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| An Unnoticed Menace |
August 3rd, 2003.
By Professor Fabio Cupul
Permanent Member of the Mexican Association for
the Dissemination of Science and Technology. |
In most cases, we only consider dangerous
to our physical integrity those things which we can
perceive clearly with our senses or which, because of
their unpleasant or ferocious appearance, may be considered
a menace. Thus it is not strange to find out that many
people dream or think of sharks, crocodiles, lions or
poisonous snakes as cruel, bloodthirsty assassins of
defenseless humans.
Contrary to our “reasoning”,
fueled for years by Hollywood’s film industry,
sharks only consider an average of six people per year
as part of their dietary complement. For their part,
crocodiles only have one fatal encounter per year with
people in the United States and Mexico.
The tendency to consider those animals
dangerous, a potential menace to mankind, able to put
an end to human civilization, is a product, in part,
of our fabulous communication media that is able to
convert an isolated and infrequent event into a common,
global one. As example, we just have to look at the
recent outbreak of SARS that affected a few hundred
people around the world but whose contagiousness, due
to its exaggerated dissemination, generated worldwide
panic. In fact, it is more probable that one may lose
his life to a drunken driver or be prey to government
corruption.
Curiously enough, the communication
media also tend to generate the opposite effect in minimizing
events of great magnitude and importance. Do you happen
to remember the 40 million people around the world who
die of hunger every year?
It would appear that we are only
concerned with what we can plainly see or that which
affects us directly. It is curious that while our great
enemy is taken so lightly and we look for ways to eliminate
crocodiles, lions or sharks from “our” spaces
at any cost, we aren’t doing anything to fight
the mosquitoes that transmit diseases such encephalitis,
elephantiasis, the Nile virus, malaria or dengue, all
of which truly have the potential to exterminate entire
populations at a rate of two million deaths per year.
The first thing a good war strategist
does to get an advantage over his enemy is to get to
know him. Thus, we will proceed to speak of certain
aspects of the fascinating and revealing life of mosquitoes
– our unnoticed menace.
Mosquitoes are winged insects that
appeared in the history of evolution approximately 150
million years ago. Today there are around 2,000 species
among which only a few are carriers of diseases. Their
life cycle goes through various stages: an egg from
which an aquatic larva emerges that can survive those
conditions thanks to a siphon that enables it to breathe
the air in the atmosphere, then passing on to a chrysalis
stage from which the adult specimen emerges in the form
we recognize so well by the specific sound it makes
as it flaps its wings 600 times per second.
Although the vampire bat is the one
that enjoys a very bad reputation because of its habit
of feeding on blood (even though it does so without
causing any pain to its victim and nearly never causing
death), there is no question that it is the female mosquitoes
that should bear the name of the Romanian Count of Transylvania
that immortalized British writer Bram Stoker (1847-1912).
After all, they are the ones that cut their victims’
skin to introduce their sucking organ and thus extract
the vital fluid drop by drop (females feed on blood
because they need proteins for the hard labor of reproduction
and production of eggs).
Besides their maddening buzzing,
female mosquitoes also notify us of their presence (a
little late for our bodies) through the intense stinging
they provoke in our skin at the moment of the sting
as well as during and after the bloodsucking process.
This occurs because the mosquitoes’ saliva, that
prevents the coagulation of blood in the wound to facilitate
its suction, possesses a protein that causes an allergic
reaction in most people, manifesting itself as itching
and swelling in the affected area.
The buzzing of the female mosquito’s
wings is without a doubt most unpleasant to our ears,
but to the male it is notes of love that invite him
to an encounter during which they will let their sexual
instincts loose. These love notes generated by the female’s
wings flapping will only be generated when she is ready
to mate. Until then, she can fly through a crowd of
males without being bothered.
Mosquitoes detect their potential
sources of food through smell. They do so by placing
themselves downwind in order to detect any scents. But
to guide them as they fly against the wind, they use
their sense of sight. Also, not everything about mosquitoes
is negative. Its role in nature as a link in the food
chain is obvious. Its aquatic larvae that feed on rotting
vegetable or animal remnants as well as excrements,
also work as small purifying plants that maintain the
environment where they develop in a clean state.
During the history of cohabitation
of humans and mosquitoes, the latter have proliferated
due to the public works of the former that generate
residual pools, flooded gutters and conditions that
are generally optimal for their multiplication. By deforesting
natural areas, we are allowing for more solar radiation
which, combined with humidity, expands the mosquito’s
habitat and reproduction stage. In addition, the growing
intercontinental mobility of the human population represents
another contributing factor to the increase of the impact
of certain diseases that mosquitoes may transmit, either
directly or through other animals.
Finally, it has been proven that
one of the biggest stimuli to the proliferation of mosquitoes
has been insecticides. At the time, products such as
DDT were effective in the eradication of problems with
malaria. However, as they have done in many other experiments,
organisms have become resistant to the most potent chemical
products. That shows that we are simply providing greater
advantages for the mosquito’s development when
we should really be changing our battle strategies.
Vallarta’s
Nature Field Guide - File 1: Possum Wood
 The
photograph that accompanies this text clearly shows
the spine-covered trunk of the tree called the “Bean
of San Ignacio” (Hura polyandra), also known as
“Possum Wood” or “Habillo” in
Spanish.
This tree reaches 20 meters in height
and up to 50 cm in diameter. The trunk is straight,
covered with many sharp spines that stick out of circular
cones. They grow along the slopes of the Gulf of Mexico
from the center of Veracruz, Tabasco, eastern Puebla,
northern Chiapas, to the Yucatán peninsula and
along the slopes of the Pacific coast from Sonora to
Chiapas. Its main product is the wood it provides for
rural construction.
The latex that flows from the trunk
is caustic and causes skin inflammation and burns in
some people. In some localities, it is used to “stun”
river fish so that they may be caught more easily.
The seeds are poisonous. In some
regions, they are used in small doses as a laxative,
but their use can be quite dangerous. The ingestion
of seeds in higher doses can produce nausea, vomiting,
stomach aches, bloody diarrhea, accelerated pulse, loss
of vision, convulsions and finally death.
Professor Cupul is a Permanent
Member of SOMEDICYT, the prestigious Mexican Society
for the Dissemination of Science and Techniques
cupul@pvmirror.com Archives
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