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Title: Our insect enemies

Author: Vance Randolph

Editor: E. Haldeman-Julius

Illustrator: Peter Quinn


        
Release date: August 4, 2026 [eBook #79263]

Language: English

Original publication: Girard: Haldeman-Julius Company, 1925

Other information and formats: www.gutenberg.org/ebooks/79263

Credits: Tim Miller, Sam Lamb and the Online Distributed Proofreading Team at https://www.pgdp.net


*** START OF THE PROJECT GUTENBERG EBOOK OUR INSECT ENEMIES ***




 LITTLE BLUE BOOK NO. 860
 Edited by E. Haldeman-Julius

 Our Insect Enemies

 Vance Randolph

 Drawings by Peter Quinn

 HALDEMAN-JULIUS COMPANY
 GIRARD, KANSAS


 Copyrighted, 1925,
 Haldeman-Julius Company




CONTENTS


                                  Page

 Houseflies and Their Kindred       4

 Mosquitoes and Disease            28

 Life Among the Bedbugs            43

 Lice, Crabs and Cooties           47

 Our Friend the Cockroach          54

 Chiggers, Ticks and Fleas         57


PRINTED IN THE UNITED STATES OF AMERICA




LIST OF ILLUSTRATIONS

                                                                     Page

 Fig. I. The Metamorphosis of the Housefly (_Musca domestica_).       12

 Fig. II. Malaria and its Carrier.                                    33

 Fig. III. Three kinds of Lice.                                       51

 Fig. IV. Some Common Cockroaches.                                    58

 Fig. V. Chiggers and Ticks.                                          61






OUR INSECT ENEMIES




HOUSEFLIES AND THEIR KINDRED


The common housefly (_Musca domestica_) is perhaps more thoroughly
domesticated than any other insect; it lives and flourishes wherever
man has established his settlements, and does not thrive elsewhere. It
is mentioned by many of the ancient writers, and has evidently been
associated with man from the remotest antiquity, doubtless adapting
itself gradually to his changing modes of life. It still breeds in the
refuse which accumulates about his buildings, and still invades his
home to partake of his food. When one considers the number of flies
which get into modern dwellings despite glass and wire and modern
insecticides, it is difficult to understand how our sturdy fathers
managed to survive the summers in mediaeval Europe. Picture Thomas
Aquinas battling with swarms of flies for his food! The housefly’s
favorite breeding place has always been in horse manure, and man has
until recent years had great quantities of this nutritious substance
about him; with the coming of the automobile this condition has been
changed somewhat, but even the cleanest of American cities still
affords sufficient decaying matter to assure a bountiful crop of flies.
At some future day perhaps we shall have cities so spotless that there
will be nowhere a speck of garbage large enough to nourish a maggot,
but that day is still to come, and it doth not yet appear what we shall
be.

Meanwhile, as Herrick says, the housefly is with us always. “They are
present from early spring to late fall, even remaining far into the
winter. They are troublesome in kitchens and dining rooms because of
their abundance, their proneness to get into food, and their generally
filthy habits. Until recent years the housefly has been generally
regarded as somewhat of a scavenger and has been considered of value
to humanity because of its aid in the removal of wastes that are a
menace to human welfare. The eggs of the housefly are often deposited
on decaying vegetable matter that is allowed to accumulate in the
vicinity of human habitations and the maggots that hatch from the eggs
live on this decaying matter and aid in destroying it. Thus it must be
conceded, perhaps, that houseflies do assist somewhat in the removal of
foul and dangerous waste matters and, to this extent, are of benefit.
On the other hand, it has been conclusively shown that this modicum
of benefit is greatly overbalanced by their role in disseminating
dangerous diseases. It has been shown that houseflies carry the germs
of cholera, typhoid fever, cholera infantum, and tropical dysentery on
their feet, legs, bodies and in their digestive tracts. There can be no
doubt of the responsibility of the housefly for much sickness and many
deaths.”

Although the adult housefly is equally fond of fresh and putrid matter,
flitting from filth to food and back again, the eggs are always laid in
decaying substances, preferably horse manure. In the absence of this
delicacy the eggs may be deposited in human excrement, or even cow
manure if it is not too dry. A single female fly often deposits one
hundred and fifty eggs at a single sitting, and lays as many as six or
seven hundred in the course of a season.

The egg is white and shaped like a grain of wheat; it measures
about one-twentieth of an inch in length, and hatches in from ten
to twenty-four hours, the period of incubation varying with the
temperature. The second or larval stage is represented by a wormlike
creature called a maggot, which crawls about and devours great
quantities of nourishing manure. When the maggot is about five or six
days old it has attained a length of nearly three-eighths of an inch,
and transforms into the pupa; it is no longer active, ceases to take
food, and the outer skin turns into a hard, brown, dry case called a
puparium. After five or six days of rest the puparium is burst open and
the adult fly crawls out.

The newly emerged flies mate within two or three days, and the young
females are soon laying their first batch of eggs. Thus the whole
development may occur in about fourteen days, and Herrick thinks that
in Washington, D. C., it may be complete in ten days or less, according
to the temperature, with ten or twelve generations in a summer. “One
can hardly realize,” says Herrick, “the enormous numbers that such
rapid development is capable of producing. Inside of two months, one
female fly can give rise to many millions of progeny. For the purpose
of illustration, we will assume that a female fly lays 100 eggs. If
these hatch and all the larvae come to maturity, about one-half will
probably be males and the other half females. Then at the end of the
first generation there will be fifty egg-laying females. At this rate,
at the end of the eighth generation there would be produced about
1,875,000,000,000 adults. Of course, in nature, a very large part of
these would die before reaching maturity, so that actually one female
would probably never produce such an enormous number of individuals.
However, even under normal conditions tremendous numbers are produced.”

The adult housefly is unhappily too familiar to require a lengthy
description. The total length is about one-fourth of an inch, there are
two membranous wings and six hairy legs, while the thorax is gray with
four dark longitudinal stripes above. Besides the hairs and bristles on
the body and legs, which entangle great numbers of germs, the sticky
_pulvilli_ of the feet gather bacteria as if they had been especially
developed for that purpose. Thus every housefly scatters bacteria
broadcast wherever he goes; one has only to allow a fly to walk
across a plate of sterile gelatin to see large colonies of bacteria
produced in every foot-print. Esten and Mason’s examination of some 400
specimens showed that the number of bacteria carried ranged from 550 to
6,600,000 per fly, with an average of nearly a million and a quarter.

The general impression is that the housefly does not travel any great
distance from its birth-place, but there is considerable doubt
about this matter. Hewitt has taken them flying at least eighty feet
above the ground, and it is obvious that small insects which rise
so high may be carried long distances by the wind. Copeman, Howlett
and Merriman have attacked the problem by marking large numbers of
specimens, releasing them, and then watching for them in traps set at
various distances; they recovered several which had travelled more than
three-fourths of a mile. Dr. Hodge found plenty of houseflies on the
cribs of the Cleveland waterworks, which are located six miles out in
Lake Erie, and which offer no breeding places for flies. He naturally
concluded that they were blown six miles by the wind.

It has been pretty well established that adult flies do not retain
and disseminate disease germs which they swallowed as maggots in the
manure, but only those which they acquire in the adult state. It has
been definitely proved, however, that the bacilli of typhoid fever are
carried on the bodies and legs of houseflies, and also that the bacilli
are often swallowed and survive the passage through the body, as living
bacilli have frequently been demonstrated in flyspecks. The most
important practical consideration is, of course, the actual frequency
with which houseflies do transfer pathogenic organisms from filth to
food intended for human consumption, thus spreading disease, and this
is in its very nature a difficult matter to investigate.

Typhoid fever is a disease affecting the intestines, and the bacilli
which cause it frequently remain in the body for long periods after
the patient has apparently recovered. The germs are passed out in the
urine and fecal matter. As Herrick puts it: “If the excreta or urine
containing these bacilli are deposited where they are accessible to
flies, for instance in open privies, the chances are high that the
bacilli will be carried on the bodies of these insects back to the
kitchens and dining rooms and be deposited on our food. During the
Spanish-American War, flies were traced by their whitened feet from
the lime-sprinkled, open latrines or privies to the dining tables of
the soldiers in camp. It makes one shudder to think of the thousands
of open closets in the small towns of the United States to which flies
have access and in which they breed and from which they may come direct
to our kitchens and dining rooms.”

Excluding the greater variability of the water supply, the fact that
typhoid is so much more prevalent in country districts than in the
city may be due almost entirely to the abundance of flies, since
other opportunities for infection are no greater than in the city.
Certain South American cities have very good water, but typhoid rages
nevertheless, because the natives expose their excreta within a few
feet of the street markets, and myriads of flies carry the bacilli
from the dunghill to the food. “In our own country,” says Brues, “the
seasonal incidence of typhoid fever corresponds to some extent with fly
prevalence, and still more significant is its greater summer prevalence
in regions where systems for sewage disposal are not generally
installed.... The greater uniformity throughout the year in New York,
where the opportunities for fly-borne infection are curtailed, is very
marked. Another way in which the housefly can aid in the spread of
typhoid is through infecting milk on dairy farms where carriers are
present and offer the flies a chance to become infected.”

