Finding bed bugs in a dark room is a difficult task, but UV light can make it easier to see them. Bed bugs are hiding experts, so anything that makes detecting bed bugs easier can be beneficial.
Phosphors in many insects’ shells absorb ultraviolet light and give off visible light. UV light makes bed bugs more visible. You can even kill bugs with UV light, although it isn’t an effective treatment.
But even if UV light does make bed bugs glow, it isn’t necessarily an effective strategy. There are passive means of detecting bed bugs which are easier and work better than manually searching.
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How Does UV Light Detect Bed Bugs?
UV light is similar to regular light. Both are kinds of radiation. Both are produced by bodies like the sun, and both act in the same way. The only difference is where they are on the spectrum of light.
Visible light refers to light we can see. Different wavelengths of light appear different colors to us, e.g. blue, red, yellow, and green. The higher the wavelength, the more energy the light has.
Ultraviolet light has more energy than visible light, so it’s a higher wavelength. It isn’t visible to the naked eye. When you switch on a blacklight (UV light), it may appear dark purple. That’s because dark purple/blue is the highest wavelength of visible light we can see. The rest of the light emitted is invisible to us.
Either way, ultraviolet light interacts with substances called phosphors. A phosphor is anything that’s luminescent, i.e. absorbs energy and releases it as light. Examples of phosphors include:
- Nails and teeth
- Certain kinds of ink
Phosphors absorb some of the energy of ultraviolet light. They then give off energy, not in the form of heat like other substances, but the form of visible light.
We take advantage of this physical reaction by using special inks on banknotes that only show up under UV light, for example.
Do Bed Bugs Glow in UV Light?
Many arthropods, including insects, glow under UV light. The biological reasons behind their glow aren’t fully understood. However, we do know that they have exoskeletons made from a similar material to nails.
One animal that glows under a blacklight is a scorpion. They appear a luminous, washed-out blue color. Spiders, grasshoppers, and many more also glow.
The reason they glow isn’t known either. It’s thought that it may be a leftover from an earlier evolutionary period, where larger predecessors needed to spend more time in the sun, and had to block incoming UV rays. Or it could be to help them spot one another.
Whatever the case, this is the reason why searching for bed bugs with a blacklight is possible. They glow when exposed to ultraviolet rays.
Can Bed Bugs See UV Light?
Other animals don’t have the same vision as humans. What we can see as visible light may be invisible to other animals. And other animals can sense infrared light (like snakes), while others can see ultraviolet.
According to PLoS One, most insects can detect ultraviolet light, as well as blue and green. However, they struggle to see red like we can. This would have implications for whether bed bugs are attracted to UV light, or whether they would try to avoid it.
Are Bed Bugs Attracted to UV Light?
Bed bugs aren’t the only bug that can see ultraviolet light. Most others can too. Nocturnal insects, especially, use UV light to see when there’s little visible light to go by. Seeing a broader spectrum gives them better vision.
Some insects are even attracted to UV light. Moths are attracted to light generally, because they use the moon to navigate. Beetles and other bugs are too. Entomologists (bug scientists) attract bugs using UV lights during studies.
But bed bugs have different instincts to moths and other beetles. They don’t like the light. They’re photophobic, which means that they avoid light. This is a behavior they developed over thousands of years. It helps them stay hidden.
Shining a UV light won’t make bed bugs come out of their hiding places. If anything, it will make them hide deeper inside.
How to Detect Bed Bugs with UV Light
To detect bed bugs with a UV light, you might be tempted to turn over your mattress and get started. But you should be more careful than that. Flipping the mattress makes them scatter. You should take care to prepare your room before you begin searching. Follow these guidelines:
- Clean up any mess that may be lying around. Any clothes, books, or electronics are potential hiding places. Ideally, bag up your things to be treated later on.
- Seal off any entry and exit points to your bedroom. The main one will be under your door. If there are cracks in the wall and sideboard, these are exit points too.
- Move your bed to the middle of the room. Set it apart from other furniture so that the bed bugs can’t easily spread.
Only then should you consider searching for bed bugs. Once your room is prepped, you can start.
How to Search for Bed Bugs with a UV Light
Take the bedding from the top of the bed and bag it up. Alternatively, put it into a clear plastic tub. So long as you can seal the container, that’s fine. You’ll want to inspect your bedding later.
