A mosquito passes through four stages in its life cycle. The stages are the egg, larva, pupa and adult. Eggs, larvae and pupae must have standing water to develop. There are four larval growth stages, called "larval instars." All larval stages resemble each other, except each is larger than the preceding one. The first stage hatches from the egg and the fourth stage molts to become the pupa.
Female mosquitoes lay their eggs on the water surface or in places that later become flooded. Eggs are elongate, about 1/40 inch (0.6mm) long and are dark brown or black when ready to hatch. Eggs are laid singly or in batches of 50 to 400. Several batches may be laid by one female. Usually, bloodsucking females require a blood meal before producing each batch of eggs.
Eggs of most mosquitoes hatch in two to three days, whereas others require a drying period and may remain dormant for many months or years, then hatch within minutes or days after being flooded by rainfall or a tide.
Larvae or "wigglers," which hatch from the eggs, feed on bits of organic matter in the water. Most larvae come to the surface of the water for air. Larvae mature in seven to ten days and change into a pupa or "tumbler" stage. Pupae are commashaped forms, called tumblers because of their tumbling motion when disturbed in the water.
Pupae usually transform into adults two to three days later. In another one to two days, females are ready to bite. The time required from egg hatch to adult may be as short as ten days or as long as seven months, depending on environmental conditions. Cool weather will delay development. Some mosquitoes have only one generation each year, whereas others may have four or more generations each year, building to large populations by late summer.
Adults usually remain close to the hatching areas; however, they can be blown by the wind for distances up to 40 miles. The usual range of migration is five to ten miles. Adult mosquitoes may live three weeks or more.