Virtually all Bug Zappers and Bug Traps use a black light bulb, or at least a purple tinted light bulb, to attract insects to the machine. How effective are they? University studies have shown that the Zapper they tested killed very few female mosquitoes. Less than 2% of the bugs killed were female mosquitoes. How they could tell what the fried bugs were is a bit of a mystery, but these guys went to college for this.
My experience with Bug Zappers goes back around 30 years. They all would be zapping away at night, but I was still getting bit by mosquitoes. When something that looked like a mosquito would start to build up a layer on the zapping grill, this layer would expand each night. I theorized that the dead bugs stuck on the grid were heating up and releasing CO2, attracting more mosquitoes to their death. It is hard to tell what a dead fried bug is, but the ones sticking to the advertised non-stick grill certainly looked like mosquitoes. I also observed moths and other non-biting bugs attracted to the black light, and occasionally getting past the outside grill and getting fried. They were the ones that would make a longer, loud sizzling sound, and release a puff of smoke.
I put little faith in the University studies that said I really wasn’t killing that many actual biting mosquitoes. I also knew that to really reduce the mosquito population, I had to wait a few weeks for the ones that I killed to break the reproduction cycle enough to make a noticeable difference. The problem with this type of thinking is that the life cycle of a mosquito is only a couple of weeks. If you had a large explosion of mosquitoes, like after heavy rains, they will be gone in a few weeks anyway without doing anything, unless they were continually breeding.
Using a Bug Fan, you can see the actual bugs you catch while still alive, making identification easy until they die and dry out to dust. To test the efficiency of using a black light, I ran two identical Bug Fans, one with a black light attached to the back, and one without. The black light used was a CFL bulb, cost around $5, inserted in what is commonly called a “trouble light”, cost around $15. The CFL bulb is the curled compact fluorescent bulbs, which have a lifetime of 10,000 hours or more. These are also made in the older technology of incandescent, which don’t work nearly as well, and have a life time of maybe 1,000 hours, and use several times more electricity. For a comparison, the black light bulb for a Zapper is usually around $15-20, and they seldom lasted an entire season.
My results were surprising, if you thought that the black lights attracted mosquitoes. I caught about the same in both Bug Fans, with the non-lighted Bug Fan catching mostly just mosquitoes. The Bug Fan with the black light caught many more times the amount of bugs. Moths, gnats, smaller black type flies, small flying beetles, and other bugs I didn’t even know were flying around my porch ended up in the net each night. Now, when the bugs are heavy, I run one Bug Fan with a black light, and the others without. Each morning when I look at the nets, I know that I am putting a dent in the mosquito population, because I can see the ones that flew onto my porch. I can also see the results when I sit outside. The mosquitoes, gnats, and other flying bugs are greatly reduced or eliminated immediately, without waiting for their life cycle to end.
In conclusion, while a black light doesn’t necessarily attract mosquitoes, it doesn’t repel them either. It does attract most other flying bugs, which is good, and makes the owners of Bug Zappers feel good about their purchase as they hear it zapping all night long. Since none of these bugs would be considered beneficial, get a black light, get a Bug Fan, and get rid of the bugs.