INSECTS AND HEALTH
=Malaria or Chills and Fever.=--Malaria is a disease in which the
patient usually has a chill followed by a fever at the same time each
day or every other day. Thousands of people suffer from this sickness
in the warm parts of our country and hundreds of them die every year.
In some regions people cannot live because this sickness attacks every
one who comes there.
Many years ago a doctor found in the blood of malaria patients tiny
animals. He thought that they might be the cause of the illness, but
he could not find out how they got into the blood.
=Finding out how Malaria Germs get into the Blood.=--It had been
noticed for many years that mosquitoes were always found wherever
there was malaria. In the year 1900 two men decided to find out if
they could live in a malaria region and not have the disease when the
mosquitoes were kept from biting them.
[Illustration: FIG. 73.--Position of the common humpback mosquito at
rest with body full of blood sucked by thrusting the bill into the
flesh.]
They made their home a whole season in a cottage in the midst of many
persons who were sick with malaria. They breathed the same air, ate
the same kind of food, and drank the same kind of water as those who
suffered from the disease, but they remained well. The only thing that
they did different from those who got sick was to keep the mosquitoes
out of their rooms at night by means of screens. This experiment and
many other studies have shown that we catch malaria only by the bites
of mosquitoes.
[Illustration: FIG. 74.--Position of the malaria mosquito at rest.]
=Only a Few Mosquitoes carry Malaria.=--Malaria is not common in all
regions where mosquitoes live, and it has been found that only one
group of mosquitoes carries the germs. The two common groups are the
straight-backed and the humped. To prove that the straight-backed ones
did the harm several of them were allowed to suck blood from a man
sick with malaria in Italy. They were then sent to London and let
bite a healthy man. In a few days he became sick with malaria. Many
experiments with the humped-back mosquitoes, found nearly everywhere
in our country, show that they do not carry malaria germs.
=Yellow Fever.=--Until 1901 yellow fever was the scourge of many
cities in the South. Thousands of persons lost their lives from it.
Wherever the dread disease broke out in a city many persons would flee
to the country because they thought that they could not breathe the
air without getting the germs.
Some persons thought that mosquitoes might cause the disease, and in
1900 experiments were carried out in Cuba to learn whether mosquitoes
really did carry yellow fever germs. Seven men made their home in a
room well screened to keep out the mosquitoes. They used clothing
which had been worn by others sick with the fever and even slept on
pillows and blankets on which yellow fever victims had died. Many
persons thought that these bedclothes were full of fever germs and
that all the men would surely get the disease. Not one of them,
however, got sick although they lived in the midst of these soiled
materials for three weeks.
[Illustration: FIG. 75.--The yellow fever mosquito biting the finger.
Note how the lower lip is bent.]
Seven other men were chosen for another experiment. A large room was
prepared and made thoroughly clean. Only clean bedding and clean
clothes were used. The men were given pure food and pure water, but
into the room were let loose mosquitoes which had been sucking blood
from a person sick with the fever. In a few days six of the seven men
became sick with the fever and one of them died. From these
experiments and other studies we now know that _this dreadful fever is
carried from the sick to the well only by the bites of mosquitoes_.
[Illustration: FIG. 76.--A bunch of mosquito eggs floating on the
surface of the water. Enlarged about fifteen times.]
=How Mosquitoes Live.=--Before we can get rid of any pests we must
know where the eggs are hatched and the young pass their early life.
The eggs of mosquitoes are laid on standing water. The water may be in
an old tomato can, a rain barrel, a cistern, or a large pond. A day or
two after the mother lays one or two hundred eggs, they hatch into
dark, wriggling objects called _wigglers_. In from ten to twenty days
later they change into flying mosquitoes. These habits of life show
that the easiest time to kill them is when they are young.
[Illustration: FIG. 77.--Photograph of wigglers, the stage in which
the mosquito lives a week or two in water.]
=Getting rid of Mosquitoes.=--During warm weather mosquitoes cause the
death of more than a thousand persons in the world every day besides
making many others very sick. To get rid of mosquitoes is to prevent
sickness and death. In one year yellow fever killed over five thousand
people in New York and Philadelphia because the doctors did not know
how to stop the disease from spreading.
When this fever broke out in New Orleans in 1905, less than five
hundred persons died of it because the doctors had then learned that
the disease is spread only by the yellow fever mosquito. They
therefore began killing the mosquitoes. Kerosene was poured over all
the ponds and stagnant pools of water which could not be drained. This
kills the young mosquitoes because the oil gets into their breathing
tube which they stick up to the surface of the water to get air. All
rain barrels and tin cans were emptied and cisterns were tightly
covered. Men, women, and children worked week days and Sundays killing
mosquitoes because they knew that they were saving human life. The
destroying fever was stopped.
[Illustration: FIG. 78.--Photograph of eggs laid on waste matter by
two flies in one hour.]
=Flies cause much Sickness.=--Very few people are afraid of house
flies because they do not bite. Although they are so small and
seemingly harmless yet we know that they cause many more deaths every
year than mad dogs, poisonous snakes, and all wild beasts.
Flies crawl around among slops, in spittoons, and in other unclean
places. In this way they get thousands of germs of tuberculosis,
typhoid fever, and cholera on their feet and then scatter them over
our food as they crawl about on the table, in the grocery store, or
among the milk cans. In our last war with Spain more than a thousand
of our soldiers were made sick with fever carried to them by flies.
In Denver, Colorado, in 1908 fifty persons were made sick with the fever
by flies which fed on the slops from a sick room and then crawled
around in the milk cans from which those who became sick used milk.
[Illustration: FIG. 79.--Photograph of the worm stage or larva of the
fly at the left and three of the sleeping stage or pupae at the right.
Twice the natural size.]
=How to fight the Flies.=--House flies lay at one time about one
hundred eggs in the dirt thrown out of horse stables, in garbage cans,
or in any other unclean place. In a day or two the eggs hatch into
little white worms which feed on the dirt. One or two weeks later the
worms change to flies.
Flies may be kept out of houses by putting screens in the windows and
doors or by darkening the rooms when they are not in use. The few
which gain entrance may be caught in fly traps. All food in the store
or the home should be kept covered. It is not safe to eat candy on
which flies have wiped their feet or to drink the milk in which they
have washed them.
[Illustration: FIG. 80.--Photograph of a half handful of manure which
had been thrown out of a horse stable. Note more than one hundred
houseflies in the sleeping stage.]
The surest way to get rid of flies in any community is for all the
people to work together and keep the entire neighborhood clean. No
dead grass, weeds, or rags should be allowed to lie in the backyards
or alleys. The cleanings from stables should be hauled away every
week or stored in tightly covered boxes. Garbage cans must have
close-fitting lids, so that there will be no place in which the young
may hatch and grow.
=Other Insects which carry Disease.=--In certain parts of Africa, the
_sleeping sickness_ has made ruins of prosperous villages. Thousands
of the natives are dying yearly from this disease. The germs are
carried from one person to another by the bite of a fly.
Some fleas carry the germs of _plague_, which a few centuries ago
swept across Asia and Europe destroying hundreds of lives daily. The
plague is now common in India and was present in California in 1908
and 1910. The bedbug spreads several kinds of fevers in warm countries
and may also be a carrier of leprosy and typhoid fever. These facts
show that insects are dangerous and should be kept out of the home.
Any one troubled with these little pests in the house may learn how to
get rid of them by writing to the Department of Agriculture,
Washington, D.C.