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PARASITOLOGY

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A LABORATORY GUIDE TO THE STUDY OF

PARASITOLOGY

BY
W. B. HERMS

UNIVERSITY OF CALIFORNIA, BERKELEY, CALIFORNIA

THE MACMILLAN COMPANY
1913

All rights reserved

350LOGY
LIBRARY

Copyright, 1913,

BY THE MACMILLAN COMPANY
Set up and electrotyped. Published May, 1913

PBB38 OF T UOBET & SOW,
GREENFIELD, MASS., V. 3. A.

FOREWORD

With the rapid growth of Parasitology there is also a growing
demand for laboratory instruction in this field. The author's
greatest desire during the time that he has been engaged in
teaching this subject has been to place the work upon a good
systematic footing, giving it proper rank with other phases of
applied biology. The following exercises are based upon several
courses in Parasitology (now merged into two) that have been
given by the author at the University of California during the
past four years, including two summer sessions. Each exercise
has had careful testing in the laboratory and is practical.

The aim of this Guide is to give the student a wide practical
view of the field so that he might have a fair grasp of the general
subject in its application to the health and well-being of man and
beast. The exercises are in sufficient detail so that the student
is enabled to continue work on some specific group or species if
he so chooses.

The exercises are arranged to provide sufficient matter for a
laboratory session requiring from two and a half to three hours
for each. A number of the exercises are divided into two or
three parts, and this may be useful in cases where less time is
available. The two standard courses given at the University of
California upon which these exercises are based are Human
Parasitology (first half year) and Veterinary Parasitology
(second half year), each with three lectures per week and two
laboratory sessions of from 2>£ to 3 hours.

The author wishes to gratefully acknowledge the very able
assistance rendered by Mr. A. B. Shaw, Jr., in the preparation
of this laboratory guide.

W. B. H.

BERKELEY, CALIFORNIA,
August 5, 1912.

T

7 ft

CONTENTS

PAGE

Introduction. . xi

PART I

MEDICAL ENTOMOLOGY

Insects and Disease. (Discussion.) I

A Study of Insect Mouthparts. (Exercise i.) 8

A. Orthopteron type.

B. Hymenopteron type.

Insect Mouthparts (cont.). (Exercise 2.) 10

C. Hemipteron type.

D. Lepidopteron type.

E. Dipteron type.

a. First subtype, the Mosquito.

Insect Mouthparts (cont.). (Exercise 3.) n

F. Dipteron type (cont.).

b. Second subtype, the Horsefly.

c. Third subtype, the Stablefly.

d. Fourth subtype, the Housefly.

Internal Anatomy of an Insect. (Exercise 4.) '. . 13

Comparative Study of the Biting and Sucking Lice. (Exercise 5.) .... 14

Biting Lice (Order Mallophaga). Anatomical Study. (Exercise 6a.) .. 15

Biting Lice (Order Mallophaga). Systematic Study. (Exercise 6b.) .. 16
The Sucking Lice of Mammals (Family Pediculidae). Anatomical

Study. (Exercise ya.) 16

The Sucking Lice (Family Pediculidae). Systematic Study. (Exer-
cise yb.) 17

The Bedbug (Family Acanthiidae). (Exercise 8a.) 18

The Cone-noses (Family Reduviidae). (Exercise 8b.) 18

The Mosquitos (Family Culicidas). (Exercise 9.) 19

The Buffalo Gnats (Family Simuliidae). (Exercise loa.) 21

The Horseflies (Family Tabanidae). Anatomical Study. (Exercise lob.) 21

The Horseflies (Family Tabanidae). Systematic Study. (Exercise IDC.) 22
The Housefly and the Stablefly (Family Muscidae). A Comparative

Study. (Exercise n.) 22

vii

viii CONTENTS

PAGE

The Stablefly and the Hornfly (Family Muscidae). A Comparative

Study. (Exercise 12.) 24

The Fleshflies (Family Sarcophagidse). (Exercise 13.) 25

The Botflies and Warbleflies (Family (Estridae). (Exercise 14.) 26

The Fleas (Order Siphonaptera). Anatomical Study. (Exercise isa.). 27

The Fleas (Order Siphonaptera). Systematic Study. (Exercise isb.). 28

The Louseflies (Family Hippoboscidae). (Exercise 16.) 29

The Ticks (Family Ixodidae). Anatomical Study. (Exercise i7a.) . . . 29

The Ticks (Family Ixodidas). Systematic Study. (Exercise lyb.). ... 31

The Ticks (Family Ixodidae). Other Species. (Exercise i8a.) 31

The Ticks (Family Ixodidae). Life History Study. (Exercise i8b.) ... 32

The Mites (Family Gamasidae). (Exercise iga.) 33

The Mites (Family Sarcoptidae). (Exercise i9b.) 34

The Mites (Family Sarcoptidae) (cont.). Psoroptic species. (Exercise

20.) 34

The Insect Sting. (Exercise 2ia.) 35

Venomous Spiders and Scorpions. (Exercise 2ib.) 36

Parasiticides. (Exercise 22.) 37

The Amoebae. (Exercise 23a.) 40

The Trypanosoma. (Exercise 23b.) 41

The Malaria Parasites. (Exercise 24.) 42

PART II

HELMINTHOLOGY

Introduction 45

The Roundworms (Family Ascaridae). (Exercise 2$a.) 46

Other Ascaridae (Oxyuris and Heterakis). (Exercise 25b.) 48

The Thornheaded Worms (Class Acanthocephala). (Exercise 25c.) ... 48

The Hookworms (Family Strongylidae). (Exercise 26.) 49

The Hookworms (cont.). (Family Strongylidae). (Exercise 27.) 50

The Lungworms (Family Strongylidae). (Exercise 28.) 51

The Whip worms (Family Trichotrachellidae). (Exercise 293.) 52

The Trichina (Family Trichotrachellidae). (Exercise 29b.) 53

The Filarise (Family Filariidae). (Exercise 3oa.) 54

The Leeches (Order Hirudinea). (Exercise 3ob.) 55

The Sheep Liver Fluke (Family Fasciolidae). (Exercise 31.) 56

Other Trematodes. (Exercise 32.) 58

The Tapeworms (Class Cestoda). Morphological Study. (Exercise 33.) 59

The Tapeworms (Class Cestoda). Systematic Study. (Exercise 34.) . . 61

CONTENTS ix

PAGE

Other Tapeworms (Class Cestoda). (Exercise 35.) 63

Larval Forms of Tapeworms. (Exercise 36a.) 63

Helminth Ova. (Exercise 360.) 65

Insect Larvae (To Distinguish from Worms). (Exercise 37.) 65

Anthehnintics. (Exercise 38.) 66

PART III

LIFE HISTORY STUDIES ON LIVING PARASITES

Introduction: How to Proceed 69

Life History of the common Housefly. (Exercise 39.) 70

Life History of the Mosquito. (Exercise 40.) 71

Life History of a Flea. (Exercise 41.) 72

INTRODUCTION

The object of the following exercises is to acquaint the stu-
dent with the commoner animal parasites of man and of the
domesticated animals, including insect carriers of disease. In
studying the parasites here considered, the student should
bear in mind the following statements and make observations
accordingly.

A parasite can only be a parasite as it lives directly at the
expense of another organism, whether plant or animal. This
definition leaves few if any animals out of this category, inas-
much as the dependence of animals directly upon other animals
or upon plants for food is obvious. But if we restrict this mean-
ing to position, living in or upon another animal or plant for
purposes of feeding, we come nearer to the thought. But even
here there are many organisms which live in or upon living
animals or plants, merely sharing their food with them without
injuring the host. This we call commensalism. Furthermore,
organisms feeding in or upon dead bodies would not be termed
parasites, except as they also attack or feed upon living tissue,
as occurs in certain flesh flies, e. g. the Texas Screwworm fly
(Chrysomia macellaria) , which as a larva may feed upon the
flesh of dead or living animals. Thus our definition revolves
about the idea of feeding upon living organisms, to which
should be added that the host must not be killed before at
least the developmental period or larval period of the parasite
is completed, otherwise the result would be the destruction
of the parasite as well as the host. Parasitism then involves
slow death to the host, if fatal consequences are at all in-
volved. The definition given by Braun is, viz., "By the term
Parasites is understood living organisms which for the purpose

ri

xii INTRODUCTION

of procuring food, take up their abode temporarily or perma-
nently, on or within other living organisms." This definition will
exclude predaceous animals (Raubtiere), which capture their
prey alive, and usually kill it outright for purposes of food.

Classes of parasites. Other than the two general classes,
Ectoparasites (external parasites), and Entoparasites (internal
parasites), all parasites may be placed in one or another of the
following divisions, according to the time spent in or upon the
host. Facultative parasites have the power of changing from one
host to another of a different species, e. g. the cat and dog flea,
Ctenocephalus canis, which may be found upon the cat, the
dog, the rat and man; the rat flea, Ceratophyllus fasciatus, upon
the rat and upon man; the wood tick, Dermacentor variabilis,
may be found on nearly all species of domesticated animals and
man. Obligatory parasites are restricted to one species of host,
e. g. the biting bird lice (Mallophaga), which perish sooner or
later if transferred to another species of host. Intermittent par-
asites are such as prey upon the host for food, as in the female
horseflies (Tabanidae) attacking horses and cattle for the pur-
pose of sucking blood and leaving the host after a meal. Tran-
sitory parasites are such as pass part of the life history at the
expense of the host, for example, the botflies (CEstridae) which
pass the larval period of development within the body of the
host, while the adult botflies are free living and do not attack
other animals for food.

Effect of parasitism on the host. That an animal is para-
sitized does not necessarily involve it in death, not even in great
inconvenience, although the parasite is actually living at its
expense. The presence of a few bots in the stomach of a horse
may not affect that animal in the least, nor would the presence
of a few lice on the body of an animal, but with the multiplica-
tion of these parasites there will be increased inconvenience to
both hosts. The presence of a few maggots in the fleshy part of
a sheep's leg might cause little damage, but let these be in the
nasal sinuses or at the base of the brain, and the gravity of the

- INTRODUCTION xiii

situation will be greatly augmented. Thus the effect of parasi-
tism on the host depends both on the number and position of
the parasite.

Effect of parasitism on the parasite. All parasites are
more or less specialized in the direction of their habits, e. g. fleas
are laterally compressed to effect ease of motion between hairs;
lice are horizontally flattened and are provided with strong
clasping organs to hold fast to hairs, and both of these examples
are wingless and have sacrificed much of the ordinary means of
locomotion. Entoparasites are usually provided with special-
ized hooks, barbs, suckers, etc., for purposes of attachment to
the alimentary canal or other organs, e. g. the botfly larvae,
and among the Helminths, the flukes (Trematoda), the tape-
worms (Cestoda), etc. Perhaps because of the ease in securing
food the sense organs are usually not strongly developed, the
eyes may be wanting or very simple. The mouthparts differ in
the several groups, depending on their special adaptation of
habit. It is interesting to note that the parasitic habit has re-
sulted in the development of structural similarity. This is
especially prominent in the clasping structures of the biting and
sucking lice, which belong systematically to two different orders,
namely, the Mallophaga and the Hemiptera.

Origin of parasitism. Modern parasites are restricted
more or less completely to a particular host animal, which would
necessitate the deduction that the parasite must have developed
its habit after the existence of the host, and in consequence that
parasitism must be a recently acquired habit. This thought is
further expressed by the study of the life history of the parasite.
Invariably the earlier stages point to a free living existence.
Perhaps the ancestors of a given group of modern parasites were
attracted to the waste food, offal and exudations of certain
animals; the search for food may have become simplified; they
began living as messmates or commensalists, or as scavengers;
the association between the species may have become closer and
the eventual line of parasitism completed. This is also borne

xiv INTRODUCTION

out by a study of the nearest allies of a given parasite and mem-
bers of a given family of parasites, in which the gradation from
free living animal to parasite may often be traced. Among the
biting lice (Mallophaga) there are species which have the power
of running freely, e. g. Menopon pallidum, the common hen
louse, which may live for a considerable length of time off its
host, while other species have become quite sessile, as in the case
of the worm-like louse Menopon titan, which inhabits the pouch
of the pelican. Among the fleas there are also good examples
of this gradation in habit and structure, e. g. the human flea,
Pulex irritans, while it has developed the springing power, is
comparatively free to move from place to place, while the hen
flea, Xestopsylla gallina, is quite sessile and holds fast at one
point to draw blood much like a tick.

The ectoparasites will be studied first, on account of the
greater ease of handling them. In the meantime the student
will gain greater efficiency, preparatory to studying the more
difficult entoparasites.

DIRECTIONS

The student should provide himself with a hand lens and
loose leaf drawing paper and notebook.

Drawings should be made with a hard pencil, preferably 3H.
Do not use a fountain pen or soft pencil for this work.

Notes should be taken on each exercise and properly inter-
leaved.

Each exercise will provide enough material for a laboratory
session of from 2^2 to 3 hours.

Specimens, whether mounted dry, on slides or otherwise
prepared must be handled with care.

Special care must be exercised in studying microscopic slides
under the compound microscope. Do not crush the specimen
by running the objective down upon it.

INTRODUCTION xv

SUGGESTIONS

Students are strongly urged to be on the "lookout" for cases
of parasitism, not only because this lends emphasis to the work
in hand, but also because of the scientific importance and value
of such observations and collections.

Internal parasites (taken wet) such as tapeworms, round-
worms, bots, warbles, etc., may be preserved in 75% alcohol or
4% formaldehyde, preferably the latter. If alcohol is used as a
preservative the specimens should be run into the higher grades
of alcohol gradually, beginning with 25% and allowing 2 or 3
hours between each change (25%, 35%, 50%, 75%).

Insect specimens may be mounted on pins or points or may
also be preserved as above.

PARASITOLOGY

PARASITOLOGY

PART I
MEDICAL ENTOMOLOGY

INSECTS AND DISEASE

DISCUSSION
HOW PATHOLOGICAL CONDITIONS ARE PRODUCED

General considerations. By pathological conditions we
would have understood a diseased state of tissue, deranged
function or the like, — an abnormal condition of the body. Ani-
mal diseases may be produced in many ways, and it is not the
object of this exercise to give a complete discussion of even the
general principles of pathology, except only in so far as insects
are concerned. In this work we cannot merely define those in-
sects as parasites in the usual acceptance of the term as defined
by Braun, "living organisms which take up their abode, for the
purpose of procuring food, temporarily or permanently, on or
within other living organisms," because there are certain insects
which are not usually considered as parasites, but are never-
theless the grossest transmitters of diseases, e. g. the housefly,
as a transmitter of certain enteric affections.

