Scientist places emperor scorpions (Pandinus imperator) under ultraviolet light in this laboratory demonstration showing arthropod fluorescence. Scorpions glow due to fluorescent chemicals in the cuticle making up their exoskeleton. While a number of arthropods fluoresce, including some insects and spiders, this phenomena is especially strong among scorpions and whip scorpions (vinegaroons). No one is sure if fluorescence has a useful purpose and is likely just a random act of evolution. The emperor scorpion is native to much of Africa and can reach 20 cm in length.