Scorpions under UV-light

Sunday, 07 March 2010 10:39 |

(4 votes, average 5.00 out of 5)

Inova - X5 UV LED torch A couple of months ago I read an article in Africa Geographic about finding and photographing scorpions using Ultra Violet (UV) light. A compound in the exoskeleton of the scorpion, called a coumarin, refracts ultra-violet light in the visible spectrum, usually green, and causes them to fluoresce (or glow in plain English). The fluorescence is thought to serve as an ultraviolet sensitivity mechanism, perhaps allowing the scorpion to avoid damaging light levels. Because the exoskeloton glows in UV light it's very easy to find scorpions at night using a torch with UV LED's. If you use a UV torch and walk around campsites in Africa at night you have an excellent chance of finding scorpions. Depending on the UV output of the torch you'll be able to find scorpions from a distance of 1-10 meters. The scorpions will have a greenish glow and will be easy to spot against the grounds dark background. The scorpions don't seem to suffer any ill effect of the UV light and don't react to the UV light at all.

It's always a good plan to check for scorpion holes during the daytime so that you know in what area to look for the scorpions at night. A scorpion hole is easy to recognise. The burrow entrances are usually situated in open ground and look like oval shaped smallish holes. Windy nights seem to be the best nights to go out to find scorpions. I'm not sure why that is the case, but I guess it's easier for the scorpions to catch prey on a windy night.

Photography

To be able to take pictures in UV-light you need a fairly powerful UV-light and a camera that you can set to a high ISO setting. I use an Inova X5 UV light and a Canon 1D Mark III in combination with a 100mm f/2.8 macro lens myself . Using a small one UV LED torch you'll be able to find the scorpions, but you won't have sufficient light for photography. Using my UV light I'm able to take pictures at 3200 ISO, but even with the five LEDs of the Inova X5 I get shuttertimes that are only around 1/25 to 1/50 sec @f/4. Holding a UV light and taking pictures at the same time is kind of cumbersome. I use a 100mm f/2.8 macro lens for all my scorpion shots and it's hard to keep the light on the scorpion while trying to keep the camera steady. Depth of field (DOF) is shallow when using a macro lens, and the DOF in combination with the slow shutter speeds and the aiming of the UV light is unfortunately a perfect combination for unsharp pictures. When my wife isn't bored with me taking pictures yet she'll sometimes hold the UV light which helps a lot. When I'm on my own I use a bean bag to place my camera on, this helps a lot. In both cases I shoot in high speed mode to give me the best chance of a couple of sharp pictures. With scorpion photography in UV light my keeper ratio is about 15%.

A word of caution

Please be careful when you go scorpion hunting and keep in mind that some scorpion species are venemous. All scorpion stings are extremely painful so avoid any risk of being stung. Also keep in mind that although scorpions glow in UV light aardvark burrows, barb wire, snakes and other nasties don't share that characteristic so watch your step when looking for scorpions. Please remember that scorpions with big pincers and a small stinger are not, or at least only mildly, venomous while scorpions with small pincers and a large stinger are venomous. When taking pictures please make sure that your safety comes first.

Buying a UV torch

I bought my UV torch through a US based Internet shop. I recently found a website in South Africa that sells UV torches specifically for finding scorpions. This website sells UV torches with 8, 12 and 41 UV LEDs. I don't know if this shop ships to international customers, but if you're based in South Africa then this website looks like the place to check for UV torches.

Photo gallery

In January 2008 I used my Inova X5 UV light to search for scorpions in Nossob camp (Kgalagadi Transfrontier Park in South Africa). I found myself literally surrounded by scorpions in some areas of the camp. The sorpions that I found ranged in size from 1cm to around 8cm. I found both the venomous as the non-venomous kind of scorpion in camp. Some of the pictures I took are shown below.

Last Updated (Tuesday, 30 March 2010 08:02)

Arnoud Quanjer Wildlife Photography