Fun Fact: Most moths remember being caterpillars!
About a month ago, I was talking to a kid and their parent about butterflies, because I will talk to anyone and everyone about bugs if given the opportunity. As a throw away comment, I told the child that they should always be kind to caterpillars, because they will remember it as butterflies!
The main reason I said this was to remind the child to be respectful to living things in general, but the parent expressed shock at this tidbit and asked me how on earth scientists could possibly have figured that out. So I told her, and now I’m going to tell all of you!
The short answer is that, basically, we gave a bunch of caterpillars an education, and then, after they transformed into moths, we tested their memory!
(The caterpillar and moth pictures used in this post are not the same species as was used in the study, which were Manduca sexta, and in fact these pictures are of two different species, but shhhh)
Of course, caterpillar school isn’t the same as human school. Instead, the caterpillars were taught to associate a little shock (similar to a static shock from a doorknob) with a very specific scent.
After a few repetitions, the caterpillars were individually given the choice to travel down one of two paths: one with the scary scent and one with “clean air”.
Before metamorphosis, 80% of the caterpillars chose the “clean air” path.
After the caterpillars metamorphosised into moths, they were tested again, and it was found that 77% of moths went down the path with “clean air”.
This means that approximately 54% of the moths remembered their training as a caterpillar!
But wait, didn’t 77% of the moths choose “correctly”? Shouldn’t that mean that 77% of the moths remember being a caterpillar?
Nope! Why not? Well, mostly due to math (my frenemy).
See, when the scientists tested untrained moths (and also ones who were only exposed to the shock, or only exposed to the scent as a caterpillar) they found that they went down the clean air path about 50% of the time, which is about what we would expect if the moths were choosing randomly.
This means that, among the moths who completely forgot their training, we would expect approximately 50% of them to select the “clean air” path”. In other words, about half of the forgetful moths in this test were “correct” by accident, sort of like guessing the answer for a True or False question.
54% may or may not be better than the percent of humans who remember literally anything they learned while in school (see: me googling how to do basic algebra to figure out that 54% number). I don’t know what percent of my schooling I remember, but it definitely isn’t 100%
Still, considering how much of the caterpillar becomes mush during metamorphosises, even 54% of the moths remembering is really, really impressive!
Now, these numbers are inexact, simply because we’re working with probability and also because we have to make a few assumptions.
For example, we are assuming that EVERY moth that remembered their training would have avoided the scary scent and taken the “clean air” path. However, this is not actually guaranteed! Maybe some moths remembered the scary scent and still decided to take the scary air path.
Why would they do this? Well, we can’t be sure, but I’m going to imagine it’s because of something like this:
So there you have it! This is how we know that most moths (and presumably butterflies) remember being caterpillars!
This has been Fun Fact Friday, warning you to treat caterpillars kindly, just in case one decides to come after you for VENGENCE as a butterfly.
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