MOSQUITOS

Mosquitos are 1/4 to 2/5 of an inch (4-10 mm) long. They are long-legged insects that have a long, sharp mouthpiece used to puncture skin and suck blood. Mosquitos have delicate wings and can easily be heard when hovering around a host preparing for a blood meal. They are more active at dusk or at night in swampy and woody areas.

Mosquitos require stagnant water to breed (black flies need fresh, running water). Stagnant water sources can be found in buckets, tires, pools, marshes or containers left around a property.  Mosquitoes have four stages of development.  This is called complete metamorphosis. These stages are, egg larva, pupa and adult. Eggs must be near water to hatch.  Both the larval and pupa stages are aquatic.  The Adult stage is when the mosquito is free-flying.

Egg:  Female mosquitoes choose locations to lay their eggs where there will be suitable conditions for the larval stage of development.  The characteristics of the eggs follow one of three patterns.  The first is an egg laid singly on the water surface.  These eggs will hatch two or three days later.  The second pattern of egg lying is when eggs are glued together and float on the surface of the water, these are called egg rafts.  These eggs also break apart and hatch two or three days later.  The third pattern is an egg laid singly out of the water.  These eggs are adapted to withstand dry conditions until there are floods and they can hatch.  The pattern of egg lying depends on the specific type of Mosquito.   

Larvae:  Mosquito Larvae have three distinct body regions, head thorax and abdomen.  The structures of the hairs on both the abdomen and the thorax can be used to determine what species of mosquito the larva is.  Water is required for larval development.  The water must be either stationary or very slow moving, there must be a food source (bacterial, fungal, or algal), and there also must be some sort of protection from wind and waves.  Mosquitoes go through 4 stages during the larval stage called instars.  The larvae shed their skin after each stage of development.  At the end of the fourth stage the shed their skin and become pupae. 
 

Pupa:  This stage is a short two or three days.  During this stage the mosquito pupae do not eat.  Pupae breathe air through tubules surrounding the openings to the respiratory system.  The pupae stage is also an aquatic stage.  When this stage is complete, the pupae skin splits and an adult mosquito emerges.
 

Adult:  Adult mosquitoes have three body regions, head, thorax and abdomen.  They also have one pair of wings, and three pairs of legs.  Scales on the body regions can be used to identify species.  Both male and female mosquitoes drink nectar and other plant juices.  Only females take a blood meal.  The protein from the blood is used to produce eggs.  The life span of mosquitoes varies.  Males usually live a few days to a week, while females may live a few weeks to a few months, depending on species and location.  Mosquitoes are generally inactive during the day, hiding in grass or shaded areas. Feeding and mating takes place from dusk until just after dawn.

The first three stages occur in water with the amount of time for each stage depending on water temperature and food availability.  After emergence, the adults mate and the female seeks out a blood source before laying its eggs.  Up to 100 eggs are laid, either in water, on grass or other vegetation or in soil close to the water source.   When water is present, eggs hatch into the larval stage (two to three days), although some species produce eggs which overwinter.  Larvae are worm-like organisms which constantly wriggle around in the water.  Adults also get nourishment from flower nectar.

Source:  Unknown

Most mosquitoes stay close to where they were hatched so they can raise another brood. Some mosquito species only have one generation each year. Others can have four or more!

In the winter, most mosquitoes survive as eggs in the soil. These eggs are in a dormant stage called "diapause" which prevents them from hatching if it floods. They'll only hatch out of the diapause stage when the day length gets longer. Some adult females and also some large pupae can survive the winter (also in a diapause stage) if they can find a protected spot.

Mosquito Borne Diseases in Michigan:

Mosquitoes are the number one killer of humans of all animals. Some of the Mosquito-Borne diseases include, St. Louis Encephalitis (SLE), Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), California Encephalitis (CE), West Nile Virus, and Dog Heartworm. 

