Moths represent the vast majority of the insect group Lepidoptera, with approximately 160,000 species known globally. Most species are active at night, serving as nocturnal pollinators and a foundational food source for many other animals. While these creatures navigate the darkness using highly refined senses, artificial light and potent scents in human environments can strongly draw them into outdoor spaces.
The Disorienting Power of Artificial Light
The most commonly observed attraction is the tendency of moths to flutter around porch lights and streetlamps, a behavior known as positive phototaxis. This instinct is a byproduct of the moth’s ancestral navigational system, called transverse orientation. For millennia, moths maintained a straight flight path by keeping a constant angular relationship with a distant celestial light source, such as the moon. Because the moon is extremely far away, its light rays are parallel, allowing the moth to fly in a straight line while keeping the light at a fixed angle to its body.
When a moth encounters a close, artificial light source, this system fails because the light rays diverge rapidly. To maintain the fixed angle, the moth instinctively attempts to correct its flight path by turning toward the light. This results in a continuous spiral that pulls it closer to the bulb, trapping the insect in an orbit, wasting energy, and making it vulnerable to predators.
Moths are strongly attracted to short-wavelength radiation, particularly ultraviolet (UV) and blue light, which mimic the natural light spectrum they use for navigation. Lamps emitting UV light often attract the highest percentage of moths. Even small amounts of UV or blue light from common outdoor fixtures contribute to light pollution that disrupts their nighttime activities. Scientists suggest that artificial lights do not necessarily draw moths out of the dark but rather trap the insects that fly past them, essentially acting as a net.
Chemical Trails: Scent and Food Attraction
Beyond light, chemical signals play a major role in attracting moths, particularly over long distances. Chemoreception, or the sense of smell, guides moths to both mates and food sources through the detection of volatile organic compounds (VOCs). The most potent chemical attractors are sex pheromones, which female moths release to signal their readiness to mate.
Male moths possess highly specialized antennae covered in sensory hairs, allowing them to detect pheromones in turbulent air from up to 1,000 meters away. The male tracks the source by flying upwind and following intermittent “whiffs” of the chemical plume. This extreme sensitivity allows them to distinguish the species-specific pheromone blend from a background of other odors.
Moths are also drawn to VOCs released by non-living food sources, such as fermenting tree sap, molasses, or rotting fruit. These fermenting substrates attract both male and female moths seeking sugar and nutrients. The process of fermentation produces alcohols and esters, which are highly attractive to many species, especially noctuids. For instance, the compound isoamyl alcohol is a known volatile that moths can track over long distances to find a suitable food source.
Specific Host and Nectar Plants
Moths are attracted to living plants that provide resources for feeding and reproduction. Adult moths rely on nectar for energy and are drawn to flowers that have evolved to attract them after sunset. These moth-pollinated flowers are typically pale or white, making them more visible in low light, and release sweet fragrances only after dusk.
Night-blooming nectar sources often feature trumpet shapes to accommodate the moth’s long proboscis. Common examples include:
- Evening primrose
- Gardenia
- Tobacco
- Yucca
Moths are also attracted to specific host plants as sites for egg-laying, not for adult feeding. Female moths must find the exact species of plant that their larvae, or caterpillars, require for food upon hatching. This species-specific process is necessary because many caterpillars only feed on a narrow range of plants, such as oak, birch, or willow trees.