The Glow Is in the Exoskeleton, Not the Venom
Shine a UV torch on any scorpion and it lights up blue-green in the dark. The source is a set of beta-carboline compounds and coumarins embedded in the hyaline layer of the scorpion's cuticle, the thin, hard outer shell beneath the waxy surface coat. These molecules absorb ultraviolet radiation and re-emit it as visible light in the 500 to 530 nanometre range, which the human eye reads as blue-green. The fluorescence is so reliable that entomologists and herpetologists routinely use handheld UV lamps to survey scorpion populations at night in the field.