The vessels in an ordinary country dairy are nearly always more or less
accessible to flies, and warm milk is an excellent medium in which to
cultivate bacteria. When a fly which has been feeding on the excreta
of a typhoid patient falls into a can of milk, there is a very good
chance that the disease may be spread all along the milkman’s route.
Dr. Taylor, of the Colorado State Board of Health, reports a case of
this sort: “In the city of Denver we had a very sad as well as a plain
demonstration of the transmission of typhoid fever by flies and milk.
Early in August of this year the wife of a dairyman was taken with
typhoid fever, remaining at home about three weeks before her removal
to the hospital, August 28. During the first two weeks of September we
received reports of numerous cases of typhoid fever in the northern
portion of Denver, and upon investigation found that all these cases
had been securing their milk from this dairy.

“An inspection of the dairy was then made, and in addition to learning
of the illness of the dairyman’s wife, we also found the dairyman
himself suffering with a mild case of typhoid, but still up and
delivering milk. The water supply of the dairy was fairly good.
However, we found that the stools of both the wife and husband
had been deposited in an open privy vault located only thirty-five
feet from the milk house, which was unscreened and open to flies.
The gelatin cultures exposed for thirty minutes in the rear of the
privy vault and in the milk house among the milk cans gave numerous
colonies of typhoid bacilli, as well as colon bacilli and the ordinary
germ-life. The source of infection in the dairyman’s wife’s case is
unknown, but I am positive that in all the cases which occurred on this
milk route the infection was due to bacilli carried from this vault by
flies and deposited upon the milk cans, separator and utensils in the
milk house, thereby contaminating the milk. The dairyman supplied milk
to 143 customers. Fifty-five cases of typhoid fever occurred and three
deaths resulted therefrom.”

As long ago as 1873 Dr. Nichols noted that the number of cholera cases
on his ship seemed to vary directly with the abundance of flies. Later
experiments demonstrated the presence of the cholera bacillus upon the
bodies and in the excreta of flies fed upon cholera-infected material,
and it has been shown that flies sometimes transfer the cholera bacilli
from human excreta to milk. Dr. Tsuzuki, of the Japanese Army Medical
Service, found the germs of cholera upon flies taken in cholera-ridden
houses, and demonstrated that flies carry the organisms from place
to place. Macrae, commenting on an outbreak of cholera in a jail in
India, remarked that the place was infested with “a plague of flies ...
which were present in swarms when the disease broke out, and it was
an observation of daily experience to see them settling on cholera
stools whenever possible.” Dr. Macrae goes on to say that the flies
undoubtedly carried the cholera germs to the prisoners’ food, and adds:
“The practical lesson is, that flies should be looked upon in the light
of poisonous agencies of the worst kind during cholera epidemics, and
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.”

Because of the flies’ liking for expectorated saliva, it has long been
suspected that tuberculosis may be carried about by these insects.
Several investigators have carried out experiments in which flies have
been fed upon the sputa of consumptives, and the tuberculosis bacilli
have been found in their intestines and fly specks. Frederick T. Lord,
after a long series of laboratory investigations, concluded that: “(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, infection
of the surrounding air may occur.” Dr. Lord goes on to suggest that
“tubercular material (sputum, pus from discharging sinuses, fecal
matter from patients with intestinal tuberculosis, etc.) should be
carefully protected from flies, lest they act as disseminators of
the tubercle bacilli. 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. As these precautions would not eliminate fly infection by
patients at large, foodstuffs should be protected from flies which may
already have ingested tubercular material.”

[Illustration:

  Fig. I. The Metamorphosis of the Housefly (_Musca domestica_). A,
  eggs, considerably enlarged; B, young maggot; C, puparium; D, pupa;
  E, adult.
]

Numerous British army surgeons long ago hazarded the guess that flies
carry dysentery, but the first clear case is that of an epidemic which
occurred in the Worcester State Hospital in 1910. Houseflies were
especially abundant at the time, and Dr. Orton, after a painstaking
experimental study of the affair, concluded that flies were entirely
responsible for the epidemic.

There is now a fairly general agreement that flies spread the organisms
which cause the infantile diarrhea known as summer complaint, which
kills more infants than any other single cause except lack of
sufficient and proper food. Fraser, Nash and others have noted that the
more flies the more cases of summer complaint, and Sandilands explains
the immunity of the children of the rich by the smaller number of flies
in their houses. It is certainly true that the mortality of bottle-fed
infants is very much higher than of breast-fed babies, but whether
Jackson is justified in attributing this mainly to the infection of
cow’s milk by flies is a question.

Lucian Howe has long contended that purulent ophthalmia--the sore-eye so
common up and down the valley of the Nile--is distributed mainly by
the housefly. The disease is always most prevalent where the flies are
most abundant, and in flyless desert regions there is practically no
ophthalmia. The natives are singularly dirty and indolent, and flies are
often seen to settle undisturbed about a pair of badly infected eyes.
Dr. Howe has captured a number of these flies, and found that their
feet were covered with the same bacilli found in the secretion of the
inflamed conjunctiva.

Braun, Demetriades and others report that gonorrheal and other eye
infections are often carried by houseflies. Welander, in 1896,
according to Howard, “observed an interesting case where an old
bed-ridden woman in a hospital became infected. It seems that her bed
was along side that of another patient who had blennorrhea, but that
a screen which did not reach the ceiling separated the beds. Thus all
means of infection except through the agency of flies was apparently
absent. The investigator found that flies bore living gonococci upon
their feet three hours after they had been soiled with secretion, since
they infected sterilized plates with which they came in contact.”

Nuttall and Jepson, after reviewing the entire literature of the
subject, think that “the evidence 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.”

Bubonic plague is now definitely known to be spread by fleas which are
parasitic on rats, but many observers still cling to the view that the
housefly also acts as a distributor. It is certainly true that flies
are killed by feeding upon the bodies of persons who die of the plague,
and Yersin, at Hong Kong in 1894, showed that these dead flies contain
active plague bacilli. Whether the fly plays any serious part in the
actual spread of bubonic plague is still a mooted question.

The housefly has plenty of natural enemies, but they do not seem to
reduce the number to any material extent. One of the most destructive
is a minute fungus which grows inside the fly’s body until it finally
causes death. The dead flies one finds on window panes in the fall,
surrounded by a whitish ring, are the victims of these fungus growths.
There are several species of these fungi; in some cases at least the
attack begins with a spore which attaches itself to the outside of the
body, and grows a long thread-like root which enters the body through
one of the spiracles or breathing pores.

Several species of protozoan parasites have been found in the
intestines of flies, along with a few minute parasitic worms, but
they are not known to cause any great amount of inconvenience. Small
red mites are often seen fastened to flies’ bodies; some of them are
true parasites which suck the juices from the body of their host, and
look very much like the chiggers which annoy the higher animals in the
Southern States. With other mites, according to Howard, “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 attached
themselves to the fly.”

Spiders, if given an opportunity, destroy a great many flies, but as
the webs are usually destroyed by the housekeeper’s broom they do very
little execution. The little centipede known as the water bug kills a
great many flies, but as it works at night gets little credit for its
good offices.

Hornets are sometimes seen to capture and carry off houseflies, but
it is doubtful if any great number of the pests are killed by these
insects. An English entomologist named Westwood once circulated a story
to the effect that “the Americans, aware of their service in destroying
flies, sometimes suspend a hornet’s nest in their parlors.” A little
later one Benjamin D. Walsh, an American, wrote that “some persons in
America have turned the insect-devouring propensity of the hornets to
good purpose by suspending one of their nests in a house much infested
by the common housefly. In such a situation we have been told that they
soon make a clearance of the obnoxious flies; and so long as you do
not meddle with them they will not meddle with you.” To me these two
quotations are the sheerest nonsense; any one who has any acquaintance
with hornets will find it difficult to visualize an American farmer
intentionally filling his house with hornets for any reason whatsoever.
I have never been able to find anybody who has tried out this method;
if there are any such among my readers I should like very much to hear
from them. Please address me in care of the publisher of this booklet.

The logical way to combat the housefly would be to destroy the eggs and
maggots as we do in the case of the mosquito, but it is not practical
at present. In rural districts, where the dung of livestock is always
lying about, and the human excreta exposed in shallow open closets,
very little progress has been made. Of course, the danger of typhoid
may be avoided by keeping the excreta of typhoid patients where flies
cannot get at it, and the flies certainly could not spread tuberculosis
if no tubercular sputum was exposed. These facts are taken advantage
of in the cities, where there are plenty of flies, but very little
typhoid, because the water closet system is such that flies cannot get
access to the excreta. In communities where there is no adequate sewage
disposal and where flies are plentiful, the individual can only screen
them out of his own dwelling as best he can. Howard estimates that more
than $10,000,000 are spent every year for screen wire in the United
States alone.

Many ingenious devices for destroying flies inside houses are on the
market--poisons, sticky fly paper, fly traps and fly swatters. One
of the most useful of these is sticky fly paper cut in strips and
suspended from the ceiling. This will often clear a room of flies
when the ordinary sheets of the same paper lying flat on a table are
quite inefficacious. In Japanese hospitals, says Howard, “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 patient’s
bed on a cord. The flies all gather on the potato, 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.”

