Some Undesirable Neighbors
( Originally Published 1920 )
The Fly Family. When the flies buzz about on the window pane and tickle your face in the early morning and bother you at mealtimes by running over the sugar and getting into the jug of cream, did you ever wonder where they come from? They are neighbors of ours and often uninvited guests in our houses and at our tables. We ought to know a little about their habits, so that we may find out whether they should be welcome guests or not.
Mother Fly has quite a large family, a hundred or more children at a time. She lays her eggs—tiny white eggs so small that you can just barely see them—in horse manure about stables if she can find it, or in almost any kind of decaying material. Then she flies away. In about a day the eggs break open, and out of each one comes—what do you suppose—a little fly? Not at all. There comes out of each egg a tiny white worm (just as there comes from the egg laid by a butter-fly, not a butterfly but a caterpillar).
The fly maggot or larva, as the little worm is called crawls about in the manure and feeds upon it. It grows and thrives on this unpleasant food, till after four or five days it is about three-eighths of an inch long.
Then it burrows down into the ground underneath, or out into the dry edges of the manure pile, and there its skin splits open and uncovers a little brown thing like a seed, which is called a pupa.' In just the same way, as perhaps you may have seen, a caterpillar (which is the larva of a butterfly) changes into a pupa.
Inside the pupa case, the young fly sleeps for four or five days more. At last the brown pupa skin splits, just as the skin of the larva did, and there comes out a full grown fly, just like its mother. It wriggles up to the air and soon flies away, to seek out your sugar bowl or cream pitcher and have a meal.
Is the Fly a Good Neighbor? Now that you know the history of the Fly children, I think you can make up your mind for yourself whether they are desirable guests at the dinner table or not.
A fly's feet seem quite dainty and small. If you looked at them under a microscope, however, you would see that they have claws and soft sticky pads on the end (by the use of which the fly can walk on the wall or ceiling just as easily as on the floor). On these claws and pads there is plenty of room for microbes. It has been found, by the men and women who study germs, that thousands of microbes are actually carried by these tiny feet from the filthy places where flies live. It is not pleasant to think that even one fly has been tracking his dirty feet over our food. Worst of all, however, is the fact that every now and then the fly has been walking where there were germs of some special disease like typhoid fever; and if these germs are carried to the food, an outbreak of disease is very likely to result.
Little babies often suffer in summer from diseases of the intestines. Studies made in New York City showed that half of this kind of sickness could be prevented by keeping flies out of the baby's room and away from its food.
Fighting the Fly. From these facts you will realize that in every town and every school and every household there must be a vigorous fight made against the Fly Family.
Sometimes people who want to get rid of flies try to do it by killing them by hand.
We hear now and then about a "Swat-the-Fly" campaign. Fly killers are often useful to get rid of the flies that are actually in our houses, though sticky fly paper is generally more effective. But we can never destroy all the flies indoors if they are coming in freely from the outside. So doors and windows should all have tightly fitting screens in summer; and remember that a screen door is not very useful if it is held open while a child stands on the step and talks to some one outside—as I have seen some children do.
A great many flies can be caught in traps. A fly trap is usually a cage of wire netting, which has inside a cone of wire, with a large opening at the bottom and a small opening at the top. Underneath the lower opening of the cone is placed a bait of some food that flies like. The flies which come to feed on this bait will fly and crawl up through the cone into the cage. Once inside, they do not know enough to find the hole and get out again.
The best way of all to fight against the Fly Family is to prevent the fly babies from growing up at all in the neighborhood of our houses. If stable manure is kept in tight covered bins, and if refuse of all kinds is cleared away from back yards and open lots, there will be no places for flies to breed.
Mrs. Mosquito and Her Habits.—There is another summer neighbor of ours whom we ought to know something about, and that is Mrs. Mosquito, who buzzes about our beds at night and gives us the bites that itch and sometimes smart so painfully.
Mrs. Mosquito is much more cleanly in her habits than Mrs. Fly. When she starts her family off in life, she seeks, not a manure pile, but a pool of stagnant water, or a slowly running stream half choked up with weeds, or perhaps an old rain barrel, or even a tin can in the back yard in which a little rain water has collected. She lays her eggs on the surface of the water, for her babies live in water, as Mrs. Fly's children live in decaying matter. The larvæ which hatch out from Mrs. Mosquito's eggs are little brownish creatures with tufts of hair on their bodies. They are often called "wigglers," because of the way they swim about in the water by jerking their bodies from side to side.
