water plants that choke the creeks, or
igarapes, dividing the various sections
of the town . These creeks also harbored
the remarkable larvse of Mansonia,
which, unlike those of most other
mosquitoes, do not come to the surface
to breathe, but attach themselves to
the roots of floating vegetation, espe-
cially of water lettuce (Pistia stratiotes) ,
cutting the bark of the root with their
sharp air-tubes. The adults of most
IMansonite are severe biters and those
of Mansonia titillans fly considerable
distances often entering houses of
Manaos.
During the short trip on the lower
Rio Xegro and Rio Branco, we became
acquainted with several insect pests not
encountered before. One of these,
which no member of the party is h'kely
to forget, was the minute black fly
locally known as piwn (Svmulium
amazonicum) . It torments the traveler
all day long, but especially in the
morning and before dusk. H. W.
Bates's account of its activities can
hardly be improved upon:
We made acquaintance on this coast (viz.
the southern shore of the Amazon, near the
mouth of the Rio Negro) with a new insect
pest, the â– pium, a minute fly, two-thirds of a
hne in length, which here commences its reign,
and continues henceforward as a terrible
scourge along the upper river, or SoUmoens,
INSECTS AND MAN IN TROPICAL AMERICA
141
to the end of the navigation on the Amazons.
It comes forth only by day, reheving the mos-
quito at sunrise with the greatest punctuaUty,
and occurs only near the muddy shores of the
stream, not one ever being found in the shade
of the forest. In places where it is abundant,
it accompanies canoes in such dense swarms
as to resemble thin clouds of smoke. It made
its appearance in this way the first day after
we crossed the river. Before I was aware of
the presence of flies, I felt a slight itching on
my neck, wrist, and ankles, and on looking for
the cause saw a nunilior of tiny objects having
number of discolored punctures that are
crowded together. The irritation they produce
is more acutely felt by some persons than
others. I once traveled with a middle-aged
Portuguese, who was laid uj) for three weeks
from the attacks of jnilm, his legs being swollen
to an enormous size, and the punctures
aggravated into spreading sores.
I have by no means exhausted the
Hst of the insects of medical importance
which I observed during my short trip
to the Amazon. Enough has been said,
fj.'^^" Deaths, annual/ii in this country, due to Malaria and Intestinal Diseases , and onlu
7.000 due to Railroad Accidents.
5,000 Men died of Fit/ -home Diseases m the
3 00 LUere Hilled i>ij Sjoanish Bullets.
The importance of insects as shown by their e.Tect upon human life. The figures are, of course, only ap-
proximate. From an exhibit in the Hall of Insect Life, American Museum
a disgusting resemblance to lice, adhering to
the skin. This was my introduction to the
much-talk^d-of -pium. On close examination
they are seen to be minute two-winged insects,
with dark-colored bod.v and pale legs and
wings, the latter closed lengthwise over the
back. They alight imperceptibh', and squat-
ting close, fall at once to work, stretching
forward their long front legs, which are in
constant motion and seem to act as feelers,
and then applying their short, broad snouts to
the skin. Their abdomens soon become dis-
tended and red with blood, and then, theii-
thirst satisfied, they slowlj^ move off, some-
times so stupefied with their potations that
they can scarcely fly. No pain is felt whilst
they are at work, but they each leave a small
circular raised spot on the skin and a disagree-
able irritation. The latter may be avoided in
great measure bj' pressing out the blood which
remains in the spot; but this is a troublesome
task, when one has several hundred puncture^
in the course of a day. . . In the course of a
few days the red spots dr}^ up, and the skin in
time becomes blackened wdth the endless
however, to make it quite clear that the
complete control of insect pests in Ihe
tropics is a truly Herculean task. Per-
haps the reader may even have gathered
the impression that the fight is too
formidable for the puny efforts of
mankind. Yet the findings of ento-
mologists have already paved the way
for the ultimate victory, as I purpose
to show by two examples taken from
the history" of yellow fever and malaria.
The conquest of yellow fever and it.>«
far-reaching results in opening up the
tropics would be a fit subject for an epic.
For two hundred years at least this
dreaded disease had caused great loss
of life and much destruction of wealth.
