Electrocution Shows Moths Remember Their Caterpillar Memories

Recently scientists trained tobacco hornworm caterpillars to avoid a nail polish-like odor delivered in association with a mild shock in the lab. After the caterpillar entered the pupal stage and changed into a moth they still avoided the nail-polish odor, this showing that they retained the memory of their youth.

"We concluded that indeed the association does persist and is accessible to the adults in this artificial scenario," said study senior author Martha Weiss, a biologist at Georgetown University in Washington, D.C.
The finding also supports the idea that a piece of the caterpillar brain persists through metamorphosis, she added.

Scientists have long wondered whether memory could survive the dramatic reorganization of the moth brain during metamorphosis, Weiss noted. "The transition from a caterpillar to a moth or butterfly is really very dramatic," she said. For example, caterpillars and moths move, eat, and sense the world differently—not to mention appear nothing alike. (see previous post: Bird Poop Bugs)

Caterpillars younger than three weeks old learned to avoid the nail-polish odor but could not recall the information as adults. However caterpillars trained to avoid the nail-polish odor in the final stages before puation retained the lessons.

Larvae trained during the mid stage of caterpillars growth showed that in the final stages before pupation, they would avoid the odor. However this was not the case when they grew to moth adults.

The research may help explain how adult female moths that can eat a variety of food choose to lay their eggs on the same type of plant they fed on as larvae. If the moths retain some memories from their larval stage, as this research shows, then they could remember what they ate as "kids."

Study author Weiss describes it as an "if it was good enough for me, it's good enough for my kids" type of selection.