After a week or so these larva, like those of the fly, change to pupa. The mosquito pupa are not motionless like the fly pupa. They can still jerk themselves about in the water. They do not eat, however, but rest quietly at the surface, unless they are disturbed. After a few days they change again. The pupa skin splits up the back and the grown-up winged mosquito comes out. For a few minutes it stands on the old pupa skin to dry its wings and then it flies away.
Why Mosquitoes are Dangerous.—We all know that mosquitoes are a nuisance because they sting us and keep us awake at night. You might not think they would do any harm, however, since they breed in pools, and streams instead of in dirty places as the flies do. Yet some kinds of mosquitoes are even more dangerous than flies in spreading the germs of disease.
In many parts of the United States, and in most of the warmer countries of the world, a disease called malaria is common. The germ which causes this disease lives in the blood and attacks the red cells, which carry oxygen to the different organs. This germ is carried from one person to another by a mosquito. The insect bites a person who has the malaria germ in his blood. In sucking out the blood, the mosquito sucks out also some of the malaria germs. Then it bites a second person and introduces the germ into his blood, giving him the disease in turn.
Long ago it was noticed that malaria was generally found in the low lands near streams and swamps, and people thought there was something mysterious in the air of such places that caused the disease. Now we know that what made the air unhealthful was simply the mosquitoes which were flying in it; and the reason why malaria occurred near swamps was because there was stagnant water there in which mosquitoes could breed.
Only certain kinds of mosquitoes can carry malaria in this way; and you can easily tell the difference between the malverdana mosquitoes and the ordinary kinds. The wings of the malverdana mosquitoes are spotted, while the wings of the commoner kinds are not. The position of the malverdana mosquitoes, when resting on the wall, is different, too. They hold their bodies out in a straight line from the wall, while the common mosquitoes sit in a sort of hump-backed position, as you can see by looking at Fig. 69.
Even the larve of these two sorts of mosquitoes can quite easily be distinguished. The larva of the malverdana mosquito, when they are at rest in the water, lie flat against the surface, while the larvæ of the common mosquito hang at an angle with the surface, their tails only touching it.
How to Get Rid of Mosquitoes.—Screens will help to keep mosquitoes, as well as flies, out of our houses. But with mosquitoes, as with flies, the best thing to do is to prevent the insects from breeding at all. e can do this by draining the marshlands, by ging ditches through which the water can flow out instead of standing in little pools. We can clear small streams of weeds and grass so that the water will run rapidly, for Mrs. Mosquito will not lay her eggs in water that is flowing fast. We can empty our old barrels and tin cans and all such collections of water, so that there may be no place where the little wigglers can live.
Sometimes when it is not possible to drain away marshy pools in which mosquitoes might breed, oil is sprayed over the pools. As oil is lighter than water, it spreads out in a very thin layer over the top and kills the mosquito larvæ. The breeding of mosquitoes may often be stopped by putting fish into a pond, for many kinds of fish will eat up mosquito wigglers (see Fig. 7o).
How America Built the Panama Canal.—One of the great things our country has done, of which all Americans are proud, is the building of the Panama Canal. You have probably learned in your geography about this famous canal, which cuts through the Isthmus of Panama between North and South America and makes it possible for ships to pass directly from the Atlantic into the Pacific, without going all the way around Cape Horn, as they used to do.
Long ago the French tried to build a canal across this isthmus. One of the chief reasons why they did not succeed was that their workmen fell sick of malaria and other diseases, and particularly of one very terrible disease called yellow fever. No one knew at that time what caused either malaria or yellow fever, and there was therefore no way to protect the people who tried to live and work in warm countries, where these diseases prevailed.
At last it was found out that malaria, as we have seen, is spread by the bite of a certain mosquito. A group of American army doctors, headed by Walter Reed, then went to Cuba, where yellow fever was common, to try to learn how to control it. They soon proved that yellow fever, too, is spread by a mosquito, but by a different kind from the one that carries malaria.
