mosquito

All about the Mosquito       
Mosquito (from the Spanish meaning little fly, is a common insect in the family Culicidae (from the Latin culex meaning midge or gnat. Mosquitoes resemble crane flies (family Tipulidae) and chironomid flies (family Chironomidae), with which they are sometimes confused by the casual observer.
Mosquitoes go through four stages in their life cycle: egg, larva, pupa, and adult or imago. Adult females lay their eggs in water, which can be a salt-marsh, a lake, a puddle, a natural reservoir on a plant, or an artificial water container such as a plastic bucket. The first three stages are aquatic and last 5–14 days, depending on the species and the ambient temperature; eggs hatch to become larvae, then pupae. The adult mosquito emerges from the pupa as it floats at the water surface. Adult females can live up to a month – more in captivity – but most probably do not live more than 1–2 weeks in nature.
Mosquitoes have mouthparts which are adapted for piercing the skin of plants and animals. They typically feed on nectar and plant juices. In some species, the female needs to obtain nutrients from a "blood meal" before she can produce eggs.
There are about 3,500 species of mosquitoes found throughout the world. In some species of mosquito, the females feed on humans, and are therefore vectors for a number of infectious diseases affecting millions of people per year.
 
 
The duration from egg to adult varies considerably among species and is strongly influenced by ambient temperature. Mosquitoes can develop from egg to adult in as little as five days but usually take 10–14 days in tropical conditions. The variation of the body size in adult mosquitoes depends on the density of the larval population and food supply within the breeding water. Adult flying mosquitoes frequently rest in a tunnel that they build right below the roots of the grass.
Adult mosquitoes usually mate within a few days after emerging from the pupal stage. In most species, the males form large swarms, usually around dusk, and the females fly into the swarms to mate.
Males live for about a week, feeding on nectar and other sources of sugar. Females will also feed on sugar sources for energy but usually require a blood meal for the development of eggs. After obtaining a full blood meal, the female will rest for a few days while the blood is digested and eggs are developed. This process depends on the temperature but usually takes 2–3 days in tropical conditions. Once the eggs are fully developed, the female lays them and resumes host seeking.
The cycle repeats itself until the female dies. While females can live longer than a month in captivity, most do not live longer than 1–2 weeks in nature. Their lifespan depends on temperature, humidity, and also their ability to successfully obtain a blood meal while avoiding host defenses.
Length of the adult varies but is rarely greater than 16 mm (0.6 in), and weigh up to 2.5 mg (0.04 grain). All mosquitoes have slender bodies with three sections: head, thorax and abdomen.
The head is specialized for acquiring sensory information and for feeding. The head contains the eyes and a pair of long, many-segmented antennae. The antennae are important for detecting host odors as well as odors of breeding sites where females lay eggs. In all mosquito species, the antennae of the males in comparison to the females are noticeably bushier and contain auditory receptors to detect the characteristic whine of the female. The compound eyes are distinctly separated from one another.
 Their larvae only possess a pit-eye ocellus. The compound eyes of adults develop in a separate region of the head. New ommatidia are added in semicircular rows at the rear of the eye; during the first phase of growth, this leads to individual ommatidia being square, but later in development they become hexagonal. The hexagonal pattern will only become visible when the carapace of the stage with square eyes is molted.[6] The head also has an elongated, forward-projecting "stinger-like" proboscis used for feeding, and two sensory palps. The maxillary palps of the males are longer than their proboscis whereas the females’ maxillary palps are much shorter. (This is typical for representatives of subfamilies.) As with many members of the mosquito family, the female is equipped with an elongated proboscis that she uses to collect blood to feed her eggs.
The thorax is specialized for locomotion. Three pairs of legs and a pair of wings are attached to the thorax. The insect wing is an outgrowth of the exoskeleton. The Anopheles mosquito can fly for up to four hours continuously at up to 1–2 km/h travelling up to 12 km (7.5 mi) in a night.
The abdomen is specialized for food digestion and egg development. This segmented body part expands considerably when a female takes a blood meal. The blood is digested over time serving as a source of protein for the production of eggs, which gradually fill the abdomen.
Both male and female mosquitoes are nectar feeders, but the females of many species are also capable of hematophagy (drinking blood). Females do not require blood for their own survival, but they do need supplemental substances such as protein and iron to develop eggs.
In regards to host location, carbon dioxide and organic substances produced from the host, humidity, and optical recognition play important roles. In Aedes the search for a host takes place in two phases. First, the mosquito exhibits a nonspecific searching behavior until the perception of host stimulants then it follows a targeted approach.
Most mosquito species are crepuscular (dawn or dusk) feeders. During the heat of the day most mosquitoes rest in a cool place and wait for the evenings, although they may still bite if disturbed. Some species, like Asian tiger mosquito, are known to fly and feed during daytime.
Mosquitoes are adept at infiltration and have been known to find their way into residences via deactivated air conditioning units.
Prior to and during blood feeding, they inject saliva into the bodies of their source(s) of blood. This saliva serves as an anticoagulant: without it, the female mosquito's proboscis would quickly become clogged with blood clots. Female mosquitoes hunt their blood host by detecting carbon dioxide (CO2) and 1-octen-3-ol from a distance.
Mosquitoes of the genus Toxorhynchites never drink blood. This genus includes the largest extant mosquitoes, the larvae of which prey on the larvae of other mosquitoes. These mosquito eaters have been used in the past as mosquito control agents, with varying success.
 
In order for the mosquito to obtain a blood meal it must surmount the vertebrate physiological responses. The mosquito, as with all blood-feeding arthropods, has mechanisms to effectively block the hemostasis system with their saliva, which contains a mixture of secreted proteins. Mosquito saliva negatively affects vascular constriction, blood clotting, platelet aggregation, angiogenesis and immunity and creates inflammation.Universally, hematophagous arthropod saliva contains at least one anticlotting, one anti-platelet, and one vasodilatory substance. Mosquito saliva also contains enzymes that aid in sugar feedingand antimicrobial agents to control bacterial growth in the sugar meal. The composition of mosquito saliva is relatively simple as it usually contains fewer than 20 dominant proteins.
Despite the great strides in knowledge of these molecules and their role in bloodfeeding achieved recently, scientists still cannot ascribe functions to more than half of the molecules found in arthropod saliva. One promising application is the development of anti-clotting drugs based on saliva molecules, which might be useful for approaching heart-related disease, because they are more user-friendly blood clotting inhibitors and capillary dilators. 

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