MEDICAL

LMBT&AflSY

GIFT OF THE

SAN FRANCISCO COUNTY

MEDICAL SOCIETY

CAMBRIDGE PUBLIC HEALTH SERIES

UNDER THE EDITORSHIP OF
G. S. Graham-Smith, M.D. and J. E. Purvis, M.A.

University Lecturer in Hygiene and
Secretary to the Sub-Syndicate for
Tropical Medicine

University Lecturer in Chemistry
and Physics in their application
to Hygiene and Preventive Medi-
cine, and Secretary to the State
Medicine Syndicate

FLIES IN RELATION TO DISEASE

BLOODSUCKING FLIES

sv

CAMBRIDGE UNIVERSITY PRESS

C. F. CLAY, Manager

ILontlon: FETTER LANE, E.C.

lElrmburgf): ioo PRINCES STREET

dl

HonSon: H. K. LEWIS, 136 GOWER STREET, W.C.

ILontlon: WILLIAM WESLEY AND SON, 28 ESSEX STREET, STRAND

tfieto gorfe: G. P. PUTNAM'S SONS

Bombas ant Calcutta: MACMILLAN AND CO. Ltd.

Toronto: J. M. DENT AND SONS, Ltd.

£ofcgo: THE MARUZEN-KABUSHIKI-KAISHA

All rights reserved

FLIES IN RELATION

TO DISEASE ^^

BLOODSUCKING FLIES

by
EDWARD /HINDLE, B.A., Ph.D.

Assistant to the Quick Professor of Biology, Cambridge

Mb

Cambridge :

at the University Press
1914

7-\&l4-

TO
OTTO BEIT

IN RECOGNITION OF

HIS GENEROUS GIFTS TOWARD

THE ADVANCEMENT OF

SCIENTIFIC RESEARCH

EDITORS' PREFACE

IN view of the increasing importance of the study of public
hygiene and the recognition by doctors, teachers, adminis-
trators and members of Public Health and Hygiene Committees
alike that the salus populi must rest, in part at least, upon a
scientific basis, the Syndics of the Cambridge University Press
have decided to publish a series of volumes dealing with the
various subjects connected with Public Health.

The books included in the Series present in a useful and
handy form the knowledge now available in many branches
of the subject. They are written by experts, and the authors
are occupied, or have been occupied, either in investigations
connected with the various themes or in their application and
administration. They include the latest scientific and practical
information offered in a manner which is not too technical.
The bibliographies contain references to the literature of each
subject which will ensure their utility to the specialist.

It has been the desire of the editors to arrange that the
books should appeal to various classes of readers : and it is
hoped that they will be useful to the medical profession at home
and abroad, to bacteriologists and laboratory students, to munici-
pal engineers and architects, to medical officers of health and
sanitary inspectors and to teachers and administrators.

Many of the volumes will contain material which will be
suggestive and instructive to members of Public Health and
Hygiene Committees ; and it is intended that they shall seek
to influence the large body of educated and intelligent public
opinion interested in the problems of public health.

72674

PREFACE

ALTHOUGH it is now generally recognized that flies
are very important agencies in the dissemination of
infectious diseases, few people are aware of the remarkable
advances which have resulted from modern research in this
field. To the general public the practical application of
these researches appeals with greater force than the detailed
accounts of investigations, of absorbing interest though many
of them are, in the varied subjects which have to be called
to our aid in combating disease. Some of the results hitherto
obtained may be illustrated by two examples, both of which
have brought this subject into some prominence.

In the first of these, Yellow Fever, owing to the factors
involved being relatively simple, it is literally possible within
a few months to remove this most deadly disease from the list
of human ailments. All that is required is public appreciation
of the remedies at our disposal, as demonstrated by the result
of the admirable measures adopted by the Americans first in
Cuba and afterwards in Panama, which alone rendered possible
the completion of the Canal. Similar measures in other
regions directed against the mosquito (Stegomyia fasciata),
which is responsible for the transmission of the infection,
would render the reappearance of Yellow Fever in the highest
degree improbable in the future.

Sleeping Sickness may be taken as our second example.
The difficulties in this case are undoubtedly more formidable,
owing to the extreme complexity of the modes of dissemination.

Vlll PREFACE

Nevertheless much has already been accomplished, though it
is little to what might be done if more adequate funds were
at the disposal of our Colonial Medical and Administrative
Authorities. The enlightened policy of the Colonial Office
contrasts sadly with the lack of interest displayed by the
public as a whole, both at home and in the Colonies affected.
Public and private funds could not be directed more profitably
to the service of humanity than in the fields which the far-
sighted enterprise of this Department has opened up of recent
years.

New and formidable developments in the problem of
Sleeping Sickness, to confine ourselves to the second example
we have chosen, render it imperative that immediate steps
should be taken to combat the spread of a particularly deadly
variety of this infection, which, although at present confined
to small areas in Nyasaland and the adjoining provinces,
threatens to extend over a large part of Africa.

In addition to these two examples, Malaria in all its forms
is gradually becoming subject to human control, though some
countries are slow to realize that they cannot remain neutral
in this war waged by science against their most deadly internal
enemies, the mosquitoes. Verily the fly's proboscis is more
successful in retarding the progress of civilization and the
alleviation of human suffering than all the armaments of our
most Christian Powers !

The author's main object in writing this book has been
to collocate the more important observations concerning the
part taken by biting flies in the transmission of disease. In
doing this it seemed advisable to include notes on the classi-
fication of the flies concerned and also descriptions of the
infections transmitted, but no attempt has been made to give
any account of the clinical symptoms of the various diseases,

PREFACE IX

whether of man or animals. Special attention has been
devoted to the modes of life of the more important insects
mentioned, to the manner in which the infection is transmitted
from one host to another, and also to any preventive measures
directed either against the flies or the infections themsel

Hitherto those interested in this subject have been obliged
to refer to entomological treatises for a knowledge of the
insects, while information concerning the infections trans-
mitted was only likely to be contained in medical or zoological
publications. Thus there is danger of the interdependence of
the two subjects being overlooked. The entomologist work-
ing in this field, without a more or less complete knowledge
of the factors influencing the transmission of any particular
malady, is liable to waste his efforts in unprofitable directions ;
whilst the Medical Officer or Administrator who is ignorant
of the main results of entomological research is equally handi-
capped in his attempts to combat the group of diseases under
discussion. It is hoped, therefore, that this book will appeal
to both classes and at the same time that its significance for
the prevention of disease will be apparent to that wider public
already indicated.

The present volume together with that published by
Dr Graham-Smith in the same series1, covers the whole field
marked out by their general title, Flies and Disc

It may be useful to give the reader some idea of the general
arrangement of the subject matter that we have adopted.
After a short introduction, follow chapters on the structure
and classification of the Diptera, accompanied by a list of
biting fiies known to transmit any infection. Each family,
including any such carriers of disease, is then dealt with

1 Craham-Smith. Flies and Disea
Public Health S

X PREFACE

separately and in most cases some important member of the
family is described in greater detail. As far as possible the
description of the infections immediately follows that of the
family concerned in their transmission. Thus the account of
the Psychodidae and Phlebotomus is succeeded by a chapter
devoted to Pappataci Fever (Three Day Fever), whilst the
account of Malaria follows that of the Anophelinae. Certain
difficulties have arisen in the case of diseases (e.g. trypano-
somiasis) transmitted by members of more than one family,
but such infections have been described in connection with
their more important carrier. At the end of each chapter are
given a few references to the literature on the subject, but it
should be emphasised that the bibliography is not in any
way complete, but merely contains the titles of publications
that will be of assistance to students requiring detailed in-
formation in any particular branch. The present edition
does not profess to deal with works published later than
the beginning of 1913, although in isolated cases it has been
found possible to include references to later work.

The writer has great pleasure in acknowledging the
extremely valuable assistance which he has received from
Major S. R. Christophers, I. M.S., in the preparation of chapters
VIII and IX, devoted respectively to the classification of
the Culicidae, and an account of Malaria. These are almost
entirely the work of that distinguished authority and con-
sidering their importance in the present work, his name ought
to have appeared as a joint author. However, Major Christo-
phers would not consent to this arrangement and therefore
the author can only express his great indebtedness for this
generous help.

For permission to reproduce illustrations, which had
previously appeared in other publications, and also for the

PREFACE XI

loan of the original blocks, I am indebted to the following :
the Publisher (G. Fischer) and Editors of the Archiv fur
Protistenkunde, for permission to reproduce Fig. 87) the
Editor of the Bulletin of Entomological Research for the loan
of the blocks of Figs. 18, 19, 59-61, 67, 73 and 74 ; the President
and Fellows of the Cambridge Philosophical Society for the
loan of the block of Fig. 57; the Editors of the Journals of
Parasitology and Hygiene for the block of Fig. 41 and permis-
sion to reproduce Figs. 4, 8, 25, 26, 27, 29 and 31 ; the Director
of the Tropical Diseases Bureau for the loan of the blocks of
Figs. 42-45 and 65 ; Dr P. H. Bahr and Messrs Witherby
and Co. for the loan of the blocks of Figs. 54 and 56 ; Maclure,
Philips and Co. for permission to reproduce Figs. 46, 47 and 49.
Dr E. Roubaud for the loan of the blocks of Figs. 62, 64,
66, 68, 70, 76-78 ; Dr G. S. Graham-Smith for the loan of the
blocks of Figs. 1-3 and 82 and 83 ; Professor G. H. F. Nuttall
for permission to reproduce Figs. 30, 32 and 55 ; Surgeon-
General Sir David Bruce for permission to reproduce Figs.
79 and 80; and Miss Muriel Robertson for permission to
reproduce the drawings from which Fig. 75 was constructed ;
Mr Edwin Wilson, F.E.S., kindly prepared the drawing of the
stridulating organ of Anopheles (Fig. 28).

It is the author's pleasant duty to return thanks for the
assistance afforded by these gentlemen.

In conclusion, I should like to express the great debt I owe
to Professor G. H. F. Nuttall, who by his friendly criticism and
helpful suggestions has lightened the author's labours and
also prevented many serious omissions.

E. H.
September, 191 4.

CONTENTS

CHAP.
I.

II.

III.

IV.
V.
VI.

VII.

VIII.

IX.

X.

XI.

XII.

XIII.
XIV.

XV.

XVI.

XVII.

XVIII.

XIX.

XX.

XXI.

XXII.

XXIII.

Introduction .......

Diptera — General description and classification
Biting-Flies as carriers of disease
Orthorrhapha Nematocera ....

Family Psychodidae (Moth-flies and Sand-flies) .
Diseases carried by Phlebotomus — Pappataci Fever
Family Culicidae (Gnats or Mosquitoes)
Culicidae (Mosquitoes) continued. Classification
Anopheline-transmitted diseases
Culicinae ........

Diseases transmitted by Culicinae. Yellow Fever
Dengue, Bird Malaria, etc. ....

Diseases transmitted by Anophelinae and Culicinae
Filariasis .......

Orthorrhapha Brachycera .....

Family Tabanidae (Breeze-flies, Cleggs, Horse-flies
Gad-flies, Seroot-flies) ....

Cyclorrhapha Schizophora .....

The Tsetse-flies — Genus Glossina Wied., 1830

Glossina and Disease. The Trypanosomes

Glossina and Disease (continued)

Stomoxys .....

Infections transmitted by Stomoxys

Lyperosia ...

Family Hippoboscidae (Tick-flies)

Infections transmitted by Hippoboscidae

Index

PAGE

1
12
25
32
35
44
50
75
119

165

177

202
224

226
239
243
293
300

355
361

369
372
379
387

LIST OF FIGURES

FIG.
I.

3-
4-

5-

6.

7-

8.

9-
io.
ii.

12.

13-
I4.

15-

16.

17-
18.
19.
20.
21.
22.

23-

24.

25-

26.

27.

28.

29.

An Anthomyid fly immediately after emerging from the
puparium .......

Ventral view of head of the same fly

Side view of head of the same fly

Side view of a female Anopheles maculipennis Meigen
( x about 20) ......

Wing of Tabanus sp. shewing the venation

Acephalous larva of Stomoxys calcitrans (x 7) .

Eucephalous larva of Phlebotomus papatasii

Obtectate pupa of Anopheles maculipennis

Coarctate pupa of Stomoxys calcitrans

Wing of Kelloggina, a blepharocerid

Thorax of Tipula ......

Wing of Ryphus ......

Wing of Cecidomyia ......

Antenna of Orphnephila .....

Right hind-leg of Mycetophilus

Head of Bibio .......

Wing of Chironomus sp. .....

Head of Phlebotomus papatasii ....

Wing venation of Phlebotomus papatasii .

Phlebotomus papatasii. Male ....

Phlebotomus papatasii. Female

Freshly extruded egg of Phlebotomus papatasii .

Adult larva of P. papatasii ....

Pupa of P. papatasii .....

Anopheles maculipennis. A , enlarged view of male ; B
of female .......

Transverse section through proboscis of a female Anopheles
maculipennis , shewing the relative position of the parts
when at rest .......

Side view of the head of a female Anopheles maculipennis
with the various mouth parts separated, but in the
relative position in which they lie when enclosed in
the groove of the labium .....

View of under-surface of the base of the wing of Anopheles
maculipennis, shewing stridulating organ .

Schematic longitudinal section of a female Anopheles nicieu-
lipennis .........

head

PAGE

14
14
x4

16

17
20
20
22
22
34
34
34
34
34
34
34
34
36
36
37
38
40
40
4i

5i
52

33
55

57

XIV LIST OF FIGURES

FIG. PAGE

30. Diagram shewing the corresponding stages in the life-cycle

of Anopheles and Culex ...... 63

31. Anopheles maculipennis.. A, side view and B, dorsal view

of egg ; C, young larva and D, fully-grown larva ;
E flabellum, or flap overhanging base of certain thoracic
hairs ; F, a palmate hair ; G, ventral view of head of
fully-grown larva ....... 65

32. Anopheles maculipennis <$, captured in Cambridge, shewing

acarine parasites attached to the body . . . 73

33. Anopheles bifurcatus ....... 80

34. Anopheles (Patagiamyia) gigas ...... 82

35. Anopheles (Myzorhynchus) barbirostris .... 84

36. Anopheles (Myzomyia) listoni ... . . . 86

37. Anopheles (Pyretophorus) neavei ..... 88

38. Anopheles (Nyssorhynchus) maculatus . . . . 91

39. Anopheles (Cellia) pulcherrimus ..... 93

40. Diagrammatic representation of the life-cycle of the

parasite of pernicious malaria . . . . . 130

41. Photomicrograph of sporozoites of malaria from salivary

glands of Anopheles (Pyretophorus) costalis . . . 135

42. Breeding places of Anophelines. Railway cutting at

Kurunegala . . . . . . . . 137

43. Breeding places of Anophelines. Flooded Paddy Fields

in Ceylon . . . . . . . . . 139

44. Indian fish of utility as mosquito-destroyers. A (q) and

B ($) , Lebias dispar ; C, Nuria danrica . . . 150

45. Indian fish of utility as mosquito-destroyers. A , Haplochilus

panchax ; B, Ambassis ranga; C, Trichogaster fas-

ciatus . . . . . . . . . 152

46. Stegomyia fasciata, adult female . . . . . 166

47. Stegomyia fasciata, adult male ..... 168

48. Distribution of Stegomyia fasciata . . . . . 169

49. Larva and pupa of Stegomy ia fascia ta . . . . 174

50. Approximate distribution of Yellow Fever . . . 179

51. Distribution of Dengue . . . . . . . 191

52. Distribution of Culex fatigans ...... 193

53. Stomach of Culex shewing large numbers of the sporocysts

of Plasmodium prcecox on its walls . . . . 199

54. Microfilariae of F. bancrofti emerging from the uterus of the

parent filaria . . . . . . . . 207

55. Filaria bancrofti. Stages in development within mosquito 211

56. Head and proboscis of Stegomyia pseudoscutellaris , 15 days

after feeding, shewing two filarial lying in the head and

three in the proboscis . . . . . . 213

57. A , view of the heart of a dog infested with Filaria immitis ;

B, a female worm removed from the heart to shew its
length ......... 220

LIST OF FIGURES XV

FIG. PAGE

58. Part of the Malpighian tubule of an Anopheles claviger,

infected with the embryos of Filaria immitis . . 221

59. Tabanus kingi $ ........ 227

60. A rock at Khor Arbat, Anglo-Egyptian Sudan, shewing

sites selected by Tabanus kingi for ovipositing . . 228

61. Egg-mass and mature larva of Tabanus kingi . . . 229

62. Comparative morphology of the proboscis of Glossina (I),

Melophagus (II) and Stomoxys (III) .... 244

63. Wing of Glossina palpalis to shew the venation . . 245

64. Gravid uterus of G. palpalis, containing a larva at an ad-

vanced stage of development ..... 246

65. Glossina palpalis. Photographs shewing the flies in a

position of rest ........ 257

66. Internal anatomy of Glossina palpalis .... 259

67. View on River Gambia to shew a typical haunt of Glossina

palpalis ......... 261

68. Glossina palpalis in the act of feeding .... 264

69. Glossina palpalis. Female in the act of parturition . . 266

70. Freshly laid larva of G. palpalis shewing the changes in

the body form ........ 267

71. G. palpalis. Puparia before and after the escape of the

imago ......... 268

72. Glossina morsitans. Dorsal view of female . . . 276

73. Path through thin deciduous bush, to shew a typical haunt

of G. morsitans . . . . . . . . 279

74. Base of a tree in Nyasaland shewing one of the positions

in which the pupae of G. morsitans may be found . . 284

75. Diagram of the life-cycle of Trypanosoma gambiense . . 312

76. Transverse section (semi-diagrammatic) of the proboscis

of an infected Glossina . . . . . . 314

77. Culture of Trypanosoma pecaudi, from the intestine of

G. palpalis ........ 334

78. Culture of Trypanosoma congolense from the intestine of

G. palpalis . . . . . . . . 351

79. Trypanosoma simice. Successive stages in the division . 354

80. Trypanosoma simice. Large multinucleate form . . 354

81. Wing venation of Stomoxys calcitrans .... \^b

82. Side view of head of Stable-fly. A, proboscis in resting

position ; B, proboscis extended .... 356

S3. Stable-fly, Stomoxys calcitrans . . . . . . 357

84. Stomoxys calcitrans. Eggs . . . . . . $59.

85. Lynch 1 a ma ura $ ....... .

86. Hippobosca rufipes . . . . . . . . ^;S

87. Developmental cycle of Hcemoproteus Columbia

^. Trypanosoma theileri. A, small crithidial form ; B, Large
Individual from blood of cow .....

ERRATA

p. 37. After Fig. 20 insert the words ''After Newstead."
p. 38. After Fig. 21 insert the words " After Newstead."
p. 87. For A. agripi Patton read A. azriki Patton.

CHAPTER I

INTRODUCTION

Although biting-flies had long been suspected of being
responsible for the spread of various diseases, it was not until
1877 ^na-t any direct proof was brought forward in support of
this hypothesis. In that year Manson, working in China,
discovered that the minute worm, Filaria bancrofti, present
in the blood of a large percentage of the natives that he
examined, underwent a development inside the body of
the common grey-legged mosquito, Culex fatigans. Although
these observations were incomplete and the exact mode of
transmission remained undiscovered until more than twenty
years later, yet they were of the highest importance, since
Manson's work laid the foundation for all subsequent inves-
tigations on the part played by biting-flies as carriers of disease.

With the exception of these few observations on the de-
velopment of Filaria in the mosquito, practically the whole
of our knowledge of the transmission of disease by insects,
has been acquired within the last twenty years. Thus Bruce,
in 1895, discovered the cause of Nagana, Trypanosoma brucei,
and its transmission by the tsetse-fly, whilst two years later
Ross, by his brilliant researches on the development of Proteo-
soma and the manner in which it is spread by the mosquito,
placed the methods of eradicating malaria on a scientific basis.
The rapid progress in this subject may be appreciated by the
fact that, with the exception of the specific descriptions of
certain insects and the above-mentioned work on Filaria, the
present volume is entirely concerned with discoveries of the
last twenty years. Within this period biting-flies have been

H. B. F. 1

2 DIRECT TRANSMISSION [CH.

shewn to transmit in addition to numerous infections of animals
the following human diseases : malaria, sleeping sickness,
yellow fever, three-day fever ; and evidence has been brought
forward also suggesting that dengue and epidemic polyomyelitis
are spread by these insects. Before proceeding to a discussion
of individual infections, however, and the part played by flies
in their transmission, it will be convenient to give a short
general account of some of the problems connected with this
subject.

It has never been proved that, under natural conditions,
biting-flies normally transmit any other than animal parasites
from one host to another. In those cases in which the patho-
genic agent is unknown, e.g. yellow fever, three-day fever, the
clinical symptoms seem to indicate that these diseases are
also due to animal parasites and not to bacteria. There is no
a priori reason why biting-flies should not transmit bacterial
infections as well as animal, but certainly no bacterial disease
is known to be normally transmitted by these insects. Since
a biting-fly feeds on blood and can only become infected by
ingesting the parasite, it necessarily follows that the latter, at
least during some part of its life-cycle, must be present in the
blood of the vertebrate host, and the manner in which the
infection is conveyed by the insect may be either " direct "
or " indirect."

(a) Direct transmission.

When the pathogenic agent does not develop in the body
of the biting-fly, but is merely carried on the mouth-parts
and directly inoculated into the next host which the insect
feeds upon, the transmission is said to be direct or mechanical.
This kind of transmission somewhat resembles the method of
infecting a healthy animal by means of the prick of a needle
that has been thrust previously into an infected animal and
which is thereby soiled with the infective blood from the latter.

The efficiency of any particular species to act as the direct
carrier of a disease agent obviously depends on such mechanical
details as the size and shape of the mouth-parts, the number
of parasites in the blood, etc. It is possible that bacterial as

I] DIRECT TRANSMISSION 3

well as animal infections may be occasionally carried in this
manner, especially in those cases where the bacteria are present
in the peripheral circulation in considerable numbers, e.g.
anthrax, Mediterranean fever. Moreover, by feeding sufficient
numbers of any species of biting-fly on an animal containing
large numbers of some parasite in its blood, and subsequently,
without any interval, on a normal susceptible animal, it is
possible to obtain experimentally the direct transmission of
practically any blood-inhabiting parasite. Employing such
methods the transmission of sleeping sickness and relapsing
fever may be effected by means of the bites of Stegomyia, and
Mediterranean fever by the bites of Culex ; it is almost certain,
however, that such transmission rarely, if ever, occurs in nature.
Nevertheless, the possibility must not be ignored and all
biting-flies should be regarded with suspicion from the point
of view of preventive medicine.

Although under experimental conditions it is comparatively
easy to demonstrate the direct transmission of certain diseases
it is becoming more and more evident that, compared with in-
direct transmission, this mode of infection plays a relatively
unimportant part in the spread of disease. The pathogenic
agent of the disease, even under the most favourable conditions,
can only survive for a very limited time (at most two to three
days) on the mouth-parts of the biting-fly and unless the latter
feeds on another host before the expiration of this period no
infection is produced. As a rule a fly which has had a full meal
of blood rarely desires to feed again for some days and it is
only those flies which are interrupted during their feeding that
are liable to bite another host within a short space of time.
El Debab, a trypanosomiasis of camels occurring in North
Africa, is one of the best examples of a disease which seems to
be transmitted in this manner. Edmond and Etienne Sergent
have shewn that the outbreaks of this disease can be explained
on the supposition that it is directly transmitted from infected
to healthy animals by various species of tabanids, and they
note that in nature these insects frequently bite two or more
animals in quick succession, being disturbed whilst feeding,
through the efforts of their unwilling victims.

4 INDIRECT TRANSMISSION [CH.

It is, of course, quite possible for a biting-fly to transmit
any particular infection both directly and indirectly, as in the
case of the transmission of Nagana [Trypanosoma brucei) by
Glossina pallidipes. Bruce shewed that if a tsetse fed on
blood containing these trypanosomes, the fly remained infec-
tive for about forty-eight hours, during which period, if it
bit another animal, the latter became infected. It has since
been proved, however, that in addition this trypanosome
develops in the alimentary canal of the tsetse-fly and after a
certain incubation period, during which the fly is non-infective,
it again becomes infective. This infection, therefore, is trans-
mitted both directly and indirectly, but the epidemiology of
the disease is strongly against the view that transmission is
usually effected by the direct method.

(b) Indirect transmission.

When the pathogenic agent causing the disease undergoes
some developmental cycle in the biting-fly, resulting in the
latter becoming more or less permanently infective after this
development has taken place, the transmission is said to be
indirect or cyclical. In these cases there is always a definite
biological relationship between the biting-fly and the parasite
which it conveys, and the latter is only capable of development
within the members of certain species or families of insects.
The best known example of this indirect method of transmission
is that of the malarial parasite by the mosquito. When the
parasite, at a suitable stage of its life-history, is taken into
the stomach of a susceptible species of mosquito, it undergoes
a complicated cycle of development in its new host, finally
resulting in the salivary glands of the latter becoming invaded
by a stage of the parasite adapted for entry into the blood of
the next person that the mosquito bites.

It will be noticed that in this, and all other cases of indirect
transmission by biting-flies, the parasite develops in two hosts,
vertebrate and invertebrate, respectively. The host in which
the parasite undergoes its sexual life-cycle is called the
definitive host. In the case of the majority, if not all,

I] INTERMEDIATE HOST 5

protozoal parasites, the sexual part of their life-cycle takes
place in the invertebrate carrier, and therefore the latter is
the definitive host. On the other hand, the sexual cycle of
Filaria bancrofti takes place in its vertebrate host, man, and in
this case man is the definitive host.

The host in which the parasite merely multiplies asexually
is called the intermediate host, and in the case of protozoal
infections is the vertebrate, but in Filaria is the invertebrate,
host.

The term " intermediate host " has given rise to much con-
fusion, for many writers still persist in considering the expression
synonymous with " invertebrate host." As a matter of fact,
in the majority of cases the vertebrate is the intermediate
host, and it is only obscuring the true relations of parasite
and host to persist in the erroneous application of this term.

In all cases the equilibrium between parasite and host is
much better established in the definitive than in the inter-
mediate host. As a general rule parasites do not have a very
harmful action on their definitive hosts, whether inverte-
brate or vertebrate, whilst on the other hand there are many
examples of parasites seriously affecting the health of their
intermediate hosts. Thus the malarial parasite does not seem
to affect injuriously the health of its definitive host, the mos-
quito, whilst in the intermediate host, man, it produces malaria,
a serious and often fatal disease. Similarly, the presence of
Filaria bancrofti in its definitive host, man, does not produce
any obvious ill-effects, whilst a large proportion of the infected
mosquitoes succumb to the infection.

Although so many parasites have an injurious effect upon
their hosts, sometimes causing death, it is obviously a short-
sighted policy for a parasite to kill its host, as by so doing it
also destroys itself. A parasite which invariably killed its
host would eventually die out, owing to the extermination
of the latter, and it is not inconceivable that, in this way,
excessively fatal infections have disappeared from the world,
together with the animals they affected.

At the present time the great majority of blood parasites
do not cause the death of their hosts. An equilibrium between

6 CONDITIONS AFFECTING TRANSMISSION [CH.

the parasite and its host has become established and the former
does not increase beyond a certain limit, with the result that
the health of the animal from which it is deriving nourishment
is not very seriously affected. This is the case with numerous
parasites, such as the majority of trypanosomes in vertebrates,
Hcemoproteus in birds, Haemogregarines in reptiles, etc. It is
only in rare cases that the parasites increase to such an extent
that they markedly affect the health of their hosts, but since
our attention is only called to diseased animals, the cases in
which disease is caused by the parasites are more generally
noticed.

A pathogenic blood parasite cannot persist indefinitely
unless one or more of the following conditions are fulfilled :

(i) The disease which it produces may be of long duration
so that the invertebrate host has numerous opportunities of
becoming infected with the parasite and spreading the infec-
tion to other hosts. Of course the parasite must be present
in the blood in sufficient numbers and at a suitable stage of
development to ensure the infection of the biting host which
transmits the disease. If these conditions were fulfilled an
excessively fatal, though chronic disease, possessed of efficient
means of distribution would be able to persist until the exter-
mination of its host had been accomplished, after which it would
also cease to exist, unless it became adapted to some other host.

(2) The infection may be hereditarily transmitted in the
invertebrate host, so that the offspring of an infected parent
also carries the infection. Fortunately, with the doubtful
exception of yellow fever in Stegomyia, no biting-fly is known
to transmit any disease agent to its offspring. One of the
best examples of this mode of hereditary infection in other
groups is that of Spirochceta duttoni in its invertebrate host
the tick, Ornithodorus moubata.

(3) The parasite may infest more than one species of
vertebrate host, in one or more of which the equilibrium be-
tween parasite and host has become established. This is by
far the most important condition from an epidemiological
point of view. If a parasite is able to live in several verte-
brate hosts and is non-pathogenic towards any one of them,

I] CONDITIONS AFFECTING TRANSMISSION J

the latter serves as a reservoir for the infection and in the
presence of an efficient transmitting agent the parasite may
persist indefinitely.

It is now known that the parasite of sleeping sickness
{Trypanosoma gambiense) is maintained in this manner, since
in addition to man it infests other vertebrate hosts, e.g. ante-
lopes, which are practically unaffected by it.

In the case of the malaria parasite an equilibrium is becom-
ing established between it and its vertebrate host, man, but
only in those races that have been exposed to infection for a
considerable period. As a result the latter serve as reservoirs
of infection for those races that have not become immunized,
in whom the parasite produces malaria, a disease which is
often fatal unless checked by suitable treatment.

The relations between the parasites and their hosts are very
complicated and are not yet thoroughly understood. From a
biological point of view, it is probable that all protozoal blood
parasites carried by biting-flies are primarily insect parasites
and have only secondarily become adapted for living in the
blood of vertebrates. Certainly in every case where the life-
cycle of the parasite is known the insect is the definitive host,
and the equilibrium between the parasite and its insect host
seems to be well established, whilst this is not the case with
regard to the mutual relations in the vertebrate host.

The extreme pathogenicity of certain protozoal infections
in vertebrates, e.g. yellow fever in man, the various trypano-
somiases of man and animals, etc., strongly suggests that these
diseases are of comparatively recent origin and there has not
yet been time for any balance to become established between
the parasites and their respective hosts.

The trypanosomes constitute an excellent example of a
group of flagellates which primitively inhabited the alimentary
tracts of various invertebrates, and have recently become
adapted to a parasitic mode of life in the blood of vertebrates.

A large variety of insects, both biting and non-biting,
contain parasitic flagellates, Crithidia, Lcptomonas, etc., in
their digestive tracts, and there are all stages between fla-
gellates which are just capable of living in the blood of

8 CONDITIONS AFFECTING TRANSMISSION [CH.

vertebrates, but are usually insect parasites (e.g. Trypanosoma
boylei Lafont), and such forms as Trypanosoma gambiense, which
have become well-adapted to a parasitic mode of life in many
of the larger vertebrates. In the latter case the tsetse-fly,
the insect host of T. gambiense, has apparently developed an
immunity against infection with this flagellate, for only a com-
paratively small proportion of the flies becomes infected after
ingesting blood containing the parasites.

When once a biting-fly becomes infected with the par-
ticular species of blood parasite of which it is the definitive
host, it generally remains infective for a very considerable
period, often for the remainder of its life. It is obvious,
therefore, that when a parasite is transmitted by a true defini-
tive host, it is much more difficult to eradicate than when it is
spread mechanically. In the latter case it is only necessary
to protect all infected vertebrates from the bites of flies for a
period of not more than three days and the insects cease to
be infective. In the former case, however, the eradication of
the parasite can only be accomplished effectively by the destruc-
tion of the insect host. In fact the prevention of protozoal
infections, which include many of the more important tropical
diseases, is mainly an entomological problem, as it depends on
the destruction of insects and to do this a knowledge of their
habits and life-cycles is essential.

In the case of yellow fever the destruction of the invertebrate
host, Stegomyia fasciata, is comparatively simple, and as a
result this disease is rapidly disappearing from the more
civilized parts of the world. On the other hand, no effective
means have yet been discovered of destroying Glossina mor-
sitans, one of the most important disease carriers in Africa.
Yet there is little doubt that when we have acquired a complete
knowledge of the bionomics of this redoubtable insect, it will
be possible to devise some means of considerably reducing its
numbers.

An infected invertebrate host may spread infection from
one vertebrate to another in a variety of ways, but in the case
of biting-flies, the infected insect whilst feeding generally
inoculates the parasite directly into the body of the host.

I] DEVELOPMENT OF PARASITE 9

The possibility of other modes of infection, however, should
not be ignored, for they are known to occur in closely related
groups, and therefore it is considered advisable to include a
short account of some of the ways in which the infective agent
may be spread by its invertebrate host.

The simplest case is that in which the parasite, without
undergoing any morphological or biological changes, merely
multiplies in the alimentary canal of its invertebrate host.
The parasite may then enter a vertebrate either by regurgi-
tation of the contents of the alimentary canal when the inverte-
brate host is feeding, or else by the faeces of the latter, containing
the parasites, entering the open wound caused by its bite.
The plague bacillus, which multiplies in the gut of the flea, is
probably transmitted in this way.

Usually, however, the parasite undergoes a cyclical develop-
ment, passing through various stages that are generally incapa-
ble of living in the blood of vertebrates, and therefore during
this developmental period the host is non-infective. This
negative interval is known as the incubation period and may
vary from two or three days up to as long as 12 or 13 weeks,
its duration depending mainly on the temperature, as develop-
ment is accelerated by increased warmth and retarded, or even
completely arrested, by cold.

The development of various species of trypanosomes in the
alimentary canal of the tsetse-fly includes some of the simplest
examples of cyclical evolution. In the case of Trypanosoma
cazalboui, when ingested by the tsetse some of the parasites
remain in the fly's proboscis. In this region they develop,
also undergoing certain biological changes, and for a period
of about seven days they are incapable of living in the blood
of vertebrates. At the expiration of this short incubation
period, however, the trypanosomes recover their infectivity for
vertebrates, and after this the tsetse is infective for a consider-
able period. In other trypanosomes, e.g. T. gambiense and
T. brucei, the evolution in the tsetse-fly is more complicated,
the parasites developing in the digestive tract and passing
through a crithidial stage before finally becoming infective,
but in every case during this development they are restricted

IO DEVELOPMENT OF PARASITE [CH.

to the lumen of the alimentary canal and its ducts. It is
probable that the evolution of Hcemoproteus columbce is also
restricted to the alimentary canal of its invertebrate host,
Lynchia, but in this case the development is rather more
complicated than that of the trypanosomes, as it includes a
sexual phenomenon.

The most complex type of evolution is that of the malaria
parasite (Plasmodium) in its definitive host, the mosquito. In
this case the development commences with the production of
sexual forms which only become mature in the stomach of the
mosquito, and the result of conjugation is a motile body which
bores its way through the gut-wall and comes to rest in or near
the outer lining of the gut. It then grows at the expense of
the tissues of the mosquito and forms a large spherical cyst
in which are developed minute sickle-shaped bodies, the
sporozoites. Eventually the latter are set free into the body-
cavity of the insect and make their way to the salivary glands,
where they come to rest in the salivary ducts. These forms
are capable of developing in the blood of the vertebrate host
and are inoculated, together with the salivary fluid, when the
mosquito feeds. The development of the Haemogregarines
and Piroplasmidae in their respective invertebrate hosts seems
to resemble that of Plasmodium. Between the simple evolu-
tion of T. cazalboui and the highly complicated development
of Plasmodium there are numerous gradations, but the
majority of protozoal parasites probably pass through a life-
cycle comparable with that of Plasmodium.

The development of the ultra-microscopic virus of yellow
fever is peculiar from the fact that it is possible to transmit
the infection from one mosquito to another without the media-
tion of the vertebrate host. The incubation period of the
virus in the mosquito is about 12 days, but after the insect
has become infective, if it. is crushed up and fed to another
Stegomyia the latter becomes infective.

The evolution of Filaria in the invertebrate host is very
different from that of the Protozoa, as the sexual part of the
life-cycle takes place in the vertebrate, in this case the defini-
tive host, and the embrvonic filariae, contained in the blood,

IJ MODES OF INFECTION II

merely require to complete part of their larval development
in the tissues of the mosquito.

The manner in which the infective agent re-enters the
vertebrate host is of considerable interest and varies in dif-
ferent cases.

As a rule the infective agent is directly inoculated into the
body when the infected invertebrate feeds on some vertebrate
host. The parasites may be present in the proboscis of the
infected arthropod or leech, or contained in the salivary fluid,
but in either case the result is the same and the infection is
passed directly into the blood.

In the case of Filaria, the parasite is contained in the
proboscis of the infected insect and when it feeds escapes on
to the surface of the skin. The parasite subsequently bores
its way through the skin and thus reaches the general circula-
tion of its vertebrate host.

Sometimes the infective agent is merely deposited on the
surface of the skin in the faeces of the invertebrate host.
From this site the parasite may reach the blood circula-
tion by means of the open wound caused by the bite of the
invertebrate host (as in the case of Spirochceta duttoni), or
through an excoriated part of the skin.

Sometimes the same result is obtained by the host licking
up the parasite from the surface of its body. This is one of
the modes of infection of Trypanosoma lewisi, in which the
infection reaches the circulation through the mucous membrane
of the alimentary canal of the rat.

The transmission of Spirochceta recurrentis by the louse is
comparable with that of S. duttoni by the human tick, for in
the former case the parasites, set free only by crushing the
insect, pass through the excoriations produced by scratching
with the finger-nails. As lice are frequently crushed between
the nails, it is easy to see how the infective agent can reach
the circulation.

Occasionally it is necessary for the vertebrate to swallow
the parasite, which subsequently bores its way through the
alimentary canal. The best known example of this method is
that of Filaria medinensis, which develops in the body of

12 DIPTERA [CH.

Cyclops. When an infected specimen of the latter is taken into
the stomach, the filariae are set free and penetrate into the tissues
of the vertebrate host. The transmission of the Leucocytozoon
of the rat by Lcelaps is of the same nature, for the rats can only
become infected by swallowing Lcelaps containing the parasites.
As mentioned above the transmission of Trypanosoma lewisi
by the rat -flea is also of this nature, and Strickland has shewn
that the surest way of infecting rats with this trypanosome
is to feed them with fleas containing the parasite.

REFERENCES.

Brumpt, E. (1910). Precis de Parasitologie. Paris : Masson et Cie.
Castellani and Chalmers (191 2). Manual of Tropical Medicine, 2nd

edition. London : Bailliere, Tindall and Cox.
Hindle, E. (191 1). The Transmission of Spirochceta duttoni. Para-
sitology, vol. iv. pp. 133-149.
Manson, P. (1908). Tropical Diseases, 5th edition. London : Cassell

and Co. Ltd.
Mesnil, F. (1912). Modes de propagation des Trypanosomiases. Les

Trypanosomes chez l'hote invertebre. Bull. Inst. Pasteur, vol. x.

pp. 1-17 and 49-63.
Minchin, E. A. (1912). An Introduction to the Study of the Protozoa.

London : Edward Arnold.
Strickland, C. (191 1). Mechanism of Transmission of T. lewisi by the

Rat-flea. Brit. Med. Journ. 191 1, p. 1049.

CHAPTER II

DIPTERA. — GENERAL DESCRIPTION AND CLASSIFICATION

Definition. The large Order of Diptera includes all those
insects provided with two well-developed wings and, in addi-
tion, a hinder pair of rudimentary wings known as halteres, or
balancers. The mouth-parts are usually adapted for piercing
and sucking, and are more or less modified according to the
habits of the insect. The various stages of development, larva,
pupa, and adult, or imago, are quite distinct, metamorphosis
being complete. In addition, all the members of the Order

Il] GENERAL MORPHOLOGY 13

possess a distinctly segmented abdomen with the exception
of the Pupipara, a very aberrant group which has become
modified for an exclusively parasitic mode of existence.

General Morphology.

The head is connected with the thorax by an extremely
slender neck and in consequence is very mobile, being capable
of undergoing semi-rotation. The majority of the exposed
surface is occupied by the large faceted eyes, which are usually
much larger in the male than in the female, probably owing
to the fact that the former has to seek out its mate. The
eyes may actually meet in the middle line, in which case they
are termed holoptic, in contradistinction to when they are
separate, or dichoptic. The holoptic condition is especially
characteristic of the male but occasionally is found in both
sexes.

In certain families, e.g. Muscidae, the head shews anteriorly
a small depression, the lunula, which is bounded by an arched
suture passing over the bases of the antennae. This structure
is the remnant of a peculiar organ, the ptilinum, which, in
the fly emerging from the pupal case, appears as a bladder-
like expansion of the front of the head. The ptilinum can
be expanded and retracted and consequently it is of great
use in helping the fly to break through the pupal case, and
also to force its way through any material in which the latter
may be buried. It is only present during the first few hours
after the fly has emerged and subsequently it becomes com-
pletely introverted, forming the inconspicuous lunula of the
mature fly (Figs. 1-3).

The antennae are of great use to the systematist as they
offer a simple means of classification, the number of segments
being of considerable importance.

In the more primitive families of the Order, e.g. Culicidae,
there are a series of segments of approximately equal size,
the number of which varies from eight to sixteen. In some
cases the antennae of the male are larger and composed of more
segments than those of the female. The majority of flies,

14

DIPTERA — MOUTH-PARTS

CH.

however, possess antennae of a totally distinct form, peculiar
to the order, consisting of three segments, the outer one of
which, at its distal extremity, bears a fine process known as the
arista, which is occasionally segmented and often covered with
hairs. It probably represents the remaining segments of the
more primitive type of antennae.

Fig. i. An Anthomyid fly immediately after emerging from the puparium,
shewing the greatly distended ptilinum and unexpanded wings.

Figs. 2 and 3. Ventral and side views of the head of the same fly. After
Graham-Smith.

The mouth -parts are composed typically of the following
structures : labrum, epipharynx, maxillae, mandibles, hypo-
pharynx and labium. These are liable to great variation,
even within the same family, but all blood-sucking Diptera
agree in the possession of a mouth that is adapted for piercing
and cutting. The labrum, or upper lip, together with the
epipharynx, is usually elongated ; the hypopharynx, or tongue,
is also much prolonged and, together with the labrum, may
form a tube for the ingestion of blood or other liquids ; the

IlJ THORAX AND ABDOMEN 1 5

labium, or lower lip, is more or less membranous or fleshy,
and usually functions as a sheath for the protection of the other
mouth-parts. The mandibles and maxillce are each represented
by a pair of long pointed processes adapted for piercing. In
addition, a pair of well-developed maxillary palps is always
present, situated one on each side of the base of the labium.
The palps are extraordinarily well developed in the Culicidae
(Fig. 4), in the genus Megarhinus being nearly as long as the
whole body of the insect.

The thorax is composed almost entirely of mesothorax,
the prothorax and metathorax being very small and fused
with it. A small part of the metathorax projects backwards
over the base of the abdomen and is known as the scutellum.

The abdomen is composed of a variable number of segments,
more or less closely fused together. The number of segments
externally visible may vary from nine to five, or rarely four.
In certain cases the first two segments are fused together and
the first one is often very much shortened. In the male the
terminal segments are curled under the body, forming what is
termed the hypopygium, which serves to protect the copulatory
appendages.

The three pairs of legs are attached to the prothorax,
mesothorax and metathorax, respectively. The legs are in-
variably composed of five parts known as the coxa, trochanter,
femur, tibia and tarsus. The tarsus is generally five-jointed ;
its terminal joint bears a well-developed pair of claws, and
underneath each of these is often a free pad or membrane,
the pulvillus. This structure is often absent amongst the
Orthorrhapha and is usually better developed in the male
than in the female. Between each pair of claws is situated
a median structure known as the empodinm, which may have
the form of a pad, or a bristle. Occasionally the pulvilli are
absent and the empodium takes on their function.

The wings are of very great importance from a classificatory
point of view. As in all insects they consist of simple folds
supported by veins or nervures, the arrangement of which is
known as the venation. The wings are membranous but may
be covered with hairs or scales, and the shape and disposition

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II] WING VENATION 1J

of the latter is of great use in the identification of various species
of mosquitoes. The venation, although comparatively simple,
has been greatly complicated by the fact that entomologists
are not agreed as to the terminology of the various parts and
in consequence different writers use different names for the
same structures.

In the following description of the wing of Tabanus, which
is taken as an example because the venation is rather compli-
cated, we have adopted the system of nomenclature most
generally used by descriptive entomologists.

Anterior cross-vein
Costal vein

Auxiliary nerve

vx Subcostal

Humeral cross-vein

IF

V
Posterior cross-vein

Anteriorbasal cross-vein

Fig. 5. Wing of Tabanus sp. shewing the venation. The numbers I, II,
III, etc. indicate respectively the first, second and third longitudinal
veins, etc.

The most easy way of recognizing the veins is to commence
with the discal cell, which is a large cell situated about the
middle of the wing. It is present in the great majority of flies,
but is absent in the Culicidae. Anteriorly, the discal cell is
bounded by the fourth longitudinal vein, and somewhere along
its length will be seen a short connecting vein, the anterior
cross-vein. The latter is constantly present in all flies. In
front it is connected with the third longitudinal, and behind
with that part of the fourth longitudinal that bounds the
discal cell.

H. B. F. 2

1 8 DIPTERA [CH.

Counting forwards from the third longitudinal, which is
forked, occur the second and first longitudinals, these three
veins arising from a common stem and radiating to the costal
vein, which runs round the edge of the wing. Between the
costal vein and first longitudinal, is present an auxiliary, or
subcostal vein, which runs parallel with the costal for a short
distance and then curves into it. Near the base of the wing
the two latter veins are connected by the short humeral cross-
vein, which is very constant. The subcostal, and the first
three longitudinals support the anterior half of the wing. The
fourth and fifth longitudinals arise together and diverge towards
the margin ; each of them forks before reaching the edge of the
wing. The sixth longitudinal arises more or less independently,
and runs towards the hind margin of the wing. The three
latter veins together support the posterior half of the wing.
The fourth and fifth longitudinals are connected by two cross-
veins, the anterior basal near the axil and the posterior cross-
vein in the outer half of the wing. Between the fifth and sixth
longitudinals is a posterior basal cross-vein. It will be seen
that the wing is divided by its longitudinal nervures into two
fields separated by an interval which is traversed only by the
anterior cross-vein.

The various spaces or cells included between the veins are
distinguished by special names ; their arrangement may be
understood by referring to the figure (Fig. 5).

In addition to this system of nomenclature, that proposed
by Schiner is used by a certain number of writers. One great
source of confusion between this and the older system is the
different meaning of the subcostal ; Schiner employs the term
mediastinal for the subcostal, and subcostal for the first longi-
tudinal ; moreover, the corresponding cells are similarly named.

The surface of the body in flies differs considerably in the
nature of its vestiture. Sometimes the integument is almost
naked, but generally it is covered with hairs, or bristles, or
sometimes scales. Those flies which are provided with an
armature of bristles, or macrochcetcB, may be termed chceto-
phorous ; and where there is no definite arrangement of
bristles, the fly is said to be eremochcetous. Osten Sacken

II] INTERNAL ANATOMY 19

has drawn up an elaborate system of nomenclature for the
arrangement of the bristles, which is of considerable value for
purposes of classification.

Internal Anatomy.

The alimentary canal is provided with a muscular
pharynx. The ceosphagus usually gives off a large diverti-
culum known as the crop or sucking stomach, but in some
insects, e.g. Culicidae, its place is taken by two or three long
thin-walled sacs, the oesophageal diverticula. The stomach
is large and consists of an anterior portion, the proventriculus,
and a true stomach behind it ; the latter usually gives off
caeca. The intestine is coiled and ends in a rectum ; at its
junction with the stomach open the long Malpighian tubules,
generally four in number. The salivary glands are large and
their common duct opens at the top of the hypopharynx.

The heart consists of a thin-walled tube running along
beneath the dorsal surface of the insect. Usually it is divided
into several chambers but in the more specialized families
there are only two.

The respiratory system consists of two main tracheae
running longitudinally one on each side of the body and open-
ing to the exterior by means of the spiracles. The latter are
arranged on each side of the body, two large pairs in the thorax
and one pair to each abdominal segment. The two main
tracheal trunks expand at the base of the abdomen into con-
spicuous air-sacs, which are probably of use when the insect
is flying.

The nervous system is very variable. In the elongate
Nematocera there are five or six abdominal ganglia and three
distinct thoracic ganglia, but in the more specialized forms,
such as the Muscidae, all the thoracic and abdominal ganglia
are fused into a single mass. Various gradations may be
found between these two extremes and it is interesting to trace
the gradual concentration of the nervous system side by side
with the higher specialization of the insects.

The reproductive organs present some interesting
peculiarities. The ovaries consist of a very large number of

2 — 2

20

DIPTERA

[CH.

egg-tubes. The female, in addition, has three spermathecae,
paired accessory organs, and no true bursa copulatrix. The
male has two oval testes with short ducts, communicating with
a well-developed penis, surrounded by accessory copulatory
appendages.

Reproduction.

The great majority of flies lay eggs, which are generally
deposited in such a position that the young larva will be in
easy reach of its food-supply. A number of families, however,
are more or less viviparous, the eggs hatching within the body
of the parent and the resulting larvae nourished for varying
periods before being liberated. In the majority of such cases
the larvae are deposited whilst quite young, but in the Pupipara
and Glossina the larvae are nourished within the oviduct of the
mother until quite full-grown and when set free at once proceed
to pupate.

4— est

Fv.

CLSt

Fig. 6.
Fig. 6. Acephalous larva of Stomoxys calciirans ( X 7). After Newstead.

est, compound thoracic stigmen ; ast, posterior stigmen.
Fig 7 Fucephalous larva of Phlebotomus papatasii. After Newstead.

IIJ LARVA 21

The larvae are generally of the form known as maggots.
They are without exception destitute of true thoracic legs,
although in some groups stumpy pseudopods, resembling those
of the caterpillar, may be present. These pseudopods vary
greatly in their arrangement ; sometimes they are provided
with recurved hairs.

The larvae may be divided into two groups according to
the size of the head. In the eruciform maggots the head is
so small as to be almost invisible and these are termed acepha-
lous larvae (e.g. Glossina). In the. eucephalous larvae there is
a well-marked head provided with mandibles, and usually
there is a distinct thorax and abdomen (e.g. Anopheles).

The tracheal system exhibits great variety and the larvae
may be classified according to the arrangement of their spiracles.
In the peripneustic forms, the spiracles are arranged along the
sides of the body, one pair to each segment ; in the amphi-
pneustic forms there are two pairs of spiracles, one at each end
of the body ; whilst in the metapneustic forms there is only one
pair of spiracles placed at the posterior extremity of the body.
The great majority of aquatic larvae belong to the latter
type and there are often very elaborate devices for keeping
the tip of the body in communication with the atmosphere
so that air can enter the spiracles.

The habitat of the larvae is much more variable than their
structure, and they display great diversity in their mode of
life. The majority of the maggot-like forms live in decaying
organic matter, whilst nearly all the eucephalous larvae are
aquatic, occurring in both fresh- and salt-water and feeding
either on vegetable matter, or preying on other small animals.
A certain number of them are parasites, occurring in both plants
and animals, and there is one form, the Congo floor-maggot,
which sucks the blood of human beings and in its method of
feeding somewhat resembles the bed-bug.

The pupa may be either obtectate or coarctate. In the former
case the pupa is merely protected by a thin chitinous pellicle
and the outlines of the various appendages of the future insect
can be clearly distinguished through this covering — as, for
example, in the mosquito. In these obtectate forms the

22

DIPTERA — PUPA

[CH.

larva casts off its skin before pupating. This type of pupa
is found, with few exceptions, throughout the members of the
Brachycera and Nematocera. In the coarctate forms there are
no external protuberances, with the possible exception of a
pair of projections at one end of the body, but the whole
pupa looks like a tiny barrel, with rounded ends. In this
case the pupating larva does not escape from its skin at the
last moult but merely shrinks within it, and the larval skin

tr.

Fig. 9.

Fig. 8.
Fig. 8. Obtectate pupa of Anopheles maculipennis. tr, respiratory trumpet.

After Nuttall and Shipley.
Fig. 9. Coarctate pupa of Stomoxys calcitrans. After Newstead.

is strengthened by the secretion of chitin so that it forms an
adequate protection for the pupa. The external case is fre-
quently known as the puparium. This type of pupa is found
in the Cyclorrhapha, which includes the house-fly, Stomoxys,
Glossina, etc.

The adult fly escapes from the pupal case in one of two
ways. In the obtectate forms the dorsal surface of the pupal
sheath splits longitudinally or in a T-shaped fashion, and the
insect draws itself out through the opening. In the coarctate
pupce the anterior end of the pupal case is pushed off by means
of the expanded ptilinum of the emerging fly (vide supra, p. 14).

II] CLASSIFICATION 23

The obtectate pupae, as for example in the mosquito, are
often actively motile, progressing almost as freely as the larvae.
The coarctate pupae, however, are devoid of all movement
and are usually to be found buried in the earth, in crannies,
or in similar localities. The mature fly, after breaking out of
the pupal case, is aided in forcing its way through any covering
of earth, or similar material, by the alternate expansions and
contractions of the ptilinum, which becomes completely
retracted soon after the fly has emerged.

Classification.

The most generally adopted classification is that of Brauer
who divides the Diptera into two suborders, the Orthorrhapha
and Cyclorrhapha, according to the manner in which the adult
fly emerges from the pupal case, either by a T-shaped opening
along the back (Orthorrhapha) or by a circular opening at the
anterior extremity (Cyclorrhapha). Although this distinction
is of great importance it is rather difficult of practical applica-
tion when the immature stages are unknown, and the only
method of distinguishing the adult fly is the presence or
absence of a suture over the insertion of the antennae. The
position of the Pupipara is somewhat doubtful, but from
Roubaud's researches it seems probable that the Hippoboscidae,
at any rate, are merely a highly specialized group of the
Muscidae. For the present, however, they will be regarded as
a separate division and accordingly, following Sharp's arrange-
ment, the Diptera may be divided into five sections :

Series 1. Orthorrhapha Nematocera. Flies in which the
antennae are composed of more than six segments of which all
except the first two are equal in size. An arista is not present.
The palpi are long and flexible, and usually four- or five-jointed.
The second longitudinal vein is often forked and with the
exception of the Tipulidae and Rhyphidae a discal cell is not
present. This section includes the mosquitoes, sand-flies,
Chironomus, etc., all of which are what may be termed gnat-
like flies.

Series 2. Orthorrhapha Brachycera. Flies in which the
antennae are composed of three dissimilar segments, the last

24 CLASSIFICATION OF DIPTERA [CH.

of which often carries an arista, usually terminal in position.
When an arista is not present the flagellum ends in an append-
age consisting of a number of indistinctly separated segments.
The maxillary palps are composed of one or two segments
and are not flexible. There is no definite arched suture above
the insertion of the antennae. The second longitudinal vein is
not forked, but frequently the third is forked ; the venation
is often very complex. This section includes the important
family of Tabanidae, in addition to a few other less well-known
forms.

These first two divisions together constitute Brauer's sub-
order Orthorrhapha, which includes all those Diptera in which
the imago escapes from its pupal case by means of a dorsal
T-shaped opening or longitudinal slit ; accordingly ptilinum
and lunula are absent in the adult insect. The larva possesses
a distinct head and the pupa is usually obtectate.

Series 3. Cyclorrhapha Aschiza. Flies without a frontal
suture and with a somewhat indefinite lunula. The antennae
are composed of not more than three segments of which the
end one bears an arista, which is not terminal, but usually
superior, in position. This group includes a large number of
very minute flies and also the great family Syrphidae, but none
of the members are known to suck blood and are therefore
of no interest in the present connection.

Series 4. Cyclorrhapha Schizophora or Eumyiid flies. Flies
in which the antennae are composed of three segments and an
arista. None of the veins of the wing are forked. In the
Calyptratae the frontal suture is well-marked leaving a distinct
lunula over the insertion of the antennae. In the Acalyptratae,
the form of the head is less characteristic, but the members
of this section can generally be distinguished from the Bra-
chycera by their less complex wing venation. This group
includes the important family Muscidae, of which the common
house-fly, also Stomoxys, and Glossina are well-known examples.

The latter two series together constitute the suborder
Cyclorrhapha, which may be defined as Diptera in which
the imago escapes from the pupal case by means of a circular
aperture at the anterior extremity produced by the pressure

Il] BITING-FLIES AS CARRIERS OF DISEASE 2j

of the expanded ptilinum. In consequence a frontal lunula
is generally present. The larva is without a distinct head
(maggot-like) and the pupa is coarctate. The antenna is
composed of three segments, the terminal one of which bears
an arista, usually dorsal in position. The maxillary palps are
each composed of a single segment, the maxillae are rudimentary
and the mandibles absent. The third longitudinal vein is not
forked and there are not more than three complete posterior
cells. The number of abdominal segments never exceeds
seven and is usually less.

Series 5. Pupipara. Abnormal Diptera of parasitic habit
in which the wings are often rudimentary or absent. The
head fits into a hollow of the thorax and the abdomen is not
distinctly segmented. The larva, until it is mature, develops
within the body of the female and when deposited at once
pupates.

This group consists of an assembly of diverse forms, pro-
bably of varied affinities but all agreeing in their habit of
depositing fully-grown larvae. The best-known family is the
Hippoboscidae, including Hippobosca, and Melophagus, the
sheep-ked.

REFERENCES.
Alcock, A. (1911). Entomology for Medical Officers. London: Gurney

and Jackson.
Brauer, F. (1880). Denk. Kais. Akad. Wissensch. Math.-Naturivissensch.

Klasse, vol. 42, p. 105.
Sharp, D. (1899). Insects, Part 11 in the Cambridge Natural History.

London : Macmillan and Co.
Williston, S. W. (1908). Manual of North American Diptera. New

Haven, U.S.A. : G. T. Hathaway.

CHAPTER III

BITING-FLIES AS CARRIERS OF DISEASE

The term " Biting-Flies " has been selected in order to
include all those members of the Order of Diptera that either
habitually, or occasionally, feed by sucking the blood of verte-
brates. As a result of their feeding habits they are mainly

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32 ORTHORRHAPHA NEMATOCERA [CH.

responsible for the transmission of the large number of parasitic
animals that occur in the blood of vertebrates, especially in
the tropics. Their great economic importance as carriers of
disease agents has become universally recognized during the
past twenty years and at the present time it is unnecessary
to dwell on this point. In fact there seems to be a tendency
for authors to go to the other extreme and credit biting
insects with the spread of almost every disease in which the
mode of infection remains unknown. Nevertheless, a large
number of species of biting-flies have been shewn to be respon-
sible for the spread of various diseases as may be seen from the
preceding table, in which are included all biting-flies that are
known to carry infections, together with the infection, or
infections, which they transmit (Table I).

CHAPTER IV

ORTHORRHAPHA NEMATOCERA

Definition. As a rule a member of this series may be
easily recognized by its long thin body, slender legs and long
narrow wings. Moreover the antennae are long and filiform,
being composed of 6 to 15 segments that often bear whorls
of hairs, especially in the male. The larvae are aquatic, or
live in decaying organic matter (e.g. Phlebotomus) .

The Nematocera includes some of the most important
biting-flies that carry disease, as the great family of mosquitoes
belongs to this group.

Classification. YVilliston divides them into 12 families, of
which four are known to include members that either occasion-
ally or habitually feed on blood. In the present work his
method of classification has been adopted and the following
table includes all the families of the Nematocera. Those which
include any members that are known to carry disease are
printed in capital letters and will be discussed more fully.

IVl ORTHORRHAPHA XEMATOCERA

Synopsis of the Families of Orthorrhapha Nematocerd1

33

(

Body and wings thickly covered with hairs; flies resembling moths
(Fig. 20) =Psychodid^e.

I Flies not resembling moths =2.

f Wings with a network of fine vein-like creases besides the ordinary
■{ veins (Fig. 10) = Blepharocendce2.

I Wings without any additional network of vein-like creases = 3.

C Scutum usually with a V-shaped transverse suture (Fig. 11); wings
< usually with a discal cell - Tipulidce.

I Scutum without a transverse suture =4.

fWi

IWi

ngs with a discal ceil (Fig. 12) =Rhypiiidce.

ings without a discal cell =5.

r Antennae abnormal, apparently consisting of two segments and a
5 < terminal arista (Fig. 14) = Orphnepkilidre.

I Antennae normally nematocerous =6.

r Posterior edge of wing fringed with scales (Fig 25) =Culicid/£.
\ Posterior edge of wing not fringed with scales = 7.

f Minute fragile midges ; wings commonly with only three longitudinal
J veins (Fig. 13) =Cecidomyidce.

7 J Not abnormally delicate and fragile ; wings usually with numerous
I veins.

ems. = 8.

{Ocelli present (Fig. 16, oc) =9.

Ocelli absent = 10.

r Coxae elongate ; antennae usually elongate ; all the tibiae end in spurs
9 ^ (Fig. 15) =MycetophilidcB.

I Coxae short; antennae usually shorter than thorax —Bibinnidce.

{The costal vein extends all round the wing = Di.xidce.

The costal vein stops at or near the tip of the wing (Fig. 17) -11.

(-Gnat-like llies with long slender legs; antennae filiform, often with
whorls of hairs =Chironomida>z.

11 <J Thick-set flies with stout legs ; antennae stout and stiff, hardly longer
than the head, and never having whorls of hairs : wings remarkably
v. broad =Simtiliida*.

1 From Alcock's Entomology for Medical Officers, p. 46.

- Some of the females belonging to Curupira have been suspected oi blood-
sucking habits.

, nines that some of the members of these families are known to suck
blood.

H. B. F.

34

ORTHORRHAPHA NEMATOCERA

CH.

14

Fig. 10. Wing of Kelloggina, a blepharocerid, shewing the network of fine
vein-like creases (X12).

Fig. 11. Thorax of Tipula, with V-shaped transverse suture on scutum ( X 8).

Fig. 12. Wing of Ryphus (X12). The costal vein does not extend beyond
the apex of the wing.

Fig. 13. Wing of Cecidomyia (X12). The costal vein extends completely
round the wing.

Fig. 14. Antenna of Orphnephila (x8o).

Fig. 15. Right hind-leg of Mycetophilus, shewing the tibial spurs (X8).

Fig. 16. Head of Bibio (X12); oc, ocelli.

Fig. 17. Wing of Chironomus sp. (X8).

V] FAMILY PSYCHODID^ 35

CHAPTER V

FAMILY PSYCHODID.E (MOTH-FLIES AND SAND-FLIES)

Definition. The members of this family are small insects,
generally not exceeding 5 mm. in length, which somewhat
resemble moths, as the body and wings are thickly covered
with hairs, amongst which patches of scales may occur. The
wings are unlike those of any other Nematoceran, being oval
or lanceloate in form (Fig. 19), and with a somewhat striking
venation. The second longitudinal vein branches into three near
the base of the wing, and as the transverse veins are very faint,
the wing appears to contain nine or ten longitudinal veins
without any connections. The antennae are long, being com-
posed of 16 segments, which often carry whorls of hairs. The
larvae, as a rule, live in decomposing vegetable matter.

The Psychodidae are cosmopolitan, but are most abundant
in tropical and subtropical regions. The species belonging to
the genus Phlebotomus are the only ones which are known to
suck blood habitually.

Phlebotomus.

General account. All the members of this genus are small
inconspicuously coloured insects, the females of which feed by
sucking the blood of vertebrates. In some species the male
also sucks blood, and it often possesses mouth-parts resembling
those of the female. The flies are commonly known as " Sand-
Flies," or, in Southern Europe, " Pappataci Flies," and on
account of their voracious habits and the fact that their small
size enables them to creep through the meshes of an ordinary
mosquito net, they are a source of much annoyance in those
parts of the world in which they occur, especially as their bite
causes great local irritation. Moreover, the well-known
" Pappataci Fever," or " Three-Day Fever," is certainly
carried by P. papatosii, and probably by other species of the

3—a

36

PHLEBOTOMUS

[CH.

genus, which is, therefore, of considerable importance from a
medical point of view.

pro.

Fig. 18. Head of Phlebotomus papalasii ; ant, antenna ; e, eye ; cl, clypeus ;
pal, palpus ; pro, proboscis. After Newstead.

Definition. The genus Phlebotomus may easily be dis-
tinguished by the following characters :

Psychodidae in which the mouth is modified for piercing
and sucking. The antennae are long and slender, composed of

Fig. iq. Wing venation of Phlebotomus papatasii ; upper, ? ; lower, 3 .
After Newstead.

16 segments, and the joints are not markedly constricted.
The wings are narrow, covered with hairs, and in repose are

V] BIONOMICS 37

always carried uplifted so that the insect resembles a tiny
moth. The second longitudinal vein branches twice, all three
branches being distinct. The body is hairy. Sexual dimor-
phism is distinct. The total length never exceeds 3 mm.
and is usually much less.

Phlebotomus papatasii is the most important member of
the genus and the following remarks apply especially to this
species.

Bionomics. When P. papatasii is feeding it lifts its wings
up to an angle of about 450, this characteristic attitude being
well shewn in Fig. 21. On the slightest disturbance the insect

Fig. 20. Phlebotomus papatasii, Scop. Male.

moves suddenly to either the right or left by short rapid flights,
somewhat resembling the movements of a flea. If undisturbed
the females rapidly gorge themselves with blood and then
silently fly away to some dark corner. In rooms they usually
hide behind pictures, underneath clothes or in similar pla-
in Malta, where they have been studied by Marett and New-
stead, their favourite localities during the day seem to be the
numerous small caves and catacombs, and also the interstices
of stone walls. Atmospheric conditions have a marked effect

38 PHLEBOTOMUS [CH.

on the flies, for on still warm nights they are found in large
numbers in houses. On the other hand, they rarely appear
when cool fresh breezes are blowing, in this respect resembling
the common midges of England. The chief breeding places
seem to be the crevices between rocks, in loose stone walls,
caves, also dark cellars, and especially on the sides of drains
kept moist by the occasional splashing of water. Unfortu-
nately, much work remains to be done on this subject, for
the task of finding the minute larvae or pupae is very difficult,

/

Fig. 21. Phlebotomus papatasii, Scop. Female.

and little is known about their habits. The difficulty of find-
ing the larvae is still further increased by their peculiar habit,
when exposed to light, of flicking themselves off the surface of
the object on which they are resting. The pupae are even
more difficult to detect, for not only are they very minute,
but closely resemble the colour of their surroundings. It is
therefore not surprising that so little is known about their
habits, in spite of the importance of this knowledge from a
prophylactic point of view.

The flies are very unequally distributed even in regions
that seem to present the same conditions, such as an abundance
of stone walls for breeding places. Moreover, some houses are
visited much more frequently than others without any apparent

V] LIFE-CYCLE 39

reason. In Malta, Newstead found that bedrooms on the first
floor facing the sheltered side of the house were much more
favoured than those of the opposite side ; and only a single
example was ever found in rooms on the second floor. Some
persons seem to be immune to the attacks of these insects,
as for some reason they have their likes and dislikes with regard
to hosts, as well as habitat. It is probable that reptiles
constitute the main hosts of these insects, for in West Africa,
Roubaud found a lizard covered with gorged females of
P. minutus. More recently Howlett has brought forward
convincing evidence to shew that in India geckos are the
chief hosts and are preferred to man.

The flies are especially abundant in the hot season of the
year but in tropical countries they may be found at all times.
When kept in captivity on wet blotting-paper P. papatasii
lives but a short time (3-9 days), even though fed on human
blood and kept under the most favourable conditions. The
life of the adult therefore is probably of but short duration.
The females readily oviposit in captivity but often die during
the process. From an examination of the ovaries, the number
of eggs is found to be from 40 to 50, so that the insect is
comparatively little prolific.

Life-cycle. After copulation, the female seems to require a
feed of blood before being able to lay any eggs. This condition
having been fulfilled, the insect then retires to some dark corner
and deposits her eggs either singly or in clusters, the total
number varying from 30 to 80, according to the species. The
act of oviposition is accompanied by very extraordinary move-
ments on the part of the female. The whole process has been
described by Newstead in the case of P. papatasii. A gravid
female was placed into a glass-topped box and supplied with
wet blotting-paper, when the insect at once settled on the paper
and brought her proboscis into contact with it. After a few
seconds she appeared to become intoxicated and collapsed,
crossing the middle- and hind-legs behind the abdomen, whilst
the front pair remained in their normal position. The abdomen
was then raised and fully extended, after which three eggs
wore laid at short intervals. Each egg was ejected with

40 PHLEBOTOMUS [CH.

considerable force to a distance at least three times the length of
the abdomen. The whole process occupied about two minutes,
after which the insect appeared very fatigued and rested for at
least three hours before continuing the egg-laying.

The eggs are almost transparent when first laid, and are
covered with a thin coating of sticky substance which causes
them to adhere to any surface. They are very elongate in
form, dark brown, shining, with longitudinal black wavy lines,
which are slightly raised and joined by very fine cross-lines.
The length of the egg varies from o'i to 0*15 mm. (Fig. 22.)

The incubation period is usually from six to nine days, but
the eggs are very susceptible to external conditions and will
only hatch if kept in a moist atmosphere.

Fig. 22. Fig. 23.

Fig. 22. Freshly extruded egg of P. papatasii. After Newstead
Fig. 23. P. papatasii ; adult larva. After Newstead.

The larva lives in damp earth and is very curious in form.
It possesses a large well-marked head with big jaws, the latter
being provided with four distinct teeth. The body is covered
with toothed spines that may serve as a protection against
enemies, and the posterior end bears two pairs of black caudal
bristles. The bristles of one pair are almost as long as the
body, whilst those of the other pair are short, but increase in
length in the later stages (Figs. 7 and 23).

The length of the full-grown larva is about 2*3 mm. In
India the larval stage usually lasts from about three weeks
to even as long as two months, but its duration depends mainly
on the temperature, being much prolonged in cold weather.

The larva closely resembles a caterpillar in its movements ;

BREEDING LOCALITIES

41

it progresses slowly and continually pecks at the stone on which
it is placed. The caudal bristles are kept raised and extended
in a fan-shaped manner, thus presenting a somewhat charac-
teristic appearance. The larva feeds on semi-decaying vege-
table matter and after undergoing a certain number of moults
turns into the pupa.

The pupa (Fig. 24), which is found on damp earth and under
the surface of stones, is remarkable for the large ridges and
excrescences on its thorax. The larval skin, with the bristles
still attached, usually remains adhering at the caudal extremity.

The fly generally emerges from the pupa after about six to
ten days, but as in the other stages this period may be con-

Fig. 24. Pupa of P. papatasii
After Newstead.

Is, larval skin with anal bristles attached.

siderably prolonged by a low temperature. In India, accord-
ing to Howlett, the life-cycle of the sana-fly varies in duration
from a month in the hot weather to six to eight weeks in the
cold season, but in Malta Marett found the life-cycle occupied
about three months.

Breeding localities. Further information with regard to the
breeding places of Phlebotomus is much to be desired. Captain
Marett finds that in Malta the chief localities are the crevices
in stone walls and the fissures between rocks in caves.

In Italy Grassi found specimens in dirty cellars and similar
dark places containing rubbish of various kinds. He states
that the larvae live in dark and damp places amid all kinds of

42 SPECIES OF PHLEBOTOMUS [CH.

rubbish ; they prefer underground situations such as cellars
and more especially those parts of drains that can only be
reached by splashes of dirty water. Although the adult fly
is usually excessively abundant in those localities that it infests,
no observer has yet succeeded in finding larvae in any con-
siderable numbers. There are good reasons for believing that
one of the breeding places may be the dark and damp inner
surfaces of the walls of latrines, and cesspools. The flies are
notoriously common in latrines and in the case of a military
camp in Herzegovina, Doerr brought forward evidence to shew
that in summer the latrines were the only possible breeding
places for the swarms of Phlebotomus that infested the camp.
Phlebotomus and disease. The only disease1 which is known
to be transmitted by members of this genus is the notorious
Three-Day Fever, or Pappataci Fever. P. papatasii Scopoli is
the only species that has been definitely proved to carry the
infection, but it is almost certain that P. minutus and other
members of the genus are equally capable in this respect ;
therefore we append a short synopsis of the known species
of Phlebotomus together with their distribution.

Synopsis of known species of Phlebotomus.

European species'1.
A . Abdominal hairs recumbent.

(i) Integument black. Second segment of palpi slightly longer than
third. Legs pale ochreous buff, with ochreous white refulgence. Length of
female 2*5 mm. nigerrimus, Newstead.

1 Since the above account was written Townsend (Journ. Amer. Med.
Assoc, vol. 61, p. 1 71 7) has brought forward evidence in support of the view
that Verruga Peruviana is transmitted by Phlebotomus. These flies were
found to be very abundant in the infected districts especially in the Verrugas
Canyon. To prove this theory of transmission the author obtained two
hairless Mexican dogs. After they had been kept under observation for
nearly three months, one of them was inoculated subcutaneously with the
ground-up bodies of 20 female Phlebotomus collected the night before in the
Verrugas Canyon. On the fifth day this clog appeared ill and its blood was
found to contain the peculiar endoglobular forms known as Barton's X-bodies,
and also nucleated and broken down red cells. On the sixth day a typical
nodular eruption was noticed on the right hind-foot and smears from one of
the papules shewed bodies resembling Leishmania. On the eighth day the
dog began to improve. The control dog remained in perfect health.

2 Modified from Alcock's Entomology for Medical Officers.

V] SPECIES OF PHLEBOTOMUS 43

(2) Integument ochreous. Second segment of palpi one-half the length
of the third. Length of female 2 mm., male considerably less.

minutus, Rondani.
H. Abdominal hairs erect.

(3) Terminal segment of upper clasper of male hardly half the length
of lower clasper. Legs relatively short ; average length of hind-leg 3 mm.
Length of female, 1-9-2 "2 mm. perniciosus, Newstead

(4) Terminal segment of upper clasper of male slightly longer than lower
clasper. Legs relatively long ; length of hind-leg 4 mm. Thorax with a
dull red-brown median stripe and a spot on each side. Length of female
2*5-2*65 mm. papatasii, Scopoli.

(5) Resembling the preceding species in every respect except the form
of the male claspers, the five spines of the terminal segment of the latter
being long and falciform. mascittii, Grassi.

African species.

P. papatasii has been described from Algeria and Tunis and probably
occurs throughout the whole of North Africa.

General colour pale-yellow. Wing narrow, about three times as long as
broad ; second marginal cell less than a third the length of the wing. Length
of female 2 mm. ; male considerably less. duboscqnii, Neveu-Lemaire.

Pleurae clothed with large flat scales like those of mosquitoes. Third segment
of palps with a compound group of minute modified spines, spathuliform with
short pedicels. Khartoum. squamipleuris, Newstead.

Resembling minutus but with shorter and stouter legs. Third to the
thirteenth antennal segments bead-like. Gold Coast.

antennatus, Newstead.

Oriental species.
P. papatasii is said to occur all over India and P. minutus (syn. babu
Annandale) has also been recorded. In addition the following species have
been described :

Head and abdomen brown ; dorsum of thorax dark brown or blackish ;
sides of thorax, coxae, and trochanters yellowish ; legs, antennas, and palpi
grey ; the whole, especially the legs with a silvery sheen. Greatest breadth
of wing about a third its length ; greatest length of second marginal cell
(" first fork-cell ") about a third the length of the wing.

argentipes, Annandale.

Uniform grey with strong silvery lights, disk of wings with a bluish

iridescence. Greatest breadth of wing not quite a third its length ; greatest

length of second marginal cell a little more than a third the length of the wing.

major, Annandale.

Thorax, abdomen, and legs (except coxae and trochanters) brown with

a tinge of purple and with silvery lights ; wings purplish, strongly iridescent.

Greatest breadth of wing about a third its length ; greatest length of second

marginal cell nearly half the length of the wing. South India.

malabaricus, Annandale.

Yellowish-grey with silvery lights. Greatest length of wing slightly over

one-fourth its length ; greatest length of second marginal cell a little more

than a third the length of the wing. Himalayas, between 4000 and 7000 feet.

himalayensis, Annandale.

44 PAPPATACI FEVER [CH.

Head and thorax yellowish-brown, abdomen brown with darker glistening
hairs ; femora yellow with brown tip ; tibiae and tarsi brown with silver
sheen. Greatest breadth of wing one-third its length ; greatest length of
second marginal cell a little more than one-fourth the length of the wing.
Batavia. perturbans, Meijere.

American species.

Yellow, mesonotum brown ; legs appear brown in certain lights but are
covered with white tomentum ; second marginal cell slightly more than twice
the length of its petiole. North America. vexatov, Coquillet.

Resembling vexatov, except that the hairs are mostly yellow, and the second
marginal cell is about thrice the length of its petiole. Guatemala.

cruciatus, Coquillet.

In female length of head with proboscis, half that of the rest of the body.
Wing venation resembling that of malabaricus. In the male greatest length
of wing 3+ times the greatest breadth. Wings bluntly pointed ; hind border
not much more strongly arched than the front. Length of second marginal
celt three-eighths that of the wing ; third marginal, six-elevenths the length.
Halteres long and large. Brazil and Peru. rosfrans, Summers.

Dorsal surface of abdomen with numerous scales between the hairs.
Palp index 4, 5, 3, 2. Length of body 2 mm. Para.

squamiventris, Lutz and Neiva.

Dorsal surface of abdomen without scales. Last segment of palps longer
than the others ; palp index 4, 2, 3, 5. Length of body about 2 mm. St Paul
and Minas. longipalpis, Lutz and Neiva.

Dorsal surface of abdomen vithout scales. General colour brownish-
vellow, the upperside darker. Palp index 5, j, 3, 2.

intermedins, Lutz and Neiva.

CHAPTER VI

DISEASES CARRIED BY PHLEBOTOMUS

Pappataci Fever.

Synonyms. Sand- Fly Fever ; Three-Day Fever ; Phle-
botomus Fever ; Simple Continued Fever ; Pink Eye ; Som-
merfieber ; Hundskrankheit ; Sommerinfluenza ; Soldaten-
fieber ; Endemischer Magencatarrh ; Febbre dei tre Giorni ;
Mai della secca ; Febbre estiva ; Chitral Fever ; Fievre de Toga.

History. This malady seems to have been known for many
years in both Italy and India, but was first recognized as a
definite disease by Pick in 1886. Taussig, in 1905, noticed that
it was connected with the sand-fly and later, in 1908, the

VI] DISTRIBUTION AND SYMPTOMS 45

researches of Doerr, Franz, and Taussig, clearly demonstrated
the nature of this disease and its mode of transmission.

Some authors, especially the French, regard Pappataci Fever
as merely a form of dengue, but the febrile symptoms are rather
different in the two cases and therefore, for the present, it seems
advisable to consider them distinct.

Distribution. Pappataci Fever occurs in various parts of
Italy and is especially prevalent in Dalmatia, Istria, Herze-
govina and various other parts of Austria-Hungary, and has
also been recorded from Portugal. It is said to occur in
Asia Minor, the Balkan Peninsula, North Africa and the
Sudan. The majority of the islands in the Mediterranean
seem to be liable to outbreaks, for the disease has been recorded
from Corsica, Sicily, Malta, Crete and Cyprus, and probably
occurs in most, if not all the islands of the Greek Archipelago.
According to Robinson and Blackham the "Seven-Day Fever"
of the Peshawur valley is also a variety of Sand-Fly Fever and
is carried by Phlebotomus. In other parts of India, epidemics
probably due to this infection have been observed, but the
symptoms in many cases closely approximate those of dengue.
The disease is said to occur in China.

Symptomatology. In view of the fact that this disease has
only recently been distinguished, a short account of the symp-
toms is included.

Different outbreaks shew considerable variations in the
symptoms. The onset of the disease is usually sudden, with
febrile symptoms, headache and pains, especially in the extremi-
ties. The fever continues for one or two days and usually
disappears on the third, fourth, or fifth day, but in some
cases may persist as long as seven days. During the attack
nervous symptoms are very pronounced ; headache, usually
frontal, is constantly present and pains in the back, loins and
lower extremities occur in the majority of cases. Muscle pains
are frequently present, being chiefly located m the intercostal
and lumbar muscles, and the muscles of the calves. On the
other hand the joints are very seldom affected and this con-
stitutes one of the means of distinguishing this disease from
dengue.

46 PAPPATACI FEVER [CH.

The eyes are injected, especially across the middle of the
conjunctivae, and the bulbi are painful on pressure. The distur-
bances of the digestive system are very inconstant ; vomiting
occurs in about one-third of the cases, usually as an initial
symptom. Constipation is the rule when the temperature is
high, but later on, diarrhcea often sets in and the liquid stools
may contain blood. Epistaxis is a common phenomenon.

Various cutaneous eruptions may occur, in the nature of
erythema of a morbilliform or multiform character, and a few
roseolae.

The examination of the blood reveals no changes in the
number or morphology of the red corpuscles. A pronounced
leucopenia has been observed on the first day, and the numbers
of leucocytes may fall as low as 1400 per c.mm. on the second
day, after which the numbers slowly increase from the third
day onwards.

The percentage of polymorphonuclears varies between 80
and less than 50, and Gabbi finds a slight increase of the mono-
nuclears. Eosinophile leucocytes are very scarce, their number
being below the normal.

The prognosis is invariably good and the patient's recovery
is usually complete within two or three weeks after the begin-
ning of the disease.

In the absence of any knowledge of the causative agent of
this disease, the diagnosis can only be based on clinical observa-
tions and it is extremely difficult to distinguish between Pap-
pataci Fever and various other febrile diseases. The presence
of the transmitting agent may be of some help in establishing
the diagnosis, but the discovery of the specific microbe is neces-
sary before this disease can be distinguished with any certainty.

Mode of infection. Pappataci Fever is transmitted by the
agency of Phlebotomus papatasii, the sand-fly. Possibly P. per-
niciosus, minutus, and other species of the genus are also capable
of spreading the disease, but up to the present, with the possible
exception of Aden1, no cases have been recorded from localities
in which P. papatasii is not known to occur.

1 Sand-Fly Fever is said to occur in this region. The only species of
Phlebotomus hitherto recorded from Aden is P. minutus.

VI] MODE OF INFECTION, ETC. 47

Following the bite of an infected fly, there is an incubation
period of from 3J to 7 days, during which the blood of the
patient is not infective. Then follows the first day of the attack
during which the blood becomes virulent and is capable of
infecting any Phlebotomus that may feed on it.

The blood loses its infectivity within a very short period,
probably not more than 24 hours, and after recovery the
patient is immune against any further attacks of the disease.

The flies become infected only if they feed on a patient
during the short time that his blood is infective. After ingest-
ing the virus, there is an incubation period of seven to ten
days before the insects become infective and beyond this
period they may again become non-infective, but experiments
on this point are far from complete.

Causal agent. Up to the present the causal agent of Pap-
pataci Fever has not been discovered, but it belongs to the
group of ultra-microscopic organisms which cause dengue,
yellow fever, etc. Its presence in the blood is proved by the
fact that the disease may be produced by the inoculation
into a non-immune person of blood taken from an infected
patient on the first day of the attack. Moreover, the injection
of a small quantity of diluted serum filtered through a Cham-
berland F filter is also followed by a typical attack of fever.
The virus is sufficiently resistant to maintain its activity for
a week in vitro.

It is evident that the fly is a true host for the organism
that causes the disease. If the Phlebotomus were only infec-
tive up to the seventh day after an infective feed, there would
be a strong suggestion that the virus was merely retained in
the alimentary canal and regurgitated at subsequent meals.
This supposition is disproved by the occurrence of a negative
phase of about seven days, during which the infective agent of
the disease undergoes some development, finally resulting in the
fly becoming infective.

Prophylactic measures. In view of the limited number of
observations on the breeding habits of Phlebotomus it is some-
what premature to advance any definite prophylactic measures.
If crevices in stone walls and amongst rocks constitute the

48 PAPPATACI FEVER [CH.

main breeding places, the task of destroying the immature
stages is practically insurmountable. At present it is only
possible to take precautions against being bitten by the insects
and the simplest method is the use of repellents. Major Craw-
ford recommends the following mixture which is said to be a
very efficient deterrent : 01. Anisi, 3 grs. ; 01. Eucalypti, 3 grs. ;
01. Terebenth, 3 grs. ; Ung. Acid Borac.

The use of ordinary mosquito nets is of course impossible,
as the flies are able to creep through the meshes, but spraying
the net with a 1 per cent, solution of formol, or some other
repellent, is said to be effective in keeping away these pests.
By employing a screen of chiffon or some similar material,
it is possible to exclude the flies altogether, but such a method
is quite impracticable on warm nights, when the Phlebotomus
are especially abundant. A brightly burning lamp appears to
attract the flies more than a sleeping human being and is very
useful in the absence of a net or punkah. As they are very
sensitive to wind, the use of electric fans in rooms would pro-
bably succeed in keeping them away and some such method
might well be adopted in the case of patients suffering from
Pappataci Fever, for by the careful isolation of all persons
suffering from the complaint, the number of cases would be
reduced. As the flies seem to avoid the upper stories of houses
it might be advisable to keep patients suffering from the disease
in upper bedrooms.

By preventing the flies from feeding on the blood of infected
persons it is even possible that the disease might be eradicated,
and this is the only method that seems practicable at the pre-
sent time.

REFEREXCES TO LITERATURE OX PHLEBOTOMUS
AND PAPPATACI FEVER.

Annandale, X. (1910). The Indian Species of Papataci Fly {Phle-
botomus). Rec. Ind. Mus. vol. iv. pp. 35-52. With 3 plates.

Birt, C. (19 10). Phlebotomus fever in Malta and Crete. Journ.
R.A.M.C. vol. xiv. pp. 142-159 and 236-258.

(1910). Sand-fly fever in India. Journ. R.A.M.C. vol. XV.

pp. 140-147-

VI] REFERENCES 49

Crawford, G. S. (1909). On the beneficial results of recent sanitary

work in Malta. Brit. Med. Journ. vol. 11. pp. 383~385-
Doerr, Franz and Taussig (1909). Das Papp atari fieber. Leipzig and

Wien : Franz Deuticke.
Franca, C. (191 3). Phlebotomus papatasii (Scopoli) et Fievre a Pap-

pataci au Portugal. Bull. Soc. Path. Exot. vol. vi. pp. 123-124.
Gabbi (1910) . Sulla febbre dei tre giorni o febbre da pappataci. Patho-

logica, vol. 11. pp. 546-550.
Grassi, B. (1907). Ricerche sui flebotomi. Mem. d. Soc. Ital. d.

Scienze, Ser. 3 a, vol. xiv. pp. 353-394* with 4 plates.

(1908). Intorno ad un nuovo flebotomo. Att. R. Accad. Line.

Ser. 5«, vol. xvn. pp. 681-682.

Howlett, F. M. (1909). Indian Sandflies. Trans. Bombay Med. Congr.
Ser. 3, pp. 239-242.

(1913). The Natural Host of Phlebotomus minutus. Ind. Journ.

Med. Research, vol. 1. pp. 34-38.

Leger, M. and Seguinard, J. (191 2). Fievre de Pappataci en Corse.

Bull. Soc. Path. Exot. vol. v. pp. 710-713.
Lutz and Neiva (191 2). Contribuicao para o Conhecimento das

Especies do Genero Phlebotomus existentes no Brazil. Mem.

Inst. Oswaldo Cruz. vol. iv. pp. 84-95.
Marett, P. J. (1910). Preliminary report on the investigation into the

breeding-places of the sand-fly in Malta. Journ. R.A .M.C. vol. xv.

pp. 286-291.

(191 1). The life-history of Phlebotomus. Ibid. vol. xvn.

pp. 13-29, with 1 plate.

Newstead, R. (191 1). The papataci flies [Phlebotomus) of the Maltese
Islands. Bull. Entomol. Research, vol. 11. pp. 47-48.

(191 2). Notes on Phlebotomus, with Descriptions of New Species.

Part 1. Ibid. vol. in. pp. 361-367.

Robinson and Blackham (191 2). Sand-flies and Sand-Fly Fever on

the North- West Frontier of India. Journ. R.A. M.C. vol. xix.

pp. 447-452.
Seidelin, H. (1912). Pappataci Fever. Yellow Fever Bull. vol. 11.

pp. 74-84.
Summers, Sophia L. M. (1913). A Synopsis of the Genus Phlebotomus.

Journ. Lond. School Prop. Med. vol. n. pp. 104-116.

H. B. F.

50 culicim: [ch.

CHAPTER VII

FAMILY CULICID.E (GNATS OR MOSQUITOES)

General Account.

Definition. The Culicidae are slender flies easily distin-
guished from all other Nematocera by the presence of a row
of scales on the posterior margin of the wings. In addition,
the long projecting proboscis, and the plumose antennae of
the males are characteristic features.

External anatomy. The head is small and subspherical ;
the occiput is always more or less covered with scales of various
forms. The eyes are large and reniform and may, or may not,
meet in the middle line ; in the living insect they are often
brilliantly coloured, but in preserved specimens these colours
usually fade. Ocelli are absent. The antennae are long and
slender, composed of 14 or 15 -segments ; the basal segment
is large, round, and is sometimes provided with scales. The
second segment fits into a depression at the apex of the first,
and the remaining segments are all more or less elongated
cylinders. Just above the base, or in the middle, of each
segment arises a whorl of long thick hairs, which are some-
what scanty in the female, but in the male are so thick-set
as to give the antenna the appearance of a bottle-brush ;
in addition, the last two segments of the male antenna are
nearly always more elongated and nearly bare.

The mouth-parts consist of the following appendages :

(i) A pair of mandibles, each of which is an extremely
delicate chitinous blade adapted for piercing the skin. In the
male the mandibles are absent (Figs. 26 and 27).

(ii) The first pair of maxillae, generally known simply as
the maxillae, are extremely fine stylets usually longer than
the mandibles. In the male the maxillae are sometimes rudi-
mentary. From the outer side of the base of each maxilla,
arises a maxillary palp, the form of which varies according to
the sex.

VII

EXTERNAL ANATOMY

51

25- Anopheles maculipennis. A, enlarged view of male; A', diagram of
ditto to shew the natural size ; B. head of female. Modified from
Nuttall and Shipley.

4—-

52

CULICID^E

[CH.

In Anopheles the palps are five- jointed and as long as the
proboscis in both male and female ; in the female Culex they
are very short three- to four- jointed structures, whilst in the
male Culex they are five- jointed and at least as long as in
Anopheles ; in Aides the palps are short in both sexes.

