Derek Muller of Veritasium (previously) consulted with Dr. Carl Kloock of California State University at Bakersfield to understand how and why scorpions glow neon green under ultraviolet light, either artificial (blacklight) or natural (moonlight). As it turns out, there’s no real answer to a scorpion’s bioluminescence, but it may help them determine when UV light is available so they know when to hide.
What we don’t know is why they want to detect ultraviolet light so badly that they’ve turned their whole body into a photon detector. The suspicion is that it has to do with determining whether or not they should come out at night.
This bioluminescence can also be incredibly helpful to humans as to where not to step.