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UNITED STATES DEPARTMENT OF Fa a

BULLETIN No. 248

Contribution from the Bureau of Entomology
L. O. HOWARD, Chief

Washington, D. C. Vv / Bre August 14, 1915

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Core

FLEAS, <<"

By

F. C. BISHOPP, Entomological Assistant, Southern
Field Crop Insect Investigations

CONTENTS

Introduction 3 The Jumping of Fleas and Other Means
Hosts of Fleas Sato Of Spread es. ita eee ai runany

Biting Habits Pair Ne eee 2 Fleas as Carriers of Disease

Life History ..... ee Mrepiital (is Fleas as Parasites of Man and Animals .
Length of Life of the Adult Natural Control

Breeding Places .. Artificial Control

Factors Influencing Flea Abundance . . Remedies for Bites

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WASHINGTON
GOVERNMENT PRINTING OFFICE
1915

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UNITED STATES DEPARTMENT OF AGRICULTURE —

BULLETIN No. 248 # gh

Contribution from the Bureau of Entomology
L. O. HOWARD, Chief.

Washington, D. C. v August 14, 1915

FLEAS.

By F. C. BISHOPP,
Entomological Assistant, Southern Field Crop Insect Investigations.

CONTENTS.

Page. : Page.
linnodtetion aaa a eae ete 1 | The jumping of fleas and other
TESTO) SS GSO ete aS ne I 2, MEANS Oh: Spreads Sera 10
BigMechapiterte: secre ero BRS 9 | Fleas as carriers of disease——_—_~_ ala

A f Fleas as parasites of man and ani-
Neri WN IS GO Te yore ee a ae INIA a 4
NY AT SEAR TREN SN NDR 16
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ISTRSSOONE (MENGES a te Sule vArtinictaliecomtrol-so soe eenn os 4493
Factors influencing flea abundance__ ore Remedies) tor bites=2_- =" == _. 31
INTRODUCTION.

v

Fleas have forced themselves on man’s attention for many cen-
turies. All are familiar with these elusive little pests, knowing well
their brownish color, peculiar flattened shape, apparent ability to
sense the approach of danger, and the proverbial ease with which
they escape. Their propensities for annoying man by inflicting bites
in rapidly changing situations and for persistently worrying dogs and
cats are well known.

However, it is not only in the role of annoyers of man or beast
that fleas assume importance, for within the last decade the world has
come to know fleas in their most important relationship to the welfare
of mankind—that of transmitters of disease, and particularly of the
dread disease known as plague. Aside from plague, which levies a
death toll well into the hundreds of thousands yearly, attention is
directed to fleas as important insects on account of their probable

NotTE.—The activities of fleas as carriers of bubonic plague’ and other diseases, as
parasites upon poultry, and as pests to man and other animals are presented in this
bulletin. Descriptions, life history, breeding places, hosts, and methods of eradication and
control are given.

92999°—Bull. 248—15—_1

2 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

connection with the disease of warm climates known as infantile
kala-azar. There is also reason to believe that fleas play some part
in transmitting leprosy. It has been found that the tapeworm of
the dog, which has been known to attack man, is dependent upon
some insect in which to develop one of its stages, and the dog flea
often serves in this capacity. Another interesting role which a
certain species of flea has been found to fill, though of no known
direct importance to man, is the transmission of a blood parasite of
the rat known scientifically as Trypanosoma lewisi. One kind of
flea which is becoming widely distributed in the Tropics has the
peculiar habit of burrowing into the flesh of man, especially around
the toes. This species causes severe sores and often permanent
crippling. In the United States, aside from their connection with
plague transmission, we are concerned most with insects of this group
as annoyers of man and animals. In the latter case the pests often
become so numerous as to cause more or less loss. This is particularly
true of the chicken flea, or “ sticktight,” which will be discussed in the
following pages.

Fleas, as is generally known, are true insects. They have been
thought by many entomologists to be closely related to the Diptera,
or two-winged flies, but now they are usually considered to constitute
a separate order of insects. Their peculiar shape, flattened from side
to side, and armature of spines and bristles are closely correlated with
their parasitic habits, enabling them to move rapidly between the
hairs or feathers of their hosts.

HOSTS OF FLEAS.

Fleas in the adult stage may be said to be parasitic exclusively on
warm-blooded animals. A single exception has been recorded—that
of one flea which was found attached to a land snake in Australia.

A great many species of birds and most mammals have been found
to be infested by these parasites. The group of animals of which the
- horse, ox, and sheep are representative are probably least subject to
attack. It is not the purpose to convey the idea that there are as
many kinds of fleas as there are birds and animals. In fact, the num-
ber of distinct species of fleas now known is probably not greatly in
excess of 400. In general, there are certain birds or animals, spoken
of as hosts, upon which these insects prefer to feed.

Some species of fleas appear to have much more restricted host re-
lationships than others; that is, they are found on comparatively
fewer animals. In cther instances fleas may not be found uncom-

1 Some knowledge of the structure of a few of our common kinds of fleas may be derived

from an examination of the illustrations in the following pages, which, with the exception
of figure 1, were drawn by Mr. Harry B. Bradford.

FLEAS. Sa

monly on certain hosts, but they are not at home on these and would
probably not live long or reproduce if made to feed on them. ex-
clusively. This class of hosts usually becomes infested by being
closely associated with the true host of the fleas, as, for instance, in
case of a rat entering a squirrel burrow or a carnivorous animal de-
vouring a flea-infested rodent and thus getting the insects upon its
body. Such hosts are usually spoken of as accidental or temporary.
While infestations of this kind are seldom of importance to the host
animal from the standpoint of direct injury, they may have a vital
influence by transmitting disease and may also have an important
bearing on control. As a result of this habit of fleas of clinging to,
or temporarily feeding on, hosts which are not necessarily congenial,
long lists of species of fleas accredited to a single kind of animal or
bird are often found. For instance, more than 20 species of fleas
have been taken on common wharf rats.

BITING HABITS.

The sensation produced by the biting of a flea is well known to
most persons. The annoyance, however, is partly produced by the
movements of the insect and by the mental unrest caused by the
knowledge that fleas are present beneath the clothing. The effect of
flea bites on man is discussed further on page 16. With very rare
- exceptions, adult fleas partake of no food other than the blood of
warm-blooded animals, and it appears that reproduction never takes
place until the fleas have partaken of such blood.

The mouth parts are well adapted to piercing the skins of their
hosts and sucking up the blood. The essential piercing organ con-
sists of three slender parts. A groove along the inner sides of two
of these, the mandibles, with the closely apphed third, forms a chan-
nel through which the salivary fluid is forced into the wound and
through which the blood is pumped into the body. An idea of the
structure of the mouth parts may be gained by referring to figure 1,
e and g.

Most species are easily disturbed when feeding, and this accounts,
in part at least, for the frequency with which a single flea may bite.

With the exception of the “ sticktight ” flea and certain of its rela-
tives, fleas do not remain attached to their hosts for long periods. The
amount of time spent off the hosts seems to vary much with the spe-
cies. Normally the adults feed every day and possibly oftener, but in
the case of interrupted meals, as has been mentioned, they may bite a
great many times during a day, and some species, such as the cat and
‘dog fleas, probably remain on the host almost continuously, feeding
at very frequent intervals. A great many fleas are nocturnal. These

4 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

depend largely on finding a host at night, and they tend to keep
secluded during the day.

In the case of inoculation of an animal with plague bacilli by a
flea it has been observed that there is a relationship between the
point of flea attack and the formation of the sweelings, or buboes.
In this connection it is interesting to note that certain species show
a marked tendency to infest certain portions of the host animal.

LIFE HISTORY.

The fleas pass through four distinct stages of development, viz,
the egg, the larva, the pupa or resting stage, and the adult. All of

Fie. 1.—The dog flea (Ctenocephalus canis): a, Egg; b, larva in cocoon; ec, pupa; d, ~
adult; e, mouth parts of same from side; f, antenna; g, labium from below. J, ¢, d,
Much enlarged; a, e, f, g, more enlarged. (From Howard.)

the different kinds of fleas resemble one another rather closely in these

different stages.
THE EGG.