Insects and arachnids may relate to pathological conditions,
whether serious or of little consequence, in one or more of the
following ways, first, through direct infection, second, through

2 : M^DIC&L ENTOMOLOGY

indirect infection, third, through internal parasitism, fourth,
through external parasitism, and lastly, through insect venoms.
The same species may fall as legitimately into two divisions, as,
for example, the Texas fever tick, which if not infected with the
causative organisms of the fever need only be considered as an
external parasite, but when the causative fever organisms are
present in the tick would relate it also to direct infection.

Direct infection. Direct infection under ordinary conditions
can only be produced by an insect or arachnid possessing pierc-
ing mouthparts, and here no special order or larger group can
well be referred to, inasmuch as closely related insects may have
very different mouth structures. The common housefly and the
stable fly, for example, belong to the same family, therefore are
closely related, yet have very different mouthparts; though both
are suctorial, the former is unable to pierce the skin, whereas the
latter can do so with ease.

By direct infection is meant the introduction of a pathogenic
organism, whether bacterial or protozoan, into the circulation
of a higher animal. The Anopheles mosquito is thus related to
this manner of transmission, since this insect introduces the
malaria parasite directly into the blood stream of man. The
same is true of the Stegomyia mosquito and yellow fever, the
Glossina flies and sleeping sickness, the horseflies and anthrax,
the Texas fever tick and Texas fever, etc. Direct infectors are
usually temporary ectoparasites (intermittent parasites), per-
mitting transfer of activity from animal to animal.

While the conditions just discussed are to be referred to direct
infection, there is still a possibility for an insect with mandibu-
late mouthparts or with haustellate mouthparts of non-piercing
form to infect an animal as directly as one possessing piercing
mouthparts. Thus the housefly may, by means of mouthparts
and foot structures, transmit gangrene from an animal thus
affected to an animal undergoing surgical operation, or suffering
from an open wound. Pustular matter might be transmitted
in an equally direct manner.

INSECTS AND DISEASE 3

Indirect infection. This form of infection relates chiefly to
enteric diseases in the causation of which the pathogenic organism
is deposited upon the food of the higher animal by the insect.
Thus the food is first infected, and through this the pathogenic
organism is implanted within the alimentary canal of the victim;
in this way the insect is concerned only indirectly. The housefly
which is quite certainly one of the grossest transmitters of
enteric diseases is so only because of accident of habit and struc-
ture, feeding as it does indiscriminately upon excrement and
upon the food of higher animals. The structure of the proboscis
and feet is such as to make it quite difficult not to carry particles
of the excrement to the food. Thus if disease producing " germs ' '
are present the result is inevitable.

Insects possessing mouthparts not adapted to piercing the
skin (whether biting or sucking) can relate only to this form of
infection, and indeed any insect or arachnid may be an indirect
carrier by accident. Furthermore insects ordinarily relating
only to indirect infection may produce direct infection of certain
kinds, where there is access to an open wound; for example, the
transmission of gangrene through the agency of the common
housefly from a diseased animal to another animal which presents
an open wound, cut or sore.

Internal parasitism. There are no insects as far as is known
which spend their entire life history in the form of internal
parasites. There are, however, a number which pass their larval
period (period of growth) within the alimentary canal or in the
muscle tissue of higher animals. The best known representatives
of this group are the botflies and the warble flies, the former
found mainly in the stomach of equine animals, while the latter
are found in the muscle tissue of bovine and equine animals,
rodents and sometimes man. The damage done by internal
parasites is of various kinds; first, disturbed nutrition, and
secondly, irritation caused by the burrowing parasites in the
muscles or by the attachment of hooks to the intestinal lining
for the purpose of prehension.

4 MEDICAL ENTOMOLOGY

External parasitism. The most important and most abun-
dant external parasites of man and of the domesticated animals
are found among the insects and arachnids. Very serious and
often fatal results are due to this form of irritation, and the loss
of blood due to an abundance of any blood-sucking species must
not be overlooked. External parasites may be either permanent
or temporary with relation to their host. The commonest
permanent parasites are the biting and sucking lice, which are
usually transferred from host to host by close association of
mammals while sleeping together, or in close quarters or in
copulation; in poultry generally while roosting. While per-
manent ectoparasites are not so largely concerned in the direct
transmission of infectious diseases, certain sucking lice are
known to be agents in the transmission of Trypanosomes. The
temporary (intermittent) ectoparasites are the most important
of all disease carriers, on account of their change of host, drop-
ping off or flying away from one animal to another of the same
or a different species. It may well be seen that herein lies the
danger of transmitting infectious diseases from animal to
animal. The temporary ectoparasites are well represented by
the fleas, bedbugs and ticks.

Insect venoms. Another form of irritation is produced by
the inoculation of a specific poison into a wound produced by a
piercing or stinging insect. Many insects produce severe irrita-
tions by their bites, which fact can be accounted for by the
presence of a venom-secreting gland, often salivary. The cone-
noses or kissing bugs (Reduviidae) inflict a very painful wound
which is aggravated by a poison; other insects produce nettling
when handled, e. g. the blister beetles (Meloidae). Again, the
familiar sting of the bee and the wasp is chiefly painful because
of the injection of a specific poison.

INSECTS AND DISEASE 5

HOW INSECTS CARRY DISEASE

In the above section we have seen how insects relate to the
causation of disease. It is obvious that we may view the field
from a slightly different angle, i. e. our classification may be
based on transmission as well.

The simplest way in which insects enter in as a factor in the
transmission of disease is through soiled feet and mouthparts.
Any insect might accidentally become contaminated with infec-
tive sputum or fecal matter and in turn might accidentally come
in contact with human foods, thus becoming an indirect infector,
as already explained. In this connection the normal habit of
the insect must be considered, i. e. its breeding habits, food
habits and general behavior. Thus the housefly enters in as a
factor in the transmission of such diseases as typhoid fever and
tuberculosis, because of its normal habits and is a carrier in the
simplest possible manner.

A second purely mechanical method of transmission, though
more restricted, is by means of a soiled piercing proboscis, in cases
of certain blood diseases. In the foregoing class the type of
mouthparts does not enter as a restrictive factor, but in order
that the proboscis may become soiled with blood the mouthparts
must be capable of piercing the skin, thus coming in contact
with the blood and its contained parasites, if present. The
inoculation of the second host may be purely mechanical. In-
sects that belong to this class of carriers ordinarily have heavy
piercing mouthparts drawing considerable blood, are inter-
mittent parasites, and often go from host to host within a short
time. The horsefly (Tabanus) is a good representative of this
class in its chance relation to anthrax.

A still more highly specialized method is involved in the trans-
mission of bubonic plague by fleas. In this case the carrier has
piercing mouthparts, is bloodsucking and an intermittent para-
site, but it does not inoculate the second host by means of a
soiled proboscis as far as is known. The plague bacilli when

6 MEDICAL ENTOMOLOGY

taken into the stomach of the flea increase in numbers and do
not become attenuated, but pass out with the feces or even in
undigested blood per anum in a virulent condition; the direct
inoculation must be through a "rubbing in" process onthe part
of either the host or the flea. ^K:

The greatest complexity is involved in such cases in which the
carrier is a necessary factor in the life history of the pathogenic
organism, e. g. the Anopheles mosquito has piercing mouthparts,
is bloodsucking, and an intermittent parasite, in which a given
period of time must elapse before it can transmit the causative
organism of malaria, once it has become infected. This period
of time corresponds to the time required for the Plasmodium to
pass through its sexual cycle and find its way back into the
proboscis, i. e. into the salivary glands, ready to be reinoculated.

INSECT MOUTHPARTS

Importance of mouthparts. It becomes evident that an
insect possessing mouthparts capable of piercing the skin of the
higher animals must be looked upon as a possible carrier of
blood infection, although it may in actual experience never
attack other animals. If the insect is provided with mouthparts
of the usual biting type it cannot relate to infection introduced
through the circulation except by rare accident through a pre-
^fcwisly inflicted open wound.

The mosquito would be harmless as far as malaria and yellow
fever are concerned if the mouthparts were of the mandibulate
or biting type. These insects together with certain other species
such as the stablefly, Stomoxys calcitrans, the tsetse flies and the
ticks are important because of the power which they possess of
piercing the skin of higher animals and introducing parasitic
organisms into the blood. The housefly on the other hand cannot
introduce organisms directly into tjie circulation because its
mouthparts are not of the piercing type. These creatures are
attracted by and often breed in excrementous matter, are then

INSECTS AND DISEASE 7

attracted to the food of human beings, and introduce thereon
the pathogenic organisms from their mouthparts and feet.

The actual measures of control are quite often dependent on a
knowledge of the mouthparts of the insect concerned.

Inadequacy of old systems. In the study of Medical Ento-
mology it is no longer sufficient to divide the insects into only
two groups as based on the mouthparts, namely, Mandibulate,
or biting, and Haustellate, or sucking. This fact becomes
clearer when it is considered that the housefly (Musca domestica)
and the stablefly (Stomoxys calcitrans) both have sucking
mouthparts and belong to the same family, Muscidae, hence
are systematically very closely related, yet from the standpoint
of disease transmission are widely different. By virtue of the
piercing structures composing the mouthparts of the stablefly it
relates to direct infection, while the housefly's proboscis, quite
ineffective as a piercing structure, relates it to indirect infection,
— not however of less importance as a disease transmitter.

Because of the deficiency of the older systems of mouthpart
classification the following types will be considered.

Types of insect mouthparts. The following types of mouth-
parts may be recognized:

1. Orthopteron type, — biting or chewing structures, as in the
grasshopper.

2. Physopodan type, — transitional mouthparts of biting form
but functionally serving as suctorial organs, as in the thrips. •

3. Eemipteron type, — suctorial organs enclosing three or four
piercing setae closely ensheathed within the labiurn, as in the
cone-noses.

4. Dipteron type, — suctorial organs; no special example being
available for the entire order, the following subtypes must be
recognized:

A. First subtype — Mosquito, loosely ensheathed piercing
bristle-like structures, six in number.

B. Second subtype — Horsefly, piercing blade-like structures,
six in number, loosely ensheathed.

8 MEDICAL ENTOMOLOGY

C. Third subtype — Stablefly, closely ensheathed heavy pierc-
ing structures, two in number.

D. Fourth subtype — Housefly, suctorial muscular proboscis,
but not suited to piercing.

5. Hymenopteron type — suctorial, lapping form, as in the
honeybee and ant, mandibles modified for portage and combat.

6. Lepidopteron type — suctorial, coiled tube form, as in the
cabbage butterfly.

EXERCISE 1

A STUDY OF INSECT MOUTHPARTS

A. Orthopteron type.

To illustrate this type either the grasshopper or the cockroach
may be used, but since the former is more easily obtainable and
can be handled more satisfactorily it will serve this purpose very
well. This type, the mandibulate or biting, is the generalized or
primitive form, and will serve as a basis for later comparisons
and derivations.

If the head of the grasshopper is viewed from the side and
again from the front the relative position of the parts will be
better understood.

Separating the structures composing the mouth of the grass-
hopper, the following pieces will be observed. In front, low
down on the head, hangs the labrum, or upper lip, attached to
the clypeus, easily lifted as one would raise a hinged lid, the
hinge line being at the lower part of the sclerite known as the
clypeus.

The labrum functions as does the upper lip in higher animals,
in that it draws the food toward the mandibles. In this the
labrum is greatly aided by a rough toothed structure called the
epipharynx, which forms the inner lining of the labrum and the
clypeus. Because of the close association of these two structures
they are often referred to as a double organ, the labrum-epi-

A STUDY OF INSECT MOUTHPARTS 9

pharynx. Removing the labrum the pair of heavy black oppos-
able jaws, or mandibles, is exposed. These are biting structures
par excellence. They are toothed and movable laterally, in-
stead of vertically as in the vertebrates. Dislodging the man-
dibles brings the pair of maxilla, or accessory jaws, into view.
These organs are also called^/ maxilla. These are composite
structures, each separable into lacinia, galea, palpus, cardo and
stipes, which should be carefully noted, inasmuch as they undergo
great modification in the remaining types of mouthparts. The
two supporting sclerites are called the cardo (basal), and stipes
(the second) while the distal lobes are called, i, the maxillary
palpus (a jointed structure), 2, the galea (median and fleshy),
3, the lacinia (inner and toothed, capable of aiding in comminut-
ing food).

Underneath the maxillae and forming the floor of the mouth,
lies the lower lip, or labium, a double structure, frequently called
the second maxilla. On the same plan as the maxillae, the
labium consists of a basal sclerite, the submentum, followed by
the mentum, upon which rest the labial palpi (a pair of outer,
jointed structures, to the right and left) and the lignite (a pair
of straplike pieces which together correspond to the upper lip).
The labium is, like the maxillae, also subject to much modifica-
tion.

The fleshy organ still remaining in the mouth cavity after the
parts just described have been removed, is the tongue, or hypo-
pharynx, functionally comparable to the tongue of vertebrates,
an organ of taste.

Draw side and front view of grasshopper's head; also make a
drawing of each mouthpart separately, labelling all parts.

B. Hymenopteron type.

In this type the two general classes of mouth structures, the
Mandibulate and Haustellate, find a rather strong development
in the same species, though the former structures are not con-
cerned as comminuting organs with respect to food. The honey-

io MEDICAL ENTOMOLOGY

bee will serve as a representative species. Examine mounted
specimens of mouthparts as well as complete heads. The
labrum, above, is narrow and quite simple. The mandibles are
easily distinguishable and are useful wax implements. In ants
the mandibles are highly efficient carrying organs and weapons
of defense. The maxilla form the lateral conspicuous wings of
the suctorial parts; the lacinia and galea are fused into one
piece, and the maxillary palpi are quite minute. The labium is
represented by the long structures to the right and left of the
middle tube, which is probably the hypopharynx. The hypo-
pharynx terminates in a spoon or bouton, which completes the
lapping character of the type.
Draw and label parts.

EXERCISE 2

INSECT MOUTHPARTS (cont.)

C. Hemipteron type.

A very different sort of organ than the above described types
is found in the Hemiptera. Here the labium forms a prominent
beak, which is usually three (rarely one or four), jointed, and
telescopic. Examine mounted specimens of mouthparts of a
cone-nose, — Reduviidae. The beak encloses a pair of mandibles,
often provided with cruel barbs at the distal end, and the
maxilla, all bristle-like, and of great efficiency in piercing the
skin. The maxillae are more or less completely joined, forming
a tube, so that often only three bristles or stylets can be seen on
examination. The labrum is quite short and inconspicuous.

