Meet Jo Nagai: 10-year-old Japanese student who discovered butterflies can remember their time as caterpillars after he noticed that the caterpillars he had raised to recognise him after turning into butterflies

A 10-year-old student from Japan has captured worldwide attention after his fascination with butterflies led to a remarkable scientific study that is challenging long-held assumptions about insect memory. Jo Nagai, an elementary school student from Kobe, spent years carefully observing the Asian swallowtail butterflies he raised at home. His curiosity was sparked when he noticed that the butterflies appeared to recognise him even after undergoing metamorphosis from caterpillars. Determined to understand whether memories formed during the caterpillar stage could survive this dramatic transformation, Jo designed a series of experiments that have since been presented before professional scientists, generating discussions about animal cognition, metamorphosis and inherited behaviour. While some of his findings still require independent verification, his work has made him one of the youngest researchers to gain international recognition.

Who is Jo Nagai, the 10-year-old Japanese student behind the butterfly discovery?

Jo Nagai is a 10-year-old student at Ibuki East Elementary School in Kobe, Japan. He is also a scholar of the Son Masayoshi Philanthropic Foundation, which supports exceptionally talented young people across the country. Passionate about insects since early childhood, Jo has reportedly filled hundreds of handwritten pages with observations of insect behaviour. Despite gaining international recognition for his butterfly research, he says his long-term ambition is to become a veterinarian, reflecting his lifelong love for animals and nature.

The observation that started Jo Nagai’s butterfly research

Jo’s research did not begin in a laboratory or as part of a school assignment. Instead, it started with a simple observation while raising Asian swallowtail butterflies. He noticed that wild butterflies usually flew away when approached, but the butterflies he had raised from caterpillars often returned to his hand even after being released into the wild. This unusual behaviour led him to wonder whether butterflies could retain memories formed during their caterpillar stage despite undergoing complete metamorphosis. Motivated by that question, he spent several years documenting their behaviour and developing carefully planned experiments.

What did Jo Nagai’s butterfly experiments reveal?

To investigate his hypothesis, Jo exposed swallowtail caterpillars to the scent of lavender while simultaneously applying a mild vibration stimulus using a muscle-therapy device. After the caterpillars completed metamorphosis and emerged as butterflies, he tested them using a Y-shaped tube maze. According to his findings, around 70% of the adult butterflies avoided the lavender scent, suggesting they had retained memories formed before metamorphosis. These observations challenge the traditional belief that an insect’s nervous system is completely rebuilt during the pupal stage, erasing all previous memories. His findings add to a growing body of scientific research suggesting that some forms of memory may survive metamorphosis.

Possible evidence of inherited butterfly memories

One of the most striking aspects of Jo’s research involved studying later generations of butterflies. After breeding the conditioned butterflies, he reported that their offspring and even grandchildren also showed an increased tendency to avoid the lavender scent despite never being exposed to the original conditioning. He suggested that this behaviour could be explained through transgenerational epigenetic inheritance, a process in which environmental experiences may influence later generations without changing DNA sequences. However, scientists emphasise that this conclusion remains preliminary and will require further independent studies before it can be accepted as established scientific evidence.

How scientists are viewing Jo Nagai’s findings

Jo’s work has attracted considerable interest because it aligns with an emerging field of research exploring how insect memories survive metamorphosis. His study has been presented at scientific meetings, including the International Congress of Entomology in Kobe, where professional entomologists reviewed his findings. Although the research has generated significant discussion within the scientific community, it has not yet been published in a peer-reviewed scientific journal. Experts regard his work as an impressive contribution from a young researcher while noting that replication by independent scientists will be essential to confirm the results.

Why Jo Nagai’s butterfly research went viral

Jo’s story has spread rapidly across social media because it combines childhood curiosity with genuine scientific investigation. Many people have been amazed that a 10-year-old produced a detailed 33-page research paper and presented his findings before experienced scientists. Videos of his presentations and summaries of his work have attracted millions of views online, with many praising his dedication, patience and scientific thinking. At the same time, some users questioned the ethics of using an aversive stimulus on caterpillars, prompting debates about the methods used during the experiments. Others defended the study, noting that the procedures were designed to trigger natural defensive responses rather than intentionally harm the insects.

The scientific significance of Jo Nagai’s discovery

If future research confirms Jo’s findings, they could deepen scientists’ understanding of insect memory, metamorphosis and the possible role of epigenetics in transmitting learned behaviours across generations. His work also highlights how careful observation and curiosity can lead to meaningful scientific questions regardless of age. Beyond its scientific implications, Jo Nagai’s story has become an inspiring example of how young minds can contribute to real-world research, encouraging children around the world to pursue their curiosity, ask thoughtful questions and explore science through observation and experimentation.