Student Reading Selections: Grade 5

About Mosquitoes

Copy Masters
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This is a mosquito. It is an insect. The mosquito is sometimes a carrier of diseases, such as malaria, encephalitis, yellow fever, dengue fever, dog heartworm, West Nile virus, and others.
The West Nile virus is caused by a bite from a mosquito that is already infected with the virus. Mosquitoes become infected by biting animals, such as crows, that already have the disease. Very few mosquitoes in an area affected by West Nile will actually be infected with the virus. Not everyone who gets bitten by an infected mosquito will get the virus. Although kids can get West Nile virus, it is rare for them to become very sick from it. In order to protect yourself from mosquito bites it is helpful to know about the life cycle of the mosquito.
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Mosquitoes hatch from eggs. Female mosquitoes lay their eggs in water. The mosquito can only live where there is standing water or areas that will be flooded when the snow melts or it rains. Some mosquitoes lay hundreds of eggs in groups. The egg groups float on the water like a raft. Other mosquitoes lay their eggs in places that will be flooded after it rains. Eggs hatch in 1 to 5 days.
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Mosquito eggs hatch into tiny larvae. Mosquito larvae live in water. They look like worms. They are sometimes called wrigglers at this stage because they just kind of wriggle through the water.
The body of the larva consists of a dark brown head, the thorax and the abdomen. The dark spot on the side of the head is the eye and next to it are the mouth brushes.
The mosquito larva breathes air through a tube in its tail called a siphon. It pokes the tube above the surface of the water like a skin diver uses a snorkel. This way the larva's head stays in the water so it can eat using its fine mouth brushes.
Larvae eat all the time, feeding on bacteria, algae and plant particles in the water. Larvae grow very quickly. They molt four times as they grow. This stage lasts from one to four weeks.
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After the larva molts for the last time, a very different looking creature comes out. This stage is called the pupa. Inside the pupa, big changes are happening. Unlike the mosquito larva, the pupa does not feed. The legs, wings, eyes, and other adult parts are developing.
The pupa breathes air through tubes called trumpets. Pupae move by rolling around through the water. They are often called tumblers at this stage. The pupal stage lasts from one to four days.
After three or four days a full grown mosquito is ready to break out. To do this the pupa finds a quiet spot and begins to swallow air, lots of air, like blowing up a balloon. And just like a balloon popping, the pupal skin splits open along the top. This allows the full grown adult mosquito to crawl out. The head comes out first, followed by the wings and antenna. Next the six legs tucked under the body unfold.
The whole process only takes about five minutes. The new adult mosquito floats on the surface of the water for a few minutes. Its new body and wings harden and dry. Then it flies away.
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The adult mosquito has three body parts: the head, the thorax, and the abdomen. It has two wings and six long legs.
Mosquitoes feed on plant nectar. The mosquito has a long, thin mouth called the proboscis. The proboscis is a good tool for sucking up the nectar.
Female mosquitoes need to feed on the blood of animals before they can lay eggs.
Once the female mosquito lands, it pokes around on your skin looking for blood. It pushes its stylets through your skin looking for a blood vessel. When it does that, it pushes back the labium which is a sheath over the sharp stylets. When the female locates a small blood vessel, muscular pumps in the head begin pumping blood into the stomach. It takes about three minutes to suck up enough blood for a hungry mosquito.
While the female mosquito is sucking up the blood it pumps saliva into the skin. The saliva works as an anesthetic so you won't feel the bite. It also keeps blood from clotting and clogging the food canal. It is the saliva that makes mosquito bites itch. Your body knows that the saliva should not be there and reacts to its presence by swelling and itching. If the female mosquito is infected with a virus or parasite, she may inject these disease-causing agents along with the saliva.
After the female mosquito finishes feeding it will find a quiet place to digest the blood and develop a batch of eggs. In about three days it will find some standing water, a treehole or other container in which to lay its eggs. Then it will be ready to take another blood meal.

The West Nile Virus

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Sometimes mosquitoes can get diseases from the animals they bite.One of those diseases is The West Nile Virus.
Most people infected with West Nile virus got it from the bite of an infected mosquito. A mosquito becomes infected when it feeds on the blood of a bird that is infected with the virus. About two weeks later, the mosquito becomes capable of passing the virus to people and animals by biting them.
The virus has been found in more than 150 bird species in North America. Some species may not seem sick when infected. Others, such as crows, blue jays, magpies and ravens, get sick more often and can die.
There are 74 known species of mosquitoes in Canada. West Nile virus infection has been found in 10 of these, but it is more common in species that feed on birds.
Scientists estimate that fewer than 1% of mosquitoes in any area are infected with West Nile virus. This means the risk of being bitten by an infected mosquito is very low.
Not every one who is infected with West Nile virus gets sick. Many people infected with the virus have mild symptoms, or no symptoms at all. People with weaker immune systems and people who are already ill with diseases such as cancer or diabetes, may possibly get sicker.
If you have the virus, you may feel like you have the flu. You might have a fever, headache and body aches. Some people may also develop a mild rash, or swollen lymph glands.
If you have been bitten by a mosquito and feel ill, you should tell your parents who may want to talk with your doctor.
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It is important to remember that the risks of being bitten by a mosquito infected with West Nile virus are low. The chances of becoming seriously ill are even lower.
If you live in an area that has infected mosquitoes, it's still important to use common sense and protect yourself.
To protect yourself, you should try to avoid being bitten by mosquitoes.
There are two important ways you can do this.

1. Cut down your exposure to mosquitoes.

  • When going outdoors, use insect repellents that contain DEET or other approved ingredients.
  • Try to stay inside at dawn and at dusk when mosquitoes are most active.
  • Wear protective clothing such as long-sleeved shirts, long pants and a hat. Light coloured clothing is best because mosquitoes are more attracted to dark colours.
  • Make sure that door and window screens fit tightly and have no holes that may allow mosquitoes indoors.

2. Get rid of places where mosquitoes may lay eggs around your home and cottage. Even a small amount of water, for example, in a saucer under a flower pot, is enough for mosquitoes to lay eggs. It is important to get rid of as much standing water around your home as possible by:

  • Regularly draining standing water from items like pool covers, saucers under flower pots, recycle bins, garbage cans, etc.
  • Remove old unused items from around your property including old tires, that might collect water.
  • Change the water in wading pools, bird baths, pet bowls and livestock watering tanks twice a week.
  • Cover rain barrels with screens.
  • Clean out eaves troughs regularly to prevent clogs that can trap water.
  • If you have an ornamental pond, consider getting fish that will eat mosquito larvae.
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Safety Tips for Using Insect Repellent
Always read the label carefully before using. Follow all of the label directions.
Just put on a little bit of the repellent. You don't need a lot.
Only use the repellent on exposed skin surfaces or on top of clothing. Do not use it under clothing.
Do not get the repellent in your eyes. If you do get repellent in your eyes, rinse immediately with water.
Do not use the repellent on open sores, or if your skin is irritated or sunburned.
Be extra careful with spray repellents. Don't breathe in the spray mists. Never apply sprays inside a tent. Only use sprays in well-ventilated areas. Do not use them near food.
Wash treated skin with soap and water when you come back inside or when you no longer need the protection.
Keep all insect repellent containers out of the reach of children. Always make sure an adult puts the repellent on little children.
Don't put repellent on young children's hands so they won't get it in their eyes and mouths.