Why Are We Infested With Cellar Spiders?

The term cellar spiders refers to a common group of spiders that have small bodies and long legs. They prefer damp places, such as basements, crawlspaces, closets, attics, pantries and warehouses. They also sometimes live outside, such as in caves or rock piles. Cellar spiders aren't poisonous, but their large, messy, cobweb-like webs may become annoying. Infestations of cellar spiders typically occur when a home has a large population of other insects.

Appearance and Behavior

Cellar spiders belong to the family Pholcidae; about 20 species of cellar spiders live in the U.S. Cellar spiders are classified as short-bodied or long-bodied. Short-bodied cellar spiders have legs that are approximately 5/16 inch long, while long-bodied cellar spiders have legs about 2 inches long. The spiders resemble daddy long legs. They hang upside down from their massed, messy webs, which they often build in corners, until an insect wanders into the webs. The cellar spider then shakes the web to trap the insect further.

Infestations

Cellar spiders aren't poisonous or harmful. They don't bite humans, and although their webs can be a nuisance, occasionally encountering a cellar spider isn't cause for concern. In fact, they may help control the populations of other nuisance insects, such as flies, mosquitoes and moths. If you have a large amount of cellar spiders in your home, however, you can reduce the infestation with nonchemical and chemical means of control.

Nonchemical Control

If you have a lot of cellar spiders in your home and want to get rid of them, begin by removing the webs with a broom or vacuum. Next, take steps to reduce the insect population of your home, which provides prey for the spiders. For example, keep your home clean, lower the humidity and replace exterior white lighting with sodium vapor lighting. Sealing cracks in your foundation and in doors and windows also helps to keep spiders out.

Chemical Control

Insecticides labeled as appropriate for eliminating cellar spiders can also be used to help control an infestation of spiders. However, insecticides are not a replacement for good sanitation practices, and without proper sanitation, spiders and insects will quickly return. Use nonchemical control methods before using insecticides, and only use insecticides if nonchemical means of control do not work. If you use insecticides, read the label directions carefully before use, and follow all safety precautions. Consider contacting a licensed pest control company for assistance in controlling large infestations.