Draw side views of the head of the cone-nose, showing the
proboscis and stylets. Label the parts.

D. Lepidopteron type.

This type, represented by the commoner butterflies and moths,
is typically a coiled, sucking tube, capable of great elongation.

A STUDY OF INSECT MOUTHPARTS n

Taking the cabbage butterfly (Pieris rapa) as an example, the
labrum is seen to be greatly reduced, the mandibles absent. The
mandibles may be weakly present in the lower Lepidoptera.
The maxillae are apparently only represented by the galea,
which by the close approximation of their inner grooved surfaces
form the proboscis, long and coiled. The double structure of the
proboscis can easily be demonstrated by manipulation. The
labium is represented by the labial palpi.
Draw and label parts.

E. Dipteron type.

a. First subtype, the mosquito. The more generalized type
of Dipteron mouthparts is found in the mosquito, hence here we
find the maximum number of stylets or bristles, representing the
parts of the more generalized types, loosely ensheathed in the
elongated labium, the whole forming the prominent beak, or
proboscis. The identity of the six stylets is not well established,
though it is generally accepted that they represent the two
mandibles, the two maxilla (distinctly serrated distally), the
hypopharynx, and the labrum. The palpi are conspicuous struc-
tures in all mosquitoes, and are useful as a means for classifica-
tion. These represent the maxillary palpi of the grasshopper
while the pair of flattened lobe-like organs forming the distal
portion of the proboscis are said to represent the labial palpi,
and are called the lobelia.

Draw and label parts.

EXERCISE 3

INSECT MOUTHPARTS (cont.)

E. Dipteron type (cont.).

b. Second subtype — the horsefly. While retaining the same
number of parts as in the mosquito, this subtype is distinctly
characterized by the flattened blade-like condition of these

12 MEDICAL ENTOMOLOGY

organs, rather than the bristle-like or stylet form of the first
subtype. That these mouthparts serve quite largely as cutting
structures is evident from the large wound made and the quan-
tity of blood drawn by the "bite" of a horsefly, especially one of
the larger species, such as the black horsefly (Tabanus atratus).
The labium is the conspicuous median portion, loosely ensheath-
ing the blades, and terminating in large lobelia. The mandibles
are distinctly flattened and sabre-like, while the maxilla are
narrower and provided with conspicuous palpi. The hypo-
pharynx and labrum-epipharynx are both lancet-like. In the
male these piercing parts are very weakly developed, and are not
useful as weapons of attack.
Draw and label parts.

c. Third subtype — the stablefiy. This subtype represents a
group of piercing flies in which the mouthparts are distinctly
specialized, and show, together with the next subtype, to what
extent these structures may become differentiated within the
same family of insects.

The proboscis at rest is carried at the position of a bayonet
at charge, and is therefore provided with a prominent knee or
elbow, which portion is highly muscular. This conspicuous
organ is the labium, terminating in the labella, which are pro-
vided with a complex series of cutting and adhesive structures.
Within the folds of the labium and easily removable through
the upper groove lie two sharp, heavy, bristle-like structures,
the labrum, the uppermost and heavier stylet, and the hypo-
pharynx, a lower and weaker structure, the two forming, as
in other Muscidae, a sucking tube supported within the folds
of the labium. The maxillary palpi are less prominent than in
the other Muscidae, but are similarly located, at the proximal
end of the proboscis.

Draw and label parts.

d. Fourth subtype — the housefly. Here the prominent fleshy
proboscis consists mainly of the labium, which terminates in a
pair of corrugated rasping organs, the labella, and is attached in

INTERNAL ANATOMY OF AN INSECT 13

knee-like form to the elongated head. The entire mass is highly
muscular, and may either be protruded, as in feeding, or quite
largely withdrawn, while at rest. Lying on top of the grooved
labium is the inconspicuous prolonged spade-like labrum, which
forms with the hypopharynx a sucking tube, supported by the
labium, which latter also encloses the salivary canal. By an
examination of the labrum it will be seen that it forms a kind of
convex cover to the concaved hypopharynx, thus giving rise to
a food tube. The maxillae have evidently become fused with
the fleshy knee of the proboscis, and only the prominent max-
illary palpi remain.
Draw and label parts.

EXERCISE 4

INTERNAL ANATOMY OF AN INSECT

It is important that the student familiarize himself with the
internal anatomy of an insect, with special reference to the di-
gestive system and its accessory structures, such as the salivary
glands. For this purpose a grasshopper is to be dissected, ow-
ing to ease of manipulation. If the student has time it is recom-
mended that the internal anatomy of a stablefly be studied for
the sake of comparison.

With fine pointed needles or scissors open the dorsal abdominal
wall, separating the right and left sides to expose the intestine.
Small pins will be found convenient to pin down the parts and
thus allow more freedom in working. The insect should be
dissected under water in a dish with a paraffin floor.

A. Determine the following parts, drawing and labelling the
same.

a. The mouthparts, without reference at this time to details;
these have already been studied.

b. The oesophagus, a straight tube leading from the pharynx
to the crop.

I4 MEDICAL ENTOMOLOGY

c. The opening of the salivary ducts, emptying into the
oesophagus, and the pair of salivary glands.

d. The crop, or short food-receiving chamber, emptying into
the stomach proper, a longer cylindrical chamber, anterior to
which are the gastric caeca, and posterior the hair-like malphigian
tubules.

e. The intestine, a long, slender, coiled tube posterior to
the stomach, consisting of three parts, the ileum, colon and
rectum, the latter a short straight tube ending in the anus.

B. If time remains the student is urged to study the internal
anatomy of a stablefly for purposes of comparison.

a. Note the connection between the blood-sucking proboscis
and the oesophagus. x

b. How does the crop compare with the crop of the grass-
hopper? Note its adaptation to the storage of blood.

EXERCISE 6

COMPARATIVE STUDY OF THE BITING AND SUCKING LICE

Use for this exercise slide mounts in balsam of Hamatopinus
piliferus, the sucking louse of the dog, and either Trichodectes
lotus, the biting louse of the dog, or Trichodectes scalaris, the
biting louse of cattle.

The biting lice belong to the order Mallophaga, while the
sucking lice belong to the Order Hemiptera, Family Pediculidae.
These two groups of parasites are not always easily distinguish-
able without the use of a compound microscope. The bodies of
both are flattened dorso-ventrally, and in both wings are absent.

With a mounted specimen of each in hand, examine them
under a compound microscope (low power) and determine the
following characters, drawing each specimen. Your drawings
should be large enough to cover at least half a page of ordinary
notebook size.

ORDER MALLOPHAGA 15

a. Compare the head, thorax and abdomen, noting the rela-
tively small thorax as compared with that of the housefly, for
example.

b. The appendages differ how? Note the claws of each
species and explain the difference on the basis of the relative
activity of the insects. The sucking lice generally and many
species of the biting lice have heavy clasping structures.

c. Determine the position of antenna and eyes, if present.

d. Study the mouthparts of each species. Note the rather
sharp mandibles of the biting louse. Where are the mouthparts
located? Observe the proboscis of a sucking louse in which that
organ is protruded. What is the position of that organ when
the insect is not actively feeding?

e. Search for traces of blood in the stomachs of both species.

EXERCISE 6a

ORDER MALLOPHAGA (BIRD LICE)

Anatomical Study.

Using a slide mount of the common hen louse (Menopon
pallidum) determine the following parts, making a large drawing
of the specimen:

a. Head, thorax, abdomen.

b. Antenna, — are they clavate (club-shaped) or capitate
(ending in a distinct knob)? Determine number of segments.

c. Mandibles.

d. Eyes.

e. Temples, posterior lateral portions of the head.

f . Ocular emarginations, a bending in of the lateral margins of
the head just in front of the eyes.

g. Sternal markings, — blackish markings, bars or spots, on
the ventral aspect of the thorax. (May not be visible.)

h. Tarsal claws, whether paired or single, whether strongly
adapted for clasping hairs and feathers or not.

1 6 MEDICAL ENTOMOLOGY

EXERCISE 6b

ORDER MALLOPHAGA (BIRD LICE)

Systematic Study.

As representatives of the families of the Order Mallophaga
the following are available:

A. Suborder Ischnocera.

a. Family Trichodectidae.

Genus Trichodectes, examples, T. latus and T.

b. Family Philopteridae.

Genus Lipeurus, example, L. polytrapezius, the long turkey
louse.

Genus Goniodes, examples, G. stylifer of the turkey and
G. dissimilis of the hen.

B. Suborder, Amblycera.

a. Family Gyropidae.

Genus Gyropus, examples, G. sp. from ground-squirrel.

b. Family Liotheidae.

Genus Menopon, examples M. pallidgm. the common hen
louse and M. biseriatum, also from hens.

Genus Trinoton, example, T. luridum, the duck louse.
As representatives of the Trichodectidae and Liotheidae have
previously been drawn, draw one example each of the two re-
maining families, Philopteridae and Gyropidae.

EXERCISE 7a

ORDER HEMIPTERA, SUBORDER PARASITA, FAMILY PEDICULID^

THE SUCKING LICE OF MAMMALS

Anatomical Study.

The suctorial lice are wingless, as are the biting lice, and the
two may be confused, if attention is not paid to the structure of

ORDER HEMIPTERA 17

the mouthparts. Furthermore, the heads of members of the
former order are usually much more elongate in proportion to
the size of the body than is the case in the Mallophaga. The
claws of the Parasita are also strongly developed for clasping and
clinging to hairs.

Examine a mounted specimen, using the hog louse (Hcema^
iopinus suis} as an example of the order, and note the distinctions
above mentioned.

The proboscis of the sucking louse is fleshy and un jointed, sur-
rounded at its base by a circlet of barbs, and is in the form of an
extensile tube provided with lancets. The legs are short and
stout, and the tarsus is provided with a strong opposable claw.

Draw the specimen, showing the general structure.

EXERCISE 7b

ORDER HEMIPTERA, SUBORDER PARASITA, FAMILY PEDICULIDJE

Systematic Study.

The Suborder Parasita includes two families, only one of
which needs to be considered here. The other family is Oriental,
and is found solely on bats.
Family Pediculidae.

Genus Pediculus, examples, P. capitis, the head louse of man,
and P. vestimenti, the body louse of man.

Genus Phthirius, example, P. inxuinalis. the crab louse of man.

Genus Haematopinus, examples, H. piliferus, the sucking
louse of the dog, H. suis, of the hog, H. macrocephalus, the
horse louse, and H. spinulosus, the sucking louse of the rat.

Examples of the Genus Haematopinus having been drawn
previously, make large drawings of one example each of the
genera Pediculus and Phthirius.

1 8 MEDICAL ENTOMOLOGY

EXERCISE 8a

THE BEDBUG

ORDER HEMIPTERA, FAMILY ACANTHIID,E

A. Characteristics of Hemiptera.

The Hemiptera usually possess two pairs of wings (except,
e. g. the Acanthiidae and Pediculidae), the front wings (wing-
covers) in the Hemiptera-Heteroptera are partly leathery, and
membranous at the apices. The mouthparts, as already studied,
are piercing, suctorial, typically three- jointed, closely ensheath-
ing three or four setae.

B. Characteristics of Acanthiida.

A group of wingless insects with extremely flattened bodies,
giving off a pungent odor. The color is reddish brown. An-
tennae are four-jointed.

a. Examine a mounted specimen of Cimex kctulariys, the
common bedbug, for the above indicated characteristics. Draw
the specimen.

EXERCISE 8b

THE CONE-NOSES

ORDER HEMIPTERA, FAMILY REDUVIIDJE

A. Characteristics of Redumida.

This is a group of predaceous insects, fore wings partly
leathery, distal portion membranous. The head is long and
joined to the body by a slender neck. The tip of the head is cone-
shaped, with a three-jointed heavy rostrum which curves under-
neath the body. The antennae are long and slender. The legs
are prominent and give the insect a sprawled out appearance.

MOSQUITOES 19

B. Examine the following common species, noting color and
color markings in particular. Draw side view of (a), and dorsal
view of (d).

a. Melanolestes picipes — the China bedbug.

b. Melanolestes abdominalis — also called the China bedbug.

c. Reduvius personatus — the Eastern kissing bug.

d. Rasahus biguttatus — the two spotted corsair.

e. Conorhinus sanguisuga — the blood-sucking cone-nose.

EXERCISE 9

MOSQUITOES

ORDER DIPTERA, FAMILY CULICIDuE

With specimens of mosquitoes before you, study them with
a hand lens for (A) and with a compound microscope for (B).

A. a. One pair of membranous wings.

b. The legs are long and slender. Note the following parts,
femur, tibia, and tarsus, the latter segmented.

c. On the head are located the prominent eyes, the antenna,
and proboscis, with its pair of palpi. Note the relative length
of the palpi with reference to the proboscis.

B. a. Examine the wings and body for scales, a feature char-
acteristic of the mosquitoes.

b. Examine the tarsal claws, noting whether they are double
or single toothed or not toothed.

Draw a number of head scales, and the tarsal claws.

C. Sexual differences.

a. Examine the antenna of a male and of a female specimen,
and note the plumose condition in the former sex.

D. Characteristics of the Anopheles, or malaria mosquito, as
compared with the Culex, or rain-barrel mosquito.

a. Is there any difference in size?

20 MEDICAL ENTOMOLOGY

b. Compare the palpi, note the extreme length in Anopheles,
nearly as long as the proboscis, while in Culex they are less than
half as long.

c. Examine the wings for markings, spots, etc. Note that
Anopheles has spotted wings, which is the case in only a very
few species of Culex.

Draw the head and its appendages in Anopheles.

E. Compare the larva (wrigglers) of Anopheles and Culex.

a. Note the long prominent breathing tube or anal siphon of
Culex, short in Anopheles.

b. Note the arrangement of the tufts of hairs on the thorax
and abdomen. The anal tuft is especially prominent.

c. Count the number of body segments comprising the ab-
dominal region.

d. Examine the palmate hairs situated dorsally on abdominal
segments.

e. On the head note the presence of eyes, antenna and mouth
brushes.

Draw the larvae of both species, and label parts.

F. Compare the pupa (tumblers) of Anopheles and Culex.

a. Examine the prominent breathing trumpets (air siphons)
situated laterally and dorsally on the thorax. Compare the
breathing trumpets as to shape and position.

Draw an Anopheles tumbler.