SLE: This disease is spread by what is called a “natural” transmission cycle.  The virus is present in infected birds, and the mosquito will take her blood meal she will ingest the virus.  Then the virus will reproduce and move to the salivary glands.  Once the mosquito is infected with the virus, she can pass it every time she takes a blood meal.  Humans are “dead end hosts” for this virus, meaning they can contract it from and infected mosquito but the mosquito will not contract it from a human.  SLE reactions in humans may include sub clinical symptoms up to severe central nervous system symptoms.  These may produce temporary or permanent physical conditions.  Generally, people over the age of 50 have a higher fatality rate and higher risk for permanent damage.  In the eastern U.S. SLE occurs primarily in densely populated urban and suburban areas where birds and mosquitoes live close to humans.  The mosquito that transmits this disease is the Culex pipien, or the northern house mosquito.  This mosquito is one of the most common mosquitoes found in urban/suburban areas.  They mostly breed in containers that can hold water, which includes trash cans, flower pots, buckets, gutters, bird baths, etc.  They also live in catch basins, septic tanks, cesspools, sewage lagoons or anything like these.  Culex pipiens over winter as adults, in protected areas such as garages, but they are mostly active during the warm months of the year. 

EEE: Eastern Equine Encephalitis is a virus that causes severe nervous system damage in humans as well as horses.  The fatality rates in humans are 50-70 percent and 90-95 percent in horses.  Those who survive may suffer mental retardation, convulsions and paralysis.  Human cases are rare but horse cases appear every summer.  The primary mosquito vector is the Culiseta melanura, this mosquito is a fresh water swamp mosquito. These mosquitoes feed primarily on birds; some examples of these birds are blue-jays, cardinals, and catbirds.  There is evidence that humans and horses contract the virus from many other mosquito vectors, but the significance of these vectors is not known.

WEE: This occurs in the Western United States and Canada.  It occurs in mostly rural areas, similar to EEE.  It occurs in both humans and horses, but is most severe in children.  Symptoms may include headaches, vomiting, stiff neck, confusion, coma and severe central nervous system damage. Adults completely recover from this, but children may suffer from permanent damage.  Many mosquitoes are known to transmit this virus but the main vector is the Culex taralis. They usually breed in ground water with high organic content. 
 
West Nile Virus: West Nile Virus in the United States started in the Eastern states and is making its way across the country.  It was found in Michigan in 2001.  The virus causes flu-like symptoms in humans and may cause death.  There were 614 cases reported and 51 deaths in Michigan in the year 2002.  The disease is similar to St. Louis encephalitis.  The disease is most severe in children and elderly people, or people with weak immune systems.  The mosquito vector is the Culex pipien, which was mentioned earlier. 

Dog Heart Worm: Adult heartworms attach to the right heart chamber of the infected animal.  Once the adult female is fertilized she begins to release microscopic offspring, they are ingested into the blood and develop in the mosquito.  The worm migrates to the mouthparts and then is transmitted when the mosquito takes her blood meal.  The worm is still microscopic in size but is able to migrate to the heart.  The severity of the disease depends on the age and health of the dog.  If dogs are not given the proper medication the worm can live up to five years inside the dog’s heart.  Also if the dog is not treated mosquitoes that are infected with the disease may continue to transmit more heart worms to the specific dog.  Several hundred worms can accumulate in the dog’s heart.  Heartworms affect the blood flow of the dog and my cause physiological changes in the animal.  Other animals can get heartworms such as foxes and wolves.  Cats may also be affected by the worms, but are affected in different ways. 

WHAT CAN YOU DO TO PREVENT MOSQUITOS IN YOUR BACKYARD???

