Why (AND How) Do Scorpions Glow Under Ultraviolet Light?

Similar to other arachnids, scorpions have an amazing glowing ability. There’s still a lot left to be discovered when it comes to the purpose of the mysterious natural occurrence. However, if you want to know why scorpions glow under ultraviolet light, it’s important to understand the mechanism by which they are able to glow.

The outer layer of a scorpion’s exoskeleton is called the cuticle, which is composed of hardened minerals and proteins. The cuticle has a thin hyaline layer which produces a substance that reacts to ultraviolet light. This substance is what causes scorpions to glow. However, there’s still a lot of mystery surrounding the origin and exact purpose of this substance.

Scorpions glow under UV light because they produce a fluorescent substance during the hardening process of their cuticle. However, scientists have yet to determine the exact purpose of this glowing ability. Based on prevailing theories, scorpions may use it for protection, sensory purposes, identification, and defense.

A By-Product of a Chemical Reaction

The substance is theorized to be the by-product of a chemical reaction involving two compounds, beta-carboline, and 4-methyl-7-hydroxycoumarin. And it’s only produced sometime after scorpions have molted and shed their outer skin. The new hyaline layer will not fluoresce under ultraviolet light until the new mushy cuticle has hardened.

As such, it has been suggested that scorpions’ fluorescence has to do with the hardening process of the cuticle. With cuticular fluorescence, the molecules in a scorpion’s exoskeleton absorb UV light and re-emit it as a vibrant blue-green light.

The hyaline layer is tough and durable, which allows a scorpion’s glowing ability to endure for a very long time. When a scorpion is preserved in alcohol, the liquid will also be able to glow under ultraviolet light. This fluorescent ability has even been observed in scorpions’ hyaline that has been fossilized for hundreds of millions of years [source]. 

Check out the following video to see what it looks like to locate scorpions with a blacklight:

Potential Explanations of Why Scorpions Glow Under Ultraviolet Light

Now that you know why scorpions glow, it’s time to discover the prevailing theories for why these arachnids evolved this fluorescent ability. The first possible reason is for protection — particularly protection from sunlight.

Protection from Sunlight

Scorpions are nocturnal creatures and sensitive to light, so they tend to stay hidden during the daytime. The amount of UV light on their exoskeleton can tell them how much sunlight or moonlight there is. If they are glowing a bright blue-green color, they might decide to stay underground because that means that there is still a lot of light. Conversely, a low amount of UV light might encourage them to come to the surface and hunt for prey. They can also use the UV light emitted by their exoskeleton to find shelter in the darkest hiding places as possible.

For Navigation

Another theory used to explain scorpions’ glowing ability is for sensory purposes. Scorpions have overly sensitive eyes and cannot see very well. Thus, their glowing ability could help them navigate their way. With more UV light, they know that they are more exposed to predators. So, if a scorpion senses that it is glowing, it will take it as a signal to hide somewhere darker. Scorpions can also use their sensibility as a signal for when it’s night and time to eat.

Identify Fellow Scorpions

One more potential reason discusses for scorpions’ glowing ability is for identification. It can help scorpions find others of their kind when in the dark. There has also been a suggestion that the glowing ability helps scorpions confuse their prey and this, in turn, makes them easier to catch. However, since most insects tend to avoid fluorescence, there are some doubts as to whether glowing can help scorpions catch more prey.

For humans, on the other hand, there is one great benefit to scorpions’ fluorescence. It allows us to see them in the dark and avoid getting stung. 

Does UV Light Hurt Scorpions?

Does UV Light Hurt Scorpions?

Yes, ultraviolet light can hurt scorpions just like it can hurt all other living creatures, including humans! For humans, exposure to the sun’s rays can cause sunburn and premature skin aging as well as serious health conditions, such as melanoma and other skin cancers.

In scorpions, exposure to ultraviolet light can cause blindness, stress, and even death. Prolonged exposure to ultraviolet light also lessens the intensity of their fluorescent glow. So, if you are raising scorpions, it’s important to keep them out of prolonged direct sunlight as well as UV light although it it is cool to see them glow.

