Cellar spiders, members of the Pholcidae family, are common arachnids often found in human dwellings. They are frequently recognized by the informal name “daddy longlegs,” a term also sometimes used for harvestmen and crane flies. These spiders are globally distributed, with approximately 20 species found across the United States and Canada. Despite their widespread presence, cellar spiders are generally harmless to humans and are a natural part of indoor ecosystems.
Identifying Cellar Spiders
Cellar spiders possess distinct physical characteristics. They have small bodies, about 2 to 8 millimeters long, with exceptionally long, thin legs that can extend up to 50 millimeters. Their coloration varies, often appearing pale yellowish, light brown, or gray, with some exhibiting darker markings on their leg joints. They have eight legs and two main body segments: the cephalothorax and the abdomen.
These spiders construct loose, irregular, and often messy webs. Cellar spiders prefer dark, damp, and undisturbed areas, such as basements, cellars, crawl spaces, garages, and quiet corners of rooms. They commonly hang upside down in their webs, waiting for prey. When disturbed, many species rapidly vibrate or “bounce” in their webs, creating a blur that helps them avoid detection.
Their Role in Pest Control
Cellar spiders play a role in natural pest control within homes. They are predatory arachnids that feed on a variety of common household pests. Their diet includes insects such as mosquitoes, gnats, moths, and flies, helping to manage these populations indoors. Cellar spiders are opportunistic hunters and consume almost anything that becomes entangled in their webs.
Beyond general insects, cellar spiders prey on other spiders. They have been observed capturing and feeding on larger spiders, such as house spiders, and even venomous species like brown recluse spiders and black widows. Cellar spiders use their long legs to wrap prey in silk from a safe distance, then bite and inject venom to immobilize them. Their presence can help reduce the number of other unwanted arthropods in a living space.
Are They a Threat to Humans?
Despite common myths, cellar spiders are not dangerous to humans. They possess venom, but it is mild and not medically significant to people. Studies show that cellar spider venom is comparatively weak. While they have fangs, these are short and not strong enough to easily penetrate human skin.
Bites from cellar spiders are rare and usually occur only if the spider feels provoked or threatened. If a bite occurs, the effects are minor, resulting in a mild, localized irritation or sting without lasting consequences. The urban legend that cellar spiders have highly potent venom but fangs too short to bite humans is a myth without scientific backing. Overall, cellar spiders pose no significant health risk to people or pets.