Yellow light bulbs. You’ve probably seen them. Maybe some of your neighbors have them, or you’ve seen them on the shelf at a store. The most common ones are standard A19 60-watt bulbs with a medium (E26) screw base. They can be used anywhere a regular bulb can be used. The only difference is that when you turn them on, you get yellow light instead of white light.
You may have noticed you see more of them in the summer and that the most common place to see one is in a porch light. But why is that? What’s the point? Why do some people do that?
What It Does
Yellow light cuts down on the number of flying insects flying around it or hanging on the wall under it or the screen door. Have you ever noticed how many insects are around when you have a regular light bulb in your porch light?
Does It Work?
In a word, yes. Installing a yellow light bulb in your porch light, or any outdoor fixture will cut down the number of insects around it so much that you may think it’s eliminated them. It hasn’t. You’ll still have bugs, and they’ll still check it out. The difference is that they’ll move along instead of hanging around.
How Does It Work?
First, let's review some things the light doesn’t do. Yellow light doesn’t repel insects, and white light doesn’t attract them. And neither light kills insects. The light in a “bug zapper” doesn’t kill them either. They will swarm around that light, but it’s the charged mesh in front of the light that zaps them.
Beyond that, there appears to be some debate about this. The folks at eHow reference GE lighting and talk about the spectrum and wavelength and wind up saying, essentially, that flying insects can’t see the yellow light—just as you and I can’t see infrared or ultraviolet light with our unaided eyes.
At 1000bulbs, they add in color temperature and include a very nice graph of the visible spectrum—the portion of the spectrum that’s visible to us, that is. They do a nice job of explaining how the light source works, but they don’t say why they think bugs will swarm around a white light but not around a yellow one.
They do, however, make an important point: “[N]ot all insects are the same; different bugs see slightly different wavelengths.” That, plus the fact that we’re dealing with nocturnal insects here—that is, bugs that have evolved over eons, literally, to fly and feed at night—brings us to a preferred explanation:
Debbie Hadley, an expert on insects, says the bugs are mistaking a white light for the moon, which they use to navigate a straight path. The problem is that the light bulb is close enough to touch, so it’s useless as a navigational aid over any distance.
It’s about the color, or color temperature, of the light. That’s something all of these references agree on.
No, it’s not that the bugs can’t see it. Maybe not all of them and maybe not as well as they can see the moon, but they can. They still come up to it, but they don’t get stuck there.
Finally, the close resemblance between a round, white light bulb and the round, white moon makes the possibility of confusing the two very real. It’s been known to happen to humans.
They're confused by a light that resembles the moon, and not so much by one that doesn't.
Where Can I Get One?
Yellow bug lights, or “Bug Away” lights, can usually be found in most hardware and home improvement stores. If that isn’t working for you, they’re available online. It might be helpful to compare prices. Either way, you can find them in fluorescent, or CFL, as well as incandescent which saves money and keeps on burning.
Don’t Be Bugged by Insects Seeing the Light. NC State Extension