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. As opposed to a syringe's typically smooth needle, the mosquito proboscis is highly serrated, which leaves a minimal number of points of contact with the skin being pierced — this reduces nerve stimulation to the point where the "bite" is not felt at all, which is generally the case (see the Mosquitoes and health section below for an explanation on the swelling). The females require protein for egg development and laying, and since the normal mosquito diet consists of nectar and fruit juice, which has no protein, most must drink blood. Males differ from females, with mouth parts not suitable for blood sucking.
Mosquito larvae, "blood worms" or "wrigglers," grow in water.The mosquito undergoes complete metamorphosis, going through four distinct stages in its life cycle: egg, larva, pupa, and adult — a process that was first described by the Greek philosopher Aristotle. The length of the first three stages is dependent on the species and temperature. 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, whereas in other species some adult females can live through the winter, laying their eggs in the spring. Many species of mosquito live their adult stage in roughly two weeks to two months. The larvae are the "wrigglers" or "tumblers" found in puddles or water-filled containers. These breathe air 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.
A mosquito larvaThe 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. Empirical studies of mosquito bites suggest that the risk of being bitten follows an approximately negative binomial distribution. 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.
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