(iii) The second maxillae are united together to form the
labium, which ensheaths all the other mouth appendages with
the exception of the palps, and the whole structure is generally
known as the proboscis. It consists of a soft dorsally-grooved
rod which bears a pair of small labellae at the distal extremity.

Icce

sdl

Fig. 26. Transverse section through about the middle of the proboscis of
a female A nopheles maculipennis shewing the relative position of the parts
when at rest. Two tracheae (tr) and two pairs of extensor and flexor
muscles (mus) are seen in the labium. After Nuttall and Shipley.
Lettering as in Fig. 27.

Each of the latter represents the distal segment of the two-
jointed second maxillae, the proximal segments of which are
completely fused together. The labellae serve to guide the
piercing organs of the mosquito. The cavity of the labium is
hollow and it is within this space that the embryos of Filaria
bancrofti and F. immitis come to rest after leaving the thoracic
muscles or Malpighian tubules of an infected mosquito. The
labium is covered by a thin cuticle and the filariae escape by
rupturing this membrane when the insect feeds.

In addition to the paired appendages mentioned above,
there are two very important median structures.

(iv) The labrum, or upper lip, which is united with the
epipharynx, is an incomplete tube, in cross-section appearing

VII

EXTERNAL ANATOMY

53

something like an il ; the slit-like opening is placed ventrally.
At its distal extremity the labrum of the female narrows to
a sharp point, whilst in the male the tip is truncated.

(v) The hypopharynx arises just above the base of the
labium and in the female is shaped " like a two-edged sword."
When applied to the labrum it closes the ventral slit and the
two structures together form a suctorial tube. In the male
the hypopharynx is frequently fused with the labium and is

Fig. 27. Side view of the head of a female Anopheles maculipennis, x about
26, with the various mouth-parts separated, but in the relative position
in which they lie when enclosed in the groove of the labium. After
Nuttall and Shipley.

a, antennas ; cl, clypeus ; cs, cephalic scales ; hp, hypopharynx ; It,
labium; Ixe, labrum + epipharynx ; mn, mandibles; mp, maxillary palps;
mx, first maxillae.

never adapted for piercing. In both male and female the
thickened ventral part of the hypopharynx is traversed by the
median salivary groove, ending at the distal extremity.

The relative position of the mouth-parts is well shewn in
the accompanying diagram (Fig. 27).

The thorax is by far the largest of the three divisions of
the body, being some 12-15 times as Large as the head, and

54 CULICID.E [CH.

4-6 times as large as the abdomen. The major portion is
taken up by the mesothorax, which forms the chief region of
the mid-body. Its dorsal element, the scutum, is a large
plate projecting slightly over the head ; posteriorly it is
bounded by a curved narrow thickening of the integument
known as the scutellum, which often bears conspicuous rows
of hairs. Behind this comes the post-scut ellum, or metathorax,
a triangular plate which overlaps part of the first abdominal
segment. The presence or absence of hairs and scales on the
post-scutellum is of generic importance.

At each side of the thorax are two large spiracles, respec-
tively pro- and meso-thoracic in origin (Fig. 4).

The six legs are each composed of the typical insect parts, viz.
the coxa, trochanter, femur, tibia and tarsus, the last of which
is five-jointed and ends in a pair of claws. The four proximal
joints are often covered with scales. The first joint of the
tarsus is long and hairy and its proportionate length with the
tibia is of specific value. The shape of the claws varies accord-
ing to the sex ; in the female they are equal and simple or
may have a single tooth ; in the male those of the fore-legs
are usually unequal and toothed.

The wings are long and narrow and while at rest lie flat
over the abdomen. The venation is very characteristic, there
being six distinct longitudinal veins and two prominent fork-
cells, and the costal vein extends completely round the edge
of the wing (Fig. 28).

The auxiliary vein is distinct, sometimes extending beyond
the middle of the wing. The second, fourth, and fifth longi-
tudinal veins are furcate.

The hind margin of the wings is fringed with a row of hairs
or scales and in addition all the veins are more or less covered
with scales. The shape and arrangement of these scales varies
in different groups and is the chief basis of Theobald's classi-
fication.

On the under surface, at the base of the wing, is a curious
stridulating organ, consisting of a complex system of chitinous
bars, by means of which two ridged surfaces are made to rub
against each other when the wings vibrate (Fig. 28). It is

VII]

EXTERNAL ANATOMY

55

probable that this organ is responsible for some of the charac-
teristic buzzing of the mosquito.

Each halter consists of a short chitinous rod arising from
a basal plate and ending in a rounded knob. The concave
basal plate and a knob at the base of the halter are covered
with small papillae, and Shipley and Wilson have suggested
that by these two surfaces rubbing against each other when
the halter vibrates, a faint note may be produced

Fig. 28. View of under surface of the base of the wing of Anopheles maculi-
pennis, shewing stridulating organ. After Shipley and Wilson.

A, right half of thorax with right wing. The shaded portion indicates
the area which bears the stridulating organ. B, the stridulating organ,
highly magnified, bl, ridged blade ; h, haltere ; kn, knob ; scl, sclerites ;
tb, toothed bar.

The abdomen consists of eight segments, each composed of
a dorsal chitinous plate, the tergum, and a ventral chitinous
plate, the sternum, between which is a soft membrane, the
pleuron. On each side are six abdominal stigmata opening
in segments two to seven inclusive. The surface of the abdo-
men may be covered either with scales or hairs. The terminal
segment is bilobed and in the male each lobe terminates in a
long chitinous claw, the clasper.

56 CULICID.E [CH. VII

Internal anatomy. The internal anatomy of the Culicidae
is very constant and the following description of Anopheles
maculipennis will apply, with but slight modifications, to any
other member of the family. This example has been selected
since it has been minutely described by Nuttall and Shipley,
from whose account the present description is largely taken.

(a) Digestive organs. According to the above-mentioned
authors the alimentary canal may be divided into eleven parts as
follows : mouth ; buccal cavity ; pharynx or pumping organ ;
oesophagus, with which are connected three diverticula, two
dorsal and one ventral ; oesophageal valve ; mid-gut ; ileum ;
colon ; rectum ; and anus.

The mouth is that region where the various mouth-parts
coalesce and is of no special interest. The buccal cavity extends
from the mouth to a valvular arrangement situated at the com-
mencement of the pharynx. It is lined with chitin throughout,
that of the floor being much stouter than that of the roof,
which forms a kind of soft palate capable of being raised or
depressed by means of muscles. Accordingly the size of the
buccal cavity can be increased by these means and it may
at times assist in suction. At the junction of the buccal cavity
and pharynx is situated a valvular apparatus, formed by a
double row of chitinous hairs attached to the ventral surface.
These hairs, in addition to acting as a valve, may also serve
as a kind of filter and keep out large particles.

The pharynx, or pumping organ, extends from this valve
to the commencement of the oesophagus, and consists of a
thick-walled tube composed of three longitudinal, chitinous
plates, conjoined by a fold of chitin at their margins. The
lumen of the tube is triangular in shape, and powerful
muscles, arising from each of the three chitinous plates and
attached to the exoskeleton, serve to separate the walls and
increase the capacity of the pharynx. By means of the power-
ful pharyngeal muscles, which almost fill the head of the
mosquito, the insect is enabled to suck up liquids into its
pharynx, and after the relaxation of the muscles the walls
contract again, by virtue of the elasticity of the chitinous
supporting plates. Any ingested liquid is thus forced out of

■ ca/m/ju

dataal Sbe&e/iyvoiA*!

'amdoojeca.

i7udtyul&>gvn<j

'^tfcmiacA" -\

tncUp/upia/ri UU>£

Tncd^UenaU

Fig.

29. Anopheles maculipennis. Schematic longitudinal section of a
female insect shewing the relations of the various parts of the alimentary
canal to each other, and to the exoskeleton, also the salivary glands of
one side with their duct joining the common duct, which is prolonged into
the hypopharynx. The ventral reservoir is rilled, the stomach contracted.
One of the dorsal reservoirs is cut oil near to where it joins the oesophagus.
After Nuttall and Shipley.

58 culicid^e [ch.

the pharynx into the next region of the alimentary canal.
The pharynx of the female mosquito is both larger and stronger
than that of the male, this being the result of the more voracious
habits of the former.

The oesophagus is a short, circular tube, extending from the
posterior end of the tri-radiate pharynx to the oesophageal valve.

Into its posterior end, about on the level of the origin of
the first pair of legs, open the three oesophageal diverticula.
The largest of these is the ventral diverticulum opening into
the oesophagus by means of a single median pore and extend-
ing backwards beneath the alimentary canal as far as the
sixth or seventh segment. The other two dorso-lateral diver-
ticula are much smaller and open one on each side of the
oesophagus.

The function of these sacs is still far from being settled,
for although Nuttall and Shipley have shewn that food material
is passed into them, yet it is doubtful whether their chief
function is to serve as reservoirs.

The sacs generally contain small bubbles of carbon dioxide
and also larger or smaller numbers of a small round fungus
belonging to the Entomophtoracese.

The presence of these bubbles in the sacs has caused certain
authors to suppose that there was some connection between
them and the tracheal system, whilst others, noticing the
rhythmic contractions of the ventral sac, have supposed that
it was an accessory pumping apparatus. The main function
of the diverticula is probably to assist in the feeding of the
mosquito and the manner in which this is affected will be
described later (vide habits).

The oesophageal valve is homologous with the proventriculus
of many insects, and serves as a valve between the oesophagus
and the mid-gut. It is little more than a slight invagination
of the intestinal wall surrounded by a very thick sphincter
muscle. Six small protuberances, the remnants of the csecal
appendages of the larva, can usually be seen in the walls of
the valve.

The mid-gut is the only part of the alimentary canal that
is not lined with chitin and consequently the only part in which

VII] INTERNAL ANATOMY 59

any food absorption takes place. Commencing at the oeso-
phageal valve it consists of a straight tube expanded posteriorly,
extending to about the posterior limit of the sixth segment.
The expanded posterior region is commonly termed the " sto-
mach " and this term may conveniently be retained ; it is in
this hinder region of the mid-gut that the malarial parasite
develops. The wall of the mid-gut is surrounded by both
longitudinal and circular muscle layers and the latter throw
the surface into a series of folds so that this region of the
alimentary canal has an annulated appearance. The mid-gut
is extremely well supplied with tracheae, which branch in such
a manner that the whole surface is covered with fine air-
capillaries. The interior is lined by a layer of large cubical
cells, some of which are secretory in function.

The ileum commences at the junction of the Malpighian
tubules with the mid-gut ; it is a thin-walled tube lined with
chitin raised up in the form of ridges. It passes insensibly
into the colon, which is merely a straight tube opening suddenly
into the large oval rectum. The latter contains six large ovoid
papillae which considerably diminish the size of the chamber.
These rectal papillae are abundantly supplied with tracheae
and their function is possibly respiratory.

The rectum narrows just before the anus, which opens in
the last segment of the body, immediately beneath the genital
aperture. It is guarded by two short lateral papillae.

The Malpighian tubules are five in number, opening into
the alimentary canal at the junction of the mid- and hind-gut.
The wall of each tubule is composed of large secretory cells
abundantly supplied with tracheae. These cells are excretory
in function, for the Malpighian tubules often contain uric acid
and other waste nitrogenous products.

The Malpighian tubules are frequently the haunt of pro-
tozoal parasites, the lumen of the tubes being a common place
in which to find insect flagellates.

The salivary apparatus ; commencing with the opening at
the tip of the hypopharynx, it consists of the following parts :
a median groove, or " salivary gutter," extending from the tip
to the base of the hypopharynx. This groove is arched over

60 CULICID.E [CH.

by thin chitinous lamellae and therefore serves the purpose of
a duct. At the base of the hypopharynx is the salivary
receptacle or pump, connecting the salivary groove with the
common salivary duct. The pump is somewhat drum-like in
form, its membrane being moved by muscles by means of
which the saliva is first pumped out of the glands and then
down the salivary groove to the tip of the hypopharynx. The
salivary pump is situated beneath the floor of the buccal cavity.
From its posterior end a median, common salivary duct extends
backwards until it reaches the commencement of the pharynx,
at which point it branches into two. These secondary ducts
run side by side along the ventral wall of the neck into the
thoracic cavity, where they diverge and each branches into
three smaller ducts. Each of the latter terminates in a salivary
gland, there being three glands on each side.

These three salivary glands are at first arranged in the form
of a triangle but subsequently their position changes and the
gland which at first occupies a dorsal position comes to lie in
between the other two glands. It is usually known as the
"central gland" and differs both in size and structure from
the other two, known as the " lateral glands."

The size of the glands varies according to the size of the
insect but is always greater in the females than in the males.
The dimensions of the glands of an average-sized female are
as follows : length of lateral glands, 880 ^ ; length of central
gland, 510/u,; width of glands, 85 /x. In the male the large
glands only measure about 200 /jl in length by 50 /x in breadth.

The salivary glands are of very great importance from a
parasitological point of view, since the infective sporozoites
of malaria congregate within the cells of these organs and are
passed out with the salivary secretion. Therefore by a micro-
scopical examination of these glands it is possible to find out
whether or not a mosquito is infected.

The structure of the three glands is similar, each consisting
of an elongated sac the lumen of which is surrounded by a single
layer of secretory cells, but they differ somewhat in their finer
details. The acinus of each of the lateral glands is more or less
filled with an abundant secretion, which also fills the secretory

VII ] INTERNAL ANATOMY 6 1

cells to such an extent that their nuclei are forced to the
periphery. Moreover, these cells are granular in appearance,
in contradistinction to those of the central gland, which are
clear The lumen of the central gland is much smaller than
that of each lateral gland, and the clear secretion almost
entirely fills the cells.

This central gland has long been supposed to be the source
of the irritating substance which is inoculated when a mosquito
begins to feed, and accordingly is still commonly known under
the name of " Poison-Gland." Schaudinn, however, has
shewn that its secretion produces no effect when injected into
the skin and the irritation following a bite is due to the entrance
into the wound of a fungus, which is derived from the oeso-
phageal diverticula.

(b) The reproductive organs. The genital organs of the
female consist of a pair of lobulated masses containing numerous
eggs in various stages of development. From each a short wide
duct leads into a common oviduct opening to the exterior in
the eighth segment. Into the common duct open three short
seminal receptacles and also a cement-gland. The function of
the latter is probably to secrete a protective coating for the
eggs.

The male genital organs consist of a pair of minute testes
situated in the eighth segment. From each arises a simple
tube, the vas deferens, and the two unite just before the
opening to the exterior, forming a common ejaculatory duct.
The latter ends in a short penis and the external aperture,
situated on the ninth segment, is guarded by an elaborate
arrangement of claspers, or gonapophyses, that are of some
importance from a classificatory point of view. The sper-
matozoa are stored, and also complete their development, in
two receptacuke seminales, opening one on each side into the
vasa deferentia immediately before their junction.

(c) The respiratory system. This consists of two large
tracheae running longitudinally one on each side of the body
and giving off branches to all the internal organs. Each
main longitudinal trunk is connected by means of short branches
with the stigmata, or breathing pores, of which there are two

62 CULICID.E [CH.

pairs of large thoracic, situated on the mesothorax and meta-
thorax respectively, and six pairs of abdominal, on the second
to the seventh segments.

(d) The circulatory system. As in the majority of insects
the circulatory system consists of a dorsal tube or heart con-
tained within a pericardium. The heart is provided with
valves and by its rhythmic contractions the blood, which
bathes all the organs, is kept circulating round the body.

(e) The nervous system. This consists of a double ventral
nerve-cord uniting a series of ganglia, one to each segment.
The anterior or cephalic ganglion, situated in the head and
supplying nerves to the appendages of this region, is remark-
able for its large size in comparison with that of the insect.
From this ganglion the ventral nerve-cords pass one on each
side of the oesophagus, to unite in an infra-oesophageal ganglion.
The double ventral nerve-cord continues posteriorly from this
ganglion and in each segment, except the last, is enlarged into
a segmental ganglion.

Life-cycle. The life-cycle of all species of mosquitoes may
be briefty outlined in a few words. The female, after being
fertilized, deposits her eggs on, or near, the surface of some
water. After a short interval these hatch out giving rise to
young aquatic larvae, which grow until they reach a certain
size and then pupate. The resulting pupa is actively motile
and swims about in the water as vigorously as the larva.
After a comparatively short existence the anterior dorsal
region of the pupa splits and the adult insect emerges.

The egg. The number of eggs laid by the female varies
considerably, from 40 to 100 (A. maculipennis) , up to as many
as 400 (Culex pipiens). The eggs may occur singly, as in the
case of Anopheles and Stegomyia, or adhere together forming
boat- or raft-shaped masses, as in Culex and many other Culi-
cinse, and being provided with air-chambers, they invariably
float on the surface of the water. The shape of the eggs is
different in each genus ; those of Anopheles are boat-shaped
with a distinct float at the sides, growing broader in the
middle (Fig. 31, A, B), whilst those of Culex are fusiform (Fig. 30).
In the great majority of mosquitoes the eggs are laid on the

VII

LIFE-CYCLE

63

surface of the water and the larvae hatch out after two or three
days.

In A edes and Psorophora, however, the eggs are laid singly,
in most cases not upon the surface of water, but in such situa-
tions that the egg lies dormant for some time awaiting favour-
able conditions for the development of the larvae. In Northern

4fe

14mamwimi,^--

i

OVUM

Fig. 30. Diagram shewing the corresponding stages in the life-cycle of
Anopheles (on the left) and Calex (on the right). From a wall diagram
drawn by Professor Nuttall.

regions it seems that some of the eggs, although they may be
repeatedly submerged, will not hatch until they have been
frozen, and it is by means of these eggs that the mosquitoes
manage to persist through the winter.

The larva. So far as known the larvae of all mosquitoes are
entirely aquatic in habit. The larva possesses a distinct head

64 CULICID/E [CH.

provided with strong mandibles adapted for biting. The shape
of the head varies in different families, being long and narrow
in the majority of Anophelinae and large and broad in the
Culicinae. The thorax is broad and its three segments are
fused together to form a single mass. The abdomen is long
and slender, and is composed of nine distinct segments. The
anus opens at the apex of the terminal segment and is sur-
rounded by four, more or less well-developed, tracheal gills.
The respiratory system consists of two main longitudinal
tracheae opening on the dorsal surface of the eighth abdominal
segment, either by two separate apertures in a hollow at the
base of a papilla (as in the Anophelinae) or at the apex of a
distinct breathing tube or syphon of varying length (as in the
Culicinae). The presence or absence of this structure furnishes
an easy method of distinguishing the larvae of Anophelines from
those of the Culicines.

Moreover, it is possible to distinguish different genera and
even species by means of the larval characters, such as the
arrangements of the hairs on the segments, the form of the
mandibles and other head appendages, the shape of the
syphon, etc.

The larva progresses in the water by means of energetic
wriggling movements, but the larvae of Culicines are generally
more active than those of the Anophelines. Moreover, in the
latter, because of the situation of the respiratory apertures,
and the presence of the palmate hairs, the larvae float hori-
zontally under the surface of the water, and closely resemble
bits of floating sticks. The Culicine larvae merely bring the
tip of the breathing syphon in contact with the surface film
of the water and then hang downwards so that their bodies
make an angle with the surface of the water. This position
is also partly due to the heavy jaws and head, which weigh
down the anterior end. The difference in the attitude assumed
by the larvae when at the surface of the water is very
characteristic and constitutes one of the simplest methods of
distinguishing between Anophelines and Culicines at this stage
of development (Fig. 30).

The larvae may be either herbivorous or carnivorous. As a

VII

LIFE-CYCLE

65

Fig. 31. Anopheles maculipennis. A, side view, and B, dorsal view of egg;
C, young larva, and D, fully-grown larva ; E, flabellum or flap overhanging
the base of certain thoracic hairs ; F, a palmate hair ; G, ventral view of
head of fully-grown larva. After Nuttall and Shipley. Lettering :
ant, antenna ; ap, anal papillae ; b, brush ; fl, float ; h, stout hairs of
mandible which arrange the brush ; m, hooked hairs at edge of maxilla ;
nip, palp of maxilla ; mst, the " under-lip," or metastoma ; mt, median
tuft of hairs ; ph, palmate hair ; st, stigma.

H. B. F.

66 CULICID.E [CH.

general rule they feed on algae, but many species swallow any
kind of minute object that may be in the water. By means
of the mouth-brushes (Fig. 31, G, b) currents are set up towards
the mouth, and any small particles are carried with the stream
and swallowed. Certain larvae (e.g. Culex pipiens) seem to
thrive best when the water is charged with animal refuse,
whilst the larvae of Psorophora, Lutzia and some other genera
are actively predacious, feeding upon other mosquito larvae.

When food is abundant and the temperature favourable
the larva grows rapidly and may become full-grown in little
more than a week. The duration of the larval stage, how-
ever, is extremely variable, for the larvae of some species
(e.g. Wyeomyia smithii) can live for nearly a year without any
food. The duration is also greatly prolonged by low tempera-
tures and it is probable that some species pass through the
winter in the larval form.

During its growth the larva moults four times, the last of
these moults giving rise to the pupa.

The pupa is also aquatic, and swims actively through the
water, though of course it is unable to take in any food, the
appendages of the head and thorax of the future fly being
enclosed in a common chitinous covering. The pupa respires
by means of a pair of appendages on the thorax, the respiratory
trumpets, or horns (Fig. 8, tr) . These trumpets communicate
with the anterior pair of thoracic spiracles and when the pupa
is at the top of the water they break through the surface film
and thus admit air to the spiracles. The pupa is kept floating
at the surface by means of a pair of fan-like tufts of hairs,
situated on the dorsal surface of the first abdominal segment.
The abdomen is composed of nine distinct segments ; the
eighth bears at its apex a pair of large chitinous plates, the
paddles or fins. The shape of the trumpets and paddles varies
in different species but these characters are of no generic value.

The duration of the pupal stage as a rule does not exceed
more than two or three days, but as in the case of the other
stages may be prolonged by low temperatures. Towards the
end of this period the pupa becomes inflated with air and
when the adult is about to emerge it gradually straightens

VII] BIOLOGY OF ADULT MOSQUITO 67

its abdomen and floats almost horizontally on the surface of
the water. The thoracic region then splits longitudinally and
the adult mosquito gradually draws itself out of the skin and
after a few minutes is able to fly away.

Biology of the Adult Mosquito.

Food-habits. Although the females of a large number of
species of mosquitoes habitually feed on blood, the habit is
by no means universal throughout the family, as practically
all the males and a considerable number of the females feed
on various plant juices. Some species, e.g. Stegomyia fasciata,
attack man much more readily than others. The majority
of the Culicinae seem to be mainly parasitic on birds.

Mosquitoes are very susceptible to heat and cold, for during
the winter they never bite except on occasional warm days.
The reaction to heat is so striking that this is probably one
of the main reasons of their being attracted towards warm-
blooded animals and other warm objects. Howlett has shewn
that hungry female mosquitoes {Anopheles and Cnlex) will bite
viciously at a test-tube of boiling water, or even of hot copper
sulphate solution. In the latter case the insects could be
observed to thrust their proboscides into the crust of copper
sulphate that had crystallized on the outside of the tube. It is
possible that the blood-sucking habit may have been derived
from what was originally a simple thermotropism (attraction
by heat). A large number of mosquitoes feed only at night,
but Stegomyia fasciata and most of the northern species, and
also those inhabiting jungle, feed during the day-time

The method of feeding. When a female mosquito commences
to feed, the tip of the labrum is placed against the surface,
and then the sharp maxillae and mandibles are thrust into the
skin. The labrum is then forced into the wound and thus
the whole six stylets of the proboscis enter the skin, being
guided by the labium. The latter is doubled back as the
mouth-parts enter deeper into the host.

The subsequent processes can onlv be conjectured from
experiments on mosquitoes under artificial conditions, but arc
probably as follows.

5—2

68 BIOLOGY OF ADULT MOSQUITO [CH.

After piercing the skin the insect begins to pass its salivary
secretion along the groove in the labrum. The function of
this secretion is, however, quite unknown. Meanwhile the
amount of carbon dioxide in the tracheae of the insect increases
considerably owing to its proximity to the body of its host
and as a result the muscular contractions are considerably
augmented. The effect of this increase in the muscular con-
tractions is to cause compression of the oesophageal diverticula,
and their contents, consisting of bubbles of carbon dioxide
and also of a fungus, are forced into the oesophagus and for-
wards through the proboscis into the wound caused by the
bite. The lumen of the proboscis, buccal cavity and oeso-
phagus is thus filled with carbon dioxide, derived from the
diverticula, and this gas is supposed to retard the coagulation
of the blood. The fungus, which is also extruded from the
diverticula, enters the skin and is the cause of the great irritation
and local swelling that often follow the bite of a mosquito.
The association of this fungus with the mosquito constitutes
one of the most interesting cases of commensalism hitherto
described. The fungus is present in the egg, larva and pupa,
and can always be found in the oesophageal diverticula of
freshly emerged mosquitoes. In this region it multiplies on
the food which is taken into the diverticula, and during its
growth produces bubbles of carbon dioxide. When the mos-
quito feeds, the majority of the fungi and the bubbles of
carbon dioxide are extruded, but the few remaining fungi
rapidly grow on the blood which passes into the diverticula
during the meal, and thus more carbon dioxide is produced.
Schaudinn shewed that the inoculation of the salivary glands
of the mosquito into the skin did not produce any effect,
whereas the inoculation of the contents of the ventral diverti-
culum was followed by the formation of an irritant swelling
resembling that caused by the bite of a mosquito. These
results have also been confirmed by Major Williams, I. M.S.,
whilst working in the Quick Laboratory, Cambridge.

Colour. Mosquitoes, like all other blood-sucking insects,
have a decided preference for dark colours and avoid lighter
shades. Nuttall found that dark blue and dark red were the

VII

EFFECT OF COLOURS

69

most attractive colours to Anopheles maculipennis, whilst
yellow, white, and orange seemed to repel the insects. His
experiment is of sufficient interest to be reproduced in detail :
I To test the influence of colour a number of pasteboard
boxes were taken, which measured 20 by 16 cms. and had a
depth of 10 cms. The boxes were lined with cloth, having a
slightly roughened surface, to which the insects could com-
fortably cling. All of the fabrics had a dull — not shiny —
surface, and each box was lined with cloth of a different colour.
The boxes were placed in rows upon the floor and upon each
other in tiers, the order being changed each day after the
observations had been made. The interior of the boxes was
moderately illuminated by light reflected from the surface of
the white tent. On 17 days during a month beginning with
the middle of June, we counted the number of flies which had
accumulated in the boxes. Counts were actually made on
17 sunny and cloudy days, and with the following result :

Number of A . maculipennis counted
7 days

Colour of box in each bo>

: during i

Navy blue

108

Dark red

90

Brown (reddish)

81

Scarlet

59

Black

49

Slate grey

3i

Dark green (olive)

24

Violet

18

Leaf green

17

Blue

14

Pearl grey

9

Pale green

4

Light blue (forget-me-not)

3

Ochre

2

White

2

Orange

1

Yellow

0

*• It is evident, therefore, that white or khaki-coloured
clothing is the most suitable in regions where mosquitoes arc
troublesome."

70 BIOLOGY OF ADULT MOSQUITO [CH.

Sound. We have already referred to the stridulating
apparatus described by Shipley and Wilson, by means of
which the insect emits a sound whilst flying. Certain males
seem to be very susceptible to notes resembling the hum of
the female and the insects have been noticed to swarm around
instruments emitting particular notes. At Grantchester, near
Cambridge, where Anopheles maculipennis and Culex pipiens
are fairly common, the writer has noticed that these insects
may be aroused to activity by the sound of a piano or violin.

Howard was informed by Mr A. De P. Weaver, that while
engaged in some experiments in harmonic telegraphy, in
which a musical note of a certain pitch was produced by
electrical means, he found that when the note was raised to
a certain number of vibrations per second, all mosquitoes, not
only in the same room but also from other parts, would con-
gregate near the apparatus and would be precipitated from
the air with considerable force. He therefore covered a large
surface with sticky fly-paper and after sounding the note for
a few seconds caught all the mosquitoes in the vicinity.

Habitat and modes of dissemination. As a rule mosquitoes
do not wander more than one or two hundred yards from their
breeding places (see page 72). Nevertheless, occasionally
migratory flights have been noticed during which the insects
travelled many miles. Such a mode of dissemination, how-
ever, is certainly very rare and generally mosquitoes are spread
by human agency. Ships and trains are both responsible for
the introduction of species into fresh localities, as the females
may remain in the holds of ships or in the carriages of trains
for several days, and thus be carried hundreds of miles. The
occurrence of certain species at scattered seaports in various
parts of the world shews that this mode of dissemination has
been of considerable importance in the past, when ships carried
unprotected tanks of water.

Resting position. When at rest an Anopheline can generally
be distinguished from a Culicine by the attitude of the body
and the legs. Anophelines usually rest with the proboscis
pointing towards the surface, and as the proboscis and the rest
of the body are in a straight line, the insect has a very

VII] HIBERNATION AND LONGEVITY ?I

characteristic appearance and seems to be standing on its head.
On the other hand, in the Culicinae the proboscis forms an angle
with the rest of the body and therefore the insect has a hump-
backed appearance ; moreover, it generally rests with its body
parallel to the surface, or with the posterior extremity bent
towards the surface. These differences in the position of rest,
whilst being useful for the recognition of living mosquitoes,
are by no means constant, as Anopheles sometimes settles in
the same manner as Culex. The differences between the two
positions are well shewn in Fig. 30.

Hibernation. In cold regions mosquitoes generally pass
through the winter in the egg stage, but in addition some
of the females hibernate in dark corners. During last
winter several females of A. maculipennis and Theobaldia
annulata hibernated at the top of a wardrobe in the author's
bedroom at Grantchester, disappearing after the warm weather
in April. In tropical countries mosquitoes generally hibernate
during the dry season, when all the breeding pools disappear.
In addition, however, some of their eggs may remain in
the mud at the bottom of dried pools and develop when these
are again filled with water.

Longevity. There are very few observations on the longevity
of mosquitoes, but the length of life of the female seems to be far
greater than that of the male. Those females which hibernate
may live for nearly a year, but in confinement Anophelines have
not been kept alive for more than about a month. In the case
of Aedes Knab has found that the female may live for at least
three months, and Stegomyia has been kept alive for 154 days.

Mating habits. In many species, e.g. Culex pipiens, the
males form large swarms, to which the females seem to be
attracted. The latter, however, merely fly to the swarm in
order to secure a mate, and as soon as this is effected the pair
at once drops out of the swarm. This habit of forming swarms
is not entirely confined to the male sex, for swarms of females
have been observed side by side with those of males.
Copulation may be accomplished either on the wing, as in the
case of Stegomyia fasciata, or whilst resting, and is generally
of but short duration.

72 culicid^: [CH.

Flight. Although long flights have been recorded in isolated
cases, there is little doubt that as a rule the flight of mos-
quitoes is very limited, rarely exceeding a quarter of a mile.
From a prophylactic point of view, the distance they are
capable of travelling is of great importance, for in most coun-
tries it is only possible to keep circumscribed areas free from
mosquitoes, and if the insects were able to travel any con-
siderable distance these areas would be continually invaded by
mosquitoes from the surrounding country. It is known that this
does not happen to any marked degree, but occasionally long
flights have been recorded suggesting that under some con-
ditions the Culicidae may travel considerable distances. The
majority of such flights seem to be of a migratory nature and
the cause of them is unknown. The most authentic accounts
all come from America, where the salt-marsh species belonging
to the genus Aedes are certainly capable of travelling five to
ten miles, whilst distances of as much as 40 miles have been
recorded. Such flights, however, must be regarded as very
exceptional and, from a prophylactic point of view, may be
disregarded.

Enemies. In the section on the methods of destruction
of these insects, we shall have occasion to refer again to some
of the natural enemies of the mosquitoes. The greatest
mortality takes place amongst the immature stages, which
are exposed to the attacks of countless enemies. In fact the
observations of Nicholls and others have shewn that the larvae
of mosquitoes are practically unable to exist in permanent
waters, as the latter contain such large numbers of predaceous
aquatic animals, such as fish, dragon-fly larvae, beetles, etc.
The importance of fish in destroying larvae is now generally
recognized, but unfortunately in many cases it is rather difficult
to employ this means of destruction, as the mosquitoes can
breed in small pools of water where fishes cannot live.

The bladder-worts, Utricularia, capture various animals in
their small bladders, and in this way considerable numbers
of the larvae may be destroyed, as the plants will grow in
stagnant pools. In addition another insectivorous plant,
Aldrovanda vesiculosa, a member of the sundew family, captures

VII] ENEMIES 73

mosquito larvae, its leaves closing quickly on any animal that
touches them.

The larvae are sometimes destroyed by fungi and bacteria,
but these groups of organisms are neither of them very im-
portant enemies.

Both the adult insect and its immature stages are para-
sitized by various species of Protozoa and also by nematodes
and trematodes. Insect enemies are responsible for the
destruction of enormous numbers of mosquitoes. The larvae
of Hydrophilidae and Dytiscidae devour large numbers of larvae,

Fig. 32. Anopheles maciilipennis J captured in Cambridge, shewing acarine
parasites attached to the body. (From a photograph taken by Professor
Nuttall.)

and one Dytiscus larva has been known to destroy 434 mos-
quito larvae in two days. Whirligig beetles (Gyrinidae) are
also great enemies of the larvae, and no Anopheles has a chance
in any water inhabited by them. Similarly the various species
of aquatic Hemiptera destroy the larvae and also emerging
imagoes, or females laying their eggs. Dragon-flies in the
adult stage feed on other flying insects, and in their immature
stages devour mosquito larvae, etc. Their voracious habits, in
all stages, are notorious, and they must destroy enormous num-
bers of Culicidae along with other Dipt era. Some of the most
formidable natural enemies of the mosquito larvae are to be

74 culicid^ [ch.

found amongst the family Culicidae itself. The predaceous
and cannibalistic larvae of Psorophora, Lutzia, Megarhinus, etc.,
readily attack larvae either of their own, or other species. The
larva of Lutzia is so effective that in Rio de Janeiro it has been
employed to destroy the larvae of the more dangerous Stegomyia
fasciata. The immature stages of many other aquatic Diptera
also prey on the Culicidae.

Various predaceous Diptera, especially the Empididae, capture
mosquitoes along with other insects ; a blood-sucking fly, Sitnu-
lium, has been observed to kill mosquitoes by sucking the blood
out of them. A most curious case, however, is that of an
Anthomyid fly, Lispa sinensis, which has been seen to catch
and eat the larvae of mosquitoes in Hongkong. A Dolicho-
podid fly of Panama also attacks the larvae in a similar manner.

Mites have frequently been seen attached to the bodies of
both the adult and immature stages of mosquitoes. In some
regions, e.g. Uganda, as many as 50 per cent, of the mosquitoes
may be attacked. The presence of these mites, however, does
not seem to affect seriously the health of the host, though no
doubt it may be weakened. Spiders undoubtedly destroy
large numbers of mosquitoes, and are amongst the most efficient
natural enemies of the adult insects. The jumping spiders
of the genus Salticus are very common in houses in the tropics,
and are a most valuable aid in the destruction of both mos-
quitoes and flies.

Newts and the aquatic larvae of salamanders readily devour
mosquito larvae, and the latter are rarely found in pools
inhabited by these batrachians.

In India the common gecko lizard destroys large numbers
of Culicidae in houses, and therefore should be encouraged
as it is quite harmless.

Birds and bats, however, must be regarded as the most
important vertebrate enemies of the adult mosquitoes. The
smaller insectivorous birds, night-hawks, swifts and swallows,
all devour enormous numbers of Diptera. More than 600
insects, mostly mosquitoes, have been counted from the stomach
of an American swift (ChcBtura pelagica). In addition aquatic
and shore-birds eat considerable numbers of the larvae. At

VII] CLASSIFICATION 75

least nine species of shore-birds, mostly phaloropes and sand-
pipers, are known to eat mosquitoes, and any such birds should
be strictly protected.

REFERENCES.

Howard, L. O. (1902). Mosquitoes. New York: McClure, Phillips

and Co.
Howard, L. O., Dyar, H. G. and Knab, F. (191 2). The Mosquitoes of

North and Central America and the West Indies. Carnegie Institute

of Washington. Publication No. 159. (Contains complete re-
ferences to literature on the subject.)
Howlett, F. M. (1910). The Influence of Temperature upon the Biting

of Mosquitoes. Parasitology, vol. in. pp. 479-484.
Imms, A. D. (1907-8). On the Larval and Pupal Stages of Anopheles

maculipennis , Meigen. Journ. of Hygiene, vol. vu. pp. 291-318,

and Parasitology, vol. 1. pp. 103-133.
Nicholls, Lucius (191 2). Some observations on the Bionomics and

Breeding-places of Anopheles in Saint Lucia, West Indies. Bull.

Entomol. Research, vol. 111. pp. 251-268.
Nuttall, G. H. F. and Shipley, A. E. (1901-1903). The Structure and

Biology of Anopheles. Journ. of Hygiene, vol. 1. pp. 45-77, 269-276

and 451-484 ; vol. 11. pp. 58-84 ; vol. 111. pp. 166-215.
Schaudinn (1904). Generations- und Wirtswechsel bei Trypanosomen

und Spirochaeten. Arb. a. d. Kaiserlichen Gesundheitsamte , vol. xx.

pp. 387-438.
Shipley, A. E. and Wilson, E. (1902). On a possible stridulating organ

in the Mosquito {Anopheles maculipennis Meigen). Trans. Roy.

Soc. Edin. vol. xl. pp. 367-372.
Theobald, F. V. (1901-10). A monograph of the CulicidcB of the World.

London : Brit. Mus. Vols. l-v.

CHAPTER VIII

culicid^e (mosquitoes) continued, classification

The most recent classification of the Culicidae is that given
by Edwards, and is as follows.

Family. CULICID.K.

Sub- family. Culicinae. (Ordinary mosquito with long proboscis.)

1. Tribe. Anophelinne.

2. Tribe. Mcgarhininae.

j6 CULICID^E [CH.

3. Tribe. Culicinae

r Culicinae ^1

= Metanotopsilse <, Aedinae J> of Theobald.

I Uranotaeninae J

4. Tribe. Sabethinae

r Trichoprosoponinae "^ . _
= MetanototrichaB ( DendromyinaP } of Theobald.

Sub-family. Chaoborin^;. (Midge-like mosquitoes without piercing

proboscis.)
= Corethra. Meigen.
= Sayomyia. Coquillet.

Sub-family. Dixin^e. (No piercing proboscis.)

Tribe i. Anophelin^e.

Female palps as long as the proboscis. Male palpi clubbed.

Scutellum simple and bar-shaped.

Larva without respiratory tube.

According to Theobald and others adopting his views the
Anophelinse consist of some 20 or more genera distinguished
by differences in scale structure. The general nature of this
subdivision and the more important genera are shewn in the
following scheme :

I. No true scales1 on either thorax or abdomen.

a. Upright head scales are narrow and rod-like Stethomyia. Theobald.

b. Upright head scales are of ordinary expanded type.

(a) Wing scales moderately broad, widest ia the middle.
Without prothoracic tuft .'. .. Anopheles Meigen.
With prothoracic tuft . . . . Patagiamyia. James.

(b) Wing scales narrow, widest towards free end

Myzomyia. Blanchard.

(c) Wing scales inflated . . . . . . Cycloleppteron. Theobald.

II. No true scales dorsally on either thorax or abdomen,
but there is a tuft of scales ventrally on the penultimate abdo-
minal segment. Myzorhynchus Blanchard-

1 A very useful distinction has been made by James between true and false
scales. True scales, besides being broader, have striations which can readily
be counted. False scales, which correspond roughly to the hair-like scales of
Theobald, shew only indistinct striations which are too indefinite to be counted.

VIII] TRIBE ANOPHELIN.ZE 77

III. Thorax covered with true scales.

a. No scales on abdomen.

Head scales of ordinary type . . . . Pyretophovus. Blanchard.

Head scales rather flattened . . . . Myzorhynchella. Theobald.

b. Scales on last few segments of abdomen only

Nyssorhynchus. Blanchard.

c. Many scales on abdomen but no lateral tufts

Neocellia. Theobald.

d. Lateral scale tufts as well as other scales on the abdomen.

Cellia. Theobald.

In addition there are genera represented by only one
or two species. Thus there is Feltinella Theobald, near
Patagiamyia, for F. pallidopalpi Theo. (basal lobes of male
genitalia jointed) ; and Lophoscelomyia Theo. for L. asiatica
Leicester, a peculiar species with scale tufts on the femora,
also related to Patagiamyia. Near Myzomyia come Pseudo-
myzomyia Theo., for P. rossii Giles1, and Neomyzomyia Theo.,
for N. elegans James. Kerteszia Theo., for K. boliviensis Theo.,
and Manguinhosia Cruz, for M. lutzi Cruz, are also genera
without scales on the thorax, but with scales on the last segments
of the abdomen. Both are of new world distribution. Near
Neocellia, but with a complete row of ventral scale tufts, is
Christophersia James, for Ch. kochii Donitz, and near Nyssorhyn-
chus, but with outstanding scales on the antenna, is Calvertina
Ludlow, for C. lineata Ludlow. Very peculiar genera are
Christy a Theo., for C. implexa Theo., an immense Anopheles
with long lateral tufts of hair-like scales on the abdomen,
Chagasia Cruz, for C. fajardoi Cruz, a species with Culex-like
attitude, and Arribalzagia Theo., for A. maculipes Theo., and
two other species of elaborately ornamented and very large
Anophelines from Brazil. The genus Bironella Theo., for
B. gracilis Theo., a species known only from a single male
specimen, has very short forked cells. It is not quite certain,
however, that it is an Anopheline.

Edwards sinks all these genera excepting Bironella under
A nopheles Meigen, maintaining that the differences in scale

1 .1/. rossii (iiles is the type species of Myxomyia. Therefore the forma-
tion of a genus Pseudomyzomyia having M. rossii as the type species is not
allowable.

?S TRIBE ANOPHELINAE [CH.

structure are insufficient upon which to found genera. In this
case the Anophelinae are considered as represented by a single
genus (Anopheles Meigen, type species A. maculipennis Meigen)
containing some hundred or more species.

These conflicting views regarding nomenclature make it
very difficult at present to treat of the systematic arrangement
of this sub-family. The most that can be done is to give some
classified tabulation of the species based on their more con-
spicuous characters, and to indicate as far as possible groups
of species corresponding to a particular scale structure and
hitherto given generic rank. In this respect use has been made
of the general scheme of the natural affinities of the Anophe-
linae given by Christophers. In this scheme the Anophelinae
are subdivided into three main natural divisions, the relation
of these divisions to the genera already mentioned being as
follows :

A. Protoanopheles.
Stethomyia.

Anopheles, Patagiamyia and Lophoscelomyia.

Myzorhynchus, Cycloleppteron, Arribalzagia and Notonotricha (Coquillet).

B. Deuteroanopheles.
Myzomyia and Pyretophorus.
Pseudomyzomyia.
Xyssorhynchits, Neocellia and Cellia.

C. Xeoanopheles.
Xeomyzomyia, etc.

In the following table the known species of Anophelinae
are arranged in the form of a synoptic table. In this table
12 groups more or less readily differentiated both by general
characters and by scale structure are given. The species which
compose these groups often so closely resemble one another that
they differ only in a few minute details, a generalized descrip-
tion serving for the chief characters of all the species in the
group. The chief characters of any species, therefore, to a
large extent can be gleaned from the table, but for a full
description of each species the present space is inadequate,
and systematic works on the Culicidae must be consulted.

A second table is given shewing all described species of
Anopheles, with their synonymy if necessary, and their relation
as far as is known to the transmission of malaria.

VIII] SPECIES OF AXOPHELIX.E 79

Dichotomous Table shewing Natural Grouping of Species
of Anophelince.

1. Costa has less than four main dark spots . . . . . . . . 2

Costa has at least four main dark spots . . . . . . . . 6

2. Costa without any pale interruption even at apex . . 3
Costa with at least one pale interruption . . . . . . . . 4

3. Female palps with second segment disproportionately long

Group 1. (Stetkomyia.)
Female palps of ordinary Anophelme type

Group 2. {Anopheles.)

4. No true scales on mesothorax . . . . . . . . . . 5

Mesothorax with true scales . . Group 5. (Arribalzagia.)

5. Wing veins without mixed dark and light scales

Group 3. {Patagiamyia.)
Wing veins with mixed dark and light scales

Group 4. (MyzorhyncJnis.)

6. Not more than three dark spots on sixth vein . . . . . . 7

More than three dark spots on sixth vein Group 12. (Neomyzotnyia.)

7. Terminal segment of female palps considerably less than half length of

penultimate segment
Terminal segment at least half length penultimate . . . . 9

8. Mesothorax without true scales . . Group 6. (Myzomyia.)1
Mesothorax with true scales . . Group 7. (Pyretophorus.)1

9 Mesothorax not clothed with true scales Group 8. {Pseudomyzomyia.)1
Mesothorax covered with true scales . . . . . . . 10

10. Abdomen without lateral tufts .. .. .. .. .. 11

Abdomen with lateral tufts .. .. Group 11. (Cellia.)

n. Palps very shaggy as in Myzorhynchus Group 10. (Myzorhynchella.)
Palps not so shaggy . . . . . . Group u. (Xyssorhynchus.)

Table shewing Detailed Tabulation of Species of
AnophelincE.

A. Protoanopheles.

Number of main dark costal spots is less than four.
Junctions of cross-veins with longitudinal veins and bifurca-
tions of second and fourth veins dark scaled.

A'. Costa devoid of any pale areas even at apex of wing.

Group 1. Female palps with the second segment disproportionate I
segments three and four both being short.
(Stethowyia. Theobald. Type species 5. nimba. Theo.)
General characters of groups.

Appearance. Attitude Culex-like, legs thin and slendci . Palps
long and thin.

1 Vide, however, remarks on the type species of these genera and nomen-
clature.

8o

SPECIES OF ANOPHELIN.E

[CH.

Markings. Wings. Unspotted.
Palps. Unbanded.
Legs. Entirely unornamented.
Scale structure. Head scales narrow and linear, not expanded as
in all other Anopheles. No scales on pro-
thorax, mesothorax or abdomen.
Species.

A. nimba. Theobald.
A. aitkeni. James.
A. culiciformis. James and Liston.
A. corethroides. Theobald.
Synonymy.

A. pallida. Ludlow = „-J. aitkeni (James).
A. fragilis. Theobald — A. aitkeni (James).
A. trcacheri. Leicester = yL aitkeni (James).

Differentiation of species.
Thorax adorned.

Silvery median and lateral lines . . A . nimba.

No silvery lines . . . . . . A . corethroides.

Thorax not adorned.

Anterior forked cell very long . . . . A . aitkeni.

Anterior forked cell not unusually long A. culiciformis.

Group 2. Second segment of female palps not disproportionately long,
terminal segment not less than half length of penultimate
(orthodactylous).
( Anopheles Meigen, s^wsw. James. Type species A. maculipennis. Meigen.)

Fig. 33. Anopheles bifurcatus. (Group 2.)

General characters of group.

Appearance. Attitude Anopheles-like. Mostly large species with
thin palps and slender limbs.

VIIl]

SPECIES OF ANOPHELIN^E

8l

Markings. Wings devoid of any pale spots (except A. crucians and
A. eiseni).
Palps. Unhanded (except in A . smithii and faint bands

in A. immaculatus).
Legs. Unornamented except for pale areas at tibio-
femoral and tibio-tarsal joints. Tarsi unbanded.
Scale structure. Head scales expanded. No prothoracic tuft. No
scales on mesothorax or abdomen. Wing scales
moderately broad.

Species.
A.
A.
A.
A.
A.
A,
A.
A.

Coquillet.

maculipennis. Meigen.

bifurcatus. Linnaeus.

plumbeus. Haliday.

algeriensis. Theobald.

barianensis. James and Liston.

barberi. Coquillet*.

immaculatus. James.

smithii. Theobald.
A. eiseni. Coquillet.
A. crucians. Wiedemann.

* Ccelodiazesis barberi.
Synonymy.

C. bifurcatus. Meigen

quadrimaculatus . Say

annulimanus. Van der Wulp

claviger. Fabricius \ —A. maculipennis. Meigen.

grisescens. Stephens J or A. bifurcatus. Linn.

atropos. Dyar and Knab "»
A . occidentalis. Dyar and Knab J
C. trifurcatus. Fabricius "|

A. villosus. Desvoidy y = A. bifurcatus. Linnaeus.

A. walkeri. Theobald J
A. nigripes. Staeger = yL plumbeus. Haliday.
A. ferruginosus. Wied. = y4. crucians. Wied (?).

= A. maculipennis. Meigen.

? A. maculipennis. Meigen.

Differentiation of species.
Wings without pale spots on any of the veins
Dark spots at cross-veins and bifurcations
Wings uniformly dark without any spots,
(i) Palps unbanded.

Petiole of first forked cell more than £ length of cell

Thorax with pale but not white streak anteriorly.

Abdomen with yellow hairs

Abdomen with brown hairs

Abdomen with black and white hairs

Thorax with white streak

Petiole of first forked cell £ length of cell

(ii) Palps banded.

Banding indistinct, light mosquito ..
Banding narrow but distinct, dark mosquito

A . maculipennis.

.. A.
.. A.

. . A.

bifurcatus.
algeriensis.
barianensis.

.. A.
. . A.

nigripes.
barl H I

A.

ulatus.

A.

smithii.

H. B. F.

82 SPECIES OF ANOPHELIN.E

B. Wings with some pale areas.

Hind tibiae with broad, white, apical band
Hind tibiae without broad band

[CH.

A. eiseni.
A. crucians.

" . Costa shews at least one pale interruption.
(a) No true scales on mesothorax.

Group 3. Wing veins do not shew any conspicuous admixture of dark
and light scales.

(Patagiamyia. James. Type species A. gigas. Giles.)

Fig. 34. Anopheles {Patagiamyia) gigas. (Group 3.)

General characters of group.

Appearance. Attitude Anopheles-like. Usually rather large Ano-
phelines of brownish colour.

Markings. Wings spotted. Dark costal spots may be distinct and
well separated by pale areas but there are not four
main dark spots.
Palps. Unbanded or with four narrow bands including

pale apex.
Legs. Knee spots present. Tarsi unbanded or banded,
but not conspicuously. Except for a white band on
femur present in some species no other ornamentation
of legs.

Scale structure. Head scales expanded. No prothoracic tuft. No
true scales on mesothorax. Abdomen may or
may not have scales on last few segments of
abdomen, but some scales are usually present,
especially in male.

VIII] SPECIES OF ANOPHELIN.E 83

Species.

A. gigas. Giles.

A. simlensis. James and Liston.
A . punctipennis. Say.
A. formosus. Ludlow.
*A. pallidopalpi. Theobald.
**A. lindesayi. Giles.
**A. lindesayi var. maculata. Theobald.
**A. asiatica. Leicester.
**A. wellingtonianus . Alcock.
A. atratipes. Skuse.
A. franciscanus. McCracken.
A. perplexans. Ludlow.
A. pseudopunctipennis. Theobald.
*Feltinella. Theobald. Type species F. pallidopalpi.
**Lophoscelomyia. Theobald. Type species L. asiatica. Leicester.

Synonymy.

A. (Culex) hyemalis. Filch = ^4. punctipennis. Say.
Lophomyia. Giles = Lophoscelomyia. Theobald.

Differentiation of species.

Costa with large prominent dark spots.

Palps not banded

.. A.

gigas.

Palps banded.

Tarsi banded.

A.

simlensis

A.

formosus.

Tarsi unbanded.

Fringe spots present at all vein endings

A. pseudopunctipennis.
A . franciscanus.
Fringe spots absent

A. punctipennis.
A. pallidopalpi.
One fringe spot present . . . . A . perplexans.

Costa with narrow interruptions only.
Femur with broad white band.
Ruff of scales on femur.
White band apical
White band not apical
No ruff of projecting scales
Femur without pale band

A. asiatica.

A. wellingtonianus.

A. lindesayi.

A. atratipes.

Group 4. Wing scales with conspicuous admixture of dark and light
scales.
(Myzorhynchus. Blanchard. Type species M. sinensis. Wied.)
General characters of group.

Appearance. Large species, black or nearly so. Anopheles-attitude
strongly developed. Palps markedly sha^ .

(>— 2

§4

SPECIES OF ANOPHELIN^E

[CH.

Markings. Wings dark with minute pale interruptions on costa
usually only two in number, one at apex and one at
junction of subcosta with costa. Sixth vein has two
conspicuous dark spots, the scales forming which
aggregated. Light spots on upper surface of wing
not in all cases reproduced below.
Palps. Unbanded or with four narrow pale bands

including pale apex.
Legs. Knee spots, banded tarsus, and in some cases
further ornamentation.
Scale structure. Head scales expanded. Prothoracic tuft present.
No scales on mesothorax. May or may not be
scales on terminal portion of abdomen. A tuft
of scales usually present on ventral surface of
penultimate abdominal segment. Wing scales
very broad.

Fig. 35. Anopheles {Myzorhynchus) barbirostris. (Group 4.)

Species.

A. barbirostris. Van der Wulp.
A. pseudobarbirostris. Ludlow.
A . bancroftii. Giles.
A. umbrosus. Theobald.
A. albotcsniaius. Theobald.
A. strachani. Theobald.
A. sinensis. Wiedemann.
A. sinensis var. indiensis. Theobald.
A. psendopictus. Grassi.
A. paludis. Theobald.
CA. paludis var. similis. Theobald.
\A. mauritianus. Grandpre.
*A. 'grabhamii. Theobald.
* Cycloleppteron. Theobald. Type species C. grabhamii. Theobald.

VIII

SPECIES OF ANOPHELINiE

85

=A. sinensis. Wied.

}-

. >=A. pseudopictus. Grassi.

Synonymy.

A. vanus. Walker

A. annularis. Van der Wulp

A. jesoensis. Tsuzuki

A. plumiger. Donitz

A. minutus. Theobald

A. uigerrimus. Giles \= A. sinensis var. indiensis.

A. nigerrimus . James and Liston J Theobald.

A. separatus. Leicester \ - . . TTT. ,

A . ,.. ■ , T ■ r = }A. sinensis. Wied.

A. peditfpniatus. Leicester J

A. brachypus. Donitz = (?) A. sinensis. Wied.

A. alb o annul atus. James and Liston = ^4. albotcsniatus. Theobald.

A. paludis var. similis. Theobald = ^4. mauritianus. Grandpre.

A. mauritianus. Grandpre = (?) A. paludis. Theobald.

A . coustani. Laveran

A. ziemani. Van Griinberg } =A. mauritianus. Grandpre.

A. tenebrosus. Donitz

A. pictus. Loew

A. pictus. Ficalbi

Differentiation of species

A. Wing scales not inflated (Myzorhynchus).
Tip of hind tarsus not white.
Palpi not banded.
Hind tarsal points narrowly banded.

No fringe spots

One fringe spot

Two fringe spots.
Legs not mottled
Legs mottled

Several fringe spots
Hind tarsi broadly banded
Palpi banded.

Wing fringe with one pale spot

Wing fringe unspotted

B. Wing scales inflated (Cycloleppieron) . .

(b) Mesonotam with true scales.

Group 5. Costa with broad pale interruptions.

{Arribalzagia. Theobald. Type species A. maculipes. Theobald.)
General characters of group.

Appearance. Large highly ornamented species.
Markings. Wings prominently spotted, but with three main dark
spots only. Small accessory spots present in addition
to those at base of costa. Pale spots on upper surface
of wing in many cases not represented beneath
Sixth vein with more than two spots.
Palps. Four pale bands.
Legs. Speckled and ornamented.

.. A.

strachim.

.. A.

umbrosus.

.. A.

barbirostris.

.. A.

pseudobarbirostris

.. A.

bancroftii.

.. A.

alb otceni atus.

.. A.

sinensis.

.. A.

pseudopictus.

.. A.

grabhamii.

86

SPECIES OF ANOPHELIN.E

[CH.

Scale structure. Heavily scaled species. Head scales expanded.
Prothorax with tufts. Mesothorax with broad
scales. Abdomen with scales and lateral tufts.
Species.

A. maculipes. Theobald.

A. pseudomaculipes. Chagas.

A. malefactor. Dyar and Knab.
*A. mediopunctatus. Theobald.
*A. intermedium. Chagas.

* Notonotricka. Coquillet. Type species Ar mediopunctatus.

B. Deuteroanopheles.

Number of main dark costal spots, four. Not more than
three dark spots on sixth vein. Junctions of cross-veins with
longitudinals and bifurcations of second and fourth veins the
seat of light interruptions (except Myzorhynchella) .

B'. Female palps with terminal segment considerably less than
half penultimate. Tarsi not broadly banded. Tips of hind-
legs not white.

Group 6. Mesothorax without true scales.
{Myzomyia. Blanchard1.)

Fig. 36. Anopheles (Myzomyia) listoni. (Group 6.)

1 The type species of Myzomyia is M. rossii Giles, but this species does not
conform to the characters of Myzomyia as now usually understood. Group 6,
therefore, though it contains most of the well-known Myzomyice [A . funesta,
A. listoni, etc.) cannot correctly be described as Myzomyia, which name ought
to be retained for whatever group M. rossii represents. Similarly, the name
Pseudomyzomyia proposed by Theobald for M. rossii is incorrect.

VIIl] SPECIES OF ANOPHELIN.E 87

General characters of group.

Markings. Small brownish species. Wings with four main dark
costal spots. Middle spot not completely broken
{i.e. shewing double interruption on first longitudinal
as in A. maculatus. Theobald). Sixth vein with two
or fewer dark spots (except A. albirostris Theobald,
which has three). Fringe spots usually absent at
sixth vein and often deficient at other vein endings.
Palps. Three pale bands, the apical one including the

whole of the apical segment1.
Legs. Knee spots and sometimes narrow and incon-
spicuous tarsal banding, but no other ornamentation.
Scale structure. Head scales expanded. No prothoracic scale tufts.
Mesothorax without true scales. Abdomen without
scales. Wing scales narrow.
Species.

A. funesta. Giles.

A. funesta var. subumbrosa. Theobald.

A. funesta var. umbrosa. Theobald.

A. listoni. Liston.

A. rhodesiensis. Theobald.

A. culicifacies . Giles.

A . nili. Theobald.

A. turkhudi. Liston.

A. hispaniola. Theobald.

A. albirostris. Theobald.

A. hebes. Donitz.

A. flavicosta. Edwards.

A. impunctus. Donitz.

A. longipalpis. Theobald.

A. pyretophoroides. Theobald.

A. agripi. Patton.

A. d'thali. Patton.

A. jehafi. Patton.
Synonymy .

A. listoni. Giles ^1

A. turkhudi. Giles r=A. culicifacies. Giles.

A. indica. Theobald J

A. leptomeres. Theobald = (?) A . culicifacies. Giles.

A. kumassii. Chalmers = A. funesta. Giles.

A. umbrosa. Edwards (nom. pveoc.) = A. funesta var. umbrosa,
Theobald.

A. ihtviatilis. Stephens and Christophers. MSS. \= A. listoni.

A . Christopher si. Theobald J Liston.

A. christophersi var. alboapicalis. Theo. = --L albirostris. Theo.

A. albirostris. Theo. = (?) A. aconita. Donitz.

. .' . formosaensis.' Tsuzuki = (?) A. aconita var. cohcesa. Donitz.

A. impunctata. D6nitz-Blanchard = .L impunctus. Donitz.

A. pictus. Macdonald = A . hispaniola. Theobald.

A. cruzii. Dyar and Knab = J. lutzi. Theobald.

1 In A. turkhudi and A. hispaniola the tip is dark.

88

SPECIES OF ANOPHELIN.E

[CH.

Differentiation of species.
Proboscis unbanded.
Apex of palps pale.

Fringe spots present at all veins except sixth.
Tarsal banding distinct though not conspicuous.
Third longitudinal light
Third longitudinal dark

Tarsal banding absent or very narrow and indistinct

A.

Fringe spots absent or present only at two or three veins
Palps with three pale bands.

No fringe spots . . . . . . . . A .

Two fringe spots . . . . . . . . A .

Palps with pale apex only . . . . . . A .

Apex of palps dark.

Black apex narrow . . . . . . . . A .

Black apex broader . . . . . . . . . . A.

Proboscis with apical half white . . . . . . A .

funesta.
funesta var.
umbrosa.

listoni.

Group 7. Mesothorax with blue scales.
(Pyretophorus1. Blanchard.)

rhodesiensis.
culici fades,
nili.

turkhudi.
hispaniola.
albirostris.
aconita.

Fig. 37. Anopheles (Pyretophorus) neavei. (Group 7.)

General characters of group.

Appearance. Mostly rather light brown species with notably long

and thin palps.
Markings. Wings with four dark spots usually not completely
broken. Wing fringe spots most frequently absent
from sixth vein.
Palps, With three bands or four. Sometimes with dark

apex.
Legs. Free from speckling or marked banding of tarsus.

1 Though most of the members of the genus Pyretophorus are included
here, this generic name cannot be employed, as P. costalis Loew, the type
species, clearly belongs to a separate group.

VIII] SPECIES OF ANOPHELINiE 89

Scale structure. Head scales expanded. No prothoracic tuft. Meso
thorax scaled. Abdomen completely devoid of
scales.
Species.

A. superpictus. Grassi.

A. nursei. Theobald.

A. nigrifasciatus. Theobald.

A. cleopatrce. Willcocks. MSS.

A. cardamitisi. Newstead and Carter.

A. distinctus. Newstead and Carter.

A . distinctus var. melanocosta. Newstead and Carter.

A . palestinensis. Theobald.

A. cinereus. Theobald.

A . sergentii. Theobald.

A. jeyporensis. James.

A. myzomy fades. Theobald.

A. chaudoyei. Theobald.

A. transvaalensis. Carter.

A . minimus. Theobald.

A . pitchjordi. Power.

A. arabiensis. Patton.

A. austenii. Theobald.

Synonymy .

A. nursei. Theobald = (?) A. nigrifasciatus. Theobald variety
A. chaudoyei. Billet = A. chaudoyei. Theobald.

Differentiation of species.

Palps with one broad pale band.
Apex of palps light.

Third costal spot not completely broken.

Sixth vein with two dark spots .. .. A. sergentii.

Sixth vein with three dark spots.

Costal spots more or less confluent .. A. distinctus

Costal spots distinct.
Tarsi not banded.

(A. nursei.
A. cleopatYcP.
A. palestinensis.
A. minimus.
Fore and hind tarsi banded . . . . A . cinereus.

.,,,.,,, (A. cardamatisi.

All tarsi banded . . . . . . . .

(A. superpictus.

Apex of palps dark.

Tarsi not banded .. .. .. .. ..A. nigrifi

Tarsi not banded.

Three dark lines on mesonotum .. .. A . myxomyfacies.

Two dark lines on mesonotum .. .. A. chami

Palps with two broad pale bands A. austenii.

90 SPECIES OF ANOPHELIN.E [CH.

B". Apical segment of female palps at least half length of
penultimate. Tarsi broadly banded.

(a) Mesothorax not completely clothed with true scales.

Group 8.

{Psendomyzomyia. Theobald1. Myzomyia. Blanchard. Type species,
Ps. rossii. Giles.)
General characters of group.

Appearance. Light fawn to moderately dark species. Palps rather

shaggy.

Markings. Wings with light areas much developed. Costa with

four main dark spots. Third spot completely broken.

Sixth vein with two dark spots. Fringe spots at all veins.

Palps. Three light bands, the apical one including

whole of last segment.
Legs. Tarsi banded. May be speckled. Tips of hind
tarsi not white.
Scale structure. Head scales expanded. No pro thoracic tufts.
Mesothorax mostly with narrow hair-like scales.
Abdomen with some scales on last segment,
especially in male.
Species.

A. rossii. Giles.
A. indefinata. Ludlow.
A. ludlowi. Theobald.
A. mangy ana. Banks.
Synonymy.

A. mangy ana. Banks = (?)^. ludlowi. Theobald.

A. vagus. D6nitz = yL rossii. Giles.

A. rossii var. indefinata. Ludlow = ^4. indefinata. Ludlow.

Differentiation of Species.

Legs not speckled.

Apical palpal band very broad . . . . A . indefinata.

Apical band not so broad . . . . A . rossii.

Legs speckled.

Large species . . . . . . A . ludlowi.

Smaller species . . . . . . . . A . mangyana.

(b) Mesothorax completely clothed with true scales.
Abdomen without lateral tufts.
Group g. Palps moderately shaggy only. Bifurcations of second and
fourth veins both sites of pale interruptions. Head scales as
in majority of Anophelines.
(Nyssorhynchus. Blanchard2.)

1 Vide footnote to Group 6, on page 86.

2 Here again there is confusion in the nomenclature. The type species of
haver ania Theobald ( = Nyssorhynchus Blanchard) is A. (Cellia) argyrotarsis.
The well-known group of so-called Nyssorhynchus, therefore, is incorrectly so
called.

VIII] SPECIES OF AXOPHELIX.E 91

General characters of group.

Appearance. Highly ornamented species. Tips of hind tarsi

always white.
Markings. Wings clearly spotted. Fringe spots at all vein endings.
Sixth vein with three spots.
Palps. With three bands.
Legs. With white hind tarsi often speckled.
Scale structure. Head scales expanded. Mesothorax covered^witb
scales. Abdomen with some scales.

-v .---jc-:-^

Fig. 3S. Anopheles {Xyssorhynchus) maculatus. (Group 9.]

Species.

A. fuliginosus. Giles.

A. nivipes. Theobald.

A. freer a. Banks.

A. philippinensis. Ludlow.

A. fowleri. Christophers.

A. jamesii. Theobald.

A . pretoriensis. Theobald.

A. maculipalpis. Giles.

A . maculatus. Theobald.

A . theobaldi. Giles.
*A. wiUmori. James.
*A. stephensi. Theobald.

A . cos talis. Loew.

A. costalis var. melas. Theobald.

A. pseudocosialis. Theobald.

A. merits. Donitz.

A . marshallii. Theobald.
|.-L kochii. Donitz.

A. kamvari. James and Liston.

A . ardensis. Theobald.

A. aurcosquamiger. Theobald.
* Xcn-ellia. Theobald. Type species A . willmori. Jam<
t Christophersia. James. Type species A . kochii. Don

92

SPECIES OF ANOPHELIN^

[CH.

ff^. lineata. Ludlow.
A. flava. Ludlow.
A. waponi. Edwards.
A. tibani. Patton.
ff Calvertina. Ludlow. Type species A. lineata. Ludlow.

Synonymy.

A. gambit Giles \=A% costdUs. Loew.

A. gracilis. Donitz J

A jamesii. Listen \=A . fuliginosus. Giles.

A. leucopus. Donitz J

A. dudgeoni. Theobald = ^4. willmori. James.

A. indica. Theobald = A. willmori var. James.

A . pseudowillmori. Theobald. ^

A. ivillmori. Leicester > =A. maculatus. Theobald.

A. willmori. Watson J

A. maculipalpis. James and Liston \=A. maculipalpis var.

A. indiensis. Theobald J indiensis. Theo.

A. nigrans. Staunton = ^. karwari. James.

A. halli. James = yL kochii. Donitz.

A. intermedia. Rothwell "\ , , . ,

_, , , , >=A. stebhensi. Theobald.
A. metaboles. Theobald

\=A. stepht

Differentiation of species.

A. Tips of hind tarsi white.

Palps with not more than one broad band.
(a) Legs not speckled.

White band at junction of first and second tarsal segment.

r A . fuliginosus .

Very closely related species .. .. ' ' \ a' f

L A. philippinensis.
No white band at junction of first and second tarsal segments

A. fowleri.
{b) Legs speckled.

Palpi with speckling in addition to bands .. A. maculipalpis.
Palps without speckling.

Three tarsal segments pure white . . . . A . jamesii.

Two tarsal segments pure white . . . . A . pretoriensis.

Palps with two broad bands.

Two tarsal segments altogether white . . . . A . theobaldi.

One tarsal segment only altogether white.

Scales on last few segments of abdomen .. A. maculatus.
Scales on all segments . . . . . . A . willmori.

Palp with more than two broad bands.

Palps with five white bands .. .. .. A. kcchii.

Palps with four white bands .. .. . . A. karwari.

VIII]

SPECIES OF ANOPHELIN^E

93

B. Tips of hind tarsi not white.
Apical band of palps only broad.
First tarsus not spotted.
Fringe spots narrow.
Femur speckled
Femur not speckled
Fringe spots broad
First tarsus spotted
Two palpal bands broad.
A few scales on abdomen
Many scales on abdomen . .

Group 10.

A. coslalis.

A. pseudocostalis.

A. merus.

A. ardensis.

A. marshallii.
A. stephensi.

Palps markedly shaggy. Bifurcations of second and fourth
veins (one or both) dark scaled. Head scales flattened.
(Myzorhynchella. Theobald. Type species M. nigra. Theobald.)
General characters of group.

Appearance. Black species. Palps shaggy.

Markings. Costa with four main dark spots, the light interruptions
in some cases bridged by dark on first longitudinal.
Palps. Unbanded or with four bands.
Legs. May be ornamented.
Scale structure. Head scales flattish.
Mesothorax scaled.

Prothoracic tuft present.
Abdomen free from scales.

Species.

A. nigra.
A. lutzi1.
A. parva,

Theobald.

Cruz.

Chagas.
A. nigritarsis. Chagas.
A. tibiomaculata. Neiva.
A. gilesa. Neiva.

(c) Abdomen with lateral scale tufts.
Group ii.

(Cellia. Theobald. Type species A. pharoensis. Theobald.)

&-V ^:- £"- "-:_- "-' **- ---— ^-^ m

' r g r * > 'jtf-H?

Fig. 39. Anopheles (Cellia) pulcherrimus. (Group 11.)

1 There arc three species i^( A . lutzi, of which A.
was first so named. A. {Myxorkynckella) In!:: Cruz, then
renaming if generic distinctions between the Anophelina are

94 SPECIES OF ANOPHELIN^E

General characters of group.

Markings. Costa with four main dark spots.

[CH.

Fringe spots at all

Palps. With four light bands.
Legs. Ornamented.
Scale structure. Head scales expanded. Prothorax may have a few
scales or a tuft. Mesothorax covered with scales.
Abdomen with scales and lateral scale tufts.
Species.

A.
A.
A.
A,
A.

A. argyrotarsis. Desvoidy.
A. albimanus. Wied.
A. jacobi. Hill and Haydon.
A . cincta. Newstead and Carter
A. pulcherrima. Theobald.
A . pharoensis. Theobald.

Ventrillon.

pharoensis var. alba.

bigotii. Theobald.

gorgasi. Dyar and Knab.

squamosa. Theobald.

squamosa var. arnoldi. Newstead

and Carter.

Synonymy .
A. albipes. Theobald ^

A cubensis. Agramonte ' alUmanus. Wied.

A. tarsi-maculatus. Goeldi f
A. argyrotarsis. Theobald J

A. albitarsis. Arribalzaga = A . argyrotarsis. Desvoidy.
A. albofimbriata. Gi\es = A. pharoensis. Theobald.
A. bozasi. Neveu-Lemaire = (?) A. pharoensis. Theobald.
A. braziliensis. Chagas = ( ? ) ^4 . argyrotarsis. Desvoidy.
A. punctipennis. Bigot. MSS.=y4. bigotii. Theobald.

A. squamosa arnoldi. Stephens and Christophers = A . squamosa var. arnoldi.
Stephens and Christophers.

Differentiation of species.
Tips of all legs pale.

Metatarsus with distinct bands

Metatarsus with flecks of white only
Tips of hind-legs only pale.

(a) Three segments of hind tarsus altogether white.
Apex of abdomen dark

Apex of abdomen whitish grey

(b) Three segments of hind tarsus white except for
small dark band on last segment

(c) One segment only of hind tarsus white.
Femora and tibiae mottled

Femora and tibia? not mottled
Tips of hind-legs not pale

A. cincta.
A . jacobi.

A. argyrotarsis,
A. braziliensis.

A. albimanus.

A. pharoensis.
A. bigotii.
A. squamosa.

C. Neoanopheles.

Costa with four main dark spots. Sixth vein with more
than three dark spots. Junctions of cross-veins with longi-
tudinal veins and bifurcations of second and fourth veins the
seat of pale interruptions.

VIII] SPECIES OF ANOPHELIN.E 95

Group 12.

(Neomyzomyia. Theobald. Type species A . elegans. James.)
General characters of group.

Markings. Wings with a large number of spots on veins. Third
longitudinal with several dark and light areas. Sixth
vein may have five or six dark spots.
Palps. With well-marked white bands.
Legs. Speckled and ornamented.
Scale structure. Prothorax usually with scale tuft.

Species.

A. elegans1. James. A. punctulata. Donitz.

A. annulipes. Walker. A. tessellatus. Theobald.

A. masteri. Skuse. A. natalensis. Hill and Haydon.

A. deceptor. Donitz. A. watsoni. Leicester.

Synonymy .

A. ceylonica. Newstead and Carter = (?) A. tessellatus. Theobald.

A. leucosphyrus. Donitz = (?) ^4 . elegans. James.

A. muscivus. Skuse = vL annulipes. Walker.

A. ocellatus. Theobald = yL punctatus. Donitz.

A. punctulatus. Theobald — A. tessellatus. Theobald.

A. punctulata. James = /L tessellatus. Theobald.

A. thorntonii. Ludlow = (?)yL tessellatus. Theobald.

Peculiar Anophelines not placed in Table.

A. rajardoi. Lutz (Chagasia, Cruz).

A. boliviensis. Theobald (Kerteszia, Theobald).

A. lutzi. Cruz (Manguinhosia, Cruz).

A. gracilis. Theobald (Bironella, Theobald).

A. implexa. Theobald (Christya, Theobald).

A. lineata. Ludlow (Calvertina, Ludlow).

A. brunnipes. (? Nyssorhynchus.) Theobald.

A. christyi. (? Nyssorhynchus, Neocellia.) Newstead and Carter.

A. lutzi. (? Myzomyia.) Theobald.

A. wellcomei. (? Anopheles.) Theobald.

A. pseudosquamosa. (? Cellia.) Newstead and Carter.

Insufficiently described or doubtful Species.

A. annulipalpis. Arrib. A. maculicosta. Becker.

A . annulipes. Arrib. A . martini. Laveran.

A. antennatus. Becker. A. multicolor. Camboulin.

A. cohcesus. Dounc -. A. pursati. Laveran.

A. error. Theobald = (no species). A. stigmaticus. Skuse.

A. farauti. Laveran. A. subpictus. Grassi.

A. formosaensis II. Tsuzuki'-'. A. vincenti. Laveran.
A . neiriti. Yentrillon.

1 Neomyzomyia Theobald.

- According to Kinoshita, A. cohcesus and A . formosaensts = A . listoui.

Table II. The known species of Anophelines, with their

their habitat and connection

Present group tabulation

Species and Synonyms

and generic synonymy

Distribution

I

A . aconita Donitz [3]

6. {Myzomyia)

. . Malay

2

A. aconita var. cohcesa Donitz [4] . .

b. (Myzomyia)

Malay

3-

A. aitkeni James [ia] (i9°3)

1. (Stethomyia)

India, Malay

4-

*A . albimana Wiedemann [1]

II. (Cellia)

S. & C. America

5-

A . albipes Theobald [2]

11. (Cellia)

W. Indies, S. America

6.

*A . albirostris Theobald [6] . .

6. (Myzomyia)

Malay, etc. . .

7-

A . albitarsis Arribalzaga [3]

—

8.

A. alboannulatus James & Liston [4]

4. (Myzorhynchus

Malay

9-

A. albofimbriata Giles (1904)

11. (Cellia)

. . Egypt

IO.

A . albotceniatus Leicester [2]

4. (Myzorhynchus

Malay

ii.

*A. algeriensis Theobald [6] (1903) • •

2. (Anopheles)

N. Africa

12.

A . annularis Van der Wulp [4]

4. (Myzorhynchus

Malay

*3-

A . annulimanus Van der Wulp [2] . .

2. (Anopheles)

—

14.

A . anmdipalpis Arrib. [1] . .

—

Argentine

15-

A. annulipes Walker [3]

12. (Nyssorhynchus

) Australia

16.

A. annulipes Arrib. [1]

Argentine

17-

A . antennatus Becker

—

—

18.

A. ardensis Theobald [11] . .

10. (Pyretophorus)

. Natal

19.

A . argyrotarsis Desvoidy [1]

11. (Cellia)

West Indies,
S. America, etc.

20.

A . avabiensis Patton

?IO.

Aden

21.

A. arnoldi Stephens & Christophers

11. (Cellia)

Transvaal

22.

A . adatica Leicester [1]

3. (Lophoscelomyia) Malay

23-

A . atratipes Skuse [1]

3. (Pyretophorus)

. Australia

24.

A . atropos Dyar & Knab [2]

2. (Anopheles)

N. America

25-

A. aureosquamiger Theobald [14] . .

10. (Nyssorhynchus

Transvaal

26.

A . aurirostris Watson

—

—

27.

A. austenii Theobald [10]

7. (Pyretophorus) .

Angola

28.

A . azriki Patton

6. (Myzomyia) (?)

Aden

29.

A . bancroftii Giles [4?)]

4. (Myzorhynchus)

Australia

3°-

A. barberi Coquillet [4] (1903)

2. (Anopheles)

—

31.

A . barbirostris Van der Wulp [4] . .

4. (Myzorhynchus)

India, Malay, China

32<

A. bavianensis James & Liston [4]

(1911)

2. (Anopheles)

India

33-

A . bellatov Dyar & Knab [2]

6. (Myzomyia) (?)

34-

*A. bifurcatus Linnaeus [2] (1758) . .

2. (Anopheles)

Europe

35-

A . bifurcatus Meigen [1]

2. (Anopheles)

Europe

36.

A . bigotii Theobald [2]

11. (Cellia)

Chili

37-

A . bisignata

6. (Myzomyia)

—

38.

A. boliviensis Theobald [12]

(Kerteszia)

S. America

39-

A . bozasi Neveu-Lemaire [3]

11. (Cellia)

N. Africa

40.

A. br achy pus Ddnitz

4. (Myzorhynchus)

Malay

'esent classification and generic synonymy, and notes on
ith malaria.

ransmission experi-
ments.
,'ycle observed of —
r. Malignant tertian,
.T. Simple tertian,
q. Quartan ;
z. to zygote stage,
nd S, to sporozoite
stage

Observations regarding
transmission in nature.

(z) Zygote and

(s) Sporozoite stage

observed

Epidemiological
evidence of
transmission

irling, s.t. Darling, (t)
;), m.t. (s)

lunton.M.T. Staunton, (z)

Ed.&Et.Sergent,(s)

moshita,

T.

Daniels, ( + )?
Christophers
( + )?

James, Staun-
ton, ( + )

Remarks

= A. albirostris Theobald (?).
= A. formosaensis II Tsuzuki.
Forest and jungle species biting by da}
like a Stegomyia.

Commonest carrier in Central and Tropi
cal S. America. 70 % of those fee
by Darling became infected.

= A. albimana Wied.

Important carrier in Malay.

= A. argyrotarsis.
= A. albotamiatus.
= A. pharoensis.

Important carrier in Algeria (littoral)

= A. sinensis Wied.

= A. maculipennis Wied.

Common Australian species.

rling, (f) Darling, m.t. (?), (z)
Patton, (s)

Important carrier in Aden Hinterland
= A. squamosa var. avnoldi Newsteac
and Carter.

phens & Doubtful (Christo-
lristophers phers)

T.

? A. albirostris Theobald.

Unlikely to Hill species. Sooo ft.

carry in nature
owing to distri-
bution

issi, (t) . . Grassi, (t)

Common English Anopheles.
— A. maculipennis Meigcn.

= A. sinensis (?).

H. B F.

Table II (continued). The known species of Anophelines,

notes on their habitat and

Species and Synonyms

41. A. braziliensis Chagas

42. A. brunnipes Theobald [17]

43. A. cardamitisi Newst. & Carter [1]

44. A. ceylonica Newst. & Carter [1] . .

45. A. chaadoyei Theobald [6]

46. A . chaadoyei Billet

47. A . christophersi Theobald [4]

48. A. christophersi var. alboapicales

Theobald [17]

49. A. christyi Newst. & Carter [2]

50. A . cincta Newst. & Carter [1]

51 . A . cinerens Theobald [2]

52. A. claviger Fabricius

53. A. cohcesus Doune

54. A. corethroides Theobald [14] (1907)

55. *A. costalis Loew [2] . .

Present group tabulation
and generic synonymy

62.

63.
64.
65.

66.
67.
68.
69.

70.

72.
73-
74-
75-
76.

77-
78.

79-
80.

A. costalis var. melas Theobald [6]

A . coustani Laveran [2]

A. crucians Wied. [2] (1828)

A . cruzii Dyar and Knab [1]

A . cubensis Agramonte

A . culicifacies Giles [3]

A. culiciformis James & Listen [4]

(1904)

A . deceptor Donitz [2]

A . distinctus Newst. & Carter [2] . .

A . distinctus var. melanocosta

Newst. & Carter [2]
A . d'thali Patton
A. dudgeoni Theobald [16]
A. eiseni Coquillet [3] (1902)
A. elegans James [la]

A . error Theobald [2]
A. fajardoi Lutz [1] . .
A . farauti Laveran [3]
A . ferruginosus Wied. [2] . .
A . flava Ludlow [5] . .
A. flavicosta Edwards [1]
A. fluviatilis Stephens & Christo-
phers MSS.
A . formosaensis I Tsuzuki

A. formosaensis II Tsuzuki

A . formosus Ludlow [6b]

A . fowleri Christophers [1] . .

{Cellia)

(Nyssorhynchus)
(Pyretophorus) . .

(Pyretophorus) . .

Distribution

S. America . .
Angola
Greece
Ceylon
Algeria, etc. . .

II.
II.

(Neocellia)
{Cellia)

Uganda
West Africa .

7-

{Pyretophorus) . .

Africa

1.

10.

(Stethomyia)
(Pyretophorus) . .

Australia
Africa

10.

(Pyretophorus) . .

Africa

2.

(Anopheles)

N. America .

6.

(Myzomyia)

India

12.

(Stethomyia)
( )

India
Malay

7-

(Pyretophorus) . .

Rhodesia

7-
6.

11.
2.

12.

(Pyretophorus) . .
(Myzomyia) (?)
(Neocellia)
(Anopheles)
( Neomyzomyia )

Rhodesia
Aden

C. America .

(Aldrichia)
(Chagasia)

Brazil

10.

(Nyssorhynchus)
?

Nigeria

6.

(Myzomyia)

Formosa

?

Formosa

3

(Patagiamyia) . .

Formosa

10.

(Nyssorhynchus
or Neocellia)

India

ith their present classification and generic synonymy, and
inflection with malaria.

ransmission experi-
ments,
^ycle observed of —
t. .Malignant tertian,
.t. Simple tertian,

Q. Quartan ;
f z, to zygote stage,
nd s, to sporozoite
stage

Observations regarding
transmission in nature.

(z) Zygote and

(s) Sporozoite stage

observed

Epidemiological
evidence of
transmission

Remarks

= A. argyrotarsis (?).

— =A. tessellatus Theobald.

Billet, ( + ) .. Common Anopheles in oases, breedii
in saline waters.

— =A. chaudoyei Theobald.

— =A. listoni Liston.

A. albirostris.

A. maculipennis Meigen.
A. bifuvcatus Linnaeus.

oss, Annett Ross, Stephens &
Austen Christophers, etc.

.T. Q. M.T.

:ephens &
hristophers,

>.T. Q. M.T.

(s)

Stephens & Christo-
phers, (s)

Active and common transmitter i
Tropical Africa.

= A. mauvitianus Grandpre.

= A. {Myzomyia) lutzi Theobald.
= A. albimana Wied.
Commonest Indian carrier.

Patton, ( + ?)

illmoyi James.

Forest species in Andamans (Christc
phers), ? any part in transmissior
= no species.

= A. crucians (?).

suzuki. m.t. Tsuzuki (s)

s)

suzuki, m.t. Tsuzuki (s)

s)

Tsuzuki, ( + )
Tsuzuki, ( + )

— A. listoni Liston.

= A. aconita var. cohcesa Donitz (?).

Table II (continued).

The known species of Anophelines,
notes on their habitat and

Species and Synonyms

8 1 . A. fragilis Theobald [8]

82. A. franciscanus McCracken [i'_

83. A. freer ce Banks [1] . .

84. *A. fuliginosus Giles [4a]

Present group tabulation
and generic synonymy

Distribution

? (Anopheles) . . California, etc.
10. (Nyssorhynchus) Philippines . .
10. (Nyssorhynchus) India, etc.

85. *A. funesta Giles [2]

6. (Myzomyia)

Africa

86.

A. funesta var. subumbrosa Theo-

bald [6]

6.

(Myzomyia)

Africa

. .

87.

A . funesta var. umbrosa

6.

(Myzomyia)

Africa

88.

A. funesta var. neiriti Blanchard .

6.

(Myzomyia)

Africa

89.

A . gambles Giles [46]

—

—

90.

A . gigas Giles [3]

3-

(Patagiamyia)

India

91.

A . gilesi Neiva

9-

(Myzorhynchella)

Brazil

92.

A . gorgasi Dyar and Knab

n.

(Cellia)

C. America . .

93-

A . grabhamii Theobald

4.

(Cycloleppteron)

W. Indies

, S. America

94.

A. gracilis Theobald [12]

(Bironella)

—

95-

A . gracilis Donitz

—

—

96.

A . grisescens Stephens [2] . .

—

—

97-

A. halli James [3a]

—

—

98.

A . hebes Donitz [3] . .

\ 6.

(Myzomyia)

East and S.W. Africa

99.

*A . hispaniola Theobald [6] . .

6.

(Myzomyia)

N. Africa,

Spain

100.

A. (C.) hyemalis Fitch

—

—

101.

A. immaculatus James [1] (1902) .

2.

(Anopheles)

India

102.

A . implexa Theobald [7]

(Christy a)

Africa

. .

103.

A . impunctus Donitz

6.

(Myzomyia)

Egypt

104.

A . indefinata Ludlow [4]

—

—

105.

A. indica Theobald [14]

. 10.

(Neocellia)

India

..

106.

A . indica Theobald [2]

6.

(Myzomyia)

India

107.

A. indiensis Theobald [14] . .

10.

(N yssorhynchus)

India

108.

A . indiensis

4.

(Myzorhynchus)

India

109.

A . intermedia Rothwell

—

India

no.

A . intermedium Chagas

5-

( Cycloleppteron,
Notonotricha)

Brazil

. .

III.

A . jacobi Hill and Haydon ...

n.

(Cellia)

Natal

112.

A . jamesii Theobald [2]

10.

( Nyssorhynchus )

India

"3-

A . jamesii Liston

—

—

114.

A . jehafi Patton

—

—

"5-

A . jesoensis Tsuzuki

—

Formosa,

etc.

116.

A. jeyporensis James [1]

7-

(Pyretophorus) . .

India

117.

A. harwari James & Liston

10.

( Nyssorhynchus )

India, Malay

118.

A . kochii Donitz [1]

—

—

119.

A . kumassii Chalmers

120.

A . leptomeres Theobald [6] . .

—

—

121.

A . leucopus Donitz [1]

—

—

with their present classification and generic synonymy, and
connection with malaria.

Transmission experi-
ments.
Cycle observed of —
M.T. Malignant tertian,
S.t. Simple tertian,

Q. Quartan ;

of z, to zygote stage,

and s, to sporozoite

stage

Observations regarding
transmission in nature.

(z) Zygote and

(s) Sporozoite stage

observed

Epidemiological
evidence of
transmission

Remarks

Stephens &
Christophers,
M.T. (z) Q. (z).
Ross, Annett
Austen,

S.T. Q.

Daniels, M.T.

Adie, (s)

Stephens & Christo-
phers, (s) ; some-
times 50 % infected

Not an active carrier as far as kno\
Adie found only 1 in 200 infect

Active and important common can
in Tropical Africa.

Improbable act-
ing as carrier
owing to dis-
tribution

vide A. neiviti Ventrillon [1].
= A. funesta Giles.
Hill species.

Ed. & Et. Sergent,
(t) (s)

Negative in Anda-
mans (Christophers)

ruz, (t)

= A. costalis Loew.

= A. maculipennis or A. bifurcatus.

= A. kockii Donitz.

Common carrier, Algeria and S. Spa

= A. panctipennis Say.

=A. wiUmori James var.

= A. culici fades Giles.

=i4. )naculipa!; iiensis Thi

= A. sinensis var. indiensis Theoba

= A. stephensi Liston.

A . fuh riles.

•A.cinereus (?) (Theobald).

Staunton (sus-
pected)

Daniels, ( + ) pro-
bable

A. funesta Giles.

A. cuhcifmcUs Giles (?).

A, fuh ;les

Table II [continued). The known species of Anophelines,

notes on their habitat and

122.

A

123.
I24.

A
A

125.

126.

A
*A

Species and Synonyms

leucosphyrus Donitz [1] . .
lindesayi Giles [4a]
lindesavi var. maculata Theo-
bald [17]

lineata Ludlow
listoni Liston [1] . .

127. A. listoni Giles

128. A. longipalpis Theobald [6]

129. *A. ludlowi Theobald [6]

130. A. hitzi Cruz

131. A. lutzi Cruz

132. *A. lutzi Theobald

133. *A. maculatus Theobald [2]

134. A . maculicosta Becker

135. A. maculipalpis Giles [4ft] . .

136. A. maculipalpis James & Liston .

137. *A. maculipalpis var. indiensi

Theobald

Present group tabulation
and generic synonymy

Distribution

138. *A. maculipennis Meigen [2] (18 18) .

139. A. maculipes Theobald [6] . .

140. f-4 . malefactor Dyar and Knab [ia] .

141. A. mangyana Banks [1]

142. A. marshallii Theobald [6] . .

143. A. martini Laveran [3]

144. A . mauritianus Grandpre ..

145
146

147
148

149
150
151
152
153
154
155
156
157
158
159
160
161
162

A . masteri Skuse [1] . .

