Written by Joe Ballenger
Ultraviolet light is pretty nasty stuff. It’s known to cause skin cancer in humans. UV light is a standard material for inducing mutations in lab experiments. It’s also used to sterilize biological safety hoods. It has a wide spectrum of lethality because it mutates the genetic code into nonsense. If the organism can’t read the genetic code, it can’t go on living.
Ultraviolet light does kill insects as well, and it’s commonly used in quarantine labs to keep potentially dangerous insects from escaping into the environment. It’s also been investigated as a way to kill stored product pests without resorting to pesticides. This doesn’t mean it would be a good idea for home use, because the lights are set up in such a way that scientists are only exposed for a few seconds at a time, but UV light does kill insects.
This is where I originally intended to end the post, because it’s a fairly straightforward answer. UV light kills insects, and even has some applications in industry and agriculture because of this property. It’s a safety hazard, and shouldn’t be used in the home…but insects aren’t immune to the effects of UV light.
While writing this article, I was reminded of a rather interesting paper I read awhile back. It turns out that UV light isn’t the only harmful type of light. It also turns out that blue light might kill insects as well.
Late last year there was a paper titled Lethal effects of short-wavelength visible light on insects published in the journal Scientific Reports. Scientific Reports is kind of Nature’s answer to PLOS One in that it’s open access, and focuses on papers that are a bit unusual. The paper was shown to me by a colleague, and I wasn’t quite sure what to think about it at the time. I’m still not sure what to think, although I do find the data very convincing.
It’s thought that blue light is a major cause of vision problems as a result of aging. I admit I’m not familiar with the effects of blue light in general, but it appears to act somewhat similar to UV light by causing chemical changes in tissues which result in damage. The chemicals damaged are different between UV and blue light, but both UV and blue light are very high energy wavelengths which transmit a lot of energy to tissues.
Bill Nye does an awesome job of explaining the light thing. All organisms absorb and reflect certain wavelengths of light, which gives them different colors as Nancy noted in an earlier post.
So…light can cause damage in sensitive tissues in humans but it’s not known how it affects more robust tissues in humans or any other animals. UV light is a high energy wavelength, and blue light is also a high energy wavelength…so it makes sense that blue light would have an effect on sensitive tissues.
The paper by Hori and colleagues compared how insects fared when reared under different light wavelengths. When reared under certain colors, they were fine…but when reared under blue light the insects usually died or suffered very high mortality. The optimal wavelength was slightly different for every insect, which could imply that different systems are affected, but in each case the most effective wavelength was in the blue range.
I’ve thought a lot about this paper since I read it, and as far as I can tell the data is pretty solid.
- The insects used are all very hardy laboratory model animals, and are very easy to maintain in the lab.
- They controlled for stress of rearing under continuous light.
- Their lights emitted very narrow wavelengths of light, and didn’t appear to ‘leak’ into UV spectra.
- LEDs don’t emit a whole lot of heat, and the temperatures were pretty standard for insect rearing temperatures.
- The intensity of light is similar to what they’d be exposed to in direct sunlight, and all insects were exposed to similar amounts of light.
This is the kind of paper which gets me excited. If someone would have told me about this over lunch, I probably wouldn’t have believed them. Even though the results aren’t as extreme as those seen with UV light, I think the paper makes a pretty compelling case that blue light does harm insects.
Hori M, Shibuya K, Sato M, Saito Y. 2014. Lethal effects of short-wavelength visible light on insects. Scientific Reports 4 : 7383 | DOI: 10.1038/srep0738.