Mosquito
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| Mosquitoes Conservation status: Secure | ||||||||||||
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 Anopheles gambiae | ||||||||||||
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The mosquito (pl. mosquitos, mosquitoes) is a member of the family Culicidae; these insects have a pair of scaled wings, a pair of halteres, a slender body, and long legs. The females of most mosquito species suck blood from other animals. Size varies but is rarely greater than 15 mm (0.6 inch). Mosquitoes weigh only about 2 to 2.5 mg (0.03 to 0.04 grain). They can fly at about 1.5 to 2.5 km/h (0.9 to 1.6 mph). Mosquitoes have been around for 170 million years.
The family Culicidae belongs to the order Diptera and contains about 2700 species in about 35 genera including Anopheles, Culex, Psorophora, Ochlerotatus, Aedes, Sabethes, Wyeomyia, Culiseta, and Haemagoggus.
"Mosquito" is a Spanish or Portuguese word meaning little fly, and its use dates back to about 1583. Before then, they were called "biting flies" in English, but the term "mosquito" was adopted to prevent confusion with the house fly.
The female mosquito (in many common species) sucks the blood of mammals, including humans, which is commonly referred to as a bite. Mosquito bites often swell up hours after happening, causing a red ringed white bump about a centimeter in diameter. This bump can itch for days and over-scratching the bite can also cause it to bleed. Mosquito bites can transmit diseases, such as Malaria and West Nile Virus, so many areas take measures to reduce mosquito populations through pesticides or more organic means. An easy way to reduce mosquito populations in a residential area is the removal of standing water (where mosquitoes breed), and the use of repellants, such as citronella candles.
Natural History
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In most female mosquitoes, the mouth parts form a long proboscis for piercing the skin of mammals (or in some cases birds or even reptiles and amphibians) to suck their blood. The females require protein for egg development, and since the normal mosquito diet consists of nectar and fruit juice, which has no protein, most must drink blood to get the necessary protein. Males differ from females, with mouth parts not suitable for blood sucking. There is one genus of mosquitoes, Toxorhynchites, that never drinks blood. The larvae of these large mosquitoes are predatory on other mosquito larvae.
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The mosquito undergoes complete metamorphosis, i.e. it goes through four distinct stages in its life cycle: egg, larva, pupa, and adult. The length of the first three stages is species- and temperature-dependent. Culex tarsalis may complete its life cycle in 14 days at 20 °C (68 °F) and only ten days at 25 °C (77 °F). Some species have a life cycle of as little as four days or up to one month. The larvae are the "wrigglers" or "wigglers" found in puddles or water-filled containers. These breathe atmospheric oxygen through a siphon at the tail end. The pupae are nearly as active as the larvae, but breathe through thoracic "horns" attached to the thoracic spiracles. Most larvae feed on microorganisms, but a few are predatory on other mosquito larvae. Some mosquito larvae, such as those of Wyeomyia live in unusual situations. These mosquito wigglers live either in the water collected in epiphytic bromeliads or inside water stored in carnivorous pitcher plants. Larvae of the genus Deinocerites live in crab holes along the edge of the ocean.
Most mosquito species outside of the tropics overwinter as eggs, but a significant minority overwinter as larvae or adults. Mosquitoes of the genus Culex (a vector for St. Louis encephalitis) overwinter as mated adult females.
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The females of blood sucking species locate their victims primarily through scent, they are extremely sensitive to the carbon dioxide in exhaled breath, as well as several substances found in sweat. Some people seem to attract mosquitoes more than others. Being male, being overweight, and having type 'O' blood may increase the risk of being bitten. Mosquitoes can detect heat, so they can find warm-blooded mammals and birds very easily once they get close enough.
Mosquitoes and health
Some mosquitoes are capable of transmitting protozoan diseases such as malaria (see Plasmodium falciparum), filarial diseases like filariasis, and viral diseases such as yellow fever, dengue, encephalitis, and West Nile virus.
