Scorpions and the benefits of glowing

It seems that it’s scorpion season here in Costa Rica.  I found this one outside my cabin one evening recently … and then cleared out two more from inside.  They tell me that it’s pretty common to come across them this time of year.  I was at a friend’s house one evening and a little one squeezed itself out of a small crack in the wooden ceiling … then climbed back in when it couldn’t find a foothold to follow.  I’m not used to living around scorpions in New England, so thinking about them sometimes gives me the creeps at night.  I just try not to think about them (and check under the bed with a flashlight several times).  They really aren’t that harmful, though.  Their sting reportedly hurts about as much as a wasp.

However, one thing that’s really fascinating about them (try to look on the bright side, right?) is that they glow a really great greenish-blue color if you direct a UV light on them at night.  This has been know for a while now, and it’s a good way to search for them.  I took this quick (blurry) picture of one of them glowing brightly on a night hike with a group last year.  But why do they glow in UV light?  Does it offer some advantage? It likely requires a costly investment of energy and resources to create the pigments that emit photons in the presence of UV light, so having this ability to glow probably serves some function or provides some advantage for them.

Recent research suggests that scorpions are able to sense the UV light hitting their body and respond to it.  One study covered the “real” eyes of scorpions with foil and the critters still moved around in after being lit up with a UV light.  Since scorpions are nocturnal they may be able to use this ability to sense where “shady” spots are at night, in the absence of sunlight, and hide away from predators (or wait quietly for prey?).  They are often found under blades of grass or some other bit of shade at night.

There a couple of good blog articles describing this research … including some incredible photos of the fascinating creatures showing off their glowing bodies.

Ed Yong writes one of my favorite science blogs called Not Exactly Rocket Science.  I don’t know how he finds the time to write so many excellent stories.

Dave Mosher at Wired Science writes a good piece about the fluorescence phenomenon too, which includes an amazing photo of a scorpion eating a cricket.  Don’t miss it!