The presence of spiders near artificial light sources often leads to the assumption that these arachnids are drawn to light. However, this is a misconception. Spiders are not directly attracted to illumination.
Spider Vision and Light Perception
Spiders possess a varied visual system, typically featuring eight simple eyes, though some species have fewer. Unlike the complex, image-forming eyes of humans, most spider eyes are primarily adapted for detecting changes in light intensity and movement, rather than forming sharp, detailed images. This adaptation is crucial for their survival, aiding in the detection of prey and the avoidance of predators.
While some hunting spiders, like jumping spiders and wolf spiders, exhibit better vision and can perceive details and even color, many common species have poor eyesight. These spiders rely more heavily on other senses, such as vibrations and touch, to navigate their environment and locate food. Their eyes often contain a light-reflecting layer called a tapetum, which enhances their ability to see in low-light conditions, but still results in a blurry view compared to human vision.
The Indirect Attraction to Light
Spiders are not directly drawn to light, but rather to the abundance of prey that congregates around light sources. Many insects, including moths, flies, beetles, and gnats, are strongly attracted to light. These insects use natural light sources like the moon for navigation, and artificial lights can disorient them, causing them to swarm or circle.
This congregation of light-attracted insects creates a prime hunting ground for spiders. Spiders, particularly web-building species like orb-weavers, construct their webs near outdoor lights to capitalize on this readily available food source. Active hunting spiders, such as wolf spiders, also benefit from increased prey availability in lit areas. The apparent attraction of spiders to lights is a secondary effect, driven by their predatory instincts and the behavior of their prey.
Practical Implications for Your Home
Understanding that spiders are drawn to light indirectly, through their prey, provides practical ways to manage their presence around your home. Switching to specific types of outdoor lighting can reduce the number of insects, and consequently, spiders. Warm-colored LED bulbs, particularly those emitting yellow or amber hues, attract fewer insects compared to cool white or blue-toned lights, or traditional incandescent bulbs. Sodium vapor lamps also attract fewer insects.
Turning off outdoor lights when not needed can also diminish the insect population around your home, reducing the appeal for spiders. Sealing cracks and openings around windows and doors prevents both insects and spiders from entering your living spaces. Using blinds or curtains indoors to block light from spilling outdoors can further limit the attraction of insects. Regularly cleaning around light fixtures and removing existing webs helps to deter spiders from establishing themselves.