Perhaps the deadliest epidemic that ever
visited the United States was that of
yellow fever in 1878. when in the Mis-
sissippi Valley alone more than thirteen
142
NATURAL HISTORY
thousand people lost their lives. The
Spanish-American War finally focussed
attention upon the need of eliminating
this disease. At the time it was be-
lieved that no newcomer to Cuba
could escape it. During the early years
of the American occupation of the
Shake, from the deep foundations of the world,
Th'imprisoned plagues; a secret venom oft
Corrupts the air, the water, and the land.
It is true that ever since 1881 Dr.
Carlos Finlay had contended, from epi-
demiological evidence, that a mosquito
conveyed the disease, and that he had
Yellow fever is steadily retreating before the attacks of entomologists as is shown by the
blackened areas on these maps. Courtesy of the Rockefeller Foundation
island, all efforts to combat it were in
vain, simply because the relation be-
tween the disease and a certain mosquito
was unknown. At Havana, in 1900,
there were a greater number of cases
than there had been for several years.
At the dawn of the century exact
knowledge of yellow fever was not
much more advanced than when Arm-
strong wrote:
And though the putrid south
Be shut; though no convulsive agony
even positively incriminated the true
culprit, Aedes segypti. But too little
was known at that time of insects as
potential carriers of germs for Finla3^'s
arguments to make much impression
upon the physician. In 1877 Patrick
Manson had shown that a worm, Filaria
hancrofti, which lives in the human
body, develops in the common five-
banded mosquito of the tropics [Culex
quinquefasciatus). So novel was this
discovery that even eminent parasit-
INSECTS AXD MAX IX TROPICAL AMERICA
143
ologists received it with scepticism.
It was not until 189S, when Ronald
Ross, in India, and Grassi, in Italy,
demonstrated that malaria is invar-i-
ahly carried by anopheline mosquitoes,
that the medical world was inclined to
approach the problem of yellow fever
with a more open mind. At Havana,
in 1900, an American Commission,
headed by Dr. "Walter Reed, succeeded
in transmitting the disease from a sick
to a healthy person by the bite of
gnats, Aedes segypti. raised from eggs.
In the course of the experiments several
other impoi'tant facts were discovered.
These, together with a knowledge of the
habits of the mosquito, made it pos-
sible to devise effective measures of con-
trol. Within a few months yellow fever
was eliminated from Havana where it
had existed continuously since 1762,
and where even in 1900 it caused 310
deaths. The last case of the year 1901
occurred in September. Fifteen years
later Colonel Gorgas was able to write
that "with one exception there has been
no case of this disease in Havana since
that date." Nowadavs Havana is a
The yellow fever mosquito. From an
enlarged model in the American ^Museum
much-vaunted winter resort, while onlj'
twenty-five years ago even a brief stay
in the city was regarded as almost cer-
tain death to the outsider.^
'The fascinating storj- of the conquest of yellow fever
may be read in Rubert Boyce's Yellou- Fever and itn
Prevention (New York, E. P. Dutton and Company,
1911.)
A glance at the interesting map re-
cently published by the Rcjckefeller
Foundation (p. 142) clearly indicates
how a knowlodge of the mosquito and its
ways is rapidly driving yellow fever
from the face of the earth. Formerly
this disease was more or less endemic
Mr. Koch-Grlinberg. a member of the
Rice Expedition, who died of malaria, follow-
ing a mosquito's bite. Photograph by Hamil-
ton Rice
along the Amazon: in 1906 it killed
253 persons at Para; from 1893 to
1903 there were 142 deaths from yellow
fever at Manaos and the number in-
creased to 1386 during the brief period
between 1905 and 1913. ]\Ieans of
controlling the transmission of the
disease by the mosquito were then
applied, with the result that only one
fatal case has occurred since at Manaos.
At the time of our ^^sit yellow fever
was utterly absent from the Amazon
Basin, although its carrier, Aedes
segypti. was extremely abundant in all
settlements and on board ship.
144
NATURAL HISTORY
Malaria-ridden Vista Alegre. In the foreground is the expedition's launch, named for
Mrs. Rice. Photograph by Hamilton Rice
With yellow fever so successfully
eliminated, malaria is at present
the foremost sanitary problem of
Amazonia. The ravages of this disease
are not so spectacular as those of yellow
fever, yet they are perhaps much more
important social and economic factors.
A very large proportion of the popula-
tion along the Amazon and its affluents
may be said to be more or less chroni-
cally infected, which goes far to explain
the prevalent lack of ambition and the
physical and mental weakness of the
people. Although with length of time
the adult natives acquire a certain
degree of immunity, thej' still pay a
heavy death toll to paludal fevers.