A . mediopunctatus Theobald [6j

A . merus Donitz

A . metaboles Theobald [4]

A . minimus Theobald [2]

A. minutus Theobald [6]

A . multicolor Cambouln

A. muscivus Skuse [1]

A. myzomyfacies Theobald [14]

A . natalensis Hill & Haydon

A . nigerrimus Giles [4a]

A. nigerrimus James & Liston [4]

A. nigra Theobald [14]

A . nigrans Staunton

A. nigrifasciatus Theobald [14]

A . nigripes Staeger

A . nigritarsis Chagas [1]

A . nili Theobald [9]

12.
3-

3-
6.

Neomyzomyia) Malay, etc.

Patagiamyia) India

Patagiamyia) India

Calvertia) . . Philippines

Myzomyia) . . India

Myzomyia)
Pseudomyzomyia )

Central Africa
Malay

Myzorhynchella) Brazil

Manguinhosia) Brazil

Myzomyia ?) . . Brazil

Nyssorhynchus) India

Nyssorhynchus) China

10.

(Nyssorhynchus)

India

2.

{Anopheles)

Europe, America

5-

5-

(Arribalzagia) . .
(Arribalzagia) . .

Brazil
Brazil

10.
4-

(Pyretophorus) . .
(Myzorhynchus)

Mashonaland

Cambodia

Mauritius.Madagascar

12.
5-

{Nyssorhynchus)
( Cycloleppteron )

Australia

Brazil

Africa

7-

(Pyretophorus) . .

China

7-
2.

(Pyretophorus) . .
(Myzorhynchus ?)

Algeria
Natal

9-

( Myzorhynchella )

Brazil, etc.

7-

(Pyretophorus) . .

India

9-
6.

( Myzorhynch ella )
(Myzomyia)

Brazil
Africa

with their present classification and generic synonymy, and
connection with malaria.

Transmission experi-
ments.
Cycle observed of—
m.t. Malignant tertian,
S.T. Simple tertian,

Q. Quartan ;

of z. to zygote stage,

| and s, to sporozoite

stage

Observations regarding
transmission in nature.

(/.) Zygote and

(s) Sporozoite stage

observed

Epidemiological
evidence of
transmission

Remarks

Kinoshita, (t) Stephens & Christo-
phers, (s)

Hill species.

Active and important carrier in cerl

terai tracts in India.
= A. culicifacies Giles.

Christophers, (z) Christophers Important salt-swamp breeding

m.t. (carrier in An- littoral malaria carrier,

damans)

Staunton, m.t.

Watson (N. willmori
Watson = N. macn-
latus), Staunton

Lutz, (t) .. Forest carrier,breeding in bromelias,

— Common terai species, India. Comn

carrier, Malay States (referred
as N . willmori by Watson).

Stephens &
Christophers,
m.t. (z)
Grassi, etc.

Darling, (f)

Cruz, (t)

Robertson, Liston,
Bentley, (s)

Grassi, etc.

Ed. Sergent, (s)

= A. maculipalpis var. indiensis Th
Common carrier in X.W. Terai.

— Common carrier in Europe and No

America.

— Not concerned in transmission

Panama (Darling).

— =A. ludlowi Theobald (?).

Laveran, ( + ) —

Ross. Doubtful Probably = A. paludis Theobald,
carrier not act-
ively transmit-
ting in Mauritius

= A. stephensi Liston.

= A. siiier.

= A. annulipcs Walker.

=sA . sinen

= A . sine*

= A . hat n .>>: }..

— A. plumbeus Haliday.

Table II (continued).

The known species of Anophelines,
notes on their habitat and

Species and Synonyms

163. A. nimba Theobald [6] (1903)

164. A . nivipes Theobald [8]

165. A. nursei Theobald [14]

166. A. ocellatus Theobald

167. A. occidentalis Dyar & Knab

168. A. palestinensis Theobald [6]

169. A . pallida Ludlow ..

170. A. pallidopalpi Theobald [14]

171. A. paludis Theobald [1]

172. A. paludis var. similis Theobald [6]

173. A . parva Chagas [1] . .

174. A. peditamiatus Leicester [2]

175. A . perplex ans Ludlow

176. A. pharoensis Theobald [2]

177. A. pharoensis var. alba Ventrillon

178. A. philippinensis Ludlow [1]

179. A. pictus Loew [1] . .

180. A. pictus Ficalbi [2] . .

181. A . pictus Macdonald

182. A. pitchfordi Power

183. A. plumbeus Haliday (1828)

184. A . plumiger Donitz [1]

185. A. pretoriensis Theobald [6]

186. A. pseudobarbirostris Ludlow [2]

187. A. pseudocostalis Theobald [17]

188. A. pseudomaculipes Chagas [1]

189. A. pseudopictus Grassi [1] . .

190. *A. pseudopunctipennis Theobald [3]

Present group tabulation
and generic synonymy

Distribution

i. (Stethomyia) . . Brazil, etc.
10. (Nyssorhynchus) Malay
7. (Pyretophorus) . . India

7-

(Pyretophorus) . .

Palestine, Cyprus

3-
4-

(Feltinella)

( Myzorhynchus )

Sierra Leone

9-

(Myzorhynchella)

Brazil

3-
11.

(Anopheles)
(Cellia)

N. America . .
Egypt

n.

10.

(Cellia)

( Nyssorhynchus )

Philippines . .

7-
2.

(Pyretophorus) . .
(Anopheles)

Africa
Europe

10.

4-
10.

5-

4-
3.

(Nyssorhynchus)
(Myzorhynchus)
(Pyretophorus) . .
(Arribalzagia) . .
(Myzorhynchus )
(Anopheles)

Transvaal

Philippines . .

Africa

Brazil

Europe

N. America . .

191. A. pseudosquamosa Newst. & Carter

[2]

192. A. pseudowillmori Theobald [17]

193. A . pulcherrima Theobald [4]

194. \A. punctipennis Say [1]

195. A. punctipennis Bigot MSS.

196. A. punctulata Donitz [1]

197. A . pursati Laveran [3]

198. A. pyretophoroides Theobald [14]

199. A, quadrimaculatus Say [2]

200. A . rhodesiensis Theobald [2]

201. \A. rossi'i Giles [1]

(Cellia)

Rhodesia

II.
3-

(Cellia)
(Paiagiamyia) .

India

N. America . .

12.

(Cellia) . .

East Indies, etc

6.

(Myzomyia)

Transvaal

6.

(Myzomyia)

Africa

(Pseudomyzomyia) India, China

202. A. rossii var. indefinata Ludlow [4]

203. A. separatus Leicester

204. A. sergentii Theobald [14] ..

205. A. simlensis James [4]

( Myzorhynchus )
(Pyretophorus) .
(Paiagiamyia) .

Malay

Algeria

India

with their present classification and generic synonymy, and
connection with malaria.

Transmission experi-
ments.
Cycle observed of —
m.t. Malignant tertian,
s.t. Simple tertian,

Q. Quartan ;

of z, to zygote stage,

and s, to sporozoite

stage

Observations regarding
transmission in nature.

(z) Zygote and

(s) Sporozoite stage

observed

Epidemiological
evidence of
transmission

Remarks

Newstead,
Dutton &
Todd, (t)

Possibly = A. nigyifasciatus var.
= A. punctulatus Donitz.
= ( ? ) A . maculipennis.

= A. aitkeni James (?).

= A. mauritianus Grandpre.
= A. sinensis.

A. pseudopiclus Grassi.
■A. pseudopiclus Grassi.
A . hispaniola.

= A. sinensis

Cruz, (t)
Darling, m.t.

(8)

Only slightly concerned in t
mission in Canal Zone (Dar
12-9 % of those fed by Dc
became infected.

= A . maculatus.

Hirschberg,

(F)

Stephens &
Christophers,
Q. m.t.

James, Stephens &
Christophers, (f) ;
Bentley, Staunton

Laveran, ( + )

Little relation

—A. bxgotxx,

=A.macuhj \merican).

Apparently transmit very little,
all, in "nature, thouch commi
Indian sp

= A. indefinata Liull

= ? A .

Unlikely to be Hill S]
transmitter
from distribu-
tion.

Table II [continued)

The known species of Anophelines,
notes on their habitat and

Species and Synonyms

206. *A . sinensis Wiedemann [2]

Present group tabulation
and generic synonymy

4. {Myzorhynchus)

Distribution

India, China, Malay

207. A. smithii Theobald [10] (1905)

208. A. squamosns Theobald [2]

209. A. squamosns var. arnoldi Newst.

& Carter [2]

210. *A. stephensi Liston [1]

211.
212.
213.
214.

A. stigmaticus Skuse [1]
A. strachani Theobald [14]
A . subpictus Grassi . .
A. superpictus Grassi [1]

215. A. tarsimaculatus Gceldi

2. {Anopheles)
11. [Cellia)

11. {Cellia)
10. {Nyssorhynchus,
Neocellia)

4. {Myzorhynchus)
7. {Pyretophorus) .
11. (Cellia)

Sierra Leone
Africa

Africa
India

Australia
W. Africa
India
Europe

S. America

216. A. tenebrosus Donitz

217. A. tessellatum Theobald [2]

218. *A. theobaldi Giles [3]

12. — Malay

10. {Nyssorhynchus) India

219. A. thorntonii Ludlow (1904)

220. A. tibani Patton

221. A. tibiomaculata Neiva [1]

222. A. transvaalensis Carter

223. A. treacheri Leicester

224. A. trifurcatus Fabricius [1]

225. A. turkhudi Liston [1]

— Aden

9. {Myzorhynchella) Brazil
7. {Pyretophorus) . . Transvaal

6. (Myzomyia)

India

226.

227.

A . umbrosa Edwards [1]
A. umbrosus Theobald [6]

6. {Myzomyia) . . Africa
4. {Myzorhynchus) Malay

228. A . unicolor

229. A . vauus Donitz [3] . .

230. A. nanus Walker [4]

231. A . villosus Desvoidy [1]

232. A, vincenti Laveran [ia]

233. A. ivalkeri Theobald [2]

234. A. watsonii Edwards [1]

235. A. watsonii Leicester [2]

236. A. wellcomei Theobald [9] .

237. A. wellingtonianus Alcock .

238. *A. ivillmori James ..

239. A. willmori var. maculosa J;

240. A. willmori Leicester

241. A. ziemani Van Grunberg .

{Myzomyia)

10.

{Nyssorhynchus)

Nigeria

12.

{Anopheles)

Malay

3-

{Patagiamyia,
Myzorhynchus )

10.

{Nyssorhynchus)

India

10.

{Nyssorhynchus)

India

with their present classification and generic synonymy, and
connection with malaria.

Transmission experi-
ments.
Cycle observed of —
m.t. Malignant tertian,
S.T. Simple tertian,

Q. Quartan ;

of z, to zygote stage,

and s, to sporozoite

stage

Tsuzuki, q, &
others Kino-
shita, s.t.

Q.M.T. = F

Observations regarding
transmission in nature.

(z) Zygote and

(s) Sporozoite stage

observed

Epidemiological
evidence of
transmission

Remark-

Stephens & Liston, (t) ; Bent-
Christophers ley, (t)

Important and active carrier. C
in towns owing to power of bn
in cisterns, wells, etc.

Darling,

00

Grassi, (t) ; Bignami
& Bastianelli, (t)

= {})A. albimana. Considered
tinct by Dyar and Knab. 60
those fed by Darling becarc
fected.

= A. mauritianas.

Stephens &
Christophers,
m.t. (z) q.(z)

Probably transmits in terai and
parts of India.

= A. tessellation.

Stephens &
Christophers,
m.t. (z)

Staunton,
m.t. (f)

—

=A. aitkeni James.

—

= A. bifurcatus Linnaeus

Gill. Large

Probably transmits

numbers in

very malarious

spot

Watson con-

—

siders to be

carrier

= A. rossii Gil<

—

= A. sinensis Wied.

—

= A. bifurcatus Linnaeus.

= A. bifurcatus Liir

Adie (Mrs), (s)

Carrier in terai country.

Theobald
- .1 . ■ ndpre.

108 megarhinin.e [ch.

Tribe 2. Megarhinin^e.

Proboscis with the apical half much thinner than the basal,
and bent downwards at an angle with it. Scutellum evenly
rounded. Wings long and narrow ; fork cells both very short,
but with the first much shorter than the second. Large species
completely clothed with flat, more or less metallic, scales, usually
blue or green. Larvae predaceous ; adults not bloodsuckers.

The Megarhininae are popularly known as Elephant mos-
quitoes owing to their enormous size. None of the species
have been shewn to be directly concerned in the spread of
disease, but the predaceous larvae of some species play an
important role in keeping down the number of other species
of mosquitoes. T. immisericors (Walker), the common Elephant
mosquito of India and Burmah, for example, in the larval stage
is generally found living on the larvae of Stegomyia. The two
chief genera are Megarhinus and Toxorhynchites, the former
of new world and the latter of old world distribution.

Tribe 3. Culicinae.

Thorax more or less rounded ; metanotum without
bristles ; scutellum more or less distinctly trilobed. Larvae
with air tube and median ventral brush on anal segment (after
the first stage).

This sub-family includes over 600 species and, next to the
Anophelinae, is the most important from the point of view of
the transmission of disease. Theobald in his monograph
recognizes nearly 100 genera, arranged as follows :

Palpae of male long

Culicince.

Palpae of male short.

First forked cell of wing long

Aedina.

First forked cell of wing very short

Uvanot&nince

In addition certain peculiar forms have been given the
rank of a sub-family by Theobald. In other respects having the
characters of Culicinae, but differing in having a seventh vein
on the wing with scales, is Heptaphlebomyinae. Also resembling
Culicinae, but having a very long second segment of the antenna,
is Deinoceratinae.

VIIl] GENERA OF CULICIN^E IO9

Edwards divides the Culicinge into two main groups :

(i) Culex group. Eggs laid in masses ; last segment of

female abdomen broad, immovable ; claws of female never

toothed.

Genera : Culex, Tcsniorhynchus, JEdomyia, Theobaldia, Uranotcenia.

(2) Aedes group. Eggs laid singly ; last segment of
female abdomen narrow, usually completely retracted into
the penultimate ; claws of female, at least on the four anterior
legs, nearly always toothed.

Genera : Mucidus, Psorophora, Janthinosoma, Ochlerotatus, Stegomyia,
Aedes.

The following scheme is that of Edwards, giving the chief
characters of the more important genera.

Table of Genera of Culicincz (Edwards).

Claws of female toothed . . . . . . . . . . . . 2

Claws of female simple . . . . . . . . . . . . 5

Posterior cross-vein slightly beyond mid cross-
vein ; legs shaggily scaled ; female palpi half
as long as proboscis .. .. .. .. Mucidus.

Posterior cross-vein before mid cross-vein ; legs
not shaggily scaled ; female palpi not half as
long as proboscis . . . . . . . . . . . . 3

Male palpi with two apparent joints . . . . Banksinella.

Male palpi with three apparent joints .. .. .. .. 4

Last two joints of male palpi thin, about equal in
length ; black and white species ; head all flat-
scaled Stegomyia.

(Includes Stegomyia, Dcsvoidya, Leicesteria, Scutomyia and Kiv.gia of
Theobald.)

Last two joints of male palpi more or less thickened,
especially the penultimate, which is longer than
the terminal ; not usually black and white
species, head not usually flat-scaled above . . Ockle\

(Includes Acartomyia, AEdimorphus, Andersottia, BaiM
Culicada, Culicelsa, Danielsia, Duttonia, Eccu".
Gualteria, InimetocuUx, Lepidoplatys, L
Molpemyia, Myxosquamus, Neopecomyic
leptiomyia, Protoculcx, Protomach\;
Pseu,: skusea, R

of Theobald ami others.)

110 GENERA OF CULICIN^ [CH.

5. Eighth segment of female abdomen slender,

retractile ; male resembling a Stegomyia . . Howardina.
Eighth segment of female abdomen broad trun-
cate (except in Mimomyia), not retractile . . . . . . 6

6. Head without any flat scales in the middle above ;

proboscis never swollen at tip . . . . . . . . . . 7

Head with at least a row of flat scales round the
eye margins, usually almost entirely clothed
with flat scales ; proboscis often swollen at

tip 13

7. Wing scales very broad and dense . . . . . . . . 8

Wing scales not very broad . . . . . . . . . . 9

8. Male palpi as long as proboscis, thin last joint very

short . . . . . . . . . . . . Mansonioides.

Palpi similar in both sexes, very short ; middle

femora with a tuft of scales at the tip . . Mdomyia.

9. Fork cells very short ; wings nearly bare ; male

palpi two-jointed . . . . . . . . Mimomyia.

(Includes Boycia, Conopomyia, Hispidimyia, Ludlowia, Mimomyia,

Radioculex, of Theobald, etc.)
Fork cells not very short ; male palpi three-
jointed .. .. .. .. .. .. .. .. jo

10. Metatarsus of bind-legs distinctly shorter than the

tibia ; male palpi long, the last two joints

swollen . . . . . . . . . . . . . . . . 11

Metatarsus of hind-legs at least as long as the tibia,

male palpi thin . . . . . . . . . . . . . . 12

11. Penultimate joint of male palpi thicker and some-

what longer than terminal one, usually yellow

species . . . . . . . . . . . . T csniorhynchus .

(Includes T csniorhynchus and Mansonia of Theobald.)
Penultimate joint of male palpi thinner but not

longer than terminal one ; not yellow species ;

cross-veins almost in a line . . . . . . Theobaldia.

12. Male palpi longer than proboscis, last two joints

curved upwards . . . . . . . . . . Culex.

(Includes Aporoculex, Heptaphlebomyia, Lasioconops, Leucomyia, Ltitzia,

Maillotia, Melanoconion, Microculex, Oculeomyia, and Trichopronomyia

of Theobald.)
Male palpi shorter than proboscis, straight . . Protomelanoconion.

13. A row of small flat scales round the eyes ; basal

joint of male palpi with a row of projecting

scales ; otherwise like Culex . . . . . . Culiciomyia.

(Includes Culiciomyia, Trichorhynchus, Neomelanoconion, and Pectino-
palpus of Theobald.)

Head mostly or entirely flat-scaled in middle . . . . . . 14

14. Proboscis not swollen at tip ; fork cells not very

short . . . . . . . . . . . . . . . . 15

Proboscis swollen at tip or fork cells very short,

first shorter than second . . . . . . . . . . 17

VIII

GENERA OF CULICIN^E

I I I

r5. Lateral vein scales with apices simple, 4 antennae

plumose . . . . . . . . . . . . . . 1 6

Lateral vein scales with apices dentate, $ antennae

pilose . . . . . . . . . . . . Hodgesia.

1 6. Medium-sized species, pale palpi thin, almost

without hairs and slightly shorter than the

proboscis . . . . . . . . . . . . Eumelanomyia.

Very small species, male palpi short like those of

the female . . . . . . . . . . Micra'edes.

17. Fork cells very short, first shorter than second .. .. 18
Fork cells not very short, first not shorter than

second . . . . . . . . . . . . . . . . 19

18. Lateral vein scales absent ; male palpi long, two-

jointed, apical one swollen ; fore and mid-claws

of male unequal, toothed . . . . . . Mimomyia.

Lateral vein scales present, broad ; male palpi
very short ; male claws not toothed, the front
pair small and equal . . . . . . . . Uvanotcenia.

(Includes Uranot&nia, Pseudouranotcpnia, Anisocheleomyia, Pseudo-
ficalbia of Theobald.)

19. Proboscis not hairy . . . . . . . . Ingramia.

( = Dasymyia . Leicester. )
Proboscis with long hairs . . . . . . . . Harpagnmyia.

( = Malay a. Leicester.)

Of the genera noted above some are more important than
others, both as regards the number of species and their relation
to disease transmission.

Mucidus (seven species). The larvae are predaeeous and, like those of the
MegarhinincB, feed on other mosquito larvae. Species of Mucidus have a
very striking " mouldy " appearance, due to the long outstanding scales
on the legs, etc. Not one of the species has been noted as concerned in
the transmission of disease.

Banksinella (five species). Some species at least suck human blood with
avidity. No species has been proved to transmit any disease.

Stegomyia and Kingia (over 40 species). Mosquitoes of the genus S

are medium-sized, brilliantly banded and marked with black and silvery
white. The head is entirely covered with flat appressed scales and all
lobes of the scutellum likewise carry broad Hat scales.

The following is Theobald's table for the differentiation oi
the species of Stegomyia^ with some additional ones described

since his work was published.

112 SPECIES OF STEGOMYIA [CH.

Genus Stegomyia Theobald (1910;.
A. Proboscis banded.

a. Legs basally banded.

Thorax brown, with scattered creamy-white scales

annulirostris. Theobald.
Thorax black, with narrow-curved golden scales

periskeleta. Giles,
act. Legs with basal and apical banding.

Forelegs with no bands ; mid with apical and basal bands on first
tarsal and second tarsal ; hind with basal bands.
Thorax white in front, with a brown eye-like spot on each side.

thomsoni. Theobald.

AA. Proboscis unbanded

)8. Legs basally banded.

7. Abdomen basally banded.

Thorax with one median silvery-white line scutellaris. Walker.

Thorax similar, but two white spots near where line ends

gebeleinensis. Theobald.

Thorax with a white line on each pleuron in addition to a median
silvery- white line . . . . pseudoscutellaris. Theobald.

Thorax with two median yellow lines and lateral curved silvery
lines . . . . . . . . . . fasciata. Fabricius.

Thorax with two short median lines and a white patch on each
side .. .. .. .. .. .. nigeria. Theobald.

Thorax with large lateral white spots in front, smaller ones by
wings, two narrow median yellow lines, and two posterior sub-
median white lines . . . . . . . . lilii. Theobald.

Thorax with a white W-shaped area in front, a prolongation
curved on each side enclosing a brown eye-like spot

W-alba. Theobald.

Thorax with white frontal median spot, two large lateral spots,
a small one in front of the wings, a narrow median white line
and narrow sub-median ones on posterior half. Last two hind
tarsi white . . . . . . . . wellmanii. Theobald.

Thorax brown, with broad white line in front extending laterally
towards wings, where they swell into a large patch; a white line
on each side just past wing roots. Last two hind tarsi white

desmotes. Giles.

Thorax with silvery-white spot on each side in front, small one
over root of wings, and white over their base. Last two hind
tarsi white . . . . . . . . pseudonigeria. Theobald.

Thorax with two lateral white spots, front one the largest, small
median one near head, two yellow median lines, a short silvery
one on each side before scutellum . . simpsoni. Theobald.

Thorax with a silvery-white scaled area in front and another each
side in front of wings . . . . argentecmaciilata. Theobald.

VIII] SPECIES OF STEGOMYIA II3

Thorax with median yellowish-white line, a silvery patch on each
side in front of wings, extending as a fine yellow line to scutellum,
and another silvery spot before base of each wing

poweri. Theobald.

Thorax with small grey scaled area in front of roots of wings and

three short creamy lines behind . . minutissima. Theobald.

Thorax ? (denuded). Abdomen black ; fifth segment with

yellow basal band ; sixth, unbanded ; seventh, two median

lateral white spots ; eighth, two basal lateral white spots ;

second hind tarsal nearly all white . . dubia. Theobald.

Thorax dark brown ; abdomen with dark scales arid basal

ochraceous bandings well-marked on segments 2, 3, 4 and 5

quasinigritia. Ludlow.

Thorax dark brown. Abdomen dark brown, with brilliant lateral

white spots, sometimes extending across tergum as basal bands

nigritia. Ludlow.
77. Abdomen unbanded.

Third hind tarsal nearly all white.

Thorax with two lateral white marks directed upwards

africana. Theobald.
Thorax with white spot in front and another in front of each wing

apicoargentia. Theobald.

First hind tarsal all white, second basally white, last two dark.

Thorax chestnut-brown with a broad patch of white scales on each

side in front and a median pale fine . . terrens. Walker.

First hind tarsal with very small basal white spot ; second tarsal

mostly white, other segments black . . pollinctor. Graham.

j3/3. Legs with white lines as well as basal bands.

Thorax brown with white lines ; abdomen with basal bands

grantii. Theobald.
j3j8/3. Fore and mid-legs with apical bands ; hind basal.
Fourth tarsal of hind-legs nearly all white

mcdiopunctata. Theobald.

Mid metatarsi with basal pale banding, base and apex of hind,

also base of first tarsal .. .. .. assamensis. Theobald.

Basal two-thirds of hind femora white, metatarsus and first three
tarsal joints with basal white bands . . imitator. Leio

j8/3j8/3. Fore and mid-legs unbanded; hind femora white basally and at apex.
Thorax black scaled in female and golden scaled in the male.
Abdomen unbanded dorsally but banded ventrally with
square pearly white spots laterally .. dissimilis. Lei<
-;. Legs unbanded.
5. Abdomen basally banded.

Thorax, front half white, rest bronzy-brown

pseu Theobald.

Thorax deep brown, with scattered golden scales, shewing
dark eye-like spots; head white, dark on each side and behind

Theobald.
Thorax brown, with golden stripes ; abdomen with DVT
bands fifth and sixth segments raly

H. B. F.

114 SPECIES OF STEGOMYIA [CH.

55. Abdominal banding indistinct.

Thorax with broad silvery- white patch on each side in front

albolateralis. Theobald.
555. Abdomen unbanded.

Thorax, six silvery spots . . . . argenteopunctata. Theobald.

Thorax with dark-brown narrow curved scales. Scutellum with
very marked meridian lobe . . . . hatiensis. Carter.

5555. Abdomen with apical white lateral spots.

Thorax unadorned, except for pale scaled lines internally

punctolateralis. Theobald.
Abdomen with basal white lateral spots.

Thorax with two pale indistinct median parallel lines and two
silvery lateral spots . . . . . . minuta. Theobald.

Thorax unadorned.

White spot mid head . . . . . . tripunctata. Theobald.

No white spot . . . . . . amesii. Ludlow.

Thorax brownish-black with dark bronze scales. Abdomen clad
with purple-black scales and white triangular lateral spots

fusca. Leicester.

55555. Abdomen with silvery apical lateral spots on all segments except

first two . . . . . . tasmaniensis. Strickland.

AAA. Proboscis yellow basally, dark apically.

Abdomen with apical pale bands .. . .crassipes. Van der Wulp.

AAAA. Proboscis with median interrupted white lines on
basal half.

Head black, anterior margin grey . . albomarginata. Newstead.

Desvuidya (five species). Large mosquitoes active by day like Stegomyia,
small with silvery venter, but less ornamented than Stegomyia.

Leicesteria (ten species). Resembling Desvoidya, but the female pupae are
half the length of the proboscis.

Ochlerotatus. This genus as reconstructed by Edwards is an important one
from the large number of different forms included. Of the original genera
now sunk under Ochlerotatus, many contain but few species, and have not
been shewn to play any part in disease transmission.

Culicada is a genus represented by many species and especially occurs in
North America and Europe.

Howardina (seven species). The best known species in this genus is the
common H. sugens {Scutomyia Meigen = Stegomyia Meigen).

Grabhamia (twenty-eight species). There are a large number of common species
of this genus which usually have a characteristic floury appearance.
They are of active bloodsucking habits.

Mansonioides (three species). These have an even more pronouncedly floury
or " pepper and salt " appearance.

Aedomyia and Numomyia. These are now domestic species, having no rela-
tion to any disease. Many do not, under ordinary circumstances, feed
upon man.

VIII] PUBLICATIONS ON CULICID.E 115

Tcsniorhynchus and Mansonia. Mosquitoes of the genus Mansonia are
especially characteristic of swamp country, and occur in enormous
numbers in many parts of Tropical Africa and elsewhere. They are
concerned in the transmission of Filariasis.

Theobaldia. Large gnats common in the temperate zone.

Culex (several hundred species). Culex pipiens = common English gnat.
Culex fatigans-— commonest mosquito of tropics acting as transmitting
agent of Filariasis. It is also the definitive host of Plasmodium prczcox, the
malarial parasite of birds. Culex concolor as a larva has actively cannibal
habits, and plays an important part in keeping down the numbers of the
common C. fatigans and its near allies.

Culiciomyia, and other genera of little importance as carriers, etc.

Tribe 4. Sabethin^e.

The members of this tribe are not known to carry any disease.

PUBLICATIONS OF IMPORTANCE IN CONNECTION WITH
NOMENCLATURE AND SYSTEMATIC WORK ON CULICIDJE.

The numbers in brackets refer to the data given in the Table o
species of Anopheles (pp. 96—107).

The asterisks mark recent and important papers, or those in which
recognized species of Anopheles are described.

Agramonte (1900). El progresso medico, x. p. 460.
Arribalzaga [1] (1878). El naturalista Argentino.
[2] (1883). Bol. Acad. nac. d. Ciencias, iv.

* [3] (1891). Rivista del Museo de la Plata (Culicida).

♦Bancroft (1908). Annals of the Queensland Museum, No. 8.
♦Banks (1906). Philippine Journal of Science, vol. 1. No. 9.

Becker (1903). Mitteilungen aus dem Zool. Mus. in Berlin, 11. p. 68.
♦Blanchard [id] (1901) [ib] (1905). Les moustiques, histoire natui
et mddicale. Paris.

* [2] (1901). Compt. rend. Soc. Biol. vol. liii. p. 1045.

* [3] (1902). Ibid. vol. liv. p. 793.

♦Bourroul (1904). Mosquitos do Bras 1 1. Bahia.

Camboulin (1902). C. R. Acad. Sc. cxxxv. p. 704.
♦Carter [1] (1910). The Entomologist, vol. xliii. p. I
♦Chagas [1]. In Peryassu.

Chalmers [1] (1900). Lancet.

[2] (1905). Spolia Zeylandica, 11. 8, p. 1

♦Christophers [1] (1911)- Paludism, No. 2.

Coquillet [1] (1896). Canadian Entom. xxvm.

* [2] (1900). U.S. 1' »S md

Series, No. 40.

* [3] (1902). New York S -• x P i9i-

Il6 PUBLICATIONS ON CULICID^ [CH.

*Coquillet [4] (1903). Canadian Entom. xxxv.

* [5] (1900). U.S. Depart, of Agric, Bureau of Entom. Tech.

Ser. No. 11.

Cruz [1] (1906). Brazil Medico, xx. 20, p. 199.

* [2] (1908). In Peryassu.

Desvoidy [1] (1827). Mem. d. 1. Soc. d'Hist. Nat. de Paris, III. p. 411.

[2] (1828). Ibid. vol. iv.

♦Donitz [1] (1901). Insekten Borse, xvm.

* [2] (1902). Zeits. f. Hygiene, xli. p. 15.

* [4] (1903). Ibid, xliii. p. 215.

*Dyar and Knab [ia] (1907). Journ. New York Entom. Soc. xv. p. 198.

* [16] (1909). Proc. of the U.S. Nat. Museum, xxxv. p. 53.

* [2]. Proc. Biol. Soc. Washington, xix. p. 160.

*Edwards [1] (191 1). Bull. Entom. Research, 11. part 2, p. 141.

* [2] (191 1). Ibid. 11. part 3, p. 241.

* [3] (191 2). Ibid. in. part 1, p. 1.

* [4] (1912). Ibid. in. part 3, p. 241.

Fabricius [1] (1775)- Sy sterna entomologica, etc.

[2] (1777). Genera insectorum.

[3] (1781). Species insectorum, etc.

[4] (1877). Mantissa insectorum, etc.

[5] i1 794)- Entomologia systematica emendata et aucta.

[6] (1805). Syst. Antliatorum, etc. 6, p. 35.

Ficalbi [1] (1896). Bull. Soc. Entom. Ital. xxviii.

* [2] (1899). Ibid. xxxi.

Fischer [1] (1812). Mem. Soc. Imperiale Nat. Moscou, iv. p. 167.
Fitch (1885). New York State Museum, 2nd Entom. Report.
*Giles [1] (1899). Jour. Prop. Medicine, 11. p. 62.

* [2] (1900). Liverpool School of Prop. Med., Memoir 11.

* [3] (1901). Entom. Monthly Mag. xn. p. 196.

* [4a] (1900) [46] (1902). Handbook of Gnats or Mosquitoes.

London.

* [5] (1904). A Revision of the AnophelincB (supp. to handbook).

*Goeldi (1905). Os mosquitos no Para. Para.

♦Grandpre [1] (1900). Planters' Gazette Press. Port Louis.

[2] (1902). Zool. Anz. xxv. No. 677, 21 July.

♦Grassi [1] (1899). Atti Accad. d. Lincei, Ser. 5, Memor. in.

Griinberg (1905). Zool. Anz. xxix. p. 377.
Haliday [1] (1828). Zool. Journal, xn.

[2] (1833). Entom. Magazine, 1.

[3] (I839). Annals of Natural History.

♦Hill and Haydon (1907). Annals of the Natal Gov. Museum.
♦Howard (1901). Mosquitoes ; how they live, etc. New York.

* Dyar and Knab (1912). The mosquitoes of North and Central

A merica and the West Indies . Publ .159. Carnegie Inst. Washington .

♦James [1] (1902). Set. Memoirs Med. and San. Departs, of Gov. of
India, No. 2

VIII] PUBLICATIONS ON CULICID^ 117

* James [ia]. In Theobald, vol. III.

* [2] (1910). Records of the Indian Museum, iv. No. 5.

* [3] (1910). Paludism, No. 1.

*James and Liston [4a] (1904) [46] (191 1). The Anopheline Mosquitoes
of India. Calcutta.
Kertesz (1904). Allattan Kozl. III.
Laveran [ia] (1901). C. R. Soc. Biol. xxm. p. 993.

[ib] (1901). Ibid. liii.

[2] (1902). Archiv d. Parasit. vi. p. 359.

[3] (1902). C. R. Soc. Biol. liv. p. 907.

♦Leicester [1] (1904). The Entomologist, xxxvu. p. 13.

* [2] (1908). Studies from the Instit. for Med. Research {Federated

Malay States), vol. in.

Linnaeus [1] (1746). Fauna Suecica.

[2] (1735). Sy sterna Natures.

*Liston [1] (1901). Indian Med. Gazette, xxxvi. pp. 361, 441.

[2] (1901). Bombay Med. and Phys. Soc. v. No. 8.

Loew [1] (1845). Dipterologische Beitrdge.

[2] (1866). Entom. Zeitschr.

*Ludlow [1] (1902). Jour. Amer. Med. Assoc, p. 426.

* [2] (1902). Jour. New York Entom. Soc. x. p. 127.

* [3] (1903). Ibid. xi.

* [4] (1904). Canad. Entom. xxxvi. p. 297.

* [5] (1908). Class. Geo. Dist. and Seas flight Mosq. {Philippine

Islands).

* [6] (1909). Canad. Entom. xli.

*Lutz [1] (1904). In Bourroul.

McCracken [1] (1904). Entom. Mus. ix. Jan. 1904.
Macquart [1] (1825). Mem. d. 1. Soc. R. des Sciences de I'Agric. et
des Arts de Lille.

[2] (1834). Histoire naturelle des Insectes Dipteres. Paris.

[3] (l854)- Mim. d. 1. Soc. R. des Sciences de I'Agric. et des

Arts de Lille.

Meigen [1] (1804). Klassifikation und Beschreibung der 1
Insekten, Bd. I.

[2] (1818). Syst. Besch. der bekamit. Europ.

vol. 1.

•Neiva (1908). In Peryassu.
Neveu-Lemaire [1] (1902). Mem. d. I. Soc. Zool. d\ XV.

[2] (1902). C. R. Soc. Biol. LIV.

* [3] (1905). Archiv d. Parasit. x. p.

♦Newstead and Carter [1] (1910). Annals of Trop. Med. and Par. iv.
No. 3.

* [2] (191 1). Ibid. v. No. 2.

♦Newstead, Button and Todd (1907). Ibid. 1. No. I.
Patton (1905). Jour. Bombay Nat. Hist. Soc. p. I
Rothwell (1907). The Entomologist, xlv p. 34.

Il8 PUBLICATIONS ON CULICID^E [CH.

♦Skuse [i] (1889). Proc. Linnean Soc. N. S. Wales. 2nd Ser. 111.

[2]. Indian Museum Notes, ill. Calcutta.

Smith [1] (1901). Jour. Boston Soc. of Med. Sc. v. p. 34.

[2] (1904). New Jersey Agric. Exp. Sta. pp. 1-40.

Staeger [1] (1839). Syst. for. 0. d. c. Denmark nid HI fundre Dipt.
Stephens [2] (1828). Zoological Journal, xn.

♦Stephens and Christophers (1908). The Practical Study of Malaria,

3rd ed.
♦Theobald [1] (1900). Reports to the Malaria Comm.of Royal Society, 1.

* [2], [3] (1901). Monograph of the Culicidce of the World, vol. 1

and 11.

* [4] (1902). Proc. Roy. Soc. lxix. p. 367.

* [5] (1902). Journ. Trop. Med. v. p. 181.

* [5a] (1903). Ann. d. I' Inst. Pasteur, XVII. 2.

* [6] (1903). Monograph of the Culicidcs, vol. III.

* [7] (1903). Reports of the Sleeping Sickness Commission.

* [8] (1903). The Entomologist, xxxvi. p. 256.

* [9] (1904). First Report Gordon College, Welle. Labs. 1. p. 62.

* [10] (1905). The Entomologist, xxxvin. p. 101.

* [11] (1905). Jour. Econ. Biology, 1. No. i, p. 17.

* [12] (1905). Ann. Mus. Nat. Hung. in. p. 65.

* [13] (1905). Genera Insectorum Fam. Culicidcs. Brussels.

* [14] (1907). Monograph of the Culicidcs, vol. iv.

* [15] (1909). Records of the Indian Museum, in. No. 3.

* [16] (1910). Ibid. iv. No. 1.

* [17] (1910). Monograph of the Culicidcs, vol. v.

* [18] (1901). Jour, of Trop. Med. iv. p. 229.

♦Theobald and Grantham (1905). Mosquitoes of Jamaica.

Tsuzuki (1902). Cent. f. Bakt. xxxi. pp. 15, 763.

Van der Wulp [1] (1839). Naturhist. Tijdschr. n. p. 252.

[2] (1869). Tijds. voor Entom.

[4] (1884). Ley den Museum Notes.

Ventrillon [1] (1906). Bull. d. Mus. d'Hist. Nat. xn. p. 100.

[2] (1906). Ibid. xii. p. 198.

Walker [3] (1850). Insecta Saundersonii, 1.

Watson (1910). Annals of Trop. Med. and Par. iv. No. 2.
Wiedemann [2] (1828). Ausser Eur op. Zweif. Insekten, 1.

IX] MALARIA 119

CHAPTER IX

ANOPHELINE-TRANSMITTED DISEASES

MALARIA.

Synonyms. Ague, Paludism, Intermittent fever, Remit-
tent fever ; Marsh, Climatic, Jungle, Hill, Mountain and
Coast fever, Plasmodiose, Fievre palustre, Wechsemeber,
Kaltesfieber, Ylvperos, Bimbi ou Moustique (Galla), Mbou ou
Moustique, and also many local names such as Roman fever,
Sierra fever, etc., etc.

Definition. Under the term malaria is grouped together
a number of intermittent fevers caused by plasmodial parasites
living in the red blood corpuscles At the present time only
three distinct species of these parasites are usually recognized,
viz. Plasmodium malaria, P. vivax, and P. falciparum ( = La-
verania malarice) ; each gives rise to a distinct type of fever
and is transmitted by various Anopheline mosquitoes.

The common features of the disease, in addition to fever,
are anaemia, hypertrophy of the spleen, and sometimes the
liver, and the deposition of pigment (melanin) in the various
organs and integument.

Historical. The periodicity of the febrile attacks of
malaria had attracted attention long before the parasitic
nature of this disease was known, or its transmission by mos-
quitoes suspected. Certain references have been taken
shewing that malaria was recognized even in the time of Homer
(1100 B.C.) and in the Hippocratic Books (500 B.C.) \v\
having quotidian, tertian and quartan periodicity are described.
This characteristic periodicity, which finds expression in the
term intermittent fever, even now sometimes used, represent
however, practically everything that was known about the
disease in these early times.

A much more precise knowledge of malaria and a dear
recognition of remittent and pernicious forms of the d
where periodicity is not a feature, followed the introduction

120 MALARIA [CH.

to Europe in the seventeenth century of Cinchona and its
alkaloids, it being then possible to distinguish types of fever
curable by quinine from those not affected by this drug.

A third feature of malaria, namely its frequent association
with paludic conditions, although it seems to some extent
to have been known to the ancients [e.g. Varro, 116 B.C.), was
first fully realized as a result of the work of Doni, Morton,
Lancisi and others, from the seventeenth century onwards.
This association was explained as shewing that malaria was due
to exhalations from decaying vegetable matter, or to minute
forms of life present in such exhalations. Hence there resulted
the Miasm theory of malaria, a theory universally held by
mankind up to a few years ago and responsible for the name
" Malaria " (=bad air).

In 1847 the occurrence of the characteristic pigment of
malaria in the blood and organs was discovered by Meckel ;
this pigment, it was thought, was the result of the chemical
action of miasm on the blood.

In 188 1 Laveran discovered the organism containing this
pigment now known as the malarial parasite. Within a few
years Laveran's organism, the first discovered protozoon
parasitic in man, was universally recognized as the cause of
malaria. Thus in modern usage it has followed that no diag-
nosis which has not been based upon the demonstration of this
parasite, or its characteristic pigment in the blood, is accepted
as of any value in a crucial case, malaria now being an example
of a disease defined not on clinical but on parasitological
grounds.

In 1886 Golgi demonstrated the nature of the life-cycle of
the parasite in man, and shewed that the periodicity of the
febrile attacks was dependent on the length of the cycle of
development of successive broods of the parasite, and that the
attack of fever occurred at the time when such broods simul-
taneously broke up into the spores which restarted the cycle.
Golgi also differentiated two species of malarial parasite, the
parasites of quartan and of tertian malaria, respectively.

In 189 1 Marchiafava and Bignami, after studying certain
irregular fevers prevalent in Rome in the summer and autumn,

IX] HISTORICAL 121

announced the existence of a third species of parasite, charac-
terized by the occurrence of very minute forms, and now known
as the cestivo-autumnal, malignant tertian or tropical parasite.
It was shortly afterwards discovered that certain large and
peculiar crescentic forms of the parasite, now very familiar
as crescents, were a stage in the life-cycle of this third species.
In addition these and other Italian workers by their collective
researches made quite clear the real parasitic nature of Laveran's
bodies and by elaborating methods by which they could be
demonstrated, laid the foundation for the study of the malarial
parasite by observers in other parts of the world.

In the decade or so following upon these early observations
a great many important facts in regard to malaria were elicited.
It was shewn that infection could be conveyed to healthy
persons by the subcutaneous or intravenous inoculation of the
blood of malarial subjects. It was also proved that in such
cases only that form of parasite appeared which had been
present in the original infection, thus greatly strengthening
the view of a plurality of species. Other species more or less
resembling the malarial parasite, but shewn to be distinct, were
also found to occur in birds, bats and other animals, and were
closely studied. Special methods of staining were elaborated
and much work was done with regard to the peculiar crescent
bodies and the process of exflagellation exhibited by these
and by certain other forms of the parasite.

All efforts to discover how the parasites gained an entrance
to the blood of man, however, failed. Experiments (Marchia-
fava ; Celli, 1885 ; Marino, 1890, and Zeri, 1890, etc.), under-
taken with a view to producing malaria in healthy pers
by causing them to drink water from notoriously malarious
places, were without result. When marsh water was inje
into animals a condition thought at first to be malaria was
produced, associated with tumefaction of the spleen and the
appearance of pigment in the organs. Bui it is now obvi
that this condition was one of septicaemia! and with the dis-
covery of the malarial parasite any significance attaching to
these experiments had to be abandoned.

The possibility that mosquitoes might be concerned in the

122 MALARIA [CH.

transmission of malaria had been put forward already by
King (1883). That mosquitoes might convey malaria was also
definitely suggested by Laveran on the analogy of the develop-
ment of filarial embryos in the mosquito (1884). But it was
Manson (1894) who more especially elaborated and emphasized
the probability of mosquito transmission, and who by his
remarkable deductions, based on the behaviour of the flagellate
bodies, led directly to Ross's efforts to demonstrate this rela-
tion experimentally.

But none of these hypotheses, not even Manson's carefully
thought out deductions, anticipated the mosquito cycle as we
now know it, as a result of Ross's brilliant research, in all its
beautiful simplicity. According to Manson it was the flagella
breaking away from the parasite that underwent development
in the mosquito, and it was by the medium of water in which
the mosquito eventually died that it was supposed re-infection
of man took place. Ross's discovery of the cycle of develop-
ment of Proteosoma shewed that it was the whole parasite
which underwent development, and that re-infection did not
take place through water, but that the parasites underwent
growth and multiplication in the body of the mosquito, eventu-
ally rinding their way to the salivary glands, to be injected
with the salivary secretion when the mosquito next fed. The
significance of flagellation was almost coincidently shewn by
MacCallum, who observed in Hcemoproteus (= Halteridium),
another parasite of birds, the fertilization of the female form,
or macrogamete, by the flagella, or microgametes, liberated
from the microgametocyte, or male form, of the parasite.

The discovery of the life-cycle of Proteosoma, and the fact
that the protozoa, like the parasitic worms, might exhibit
melaxeny, or the utilization of two or more hosts in their
development, gave the clue to the method of transmission of
human malaria, and the mosquito cycle of the malarial para-
site, as worked out by Grassi and others, was found to
follow almost exactly the development previously noted by
Ross in the case of Proteosoma. But whereas the parasite of
birds underwent development only in mosquitoes of the genus
Culex (C. fatigans), that of man required those of the genus

IX] HISTORICAL 123

Anopheles. {A. maculipennis and an Anopheles in which Ross
had already seen zygote stages of the malarial parasite in India.)

Observations and experiments in Rome shewed that the
occurrence of Anopheline mosquitoes was especially charac-
teristic of malarious localities, and still more important that
patients contracted the disease when exposed to the bites of
Anopheles brought from notoriously malarious districts, or
those which had been previously fed on malarious subjects.
A final proof was the classical experiment of Manson, in which
Anopheles infected in Italy were allowed to feed upon two
volunteers in England, both of whom as a result contracted
malaria.

This discovery, one of the most remarkable in the history
of medicine, was so opposed to popular ideas of the way in
which malaria was contracted, that for a time there were some
who doubted whether the simple explanation given by Ross's
experiments could explain all the facts regarding malaria
transmission. Especially the idea that malaria was supposed
to be contracted in remote and uninhabited swamps led to the
frequently expressed suggestion that there might be channels
of infection other than the mosquito, and a good deal was made
of certain bodies found by Ross within the parasitic cysts, and
called by him " black spores," as shewing that there might be
a cycle of development over and above that already known.
In order to explain the deadliness of tropical swamps and
jungles, others suggested that Anopheles obtained infection by
hereditary transmission from mosquito to mosquito, or from
the blood of bats or other wild animals. " Black spor
however, are now known to be a species of Nosema attack
the mosquito independently of malarial infection, whilst it is
now generally recognized that, contrary to current belief,
remote jungles and swamps in themselves are harmless, in the
absence of human inhabitants to yield infection. Neither
hereditary infection of mosquitoes nor their infection from wild
animals is now considered probable, and the view universally
held at the present time is that malaria is an infectious dis<
passing from man to man, but requiring for this purpose the
presence of an intermediary transmitting host, the mosquil

124 HISTORY OF MALARIA [CH.

This view, that malaria is a disease transmitted by Anopheles,
but essentially of an infectious nature depending on pre-existing
human infection for its origin, may be said to be that upon
which all present day conceptions regarding the epidemiology
and prevention of malaria are based. Such a conception of
malaria is of course entirely opposed to the older notions of
a " telluric " disease, and as a result the whole method of
approaching malaria problems has so changed that writers
sometimes refer to researches they may have conducted as
being directed from the New ^Etiological Standpoint.

But though all the more modern work upon malaria has
been based upon the discovery of the mosquito cycle; yet it
would be a mistake to suppose that no considerable advance
in the knowledge of malaria has been made since this great
discovery. Not only has there been a vast accumulation of
knowledge regarding the circumstances connected with malaria
in almost all parts of the world, but even in some cases a distinct
modification, or rather expansion, of original conceptions of the
disease has resulted. Thus the idea of malaria as an infectious
disease requiring some previous case of fever from which infec-
tion was to be derived, has been modified, at least as far as
tropical countries are concerned, and brought more into touch
with the old telluric views by the discovery of the almost
ubiquitous latent infection of native indigenous races and of
the part played by native communities as " reservoirs of
infection." Equally important have been the striking advances
in the conception of the part played by economic influences in
determining the degree of prevalence of malaria, for as stated
by Celli it is not merely malaria parasite + Anopheles + man
which determines the prevalence of malaria, especially the
prevalence of this disease in epidemic form, but the formula
malaria parasite 4- Anopheles 4- man + X. It is in fact the com-
plicated factors involved in this unknown X with which the
most recent investigations on malaria have been mainly con-
cerned, and the complete elucidation of Celli's formula will
constitute still another step of no mean importance in the history
of malarial research.

Again, with regard to advances in connection with

IX] LIFE-CYCLE OF MALARIAL PARASITE 125

preventive measures directed against malaria, there has not only
been a great increase of practical experience of such action
under particular circumstances, but methods of combating the
disease have sometimes become possible which at first sight
were not self-evident. As examples may be mentioned the
important method of dealing with malaria known as Segregation,
now largely employed in Tropical Africa, and the no less remark-
able development of prophylaxis as recently applied among
British troops in India, where malaria has been combated not
only by direct, but by a host of indirect and often extremely
ingenious devices.

Life-cycle of the Malaria Parasite in Man and in
the Mosquito.

Like many other parasitic Protozoa, the malarial parasite
has two periods of multiplication in its life-cycle, one in which
it multiplies and over-runs its mammalian host, the other in
which, to ensure its eventual translation to a fresh host, it
multiplies in the body of the mosquito. The first period of
multiplication in the blood of man, since it occurs independent ly
of any fusion of male and female elements (syngamy) , is known
as the asexual, or, from the fact that multiplication goes on
by a process of schizogony , the schizogonous cycle. The period
of multiplication, which starts with the entry of blood contain-
ing suitable forms of the parasite into the stomach of the
mosquito, is dependent on the fertilization of the female element
(macrogamete) by a male element (tnicrogamete) and is known
as the sexual or sporogonous cycle, sporogony being the term
applied to the analogous part of the life-cycle in other Sporoz

The schizogonous cycle can be repeated, as far as is known,
an indefinite number of times, and apparently without the inter-
vention of any sexual process may keep up a condition of
infection of the host lasting for several years. Sporogony, on
the other hand, occurs but once, with the formation of a •
number of the forms known as sporozoites, which, after accumu-
lating in the salivary glands of the mosquito, remain without
further development until introduced into the bl< .in.

126 LIFE-CYCLE OF MALARIAL PARASITE [CH.

Schizogony occurs only in man, and the schizont forms, if
ingested by the mosquito, are simply digested. But whilst
the greater part of the sporogonous cycle takes place in the
mosquito, the early stages, as far as the formation of the sexual
forms is concerned, takes place in the blood of man. Thus in
the blood of a malarious patient both asexual and sexual forms
may be seen ; the former are those concerned in the production
of fever and the clinical effects of malaria generally, the latter
are of importance only if they are taken up by a suitable
mosquito.

Although three species of Plasmodium occur in man and
give rise each to a distinct type of fever, their methods of
development and multiplication are essentially the same.

Asexual cycle. — Schizogony. We will commence with a
description of the parasite as it is introduced into the blood
by the bite of an infected mosquito. At this stage it consists
of a small sickle-shaped body, about 10-20/x in length by 1-2^
in diameter. It is known as the sporozoite, and large numbers
of these are extruded with the salivary secretion of an infected
mosquito, as may be seen by allowing the insect to feed on a
drop of glycerine on a slide. The sporozoite consists of a
central nucleus surrounded by a uniformly staining elongate
mass of cytoplasm. It is pointed at both ends, and by
means of flexion is capable of progressive movements in the
blood plasma. After being introduced into the blood of a
human being three possibilities are open to these sporozoites.
They may be killed in the body and thus produce no infection ;
they may remain latent in the spleen or some other internal
organ until a favourable opportunity to develop presents itself ;
and lastly, they may proceed at once to develop and give rise
to the characteristic fever after a certain incubation period.

The sporozoite begins to develop by first boring into a red
blood corpuscle and thus becoming an intracellular parasite.
Once it has entered the red cell it assumes a rounded amoeboid
form, which is known as the trophozoite.

The young trophozoite is actively amoeboid, giving off
pseudopodia and absorbing nourishment from the contents of
the red cell. At first it consists of a uniform mass of cytoplasm

IX] LIFE-CYCLE OF MALARIAL PARASITE 1 27

containing a single nucleus, but soon a " vacuole " appears in
the parasite, causing it to assume a ring form (Fig. 40, 1).

As the parasite grows it feeds on the substance of the red
corpuscle, and gradually destroys the whole cell, but during
this process certain waste products are formed, one of which
is deposited within the cytoplasm of the growing trophozoite
in the form of pigment granules. These granules are composed
of a brown or black substance allied to melanin, to which the
name " haemozoin " is sometimes applied. This substance is
chiefly the result of the decomposition of the haemoglobin, and
has very pronounced physiological properties, being mainly
responsible for the febrile attacks that occur in patients suffer-
ing from malaria.

The trophozoite grows until it reaches a certain size — about
three-quarters the diameter of the red cell — when it becomes
rounded off and withdraws all pseudopodia. The full grown
trophozoite is then known as the schizont, and consists of a
rounded mass of cytoplasm containing numerous pigment
granules and a nucleus situated to one side of the centre. This
nucleus now begins to divide, according to the species of Plas-
modium, into 6 to 20 smaller nuclei (Fig. 40, 5), which become
arranged around the periphery of the parasite. Each of the
nuclei then becomes surrounded by a mass of cytoplasm which
separates off from the remainder, and thus a number of small
parasites are formed. These are known as the merozoites and
are usually ovoid bodies, about 2/j. by i/x, each containing
single nucleus. In the above-described process a certain
amount of cytoplasm, containing all the pigment granules,
is left unsegmented at the centre of the cell. After segmen-
tation is complete the wall of the red cell bursts and the mi
zoites, together with the residual protoplasm and pigment
granules, escape into the blood stream.

Many of the merozoites are now ingested by the leu
but a certain number escape and at once proceed to attack other
red cells. Unlike the sporozoite, the merozoite does Dot
directly bore its way into the red cell, but usually becomes
attached to the surface of the cell.

Very soon after the young parasite has attached ttseti

128 LIFE-CYCLE OF MALARIAL PARASITE [CH.

cytoplasm becomes spread out and exhibits a characteristic,
comparatively large, clear, central vacuole, the effect of which
is to give the parasite the appearance of a ring, such ring
forms occurring in the early stages of development of all three
forms of the parasite. In fresh preparations these ring forms
can be seen to possess on one part of their circumference a
swelling like the stone of a signet ring which is the nucleus,
and to extrude small pseudopodial processes, which in some
forms are very long and slender, in others more lobose. In
specimens stained by the Romanowsky method the nuclear
portion is conspicuous as a bright red mass, whilst lying around
the vacuole is a thin crescentic portion of delicate blue-staining
cytoplasm.

Many of the ring forms, especially in the case of the malig-
nant tertian parasite, remain for some time attached to the
surface of the red blood corpuscle, such forms being termed
accole or attached parasites. Eventually in all species the
parasite sinks into the substance of the cell.

The subsequent development is identical with that pre-
viously described, the termination of which is the formation
of a schizont and the subsequent liberation of a number of
merozoites into the blood stream. This cycle may be repeated
any number of times until a large proportion of the red cells
is infected.

The asexual method of multiplication in the blood of the
vertebrate host is characteristic of all species of Plasmodium.
By this means the infection is carried from one cell to another
within the vertebrate host, and very rapidly millions of the
blood corpuscles become infected. The destruction of the
blood cells thus entailed rapidly produces anaemia in the affected
patient, but much more harm is done by the waste products of
the parasites. These consist of the pigment granules and
various other products of metabolism which are left behind in
the residual protoplasm when schizogony occurs. As they
can only escape into the blood stream when the red cell
bursts, these various toxic waste products are liberated together
with the merozoites, and as most of the infected corpuscles
rupture about the same time, the effect of the accumulated

IX] LIFE-CYCLE OF MALARIAL PARASITE 120,

products is so considerable as to produce an attack of fever
in the patient. The febrile attacks only occur when schizogony
is taking place and the merozoites are being liberated into the
blood stream. The interval between the attacks indica1
therefore, the time taken by the parasite to develop from the
merozoite through the trophozoite stages up to the schizont;
and to subdivide into a number of merozoites, or, in other
words, to pass through the complete asexual cycle. It has been
found that the time taken for the completion of this cycle
varies in different species of Plasmodium, being 72 hours in the
case of P. malaria, 48 hours in P. vivax, and from 24 to 48 hours
in P. falciparum. Hence the fevers caused by each of these
parasites differ from one another by the intervals elapsing
between the febrile attacks. The full description of these
species, together with their distinguishing characteristics, is
described below (vide p. 155).

In these few words we have briefly described the asexual
cycle of development that takes place in the vertebrate host,
but, as will be obvious, the only method by which the meroz< >i
could infect another host would be by the inoculation of blood
containing them. This method of transmission is successful,
for if blood containing malarial parasites is inoculated into a
normal human being, the latter becomes infected with malaria.
However, such a mode of transmission probably never occurs
in nature, for the merozoites are incapable of withstanding
desiccation, or any other of the vicissitudes to which they
would be exposed on the proboscis of a biting arthropod, the
only conceivable agent for such direct transmission. Con-
sequently, in addition to its asexual multiplication, which
merely serves to increase its numbers in the infected individual,
it is necessary for the parasite to possess some mean- oi being
carried from one host to another. We shall see that provision
is made for this transmission, but first it is necessary to describe
another development that the young trophozoite may und< i
in the red cell.

Development of the sexual forms in the blood. About a week
after a patient becomes infected with malaria certain lai
intracorpuscular forms may be observed that do not go through

H. B. F.

12a

£13 a

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Fig. 40. Diagrammatic representation of the life-cycle of the malarial parasite
of pernicious malaria. 1-6. The schizogonous cycle shewing successive
stages in growth from the young ring form (1) up to the fully-grown
parasite (4) in which tlie nucleus has divided. 5 and 6. Division of the
body of the parasite to form the merozoites. 7. A single merozoite, which

CH. IX] LIFE-CYCLE OF MALARIAL PARASITE 131

is capable of entering another red cell and repeating the above-described
cycle. 8-1 1. Formation of the gametocytes ; these arise by growth of
merozoites and after reaching a certain size (10) develop into either male
or female gametocytes (11a and 116) ; in the male gametocyte (116) the
nucleus is larger and more scattered than in the female (11a).

12-16. Stages of the sexual generation in the stomach of the
mosquito. 12a, 13a and 14a. The formation of the female gamete. 126,
136 and 146. Stages in the formation of the male gametes. 15. Fertiliza-
tion, resulting in the formation of a zygote (16), which then becomes
motile and is known as the ookinete (17).

18-22. Stages in the sporogonous cycle in the mosquito. The
ookinete (17) bores into the stomach wall and forms a cyst (18) ; it
increases in size, its nucleus multiplies and eventually each nucleus
becomes surrounded by a mass of cytoplasm, forming a number of sporo-
blasts (19) ; each of these sporoblasts gives rise to numerous sporozoites
(20-21). The ripe sporocyst is represented in 21, and the escaping
sporozoites (22) enter the salivary gland of the mosquito and escaping
with the salivary secretion, enter the blood and are capable of repeating
the cycle.

the process of schizogony. These are the sexual forms, and
are of two kinds, male and female. It is probable that the
merozoites differentiate sexually at an early stage of the disease,
but what determines the sex is unknown.

In its earliest stages the young sexual form is indistinguish-
able from an ordinary trophozoite, but it grows extremely
slowly and never assumes the ring form.

As it grows its cytoplasm becomes filled with granules of
pigment and soon certain differences can be noticed in the
staining reactions of the protoplasm, resulting in the differentia-
tion of what are known as the macrogametocytes and micro-
gametocytes respectively. The former are destined to give
rise to the female gametes, and are characterized by the pos-
session of a small feebly-chromatic nucleus and a dense cyto-
plasm containing numerous granules and much pigment. The
microgametocytes, which give rise to the male gametes, haw
each a large densely chromatic nucleus extending across the
middle of the cell, and the cytoplasm is clearer and contains
less pigment.

When full grown, the sexual forms are larger than the red
cells which contain them ; consequently the latter are consider-
ably distorted by the parasite and form conspicuous objects
that were noticed long before their true nature was recognized.

9—2

I32 LIFE-CYCLE OF MALARIAL PARASITE [CH.

At this stage there are now three types oi parasites, viz.
the schizonts, macrogametocytes and microgametocytes, the
two latter belonging to the sexual and the former to the asexual
cycle.

The sexual cycle cannot be completed in the blood but
only in the internal organs of those species of mosquito which
transmit the infection. In the absence of these the micro-
gametocytes soon die off without any further development
taking place.

The macrogametocytes, on the other hand, are much more
resistant, and can remain in the body for very considerable
periods. These are the forms that are supposed to be respon-
sible for the cases of latent malaria, in which a patient may
remain in good health for some years and then suddenly develop
typical malaria without having been exposed to the possibility
of re-infection. In these cases it is the macrogametocytes that
have remained dormant in the body waiting for a convenient
opportunity to develop, such as that afforded by a chill or any
other diminution in the vitality of the patient. Under these
circumstances the macrogametocyte develops parthenogeneti-
cally. Its nucleus divides into two parts, one densely chromatic
and the other poor in chromatin. The pigment granules and
other waste products gather round the latter, and the whole
is divided off from the remaining protoplasm and constitutes
a sort of residuum similar to that left behind by the merozoites.
Th° remaining part of the macrogametocyte, now much
clearer by the loss of its pigment granules, divides up into a
number of merozoites in exactly the same way as an ordinary
schizont, and the merozoites escaping into the blood plasma
penetrate other red cells and thus start another cycle of
schizogony.

Sexual cycle. — Sporogony. As mentioned above the macro-
and microgametocytes only complete their development
in the internal organs of the mosquito that is responsible
for their transmission. When such a mosquito — in the
case of malaria only Anophelines — feeds on the blood of
a patient containing sexual forms, in addition to the
latter, it ingests many parasites belonging to the schizogonous

IX] LIFE:CYCLE OF MALARIAL PARASITE 133

cycle. All these are digested, the macro- and microgame-
tocytes being the only forms that are capable of re-
sisting the secretions in the stomach of the mosquito. Here
they undergo further development, the stimulus for which
is probably the reduction in temperature, combined with
the dilution of the blood that takes place in the gut of the
insect.

The macrogametocyte escapes from its red cell and becomes
spherical ; then its nucleus divides and one of the daughter-
nuclei, together with a small amount of cytoplasm, is extruded
as a polar body (Fig. 40, 14 a). After this maturation process
is complete the parasite is now ready for fertilization, and is
known as the female or macrogamete.

The microgametocyte undergoes a different kind of develop-
ment, for after becoming spherical and escaping from the red
corpuscle, its nucleus breaks up into a number of fragments,
sometimes known as chromidia, which travel outwards and
become arranged round the periphery of the cell. Part of the
nucleus remains behind at the centre as a residuum and is not
used up in the subsequent development. The surface of the
microgametocyte now grows out into a number of nagellum-like
processes into each of which passes one of the nuclear fragments.
These processes are highly motile, and by their lashing about
cause the parasite to resemble a flagellate. In consequence
the earlier observers referred these forms to the genus Polymitus,
and they are still often referred to by this name. Each of the
flagellum-like processes finally becomes free and swims away
as an independent organism. These are the male or micro-
gametes. The microgametocyte usually produces four to six
of these microgametes which in their formation use up the
protoplasm of the gametocyte, merely Leaving a residuum com-
posed of all the pigment granules, together with part of the
original nucleus and a small amount of cytoplasm. The
microgamete consists of an elongated filament with a slight
thickening about the middle of its length, caused by the nuclear
matter. It progresses by rapid wave-like movements and as it
is only about 0*5/1 in diameter, is extremely difficult to observe
in the living state.

134 LIFE-CYCLE OF MALARIAL PARASITE [CH.

Conjugation now takes place, one of the microgametes
boring its way into a macrogamete. This is followed by union
of the two nuclei, and the resulting structure is known as the
zygote. At first the zygote is spherical, but it soon elongates
into a small worm-like body which is actively motile, moving
about in much the same way as a gregarine. The zygote is
then known as the ookinete or, by some writers, the vermicide,
because of the character of its movements.

The whole of this process, including the formation of the
gametes and their union to form the ookinete, takes place in
the stomach (= hinder part of the mid-gut) of the mosquito,
and is completed within a comparatively short time. All the
above stages may be observed by placing a drop of blood con-
taining the gametocytes on a slide and slightly breathing on
it. If the preparation be now covered with a cover-glass and
examined under an oil-immersion lens, all the stages in the
evolution of the micro- and macrogametes, and their subse-
quent union to form the ookinete, maybe followed in the living
state.

The subsequent development of the ookinete can take place
only in the mosquito, and we shall proceed with the description
of the changes which it undergoes in this site.

After moving about for some time, the ookinete bores
through the epithelium of the gut-wall and comes to rest
between this layer and the tissues immediately surrounding
it. Here the parasite becomes rounded off and secretes a thin
cyst- wall. This form is known as the oocvst and is parasitic
upon the mosquito, for it grows considerably in size, absorbing
nourishment from the surrounding tissues. During its growth,
the gut-wall is bulged out towards the body-cavity, and conse-
quently at this stage the stomach of the infected mosquito
has a very characteristic appearance (Fig. 53). As many as
500 oocysts have been found in the stomach-wall of a single
infected Anopheles.

As the oocyst grows, its nucleus divides into a number of
daughter-nuclei, each of which becomes surrounded by a mass
of cytoplasm and gradually separated off from its neighbours.
These are known as the sporoblasts ; they are irregular in form

IX] LIFE-CYCLE OF MALARIAL PARASITE 135

and remain slightly connected together by means of cytoplasmic
processes. After the formation of the sporoblasts a certain
amount of protoplasm is left over, containing all the waste
products and also some of the pigment granules originally
present in the macrogamete.

The nucleus of each sporoblast now divides into a large
number of smaller ones which become arranged around the
periphery. The surface of the sporoblast then exhibits a number
of cytoplasmic projections, each of which increases in length
and takes with it a daughter-nucleus. Eventually the spindle-
shaped process, with its contained nucleus, becomes free from

Fig. 41. Photomicrograph of sporozoites of malaria from the salivary glands
of Anopheles (Pyretophnrus) costalis. x about 1000. After Hill and
Haydon.

the mother sporoblast, and is then known as the sporozoite.
Each sporoblast produces large numbers of these bodies, but
a certain amount of protoplasm containing waste products is
always left unused in their formation. The oocyst, which con-
tains the whole of the sporozoites derived from the many
sporoblasts, and by this time has increased enormously in size,
eventuallv bursts, and the sporozoites are set free in the body-
cavity of the mosquito. As the coelomiq fluid bathes all the
organs of the mosquito, the sporozoites are brought in contact
with all parts of the body. They appear to have a predilection
lor the salivary glands and the majority bore their way into

136 MOSQUITOES IN RELATION TO MALARIA |"CH.

these organs and may be seen filling the secretory cells and also
becoming free in the lumen. The sporozoites are now incapable
of further development in the mosquito, but if the latter feeds
on a human being, large numbers of them are introduced into
the wound together with the salivary secretion. They thus
enter the blood and there penetrate into the red blood corpuscles
and start the schizogonous cycle with which we commenced.

The whole of this process, from the differentiation of the
macro- and microgametocytes to the formation of the sporo-
zoites, is known as the sexual or sporogonous cycle, and is
completed in from ten to twelve days. Thus a mosquito that
has ingested blood containing the gametocytes does not become
infective until this incubation period has elapsed. Then its
salivary glands contain the sporozoites, and the insect probably
remains infective during the remainder of its life.

Bionomics of Mosquitoes in Relation to Malaria.

The habits of the particular species of mosquito concerned
in the transmission of malaria in any particular locality are of
the highest importance, and therefore, at the risk of repetition,
some of the more important features may be briefly mentioned.

The majority of Anophelines are more commonly associated
with village life, and are especially prevalent in more or less
uncultivated districts, and, unlike the Culicines, their breeding
habits are usually unsuitable for their persistence in towns.

With respect to this point, however, there are exceptions,
and it will be necessary to refer to the connection between the
habits of various species in relation to the spread of malaria.

At the time of the discovery of the mosquito cycle, only
some half-dozen species of Anopheles were known, most of
which are European species. There are now more than 100
well defined and accurately described species, as well as many
named varieties, and these taken collectively have a distribu-
tion which extends almost all over the globe. These species
differ not only in morphological details, but what is more
important from our present point of view, they vary greatly
in their habits and in their relation to malaria.

IX

MOSQUITOES AND MALARIA

137

Among habits affecting the conditions of malarial dissemina-
tion may be mentioned the predilection of particular species for
particular kinds of breeding place. Some species are essentially
stream breeders and are even adapted by their habits, and
probably to some extent by structure, to prevent themselves
being carried away by flood conditions. An example of a species

Fig. 42. Breeding places of Anophelines. Railway cutting at Kurunegala.
The water course flowing on each side of the permanent way supplying
the engines with water. These channels are blocked with weeds, from
amongst which larva? of A. ailicifacies and A. rossii have been taken.
After Bahr (from the Tropica! Diseases Bulletin).

having this habit is A. (Myzomyia) listoni [M. christopht
Theobald), which swarms in the streams of the sub-Himalayan
terai, and is largely responsible for the high prevalence of
malaria in these regions. Another example is A . (Nyssorhynchus)
willmori, a species which is very difficult to eradicate, because
of its power of breeding freely in the small streams of Malay

I38 MOSQUITOES AND MALARIA [CH.

Other species are pool-breeders, and some may even restrict
themselves, or be able to nourish only in some particular kind
of pool. Thus the numerical prevalence of the common Indian
species A. (Myzomyia) rossii is dependent usually on the occur-
rence of small freshly-filled shallow muddy ram-pools, such as are
formed in countless thousands during the Indian monsoon. In
the forests of South America a malaria-transmitting species, A.
(Myzomyia) lutzi, breeds in various pitcher-plants, and especially
in the cups of various epiphytic tree pines. An even more
remarkable choice of breeding place is seen in the Malayan
species A. (Lophoscelomyia) asiatica, which is found breeding
only in bamboos that have been perforated by a borer.

Over a large tract of the earth's surface, where mangrove
swamps and salt marshes are a feature of the sea coasts, the
species A . (Myzomyia) ludlowi breeds in brackish water, in pools
that are entered by the sea at spring tides. In the case of the
Andaman Islands, Christophers has recently shewn that this
species is the chief carrier of malaria, and as it is not found at a
greater distance than half-a-mile from the coast, is the cause
of a littoral distribution of malaria in these islands.

Another good example of the extent to which habits of
particular species in regard to the choice of breeding place may
affect the dissemination of malaria is seen in the case of the
very interesting A nopheles, A. (Nyssorhynchus) stephensi. This
species ordinarily is found in pools in large sandy river beds,
and has a predilection for quite small collections of water,
such as the hoof-marks made by cattle coming to drink, or
shallow surface wells made in the sand at the river margin.
It was found, however, by the Royal Societies Commission,
to possess, like Culicines, the power of breeding in water pots
and other domestic utensils, when these were filled with com-
paratively clean water. More recently this species has been
shewn by Liston and by Bentley to be the species concerned
in the spread of malaria in Bombay City, where the population
is as dense as in the heart of London, and under conditions where
no other species of this genus has been able to survive. It is
entirely due to the power of N. stephensi to breed in wells,
covered cisterns, and such like places, that it has been able to

IX]

MOSQUITOES AND MALARIA 139

to the genus as a whole,

establish itself in these novel and
quite unsuitable surroundings.

Apart from the differences in regard to the ability to flourish
in particular kinds of breeding places, are other habits which
sometimes influence very considerably the epidemiological
conditions under which malaria is spread. Thus many species of

Fig. 43. Flooded Paddy Fields in Ceylon. The picture shews in the fore-
ground the pools formed by the hoof-marks of cattle ; in these Anophelines
breed. After Bahr (from the Tropical Diseases Bulletin).

Anopheles are naturally little addicted to entering or remaining
in human habitations, and in nature are not found particu-
larly associated with man. Other species readily take up a
life of dependence on man and utilize his dwellings as shelter.
It is to this latter class that the more important malaria earners
belong. Again, under ordinary circumstances, some spe
are entirely nocturnal in their habits, whilst ethers bite freely

140

MOSQUITOES AND MALARIA

[CH,

on cloudy moist days, and others again may have actively diurnal
habits and feed by day like Stegomyia. An example of the
latter habit is seen in the species A. (Myzorhynchus) barbirostris,
which swarms in the forests of Malay and is most bloodthirsty
throughout the daytime. Another diurnal species is Anopheles
aitkeni. Even the boldness and persistence, or even the small
size of particular species, may add greatly to their effect in
transmitting malaria under particular circumstances.

But in addition to these differences in habits which indirectly
affect the transmission of malaria, there is the very important
question of the relative suitability of different species of Ano-
pheles for the development of the parasite. When it was shewn
that certain species of Anopheles carried malaria and that
Culex and other biting insects did not, it was assumed that
the power to act as a suitable host to the malaria parasite was
common to all Anophelines. The first instance of an Anopheles
being shewn not to transmit malaria was in the case of the
common Indian species A. (Myzomyia) rossii. This species is
found quite commonly in very large numbers associated with
every degree of prevalence of malaria, but it has not yet
been shewn to act as a transmitting agent under natural
conditions, though it can be infected experimentally. Not
infrequently this species occurs along with others which are
actively concerned in the spread of malaria, but though under
these circumstances a considerable percentage of both A. (Myzo-
myia) culicifacies and A. (Nyssorhynchus) stephensi have been
found with sporozoites in the salivary glands, A. (Myzomyia)
rossii has never been found infected. This peculiar fact, re-
garding which the following independent figures have been
given, is not easy to explain, but there seems little doubt that

Stephens and Christophers

Lahore (Punjab)

Ennur (Madras)
Bentley

Bombay

M. culicifacies

6%
6%

N. stephensi

3*5 7c

Myzomyia
rossii

IX] MOSQUITOES AND MALARIA 141

for some reason, A. rossii is not an active transmitter of
malaria, if it transmits at all, under natural conditions.

Another species not suitable as a carrier, and which in this
case was refractory even to experimental infection, is the
North American species Anopheles punctipennis. In this case
A. maculipennis and A. punctipennis were fed together on an
infected patient ; the former became infected whilst the latter
remained free from infection.

The development of the three species of malarial parasites
does not take place with the same facility in any given species of
mosquito. Thus Kinoshita found that in Formosa, Plasmodium
falciparum was incapable of development within A. (Myzo-
rhynchus) sinensis, whilst this species of mosquito could easily
be infected with Plasmodium vivax (seven times out of eleven)
and less easily with Plasmodium malarice (one in seven). In
the same region A. (Myzomyia) Christopher si almost invariably
became infected when fed on a patient containing the gametes
of P. falciparum in his blood.

Other species have also been noted as probably not taking
an active part in malaria transmission or to be actually refrac-
tory to experimental infection with the malaria parasite.

But though some species are possibly incapable of acting as
hosts, and whilst some are more suitable hosts than others, there
is reason to believe that very many of the species are at least
potential transmitters. Thus in India, Stephens and Christo-
phers succeeded in experimentally infecting all but one species
out of a considerable variety of Anophelines. Similarly.
Darling at Panama has produced infection in many of the
Anophelines of that region.

The most important point in regard to the transmitting
power of a species is the extent to which it is found actively
concerned in transmission under natural conditions. In this
respect there are certain species which must be looked upon as
the chief carriers in particular parts of the world.

In Europe the common carrier is Anopheles maculipennis,
but the common species, Anopheles bi fur coins, is also capable
of transmitting malaria. A. maculipennis is the common
carrier in the Mediterranean islands and is largely concerned

I42 MOSQUITOES AXD MALARIA [CH.

in the spread of malaria in Algeria and Palestine. It is also
the chief agent in North America.

In Algeria, besides A. macidipennis, the species incriminated
are : Anopheles algeriensis (Ed. and Et. Sergent, 1905), especi-
ally occurring in the coast regions; A. hispaniola (Sergents,
1905), found chiefly in the hilly broken country; A. (Pyreto-
phorus) myzomyfacies (Ed. Sergent) ; A. (P.) superpictus and
A. (P.) chaudoyei. A. chaudoyei is capable of breeding freely
in saline waters and is the species chiefly concerned in malarial
transmission in the Saharan oases.

In Egypt, A. (Cellia) pharoensis is a proved and important
carrier.

Anopheles funesta and A. costalis have both been shewn by
Ross to transmit the infection, and are the most important
and widely distributed carriers of malaria in Tropical Africa.

In India, Stephens and Christophers shewed that A. (My-
zomyia) listoni is a very actively transmitting agent in the Duars
or terai country at the foot of the Eastern Himalayas. A more
general, and perhaps the commonest Indian transmitter is A.
(Myzomyia) culicifacies. A. fuliginosus Giles has also been
shewn to transmit the disease, but apparently is not a very
important carrier. A. maculipalpis has been found infected
in nature in various parts of India. Amongst the most impor-
tant and active Indian carriers are A. (Nyssorhynchus) stephensi
and A. (N.) willmori.

In Malay, in addition to M. listoni, the proved carriers in
nature are A. (Myzomyia) albirostris, A. (Myzomyia) ludlowi,
and A. (Nyssorhynchus) willmori.

In Central America a number of species are active carriers,
the most important being A. (Cellia) argyrotarsis and A. (C.)
albimana.

In addition there are numbers of species very probably
concerned in malaria transmission, perhaps even important
carriers in particular parts of the world, e.g. A . formosaensis in
the island of Formosa ; A. arabiensis in the Aden hinterland;
A. (Myzomyia) lutzi in the forests of Brazil; and A. (Nys-
sorhynchus) annulipes in Formosa, Australia, etc.

IX] MOSQUITOES AND MALARIA 143

Influences affecting Malaria through the Transmitting Host.

The most powerful influences affecting Anopheles are tem-
perature, rainfall and humidity. Added to these must be
considered the physical characters of the country under con-
sideration, the nature of the soil, the prevalence of natural
enemies, and even the races of mankind inhabiting the countries.

With regard to physical conditions, generally hot moist
climates are suitable, cold and also excessively dry climates
unsuitable, to the development of Anopheles. In this respect,
however, the question of species and even of special adaptive
habits becomes important.

Temperature plays a double role. If low it not only delays
or prevents the propagation of Anopheles, but it even more
actively interferes with the development of the parasite within
the mosquito. A perennial low temperature may altogether
prevent the propagation of the parasites, for it is found that the
gametocytes cannot develop below a temperature of about
15° C. As a result, one can trace northern and southern limits
to the occurrence of malaria, corresponding to the mean sum-
mer isotherm of 150 to 160 C. Moreover, the different species
of malaria require different degrees of warmth in order to ensure
their development. Thus Plasmodium malaria develops best
at comparatively low temperatures, and consequently is found
in much colder regions than the other two species. On the
other hand P. falciparum will only develop at comparatively
high temperatures, and therefore in temperate regions it only
occurs during the summer and autumn months, whilst
throughout the tropics it is prevalent the whole year round.
Plasmodium vivax occupies a somewhat intermediate position,
for it is capable of development throughout a wide range of
temperature and, as one would expect, this species is the
most widely distributed, occurring in both tropical and tem-
perate regions. A perennial low temperature within limits,
however, does not prevent the propagation of certain specie 5
Anopheles, e.g. A. bifurcaius reaches a particularly large size
in the north of Scot land. Still less does a temporary or

SOnaJ period of low temperature destroy or permanently

144 MOSQUITOES AND MALARIA [CH.

affect the prevalence of Anopheles, such periods being tided
over by " hibernation." It is thus easy to see how, as regards
the northern and southern limits of malaria, we may have
these fairly corresponding with the limits of the distribution
of Anopheles, and to understand how, even apart from any
other reason, a considerable altitude may be associated with
a freedom from malaria, even though Anopheles are still found.

Rainfall, up to a certain point, is very favourable to Ano-
pheles, but if excessive it may have an adverse effect by washing
away the larvae and destroying them. Humidity would seem
to be entirelv a favourable circumstance, and has been shewn
to affect favourably the development of the malarial parasite
within the mosquito.

The nature of the soil may affect conditions as regards
Anopheles, not only by its power to retain surface water or to
allow of the formation of springs, but often by reason of its
chemical nature ; surface waters in some soils readily develop
a ferruginous scum or other conditions, unsuitable to the
development of mosquitoes.

The occurrence of natural enemies, especially circumstances
which favour the general presence in surface waters of small
fish, is a most powerful influence checking the multiplication
of A nopheles. Under conditions of alternate rainfall and drought
many pools utilized by Anopheles are of too temporary a nature
for the presence of fish, or even of other natural enemies, such
as various predaceous insect larvae. On the contrary, in very
moist countries, even the smaller pools are usually stocked
with fish and other predaceous animals. There may thus often
be a very fortunate regulating mechanism which may com-
pletely reverse the normal order of affairs and make Anopheles
comparatively scarce under conditions that at first sight might
appear wholly favourable.

Besides being open to attack by fish and various predaceous
aquatic insects, .4 nopheles are frequently the victims of parasites.
Among such may be mentioned acarid ectoparasites, an encysted
trematode, nematodes, gregarines, flagellates of the genus
Leptomonas, and at least one species of Nosetna. They are also
liable to invasion by certain fungi.

IX] MALARIA IN RELATION TO MAN 145

The part played by Anopheles in the transmission of malaria
is often distinctly modified by the method of life and customs
of man. Thus the type of dwelling may be such as to minimize
the chances of Anopheles obtaining human blood or, on the other
hand, to greatly favour such a chance. Thus, the introduction
of glass windows into English houses may well have hastened
the disappearance of malaria from this country. Again,
communities, by housing cattle or other domestic animals,
often favour the occurrence of Anopheles, whilst the amount of
clothing worn and special modes of livelihood, may similarly
affect the prevalence of malaria.

Malaria in Relation to Man.

So long as man was supposed to be the victim of animal-
culae, that before entering his body lived a free life in marsh
water, etc., the part man himself played in the continuance and
preservation of the parasite was not considered. But as we
now understand the rationale of malaria transmission, it is
evident that man, no less than the mosquito, is essential to the
continued life of the parasite, and the nature of man's influence
as a host is at least equal in importance to those circumstances
we have discussed in the previous section.

It will be evident from what has already been said that it
is man and not the mosquito which forms the chief reservoir
of infection. A man once infected, even though no longer
exposed to re-infection, may harbour the parasite for years.

So long as he does so, and is liable to relapses with the
formation of gametes, such a man is capable of infecting mos-
quitoes and of restarting active transmission of the disease.
The ability to maintain a prolonged state of infection in man
is therefore a very valuable asset to the parasite, and all con-
ditions which favour or are adverse to a maintenance of the
parasite in the blood of man are of epidemiological importance.
Similarly, the amount of infection passed on to the mosquito
has been shewn to be an important matter, a mosquito which
has taken in blood containing many gametes being capable
of giving rise to a much more severe in feet ion than one which

H. B. 1 IO

I46 MALARIA IN RELATION TO MAN [CH.

has taken in but a few parasites. Thus questions of suscepti-
bility and immunity, whether natural or acquired, or due to
the use of drugs, have to be considered. Also the condition
of nutrition of the members of a community, and its effect
on the natural resistance of the human organism against the
parasite, and the extent to which influences favourable to
relapses prevail, are all factors in the epidemiology of malaria.

Susceptibility to malaria may be evidenced either by in-
creased liability to infection, or by the degree to which toleration
of the presence of the parasite exists. In the case of primitive
and aboriginal races there is evidence to shew that apart from
any possible lessened liability to infection, there is often a greater
degree of toleration than is exhibited, for example, in Europeans.
A real immunity with a lessened liability to infection is also
undoubtedly developed in those persons long exposed to
malarial infection. When in any race toleration and immunity
are well marked, a considerable degree of malaria may occur
in a latent form. In such cases susceptible strangers suffer
far more than the native residents.

The importance of the part played by susceptibility and
immunity in malaria was demonstrated by Koch at Stephansort
in New Guinea, where, at the time his observations were made,
malaria was very prevalent. Koch was able to shew that after
a batch of Chinese immigrant coolies, who formed a large portion
of the population, had been resident for some years in the
colony they suffered distinctly less from malaria than they did
on their first arrival, and that in the absence of fresh immigration,
malaria amongst the community, as a whole, shewed a steady
decline, but with each successive large immigration of new
coolies there was a marked recrudescence of the disease. These
observations of Koch establish a principle in malarial epide-
miology which may be termed the law of non-immune immi-
gration (Christophers and Bentley), and which applies to all
immigration of susceptible individuals into a malarial focus.

Where the number of strangers is small, the effect is chiefly
exhibited upon them, as in the case of Europeans residing in
Africa. Here, as shewn by Stephens and Christophers, the
whole epidemiological outlook as regards the European is

IXl MALARIA IN RELATION TO MAN 147

dominated by the presence of a more or less latent native
malaria.

Where the influx of strangers is comparatively very large,
the whole community is adversely affected, and under certain
circumstances the prevalence of malaria through a whole tract
of country may be greatly increased.

Since the new-born child is, in a sense, an immigrant, in
any community the young children are especially affected.
Where malarial infection is intense, but the population is stable
and possibly possesses a certain degree of racial tolerance, the
amount of infection is highest in the young children and at a
minimum in the adults. In this case the children go through
life more or less permanently infected and with a certain amount
of splenic enlargement. At about the age of puberty, they
cease to shew parasites in their blood, or to exhibit enlarge-
ment of the spleen.

W7here malaria is more or less seasonal in its occurrence,
or where there is any serious degree of immigration or shifting
of populations, the restriction of infection to children is less
marked. All grades of difference in this respect may be en-
countered, the usual rule being that strictly indigenous and
primitive tribes shew the greatest amount of tolerance, and
along with a high proportion of infection amongst children,
exhibit the greatest adult immunity from infection.

Recently much stress has been laid upon the influence of
economic factors in determining a high or a low degree of
malaria prevalence. Poverty stricken and squalidly living
communities in malarious countries usually exhibit a far
greater degree of malarial infection than do communities in a
condition of prosperity. Besides the "social " distribution of
malaria, very grave manifestations may be brought about at
least partly by conditions of general stress, such as the occur-
rence of famines or scarcity following failure of rainfall, especially
when this is followed by floods still further adding to the disl i
and supplying all the requisites for an active transmission of
the disease by Anopheline mosquitoes. Thus, in Denmark.
epidemics of great severity have frequently followed great
storms, which had led to extensive inundations associated

I48 PREVENTION OF MALARIA

CH.

with much hardship, and a similar condition has been described
in India, where, during exceptional monsoons, many large
rivers overflow their banks, causing extensive inundations.
Under such conditions malaria may prevail with such intensity
as to cause a mortality with which it is not usually associated,
and may equal or exceed the ravages of even bubonic plague.

Besides purely economic influences, the prevalence of
malaria is often greatly enhanced in a community, or even in
a population, by circumstances leading to unusual conditions
of labour, increased physical fatigue, exposure to the sun and
to rain. In such cases the mere production of relapses alone
may lead to a greatly increased prevalence of malaria, but where
Anopheles are present there is naturally associated with an
increased output of parasites an increased transmission of the
disease. Malaria may from such reasons be greatly increased
during certain seasons, e.g. the rainy season in the Canal Zone,
even though the number of Anopheles has not been increased.
An increase of malaria during the harvests is another familiar
example.

Where unusual exposure and hardship are associated with
inadequate food and general distress, the result is usually for
malaria to assert itself in a very grave form, even though the
conditions as regards Anopheles are not especially favourable.

The Prevention of Malaria.

Under present-day conceptions there can be no transmission
of malaria under any of the following conditions :

1. Absence of Anophelines, by which infection would be
conveyed.

2. Absence of infected persons in the community, from
whom infection could be obtained by the mosquitoes, even if
these were present.

3. The existence of adequate " protection " by means of
which either

(a) The healthy cannot be bitten.

(b) The infected cannot be bitten.

IX] OBLITERATION OF BREEDING PLACES 149

Preventive action therefore aims at bringing about more
or less perfectly one or more of these conditions. Theoretically
any one of the three, if completely realized, would suffice to
prevent any fresh transmission of malaria, and finally to ex-
terminate the disease. Unfortunately in practice it is usually
possible only very imperfectly to achieve the desired end in any
of these directions, and it becomes necessary to combine the
effects of as many methods as possible. Circumstances alone
can determine in any given case which line of action is most
called for, or what combination of methods is likely to be most
effective.

Under the first head come all measures which have as their
object the reduction in the number of Anophelines present.
Such action may be direct, as in the case of anti-mosquito
campaigns, or indirect as by the extension of agriculture, or
large drainage measures. Under the second head come various
methods of quinine prophylaxis, all agreeing in the use of
quinine as a destroyer of the parasite in the human host, but
differing a good deal in the immediate object arrived at. Under
this head also come certain measures applicable to mixed
communities as the " Removal or prophylactic treatment of
the reservoir of infection," " Segregation of the healthy," and
the avoidance by the individual of sources of infection generally.
Under the head of protection are included such measures as
the screening of dwellings and barracks, the use of suitable
protective clothing, and the use of the mosquito net.

1. Many methods of attacking Anopheles are now known,
the more important being :

The obliteration of breeding places. By minor drainage
measures, filling up pools or depressions with earth and, in
some cases, subsoil drainage, pools utilized by Anopheles for
breeding may be completely done away with. In cases where
it is difficult or impossible to carry out such action, breeding
places may be made less suitable by clearing out weeds, deepen-
ing, and perhaps even lining with masonry, the edges of large
sheets of water. Not infrequently the chief sources of An&phi
are to be found in connection with small streams, in which
training in some form or another should be performed. Where

sawwHsa'

Fig. 44. Indian fish of utility as mosquito-destroyers.
Chaudhuri (from the Tropical Diseases Bulletin).
A ( 3 ) and B ( 9 ). Lebias dispar (nat. size).
C. Nuria danrica (nat. size).

