifiirax raptor. This is another small,
clear-winged species, black in color, which was reared
in some numbers from puparia of the typhoid fly at
Urbana and Champaign, Illinois. It also breeds in
the puparia of other flies, is solitary in its habits, and
more sensitive than the Nasonia which the experiment¬
ers have described so fully. They state that the bio¬
logical history of the species can be learned with ease
in the laboratory, as the females are not at all averse

94- THE HOUSE FLY— DISEASE CARRIER

to ovipositing in confinement ; they are, however, seem¬
ingly not as prolific or as generally parasitic as Nasonia.

The writers did not obtain certain data concerning
the entire seasonal history of this parasite, but they
think that it confines itself principally to the puparium
stage of the house fly, hibernating in the puparium as
a larva and pupating itself and emerging early in the
spring as an adult four-winged parasite. The first
specimens found by them emerged the first week in
September, and from that time on until frost it was
comparatively abundant. It was reared from puparia
collected on September 23d and again from some col¬
lected on October 21st, emerging from these Novem¬
ber 6th. Hibernation probably commenced about Oc¬
tober 2 1 st.

Examination of the house fly pupae, after the para¬
sites have emerged, indicates that the larva of the para¬
site feeds externally on the pupa of the fly, sucking its
juices. The attachment is to any portion of the body
of the pupa. Opening a puparium from which the
adult parasite had emerged revealed the blackened and
shrunken remains of the fly pupa lying in its natural
position along the floor of the pupal shell.

The meconium, or excrement passed by the para¬
site larva when about to change to pupa, is distinctive
— dark in color and round-angled, looking like a small,
solid, black, round bit, resembling somewhat a coarse
grain of powder but not as irregular or angular. It
differs from the meconium of the other parasites of the
house fly studied by the authors mentioned. The adult

NATURAL ENEMIES

parasite issues through a single rounded hole cut in
the pupal skin of the fly. The two sexes issue almost
simultaneously, the males a little before the females.
Each female appears to lay thirty to forty eggs. Out
of 288 specimens reared, eighty-five were males and
203 females, and the average duration of the life cycle
was nineteen days and seventeen hours.

Girault will continue his intensive study of fly para¬
sites and will undoubtedly learn many new and im¬
portant facts. Additional species have already been
reared by him and await systematic study.

Vertebrate House Fly Enemies

The common garden toad, the great collector of in¬
sects, will catch a house fly whenever it is able to do so.
It is, in fact, a pleasing occupation to feed house flies
to a good-sized toad, in order to ascertain his capacity.
But these animals are not inhabitants of houses.

Some of the lizards that run about houses in tropical
regions feed upon flies, and the occupancy of houses
by these creatures is not objected to by natives, for this
as well as for other reasons.

Birds are not effective as house fly enemies. Of the
wild birds, comparatively few feed upon them at all,
although there are many insectivorous species which
would do so if they were allowed to nest in houses. As
a matter of fact, however, in all the records of the Bu¬
reau of Biological Survey of the U. S. Department of
Agriculture, which represent the examination of the
contents of the stomachs of many thousands of birds,

96 THE HOUSE FLY— DISEASE CARRIER

there are only two records of the finding of house flies,
and one of these is somewhat doubtful.

One of their records shows the finding of thirty-three
larvae in the stomach of a horned lark, but it is quite
possible that these larvae were not those of Musca do-
mestica. The other record shows the finding of a single
adult house fly in the stomach of a white-eyed vireo.
The writer has watched the house wren feeding its
young hour after hour, and has noticed that the in¬
sects brought to the nest were for the most part small
caterpillars, although there were plenty of flies on the
porch where the nest was built.

The great group of .insectivorous birds known as the
fly-catchers as a matter of fact do not prefer the flies.
As the writer has been told by Prof. F. E. L. Beal, an
authority on the subject, they feed by preference upon
winged hymenopterous insects, which constitute the
bulk of their food.

W. D. Doan in Bulletin 3 of the West Virginia Ex¬
periment Station records finding house flies in the
stomachs of the cedar bird, the wood pewee, and the
palm warbler.

Domestic poultry, however, when given the oppor¬
tunity, will feed with some avidity upon house fly lar¬
vae. Hens given the run of a barnyard destroy very
many larvae in scraping about the edge of the manure
pile, and more than one letter has been received from
persons who, admitting flocks of poultry to the barn¬
yard for the first time, have discovered an appreciable
reduction in the number of adult flies visiting the house.

NATURAL ENEMIES

Fly-Catching Rats

A number of mammalia in captivity have been seen
to capture flies, but as a rule they seem to do this very
much as the idle house dog wiil snap at the fly circling
about his head. A most interesting observation, how¬
ever, has been made by Prof. B. W. Evermann, of the
Bureau of Fisheries in Washington. At a meeting of
the Biological Society of Washington, held January
7th, he gave an account of a visit in early July of 1910,
at Kokomo, Indiana. He stopped at a hotel and was
sitting on the piazza on the evening of his arrival. Back
of him was a window which opened into a storeroom
for provisions, etc. Inside the window was a lace cur¬
tain which hung closely, and uniformly covered the
entire window. Happening to look at the window quite
by accident, Professor Evermann saw a brown rat run
back and forth on the window-sill inside. It seems that
a large number of flies had accumulated between the
curtain and the window, probably attracted by the light
from outside, and the rat was engaged in catching these
flies.

In Professor Evermann’s words, “It was very expert.
It would move back and forth the full length of the
window-sill, catching such flies as it could reach. It
would frequently stand upon its hind legs to its full
length with its fore paws and body resting against the
glass and move backward and forward across the win¬
dow. It ordinarily caught the flies with its paws, by
raking the fly with one paw over against the other or

98 THE HOUSE FLY— DISEASE CARRIER

bringing the two paws together on a fly and then feed¬
ing it into its mouth.”

The observer watched it for some little time and
must have seen it catch more than one hundred flies.
Next morning the same performance was repeated, and
a large number of flies were captured. Moreover, a
second rat appeared during the time the observer was
watching the first one, and its methods were the same.
Inquiry from the clerk at the hotel indicated that the
people of the hotel had noticed the rats engaged in this
occupation and had refrained from disturbing them.

Mr. W. L. McAtee, recently, in looking over an old
file of The Rod and the Gun found the following item
in the number of September 25, 1875. It is quite be¬
lievable in view of Doctor Evermann’s personal ob¬
servations :

“Mr. C. B. Odell, at his hotel on Front Street, is the
happy owner of a fly exterminator, which, for thor¬
ough work, is unsurpassed by anything we have ever
seen. In one of the windows facing Front Street,
where samples of his wares are occasionally shown, a
rat began several weeks since to make sly visits, and
secured a good meal as often as he came by catching
the many flies which are on the panes of glass. He
grew very expert at it, and though at first quite shy,
soon became emboldened when he found he was not
disturbed in his foraging expeditions, and would pur¬
sue his business not in the least intimidated by spec¬
tators, who were only separated from him by a pane
of glass. He obtained entrance to this window by

NATURAL ENEMIES

gnawing a hole through the wooden base, coming from
below. For weeks he has pursued his fly-hunting busi¬
ness undisturbed.

“On Sunday one of the waiters discovered him in
the act of introducing a friend or member of his family
to his foraging ground. The newcomer was very shy,
and only put his head through, while the old habitue
tried to coax him in the window. He would catch a
fly, gravely hand it to his friend, who would as gravely
eat it, and look for more. By degrees he lost a little
of his fear, walked out, and soon became an expert in
the new business. Either one or both may be seen al¬
most any day by any one who may be patient enough to
wait for their appearance a short time. It is certainly
a very novel sight, and well worth a few minutes’ time
to see. — Newburgh Telegraph ”

Mr. Nat. C. Dearborn, of the Biological Survey of
the U. S. Department of Agriculture, states that he has
frequently seen evidence of the destruction of adult
flies by mice on window-sills, the work having been
done at night.

Ill

THE CARRIAGE OF DISEASE BY FLIES

IT would probably be impossible to trace the first sug¬
gestion of the carriage of disease by flies. They
have been conspicuously connected with accounts of
epidemics of one kind or another for hundreds of years,
and before discussing some of the specific diseases
which they are thought to carry some attention may be
given to some of these early suggestions. It should
be pointed out before taking up this subject, however,
that the house fly is simply a carrier of disease germs,
and that it differs in its relation to disease from the
malarial mosquitoes, which are the necessary secondary
hosts of the causative organisms of malaria, in that
only in mosquitoes of the genus Anopheles can the
germs complete their life round and develop sexual
forms.

In this they differ also from the yellow fever mos¬
quito ( Aedes calopus), since, although the causative
organism of yellow fever has not yet been discovered,
close analogy shows that it must be a protozoan de¬
pendent for its full development upon a lodgment in
the stomach of the mosquito in question. It differs
in the same way from the bedbug, which has more re¬
cently been seen to be probably the necessary secondary
host of the causative organism of kala azar. The house
fly simply carries the germs of disease, either on its

ioo

CARRIAGE OF DISEASE

101

legs or in its alimentary canal, just as these germs could
be carried in any other way — by water, by shell-fish, by
unwashed and uncooked vegetables grown in land
dressed with night-soil, on dust particles, or by personal
contact.

Most of the writers who have collected data on this
subject refer to the statement by Sydenham, who is
said to have lived between 1624 and 1689, to the effect
that if house flies are abundant in the summer the
autumn will be unhealthy, and very many people hold
that view; but Sydenham was by no means the first
to believe that the house fly is insanitary. There are
many references to this insect in the Hebrew Scrip¬
tures, and the sanitary regulations of the camps of the
children of Israel in their march through the wilder¬
ness refer to flies in terms which indicate that the au¬
thors of the regulations were almost as well posted on
the subject of the danger of flies as the Japanese sur¬
geons in the recent Japanese-Russian War. I have
often wondered whether the twenty-fourth verse of
the eighth chapter of Exodus, “and there came a griev¬
ous swarm of flies into the house of Pharaoh, and into
his servants’ houses, and into all the land of Egypt:
the land was corrupted by reason of the swarm of
flies,” did not mean that the flies corrupted the land,
and whether there is not something very significant in
the statement that among the plagues that followed
were the murrain of cattle and the death of all the first¬
born of Egypt.

Several of the great surgeons of the seventeenth and

102 THE HOUSE FLY— DISEASE CARRIER

eighteenth centuries have referred to this possibility,
and our own Leidy, in 1871, said that he believed that
house flies were responsible for the spread of hospital
gangrene during the Civil War. In that same year
(1871) Lord Avebury (then Sir John Lubbock), in
an article in the London Lancet, mentioned the fact
that flies alight on decomposing matter and carry se¬
cretions with them. He uses this significant sentence :
“Far from looking upon them as dipterous angels danc¬
ing attendance on Hygeia, regard them rather in the
light of winged sponges spreading hither and thither
to carry out the foul behests of Contagion.”

Exact Experiments

There was, for a long time, no experimental proof of
such carriage. There have been outbreaks of disease
and single cases of disease where the carriage of the
causative organism by house flies seemed to be the best
explanation. Actual experimental proof satisfactory to
the laboratory worker, however, has been of recent ac¬
quirement, and it will be well before entering upon the
subject of specific diseases to mention some of this work.

One of the latest and one of the most careful series
of laboratory observations has been made by Doctor
Graham-Smith (1910). His experiments covered a
wide range and seem to have been carried out with the
utmost pains. The most satisfactory method of con¬
veying his results is to give his conclusions in his own
words :

“Infection experiments show that non-spore-bearing

CARRIAGE OF DISEASE

103

pathogenic bacteria do not usually suryive more than
a few hours (five to eighteen) on the legs and wings.
Nevertheless, flies allowed to walk over sterile agar
plates may cause infection for several days. This
seems to be due to the fact that they frequently attempt
to suck the surface, and in so doing infect it with fluid
regurgitated from the crop. Within the crop non-
spore-bearing bacteria frequently survive for several
days, and they usually survive even longer in the
intestine. No evidence of multiplication in either df
these situations has been obtained. The feces deposited
by such flies often contain the organisms in consider¬
able numbers for at least two days, and are frequently
infective for much longer periods. Anthrax spores
survived for many days on the exterior and in the ali¬
mentary canal.

“Experiments with B. prodigiosns show that flies
may infect sugar forty-eight hours after feeding on
infected material, and that clean flies may infect them¬
selves by feeding on the recent deposits of infected
flies. In the few experiments which were tried, milk
and meat were not infected. Flies fed on anthrax
spores did, however, infect the syrup which' was given
to them as food.

“In the experiments which have been described, very
gross infection was produced in most cases by emul¬
sions of pure cultures. It is improbable, however, that
under natural conditions flies would often have the op¬
portunity of feeding on materials which contain path¬
ogenic organisms practically in pure culture. The ef-

104 THE HOUSE FLY— DISEASE CARRIER

fects of contaminating with non-pathogenic and putre¬
factive bacteria have as yet not been studied, and the
effects of season, temperature, atmospheric conditions,
different diets, irregular and scanty feeding, and other
disturbing factors have not received sufficient attention.

“Consequently it would be premature to conclude
that the experiments and observations described in this
paper do more than indicate that, under exceptionally
favorable conditions, certain bacteria can be recovered
from the contents of the alimentary canal and fecal
deposits of infected flies for several days after infec¬
tion; and that these flies are capable of infecting cer¬
tain materials on which they feed for several days. The
experiments with tubercular sputum and anthracic
blood alone afford evidence as to the duration of life
in the contents of the alimentary canal of pathogenic
bacteria taken up under natural conditions.

“That flies sometimes do become grossly infected
under natural conditions is shown by the fact that in
a few instances pathogenic bacteria have been isolated
from naturally infected flies. Simmons (1892) iso¬
lated cholera vibrios from flies which were captured
in a post-mortem room in which the bodies of persons
dead of cholera were lying. Tsuzuki (1904) was able
to cultivate the same organism from flies captured in
a cholera house, and Tizzoni and Cattani (1886) ob¬
tained cultures from flies caught in cholera wards.
Hamilton (11. 1903) and Ficker (1902) isolated B.
typhosus from flies caught in houses in which persons
were lying ill of typhoid fever, and Faichnie ( 1909)

CARRIAGE OF DISEASE

105

obtained B. typhosus from a number of flies caught in
various places where typhoid fever prevailed. He
further showed that B. typhosus or B. paratyphosus
(A) could be cultivated for several days from the in¬
testines of perfect insects which emerged from larvae
fed on feces containing these organisms.

“Several observers [Celli ( 1888), Hayward (1904),
Lord (1904) and Buchanan (1907)] have shown that
the feces of flies which have fed on tubercular sputa
contain virulent tubercle bacilli. Buchanan (1907)
demonstrated that flies which had walked over nat¬
urally infected anthracic meat were capable of infect¬
ing agar plates. Yersin (1894) in Hong- Kong ob¬
served many dead flies lying about in his laboratory
where he made autopsies on plague animals. He dem¬
onstrated by inoculation into animals that a dead fly
contained virulent plague bacilli.

“Finally the experiments of Macrae ( 1894) at the
Gaja jail show that exposed milk may become infected
by the agency of flies.

“Even these observations only prove that cultures
of pathogenic organisms may occasionally be obtained
from naturally infected flies, and they do not afford
conclusive evidence that such flies are a frequent source
of disease in man by infecting food materials. Though
many of the observations cited by Nuttall and Jepson
seem to indicate that flies have frequently acted as car¬
riers of disease, it has only once (Macrae) been dem¬
onstrated that food has actually been grossly contam¬
inated by them.”

106 THE HOUSE FLY— DISEASE CARRIER

Early laboratory experimental work in the labora¬
tory was carried on in this country by Dr. Jocelyn Man¬
ning (1902) of Eau Claire, Wis., who succeeded in
making pure cultures from infected flies of the fol¬
lowing bacteria : Bacillus pyocyaneus, Staphyllococcus
pyogenes aureus , Bacillus typhi abdominalis and B.
coli communis .

The care with which Doctor Graham-Smith sum¬
marizes the results of his experiments and the similar
observations of previous workers, in order to preserve
an exactly judicial and thoroughly scientific frame of
mind, is worthy of all praise, but the accumulation of
evidence which has been gathered and which will be
displayed in our consideration of the different diseases
is so overwhelming, both from the standpoint of exact
observation and of sound inference, that surely every
possible effort to do away with Mnsca domestica is am¬
ply justified on the disease-bearing ground.

Other laboratory observations have been made by
trained bacteriologists and mycologists in the direction
of the carriage of micro-organisms by flies. One inter¬
esting series, to which the writer has referred else¬
where, was published by W. N. Esten and C. J. Mason
(1908). The following table and the two subsequent
paragraphs are quoted from their bulletin:

Table of Sources of Bacteria from Flies.

CARRIAGE OF DISEASE

107

108 THE HOUSE FLY— DISEASE CARRIER

“From the above table the bacterial population of
414 flies is pretty well represented. The domestic fly
is passing from a disgusting nuisance and troublesome
pest to a reputation of being a dangerous enemy to hu¬
man health. A species of mosquito has been demon¬
strated to be the cause of the spread of malaria. An¬
other kind of mosquito is the cause of yellow fever,
and now the house fly is considered an agency in the
distribution of typhoid fever, summer complaint, chol¬
era infantum, etc.

“The numbers of bacteria on a single fly may range
all the way from 550 to 6,600,000. Early in the fly sea¬
son the numbers of bacteria on flies are comparatively
small, while later the numbers are comparatively very
large. The place where flies live also determines
largely the numbers that they carry. The average for
the 414 flies was about 1,250,000 bacteria on each. It
hardly seems possible for so small a bit of life to carry
so large a number of organisms. The method of the
experiment was to catch the flies from the several
sources by means of a sterile fly net, introduce them into
a sterile bottle, and pour into the bottle a known quan¬
tity of sterilized water, then shake the bottle to wash
the bacteria from their bodies, to stimulate the number
of organisms that would come from a fly falling into a
lot of milk.

“In experiments ‘d,’ ‘e,’ and T the bacteria were
analyzed into four groups. The objectionable class,
coli-cero genes type, was two and one-half times as
abundant as the favorable acid type. If these flies

Fig. 18. — Colonies of bacteria on a sterilized plate, arising from fly
tracks. (From photograph by William Lyman Underwood.)

CARRIAGE OF DISEASE

109

stayed in the pig-pen vicinity, there would be less ob¬
jection to the flies and the kinds of organisms they
carry, but the fly is a migratory insect and it visits
everything ‘under the sun.’ It is almost impossible to
keep it out of our kitchens, dining-rooms, cow stables,
and milk rooms. The only remedy for this rather
serious condition of things is, remove the pig-pen as
far as possible from the dairy and dwelling house. Ex¬
treme care should be taken in keeping flies out of the
cow stables, milk rooms and dwellings. Flies walking
over our food are the cause of one of the worst con¬
taminations that could occur from the standpoint of
cleanliness and the danger of distributing disease
germs.”

A great deal of work of this general nature in re¬
gard to the carriage of micro-organisms by flies with¬
out specific reference as to the character of the organ¬
isms has been done and the results have been published
here and there. The illustration shown at Fig. 18 is
an early one made from a photograph taken by Wil¬
liam Lyman Underwood of a gelatin plate over which a
fly, captured by chance in a room, was allowed to walk.
On each spot which the fly’s feet touched there grew a
colony of bacteria.

Cobb ( 1906) studied the spores of a sugar cane fun¬
gus left by the feet of a fly which had been feeding
upon the fungus on the sides of a glass vessel. The
spores from five of the tracks on the glass were cal¬
culated and the number per track was found to be
860,000. A second calculation gave 700,000 per foot-

110 THE HOUSE FLY— DISEASE CARRIER

print. Germination experiments showed that spores
carried about in this way, if deposited in suitable loca¬
tions, will germinate, and therefore the fungus may
sometimes be spread in this way.

Other work of this kind, but devoted to specific dis¬
ease germs, will be mentioned under the different dis¬
eases in the following pages. But in order perhaps to
remove at once the impression which may be left by the
cautious words of Doctor Graham-Smith, we may read
the conclusions of Professor Nuttall and Mr. Jepson,
of Cambridge University, England (1909), both in¬
vestigators of the highest type, after their critical exam¬
ination of the accounts of experiments made in this
direction :

“Although there were some who at a very early date
looked upon the common house fly with suspicion, it is
only of recent years that ‘flies’ have come to be regarded
as a serious factor in the spread of infective diseases.

“The evidence we have sifted and ordered in these
pages is obviously very unequal in value, the most im¬
portant relating to cholera and typhoid fever — in both
cases the evidence incriminating house flies, of which
Musca dome stic a may be regarded as the type, appears
to be quite conclusive, and these agents will have to
henceforth receive the serious attention they demand
at the hands of sanitary authorities. From a practical
point of view, it scarcely appears necessary to charge
the house fly with more misdoings, bacteriological tests
having shown that they are capable of taking up a
number of different pathogenic germs and of transport-

CARRIAGE OF DISEASE

111

ing them from one place to another. We regard it as
certain that they convey cholera and typhoid fever,
and we look forward with confidence to the complete
demonstration that they convey the causative agents
of infantile diarrhea and of dysentery, always remem¬
bering that there are other vehicles, water, milk, etc., by
which these diseases may be communicated.

“It should be remembered that a fly may cause rela¬
tively gross infection of any food upon which it alights
after having fed upon infective substances, be they
typhoid, cholera, or diarrhea stools. Not only is its
exterior contaminated, but its intestine is charged with
infective material in concentrated form which may be
discharged undigested upon fresh food which it seeks.
Consequently, the excrement voided by a single fly may
contain a greater quantity of the infective agents than,
for instance, a sample of infected water. In potential
possibilities the droppings of one fly may, in certain
circumstances, weigh in the balance as against buckets
of water or of milk !”

Surely no more authoritative or complete statement
than this could be made by scientific men.

The whole literature of the subject of the transfer of
disease by insects and like creatures was first compre¬
hensively studied and collected by' Dr. George H. F.
Nuttall and published in 1900 in an admirable and ex¬
tended paper in the Johns Hopkins Hospital Reports,
entitled “On the Role of Insects, Arachnids and Myria¬
pods-, as Carriers in the Spread of Bacterial and Para¬
sitic Diseases of Man and Animals. A Critical and

112 THE HOUSE FLY— DISEASE CARRIER

Historical Study.” This paper has been of the greatest
use to physicians and to naturalists, and few general
articles on this subject have been written in the last
ten years without the freest use of the data collected by
Doctor Nuttall. In many cases writers have gone to
original sources, but it is safe to say that for the most
part they have learned of these original sources through
Doctor Nuttall’s bibliography. The writer, among
others, in the numerous papers he has published on this
general subject during the years since 1900, has had
constant occasion to refer to this paper, and gladly ex¬
presses his obligations to its author.

More recently ( 1909), Doctor Nuttall (now of Cam¬
bridge University, England) in collaboration with Mr.
Jepson, of Cambridge, has published a series of ab¬
stracts of literature and a bibliography relating solely
to the carriage of disease by the house fly and allied
non-biting flies, which has been freely used in this book
and will be later referred to simply by references to
Nuttall and Jepson.

Typhoid or Enteric Fever

Typhoid fever is a disease which has been differen¬
tiated from other fevers and especially from typhus
within the last eighty years. It is a disease of civiliza¬
tion, or rather, as Doctor Sedgwick has beautifully
expressed it, “a disease of defective civilization.” It
depends upon defective sanitation, and surely, as Sedg¬
wick says, defective sanitation means defective civiliza¬
tion.

CARRIAGE OF DISEASE

113

The true cause of the disease was not known until
1880, when it was discovered by Eberth, and it was
not long before it was isolated and studied in pure cul¬
ture. Technically this organism is known as Bacillus
typhosus. It is isolated from persons who are sick with
typhoid fever or who have been sick from it, and only
from such persons. The disease which it causes is an
intestinal disease, and through the multiplication of
the bacilli in the body, and with a poisonous substance
which it produces, conditions are caused which give
rise to the characteristic symptoms of the disease.

Ulcerations of the intestines and enlargements of the
spleen and mesenteric glands follow, and the bacilli
frequently invade other portions of the body, such as
the kidney, the liver, spinal column, the lungs, and
they have even been found in the brain. They are
given off from the body in the excrement and in the
urine. The characteristic symptoms of the fever are
an increasing temperature which fluctuates rather regu¬
larly, and rose rash over the abdomen, diarrhea or
constipation, distention of the intestines, emaciation,
and sometimes intestinal hemorrhages and delirium.
The average period is four or five weeks, and this
is followed by a long period of convalescence. Re¬
lapses are frequent and are dangerous and may cause
death. Fatal cases before a relapse usually terminate
during the fourth or fifth week.

Typhoid is thus a parasitic disease, and its onset
depends upon the introduction into the system of the
typhoid bacillus. Its presence in the human body is

114 THE HOUSE FLY— DISEASE CARRIER

brought about by eating or drinking something carry¬
ing the bacilli. Water, milk, oysters, raw vegetables
may and do carry them. They may be carried to food
in other ways : by contact ; by dust ; and by certain
household insects, such as cockroaches, household ants,
and undoubtedly frequently by the typhoid fly, the
most numerous of all household insects, and the one
which breeds in substances which may be normally
swarming with typhoid bacilli.

Suspicions of the Carriage of Typhoid by Flies

Probably the first American to point out the prob¬
able transference of typhoid germs from box privies
to food supplies by the agency of flies was Dr. George
M. Kober, of Washington, D. C. In “Report on the
Prevalence of Typhoid Fever in the District of Colum¬
bia,” published in 1895, under the caption of “Chan¬
nels of Invasion and Mode of Dissemination,” Doctor
Kober wrote:

“The agency of flies and other insects in carrying
the germs from box privies and other receptacles for
typhoid stools to the food supply cannot be ignored.”
On the following page he gave an account of certain
cases on the Ivy City and Bladensburg Road, in the
course of which he used the following words, “There
is abundant evidence of unlawful surface pollution,
* * * and as the germs find a suitable soil in such

surroundings, it is possible that the flies which abound
wherever surface pollution exists may carry the germs
into the houses and contaminate the food. * * *

CARRIAGE OF DISEASE

115

There was nothing in common in the milk supply of
the different houses, and as there was no well liable
to contamination from the first source, it is not im¬
probable that the infection was conveyed in the man¬
ner indicated.”

Writing of nine cases occurring in a certain locality
in Washington, he says, “There was nothing in com¬
mon in the milk supply, and the fact that the cases oc¬
curred at considerable intervals indicates with more
or less certainty that the first case was a focus of in¬
fection; but how the germs were carried, unless by
flies, or through the air, is a matter impossible to de¬
termine.” Later, in writing of methods foi1 the dis¬
posal of human excreta, he says, “These boxes, even
if there are no wells, are still a source of danger in
so far as they favor the transmission of germs by
means of infected flies.” In his conclusion, he writes,
“A large percentage of the cases occurred in houses
supplied with box privies which, apart from being an
important cause of soil pollution, are believed to be
otherwise instrumental in the dissemination of germs,
chiefly through the agency of flies

The attention of all interested was riveted to the
question of the agency of flies by the results of the
investigations carried on during the Spanish- American
War in 1898. In his first circular of directions to army
surgeons, the Surgeon-General of the Army, Dr.
George M. Sternberg, gave explicit directions regard¬
ing sinks, which, if followed carefully, would have pre¬
vented the spread of typhoid by flies, and he definitely

116 THE HOUSE FLY— DISEASE CARRIER

stated that no doubt typhoid fever and camp diarrhea
are frequently communicated to soldiers in camp
through the agency of flies which swarm about fecal
matter and directly convey infectious material attached
to their feet or contained in their excreta to the food
which is exposed while being prepared at the common
kitchen or while being served in the mess tent. These
directions from the Surgeon-General, however, were
ignored, with the result that the world got its first
large-scale and convincing demonstration of the car¬
riage of typhoid by flies, although the laboratory
method was not used in this demonstration.

Inferential Proof

One of the volunteer surgeons, Dr. M. A. Veeder,
who had already been interested in the subject, wrote
articles before the close of 1898 calling attention to
observations upon flies traveling back and forth between
the latrines and the cooking tents in concentration
camps in the Southern United States, and concluded
that the conveyance of typhoid infection in the man¬
ner indicated “is the chief factor in decimating the
army.” Before Veeder’s articles had been published,
typhoid was rampant in many of the concentration
camps, and an army typhoid commission was appointed
in August of that year, consisting of Drs. Walter Reed,
U. S. A. ; Victor M. Vaughan, U. S. V. ; and E. O.
Shakespeare, U. S. V. These men were all of high
scientific standing, the chairman being the now fa¬
mous discoverer of the true etiology of yellow fever.

CARRIAGE OF DISEASE

117

The investigation was thorough, and at the annual
meeting of the American Medical Association in June,
1900, Doctor Vaughan presented a paper entitled “Con¬
clusions Reached after a Study of Typhoid Fever
among American Soldiers in 1898.” This report com¬
prised fifty-three categorical conclusions. The one re¬
lating to flies was as follows :

“27. Flies undoubtedly served as carriers of the in¬
fection.

“My reasons for believing that flies were active in
the dissemination of typhoid may be stated as fol¬
lows :

“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 con¬
tents 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 ty¬
phoid 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 mechan¬
ically transported. In the second place, it is possible
that the typhoid bacillus may be carried in the digestive

118 THE HOUSE FLY— DISEASE CARRIER

organs of the fly and may be deposited with its excre¬
ment.”

There were many other important conclusions which
bear upon the fly question. For example, it was shown
that every regiment in the United States service in
1898 developed typhoid fever, nearly all of them within
eight weeks after assembling in camps. It not only
appeared in every regiment in the service, but it be¬
came epidemic both in small encampments of not more
than one regiment and in the larger ones consisting of
one or more corps. All encampments located in the
Northern as well as in the Southern States exhibited
typhoid in epidemic form. The miasmatic theory of
the origin of typhoid fever and the pythogenic theory*
were not supported by the investigations of the com¬
mission, but the doctrine of the specific origin of fever
was confirmed. The conclusion was reached that the fe¬
ver is disseminated by the transference of the excretions
of an infected individual to the alimentary canals of
others and that a man infected with typhoid fever may
scatter the infection through every latrine or regiment
before the disease is recognized in himself, while germs
may be found in the excrement for a long time after
the apparent complete recovery of the patient. Infected
water was not an important factor in the spread of
typhoid in the national encampments of 1898, but about

*This theory is founded upon the belief that the colon germ
may undergo a ripening process by means of which its virulence
is so increased and altered that it may be converted into the
typhoid bacillus or at least may become the active agent in the
causation of typhoid fever.

CARRIAGE OF DISEASE

119

one-fifth of the soldiers in the national encampments
in the United States during that summer developed
this disease, while more than eighty per cent, of the
total deaths were caused by typhoid.

About the same time that Doctor Vaughan’s report
was presented, Dr. R. H. Quill, in a “Report on an
outbreak of Enteric Fever at Diyatalawa Camp, Ceylon,
among the Second King’s Royal Rifles during the
period they acted as guard over the Boer prisoners of
the war,” stated that “during the whole period that
enteric fever was rife in the Boer camp, flies in that
camp amounted almost to a plague, the military camp
being similarly infested, though to a lesser extent.”

During the Boer War again and again the connec¬
tion between flies and enteric fever was noted. Nut-
tall and Jepson have collected some significant quota¬
tions from different writers of that period. These may
be quoted as follows:

“Tooth and Calverley (1901, p. 73), writing of ty¬
phoid in camps during the South African War, state
that ‘In a tent full of men, all apparently equally ill,
one may almost pick out the enteric cases by the masses
of flies that they attract. This was very noticeable at
Modder River, for at that time there wrere in many
tents men with severe sunstroke who resembled in some
ways enteric patients, and it was remarkable to see how
the flies passed over them to hover round and settle on
the enterics. The moment an enteric patient put out
his tongue, one or more flies would settle on it.’

“The authors further state that : ‘At Bloemfontein

120 THE HOUSE FLY— DISEASE CARRIER

the flies were a perfect pest ; they were everywhere, and
in and on every article of food. It is impossible not to
regard them as important factors in the dissemination
of enteric fever. Our opinion is further strengthened
by the fact that enteric fever in South Africa practi¬
cally ceases every year with the cold weather, and this
was the case at Bloemfontein. For though the days
after io a.m. were as an English summer day, and the
temperature in our tents was rarely below 70° and
often about 8o° F., the nights were very cold, and
often frosty, and with the cold nights the flies disap¬
peared. It seemed to us that the cold weather reduced
the number of enteric cases by killing these pests.’

