also: つちぼたる
Refers to the larval or larviform female of certain firefly species that live in soil and emit light. In Japanese, it often specifically means the larvae of the Genji or Heike fireflies, or the wingless female glowworm.
On a summer night, glowworms were glowing on the embankment.
Glowworms glow while still in their larval stage.
蛍 is the general term for firefly, including both adult flying fireflies and glowworms. 土ボタル specifically refers to the soil-dwelling, often wingless, glowing forms.
Most common spelling, combining kanji 土 (earth) with katakana ボタル (firefly).
Full kanji spelling; less common but still used.
Variant kanji spelling using 地 (earth/ground) instead of 土.
Obscure spelling using 蛆 (maggot), reflecting the larval appearance.
Full katakana spelling, sometimes used in field guides or for emphasis.
From 土 “earth, ground” and ホタル “firefly,” with voicing to ボタル in the compound. The name likens a ground-dwelling luminous insect larva to a firefly.