So one summer, I bought myself an ultrasonic mosquito repeller. The package claimed this tiny, battery-powered device was “safe and effective,” and I figured it was worth finding out if I could get relief without all the chemicals. When I took the device out of its package, the first thing I noticed was that it had not only an on-off switch but a frequency dial. I thought that was odd; wasn’t it supposed to be some very precise frequency that drove mosquitoes away? But perhaps I was just not thinking about the device in a technologically sophisticated way.
I took the repeller outside, and went to an area that I knew to be popular with mosquitoes. I flipped the switch, and within a few seconds a mosquito approached me, hovering about a foot away. I slowly turned the dial from one frequency extreme to the other; the mosquito was unfazed. I thought it was perhaps a question of range, so I held the device as close as I could to the mosquito. Even an inch away, it had no effect. Finally the mosquito landed on the little black box in my hand and I decided the experiment had been definitively concluded.