“Smith (1903), also writing of South Africa, states
that a neglected trench ‘becomes an open privy with an
infected surface soil around it; the flies browse in it
in the daytime and occupy the men’s tents at night.
On visiting a deserted camp during the recent campaign
it was common to find half a dozen or so open latrines
containing a fetid mass of excreta and maggots; this
because the responsible persons so often failed to com¬
ply with the regulations for encampments by filling in
latrines on the departure of the troops.’

“Austen ( 1904, p. 656) vividly recalls ‘a latrine in
a certain standing camp in South Africa during the
late war, in which the conditions as regards flies were
precisely as described by Major Smith. It is only fair
to say that the ground was extremely hard and stony,
so that very little soil was available for covering up
the contents of the trench. On visiting the latrine

CARRIAGE OF DISEASE

121

after it had been left undisturbed for a short time, a
buzzing swarm of flies would suddenly arise from it
with a noise faintly suggestive of the bursting of a
percussion shrapnel shell. The latrine was certainly
not more than one hundred yards from the nearest
tents, if so much, and, at meal times, men’s mess tins,
etc., were always invaded by flies. A tin of jam in¬
cautiously left open for a few minutes became a seeth¬
ing mass of flies (chiefly Pycnosoma chloropyga
Wied.), completely covering the contents.’

“F. Smith (1903, p. 331) refers to his experience in
the South African War in seeing flies go from bed-
pans to milk, etc., and discusses in detail methods of
sewage disposal in warm countries.”

Still later observations of a similar character have
been made, not in war times but in times of peace, at
army stations and encampments during practice maneu¬
vers. A report by Maj. C. F. Wanhill on typhoid con¬
ditions in Bermuda, for example, shows that from 1893
to 1902 Bermuda had the highest enteric fever rate
among the troops of any command occupied by British
troops. Major Wanhill was placed in charge in 1904,
and in two years almost wiped the disease out. He
considered that carriage of the germs by flies was the
most important mode of transfer.

With regard to the British army stations in India,
the Journal of the Royal Army Medical Corps for the
past six years has contained many suggestive and im¬
portant articles written by different members of the
Royal Army Medical Corps which emphasize to a strik-

122 THE HOUSE FLY— DISEASE CARRIER

ing degree the attention which is now being paid to.
the house fly and its near relative Musca entconiata.
More or less definite proof of the connection between
flies and enteric fever is given again and again and
great attention has been paid to the question of latrines.
For example, Lieut. Col. F. W. C. Jones (1907) uses
the following phraseology: “Believing as we do that
flies are the chief carriers of enteric fever in India, any
plan which gets rid of them is worthy of considera¬
tion.” And then the author proceeds to discuss the
relative merits of incineration of excreta and other
plans. Of course the officers of the army have con¬
trol over their camps, but in India great difficulty has
been experienced in enforcing the proper views upon
high-caste natives.

Colonel Jones, in the article just cited, found a cer¬
tain line of reasoning very useful, not only with high-
caste native officers but with men on maneuvers. This
consisted in an explanation of the meaning of the word
kakophagy, which, being translated from the Greek,
means excrement-eating. Colonel Jones writes. “I pre¬
sume no one wishes to be a kakophagist ; yet we are so
in spite of ourselves, if flies bred in filth pits alight on
our food just before we eat it.” The high-caste officers
at first looked upon sanitary measures as being only
meant to worry them, but Colonel Jones got several of
them together and to the best of his ability explained
that men who took no precautions in camps to prevent
the breeding of flies must of necessity be kakophagists.
He found that this appealed to them most strongly, and

CARRIAGE OF DISEASE

123

he had no further trouble. Does it not at once occur
to the reader that to almost every American this ob¬
jectionable term might with justice be applied?

Any quantity of inferential proof continues to ac¬
cumulate. The Merchants’ Association of New York
has accumulated the opinions of many health officers
and physicians as well as of entomologists and has pub¬
lished them in convincing form. At the December,
1910, meeting of the American Association for the Ad¬
vancement of Science, at Minneapolis, Prof. F. L.
Washburn gave a lecture entitled “The Typhoid Fly
on the Minnesota Iron Range,” in which he gave the
results of a careful study of the conditions in certain
mining towns in that State during the summer of 1910,
in which the conditions were such as to make it
perfectly plain that the main etiological factor in
the typhoid epidemic then existing was Musca domes-
tica.

The length of time that the typhoid bacillus will live
in various substances from which it is likely to be car¬
ried by flies to food substances is important and has
received some consideration. The length of time in
which the bacillus will live in food substances, how¬
ever, is even more deserving of consideration. Milk,
commonly charged with the carriage of typhoid fever,
is hardly of the greatest importance in this connection,
since milk is such a short-lived food substance itself,
although it is often contaminated with typhoid bacilli
through the washing of the vessels which contain it

124 THE HOUSE FLY— DISEASE CARRIER

in contaminated water and by infected flies dropping
into it.

When it comes to butter and cheese, however, we
have long-lived foods, and the possibilities of their con¬
tamination by flies and their subsequent use is of espe¬
cial interest, and more particularly as to the length of
time that they will harbor virulent germs gained in this
way or in any other.

Dr. John R. Mohler, of the Bureau of Animal In¬
dustry of the United States Department of Agriculture,
informs the writer that investigations made in his of¬
fice show that typhoid bacilli will live in butter under
common market conditions for 15 1 days, and still be
able to grow when transferred to suitable conditions.
In milk under market conditions they retain active mo¬
tility for twenty days, after which time there is a lessen¬
ing in numbers until on the forty-third day of the test
they disappear from view. At certain seasons of the
year large numbers of flies collect upon the vats in
which milk and cream are being stored in dairies and
creameries ; many flies fall in, their bodies being
strained out when the cream is sent to the churn. If
any of these flies carry typhoid bacilli these are washed
off by the milk and remain in the butter or cheese made
from it. Thus the eating of butter contaminated in
this way may account for very many cases of typhoid
fever the cause of which cannot otherwise be traced.

CARRIAGE OF DISEASE

125

Exact Proof

From the laboratory point of view, a number of ex¬
act experiments have been made, and we quote the fol¬
lowing paragraphs from Nuttall and Jepson:

“Celli (1888) fed flies with pure cultures of the
Bacillus typhosus and examined their contents and de¬
jections microscopically and culturally. Inoculations
on animals were also made, proving, as he supposed,
that the bacilli which passed through flies were viru¬
lent. (He made similar observations with the Spiril¬
lum Finkler-Prior.)

“As Ficker ( 1903, p. 274) properly points out,
Celli’s statement has less value to-day, since at the time
he carried out his experiments no suitable means ex¬
isted for properly differentiating B. typhosus from
other organisms of similar character.

“Firth and Horrocks (1902) kept M. domestica
(also blue-bottles) in a large box measuring four by
three feet, with one side made of glass. They were
fed on material contaminated with cultures of B.
typhosus. Agar plates, litmus, glucose broth, and a
sheet of clean paper were at the same time exposed in
the box. After a few days the plates and broth were
removed and incubated with a positive result. The
flies’ excreta on the paper yielded B. coli almost in pure
culture. In a second experiment some fresh typhoid
stool to which a typhoid culture had been added was
dusted with earth and served as the infective material ;
colonies of B. typhosus appeared on the plates. In a

126 THE HOUSE FLY— DISEASE CARRIER

third experiment the infected flies were captured and
killed. By means of sterile forceps their heads, wings,
legs, and bodies were separated and respectively placed
in sterile broth. Sub-cultures of the broth all gave a
positive result. The authors conclude that M. domes-
tica can convey B. typhosus from infected sources to
objects upon which they walk, rest, or feed, and that
bacilli adhere to the external parts of flies. ‘It has not
been proved that the enteric bacillus passes through the
digestive tract of the fly.’

“Hamilton (II. 1903) in Chicago, caught eighteen
flies in and about houses and rooms occupied by ty¬
phoid cases, and states that she found B. typhosus in
five of them.

“Ficker (1903) caught flies in a house in Leipzig
where eight cases of typhoid had occurred. He isolated
B. typhosus from the flies. He carried out experiments
with M. domestica kept in ten-liter flasks into which he
introduced some sugar, strips of filter paper, and cul¬
ture of typhoid bacilli in bouillon. This was spread
on the glass and partly absorbed by the filter paper.
After eighteen to twenty-four hours the flies were trans¬
ferred to clean flasks. He found the flies to survive
over four weeks in captivity if protected from the cold
and fed on sugar, bread and water, or milk. He notes
that flies may all die during a cold night, irrespective
of typhoid bacilli being present in their food. The
flies were transferred to clean flasks every two or three
days. The flies to be examined were etherized and
rubbed up in a mortar — the crushed material being

CARRIAGE OF DISEASE

127

used for making the plates on gelatin and special media.
B. typhosus was recovered from the flies twenty-three
days after they had been infected.

“Buchanan (1907) allowed M. domestica to walk
over the surface of a Petri dish smeared with typhoid
dejections. The flies (number?) were immediately
afterwards allowed to walk over the surface of media
in Petri dishes. Naturally, some plates became in¬
fected.

“The evidence regarding the part that flies may play
in the spread of typhoid fever may therefore be ac¬
cepted as quite conclusive. ”

In addition to the experiments by Nuttall and Jep-
son given above should be mentioned the experiments
recorded by Major N. Faichnie ( 1909). Major Faichnie
states that he was recently sent to investigate a small
outbreak of enteric fever at Kamptee, where he was
obliged to suspect flies, after excluding all other causes.
Flies were not over-numerous, but twelve from the
artillery lines were mashed up in sterile salt solution,
and Bacillus typhosus was separated. Twelve flies from
the infantry kitchen were then captured. Each was
transfixed with a sterile needle, passed two or three
times through a flame until the legs and wings were
scorched, and was then put in a normal salt solution
and stirred. After this they were mashed up and B.
typhosus was found. Before mashing it was not found.
The demonstration that the bacillus was present in the
intestines was therefore good. His conclusions are
that while experience seems to show that infection con-

128 THE HOUSE FLY— DISEASE CARRIER

veyecl by flies’ legs is not common in times of peace,
“infection by the excrement of flies bred in infected
material explains many conclusions formerly difficult
to accept.”

Chronic Carriers

It becomes necessary at this stage to discuss the ques¬
tion of persons who become chronic carriers of typhoid
germs, giving them out in their excreta and in their
urine for perhaps many years. The application of this
phenomenon to the fly question will be dealt with later.
It was known in the United States prior to the Span¬
ish- American War that typhoid patients would give out
bacilli in this way before the disease was diagnosed,
and it was also known that some of them would give
out the germs for perhaps several weeks after the fever
abated and the patient was practically cured. And of
course the walking typhoid or “ambulatory enteric”
was known to exist; that is to say, slight cases which
did not bring the patient to bed but during which germs
must have been given off. True chronic carriers were
not known in this country at that time, and the develop¬
ment of this extremely important phase of the typhoid
question has been a recent one. The phenomenon was
known in Germany before it was brought vividly to
the attention of the American people.

The first case here to receive general notice was that
of “Typhoid Mary,” an Irish cook, who was discovered
by Dr. George A. Soper, of New York. She had been
cook with a family on Long Island, and during the
summer of 1906 several cases of typhoid occurred. The

CARRIAGE OF DISEASE

129

‘writer was consulted, and advised that Doctor Soper be
called in to make a thorough investigation. The results
of Doctor Soper’s search were most interesting. Af¬
ter studying every possible source with absolutely nega¬
tive results, the proper examinations were begun, and
it was discovered that Mary, the cook, was a chronic
carrier. Her past history was looked into, and it was
found that for several years there had been typhoid
cases in nearly every family who had engaged her.
She was immediately isolated, and kept in custody for
three years. Then she was released, promising never
again to engage as cook and to report at frequent
intervals. She returned after four months saying that
she could get no work and was placed by the New York
City Department of Health in one of the laundries of
a public institution, where she still remains.

Much space was devoted to accounts of this case in
the daily newspapers and other publications at the time,
and about that time and subsequently many investi¬
gators began to look into the general subject of typhoid
carriers, with remarkable results. For example, a dairy
maid was found at Killworth, England, in 1909,
through the investigations which followed a typhoid
outbreak. It was discovered that she had had the fever
in 1903, and that families with whom she subsequently
lived had typhoid cases. Finally she became attached
to a dairy which furnished milk to an army post, and
when the milk was not boiled many cases of typhoid
resulted.

In another instance an epidemic of typhoid in the

130 THE HOUSE FLY— DISEASE CARRIER

Tenth German Army Corps in the summer of 1909
was traced to a chronic carrier in the case of a woman
who prepared vegetables and who had assisted in the
preparation of vegetable salads. The typhoid bacillus
grows on the surface of potatoes readily, and this ac¬
counted for the outbreak, on the necessary supposition
that the woman was of uncleanly habits. The curious
point in this case was that she had had typhoid thirty-
six years previously for the only time. In the same
summer there was an epidemic of the fever in George¬
town, D. C. This was traced by milk routes to a cer¬
tain milk dealer, who was a woman and who on ex¬
amination was shown to be a chronic carrier.

In the same year, Aldrich, in the Journal of the
Royal Army Medical Corps for September, page 225,
made the generalization that the combined observations
of a large number of investigators in various countries
showed that about three per cent, of the convalescent
typhoid patients become chronic carriers, and of these
eighty per cent, are women. About this time the Ger¬
man Government conducted an anti-typhoid campaign
in Southwest Germany, and in his report Klinger
/ showed that 400 chronic carriers were found and that
there were probably others.

Earlier than this, Dr. W. G. Savage (1907) made
three points of interest in this connection : ( 1 ) Ty¬
phoid bacilli are frequently excreted in the urine in
about twenty per cent of the cases, but the obvious
practical measures resulting from this knowledge are
not habitually taken. (2) Typhoid bacilli may persist

CARRIAGE OF DISEASE

131

in the body and be found in the feces and gall blad¬
der long after all clinical symptoms have ceased ; it
appears that women form a large percentage of chronic
bacilli carriers; sixteen out of twenty-two cases (Lutz)
and nine out of twelve cases (Klinger). (3) Typhoid
bacilli may be found in the excreta of healthy persons
who have apparently never suffered from typhoid
fever ; they have been in contact with cases of typhoid
and are analogous to the contact cases of diphtheria
outbreaks.

Nature, in a review of scientific memoirs by officers
of the Medical and Sanitary Departments of the Gov¬
ernment in India, No. 32, Calcutta, 1908 (Review, Na¬
ture, November 5, 1908, p. 21), shows, as a result of
this Indian work, that the typhoid bacillus continues
to be excreted for long periods in the urine and feces
of a certain percentage of patients convalescent from
enteric fever, the number in the urine being very large
and the excretion being markedly intermittent. The
general conclusion arrived at was that the problem of
the prevention of enteric fever among the British troops
in India is the detection and isolation of the individual
harboring the Bacillus typhosus.

As a matter of course, the typhoid patient himself
is a much more frequent cause of infection than the
healthy typhoid carrier. Klinger, in the report of the
anti-typhoid campaign in Southwest Germany, pre¬
viously referred to, found that the typhoid patient was
the source of infection in 1,272 cases and the healthy
typhoid carrier in 125 cases. He concluded therefore

132 THE HOUSE FLY— DISEASE CARRIER

that typhoid patients should be considered the chief
source and that this was due to their being not only
more numerous than the carriers, but also to the fact
that the germs passed by them are usually more dan¬
gerous. On the other hand, every infection by a ty¬
phoid carrier may be the first in a long series of cases ;
in fact, he may be responsible for a whole epidemic.
His importance cannot be over-estimated. As Klinger
says, “He is an important factor, and typhoid houses
and typhoid areas seem to be his work.”

In an article in the Boston Medical and Surgical
Journal* we find the following very interesting state¬
ments and reports of cases of this sort, that mentioned
in the final paragraph evidently being Typhoid Mary :

“It is asserted by Kutscher that, in Southwestern
Germany, direct contact is a more important factor in
the spread of typhoid fever than polluted water, and
that about four per cent, of typhoid patients become
chronic carriers of the specific bacilli, which they ex¬
crete in both urine and feces, sometimes for long peri¬
ods. Doerr, for example, cites cases reported by
Drober and Hunner, in which the bacilli were isolated
from the gall bladder seventeen and twenty years after
recovery, and Lentz asserts that if after ten weeks from
convalescence the excretion of the bacilli has not ceased,
it will most likely continue permanently and uninter¬
ruptedly, in spite of medication. He cites a number of
cases in which, after ten, thirty, and even forty-two

*The exact reference to this important article has been lost and
cannot be found.

CARRIAGE OF DISEASE

133

years after recovery, the excretion continued. Levy
and Kayser report that in the autumn ol 1905 a num¬
ber of cases of typhoid fever occurred in an insane
asylum, in which two years previously an inmate had
had the disease and had recovered. On the appear¬
ance of these later cases, this person was examined and
was found to be excreting the bacilli in her feces. Fur¬
ther examinations were made at intervals of several
weeks, and the bacilli were found ten times. In Oc¬
tober, 1906, she died of a typhoid bacillary septicemia,
due to auto-infection from the gall bladder; and on
autopsy the bacilli were isolated from the spleen, liver,
bile, wall of the gall bladder and from the interior of
a large gall-stone.

“A somewhat similar case is reported by Nieter and
Liefmann, also from an insane asylum in which the
disease had been endemic for many months. A patient
dead of chronic dysentery was examined and typhoid
bacilli were found in the intestines and in pure culture
in the gall bladder, in which were gall-stones. Among
250 inmates were found seven typhoid carriers.

“Klinger found, among 1,700 persons, twenty-three
typhoid carriers, ranging in age from eighteen months
to sixty years, eleven of whom had no typhoid history.
Of 842 convalescents from the disease, sixty-three, or
thirteen and one-tenth per cent, were found to be excret¬
ing the bacilli, and eight were still doing so six weeks
after recovery.

“Kayser, tracing outbreaks to their sources, found
a boy of twelve years, a member of a milkman’s fam-

134 THE HOUSE FLY— DISEASE CARRIER

ily, to be a chronic carrier and the probable source of
infection in a number of cases. Another outbreak in
which seventeen persons were seized (two deaths) was
traced to a woman who had no typhoid history but
was excreting the specific bacilli. She was employed
in the dairy from which the persons seized had obtained
their milk. Of 260 cases of typhoid fever investigated,
sixty were traced to infected milk. Among the sixty
victims were thirty maids and kitchen girls, twelve
bakers and forty-four persons engaged more or less in
kitchen work. In all, twenty-eight cases were traced
directly to apparently healthy typhoid carriers.

“Minelli examined 250 prisoners who had not been
in contact with typhoid cases, and found but one who
had the specific organism constantly in the feces. The
agglutinative test was positive.

“Etienne and Thiry report the case of a man, sixty-
four years of age, who, after four years in a hospital,
under treatment for tabes and hemiplegia, had two at¬
tacks of jaundice, and on examination was found to be
excreting typhoid bacilli in the feces.

“A series of twenty-six cases of the disease in fifteen
families of a village in Lorraine is described by Seige,
who states that diligent investigation by the district
physician, the village authorities and the Bacteriological
Institute of Saarlouis placed the responsibility upon a
woman who was a chronic typhoid carrier.

“An interesting case of infection from direct contact
is reported by Dr. H. MacKenzie and by Mr. W. H.
Battle. More than two years after a severe attack of

CARRIAGE OF DISEASE

135

typhoid fever, a man had an attack of femoral osteo¬
myelitis, caused by B. typhosus. After operation the
patient was discharged, but some time afterwards a
sinus formed, the purulent discharge from which con¬
tained typhoid bacilli. The patient’s wife had not been
in contact with any other case, but frequently removed
and burned the dressings. After a time she fell sick
with typhoid fever, and died.

“In a letter to the writer, under date of April 3, 1907,
in response to a request for information concerning a
woman described in the press as a ‘typhoid factory’ and
held under detention by the Department of Health of
the city of New York, Dr. Walter Bensel says : ‘The
woman of whom you write has given a history of a
probable mild attack of typhoid fever about six years
ago. Since that time there have been undoubtedly
twenty-eight cases of typhoid fever in the families in
which she worked. The number of cases occurring
in a family within a few weeks of her advent varied
from one or two up to six out of seven members. The
evidence seemed so strong that she was a carrier of
typhoid fever that she was removed to Reception Hos¬
pital by force. Examinations of her feces and urine
were made, and the typhoid bacilli found in her feces
confirmed positively our suspicions with regard to the
possibility of her conveying typhoid fever.’ ”

Maj. J. C. Morgan and Capt. D. Harvey, Royal
Army Medical Corps ( 1909), give an account of inves¬
tigations which they had made on the viability of the
typhoid bacillus as excreted under natural conditions

136 THE HOUSE FLY— DISEASE CARRIER

by the chronic carrier. As it happens, they had several
cases of chronic carriers under observation. In their
first experiment, typhoid bacilli were recovered from
polluted soil six hours after pollution, but thirty hours
after none could be recovered. In a second experiment,
bacilli were recovered five and one-half hours from
soil pollution. In a third experiment, bacilli were re¬
covered five hours after pollution, and again thirty
hours after pollution of the soil ; none later. In a
fourth experiment, bacilli were recovered twenty-four
hours after contamination.

The sixth and seventh experiments were made with
toweling, to indicate the viability of the typhoid bacillus
on cotton fabrics. A piece of toweling was soaked in a
sample of urine which was found to contain 50,000
bacilli per cc. It was then cut into pieces and put into
petri dishes, with the result that bacilli were found
upon some of the pieces up to and including the fourth
day after pollution, where the pieces had been exposed
to daylight. Pieces kept in the dark were found to be
infested with living bacilli up to and including the
eleventh day.

In another experiment, one of the carriers voided
his excrement in a dry-earth latrine, with the result
that it was found that, under the conditions of a dry-
earth closet and of drv-earth methods of disposing of
excreta, typhoid bacilli can readily be recovered up
to a week, and can exist in the interior of a dry fecal
mass up to eighteen days. This indicates, say the
writers, how easily the infection could be conveyed

CARRIAGE OF DISEASE 137

by flies from such material when left exposed in a
latrine pan.

Another experiment, with a woolen blanket smeared
with a fresh sample of feces from a carrier and doubled
so that the smear was outside, gave the result that the
bacillus was recovered at every examination up to and
including the fortieth day. In this experiment the
sample used was a liquid stool, the result of a saline
aperient, and portions of the blanket fiber were
pulled out from the soiled portion and used for the
experiment.

The latest contribution to the subject at this time
of writing is Dr. J. C. G. Ledingham’s report (1910).
In an introduction to this report, Dr. Theodore Wilson
states that the difficulty of dealing with carriers is very
great indeed, since they may harbor the infection for
long periods and it is extremely difficult to free them
from it. It is most important, however, that all possi¬
ble efforts should be made to detect carriers and to
endeavor to secure on their part those precautions of
strict personal cleanliness and of disposal of dejecta
which will minimize the risk of infecting other peo¬
ple. Furthermore, Doctor Thompson points out that
it is equally important that an attempt should be
made to prevent such carriers from taking any part
in the milk trade or in the preparation or handling
of food.

An excellent review of Dr. Ledingham’s report by
Dr. R. M. Grimm will be found in Public Health Re¬
ports xxvi, No. 4, March 17, 1911.

138 THE HOUSE FLY— DISEASE CARRIER

Influence of Flies in the Carriage of Typhoid in Cities

Much of what we have just written refers to the
carriage of typhoid by flies in encampments of troops
and, in such facts as we have given about the Spanish-
American War and the Boer War, to their effective
carriage in temporary camps. We have equally shown
their influence, however, at more or less permanent
army posts and the certainty of the inference under
these conditions is acknowledged by practically every
one. And the same free acknowledgment must be
made in the case of any emergency which calls together
for temporary purposes large bodies of men, engaged
on great public works, for example, as the Panama
Canal or the construction of great reservoirs, or in
mining camps. Any slight lack of care in the disposal
of excreta under such conditions almost invariably
brings about an outbreak of typhoid, and most often
by the carriage of the causative organism by flies. But
does the same thing hold for cities? The opinion of
a certain class of conservative medical men on this
point is well expressed in a recent editorial in the Jour¬
nal of the American Medical Association, as follows :

“It is sometimes easier to implant a new idea in the
human mind than to extract it or modify it when it
has once taken firm root. The notion that bad smells
from faulty sewers give rise to specific infections, such
as diphtheria and typhoid fever, or that piles of gar¬
bage ‘breed disease,’ are cases in point. In the public
mind, methods of garbage disposal and elaborate

CARRIAGE OF DISEASE

139

plumbing ordinances often loom large as the chief
weapons of combating disease. Too often attention is
diverted from really significant and tangible dangers
to health by the cry that the garbage dump or the sew¬
age manhole is emitting vile odors. It is of course
well known to physicians that there is no evidence that
disease can be spread by odors, although foul air may
possibly impair health and render the body less re¬
sistant to disease.

“Many sanitarians are beginning to fear that a sim¬
ilar misapplication or misunderstanding of the relation
of the house fly to typhoid fever is coming about. No
one questions that the house fly is an unmitigated nui¬
sance. Neither is there any doubt that under certain
conditions, such as prevail in military or mining camps
or on many a country farm, or even in cities that allow
the crude type of privy, the house fly is an exceedingly
important agent in the transmission of infection. This
has been abundantly proved. There is observable, how¬
ever, a tendency to assume a connection much wider
than this and to attribute to fly infection a portion,
sometimes the major portion, of the typhoid fever oc¬
curring in large and well-sewered cities.

“Several instances of this misguided enthusiasm have
come to notice within the last few months. It need
hardly be pointed out that the house fly, no matter how
disgusting its origin or habits, cannot convey the spe¬
cific germ of typhoid fever to any food substance un¬
less it has access both to food substances and to typhoid
germ. Those amateur investigators who assume that

140 THE HOUSE FLY— DISEASE CARRIER

they have discovered the origin of a typhoid epidemic
if they observe a few piles of horse manure in the
alleys of a city take a wide leap over logical difficulties.
Their mode of reasoning seems to be this: Flies can
breed in horse dung, flies can convey typhoid fever,
therefore flies bred in these dung heaps have caused or
are about to cause typhoid fever. One other essential
condition, namely, the existence of infected material
to which the flies have access, is left out of account in
such hasty judgments.

“As a matter of fact, grave as is the danger of fly
transmission of typhoid under rural conditions, it does
not seem to be an important factor in the production
of urban typhoid. As is well known, the intensive
stud)'’ of typhoid fever in Washington, D. C., which
extended over several years, yielded no evidence that
fly transmission had any noteworthy share in typhoid
fever causation in that city.

“One of the most experienced American health of¬
ficers has taken a decided stand on this question in a
book recently published.* While recognizing the de¬
sirability of treating garbage in such a way as to pre¬
vent a nuisance, and admitting the possibility of fly-
borne infection where open privy vaults exist, he de¬
clares very plainly that ‘there is no evidence that in
the average city the house fly is a factor of great mo¬
ment in the dissemination of disease.’ . There can be
no doubt that in any reasonably clean and well-

*Chapin, Charles V.: Sources and Modes of Infection. New
York. 1910.

CARRIAGE OF DISEASE

141

sewered city the cases of typhoid infection due to
direct fly transmission are relatively very few com¬
pared with the number due to water, to milk and to
contact (including contact with carriers). As one
writer has said, in discussing this question, ‘We
need more scientific knowledge and less repetitious
babble of sentiment in dealing with flies or any other
nuisance.’ ”

Such ideas as this are likely to do harm. From
every point of view it is desirable to rid communities
from flies, and the only danger of over-emphasizing the
importance of the typhoid fly in its relation to typhoid
fever is that it may be accepted as the principal cause
of the spread of the disease in certain cases where care¬
ful investigation would indicate other and perhaps eas¬
ily controllable causes. Therefore, while we are in¬
clined to agree with the writer of the editorial that
statements should be cautious to a reasonable extent,
the general tone of the editorial undoubtedly far too
greatly minimizes the importance of flies from the dis¬
ease point of view in modern cities.

Reference is made to “any reasonably clean and well-
sewered city.” The city of Washington has the repu¬
tation of being perhaps the cleanest and best-sewered
city in the United States, and yet it is possible any
summer morning to find human dejecta in alleyways
and vacant lots deposited there over night by irrespon¬
sible persons, and in the light of day swarming with
flies. In the poor quarters of the city uncared-for chil¬
dren of the indigent ease .themselves almost wherever

142 THE HOUSE FLY— DISEASE CARRIER

they happen to be.* The writer. has shown that the
typhoid fly oviposits upon such individual dejecta and
that its larvse successfully breed in them, and that the
adult flies of the next generation issue from them un¬
der the ordinary summer moisture conditions that pre¬
vail in Washington, f With the now well-known per¬
centage of chronic typhoid carriers (from three to four
per cent.) and with the hundreds of cases of typhoid
that have occurred annually in the city of Washington
during the past ten years, and with the existence as ac¬
tually observed of such loose and ill-placed dejecta,
and with flies feeding upon them and breeding in them
within short distances from unprotected kitchens and
pantries, to say nothing of markets and food shops,
how is it possible that flies should be factors of no great
moment? Surely there must be scores of typhoid car¬
riers living in Washington to-day.

Moreover, there still exists in portions of even the
cleanly city of Washington the uncared-for box-privy
nuisance. The judgment in this case is not hasty. It

*This occurs in every city. Newstead in his Liverpool (Eng¬
land) report writes: "In the course of my investigations, more
especially on hot days, numbers of house flies were seen hovering
over or feeding on such matter [human droppings]. The feces
were generally those of children, and were lying, as a rule, a few
feet from the doorways, in the courts or in the passages behind
the houses. In one instance no less than five patches of human
excreta were lying in one court, and all of them were attended
by house flies.”

tThe exact records of these experiments and rearings will be
found in the writer’s 1900 paper. The especial cases in point are
mentioned on p. 572, as many as thirty-one house flies being
reared from a single dropping of a child. We have elsewhere
mentioned Major Faichnie’s record of the rearing of 500 flies
from a single dropping.

CARRIAGE OF DISEASE

143

may be difficult to prove directly and to the laboratory
man that any certain percentage of typhoid cases are
caused in this way, but how much more difficult will
it be to prove that they are not? And is not a great
preponderance of such evidence as we have in favor
of the conclusion that house flies are great dangers even
in cities as well cared for as the best of our American
cities ?

As to the “repetitious babble of sentiment in deal¬
ing with flies/'’ is it not a mistake to apply such words
to a conscientious effort to warn the public of a danger
which surely exists under certain conditions and most
probably exists in all?

It was stated in the editorial which we are consid¬
ering that the intensive study of typhoid fever in Wash¬
ington, D. C., which extended over several years yielded
no evidence that fly transmission had any noteworthy
share in typhoid causation in the city. This statement
was based largely upon the fact that the fever for the
most part was absent or rare in portions of the city
where the box-privy nuisance still exists (and it should
be stated that the health officer has every one of these
nuisances carefully marked on a map) and that an ef¬
fort made during the summer of 1908 to ascertain
whether there was any relation between the curve of
typhoid increase and the curve of fly increase resulted
in apparent failure.

The effort was undertaken by the Bureau of En¬
tomology of the U. S. Department of Agriculture in
co-operation with the Public Health and Marine-Hos-

144 THE HOUSE FLY— DISEASE CARRIER

pital Service. The fly gatherings were begun about
June 19th and continued to October 19th, having cov¬
ered a period of four of the hottest months in the sea¬
son and those in which flies are most troublesome. The
method used was to supply such of the members of the
Bureau force as lived in distinct and separate sections
of the city with a quantity of sticky fly paper with in¬
structions to expose a sheet every other day for a
period of forty-eight hours. The sheets were then re¬
turned to the Bureau and the flies carefully counted
and recorded upon specially prepared cards bearing ad¬
dress and date of each exposure, together with such
data as could be secured concerning the conditions of
nearby stables and manure heaps. Certain parts of the
city, among the slums and along the water front, were
not reached by the regular employes of the Bureau,
but, that these sections might be represented in the re¬
port, two assistants were detailed for the purpose and
made regular rounds on bicycles, collecting fly-laden
sheets and leaving fresh paper three times a week. Sun¬
day, of course, was a day of rest, and this fact inter¬
fered to some extent with the counts, since in case of
papers exposed in meat shops and restaurants flies were
usually so plentiful that the maximum catching ca¬
pacity of the paper was reached within forty-eight
hours.

