|Do flies remember experiences gained as larvae?
|Question Date: 2004-10-22|
That's an excellent question.
After all, the
animal completely reorganizes its body during
metamorphosis, so how can memories remain intact?
But apparently ants can use larval memories as
adults. Researchers tested this by keeping
newly-hatched larval ants with nestmates, with
ants from another colony, or by themselves. Then
they tested the ants when they were adults to see
which kind of larvae they cared for the most.
They found that ants gave more care to the type of
larvae that they had spent time with when they
were larvae. In other words, they did remember
something about what had happened when they were
That's a very interesting question. Flies
certainly don't seem very smart,and if you don't
observe them very carefully, you'd probably guess
that they do not remember very much of what they
encounter. Many scientists use flies to study
learning and memory, though. Those scientists look
very carefully,and they use very clever tests, and
they find that flies remember a lot more about
their experiences than most people would have
thought possible. They even use flies to find
genes involved in memory, or to study the effects
of alcohol and drugs on memory. Most of this
research is done on adult flies,so I don't know
how good larvae are at remembering things. I
suspect that they're not as good as the adults,
but still better than most people think.
All questions about memory and consciousness in
animals are difficult to answer, because we can't
just ask them questions about their memory like we
can do with other humans. But we can still find
out things about the way flies think by doing
experiments on their behavior. These sorts of
experiments mostly tell us that instead of having
complex behaviors and long memories like humans
do, flies and other insects behave according to a
basic set of rules that don't change over their
For example, when you see a peanut
butter and jelly sandwich on your plate, you might
think back to all the PB&Js you've eaten in your
life, and remember that you like grape jelly
better than strawberry, or that you like the crust
cut off instead of left on, and then decide
whether or not you want to eat the sandwich. On
the other hand, a fly's thinking might go like
this: I have landed on something. It is sugary.
I eat sugary things. I will eat this.
takes a lot of energy to have a big, complicated
brain that can hold on to memories and make
decisions using those memories, and a fly's brain
just isn't that complicated. So flies probably
don't really remember things in the same way that
you and I remember things. (By the way, those set
of rules that flies and other animals use to make
decisions are often called "instincts"). Plus,
there's really no reason for a fly to need to
remember something that happened when it was a
As you've learned, fly larvae are very
different from adult flies. Larvae eat different
kinds of food, have different enemies, and move in
a different way from adults. These differences
ensure that young larval flies don't have to
compete with their parents for food and space.
These differences also mean that there's not much
that happens to a larval fly that an adult fly
would need to remember. What good would it do an
adult fly to know what kind of rotting flesh
tastes good, when adult flies are busy eating
PB&Js instead? Since having a big, complicated
brain that can remember things takes a lot of
energy, and flies don't need to remember things,
they probably save energy and just don't hang on
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