NOTES

ON: )

ANIMAL PARASITES |
AND PARASITISM

_ LECTURE OUTLINES OF

A COURSE IN PARASITOLOGY

_ WITH SPECIAL REFERENCE TO FORMS OF —
ECONOMIC IMPORTANCE

By WILLIAM A. RILEY

Department of Entomology, Cornell University

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NOTES

ON

Animal Parasites and Parasitism

LECTURE OUTLINES OF

A Course in Parasitology

WITH SPECIAL REFERENCE TO FORMS OF ECONOMIC
IMPORTANCE

By WILLIAM A. RILEY

Department of Entomology, Cornelf University

1912
Li.

PREFACE

This pamphlet is not intended as a text-book on the subject of
animal parasites and parasitism. It consists merely of the out-
lines of an elementary and very brief course on the subject, given
primarily from the general zoological viewpoint. They are printed
in this form to facilitate the taking of notes and to point out the
more important sources of information.

Any such course must be under heavy obligations to the classical
works of Leuckart, Cobbald, Neumann, Railliet, Blanchard, and
other pioneers in the field, and to the work of Stiles, Ward, Ransom,
Law, and their staffs in this country. The little booklet by Franz
von Wagner, entitled ‘“Schmarotzer and Schmarotzertum in der
Tierwelt,” though out of date in some respects, is a most helpful
and suggestive discussion of the general subject.

The bibliographies given are far from complete but indicate
the more important available discussions. Much of the funda-
mental work appears in foreign publications and, as in all scientific
work, a knowledge of at least French and German is invaluable
to the student. It is urged that the opportunity to become ac-
quainted with original papers treating of the subject be improved
whenever possible.

INTRODUCTION

Object of the course—Primarily a study of parasitism from a
biological viewpoint. Nowhere more striking illustrations of the
adaptation of the organism to its mode of life, or more wonderful
life histories. Such studies must underlie rational methods of
control.

Species of economic importance will be discussed when they serve
equally well as others for illustrating the points under considera-
tion. Often a species of no apparent economic importance will
be selected because its life history or habits may best aid in an
understanding of those of more complicated forms.

The relation of parasites to disease an important phase of the
subject which can only be touched upon here. The pathology and
therapeutics of parasitism are subjects of other courses and only
incidentally discussed here. So also the wide series of plant para-
sites, including the bacteria, is omitted, though it includes some of
the most important forms.

The more important text-books and special articles—These
will be listed in the bibliography alphabetically, according to author.
In the text, special references will be to author and date of publica-
tion and the full reference can be found by turning to the bibliog-
raphy. Though the list is far from complete, it may be supple-
mented by the bibliographies in most of the articles included, and
by special lists, such as the “Index Catalogue of Medical and Veteri-
nary Zoology” by Stiles and Hassall, and the “Zoological Record.”

GENERAL PART

GENERAL REFERENCES

Braun, ’06; Ktichenmeister, 57; Law, ’03; Leuckart, ’86; Linstow, '78;
Manson, ’07; Neumann, '92; Neveu-Lemaire, ’08, '12; Perroncito, '01; Rail-
liet, ’95; Stiles, ’07; Wagner, ’02.

Definition of the term “parasite’—Not easily limited. Often
defined as “‘An organism which lives at the expense of another.”
This definition applicable to a predatory species or, in its broadest
sense, to,all organisms. Parasitism not an isolated phenomenon.
For the purpose of this course we may say:

A parasite is an organism which, during the whole or a part of its
life, lives on or in the body of another organism, from which it obtains
its sustenance.

The infested organism is known as the host.

Parasites distinguished from saprophytes, which live on decaying
organic matter. Impossibility of drawing a sharp line between this
method of life and that of true parasites.

Distinguished from predatory species, which typically live on
organisms smaller than themselves, and which immediately kill their
prey. Intergrading.

Parasitism a form of symbiosis.

Symbiosis defined—Symbiosis (syn=together, bios=life) is the
living together or two dissimilar organisms. Parasitism contrasted
with mutualism (typical symbiosis) and with commensalism.

Forms of parasitism—In considering the forms of parasitism one
may distinguish:

Ectoparasites, those which live on the exterior of their host or,
more rarely, in cavities which communicate freely with the surface.
Also known as epizoa.

Endoparasites, those which live within the internal organs.

Temporary parasites, those which visit the host only at intervals,
. contrasted with stationary parasites. Of the latter we may have
periodic parasites, such as bot-flies, or ichneumon flies, parasitic in

only a stage of the life cycle; and permanent parasites, parasitic for
life.

y

6

Facultative, or pseudoparasites are species which are normally.
free-living, but which are able to exist as parasites when accidentally
introduced into the body of another animal. Ex., vinegar-eels,
larvae of blow-flies.

Spurious parasites are objects which have been mistaken as para-
sites and, sometimes, even been given specific names. Ex., plant
hairs, bits of gristle, banana cells, etc. Grosser illustrations are
cases of frogs and lizards claimed to have lived within the human
body.

Structure of the parasite—Adaptation to environment nowhere
more strikingly shown than in the case of parasites. With all the
variety of structure, there are yet certain characteristic modifications
which accompany parasitic life.

Adaptations of two general types:

A. Neoformations—Organs of attachment, as, modified tarsi of
hair-inhabiting lice; suckers of leeches, tapeworms, et al; hooks of
various intestinal parasites. Adaptations in sexual organs, illus-
trated by hermaphroditic forms. Adaptations in eggs of parasites.

B. Degenerations—Reduction of organs of locomotion, as, loss of
wings in parasitic insects; of legs and other appendages of crustacea;
fusion of body-segments; loss of cilia.

Correlated changes in the muscular system. Reduction of the
nervous system and sensory organs.

Loss of alimentary canal.

While these various changes are usually spoken of as degenerations,
it must be remembered that they all have for an end the better
adaptation of the parasite to its manner of life.

Occurrence of parasites—Practically all animals subject to attack—
From amoeba with parasites in its nucleus, or in its body-protoplasm,
to man. Leuckart, ’76, lists 33 species parasitic in man but now
(Neveu-Lamaire, ’08) over 150 species infecting man are known.

Parasites themselves may be infested by other parasitic species
which are then known as hyperparasites.

Numbers which may occur in a single host—In the case of protozoan
parasites of the higher animals there may be countless myriads of
individuals. Of higher forms of parasites a crow examined here had
as many as 2,000 nematode worms in a single drop of blood; chicken
had over 1,000 tape worms. 3500 hookworms have been expelled

7

from man; it has been estimated that in a severe case of trichinosis
60,000,000 of the worms may be present.

Concurrent infection by two or more species in the same individual
is very common. Krause, cited by von Beneden, found in a single
horse over 500 Ascaris, 170 Oxyuris, “‘several millions’’ of Strongylus,
214 Sclerostomum, 69 Taenia, 287 Filaria, and 6 cysticerci! In men,
as many as five species of intestinal parasites at a time, have been
reported (Riley, ’12).

Location within the host—Larger number of species of parasites
occur on the surface of their host or in cavities opening to the surface,
such as the alimentary canal, respiratory, and urinogenital passages.
Other species occur in the muscles, connective tissue, nervous tissue,
the blood, and the lymph. They may live freely within a cavity or
inside of cells or even of cell nuclei.

Early views regarding the origin of parasites—Theory of abiogene-
sis, or spontaneous generation taught by the earlier zoologists and
popularly accepted, even today. Redi’s work in 1668. Others sup-
posed parasites inherited.

Theory of biogenesis or development from pre-existent living forms
extended to internal parasites by beginning of 19th century, but by
most authorities it was then believed that such species originated
from free-living protozoa or other organisms, the theory of hetero-
genesis, or chance development from wholly different species.

The development of the experimental method of study furnished the
key to the problem. Feeding experiments by Ktchenmeister, ’44,
followed by Leuckart, Haubner, Cobbald, and many. others.

Life history of the parasite—‘‘If we only know concerning a certain
animal that it is a parasite, we know but little; thoroughly to under-
stand its history, we must follow out all the separate stages and
conditions of its existence, and especially the circumstances under
which it becomes a parasite.’”—Leuckart, ’86, p. 42.

As regards relation to host, parasites may be grouped as:

a Monoxenous parasites (monos, one; xenas, host), such as live
only in one genus or species of host.

b Heteroxenous parasites (heteros, different; xenas, host), such
as pass different stages of their lives in different hosts, usually belong-
ing to different genera, and often widely distinct.

Intermediate host—Supports asexual or immature form.

8

Definitive host—Supports the sexually mature form.
Passive transfer—Ex., embryos taken with food or drinking water.
Active transfer—Ex., larval hookworms boring into the skin.

Alternation of generations, one or more asexual generations followed
by a sexual generation, very common among parasites.

Simple alternation of generations illustrated by the life history of
the malarial parasite, Plasmodium praecoz. Sexual stage in mosqui-
toes of the genus Anopheles; asexual stage in blood of man.

A complicated type, introducing several generations into the life-
cycle, illustrated by the life-history of the liver-fluke of the sheep,
Fasciola hepatica. Adult in liver of sheep; ciliated embryo in water;
sporocyst in body of snail, giving rise to several generations of rediae;
development of cercariae, which pass into the water, become encysted
on herbage, and are taken up by sheep, in which they become sexually
mature.

The reproduction of parasites—Complicated life-history a disad-
vantage in that it enormously lessens the chances of the species per-
petuating itself. Compensating advantages. The handicap met by:

Enormous fertility typical—Estimated that the beef tape worm
of man produces 150,000,000 eggs per year. Polyembryony of certain
parasitic insects, a hundred or more embryos developing from a single
egg. .

Resistance of eggs and larve of many species—Thick-shelled eggs
of tapeworms, whipworms. Living embryos have been found in
Ascaris eggs preserved for months in strong formalin and other
chemicals. Trichinz may live for months after the infested hog is
killed.

Hermaphroditism commonly met with in parasites, providing
for perpetuation of species by a single individual.

Action of parasites upon their host—Extreme divergence of
views as to injuries caused by parasites. The prevailing views
among medical men and veterinarians who have not especially
studied the question, underestimate possible effects.

Seriousness of direct action largely dependent upon the situation
of the parasite—Multiceps cenurus in the brain causing death of
sheep. :

Drain on nourishment of the host—Direct, or by taking blood.

9

Mechanical disturbances by parasites—Filaria causing elephanti-
asis by stoppage of the lymph passages. Abundance of round-
worms in chickens sometimes causes plugging of the alimentary
canal.

Production of specific poisons by the parasite—By the hookworm,
certain tapeworms, e¢ al.

Centers of infection produced—Injury to intestinal mucosa, or to.
skin.

Dangers from intermittent parasites—Disease carriers.