According to Dr. Alfredo da Matta, the
eminent physician of Manaos, in that
city between the years 1895 and 1914
no less than 12,209 deaths were due to
either acute or chronic malaria, ac-
counting for more than 34 per
cent of the total death rate. Still,
Manaos, Para, and some of the larger
towns along the Amazon maj^ be re-
garded as relatively salubrious, as
much work in sanitation and prophy-
laxis is carried on, while doctors and
hospitals are available for the treat-
ment of cases. Conditions are much
worse in the smaller settlements, and
in certain areas along the Rio Branco
malaria of the most dangerous type is
rife. Brazilian as well as foreign ob-
servers all come to the conclusion that
it is the cause of much poverty and mis-
ery and one of the chief reasons for
the country's economic stagnation.
Investigation has shown that three
factors ai'c needed for the spreading
of paludal fevers: man, the malarial
germ, and an anopheline mosquito.
Malaria is due to a microscopic germ
developing in the blood. In order to
infect another human being, the germ
must pass through an anopheUne mos-
quito, where it undergoes a definite
C3"cle of development. Eventually it
produces a form, which, upon being
injected into the blood by the bite of
the gnat, again causes fever in man.
If any one of the three links of the
chain be broken, the disease is unable to
INSECTS AND MAN IX Th'OI'/CAL AMKUICA
145
A typical scene in a tropical city that has not yet adopted good sanitation
graph by James P. Chapin
I'hoK
propagate and soon dies out. This is
the basic idea underlying all attempts
at controlling malaria. A healthy com-
munity may, for instance, keep out
paludal fevers, even when anophelines
are present, by excluding all infected
outsiders or by isolating them in
screened rooms until they are cured.
Sometimes it is possible to extirpate
malaria from an infected locality by
isolating and curing all cases, thus
preventing the mosquitoes from acquir-
ing the germ. In practice, however, it
has been found that it is difficult com-
pletely to eliminate all human carriers
of malarial germs or to prevent ano-
phelines from becoming infected. As a
matter of personal safety in malarious
countries one should live in mosquito-
proof houses and sleep under a properly
adjusted mosquito bar, — the conopeum
of the Romans; the judicious use of pre-
ventive quinine may also be helpful.
Sanitarians are now fairly well agreed
that in order to eradicate malaria a
relentless and intelHgent war must be
waged against the mosquito carrier.
Undoubtedly in certain regions ano-
phelines are present, while malaria is
imknown, because the disease either
was never introduced or it disappeared
for some reason or other. On the other
hand, we may feel quite satisfied that,
where anophelines are absent, paludal
fevers are not onty unknown but are
unable to attack the inhabitants even
when cases of the disease are intro-
duced from malarious areas. To fight
"From the frying pan into the fire": the
moat protects the tree from leaf-cutting ants
but breeds mosquitoes. Photograph by
James P. Chapin
146
NATURAL HISTORY
the anophelines with any chance of
success, a thorough knowledge of their
habits is a prerequisite. The eggs are
laid singly at the surface of the water,
where they float for a time before
hatching. The larv£e are aquatic, as
are those of non-malarial mosquitoes,
but, unhke these, they lie horizontally
at the surface of the water. The pup®
also live in the water. Both larv« and
pupse are able to move about and to
dive, but they cannot stay any length
of time below the surface without
drowning. It is in the larval and
pupal stages that mosquitoes are most
vulnerable, so that the main efforts
of the sanitarian must be directed
against the breeding places.
The bearings of malaria and other
insect-borne diseases on human culture
and progress are undeniable. Some
years ago, Sir Ronald Ross, while
travehng in Greece, was forciblj^
impressed by the prevalence of paludal
fevers in what was at one time the
cradle of Western civihzation. He
argued that the valleys of Greece in
the time of the Persian wars could not
possibly have been as malarious as thej^
are now\ The disease, he supposed,
entered the country about 500 b.c. or
later, by the introduction of AnoipJieles
macuUpennis or of infected soldiers or
slaves from Asia. It then crept slowly
up the valleys, destroying the rural
prosperity, without which the subse-
quent decHne of the country was but a
matter of time.- I am well aware that
the argument will hardly appeal to the
2The Mstorical foundation for Ross's theory may be
found in W. H. S. Jones's Malaria. A Neglected Factor
in the History of Greece and Rome (1907) and Malaria
and Greek History (1909.)
average historian, especially if he be
imbued with what may perhaps be
called the "race complex." Yet much
might be said to support the biologist's
view that there is " no reason to suppose
that the Roman and the Megatherium
were not struck down by similar
causes" (Ross).