C. F. Hodge is all for building large traps and placing them out of
doors in early Spring, arguing that a great many newly emerged flies
are thus caught before they reproduce, and that it is better to catch
one fly in the Spring than thousands in the Autumn. Brues even says
that “practical traps whereby fly-larvae in stored manure may be caught
and destroyed before transformation have also been devised.”

Some progress has been made in the treatment of manure piles with
poisons. Howard found that either chloride of lime or kerosene kill
the maggots all right, but the cost of both is prohibitive. Davis
worked with iron sulphate and reported that manure could be cleaned
of maggots and deodorized at a cost of about two cents per horse per
day. Howard, Herns and others have advocated fly-tight pits or bins for
the reception of manure, and these have been adopted in many places,
particularly in California. The regulations of the District of Columbia
specify that all manure must be kept in “covered receptacles,” and it
has been found that a tight-covered barrel suffices for a one-horse
stable. Some workers in the Federal Department of Agriculture have
carried out a series of experiments indicating that borax, hellebore,
and calcium cyanide are highly destructive to maggots in horse manure,
and it is quite probable that some very cheap and simple treatment will
soon be developed.

The proper disposal of human excreta is another problem that is vitally
connected with the checking of germ-laden flies. As Howard says, “the
average person in the large city has no idea of the fact that there
are many comparatively intelligent citizens 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 of 4,825 farm houses 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.”
Herrick points out that “there is no longer any excuse for the old
open box privy, cleaned out once a year. It is a menace to every house
in the vicinity as well as to individuals living perhaps hundreds of
miles away because of its possibilities in contaminating milk. Some
form of sanitary closet must be substituted.” One of the very best is
that designed by Stiles, and described in Farmer’s Bulletin 463, U. S.
Department of Agriculture. The bulletin is free, and the privy can be
built at a cost of five or six dollars.

Another fly which looks almost exactly like the ordinary housefly
is _Stomoxys calcitrans_, usually known as the biting housefly, but
sometimes called the stable fly because of its great abundance about
horses and cattle. The stable fly may be recognized by the fact that it
holds its head higher than the housefly, but Howard says that “the best
way to distinguish between the two flies is to allow them to walk over
your hand; if it bites it is _Stomoxys_; if it does not it is probably
the housefly.” The housefly has no mouthparts adapted for biting, but
the stable fly is provided with a sharp awl-like proboscis, and sucks
the blood from its victims. It is a great lover of direct sunshine,
and, when not engaged about cattle and horses may be seen sunning
itself on walls and fences. In damp weather it invades houses and
verandas, and it is then that the silk-clad ankles suffer. This habit
has given rise to the popular idea that houseflies bite just before a
storm. The bite is painful at the moment, but there is no subsequent
swelling or irritation; the puncture, according to Howard, does not
seem to be poisonous to man, and aside from the pain given it is far
less dangerous than a mosquito bite.

The life history of _Stomoxys_ has been worked out by Newstead, who
found that the creamy-white eggs are laid about sixty at a time in
irregular clusters, usually in manure of some kind, but frequently
in piles of decaying grass or straw. Howard reared the fly from cow
manure, and says that the egg usually hatches in two or three days.
“The larva need not be described,” he says, “because it is so similar
to that of the housefly.” Newstead 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-eight days. In the puparium the insect remained from nine to
thirteen days. The development of the species is therefore much slower
than that of the true housefly. It is Newstead’s opinion that the
winter is passed chiefly in the pupal condition.

The stable fly is considered by Austern and others to distribute
various diseases among cattle, but is probably not dangerous to
man. Brues remarks that it was once “thought to be a carrier of
poliomyelitis (infantile paralysis) but it now seems probable that
such is not the case.” Howard says, “I judge from the fact that it is
attracted to human excreta that it may become a carrier of intestinal
diseases,” but it has never been proved to be more than an accidental
agent in this matter.

Bishop reports a great outbreak of this pest in Texas, where they were
found breeding in straw stacks, and caused serious injury to cattle and
horses. A similar case recorded by Lucian Iches of Santa Fe, Argentina,
is described by Howard: “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 principal
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 debris burnt within forty-eight
hours after the completion of the threshing, the ashes being used for
fertilizing purposes. It turned out that there was an old provincial
law in the province of Santa Fe ordering the burning of all debris
after threshing, but it had not been carried out during recent years,
and therefore the _Stomoxys_ multiplied until this veritable plague
ensued.”

Another plague of stable flies occurred some years ago in Oregon, but
the life history was not known there and the breeding places were never
found. The severity of the pest’s bite is remarked by Osborne: “It
causes a great deal of annoyance to horses, cattle and other domestic
animals, and is frequently very troublesome to people working in places
where it abounds: Its bite is not poisonous and aside from the pain
given and the possibility of its disseminating disease, it is less
injurious than some other members of the group. When abundant, however,
the annoyance may be very great.” Bold describes the pitiable condition
of cattle bitten by the stable fly: “In some of the severe cases the
joints were so much swollen that the poor animals could not bend their
legs to lie down; and in them the inflammation rose so high as to
cause the loss of the outer skin and hair.”

The cluster fly (_Pollenia rudis_) is a little larger than the
housefly, and appears longer because the wings overlap in such a
fashion as to make the body appear very slender. The thorax bears
many short, yellow hairs, and the grayish abdomen inclines to be
iridescent. During the Summer this fly lives upon flowers and fruits,
and does not come near houses, but the adults seek sheltered places
in the Fall, and spend the Winter in large groups or clusters--hence
the name. When the clustering process happens to take place within a
human habitation the flies become a nuisance. Howard quotes one of his
correspondents from Illinois: “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 edges of the
ceiling. They cannot be driven out like 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 was recommended to
us, with no effect. 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.”

They enter one by one through small cracks or crevices, and, as one of
Herrick’s correspondents writes, “screens and other devices which work
perfectly in excluding the ordinary fly are useless in keeping these
out.” W. H. Dall, describing the pest at Geneva, New York, states that
“people soon learned to look everywhere; in beds, in pillow-slips,
under table covers, behind pictures, in wardrobes, nestled in bonnets
and hats, under the edge of carpets, etc.”

We are singularly ignorant of the life history of this insect. Macquart
and Desvoidy have found _Pollenia_ larvae in manure, and the Bureau
of Entomology people reared a single specimen from cow dung. Keilin,
however, claims to have discovered the maggot living as a parasite
in certain species of earth-worms. It is said that the adults are
particularly susceptible to the same fungous diseases which attack the
housefly.

The lesser housefly (_Homalomyia canicularis_) is generally regarded by
laymen as an immature specimen of the common housefly, but is really
a distinct species, belonging to a different family altogether. The
housefly, or any other fly for that matter, does not grow at all in the
winged state--the newly emerged adult is quite as large as it will ever
be. The _Homalomyia_ maggot is very different from that of the ordinary
housefly; it measures only about one-fifth of an inch in length, and is
covered with spiny processes, to which the dirt clings and gives the
creature a mottled, dirty appearance. They develop in various kinds of
garbage and manure, being especially partial to human excrement. Hewitt
has found them very abundant in privies, and Herrick remarks that “this
habit of breeding in excreta of various kinds makes the flies dangerous
inhabitants of our rooms. They may act as conveyers of disease germs
quite as readily as the housefly. They are rapid breeders, for a
generation may be produced in two weeks in hot weather.”

The blue-bottle fly (_Calliphora erythrocephala_) has a dull-colored
thorax and a dark metallic blue abdomen. It is sometimes known as the
blow-fly, and lays its eggs on meat and dead animals, or even in sores
upon living creatures. A single female has been known to lay more than
six hundred eggs, and Hewitt says that twenty-three days is sufficient
to produce a generation. The blow-fly ordinarily lives in the open air,
but occasionally gets into houses, particularly in stormy weather.
Herrick remarks that “it has been found frequenting human feces and
for this reason may be suspected of bearing intestinal bacteria, thus
making it a fly to be dreaded.”

The so-called cheese fly (_Prophila casei_) is a little shiny black
fellow which develops in cheese, bacon, ham, chipped beef and the like.
The larva is known as the cheese skipper because of its remarkable
agility. Howard says that it will sometimes jump three or four inches,
and I have myself seen these vigorous little maggots, stimulated by
the heating of their home in a piece of Southern bacon, leap clear out
of the frying pan into the camp fire. The cheese fly is not native to
America and was probably imported in an early shipment of Swiss cheese.
The insect is not particularly dangerous, but as Howard says “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 moth fly (_Psychoda minuta_) is a very fragile little insect whose
broad wings are hairy like those of a moth. It is very common among
weeds, clinging to the under surfaces of leaves, and often enters
houses, passing easily through the ordinary fly screen. According to
Herrick, “the larvae of some of these flies live in cow dung, others in
decaying vegetation, while some live in water, especially sewage water
or drain water from kitchens. We have often seen hundreds of these
moth flies among the weeds overhanging a ditch carrying the drainage
water from a kitchen. We have also seen them in abundance along ditches
carrying sewage water from houses. In the first-mentioned instance they
were always present on the window panes of the kitchen, readily passing
through the ordinary wire screen. Judging them from the places in which
they breed, we would consider them unwelcome guests in our houses.” The
moth flies of Southern Europe bite human beings, and are carriers for a
disease called phlebotomus fever, but the species so far identified in
the United States probably do no particular damage.