Economic value of parasites—From our viewpoint, not all para-
sites novious—Parasites an important factor in the control of injurious
species. Fighting insect pests by the introduction of their para-
sites. Hyperparasites of injurious parasites.

Determination of parasites in the living host—Ectoparasites—
Diagnosis usually simple, but cases sometimes complicated by
secondary infection.

Endoparasites—1. Examination of feces for protozoa, eggs
and larve of intestinal and liver parasites (Hall, ’°11). 2. Examina-
tion of sputum for evidence of lung parasites. 3. Examination of
urine for evidences of kidney, bladder, or certain blood parasites.
4. Examination of blood, not only for blood parasites but for patho-
logical conditions indicative of the presence of certain parasites
elsewhere in the body. 5. ‘‘Harpooning”’ for trichine. 6. Clinical
symptoms sometimes sufficient.

Methods of control of parasites—Must be mainly preventive.

Such measures must be based on a knowledge of the life-history of
the parasite.

Destruction of intermediate hosts, when feasible—Mosquitoes
for malaria; stray dogs and coyotes for certain sheep parasites, etc.

Sanitary methods—Cleanliness; sewage disposal; meat inspec-
tion in local slaughter houses; thorough cooking of food; inspection
of uncooked foods; avoidance of infection through drinking water.

Origin of parasites—Parasitic habit not a basis of classification—
A tendency to regard parasites as constituting a natural group.
Older writers grouped various endoparasites together as “helminths.”

10

Relation to free-living forms—Readily seen in ectoparasites and
in certain endoparasites. Clearly shown by the developmental
history of others. All evidence shows that,—

Parasitism is an adaptive phenomenon, originating independently
in widely different groups.

We shall therefore briefly outline the major groupings of animals,
before considering more fully the parasitic forms.

THE ZOOLOGICAL RELATIONS OF PARASITES

INTRODUCTION

Zoological classification—Necessity for classification—Great
variety of animals. Some estimates place number of species as
high as 10,000,000. Popular attempts at classification based on
superficial characters.

Bearing of the theory of evolution on zoological classification—Aim
of naturalists to work out a natural classification, one that will
express blood relationship.

Names and sequences of the different kinds of growps—Animal
kingdom, phyla or sub-kingdoms, classes, orders, families, genera,
species, varieties, individuals.

Characteristics of these groups—Definition of species—‘‘In
general terms, a species is a collection of individuals which resemble
each other as closely as the offsprings of a single parent. As a rule
the pairing of sexes of different species will not be fertile.”—Com-
stock.

Zoological Nomenclature—Necessity for an international code
of nomenclature—(See, Stiles, 05, which should be obtained by
students planning to specialize along zoological lines). Same
species often named independently by two or more workers. Especi-
ally true of parasites, which have been often named by physicians
or others with little zoological training. One species of tapeworm
has received 110 different names.

The more important rules of zoological nomenclature—

1. The name of a species must consist of two words, and only
two, one indicating the genus to which the species belongs and the
second used to designate that particular species.

11

2. The names must be Latin in form.
3. After the name of the species may be the name of the author

who first described it.

4. The valid name of a genus or species can be only that name
under which it was first designated and defined in some published
work, except specific names published before 1758, or changes due
to subdivision of groups. This is known as “The Law of Priority.”

CLASSIFICATION

See Parker and Haswell’s Text-book of Zoology, or their Manual
of Zoology.

Phylum PROTOZOA
Animals in which the entire body consists of a single animal cell.

Subphylum Sarcodina—Protozoa in which the motile organs are
pseudopodia.

Class Rhizopoda—Sarcodina without axial filaments in the pseudo-

podia.

,

Ameba proteus as an example of this class. Habitat of Amceba.
Form. Pseudopodia. Mode of movement. Substance of which
body is composed termed protoplasm. Division of the body into
ectosare and endosarc. Nucleus. Contractile vacuole. Taking of
food. Growth. Reproduction by simple or binary fission. Charac-
teristics of living beings. Definition of the term cell.

Subphylum Mastigophora—Protozoa with an outer cell-integument
and in which the motile organs are flagella.

Subphylum Infusoria—Protozoa with an outer cell-integument and
which are always ciliated either through life or in the young
condition.

Subphylum Sporozoa—Parasitic Protozoa typically without organs
of locomotion, and which reproduce by spore-formation. Group
not a natural one.

Phylum PORIFERA

Not discussed in this course.

Phylum C@hLENTERATA

Not discussed in this course.

12

Phylum PLATYHELMINTHES °
The Platodes or Flat-worms

The flat-worms are bilaterally symmetrical animals, which are
devoid of true metameric segmentation, and which have no body
cavity between the alimentary canal and the integument. There
is no blood-vascular system; but there is an excretory (water-
vascular) system. The alimentary canal when present has only a
Single opening, and is much branched.

Class Trematoda—Parasitic flat-worms, without a covering of cilia
in the adult state, with a well-developed digestive apparatus,
and with the mouth at the cephalic end of the body. The liver-
fluke is an example of this class.

Class Turbellaria—Non-parasitic flat-worms, with a ciliated epider-
mis. Not discussed.

Class Cestoda—Endo-parasitic flat-worms, without cilia, and with-
out a digestive cavity; usually becoming segmented by budding.
This class includes the tapeworms.

Phylum NEMATHELMINTHES
The Thread Worms

The body is cylindrical, spindle-shaped, or threadlike, unseg-
mented, and covered with a thick cuticle; the body cavity is usually
spacious.

Class Nematoda—Possess a complete alimentary canal. To this
class belong most of the thread worms. The most familiar
examples are Ascaris, Oxyuris, and Trichina.

Class Acanthocephala—Lack alimentary canal; possess a protrusible
proboscis which is covered with many rows of recurved hooks.

Phylum ECHINODERMATA

“Not discussed in this course.

Phylum MOLLUSCOIDA

Not discussed in this course.

13

Phylum ANNULATA
The Segmented Worms

Bilaterally symmetrical animals with the body composed of
similar segments or metameres, without jointed legs, and with an
alimentary canal furnished with two openings. Only one of the
classes discussed in this course.

Class Hirudinea—Segments of body marked externally by secondary
rings. Each end of the body is furnished with a sucker. The
medicinal leech is an example of this class.

Phylum ARTHROPODA

See Comstock’s ‘Manual for the Study of Insects’? and “The
Spider Book.”

Bilaterally symmetrical animals in which the body is segmented
. and bears a pair of jointed appendages on each or on some of the
segments.

Class Crustacea—The members of this class are aquatic Arthropoda,
which breathe by true gills. They have two pairs of antenne
and at least five pairs of legs.

Class Arachnida—The members of this class are air-breathing
Arthropods, in which the head and thorax are grown together,
forming a cephalothorax; which have four pairs of legs fitted for
walking, and which have no feeler-like antenne. To this class
belong the spiders, ticks, mites, and others.

Order Acarina—This order includes the mites; these differ from
other Arachnida in that the abdomen is fused with the cephalo-
thorax, giving the entire body a more or less saclike appearance.

Class Myriapoda—This class includes the centipedes and the milli-
pedes, air-breathing Arthropoda in which the thorax and abdomen
form a continuous region, with from six to two hundred segments,
each bearing a pair of legs.

Class Hexapoda—Air-breathing Arthropoda, with a distinct head,
thorax, and abdomen. They have one pair of antenne, three
pairs of legs, and usually one or two pairs of wings in the adult
state. This class is composed of the different orders of insects;
among these are the following:

14

Order Mallophaga—This order includes the bird-lice; these are
wingless parasitic insects, with biting mouth-parts; their meta-
morphosis is incomplete.

Order Hemiptera—This order includes the bugs, lice and others.
The winged members have four wings, but the lice and some
others are wingless; the mouth parts are formed for sucking;
the metamorphosis is incomplete.

Order Diptera—This order includes the flies, among which are the
mosquitoes, bot-flies, the sheeptick, and many others. The
winged members have only two wings; the mouth-parts are
formed for sucking; the metamorphosis is complete.

Order Siphonaptera—This order includes the fleas; the members
of it are practically wingless, the wings being represented only
by minute early plates; the mouth-parts are formed for sucking;
the metamorphosis is complete.

Phylum MOLLUSCA

Not discussed in this course.

Phylum CHORDATA OR VERTEBRATA

Not discussed in this course.

15

SPECIAL PART

I. REPRESENTATIVE PARASITIC PROTOZOA

IMPORTANT GENERAL REFERENCES

Calkins, ’09; Castellani and Chalmers, '10; Crawley, ’12; Doflein, ‘09;
Lankester, ’03; Manson, '07; Ward, ’08.

INTRODUCTION

Parasitic Protozoa—Importance for years overlooked. Pasteur’s,
’58, study of the protozoa causing silkworm disease had great in-
fluence on development of germ theory of disease. In 1880, Laveran
discovered the malarial parasite, but it was not until the beginning:
of the present century that much attention was devoted to parasitic
Protozoa.

Groups of Protozoa concerned—Parasitic forms now known in all
groups except Radiolaria and Foraminifera.

Habitat—Organ, tissue, and cell parasites,—even nuclear parasites
known.

Adaptations—Comparable to those seen in other parasitic groups.

Sub-Phylum SARCODINA

Entameba dysenterie—Ameba coli Loésch; Entameba hystolytica
Schaudinn). Supposed cause of a type of tropical dysentery.
Since Lambl, 1859, amceba known to occur in human intestine but
pathogenic nature disputed. Since work of Schaudinn, ’03, known
that there are two species; one, at least, pathogenic. See, Strong, ’07.

Habitat—Human colon, intercellular; occasionally lower part of
small] intestine and even liver. Walls of intestine greatly thickened
and, in serious cases, ulcerated.

Structure—Essentially that of Amceba (see p. 11); one or two
pseudopods; endosarc granules, frequently containing red blood cor-
puscles; nucleus eccentric, with sparse chromatin.

Reproduction—Two types: Ist, simple division, or budding;
2d, by encystment and spore formation. Autogamy. Method of
dissemination of the parasite. ,

Prophylaris—Heat sterilization of food and drinks.

16

Neuroryctes hydrophobie—(Negri bodies). Diagnosis of rabies a
slow process until Negri’s discovery, in 1903, of peculiar bodies
found in nerve cells of animals affected. Most numerous in cells of
hippocampus major. Size up to 254. Believed by good authorities
to be protozoon in nature because evidence of typical nucleus, growth,
reproduction by simple division and budding. Sarcodina?

Sub-Phylum MASTIGOPHORA

Trypanosoma brucei—The cause of the tsetse-fly disease or
“nagana”’ of domestic animals in South Africa. Duration of diseases
few days or weeks to many months but always fatal in horse and
donkey, very few cattle recover. Supposed to be due to bite of
tsetse-fly. Parasite discovered by Bruce, 1874, free in blood plasma.
See Bruce, ’07, and Laveran and Mesnil.

