The question of whether spiders are beneficial housemates is often met with discomfort, but it is a matter of simple ecology. These eight-legged residents have adapted to coexist with humans globally. Their presence inside a home is generally a response to available resources, namely food and shelter. Understanding the specific role these arachnids play can help determine if their benefits outweigh the discomfort of sharing a space.
Spiders as Natural Indoor Pest Controllers
Spiders function as efficient, built-in pest control agents, preying on nuisance insects that seek shelter in human dwellings. Their carnivorous diet targets common household invaders, including house flies, mosquitoes, and clothes moths, often caught in their silk snares. This natural predation helps keep flying pest populations in check without human intervention.
Many spiders also hunt down crawling pests such as cockroaches, earwigs, and silverfish, which are difficult to eliminate with typical household measures. By consuming these insects, spiders indirectly reduce food sources that might attract other pests. Allowing spiders to maintain their presence provides a continuous, non-chemical method of pest management, reducing reliance on indoor insecticides.
Identifying Common Household Spiders
One frequently encountered species is the American House Spider, Parasteatoda tepidariorum, identified by its messy, irregular webs, often called cobwebs. This spider has a mottled appearance, typically brown to grayish, with a bulbous abdomen. They build their tangled webs in undisturbed, low-traffic areas like upper corners of rooms, basements, and closets.
Another common resident is the Cellar Spider, or “Daddy Long Legs,” Pholcus phalangioides, characterized by its small, pale body and extremely long, thin legs. These arachnids construct large webs in damp, dark environments such as crawlspaces and unfinished basements. Cellar spiders are known to prey on other spiders, including some medically significant species.
Sac Spiders, belonging to the genus Cheiracanthium, are hunting spiders that do not rely on a permanent web. They are pale yellow or light brown and are typically found near the junction of walls and ceilings, where they construct a small silk sac for daytime retreat. Unlike web-builders, sac spiders are nocturnal wanderers, often entering homes in the fall as they seek warmth and search for insects.
Understanding Venom and Safety Concerns
The primary anxiety regarding indoor spiders is the threat of a bite, yet almost all common house spiders pose virtually no danger to humans. While nearly all spiders are venomous, using venom to subdue insect prey, the fangs of most household species are too small or fragile to penetrate human skin. Bites from common spiders are exceedingly rare and typically occur only when the spider is accidentally pressed against the skin.
When a bite does occur, the reaction is usually mild, resulting in minor irritation, redness, or a bump comparable to a mosquito bite. The two species in North America considered medically significant are the Black Widow (Latrodectus) and the Brown Recluse (Loxosceles reclusa). These spiders are not typical house residents; they are generally reclusive, found primarily in specific geographic regions, and their presence indoors is rare, usually confined to undisturbed storage areas.
Humane Ways to Discourage Indoor Spiders
For those who prefer not to share their living space, discouraging spiders can be achieved through non-lethal methods focused on exclusion and environmental management. Sealing potential entry points is a highly effective preventative measure, involving the use of caulk to close gaps around utility penetrations, window frames, and doors. Installing weather stripping and ensuring window screens are in good repair prevents easy access from the outdoors.
Reducing the availability of food and shelter also makes a home less attractive to spiders. This involves controlling other insect populations through regular cleaning and reducing clutter, especially in dark areas like basements and attics. If a spider is found, it can be humanely relocated using a cup-and-card method or safely removed with a vacuum cleaner.