Hello nightmares – why scorpions glow in the dark

I’m pretty sure that almost no-one loves scorpions – they’re not far behind spiders in the ‘primal nightmare’ stakes, given the whole scuttling thing and the poisonous sting. But they are fascinating for at least one reason: they glow under UV light.

You might wonder why this happens – after all, you’d think a glowing scorpion would be easy prey to any aerial predator on the hunt for something crunchy. But it seems that they use this facility to hide from predators.

“How’s that?” I hear you ask. Well, it seems that the scorpions can sense UV light over their entire bodies, which allows them to scuttle under the nearest bit of shelter. In effect, the scorpions are using their entire bodies as an eye, to sense UV light.

This makes sense, since scorpions are more active soon after sunset, which is the only time at which UV light is more common than other frequencies. And if they’ve been overexposed to UV, which uses up the fluorescing chemicals in their skin, they spend more time in the open.

Given that they like shelter, then, you might want to carry around a UV light – that’ll send any that get indoors scuttling under the furniture and out of the way of unwary feet. And check the bedding carefully if you live in the desert: a cousin of mine living at Coober Pedy found a big hearty specimen inside the bed. Not exactly a recipe for sweet dreams.

[Feature image: Scorpion under UV light. Photographer: Alan Henderson. Source: Museum Victoria]