This doctoral thesis aims to study the effects of light pollution, e.g. nightly artificial light, on animal behavior, especially the reproduction of the glow-worm. The global increase in nightly light is a problem, as it disturbs and fragments the nightly environment. Glow-worms need darkness, as a female glowing in light is less likely to attract a mate or reproduce. Knowing the effects of light pollution supports both planning of conservation efforts and spreading of awareness.