The eggs are ovoid in shape and white or creamy in color, some
strongly reminding one of miniature china eggs. Although rather
small, they are readily seen with the naked eye, especially if placed on
a dark piece of cloth or paper. (Fig. 1, a.) They are formed after
the female has been feeding on a host for a few days and are usually
deposited while the flea is on the host, but are not glued to the
hairs or feathers, as is the case with lice and some other insects. The
human flea probably deposits most of its eggs while free from the
host. The eggs usually fall from the animals in their nests; hence

FLEAS. 5

there is a tendency for the young and, of course, the resulting adults
to concentrate in the vicinity of the sleeping places and most fre-
quented haunts of the host. This serves the fleas in three ways: (1)
By giving them the protection of the bed of the animal in which to
develop; (2) by furnishing food to the young in the form of partly
digested blood excreted by the adults while on the host; (8) by keep-
ing these parasites concentrated where they can easily secure access to
the host when they become mature. This habit is also important
when we attempt to control the fleas and is referred to again under
that topic (pp. 25-28).

The number of eggs deposited by a single female and the rate of
deposition undoubtedly vary largely with the species, the abund-
ance of food, and climatic conditions. Prof. Bacot, of the Lister
Institute, London, in his extensive studies of fleas has conducted a
number of experiments bearing on this point. The number of eggs
deposited daily 1s small, but deposition may continue for many
weeks. Bacot records 448 eggs as the greatest number observed by
him to have been deposited by a single female of the human flea. In
some of these experiments he found that the female would continue
to deposit eggs for a period of over three months.

THE LARVA.

Within from 2 to 12 days, depending on temperature and moisture
conditions, the eggs hatch into minute, whitish, legless, and eyeless
maggots. These are not parasitic, but move about actively in the dust
and débris in or near the nest of the host. Under favorable condi-
tions the growth of the larve is rather rapid. Flea larve usually
molt twice. The larvee of the dog flea may molt three times, accord-
ing to observations made by Mr. Theodore Pergande, of the Bureau
of Entomology. The first molt takes place in from 2 to 7 days after
hatching, the second from 2 to 6 days later, and the third about 5 days
after the second. The shortest larval period observed in these experi-
ments was 7 days. In England Mr. Bacot found that the larval
period in the dog flea ranged from 11 to 142 days; in the human flea,
from 9 to 102 days; in the European rat flea, from 15 to 114 days; and
in the Indian rat flea, from 12 to 84 days. Food, humidity, and tem-
perature are all important factors in influencing the rapidity of de-
velopment. The larve, or maggots, are slender, and each joint is pro-
vided with a number of hairs or bristles which assist it in crawling.
The head differs slightly in appearance from the other segments and
bears some of the usual head appendages with which most insects
are supplied. These include short, stout antenne, or feelers, and a
pair of mandibles fitted for biting. The top of the abdomen is pro-
vided with two fleshy fingers which aid the larva in its movements,

6 - BULLETIN 248, U. S. DEPARTMENT OF, AGRICULTURE.

and a comb of fine hairs. When full grown the maggots are usually
less than one-fifth of an inch in length. The larva of a common
species is illustrated in figure 3 (p. 14). 7 |

The food of the larve appears to vary somewhat with the species,
since some seem to thrive on a considerable variety of foods, while
others are more restricted in their diet. In nearly all species it
seems certain that the partially digested blood voided by the adult
flea in feeding constitutes an important part of the diet of larve,
especially when newly hatched. The remainder of the food consists
of particles of organic matter, either of animal or vegetable origin,
which are found in the cracks of floors, in the nests of the host, or
even mingled with the sand near the habitations of the host.

THE COCOON AND PUPA.

When the larve have attained full size they spin cocoons of more
or less oval shape (fig. 1, G; fig. 4). These vary from almost white
to brownish, but owing to the particles of sand and dust usually at-
tached the color is often dark. The insect in this stage thus is
rendered inconspicuous. In structure the cocoons range from rather
light, flimsy silken coverings to very thick tough or even thick brittle
encasements. Within the cocoon the larva molts its skin and enters
the pupal, or resting. stage (fig. 1, ¢), which somewhat resembles the
adult insect. At first the pupa is very pale in color, but it grad-
ually darkens as the time for the appearance of the adult approaches.
The length of time spent in the cocoon varies with climatic condi-
tions. At Washington, D. C., Mr. Pergande found that the dog flea
would emerge as an adult within from 7 to 9 days after spinning the
cocoon. In his experiments in England Mr. Bacot found the period
from spinning of cocoons to the emergence of adults to range as fol-
lows: European rat flea, from 8 days to over a year; human flea,
from 7 to 239 days; dog flea, from 7 to 354 days; and Indian rat flea,
from 7 to 182 days.

In these experiments Mr. Bacot found that the period within the
cocoon varied markedly with the temperature. This was particularly
true with the Indian rat flea, which had its cocoon stage greatly
lengthened when the daily mean temperature fell below 65° F. These
long resting periods were generally not produced in the case of the
human flea until the mean temperature fell to 50° F., and to 40° or 45°
F. with the European rat flea. The work of this investigator sug-
gests that the winter is passed in this stage, and that fleas may thus
tide over dry hot periods. It is certain that the cocoon offers much
protection from adverse weather conditions. The larva may remain
quiescent for long periods within the cocoon before actually pupating,
and another resting period may occur within the cocoon after the

FLEAS. a

insect has become adult. Observations made in India and in our
own country in the vicinity of San Francisco show that there is no
complete cessation of activities in the winter. ‘This is also true as
observed in several species by Mr. A. H. Jennings, of the Bureau of
Entomology, while in Panama, and the author has observed con-
siderable numbers of fleas on hosts in the Southern States in mid-
winter. These included the dog flea and the chicken flea, or “ stick-
tight,” as it is colloquially known.

LIFE CYCLE.

The total period from the deposition of the egg to the emergence
of the adult, in tests with the dog fiea conducted during the summer
time at Washington, ranged from 17 to 35 days. The length of the
different stages and total life cycle of some of the common species of
fleas may be shown best by presenting a table compiled by Mitzmain
from the works of various authors, and amplified to include recently
published results. ;

TABLE I.—Life cycle of jfieas in different countries.

Length of | Length of | Length of
Country and species of flea. ene of larval cocoon complete
ces ee: stage. stage. cycle.
United States: |
Atlantic coast— Days. Days. Days. Weeks.
Wo gelearCCPscamis) eens eee cs wu ere ee: 2to 4 8 to 24 AKO) <7 2to 4
Pacific coast—
iEumanth Car CRAinntta is) yee eee ae ee ae 7to 9 28 to 32 30 to 34 9to 11
European rat flea (C. fasciatus) ............-.-- 5to 6 4to 7 24 to 26 (ELOWS
dneianwrat ea (xncheopis) < 2.5 sees ts 9 to 13 32 to 34 25 to 30 9to 11
Ground squirrel flea (C. acutus)....-...---.---- 7to 8 26 to 28 24 to 27 8to 9
Europe: E : Days.
MEETS UEUTL UTR Ey eps ee acy a eee Sey Phra phen te SEO E NS | 4 to 12 8 to 100 6 to 220 19 to 264
1D) © Baile ceerery serene Oreste ION nme enema ee Ugur": 8 to 14 12 to 142 10 to 354 35 to 366
Buropeanma blenny: s-syya es kee ese endear py 5 to 14 12 to 114 3 to 450 20 to 467
HMI ATABT EY GALL eee were pe nie oy es ery ey ol ora pu SIRT 10orless| 14to 84 9 to 191 31 to 256
A ap te eR CC GPU D sna sbaveccdosehcosadeseeusaost 7orless| 13to 50 6 to 70+ 26 to 127
ndia:
Avice, tril Cae see ree tome oe sey ek agri sk 2 Uf 7to 14 21 to 22
Australia: Weeks.
AETV EY UERTD ST ea ao es og oe atl ve A TY 6 12 14 4to 6

LENGTH OF LIFE OF THE ADULT.