Sixty-two stations were located throughout the city.
At the end of the season the results were tabulated and
the curve of increase was plotted. At the same time
the Public Health and Marine-Hospital Service had

CARRIAGE OF DISEASE

115

been plotting the curve of typhoid prevalence, and on
comparison it was found impossible to derive any dis¬
tinct connection between the two curves — such connec¬
tion as would be suggestive of cause and effect.

During the summer of 1909 a series of investigations
of a very similar character was carried on in Provi¬
dence, R. I., by Prof. G. F. Sykes (1910), of Brown
University. The conclusions reached by him were as
follows: (1) Fly nuisance is local. (2) Geographic
distribution of pestiferous flies is determined by local
sanitary conditions. (3) The seasonal distribution is
conditioned by meteorological influences (temperature
and sunshine). (4) Over ninety-nine per cent, of the
flies caught were Musca dornestica, the remaining frac¬
tional per cent, being Lacilia ccesar. (5) The plotted
curve for typhoid cases did not show a close relation
to the fly curve, but did show a close parallel to the
temperature curve. (6) The high-water mark for
deaths from diarrhea antedated that for the fly season
by fully three weeks, and followed from one to two
weeks after a noticeable rise in temperature.. (7) The
geographic distribution of typhoid cases over the city
was largely independent of areas known as “unsani¬
tary” and as “fly centers.”

It is to be mentioned that the flies caught by Pro¬
fessor Sykes were collected in three kitchens, the Wash¬
ington observations covering sixty-two stations.

It is possible that Doctor Chapin, of Providence, the
writer referred to in the editorial under consideration,
was confirmed in his opinion by the result of Professor

146 THE HOUSE FLY— DISEASE CARRIER

Sykes’s observations in his own home city, but never¬
theless Doctor Chapin is a well-known man of high
scientific standing and his conclusions must be viewed
with all respect. When we come to analyze the situa¬
tion, however, it becomes at once apparent that in cities
the correlation or non-correlation of the curve of house
fly abundance and of the abundance of typhoid has
practically no effect upon our conclusions as regards
the possible transfer of the disease by flies.

Flies are numerous at all times during the summer,
and wherever excreta carrying virulent germs can be
reached by them it is sure to be covered by them —
whether in early June or in October — and the chances
are almost as great that food supplies will be reached
by these flies whether there are 500 of them or 600 of
them. The fact that typhoid fever does not develop
in localities where flies are most numerous does not
mean that it is not carried by flies, but simply means
that the flies in that locality have had no opportunity
to visit substances containing virulent germs. A cor¬
relation of the two curves in question has been found
by Doctor Jackson in his report to the Merchants’ As¬
sociation of New York, and it has been found by Cap¬
tain Ainsworth in his studies of the house fly and
enteric fever in India, by Purdy (1910) in New
Zealand, and by Osmond (1909) in Cincinnati, and
where it is coincident it may serve to attract the atten¬
tion of people to the subject, but the absence of the
correlation in any given case is a most inconclusive ar¬
gument.

CARRIAGE OF DISEASE

147

A most careful and thoroughly scientific study of
the seasonal prevalence of typhoid has been made by
Sedgwick and Winslow (1902). Their investigation
included an examination of the published data for all
countries. They conclude that the increase of typhoid
with a gradual rise in the mean air temperature is so
widespread and significant as to indicate an undoubted
relationship. There is no doubt that a similar rise of
temperature hastens the rapidity of breeding of the
house fly until at the culmination of the heated term
they are present in countless numbers, as we have seen.
This fact was fully appreciated by Sedgwick and Win¬
slow, who in their conclusions use the following words :

“Of the three great intermediaries of typhoid trans¬
mission, fingers, food, and flies, the last is even more
significant than the others in relation to seasonal varia¬
tion. * * * There can be little doubt that many of

the so-called ‘sporadic’ cases of typhoid fever, which
are so difficult for the sanitarian to explain, are con¬
ditioned by the passage of a fly from an infected vault
to an unprotected table or an open larder. The relation
of this factor to the season is of course close and com¬
plete : and a certain amount of the autumnal excess of
fever is undoubtedly traceable to the presence of large
numbers of flies and to the opportunities for their per¬
nicious activity.”

The real explanation, according to these authors, of
the seasonal variations of typhoid fever is a direct ef¬
fect of temperature upon the persistence in nature of
germs which proceed from previous victims of disease.

148 THE HOUSE FLY — DISEASE CARRIER

This, of course, means that there are more typhoid
germs in late summer and autumn, and as there are
at the same time more flies to carry them, the necessity
of destroying flies, especially in the early summer, is
emphasized by this conclusion.

Other Points

It may be that enough has been said on the subject
of the carriage of typhoid by flies, but there is a great
deal of evidence that has not been touched upon at all.
Dr. J. W. Palmer of Ailey, Ga., for example, who has
had much experience with typhoid in a region for the
most part agricultural, although in a rich part of the
State of Georgia, informed the writer in the autumn
of 1910 that in order to emphasize the importance of
flies in the distribution of this disease and to carry
conviction to his patients as to the necessity of screen¬
ing their houses and avoiding flies, he promises to treat
without charge all cases of typhoid fever that develop
in houses well protected from flies, and states that he
has never had a case develop in such a house.

In the Transactions of the Medical Association of
Georgia for 1910, an article by Doctor Palmer is pub¬
lished on pages 149 to 157. In this paper he states
that he estimates that ninety-five per cent, of the ty¬
phoid fever in rural districts may be laid to the typhoid
fly. He states that during the past typhoid season he
treated fever in several families, and especially noticed
that in the families which controlled the flies as di¬
rected by him no new cases developed, while families

CARRIAGE OF DISEASE

149

which did not control the flies had anywhere from one
to four cases in each family. He points out that in one
year typhoid causes more deaths than yellow fever in
fifty years.

The Georgia State Medical Association as early as
April, 1909, appointed an executive committee of five,
known as the “Fly Committee,” and this committee ap¬
pointed a sub-committee consisting of one member from
each county, whose duty it has been to give public
lectures on the dangers of the common house fly, espe¬
cially in every public school in their respective counties.

Capt. R. B. Ainsworth, of the Royal Army Medical
Corps (1909), gives an admirable summary of impor¬
tant observations in India, from which he concludes that
flies are of the greatest importance. He refers to much
the same general tone of the medical profession as that
indicated in the quoted editorial in our previous sec¬
tion. He writes, “Notwithstanding the fact that much
has been written of late regarding the life history and
habits of the common house fly, and many suggestions
made relative to its possibilities as a disease carrier, it
is to be feared that the general tone of the medical pro¬
fession with regard to the question is apathetic if not
actually antagonistic. The latter is distinctly in evi¬
dence in a rider to the recent reports of the Simla
Enteric Fever Committee, added by some members
thereof, though why they should dissent so emphat¬
ically in the face of so rapidly accumulating proof is
hard to understand.”

After his summary of the whole situation, Captain

150 THE HOUSE FLY— DISEASE CARRIER

Ainsworth concludes, “It seems to me that enteric pre¬
vention naturally groups itself under five headings,
namely, ( i ) Isolation of the human carrier, failing
(2) elimination of the bacillus by means of some drug
as yet undiscovered; (3) rendering excreta innoxious
by disinfection, water carriage, and similar sanitary
measures; (4) the establishment of immunity; and (5)
the destruction of the go-between, to wit, the fly.”

Cholera

One of the earliest accurate scientific studies of the
agency of insects in the transfer of human diseases was
with regard to flies as spreaders of cholera. The be¬
lief in this agency long preceded its actual proof. Dr.
George E. Nicholas (1873) is quoted by Nuttall as
writing as follows regarding the cholera prevailing at
Malta in 1849:

“My first impression of the possibility of the trans¬
fer of the disease by flies was derived from the observa¬
tion of the manner in which these voracious creatures,
present in great numbers, and having equal access to
the dejections and food of the patients, gorged them¬
selves indiscriminately and then disgorged themselves
on the food and drinking utensils. In 1850 the ‘Superb,’
in common with the rest of the Mediterranean squad¬
ron, was at sea for nearly six months; during the
greater part of the time she had cholera on board. On
putting to sea the flies were in great force; but after
a time the flies gradually disappeared, and the epidemic
slowly subsided. On going into Malta harbor, but

CARRIAGE OF DISEASE

151

without communicating- with the shore, the flies re¬
turned in greater force, and the cholera also with in¬
creased violence. After more cruising at sea, the flies
disappeared gradually with the subsidence of the dis¬
ease.”

C. Flugge is said by Nuttall and Jepson to have ex¬
pressed his belief in 1886 that flies may infect the food
in cholera times. Their numbers vary extraordinarily
at times and in certain places. They must play an im¬
portant part, especially when they are numerous. He
drew attention to the fact that the worst cholera months
are those in which insects abound.

Dr. J. Tsuzuki, of the Japanese Army Medical Ser¬
vice, writing in 1904 upon his researches during the
cholera epidemic in North China in 1902, stated that
flies in China are a terrible infliction to the stranger,
and that if they are capable of carrying the cholera
germ they must play an important part in the spread
of the disease. He captured flies in Tientsin in houses
in which there were cholera patients, and succeeded in
isolating cholera vibrios from them. He also placed
flies in a cage with a cholera culture and a dish con¬
taining sterilized agar, with the result that cholera col¬
onies developed upon the agar.

But this was not the first definite and conclusive ex¬
periment in this regard, since Nuttall and Jepson point
out that something had been done in 1886 by two
Italian physicians in Bologna, and that Sawtchenko, of
St. Petersburg, in 1892, found that when flies had fed
for some time on a cholera culture almost no other

152 THE HOUSE FLY— DISEASE CARRIER

bacteria could be isolated from their dejections. In
the same year M. Simmonds studied the flies in a hos¬
pital in Hamburg, especially those present in the post¬
mortem room, where many bodies and intestines of
persons dead of cholera were lying. He was able to
isolate cholera vibrios from the first fly caught. He
had the room cleaned at once, and after this was unable
to obtain cholera germs from flies caught. He found
that healthy, active cultures could be made from flies
for an hour and a half after they had visited infected
material.

Much the same work was done in that year and sub¬
sequent years by Uffelmann, and in 1905 Chantemesse
succeeded in isolating cholera vibrios from the feet of
flies seventeen hours after they had been contaminated.
In 1908 Ganon stated that flies can transmit infection
for at least twenty-four hours after a meal of infected
material, and showed that that period is sufficient to
allow them to be carried for a long distance in railway
trains. Nuttall and Jepson point out that the various
experiments made during this period gain in value from
the fact that the investigators were to a large extent
ignorant of the work done by others, and they add that
a number of authors, without contributing any personal
evidence on the subject, express their conviction that
the house fly carries cholera. They consider that the
body of evidence which they present as to the part
played by flies in the dissemination of cholera appears
to be quite convincing.

An interesting and important piece of work in this

CARRIAGE OF DISEASE

153

direction was done by Surgeon Major R. Macrae
(1894), the civil surgeon of Gaya, India, at the time
of an outbreak of cholera in the jail at that place. He
had in the case of the jail at Gaya a definite structure
composed of eight yards, and thus his observations were
condensed, and his medical authority enabled him to
control the situation to a sufficient extent to prove his
conclusions to his satisfaction and practically to that
of every one else. With much detail he gives a map
of the jail enclosures and a description of them, to¬
gether with an account of the distribution of the pris¬
oners. The cholera outbreak was under his charge and
thorough examinations were made of all of the possible
means of spread. The water supply was shown to be
above suspicion. The milk was of excellent quality and
the food as well. A high wall separated the male de¬
partment from that of the females and cut off the fly
infection; no cases of cholera occurring in the female
side. As Macrae states : “It was observed before the
epidemic Occurred that the jail was infested with a
plague of flies ; disinfectants of various kinds were
used, but they could not be got rid of. The moist,
steaming weather appeared to favor their development.
They were present in swarms when the disease broke
out, and it was an observation of daily occurrence to
see them settling on cholera stools wherever possible.
The rest can he imagined! As soon as feeding time
arrived and the food was distributed in the usual way
on open iron plates on the feeding platforms, there was
at once a crowding of flies towards the platforms, and

154 THE HOUSE FLY— DISEASE CARRIER

a struggle between them and the prisoners for the
food. An active prisoner might possibly be able to
protect his plate from contact with them ; but many
are careless and do not seem to mind much.” Actual
experiments were made by exposing boiled milk ; and
that exposed on the male side became infected with the
cholera germ. In conclusion, Macrae writes:

“The practical lesson the experiments teach is, that
flies should be looked upon in the light of poisonous
agencies of the worst kind during cholera epidemics,
as it is clear that if they find access to poison they will
carry and distribute it, and every possible means should
be taken to prevent their getting into contact with either
food or drink of any kind, and to those having to deal
with large bodies of men it is a lesson more easily
learnt than put into practice.”

Another interesting instance of a somewhat similar
nature is cited by Nuttall and Jepson, in which they
state that W. T. Buchanan, in 1897, described a jail
epidemic which occurred at Burdwan in June, 1896.
This was also the case of a prison. Outside of the
prison there were some huts where cholera prevailed.
It is said that a strong wind blew great numbers of
flies from the side where these huts were into the prison
enclosure, where they settled on the food of the pris¬
oners. It resulted that only those prisoners who were
fed at the jail enclosure nearest the huts came down
with cholera, while the others remained healthy.

CARRIAGE OF DISEASE

155

Dysentery

The probability of the carriage of dysentery as an
intestinal disease has been suggested by several writers
and especially by medical officers of the English army
in India, and two of these were referred to by Nuttall
and Jepson in 1909, but at that time these authors were
obliged to state that there was no direct evidence bear¬
ing upon flies in relation to dysentery. Since the publi¬
cation of their abstract of the literature, however, an
important paper has been published by Orton and
Dodge (1910). We have previously referred to this
paper under the heading “Substances in which the early
life is passed.”

It seems that during 1910 an epidemic of 136 cases
of bacillary dysentery occurred in the Worcester State
Hospital and Doctor Orton found that the epidemic
had spread gradually. It was not characterized by a
sudden general series of cases. This, of course, argued
against the theory of a water-supply infection, and it
also argued equally well against milk infection and in¬
fection from raw foodstuffs. It is obvious that with
infection from any of these sources a large number of
patients would have become ill at the same time. House
flies were unusually abundant in the hospital in spite
of screening, and these were considered to be the car¬
riers of the dysentery. We have elsewhere shown that
it was finally discovered that the unusual number of the
flies was due to certain piles of spent hops and barley
malt which had been hauled in as fertilizer on the
grounds near the buildings.

156 THE HOUSE FLY— DISEASE CARRIER

The case reported is interesting and unusual on ac¬
count of the fact that the hospital in question is a hos¬
pital for the insane, and that it is impossible in such
an institution to control the intestinal discharges of
the patients and confine them to one place. In the
hospital all bedding and clothing were brought for
cleaning to the laundry, and the laundry contained
many flies, and in the laundry colonies of Bacillus
prodigiosus were exposed under experimental condi¬
tions. Subsequently at varying intervals flies were
caught in the other rooms of the hospital, and upon
test from a large number of them cultures of the Bacil¬
lus were had.

Doctor Orton’s conclusion as published is that flies
were entirely responsible for the epidemic. It is rather
a pity that the causative organism of the dysentery
could not have been used in this experiment, but that
was of course impossible on account of the danger, and
it is altogether probable that Doctor Orton’s conclusions
from his experiments with the other Bacillus were per¬
fectly correct.

Dr. C. W. Stiles tells the writer that the causative
organism of amoebic dysentery sporulates more readily
as the feces dry. Therefore under a dry-privy system
this disease is the more likely to be carried by flies.

Diarrhea in Infants

Diarrhea and enteritis, commonly known as summer
complaint, cause a great mortality among children in
the United States. It is doubtful whether the average

CARRIAGE OF DISEASE

157

person begins to realize the full extent of the ravages
of this disease, and indeed of the mortality rate among
young children. The Census Bureau shows that in
1908 nearly one-fifth of the deaths in the registration
area of the United States, comprising about one-half
of the population of the country as a whole, were of
children under one year, and that the deaths of children
under five years comprise more than one-quarter of the
whole number of deaths. Ratios are not as convincing
or as strong as actual figures, so that we may say in
other words that the deaths in the registration area in
1908 amounted to 691,574; those of children under one
year to 136,452, and of those under five years 189,865.
It is a recognized fact that the general death rate of
the country is largely dependent on its infant mor¬
tality.

The number of deaths among children becomes even
more striking when we consider that in 1908, according
to the census, 197.3 out of every 1,000 under one year
died, while 274.5 out of every 1,000 under five years
died. It is clearly shown that summer complaint is the
most important cause of infant mortality. Irving
Fisher, in his estimate of lives that could be saved,
states that sixty out of every one hundred dying from
this disease could have been saved. The actual num¬
ber of deaths from summer complaint in 1908 was 52,-
213, of which 44,521 were under two years.

Of course there is no way of showing in what pro¬
portion of these cases of summer complaint the house
fly was instrumental, but under conditions that exist

158 THE HOUSE FLY— DISEASE CARRIER

practically everywhere in midsummer, both as to the
swarms of flies and the lax care of excreta among
small children, it is impossible to avoid the conclusion
that flies bear a very important relation to the number
of cases and therefore to the number of deaths.

Nuttall and Jepson have abstracted a number of pub¬
lished papers on this subject, with the following re¬
sults :

“The relation of flies to the spread of summer diar¬
rhea has aroused special interest of recent years. Fraser
(1902), referring to epidemic diarrhea in Portsmouth,
states that ‘on visiting the houses in question I find
that in all, almost without exception, the occupants
have suffered from a perfect plague of flies. They told
me every article of food is covered at once with flies.
* * * I repeat that to this, and this alone, I at¬
tribute the diarrhea in the Goldsmith Avenue district.’

“Nash (1903, p. 128) pointed out that there were
twenty-three cases of the disease in Southend-on-Sea in
1901, whilst there were none in the summer of 1902.
M. domestica was completely absent in the wet summer
of 1902, but appeared in September of the same year;
coincident therewith there occurred thirteen cases of
infantile diarrhea. Nash (1904) considers that M.
domestica is the chief carrier of diarrhea-causing bac¬
teria.

“Newsholme (1903. p. 21) has expressed the opin¬
ion that food in the houses of the poor can scarcely
escape fecal infection. ‘The sugar used in sweetening
milk is often black with flies, which may have come

CARRIAGE OF DISEASE

159

from a neighboring dust-bin or manure heap, or from
the liquid stools of a diarrheal patient in a neighboring
house. Flies have to be picked out of the half-empty
can of condensed milk before its remaining contents
can be used for the next meal.’ Newsholme considers
the greater prevalence of diarrhea among infants fed
on Nestle's milk as due to the fact that flies are more
attracted to it than to ordinary cow’s milk because of
its sweetness.

“Copeman (1906, p. 18), in a report to the Local
Government Board dealing with epidemic prevalence of
infantile diarrhea at Wigan, says : ‘At the Miry Lane
Depot there is always stored (awaiting removal by
farmers) an enormous amount of night-soil mixed with
ashes which, in hot weather especially, is not only ex¬
ceedingly offensive, but is beset by myriads of house
flies. As the result of personal enquiry at the various
houses in the neighborhood in which, during the year
1905, deaths from diarrhea had occurred, I learnt that
considerable nuisance from the foul odors was apt to
be experienced during the prevalence of hot weather,
especially with the wind in the south or southwest, i. e.,
blowing from the Depot to the special area, so much
so on occasions as to render it necessary to shut all the
windows, while the inhabitants of houses nearest the
Corporation Depot stated that at certain times of the
year their rooms were apt to be invaded by a veritable
plague of flies, which swarmed over everything of an
edible nature on the premises. This being so, it would
appear not improbable that these flies, some of which

160 THE HOUSE FLY— DISEASE CARRIER

have doubtless had opportunity of feeding on and be¬
coming contaminated with excremental material of
human origin, may have been a means of carrying in¬
fected material to certain foodstuffs, such, more par¬
ticularly, as milk and sugar, and so, indirectly, of
bringing about infection of the human subject.’

“Snell (1906), Medical Officer of Health, Coventry,
is stated by Ainsworth (1909) to have shown that
seventy per cent, of the ‘cases of infantile diarrhea oc¬
curred in the northeast part of his district, close to a
large collection of refuse where flies swarmed.’

“Sandilands (1906, p. 90) considers that there are
‘good grounds for the supposition that in this disease,
which in some respects is analogous to typhoid fever
and cholera, flies may be carrying agents of the first
importance.’ He notes that the meteorological condi¬
tions which influence the prevalence of diarrhea ‘exer¬
cise a precisely similar effect upon the prevalence of
flies.

“ ‘The immunity of well-to-do infants may be ex¬
plained partly by the distance that separates the sick
from the healthy and partly by the small number of
flies in -their neighborhood. In poorer districts six or
seven babies may occupy the tenements of one house
with a common yard where the flies congregate and
flit in and out of the open windows, themselves con¬
veying infected excrement to the milk of healthy in¬
fants, or depositing the excrement in the dust-bin,
whence it may again be conveyed into the house by
other flies. Calm weather promotes diarrhea, and high

CARRIAGE OF DISEASE

161

winds are unfavorable to the spread of diarrhea and to
the active migration of flies alike. Loose soil and fis¬
sured rock, containing organic filth in its crevices, favor
the spread of diarrhea and the breeding of flies, whilst
solid rock is unfavorable to both.’ (See also News-
holme, 1906, p. 145.)

“Hamer (1908), who has studied the relation of fly-
prevalence ( Mnsca , Homalomyia ) to diarrhea from an
epidemiological point of view, appears to be somewhat
sceptical as to flies being active agents in the spread of
infection. He considers that the increase in flies and
diarrhea may be due simply to a coincidence.

“Ainsworth (1909, p. 498) has studied the relation
of infantile diarrhea to flies in Poona and Kirkee, India,
and illustrates the relation by means of a yearly curve
which is very striking as affording evidence that flies
stand in causal relationship to diarrhea.

“All authorities agree that flies rest under strong
suspicion of serving as disseminators of diarrheal in¬
fection.”

Jackson ( 1907) gives the results of numerous ob¬
servations upon the relation of flies to intestinal dis¬
eases (including infant diarrhea) and the relation of
deaths from intestinal diseases in New York City to
the activity and prevalence of the common house fly
is indicated not only by repeated observations but also
by an interesting plotting of the curve of abundance
of flies in comparison with the plotted curve of the
abundance of deaths from intestinal diseases, indicat¬
ing that the greatest number of flies occurred in the

162 THE HOUSE FLY— DISEASE CARRIER

weeks ending July 27th and August 3d, and also that
the deaths from intestinal diseases rose above the nor¬
mal at the same time at which flies became prevalent,
culminated at the same high point, and fell off with a
slight lag at the time of the gradual falling off of the
prevalence of the insects.

Tuberculosis

The typhoid fly also possesses importance as a dis¬
seminator of the bacilli of tuberculosis. We have seen
on an earlier page the method by which the adult fly
feeds upon sputa. They are attracted to all sputa and
feed upon them with avidity. One of the writer’s as¬
sistants (himself a tuberculous patient) more than ten
years ago wrote him from a Colorado resort telling of
the lax care of the sputa of the consumptives, and
stating that he had seen numbers of patients sitting
upon a veranda and occasionally expectorating over the
railing upon the ground where numerous flies had con¬
gregated and were feeding. The significant part of the
letter, however, was the statement that the open win¬
dows of the kitchen were not many feet away from this
particular portion of the veranda.

It is not difficult to understand the danger of the
transfer of the causative organisms of the diseases of
the alimentary tract by flies, but in regard to tubercu¬
losis of the lungs, it should be stated that the observa¬
tions of Nicolas and Descas (quoted by Cobb) indi¬
cated that fasting dogs fed with bouillon containing
quantities of bacilli were shortly after examined and

CARRIAGE OF DISEASE

163

smears were taken from the thoracic duct which indi¬
cated tubercle bacilli, thus showing how easily these
bacilli can enter the general circulation.

Dr. Frederick T. Lord ( 1904), after a series of long
and careful laboratory investigations, reached the fol¬
lowing conclusions:

“1. Flies may ingest tubercular sputum and excrete
tubercle bacilli, the virulence of which may last for at
least fifteen days.

“2. The danger of human infection from tubercular
fly-specks is by the ingestion of the specks on food.
Spontaneous liberation of tubercle bacilli from fly-
specks is unlikely. If mechanically disturbed, infec¬
tion of the surrounding air may occur.

“As a corollary to these conclusions, it is suggested
that —

“3. Tubercular material (sputum, pus from dis¬
charging sinuses, fecal matter from patients with intes¬
tinal tuberculosis, etc.) should be carefully protected
from flies, lest they act as disseminators of the tubercle
bacilli.

“4. During the fly season greater attention should
be paid to the screening of rooms and hospital wards
containing patients with tuberculosis and laboratories
where tubercular material is examined.

“5. As these precautions would not eliminate fly in¬
fection by patients at large, foodstuffs should be pro¬
tected from flies which may already have ingester tu¬
bercular material.”

According to Nuttall and Jepson, the first investi-

164 THE HOUSE FLY— DISEASE CARRIER

gators to study the house fly in relation to the possible
dissemination of tubercle bacillus were Spillman and
Haushalter in 1887. They found tubercle bacilli in the
intestinal contents of flies and in their dejections as
well, the flies having fed upon tubercular sputum. They
also show that Hofmann, in a paper published in 1888
on the spread of tuberculosis through house flies, re¬
ported certain observations under natural conditions.
He examined flies captured in the room of a tubercu¬
lous patient and found bacilli in four out of six flies ex¬
amined, as well as in the fly-specks scraped from the
walls, door and furniture of the room. Similar ob¬
servations are reported to have been made by Hayward
(1904), Buchanan (1907) and Cobb (1905).

Much stress is now being laid upon the alimentary
transmission of tuberculosis, and in view of the facts
just stated it can hardly be denied that the house fly is
a serious danger in the carriage of the “white plague.”

Anthrax

Anthrax is an infectious and usually fatal bacterial
disease of cattle, sheep, and other animals, producing
ulcerations. It occasionally occurs in man, and is usu¬
ally known by the name “malignant pustule.” It has
been shown by many authors that the bacillus of an¬
thrax is carried by several species of flies, and Celli of
Rome, as early as 1888, found that anthrax bacilli pass,
unimpaired in virulence, through the alimentary tract
of flies. Other observers have accomplished the trans¬
fer of anthrax by means of flies from experimental

CARRIAGE OF DISEASE

165

animals to sterilized culture plates. It seems perfectly
demonstrated that flies pick up anthrax bacilli when
they walk about and when they feed upon infected ma¬
terial. It has not, however, been shown how long they
may carry the bacillus, and it is not known whether its
virulence is reduced by passage through their bodies.
Nuttall suggested as early as 1899 that it appears prob¬
able that non-biting flies, like the house fly, may, when
infected, spread anthrax by depositing the bacilli upon
wounds, or food.

It may be remarked incidentally that biting flies, such
as the stable fly ( Stomoxys calcitrans ) or any of the
gad-flies, biting an animal affected by the disease, might
naturally be supposed to carry the Bacillus anthracis
into the circulation of a human being by a puncture
after a short period, and cases have been reported where
malignant pustule apparently followed the bite of some
fly. Efforts to prove this by experiment with biting
flies and guinea-pigs, however, have not been successful.
Nuttall in 1899 concluded that while it is conceivable
that infection may occur in this way, it is probable that
it is the exception and not the rule.

Yaws (Frambcesia tropica )

Yaws is a tropical disease, contagious and innocu-
lable, characterized by the appearance of papules which
develop into a fungus-like, incrusted, and excessively
disagreeable eruption. It is widely distributed through¬
out the greater part of the tropical world, being very
common in tropical Africa, especially on the west coast,

166 THE HOUSE FLY— DISEASE CARRIER

in many of the West Indian Islands, in Ceylon, Java,
in Fiji, and Samoa, and other Pacific islands. It oc¬
curs in China, but is rare there. It is highly contagious,
but simple contact of the skin is not sufficient — an
abraded surface is necessary. Sir Patrick Manson says
that probably the virus is often conveyed by insect bites
or by insects acting as go-betweens and carrying it from
a A'aw sore to an ordinary ulcer ; thus the disease often
commences in a pre-existing ulcer. It is neither hered¬
itary nor congenital.

Prof. E. W. Gudger, of the State Normal College
at Greensboro, N. C., has called attention to a very
early idea as to the carriage of yaws by flies, on pages
385 to 386 of Dr. Edward Bancroft’s “An Essay on
the Natural History of Guiana in South America,”
published in London in 1769. Doctor Bancroft writes,
“The yaws are spongy, fungous, yellowish, circular pro¬
tuberances, not rising very high, but of different mag¬
nitudes, usually between one and three inches circum¬
ference. These infest the whole surface of the body
and are commonly so contiguous that the end of the
finger cannot be inserted between them, and a small
quantity of yellowish pus is usually seen adhering to
their surface, which is commonly covered with flies
through the indolence of the negroes. * * * It is

usually believed that this disorder is communicated by
the flies which have been feasting on the diseased ob¬
ject to those persons who have sores or scratches which
are uncovered ; and from many observations I think
this is not improbable, as none ever receive this dis-

CARRIAGE OF DISEASE

167

order whose skins are whole; for which reason the
whites are rarely infected ; but the backs of negroes, be¬
ing often raw by whipping, and suffered to remain
naked, they scarce ever escape.”

Nuttall and Jepson state that Wilson (1868) says
that the belief prevails in the West Indies that this dis¬
ease is carried by flies. They also show that Hirsch
(1896) reports two cases in which he thinks the dis¬
ease was conveyed by flies. They also quote Cadet to
the effect that lesions of the skin are necessary for in¬
fection, and that this may occur through direct contact
with infected clothes or flies, the latter transporting
the virus on their feet, which are soiled with diseased
secretions.

The causative organism of yaws is supposed to be
an extremely delicate spirochaete very much like that
of syphilis. Castellani (1907) reports experimental in¬
vestigations showing that with monkeys the disease can
be conveyed by inoculation, showing also that yaws
and syphilis are different diseases. The causative or¬
ganisms of the two diseases appear to be distinct, that
of yaws being called Spiroch&ta pertenuis. He makes
the statement that there can be no doubt of the con¬
veyance of the disease by direct contact from person
to person, and that under certain conditions it may be
conveyed by flies and possibly by other insects.

Ophthalmia

A number of years ago, while studying the habits
of certain minute flies of the genus Hippelates, which

168 THE HOUSE FLY— DISEASE CARRIER

are commonly seen flying about the eyes of domestic
animals, the writer was informed by the late Henry G.
Hubbard that he believed these little flies to be respon¬
sible for the transfer of the pink-eye among the school
children of Florida. He had known this disease to
run rapidly through a school and had observed that the
little Hippelates flies were always present and were
much attracted to the inflamed eyelids.

When this observation of Hubbard’s was mentioned
to Dr. Lucien Howe of Buffalo, Doctor Howe informed
the writer that in his opinion the ophthalmia of the
Egyptians is also transferred by flies, and presumably
by the house fly, and referred the writer to a paper
which he had read before the Seventh International
Congress of Ophthalmology at Wiesbaden in 1888. He
referred to the extraordinary prevalence of purulent
ophthalmia among the natives up and down the River
Nile and to the extraordinary abundance of the flies
in that country. He spoke of the dirty habits of the
natives and of their remarkable indifference to the vis¬
its of flies, not only children, but adults allowing flies
to settle in swarms about their eyes sucking the secre¬
tions and never making any attempt to drive them
away. Doctor Howe called attention to the fact that
the number of cases of this eye disease always increases
when the flies are present in the greatest numbers and
that the eye trouble is most prevalent in the place where
the flies are most numerous. In the desert where flies
are absent, eyes as a rule are unaffected. He made an
examination of the flies captured upon diseased eyes,

CARRIAGE OF DISEASE 169

and found on their feet bacteria which were similar to
those found in the conjunctival secretion.

