54 | New Scientist | 11 December 2021The back pages Almost the last word
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From a human perspective,
mosquitoes don’t have many
positives. What would be the
ecological consequences if
they were eradicated?Jane Monroe
Arcata, California, US
Mosquitoes are a major food
source for many bird and bat
species, and larval mosquitoes
are regularly eaten by various
freshwater fish and aquatic insects
such as backswimmers, larval
dragonflies and diving beetles.
These mosquito consumers
in turn provide food and other
resources for other organisms.
Bats, for example, play a critical
role in the health of cave
ecosystems; they also
consume, and help control,
many agricultural pests.
The eradication of mosquitoes
might please humans in the
short term, but would eventually
damage many ecosystems due to a
cascade of negative consequences
as more and more species wereaffected. A better plan might be
to eradicate the disease-causing
parasites that use mosquitoes
as a vector.Jonathan Wallace
Newcastle upon Tyne, UK
This is a variant of the “what is
the point of...?” question that
often gets posed about species
we consider to be pests.
The eradication of
mosquitoes would certainly
have consequences. Firstly,
there is the question of how the
mosquitoes would be eradicated.
Spraying pesticides is the most
common method, and it is
inevitable that non-target
species are also affected.DEEP
OL
BYPLAINPICTURE
/FRED
ER
IC^ CIROUThe second question is what
effect would the absence of
mosquitoes have? Although
we are mainly familiar with
the bloodsucking habits of
mosquitoes, their principal food
source is flower nectar. Blood is
only consumed by females to
provide the additional protein
required for egg production.
Through their flower visiting,
they are part of the overall guild
of insects that act as pollinators.
Another potential impact of
mosquito eradication is on the
behaviour of other species. In
places with many flying biting
insects, cattle, horses and other
large grazers spend parts of the
day resting in dusty, vegetation-
free areas that are exposed to
the wind, as a means of gaining
respite from the insects.It is possible that wiping out
the biting flies could remove a
behavioural constraint on these
herbivores that would enable
them to graze for longer in
areas that are currently only
tolerable for short periods of
time due to the fly density. Who
knows what impact this might
have on the vegetation?Eric Kvaalen
Les Essarts-le-Roi, France
A 2010 article entitled “Ecology:
A world without mosquitoes”,
in the journal Nature, discussed
the idea of totally eradicating
mosquitoes. It concluded:
“Ultimately, there seem to be few
things that mosquitoes do that
other organisms can’t do just as
well – except perhaps for one. They
are lethally efficient at suckingblood from one individual
and mainlining it into another,
providing an ideal route for the
spread of pathogenic microbes.”Double dipper
The constellations are pictures
we perceive by “connecting the
dots” of random stars, but it
seems incredible that we have
two dippers in the night sky with
similar shapes and proportions.
Is this just a coincidence or is
there an explanation?Garry Trethewey
Cherryville, South Australia
The explanation isn’t in the sky, it
is in our pattern recognition. Our
brains actively connect the dots
and exclude other dots to produce
shapes that are meaningful to us.
I am sure that any random
spatter of variable dots could
produce a group that looks like
a dipper: four dots that look
vaguely square with a line
emerging from a corner. If you
preferred pentagons or triangles,
you would find them too.Hillary Shaw
Newport, Shropshire, UK
Our ancestors looked at the
brightest stars and joined the dots
to make objects they were familiar
with. A random scatter of points
on a surface will almost inevitably
lead to several quartets of four in a
rough rectangle, with a few more
off one corner making a “handle”.
Since water is the second most
urgent human need after air, our
ancestors would be familiar with
ladles, or dippers, to lift water,
with bent handles for leverage,
and saw them in the stars.
Looking at a diagram of the Big
Dipper, one can easily make other
patterns. For example, join the star
Phecda with Alkaid instead of with
Megrez and you get a convex wall,
or maybe a reclining chair.
Perhaps it is surprising we only
have two dippers.This week’s new questions
Rousing stuff Why does stretching and yawning
after waking up feel so pleasant and what are the
benefits? Ashley la Grange, Watford, Hertfordshire, UKImpending doom Do any animals, other than
us, have an awareness of their own mortality?
Stefan Slater, Tideswell, Derbyshire, UKCats, dogs and humans all
instinctively stretch and yawn
after waking, but why?“ The eradication of
mosquitoes might
please humans in the
short term, but would
eventually damage
many ecosystems”