There are three main types of ultraviolet rays: UVA, UVB, and UVC

  • UVA has the longest wavelength (400-320nm) and produces the least amount of energy. It’s the closest to visible light. UVA can penetrate through the skin’s layers and cause long-term damage in collagen. Resulting in fine lines, wrinkles, and thicker skin texture.
  • Meanwhile, UVB has a medium wavelength (320-290nm) and produces a moderate amount of energy. UVB directly penetrates DNA in skin cells. It causes sunburns and most types of skin cancer.
  • UVC has the shortest wavelength (290-100nm) and has the most energy. It’s germicidal and can cause a lot of damage to living creatures. UVC rays from the sun are unable to penetrate the ozone layer in the atmosphere. However, you can still be exposed to UVC through man-made sources. For example, UVC is used in laboratories and food preparation facilities to disinfect and eliminate bacteria.

If you’re planning to get a UV light to detect scorpions, you should choose a blacklight instead. They utilize UVA and have negligible UVB and UVC output — if any at all. Blacklights usually have a peak emission of about 390-300nm, which barely enters the UV spectrum. Thus, they are the safest to use, and they lack the energy to cause any significant damage to any living organism. However, there might be mild discomfort if you accidentally look at the light directly.

Best Black Lights to Use for Finding Scorpions

All scorpions are venomous; however, only a few species are truly lethal to humans. Nevertheless, a scorpion sting can still cause moderate to severe pain. So, if you’re spending time outdoors, especially if it’s a desert region with a known scorpion population, it’s important to have a blacklight that can help you find scorpions.

At the same time, you will want something safe and won’t cause your body any damage. There are a lot of blacklights available, but here are the best ones that we recommend:

Escolite UV Flashlight Black Light

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The Escolite UV Flashlight Black Light features 51 UV LEDs to give you a strong beam that covers a large surface area. It has a 390-395nm wavelength so that you’re easily able to find scorpions. This blacklight is 30% brighter than other blacklight competitors.

The Escolite UV Flashlight Black Light has an aluminum alloy body that is durable and long-lasting. It also features an anti-slip design to provide you a better grip when finding scorpions as well as waterproof capabilities. The blacklight uses 3 AA batteries, which will last 4-6 hours. If you desire protection from scorpions throughout the night, just make sure to carry spare batteries. 

Vansky LED Ultraviolet Blacklight

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The Vansky LED Ultraviolet Blacklight comes with 51 LED bulbs that will last you up to 12 years. It has a 395nm wavelength so that you’re able to find scorpions without breaking a sweat. The blacklight produces a strong light even while covering a larger surface area. It’s also 30% brighter than most other blacklights in the market.
The Vansky LED Ultraviolet Blacklight is compact and only weighs 7.2 ounces. It’s also durable with an aluminum alloy body. The blacklight uses 3 AA batteries. The blacklight is multi-purpose as you can also use it to locate pet urine, food stains, and as a bed bug detector.

TaoTronics UV Blacklight Flashlight Detector

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The TaoTronics UV Blacklight Flashlight Detector features 52 UV LEDs that have a 15-year lifespan. It has a 395nm wavelength, so it’s another viable option for finding scorpions. This blacklight is lightweight at 6.9 ounces, and it has an ultra-compact design so it can easily fit your pocket.
The TaoTronics UV Blacklight Flashlight Detector also comes with UV-safety glasses to protect your eyes when in use. It is powered by 3 AAA batteries. When you’re not busy hunting for scorpions, you can also use the blacklight for detecting pet urine, bed bugs, and food stains.

In Conclusion

The scorpion’s ability to emit a vibrant blue-green glow under ultraviolet light is a natural occurrence that has piqued the curiosity of most people. Scientists have yet to establish the exact reason as to why it evolved. The mechanism for the scorpion’s glow is related to the hardening process of their new cuticle after molting. The scorpion’s fluorescence might also have some benefits as it helps these arachnids sense and protect themselves from sunlight. Prolonged ultraviolet light can be harmful to scorpions so if you want to be able to find them without hurting them, your best bet is a blacklight that utilizes UVA rays.

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