Cellar Spiders Explained

Habits and Traits of Cellar Spiders

Cellar spider.
The longbodied cellar spider is probably the most common spider found in basements. Joseph Berger, Bugwood.org

People often refer to cellar spiders (Family Pholcidae) as daddy longlegs, because most do have long, slender legs. This can create some confusion, however, because daddy longlegs is also used as a nickname for harvestman, and sometimes even for craneflies. To keep things clear, I'll refer to members of the spider family Pholcidae only as cellar spiders from this point forward.

Description

If you want to observe cellar spiders, I'll give you one guess where you should look!

If you haven't guessed already, pholcid spiders often take up residence in basements, sheds, garages, and other similar structures. They construct irregular, stringy webs (another way to differentiate them from harvestman, which don't produce silk).

Most (but not all) cellar spiders have legs that are disproportionately long for their bodies. The species with shorter legs typically live in leaf litter, and not your basement. They have flexible tarsi. Most (but again, not all) pholcid species have eight eyes; some species have just six.

Cellar spiders are usually dull in color, and less than 0.5 inches in body length. The largest known pholcid species in the world, Artema atlanta, is only 11 mm (0.43 mm) long. This species was introduced to North America, and now inhabits a small area of Arizona and California. The long-bodied cellar spider, Pholcus phalangioides, is a very common find in basements throughout the world.

Classification

Kingdom – Animalia
Phylum – Arthropoda
Class – Arachnida
Order – Araneae
Infraorder - Araneomorphae
Family - Pholcidae

Diet

Cellar spiders prey on insects and other spiders and are particularly fond of eating ants. They are highly sensitive to vibrations and will close in on an unsuspecting arthropod rapidly if it happens to wander into its web.

Cellar spiders have also been observed purposely vibrating the webs of other spiders, as a tricky way of luring in a meal.

Life Cycle

Female cellar spiders wrap their eggs loosely in silk to form a rather flimsy but effective egg sac. The mother pholcid carries the egg sac in her jaws. Like all spiders, the young spiderlings hatch from their eggs looking similar to adults. They molt their skin as they grow into adults.

Special Adaptations and Defenses

When they feel threatened, cellar spiders will vibrate their webs rapidly, presumably to confuse or deter the predator. It's unclear whether this makes the pholcid more difficult to see or catch, but it's a strategy that seems to work for the cellar spider. Some people refer to them as vibrating spiders because of this habit. Cellar spiders are also quick to autotomize (shed) legs to escape predators.

Although cellar spiders do have venom, they aren't a cause for concern. A common myth about them is that they are highly venomous, but lack fangs long enough to penetrate human skin. This is a total fabrication. It's even been debunked on Mythbusters.

Range and Distribution

Worldwide, there are nearly 900 species of cellar spiders, with most living in the tropics.

Just 34 species live in North America (north of Mexico), and some of these were introduced. Cellar spiders are most often associated with human dwellings, but also inhabit caves, leaf litter, rock piles, and other protected natural environments.