At the time when Doctor Howe told the writer of
this paper, the latter was so filled with the idea that
horse manure was far and away the most abundant
producer of house flies that, inasmuch as there are com¬
paratively few horses in the Nile Valley, he was in¬
clined to suspect that the fly concerned in the carriage
of this disease as pointed out by Doctor Howe might
be some other species breeding by preference in camel
dung or perhaps in some other substance. He there¬
fore sent to Egypt and secured specimens of the flies
commonly swarming about the eyes of ophthalmic pa¬
tients, and on their receipt in Washington they were
readily determined as Musca domestica by Mr. D. W.
Coquillett of the Bureau of Entomology.

Nuttall and Jepson show that Budd, as early as 1862,
considered that it was fully proven that flies served as
the carriers of Egyptian ophthalmia, and Laveran, in
1880, writing of Biskra, says the same. These writers
also point out that Braun (1882), Demetriades (1894)
and German (1896) agree that gonorrheal and other
infections of the eye may be carried by flies. They
state that Welander (1896) observed an interesting
case where an old bedridden woman in a hospital be¬
came infected. It seems that her bed was alongside
that of another patient who had blennorrhea, but that
a screen which did not reach to the ceiling separated
the beds. Thus all means of infection except through
the agency of flies was apparently absent. The inves-

170 THE HOUSE FLY— DISEASE CARRIER

tigator found that flies bore living gonococci upon their
feet three hours after they had been soiled with secre¬
tion, since they infected sterilized plates with which
they came in contact.

Nuttall and Jepson conclude their consideration of
ophthalmia with the following statement: “The evi¬
dence regarding the spread of Egyptian ophthalmia by
flies appears to be conclusive, and the possibility of
gonorrheal secretions being conveyed by flies cannot be
denied.”

Diphtheria

Nuttall and Jepson have been able to find only one
reference to the dissemination of Bacillus diphtheric u
by flies. They state that Dickinson (1907) cites Smith
( 1898) as having tried the oft-repeated type of experi¬
ment of allowing house flies to walk over infected ma¬
terial and then over sterile media. A positive result
was obtained as a matter of course. The authors state
that there is no evidence that under natural conditions
flies have anything to do with the spread of diphtheria,
but indicate that it is of course conceivable that they
may convey the infection under suitable conditions.

Small-pox

The only published account of the possible relation
of flies to small-pox cited by Nuttall and Jepson is
taken by them from a paper by Hervieux, read June 5,
1904, to the Academy of Medicine at Paris, in which
he states that Laforgue at a locality in the province of
Constantine observed that during an epidemic of small-

CARRIAGE OF DISEASE

171

pox the children who were attacked all lived in the
southwest of the village, the northern part of the vil¬
lage remaining free from the disease. This distribu¬
tion was thought to be due to the direction of the pre¬
vailing winds, and observations were made to the effect
that flies and mosquitoes were distributed with the
wind. Laforgue himself believed that flies played an
important part in the spread of the virus of small-pox.

Plague

So much is now known concerning the specific origin
of bubonic plague and concerning its carriage by the
several species of fleas which occur upon rats, which
are also subject to the same disease, that house flies
cannot be claimed to be of importance in this connec¬
tion ; but old writers have noted the occurrence of flies
in large numbers in plague years, and one of them at
least considered that house flies carried the disease,
simply from the fact that they visited food after they
had abandoned plague patients.

Nuttall and Jepson call attention to the fact that
Yersin, in writing upon bubonic plague at Hong-Kong
in 1894, stated that he saw many dead flies lying
around in his laboratory when he was conducting au¬
topsies on animals killed by the plague. He demon¬
strated by inoculation into animals that a dead fly con¬
tained virulent plague bacilli.

Nuttall himself had in 1897 already experimented
with the house fly, feeding it upon organs of animals
dead by the plague. He found that the flies might

172 THE HOUSE FLY— DISEASE CARRIER

survive for eight days after feeding on infected organs
and that they still harbored virulent bacilli forty-eight
hours and more after they were transferred to clean
vessels. At high temperatures the infected flies died
more rapidly than controlled flies which were fed on
the organs of healthy animals, from which he concluded
that the plague bacillus may be fatal to house flies un¬
der suitable conditions of temperature. This possibly
accounted for the dead flies noted by Yersin in his
Hong-Kong laboratory. Nuttall also points out that
a French observer, Matignon, observed in 1898 that
flies died in large numbers in Mongolia during plague
times.

Tropical Sore

This disease is referred to by Nuttall and Jepson
under this name aftd also under the name “Bouton de
Biskra.” They state that it is asserted by Laveran
and Seriziat (1880) that flies convey this trouble. In
other localities, the natives declare that the disease is
caused by the bite of certain insects. It is said that
Seriziat asserts that a lesion of the skin is always neces¬
sary for an infection to take place, and that it unques¬
tionably results at times as a consequence of mosquito
bite. Laveran in his observations at Biskra stated that
from September to October the slightest wound tends
to be transformed into the bouton. He has seen it graft
itself upon pustules of acne, upon vaccine pustules, and
upon wounds following burns or blisters. He does not
doubt that it is carried by flies on their feet and on their
beaks.

CARRIAGE OF DISEASE

173

Parasitic Worms

Nuttall and Jepson refer to the experiments made by
Grassi in 1883. When he broke up segments of the
human tapeworm in water after these had been pre¬
served some months in alcohol, he saw that the flies
came and sucked up the eggs with the water and that
the eggs were passed unaltered through the bodies of
the flies. He had the same results with the eggs of Ox-
yuris, one of the so-called “thread-worms” or “pin-
worms.”

While experimenting with the unsegmented eggs of
still another of the genus Trichocephalus (one of the
so-called “whip worms,” having a long, slender neck
like a whip lash), which were placed upon a table, he
saw flies feed on them and later found the eggs in the
fly-specks which had been deposited in the kitchen on
the floor beneath, ten yards away from the place where
the insects had been fed. He caught some flies whose
intestines were full of the eggs.

Nuttall also records an observation of Dr. C. W.
Stiles, of the Public Health and Marine-Hospital Ser¬
vice, which had been sent to him in a personal letter,
showing that Stiles had placed fly larvae with the fe¬
male of Ascaris lumbricoides (the most abundant of
the “round worms,” which inhabit the small intestine,
especially with children), which they devoured together
with her eggs. He afterwards found that the larvae
and the adult flies contained the eggs of the Ascaris.
The experiment was made in very hot weather. The

174 THE HOUSE FLY— DISEASE CARRIER

Ascaris eggs developed rapidly and were found in dif¬
ferent stages of development in the insects, thus prov¬
ing that the flies may serve as disseminators of the para¬
site. “Provided that the eggs attained the proper stage
of development, the fly, acting simply as a carrier,
might convey the parasite to man by falling into, or
depositing its excreta on, the food.”

REMEDIES AND PREVENTIVE MEASURES
O avoid only the danger from flies, you must de-

i stroy or protect from them all substances contain¬
ing disease germs. This is done in large part, so far as
intestinal diseases are concerned, by the water-closet
system in cities, and it may be done by sanitary privies
in villages and country houses and in mining and con¬
struction camps ; and also by properly cared-for trenches
or latrines at temporary army posts. To avoid danger
from flies in the case of lung troubles, the proper care
of the sputa is essential.

To avoid the nuisance of flies it becomes necessary
practically to get rid of them, and in doing this of
course we get rid of the danger at the same time. It
has always seemed to the writer that the truest and
simplest way of attacking the fly problem is to prevent
them from breeding, by the treatment or abolition of all
places in which they can breed. To permit them to
breed undisturbed and in countless numbers, and to
devote all our energy to the problem of keeping them
out of our dwellings or to destroying them after they
have once entered in spite of all obstacles, seems the
wrong way to go about it. To the individual who has
control of the grounds for some distance about his
abiding place, the former method is undoubtedly the

175

176 THE HOUSE FLY— DISEASE CARRIER

best, and it would also undoubtedly be the best in any
event if, by co-operation of the residents or by the
active efforts of a central body, like the boards of health
in cities, it were possible to do thorough work with the
breeding places.

In cities and in towns, however, where the requisite
co-operation cannot be obtained, and where boards of
health are still indifferent, careful consideration must
be given to the second method, namely, keeping flies
out or killing them after they enter.

A third method has been proposed and is enthusi¬
astically advocated by Professor Hodge, of Clark Uni¬
versity, Worcester, which is based upon the supposed
time elapsing between the issuance of the adult fly and
the period when it lays its first eggs. Professor Hodge,
as will be shown later, thinks that it is quite possible
to trap these sexually immature adults during this
period, which now seems comparatively long, and thus
to prevent not only their entrance into houses and shops
and markets, but to destroy so many of them that the
comparatively few which reach sexual maturity will
not be able to lay their eggs in sufficient numbers to
make the next generation a nuisance. In other words,
he thinks that it will be possible to bring about such a
condition that the manure pile may be left undisturbed
until it is needed to fertilize the land.

Whether this can be done or not — and Professor
Hodge’s argument seems reasonable — will again de¬
pend upon co-operation in communities, although indi¬
vidual effort in isolated places may bring it about.

PREVENTIVE MEASURES

Success will also to a great degree depend upon the
applicability of Doctor Hewitt’s isolated observations
upon the period between issuance and sexual maturity
to other seasons and to other parts of the world.

Screening

Three years ago I made an attempt to estimate the
amount of money spent annually in screening houses
in the United States. As close an estimate as could
conscientiously be made seemed to indicate that more
than $10,000,000 are spent every year for this kind
of protection against flies and mosquitoes. In fly-rid¬
den localities the expense is undoubtedly justified, since
the majority of the flies are kept out by careful screen¬
ing. No system of screening, however, seems to be so
perfect as to keep them all out. They get in, one way
or another, in spite of care; even where double doors
are used they eventually gain entrance. In the summer
time, in country houses having large open fireplaces
disused during warm weather, flies undoubtedly come
down the chimney, and it is necessary under those con¬
ditions to arrange a wire screen before the open fire¬
place in such a way that it can easily be removed on a
cold day.

The whole expense of screening, however, should be
an unnecessary one, just as efforts to destroy flies in
houses should be unnecessary. Their breeding should
be stopped to such an extent that all these things would
be useless.

178 THE HOUSE FLY— DISEASE CARRIER

Fly Traps and Fly Poisons

In the effort to destroy the flies which have gained
access to houses many devices have been invented, and
many of them have been patented. Nearly all of the
traps which are on the market are reasonably effective,
and it will be unfair to mention any one or two or three
where so many are good. They are all cheap and it
is a simple matter for one to test them one after an¬
other until the most satisfactory one is found. Very
effective traps are made of sticky fly paper — flat sheets
to be laid on tables, bookcases, or in other places.

A recent idea, gained from the observation that flies
in rooms where there is no food seem frequently to
rest by preference upon vertically hanging cords of
window curtains, on the supports of chandeliers, and
objects of that general character, has resulted in several
arrangements by which strips of sticky fly paper are
suspended in this way, and this has given in many
cases satisfactory results. One of the writer’s friends,
in experimenting with one of these devices, examined
the room carefully and noted eleven flies. After the
apparatus was hung he found rather to his surprise
that he had caught thirteen flies! He became rather
enthusiastic over the merits of the device. These
sticky fly papers are not poisoned, and depend for their
efficacy upon the catching of the flies.

Poisoned fly papers were at one time very much in
use and are still in some localities. The old dispensa¬
tories give an account of a harmless fly poison prepared

PREVENTIVE MEASURES

179

in the following way: “Macerate during twenty-four
hours 1,000 parts of quassia wood with 5,000 parts
of water, then boil for half an hour; set aside for
twenty- four hours and press. Mix the liquid with 150
parts of molasses, and evaporate to 200 parts. A
weaker decoction of the quassia does not kill the flies.
From this the fly water or fly plate is prepared as fol¬
lows: Mix when needed and dispense without filter¬
ing, 200 parts of syrup of quassia, fifty parts of alcohol
and 750 parts of water. It is used by moistening with
the mixture a cloth or filtering paper on a plate.”

The native ore of speiss cobalt is found in commerce
under the name of flystone, and was at one time ex¬
tensively used for poisoning flies by roughly grinding
it and putting a small quantity in a saucer with sweet¬
ened water.

It is possible to poison flies rather satisfactorily by
putting a lump of sugar in a saucer partly filled with
water and adding white arsenic. This, of course, is
dangerous where there are children or house dogs or
cats about.

Of the unpatented fly traps, a device was recom¬
mended by Mr. P. J. Parrott, Entomologist of the
Kansas Experiment Station, in Bulletin 99 of the Sta¬
tion (October, 1900), as follows:

“The department of entomology, after experimenting
upon various mechanical devices for catching flies, has
contrived a trap and recommended it for trial on ac¬
count of its effectiveness and cheapness. Anybody
with an average amount of mechanical ingenuity can

180 THE HOUSE FLY— DISEASE CARRIER

make and attach the trap, with a cost of but a few
cents. It is made as follows:

“Take a flat strip of tin two and one-fourth inches
wide and one and one-half inches longer than the dis¬
tance between the side rail or stile and middle rail of
the sash, as from c to d, Fig 3, which in this case meas¬
ured twenty-one inches. For this window, the strip
must be twenty-two and one-half inches in length.
With the tin lying on the flat surface, bend the tin
along the lines ab and cd, Fig. 1, which are three-
quarters of an inch from their respective sides, so that
the space abdc forms the bottom of a box and the lat¬
eral parts the sides. To close the ends, cut small in¬
cisions three-quarters of an inch deep at the points
a, b , c, and d, as ay and cx, Fig. 1. Bend the flaps
thus made at right angles to their respective parts.
We then have a box twenty-one inches long, three-
quarters of an inch wide, and three-quarters of an inch
deep, as at Fig. 2.

“To make the box water-tight, solder the joints, or
if solder is not handy try moistened plaster of Paris.
When properly made, the box should fit snugly be¬
tween the middle and side rail or style. The corners
should be square and the edges straight, so as to leave
no passageways between the box and the glass. The
box should rest on top of the bottom rail, and can be
held in place by two or three tacks or pins thrust into
the rail from the back side. When the pane is very
large it is well to attach another trap half way between
the top and the bottom.

PREVENTIVE MEASURES

181

a. _l£. _

c — S -

Lj -

Fig. 19. — Details of window trap. (Redrawn from Parrott.)

182 THE HOUSE FLY— DISEASE CARRIER

“After the traps have been attached, some substance
should be put into them that will either kill the insect
upon falling into it, or on account of its sticky nature
will hold the insect so that it cannot escape. For the
first, kerosene, kerosene emulsion, soapsuds and py-
rethrum are the best ; and for the second, molasses, or
a mixture of castor-oil and resin. For general use, the
soapsuds are to be recommended. When using the
liquids, fill the traps two-thirds full.

“There should be one trap for every pane of glass
of at least one window in the house. For instance,
when the sash contains two panes of glass, as in the
cut, there should be two traps, one at the base of each
pane. When the sash contains four panes, there should
be four traps, two on the bottom rail and two on the
cross-bars or munting. It is not necessary to apply
traps to all the windows. Attach traps to one or two
windows in the sunny part of the house, and pull down
the blinds of the remaining windows. The flies will
seek the lighted rooms, and especially the windows.

“When the traps are full of flies, remove them from
their fastenings, empty out their contents, and fill them
with fresh material.

“A temporary trap can be made of flexible card¬
board, following the same directions as for those made
of tin. Use glue or pins to fasten the ends. To render
the trap water-proof, paint the inside with melted par¬
affin. This will hold any of the above remedies except
the pure kerosene.”

A correspondent, Dr. D. S. Hager, has made a sue-

PREVENTIVE MEASURES

183

cessful fly trap which cost for material about fifteen
cents, and writes that any bright boy can make one of
them in an hour or two. He took two pieces of board
one inch thick and about a foot square; tacked them
together, sawed them round, and in the center sawed
a hole eight inches in diameter. He then separated
the boards, and into one he fitted a funnel-shaped piece
of wire screen about ten inches high, which was fas¬
tened to the board with tacks driven on the inside of
the round hole and fastened together funnel-shaped
with a strand of the wire selvage. A small hole, large
enough to admit a lead pencil, was left at the apex of
the funnel for the flies to creep through. He then
tacked a piece of wire netting, eighteen inches wide, to
the outside circumference of each of the round boards,
with the .funnel-shaped wire on the inside. The out¬
side of the wire was again fastened with the selvage
of the wire. On the top he tacked a piece of wire
screen in such a way that he could readily remove it to
empty out the flies. He then nailed lengthwise on the
outside of the trap a few laths to make it more firm.
He then made feet by screwing into the bottom piece
containing the funnel four wire coat-hangers about five
inches high.

He placed these traps (he made two at the same
time) one on each side of the front porch, and under
each he placed a plate with some sugar on it and a cup
of sweetened water in the plate. Flies were attracted
by the sugar and sweetened water, and as they flew
over the bait they crawled through the hole in the fun-

184 THE HOUSE FLY— DISEASE CARRIER

nel up into the trap. The traps caught many each day,
and were soon filled with a buzzing mass. He suggests
that a trap of this kind should be placed near the door
of a house, as flies will congregate at the top of the
screen door and enter the house when the door is
opened.

He caught quarts of flies, and at first killed them by
pouring scalding water over them, but this had a detri¬
mental effect upon the wood and wire of the trap, so
he killed them by fumigating with sulphur, setting a
large paper packing box over all, destroying them in
this way in about two and a half minutes.

Many different kinds of fly traps are used in differ¬
ent parts of the world. We read, for example, in the
Journal of the Department of Agriculture of Western
Australia that flies may be effectually destroyed by
putting a half spoonful of black pepper in powder on
a teaspoon ful of brown sugar and one teaspoonful of
cream. Mix all together and place in a room where
flies are troublesome and it is said they will soon dis¬
appear.

Dr. Paul Freer of Manila tells the writer that in the
Japanese hospitals they take a whole potato and stick
it full of toothpicks, put fly paste on the toothpicks,
and hang the potatoes from the ceiling over the pa¬
tient’s bed on a cord. The flies all gather on the po¬
tato, and when it is full they throw the potato away
and make a new trap. The toothpicks' are placed about
one-fourth of an inch apart, and the potato presents
the appearance of a porcupine.

PREVENTIVE MEASURES

185

Formalin

Ten years or more ago, when formaldehyd gas was
found to be a good germicide, experiments were made
with it against different insects without success ; but
the evaporation of formalin has continued to be of use
in sick rooms. Quite by accident it was discovered by
different people, apparently in different parts of the
world, that a formalin solution is a good mixture with
which to poison flies in the house. So far as we know,
the first person in this country to ascertain this was
Mr. C. H. Popenoe, who at that time was at the Kan¬
sas Agricultural College. In the summer of 1903, dur¬
ing the prevalence of an unusual number of house flies,
while mixing a solution of formaldehyd for the pres¬
ervation of insects (four per cent, formaldehyd, or di¬
lution to ten per cent, commercial), a quantity of the
mixture was left in a mixing dish on the table. Sev¬
eral flies were noticed to alight and drink of the mix¬
ture, quickly succumbing to its influence. A quantity
was therefore placed on a deep plate and set upon the
table. This remained on the table all the afternoon,
and in the evening was surrounded by many dead flies.
The room was practically cleared of the pests. The
dish of formaldehyd was used many times during that
summer and in subsequent years with excellent effect
as a fly poison. The flies seemed not to object to the
presence of the formalin, drinking the water with avid¬
ity and dying close to the plate or saucer, where they
were readily swept up.

186 THE HOUSE FLY— DISEASE CARRIER

Some one else in England and possibly some one
else in France seem to have discovered the same fact
in very much the same way. According to Galli-
Valerio (1910), a ten-per-cent, formalin solution has
been recommended by certain European writers. Tril-
lat and Legendre, for example, advised ten-per-cent,
formalin solution with the addition of twenty per cent,
milk. The Fly Committee of the Merchants’ Associa¬
tion of New York, on the basis of an item in the Lon¬
don Lancet, have advised the use of formaldehyd. A
number of correspondents, however, have written that
they found it unavailing. Dr. Daniel S. Hager, of
Chicago, for example, used formaldehyd in water and
also formaldehyd in milk ; a few flies were found about
the receptacle, but the results as compared with the
results of fly paper were insignificant.

Hodge (1911) states that he has been successful
in the use of a teaspoonful of formalin to a teacupful
of water. He fills a big bottle with the mixture, in¬
verts it in a saucer and mounts the whole in a most
likely place. Sweetening it or mixing it with milk or
other foods to make it more attractive will, he says,
result in the destruction of flies.

Herms, of the University of California (1910),
states that formaldehyd has given thorough satisfaction
as a substitute for poisons. He points out that it is
non-poisonous to man, and may therefore be used with
impunity around food. It is a powerful germicide and
does not injure delicate fabrics. He states that forma¬
lin as purchased in the drug store is in about forty-per-

PREVENTIVE MEASURES

187

cent, solution and should be diluted with water down
to five per cent, or eight per cent. ; in other words, add
five to six times as much water. This solution, he
says, should be sweetened with sugar or made attractive
by adding milk.

He advises partly filling a shallow vessel, such as an
individual butter dish, and placing it upon the table
or in the show window. He states that the flies drink
this material and die not far from the containers. In
the dining-room where there is water, milk, or other
liquid food, flies are said not to be so greatly at¬
tracted to the formalin, but where this is made the
only source of drink for the insects the results are
said to be remarkable. Herms recommends that all
other liquids except the formaldehyd dishes in a
given room should be removed or securely covered
in the evening, so that the flies have only the formal¬
dehyd to drink early in the morning when they begin
to fly.

Some careful experiments were tried during early
February, 1911, at New Orleans, La., at the request
of the writer, by Mr. T. C. Barber. Mr. Barber’s notes
indicate success. The mixture used was formaldehyd
( forty-five per cent. ) , two ounces ; sugar, two ounces ;
water, ten ounces. On February 14th he placed some
of this solution in an open saucer in the show window
of a grocery store, where a few flies were present.
After being left about one hour, seven dead flies were
found in the window, which had previously been thor¬
oughly cleaned. He then placed the material in two

188 THE HOUSE FLY— DISEASE CARRIER

saucers with a piece of bread in each. The bread
soaked up the solution until it was saturated, and was
left over night. The next morning a large number of
dead flies were found in the neighborhood of the sau¬
cers, and were removed. The next day many more
dead flies were found, and very few could be found in
the shop.

On February 15th, he placed some formalin mixture
in a petri dish on one of the meat shelves of a private
meat market. Flies were very abundant. He had no
bread to put in, and so went down to a corner grocery
about one square away to get some. He was absent
ten minutes, and on returning found about one hundred
dead flies on the table where the solution had been
placed. The next day he examined the place in the
morning, and found hundreds of dead flies lying
around, and the numbers in the room were reduced
very materially. The test was conducted under fa¬
vorable conditions, and gave excellent results. Other
experiments by Mr. Barber produced similar results.

Pyrethrum and Carbolic Acid

The fly-fighting committee of the American Civic
Association recommend the burning of pyrethrum
powder and also the dropping of twenty drops of car¬
bolic acid upon a hot shovel, stating that the vapor kills
the flies. The Secretary of the Association, Mr. Wat-
rous, informs the writer that correspondents have com¬
plained that neither the pyrethrum nor the carbolic
acid was in the least effective. I have never tried the

PREVENTIVE MEASURES

189

carbolic acid, but pyrethrum powder is certainly ef¬
fective when at all pure.

Many of the so-called pyrethrum or Persian insect
powders sold in the shops are impure. The powder
itself is made from the ground flower-heads of two
species of the genus pyrethrum, which are composite
plants not unlike the common ox-eye daisy. It is a
not uncommon practice for makers of these powders
to grind the stems as well as the flower-heads, thus
producing a dilution which greatly lessens the effect
of the powder. The insecticidal element in this pow¬
der seems to be an oleo-resin, and therefore a freshly
ground powder is more effective than an old one. In
most of the pyrethrum powders to be found in the
shops the heads have been imported from Europe and
ground in this country.

There are, however, powders of a somewhat higher
price made from pyrethrum flower-heads grown in
California in the vicinity of Stockton. These appear
to be the freshest and strongest, but they cost more.
It has been the experience of the writer that these
California powders are effective against house flies
either when puffed into the air or when burned by
puffing through a gas jet, or by making moistened
cones put upon earthen dishes and ignited at the top.

Repellents

Flies do not seem to be repelled by odors to the same
extent that mosquitoes are. Some old ideas in this
direction, however, may be mentioned. It is stated

190 THE HOUSE FLY— DISEASE CARRIER

that the butchers of Geneva have from time immemorial
prevented flies from approaching the meat which they
expose for sale by the use of laurel oil. This oil —
the odor of which, although a little strong, is not very
offensive — is said to drive away flies, and they are
said not to come near walls which have been rubbed
with it. Furthermore, an item in the Journal of the
Department of Agriculture of Western Australia states
that flies may be kept out of stables by using sawdust
which is saturated with carbolic acid diluted — one part
of the acid to one hundred parts of the water. It is
said that this sawdust scattered about stables keeps all
flies away.

The idea prevails in some parts of the country that
the hop vine grown over a country house keeps the
flies away. Positive testimony to this effect has come
to the writer from several correspondents, but he has
not tested it and mentions it on hearsay evidence only.
An American correspondent who lived in Dalmatia,
for example, was troubled by flies, and was told by
natives to grow hop vines over the side of the house
towards which the flies appeared to come. She did
so, and states that the fly invasion was stopped after
the vines reached a certain height. There was, how¬
ever, possibly some explanation of this aside from the
hop plants.

Search for Breeding Places

In a general way the character of the breeding places
of flies has been described in Chapter I, and the state-

PREVENTIVE MEASURES

191

ment is there made that they will breed in almost any
fermenting organic material. They prefer horse ma¬
nure, but will breed in human excreta, in cow dung,
and the dung of pigs, fowls, and other animals, in fer¬
menting spent hops, bran, in ash barrels containing
more or less organic matter, and in everything of the
sort. Search must therefore be made for every ac¬
cumulation of refuse of this kind within a large radius.
To gain the requisite conditions for fermentation, it is
necessary as a rule for the substances in which flies
will breed to accumulate until a considerable quantity
is reached, at least such an amount as will be readily
noticeable; so that the search for the breeding places
of the bulk of the flies of a given neighborhood need
not be a very close one.

The question arises, however : In how small an
amount of breeding material will fly larvae be found ?
Certain breeding materials will remain moist in small
quantity longer than others; a single dropping from
a cow is very liquid, but it hardens so rapidly on top
and its exterior becomes so tough that the house fly
seems to find difficulty in issuing from it, and perhaps
that is one of the reasons why this substance is not a
more prolific breeding place for this species than it is;
though certain other flies, such as the horn fly of cattle,
breed in cow dung in great numbers.

Horse dung is so mixed with the materials which
have been eaten that it dries very quickly indeed all
through the mass ; so that a single dropping of a horse
in a pasture under ordinary summer conditions will

192 THE HOUSE FLY— DISEASE CARRIER

dry so quickly from top to bottom that, although flies
may and do lay their eggs on it, the larvae are for the
most part destroyed by the drying. When the weather
is at all moist, however, these individual horse drop¬
pings will give out their supply of flies. Again, if the
drying of the manure is delayed only until the larvae
have reached a certain size, they will still be able to
transform. An experiment made by Hine in this direc¬
tion is of interest as showing the vitality of larvae
under adverse conditions. Several glass jars were
partly filled with thoroughly air-dried horse manure;
then from a manure pile larvae of different sizes were
procured, sorted, and put into the jars; flies issued in
every case, but those from the larvae that were small¬
est when sorted out were not more than half normal
size. This suggests that larvae do not have to be very
large before they are in position to contend with ad¬
verse conditions and produce adults even when the
food supply is shut off, since it seems reasonably cer¬
tain that larvae will not feed upon perfectly dry sub¬
stances.

As to human excreta, observations have shown that
single droppings in the field or elsewhere will support
a generation of flies perfectly. In Washington in the
summer of 1900 this was proved on numerous occa¬
sions during June and July.

The possibility of fly breeding from spread manure
is another important and very practical point. Hine’s
unpublished observations on this point are interesting.
Cages covering twenty-five square feet of surface were

PREVENTIVE MEASURES

193

constructed, and horse manure infested with larvae was
spread at the rate of one quart to a square foot. Flies
came out in abundance in these cages, although the
weather was such that the manure and the soil beneath
it were very dry during the time the observations were
taken. After the flies from the larvae that were in the
manure at the time it was spread out all emerged, the
cages were kept in place for several weeks, but another
generation of flies did not appear, indicating that the
careful spreading of manure in the fields in the sum¬
mer does not cause the death of the pupae and of the
majority of the larvae that are in it at the time the
spreading is done, but it does, on the other hand, pre¬
vent the development of future generations in this same
manure.

Thus it often happens that after a lawn has been
heavily manured in early summer the occupants of the
house will be pestered with flies for a time, but finding
no available breeding places these disappear sooner or
later. Another generation will not breed in the spread
manure.

In the search for breeding places no accumulations
of rubbish of any kind must be ignored. Even old
rags and paper under proper moisture conditions will
afford breeding places. All such substances should be
removed or destroyed.

The Treatment of Horse Manure

Some experiments were tried by the writer in the
summer of 1897, with the intention of showing

194 THE HOUSE FLY— DISEASE CARRIER

whether it would be possible to treat a manure pile in
such a way as to stop the breeding of flies. Previous
experience with the use of air-slaked lime on cow
manure to prevent the breeding of the horn fly sug¬
gested the experimentation with different lime com¬
pounds. It was found to be perfectly impracticable
to use air-slaked lime, land plaster, or gas lime with
good results. Few or no larvae were killed by a thor¬
ough mixture of the manure with any of these sub¬
stances.

Chloride of lime, however, was found to be an ex¬
cellent maggot-killer. Where one pound of chloride
of lime was mixed with eight quarts of horse manure,
ninety per cent, of the maggots were killed in less than
twenty-four hours. At the rate of a quarter of a pound
of chloride of lime to eight quarts of manure, however,
the substance was not sufficiently strong. Chloride of
lime, although cheap in Europe, costs at least three and
one-half cents a pound in large quantities in this coun¬
try, so that frequent treatment of a large manure pile
with this substance would be out of the question in ac¬
tual practice. Moreover, if the manure receptacle is in
the stable where horses are kept, or in close proximity
to it, the chlorine fumes arising from a pile thus treated
would be an irritant to the eyes of the live stock.

After these experiments with lime, kerosene was
used. It was found that eight quarts of fresh horse
manure sprayed with one pint of kerosene which was
afterwards washed down with one quart of water was
thoroughly rid of living maggots — every individual

PREVENTIVE MEASURES

195

was killed by the treatment. This experiment and
others of a similar nature on a small scale were satis¬
factory. Practical work during the summer of 1898,
however, demonstrated that on a large scale' this sub¬
stance cannot be used to good effect. A large manure
pile containing the accumulations of a week or ten days
or two weeks and coming from a stable in which four
horses were kept was sprinkled thoroughly with kero¬
sene and an attempt was made to wash the kerosene
down to a certain extent with water. The experiment
was begun early in April and was carried on for some
weeks. While undoubtedly hundreds of flies were de¬
stroyed in the course of this work, it was found by the
end of May that it was far from perfect, since if used
at an economical rate the kerosene could not be made
to penetrate through the whole pile of manure. A con¬
siderable proportion of larvae escaped injury from this
treatment, which at the same time was found to be very
laborious. It was a measure, in fact, which almost no
one could be induced to adopt practically.

The actual experiments indicated the following facts :

Eight quarts of fresh horse manure alive with mag¬
gots were mixed August 5th with two quarts of air-
slaked lime. August 7th no larvae were dead, and on
August 9th very many had hardened into puparia.

August 6th, eight quarts of horse manure were thor¬
oughly mixed with two quarts of gypsum or land plas¬
ter. No larvae were dead three days later.

August 7th, eight quarts of horse manure alive with
larvae were thoroughly mixed with two quarts of gas

196 THE HOUSE FLY— DISEASE CARRIER

lime and spread out in a large tin pan. Two days later
most of the larvae were found to have hardened into
puparia, but none was killed.

September 4th, eight quarts of fresh horse manure
containing larvae were spread out in a tin pan and
sprayed with one pint of kerosene washed down with
one quart of water. September 7th, three days later,
twenty per cent, of the larvae were still living.

September 7th, eight quarts of fresh horse manure
containing house fly larvae were placed in a tin pan,
sprayed with one pint of kerosene, washed down after¬
wards with one quart of water. The manure was then
mixed and a little more water poured on. Twenty-four
hours later every larva in the mass was dead.

