blooded animals must be made also of
the insects if we are to begin to know
them as they should be known and
if we are ever to control them. How
can such vitally necessary work be
done?
One cannot blame a busy Congress,
harassed bj^ the insistent urge of the
country's crying needs, absoi'bed in its
efforts to respond to the most urgent,
the most immediate of these needs,
without compromising the financial
position of the public treasury, if it
fails to do more than try to meet situa-
tions as they exist at the present mo-
ment. There is no present hope, then,
from government.
But there should be a permanent
foundation for the study of the funda-
mentals of insect life, administered by
the Smithsonian Institution possibly-,
or possibly in some other way. Such a
foundation should organize a large
group of the best-trained men, who
should be charged with the careful
study of every phase of insect life from
the chromosome to the last reaction of
the adult throughout the enormous
range of variation that exists in this
now almost mysterious insect complex.
From the work of such a group of
men would come ultimately a wealth of
knowledge that would enable civiUzed
man to fight his worst enemies, not
half blindly as now, but with a perfect
understanding of everything about them.
An enlarged photograph of the
Cotton-boll Weevil, a Mexican insect
that has invaded southern United
States
With such knowledge, the control of
insects may possibly prove to be a
comparatively simple thing. Without
it, we are working more or less in the
dark.
The Pariina Rivernear the terminus of the Rice ExpecUtion. Ph()t()nrai)h 1)\ Ilainilinn Rice
Insects and Man in Tropical America
IMPRESSIONS FORMED ON A JOURNEY TO THE RIVER AMAZON" AS
ENTOMOLOGIST OF THE THIRD HAMILTON RICE EXPEDITION
By J. BEQUAERT
Department of Tropical Medicine, Harvard Medical School
Theodore Roosevelt said, on his return from South America, that the most dangerou-s
animals he met were insects. Doctor Bequaert is an international authority on these foes of
man's health and vividly describes them here. However, as he shows, the case is far from
hopeless and we may look forward to the day when "'jungle peril" will be a thing of the past.
— The Editor.
DURING the summer of 1924, I
was given the welcome oppor-
tunit}^ of visiting the River
Amazon, a region of unusual fascina-
tion to the naturalist. The party to
which I was attached as entomologist
was organized by the department of
tropical medicine of the Harvard
University ]\Iedical School, under the
leadership of Dr. R. P. Strong. It was
itself the medical branch of the Third
Hamilton Rice Expedition to South
America. It is characteristic of the
rapid growth of medical entomology
that nowadays no medical expedition
to the tj'opics deems it feasible to dis-
pense with the services of an entomolo-
gist. A brief narrative of my experi-
ences in South America will, perhaps
better than an academic disquisition,
make it clear why so much importance
is attached at present to the investiga-
tion of insects in their relation to health.
The main purpose of Doctor Rice's
expedition was a geogi-aphical siu'vey
of the Uraricuera and Parima I'ivers,
which form the western headwaters of
the Rio Branco, on the borderland
between Venezuela and Brazil. This
objective was successfully reached by
Doctor Rice in the early part of 1925,
though not without much hardship
and danger. Lack of time, however,
prevented most of the medical party,
including myself, from traveling beyond
Caracaraj^, a small Brazilian settle-
ment at the head of steam navigation
on the Rio Branco.
On the evening of June 25, I sailed
from New York on a steamer of the
Booth Line, and early in the morning
of Juh' 11 sighted the coast of Brazil,
133
134
NATURAL HISTORY
at the mouth of the Para River,
where I joined the rest of the party.
A modern liner on the high seas
is probably the last spot an ento-
mologist would choose as a promising
field for research. Yet a little investi
gation of forecastle, hold, or pantry
discloses the presence of many insects
that either have elected the vessel as a
permanent abode or travel as stow-
aways, having gained access acci-
dentally in merchandise or supplies.
I do not refer here to any of the few
insects of unsavory reputation that
insist upon claiming man as their
closest friend. I wish rather to call
attention to a multitude of stragglers
of. more independent habits: beetles
whose grubs live in foodstuffs, in tim-
ber, or in raw materials; roaches that
pilfer the provisions; ants that nest in
hidden corners and make steady raids
upon the pantry ; flies that bite animals
and man or whose maggots thrive in
refuse; parasitic wasps that merely
prey upon their neighbors; and many
others. This assemblage of insects,
highly artificial to be sure, neverthe-
less is unique in that its members are
all domestic; having adapted their
habits to those of man. They form a
true entomological underworld, with
all the cunning and endless ramifica-
tions the word implies.