Structure—Spindle-shaped body, with a more or less spiral
twist and with one edge provided with delicate, undulating membrane.
Flagellum arising near posterior end at a highly refractile granule
known as the “blepheroplast”’ and continuing as the thickened edge
of the undulating membrane, to project at anterior end. A micro-
and a macro-nucleus present.

Movements—Exceedingly rapid. When parasites are abundant,
they may be detected under moderate power by motion of blood
corpuscles. Usually present in small numbers and blood must be
centrifuged to find them. Euglenoid movement.

Reproduction—Longitudinal division. Sexual reproduction in
dispute.

Artificial culture—One of the few forms of protozoa which has
been artificially grown with marked success. First grown by McNeal
and Novy, ’03, on nutrient agar and defibrinated rabbit’s blood.
Influence of this work on study of parasitic protozoans important.

Method of transferral—Solely by tsetse-fly, as shown by Bruce’s
experiments, 1894. Infective for 48 hours after feeding on sick
animals. Evidence that there is then a latent period after which the
flies again become infective.

Prophylaxis—Protection of cattle from bites of the fly. Destruc-
tion of big game.

Related species—Group a large one, over sixty species being known,
some apparently harmless but among them some of the most danger-
ous parasites.

17

Tryanosoma gambiense cause of “sleeping sickness” of man;
T. evansi causes “‘surra’”’ a fatal disease affecting especially horses
and mules in the Philippines, India; 7. equiperdum produces “‘maladie
du coit,” or “dourine,” a venereal disease of horses, of which there
have been serious outbreaks in this country. T. lewisit is apparently
harmless parasite of rats, the world over.

Spirocheta recurrentis Lebert, 1874. (S. obermeirt Cohn 1875).
The cause of European relapsing fever of man. The organism as
seen in the blood is a slender, flexible spiral, pointed at the ends,
with an undulating membrane, but without cilia. Transferred by
bite of the bed-bug. Long classed with bacteria but differ in pos-
session of undulating membrane, reproduction by longitudinal
division and in biological characters. See Nuttall, ’08.

Related species—A number of species infesting man and animals
are known. Disease known collectively as “‘spirochetoses.” In
cases best known the parasites are transferred by ticks.

Trichomonas—Several species of this genus live in alimentary
canal of mammals, birds, snakes, batrachians and lizards. Usually
small, pear shaped; with three or four cilia arising from the anterior
end and an undulating membrane which runs spirally around the
body.

Lamblia intestinalis—Parasite of man and various animals, and
in some cases supposed to cause dysentery. Anterior end of parasite
hollowed out to form a saucer-like depression, which fits over the
epithelial cells. About this depression six flagella and posteriorly,
two others. Cysts containing two individuals to be found in feces.

Sub Phylum INFUSORIA

Balantidium coli In rectum of man and swine. Usually associa-
ted with intestinal diseases when found in man, but causative action
disputed.

Form and structure—Large, 200” long by 50” wide, resembling
somewhat a Paramecium. Body covered with cilia which are longer
and coarser about the peristome or “mouth.” Ectosare and endo-
sare distinct, body with longitudinal stris, or ‘“‘myonemes.” Two
contractile vacuoles. Nucleus bean- or kidney-shaped.

Reproduction—By simple cross-division. Conjugation occurs.
Encysted forms to be found in feces.

18

Balantidium entozoon—This species is commonly found in the
rectum of frogs and will be studied in the practicum. Possesses four
contractile vacuoles.

Various other species of Balantidiwm also infest frogs and certain
ones have been found in the body cavity of annelid worms.

Nyctotherus cordiformis is a form found in the large intestine
of the frog and sometimes mistaken for Balantidium entozoon. Differs
in being larger, having one contractile vacuole, more prominent.
persistome, and less strongly curved nucleus.

Opalina ranarum—Rectum of frog.

Form and structure—Large enough to be seen as minute, whitish,
actively moving spots, 600-800/ in size. Body flat, disk-like, or
oval; divided into ectosare and endosarc. Cilia uniform in size.
Multinucleate. Mouth, gullet, and contractile vacuole lacking,
food being directly absorbed.

Reproduction—Ordinary cross or oblique division. Also, repeated
binary fission, the minute forms so produced encysting and passing
out with feces of the frog, at the breeding season. Taken up by
tadpoles, cyst dissolves, liberating a lanceolate, uninucleate form,
which develops into the adult, multinucleate Opalina.

Sub Phylum SPOROZOA
Order Gregarinida

Coelom-inhabiting sporozoa, reproducing usually by spore-
formation alone, and after the fertilizing union of but slightly dif-
ferent gametes. Following Lankester, ’03, take as a type:

Monocystis agilis—Found in the seminal vesicles of the common
earthworm. The majority of individuals of this worm are infested.

Trophozoite, earliest known stage, minute, nucleated, amceboid.
Lives in one of the sperm morule floating in the sperm sac, and grows
at the expense of the developing sperm cells. Ectosarc and endosarc
present. Motility due to longitudinal myonemes. Adult tro-
phozoite known as

Gametocyte, which is ready for reproduction. Two gametocytes
associate and form a cyst, but do not fuse. Independently within
each gametocyte there is a formation of a segmentation nucleus
which divides repeatedly and with their surrounding protoplasm
constitute the gametes. These fuse in pairs to form

19

Zygotes, or definitive sporoblasts, which by the secretion of tough
membranes, or sporocysts, become spores. Within the spores

Sporozoites are formed by the nucleus of the spore dividing into
two, four, and, finally, into eight nuclei, around each of which some
of the protoplasm of the spore becomes aggregated.

Dissemination of the parasite—By analogy from known forms,
spores pass to exterior, are scattered and then swallowed accidentally
by an earthworm with its food, sporocysts dissolved by digestive
juices, and liberated sporozoites bore through tissues.

Occurrence of Gregarinidee—Invertebrate hosts, mainly insects,
but generalized life cycle makes them important objects of study.
Disseminated passively, infection of host being by way of the ali-
mentary canal. Majority of species probably harmless to their hosts.

Order COCCIDIIDIA

Cell-infesting sporozoa which usually reproduce intracellularly by
asexual spore formation (schizogony), as well as by true sporogony,
thus giving a life-cycle with an alternation of asexual and sexual
generations. After fertilization the oosphere forms sporoblasts
which may or may not be covered by a sporocyst membrane, and
which may each become transformed into one or several sporozoites.
Take as a type

Coccidium schubergi—(See Leuckart-Chun’s Chart 103, and
Schaudinn’s explanation thereto. For detailed account see Schau-
dinn, 00). Intestinal parasite of a myriapod, Lithobius forficatus.
Infection by encysted sporozoites taken up with food. Alternation
of generations.

Sporozottes released from cyst by action of digestive juices of host,
fig. 1. Penetration of epithelium, fig. 2. Mature sporozoite known
asa

Schizont, (fig. 4), Nuclear division. Schizogony, giving rise to
numerous

Merozoites, (fig. 5), as the asexual elements are called, in contra-
distinction to the serually produced sporozoites. Repeated
schizogony. From certain merozoites develop

Gametes—Macrogametes, (fig. 6). Microgametoblasts, (fig. 6a).
Maturation of the macrogametes. Formation of the microgametes

20

from the microgametoblast, (figs. 7a and 7b). Fertilization of the
macrogamete and formation of an

Oocyst—Segmentation nucleus. Sporogony, (figs. 10-13), the
breaking up of the oocyst content to form

Sporoblasts, (fig. 11), which by further division give rise to
Sporozoites—Migration of the sporozoites.

Eimeria stiedea—(Better known as Coccidium oviforme). Causes
common and very serious disease of rabbits, occurs rarely in man.

Description—Infests epithelium of bile ducts, as egg-shaped bodies
varying considerably in size (the smaller 26-35 long by 14-20, wide;
larger ones 40-49" long by 22-28 wide); with smooth, thick shells
having a micropylar-like depression at one pole. Granular contents
sometimes distributed uniformly or sometimes collected into a
spherical mass. Resemble very greatly eggs of certain parasitic
flukes and have been so described. In this stage they pass from the
liver and intestines to the exterior where, in presence of moisture,
their contents segregate into four oval spores which become sur-
rounded by a tough sporocyst. Within each sporocyst are formed
two sporozoites. (Note that the excellent account of Leuckart, ’86,
erroneously refers to these spores as developing into a single sporozoite.)
Sporocysts taken up with food by rabbits and the released sporozoites
by amceboid motion pass into the tissues. Useless to treat diseased
animals. Avoid crowding, isolate diseased rabbits, and keep runs
dry and clean.

Order HEMOSPORIDIA

Blood dwelling sporozoa, intracorpuscular or free in the blood-
plasma; with or without alternation of hosts. A somewhat hetero-
geneous group, of which we shall consider two representatives.

Plasmodium praecox—The genus Plasmodium contains the
organisms of malarial fever. Three species generally recognized.
True alternation of generations, combined with a change of host.
The asexual reproduction, or schizogony occurs in the blood of man;
the sexual sporogony in the alimentary canal of a mosquito. Follow-
ing Schaudinn, we shall describe the life cycle best worked out, that
of P. praecox, the cause of pernicious malaria. See Leuckart-Chun’s
Chart, 102, and Schaudinn’s explanation thereto. Compare the life
cycle of Coccidium schubergii, as given above.

Q1

Schizogony. (Figs. 1-6). Sporozoite penetrating a red blood
corpuscle and developing into a schizont. Nuclear multiplication.
Schizogony, producing merozoites.

Gamete-development. Under certain conditions there appear
sexual forms whose further development can take place only in the
body of a mosquito. (Figs. 7-11). Macrogamete corresponding to
the egg. Maturation. Microgametoblast from which develops the
microgametes. Fertilization. Migratory ookinete penetrates the
epithelium of the mosquito’s stomach, (cf. the encysted oocyst of
Coccidium).

Sporogony—Oocyst in submucosa of mosquito intestine. Forma-
tion of sporoblasts. Sporozoites. Escape of sporozoites into body
cavity and collecting in salivary glands.

Dissemmination of disease. Solely through mosquitoes of the
genus Anopheles. Methods of control considered more fully in
discussing mosquitoes.

Babesia bovis—(Pyrosoma bigeminum Smith and Kilborne;
Piroplasma bigeminum Patton.) The “Texas fever’ organism,
discovered by Smith and Kilborne, 1893.

Form and habitat of asexual phase—Lives within the red blood
corpuscles and in fresh preparations appear as minute homogeneous
pale pear-shaped spots, usually two in a corpuscle. From 2—4z in
length and 1.5-2» at widest portion. The common appearance of
two associated parasites is due to dividing forms. Live at expense
of red corpuscles, as many as 50 per cent of which may be infested.
Bloody urine, characteristic of disease, due to breaking down of
corpuscles.

