Illinois Natural History Survey Reports

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R e p o r t s
Summer 2008
No. 396
Effects of Stocked Sport
Fish on Aquatic Food
Webs
3
Soil Impoverishment and
Prairie Plant Growth
4
Vegetation Structure and
Composition of Arabuko-
Sokoke Forest, Kenya
5
Species Spotlight:
Prothonotary Warbler
6
The Naturalist's
Apprentice: Animal
Homes Made by Humans
7
New INHS Publications
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INSIDE
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150 years 1858 to 2008
The house mosquito (Culex pipi-ens
Linnaeus) is the most widely
distributed mosquito species in
the world, and is encountered
in all geographic regions except
Antarctica. The name “house
mosquito” comes from its close
association with human settle-ments.
Although Culex pipiens
breeds in rural areas including
marshlands, swamps, temporary
ponds, and irrigation schemes,
this mosquito thrives particularly
well under urban conditions.
Gravid females lay their eggs
in the form of rafts primarily in
polluted (high organic content or
eutrophic) water in waste tires,
abandoned cans, clogged roof
gutters, barrels, birdbaths, or any
place that can hold water long
enough for eggs to hatch and
the aquatic stages to complete
development. This allows them to
take advantage of habitats many
mosquito species avoid. After
emergence, adults will frequently
enter houses and feed on humans
during the night. The advent of
air conditioning greatly reduced
the presence of many mosquito
species in modern homes, but
species like Culex pipiens still
remain near residential areas due
to the abundance of urban larval
habitats, including catchbasins.
This species tends to feed within
a couple hours after dusk and be-fore
dawn, although environmen-tal
conditions can shift the peak
feeding until later at night.
Culex pipiens is so wide-spread
in North America that it is
difficult to believe that this mos-
The House Mosquito Culex pipiens:
A Threat in Your Backyard
quito species was unknown to the
Americas in the pre-Columbian
era. It was introduced to America
from Africa and Europe on ships,
probably on several occasions,
during the slave trade and Eu-ropean
colonization. In a short
period of time, these mosquitoes
were able to disperse throughout
the entire New World.
Culex pipiens has been a
difficult “nut to crack” for tax-onomists
and
vector bi-ologists.
Early
studies
of the
biology
of this
mosquito
often
resulted
in con-flicting
conclu-sions.
	
While
some researchers described this
mosquito as an annoying fierce
man-biter, others viewed it as an
insect with little or no interest in
humans, describing it as primar-ily
a bird feeder. Differences in
feeding behavior and diapause
capability of the northern form
and southern form of this species
led to the recognition of the group
as a species complex (sibling spe-cies).
Despite their ecological and
behavioral differences, adult fe-males
and immature stages of the
Culex pipiens complex cannot be
reliably distinguished based upon
their morphology alone. The only
reliable morphological character
that discriminates within the
group is the DV/D ratio of male
genitalia. This is an estimate of
the distance between the tip of
the dorsal (D) arm and the ventral
arm (V) and the distance separat-ing
the two dorsal arms (D). (See
photo on next page). The DV/D
ratio is not useful for identifying
adult females (see photo above),
which is the only life stage that
takes blood meals and thus can
transmit diseases.
The northern house mosquito
(Culex pipiens pipiens L), and the
southern house mosquito (Culex
pipiens quinquefasciatus Say)
are the most common forms of
the complex. The northern house
mosquito has a DV/D ratio <0.2,
Female of Culex pipiens pipiens. Photo by Michael Jeffords, INHS Office
of the Chief