The name, cellar spider, comes from the location where they are often found: damp cellars, basements, and crawl spaces. They have very long, thin legs and are often confused with the harvestmen or daddylonglegs. Cellar spiders are also one of the more common spiders that infests warehouses. There are approximately 20 species of cellar spiders found in the United States and Canada.
The two more commonly seen species are the long-bodied and short-bodied cellar spiders. The female long-bodied cellar spider is approximately 1/4-5/16 inch long with legs extending another 2 inches. The female short-bodied cellar spider has a 1/16 inch long body with legs extending about 5/16 inch.
Habits. Female long-bodied cellar spiders produce about three egg sacs over a lifetime, each containing 13-60 eggs each. The short-bodied cellar spider females produces about 10-27 eggs per case. Both species carry the egg sacs in their mouthparts instead of attaching them to the web like many other spiders. Once the eggs hatch the spiderlings crawl onto the mother’s body for a short time. Development from egg to adult usually takes about one year. Adult cellar spiders may live for an additional two years.
In instances where cellar spiders are pests, it is due to the large amounts of webbing they produce. Many species of spiders consume their old web before making a new one, but cellar spiders do not. They continuously add to it, creating large amounts of webbing which becomes a nuisance to remove. Cellar spiders construct loose haphazard webs, often in corners, to catch insect prey. They hang upside down on the web until a food item gets tangled.
Once prey is captured, cellar spiders vigorously shake their webs to further entangle their meal.
Several non-chemical measures can be taken to reduce the presence of cellar spiders from around a home or business. Spider webs, egg sacs, and individual spiders can be removed with a broom or vacuum. This can be very effective in reducing the number of spiders in a relatively short time. Removing the webbing also allows for easy reference of future spider activity.
One key feature of spider control is to reduce the available food source. Adequate insect control through proper sanitation, maintenance and insecticide use (if necessary) will help prevent spiders from becoming established. Lowering the relative humidity in the area where cellar spiders are found may help eliminate them because lower humidity will deter insects from entering the building. Humidity can be controlled in many ways such as a dehumidifier or through proper ventilation.
Replacing exterior white lights to a less attractive yellow or sodium vapor lamp can indirectly reduce the number of spiders because yellow light is less attractive to insects. At commercial locations, replace lights on buildings, especially over doors. Use pole lights away from the structure but directed back to illuminate entrances to reduce insects and spiders around the building.
By sealing cracks and crevices around doors and windows or other entry points, insect and spider access into the structure will be deterred. Installing weatherstripping and a proper threshold with a door sweep can prevent access into the building.
Appropriately labeled insecticides can be used to temporarily reduce cellar spiders; however, their use should be minimal and not used as a substitute for proper sanitation and proper maintenance.