Moreover, whatever lessons the past
might have to teach us, the chief in-
terest of mankind centers in the future.
The time is at hand when the most
progressive races of mankind wiU be
driven by dire necessity to the virgin
fields of endeavor in the tropics. We
are far beyond the stage in which
mere courage and physical strength ful-
fill the requirements of success in
tropical enterprise. The tropics and
their riches will ultimately belong to
those peoples who skilfully apply the
multiijle resources of human knowledge.
To insure a healthy, productive, and
contented fife will be the first problem
to solve. It is therefore safe to predict
that entomology will have an ever-
increasing share in the settlement of
equatorial regions. When one reflects
upon the present importance of the
study of insects in the reahn of theo-
retical as well as of practical science, it
is hard to beheve that twenty-five
years ago entomology was the neglected
stepchild of biology. But, like Cin-
derella, she has come into her own and
begins to receive the homage even of
those who formerly snubbed her.
However, her true triumphs are yet to
come in the tropics, where the struggle
between insect and man assumes a
fierceness not dreamt of by dwellers
in temperate chmes.
<:6^>=^^=)®®®(^^^=0*>
The Friendly Insects^
By frank 1^]. LUTZ
IT is quite natural that the "average
man," whatever that means, thinks
that insects in general are pests.
The only insects which he notices
closely are those that force themselves
into his field of thought by attacking
his prized possessions or even his more
intimate person. It was for this reason
that the Persians considered Beelze-
bub, the "Prince of Insects," to be a
devil, and today ''bug" means some-
thing that does not accord with our
notions of what ought to be, whether
it is 'a man who differs from us in
opinions and hobbies or a flat; brown
creature that Hves in some people's
beds.
Without doubt there are insects
which, so far as man is concerned, are
now unmitigated nuisances. In former
times, however, even some of the most
loathesome of these were made use of.
In the days of Dioscorides "nine bed-
bugs enclosed in a bean" cured fever
and Pliny said that a hen which had
eaten one bed-bug would be immune
for twenty-four hours to the bite of
an adder — a sort of a prototype of
"an apple a day keeps the doctor
away" — but in these enlightened days
we take quinine for fever and we have
found simpler methods of raising
chickens.
However, there are more than half a
million different kinds of insects and the
wholesale condemnation of the class
has been based on sad experiences with
one or two hundred. Is that fair?
And might it not be well to wonder
whether in the remaining hundreds of
thousands we have friends as helpful
as the few which we are forced to notice
are powerful foes? Also, are there
neutrals?
There is almost no mammal, bird,
fish, or any other back-boned animal,
including man, that does not live at
the expense of other living things, plant
or animal. Live by killing or injuring
is the rule of "higher" animals. If
most insects follow the same rule, is
that to their discredit? But there is an
interesting thing about the food of
insects : a given species is quite likely to
have a very limited menu. A rabbit
will nibble any plant that is not actu-
ally distasteful or difficult to chew and
a cat will eat any kind of bird that it
can catch or of mice or of fish or even
of grasshoppers, but it is somewhat
exceptional to find a species of insect
that feeds on anji^hing but closeh^ re-
lated plants, if it be a plant-feeder, or
on an}i:hing but closely related ani-
mals, if it lives on meat. Indeed, some
species of plant-feeding insects confine
their attention exclusively to a single
species of plant and a similar hmited
taste is possessed by many meat-eaters.
Man, either because of his inherent
egotism or for some other reason,
thinks that the world — and, indeed,
the whole universe — exists solely for
him. At the same time, there are many
kinds of plants for which he has no
particular use and the thousands of
kinds of insects which feed on nothing
but these cannot logically be con-
sidered as injurious to him.
Then there are the weeds. " Weed "
has been defined as "a plant out of
place" and man has usually done the
'One of the American Museum's radio broadcasts.
