The bug that poops candy - George Zaidan
This is Mabel.
Mabel is an aphid, a small insect
in the same order as cicadas, stink bugs,
and bed bugs.
All these bugs pierce their prey
and suck out vital fluids.
Aphids’ prey are plants.
And what aphids are after
is buried within the plant,
flowing in tubes made from single cells
strung end-to-end.
These are called sieve tubes and together
they form the plumbing system
for a plant’s most valuable resource: sap.
Sap is mostly water and sugar.
Some species’ sap has as much sugar
per liter as a can of soda.
Photosynthesis is constantly
producing sugar.
You can think of it as a chemical “pump”
which generates incredibly high pressure—
up to 9 times that of a car tire—
in the sieve tubes.
To feed, Mabel uses her stylet,
which is a long, flexible needle.
She slowly worms it into the tissue,
between the plant’s cells,
until she pierces
one of those sieve tubes.
Because the sap
is under so much pressure,
Mabel doesn’t even have to suck it out
of the plant.
She just opens a valve in her head
and lets the pressure push the sap
through her digestive system.
We’ll come back to what comes out
of her butt, but for now,
you should know that plants don’t want
to be punctured and sipped.
So they try to defend themselves.
One defense is the sap itself.
To see how that works, let’s
hypothetically hook up
some other insect’s digestive tract
to a steady stream of sap.
When that sap touches the insect’s cells,
its high sugar content
encourages the water in the cells
to come out by osmosis…
exactly like salt encourages water
to come out of a slug.
The more sap that passes through
the insect, the more water it loses.
Eventually, it shrivels up and dies.
Mabel’s gut, however, is packed
with an enzyme called sucrase,
which takes two molecules of sucrose
and converts them into one molecule
of fructose and one of…
this three-unit sugar.
Mabel burns the fructose for energy,
leaving the three-unit-sugar behind.
Now, how does that help her?
The more molecules of sugar
that are dissolved in the sap,
the more water it can suck out
of Mabel’s cells.
By reducing the number of molecules
of sugar in the sap,
Mabel reduces its ability to suck water
out of her cells.
Plant sap neutralized.
Now that means Mabel can feed for days,
getting all the energy
she needs to reproduce.
Some aphid species
have an incredible life cycle.
For example, the green peach aphid.
During the fall, males and females mate,
and the females lay eggs.
But in the spring, when the eggs hatch,
all the nymphs that emerge are female.
When those females reach maturity,
they don’t lay eggs.
Instead, they give birth to live young…
that are clones of themselves…
and already pregnant…
with their own clones.
So, these female aphids have
two generations of baby aphid clones
forming inside themselves
at the same time.
Scientists call this
telescopic development.
That means that aphids can make
more of themselves fast—
there can be 20 generations
within a single season—
and that means lots of aphid poop.
Mabel can poop her entire body weight
every two hours,
making her one of the most prolific
poopers on the planet.
Some aphid populations can produce
hundreds of kilograms of poop per acre.
Now, aphid poop is not like your poop.
Chemically, it’s not all that different
from sap;
it’s a clear and colorless sweet,
syrupy liquid.
You might already know it
by a different name: honeydew.
Other species love honeydew.
Some species of ants love it so much
they sort of
herd and defend entire aphid colonies.
In return, the ants get a steady supply
of sweet honeydew,
which they can drink directly
from the aphids’ butts.
Bottom’s up!
Humans love honeydew, too.
Several Native American tribes
used to harvest it from tall reeds
and make it into cake.
And some species of bee make honey
from honeydew,
which humans then harvest and eat.
So plants make the sap,
which is eaten and pooped out by aphids,
regurgitated by bees,
harvested by humans,
and dolloped into a cup of Earl Grey tea.