Food is the most important single factor in longevity of the flea.
Comparatively cool, humid weather greatly lengthens life. Mod-
erately warm, moist weather is more favorable than cool weather for
egg laying, but shortens the total life period. Hot, dry weather soon
proves fatal to the adult. In connection with this subject reference
is made to the work of Mr. Bacot in England, as he has conducted the
most complete set of experiments yet published to determine adult
longevity. When the temperature registered from 45 to 50° IF. and
the air was nearly saturated with moisture, this investigator found
that specimens of the human flea lived for 125 days, the European rat

8 BULLETIN 248, U. S. DEPARTMENT OF’ AGRICULTURE.

flea 95 days and the dog fiea 58 days, the Indian rat flea 38 days, and
a species of bird or chicken flea (Ceratophyllus gallinae) 127 days.
These records were made with individuals which received no food
whatever. When kept ina box and fed at frequent intervals, he found
the human flea to live for more than 513 days. The European rat flea
lived 106 days, the dog flea 234 days, the Indian rat flea fed on man
100 days, and the above-mentioned chicken flea 345 days.

In Texas the author has observed the “ sticktight,’ or chicken
flea, to live for several weeks attached to a host, but the greatest
possible longevity has not been determined. |

In experiments conducted in California Mitzmain had specimens
of the European rat flea alive for 160 days when fed frequently, the
Indian rat flea for 49 days, and the common ground-squirrel flea
(Ceratophyllus acutus) more than 64 days. |

In India and California the longevity with unfed fleas was found
to be much shorter than is.indicated by the records made in England.
Usually the maximum longevity of unfed rat fleas in these warmer
climates is but a few days. |

Experiments made by Mr. C. Strickland in England, and some con-
ducted by the author in Texas, indicate that the presence of rubbish,
dust, or sand, in which the adults may secrete themselves, is an im-
portant factor in increasing longevity of unfed fleas. This is espe-
cially true during hot, dry weather.

BREEDING PLACES.

Tn addition to having suitable hosts upon which the adult fleas may
feed and thus produce eggs, it is essential that the eggs, the maggots
which hatch from them, and the pupe which finally again produce
adults have favorable conditions for development. In houses these
conditions are usually found in the cracks of the floors or under mat-
ting or carpets. Rat fleas often breed in numbers in granaries, barns,
warehouses, and basements, particularly when these are not in con-
stant use or when gunnysacks and rubbish are allowed to accumulate
in such places. The immature stages of “sticktight” fleas breed
mainly in buildings, such as chicken houses, barns, and sheds which
are inhabited by the principal hosts.

Dirt floors in chicken houses or sheds seem to be more favorable
than wooden floors for flea development. The young fleas may be
found amongst the partially dried excrement, straw, feathers, and

other waste in such situations. Fleas have been found also to repro- —

duce in great numbers under corncribs and buildings where dogs sleep
or chickens go during the heat of the day. Here the maggots are in-

termingled with and feed upon the animal and vegetable matter —

which has accumulated on the soil.

FLEAS. 9

Occasionally fleas, particularly the human fiea and dog flea, may
breed out of doors. Mr. D. L. Van Dine has recorded an instance in
Hawaii where a lawn was infested with the dog flea, and instances are
known in the United States of this flea and the human flea breeding
in protected situations, as under shrubbery or in the shade of build-
ings in sand which contains a considerable amount of animal or vege-
table matter.

In nearly all cases the breeding places are very closely associated
with the haunts or resting places of the host. Instances where adult
fleas get upon man well away from such haunts must usually be con-

sidered as being the result of the adult fleas having become detached
from a host rather than by the fleas having been reared in such
situations.

FACTORS INFLUENCING FLEA ABUNDANCE.

Everyone familiar with the flea knows that there is marked sea-
sonal variation in abundance and often distinct variation from year
to year. As has been stated, fleas continue to breed throughout the
year in California and in parts of our Southern States. This is even
more marked in India, Panama, and other tropical countries. The
human flea and dog flea are seldom found to worry man during the
winter months. This is explained by a falling off in the rapidity of
breeding, the comparative inactivity of the adult fleas, and, as Mr.
Mitzmain has shown, the tendency for the human flea to remain
largely on the lower animals during winter. Throughout the United
States the fleas which attack man are most prevalent during the
summer months. In India there is a marked decrease in numbers
with the oncoming of the hot, dry season. This was particularly
noticeable in the case of the European rat flea, which, according to
observations of the Indian Plague Commission, began to disappear

early in April, and from May 15 to the beginning of November not
a single specimen was seen.

The variation from year to year is no doubt principally due to
weather conditions. Dr. Howard states that he believes the years
of greatest flea abundance are those in which the summer rainfall is
above normal. No doubt humid summers, even though the rainfall
were not abundant, would produce the same results. These statements
are borne out by ‘le effects of dry conditions on the various see of
fleas as observed by several investigators.

Although fleas of one kind or another are to be found all over the
United States, there are certain regions where one or more species
are especially abundant. In general, in those portions of the coun-
try where mild winters and comparatively humid summer atmos-
pheric conditions are the rule fleas are found most prevalent... The
amount of rainfall is also a factor in this regional abundance. While

- 92999°—Bull. 248152

10 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

extreme drought is detrimental to reproduction of fleas, excessive
rainfall also has a restraining influence. These conditions influenc-
ing flea abundance are dependent to some extent on the character of
the soil and the presence of hosts and breeding places. Sandy soil
is best fitted for flea breeding, as drainage is facilitated and the
surface is not so apt to become dried out as on many other soils. In
other words, it provides more uniform moisture conditions. It is
also probable that sandy soil is of some benefit to the flea by offering
more protection to the adult insect.

The local abundance of fleas is, of course, dependent upon factors
mentioned in the preceding paragraphs, but in addition the abun-
dance of hosts, their relationship to one another, and the presence of
breeding places are of much importance. The abundance of rats in
seaports is often responsible for a large flea population, and the
continued destruction of the rodents often correspondingly reduces
the number of fleas. As has been explained, fleas often feed on
several different animals, and when these animals associate they each
contribute to the breeding of fleas. An example of this occurs in
the instance of the chicken flea, or “sticktight.” This flea feeds in
great numbers on dogs and cats, and when these animals sleep in
and around chicken yards they and their beds are often the source
of great numbers of fleas which attack the poultry. Another in-
stance of the effect of the association of hosts and presence of
breeding places for fleas may be given. Often untold numbers of fleas
may continually infest houses and annoy the inhabitants as a result
of hogs, dogs, or other animals being allowed to go beneath the
house to make their beds. —

THE JUMPING OF FLEAS AND OTHER MEANS OF SPREAD.

The question of the distance a flea can Jump, especially in a vertical
direction, is important in considering isolation of man or animals
from them. The jumping powers of fleas are exaggerated in the
minds of most people. The human flea is probably the strongest
jumper. Mitzmain, working in California, found the maximum
horizontal distance this species could jump was 18 inches. He found
a few specimens could jump to a height of 7? inches. Five inches has
been recorded as the maximum horizontal jump of the Indian rat
flea by the Indian Plague Commission, and in experiments conducted
by Mitzmain 34 inches was the greatest height to which this species
could jump. In other tests investigators found that the European
rat flea and common ground-squirrel flea (Ceratophyllus acutus)
could jump slightly less than 84 inches in a vertical direction. Ob-
servations of the writer on the sticktight flea indicate that its jump-
ing power is almost nil. The legs of this species are comparatively

FLEAS. lel

small, not being developed for jumping like those of the human flea
and other species. |

Nearly all fleas have more or less difficulty in crawling on smooth
surfaces or on clothing, yet in time they are capable of making con-
siderable progress on clothing, either in a vertical or a horizontal
direction. :

The movements of the fleas themselves are of little direct impor-
tance in spreading the species. Their jumping powers, however, aid
them in finding hosts and securing attachment thereto, and upon the
hosts, whether normal or temporary, they may be carried considerable
distances. The species are further disseminated by the scattering of
egos as an infested host goes from one place to another and by the
dislodgment of the females from the host. Since the fleas leave a
dead animal, in this way adults are scattered, and in some instances
they may be infected with the disease from which the host died.
The greatest spread of fleas is no doubt brought about through the
transportation of infested animals from one place to another through
the agency of man. In this way rat fleas may be carried between
ports in all quarters of the globe on rat-infested ships. Chicken
fleas and dog and cat fleas may also be shipped long distances on
infested hosts. It is also possible to spread fleas in merchandise,
either in the adult or immature stages. Consideration of these points
is of much importance in preventing the spread of plague from one
locality to others.

FLEAS AS CARRIERS OF DISEASE.
BUBONIC PLAGUE.

Although the dread disease of man known as bubonic plague has
occurred in the United States, the most important outbreak being in
San Francisco during the last few years, fortunately it was restricted
closely to the portions of the country where it was introduced.

