A warm June night, silence by a stream — and dozens of flickering lights rise above the grass. Fireflies enchant people around the world, and in Japan watching them has become a true tradition. Here is how living light works and where to see fireflies.
Living nature in your home: potted plants and flower baskets.
Fireflies are beetles of the family Lampyridae, with about two thousand known species. They glow to find a mate: males and females exchange light signals, and each species has its own flash code. The larvae of many species glow too, probably as a warning to predators that they taste bad.
Light is produced in special organs on the abdomen: luciferin is oxidised with the help of the enzyme luciferase, oxygen and ATP. Almost all the energy becomes light rather than heat, which is why it is called cold light.
In Japan fireflies are called hotaru, and firefly viewing, hotaru-gari, has a long history. The best-known species are the Genji and Heike fireflies. Activity peaks mainly in June, when firefly festivals are held in the evenings by clean rivers and rice fields. Genji firefly larvae live in water and feed on snails, so fireflies there signal clean streams.
In Ukraine the most common species is the common glow-worm. Its wingless females sit in the grass glowing greenish light, and the males fly in to the signal. You can see them on warm nights in late June and July at forest edges, in meadows and by water — away from street lights.
Another remarkable natural phenomenon is spider web trees; and for flowers that open at night for moths, see why do flowers smell.
The main causes are light pollution, pesticides and the loss of damp meadows and woodland edges.
No, they are harmless to people.
Author: Maria Svitlovir
Graduated from Taras Shevchenko National University of Kyiv, Institute of Biology and Medicine (2001). BSc in Biology, MSc in Horticulture. Writes about plants, works at a garden centre selecting and repotting plants, and contributes to plant reference guides.
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