G. Examine a slide of mosquito eggs.
Draw several specimens.

H. a. Examine specimens of the yellow fever mosquito (Steg-
omyia calopus} and note the prominent silvery markings. How
are these markings distributed?

b. What is the length of the palpi as compared with the pro-
boscis? Note other characteristics.

Draw a dorsal view of the insect.

THE HORSEFLIES 21

EXERCISE lOa

BUFFALO GNATS
ORDER DIPTERA, FAMILY SIMULIID^

A. The buffalo gnats or black flies are widely distributed; all
species are small, the largest less than % inch in length. Any
of the common species of Simulium will serve for this study.
Specimens mounted in balsam are needed for microscopic study.

a. Note the humped condition of the thorax, giving the insect
a buffalo-like appearance.

b. The antenna are short and stalky, but Nematoceron in
character.

c. Notice the characteristic venation of the rather large broad
wings. The first three longitudinal wing veins are very much
stronger than the rest.

d. Examine the mouthparts carefully. To what subtype to
the mouthparts belong?

Draw the specimen in outline.

B. If larvae of the buffalo gnats are available examine speci-
mens carefully and determine their adaptation to an aquatic
habitat.

Draw a specimen.

EXERCISE lOb

THE HORSEFLIES
ORDER DIPTERA, FAMILY TABANIDJS

Anatomical Study.

With a specimen of Tabanus stygius, Tabanus punctifer or
other allied species before you, note the following characteristics,
and make drawings of the parts.

22 MEDICAL ENTOMOLOGY

a. Antenna, — three-jointed, terminal segment annulated, and
not possessing the arista of the housefly and its allies.

b. Last tarsal segment, note the claws, pulvilli and empodium
between.

c. Head, note the large compound eyes, separated in the female
and contiguous in the male; note the sexual difference in size of
mouthparts.

EXERCISE lOc

THE HORSEFLIES

Systematic Study.

Family Tabanidae, antennae porrect, without arista, medium
sized to large flies.

1. Genus Tabanus, — hind tibiae without spurs, third seg-
ment of the antennae with a well developed basal process, ex-
amples, T. stygius, the black and white horsefly; T. punctifer;
T. atratus, the black horsefly; T. costalis, the greenhead; and
T. lineola, the lined horsefly.

2. Genus Chrysops, — (Earflies or Deerflies) — hind tibiae with
spurs at tip, third segment of the antennae composed of five
annuli; second segment of the antennae but little shorter than
the first; wings with a dark picture; examples, C. niger and C.
bruneus.

Draw one example each of the two genera mentioned above.

EXERCISE 11

THE HOUSEFLY (MUSCA DOMESTICA) AND THE STABLEFLY
(STOMOXYS CALCITRANS)

ORDER DIPTERA, FAMILY MUSCID®

A Comparative Study.

It will be remembered that while these two species of flies

THE HORSEFLIES 23

belong to the same family of insects (Muscidae), they differ
nevertheless greatly in their powers of disease transmission, the
former relating to indirect infection and the latter to direct
infection.

With a specimen of each species of fly before you, note the
distinguishing features, indicating the same by means of separate
drawings of the parts, and by description in your notebooks.

a. Mouthparts; note the characteristic position of these organs
at rest.

b. Wing venation; draw the right wing of each species, care-
fully drawing in the wing veins. Note the differences in venation
by crossing (x) the parts that vary, both cells and veins.

c. Coloration; indicate any differences in color, or color mark-
ings, that you may observe.

d. Note any other differences in position of the wings, relative
length of body, size, etc.

e. Sexual differences; ask your instructor for specimens of the
housefly representing the two sexes. Note that in the female
the compound eyes are widely separated, whereas in the male
the dorsal borders come close together. In the female the
terminal segments are protrusible, which should be demonstrated
by pinching the abdomen with the finger or forceps. The pro-
trusible segments make up the ovipositor.

f. Study a life history preparation of both the housefly and
the stablefly, showing the egg, larva and pupa. Compare es-
pecially the posterior spiracles of the larva, and pupa with refer-
ences to position, form and size. (Draw.)

24 MEDICAL ENTOMOLOGY

EXERCISE 12

THE STABLEFLY (STOMOXYS CALCITRANS) AND THE HORNFLY
OR TEXAS FLY (HEMATOBIA SERRATA)

ORDER DIPTERA, FAMILY MUSCID2E

A Comparative Study.

With specimens of each species of fly before you, note the
distinguishing characteristics, indicating the same by means of
separate drawings of the parts and by description in your note-
book.

These two species of flies belong to the blood-sucking branch
of the Family Muscidae, to which also belongs the genus Glos-
sina (Tsetse flies).

a. Mouthparts. The palpi of Stomoxys are relatively short,
while those of Haematobia are long and flattened. The pro-
boscis of the latter is also relatively more plump and is not so
well thrown forward, when at rest, as in the Stomoxys, due in
the latter to a well developed joint at its base.

b. Wings. Note the close similarity in wing venation. The
wings of the stablefly are thrown wide apart when at rest. f

c. Size. With at least half a dozen specimens of each species
before you note the relative size of the individuals. Measure
the length of these specimens in terms of millimeters.

d. Make a large drawing of the head of the hornfly, side view,
to show the following parts, compound eye, antenna, and pro-
boscis with palpi.

e. Draw the egg of the hornfly; note the brownish color. En-
large sufficiently to indicate general characteristics.

f. Note differences in the sexes as indicated by the segments
of the abdomen.

FLESH-FLIES 25

EXERCISE 13

FLESH-FLIES

*- • w

ORDER DIPTERA, FAMILY SARCOPHAGIDJE .

Family Sarcophagidae — thorax and abdomen provided with
stiff bristles. (Do not confuse with the Tachinidae.)

A. The Texas screw worm fly, Chrysomyia (Lucilia) macel-
laria.

a. Coloration; general color of the body is metallic green; the
thorax bears three longitudinal black dorsal stripes. The head
is distinctly reddish brown in color.

b. Size; the size of all species of flesh flies may vary consider-
ably within each group, due largely to lack of food during the
larval period. (See Herms, "An Ecological and Experimental
Study of Sarcophagidae," 1906.) However the screw worm fly
is a medium-sized fly, never attaining the size of the larger
species of flies, such as the blowfly, Calliphora wmitoria, for
example.

c. Mouthparts; compare with mouthparts of housefly.

d. Wing -venation; compare with venation of housefly.

e. Note the scissors-like folding of the wings. Draw the
specimen, indicating the striping and the characteristic folding
of the wings, in particular.

B. Examine and draw a specimen of the bluebottle fly, Cal-
liphora wmitoria. What are its characteristics?

C. Examine and draw a specimen of the greenbottle fly,
Lucilia c&sar. How does this species differ from Chrysomyia?

D. Study and draw mounted specimens of flesh fly larvae,
noting the oral hooks, or mandibles, shape, color and posterior
spiracles.

26 MEDICAL ENTOMOLOGY

EXERCISE 14

THE Box AND WARBLE FLIES

ORDER DIPTERA, FAMILY CESTRnXdE

A. With two specimens of (Estridae before you, one Gastro-
philus equi, the horse hot, and one Hypoderma lineata, the
ox warble fly, study the following characters, noting that the
examples are rather thickset and covered with hair, and that
the mouthparts are vestigial, the eyes small and bare, the
squamae large.

a. Antenna are small, three-jointed and decumbent, as in the
Muscidae. In the horse bot the arista is bare, while in the
warble fly it is plumose.

b. Tarsi of front legs, broad, flattened and hairy in Hypo-
derma, while they are slender and less hairy in Gastrophilus.

c. Wing venation; note the difference between the genera.

d. Sexual characters; notice the difference between the sexes
in the terminal abdominal segments.

Draw the characteristic details.

B. Larval Characters.

a. Segmentation; count the segments, paying especial attention
to the terminal ones.

b. Booklets; in the horse bot note the presence of a pah- of
outer booklets used for attachment to the walls of the stomach.
Note also a pair of inner straight points (not hooked). Are these
anterior or posterior?

c. Tubercles; in the warble notice the dorsal spindle-shaped
tubercles on the median segments and then* arrangement.

d. Examine a specimen of the head maggot of sheep ((Estrus
ovis).

Draw a specimen of each.

THE FLEAS 27

EXERCISE 15a

THE FLEAS

ORDER SIPHONAPTERA

Anatomical Study.

In order to find the following characters two species of fleas
should be used, namely, the human flea (Pulexirritans), and the
dog flea (Ctenocephalus canis). Note the entire absence of
wings and the characteristic laterally compressed condition of
the body ,with legs strongly developed for springing.

a. Legs; observe the greatly elongated coxa, and other seg-
ments.

b. Mouthparts; composed of sharp piercing structures; a de-
tailed study of which may be omitted here.

c. Antenna; short, three-segmented, usually sunken in a pit.
The terminal segment is swollen and annulated.

d. Combs; rows of spines on the head (oral), and thorax (pro-
notal), forming combs (ctenidia) are used to separate the fleas of
the family Pulicidae into the combed and non-combed species.
The number of spines in each comb is also useful for classifica-
tion. In the dog flea notice the two rows of combs and count the
number of spines in each.

e. Eyes, which may be present or absent, are of a simple type.

f. Examine and draw a specimen of flea larva.

g. Examine and draw specimens of flea eggs.
Draw one example of each species of flea.

28 MEDICAL ENTOMOLOGY

EXERCISE 16b

THE FLEAS

ORDER SIPHONAPTERA

Systematic Study.

Order Siphonaptera — wingless insects, laterally compressed,
body highly chitinized, provided with many regularly arranged
spine-like hairs.

A. Family Sarcopsyllidae, "Small fleas with disproportion-
ately large heads; female a stationary parasite with worm-like
or spherical abdomen, burrowing into the flesh of the host; labial
palpi one-segmented; no * combs' of spines on head, thorax or
abdomen" (Kellogg).

a. Examples, Sarcopsylla penetrans, the jigger-flea or chigoe
of mammals, including man.

b. Xestopsylla gallina, the hen flea.

B. Family Pulicidae, "larger fleas with proportionately small
head; adults active temporary parasites, with abdomen always
compressed; labial palpi 3 to 5 segmented; head, thorax or
abdomen often with 'combs' of spines" (Kellogg).

a. Examples, Pulex irritans, the human flea, non-combed.

b. Ctenocephalus canis, the dog and cat flea, two sets of
combs, one oral and one thoracic.

c. Ceratophyllus fasciatus, the rat flea, thoracic comb present,
but oral comb absent.

d. Ceralophyllus acutus, the squirrel flea, thoracic comb
present, consisting of nine spines on one side.

Draw the hen flea and either the rat flea or the squirrel flea.

THE TICKS 29

EXERCISE 16

LOUSE FLIES

ORDER DIPTERA, FAMILY HIPPOBOSCIDdE

A. The louse flies are extremely chitinous, dorso-ventrally
flattened insects, with suctorial mouthparts. Most of the
species are winged, and are often also called forest flies; the
wingless species are called "ticks," but should not be confused
with the true ticks (Ixodidae).

B. Study a specimen of the sheep "tick," Melophagus ovi-
nus, noting the following characteristics:

a. Louse-like form and reddish color.

b. The head is extremely small and the proboscis is prominent.

c. The species is wingless.
Draw the specimen.

C. Examine a puparium of Melophagus ovinus.

D. If available, compare a deer "tick," Lipoptena depressa
with the above.

E. The forest fly, Hippobosca equina, is a winged species.

a. In what respects does this species differ fromMelophagus
ovinus? In what respects do the two agree?
Draw the specimen.

-:.>VU^W>

EXERCISE 17a

THE TICKS

ORDER ARACHNIDA, FAMILY IXODIDAE

Anatomical Study.

Ticks belong to the same group as do the spiders, and therefore
have four pairs of legs in the adult stage. With a specimen of the

30 MEDICAL ENTOMOLOGY

wood tick (Dermacentor variabilis) or the Texas fever tick
(Mar gar opus annulatus), before you, study and draw the follow-
ing characters, making one drawing of the whole animal and
separate drawings necessary to show the details.

a. Rostrum, consisting of the head and mouthparts.

b. Labium or hypostome, a continuation forward of the head
(snout-like) possessing longitudinal rows of teeth.

c. Mandibles or cheliceres, one pair, terminating in well de-
fined teeth. The cheliceres work, each in a separate sheath.

d. Palpi or pedipalpi, segmented structures varying consider-
ably in relative length in the various genera.

e. The eight legs are composed of the following parts: coxa,
trochanter, femur, tibia, protarsus, tarsus, ungues (claws) and
pulvillus (absent in Argasinae).

f . Scutum or shield, a chitinous plate covering a portion of the
dorsal part of the body back of the head. This shield is often
ornamented with spots, furrows and perforations.

g. Eyes, present in Dermacentor and a few other genera, but
absent in a number of other genera, including Margaropus.

h. Anus, ventrally located, removed from the posterior border
and guarded by anal plates.

i. Anal groove, a furrow either posterior or anterior to the
anus, depending on the genus, and useful in classification.

j. Spiracles with guard plates, — situated laterally and ven-
trally, in some species in front of the fourth coxae, or in some
behind the fourth coxae.

fc. Marginal festoons; the marginal border of the abdomen is
often crenellated.

1. Sexual differences; the shield or scutum of the male covers
the greater part of the dorsum, while in the female it extends
over only a small portion posterior to the head. The male is
usually considerably the smaller and more slender, and is louse-
like in appearance. Though this is true for the Ixodinae, to
which group the specimens studied belong, in the Argasinae the
sexes are more difficult to distinguish.

OTHER TICKS 31

EXERCISE 17b

THE TICKS

ORDER ARACHNIDA, FAMILY IXODIRffi

Systematic Study.
Family Ixodidae.

A. Subfamily Ixodinae, scutum present, pulvilli present,
mouthparts projecting in front.

a. Examples: Mar gar opus annulatus, Texas fever tick or blue
tick, scutum uniformly chestnut brown in color, labium or
hypostome with eight rows of teeth. Front pair of legs emerging
from the shoulders. What is the form of the guard plates of the
spiracles?

b. Dermacentor variabilis, American dog tick, scutum spotted
with silver. Front pair of legs emerging close to capitulum.
What is the form of the guard plates of the spiracles?

B. Subfamily Argasinae, scutum absent, pulvilli absent,
mouthparts hidden under body.

a. Examples: Argas miniatus, American poultry tick, body
flat with thin edges, body oval, with rectangular marginal fes-
toons.

b. Ornithodorus megnini, the spinous ear tick, body lyre-
shaped and covered with spines.