Ever since the early Egyptians and
Phoenicians raised shipbuilding and
navigation to an art, insects of many
kinds have traveled back and forth
between the continents. The opening
up of the route to India and the dis-
covery of the Americas gave a tremen-
dous impulse to these exchanges, which
became still more frequent after steam
navigation and railroads practically
annihilated distances. Some insects
have now become such thorough cos-
mopolites that their original home is as
difficult to trace as the ancestrj' of the
American Indian. The whole subject
is of much interest to the biologist: it
not only gives a clue to the present
world-wide range of certain insects,
but incidentally throws much light
upon the problem of migration and
upon the various ways in which ani-
mals become adapted to a new environ-
ment.
Moreover, insect tramps are of fore-
most importance to the sanitarian,
since they are so often instrumental
in the spread of epidemics. It is no
longer necessary to dwell upon the
transmission of plague by rat fleas
and the role ships play in carrying this
dreadful scourge into healthy territory.
Perhaps it is not so clearly realized
that the yellow-fever mosquito (Aedes
segypti, or Stegomyia fasciata, as it is
more commonly known by medical
men) and the disease which it trans-
mits owed their wide extension in trop-
ical and subtropical regions to trans-
portation by ships. From the fifteenth
century to the present day yellow
fever was one of the diseases most
frequently afflicting those traveling by
ship, so much so that it was familiarly
known as "ship's fever" or "yellow
jack." Everybody who has visited
tropical harbors knows from experi-
ence that mosquitoes readily enter
ships that are at a wharf or along-
side lighters that come from the
shore. But, while most of the species
disappear soon after the vessel leaves
port, living Aedes segy-pti may be
carried great distances. Repeatedly
they have been found alive in temperate
harbors even on modern steamers
coming from mosquito coasts. In
the old days of sailing-ships, the
damp, dark, and stuffy living quarters
offered almost ideal conditions for the
adult yellow-fever gnat. In addition,
INSECTS AND MAN IX Th'oriCAL AMERICA
135
it could breed freely during (he voyage
in the storage tanks and casks, or in
the rain collected in a sail, wiiich \v(M-e
then the only sources of di'inkiug water.
Indeed, the transmission of yellow-
fever from port to port was clearly
recognized long before the role of the
mosquito became known. The slave
ships were looked upon with particular
suspicion and one well-meaning writer
even stated that yellow fever was the
price Europe paid for the slave trade.
There can be little doubt that the
yellow-fever mosquito was carried by
ship from West Africa, probably its
original home, to the Americas, where
it is now found in the tropical and sub-
tropical parts; along the Amazon and
its affluents it has extended as far as
steam navigation reaches. Since, once
infected with yellow fever, Aedes
aegypti may transmit it to man for at
least from fifty to sixty days there-
after, the rapid spread of the disease
over a large territory is easily under-
stood.
After a long ocean journey the
approach to a new tropical coast has
for the naturalist a charm of its own,
compounded of a peculiar mixture of
glad excitement over having reached a
promised goal and of subdued anxiety
before the mysteries of the unknown.
Many subtle influences seemingly con-
spire to render it an experience not to
be forgotten. My first acquaintance
with Brazil was no exception to the
rule. For some hours before we
descried the coast, turbid waters,
unwilling to lose their identity in the
brine of the ocean, had heralded the
river of the legendary Amazons. A
soft, strangely scented land breeze
greeted us long before the low shores
began to show as dim specks at the
horizon. With dawn we found our-
selves entering the broad estuary of the
Parn i^ver and soon the first messen-
K('i's \'y t he tropical land came aboard :
large liMU'k inotlis and elegant l)utter-
fli(>s grax-efully fluttered over the decks,
and swift dragon flies I'csted for a while
in the riggings. As the shij) closed in
on the shore, insect life became more
obtrusive: soon the first hoi-seflies
were netted, while a good-sized, black
Animnphila wasp caused some commo-
tion by stinging one of the lady passen-
gers without the slightest provocation.
Thus, in various ways Nature warned
us that we were about to enter the
domain not of man but of the insect.
Soon the white towers of the cathe-
dral of Belem do Para (as the city of
Para should properly be called)
appeared above an agglomeration of
low houses. We passed an old, circular
fort of red bricks, built upon a rock in
midstream, and entered port. Even-
tually, after the tedious formalities of
debarking, we were installed at a
comfortable hotel. Here none of the
windows were screened and no mos-
quito bars were provided in the rooms.