After Sewell and

CH. IXJ LARVICIDES I3I

wells are an important source of Anopheles they often require
special devices to prevent them being a source of danger whilst
allowing water to be obtained from them, and other breeding
places of a special nature may require special measures to deal
with them. On the whole the most important consideration
in such measures is that the action taken should be of as per-
manent a nature as possible.

The use of larvicides. Many substances have been experi-
mented with in respect to their lethal effect upon the larvae
of mosquitoes. The larvicide in most general use is some form
of kerosene or mixture containing this substance. The oil
floats on the surface of the water and thus interferes with the
respiration of the larvae and pupae. Certain aniline dyes, and
other chemical bodies which dissolve in the water, have very
powerful larvicidal properties, and their use has been suggested.
The chief difficulty with regard to ail larvicides is the temporary
nature of the effect they produce, and the necessity for regular
and periodical treatment of the breeding places attacked in
this way. Ordinarily such substances are now used only where
more permanent measures are not possible.

The introduction of natural enemies. So far the hope that
by the introduction of some natural enemy, the number of
Anopheles in a country could be at all affected, has not met
with much encouragement. Nevertheless, under certain cir-
cumstances, the use of suitable small fish has an application.
The most effective larvae-eating fish for the most part belong
to the family Cypriondontidce, but species of Anabas, Ophio-
cephalus and others are also of practical use in this respect.

Measures directed against the adult mosquito. The fumigation
of houses with burning sulphur, pyrethrum and other sub-
stances, has been found of use. In Panama the catching of
adult mosquitoes by children for a small reward is said to be
wry effective. Whitewashing and improvement in lighting
during the daytime may be called for sometimes.

The various measures briefly outlined above are but some
of the tools in the hand of the sanitarian, to be used as circum-
stances require them. Before they can be applied with suc>
it is almost always necessary for the conditions relating to

^s**^

Fig. 45. Indian fish of utility as mosquito-destroyers.
Chaudhuri (from the Tropical Diseases Bulletin).

A. Haplochilus panchax (nat. size).

B. Ambassis ranga (nat. size).

C. Trichogaster fasciatus (nat. size).

After Sewell and

CH. IX] QUININE PROPHYLAXIS 153

transmission to have been very thoroughly studied and the
whole area accurately and thoroughly surveyed.

Of measures indirectly affecting the prevalence of Anopheles,
the most important are " drainage " and " agriculture." The
drainage of marshes, lakes, etc. has long been known to have
a favourable effect upon malaria. Agricultural operation, by
which waste lands are reduced to the condition of tilled fields,
is another general measure having a very definite influence
upon malaria. Both these measures, though they do not aim
directly at mosquito reduction, bring about this result indirectly
by lowering the level of the subsoil water, lessening humidity
and so forth. A measure of this general kind, which may
assume importance under certain circumstances, is protection
against flooding. It has recently been shewn that some of
the worst manifestations of epidemic malaria follow in the wake
of floods, arising from the overflowing of rivers and swollen
mountain torrents. In such cases various engineering devices
may be important anti-malarial measures of this general kind.

2. Where preventive action against malaria takes the
form of attacking the parasite in the human host it usually
consists of some method of quinine prophylaxis. In the
method advocated by Koch an attempt is made to sterilize,
as far as the malarial parasite is concerned, the blood of every
member of the community by systematically searching out
and treating every infected person. The method to which the
term quinine prophylaxis is generally applied, is one in
which as many of the community as possible are persuaded to
take quinine regularly and systematically. Where large and
at the same time poor and ignorant populations are concerned,
it has generally been found impossible to apply either of the
above measures sufficiently thoroughly to be effective, and it
is now recognized that under these circumstances the greatest
benefits are obtained by treating the sick and encouraging in
every way the use of quinine in its curative rather than its
prophylactic capacity. This method is usually designated
quinine treatment of the sick. Though directed especially
to the saving of life, it has been found also to have a general
influence upon malaria.

154 SEGREGATION [CH.

In addition to this direct action of quinine upon the source
of infection in man, there are a number of indirect methods of
reducing the sources of infection.

3. (a) Very often where mixed communities are con-
cerned, it may be desirable to protect especially the more
susceptible class of individuals. When possible this is brought
about by some form of segregation. Where the reservoir of
virus is small in comparison with the community of susceptibles,
as frequently happens in Algerian stations, segregation takes
the form of removal of the indigenous community to a short
distance from the station. Where the number of the suscep-
tible persons is small in comparison with the reservoir, as is
usual in the case of Europeans in Africa, it is advisable to build
quarters for this community at some distance from the native
settlement. In some cases it may be desirable to undertake
measures against malaria in a small community acting as a
" reservoir," not so much for the direct effect upon this com-
munity, as for the indirect effect upon the larger susceptible
community surrounding it. In this way, the actual application
of segregation may vary, though the principle remains the
same.

Still another indirect method of diminishing the amount
of human infection, and thus reducing the activity of malaria
transmission, is the protection of a community from influences
likely to bring about repeated relapses. For example, among
labourers or convicts, or even among agricultural people, any
amelioration of the conditions under which they are living may
be looked upon as an anti-malarial measure coming under this
head.

(b) Protection against the bites of Anopheles by the
screening of dwellings with wire gauze, etc. is a measure which
has been found especially valuable in Panama and elsewhere.
The protection brought about by the habitual and careful use
of a mosquito net is perhaps the most effective measure of
private prophylaxis known against malaria, and with some
other minor precautions is quite sufficient to enable the educated
individual to enter the most malarious tracts unharmed. The
use of mosquito nets by the sick is a valuable prophylactic

IX] PLASMODIUM VIVAX 155

measure in hospitals, where in the absence ol any such pre-
caution the dissemination of malaria may result from the
bringing together of many cases of the disease.

Descriptions of the three Plasmodia causing Malaria.

I. Plasmodium vivax (Grassi and Feletti, 1890)
and Tertian Malaria.

Synonyms : Oscillaria malaria Laveran, 1881, pro parte.
Hcemosporidium tertianum Lewkowicz, 1887. Plasmodium
var. tertiana Golgi, 1889. Hcemamceba vivax Grassi and Feletti,

1890. Plasmodium malarice var. tertiance Celli and San Felice,

1891. Hcemamceba laverani var. tertiana Labbe, 1894. Plas-
modium malarice tertianum Labbe, 1899. Hcemamceba malarice
var. magna Laveran, 1900. Hcemamceba malarice var. tertiance
Laveran, 1901. Plasmodium tertiance Billet, 1904, pro parte.

Description. The young trophozoite appears in the red
blood corpuscles as a very actively amoeboid body about
1-2 tx in diameter. It is much more active than the other
two species of malarial parasites and it was because of this
feature that the specific name vivax was applied to it. The
young trophozoite very soon assumes the ring form, and by
means of its pseudopodia and the large amount of exposed
surface, it grows rapidly at the expense of the contents of the
red cell. The latter becomes pale and swollen, and on staining
with Giemsa its protoplasm presents certain degeneration
phenomena, taking the form of scattered red granules, known
as Schurrner's dots. The presence of these dots in the proto-
plasm of the infected red cells generally serves to distinguish
P. vivax from the other malarial parasites, but similar ap-
pearances occur in the red cells of dogs infected with Babe
(Piroplasma) cam's.

As the trophozoite grows, melanin is formed and deposited
in the form of fine rods scattered throughout the cytoplasm
of the parasite. The period of growth occupies about
hours, by which time the trophozoite almost fills the corpuscle,
the fully formed schizont being 8*5-10^ in diameter.

156 PLASMODIUM VIVAX [CH.

From the thirtieth to the forty-eighth hour the schizont
divides up into from 15 to 20 merozoites, or rarely as many as
24. The stages in this process have been described above,
but it may be well to repeat that all the melanin, together with
a certain amount of waste protoplasm is left unused. The
melanin granules are packed together in the form of one or two
conspicuous brown masses, usually situated at the middle of
the parasite.

The merozoites are somewhat irregularly arranged, often
in two concentric circles ; rosette forms, such as occur in
P. malaria and P. falciparum, are absent.

About the forty-eighth hour the wall of the red cell bursts
open and the contained merozoites together with the melanin
and other waste products are liberated in the serum. The
cycle of schizogony therefore occupies 48 hours, and in conse-
quence the febrile attacks recur after this interval.

In P. vivax the gametocytes are common in the peri-
pheral circulation as well as in the internal organs, and con-
sequently their development can be followed without much
difficulty. The macrogametocytes are large spherical bodies
about 12-16 ^ in diameter, and in addition to their size may
be distinguished from the schizonts by their denser protoplasm
and larger and more numerous melanin granules. The nucleus
is usually situated at the periphery and is an oval structure
containing numerous chromatinic granules. The microgameto-
cytes are similar in shape to the macrogametocytes, but are
much smaller (9-1 1 /n), and in addition maybe distinguished
from the latter by their large densely staining nucleus. In
addition, the cytoplasm is very much lighter and less granular.

Both the kinds of gametocytes originate from ordinary
merozoites, but during their development can be distinguished
from the schizonts by their much slower growth and absence of
active amoeboid and ring forms.

The development of P. vivax in the mosquito was first worked
out in Anopheles maculipennis, one of the common mosquitoes
of Europe, but many other species are known to transmit the
infection equally well. When ingested by the mosquito, the
development of the gametes will not take place below 160 C,

IX] LIFE-CYCLE 157

but the most favourable temperature is much higher (24-
30° C).

The microgametocyte gives rise to 4 to 8 microgametes,
and the macrogametocyte undergoes division of the nucleus
and extrusion of a polar body before becoming a macro-
gamete ready for fertilization. After this process has
taken place, the male and female pro-nuclei are said to remain
apart for some time before uniting to form the single nucleus
of the ookinete. At a temperature of 280 C. the latter has
penetrated the gut-wall and become an oocyst by the end of
about 40 hours after the mosquito's feed. At this stage the
oocyst is an almost transparent spherical body containing
thin brown strands of melanin, and is surrounded by a well-
defined wall. The nucleus has already commenced to divide
and several daughter-nuclei are scattered through the cyto-
plasm.

The following day the oocyst increases in size and the sporo-
blasts begin to separate off from each other. The melanin is
aggregated together into clumps lying between the sporoblasts.
On the fourth day the oocyst is now seen to contain well-defined
sporoblasts, each of which is covered by the growing sporo-
zoites. During the fourth and fifth days the oocyst still
continues to grow, attaining a diameter of about 50 /* and
projects outwards into the ccelom of the insect. The sporo-
zoites become completely formed and thus the oocyst is trans-
formed into a hollow sphere containing innumerable sporozoites
each about 14 p in diameter. About the seventh or eighth
day the cyst ruptures and the numerous sporozoites are liberated
into the ccelomic fluid. From here large numbers find their
way to the salivary glands, but some of them bore into the
developing eggs in the ovary. The fate of these latter is un-
known, for up to the present, beyond this fact, there is nothing
to support the view that the infection is transmitted to the
offspring of an infected mosquito.

The above cycle of sporogony is thus complete in about
eight days, under these favourable conditions of temperature,
and after the sporozoites have entered the salivary glands
the mosquito becomes infective. At lower temperatures the

158 PLASMODIUM MALARIiE [CH.

development is very much prolonged and consequently the
mosquito does not become infective until after a much longer
incubation period.

The length of time that a mosquito remains infected has
never yet been proved, but it is probably for the remainder of
its life.

Distribution. This species is widely distributed throughout
the world, occurring in most tropical and subtropical regions.
It also occurs somewhat scantily in Northern Europe below 6o°
north latitude.

As a result of successful mosquito campaigns and other
prophylactic measures the distribution of the disease is being
restricted, and it has been eradicated from some parts of the
world. Tertian fever or ague was formerly prevalent in Britain
and it is interesting to note that one or two isolated cases
of malaria in patients that had never left England have been
recorded within the present century. Consequently the con-
ditions for the transmission of the disease have not yet entirely
disappeared from this country.

II. Plasmodium malaria (Laveran, 1881) and Quartan Fever.

Synonyms : Oscillaria malaria Laveran, 1883. Plasmo-
dium var. quartana Golgi, 1890. Plasmodium malaria var.
quartance Celli and San Felice, 189 1. Hamamceba malaria
Grassi and Feletti, 1892. Hcemamceba laverani var. quartana
Labbe, 1894. Hcemosporidium quartana Lewkowicz, 1897.
Plasmodium malaria quartanum Labbe, 1899. Hamomonas
malaria Ross, 1900. Hamamceba malaria var. magna Laveran,
1900. H. malaria var. quartana Laveran, 1901. Plasmodium
golgii Sambon, 1902. Plasmodium quartana Billet, 1904.
Laverania malaria Jancso, 1905.

Description. The young trophozoite is somewhat smaller
than that of P. vivax, and also much less active. The pseudo-
podia are usually blunt, so that the parasite is rather com-
pact in appearance. The pigment is deposited in the form of
very coarse darkly-coloured granules, or rodlets, which are

IX] LIFE-CYCLE 1 59

commonly gathered at the periphery of the parasite. In contra-
distinction to the granules of the other species of malarial
parasites, those of P. malarice are non-motile. A vacuole
is formed, but is comparatively small and disappears during
the growth of the trophozoite. The presence of the parasite
in the red cell does not produce any evident changes in the cor-
puscle beyond a slight decrease in size and a darker colour.
The trophozoite takes about 60 hours to grow up into the
mature schizont, which is a somewhat angular body 6-7 /x in
diameter.

During the next 12 hours the nucleus of the schizont
divides up into 6-12 smaller ones, which become arranged
in a single circle at the periphery. Each becomes surrounded
by a mass of cytoplasm which separates off from its neighbours
and thus a regular circle of 6-12 merozoites is formed. The
pigment granules form a dark clump at the centre and as the
merozoites radiate from it, a very typical rosette appearance
is produced.

The merozoites (about 1*75 u in diameter) are now set free
by the rupture of the corpuscle and may enter another red cell
and repeat the cycle. More often, however, they seem to be
killed off by the phagocytes, and thus it is only rarely that this
parasite produces fatal effects in its host.

The whole of the above cycle takes place in the peripheral
blood, and occupies 72 hours.

Accordingly the fever which is caused by this parasite
occurs every fourth day (hence the name Quartan Fever
after the schizogony takes place.

In addition to the simple quartan fever in which the attacks
recur every fourth day, cases of double and triple quartan are
also met with. In double quartan fever the attacks recur
on the first, second, fourth, fifth, seventh, eighth days. etc.
This is merely a case of a double infection, and the parasites
being the descendants of two separate lots of sporozoites. are
at different stages of development. The first infection will
undergo schizogony on the fourth, seventh, tenth days. etc.
after the entry of the sporozoites, whilst if the second infection
occurs on the day following any of these attacks the latter

j6o PLASMODIUM FALCIPARUM [_CH-

parasites will complete their cycle of schizogony every 72 hours
from this date onwards, i.e. on the fifth, eighth, eleventh days, etc.
The result of such a double infection will be the occurrence of
febrile attacks on two successive days followed by an interval
of one day, and to this type of fever the term Double Quartan
is applied.

In the same way a patient may again become infected on
the only day on which schizogony is not taking place, and after
this last infection has developed will shew a rise in temperature
every day. This type of fever is known as Triple Quartan
Fever ; it may be distinguished from the other kinds of malaria
by the shape of the parasites.

III. Plasmodium falciparum (Welch, 1897) and Quotidian,
Malignant Tertian, or ^Estivo- Autumnal Malaria.

Synonyms : Oscillaria malarice Laveran, 1881, pro parte.
Hcemamceba prcecox Grassi and Feletti, 1890. Hcemamceba
malarice prcecox + H. malarice immaculatum Grassi and Feletti,
1890. Laverania malarice Grassi and Feletti, 1890. Plasmo-
dium malarice var. quotidiance Celli and San Felice, 1890.
Hcemosporidium undecimance Lewkowicz, 1892. H. sedeci-
mance Lewkowicz, 1892. H. vigesimotertiance Lewkowicz,
1892. Hcemamceba laverani Labbe, 1894. Hcematozoon falci-
parum Welch, 1897. Hcemamonas prcecox Ross, 1899. Plasmo-
dium malarice prcecox Labbe, 1899. Plasmodium prcecox
R. Blanchard, 1900. Hcemamceba malarice vTar. parva Laveran,
1900. Plasmodium immaculatum Schaudinn, 1902. Laverania
prcecox Xocard and Leclainche, 1903.

Description. This is the smallest of the three species of
Plasmodium affecting man, the fully developed schizont being
not more than about 5^ in diameter. The young sporozoite
is very small and, after penetrating a red cell, as a rule at once
assumes the ring form. The latter is characteristic in appear-
ance as the nucleus is always peripheral and the contours of
the ring are very dark and clear. The trophozoites have the
peculiarity of frequently appearing at the surface of the red cell.
They are distinguished from those of the other two species of

IX] LIFE-CYCLE l6l

malaria by their active amceboid movements. The tropho-
zoites grow rapidly and assume an oval form ; they contain a few
pigment granules which are small, irregular and only feebly
motile. During its growth the parasite causes an alteration
in the substance of the red cell, which in stained preparations
is seen to contain a number of granules known as Maurer's
dots. Otherwise the erythrocyte remains unaltered in ap-
pearance until the formation of the merozoites results in its
destruction.

The fully developed schizont is 4-5 to 5//, in diameter, and is
very rarely present in the peripheral circulation. It segments
into 8-10 or sometimes 15 merozoites, which may either be
arranged in the form of a rosette, or irregularly. The segmenta-
tion almost invariably takes place in the capillaries of the
internal organs, and when it is in process there is a tendency
for the red cells to cling together and also adhere to the wall of
the blood-vessel, thus causing obstruction of the circulation.

The whole cycle of schizogony takes from 24 to 48 hours
to be completed, and thus the febrile attacks are more or less
irregular, but often occur each day.

The gametocytes develop from the trophozoites in the usual
manner, but are distinguished from those of the other two
human species of Plasmodium by their crescentic form. The
macrogametocyte may be distinguished by the arrangement
of the pigment, which is usually concentrated in the neighbour-
hood of the compact nucleus, leaving the remainder of the
cytoplasm clear. In the microgametocyte the pigment is
irregularly scattered through the cytoplasm and the nucleus
is somewhat diffuse. Moreover the shape of the two kinds of
gametocytes is different, being long and thin in the case of the
former, and broad and somewhat rounded in the latter. The
remains of the distorted red cell may be seen surrounding the
" crescents," the haemoglobin often being concentrated in the
form of a small clump attached to the side of the parasite. The
dimensions of a fully grown macrogametocyte are about

12- X 4 .

These gametocytes are very conspicuous in the circulation
of patients suffering from P. falciparum, and under the name of

H. B. F. II

1 62 MALARIA [CH.

" crescents " were known for many years before their true
nature was discovered. On being taken into the gut of a sus-
ceptible species of mosquito, the gametocytes escape from the
red cells and give rise to the gametes. The macrogamete is
vermiform, whilst the microgametocyte becomes spherical
before giving rise to the microgametes. The cycle of develop-
ment in the mosquito at the most favourable temperature,
28-300 C, is complete within eight days. In this species
development cannot take place below 180 C, and consequently
it is only found in warm countries, the disease to which it gives
rise being often known as " Malaria Tropica." The develop-
ment of P. falciparum in the mosquito is more easily followed
than that of the other species of malarial parasites, for when a
mosquito is susceptible to this species, as in the case of
A. (Myzomyia) Christopher si, practically all the insects become
infected when fed on a patient suffering from this infection.

In consequence of the comparatively high temperature
required for the development of P. falciparum within the
mosquito, the disease does not occur in temperate regions
except during the summer. Usually associated with P. vivax,
it is found throughout the whole of the tropics, except in regions
like the Sahara, where mosquitoes are absent owing to the lack
of water.

LITERATURE.

The more important and accessible general treatises upon malaria,
and papers dealing with recent work upon epidemiology and preventive
measures against malaria.

fBahr, P. H. (1913)- Malaria in Kurunegala. Report Colonial Office.

April, 191 3.
fBentley (1910). Malaria in Bombay (Report). Govern. Central Press,

Bombay.
j-Celli (1901). Malaria according to the New Researches. Longmans,

Green & Co. London, 1901.
t Christophers. Malaria in the Punjab. Scientific Memoirs by Officers

of the San. and Med. Depart, of the Gov. of India, No. 46.

t Malaria in the Andamans. Ibid. No. 56.

Christy. Mosquitoes and Malaria. Good elementary account.
Craig (1909). The Malarial Fevers, H cemoglobinuric Fever and the Blood

Protozoa of Man.

t Works representative of the more recent lines of investigation on malaria.

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IX] LITERATURE 163

Darling (1910). Factors in the Transmission and Prevention of Malaria

in the Canal Zone. Annals Trop. Med. and Parasitology, iv. part 2.

Droderick (1909). A Practical Study of Malaria. Saunders & Co.

Philadelphia.
Grail and Marchoux (1910). TraiU de Pathologie Exotique. Bailliere

et fils. Paris.
Hirsh (1883). Handbook of Geographical and Historical Pathology.
New Sydenham Society. Vol. 1.
♦Laveran (1907). TraiU du Paludisme. Masson & Co. Paris.
Liihe (1906). Article on Blood Protozoa in Mense's Handbuch der

Tropenkrankheiten.
Mannaberg (1905). Malaria, in Nothnagel's Encyclopedia. English
edition.
fMathis and Leger (191 1). Recherches de Parasitologic et de Pathologie

humaines et animates au Tonkin. Masson & Co. Paris.
jRoss, R. (1909). Report on the Prevention of Malaria in Mauritius.
Waterlow and Sons. London.

f (191 1). The Prevention of Malaria. John Murray. London.

Ruge, R. (1903). Introduction to the Study of Malarial Diseases-
Rebman, London.
t (191 2). Malariaparasiten. In Kolle and Wassermann's Hand-
buch (a comparatively short but very complete account),
f Sergent, Ed. and Et. Campagne antipaludique en Algerie, etc. Annals
de I'Instit. Pasteur. Jan. 1903, Feb. and Mar. 1904, April and May
1906, Jan. 1907, May 1908, and Campagne antipaludique (Gov. gen.
de l'Algerie), 1908-10.
Stephens and Christophers (1907). The Practical Study of Malaria
(deals with technique, Malaria Survey, etc.).
t Watson (1910). Prevention of Malaria in the Federated Malay States.

University Press, Liverpool.
*Ziemann. In Mense's Handbuch, 1906.

Vide also :
■\Atti delta Soc. per gli studi delta Malaria. Annual volume. 1 899-1 908.
^Malaria. Vols. 1 and 11, now discontinued.
\Paludism. Nos. 1-5.
| Various articles in Ross's Prevention of Malaria.

The more important publications dealing with the question of
transmission of malarial parasites by particular species of Anopheles.

Adie (1903). A note on Anopheles fuliginosus and Sporozoites. Indian

Med. Gazette, xxxviii. p. 246.
Adie, Mrs (191 1). Ne. Willmori, a proved carrier in nature. Paludism,

No. 3.
Banks (1907). Experiments in Malarial Transmission by means of

M. ludlowi. Philippine Journal of Science, B. vol. 11. No. o, p. 513.

* Complete treatises dealing minutely with every side of the subject.
t Works representative of the more recent lines of investigation on malaria.

11 — 2

164 MALARIA [CH.

Bastianelli and Bignami (1899). AHi d. Soc. per gli studi d. Malaria, 1.

p. 28.
Bastianelli, Bignami and Grassi (1898). Atti d. R. Accad. dei Lincei,

vii. p. 313.
Bentley (191 1). Myzomyia rossi and Malaria. Paludism, No. 2.

(191 1). The Seasonal Malarial Infection of M. stephensi in

Bombay. Paludism, No. 2.

(19 1 2). Malaria in Bombay. Gov. Central Press, Bombay.

Billet (1903). Sur un Espece nouvelle d' Anopheles {A. chaudoyei) et sa

relation avec le paludisme a Touggart. C. R. Soc. Biol. lv. p. 565.
Christophers (1912). Malaria in the Andamans. Sci. Memoirs by

Officers of the San. and Med. Departs, of Gov. of India, No. 56.
Cruz (1910). Prophylaxis of Malaria in Central and Southern Brazil.

In Ross's Prevention of Malaria.
Daniels (1900). Development of Crescents in the small dark A nopheles

prevalent in British Central Africa. Reports to Mai. Com. of R. S.

Ser. V.
(1909). Mosquitoes in the Federated Malay States. Studies

from the Institute for Med. Research {Fed. Malay States), vol. in.
Darling (1909). Transmission of Malarial Fever in the Canal Zone by

Anopheles Mosquitoes. Jour. Amer. Med. Assoc. Lill, p. 2051.

(1910). Factors in the Transmission and Prevention of Malaria

in the Canal Zone. Annals of Prop. Med. and Par. iv. part 2.

Grassi (1902). Die Malaria, Studien eines Zoologen. 2. Aufl. Jena.

Hill and Haydon. Annals of the Natal Government Museum.

Hirshberg (1904). An Anopheles mosquito which does not transmit
malaria. Phe Johns Hopkins Hosp. Bull. Feb. 1904.

James (1902). Malaria in India. Sci. Memoirs by Officers of the San.
and Med. Departs, of the Gov. of India, No. 2.

James and Liston (191 1). The Anopheline Mosquitoes of India. Cal-
cutta.

Jancso (1904). Zur Frage der Infektion der Anopheles claviger mit
Malariaparasiten bei neiderer Temperatur. Cent. f. Bakt. xxxvi.
p. 624.

(1905). Der Einfluss der Temperatur auf die geschlechtliche

Generationsentwicklung der Malariaparasiten, etc. Cent. f. Bakt.
xxxviii. p. 650.

Kinoshita (1906). Uber die Verbreitung der Anophelen auf Formosa

und deren Beziehung zu der Malariakrankheiten. Arch. f. Schiffs-

u. Tropen-Hyg. x. p. 708.
Koch (1899). Uber die Entwicklung der Malariaparasiten. Zeit. f.

Hygiene, xxxn.
Liston (1908). The present Epidemic of Malaria in the Port of Bombay.

Jour. Bombay Nat. Hist. Soc. 15 Nov.
Lutz (1903). Waldmosquitos und YValdmalaria. Cent. f. Bakt. xxxiii.

p. 282.
Macdonald (1910). Malaria in Spain. In Ross's Prevention of Malaria.

IX] LITERATURE 165

Newstead, Dutton and Todd (1907). Insects and other Arthropoda
collected in the Congo Free State. Annals of Trop. Med. and Par.
1. p. 10.

Patton (1905). The Culicid Fauna of the Aden Hinterland. Jour.
Bombay Nat. Hist. Soc. p. 623.

Ross (1908) . Report on the Prevention of Malaria in Mauritius. London.

(1910). The Prevention of Malaria. London: John Murray.

Ross, Annett and Austen (1900). Report of the Malaria Expedition of

the Liverpool School of Tropical Medicine. Memoir 11.
Schaudinn (1904). Die Malaria in dem Dorfe " St Michele di Lerne "

in Istria, etc. Arb. a. d. Kaiserl. Gesundh. xxi. p. 403.
Schuffner (1902). Die Beziehungen der Malariaparasiten zu Mensch

und Miicke an der Ostkuste Sumatras. Zeits. f. Hygiene, xli. p. 89.
Sergent, Ed. and Et. (1905). Anopheles algeriensis et Myzomyia

hispaniola convoient le Paludisme. C. R. Soc. Biol. lix. p. 499.

(1908-10). Campagne antipaludique en Algerie. Ann. Inst.

Pasteur, vols. xxn. and xxiv.

Staunton (191 3). The Anopheles Mosquitoes of Malaya and their Larvae,
with some notes on Malaria-carrying Species. Jour, of the London
School of Trop. Medicine, vol. II.

Stephens and Christophers (1 899-1 902). Reports to the Malaria Com-
mittee of the Royal Society, i-viii.
(1907) The Practical Study of Malaria. University Press, Liverpool.

Tsuzuki (1902). Malaria und ihre Vermittler in Japan. Arch. f. Schiffs-
u. Trop.-Hyg. vi. pp. 9, 285.

Van der Scheer and V. Berlekom (1900). Malaria and Mosquitos in
Zealand. Brit. Med. Jour. 1. p. 202. 26 Jan. 1901.

Vogel (1910). Myzomyia rossi as a Malaria Carrier. Philippine Jour,
of Science, vol. v. No. 3, p. 277.

Watson (1910). The Prevention of Malaria in the Fed. Malay States.
University Press, Liverpool.

CHAPTER X

culicin^e

The main characters of the Culicinse have already been
described in Chapter VIII and therefore we shall at once proceed
to a description of by far the most important member of the
group, namely, Stegomyia fasciata, notorious as one of the
commonest domestic mosquitoes and also for the part it plays
in the transmission of Yellow Fever.

i66

STEGOMYIA FASCIATA

[CH.

Stegomyia fasciata (Fabricius, 1805)1. The Tiger Mosquito.

Synonyms: Culex fasciatns Fabricius, 1805. C. calopus Meigen, 1818.
C. frater Desvoidy, 1827. C. tceniatus Wiedemann, 1828. C. konoupi
Brulle(?), 1832. C. viridifrons Walker, 1848. C. annnlitarsis Macquart,
1848. C. excitans Walker, 1848. C. inexorabiJis Walker, 1848. C. formosus
Walker 1848. C. exagitans Walker, 1856. C. impatibilis Walker, i860.
C. bancroftii Skuse, 1886. C. mosquito Arribalzaga, 1891. C. elegans Ficalbi,
1896. C. rossii Giles, 1899. Stegomyia fasciata Theobald, 1901.

Description. In addition to possessing the characters of
the genus (p. 109), according to Theobald this species may be
distinguished by the following features :

" Thorax dark-brown to reddish-brown, with two median
parallel pale lines and a curved silvery one on each side, a
small line in front between the two median ones. Abdomen
black, with two white basal bands and lateral spots. Legs
black, with basal white bands, last joint of hind-legs pure
white." (Theobald.)

The female has a head densely covered with broad flat scales, which are
black and grey on each side. There is a white patch on each side and another

Fig. 46. Stegomyia fasciata, adult female ; enlarged. (After Howard.)

1 According to Howard, Dyar and Knab (191 3) the correct name of this
species is A'edes calopus.

X] DESCRIPTION 167

in the median line extending from in front back to the neck. The scales at
the back of the head are in the form of long black bristles and project forward.
The eyes are black surrounded by a white border and sometimes contain
white patches.

The antennae are brown, excepting the basal segment, which is black with
a patch of white scales on its inner side. They are longer than the proboscis
and have a banded appearance. The proboscis is brown, almost black towards
the extremity, but lighter about the middle. The palps are black, and only
about one-third the length of the proboscis ; each is composed of three seg-
ments covered with large flat scales, those of the first two being brown, and
silvery-white on the last segment.

The dark-brown thorax is covered with reddish-brown, pale-golden and
cream-coloured scales and is ornamented with various white spots and
lines. In front, near the neck, there is a white spot on each side. The dorsal
surface has a white, broad curved band on each side extending from the
anterior edge of the thorax and curving inwards about the middle of the
mesonotum, from which it is continued backwards as a thinner pale line to
the scutellum. Between them are two parallel pale lines extending about
half way across the mesonotum and on to the scutellum, and anteriorly is a
short white line between these two. The scutellum has a thick row of white
scales and also three tufts of bristles. The metanotum is brown. The
pleurae are dark-brown with several patches of white scales.

There is much variation in both the size and colour of the thoracic scales
and many of the varieties have been described as distinct species. The
arrangement of the ornamentation is however very constant and will serve
to distinguish fasciata from any other species of the genus Stegomyia.

The abdomen is brownish-black, circled with a white band at the base
of each segment ; the posterior four bands before the last one are more or
less tinged with yellow. There is a triangular white spot on the sides of each
segment, and in addition the first segment is almost covered with cream-
coloured scales and edged with pale hairs.

The legs are brown, circled with white. The coxae are yellowish. The
femurs are yellowish towards the base, brown towards the apex, but with
white scales on the ventral surface, and finally the extreme tip is pure white.
Those of the third pair are swollen at the extremity. The tibiae are black.
The metatarsi have basal white bands. The fore tarsi have the first joint
basally white and the rest black ; the mid tarsi are the same. The hind tarsi
are all basally white except the last joint, which is white, and the penultimate
segment, which is white with the exception of a black apex. The claws of
the first two pairs of legs are toothed and those of the hinder pair without
teeth.

The wings are clear, unspotted, a little longer than the abdomen, with
brown scales, those of the lateral nervures being very long and narrow, and
of the median, short and broad. The first sub-marginal cell is longer and
only slightly narrower than the second posterior cell, and the base of the
former is a little nearer the base of the wing than the latter. The posterior
cross-vein is about one and a half to twice its length distant from the mid
cross-vein. The latter unites with the supernumerary forming a very obtuse
angle, almost straight. The balancers are ochraceous and sometimes the
knob is slightly fuscous.

The length is 3-5 to 5*0 mm.

i68

STEGOMYIA FASCIATA

[CH.

The male is darker than the female. The head is black with white scales
in front and in the middle. The antennae are brown, marked with paler
bands, sometimes almost white. The proboscis and palps are black, the
latter possessing four white basal bands. The thorax is marked in the same
way as the female, but the scales are more silvery and the markings more
distinct.

The first segment of the abdomen is covered with cream-coloured scales,
the bases of the second to the fifth with white, and the fifth to the eighth have
clear white lateral spots. The latter also occur on the sides of the anterior
segments.

The claws of the fore-legs are unequal, the larger one being toothed and
the smaller, simple ; those of the mid-legs are simple, and unequal ; the hind
claws are equal and simple.

The genital armature is of the usual form.

The length is 3*0 mm. to 4*5 mm.

Fig- 47- Stegomyia fasciata, adult male; enlarged. (After Howard.)

Habitat. This is one of the commonest species of mosquitoes
and is widely distributed throughout almost all tropical and
subtropical regions. Although sometimes occurring in tem-
perate countries it is essentially a tropical species, for below a
temperature of 230 C. the female refuses to feed and at 200 C.
loses all activity and will not oviposit. The most favourable
climatic condition for its development is a humid atmo-
sphere, at a temperature of 25-300 C. all the year round.

x]

HABITAT

169

In the laboratory S.fasciata may be kept alive for some time
at 7-8 ° C, if kept in a refrigerator and thereby protected
from currents of air. When exposed to a similar temperature
in the open air it soon dies. At o° C. the insect succumbs in
a few seconds and, on the other hand, a temperature of 37° C.
is also rapidly fatal.

This susceptibility to variations in temperature causes this
mosquito to be confined to certain degrees of latitude, from
400 N. to 400 S., or more exactly between the two isothermal
lines of 200 C. Owing to the ease with which it may be carried
from one country to another by means of ships, the species is
now found in most of the regions between these limits. The
accompanying map (Fig. 48) represents the distribution of

Fig. 48. The distribution of Stegomyia fasciata.

S. fasciata, and it will be noticed that the insect especially
occurs along the coast lines and the banks of large ri\
where the requisite conditions of humidity are fulfilled. It 1-
absent from those regions in which the temperature dm
the night falls so low as to be harmful to reproduction.

170 STEGOMYIA FASCIATA [CH.

In addition to its susceptibility to cold Stegomyia is even
more affected by dryness, especially when accompanied by
heat. The insect is somewhat protected from the vicissitudes
of the climate by its domestic habits, as it is generally found
inside houses. In fact its fondness for houses is so great
that, according to Boyce, it is never found breeding at distances
of more than 50 to 100 yards from buildings.

On emerging from the pupa, the imago at once flies into
a house or other shelter, and generally settles down in some
dark corner and, like most other blood-sucking flies, it has a
great preference for dark-coloured objects.

If the mosquitoes are breeding close to ships they often
enter them, and in consequence Stegomyia is the commonest
species found on board ship. In the old sailing ships, not
only could these insects live for weeks in the cabins, store-
rooms, holds, etc., but actually breed in the water that was
often left exposed in various receptacles. Although modern
steamers do not afford such facilities for the persistence of this
insect on board, yet recently there have been cases in which
live Stegomyia fasciata were found on ships that had been at
sea 13 to 20 days.

Feeding habits. As in the majority of mosquitoes the female
Stegomyia is the only one which feeds on blood and this food
is necessary before the insect is able to lay its eggs. The male,
which is fully developed on emergence, does not bite, in spite
of statements to the contrary. It feeds on fruit juices and
also settles on the skin, to which it is attracted by the secre-
tions of the body. Although the male does not actually bite,
the singing noise produced by its wings is very annoying ; its
note is much higher than that of the female.

The female does not feed on all persons indiscriminately,
but seems to exercise some choice in the selection of its victims.
Thus it prefers white people to black, in spite of its fondness
for dark objects. Similarly blondes are preferred to brunettes,
children to adults, and fresh arrivals from temperate regions
suffer more than acclimatized persons. The factors which guide
the insect in the selection of its host are not known, but scent
is probably the most important, after the effect of the body-heat.

X] BIONOMICS 171

According to Marchoux, who has given one of the most
complete accounts of 5. fasciata, the female is entirely nocturnal
in its blood-sucking habits, except for a short time after it
emerges from the pupal case. Under these latter conditions
the insect is so hungry that as soon as it is able to fly it sets
off to find a host. Once having succeeded in obtaining a meal,
the female comes to rest in some dark corner, and in future
only attempts to feed towards the evening, or at night. This
statement, however, as to the nocturnal feeding habits of
S. fasciata has been denied by many subsequent investigators,
who agree in the view that this mosquito is mainly diurnal in
its feeding habits. Although in nature blood appears to be the
only food of the females, Goeldi succeeded in keeping them alive
for more than three months on a diet of honey. These insects,
however, were unable to lay any eggs.

Length of life. In a state of captivity, female 5. fasciata
have been kept alive for a period of more than four months,
so that their duration of life is comparatively long, but in
nature, it is doubtful whether an insect would often be able
to live such a long time. The occurrence of isolated cases of
yellow fever long after an epidemic has ceased may be due
to the persistence of infected mosquitoes or, on the other
hand, to the presence of mild and unrecognized cases of the
disease.

The male has a much shorter life than the female, for
as it feeds on the nectar of flowers, and moreover is very active,
it requires to feed much oftener. As a result of its continual
search for nourishment, and also for females, the male is con-
tinually exposed to accidents and soon loses his protective
scales. From this moment the slightest drop of moisture is
sufficient to cause the suffocation of the insect.

The maximum period that female S. fasciata have been
kept alive when nourished on honey is 102 days, whilst under
similar circumstances males only lived for periods varying
from 28 to 72 days.

Fertilization and egg-laying. Copulation is usually accom-
plished in the open air, especially during the warm hours oi
the day. The union is made when the insects arc flying, only

172 STEGOMYIA FASCIATA ~CH.

rarely when at rest, as the two ventral surfaces are brought
in apposition.

The spermatozoa are stored in the spermathecae, but
although a fertilized female may thus remain fertile for a
long time, eventually the sperm becomes used up and another
copulation is necessary before more fertile eggs can be pro-
duced.

The female lays the first batch of eggs a few days after
taking its first meal of blood, the exact period varying accord-
ing to the conditions of temperature and humidity. When
these are very favourable the period may be as short as two
days, but at temperatures below 200 C. the interval may be
prolonged indefinitely and two or three feeds may elapse before
egg-laying commences. The average number of batches of
eggs laid is usually two or three, but in individual cases as
many as nine batches have been observed.

The eggs are extruded singly and the number laid on the
first occasion is generally 60 to 90. The number of eggs
comprising the subsequent batches is always less than that
of the first one, this being the most important. Goeldi has
found that the females usually die immediately after the final
act of parturition, though in two instances individuals survived
12 and 14 days respectively.

The same author also states that fertilized eggs may remain
latent in the body of the female for from 23 to 102 days.
A meal of blood was capable of causing the female to lay her
eggs after these two periods respectively.

The eggs are generally laid at night, on the surface of
almost any stagnant water. They may be found in the water
collected in old tins, saucepans, rain-tubs, broken bottles,
holes in trees, and practically in every accumulation of water,
however slight, occurring in the vicinity of the houses the mos-
quito inhabits. The nature of the water seems to be indifferent,
for the eggs hatch out in the most stagnant and evil-smelling
water, almost as readily as in pure water.

The egg. The egg consists of an ovoid body, rather more
pointed at one end than the other, and is blackish in colour,
dotted over with small white hemispherical particles of

X] LIFE-CYCLE 173

excretory matter. In addition the egg is surrounded by a series
of small air-chambers which help to keep it afloat.

As each egg is laid by the female a small drop of liquid is
also extruded on the surface of the water and may help to keep
the egg floating, as this secretion is of somewhat oily consistency.
Certainly a slight agitation of the water is sufficient to cause
the eggs to sink, but development proceeds almost as well
beneath the water as at the surface. In the former case,
however, the eggs are more liable to the attacks of bacteria,
etc. Under favourable conditions the eggs hatch out in about
two or three days. In the Amazons the normal incubation
period is said to be from three to eight days, but its duration
depends almost entirely on the temperature. If this falls
below 200 C. the eggs are unable to develop, and if the ther-
mometer falls to this temperature for a few hours each day
the development is greatly prolonged.

The eggs are very resistant and can withstand long exposures
to cold and dryness. They may be exposed to a temperature
of 370 C. for one hour, or kept at o° C. for many days, without
their vitality being affected. Eggs have been maintained for
several months between io°C. and 200 C. and when the tem-
perature was raised, about one-twentieth of them hatched out.

The most striking results, however, are those obtained
with eggs that have been dried. These may be kept for three
months without more than 40 per cent, of them dying. Francis
has also shewn that they may remain alive for six and a half
months if kept dry. Xewstead describes an experiment with
eggs of 5. fasciata that had been sent from Manaos on the
Amazon. The eggs had been laid on moist white filter paprr ;
they were then dried in air and subsequently for 24 hours
over calcium chloride. They were then packed in tubes and
sent across to England. Forty-five to 47 days later, on their
arrival at Liverpool, they were placed in water at and

several larvae hatched out within 12 hours. Moreover, these
Larvae developed very rapidly and the adult insects emerj
within 12 days. From these results it is evident that the eggs
of S. fasciata under certain conditions may remain alive for
considerable periods without developing.

174

STEGOMYIA FASCIATA

[CH.

The larva. The egg gives birth to a small, colourless, and
very active larva, which occasionally swims and wriggles along
the surface of the water in the same manner as certain Ano-
phelines. This larva under favourable conditions grows rapidly,
and after a succession of moults attains the pupal stage.

Fig. 49. Larva and Pupa of Stegomyia fasciata, with enlarged parts. (After
Howard.)

The larva of Stegomyia may generally be distinguished by
two characters, viz. its comparatively colourless appearance
and the short black respiratory syphon, one-quarter the total
length of the abdomen. The larvae of Culex are darker coloured

X] LARVA I75

and generally possess long respiratory syphons. In addition
the larvae of S. fasciata possess the following characters :

The antennae are smooth, the tuft being represented by a
single short hair. At the apex there is a minute but distinct
second joint and a few delicate hairs. The labial plate pos-
sesses one large terminal tooth and 11 or 12 smaller ones on
each side of it. The thorax is rather hairy and bears four
large chitinous hooks, two on each side. Each of these hooks
gives off one or two hairs. The abdomen is very broad, and
is almost the same width all the way down.

The two lateral combs, situated on the eighth segment,
each consist of eight to ten serrated spines, varying in size
and the number of serrations. The syphon is comparatively
short and stumpy, being only one-quarter the total length
of the abdomen, and about two and a half times as long as its
width at the base. The syphon spines vary both in number
and arrangement ; they are succeeded by a triple hair. The
terminal segment of the abdomen is very short and almost
rectangular and bears a number of blunt bifurcate hairs.
The papillae are broad and rounded ; their length is about
one and a half times that of the last segment.

The larvae feed on decaying organic matter, especially on
nitrogenous substances. They thrive best in neutral or slightly
alkaline water, and soon die if free acids are present. Although
still capable of development in very brackish water, 5. fasciata
cannot live in sea-water, as at least one other species of the
genus (5. pseiidoscutellaris) has been shewn capable of doing.

After a number of moults the larva gives rise to the pupa.
The duration of the larval stage at fairly warm temperatures
varies from seven to fifteen days, but a temperature of below
200 C. will prolong development almost indefinitely. The young
larvae are remarkably tenacious of life under water and will
stand submersion for three to five hours. The fully grown
larvae can still endure a submergence of at least one and a
half to two hours, a property which enables them to feed at
the bottom of comparatively deep water.

There is no record of the live larvae of 5 \yia ever

having been found in ice, as in the case of those of the allied

176 STEGOMYIA FASCIATA [CH.

genus Culex. Miss Mitchell has found them in water at i° C.
and states that some pupated at 120 C, but in the labora-
tory the larvae generally die if the temperature falls to io° C.
It is noteworthy that these low temperatures are more fatal
to the fully grown larvae than to the earlier stages.

If the temperature of the water in which the mosquitoes
are developing falls daily below 200 C, the duration of the
larval stage may exceed a month. The adults which eventually
emerge, moreover, are generally so weak and unhealthy that
they are unable to feed and soon die.

The pupa. The duration of the pupal stage varies from one
to five days, after which the adult insect emerges. The pupae
are very sensitive to cold and a fall of temperature is almost
invariably fatal to them, as their organization is not adapted
to withstand the vicissitudes of climate. The pupae resemble
those of Culex in their general appearance.

The duration of the complete life-cycle from the new laid
egg to the emergence of the imago maybe as short as n days,
but is usually from 15 to 20 days. A prolonged exposure to
cold, on the other hand, may increase this period to as much
as five months, and as mentioned above, the dried eggs are
capable of living for long periods without developing.

Stegomyia fasciata and disease. In addition to being one
of the commonest species of mosquito occurring in the tropics,
Stegomyia fasciata is entirely responsible for the transmission
of " Yellow Fever." It also has been shewn capable of trans-
mitting Filaria bancrofti to man, but as this parasite is more
commonly carried by members of the genus Culex, the infection
will be described later.

Ed. Sergent and Neumann have shewn that Plasmodium
(Proteosoma) prcecox or relicta, parasitic in birds, will develop
in S. fasciata. Finally, Fiilleborn and Mayer, by feeding this
mosquito on the blood of animals swarming with trypanosomes
and subsequently, after short intervals, on normal animals,
have succeeded in the mechanical transmission of Trypanosoma
gambiense. It is very doubtful, however, whether in nature
S. fasciata ever carries sleeping sickness, and in any case such
transmission can only be very exceptional.

Xl] YELLOW FEVER 177

REFERENCES.

Boyce, R. (191 1). Yellow Fever and its prevention. John Murray.

London.
Francis, S. W. (1907). Observations on the life-cycle of Stegomyia

calopus. Publ. Health Reports, vol. xxn. pp. 381-3.
Goeldi, E. A. (1904). Os Mosquitos no Para. Bol. Mus. Goeldi {Para),

vol. iv. fasc. 2, pp. 129-197.
Howard, L. O. (1901). Mosquitoes. McClure, Phillips and Co. New

York.
Dyar and Knab (191 2). The Mosquitoes of North and Central

America and the West Indies. Publ. 159. Carnegie Inst. Wash-
ington.
Marchoux, E. (1910). Fievre Jaune, in Chantemesse and Mosny's

Traite d' Hygiene. Bailliere et fils. Paris.
Theobald, F. V. (1901-10). A Monograph of the Culicidce or Mosquitoes.

Vols. 1 to v. Brit. Museum, London.

CHAPTER XI

DISEASES TRANSMITTED BY CULICIN^. YELLOW
FEVER, DENGUE, BIRD MALARIA, ETC.

I. Yellow Fever.

Synonyms. Bilious remittent fever. Tropical toxaemic
jaundice. Typhus Icteroides. Pestis Americana. Febris Flava.
Yellow Jack. Magdalena fever. Fievre Jaune. Gelbfieber.
Febbre Gialla. Fiebre Amarilla. Typhus Amaril. Matla-
zahuatl. Coup de Barre.

General account and history. Yellow fever is an acute non-
contagious fever, usually characterized by the occurrence of two
paroxysms of fever separated by an intermission, and accom-
panied by albuminuria, haemorrhages and jaundice. The
presence of the latter symptom has given rise to the name by
which the disease is usually known, but it should be emphasized
that this feature is often absent in mild cases. The disease is
widely distributed in tropical and subtropical America, and
also, according to most authorities, on the West Coast of Africa.
It is endemic only in those regions where Stegomyia fascial*

H. B. F. 1 -

I78 YELLOW FEVER [CH.

can exist all the year round, and in consequence only appears
sporadically in subtropical and temperate regions. It is
mainly a disease of seaport towns and practically all the great
epidemics have occurred in such localities.

About the early history of yellow fever very little is
certain. It is said to have been known by the Aztecs under
the title of " Matlazahuatl." Other authorities believe that
the disease originally occurred in the Antilles and was carried
by the Spaniards to the mainland of America. There is little
doubt that the disease originated in America and was fully
established by the time that the early explorers arrived from
Europe.

On the other hand certain authors have thought that it
might have been introduced from West Africa by the slave-
boats, but such a view is not in accordance with the fact that
the disease seems to have been already known in America when
Columbus discovered the continent. From Central America
yellow fever has been carried by ships to various parts of the
world, in some of which it has become endemic, and in others
only occurred in epidemic form.

Its distribution is shewn in Fig. 50, which represents
the extreme range of all places in which yellow fever has been
known to occur within recent times. At present many of
these localities are quite free from the disease and, as a result
of anti-mosquito campaigns, many more are likely to become
so in the near future.

At present the chief endemic foci of the disease are the
States of Central and South America, with the exception of
Panama, and the West Coast of Africa. In the United States,
the Gulf States have frequently been the site of great epidemics,
but the climatic conditions prevent the disease from becoming
endemic. In West Africa yellow fever seems to have been
known since 1778, when it was recorded from St Louis. The
fact that the disease has existed in an unbroken line for more
than a century, is strong evidence of its endemic character in
West Africa, and although there have been no outstanding
epidemics, yet the number of patients who annually succumb
to " Bilious Remittent Fever " is considerable. One of the

XI]

HISTORY

179

greatest difficulties in the way of studying the disease is the
fact that mild cases of yellow fever cannot be diagnosed
with any certainty. As a result, although the natives of
endemic regions must frequently harbour the virus in their
blood, up to the present it has been impossible to discover
any direct proofs of it.

Fig. 50. The approximate distribution of Yellow Fever at the present time.
Infected regions are coloured black.

The cause and method of infection of yellow fever have
been a puzzle ever since the disease became known, and altln >ugh
the latter of these two points has now boon settled the causal
agent is still a matter of discussion.

In early times it was believed that the virus was in some
way transmitted through the air, and the fact that it usually
occurred in the vicinity of water lod to the belief that it was
produced by bacterial fermentation. Subsequently a number

1 j-

l80 YELLOW FEVER [CH.

of bacteria were described as the cause of the disease, but all
of them have been shewn to be merely secondary invasions.

In addition to being regarded as a highly infectious disease,
yellow fever was always considered to be contagious, and
patients suffering from it were strictly isolated and their cloth-
ing, etc. thoroughly sterilized. In spite of this isolation of
patients, however, epidemics were not checked, and it was
noticed that many persons became infected without ever
having come in contact with infected cases, whilst frequently
doctors and nurses, who worked in the same rooms as the
patients, did not suffer from it.

It was also observed that ships coming from infected ports
frequently carried the infection and consequently quarantine
ordinances were brought into force, which to some extent
reduced the spread of the disease, but the wars at the end of
the eighteenth century caused these measures to be relaxed,
with the result that some very serious epidemics occurred
about this time. These afforded some opportunities for the
study of the disease and several American observers called
attention to the large numbers of mosquitoes and other insects
that occurred during yellow fever epidemics. In 1848, Nott,
of Mobile, accused some insect or mosquito of being the possible
carrier. It was not, however, till 1881 that Charles Finlay of
Havana definitely attributed the transmission of the disease
to a mosquito. He had noticed in Cuba the connection that
seemed to exist between the prevalence of yellow fever and
the presence of large numbers of the tiger mosquito, 5. fasciata.
Accordingly, he attempted to transmit the infection experi-
mentally by feeding mosquitoes on patients suffering from the
disease and subsequently on normal persons. Although his
experiments were open to many objections, there is no doubt
that Finlay did succeed in transmitting the disease by means
of the bites of mosquitoes and he energetically advanced his
theory in a number of articles. Eventually his views began
to attract the attention they deserved and finally, in 1899, an
American Commission was sent to Cuba to study the disease.

This commission was composed of four members, Reed,
Carroll, Lazear, and Agramonte, and the way in which they

XI] HISTORY l8l

investigated the problem of the transmission of yellow fever
will always remain famous. During their investigations
Dr Lazear succumbed to the disease, but the research was
carried on by his fellow workers, who succeeded in proving
beyond all doubt that yellow fever is carried by the tiger
mosquito, Stegomyia fasciata.

The earlier work of the commission was devoted to an
examination of the various bacteria that had been described
as the cause of the disease. Of these the most notorious were
Sanarelli's Bacillus icteroides, and Sternberg's Bacillus X,
which had been found in a certain number of cases. Reed and
Carroll found that both these bacteria played no part in the
aetiology of the malady, but were merely the result of a
secondary infection. Subsequently, in 1900, Reed, Carroll,
Agramonte and Lazear shewed that the disease could be pro-
duced in non-immune persons by the subcutaneous inoculation
of blood from an infected patient. They also proved that the
disease was not contagious but could only be spread by the
bites of infected S. fasciata. These results have been thoroughly
confirmed by subsequent investigators.

The work of the French Commission, composed of
Marchoux, Salimbeni and Simond, is the most important of all
subsequent researches on the disease, for these authors were
able to elucidate some of the necessary conditions for the
transmission of the malady. They also found that the first
generation of the offspring from an infected mosquito is
capable of infecting persons. Their results will be considered in
detail in the section devoted to a description of the mode of
transmission of yellow fever.

The practical benefits that have resulted from the applica-
tion of the discovery of the mode of transmission of yellow
fever are only paralleled by those following Ross's work on
the development of Plasmodium in the mosquito.

In the Panama Canal zone, which used to be one of the
worst endemic regions in Central America, as a result of anti-
mosquito campaigns the number of cases of yellow fever was
reduced so rapidly that within five years the disease had com-
pletely disappeared from this region.

1 82 YELLOW FEVER [CH.

Geographical distribution. In considering the distribution
of yellow fever it is necessary to emphasize the fact that the
disease is being rapidly eradicated from the more civilized
regions of the world, and comparatively few endemic centres
exist at the present time.

The most important of these are the following :

Guatemala, Nicaragua, Costa Rica, Ecuador, Spanish
Honduras, Venezuela, French Guiana, certain parts of Mexico
and the West Indies, and along the banks of the Amazon,
Orinoco, and Magdalena Rivers. It will thus be seen that the
States of Central and South America are the great centres of
the disease, and from these regions it has spread into many
other countries. It is probably endemic in West Africa for the
continual recurrence of small epidemics cannot be explained on
the supposition that these represent infections introduced by
ships.

The endemic centres of yellow fever do not extend beyond
latitudes 400 N. and 400 S., where the mean isotherm is not
below 260 C. The malady, however, often extends into colder
regions during the summer months, and may produce great
epidemics, which, however, always disappear on the return of
cold weather.

Great epidemics of yellow fever have occurred in many of
the seaport towns of the Southern United States, especially
in New Orleans where, in 1878, there was a record of 4046
deaths as the result of one epidemic. The Gulf ports were
probably endemic centres during the eighteenth century and
first half of the nineteenth, but as the result of improved
hygienic conditions and better drainage the breeding places
of the mosquitoes have been reduced until now the disease is
almost extinct.

The Atlantic ports, as far north as New York, were also
frequently visited by more or less severe epidemics, as the
disease was continually being introduced by ships coming
from Cuba and other endemic centres. The infected Stegomyia
carried from these places would be able to live on board for
some weeks and thus be capable of spreading the infection at the
ports at which the ship called.

XI] GEOGRAPHICAL DISTRIBUTION 183

On the West Coast of America the general conditions are so
unfavourable to the breeding of the mosquito, that the disease
has not been able to establish itself and has only appeared
sporadically in one or two localities, with the exception of
the Isthmus of Panama, which until recently was one of the
noted endemic centres. With this exception, therefore, the
West Coast has never been the scene of any severe epidemics, for
comparatively few ships sail up the coast and consequently there
has been little chance of their spreading infected mosquitoes.
Colon is practically the only port that has hitherto been liable
to infection, but with the opening of the Panama Canal and
the increase in trade which this is sure to effect, the question
of the possibility of thus extending the range of yellow fever
will have to be carefully considered. The recent outbreak at
St Nazaire in 1908 has shewn clearly that even modern ships
are capable of carrying infected Stegomyia for considerable
distances.

In Europe the appearances of the disease have been
very similar to those in North America, and many epidemics
occurred during the eighteenth and nineteenth centuries,
when the growth of commercial intercourse resulted in an
increase in the number of ships coming from endemic centres.

In Southern Europe numerous epidemics of considerable
severity have occurred, and the ports of France, and even
Swansea and Southampton in England, have been the scenes
of small outbreaks. In the south of Europe Stegomyia fasciata
is capable of breeding, and therefore epidemics could easily
become established during the summer months, but in the
more northerly regions this is out of the question. In these
cases the infection is strictly limited to persons who have
been near a ship carrying infected mosquitoes on board.

Thus in the case of the outbreak at St Nazaire in iqoS,
infected Stegomyia were taken on board a ship at Martinique.
These were carried across the Atlantic and on arrival at
St Nazaire, several of the mosquitoes escaped and fed on
persons either on board or in the vicinity of the ship. Eleven
individuals were known to be infected in this way, of whom
seven died.

184 YELLOW FEVER [CH

Unless greater care is taken to screen ships during their
stay in infected ports, there is little doubt that occasional
epidemics of this nature now and then will appear. In North
Europe, where the absence of Stegomyia prevents any further .
spread of the infection, these slight outbreaks are of com-
paratively slight danger, but in regions where the mosquito
is abundant, e.g. Malay and India, the introduction of a few
infected Stegomyia might lead to the production of terrible
epidemics, such as those which raged in Barcelona during
the eighteenth century.

Mode of infection. The various theories as to the nature of
this disease have been sufficiently discussed in the previous
chapter, and we shall at once proceed to a description of the
work of the American Commission of 1899, on the transmission
of yellow fever

The first attempts of this commission to transmit the
disease by mosquitoes were made with some Stegomyia fasciata
that hatched in the laboratory from eggs supplied by Finlay.
These insects were fed several times on patients suffering from
yellow fever at various stages of the illness. Eleven persons
having offered themselves for experiment, each day these
infected mosquitoes were fed on a fresh human subject. Only
two of these persons became infected, and both of them had
been bitten by mosquitoes that had fed 12 days previously on
the blood of a yellow fever patient in the first stage of the
disease.

In this preliminary experiment the possibility of these two
patients having become infected by other means had not been
definitely excluded. It was decided, therefore, to continue
these experiments, after taking more rigorous precautions
against any external contamination. A camp was established
in the neighbourhood of Tuemados, on a plateau that was well
drained, and absolutely free from yellow fever. Twenty-
eight non-immune subjects, mostly Americans and Spaniards,
were shut up in this camp and carefully examined for several
days in order to make sure that none of them were infected.
If any of the patients shewed the slightest febrile symptoms
they were at once removed from the camp, but none of the

XI] MODE OF INFECTION 185

others were allowed to go out of it. After these preliminary
precautions, some Stegomyia that had fed 12 days previously
on a yellow fever patient in the first stages of the disease, were
allowed to bite twelve persons. Ten of them became infected
after incubation periods varying from 41 hours to five days.
Twelve other persons who remained in the camp never shewed
the slightest signs of infection, although living in close proximity
with these yellow fever patients.

This experiment proved that not only is this mosquito the
carrier of the infection, but that contact with patients is
harmless. The latter is most important from an economic
point of view, and therefore the commission carefully inves-
tigated the question.

A mosquito-proof house was constructed so as to present
the worst possible hygienic conditions. It was badly venti-
lated, and badly lighted, and the windows were kept shut all
day. The air inside the house was very humid and the tem-
perature often rose to 350 C. Into this house was introduced
the soiled linen from beds that had been occupied by yellow
fever patients. A certain number of persons occupied this
house for 20 days, sleeping between bed-clothes that had been
soiled by the excrement and black vomit of yellow fever
patients. In spite of these conditions none of the persons
occupying the house became infected and the experiment has
been repeated several times with similar results. No matter
under what conditions of sanitation, etc., in the absence of
Stegomyia, nobody became infected with the disease.

Finally, a house was constructed of the same dimensions
as the preceding, but well lighted and ventilated, so as to
present the best hygienic conditions. This house was rendered
mosquito-proof by wire gauze, and also was divided into two
halves by means of a partition of the same material. On one
side the persons occupying the room were exposed to the same
conditions as in the preceding experiment, namely, sleeping
between the soiled bed linen from yellow fever patients, etc.
In the other half only carefully sterilized materia] was allowed
to enter but, in addition, there were introduced 15 mosquil
that had fed, at least 12 days previously, on patients at the

1 86 YELLOW FEVER [CH.

commencement of their infection. A young American doctor,
Dr Moran, entered this half of the house and was bitten by
a number of the mosquitoes. After a short incubation period,
he developed a typical attack of yellow fever, whilst persons
who occupied the other half of the house for at least 20 days
remained healthy.

In this manner was established the important truth that
yellow fever is only carried by means of the mosquito, and the
above-mentioned results have been repeatedly confirmed by
subsequent investigators.

The causal agent. In spite of numerous researches the
causal agent is still under discussion, for most of the organisms
that have been described from yellow fever patients may be
explained as the result of secondary infection, or in other cases,
as artefacts. Because of the many points of resemblance be-
tween relapsing fever and yellow fever, it has been suggested
that the latter is also due to a spirochete. Recently Seidelin
has described the occurrence of a parasite, belonging to the
Babesiidae, in the blood and organs of yellow fever patients.
To this parasite Seidelin has given the name of Paraplasma
flavigenum, and he considers it to be the causal agent of yellow
fever.

Whatever the causal agent may be, it is present in the
circulation in large numbers, for the subcutaneous injection of
minute quantities of infected blood into a non-immune person
is followed by an attack of yellow fever. It is said to be
present in the circulation only during the first three days of
an attack, for blood taken from a patient on the fourth day,
when his temperature was still high (400 C.) was found to be
non-infective. However, as there has only been one attempt
made to infect persons with the blood taken from patients
after the third day, this statement is still open to question.
On the whole it seems probable that yellow fever patients may
remain infective even after all signs of the disease have dis-
appeared, for it is difficult to explain its prevalence in certain
cases except on the theory of latent infections. The organism
must be excessively minute for it can easily pass through a
Chamberland Filter F. When the infected serum is diluted

XI] DEVELOPMENT IN MOSQUITO 187

with an equal quantity of water the virus is even capable of
passing through a Chamberland Filter B, 0-033 c-c- of the
filtrate producing a typical attack when injected into a non-
immune person.

The virus is extremely fragile, for a drop of infected blood
may be placed on an excoriated part of the skin with impunity,
as the slightest desiccation destroys the disease agent. More-
over, it is very susceptible to heat, for at a temperature of
550 C. it loses its virulence within five minutes.

Development within the mosquito. Under ordinary cir-
cumstances when a Stegomyia has fed on the blood of a yellow
fever patient during the first three days of an attack, it
becomes infective after an incubation period of about 12 days.
The conditions of development within the mosquito are very
uncertain, however, for it often happens that mosquitoes remain
uninfective, even though fed on infected blood.

The effect of temperature is very important and probably
accounts to some extent for the restricted range of the disease.
If a mosquito is kept at a temperature of about 220 C, instead
of becoming infective 12 days after an infected feed, the incu-
bation period is prolonged to three or four weeks. At 200 C.
the virus is incapable of developing within the mosquito and
thus the latter does not become infected.

If an infected mosquito, capable of transmitting the disease,
is exposed to a low temperature, it ceases to be infective, but
recovers this power on again being warmed. It is possible
that changes in temperature alter the virulence of the disease,
for during the cool season the cases of yellow fever are often
benign, the most severe ones occurring during the hot weather.

Under certain conditions it seems that the infection may
be transmitted to the offspring of an infected mosquito.

Marchoux and Simond kept a female Stegomyia, which laid
its eggs 16 days after an infective feed. These eggs were kepi
at a temperature of about 280 C. and developed in a com-
paratively short length of time into the adult insects. The
latter were found to be infected and produced a typical attack
of yellow fever when fed on anon-immune subject. Although
no one else has succeeded in repeating this experiment, the

1 88 YELLOW FEVER [CH

French investigators were so careful to exclude all chance of
error, that there is little doubt that under certain conditions,
a Stegomyia infected with yellow fever is able to transmit the
infection to its offspring. The reappearance of yellow fever in
places where it had apparently become extinct may possibly
be explained by this factor.

Once a mosquito has become infected, it probably continues
so for the remainder of its life, but there are not sufficient
observations on this question. In nature the insects are
certainly still infective after being nourished on sugar for two or
three weeks, as shewn in the case of the St Xazaire epidemic.

It is possible for the virus of yellow fever to be preserved
indefinitely in the mosquito and thus the cycle of development
must be quite different from that of Plasmodium. This was
clearly shewn by an interesting experiment performed by
Marchoux and Simond. Mosquitoes, that had fed on an
infected patient more than 12 days previously, were ground
up in thick syrup and some freshly hatched Stegomyia fed on
this mixture. Fifteen days later these insects were found to
be infected, although they had never fed on a yellow fever
patient.

Vaccination. Although no successful means of preventing
infection by this means have yet been discovered, the results
obtained by the use of various sera are of some interest.

We have previously referred to the extreme susceptibility
to temperature of the virus of yellow fever. Warming for
five minutes at 550 C. destroys all its activity. If preserved
at a temperature of 290 to 300 C. in an ordinary tube
plugged with cotton, the serum loses its virulence within
48 hours. The same temperature acts much more slowly if
the infected serum is covered with a layer of oil in order to
protect it from the air. At the end of five days some serum
kept in this manner was still infective, and produced an attack
of yellow fever when injected into a non-immune person. It
should be added that it only produced a very mild attack.
After being thus preserved for eight days the serum lost its
virulence entirely and could be injected into non-immunes
without producing any infection.

XI] VACCINATION 189

The inoculation of serum that had either been warmed, or
kept for eight days at 250 C, was found to confer a partial
immunity against yellow fever. All the subjects that had
received such injections, were subsequently inoculated with
a virulent strain of yellow fever, and in every case the resulting
attack was found to be extremely mild in character, shewing
that the serum had had an immunizing effect.

During the course of an attack of yellow fever the presence
of antibodies in the blood of the patient may easily be demon-
strated. The serum of a patient taken on the eighth day of
an attack and injected into a non-immune person, completely
protected the latter against infection when subsequently inocu-
lated with virulent blood. The serum of a convalescent patient
is even more effective, and if injected into non-immune persons
will protect them against all attempts at infection for a period
of about 20 days. By the twenty-sixth day the immunity
begins to disappear but is still present, for the inoculation of
virulent blood only produces a slight attack of fever.

Such immune serum may also be applied therapeutically,
and when injected into infected patients is said to diminish
the severity of the symptoms and hasten the recovery.
Unfortunately, all these methods are of little use, because
they require the presence of infected patients and conva-
lescents to furnish the necessary materials.

REFERENCES.

Boyce, R. (191 1). Yellow Fever and its prevention. London : John

Murray.
Clarac, A. and Simond, P. L. (191 2). Fievre Jaune, in Grail and

Clarac's Traite Pratique de Pathologie Exotique. Paris. Vol. in.

pp. 21-176.
Finlay, C. (1883). Sur une nouvcllc theorie de la fievre jaune. Ref.

Arch, de mid. nav. January, 1883.
Marchoux, E. (1910). Fievre Jaune, in Chantemesse and Mosny's

Traite d'Hygi&ne. Paris : Bailliere et fils.
Marchoux, Salimbeni and Simond (1903). La fievre jaune. Ann. Inst.

Pasteur, vol. xvn. pp. 665-731.
Marchoux and Simond (1906). Etudes sur la fievre jaune. Ibid, vol xx.

pp. 16, 104 and 161.
Reed, Carroll, Agramonte and Lazear (1900). Preliminary note 00 the

Etiology of Yellow Fever. Phil. Med. J cum. Oct, 27.

I90 DENGUE [CH.

Reed and Carroll (1902). Recent researches concerning the etiology,
propagation, and prevention of Yellow Fever, by the U.S. Army
Commission. Journ. of Hygiene, vol. II, pp. 101-119.

Sanarelli, G. (1897). Etiologie et pathogenie de la rievre jaune. Ann.
Inst. Pasteur, xi. p. 433.

Seidelin, H. (191 1). The Etiology of Yellow Fever. Yellow Fever
Bulletin, vol. 1. pp. 229-258.

For a complete bibliography see the Yellow Fever Bulletin, and
also Scheube's Die Krankheiten der warmen Lander. (Jena : G. Fischer.)

II. Dengue.

Synonyms. The synonymy of this disease is very extensive,
upwards of 100 names having been applied to it. The most
important of these are as follows : Dandy Fever ; Breakbone
Fever ; Febris Endemica cum Roseola ; Exanthesis Arthrosia ;
Arthrodynie ; Knokkelkoorts ; Eruptive Rheumatic Fever ;
Fievre rouge, etc.

History. The first records of dengue do not appear before
the end of the eighteenth century, though there is some possi-
bility that an epidemic noted by Pazzio as occurring in Seville
from 1764 to 1768 was caused by this disease.

In 1779 dengue was noted in Cairo and Arabia, by Gaberti ;
in India, by Persin ; and also in Batavia, by David Bylon.
The following year Rush described an epidemic occurring in
Philadelphia, and in 1784 the disease was introduced from the
West Indies into Spain, where it caused severe epidemics in
Cadiz and Seville, which were well described by Cristobal
Cubillas.

During the nineteenth century epidemics have been recorded
from most tropical and subtropical regions. According to
Manson there is a tendency for these epidemics to occur at
intervals of about 20 years. The last epidemic to occur in
Europe was in 1889, when the disease was especially prevalent
in Turkey, Greece, and the Eastern Mediterranean region
generally.

Distribution and epidemiology. Dengue is essentially a
tropical disease, but occasionally it extends into subtropical
regions. It has occurred in practically every country between

XI

DISTRIBUTION

I9I

32° 47' N. and 230 23' S., and during the summer months it
may extend up to as much as 420 N. The disease is usually
more prevalent in low-lying lands well supplied with water,
probably because such sites provide better opportunities for
the breeding of Culex. There are exceptions to this rule,
however, for during the epidemic in Syria in 1888-9 the disease
extended to villages having an altitude of nearly 4000 feet.

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Fig.

51. The distribution of Dengue. The countries from which cases
have been recorded are coloured black. (Compare this chart with
that on page 193, shewing the distribution of Culex fatigans.)

The distribution of dengue, past and present, is represented
in the accompanying map (Fig. 51). At the present time
the chief endemic centres of the infection are India and the
East Indies, and, in the New World, the Wes1 hulk- and
Central America. From these centres the disease, in warm
summers, may even extend into temperate regions, but on
the approach of winter it gradually disappears, as a certain
amount of heat seems to be necessary for its transmission.

I92 DENGUE [CH.

Neither age, sex, race, nor social conditions, seem to have
any effect on this disease, which attacks rich and poor, old
and young, black and white, with the utmost impartiality.

The rapid spread of epidemics of dengue is another feature
which was noticed even by the earliest observers. The rapidity
with which it extends is probably unequalled by any other
malady, and usually within a few days of its appearance in any
particular locality a considerable proportion of the population
will be found suffering from the disease. In 1884 an epidemic
in Noumea broke out so suddenly that the majority of the
public services were disorganized ; a regiment of marines was
reduced to less than one section, and so many of the sailors
were affected that the ships were temporarily put out of action.

The disease is usually conveyed from one place to another
by means of ships carrying infected passengers. Thus dengue
was introduced into Tahiti by a steamer that carried a single
infected passenger, who had contracted the disease in Noumea.
This case was sufficient to start an epidemic in the island.

When any particular maritime locality becomes the
centre of an epidemic, all ships visiting the place are liable to
become infected. Occasionally the disease is spread by means
of trains as, for example, in India, where it was carried from
Calcutta across Bengal by these means. Such a method of
expansion, however, is somewhat unusual and seaports
continue to be the localities most visited by epidemics, the
infection being introduced by ships. An epidemic generally
lasts for about five or six months, gradually diminishing in
the number of cases until it finally disappears.

It is interesting to note that the distribution of dengue
shews a remarkable coincidence with that of Culex fatigans.
(Figs. 51 and 52.)

Causal agent. Our knowledge of dengue is still very im-
perfect and in spite of numerous researches the cause of the
disease remains unknown. McLaughlin, in 1886, found a
micrococcus in the blood of infected patients and supposed
that this was the causative agent, but his results have been
disproved by subsequent investigators. In 1903, Graham
believed that he had discovered the cause of the disease, in

XI

CAUSAL AGENT

193

the form of small hyaline bodies occurring in the red cells,
which he considered to be related to Babesia. In addition, he
fed Culex fatigans on infected patients and claimed to have
found his parasites in the insects up to the fifth day after
feeding, without, however, observing any signs of their develop-
ment. Nevertheless the salivary glands were said to contain
spores from two days up to a month after the mosquito had

Fig. 52. The distribution of Culex fatigans.

fed on infected blood. A typical attack of dengue was pro-
duced in a healthy person by the injection of the salivary
glands of a mosquito, that had fed on an infected patient
24 hours previously.

Although Graham's work on the transmission of dengue by
Culex fatigans has been confirmed, the organism which he
described has never been observed by any subsequent investi-
gators, but from the nature of the disease there seems little
doubt that it is caused by some protozoal parasite living in
the blood. Ashburn and Craig have studied the aetiology

H. B. F.

13

194 DENGUE [CH.

and transmission of dengue in the Philippines, and were able
to produce the disease in normal persons by the intravenous
injection of 20 c.cs. of blood from an infected patient. The
incubation period was two to three days, and was followed by
typical attacks of dengue. These authors also found that
'the pathogenic agent was so small that it would pass through
the pores of a filter which retained organisms o-4 ^ in diameter,
filtered serum being equally as infective as non-filtered blood.

The blood shews little alteration except in the leucocyte
count, a slight or well-marked leucopenia being a fairly constant
character. The number of polymorphonuclear leucocytes may
be reduced to forty or fifty per cent., but at the same time
there is an increase of the large mononuclears and lymphocytes,
the latter predominating. Some authors maintain that the
leucocyte formula remains essentially the same throughout
the disease, whilst others are of the opinion that considerable
variations occur. Dengue is not accompanied by any anaemia,
the red cells remaining normal both in number and ap-
pearance.

Mode of infection. The transmission of this disease is still
somewhat obscure in spite of the work of Graham, and Ashburn
and Craig. For a long time it was considered to be a highly
contagious infection and During recorded a case in which
five families that received their washing from the same laund-
ress all became infected about the same time and before the
other inhabitants.

Arnold, in 1846, was the first to support the idea that
the disease is not contagious and based his theory on two
facts noticed in Havana, namely, that the epidemic was
localized in the town and did not spread into the surrounding
country, and that among the first cases, not any of the patients
had been in contact with one another, either directly or in-
directly.

The belief in the contagious nature of dengue has now been
abandoned by the majority of investigators, but, in addition
to the idea that it is carried bv Culex, various other theories
of animal transmission have been advanced. In America it is
a common idea that the spread of the disease depends in some

XI] MODE OF INFECTION 195

way on the cattle. In India, Martialis has noticed that the
cows and horses are sometimes attacked by dengue, often
presenting a temporary paralysis of one or more legs, but
usually recovering after three or four days. Also, Duchateau,
during an epidemic in the Senegal, noticed that it coincided
with a high mortality amongst the wild birds and fowls.

None of these theories has received any support from
experiments, for up to the present all attempts to infect
animals have remained negative.

Finally, in 1903, Graham propounded the theory that
Culex fatigans is responsible for the transmission of this disease
and supported his theory by experiments. Ashburn and
Craig, however, are the only investigators who have actually
succeeded in transmitting the disease by the bites of infected
Culex fatigans. It should be noted, however, that they only
succeeded on one occasion and their results have not been
confirmed.

The details of Ashburn and Craig's experiments are as
follows :

On September 12th, a non-immune soldier was placed
under a mosquito net with about 20 Culex fatigans that had
fed on a dengue patient the previous night. The man was
bitten on the night of the 12th, approximately one day after
the mosquitoes had fed. About three and a half days later he
shewed a distinct rise of temperature and a day later developed
a typical attack of dengue.

It is evident that in this experiment the parasite causing
the disease had no time to undergo any cycle of development
in the mosquito, except a very short one. As all attempts to
infect persons by the bites of mosquitoes after an interval of
more than one day gave negative results, Ashburn and Craig
are of the opinion that the parasite of dengue is merely capable
of living in the stomach of the mosquito and does not need to
undergo any cycle of development before becoming infective.

It must be admitted that the experimental evidence in
support of the mosquito transmission theory is very incomplete,
but a consideration of its epidemiology Leaves no doubt as to
the usual mode of infection

1 >--

I96 BIRD MALARIA [CH.

In the first place the disease has been definitely proved to
be non-contagious, but is infectious in the same way as yellow
fever and malaria. Secondly, the distribution of dengue more
or less coincides with that of Culex fatigans. Additional
support, however, is that brought forward by E. H. Ross,
who shewed that in Port Said, Egypt, dengue entirely dis-
appeared after the destruction of mosquitoes. Previously the
town had been subject to severe epidemics, but since the
extermination of the mosquitoes, not a single case of dengue
has been recorded, although the disease has been rife in other
parts of Egypt.

Of course, it is possible that other Culicines may be capable
of transmitting the infection, and the observations of Legendre
in Hanoi suggest that Stegomyia is probably a carrier of the
virus.

REFERENCES.

Ashburn and Craig (1907). Experimental investigations regarding the

etiology of Dengue Fever. Philippine Jour. Sci. Sect. B, Med. Sci.

vol. 11. No. 2.
Graham (1903). The Dengue; a study of the pathology and mode

of propagation. Journ. Trop. Med. 1903, p. 209.
Legendre (191 1). Bull. Soc. Path. Exot. vol. iv. p. 26.
Seidelin, H. (1913)- Dengue. A summary. Yellow Fever Bulletin,

vol. 11. pp. 335-358. (Contains a very good general account of the

disease.)

III. Bird Malaria {Plasmodium prcecox [Grassi and Feletti]).

General account. A great variety of birds, such as finches,
sparrows, crows, etc., have been found infected with a parasite
closely resembling the Plasmodia of man. By some authors
this bird parasite has been separated off into a distinct genus,
Proteosoma, but the differences between it and Plasmodium are
so slight that now the two are generally united. There is also
some doubt as to whether all the Plasmodia occurring in birds
should be regarded as one species, and some observers have
preferred to give specific names to the Plasmodia from different

XI CAUSAL AGENT

197

species of birds, but there is no justification for this course, as
hitherto all attempts to find any specific differences, apart
from the kind of host, have failed. Therefore, for the present,
all the plasmodial parasites occurring in birds may be regarded
as belonging to one species, Plasmodium prcecox (Grassi and
Feletti, 1890).

The parasites have a decidedly pathogenic action upon the
birds they infest. They grow at the expense of the red cor-
puscles, which lose their haemoglobin, and gradually degenerate.
As a result infected birds become anaemic and, in addition, the
substances produced by the parasites seem to have a general
toxic effect upon the organs of the body. As in the case
of human malaria, the body temperature rises, but rarely
more than 1-1*5° C. Birds not infrequently succumb to the
infection, especially during the early part of the year, when
climatic conditions are somewhat severe.

Causal agent. Plasmodium prcecox in its general form
somewhat resembles P. vivax. The small amoeboid sporozoites
penetrate into the red cells and there generally assume a some-
what triangular form, with a round vesicular nucleus containing
a karyosome. This young trophozoite grows at the expense of
the contents of the red cell and deposits waste materials in
the form of pigment granules, which are scattered through its
protoplasm. Danilewsky refers to these young forms as
" pseudo- vacuolar." The protoplasm is finely granular and
contains numerous vacuoles.

According to Labbe there are two kinds of schizogony in
the circulating blood. Sometimes the parasite divides up
into six or seven merozoites arranged in the form of a rosette,
whilst at other times the parasite divides up into very numerous
merozoites scattered irregularly throughout the infected blood
corpuscle. In both cases the pigment and waste materials
are left behind in the form of a residual body. The merozoites
escape and penetrate other blood corpuscles, where they either
develop and repeat the schizogonic cycle, or cue rise to the
gametocytes. The development of the latter closely resembles
that of the corresponding forms in other species of Plasmodia
(e.g. P. vivax).

ig8

BIRD MALARIA

[CH.

The Morphological Changes.

Development in the mosquito. The experiments of Ross,
Sergent, Ruge and Neumann have shewn that at least four
species of Culicinae are capable of transmitting P. prczcox,
viz. Culex pipiens, C. fatigans, C. nemorosus and Stegomyia
fasciata. In all these species the development of the parasite
is practically identical with that of P. vivax in Anopheles,
and therefore it is unnecessary to describe it in detail.

The development, however, does not take place with equal
facility in all these species, even under the same conditions of
temperature and humidity.

Thus Neumann found that out of 501 Stegomyia fasciata
which fed on an infected canary, only 57 (= 11*4 per cent.)
subsequently shewed the development of ripe cysts and the
sporozoites of the parasite. On the other hand out of 104
Culex pipiens fed under similar conditions, 85 (= 817 per cent.)
became infected. Moreover the time occupied in the develop-
ment of the parasite, from the ingestion of the gametocytes
to the appearance of sporozoites in the salivary gland of the
mosquito, was longer in the case of Stegomyia than in Culex.

At a temperature of 270 C, with a relatively high humidity
of about 75 to 80 per cent., the times occupied by the various
stages of development were as follows :

Formation of microgametes

Copulation

Formation of ookinete,
commencement of
majority formed . .

Disappearance of ookinetes from
the stomach

Formation of sporocyst . .

Development of sporozoites in the
cyst

Total developmental period, from
the ingestion of the infected
blood to the appearance of
sporozoites in the salivary
glands of the infected mosquito

In Culex
30 to 45 mins.
30 to 60 mins.

About 10 to 12 hours
20 hours

After 48 hours
About 30 hours

6 to 7 days

9 to 11 days

In Stegomyia
30 to 60 mins.
39 to 90 mins.

About 16 hours
26 hours

After 72 hours
Not before the
3rd or 4th day

8 to 10 days

13 to 15 days

XI]

DEVELOPMENT OF PARASITE

I99

At a temperature of 200 to 220 C. the formation of the
ookinete and its subsequent development is very greatly
prolonged, but the liberation of the microgametes and the
process of copulation does not seem to be delayed.

If the humidity is lowered to about 40 per cent, the develop-
ment of the cysts is prolonged for at least two days, so it
seems that a dry atmosphere is relatively unfavourable to the
infection of mosquitoes.

Fig. 53. View of the stomach of a Culex shewing large numbers of the
sporocysts of Plasmodium prcecox on its walls. (After Ross.)

Neumann kept very large numbers of Culex and fed them
entirely on the blood of an infected canary. Although the
majority of these mosquitoes were heavily infected with the
Plasmodium, none of them seemed to shew any ill-effects from
the presence of these parasites. On the other hand Koch, who
similarly fed a number of Culex nemorosus on birds infected
with P. pvcecox, found that many of the insects succumbed to
the infection.

REFERENCES.

Grassi, B. (1901). Die Malavia-Studien eines Zoologen. Jena: Fischer.
Koch, R. Ueber die Entwicklung der Malariaparasiten. Zeitschr. /.

Hyg. u. Infektionskrankh. vol. xxxn.
Neumann, R. O. (1909). Die Obertragung von Plasmodium prcrcox auf

Kanarienvogel. Arch. f. Protistoikunde, vol. XIII. pp. 23-69,
Ross, R. (1905). Nobel Prize Essay, 1905.
Ruge, R. (1901). Untersuchungen iiber das deutsche Protcosotia.

Centralbl. f. Bakt. 1. vol. xxix. pp. 187— 191.
Sergent, Ed. and Et. (1907). Etudes sur les Hematozoaires d'Oiseaux.

Ann. Inst. Pasteur, vol. xxi. pp. 251-280.

200 schaudinn's researches [ch.

IV. Appendix. The Blood Parasites of Athene noctua.

In addition to the above-mentioned infections, it is
probable that most of the blood parasites of birds are trans-
mitted by the agency of some species of mosquito. Schaudinn,
in his famous memoir on the life-cycles of the parasites of the
Little Owl [Athene noctua), described the development of
these organisms in the alimentary canal of the common gnat,
Culex pipiens.

The Little Owl harbours in its blood at least six forms of
avian parasites, namely, (i) a proteosoma ; (2) a halteridium ;
(3) a small form of trypanosome ; (4) a large form of trypano-
some ; (5) a leucocytozoon ; and (6) a spirochete.

According to Schaudinn all these forms belong to the life-
cycle of only three species of parasites. The proteosoma is
certainly a distinct form unrelated to any of the others. On
the other hand the halteridium and the small trypanosome
were said to be phases of the same parasite, whilst the large
trypanosome, leucocytozoon and spirochete were considered as
stages in the development of another parasite.

The halteridium was supposed to be the resting intra-
corpuscular stage of the small trypanosome, which at night
developed a locomotor apparatus, became free from the red
cell and swam about as an ordinary trypanosome ; in the
morning it penetrated another red cell, its locomotor apparatus
disappeared, and it again became a halteridium. Three forms
of the parasite were distinguished, known respectively as male,
female and indifferent forms. The latter were the forms which
multiplied in the blood, and from these small trypanosomes
either indifferent, male, or female forms, might develop.

The two latter developed slower than the indifferent forms,
and as they grew larger were unable to change from the hal-
teridium to the trypanosome form, but became exclusively
intracorpuscular or halteridium forms. The further develop-
ment of these sexual forms could only take place if they were
ingested by a gnat, Culex pipiens. In the alimentary canal
of this insect the male and female forms became free and
copulated, forming typical ookinetes. The latter developed

XlJ HALTERIDIUM OF ATHENE NOCTUA 201

into trypanosomes which again might be either female or
indifferent, or divide up into a large number of male forms.
Ultimately the indifferent and male trypanosomes were inocu-
lated back again into an owl ; the female trypanosomes being
too bulky could not pass through the proboscis of the gnat, and
as the male forms soon died out in the blood the new infection
was started by the indifferent trypanosomes.

This extraordinary account of the life-cycle of the parasite
of the Little Owl has been the subject of much discussion
during the past few years.

Mayer has brought forward evidence in support of one of
Schaudinn's statements, for he found that when owl's blood
containing only halteridia was kept in hanging drops under
the microscope, eventually trypanosomes made their appearance
and these could only have come there by the transformation of
the halteridia.

On the other hand no other confirmation of the life-cycle
has hitherto been published, whilst there are many serious
objections to it. In the first place the careful researches of
Minchin and Woodcock, who worked at Rovigno, the place
where Schaudinn made his observations, have shewn that in
the blood of Athene noctua there is every stage between the
small trypanosomes and the large ones, and there is every
reason to suppose that in this case, as in many other verte-
brates, these are all merely forms of one polymorphic try-
panosome.

Further the development of Hcemoproteus columbce, the
halteridium of the pigeon (v. Chapter XXIII), is of a totally
different kind, as the transmitting host is not a mosquito and
moreover the development does not include any trypanosome
phases.

Minchin suggests a solution of the difficulty by supposing
that the trypanosome of the Little Owl, like other known
species of trypanosomes, has intracorpuscular forms which
have been confused with true halteridia.

With regard to Schaudinn's account of the life-cycle of
the Leucocytozoon there is not the slightest doubt that do
relation exists between this parasite and the spirochetes and

202 FILARIASIS [CH.

trypanosomes, which are supposed to be stages in its develop-
ment.

The bacterial nature of the spirochetes is now generally
admitted, and the life-cycles of those species that have been
investigated have been found to be of the simplest nature,
not involving any sexual phenomena, or anything in the
slightest degree comparable with Schaudinn's account. Up
to the present, no observer has succeeded in working out the
life-cycle of any Leucocytozoon, but it is unlikely that a gnat
is responsible for its transmission.

On the whole, therefore, it seems better to disregard
Schaudinn's statements concerning this parasite, and to con-
sider its life-cycle as still an open question.

REFERENCES.

Dobell, C. C. (1912). Researches on the Spirochaets and related
organisms. Arch. f. Protistenkunde, vol. xxvi. pp. 117-240.

Mayer, M. (191 1). Uber ein Halteridium und Leucocytozoon des
Waldkauzes und deren Weiterentwicklung in Stechmucken. Ibid.
vol. xxi. pp. 232-254.

Minchin, E. A. (1912). An Introduction to the Study of the Protozoa,
pp. 389-394. London : Edward Arnold.

Minchin and Woodcock, H. M. (191 1). Observations on the Trypano-
some of the Little Owl (Athene noctua). Quart. Joum.Micr. Sci.
vol. lvii. pp. 141-185.

Schaudinn, F. (1904). Generations- und Wirtswechsel bei Trypano-
soma und Spirochete. Arb. a. d. kais. Gesundheitsamt. vol. xx.
P- 387.

CHAPTER XII

DISEASES TRANSMITTED BY ANOPHELIN^ AND
CULICIN^E. FILARIASIS

I. Filaria bancrofti Cobbold, 1877.

Synonyms. Trichina cystica Salisbury, 1868. F. sanguinis
hominis Lewis, 1872. F. sanguinis hominis cegyptiaca Sonsino,
1874. F. dermathemica da Silva Aranjo, 1855. F. wucheresi
da Silva Lima, 1877. F. sanguinis hominum Hall, 1885.
F. sanguinis hominum nocturna Manson, 1891. F. nocturna

XII] HISTORY 203

Manson, 1891. Microfilaria nocturna Manson, 1891. F. phi-
lippinensis Ashburn and Craig, 1906.