For now, concentrate on your mattress and bed frame. These are the bed bug’s favorite place to be. If there are any bedsheets, take them off and bag them up too. Then, flip the mattress over. Inspect:
- Underneath all the piping around the sides of the mattress
- Underneath any buttons that are part of the mattress
- Underneath any zips
Any part of the mattress that has a fold or something to hide under is a prime hiding spot. And you aren’t only searching for bed bugs, either. Search for their old shells, which glow too. Besides that, search for eggs and feces.
If possible, turn the bed frame over too so that you can examine that. Pay close attention to any joints, gaps, and holes, as these are the places they lay their eggs.
After you’re finished with your bed frame and bedding, move onto other places they’re likely to hide. Other bedroom furniture is a good place to start. They may also hide in furniture in other rooms, e.g. the couch.
What to Do When You Find a Bed Bug
When you do find a bed bug, your first instinct will be to squash it. But this is a pointless exercise. Unless there’s only one bug there, you’d have to squash dozens before you’re done. Instead, catch the first bed bug you see in a Ziploc bag. You can then show the bug to:
- An exterminator, to confirm that bed bugs are the issue
- Your block manager or landlord, to prove there are bed bugs and that treatment is necessary
- To the municipal council, which may be necessary if you have to prove bed bugs are living there
Once you have one, you’re free to squash the rest. But a less disgusting way of killing them is with a bed bug spray. It’s as effective, but doesn’t get your hands dirty. You could hire an exterminator. Exterminators are more effective than any DIY bed bug solution.
Should You Use UV Light to Detect Bed Bugs?
Using a UV light to detect bed bugs is a good idea. Because UV light makes them glow, it may make the bed bugs easier to spot.
Another reason why you should consider doing so is that old bed bug shells glow too. Bed bugs periodically shed their old shell as they grow to adult size. These shells don’t rot because they’re made from a fingernail-like substance. However, there are negatives to this method:
- Physically searching for bed bugs isn’t the best way to identify a budding infestation.
- Disturbing the bed bugs in this way would encourage them to spread. This would make the problem of killing your infestation harder to solve.
- The bed bugs may be hiding somewhere you would never expect.
- If you need to search for bed bugs, there likely aren’t that many. Finding one on its own is like searching for a needle in a haystack.
Far better is to use passive means of searching for bed bugs. A bed bug interceptor is like a trap that they can climb in, but can’t climb out of. They sit around the feet of your bed and catch any bed bug that tries to climb them.
Interceptors are perfect because they work without you having to do anything. You put them around the feet of your bed and leave them there. You periodically check to see if there are any bugs there, but that’s all.
They’re especially useful for capturing individual bed bugs about to set up an infestation.
Can You Kill Bed Bugs with UV Light?
UV light is bad for living organisms. If you put sun cream on before you go out on a sunny day, the reason why you do is so that you can block the sun’s UV rays. They can do your skin serious damage.
That’s because UV rays damage DNA and RNA. When damaged, they may still be capable of reproducing themselves. But they would be wrong. That’s how cancer starts.
In the same way, UV light can damage insects. According to the Asian Pacific Journal of Tropical Biomedicine, UV-C rays are lethal to many different organisms. The team that ran this study tested UV rays on mites, which were killed by direct irradiation at 10cm for 60 minutes.
It stands to reason that the same would apply to bed bugs, even if the time it took were different.
Should You Kill Bed Bugs with a UV Light?
However, that doesn’t mean that using a UV light would be a good idea. There are good reasons why it wouldn’t work:
- Bed bugs may have the same photophobic reaction to UV light as to regular light.
- You can’t keep bed bugs still and in the open for that amount of time. They would escape long before the UV light had its full effect.
- Some bed bugs would stay hidden throughout the entire process. They would be entirely unaffected.
- You may not know every place that the bed bugs are hiding. While you focus on your bedding, they may be living in your furniture.
Using a UV light to kill bed bugs is a bad idea. Using a handheld bed bug spray isn’t an ideal treatment method, but is far better than using UV.
But it can still be a useful detection tool. If you do find evidence of bed bugs, hire a professional. The most effective way of killing bed bugs is heat treatment.