We were confidentlj' told that mos-
quitoes were unknown and, as a matter
of fact, owing to the drought prevailing
at the time, very few of them were in
evidence. We devoted the next few
days to the fauna and flora of the
vicinity. Although we found much
to interest us, the localitj^ is no longer
the naturalist's paradise described in
such glowing terms by H. W. Bates.
The reason is not far to seek. At
Bates's time Para had a population of
less than 20,000 inhabitants, while
today it has more than 200,000 and
extends over a large area. On our very
first walk we became acquainted with
that minute, but extremely trouble-
some pest of the American tropics
known as the red-bug or harvest mite,
commonly called ''chigger" in the
136
NATURAL HISTORY
United States and "mucuim" in Brazil.
These mites are the larval stages of
certain species of Trombicula, the adults
of which are much larger, velvety
red, predaceous creatures. The red-
bugs themselves are extremely minute,
generally bright red, spider-like, six-
legged creatures, just barely visible to
the naked eye. They often occur in
abundance on low vegetation, particu-
larly in pastures, in certain cultivated
fields, and in waste places covered with
rank weeds. Here they await a chance
to reach the body of some animal on
which they suck blood for a time.
When they find their way to man, they
attack the skin, causing intolerable
itching, followed by papules surrounded
by red or violaceous spots. In certain
persons who are particularly sensitive,
the effects may be extremely serious.
There is no evidence that the American
red-bugs carry a specific disease, but a
species in Japan, Trombicula akamushi,
transmits the tsutsugamushi, or Jap-
anese flood river fever, from a rodent
to man.
Our stay at Para was all too brief.
Late in the evening of July 19 we em-
barked on a steamer of the Lloyd
Brazileiro for Manaos. The next
morning found us travehng through
the Furo, or Narrows, of Breves, a
series of winding channels, two hundred
to three hundred fifty yards wide,
which connect the estuary of the Para
and Tocantins with that of the Amazon.
The low, muddy banks, periodically
flooded by the tide, are densely covered
with a maze of luxuriant vegetation,
where the crude huts of the cahoclos,
or half-Indians, nestle between the
dehcate fronds of elegant assahy palms
(Euterpe). The whole region is, how-
ever, very unhealthful and a hotbed
of malarial fever, so that we were
glad to leave it before sunset and
to enter the southern l)ranf'h of the
Amazon delta.
For the next three days we feasted
our eyes upon the glorious scenery of
the mightiest river of the world and,
in the cool, breezy evenings, enjoyed
the magic of the brief tropical twilight.
This monarch of rivers is so wide and
deep and carries such a huge volume of
water that, were it not for the speedy
current, one might easily mistake it for
an inland sea — the Rio Mar of the
Portuguese. Although innumerable
low, marshy islands generally, obstruct
the view of the main banks, there are
many stretches of open water eight
miles or more in width, where both
shores are barely visible at the same
time. When the ship followed the
banks, we could study the vegetation
at leisure. The immensity of the
Amazonian forest is proverbial and
somewhat appalhng to the newcomer.
Its dangers, imaginary and real,— the
worst of which is perhaps famine —
seem to produce a kind of mental
paralysis upon the mind of the aver-
age explorer, who all too readily
describes it, with Alberto Rangel, as a
" green Inferno. ' ' Throughout the low-
lands of Amazonia the vegetation is
generally a rain forest perennially
green. The most striking points of
difference from temperate woods are
the huge dimensions of many of the
trees; the unchecked growth, most of
the plants being evergreens and very
few of the trees ever shedding all the
leaves at once; the endless variety of
the flora; the abundance of creepers, or
lianas, and of epiphytes, or air plants;
the predominance of certain strange
trees, such as pahns; and finall}^ the
almost total absence of grasses. In
Amazonia, however, as elsewhere in the
tropics, there are three quite distinct
types of forest, each with its own inter-
INSECTS AM) MAX /.V Th'ol'/CAL AMERICA
137
est foi- tln" iiat ui:ilist aiul willi its
peculiar pioMcins \\)v the sanitarian.