History. The embryo of this species was discovered by
Demarquay in 1863, in the chylous fluid from a case of dropsy
of the tunica vaginalis, occurring in the West Indies. Wucherer
in 1866 noticed the parasites in the urine of several cases of
tropical chyluria, and in the next few years these embryos
were found in similar cases from various parts of the world.
In 1872 Lewis found that the parasites occurred in the blood
of man, and Manson, da Silva Lima and Crevaux established
the identity of these blood filariae with those occurring in cases
of chyluria and lymph scrotum. In 1876 the adult filaria
was discovered by Bancroft in an abscess of a lymphatic gland
of the arm and also in a hydrocele of the spermatic cord.
Manson studied the disease in China, and was the first to notice
the periodic increase and decrease in the number of parasites
in the peripheral circulation. From these observations he
deduced that some blood-sucking insect was responsible for
the spread of the infection, and his discovery in 1878 that
mosquitoes were the agents in the transmission of the disease
constitutes one of the landmarks in the history of tropical
medicine. In 1879 he described the changes undergone by
the filaria in the body of the mosquito, Culex pipiens, but the
method in which the parasite again reached man remained
undiscovered till 1900, when Low observed the worms in the
proboscides of mosquitoes infected with Filaria bancrofti.

Distribution. This species has been recorded from tropical
and subtropical countries in most parts of the world. In
Europe one case has been observed in Spain and another in
Italy ; it is also probable that it occasionally occurs in Greece
and Turkey. In Asia this filaria is widely spread throughout
China, Japan, the Philippines, and India. It is rare in Indo-
China. In Oceania it is extremely common in the majority
of the islands, and in Samoa at least one half the inhabitants
are said to be infected. In Australia it occurs as far south as
Brisbane. In Africa it has been recorded from many Localities
in the north, east and west, and probably occurs throughout the
whole continent north of latitude 20 S. It is also common

204 FILARIA BANCROFTI [CH.

in Mauritius, Reunion and Madagascar. In America, it is
common in many parts of the West Indies and Brazil,
and cases occur in the southern United States up to lati-
tude 400 N.

Description. The adult filariae do not occur in the peripheral
blood circulation, but are found in various parts of the lym-
phatics. The males and females generally occur together,
often coiled about each other. Sometimes several occur
together in small cyst-like dilatations of the distal lymphatics ;
they are also found in the larger lymphatic vessels and in the
glands themselves, and, probably not infrequently, in the
thoracic duct.

The female is a long, hair-like, transparent, motile worm,
50-155 mm. in length, and 0-15-0715 mm. in breadth.
The two uterine tubes, easily seen through the transparent
integument, occupy the greater length of the body, and are
filled with ova and embryos at various stages of development.
The body is plain, tapering rather abruptly towards the anterior
end to form a distinct neck, beyond which is the slightly en-
larged rounded oral extremity. The tail is also tapered, but
ends rather abruptly. The cuticle is finely striated. At a
short distance behind the head a luminous V-shaped spot is
visible, that may represent the water- vascular system. The
vulva is situated on the ventral surface at a distance of about
2*56 mm. from the anterior extremity. The anus opens
immediately in front of the tail, 0-13-0-28 mm. from the
posterior extremity. The worm is ovo-viviparous. The ova
measure 25-38 n in length by 15 fi in breadth.

The male resembles the female in its general appearance
but is somewhat smaller, usually about 70-80 mm. in length
by 0-40 mm. in breadth. When living it may further be dis-
tinguished from the female by its marked tendency to curl, and
also by the shape of the tail, the extremity of which is sharply
incurvated, often making one or two spirals. The anus is
situated O'li mm. from the posterior extremity and from its
aperture emerge two slender, unequal spicules, respectively
0*2 and 06 mm. in length. According to Looss there are
three pairs of post-anal papillae ; pre-anal papillae seem to be

XII] DESCRIPTION 205

absent. The anterior end is rounded and not marked off from
the rest of the body by a distinct neck as in the case of the
female.

The embryos, or microfilariae as they are frequently termed,
occur in the peripheral blood. Manson describes the move-
ments of the living parasite in the following words : "In fresh
blood, F. nocturna (== bancrofti) is seen to be a minute, trans-
parent, colourless, snake-like organism which, without materi-
ally changing its position on the slide, wriggles about in a state
of great activity, constantly agitating and displacing the cor-
puscles in its neighbourhood. At first the movements are so
active that the anatomical features of the filaria cannot be
made out. In the course of a few hours the movements slow
down, and then one can see that the little worm is shaped
like a snake or an eel — that is to say, it is a long, slender,
cylindrical organism, having one extremity abruptly rounded
off, the other for about one-fifth of its entire length gradually
tapering to a fine point. When examined with a low power, it
appears to be structureless ; with a high power, a certain
amount of structure can, on close scrutiny, be made out.
In the first place, it can be seen that the entire animal is en-
closed in an exceedingly delicate, limp, structureless sack, in
which it moves backwards and forwards. This sack or
" sheath " as it is generally called, although closely applied
to the body, is considerably longer than the worm it encloses,
so that that part of the sack which for the time being is not
occupied is collapsed, and trails after the head or tail or both,
as the case may be. It can be seen also that about the posterior
part of the middle third of the parasite there is what appears
to be an irregular aggregation of granular matter which, by
suitable staining, can be shown to be viscous of some sort.
This organ runs for some distance along the axis of the worm.
Further, if high power be used, a closely set. very delicate
transverse striation can be detected in the museulo-cutan
layer throughout the entire Length of the animal. Besides
this if carefully looked for at a point about one-fifth of the
entire length of the organism backward- from the head end.
a shining triangular V-shaped patch is always visible, This

206 FILARIA BANCROFTI [CH.

V-spot is brought out by very light staining with dilute
logwood. The dye brings out yet another spot, similar to
the preceding, though very much smaller ; this second spot
is situated a short distance from the end of the tail. The
former I have designated the V-spot ; the latter the " tail
spot." Staining with logwood also shows the body of the
little animal is principally composed of a column of closely
packed, exceedingly minute cells enclosed in the transversely
striated musculo-cutaneous cylinder ; at all events, many
nuclei are thereby rendered visible. Dr Low has recently
pointed out to me that the break seen in all stained specimens
in the central column of nuclei occurs at a point slightly
posterior to the anterior V-spot. This break can only be
recognized in stained specimens."

According to Annett, Dutton and Elliott, if preparations
of the living filaria are examined directly after being made
from the patient, the embryos are seen to exhibit, for a
short period, a rapidly progressive movement across the field
of the microscope — at first so rapid that the parasites can
only be traced with difficulty. This movement quickly ceases,
as the sheath of the embryo soon becomes attached to the slide,
as described above.

The embryos vary from 270 to 340 m in length, by 7
to 11 fi in breadth.

Life-cycle in the vertebrate host. We shall commence with
the adult female in the lymphatics of the infected patient.
The fertilization is internal and the fertilized female usually
contains large numbers of embryos at various stages of
development. As this animal is ovi- viviparous, the eggs are
not liberated from the body of the parent until the embryonic
filariae (= microfilariae) are well formed and capable of inde-
pendent motion. The egg is surrounded by a transparent
sheath, within which the embryos are enclosed the whole
time they remain in the vertebrate host. The young filariae,
each enclosed in its sheath, on being liberated make their way
into the blood-vessels of the host and may be found in the
peripheral circulation. Whilst remaining in the blood they
are incapable of further development, but are enclosed

XII

PERIODICITY

207

within their sheaths, presenting an appearance similar to that
shewn in Fig. 54.

These are the filariae that one encounters on examining
the blood of a filarious patient, and as will be seen they are
merely immature forms and, consequently, it is very difficult
to classify them, as the various species are distinguished
mainly by the characters of the adults. These embryos arc-
often termed " microfilariae " in order to distinguish them from
the mature " filariae," but it should be remembered that such
a term cannot be used in a generic sense.

Kig. 54. Microfilariae of F. bancrofti emerging from the uterus of the parent
filaria, uncoiling in their chorionic envelopes. {After Bahr, from
Filariasis and Elephantiasis in Fiji.)

Periodicity. The number of filariae in the peripheral cir-
culation presents remarkable periodic variations, a pheno-
menon which was first noticed by Manson. In the
Filaria bancrofti, this author found that, in China, the parasites
were present in the peripheral circulation during the night,
but disappeared during the day : and he proposed the specific
name nocturna in order to express this habit, ruder normal
conditions of health and habit, during the day the parasite is

208 FILARIA BANCROFTI [CH.

rarely seen in the blood of a patient, or, if present, only in very
small numbers, but as evening approaches about five or six
o'clock the filariae begin to enter the peripheral circulation in
gradually increasing numbers. The maximum is usually
attained about midnight, when it is no uncommon thing to
find 300, or even 600, in every drop of blood. The numbers
then begin to diminish, and by eight or nine o'clock in the
morning the filarial have disappeared again for the day. This
diurnal periodicity may be maintained with regularity for
years. Manson was able to shew that during the daytime the
parasites retire to the lungs, heart and larger arteries, where
they may be found in enormous numbers. In the case of a
filarious patient who had committed suicide during the daytime,
the parasites were found to occur in the various organs in the
following numbers, which indicate the average per slide :
liver, § ; spleen, r ; brachial venae comites, 28 ; bone marrow, o ;
muscle of heart, 122 ; carotid artery, 612 ; lung, 675. In the
lungs the filariae were found lying outstretched or coiled in
the blood-vessels, both small and large. In the carotid they
occurred in enormous numbers on its inner surface, though
how they managed to maintain their position in the blood
current remains unexplained.

Many authors have attempted to explain this remarkable
periodicity in the occurrence of the parasites in the peripheral
circulation. Mackenzie shewed that it was in some way con-
nected with sleep, for by reversing the usual habits, and
making a patient sleep during the day and work at night, it
was found that, after a few days of hesitation, the filariae
became diurnal instead of nocturnal. These results have also
been confirmed by Annett, Dutton and Elliott working in
Nigeria. Carter supposed that the embryos were carried into
the circulation at the end of each day by the overflowing of
chyle that follows alimentation. Myers suggested that the
embryos are only laid at night and all die before the morning.
Scheube supposed that the passage of the embryos from the
lymphatics into the blood was prevented during the day by
muscular work and digestion, and facilitated at night by the
relaxation of the muscles. Von Linstow explained it on the

XII] LIFE-CYCLE IN MOSQUITO 209

supposition that during the night the dilatation of the cutaneous
capillaries facilitated the entrance of the filariae into the cir-
culation.

Against all these theories can be brought the objection that
a closely related species, Filaria diurna, is normally diurnal,
and yet presents a somewhat similar life-cycle to that of
F. bancrofti. A still more serious difficulty in the way of any
mechanical explanation is the occurrence, in some parts of the
world, of varieties of F. bancrofti that are diurnal in habit,
and yet others which exhibit no periodicity. The researches
of Bahr have shewn that in Fiji and Oceania generally, the
filariae occur in the blood of patients in no regular manner, and
yet the parasites are morphologically identical with F. bancrofti.
Similarly, Ashburn and Craig, because it exhibited no perio-
dicity, considered the human filaria of the Philippines to be a
distinct species, and gave it the name of F. philippinensis , but
Low has shewn that it is identical with F. bancrofti.

Bahr's observations are of great interest, for they suggest
that in Fiji the absence of periodicity in the filaria is a partial
adaptation to the habits of its usual invertebrate host in this
locality, Stegomyia pseudoscutellaris, a mosquito which only
feeds during the day.

At present, however, there is no hypothesis that will satis-
factorily account for the phenomenon of filarial periodica \ .

Life-cycle in the mosquito — the intermediate host. As men-
tioned above, the filarial embryos are incapable of further
development within the body of their host, but require to be
ingested by a mosquito belonging to one of the species that
serve as the invertebrate hosts for F. bancrofti. Then the
parasites undergo further evolution in the body of the mosquito.
The various stages in the metamorphosis of this specirs in
the body of Culex pipiens have been worked out by Manson.
The development maybe conveniently divided into seven sta§

First Stage. Shortly after being ingested by the mosquito
the transverse striation of the embryo becomes well marked,
as if from longitudinal shrinking. Within about one hour the
embryo breaks out of its sheath and then shews active move-
ments. The parasite bores its way through the walls of the

H. B. f. 14

210 FILARIA BANCROFTI CH.

stomach and eventually comes to rest in the thoracic muscles
of the mosquito. This process is usually complete in about
12 to 18 hours, but some of the worms die in the stomach.
In the thorax all movement ceases, the striation disappears
and various changes take place in the interior of the filaria.

Second Stage. This generally occupies about two to three
days, during which the body thickens, and a mouth begins to
appear. The posterior V-spot appears as a large vacuole and
the anterior V-spot becomes very distinct.

Third Stage. The mouth becomes open and four large fleshy
lips are formed. The posterior V-spot enlarges and definitely
becomes the anus, appearing in front of the tail as a break in
the cuticle, from which granular matter exudes. A row of
cells appears in the previously apparently homogeneous body
and terminates in front of the anus in some large cells. This
row of cells later gives rise to the alimentary canal and a
tegumentary layer with a cavity between. The larva is now
0-03-0-3 mm. in length by 0-029-0-05 mm. in diameter.
At this stage the tail becomes large and sickle-shaped and the
cells of the body usually dip into it. The alimentary canal
extends from the mouth to the anus. Motion is entirely sus-
pended.

Fourth Stage. Rapid growth takes place and the body
retracts from the tail, which becomes a mere appendage.
The length of the worm varies from 0-35-0-5 mm.

Fifth Stage. When the body has attained its maximum
thickness the anterior end commences to elongate and become
thinner, and the mouth begins to close. The anterior and
posterior ends may elongate simultaneously, but more often this
process occurs along the whole length of the larva. The mouth
eventually closes and all, or nearly all, traces of the viscera
disappear. About the seventh day of development the body
of the worm assumes a fibrous and very transparent appearance,
but before this stage is reached a well developed alimentary
canal with pharynx and oesophagus may be distinguished.
Slight movements now commence at the neck of the animal
and extend downwards, and about this stage a general ecdysis
takes place and the sickle-shaped tail is cast off, a new skin

XII

DEVELOPMENT IN MOSQUITO

211

being developed within the old one. Large cells appear at the
end of the tail and form three or four papillae which characterise
the larva at the end of this and during the next stage.

V

Fig. 55. Filaria bancroftix 200. Stages in the development within the
mosquito. (After Nuttall.) a, young filaria immediately after escaping
from the sheath ; b, 5 days, c, 10 days, and d, 10 days after ing
by the mosquito.

The worm is now about 1-5 mm. in Length, and its breadth
has diminished to about one-half. The anterior end ta]
but is abruptly rounded off ; the posterior end also ta:

' ! — -

212 FILARIA BANCROFTI [CH.

slightly from the anus backwards, and bears the above-men-
tioned papillae.

Sixth Stage. The movements now become more active.
The lips of the mouth are closely pressed together in the form
of a cone and minute horny papillae are present. The worm
now measures about i"5 mm. by 0*03 mm.

Until 1900 it was supposed that this was the final stage in
the development, and that the worm now required to escape
into some water, in which it swam about until it was taken up
by man in drinking water. In that year Low shewed that
there was yet another stage.

Seventh Stage. When the filariae have reached their highest
development in the thoracic muscles they leave that tissue
and begin to travel forwards, probably as a result of some
chemiotactic attraction. They pass into the loose cellular
tissue in the prothorax near the salivary glands, then force
their way through the neck and coil themselves up in the
loose connective tissue just below the cephalic ganglion and
salivary sac. Finally, they pass into the proboscis of the
mosquito by making an independent passage through Dutton's
membrane at the base of the labrum, and pushing forward
between the labrum and hypopharynx amongst the stylets.
Here the worms are found stretched along the length of the
proboscis, head foremost Two worms, probably male and
female, are nearly always found together.

In this stage the worm is usually about 1 mm. in length
and 0*025 mm. in breadth'. It tapers slightly towards each
extremity, and at the anterior end the cuticle is thickened in
places to form a few small papillae arranged round the terminal
mouth. The posterior end, which is rounded off, is provided
with three papillae almost at right angles to the axis of the
body of the worm. The alimentary canal is straight and shews
no marked differentiation into oesophagus and intestine.
Towards the anterior end, 0*14 mm. from the extremity,
there is an indication of the presence of an orifice, towards
which the genital duct is seen to bend.

These young filariae remain in the proboscis of the mosquito
until it feeds on some host. The worms then escape and may be

XII]

DEVELOPMENT IN MOSQUITO

213

214 FILARIA BANCROFT! [CH.

found on the skin in the neighbourhood of the wound caused
by the bite of the insect. If the skin is sufficiently moist
the filariae then bore their way through the epidermis into
the subcutaneous tissues. In some cases they may select the
wound caused by the mosquito as the point of entrance into
the body of their vertebrate host, but in most cases it is pro-
bable that they make an independent entrance through the
undamaged skin, as Looss has shewn to be the case for the larvae
of Agchylostoma duodenale. Moreover, Bahr has actually
observed the larvae of Filaria bancrofti bore into the pores of
the skin. The filariae were dissected out of infected mosquitoes
and placed in a drop of saline on the back of a man's hand.
The larvae could easily be seen wriggling about in the water,
but when placed on the skin, after a few convulsive move-
ments, they suddenly disappeared, apparently through the
orifices of the gland ducts. Six filariae were observed to
disappear in this manner, ''with almost lightning-like rapidity."

When the skin is very dry the young filariae often die before
they are able to effect an entrance, and therefore a person may
be bitten by an infected mosquito .without developing filariasis.
If, however, the young worms effect an entrance, they make
their way to the lymphatics of their host and there develop
into the adult filariae. After fertilization the females then
develop embryos, which, on being liberated, make their way to
the blood circulation, and thus the life-cycle may be repeated.

Conditions affecting the development of the filaria within the
body of the mosquito. One of the most important factors in-
fluencing development is the species of mosquito in which this
process takes place. In some species development occurs much
more readily and occupies a shorter period than in others.
For example, in Fiji, Bahr found that F. bancrofti developed
very readily in Stegomyia pseudoscutellaris, under favourable
conditions, the young worms appearing in the proboscis within
ten days. On the other hand, in Culex fatigans the develop-
ment proceeded much less regularly and occupied a longer
period, whilst in C. jepsoni and S. fasciata the worms developed
very slowly, and eventually degenerated in the thoracic muscles
without arriving at maturity. The effect of different species

XII]

INVERTEBRATE HOSTS

215

on the development is well shewn by the number of nlariae
that developed in each species. Stegomyia pseudoscutellaris and
Culex fatigans are both efficient intermediate hosts for F. ban-
crofti ; but in the former practically all the embryos develop
in the insect and come to maturity, whereas in the latter only
two or three ever complete their development.

The effect of temperature on the rate of development is
very marked ; at a high temperature the worms may be found
in the proboscis after six days, but during cold weather the
same evolution is not complete for at least 20 days, or may
even be totally arrested.

The following species of mosquitoes are capable of acting as
the intermediate hosts for F. bancrofti, and with further re-
searches there is little doubt that the list will have to be
considerably extended. In many cases the development in
the mosquito has not been followed completely :

Species

Locality

Observer

Anophelines :

A. {Myzomyia) rossii1 ..

India

James

„ (Pyretophorus) coslalis1

West Africa

Annett, Dutton
and Elliott

,, (Myzoyhynchus) sinensis2 . .

Malay

Leicester

barbirostris2

> > ' '

,,

,, ,, peditceniatus*

,,

,, (Cellia) argyrotarsis2

West Indies

Low

,, ,, albipes2

)(

Vincent

Culicines :

Culex pipiens1 . .

China

Manson

[Australia

Bancroft

jaiigansx

1 St Lucia
1 West Indies
I Philippines

Low

Ashburn and Craig

gelidus2}

(Malay, Sumatra,

the

Leicester

sitiens2 \

"( Celebes and Malacca

Stegomyia fasciata3

St Lucia, W. Indies,

Low etc.

,, gracilis2 j
perplex a2 t

Malay

Leicester

scutellaris2 )

pseudoscutellaris1

Fiji

Bahr

Mausonia unifortnis (? africana)

1 Central Africa

Daniels

,, a)i)iulipes2 )

Scutomyia albolincata2 I . .

Malay

Leicester

Taniorhynchus domesticus* |

1 Species in which complete development has boon observed.

2 Species in which in all probability complete development takes place,
but forms have not boon actually seen in proboscis.

3 Species in which an incomplete partial development occurs. Forms
never reach stage suitable for proboscis.

2l6 FILARIA BANCROFTI [CH.

Effect of filarice on the mosquito. The developing filar iae
have a very deleterious effect on the health of the mosquito,
and heavily infected individuals can easily be recognized by
their sluggish appearance. When a very large number of
embryos are ingested by a favourable intermediate host, the
resulting development usually causes the death of the mos-
quito. In the case of S. pseudoscutellaris, Bahr noticed that
when mosquitoes were fed on a slightly infected patient nearly
all of them were alive 21 days later, but out of a batch of
200 insects that fed on a patient shewing very numerous
filariae in his blood, only 17 managed to survive an equal length
of time. The period at which the infected mosquitoes died
was dependent apparently upon the degree of development of
the filariae. Thus, in warm weather most of the insects died on
the sixth day after feeding, and in the cooler season on the tenth.
The last stages of development, when the filaria is entering the
proboscis, seem to be the most critical time for the mosquito,
as in one batch 23 Stegomyia were alive on the 15th day after
infection, but only three of them lived four days longer.

Possibility of another "indirect" mode of transmission by
the mosquito. The pathogenic effect of F. bancrofti upon its
intermediate host is of considerable interest, for it suggests
that the worm has only recently become adapted to its present
mode of transmission. Moreover, it seems possible that
Manson's theory that the filariae first escape into water and
subsequently enter man, has been discarded rather too hastily.
When the mature larvae migrate from the thoracic muscles,
although most of them come to rest in the proboscis, it is no
uncommon occurrence to find them in the legs and other regions
of the mosquito. These " mistakes " on the part of the larvae
also afford support to the theory that this filaria has only re-
cently adopted its present mode of entry into the body. When
the young filaria escapes from the proboscis of the mosquito on
to the skin, it is only capable of penetrating the surface in the
presence of moisture. On the other hand the young filariae
will live in water for several hours, and if a drop of water con-
taining them is placed on the skin the parasites at once disappear
down the openings of the gland-ducts.

XII] ELEPHANTIASIS 21/

It is evident, therefore, that if this filaria escapes into water,
either by the death of its insect host, or some other cause, it is
perfectly adapted for the penetration of any skin with which it
may come in contact. This was probably the original manner
in which the parasite was carried by mosquitoes, and the
possibility of the occurrence of such an " indirect " mode of
transmission, concurrently with the more recently acquired
" direct " method, should not be ignored.

Pathological effects. In most cases F. bancrofti does not seem
to exercise any marked injurious effect on its host ; patients
often shew filariae in their blood for many years and all the time
appear in perfect health. Under certain conditions, however,
the adult filaria may give rise to various pathological symptoms,
mainly as a result of obstructing lymphatics. Amongst these
affections may be mentioned chyluria, lymph scrotum, vari-
cose groin glands, etc. In some instances a living worm, or a
bundle of worms, may plug the thoracic duct and act as an
embolus, or originate a thrombus ; in others, they give rise
to inflammatory thickening of the walls, as a result of irritation,
and thus lead to obstruction from the consequent stenosis.
In such cases the embryos may disappear from the blood,
usually as a result of the death of the adults.

Sometimes adult filariae occur in large numbers in the lym-
phatic glands and also in the epididymis, testis and tunica
vaginalis. In these situations the worms may die and become
cretified, and whether alive or dead they cause fibrosis and
blocking of the glands.

Elephantiasis. Of all the affections that are supposed to
be due to filariasis, elephantiasis is the most important, as it
occurs in most tropical countries. The disease may be defined
as a chronic inflammatory hypertrophy of the fibrous con-
nective tissue in some region of the body, induced by Lymph
stasis and resulting in a considerable hypertrophy of the skin
and subcutaneous tissues. It most commonly affects the 1 gs
scrotum, vulva, arms and breast. The resulting growths may
become of enormous size, especially in cases ^\ elephantiasis
the scrotum, in which this organ may attain the weight ol over
230 pounds. According to Manson the condition ol Lymph

2l8 ELEPHANTIASIS [CH.

stasis, necessary for the production of elephantiasis, may be
due to the blocking of the lymphatic ganglia by the unripe
eggs of filariae, expelled from the parent before the embryos
are able to uncoil. These eggs are five times as wide as the
embryo, and being more or less rigid would be incapable of
passing through any lymph glands. This theory accounts for
the fact that the filaria embryos are rarely found in the cir-
culation of patients affected with elephantiasis.

The reasons for regarding elephantiasis as a filarial disease
are given by Manson as follows :

" (i) The geographical distribution of Filaria bancrofti and
of elephantiasis correspond ; where elephantiasis is common
there the filaria abounds and vice versa. (2) Filarial lym-
phatic varix and elephantiasis occur in the same district and
frequently concur in the same individual. (3) # Lymph
scrotum, an unquestionably filarial disease, often terminates
in elephantiasis of the scrotum. (4) Elephantiasis of the
leg sometimes supervenes on the surgical removal of a lymph
scrotum. (5) Elephantiasis and lymphatic varix are essen-
tially diseases of the lymphatics. (6) Filarial lymphatic
varix and true elephantiasis are both accompanied by the
same type of recurring lymphangitis. (7) As filarial lym-
phatic varix is practically proved to be caused by the
filaria, the inference that true elephantiasis — the disease with
which the former is so often associated and has so many
affinities — is attributable to the same cause, appears to be
warranted."

On the other hand the filarial nature of elephantiasis is
strongly opposed by certain authors, who bring forward argu-
ments in support of the view that the disease is caused by
bacteria. Le Dantec considers it due to a symbiotic infection
with a Streptococcus and a Dermococcus. Dubruel obtained
Streptococci in pure culture from cases of elephantiasis, and
lately favourable results in the treatment of the disease seem
to have been obtained by employing a vaccine prepared from
this streptococcus. This author remarks that in the Island of
Moorea (Tahiti), where about one-twelfth of the inhabitants
shew elephantiasis, he examined the blood of 200 persons

XII] FILARIA IMMITIS 210,

without finding a single filaria. Moreover, he cites examples
in which the contagious nature of the disease seems to be
admissible.

REFERENXES.

Annett, Dutton and Elliott (1901). Report on the Malaria Expedition

to Nigeria. Part II, Filariasis. Liv. Sch. of Trop. Med. Liverpool.
Ashburn and Craig (1907). Observations upon Filaria philippinensis

and its development in the mosquito. Phil. Journ. Sci., Sect. B,

vol. 11. pp. 1-14.
Bahr, P. H. (1912). Filariasis and Elephantiasis in Fiji. Journ. of

the School of Trop. Med., Supplement No. 1.
Bancroft, T. (1900). On the Morphology of the young form of Filaria

bancrofti Cobb, in the body of Culex ciliaris. Proc. Roy. Soc. N.S.

Wales, vol. xxm. p. 48.
Cobbold (1879). The life-history of Filaria bancrofti. Journ. Linn.

Soc. Zool. vol. xiv. p. 356.
Demarquay (1863). Note sur une tumeur de bourse. Gaz. mid.

Paris (3), vol. xvm. p. 665.
Le Dantec (1900). Precis de pathologie exotique. Paris.
Lewis, T. R. (1872). On a FLcematozoon inhabiting Human Blood.

Calcutta, 1872.
Linstow, v. (1900). Ueb. d. Art. d. Blutfil. d. Mensch. Zool. Anz.

vol. xxm. p. 26.
Low, G. C. (1900). A recent observation on Filaria nocturna in Culex.

Brit. Med. Journ. 1. p. 1456.
Manson, P. (1884). The metamorphosis of Filaria sanguinis hominis

in the mosquito. Trans. Linn. Soc. Zool. vol. 11. pp. 10 and 367.

Tropical Diseases. London : Cassell and Co.

Nuttall, G. H. F. Encycl. Medic a, Edinburgh, vol. vm.

Scheube (1883). Die Filar iakrankheit. Volkmann's Samml. kl. Vortr.

No. 232.

II. Filaria immitis (Leidy, 1S56).

Synonyms. F. canis cordis Leidy, 1850. F. papillosa,
hcematica canis domestici Gruby and Delafond. [852.

General account. This parasite occurs in the dog. in which
it was first seen by Panthot in 1679 anc* afterwards by Pey-
ronnie in 1778. It has also been found in the fox. and the
wolf. Noe and Fiilleborn shewed that Anopheles maeuliper.
and also Stegomyia faseiata. serve as the intermediate lu>st~
this species.

220

FILARIA IMMITIS

[CH.

Distribution. F. immitis is very common in China and
Japan where most of the dogs are infected. It is also common
in Italy, especially in the marshy districts round Pisa and Milan.
It has also been recorded from England, France, Denmark,
Germany, Australia, Fiji, the United -States and Brazil.

Fig. 57. A, view of the heart of a dog infested with Filaria immitis
Leidy ( X |) ; the right ventricle and base of the pulmonary artery have
been opened, a, aorta ; b, pulmonary artery ; c, vena cava ; d, right
ventricle ; e, appendix of left auricle ; /, appendix of right auricle.
B, a female F . immitis removed from the heart to show its length.
Natural size. (After Shipley.)

Description. The adult is a filiform whitish worm, tapering
at both extremities, especially at the tail, and rounded ante-
riorly. The mouth is terminal, and surrounded by six, small,
indistinct papillae. The anus is near the end of the tail. The
male is 12-18 cm. in length by 07-0-9 cm. in breadth,
and possesses a spirally wound tail, bearing two small lateral
ridges supported by papillae. According to Schneider there
are n papillae, six of which are post-anal. From the anus

XIIJ LIFE-CYCLE 221

arise two spicules of unequal length. The female is 25-30 cm.
in length, by 1-1*3 mm- m breadth. The tail is short and
blunt, and the vulva is situated near the origin of the intestine,
a distance of about 7 mm. from the mouth. The eggs hatch
in the uterus, liberating embryos about 285 to 295 p> in length,
by 5 ^ in breadth ; their anterior ends are somewhat tapered,
whilst posteriorly the body tapers off into a long and delicate
tail.

Life-cycle. As in the case of F. bancrofti, the embryos of
F. immitis are liberated into the blood and appear in the
peripheral circulation. According to Manson the embryos of
this species, as in bancrofti, are more common in the blood
during the night, thus exhibiting a nocturnal periodicity, but
this is denied by Fiilleborn. If the embryos are injected into
the blood of a healthy dog, they will persist in the circulation
for several months.

Fig. 58. Part of the Malpighian tubule of an An phel infected

with the embryos of Filaria immitis. (Alter Noe .)

222 FILARIA IMMITIS LCH.

The further development of the embryos takes place in
certain species of mosquito and has been carefully investigated
by Noe and Fulleborn. The most efficient intermediate host
was found to be Anopheles maculipennis , which invariably
became infected by feeding on blood containing the embryos.
On the other hand, under similar conditions only about 20 per
cent, of Stegomyia fasciata shewed any development of the
filariae within their bodies. Noe found that development would
also take place in a large number of Anophelines, including
Anopheles bifurcatus, Myzorhynchus pseudopictus and Myzomyia
superpicta, and also in the following Culicines : Culex penicil-
laris, C. malaria and C. pipiens.

When a mosquito has fed upon an infected dog, three or four
times as many filariae are found in the stomach of the insect
as in the blood of the dog. The reason for this apparent
increase is the concentration of blood that takes place in the
gut of the mosquito, most of the serum being excreted within
an hour after a meal.

Within 20 to 40 minutes after being ingested by an
Anopheles, the filariae are found in the Malpighian tubules, in
which site they undergo their further development. The
worms are guided to the tubules by some chemiotactic influence,
for they have been shewn to be attracted towards the mouth
of an open capillary tube containing an emulsion of a Mal-
pighian tubule in normal saline.

The embryos, during their development in the mosquito,
cause a marked alteration in the character of the epithelium
of the Malpighian tubules, which may be the cause of the high
mortality amongst infected insects. The rate of development
of F. immitis, as in the case of bancrofti, depends mainly upon
the temperature, for at 260 C. the whole process is complete
within ten days, whereas at 200 to 210 C, it is very much
prolonged. When the development is complete, the young
filariae bore through the walls of the Malpighian tubule into
the body-cavity of their host, and migrate towards the
head. They usually come to rest within the sheath of the
proboscis, but isolated examples may be found in the palps
and legs.

XIIJ REFERENCES 223

When an infected Anopheles, containing filariae in its
proboscis, feeds on a dog, the worms escape through the fine
membrane (Dutton's membrane) uniting the labellae, and thus
get on to the surface of the skin. If this is sufficiently moist
they penetrate the epidermis, and may be found in the sub-
cutaneous tissues. The young filariae then make their way
towards the heart and great vessels of the dog, and there
develop into the adults. The worms may also be found in
other regions of the body, but in any case the embryos, on
being liberated, make their way into the circulation. Accord-
ing to Galeb and Pourquier the embryos may pass into the
foetal circulation, and therefore the disease may be transmitted
hereditarily.

The pathogenic effects on the dog vary considerably ; weak-
ness, anaemia, cough, icterus, ascites and lameness may be
observed and a fatal result is frequent. No effective treat-
ment is known.

Filaria recondita Grassi, 1890. This filaria, which also inhabits the dogs
in many parts of the world, is closely related to F. immitis. Grassi and
Calandruccio have shewn that the embryos develop in the body of the dog-
flea {Pulex serraticeps), the cat-flea (Pulex irritans), and also in a tick (Rhipi-
cephalus siculus Koch). Although infection experiments with fleas gave no
positive results, it seems probable that these insects may serve as the inter-
mediate hosts for this filaria.

REFERENCES.

Calandruccio (1892). Descrizione degli embrioni e delle larve della

filaria recondita (Grassi). Atti dell' Accad. Giornia, vol. lxix.
Fiilleborn, F. (1908). Ueber Versuche an Hundefilarien und deren

Uebertragung durch Mucken. Arch. f. Schiffs. u. Trope

vol. xii. Suppl. S, 43 pp. 4 pis.
(191 2). Untersuchungen iiber die chemotaktische Wirkung der

Malpighischen Gefasse von Stechmuckeii auf Hundemikrofilarien.

Centralbl. f. Bakter. vol. lxv. pp. 349-352.
(1912). Zur Morphologie der Dirohluria immitis Leidy, ifi

Ibid. vol. LXV. pp. 341-349,
Grassi and Nod (1900). Uebertragung dor Blutfilari auf-

schliesslich durch den Stich von Stechmucken. CeniralbLf. I

Orig. vol. xxviii. No. 19.

224 ORTHORRHAPHA BRACHYCERA [CH.

Noe, G. (1901). Sul circlo evolutivo della Filaria bancrofti (Cobbold)
e della Filaria immitis (Leidy). Ric. f. n. laborot. d. anatomia
normale d. R. Univ. di Roma, vol. vm. pp. 275-353.

(1903). Ulteriori studi sulla Filaria immitis. Rend. Ace. d.

Lincei. vol. xn. pp. 476-483.

Shipley, A. E. (1896). Nemathelminthes and Chaetognatha, in Cam-
bridge Natural History. London : Macmillan and Co.

CHAPTER XIII

ORTHORRHAPHA BRACHYCERA

The flies belonging to this series are characterised by the
form of the antennae, which, although variable, are never truly
Nematocerous, nor yet like those of the Cyclorrhapha. They
are usually composed of three dissimilar segments, of which
the third is sometimes elongate and subdivided into a number
of indistinctly separated segments. When an arista is present
it is always terminal in position, and never superior as in the
Cyclorrhapha. Rarely, as in the Leptidae, the antennae may
be divided into more than three segments. The palpi are one-
or two-jointed. Around the base of the antennae there is
no definite arched suture enclosing a small depressed space,
as in the Cyclorrhapha Schizophora. The venation of the
wings is usually more complex than that of any of the other
divisions ; the second longitudinal vein is simple, but the third
and fourth veins are often forked. The anal cell is closed
before the border of the wing, or distinctly narrowed at the
border. A discal cell is practically always present.

This group includes 16 families of flies, of which only one —
the Tabanidae — is of any interest from the present point of
view. Two other families, the Leptidae and Asilidae, include
a few blood-sucking species, but are o*f little importance. As,
however, many of the species belonging to these and other
families, are habitually predacious on insects, they have an
economic interest, and therefore we append the following
synopsis. The only one of these families that includes species
known to carry disease is the Tabanidae.

XIII] SYNOPSIS OF FAMILIES 22 ;

Synopsis of the families of Orthorrhapha Brachycera1.

I. Third antennal segment composed of a series of in-
distinctly separated subsegments ; empodia pulvilliform ; third
and fourth longitudinal veins forked.

(a) Costal vein extending all round the wing ; squamae large ; the third
antennal segment never has a style or arista . . . . Tabanidce.

(b) Costal vein extending all round the wing ; squamae small ; third
antennal segment may have a style, or arista, or not, or the antenna may
consist of a large number of segments . . . . . . . . Leptidce.

(c) Costal vein not extending beyond tip of wing, longitudinal veins not
crowded anteriorly ; two sub-marginal and five posterior cells always present,
the fourth closed. Third antennal joint composed of seven annuli, with a
terminal style or arista . . . . . . . . . . Acanthomeridcz ,

(d) Costal vein not extending beyond tip of wing ; longitudinal veins
usually more or less crowded anteriorly, posterior ones often weak ; four or
five posterior cells, the fourth rarely or never closed . . Stvatiomyidcs.

II. Third antennal segment simple, with or without a
terminal style or arista ; empodia pulvilliform.

(a) Head small, formed almost entirely by the eyes ; thorax large and
humped ; squamae peculiarly large . . . . . . . . Acrocerida.

(6) Squamae small or moderate ; venation of wings peculiarly intricate

NemestrinidcB.

(c) Squamae small ; wing venation more or less resembling that of
Tabanus . . . . . . . . . . . . . . . . Leptidce.

III. Third antennal segment simple, with or without a
terminal style or arista ; empodia, when present, bristle-like ;
third longitudinal vein, and often the fourth, forked.

(a) Crown of head concave between the eyes :

(i) Proboscis a rigid chitinous dagger ; flies bristly and hairv

A si! id (P.
(ii) Proboscis with fleshy labella ; antennae composed of four segn.
flies without bristles .. .. .. .. .. •• Mydaidcp.

(b) Crown of head not excavated between the eyes :

(i) Wing with five posterior cells ; third and fourth longitudinal
veins curve forwards . . . . . . . • • •

(ii) Wing with five posterior cells; fourth longitudinal vein does not
curve forwards ; predaceous flies . . . . . . • • • • Thett

(iii) Wing with three or four (rarely five) posterior cells and often
with dark markings; anal cell large; usually hairy bee-like flies, often with
a Long slender proboscis used for sucking the nectar from flowers

1 Modified from Aleock, loc. cit. p. 13 2.
H. B. F. l5

226 TABANID.E [CH.

(iv) Wing with three or four posterior cells, anal cell often small ;
femora and tibiae often with combs of spinules ; small dull-coloured pre-
daceous flies usually with a stiff proboscis for impaling prey . . Empididce .

(v) Wings with three posterior cells ; proboscis not projecting ;
small flies often found on windows . . . . . . . . Scenopinidcs .

IV. Third antennal segment simple, with or without an
arista ; the empodia, when present, are bristle-like ; third
longitudinal vein not forked.

(a) Wings shaped like a lance-head, the venation somewhat as in the
Psychodidae . . . . . . . . . . . . . . LonchopteYidcs .

{b) Second basal cell confluent with discal cell ; anal cell, if present,
small ; usually brilliantly coloured flies with metallic sheen . . DolichopodidcB .

(c) Second basal and discal cells either confluent or distinct ; anal cell,
if present, small ; not brilliantly coloured flies . . . . . . Empididcs .

(d) Antennae apparently two-jointed, with a three-jointed arista ; wings
(rarely wanting) with several stout veins anteriorly and other, weaker ones
apparently connected with them and running obliquely across the wing ;
small hunchbacked, quick running, bristly flies.. .. .. Phoridce.

CHAPTER XIV

FAMILY TABANID^E (BREEZE-FLIES, CLEGGS, HORSE-
FLIES, GAD-FLIES, SERUT-FLIES)

Description. The members of this extensive and important
family are usually large and strongly built flies, the females
of which feed on blood. The head is large ; the antennae are
projecting, and the third joint is composed of four to eight
indistinct segments, or annuli. The eyes are very large and
laterally extended ; in the male they meet along the middle line
(holoptic), but in the female the eyes are smaller and a narrow
streak is left between them (dichoptic). In the living insect
the eyes are often iridescent and usually marked with green,
purple, or brown bands, or spots.

The proboscis is projecting, sometimes as long as, or longer
than, the body, and the mouth parts are adapted for piercing
and cutting. Generally the labium is coarse and fleshy
and the labella are large ; the epipharynx and hypopharynx
are strong dagger-shaped structures ; the mandibles are

XIV] DESCRIPTION 227

sharply pointed and the maxillae have serrate edges. The
palpi are distinct and two-jointed ; the terminal joint is
inflated and hangs in front on each side of the proboscis. The
thorax and abdomen are clothed with fine hairs, never with
bristles, and are often striped or marked with dull colours.
The abdomen is broad, never constricted at the base, and com-
posed of seven visible segments. The legs are stout and the
tibiae sometimes dilated ; the pulvilli and empodia are in the
form of large membraneous plates. The venation of the wings
is very constant ; the third and fourth longitudinals are forked,
so that two marginal and five posterior cells are always present ;
the basal cells are large and the anal cells usually closed. The
marginal or costal vein encompasses the entire wing (Fig. 5) .
The squamae are large.

Fig- 59- Tabanns kingi Austen, ? ( X 3). (After Austen.)

Habitat. The members of this family arc widely distributed
throughout the world and about 1800 different species have
already been described. They are especially evident on clear
warm days, as soon as the sun has warmed the air, and arc
usually most active towards midday, but near Sedbergh, York-
shire, the writer has been badly bitten by ILrmatopotd in the
early mornings.

228

TABANID.E

[CH.

The males live entirely on the juices of flowers, honeydew,
etc., and, in the absence of other food, the female will also feed
on these substances. By nature, however, the female feeds on
blood, and is one of the most blood-thirsty of all insects. Its
bite is painful, but usually is not followed by any marked
inflammation, or swelling.

Life-cycle. The eggs of the Tabanidae are commonly laid
in large shapely masses on the leaves and stems of plants
growing in marshy ground, or overhanging water. In some
species they are deposited on stones or rocks above the water
of streams, and are very difficult to discover.

Fig. 60. A rock at Khor Arbat, Anglo-Egyptian Sudan, showing sites
selected by Tabanus kingi for ovipositing (indicated by crosses); the
three lower crosses represent freshly laid egg-masses. (After King.)

The eggs of Tabanus par were observed by King to be laid
separately on the under surface of the leaves of water-plants.
The colour of the eggs is usually brown or black, and at ordinary
summer temperatures they hatch out in from seven to nine days.

XIV

LIFE-CYCLE

229

The larvae may be found in rotting logs and stumps, in the soil
at the edges of pools and streams, under stones in ditches, or
swimming free in the water. If kept supplied with a diet of
angle- worms the larvae can easily be reared, either in jars of
moist earth, or in jars containing sand and water. As a rule
they are cannibalistic in habit and only one can be reared in
each jar, but T. biguttatus is an exception to this rule, and in
this species several can be reared together in the same receptacle.
The larvae are cylindrical in form, pointed at both ends ; the
body is composed of eleven segments, each of which is usually
encircled by a prominent fleshy ring, or row of protuberances,

Fig. 61. Egg-mass and mature larva of Tabanus kingi Austen, a, egg-
mass, x6 ; b, lateral view of larva, X3 ; c. lateral view 01 4th and 5th
abdominal segments, x6 ; d, posterior view of anal segment (inverted),
X6 ; e, lateral view of anal pseudopod. (After King.)

which are most pronounced on the ventral side, where th
as prolegs. The head is small, but distinct, and the mouth parts
are very peculiar ; the mandibles are attached so as to m
antero-posteriorly ; when they are retracted the anterior ends
point forwards, but when extended they point downws
backwards, thus forming a pair of hooks that serve to hold prey.
The duration of the larval stage depends upon the temperature.
In temperate countries the larva usually lives through the

230 TABANID^E [CH.

winter and only pupates the following spring, but in Egypt
King was able to rear T. par, from the freshly hatched larvae to
adults, in three and a half months. The pupal stage is usually
completed in three to four weeks, and as the whole development
generally takes about eleven months, the duration of the larval
stage is very considerable. In some cases it probably takes
more than one year for its development. When fully grown
the larva buries itself in the sand, or earth, in its immediate
neighbourhood, and then pupates.

Classification. The following synopsis of the genera of
Tabanidae is taken from Miss Ricardo's Revision of the Family ;
the more important genera, which have a world-wide distribu-
tion, are printed in capitals :

Synopsis of Genera of Tabanida.

1. Tabanin^e.

Ocelli absent ; hind tibiae not spurred.

I Third antennal segment composed of four subsegments or rings, and

i i not angulated or spurred at base =2

I Third antennal segment composed of five subsegments or rings = 5
f Rings so distinct that the antenna appears to consist of six segments

2 ] Hexatoma Meigen (Europe).
L Rings not so distinct as to modify the appearance of the antenna = 3
f Wings with a profusion of ring-like and scroll-like markings

3 4 HLematopota.

I Wings without circles and scrolls = 4

f First and second antennal segments pubescent in the male, third segment

4 <J longer than the first ; eyes hairy

^ Dasybasis Macquart (Chili and Australia),

f First antennal segment globose, situated on a frontal protuberance

5 J Bolbodimyia, Bigot (Venezuela).
I First antennal segment not globose =6

6 /Third antennal segment not angulated or toothed at base . . =7
\ Third antennal segment angulated or toothed at base . . . . =9
f Body covered with metallic scales

I Lepidoselasa Macquart (South America).

7 i Body metallic in colouring Selasoma Macquart (South America)

Body not in any way metallic ; first antennal segment longer than is

usual in Tabanus ; wings commonly with brown markings = 8

r Antennae long, the third segment cylindrical, and situated on a pro-

8 > jecting tubercle . . . . Udenocera Ricardo (Ceylon).
I Antennae not as in Udenocera

Diachlorus Osten Sacken (America and Philippines).

XIV] CLASSIFICATION 23 1

/Abdomen short, stout, very convex Stibasoma Schiner (America).

\ Abdomen not as in Stibasoma . . .. .. .. = 10

f Antennae long and slender, first segment long
10 ■{ Acanthocera Macquart (South America).

I Antennas not as in Acanthocera . . .. .. .. =11

[ Slenderer in build, usually with thorax and abdomen banded ; third
J antennal segment slender, wings mostly with brown markings

1 Dichelacera Macquart (South America).

I Stouter in build, third antennal segment stout . . Tabanus Linn.

II. Pangoniin^.

Ocelli usually present ; hind tibiae spurred.

f Third antennal segment composed of eight or seven subsegments or

I <! rings ; proboscis usually elongate . . . . . . . . = 2

I Third antennal segment composed of five rings; proboscis short =14
/Third antennal segment with a tooth Dicrania Macquart (Brazil).

\ Third antennal segment not toothed . . . . . . = 3

/Wings short ; body flat, elliptical Apocampta Schiner (Australia).

3 \ Wings not short . . . . . . . . . • • • = 4

f Third antennal segment with each subsegment branched

4 <( Pityocera Tos (Central America).

L Third antennal segment not branched . . . . . • • • =5

f Upper corner of eye terminating in an acute angle

5 i Goniops Aldrich (North America).

I Upper corner of eye not terminating in an acute angle . .
f Antennas deep-seated, inclined downwards ; palpi very large

6 <J Cadicera Macquart (South Africa)

I Antennae and palpi not as in Cadicera

f Antennas awl-shaped ; end of proboscis hatchet-shaped ; anal cell
J open and anal vein curved

7 ) Pelecorhynchus Macquart (Australia and S. America).
I Antennas, proboscis, etc., not as in Pelecorhynchics

f Proboscis scarcely extending beyond palpi
3 j Apotolestes Williston (California).

L Proboscis extending beyond palpi = 9

/Wings with fourth posterior cell closed = IO

9 \ Wings with fourth posterior cell open ll

fEyesbare .. .. .. Dorcalcrmus Austen (South Africa).

10 \Eyes not bare Scione Walker (South America, Seychelles, Australia).
/ Wings with first posterior cell closed . . • • l -

II \ Wings with first posterior cell open .. •• •• •• =I3

/Eyes bare . . . . Pangonia Latr. (subgenus I

12 \ Eyes hairy .. .. Pangonia Latr. (subgenus ;
/Eyes hairy .. DlATOMlNKURA Rond. (subgenus

13 \ Eyes bare .. DiATOMiNXURA Rond. (subgenus < rm Rond.)
/First and second segments oi antenna- short . . =15

14 \ Fust and second segments oi antennae Long •• Chbysops M

232 TABANID.E AND DISEASE [CH.

f Second segment of abdomen unusually large, spurs of tibiae small
15 -=( Pronopes Loew (Cape Colony).

I Abdomen and tibiae not as in Pronopes . . . . . . . . =16

fi /Face concave in the middle Rhinomyza Wied. (Cape Colony and Java).
\ Face not concave .. .. .. .. .. .. .. =17

f Wings with first posterior cell open Silvius Meigen (subgenus Silvius).

I Wings with first posterior cell closed
17 -{ Silvius Meigen (subgenus Esenbeckia Rond., Brazil).

I Third segment of antennae with an acute spine

I Gastroxides Saunders (India).

Tabanidce and disease. It must be admitted that the
evidence in support of the view that Tabanidae act as disease
carriers is rather unsatisfactory. Their voracious blood-sucking
habits and conspicuous size have given the flies a bad reputa-
tion in many parts of the world, and natives frequently assign
various ill-effects to their bites.

Most of these accusations, however, have not yet been
justified, although it seems probable that certain trypano-
somiases of animals, especially Surra, may be carried by
Tabanidae.

There are many difficulties in the way of conducting experi-
ments with these flies. They are always very impatient of
captivity and spend most of their time attempting to escape.
As a result it is difficult to make them feed on any particular
animal, and the flies soon die. Up to the present time hardly
a single experiment has been recorded in which the possibility
of a cyclical mode of transmission of trypanosomes by Tabanidae
has been investigated, for in no case have the flies lived a
sufficient length of time to decide the point1. Possibly the
best way of testing whether Tabanids act as the true inver-
tebrate hosts for any disease, would be to capture large numbers
of wild flies and feed them on susceptible animals. In this
manner, the presence of any naturally infected insects might
be detected. The occurrence of flagellates in the alimentary
canal of a large proportion of Tabanids is certainly rather
suspicious, for in many cases it is difficult to distinguish

1 Mitzmain has recently conducted experiments on the transmission of
Surra by Tabanus striatus and has definitely excluded the possibility of a
cyclical development, but has succeeded in obtaining direct transmission.

XIVJ TRYPANOSOMIASIS 233

between developmental forms of ingested trypanosomes and
the various insect flagellates.

It has been shown repeatedly that when Tabanidae, inter-
rupted in a feed on an infected animal, are at once transferred
to a healthy one, the latter may become infected as a result of
their bites. In these cases the parasites, present in the blood,
are simply mechanically transferred from the first animal to the
second by means of the proboscis of the insect. Almost any
blood-sucking insect is capable of such transference of in-
fection, but the importance of this mechanical transmission
should not be under-estimated.

With the exception of El Debab (T. soudanense), there now
seems little doubt that the pathogenic trypanosomiases of
Africa are all transmitted by various species of Glossina, which
serve as the true invertebrate hosts and, once infected, remain so
for considerable periods. On the other hand, there is evidence
to shew that these diseases, once started, may continue to spread
in the absence of tsetse-flies.

In this connection the outbreak of Trypanosoma peconim
infection in a herd of cattle belonging to the Uganda
Sleeping Sickness Commission is of some interest, for there
seems to be little doubt that in this case Tabanus sccedcns
Walk, was responsible for spreading the infection. The herd
contained a few animals that had been experimentally infected
with T. pecorum. Shortly after the appearance of swarms
of Tabanus, large numbers of the cattle, that had remained
healthy for a year, shewed signs of infection with T. pecorum.
It should be noted, however, that Glossina pa! pa! is weir also
found in small numbers after the Tabanids had disappeared,
and their presence might have been overlooked previously.

Jowett made some experiments near Cape Town with a
cattle trypanosome of the Dimovphon type, obtained near Beira,
Portuguese East Africa. As this infection seems to spread in
the absence of tsetse-flies, transmission experiments were made
with Hwmatopota and Stomoxys.

" Numbers of Huniatopota and Stomoxys were collected at
frequent intervals and placed in Large glass lamp chimneys, the
ends of which had been closed with mosquito netting. A

234 TABANID.E AND DISEASE [CH.

having shaved and damped a patch of skin on the trypanosome
infected subject, one end of such a tube was then applied to
the latter. As soon as it was seen that a number of flies had
commenced to feed on this animal, the tube was removed and
without delay applied to the skin of a healthy animal, the flies
being allowed to finish their meal on the latter. At the con-
clusion of the experiment the flies in most instances were
killed. Occasionally they were dissected. Only on two or
three occasions were they kept and used for feeding a second
time during the following days. The experiment therefore,
permitted only of mechanical transmission."

Only one positive result was obtained out of five experiments.
In this case 122 Stomoxys were fed in the course of 14 days on
an infected sheep and afterwards on a healthy sheep. After
an interval of six days three Hczmatopota, of which one was seen
to bite, fed similarly. Trypanosomes were found in the blood
of the sheep 13 days later, and it died after another 10 days.
The experiment shews that this trypanosome can be conveyed
mechanically by one of these species, and Jowett thinks that the
Hcematopota were responsible.

Hart records an experiment in Xorth-Eastern Rhodesia
supporting the view that Pangonia and Stomoxys may transmit
trypanosome infections.

An outbreak of trypanosomiasis (T. dimorphon, or pecaudi)
occurred on a farm fifty miles from Fort Jameson. The
owner stated that tsetse-fly had never been seen, but Pangonia
had been numerous. Two bullocks infected with trypanosomes
were kept at the farm and the remainder sent away. Then
three healthy cows were brought from Fort Jameson and
kraaled with the two bullocks, and to eliminate the chance of
their being bitten by a stray tsetse-fly, the animals were fed
close to the house. The experiment began on April nth and
the animals were at once bitten by Pangonia and Stomoxys nigra.
On May 27th trypanosomes were seen in one of the cows, and
the remaining two died of trypanosomiasis at the beginning of
July. It is impossible to decide whether the infection was due
to Pangonia or Stomoxys, or both, and the possibility of stray
tsetse-flies having bitten the animals is also not excluded.

XIV] EL DEBAB 235

Captain Hadow sent to the Wellcome Research Laboratories
blood smears from two sick bulls at Kadugli, Kordofan. These
were examined by Dr Balfour and found to contain numerous
trypanosomes, the species probably being T. brncei {ox pec audi).
These bulls could not have been bitten by tsetse-flies, for the
only tsetse area in Kordofan is at Kawalib, sixty miles from
Kadugli. The infection was attributed by the Arabs to the
serut fly (T aba tuts or Pangonia).

The circumstantial evidence in support of the view that
El Debab, a disease affecting dromedaries in the North of Africa,
is mainly carried by Tabanids. is much stronger than in the
case of the other African trypanosomiases. The natives of
North Africa from time immemorial have accused the serut
flies of inoculating this disease into the dromedaries. When
these animals remain during the summer in regions where
Tabanids are numerous, the mortality from El Debab in the
following months is very great. On the other hand, if Tabanids
are few or absent, the disease seems to be unable to become
established.

In Algeria the majority of the Tabanids appear between
the 1st and 15th of June ; they last for about forty days and
then disappear, as soon as their enemies the Asilids begin to
hatch out. The Tabanids live in the damp valleys and often
frequent the tufts of T hap si a, appearing as soon as this plant
flowers, and disappearing after it has withered.

Experimentally, Drs Edmond and Etienne Sergent. in
Algeria, have been able to transmit T. soudaticttse, the patho-
genic agent of El Debab, by the bites of Tabanus nctnoralis,
Mg. and T. tomentosus Macq.

The flies were first allowed to bite heavily infected ra:~
mice and subsequently fed on healthy animals. When there
was no interval between the two feeds, rive successful trans-
missions were obtained, and in one case after an interva
22 hours the flies were still infective. Throughout t:
experiments only rats and mice were employed, never the
natural host of the trypanosome.

These results are in harmony with what is known about the
history of the disease.

236 TABANIDJS AXD DISEASE [CH.

Generally the infection lasts at least one year in camels,
and in the month of June practically every herd contains
several individuals with numerous trypanosomes in the blood.
These animals would act as centres from which the infection
could be spread by the Tabanids. These latter feed during
the sunny hours of the day and usually attack the herd in
swarms. As a result of the active movements of the camels,
the insects are continually flying from one animal to another,
and the conditions are very favourable to the spread of any
infection.

Horses may also be infected by the agency of these same
insects, but such cases are rare, as horses are not usually kept
in the neighbourhood of herds of camels.

Three other trypanosome diseases, viz. Xagana, Mai de la
Zousfana and Dourine, have been transmitted experimentally
by the bites of various species of Tabanidae in Algeria.

Transmission was only effected when the insects fed on the
healthy animals immediately after having bitten an animal
containing a great many trypanosomes in its blood. In no
case was any infection produced if there was an interval of
more than a few minutes between the two bites. A single
bite was sometimes sufficient to cause inoculation of the disease,
and therefore, under suitable conditions, it is probable that this
mode of transmission can assume great importance.

According to Cazalbou, the disease of dromedaries at
Timbuctoo known as Mbori, and also Souma (T. cazalboui) at
Segou, a disease affecting horses and cattle, are both propagated
by Tabanas tceniatus, Macq. and T. biguttatits, Wied.

There is evidence showing that Tabanidae are agents for the
transmission of Surra (T. evansi). Thus Rogers, in the Fede-
rated Malay States, invariably produced the infection in dogs
and rabbits by the successive bites of many Tabanids. A dog
bitten by 12 flies that had just previously sucked blood from
another dog. heavily infected with T. evansi, shewed parasites
after an incubation period of seven days.

Fraser and Symonds repeated these experiments employing
various species of Tabanus, Hcematopota and Stomoxys. With
four species of Tabanus — T. fumifer, T. partitus, T. vagus, and

XI V] SURRA 2 -

T. minimus — they had four successes, three when there was no
interval between the two feeds, and one after a five-minute
interval. Ten experiments were performed and in each
only one or two flies were used. Five experiments with
Stomoxys and two with Hcematopota under similar condir.
gave negative results. A number of Tabanidae were then fed on
infected animals and, at varying intervals, emulsions of the
body contents of the flies inoculated into susceptible animals.
It was found that the trypanosomes in the alimentarv canal
of Tabanus remained infective for 24 hours, but after longer
periods lost their virulence.

Leese studied the natural transmission of Surra at Mohaud,
India, and made experiments with mosquitoes, Stomoxys,
Tabanus, Hcematopota and sand-flies. Four Tabanus. which were
fed on camels, in two of which trypanosomes were numerous,
and transferred immediately to a white rat, produced infection
in the latter, and under similar conditions ten Hcematopota
produced infection in a guinea-pig. Of three similar experi-
ments, employing Stomoxys, only one gave positive results -
it seems that Tabanus is able to transmit Surra better than
Stomoxys. On the other hand, Leese is strongly of the opinion
that Tabanus and Hcematopota are not specific transmitter^
outbreaks of the disease have occurred under circumstances that
precluded the possibility of their being the carriers. Never!
less, in the Punjab the worst " Surra zones " seem to be in
places where Tabanus is most numerous. Baldrev has
performed some experiments on the transmission of Surra by
various Tabanids and found that the trypanosomes remained
virulent in the gut for not longer than 24 hours. An attempt
was made to test the possibility of a cyclical m-»de oi t:
mission, but all the Tabanids died by the end of the ni:
day. Up to this date the inoculation of their body
into susceptible animals gave negative results.

In America, Mohler and Thompson noted an
Surra following the importation of zebus from India. This
herd consisted of 51 cattle that had been imported from
where their blood was examined twice with negativ
On arrival in New York they appeared tot

238 SURRA [CH.

but 2 ccs. of blood from each animal were injected into rabbits.
Three of these rabbits showed T. evansi in their blood, and after
some delay the three cattle thus shewn to be infected were
destroyed and the remainder screened. At this time there were
many Tabanus atratus present, together with other Tabanidae
and Stomoxys calcitrans.

In subsequent series of inoculations, 13 more animals were
found to be infected and removed ; finally, the remainder were
put in fly-proof box-stalls in a fly-proof stable, and these cattle
all remained healthy. The authors are of the opinion that
Tabanus atratus was responsible for the spread of the infection
amongst the herd, but the results are not very conclusive, as
the cattle may have been infected before they arrived.

In the Philippines, Mr M. B. Mitzmain informs me that he
has succeeded in obtaining the direct transmission of Surra
by means of Tabanus striatus. The flies were bred in captivity
and transmission was successful from guinea-pig to monkey,
and from horse to horse. In addition, this observer states that
T. striatus is undoubtedly the carrier of Surra in extensive
epidemics throughout the Philippines, and that there is a " very
decided correlation between the predominance of this fly and
outbreaks of Surra."

On the whole, the available evidence supports the view that
Surra may be directly transmitted by the bites of various
Tabanidae, and that in nature they play a very important part
in the spread of the infection. It is doubtful, however, whether
the transmission is always mechanical, and further experiments
on this point are much to be desired.

Since the above account was written, Leiper, in West Africa,
has discovered that two species of Chrysops serve as the inter-
mediate hosts of Filar ia loa. At present no details are available,
but this discovery is especially interesting, as it is the first
record of any Tabanid having been shewn to be responsible
for the transmission of a human disease.

XV] CYCLORRHAPHA SCHIZOPHORA 239

REFERENCES.

Alcock, A. (191 1). Entomology for Medical Officers.

Austen, E. (1909). African Blood-sucking Flies. British Museum.

Cazalbou (1904). Recueil de Med. Veterinaire, vol. lxxxi. p. 615.

(1906). Rev. Generate de Med. Vet. Nos. 89-90.

Fraser and Symonds (1908). Studies from the Institute for Medical

Research. Federated Malay States, No. 9.
Hart, R. (191 1). Journ. Comp. Path, and Therap. Dec. 191 1, p. 354.
Jowett, W. (191 1). Ibid. vol. xxiv. p. 21.
King, H. H. (1908). Third Report Wellcome Research Laboratories,

Khartoum. London : Bailliere, Tindall and Cox, p. 213.
Leese, A. S. (1909). Journ. Trop. Vet. Sci. vol. iv. p. 107.
Mohler, J. R. and Thompson, W. (1911). 26th Annual Report (for 1909),

Bureau Animal Industry. Washington, p. 81.
Montgomery and Kinghorn (1907). Ann. Trop. Med. and Parasit.

vol. 11. p. 130.
Ricardo, G. (1901-1904). Ann. and Mag. Nat. Hist.
Rogers, L. (1901). Proc. Roy. Soc. B. vol. lxviii. p. 163.
Sergent, Ed. and fit. (1905). Ann. Inst. Pasteur, vol. xix. p. 17.

(1906). Ibid. vol. xx. p. 665.

CHAPTER XV

CYCLORRHAPHA SCHIZOPHORA

General description. All the members of this series are
distinguished by the presence of a distinct frontal lunula and
frontal suture. The antennae are composed of three segments
of which the terminal bears an arista, almost invariably dorsal
in position, and never thickened into a terminal style. There
are never more than three posterior cells present (Fig.
the first of which may be closed or narrowed in the margin,
but the others remain open. None of the longitudinal wins
are forked ; the marginal and sub-marginal cells are never
closed ; and the anal cell very rarely extends towards the
margin of the wing. The flies are all more or Less bristly.

This very large division, including several families, is termed
by Williston, the Myodaria. It may be divided int.* I
groups, the Acalyptratae and Calyptratae, which are distinguished
as follows :

240 CYCLORRHAPHA SCHIZOPHORA [CH.

(i) Acalyptratae.

The squamae are always small, or vestigial, so that they do
not conceal the halteres when viewed from above. The
auxiliary vein is often indistinct or vestigial, or close to the first
longitudinal, with which it may be fused. The basal cells are
small, and the posterior ones indistinct or wanting. The males
are never holoptic and the front is never markedly constricted.
The thorax is without a complete transverse suture and the
posterior callosity is usually absent. The members of this
group are never large flies, but usually small, or very small.
None of them are known to suck blood, but certain species,
e.g. Sepsis, are probably concerned in the transmission of
disease1.

(2) Calyptratae.

The squamae are well-developed, never vestigial, and
generally conceal the halteres when viewed from above. The
auxiliary vein is always distinct along its whole course and the
first longitudinal is usually of considerable length, never very
short. The males are often holoptic or the front markedly
constricted. The thorax has a complete transverse suture in
front of the wings and a posterior callosity is present. The
members of this group are generally flies of moderate or con-
siderable size and are never very small. The house-fly and
tsetse-fly are two well-known examples of this large and im-
portant group, which is of the highest economic importance.
Williston divides them into six families, of which the only one
that we shall consider is the Muscidae.

Synopsis of Families of Calyptratce.

f Mouth and mouth-parts small or vestigial ; first posterior cell closed

1 -{ or narrowed (except in Gastrophilus). Bot-flies . . = Oestridce

I Mouth of usual size, mouth-parts not vestigial . . . . . . = 2

r Hypopleurae with a tuft of bristles ; first posterior cell narrowed or
I closed . . . . . . . . . . . . . . = 3

I Hypopleurae without a tuft of bristles ; first posterior cell narrowed or
fully open in the margin . . . . . . . . = 6

1 Vide Graham-Smith, G. S. (1913), Flies and Disease. Non-bloodsucking
Flies (Cambridge University Press).

xv] muscid^ 241

/ Antennal arista bare or somewhat pubescent . . = Tachinidce.

3 \ Antennal arista plumose or distinctly pubescent .. .. .. =4

f Antennal arista bare on the distal half; bristles rarely present on the

4 <J dorsal surface of the anterior segments of abdomen = Sarcophagid<2.

L Antennal arista plumose or pubescent to the tip . . . . . . =5

f Dorsum of abdomen usually bristly on anterior part ; legs usually long

- J = Dexiidce.

I Abdominal segments without bristles, except more or less near the tip ;

I legs not markedly elongated . . . . . . = Muscidae.

r First posterior cell narrowed or closed ; arista plumose to the tip
J = Muscidae.

] First posterior cell very slightly or not at all narrowed in the margin ;
[. arista plumose, pubescent or bare . . . . =Anthomyidce.

Family Muscim:.

The various individuals of this family are distinguished by
the absence of bristles on the abdomen, except at the tip, and
by the narrowed first posterior cell. The antennal arista is
usually plumose to the tip, sometimes only on the upper
side, and rarely bare. The eyes of the male are approximated
or contiguous, and the front of the female broad. The eyes
may be either bare or hairy. With the exception of Glossina,
the abdomen is composed of four visible segments. The
members of this family are generally of moderate size, and are
never elongate, very hairy, or bare flies.

For the sake of convenience, we have followed Alcock in
dividing the Muscidae into two artificial groups according to
whether the adults suck blood or not. The importance of the
latter group (including house-flies, blowflies, etc.) as can
of disease, has been described by Graham-Smith (loc. cit.) and
it is unnecessary to give any further description of them in
the present account. On the other hand, the blood-sucking
Muscidae include some of the most formidable biting-flies that
carry disease.

Blood-sucking Muscidae1.

In the majority of blood-sucking Muscidae the proboscis is

strongly chitinized and rigid, is slightly or not at all retractile,
and is more or less slender and tapering, and the labella are
small, rigid and strongly chitinized, and serrated or spinos

1 Alter Alcock. I C. cit.
H. B. V. l6

242 BLOOD-SUCKING MUSCIDiE [CH.

that the proboscis forms a very efficient apparatus for piercing
the skin. Occasionally the proboscis is only partly chitinous
and is retractile, and the labella are large and fleshy, but even in
these cases strong teeth, capable of cutting through the skin,
are present. In other respects the proboscis resembles that
present in the non-biting Muscidae, being longitudinally grooved
on its dorsal surface, so as to ensheathe the epipharynx and
hypopharynx, which together form a tube, by apposition and
basal interlocking. The blood-sucking habit is equally well
developed in both males and females.

Although Glossina and Stomoxys are the only two genera
that have been proved to carry infection, there is every possi-
bility that other members of the group may suddenly acquire
unenviable notoriety from this point of view, and therefore
we include the following table of the genera, taken from Alcock :

Genera of Blood-sucking Muscidce.

f Arista feathered only on the dorsal surface, individual hairs being also
feathered. Proboscis with a bulbous base and very slender shaft.
Maxillary palps long and slender, forming a sheath round the pro-
boscis. Fourth longitudinal vein curved in its proximal portion so
as to enlarge the anterior basal cell distally and to contract the
discal cell basally ; and sharply bent forward in its distal portion
in line with the posterior cross-vein so as to nearly close the first
posterior cell at a point much anterior to the tip of the wing.
Abdomen composed of seven visible segments . . . . =Glossina.

Individual hairs of arista not feathered. Shaft of proboscis not remark-
ably slender. Maxillary palps not forming an obvious sheath for
the proboscis. Fourth longitudinal vein not markedly sinuous in
its proximal portion and bending forwards in its distal portion at
a point considerably beyond the posterior cross-vein. Abdomen
composed of four visible segments . . . . . . . . —2

f Maxillary palps slender, less than half the length of the proboscis.
(Arista feathered dorsally only. Third longitudinal vein with some

2 *{ bristles on its proximal part.) .. .. .. .. = Stomoxys.

I Maxillary palps more or less spatulate, almost as long as the proboscis.
I always much more than half its length . . . . . . =3

f Proboscis chitinous in all its extent, the labella small . . . . =4

Proboscis with the distal part, and large labella, fleshy. Terminal
fleshy part of proboscis reflexed beneath the chitinous part in repose.

3 <( Arista feathered dorsally and ventrally ; third longitudinal vein not

bristly ; fourth longitudinal vein abruptly bent so as nearly to
close the first posterior cell
^ = Philcematomyia (including ? Pristorhynchomyia).

XV] TSETSE-FLIES

243

/Arista feathered only on dorsal surface . . . . . . . . =5

\ Arista feathered on both dorsal and ventral surface . . . . =0

f Proboscis long and tapering ; fourth longitudinal vein gently curved
distally so as to leave the first posterior cell wide open ; third longi-
tudinal vein without bristles . . . . . . = Lyperosia.

I Proboscis short and stumpy ; first posterior cell narrowly open ; third
I longitudinal vein with some bristles proximally =Stygeromvia.

f Fourth longitudinal vein strongly curved distally, so as to leave first
posterior cell narrowly open. Third longitudinal vein without
1 bristles . . . . . . . . . . . . — Hcsmatobosca.

I Fourth longitudinal vein slightly curved distally. so as to leave first
[_ posterior cell widely open . . . . . . . . _ 7

/Third longitudinal vein with some bristles proximally =Hcsmatobia.

\ Third longitudinal vein without bristles . . . . =Bdellolarynx.

CHAPTER XVI

THE TSETSE-FLIES — GENUS GLOSS/NA, WIED., 183O

Diagnosis. The genus Glossina is sharply distinguished from
all other members of the Muscidae by its viviparous mode of
reproduction, which resembles that of the Pupipara, and also
by certain peculiarities in the structure of the antennae and in
the wing venation. Austen gives the following diagnosis of
the genus :

" Narrow-bodied, elongate, dark brown, blackish, yellowish-bro\
yellowish flies belonging to the Family Muscidae, ranging in size from about
6 or 8 mm. in the case of Glossina tachinoides, Westw., to as much as 13 or
13-5 mm. in that of a large female of G. brevipalpis, Newst., or longifennis,
Corti ; recognisable when alive and at rest by the wings being closed flat one
over the other above the abdomen (beyond which they project considerably),
instead of divaricate (as in the case of Stomoxys) or tectrform (as in .
pota), and by the proboscis {i.e. proboscis ensheathed in the palpi). :
horizontally in front of the head ; palpi, as seen in the natural position extend-
ing slightly beyond the proboscis, their inner sides groov< nn a
sheath for the latter, to which in life they are applied so closely .
to conceal it ; base of proboscis suddenly expanded beneath into a la: -
shaped bulb."

General description. In addition to the above-menti
characters, there are certain others which aid in the differentia-
tion of the genus. The antenna, in both sexes, contains in the

244

GLOSSINA

[CH.

second and third segments a curious sense-organ, consisting
of a number of sacs lined with sensory epithelium and opening
to the exterior by a well-marked pore on the inner surface of
the third segment. From the structure of this organ it is
supposed to be auditory in function. The arista of the antenna
is three jointed, the first two joints being very small, the terminal
one broad and compressed, and feathered on its upper side
with about 22 or 23 fine branching hairs.

The eyes are large and in both sexes are well separated ;
the anterior facets towards the inner margin are much larger
than those behind.

Fig. 62. Comparative morphology of the proboscis of Glossina (I), Melo-
phagus (II) and Stomoxys (III).

B, proboscis bulb ; G.S., common salivary duct ; Hyp., hypopharynx ;
L., labellae ; Lab., upper lip (labium) ; L. inf., lower lip. I, Glossina
palpalis; II, Melophagus ovinns ; III, Stomoxys calcitrans ; X35. (After
Roubaud.)

The horizontally projecting proboscis is strongly chitinized
and consists of a bulbous base contracting to a long and very
slender shaft. The base of the proboscis, or proboscis bulb, is
surrounded posteriorly by a fold of skin forming the hind-wall
of the buccal cavity. The proboscis is grooved dorsally to

XVI] DESCRIPTION 245

contain the stylet-like epipharynx and the tubular hypopharynx
which, by apposition, form a suctorial tube.

The maxillary palps are slender and as long as the proboscis,
round which they form a loose sheath when the insect is resting.

The wings possess a very striking venation which is quite
sufficient in itself to distinguish the genus. The fourth longi-
tudinal vein is strongly curved in its proximal portions. The
anterior basal transverse vein, at the base of the discal cell,
is very short, and this first curve of the fourth longitudinal vein
reduces the basal half of the discal cell, whilst the anterior
basal cell is correspondingly increased. The fourth vein then
bends upwards to join the anterior transverse vein, after which

Anterior cross-vein
Auxiliary vein

Fig. 63. Wing of Glossina palpalis to shew the venation.

it runs obliquely downwards almost at right angles to its
former course. After joining the posterior transverse vein it
again bends upwards and reaches the margin of the wing some
distance before the apex. The second, third and fourth
longitudinal veins all turn upwards at their tips and the anterior
transverse vein is very oblique.

The sexes of Glossina can be readily distinguished, as m
the male the external genitalia form a large oval swelling, the
hypopygium, lying beneath the ventral surface oi the seventh
abdominal segment. The anus forms a median slit in the front
part of this hypopygium and anteriorly on the venter oi the
sixth abdominal segment is a pair oi smaller swellings, termed

246

GLOSSINA

[CH.

hectors. When the hypopygium is turned back a system of
complicated appendages is displayed, the arrangement and
structure of which have been shewn by Newstead to be of great
use in classification. These appendages are briefly as follows :
the superior claspers, whose chief function is apparently to
grip the abdomen of the female ; the editum ; the inferior
claspers, which present very striking morphological differences

Fig. 64. Gravid uterus of G. palpalis containing a larva at an advanced stage
of development. Dorsal view x 10.

C.G.gl., common excretory duct ; CL.gl. principal lateral trunk of
the uterine glands ; L, body of the larva ; O.O. , ovary ; Pr., caudal
protuberances of larva ; R.gl., ramifications of uterine gland ; Sp,
spermatheca ; Ul, uterus ; V, vagina. (After Roubaud.)

in the various groups ; the harpes, small bilateral appendages
most highly developed in the fusca group and rudimentary or
absent in the remaining groups ; the juxta, or penis sheath ;
the penis ; the median process, present only in the fusca group,
lying in the middle line between the inferior claspers ; and the
connecting membrane, present in the palpalis and morsitans
groups, but absent in the fusca group.

XVI REPRODUCTION

247

The method of reproduction, discovered by Bruce, is very
remarkable, resembling that of the Pupipara, and is probably
the result of their exclusively blood-sucking mode of life.
The female lays a single larva at a time, which is retained and
nourished in the oviduct until it is full grown. After the
larva is born, it at once burrows into the ground and pupates.
The larva is generally of a yellowish-white colour and bears at
its posterior extremity a pair of large dark-coloured protu-
berances and between them is a depression into which open
the spiracles (Fig. 70). The pupa is dark brown in colour
with a slight sheen. It is broadly ovoid in shape and the
larval protuberances are equally conspicuous, forming, to-
gether with the size and shape of the depression between them,
a means of identifying the immature stages of different species.

Distribution. The members of this genus are entirely re-
stricted to Africa and the south-west corner of Arabia, together
forming the Ethiopian region, and range between the latitudes
of 180 N. and about 310 S. Within these limits the tsetse-flies
are not found continuously but are generally confined to belts
or patches of forests, bush, and warm and damp situations where
shade can be obtained. The areas in which the tsetse- fly
occurs are commonly known as " fly-belts " and are well
exemplified in the case of G. morsitans. Tsetse-flies are said
to be absent from dry open plains without shade.

Determination of the species of GlOSSINA.

It seems probable that most, if not all, of the specie
the genus Glossina, are of importance as carriers of dis
and therefore we include the following table for their determina-
tion. In the classification, the important work of Austen has
been followed throughout, and according to Ins scheme the
species may be divided into four group- :

248

GLOSSINA

[CH.

Synopsis of species of Glossina, after Austen1.

Tarsi of hind-legs entirely) Glossina palpalis Group (I), also G. morsitans
dark brown or black J var. paradoxa {vide infra).

( Species of small size, '

length not exceeding

10-5 mm., usually

much less ; wing ex-
pansion not greater

than22'5mm. Upper

surface of abdomen

distinctly banded,

with conspicuous dark

brown transverse

■{ marks on a pale
I ground colour.

Only the two
last joints of
hind tarsi are
dark-coloured,
thus forming
a conspicuous
contrast with
the remaining
joints which
are pale.

Species of large size, ^ Wings fairly dark.

exceeding 10-5 mm.

at I

Wing expansion
least 25 mm.
Upper surface of ab- 1
domen not marked
with distinct bands as |
in the previous group. )

Palpi long and
slender (except in

tabaniformis).

Glossina
morsitans
Group (II).

Wings pale,
short.

Palpi

Glossina

fusca

Group {III).

Glossina
brevipalpis
Group (IV)

I. Glossina palpalis group.

Dorsum of abdomen ochraceous-buff or buff ; third and following segments
exhibiting sharply defined, dark brown or clove-brown interrupted transverse
bands. Length not more than 8 mm. . . . . tachinoides, Westw. (p. 253).

Closely resembling tachinoides, but distinguished by its bright ochraceous
colour and relatively narrow head. Length of $ (only specimen known) 7 mm.

austeni, Newstead.

Third joint of antenna? pale, clothed with long and fine hairs, forming a
conspicuous fringe on front and hind margins. Length 8 to 9 mm.

pallicera, Bigot.

Dorsal surface of abdomen dark sepia-brown ; median paler area on
second segment broad and more or less quadrate or irregular in outline.
Hypopygium of male buff or ochraceous-buff . . . . caliginea, Austen.

Dorsal surface of abdomen blackish-brown ; median pale area triangular
in outline. Hypopygium of male grey. Length of male always exceeding
8-5 mm. .. .. .. .. palpalis, Rob. Desv. (p. 256).

1 Handbook of the Tsetse-Flies, 1911,

XVI] CLASSIFICATION 249

II. Glossina morsitans group.

1. Last two joints of front and middle tarsi with sharply defined, clove-
brown or black tips . . . . . . . . . . . . . . . . =2.

Last two joints of front and middle tarsi either entirely pale or, at most,
faintly brownish at the tips, never so dark as to form a sharp contrast with the
remaining joints .. .. .. .. —pallidipes. Austen (p. 271).

2. Third joint of antennae fringed with fine hairs on front margin. The
dark brown transverse abdominal bands extending close to the hind margins
of the segments . . . . . . . . . . = longipalpis, Wied. (p. 274)

Third joint of antennas not fringed with fine hairs on front margin. Trans-
verse abdominal bands not extending close to the hind margins of the segments.

= morsitans, Westw. (p. 276).

(a) Markedly paler than typical morsitans, but more or less agreeing in
its general characters . . . . . . . . morsitans var. pallida, Shircore.

(b) Resembling morsitans but distinguished by having all the joints of
hind tarsi dark as in palpalis group . . morsitans var. paradoxa, Shircore.

III. Glossina fusca group.

f Third joint of antennae fringed with fine hairs on anterior and posterior
margins. Fringe on anterior margin conspicuous under a hand lens
( X15) when fly is examined in profile . . . . . . = 2

I Third joint of antennae with fringe of hairs on anterior margin so short as to
be scarcely noticeable under a hand lens, the longest hairs not exceed-

I ing one-sixth the width of the third joint. Palpi long and slender =3

f Length of longest hairs on anterior margin of third joint of antenna? equal
■{ to from one-fourth to one-third of the width of joint. Palpi of moderate

L length. Number of hairs on arista 18 to 23 —taba).

f Pleurae drab-grey or isabella-coloured ; hind coxae buff or greyish-butt
<( = fusca, Walk.

L Pleurae dark grey ; hind coxae mouse-grey .. —fuscipleu\

IV. Glossina brevipalpis group.

f Dorsum of thorax with four sharply defined, dark brown •

or elongate spots, arranged in a parallelogram, two in froni
J behind the transverse suture. Proboscis bulb with a sharply

I brown or dark brown tip .. .. =/<

I Dorsum of thorax without such spots Pt iboscis bulb Dot dark "r I

I at tip

f* Wings with upper, thickened portion of anterior tl

I darker in colour than adjacent veins and t:

<(' ously against the rest of the wing

i Wings with the part in question not darker than the

I wings being practically unicolonrons

2.50 GLOSSINA AND TRYPANOSOMIASES [CH.

Glossina and Disease.

The more common members of this genus have all been
proved to be capable of serving as the invertebrate hosts of
various species of trypanosomes, and in addition may carry
infection directly from one animal to another, when there is no
long interval between the bites. Some species of trypanosomes
seem to be mainly spread by only one species of Glossina, as in
the case of sleeping sickness (T. gambiense), which seems to be
restricted to regions where G. palpalis is present. Nevertheless,
G. morsitans has been shewn experimentally to be capable of
transmitting T. gambiense and it is difficult to see why such
transmission does not take place in nature. Fortunately, this
trypanosome seems to be unable to readily adapt itself to
development in more than one species of Glossina, but some
of the cattle trypanosomes, e.g. T. cazalboai and T. dimorphon,
seem to be able to develop in any species of Glossina, though
not with equal facility in all of them.

Probably the most important factor restricting the spread
of trypanosomiases is the difficulty with which the tsetse-flies
become infected. When several Glossince are fed on an animal
containing trypanosomes in its blood, only a relatively small
proportion of the flies become infected, the number depending
on a variety of conditions which are not thoroughly under-
stood.

Attention may be called to Miss Robertson's experiment
with T. gambiense and G. palpalis, reproduced in tabular form
on page 309, from which it appears that the percentage of
flies in which the trypanosomes develop, depends to some
extent on the stage of the infection in the vertebrate host.
Yet another important condition is the interval that elapses
between an infective and the subsequent feed. In the case of
T. gambiense and G. palpalis, the trypanosomes that may have
developed in the gut of the fly after the first feed are frequently
swept out by the next influx of blood and thus no infection
is produced. Strange as it may seem, from Miss Robertson's
experiments there can be little doubt that when flies are fed
every two or three days there is much less chance of them

XVIJ CONDITIONS AFFECTING TRANSMISSION 25 1

becoming infective than if they are starved after a meal of
infected blood.

Probably temperature exercises a greater influence than any
other known factor on the development of trypanosomes in the
tsetse-fly. Kinghorn and Yorke have shewn that T. rhodesiense
can only complete development in its invertebrate host,
G. morsitans, at a temperature of at least 750 to 8o° F. Similarly
Kleine and Fischer on Lake Victoria were quite unable to
transmit T. gambiense by means of G. morsitans, whilst on the
warmer shores of Tanganyika, Taute, employing the same
species, succeeded without much difficulty (vide p. 306).

The observations on the natural infections of tsetse-flies
have shewn that flies of different species frequenting the same
district are not infected in the same proportions, nor in the
same manner. Moreover these proportions, even for the same
species, vary in different localities, as for example in \\
Africa. Thus Bouet and Roubaud found that in Lower
Dahomey T. cazalboui predominated in G. longipalpis and
palpalis, T. dimorphon in longipalpis and tachinoides, and
T. pecaudi in longipalpis. On the other hand, in Upper
Dahomey, T. pecaudi was most predominant in G. morsitans,
and in Casamance T. dimorphon in morsitans. The number of
G. palpalis becoming infected with T. cazalboui when fed on an
animal suffering from this infection, was 40 per cent, in
Middle Dahomey, and nil in Upper Casamance, although
repeated attempts were made to infect the flies. These experi-
mental results were confirmed by an examination of natural
infections. In Middle Dahomey one fly in thirty was naturally
infected with T. cazalboui, whilst in Upper Casamance out of
560 flies examined only one shewed infection of the pro-
boscis.

Souma (T. cazalboui) exists in both regions, but it is evident
that some other species of tsetse besides palpalis must be
responsible for its transmission in Casamance. From t:
data Roubaud deduces that the receptivity of a given
of Glossina for any particular virus, is not uniform throughout
the region of the flies' distribution. In other v.
only endemic where there are receptive races of tsetse-fl

252 GLOSSIXA AND DISEASE [CH.

From this point of view it is worthy of notice that, in spite
of numerous experiments, up to the present no one has suc-
ceeded in transmitting T. gambiense by G. palpalis — or any
other tsetse-fly — on the west side of Africa. It seems that
the West African races of G. palpalis, are more or less refractory
to infection with T. gambiense, for the climatic conditions in
Dahomey, Casamance and in Uganda, do not differ sufficiently
to explain the difficulty of transmission in the two former
districts.

Thus the evolution of trypanosomes in the invertebrate
host is a very complex problem and, before commencing pro-
phylactic measures in any particular district, it is first of all
necessary to determine, by careful experiments with the local
races of Glossina, which species are responsible for the spread
of the local strains of trypanosomiasis. If this is not done,
there is a great danger of administrative efforts being wasted in
the attempt to destroy a comparatively harmless species of
Glossina, whilst the more important carrier escapes. The results
of experiments in other neighbourhoods are of very little use,
for, as mentioned above, in one district T. cazalboui is carried
by G. palpalis, whereas in another all attempts to infect this
tsetse with the same trypanosome have been unsuccessful.

In the following pages we have summarized the available
information concerning the bionomics of all species of Glossina
that have been proved to carry any infection, together with a
brief mention of the infections they are known to transmit.
Further details of the experiments and observations on the
latter point will be found under the heading of the various
species of trypanosomes (Chapter XVIII).

REFERENCES.

Austen, E. (191 1). Handbook of the Tsetse-Flies. British Museum,

(Nat. Hist.) London.
Newstead, R. (191 1). Bull. Ent. Research, vol. 11. p. 9.

(1912). Ann. Trop. Med. and Parasit., vol. vi. p. 129.

XVf GLOSSINA TACHINOIDES

Glossina tachinoides Westwood, 1850.

nyms. G. palpalis var. tachinoides Austen, 1903. G. a.
Brumpt, 1904.

Description. Glossina tachinoides is one of the smalles
the known tsetse-flies, the length of the female being from
6*S to 8*4 mm. and of the male 6*o to 675 mm. Among tl
species having all the tarsi of the hind-legs dark, it may easily
be recognised by its small size and its very distinctly banded
abdomen. On the dorsum of the second segment of the
abdomen there is a median quadrate pale area, which is very
conspicuous and is one of the distinctive characters of the
species.

Distribution. G. tachinoides is widely distributed through-
out West Africa having been recorded from the Senegal to the
French Congo, including Gambia, Gold Coast, the Northern
Territories. Togoland. French Guinea, Ashanti, German Came-
roons, and Nigeria, where it is especially abundant in the north.
In addition the species occurs in the French Sudan, on the si.
of Lake Chad, and has been recorded from Southern Arabia
and German East Africa. According to Neave, the tachin<
recorded from the last named locality may prove to be
G. austeni. Newstead.

Bionomics. G. tachinoides closely resembles palpalis in its
habits, being found in the vicinity of water, especially along the
banks of rivers. It generally prefers rather more open wooded
tracts than palpalis and is not found in the groves of wild
palms along the small streams. According Sim] the

species is most abundant where the country is open
sparse, the dry season well-dehned and the rain-fall sli§
It is the predominant tsetse-fly occurring along the rivers in
the redon bordering on the Sahara and - >me

from the north.

Dr Alexander, in Northern Nig ria, found
large marsh consisting elephant '

clumps of palm trees and thick un :h. thor.. riled

to rind the rlv on the banks of a river about three quar
mile away.

254 GLOSSINA TACHINOIDES [CH.

Although usually confined to the vicinity of water, in
Southern Arabia G. tachinoides occurs in thick belts of euphorbia,
tamarisk and cactus, often some distance from the edge of
any water, but is never seen in the date groves or along the
patches of cultivation.

Moiser has recently given an interesting account of the
habits of G. tachinoides in the Bornu Province, Northern Nigeria,
where the flies have existed for an indefinite period confined to
the thick bush. In order to study the vertical range of the
flies, men were posted up trees at heights varying from 10
to 25 feet, but in no case were any of the insects seen,
although there were several on the ground. As a result of his
observations Moiser comes to the following conclusions : —
Deep shade and proximity to water appear to be the main factors
influencing the distribution of the flies. Their natural resting
place is on the lower side of twigs and branches of undergrowth,
under the shade of large trees, at a height usually not greater
than a foot above the ground. The flies are very restless and
the observer is of the opinion that during the day they are
continually moving about from place to place within the fly-
belt and only for short periods rest on the under surface of
twigs and small branches and perhaps on the ground. They
do not usually travel higher than four or five feet and probably
never as high as ten feet, therefore it is unlikely that the flies
feed on monkeys or birds, but on the ground animals, e.g. the
warthog, duiker or bushbuck.