The tsetse fly (_Glossina palpalis_), the sole distributor of the
deadly sleeping sickness which has decimated the native population
of equatorial Africa, is a near relative of our common housefly. The
reproduction of the tsetse fly is very different from that of most
insects, however. According to Brues, “the female does not deposit her
eggs, but a single one develops to the fully grown larval condition
before being deposited. This larva soon pupates in the shade beneath
the brush bordering the water where it has been dropped by the parent
fly, and later emerges in the winged adult condition. The pupae
requires such moist shade, and it is apparently for this reason alone
that the flies never occur away from the immediate vicinity of the
water. As a result of their method of development, the tsetse flies
do not multiply rapidly, and even under favorable conditions only one
larva is produced in a ten-day period.... It was thought at first
that by moving all the natives back from the edges of the water, the
flies thus left without opportunities for reinfection, would become
free from trypanosomes (the organisms causing the disease) and that
by isolating and treating cases of the disease in fly-free areas it
would be possible to eliminate them entirely. In conjunction with
this, the cutting of brush, especially about boat landings and
watering places, has been practiced as far as possible. Contrary to
expectations, it has been found that even after three or four years,
infected flies still occur along the uninhabited shores. This led to
experimentation upon animals and it is now known that various wild
antelopes as well as certain domestic animals may act as reservoirs for
the virus of sleeping sickness, which may thus persist in the complete
absence of any human subjects. As a result of this discovery the great
difficulties of combating the disease ... have been vastly increased.”




MOSQUITOES AND DISEASE


The mosquito is nothing more than a small, slender fly, very similar
to the housefly in every essential detail of its structure. There
are about sixty species and varieties in America, but the three
most common and important species are: the ordinary house mosquito
(_Culex pipiens_) which does not carry disease, the malarial mosquito
(_Anopheles quadrimaculatus_) which disseminates malaria, and the tiger
mosquito (_Aedes calopus_) which is a carrier of yellow fever.

The common house mosquito has perhaps no equal as a persistent and
universally damned destroyer of human tranquility. Heartily detested
everywhere, even by entomologists, no serious studies of the life
history were made until comparatively recent years. The female deposits
her eggs upon the surface of still water in boat-shaped masses, each
mass containing from fifty to two hundred eggs. The floating egg-mass
is always large enough to be seen with the naked eye, and often
measures a quarter of an inch in length. The eggs usually hatch in two
or three days, and the larva is the well-known wiggler which swims with
a peculiar jerky motion in every rain-barrel and roadside pool in the
country. The wiggler breathes through a tube near the caudal end of
its body, and usually hangs head downward at the surface of the water,
with the tip of the breathing tube in contact with the air. The food
consists largely of minute organisms collected by two vibrating tufts
of hair about the mouth. After a week or so of this wriggling life, the
larva is transformed into another stage called the pupa, which has a
larger head and thorax, and rides differently in the water because the
breathing tubes have shifted to the upper part of the body. In five or
six days more the skin of the pupa splits open and the adult mosquito
slowly emerges. It usually rests quietly on the floating pupa-skin for
a few moments, and then, as soon as its wings are sufficiently dried,
flies away in search of food and mates.

The male _Culex_ is much handsomer than the female, being provided
with large plume-like feelers or antennae, by which he may be easily
recognized. Another important sex-difference is that the _male doesn’t
bite_, but lives by sucking the nectar of flowers, like a bee. The
female of the species is deadlier than the male, even among mosquitoes,
and it is the female that does the blood-sucking. The mosquito’s beak
consists of several sharp lances inside a sheath, the whole apparatus
admirably adapted to pierce the human skin and transfer human blood to
the stomach of the mosquito. Incidentally some poisonous substance,
probably a salivary secretion, flows into the wound and produces more
or less inflammation and swelling. The _Culex_ or house mosquito, so
far as is known, does not transmit any disease to human beings--it is
detested only because of the pain which follows its bites, and its
intolerable buzzing.

The malarial mosquito (_Anopheles quadrimaculatus_) deposits its eggs
singly on the surface of the water, never in rafts like those of the
house mosquito. The eggs are very seldom found in barrels or tubs about
houses--the _Anopheles_ prefers ditches, or creeks, or the shallows of
slowly flowing rivers. The malarial larvae do not hang head downward at
the surface as the _Culex_ wigglers do, but lie flat just beneath the
surface film, and may be identified by this characteristic horizontal
position. The _Anopheles_ pupa does not differ greatly in appearance
from that of the house mosquito. The adult is somewhat larger than
_Culex_, and the wings are gray-spotted instead of clear. Another
important difference is this: _Culex_ alights and rests with its body
parallel to the surface which supports it, while _Anopheles_ rests with
its body at an angle--head down, tail up. Herrick says that he has seen
them “clinging to the ceiling of a horse stall by their four front
legs, with their bodies hanging almost straight downward.”

It has been known for a long time that malaria, otherwise known as
ague, or chills-and-fever, was connected in some way with stagnant
water. It was obvious enough to everybody that the disease was most
prevalent in low, swampy regions, and most people regarded it as a
result of poisonous gases which somehow arose from the surface of the
waters. The word _malaria_ means _bad air_. It was later discovered
that the real cause of the disease is a microscopic bit of jelly-like
protoplasm--a protozoan parasite which lives in the red cells of the
blood. Brues tells us that “the protozoan blood parasites which cause
malaria were first demonstrated many years ago, in 1880, by a French
surgeon, Laveran, who discovered them in the blood of persons suffering
from malaria. Five years later an Italian, Golgi, distinguished
three kinds, each associated with one of the more familiar types of
malaria. They were found to go through a regular life cycle in the red
blood corpuscles and, from analogy with other known protozoa, it was
suspected that in addition to their non-sexual generations in the human
blood there must be a sexual development in some cold-blooded animal.
Manson was led to suspect that some insect might be the secondary
host and, working on this hypothesis, Ross in India first found the
malarial parasites in a certain kind of mosquito in 1898. He had
worked for nearly three years with a common mosquito belonging to the
genus _Culex_ without result, but finally in a mosquito of the genus
_Anopheles_ was able to trace the development of the parasite. His
epoch-making discovery has since been amply confirmed and extended by
experimental proof until we now know that the various types of malarial
blood parasites complete their life cycles in anopheline mosquitoes,
the latter acting as the sole carriers of the disease.”

Malaria, then, is acquired in one way only, and that is through the
bite of the malarial mosquito. A mosquito sucks a little blood from a
malarial patient, this blood containing some of the protozoan germs
which are the immediate cause of the disease. In the stomach of the
mosquito the parasites reproduce sexually, penetrate the stomach
walls, and proceed finally to the salivary glands, from which position
they are injected into the blood of the next victim of the mosquito’s
blood-lust. The parasites reproduce asexually in the man’s red blood
corpuscles, and then burst out by millions into the liquid part of the
blood. This happens simultaneously in all parts of the body, and the
patient is shaken by the chills characteristic of the disease. Some
varieties of the germs reproduce every two days, producing what is
known as tertian fever; other types form spores every three days, and
the resulting disturbance is known as quartan fever. After a while male
and female germs appear in the patient’s blood plasma, but these never
develop unless the sufferer is bitten by another mosquito. When this
occurs, the sexual germs pass into the mosquito’s stomach, reproduce
sexually, and are distributed as described above. Another man bitten,
more non-sexual reproduction, more chills and fever, and so on _ad
infinitum_.

A healthy person may, of course, be bitten by _Anopheles_ and have
a great many malarial germs in his body without developing malarial
fever, as they sometimes lie dormant in the blood without reproducing
at all. Ross has estimated that “something like a quarter of a billion
of them must be present to produce fever.” The more infected mosquitoes
that bite one, the larger the number of germs that will be introduced,
and the more severe the disease. The essential result of all the
investigations is concisely stated by Herrick: “Malaria is caused by a
minute animal parasite that lives within the red blood corpuscles of
human beings. The parasite destroys millions of the red blood cells
that are so necessary to life, and, in addition, secretes certain
poisonous substances known as toxins, which lodge in various parts of
the body.... Since this parasite lives only in man and the mosquito,
it can get from one person to another only through the agency of these
insects. In other words, a person once free from the malarial parasite
will remain free just so long as the bites of certain species of
mosquitoes can be avoided.” One acquires malaria in one way only, and
that is by being bitten by _Anopheles_ mosquitoes.

[Illustration:

  Fig. II. Malaria and its Carrier. A, the malarial mosquito,
  _Anopheles quadrimaculatus_. B, chart showing the seasonal prevalence
  of malaria in the United States.
]

The tiger mosquito (_Aedes calopus_) is not native to the United
States, but has been introduced from the tropics. Today, however, it
is widely distributed in the Southern States, and has been found as
far north as New York. The eggs are laid singly or in small groups in
stagnant water, and hatch in from twelve hours to three or four days.
The larval life lasts about nine days, and the larvae are much more
active than the other mosquito wigglers. The tiger mosquito is not
often found in the country, but always near human dwellings, and it
prefers to deposit its eggs about houses, in vessels containing only a
little water--tubs, cisterns, rain barrels, old tin cans and the like.
The pupa state lasts only about two days, and the whole development
from egg to adult is sometimes passed in less than a fortnight. The
adult is considerably smaller than the other mosquitoes described here,
and is conspicuous for its white banded legs, and the prominent white
stripes on the thorax.

