Japanese in Tokyo recently celebrated a Hotaru (in English, “firefly”) Festival by lighting up the Sumida River with 100,000 softball-sized, blue LED balls.

The balls drifted slowly down the river, creating a glowing blur when viewed from afar. They were powered by the sun, and they were collected by a large net at the end of their route.

The Firefly Festival, which celebrates those magical little insects whose glowing butts are mesmerizing to us human types, is a fairly new fĂȘte tacked onto the end of Japan’s Golden Week, which contains such national holidays as Greenery Day, Children’s Day, and Constitution Memorial Day. The holiday has its roots in 17th-19th century traditions of catching fireflies by the Sumida in spring; fireflies are no longer found along the banks of the Sumida, which today winds through the center of a global metropolis.

Panasonic provided the orbs, which also functioned as an opportunity for the corporation to promote its LED lightbulbs.

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