Illuminating desert’s night creatures
The heat of the late summer evening was still simmering as I gazed into the sky to find Antares, the bright red heart of the constellation Scorpio.
Hanging above me at the western edge of the Milky Way, this mythical figure stood out brightly in the inky desert darkness.
While I had found the scorpion constellation, I was actually here to find the earthly version as they emerge at night to wander the desert sands in search of food.
To help me with my search, I was equipped with an ultraviolet, or blacklight, flashlight that makes these nocturnal creatures stand out distinctly.
Did you know that scorpions glow a bright, fluorescent blue-green when illuminated by ultraviolet light?
That was something I discovered decades ago when I borrowed a heavy, cumbersome blacklight from my science teacher and took it with me on a camping trip. My goal was to search for gems like calcite, fluorite, agate or any of the many “ites” that glow under ultraviolet light.
Like most kids, I was energetic and spent an evening wandering about the desert, nose to the ground, looking for the magic rock glowing in the dark.
I got more than I bargained for.
The first thing to glow in the dark was not a rock at all. I was somewhat startled when I came face to face with a brightly glowing scorpion.
I began to research these reclusive creatures and discovered they are night feeders, especially on warmer summer nights.
So now, a bit older, but just as curious as decades before, I picked a dark summer night to begin my renewed exploration. This time I was equipped with an inexpensive, lightweight blacklight ordered from an online retailer.
It didn’t take long to find my prize. In fact, I found several large scorpions during my wandering. Enough, in fact to remind me never to be out and about at night in bare feet.
The three most common scorpion species found in San Diego County include the giant hairy scorpion, the Arizona bark scorpion and the stripe-tailed scorpion. The scorpions I found on my evening walk were large enough that I suspect they were the giant hairy scorpion species.
The fluorescent glow of these spider-related creatures is startling. The blacklight is not bright, in fact, casting a soft, violet-blue glow on the ground. When a scorpion falls into the beam, however, it glows intensely.
Why, exactly, do scorpions glow in ultraviolet light?
The exoskeleton, or outer covering of this creature contains a substance that fluoresces under ultraviolet and moonlight. The unknown substance is contained in a very thin but tough coating called the cuticle.
What isn’t known is why this happens.
Some of the theories include that it helps them find each other, confuse prey, or protect them from sunlight.
Another theory suggests they may use this characteristic to determine when it is safe to come out of their underground lairs. Their decision to emerge could be based on how much ultraviolet shines upon them.
This concept comes from the fact that scorpions are less active on moonlit nights, and generally avoid harsh ultraviolet daylight.
My desert exploration proved to be fascinating. Scorpions seemed unaffected by my blacklight, but the illumination attracted small moths. The scorpions would use their lobster-like pincers to reach out and capture a moth and quickly eat it.
A very obvious feature of my nighttime companions was a formidable stinger at the end of their tails.
Fortunately, none of the scorpions found in San Diego County are deadly or even require medical treatment.