That sounds very simple, perhaps; but it was not at all an easy thing to prove. The doctors suspected that a special kind of mosquito carried the germ of yellow fever. It was necessary to let these special mosquitoes first bite people sick with yellow fever, and then bite other well people, and see whether these well people would become ill. It was a brave thing to do, to take an almost certain risk of getting such a disease-as brave as anything our soldiers have done in the trenches in France. The men who were bitten by the mos. quitoes which carried the germ developed yellow fever, and one of them, Jesse W. Lazear, died of it. By their heroism, they showed the world how yellow fever was really caused, and therefore how it could be controlled.
It was soon after this that the United States began its attempt to build the Panama Canal. In view of the discoveries made in Cuba, it was clear that it was the presence of mosquitoes which made Panama such a dangerous place. So Dr. W. C. Gorgas (who later became the head of the Medical Corps of the whole United States Army) was sent to Panama and placed in charge of a campaign against these insects. He was so successful that he wiped out yellow fever on the Isthmus, and nearly abolished malaria as well. The great canal was built; and one of the chief things that made it possible to build it was the knowledge of how to control yellow fever and malaria.
Other Insect Bearers of Disease.—There are many other insects which may spread the germs of disease, particularly in the warm countries of the Tropics. In the trenches during the World War many diseases were spread from one man to an-other by lice diseases which used to be very common everywhere in old times, when people did not keep as clean as they do nowadays. It is important that the greatest care should be taken al-ways to keep the head and body and clothes clean, so that these dangerous insects may not find a chance to develop.
How Children can Help to Fight the Mosquito and the Fly.—Children can do many things to help in the fight against the mosquito and the fly. Every good citizen is anxious to rid his neighborhood of these pests, but older people are often too busy to hunt about and find out where their breeding places are. Boys and girls, with a little help from their teacher or some other older person, can soon learn to recognize fly maggots and mosquito wigglers. Then they can organize scouting parties to find the manure piles and rubbish heaps where the flies are developing, and the pools and rain barrels and other places from which the mosquitoes come.
If Boy Scouts or other groups of children will hunt out the insect pests in this way and report to their scoutmaster or parents or teachers where the trouble lies, the breeding places can often be done away with and the whole neighborhood made pleasanter and safer to live in.
An Evening Talk.—One evening in midsummer Mrs. Mosquito was sitting on the wall of the barn, just under the eaves where it is warm and pleasant. All at once there was a great buzzing, and Mrs. Fly came flying along and settled down beside her, very much hurried and out of breath.
"Good evening, my dear. You seem a little flustered," she said to the newcomer politely, "Is any-thing the matter?"
"Everything is the matter, indeed," replied Mrs. Fly in a tone of bitter disgust. I have just been chased out of the house by a little girl with a fly-killer. I don't mind that so much, because she never could get near me. I took care of that. But inside the house every single bit of food was covered so that I could get nothing to eat. The lid was on the sugar bowl and a napkin over the top of the cream pitcher."
"It's too bad," Mrs. Mosquito answered feelingly. "I have had a hard time, too. I have been' looking all day for a good place to lay my eggs so that my babies could grow up happily, and if you will believe it, I could not find a single one.
The swamp behind the barn has been drained, and there is a tight cover on the rain barrel, and these wretched Boy Scouts have even taken away the old tins by the fence at the end of the orchard, which used to be. full of water after every rain. Life is very difficult nowadays."
"Yes, and it's all the fault of those same Boy Scouts," broke in her friend, still bursting with indignation.
"They foundsome of my brothers and sisters feeding quietly and peaceably in the manure pile.
They told their father about it, and now he keeps the manure in a tight bin. And they have cleaned up the rubbish pile at the end of the garden. Mrs. Mosquito, this is no place for a poor insect to get a living any longer. Let us move to the next town and see if things are not better there."
"I believe you are right," said Mrs. Mosquito. "I believe you are right. Cleanville has no attraction for. insects any longer. We will leave it to the human beings, and we will carry our malaria and typhoid germs to some other place, where the people are kinder and more hospitable."
So they flew off together through the twilight; but everybody else in Cleanville said that the Boy Scouts had been doing a good summer's work.