Second growl li, <)!â– stH-oiuhiry I'oi-cst,.
is the typ(> which (he newcomer to
Amazonia is most apt to meet first,
and it unfortunately is th(> poorest of
the three. It is found in the neigh-
borhood of all towns and viHages,
where at one time or another the
primeval forest was cleai-ed awa>' by
man to make place for crops or to
furnish firewood or timber. When such
areas are permitted to return to the
wild state, they are not at once re-
claimed by the oiiginal virgin forest,
but they rapidly develop a pecuHar,
artificial plant growth, where the trees
are much less varied than in primary
rain forest, never reaching large dimen-
sions, while the undergrowth tends to
become an impenetrable jungle. In
Brazil such second-growth woods are
usually marked by dense groves of
trumpet trees or imbaubas (Cecro-
pia), which shelter stinging ants in their
hollow trunks. Favorable breeding
places in profusion are here provided
for hosts of mosquitoes, especially for
malaria-carrying anophelines, in the
stagnant, grass-grown rain puddles, in
the swampy glades, in holes of decay-
ing tree stumps, and similar places.
During, the day the insects hide in the
dense weeds and in the evening migrate
to the near-by human settlements.
The "jungle" at the outskirts of towns
is perhaps the most troublesome prob-
lem confronting anyone attempting to
control the mosquito pest in the tropics.
Too often the expense involved in
ehminating all breeding places in the
surrounding second growth is out of all
proportion to the size of the town.
As one travels along tropical rivers,
one has many opportunities of study-
ing another type of rain forest, known
to botanists as inundated forest. It
(•()\(Ms all tiiosi'strctclicsof alluvial, low
coiiiiliy that are periodically flooded
l)y tile I isiiiir rivers oi- by the rains and
that remain iiiidei- water for weeks or
months. In Amazonia such (looded
forests genei'ally go l>y the name of
igapo or {lapo, while the allu\ial areas
which th(\v c()\-er aic calle(| mirzeas.
The water-logged condition of the soil
excludes most of the ti-ees that grow in
primary rain forest on high, dry ground.
On the whole, the vegetation does not
reach any considerable height; but,
on the other hand, it grows quite close,
and the numerous intertwining lianas
and spiny creepers transform such
growth into an almost impenetrable
thicket. The unusual extent of igapo
forest is one of the most striking
pecuHarities of the Amazon Basin.
At the season of highest water, when
the Amazon rises fifteen to forty feet
above its lowest level, the whole alluvial
valley forms, as it were, a major bed
to the river, some fifteen to thirty miles
wide, where the current flows swiftly
between the very trunks of the trees.
It is then possible for canoes to travel
through the forest and pass across-
country from one affluent to another.
When the flood slowly subsides, it
leaves behind many pools and even
small lakes partly choked with floating
plants. The stagnant water as well as
the muddy shores form ideal breeding
grounds for hordes of biting insects.
Here originate myriads of winged pests
that assail the traveler on the rivers
or the venturesome camper on the
shores: mosquitoes, or mrapo/zas, some
of which (Psorophora) bite during the
day and are replaced at night bj' other
kinds (Mansonw); sand flies, or
mundm, particularly objectionable on
account of their minute size, which
facihtates their attacks, and their
persistence at dusk and dawn; and
138
NATURAL HISTORY
horseflies, or viutucas, of many species.
Even the most fastidious tourist, who
merely gathers his impi-essions of
Amazonia from a comfortable deck
chair, does not fail to make the acquaint-
ance of the little mutuca known as
caho verde (Lepiselaga crassipes). This
pernicious insect is probably respon-
sible for more bad language than any
other of the multifarious pests of
tropical America. It is about the size
of a house fly, black with clear wing-
tips, a sprinkHng of bright green scales
over head and thorax, and eyes curiously
checkered in zigzag fashion with green,
blackish purple, and bright violet blue.
Its flight is so silent and it settles so
cautiously that it generally takes its
\dctim unawares. It always reminded
me in this respect of the much-dreaded
tsetse fly of African rivers. Sometimes
the bite is hardly perceptible, but
generally it feels Hke a sharp prick of a
pin. The bitten spot swells to a large
wheal and produces intense itching,
which may last for a long time. Often
a drop of blood trickles from the gash
made in the skin by the sharp proboscis.
It is fortunate that this fly does not
carry the germ of any disease, at least
so far as we know at present.
