Crown Prince Fumihito and his wife Crown Princess Kiko attended the opening ceremony of the International Congress of Entomology held in Kyoto on August 25.

About 4,000 researchers from 77 countries and regions are taking part in the world's largest academic conference on insect science that runs through August 30.

Prince Hisahito, a high school senior, joined the opening ceremony from a seat in the audience.

Japan is hosting the event for the second time, the last time being 44 years ago.

After the opening ceremony, the imperial family watched poster exhibits submitted to the congress.

After listening to explanations from a German dragonfly researcher, Hisahito asked questions in English.

The 17-year-old prince studies dragonflies and their habitat at the Imperial Palace in Tokyo.

He is scheduled to do a poster presentation on his research at the congress.

As heavy rainfall suspended the Tokaido shinkansen bullet train service on August 25, the crown prince and his family arrived back in Tokyo more than 50 minutes behind schedule.