October 15th, one pound of chloride of lime was
mixed with eight quarts of well-infested horse manure,
which was kept in a bucket. October 16th, ninety per
cent, of the larvae were dead, the remainder having
burrowed into the large lumps of manure. October
1 8th, no living larvae could be found.

October 21st, one-quarter of a pound of chloride of
lime was mixed with eight quarts of fresh horse ma¬
nure and kept in a bucket. This treatment was unsuc¬
cessful and only two larvae were killed.

Herms also conducted certain experiments in this
direction at the University of California. He found
that the fly larvae are extremely tenacious of life, and
that insecticides which will kill them must be strong,
in fact from two to five times as strong as those which
are useful against other insects. He writes, “Chem-

PREVENTIVE MEASURES

197

icals used to destroy the larvae in the manure pile may
be roughly divided into two classes : ( i ) Contact poi¬
sons, and (2) stomach poisons. To the first class be¬
long such preparations as the kerosenes (generally
used in the form of emulsions) and the creosol prepa¬
rations, also chloride of lime. To the second class be¬
long the arsenicals, represented by arsenate of lead and
Paris green. All of these insecticides are more or less
effective when used in proper concentrations and in
sufficient quantities, but none of them can be applied
with any degree of safety to man or to the domesticated
animals because of either their inflammable, poisonous,
or corrosive nature.”

Prof. S. A. Forbes, of Illinois, also caused a series
of experiments of this sort to be carried on at the Illi¬
nois State Experiment Station at Urbana. The work
was done under his direction by Mr. J. J. Davis. The
notes have not been published, but have been kindly
sent to the writer by Professor Forbes. In these ex¬
periments it was found that three pounds of hydrated
high calcium lime of the Marblehead Lime Company,
mixed with fifteen pounds of horse manure, killed
ninety-four per cent, of the larvae; two pounds mixed
with twelve pounds of manure killed sixty-nine and
one-tenth per cent, of the larvae; four pounds with
twelve pounds of manure killed sixty-one and three-
tenths per cent. The diminished percentage in the
last two experiments is accounted for by the fact that
the larvae were nearly full-grown.

An experiment with two pounds of iron sulphate

198 THE HOUSE FLY— DISEASE CARRIER

dissolved in a gallon of water and poured upon fifteen
pounds of horse manure showed that 941 out of every
1,000 larvae, or ninety-four and one-tenth per cent.,
were killed, while the same amount poured upon twelve
pounds of horse manure killed ninety-five and seven-
tenths per cent, of the larvae. Other experiments with
the same substance indicated in one case that two and
one-half pounds of the iron sulphate to the gallon of
water poured on twelve pounds of manure killed but
seventy-one per cent, of the larvae ; in still another, two
pounds of the sulphate and two gallons of water poured
upon fifteen pounds of manure killed eighty-three and
five-tenths per cent., while one gallon .of the same solu¬
tion to eleven pounds of manure killed none. Experi¬
menting with dry powdered iron sulphate mixed with
horse manure at the rate of two and one-half pounds
to the fifteen, he found eighty-seven and two-tenths
per cent, of the larvae destroyed. At the rate of two
and three-eighths pounds to twelve, eighty-six per cent,
were killed. At two pounds to fifteen, forty-four and
three-tenths per cent, were destroyed. At the rate of
one and one-half pounds to twelve, sixty-nine and
seven-tenths per cent, were killed.

The conclusions drawn from these experiments were
that the breeding of the house fly in manure can be
controlled by the application of a solution of iron sul¬
phate — two pounds in a gallon of water for each horse
per day — or by the use of two and one-half pounds of
dry sulphate per horse per day. It was calculated that
the average city horse produces about fifteen pounds

PREVENTIVE MEASURES

199

of manure daily ; the larger work horses produce twenty
to thirty pounds per day, but, as they are out of the
stables most of the time, the actual amount to be treated
would be much less. The average cost of the treat¬
ment would be one and one-half to two cents per horse
per day. It is stated also that iron sulphate has the ad¬
vantage that it completely deodorizes the manure.

Experiments were also made under Forbes’s direc¬
tion with borax, with a mixture of sodium arsenate and
borax, with a lime-sulphur solution, with salt, and with
carbon bisulphid. It was found that a solution of thir¬
teen ounces of borax to three-fourths of a gallon of
water sprayed over fifteen pounds of infested manure
destroyed over ninety-nine per cent, of the maggots. A
gallon of water containing eleven and one-half ounces
of borax and seven ounces of sodium arsenate applied
to twelve pounds of manure killed all of the larvae. A
pint of lime-sulphur solution in a gallon of water ap¬
plied to twelve pounds of manure killed eighty-six and
four-tenths per cent, of the larvae, while a pound and
a half of salt to one gallon of water applied to twelve
pounds of manure killed eighty-eight and eight-tenths
per cent.

A fluid ounce of bisulphid of carbon evaporated in a
closed box fourteen inches by fourteen inches by nine
inches, containing twelve pounds of manure, destroyed
ninety-nine per cent, of the larvae.

Whenever the subject of treating manure, in order
to kill the maggots which are living in it, is mentioned,
the question arises : What effect will the treatment have

200 THE HOUSE FLY— DISEASE CARRIER

upon the manure itself? Will it destroy its qualities
and render it less valuable as a fertilizer? The ideal
treatment would be to kill the fly larvae and make the
manure more valuable, if that were possible. Finding
that the use of iron sulphate seemed practical, as just
pointed out, Forbes consulted a competent chemist, and
received a reply from which he quotes as follows in a
letter recently received by the writer :

“A great deal of work has been done by German
and French investigators in using sulphate of iron as
a fertilizer. On going over this work carefully, we
cannot find that sulphate of iron has ever proven in¬
jurious to the soil. On the contrary, its use gave very
beneficial results in practically all cases. When sul¬
phate of iron is added to manure it will rarely, if ever,
reach the soil; this for the reason that it will be con¬
verted either into ammonium iron compounds or de¬
composed into its elements. We have used as high as
one hundred pounds of sulphate of iron to one square
rod without rendering the ground sterile.”

Professor Forbes goes on to state that his corre¬
spondent added that sulphate of iron is now being used
in Florida by some of the most progressive orange
growers and that very many carloads of it were shipped
into that State during the summer of 1910. Further,
that the orange growers of California are also buying
it in large quantities. His correspondent concludes by
stating that the small amount of sulphate of iron neces¬
sary for the extermination of flies will not have a dele¬
terious effect upon the soil.

PREVENTIVE MEASURES

201

Dr. H. W. Wiley, the Chief Chemist of the U. S.
Department of Agriculture, was asked for an opinion
regarding the effect upon the manurial value of manure
treated by the substances experimented with under Pro¬
fessor Forbes’s direction. He replied, “The materials
which you mention would affect the agricultural value
of manure in three ways : Alkalies would drive off am¬
monia, and if in not too large quantities, would hasten
fermentation. Lime salts and iron sulphate would
tend to render the phosphates unavailable. All of these
materials mentioned, with the possible exception of
salt, would, if used in sufficient quantity, kill the bac¬
teria of the manure and thus reduce its value, as un¬
doubtedly the value of stable manure is largely due to
the great number of very active bacteria which it con¬
tains. I cannot inform you in what quantities these
various materials would be required to seriously re¬
duce the bacterial content of manure, but it would seem
that, if used in sufficient quantity to kill larvae, they
would have a decided effect on the bacterial life of the
manure.”

Removal of Manure and Receptacles for Its
Temporary Storage

The average time elapsing between the laying of the
eggs and the issuing of the adult flies, as we have seen,
is, in midsummer in the climate of Washington, about
ten days. In warmer regions, and with plenty of mois¬
ture, it may be as short as eight days. Therefore it is
by all means advisable to have manure accumulations

202 THE HOUSE FLY— DISEASE CARRIER

removed at least once a week, although from all points
of view aside from that of convenience a removal and
spreading every day would be better.

The writer has for some years advised that stables
should be fitted with fly-tight pits or closets into which
the daily manure may be shoveled, and which at the
same time should be arranged conveniently for taking
the manure away at intervals of a week. In his first
experiment with the old stables of the U. S. Depart¬
ment of Agriculture he utilized a corner closet with
a door opening into the stable. An outside door was
cut through the wall, and the place was ventilated with
screened apertures. The daily manure was shoveled
in, and conveniently removed into carts, through the
outside door at the week end. And at a large country
club, during the summer of 1910, he advised the build¬
ing of a manure pit in a convenient side hill ; the top
of the pit being near the stable and at a much higher
elevation than the other end of the pit, which was so
situated that a cart could be driven before it, the door
opened, and the manure readily shoveled out.

The regulations of the District of Columbia provide
simply for a covered receptacle, and it has been found
that a tight-covered barrel answers the purpose for a
one-horse stable.

In Berkeley, California, according to Herms (1910),
at such stables a simple galvanized iron-garbage can
has been found very useful and convenient, or even a
tight barrel covered with a tightly fitting lid. In Berk¬
eley the contents of these receptacles are removed once

PREVENTIVE MEASURES

203

or twice a week, either by the city scavengers, or by
gardeners for fertilizing purposes. In the case of a
large stable, where many horses are cared for, Herms
recommends such a closet as was used in Washington,
or the construction of a lean-to or shed connecting with
the stable by means of a small screened door. Where
it is not convenient to construct a lean-to because of
sliding doors or other obstructions, he recommends a
large bin, either of wood or of concrete, with a hinged
top. He illustrates a type of concrete bin used in one
of the fire-engine houses in Berkeley, but shows that
it is not conveniently constructed, since it is unhandy
to remove the manure. It ought not to be difficult to
construct a concrete bin with a lidded top, and a lower
hinged door from which the manure can be removed
conveniently.

The Sanitary Privy

The uncared-for privy, both on farms and in towns,
will eventually disappear, and the sooner it goes the
better it will be for human health. It is a prolific
source of soil contamination and a prolific breeder of
germ-laden flies. Who can estimate the number of
lives that have been lost through the persistence of this
primitive and persistent blot upon conditions of life
which might otherwise be called civilized?

Hardly any one realizes the extent to which this
semi-barbaric institution exists in many parts of the
country, and as a matter of fact I am sure that the
average person in the large city has no idea of the

204 THE HOUSE FLY— DISEASE CARRIER

fact that there are many comparatively intelligent citi¬
zens who in sanitary matters have not even reached
the grade of civilization which demands the sanitary
privy. Stiles, in the course of his great work in the
Southern States, has brought together some startling
figures. He is responsible for the statement that with
4,825 American farmhouses in six different States
2,664, or fifty-five per cent., have no privies of any
kind ; of 2,499 houses inhabited by white people, thirty-
five and three-tenths per cent, have absolutely none,
and of 2,326 inhabited by negroes seventy-six and
eight-tenths per cent, have none. And what shall be
said of the condition of a large part — the very great
majority — of those which do exist? The uncared-for
privy is still a most important factor all over the United
States, even in portions of our most cleanly cities.

In the better class of country houses, especially in
summer country communities of city people, efforts
have been made to improve this condition of affairs;
and it should be said parenthetically that the influence
of these summer country communities of city people
upon the general conditions of the life of the country
people around them is of great and growing value, for
the imitative turn of mind of the young country people
is overpowering the conservatism of the older indi¬
viduals.

But the attempts which have been made even in
some of these summer colonies to attack the privy
question have not been at all satisfactory. The earth
closet has had a great vogue and still remains to a great

PREVENTIVE MEASURES

205

extent. Confining ourselves strictly to the fly question
and to no other, an earth closet unprovided with a
removable bucket and from which the contents are re¬
moved only at considerable intervals is little better than
the uncared-for privy, except that it is usually less ac¬
cessible to flies. A slight covering of earth over the
contents is no protection against the emergence of
adult flies coming from larvae within the substance.
It is not a protection against infestation from flies
coming in from outside, since these have been shown
to lay their eggs upon the earth covering excreta.
When the eggs hatch, the young larvae, being very ac¬
tive, soon burrow to their proper food.

Accurate experiments have been made by several
observers concerning the distance which the newly
emerged fly will struggle through earth to the air.
Hine (in lit.) experimented with ordinary soil and
found in a single experiment that adults were not able
to emerge from a depth of six inches, but Stiles and
Gardner, of the U. S. Public Health and Marine-Hos¬
pital Service, have shown that, -in experiments with
sterilized sand, house flies to the number of thirty-
seven, issuing from fecal material buried in a screened
standpipe under forty-eight inches of sand, came to
the surface. Some of these flies were sent to the
writer’s office for determination and were named by
Mr. Coquillett. They were in a somewhat damaged
condition, due probably to their long struggle for free¬
dom. In the same series of experiments, other flies of
undetermined genus and species struggled up to free-

206 THE HOUSE ELY— DISEASE CARRIER

dom through seventy-two inches of sterilized sand,
truly an heroic struggle!

Dry earth, therefore, is not satisfactory, although in
earth closets provided with buckets removed daily the
problem resolves itself into the cjuestion of the proper
disposal of the contents of the buckets.

In many localities lime is used instead of dry earth.
A careful study of the lime system was made by Stiles
and Gardner in a certain industrial village of the South.
In that village the habit was to clean the outhouses
once a week and to distribute the lime free to the fam¬
ilies. The people were notified repeatedly that the lime
should be used regularly and generously, and the au¬
thorities of the village assured the observers that all
reasonable efforts were made to carry out the system
properly. It therefore seemed to the Government men
that this particular village was a very fair case to take
as a basis for observations as to the actual workings of
the system. Their observations were careful, and they
found that in thirty-two instances out of eighty-eight
the lime had actually been used, and the conclusion was
that, even where lime is furnished free of cost and the
people are urged to use it, it is not generally adopted.
Moreover, of the thirty-two outhouses in which it had
been used, it was freely used in only three cases.

The conclusion was that families cannot be relied
upon to use it properly. In not one instance of the
eighty-eight did they fail to find exposed night-soil of
easy access to flies and other insects. Live fly larvae
were found in all samples taken. It may be mentioned

PREVENTIVE MEASURES

207

also, incidentally, that live hookworm eggs were also
found. Interesting observations were made upon the
practical workings of the cleaning process, which need
not be detailed except to state briefly that the process
of cleaning was by no means perfect, and that in carry¬
ing the cartloads away flies and possibly contaminated
flies were distributed here and there and everywhere,
while the dump was inhabited by swarms.

The lime system, therefore, is a failure, even if one
can rely upon its proper administration, and it is not
only a failure, as pointed out by Gardner and Stiles,
but it is an additional menace from the feeling of false
security which it gives to the persons who use it.

It seems, as a result of the experimental work car¬
ried on by the observers mentioned above, that surface
privies should without further delay be remodeled into
a tub, pail, or barrel system, and that water or kero¬
sene and water should be used to kill fly larvae or hook¬
worm eggs or other dangerous forms found in excreta.
Their experiments indicate that a mixture of crude
carbolic acid and water will kill the fly larvae, but on
account of the dangers in the use of this mixture they
do not recommend it. Water only, placed in the bucket,
is not recommended, since not only may live eggs of
the hookworm be found in the water at the end of
twenty-four hours, but mosquitoes will lay their eggs
in the buckets and breed there. A film of kerosene
on the surface of water kills everything, including
hookworm eggs, round-worm eggs, fly larvae, and mos¬
quito larvae. The principal objection to the use of

208 THE HOUSE FLY— DISEASE CARRIER

water with a film of kerosene on top in an ordinary
unprotected tub. pail, or barrel system is that if the
water is too deep splashing occurs, and a wet system
calls for a large receptacle.

In a recent publication, Stiles (1910) covers the whole
subject, and gives directions for building a really sani¬
tary privy, indicating that any fourteen-year-old school¬
boy of average intelligence in mechanical engineering
could, by following the plans given, build a sanitary
privy for his home at an expense for building materials,
exclusive of receptacle, of from five to ten dollars, ac¬
cording to locality. The plan (directions for its con¬
struction are printed as Appendix IV) provides for a
flv-proof structure, well ventilated, with a receptacle
for the excreta mounted on a floor and protected from
behind by a hinged door through which it can be re¬
moved. The receptacle always contains the necessary
amount of water with a film of kerosene floating on it.
The most casual observation will indicate when to re¬
new the water and kerosene and when to empty the
receptacle.

Since the publication of the bulletin in question,
Lumsden, Roberts, and Stiles, of the Public Health
Service, have devised an additional arrangement which
they have had in constant use in the Hygienic Labora¬
tory at Washington for several months. Concerning
the practical workings of this apparatus they seem
very enthusiastic. The writer himself has visited it
and found it perfectly unobjectionable after being in
use for more than three months without having been

PREVENTIVE MEASURES

209

once emptied. A description of the apparatus with a
diagram of its construction will be found in Appendix
V. Its cost of construction is said to be about $1.40.

There seems no doubt that this invention of the of¬
ficers of the Public Health and Marine-Hospital Ser¬
vice is the best down to the present time in the way
of a sanitary privy. Recommendations, however, have
been made in this direction by boards of health and by
private individuals. Rev. George W. Lay (1910), for
example, has given at considerable length directions
for the construction of a good privy, and terms it “The
North Carolina Sanitary Privy.” He rather holds to
the dry-earth view, and mentions kerosene only by
stating that if a little of it is sprinkled in the privy box
it will have a tendency to keep the flies away.

Kerosene, however, should be used, not so much as
a preventive, but as a means of destroying eggs and
larvae. In communities like mill towns, where the ma¬
jority of the flies breed in the privies owing to the lack
of horse stables and horse manure, and it may be
found impossible to compel the construction of new
sheds, the use of kerosene on the dejecta will be ef¬
fective.

In 1906, the Paris journal Le Matin offered a prize
for the best methods of destroying flies. The compe¬
tition attracted a great deal of attention, which was
fostered by the newspaper by frequent articles. The
prize was finally awarded to an anonymous writer who
proposed to pour green oil of schiste in privies and
upon manure piles, mixing it in the latter case with

210 THE HOUSE FLY— DISEASE CARRIER

earth or lime. The oil of schiste is a crude petroleum
found in Europe. In the number of July 19, 1907,
the paper stated that this proceeding had given excel¬
lent results and that flies had disappeared wherever it
had been applied. At the International Congress of
Hygiene in Berlin following, Professor Bordas con¬
firmed the statements of Le Matin, and added that the
Governor of Kiaotscheau had obtained excellent re¬
sults by the oil method. Galli-Valerio (1910), being
greatly interested in this matter, wrote to Doctor Dirk-
sen, physician to the Government at Tsingtau, and
found out that only five liters of the oil of schiste were
sent to the Governor by Le Matin , and thinks that the
results of work on such a small scale are not at all con¬
vincing. Experiments made by the writer, however,
with the use of kerosene upon horse manure, convince
him that it will act equally well in privies, and in this
statement he has the endorsement of Stiles and others.

A Compulsory Sanitary Privy Law

The following paragraphs, quoted from Stiles
(1910), excellently express some very sound ideas on
this subject.

“A compulsory sanitary privy law or ordinance
should exist and be strictly enforced in all localities in
which connection with a sewer system is not enforced.

“Since, from a sanitary point of view, the privy is
a public structure in that it influences public health, it
seems wisest to have city and town ordinances which
provide for a licensing of all privies, the license being

PREVENTIVE MEASURES

211

fixed at a sum which will enable the city or town to
provide the receptacles (tub, pail, etc.), the disinfectant,
and the service for cleaning. The expense involved
will vary according to local conditions, such as cost
of labor and density of population. If the “chain gang”
can be utilized for cleaning, the expense for labor is
reduced.

“The importance of taking the responsibility for the
care of the privy out of the hands of the family is
evident when one considers that one careless family
in ten or in a hundred might be a menace to all. The
removal of garbage and of ashes is recognized as a
function of the city or town in all better-organized com¬
munities, and the idea is constantly spreading that this
service should extend to a removal of the night-soil
also.

“In correspondence with certain cotton mills, esti¬
mates for privy cleaning (once a week) vary from
about twenty to twenty-five cents per privy per month.
A privy tax of $3.50 to $5 per privy per year ought
to give satisfactory service, including receptacle, but
the exact amount of the tax must be determined by
experience in each locality.

“It is probably the exception that an economical pub¬
lic privy-cleaning service can be carried out in the open
country, on account of the distances between the
houses. To meet the difficulties involved, several sug¬
gestions may be considered, according to conditions :

“A country privy tax can be levied, the county can
furnish the pail and the disinfectant, and ( 1 ) one mem-

212 THE HOUSE FLY— DISEASE CARRIER

ber of each family or of several neighboring families
hired to clean the privy regularly; or (2) the landlord
can be held responsible for the cleaning of all privies
of his tenants, receiving from the county a certain sum
for the service; or (3) “trusties” from prisons might
possibly be utilized in some districts not too sparsely
settled; or (4) a portion of the county privy tax might
perhaps be apportioned by school districts and be dis¬
tributed as prizes among the school boys who keep
their family privies in best condition; or (5) each
head of family might be held responsible for any soil
pollution that may occur on his premises and be fined
therefor.

“Undoubtedly the problem of the privy cleaning in
the open country is much more difficult than in cities,
villages, and towns, and in the last instance involves
a general education of the rising generation of school
children, more particularly of the girls (the future
housekeepers), in respect to the dangers of soil pollu¬
tion.”

The Capture of Adult Flies Outside of Houses

Under this heading, the plan proposed by Professor
Hodge, mentioned in the introductory paragraphs of
this chapter, must be considered. His idea, it will be
remembered, is to catch the adult flies before they lay
their eggs and before they become a nuisance in houses.
Isolated observations by Dr. C. Gordon Hewitt have
shown, as elsewhere stated, that in England ten to
fourteen days elapse after an adult female fly issues

PREVENTIVE MEASURES 213

before she lays her eggs, and it is during this period
that Hodge proposes to catch her.

It is interesting to know the way in which the idea
came to his mind. In a paper entitled “Extermination
of the Typhoid or Filth Fly, a Plan of Campaign,” read
before the annual meeting of the American Civic Asso¬
ciation in Washington in December, 1910, he shows
that for eight years previously he had amused himself
in the summer by rearing native birds, especially the
ruffed grouse and the bob-white. The enormous quan¬
tity of insect food required by the young chicks led him
to what seemed to him the most effective plan of deal¬
ing with the fly problem. He needed flies with which
to feed his chicks, and the problem was to get flies in
the greatest numbers possible.

Having perfected what seemed to him an excellent
method of accomplishing this, he began to argue as
to the use of his idea as a substitute for the treatment
or removal of the manure pile or the treatment or re¬
moval of all substances in which flies will breed. Think¬
ing of the enormous multiplication of the offspring of
a single pair in the springtime, he asks the pertinent
question, “Why not catch the original pair of flies in
April?” After studying the problem for some time,
he became so enthusiastic over the prospect that in his
address he uses the following sentence: “If, beginning
next spring, every family will adopt effective meas¬
ures to kill the few hundred flies that succeed in sur¬
viving the winter, I am convinced that we could rele¬
gate our window screens to the scrap heap, so far

214 THE HOUSE FLY— DISEASE CARRIER

as our protection against Musca domestica is con¬
cerned.”

He plans certain lines of attack, all directed against
the adult fly out of doors. The first of these lines con¬
sists in the effort to trap the flies at their source of
food supply. On the supposition that everything in
the way of waste food which is attractive to flies is
or can be placed in garbage cans or swill barrels, he
believes that a double wire screen trap can be attached
to this receptacle in such a way as to catch every fly
that is attracted to it. He shows that in some cities
the rules of the boards of health require that all such
receptacles should be tightly covered. He considers
that this is a serious mistake, since it drives the flies
from the garbage into the kitchens. The garbage cans,
to his idea, can be made so attractive as to draw the
flies out of the kitchens and focus them at' one spot
and catch them as soon as they come. As fast’ as the
traps are filled, the contents are scalded and removed
and fed to chickens or put into the garbage can.

He has devised a trap attachment to garbage cans
with which on one occasion he caught 2,500 flies in
fifty-five minutes. This was back of a market in an
ice-cream stand. The can was baited with fish heads,
meat scraps, watermelon rinds and green corncobs,
over which the melted waste from the ice-cream freez¬
ers was poured. The cover of this can was held up
by strips of metal soldered to the can so as to keep
about a quarter of an inch fly space entirely around
the can through which the flies could enter. Then a

Fig. 20. — Fly trap for garbage cans; designed by Prof. C. F. Hodge.

PREVENTIVE MEASURES

215

wire gauze trap was set over a hole on the sunny side
of the top of the can. The flies crawled in, attracted
by the odor of food, and attempted to escape by the
only opening through which the light came, thus enter¬
ing the trap.

Another form devised by Hodge had a tight can
cover, the trap being contained within the cover. The
trap itself forms the only entrance to the can, and the
flies attracted by the odor enter the trap. Another
trap devised was a wire gauze cylinder fitting over a
tomato can, the can being filled with attractive sub¬
stances, and the trap being arranged so as to be scat¬
tered around stables or barnyards or wherever flies
happen to be congregating or breeding.

He made still another arrangement for a screen for
a stable cellar or manure pit window, making a small
hole in the screen near the top and providing the screen
with narrow strips of tin or wood to guide the flies to
the hole; the hole, of course, leads into a wire gauze
trap, where all the flies that emerge will be caught. In
the same way he made another, also provided with
guiding strips, on the outside, and furnished with a
trap on the inside, so as to catch all of the flies that
might be attracted to the stable to lay their eggs. This
latter idea he has not )^et tested, but he argues that
if the outside flies were shut out by screens they would
certainly find some other breeding place in which to
lay their eggs.

On the habit that flies have of being attracted to
kitchens by the odor of the cooking or by the warmth

216 THE HOUSE FLY— DISEASE CARRIER

on cool nights, he bases another line of attack, which
is to make a hole in the window screen, with the guid¬
ing strips outside and the trap inside, thus catching
all the flies that attempt to enter the kitchen in that
way. He has tested this device, but thinks that it can¬
not compete with the garbage-can trap.

Professor Hodge (1910) points out that there is
much yet to be known about the biology of the adult
typhoid fly, its favorite foods, its needs for water, its
habits in seeking shelter, length of life, and the dis¬
tance it flies, but he thinks that what little we know
indicates that the strategic point of attack is the adult.
He states that we have been long working on this
theory unintelligently and ineffectively with sticky or
poisonous fly paper and traps, but that these means
have been employed only to kill the comparatively few
flies that gain entrance to our houses.

“Carry the war into Africa; develop the means of
attack seriously and effectively in the out-of-doors, and
I fully believe that there will be no filth flies to go
back to the compost heaps and barnyards to lay their
eggs.” After using his traps for a period, he found it
possible to dine on the porch ; as he expressed it, he
had turned the tables on the flies, and put them in a
prison and let himself out. Hodge wishes to stimulate
invention towards making effective out-of-doors fly
traps, and he urges experiments with different baits.
He states that he did enough in the summer of 1910
to be convinced that any country home “a half mile
away from its nearest ignorant neighbor, or any town-

PREVENTIVE MEASURES

217

or city, could completely exterminate the filth fly by
intelligent and co-operative effort during the months
of April and May (and possibly June) of any year.”

In this connection it may be well to call attention
to the device invented by Kellers (1911), which is a
wire gauze garbage-can holder which will contain sev¬
eral garbage cans. It allows daily inspection and free
circulation of air. It aids in the suppression of the
fly nuisance and the prevention of the scattering of
putrescent material by rats, cats, and other animals.
The designer of the holder is a hospital steward in the
United States Navy, and the one first designed is in
use at the U. S. Naval Hospital, Puget Sound. Some
such arrangement for hospitals and other similar in¬
stitutions will be excellent, and the addition of Hodge’s
fly-trap idea will be easy.

Special Considerations for Towns and Cities

In the country, the individual householder should
care for his own surroundings in such a way as to
free himself from flies, but in communities this will not
be effective. A single stable owner by the proper care
of his manure may greatly reduce the local supply,
but there will still be many thousands from other stables
in the neighborhood and from other possible breeding
places nearby. It becomes necessary therefore that an
organization of some kind or some system of co-opera¬
tion should exist in communities.

218 THE HOUSE FLY— DISEASE CARRIER

Organisation

In a number of towns and cities in the United States,
the initiative in the fly crusade has been taken by health
officers, but in the majority of communities the health
officials have to be stirred up. In some cases, as in the
State of Florida, the whole State crusade has been
begun by the State officials and they have stirred up the
town officials. In a few communities — but these are
very few — private practitioners have been the exciting
cause of anti-fly work. In one State only, so far as
the writer knows, has the State medical association
established a fly committee which has taken it upon
itself to carry information concerning the typhoid fly
into every portion of the State.

Elsewhere, and here are the majority of instances in
which anti-fly work has been begun, the beginnings
have been made either by a single private individual
or by some local organization, as a civic league, a wom¬
en’s club, or a town improvement society. Women’s
clubs have done very effective' work in this direction,
and it may be parenthetically stated that a great latent
power exists in these organizations, a power which is
only just beginning to manifest itself. The energy
shown for years by these organizations, while never
misdirected, has not until very recently been directed
towards the work which is the most productive for. the
good of all, namely, general sanitary measures with a
focusing upon one point after another. The Women’s
Municipal League of Boston, as an example, has re-

PREVENTIVE MEASURES

219

cently taken up the fly question through its department
of sanitation, of which Mrs. Robert S. Bradley is the
chairman, and is doing admirable work.

In most communities nowadays, one or the other of
these organizations or all of them exist. In towns
where there are no such organizations, they should be
started at once. In such cases let any one convinced
of the necessity for an anti-fly crusade talk to his or
her friends and, unrebuffed by indifference on the part
of others, persevere until a group is formed. Then
with perseverance the growth of the organization and
the growth of public spirit in many directions will be
rapid.

The first effort of such an organization should be to
enlist the sympathy and co-operation of the health au¬
thorities of the community. This gained, every pos¬
sible effort should be made to induce the controllers of
the appropriations for the health officials to realize the
importance of this work. Health officers without funds
at their disposal for the employment of inspectors and
for the carrying out of regulations are hopeless, and
therefore the first step, after the health officials them¬
selves are convinced of the desirability of the work,
is to secure the funds. In some cases this has been
done by private subscription, the money to be expended
under the supervision of the health officers. In other
cases private individuals with sufficient leisure have
had themselves appointed as health inspectors without
salary, but by virtue of the appointment they are armed
with the legal authority which the health board has.

220 THE HOUSE FLY— DISEASE CARRIER

Continuous and successful voluntary work of this kind,
however, is not to be relied upon, and the campaign
for funds, and preferably for regularly appropriated
funds, must be a strenuous one.

Before all this, however, a campaign' of publicity
must be inaugurated, and in such a campaign the local
newspapers are of great assistance; in fact in many
cities during the summer of 1910 the local newspapers
themselves inaugurated the campaign. Four excellent
instances of this which have come under the writer’s
observation are the campaigns begun and carried
through the summer by the Minneapolis Tribune, the
Kansas City Star, the Milwaukee Sentinel, and the
Washington Evening Star.

Mr. Leroy Boughner, city editor of the Minneapolis
Tribune, wrote up his newspaper anti-fly campaign in
an excellent paper which was read before the Decem¬
ber, 1910, meeting of the American Civic Association,
and in his introductory paragraph he made the follow¬
ing explanation :

“An intelligent newspaper campaign against the
house fly is not only a great benefit to the community
in which the newspaper circulates, but it is of direct
value to the newspaper itself, both in the increased
prestige it gets as a sponsor for civic betterment and
in the advertising that accrues from dealers in
screens, drugs, and sanitary appliances. The cam¬
paign conducted by the Minneapolis Tribune in 1910
accomplished both results, and the story of how it
was done is an interesting one.” Could any but an

PREVENTIVE MEASURES 221

experienced newspaper man have written that para¬
graph ?

