Basements often serve as a dark, undisturbed refuge for spiders. While the common fear of spiders (arachnophobia) is understandable, the threat is often disproportionate to the reality. The vast majority of basement spiders are harmless creatures that play a beneficial role in controlling other household pests.
Assessing the Actual Threat
Every spider possesses venom, but it is designed to paralyze the small insects that form their diet. Most common spiders are not built to breach human skin; their fangs are often too short or fragile to penetrate the epidermis. Spider bites are statistically rare, and a skin lesion is far more likely to be caused by an insect or bacterial infection. Even when a bite occurs, the venom from typical basement dwellers is not medically significant. The mildest reaction may include a slight stinging sensation or a small, itchy bump that resolves quickly.
Recognizing Harmless Basement Spiders
Cellar spiders, often mistakenly called “daddy long-legs,” are some of the most common sights in undisturbed basement corners. These spiders are easily identifiable by their exceptionally long, thin legs and small, pale bodies, and they construct messy, tangled cobwebs. They are not known to bite humans, and their venom is mild, despite persistent urban legends claiming otherwise.
Another frequent resident is the common house spider, a species that is typically yellowish-brown with an elongated abdomen. This spider is responsible for the classic, irregular cobwebs found in the quiet, dark recesses of a basement. Although they possess venom to subdue their prey, their fangs are too small to pose a risk to people, and they prefer to flee rather than confront a perceived threat.
Wolf spiders are also common, characterized by their robust, hairy appearance and their habit of hunting on the ground instead of building webs. They are fast-moving and can be quite large, which often leads to misidentification and fear. While they can bite if they feel threatened or are directly handled, the resulting symptoms are typically mild, similar to a bee sting, and they are not considered medically significant.
Identifying the Rare Dangerous Species
In North America, two species occasionally found in basements carry medically significant venom: the Brown Recluse and the Black Widow.
Brown Recluse
The Brown Recluse spider is tan to dark brown, recognizable by a dark, violin-shaped marking on its cephalothorax. This spider has six eyes arranged in three pairs, a unique feature distinguishing it from most other spiders. Brown Recluses prefer secluded, dark, and dry areas, making undisturbed cardboard boxes or stored materials in basements ideal hiding spots. A bite may not be immediately painful, but the necrotic venom can cause a painful, slow-healing ulcer that may require medical attention.
Black Widow
The Black Widow spider is known for its glossy black body and the distinct red or orange hourglass marking on the underside of its abdomen. Female Black Widows, the only ones whose venom is a concern, are typically found hanging upside down in their messy, three-dimensional webs near ground level. Their venom is neurotoxic, affecting the nervous system, and a bite can cause severe muscle cramps, abdominal pain, and nausea. If a bite from either species is suspected, wash the area with soap and water, apply a cool compress to reduce swelling, and immediately seek professional medical care.
Controlling Spiders in Your Home
Spiders are drawn to basements primarily because these areas provide high humidity, darkness, and an abundant food source of other insects. Managing the environment is the most effective, non-chemical control method. Reducing the relative humidity in the basement with a dehumidifier makes the space less hospitable for both spiders and the insects they prey upon.
Sealing entry points is another effective strategy for preventing access. Inspect the foundation, windows, and utility line openings for cracks and gaps, and use caulk or weatherstripping to close them. Minimizing clutter by storing items in sealed plastic containers instead of cardboard boxes eliminates many of the dark, undisturbed retreats that spiders seek out.