In 1881 a man named Carlos Finlay claimed that yellow fever was
transmitted by mosquitoes, but nobody paid any serious attention
to this novel theory, as everybody thought yellow fever was highly
contagious--carried about in the clothing like smallpox. In 1900 a
commission of United States army officers--Drs. Reed, Carroll, Lazear
and Agramonte--went to Cuba to make an experimental study of the
situation there. The procedure and results are concisely summarized by
Herrick:

“In a field near Quemado, Cuba, this commission of surgeons erected
a small wooden building tightly ceiled and with the windows and doors
closely screened so that no mosquitoes could enter. In this house,
during a total of sixty-three days, seven non-immune men were kept.
These men slept in beds furnished with the unwashed pillow-slips,
sheets, and blankets that had previously been used on the beds of
genuine yellow fever patients in Havana and elsewhere. This bedding was
actually stained with the excretions of the fever patients. Neither
during that time nor subsequently did one of these seven men develop
a case of yellow fever. This indicated to the surgeons, beyond much
question, that yellow fever is not carried in clothing, as had always
been held.

“Another house was built in this same field and divided into two
rooms by means of a wire screen extending from floor to ceiling. The
doors and windows of each room were closely screened with fine wire
netting so that no mosquitoes could enter. All bedding and material
carried into the rooms were disinfected by steam, which precluded any
possibility of the yellow fever germ being present in the bedding or
clothing.

“In one of the rooms, mosquitoes of a certain kind that had previously
bitten patients sick with yellow fever were placed. In the other room
none were allowed. Non-immune men were placed in both rooms. Of those
in the room containing no mosquitoes, not one had yellow fever. Of
those in the other room that were bitten by the infected mosquitoes,
six out of seven developed cases of genuine yellow fever. This
indicated beyond much question that mosquitoes were transmitters of
this disease.

“These experiments have been extended and duplicated many times with
the same results, so that we are justified in believing that a certain
mosquito known as _Aedes calopus_ is the sole and only agent in the
transmission of yellow fever.”

Dr. Lazear died from fever during the course of the experiments--a true
martyr of medical science--and Dr. Carroll came very near losing his
life also, following the bite of an experimentally infected mosquito.
Among other things, it was discovered that a mosquito may bite a
person suffering from yellow fever without becoming infected, unless
the bite occurs during the first three or four days of illness--later
than this the poison is not present in the blood. Another interesting
fact is that the _Aedes_ cannot infect anyone until at least twelve
days after it has received the virus from a sufferer, but after this
period it remains infected for a long time, and may give the disease to
a large number of people.

The actual cause of yellow fever is as yet undiscovered. As Herrick
says, “it is either too small to be seen with any lens now made or
it inhabits some organs of the body not suspected, or its habits are
entirely different from any other parasite with which we are familiar.
In any case the germ has eluded all efforts to locate it and scientists
are still ignorant regarding its real nature, habits, and appearance.”
It has been supposed that the yellow fever organism is similar to the
protozoan which produces malaria, but we do not know. Very little of
importance has been learned about the disease or the mosquito since
the Cuba commission in 1900, but wonderful progress has been made in
the application of such information as we have. By 1902 Havana was
entirely free from the yellow fever, and Rio de Janeiro, which had been
a fever-hell for many years, eliminated the disease entirely after a
six-year fight with the mosquitoes. In the Panama Canal Zone an army
surgeon named Gorgas was very successful in combating both yellow
fever and malaria. Although the United States has never suffered as
the tropical countries have, there have been numerous epidemics, the
last of which broke out in New Orleans in 1905. Vigorous anti-mosquito
campaigns were waged and the plague stamped out in a short time. The
tiger mosquito is still common all over the South, but there are no
yellow fever patients for them to bite. When a case does appear--some
sailor from the tropics, usually--he is seized by the Public Health
Service people and placed where no mosquito can get at him, and thus
it has not been necessary to wage a general exterminative war on the
yellow fever mosquito.

When the situation gets out of hand vigorous measures for the temporary
and local eradication of the insect are of course necessary. As Brues
says: “The success of this campaign has undoubtedly sounded the death
knell of the yellow fever epidemic and panic in the United States, for
New Orleans has amply demonstrated what may be accomplished in the
control of an epidemic by an efficient group of workers backed by a
sympathetic public and supplied with reasonable funds. Even in parts
of the tropics where it persists throughout the year, it is being
rapidly and permanently eliminated. Indeed, it bids fair to be the
first disease actually to become extinct as a direct result of human
discovery and applied science.”

There is, so far as is known, no satisfactory method of destroying
mosquitoes in the adult state, so that in the war against this pest we
must direct our efforts against the eggs and young. Herrick tells us
that “the methods taken to destroy mosquitoes fall into three distinct
classes; namely, the draining of bodies of water liable to contain eggs
and wrigglers, the application of oil to bodies of water that cannot
be drained and the introduction of fish into pools that cannot be
drained or oiled.”

Probably the best way to rid one’s immediate vicinity of mosquitoes
is to drain all marshes, pools and open receptacles. The drying up of
a few acres of swamp land may cause a marked fall in the death-rate
of an entire neighborhood, particularly in regions where malaria is
prevalent. The exposure of open tanks, reservoirs and barrels in which
stagnant water stands is no less than criminal in some parts of the
South.

Very often, for economic reasons, it is not practical to drain a
swamp or to eliminate open sewage ditches. In such cases we may take
advantage of the fact that the larvae of mosquitoes do not breathe by
gills, but are forced to come to the top for air. If ordinary kerosene
oil is sprayed upon the surface of the water, it spreads to form a
thin film which the larva cannot penetrate with their breathing tubes,
and so are drowned. The kerosene also destroys the floating eggs, and
kills the female mosquitoes as fast as they attempt to deposit. Crude
petroleum has been used instead of kerosene, but it does not spread as
well, and is very little cheaper. According to Herrick, one ounce of
kerosene is enough for fifteen square feet of water surface, and half a
teacupful is plenty for a barrel of water. The most convenient way to
apply the oil to small pools and ditches is by means of a five-gallon
tank carried knapsack fashion, with a short hose and nozzle. As the
entire development of the mosquito from egg to laying female seldom
requires more than eighteen or twenty days, it is best to use the oil
once every two weeks during the mosquito season. It would seem that
an easier way to get kerosene into the sewage ditches would be simply
to pour it into the water closet, and this has proven successful in
cases where there is little or no current; on the whole, however, the
surface-spraying system is best.

Ornamental ponds and pools cannot be drained or sprayed with oil, and
the same may be said of artificial ponds where domestic animals drink.
In these cases the mosquito pest may be mitigated by introducing fish
or other small creatures which feed upon the larvae. In Japan, and
more recently in other countries, the goldfish has been found very
satisfactory for this purpose. Various species of shiners, sunfish and
top minnows have also been used. W. P. Seal, who has given a great
deal of attention to this phase of the mosquito problem, states his
results as follows: “The writer has come to the conclusion, after
many experiments in small ponds, that a combination of the goldfish,
which is ornamental and useful in the open water, the roach or shiner,
which is a very active species, two small species of sunfish, which
live among plants, and the top minnow would probably prove to be more
effective in preventing mosquitoes breeding than any other fishes.”

Vernon Kellogg, Tillyard and others have studied the habits of
dragonflies in this connection, and the latter particularly has
emphasized their value as destroyers of mosquito larvae. He saw
a single dragonfly larva eat sixty wrigglers in ten minutes, and
captured an adult dragonfly which had over a hundred mosquitoes in
its mouth--so many that the mouth could not be closed. “I believe that
a successful checking of the mosquito pest in the ornamental waters
of parks and gardens could be readily obtained by the introduction of
dragonflies whose larvae, as well as the adults, would prey upon the
nuisance.”

The use of wire screens to exclude flies and mosquitoes from dwellings
is now well-nigh universal in most parts of the United States, although
there are still many rural communities in the South in which it
appears to be quite unknown. To keep out ordinary mosquitoes the wire
should have at least fourteen meshes to the inch, and the yellow fever
mosquito will pass through any screen which has less than eighteen
meshes. It is practically impossible to fit screens and frames well
enough to exclude all mosquitoes, but it is certainly better to contend
with a few stray mosquitoes in a screened house than to do battle with
the myriads of pests which swarm into an unscreened domicile. The
fewer the bites one receives, the fewer the chances of being bitten by
an infected mosquito; the fewer infected bites, the less severe the
resulting illness will be.

In many Southern cities the use of bed nets of bobbinet or mosquito bar
has now become quite general. There is usually a kind of wire frame
over the bed, and the net is sometimes tucked under the mattress all
round, while in other cases it is long enough to reach the floor on all
sides. Many travelers who must visit small towns, where the hotel bed
nets are lacking or unsatisfactory, carry their own nets, and set them
up every night to suit their fancy. Dr. Ross says: “Perhaps our first
and best defense against malaria lies in the habitual and scrupulous
use of mosquito nets at night.... The first care of the resident in the
tropics, of the traveler, the sportsman, the soldier, the miner, the
clerk, should be for his mosquito net. Wherever he lives, wherever he
goes, he should see that his mosquito net is with him, that it is in
good order, and that it is properly arranged at bedtime.”

