No-see-ums are tiny, blood-feeding pests, typically only one to three millimeters in size. These minute insects are often described as a nuisance due to their painful bites and the itchy welts they leave behind. The question of whether artificial light attracts them stems from the common observation that many other insects are drawn to porch lights. However, the mechanisms that attract biting midges are quite different from many other nighttime fliers.
Understanding Light Attraction in Biting Midges
Biting midges exhibit a weak phototactic response, meaning they are generally not strongly attracted to broad-spectrum visible light. Unlike many flying insects, midges primarily rely on other stimuli to locate a meal.
Scientific studies show that if midges are attracted to light, it is typically to shorter wavelengths. Light in the ultraviolet (UV) and blue spectrum is generally more attractive to flies than longer wavelengths. Standard incandescent bulbs or bright white LEDs are therefore not effective for trapping or diverting these pests. Even commercial bug zappers, which rely on UV light, are not highly effective against no-see-ums.
To minimize incidental attraction, experts suggest swapping bright white or blue lights for yellow “bug lights” or those with longer wavelengths. Yellow light is less stimulating to the visual systems of many biting insects and can help reduce the overall insect population near your home. However, changing your lighting alone will not eliminate a midge problem, as light is a secondary factor in their host-seeking behavior.
Primary Host-Seeking Cues
The primary mechanisms that biting midges use to locate a host are chemical and thermal. Their most powerful long-range attractant is carbon dioxide (\(\text{CO}_2\)), which is exhaled by humans and other warm-blooded animals. \(\text{CO}_2\) guides the midges toward a potential host from a distance.
They utilize shorter-range sensory cues to pinpoint the exact location of the host. These cues include body heat and specific body odors. Compounds like lactic acid, which is present in human sweat, are highly attractive to the female midges. Females require a blood meal to develop their eggs.
After a female midge successfully locates a host, she may also release aggregation pheromones. These pheromones signal to other midges that a meal source is available. This behavior can lead to the sudden appearance of swarms.
Practical Avoidance Strategies
Avoidance strategies should focus on disrupting the midges’ ability to detect host cues and exploiting their weak flight. One of the most effective physical barriers is the use of electric fans on patios or decks. Biting midges are poor fliers, and a wind speed of just six miles per hour is often enough to keep them from landing and biting.
Chemical repellents applied to exposed skin and clothing provide a strong defense. Repellents containing DEET or Picaridin are highly effective at blocking the midges’ scent receptors. Wearing light-colored, long-sleeved shirts and pants can also reduce bites by minimizing exposed skin.
For home protection, standard window and door screens are often not sufficient to keep these tiny insects out. No-see-ums can pass through typical mesh sizes. A very fine mesh, such as 16–18 strands per inch or finer, is necessary to create an effective physical barrier. Additionally, minimizing exposure can be achieved by avoiding outdoor activity during the midges’ peak biting times, which typically occur around dawn and dusk.