Moths are nocturnal insects with highly developed senses necessary for survival and reproduction. Their visual system is specialized for low-light conditions, and their olfactory sense is extraordinarily sensitive, allowing them to detect chemical signals from great distances. These senses guide the moth toward food sources, mates, and egg-laying locations, but they can also lead them astray when encountering human-made influences. Attractants are broadly categorized as either misinterpretations of their natural navigation system or chemical signals tied to biological needs.
The Navigational Error of Light Attraction
The observation of moths circling a light bulb is not a true attraction but an error in their navigation system. Moths use transverse orientation to fly in a straight line at night. This involves maintaining a constant angular relationship with a distant light source, like the Moon or bright stars, whose light rays are effectively parallel.
When a moth encounters a nearby artificial light source, such as a porch lamp, the light rays are no longer parallel. The moth attempts to keep the light at a fixed angle to its eye. However, as it flies, the angle changes rapidly, causing the insect to continually correct its course by turning inward. This flawed correction results in the familiar spiral flight path that traps the moth near the light source.
The degree of disorientation relates to the light’s spectrum, as moths are particularly sensitive to shorter wavelengths. Ultraviolet (UV) light, abundant in many artificial sources, is especially stimulating to the moth’s visual receptors. In contrast, lights with longer wavelengths, such as warm yellow or amber-colored LED bulbs, are less disruptive to their navigation.
Chemical Scents for Feeding and Mating
Beyond light, moths rely heavily on their sense of smell to locate sustenance and a partner. The chemical cues used for these purposes are distinct and highly specific, demonstrating the power of their olfactory system.
Attractants for Sustenance
Adult moths, like many other pollinators, are attracted to floral scents that signal the presence of nectar. These scents are composed of volatile organic compounds (VOCs), which include complex mixtures of terpenoids and phenylpropanoids. Specific floral odorants, such as phenylacetaldehyde (PAA), are known to be strong attractants for numerous moth species.
When natural nectar sources are scarce, some moths seek out the volatile compounds released by fermenting or decaying organic matter. Sugary substances like tree sap or overripe fruit are colonized by yeasts, which release alcohols and esters that are attractive to certain moth species. For instance, the compound isoamyl alcohol, produced during early-stage fermentation, is a powerful lure for many noctuid moths.
Attractants for Reproduction
The most potent and specific attractant is the sex pheromone, a chemical signal released by the female to call a mate. Females emit a complex blend of these volatile molecules in short pulses that form a scent plume carried by the air. This plume can be detected by males over distances of up to several kilometers. The male moth’s antennae are highly specialized and often feathery (plumose) to maximize the surface area for detection. Specialized sensory hairs, called sensilla, house olfactory neurons that are exquisitely sensitive, allowing the male to track the pheromone trail and locate the female for mating.
Materials That Attract Household Pests
Moths are only considered household pests when the female is seeking a location to lay her eggs, ensuring her offspring have a food source immediately upon hatching. The adult moths themselves do not cause damage to stored goods or fabrics.
Stored Food
The Indian meal moth (Plodia interpunctella) is the most common pantry pest and is attracted to a wide variety of dry goods. The adult female seeks out items like grains, cereals, flour, cornmeal, dried fruits, nuts, and pet food. She deposits her eggs directly on or near the food source, and the ensuing larvae consume the material while producing silken webbing and excrement that contaminate the food.
Fabrics
The webbing clothes moth (Tineola bisselliella) is a textile pest whose larvae feed on materials containing keratin, a protein found in animal fibers. This includes natural materials like wool, silk, fur, feathers, and cashmere. The female moth is attracted to these materials, particularly if they are soiled with perspiration, body oils, or food stains, which provide moisture and trace nutrients that aid in larval development. Unlike many other moth species, the adult clothes moth actively avoids light and seeks out dark, undisturbed areas, such as closets and storage boxes, to lay its eggs.