There are several chemical substances used in driving mosquitoes out
of houses. One may rid a room of mosquitoes by the fumes of burning
sulphur, but the gas often discolors articles painted with lead
paint, and tarnishes gilt furniture and brass bedsteads. A vegetable
powder sold as pyrethrum, buhach, or Persian insect powder is made of
chrysanthemums, and is fairly effective when scattered about or blown
into cracks and crevices. It may also be burned as a smudge, but the
fumes are not as effective as those of sulphur. Many of the mosquitoes
fall to the floor in a stupor, and must be gathered up and burned, as
otherwise they will revive in an hour or so. Another fumigant much in
favor in New Orleans is a mixture of carbolic acid and gum camphor,
and is known as culicide. A heavy reddish liquid, it is evaporated by
heating slightly over a gas burner or alcohol lamp. The mixture is
inflammable but not explosive, and the fumes are not dangerous to human
life.

Hunters and campers often smear their hands and faces with various
substances supposed to discourage mosquitoes, oil of citronella being
one of the most popular. Camphor, cedar oil, kerosene and mixtures of
these substances in various proportions are also used, besides several
patented smudges and ointments. I have tried several of these, but
found them unsatisfactory. Tobacco-smoke helps a little sometimes, and
is at least free from the unpleasant and even nauseating odors of the
other mosquito repellants.




LIFE AMONG THE BEDBUGS


The bedbug (_Cimex lectularius_) has been known to man for a long
time, and has probably, as Herrick remarks, “been man’s bedfellow as
long as man has slept in beds,” if not longer. The ancient Romans
were intimately acquainted with this insect, and Pliny recommends a
mixture of macerated bedbugs in water as a cure for snake bites. It
is common in all parts of the civilized world, and doubtless came to
America with our sturdy fathers--even the Mayflower probably carried
a full cargo of bedbugs. Like its relative the stink bug, _Cimex_ has
a peculiar odor which is quite noticeable in small rooms where the
insects are unusually abundant. The full-grown bedbug is a flat-bodied,
mahogany-colored creature, with mouthparts admirably adapted to
blood-sucking. It lives in beds, window casings, cracks in floors,
etc., or in any article of furniture which affords a crevice large
enough to contain it. What we know about the insect’s life history
is mainly due to Marlatt, who did his work in 1896, and to Girault,
who carried out some further investigations some ten years later. The
eggs are very small, white and oval, and are, according to Herrick,
“laid in batches of varying numbers in cracks and crevices in the
bedsteads or other places where the bedbugs happen to be. The number of
eggs deposited by a single female is not known. Southall, Riley, and
others have made the common statement, probably not based on actual
observation, that each female lays about four batches of fifty each
during the season. Girault actually succeeded in obtaining 111 eggs
from one well-fed female between June 17 and August 19. How many she
had deposited previous to confinement for the experiment he was, of
course, unable to say. Girault’s experience with this one bug indicates
that the females may continue to lay eggs at different periods
throughout the breeding season and that there is only one generation a
year.”

The eggs hatch in about ten days, and the young bugs appear very much
like their parents--bedbugs do not pass through larva and pupa stages
like flies and mosquitoes. Bedbugs probably eat nothing but blood,
and a young individual, if properly supplied with this food, reaches
maturity in about six weeks, shedding their skins at least five times
during the period of growth. It is said that the bug feeds but once
between moults; if this is true the occupant of the bed must suffer
at least five bites in order to rear a single bedbug to maturity.
Bugs very much like _Cimex_ are found upon swallows, chimney swifts,
pigeons and martins, and many people believe that genuine bedbugs
are distributed by these birds, but this is probably not the case.
True bedbugs have never been found upon them, and although the “bird
bedbugs” are occasionally found in houses they do not seem to enter
beds and bite human beings. Bedbugs have, however, been found in
chicken houses, where they presumably bite chickens, so that there
is nothing inherently unreasonable in the view that they may be
distributed by birds.

The bedbug almost invariably lies hidden during the day, or as long as
there is a bright light in the room. As soon as the light is turned off
they sally forth to attack an exposed portion of the sleeper’s body.
It seems that they are particularly likely to be secreted about the
pillow, and as soon as the room is dark hit upon the neck as the most
desirable and accessible part of the victim’s anatomy. Only one who has
had personal experience in these matters can appreciate the vigor of
the onslaught, and the astounding rapidity with which the enemy whisks
out of sight the moment the light is flashed on. The bedbug’s bite is
not poisonous, and the pain is probably due only to the puncture, but
this is sufficient to cause considerable irritation and swelling.

Elie Metschnikoff, the author of that fascinating book entitled _The
Nature of Man_, was the first to call attention to the bedbug’s
possibilities as a carrier of disease germs. Bedbugs have been made,
under laboratory conditions, to transmit typhoid and other fevers,
and a tropical disease called _kala-azar_, but it has never been
demonstrated that the bugs actually do, under ordinary conditions,
play any part in the diffusion of these diseases. “Many writers and
experimenters,” writes Herrick, “have labored hard to prove this insect
guilty of graver offenses than that of simply stealing blood from human
hosts. The most they have been able to do so far, however, is to show
that in one case, at least, the bite of the bedbug formed a starting
point for a case of bubonic plague. As a matter of fact, this is really
a stronger indictment against the bedbug than, at first thought, might
appear. The sores resulting from bedbug bites offer ideal points of
entrance for disease-producing organisms and are a source of real
danger. Actual and definite proof that the bedbug transmits disease
is very difficult to obtain, but suspicion points strongly in that
direction.... It is extremely desirable to avoid the bites of this
insect if possible, especially in hotels where beds are occupied by so
many different people; but this is very hard to do, in fact, almost
impossible if one travels much.”

Luckily the bedbug is wingless, and therefore much easier to control
than winged pests like the fly and mosquito. If _Cimex_ were able to
fly there would be no keeping him out, as the newly hatched young could
pass through practically any sort of screen. The use of metal bedsteads
puts the bugs at a disadvantage because they afford fewer cracks and
crevices than those built of wood. Boiling water poured into the
crevices kills both eggs and bugs, but a more convenient method is to
use an oil can or squirt-gun filled with gasoline, kerosene, turpentine
or alcohol. The easiest way to rid a room completely of insects is to
fumigate with hydrocyanic acid gas, made by pouring dilute sulphuric
acid on potassium cyanide. This gas kills every living creature in
the room, but it is dangerous in the hands of careless or thoughtless
persons.




LICE, CRABS AND COOTIES


Lice have been associated with human beings as far back as our
historical records go, and are mentioned in the writings of Aristotle,
Herodotus and other ancient writers. Ordinarily cleanly and
well-dressed people today would be horrified to find lice about their
persons, as they are now confined to soldiers and others who do not
keep their bodies and clothing clean, but a few hundred years ago,
when everybody was dirty, they thought nothing of it. Samuel Pepys, an
English diarist of the seventeenth century, made the following laconic
entry in 1668: “Up betimes, finding our beds good, but lousy, which did
make us merry,” and there are many other matter-of-fact references to
these vermin in the literature of the period.

There are three common species, but they are all essentially alike in
structure, being small, wingless and provided with piercing and sucking
mouthparts. Schiödte describes the behavior of a louse on the back of
his hand: “Scarcely does the abominable little monster feel the heat
of the skin before it lays aside its former disheartened attitude,
and begins to feel at ease, its antennae oscillate for joy, and it
stretches all six legs complacently out from the body. But though the
pleasure and surprise at the sudden transportation into congenial
surroundings for the first moment eclipse everything else, hunger
soon asserts its claim, sharpened as it is by the long fast, which
has rendered its stomach and intestines quite transparent. The animal
raises itself on its legs, walks a few steps, seeking and feeling its
way with its antennae, while we follow it with a magnifier. Presently
it stops, draws in its legs a little, arches its back, bends the head
down toward the skin at an oblique angle, while it probes a small dark
and narrow organ repeatedly forward, and draws it back through the fore
end of the head; at last it stands still, with the point of the head
firmly abutted against the skin.”

All three of our species are blood-suckers, and are strictly human
parasites, being found only occasionally upon the bodies of animals
other than man. It is said, however, that they are sometimes carried
about by flies.

The head louse (_Pediculus capitis_) is usually found among the hairs
on the head, occurring elsewhere only occasionally. The female is about
one-twelfth of an inch long, while the male is only about one-half
as large; both sexes are grayish in color, but it is said that this
varies with the color of the host. Herrick quotes Murray to the effect
that lice on West Africans are black, those on Chinese yellow, those
on Hindoos smoky brown, and so on. The eggs are fastened to the hairs
by a gelatinous secretion, and the female has been known to deposit at
least fifty eggs in the course of a week. The period of incubation is
usually five or six days, and the young louse reaches maturity in a
fortnight. The movements and bites of these creatures are irritating in
the extreme, and the sufferer is sure to scratch so incessantly that
the scalp is always in an inflamed condition. The head louse is not
known, however, to carry any disease-producing organism.

