An adult female Arizona Desert Hairy Scorpion (Hadrurus arizonensis) under black light. All scorpions will glow like this when exposed to black light, with the only exception being if they just molted. The cause of this "glowing" phenomenon is the chemical makeup of a scorpion's exoskeloton fluoresces when exposed to certain wavelengths of ultraviolet light. The biological purpose for this is currently unknown.