Egg -- The small, white cylindrical eggs taper at one or both ends and darken with age. Eggs of Anopheles and Aedes mosquitoes are laid singly, while those of Culex mosquitoes are deposited in raft-like masses.
Larva -- Young larvae are difficult to see because they are light colored or nearly transparent and only about 3 mm long. Mature larvae, on the other hand, are usually greenish-brown or brown and up to 10 mm long. The head is distinct and usually dark on all four instars. Upon close inspection, most of these elongate larvae are quite hairy.
Pupa -- Smaller than mature larvae, pupae are comma-shaped with a slender, curved abdomen. They move through the water in a tumbling motion; hence, they are commonly called "tumblers."
Damage -- Mosquitoes are primarily annoyances in North Carolina. In some coastal resort areas, mosquitoes severely hamper outdoor activities and thereby influence the area's economic stability. Less often, they are vectors of disease.
Of the human diseases known to be caused by disease organisms transmitted by mosquitoes, malaria, yellow fever, and several kinds of encephalitis have been reported in North Carolina. Malaria and yellow fever have been eliminated. Heartworm disease of dog is also transmitted by mosquitoes. Only seven or eight of the over 50 known species of mosquitoes in North Carolina pose a health hazard.
Life History -- All mosquitoes require water to complete their life cycle. Some species of mosquitoes (including Anopheles and Culex) deposit their eggs on the surface of standing water in bird baths, tire tracks, swamps, roadside ditches, ponds, lakes, etc. Such water may be fresh or brackish. Each female lays batches of about 100 eggs, those of Culex being laid in a raft-like mass and those of Anopheles being laid singly on the surface of the water. Eggs laid in water usually hatch in 2 to 3 days.
The Aedes and Psorophora spp. mosquitoes, however, do not deposit their eggs on water. Instead they lay them singly in areas (containers, depressions in the salt marsh or woodlands, treeholes, old tires, etc.) That will eventually be flooded by tidal actions or rains. These eggs are drought resistant and can remain viable for several years.
Mosquito larvae, known as "wigglers," develop only in water and feed on bits of organic debris. There are four instars (larval growth stages). In North Carolina, larvae require between 5 days and 4 weeks to mature, depending on water temperature and species.
Fully grown larvae transform into active, nonfeeding pupae. Because both the larvae and pupae breathe air by species processes, they cannot remain completely submerged for very long. Usually both larvae and pupae are found together. With some species, the pupal stage lasts only a day, but in others it lasts up to a week.
A few days after emerging, adult females are ready to feed and mate. A blood meal is usually required before females can lay eggs and repeat the life cycle. The species covered here produce several generations per year, but others may complete only one or two. Some mosquitoes pass the winter as fertilized adults (Anopheles, Culex) while others overwinter as eggs (Aedes) or larvae.
Personal protection may be achieved with repellents and temporary control over community-wide areas which can be obtained with ULV sprays.