Cellar Spider

The cellar spider is a member of the family Pholcidae, sometimes casually confused with harvestmen (which are unrelated arachnids also called "daddy long-legs"). It has a small, pale, elongated body and extremely long, thin legs, giving it a delicate, spindly appearance.

This spider builds a loose, tangled, irregular web in undisturbed corners, ceilings, and crevices, where it hangs upside down waiting for prey to blunder in. It is a cosmopolitan species found closely associated with human structures across much of the world, thriving in the stable, sheltered microclimates that buildings provide.

As a web-building predator of small arthropods, including other spiders, the cellar spider fills a niche as an indoor and cellar-dwelling generalist predator, and its webs are a familiar sight in undisturbed corners of basements and garages.

• Small, pale tan to grayish, elongated cephalothorax and abdomen, roughly 2–10 mm in body length.
• Extremely long, thin, thread-like legs that can span several centimeters, far exceeding the body length.
• Builds a loose, irregular, tangled web rather than a neat orb or funnel shape.
• Hangs upside down in the web and vibrates rapidly when disturbed, blurring its outline.
• Lookalikes: harvestmen ("daddy long-legs," order Opiliones), which have a single fused, oval body segment with no narrow waist and do not build webs, unlike the two-part body of true cellar spiders.

Cellar spiders are found worldwide, especially in and around human structures, favoring dark, undisturbed corners of basements, cellars, garages, sheds, and crawl spaces. Outdoors in warmer climates they may also occupy caves, hollow logs, or sheltered rock crevices.

They are active year-round in stable indoor environments, remaining largely in one web location for extended periods unless disturbed or relocating to find better prey availability.

Cellar spiders are sedentary web-builders that construct loose, irregular, three-dimensional webs and wait upside down near the center for flying or crawling prey to become entangled, feeding on small insects and other spiders. They are notable for invading and preying upon the webs of other spider species, including much larger ones.

When disturbed, a cellar spider often vibrates rapidly in its web, a defensive display that blurs its silhouette and may deter predators. They are generally sedentary, remaining in the same web for long stretches, and are considered beneficial predators of other small household arthropods.

Females carry a loose cluster of eggs directly in their jaws (chelicerae) rather than wrapping them tightly in a dense sac, until the spiderlings hatch. Spiderlings resemble miniature adults and undergo incomplete metamorphosis, growing through a series of molts without a larval or pupal stage.

Development to maturity typically takes several months, and adults may live for one to two years in stable indoor environments. Breeding can occur across multiple seasons indoors where temperatures remain stable, leading to overlapping generations.