A regular Blog from Western Australia.
Dr. Mat will present a variety of life forms including Jumping Spiders, Velvet Worms, Fungi and more. Check out the archives for previous entries!
Welcome back to another entry of Look Closer on Aussie Macro Photos. This time we’re going to check out a very cute little scorpion and find out what happens when you shine a UV torch on it.
Let’s Look Closer at Scorpions
Scorpions, like spiders, seem to be one of those creatures that many people have a phobia of. While it is true that many species can deliver a painful sting very few can do a human significant harm.
Also, like spiders, when you get up close to them and have a good look they really are beautiful and incredible creatures.
On a recent trip into the southwestern Australian Karri forests, I came across a few scorpions ranging from almost 30mm long down to just 7mm. The one I have shot and presented here was about 25mm and is a Cercophonius granulosus, a type of wood scorpion. I found them all actively hunting at night amongst the leaf litter and moss with the littlest one being particularly active in looking for prey.
You can see from this first image that it is fairly camouflaged against the browns, blacks and greys of the sandy forest floor. The mottled colours really help to break up the shape. Once it moved onto the top of the leaf litter is was a bit easier to see against the flatter background.
So how do you find a small, camouflaged scorpion at night amongst leaf litter? You use a scorpion torch to make them glow! When I say scorpion torch really what I mean is a flashlight (or torch) that shines ultraviolet light instead of normal white light. They are also sometimes called black lights. The effect that UV light has on scorpions is quite amazing. In the first image here I have shot the scorpion under white light. You can see its camouflage is doing a pretty good job. But if we shine a blacklight on it, like in the second image, it immediately glows a very bright cyan colour that is visible to the naked eye.
This is called fluorescence and is caused by the UV light hitting a chemical in the scorpion’s cuticle exciting the chemical and making it produce its own light. One thing that I noticed while taking these shots is that the chemical that glows doesn’t seem to be present at the tip of the stinger. You can see in the UV image that it looks like the stinger is broken off. Fluorescence is the same principle used in glow-in-the-dark hands on an analog watch. Fluorescence is different to bioluminescence, in which organisms produce their own light, and different to normal photography which is reflected visible light. I’ll be making a video episode on glowing organisms of all kinds very soon so keep a look out for that one. One of the most interesting things about scorpions glowing under UV light is that we have no idea why. The chemical that glows is quite useful as it seems to act as a sunscreen, but the glowing seems to be completely useless. Think about it.
Scorpions can only glow under UV light, which in the natural environment only comes from the sun. That means the scorpion can only glow during the day. But the sun is also putting out visible light, more than enough to drown out any fluorescent cyan glow. So in a natural environment, that fluorescent glow can never be seen. The glow can only ever be seen under artificial UV light with no visible light contamination. That’s an interesting thought to finish with isn’t it? If you can think of a purpose for the glow I’d love to hear it! And while you’re pondering that thought, here is what happens when your glowing scorpion moves in the middle of your shot! While it may not be technically correct or even what I was trying to do, I actually quite like the effect.
Did you enjoy this Look Closer at Scorpions Blog? Leave me a comment below.