G. tachinoides requires a meal fairly frequently and accord-
ing to Moiser cannot withstand starvation without water for
longer than 24 to 30 hours. On the other hand Roubaud
kept ten flies in saturated air and all were alive after three
days, and three after ten days. In captivity they will
feed on the bodies of other tsetse-flies and it is not improbable
that in nature they feed on other insects, ticks, grasshoppers
etc. Certainly in Arabia, Carter noticed this fly in localities
where the chance of getting a feed of mammalian blood must
be very slight indeed. The flies feed voraciously on human
beings and are very troublesome, as they are quite active in
dull weather and in the very early hours of the morning, when

XVI] GLOSSINA TACHINOIDES 255

palpalis is usually quiescent. Moreover, according to Dr
Alexander the flies bite after dark, at 7.0 p.m. he having had
to take refuge in his mosquito net, and his boys remarked that
the flies were more troublesome than mosquitoes.

G. tachinoides is very resistant to heat, an exposure of one
and a half hours in a stove at 400 C. being well borne. As a
result the species is able to exist in very warm regions and
occurs in the Sudan in localities that are too hot for G. palpalis.

Reproduction. The flies copulate immediately after hatch-
ing and at 250 C. the larvae are deposited at intervals of about
eight days. The duration of the pupal stage in Dahomey (at
240 to 250 C.) was found by Roubaud to be from 28 to 35 days.

Like palpalis, the pupae will resist immersion in water for
a period of 20 hours, and are able to withstand a tempera-
ture of 350 C. for ten hours in the day, so long as the experiment
is only continued for a few days ; if it goes on for a month, all
the pupae die.

G. Tachinoides and Disease.

This species is one of the main carriers of Souma (T. cazalboui)
and T. dimorphon, in West Africa. Moreover, although direct
experimental evidence is lacking, it is likely that tachinoides
is able to transmit sleeping sickness. In Togoland on the
Oti River, a tributary of the Volta, Zupitza believes that it
takes the place of G. palpalis as a carrier of this dist

Prophylaxis. The methods that will be described for
G. palpalis (see p. 315) are also applicable to tachinoides, and
in Northern Nigeria experiments have been made on the efl
of cutting down the undergrowth on the banks of rivers. ( >ne
month after the clearing very few tachinoides could bo found
and pupae were sought without success.

LITERATURE.

Carter, R. Markham (1906). Brit. Med. Journ. Nov. 17. 1906, p. I

Moiser, B. (191 2). Bull. lint. Research, vol. in. p. 195.

Neave, A. S. (1912). Ibid. p. 275.

Roubaud, E. (1911). Compt. Rend. A

Simpson, J. J. (1912). Bull. Eni A. in. p.

Zupitza (1909). Cf. S. S. Bulletin, vol. 11. p. 1 \g.

256 GLOSSINA PALPALIS [CH.

Glossina palpalis Rob. Desv. 1830.

Synonyms. Nemorhina palpalis Rob. Desv. 1830. Glossina longipalpis
Walker {nee Wiedemann), 1873. G. ventricosa Bigot, 1885. G. tabaniformis
Bigot, 1885. G. maculata Newstead, 1907. G. fuscipes Newstead, 1910.

Description1. " Length, i 8 to 9 mm., 2 8-6 to 10-2 mm., width of head
j 2-4 to 2-6 mm., ? 2-5 to just under 3 mm.; width of front of vertex, J
o-6 mm., 2 1 mm ; length of wing, ? 7 to 8-4 mm., <r 8-4 to 9-2 mm.

" Abdomen clove-brown or blackish-brown ; thorax usually paler, with
dark brown markings on a greyish ground ; abdomen generally with at least
an indication of a pale or slate-grey longitudinal median stripe, with pale
lateral triangular markings, and usually the hind margins of the segments
narrowly pale. Femora in typical race more or less mouse-grey, greyish-brown,
or dark slate coloured ; tibiae, extreme tips of femora, and first three joints of
front and middle tarsi buff or ochraceous-buff, hind (or middle and hind)
tibiae sometimes infuscated in J ; hind tarsi blackish-brown or clove-brown
above ; wings strongly tinged with sepia-brown, but not quite so dark as in
G. caliginea.

" Head.— Face and jowls cream-coloured or cream-buff ; posterior surface
of head (occiput) entirely cinereous ; frontal stripe varying from ochraceous
to dark chestnut ; frontal margins (sides of front or parafrontals) greyish,
seen from the side with a dark brown elongate area below ; ocellar triangle
smoke-grey, enclosing the dark brown ocellar spot, which is joined posteriorly
to a sharply defined dark brown band, uniting the vertical bristles and very
conspicuous except in the darkest specimens ; second joint of antenna more
or less yellow at the apex in front, third joint narrowly buff at extreme base
on outer side, otherwise entirely mouse-grey ; arista buff, dark brown beneath ;
palpi mouse-grey, blackish on upper side, proboscis bulb dark brown.

Thorax. — Dorsum in most clearly marked specimens bluish-grey or greyish
olivaceous, with brown markings. These markings when fully visible are as
follows : a narrow stripe on each side of the median line, interrupted before
reaching the transverse suture and again before reaching the hind margin ;
the section of each stripe behind the suture is expanded posteriorly, and the
terminal portion of the stripes immediately in front of the hind margin takes
the shape of a pair of more or less confluent ill-defined spots, sometimes
confluent with the stripes in front ; next to the two admedian stripes on each
side of the suture itself a more or less sharply defined oval spot ; on the out-
side of this a longitudinal stripe, more or less interrupted and sometimes
obsolete in the middle, but in front curving round outwards behind the
humeral callus and then running backwards along the lateral margin of the
dorsum nearly to the post-alar callus ; in the area thus enclosed is a broad ill-
defined patch in front of and behind the suture while the lateral stripe itself
sends off two prolongations, which run inwards for a certain distance on each
side of the suture. Humeral callus with a spot on its upper portion, confluent
with the curved stripe behind it ; a more or less ill-defined spot on the post-
alar callus also. Pleurae olive-grey or smoke-grey in male, drab-grey or olive-
grey in female, a more or less distinct brown patch in the centre of the meso-
pleura. Scutellum buff or cream-buff, olive-grey at the base, the usual dark

1 Taken from Austen, Handbook of the Tsetse-Flies, 191 1, p. 24.

XVI

DESCRIPTION

257

brown patch on each side of the median line more or less conspicuous ; api< al
scutellar bristles in the female variable in length— (sometimes as in specimens
from the Congo Free State and Uganda) short, sometimes (as in sp
from Liberia, Sierra Leone, and the Gambia) nearly as long as in the male.

Abdomen. — Dorsum clove-brown or blackish-brown ; first segment and a
median triangular area on the second (its base resting on the front and its
apex on the hind margin of the second segment) buff-coloured or ciner*
the pale triangle continued backwards as a narrow, more or less well-defined
median stripe, usually reaching at least so far as the hind margin of the fifth
segment ; lateral margins of the segments from the second onwards grey,
expanded on the apical angles into triangular markings, extreme hind margins
of the segments from the second to the sixth usually narrowly pale or grey ;
seventh segment, as also the hypopygium in the male, entirely grey.

Fig. 65. Glossina palpalis. Photographs taken by Dr Graham, on the Cold
Coast, shewing the flies in a position of rest. The fly to the left is magnified
3^ diameters, those to the right are of natural size. (From the Sfa

Sickness Bulletin.)

Legs. — Last joint of front and middle tarsi dark brown, often more
buff at base, sometimes distal third alone dark brown, remainder buff ;
penultimate joint of front and middle tarsi dark brown, more or less buff at :

Wings as described above. Squama waxen-white, border of the antisquama

darker, fringed with short, darker hairs.

Haltet s cream-buff.

Glossina palpal is var. wellmani Austen

Synonym. G. bocaqei Franca, 1005.

" & ,? — Distinguishable from typical G, Rob.-Desv., b]

reduction in the markings of the dorsum of the thorax.

"Frontal stripe pale ochraceous ; thoracic markings much n
that the thorax hi a well-preserved specimt
markings taking the form of spots or blotches : t3
the inner extremity of the humeral callus on each side small
circular, and especially conspicuous when the inseel
slightlv from behind ; femora pale, the dark ■

H B, F. ' "

258 GLOSSINA PALPALIS [CH.

Distribution. Glossina palpalis is widely distributed through-
out the western equatorial tropical region of Africa. Along
the west coast it extends from the Senegal to Angola, where
the variety wellmani predominates. Inland it extends as far
as Bahr el Ghazal and, according to Brumpt, Lake Rudolf.
Proceeding southward the eastern boundary of the species
includes the shores of Lake Victoria in British and German
East Africa, and Tanganyika together with its rivers. In
N.E. Rhodesia the fly is common in the valley of the Luapula
River and its southern limit of distribution follows the
boundary between N.W. Rhodesia and the Congo, and across
Angola to the town of Benguela. G. palpalis has never been
found in Nyasaland or the region of Lake Nyasa.

Internal Anatomy.

The digestive tract (Fig. 66). The internal anatomy of
Glossina palpalis has been carefully described by Minchin,
whose account of the digestive tract is closely followed in the
present work, with the exception that the term proventriculus
is substituted for that of stomach.

Commencing with the oesophagus (Oes.), this portion of
the alimentary canal runs first of all upwards from the pharynx,
then bends sharply round and passes backwards through the
brain. After bending round, the oesophagus becomes extremely
narrow, but gradually widens after passing through the brain.
Immediately after entering the thorax it opens ventrally into
the proventriculus, a dilatation of the gut which marks the
commencement of the digestive region. From the point at
which the oesophagus opens into the proventriculus, the duct
of the sucking stomach, or crop, begins.

The intestine arises from the proventriculus about the
middle of its dorsal side and runs backwards through the
thorax as a straight tube of even calibre until it enters the
abdomen, where the intestine swells out into the more strictly
digestive portion of the alimentary canal,

The abdominal intestine is of great length and forms a num-
ber of complicated coils, which are represented in Fig. 66. It
may be divided into thirteen limbs, for purposes of description,

XVI]

INTERNAL ANATOMY

259

each limb being separated from the following one by a more
or less sharp bend. The filth, sixth and seventh limbs together
form a well-marked loop, which is generally the most dilated
portion of the intestine and is sometimes regarded as the true

Gl.S.

6. Internal Anatomy of Glossina palpalis. (After Minchin
Koubaud.)

A.R., rectum; Gx.g., junction of the two salivary ducts
Gl.S salivary -lands; G.J., duct of sucking stomach ; I.M., intesl

I.th., thoracic intestine; j

sking stomach : 1

pharynx ; /v.. proventriculus ; P.R., rectal papillae : /?, hind

stomach. Posteriorly the intestine passes into the capacious
rectum which has four rectal glands, each supplied by a bunch
of small tracheae.

The appendages of the alimentary tract arc the salivary
-lands, the sucking stomach or crop, and the Malpighian tubules,

17— a

260 GLOSSINA PALPALIS [CH.

The salivary glands (Fig. 66, Gl.S.) commence as two long
coiled tubes, occupying a superficial dorsal position in the abdo-
men, on each side of the heart. The coils of the glands may ex-
tend as far backwards as the fourth or fifth abdominal segment.
After many twists and turns each tube runs forward to the waist
and after passing into the thorax diminishes rapidly in diameter,
becomes more or less straight, and at the same time passes to
the ventral side of the body. From this point the salivary
gland becomes the salivary duct. In the thorax the ducts
run on each side of the duct of the crop and passing under the
proventriculus, reach the neck, where they become so extremely
attenuated that their course is difficult to follow. As they
enter the neck the ducts curve over towards each other and
pass under the brain and then under the pharynx, uniting in
a median duct shortly before opening in the hypopharynx.

The crop, or sucking stomach (Fig. 66,/.), is morphologically
a ventral diverticulum of the hinder end of the oesophagus,
arising from the point at which the latter communicates with
the proventriculus, in such a way as to appear as a direct
continuation of the oesophagus. It consists of a slender tube or
duct running backwards below the first part of the intestine
and expanding distally into a- large sac, occupying the first
two abdominal segments. Usually the crop is filled with gas
but shortly after feeding it is found filled with blood.

The Malpighian tubules arise by a pair of main stems given
off from opposite sides of the tenth limb of the intestine. Each
of these stems soon divides into two, and the four tubules
thus formed ramify throughout the body of the insect.

Bionomics. Glossina palpalis is only to be found at the
edge of water, or water courses. It especially frequents the
banks of rivers and lakes that are surrounded by overhanging
trees, or scrub, but occasionally it occurs in regions where there
is practically no shade, as for example, on Lake Tanganyika,
where the shore is bare but for the presence of a few reeds.
In the Congo the fly frequents those parts of the rivers that are
surrounded by dense forest and, according to Roubaud, this
locality is determined by the necessity of two conditions —
a high and constant temperature, and an almost saturated

XVI]

BIONOMICS

261

atmosphere. The same observer remarks on the predilection of
the fly for the neighbourhood of fords and those parts of the
river most frequented by man.

There is no record of G. palpalis from a greater altitude than
4000 feet, but it is common on the shores of Lake Victoria at
a height of 3700 feet. Such an altitude is exceptional, however,
and in most parts of Africa it is not found at so high a level,
probably owing to the unsuitable climatic conditions.

Fig. "7. View on the River Gambia beyond Barijali shewing the dens
of the vegetation, which consists ol Ferns, Palms. Pandani el
typical haunt of Glossina palpalis. (After Simpson.)

Hodges distinguishes a natural range and a "follow
range." By the former is meant the distance from water
within which the flies naturally wander in search oi food, and
in most cases this natural range does not ex< rds.

By following range is meant the distance to which flies will
follow victims who have passed through the natural rai
It rarely exceed- 300 yards, although flies have been caught
distances oi [500 yards from any water. Native water can
are sometimes accompanied for long distances, the

262 GLOSSINA PALPALIS [CH.

on their persons or on the water pail. On the other hand
Bagshawe has shewn that the fly may travel at least a mile
along the banks of water, and the observations on seasonal
distribution suggest that G. palpalis is capable of travelling for
very considerable distances.

During the rainy season the flies ascend to the upper limits
of the rivers and thus may appear in valleys that are dry for
the greater part of the year. In this manner the range of
G. palpalis may be considerably extended and there is a danger
that during an exceptionally rainy season the fly may spread
from the Congo to the Zambesi, as the upper tributaries of
these two rivers are not widely separated.

As the rivers dry up after the cessation of the rains, the flies
follow the receding waters and thus forsake those valleys that
have been temporarily filled with streams. The flies, however,
may persist in the neighbourhood of any more or less permanent
water, such as small pools left in the river-bed. It is possible
therefore to distinguish such temporary haunts, only occupied
by the fly during the rainy season, from the permanent haunts
in which the fly is present the whole year round. ■ Needless to
add, the latter constitute the sources from which the flies
migrate to the temporary haunts and are worthy of more
careful attention.

In addition the flies are subject to seasonal variations even
in their permanent haunts, the numbers greatly diminishing
during the dry summer and increasing during the rainy season.
The reason for this decrease in numbers during the dry season
has not been satisfactorily explained, but it may depend to
some extent on the breeding habits of the insect (vide infra) .

The habits of G. palpalis are fairly well known and its
presence can readily be detected when the flies are abundant.
The peculiar buzzing noise made by the insects whilst flying
and also the quick darting manner in which they flit from place
to place when not actually feeding, enable experienced ob-
servers to identify the flies without actually catching specimens.
The best way of detecting the presence of flies is to coast along
slowly in a canoe, when if the weather is favourable, the insects,
if present, soon appear in the boat. The attraction of moving

XVI] BIONOMICS 263

bodies for this species is very marked and has been noticed by
many observers.

Thus Simpson, while travelling in a river-launch up an
infested river in Nigeria, noticed that as long as the boat
remained stationary at the landing stage, no tsetse-flies at-
tempted to come on board, although swarms of them were
flying about near the banks of the stream. But as soon as
the launch moved away, the flies rose in swarms and flew after
the boat, many settling on the bows and deck and being carried
up the stream for very considerable distances.

The fly is not seen until after sunrise, the insects usually
appearing about 7 to 7.30 a.m. on bright still mornings. The
time of appearance, however, varies with the locality and in
densely shaded regions may be considerably later. In the
afternoon the numbers diminish about 4 to 4.30 p.m. and on the
approach of sunset most of them disappear ; only very excep-
tionally have they been known to feed at night. In cloudy or
rainy weather very few flies are to be seen, and wind at once
drives all of them into shelter. Although the presence of the
sun seems necessary for the fly's activity, it prefers the shade,
and indeed, if exposed to the direct rays of the sun dies in a
very short time.

It has been noticed by all observers that the tsetse-fly
prefers a dark skin to a white, and dark clothes to light ones.
Europeans wnen accompanied by natives are rarely molested
to any great degree. Ensor states that white clothing confers
the greatest degree of immunity from the attacks of t;
insects, and this statement is supported by all travellers in
fly regions. Dutton and Todd wntr as follows: "One day
while coming down the Kasai the Captain put on a blue cloth
jacket. Many more tsetses were found to settle on his 1
than on the white duck suits of the European pass ind

of the negro steersman." As a rule palpalis does no1
through clothes but it is easily able to pierce socks and ordio
white drill suits.

When feeding the fly spreads out its front pair of legs, and
then lowers its proboscis into the skin (1 It then begins

to gorge and its abdomen swells visibly And the insect may

264 GLOSSINA PALPALIS [CH.

ingest more than twice its own weight of blood. The excess
of fluid is got rid of very quickly, yellow liquid being excreted
from the anus.

There is no evidence that G. palpalis can exist without
vertebrate blood, but it will readily feed on both warm- and
cold-blooded animals. It is not dependent upon any particular
species for its food, but the experiments of Kleine shew that
the flies thrive much better on mammals and birds than on
reptiles. In one case three batches of 232 female palpalis
were fed respectively on wethers, fowls, and crocodiles, between
July 8th and August 6th. During this period there died
no less than 190 of the flies that fed on crocodiles, whereas
the numbers of flies that died in the other two batches were
respectively 25 and 35. Moreover, those nourished on the
reptilian blood never laid any larvae, whilst the flies fed on
wethers gave birth to 82, and those on fowls to 89 larvae.

Fig. 68. Glossina palpalis in the act of feeding. (After Roubaud.)

From these results it is evident that crocodile blood is a
very unfavourable diet for G. palpalis, in spite of the large
numbers of flies that may be seen feeding on these reptiles.
Koch stated that on Lake Victoria the blood of the crocodile
formed the staple diet of the tsetse-flies, but the experiments
of Kleine, confirmed by Roubaud, shew that the fly must also
derive its food from some other source in order to be capable
of breeding1.

1 This is a very good instance of the danger of introducing prophylactic
measures without a careful examination of every possible factor that might
influence the results. After Koch's observation, numerous persons advocated
the destruction of the crocodiles as a means of diminishing the number of
palpalis, whereas it is probable that the only effect of this host instead of
increasing, is to reduce the numbers of flies, by adversely affecting their repro-
ductive powers.

XVI] BIONOMICS 265

Minchin thought that the fish-eating birds of this region
might furnish a constant supply of food and this view is sup-
ported by the fact that in captivity the flies readily feed on
fowls and moreover thrive on this diet. G. palpalis has b< < 11
observed to feed on lizards, chameleons, snakes, frogs and mud-
fish, in addition to birds and mammals, but the latter constitute
the most important hosts. There is little doubt that the fly
prefers man to any other host and in captivity it thrives better
when fed on human blood than on that of experimental
animals.

As the fly feeds only during the daytime, it is evident that
the various larger animals, such as antelopes, buffaloes, etc.,
that visit the water only at night time, or in the early morning
must be excluded as a probable source of food, and it is generally
agreed that palpalis is not dependent on the presence of big
game.

Roubaud found that at 260 C. under ordinary conditions
the female flies, if permitted to gorge themselves, fed once
every three days, whereas the males would feed after two d
even when they had not digested their previous food. It the
temperature was raised to 280 C. the females could be induced
to feed more often, and at this temperature digestion
practically complete after 48 hours. In captivity the most
favourable temperature for the flies was found to be about
280 C, but this is near the limit; an alternation ol 2l '
by day and 300 C. by night was well borne, but a con-
tinuous temperature of 300 C. was rapidly fatal. The deg
of humidity has a marked effect on the ability of tin fly to
resist starvation, for at 33°C. in a saturated atmosphere ins*
were found to live six tune- longer than in one of moderate
humidity, and twelve times longer than in a perfectly dry
atmosphere. Similar results were obtained in the case ot flies
kept at 26 C, for in a saturated atmosphere a male and female
were observed to live 10 and i) (\a\^ respectively, \
in a dry atmosphere most of the flies were (UwA after
day and only one, a male, lived two days.

It follows, therefore, that dryness oi the air accelei
nutritive changes and causes the fly to feed more- frequently :

266 GLOSSINA PALPALIS [CH.

the results also explain the necessity to the flies of a humid
atmosphere such as the neighbourhood of shady rivers.

The length of life of the fly is very considerable. In the
laboratory, Kleine observed one female to live for 227 days,
which is the record up to the present. Carpenter has recently
tried to ascertain the length of life of the fly by marking large
numbers and then liberating them in order to see how long
marked specimens could be caught at the same spot. One
female was recaptured 182 days and one male 199 days after
they had been marked.

Reproduction. As in all tsetse-flies G. palpalis does not
lay eggs, but deposits the fully formed larva, after it has under-
gone a period of gestation within the uterus.

Fig. 69. Glossina palpalis. Female in the act of parturition. ( x 4.) (After
Newstead.)

The first larva is dropped three to four weeks after copula-
tion, the gestation being exceptionally long because the uterine
glands are not well developed. Afterwards larvae are dropped
at intervals of nine to ten days, so long as the temperature
remains at about 25 ° C. and the fly has abundant food. Roubaud
found that one female produced eight larvae in 13 weeks ;
when dissected, the uterus of this fly contained one egg, but
the ovary was empty. It is possible that the female may go
on producing larvae for a very considerable period, but the
observations on this subject are too few to be of any use.
Although in the laboratory the fly breeds all the year round,
it is probable that in nature the seasonal effects may be very
great, for in cold weather the tsetse does not bite readily and
food has a marked influence on its reproductive activities.
The female feeds readily at the commencement of gestation,
but as the larva approaches maturity ceases to feed until it is
born, when she again becomes hungry.

XVI]

REPRODUCTION

267

The pregnant flies are liable to certain accidents of gestation,
for in captivity they frequently abort after being disturbed.
Sometimes the larva pupates whilst still within the uterus,
and in this case both the mother and its offspring invariably
perish, as the former is unable to feed and the latter cannot
emerge from the pupal case. A high degree of humidity is
very unfavourable to reproduction, for Roubaud noticed that
when flies were exposed to a saturated atmosphere they either
aborted or did not develop larvae. These results would explain
why the females sometimes avoid the immediate neighbourhood
of water, whereas the males generally seek the damp places
where they require less food. The effect of this difference is
to cause that separation of the sexes of the flies, that has been
noticed bv manv observers.

Fig. 70. Freshly laid larva of Glossina palpalis shewing the changes in the
body form. (After Roubaud.)

When the larva is born it is a white cylindrical maj
with two black protuberances at its posterior extremity,
[ts dimensions vary from 7 to 7-4 mm. in length by - x
3-5 mm. in diameter. At first the larva is very active, present
curious alternate contractions and expansions oi it- body
(Fig. 70) causing it to assume very varied forms. U
movements enable the larva to boiv it- way into any fissn
or loose soil, and are peculiar to the members oi the genus
Glossina. In loose sand the larva usually conn1- to rest at a
depth of about half an inch to an inch and then puj I rhe

duration of the free larval stage does n I an horn

268 GLOSSINA PALPALIS [CH.

an hour and a half, but depends to some extent on the sur-
roundings. If the ground is soft and dry the larva very soon
comes to rest and often pupates within half-an-hour, whereas
in hard or damp soil it may be unable to find a suitable place
for some little time. In any case, the larva ceases to move after
a comparatively short period of active life and then pupates.

The pupa is of the usual cylindrical form, but at its posterior
extremity, it bears the two caudal protuberances that are
present in the larva. It darkens rapidly after its formation
and within four hours becomes dark brown in colour. The
dimensions of the pupa are 6\5 to 6*6 mm. in length by 3*5 mm.
in diameter.

Fig. 71. Glossina palpalis. Puparia before and after the escape of the
imago. (x.|). (After Xewstead.)

The duration of the pupal stage depends mainly on the
temperature, and may vary from 17 to 72 days. In the
laboratory pupae kept at 25°-27° C. hatch out in from
32 to 33 days, but at slightly lower temperatures Brumpt
found that the nymphal period lasted from six to seven weeks.
The optimum temperature is probably about 27 °C, for
Roubaud found that pupae exposed to higher temperatures
either did not hatch, or produced unhealthy flies. If placed
in damp sand the pupae are soon killed, and immersion in water,
for periods exceeding 24 hours, is also fatal. Moreover, a pupa
exposed to the action of the sun's ra}^ for four hours on two
successive days, failed to hatch, although protected throughout
the experiment by a layer of earth 5 cms. in thickness.

Breeding localities. In 1906 pupae of G. palpalis were
discovered by Bagshawe on the shore of Lake George and
subsequently on the shores of Lake Albert and the Victoria

XVI] BREEDING LOCALITIES 269

Nile. The pupae were all found within 10 to 25 yard- oi
water, and were in the shelter of banana plants, or of shrubs,
or of trees and tangled undergrowth, etc., where the soil con-
sisted of crumbling vegetation. The pupae lay at a depth of
from half to a little more than an inch, and the situ was always
moderately dry. Zupitza in the Cameroons found the pupae
lying somewhat superficially in the humus and moss in the
forks of branches, and cracks in the bark of trees, especially
in the angles of the leaf-sheaths of palms, at a height of a few
inches up to about 12 feet above the ground.

On the Sesse Islands, Fraser and Marshall found that the
most favourable site for the pupae was the loose dry sand on
the shore of the water, close to the undergrowth that edged
the forest and sheltered to some extent by the trees. The
distance from high water mark was usually five yards and
never more than 15. Later Fraser found that the pupae
were very numerous in sandy parts of the lake shore, as many
as 800 being collected in one day.

Carpenter, in Uganda, has confirmed these observations
and found that the locality where most pupae were obtained
(2000 to 3000 monthly) is formed of small pebbles mixed
with coarse sand, four or five feet above the present level of
the lake and about four to five yards from the water- edge.
The pupae are found at the edge of the belt of vegetation, which
faces south-east and is shaded after mid-day.

Carpenter's conclusions are as follows :

" 1. Favourite sites for depositing pupae are those which
are in shade, but where there is free air circulation.

" 2. The soil, commonly gravel or coarse -and. must be
dry and loose.

The fly does not extrude it- larva until the middle oi
the day, always selecting a shady spot."

'Natural enemies. The peculiar mode ol reproduction oi
the tsetse-flies render- the immature stages to a great 1 xtent
immune from the attacks of many insectivorous animals.

Nevertheless, the pupae musl be devoured by man}
oi birds, although up to the present there are no observati
on this point. Bagshawe observed pupal cases with a small

270 GLOSSINA PALPALIS [CH.

hole in the side ; the contents had been devoured evidently by
parasitic insects, probably belonging to the Chalcididae.

The adult fly possesses numerous enemies, none of which,
however, seem to be of very great importance in checking its
numbers. Doubtless numerous insectivorous birds and reptiles
must prey on the fly, but again precise information is lacking.
The gorged insects are often carried off by a large species
of wasp (Bembex), in order to furnish its burrows. Carpenter
found no less than 31 tsetse-flies in the burrow of a species of
Bembex occurring in Uganda. Roubaud often observed G.
palp alts captured by spiders of the genus Dolomedes, which live
on aquatic plants at the edge of streams and hunt both Diptera
and Neuroptera. Ants are said to be very dangerous enemies,
and when tsetse-flies are kept in cages they are frequently
attacked and destroyed by swarms of a very small species,
Pheidole megacephala F. The tiny ants seize hold of the legs
and wings of the flies, which soon succumb to the attacks of
these redoubtable foes.

It is possible that in nature various species of Cincindela,
the tiger-beetle, prey on the tsetse-fly, for they are common on
the banks of streams.

G. palpalis and Disease.

It is well known that in nature sleeping sickness (T. gambi-
ense) is mainly, if not entirely, transmitted by G. palpalis.
Although it may be possible to infect other species of tsetse-
flies in the laboratory, the distribution of sleeping sickness
coincides so closely with that of G. palpalis, that there can be
no doubt of its importance in the spread of the disease.

In addition a number of the trypanosomiases of animals
have been shewn to be spread by this species. Thus it is the
" host of choice " for T. cazalboui, and moreover has been
proved capable of transmitting T. brucei, T. dimorphon,
T. pecaudi, T. nanum and T. pecorum. It is probable that
the trypanosome of crocodiles is also carried by G. palpalis.

XVIj GLOSSINA PALLIDIPES 271

REFERENCES.

Austen, E. (191 1). Handbook of the Tsetse-Flies.

Bagshawe, A. G. (1909). Sleeping Sickness Bulletin, vol. 1. p. 89.

(An excellent summary of all previous observations on G. palpalis,

together with original notes and suggestions.)
Carpenter, G. D. H. (1912). Rep. S. S. Comm. Roy. Soc. p. 79.
Dutton and Todd (1906). Memoir XVIII. Liv. School Trop. Med .
Kleine (1909). Deutsche Med. Wochenschr. 1909, p. 1956.
Minchin, E. A. (1905). Proc. Roy. Soc. vol. lxxvi. p. 531.
Newstead, R. (191 2). Bull. Entom. Research, vol. in. p. 355.
Roubaud, E. (1909). La Glossina palpalis. These dc Doctorate h Set.

Nat. Paris.

(191 1). Compt. Rend. Acad. Sci. 191 1, p. 406.

Simpson, J. J. (191 1). Bull. Entom. Research, vol. n. p. 187.

Glossina pallidipes Austen, 1903.

Description. This species seems to be the eastern form
of G. longipalpis which it resembles in most of its features.
It may be distinguished from the other members of its group
by the pale colour of the last two joints of the front and middle
tarsi. It is a medium-sized or rather large species, the Length
of the female varying from 9-75 to n'25 mm. and of the male
from 8*5 to 10*4 mm.

Distribution. G. pallidipes is essentially an East African
species and has been recorded from Zululand in the south to
Uganda and British East Africa in the north. It is possible
that its range has become more restricted in modern times f< r
it is probable that it used to occur in the Transvaal, but dis-
appeared after the rinderpest.

Bionomics. G. pallidipes resembles morsitans in its habits,
but according to Neave is not so completely independent of
water. In British East Africa it is especially abundant in
certain belts along the coast, but also occurs inland, whilst in
Portuguese East Africa it is found at higher altitude- than
morsitans, going up to as much as 5000 feet. I Generally speak-
ing the fly seems to require a moderate degree of humidity,
but is more or less independent of cover.

The late Dr W. A. Densham, as recorded by Austen, found
the flies near and in a narrow belt of true forest at Kit*

272 GLOSSINA PALLIDIPES [CH.

Uganda. " They were numerous along the native path, in long
grass with scattered trees, for a quarter of a mile before reaching
the forest. They attacked freely at 8.30 a.m. on a summer
morning, were easily caught with the hand, and were observed
to bite through a worn blue service puttee. They were seen
and caught along the native path after entering the forest,
and for two miles the other side of the belt, which is only
about 300 yards in width, occasional flies being seen until the
village was reached. Half-an-hour after arrival two were
captured by my boys in camp and brought to me. On return-
ing from the village next day no flies were seen until nearing
the forest, so that the ' occasional ' flies mentioned above may
all have been ' following' flies. If so, they follow much further
than G. palpalis. There are many rhino, pig, and buffalo in
the forest, and Colobus monkeys are numerous. There are no
natives nearer than two miles, but a well-trodden path connects
two villages, and passes through the fly. The natives know of
the fly but do not consider it dangerous to animals. They
keep sheep and goats, and drive them along this path. No
cattle are kept for many miles round."

In British East Africa, Dr P. H. Ross found that G. pallidipes
generally occurs on the edge of the bush or in open spaces
where animals, chiefly goats, graze, but never at any great
distance from water. It is easily found from July to October,
the dry season, but during the rest of the year is practically
absent. In this locality the fly is frequently attracted by the
lights of trains, etc., and has been observed to enter railway
carriages and be transported a distance of at least 150 miles.

In Mozambique, Dr Sant' Anna found several areas infested
with fly. These areas consist of forests of low trees with poor
foliage and of somewhat short and scattered herbaceous vegeta-
tion, with few shrubs. The tsetse-flies are usually very rare but
in some regions they occur in large numbers. In the largest
of these areas, known as Maganja da Costa, to the east of the
river Licugo, the flies occurred in enormous numbers in the
native huts. Although the species is stated to be morsitans
all the flies sent from this locality were determined by Austen
as G. pallidipes.

XVI] GLOSSINA PALLIDIPES

G. pallidipes and Disease.

As mentioned below Austen has shewn that it is almost
certain that Bruce, in his Zululand experiments on the trans-
mission of T. brucei, employed G. pallidipes and not G. morsitans.

In addition, Dr P. H. Ross has found G. pallidipes in British
East Africa naturally infected with a trypanosome that seems
to belong to the dimorphon group. In one case a dog naturally
infected with trypanosomes on Mombasa Island, is stated to
have been almost certainly infected by the bites of G. pallidipes
on the island.

In another case wild G. pallidipes from the neighbourhood
of Kibwezi (British East Africa) were fed on a healthy monk
In all "209 flies were fed between July 15 and December 10.
The animal died on January n, and it was only after death
that trypanosomes were found. Inoculation of blood from
the dead monkey into a fresh monkey resulted in infection,
but inoculation of a dog at the same time failed. In this
infection was suspected nine days after feeding began, but
repeated examinations of the blood during rive months v
always negative. The monkey became very thin, and had all
the appearance of a trypanosome-infected monkey, and the
temperature chart was also very suggestive of trypanosomiasis.
The trypanosomes found in this animal were 17-18 mici
in length, including a short, free fiagellum, and had rath'
blunt posterior end."

In further experiments with tins trypanosom< and

sheep wire found to be immune against infection and two
monkeys that became infected were alive after five months
and a year respectively. With regard to the immunity

its and sheep, the author notes that the Wakamba nati
move their cattle to the hills in August when G. palli
about to reappear, statin- that the fly would kill them, but
they do not move their sheep and goats.

From these observations it is evident that G. pal
capable of transmitting other infections in addition to /
but up to the present there 1- noveryprecise information a- 1<> the
manner in which it i< effected. Presumably the transmission is
usually indirect, as in th< most other sped Bies,

H. B. F.

274 GLOSSINA LONGIPALPIS [CH.

REFERE^XES.

Austen, E. (1903). Monograph of the Tsetse-Flies.

Neave, S. A. (1912). Bull. Entom. Research, vol. 111. p. 275.

Ross, P. H. (1909-10). Reports of the Nairobi Bacteriological Laboratory .

Sant' Anna, J. F. (1911). Quoted in 5. 5. Bulletin, vol. 111. p. 143.

Glossina longipalpis Wied., 1830.

Description. This species closely resembles G. pall id 'i pes
in its general appearance. It is slightly larger than G. morsitans
and may be distinguished by the possession of a fringe of fine
hairs on the anterior margin of the third joint of the antennae.
In addition the dark brown, transverse, abdominal bands extend
close to the hind margins of the segments, and the last two
joints of the front and middle tarsi have sharply defined, clove-
brown or black tips. The length of the male varies from
8'4 to o/o mm. and of the female from 9-0 to ico mm.

Distribution. G. longipalpis is essentially a West African
species, its range extending from Senegal to the south-eastern
corner of the Congo Free State. In addition a single specimen
was collected in 1864, by Sir John Kirk in the Zambesi valley,
between Tete and the Victoria Falls. There are no other records,
however, of its occurrence further south than the Congo Free
State and it seems to have disappeared from the valley of the
Zambesi. Between the limits of its distribution the species
is fairly common and it is one of the most important tsetse-
flies of the West Coast of Africa.

Bionomics. G. longipalpis, although not closely restricted
to the immediate vicinity of water, is not found as far distant
from it as G. morsitans. In southern Nigeria, Simpson states
that the species is associated with a moister climate and is
especially found in denser vegetation of the mixed deciduous
forest type. On the other hand, Kinghorn states that in
Ashanti G. longipalpis is essentially an open country fly and
is not found in the forest belt. The only grass country in
which it was rare was Banda and its absence from this locality
was attributed to very large stretches of land being under
cultivation. The most important observations on the bionomics

XVI] GLOSSINA LONGIPALPIS 275

of this species are those of Roubaud in Dahomey. Jn this
region G. longipalpis is found near the streams and large n\
The separation of the sexes is well marked, the males being
met with only in the tufts of bushes along the edge of the
forest near the water courses, while the females are found in
open clearings where there are acacias and mimosas. The fly
is especially abundant during the rains, but seems to disappear
almost completely in the dry season, especially after the bush
is burnt. During the rainy season the fly extends its ra:
very considerably and may be found more and more outside
it- usual haunts, individuals occurring in the savannahs far
from any water course. The period of the north-east wind
(Harmattan) is very unfavourable to them.

G. longipalpis feeds mainly on wild mammals, accompanying
them in their movements ; it especially frequents paths recently
trodden by hippopotamus and elephant.

Reproduction. G. longipalpis has never been observed to
copulate in captivity. Moreover, it is very susceptible to the
influence of physical conditions, a temperature of 35
with either saturated or dry air, interfering with reproduction.

At 250 C, Roubaud found that the females deposited
larvae at intervals of about ten days, and the pupal stage, at
an average temperature of from 240 to 250 C, was found to
last from 26 to 35 days. The pups hatch out all the v
round, including the cold season, and the diminution of flies
in the dry season cannot be explained by the assumption that
during this period the pupal stage is prolonged.

I i. LONGIPALPIS and Disc.

This species is a most important carrier of animal trypano-
somiasis. Thus in Dahomey, Bouet and Roubaud found
that the wild flies were frequently naturally infected with
T. dimorphon, and that on the Oueme* Knar a very lai
portion of the flies were infected with T. pecaudi.
is said to be the *' hos1 oi choice " for this latter trypanosome.

In addition, this species is an efficient intermediate

azalboui.

276 GLOSSINA MORSITANS [CH.

REFERENCES.

Austen, E. (1911). Handbook of the Tsetse-Flies, p. 63.

Bouet and Roubaud (1910). Ann. Inst. Pasteur, vol. xxiv. p. 658 ; Bull.

Soc. Path. Exot. vol. ill. pp. 599, 722.
Kinghorn, A. (191 1). Cf. 5. 5. Bulletin, vol. in. p. 136.
Roubaud, E. (191 1). Compt. Rend. Acad. Sci. vol. clii. p. 406.
Simpson, J. J. (1912). Bull. Entom. Research, vol. 111. p. 137.

Glossina morsitans Westwood, 1850.

Synonym. Glossina submorsitans Newstead, 191 1.

cf , ? . Length cf 7-2 to 9 mm., ? 8-6 to 9-6 mm. ; width of head, cf
2-4 to 2-75 mm., ? 2-5 to 3 mm. ; width of front at vertex, <? o-6 mm.,
? o-8 to 1 mm., length of wing, j 7-6 to 8-2 mm., ? 8-2 to 9-5 mm.

" Dorsum of thorax light grey, olivaceous-grey, or smoke-grey in cf ,
drab-grey in ? , the thoracic markings in both sexes incompletely developed,
and reduced to brownish or mouse-grey longitudinal streaks ; dorsum of
abdomen buff to ochraceous-buff (in pinned specimens sometimes mouse-grey
or olivaceous owing to post mortem changes), with a larger or smaller clove-
brown blotch (sometimes indistinct or almost wanting) near each basal angle

Fig. 72. Glossina morsitans. Dorsal view of female.

of the second segment, and the third to the sixth segments inclusive each with
a very conspicuous clove-brown transverse band, interrupted in the median
line, not reaching the lateral margins, and not extending beyond the basal
three-fourths of the segment, if so far ; legs buff, last two joints of hind tarsi
clove-brown or black., last two joints of front tarsi and penultimate joint of
middle tarsi conspicuously tipped with clove-brown or dark brown, last joint
of middle tarsi entirely dark brown above in typical race, otherwise distal half
or third of last joint of middle tarsi alone dark brown or clove-brown, re-
mainder of joint merely brownish or even entirely pale." (Austen.)

XVI] VARIETIES 277

Glossina morsitans Westw., var. pallida Shircore.

" Thorax slate-grey, pattern Indistinguishable; scutellum with two 'lark tri-
angular areas which are contiguous at their upper inner angles. ■■ ith
the darker blotches on each side of the second segment very faint ; on the other
segments the banding is not a prominent feature, as it is in the typical form ;
the bands olive-grey, their margins being distinct and denned from the ground-
colour, which is a few shades lighter. In the middle line the banding 1- 1 nt
off square, leaving a very narrow straight line down the centre of the segments ;
the outer margins of the bands sloping away from below upwards and Leaving
light areas on each side. Legs with all the joints of the front and middle tarsi
pale, except the distal end of the latter which has a faint darkish ring ; the
last two joints of the hind tarsi faintly dark, but nothing like so dark a- in
G. morsitans. Wings tinged with light yellowish-brown.

Nyasai.and : 1 1 , Dowa district, 6. v. 1912.

Type in the British Museum.

This fly was picked out at a glance from more than a hundred G. morsitans,
and is distinctly and remarkably paler throughout." (Shircore.)

Glossina morsitans Westw., var. paradoxa Shircore.

" Superficially resembles G. morsitans in appearance and size, but tlie hind
tarsi are entirely dark, as in the palpalis group. The superior claspers of the
male genitalia resemble those of G. sabmorsitans, as figured by Prof. Xewstead,
but are more deeply pigmented throughout, and especially along the lateral
and posterior borders.

N vasaland : 1 tf , Nyamsato, near Chunzi, Dowa district, 4. vi. 12.

Tvpe in the British Museum.

If casually observed, this tsetse would probably be taken lor an ordinary
G. morsitans ; but if the abdomen had become discoloured it might well be
mistaken for G. palpalis. The superior claspers have only been looked at with
a hand-lens ( x 12) ; they were prized Open and examined in situ" (Shircore.)

Distribution. G. morsitans is by far the most widely
distributed of all the tsetse-flies, occurring from Abyssinia and
Senegambia in the north to Zululand in the south. In all
cases the fry is restricted to very definite regions known as
"fly-belts" or "fly-areas," and does not occur spread over
Large tracts of country. It is therefore difficult to give an
accurate idea of its distribution withoul going into great detail,
but the fly has been recorded from the following countri

Southern Abyssinia, Anglo-Egyptian Sudan. Babx el ( rh
Uganda, British, German, and Portugu i\ Africa. Zulu-

land, the North Eastern Transvaal, Bechuanaland, S \ 1
and X. W. Rhodesia, Nyasaland, the Congo Fre< State, Upper

278 GLOSSINA MORSITANS [CH.

Ubangi, Northern and Southern Nigeria, Dahomey, Togoland,
Gold Coast Colony, Ashanti, Northern Territories, Ivory Coast,
French Guinea, Gambia and Senegal.

Bionomics. In the present place it is only possible to give
a brief account of the more important observations on this
subject. The reader desirous of further information will find
an excellent summary of all the earlier observations on G.
morsitans in Austen's Monograph of the Tsetse-flies.

As a general rule, G. morsitans is confined to certain re-
stricted and often very well-defined tracts of country, known
as " fly-belts," the boundaries of which, however, are liable
to variation ; for Hall found that in North Eastern Rhodesia
the fly considerably extended its range of distribution between
the years 1904 and 1909, and Neave is of the opinion that the
flies are now recovering the ground lost at the time of the
rinderpest, when G. morsitans disappeared from the Transvaal.

Usually the fly prefers a region in which there is sufficient
vegetation to provide a moderate but not excessive cover, and
a hot and moderately dry climate. It seems to be almost
independent of surface water and is most active in a dry
atmosphere ; though in some districts the flies seem to be
more common in the neighbourhood of rivers.

In Nyasaland they are never found in open grass country,
but only in bush, especially in those portions of the forest where
Sanya trees and antelope are most abundant. Dense forest
is generally avoided by the flies, but they prefer regions
scattered with trees that give shade. Sir Alfred Sharpe's
observations in this region are of considerable interest, especially
on the effect of cultivation on the prevalence of the fly. He
states "lam acquainted with villages which are situated inside
fly-areas and wherever the natives build their villages in such
localities, and clear ground for their food-gardens, tsetse immedi-
ately disappear from the cleared ground. I have often noticed
that, when approaching those villages from the bush, fly which
are following the carriers, or are actually upon their persons
biting them, will gradually disappear after entering the cleared
ground, and by the time the village is reached, no fly can be
seen. On the other hand, I have known cases where villages have

XVI]

BIONOMICS

279

been abandoned, and after a time, as the natural bush has
grown up, the flies have reappeared in places where the native
food-plantations formerly were." The same observer is also
of the opinion that the tsetse is not entirely dependent for its
existence upon the blood of wild mammals. In Nyasaland,
enormous numbers of tsetse occur in districts that are almost
destitute of game and at the north end of Lake Nyasa, before
the advent of rinderpest, there were many thousands of buffalo
but no morsitans. On the other hand, it is the opinion of

Fig. 73. Path through thin deciduous bush between Yallol and Fula Fara-
feni, Bathurst, to shew a typical haunt of G. morsitans. (After Sim]

many observers that when game and especially buffaloes are
abundant, the fly also appears in large numbers and that after
the epidemic of rinderpest, following which in many regions
there was very little game and practically no buffaloes, the
fly disappeared. Amongst these conflicting statements it is
difficult to arrive at tlie truth, but certainly Sharpe's observa-
tion that the tsetse may occur in the absence of wild mammal-.
shews that any scheme of game destruction would be both rash

280 GLOSSINA MORSITAXS [CH.

and premature at the present time, considering our incomplete
knowledge of the subject. No direct evidence has yet been
published, supporting the view that morsitans takes in any
food other than blood, but the flies have been observed
apparently drinking dirty water at the edges of puddles. If
placed in a bottle with ripe water-melon the flies may be seen
to thrust their proboscides into it, but there is no evidence of
any food being ingested.

The effect of climate on the numbers of flies is very marked.
Within a " fly-area " the tsetse will not necessarily be found
there at all times of the year. It is often possible to go through
such a region without seeing a single fly. For example,
in Nyasaland, between the settlement of Zomba and the
Miange Mountains, a distance of about 40 miles, lies an extensive
plain. During the months of May or June flies are practically
absent, whereas in October, it is necessary to pass through
about 25 miles of " fly." On the advent of the first rains in
November, they begin to disappear, but may still be found
until the arrival of the cold weather in April and May. In the
Luangwa Valley, North Eastern Rhodesia, Lloyd observed that
the fly was very common during the early part of the dry
season, but the numbers diminished until the commencement
of the rains, when the numbers at once increased. At Nzoa,
in the higher ground of the Congo Zambesi watershed (altitude
4000 ft.), the fly only became numerous after the rains had
ceased. It is evident, therefore, that within any particular
fly-area, the number of tsetse may vary according to the season
of the year.

Although many observers state that G. morsitans is more
or less independent of moisture, Dr J. O. Shircore, who has
devoted a great deal of attention to this question, has clearly
shewn that in Nyasaland, and probably in other regions, the
fly is greatly affected in its distribution by the presence or
absence of moisture. At the height of the dry season the tsetse
is only found in certain restricted areas to which the term
" Primary Fly Centres " has been applied. These primary
centres are the only regions where, in the dry season, water is
actually above the earth's surface, or at no great distance below it.

XVI] BIONOMICS 28l

In these places there is light forest with fairly short grass
and occasionally open glades, whilst game is abundant, a
combination which is ideal for the flies. From these regions
they extend into the surrounding country along connecting
forest as soon as the conditions become suitable, and tin-
extension may easily be observed.

Dr Shircore, therefore, advocates the destruction oi the
primary centres by means of clearing and bush-fires, during
the height of the dry season, when there are very few tsetse-
flies in the surrounding country. As these primary centres are
often of very limited area, the destruction of the flv in these
regions is a prophylactic measure that might easily be adopted,
instead of the game destruction and wholesale clearance of the
country which is being advocated by certain individuals.

The fly will feed with avidity on almost any large mammal
or bird, and does not seem to be dependent on any particular
species for its food-supply. In Nigeria, Simpson noticed that
these insects seem to have a great predilection for baboon-,
enormous swarms accompanying the herds of these animal-,
and in the Bahr el Ghazal, Selous has noticed the same pecu-
liarity.

Usually G. morsitans becomes active about sunrise, dis-
appears during the hottest hours of the day and recomnit i
to bite when it becomes cooler and also after the sun has set.
Other observers, however, state that it is mos1 jsive

during the hottest hours of the day. Occasionally they will
feed at night, especially if a bright moon is shining, and -<>uk--
times even in its absence. As a rule the flies disappear during
a shower, but they have been known to bite during heavy rain.

Like G. palpalis, the presenl species 1- especially attracted
by moving objects, but quickly leaves them a- soon a- all
motion ceases. Thus Montgomery ami Kin-horn note that
even in its natural haunt-. G. morsitans will quickly ret-
from a person coming to a halt, although they may have been
pestilent immediately prior t<> tin-.

In addition to being attracted by dark colours, Newstead
found that the shades most preferred by tin- species v
khaki and yellowish-green, whilst white was the least ,\r-

282 GLOSSIXA MORSITANS [CH.

of all. The flies will readily bite through one thickness of
clothing and if the bottoms of the trousers are open they
frequently creep up the legs and bite above the socks.

The males feed on blood as readily as the females, and the
large swarms of tsetse are mainly composed of the former.
The females seem to be more hardy than the males, for in certain
transmission experiments with G. morsitans, Fischer employed
636 males and 766 females ; 70 days later only 135 males
had survived, whilst 265 females were still alive.

In captivity moisture is rapidly fatal to this species ; more-
over it is very intolerant of high temperatures, for Roubaud,
in Dahomey, observed that specimens exposed to 40° C. died
within an hour. The fly, however, occurs in districts, e.g. the
Luangwa Valley, where the thermometer frequently registers
420 C. in the shade.

Practically nothing is known about the natural enemies of
G. morsitans, but Xewstead in Xyasaland has found examples
of the fly in the food contents of two species of birds, viz. : the
common African Drongo (Dicrurus afer) and a small Bee-eater.
It is possible that the fly is susceptible to rinderpest for it is
difficult to explain the disappearance of this insect from South
Africa and the Transvaal on any other hypothesis.

The well-known hunter, Mr F. C. Selous, has published
some interesting observations relating to this question. It
is well known that after the great epidemic of rinderpest in
1896, G. morsitans disappeared from practically all the country
south of the Zambesi. Throughout this region the buffaloes
were exterminated, but although there seems to have been a
very close association between these animals and G. morsitans,
it is well known that the tsetse-fly can thrive on the blood of
other animals, and as zebras, giraffes, antelopes, etc. were all
left in considerable numbers it is difficult to understand why
the fly also disappeared.

It is possible, of course, that the tsetse-fly had become so
restricted in its feeding habits, that when its usual host, the
buffalo, disappeared, it was unable to adapt itself to feeding
on other animals and simply died out through lack of food,
but it seems more reasonable to suppose that the rinderpest

XVI] REPRODUCTION 283

had a directly injurious action on the fly. Further observa-
tions on this question are necessary in order to explain the
disappearance of G. morsitans from certain parts of Africa in
recent times.

Reproduction. Most of the observations on the breeding
habits of G. morsitans have been made during the past two
or three years and are still very incomplete. Unlike G. longi-
palpis, morsitans readily copulates in captivity and in conse-
quence the flies can be raised in the laboratory without much
difficulty.

Fischer found that on Lake Victoria, bred flies began to
drop larvae about the twentieth day after hatching. Kinghorn,
in Northern Rhodesia, states that 14 to 15 days is the usual
gestation period under laboratory conditions (temperature
58-5° to 77*8° F.), but much irregularity was displayed by the
females, and after the first larva had been born, many of them
did not produce a second one for a considerable time. In
Upper Dahomey, Roubaud found that the interval betw
successive deposits of larvae, at a temperature of about 32 C,
was usually eight to nine days.

Newstead found the pupae in three separate spots in the
forest, about one and a half miles from the banks of the
Shire River, at a place lying about 18 miles due north of
Liwonde, Nyasaland. The pupae were found buried in soil at
the foot of various trees. In Rhodesia, Jack has found the
pupae in several localities, e.g. under a clump of Mubula tn
on a high ant-heap ; under the exposed roots of a Baobab ;
at the base of a Mopani tree, etc. The author write- : "In all
places except two, where pupae were found, the soil was either
sandy and easily worked, often rich in humus, or covered with
leaves which afforded an easily penetrable shelter. In two
instances case- were taken from hard soil, in one instance one
and a half inches below the surface, but the chit in which forms
the case is an enduring substance in a dry situation, so that tin-
age of these eases is difficult to judge. The soil may have been
soft when the larvae entered or they may have penetrated al
a crack. It is in the highest degree improbable that a larva
could penetrate one and a half inches of hard baked ant-heap.

284

GLOSSIXA MORSITAXS

[CH.

In every instance the ground was well drained and often the
slope was very sharp. All the pupa cases except four were
from trees near the bank of a river or wet vlei, where there was
shade and where the " fly " congregates in the dry weather.
The four excepted were taken from the base of a large Baobab
tree on the summit of a hill not far from a river (the Sinyama)

Fig. 74 Base of a tree in Nyasaland shewing one of the positions (indicated
by arrows) in which the pupae of Glossina morsitans may be found. (After
Jack.)

it is true, but away from the influence of the water, there being
no shade about the roots in August. This points to the fact
that the larva? are deposited in any convenient situation, when
the fly is scattered during the wet weather... .

' The summary of the investigations into the breeding
haunts is therefore, that in the dry weather the larvae are
deposited in sheltered positions about the bases of big shady

XVlJ REPRODUCTION 2©5

trees, such as are at that time of the year practically i onnned
to the banks of rivers, pools, and vleis, dry or otherwise on the
surface. Generally the soil is easily worked, and often humus
is abundant, and the drainage is usually good. The selection
of a well drained situation may not seem necessary in the dry
weather, but the instinct to select such would doubtless be oi
great value, when the pupal period extends into the rains.
During the wet weather it is probable that the young are
deposited more generally through the bush."

Mr R. S. Harger, late of North Eastern Rhodesia, in a letter
published in The Field states that he had often watched
G morsitans depositing its eggs (= larva;) in the damp soil,
thrown up by the digging of a trench round his tent.

In captivity, when the freshly laid larva is placed on
powdered earth it immediately commences to burrow until it
is from one to two centimetres below the surface, when it at
once proceeds to pupate. Apparently the larvae are capable
of secreting a slightly viscid fluid, for in glass tube- they were
often observed to adhere to the side and Kinghorn suggests that
the purpose of this fluid is to gather the earth around the pupa.

As in all species of Glossina, the duration of the pupal
stage varies according to the temperature. In Rhodesia, at a
temperature of 150 to 250 C, Kinghorn found that the pupal
period varied from 47 to 53 days. On Lake Victoria, according
to Fischer, the period lasts on an average from 35 to 40 d
whilst Roubaud, in the Upper Dahomey, found that at a tempera-
ture of about 320 C. the duration of the pupal stage was only
23 to 2$ days. Lloyd, at Nawalia, obtained similar results,
for at temperatures ranging from 17 to _,N ( the aver
duration of the pupal period varied from 22 to 51 days.

A.s in the case of G. paipalis, intra-uterine pupation has been
observed occasionally.

G. morsitans and Disi

(',. morsitans is known to be the earner oi more trypanosome
diseases than any other species oi Glossina.

In the first place it has been proved to be the- mam it not
the only, carrier of T. rhodesiense, the path

286 GLOSSINA LONGIPENNIS [CH.

the human trypanosomiasis of Rhodesia, Nyasaland and certain
parts of German East Africa (Rovuma River). Moreover
Fischer's experiments on the Victoria Lake, clearly shew that
under experimental conditions T. gambiense may be transmitted
by this species of tsetse, in which it undergoes a cyclical develop-
ment.

In addition G. morsitans has been proved to be the inter-
mediate host of the following infections : T. brucei, T. pecandi,
T. cazalboui, T. dimorphon, T. pecoritm, T. congolense and
T. simice, each of which is described below, together with the
manner in which the fly conveys the infection.

REFERENCES.

Austen, E. (1903). Monograph of the Tsetse-Flies.

(1911)- Handbook of the Tsetse-Flies.

Fischer, W. (1913)- Arch. f. Schiffs u. Trop. Hyg. vol. xvn. p. 73.

Hall (1910). Bull. Ent. Research, vol. t. p. 183.

Jack, R. (1912). Ibid. vol. 11. p. 357.

Kinghorn, A. (1912). Ibid. vol. n. p. 29T.

Lloyd, LI. (1912). Ibid. vol. in. p. 233.

Montgomery and Kinghorn (1909). Ann. Trop. Med. and Parasit.

vol. in. p. 322.
Neave, S. A. (1912). Bull. Ent. Research, vol. 111. p. 275.
Newstead, R. (1910). Ann. Trop. Med. and Parasit. vol. iv. p. 369.
Roubaud, E. (191 1). Compt. Rend. Acad. Sci., No. 14, p. 637.
Sharpe, Sir A. (1910). Bull. Ent. Research, vol. 1. p. 173.
Simpson, J.J. (1912). Ibid. vol. 11. p. 301, and vol. 111. p. 137.
Selous, F. C. (1910). African Nature Notes and Reminiscences, London.
Shircore, J. O. (1914). Bull. Ent. Research, vol. v. p. 87.

Glossina longipennis Corti, 1895.

Description. This species resembles G. brevipalpis in its size
and general appearance, but may easily be distinguished by the
presence of four sharply defined, dark brown, more or less
elongate spots on the thorax arranged in a parallelogram, two
in front and two behind the transverse suture. The proboscis
bulb has a sharply defined brown, or dark brown, tip. The
length of the male varies from I0'2 to ir6 mm., and of the
female from 11-9 to 13*0 mm.

XVI] BIONOMICS 287

Distribution. G. longipennis seems to be restricted to the
north east corner of Africa for it has only been recorded from
Somaliland and British East Africa. It probably also occurs
in Southern Abyssinia.

Bionomics. Dr P. H. Ross states that the present species is
found all the year round in the same haunts as G. brevipalpis.
It is most easily caught after 4 p.m. resting on the red soil of
paths or caravan tracks, and seems to resemble G. brevipalpis
in its feeding habits. G. longipennis is attracted by lights at
night and is probably the commonest tsetse-fly caught in the
railway carriages. On one occasion for a night and a day the
station master's house at Kenani was occupied by these flies
in such numbers that during the night the lamps were extin-
guished, and Ross suggests that this may be an instance
of migration. Incidentally it may be mentioned that Peel,
who captured this species in West Somaliland, found that it
occurred in a definite fly-belt extending from Biermuddo to
Boholo Deno. The species seems to be independent of water and
most active in a dry atmosphere. Brumpt found that in Somali-
land it generally fed at night, attacking both man and animal-.

G. longipennis and Disease.

Brumpt is of the opinion that Aino, a cattle disease of
Somaliland caused by a trypanosome probably identical with
T. brucei, is transmitted by G. longipennis. and brings forward
evidence in support of his hypothesis. Dr P. H. R ss is the
only one who has succeeded in obtaining any experimental
proof of the disease-transmitting capabilities of this species.
A large number of freshly caught flies from the neighbourb
of Kenani were kept in an incubator at 25° C. The flies were
then led on a monkey between 5th December, 1912, and
January nth, 1913, the animal being batten 577 times. 1 rv-
panosomes were found in its blood on January 13th and the
author for the present would class them in the T. dim

group.

REFERENCES
Austen, E. (1911). Handbook of th*
Brumpt, E. (1902). Arch, de Parasitologic, vol. v. p. 1
Ross, P. 1 1. (1904 to). Nairobi Laboratory /.
Diseases Bulletin, mi| vol. 1. p. 505

288 GLOSSINA BREVIPALPIS [CH.

Glossina brevipalpis Newstead, 19 10.

Synonyms. G. fusca Austen, 1903 {nee Walker). G. tabaniformis Stuhl-
mann, 1902 (nee Westwood).

Description. Owing to an unfortunate error in Austen's
Monograph, G. brevipalpis was there described under the name
G. fusca, as with the scanty material at the author's command
it was very difficult to form correct conclusions as to the
characters of the species. As a result the majority of writers
following Austen, have described the habits and occurrence of
the present species under the name G. fusca.

G. brevipalpis is the common large tsetse-fly of many parts
of Eastern, Central, and Southern Africa. The most striking
casual feature of the species is the darkening of the wings in
the region of the anterior and posterior transverse veins, so
as to appear as dark spots on the otherwise pale wings. It may
be distinguished from G. longipennis by the absence of a dark
brown ocellar spot, of a brown tip to the proboscis bulb and of
the characteristic dark spots on the thorax. In addition, it
may be distinguished from G. fusca by having the proboscis
and palpi much shorter ; the head distinctly wider, and closer
to the thorax ; the thoracic markings and general colouration
much less distinct ; also, the size is often larger.

The length of the male varies from 10*2 to i2-25 mm. and
of the female from iro to 13-5 mm.

Distribution. This species has been recorded from British,
German and Portuguese East Africa, Uganda, Nyasaland,
Northern Rhodesia, the Katanga district of the Congo Free
State and Angola. Although occurring in the two latter
districts, G. brevipalpis has not hitherto been found on the
west coast of Africa, but is essentially an East African species.

Bionomics. The many descriptions of the habits of this
species have nearly all been given under the name of G. fusca
and this point should be remembered in looking up references
on the subject. G. brevipalpis requires only a moderate degree
of humidity and is generally found where there is fairly heavy
timber and bush. It is more adaptable to external conditions
than G. palpalis, and Stuhlmann notes that it requires an average
yearly temperature of 230 to 260 C, with a maximum of 360 to

XVI] BIONOMICS 289

37° C. and a minimum of io° to 120 C, and an average humidity
of 66 to 83 %. In British East Africa it occurs at varying
levels from the sea coast to Fort Hall, a height of 4000 feet.
According to Dr P. H. Ross, in the valley of Kibwezi it is generally
found among rocks on the hills, resting on the slightly damp
black cotton soil between boulders. It may be caught in
quantities all the year round, but is more abundant during the
wet season. It is said to be markedly nocturnal in its feeding
habits and on one occasion was met with in numbers resembling
a swarm of bees. On the other hand Milne states that the fly
generally bites between three and five in the afternoon, and in
the Kibwezi valley is more prevalent during May and June
than any other time of the year.

In German East Africa, Stuhlmann found that the fly was
present at Anami all the year round, but Keysselitz and Mayer
state that very few females could be captured during December,
January and February. Like many other species of tsetse-fly,
G. brevipalpis occasionally follows animals to some distance
from its actual haunts and Stuhlmann notes that in this way,
especially during the hot weather, isolated examples were
frequently found amongst the mountains at altitudes up to
3250 feet, whilst during December to April the flies were often
met with in the settlements.

In Nyasaland, Davey recorded the capture of a few indi-
viduals belonging to this species, all of which, with one exception,
were caught within 900 yards of the edge of Lake X\
Sanderson was informed by the natives that during the rains
(January), at which time practically the whole country is under
water, G. brevipalpis is very prevalent in North Nyasaland all
over the grassy plain lying between the shore of the lake and a
line of foot-hills some ten miles away. In June and July this
species was found, sometimes in wry large numbers, in the
beds of all the streams between Karongo and Sougive, although
many of them were dry. It was occasionally caught in the
native villages.

According to Dr Sanderson, G. brevipalpis is active ana
desirous of feeding only in the early morning before 8.0 o'clock
and in the evening after about 4.0 o'clock. During the day-

H.B.F. 19

290 GLOSSINA BREVIPALPIS [CH.

time the fly remains sheltered under the leaves of bushes, or
in the grass, always near the ground, or low down on the
trunks of trees, not more than two or three feet from the
base.

At Kaporo, near the north end of Lake Nyasa, Davey
found that they preferred to rest on trees surrounded by
creepers and undergrowth, and hidden away in crevices in the
bark or under the branches. While thus resting motionless
Sanderson states that the flies are very difficult to discover
and their presence would be entirely unsuspected.

About 4.0 p.m. when the fly is ready to feed, it emerges
from its hiding-place and settles on dried leaves, sticks or
dust on paths, apparently lying in wait for a meal. As the
wild animals on their way to the water in the evening often
stand for a time on emerging from the forest on to a path, the
flies would thus have an opportunity of feeding. According
to Davey, although G. brevipalpis as a rule seems ready to bite
human beings in the evening, it does not set to work with the
same rapidity and voracity as G. morsitans.

Stuhlmann kept large numbers of the flies in captivity at
Amani, German East Africa, and found that they required a
meal of blood at least every six or seven days, and by feeding
them every fourth or fifth day, individual females were kept
alive for upwards of four months.

Sanderson writes : " The flies bite through dark clothes,
but have never been seen to settle on white surfaces " and
Stuhlmann frequently noticed that when a light and a dark-
coloured mule were walking side by side, only the latter was
attacked.

In Nyasaland, Davey found that wherever he met with this
fly game was abundant. Once during the wet season, having
shot two bush-pigs about sunset, on going up to them he found
several G. brevipalpis apparently trying to suck blood from
the carcases, although for some time previously he had been
unable to find any of the flies.

Although in captivity approximately equal numbers of
males and females are obtained from pupae, there is an enor-
mous preponderance of males among the captured specimens.

XVI] BIONOMICS 29I

Stuhlmann found that in order to catch females it was neces-
sary to use some animal as a decoy, but even then they were
much more difficult to catch than males. The gravid females
are probably much more wary and move about less than the
males, and are consequently more rarely caught.

Reproduction. In nature the flies have occasionally been
observed in coitu on tree-trunks. Stuhlmann noticed that
in captivity only freshly hatched females received the males,
but possibly the behaviour of the flies was modified by the
artificial conditions.

Stuhlmann has given a very complete account of the
breeding habits of this species in German East Africa and the
following observations are taken from his report.

When females were kept at a temperature of 230 to 250 C,
they gave birth to larvae at intervals of about 12 days, but by
varying the temperature the interval could be varied from
10 to 21 days. In three and a half months one female gave
birth to eight larvae, of which, however, two were dead. The
extrusion of larvae apparently proceeds uninterruptedly the
whole year round, but the intervals are prolonged during the
cold season.

The freshly extruded larva is of the usual Glossina shape
and its behaviour previous to pupation has been well described.

" If the new-born larva be placed in a glass dish or on
blotting-paper, it crawls about for a time exactly like an
ordinary fly-maggot, after which it becomes stationary and
soon contracts, its chitinous integument thickens and darkens,
and in about three-quarters of an hour it has assumed the
appearance of a coarctate pupa. If, however, the larva be
transferred to moderately damp sand, it at once burrows into
it, making a straight tunnel ; thus in one case a larva penetrated
to a depth of 8*5 cms. Under such conditions, from an hour
and a quarter to an hour and a half elapsed before the change
to the pupal state was completed. In dry sand a larva did not
burrow so deeply, since, as it burrowed, the sand continually
fell in, but nevertheless it reached a depth of 2 to 3 cms. We
may assume that in nature the larvae behave in a similar wa
the fly will deposit its offspring on a spot which is sheltered

292 G. BREVIPALPIS AND DISEASE [CH.

and slightly damp, and the larva will at once burrow beneath
the surface."

The average duration of the pupal stage at 300 C. was found
to be about 36 days, but by varying the temperature it could
be shortened to 30 days or prolonged to as much as 65 days.

There is some evidence to shew that this species may
reproduce parthenogenetically, for on two occasions Stuhlmann
observed fully developed larvae laid by virgin females that had
been bred in captivity.

G. BREVIPALPIS and Disease.

Although there is little doubt that the present species is
an important carrier of cattle trypanosomes precise information
is lacking. According to Stuhlmann, in German East Africa
it is one of the chief disseminators of Nagana among domestic
animals. Both Koch and Stuhlmann fed G. brevipalpis on
animals infected with T. bmcei and attempted to trace the
development of the parasite within the vertebrate host. The
latter author gives an interesting description of the various
supposed developmental changes undergone by the trypano-
somes, but in no case did any direct inoculation experiments
give positive results and therefore the transmission of T. brucei
by G. brevipalpis remains as yet unproven.

Similarly in the case of T. gambiense, Koch observed a
commencement of its development in the gut of G. brevipalpis
and Fischer is of the opinion that this species may occasionally
act as an intermediate host for sleeping sickness.

Dr P. H. Ross has shewn that the fly is able to transmit
mechanically T. gambiense from infected to healthy monkeys.
During 91 days, 51 flies were fed first on an infected monkey
and eight hours later on a healthy one. The latter shewed
parasites in its blood on the ninety-fifth day.

Later the same investigator had two positive results in the
transmission of T. gambiense by G. brevipalpis employing the
" interrupted " method of feeding, but as the flies were caught
in nature there is a slight doubt as to whether the trypanosome
was really gambiense.

XVl] THE TRYPANOSOMES 293

REFERENCES.

Austen, E. (1903). Monograph of the Tsetse-Flies, p. 95.

(1911). Handbook of the Tsetse-Flies, p. 85.

Davey, J. B. (1910). Bull. Entom. Research, vol. 1. p. 143.
Koch, R. (1905). Deutsche Med. Wochenschr. vol. xxxi. Nov. 23.
Milne, A. D. (1910). S. S. Bulletin, vol. 11. p. 37.

Neave, S. A. (1912). Bull. Entom. Research, vol. ill. p. 275.
Newstead, R. (1910). Ann. Trop. Med. and Parasit. vol. vi. p. 372.
Ross, P. H. (1908). Colonial Report East African Protectorate, No. 6490.

(1910). Nairobi Laboratory Reports, vol. 1.

Sanderson, M. (1911)- Bull. Entom. Research, vol. 1. p. 292.
Stuhlmann, F. (1907). Arb. Kais. Gesundheitsamte, vol. xxvi. p. 301.

CHAPTER XVII

GLOSSINA AND DISEASE
THE TRYPANOSOMES

Diagnosis, etc. The trypanosomes constitute a well-defined
group of flagellates inhabiting the blood of vertebrates, and
with few exceptions the known pathogenic species are mainly
transmitted by various species of Glossina. As many of them
are carried by more than one kind of tsetse-fly, it will be
convenient to discuss them collectively, instead of describing
each trypanosome separately under the heading of one of its
carriers.

The genus Trypanosoma includes all those flagellates
characterised by the possession of a more or less elongated
fusiform body and a single anterior flagellum, which, at 1
during some part of the life-cycle, arises near the posterior end
of the body, and for the greater part of its Length is attached
to a fold of the periplast, known as the undulating membrane.
Occasionally the flagellum does not become free anteriorly but
is attached to the undulating membrane along its whole Length,

The dimensions of different species, or even oi different
stages of the same species, may range from a- -mall a- 12
microns in length by 1-5 microns m breadth, up to more than

294

TRYPANOSOMES [CH.

ioo microns in length by 10 microns in breadth ; but the great
majority of them are between 20 and 30 microns in length, by
i*5 to 2-5 microns in breadth.

General description. The body of a trypanosome consists of
an elongated fusiform mass of cytoplasm containing two nuclei
and bounded by a more or less distinct periplast. The
cytoplasm may stain uniformly, but frequently contains
numbers of chromatic granules, the presence or absence of
which is sometimes of use for classificatory purposes. The
larger of the nuclei is usually situated about the middle of
the length of the body and is known as the trophonucleus.
Typically it consists of an oval, lightly-staining vesicle, con-
taining a deeply-staining, central karyosome. The smaller
nucleus, known as the kinetonucleus, is generally situated at,
or near, the posterior, non-flagellate extremity of the try-
panosome. The kinetonucleus is also known as the centrosome,
blepharoplast, or micro-nucleus, but all these terms are liable
to lead to confusion. The term blepharoplast, or centrosome,
should be reserved for the small basal corpuscle, or end-bead,
situated close to the kinetonucleus, from which arises the
flagellum, running forward attached to the surface until it
reaches the anterior extremity of the body. In its course along
the body the flagellum is attached to the surface by means
of a transparent membrane, the undulating membrane, which
varies considerably in its development in different species, but
is always distinct. The parasite mainly progresses by the aid
of wave-like motions of this undulating membrane, accompanied
by wriggling of the whole body. The movements of the living
trypanosome are sometimes of use in identifying the species,
the very quick darting motions of T. lewisi and T. cazalboui
being very characteristic.

The relative positions of the two nuclei serves as a means
of distinguishing T. rhodesiense, and the size of the kineto-
nucleus is a character of considerable value, but the dimensions
of the parasite probably constitute one of the most useful
means of identifying the various species.

In giving the dimensions of any particular species it is
necessary to give the measurements of a moderately large

XVIlJ MODE OF DIVISION 295

number of individuals, and the most convenient way of pre-
senting the result of such a series of measurements is by means
of a Galtonian curve. With this graphic method it is possible
to detect whether the species is dimorphic or monomorphic,
and Bruce has shewn how it is possible to distinguish species
that have the same range of dimensions, e.g. T. brucei and
T. evansi.

Mode of division. In the blood, the parasites multiply by
longitudinal fission, the details of which are essentially the same
in all species of trypanosomes. The first sign of division is
usually seen in the kinetonucleus, which seems to swell up,
resulting in the formation of an oval vesicle, throughout which
the chromatin is evenly distributed. The chromatin then
aggregates together in the form of a band lying across the middle
of the vesicle, which now becomes slightly elongated. This
band then divides transversely and the two halves move apart,
one of them usually approaching the trophonucleus, and appar-
ently without any further changes, beyond the disappearance
of the vesicle, these two bands constitute the two daughter
kinetonuclei. The details of this process can only be observed
in those trypanosomes possessing a comparatively large
kinetonucleus and have not been followed in the case of those
species with excessively small ones.

The end-bead, often with the basal part of the flagellum,
divides at the same time as the kinetonucleus. In some forms
the flagellum together with the undulating membrane divides
along a considerable part of its length, so that the new flagellum
is formed by splitting of the old one, whilst in other cases an
entirely new daughter flagellum develops from one of the daugh-
ter end-beads.

The trophonucleus usually divides shortly after the division
of the kinetonucleus is complete. The central karyosome
divides, and the two halves move apart until they are situated
one at each pole of the nucleus, still remaining connected,
however, by a fine line. In some species the chromatin may
become arranged in the form of an equatorial plate, which then
splits transversely, each half moving up toward- it- respective
pole. In other species no equatorial plate is formed, but the

296 TRYPANOSOMES [CH.

chromatin merely becomes aggregated around each pole and
division is more or less direct. In either case the connecting
line eventually disappears and the two daughter nuclei gradu-
ally assume the usual form. Meanwhile the new flagellum
has become nearly as long as the old one. The animal then
splits longitudinally, the fission commencing at the anterior
end and extending down until the two halves are connected
merely by their posterior extremities, in which position they
may remain for some little time before finally separating.

In some species, e.g. T. lewisi, the trypanosomes multiply
by a process of schizogony, and multinucleate forms are not
infrequently found in many other species. The presence or
absence of such forms occasionally gives some help in the
determination of the species.

Biological characters. Certain trypanosomes will only live
in one particular vertebrate host and when injected into other
species are unable to survive. None of the pathogenic
trypanosomes, however, are restricted to one species, the
nearest approach to it occurring in the case of T. sirnice, which
only affects monkeys and goats.

The great majority of trypanosomes have little or no effect
upon the health of their hosts and accordingly are termed non-
pathogenic. On the contrary, the most important parasites
from the present point of view — the pathogenic trypano-
somes— have a marked injurious effect on the health of the
animals they inhabit.

The effect of these parasites on their hosts is of help in
distinguishing the various forms, as the incubation period,
duration of the disease, symptoms, etc, etc., all furnish useful
indications.

Yet another means of distinguishing these pathogenic
trypanosomes is furnished by the results of inoculating the
parasites into various experimental animals. The smaller
animals are refractory to certain trypanosomes that are patho-
genic to ruminants, and on the other hand some parasites have
a much more pathogenic effect on small animals than on large
ones.

The method of infection is another important character.

XVII] BIOLOGICAL CHARACTERS 297

Some trypanosomiases are transmitted entirely by coitus
others by tsetse-flies, and yet others by Stomoxys and Tabanid>.
In those few cases in which the life-cycle of the trypanosome
in the tsetse-fly (Glossina) has been followed, the evolution of
the flagellate within the body of the fly is found to differ in
different species, and in future this may furnish an important
means of distinguishing them. At present it is possible to
distinguish those trypanosomes which infect the whole length
of the alimentary canal of the fly (infection totale), from those
that are restricted to the proboscis.

Cross immunity reactions. The most certain method of
distinguishing any two races of trypanosomes is by means of
their immunity reactions. Thus, given two races of trypano-
somes A and B, an animal having recovered from A is inocu-
lated with B, in order to determine whether or not it possesses
immunity against the latter, and vice versa. If an animal
which has recovered from A is still susceptible to B, one as-
sumes that A and B constitute distinct species. On the other
hand if an animal which has recovered from A, and therefore
is immune against this strain, is also immune against B, the
two are considered to be identical.

This method is only capable of application in the laboratory
and cannot be used during expeditions in the tropics.

Sero-diagnostic methods. Laveran and Mesnil have also
called attention to the possibility of employing sero-diagnostic
methods in the identification of trypanosomes. The serum oi
an animal which has acquired immunity against any particular
trypanosome, is often active when mixed with blood containing
this trypanosome, and inactive when mixed under similar
conditions with other species of trypanosomes. Unfortun-
ately the activity of the immune sera is too variable to give any
wry certain results, and this method, therefore, only gives
useful indications.

The production of agglutination by means of the addition
of immune serum of the same species of trypanoson*
of use in some cases, but is very inconstant.

Classification. The identification of the various sped
trypanosomes has become a matter of great difficulty, especially

298 AFRICAN PATHOGENIC TRYPANOSOMES [CH.

in the case of the numerous cattle trypanosomes of Africa, and
at the present time there is no simple method by which the
different varieties can be distinguished with any certainty.
In some cases the morphology is sufficiently distinctive, but in
most cases the trypanosomes are chiefly distinguished by their
biological characters, and these are often very difficult to observe
even in well equipped laboratories. In every case, there-
fore, species should be distinguished as much as possible by
morphological characters, for the present practice of giving
specific names to merely " physiological varieties " is of
questionable value.

In the following table we have adopted Laveran and
Mesnil's method of sub-dividing trypanosomes into three groups,
according to the presence or absence of a free flagellum, or
those strains in which both forms occur. It has been found
necessary to omit many so-called species that have been in-
sufficiently described, and whose identification is very uncertain,
if not impossible.

Key to the pathogenic trypanosomes of Africa.

A. Trypanosomes in which the flagellum always possesses
a free part anteriorly.

f Living trypanosome extremely active, frequently darting across the field
of the microscope. Dogs, monkeys, rats and mice all refractory to

1 ■{ infection ; ruminants and horses susceptible

— cazalboui, Laveran ( =vivax, Bruce etc. nee Ziemann).
I Dogs, rats and mice susceptible to infection . . . . . . =2

C Monkeys and ruminants more or less refractory to infection. Horses

2 <J susceptible . . . . . . . . = equiperdum, Doflein.

[_ Monkeys and ruminants susceptible to infection . . . . =3

f Parasite more or less dimorphic . . =brucei, Plimmer and Bradford.

3 J fevansi, Steel.

I -p, ., , . J evansi var. mbori, Laveran.

I Parasite monomorphic .. .. = < , M .,,.„.

I togolense, Mesnil and Bnmont.

^soudanense, Laveran.

The latter four trypanosomes are distinguished by their cross immunity
reactions.

XVII] AFRICAN PATHOGENIC TRYPANOSOMES 299

B. Trypanosomes in which the flagellum does not become
free anteriorly.

/Parasite distinctly dimorphic . . = dimorphon, Laveran and Mesnil.

\ Parasite monomorphic . . . . . . . . . . . . =2

Monkeys, dogs, rabbits, etc., refractory to infection =nannm, Laveran.
Monkeys and goats susceptible ; dogs, rabbits, etc., refractory to infection
= simice, Bruce, Harvey, Hamerton, Davey, and Lady Bruce *.
.Monkeys, dogs, rabbits, etc., susceptible to infection

_ j congolense, Broden.

~ \pecorum, Bruce, Hamerton, Bateman, and Mackie.

The latter two species are distinguished by cross immunity reactions. In
addition T. pecorum is more virulent than T. congolense.

C. Trypanosomes having forms with a free flagellum and
forms without a free flagellum.

/Trypanosomes immobilised by human serum . . =pecaudi, Laveran.

\ Trypanosomes unaffected by human serum .. .. .. =2

fin rats, trypanosome shewing a variable proportion of forms with the
trophonucleus at the posterior end of the body
2 -{ —rhodesiense, Stephens and Fantham.

I Trypanosomes never shewing any posterior nuclear forms
I. =gambiense, Dutton,

* In this species the extreme tip of the flagellum may sometimes become
free for a length of 2-3 microns.

REFERE^XES.

Laveran and Mesnil (191 2). Trypanosomes et Trypanosomiases, 2nd
edition. Masson et Cie. Paris. (Contains a very complete account
of the literature on the subject.)

300 SLEEPING SICKNESS [CH.

CHAPTER XVIII

glossina and disease [continued]
SLEEPING SICKNESS [T. gambiense)

Synonyms. African Trypanosomiasis (pro parte) ; African
Lethargy ; Trypanosome Fever ; Sleeping Dropsy ; Morbus
Dormitious ; Maladie du Sommeil ; Schlafkrankheit ; Doenca
de Sonno ; Letargia dei Negri ; Malattia del Sonno. Also a
very large number of native names.

Definition. Sleeping Sickness is an acute or chronic infec-
tion with Trypanosoma gambiense Dutton, characterised by an
inflammatory condition of the lymphatic system, leading to a
meningo-encephalitis and a meningo-myelitis. The disease is
usually transmitted by Glossina palp alls Rob.-Desv., but
G. morsitans and probably some other species of the same
genus are capable of becoming infective.

History. The first mention of this disease occurs in 1734,
when John Atkins, a Naval Surgeon, gave a clear description
of cases of the disease on the Guinea Coast. In the appendix
to his book, entitled The Navy Surgeon, occurs the following
passage : "The Sleepy Distemper (common among the negroes)
gives no other previous Notice, than a want of Appetite two or
three days before; their sleeps are sound, and Sense and Feeling
very little ; for pulling drubbing or whipping will scarce stir
up Sense and Power enough to move ; and the Moment you
cease beating the smart is forgot, and down they fall again into
a state of Insensibility, drivling constantly from the Mouth as
if in deep salivation ; breathe slowly, but not unequally nor
snort.

" Young People are more subject to it than the old ; and
the Judgement generally pronounced is Death, the Prognostick
seldom failing. If now and then one of them recovers, he
certainly loses the little Reason he had, and turns Ideot

" In Searching for the Cause of this Distemper it will be
necessary to repeat what I have observed, that the Bulk of

XVIII HISTORY

Slave-Cargoes mostly consist of Country People, as distin-
guished from the Coast People, apparently if the principal Way
of Supply be considered. At YYhydah more Slaves are brou
than on the whole Coast besides ; and why ? The K
that Country, and his next neighbours, understand - ntv

better than others, and often make War (as they call it
bring in whole villages of those more simple Creatures inland, to
be sold at Market, and exchanged for the Tempting Commodi-
ties of Europe, that they are fond and mad after.

' The immediate cause of this deadly sleepiness in the
Slaves is evidently a Super-abundance of Phlegm or Serum,
extravased in the Brain, which obstructs the Irradiation of the
Nerves ; but what the procatartick Causes are, that exert to
this Production, eclipsing the Light of the Senses, is not so
easily assigned ....

" The cure is attempted by whatever rouses the Spirit- ;
bleeding in the jugular, quick purges, Sternatories, Vesicato:
Acu-Puncture, Seton, Fontanels, and Sudden Plunges into the
Sea ; the latter is most effectual when the Distemper is new.
and the Patient as yet not attended with a drivling at Mouth
and Nose."

From this account there can be no doubt that the author
had observed cases of sleeping sickness, but no further mention
of the disease occurs until 1S03, when Winterbottom -
fairly clear account of the malady as he saw it on the v
coast of Africa, near Sierra Leone. Whilst the slave trade
was in progress, some of the natives infected with -
sickness were carried across to the West [ndies, and in :
Moreau de Jonnes recorded its presence amongst the n
slaves in the Antilles.

In 1840. Clarke wrote a more complete are. .unt ofth<
based upon observations made at Sierra Leone, and during the
next twenty years a number of English and French
published various descriptions of sleeping sickn< —

In 1869, Guenn met with the disease in the island oi Mar-
tinique among the slaves who had been imported from the •
coast of Africa. The disease never spread in these count]
to which it had been imported, and liuerin was able to shew

302 SLEEPING SICKNESS [CH.

that in Martinique the infection was certainly not contagious.
Dr Corre, in 1876, gave a good description of the disease as
observed in the Senegal and attributed it to a kind of ergotism,
or scrofula, and to the moral condition of the people. In
addition he describes the ravages of sleeping sickness in the
Senegambia, where whole villages had been swept away and
many towns abandoned as a result of " Nelavane," the local
name for the disease.

Mense, in 1885 to 1887, found sleeping sickness widely
distributed throughout the navigable reaches of the Congo
as far up as the Stanley Pools, and the disease had not been
lately introduced into this region for it was well known by the
natives. In 1871, the first case of this disease appeared on
the banks of Quanza, in Angola, and since that date thousands
of victims have been claimed and numerous villages abandoned.

Until this outbreak in Angola, for many generations sleep-
ing sickness seems to have been confined to certain parts of
the west coast of Africa, especially the Congo, which also
formed its southernmost limit, and the Senegambia. Although
the disease has now spread to the south into Angola, up to the
present the region of the Gambia still forms its northern limit,
and it is interesting to note that the natives of this region have
a superstition that sleeping sickness came from the provinces
to the south of them.

In the eighties of the last century, the malady was still
restricted to the west of Africa, but after this date began that
opening up of Africa, that has resulted in sleeping sickness
spreading inland as far as Uganda and the great lakes. It is
believed that unwittingly Stanley, the African Explorer, was
responsible for the introduction of the disease into the lake
region during his expedition for the relief of Emin Pasha. In
1887, Stanley travelled up the Congo with a large force
and eventually reached the shores of Lake Albert Nyanza
where he found Emin Pasha. Regarding this expedition
Mense states : " Stanley's expedition for the relief of Emin
Pasha, which travelled in 1888 from the Congo to the Nile, and
which hired carriers from the Lower and Middle Congo, must
certainly have brought many infected men along with it to the

XVIII] HISTORY 303

Lake region, and possibly introduced the disease there. I
myself was the witness of sick men regardlessly abandoned, of
dead and dying, who marked the way even in the Cataract
region."

After Stanley had met Emin they eventually proceeded to
Zanzibar but a large number of soldiers and followers were left
behind in a district to the west of the Lake Albert Nyanza.
When Captain (now General Sir Frederick) Lugard arrived in
Uganda in 1908, after deposing Kabarega, he went to Albert
Nyanza and recruited a body of Sudanese, the remnants of
those left behind by Stanley and Emin Pasha. About 400 to
500 able-bodied men were enlisted as soldiers and they, with
their rabble of 7000 wives, children and followers, were settled
in South Toro in 1891. A year later it was found advisable
to move them to Busoga where they could be under better
control, and for some years there continued recruiting of Sudan-
ese soldiers brought to this province.

Sleeping sickness was then unknown in this part of Africa
for none of the chiefs or missionaries had ever seen it and the
symptoms are so evident that cases could hardly have been
overlooked. In 1901 the disease was first recorded from Busoga
and on investigation Dr Hodges found that sleeping sickness
had occurred in one district of this province for six years
previously and that many hundreds of natives had already
died of it. As many of the settlers in Busoga had originally
come from the Congo with Stanley's force, there can be little
doubt that they were responsible for the introduction of the
disease. In the next seven years the epidemic assumed such
proportions that in Busoga alone no less than 200,000 people
out of a total population of 300,000 died of ski pm- sickness.
The disease was also prevalent in Uganda, occurring along the
shore of Lake Victoria and on the islands.

In 1901, Forde noticed some peculiar parasites in the bl
of a patient who was admitted into the hospital at Bathurst,
suffering from an unknown type of fever. The follow.-
Dutton examined the blood of this patient and found the
peculiar parasites noted by Dr Forde, and recognized that
they were trypanosomes. Subsequently trypanosomes were

304 SLEEPING SICKNESS [CH.

observed in the blood of a native in the Gambia and therefore
Dutton considered that it was probably a new parasite and
gave it the name of Trypanosoma gambiense. In 1902, Dutton
and Todd proceeded on an expedition to the Senegambia in
order to make further investigations into the nature of this
infection. They came to the conclusion that trypanosome
fever, or trypanosomiasis, was in natives a particularly mild
disease for many of those whose blood contained the parasites
appeared to be in perfect health, and none of them were serious-
ly ill. Owing to the fact that these investigators had to
travel about, the cases could not be kept under observation for
any length of time and the relation between trypanosome fever
and sleeping sickness was not discovered.

In 1901, an epidemic of sleeping sickness broke out in
Uganda and the number of cases increased so rapidly that in
1902 the Royal Society sent out a Commission to investigate
the causes of this outbreak. This Commission composed of
Drs Castellani, Christy and Low, arrived in Uganda in 1902,
and at once commenced to work on the etiology of the disease.
Whilst Castellani was examining the brains and spinal cords of
persons who had died of sleeping sickness in the attempt to
find the cause of the malady, the other two members of the
Commission travelled about and eventually proved that the
area of infection was confined to a narrow strip of country
surrounding the lake shores and on the islands of Lake
Victoria. This restricted distribution had previously been
noticed by Hodges, and clearly shewed that there was no
relation between sleeping sickness and Filaria perstans, as
suggested by Manson, for the areas of infection were quite
different. In 1903, Castellani noted the presence of trypano-
somes in the cerebro-spinal fluid of patients infected with
sleeping sickness, and the same year Bruce and Nabarro
arrived in Uganda to continue these investigations. Bruce
at once recognised the possibility that this trypanosome might
be the cause of sleeping sickness and on further examination
Castellani found that 70 per cent, of the cases contained these
parasites in the cerebro-spinal fluid.

