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Do flies remember experiences gained as larvae?
Question Date: 2004-10-22
Answer 1:

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 nest-mates, 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 larvae. Pretty amazing.

Answer 2:

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.

Answer 3:

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 lifetime. 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.

It 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 larva.

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 to memories.

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