The earliest records of the disease connect the outbreaks in the
human family with death among rats. At the present time the dis-
ease is considered to be essentially a disease of rats. Man and other
animals become infected through the agency of fleas as a result of
these epizootics among rats.

The malady has a history dating far back in Biblical times. Prob-
ably the worst outbreak known began in the eleventh century and
culminated in the fourteenth. During this period practically the
entire Kastern Hemisphere was swept, and the number of deaths due
to the “ black death,” as it was known in parts of Europe, was appall-
ing. Within the last 18 years this malady has caused the death of
over 7,000,000 in various parts of the world. During the last decade
the disease has broken out in various parts of Africa, Europe, Aus-
tralia, Japan, South America, West Indies, and in the United States.

~

12 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

As a result of international regulations, including quarantines, and
owing to the work of the Public Health Service, the disease has
not assumed serious proportions in this country. Although the mal-
ady has persisted for some time among rats and ground squirrels
in and near San Francisco, very few human cases have developed,
and the malady has been entirely stamped out in that vicinity. The
occurrence of plague in New Orleans during 1914 caused some excite-
ment, but by prompt action by the State and Federal authorities the
outbreak has been limited to that city and the number of human cases
has been small. In India, China, and a number of other countries the
disease is still present in epidemic form, despite the work of the
Indian Plague Commission and other organizations for the further-
ance of control work. Marked progress is being made, however, and
the ultimate stamping out of the pestilence may be expected.

As has been stated, the flea is the medium by which the disease
is spread from rats and ground squirrels to man. These insects also
act as carriers from rat to rat. That the flea is responsible for the
transmission of plague has been determined within the last two
decades as a result of studies conducted by a number of investiga-
tors in various parts of the world. The importance of an accurate
knowledge of these insects in this connection is apparent to all. It
has been determined by the Plague Commission of India and other
investigators that several species of fleas may serve as vectors of
plague. Those which are commonly found on rats and ground squir-
rels and which may carry plague under certain conditions include
the following species:

The Indian rat flea (Xenopsylla cheopis Roth.).

The European rat flea (Ceratophyllus fasciatus Bosc.).

The human flea (Pulex irritans L.).

The European mouse flea (Leptopsylla musculi Dugés).

The dog flea (Ctenocephalus canis Curtis).

The squirrel fleas (oplopsyllus anomalus Baker and Ceratophyl-
lus acutus Baker).

The cat flea (Ctenocephalus felis Bouché).

The rat fleas Ceratophyllus anisus Roth. and Pygiopsylla ahalae
Roth.

The former of the last two mentioned occurs in the East Indies,
where it has been shown to be capable of carrying plague, and the
latter takes the place of the European rat flea in China and Japan.
All of these species, with the exception of the last two named, are
found in the United States.

The very severe outbreak of plague in Manchuria a few years
ago is thought by many to have started among trappers of the
“tarbagan,” or groundhog, as a result of having been bitten by the
flea, Ceratophyllus silantiewi Wagner, which is abundant on this
animal.

TCs ge eee

FLEAS. | | 13

The Indian rat flea has been found to be by far the most im-
portant in plague transmission in India, and this species is now
widely distributed throughout the Tropics and in seaports which
have direct trade with the Orient. At the present time this species
is abundant in parts of the seaport cities on the Pacific and Gulf
coasts of the United States. Away from the water front its place
as a rat parasite is largely taken by the European rat flea (C. fasci-
atus Bose.) and the mouse flea (Leptopsylla musculi Duges). The

:
sae ter ie

SR
ceksalgate!

Yee

Fic. 2,—The European rat flea (Ceratophyllus fasciatus) : Adult female. Greatly enlarged.
(Original. ) \

human flea is common in many parts of the country, and the squirrel
fleas mentioned are abundant on ground squirrels (Citellus beecheyi)
in the western part of the United States. All of these fleas have
been found to bite man and will feed on rats. The adult European
rat flea is illustrated in figure 2, the larva of this species in figure
3, and the cocoon in figure 4.

As has been stated, plague always occurs among the rodent popula-
tion before any number of cases develop in man. The rats in a
plague-free community usually receive their initial infection from a
diseased rat which has been imported from some plague center. This,

14 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

together with the favorable conditions as regards rats and fleas in
seaports, accounts for the fact that the disease usually first breaks out
in such places. The pestilence, when once introduced, is carried
rapidly from rat to rat by the fleas. This spread is increased by the
fact that most of the fleas leave the rats as they die and pass to others.
It is these fleas, set free by the death of their plague-stricken hosts,
which form the chief menace to man.
The method by which fleas convey plague germs has received con-
siderable attention,
and various theo-
ries have been ad-
vanced from time
_ to time in an effort
+ to explain the mech-
Fig. 3.—The European rat flea: Larva. Greatly enlarged. : 5
(Original.) anism of transmis-
sion. It appears
that the two most important methods are by contamination
of the skin of man or other host by excrement voided by the
infected fleas while feeding and the subsequent rubbing or scratch-
ing in of the germ-laden material and by the injection of the
disease organism into the wound made by the flea at the time of
feeding. Researches made by Mr. A. W. Bacot, of the Lister Insti-
tute, have proven this last method to be an important one. He
showed that the entrance to the stomach of some of the fleas becomes
plugged by a growth of the plague germs. This ultimately prevents
the passage of food backward into
the stomach, but does not prevent
the flea from sucking up small
quantities of blood,some of which
is forced back into the wound
after becoming laden with the
disease organism.
Close trade communication be-

; Fie, 4.—The European rat flea: Cocoon.
tween the nations of the world Greatly enlarged. ‘Note the particles

of sawdust and dirt adhering to the

gives increased channels for the subtace, ORR

dissemination of various pests and

diseases as well as opportunities for the furtherance of knowledge and
the exchange of trade commodities. The colonization of new lands
in the Tropics, the opening of a great artery of trade intimately
connecting many of our ports with the commerce of the world, the
immigration brought about by the present European strife—these,
when considered together with the fact that plague is now present
in many quarters of the globe, should impress all with the importance
of exercising great care to exclude the disease from our shores.
Knowing that this pestilence spreads among people only as a result

ry

x

BS
=

FLEAS. en

of the dissemination of the disease among rodents by fleas, the im-
portance of rodent destruction and of flea control, which go hand
in hand, needs no further emphasis. It is not sufficient for the
farmer, merchant, and others concerned to depend upon the quaran-
tine authorities to keep plague from being introduced. They must
aid the quarantine officers by waging war on the rats and ground
squirrels and by preventing flea breeding.

Turning from the rat as a sanitary menace, ample argument is
found for its destruction on account of its importance as a destroyer
of various agricultural and food products. It has been conserva-
tively estimated that there are in the United States at least as many
rats as people. It has also been computed that the annual upkeep
of each animal amounts to between $1 and $2. From these figures
it is seen that the annual loss due to these rodents must be upward
of $100,000,000.

The control of rats is difficult but not impossible, the principal
methods being trapping, poisoning, destruction by natural enemies,
and, probably most important of all, rat proofing. The question of
the relation of rats to man has been treated in publications of the
Public Health Service and of the Bureau of Biological Survey.’

This work of rodent destruction, clearing up of breeding places,
and rat proofing of buildings has an important beneficial influence
on flea conditions. Some of the hosts of the fleas are removed and
the breeding places of the insect destroyed to some extent. How-
ever, these practices can not be depended upon to control all of the
species of fleas important as pests.

KALA-AZAR.

One form of another important group of diseases of the Tropics,
known as kala-azar, an infectious fever, is considered by some au-
thorities to be carried by the dog flea and human flea. The par-
ticular form of the malady in question occurs in the Mediterranean
region. On these shores dogs and children are attacked by a similar
disease. Investigators have produced strong evidence that the dis-
ease is identical in the two hosts and that fleas are responsible for
its transference from the one to the other.’

1Lantz, D. EH. How to destroy rats. U.S. Dept. Agr., Farmers’ Bul. 369, 20 p., 5 fig.,
1909.

2HWleas and dogs.—In Hurope with regard to infantile kala-azar, the dog has been found
to harbor Leishmania, and a fairly presumptive case has been made out as to the part this
animal plays as an intermediary host, the dog fiea being the actual transmitter. Donovan
believes, however, that the evidence adduced so far is not in all respects convincing. The
occurrence of a natural flagellate of the flea has evidently not been taken into sufficient
account. (Donovan, Lieut. Col. C. Kala-azar, its distribution and probable modes of
infection. In Jour. Trop. Med. London, v. 16, no. 16, p. 2538-255, 1913.)

