A couple things to add to the previous answers:
"There are about 170 different kinds of mosquitoes in North America." Pest World for Kids (I found the site at the Internet Public Library.)
"A mosquito passes through four distinct stages during its life: egg, larva, pupa, and adult. Eggs are laid either singly or in clusters; if in clusters, up to 300 eggs are attached together to form a sort of "raft." The females of some mosquito species lay their eggs on the surface of calm water (e.g., small ponds and puddles sheltered from wind by grass and other vegetation, or human-made "containers" such as birdbaths, old tires, and plastic swimming pools), whereas the females of other species lay their eggs on damp soil destined to be flooded; either way, the eggs end up floating at the water’s surface. While most eggs hatch into larvae within 2-3 days, those of some species that are laid late in the season may withstand the harsh conditions of winter and hatch the following spring. (The eggs of some species are more resistant to drying out than others; some even require drying out before subsequent flooding can induce them to hatch.) Mosquito larvae – "wigglers" - live from 4-14 days in the water; most breathe air through a tube to the surface and eat microorganisms and other organic matter that they filter from the water. They then metamorphose into pupae ("tumblers") - the "resting" or non-feeding stage – which float at the surface but are capable of diving/tumbling to safety when disturbed. The pupal stage lasts from 1-4 days, as development to the adult stage continues inside the protective covering. When fully developed, the adult mosquito breaks out of the pupal case and finds its way to the surface of the water, where it rests until its body dries and hardens. Mating and blood feeding generally do not occur for a couple of days after adults emerge.
"Outdoor temperatures and species-specific characteristics determine the rate at which mosquitoes pass through these stages (and the rate at which WNV is replicated inside infected mosquitoes; see "The Virus"); under favorable – warm - conditions, some mosquitoes can develop into adults from eggs in less than a week. Most adult female mosquitoes live for about two weeks before they are parasitized or eaten by birds, bats, amphibians, or spiders (males live about one week); lucky females may survive 2-3 months. Adult females that emerge late in the season may hibernate through the winter, to begin laying eggs again in the spring."
US Government Science Site