Many counties of the State of Michigan do not have mosquito management programs, so the individual must take to initiative to protect his or her home.  There are many ways in which a homeowner can protect himself or herself from mosquito bites.  These are grouped into three primary management areas. Personal protection is a way to prevent yourself from getting bitten by adult mosquitoes and prevent mosquito-borne diseases from affecting you.  Larval control is a way of source reduction, or eliminating breeding sites for mosquitoes.  Adult mosquito control is another protective measure to reduce adult mosquito populations in your yard as well as a way to prevent mosquito bites from occurring.  Below are some suggestions about protecting yourself and our yard from mosquitoes.

Personal Protection:
1.    Screening: Make sure screen doors are tight fitting and in good repair.  Also make sure camping tents and trailers are also properly screened.  When cabins are not properly screened use a bed net or mosquito bar when sleeping.
2.    Avoiding Mosquitoes: Try to avoid areas where mosquitoes may be such as twilight hours or wooded areas.  When in these areas be sure to wear protective clothing.
3.    Protective Clothing:  Protective clothing is tightly woven materials that cover arms and legs. Studies show that mosquitoes are attracted to dark clothing.
4.    Repellents: DEET is the most commonly used mosquito repellent.  A small amount of repellent can last from two to four hours, the higher percentage of active ingredients the longer the repellent will last. Repellents can be applied to skin and to clothing.  On clothing the repellent will last longer.  Be sure to avoid eyes, lips and other sensitive areas when applying repellents.

Larval Mosquito Control:
1.    Eliminate any item which can retain water such as tin cans, tires, jars, bottles, old appliances, broken toys, etc.
2.    Repair leaky pipes or outdoor faucets.
3.    Empty and clean children’s wading pools at least once a week, also store in an area where they will not collect rain water.
4.    Empty and refill pet water containers daily.
5.    Cover garbage cans to prevent water accumulation.
6.    Keep eaves troughs clean so water can flow freely and not collect.
7.    Fill tree holes or stumps with sand or concrete.
8.    Keep ornamental ponds stocked with mosquito eating fish and keep vegetation trimmed.
9.    Store boats upside down so they do not collect water.
10.    When watering plants or lawn, be sure not to let puddles form.
11.    Drain and fill low areas in your yard to prevent water accumulation.

Adult Mosquito Control:
1.    Keep grass cut short.
2.    Cut and remove weeds and brush from yards and adjacent lots.
3.    Trim trees and shrubs so that light shows through.
4.    Screen outbuildings.
5.    Store firewood or lumber ten to twelve feet above the ground and away from and structure.
6.    Screen accesses underneath or into attics of all structures including basements and cellars.
7.    Make wells septic tanks, cesspools; water tanks, etc are tightly covered and insect proof.
8.    Use citronella candles on porches or when camping.

Many people use electronic bug killers to reduce adult mosquitoes, remember that moths flies and other insects are attracted to ultraviolet light while studies show that mosquitoes are attracted to the human body!

Did you know that:

There are over 3,000 mosquito species worldwide
Mosquito eggs can survive for more than five years.
One female mosquito can lay over 200 eggs at one time.
Only female mosquitoes bite and take blood. Male mosquitoes feed only on plant nectar.
Not all mosquito species bite people. Some prefer birds, or horses, or even frogs and turtles.
All mosquitoes need water to complete their life cycle.
A mosquito weighs about 2 to 2.5 milligrams.
Mosquitoes can fly about 1 to 1.5 miles per hour.
Mosquitoes find hosts by sight, by infrared radiation and by chemicals.
Mosquitoes infect 500 million people around the world each year with diseases, such as encephalitis and malaria.
Mosquito-induced diseases kill more than 2 million people around the world each year.
Mosquitoes are the primary food for many birds and bats. One bat can eat 200 mosquitoes in one night and birds eat hundreds of mosquitoes every day. Without these mosquito predators, we would really have a mosquito problem!

Parts pf the web page were compiled by Kari Kenel, a GEO 333 student.

This material has been compiled for educational use only, and may not be reproduced without permission.  One copy may be printed for personal use.  Please contact Randall Schaetzl (soils@msu.edu) for more information or permissions.