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Mosquitoes are insects belonging to the order Diptera, the True Flies. Like all True Flies, they have two wings, but unlike other flies, mosquito wings have scales. Female mosquitoes mouthparts form a long piercing-sucking proboscis. Males differ from females by having feathery antennae and mouthparts not suitable for piercing skin. A mosquito’s principal food is nectar or similar sugar source. There are over 2500 different species of mosquitoes throughout the world. Scientific investigators (taxonomists) are constantly looking for new mosquitoes, as well as reviewing previously identified specimens for new information or identifying characteristics. Better microscopic equipment developed in the last 20 years has improved the taxonomist’s ability to determine differences between species. Recently such a review by Dr. John Reinert (2000) led to a change in the name of many mosquitoes belonging to the genus Aedes. Using improved methods and over 30 years' experience he elevated a subgenus of Aedes (Ochlerotatus) to the status of genus. This will necessitate the renaming of many mosquitoes previously named Aedes to the genus Ochlerotatus and the rewriting of many taxonomic keys important to public health entomologists working in mosquito control.
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The Spanish called the mosquitoes "musketas," and the native Hispanic Americans called them "zancudos." "Mosquito" is a Spanish or Portuguese word meaning "little fly" while "zancudos," a Spanish word, means "long-legged." The use of the word "mosquito" is apparently of North American origin and dates back to about 1583. In Europe, mosquitoes were called "gnats" by the English, "Les moucherons" or "Les cousins" by French writers, while the Germans used the name "Stechmucken" or "Schnacke." In Scandinavian countries mosquitoes were called by a variety of names including "myg" and "myyga" and the Greeks called them "konopus." In 300 B.C., Aristotle referred to mosquitoes as "empis" in his "Historia Animalium" where he documented their life cycle and metamorphic abilities. Modern writers used the name Culex and it is retained today as the name of a mosquito genus. What is the correct plural form of the word mosquito? In Spanish it would be "mosquitos," but in English "mosquitoes" (with the "e") is correct. Mosquitoes can be an annoying, serious problem in man's domain. They interfere with work and spoil hours of leisure time. Their attacks on farm animals can cause loss of weight and decreased milk production. Some mosquitoes are capable of transmitting diseases such as malaria, yellow fever, dengue, filariasis and encephalitis [St. Louis encephalitis (SLE), Western Equine encephalitis (WEE), LaCrosse encephalitis (LAC), Japanese encephalitis (JE), Eastern Equine encephalitis (EEE) and West Nile virus (WN)] to humans and animals.
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Length of life stage is temperature dependent
The mosquito goes through four separate and distinct stages of its life cycle: Egg, Larva, Pupa, and Adult. Each of these stages can be easily recognized by its special appearance.
Egg: Eggs are laid one at a time or attached
together to form “rafts.” They float on the surface of the water. In
the case of Culex and Culiseta species, the
eggs are stuck together in rafts of up to 200. Anopheles,
Ochlerotatus and Aedes, as well as many other
genera, do not make egg rafts, but lay their eggs singly. Culex,
Culiseta, and Anopheles lay their eggs on the water
surface while many Aedes and Ochlerotatus
lay their eggs on damp soil that will be flooded by water. Most
eggs hatch into larvae within 48 hours; others might withstand subzero
winters before hatching. Water is a necessary part of their habitat. The larva (plural - larvae) lives in the water
and comes to the surface to breathe. Larvae shed (molt) their skins four
times, growing larger after each molt. Most larvae have siphon tubes for
breathing and hang upside down from the water surface. Anopheles larvae
do not have a siphon and lie parallel to the water surface to get a
supply of oxygen through a breathing opening. Coquillettidia and Mansonia
larvae attach to plants to obtain their air supply. The larvae
feed on microorganisms and organic matter in the water. During the
fourth molt the larva changes into a pupa. The pupal stage is a resting, non-feeding stage
of development, but pupae are mobile, responding to light changes and
move (tumble) with a flip of their tails towards the bottom or
protective areas. This is the time the mosquito changes into an adult.
