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Mosquito Life Histories
Nature Bulletin No. 682 June 2, 1962
Forest Preserve District of Cook County
John J. Duffy, President
David H. Thompson, Senior Naturalist
MOSQUITO LIFE HISTORIES
Everybody knows that a mosquito is a small, long-legged
insect that bites. However, there are many kinds of them
each with its own peculiarities of life history and habits.
Some are produced in marshes or in flood plains of streams,
some in puddles, some in woodlands, and others in cities
and towns. Here in the Chicago region, although
mosquito-borne diseases are no longer a danger, they
become nuisances in many places at certain times in
almost every year. In times past and in many countries
the mosquitoes which carried malaria, yellow fever
and other infections shaped the course of history.
Hundreds of scientists have studied them for years
but much remains to be learned.
All mosquitoes pass through four distinct stages in
their life history -- egg, larva, pupa and the flying
adult. The mosquito larva is commonly called a wiggletail,
wiggler or wriggler; and the pupa a tumbler.
The eggs of mosquitoes have shapes like spindles --
but so small that a single egg can scarcely be seen with the
naked eye. The females of the twenty or thirty species in
this region lay their eggs in one of three ways. The rather
rare malaria mosquito, Anopheles, for example, lays eggs
singly on weedy backwaters and pools where they hatch
after a few days. The widespread house mosquito, Culex
pipiens, is typical of several local species of a second type.
It glues a hundred or more eggs into a tiny floating raft on
the stagnant or polluted water collected in garden pool s,
catch basins, clogged gutters and junk heaps. The extremely
troublesome floodwater mosquitoes are a third type. They
lay their eggs in damp places just above the water line of
swamps and marshes. The eggs lie dormant until they are
flooded by a warm rain, then hatch in a matter of hours. The
eggs of our most abundant floodwater species, Aedes vexans,
may produce a new generation every few weeks or hold over
for two years or more, depending on summer water levels.
That fierce biter, Aedes stimulans, must have its eggs frozen
before they hatch.
All mosquito larvae, or wigglers, live in water -- even in tree
holes, pitcher plant leaves and flowing streams. They feed on
small plant and animal life, either alive or dead, which they
scoop into their mouths with brushlike rakes. The larvae of
one kind devours other mosquito wigglers. As they grow they
shed their skins four times for new and larger ones. They breathe
air at the surface either through a snorkel tube or a plate on
the rear of the body. When alarmed they dive tail first to the
bottom with whip-like somersaults. An exceptional species
gets its oxygen by piercing the underwater air chambers of
cattails and other water plants.
After a week or two as wigglers, they change into acrobatic
tumblers shaped like big-headed question marks. These breathe
air through a tube on the back but they do not eat. After a few
days, they come to the surface, the skin pops open, the adults
crawl out onto the water, the wings unfold, then they fly away.
Both
sexes hum or "sing" in flight but only the females suck
blood. The males feed on nothing but plant juices and nectar.
The females of most species require a meal of blood before
they can produce eggs but usually get it from our livestock
and wild mammals. A few prefer birds' blood but one of our
most common kinds never takes blood. A few bite in the shade
in daytime but the worst pests are active in the evening and
at night.
The entire life cycle of the mosquito can be watched in the
schoolroom or laboratory by bringing in some stagnant water
with an egg raft of the house mosquito, or by soaking a piece
of sod from a dried-up marsh containing the eggs of
floodwater mosquitoes.
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Update: June 2012
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