CHAPTER XVII
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.
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.
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.
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.
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.
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.
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.
Fig. 79 —Photograph of the worm stage or larva of the fly at the left and three of the sleeping stage or pupæ 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.
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.