This process is similar to the metamorphosis seen in butterflies when
the butterfly develops - while in the cocoon stage - from a caterpillar
into an adult butterfly. In Culex species in the southern United
States this takes about two days in the summer. When development is
complete, the pupal skin splits and the adult mosquito (imago) emerges. The newly emerged adult rests on the surface of
the water for a short time to allow itself to dry and all its body parts
to harden. The wings have to spread out and dry properly before it can
fly. Blood feeding and mating does not occur for a couple of days after
the adults emerge.
Mosquito Egg Raft
Many mosquitoes,
such as Culex quinquefasciatus, lay their eggs on the surface of
fresh or stagnant water. The water may be in tin cans, barrels, horse
troughs, ornamental ponds, swimming pools, puddles, creeks, ditches,
catch basins or marshy areas. Mosquitoes prefer water sheltered from the
wind by grass and weeds. Anopheles, Culex and Mansonia eggs are more susceptible to long periods of drying out.Anopheles and many other mosquitoes lay their eggs singly on the water surface. Aedes and Ochlerotatus mosquitoes lay their eggs singly, usually on damp soil. Aedes and Ochlerotatus eggs are more resistant to drying out (some require complete drying out before the eggs will hatch) and hatch only when flooded with water (salt water high tides, irrigated pastures, treeholes flooded by rains, flooded stream bottoms). Tiny mosquito larvae emerge from the eggs within 24 - 48 hours almost
in unison. Mosquito Larva
Mosquito larvae, commonly called "wigglers,"
live in water from 4 to 14 days depending on water temperature.
Mosquito Pupa
Mosquito pupae, commonly called "tumblers," live in water
from 1 to 4 days, depending upon species and temperature. The metamorphosis of the mosquito into an adult is completed within the pupal case. The adult mosquito splits the pupal case and emerges to the surface of the water where it rests until its body dries and hardens.
Mosquito Adult
Only female mosquitoes require a blood meal (protein) and
bite animals – warm or cold blooded – and birds. Stimuli that
influence biting (blood feeding) include a combination of carbon dioxide,
temperature, moisture, smell, color and movement. Male mosquitoes do not
bite, but feed on the nectar of flowers or other suitable sugar source.
Acquiring a blood meal, i.e., protein, is essential for egg production,
but mostly both male and female mosquitoes are nectar feeders. Female Toxorhynchites
actually can’t obtain a bloodmeal and are restricted to a nectar diet.
Of those female mosquitoes capable of blood feeding, human blood meals are
seldom first or second choices. Horses, cattle, smaller mammals and/or
birds are preferred.
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Mosquito control can be divided into two areas of responsibility: individual and public. Mosquito control includes mosquito surveillance measures, source reduction, a biological control strategy, ground and aerial application of insecticides and public education. The applications of adulticides or larvicides are made after the presence of mosquitoes has been demonstrated by surveillance procedures.
Adult Mosquito Control Repellent: Repellents are substances that make a mosquito avoid biting people. Persons working or playing in mosquito-infested areas will find repellents very helpful in preventing mosquito bites. Repellents are formulated and sold as aerosols, creams, solids (sticks) and liquids. Use repellents containing ingredients such as diethyl phthalate, diethyl carbate, N, N-Diethyl-3-Methylbenzamide (DEET), and ethyl hexanediol. For more than 40 years, DEET has been the standard in mosquito repellents. Check the label for these active ingredients. Permethrin-containing repellents (Permanone) are recommended for use on clothing, shoes, bednets and camping gear. Permethrin is highly effective as an insecticide/acaricide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes and other arthropods and retains this effect even after repeated laundering. Permethrin-treated clothing should be safe when label directions are followed. Permethrin repellents do not offer any protection from mosquitoes when applied to the skin. It is often helpful to use spray repellents on outer clothing as well as the skin. Protection generally may be expected up to 6 hours following application. Oil of citronella is another type of mosquito repellent for space repelling. Oil of citronella is the active ingredient in many of the candles, torches, or coils that may be burned to produce a smoke that repels mosquitoes. These are useful outdoors only under windless conditions. Their effectiveness is somewhat less than repellents applied to the body or clothing.