The parasite was described under the name of Trypanosoma

XVIIll HISTORY

J05

ugandense, as Castellani considered that it was distinct from
T. gambiense Dutton. Subsequently Bruce and Xabarro found
trypanosomes in the cerebro-spinal fluid of practically all cases,
but were puzzled by the fact that some natives shewed these
parasites in their blood without presenting any very serious
symptoms. Later, when patients suffering from trypanosome
fever were kept under observation, it was found that this
was merely an early symptom of sleeping sickness and that in
the later stages the parasites appear in the cerebro-spinal fluid
and the characteristic lethargic symptoms follow. The iden-
tity of T. gambiense and T. ugandense was also established by
means of inoculating animals with the two strains, when they
were found to produce exactly similar effects.

In 1903, Bruce and Xabarro shewed that sleeping sickness
was carried by means of Glossina palpalis, and the manner in
which they arrived at this discovery is of some interest. When
it was proved that sleeping sickness was caused by the presence
of a trypanosome in the blood, Bruce at once considered the
possibility of the transmitting agent being a tsetse-fly as he
had already proved to be the case in Zululand for another try-
panosome disease, Xagana. Large numbers of tsetse-flies were
found in the neighbourhood of Entebbe, but these belonged
to a different species, Glossina palpalis, from the tsetse-fly of
Zululand, G. pallidipes. The Commission, however, decided to
find out the distribution of Glossina palpalis, in order to deter-
mine whether it bore any relation to that of sleeping sickn
and with this object tsetse-flies were collected from all parts
Uganda together with any records of the disease. When all
the information was put together the evidence in favour of the
tsetse theory of transmission was almost overwhelming, for in
every locality from which sleeping sickness had been recorded
the tsetse-fly was found to be present.

The final proof of this theory was obtained by feeding
tsetse-flies on patients suffering from sleeping sickness, and
subsequently, alter various intervals, on healthy monk
The latter wen- found to become infected with I
thus proving that Glossina palpalis can convey trypan
from sleeping sickness patients to healthy individuals. It was

H. B. F.

306 SLEEPING SICKNESS [CH.

next shewn that if large numbers of the wild tsetse-flies in the
neighbourhood of Entebbe were caught and fed on healthy
monkeys the latter became infected with sleeping sickness.

The discovery that the tsetse-fly is the carrier of the disease
explained why sleeping sickness had not spread in the West
Indies in spite of the frequent importations of infected negroes.
In the absence of its invertebrate host the disease could not be
transmitted from the patients to other persons.

In 1909, Kleine discovered the very important fact that
T. gambiense undergoes a cyclical development in the body of
Glossina palpalis, and that once infected the tsetse-fly may
remain infective for a considerable period of time. In 1911,
Taute, whilst experimenting on the shore of Lake Tanganyika,
shewed that G. morsitans was also capable of acting as the
invertebrate host for T. gambiense, and that the trypanosome
underwent a cycle of development within the body of the insect
resembling that in G. palpalis. Finally, Bruce, Hamerton and
Bateman, in 191 1, shewed that the wild game served as a
reservoir for sleeping sickness, as antelopes and reed-bucks
could remain infected, and infective, for long periods without
presenting any signs of disease. The importance of this
discovery from a prophylactic point of view cannot be over-
estimated.

Distribution. At the present time sleeping sickness extends
along the west coast of Africa from St Louis in the Senegal,
to Benguella in the province of Angola, and inland as far East
as the Omo River (Brumpt) and the Victoria Nyanza. The
main centres of the disease are the Congo Free State, French
Congo, Cameroons, Angola, Senegal and Senegambia, Uganda
and along the shores of Lake Victoria and Tanganyika.

Life history within the vertebrate host — Endogenous cycle. —
The life-cycle of T. gambiense has been elucidated by the
researches of Minchin, Roubaud, Bruce, Kleine, and Miss
Robertson. The last named investigator has given a complete
description of all stages in the development, from which the
following account is taken.

In the blood the short forms (so-called female forms) about
13 to 20 microns in length (Fig. 75) are the adult type. They

XVIII] LIFE-CYCLE OF T. CAMBIENSE 307

have the longest duration in the circulation and appear to be
the type from which the individuals capable of carrying on
the cycle in the intermediate host, are derived. The blood of
a monkey is infective to Glossina only as long as this form is
present in sufficient numbers and moreover in a healthy state,
for at times, in very heavy infections, the flagellates seem to
become exhausted. These short forms grow up into the so-
called intermediate or "indifferent" forms, that are an ill-
defined and artificial group, chiefly to be recognised by their
increased length and longer free flagellum. The intermediate
forms are merely a step in the development of the division
forms, which are the culminating stage of this process. The
long slender forms that have been known as the male forms,
are merely the individuals that are about to divide. It is,
therefore, incorrect to speak of male, female, and indifferent
forms, as these are all stages in the development of the short
forms. Multiplication takes place in the circulating blood and
the details are as follows : the first sign of division is the
doubling of the kinetonucleus together with the end-bead,
situated at the posterior end of the trypanosome. The flagel-
lum then splits longitudinally, but only for about two-thirds
of its length, when it becomes free. Previous to division the
trophonucleus shews two well-marked dark granules, one at
each pole, and these are joined together by a fairly thick line
to the karyosome. The nucleus then divides, the chromatin
becoming aggregated about each pole. By this time the body
has become long and slender in form and eventually this 1
trypanosome separates into two daughter individuals that are
of the short form.

No other mode of multiplication within the blood is known,
although at times the nuclei may divide repeatedly without
division of the cytoplasm. In such cases large multinucL
forms may be produced but they are merely the resull oi
delayed division and not examples of true schizogony. In
addition, certain authors haw described various latent h
or spores, small rounded nonflagellate forms, thai are supp
to be capable of remaining dormant in the internal organs for
considerable lengths of time and thus be the cause of the

20 — 2

308 T. GAMBIENSE [CH.

relapses. It is possible that some latent forms are produced,
but up to the present the evidence for their existence is
inconclusive.

One of the most noticeable features of the infection in the
blood is the periodic increase and decrease in the number of
trypanosomes in the peripheral circulation. It was formerly
believed that the parasites completely disappeared from the
circulation at certain times, but Ross and Thomson have shewn
that when once a person becomes infected trypanosomes are
constantly present in the blood. During the so-called negative
periods the parasites are in such few numbers that their pres-
ence can only be detected by the examination of large quantities
of blood, either by centrifuging or some similar means. These
alternating periods of increase and decrease in the circulating
blood are of irregular duration, and the circumstances which
bring about the disappearance of the majority of the parasites
are not thoroughly understood. After a period of depression
the following increase in the number of flagellates is always
accompanied by division in the peripheral blood.

These variations in the number of trypanosomes are accom-
panied by differences in their infectivity when ingested by the
tsetse-fly. Thus it has been shewn that monkeys infected
with T. gambiense have negative periods during which they are
not infective to the fly, and moreover the percentage of flies
that become infected after any particular feed varies with the
stage of infection.

From this point of view, the following table, given by Miss
Robertson, is of considerable interest. Monkey 113 was
infected by wild G. palp alls from the shore of Lake Victoria,
and first shewed trypanosomes in its blood on July 25th.
From August 23rd up to the time of its death, fresh lots
of flies were fed on this monkey and the percentage number
of these flies that became infected is shewn in the table.

It is evident, therefore, that there is a marked difference in
the infectivity of the parasite at different stages of its develop-
ment, but in addition, different strains vary considerably in
this respect. Thus, another monkey was infected by the
direct injection of blood from a bush-buck which had been

25

o

34

o

07

1-8

XVIII] LIFE-CYCLE 309

Monkey 113.

Percentage

for- of flic

Condition of blood examined laboratory bred Number of becoming

Date alive flies flies M infected

Aug. 20-22 No trypanosomes seen in blood No flies fed — —

23 Few ,, ,, ,, „ — 101 o

24 Numerous trypanosomes in blood + 45 11 1
» 25 „ „ „ „ ,, + 53 37

26 Wry numerous trypanosomes in

blood . . . . . . — 8g o

27 Very few trypanosomes in blood No flies fed

28 /No trypanosomes seen in blood Flies fed

29 \ both days

30 Few trypanosomes in blood —

Sept. 1-3 Not examined

4 Very few trypanosomes in blood — 32 o

5 ,. ,, ,, ,, ,, No flies fed — —

6 Moderate number of trypano-

somes, dimorphism of broad

and narrow forms very marked 40 o

7 Moderate number of trypano-
somes . . . . . . No flies fed —

8 Trypanosomes very numerous
indeed .. .. .. + 95 21

9 Fair number of trypanosomes
but much fewer than on 8 th No flies fed —

10 Not examined . . . . No flies feci — —

1 1 Few trypanosomes

12 Trypanosomes very numerous
indeed . . . . . . + 70 14

13 Trypanosomes very numerous
indeed .... . . No flies fed 70 i|

14 Trypanosomes very numerous
indeed . . . . . . ,, — —

13 Blood swarming with trypano-

somes ...... + 20 10

infected with T. gambiense by laboratory bred flies. The bush-
buck had harboured the trypanosome for about fifteen months.
This monkey shewed infective and non-infective periods in
exactly the same way as other infections, but the infective
periods gave a remarkably Large percentage oi flies harbouring
trypanosomes. Out of 150 G. palpalis thai were ivd on this
monkey, 16 became infected, a percentage oi io«6 per cent.,
which is remarkably high, Eor Bruce, Hamerton, Bateman
and Mackie found that the normal proportion of infected flies

310 T. GAMBIENSE [CH.

produced by the Uganda strain of T. gambiense in monkeys
was only about one in 40.

Life history within the invertebrate host, G. palpalis —
Exogenous cycle. — In addition to the initia linfectivity of the
trypanosome mentioned above, several other conditions have
a marked effect upon the development of T. gambiense in its
invertebrate host, the tsetse-fly. A certain degree of warmth
is essential and the more favourable results obtained on
Tanganyika than in Uganda, in the transmission of T. gambiense
by G. morsitans, can be explained by the differences in tem-
perature between these two localities.

One of the most important conditions affecting develop-
ment is the interval that elapses between the feed of infected
blood and the following meal. When a newly-hatched fly is
fed, it usually ingests sufficient blood to fill both its crop and
gut. The next feed, taken in two or three days later, may
either entirely replace the undigested remains of the first meal,
or some of the first feed may remain in the crop and the fresh
blood be taken on top of it. Occasionally the blood may be
taken directly into the gut without even going into the crop.

If a fly has ingested trypanosomes at its first feed, the
result of subsequent clean feeds varies in different individuals.
The trypanosomes may be digested and disappear from the
alimentary canal of the Glossina during the first 50 to 72 hours,
without the intervention of a second feed. In other cases the
flagellates survive in the gut in small numbers but disappear
during the early stages of digestion of the new blood. It is
evident from these two results that all trypanosomes cannot
withstand the digestive processes and, of course, in such cases
the fly does not become infected. In some flies the trypano-
somes may survive and multiply in the gut in the blood
retained from the first feed, although a second feed has been
taken in on top. In these cases the trypanosomes may be swept
out when the original blood is digested, and thus no infection
be produced. The trypanosomes may survive and develop in
the crop for as long as 12 days, providing that blood is con-
stantly present. The gut of these flies may often shew no
signs of flagellates, in which case the insect will not become

XVIII] LIFE-CYCLE 311

infected, as there is never a permanent infection of the crop.
When trypanosomes persist in greater or less numbers in the
gut and crop of the same fly, the issue is somewhat doubtful as
the flagellates may be swept out by subsequent clean feeds.

A permanent infection of the fly is obtained when the whole
material of the first feed has been displaced from the gut by the
second feed, and the trypanosomes still persist. Once parasites
are well established in the new blood the rate of multiplication
is such that there is little chance of their being destroyed at the
next influx of blood.

There is no doubt that the critical time for the parasite is
this influx of fresh blood after an infected feed. This is shewn
by the very much larger percentage of infected flies found
amongst those individuals that had only one feed and this
the infecting one, than among those that had been subsequently
fed every two or three days in the usual way. Out of 103
starved flies trypanosomes were found in 22 between the 6th
and 12th day. 16 or 15-5 per cent, of these starved flies shewed
a well developed infection of the gut, whereas under ordinary
feeding conditions only about 3 per cent, of these flies became
infected.

In the early days of the cycle in the alimentary tract of the
fly many forms of parasites may be observed, depending on the
various conditions. The trypanosomes may persist without
multiplying, under which circumstances they degenerate and
disappear within three to four days. In other cases the parasi tes
persist in small numbers and begin to multiply, but when the
adverse conditions of a new feed come upon them, they are
unable to withstand them, and dividing and degenerating speci-
mens may thus be found side by side. Persistence and quite
normal development may occur in the crop and continue till
the 10th or 12th day, so that it is evident that the stimulus
development in the fly is not dependent upon the digestive
action of the gut fluid upon the blood.

The very large number of cases where the attempted multi-
plication fails to establish an infection, indicate- the presence
of a general inhibiting property in the Glossina and is a fairly
constant factor in experiments with freshly hatched flies.

312

T. GAMBIENSE

[CH.

Fig- 75- (1-19)- Trypanosoma gambiense. X about 2000 diameters.

(After Muriel Robertson.)
1-4. Trypanosomes from the blood of a monkey.
5-6. Division of blood- types.
7-8. Trypanosomes in the middle intestine of Glossina, 36-48 hours

after ingestion.
9-10. Slender proventricular types, final form of the gut development.
11-12. Specimens newly arrived in the salivary gland.
13-15. Typical salivary gland form, shewing the crithidial condition.
16-17. Division of salivary gland forms.

18-19. Final trypanosome types in the salivary glands, probably the in-
fecting form.

XVIII] LIFE-CYCLE ;i |

Individual strains of T. gambiense vary greatly in the percent-
age of infected flies they produce, this being due to the greater
or less vigour of the trypanosomes interacting with the inhibit-
ing forces of the fly. The negative blood periods, during which
the parasite is not in a fit state to carry on the cycle, are as
well marked in very vigorous strains as in those of less I
vitality.

When the conditions are favourable to development in the
fly, the trypanosomes first become established in the posterior
region of the mid-gut. Here multiplication takes place and
trypanosomes of very varying sizes are produced, though the
parasites rarely surpass a length of 34 to 35 microns.

About the tenth day numerous trypanosomes are present,
and the characteristic slender forms may begin to appear, but
only in small numbers.

The method of division in these forms is essentially similar
to that in the circulating blood, but the final division of the
protoplasmic body is very characteristic. Instead of the two
daughter individuals swinging out so as to be arranged kineto-
nucleus to kinetonucleus as in the majority of trypanosome
divisions, there is no longitudinal splitting of the parent organ-
ism, but the young specimen is pushed off at the posterior end
(Fig. 75, 17) and division is practically tram\ < 1

After the 10th to the 15th day the slender form> thai
constitute the pro ventricular type gradually develop from the
broader forms, and as their numbers increase move forward into
the proventriculus, where they are the dominant type. There
is only one important point in which they differ from their
predecessors. The body is long and slender, the cytoplasm
finely granular and much less dense than in the broader forms,
but the trophonucleus shews a distinct change. The kar
some has become much smaller and the membrane ha- become
much more marked and stains deeply. In the fully developed
slender tvpes, division rarely seems to occur.

The infection grows forward by sheer torn of multiplication
until it tills the whole of the middle and hinder intestine and
the posterior part of the anterior intestine. The anterior
portion of the anterior intestine and the proventriculus she*

314 T. GAMBIENSE [CH.

the typical long slender forms and are only invaded about the
middle of the developmental cycle. There seems to be some
difficulty in the trypanosomes reaching the proventriculus and
once arrived there they cannot maintain themselves if the fly
is exposed to too long a fast. If there is any considerable
interval before another meal the trypanosomes gradually ebb
backwards to the posterior part of the anterior intestine and
only gradually recover their position again after the next feed.
The intestinal infection is thus the focus from which the sub-
sequent stages are derived.

Fig. 76. Transverse section (semi-diagrammatic) of the proboscis of an infected
Glossina. The section shews the arrangement and aspect of the trypano-
somes attached to the walls of the labrum (L) and the hypopharynx
(Hyp.), (xaboutyoo.) (After Roubaud.)
L, labrum ; Hyp. hypopharynx ; M, M' , muscles ; L. inf., under lip.

After becoming established in the proventriculus the slender
forms pass up into the hypopharynx and then along the salivary
ducts into the salivary glands. The period at which this happens
depends upon the virulence of the trypanosomes, and early
infectivity is generally a character found in a strain which
produces many positive flies. The trypanosomes settle down
in the salivary glands in the cellular part of the lumen immedi-
ately above the narrow tubular part of the duct. At first they
are slender forms attached to the wall of the gland by their
flagella, but later they gradually change into broad crithidial
forms.

XVIII] LIFE-CYCLE 315

These crithidial flagellates multiply and finally All up i
portions of the gland with flagellates in all stages from typical
crithidial forms, attached by the flagellum, to free-swimming
trypanosomes closely resembling the blood type. The fly never
becomes infective until the trypanosomes have invaded the
salivary glands. The proventriculus and gut forms when
injected into monkeys never produce an infection. The inva-
sion of the glands usually occurs about the 20th day, but
occasionally it may take place earlier, in one case a salivary
gland being found infected on the 12th day. The Glossina
seems to become infective two to five days after the trypano-
somes have invaded the gland. During this period the para-
sites pass through the crithidial cycle, which seems to be a
necessary feature in the development of the trypanosome in
the invertebrate host before the latter can become infective.

The whole cycle from the ingestion of the trypanosome- to
the appearance of young blood forms in the salivary glands
generally occupies from 20 to 30 days, after which the Glos-
sina becomes infective and probably remains so for the
remainder of its life. When an infected fly bites an animal the
young trypanosomes in the lumen of the salivary glands are
passed dowrn the duct together with the salivary secretion and
thus injected into the wound caused by the mouth parts of the
insect.

Prophylaxis of Sleeping Sickness.

In spite of the experimental evidence to shew that Glossina
morsitans, G.fusca, and G. tachinoides, and probably the other
members of the genus, are all capable of transmitting sleeping
sickness, the epidemiological evidence in support of the view
that G. palpalis is the main carrier, is overwhelming. A >rd-
ingly, for the time being, in combating the spread i >f t he (li-
the other species of tsetse-flies may be ignored. The prophy-
lactic measures fall into two main classes. In the first place
we may prevent the access of trypanosome carriers to fl]
and in the second, we may attempt the destruction of the fly.

With regard to the former of these two methods, the diffi-
culties in the way oi preventing the flies becoming inf<

316 SLEEPING SICKNESS [CH.

have been enormously increased by the discovery that the
wild game may serve as a reservoir for sleeping sickness. When
it was discovered that the tsetse-flies along the shores of Lake
Victoria were infected, the government of Uganda ordered the
removal of all the population from the infested regions and by
means of stringent regulations prevented any persons living
on the lake shores or on any of the islands. Nevertheless three
years later the tsetse-flies were still infected with sleeping
sickness, although during this period they could not have had
the opportunity of feeding on the blood of any human being
suffering from the disease. It is evident, therefore, that the
wild game serves as an efficient reservoir for sleeping sickness
and as there is no possibility of exterminating all the mammals
in the infected regions, the idea of eradicating the disease in
this manner must be abandoned.

Nevertheless, it is very important to prevent any infected
person entering a fly area in which sleeping sickness does not
already exist. The danger of this has been well exemplified
in the case of Uganda, where, owing to the entrance of a few
infected natives from the Congo, the disease was introduced
among the previously uninfected Glossina palpalis, along the
shores of Lake Victoria. Dr Bagshawe in his excellent article
on this subject, advises the removal of healthy persons from
the vicinity of the fly, or their protection from fly bites. This
may be effected in a variety of ways amongst which may be
mentioned the following :

Whenever possible villages or markets should be removed
to fly-free areas as has been done in Uganda. In many districts,
however, the difficulties in the way of such a scheme are almost
insuperable, and even in Uganda it has not been found practic-
able to deal in a similar way with the infected districts near
the Albert Lake and White Nile. Needless to add, any camps,
whether temporary or permanent, should not be pitched in
the fly regions.

All occupations carried on in fly-areas should be discouraged
or prohibited. The most important of these is fishing, as river
and lake-side natives usually spend all their time in this occu-
pation, unprotected by any clothes and constantly being bitten

XVIII] PROPHYLAXIS )\J

by the tsetse-flies. The rapid spread of sleeping sickness in
Uganda was the result of the fishing habits of the nati\
Fishermen should be recommended to cultivate the soil or
raise stock, and regulations prohibiting fishing in fly infested
regions should be enforced. Brumpt has suggested that the
natives who live on fish might be persuaded to grow vegetables
by importing dried sea fish in exchange for their vegetable
produce. Rubber collecting in palpalis areas should also be
abandoned and there is little doubt that the prevalence
sleeping sickness in the Congo is largely due to this occupation.

During the heat of the day all fly areas should be avoided
as the insects are especially active during these hours. Any
visits to the water that may be necessary should be made
either in the early morning or late evening.

Whenever possible roads should be selected that do not
traverse fly areas, and when travelling fly-infested ferries and
fords should be avoided. If caravans are obliged to a
such rivers at hours when the fly is active, they should not
be allowed to halt within a distance of at least ioo yards
of the water. In the construction of railways, fly areas might
also be avoided, for there is a great danger of these in-
being carried very considerable distances in the carriages of
trains. When trains have to travel through infested regions
the carriages and trucks should be protected with wire gauze ;
similarly, steamers that ply on fly-infested hikes or n
should have some portion of the upper deck protected. The
protective effect of clothing is well known and the comparative
immunity of Europeans and native chiefs is mainly due to their
practice of wearing clothes. The peasants who go about i<»r
the most part naked are particularly liable to the bites oi the
flies, and therefore they should be instructed a- to the pi

ect of clothes. Europeans when travell
regions should take great care to protect their legs ami ai
and if the tin- are numerous it is advisable to wear both \

a\u\ gloves. It is possible that some substance may be round
which will be repellent to the flv and when rubbed on the skin
will keep it away, but up to the present ^^ satisfactory repellent
has been diso rvered.

318 SLEEPING SICKNESS [CH.

The instruction of the natives and also Europeans, as to
the danger of being bitten by tsetse-flies, should be carried
out systematically in all infected regions, for without the co-
operation of all persons it will be impossible to prevent the
occurrence of cases of sleeping sickness.

It is most important that no person harbouring trypano-
somes in his blood should be allowed to travel from one
district to another. All sick persons should be segregated in
treatment camps, away from any species of tsetse-fly. The
employment of these segregation camps in Uganda has greatly
reduced the number of deaths from sleeping sickness, but unfor-
tunately such methods can never entirely eradicate the disease.

It should be forbidden to recruit soldiers, carriers or
labourers in infected districts and bring them into any other
districts which contain fly areas. The importance of such pre-
ventive measures in the case of uninfected districts containing
G. palpalis is obvious, but the passage of persons harbouring
trypanosomes from one infected district to another should also
be avoided. Dr Bagshawe has called attention to the impor-
tance of this measure, for the strains of T. gambiense vary in
virulence. There is some evidence that in consequence of the
introduction of a virulent strain into a region where a mild
strain previously existed, a small endemic focus of sleeping
sickness has been succeeded by a great epidemic. It is also
possible that an epidemic which is gradually losing its virulence
and tending to die out may be kept alive by the introduction
of persons harbouring virulent trypanosomes in their blood.

The only effective way of suppressing sleeping sickness is
by the extermination of the tsetse-fly, and, therefore, the most
important of all prophylactic measures are those directed
against the fly. In fact, the control of this disease is essentially
a problem for the entomologists. There are no doubt enormous
difficulties in the way of exterminating an insect ranging over
some millions of square miles of Tropical Africa, but the manner
in which Stegomyia and other mosquitoes are disappearing during
campaigns against yellow fever and malaria should make one
hesitate before considering such a task impossible. A complete
knowledge of the bionomics of G. palpalis, including its natural

XVIII PROPHYLAXIS

319

enemies and diseases, would be of immense value, and yet up
to the present comparatively little work has been done on this
subject.

Bagshawe advises the use of the following measures against
the fly :

(a) The clearing of fly-infested scrub.

(b) The filling up or draining of pools when it is practicable.

(c) The cultivation of plants noxious to the fly.

(d) The destruction of animals on which the fly feed-.

(e) The encouragement or introduction of animals or

plants (Fungi) which attack the fly in its adult or

pupal stages.
(/) The collection or destruction of pupae or of the flies

themselves.
The clearing of fly-infested scrub has been found to be of
great value in Uganda, but it is rather difficult of application
over wide areas. As the natural range of palpalis does not
exceed 30 yards from the water, a clearance of this strip
will cause the disappearance of the fly. According to Roubaud,
in the Congo it is sufficient merely to thin out the vegetation
on each side of the water, but in most localities it is necessary
to remove thoroughly all brushwood and scrub which shelter
the fly and its pupae. The cleared areas must either be kepi
free from scrub-vegetation, or some crop planted which will not
give the flies any shelter. Citronella is one of the most suitable,
as the grass repays cultivation and its smell may be repugnant
to the fly. No clearing should be attempted unless it is p ►ssible
to make it efficient and keep the cleared spaces free from --rub.
and before undertaking any such measure the locality should be
carefully examined. The flies and pupae may be restricted to
certain parts of the shore, in which case it is only necessary to
clear these areas. It is advisable to clear the following Locali-
ties : boat and steamer landing-places on lakes or rivers : dipping
and washing places : stations on railways that traverse t>m
areas ; ferries and fords ; and the sites of market- or camps.

The clearing should be performed during the dry season,
because the flies are then less numerous.

In the Senegal, where clearing has been practised on a

320

SLEEPING SICKNESS fCH.

large scale, whole tracts of country have been deforested, and
in consequence, the streams have dried up and the tsetse-flies
have disappeared.

The destruction of animals on which the flies feed is a
proposal that needs very careful examination. Koch advocated
the destruction of the crocodile, but as mentioned above
(p. 264) it is very doubtful whether this scheme would be of
much use, and the available evidence is decidedly against it.
The destruction of the big game is not likely to affect the
numbers of G. palpalis, for it rarely feeds on these animals, as
they mostly come to the water at early morning or late evening,
when the flies are not about. The main food supply of this
insect has not yet been satisfactorily decided.

Minchin has suggested the introduction of jungle-fowl,
which might scratch up the pupae and devour them, but it is
possible that the birds might find plenty of other food. In
any case the experiment might be tried, for at present we know
very few enemies of this redoubtable insect. A knowledge of
the insectivorous birds that prey upon the tsetse-fly is much
to be desired, for we are almost in complete ignorance of this
subject.

With regard to the collection or destruction of the pupae or
of the flies themselves, there is little hope of any considerable
reduction in numbers being effected by these means. Dr Bal-
four is of the opinion that fly-traps might be of some use and
mentions an incident in support of this view. In the Sudan
occurs a limited fly-belt, about twenty miles long and three or
four miles in breadth. The fly is G. morsitans which in this
locality haunts the neighbourhood of wells. " This limited and
peculiar distribution is said by the natives to be due to the fact
that the fly was intentionally brought here from the river for
purposes of revenge! This may or may not be true, ...but
certain it is that at the present time the natives trap the fly in
gourds containing blood as a bait, and then liberate them in
spots where the cattle or horses of their enemies are grazing or
are collected together. The trap is a spherical gourd with a
hole cut in the top. It is half-filled with blood, and carefully
watched. As soon as a number of flies have entered it in quest

XVIII] REFERENCES 321

of food the native rushes forward and claps his hand over the
aperture. He then closes the hole in some more permanent
fashion, and carries off the flies in triumph for the future
discomfiture of those with whom he has a feud. This native
custom would certainly seem to indicate that a blood trap is a
feasible method of dealing with one of the greatest pests from
which Africa, the land of pests, has ever had to suffer."

Mr Maldonado, manager of one of the estates in the Isle of
Principe, caught large numbers of G. palpalis, by making his
labourers wear a black cloth, coated with bird-lime, on their
backs. This method of trapping tsetse-flies, however, has not
given good results in other localities, for it has been shewn that
a single fly-catcher can capture far more flies in a single day
than twenty or thirty fly-papers.

REFERENCES.

Bagshawe, A. G. (1908). Sleeping Sickness Bulletin, vol. 1.

Balfour, A. (1908). Third Report Wellcome Research Laboratories.

Khartoum.
Bruce and Nabarro (1903). Progress Report on Sleeping Sickness in

Uganda. Reports S. S. Comm. of Roy. Soc. No. 1.
Bruce, Hamerton and Bateman (191 1). Proc. Roy. Soc. B, 564,

pp. 311-327-
Bruce, Hamerton, Bateman, Mackie and Lady Bruce (191 1). Eleventh

Report of S. S. Commission of the Royal Society. H. M. Stationery

Office, London.
Castellani (1903). Rep. S. S. Comm. of Roy. Soc. 1903.
Duke (1912). Proc. Roy. Soc. vol. lxxxv. pp. 156-69.
Dutton (1902). Trypanosoma in man. B.M.J. Jan. 4, p. 42.

and Todd (1903). First Report of the Trypanosomiasis expe-
dition to Senegambia. Liv. Sch. of Trop. Med. Memoir xi.

Kleine (1909). Deutsch. Med. Wochenschr. May 27, pp. 024 23.
Laveran and Mesnil (1912). Trypanosomes et Trypanosomiases. Masson :

Paris.
Martin, Lebceuf and Roubaud (1909). Rapport de la Mission d*4tueles

de la maladie du sommeil au Congo Francais, 1906-1908. Masson :

Paris.
Mense (1906). Handbuch der Tropenkranhheitcn vol. m.
Minchin (1908). Quart. Journ. M 1 1 S^ i. vol. LI I. pp. 159
Robertson, M. (1912). Proc. Roy. Soc. B, 57s, pp. 24]

(1913). Trans, Roy. Soc. B, vol. 23, pp. i"i

Ross and Thomson (1911)- Proc. Roy. Soc. B 563, pp
Sandwith (1912). Sleeping Sickness. Macmillan 4 Ion.

Taute (1911). Zeitschr.f. Hyg. u. Infeki vol. 1 xix. pp. J

H. B. F. -1

322 TRYPANOSOMA RHODESIENSE [CH.

Trypanosoma rhodesiense Stephens and Fantham, 19 10.

General account. Until 1909 it was generally supposed that
human trypanosomiasis was restricted to regions in which
Glossina palpalis occurs, for there were no records of any cases
occurring outside such areas.

In that year Hearsey published an account of six cases of
trypanosomiasis in persons who had not visited any palpalis
region. The infections in every case must have been contracted
either in Nyasaland or North-Eastern Rhodesia, or Portuguese
East Africa. Subsequently a number of additional cases were
recorded, especially along the shores of Lake Nyasa and in
the Luangwa Valley.

In 1910, the first of these cases reached England and was
studied at the Royal Southern Hospital, Liverpool. The
history of this patient is of some interest as it was in his blood
that this trypanosome was first observed, and it is the only
strain of the virus which has yet reached Europe.

W.A., a male aged 26, first went to South Africa in July,
1904, living in Johannesburg till the end of 1906. He then
went to Salisbury for two years. About the end of November,
1908, he left Salisbury for North-Eastern Rhodesia with a view
to prospecting for minerals. On the journey northwards
he passed through Fort Jameson, Landazi, and Chinsali to
Kasama, arriving at the latter place about the beginning of
June, 1909. During this journey the patient traversed an
area infested with Glossina morsitans. He stayed two months
at Kasama, a place apparently free from tsetse-flies. On
the return journey he called at Mpika (where Glossina
morsitans occurs), Serenje and Mzaza (G. morsitans present).
On September 10, he left Mzaza and travelling along the
Luangwa River reached Feira on September 28. During
this part of the journey he would pass through an area infested
with Glossina fusca, between Mzaza and Hargreaves.

The patient first became ill on September 20th, but after a
rest of two days continued his journey. A short stay was made
at Feira and then the return journey was continued through the
Hartley District to Salisbury, where it was found that he was

XVIII] GENERAL ACCOUNT 323

suffering from trypanosomiasis, parasites Deing found in his
blood on November 17th, 1909.

The patient subsequently returned to England and in 1910
was admitted into the Royal Southern Hospital.

The same year Stephens whilst examining a stained speci-
men of the blood of a rat infected with this race of trypanosomes
observed a marked peculiarity in its morphology, and in
November, 1910, Stephens and Fantham gave a full description
of this new species of human trypanosome under the name of
T. rhodesiense.

The announcement of the discovery of a new species of
human trypanosome has given rise to a great deal of discussion
as to the nature of T. rhodesiense and its relation to pre-existing
species of trypanosomes. Whereas some authors tend to regard
it as merely a variety of T. gambiense, hardly distinct, others
consider it to be a form of T. brucei that has acquired patho-
genic properties for man. The latter view seems rather unlikely,
for on two or three occasions man has been shewn to be
immune against experimental infection with T. brucei, and,
moreover, human serum has a curative action on nagana in
experimental infections.

By means of cross-immunity reactions Laveran and Mesnil
have shewn that rhodesiense is distinct from both gambiense
and brucei, and therefore it must be regarded as a new species
of human trypanosome.

There can be little doubt that T. rhodesiense has arisen
within the last few years and that it is an interesting example
of the origin of a new species at the present time. As the
transmitting agent G. morsitans is widely distributed through-
out Rhodesia and East Africa, there is no reason why this
disease, had it previously existed, should not also have had
a wide range of distribution, instead of being restricted to one
or two valleys in Nyasaland and Rhodesia, and the symptoms
are so characteristic that the disease could hardly have re-
mained unnoticed.

Since the discovery of the trypanosome, however, its range
of distribution has increased considerably and already cases
have occurred south of the Zambesi. The sudden appearance

21 — 2

324 TRYPANOSOMA RHODESIENSE [CH.

of this disease in one small region, followed by such a rapid
spread, can only be explained on the supposition that it is an
entirely new form of sleeping sickness. Moreover, its extremely
deadly effect on its vertebrate host, man, is further evidence
in support of the same view.

T. rhodesiense is remarkably pathogenic to the majority of
experimental animals, the duration of life of monkeys infected
with this species being only about 8 to 14 days, as compared
with 27 to 149 days in the case of T. gambiense. It is evident,
therefore, that this new trypanosome is extraordinarily virulent,
and it is also very resistant to treatment, atoxyl apparently
having no effect on it.

In man the course of the disease is much more rapid than
in the case of ordinary sleeping sickness (T. gambiense) and
death usually takes place within three or four months of
infection.

At present T. rhodesiense is restricted to Southern Nyasaland,
North-Eastern Rhodesia, especially in the Luangwa Valley, and
Portuguese East Africa, but it seems to be extending its range
and unless effective preventive measures are discovered there
is reason to fear that it may give rise throughout Africa to an
epidemic, besides which the ravages of gambiense would appear
almost mild in comparison.

Morphology of the parasite. T. rhodesiense in most respects
resembles T. gambiense, but is characterised by the occurrence
of stout or stumpy forms in which some have the trophonucleus
at the posterior end. Stephens and Fantham give the following
account of the parasite : " Rats inoculated with this Rhodesian
strain usually shew a few long thin trypanosomes in the
peripheral blood in about three days. The stumpy forms of
trypanosomes with the trophonucleus posterior appear about
the fifth or sixth day and from this time onwards somewhat
increase in number up to the seventh or eleventh day- They
then form about six per cent, of the trypanosomes present, but
may decrease again, varying from day to day."

The dimensions of stumpy forms with a posterior tropho-
nucleus vary from 17 to 21 microns in length by 2 to 3
microns in breadth. There is a well-marked kinetonucleus

XVIII] MORPHOLOGY AND TRANSMISSION 325

and the flagellum terminates in a short free portion. The cyto-
plasm is coarsely granular, especially at the anterior end.

In addition Stephens and Fantham mention the occurrence
of " snout " forms with an elongated posterior end. These
forms are present especially during the first half of the infection,
and although not absent from the ordinary strains of T. gam-
biense are much more numerous in the case of rhodesiense.

It is important to note that the posterior position of the
trophonucleus has never been observed in trypanosomes in the
blood of man, but only in experimental animals. Wenyon and
Hanschell found that the percentage of posterior nuclear forms
varies very much, not only with the stage of infection but also
with the strain employed. In three strains of rhodesiense in
rats the percentages of these forms were found to vary in one
strain from o to 0-9 per cent., in the second from 3 to 7 per cent,
and in the third strain from 13 to 40 per cent.

T. rhodesiense, like gambiense, is markedly dimorphic, for
there are long slender forms and short stumpy forms, together
with intermediate forms. The numerical relations between
these various forms are extremely variable, depending on the
stage of infection. The dimensions of the parasites vary from
I3 to 39 microns in length, but the majority of them fall between
17 and 30 microns.

Mode of transmission. In 1912, Kinghorn and Yorke
demonstrated the transmission of T. rhodesiense by Glossina
morsitans, the experiments being carried out at Nawalia,
Northern Rhodesia, on the Nyamadzi River, a tributary of the
Luangwa.

About five per cent, of the flies were found to become infected
when fed on patients or animals containing trypanosomes.
The development in the fly is of the cyclical type, the insect
becoming infective after an incubation period of about fourteen
days. Once infected a fly remains infective for the remainder
of its life and may infect fresh animals at each successive feed.

Temperature has a marked effect on the development of
rhodesiense in the intermediate host as shewn by the following
experiment.

" Two batches of wild G. morsitans, batch A 95 flies, batch

326 TRYPANOSOMA RHODESIENSE [CH.

B 119, shewn to be non-infective by feeding upon clean mon-
keys, were fed for three days on a rhodesiense-iniected guinea-
pig. Each batch was then fed on a healthy monkey until the
fortieth day, the mean temperature being 590 F. Neither
monkey became infected. The 42 flies remaining of batch A
were placed in the incubator at 85 ° F., and the 58 flies of batch
B were left at laboratory temperature. Of the batch A flies,
on the 43rd day only six were alive. From the 41st to the 47th
day the flies of batch A were fed on a monkey (which died) ;
from the 48th day on a rat. The rat became infected, shewing
that batch A contained an infective fly on the 48th day, eight
days after being placed in the incubator. The four flies still
alive on the 53rd day were fed on four clean rats, three of which
became infected.

On the 61st day the 38 flies of batch B, which had then
failed to infect the monkey, were put in the incubator at 830 F.,
and from that day till the 75th were fed on a healthy monkey.
The animal unfortunately died. All the flies were dissected as
they died. One was found to harbour trypanosomes in the
salivary glands and gut, and animals inoculated with the con-
tents became infected. In the first part of the experiment the
relative humidity in the incubator was 36 per cent., in the
second, 72 per cent."

This experiment clearly shews that at a comparatively low
temperature the early stages of the trypanosomes may persist
in the alimentary canal of the fly for sixty days, but that for
the completion of the cycle of development a higher tempera-
ture is required (75 ° — 85° F.) . The necessity of a certain degree
of heat, before the fly can become infective, explains why
Kleine was unable to transmit T. gambiense by G. morsitans on
Lake Victoria, where the temperature is not high enough.

The life cycle of T. rhodesiense within the tsetse-fly has not
been thoroughly worked out, but seems to present many points
of resemblance to that of T. gambiense in G. palpalis. The
trypanosomes first become established in the intestine and in
every case the salivary glands are invaded before the fly
becomes infective. The manner in which the glands become
infected is uncertain, but it is apparently secondary to the

XVIII] TRANSMISSION 327

intestinal infection, and it only occurs when the trypanosomes
in the gut have reached a certain stage of development, and
even then only when the conditions of temperature are suitable
for the further development of the parasites. It was found
that on every occasion on which the salivary glands were infec-
tive, the trypanosomes in the intestine were also virulent

As a large number of the wild game harbour T. rhodesiense,
in nature the fly is frequently infected. In the Luangwa
Valley, Kinghorn and Yorke found that about 0-18 per cent, of
the morsitans were infected with rhodesiense.

Recently, however, Taute has published an important
paper in which the validity of these results is questioned.
This investigator carried out experiments at Lubimbinu,
Portuguese Nyasaland, and found that a large proportion
(16-2 per cent.) of the big game of that district was infected
with a trypanosome closely agreeing with T. rhodesiense in its
general characters. Nevertheless this parasite was shewn to be
non-pathogenic for man, as Taute fed laboratory-bred Glossina
morsitans on a monkey infected with the wild game strain, and
subsequently on a number of animals and also himself. After
the usual incubation period the flies became infective and all
the experimental animais (goats, dogs, and monkeys) on which
they were fed became infected and died of trypanosomiasis.
On the other hand, although Taute fed these same tsetse-flies
on himself for four days after they had been proved to be infec-
tive for animals, yet he remained well. This experiment was
repeated, with the same results, and in addition the author
injected himself with 2 c.c. of blood from a naturally infected
dog, without ever developing any symptoms of trypanosomiasis.

These results suggest that game and domestic animals may
not play the part in the spread of human trypanosomiasis that
certain authors have supposed, and trypanosomes from such
sources can only be regarded with certainty as factors in the
spread of sleeping sickness when they have been shewn to be
pathogenic for man.

328 TRYPANOSOMA BRUCEI [CH.

REFERENCES.

Hearsey (1909). Nyasaland Sleeping Sickness Diary. Part vni.
Kinghorn and Yorke (1912). Ann. Trop. Med. and Parasitology, vol. vi.

pp. 1-23, 301-15 and 317-24.
Laveran and Mesnil (191 2) . Trypanosomes et Trypanosomiases , 2nd edit.

Masson : Paris.
Shircore, J. O. (1913). Trans. Soc. Trop. Med. and Hyg. vol. vi.

pp. 131-42.
Stephens and Fantham (1910). Proc. Roy. Soc. B, 561, pp. 28-32.
Taute, M. (1913). Arbeit a. d. Kais. Gesundheitsamte, vol. lxv.

pp. 102-112.
Wenyon and Hanschell (1912). //. Lond. Sch. of Trop. Med. vol. 11.

PP- 34*35

Nagana (T. brucei Plimmer and Bradford, 1899).

General account. Nagana, or the " tsetse-fly disease," is
the most widely distributed and best known of all the cattle
trypanosomiases of Africa. For many years the common
tsetse-fly, Glossina morsitans, was known to be the cause of
the disease and the popular belief was that the fly injected
into the bitten animal some poison that caused the well-known
symptoms of the " fly disease."

In 1895, Bruce, together with his wife, investigated the
disease as it occurred in Zululand and discovered that it was
caused by the presence of a trypanosome in the blood. This
parasite was found to be conveyed from diseased to healthy
animals by the common tsetse-fly, and was present in the blood
of all affected animals. Bruce gives the following account of
the infection.

" Nagana, or the fly disease, is a specific malady appearing
in horses, mules, donkeys, cattle, dogs, cats, and many other
animals, and of which the duration varies from a few days to
some weeks or even up to some months. It is invariably fatal
in the horse, ass and dog ; but a small percentage of cattle
recover. It is characterised by fever, by an infiltration of
coagulated lymph into the subcutaneous tissue of the neck,
abdomen or the extremities, giving rise to a swelling of these
regions ; by a more or less rapid destruction of the red cells of
the blood, an extreme emaciation, often blindness, and by the

XVIIl] GENERAL ACCOUNT 329

constant presence in the blood of an intusorian parasite — a
trypanosome."

It is generally supposed that Bruce employed Glossina
morsitans in these transmission experiments, but, according to
Austen, from a consideration of the description and figures
given in Bruce's Report on the tsetse-fly disease, or nagana, in
Zululand, there can be little doubt that G. pallidipes was the
species employed.

T. brucei is one of the best known of all the trypanosomes,
as a dog infected with the parasite reached England in 1898,
and subsequently was sent to most of the laboratories of
Europe. As a result this parasite is the one most often employed
in treatment experiments and other observations on the
biology of trypanosomes under experimental conditions.

The disease is widely distributed in Africa, where, in addition
to Zululand, it has been recorded from the basins of the Limpopo
and Zambesi, Nyasaland, Northern Rhodesia, German and
British East Africa, Uganda, Bahr el Ghazal, and in the region
of the White Nile.

It is also possible that the disease may occur in Somaliland
and Galla, for the trypanosome causing the camel disease
known as Aino is indistinguishable morphologically from
T. brucei.

Nagana is one of the most deadly of all trypanosomiases
and the majority of animals succumb to the infection after a
comparatively short illness.

With regard to the virus as it occurs in the laboratories of
Europe, Laveran and Mesnil divide the mammals into three
groups according to their susceptibility.

(1) Animals in which nagana produces an acute infec-
tion : mice, rats, marmots, hedgehogs, dogs and monkeys.

(2) Animals in which nagana produces a sub-acute
infection : rabbits, guinea-pigs, dormice, horses, donkeys,
mules and pigs.

(3) Animals in which nagana produces a chronic infection :
cattle, goats and sheep."

In nature the disease affects horses, ruminants and dogs,
and also the wild game, such as antelopes, waterbuck, etc .

330 TRYPANOSOMA BRUCEI CH.

are frequently infected with the trypanosome. These wild
animals, however, seem to have become immune against the
disease, for they may harbour the parasite in the blood for long
periods without suffering from any apparent ill-effects.

The wild game, therefore, serves as a reservoir for the
infection, as in the case of T. gambiense, and thus, in nature,
generally a large proportion of G. morsitans and pallidipes are
infected with T. brucei.

The morphology of the parasite. In the living state, T.
brucei displays active movements, as its undulating membrane
is well developed. Its translatory powers, however, are far
inferior to those of T. cazalboui and it rarely moves out of the
field of the microscope.

The dimensions of the parasite according to Bruce vary
from 15 to 34 microns in length. Moreover the species is
somewhat dimorphic, the short stumpy forms measuring from
2 to 5 microns in diameter and the elongated forms only about
i*5 microns in diameter. According to Laveran and Mesnil
the average length of the parasite in horses is 28 to 33 microns
and in dogs and the smaller rodents 26 to 27 microns.

In stained specimens the protoplasm usually contains
numerous granules, especially in the anterior region of the
body. The kinetonucleus is distinct, and is generally situated
near the posterior extremity, especially in the shorter forms.
The undulating membrane is much folded and the flagellum
usually becomes free at its anterior extremity.

The trypanosome multiplies by simple longitudinal division.

Mode of infection. The experiments of Bruce in Zululand
shewed that Glossina pallidipes and morsitans were able to
transmit T. brucei, but the exact mode of infection remained
unknown until Kleine's observations were published.

In 1909, Kleine shewed experimentally that G. palpalis is
able to transmit this disease, and in addition that the trypano-
some underwent a cyclical development in its invertebrate host.
The account of the first experiment in which this important
discovery was made is as follows :

Since nagana did not exist in the Kirugu region (in German
East Africa) some sheep and a mule were brought from a place

XVIII] MODE OF INFECTION 331

seven days' march away ; these animals had been naturally
infected with nagana by the bites of G. morsitans. Fifty G.
palpalis were fed on three of these infected animals for three
successive days and from the fourth day onwards daily on fresh
healthy animals. From the fourth to the seventeenth day
inclusive the flies fed on a new animal each day, but none of
them became infected. From the eighteenth to the twenty-
fourth day the flies fed on the same sheep, and from the twenty-
fifth to thirty-ninth day on the same ox. On the twelfth day
after the flies were put on this ox, numerous trypanosomes were
found in the blood and the sheep was also found to be infected.
All the other animals remained healthy. Continuing this experi-
ment from the fortieth to the fiftieth day the flies, now reduced
in number to twenty-two, were fed on two goats, two calves
and two sheep. All these animals became infected after incu-
bation periods varying from five to eight days.

This experiment clearlv shews that G. palpalis remains non-
infective for many days after the ingestion of blood containing
T. brucei, but that after this negative incubation period the flies
become infective and may remain so for a considerable length
of time.

Later these experiments were repeated employing Glossiua
morsitans instead of palpalis. It was found that the animals
bitten during the three days following the feed on an infected
animal, all became infected, the transmission being direct, as
in the case of the Zululand experiments. The animals bitten
from the fourth to the tenth day remained healthy, whilst all
those that were bitten by the flies from the eleventh to the
forty-fourth day became infected. Moreover, Taute has shewn
that Glossina morsitans may remain infective for at least
83 days.

The evolution of T, brucei within the intermediate host has
not been fully worked out, but the parasites seem to multiply
within the alimentary canal and subsequently invade the
proboscis in a manner similar to T. gambicnse.

332 TRYPANOSOMA PECAUDI [CH.

REFERENCES.

Austen (1911). Handbook of Tsetse Flies.

Bruce (1895). Preliminary Report on the Tsetse Fly disease or Nagana

in Zululand. Ubombo, Zululand. Further Report, 1896.
Bruce, Hamerton, Bateman and Mackie (1910). Proc. Roy. Soc. B,

vol. LXXXIII.
Kleine (1909). Deutsche Med. Woch. Nos. 11, 21, 29 and 45.
Kleine and Taute (191 1). Arb. a. d. Kais. Gesundheitsamte , vol. xxxi.
Laveran and Mesnil (191 2). Trypanosomes et Trypanosomiases. Paris :

Masson et Cie.

Baleri (T. pecaudi Laveran, 1907).

General account. In 1904, Cazalbou observed a trypanosome
in the blood of a horse from the Bani region of Northern Nigeria.
This animal was suffering from a disease known by the natives
as Baleri. In 1907, Laveran described the trypanosome under
the name of T. pecaudi, and since this time Baleri has been
recorded from many parts of Tropical Africa.

It is common in the Upper Senegal and Nigeria, especially
in the basins of the Niger, Bani, and the Upper Volta. It has
also been observed in the Lower Senegal, Ivory Coast, Dahomey,
French Congo, and in the region of Chari. In Bahr el Ghazal,
Balfour and Wenyon have observed in dromedaries and horses
infections probably due to T. pecaudi.

Baleri is especially a disease of horses and donkeys, but
cattle are also susceptible to infection. The disease is charac-
terised by the occurrence of febrile attacks that are repeated
every three, four or five days. The trypanosomes are generally
numerous during the first attacks, becoming rare towards the
end of the infection. In horses the disease is practically always
fatal, after a duration of from three to four months. Donkeys
are less susceptible and may remain infected for nearly two
years before death supervenes.

A large number of animals may be experimentally infected
with T. pecaudi and the symptoms vary according to the species.
Cattle, goats, sheep and pigs are very resistant to the infection
and generally recover. On the other hand, monkeys, dogs,
cats, guinea-pigs, rats and mice are all susceptible and the

XVIII] MORPHOLOGY AND TRANSMISSION 333

infection is invariably fatal. In these animals the parasites
are numerous in the late stages of the disease.

Morphology of the parasite. In the living state the move-
ments of the trypanosome are very active. In stained
preparations two types can be distinguished, namely, long thin
forms and short broad forms.

The long thin forms measure about 25 to 35 microns in
length by about 1-5 microns in breadth. The posterior ex-
tremity is drawn out to a point. The undulating membrane
is very narrow and the flagellum anteriorly is free for about
one-quarter of its length. The elongate trophonucleus is
situated about the middle of the body and the kinetonucleus
is some distance away from the posterior extremity. The
cytoplasm is free from granules.

The short forms measure from 14 to 20 microns in length
by 3 to 4 microns in breadth. They are stumpy in ap-
pearance and the undulating membrane is very well developed ;
there is no free flagellum. The trophonucleus is large and round
and the kinetonucleus is situated almost at the posterior
extremity. The cytoplasm often contains numerous granules.
In the Bahr el Ghazal strain, Wenyon found many forms in
which the kinetonucleus was near to the trophonucleus and a
few in which the latter was at the posterior end of the body.

Both the long and short forms multiply by ordinary longi-
tudinal division.

Mode of infection. T. pecaudi is transmitted mainly if not
entirely by tsetse-flies. The experiments of Bouet and Roubaud
in Dahomey have shewn that, in this region, G. longipalpis
is the most favourable intermediate host, but tachinoides,
palpalis and morsitans, can also carry the disease.

These two authors found that the longipalpis caught on the
banks of the Oueme River, in the neighbourhood of Agouagon,
were heavily infected with T. pecaudi. Thus batches of 45
flies and upwards, almost invariably produced infections of
pecaudi when fed on susceptible animals. On the other hand.
several hundred palpalis and tachinoides captured in the same
area and similarly fed on susceptible animals never produced
any infection, so it is evident from the epidemiological point

334

TRYPANOSOMA PECAUDI

[CH.

of view that longipalpis is the species which in this region
constitutes the reservoir fly of T. pecaudi, to the exclusion of
the others. The incubation period of the parasite in G. longi-
palpis is about 23 days. In addition, 60 G. tachinoides were fed
on a guinea-pig infected with T. pecaudi and then on a series
of healthy guinea-pigs. Two of these guinea-pigs became
infected, giving an incubation period in the fly of 26 days,
whereas the others remained normal. In this region experi-
ments with G. palpalis gave entirely negative results, but
Bouffard previously succeeded in the transmission of T.
pecaudi by means of this species, though only with difficulty.

Fig. 77. Culture of T. pecaudi, in the intestine of G. palpalis ( x 1200).
a, b, normal forms from the circulating blood ; 1-5 forms 18 hours after
ingestion; 1,2, involution forms; 3, slender form; 4, 5, large forms;
6, 7, large forms 56 hours after ingestion. (After Roubaud.)

In the Nigerian Sudan, Bouet and Roubaud, during the dry
season, found that the morsitans of that region were naturally
infected with T. pecaudi.

It appears, therefore, that longipalpis and morsitans are
the two most favourable hosts for this parasite, and that
tachinoides and, exceptionally, palpalis may also be infected.

Every infected fly that was dissected contained flagellates
along the whole of the digestive tract from the proboscis
to the hinder intestine. The trypanosomes multiply in the
intestine up to 48 hours after ingestion in a modified form

XVIII] TRYPANOSOMA CAZALBOUI 335

called by Roubaud the " intestinal trypanosome form." Under
favourable conditions these multiply very rapidly and in seven
to nine days invade the whole of the intestine as far as the
pharynx. These flies are not infective until the parasites have
invaded the proboscis and passed through the Crithidia and
Leptomonas phase. These proboscis forms multiply and some
reach the hypopharynx, where they assume the " salivary
trypanosome form " and are then capable of infecting any
susceptible animal.

REFERENXES.

Bouet and Roubaud (1910). Bull. Soc. Path. Exot. vol. III. p. 599.

(1911). Ibid. vol. iv. p. 539.

Bouffard (1908). Ann. Inst. Pasteur, vol. xxn. p. 15.
Cazalbou (1904). Rec. de Med. Veter. vol. lxxxi. p. 615.
Laveran (1907). Compt. Rend. Acad. Sci. vol. cxliv. pp. 243-247.
Balfour and Wenyon (1908). Rep. Wellcome Research Lab. Khartoum.

Souma (T. cazalboui Laveran).

General account. In 1904, Cazalbou described, from the
Upper Niger Territories, a cattle trypanosomiasis known to
the natives by the name of Souma. Two years later, Laveran
described the trypanosome causing this disease under the name
of T. cazalboui, and also gave an account of its biological
properties.

The disease has subsequently been observed in most of the
provinces of West Africa south of latitude 17 ° X., especially
along the upper valleys of the Niger and Volta. It is common
in Uganda and has also been recorded from the French Congo,
Congo Free State and Rhodesia.

Souma is a very widespread disease affecting cattle, h<
mules, and donkeys; goats, sheep and antelope are also suscep-
tible to the infection, but contrary to the general rule for the
group of trypanosomes to which it belongs, dogs, cats, monk-
pigs, rabbits, guinea-pigs, rats and mice are all refractory, and
this constitutes one of the principal means of distinguishing
T. cazalboui from allied forms.

T. vivax and T. uniforme are very closely related to this

336 TRYPANOSOMA CAZALBOUI [CH.

species and may subsequently prove to be identical, but at
present it is impossible to unite them without increasing the
confusion of the subject.

The incubation period is usually about seven days. The
course of the disease is variable and may be either acute,
subacute, or chronic. In the former case, cattle may succumb
in as short a time as eight days after infection. The average
duration of the malady is about two months, being terminated
by the death of the infected animal, but in some cases the dis-
ease lingers on for more than a year, and recoveries are not
unknown.

The parasites are usually rare in the peripheral circulation,
but often increase in numbers previous to the death of the
host.

Morphology of T. cazalboui. The movements of the living
parasite are very active and it frequently darts across the field
of the microscope.

It is a monomorphic species and its dimensions are very
constant ; in stained specimens about 24 microns in length, by
1*5 to 2 microns in breadth. The trophonucleus is oval and
situated about the middle of the body, whilst the distinct
and spherical kinetonucleus is situated very close to the
rounded posterior extremity. The undulating membrane is
not markedly folded, resembling that of T. lewisi ; the flagel-
lum is always free at the anterior extremity.

Division is of the usual longitudinal type.

Mode of infection. The principal agents for the transmis-
sion of Souma are tsetse-flies, four species of which, viz.,
G. palpalis, tachinoides, longipalpis and morsitans, have been
proved capable of carrying the infection. In addition, Bouffard's
experiments have shewn that Stomoxys may serve as a direct
carrier (vide p. 362).

The distribution of Souma seems to shew that Glossina pal-
palis is the usual intermediate host, and Bouffard found that
in Upper Guinea this species was commonly infected with T.
cazalboui. Experimentally, both G. palpalis and G. tachinoides
have been proved to be very liable to become infected when fed
on an animal containing the trypanosomes in its blood, for

XVIII MODE OF INFECTION

Bouffard found that out of 224 tsetse that ingested T. caz

no less than 38-8 per cent, became infected. In Uganda,

Bruce and his collaborators found that under similar circum-
stances about 20 per cent, of palpalis shewed a development
of trypanosomes in the proboscis

The effect of climate on the development of this trypanosome
in the intermediate host is well shewn by the results of Bouet
and Roubaud in Upper Dahomey and the Nigerian Sudan,
during the dry season. In these regions only two species of
Glossina, namely tachinoides and morsitans, were found during
the summer, all palpalis having disappeared as a result of the
dry weather. Experiments were undertaken to determine
which of these species was most liable to infection with T.

.boui. Although in Middle Dahomey tachinoides was as
efficient a carrier as palpalis, in the dry regions of Upper
Dahomey and the Nigerian Sudan the same species was only
infected with great difficulty, the authors concluding that during
the dry season, at any rate, G. tachinoides of the regions between
12 and ly north latitude is unable, or only slightlv able, to
infect with the endemic viruses, or those which it is able to
transmit outside these areas. On the other hand, about 50 per
cent, of wild morsitans captured at random were found to be
infected ; the development of the trypanosome in this spe
however, is somewhat slower than in palpalis, tachinoides and
longipalpis, respectively. In the Katanga district the mem-
bers of the Belgian Sleeping Sickness Expedition (1 912
found an equally large percentage of morsitans infected with
cazalboui.

The development of the trypanosome in the tsetse-fly is
restricted to the proboscis, the flagellates never multiplying in
any other part of the alimentary canal. Palpalis, tachino:
and longipalpis, become infective about six to seven d
after an infecting feed, whilst in the case of morsitans this
developmental period is prolonged to eight to ten d;

In Uganda, the development of T. cazalboui is much slower
than in the West African Provinces, for the members of the
Sleeping Sickness Commission at Mpumu. found that the non-
infective period varied from n to 35 days.

H. B. F.

33$ TRYPANOSOMA CAZALBOUI [CH.

It is possible that this remarkable difference in the rate of
development may be accounted for by the difference in climate,
for Bamako, on the Niger, the locality where Bouffard performed
his experiments, is less than iooo feet above sea-level, whereas
Mpumu is more than 4000. Moreover, the mean temperature
of Uganda is far below that of Bamako and the influence of
this factor is most important.

After being ingested some of the trypanosomes remain in
the proboscis of the fly and change into Leptomonas or Crithidial
forms. These become attached to the walls of the labrum and
undergo rapid multiplication, resulting in the production of
large clusters of flagellates, which may almost obstruct the
cavity of the proboscis. Under the influence of the salivary
secretion some of these fixed flagellates develop into small
actively motile trypanosomes closely resembling the blood
forms. These free trypanosomes are found in the hypopharynx
and escape together with the salivary secretion when an infected
fly feeds on any host.

Once a fly becomes infected it may remain infective for at
least two and a half months and probably for the remainder of
its life. If the air is very dry, however, the flagellates may
disappear from the proboscis and the fly cease to be infective.
Thus Bouet and Roubaud found that in Upper Dahomey
during the dry season about 50 per cent, of freshly caught
morsitans shewed infection of the proboscis, but when these
flies were kept and examined 20 to 31 days later the proportion
of infected flies was only two in thirteen.

Roubaud has performed some very interesting experiments
on the effects of various conditions on the development of T.
cazalboui in G. palpalis, which supplement the observations of
Bouet and Roubaud in Upper Dahomey. Twelve G. palpalis,
caught in nature, were placed in a dehydrated atmosphere.
Twelve hours later and twice in the three succeeding days they
were allowed to feed on a goat infected with T. cazalboui. Four
days later they were fed on a healthy kid for two days. On
the ninth day the flies were dissected and found to be uninfected
and also the kid remained healthy. In another experiment
eight flies were fed for two days on the infected goat and then

XVIII] TRANSMISSION 339

placed in a partially dehydrated atmosphere. They were fed
every day on a healthy kid until the ninth day when they were
dissected and four were found to be infected. In another
similar experiment three out of fifteen flies became infected
and the kid succumbed to trypanosomiasis caused by their
bites In two control experiments, during which the flies
were kept in the ordinary atmosphere, eight out of twelve and
eight out of nine flies shewed flagellates and also infected a
succession of healthy kids on which they were fed.

In another experiment, six flies hatched from pupae that
had been kept in dry air from their formation, were fed
on July 7, 8, and 9 on an infected goat and then returned
to dry air. On the 18th and 19th they were allowed to bite a
healthy kid and on the 27th and 28th yet another normal kid.
The next day the flies were dissected and two out of six were
found to be infected, moreover both kids suffered from a very
severe attack of trypanosomiasis. Roubaud accordingly is
of the opinion that if the modifying influence, such as dry air,
acts for a long time before the infecting feed is given, the
saliva regains its suitability as a medium for the development
of the trypanosomes.

The action of saturated air was similarly tested and respec-
tively, one fly in eight and one in fifteen became infected, without,
however, infecting a kitten on which they were fed. These
results tend to explain the author's observation that, in nature,
during the dry season more flies were found to be infected than
during the wet.

REFERENCES.

Bouet and Roubaud (191 1). Bull. Soc. Path. Exot. vol. IV. p. 539.
Bouffard, G. (1909). Bull. Soc. Path. Exot. vol. II. p. 599.

(1910). Ann. Inst. Pasteur, vol. xxiv. p. 276.

Cazalbou, L. (1905). Compt. Rend. Soc. Biol. vol. lviii. pp. 564—565
Laveran, A. (1906). Compt. Rend. Acad. Sci. vol. cxliii. pp. 94-97.

(1910). Bull. Soc. Path. Exot. vol. III. p. 80.

Rodhain, Pons, van den Branden and Bequaert (191 2). Bull. Soc. Path.

Exot. vol. v. pp. 45-50 and 281-84.
Roubaud, E. (1909). These de doctorat es sci. not. Paris, June. 1009.

(1910)- Compt. Rend. Acad. Sci. 1910, pp. 729-32.

340 TRYPANOSOMA VI VAX [CH.

Trypanosoma vivax Ziemann, 1905.

In 1905, Ziemann described under the name of T. vivax a
trypanosome occurring in the blood of cattle, sheep, and goats
in the Cameroons. The symptoms of the disease it produces
are almost identical with those of Souma, and moreover, in
its morphology, T. vivax closely resembles cazalboui. But
Ziemann definitely states that rats are susceptible to T. vivax,
eight of them dying from the infection after eight, nine and
eleven days. Also a dog and a pig both shewed a temporary
infection. On the other hand, rats are absolutely refractory
to T. cazalboui and this constitutes a method of distinguishing
the two.

Bagshawe has called attention to the resemblance between
the two forms, and inclines to consider them as constituting a
single species. This view has been opposed by Laveran, and
certainly as long as " species " of trypanosomes are distin-
guished mainly on the basis of cross-immunity reactions and
the susceptibility of laboratory animals, it is impossible to unite
two forms differing so markedly in the latter feature.

Bruce and his colleagues on the basis of a microscopic exam-
ination of Ziemann's slides came to the conclusion that T.
cazalboui Laveran was synonymous with T. vivax Ziemann.
Accordingly throughout their reports they have employed the
latter name for a trypanosome which is undoubtedly identical
with the T. cazalboui of the French and Belgian authors. A
careful comparison of Ziemann's original description with
the accounts of cazalboui, shew that although very closely
related the two forms may be easily distinguished by their
respective animal reactions. Thus, all small laboratory animals
and the pig are refractory to cazalboui, whereas rats are very
susceptible to vivax and die within eleven days ; also a dog and
a pig shewed a temporary infection.

As rats as well as the other small experimental animals are
not susceptible to the Uganda virus, it is evident that the species
of that region, which has been referred to as T. vivax, should
be known correctly as cazalboui.

XVIIl] TRYPANOSOMA UNIFORME 341

Undoubtedly the two forms are closely related, but as long
as the reaction of experimental animals constitutes one of the
means of distinguishing varieties of trypanosomes, it is only
increasing the confusion of the subject to unite vivax and
cazalboui on purely morphological grounds.

REFERENCES.

Bruce, Hamerton, Bateman and Mackie (1910). Proc. Roy. Soc. B,

vol. 556, p. 368 and vol. 561, p. 1.
Bruce, Hamerton, Bateman and Lady Bruce (191 1). Eleventh Report

Sleeping Sickness Comm. of Roy. Soc.
Yorke and Blacklock (191 1). Ann. Trop. Med. and Parasit. vol. v.

P- 413.
Ziemann, H. (1905). Centralbl. f. Bakter. I. Orig. vol. xxxvui. p. 9.

Trypanosoma uniforme Bruce, Hamerton, Bateman
and Mackie, 191 1.

This parasite was first noticed in the blood of oxen in
Uganda. It closely resembles T. cazalboui, but may be distin-
guished by its smaller size.

T. uniforme causes a very fatal disease, for two naturally
infected cattle died after 5 and 79 days respectively. Goats
inoculated with the parasite lived on an average 29 days, but
out of three sheep inoculated only one became infected. Fraser
and Duke found that two out of 30 bushbuck and sitatunga
(Tragelaphus spekei), obtained within two miles of the shore
of Lake Victoria, were naturally infected with T. uniforme.
Monkeys, pigs, dogs, cats, guinea-pigs and white rats are all
refractory to this parasite, another characteristic in which this
species resembles cazalboui.

According to Laveran and Mesnil, uniforme is probably the
same as cazalboui, but its small size seems to be a sufficient
means of distinction.

Morphology. T. uniforme is a small and active trypanosome
with marked translatory movement, though inferior to that
of cazalboui. The parasites are remarkably uniform in size and
appearance, the average dimensions being 16 microns in Length
by i*5 to 2-5 microns in breadth. The extreme range of
variation in the length is onlv from a minimum of 12 to

342 TRYPANOSOMA DIMORPHON [CH.

a maximum of 19 microns. The free part of the flagellum
is from 1 to 5 microns in length. In all other characters
T. uniforme is the same as cazalboui, with the exception that
there is no marked narrowing opposite the trophonucleus as in
the case of the latter species.

Mode of infection. Fraser and Duke have shewn that the
Glossina palpalis in the neighbourhood of Lake Victoria are
naturally infected with this trypanosome, for after 1020 flies
from the lake-shore had been fed on a goat it became infected
with T. uniforme. Also it was shewn experimentally that
laboratory-bred palpalis were capable of transmitting this
species of trypanosome from infected to healthy animals. Of
six experiments four were successful. The flies became infective
in from 27 to 37 days, and the infection in the fly was always
limited to the proboscis as in the case of cazalboui.

REFERENCES.
Brace, Hamerton, Bateman and Mackie (191 1). Proc. Roy. Soc. B, 563,

p. 176.
Fraser and Duke (1912). Ibid. B, vol. lxxxv. p. 1.

Trypanosoma dimorphon Laveran and Mesnil, 1904.

Synonyms. T. confusum Montgomery and Kinghorn, 1909.
T. frobeninsi Weissenborn, 191 1.

General account. In 1902, Dutton and Todd in the course
of their expedition to the Gambia observed trypanosomes in
the blood of some of the horses in that region.

Under the title of " Horse trypanosome " they described
and figured the parasites occurring in one of these horses. The
.emarkable feature about the infection was the occurrence of
small tadpole-shaped trypanosomes without any free flagellum,
side by side with long and slender forms with a long free flagel-
lum. Dutton and Todd did not name their horse trypano-
some, a fortunate omission, since there is practically no doubt
that several distinct species were in their hands. One of these
infected horses was sent over to Liverpool and from here the
strain was sent across to Laveran and Mesnil in Paris, where
they studied the morphology of the trypanosome, and, in 1904,
published a description of it under the name of T. dimorphon.

XVIII] GENERAL ACCOUNT 343

The name T. dimorphon, therefore, is only applicable to the
trypanosome which reached Europe and was described by
Laveran and Mesnil. This parasite, as pointed out by the
authors, differs considerably from Dutton and Todd's description
of the " Horse trypanosome," especially in the absence of any
forms provided with a free flagellum. T. dimorphon Laveran and
Mesnil, is the ordinary dimorphon of the laboratories ol Europe,
and it is important that the use of this name should be abso-
lutely restricted to trypanosomes agreeing with Laveran and
Mesnil's original description (1904). Montgomery and King-
horn wish to reserve the name T. dimorphon for the forms
described by Dutton and Todd and apply the term T. confusum
to the parasite described by Laveran and Mesnil. Such a
course, however, is illegitimate, for the name dimorphon was
only applied to the latter, and never to Dutton and Todd's
original description.

The occurrence of mixed infections in many animals is a
source of great difficulty in identifying the species of trypano-
somes, for Yorke and Blacklock have shewn that dimorphon
and cazalboui may occur side by side in horses from the
Gambia.

T. dimorphon is widely distributed throughout West Africa
and has been recorded from the following localities : Gambia,
Senegal, Casamance, Upper Gambia, French Guinea, Sierra
Leone, Ivory Coast, Togoland, Dahomey, French Sudan and
French Congo. In the Congo Free State, Rhodesia, Zululand,
Portuguese East Africa, Zanzibar, Bahr el Ghazal, and Somali-
land, trypanosomes of the dimorphon type have been observed,
but it is difficult to say whether they should all be referred to
T. dimorphon Laveran and Mesnil.

Horses, mules, cattle, goats, sheep, pigs, dogs, cats, mon-
keys, and all the smaller laboratory animals are susceptible to
infection with T. dimorphon. As a rule, in the larger animals.
the course of the disease is slow, and death only occurs after
trypanosomes have been present in the blood for several months.
In some cases the animals recover and trypanosomes may be
present in the peripheral circulation for some years, without
apparently producing any pathogenic symptoms.

344 TRYPANOSOMA DIMORPHON [CH.

Morphology of the parasite. In the fresh state, the dimorphic
nature of this species is easily recognisable. The most common
forms are only 12 to 14 microns in length and 1 micron in
breadth, with a rounded posterior extremity and a body which
gradually tapers towards the anterior extremity. These short
forms present a somewhat characteristic movement ; after
progressing forward for some little distance, wriggling after
the manner of a tadpole, they stop abruptly, and then move
on again in the same fashion. The undulating membrane is
very slightly developed.

The long forms of dimorphon are less common than the pre-
ceding and may occasionally be absent. They range from 20
to 25 microns in length, by 1-5 microns in breadth. The
undulating membrane is only slightly developed and the
parasites, although more active than the short forms, do not
present as lively motions as T. brucei.

These two forms are connected by intermediate stages, and
therefore the short trypanosomes might be regarded as a
young form of the large, were it not for the fact that they both
reproduce by longitudinal fission.

In Giemsa-stained specimens, a remarkable feature of
dimorphon is the extremely dense blue colour of the protoplasm.
The kinetonucleus is situated close to the rounded posterior
extremity. The undulating membrane is never very marked
and in every case the protoplasm is continued along to the
extremity of the flagellum. This latter feature, together with
the dimorphism, is very characteristic. Division is of the
usual longitudinal type.

Mode of infection. Bouet, in 1907, succeeded in transmitting
T. dimorphon by the bites of Glossina palpalis that had fed on
an infected animal 24 hours previously. In this experiment
the transmission was merely mechanical.

In Dahomey, Bouet and Roubaud have demonstrated the
part played by G. palpalis, tachinoides and longipalpis in the
transmission of this parasite. Palpalis captured in nature,
were fed on two dogs, a sheep, and a kid, and these animals
became infected with dimorphon after incubation periods vary-
ing from 14 to 20 days. The same flies were fed on guinea-pigs

XVIII] TRANSMISSION 345

but produced no infection, thus shewing that these animals are
only slightly susceptible to this trypanosome.

G. morsitans is also capable of transmitting T. dimorphon,
and thus four species of tsetse-flies in West Africa are all
efficient intermediate hosts for the parasite.

The experiments with regard to the infection of the fly are
somewhat inconclusive, but from an examination of " wild "
tsetse it appears that longipalpis is the most often infected,
then tachinoides, whilst the proportion of palpalis containing
dimorphon is very much less, being only about one per cent.

In Dahomey, the negative period of incubation in the fly is
said to be more than 18 days, but as Bouet and Roubaud worked
entirely with wild flies the exact period could not be decided.

The infection in each species of fly is what is known as
" total." The trypanosomes become established in the hind
intestine and gradually extend forwards until they reach the
proboscis, when they become fixed and assume the Leptomonas
or Crithidial form. These proboscis forms of dimorphon may be
distinguished from those of congolense by the frequent occur-
rence of giant forms like those of cazalboui, but differing in the
flattened appearance of the posterior prolongation. The inocu-
lation of intestinal forms produced no infection, whereas when
the proboscis was inoculated a positive result was obtained.

It is evident, therefore, that the evolution of T. dimorphon
in Glossina longipalpis, tachinoides, palpalis, and morsitans,
respectively, is of the usual type, first a multiplication of try-
panosomes in the intestine, during which period the fly is non-
infective, followed by an invasion of the proboscis where the
Leptomonas or Crithidial stage is gone through, after which
the fly becomes infective.

REFERENCES.

Bouet (1907). Ann. Inst. Pasteur, vol. XXI. p. 474.

and Roubaud (1910). Bull. Soc. Path. Exot. vol. III. p. 722

Dutton and Todd (1903). Liverpool Sch. of Prop. Med. Memoir XI.
Laveran and Mesnil (1904). Compt. Rend 1. vol. cxxxvin. p

Montgomery ami Kinghorn (1909). Lancet. Sept. 25, iq
Yorke and Blacklock (1911). Ann. Prop. Med. and Parasit. vol. v. p.
I 1 3 and vol. VI. p. 107.

346 TRYPANOSOMA PECORUM [CH\

Trypanosoma pecorum Bruce, Hamerton, Bateman
and Mackie, 1910.

General account. In 1910, Bruce and his collaborators
observed a trypanosome in the horses and cattle of Uganda.
This parasite was supposed to be identical with T. dimorphon
and T. congolense, and, therefore, all three were united under the
name T. pecorum. Laveran, however, has shewn by means of
cross-immunity reactions that T. pecorum is a distinct species,
but is closely related to dimorphon, congolense and nanum.

Recently Kinghorn and Yorke have found T. pecorum
present in the wild game of the Luangwa Valley, North-Eastern
Rhodesia.

The incubation period in cattle inoculated with T. pecorum
is on an average about six to seven days. The duration of the
disease may vary from 26 up to as long as 287 days. It is
invariably fatal, the symptoms being weakness and emacia-
tion, accompanied by anaemia. Cattle, goats, sheep, monkeys,
dogs, rabbits, guinea-pigs, rats and mice are all susceptible to
infection with T. pecorum, and this constitutes a means of
distinguishing it from nanum. Duke's experiments have shewn
that the bushbuck is also susceptible and may remain infective
for at least 323 days, therefore the wild game may serve as a
reservoir for this trypanosome.

Morphology of the parasite. In the living state T. pecorum
is remarkable for its habit of exhibiting alternate periods of
quiescence and activity. When quiescent it usually buries
itself under clumps of red cells and is thus difficult to detect.
The movements are active but, as in the case of T. congolense,
not translatory ; therefore, the parasites do not travel across
the field of the microscope.

In stained specimens the trypanosome is practically indis-
tinguishable from T. nanum and T. congolense.

It is a monomorphic species ; the extreme variations in
length are 8 to 18 microns, but the average dimensions,
comprising the majority of individuals, are 14 microns in length
by about 3 microns in breadth, including the undulating
membrane. The posterior extremity is rounded ; the anterior

XVIII] TRANSMISSION 347

is more or less tapering. The undulating membrane is well
developed, being larger than that of T. nanum, and there is no
free flagellum. The oval trophonucleus is situated about the
middle of the body and the small spherical kinetonucleus is at
the posterior extremity. The cytoplasm is generally homo-
geneous and not very granular.

Mode of infection. The results of Kinghorn and Yorke in
the Luangwa Valley have shewn that Glossina morsitans is
probably the most important agent for the spread of this
infection. By collecting large numbers of these tsetse-flies
and feeding them on healthy monkeys, out of 3202 flies at
least two were found to be infected with T. pecorum.

Under experimental conditions, Glossina palpalis can also
serve as the intermediate host for this species and animals may
be infected by the bites of palpalis that have previously ingested
blood containing T. pecorum. The mode of transmission is
indirect, that is to say the trypanosome undergoes a cyclical
development within the alimentary canal of the fly, but this
development is so extremely slow that it is evident that G.
palpalis is not the usual intermediate host of this parasite. It
is also significant that wild palpalis has never been found
naturally infected with pecorum. The stages in the develop-
ment of T. pecorum in the alimentary canal of G. palpalis have
been observed by Fraser and Duke, and also by Miss Robertson.

Although these two species of Glossina have thus been proved
capable of transmitting this infection, there is considerable
evidence to shew that the disease can exist in the absence of
tsetse. Thus Bruce and other members of the Sleeping Sick-
ness Commission saw an outbreak of T. pecorum infection
under the following circumstances. The cattle belonging to
this Commission grazed at the foot of Mpumu Hill, half to the
east and half to the west. Tdbamts and Hcematopota were
occasionally seen but always in very small numbers. In
September, 1909, swarms of Tabanus secedens Walk, suddenly
appeared to the west of the hill and a month later to the east.
Soon afterwards the cattle, which had been healthy for a war.
shewed signs of T. pecorum infection, first those which -razed
to the west, then those which mazed to the east. It should be

348 TRYPANOSOMA NANUM [CH.

noted that there were a few pre-existing cases of infection in
the herd. Afterwards a few Glossina palpalis were found at
the foot of the hill.

Nevertheless, although this circumstantial evidence is so
strong, all attempts to transmit the disease experimentally by
the bites of either Tabanids or Stomoxys have given uniformly
negative results.

Development within the intermediate host. The development
of T. pecorum within the alimentary canal of Glossina palpalis
in all essential features resembles that of T. nanum, but is
excessively slow, so that it seems probable that this species of
tsetse only exceptionally serves as its intermediate host.

The parasites develop in the hinder intestine and give rise
to a large number of trypanosomes of very varying size.
Eventually, the slender forms are produced and these are
extraordinarily attenuated ; in addition the nuclear changes
occurring at this stage in the cycle of T. gambiense, also take
place in T. pecorum. The invasion of the proventriculus usually
occurs about the 45th day and no proboscis infection was found
before the 76th day. The Crithidial phase is passed through in
the proboscis, as in the case of T. nanum, and the salivary
glands are never invaded.

LITERATURE.
Bruce, Hamerton, Bateman and Mackie (1910). Proc. Roy. Soc. B,

vol. lxxxii. p. 468.
Duke, H. L. (1912). Proc. Roy. Soc. B, vol. lxxxv. p. 554.
Kinghorn, A. and Yorke, W. (191 2). Ann. Trop. Med. and Parasit.

vol. vi. pp. 301 and 317.
Laveran, A. (1910). Bull. Soc. Path. Exot. vol. in. p. 718.
Robertson, M. (1913). Trans. Roy. Soc. B, vol. ccm. pp. 161-184.

Trypanosoma nanum Laveran, 1905.

General account. This parasite was first discovered by
A. Balfour in 1904, in the blood of cattle from the Anglo-
Egyptian Sudan. It has since been recorded from various
other localities of this region and also in Uganda, where Bruce
and his collaborators found it in the blood of cattle.

XVIII] MORPHOLOGY 349

Kleine and Fischer, in the region of Lake Tanganyika, have
found both sheep and antelopes naturally infected with a try-
panosome that seems to agree with nanum in its characters.

In cattle, T. nanum produces a disease which develops
slowly ; the main symptom is the well-marked anaemia, which is
accompanied by a gradual emaciation and usually ends in the
death of the infected animal.

The parasites are usually present in the peripheral circula-
tion, sometimes in considerable numbers, and can be easily
recognised.

T. nanum can readily be inoculated into cattle and goats,
but all the smaller laboratory animals are refractory to infec-
tion, for monkeys, dogs, rats and mice have been inoculated
without becoming infected.

Morphology of the parasite. Laveran has given the following
diagnosis of Trypanosoma nanum :

' The trypanosomes measure 10 to 14 /x in length, by 1-5
to 2 /a in breadth. Their structure is that of flagellates
belonging to the genus Trypanosoma ; yet, contrary to the
rule, the protoplasm is prolonged at the anterior end, in such a
manner that there is no free flagellum, or the free part of the
flagellum is extremely short. The undulating membrane is
very narrow and in consequence only slightly evident. The
posterior extremity is conical, not drawn out, otherwise a little
variable in form."

" The oval nucleus is situated about the middle of the body
of the parasite. The centrosome (= kinetonucleus), rounded
and rather large, is found almost at the posterior extremity.

" The protoplasm is homogeneous, without granulations.

" Some of the forms, a little larger than the others, shew
two centrosomes and a flagellum divided for a greater or 1<
extent from the origin in the centrosome ; these are evidently
multiplication forms."

In Uganda the length of the parasite may extend up to
16 microns as shewn by Bruce, Hamerton, Bateman and Maekie.
and also by Duke.

Mode of transmission. The experiments of Duke in Uganda
have shewn that Glossinapalpalis may serve as the intermediate

350 TRYPANOSOMA NANUM [CH.

host for T. nanum. Laboratory bred flies were fed on an
infected sheep and subsequently on a calf, which developed
a typical infection with this trypanosome. About five per cent,
of the flies fed on this sheep were found to be infected.

Kleine and Fischer are of the opinion that Glossina morsitans
is the intermediate host of T. nanum in the region of Lake
Tanganyika.

Development of the parasite. In the blood the trypanosome
multiplies in the usual manner by means of longitudinal division.

When taken into the gut of G. palpalis the resulting changes
are exactly comparable with those that take place in the case
of T. gambiense, described above. The trypanosomes begin to
develop in the hinder intestine and by the ioth day numerous
parasites may be found in the hinder and middle intestine.
The slender forms begin to be produced from the ioth to the
14th day onwards, and the proventriculus is usually invaded
about the 20th day. The proventricular forms are not quite
so uniformly slender as in the case of T. gambiense. Moreover,
there are no marked changes in the appearance of the nuclei
of T. nanum. About the 25th day the trypanosomes invade
the proboscis, where they may be found attached to the labrum,
often lying in clusters. They then pass through the Crithidial
phase, many of them being extremely long and slender.
Subsequently trypanosome forms are produced which may be
found free, sometimes in the hypopharynx and at other times
in the labrum.

The salivary glands never become infected in the case of
T. nanum, the proboscis infection apparently playing the same
part as the gland infection in the cycle of T. gambiense.

LITERATURE.

Laveran, A. (1905). Compt. Rend. Soc. Biol. vol. lvii. p. 292.

Balfour, A. (1904). B. M. J. Nov. 26, 1904.

Bruce, Hamerton, Bateman and Mackie (1910). Proc. Roy. Soc. 1910,

B, vol. lxxxiii. p. 180.
Duke, H. L. (1912). Proc. Roy. Soc. B, vol. lxxxv. p. 4.
Kleine and Fischer (1911). Zeitschr. f. Hvg. u. Infectionskr. vol. lxx.

p. 18.
Robertson, M. (1913)- Phil. Trans. Roy. Soc. B, vol. ccm. p. 161.

XVIII

TRYPANOSOMA CONGOLENSE

Trypanosoma congolense Broden, 1904.

This parasite, which very closely resembles T. pecorum and
T. dimorphon, was first described by Broden, who found it occur-
ring in the blood of a donkey and sheep in the Congo Free State.
Subsequently the parasite was also observed in the blood of
cattle and dromedaries in the same locality and also in cattle,
sheep, goats and dogs in the French Congo, where, according
to Martin, Lebceuf and Roubaud, it is widely distributed. In
North-East Rhodesia, Montgomery and Kinghorn have observed
T. congolense in the blood of cattle. It is doubtful whether
the trypanosomes occurring in dogs on the shores of Tanganyika
should be referred to this species or to T. pecorum.

T. congolense is only distinguishable from T. pecorum by
cross-immunity reactions, for Laveran and Mesnil shewed that
a goat immune against T. congolense was susceptible to infec-
tion with pecorum. Otherwise the two forms are practically
identical and it is questionable whether they should be regarded
as distinct species.

Fig. 78. Culture of T. congolense in the intestine of G. palpalis. ( x about
1000). a, b, normal forms from the circulating blood ; 1,2, forms
24 hours after ingestion ; 3, 5, forms after 48 hours ; 6, 7, forms alter
56 hours. (After Roubaud.)

In addition to cattle, sheep, goats and dogs, all the usual
experimental animals may be infected with congolense, but
the course of the disease is usually very slow, resembling that
of dimorphon. The constant susceptibility of guinea-pigs is,
however, in marked contrast with that of other Laboratory

352 TRYPANOSOMA CONGOLENSE [CH.

animals, for Laveran and Mesnil found that the average
duration of the disease in this species was only two weeks and
invariably resulted in the death of the animal.

Morphology of the parasite. The living parasite exhibits
active wriggling movements without, however, progressing
across the field of the microscope. The trypanosomes are often
attached to the leucocytes by their anterior extremities.

The dimensions of the majority of the individuals vary
between 10 to 13 microns in length, by 1 to 2 microns in
breadth, and the largest forms are never more than 17 microns
in length, a means of distinguishing this species from dimorphon.
In stained specimens the posterior extremity is rounded and
anteriorly the body of the parasite gradually tapers, the
protoplasm being prolonged to the extremity of the flagellum.

The trophonucleus is situated about the middle of the
length of the parasite ; the kinetonucleus is very distinct and
is usually close to the posterior extremity. The protoplasm is
somewhat clear and rarely contains chromatophilous granules.

Mode of infection. There is some little doubt as to whether
G. palpalis is capable of transmitting congolense, for the only
positive experiments with this species of tsetse-fly that have
been recorded up to the present are those of Roubaud, and this
author states that the observations were made with " T. con-
golense (vel dimorphon)."

In the alimentary canal of G. palpalis Roubaud observed
the commencement of a development of this trypanosome
somewhat resembling that of T. gambiense, but the parasites all
disappeared by the end of the third day.

Rodhain, van den Branden, Pons and Bequaert, found
that the G. morsitans in the Katanga region were naturally
infected with congolense. In addition an experiment was made
with 23 flies born in the laboratory. These were fed on an
infected goat and subsequently on healthy animals. After an
incubation period of 23 days one of the flies became infective.
This individual on dissection was found to present an " infec-
tion totale " of the alimentary canal. The parasites in the
intestine were nearly all of the trypanosome type and some
were of the blood form. In the proboscis the hypopharyngeal

XVIII] TRYPANOSOMA SIMI^ 353

tube was filled with small trypanosomes of the congolense type
without any free flagellum, whilst the parasites that swarmed
in the labrum were of the Leptomonas type.

REFERENCES.
Broden, A. (1904). Bull. Soc. d' Etudes Coloniales, Bruxelles, February,

1904.
Laveran and Mesnil (191 2). Trypanosomes et Trypanosomiases.
Montgomery and Kinghorn (1909). Ann. Trop. Med. and Parasit.

vol. in. p. 349.
Rodhain, van den Branden, Pons and Bequaert (1912). Bull. Soc.

Path. Exot. vol. v. p. 281.
Roubaud (1909). These de doct. es sci. nat. Paris, pp. 153 and 161.

Trypanosoma simiae Bruce, Harvey, Hamerton, Davey and
Lady Bruce, 1912.

Synonym. T. ignotum Kinghorn and Yorke, 1912.

General account. This species of trypanosome has been
recorded from Nyasaland, Central Angoniland, and Xorth-
Eastern Rhodesia, where a large percentage of Glossina mor-
si tans are naturally infected with the parasite. Its pathogenic
properties are very remarkable, since it only affects such widely
different animals as monkeys and goats. Oxen, baboons, dogs,
guinea-pigs, and white rats, seem to be immune.

In goats T. simiat sets up a chronic disease, but in monkeys
the infection is rapidly fatal, for in a series of 19 the average
duration of life after the trypanosomes were first seen in the
blood was only 2-9 days.

Morphology. When living the parasite shews active pro-
gressive movements, some individuals passing complete ly
across the field of the microscope. The dimensions of the
trypanosomes as found in the monkey and the goat, are
found to vary from 14 to 24 microns in length, by I to 2*75
microns in breadth, the mean being 18 microns in Length by
175 in breadth. The parasites are monomorphic and. as a
rule, fairly uniform in shape. The authors give the following
summary of its characters :

" Elongated, narrow, undulating body : posterior extremity
bluntly pointed or rounded ; anterior extremity pointed :

354

TRYPANOSOMA SIMILE

CH

nucleus oval ; micronucleus small, round, situated about 1-5
microns from posterior extremity, placed laterally, protuberant ;
undulating membrane marked, thrown into bold folds ; flagel-
lum frequently not projecting beyond undulating membrane,
sometimes 1 to 2 microns of the extremity apparently
free."

