Insects swarm at gas station light, July 2006, (photo by cgpgrey, CC BY 2.0, via Wikimedia Commons)

3 November 2026

Remember when you used to encounter swarms of insects around outdoor electric lights? Their well known attraction to outdoor lights is used by entomologists and moth lovers to conduct insect surveys. All you need is a light and a white sheet to see who’s flying at night.

Light trapping for insects at Maui (photo by Forest & Kim Starr, CC BY 3.0, via Wikimedia Commons)

Nowadays, if you want to attract insects, you have to be picky about the light you use. As everyone changes over to LED lights, we see the color difference but we can’t see the crucial difference in insect attraction between incandescent and LED.

Odd one out, LED streetlight by John Goldsmith, CC BY-SA 2.0, via Wikimedia Commons

Our guide Roland Rumm on the WINGS Veracruz trip explained what happens with insects in the switch to LED lights. His family has an outdoor dining space that is well lit with artificial light. As a child he loved to watch the geckos climb to the lights and eat the insects. (This gecko can change to a bland gray color when he needs to.)

Bay Island least gecko looking colorful (photo by Laura Gaudette, CC BY 4.0, via Wikimedia Commons)

In recent years the family changed over to LED lights and the geckos disappeared. Were the geckos gone? No. But far fewer insects were attracted to the LED lights so the geckos had no reason to show up.

In 2024 the BBC wrote about Why insects are drawn to artificial light at night:

Flying insects use moonlight to navigate. Since the moon is always above them, they orient themselves so that the light shines on their backs. That’s how they stay upright in flight.

Moonlight contains ultraviolet (UV) and infrared wavelengths because it is merely reflected sunlight. Insects cue on UV, believing it to be the moon. When artificial lights transmit UV they look like moonlight so insects orient their backs to it. Consequently they circle the light and even flip upside down when the artificial light is pointing up to the sky!

Incandescent lights transmit UV but LEDs do not. Insects are far less attracted to LED.

In 2016 scientists at the University of Bristol, UK ran experiments to compare insect attraction to four types of light: Incandescent (tungsten filament), Compact fluorescent, “Cool-white” LED and “Warm-white” LED.

We conducted field experiments to compare the relative attractiveness of four commercially available “domestic” lights, one traditional (tungsten filament incandescent) and three modern (compact fluorescent, “cool?white” LED and “warm?white” LED), to aerial insects, particularly Diptera. We found that LEDs attracted significantly fewer insects than other light sources, but found no significant difference in attraction between the “cool?” and “warm?white” LEDs. Fewer flies were attracted to LEDs than alternate light sources, including fewer Culicoides midges (Diptera: Ceratopogonidae). Use of LEDs has the potential to mitigate disturbances to wildlife and occurrences of insect?borne diseases relative to competing lighting technologies.

Here’s what they found. NOTES: CFL = Compact fluorescent, FIL = incandescent (the old lightbulb), LEDC = LED cool white, LEDW = LED warm white light.

Average insect trap catch in the “evening” sampling periods commencing at sunset (17 sites). Lights were compact fluorescent (CFL), tungsten filament (FIL), light?emitting diode “cool?white” (LEDC), and light?emitting diode “warm?white” (LEDW). Error bars indicate SE. From: Experimentally comparing the attractiveness of domestic lights to insects: Do LEDs attract fewer insects than conventional light types?

Typically LEDs do not emit UV light and are more energy?efficient than traditional technologies. Electrical energy is converted almost entirely into electromagnetic (EM) radiation within the range of the visible light spectrum (400–700 nm) and therefore not wasted on producing wavelengths of light invisible to the human eye, that is, UV and infrared (IR). Thus, LEDs are less attractive to many insects than lights which emit UV light. 

So that’s why there are very few bugs circling LED lights at night.

Street lamp with new multiple LEDs as light source, shines down on a rowan branch with leaves at night, May 2024, Tuntorp, Sweden (photo by W.carter, CC BY-SA 4.0, via Wikimedia Commons)

This trait of LEDs is a good thing because UV artificial light at night distracts insects so much that it’s considered a major reason why insect populations have declined. See: The impact of artificial light at night on nocturnal insects: A review and synthesis.