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Encyclopedia > Mosquitos
This article is about the insect; for the WWII aircraft see De Havilland Mosquito.
Mosquitoes

Anopheles gambiae
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Suborder: Eudiptera
Family: Culicidae
Genera

See text.

Mosquitoes are insects belonging to the order Diptera; genera include Anopheles, Culex, Psorophora, Ochlerotatus, Aedes, Sabethes, Wyeomyia, Culiseta, and Haemagoggus with a total of around 35 genera into which are placed about 2700 species. Mosquitoes have been around for 170 million years. They have two scaled wings, halteres, a slender body, and long legs; size varies but is rarely greater than 15 mm (0.6 inches). Mosquitos weigh only about 2 to 2.5 mg (0.03 to 0.04 grains). They can fly at about 1.5 to 2.5 km/h (0.9 to 1.6 mph).


"Mosquito" is a Spanish or Portuguese word meaning little fly, and its use dates back to about 1583. Mosquitoes are not indigenous to Britain, but their close relative, the midge, is prevalent in certain areas, particularly Northern England and Scotland.

Contents

Natural History

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.

Enlarge
Mosquito larvae, or "wigglers," grow suspended in stagnant pools of water and breathe air through siphons in their tails

The mosquito 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 20C (68F) and only ten days at 25C (77F). Some species have a life cycle of as little as four days or up to one month. The larvae are the "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 lavae or adults. Mosquitoes of the genus Culex (a vector for St. Louis encephalitis) overwinter as mated adult females.


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 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 has.


When a mosquito bites, 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, sensitivity 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 may become desensitized to mosquitoes, and not have any reaction to their bites, but others can become hyper-sensitive; bites cause large painful red welts.


Mosquito Prevention and control

Much of modern mosquito control is no longer dependent on dangerous pesticides but specialized organisms that eat mosquitos, 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.


Mosquito repellents 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.


Bibliography

  • Gillett, J. D. 1972. The Mosquito: Its Life, Activities and Impact on Human Affairs. Doubleday, Garden City, NY, 358 p. ISBN 0385011792
  • Spielman, A., and M. D'Antonio. 2001. Mosquito: A Natural History of Our Most Persistent and Deadly Foe. Hyperion Press, New York, 256 p. ISBN 0786867817

External links


  Results from FactBites:
 
Untitled Document (1106 words)
mosquitoes lay their eggs one at a time, sticking them together to form a raft of from 200- 300 eggs.
mosquitoes are strong fliers and are known to fly many miles from their breeding sources.
mosquitoes are painful and persistent biters also, but prefer to attack at dusk and after dark, and readily enter dwellings for blood meals.
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