Second Grader Proves Butterflies Remember Their Past Lives

When Jo Nagai released the butterflies he'd raised from caterpillars, something strange happened. They kept coming back to him.

The second grader from Kobe, Japan wondered if his butterflies somehow remembered him from their caterpillar days. Most people would assume metamorphosis erased all memory, but Nagai wasn't convinced.

He found Dr. Martha Weiss, a Georgetown entomologist who had studied moth memory in 2008. Nagai wrote her a four-page letter introducing himself and asking for help with his butterfly experiment.

"When I found your research on the internet, I was so delighted!!" the seven-year-old wrote. Weiss initially doubted a second grader could replicate her complex lab study, suggesting he try something simpler instead.

Nagai refused to give up. "I really want to prove it's possible that my butterflies can remember what they learned as a caterpillar," he insisted in his next letter.

His determination won Weiss over. She helped him design an experiment he could run at home using materials he had access to.

Nagai created two groups of caterpillars. He exposed one group to lavender oil while giving them gentle shocks from a miniature muscle therapy device. The control group received no training.

After the caterpillars transformed into butterflies, 80% of the trained group avoided the lavender smell. His butterflies remembered their caterpillar experiences.

He sent Weiss a 33-page document detailing his findings. "I was flabbergasted and delighted," Weiss said on the Signal Hill podcast. "I thought, 'Holy cow, he's a real scientist, and he's figuring out new stuff.'"

In 2022, the same year he graduated from second grade, Nagai presented his research to scientists at three Japanese universities. He didn't stop there.

A year later, Nagai discovered something even more remarkable. His butterflies appeared to pass these memories down to their offspring. Soon, he and Weiss will publish their findings in the Journal of the Lepidopterists' Society.

Sunny's Take

At 10 years old, Nagai is already collaborating with top scientists and challenging what we know about insect memory. When Weiss visited Japan to meet him, she gave him a magnifying glass like the one she wears, a symbol of their scientific partnership.

When asked about his future career, Nagai surprised everyone. He doesn't want to be an entomologist but an insect veterinarian instead. "I can fix caterpillars and insects both," he explained.

There are no insect vets yet, so he'd be the first.