Life cycle—Transferred from animal to animal solely by cattle
ticks (Boophilus annulatus) of the second generation. By analogy,
a sexual cycle in the tick, but it has not been satisfactorily worked
out. Note that we have here a case of true hereditary transmission
of a disease, the adult ticks passing it on to the second generation
which, in turn, infects cattle.

Methods of control—Primarily a problem in economic entomology,
—the protection of cattle from the tick and the extermination of the
tick.

Related species—Babesia parvum, in African cattle; B. canis,
in dogs; B. ovis, in sheep; and various others, causing similar

22

diseases of the type known as piroplasmosis. Babesia hominis
cause of ‘spotted fever” of man in Montana and Idaho.

Order SARCOSPORIDIA

Sporozoa found in or between the muscle-cells of vertebrates,
appearing as whitish, elongate-ovoid bodies. Great sac-like spore
cases, with double membranes, are formed. Take as a type.

Sarcocystis miescheriana—Trophozoites occur commonly ard
in great abundance in the muscles of hogs. Large, .6 or even 2-3mm.
in length, and sometimes visible to naked eye as greyish points. Wall
of a thick cuticle, transversely striated. Content, even in very early
stages granular from ‘presence of great numbers of rounded “‘pan-
sporoblasts.”’ The content of pansporoblasts divides to form finely
granular, pale sporoblasts, in each of which develops a spore. Method
of transfer from host to host unknown. Effect on host disputed but
where they occur so abundantly they must cause injury. Evidence
that there is an active poison secreted by the parasite itself. Laveran
and Mesnil claim to have isolated such a toxin, which they call sarco-
cystin, from Sarcocystis tenella, of the sheep.

Order MYXOSPORIDIA

Parasites of cold blooded animals, especially known as causing
serious epidemics among fish and in silk worms. Often called
psorosperms. Characterized by facts that the trophozoite is amoe-
boid; spore formation commences at an early stage and proceeds
continuously during the growth of the trophozoite; spores are pro-
duced within the protoplasm of the trophozoite, and each spore
always possesses one or more very distinctive structures known as
“polar capsules’’—Lankester, ’03.

Nosema bombycis—The cause of ‘‘pebrine” or silkworm disease
which, until the work of Balbiani and of Pasteur, threatened to wipe
out the silk industry of France.

Form—In tissues of host as a microscopic corpuscle enclosing
numbers of spherical sporoblasts from which develop many sporozo-
ites. Spores oval, 3 long by 1.5u wide, characterized by the peculiar
“polar-capsule” and by a polar filament which is rendered visible by
the action of reagents.

23

Development—Two methods of spread of the disease. Ist, spores
scattered on leaves are swallowed by young caterpillars, the polar
filament is expulsed, the capsule splits and an amoeboid trophozoite
emerges which bores into the tissues of the caterpillar. 2d, the
parasites reach the ovaries and infest the eggs of the host. From
these infested eggs are hatched weak, diseased caterpillars which,
though they soon die, contaminate the food.

24

II. REPRESENTATIVE PLATHYELMINTHES

Class TREMATODA
IMPORTANT REFERENCES

In addition to the general works of Braun, Leuckart, Neumann, Railliet,
et al., see, Benham, ‘03; Braun, ’89; Gamble, '96; Loos, '94; Stiles, ‘04;
Ward, ‘04.

Order MONOGENEA

Almost exclusively ectoparasites. With more than two suckers
and often with hooks. Development direct and without change
of host. Take as an example:

Polystomum integerrimum—Lives in bladder of frogs.

Description—Mature fluke .5cm. long by .15cm. wide, flattened,
with four eye spots on anterior end. Alimentary canal bifurcate,
the two branches connected by many cross-canals. Six suckers at
posterior end and between them attachment hooks.

Life history—Eggs laid in water by protrusion of body of the
parent through urinary aperature of the frog. About 1000 eggs in
tendays. After about six weeks free swimming ciliated larva hatches,
but perishes if it does not meet a tadpole within twenty-four hours.
If fortunate, attaches to gills of the tadpole, loses cilia, and remains
eight to ten weeks, forming suckers from behind forwards. When
tadpole transforms the Polystomum enters oesophagus, passes down
intestine and enters bladder of the frog. Said to require three years
to reach sexual maturity.

Diplozoon paradoxum— Well named, for one of the most puzzling
of animal forms. Adult X-shaped organism made up of two fused
individuals. Eggs on gills of various small fish give rise to ciliated
larvee which, if they succeed in attaching to a minnow develop into
a larval form long known independently under generic name Diporpa.
These Diporpa develop and mature sexual organs only by conjuga-
tion in pairs. Fuse at point of contact and within each complete
sets of genitalia develop.

25

Order DIGENEA

Exclusively endoparasites. Not more than two suckers, and
without hooks. Development with heterogony and with change of
host; the sexual generation in vertebrates, the asexual in inverte-
brates. Take as an illustration

Fascolia hepatica—(Distomum hepaticum)—The liver-fluke of the
sheep and other ruminants. Adult in liver, causing “rot.” Though
not common in the United States, it is one of the most dangerous
parasites of sheep, sometimes causing enormous loss in Europe.
Youatt estimated that in Europe alone more than 1,000,000 sheep
die annually from its attacks.

Structure—Adult flat, unsegmented, oval, enlarged in front,
about 3.4 cm. (1.5 inch) inlength. Two suckers near anterior end,
cuticle covered with minute backwardly directed spines. Digestive
system branched, ramifying all over the body. Excretory system
much branched, main duct opening to exterior caudal end. Re-
productive system hermaphroditic, with very prominent yolk glands.

Life history—Adult in liver of a sheep; discharges of eggs via
the bile ducts of the sheep; development of eggs only in water
to form the ciliated embryo; entrance of embryo into the body of
a snail; change to a sporocyst; development of redie in sporocyst;
second generation of redie; development of cercarie; passage of the
cercarize into the water; encysted cercarie; passage of young fluke
to the liver of asheep; development into an adult fluke.

Methods of control—Medical treatment of little avail and _pre-
ventive measures very important. Drain pastures to destroy snails;
keep sheep away from damp pastures. Carp, frogs and toads may
play an important role by feeding on snails. Destroy bodies of
diseased animals and spread manure from such animals only on dry
ground.

Related species—Stiles, °94, lists twelve species of liver-flukes
found in man and the higher animals. Of these the following are
especially deserving of mention:

Fasciola magna—Widely distributed in the United States, espec-
ially Southern, being apparently much more common in sheep and
cattle in this country than T. hepatica.

Opisthorchis pseudofelineus Ward 1901, found in gall ducts of the

domestic cat. Closely related species 0. felineus in Europe occasional
parasite of man.

26

Paragonimus westermanni—The lung-fluke of hogs, cats, dogs;
causes a very serious lung disease of man. Symptoms sometimes
mistaken for those of tuberculosis. Asiatic disease but the species
has in recent years been found in United States (see Ward, ’95).
Readily diagnosed by presence of eggs in sputum, as many as 12,000
daily discharged in one case studied.

Schistosoma haematobium, the ‘‘blood-fluke” of man. The worms
occur in pairs in portal vein and in veins of intestine and bladder
wall. Eggs, provided with a stout terminal spine work through
tissues into the lumen of the intestine and bladder, often causing
serious malady. In Porto Rico and South America occurs a form
with lateral spined eggs, Schistosoma mansoni.

Class CESTODA

IMPORTANT REFERENCES

Braun, '94—’00; Cobbald, ‘79; Davaine, ’77; Hall, '12; Stiles, ’98 and ‘06;
Ward, ’or.

The greatest confusion still exists in the classification of the
Cestoda. This is due to the facts that the same species has been
independently described and named from different hosts, or that
different stages have been known under different names, and more
to the fact that the life histories of many common species are un-
known. We shall discuss a few representative forms, using as a type:

Taenia solium—The pork tape-worm of man. About ninety
synonyms. Adult in small intestine of man. Immature stage
primarily in hogs but occasionally in man, and reported for dog,
eat, black rat, and various other animals.

Form and structure—Body ribbon-like, forming a chain of many
segments; total length usually 2-4 meters. Head, or scolex, minute
(1 mm.) globular, with apical rostellum provided with a double row of
hooks, and with four suckers. Head followed by a short unseg-
mented neck, following which is a series of segments or proglottids,
800-1000 in number. Alimentary canal, circulatory, and respiratory
apparatus entirely lacking. Nervous system of two longitudinal
cords connected in the head and extending throughout the
body. Excretory system of two longitudinal canals communicating
by cross branches in each proglottis. Near middle of one side of
each proglottis a genital papilla, or pore. Reproductive organs occupy
almost entire segment, hermaphroditic, male organs developing

Q7

before the female. Male organs: testes, efferent ducts, vas deferens,
cirrus, or penis, penis sac. Female organs: ovaries, oviduct, yolk
gland, shell gland, uterus, receptaculum seminis. Ripe proglottids
have sex organs, except enormously enlarged uterus, atrophied;
are little more than sacs of eggs, of which it is estimated that there
may be as many as 50,000 in each. Terminal proglottids break off
and pass out with feces.

Life history—Independent life of the free proglottid; scattering
of the eggs; the six hooked embryo taken up with food by hog or man;
migration of the embryo from the alimentary canal of its host (swine
or man) to the muscles or other organs; formation of cysts, ‘‘measles”’
each containing the invaginated head of the future tapeworm, (the
Cysticerus stage). Development of the adult from the cystic state.
Possibility of autoinfection renders T. solium a dangerous species.

Interpretation of structure and life history—Two views; Ist, that
there is a true alternation of generations, the tape-worm representing
a linear colony of which the proglottids are the sexual individuals,
produced by budding from an asexual scolex. 2d, that it is to be
regarded as a segmented individual, comparable to an Annelid.
Anatomical facts opposed to “‘colony”’ theory. According to second
theory, the formation of proglottids a process of accelerated re-
generation.

Frequency of occurrence in man—Relation to food habits. Very
uncommon in U.S. Confusion with 7. saginata.

Prevention—Avoiding imperfectly cooked pork; meat infection.

Other species infesting man in this country—T. saginata, the
beef tape-worm; Hymenolepis nana; Echinococcus granulosus, adult
in dogs; Dipylidium caninum, normal host, dogs; Dzbothriocephalus
latus, larva in fish.

Dipylidium caninum—(Taenia cucumerina). Commonest para-
site of pet cats and dogs. Occasionally in children. Size small,
15-30 cm. Structure, head with retractile rostellum, 4 rows of hooks;
proglottids resemble cucumber seeds in shape; two genital pores and
double sets of sexual organs.

