All scorpions are fluorescent. This means that they glow when shone with ultraviolet light. This rather funky property is an accidental side effect of the way their armour plating is constructed. When scorpions first shed their skin, the new skin underneath is soft and vulnerable. To harden it up, the protein chains are cross-linked using other compounds. This process is called sclerotisation and is similar to the way that cowhide is turned into leather. In scorpions, the cross-linking compound is beta-carboline, which is strongly fluorescent. As a result scorpions glow more and more brightly under UV light with each successive moult.