The cellar spider (family Pholcidae) is a common arachnid often found in homes worldwide. It is popularly known as “Daddy Long-Legs” due to its extremely long, thin legs, though it is frequently mistaken for the unrelated harvestman. The spider’s body is typically seven to eight millimeters long, but its front legs can span up to 50 millimeters. Cellar spiders are inconspicuous, usually appearing gray, tan, or yellowish, and prefer to establish their loose, messy webs in undisturbed, cooler areas like cellars, basements, crawl spaces, and sheds.
Primary Prey and Common Insects
The cellar spider’s diet primarily consists of small household arthropods that accidentally blunder into their unorganized webs. These spiders are opportunistic predators, readily consuming insects such as mosquitoes, gnats, flies, and small moths. Their ability to capture and consume these pests makes them a helpful form of natural insect control within human dwellings.
Because their webs are non-sticky, the spiders rely on the messy structure to entangle and confuse the prey. Once an insect makes contact, the spider uses its high sensitivity to vibration to pinpoint the creature. These generalist feeding habits ensure they maintain a steady caloric intake from the most abundant food sources in their environment.
Specialized Hunting of Other Spiders
Cellar spiders have a specialized diet of other spider species, a behavior known as araneophagy. Despite their fragile appearance, they are highly effective predators of much larger and sometimes dangerous arachnids. Their prey includes wolf spiders, certain funnel-web spiders, and even black widows.
The cellar spider’s long legs offer a significant advantage during an attack, allowing them to maintain distance and keep their body out of reach of the rival’s counter-attack. They can enter the sticky webs of other spiders without becoming ensnared themselves. They use this access to directly attack or mimic a trapped insect, luring the unsuspecting web owner into a vulnerable position.
Hunting Strategy and Feeding Behavior
The cellar spider’s web is a loose, irregular, and tangled structure that serves as a sensory net rather than a purely adhesive trap. When a potential meal is detected by the web’s vibration, the spider approaches. It swiftly envelops the prey with silk, often throwing silk from a distance to securely bind the creature before delivering a fatal bite.
A distinctive behavior is the “vibration strategy,” where the spider rapidly shakes its web when a large insect or predator is detected. This gyrating motion blurs the spider’s outline, making it difficult for a predator or large prey to locate its body. Some cellar spiders also employ aggressive mimicry by vibrating the webs of other spiders to imitate the struggles of a trapped insect, baiting the owner to investigate. Once a meal is secured, the spider liquefies its food with digestive enzymes and may consume the prey immediately or store it for later consumption.