Life history—Eggs in capsules. Larva a cysticercoid, parasitic in
dog louse or dog flea. Transfer by dog biting infested fleas. Infec-
tion of humans by accidental ingestion of an infested flea, (see
Blanchard, ’07).

28

Echinococcus granulosus—The hydatid tape-worm. According
to Styles, there are 110 synonyms. Often known as Taenia echino-
coccus. Adult in dog, .20 inch or less in length. 3 segments and head.
Larva in a great variety of hosts, man, cattle, sheep, hogs, et al.

Life history—Cystic stage may attain size of an orange, or even
of a child’s head. Within this cyst there develop by budding a great
number of broad capsules, each containing from 1-120 heads capable
of developing into tapeworms. For detailed account of life history,
see Leuchart, ’86.

Multiceps coenurus—(Taenia coenurus, Coenurus cerebralis).
The tapeworm whose larva in the brain or spinal cord of sheep
produces the fatal disease known as “‘gid’’. Adult in small intestine
of dog, eggs scattered with feces over herbage and taken up by sheep.
Embryos migrating to brain develop into cysts which may reach
size of a hen’s egg. On the interior of these cysts are to be found
many invaginated heads of the future worm. May be as high as
500 to a cyst.

Prophylazis—Burn infested heads of sheep to prevent infection
of dogs; by direct treatment keep dogs free from the tapeworms,
and avoid possible contamination of pastures. The parasite has not
yet gotten established in this country and law requires quarantine
and examination of feces of all imported collies. (See Ransom, ’05).

III. REPRESENTATIVE NEMATHELMINTHES

REFERENCES
In addition to the general texts already cited see, especially, Hall, °12;
Neveu-Lemaire, 12; Ransom, '11; Stiles, ‘07; Ward ’03; and the special arti-
cles cited in discussing various species.

Class NEMATODA

The great majority of the Nematoda, or “‘thread-worms,” are
internal parasites of animals in the whole or part of their life but
some infest plants and many live free either in water or damp earth.
The classification of this group is in a very unsatisfactory condition,
but we shall follow Neveu-Lemaire in arranging the families and
shall discuss a representative of each. This grouping does not
differ essentially from that used by Ransom, ’11.

FAMILIES OF NEMATODA
(As defined by Neveu-Lemaire, *12)

Ascaridae—Body relatively thick; mouth usually surrounded
by three lips, which are often supplied with papillae. One lip dorsal,
the two others touching on the median line of the ventral surface.
Oesophagus long, muscular, swollen posteriorly and at times followed
by an oesophageal bulb. Males provided with one (Oxyuris) or usu-
ally, two spicules. Females with a double ovary; oviparous.
Development direct. Ascaris, Heterakis, Oxyuris, et al.

Strongylide—Body elongate, cylindrical, rarely filiform. Mouth
in some cases terminal, in others inclined towards the dorsal or ventral
surface. Oesophagus more or less swollen posteriorly but never
with a posterior bulb. Males with a caudal bell-shaped bursa
supported by thickened rays, the so-called hooks, and with two
equal or subequal spicules. Vulva may be in front of the middle of
the body but is usually behind the middle. Many species formerly
included under the genus Strongylus are included in this family
under various generic names; includes also the hookworms, gape-
worm, et al.

30

Trichotrachelidae—Body very long, anterior end produced into
a long and slender portion; posterior more or less swollen, containing
the genital organs. Mouth round and devoid of papillae; oesophagus
very long and traverses a peculiar strand of ‘cells; no oesophagus.
bulb. Anus terminal. Males with single or no spicule. Only one
ovary; vulva at the origin of the swollen part of body. Represen-
tative genera Trichuris and Trichinella.

Eustrongylidae—Caudal bursa without thickened rays and with
asingle spicule. Eustrongylus, Hystrichis.

Spiruridae—Caudal bursa closed and vesiculate, entirely embrac-
ing the posterior extremity of the body. The two spicules unequal.
Physaloptera. :

Filaridae—Body long and filiform; mouth, of variable form, with
papille, or with two lips. Oesophagus slender; no oesophageal bulb.
Males with coiled tail and with a single spicule or two unequal spicules.
Females with two ovaries; vulva at the anterior part of the body.
Representative genera Filaria, Spiroptera, Dispharagus.

Gnathostomidae—Body cylindrical, covered for all its length or
merely anteriorly by chitinous lamellae, most of which have the
posterior border spinulate. Anterior extremity often swollen into
a globular head clothed with simple spines. Mouth with two lips,
a dorsal and ventral. Males with a spirally-coiled tail, whose
ventral face is provided with papallae, and with two spicules. Ovary
double, vulva back of middle of body. Oviparous.

Anguilluidae—Small size, filiform; mouth followed by a small.
cavity, the vestibule, containing a chitinous spine, or teeth. Oesopha-
gus swollen into a fusiform bulb, often followed by a second bulb,
with or without a dental armiture; posterior third of the oesophagus
may be simply thickened. Males with two equal spicules; at times
with a caudal cuticular expansion. Ovary double; vulva posterior
of middle. Oviparious. Most of this group are free-living. Anguil-
lula.

Angiostomidae—Heterogenos forms, that is, having two types
of sexual generations. Genus Strongyloides.

31

Family ASCARIDAE

Ascaris lumbricoides—Intestinal parasite of man and of hog.
That of the hog has been regarded by some writers as a distinct
species, Ascaris suilla.

Form and structure—Body milky-white, long (males 15-17 em.;
females 20-25 cm.); elastic and pointed at the extremities. Resem-
bles a large earthworm. Head with three lips,—a dorsal and two
ventro-lateral,—bearing papillae. Male has caudal end curved
towards the ventral side and bearing two spicules. Female with
caudal end conical and straight; vulva about the anterior third of
the body.

Development—The ellipsoidal egg 60-75 long covered by a
transparent mammillated sheath which gives it a very characteristic
appearance. Scattered with feces, are capable of direct develop-
ment, without any intermediate host, when ingested by man or hogs.

Heterakis vesicularis—A roundworm of chickens. Lives in
caecum and sometimes present in such numbers as to cause death
by mere mechanical obstruction. Males 7-13 mm. long, spicules
unequal; female 10-15 mm. long. Adults and eggs pass out with
droppings of the fowls and, developing in presence of moisture,
without intermediate host, give rise to adults when swallowed by
chickens. Best controlled by cleanliness in yards, shifting to un-
contaminated soil, soil sterilization or even by deep ploughing or
spading.

Family STRONGYLIDAE

Bunostomum phlebatomum—(Monodontus phlebatomus). A
“hookworm”’ of cattle, occurring in the small intestine. See, Conradi
and Barnett, Bull. 137, South Carolina Exper. Sta. Male 10-12. mm,
female 16-19 mm. Mouth cavity enlarged to form a buccal capsule,
with strong dorsal tooth projecting forward into its cavity and with
two ventral buccal teeth and two subventral buccal teeth or lancets.

Necator americanus—(Uncinaria americana, Ankylostoma ameri-
cana). The American hookworm. The cause of uncinariasis, one
of the most important and most common diseases of the South,
Porto Rico, Cuba and other parts of tropical America. Charac-
terized by great anemia, weakness, colicky pains, perverted appetite,
such as “dirt eating’, inertia. Victims often underdeveloped

32

mentally. Disease sometimes fatal. See Ashford and Igaravidez,
11; Stiles, °03, and the publications of the Rockefeller Sanitary
Commission.

Description—Adults 7-11 mm. long, possesses a dorsal and a
ventral pair of lips, a prominent dorsomedian tooth and four lancets.
As in other Strongylidae, the bell-shaped caudal bursa of the male
is supported by ray-like thickenings which form the so-called ‘‘hooks’’.
Females contain segmenting eggs; vulva in the anterior half of the
body.

Development—The thin-shelled eggs, 64-72 long by 36-40 broad
are deposited in early segmentation stage, reaching the open with
feces. In warm weather larva 210 long will escape before end of
first day, or at any rate soon after. In a few days larva grow to
560-600» and molt; soon a second molt occurs but old larval skin is
not cast off. In this condition many live for four or five months.
Enters man either through the skin (causing the well-known “ground
itch” or, occasionally, with water or food.

Prophylaxis—Avoidance of soil pollution; use of sanitary privies,

wearing of shoes. Medical treatment simple but should be under
control of a physician.

Related species—Agchylostoma duodenale, the Old World hook-
worm of man long known as cause of “tunnel disease’, ‘‘miners
anaemia”’, etc. Agchylostoma caninum cause of a pernicious anaemia
of dogs.

Syngamus trachealis—The gapeworm of birds. Lives in the
trachea and large bronchi of many species of birds. Causes enormous
loss of young chicks and pheasants. See Theobald, 96; Megnin, ’06.

Description—Body cylindrical, red, head broad and truncated.
Mouth large, circular depression, supported by a circular capsule;
at the base of this capsule are six horny, pointed processes around
the opening of the oesophagus. Male from 2-6 mm. long, the female
varies from 10-20 mm. (Theobald). Mature male permanently
attached to the female, the two forming a V-shaped compound.

Development—Eggs not laid but escape by the rupture of the
parents body, being coughed up by the birds. Develop in water or
damp ground in 7 to 40 days, according to temperature, and when
taken up by birds reach the air passages and develop into adults.
No intermediate host necessary, though embryos may remain alive

33

in alimentary canal of earth worms and thus be transferred to
chickens.

Symptoms of the disease—Chief symptom the “yawning’’ or
“oaping” with widely opened beak and straining forward of the
neck. Wheezing cough and frothy saJiva sometimes to be noted.

Prophylaxis—Remove all fowls known to be infected; bury
deeply or, better, burn heads and necks of all dying from the disease.
Disinfect houses and runs with one per cent solution of sulphuric
acid or by heat. Frequent change of yards, and care to have yards
in dry clean places will do much to lessen disease. Mechanical
removal of parasites from trachea unsatisfactory.

Family TRICHOTRACHELIDAE

Trichinella spiralis—(Trichina spiralis). The cause of trichinosis,
a serious disease of man caused by eating pork infested with the
larvae of this worm. See Leuckart, ’66; Ransom, ’07; Stiles and
Hassall, 01.

Description—Adults inhabit the small intestine of man, hogs,
rats, and various other mammals for a short period after ingestion
of infested meat. Very small, barely visible to the naked eye.
Males 1.4-1.6 mm. in length, no spicules, but with two conical caudal
appendages, behind which are four papillae. Females 3-4 mm. in

length, viviparous, possess but one ovary; vulva ventral in anterior
fifth of body.

