When Jo Nagai noticed that butterflies he had raised as caterpillars kept flying back to land on him, he didn’t just wonder why — he designed an experiment to find out. The 10-year-old elementary school student from Kobe, Japan ended up producing evidence that caterpillar memories survive metamorphosis, a finding that professional entomologists had largely assumed was impossible. And then he found something even stranger: the butterflies’ offspring remembered too.
What a kid from Kobe figured out that scientists hadn’t
The core question Jo Nagai was asking sounds almost philosophical: if a caterpillar’s body dissolves into a cellular soup inside a chrysalis before rebuilding itself into a completely different animal, does anything from its former life survive? Most biologists would have told you no. The nervous system effectively liquefies during metamorphosis — it seemed unreasonable to expect memories to make it through intact.
Jo set up a home lab and reached out to Dr. Martha Weiss, an entomologist at Georgetown University who had previously researched memory in moths. Impressed by the detail and seriousness of his letter, Weiss agreed to mentor him remotely. What followed was a months-long classical conditioning experiment using Asian swallowtail caterpillars, a Y-shaped test chamber, and lavender oil as the key stimulus. One group of caterpillars was repeatedly exposed to the lavender scent alongside a mild vibration pulse from a handheld muscle therapy device — essentially the kind of low-frequency unit used in physical therapy, not a torture instrument, despite what some corners of the internet concluded. A control group received no training at all.
Once both groups completed metamorphosis, Jo placed the butterflies in the Y-chamber: one path smelled of lavender, the other was scent-free. The control butterflies split roughly 50/50. The trained butterflies avoided the lavender path roughly 80% of the time. The memory had survived the complete structural dismantling of their bodies. the science of how memory forms and disappears
The part that stunned even the scientists mentoring him
The 80% avoidance result was already significant. But Jo didn’t stop there.
He bred the trained butterflies and ran the same lavender-path test on their offspring — caterpillars that had never been exposed to the scent or the vibration pulse. Those offspring also avoided lavender at rates well above chance. This points toward a rare form of transgenerational epigenetic memory inheritance: the idea that an experience lived by one generation can leave a biological imprint that shapes the behavior of the next, without the offspring ever living through the original event themselves. It has been documented in some plants and a handful of animal species, but finding a signal of it in insects — and in a home lab in Kobe — is the kind of result that makes researchers want to replicate it immediately.
Jo compiled his findings into a 33-page paper, presented at university scientific conferences, and co-authored a formal study with Dr. Weiss. The controversy that spread online — fueled partly by the censored description of ‘electric shocks’ — largely misread the methodology. The pulse used was clinically mild, equivalent to what a physiotherapist might use on a human muscle. The adults who supervised the project, including a credentialed academic partner, were not enabling cruelty. They were enabling science. And the science, improbably, worked.
He wants to be an insect veterinarian when he grows up
For all the attention the study attracted — international headlines, entomology forums lighting up, the viral backlash and its subsequent debunking — the detail that lands hardest is the one at the end of his biography. When asked what he wants to do when he grows up, Jo Nagai said he wants to become an insect veterinarian so he can help cure sick bugs. The boy who proved butterflies carry memories across one of nature’s most radical transformations wants, above everything else, to make sure they’re okay. That is not a footnote. That is the whole story.
- remarkable child scientists who changed what we know