Draw from specimens, using hand lens or binocular micro-
scope the three species not previously drawn.

EXERCISE 18a

OTHER TICKS

As far as it is possible to secure material examine specimens of
the following species of ticks, taking notes and making drawings

32 MEDICAL ENTOMOLOGY

of the same to fix the general characteristics of each in your
mind.

A. Ixodinae.

a. Amblyomma americanum is the Lone Star tick. Notice
the bright silvery spot at the posterior end of the scutum.

b. Dermacentor venustus is the Rocky Mountain spotted
fever tick. Notice the large size of the scutum, which has a
dark lyre-shaped figure upon it on a silvery background.

c. Rhipicephalus sanguineus is the brown dog tick.

d. Ixodes scapularis is the black legged tick or American
castor bean tick; the scutum is chestnut colored as in the Texas
fever tick, but the body has the shape of a castor bean, the legs
are black, and emerge from the body quite close to the mouth-
parts.

e. Rhipicephalus appendiculatus is one of the ticks respon-
sible for the transmission of African coast fever of cattle.

B. Argasinae.

a. Ornithodorus moubata is responsible for the transmission
of African relapsing fever of man.

b. Argas persicus is the Persian poultry tick, to which Argas
miniatus is very closely related. These ticks are responsible for
the transmission of Fowl Spirochaetosis.

EXERCISE 18b

LIFE HISTORY STUDY OF THE TICKS

A. Examine a prepared slide of tick eggs.

B. If available, examine an ovulating female tick. Notice
that the mass of eggs lies anterior to the body, with the head
buried in it. Why?

C. Examine mounted specimens of ticks that have recently
emerged from eggs, noting particularly the number of legs. ;

THE MITES 33

D. Compare specimens of young female ticks with specimens
that are fully engorged.

E. Examine again a series of males and females of several
species, to determine sexual differences.

EXERCISE 19a

I

THE MITES

CLASS ARACHNIDA, ORDER ACARINA, FAMILY GAMASIH£

A. General characteristics of mites; usually quite small, just
about visible to the naked eye, some larger. The body portions
are more or less closely united. The mouthparts are piercing
and sucking structures. The four pairs of legs are generally
well developed, terminating in suckers. The sexes are separate.
The young are hexapod.

B. Characteristics of Gamasidce; the legs are six-segmented and
terminate in a pair of ungues and a sucker-like disc. The
stigmata or breathing pores are located between the third and
fourth pairs of legs.

C. The poultry mite, Dermannyssus gallina. Study speci-
mens mounted in balsam.

a. Measure size of the specimens. How do the males and fe-
males differ in this respect?

b. Note the position of the legs with respect to the body
divisions.

c. Count the segments of a leg and note the terminal struc-
tures.

d. Locate the stigmata.

Draw the specimen, labelling the parts.

34 MEDICAL ENTOMOLOGY

EXERCISE 19b

THE MITES

CLASS ARACHNIDA, ORDER ACARINA, FAMILY SARCOPTID2E

A. Characteristics of Sarcoptida. The legs are six-segmented,
short and thick, and terminate in a sucker or a slender bristle
ending in a disc-like sucker.

B. Sat -copies scabei var. suis. This variety of itch mite in-
habits the skin of the domestic pig, tunneling its way through
the epidermis, causing a scaly appearance. This variety may
also attack man.

a. Note the minute size of this species. How does it compare
with the poultry mite in this respect?

b. How does it compare in color with the poultry mite?

c. What is the form of the body and position of legs?

d. Note the transverse rows of bristles on the dorsal surface of
the mite.

e. Study the .terminal structures of the leg, noting especially
the spines and sucker (ambulacrum).

Draw the specimen.

EXERCISE 20

OTHER MITES

CLASS ARACHNIDA, ORDER ACARINA, FAMILY SARCOPTHXE (cont.)

A. Psoroptes communis var. ovis is the scab mite of sheep,
producing scabies. Comparing this Psoroptic mite with the
Sarcoptic mites, notice the following characteristics:

a. The body is elongate oval.

b. All four pairs of legs appear beyond the margin of the body.

THE INSECT STING 35

c. The third pair of legs is devoid of ambulatory suckers, and in
their place note a long pair of bristles for each leg.
Draw a female specimen.

B. Psoroptes communis var. boms is the mange mite of the ox.
a. Can you find any perceptible difference between this

species and the one above?

C. Psoroptes communis var. equi is the mite which causes
humid mange of the horse.

a. The rostrum is characteristically long, twice as long as
broad, otherwise the species differs but imperceptibly from the
species above.

D. Sar copies scabiei var. canis is one of the mange mites of
the dog.

a. Notice similarity to the variety inhabiting swine.

E. Sarcoptes mutans is the parasite which causes scaly leg
in poultry.

Examine a bit of mounted scrapings from the leg of a hen
affected with scaly leg. The circular mites (typically Sarcoptic)
are easily visible.

Draw the specimen.

EXERCISE 21a

THE INSECT STING

The insect sting, as found in the Hymenoptera (bees, wasps
and ants) is a modified ovipositor, the function having been
changed from that of an egg apparatus to that of a defensive
weapon. In many insects the sting still serves both purposes.

A fresh worker bee should be used for study; these can usually
be procured at a nearby apiary, or bees may be killed hi the
field just before using.

With a needle remove the last evident scale-like segment of
the abdomen, which will bring with it the sting, the venom sac

36 MEDICAL ENTOMOLOGY

and much of the alimentary canal. The sting can be recognized
at once as a fine needle-like structure, and the venom sac as a
very small semi-transparent sac. With needles carefully sepa-
rate the sting with the sac and other accessory structures.
Teasing out these structures can well be accomplished under
water, with the aid of a dissecting microscope or binocular. The
following parts should be noted, drawn and labelled:

a. The sting proper, consisting of two darts, ending in distinct
serrations and bending at the base to either side for muscular
attachment and leverage.

b. The sheath, partly enclosing the upper part of the darts,
and terminating in a fine cutting edge at the distal edge of the
sting proper. It also serves to direct the flow of venom into the
wound.

c. The sting palpi, situated on either side of the darts.

d. The venom sac, emptying by means of a broad neck into
the poison channel.

e. The poison gland, recognizable as a long coiled tube leading
into the anterior end of the venom sac.

EXERCISE 21b

VENOMOUS SPIDERS AND SCORPIONS
CLASS ARACHNIDA, ORDER ARANEIDA AND ORDER SCORPIONIDA

A. The most venomous of our few dangerous spiders is Lac-
trodectes mactans. With a specimen of this spider before you,
note the following characteristics:

a. It is a medium-sized spider.

b. The color is brownish black to inky black.

c. Notice two brick red triangular spots on ventral side of
abdomen.

PARASITICIDES 37

d. Notice the comparative absence of hairs on the body of
this species.

e. Notice the mouthparts. How does the spider "bite"?
Draw the specimen.

B. Our commoner scorpions are represented by the three
genera, — Centrums, Hadrurus, and Uroctonus.

Examine a specimen for the following characteristics:

a. What is the form of the moiUhparts?

b. What is the form and function of the chelicerce?

c. How many walking appendages has the scorpion?

d. Examine the sting at the tip of the abdominal appendage.
Draw the specimen.

C. Examine specimens of the whip scorpion (Order Pedipalpi).

'' //XV2MA/U < ..'•

EXERCISE 22

A^n

PARASITICIDES

Poisons and repellents. The student should familiarize him-
self with at least a few of the commoner materials used to de-
stroy or repel parasites of man and the domesticated animals.
Samples of each of the following materials should be examined,,
and notes should be taken describing the physical properties,
such as color, smell, weight, whether liquid or solid, whether
homogeneous or a mixture, etc. Caution! Do not taste these
materials; they are Poisons.

a. Nicotine (tobacco decoction) is used as a dip for the
destruction of scab mites on sheep and also against lice and
mites on other animals which do not vomit. Nicotine is a poison.
The proportion of tobacco decoction used depends on the
nicotine content. " Black leaf 40," a commercial brand, has a
high nicotine content. One pound of a forty per cent solution of
nicotine to 100 gallons of water (soft water) would make a dip
answering the requirements of the U. S. Bureau of Animal

38 MEDICAL ENTOMOLOGY

Industry as used against sheep scab, but the addition of sulphur
(16 pounds to the above formula) is recommended.
Examine a sample of tobacco decoction.

b. Lime and sulphur form the active ingredients for a dip
used against scab mites of both sheep and cattle. When used
for scab in sheep the following formula is recommended: 24 Ibs. -
flowers of sulphur, 8 Ibs. of unslaked lime to 100 gallons of soft
water; when used for cattle scab or mange, the lime should be
increased to 12 Ibs.

Examine a sample of lime sulphur solution.

c. Cresol is a coal tar product of high cresylic acid content
(from 90% to 98%) and is ordinarily a straw-colored liquid.
Cresol is poisonous, and corrosive. In order to produce a
mechanical mixture with water, cresol is carefully mixed with lin-
seed oil or soap, and when prepared according to the U. S. Phar-
macopeia is known as " liquor cresolis compositus." As a disin-
fectant, it is useful diluted with water at from 2 to 4%. It is also
used as an ingredient in sheep dip. The percentage of cresol
used with water depends on the government rating of the cresol.

Examine a sample of cresol, and of liquor cresolis compositus.

d. Crude Carbolic Acid is a, coal tar product with a low phenol
and cresylic acid content. It is poisonous. (Pure carbolic acid —
phenol — must not be confused herewith.) In using carbolic acid
as an ingredient for dips and disinfectants, the phenol content
should be known, since there is considerable fluctuation in the
amount of this ingredient. Dilution with water to 2 to 4% of
its phenol content is sufficient for disinfection. For dipping the
same may be said as for cresol.

Examine a sample of crude carbolic acid, and samples of
carbolic acid crystals, which are pure phenol.

e. Creoline is a coal tar product of a low phenol content. It
is poisonous. Creoline is much used for dipping and disinfection.
Drop a little in water and notice the result. For dipping "pur-
poses dilute with water to from 2 to 4%. It is useful in destroy-
ing lice, and less so for scab mites, on domesticated animals.

PARASITICIDES 39

For human head lice, creoline (2%) may be applied by means
of a fine tooth comb.

f. Kerosene is an extremely useful insecticide, but must be
diluted to prevent injury to animals, and is therefore preferable
as a spray for coops and stalls infected with mites or lice. Kero-
sene may be used pure for the latter purpose, or as an emulsion
not weaker than i to 10. The emulsion is prepared by dissolving
y£ lb. of soap in one gallon of hot water and adding one gallon
of kerosene. This forms a stock solution, and illustrates the
proportion for all practical purposes.

Examine a sample of kerosene emulsion, both in stock and
diluted one to ten.

g. Arsenic may be used as the active ingredient for sheep dips
and cattle dips. It is extremely poisonous, and the heads of
animals dipped must be kept out of the solution and the cattle
prevented from licking themselves or each other. Persons
employed in dipping operations must proceed with caution.
Dipping vats and stock solutions must be kept tightly closed to
prevent animals from drinking the poison. Dripping animals
must not be permitted where there is green herbage.

Examine a sample of arsenic crystals.

h. Pyrethrum powder, or buhac, is a fine yellow dust made
from the flower of Chrysanthemum cinerariafolium. This
powder is useful against lice and fleas. It is applied by means of
an insufflator or duster, and must be freely used.

Examine a sample of pyrethrum powder or buhac.

i. Naphthalene flakes are very useful as a repellent. The flakes
are dusted on the animals, and brushed into the hair freely.
Lice and fleas are strongly repelled.

Examine a sample of naphthalene flakes.

j. Tobacco dust or snuff, added in equal parts or one to three
of road dust is extremely useful as a dust bath for poultry.
Some sulphur may well be added.

Examine a sample of tobacco dust.

k. Sulphur may be used in cones, with wicks, for fumigating

40 MEDICAL ENTOMOLOGY

purposes, or as flowers of sulphur, to be mixed with tobacco
dust, as above, or in the form of an ointment, against scab and
mange mites on domesticated animals, or for human scabies
(itch). An effective sulphur ointment is prepared as follows:

Sulphur, i oz., carbonate of potash y£ oz. and lard 4 oz.

Examine some flowers of sulphur and a sulphur cone.

1. Formaldehyde is a splendid disinfectant and a good stomach
poison for flies, but is useless as a spray against insects. As a
fly poison formaldehyde purchased in about 38% to 40% solu-
tion must be diluted with water to about 2% or even less, that
is, one part to twenty or thirty parts of water. This must be
made accessible to the flies in shallow vessels.

Examine some formaldehyde.

m. Oil of Citronella is a good repellent against mosquitoes,
black gnats, etc. It should be applied full strength to the hands
and face.

Examine a sample of oil of Citronella.

m. Larkspur (Delphinium staphisagria) is useful in the de-
struction of both the human head louse and the crab louse. It
is ordinarily used in the form of tincture or ointment (Unguen-
tum Staphisagria) 10%.

Examine a sample of tincture of larkspur.

EXERCISE 23a

THE AMCEB.S:
PHYLUM PROTOZOA, CLASS RHIZOPODA (SARCODINA), ORDER

AMCEB^A

A. In prepared specimens on slide of Entamoeba histolytica,
the amoeba of Oriental dysentery, note the following: (The
student is cautioned against confusing these with leucocytes
and foreign matter.)

THE TRYPANOSOMES 41

a. Outer clear portion, the ectosarc.

b. Inner granulated portion, the entosarc.

c. The irregular projections, the pseudopodia, in which the
ectosarc is best seen. These are organs of locomotion.

d. In the entosarc a dark globular body is visible, the nucleus.

e. Some specimens may show one or more clear globular
bodies in the entosarc, the vacuoles.

Draw several specimens.

B. Examine the slide for encysted amoebae.

EXERCISE 23b

THE TRYPANOSOMES

PHYLUM PROTOZOA, CLASS FLAGELLATA (MASTIGOPHORA), ORDER
LISSOFLAGELLATA

A. In prepared samples of blood smears from an animal af-
fected with Nagana, note the presence of spindle-shaped organ-
isms with a whip-like appendage, Trypanosoma brucei, the try-
panosome of Nagana.

a. A single whip-like appendage, the flagellum.

b. A thin fold along the dorsal edge, the undulating membrane.

c. Near the middle of the body a dark object, the nucleus.

d. Near the anterior end (the flagellum end) of the body, a
small mass of chroma tin, the blepharoplast.

Draw several specimens.