Life history—Female is fertilized while in the intestine of host
and soon begins to produce young,—1,500 or more, each—which
both by active migration and by transfer by the lymph or blood are
distributed throughout the entire body. Begin to reach the striated
muscles about the tenth day after infection, and up to the eighth
week enter fibers and there encyst. Lemon shaped cysts, formed by
modified tissues of host, each containing a coiled sexual larva. An
ounce of badly infested meat may contain 4,000 cysts. Cysts may
become calcified and larvee remain alive in them for many years.
When the infested flesh is eaten the larvee are released and obtain
sexual maturity in two days.

Symptoms of trichinosis in man—Severity of symptoms depends
on number of larve ingested. While in the intestine, may cause
gastro-intestinal irritation, nausea, abdominal pains, diarrhoea and
fever. From the seventh to the tenth day and later, the migrating

34

larvee cause more or less fever, muscles tense, swollen, and painful
on movement or pressure. Trichinosis often mistaken for typhoid,
and muscular pains sometimes mistaken for rheumatism.

Diagnosis—Examine suspected port for cysts. During first two
weeks after suspected infection examine feces for adult worms.
Marked eosinophilia accompanying ‘‘muscular rheumatism” may
be indicative of trichinosis and in such cases excision of a minute
piece of patient’s muscle, and microscopic examination may reveal
cysts.

Prophylaxis—Avoidance of imperfectly cooked pork in any form.
Microscopic inspection not trustworthy. Destruction of rats,
which seem to be the normal host of this worm.

Family EUSTRONGYLIDAE

Eustrongylus visceralis*—The giant strongyle, or kidney-worm
of the dog is the largest of nematode worms. Males may attain
length of 40 cm., females even 1 meter, blood red in color. Eggs pass
out with urine and embryo develops in presence of moisture. Further
development not known; has been thought to occur in fish but
experiments have failed to justify this view.

Family SPIRURIDAE

Unimportant and not discussed in this course.

Family FILARIIDAE

Filaria immitis—Adults found in the right half of the heart of dogs,
usually causing death. Larval forms in enormous numbers in blood
of host. For good, up-to-date summary see Neveu-Lemaire, 12;
or Manson’s, ’07, discussion of F. bancrofti.

Deseription—Adults have the general family characteristics of
Filariidae. Males 12-18 cm. long, tail tapering, spiral, and with two

lateral wings. Two unequal spicules. Females 25-30 cm. long, tail
short and obtuse.

Life history—Female viviparous, larvae 290” long, escape into
blood of host whence they are taken by a mosquito. In the body

*According’ to the rules of zoological nomenclature this name must be re-
placed by Dioctophyme renale (Goeze 1782) but in order to avoid confusion we
have followed Neveu-Lemaire’s in the generic as well as the family name.

35

of the mosquito they enter the Malpighian tubes, undergo a meta-
morphosis, develop rudimentary sexual organs, and finally, about the
twelfth day, destroy the tubes of the mosquito and come to lie in
the proboscis. When such an infected mosquito bites a dog the
larvee pass to the heart of the dog and there develop into the adult
stage.

Related species—Filaria bancroft? a very common parasite of
man in the tropics, being one of the causes of elephantiasis. It was
in this species that the agency of the mosquito as an intermediate
host was first worked out. F. medinensis, or guinea-worms undergo
one stage in crustaceans Cyclops. Another species of Filaria is very
common in the blood of crows, almost 50 per cent of those about
Ithaca being infested. Its life cycle has not been satisfactorily
worked out.

Dispharagus hamulosus—A representative of the family Filariidae
which infests the gizzard of chickens, being imbedded in the muscles.
It has been reported a few times from widely remote regions (Brazil,
Italy), but seems to be not uncommon in New York State. Life
history not known but it has been thought that the sow-bugs or pill
bugsq (Oniscus) serve as intermediate hosts. The ravages of this
parasite seem to be serious and the writer would be glad to receive
specimens or any data to aid in a study of life history.

Family GNATHOSTOMIDAE

Gnathostomum hispidum—Found in the stomach of hogs. Not
discussed in this course.

Family ANGUILLULIDAE

_ Anguillula aceti—The vinegar eel. This nematode which nor-
mally lives free and is very commonly found in vinegar, has been
reported several times as occurring in the human bladder. See Stiles
and Frankland, ’02.

Other species of this family, normally living on vegetables, have
been occasionally ‘reported as parasites of man.

Family STRONGYLOIDES

Strongyloides stercoralis—The Cochin China diarrhoea worm.
Occurs primarily in the tropics but cases are occasionally imported.

36

Description—Like others of the family Strongyloides this species
occurs under two forms, a parasitic generation and a free-living genera-
tion. The parasitic adults are females only, reproducing parthenoge-
netically. They measure 2.2 mm. in length, four lips, oesophagus
one-fourth as long as body. Anus opens shortly in front of the
pointed end of the body; genital opening in the posterior third of
the body. Free-living adults are of both sexes. Males .7 mm. long,
posterior end rolled up to form a hook; the two spicules small and
much curved. Females 1 mm. long or a little more; tail end straight
and pointed.

Life history—The parasitic forms bore into the intestinal mucosa
and deposit their segmenting eggs, 50-59 x 30-34 in size. These
hatch out into the so-called rhabditiform embryos about .2 mm. in
length which grow to double or three times that size in the lumen
of the intestine end and are passed out with the feces. Under
favorable conditions they molt and become mature in a day or so,
copulate, and females deposit thirty to forty eggs from which there
develop a generation of free-living rhabditiform young. These molt
and transform into larvee which resemble the adults found in the
intestine. It is these ’’Strongyloid” larve which infect man, either
by being taken in with water or food or by boring into the skin as do
the hook worms.

Diagnosis—Examination of feces for the rhabditiform larve.

37

IV. REPRESENTATIVE ARTHROPODA*

IMPORTANT REFERENCES t+

In addition to the general references and to special papers cited in the text,
see Comstock, ’95, ‘12; Huber, ’99-03; Megnin, ’80, ’06; Nuttall, ‘99;
Osborn, ’96.

Class ARACHNIDA
Order ACARINA

For characteristics of this order, see p. 13 of this outline and for
general discussion of the group see, especially, Banks, ’04, Ewing, 712.

Superfamily TROMBIDOIDEA

Harvest mites—Last part of palpus forms a thumb to the preced-
ing, which ends in a claw.

Trombidium holosericeum—‘‘Leptus irritans’’, the “red -bug’’,. or
so-called “‘jigger” or ‘“‘chigger”’. Minute, exceedingly annoying
parasite of man and some animals in our central and southern states,
England, South of France, Germany, and tropics, burrowing into
the skin and causing intense itching, redness and swelling. Distinct
from the true “‘chigoe’’, or jigger, which is a flea.

Description—Red, almost microscopic. 230 longest diameter,
larva of a free living mite. Six legs, with prominent claws on the tips,
and with a powerful hypostome which they drive through the skin.

Habits and life history—Only the larvee parasitic and they on man
abnormally so, for they die after entering the skin. Common
species on the housefly in autumn and on grasshoppers. Adults
predaceous, one species commonly feeds on grasshopper eggs. Adults
hibernate and deposit eggs in or on the ground.

*The question of the relation of Arthropods to disease is the subject of a
special course, and hence this important phase will be but incidentally consid-
ered here. For special bibliography see Riley, ’12a.

tIn addition, the publication of the Bureau of Entomology and the Bureau
of Animal Industry should be consulted, whether specifically cited or not. The
bulletins of the Public Health and Marine Hospital Service also contain much
of importance along this line.

38

Relief from attacks—Flowers of sulphur or powdered naphthalene
in stockings and underclothing, or rubbing in vaseline or bland oil
protects. As palliatives, warm, salt baths, ammonia, or sulphur
ointment. Destruction of mites on lawns, etc., by close cropping
sometimes feasible.

Superfamily IXODOIDEA

Ticks—Large, breathing pore on each side of the body, above
3d or 4th coxa; ‘“‘tongue’”’ large and roughened with sharp teeth.
Not only many serious parasites, but various species are now known
to play important roles in the transmission of diseases of man and
animals. See Banks, ’08; Nuttall, 08-12; Salmon & Stiles, ’02,
and many valuable reports of the Bureau of Entomology and the
Bureau of Animal Industry, on life history, habits and classification.
Two families.

A—Argasidae—Lack scutwm (firm, chitinized dorsal shield); no
marked differences in general appearance between sexes. Palpi
composed of long, cylindrical joints which enable them to move in
a leglike manner. Nymphs and adults moderate and rapid feeders,
engorging and then leaving host and hiding in cracks and rubbish.
As an illustration:

Argas persicus, a chicken tick. (See Hassall, 00). Cosmopolitan
in distribution, occurring among other regions in southern United
States, South America, Persia, Egypt, Australia, et. al., though it
has often been renamed, as a new species. In some regions transmits
a serious disease (spirochaetosis) of fowls.

Description—Body usually flat and thin, much like a bedbug,
one-fourth inches long, outline oval, deep reddish brown. Tegument
roughened by wrinkles and folds and marked by circular pits. Head
or capitulum ventral.

Life history and habits—Eggs laid in hiding places of the adults,
in cracks, crevices, etc., in batches of 20-100 more or less. Hatch
in about three weeks into six legged larvae or “‘seed ticks’’ which after
several days feeding drop from host and molting in about eight more
days into the first nymphal form, feeding intermittently and rapidly
for about two weeks when they again molt and the second nymphal
form is assumed. After some weeks these molt to form the adult.
Adults feed about once a month in hot weather, at longer intervals

39

when it is cool. Lounsbury found that entire life cycle from egg to
egg required 10 months in one case studied. Great longevity; we
have kept specimens unfed and in a dry tin box alive for nearly two
years. Instances on record of survival for three years. (See,
Nuttall, 708).

Economic importance—Bite often causes serious injury to man.
Aside from importance in some regions as transmitters of poultry
. disease, they are directly responsible for the death of many fowls
and for much loss due to depleted condition.

Means of control—Cleanliness of poultry houses and yards, white-
washing (filling all cracks), removal of rubbish under which ticks
can hide. Use of dips to kill the ticks on fowls.

B—Ixodidae—Dorsal shield or scutwm present; sexes very distinct
in appearance; palpi relatively short and rigid. Nymphs and adults
remain attached to host for days or months, increasing enormously
in size when gorged. Not so long-lived as typical Argasidae.

Boophilus annulatus—“‘Margaropus annulatus’’, the Southern
cattle tick. Causes enormous direct loss, but it is as a carrier of
Texas fever of cattle that it becomes one of the most important
pests of the South. Conservative estimates place losses to the South
due to it as $40,000,000 annually.

Life history—Mate on host, female drops to the ground and
deposits many eggs. After twenty to twenty-five days in summer,
or months in the fall, ‘‘seed ticks’’ or larvee emerge, crawl to top of
grasses and bushes, where they await their host. After six or seven
days on the host molt and form nymphs with eight legs. During
nymphal stage sexual organs develop. In from five to eleven days
the nymphs molt and appear as adults. In summer, female feeds
six to twenty days after copulation before dropping from the host to:
lay her eggs.

