Fauna
Insect

Genji Firefly

Luciola cruciata

Also known as Genji-botaru, Genji Lightning Bug

Genji fireflies illuminate Japanese stream banks during early summer nights with a slow, synchronized rhythmic flashing. The aquatic larvae live in clean, running water where they hunt freshwater snails before pupating in the damp soil nearby. These beetles hold a deep cultural significance in Japan, celebrated in annual viewing festivals and serving as indicators of healthy, unpolluted freshwater ecosystems.

NocturnalBioluminescentAquatic Larvae
Genji Firefly reference
(c) Alpsdake, some rights reserved (CC BY-SA) · cc-by-sa
—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & preyFreshwater snails, Small aquatic invertebrates
Predators
  • Frogs
  • Spiders
  • Bats
ThreatsWater pollution, river channelization, and light pollution
HabitatsClear streams, irrigation ditches, and wet paddy fields
Life span1 to 2 years
Classification
  1. FamilyLampyridae
  2. SpeciesLuciola cruciata
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Safe to observe at a normal distance.
What to notice
Look for large beetles with a black cross-like mark on a pinkish-red pronotum flashing green-yellow light.
Support conservation
Never capture wild adults or disturb stream margins where larvae and pupae develop.
Responsible observation
  • Avoid artificial light: Turn off flashlights and phone screens to prevent disrupting their mating flashes.
  • Watch the weather: Look for them on warm, humid, windless nights after rain for the most active displays.
  • Protect stream banks: Keep to designated paths to avoid crushing pupating larvae in the riverside soil.
Related species
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