B. In a suitable blood smear from a rat, examine for try-
panosomes, in this case Trypanosoma lewisi.

Compare A and B.

C. In a blood smear taken from a patient suffering from Afri-
can sleeping sickness, first stage, examine for Trypanosoma gam-
biense.

Compare this with A and B.

42 MEDICAL ENTOMOLOGY

D. Examine a specimen of Tsetse fly, the carrier of A and C.

a. Examine the moulhparts.

b. Examine the antenna with plumose arista.

c. Note general form of the fly, constricted " waist."
Draw the specimen in outline.

E. As a matter of comparison, in a suitable preparation from
a fowl suffering with Spirochaetosis, study and draw the causa-
tive organism, Spirochceta gallinarum, and compare this further
with Treponema pallida of Syphillis.

EXERCISE 24

THE MALARIA PARASITES
PHYLUM PROTOZOA, CLASS SPOROZOA, ORDER KffiMOSPORIDIA

NOTE: — It is expected that the student will read some concise
account of the normal constituents of the blood before proceed-
ing with this exercise, e. g. at least the first 9 pages of Chapter I,
" Practical Study of Malaria," by Stephens and Christophers.

A. Sporozoan of quartan malaria, Plasmodium malaria.

For this exercise use stained blood films from malarial patients.

Examine slides from cases of quartan infection (malaria with
fever recurring every three days, 72 hours). Look for pig-
mented bodies inside of red corpuscles. Determine the follow-
ing stages:

a. Small round pigmented body shortly after having entered
the corpuscle.

b. Signet rings, young intracorpuscular parasites.

c. The parasite nearly filling the corpuscle, showing as a
deeply pigmented body consisting of coarse granules. A num-
ber of darker bodies may be seen in the parasite, indicating the
presence of the micleoli preparatory to sporulation.

d. Find a corpuscle showing the parasite in a segmented con-

THE MALARIA PARASITES 43

dition, each spherical element provided with a nucleolus and the
eight or ten elements arranged so as to give the appearance of a
daisy.

e. Find a corpuscle that has been broken down, thus liberating
the sporulated parasite.

Draw several stages.

B. Sporozoan of benign tertian malaria, Plasmodium vivax.
Examine blood slides from cases of tertian infection (malaria

with fever recurring every two days, 48 hours).

a. Note the fact that the pigmented granules of this parasite
are considerably finer than in the quartan.

b. Signet rings as in A.

c. In the segmentation stage of this form note the irregularity
in arrangement of the elements and their greater number.

Draw several stages.

C. Sporozoan of malignant tertian fever, Plasmodium pracox.
In a slide taken from an advanced case of malignant tertian

malaria (aestivo-autumnal fever) note the presence of:

a. Crescent-shaped bodies either free or intracorpuscular
(usually only one in a red corpuscle). The crescent stage in this
variety of parasite represents a condition just previous to the
sexual changes undergone in the body of the Anopheles mos-
quito, or on contact with the air (see below). Female crescents
have the chromatin massed centrally while the male crescents
have it distributed and are hyaline.

b. The parasite of malignant tertian malaria (Plasmodium
pracox) is said to be smaller in the mature form than is the
benign tertian parasite.

c. Examine signet rings for double nuclei.
Draw crescents.

D. The stained parasites of malaria often show ring forms,
and when stained with Romanowsky stain, the red nucleus may
be between the ends of the slender crescent, forming thus a
" signet ring"

a. Examine slides for the "signet ring" forms.

44 MEDICAL ENTOMOLOGY

E. Outside of the corpuscles in the preparations already ex-
amined search for flagellated bodies, the microgametes (sperma-
tozoans), or male sexual elements. These are produced from
crescent-containing blood on exposure to air for a few minutes.
(Some species do not form crescents before flagellation, e. g. the
benign tertian and the quartan.)

F. In a stained preparation of the salivary glands of a malaria-
infested Anopheles mosquito determine the presence of sporo-
zotts, recognizable as slender, slightly curved rods.

G. In a stained preparation of the midgut of a malaria-
infested Anopheles mosquito, determine the presence of sporo-
blasts, as pigmented bodies (elongate, as sporozoits when ad-
vanced) inside of cysts recognizable as wart-like bodies external
to the gut.

H. As a matter of comparison examine a blood smear of Texas
cattle fever, and study and draw the causative organism Babesia
(Piroplasma) bigeminum with reference to form and relative
size. This organism is carried by the cattle tick, Margaropus
annulatus.

PART II

HELMINTHOLOGY
INTRODUCTION

The object of the following exercises is to acquaint the student
with the commoner parasitic worms infesting man and the do-
mesticated animals.

Formerly the term Vermes was used to cover all groups of
worms. This group is now divided into a number of phyla, of
which the following include parasitic forms:

a. Nemathelminthes. Commonly called thread worms, or
roundworms, they are cylindrical, non-segmented animals, usu-
ally more or less tapering at both ends. The alimentary
canal is simple and well developed, except in the Acantho-
cephala. The water-vascular canals are usually conspicuously
located on both sides, longitudinally. The sexes are separate and
development is usually direct, i. e. without a necessary inter-
mediary host. Examples are the roundworm of the horse,
(Ascaris megalocephala), and the trichina of swine, rats and man,
(Trichinella spiralis).

b. Annelida. Worms composed of a series of rings, this seg-
mentation often affecting the internal organs. The number of
segments is usually large, a fact that will differentiate these
worms from certain parasitic insect larvae, in which the seg-
ments are generally n or 12, never more than 19 or 20. In-
ternally, of course, the presence of a tracheal respiratory system
will differentiate the latter. Examples are the common earth-
worm (Lumbricus terrestris) and the medicinal leech (Hirudo
medicinalis). (The latter only need be considered here.)

45

46 HELMINTHOLOGY

c. Platyhelminthes. In this group of worms the body is more
or less flattened dorso-ventrally. The digestive tract may be
entirely lost, as in the tapeworms, or may consist of a blind sac,
more or less branched, as in the flukes. An anal aperture is
never present. The flat-worms are usually hermaphroditic, and
development in the parasitic species is usually indirect, i. e.
through an intermediary host. Examples are the pork tape-
worm of man (Tania solium) and the liver fluke of sheep [Fas-
ciola (Distoma) hepatica}.

To distinguish worms from insect larva. When insect larvae
(parasitic in the body of higher animals) are encountered, there
may be some difficulty in differentiating them at once from
worms, because of their environmental setting. Instances of
this are bots and warbles ((Estridae), screw worms (Chrysomyia
macellaria) and flesh fly larvae (Sarcophagidae) in intestinal
myiasis. Usually these larvae, are short and plump, with well-
marked segments, few in number, usually n or 12, certainly not
more than 20. Furthermore, microscopic examination will re-
veal a system of tubules in the insect, extending internally to
all parts of the body, the tracheal breathing system.

EXERCISE 25a

THE ROUNDWORMS

PHYLUM NEMATHELMINTHES, CLASS NEMATODA, FAMILY
ASCARID^E

The roundworm of the horse — Ascaris megalocephala.

A. Characteristics of Nematoda. The roundworms or thread-
worms may be recognized by their cylindrical, non-segmented
or non-jointed form, covered with a rather thick cuticle, and
the presence of a simple, well-developed alimentary canal; also
a pair of lateral longitudinal water-vascular canals, usually

THE ROUND WORMS 47

conspicuous. The mouth is terminal. The sexes are separate,
and the males are generally shorter and more slender than the
females. The development is usually direct (exceptions) and
requires no intermediate host (exceptions).

B. Characteristics of Ascaridce. The Ascaridae are generally
large-sized worms (more than 2 mm. in thickness at the middle
in the typical Ascarids, much less in Oxyurids). The terminal
mouth is surrounded by three prominent papillae or lips, one
situated dorsally and two ventrally. The anus is located ven-
trally just anterior to the termination of the body.

C. Examine specimens of Ascaris megalocephala, the round-
worm of the horse. This species is chosen for use because of its
convenient size and typical characteristics.

a. Note sexual differences in size and the presence of two
terminal spicules of equal length in the male.

b. Examine the oral papilla or lips, and the ventral trans-
verse anal aperture. How can you locate the dorsal and ventral
sides of the animal?

c. Notice the two lateral longitudinal water-vascular canals.

d. Measure the length of several specimens in centimeters.
Draw a specimen and label the parts.

e. Examine several posterior and median cross-sections of a
female Ascaris, noting the presence of the intestine, and uterus
with ova.

D. Examine other species of Ascaris, noting especially size
and color, viz. :

a. Ascaris lumbricoides of man.

b. Ascaris suilla of swine.

c. Ascaris vitulorum of cattle.

d. Ascaris mystax, the mawworm of dogs and cats.

\

48 HELMINTHOLOGY

EXERCISE 25b

OTHER ASCARIDJS

A. Study mounted specimens of Oxyuris vermicularis, the
pinworm of man, noting,

a. The length in millimeters.

b. The form of the body, tapering from the middle toward the
blunt anterior end, with thrice papillated mouth, and terminat-
ing posteriorly in a fine pointed tail.

c. What are the sexual differences?
Draw male and female specimens.

B. Examine specimens of Oxyuris curuula of the horse, and
the long-tailed species of the same host, Oxyuris mastigodes.

C. Study mounted specimens of Heterakis papillosa, the
caecum worm of the hen.

a. Notice the three-lobed lips or papilla.

b. What is the average size and form of this species?

c. Examine male specimens, locating the two posterior
spiculce.

Draw male and female specimens.

EXERCISE 25c

THORN-HEADED WORMS
PHYLUM NEMATHELMINTHES, CLASS ACANTHOCEPHALA

The thorn-headed worm of swine, — Echinorhyncus gigas.

A. Characteristics of Acanthocephala. Ascaris-like worms,
with a rostrum covered with recurved hooks; intestine absent.

B. Echinorhynchus gigas. Examine specimens of the thorn-
headed worm of the pig for the following characters:

THE HOOKWORMS 49

a. Measure the length of the specimens. How do the sexes
compare in this respect?

b. Examine the rostrum and note the position of the booklets.

c. Examine a cross-section of this worm.

d. How does this worm procure its food?

Draw a specimen to show general form, and make a detailed
drawing of the rostrum, showing the booklets.

C. Examine a specimen of one of the beetles which serve as
intermediary host, e. g. Melolontha vulgaris, the European May
beetle or a species of Lachnosterna. fe&A

^'^

, .^

EXERCISE 26

THE HOOKWORMS

PHYLUM NEMATHELMINTHES, CLASS NEMATODA, FAMILY STRON-

GYLID.E

A. Characteristics of Strongylidce. Nematode worms with six
circumoral papillae, with or without a buccal capsule, in either
case may have an armature of teeth or hooks. Females have
two ovaries, with genital pore usually posterior, but may be in
front of middle; oviparous, with direct development. Caudal
bursa of males is lobed, each lobe with supporting rays, and two
spiculae about equal in length.

B. Ankylostoma duodenale is the European hookworm of
man.

a. Measure length of several specimens, determining first the
sex.

b. Just inside the oral aperture notice the presence of re-
curved teeth. How many teeth are there in all and what is the
arrangement?

c. At the base of the buccal cavity there are also present
several chitinous processes.

50 HELMINTHOLOGY

d. Notice the long slender spicules of the males. Are they of
equal length or not, and how many are there?
Draw male and female specimens.

C. Necator (Uncinaria) americana is the American hook-
worm of man.

a. How does it compare with the above species in form and
size?

b. Is the buccal capsule as large as the above?

c. Compare the form and arrangement of the teeth with the
above.

Draw a specimen, showing only the anterior end with buccal
cavity and teeth.

D. Strongylus edentatus is the blood-sucking strongylid of
the horse. Examine specimens of this or the related species,
Strongylus (Sclerostoma) armatus.

a. Strongylus edentatus is called the "Toothless Strongylid."
Are there no teeth in the buccal cavity?

b. Examine specimens of both males and femafes and com-
pare these with human hookworms as to size, form and other
characters.

Draw a specimen to show general outline.

EXERCISE 27

OTHER HOOKWORMS

A. Monodontus phlebotomus is commonly called the hookworm
of cattle, and is the probable cause of salt sickness. Exam-
ine mounted specimens and make the following determina-
tions:

a. What Strongylid characters do these worms possess?

b. Examine the large buccal capsule, "provided at its base
with a strong dorsal tooth projecting into its cavity, and with
four ventral teeth or lancets." (Ransom.)

THE LUNGWORMS 51

c. What is the relative length of males and females?
Draw a complete specimen and make a separate drawing of
one showing the details of the buccal cavity.

B. Examine a specimen of Monodontus trigonocephalus, the
hookworm of sheep. What are the main points of contrast with
the above?

C. Study mounted specimens of (Esophagostomum colum-
bianum, the cause of nodular disease of the intestine of sheep.
How does this compare with the bovine-inhabiting species as to
relative size of buccal cavity?

Draw the specimen.

D. Another common Strongylid parasitic in the intestine
(fourth stomach) of sheep is H&monchus contortus, also a hook-
worm, but possessing a narrow buccal cavity. Notice the
twisted condition of the body in the female, due to ovaries
wound spirally around the intestine.

Examine and draw specimens of male and female.

EXERCISE 28

THE LUNGWORMS

PHYLUM NEMATHELMINTHES, CLASS NEMATODA, FAMILY
STRONGYLID^

A. Dictyocaulus viviparous (Strongylus micrurus) is the
lungworm of cattle. The worms inhabit the bronchia and lungs
of young calves, especially. Eggs are deposited in the lungs and
air passages and are coughed out by the host.

a. Examine a portion of the lung of an infested calf in which
the worms are present in "pockets." If available examine an
infested lung which has been cut open. What can you say about
the distribution of the worms in the lung? Strongylosis is the
term applied to this infestation.

52 HELMINTHOLOGY

b. Study a mounted specimen under a low power. Note the
presence of six circumoral papilla.

c. In a stained female specimen note the presence of two
ovaries.

d. In a mounted male specimen notice the presence of a pair
of caudal spicules. Are the spicules of equal length? Examine
the caudal membrane for ribs. How many ribs are there?

Draw both specimens, showing details.

C. Examine a slide with young and embryo Strongylids.
Draw an example of Strongylid larva.

D. Study specimens of Strongylus ovis pulmonis, the lung-
worm of the sheep. Describe the specimen and determine main
points of difference as compared with the above species.

E. Study specimens of Syngamus trachealis, the gapeworm
of chicks.

Draw a specimen.