Relation to Texas fever—Since the discovery of the causative
organism of Texas fever by Smith in 1889, it has been clearly demon-
strated that the disease is not transmitted by saliva, urine, or manure
of diseased animals but solely by the cattle ticks, hatching from eggs
laid by individuals which had fed on diseased cattle or on apparently
healthy Southern cattle which carried the parasite in their blood.
Not only the clearest of circumstantial evidence, but proved experi-
mentally very many times.

40

Methods of control—Establishment of a quarantine line limiting
area infested by the tick and prohibiting removal of cattle, except
for immediate slaughter, during the period when the tick could live
and develop in the North. Cattle going to market during the
closed season must be shipped in special cars or boats and, when
unloaded for feeding, watering, or sale, are placed in special pens.
Cars and boats must be disinfected before other stock can be carried.
Cattle may be freed of ticks by hand-picking, greasing, dipping, or
spraying. The most important measures are those which, by taking
advantage of a minute study of the biology of the tick, render it
possible to free infested pastures. Essentially, exclude from the
pasture from June until late fall all cattle or horses and mules which
might carry ticks. In the meantime, cattle from the infested field
are freed from ticks by placing in a tick-free feed lot for three weeks
by which time many ticks would drop off, but seed ticks would not
have hatched. Then place in a second tick-free lot for twenty days,
and finally, for certainty that ticks had all dropped off, place in a
third lot. By this time the tick-free cattle should be placed in a
forage field until mid-November, by which time all the ticks in the
original pasture will have died. By essentially this method large
areas of the quarantined region are being freed from ticks and hopes
are entertained that the tick may be exterminated. For details see
Farmers’ Bulletin 378, “Methods of Exterminating the Texas Fever
Tick” and various publications of the Bureau of Animal Industry
and of the Bureau of Entomology.

Superfamily GAMASOIDEA

Abdomen not annulate; ‘tongue’ small, without teeth, venter
without furrows, body often with coriaceous shields, posterior margin
never crenulate; no eyes. This family includes many species free-
living or attached to insects, but one group is parasitic on birds, bats,
rodents, etc. One species of very great economic importance is:

Dermanyssus gallinae, the red chicken mite. Incorrectly called
“chicken tick”. Most destructive external parasite of fowls.

Description—“Body ovopyriform, posterior end largest, slightly
- flattened from above to below; abdomen margined by short, well-
separated bristles; color varying from yellowish-white to dark red,
according as the insect is fasting or more or less replete; the intestinal

41

tube, gorged with blood, can be seen as a variously shaped figure.
The ovigerous female is .70 mm. long and .40 mm. broad; the male,
.60 mm., and .32 mm. broad.’’—Neumann.

Life history and habits—Eggs laid in cracks and crevices or in
rubbish, singly, about one a day. Hatch in three or four days and
after two or more molts become mature in about ten days under
favorable conditions. Intermittent feeders, most active at night,
and hiding during the day. May attack man and domestic animals.
Very long-lived, specimens having been kept in a pill box without
food for at least three months. Dispersal by shipping crates, show
crates, etc.

Methods of control—Cleanliness and sunlight, removal of manure,
litter, superfluous boxes, boards, and all trash. Whitewashing,
with addition of four ounces of carbolic acid to each gallon of white-
wash. Spraying with kerosene emulsion; must be thorough, and
repeated in three or four days to kill mites which have hatched from
eggs.

Superfamily SARCOPTOIDEA

Itch mites, hair and feather mites—Small, palpi small, 3-jointed;
no eyes; no spiracles; tarsi often end in suckers. The itch mites
belong to the family Sarcoptidae, illustrated by:

Sarcoptes scabei, parasitic within the skin of man and other
mammals, causing a diseased condition known as the ‘“‘itch’’, scabies,
or mange.

Description—Body oval or nearly circular, 200-2354 x 145-190p
in the male, 330-450» x 250-350 in the female. Whitish, marked
by transverse folds partly interrupted on the back. Chitinous
hairs at the base of the legs and the first two pairs of legs are pro-
vided with pedunculated suckers in both sexes; the third and fourth
pair in the female terminate in long bristles, while the fourth pair
in the male has a pedunculated sucker.

Life history and habits—Lives in tunnels that it excavates in the
epidermis, the female at the bottom, the male near the opening.
The tunnels contain excrement and the minute eggs from which
hatch the hexapod lJarve. Enormous. rapidity of increase. Disease
spread by contact, or, rarely by clothing or bedding of those infested;
may be contracted from horses and other animals infested.

42

Diagnosis and treatment—In man, the diagnosis of a simple case
is readily made by finding the galleries with the female at the end,
but there is often secondary infection, due to scratching. Treatment
consists in preparatory warm bath, or for cleaning off scales, incrusta-
tions, etc., and softening of the skin and then in applying a sulphur
ointment.

Psoroptes communis ovis, mite of common sheep scab, the most
prevalent and most injurious malady of sheep. May begin attacks
in almost any part of body but usually in parts covered by wool;
wool falls out, scabs are formed, and finally the skin becomes more
or less bare, parchment like, greatly thickened, furrowed and bleed-
ing in the cracks.

Description—One of the larger mites, males 500-600 x 340-3701,
female 670-740» x 450-4604, quite easily seen with naked eye.
Rostrum or beak elongated, conical. Ambulatory suckers on long,
3-jointed pedicle, on first three pairs of legs in the male, and on first,
second, and fourth legs of the female. Male with copulatory suckers
and abdominal prolongations.

Life history—Female lays 15-24 eggs on the skin, or fastened to
the wool near the skin. In three or four days the six-legged larva
hatches and three or four days later molt to form nymphs which pair,
molt twice more and begin to lay eggs. Gerlach estimates fifteen
days as an average for a generation and that under ideal conditions
a single pair of mites may produce 1,500,000 individuals in three
months.

Methods of control—Preventive and curative. Exceedingly con-
tagious and penalties for shipment of diseased sheep are heavy.
Contagion may be direct, by contact of sheep with one another or
indirect, from fences, posts, etc. or from places where infested sheep
have been ‘‘bedded” down. Hence, if pastures, corrals, or sheds
become infested leave them vacant for at least four weeks before
using for clean sheep. Curative treatment, some external application
which will kill the parasites. Various dips used. For details see
Bureau of Animal Industry Bul. 21 “Sheep Scab, its Nature and
Treatment’, or more recent publications of the Bureau.

43

Superfamily DEMODECOIDEA

The hair-follicle mites—Very small, abdomen annulate, elongated,

Demodex folliculorum, very common in the sebaceous glands
and hair follicles of man, usually with no ill results. A variety of the
same species on dogs gives rise to a very serious disease, demodecic
scabies.

Description—Very small, 300-380" x 45, elongate, veriform,
with eight short 3-jointed legs and in front a short, median, sucking
rostrum. Abdomen tapering transversely striated and rounded at
the tip.

Life history and habits—Deposit fusiform eggs, 70-90» x , 25.
Multiplies very slowly; hexapod larva, two nymphal stages. Mites
migrate over the skin to enter new glands.

Class HEXAPODA
(True Insects)

Review the characteristics of the four orders discussed, as given
on page 14.

Order MALLOPHAGA

Includes all biting lice infesting birds and mammals. Illustrated
by:

Menopon pallidum, the common hen louse. Responsible for
much loss to poultrymen, through reduced vitality and even death
of birds, and failure to incubate eggs properly.

Description—Elongate oval, very flat, pale yellow body 1-1.5 mm.
long. Head triangular, semilunate, antennae 4-jointed, mouth
parts fitted for biting.

Life history and habits—Eggs laid at base of feathers, especially
around the vent, hatching in six to ten days. Nymphs molt five or
six times. Lice very active; unlike the chicken mite, they remain
on the host and die soon after its death. Accounts of their occurrence
on horses confused with cases of the mite or of other species of biting

lice. The lice spread from bird to bird by infested mother hen, cock-
birds and to a less extent, by infested nests, ete.

Methods of combatting—Roomy, dry, and sunny dust baths.
Various dusting machines for treating individual birds are on the

44

market. Dipping fowls in 114 ounces of pure carbolic acid to a
gallon of warm water. Proprietary remedies.

Related species—Various species of the genus Trichodectus parasitic
on domestic mammals. Biting mouth parts, antennae 3-jointed.

Order HEMIPTERA

Includes the true bugs and the sucking lice. Take as illustrations:
Cimex lectularia, the bed-bug. World-wide in distribution.

Description—Reddish-brown, broad and very greatly flattened.
Head short, broad, two prominent eyes, but,no ocelli; mouth parts
for sucking. Peculiar “buggy”? odor due to secretion of sac-like
glands at the base of the abdomen.

Life history and habits—Eggs laid intermittently for a long period,
in cracks, under wall-paper, etc. Hatch in 7-10 days. Nymphal
stages five, total period to development of adult varying from 40-150
days or more. May live for months without food. In cases of
deserted houses, may feed on mice or other mammals. Invasion of
a house not necessarily due to neglect as the bugs may migrate, be
brought in with baggage, laundry, furniture, or otherwise.

Methods of combatting—Use of iron bedsteads and reduction of
hiding places. Gasoline or alcohol squirted into cracks and crevices.
In more general infestations, fumigation with sulphur, 2 pounds to
1,000 cubic feet. Under proper precautions, fumigation with
hydrocyanic acid gas (See U. 5. Bureau of Entomology Circ. 46
“Hydrocyanic acid gas against household insects’’).

Haematopinus eurysternus, the short-nosed sucking louse of
cattle. Found especially on ears, back of head, mid back and places
where hair is long and they cannot be readily reached by the animal.

Description—Bluish-gray, males 244 mm., females 3 mm. in
length. Mouth parts and unjointed beak capable of great extension,
with a chaplet of barbs at base, for attachment. Wings lacking,
legs highly specialized for clasping.

Life history—Remain on the host. Eggs, or so-called “nits”
pyriform and attached to the hairs by an adhesive substance. Hatch
very soon and young escape through a caplike covering at top of egg.

Methods of combatting—Cleanliness, keeping infested animals
apart from others if possible. Washes of kerosene emulsion or

45

tobacco infusion plus kerosene, or carbolic acid. Fumigation
with sulphur or tobacco for 20-30 minutes in a tight box stall with
an opening for the head of the animal.

Pediculidae of man—Three species of sucking lice infest man,
Pediculus humanus, or head louse (usually referrred to in medical
works as P. capitis), P. corporis, or body louse, and Phthirius inguina-
lis, pubic louse.

