Cellar Spider Identification & Control

Quick Identification

• Size: Body about ¼ to ⅓ inch; leg span up to 2 inches — legs are disproportionately long relative to body
• Color: Pale gray to tan, nearly translucent
• Key Features: Extremely long, thin legs; small cylindrical body; builds loose, irregular webs; vibrates rapidly in web when disturbed
• Common Names: Daddy longlegs (colloquial — though true daddy longlegs are harvestmen, a different arachnid entirely)
• Active Season: Year-round indoors; prefers damp environments
• Risk Level: None — completely harmless

What You Need to Know

Cellar spiders are among the most common indoor spiders in Illinois, and they’re easy to recognize by their comically long, thin legs and small bodies. They build loose, irregular webs in basements, crawl spaces, garages, and any damp, dark area of your home. When disturbed, they vibrate rapidly in their web — a defensive behavior that makes them harder for predators to target.

Despite the persistent urban myth, cellar spiders are not “the most venomous spider in the world with fangs too small to bite.” This is false on both counts — their venom is mild and their fangs can technically penetrate skin, though they almost never bite. They’re genuinely harmless. However, they accumulate in large numbers in damp environments, and their layered webs create heavy cobweb buildup in basements and crawl spaces. If cellar spider populations are heavy in your home, it’s likely a sign of excess moisture — addressing humidity with dehumidifiers and ventilation will reduce their numbers naturally. For persistent problems, contact Sanctuary Pest Control at 815-993-3472.