Jo Nagai of Kobe, Japan began hand-raising swallowtail butterflies when he was just a second grader.

But when it came time to release them to the wild, Nagai realized a peculiar pattern of behavior — the butterflies often lingered after release, even flying back to him at times.

It made him wonder: Did his caterpillars still remember him, even after they had experienced metamorphosis?

To find out, Nagai reached out to esteemed Georgetown entomologist Dr. Martha Weiss, who has long studied the behavior and the memory of insects — particularly moths.

He had been intrigued by a study she published in 2008 on an adult moth’s ability to retain memories even after its body had broken down and rebuilt itself.

In a four-page letter, Nagai introduced himself. Weiss later read the letter aloud on the Signal Hill podcast.

NAGAI AND WEISS. SIGNAL HILL PODCAST

“To Martha Weiss,” she said. “Hello. Nice to meet you. My name is Jo Nagai. I’m from Japan. I live in Kobe, Japan. I’m in the second grade at Ibuki Elementary School. When I found your research on the internet, I was so delighted!!”

Annie Rosenthal, who is both a Signal Hill editor and Weiss’ daughter, noted the “two exclamation marks” in their interview.

“Two bold exclamation marks,” Weiss confirmed.

In the letter, Nagai asked Weiss about her landmark study on moth memory and asked how he could expand it to his butterflies.

At first, Weiss doubted whether an elementary school student could recreate the same experiment that she and her grad student, Doug Blackiston, had established in a secure lab setting over a decade earlier.