EXERCISE 29a

THE WHIPWORMS

PHYLUM NEMATHELMINTHES, CLASS NEMATODA, FAMILY TRICHO-
TRACHELLID^

A. Characteristics of Trichotrachellidce. " Recognizable by the
oesophagus, which resembles a necklet of pearls; the anterior
part of the body is usually of thread-like slenderness, the pos-
terior part of the body, which contains the genitalia, is more or
less thickened; there may be no spicules or only one. There is
a single ovary; vulva situated at the border line between the
anterior and posterior parts of the body." (Braun.) In the
subfamily Trichurinae there is a single spicule in the male;
development is direct, without encysted larval stage; and eggs
pass out of the body of the host and do not hatch until taken

TRICHINA 53

into the body again. In the genus Trichuris, the typical whip-
worm, the anterior portion of the body is of thread-like slender-
ness and longer than the posterior heavy portion of the body.

B. There are several species of whipworms belonging to the
genus Trichuris, all of which partake of the characters above
mentioned.

Examine and draw specimens of the following species.

a. Trichuris (Trichocephalus) trichuris is a common whip-
worm of humans. Note the following characters; position of
mouth, length of thread-like cesophageal region as compared
with the thick body; total length, color. In a male specimen find
the spicules.

b. Trichuris oms is a common whip worm of sheep, cattle and
goats.

EXERCISE 29b

TRICHINA
PHYLUM NEMATHELMINTHES, CLASS NEMATODA, FAMILY TRICHO-

TRACHELLID.E

Trichinella spiralis is the cause of trichinosis of humans and
other mammals. The adult trichinae inhabit the large and
small intestines of several species of mammals, among them
man, the domestic pig and the rat. The worms find their way
into the intestine with infested flesh eaten by one of the animals
mentioned. In the intestine copulation takes place between
male and female trichinae; the female gives birth to living young
in great numbers; these are carried by the lymph and blood to
many parts of the body, finally finding lodgment in the muscles,
where they invade the connective tissue and even the fibres,
later becoming encysted.

a. Examine under a compound microscope a prepared piece

Ib

54 HELMINTHOLOGY

of diaphragm of the rat or pig infested with Trichinella spiralis.
Count the number of cysts for a given area, e. g. i sq. cm.

b. Examine the specimen with the naked eye. Can you see
the cysts?

c. Is there any general position that the trichina has taken
within the cyst?

d. Find trichinae that show advanced stages of calcification.

e. Examine the adjacent muscle fibres to determine effect on
the same.

Draw a characteristic specimen of trichina, showing it in its
relation to the muscle.

EXERCISE 30a

THE FILARIJE

PHYLUM NEMATHELMINTHES, CLASS NEMATODA, FAMILY
FILARIIDJ2

A. Characteristics of Filariida. "Body long, filiform; mouth
surrounded with papillee, or provided with two lips ; oesophagus
slender, without posterior bulb. Males with single spicule or
two unequal spicules. Females with two ovaries, vulva usually
in front of middle of body. Usually oviparous. Development
in many cases requires an intermediate host." (Ransom.) The
Filariae are extremely slender hair-like worms inhabiting the
blood and lymphatic fluids. They range in length from micro-
scopic species, such as Microfilaria bancrofli, to the extremely
long guinea worm, Filaria medinensis, which probably averages
90 cm. in length. (Manson.)

B. Microfilaria bancrofli (Filaria nocturna). Examine a
prepared slide of human blood taken from a patient suffering
from elephantiasis, a disease caused by the presence of filariaa
in the lymphatic vessels.

THE LEECHES 55

a. Under a moderately high power of the microscope, note
that the filarise have an eel-like form, with the anterior portion
truncated, while the posterior portion gradually tapers off to a
point.

b. Notice the clear sheath enclosing the entire worm. The
mosquito, Culex fatigans, is the intermediary host for the
species.

Draw the specimen.

C. Examine and draw filariae in a blood smear from a ground-
squirrel.

D. Examine specimens of Filaria ceruina, a filarious worm
inhabiting the peritoneum of cattle and other ruminants. Note
the number of papilla around the mouth, the number of spicules
in the male, and whether the vulva of the female is anterior or
posterior.

EXERCISE 30b

THE LEECHES
PHYLUM ANNELIDA, CLASS HIRUDINEA

A. Characteristics of Annelida (Annulata). Worms belonging
to the Phylum Annelida consist of a series of rings or segments;
there are no jointed appendages, the alimentary canal is well
developed.

B. Characteristics of Hirudinea. The leeches are character-
ized by the possession of a sucker at each end of the body; the
internal segmentation and the number of body rings do not
correspond.

C. With a specimen of a leech before you, notice the following
parts:

a. The mouth, situated in the anterior sucker.

b. The anus is located dorsal to the posterior sucker.

c. Count the number of segments or annuli.

56 HELMINTHOLOGY

d. Examine the buccal cavity of the specimen for jaws. What is
the arrangement of the jaws? Some leeches do not possess jaws.

D. Examine a specimen of the medicinal leech, Hirudo
medicinalis.

a. Examine the jaws for teeth.

b. What is the color of the specimen, noting longitudinal
striping?

Draw the specimen.

E. If available examine and describe a specimen of the horse
leech, Hcemopis sanguisuga.

EXERCISE 31

THE SHEEP LIVER FLUKE — DISTOMUM HEPATICUM

ORDER PLATYHELMINTHES, CLASS TREMATODA, ORDER MALACOCO-
TYLEA, FAMILY FASCIOLID.E

A. Characteristics of Platyhelminthes. Body more or less
flattened dorso-ventrally; alimentary canal, absent entirely in
the tapeworms, consists of a blind sac more or less branched.
No anus. Usually hermaphroditic, and development in the
parasitic species is usually indirect, i. e. through an intermediary
host. The phylum is divided into three classes: i, Turbellaria,
free living, non-parasitic; 2, Trematoda, flukes; and 3, Cestoda,
tapeworms.

B. Characteristics of Trematoda. Usually leaf-shaped, but in
a few species conical; sucking discs are commonly found on the
anterior and posterior extremities, and the ventral surface.
Mouth is at anterior end, and sexual openings in the ventral
sucker.

C. Characteristics of Fasciolida. One oral and one ventral
sucker; excretory pore discharges at posterior border.

D. Distomum (Fasciola) hepaticum. This liver fluke in-

THE SHEEP LIVER FLUKE 57

habits the bile ducts of such herbivorous animals as sheep,
goats, deer and cattle. It is a cosmopolitan form, being found
in North and South America, Europe, Asia, Australia and Africa.
In many countries sheep raising is considerably hampered by
liver rot caused by the presence of these parasites. The species
undergoes a very characteristic complex metamorphosis, part of
which is passed in the body of a snail of the genus Limnaeus,
and part in the herbivorous host.

Life history. The eggs are deposited by the hermaphroditic
adult liver fluke in the bile ducts of the host, thence are washed
out through these passages into the intestine and pass out of the
host with the faeces. If the ova chance to reach water, the
ciliated embryos, called miracidia, emerge. The miracidium
soon penetrates the intermediary host, usually a small snail
(Limnseus) entering through the pulmonary passage. Within
the snail the miracidium transforms into the sporocyst, in which
a number of bodies are formed, each of which develops into the
next stage, the redia. Thus one egg may give rise to a number
of individuals, through this sporulating process. The redia
next develop into the tailed cercaria, in which condition the
intermediary host is abandoned. The cercaria swim about in
the water, finally losing the tail, and becoming encysted on a
grass blade or other plant, which is eaten by the sheep or other
herbivorous animal, resulting in infestation. In some species
the cercaria bore into a second intermediary host, in which they
become encysted and are swallowed by the animal together with
this second intermediary host. Once within the alimentary
canal of the final host the young flukes find their way to the bile
ducts and reach sexual maturity.

E. Structure. With several specimens of the adult liver fluke
before you, one of which should be stained and mounted in
balsam, note the following characteristics:

a. Form, is leaf-like and flattened.

b. Suckers, with a hand lens note a terminal oral sucker, and
a -ventral sucker, whence the name Distomum.

58 HELMINTHOLOGY

c. Sexual organs, just back of the neck-like portion, in the
region of the ventral sucker, notice the coiled uterus, yellowish
in color, and filled with eggs. The yolk reservoir may be located
just back of the uterus in the median line, as a dark colored more
or less triangular organ, two ducts leading to it from the sides;
these ducts in turn lead off to the finely branched yolk glands,
seen as tiny dark spots on both sides of the body. The ovary is
a definitely branched body lying to one side in front of the yolk
reservoir. The ovary can be easily distinguished from the
similarly branched testes, which are paired, by the fact that the
latter occupy the greater part of the central area of the fluke.
The ovary is usually darker and more compact. The penis
and the genital pore are located within the area of the ventral
sucker.

d. Digestive system. This consists of the mouth, located
within the oral sucker, leading to a prominent pharynx, in turn
leading to the bifurcated intestine, which lies along the lateral
margins of the body, is much branched, and ends blindly.

e. Excretory system. The excretory system may be distin-
guished as a median light canal extending forward from the
posterior end of the body.

Draw the specimen, indicating and labelling the parts seen.
F. Examine a portion of an infested liver, and notice the
characteristic lesions produced by the fluke.

EXERCISE 32

OTHER TREMATODES

A. Dicroccdium (Distomum) lanceolatum is the lancet fluke
of sheep and cattle. Examine several specimens of this species.

a. How does it differ in size from Fasciola hepatica? . b

b. Does the form of the fluke justify the specific name?
Describe its form.

THE TAPEWORMS 59

c. Locate the following parts, i, ventral sucker, 2, uterus, 3, in-
testinal branches, 4, ovarium.

Draw a specimen, and label all the parts named in the preced-
ing exercise that you can find.

B. Examine specimens of Fasciola americana (Distomum
magnum) the giant fluke of cattle, infesting both the liver and
lungs of the host. Compare these specimens with specimens of
Distomum hepaticum, as to size, shape, color, absence in this
species of superficial spines, etc.

C. Paragonimus westermanni is the lung fluke of man, occa-
sionally found in other animals. This fluke is the cause of a
Hemoptysis.

a. What is the form and size of this fluke?

b. Locate i, the uterus, 2, the ovarium, 3, two testes.
Draw the specimen.

D. Schisostomum hcematobium (this fluke, unlike all the
above, which are Distomidae, belongs to the Family Schistoso-
midae) is a Trematode producing h&maturia or Bilharzia disease
of humans.

Examine a specimen and describe it.

EXERCISE 33

THE TAPEWORMS— A MORPHOLOGICAL STUDY

PHYLUM PLATYHELMINTHES, CLASS CESTODA

The following tapeworm characters cannot well be studied
without specimens of both the beef tapeworm, T&nia saginata,
and the fish tapeworm, Bothriocephalus latus, or closely related
genera, before you. Mounted and stained parts as well as un-
mounted specimens are needed.

A. General.

a. Tapeworms are more or less ribbon-like inform.

60 HELMINTHOLOGY

b. The head, or scolex, is at the tapering end of the worm, and
is more or less globular.

c. Back of the head are the gradually broadening segments,
or proglottides. The oldest proglottides are the farthest removed
from the head, and these drop off most readily.

B. Under a compound microscope examine stained and
mounted specimens of heads and proglottides from T&nia sagi-
nata, the beef tapeworm of man, and Dibothriocephalus latus,
the fish tapeworm (closely related species will serve just as well).

a. Head of Tcenia saginata. Notice the four cup-shaped
suckers, and a projecting rostellum, on which there are no hooks.

b. Head of Bothriocephalus latus. Notice the presence of
two groove- or slit-like suckers; the rostellum is absent.

c. A stained proglottid (not too mature) of Tcenia saginata
should show, i, the uterus as a median-branched tube, tree-like
in form, which extends nearly the entire length of the proglottis,
2, the ovaries, bilobed, finely branched bodies situated in the
posterior end of the proglottis, uniting medianally with, 3, the
vitellogene gland, situated along the median posterior border;
4, the vagina, a straight tube extending from the median pos-
terior field to 5, the genital pore, on the median lateral border;
6, the testes, consisting of a large number of bodies distributed
throughout the field as fine dots, and joined by 7, the vas efferent,
which again connects with 8, the vas deferens, a coiled tube
paralleling the vagina and also connecting with the genital pore,
through 9, the cirrus pouch; 10, the excretory system may be seen
as two transparent collecting tubes on either lateral border (four
longitudinal tubes and a transverse connecting tube along the
posterior border).

C. Compare with the above a stained proglottid of Both-
riocephalus latus, the fish tapeworm already mentioned in B, as
to form and position of the uterus and the position of the genital
pore.

Draw a head and a proglottis of each species, labelling all the
parts found.

THE TAPEWORMS 61

EXERCISE 34

THE TAPEWORMS— A SYSTEMATIC STUDY

PHYLUM PLATYHELMINTHES, CLASS CESTODA

A. Characteristics of Cestoda. These flat-worms consist usu-
ally, in the adult form, of a small globular head or scolex, and
a chain of segments called proglottides. In the adult stage they
are parasitic in vertebrate animals, having the larval (bladder
worm) stage in a secondary host, frequently invertebrate.

B. Examine specimens of the following species as far as avail-
able included in the two most important tapeworm families.
The following list is only partial, and is meant to give the student
merely a hint as to classification. Take notes on the specimens,
with reference to characteristics.

a. Family Bothriocephalida. "Head provided with two
groove- or slit-like suckers; rostellum wanting; uterus with
special pore; genital pores generally (possibly always) dorsal or
ventral." (Stiles.)

i. Genus Bothriocephalus, two elongate groove-like suckers
present; the sexual pore opens in the mid- ventral region.

E. g. Bothriocephalus latus, the fish tapeworm of man, also
found in dogs and other animals experimentally. May reach a
length of 20 to 30 feet, with some 4000 proglottides. The
middle proglottides are about three times as broad as long. The
larva is a plerocercoid inhabiting the muscular system of certain
fresh water fishes.

b. Family Taniida, "Head with four cup-shaped suckers;
rostellum present but not always evident; uterine pore wanting;
genital pores generally marginal; body always segmented."
(Stiles.)

i. Genus Tania, scolex with a rostellum usually provided
with hooks; mature proglottides longer than broad; genital

62 HELMINTHOLOGY

pores projecting at the lateral borders and alternating irregu-
larly.

E. g. Tcenia solium, the pork tapeworm of man. The ros-
tellum is short and is provided with a double circle of hooks.
The average length of the tapeworm is said to be from 8 to 12
feet, with 800 to 900 proglottides. The mature proglottides
measure from " 10 to 12 mm. in length by 5 to 6 mm. in breadth."
(Braun.) The larva is Cysticercus celMosa, whose habitat is
the connective tissue of swine.