Mr. Boughner goes on to describe how the literature
furnished by the American Civic Association and by
various State and city boards of health and other
organizations was collected and from these were culled
hundred-word articles, general in nature, but prepared
in such a way as to attract the attention of every reader.
These were started in April, and after they had been
running for a week or so letters were sent to every
club in Minneapolis suggesting that they endorse the
campaign, and these resolutions kept coming in for a
month or more, and were printed, giving a local tinge
to the campaign. Then the local and State health of¬
ficials were interested and were quoted wherever it
seemed necessary. Then the State Entomologist was
approached, and he was quoted. The use of gruesome
pictures was avoided as a rule, but occasionally the
readers were startled with a statement and a picture
that helped to intensify the interest. When the Tuber¬
culosis Committee of the Associated Charities advised
drug store keepers to cover their wares, the Tribune
took the matter up and drew a fly moral from it. Very
often it happened that the ammunition furnished by
this paper was most valuable, and as an example Mr.
Boughner states that seven cases of typhoid in a suburb
of Minneapolis were traced to the typhoid fly. Every
change of weather was used as a pretext for a new
editorial, and at the conclusion of the campaign a big
story was written summing up the results. *

222 THE HOUSE FLY— DISEASE CARRIER

As a rule the newspaper can be relied upon in such
a meritorious campaign as this, and city editors should
if possible be placed upon the committees of the civic
organizations. The newspapers, however, should be
supplemented by posters, and by tracts explaining the
whole situation in a few striking sentences. This has
been done very extensively in some cities. It is im¬
portant that the organization should not rest with a
single poster or with a single tract, but the subject
should be emphasized again and again, just as some
of the newspapers did last summer. In this way the
whole community becomes at least educated upon the
subject, and, with a very general knowledge of the
fact that flies are dangerous as well as burdensome and
of the fact that they can be controlled, a great step has
been gained. In other words, with this education prac¬
tically the whole community will be found to support
the movement.

Let us take the case of a community in which such
work has not yet been undertaken ; let us suppose it to
have been started in any one of the ways which we have
mentioned ; let us suppose that an organization has been
perfected or is in process of being perfected, and that
the campaign for publicity is about to begin. The
easiest way to get ammunition is to write to the Secre¬
tary of the American Civic Association, Mr. Richard
B. Watrous, whose address is Union Trust Building,
Washington, D. C. The fly Committee of this asso¬
ciation, of which Mr. Edward Hatch, Jr., of New
York, is the chairman, has done some very energetic

PREVENTIVE MEASURES

223

work, and the whole association seeks the opportunity
to co-operate directly with civic societies of every char¬
acter, such as women’s clubs, local civic leagues, con¬
sumers’ leagues, school improvement societies, and all
organized bodies, in a direct crusade against the ty¬
phoid fly.

The association publishes bulletins with full infor¬
mation as to the life history and habits of this fly and
with the most practical suggestions, secured after con¬
ference with the leading physicians and entomologists.
These bulletins are sent to societies in quantities, but
there is sometimes a small charge for very large quan¬
tities. The association also co-operates directly in pro¬
viding press clipping sheets that may be used to great
advantage with local newspapers, calling attention to
the dangers in permitting flies to breed unrestrictedly.
It maintains also a department of lantern slides, which
includes a large collection of pictures, some of them
descriptive of the life history of Musca domestica, and
others being reproductions of striking cartoons from
the newspapers, and of effective posters that have been
used by health boards and may be used for display in
public places, such as shops, railroad stations, and on
the street cars, to call attention to the dangers sur¬
rounding the existence of the fly. It has also a very
effective moving-picture film which can be rented by
societies and which is a most effective manner of pre¬
senting vividly the objectionable habits of the house
fly.

The association has also, for use by societies willing

224 THE HOUSE FLY— DISEASE CARRIER

to pay express charges, a large cabinet containing ex¬
hibits of every character, such as posters, bulletins, and
actual pictures of flies in their breeding places and as
distributers of disease. This cabinet can be set up in
public places to great advantage. One of the pictures
in this cabinet indicates the air-line flight of the typhoid
fly from the garbage pail to the breakfast table; an¬
other shows a stable with an enormous manure pile,
and enlarged figures on the development of the fly. A
third pictures food exposed on the streets and swarm¬
ing with flies. A fourth is a photograph of a privy
vault swarming with flies, close to the kitchen door.
Another is a reproduction of the striking fly poster
of the Florida State Board of Health (shown in Fig.
2i ). An admirably worded placard reads, “If there
is any contagious disease in the neighborhood, beware
of flies.”

Interesting the Children

Considering the exasperating conservatism of the
public at large when the anti-mosquito campaigns be¬
gan to be inaugurated ten years or more ago, and the
fact that even after mosquitoes had been written about
and preached about until it would seem that no intelli¬
gent citizen in the country could have failed to be con¬
vinced of such admirably demonstrated facts as the
carriage of malaria and yellow fever by certain of these
dangerous creatures, and of the perfect practicability
of a startling reduction in their numbers by the ex¬
penditure of a certain amount of money and hard work,
the majority still remained ignorant or unconvinced;

From FLIES and FILTH
to FOOD and FEVER

Fig. 21. — Poster issued by the Florida State Board of
Health ; greatly reduced.

PREVENTIVE MEASURES

225

considering this delay, it is a delight to see the com¬
parative rapidity with which the anti-house-fly idea is
spreading. Possibly had this latter crusade been be¬
gun first it would not have moved so rapidly ; possibly
the education which people have had in regard to mos¬
quitoes makes them more ready to accept the ideas that
are being put forward by the anti-fly movers.

But in the case of mosquitoes, in more than one com¬
munity it was found absolutely impossible to do any¬
thing with the adults, and education was begun with
the children in the schools. Probably the first of this
work was carried on by Prof. C. F. Hodge in Worces¬
ter, Mass., in 1901 or 1902, and he was very successful
in interesting the school children in the search for mos¬
quito breeding places.

The most serious and productive effort, however, was
made at San Antonio, Texas, a year or two later, at
the initiative of Dr. J. S. Lankford. The school board
approved the idea of endeavoring to educate all of the
school children of the city in prophylaxis, and to make
sanitarians out of all of them. The best medical lit¬
erature on the subject was procured and furnished to
the teachers. A circular letter was sent to them out¬
lining the proposed course, and offering a cash prize
for the best model lesson on the subject. Teachers
became greatly interested ; a crude aquarium with
eggs and wrigglers was kept in every schoolroom where
the pupils could watch them develop, and large mag¬
nifying glasses were furnished in order that they might
study to better advantage. The children were en-

226 THE HOUSE FLY— DISEASE CARRIER

couraged to make drawings on the blackboard of mos¬
quitoes in all stages of development. Lessons were
given; compositions were written on the subject; com¬
petitive examinations were held, and groups of boys
and girls were sent out with the teachers on searching
expeditions for the breeding places.

Rivalry sprang up between the 10,000 public school
children in the city in finding and reporting to the
health office the greatest number of breeding places
found and destroyed. Records were kept on the black¬
boards in the schools of the progress of the competi¬
tion, and great enthusiasm was stirred up. In addition
to these measures a course of stereopticon lectures was
arranged, grouping the pupils in audiences of about
1,000, from the high school down, and in Doctor Lank¬
ford’s words, “It was an inspiring sight to watch these
audiences of 1,000 children, thoughtful, still as death,
and staring with wide-open eyes at the wonders re¬
vealed by the microscope. It seemed to me that in
bringing this great question of preventive medicine be¬
fore public school children we had hit upon a power
for good that could scarcely be over-estimated.” As
a result there was a decided diminution in the numbers
of mosquitoes in San Antonio. There was some oppo¬
sition among the people, but the movement on the
whole was very popular, and the mortality of the city
from malarial trouble was reduced seventy-five per cent,
the first year after the work was begun, and in the
second year it was entirely eliminated from San An¬
tonio !

PREVENTIVE MEASURES

22T

It follows that in organizing community work, not
only against mosquitoes but against flies as well, the
school children must be counted upon as a most im¬
portant factor. Almost all children are born naturalists,
and interest in such things comes to them more readily
than anything else outside of the necessities of life.
They are quick-witted, wonderfully quick-sighted, and
as finders out of breeding places they cannot be ap¬
proached except by adults with the most especial train¬
ing.

The specific question of interesting school children
in the house-fly campaign was brought up at the De¬
cember meeting of the American Civic Association.
It was introduced by the writer and had also been
previously considered by the Fly Committee of the as¬
sociation, of which, as previously stated, Mr. Hatch
is the chairman. The association plans to offer prizes
for school children in certain selected cities, prizes ag¬
gregating for the ordinary town say from thirty to
fifty dollars. These are to be competed for by chil¬
dren of the public schools, and in two classes : first,
young children between the ages of nine and eleven ;
and, second, children from twelve to fifteen ; so that
the younger children will not come into competi¬
tion with the older and presumably better prepared
ones.

It will be necessary in order to do this, in some cases,
to do a little work with school boards, so that they
may be willing to admit into the schools the literature
which will be the basis of the essays. Health boards

228 THE HOUSE ELY— DISEASE CARRIER

and medical societies, however, will naturally be will¬
ing to co-operate. The association hopes that there
will be public-spirited citizens in the various towns
who will themselves institute competitions of this
sort.

Referring to this matter, in a paper read later at
the meeting, Doctor Woods Hutchinson said, “I be¬
lieve that we could utilize an enormous amount of
good enthusiasm and good human activity going to
waste under the name of ‘mischief,’ and if we could
take the enthusiasm of a boy and his delight of get¬
ting into mischief and put him to work on the fly
problem, I believe we could do a great deal towards
putting any community into a practical process of
cleansing.”

An important point which we have not yet men¬
tioned is that it will be important to have one or more
well-posted physicians on the advisory board of any
fly-fighting organization, in order that the tendency
of enthusiastic people to make extreme statements
which are unscientific and not perfectly justified by
facts may be held within bounds by others posted as
to scientific methods and as to the exact truth of the
sanitary aspects of the crusade. The advisory com¬
mittee, and especially its medical members, will find
themselves much embarrassed by the difficulty of re¬
fraining from over-statements.

The fly situation is an extremely bad one in all truth,
but if it is exaggerated in order to attract and inten¬
sify universal popular interest, the very exaggeration

PREVENTIVE MEASURES

229

will have the contrary effect upon the minds of con¬
servative people, and upon medical men who stand
for absolute exactness of statement. Moreover, there
are in every large community scientific men trained in
laboratory methods, who believe that exact truth can
be obtained only by laboratory methods and who hold
the verdict of “not proven” against certain things which
on the strongest circumstantial evidence have been
claimed against the fly. It is best to carry this con¬
servative class with you if you can, and this can be
done by a certain moderation in statement and by the
avoidance of methods which may be termed ultra-yel¬
low-journalistic.

And there is the quandary : how to frighten the ig¬
norant and slothful and educate them on the fly ques¬
tion without creating a distaste for your methods and
a consequent lack of helpful interest on the part of
some who could be of the most valuable assistance. The
writer, although he was trained to scientific methods
and has followed them for many years, is inclined to
think that over-statement to bring about a great san¬
itary reform may be justified so long as this over¬
statement is based upon sound circumstantial evidence.

He is thoroughly optimistic as to the progress, in
the immediate future, of the campaign of education
against the typhoid fly, and he is certain in his own
mind that, take the country by and large, and includ¬
ing all classes of citizens, whether living in cities, towns,
villages, or on farms, there is no single way in which
the mortality rate of the country can be so rapidly de-

230 THE HOUSE FLY— DISEASE CARRIER

creased, and, per contra, the health of the people so
easily bettered, as by the reduction of the numbers of
the house fly to a negligible quantity.

Boards of Health

The health officers, both State and local, of the coun¬
try have their associations and organizations of one
kind or another. Probably all of them are members
of the Public Health Association of the United States.
All are thus, or should be, acquainted with the work
of all the rest, since there is a constant interchange of
ideas at the meetings and a constant interchange of
publications in the intervals between the meetings. But
it is well for citizens' associations, civic leagues, wom¬
en’s clubs who take up sanitary matters, and public-
spirited citizens generally, to know what an effective
health officer or board of health should do, in order
that they may intelligently criticise the administration
of such matters by their own local officials in case,
when, as it sometimes happens, these are lax; or, on
the other hand, back up efficient officials where village
trustees or town councils or city boards of aldermen
are not disposed to grant the funds necessary to carry
out proper sanitary regulations.

This is our excuse for quoting at length the sanitary
regulations of the District of Columbia in so far as
they relate to the fly problem. The regulations are
sound and the citizens of the District have no cause
in this respect to criticise the health officer, but the
appropriating body in this case (and it happens to be

PREVENTIVE MEASURES

231

the Congress of the United States) has not down to
the present time appropriated sufficient funds to carry
these regulations into full effect. Good regulations
require an efficient force of inspectors, and efficient in¬
spectors must be paid. Dr. William C. Woodward,
the health officer of the District, has called the writer’s
attention to the fact that it really requires, from the
practical standpoint, two inspectors to do one inspec¬
tor’s work, since a solitary inspector, coming into court
with a charge of violation of the regulations against
a given citizen, is invariably confronted with such a
mass of testimony against his charge that he is sworn
out of court. He must take some one along with him
to prove it. The orders in question may be briefly con¬
densed as follows ; their full text will be found in Ap¬
pendix III :

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 there¬
with, 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

232 THE HOUSE FLY— DISEASE CARRIER

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 any of 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 ist and October 31st, and at least once
every week between November ist and May 31st 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 effectu¬
ally 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 per¬
mit from the health officer. Any person violating any
of these provisions shall, upon conviction thereof, be
punished by a fine of not more than forty dollars for
each offense.

In addition to this excellent ordinance, others have
been issued from the health department of the District
of Columbia which provide against the contamination
of exposed food by flies and by dust. The ordinances
are excellently worded so as to cover all possible cases.
They provide for the registration of all stores, markets,
cafes, lunch rooms, or of any other place where food
or beverage is manufactured or prepared for sale,

PREVENTIVE MEASURES

233

stored for sale, offered for sale, or sold, in order to
facilitate inspection, and still more recent ordinances
provide for the registration of stables. An excellent
campaign was begun during the summer of 1908
against insanitary lunch rooms and restaurants. A
number of cases were prosecuted, but conviction was
found to be difficult for the reasons already mentioned.

All boards of health should follow, and doubtless
are following, the very interesting experiment which
the Louisiana Board is now making, of sending out
a “Health Train” and visiting one town after another,
conducting health demonstrations and lectures and
showing moving pictures which appeal directly to the
intelligence of every one. Three hundred and fifty
towns in Louisiana have already .been visited in this
way, and education on the house fly has been a very
important part of the work. The first train was sent
out from New Orleans November 5, 1910, and con¬
sisted of two especially equipped cars. An illustrated
article on the subject was published in the Quarterly
Bulletin of the Louisiana State Board of Health, i,
No. 4, November 15, 1910.

Army Camps

The severe lessons of the past in regard to fly-borne
typhoid in army camps have borne fruit, and there is
reason to believe that among the more civilized nations
in the future there will be no recurrence of the frightful
experiences of the summer of 1898 and of those in
South Africa. It is with the greatest pleasure that the

234 THE HOUSE FLY— DISEASE CARRIER

writer learns, just as this book is going to the press,
of the regulations in force at San Antonio, Texas, in
the large encampment of troops there present. The
camp sanitary regulations appear to be of the most
perfect kind and to be admirably enforced. An account
of the methods used will doubtless soon be published
by the Medical Corps of the Army, and the writer re¬
frains from anticipating such publication, since the ob¬
servations on which he bases this statement of the per¬
fection of the arrangements have been made by persons
not connected with the service. He may state however
that the Medical Corps deserves the greatest praise for
the introduction of novel and very perfect arrangements
for the disposal of all camp waste.

OTHER FLIES FREQUENTING HOUSES

IN a series of experiments carried on during the sum¬
mer of 1900, flies were collected in the kitchens and
dining-rooms of many houses in many different parts
of the country. These collections were made in the
States of Massachusetts, New York, Pennsylvania,
District of Columbia, Virginia, Florida, Georgia, Lou¬
isiana, Nebraska, and California. In all, 23,087 flies
were thus collected. On critical examination in Wash¬
ington by Mr. Coquillett, 22,808, that is to say, ninety-
eight and eight-tenths per cent, of the whole number
captured, were Musca domestica. The remainder, con¬
sisting of one and two-tenths per cent, of the whole,
comprised various species, none of them of any espe¬
cial significance. These and a few others will be con¬
sidered in more or less detail in the following para¬
graphs.

Of course there are other flies than these occasionally
found in houses, and some quite commonly so. Mos¬
quitoes are flies, that is to say, they belong to the or¬
der Diptera, but they form no part of the present book :
they are treated in other volumes. Aside from those
especially mentioned here, other flies of the same group
are occasionally found, not attracted to a house, but
trying to escape from it. Occasionally, however, some
235

236 THE HOUSE FLY— DISEASE CARRIER

of the biting flies known as gad flies or horse flies, of
the family Tabanidje, enter houses seeking blood. They
bite painfully, but for the most part prefer to stay out
of doors, although they frequent shady situations as a
rule. They are common in pine woods, and the in¬
habitants of summer houses built in such locations are
occasionally bothered by them to some extent. Trav¬
elers in Alaska, where some of these gad flies abound
during the short and damp summer, have stated that
they sometimes become almost a scourge in the
cabins.

The species which we are about to mention more
fully, however, are the commonest of the flies found
in houses, although their numbers are so insignificant
as to be almost disregarded when compared with Musca
domestica.

The Cluster Fly ( Pollenia rudis Fabr.)

There is a rather sluggish fly, a little larger than the
house fly, which is frequently found in houses, espe¬
cially in the spring and fall. It has a dark-colored,
smooth abdomen and a sprinkling of yellowish hair.
It is very sluggish, in the fall especially, and at such
times it may be picked up readily. It is subject to the
attacks of a fungous disease which causes it to die
upon window panes, where it is often seen surrounded
with a white efflorescence. (Fig. 22.)

The cluster fly is a European species, and the date
of its introduction into the United States is not known.
It could easily have been brought over upon slow sail-

THE CLUSTER FLY

237

ing vessels, especially in the cooler season of the year,
since it apparently hibernates in the adult condition and
seeks the shelter of cracks and crevices. It is men¬
tioned by Loew in 1864 as one of the flies common to
Europe and America. Attention was first particularly
called to it and to its house habits by Dr. W. H. Dali,
of the Smithsonian Institution. In an article published
in the Proceedings of the U. S. National Museum for
1882 (Vol. V, pp. 635-636) Doctor Dali related that
for several years he had heard of a fly which was a
great nuisance in country houses near Geneva, N. Y.
He secured specimens of the fly, which were turned
over to professor Riley for identification.

One of his relatives in Geneva wrote him that it was
probably thirty years since the fly had first appeared
in that neighborhood. They were at once a terror to
good housekeepers and a constant surprise, since they
were found in beds, in pillow slips, under table covers,
behind pictures, in wardrobes, and in all sorts of places.
In clean, dark bedchambers seldom used, they would
form in large clusters about the ceilings. They seemed
oily, and if crushed left a great grease spot on the floor.
The correspondent stated that about the first of April
they came out of the grass and flew up to the sunny
side of houses, which they entered. They remained in
evidence until some time in May, and then disappeared
and were not seen again until September, when they
came and remained all winter. They were stated to be
very sluggish — to crawl rather than to fly away when
disturbed. They were said to be often found in incred-

238 THE HOUSE FLY— DISEASE CARRIER

ible numbers under buildings, between the earth and
the floor.

Dr. J. A. Lintner, in his Ninth Report of the State
Entomologist of New York (Albany, 1893), gave a
number of instances of like occurrences of this fly in
houses, both in spring and in winter, in various parts of
New York State. A good description was given by a
correspondent of the Washington Bureau of Entomol¬
ogy, living in Lasalle County, Illinois. The corre¬
spondent stated that the cluster fly had been a pest in
her household for fifteen years. She wrote, “They
seem to prefer to occupy the rooms on the north side
of the house and those that are used but little. They
gather in large bunches in the corners and along the
edge of the ceiling of the room. They cannot be driven
out as other flies, but must be killed outright to get
rid of them, and when you mash them the odor is like
that of honey. We have tried nearly everything that
we heard of that was recommended to us, with no ef¬
fect. It seems impossible to get rid of them or to keep
them out of the house, for they crawl in through the
smallest places in the windows.”

Other correspondents have reported the odor of the
crushed bodies as being very disagreeable.

Incredible as it must seem, practically nothing is
known about the early stages of this abundant and trou¬
blesome fly. European writers either admit that they
know nothing about it or give rather vague statements.
Robineau Desvoidy, speaking of the genus Pollenia as
a whole, states that their eggs are laid in decomposing

Fig. 22. — The cluster fly ( Pollcnia rudis ) ; greatly enlarged. (Original.)

Fig. 23. — The biting house fly ( Stomoxys calcitrans) ; larva and pupa at
right; head at left and anal spiracle of larva below; greatly
enlarged. (Author’s illustration.)

THE CLUSTER FLY

239

animal and vegetable matter. Macquart, also speaking
of the genus and not especially of this species, states
that the larvae develop in the manure pile and cow
droppings. The only definite recorded observation
which seems to have been made upon the actual breed¬
ing habits of this species, in fact, is the rearing of a
single specimen from cow dung. This single specimen
was reared in the Insectary of the Bureau of Entomol¬
ogy December 23, 1899. The writer has, however,
received a letter from Prof. J. S. Hine, of the Ohio
State University, in which he states that during the
summer of 1910 he reared numbers of cluster flies, to¬
gether with other dipterous insects from accidental cow
droppings in the pasture.*

In the absence of further exact observations, it is
fair to suppose that the cluster fly breeds in decompos¬
ing animal matter of some kind or other, and it is alto¬
gether likely that measures taken against the breeding
places of the true Musca domestica will also be meas¬
urably effective against this species. There is as yet,
however, the possibility that it may breed in rich soil
or decomposing vegetable substances. It is difficult to
keep out of the house by screening, but it may be killed
by a light kerosene spray or by the free use of a fresh
pyrethrum powder.

Marlatt (Insect Life, Vol. IV, 1891) records an ex¬
traordinary mortality among these flies which he no¬
ticed on the grounds of the Department of Agriculture
in the autumn of that year. He found often as many
as eight or ten flies fastened by a fungous growth to

*D. Keilin (C. R. Soc. de Biologie, Vol. 67, p. 201) states that
the larvae of Pollenia are parasitic in certain earth-worms.

240 THE HOUSE FLY— DISEASE CARRIER

the under side of leaves near the buildings. Specimens
of these fungus-infested flies were sent to Doctor Thax-
ter of Harvard University, and the organism that killed
them was found to be, not Empusa muscce, as was
thought, but Empusa americana.

The Biting House Fly ( Stomoxys calcitrans L.)

This insect is rather closely related to the house fly
and greatly resembles it in appearance, in fact it is dif¬
ficult to distinguish one from the other except by the
closest observation. Raillet has stated that the Sto¬
moxys holds its head up while the house fly holds its
head down, but there are other ways of telling them
apart, as can be seen by comparing the illustrations of
the two species. The Stomoxys is of the same gray
color with dark lines, but its mouth parts are quite dif¬
ferent; in fact a good way to distinguish between the
two flies is to allow them to walk over your hand ; if
it bites, Stomoxys; if it does not it is probably the
house fly. It is this other species about which we are
writing that gave rise to the old saying that flies begin
to bite before a rain, since the biting house fly is not
normally a house fly at all, but loves the out-of-doors.

It has not yet and probably never will become as
truly a domestic species as Musca domestica. It is not
attracted to the garbage pail and the kitchen and din¬
ing-room for food, but finds plenty of food on cattle
and horses and other domestic and also wild animals.
Under certain circumstances, however, it may become
a very common resident of houses. (Fig. 23.)

THE BITING HOUSE FLY

241

Dr. John B. Smith, at a meeting of the Entomolog¬
ical Society of Washington, once stated that these
flies were very abundant at his house; that he had
not been able to observe any increase in numbers in
rainy weather, but on the contrary he had found
them gradually becoming more abundant until at
that time (November ist) they had almost replaced
the common house fly, which was being rapidly killed
off by the fungous disease mentioned in a previous
chapter.

Hewitt states that in England it is often found in
houses, and he himself has found it in large numbers
in the windows of a country house in March and April.
He states that it is popularly known in England as the
“storm fly” from its habit of seeking the shelter of
houses during wet weather.

Newstead states that in England (and the same con¬
ditions hold for this country) farm yards and stables
are the favorite haunts of this fly, but that it occurs
also in the fields and parks and open woods, especially
where cattle are grazing. He has seen it resting on
the shop fronts of the main streets of both Liverpool
and Chester, and states that it is fond of resting on
surfaces fully exposed to the sun and that painted sur¬
faces are also attractive to it. The greatest number
he ever saw congregated together was on the sunny
side of a red-painted iron tank at the old Chateau de
Goumont, Waterloo, Belgium. At night, he states,
they retire to some sheltered spot, and numbers may
be found at rest on the beams and rafters in open sheds

242 THE HOUSE FLY— DISEASE CARRIER

at farm yards, where they remain until the morning sun
tempts them out.

Both males and females suck blood. According to
Osborn, while this fly inflicts a deep bite it does not
gorge itself at a single animal, but may fly from one
to another in securing a meal. From this fact he thinks
the idea that this fly is apt to be a transmitter of glan¬
ders from diseased to healthy horses, and anthrax
among cattle, receives important support. The punc¬
ture under ordinary circumstances does not seem to be
poisonous to men, and aside from the pain given it is
less dangerous than a mosquito bite. Newstead no¬
ticed a female drive its proboscis into the thorax of a
dead companion and apparently suck up the juices of
its body. The same writer permitted one to suck blood
from his hand and observed it carefully during the
process. The insect sat high on its legs, the whole of
the proboscis was straightened and held vertically, and
the lower third was driven into the flesh. During the
process, which lasted fifteen minutes, the proboscis was
constantly but somewhat slowly moved up and down,
and also with an occasional semi-rotary movement, like
the action of a quarryman’s hand drill. There was no
subsequent irritation or soreness of any kind. The
fly died twelve hours after feeding. During other ob¬
servations Newstead found that the flies lived for sev¬
eral days in captivity, and that the females died either
immediately or shortly after laying their eggs.

The biting house fly has almost as wide a geographic
distribution as the true house fly. It was probably orig-

THE BITING HOUSE FLY

213

inally an European species and has spread by the help
of commerce to many parts of the world. It occurs
all over North America and is also to be found in Cen¬
tral and South America. It is also found in Australia,
China, India, and the Canary Islands.

The writer has reared the biting house fly from cow
manure and from horse manure. I judge from the
fact that it is attracted to human excreta that it may
become a carrier of intestinal disease. It has been
reared from sheep’s dung and from warm decaying
vegetable refuse, especially from piles of fermenting
lawn grass.

Lucien Iches, in the Bulletin de la Societe Nationale
d’Acclimatation de France, March, 1909, published a
very interesting article on Stomoxys calcitrans and Ar¬
gentine cattle, giving the results of a brief investigation
made by him in 1908 in the province of Santa Fe, Ar¬
gentina. The biting flies swarmed on a large estate in
almost incredible numbers. The cattle were driven
nearly crazy by them. Certain valuable Durham bulls
which were observed were covered with the flies. They
had lost their hair in large spots and the skin was
cracking.

Monsieur Iches naturally sought at once for the prin¬
cipal breeding places of the flies, and found them to be
in the stacks of debris from the threshing of wheat and
flax. Larvae and puparia were found by the millions
in the lower portions of these piles of straw, where
some fermentation had already begun. The sensible
measure which he recommended was to have this de-

244 THE HOUSE FLY— DISEASE CARRIER

bris burned within forty-eight hours after the com¬
pletion of the threshing, the ashes being used for fer¬
tilizing purposes. It turned out that there was an old
provincial law in the province of Santa Fe ordering
the burning of the debris after threshing, but it had
not been carried out during recent years, and therefore
the Stomoxys multiplied until this veritable plague en¬
sued. In 1888 this Stomoxys made its appearance in
extraordinary numbers near Salem. Oregon, and it is
altogether likely that there was some similar reason
for its extraordinary abundance that year. At that
time, however, its true breeding places were not known
and the cause of the outbreak was not found.

There are undoubtedly many substances in which
the biting house fly breeds, and it evidently requires
about the same conditions as does the true house fly.

The larvie and puparia of this species have been
figured by the writer, but the full life history has been
carefully studied by Xewstead. He found that the eggs
are laid in an irregular heap and that the average num¬
ber deposited is about sixty. The egg is much like that
of the house fly, and is one millimeter long. It hatches
in from two to three days in an average temperature
of 72 0 F. in the day and 65° F. in the night. The
larva need not be described, since it is similar to that
of the house fly. Xewstead found that in this stage
they lived from fourteen to twenty-one days, but that
the absence of excessive moisture and the admission of
a little light materially retarded development, which
then extended over a period of thirty-one to seventy-

THE BITING HOUSE FLY

245

eight days. In the puparium the insect remained from
nine to thirteen days. The development of the species
is therefore slower than that of the true house fly. It
is Newstead’s opinion that the winter is passed chiefly
in the pupal condition. Packard (1874) describes the
pupa of this species.

The extraordinary effects of numbers of the bites of
this fly, indicated in the account of the epidemic of
1908 in Argentina, cannot be exaggerated. Cattle and
horses suffer severely from these bites when the in¬
sects are numerous. Mr. T. J. Bold, in the Entomolo¬
gists’ Monthly Magazine for 1865, p. 143, gives an
account of the condition of these animals at Long
Benton in September of that year. Fourteen cows
were under treatment by a veterinary surgeon at one
time. The animals were generally bitten on the out¬
side of the legs, on the shoulders, and, rarely, on the
neck. In severe cases the joints were so much swollen
that the animals could not bend their legs to lie down,
and the swelling from the inflammation was so great
that the outer skin cracked and the hair fell off. It
is stated that the flies appeared to prefer the knees and
upper portion of the foot of the cow, frequently crawl¬
ing from them to the hands of the veterinary, but their
bites had no bad effect on him. It would seem from
this as though animals are more susceptible than man.

This biting fly has often been thought to be a dis¬
ease carrier and especially of blood parasites of do¬
mestic animals. The evidence for and against has been
carefully considered by Austen (1909. p. 153), who

246 THE HOUSE FLY— DISEASE CARRIER

summarizes his conclusions in the following words :
“It may be regarded as proved that Stomoxys calcitrans
L., as also A. nigra, Macq., and probably other species
of the genus, can convey trypanosomes directly from
an infected to a healthy animal, when the bites follow
one another immediately. On the other hand, the evi¬
dence tends to show that when the interval between
the bites is longer (the maximum period within which
a bite is infectious has not yet been determined), al¬
though active trypanosomes may be present in the in¬
testine of the fly, its life is innocuous. There is no
indication that trypanosomes ingested by A. calcitrans
pass through a developmental cycle, and they appar¬
ently disappear within twenty-four hours. With re¬
gard to diseases other than trypanosomiases, there are
some grounds for thinking that A. calcitrans, like other
biting flies, may occasionally disseminate the bacillus
of anthrax, and, in Europe, it would appear that the
fly is the intermediate host of a species of Filaria para¬
sitic in cattle.

The Little House Fly
( Fannia [ Homalomyia ] canicularis L.)

In discussing the size of the adult house fly in Chap¬
ter I, we mentioned this little fly which is found rather
commonly upon window-panes in houses, and stated
that it was the source of the prevalent error to the
effect that house flies grow after they become winged
and that these little flies are the young of the larger
flies. They belong, however, not only to an entirely

Fig. 24. — The little house fly ( Homalomyia brevis ) ; antennae and larva
at right; greatly enlarged. (Author’s illustration.)

Fig- 25. — The stable fly ( Muscina stabulans ) ; larva at right ; greatly
enlarged. Anatomical details b, c, d, e, g, h, i, still more
enlarged. (Author’s illustration.)

THE LITTLE HOUSE FLY

247

distinct species but to a different family, these little
ones being members of the family Anthomyidae. There
are several of these species of Homalomyia, including
not only canicularis, but H. brevis Rond, and II.
scalaris Fab., but canicularis is the one found most
abundantly in houses. The name “little house fly” has
not been definitely applied to it in this country, but
it is a translation of the German popular name, “Kleine
Stubenfliege.” The larvae of this species live in de¬
caying vegetable material and have also been found
living in dead insects of different kinds. They have
even been found in the nests of the common bumble¬
bee. They will breed also in excreta of animals and
in human excreta, and therefore would be quite as
dangerous as the true house fly were they as numerous.
They make their appearance early in the summer and
persist until autumn.

The allied species, H. brevis, is not so common in
houses as the one just mentioned, but it is an abundant
breeder in human excrement.

