Adult mosquitoes are small, fragile insects with slender bodies; one pair of narrow wings and three pairs of long slender legs. They vary in length from 3/16 to 1/2 inch. Mosquitoes have an elongated "beak" or piercing proboscis with which the female bites and feeds on blood. Usually a blood meal is required before producing each batch of eggs. Male mosquitoes feed upon plant nectar. Eggs of most mosquitoes hatch in two to three days. Larvae, which hatch from eggs, feed on organic matter in water. Larvae mature and change in seven to ten days. Pupae, shaped like commas, 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 to adult may be as short as 10 days or as long as months, depending on environmental conditions. Cool weather delays development. Some mosquitoes have one generation each year, while others may have four or more generations, building up to large populations by later summer.