Aedies Aegypti

Aedes Aegypti
The mosquito that has attracted the most attention is the mosquito Aedes
aegypti. It belongs to the family Culcidae, consisting of about 2,500 species
(Encyclopedia Britanica 1999), along with other genera of mosquitoes such as
Anopheles, Culex, Orthopodomyia, and the Toxorynchites, to name a few (Womack
1993, E.B. 1999). This mosquito has been known best for transmitting yellow fever and
human dengue throughout the tropic and subtropic of the Americas (Womack, M 1993).
This mosquito along with others are looked upon as pests and nuisances in modern day
society because of their attraction to moisture, lactic acid, carbon dioxide, body heat and
movement (E.B. 1999) but we can not confuse the Aedes aegypti with any other
mosquito for it has a very distinct look to it as well as a specific habitat. It has many
related species and it’s geographic distribution is extremely wide and varied.

The Aedes aegypti, with regard to both sexes, are generally similar in coloration
(Womack 1993). The female adult is noticed by it’s small dark figure that is colored by
white markings and banded legs. Its proboscis or snout is mostly black with regard to
the white palp tips (Russel 1996). The dorsal pattern of white scales on the scutum is in
the shape of a lyre’ with two central based stripes that contrast with the dark scales
present on the insect (Womack 1993,
Russel 1996). Its wings are dark scaled and femur and hind legs are pale scaled for
about three-quarters, and dark scaled for about two-thirds (Russel 1996).
The first through the fourth segments of the hind tarsi are characterized by white rings
and the fifth segment is all white.

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Adults can be found in abundance in towns and cities near human dwelling
places., living in trees, herbaceous plants, dim closets, cabinets or even old automobile
tires (Womack 1993, Juliano 1998). The species feeds mostly during the day increasing
its feeding rate two hours after sunrise and several hours before sunset ( Womack
1993, Geographical Magazine 1998), while it is not rare for females to feed under
artificial light at night. The above feeding habits of the Aedes aegypti contributes to the
species’ life span which is dependent on nutrition, temperature and humidity (Womack
1993) as well as its ability to avoid predators such as reptiles or even sometimes other
types of mosquitoes (E.B. 1999). The male mosquito can only live a short time ranging
from a few days to a couple weeks whereas the female can live up to a month which
allows her to reproduce longer (Womack 1993).
They lay their eggs in artificial containers on damp surfaces such as jars, urns,
cans or anything that can contain rain water (Womack 1993, Juliano 1998). The eggs
hatch when they become flooded by deoxygenated water, except during winter(Womack
1993, Juliano 1998) and after which can only survive in temperatures above ten degrees
or below 44 degrees Celsius (Womack 1993). The larvae feed on aquatic microbiota
which develops inside the artificial
containers in which the eggs are laid (Womack 1993). In the pupal stage they are free
swimming and active and breathe by means of tubes on the thorax (E.B.
1999). The limitations of availability of habitat has greatly affected the geographic
distribution of the species.

They have a “cosmopolitan range extending from 40 degrees N to 40 degrees S
latitude.” says Womack (1993). It is found throughout the world in tropic and subtropic
regions (Womack 1993). The species has been distributed throughout New England
staying close to the marshes and damp areas and away from dry and cold climates. It is
not only the dry and cold climates that threaten the Aedes aegypti but one of its
associated species as well.
The Aedes albopictus is an Asian mosquito that was introduced to North America
in the 1980s (Hawley 1988, OMeara et al. 1992,1993,1995, Juliano 1998). It has spread
throughout the north and now threatens declines in the Aedes aegypti because of its
“positive population growth at higher combined density and lower per capita resource
availability” (Juliano 1998). The A. albopictus is a successful invader because of its
generalized habitat, its adaptation to many climates, ability to live in human dominated
areas, as well as its food requirements and its desiccation resistant eggs (Hawley 1988,
Focks et al. 1994, Juliano 1998). The “primary determinant of success” says Juliano
(1998) “was survivorship to adulthood.” The Aedes aegypti only survived well in it’s
environment when it was raised alone at a low density with a high resource availability
(Juliano 1998). Competition for these resources among larvae is what seems to
sufficient in accounting the near replacement of the A. aegypti with the A. albopictus. It
is a species that lives to survive, feed and reproduce and although this may not seem
difficult, Juliano has shown us that Darwin’s theory of evolution and natural selection is
one that prevails in all species of organisms and in this battle the A. aegypti is losing to a
fellow, more adapted mosquito the A. abopictus.

Some other related species of the A. aegypti are the A. notoscriptus (Russel
1996), the A. triseriatus, A. atropalupus, Othopodomyia signifera, Toxorhynchites rutilis,
Culex nigripalpus, Culex quinquefasciaus, Culex resuans, and Culex salinarius
(Womack 1993).

The A. aegytpi is a species best known for infecting people with such diseases as
yellow fever and human dengue. Its life cycle is very simple compared to many other
organisms. The female feeds on a blood diet to mature her eggs (E.B. 1999), and she
lays them in a damp artificial container. The time for development of these eggs to
mosquitoes is anywhere from four to ten days depending on the water temperature and
the food supply (Womack 1993). Soon after the organism passes through the pupal
stage they mate and start the cycle over again.