The Brown Marmorated Stink Bug (BMSB), an invasive pest from Asia, is the primary species of concern for homeowners. Recognized by its shield shape, it is an annoyance largely because of its habit of seeking indoor shelter and its defensive odor. The direct answer to whether stink bugs are attracted to light is yes, they exhibit a positive response to light stimuli, though this attraction is highly dependent on the light’s characteristics and the bug’s seasonal motivation.
The Direct Answer: Stink Bugs and Phototaxis
Stink bugs display a behavior known as positive phototaxis, meaning they move toward a light source. This response is a general characteristic of many insects, but for the BMSB, this attraction is particularly strong toward shorter wavelengths of light, such as ultraviolet (UV) and blue light. Laboratory studies have demonstrated that adult stink bugs are most attracted to light sources that emit in the UV-A and visible blue-to-green spectral range, specifically between 368 and 455 nanometers.
While white light is generally the most attractive stimulus in broad comparison, this is because common white light sources, like fluorescent or incandescent bulbs, contain a significant component of these preferred short wavelengths. Adult males, in particular, have been shown to be significantly more attracted to light sources than females or nymphs.
Seasonal Behavior and Shelter Seeking
The most noticeable light attraction occurs in late summer and throughout the fall, connected to a major shift in the insect’s behavior. As temperatures begin to cool, adult stink bugs enter diapause, a period of metabolic inactivity similar to hibernation. Their primary goal is to find sheltered, warm structures for overwintering, and light often serves as a beacon guiding them to a potential site.
The light itself is not the ultimate destination, but rather an indicator of a large, warm structure, such as a home or building. Stink bugs are frequently found congregating on the sunny, south-facing walls of buildings, which absorb the most heat throughout the late afternoon. The exterior lights of a home draw the bugs toward the structure, where they then seek out small cracks and crevices to gain entry. This search for shelter is a stronger motivation than the simple attraction to light, which explains why they may fly toward a light initially but then immediately crawl upward and seek a dark, protected space once they land on the building.
Practical Light Management for Prevention
Homeowners can significantly reduce the number of stink bugs attracted to their property by altering their exterior lighting choices. Switching from traditional white incandescent, fluorescent, or mercury vapor lamps to yellow-spectrum bulbs is highly effective.
Yellow LED bulbs or low-pressure sodium vapor lamps emit light with a significantly longer wavelength, which is far less attractive to stink bugs and many other nuisance insects. Furthermore, limiting the use of exterior lighting during the peak migration period, which generally runs from late August through October, can prevent the bugs from being drawn toward the structure. Simply turning off porch lights and drawing window blinds at night reduces the light pollution emanating from the home, making the structure less visible as an overwintering target.