What is the German 'Leuchtkäfer' in English?

Answer 1

"Firefly" or "Lightning bug" may be English equivalents of "Leuchtkäfer" (Lampyridaefamily).

Thus far, there are around 2,000 known species of fireflies or lightning bugs. Worldwide, they may be found in temperate and tropical environments. Some species may be seen during the evening and night, and others during the day. Those species that are active during the day tend to have the distinctive firefly green, red or yellow glow only if they spend most of their time in shaded environments, such as around tall trees.

Answer 2

Leuchtkäfer = firefly

Leuchtkäfer = lightning bug