Awesome Animal Fact - Did you know scorpions glow under UV light?

First, in case you don't know, scorpions belong in an order of arachnids (spiders and kin), with 2,500 species around the world, on every continent except Antarctica. Scorpions have been around for 435 million years. They mostly live in desert regions, but some are adapted to other environments, including the striped bark scorpion that lives here in Missouri. The first photo is a striped bark scorpion I found under a rock near our home.

The second photo is another striped bark scorpion, this one under a blacklight, which emits ultraviolet light. Scorpions glow a vibrant blue color in UV light, which can come from an artificial blacklight or from natural moonlight.

But how? And why? Let's figure this out.

Interestingly, each time a scorpion sheds its exoskeleton, the scorpion doesn't glow like this until the new exoskeleton hardens. There is a biofluorescent chemical in the exoskeleton that glows, but that chemical doesn't appear there until the shell hardens (which takes about 90 minutes). The chemical could be a by-product of the hardening process, or it could be secreted soon after the shell hardens. We don't know for sure.

Anyway, the bioflourescent chemical absorbs UV light, then re-emits it as visible blue light.

That's the how. Now let's consider the why. Well, no one is really sure why scorpions glow in UV light. One idea is that it helps scorpions find each other. Another idea is that it might confuse their prey, making it easier for them to hunt.

A particularly intriguing idea (my favorite) is that the bioluminescent material makes the scorpion's entire body a kind of eye, to help the animal avoid sunlight. In general, scorpions avoid sunlight and moonlight (which is sunlight reflected off the moon). Scorpions are nocturnal, and they are much less active on moonlit nights. If the scorpion's body detects very much UV light (and therefore glows), this tells the scorpion to stay underground instead of hunting.

Photo Credits:
- Striped Bark Scorpion (daylight) - Stan C. Smith
- Striped Bark Scorpion (blacklight) - DepositPhotos