The best way to get rid of the head louse, according to a circular
memorandum prepared under the direction of Surgeon General M. W.
Ireland, of the United States army, is to “clip the hair of the head
with a hair clipper and wash with a mixture of equal parts of kerosene
and vinegar. This should be followed in a few hours with a bath of soap
and hot water.... The hair should be caught in bags and burned. In
order to reduce the liability to infestation, the hair should be kept
close at all times.” Sulphur ointment may be used without sacrificing
the hair, but it is not so effective as the kerosene mixture.

The body louse (_Pediculus corporis_), known also as the gray-back and
the cootie, is somewhat larger than the head louse, and is usually
of a dirty white color. These creatures dwell in the seams and folds
of clothing, and are therefore known to some writers as _Pediculus
vestimenti_. They are difficult to find and to dislodge, as they do
not often cling long to the skin, but retire to their hiding places
in the clothing as soon as their blood-sucking is done. The eggs are
laid in the seams and wrinkles of the clothing, that made of wool being
given the preference. When one has no opportunity to change or wash
one’s clothes the pests become so abundant as to be quite unbearable.
Soldiers, inmates of prison camps and such people are particularly
liable to be abundantly supplied with body lice; they may pass from one
person to another when the bodies are brought into actual contact, or
one may become infested by sleeping in louse-ridden beds.

The Dutch scientist Leeuwenhoek, more than two hundred years ago,
carried out some experiments which are pleasantly reviewed by Herrick:
“Leeuwenhoek ... made an attempt to find out something definite about
the life history and rate of development of the body louse. He did not
believe the popular saying that a louse could become a grandfather in
twenty-four hours. At first he thought of hiring some person to act as
host for the lice. Later he changed his mind, overcame his own natural
aversion to these pests, and enclosed two large females within a fine
black stocking, the top of which he fastened tightly around his leg
above the knee. Here he allowed the two lice to live for six days and
obtain their sustenance from his leg. At the end of this period he
removed the stocking and found fifty eggs around one of the females
and forty eggs in another part of the stocking, evidently laid by the
second female, which, however, had escaped. He wore the stocking for
yet ten days, when on examination he found twenty-five young lice which
so disgusted him and dampened his enthusiasm that he threw the whole
thing into the street. Since Leeuwenhoek’s time the author is not aware
that any scientist has ever tried in the same way to study the life
history of these lice.”

[Illustration:

  Fig. III. Three kinds of Lice. A, the head louse, _Pediculus
  capitis_; B, the body louse, gray-back, or cootie (_Pediculus
  corporis_); C. the crab or crab louse, _Pediculus pubis_.
]

_Pediculus corporis_ is the only species of louse known to act as
a carrier of disease. Its connection with typhus and trench fever
is admirably described by Brues: “Typhus fever has been well-known
for many years and regarded as a disease characteristic of filthy
surroundings. During our own civil war it claimed many victims among
the inmates of army prisons, and has been endemic though not very
prevalent in many parts of the world in times of peace. Through the
researches of Ricketts and others we now know that typhus is spread
by the body louse and its epidemiology is at once made clear. When
it broke out in Serbia in severe epidemic form, a knowledge of the
method of its transmission made control possible, even under extremely
difficult and unfavorable circumstances.

“Trench fever has attracted notice in the European war zones, to which
it appears to be restricted so far as present knowledge extends.
That it is a new disease is, however, without question an utterly
unwarranted assumption, for it has undoubtedly been brought to Europe
from some little-known quarter of the globe, unless it may have
previously existed in Europe which does not appear probable. During the
latter part of the war it was successively recognized as a distinct
disease, suspected of association with the louse, and soon proved
actually to be louse-borne. We now know that the disease is due to a
living microorganism, probably of such small size that it cannot be
recognized under the microscope. This virus is obtained by the lice
with their meal of blood taken from an infected person. At least five
days must elapse before the louse becomes capable of transmitting the
disease, indicating that the organism must undergo a development of
definite periodicity in the insect. If it is transferred to another
person its bite is not or only rarely infectious, but its excrement
contains the virus and if scratched into the skin, trench fever
develops. Typhus fever is a very dangerous disease with a quite high
death-rate, but trench fever is non-fatal and its importance in the war
zones has been due to its great prevalence and the fact that persons
afflicted with it are often incapacitated for long periods.”

As body lice do not cling to the body except when actually biting, it
is a comparatively easy matter to get rid of them. One has only to
bathe while his clothing is being steamed or soaked in gasoline. The
United States Army set up delousing plants which were nothing but steam
sterilizes on a large scale, and they proved very satisfactory.

The crab louse (_Pediculus pubis_) is short and stout-legged, whitish
on the back, with a distinct reddish cast about the legs. It usually
inhabits the hairy areas about the sex organs, clinging close against
the skin, but is not uncommon in the armpits, and has been found upon
practically every part of the body except the head. The eggs are
attached to the hairs, like those of the head louse; they hatch in less
than a week, and the young crab reproduces at an early age. This little
pest multiplies much more rapidly than either of the other species,
and is besides more easily transmitted from one person to another.
Although the usual means of communication is direct bodily contact,
as in the sexual embrace, it may be transmitted otherwise. The United
States Army memorandum informs us that “this insect is transmitted
mainly by contact in lodging houses, houses of prostitution, bathtubs,
and perhaps occasionally from toilet seats.... Although the crab louse
has not been shown to be a transmitter of disease, still it is very
annoying, and its presence is a reflection on a man’s cleanliness....
The treatment for this condition is to shave the hair of the pubic
region, axillae, chest and legs. This should be followed by an
application of the kerosene and vinegar mixture, followed by a bath
with soap and warm water.” The usual treatment among civilians is the
application of a little mercurial or blue ointment.




OUR FRIEND THE COCKROACH


There are four common species of cockroaches in the United States,
only one of which is native to this country. The American cockroach
(_Periplaneta americana_) is the large winged species so common in
the Middle and Southwestern states. They devour nearly any sort of
food, and have been known to eat the corks out of bottles, while no
less an authority than Vernon Kellogg says that some sailors in San
Francisco sleep with gloves on to keep roaches from gnawing off their
finger-nails. The German roach (_Ectobia germanica_), known also as
the croton-bug, is common in the eastern part of the United States. It
is the smallest species we have, being seldom more than five-eighths of
an inch in length. For some reason or other these roaches are usually
found about water pipes, and are not common in small communities which
have no water systems. The Oriental cockroach (_Blatta orientalis_) is
common also in England, and came to America with the early colonists,
although it is supposed to have originated in Asia. It is larger and
stouter than the croton-bug, and is dark brown or black in color. The
males have short wings, but the females are wingless or practically so.
The Australian roach (_Periplaneta australasiae_) is very much like the
American variety, except for some yellow spots and bands on the thorax
and shoulders. It is less common than any of the others, being found
chiefly in the South.

The life histories of all four species are essentially identical. The
eggs are not deposited singly, but in clusters enclosed in a horny
capsule, the end of which may often be seen projecting from the abdomen
of the female. The young roaches appear very much like their parents,
but do not reach maturity for several months. The flat bodies of
these insects allow them to crawl into small cracks in woodwork and
furniture, and they usually remain hidden during the day, coming out
at night to seek what they may devour. They are really scavengers,
and under certain conditions may be useful in this capacity, but
their omnivorous habits and the intolerable stench of their bodies and
excreta make them the bane of the careful housewife.

“Cockroaches,” observes the indefatigable Herrick, “are among the
most difficult to control of the household pests. They are difficult
to reach because they are especially adapted with their thin, flat
bodies for hiding away in inaccessible cracks, crevices and crannies.
Moreover, they are wary and shy of all baits and traps. The croton-bug
is the most difficult of all to get rid of. It seems to display more
caution in avoiding traps and baits than most of the others, and as it
increases faster, it becomes much more abundant.” Several traps have
been devised and used with some measure of success, and roaches may
often be killed by feeding them plaster of paris mixed with flour, or
by exposing deep jars of stale beer, a delicacy in which they hasten to
drown themselves. Herrick quotes Washburn to the effect that powdered
borax scattered about the kitchen will clear a house of cockroaches.
The best way to completely rid a house of these pests is to fumigate
with hydrocyanic acid gas, made by pouring dilute sulphuric acid on
potassium cyanide. But this method, as I have pointed out elsewhere in
this booklet, is too dangerous for awkward or absent-minded people to
experiment with.




CHIGGERS, TICKS AND FLEAS


The chigger (_Leptus irritans_) is not a true insect, but the immature
form of a mite, related to the spiders. The eggs are laid upon the
ground in the Spring, and when the young chigger hatches it climbs up
a blade of grass and awaits the coming of some animal to which it can
attach itself. At this time it is a very small red creature, barely
large enough to be seen with the unaided eye. It clings to any moving
object which presents itself--usually some passing insect, but quite
frequently a bird or one of the higher animals. After having fed for a
time upon the blood and juices of its mount, the chigger drops off and
changes into the adult mite, which is not parasitic, but feeds largely
upon plant lice.

