Nocturnal insects swarming around artificial lights is a familiar summer phenomenon. Moths, beetles, and other flying insects gather around porch lights or streetlamps, prompting curiosity about why they are drawn to these luminous displays.
Why Insects are Drawn to Light
The primary scientific explanation for insects’ attraction to light centers on a concept known as the dorsal light response, which is a reflex where insects try to keep the brightest part of their visual field on their backs to maintain proper orientation during flight. For millions of years, the brightest part of the night sky was the moon or stars, which served as reliable celestial compass cues for navigation. Artificial lights, being much closer and often brighter than natural celestial sources, disrupt this ancient navigational system.
When an insect encounters an artificial light source, its instinct to keep light above its back causes it to continuously adjust its flight path. This results in erratic, circling, or spiraling patterns around lamps. Rather than being directly attracted to the light, insects become disoriented and trapped in a localized area due to this corrupted sense of vertical orientation. Older theories, such as insects mistaking artificial lights for escape routes or being drawn to the warmth of older bulbs, have largely been disproven by studies using modern, low-heat LED lights.
Light Spectrum and Attraction
Insects perceive light differently from humans, with their vision extending into the ultraviolet (UV) spectrum, a range invisible to the human eye. Many insects have photoreceptors sensitive to UV, blue, and green light wavelengths, peaking around 350 nm, 440 nm, and 530 nm respectively. This heightened sensitivity to shorter wavelengths means that UV and blue light are particularly attractive to many species.
Traditional white incandescent and fluorescent lights, as well as many cool-toned LEDs, emit a significant amount of UV and blue light, making them highly appealing to insects. This is why “bug zappers” often incorporate UV-A fluorescent lights to effectively lure insects to an electrified grid. Conversely, longer wavelengths, such as yellow, orange, and red light, are less visible and therefore less attractive to most insects.
Insects Commonly Attracted to Lights
Many nocturnal insects are commonly attracted to artificial lights. Moths are perhaps the most well-known examples, frequently seen fluttering around porch lights and streetlamps due to their positive phototaxis. Beetles, including species like June bugs, are also often drawn to lights, particularly those emitting UV light, and can swarm around bright sources during evening hours.
Mosquitoes, while primarily attracted to carbon dioxide, body heat, and certain scents, can also be indirectly drawn to lights. This happens because lights attract other insects that mosquitoes prey upon, bringing them closer to the illuminated area. Gnats, midges, caddisflies, and some types of flies also congregate around artificial light sources.
Strategies for Reducing Light Attraction
Minimizing insect attraction to outdoor lights involves choosing appropriate light sources and smart lighting practices. Switching to warm-colored LED bulbs, such as yellow or amber light (2,000-2,700 Kelvin), can significantly reduce the number of insects drawn to your property. These bulbs emit fewer of the UV and blue wavelengths that insects find most appealing.
Strategic placement of lights can help; positioning them away from doors, windows, and main gathering areas like patios can divert insects to less frequented zones. Motion-sensor lights ensure illumination is only active when needed, reducing the time bugs have to congregate. Installing light fixtures with shields that direct light downward can minimize light spillage and reduce visibility to flying insects.