West Nile virus was accidentally introduced into the United States in 1999 and by 2003 had spread to almost every state. Through the transmission of such diseases, it can be argued that mosquitoes have caused more human deaths than any other animal.
When a mosquito first bites a human, she injects saliva and anti-coagulants. When one is first bitten there is no reaction, but after several bites the body's immune system becomes sensitized and an itchy red mark appears about a day after the bite. This is the usual reaction in young children.
After many more bites, the sensitivity of the human immune system increases, and an itchy red hive appears in minutes where the immune response has broken capillary blood vessel and fluid has collected under the skin. This type of reaction is common in older children and adults.
Some adults could possibly become desensitized to mosquitoes, and not have any reaction to their bites, but others can become hyper-sensitive; bites cause large painful red welts.
Mosquitoes are also very irritating as sometimes they tend to fly around the ears of humans thus their wingbeats coming within audible range of the human ear. This is especially more pronounced during the monsoon season in tropical climates when the incidence of mosquitoes increase manyfold. The buzzing noise wakes up people who would otherwise have not been disturbed by the mosquito bite alone. This has prompted many to stuff their ears with cotton to shut out the buzzing of the mosquitoes.
Mosquito control
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Much of modern mosquito control is no longer dependent on dangerous pesticides but specialized organisms that eat mosquitoes, or infect them with a disease that kills them. Such methods can even be used in Conservation Areas, like the "Forsyth refuge" and the Seaview Marriott Golf Resort, where some major mosquito control is performed and monitored using "killifish" and juvenile eels. The success is documented with most advanced underwater microscopes like the ecoSCOPE. However, outbreaks of human mosquito-borne diseases may still result in fogging with chemicals that are less toxic than those used in the past.
Dragonflies, also known as mosquito hawks, are excellent control agents. Dragonfly naiads consume mosquito larvae in the breeding waters, and adult dragonflies eat adult mosquitoes, particularly the day flying Asian Tiger Mosquitoes. Fogging for adult mosquitoes can backfire and increase long term populations if it removes dragonflies and other natural controls. Lizards are also useful predators which eat mosquitoes indoors.
Mosquito repellants generally contain one of the following active ingredients: DEET, Catnip oil extract, nepetalactone, citronella, or eucalyptus oil extract. Often the best "repellant" is a fan or gentle breeze as mosquitoes do not like moving air.
The most effective solutions for malaria control efforts in the third world are: mosquito nets, insecticide-laced mosquito nets, and DDT. Plain mosquito nets are cheap, they are completely effective in protecting humans within the net, they do not adversely affect the health of natural predators such as dragonflies, and do not require sophisticated public health capacity on the part of the government. The role of DDT in combating mosquitoes has been the subject of considerable controversy. While some argue that DDT deeply damages biodiversity, others argue that DDT is the most effective weapon in combating mosquitoes and hence malaria. While some of this disagreement is based on differences in the extent to which disease control is valued as opposed to the value of biodiversity, there is also genuine disagreement amongst experts about the costs and benefits of using DDT. Moreover DDT resistant mosquitoes have started to increase in numbers, especially in tropics due to mutations reducing the effectiveness of this chemical.
Other popular methods of household mosquito control are the use of small electrical mats plugged into a socket, mosquito repellent vapour and mosquito coil all having a form of allethrin - a chemical commonly used to combat mosquitos and other pests in general. Mosquito repellant candles containing Citronella oil is another method to keep mosquitoes at bay. Some more lesser known methods use the cultivation of plants like wormwood or sagewort, Lemon grass, lemon thyme and the mosquito plant (Pelargonium) which act against mosquitoes. However scientists have added that these plants are effective only when the leaves are crushed and used.
One of the non conventional methods of mosquito control is the use of electromagnetic, ultrasound devices designed to confuse mosquitoes. It has found use in a variety of devices including a downloadable software which is claimed to thwart the insects using PC speakers. However the effectiveness is questionable since computer speakers aren't designed for high frequency sounds (15-20 KHz range)