Insects Don't Swarm at LED Lights

Outdoor lights once commonly drew dense clouds of insects, providing easy prey for animals such as geckos. After one family replaced its outdoor bulbs with LEDs, the geckos stopped visiting - not because they had disappeared, but because fewer insects gathered around the new lights. The change reflects a difference largely invisible to people: incandescent bulbs emit ultraviolet wavelengths, while typical LEDs do not. Many flying insects use ultraviolet light as a cue for moonlight, which helps them orient during flight. Artificial lights containing UV can disrupt that navigation, drawing insects into circling patterns around lamps.

A 2016 field experiment compared insect catches around incandescent, compact fluorescent, cool-white LED, and warm-white LED bulbs at 17 sites. Both LED types attracted significantly fewer insects than the other light sources; researchers found no meaningful difference between the two LED color temperatures. The reduced attraction may also mean fewer flies and biting midges near lights, with possible benefits for wildlife and reduced exposure to insect-borne disease. More broadly, artificial light at night is considered a contributor to declining insect populations because it interferes with their behavior. LEDs therefore offer more than energy savings: by emitting less ultraviolet light, they generally attract fewer insects and can lessen one form of nighttime disturbance.