16 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

LEPROSY AND OTHER DISEASES.

Leprosy is another serious malady with which, according to some
investigators, fleas may be connected. This relationship has not been
established, but it is well for us to consider all such possibilities.
The part fleas play in the life economy of certain tapeworms has
been mentioned, as has also their connection with certain rat-infesting
organisms. Various other low forms of animal life, many of which
are no doubt parasites of the flea itself, have been found in the organs
of that insect in different stages of its life.

FLEAS AS PARASITES OF MAN AND ANIMALS.

As has been shown, a considerable number of the common fleas of
this country may be concerned in the transmission of certain dis-
eases if these are once introduced. Several species are, however, of
much importance to man aside from their possible connection with
disease. It is with the fleas which annoy man or attack poultry or
dogs that the people in general are most concerned.

The effect of the bites of fleas varies much with the teal
attacked and also with the identity of the flea concerned. The direct
effect of these bites, aside from disease transmission, has received
little attention. Usually in man pronounced red, itching papules,
in some cases with whitish centers, occur at the site of the puncture.
Some more susceptible individuals show marked irritation, swelling,
and even ulceration following attack. The papules may persist for
several days, but usually disappear within a few hours. The irrita-
tion is probably induced largely by the injection of the salivary secre-
tion into the wound. This injection causes a rush of blood to the
spot, which facilitates the feeding of the insect and in turn causes
irritation in the host. The question of acquiring immunity to an-
noyance by fleas is an interesting one. Many cases have been re-
ported wherein individuals have enjoyed marked immunity to the
effect of fleabites and comparative freedom from annoyance after
being exposed to the fleas of California. The species concerned in
these instances was without doubt the human flea. Others report a
similar diminution in the annoyance caused by the dog fiea. A brief
discussion follows of the more important species from the stand-
point of annoyance to man and domestic animals.

THE HUMAN FLEA.

The species of flea known scientifically as Pulex irritans L. has long
been considered the human flea. I{t is to be found in practically
every portion of the earth frequented by man. It is quite distinct
from other fleas in structure (figs. 5 and 6), and is largely dependent

FLEAS. 1%

upon man as a host, although in Europe it seems to thrive on the
badger, while in the United States it 1s commonly taken on the
skunk. It has also been taken on hogs, rats, and various other ani-
mals, but these are usually but temporary hosts and insuflicient to
maintain the species.

On the Pacific coast the species is responsible for practically all
annoyance to man due to this group of parasites. It has been found
to be the one concerned in nearly all cases of house infestation in
that section. In the Southern and Eastern States, as will be pointed

Fic. 5.—The human flea (Pulex irritans): Adult female. Greatly enlarged.
(Original. )

out later, the dog flea is more important as a pest to man than the
human flea. Our main interest in the human flea is on account of its
annoyance to man, as it is not as yet known to play any part in dis-
ease dissemination in this country. Nevertheless, the possibility of
its being an occasional carrier of plague and also that it may trans-
mit the infectiows fever kala-azar of the Mediterranean region should
not be lost to sight.

Curiously enough, the human flea appears to have adapted itself
to the varied conditions under which man lives. It breeds freely in
all situations occupied by man, and in the immature stages is one of

the most hardy species known to science. The biology of this species,

'
ee ee

Sas

18 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

as compared with others, has been briefly outlined in the preceding
pages, and control measures, applicable to this and most other species,
are discussed in the following pages.

THE DOG FLEA.

The dog is undoubtedly the normal host for the flea which is
known scientifically as Ctenocephalus canis Curtis (fig. 1) ; neverthe-
less the insect is not averse to partaking of a meal of blood from man
or a cat, especially when its normal host is not at hand. Like the

Fic. 6.—The human fiea: Adult male. Greatly enlarged. Note the difference in the
shape of the abdomen of the male as compared with the female (fig. 5). (Origi-
nal.)

human flea, this species has a wide distribution throughout the world;
in fact, it is generally considered the most widely distributed species
of flea. :

_ As an annoyer of man the dog flea ranks next to the human flea.
In the eastern United States, as has been pointed out by Dr. Howard,
instead of the human flea this is the species usually reported as infest-
ing houses. In some instances reported to the Bureau of Entomology
houses have been rendered almost uninhabitable by this aggressive
insect. The most severe infestations, as reported by Dr. Howard,
have occurred in cases where dwellings have been closed up during
summer, and when opened upon returning the occupants were greeted

FLEAS. 19

by hundreds of fleas. Rainy summers are most favorable for such
development, supplying enough dampness to the dust, which is left
undisturbed in the cracks, successfully to mature the eggs and fleas
which are present. The original stock of fleas must, of course, be
derived from pet dogs or cats which occupied the house before it was
vacated, or, as often happens, dogs may take up their abode under or
around the house in the absence of the occupants. Thus great num-
bers of eggs are dropped, and breeding proceeds undisturbed. It
should be noted that the stray dogs and cats which are likely to find
homes in unoccupied buildings are often heavily infested with fleas,
usually much more so than animals with a home and having more or
less attention paid to them.

In this country the dog flea is not known to be responsible for the
transmission of any disease, but it holds a position of distinct im-
portance as a household pest. Its importance as an enemy of the
dog and cat is not small. Breeders of fine cats and dogs often have
considerable trouble in ridding their stock of fleas, and hunting and
other dogs, particularly in the South, are kept in poor condition as
a result of gross infestation. The fact that one stage of a tapeworm
which commonly infests dogs and occasionally children in this coun-
try lives within the dog flea still further increases the importance

of this parasite.
: THE STICKTIGHT FLEA.

One need but visit a few poultry farms or inquire of almost any
farmer with his little flock of chickens for home use in the southern
and southwestern portions of the United States to get some idea of

the importance of the so-called “sticktight flea” (Hchidnophaga
gallinacea Westw.). Other colloquial names which are applied to
the insect are “third-party flea,” “chicken flea,” or “black flea.”
The name chicken flea is applied because of the frequency with which
chickens are infested. Black flea isa name applied less frequently and
is given on account of the very dark color of the adult fleas. The name
“ sticktight ” is used most generally in the South, and it is aptly ap-
plied. The species differs markedly in feeding habits from most of
our common species. It seldom hops about, biting here and there, as
in the case of the dog and human fleas, but when a suitable host is
found it settles down, deeply inserting the mouth parts, and remains

1In a publication just issued (Herrick, Glenn W. Some external parasites of poultry
with special reference to Mallophaga, with directions for their control. Cornell Univ.
Agr. Expt. Sta. Bul. 359, p. 230-268, fig. 95-116, Apr., 1915.), the point is brought out
that the European hen flea, Ceratophyllus gallinae, was received from Abington, Mass.,
and Barker, N. Y. In each of these cases the flea was collected in hen houses, and the
collectors state that the insect was very annoying, especially to human beings. Prof.
Herrick calls attention to the fact that Mr. C. F. Baker reports the collection of a single
specimen of this flea at Ames, Iowa, and refers to a note by Dr. M. Francis to the effect

that the species occurred at Bryan, Tex. It is possible that in time this insect may
become a pest of some importance to poultry in the United States.

———— a ee

ee

SMTA SRE

ee

20 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

for days or weeks. Its hold on the host is difficult to loosen. Another
marked tendency is for the adults to attach to hosts in dense masses.
A chicken is frequently seen with a large portion of her head closely
set with these fleas, making it appear almost black. These dense
masses are often seen on the ears of dogs or cats, particularly at the
very edge of the ear. The characteristic appearance of an infested
chicken’s head is shown in figure 7.

The hosts of this flea are, unfortunately, rather numerous. As
has been stated, chickens are commonly attacked, and it is on this
host that the species assumes its greatest importance as a pest. In
the investigations by the author it has been found in abundance on-
dogs, cats, tame rabbits, ducks, and turkeys. It is not infrequently
found on people who go about infested poultry yards, and children,

crawling beneath houses where
infested animals go, are often
bitten. The species does not at-
tack man very freely. It is sel-
dom found in houses except on
rare occasions, when a few speci-
‘mens may be brought in on the
clothing. In one instance in
western Texas a burrowing owl
was killed and found to be heay-
ily infested about the head with
this flea. In another instance
in the same region a wood rat,
or pear rat, as it 1s commonly
known there, was found to har-
Fic, 7.—Head of rooster infested with the bor a number of sticktight fleas.
sticktight flea (Hchidnophaga GOUENEe Several years ago Prof: 2G:

cea). Somewhat reduced. (Original.) .

