SciSun: By the Light of the Moon   Leave a comment

At night, the desert can be a cold, dark, silent, and sometimes frightening place for those not accustomed to this unique environment. Similarly, the wildlife that make their homes among these harsh surroundings are often themselves cold (reptiles and insects); silent (eyesight and smell is often more important then sound among the sand and rocks), and sometimes frightening – but these creatures are not always dark (unless they really felt out of place in high school and started wearing black and listening to sad music).

Of all desert animals, what might be considered the darkest of creatures might also be the lightest: The Giant desert hairy scorpion (Hadrurus arizonensis) not only has what most people regard as a rather creepy appearance – aside from the standard stinging tail and pinching pincers and multiple legs, at six inches or more in length it’s the largest scorpion in North America – it’s also the only desert species that glows a bright blue-green under ultraviolet light and, some claim, can glow at night under regular moonlight. Which can be very frightening, if you’re in the desert at night and see half-foot long glowing scorpions running around.

The light we (as humans) see is in the visible spectrum. This ranges from reds; through oranges; yellows; and into greens and blues. Depending upon who you ask, white and black are either, respectively, the absence of all color; or the presence of all color (so it really is a question of Black and White). Beyond the visible spectrum are infrared (IR), on one end of the spectrum, and ultraviolet (UV), at the opposite end, which humans generally can’t see but other species can: Bees and other insects are among the most widely known animals that see colors we can’t, and that helps attract them to what may look like a plainly-colored flower to us is a literal bouquet of colors to the bee. Some fish are believed to use UV vision to find food; as well as reindeer who look for hard-to-find lichen by the amount of UV the plants reflect. While the light is there, but unseen to us, is one important reason to wear UV-protected sunglasses when outside. And it might also explain why reindeer so seldom wear sunglasses despite how much time they spend outdoors.

Scale this guy up by about 1000 times and you've got a great monster movie.  Or a free light source for a parking lot.

Scale this guy up by about 1000 times and you’ve got a great monster movie. Or a free light source for a parking lot.

To be fair (to the scorpions), virtually all adult scorpions can glow under UV light, as well as other species from millipedes to ground sloths (it’s not really the sloth that’s glowing, it’s the algae that often coats the sloths fur), to carnivorous plants to genetically-modified cats that now glow in the dark (who’s idea was that?). What makes the Giant unique – aside from his size – is the characteristic, some observers affirm, that these arachnids (related to spiders, mites and ticks – not insects) glow under the light of a full or not-so-full moon. But because the moon doesn’t actually create light, but serves as a giant reflector of sunlight – and at that, only reflects a small percentage of that light – we know the amount of UV reflected at night is very, very low; too low to result in triggering the glow-in-the-dark effect. Why then, do scorpions glow at all, not to mention Giant here, who seems to glow when he shouldn’t? No one knows. Despite research and study and examination, there are many theories why scorpions glow, yet none of them have been accepted as the answer: Are scorpions acting as their own flashlight, so they can see in the dark? Maybe the light attracts other animals, which become the scorpions next meal. Could the UV glow just be a random side-effect of some other characteristic? One direction of current research believes that the scorpions body acts as a giant light receptor – and based upon how much light is affecting which parts of the body, helps the animal sense his surroundings and in effect makes every surface of the scorpions body a type of ‘eye’. Which is really even more creepy than anything we knew about the scorpion before. But we think this glow came about because at one time, thousands of years ago, there was a even more frightening predator that attacked and ate scorpions and the blue-green light evolved to warn these predators ‘don’t eat me! I’m a venomous scorpion!”. Of course that makes us wonder what those scorpion-eating predators may have evolved into….


Michonne Says: Is this something I really needed to know about? Now I’ll be thinking about this all day. And being extra-careful where I walk. And not wanting to go out at night at all. At least they are all glow-ey so you can see where they are. If I ever see anything like that I’m running away because it’s just not normal.

Posted October 5, 2014 by ECOVIA eco-adventure® in SciSun

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