| 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 moving
(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.
How long each stage lasts depends on both temperature
and species characteristics. 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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