Mosquitoes undergo complete metamorphosis, passing through four distinct stages during their life cycle: egg, larva, pupa, adult/imago.
A complete cycle from egg to egg (whole developmental cycle) can be as fast as about 14 days or as long as several months in diapausing species. Larval diapausing as well as hibernation or aestivation in females has been reported in some mosquito species.
The eggs of mosquitoes are brown or blackish and are laid singly or in rafts
(1) on the water surface of diverse types of water collections;
(2) on the undersides of floating vegetation, to which they are 'glued'; and
(3) on wet mud, leaf litter or other damp substrates near the edge of water. In the latter case they usually hatch when flooded.
In detail, anopheline eggs are black, laid on the water surface and possess lateral floats. They cannot withstand desiccation and hatch within 2-3 days, although hatching can take up to 2-3 weeks in colder climates.
Regarding culicine eggs, eggs of Aedes and Ochlerotatus species are black and usually deposited on damp substrate just beyond the water-line. They can withstand desiccation, and dry eggs may remain viable for months or even a few years. They hatch when becoming flooded. Eggs of Culex and Coquillettidia are brownish and laid upright and together, thus forming egg rafts that float on the water surface. Eggs of Mansonia are laid in a sticky mass that is glued to the undersides of floating vegetation.
In nature, usually 4 to 5 ovipositions per female occur, with 30-500 eggs each. The site of oviposition is species-specifically chosen according to water chemistry and a circadian rhythm.
In the tropics, eggs hatch within 1-2 days, in cooler climates this process might take 1-2 weeks.