Mosquito Traps: Insect electocutors (bug zappers) and mosquito trapping devices are 20th century control measures. Manufacturers modernized 19th century mosquito trapping devices such as the New Jersey light trap with more “bells and whistles” to improve its appeal to the public. Insect electrocuter light traps have been extensively marketed for the past several years claiming they can provide relief from the biting mosquitoes and other pests in your back yard. Numerous devices are available for purchase that claim to attract, repel or kill outdoor infestations of mosquitoes. They should be thoroughly researched before being purchased.
Space sprays: Mosquitoes can be killed inside the house by using a flit gun (seldom used any longer) or a household aerosol space spray containing synergized pyrethrum or synthetic pyrethroids (allethrin, resmethrin, etc.). The major advantage of space treatment is immediate knockdown, quick application, and relatively small amounts of materials required for treatment. Space sprays are most effective indoors. Outdoors, the insecticide particles disperse rapidly and may not kill many mosquitoes. The major disadvantage of space spraying is that it will not manage insects for long periods of time. Only insecticides labeled for flying insect management should be sprayed into the air. Best results are obtained if doors and windows are kept closed during spraying and for 5-10 minutes after spraying. Always follow directions on the label.
Outdoor Control: Homeowners, ranchers or businesses may use hand-held ULV foggers, portable or fogging attachments for tractors or lawn mowers for temporary relief from flying mosquitoes. Pyrethrins or 5% malathion can be fogged outdoors. Follow instructions on both the insecticide label and fogging attachments for application procedure.
Mechanical Barriers: Mosquitoes can be kept out of the home by keeping windows, doors and porches tightly screened (16-18 mesh). Those insects that do get into structures can be eliminated with a fly swatter or an aerosol space spray containing synergized pyrethrum.
Vegetation Management: Adult mosquitoes prefer to rest on weeds and other vegetation. Homeowners can reduce the number of areas where adult mosquitoes can find shelter by cutting down weeds adjacent to the house foundation and in their yards, and mowing the lawn regularly. To further reduce adult mosquitoes harboring in vegetation, insecticides may be applied to the lower limbs of shade trees, shrubs and other vegetation. Products containing allethrin, malathion or carbaryl have proven effective. Paying particular attention to shaded areas, apply the insecticides as coarse sprays onto vegetation, walls and other potential mosquito resting areas using a compressed air sprayer. Always read and follow label directions before using any pesticide.
Many of the mosquito problems that trouble homeowners and the general population cannot be eliminated through individual efforts, but instead, must be managed through an organized effort. These organized management programs incorporate the IMM (Integrated Mosquito Management)strategies mentioned above which include permanent and temporary measures. Permanent measures include impounding water and ditching, and draining swampy mosquito breeding areas. Temporary measures include treating breeding areas to kill larvae and aerosol spraying (ULV) by ground or aerial equipment to kill adult and larval mosquitoes.
Larval Control The most effective way to control mosquitoes is to find and eliminate their breeding sites. Eliminating large breeding areas such as swamps or sluggishly moving streams or ditches may require community-wide effort. This is usually a task for your organized mosquito control program. Homeowners, however, can take the following steps to prevent mosquito breeding on their own property: 1. Destroy or dispose of tin cans, old tires, buckets, unused plastic swimming pools or other containers that collect and hold water. Do not allow water to accumulate in the saucers of flowerpots, cemetery urns or in pet dishes for more than 2 days. 2. Clean debris from rain gutters and remove any standing water under or around structures, or on flat roofs. Check around faucets and air conditioner units and repair leaks or eliminate puddles that remain for several days. 3. Change the water in birdbaths and wading pools at least once a week and stock ornamental pools with top feeding predacious minnows. Known as mosquito fish, these minnows are about 1 - 1-1/2 inches in length and can be purchased or native fish can be seined from streams and creeks locally. Ornamental pools may be treated with biorational larvicides (Bacillus thuringiensis subsp. israelensis (Bti) or methoprene (IGR) containing products) under certain circumstances. 4. Fill or drain puddles, ditches and swampy areas, and either remove, drain or fill tree holes and stumps with mortar. These areas may be treated with the above Bti or methoprene products also. 5. Eliminate seepage from cisterns, cesspools, and septic tanks. 6. Eliminate standing water around animal watering troughs. Flush livestock water troughs twice a week. 7. Check for trapped water in plastic or canvas tarps used to cover boats, pools, etc. Arrange the tarp to drain the water. 8. Make sure window and door screens are "bug tight."9. Replace your outdoor lights with yellow "bug" lights 10. Check around construction sites or do-it-yourself improvements to ensure that proper backfilling and grading prevent drainage problems. 11. Irrigate lawns and gardens carefully to prevent water from standing for several days. 12. If ditches do not flow and contain stagnant water for one week or longer, they can produce large numbers of mosquitoes.
