Pholcus phalangioides, commonly called the Cellar Spider or Long-bodied Cellar Spider, is a cosmopolitan arachnid frequently found in human-made structures worldwide. These spiders prefer dark, sheltered, and undisturbed domestic environments such as basements, garages, and cellars, often positioning themselves high on ceilings or in quiet corners. Despite their delicate appearance, these spiders are highly effective generalist predators, consuming a wide variety of prey.
The Primary Diet of Small Arthropods
The bulk of the Cellar Spider’s diet consists of small arthropods that share its domestic habitat. They are carnivorous, preying on small insects and other invertebrates that inadvertently wander into their webs. Common prey items include small flies, such as gnats and fruit flies, as well as mosquitoes and moths.
The spider also regularly consumes other small, soft-bodied invaders like silverfish, woodlice, and earwigs. As a sit-and-wait predator, its diet is dictated by the specific small creatures that are abundant and stumble into the immediate vicinity of its web. The spider often constructs its loose web near a light source or an entryway to maximize prey encounters.
Hunting Strategy and Web Construction
The hunting success of Pholcus phalangioides begins with the unique architecture of its web, which is a tangled, three-dimensional mesh of silk threads. Unlike the symmetrical, sticky orb webs of some other species, the Cellar Spider’s web is non-adhesive, relying on its irregular, loose structure to confuse and entangle passing insects. The silk strands act as trip wires, signaling the spider when prey makes contact.
Once a creature is entangled, the spider rapidly approaches and uses its long, slender legs to throw strands of silk over the prey. This wrapping technique immobilizes the victim while allowing the spider to maintain a safe distance, preventing any counterattack. After the prey is thoroughly bound, the Cellar Spider delivers a venomous bite to subdue and begin digesting its meal. The spider may also initiate a rapid vibrating or “whirling” motion in its web, which can further entangle prey or obscure the spider from a potential threat.
Specialized and Unusual Prey
Beyond common insects, the Cellar Spider is known for its specialized diet of other spiders, a behavior called araneophagy. Despite their comparatively fragile build, these spiders successfully attack and consume much larger arachnids, including house spiders and wolf spiders. They achieve this by actively invading the webs of other species.
The spider uses aggressive mimicry by vibrating the host spider’s web in a specific rhythm that imitates the struggle of an ensnared insect. When the web’s owner approaches its supposed meal, the Cellar Spider attacks, quickly wrapping the victim in silk. This predatory versatility extends to highly venomous species, as the Cellar Spider has been observed successfully preying on Black Widow and Redback Spiders. Their ability to kill such dangerous prey is not due to potent venom, which is comparatively mild, but rather to their long legs which allow them to wrap the victim from a safe distance.