^%^

Fig. 79. Trypanosoma simice. Successive stages in the division shewing the
peculiar manner in which the two daughter trypanosomes seem to " slip "
past each other, until they are only joined by their non-flagellate ends.
(After Bruce, Harvey, Hamerton, Davey and Lady Bruce.)

In the blood of the monkey these trypanosomes swarm in
enormous numbers and numerous division forms can be seen,
often four or five in a field. When dividing the trypanosomes
appear to slip past one another until they are only joined by
their posterior extremities, as shewn in Fig. 79. Multiplication
often takes place so rapidly that the individual trypanosomes
have not time to disengage themselves and thus large multi-

Fig. 80. Trypanosoma simice. Large multinucleate form. (After Bruce,
Harvey, Hamerton, Davey and Lady Bruce.)

XVIII] stomoxys 355

nucleate masses are produced, sometimes filling the whole field
of the microscope (Fig. 80).

The life history of this parasite in its intermediate host,
Glossina morsitans, has not yet been worked out. Its extreme
pathogenicity in monkeys is very remarkable and suggests
that T. simice is a species that has only recently become adapted
to its present mode of life.

LITERATURE.

Bruce, Harvey, Hamerton, Davey and Lady Bruce (191 2). Proc. Roy.

Soc. B, vol. lxxxv. p. 477.
Kinghorn and Yorke (1912). Ann. Trop. Med. and Parasit. vol. vi.

pp. 301-315 and 317-324.

CHAPTER XIX

STOMOXYS

General description. The members of the genus Stomoxys
may be distinguished from other blood-sucking Muscidae by
the following characters :

The proboscis protrudes horizontally in front of the head
and is pointed towards its anterior extremity. The maxillary
palps are cylindrical and slender, less than half the length of
the proboscis. The first longitudinal vein opens into the wing
about mid-way along its length, almost opposite the small
transverse vein. The first posterior marginal cell opens widely
at the tip of the wing. Between the posterior transverse vein
and the margin of the wing the fourth longitudinal vein is
arched like a bow with the concavity facing the third longi-
tudinal vein (Fig. 81).

The flies belonging to this genus are all moderate sized
(5 to 7 mm.) dull-coloured insects that generally feed on the
blood of cattle. They closely resemble the house-fly (Musca
domestical] in general appearance, but may be readily distin-
guished by the presence of the proboscis, and also Stom
rests with its wings widely divergent whilst in Musca they are

356

STOMOXYS

[CH.

held closer together

The most abundant species is Stomoxys
calcitrans, the common stable-fly of this country, but in addition
to this insect, 5. nigra is also supposed to be concerned in the
spread of disease.

Auxiliary vein

Anterior cross-vein

Fig. 8i, Wing venation of Stomoxys calcitrans.

Stomoxys calcitrans Linn.
General description. This insect closely resembles the
common house-fly in colouration and general appearance, but
as mentioned above, may be easily recognised by the pres-
ence of the biting proboscis and the attitude of the wings.
In addition 5. calcitrans is distinguished by the following
characters :

A B

Fig. 82. Side view of head of Stable-fly; A, proboscis in resting position
B, proboscis extended. (After Graham-Smith.)

XIX

DESCRIPTION

357

The lower part of the face is white, frequently with a yel-
lowish tint, which is especially visible upon the sides of the
forehead. The latter is marked with black or reddish-brown
stripes ; the antennae are brown, at times lighter dorsally.
The maxillary palps are short, scarcely protruding, and yellow
in colour. The dorsal surface of the thorax is marked with
four dark longitudinal stripes, two on each side, extending
from the shoulders to the scutellum, but interrupted in the
middle of their length by the transverse suture. The abdomen
has a yellowish-brown tint and is marked with three indistinct
dark spots on the second segment and some on the following
segments. The legs are blackish-brown with reddish-yellow
knees. According to Austen, the African examples of this species
are smaller than British specimens and the abdominal spots
shew considerable variation in size and shape. The insect
varies from about 5-5 to 7 mm. in length.

Fig. 83. Stable-fly, Stomoxys calcitrans (Y 5). On the left, magnified view
of antenna. On the right, view of the fly in its resting position. (Nat.
size.) (After Graham-Smith.)

Distribution. S. calcitrans has been recorded from almost
every part of the world, occurring throughout both temperate
and tropical countries and even extending as far nortl
Lapland. It is especially abundant, however, in warmer
countries, or during the summer months of more temperate

regions.

Habits.

The common name of this insect, the stable-fly

35S STOMOXYS [CH.

gives a true indication of its usual habitat, and during the sum-
mer large numbers of Stomoxys may generally be found around
the cow-sheds and stables of any farmyard ; in warm weather,
however, it may be found wherever cattle are grazing ; and
during late summer and autumn they are frequently found
in houses, where they are known as " Biting House-flies."
When resting on a wall, Stomoxys generally points the head
upwards, and thus may be distinguished from the house-fly
which usually takes the opposite position.

The fly may feed on the juices from any decaying organic
matter, and also on the blood of vertebrates. It is possible
that its blood-sucking habits have been somewhat over-esti-
mated, for Xewstead kept a careful watch on both horses and
cattle in a farmyard where Stomoxys were plentiful without
seeing even one settle on an animal. During hot weather,
however, the flies become very troublesome to animals and
may even attack human beings. The voracious habits of
Stomoxys are well shewn when a number are kept together in
captivity. Under these circumstances if an individual suffers
any injury, the others at once try to feed on it and, if succer^s-
ful in piercing the integument, suck all the contents out of
their unfortunate companion.

Unlike many blood-sucking flies, the female Stomoxys will
lay fertile eggs without ever having fed on blood.

Life history. Xewstead has recently given a complete
description of the metamorphosis of this insect from which the
following account is taken. The female generally lays its eggs
a few inches below the surface in stable manure, decomposing
vegetable matter, or similar materials. Although the flight
of this insect is usually noiseless, when the female is preparing
to oviposit the noise of its wings is distinctly audible, resembling
the hum made by most other members of the Muscidae. The
eggs are generally laid in an irregular heap and their number
is usually about 50 to 70. The egg is 1 mm. in length, very
elongate, shaped somewhat like a banana, being curved on one
side and deeply grooved on the other. This groove widens
towards the anterior end. The colour of the egg is white
when first laid, but subsequently becomes creamy-white.

XIX] LIFE HISTORY 359

The larva escapes by splitting the egg membrane at the broad
end of the groove. During August, with an average tempera-
ture of 720 F. in the day and 650 at night, the incubation
period varies from two to three days.

The young larva is round, smooth, and almost transparent,
and of the usual acephalous muscid type (Fig. 6, p. 20). It
may be distinguished by the appearance of the two posterior
stigmata, which are small, circular and situated rather far apart.
Its length when full grown is about n mm. The duration of

Fi<j. S4. Stomoxys calcitrans. Eggs. The small group in the top left hand
corner represents their natural size. (After Xewstead.)

the larval stage under favourable conditions, is from two to
three weeks, but the absence of plentiful moisture or exposure
to light retards the development very considerably, to at !
a period of 78 days. Such larvae produce abnormally small
pupae and correspondingly small adults.

The process of pupation is completed within two hours.
The larva first burrows to some little depth and then shortens
itself by contraction of the front segments, thus becoming
barrel-shaped (Fig. 9, p. 22). The colour of the pupa 1- at
first terra-cotta, but it subsequently darkens to a chestnut-

360 STOMOXYS [CH.

brown. The length varies from 5 to 5-5 mm. The duration
of the pupal stage varies from nine to thirteen days under
favourable conditions, but may be considerably prolonged by
cold.

A few days before the emergence of the insect the pupal
case darkens and splits anteriorly along the lateral and median
lines and also across the fourth segment. The front region then
falls away and the fly escapes after undergoing a final moult
within the puparium. On emergence the fly at first tries to
make its way to the surface of any rubbish with which it may
be covered. This is chiefly accomplished by means of the
frontal sac, which is alternately inflated and deflated, and at
the same time the insect pushes itself forward by means of its
legs. After it has become free the hairs of the arista are care-
fully combed out, and also the frontal sac and rudimentary
wings are cleaned by means of the front pair of legs. Subse-
quently the frontal sac contracts and the head assumes a more
normal appearance, and then the insect stretches itself to the
full extent and pumps air into its body. This air is forced
along the nervures of the wings and these finally unfold, being
aided by the use of the hind-legs. The fly then remains qui-
escent for some time and when the integument and wings
are sufficiently hardened it takes flight.

The duration of the whole life-cycle from egg to imago
varies from 25 to 37 days, under favourable condition? of
temperature and moisture.

. Methods of destruction. The methods which have been used
for the destruction of the common house-fly are also appli-
cable to Stomo ys, with this difference, that whereas in the
case of the former, middens and ashpits are notorious breeding
places, the stable-fly rarely selects these localities, but chiefly
breeds in stable manure and heaps of decomposing vegetation.
The numbers of the insect would be considerably reduced in
any particular locality, if all stable manure, etc. were care-
fully removed at least every seven days, during May to October
inclusive. By this means the fly would be prevented from
breeding, as the immature stages would be removed together
with the manure. In the case of farmyards and country

XIX] STOMOXYS AND DISEASE 361

districts, where the removal of manure is impracticable, the
manure heaps should be sprayed periodically with some ins
ticide, in order to destroy any eggs, or larvae, that may be
present.

REFEREN< ES.

Austen (1909). African Blood-sucking F:lies. London : Brit. Mus
Bouffard, G. (1907). Compt. Rend. Soc. Biol. vol. lxii. p. 71.
Xewstead, R. (1907). Ann. Trop. Med. and Parasit. vol. 1. p. 76.
Tulloch (1906). Proc. Roy. Soc. vol. lxxvii. B. p. 523.

CHAPTER XX

INFECTIONS TRANSMITTED BY STOMOXYS

1. Trypanosomiases.

There is no doubt that under experimental conditions the
direct transmission of various trypanosomiases from infected to
healthy animals, is comparatively easily effected by means oi
the bites of Stomoxys, but with regard to the important •
this insect in the spread of disease, opinion is still very divided.
Surra (T. evansi) is generally stated to be transmitted by
Stomoxys as well as Tabanus, and yet Mitzmain in the Philip-
pines made a most exhaustive series of experiments on the
transmission of this disease by Stomoxys calcitrans and obtained
uniformly negative results. In Africa, Bruce, Grieg and Gray,
Bevan, and others have also been unsuccessful in attempt- to
transmit various trypanosomiases by this insect. Nevertheless
a number of observers are of the opinion that Stomoxys plays
an important part in the transmission of certain infection-.
Thus in Java, according to Schat, Surra is mainly spread by
the agency of Stomoxys calcitrans Linn, and Lyperosia exigua
de Meijere, but experimental proof is lacking. Similarly,
Musgrave and Clegg stated that in the Philippine- it has been
" conclusively shewn that Stomoxys calcitrans and other biting
flies transmit the disease," but this statement is somewhat
exaggerated.

362 STOMOXYS AND DISEASE [CH.

Bouffard at Bamako on the Upper Niger experimented on
the transmission of Souma, a trypanosomiasis of cattle caused
by T. cazalboui (vide p. 335). A calf was inoculated with this
parasite and shewed numerous trypanosomes in its blood on the
eighth day. A healthy calf was then segregated with the other
calf in a fly-proof stable, the animals being separated by a
distance of one and a half metres. Forty wild Stomoxys were
then put in the stable and were observed to feed on two after-
noons, after which they died. Twelve days later trypanosomes
appeared in the blood of the healthy calf so that it seems
evident that Stomoxys is able to carry T. cazalboui. Whether
the flies were naturally infected or not when caught, was not
decided.

In French West Africa, Bouet and Roubaud succeeded
with difficulty in the direct transmission of T. cazalboui and
T. pecaudi by means of Stomoxys, but failed to transmit
T. dimorphon. On the other hand, the trypanosomes of the
Sahara were easily transmitted by means of this insect as shewn
by their, results. Employing T. soudanense, out of five experi-
ments performed under laboratory conditions, with no intervals
between the bites of the flies, four gave positive results. In
another experiment at least 24 hours were allowed to elapse
between the feed on the infected and on the healthy animal, in
this case a dog. This animal became infected a month later
shewing that the flies were still infective after 24 hours. In
addition one experiment was made under natural conditions.
A healthy puppy from which all ectoparasites had been carefully
removed was kept on a chain during the day beside an infected
dog in a place infested with Stomoxys ( ? calcify ans and nigra) ;
at night it was removed and placed in a fly-proof cage to
prevent any nocturnal flies feeding on it. The experiment
lasted from the nth to the 19th of August and both animals
were frequently bitten by Stomoxys. On August 24th the
puppy became infected.

The results were similar on employing a strain of T. evansi
(Surra) obtained from some camels at St Louis. In three
experiments the Stomoxys were transferred from an infected to a
healthy rat and a minute later to another healthy rat. In two

XX] TRYPANOSOMIASIS 363

cases the first animal became infected whilst the second did
not ; but in the third experiment, in which only a single Stomo-
xys was used, both animals became infected after one bite. In
addition positive results were obtained in the transmission of
this virus after intervals varying up to at least three days. As
Dr Bagshawe remarks, these experiments demonstrate that the
trypanosomes of the Surra type in French West Africa may
be transmitted by Stomoxys and that the flies may retain the
infection for at least three days. But it is so obvious that
some of the flies may have been infected when caught, that
definite conclusions as to the period during which Stomoxys
retains infection, may be as misleading as were those drawn
from similar experiments with G. palpalis.

Nevertheless, the fact that a single Stomoxys was capable of
transmitting the infection shews that under certain conditions
this insect might be an important agent for the spread of the
disease. By means of interrupted feeding, that is, the fly
beginning its meal on an infected animal and at once finishing
it on another, various authors have succeeded in the experi-
mental transmission of T. brncei, T. gambiense, T. equiperdum,
in addition to T. evansi, T. cazalboui and T. soudanense.

In India, Leese is of the opinion that Surra (T. evansi)
may be naturally spread by the bites of Stomoxys, but the
results of experiments shew that Tabanus is a much more
efficient carrier as far as direct transmission is concerned
(vide p. 237). In Mauritius, where Stomoxys nigra Macq. is
very abundant, this species is believed to be concerned in the
spread of the same disease, but experimental evidence is lacking.
Finally it should be noted that in practically all experiment-
with Stomoxys in Africa, no distinction has been made between
5. calcitrans and S. nigra both species being used indiscrimi-
nately.

REFERENCES.

Austen, E. (1909). African Blood-sucking Flies.

Bagshawe, A. G. (1912). S. S. Bulletin, vol. rv. p.

Bevan, LI. (1910). Ibid. vol. 11. p. 252.

Bouet and Roubaud (1912). Bull. Soc. Path. Exot. vol. v. p. 544.

BoufTard (1907). Compt. Rend. Soc. Biol, vol, i.xn. p. 71.

364 FILARIA LABIATO-PAPILLOSA [CH.

Bruce, Hamerton, Bateman and Mackie (1910). Proc. Roy. Soc. B, 558,

p. 468.
Greig and Gray (1905). Rep. S. S. Comm. Roy. Soc. Xo. 6.
Leese, A. S. (1912). Journ. Trop. Vet. Sci. vol. 11. p. 19.
Manders, X. (1905). Journ. R.A.M.C. vol. v. p. 623.
Martin, Leboeuf and Roubaud (1908). Bull. Soc. Path. Exot. vol. 1.

P- 356.
Minchin, Gray and Tulloch (1907). Reports S. S. Comm. Roy. Soc. No.
8, p. 124.

2. Filaria labiato-papillosa Alessandrini, 1838.

Synonyms. Filaria cervina Dujardin, 1845. F. terebra
Diesing. Stomoxeos von Linstow, 1875.

Habitat. The adult worm inhabits the peritoneal cavity
and occasionally the eyes of cattle and various species of deer.
The embryos are constantly present in small numbers in the
peripheral circulation.

Description. The adult filaria is white and filiform with
the integument shewing fine transverse striations. The body
tapers towards both extremities, the anterior being blunter
than the posterior. The mouth is surrounded by a chitinous
ring and immediately behind it are four small depressions,
from each of which arises a tactile papilla. The male measures
4 to 6 cms. in length. Its tail is especially twisted and
on each side are three pre-anal, one ad-anal and five
post-anal papillae, behind which is situated a well-developed
conical process. The female measures 6 to 12 cms. in length
Its tail is also twisted but not so much as in the male. The
caudal extremity bears a large number of fine processes, in
front of which are situated two strong conical processes.

Life history. This filaria is viviparous and the embryos
when born measure 140 to 250 microns in length. Noe has
investigated the further evolution of these embryos and finds
that it takes place in the body of Stomoxys calcitrans. When
this fly ingests blood containing the embryonic filariae, the
latter bore through the gut wall and make their way into the
thoracic muscles. Here they accomplish their larval develop-
ment and when it is complete, the young filariae travel into the

XX] POLIOMYELITIS 565

labium of their intermediate host. When an infected Stomoxys
bites another animal the filarial escape from the labium and
probably bore through the skin of the host in the same way as
F. bancrofti, but this part of the life-cycle has not yet been
observed. Noe found that in Italy, where his experiments
were performed, only three to four per cent, of the Stomoxys
became infected, the remaining 96 to 97 per cent, being appar-
ently immune to infection.

Although there is little doubt that 5. calcitrans is capable
of transmitting this filaria, it is important to add that up to
the present no one has been successful in actually infecting
cattle by the bites of infected flies.

REFERENCES.
Alessandrini. Rendiconti Accad. d. Lined, vol. xn. pp. 387-393.
Neumann-Macqueen (1Q05K Parasites and Parasitic Diseases of

Domesticated Animals. London : Bailliere, Tindall & Cox.
Noe, G. (1903). Studi sul ciclo evoiutivo della Filaria labiato-papillosa.

Rend. Accad. d. Lincei, vol. xn. pp. 387-393.

Poliomyelitis.

Synonyms. Epidemic Poliomyelitis ; Infantile Paralysis ;
Epidemische Kinderlehrnung.

History. Poliomyelitis has been endemic in Northern
Europe for many years, especially in Scandinavia, but it was
only in 1907 that the disease suddenly began to extend its
range of distribution. During the past two or three years
many countries in different parts of the world have been
visited by epidemics, the origin of which has remained quite
unexplained. In America there is no previous history of a
general epidemic until 1907, although local outbreaks had
occasionally been noticed. Since this date, however, the dis-
ease has been prevalent during the summer and autumn in many
parts of the United States and Canada. It is possible that the
infection may have been introduced from Scandinavia, tor the
two great centres of the recent epidemic were the Atlantic
coast towns and the state of Minnesota, both of which received
large numbers of Scandinavian emigrants. Hut there i> no
apparent reason why the disease should not have broken out

366 POLIOMYELITIS [CH.

previously to 1907, for large numbers of emigrants had been
arriving for many years before that date, and also why
the infection should have suddenly appeared in many other
parts of the world. Since this date, however, the disease has
taken on fresh activities in its original home, and in 191 1,
Sweden was visited by a very severe epidemic.

Distribution. Poliomyelitis is especially prevalent in Scan-
dinavia and Northern Europe but, in addition, epidemics have
occurred in England, France, Germany, Italy, Austria, and
Spain ; in America large numbers of cases have been recorded
from New York and Boston in the east, to San Francisco in
the west, and a large outbreak occurred in Cuba in 1909. The
disease has also been recorded from various parts of Australia.

Causal agent. Although the most varied methods of
staining and cultivation have been employed, no parasite
has ever been detected in patients infected with poliomyelitis,
but the scarcity of polymorphonuclear leucocytes in the altered
cerebro-spinal fluid and spinal cord and the large increase in
the number of mononuclears suggest that the parasite is
protozoal in nature. The filterable nature of the virus has
since been demonstrated, for if the spinal cord of a recently
paralysed monkey is made into an emulsion with either
distilled water, or normal saline, and passed through a Berkefeld
filter, the resulting filtrate is still infective. Moreover, its
activity is very considerable, for one thousandth of a cubic
centimetre of a filtered 2-5 per cent, suspension of the spinal
cord of an infected monkey is sufficient to produce infection and
paralysis when injected into another monkey. The resistance
of the virus is extraordinary, for in dust, especially within
protein matter, it remains virulent for months. In diffuse day-
light it survives indefinitely and resists the action of pure
glycerine and 0-5 per cent, phenol for many months.

The virus may be preserved by passage through monkeys,
as these animals are easily infected by the intra-cerebral
injection of an emulsion of the brain or spinal cord of an animal
suffering from poliomyelitis. The susceptibility of monkeys
has enabled Flexner, in conjunction respectively with Lewis
and Clark, and also Landsteiner and Levaditi, to make some

XX] CAUSAL AGENT 367

observations on the development of the virus within the body
of an infected subject.

The disease is essentially one of the central nervous system
as evidenced by both the clinical and pathological features of
the infection. If the virus is injected into the sciatic nerve of
a monkey, it has been shewn that it multiplies in the nerve,
first at the site of the injection and then progresses along the
nerve until it reaches the spinal cord, when it causes paralysis
of the hind-quarters. When the virus is placed on the unin-
jured nasal mucous membrane, the infective agent travels up
the olfactory nerves and subsequently causes general paralysis.
It is evident, therefore, that nervous tissue is the one in which
the organism chiefly multiplies. From the brain and spinal
cord it passes into the cerebro-spinal fluid and thence into the
blood circulation and lymphatic system, but in these positions
it does not seem to persist for any length of time, except in the
lymphatic nodes. The presence of the virus in the lymphatics
explains why the nasal secretion becomes infected, for it has
been shewn that poliomyelitis escapes with the secretions of the
nose and throat and the discharges from the intestine of an
infected person.

Method of infection. Considering the infectivity of the
various secretions of a patient suffering from poliomyelitis, it
is only reasonable to suppose that the disease may be directly
transmitted from one person to another without the aid of
any intermediate host. Flexner supports the view that the
nasal mucous membrane is the chief site of infection, for the
virus is able to survive in the form of dust and thus mighl be
inhaled, and, in fact, the sweepings of a room occupied by a
poliomyelitis patient have been shewn to be infected.

On the other hand, as a result of very thorough epidemio-
logical studies conducted by the Massachusetts State Board
of Health, evidence has been collected which supports the
theory that the disease is spread by insects. Rosenau has
recently (1912) been able to transmit poliomyelitis from infected
to healthy monkeys by the bites of Stotnoxys cakitrans. Several
monkeys infected with the disease by intracerebral inoculation
were daily exposed to the bites of several hundred Stomoxys,

368 POLIOMYELITIS [CH.

at the same time exposing twelve healthy monkeys to the bites
of these flies. Of these twelve monkeys, six developed symp-
toms characteristic of poliomyelitis, namely, illness, followed
by more or less extensive paralysis- Two monkeys died, and
in the spinal cord of one of them was found the characteristic
lesions of this disease, i.e., perivascular infiltration and des-
truction of the motor cells of the anterior cornu.

Anderson and Frost have confirmed these experiments of
Rosenau and their results will be given in detail. On October
3rd, a rhesus was inoculated intracerebrally with an emulsion
of the spinal cord of a monkey that had died of poliomyelitis.
Two hours after inoculation it was exposed to the bites of about
300 Stomoxys collected in Washington. Each day until the
death of the monkey on October 8th, it was exposed for about
two hours to the bites of these flies, together with additional
ones that were added as they were caught. This monkey
developed the characteristic complete paralysis on October
7th and died on October 8th. Another monkey similarly
inoculated on October 5th was then daily exposed to the bites
of the same lot of flies from October 7th until October 9th,
when the second monkey died. Thus from October 4th to
the 9th inclusive, the Stomoxys had been able to feed on two
monkeys infected with poliomyelitis.

Beginning on October 4th, two fresh monkeys (Java and
rhesus) were exposed daily for about two hours to the bites of
these same flies ; and on October 5th yet a third monkey
(rhesus) was similarly exposed. On October 12th the Java
monkey was found completely paralysed and died the same
day. The second rhesus monkey also developed paralysis
during the day and was anaesthetised. The first rhesus monkey
died on October 13th after presenting the typical symptoms of
poliomyelitis.

Thus three monkeys exposed daily to the bites of several
hundred Stomoxys, which at the same time were allowed to
feed on two infected monkeys, developed typical symptoms
of poliomyelitis seven, eight and nine days, respectively, from
the date of their first exposure to the bites of the flies.

These results are of great interest and shew that the

XX] LYPEROSIA 369

disease may be transmitted by the bites of Stomoxys. It should
be added, however, that the transmission has only been effected
under experimental conditions and it remains to be seen whether
this is the usual method of infection in nature, for cases of
poliomyelitis have occurred in the absence of any Stomoxys.

REFERENCES.

Anderson and Frost (191 2). Transmission of poliomyelitis by means

of the stable-fly {Stomoxys calcitrans). Public Health Reports,

Washington, vol. xxvu. No. 43.
Brues and Sheppard (191 2). The possible etiological relation of certain

biting insects to the spread of infantile paralysis. Journ. Econ.

Entom. vol. v. No. 4.
Kling, Wernstedt and Pettersson (191 2). Recherches sur le mode de

propagation de la paralysie infantile epidemique. Zeitschr. f.

Immunitdtsforschung, vol. xii. pp. 316—323 and 657-670.
Kling and Levaditi (1913). Etudes sur la poliomyelite. Publ. de

I'lnst. Pasteur. 126 pp. Paris : Maretheux.
Rosenau (1913). Public Health Reports, Washington, vol. xxvu.

CHAPTER XXI

LYPEROSIA

General description. The genus Lyperosia is closely related
to Stomoxys, from which it may be distinguished by the shape
of the maxillary palps, which are more or less spatulate, and
as long, or almost as long, as the proboscis. When the insect is
resting the palps ensheath the proboscis, as in the case of
Glossina, and as a result the combined structures appear as a
stout rod-like process in front of the head. The proboscis is
long and tapering, chitinous throughout, and the labella are
small. The arista is feathered only on the dorsal sun
The third longitudinal vein is without bristles and the fourth
longitudinal is gently curved distally so as to Leave the first
posterior cell wide open.

All the known species of Lyperosia are small, dull, incon-
spicuous insects, not exceeding about 4 mm. in Length.

H. B. F. -4

370 LYPEROSIA [CH.

They are very common on domestic animals and generally
cluster on any small sores. They also take advantage of the
wounds caused by the bites of Tabanids, etc. In the Philip-
pines, Mitzmain has observed these insects to wait for a Tabanus
to finish feeding and then immediately suck up the drop of
blood that oozed from the open wound caused by the larger
insect. They are also capable of obtaining blood for themselves,
and the only European species, L. irritans Linn., has the
habit of clustering in a dense mass about the base of the horns
of cattle. Lyperosia rarely attacks man, but regarding a
Uganda species, L. punctigera, Austen records the following
observation by the collector (the late Dr W. A. Denshaw) :
" These flies were noticed in great numbers in one camp only
near the Nile, and were very troublesome to my boys early one
sunny morning ; they clustered thickly on any small sore, and
quickly filled themselves ; though preferring to feed in this
way, they seemed also to insert the proboscis into sound
skin."

Life-cycle. The life-history of Lyperosia irritans Linn, has
been investigated in America by Riley and Howard. The eggs
are laid singly on the surface of freshly dropped cow-dung.
They are light reddish-brown in colour and vary from 1-25 to
1-37 mm. in length, by 0-34 to 0-41 mm. in breadth. As soon
as they hatch the larvae penetrate into the dung and in this
situation complete their development. The fully-grown larva
is dirty white in colour and about 7 mm. in length. The
posterior stigmatic plates, situated on the terminal segment,
are large, very dark brown, and almost circular, but with their
inner adjacent margins almost straight, and each has a circular
central opening. On the ventral surface of the anal segment
is a dark yellow chitinous plate bearing six irregular paired
tubercles, and the whole plate is surrounded by an area of
coarsely granulated skin.

The pupae are found in the ground beneath the dung, at a
depth of about 2 cms. The puparium resembles that of
the house-fly, being dark brown in colour and barrel-shaped.
Its dimensions vary from 4 to 4-5 mm. in length, by 2 to
2-5 mm. in breadth.

XXl] LYPEROSIA AND DISEASE 371

Lyperosia and Disease

There is no direct experimental evidence in support
of the view that Lyperosia carries any infection, but certain
authors have suggested that this fly may occasionally
be responsible for the spread of various trypanosomiases
of animals. Schat is of the opinion that Lyperosia exigua
de Meijere, takes a part in the spread of Surra in Java.
Montgomery and Kinghorn, in Rhodesia, record an outbreak
of trypanosomiasis occurring under the following circumstances.
A herd of cattle in Northern Rhodesia which had been in good
health for a year was kept on a farm two-and-a-half miles
from the nearest tsetse area. In April six bullocks were sent
on a journey and as they passed through a fly belt were prob-
ably bitten by tsetse. These bullocks returned to the farm a
few days later. In June, three of these animals and also one
which had not been away shewed trypanosomes. In July,
fifteen animals were infected so all the healthy cattle were
isolated in a place that seemed free from biting-flies. Five
more of these animals shewed trypanosomes in August and were
removed, but the balance continued to remain uninfected.
The average duration of the disease was about 30 days, and the
parasite is described as T. dimorphon. The authors write :

" From an examination of all conditions, we think it prob-
able that one or more of the six cattle that went to Mwomboshi
in April contracted the disease on the road and brought it to
the farm, where, in the presence of Stomoxys and Lyperosia in
the kraals, the animals, including cows and bulls, which did
not leave the place, became infected, and that the segregation
from these flies checked its spread to the fourteen cattle which
remained healthv." Montgomery and Kmghorn believe that in
this case, Lyperosia was partly responsible for the transmission,
the trypanosomes being directly carried from infected to healthy
animals.

In India, Leese has given an interesting account of an out-
break of Surra in the Bikanir State in the desert of Rajputana.
During this outbreak the Imperial Service Camel Corps, out of
500 camels, had only 205 survivors and of these 130 were

-4—-

372 HIPPOBOSCIDAE [CH.

suffering from chronic Surra. Only 40 camels had been out-
side the State and the great majority of them had been in the
Corps so long that they could not have been infected when
purchased, therefore the infection must have chiefly spread
within the State itself. Bikanir is about 200 miles square, and
there is only one small locality in which Tabanus is known to
occur. Leese proved that the outbreak occurred and spread
when the camels were grazing in the desert portion of the
State at least 100 miles from any fly zone. In this region the
only biting fly present was Lyperosia minuta Bezzi, which
swarmed on the animals and caused great irritation so that
the camels rubbed against each other in order to dislodge
them. It seems probable, therefore, that Surra can spread in
the presence of Lyperosia alone, and Leese believes that the
transmission is probably mechanical.

REFERENCES.

Austen, E. (1909). African Blood-sucking Flies, p. 160.
Leese, A. S. (1912). Journ. Trop. Vet. Sci. vol. vn. p. 19.
Montgomery and Kinghorn (1908). Ann. Trop. Med. and Parasit. vol.

11. p. 130.
Riley, C. V. and Howard, L. O. (1889). Insect Life, vol. 11. p. 93.
Schat, P. (1903)- Mededal. Proefstation Oost-Java, 3rd ser. No. 44.

CHAPTER XXII

Family Hippoboscidae (Tick-Flies).

Description. The members of this family may be regarded
as Mnscidae that have become adapted to an entirely parasitic
mode of life on birds and mammals. As a result certain
marked changes in structure and reproduction have taken
place and the flies form such a distinct group that they are
frequently placed in a separate sub-order, the Pupipara,
characterized by their viviparous mode of reproduction. The
Hippoboscidae may be distinguished by the following charac-
ters :

XXII] DESCRIPTION AND BIONOMICS 373

The head is generally flattened and usually fits into an
emargination of the thorax. The antennae are apparently one-
jointed and are inserted in pits or depressions, situated near
the border of the mouth. The maxillary palps ensheath the
proboscis, which closely resembles that of Glossina, but never
projects in front of the head. The eyes are round or oval, and
are widely separated in both sexes ; ocelli may be present or
absent. The thorax is flattened, strongly chitinised, and
leathery in appearance ; the scutellum is broad and short.
The abdomen is unsegmented. The legs are rather short and
very strong, broadly separated by the abdomen and end in
powerful claws. The wings may be well-developed, rudimen-
tary, or entirely absent ; when present the veins are always
concentrated towards the anterior margin. The halteres are
small or rudimentary.

The length of the adult insect may vary from about 3 mm.
up to 11 -5 mm.

Bionomics. The Hippoboscidae live amongst the fur or
feathers of either mammals or birds, and by means of their
strong legs and claws are enabled to cling to their hcsts. As a
result of the adoption of this parasitic mode of life, the wings
have gradually become rudimentary and in Melophagus ovinns.
the common " sheep-ked," they are entirely wanting. They
run about on the surface of their hosts, and even when possessing
well- developed wings make little use of them. They feed
entirely by sucking the blood of birds and mammals, and
except for some special reason, such as the death of the host,
rarely leave its body. The bites of Hippoboscidae are not very
painful to man, but the sensation produced by their sharp
claws hanging to the skin is most unpleasant. However,
none of the species, except fortuitously, ever attack man.

Reproduction. As in the case of Glossina, the female
Hippoboscid at certain intervals gives birth to a fully crown
larva which at once proceeds to pupate. The body oi the
larva exhibits practically no trace of segmentation and thus
differs from those of the true Muscidae. The female may
deposit its larva either amongst the hair of its host e.g. Melo-
phagus) or on the ground (e.g. Lynch ia), but precise information

374 HIPPOBOSCIDAE [CH.

on this subject is lacking. After a variable incubation period
the pupa, which is of the usual Cyclorrhaphous type, splits off
a cap at the anterior end and the perfect insect emerges from
the circular aperture thus formed.

Hippoboscidce and disease. Up to the present no truly
pathogenic organisms have been shewn to be carried by Hippo-
boscidae, but two species of Hippobosca are said to transmit
Trypanosoma theileri occurring in cattle in the Transvaal, and
three species of Lynchia have been shewn to carry the pigeon
halteridium, Hcemoproteus columbce. The insects, therefore,
are of little importance from the point of view of disease-
carriers, but some of them are of economic interest because of
the harm they do to domestic animals, through mere irritation.

Classification. The Hippoboscidae may be divided into
thirteen genera as follows :

Synopsis of the genera of Hippoboscidce after Speiser1.

A. Wings well developed and junctional.

/Claws with the usual two points (heel and tip) ; parasitic on mammals =2
\ Claws with three teeth ; parasitic on birds . . . . . . . . =3

I^Head of normal form, not broadly impinging on thorax, freely movable ;
J ocelli absent ; wings always present . . . . = Hippobosca.

I Head flat, broadly impinging on thorax ; ocelli present ; wings sometimes
I becoming detached (in female) leaving only a shred =Dipoptena.

f Ocelli present . . . . . . . . . . . . . . . . =4

\ Ocelli wanting (no anal cell) .. .. .. .. .. .. =5

= 6
= 0mithophila.

the tip rounded = Lynchia.

than in Ovnithomyia, with

= Olfersia.

Third longitudinal vein not elbowed at the anterior transverse vein

= Ovnithomyia.

Third longitudinal vein abruptly bent forwards at the level of the anterior

transverse vein — Ornithceca.

J" Anal cell present
\ Anal cell absent . .

p Wings of a peculiarly pointed form (vide Fig. 85)
5 ■{ Wings of the ordinary form but less expanded
I broadly rounded tip

6

B. Wings rudimentary or wanting.

/Wings present, but rudimentary and functionless ; halteres present = 2
\ Wings and halteres absent . . . . . . . . =Melophagus.

1 Modified from Alcock's Entomology for Medical Officers, p. 187.

XXIl] LYNCHIA 375

/Claws with the usual two points (heel and tip) .. .. .. =3

\ Claws with three teeth . . . . . . . . . . . . =4

f Ocelli present. Wings always well developed, but always in the female
and generally in the male becoming detached, so that only shreds
remain resembling rudimentary wings . . . . = Lipoptena.

Ocelli wanting. Wings rudimentary. Legs much enlarged or elongated
*- =Allobosca.

f Ocelli present. Wings narrow, nearly ten times as long as broad, and
■< longer than the abdomen . . . . . . . . =Stenopteryx.

I Ocelli absent. Wings not more than three times as long as broad .. =5

/Wings as long as, or longer than, the abdomen . . — Oxypterum.

\ Wing rudiments much shorter than the abdomen . . . . . . =6

/Veins of the wings distinct. Asiatic species . . . . =Myiophthiria.

\ Veins of the wings indistinct. North American species = Brachypteromyia.

Genus Lynchia Weyenbergh.

Speiser1 gives the following diagnosis of the genus : " Head
without frontal eyes, antennal prolongations frequently bearing
characteristic brushes. Scutellum squarely cut off from the
thorax, almost four times as broad as long, often with con-
spicuous hairs. Legs normal, claws with accessory teeth and
rather large basal protuberances. Wings narrowly tapering,
consequently the venation is striking and characteristic. The
posterior basal cell is quite open, the posterior transverse vein
absent. The veins appear somewhat more compressed towards
the anterior border than in Olfersia Leach. Spec, typica :
L. penelopes Weyenbergh."

Certain members of this genus have been shewn to transmit
Hcetnoproteus columbce and are probably responsible for the
spread of other kinds of Halteridia.

L. lividicolor, Bigot (1885) 2 has been shewn to transmit
H. columbce in Brazil. It is easily distinguished from the other
members of its genus by the brownish colour of the wings
instead of the usual milky-white.

1 Speiser (1902). Studien liber Diptera pupipara. /.
Hymenoptett logie u. Dipt vol. 11. p. 155.

■ Bigot (1885), Ann. Soc. lint. France, p. 238.

376 LYNCHIA MAURA [CH.

Lynchia maura (Bigot), 1885.

Olfersia maura Bigot, 1885.

Description. Bigot gives the following diagnosis of this
species :

" Antennae chestnut-coloured with yellowish setae ; epistome and vertex
testaceous ; frons brown, shining on either side. Thorax brownish-black,
scarcely shining, with the shoulders and scutellum dirty fulvous. Abdomen
obscurely infuscate ; apex of the second segment with a fulvous margin.
Legs testaceous ; upper surfaces of femora slightly infuscated and with scanty
black setae ; posterior femora marked on the outside with a slender brownish
line. Wings nearly hyaline ; costal and first four longitudinal veins tinctured
with black along the whole length, and the fifth vein as far as the first black
transverse vein."

Fig. 85. Lynchia maura ? . ( x 6.) Drawn from Bigot's type specimen.

Bionomics. L. maura generally occurs on young pigeons
about 15 to 20 days old, in which the feathers have commenced
to grow. As many as 50 or 60 may be found on a nestling
pigeon, whereas it is uncommon to find any on the adult birds.

The insects usually remain hidden amongst the plumage
and their smooth flat body enables them to glide under the
feathers. If the bird is taken in the hand, or shakes itself
very thoroughly, the Lynchia take flight. They change hosts
readily and their flight is very rapid.

XXII] LIFE-CYCLE 377

The insect seems to be unable to live on any other bird
than the pigeon, and in captivity usually dies within 48
hours after being removed from its host.

The copulation takes place either during repose or whilst
the insects are flying and lasts a very long time ; during the
act the female raises its wings in order to permit the access of
the male.

Life-cycle. The larva is laid amongst the dry dust in the
pigeon-house, never in the moist excrement. When freshly
laid the larva appears as a white ovoid body with a black spot
in the form of a six-rayed star at the posterior pole. Pupation
is usually complete within an hour of the larva being born,
and is accompanied by darkening of the integument, which
becomes black. The pupa measures about 3 mm. in length
by 2-5 mm. in breadth, and closely resembles a small grain of
seed. The surface of the pupa is marked by a network of fine
lines giving it the appearance of crushed morocco.

The pupa hatches after an incubation period of 23 to 28
days, when it is kept at a temperature of 24 to 300 C. When
pupae are kept at the body temperature of the pigeon (420 C.)
they invariably die without hatching, therefore it is very
unlikely that they occur amongst the feathers on the body
of the host.

Lynchia and disease. Three species belonging to this
genus, viz. L. maura, brunea and lividicolor, have been shewn
capable of transmitting Hcemoproteus columbce. It is also
probable that certain other protozoal infections of pigeons,
such as trypanosomes and Leucocytozoa may also be carried
by these insects, but up to the present there is no experimental
proof in support of this supposition.

LITERATURE.

Bigot (1885). Ann. Soc. Entomol. de France, 6th series, vol. V. p. -
Sergent, Ed. and Et. (1907). Ann. Inst. Pasteur, vol. xxi. p. 251.

3J& HIPPOBOSCA RUFIPES [CH-

Hippobosca rufipes v. Olfers, 1816.

This species is about 1 cm. in length and is characterised
by the markings on the thorax and scutellum. The thorax is
a rich chestnut-brown colour and is bordered by a ring of
yellowish- white spots ; in addition there is a white spot in the
middle of the dorsal surface. The scutellum is marked by a
median red spot, on each side of which is a yellowish-white
spot.

Fig. 86. Hippobosca rufipes. ( x 3.)

Bionomics. H. rufipes is the common parasite of cattle
and horses in South Africa. According to von Olfers, the type
of this species was taken on an ostrich, but he suggests that
the fly may have come from a quagga, as these animals used to
mingle with the flocks of ostriches.

According to Theiler it is often found on cattle, on which it
usually settles between the hind-legs, but may occur running
over any part of the body.

This species may occasionally stray on to other hosts, for
Mr Distant states that in the Transvaal this fly often attached
itself to his neck.

A pupa of H. rufipes has been described by Austen. It is
5-6 mm. in length by 4-8 mm. in breadth and is roundly ovate
in shape. The colour is a dark seal-brown with the exception
of the posterior end which bears a black cap, separated off from

XXII] H^MOPROTEUS COLUMB^ 379

the rest of the surface by a distinct groove. The anterior end
is surrounded by a darker line, marking the line of dehiscence
of the cephalic cap. There is a longitudinal row of six punc-
tures on each side, above and below, near the lateral margin.

Hippobosca and disease. In addition to being the carrier
of Trypanosoma theileri [vide infra), Mr Hutcheon states that
a local form of anthrax, which is very common in horses in
parts of Griqualand West, is most probably due to infection
caused by Hippobosca rufipes. There is no experimental
evidence in support of this statement.

Hippobosca maculata, Leach, also occurs parasitic on horses
and cattle in many parts of the world, including South Africa,
where, however, it is comparatively uncommon. It is probable
that this species as well as rufipes is capable of transmitting
T. theileri, and in his experiments Theiler used a mixture of
the two. As, however, rufipes is the more common species in
South Africa, where T. theileri is especially prevalent, it is
only reasonable to assume that it is the usual carrier of the
infection.

CHAPTER XXIII

INFECTIONS TRANSMITTED BY HIPPOBOSCIDAE

1. Haemoproteus columbae Celli and San Felice, 189 1.

General account. Hczmoprotcus columbce, the halteridium
of the pigeon, is very common in many parts of the world,
having been recorded from Italy, France, North Africa, India
and Brazil. It is apparently non-pathogenic, for pigeons may
shew large numbers of the parasites in the blood circulation
for years, without any obvious harmful effects being produced
Et. and Ed. Sergent, in 1906, shewed that in Algeria the para-
site is transmitted by Lynchia tnaura Bigot, one ol the
Hippoboscidae. In 10,08, Aragao worked out the life-cycl<
the parasite both in the blood of the pigeon and in the inver-
tebrate hosts of this infection in Brazil, viz., Lynchia bra
and L. lividicolor (Oliv.). Aragao's account is somewhat

380 H^MOPROTEUS COLUMB^ [CH.

incomplete but such as it is does not support Schaudinn's
observations on the life-cycle of a closely related parasite, Hcemo-
proteus noctuce, occurring in the little stone owl, Athene noctua .

Life-cycle. Owing to the presence of infected flies in the
nests of the pigeons, the young birds frequently become
infected, the parasites appearing in the blood after an in-
cubation period of from 20 to 30 days.

The first stages of development take place in the white
blood corpuscles and if smears are made of the lungs of a
pigeon 13 or 14 days after it has been bitten by an infected
insect, the young forms of the Hcemoproteus can generally be
found within the leucocytes. At this stage the parasite appears
as a small mass of protoplasm about 3 to 4 microns in
diameter, containing one or two nuclei. This form lives
within the cytoplasm of a leucocyte and by repeated division
gives rise to a number of parasites, each of which contains a
single nucleus and is provided with a more or less distinct
membrane. This stage may be found in the pigeon from
15 to 17 days after the bite of the insect. Each of these bodies
then commences to grow very rapidly and produces a large
mass of cytoplasm 8 to 12 microns in diameter, containing
several small particles of chromatin, and surrounded by a
more or less definite cyst-wall. The leucocytes containing the
parasites undergo hypertrophy and become very large, up to
60 microns in diameter. This phase of development is present
about the eighteenth or nineteenth day. According to Aragao,
at this stage it is possible to distinguish two kinds of cysts
by their staining reactions, one of which will give rise to the
female and the other to the male-producing merozoites.

From the twentieth to the twenty-fourth day of development
the cysts increase enormously in size, up to as much as
50 microns in diameter. The membrane is now very distinct
and the numerous nuclei are uniformly scattered throughout
the cytoplasm. The cysts cease to grow and their protoplasm
breaks up into a number of polygonal masses with the nuclei
arranged along their edges (Fig. 87, 18), thus closely resembling
the young malaria sporoblasts. This change takes place on the
twenty-fifth day and is immediately succeeded by the division

XXIII]

DEVELOPMENTAL CYCLE

381

Fig. 87. Developmental cycle of Hcsmoproteus columba. la and id, young
halteridia in the blood corpuscles ; la to 4a and ib to 4 in the

growth of the female and male gametocytes, respectively : 5a, female
gamete ; 56, formation of male gametes ; o, fertilization ; 7, zygote ;
8 to 12, stages in the extrusion of granules from the ookinete ; 13, youi
stage in a leucocyte from the lung of a pigeon ; 14 to 20, stages in its
multiplication, accompanied by hypertrophy of the lew >, the

liberation of large numbers of uninucleate forms which enter the red cells
and there become the young halteridia. (Alter Aragfto.)

382 JLEMOPROTEUS COLUMB^ [CH.

into merozoites. Each nucleus, together with a small mass of
cytoplasm, becomes separated off, and thus, in the inside of the
cyst, hundreds of merozoites are formed (Fig. 8y, ip) . The cysts,
together with the leucocyte that contains them, then rupture,
and the merozoites are set free in the blood stream of the pigeon
about 26 days after the bite of an infected insect (Fig. 87, 20).

The merozoites then invade the red blood corpuscles and
develop into the typical halteridium forms that are found in the
circulating blood (Fig. 87, i-j), and these are incapable of any
further development within the body of the pigeon. Accord-
ingly there is no cycle of schizogony such as occurs in the case
of the malarial parasites, but after the completion of develop-
ment within the leucocytes in the internal organs, the merozoites,
as soon as they have entered the red blood corpuscles, develop
into the sexual forms, male and female.

The appearance of the male and female gametocytes of
HcBtnoproteus is practically the same as that of the corres-
ponding stages of Plasmodium. The macro-garnet ocytes stain
intensely and contain a large amount of reserve food material
in the form of granules, whilst the micro-gametocytes are
much lighter and almost free from granules.

When taken into the stomach of the invertebrate host the
gametocytes escape from the red cells and give rise to the
gametes. The macro-gamete is a large rounded body containing
a single nucleus near the middle of the cytoplasm (Fig. Sy, ja).
The nucleus of the micro-gametocyte (Fig. 8y, 4b) breaks up into
a number of small particles arranged in pairs, and each pair,
together with a small quantity of cytoplasm, becomes separated
off in the form of an elongate vermiform micro-gamete.
These swim about until they come in contact with a ripe
macro-gamete when fertilization takes place, the result of the
fusion being an ookinete. The liberation of the micro-gametes
and the process of fertilization may be observed by placing a
small quantity of infected blood on a glass slide and watching
it under the microscope. Probably as a result of the diminu-
tion in temperature, the ripening of the gametes and fertili-
zation take place in the same way as if the blood had been
ingested into the stomach of its invertebrate host.

XXIIl] LIFE-CYCLE 383

The ookinetes may be observed in the gut of Lynchia within
three hours after a meal of infected blood. Each ookinete is
an elongate, somewhat gregarine-like body, that moves about
by means of undulations of its body. The pigment granules,
that originally are scattered throughout the whole of its
cytoplasm, become concentrated in a clump at the posterior
extremity (Fig. 8j, 9-1 /), which eventually is separated from the
rest of the body. In this manner the ookinete gets rid of the
waste granules in its cytoplasm. The subsequent history of
this form is not certain, but in all probability it does not undergo
any further development in the invertebrate host. When an
infected Lynchia bites a pigeon, the ookinetes present in the
front part of the insect's alimentary canal, are introduced
into the blood of the bird and undergo further development in
the leucocytes. The cycle within the vertebrate host is then
repeated, the parasite multiplying in the leucocytes of the
pigeon in the manner described above.

It will be noticed that Hcemoprotens columbcz possesses only
one method of multiplication, there being no distinct schizo-
gonic and sporogonic cycles as in the case of Plasmodium.
The parasite is apparently unable to multiply within the body
of its invertebrate host, Lynchia, all multiplication taking
place in the vertebrate host.

H. columbcB is not hereditarily transmitted to the offspring of
infected Lynchia, for large numbers of freshly-hatched insects
may be fed on a healthy pigeon without producing any infection.

The number of halteridia appearing in the blood circu-
lation of a pigeon is directly proportional to the number of
infected Lynchia that feed on the bird. The bite of only onv
insect produces a very mild infection, whereas when 50 are led
on a pigeon, almost every corpuscle becomes infected.

REFERENXES.
Aragao (1908). Der Entwicklungsgang und die Obertragung von

Hatnoproteus columbcr. Arch. f. Protistcnkunde, vol. xn. p. 154.
Mayer, M. (1910). Die Entwicklung von Halteridium. Arch, j 5
//. Tropenhyg. vol, xiv. p. 197.

(191 1). Ein Halteridium und Leucoeyto/oon des Waldkar.

../. ProHsienkunde, vol. xxi. p. 232.
Sergent, Ed. and Et. (1907). Les Hemato/oaires d'Ois
Inst. Pasteur, vol. xxi. p. 231.

384 TRYPANOSOMA THEILERI [CH.

2. Trypanosoma theileri Laveran, 1902.

Synonym. T. transvaaliense Laveran.

General account. This trypanosome was discovered by
Theiler in 1902, occurring in the blood of cattle in the TransvaaL
It was named and described by Laveran, in 1902, who at the
same time distinguished two species of trypanosomes occurring"
in the blood of cattle in the Transvaal, viz. T. theileri and 7\
transvaaliense. Theiler has shewn that the latter is merely
a young stage in the development of T. theileri, for when blood
containing transvaaliense was injected into cattle the latter
developed infections of typical theileri.

The pathogenic effects of this trypanosome are so slight,
that no difference can be detected between normal and infected
cattle.

Since the discovery of T. theileri, non-pathogenic trypano-
somes have been found in the blood of catt e from all parts of the
world. In the majority of cases the parasites are present in
such scanty numbers that their presence can only be detected
by means of culturing the blood of the infected animals, but in
others the trypanosomes are in sufficient quantity to be evident
on ordinary microscopic examination. Considering the fact that
cattle infected with T. theileri in Africa frequently shew very
many parasites in the circulating blood, whereas in the case
of infections with T. americanum, franki, rutherfordi, etc., the
trypanosomes are always excessively rare, the specific identity
of these forms seems a little doubtful. However, there is
a possibility that the numerous non-pathogenic trypanosomes,
described under different names1 from practically every
part of the world, only constitute one species, and therefore
the observations in this chapter only refer to T. theileri as
observed in the Transvaal.

Morphology of the parasite. T. theileri is remarkable because
of its relatively enormous size. The large forms measure as
much as 60 to 70 microns in length by 4 to 5 microns in
breadth. The transvaaliense forms, which are probably stages

1 Among these may be mentioned T. himalayanum, indicum and muktesari
Lingard, 1904 ; T. franki Frosch, 1909 ; T. wrublewskii, T. americanum
Crawley, 1909 ; T. rutherfordi Hadwen, 191 2.

XXIII

MORPHOLOGY

38;

in the development of these large trypanosomes vary consider-
ably in their dimensions. The smaller parasites measure about
18 microns in length by 2 microns in breadth, and all stages
in their increase in size may be observed. In the small forms
the kinetonucleus is frequently situated alongside the tropho-

Fig. 8%. Trypanosoma theileri. x about 1500. A. Small crithidial form
B. Large individual from the blood of a cow. (After Theiler.)

nucleus in the middle of the body of the trypanosome, and the
undulating membrane is only slightly developed. In the
larger parasites of the theileri type, the kinetonucleus is situated
towards the posterior extremity and the trophonucleus about
the middle of the body. The undulating membrane is very
large and thrown into bold folds ; anteriorly the flagellum is
free for a distance equal to about one-quarter the length of the
body of the parasite. The protoplasm contains large numbers
of granules and stains very deeply.

The only mode of multiplication that has been observed is
simple longitudinal division, which is of the normal type.

Mode of transmission. Theiler has shewn that this trypano-
some may be carried from one animal to another by means
of Hippobosca. " For this purpose some flies were kept over-
night in order to make them hungry, and were then placed on
the groins of an infected calf. To give the experiment ei
chance of success, the spot where the flies were put to I
first shaved, as was also the spot on a clean animal wl
were placed for infection. Feeding by turns on a sick and on a
clean animal was thus repeated several times, in order to secure

H. B. F.

386 TRYPANOSOMA THEILERI [CH. XXIII

an infection. Out of four experiments made in this way, two
were successful. It must be stated here that the experimental
animals were kept together with control animals in a stable, to
exclude spontaneous infection, and that none of the control
animals shewed a spontaneous infection. The incubation periods
coincided typically with the period which is observed after
artificial infection with small quantities of virus " (Theiler).

Two specimens of the Hippobosca used in these experiments
were identified by Speiser as Hippobosca rufipes v. Olfers, and
H. maculata Leach, respectively. As the latter is excessively
rare in South Africa, it is probable that H. rufipes is the usual
carrier of T. theileri.

The parasite may also be experimentally transmitted to
cattle by the injection of small quantities of infected blood.
Under these circumstances the incubation period depends, to a
large extent, on the number of trypanosomes introduced ; it
averages between four and six days, but in one case a period of
18 days was noticed.

The trypanosomes are only present in the peripheral
circulation for a comparatively short time and then disappear,
leaving the animal immune against any further infection.
The longest period in which the presence of the parasite was
observed in the blood was 13 days, the average nine days, and
the shortest period, one day. While present the numbers of
the parasites may rise to 30 trypanosomes in each microscopic
field, but the average is about five per field. The disappearance
of the parasites is only apparent, however, for the blood of a
cow has been shewn to be still infective 11 months after the
animal was inoculated.

REFERENCES.
Laveran, A. (1902). Compt. Rend. Acad. Sci. vol. cxxxiv. p. 512.
Theiler, A. (1903). Journ. Com. Path, and Therap. vol. xvi. p. 193.

INDEX

Where more than one reference is given the most important
is printed in black figures

Acalyptratae 24, 239, 240

Acanthocera 231

Acanthomeridae 225

Acartomyia 109

Acroceridae 225

Aedes 63, 71, 72, 109

calopus See Stegomyia fasciata

Aedimorphus 109

Aedinae 76

Aedomyia 109, no, 114

Aestivo-autumnal malaria See Plas-
modium falciparum

African trypanosomiasis See Sleep-
ing Sickness

Agchylostoma duodenale 214

Ague See Malaria

Aino 31, 287, 329

Aldrovanda vesiculosa 72

Allobosca 375

Ambassis ranga 152

Anabas 151

Andersonia 109

A nisocheleomyia in

Anopheles 62, 63, 76, 78, 79, 95, 123,
134, 136, 144, 145, 148, 149, 154
Enemies of 144

Anopheles aconita 87, 88, 96
— var. cohcBsa 87, 96, 99
aitkeni 26, 80, 96, 105, 107, 140
albimana 94, 96, 97, 99, 107, 142
albipes 27, 94, 96, 215
albirostris 26, 87, 88, 96, 97, 99,

albitarsis 94, 96
alboa>niulatus 85, 96
albofimbriata 94, 96
albotaniatus 84, 85, 96, 97
algerunsis 26, 81, 96, 142
annularis 85, 96
ainiulnnanus Si, 96
annulipalpis 95, 96
annttlipes Walker 95, 96, 103, 142
atnntliPt's Arrib. 95, 96
antennatus 05, 96
ardensis 91, 93, 96

Anopheles argyrotarsis 27, 90, 94, 96,

97, 99, 142, 215
arabiensis 26, 89, 96, 142
arnoldi 96
asiatica 83, 96, 138
atratipes 83, 96
atropos 81, 96
aureosquamiger 91, 96
aurirostris 96
austenii 89, 96
azriki 96
bancroftii 84, 96
barberi 81, 96

barbirostris 27, 84, 96, 140, 215
barianensis 81, 96
bellator 96
bifurcatus Linn. 26, 80, 81, 96, 99,

107, 141, 143, 222
bifurcatus Meigen 96, 101
bigotii 94, 96, 105
bisignata 96
boliviensis 95, 96
bozasi 94, 96
br achy pus 85, 96
braziliensis 94, 98
brunnipes 95, 98
cardamatisi 89, 98
ceylonica 95, 98
chaudoyei Theobald 27, 89, 98, 99,

142
chaudoyei Billet 89, 98
chrisiophersi 87, oS, 141, I
Christopher si var. alboapicalis Sj,

98
christyi 95, 98
cincta 94

en. - 98, 101

clanger 8i, 98, j;i
cleopatra 89
cohepsus 95,

costalis

M-. 215
costalis var. 1 I 33

Cc'.V

3S8

INDEX

Anopheles crucians 81, 82, 98, 99
cvuzii 87, 98
cubensis 94, 98
culicifacies 26, 87, 88, 98, 101,

103, 137, 140, 142
culiciformis 80, 98
deceptor 95, 98
distinctus 89, 98
distinctus var. melanocosta 89, 98
d'thali 27, 87, 98
dudgeoni 92, 98
eiseni 81, 82, 98
elegans 95, 98
gy^oy 95, 98
fajardoi 95, 98
farauti 95, 98
ferruginosus 81, 98
yZaya 92, 98
flavicosta 87, 98
fluviatilis 87, 98
formosaensis I 26, 87, 98, 142
formosaensis II 26, 95, 97, 98
formosus 83, 98
fowleri 91, 92, 98
fragilis 80, 100
franciscanus 83, 100
freer ce 91, 92, 100
fuliginosus 27, 91, 92, 100, 101,

142
funesta 26, 86, 87, 88, 100, 101,

142
funesta var. subumbrosa 87, 100
funesta var. umbrosa 87, 88, 100
funesta var. neiriti 100
gambles 92, 100
gz'gas 82, 83, 100
gz'tes* 93, 100
gorgasi 94, 100

grabhamii 84, 100
gracilis Theobald 95, 100

gracilis Donitz 92, 100

grisescens 81, 100

Aa//i 92, 100

Ae&es 87, 100

hispaniola 27, 87, 88, 100, 105,
142

hy emahs 83, 100

immaculatus 81, 100

implex a 95, 100

impunctus 87, 100

indefinata 90, 100, 105

indica 87, 92, 100

indiensis 92. 100

intermedia 92, 100

intermedium 86, 100

jacobi 94, 100

jamesii Theobald 91, 100

jamesii Liston 92, 100

jehafi 87, 100

jesoensis 85, 100

jeyporensis 89, 100

Anopheles karwari 91, 92, 100, 103
kochii 91, 92, 100, 10 1
kumassii 87, 100
leptomeres 87, 100
leucopsus 92, 100
leucosphyrus 95, 102
lindesayi 83, 102
lindesayi var. maculata 83, 102
lineata 92, 95, 102
listoni 26, 86, 87, 88, 95, 99, 102,

137. 142
longipalpis 87, 102
ludlowi 27, 90, 102, 103, 138, 142
/wtei Cruz 93, 95, 102
Jwte* Theobald 27, 87, 93, 95, 99,

102, 138, 142
maculatus 27, 87, 91, 92, 102, 105,

107
maculicosta 95, 102
maculipalpis Giles 91, 102, 142
maculipalpis James and Liston 92,

102
maculipalpis var. indiensis 27, 92,

101, 102, 103
maculipennis 26, 51, 62, 65, 70,

71, 80, 81, 97, 99, 101, 102,

105, 141, 142, 156, 219, 222 ;

Pupa 22
maculipes 85, 86, 102
malefactor 86, 102
mangy ana 90, 102
marshallii 91, 93, 102
martini 95, 102
masteri 95, 102
mauritianus 27, 84, 85, 99, 102,

105, 107
mediopunctatus 28, 86, 102
merus 91, 93, 102
metaboles 92, 102
minimus 89, 102
minutus 27, 85, 102
multicolor 95, 102
muscivus 95, 102
myzomyfacies 27, 89, 102, 142
natalensis 95, 102
neavei 88
neiriti 95, 101
nigerrimus Giles 27, 85, 102
nigerrimus James and Liston 85,

102
m'^ra 93, 102
nigrans 92, 102
nigrifasciatus 89, 102, 105
nigripes 81, 102
nigritarsis 93, 102
m/j 87, 88, 102
nimba 79, 80, 104
nivipes 91, 92, 104
nursei 89, 104
ocellatus 95, 104
occidentalis 104

INDEX

389

Anopheles palestinensis 89, 104
pallida 80, 104
pallidopalpi 83, 104
paludis 84, 85, 103, 104
paludis var. similis 84, 85, 104
parva 93, 104

peditcsniatus 27, 85, 104, 215
perplexans 83, 104
pharoensis 93, 94, 97, 104, 142
pharoensis var. a/fra 94, 104
philippinensis 91, 92, 104
pictus Ficalbi 85, 104
pictus Lcew 85, 104
pictus Macdonald. 87, 104
pitch f or di 89, 104
plumbeus 81, 103, 104
plumiger 85, 104
pretoriensis 91, 92, 104
pseudobarbirostris 84, 104
pseudocostalis 91, 93, 104
pseudomaculipes 28, 86, 104
pseudopictus 27, 84, 85, 104, 105,

222
pseudopunctipennis 26, 83, 104
pseudo squamosa 95, 104
pseudowillmori 92, 104
pulcherrima 93, 94, 104
punctatus 95

punctipennis Bigot mss. 94, 104
punctipennis Say 28, 83, 101, 104,

141
punctulata 95, 104, 105
pursati 26, 95, 104
pyretophoroides 87, 104
quadrimaculatus 81, 104
rhodesiensis 87, 88, 104
ro5su 26, 86, 90, 104, 107, 137,

138, 140, 215
rossii var. indefinata 90., 104
separatus 85, 104
sergentii 89, 104
simlensis 83, 104
sinensis 27, 83, 84, 85, 97, 101,

103, 105, 106, 107, 141, 215
sinensis var. indiensis 84, 85, 101
smithii 81, 106
squamosus 94, 106
squamosus var. arnoldi 94, 97, 106
stephensi 91, 92, 93, 101, 103, 106,

138, 140, 142
stigmaticus 95, 106
strachani 84, 106
subpictus 95, 106
superpictus 27, 89, 106, 142, 222
tarsimaculatus 27, 94, 106
tenebrosus 85, 106
tcsscllatu))i 95, 99, 106, 107
theobaldi 27, 91, 92, io(>
thonito)!!! 95, 106
tibani 02, 106
tibiomaculata 93, [06

Anopheles transvaalensis 89, 106

treacheri 80, 106

trifurcatus 81, 106

turkhudi 27, 87, 88, 106

umbrosa 87, 106

umbrosus 27, 84, 106

unicolor 106

vagus 90, 106

vanus 85, 106

villosus 81, 106

vincenti 95, 106

walkeri 81, 106

waponi 92

watsonii Edwards 106

watsonii Leicester 95, 10C

wellcomei 95, 106

wellingtonianus 83, io5

willmori James 27, 91, 92, 99, 101,
106, 137, 142

willmori Leicester 92, 106

willmori var. maculosa 106

ziemani 85, 106
Anophelinae 26, 76, 215

Dichotomous table showing natural
grouping of species of 79

Table showing detailed tabulation
of species of 79

Introduction of natural enemies of

151

Measures directed against adult
mosquitoes 151

Obliteration of breeding- places 149
Anopheline-transmitted diseases 119
Anthomyidae 241
Anthrax 3, 31, 379
Antimosquito campaigns 149
Apioceridae 225
Apocampta 231
Aporoculex no
Apotolestes 231
Arista 14

Arribalzagia 77, 78, 79, 85 See
^4 nopheles

maculipes 77, 85
Asilidae 224, 225
^ *Aen£ woe/Ma Blood parasites of 200

Babesia cams 155

Bacillus icteroides 1 8 1

Bacillus X 181

Baleri. General account 332: Ref-
erences to literature on 335
also Trypanosoma pccauJi

Banksnieila 109, ill

Bathosomyia \

Bdellolarvnx 31. 2 13

BtWo 3 j
Bibionidae

Bilious remittent lever >V< Yellow
Fever

390

INDEX

Bird Malaria 196
General account 196
References to literature 199
See also Plasmodium prcecox

Bironella 77, 95 ; see Anopheles
gracilis 77

Biting-Flies as Carriers of Disease 25

Blepharoceridae 33

Blood-sucking Muscidae 241

Bolbodimyia 230

Bombyliidae 225

Brachypteromyia 375

Breeze-Flies See Tabanidae

Boycia no

Cacomyia 109
Cadicera 231
Calvertina 77, 92, 95

lineata 77, 92
Calyptratae 24, 239, 240

Synopsis of families of 240
Cecidomyia 34
Cecidomyidae 33

Cellia 77, 78, 79, 90, 93, 95 ; see
A nopheles

argyrotarsis 90
Celli's formula 124
Ceratopogon 26
Chagasia 77, 95 ; see Anopheles

fajardoi 77
Chalcididae 270
Chaoborinae 76
Chironomidae 26, 33
Chironomus 34
Chcetura pelagica 74
Christopher sia 77, 91 ; see Ano-
pheles

hoc hit 77, 91
Christy a 77, 95 ; see Anopheles

implex a 77
Chrysops 28, 231, 238
Cinchona 120
Cincindela 270
Citronella 319
Classification of Diptera 23
Cleggs See Tabanidae
Ccelodiazesis barberi 81
Commensalism between fungus and

mosquito 68
Conopomyia no
Corethra 76
Corizoneura 231
Crescents 161, 162
Crithidia 7

Culex 2, 62, 63, 109, no, 115, 175,
176, 191, 198

concolor 115

fatigans 1, 28, 115, 122, 195, 196
198, 215

fatigans Distribution of 193

(Leucomyia) gelidus 28, 215

Culex jepsoni 214

malaria 222

(Culicada) nemorosus 28, 198, 199

penicillaris 222

pipiens 28, 62, 66, 70, 71, 115,
198, 200, 203, 209, 215, 222

(Leucomyia) sitiens 28, 215
Culicada 109, 114
Culicelsa 109
Culicidce 13, 17, 26, 28, 33, 50

Affect of colours 68

Biology of adult 67

Circulatory system 62

Classification 75

Definition 50

Digestive organs 56

Egg 62

Enemies of 72

External Anatomy 50

Flight 72

Food-habits 67

Habitats 70

Hibernation 71

Influence of sound on 70

Internal Anatomy 56

Larva 63

Life-cycle 62

Longevity 71

Mating habits 71

Method of feeding 67

Modes of dissemination 70

Nervous system 62

Publications of importance in con-
nection with nomenclature and
systematic work on 115

Pupa 66

References 75

Reproductive organs 61

Respiratory system 61

Resting position 70

Salivary apparatus 59
Culicinae 165, 215

Diseases transmitted by 177

References 177
Culiciomyia. no, 115
Curupira 33

Cyclical evolution of parasites 9
Cyclical transmission 4
Cycloleppteron 76, 78, 84, 85 ; see
Anopheles

grabhamii 84
Cyclops 1 1
Cyclorrhapha 23
Cyclorrhapha Aschiza 24
Cyclorrhapha Schizophora 24, 30,

224, 239

General description 239
Cypriondontidae 151

Danielsia 109
Dasybasis 230

INDEX

39*

Dasymyia 1 1 1
Definitive host 4
Dendromyinae 76
Dengue 28, 190

Causal agent of 192

Distribution and Epidemiology 190

History 190

Mode of Infection 194

References to literature on 196

Synonyms 190
Dermococcus 218
Desvoidya 109, 114
Deuteroanopheles 86
Development of parasite in the in-
vertebrate host 9
Dexiidae 241
Diachlorus 230
Diatomineura 231
Dichelacera 231
Dichoptic 1 3
Dicrania 231
Dipoptena 374

Diptera

Abdomen 15

Alimentary canal of 19

Antennae 14

Classification of 23

Definition of 12

Eggs 20

General description of 12

General morphology 13

Head 14

Heart 19

Internal Anatomy of 19

Larvae 21

Legs 15

Mouth-parts 14

Nervous system 19

Pupa 21

Reproduction 20

Reproductive organs 19

Respiratory system 19

Surface of body 19

Thorax 15

Wings 15
Direct transmission 2
Dixidae },},
Dixinae 76

Dolichopodklae 74, 226
Dolomedes 270
Dorcal&mus 231
Double Quartan Fever 160
Dourim- 136
Drainage 153
Duttoma 109
Dytiscnl.r
Dytiscus 73

Ecculex tog

El Debab z, 233, 235

Elephantiasis 217

Empididae 74, 226
Empodium 15
Entomophtoraceae 58
Epidemic poliomyelitis See Polio-
myelitis
Epipharynx 14
Erephrosis 231
Esenbeckia 232
Eumelanomyia 1 1 1
Eumyiid Flies 24

Feltinella 77, 83 ; see Anopheles

pallidopalpi 77. 83
Filaria 10, 11

Filaria bancrofti 1, 5, 26, 27, 176,
202, 365
Conditions affecting development

in mosquito 214
Description 204
Distribution 203
Effect on mosquito 216
History 203

Life-cycle in mosquito 209
Life-cycle in vertebrate host 206
Pathological effects 217
Periodicity 207
Possibility of another indirect
mode of transmission by mos-
quito 216
References to literature on 219
Synonyms 202
Filaria canis cordis See F. imnutis

diurna 209
Filaria immitis 26, 219
Description 220
Distribution 220
General account 219
Life-cycle 221
Pathogenic effects 223
References to literature on 223
Synonyms of 219
Filaria labiato-papillosa 31, 364
Description 364
Habitat 364
Life-history 364
References to literature on
Synonyms 364
Filaria lou

medinensis 11
noctuna See F. bancrofti
Persians 304
phiUppinensis Sec F.
recondita 223

sanguinis hominum nocturnj
/•'. bancrofti
Filariasis 202
Finlava 109
Fish as mosquito desti
151. 15a

Gad-Flies S« Tabankte

392

INDEX

Gastvophilns 240
Gastroxides 232
Gilesia 109

Glossina 20, 233, 242, 243, 297, 373
and disease 250, 293, 300
Determination of the species of 247
Diagnosis 243
Distribution 247
General description 243
References to literature on 252
Synopsis of species of 248
austeni 248

brevipalpis 31,243,248,249,287,288
Bionomics 288
Description 288
Distribution 288
References to literature on 293
Reproduction 291
Synonyms 288
and disease 292
Glossina caliginea 248
Glossina fusca 248, 249, 288, 315, 322
fusca (Austen 1903) See Glossina

brevipalpis
fuscipleuris 249
Glossina longipalpis 30, 249, 251,
274, 283, 333, 334, 336, 337,

344. 345

Bionomics 274

Description 274

Distribution 274

References to literature on 276

Reproduction 275

and disease 275
Glossina longipennis 31, 243, 249,
286, 288

Bionomics 287

Description 286

Distribution 287

References to literature on 287

and disease 287
medicorum 249
Glossina morsitans 8, 30, 246, 247, 248 ,
249, 250, 251, 272, 273, 306,
3IQ, 315. 320, 322, 325, 326,
327, 328, 329, 330, 331, 333,
334. 336, 337. 338, 345. 347.
350. 352, 353. 355

Bionomics 278

Description 276

Distribution 277

Primary Fly Centres 280

References to literature on 286

Reproduction 283

Synonyms 276

and disease 285

var. pallida 249, 277

var. paradoxa 248, 249, 277
Glossina pallicera 248

pallidipes 30, 249, 271, 305, 329, 330

Bionomics 271

Glossina pallidipes
Description 271
Distribution 271
References to literature on 274
and disease 273
Glossina palpalis 30, 233, 244, 245,
246, 248, 250, 251, 252, 256.
300. 305. 3°6, 308, 315, 318,
319, 320, 330, 331, 333, 334,

336. 337. 338, 342, 344. 345.
347. 348. 349, 35o, 352, 363

Bionomics 260
Breeding localities 268
Description 256
Distribution 258
Internal Anatomy 258
Longevity 266
Natural enemies 269
References to literature on 271
Reproduction 266
Synonyms 256
var. wellmani 257
and Disease 270
tabaniformis 248, 249
Glossina tachinoides 30, 243, 248,
251. 253, 315, 333. 334. 336,

337. 344. 345
Bionomics 253
Description 253
Distribution 253
Prophylaxis against 255
References to literature on 255
Reproduction 255
Synonyms 253

Goniops 231
Grabhamia 114
Gualteria 109
Gyrinidae 73

Hcemamosba See Plasmodium
Hcematobia 31, 243
Hcsmatobosca 31, 243
HcBmatopota 28, 227, 230, 233, 234,

236, 237, 243, 347
Haemogregarines 10
Hcemoproteus 122, 200

columbes 10, 31, 201, 374, 475,

379

General account 379

Life-cycle 380

References to literature on 383
noctucs 28, 380
H cemosporidium See Plasmodium
Haemazoin 127
Halteridium See Hcemoproteus
Haplochilus panchax 152
Harpagomyia 1 1 1
Heptaphlebomyia no
Hereditary transmission 6
Hexatoma 230
Hibernation of Anophelines 144

INDEX

393

Hippobosca 374, 385

and disease 379

maculata 31, 379, 386

rufipes 31, 378, 386
Bionomics 378
Hippoboscidae 23, 31, 372

Bionomics 373

Classification 374

General description 372

References to literature on 377

Reproduction 373

Synopsis of genera of 374

and disease 374
Hispidimyia no
Hodgesia ill
Holoptic 13

Horse-Flies See Tabanidae
Howardina no, 114
Humidity 144
Hydrophilidae 73
Hypopharynx 14
Hypopygium 15

Incubation period 9

Indirect transmission 4

Infantile paralysis See Poliomyelitis

Ingramia in

Inimetoculex 109

Intermediate host 5

Intermittent fever See Malaria

Janthinosoma 109

Kelloggina 34
Kerteszia 77, 95

See Anopheles

boliviensis 77
Kingia 109, 111

Labium 15
Labrum 14
Lalaps 12
Larvae 2 1
Larvicides 151
Lasioconops no
Laverania 90

See Plasmodium
Lebias dispar 150
Leicesteria 109, 114
Lepidoplatys 109
Lepidoselasa 230
Lepidotomyia 109
Leptidae 29, 224, 225
Leptomonas 7, 144
Leslieomyia 109
Leucocytogoon 12, 200, 202, 377

riemanni 28
Leucomyia no
Lice 1 1
Li pop ten a 375
Lis pa sinensis 74

Lonchopteridae 226
Lophomyia 83
Lophoscelomyia 77, 83

See Anopheles

asiatica 77, 83
Ludlowia no
Lunula 13
Lutzia 66, 74, no
Lynchia 10, 373, 374, 375, 383

and disease 377

fcnmea 377, 379

brunnipes 3 1

lividicolor 3L, 375, 377, 379
Lynchia maura 31, 376, 379
Bionomics 376
Description 376
Life-cycle 377
References to literature on 377

penelopes 375
Lyperosia 31, 243, 369

General description 369

Life-cycle 370

References to literature on 372

and disease 371

exigua 31, 361, 371

irritans 370

minula 31, 372

punctigera 370

Maillotia no

Mai de la Zousfana 29, 236

Malaria 26, 27, 28, 119

Bionomics of mosquitoes in relation
to 136

Definition 119

Historical 119

Immunity against 1 }'•

Influences affecting through trans-
mitting host 143

Life-cycle of parasite 125

Literature on

New Aetiological Standpoint 1 2 }

Prevention of 148

Racial tolerance to 147

Reservoirs of 154

Segregation 125, 154

Susceptibility to 14')

Synonyms 119

Tropica See Plasmodium falci-
parum
Malaria and Nonimmune immigi

in relation to man 145
Malarial parasite See /'.

Affect of temperature on De\ 1

raent ol 1 4.3
\-< \ual cycle 126
Development ^i 9exual forms
in blood 129

Intravenous inoculation of 121
Life-cycle of 125

394

INDEX

Malarial parasite

Schizogony 126
Sexual cycle 132
Sporogony 132
Malaya ill
Malignant tertian See Plasmodium

falciparum
Malignant tertian malaria 121
Mandibles 15
Manguinhosia 77, 95
Manguinhosia lutzi 77
Mansonia 115

annulipes 29, 215

uniformis 29

uniformis (? africana) 215
Mansonioides no, 114
Matlazahuatl 178
Maxillae 1 5
Maxillary palps 15
Mbori 236

Mechanical transmission 2
Mediterranean Fever 28
Megarhininae 75
Megarhinus 15, 74
Melanoconion 110
Melaxeny 122
Melophagus 373, 374

ovinus 244, 373
Metanotopsilae 76
Metanototrichae 76
Miasm theory 120
Micraedes III
Microculex no
Mimomyia no, in
Mites 74

Modes of infection 11
Molpemyia 109
Mosquitoes See Culicidae
Mucidus 109, in
Musca domestica 355
Muscidae 13, 30, 241, 373

(Blood-sucking) 241

(Blood-sucking) Synopsis of fami-
lies of 242
Mycetophilidae 33
Mycetophilus 34
Mydaidae 225
Myiophthiria 375
Myodaria 239
Myxosquamus 109
Myzomyia 76, 78, 79, 86, 90, 93, 95

See Anopheles
Myzorhynchella 77, 79, 86, 93

See Anopheles

nigra 93
Myzorhynchus 76, 78, 79, 83, 84, 85

See Anopheles

Nagana 236

General account 328
References to literature on

332

Nagana

See also Trypanosoma brucei
Nemestrinidae 225
Neoanopheles 94
Neocellia 77, 78, 91, 95

See Anopheles
N eomelanoconion no
Neomyzomyia 77, 78, 79, 95

See Anopheles

elegans 77, 95
Neopecomyia 109
Nonimmune immigration 146
Notonotricha 86

See Anopheles

intermedium 86
Nosema 144
Numomyia 114
Nuria danrica 150
Nyssorhynchus 77, 78, 79, 90, 91, 95

See Anopheles

Ochlerotatus 109, 114
Oculeomyia no
Oesophageal diverticula 58

Function of 67
Oestridae 240
Olfersia 374, 375

maura See Lynchia maura
Ophiocephalus 151
Ornithodorus moubata 6
Ornithoeca 374
Ornithomyia 374
Ornithophila 374
Orphnephila 34
Orphnephilidae 33
Orthorrhapha 23

Brachycera 23, 29, 224

Synopsis of Families of 225
Orthorrhapha Nematocera 23

Classification 32

Definition 32

Synopsis of Families 33
Oscillaria See Plasmodium
Oxypterum 375

Paludism See Malaria
Pangonia 28, 231, 234, 235
Pangoniinae 231
Pappataci Fever 26, 44

Causal agent 47

Distribution 45

History 44

Mode of infection 46

Prophylactic measures 47

References 48

Symptomatology 45

Synonyms 44
Pappataci Flies See Phlebotomus
Paraplasma fiavigenum 186
Patagiamyia 76, 77, 78, 79, 82
See Anopheles

INDEX

Pecomyia 109
Pectinopalpus no
Pheidole megacephala 270
Pelecorhynchus 231
Pellagra 26
Phagomyia 109
Philcematomyia 31, 242
Phlebotomus Breeding localities 41,42

Definition of genus 36

Eggs 40

General account 35

Larva 40, 41

Life-cycle of 39

Pupa 41

References 48

Synopsis of species 42, 43, 44

and disease 42

and reptiles 39
Phlebotomus Fever See Pappataci

Fever
Phlebotomus antennatus 43

argentipes 43

cruciatus 44

duboscquii 43

himalayensis 43

intermedins 44

longipalpis 44

major 43

malabaricus 43

mascittii 43

minutus 43, 46

nigerrimus 42
Phlebotomus papatasii 20, 26, 43
Bionomics of 37
Wing venation 36

perniciosus 43, 46

perturbans 44

rostrans 44

squamipleuris 43

squamiventris 44

vexator 44
Phoridae 226
Piroplasma See Babesia
Piroplasmidae 10
Pityocera 231
Plasmodium 10, 181, 196
Plasmodium falciparum 129, 130,
141, 143, 156, 160
Description of 160
Synonyms of 160
Plasmodium malarice 129, 141, 14},
156, 158
Description of 158
Synonyms 158

pr&cox 28, 176, 197, 200

Development in the mosquito
198

relicta See P. />r <-/ .
Plasmodium viva* 129, 141. 143,
155. 10 2, 197
Description of 155

Plasmodium vivax

Distribution 158
Synonyms of 155
Poliomyelitis 31, 365

Causal agent 366

Distribution 366

History 365

Method of infection 367

References to Literature on 369

Synonyms 365
Polyleptiomyia 109
Polymitus 133
Primary Fly centres 280
Pristorhynchomyia 242
Pronopes 232
Proteosoma 1, 122

See Plasmodium prcecox
Protoanopheles 78
Protoculex 109
Protomacleaya 109
Protomelanoconion no
Pseudoculex 109
Pseudoficalbia in
Pseudograbhamia 109
Pseudohowardina 109
Pseudomyzomyia 77, 79, 86, 90

See Anopheles

rossii 77, 86, 90
Pseudoskusea 109
Pseudouranotcenia III
Pseudovacuolae 197
Psorophora 63, 66, 74, 109
Psychodidae 26, 33

Definition 35
Ptilinum 13
Pulex irritans 223

serraticeps 223
Pulvillus 15
Pupa 21

Pupipares 13, 20, 25
Pyretophorus 77, 78, 79, 88

See A nopheles

costalis 88

Quartan Fever See Plasmodium
malaria-

malaria 120
Quinine prophylaxis 153
Quinine treatment of the sick is J
Quotidian malaria See Pla

falciparum

Radioculex no
Rainfall 144

Relations between parasite and

Reservoirs of infection
Rkinomyxa

Rhipiccphalus sicu'.
Rhyphidae 33

30

INDEX

Sabethinae 76, 115
Salticus 74

Sand-Flies See Phlebotomus
Sarcophagidae 241
Sayomyia 76
Scenopinidae 226
Schiner's nomenclature 18
Schuffner's dots 155
Scione 231
Scutellum 15
Scutomyia 109, 114

albolineata 29, 215
Segregation 154
Selasoma 230
Sepsis 240

Seroot-Flies See Tabanidae
Silvius 232
Simuliidae 26, 33
Simulium 26, 74
Sleeping Sickness 300
Definition 300
Distribution 306
History 300
Prophylaxis 315
References to literature on 321
Synonyms 300

See also Trypanosoma gam-
biense and T. rhodesiense
Souma 236, 251

General account 335
References to literature on 339
See also Trypanosoma cazalboui
Spiders 74
Spirochceta 200
duttoni 6, 11
recurrentis 1 1
Stable-fly See Stomoxys
Stegoconops 109

Stegomyia 2, 62, 71, 109, in, 198
216
and dengue 196
africana 113
albocephala 113
albolateralis 113
albomarginata 114
amesii 114
annulirostris 112
apicoargentia 113
argenteomaculata 112
argenteopunctata 114
assamensis 113
auriostriata 113
crassipes 114
desmotes 112
dissimilis 113
dubia 113

ta fasciata 8, 28, 67, 112,
165, 166, 177, 181, 198, 214,
215, 219, 222
Description 166
Egg 172

Stegomyia fasciata

Feeding habits of 170

Fertilization and egg-laying 171

Habitat of 168

Larva 174

Length of life 171

Life-cycle 172

Pupa 176

Synonyms 166

and disease 176
fusca 114
gebeleinensis 112
gracilis 29, 215
grantii 113
hatiensis 114
imitator 113
lilii 112

mediopunctata 113
minuta 114
minutissima 113
nigeria 112
nigritia 113
periskeleta 112
perplex a 29, 215
pollinctor 113
poweri 113
pseudonigeria 112
pseudonivea 113
pseudoscutellaris 29, 112, 175, 209,

213, 214, 215, 216
punctolateralis 114
quasinigritia 113
scutellaris 29, 112, 215
simpsoni 112
tasmaniensis 114
terrens 113
thomsoni 112
tripunctata 114
W .-alba 112
wellmanii 112
Stenopteryx 375
Stenoscutis 109
Stethomyia 76, 78, 79
See Anopheles
nimba 79
Stomoxys 233, 234, 236, 237, 242,

243. 336, 348, 355. 365
General description 355
and disease 361
Stomoxys calcitrans 20, 31, 238, 244,
356, 362, 363. 364, 365. 367,
368, 369

Distribution 357

General description 356

Habits 357

Life-history 358

Methods of destruction 360

Pupa 22

References to literature on 361

and S. m'gra 31
Stomoxys nigra 234, 362, 363

INDEX

Stratiomyidae 225
Streptococcus 218
Stridulating organ $j
Stygeromyia 31, 243
Surra 232, 236, 237, 238

Tabanidae 29, 224, 225, 226

Classification 230

Description 226

Habitat 227

Life-cycle 228

References to literature 239

Synopsis of genera 230

and disease 232
Tabaninae 230
Tabanus 231, 235, 236, 237, 347,

361, 363. 370. 372

\\ ing venation of 17

atratus 29, 238

biguttatus 28, 229, 236

d 1 tee ni at us 29

fumifer 29, 236

'kingi 227, 228, 229

minimus 29, 237

nemoralis 29, 235

par 228, 230

partitus 29, 236

secedens 29, 233, 347

striatus 29, 232, 238

tceniatus 236

tomentosus 29, 235

vagus 29, 236
Tachinidae 241
Tceniorhynchus 109, no, 115

domesticus 29, 215
Tarsus 15

Tertian malaria 120, 155
Thapsia 235
Theobald i a 109, no, 115

annulata 71
There vidae 225

Thermotropism in mosquitoes 67
Three-Day Fever 26

See Pappataci Fever
Tick- Flies See Hippoboscidae
Tipula 34
Tipulidae 33
Transmission, General conditions

affecting 6
Trichogaster fasciatus 132
Trichopronomyia no
Trichoprosoponinae
Trichorhynch us 1 10
Triple Quartan Fever 160
Trypanoso))iata 200

Biological characters -

Classification

•minity reactions

oi genus 293

neral description 204

Key t>> African pathogenic

Trypanosomaia

Mode of division 295

References 299

Sero-diagnostic methods 2
Trypanosoma americanum

boy lei 8
Trypanosoma brucei 1, 9, 29, 30, 31,

235. 270, 27-

294, 298, 323, 328, 344, 363
Mode of Infection 330
Morphology 330
See also Xagana
Trypanosoma cazalboui 9, 29, 30,

236, 250, 251, 252, 25:, -
275, 286, 294, 298, 330, 335,
340, 341, 343, 362, 363

Mode of infection 336
Morphology 336
confusum See T. dimorphon
Trypanosoma congolense 28'

344- 345. 346, 351
General account 351
Mode of infection ^^2
Morphology 352
References to literature on 353
Trypanosoma dimorphon 30, 3]

234, 250, 251, 255, 27V .

275, 286, 287, 299, 342, 340,

35L 362, 371
General account 342
Mode of infection 344
Morphology 344
References to literature on 345
Synonyms 342
Trypanosoma equiperdun:

363
evansi 29, 31, 23' -

361, 362, 363
var. mbori 29, 298
franki 3S4
Trypanosoma gambiense
250, 251

292, 299, 300, 304. 306
323, 350, 363
Life-history in vertebrate 1.

Endogenous cycle
Life-history within the in\
brate host — 1
310
Trypanosoma himoij
S
indie um

muktesj
Try pci'

34'.. 347. 348
Development
•
le of transi

Keferer.

398

INDEX

Trypanosoma pecandi 30, 31, 234,
235, 270, 275, 286, 299, 332, 362
Mode of infection 333
Morphology 333
Trypanosoma pecorum 29, 30, 233,
270, 286, 299, 346, 351
Development within the inverte-
brate host 348
General account 346
Mode of infection 347
Morphology 346
References to literature on 348
Trypanosoma rhodesiense 30, 251,
285, 294, 299, 322
General account 322
Mode of transmission 325
Morphology of 324
References to literature on 328
rutherfordi 384
Trypanosoma simice 30, 286, 296,

299. 353

General account 353

Morphology 353

References to literature on 355

Synonyms 353
soudanense 29, 31, 233, 235, 298,

362, 363
Trypanosoma theileri 31, 374, 379, 384

General account 384

Mode of transmission 385

Morphology 384
togolense 298

iransvaaliense See T. theileri
ugandense 305
Trypanosoma itniforme 335, 341

Mode of infection 342

Morphology 341

References to literature on 342

Trypanosoma vivax 335, 340

References to literature on 34

Trypanosoma vivax Bruce See T.
cazalboui
wrublewskii 384

Trypanosomes 293

Trypanosomiasis 361

Trypanosomiases, Conditions affect-
ing transmission by tsetse-flies 250

Tsetse-Flies 243

Tsetse-Fly Disease See Nagana

Typhus icteroides See Yellow Fever

Udenocera 230
Uranotcsnia 109, 11 1
Uranotaeninae 76
Utricularia 72

Venation 15
Verruga Peruviana

26, 42

Wyeomyia smithii 66

Yellow Fever 8, 28, 176, 177
Causal Agent of 186
Development of virus within

mosquito 187
Distribution 179, 182
Endemic centres of 182
General account and history 177
Immune serum 189
Mode of infection 184
References to literature 189
St Xazaire epidemic 183
Synonyms 177
Vaccination 188
Virus of 10

Yellow Jack See Yellow Fever

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