Beetle trap shows how healthy a forest is

Scientists in Japan have found a new way to check the health of a forest. They count small beetles that fly into a special trap^*1. The study was published online on September 6, 2026, in the science journal^*2 Forest Ecology and Management.

People cut trees for wood, but they also want to protect the many kinds of living things in the forest. To do both, scientists need a way to measure how animals and plants react when trees are cut.

The research group, led by Minori Tokito, an assistant professor^*3 of agriculture, studied ruri stag beetles^*4. These beetles live in forests of broad-leaved^*5 trees. The young beetles grow inside old, rotten wood, and the adult beetles eat new buds^*6 high in the trees. Because of this, scientists think the beetles can show how good a broad-leaved forest is for living things.

In the past, counting these beetles was difficult. The results depended on how skilled the person was, and searching for the beetles often destroyed the places where they lay their eggs.

In 2021, the group proposed a new trap called F-FIT, or a "honey trap." A female beetle sits inside the trap. Male beetles fly toward her, hit a board, and fall into the trap. In this way, scientists can count how many beetles are caught in a set amount of time and compare the numbers.

In this study, the group placed many of these traps in a forest in Hida, a city in Gifu Prefecture in Japan. In this forest, people cut broad-leaved trees for wood. The scientists recorded where each trap was and studied the numbers together with the locations.

They found that more beetles were caught deeper inside the forest. They also found that the link between the number of beetles and how close together the trees grow may be different from place to place.

The scientists say it is not enough to think only about how each part of the forest is cut and cared for. When people take wood out of a forest, they use machines, places to pile up logs^*7, and roads to carry the logs. These make open spaces in the forest for a time. The scientists say it is important to think about these open spaces and where they are in relation to the forest that is left around them.

The group hopes to test the method in larger areas next. They also hope that people who take care of forests will start to use it.

1. *1 trap: A thing made to catch animals.
2. *2 journal: A magazine where scientists print their studies.
3. *3 assistant professor: A teacher and scientist at a university.
4. *4 ruri stag beetles: Small beetles with a shiny blue or green color. They live in Japanese forests.
5. *5 broad-leaved: Trees with wide, flat leaves, not needles.
6. *6 buds: New leaves or flowers when they are still small and closed.
7. *7 logs: Long pieces of tree trunk after the tree is cut.