Geoscience Reference
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A
B
C
Figure 7-5. Damsell y and dragonl y comparison (see Color Plate 7-5). A. Eastern forktail female damsell y ( Ischnura
verticalis ) resting with wings folded together over her back. B. Common green darner dragonl y ( Anax junius ) sitting
on foliage with its wings extended to the sides. Wing span
10 cm. C. Temperature-dependent color change of the
common green darner: left at 7 °C, right at 24 °C. Photos A and C courtesy of R. Beckemeyer; photo B by J.S. Aber.
quickly to l ight temperature in the morning
(Beckemeyer, pers. com.).
7.2.2 Mosquitos
Among all wetland insects, mosquitos are the
most hated and misunderstood. Almost every
person alive has been bitten by mosquitos.
Beyond the temporary nuisance of their bites,
mosquitos transmit human diseases, particularly
malaria, that are endemic in many parts of the
world. Among some 3500 mosquito species,
several species of the genus Anopheles are the
vectors for malaria (Curtis 2007). More than 60
mosquito species may carry the West Nile virus
in the United States, mostly in the genera Aedes
(Fig. 7-6), Anopheles and Culex (Centers for
Disease Control 2009). For this reason, individu-
als and health organizations have sought to
eradicate all mosquitos, regardless of species,
through various means, which often include the
draining and destruction of natural wetlands.
All mosquitos require water to complete their
life cycles - from a prairie marsh to a beer can
in a roadside ditch. Some mosquitos lay their
eggs on the water surface, and these eggs hatch
within one or two days. In other cases, the eggs
are laid in depressions and may remain dormant
for many years until the site is l ooded. Some
eggs may hatch with the initial l ooding event;
others may require several wet-dry cycles before
hatching (North Carolina State University 2004).
Figure 7-6. Close-up view of a female Aedes aegypti
mosquito taking a blood meal from a human host (see
Color Plate 7-6). This is the most common species of
Aedes and a major vector for West Nile Virus as well as
Dengue and Dengue hemorrhagic fever. Image by
J. Ganthany (2006), courtesy of U.S. Centers for Disease
Control and Prevention (CDC).
The authors experienced one such event in
southern Saskatchewan, Canada in 1991. After
several years of drought, a wet period caused a
massive summer outbreak of mosquitos. All
outdoor human events had to be cancelled, and
cattle were stricken in the i eld.
Mosquitos breed in many potential sites in
a typical American community (Purdue 2008).
For urban, commercial, suburban, stream, wood-
land, and catch-basin environments, mosquitos
breed and some may carry viruses that cause
human diseases. Favored breeding sites include
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