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Mosquitoes cause more human suffering than any other organism with over one million people dying from mosquito-borne diseases every year. Not only can mosquitoes carry diseases that afflict humans, but they also transmit several diseases and parasites that dogs and horses are very susceptible to. These include dog heartworm, West Nile virus (WN) and Eastern equine encephalitis (EEE). In addition, mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito's saliva - this is what causes the red bump and itching. Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases such as dog heartworm, and viruses such as dengue, encephalitis and yellow fever.
We will discuss dengue, malaria, yellow fever and west nile virus here. The malaria parasite (plasmodium) transmission by female Anopheles mosquitoes is an ancient disease originating in Africa probably (website). The term malaria is derived from the Italian, (mal-aria) or "bad air" because it was thought to come on the wind from swamps and rivers. Scientists conducted much research on the disease during the late1880s and early 1900s. Approximately 40% of the world’s population is susceptible to malaria, mostly in the tropical and sub-tropical areas of the world. More than one million deaths and over 300 million cases are still reported annually in the world for Malaria.It is reported that malaria kills one child every 40 seconds (website).
Dengue is a serious disease of Asia and Africa. It has a low mortality with very uncomfortable symptoms and has become more serious, both in frequency and mortality, in recent years. Aedes aegypti and Ae. albopictus are the vectors of dengue. The spread of dengue throughout the world can be directly attributed to the proliferation and adaptation of these mosquitoes.Over the last 16 years dengue has become more common, for example; in south Texas 55 cases were reported in 1999 causing one death. More recently, Hawaii recorded 85 cases of dengue during 2001. Yellow fever, which has a 400-year history, occurs only in tropical areas of Africa and the Americas. It is a rare illness of travelers anymore because most countries have regulations and requirements for yellow fever vaccination that must be met prior to entering the country (website). However, over the past decade it has become more prevalent. In 2002 one fatal yellow fever death occurred in the United States in an unvaccinated traveler returning from a fishing trip to the Amazon.
West Nile virus (WN) emerged from its origins in 1937 in Africa into Europe, the Middle East, west and central Asia and associated islands. Similar to the other encephalitis it is cycled between birds and mosquitoes and transmitted to mammals (including horses) and man by infected mosquitoes. While over 25 species of mosquitoes have tested positive for WN transmission, the Cules pipiens group seem the most common species associated with infecting people and horses. It first appeared in North America in 1999 in New York. with 62 confirmed cases and 7 human deaths. Nine horses died in New York in 1999. In 2001 66 cases (10 deaths) were reported in 10 states. It occurred in birds or horses in 27 states and Washington D.C., Canada and the Caribbean. There were 733 horse cases in 2001 in 19 states with Florida reporting 66% of the cases and approximately 33% were fatal. In 2001 more than 1.4 million mosquitoes were tested for WN. As of June 2002, 14 states and Canada have reported positive bird or horse cases in 2002, but no human cases have thus far been reported. It is a central nervous system infection similar to EEE. There is a vaccine for horses.
Other Resources:
Kentucky Mosquitoes and their control: University of Kentucky Entomology Alameda County Mosquito Abatement District
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Frequently Asked Question on Mosquitoes
Why do mosquitoes bite?
Why do mosquitoes seem to bite some people, but not others?
Why do mosquitoes bites itch and swell?
Where do mosquitoes breed?
What is the average lifespan of a mosquito?
Will winter bring an end to West Nile-carrying mosquitoes?
How many types of mosquitoes are there?
Courtesy: National Biological Information Infrastructure
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