Many types and styles of fly and mosquito traps appear and are sold on the market each year.
Some traps employ ultraviolet energy (black light) with an electrically charged grid to kill insects. These electrical fly and mosquito "zappers," when frying insects on the grid, can result in rather high electrical costs. Many kinds of insects, both harmful and beneficial, are attracted and killed that normally would fly out of the area if no light trap was present. One should judge a trap by the population of flies and mosquitoes remaining in the area and not by the amount caught. These traps should never be placed in doorways, windows, loading docks or other areas where concentrating these insects can become a nuisance. These traps may be helpful in small, tight, enclosed areas, especially indoors such as egg rooms, corners and stairwells where good sanitation practices are followed, However, outdoors in feedlots, open-air sheds, barns and other livestock buildings, and in areas of heavy insect and mosquito populations, traps are not effective in reducing numbers to satisfactory levels. These traps are more of an insect survey or monitoring tool than a control device. When used alone, they are not effective in and around livestock operations.
Also, strategically placed outdoor lighting can concentrate unwanted insects elsewhere. Mercury vapor lamps 150 to 200 feet away from buildings can divert nuisance insects away from high-traffic areas. By replacing a 100-watt mercury vapor light (ultraviolet energy) with a 50-watt high pressure sodium vapor light, insect concentrations are effectively reduced.
Ultrasonic pest repellers are worthless in controlling insects. These devices generate ultrahigh frequency sound waves (ultra sound) that is claimed to be disruptive to the living, mating and survival of pests. Research indicates that this sound, inaudible to the human ear and most insects, will not penetrate walls. In fact, the sound is high only at the source of output, falling off sharply beyond 15 feet and gone completely in 30 feet. Some studies have revealed that mosquitoes bite more frequently when the machine was turned on than when it was turned off. There is no difference in pest movement whether the machine is plugged in or unplugged from an electric source. Also, many insects cannot even hear the sound.