Hartsell, of Orangeburg, S. C.,
reported to the Bureau of Entomology instances where horses were
heavily infested with these fleas on the lower portions of the legs.
Others have recorded it from cattle,and a number of specimens have
been taken on rats and other hosts in different parts of the world.

The species was originally described from India, but it now ap-
pears to be widely distributed throughout the Tropics and the warm
temperate regions. In the United States it is seldom seen north of
the Southern and Southwestern States. Reports indicate that the
species is spreading; at any rate, it would seem that the South is
becoming more generally and completely infested.

No disease has been found to be carried by the sticktight flea, but
its importance as a parasite places it among the principal insect
enemies of poultry in the South. The principal direct loss is due to
the attack of the fleas on young poultry, as high as 85 per cent of young

.)

FLEAS. PAL

chickens hatched having been reported lost on account of the fleas.
In many cases young chickens, turkeys, and ducks have a combined
infestation of sticktight fleas and biting lice, and each contributes to
the worriment and weakening of the fowls. A few cases of death
observed among grown chickens apparently have been due to fleas.
In these instances not only the heads and necks of the chickens were
largely covered but numerous patches thickly set with fleas existed
under the wings and on the breast. The fowls heavily attacked be-
come droopy, lose appetite, and fall off in weight. Mild infestations on
grown fowls cause no marked injury, but no doubt egg laying is influ-
enced to some extent, and certainly infested fowls are unsightly.
The fleas are present on hosts throughout the year, but they are
usually more nu-
merous in the sum-
mer and fall. The
species appears to
thrive best in ull-
kept chicken houses,
where chickens roost
under buildings, and
where dogs and cats:
have their beds
closely associated
with the _ poultry.
This point will be
discussed further
under the general
topic of control. The
eggs are dropped by

the females while at-
tached to the host. Wie. 8.—The sticktight flea: Adult female. Much enlarged.

These fall beneath ee
the roost, hatch, and the young larve feed on the excrement of the
parent fleas and on other animal and vegetable refuse.

The species is one of the smallest fleas in this country and very
dark brown in color. The body is comparatively short and deep, and
the legs are slender, but the mouth parts are large and strong. The
male is usually slightly smaller than the female (fig. 8), almost
black, and is more frequently seen moving about on the host than the
female.

THE CHIGOE FLEA.

The flea commonly known as the chigoe or “ jigger” (Dermatophilus
penetrans .)* is related to the sticktight flea, but has different

+ This should not be confused with the “‘ chigger”’ or harvest mite, which is the larval
form of Trombidium. :

22 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

habits. Instead of remaining attached to the surface of the host,
the female, after being fertilized, burrows into the flesh until it
may become completely embedded. When it first reaches a host it
feeds much as does the sticktight flea, the burrowing tendency be-
coming evident only when the eggs are developing. A number of
hosts are attacked, particularly the hog. Cats, dogs, cattle, sheep,
horses, and even birds are attacked, but attention has been directed

to the species largely through its infestation of man. Its attack is

usually confined to the feet of the host, and in man particularly to
the toes. The females may enter between the toes or under the toe-
nails, and severe inflammation often follows, with the formation of
ulcers, frequently resulting in permanent crippling. While in the
host the eggs develop within the female and the abdomen becomes
greatly distended, often attaining the size of a small pea. The legs
of this species are not large, and when this distention takes place
they, as well as the head, become very inconspicuous.

The eggs are deposited while the flea is attached and may drop
from the wound or pass out with the detached flea. So far as known
the rest of the life history is similar to that of other species.

The chigoe is not known to be established in the United States,
although it has been reported on a few occasions from Florida. Itisa
troublesome pest in the West Indies, in parts of Mexico, and in much
of South America. It is native to the American Tropics, but about
1872 it was introduced into western Africa. The African conditions
were favorable for the pest, and it soon became established in east
Africa and Madagascar and spread to the interior of the continent.
It was introduced more recently into India, but it appears to have
spread very slowly there.

Conditions in Florida and southern Texas would seem to be favor-
able for this insect, and if care is not exercised it may be introduced
and become established in this country.

NATURAL CONTROL.

As has been stated, hot, dry weather is detrimental to flea develop-
ment. Likewise excessive moisture in a breeding place destroys the
immature stages. The direct rays of the sun in summer are important
in reducing the length of life of the adult flea and destroying the
immature stages. It is possible to take advantage of these natural
factors to a considerable extent in fighting the pest, as is brought
out later.

Little is known of the natural enemies of fleas. Certain short-
winged beetles termed staphylinids are known to prey upon the adult
fleas, and certain species of mites have commonly been found upon
them. In Texas ants have been observed to prey upon the eggs and

FLEAS. 23

larve. No doubt a number of insect enemies of the immature stages
exist, but they are probably less important in control than climatic
factors. Chickens seem to be capable under some conditions of inter-
fering with the development of the immature stages of fleas by
scratching their breeding place about, and no doubt they eat some of
the fleas in their various stages.

ARTIFICIAL CONTROL.

In order to prevent an outbreak of fleas, and more especially to
control an infestation which has become established in or about a
house, it is usually necessary and always advisable to combine two
or more of the measures discussed below in order promptly to control
the situation.

DESTRUCTION OF FLEAS ON HOSTS.

In nearly all cases of flea infestation by either the human flea or
the dog flea in houses or by the sticktight flea in poultry yards
the destruction of the fleas on the hosts is important. Dogs and cats
are the animals of particular importance in this connection, since
they act as normal hosts for the flea of the dog and cat, which often
annoys man; they sometimes harbor the human flea and are fre-
quently heavily infested with the sticktight flea. In cases of house
infestation, while it is imperative that the breeding places be treated,
attention should be given to dogs and cats. In fact, the destruction
of the breeding places and the clearing of the fleas from the hosts
should be undertaken simultaneously, as each is essential to the best
success of the other. A number of different methods of destroying
the insects on animals have been tried, and each has its advocates.
The writer has used certain creosote derivations, among them creolin,
with excellent results. There are several preparations similar to
creolin which would probably be equally effective. It is best to make
up a 8 per cent solution of creolin, or one of the similar preparations,
in warm water in a tub and place the animal into it; then with a
stiff brush to work the solution into the hair. The animal should be
kept in the solution 5 or 10 minutes, particular care being taken thor-
oughly to wet the fleas which crowd to the head of the animal. After
the host has been thus treated the creolin water may be drained off
and the animal washed with warm water and soap. This washing
is not always necessary or advisable in treating dogs, but it is desir-
able with cats. By this method the burning of the most delicate-
skinned animal is avoided. Where a graduated glass measure is not
at hand, a 3 per cent solution of the wash may be made by putting in
4 tablespoonfuls of creolin to each gallon of water.

24 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE. »

Another treatment, which is reported by Mr. A. A. Girault, of the
Bureau of Entomology, to be effective in ridding cats of fleas, is
naphthalene. Moth balls were finely pulverized and the powder
worked into the fur. The fleas soon began coming out of the hair and
on account of their stupefied condition were easily caught and killed.
The treatment slightly sickened the cats for two days, but had no
serious effect. Insect powder, sometimes called pyrethrum, buhach, or
Dalmatian insect powder, may be applied to the fur of animals in
the same way. It is not harmful to the host and causes the fleas to
come out of the fur in a stupefied condition, when they may be col-
lected on a newspaper and destroyed by burning. It is important
that fresh unadulterated pyrethrum be used to secure satisfactory
results. The destruction of the chicken flea or sticktight on poultry
seems to be rather difficult. Where heavy infestations are present
the careful application of kerosene and lard—1 part kerosene to 3
parts of lard—to the masses of fleas gives fairly good results. Care
must be taken not to apply too much of the mixture and not to get
it on the parts of the fowl where it is not ; Mecessary, a it will prove
injurious if used too freely.

CONTROL OF HOSTS.

