Mosquito Life Cycle
The mosquito goes through four separate and distinct stages of its life
cycle: Egg, Larva, Pupa, and Adult. Each of these stages can be easily
recognized by its special appearance.
Egg: Eggs are laid one at a time or attached together to
form “rafts.” They float on the surface of the water. In the case of Culex
and Culiseta species, the eggs are stuck together in rafts
of up to 200. Anopheles, Ochlerotatus and Aedes, as
well as many other genera, do not make egg rafts, but lay their eggs singly.
Culex, Culiseta, and Anopheles lay their eggs on the
water surface while many Aedes and Ochlerotatus lay their eggs on damp
soil that will be flooded by water. Most eggs hatch into larvae within 48 hours;
others might withstand subzero winters before hatching. Water is a necessary
part of their habitat.
Larva: The larva (plural -
larvae) lives in the water and comes to the surface to breathe. Larvae shed
(molt) their skins four times, growing larger after each molt. Most larvae have
siphon tubes for breathing and hang upside down from the water surface.
Anopheles larvae do not have a siphon and lie parallel to the water
surface to get a supply of oxygen through a breathing opening.
Coquillettidia and Mansonia larvae attach to plants to obtain
their air supply. The larvae feed on microorganisms and organic matter in
the water. During the fourth molt the larva changes into a
pupa.
Pupa: The pupal stage is a resting, non-feeding
stage of development, but pupae are mobile, responding to light changes and move
(tumble) with a flip of their tails towards the bottom or protective areas. This
is the time the mosquito changes into an adult. This process is similar to the
metamorphosis seen in butterflies when the butterfly develops - while in the
cocoon stage - from a caterpillar into an adult butterfly. In Culex
species in the southern United States this takes about two days in the summer.
When development is complete, the pupal skin splits and the adult mosquito
(imago) emerges.
Adult: The newly emerged adult rests on
the surface of the water for a short time to allow itself to dry and all its
body parts to harden. The wings have to spread out and dry properly before it
can fly. Blood feeding and mating does not occur for a couple of days after the
adults emerge.
The egg, larva and pupa stages depend on temperature and
species characteristics to determine how long they take for development. For
instance, Culex tarsalis , a common California (USA) mosquito,
might go through its life cycle in 14 days at 70º F and take only 10 days at 80º
F. On the other hand, some species have naturally adapted to go through their
entire life cycle in as little as four days or as long as one month.
The
following pictures show a typical mosquito egg raft, larva, pupa, and adult, and
explain more about each stage.
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