Both species are rapid breeders, and a generation is
produced every two weeks, in the vicinity of Wash¬
ington, in summer. The full development has not been
traced, but the larvae are quite different from the larvae
of the house fly. That of brevis is shown in Fig. 24.
It and its relatives are all furnished with a double row
of spiny processes on either side, giving them a very
characteristic appearance. Their larvae have occa¬
sionally been found in freshly passed human dejecta
and are surely on occasion voided by persons who have

248 THE HOUSE FLY— DISEASE CARRIER

probably swallowed them with uncooked vegetable
food.

The Stable Fly ( Muscina stabulans Fall.)

This is one of the flies which very much resemble
the house fly, and is frequently mistaken for it. It be¬
longs to the same family and is of the same general
color. It is not so abundant in houses as some of the
others we have mentioned. In 1900, out of the 23,087
flies collected in dining-rooms and kitchens in different
parts of the country, thirty-seven belonged to this spe¬
cies. It is common throughout Europe, everywhere in
the United States, and extends south to Argentina.
In England it is said to be found in and near houses.
Hewitt has found it occurring in early summer before
the house fly has appeared in great numbers. It is
somewhat larger than the true house fly, and is well
shown in the accompanying figure, which also shows
some of the structural details of both the adult and the
larva. The adult may be at once distinguished from
the house fly by the gradual curve of the vein reaching
the tip of the wing, instead of the abrupt angle in the
same vein in the house fly.

The larvae of the stable fly live upon decaying sub¬
stances, fungi, etc., but it is recorded in Europe as
feeding upon caterpillars and larval bees. Schiner
states that it breeds in cow dung, and it has also been
found in dead animals. In this country it feeds upon
the dead chrysalids of insects, and has been reared from
dying squash plants. The fly has also been reared from

THE CHEESE FLY

249

masses of the larvae and pupae of the imported elm
leaf beetle; also from a decaying squash. Aldrich in
Idaho has reared it from rotting radishes. In Wash¬
ington it has been reared from human excreta. The
complete round of a generation is said to occupy from
five to six weeks. (Fig. 25.)

This fly is one of the dangerous occasional inhab¬
itants of houses, not only because it may breed in hu¬
man excreta, but because it is greatly attracted to this
substance when it chances to be deposited in the open.
There seems to be no especial reason why it should be
called the stable fly, since the preferred food habits
of its larvae should make it more abundant away from
stables, and its scientific name stabulcins was given to
it by Fallen before its real habits were known.

It is interesting to note, by the way, that the larva
of the fly has been found to have passed through the
human stomach, to which it had probably gained en¬
trance through the eating of spoiled vegetables.

The Cheese Fly ( Piophila casei L.)

The little, shining-black flies of the genus Piophila
breed in cheese, ham, chipped beef, and other fatty or
spoiled and decaying animal matter. The eggs hatch
into small, white, cylindrical maggots which feed upon
the cheese or meat and rapidly reach full growth, at
which time they are one-half of an inch in length. The
maggot is commonly called the cheese skipper or the
ham skipper from its wonderful leaping powers, which
it possesses in common with certain other fly larvae, all

250 THE HOUSE FLY— DISEASE C ARRIER

of which lack legs. The leap is made by bringing the
two ends of the body together and suddenly releasing
them, like a spring. In this way it will sometimes jump
three or four inches. The species is cosmopolitan at
present, and it was doubtless originally imported from
Europe into the United States in old cheeses.

Careful observations have been made on the life his¬
tory of this fly by several writers. In 1892 Miss Mary
E. Murtfeldt studied the life history of the summer
generation in a western packing establishment. She
found that the eggs were laid in rather close clusters
of from five to fifteen, and were also deposited singly.
About thirty seem to have been laid by a single female.
The egg is white, slender, oblong, slightly curved, one
millimeter in length, and with a diameter about one-
fourth of its length. It hatches in about thirty-six
hours, and the larva completes its growth in from seven
to eight days, reaching a length of seven to nine milli¬
meters. Where food is sufficient the larva does not
move about, and groups of them will sometimes com¬
plete their growth in the same crevice in which the
mother fly deposited her eggs. When full grown, how¬
ever, the larva moves away to some dry spot, contracts
in length, assumes a yellowish color, and gradually
forms into a golden-brown puparium four or five milli¬
meters in length. The adult fly issues in ten days.
Thus three weeks may complete the entire life cycle,
in August, in St. Louis.

In Europe, Kessler found that the average summer
duration of this insect is four to five weeks, and states

Fig. 26. — The cheese fly ( Piophila casei ) : a, larva ; b, puparium ; c, pupa ;
d, adult male; e, adult female ; all enlarged. (Author’s illustration.)

' i

(;3

Fig. 27. — The fruit fly ( Drosophila ampelophila) ; a, adult male;
b, antennae ; c, fore tibia ; d, e, puparium ; f, larva ; g, anal segment
of larva; enlarged. (Author’s illustration.)

THE FRUIT FLIES

251

that the larva over-winters in the puparium. Other
writers say that the insect passes the winter as an adult
fly. (Fig. 26.)

In this country this fly does not play so important
a part as a cheese insect as it does as an enemy to
smoked meat. It seems certain that the mother fly
prefers the older and richer cheeses in which to de¬
posit her eggs. Her taste is excellent, and, while it
is a fair thing to say that skippery cheese is usually
the best, it will hardly do to support the conclusion
that it is good because it is skippery, although this con¬
clusion is current among a certain class of cheese eaters.

The cheese fly, under ordinary circumstances, is not
a dangerous species, but it is well to remember that
not only has it been reared from dead bodies, but that
it is also attracted to excreta of all kinds.

The Fruit Flies ( Drosophila ampelophila Loew)

The minute flies of the family Drosophilidae, com¬
monly known as fruit flies or pomace flies, are attracted
to decaying vegetation, especially to fruit, and are fre¬
quently found in houses in the autumn about dishes
containing pears, peaches, and grapes. They are at¬
tracted to fruit both for food and for places to lay
their eggs, since their larvae live in decaying vegetable
matter.

The commonest of the fruit flies in the United States
is Drosophila ampelophila. It occurs also in the West
Indies and South Europe. It does considerable dam¬
age to canned fruits and pickles, breeds in decaying

252 THE HOUSE FLY— DISEASE CARRIER

apples and the refuse of cider mills and fermenting
vats of grape pomace. It is a rather rapid breeder,
and a generation may develop in twenty days, more or
less. It is attracted especially to preserves and canned
goods, and frequently damages raspberry vinegar. It
is often very difficult to prevent the fly from entering
fruit jars.

There are about thirty species of Drosophila in
North America, and the majority of them breed in
the juices of decaying and fermenting fruit. Aside
from the one just mentioned, D. amoena, D. funebris,
D. graminum, and D. transversa are occasionally found
in houses. Another species, D. cellaris, occurs in cel¬
lars in fermenting liquids, such as wine, cider, vinegar,
and beer ; also in decaying potatoes. Another species
damages flour paste ; and still another mustard pickles.
One species, D. Haveola, does not need decaying vege¬
tation for its larval food, since its larvae mine the leaves
of cabbages and radishes.

The fruit flies may be dangerous inhabitants of
houses, since they are nearly all attracted to excreta,
and some of them breed in human excrement. The
larva and puparium, as well as the adult fly of D.
ampelopliila, are shown in Fig. 27.

The Bluebottle or Greenbottle Flies
The Blow Flies ( Calliphora erythrocephala Meig.,
Lucilia cccsar L., Phormia terr amoves Desv.)

Several species of bluebottle or greenbottle flies oc¬
casionally gain entrance to houses, and all are danger-

THE BLOW FLIES

253

ous species and liable to carry intestinal diseases. Their
larvae as a rule feed in excreta or in decaying flesh, but
a bluebottle fly in a milk jug is no more dangerous
than a house fly in the same situation.

Lucilia c cesar L. (Fig. 28) is a common and wide¬
spread form, abundant in both Europe and North
America, and is one of several species of the shining
green or bluish flies commonly found about dead ani¬
mals and different kinds of excreta. It is not ordinarily
found in houses, but may be driven in at the approach
of a heavy storm, just as is the case with the biting
house fly. On May 17, 1899, for example, a heavy
storm occurred about four p.m., and the next morning
twenty-eight specimens of this species were found to
have come into one of the rooms of my office. In
Europe L. ccesar is known as the “greenbottle fly,” and
is almost exclusively a carrion feeder.

Calliphora erythrocephala Meig. (Fig. 29) is an¬
other widespread species common to Europe and North
America. It is a large bluebottle fly of rather dull
color with black spines on the thorax. It is the com¬
mon blow fly of Europe and is the species treated by
Lowne in his classic work on the anatomy of the blow
fly. Its lame are indistinguishable from those of the
greenbottle fly. The eggs are laid on meat and dead
animals and even upon dead insects. The species is
unusual from the enormous number of eggs laid by a
single female. The Russian author, Porchinsky, re¬
cords from 450 to 600 eggs from a single female.
Hewitt records the duration of a single generation as

254> THE HOUSE FLY — DISEASE CARRIER

from twenty-two to twenty-three days. This blow fly
is a characteristically out-of-door fly, but under cer¬
tain circumstances may be found in houses in some
numbers. In October, 1899, for example, a gentleman
living in the suburbs of Washington found thousands
of these flies in his cellar. No cows or horses were
kept near the house, and there had been no dead ani¬
mals about so far as he knew. It is probable, however,
that these flies had come from some dead animal, and
had sought the cellar for hibernating purposes, al¬
though the weather was still warm.

Phormia terrcenovce Desv. (Fig. 30.) The bluebot¬
tle fly just mentioned is a rather large species. The
Phormia, however, is a medium-sized or rather small
bluebottle. It was originally described from New¬
foundland, but is widespread in the United States. It
is occasionally found in houses, and I have more than
once seen them upon window panes. It is abundantly
attracted to human excreta, and has been taken under
many varying conditions about Washington : enormous
numbers were found on one occasion in the sinks of a
deserted militia camp at Leesburg, Virginia.

The Flesh Flies ( Sarcophaga assidna Walk.)

We include under this heading the flies of the genus
Sarcophaga, on account of the significance of the sci¬
entific name, although many Sarcophagids are not true
flesh eaters. Several of them very closely resemble
the house flv, and some of them are sometimes found
in houses. The common widespread flesh fly of Europe

Fig. 28. — Lucilia ccrsar; enlarged.
(Author's illustration.)

Fig. 29. — Calliphora erythrocephala ;
enlarged. (Author’s illustration.)

Fig. 30. — Phorniia terrccnovcc; en¬
larged. (Author's illustration.)

THE DUNG FLIES

255

and Australia, a very general scavenger, is known as
Sarcophaga carnaria L., and in countries which it in¬
habits is once in a while found in houses. It does not
seem to occur in the United States, although a species
which much resembles it, S. sarracenicc Riley, is abun¬
dant throughout the country. It looks like a very large
and active house fly, and is occasionally found in
houses. It is commonly reared from the remains of
dead insects, but is also attracted to and breeds in ex¬
creta. (Fig. 31.)

A smaller species, S', assidua Walk., much resembles
the house fly and is of about the same size. It is con¬
fined to the United States and is occasionally found in
houses. It, like the preceding species, breeds in dead
insect remains, but is attracted to and breeds in ex¬
creta and is therefore dangerous.

The Dung Flies

( Sepsis violacea Meig., Scatopliaga furcata Say)

There is a little black fly known as Sepsis violacea
Meig., which is shown in Fig. 32 and which is not at
all uncommon in houses, being found as a rule upon
the window panes. It belongs to the same family as
the cheese fly, but does not attack stored foods or any¬
thing to be found in the pantry. It breeds almost ex¬
clusively in excreta and has been reared in swarms
from an old human deposit collected on the Potomac
flats near the city of Washington. It is very small in
size, glistening black in color, and of slender shape.

There is a whole family of small, brownish flies

256 THE HOUSE FLY— DISEASE CARRIER

known as the Scatophagidse, which, as the scientific
name indicates, are attracted to and breed in the dung
of different animals, and also to some extent in decay¬
ing vegetable material. They are, as a rule, rather
light-colored, bristly flies. The species shown at Fig.
33 is known as Scatophaga furcata Say. It is a North
American species of rather wide distribution, which
in its early stages lives in all sorts of excreta and is
once in a great while found in houses. It does not
hibernate as an adult fly, but in its puparia in dung.

The Moth Flies ( Psychodci minuta Banks)

There are certain very minute flies belonging to a
family known as the Psychodidse, which are very pe¬
culiar from the fact that they resemble little moths,
their broad wings being covered with hairs, making
them look like moths. They are very weak fliers, and
are frequently found upon windows and on the under
surfaces of leaves. They are so small and fragile that
they are difficult to capture and preserve. What they
do in houses no one knows, unless possibly they enter
them for protection. The larvae of some species breed
in excreta; others in decaying vegetation, and still
others in water, sewage-polluted water being preferred.
Psychoda minuta Banks has been reared from cow
dung at Washington. None of the North American
species has the blood-sucking habit, although a genus
(Phloebotomus) which occurs in Southern Europe and
in other parts of the world bites human beings and
has been accused of disease-carrying probabilities.

Fig. 32. — Sepsis yiolacea; puparium at left; enlarged antennae at upper
right; enlarged. (Author’s illustration.)

THE HUMPBACK FLIES

257

The Humpback Flies

The humpback flies of the family Phoridae need not
be mentioned here especially, except for the fact that
one of the species, Hypocera ( Phora ) femorata, occurs
occasionally in houses, and possibly others of the family

Fig. 34. — Phora femorata; greatly enlarged. (Original.)

may also be found from time to time in domiciles. In
the collection of flies made in houses in 1900 there
were thirty-three specimens of P. femorata out of the
23,087 flies captured. The larval habits of this par-

258 THE HOUSE FLY— DISEASE CARRIER

ticular species are not known, but its relatives feed in
the earlier stages on decaying vegetable matter, dead
insects, snails, etc. The species in question possibly
fed upon decaying vegetation in the neighborhood of
the houses in which it was collected.

The Window Flies ( Scenopinus fenestralis L.)

Comstock has applied the term window dies to the
little flies of the family Scenopinidie. The term, how¬
ever, does not apply to all of them ; but the best-known

Fig- 35- — Scenopinus fenestralis; a, adult; b, pupa; c, larva;
d, eggs ; enlarged. (Original.)

species, namely, Scenopinus fenestralis , is not uncom¬
monly found upon windows both in this country and
in Europe. These flies are usually black and rather
smooth, A. fenestralis being about one quarter of an

THE WINDOW FLIES

259

inch long. It has a humpbacked appearance, and the
abdomen is flattened. Osten Sacken (1886) has given
a good review of the European literature on the habits
of this fly, and has shown that it has been reared from
decaying tree fungi, from horse hair in a mattress,
from a swallow’s nest, from the cocoon of a large moth,
from carpets, from a branch of a tree, from pine boards,
from the pupa of a large moth, and from a root of
aconite.

The different European authors making these obser¬
vations from time to time have thought variously that
the window fly was carnivorous or vegetarian, in ac¬
cordance with the substances from which they reared
it. Osten Sacken, however, concludes rather positively
that it is carnivorous, that the larva does not frequent
fungi, rotten wood, swallows’ nests, etc., for the sake
of vegetable material or animal remains, but for the
sake of the pupae and perhaps also of the larvae which
it finds there. He deduces from this that when it oc¬
curs in carpets and horse hair, it is not because it feeds
on them, but because it hunts there for the larvae and
pupae of the moths or other insects that live in them.

Similarly in this country divers observations have
been made, and the records of the Bureau of Entomol¬
ogy at Washington show that it has been reared from
strawberry plants, from the egg-pods of grasshoppers,
from the hair of a Navajo blanket, from a sack of rye
infested with the grain beetle, from under carpets,
among stored oats and stored corn, from a basket con¬
taining small rolls of cotton and woolen goods, and

260 THE HOUSE FLY— DISEASE CARRIER

from the seeds of sugar beets stored in a mill; also
from larvae found with other larvae on the roots of roses,
as well as from under the bark of a post-oak pole. Ex¬
act observations have been made here showing that the
larva is undoubtedly carnivorous : it has been fed upon
the larvae of stored grain insects, and when found in
woolen goods and under carpets it is undoubtedly in
search of clothes moths upon which to feed.

The larva is long, white, and snake-like in shape,
with a dark head. It apparently has many segments to
the body, since each of the abdominal segments is di¬
vided by a strong constriction. In feed stores the flies
are nearly always to be found around the windows,
and the probability is very strong that they feed upon
such small soft-bodied creatures as flour mites .and
beetle larvae.

Nothing definite has been ascertained concerning the
duration of the different stages, but from larvae taken
in January adults issued in April, and from larvae re¬
ceived April 18th adults issued on the 9th of June;
with larvae received August 6th, one changed to pupa
on August 25th, another on August 29th, the flies issu¬
ing September 10th and 12th respectively.

It is a pleasure to state that at least one of the flies
found in houses is probably beneficial rather than in¬
jurious, and that this species is Scenopinns fenestralis.

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Subjects. London. N. S., No. 16, 13-41.

Odlum, W. H. (1908). Are flies the cause of enteric
fever? Journ. Roy. Army Med. Corps, X, 528-53°-

Orton, Samuel T. (1910). Experiments on the trans¬
mission of bacteria by flies with especial relation to
an epidemic of bacillary dysentery at the Worcester
State Hospital. Boston Medical and Surgical Jour¬
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Osmond, A. E. (1909). The fly — an etiological factor in
intestinal disease, pp. 7, 1 chart. Reprinted from The
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Osten Sacken, C. R. (1886). Notes toward the life-
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270 THE HOUSE FLY— DISEASE CARRIER

Packard, A. S., Jr. (1874). On the transformations of
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Prowazek, S. (1904). Die Entwicklung von Herpete-
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Savage, W. G. (1907). Recent work on typhoid fever
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Inst. Pasteur, 662-667.

APPENDIX I

Flies Frequenting Human Dejecta and Those
Found in Kitchens

IN summing up the results of the work carried on
by the writer, the number of species of insects found
breeding in or frequenting human excrement was very
large. There were many coprophagous beetles — forty-
four species in all — and many Hymenopterous para¬
sites, all of the latter having probably lived in the lar¬
val condition in the larvse of Diptera or Coleoptera
breeding in excrement. Neither the beetles nor the
Hymenoptera, however, have any importance from the
disease-transfer standpoint. The Diptera alone were
the insects of significance in this connection. Of Dip¬
tera there were studied in all seventy-seven species, of
which thirty-six were found to breed in human feces,
while the remaining forty-one were captured upon such
excrement. The following list indicates the exact spe¬
cies arranged under their proper families. The paren¬
thetical remarks after each species should be estimated
in the following order, from “scarce” to “extremely
abundant” : scarce, rather scarce, not abundant, mod¬
erately abundant, abundant, very abundant, extremely
abundant.

273

274 THE HOUSE FLY— DISEASE CARRIER

REARED (USUALLY ALSO CAPTURED)

Family Chironomid^:

1. Ceratopogon sp. (scarce).

Family Bibionim:

2. Scatopse pulicaria Loew (moderately abundant).

Family Empididte

3. Tachydromia sp. (rather scarce).

Family Dolichopodid^e

4. Diaphorus leucostomus Loew (scarce).

5. Diaphorus sodalis Loew (not abundant).

Family Sarcophagid,®

6. Lucilia csesar L. (abundantly captured; one reared)

7. Sarcophaga sarracenise Riley (abundant).

8. Sarcophaga assidua Walker (abundant).

9. Sarcophaga trivialis V. d. W. (abundant).

10. Helicobia quadrisetosa Coq. (very abundant).

Family Muscid,e

11. Musca domestica L. (abundant).

12. Morellia micans Macq. (abundant).

13. Muscina stabulans Fall, (abundant).

14. Myospila meditabunda Fabr. (abundant).

Family Anthomyhle

15. Homalomyia brevis Rondani (very abundant).

16. Homalomyia canicularis L. (moderately abundant)

17. Homalomyia scalaris Fabr. (scarce).

18. Hydrotsea dentipes Meig. (moderately abundant).

19. Limnophora arcuata Stein (moderately abundant).

20. Ophyra leucostoma Wied. (abundant).

21. Phorbia cinerella Fall, (abundant).

22. Phorbia fusciceps Zett. (moderately abundant).

APPENDIX I

275

Family Ortalid^e

23. Euxesta notata Wied. (moderately abundant).

Family Lonchvekle

24. Lonchsea polita Say (moderately abundant).

Family Sepsid.e

25. Sepsis violacea Meig. (extremely abundant).

26. Nemopoda minuta Wied. (very abundant).

Family Drosophilid^e

27. Drosophila ampelophila Loew (moderately abundant).

Family Oscinidze

28. Oscinis trigramma Loew (rather scarce).

Family Agromyzkle

29. Ceratomyza dorsalis Loew (rather scarce).

30. Desmometopa latipes Meig. (rather scarce).

Family Ephydrid^e

31. Scatella stagnalis Fall, (scarce).

Family Borborid^e

32. Limosina albipennis Rond, (very abundant).

33. Limosina fontinalis Fall, (very abundant).

34. Sphserocera pusilla Meig. (abundant).

35. Sphserocera subsultans Fabr. (very abundant).

Family Scatophagid.e

36. Scatophaga furcata Say (very abundant).

CAPTURED (NOT REARED)

Family Chironomkle

1. Chironomus halteralis Coq. (scarce).

Family Tipulid;e

2. Limnobia sciophila O. S. (scarce).

276 THE HOUSE FLY— DISEASE CARRIER

Family Empidid^e

3. Rhamphomyia manca Coq. (not abundant).

Family Dolichopodid^e

4. Neurigonia tenuis Loew (scarce).

Family Sarcophagid^e

5. Chrysomyia macellaria Fabr. (rather abundant).

6. Calliphora erythrocephla Meig. (rather abundant).

7. Sarcophaga lambens Wied. (rather scarce).

8. Sarcophaga plinthopyga Wied. (rather scarce).

9. Cynomyia cadaverina Desv. (rather scarce).

10. Phormia terraenovae Desv. (very abundant).

Family Muscid^e

11. Muscina caesia Meig. (scarce).

1 2. Muscina tripunctata V. d. W. (scarce).

13. Stomoxys calcitrans L. (rather abundant).

14. Pseudopyrellia cornicina Fabr. (abundant).

15. Pyrellia ochricornis Wied. (rather scarce).

Family Anthomyiid^e

16. Hylemyia juvenalis Stein (rather scarce).

17. Hydrotaea metatarsata Stein (rather scarce).

18. Ccenosia pallipes Stein (rather scarce).

19. Mydaea palposa Walker (rather scarce).

Family Ortalhle

20. Rivellia pallida Loew (rather scarce).

Family Sepsid^e

21. Piophila casei L. (rather scarce).

Family Drosophilid.e

22. Drosophila funebris Meig. (scarce).

23. Drosophila busckii Coq. (scarce).

APPENDIX I

Family Oscinidje

24. Hippelates flavipes Loew (rather scarce).

25. Oscinis carbonaria Loew (moderately abundant).

26. Oscinis coxendix Fitch (scarce).

27. Oscinis pallipes Loew (rather scarce).

28. Elachiptera costata Loew (moderately abundant).

Family Ephydrida?

29. Discocerina parva Loew (rather scarce).

30. Hydrellia formosa Loew (rather scarce).

Family Borborid/e

31. Borborus equinus Fall, (very abundant, undoubtedly

breeds here also).

32. Borborus geniculatus Macq. (moderately abundant).

33. Limosina crassimana Hal. (abundant).

Family Syrphiele

34. Syritta pipiens L. (scarce).

Family Phorim:

35. Phora femorata Meig. (scarce).

Family Scatophagidte

36. Scatophaga stercoraria L. (moderately abundant).

37. Fucellia fucorum Fall, (rather scarce).

Family Micropezhle

38. Calobata fasciata Fabr. (rather scarce).

39. Calobata antennipes Say (moderately abundant).

Family Helomyzid^e

40. Leria pectinata Loew (scarce).

41. Tephrochlamys rufiventris Meig. (scarce).

It should be stated here that this list, containing as
it does only a record of actual observations, should by
no means be considered as indicating definitely the
habits of the species or their relative abundance under

278 THE HOUSE FLY— DISEASE CARRIER

other conditions. Thus some of the species here indi¬
cated as scarce in connection with excrement may be
very common under other conditions, which would
indicate that their occurrence upon excrement was more
or less accidental. Moreover, certain of the species
which have been captured on excrement, but not reared
from it, are nevertheless undoubtedly excrement breed¬
ers, as will be proved by future observations. Thus
we have in several cases certain species which have been
reared while congeneric species have simply been cap¬
tured, as, for example, Nos. 7 and 8 of the captured
species are congeneric with 7, 8 and 9 of the reared
series; 11 and 12 of the captured series are congeneric
with 13 of the reared series; 17 of the captured series
is congeneric with 18 of the reared series; 22 and 23
of the captured series are congeneric with 27 of the
reared series; 25, 26 and 27 of the captured series are
congeneric with 28 of the reared series ; 33 of the cap¬
tured series is congeneric with 32 and 33 of the reared
series, and is undoubtedly an excrement breeder, and
the same may be said of 36 of the captured series which
is congeneric with 36 of the reared.

From these data it will be noticed that the most
abundant species reared were Helicobia qnadrisetosa,
Sepsis violacea, Nemopoda minuta, Limosina albipen-
nis, Limosina fontinalis, SpJueroccra snbsultans, and
Scatophaga furcata, while the most abundant forms
captured on excrement were Phorbia terrcenovce and
Borborus equinus. It will also be noticed that among
the reared forms there are ten others which are simply

APPENDIX I

279

entered as “abundant,” and among the captured two
others. With these facts in mind we are prepared to
examine the results of the kitchen and dining-room
captures.

The results so far stated have a distinct entomolog¬
ical interest as regards the exact food habits of a large
number of species, many of the observations being
novel contributions to previous knowledge of these
forms ; but the practical bearing of the work is only
brought out when we consider which of these forms
are likely from their habits actually to convey disease
germs from the excrement in which they have bred, or
which they have frequented, to substances upon which
people feed. Therefore collections of the Dipterous
insects occurring in kitchens and pantries were made,
with the assistance of correspondents and observers in
different parts of the country, all through the summer
of 1899 and also in the summer and autumn of 1900.
Such collections were made in the States of Massachu¬
setts, New York, Pennsylvania, District of Columbia,
Virginia, Florida, Georgia, Louisiana, Nebraska, and
California. Nearly all of the flies thus captured were
caught upon sheets of the ordinary sticky fly paper,
which, while ruining them as cabinet specimens, did
not disfigure them beyond the point of specific recog¬
nition. The others were captured in the ordinary man¬
ner.

In all there were examined 23,087 flies, which had
been caught in rooms in which food supplies were or¬
dinarily exposed ; and they may safely be said to have

280 THE HOUSE FLY— DISEASE CARRIER

been attracted by the presence of these food supplies.
Of these 23,087 flies, 22,808 were Musca domestica,
i. e., ninety-eight and eight-tenths per cent, of the whole
number captured. The remainder, consisting of one
and two-tenths per cent, of the whole, comprised vari¬
ous species, the most significant ones being Homalomyia
canicular is (the species ordinarily called the “little
house fly”) of which eighty-one specimens were cap¬
tured; the stable fly ( Muscina stabulans), thirty-seven
specimens ; Pliora femorata, thirty-three ; Lucilia cccsar ,
eighteen ; Drosophila ampelophila, fifteen ; Sarcophaga
trivialis, ten; Calliphora erythrocephala, seven. Musca
domestica is, therefore, the species of great significance.
Homalomyia canicularis is important. Muscina stabu¬
lans is of somewhat lesser importance. Drosophila
ampelophila is an important form, and had more of the
captures been made in the autumn its numbers would
probably have been greater, since beyond doubt it is
an abundant species in houses after fruit has begun to
make its appearance (say, in August and September
and on until winter time) in pantries and on dining¬
room sideboards. The Calliphora and the Lucilia are
of slight importance, not only on account of their rar¬
ity in houses, but because they are not true excrement
insects. Other forms were taken, but either their
household occurrence was probably accidental, or from
their habits they have no significance in the disease-
transfer function.

— Extracted from : A Contribution to the Study of the Insect
Fauna of Human Excrement. By L. O. Howard (p. 547).

APPENDIX II

On Some Flies Reared from Cow Manure*

IN the summer of 1889, while engaged in an investi¬
gation of the habits and life history of the horn fly
of cattle ( Hceniatobia serrata), the writer at various
times brought to Washington, from different points
in Virginia, large quantities of cow manure collected
in the field, and eventually succeeded in working out
the complete life history of the horn fly, as displayed
in Insect Life, Vol. II, No. 4, October, 1889. In this
article the statement is made, in concluding, that the
observations were greatly hindered and rendered dif¬
ficult by the fact that fresh cow dung is the nidus for
a number of species of Diptera, some about the same
size and general appearance as the horn fly, and that
no less than twenty distinct species of flies had been
reared from horse and cow dung, mainly the latter,
and six species of parasitic insects as well. The plan
finally adopted of securing the isolation of the horn
flies was to remove the eggs from the surface of the
dung and place them with dung which was absolutely
fresh and collected practically as it fell from the cow.
A report upon the other species was promised, but was
never published, although Professor Riley, in his re-

*Reprinted from an article with this title, by L. O. Howard,
published in the Canadian Entomologist, Vol. 33 (1901) , pp. 42-44.
281

282 THE HOUSE FLY— DISEASE CARRIER

port for 1890, listed eight parasites, only two of which
were specifically determined.

The writer’s recent investigations of the insect fauna
of human excrement (Proc. Wash. Acad, of Sciences,
Vol. II, pp. 541-604. Dec. 28, 1900) aroused his in¬
terest in the general subject of coprophagous insects,
and the flies reared in 1889-90, from cow dung, were
looked up and have been named by Mr. D. W. Coquil-
lett. The list is so interesting that it should be re¬
corded. It will be noticed that several of the species
are identical with those found breeding in human ex¬
crement. These are: Sarcophaga incerta, Helicobia
quadrisetosa, Musca domestica, Morellia niiccins, My-
ospila meditabunda, Ophyra leucostoma, Sepsis viola-
cea, Sphcerocera subsultans and Limosina albipennis.
The rearing of Ceratopogon specularis from cow dung
is of especial interest, since, down to the record in the
Washington Academy paper just referred to, no in¬
sects of this genus had been found to be coprophagous.
Some of the other records are interesting for the same
reason. The list follows:

Family Cecidomyid^e

Diplosis, sp. Issued Dec. 26, 1889; and Jan. 18, 1890;
4 specimens.

Family Mycetophilim:

Sciara, sp. Issued March 26 and 29, 1890; 2 specimens.
Family Chironomid^

Camptocladius byssinus, Schrank. Issued Jan. 2, 1890.
Issued Dec. 31, 1889; and March 25, 1890; 9 speci¬
mens.

APPENDIX II

283

Camptocladins minimus, Meigen. Issued Dec. 23, 26,
27. 30 and 31, 1889; Jan. 13, 18, and March 25, 1890;
12 specimens.

Ceratopogon specularis, Coq. Issued August 28, 1889.
Issued Dec. 30, 1889 ; 6 specimens.

Psychoda minuta , Banks. Issued Dec. 26, 30 and 31,
1889; and Jan. 11, 1890 ; 4 specimens.

Family Rhyphid^e

Rhyphus punctatus, Fabr. Issued Sept. 2, 3, and 4, 1889.
Issued Jan. 13, 16, 18, 20, 22, 24 and 29, Feb. 1,
March 26 and 29, and April 5 and 9, 1890 ; 64 speci¬
mens.

Family Sarcophagid^;

Sarcophaga incerta, Walker. Issued Aug. 31, 1889. Is¬
sued Aug. 30, 1889; 7 specimens.

Sarcophaga, sp. Issued April 23, 1890; 1 specimen.

Helicobia quadrisetosa, Coq. Issued Aug. 6 and 30, 1889;
2 specimens.

Pollenia rudis, Fabr. Issued Dec. 23, 1889; 1 specimen.

Family Muscidve

Musca domestica, Linne. Issued Aug. 30 and Sept. 2 and
4, 1889 ; 20 specimens.

Morellia micans, Macq. Issued Aug. 30. 1899. Issued
Dec. 23, 26. 27, 28, 30 and 31, 1889; Jan. 2, 6, 8, 9,
10, 11, 13, 14, 16, 17, 18, 20, 25 and 27, Feb. 1,
March 25, April 5 and 9, 1890; 125 specimens.

