The typical elementary-aged child in Japan spends their free time playing baseball, collecting Pokémon cards, and reading all the manga they can get their hands on. For Jo Nagai of Kobe, Japan, however, his spare time was filled with a more eclectic pursuit. He started hand-raising swallowtail butterflies. 

Asian swallowtails are identified by the bright dots that outline their wings. They’re also fantastic pollinators for local plants and flowers. As Jo cared for his insect companions, he noticed a particularly heartwarming behavior. Once he released them into the wild, the butterflies would linger for a bit, then fly right back to him. This observation sparked a curious question in the young boy’s mind: Did his butterflies actually remember him?

Reaching out to an unexpected pen pal

Determined to find an answer, Jo started looking online for scientific studies that might correlate to his question. The answer came in the form of Dr. Martha Weiss, a renowned entomologist at Georgetown University who had previously studied whether moths could retain memories from their caterpillar days. In a recent Radiolab podcast, Dr. Weiss recounts how the then second-grader Jo penned a detailed four-page letter to her. Nagai asked if she knew the best way to expand........

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