Order DIPTERA

True flies. Two suborders: NEMATOCERA, mosquitoes, gnats,
et. al., have long antennae, consisting of at least six segments.
BRACHYCERA, bot-flies, house flies, sheep “ticks”, et. al., have
short, 3-segmented antennae.

Suborder NEMATOCERA

Family Culicidae, mosquitoes. Small, 2-winged, wings narrow,
and with their veins covered with scales; antennae plumose in males,
simple in females. Females only, suck blood. Immature stages
aquatic, larvae commonly known as wrigglers; pupz active. See
the important general discussion of Howard, ’01, Smith, ’04, Mitchell,
07.

We shall consider here the general characters of the genus Culez,
as compared with those of Anopheles, the malaria bearing mosquito:

CULEX. ANOPHELES.
Adult—Wings clear Adult—Wings spotted
Palpi short Palpi long = as__ beak.
Resting position with Resting position with
body and wings paral- body at an angle to
lel to wall. wall.
Eggs—Laid in raft-shaped masses ggs—Laid singly, _—_ always
on end. lying on their sides.
Larve—Hang in water at a Larve—Lie in water with body
great angle to the sur- parallel to surface.
face. Pupe—Rest at a much smaller
Pupe—Rest almost perpendicu- angle to the surface.
lar to the © surface. Breathing siphons broad.

Breathing siphons nar-
row.

46

Economic importance and relation to disease—Direct injuries
not only annoying to man and animals but may be serious. Occur
in enormous numbers in some regions, rendering them uninhabitable.
Deprecation of real estate, retarding development of many localities.
As disease carriers, they are the sole agents in transmission of malaria,
yellow fever, filariasis and are suspected of directly transferring
some other diseases.

Methods of combatting—Efforts should be directed against the
larvee. Destruction of breeding places; drainage; oiling; introduc-
tion of minnows and other small fish. Screening against adults,
necessity of screening patients with mosquito-born diseases.

Family SIMULIIDAE, the black flies. Illustrated by:

Simulium pecuarum, the buffalo gnat. Causes enormous losses
of horses, mules, and other domestic animals in the Mississippi
Valley. See Osborn, ’96,

Description—Size minute, about 6 mm. long, body short and
stout, color black, but body covered with grayish-brown, short and
silken hairs. Antennae 10-jointed, scarcely longer than head;
wings without scales.

Life history—Early stages aquatic. Eggs laid in patches on rocks,
submerged stumps, brush, etc., in rapidly moving water. Larve
slender, cylindrical, closely crowded so as to appear like dark patches
of agal growth on the objects to which they are attached (see patches
on the brinks of falls or in rapids of any of our local streams). Pupal
case conical, grayish or brownish, and has its upper half cut squarely
off, more or less raggedly. Time of appearance of adults varies
with the earliness or lateness of the spring, and consequently much
earlier in the southern parts of the Mississippi Valley.

Habits of adults and economic vmportance—Blood-sucking exceed-
ingly active, appear in enormous swarms, attacking domestic animals
and not infrequently causing death. No evidence that losses are
due to a specific disease transmitted by the fly but rather to loss of
blood and terrible irritation caused by the myriads of poisonous bites.
Area infested, in the worst years, all of Mississippi Valley from the
mouth of the Red River, in Louisiana, to St. Louis, Mo., and land
adjacent to the tributaries of the Mississippi River in these regions.

Methods of combatting—Destruction of larvae not feasible. As
preventives, smudges in fields and yards or even in pails suspended

47

from the necks of animals which have to be on the roads. Applica-
, tion of grease, or of oil of tar to animals.

Related species—Simulium meridionale, the turkey gnat; Simul-
ium molestum, the Adirondack black-fly. It has been suggested by
Sambon that species of Simulium transmit pellagra of man; but
evidence is by no means conclusive.

Suborder BRACHYCERA

Family TABANIDAE, the horse fly, deer flies, ef. al. Medium
to large size, body broad and slightly flattened; head large and
depressed from before to behind; eyes contiguous in the males;
last segment of the antennae annulate and without stylet. Females
provided with powerful piercing mouth-parts. Life history illus-
trated by:

Tabanus atratus, the black horse-fly. Largest native species,
bite one of the most severe, attacks cattle more commonly than
horses. Eggs laid in large black masses on marsh plants. Larvae
livein mud or water; large, twelve jointed, cylindrical, tapering at
each end. Winter passed in larval stage. Pupal stage lasts but a
few days. Adults are not only pests, but may directly transmit
disease.

Family OESTRIDAE, the bot-flies—Large, or medium size, with
rudimentary mouth-parts; most of the species resemble bees in
general appearance. Adults live comparatively short time; females
lay their eggs on the bodies of mammals; larve are parasitic and
their development requires several months. We shall consider three
species:

Gastrophilus intestinalis, (G. equi), the horse bot-fly. Adults
about 12-15 mm. in length, wings transparent with dark spots;
body very hairy, head brown, with three rows of blackish spots.
Eggs light yellow in color, attached to hairs of the horse, more com-
monly on the fore legs and shoulders. Eggs hatch in two weeks or
more, escape of larva being aided by licking by the horse. Taken up
in this way or with food they reach the stomach and attach to its
walls. Winter in host as larvee and following summer pass out with
feces; pupate in the ground and after thirty to forty days emerge as
adults. Bots may be so numerous in stomach as to cause marked
pathological changes and digestive disturbance.

48

Hypoderma lineata, the oxz-warble—Larvae form more or less
conspicuous lumps under the skin of the backs of cattle during the
latter part of winter or early spring. Adult fly about 12 mm. long,
very hairy, and somewhat resembles a small black bee in appearance.
Though unable to bite, cattle have a great fear of them. Deposit
eggs, throughout the summer, on the hairs of cattle and young larvee
are taken up by licking and penetrating the walls of the oesophagus,
migrate through the tissues to reach the subcutaneous tissue of the
back of the host. In spring or early summer the grub emerges,
pupates in the ground and adults emerge in about a month. Studies
of Carpenter, ’07, indicate that larvae may possibly enter skin
directly, but this is not normal method. Estimated that loss by
injury to hides, decrease in milk and beef, and lessened vitality reaches
over $90,000,000 annually in this country. Preventive measures,
such as protection of cattle from attacks of the fly, hardly feasible.
Much may be accomplished by removal of the gruhs, by pressure,
during late winter and spring.

Oestrus ovis, the sheep bot-fly or head maggot—Adults somewhat
resembling ‘“‘an overgrown house-fly”’ appear in June and July and
deposit living larvee, or eggs ready to hatch, in nostrils of sheep.
Larve pass into frontal sinus and horns, causing disease known as
“staggers”. Mature in about ten months and are expelled by sneez-
ing of the host, pupate in the ground, and adults emerge in forty to
fifty days. Preventive measures, such as smearing noses of sheep
with oil or tar not of demonstrated value. Substances to make the
sheep sneeze and thus expel the larve no more efficient than the
irritation caused by the larve itself. Removal of immature grubs
by surgical treatment worth while in case of valuable animals.

Family MUSCIDAE, including the flesh flies, house-flies, horn-
flies, and many others—By some writers considered a superfamily,
with many families.

Musca domestica, the common house-fly—90 per cent of the flies
found in houses being of this species. Detailed description unneces-
sary, but it should be emphasized that the mouth-parts are adapted
solely for sucking and lapping. Breeds primarily in horse manure,
but also in decaying vegetation, garbage, and human feces. 120+
eggs in a batch and may deposit as many as four batches. Larve
known as maggots. Entire life cycle in hot weather may be under-
gone in ten days. Always a pest, the house-fly is now known to be

49

an important factor in the spread of typhoid, and various intestinal
diseases, and to a less extent tuberculosis, and possibly other diseases.
Methods of control by screening and trapping, destruction of breeding
places, trapping out of doors during preoviposition stage. Danger as
a disease carrier lessened by proper sewage disposal, and by dis-
infection of typhoid discharge. For detailed discussion, see Howard
“The house-fly-disease carrier’.

Haematobia serrata, the horn-fly—Now found nearly everywhere
in the United States, though introduced from Europe about 1885.
About half the size of a house-fly and very much like it in shape and
color, these flies get their name from their habit of clustering about
the base of the horn. When feeding, puncture skin and suck blood.
Remain on animal day and night and by irritation and annoyance
cause much loss through reduced vitality, lack of growth, or loss of
milk. Eggs laid in freshly dropped cow manure, hatch in twenty-
four hours; larvee transform in four or five days into pupe which
remain in the ground for ten days. Preventive measures, spraying
cattle by means of a hand spray pump with a mixture of fish oil
100 parts, oil of tar 50 parts, crude carbolic acid 1 part.

Family HIPPOBOSCIDAE, the louse flies—Abnormal flies which,
as adults live parasitically, like lice, upon the bodies of birds and
mammals. Some species winged, some wingless, others winged for a
time and then lose their wings. The most common representative is:

Melophagus ovinus, the so-called ‘‘sheep tick’—Reddish, wingless,
flattened, louse-like body, prominent proboscis, and strongly devel-
oped legs, with very prominent claws. Viviparous, each female
producing a half-dozen, more or less, full grown larvee which, attached
to the wool, quickly transform into seed-like brown puparia. When
abundant may cause death of lambs, and cause considerable damage
to old sheep. May be readily controlled by dipping sheep each year
after shearing, in any of the standard dips for lice and scab.

Order SIPHONOPTERA
True Fleas

Ctenocephalus canis, the dog flea—The most common house flea
in this country. Closely related, if not the same species, occurs on
cats.

50

Description—Reddish-brown, compressed, strongly chitinized
body; ocelli present, a comb of blunt black spines—seven to nine—
on lower border of each side of the head and of posterior border of the
thorax; no wings; legs long and stout, coxae being remarkably
developed, fitted for leaping. Mouth parts in the form of a rostrum
or beak enclosing the serrated mandibles fitted for puncturing, maxil-
lae, and labium.

Life history—Eggs scattered in dust, in cracks and in sleeping places
of the host. Veriform footless larvae, with sparse covering of hairs,
feeds on dead organic matter. In 10-12 days spins a silken cocoon,
pupates, and adult emerges in 10-12 days more. Under optimum
conditions entire life cycle may be completed in two weeks.

Control—As a household pest, controlled largely by cleanliness
and exclusion of dogs and cats. May be necessary to spray carpets
and floors with benzine. Fumigation with hydrocyanic acid gas
has been practiced with success.

Sarcopsylla gallinacea, the chicken flea,—Widely distributed in
warmer climates; is a serious pest in some of the southern states.
Unlike ordinary fleas, the chicken flea attaches itself firmly to its
host but it does not burrow under the skin as does the chigoe or true
“chigger”. Both male and female parasitic to the same extent;
attach themselves to the head, around the eyes, and neck of young
chickens in great numbers causing knots, lumps, and sores.

51

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