Myospila meditabunda, Fabr. Issued Aug. 26, 28, 29, 30,
Dec. 23, 1889; Jan. 9, March 25, 26, April 2, 9, 14,
15, 1890. Issued April 5, 1890; 48 specimens.

Hcematobia serrata, Desv. Sept. 17, 2 specimens.

Family Anthomyid^:

Hydrotcca armipes. Fallen. Issued Sept. 27, 30. Oct. 4,
1889; Jan. 2, 6, 7, 8, 9, 10, April 24, 1890; 38 speci¬
mens.

284 THE HOUSE FLY— DISEASE CARRIER

Ophyra leucostoma, Wied. Issued Sept. 6, 1889; 11
specimens.

Limnophora, sp. Issued Aug. 30, 31, 1889; 5 specimens.

Ccenosia lata, Walker. Issued April 25, 1890; 1 specimen.

Ccenosia tlavicoxce, Stein. Issued Aug. 31, 1889; 4 speci¬
mens.

Phorbia, sp. Issued March 29, 1890; 1 specimen.

Family Sepsid^e

Sepsis violacea, Meigen. Issued Aug. 28, 1889; 8 speci¬
mens.

Family Borborim:

Sphcerocera subsultans, Fabr. Issued Aug. 30, 1889; 7
specimens.

Limosina albipennis, Rondani. Issued August 28, Dec.
23, 1889; 2 specimens.

APPENDIX III

Regulations of the Health Department of the
District of Columbia Relating to House Flies

XTRACT from An Ordinance to Revise, Consol-

L-/ idate, and Amend the Ordinances of the Board
of Health, etc., as Amended by Commissioners’ Orders.

Sec. 3. That manure, accumulated in great quan¬
tities; manure, offal, or garbage piled or deposited
within 300 feet of any place of worship, or of any
dwelling, or unloaded along the line of any railroad,
or in any street or public way; cars or flats loaded with
manure, or other offensive matter, remaining or stand¬
ing on any railroad, street or highway in the cities
of Washington or Georgetown, or in the more densely
populated suburbs of said cities, are hereby declared
nuisances injurious to health; and any person who
shall pile or deposit manure, offal, or garbage, or any
offensive or nauseous substance within 300 feet of any
inhabited dwelling within the limits of said cities or
their said suburbs, and any person who shall unload,
discharge, or put upon or along the line of any rail¬
road, street, or highway, or public place within said
cities or their said suburbs any manure, garbage, offal,
or other offensive or nauseous substance within 300 feet
of any inhabited dwelling, or who shall cause or allow
cars or flats loaded with or having in or upon them

285

286 THE HOUSE FLY— DISEASE CARRIER

any such substance to remain or stand in or along any
railroad, street, or highway within the limits of said
cities or their suburbs within 300 feet of any inhabited
dwelling, and who shall fail, after notice duly served
by this board, to remove the same, shall, upon convic¬
tion thereof, be fined not less than five nor more than
twenty-five dollars for every such offense.

* * * * * * *

Sec. 18 A. No person owning, occupying or hav¬
ing use of any stable, shed, pen, stall, or other place
within any of the more densely populated parts of the
District of Columbia, where animals of any kind are
kept shall permit such stable, shed, pen, stall, or place
to become or to remain filthy or unwholesome.

Sec. 18 B. No person shall use any stable, nor
shall any person having the power and authority to
prevent permit any person to use any stable, within
any of the more densely populated parts of the District
of Columbia, after the first day of July, 1907, unless the
surface of the ground beneath every stall and for a
distance of four feet from the rear thereof be covered
with a water-tight floor laid with such grades as will
cause all fluids that fall upon it to flow as promptly as
possible, if a public sewer be available, into the public
sewer, and, if a public sewer be not available, to that
portion of the premises where they will cause the least
possible nuisance.

Sec. 18 C. Every person owning or occupying any
building or part of a building within any of the more
densely populated parts of the District of Columbia,

APPENDIX III

287

where one or more horses, mules, cows, or similar ani¬
mals 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 aforesaid, shall place such ma¬
nure in said bin or pit. The bin or pit required by this
regulation shall be located at a point as remote as prac¬
ticable from any dwelling, church, school or similar
structure, owned or occupied by any person or persons
in the neighborhood of said bin or pit, other than the
owner or occupant of the building or part of building
aforesaid, and as remote as practicable from any pub¬
lic street or avenue; shall be so constructed as to ex¬
clude rain water, and shall in all other respects be
water-tight except as it may be connected with the pub¬
lic sewer or as other definite provision may be made
for cleaning and flushing from time to time; shall be
provided with a suitable cover, and constructed so as
to prevent in so far as may be practicable the ingress
and egress of flies. No bin or pit shall be constructed
the bottom of which is below the level of the surface
of the surrounding earth unless it be of substantial
masonry and connected with the public sewer. The
provisions of this paragraph shall take effect from and
after the expiration of three months immediately fol¬
lowing its promulgation.

Sec. i 8 D. No person owning or occupying any
building or part of a building located within any of the
more densely populated parts of the District of Colum¬
bia, in which building or part of a building any horse,

288 THE HOUSE FLY — DISEASE CARRIER

mule, cow, or similar animal is kept, 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
provided for that purpose; nor shall any person afore¬
said allow any such bin or pit to be overfilled or to be
needlessly uncovered.

Sec. i8£. The provisions of paragraphs C and D
shall not apply to the keeping of manure from horses
when such manure is kept tightly rammed into well-
covered barrels for the purpose of removal in such bar¬
rels.

Sec. 18 F. No person shall permit any manure to
accumulate on premises under his control in such a
manner or to such an extent as to give rise to objec¬
tionable odors upon any public highway or upon any
premises owned or occupied by any person other than
the person owning or occupying the premises on which
said manure is located. Every person having the use
of any manure bin or pit and every person keeping
manure, in any of the more densely populated parts
of the District of Columbia, shall cause all such ma¬
nure to be removed from the premises at least twice
every week between June first and October thirty-
first, inclusive, of each year, and at least once
every week between November first of each year and
May thirty-first of the following year, both dates in¬
clusive.

Sec. i 8 G. Every person using within the District
of Columbia any building, or any portion of a building,
in the city of Washington, or in any of the more

APPENDIX III

289

densely populated suburbs thereof, as a stable for one
or more horses, mules, or cows, shall report that fact
to the health officer in writing, within thirty days after
this regulation takes effect, giving his or her name,
and the location of such stable, and the number and
the kind of the animals stabled therein ; and thereafter
every person occupying any building, or any portion
of a building, in the city of Washington, or in any of
the more densely populated suburbs thereof, for the
purpose aforesaid, shall report in like manner his or
her name and the location of said stable, and the num¬
ber and kind of animals stabled therein, within five
days after the beginning of his or her occupancy of
such buildings ; provided, that stables recorded at the
Health Office as parts of dairy farms in the District
of Columbia need not be so reported.

Sec. i 8 H. No person who has removed manure
from any bin or pit, or any other place where manure
has been accumulated, shall deposit such manure in any
place within any of the more densely populated parts
of the District of Columbia without a permit from the
health officer authorizing him so to do and then only
in accordance with the terms of such permit. The
provisions of this paragraph shall not apply to the dis¬
tribution of manure over lawns and parking when such
manure has been so thoroughly rotted or decomposed
that its distribution gives rise to no offensive odors on
adjacent properties or on public thoroughfares.

Sec. 18 1. Any person violating any of the pro¬
visions of this section shall upon conviction thereof be

290 THE HOUSE FLY— DISEASE CARRIER

punished by a fine of not more than forty dollars for
each offense.

Extract from Article IX, Police Regulations
ARTICLE IX

Sec. io. No person shall remove or transport any
manure over any public highway in any of the more
densely populated parts of the District of Columbia
except in a tight vehicle, which if not enclosed must
be effectually covered with canvas so secured to the
sides and ends of the vehicle as to prevent the manure
from being dropped while being removed, and so as
to limit as much as practicable the escape of odors from
said manure.

Sec. 20. Manure may be deposited in pits below
the surface of alleys that are not less than fifteen feet
wide, but the pit must not extend more than four feet
beyond the building line. The walls must be substan¬
tial and water-tight, with stone or iron coping, bedded
in cement, set fair with the surface of the alley. They
must be covered with heavy wrought-iron doors, flush
with the alley pavement or surface, sufficiently strong
to carry heavily loaded carts or other vehicles, and pro¬
vided with ventilation by means of a flue inside of the
stable and extending above the roof of the same, and
they must be drained by sewer connections, as directed
by the Inspector of Plumbing.

APPENDIX III

291

Executive Office

Commissioners of the District of Columbia
Ordered- Washington, April n, 1908.

That, Pursuant to the authority vested in the Commis¬
sioners by the “Joint Resolution authorizing the Commis¬
sioners of the District of Columbia to alter, amend, or
repeal certain health ordinances” approved February 28,
1899, “An ordinance to prevent the sale of unwholesome
food in the cities of Washington and Georgetown” as
amended by Commissioners’ orders of January 2, 1902 ;
April 21, 1903; October 6, 1904; April 24, 1906; May 31,
1907, and June 10, 1907, is hereby further amended by
inserting after the word “effectually” in section 13 thereof
the phrase “or effectually protected by a power-driven fan
or fans,” so that said section shall read as follows :

Sec. 13. Every manager of a store, market, dairy,
cafe, lunch room, or any other place in the District of
Columbia, where a food, or a beverage, or confectionery,
or any similar article, is manufactured or prepared for
sale, stored for sale, offered for sale, or sold, shall cause
it to be screened effectually, or effectually protected by
power-driven fan or fans, so as to prevent flies and other
insects from obtaining access to such food, beverage,
confectionery, or other article, and shall keep such food,
beverage, confectionery, or other article free from flies
and other insects at all times. Any person violating the
provisions of this regulation shall, upon conviction
thereof, be punished by a fine of not more than twenty-
five dollars for each and every such offense. This regu¬
lation shall take effect from and after the expiration of
thirty days immediately following the date of its promul¬
gation.

Official copy furnished Health Department.

By order :

WM. TINDALL, Secretary.

Officially published in the Washington Herald April
16, 1908.

292 THE HOUSE FLY— DISEASE CARRIER

Executive Department
Commissioners of the District of Columbia

Washington, December i, 1909.

Ordered :

That Section 60 of “An Ordinance to prevent the sale
of unwholesome food in the cities of Washington and
Georgetown” as amended by orders of the Commissioners
of the District of Columbia, be, and the same is hereby
amended so as to read as follows :

Sec. 60. No person shall expose for sale on any pub¬
lic highway or in any uninclosed market, store, shop,
stand, or stall, or in any open lot, or transport over any
public highway to any place for sale there or elsewhere,
in the District of Columbia, any meat, fish, plucked
poultry or game bird, dressed rabbit or squirrel, butter,
butterine, oleomargarine, lard, lard compound or sub¬
stitute, cheese, candy, cake, bread, dates, figs, or any
food whatsoever of a kind not commonly washed, peeled,
shelled or cooked, before eaten, unless the same be then
and there effectually and in a cleanly manner wrapped,
or covered and enclosed, so as to protect it from dust and
insects.

No person shall expose for Sale in any place aforesaid
between April 1st and October 31st, inclusive, of any
year, any fresh meat or fresh fish unless said meat or fish,
while thus exposed, be kept at a temperature not exceed¬
ing fifty-five degrees Fahrenheit.

Official copy furnished.

By order :

WM. TINDALL,

Secretary.

Officially published in the Washington Post , December
3, I909-

APPENDIX IV

Directions for Building a Sanitary Privy*

IN order to put the construction of a sanitary privy
for the home within the carpentering abilities of
boys, a practical carpenter has been requested to con¬
struct models to conform to the general ideas expressed
in this article, and to furnish estimates of the amount
of lumber, hardware, and wire screening required.
Drawings of these models have been made during the
process of construction (Figs. 36, 37) and in completed
condition (Figs. 38, 39). The carpenter was requested
to hold constantly in mind two points, namely, ( 1 )
economy and (2) simplicity of construction. It is be¬
lieved that any fourteen-year-old schoolboy of average
intelligence and mechanical ingenuity can, by follow¬
ing these plans, build a sanitary privy for his home at
an expense for building materials, exclusive of recep¬
tacle, of five to ten dollars, according to locality. It is
further believed that the plans submitted cover the es¬
sential points to be considered. They can be elaborated
to suit the individual taste of persons who prefer a
more elegant and more expensive structure. For in¬
stance, the roof can have a double instead of a single
slant, and can be shingled ; the sides, front, and back
can be clapboarded or they can be shingled. Instead

*Taken from Public Health Bull. No. 37, U. S. Public Health
and Marine Hospital Service. By C. W. Stiles, Ph.D., Washing¬
ton, 1910.

293

294 THE HOUSE FLY— DISEASE CARRIER

of one seat or six seats, there may be two, three, four,
or five seats, etc., according to necessity.

A Single-Seated Privy for the Home
Nearly all privies for the home have seats for two
persons, but a single privy can be made more econom¬
ically.

Framework (Fig. 36). — The lumber required for
the framework (Fig. 37) of the outhouse shown as
completed in Fig. 38 is as follows:

A. Two pieces of lumber (scantling) 4 feet long and 6

inches square at ends.

B. One piece of lumber (scantling) 3 feet 10 inches long;

4 inches square at ends.

C. Two pieces of lumber (scantling) 3 feet 4 inches long;

4 inches square at ends.

D. Two pieces of lumber (scantling) 7 feet 9 inches long;

2 by 4 inches at ends.

E. Two pieces of lumber (scantling) 6 feet 7 inches long;

2 by 4 inches at ends.

F. Two pieces of lumber (scantling) 6 feet 3 inches long;

2 by 4 inches at ends.

G. Two pieces of lumber (scantling) 5 feet long; 2 by 4

inches at ends.

H. One piece of lumber (scantling) 3 feet 10 inches

long ; 2 by 4 inches at ends.

I. Two pieces of lumber (scantling) 3 feet 4 inches long;

2 by 4 inches at ends.

/. Two pieces of lumber (scantling) 3 inches long; 2 by
4 inches at ends.

K. Two pieces of lumber (scantling) 4 feet 7 inches

long ; 6 inches wide by 1 inch thick. The ends of
K should be trimmed after being nailed in place.

L. Two pieces of lumber (scantling) 4 feet long; 6 inches

wide, and 1 inch thick.

APPENDIX IV

295

Fig. 36. — Scantling for framework of single-seated privy. (Redrawn from Siles.)

296 THE HOUSE FLY— DISEASE CARRIER

First lay down the sills marked A and join them
with the joist marked B; then nail in position the two
joists marked C, with their ends 3 inches from the
outer edge of A; raise the corner posts ( D and F),
spiking them at bottom to A and C, and joining them
with L, In, G, and K; raise door posts E, fastening
them at J, and then spike Ix in position ; H is fastened
to K. (Fig. 37.)

Sides. — Each side requires four boards (a) 12 inches
wide by 1 inch thick and 8 feet 6 inches long ; these are
nailed to K, L, and A. (Fig. 37.) The corner boards
are notched at G, allowing them to pass to bottom or
roof; draw a slant from front to back at G-G, on the
outside of the boards, and saw the four side boards
to correspond with this slant. (Fig. 39.)

Back. — The back requires two boards (b) 12 inches
wide by 1 inch thick and 6 feet 1 1 inches long, and two
boards 12 inches wide by 1 inch thick and 6 feet 5
inches long. The two longest boards (6) are nailed
next to the sides ; the shorter boards are each sawed in
two so that one piece (c1) measures 4 feet 6 inches,
the other (c2) 1 foot 11 inches; the longer portion
(c1) is nailed in position above the seat; the shorter
portion (c2) is utilized in making the back door.

Floor. — The floor requires four boards ( d ) which
(when cut to fit) measure 1 inch thick, 12 inches wide,
and 3 feet 10 inches long. (Fig. 38.)

Front. — The front boards may next be nailed on.
The front requires (aside from the door) two boards
( E ) which (when cut to fit) measure 1 inch thick, 9

APPENDIX IV

297

from Stiles.)

298 THE HOUSE FLY— DISEASE CARRIER

inches wide, and 8 feet 5 inches long; these are nailed
next to the sides. (Fig. 38.)

Roof. — The roof may now be finished. This re¬
quires five boards (/), measuring (when cut to fit)

1 inch thick, 12 inches wide, and 6 feet long. They
are so placed that they extend 8 inches beyond the front.
The joints (cracks) are to be broken (covered) by
laths one-half inch thick, 3 inches broad, and 6 feet
long. (Fig. 39.)

Box. — The front of the box may be made with
two boards, 1 inch thick, 3 feet 10 inches long. One
may measure 12 inches wide, the other 5 inches wide.
These are nailed in place, so that the back of the
boards is 18 inches from the inside of the back-
boards. The seat of the box may be made with two
boards, 1 inch thick, 3 feet 10 inches long; one
may measure 12 inches wide, the other 7 inches
wide. One must be jogged (cut out) to fit around the
back corner posts (F). An oblong hole, 10 inches
long and 7^2 inches wide, is cut in the seat. The edge
should be smoothly rounded or beveled. An extra
(removable) seat for children may be made by cutting
a board 1 inch thick, 15 inches wide, and 20 inches
long; in this seat a hole is cut, measuring 7 inches long
by 6 inches wide ; the front margin of this hole should
be about 3 inches from the front edge of the board;
to prevent warping, a cross cleat is nailed on top near
or at each end of the board.

A cover (K) to the seat should measure 1 inch thick
by 15 inches wide by 20 inches long; it is cleated on

APPENDIX IV

299

300 THE HOUSE FLY— DISEASE CARRIER

top near the ends, to prevent warping; it is hinged in
back to a strip i inch thick, 3 inches wide, and 20
inches long, which is fastened to the seat. Cleats
may also be nailed on the seat at the sides of the cover.
On the inside of the backboard, 12 inches above the
seat, there should be nailed a block ( 1 ) , 2 inches wide,
6 inches long, extending forward 3*4 inches; this is
intended to prevent the cover from falling backward
and to make it to fall down over the hole when the
occupant rises.

On the floor of the box (underneath the seat) two
or three cleats are nailed in such a position that
they will always center the tub; the position of these
cleats depends upon the size of the tub.

Back door . — In making the back of the privy the
two center boards were sawed at the height of the
bottom of the seat. The small portions (c2) sawed
off (23 inches long) are cleated (0) together so
as to form a back door which is hinged above; a
bolt or a button is sufficient arrangement to keep the
door closed.

Front door. — The front door, Fig. 38, is made by
cleating ( p ) together three boards (Q) 1 inch thick,
10 inches wide, and (when finished) 6 feet 7 inches
long; it is best to use three cross-cleats ( p ) (1 inch
thick, 6 inches wide, 30 inches long), placed on the
inside. The door is hung with two hinges (6-inch
“strap” hinges will do), which are placed on the right
as one faces the privy, so that the door opens from
the left. The door should close with a coil spring (cost

APPENDIX IV

301

about io cents) or with a rope and weight, and may
fasten on the inside with a catch or a cord. Under

Fig- 39- — Rear view of single-seated sanitary privy. (Redrawn
from Stiles.)

the door a crosspiece ( R ) i inch thick, 4 inches wide,
30 inches long (when finished) may be nailed to the

302 THE HOUSE FLY— DISEASE CARRIER

joist. Stops may be placed inside the door. These
should be i inch thick, 3 inches wide, and 6 feet 6
inches long, and should be jogged (that is to say, cut
out) to fit the cross-cleats (/>) on the door. Close over
the top of the door place a strip 1 inch thick, 2 inches
wide, 30 inches long, nailed to I. (Fig. 37). A corre¬
sponding piece is placed higher up directly under the
roof, nailed to G. A strap or door-pull is fastened
to the outside of the door.

Ventilators. — There should be five ventilators ( w ).
One is placed at each side of the box directly under the
seat; it measures 6 to 8 inches square. Another (12
inches square) is placed near the top on each side of
the privy. A fifth (30 inches long 8l/2 inches wide) is
placed over the door, between G and I (Figs. 37, 38).
The ventilators are made of 15-mesh copper wire,
which is first tacked in place and then protected at the
edge with the same kind of lath that is used on the
cracks and joints.

Lath. — Outside cracks (joints) are covered with
lath one-half inch thick by 3 inches wide.

Receptacle. — For a receptacle, saw a water-tight bar¬
rel to fit snugly under the seat; or purchase a can or
tub, as deep (17 inches) as the distance from the un¬
der surface of the seat to the floor. If it is not pos¬
sible to obtain a tub, barrel, or can of the desired size,
the receptacle used should be elevated from the floor
by blocks or boards so that it fits snugly under the seat.
A galvanized can measuring 16 inches deep and 16
inches in diameter can be purchased for about $1, or

APPENDIX IV 303

even less. An empty candy bucket can be purchased
for about io cents.

Order for material. — The carpenter has made out the
following order for lumber (pine, No. i grade) and
hardware to be used in building a privy such as has
been described :

i piece scantling, 6 by 6 inches by 8 feet long, 24 square
feet.

1 piece scantling, 4 by 4 inches by 12 feet long, 16 square

feet.

5 pieces scantling, 2 by 4 inches by 16 feet long, 54

square feet.

3 pieces board, 1 by 6 inches by 16 feet long, 24 square
feet.

2 pieces board, 1 by 9 inches by 9 feet long, 14 square

feet.

3 pieces board, 1 by 10 inches by 7 feet long, 18 square

feet.

15 pieces board, 1 by 12 inches by 12 feet long, 180 square
feet.

12 pieces board, y2 by 3 inches by 16 feet long, 48 square
feet.

2 pounds of 20-penny spikes.

6 pounds of 10-penny nails.

2 pounds of 6-penny nails.

7 feet screen, 15-mesh, copper, 12 inches wide.

4 hinges, 6-inch “strap,” for front and back doors.

2 hinges, 6-inch “T,” or 3-inch “butts,” for cover.

1 coil spring for front door.

According to the carpenter’s estimate, these materials
will cost from $5 to $10, according to locality.

There is some variation in the size of lumber, as the
pieces are not absolutely uniform. The sizes given in

304 THE HOUSE FLY— DISEASE CARRIER

the lumber order represent the standard sizes which
should be ordered, but the purchaser need not expect
to find that the pieces delivered correspond with mathe¬
matical exactness to the sizes called for. On this ac¬
count the pieces must be measured and cut to measure
as they are put together.

Estimate of Material for School Privy

The following estimate of building materials has
been made by a carpenter for the construction of a
six-seated school privy. The estimated cost of these
materials' is $25 to $50, according to locality ; this does
not include the pails, which ought not to cost over $1
apiece.

3 pieces scantling, 6 by 6 inches by 20 feet, 180 square
feet.

1 piece scantling, 6 by 6 inches by 8 feet, 24 square
inches.

Scantling, 2 by 4 inches, 165 square feet.

Boards, 1 by 12 inches, 600 square feet.

Boards, 1 by 10 inches, 185 square feet.

Boards, 1 by 8 inches, 100 square feet.

Boards, 1 by 6 inches, 80 square feet.

Boards, x/i by 3 inches, 100 square feet.

Flooring, 80 square feet.

40 feet 15-mesh copper wire screen, 12 inches wide.

12 pairs of hinges, 6-inch “strap.”

6 pairs of hinges, 6-inch “T,”

3 pounds of 20-penny spikes.

15 pounds of 10-penny nails.

8 pounds of 6-penny nails.

6 coil springs for front doors.

6 knobs or latches.

APPENDIX V

A Simple Apparatus for Use in the Safe
Disposal of Night-Soil*

HE proper disposal of human excreta is recog-

1 nized by sanitarians as the most important single
measure needed to prevent the spread of typhoid fever,
hookworm disease, the dysenteries, and certain other
widely prevalent diseases.

Where large numbers of people are gathered to¬
gether, as in cities, the removal of dejecta from per¬
sons becomes, from an esthetic standpoint at least, a
necessity, and practically all modern cities have ex¬
pended large sums of money to install sewerage sys¬
tems, which, though usually removing the sewage in
such a way as to prevent it from becoming an intoler¬
able nuisance to sight and smell, yet frequently fall
short of safety from a sanitary standpoint.

Though a city may dispose of its own sewage prop¬
erly, its people are exposed to excreta-borne infections
brought in on various food supplies from farms. Thus
the sanitation of the farm is vastly important, not only
to the rural population, but also to the urban, and there¬
fore the farm as the fountain head of various and far-
flowing streams of infection is the logical point to

*From Public Health Report No. 54. Preliminary Note on a
Simple and Inexpensive Apparatus in Use in Safe Disposal of
Night-Soil. By L. L. Lumsden, Norman Roberts, and Ch. War-
dell Stiles.

305

306 THE HOUSE FLY— DISEASE CARRIER

attack in campaigns of prevention against many of the
communicable diseases.*

Among the obstacles in progress in farm sanitation
one of the chief has been the difficulty of convincing
the farmer that the benefits which would accrue from
proper disposal of excreta would justify the expense
of constructing, and the disagreeable labor of main¬
taining, the sanitary devices proposed. Therefore,
whatever can be done in simplification and in lessen¬
ing expense and labor in the installation and mainte¬
nance of an efficient disposal system will increase the
chances of its adoption.

The apparatus described in this note has been in use
in one of the work rooms of the Hygienic Laboratory
since July 12, 1910. It has been seen by a number of
sanitarians from different sections of the country, and
several of them have expressed a desire to test it for
themselves. The details of construction are presented
at this time in order to place them at the disposal of any
persons who may desire to test the apparatus in ques¬
tion.

Starting point of studies. — Starting out on the prin¬
ciple that the forces of nature in fermentation should,
if possible, be utilized, we have sought to meet the ob¬
jections that have thus far occurred to us in respect to
the wet system. Further, the importance of economy
and of simplicity of construction has been constantly
held in mind. An effort has also been made to reduce

*Freeman, Allen W., The Farm the Next Point of Attack in
Sanitary Progress. Jour. A. M. A., August 27, 1910.

APPENDIX V

307

to a minimum the labor and skill involved in taking
care of the privy, and, finally, while sanitary safety has
been the chief object in mind, we have not ignored the
widespread demand that human excreta be turned to

308 THE HOUSE FLY— DISEASE CARRIER

Construction. — The apparatus under consideration
consists of the following parts :

1. A water-tight barrel, to be used as a liquefier.

2. A covered water-tight barrel, can, or other con¬
tainer to receive the effluent.

3. A connecting pipe about two and one-half inches
in diameter, about twelve inches long, and provided
with an open “T” at one end, both openings of the
“T” being covered by wire screens.

4. A tight box, preferably zinc lined, which fits
tightly on the top of the liquefying barrel ; it is pro¬
vided with an opening on top for the seat, which has
an automatically closing lid.

5. An anti-splashing device consisting of a small
board placed horizontally under the seat and one
inch below the level of the transverse connecting
pipe; it is held in place by a rod, which passes
through eyes or rings fastened to the box, and by
which the board is raised and lowered. The liquefy¬
ing tank is filled with water up to the point where it
begins to trickle into the effluent tank.

As an insect repellent a thin film of some form of
petroleum may be poured on the surface of the liquid
in each barrel.

Practical working of the apparatus. — When the
privy is to be used, the rod is pulled up so that the anti¬
splashing board rises to within about one inch below
the surface of the water. The fecal matter falls into
the water, but this board prevents splashing, and thus
meets one of the greatest objections thus far raised to
the wet system. After defecation the person sinks the
anti-splashing board by depressing the rod, and the

APPENDIX V

309

fecal matter then floats free into the water. We are
now working on an improvement whereby the rod will
connect with the automatically closing lid, and the anti¬
splashing board will rise and sink as the lid is opened
and closed.

Although some of the fecal matter floats, it is pro¬
tected both from fly breeding and fly feeding in the
following ways : First, by the automatically closing lid ;
second, by the water ; third, by the film of oil ; and,
fourth, for additional safety, the apparatus should be
located in a screened place. The film of oil also pre¬
vents the breeding of mosquitoes in the barrel. Ac¬
cordingly, so far as the privy as a breeding or feed¬
ing place for flies and mosquitoes is concerned, the
model in question completely solves the problem.

The fecal material becomes fermented in the water
and gradually liquefies.; the addition of excreta natu¬
rally raises the level of the liquid, and the excess flows
into the effluent tank, where it is protected from in¬
sects by the cover and by the film of oil. This effluent
may be allowed to collect in the tank until it reaches the
level of the connecting pipe, when it may be safely dis¬
posed of in various ways to be discussed later.

From July 12th to October 26th there have been
246 defecations (with urination) into the model in
question, making about two and one-third defecations
a day. The effluent has amounted to about twelve gal¬
lons of manageable fluid. It has not been found neces¬
sary to add water to the liquefying barrel since the ap¬
paratus was put into operation.

310 THE HOUSE FLY— DISEASE CARRIER

Although the period in question included the hottest
part of summer, the odor, when compared with that of
the average privy, has been negligible.

It is thus seen that this device appears to meet the
following requirements :

1. It solves the fly and mosquito problems, so far
as the privy is concerned.

2. It liquefies fecal matter and reduces its volume
so that it may be safely disposed of more easily and
cheaply than night-soil.

4. It reduces odor.

4. It reduces the labor of cleaning the privy and
makes this work less disagreeable.

5. It is of simple and inexpensive construction.

The effect of the fermentative changes in the ap¬
paratus upon the viability of typhoid bacilli and hook¬
worm eggs has not been determined, but other experi¬
ments tend to show that under such conditions the vast
majority of typhoid bacilli and of hookworm eggs in¬
troduced would die within six weeks’ to two months’
time. While the time of storage can be prolonged ac¬
cording to the capacity of vessels provided for the pur¬
pose, we believe at present that it is safer and more
practical not to depend upon storage alone to destroy
infectious organisms in the effluent, but to consider the
effluent infectious and to dispose of it accordingly.

Disposal of effluent. — ( 1 ) Heat : If a suitable (metal¬
lic) vessel is provided to receive the effluent, a fire may
be built under the vessel and the effluent heated to boil¬
ing. Or if a wooden or concrete effluent tank is used,

APPENDIX V

311

the effluent may be transferred to some other vessel
for boiling.

After boiling, the fluid may be safely used for fer¬
tilizer under any conditions.

Heat disinfection is the only measure which can to¬
day be recommended unreservedly.

(2) Burial: Burial will unquestionably decrease the
dangers of spreading infection, but in the present state
of our knowledge this method ’of disposal cannot be
relied upon as safe. If burial of the effluent is prac¬
tised, the fluid should be disposed of not less than 300
feet from and downhill from any neighboring water
supply and not less than two feet underground, and
then only provided the soil itself is a good filter. Bur¬
ial in a limestone region may contaminate water sup¬
plies miles away.

(3) Chemical disinfection: Chemical disinfectants,
such as chlorinated lime and certain coal-tar deriva¬
tives, have the great advantage of cheapness and can
be relied upon to destroy pathogenic bacteria. Our
knowledge regarding the action of chemical disinfec¬
tants upon the eggs and spores of the various animal
parasites is at present very rudimentary, but so far as
results are known, their practicable use does not seem
to be so efficient in the destruction of the zooparasitic
as of the bacterial infectious organisms. Therefore,
pending further investigations, the use of chemically
treated excrement as fertilizer should not be regarded
as unqualifiedly safe.

(4) Chemical disinfection with subsequent burial:

312 THE HOUSE FLY— DISEASE CARRIER

Inasmuch as chemical disinfection can be relied upon
to destroy pathogenic bacteria, and inasmuch as burial
greatly reduces the danger from animal parasites, a
suitable combination of the two methods (chemical dis¬
infection and burial) can be used with reasonable safety.

( 5 ) Sewers : In partly sewered towns, the effluent
from these privies may be emptied into the sewers. If
conditions are such that the addition of this material
to the sewage is dangerous, then the entire sewerage
system needs correction.

Paper. — Only toilet paper so far has been used, and
the septic action seems to digest it. Other experiments
indicate that newspaper would be disposed of by septic
action in the tank, but perhaps some increase in the
size of the tank would be required.

Cleaning. — Although no water has been added since
the model was put into operation, the contents of the
liquefying tank have remained fluid, and it is prob¬
able that in a tank having the capacity of an oil bar¬
rel, the amount of sludge from the dejecta of a family
of five people would not be sufficient to require the
cleaning of the liquefying tank oftener than once in
six months to a year.

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