It turns out that insects can remember lessons they learned as caterpillars through metamorphosis.
The researchers investigated close relatives of the caterpillars called tobacco hornworms, which pester tomato growers. Blackiston, Weiss and their colleague developmental biologist Elena Casey trained tobacco hornworm caterpillars to avoid a specific odor - ethyl acetate, the smell of nail polish remover - when they got a whiff at the same time as a mild electric shock.
The scientists found caterpillars that learned to avoid an odor when they were younger than three weeks did not retain this response as adult moths. However, older caterpillars remembered to avoid the odor after their metamorphoses. In other words, the more mature a caterpillar's brain was, the more memories carried over.
"It doesn't make sense to throw away a perfectly good brain, and even if a caterpillar's brain isn't quite right for a butterfly's or moth's body, it makes sense there are components in the brain that are worth preserving," Weiss told LiveScience.
Although vertebrates such as humans and invertebrates such as caterpillars are quite different, "it might be possible to look at metamorphosis, which involves an extensive reorganization of the nervous system, and maybe use those results to look at brain reorganization in vertebrates after damage such as a stroke," Weiss added. "That's going out on a limb a bit, but not beyond the realm of possibility."