Man’s contact with the chigger usually comes while walking through
the grass and weeds to which they cling. They cannot bear direct
sunlight, and are not common upon closely clipped lawns unless these
are very densely shaded. The tiny tormenter passes through the finest
of clothing--silk hosiery and underwear are no protection--and attaches
itself to the skin, sucking blood and setting up a severe irritation by
means of some poisonous secretion. The resultant itching is so intense
that one cannot resist the temptation to scratch the affected parts,
which may become infected and cause blood poisoning, and, according to
Hamilton, erysipelas. Although the chigger is not known to disseminate
any particular disease, it is an intolerable nuisance, and has
spoiled many a vacation in the South.

[Illustration:

  Fig. IV. Some Common Cockroaches. A, Oriental cockroach (_Blatta
  orientalis_), female. B, same, male. C, American cockroach
  (_Periplaneta americana_). D, Australian cockroach (_Periplaneta
  australasiae_).
]

Some persons avoid chiggers by wearing high boots, others, sprinkle
sulphur in their stockings, while still others use various patent
preparations both before and after the act. My own experience is
that if, directly after coming in from the field, one changes to
chigger-free clothing and rubs whiskey or gasoline upon the parts
likely to be affected, the number of bites will be greatly decreased.
Dr. Vernon C. Allison treats the inflamed areas with potassium
permanganate, but I have had no satisfaction in the use of this remedy.

The fever tick (_Dermacentor venustus_) is the carrier of the disease
known as Rocky Mountain spotted fever. This disease is now restricted
to the Northwestern states, most of the cases occurring in Idaho and
Montana. The life history of the tick is much like that of the chigger.
Hatched from eggs on the ground, the young seed tick mounts a tall
blade of grass or a weed and fastens upon the first animal which comes
along. Forcing the hooked sucking beak into the flesh of the host, it
sucks blood until it is full grown. Then it falls to the ground and
reproduces, dying soon after this duty is done.

Brues describes the fever tick situation as follows: “The _Dermacentor_
ticks occur abundantly on various small wild mammals in the younger
stages and as adults on domesticated animals, such as cattle, and from
these become transferred to man. It has been experimentally shown
that certain rodents are susceptible to the disease, and a tick thus
infected in the nymphal stage can retain the disease organism until
it becomes adult. It may then reach its human host through the medium
of domesticated animals such as cattle. It appears that this is the
ordinary way in which human cases have their origin, i. e., through the
bite of adult ticks, although the newly hatched _seed ticks_ derived
from eggs laid by infected mother ticks are known to contain the
organism also.

“Although Rocky Mountain fever is of minor importance at the present,
it is feared that it may increase its range at any time, since other
ticks of wider distribution are apparently capable of acting as
carriers. Whether this may happen is by no means certain, however,
and the vigorous measures already undertaken to reduce the abundance
of ticks on domesticated animals will undoubtedly bear fruit in the
gradual reduction of this locally much-dreaded disease.”

There are many other species of ticks in the United States, but their
life histories are all very similar. Several of them are believed to be
carriers for various diseases of cattle, but _Dermacentor venustus_ is
the only one known to distribute disease among human beings. The common
Southern cattle-tick (_Margaropus annulatus_) is the sole carrier of
the cattle disease known as Texas fever, which has caused a tremendous
pecuniary loss in several of the Gulf States. The protozoan parasite
which actually causes the trouble is called _Babesia bigemina_, and
Brues refers to the tick’s “becoming infected during its period of
engorgement when feeding on the blood of a diseased animal and then
transmitting the _Babesia_ through its eggs to the young ticks of the
next generation. These may feed on healthy animals the next season,
conveying to them the parasites that have been handed down from the
mother tick.”

[Illustration:

  Fig. V. Chiggers and Ticks. A, young and adult chigger (_Leptus
  irritans_) redrawn from Herrick. B, Rocky Mountain spotted fever
  tick, (_Dermacentor venustus_), after Brues. Male at left, unengorged
  female at right.
]

Only two species of fleas are common in dwelling-houses in the United
States. One is the human flea (_Pulex irritans_) and the other is
_Ctenocephalus canis_, found almost universally upon cats and dogs.
One must not suppose, however, that human fleas bite humans only, and
that _Ctenocephalus_ confines its attention to dogs and cats; the human
flea does not scruple on certain occasions of good omen to attack dogs,
cats, rats and mice, while the various other species of fleas bite man
also whenever the spirit moves them. The adult flea lives entirely
upon the blood of its host, obtained through the admirable piercing
and sucking mouthparts. The human flea, according to Herrick, is so
bloodthirsty that it sucks regularly more blood than it can hold, and
the surplus is seen squirting out of the anus while the creature is
sucking more in at the mouth.

The eggs are dropped almost anywhere, and the tiny white larvae develop
in cracks and crevices, feeding upon the organic matter in wood and
rubbish. The pupa is enclosed in a silken cocoon, and the adult may
appear in less than two weeks after the eggs are laid, although the
period is usually somewhat longer.

Until comparatively recent years the flea was looked upon only as
a nuisance, but it has now been discovered that some species act as
agents in spreading bubonic plague, one of the most terrible scourges
known to human history. It appears that the plague is primarily a
rat-disease, and affects the human animal only incidentally. Outbreaks
of plague among human beings are always preceded by an epidemic
among the rats of the same region. The part placed by fleas in the
matter is stated by Brues as follows: “The relation of the flea to
the transmission of plague is due to the fact that rats are regularly
infested by fleas that may become infected with the bacillus of plague,
if it be present in the blood of the host upon which they are feeding.
These bacilli remain in a viable condition for some time in the gut
of the flea and may be transferred to a human subject bitten by an
infected flea. Thus, when a rat dies of plague, its fleas leave it to
search for a new host; if they attach themselves to a rat, that animal
is liable to infection, or if they feed upon a human being, as they
frequently do, the disease may become transferred to man.... The plague
bacilli (_Bacillus pestis_) appear only in fleas that have bitten
infected persons or rats twelve to twenty-six hours previous to death,
for after this time the bacilli do not occur in the blood. The vitality
and virulence of the bacilli are preserved for nearly a week at least
and sometimes fully a month; and there is actually an increase in their
number during the first few days. Infection from these insects may then
occur through their bites, if they contain extremely virulent bacilli,
but probably occurs more commonly by the insects being crushed _in
situ_ after they have punctured the skin.”

From 300,000 to 400,000 cases of bubonic plague occur in India every
year, and nearly half of them terminate fatally. Comparatively few
cases have been reported from the United States in recent years, but
in various places, San Francisco for example, only the most vigorous
and persistent repressive warfare against rats and fleas have prevented
what might have been very serious outbreaks.




Transcriber’s Note:

- Text that was in italics is enclosed by underscores (_italics_).

- Illustrations were moved to the ends of the paragraphs in which
they originally appeared. Their original page numbers are in the list
of illustrations. The list of illustrations was not present in the
original text.

- Inconsistencies in hyphenation have been standardized.

- Minor punctuation errors have been changed without notice.

- Spelling was retained as in the original except for the following
changes:

  Page 2: “Our Friend the Cochroach” to “Our Friend the Cockroach”
  Page 3: “Europe. Picture Thomas Aquinus” to “Europe. Picture Thomas
  Aquinas”
  Page 8: “During the Spanish-American war” to “During the
  Spanish-American War”
  Page 13: “an epidemic which occured” to “an epidemic which occurred”
  Page 13: “contended that purulent opthalmia” to “contended that
  purulent ophthalmia”
  Page 14: “is practically no opthalmia” to “is practically no ophthalmia”
  Page 14: “spread of Egyptian opthalmia” to “spread of Egyptian
  ophthalmia”
  Page 16: “destroyed by the housekeper’s” to “destroyed by the
  housekeeper’s”
  Page 20: “walls and fences. in” to “walls and fences. In”
  Page 20: “and verandas, and is” to “and verandas, and it is”
  Page 21: “Lucian Iches of Sante” to “Lucian Iches of Santa”
  Page 22: “the province of Sante” to “the province of Santa”
  Page 23: “inclines to be irridescent” to “inclines to be iridescent”
  Page 25: “this habit of breding” to “this habit of breeding”
  Page 27: “a single one developes” to “a single one develops”
  Page 32: “The parasites reproduce sexually” to “The parasites
  reproduce asexually”
  According to other passages in the text, the parasite that causes
  malaria reproduces asexually in the human body and sexually in
  mosquitoes. This typo was corrected to make the text internally
  consistent.
  Page 35: “a field near Quemados” to “a field near Quemado”
  Page 37: “is that the Aedes” to “is that the _Aedes_”
  Page 42: “or Persian insect power” to “or Persian insect powder”
  Page 47: “writings of Aristotle, Heroditus” to “writings of
  Aristotle, Herodotus”
  Page 47: “ease, its antennae oscilate” to “ease, its antennae
  oscillate”
  Page 48: “antennae, while we followed” to “antennae, while we follow”
  Page 49: “is not known, howeve” to “is not known, however”
  Page 54: “application of the kerosense” to “application of the
  kerosene”
  Page 60: “cattle, but _Dermacentor venusta_” to “cattle, but
  _Dermacentor venustus_”
  Page 63: “years the flea looked” to “years the flea was looked”



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