»

One of the common practices to avoid flea infestation of houses is
to keep all dogs and cats out of doors. This is often not desirable,
and it also gives am opportunity for the infested animals to start
breeding places under the house or in the yard or barn, hence this
practice without treating the animals for fleas is objectionable. Not
keeping dogs or cats will, of course, largely solve the dog-flea prob-
lem, but this is not always feasible. Moreover, the stray animals
must also be considered as possibilities in house infestation. From
the standpoint of flea control, as well as for the prevention of im-
portant diseases, the strict enforcement of dog-control measures and
the destruction of all stray cats and dogs is imperative. Dwellings
and other buildings should be arranged to prevent cats, dogs, hogs,
chickens, and other animals from going beneath them, as the condi-
tions under buildings are often favorable for flea breeding and these
locations are exceedingly difficult to keep clean or treat after infesta-
tion is started. Numerous instances have come under observation
where such conditions were responsible for infested dwellings and
heavily infested animals.

Along this same line is the question of separation of hosts. It is
bad policy to keep all kinds of animals in close proximity in localities
where fleas are numerous. Dogs and cats sleeping around poultry
pens are often responsible for keeping chickens constantly stocked
with sticktight fleas. Horses kept in buildings where chickens roost

FLEAS. 25

or in barns adjoining chicken coops have been known to become in-
fested with sticktight fleas, and dogs and cats readily infest one an-
other with these and with other fleas. Chickens have been known to
become infested with chicken fleas and thus establish an infestation
in uninfested yards when allowed to run at large and come in contact
with infested premises.

The question of rat control logically should be discussed under this
topic, but it has been briefly taken up under “ Bubonic plague.”
Ground-squirrel destruction, aside from its direct economic impor-
tance, should also be considered in connection with the relationship
between the squirrel fleas, their hosts, and the transmission of
plague. The ground squirrels of California are discussed by Dr. C.
Hart Merriam in Circular No. 76 of the Bureau of Biological Sur-
vey. Much useful information on the control of the California
ground squirrel is given, and this is for the most part applicable to
ground squirrels in other parts of the country.

DESTRUCTION IN BREEDING PLACES.

Attention has been called (pp. 8-9) to the usual breeding places of
different species of fleas. It is evident that destruction of the adult
fleas on hosts is almost a hopeless method of controlling the pest if
no attention is paid to the breeding places of the immature stages.
As has been stated, flea eggs may produce adult fleas from two weeks
to many months later. Thus the hosts will continue to become rein-
fested as fast as the insects upon them are destroyed.

The first step in making war on the breeding places is to determine
where the fleas are coming from. Enough has been said in the dis-
cussion of life history and breeding habits of fleas to point out the
places to be considered. In other than house infestations all un-
necessary rubbish and dry animal or vegetable matter should be piled
up and burned. In the case of infested chicken houses or sheds the
manure should be hauled into an open field and scattered thinly
over the ground. When thus exposed all stages are soon destroyed.

Following this preliminary work, which is essential to the success
of the subsequent treatment, the ground, outhouse floors, and other
places where the breeding is supposed to occur should be sprayed
with kerosene, or, better still, crude petroleum should be sprinkled
freely about. To prevent reinfestation or breeding it is essential
that all waste, both vegetable and animal matter, be kept scrupu-
lously cleaned up. The most inexpensive and satisfactory preven-
tive measure following the destruction of the main infestation is a
liberal use of salt scattered about the breeding places and then
thoroughly wet down., In many instances observed in Texas the
sticktight flea has been kept out of poultry runs by cleanliness

26 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

and semiweekly wettings with water.. Along the coast salt water
from the Gulf is used extensively for this purpose. The soil must be
thoroughly wet, as light sprinklings of the surface will not suffice. ©
The watering is most effective when done in the evening, as drying
does not proceed so rapidly then as during the day. Mr. D. L. Van
Dine, in treating premises infested with the dog flea in Hawaii,
used a dressing for the ground under the houses consisting of 20
pounds of air-slaked hme, 8 pounds of, sulphur, and 1 pound of
buhach. This mixture was appled after the ground had been
thoroughly cleared of all refuse. The outbreak was completely con-
trolled in these cases, but it is difficult to say just what part the above
dressing played, as the destruction of the adult fleas was undertaken,

as well as other measures. |

The breeding of the sticktight flea may he persue to some
extent by the use of metal chicken houses, as is advocated for the
fowl tick.t These galvanized-iron houses provide less protection for
fleas than do frame structures, and the intense heat within them dur-
ing the daytime practically prohibits flea breeding. The dog house
should be cleaned out thoroughly at weekly intervals, and if any flea
breeding starts the method of destroying the insects, as outlined in
the preceding paragraphs, should be followed. By providing a few
gunny sacks or a mat for infested animals to sleep upon, it is
possible to concentrate the eggs on these. The eggs may be de-
stroyed then by shaking the cloths over a fire or even out on the
bare ground in a place exposed to the sun. This should be done
about every second day in order to prevent hatching.

Attention is directed to house infestations, which, by the way,
are often supplemented by infestations under the houses or in other
out-of-door situations. The occurrence of fleas in dwellings is
often connected with the keeping of a cat or dog indoors. If this
is the apparent source of infestation, the animal should be treated
as previously described and kept out until the indoor work is
completed.

If the hosts have been confined largely to one room, this is the one
to receive most careful attention. The floor covering should be
removed, aired, and beaten, the floor thoroughly swept, and all of
the dust obtained should be burned, as it contains many immature
fleas. It is best, then, to scrub the floor with strong soapsuds or
sprinkle it with gasoline, being careful to avoid having fires about.
After sprinkling naphthalene crystals or insect powder over the floor,
return the floor covering.

Dr. Henry Skinner, of Philadelphia, found that he could control
fleas-completely in a house by taking one room at a time, scattering

1 Bishopp, F. C. The fowl tick. U. S. Dept. Agr., Bur. Ent., Cir. 170, 14 p., 5 figs.,
1913. ‘

rane DHT

5 pounds of flake naphthalene over the floor, and closing the room
tightly for 24 hours. This remedy was found inexpensive, as the -
naphthalene could be swept up and transferred to another room.

Dr. Howard has called attention to the method of control used by
Miss Adele M. Fielde, who has had extended experience with fleas in
China. She states that it is possible to control the fleas there by
the use of alum. This substance is added to the whitewash or cal-
cimine used on the walls, paper is dipped in a solution of alum and
put under rugs and matting, and powdered alum is sprinkled on
carpets or other floor covering and swept in. It does not injure the
rugs or matting, but banishes the insects, according to Miss Fielde’s
statements.

In houses where vacuum cleaners are used at frequent intervals
the number of fleas coming from the floors may be reduced. In cases
of infested houses a thorough cleaning of the carpets and floors with
a vacuum cleaner, provided it is efficient, would largely mitigate the
. pests.

Fleas in different stages in dwellings or other buildings may be
destroyed by fumigation with sulphur fumes or hydrocyanic-acid
gas. Either of these fumigants, when properly handled, will destroy
the fleas, and has the advantage of killing the rats and mice as well.
The use of sulphur? is efficient and simple, but has the objection of
corroding metal and injuring plants. In fumigating, the infested
building should be closed up tightly and the sulphur weighed out
at the rate of 4 pounds to each 1,000 cubic feet of space. The sulphur
is piled up cone shaped in a pan or kettle, which is placed in a
larger pan or tub of water to avoid fire from the heat generated.
A depression should be made in the top of the cone of sulphur, a
httle alcohol poured into it, and a match applied. Each room to be
fumigated should have a vessel, and large rooms should have two,
one located near each end. It is preferable to do all of the fumiga-
tion simultaneously. The rooms or building should be kept closed
for from 10 to 12 hours. Although this gas is not nearly so dan-
gerous to man as is hydrocyanic-acid gas, the rooms should be
thoroughly aired before entering them. The corrosive action of the
gas on metals and its effect on plants should not be overlooked. This
may be minimized by fumigating when the atmosphere is dry.

Owing to the poisonous character of the ingredients used and the
deadliness of the gas generated, fumigation with hydrocyanic-acid
gas should not be undertaken without carefully reading the direc-
tions? for the operation, and then only by an experienced person.

1 Marlatt, C. L. Sulphur dioxide as an insecticide. In U. S. Dept. Agr., Bur. Ent., Bul.
60, p. 139-146, 1906.

2 Howard, L. O., and Popenoe, C. H. Hydrocyanic-acid gas against household insects.
U. S. Dept. Agr. Bur. Ent., Cir. 163, 8 p., 1912.

