Mosquito Life Cycle
Many mosquitoes, such as
Culex quinquefasciatus, lay their eggs on the surface of fresh or
stagnant water. The water may be in tin cans, barrels, horse troughs, ornamental
ponds, swimming pools, puddles, creeks, ditches, catch basins or marshy areas.
Mosquitoes prefer water sheltered from the wind by grass and weeds.
Culex mosquitoes usually lay their eggs at night over a
period of time sticking them together to form a raft of from 100 to 300 eggs. A
raft of eggs looks like a speck of soot floating on the water and is about 1/4
inch long and 1/8 inch wide. A female mosquito may lay a raft of eggs every
third night during its life span.
Anopheles, Culex and Mansonia eggs are more susceptible to long
periods of drying out.Anopheles and many other mosquitoes lay their
eggs singly on the water surface. Aedes and Ochlerotatus mosquitoes lay their eggs singly,
usually on damp soil. Aedes and Ochlerotatus eggs are more resistant to drying out (some require
complete drying out before the eggs will hatch) and hatch only
when flooded with water (salt water high tides, irrigated pastures, treeholes
flooded by rains, flooded stream bottoms).
Tiny mosquito larvae emerge from the eggs within 24 - 48 hours almost in
unison.
Mosquito larvae, commonly called "wigglers," live in water from 4 to 14
days depending on water temperature.
Larvae must come to the surface at
frequent intervals to obtain oxygen through a breathing tube called a siphon.
They are constantly feeding since maturation requires a huge amount of energy
and food. They hang upside down at the water surface with the breathing tube up
and the brushes by their mouths filtering anything small enough to be eaten
toward their mouths to nourish the growing larva. They feed on algae, plankton,
fungi and bacteria and other microorganisms. One mosquito species larva feeds on
larvae of other mosquitoes: Toxorhynchites, the largest mosquito known,
are predators of other mosquito larvae sharing their habitat. Their larvae
are much larger than other mosquito larvae.
During growth, the larva
molts (sheds its skin) four times. The stages between molts are called instars.
At the 4th instar, the usual larva reaches a length of almost 1/2 inch and
toward the end of this instar ceases feeding. When the 4th instar larva
molts, it becomes a pupa.
Mosquito pupae, commonly called "tumblers," live in water from 1 to 4
days, depending upon species and temperature.
The pupa is lighter than
water and therefore floats at the surface. It takes oxygen through two breathing
tubes called "trumpets." The pupa does not eat, but it is not an inactive stage.
When disturbed, it dives in a jerking, tumbling motion toward protection and
then floats back to the surface.
The metamorphosis of the mosquito into an adult is completed within the pupal
case. The adult mosquito splits the pupal case and emerges to the surface of the
water where it rests until its body dries and hardens.
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