Tokyo fireflies have mixed DNA, study finds

Fireflies in Tokyo, the capital of Japan, come from many different parts of the country. A group of scientists found this by studying the fireflies' DNA^*1. They announced the results on September 8, 2026. The study was published in the journal^*2 Conservation Genetics.

The scientists came from four universities in Japan: Meisei University, International Christian University, Kagoshima University and Saga University. They studied the Genji firefly^*3, a kind of firefly that lives in Japan. They looked at the DNA of 1,109 fireflies from 164 places across the country.

In Japan, Genji fireflies belong to three main family groups. One group lives in eastern Honshu, the largest island of Japan. One group lives in western Honshu and on the island of Shikoku. The third group lives on Kyushu, an island in the southwest of Japan.

Tokyo is in eastern Honshu, but the fireflies there were different. In more than 70% of the places in Tokyo, the scientists found fireflies with DNA from other groups. DNA from the western Honshu and Shikoku group was found often. DNA from the Kyushu group was found in some places, too. In the other parts of Japan that the scientists studied, they did not find mixing like this.

The scientists say this shows that people can change the natural groups of fireflies when they move fireflies from one place to another. These groups formed over a very long time. The scientists suggest that people who take care of the fireflies in Tokyo should treat them as one special group with mixed origins^*4.

The scientists also say that people should not add new fireflies to a place when nobody knows where those fireflies came from. When people bring fireflies back to a place, they should choose fireflies from a nearby place with matching DNA.

1. *1 DNA: The tiny code inside every living thing. Parents pass it to their children.
2. *2 journal: A magazine where scientists publish their studies.
3. *3 Genji firefly: A kind of firefly that lives in Japan.
4. *4 origins: The places where something first came from.