147
148
NATURAL HISTORY
misplacing, accidentally carrying in
his commerce the seeds from one
country, where the plant is controlled
by natural conditions, to another
favoring its immoderate spread. Man
does not like weeds and should be
grateful to the hundreds of different
kinds of insects that feed on these un-
wanted plants.
But what about the insects that feed
on the plants that man does want? It
must be admitted that there are such
''undesirables." I do not know how
many undesirable people there are per
thousand in an average community —
not really criminal but undesirable.
Are ten in every thousand, one per
cent, poor citizens? Well, there are
about 15,000 different kinds of insects
in the general vicinity of New York
Citj'' and less than one per cent of these
can be said to be even moderately in-
jurious to either man's purse or his
person; somewhat less than ''half of
one per cent" are, however, decidedly
injurious, so injurious that man must
fight them vigorously.
Where did these three or four dozen
different kinds of insects that threaten
our very existence come from? Almost
every one is a "weed," a creature that
is out of place because man has brought
it in his commerce from some other
country to this one: gypsy moth,
Japanese beetle, European corn borer,
Hessian fly, San Jose scale, and so on, to
say nothing of the domestic roaches,
house-flies, bed-bugs, and the like.
The gypsy moth is only moderately
destructive in its native Europe and
the Japanese beetle does no more harm
in Japan than do many of our closely
related "June beetles" here. Why
should the foreigners multiply so
mightily in the United States? With-
out showing how one factor after
another cannot explain the phenom-
enon, we may come immediately to
the point that, when man introduced
these insects, he failed to introduce
other insects which preyed upon and
kept them in check in their native
homes.
De Morgan (Swift wrote nearly the
same thing) was speaking in the direc-
tion of the truth when he said:
Great fleas have little fleas upon their
back to bite 'em.
And little fleas have lesser fleas and so
ad infinitium.
And the great fleas themselves, in turn,
have greater fleas to go on;
While these again have greater still, and
greater still, and so on.
Literally thousands — how many
thousands we do not yet know — of dif-
ferent kinds of tiny insects obtain their
entire food by eating and killing other
insects. Very few birds live exclusively
on other birds; very few fish live ex-
clusively on other fish; but relatively
few meat-eating insects feed on any-
thing except other insects. On the
other hand, there are few, if any,
plant-feeding insects that do not suffer
from the attacks of these parasites or
predators. That is the reason that our
native plant-feeders are rarely seriously
injurious and then not for long; there
is a " balance of nature " when man does
not upset it. This balance may swing
back and forth, as in the case of the
Tent Caterpillar, but it is there.
Now, when man's commerce brings
a plant-feeding insect to this country
from its native land, the insects which
preyed upon and kept it in check there
are left behind. The plant-feeder finds
itself in a land of plenty free from any
effective enemy. No wonder that it
multiplies if the climate and food are
at all suitable. What is man to do
about it? Man upset the balance of
nature; let him try to restore it by
importing the particular kinds of
THE FRIENDLY IX SECTS
149
insects friends tliat, all unobserved by
him, were fighting his battle for him
in the count ly from which the pest
came. This is not always easy to do,
since the parasite, despite what De
^Morgan and Swift thought, frequently
has no insect parasites from which it is
friendly insects tliat are keeping our
native plant-eaters from nmltiplying
to such an extent that our country
would become a barren waste unable to
support either beast or man.
Then, there is another thing. Sup-
pose a body of men were to say to the
Leaf-feeding caterpillars bearing on their backs the cocoons of the parasitic wasps that
keep them in check. From the film "Winning the Insect-hfe Merit-badge''
relieved when brought here, and so it has
all the disadvantages of meeting a new
environment without lea\dng the com-
pensating advantage of unusual free-
dom. If, as sometimes happens, these
''little fleas have lesser fleas," it is to
our interest to find this out and care-
fully avoid bringing our friends' ene-
mies here.
Our Govermiient has been doing just
these things and with marked success.
The work should be heartily supported
but the reason for mentioning iL here is
to emphasize the fact that we owe our
lives to thousands of kinds of insects
that are in our gardens, our meadows,
and om- woods, — to thousands of
rest of us that they would make it
possible for us to have delicious fruits
and beautiful flowers but in return their
relatives would take, say, twenty- per
cent of the fruits and flowers they make
possible. Suppose we could not get
fruits and flowers in any other way.
Would we consider that body of men or
even their relatives unfriendly because
of the twenty per cent commission?
Scarcely, although we might try to beat