A 10 year old student in Kobe Japan has shown that Asian swallowtail butterflies keep memories formed while they were caterpillars and can transmit those learned responses to later generations. Jo Nagai first noticed the pattern while raising the insects at home. The butterflies he had cared for as larvae often stayed near him or flew back after release whereas wild ones left at once. That simple difference sparked years of careful testing that produced evidence consistent with earlier laboratory work on moths and earned him a place presenting at an international scientific meeting.
Nagai began observing swallowtails in early elementary school and by second grade around 2022 he had already run small projects on their life cycles. He searched online for studies about memory across metamorphosis and found the 2008 peer reviewed paper by Martha Weiss and colleagues at Georgetown University. That work used the tobacco hornworm moth and showed that an odor paired with mild electric shocks remained aversive after the insects became adults. Nagai wrote a detailed four page handwritten letter introducing himself describing his own observations and asking for help adapting the methods to butterflies. Weiss replied and a multi year correspondence began in which she advised on experimental design while he carried out the work in a home setting. The full account of their collaboration appears on the Georgetown University biology department site.
The procedures were straightforward yet systematic. Nagai divided caterpillars into trained and control groups. For the trained group he introduced the scent of lavender oil and then applied gentle vibrations from a small muscle therapy device so the insects associated the odor with an unpleasant stimulus. He avoided harsh chemicals and kept the intensity low enough that the caterpillars were never injured. After the insects completed metamorphosis he tested the resulting butterflies in a Y tube apparatus. One arm carried lavender scent and the other held plain air. Roughly three quarters of the trained adults chose the unscented arm while the untrained controls split evenly. He then allowed the trained butterflies to breed and tested their offspring and the following generation without giving those later insects any training. The aversion to lavender appeared in both subsequent generations. He recorded every step photographed the setup and compiled the results into a 33 page report that included data tables and diagrams. The original moth study that inspired the design is freely available through the PLOS ONE journal archive.
No external research grant or institutional funding supported the work. Nagai used materials already available at home and relied on the unpaid guidance of Weiss through letters and later email. He presented early results at Japanese universities while still in elementary school and in 2024 he shared a poster at the International Congress of Entomology held in Kyoto. The official conference listing records his contribution under the title noting that swallowtail butterflies remember what they learned as caterpillars and that the sex linked memories persist for three generations. Experts who reviewed the methods described the design as sound for its scale and the outcomes as consistent with known patterns of memory retention in related insects. Weiss herself has called the effort the work of a real scientist. Further formal peer review in a journal is still in progress yet the combination of guided protocol transparent documentation and public presentation at a major congress gives the findings clear scientific standing.
The sequence shows how sustained personal curiosity paired with accessible mentoring can produce original data on a classic biological puzzle. Complete metamorphosis rebuilds nearly the entire body and nervous system yet these results indicate that certain associations and possibly epigenetic marks survive the process and can influence behavior in descendants. The home based nature of the study limits sample size compared with large laboratory projects yet the careful controls and replication across generations strengthen its value. Nagai continues his schooling and has said he hopes to become a veterinarian able to treat insects as well as other animals. His path from backyard observation to conference presentation remains a clear illustration that careful method and open collaboration can still advance understanding even when resources remain modest.