2. Genus Dipylidium. "Rostellum retractile, armed with
several transverse rows of alternating hooks; hooks with small
roots, the base being discoidal; mature segments elongate with
double sets of genital organs; pores double and opposite; ova
with double transparent membranes." (Stiles.)

E. g. Dipylidium caninum, tapeworm of dogs, also found in
cats, and occasionally in man, measures from 6 to 12 inches in
length. The mature proglottides are about J4 mcn long by y£
inch wide, and have the form of cucumber seed, hence the
synonym, Tania cucumerina. The cysticercus of this tape-
worm is found in the cat and dog flea, Ctenocephalis canis, and
the biting dog louse, Trichodectes latus.

3. Genus Drepanidot&nia. "Head provided with a single row
of uniform hooks, few (8-20) in number, with dorsal root much
longer than ventral root, the latter always small; with prong
directed posteriorly when the rostellum contracts." (Stiles.)

E. g. Drepanidotcenia infundibuliformis is a common tape-
worm of poultry. This is described as follows: "20-130 mm.,
rarely 230 mm. long. Head globular, rather depressed; ros-
tellum elongate, cylindrical or hemispherical, swollen at sum-
mit, armed with a single row of 16-20 hooks. . . . Suckers
rather small. Neck very short; anterior segments very short,
the following ones funnel-shaped, the anterior border being
much narrower than the posterior border; posterior segments
almost as long as broad; genital pores irregularly alternate."
(Stiles.)

LARVAL FORMS OF TAPEWORMS 63

The cysticercus of this species is found in the common house-
fly, Musca domestica.

Drawings should be made to illustrate the main characteristics
of the above species of tapeworms

EXERCISE 35

OTHER TAPEWORMS

With the characters studied in the preceding exercises well in
mind the student should examine carefully entire specimens in
formalin (not slide mounts) of the following species, taking notes
and making drawings such as are necessary to indicate the
characters found.

a. T&nia saginata is the beef tapeworm (fat tapeworm) of
humans, the cysticercus stage, Cysticercus bows, being found in
cattle.

b. Monieza (Tcenia) expansa is the broad tapeworm of rumi-
nants; the larval form is unknown.

c. Tania coenurus is a tapeworm inhabiting the intestine of
the dog, wolf and coyote. While not dangerous to these hosts
the larval form is the disastrous gid parasite of sheep.

d. Tania fimbriata is the fringed liver tapeworm of sheep, a
very injurious parasite of which the cysticercus stage is unknown.

e. Tania crassicollis is the thick-necked tapeworm of the cat.
The cysticercus stage is found in the liver of small rodents, such
as rats and mice.

EXERCISE 36a

LARVAL FORMS OF TAPEWORMS

Larval tapeworms are known as cysticerci (cysticercus),
cosnuri (ccenurus), or echinococci (echinococcus), depending on

64 HELMINTHOLOGY

the form of development at this stage. The cysticercus, or blad-
derworm, has a well-developed bladder, in which is found a re-
tracted head bearing all the characteristics of the adult tape-
worm head. The ccenurus, while inside of a bladder, like the
above, develops a number of daughter cysts, with not more than
one head in each, which is capable of developing into an adult
tapeworm if ingested by a second host. The echinococcus
develops a number of daughter cysts, inside of which there* may
be a number of heads. The echinococcus is ordinarily much
more vesicular in form.

a. Cysticercus cellulosa is the larva of the pork tapeworm of
man. Examine the cysticerci from the heart or voluntary
muscles of a pig. Note the size of the object and determine the
presence of a head.

b. Cysticercus tenuicollis is the diving bladderworm of the ox,
and the larval form of Tcenia marginata of the dog. It is one
of the largest bladderworms, often an inch and a half or more in
diameter. The long, slender, invaginated head can be seen
through the tissue. Examine some bladderworms from the
peritoneum of cattle.

c. Multiceps midticeps (Ccenurus cerebralis) is a larval tape-
worm found in the brain and nerve cord of the sheep, causing
the disease known as gid. Examine a specimen of this ccenurus,
noting the number of heads and the characteristics of the same.

d. Echinococcus multilocularis is found in man, cattle and
swine, and is the larval form of a tiny tapeworm found in dogs.
The echinococcus is found primarily in the liver, but may attack
other organs. Here the original cyst develops many daughter
cysts, forming an alveolar structure, often of considerable size.
Examine a section of human liver affected with echinococcus.

Drawings of the above types should be made.

INSECT LARVAE 65

EXERCISE 36b

HELMINTH OVA

In studying the characteristics of Helminth eggs the following
from Manson's "Tropical Diseases" is suggestive: "The points
to.be attended to in the diagnosis of ova are size, shape, color,
thickness, roughness, smoothness and markings on the surface of
the shell; the presence or otherwise of yolk spheres, of a differ-
entiated embryo, or in the case of the cestodes, of the three
pairs of embryonic booklets; the existence of an operculum in
the case of certain trematodes and of the broad tapeworm
(Dibothriocephalus). The ova of the same species of parasites
vary but slightly, and are in every instance stable and definite
for correct diagnosis."

With the above in mind, study, describe and draw the following
species of ova:

a. Strongylus ovis pulmonis, the lungworm of sheep.
• b. Trichocephalus trichuris, the whipworm of man.

c. Necator americanus, the American hookworm of man.

d. Ascaris lumbricoides, the roundworm of man and swine.

e. Fasciola hepatica, the sheep liver fluke.

f. Schisostomum (Bilharzia) hcematobium, a trematode of
humans which produces haematuria.

g. T&nia s,olium, the pork tapeworm of man.

I

EXERCISE 37

INSECT LARVE

This exercise is to give the student facility in distinguishing
insect larvae from worms, an important matter when it is neces-
sary to trace modes of infection and to administer remedial
measures.

66 HELMINTHOLOGY

The following examples of insect larvae should be studied care-
fully, counting the number of body segments, noting the presence
or absence of special prehensile booklets, and other external
characteristics. Draw a specimen of each.

A. Types of insect larvae.

a. Larvae of the horse botfly, Gastrophilus equi; habitat,
stomach of equine animals.

b. Larva of the ox warble-fly, Eypoderma lineata, causing
what is commonly called "grub in the back" or warbles; habitat,
the deeper layers of the skin of bovine animals.

c. Larva of the head maggot fly, (Estrus oms; habitat, nasal
sinuses of sheep and deer.

d. Larva of the warble-fly of rabbits, Cuterebra cuniculi;
habitat, deeper layers of the skin of rabbits and other rodents,
commonly found in the neck.

e. Larva of the screw worm fly, Chrysomyia macellaria;
which is commonly found in wounds and open sores of domesti-
cated animals.

f. Larva of the common blowfly, Calliphora wmitoria, a
flesh fly and scavenger.

g. Larva of the common housefly, Musca domestica.

B. Examine a dissection of a fly larva under both low and
high power objectives, noting the tracheal system, an intricate
series of tubules ramifying through all parts of the body. Draw
several tracheae.

C. Describe points of difference noted between worms and
larvae.

EXERCISE 38

ANTHELMINTHICS

While the main object in the present work is to prevent infec-
tion, the student should nevertheless be familiar with the com-
moner agents used to destroy and expel internal parasitic worms.

ANTHELMINTHICS 67

Owing to possible complications not foreseen by anyone but an
experienced physician or veterinarian, the use of anthelminthics
is not recommended except under proper prescription. Care
should also be used in handling such materials. A description
of samples may be made, based on whether the material is
liquid or solid, its color, odor and other obvious characteristics.

A. Anthelminthics for Humans.

a. Pumpkin or Melon seeds are useful when eaten fresh in
half-ounce or ounce doses, as a preparatory remedy to further
treatment for tapeworms.

b. Male Fern (Aspidium) is used in the oleoresin form (Oleo-
resina aspidii) against tapeworms. This is dangerous unless
properly used.

c. Levant wormseed (Santonica) was formerly used, but has
been largely superseded by (d).

d. Santonin (Santoninum) is one of the best remedies against
roundworms (Ascarids).

e. Turpentine is used in diluted form as a rectal wash against
pinworms (Oxyuris).

f. Thymol has been found very useful in treating uncinariasis
(Necator americana and Ankylostoma duodenale).

g. Pomegranate (Granatum) produces a volatile alkaloid,
Pelletierin, which is useful for tapeworm.

B. Anthelminthics for Domesticated Animals.

a. Areca nut (fruit of Arecha catechu) is commonly used in
veterinary medicine as an anthelminthic, either alone or to-
gether with some other ingredient, against intestinal worms, such
as roundworms and tapeworms.

b. Sulphate of iron either alone or together with some other
ingredient such as arsenious acid is useful for roundworms in
horses.

c. Arsenious acid is used in connection with sulphate of iron
for roundworms.

d. Oil of turpentine, doses with milk (i to 16 parts) dose 2 to
4 ounces against bots and other stomach worms.

68 HELMINTHOLOGY

e. Common salt, powdered ginger and saltpetre are used to-
gether in warm water against stomach worms.

f. Tartar emetic given repeatedly is a remedy recommended for
roundworms in horses and cattle.

g. Kamala is an agent used in treating cattle for roundworms
(Ascarids).

PART III

LIFE-HISTORY STUDIES ON LIVING
PARASITES

INTRODUCTION

The work in the laboratory is made very much more interest-
ing and profitable if the student has the opportunity of making
observations on living animals. Courses opening in the first
semester come early enough in the year to make it possible for
the student to collect his own material out-of-doors. For courses
beginning in the second semester the instructor is cautioned to
collect material in the autumn and continue breeding through
the winter. This is possible for at least some of the required
material. Furthermore, spring usually opens up early enough
so that living material can be secured after the course begins,
and in time to make observations on the same. It is advisable
to have either a special breeding room or a part of the main
laboratory set aside for this purpose.

By doing these exercises the student secures a knowledge of
habitat and behavior that will be of great assistance to him in
practical field work, and the impressions thus secured will be
lasting.

How to Proceed. The student must secure his own material,
either by securing the fully mature specimens (male and female)
and providing the conditions under which eggs are deposited, a
matter not so easily accomplished in all cases, or by securing
the eggs in the field under natural conditions, which plan is
recommended. Breeding jars can easily be constructed of pint
fruit jars or smaller sized glasses, covered over with fine-mesh
bobbinet, gauze or filter paper.

69

yo LIFE-HISTORY STUDIES

Since this work will go on through the greater portion of the
semester the student is expected to collect his specimens early
in the course and make observations from time to time to ascer-
tain developments. This can be done at the opening of each
laboratory period or oftener.

For notes the same sized paper is to be used as for the exercises
requiring drawings. The exercise is to be given its regular
number and title. The date of collection should be indicated,
together with place and conditions. Each day observations are
made the date should be set down, together with memoranda
as to progress in life history, continuing thus until the organism
has matured or the term has closed. If the specimens die, more
should be collected.

EXERCISE 39

LIFE HISTORY OF THE COMMON HOUSEFLY

A. The student will collect two or three dozen or more of
housefly eggs. These can be collected, either from neighboring
horse-manure piles, or adult flies may be captured and placed
in a breeding cage into which is put also a jar of horse-manure.

B. Place the eggs into a jar which is partly filled with horse-
manure. The jar should be kept in a warm room. Cover the
jar with gauze or bobbinet.

C. Observe the date on which the larvae hatch from the eggs.
You will now have the incubation period.

D. Note the date on which feeding ceases and full growth has
been reached. You will now have the period of growth.

E. After the larvae cease feeding they usually try to leave the
manure, crawling into drier portions or nearby debris and pre-
pare to pupate. This is called the prepupal period.

F. Observe the date of pupation.

G. After a given number of days in the pupal stage the fly
emerges; it is now an imago. If the fly is to live the student

LIFE HISTORY OF THE MOSQUITO 71

must provide a dish of water, which may be sweetened with
sugar.

H. Several days must elapse before the fly is sexually mature,
when copulation occurs, and the females shortly thereafter de-
posit eggs.

I. Data on the length of life of any animal is valuable, so that
the student should endeavor to keep the flies alive as long as
possible, noting the time of death.

J. Flies as carriers of bacteria.

a. Collect half a dozen houseflies out of doors, noting the
immediate environment and sex of the individuals. The flies
must be collected in sterile vials.

b. Prepare six sterile agar plates.

c. Place the agar plates under sterile bell-jars and liberate
one fly for each plate and wait until the flies have crawled about
on the agar.

d. Note the condition of the agar. Can you see any tracks
that the flies have made?

e. Place the agar plates in a bacteriological incubator and
incubate for 36 hours.

f. What changes have taken place, and what are your con-
clusions?

EXERCISE 40

LIFE HISTORY OF THE MOSQUITO

A. Collect several egg rafts of a common Culicine mosquito.
There are usually pools of standing water, or nearby horse-
troughs, on the surface of which the egg rafts can easily be seen.
Count the number of eggs in one of the rafts.

B. Place the eggs in a pint fruit jar, partly filled with water
taken from the original pool.

C. Note the date when the larvae (wrigglers) emerge.

D. Change the water in the jar from time to time by drawing

72 LIFE-HISTORY STUDIES

out the old water and adding fresh, using water from the original
source if possible.

E. Observe the feeding and breathing habits of the wrigglers.

F. Take several of the wrigglers from the jar and place them
in another jar of water. Then add a few drops of kerosene.
Note the behavior of the insects.

G. Observe the dates when the wrigglers cast their skins
(moult).

H. After a given number of days the pupal (tumbler) stage is
reached. Observe breathing methods.

I. If you wish to save the mosquitoes you must now cover the
jars with a screen, or preferably a glass funnel, which can be
plugged up, and permits one to capture the mosquitoes more
readily.

J. Transfer the mosquitoes to a breeding cage provided with
a dish of water. After allowing the female mosquitoes to have
a suck of blood, note the date of egg deposition.

EXERCISE 41

LIFE HISTORY OF A FLEA

,

A. Collect specimens of fleas from a dog and place the fleas in
a glass vial covered with gauze. The females usually deposit
eggs very readily.

B. After several days the flea larvae will emerge. You must
now add some moist sawdust and fecal material from rodents,
or dry blood. The vials must be kept in a warm place, other-
wise growth is exceedingly slow.

C. If possible follow the growth of the flea larva to the time
when it spins a cocoon and pupates.

D. Pupae can be kept under observation more readily. Note
the date when the flea emerges.

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