Friday, April 11, 2008

Mosquito

Mosquitoes are small, delicate, two-winged flies, the adult females of which are pests to humans and many other animals because they feed on blood. Because of this habit several species serve as carries of disease such as malaria, filariasis, dog heathworm, arboviral encephaitis, and yellow fever.

Mosquitoes can be distinguished from other true flies by an elongated sucking proboscis and scales along the wing veins and on the body. The scales vary in color and arrangement, giving each species a characteristic appearance. The species belong to the insect order Diptera, family Culicidae. The more than 2600 species are divided into 31 or more genera, 12 of which are found in the United States. Mosquitoes are distributed worldwide in all but the most extreme habitats.



Mosquitoes pass through four stages; egg, larva, pupa, and adult. Mosquito larva can live in water, and they usually feed on micro plankton. They move by wiggling their bodies, hence they common name "wiggler", and by the waving motion of their mouth brushes. Larvas are transformed into adults during the comparatively brief, non feeding pupal stage. Unlike most other insects, mosquito pupae are active, diving in response to potentially threatening stimuli. Most breathe at the water's surface by means of respiratory tubes or "trumpets." Adults emerge at the water's surface.



Only female are blood feeders, although both males and females feed on flower nectar. Most females require a blood meal to produce a batch of eggs. A mosquito may be attracted to its victim by warmth, odor, moisture and even carbon dioxide. Using carbon dioxide gradients, the mosquito may be able to follow a sleeping person's breath to its source.


The mosquito's mouthparts consist of two pairs of needlelike maxillae and mandibles; a food channel, which sucks up the blood or nectar, a saliva channel, and a sheath. When a mosquito bites, it first inserts the pointed, barbed pair of maxilae, which achor the mouthparts in the skin and provide leverage for the insertion of the remaining four parts. The sheath slides back as the other mouthparts pass through its tip. The mosquito's saliva, which contains anticoagulants to stop the blood from clotting, is injected into the skin, causing the area around the bite to swell and itch.


Mosquito control is effected in several ways, including draining breeding areas. Applying thin oil to water to kill the larvae, spraying with insecticides, and employing biological agents, such as small fishes that eat mosquito larvae. The incidence of mosquito-borne disease, however, is increasing rapidly. The tiger mosquito, Aedes albopicus, unlike other mosquitoes, is able to carry many disease-causing viruses. Native to Asia, it is now also found in United States.


Many kind of mosquito can transfer diseases to human, usually diseases that caused by virus. Many diseases can be transferred by mosquito like dengue fever, malaria, westnile diseases, cikungunya as in Indonesia and many others.

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