Mosquito - Life Cycle

Life Cycle

Like all flies, mosquitoes go through four stages in their life cycle: egg, larva, pupa, and adult or imago. In most species, adult females lay their eggs in stagnant water; some lay eggs near the water's edge; others attach their eggs to aquatic plants. Each species selects the situation of the water into which it lays its eggs and does so according to its own ecological adaptations. Some are generalists and are not very fussy. Some breed in lakes, some in temporary puddles. Some breed in marshes, some in salt-marshes. Among those that breed in salt water, some are equally at home in fresh and salt water up to about one third the concentration of seawater, whereas others must acclimatise themselves to the saltiness. Such differences are important because certain ecological preferences keep mosquitoes away from most humans, whereas other preferences bring them right into houses at night.

Some species of mosquitoes prefer to breed in phytotelmata (natural reservoirs on plants) such as rainwater accumulated in holes in tree trunks, or in the leaf-axils of bromeliads. Some specialise in the liquid in pitchers of particular species of pitcher plants, their larvae feeding on decaying insects that had drowned there or on the associated bacteria; the harmless genus Wyeomyia provides such examples — Wyeomyia smithii breeds only in the pitchers of Sarracenia purpurea.

In contrast, artificial water containers, such as the odd plastic bucket, flowerpot "saucer", or discarded bottle or tire, are important breeding places for some of the most serious disease vectors, such as species of Aedes that transmit dengue and yellow fever. Some of these are disproportionately important vectors because they are well placed to pick up pathogens from humans, and to pass them on to other humans. In contrast, no matter how voracious, mosquitoes that breed and feed mainly in remote wetlands and salt marshes may well remain uninfected and seldom encounter humans to infect in turn anyway.

The first three stages—egg, larva and pupa—are largely aquatic. These stages typically last 5–14 days, depending on the species and the ambient temperature, but there are important exceptions. Mosquitoes living in regions where some seasons are freezing or waterless spend part of the year in diapause; they delay their development, typically for months, and carry on with life only when there is enough water or warmth for their needs. For instance, Wyeomyia larvae typically get frozen into solid lumps of ice during winter and only complete their development in spring. The eggs of some species of Aedes remain unharmed in diapause if they dry out, and hatch later when they are covered by water.

Eggs hatch to become larvae, which grow until they are able to change into pupae. The adult mosquito emerges from the mature pupa as it floats at the water surface. Bloodsucking mosquitoes, depending on species, gender, and weather conditions, have potential adult lifespans ranging from as little as a week to as long as several months.

Some species can overwinter as adults in diapause.