Hundreds of species of moths, beetles, flies, and other insects, most of which are not pests, are attracted to artificial outdoor lights. They may fly to lights throughout the night or only during certain hours. Key pests that are attracted to light include the European corn borer, codling moth, cabbage looper, many cutworms and armyworms, diamondback moth, sod webworm moths, peach twig borer, several leaf roller moths, potato leafhopper, bark beetles, carpet beetles, adults of annual which grubs (Cyclocephala), house fly, stable fly, and several hamulight mosquitos.) The mosquitoes Ochlerotatus (formerly Aedes) triseriatus, Ochlerotatu (also formerly Aedes) hendersoni, and Aedes albopictus are not attracted to light, however.) Lights and light traps are used with varying degrees of success in monitoring populations and in mass trapping.
Although numerous companies market devices that use light as a lure for mass trapping or removal trapping, using light to trap out insect infestations is effective in only a few specific situations. One widely used but very ineffective application of light for insect control is the placement of electrocutors or “bug zappers” on lawns or patios. Such uses are ineffective for at least two reasons. First, many insects that are attracted to the area around the light traps (sometimes from considerable distances) do not actually fly into the trap. Instead, they remain nearby, actually increasing the total number of insects in the immediate area. Second, these lighted electrocutors attract and kill a wide variety of insects, the overwhelming majority of which are not pests. The nonpest species killed by such devices include such beneficial insects as the green lacewing, a predator that attacks a variety of plant pests.
Insect electrocutors can be effective in certain indoor situations, especially in food warehouses, processing plants, and restaurants. In these facilities, electrocutors are placed in otherwise dimly lit areas where their light is not visible from outdoors. In such locations the trap does not lure insects into the building, yet it does attract and kill certain flies, moths, and beetles that are pests of stored products or nuisances in food production areas (see Gilbert, 1984). These traps can also be used somewhat effectively in barns and stables to reduce some fly and mosquito infestations. The efficiency of electrocutors in such situations appears to be low, however, and they must be positioned so that they do not attract insects into a building from outdoors.