28 BULLETIN 248, U. 8S. DEPARTMENT OF AGRICULTURE.

Sodium fluorid is a comparatively new insecticide which will
probably be useful against fleas. This substance is not expensive
and not dangerous to handle. The crystalline powder is applied
by dusting it over the carpets or fioors and working it into the
cracks. For the adult fleas it may be blown about the floor and cor-
ners with a dust gun or insufflator. Although this substance has not
been tried in this way, it is possible that it can be advantageously
utilized in chicken houses, dog kennels, etc., by blowing it about the
floors with a powder gun. The fact that sodium fluorid is an excel-
lent remedy against cockroaches further commends its use about
houses infested with fleas.

A number of things should be mentioned which may be utilized
to some extent in flea-infested regions to prevent the breeding of
fleas in dwellings. As far as possible, rugs, or art squares, or other
coverings which can be taken’ up and permit keeping the floors more
cleanly, and in case of infestation make treatment easier, should be
used. Closely matched floors are beneficial, as there are fewer cracks
in which the young fleas may develop. Where cracks are present they
may be filled with plaster of Paris or putty. The use of floor oil or of
efficient sweeping compounds on floors seems to aid in preventing flea

breeding.
; TRAPPING FLEAS.

Little dependence for control of fleas can be placed on methods
designed actually to capture, repel, or exclude from the host the
adult fleas if not supplemented by the other repressive measures just
discussed. Nevertheless, under certain conditions, such as in in-
stances where a few adults ere produced in a great number of situ-
ations, thus making complete stopping of breeding very difficult, or
while the other methods of control are being put into effect, trapping,
repelling, and isolating are of some value. In localities where plague
is prevalent, or even suspected, the importance of keeping even a
single flea from biting man is apparent.

Where only a few fleas are present in a dwelling and breeding in
the floors is not suspected, the adults may be caught by placing a
number of sheets of sticky paper on the floor. In extreme cases,
where the persons attempting to rid premises of fleas are able to
injury or serious disease, the practice of wrapping fly paper, sticky
side out, around one’s legs and walking about is sometimes resorted to.
The movement causes the fleas to jump, and if they strike the paper
they are held fast. The use of sticky fly paper in this way was prob-
ably first tried by Prof. S. H. Gage at Cornell University. One of
the university buildings was cleared of fleas by having the janitor,
with legs wrapped in fly paper, walk back and forth in the infested
rooms. Mr. D. L. Van Dine also made use of this scheme in Hawaii.

FLEAS. i 29

In this instance, however, it was used mainly to protect the workmen
who were clearing up flea-infested premises.

Lights have been used as traps for the adults in some instances.
The results will no doubt vary with the species of flea concerned.
A light trap which was used by Mr. E. M. Ehrhorn, formerly of
San Francisco, 1s described by Dr. Howard, as follows:

Fill a glass three-fourths with water, on top of which pour about an inch of
olive oil, then place a night float (a little wick inserted in a cardboard disk
or in a cork disk) in the center of the oil. Place the tumbler in the center
of a soup plate filled with strong soapsuds. The wick should be lighted at night
on retiring, or may be used in any dark room. As the soup-plate soapsuds
trap is placed on the floor of the room, it does not inter-
fere with the sleeper, and the fieas which are on the
floor are attracted to the light.

%
SU eS

A small flea trap which is extensively used in
parts of China, and is said to be very beneficial,
has recently been described by Dr. E. Hindle.
In China two pieces of bamboo are used in con-
structing the trap. A modified form of this
trap, which can easily be constructed by anyone,
is illustrated in figure 9.

To construct the trap, bore two holes, about an
inch and a quarter in diameter, in a board any-
where from one-fourth to 1 inch in thickness.
With a keyhole saw or a pocket knife cut out a
disk of the board around each of the holes about
24 inches in diameter. Take a piece of wire net-
ting, with one-fourth or one-half inch square ye Ea
soldered mesh, about 2 feet wide, and tack it A
around the disks, having one at either end. Cut |
off the wire, leaving the ends long enough to Va aeons ee
overlap along the side of the cylinder, and bend movable and is cov-
the ends in to complete the cylinder. Around a cee f(a LAT
broom handle or other stick about an inch in
diameter and equal to the length of the cylinder wrap a piece of sticky
fly paper, sticky side out; tack it at each end to the stick and insert the
stick into the cylinder. The stick should be fastened in with a nail
inserted into it through a hole in the edge of one of the wooden ends.
The outer wire cylinder forms a protection for the sticky surface and
enables one to move the flea stick around between the bed sheets or to
roll it over the flea-infested floor, thus disturbing the fleas, which are
caught on the sticky paper. The stick may be easily removed and a
new piece of fly paper put on when necessary.

Animals have been used as traps for fleas in experiments conducted
by the Indian Plague Commission and others. The Commission

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30 BULLETIN 248, U. S. DEPARTMENT OF AGRICULTURE.

found that guinea pigs left free in rooms picked up considerable
numbers of fleas of different species. Men also acted as traps by
going about in an infested room, and the fleas thus picked up were
caught. No doubt rabbits, cats, or dogs could be utilized in the same
way and the fleas destroyed by the methods mentioned under “ De-
struction of fieas on hosts.” This method of picking up fleas is some-
times applicable to certain places in districts where plague exists and
it is desirable to capture and destroy the few fieas which might other-
wise get upon man.

The use of fresh meat to attract fleas onto fly paper and into traps
has been considered to have some merit, but tests made by Drs. How-
ard and Mitzmain and by others show that it is without value.

REPELLING FLEAS.

The usefulness of repellents is even more limited than that of
traps. Many things have been advocated from time to time, or in
different sections of the country, for the driving away of fleas.
Oil of pennyroyal is probably most widely used for this purpose,
and it seems to have considerable virtue as a repellent. This sub-
stance may be applied to the shoe tops, hose, and trousers, or placed
elsewhere on the body or clothing, and its use on bedding and floors
has been advocated by those in flea-infested regions. The penny-
royal plant is used for the same purpose where it grows. Buhach,
oil of cedar, eucalyptus oil, or camphor sprinkled between the sheets
give a degree of protection to those compelled to sleep in flea-infested

places.
ISOLATION FROM FLEAS.

Frequently in many parts of the country outbreaks of fleas are
experienced. In such cases extreme measures are necessary for any
degree of comfort. Knowing that fleas have very limited powers of
jumping in a vertical direction and of crawling on smooth surfaces, it
ig practicable to exclude them from beds. The higher the bed is from
the floor the better, but one may isolate the bed from fleas in most
standard-height beds if care be taken to keep the clothing from hang-
ing down. Of course it is essential that no fleas be taken into the bed
on the body or the night clothing and that the bedding does not touch
the walls or baseboard. It is possible also to isolate a bed or cot or a
person sleeping on the floor, if the floor itself is not infested, by plac-
ing a band of sticky fly paper or paper covered with a sticky sub-
stance 14 inches wide around the bed. In case the legs of a bed are
rough, which permit fleas to crawl up them, a band of sticky sub-
stance may be painted around the bottoms from 4 to 5 inches above
the floor, or, if more convenient, the legs of the bed may be placed in
large pans of water.

FLEAS. on

When the fleas are carriers of disease they are, of course, much
more dreaded than when their greatest injury is their bite. Where
extreme measures are needed the possibility of a man’s protecting
himself from fleas while working in infested locations or even while
sitting in an infested room by wrapping his legs with fly paper
should be borne in mind. A man may get considerable protection
from the sticktight flea by wearing khaki or denim trousers and
having them tucked into hightop shoes. Leather boots with the tops
on the outside of the trousers also keep many fleas from gaining
access to the body.

REMEDIES FOR BITES.

As has been stated, fleas in the act of biting inject saliva into the
wound, thus producing more or less irritation and itching. Ordi-
-narily no treatment of the bites is necessary; but where they are
numerous, especially in the case of susceptible persons, cooling
lotions will give relief. Menthol and camphor are beneficial, and
carbolated vaseline, carbolic acid in water (a 38 per cent solution),
and hydrogen peroxid are each said to relieve the itching and
inflammation. |

WASHINGTON : GOVERNMENT PRINTING OFFICH ; 1915