Montana Public Radio

Bug Bytes: Thar She Glows – Scorpions

Feb 5, 2019

There are nearly 2,000 species of scorpions in the world. And while individual species may live thousands of miles apart, they have one thing in common: they glow a beautiful blue-green color under ultraviolet light.

A thin, transparent film in the outermost layer of their exoskeleton contains a protein that glows when exposed to ultraviolet rays, which are found in regular sunlight.

By reacting to UV light, scorpions’ shells (or exoskeletons) work as one big eye; a "whole-body" sensor relaying information to the nervous system so any part of a scorpion can 'see', turning their entire body into a light collector.

While we may understand how they glow, we’re not exactly sure why they glow.

One theory is that it simply enables them to see each other and communicate with potential mates. Scorpions have poor eyesight, but their eyes are very sensitive to changes in light, especially in the color that they see best, which happens to be blue-green.

Reacting to UV may also help them hide better during the day. If any part of their body is exposed to the sun, they’ll feel it and decide to burrow deeper or find a better spot to hide from the heat of the day.

Scorpions are so sensitive to UV rays they can even tell how bright it is at night; detecting UV rays coming from moonlight and even starlight. This may help them determine whether or not to hunt on a given night, choosing to hunt on darker nights when they’ll be less visible to animals looking for a scorpion as their next meal.

No matter what the exact reason, if you’re in an area that has scorpions and are interested in finding them, it’s as easy as going for a walk on a dark night with a UV flashlight. Your glowing, blue-green little friends will certainly stand out.

BugBytes is made possible by the Missoula Butterfly House and Insectarium, and Montana Public Radio. This show is also supported by funding from the Greater Montana Foundation: Encouraging communication on issues, trends and values of importance to Montanans.