I regret to Q&y that I cannot give a
first-hand description of the third
and most interesting type of Amazonian
forest, namely, the \drgin or primary
rain forest of the upland, or what the
Brazihans call terra firma. I had no
occasion in Brazil to visit any point
away from the rivers, where the forest
had not been spoiled at one time or
other by the destructive activity of
man. From accounts by creditable
and experienced observers, such as Ule
and Le Cointe, I judge, however, that
the characteristics of primeval Ama-
zonian woods are not very different
from those of tropical African forests,
which I visited some years ago. The
immense trees, like huge pillars of a
lofty cathedral, rise from a hundred to
a hundred fihy feet in height and
support a dense canopy of foliage,
through which the fierce rays of the
tropical sun are filtered into myriad
beams of subdued Hght. The under-
growth of small trees and bushes is
rather scattered; and, as the floor of
the forest bears but few and low herba-
ceous plants, it is not so very difficult
to walk between the trees. The only
serious obstacles that impede one's
progress are the many fallen trees
and partly decayed stumps. More-
over, if one dares to straj^ away from
the beaten path, one is soon hopelessly
lost in the seemingly uniform maze,
unless one has acquired through long
experience the Indian's astute sense of
direction. An overawing silence gen-
erally reigns, and one meets but rarely
with wild animals or even with birds.
These higher forests are the most
healthful part of the country and rela-
tively free from insect pests. They,
harbor, however, the small tatukira
midge (Phlebotomus), which infects
man with the germs of cutaneous leish-
maniasis, a grave skin-disease of the
South American forests.
In spite of its many discomforts and
dangers, there is much of real beaut}'
in the equatorial forest. To me it is a
source of perennial surprise that poets
have so seldom been inspired by the
glory of the tropics. The splendor of
the "grandiose equatorial vegetation,
as it sprouts from a soil drenched with
storms and unfolds its evergreen foliage
in the scorching fight," would, it seems,
suffice to fire the imagination. Let us
hope that some future Byron will do it
justice! Perhaps the very complexity'
of equatorial nature baffles the mind
and hinders the flight of Pegasus, for
INSECTS AM) MAX /.V TUol'lCAL AMERICA
139
nowluMi' is Cioetlic's saying muix' Unv It is ;i typical tropical city, with many
that "ono sees only what one knows." ol tlic iiii.<aiiilai_\ conthtions and not a
That part of the rivei' known as the few of the discomforts which one ex-
Lower Amazon extends from the pects of such phices. It is only fair to
estuary to the coiifhieiice of the ]\io add that, through the efforts of some
Negro. It is a stretch some 1.1 00 miles far-seeing citizens, there is promise of
long. navigal)le at all times for .sea- improvement even in matters of hy-
L.
^
, â– -^
^"H '
A pool at Manao.s that is well suited to the needs of mosquitoes. Photofiiiaph by
Ralph Wheeler
going vessels. Thus the very center of
Amazonia is placed in direct connection
with all the ports of the world. The
focus of Amazonian trade is Manaos,
situated three degrees south of the
equator, on the left bank of the Rio
Negro, about six miles from the main
Amazon. Although founded in 1669,
it w'as still a small town of 5,000 in-
habitants or less at the time Wallace
and Bates visited it. Owing to the
growth of the rubber trade, it has be-
come during the last thirty" 3'ears a
city of considerable importance, and in
1914 the population was estimated as
between 60,000 and 70,000. At .present
it is struggling through a period of
dechne, but its central location in one
of the richest natural regions of the
world vouchsafes its future prosperity.
giene. Here as elsewhere, even in more
enhghtened communities, the chief
struggle is against the apathy and
ignorance of the mass of the popula-
tion, who seemingly attach more im-
portance to poHtical squabbles than to
the care of health.
I was not disappointed in my expec-
tation of finding at Manjios much of
interest in the entomological hne, even
though the original vegetation has ])een
wantonly destroyed for many miles
around the town. The region appears
to offer an environment particularly
favorable to mosquito Ufe, for no less
than thirty-two species of these insects
are already known from the town and
its immediate vicinity. Perhaps the
most common of them is the yellow-
fever mosquito {Acdes segypii), which I
140
NATURAL HISTORY
On an upper branch of the Rio Branco. Black flies breed here in countless numbers,
their larvae clinging to the stones in the swift rapids. Photograph by Hamilton Rice
found breeding in most of the freely
exposed receptacles containing pure
water, especially in tanks of drinking
water. The five-banded mosquito
{Culex quinquefasciatus) preferred dirt-
ier water, but was hardly less abun-
dant. Adult malaria mosquitoes, or
anophehnes, were rai-e, their develop-
ment seemingly checked by the
drought; but I found their larvae in
large numbers floating between the