Pholcus phalangioides

Pholcus phalangioides goes by several common names: the cosmopolitan cellar spider, the long-bodied cellar spider, or one of the types called a daddy long-legs spider. It belongs to the family Pholcidae. Swiss entomologist Johann Kaspar Füssli (also spelled Fuesslin) first described it in 1775, naming it *Aranea phalangoides*. Its "daddy long-legs" nickname should not be mixed up with the harvestmen (order Opiliones) or crane flies (superfamily Tipuloidea), which share the same common name but are different arachnids or insects.

Females have a body length of about 8 mm, while males are slightly smaller. Their legs average 5 to 6 times the body length. This spider tends to live on ceilings in rooms, caves, garages, or cellars. It is considered helpful in some regions because it hunts other spiders, including dangerous ones like redbacks, and it poses no harm to humans. There have also been reports of potential medicinal uses for its silk.

In terms of taxonomy, *P. phalangioides* is a member of the genus *Pholcus* within the family Pholcidae, sharing ancestry with roughly 1,340 similar cellar spiders. All are known for legs that stretch 5 to 6 times their body size.

Population sizes are heavily influenced by human-made buildings, as these spiders prefer warmer indoor habitats. The abundance of buildings worldwide has favored them, though populations tend to be small, widely scattered, and isolated from one another. This isolation, combined with low mobility, makes genetic drift—especially the founder effect—a major factor in population structure. Some gene flow occurs between populations, but it is much less significant than the genetic drift caused by geographic isolation. As a result, individuals within the same local population show very little genetic variation, while different populations differ substantially.

The species is sexually dimorphic: females are slightly larger. Males average about 6 mm in length (range 6–10 mm), while females average 7–8 mm. Their eight long, thin legs are covered in fine grey bristles and are roughly 5 to 6 times the body length; an adult female’s legs average about 50 mm. Like all spiders, the body splits into a prosoma (cephalothorax) and an opisthosoma (abdomen). Most of the prosoma is taken up by the brain. The opisthosoma holds the heart, respiratory system, mid-gland, reproductive system, genital tract, and silk glands. The body is translucent, grey-pale brown, with a dark spot on the back of the prosoma and blurred dark spots on the upper side of the opisthosoma. While some pholcids have six eyes, *P. phalangioides* has eight: a pair of smaller, dark eyes at the front of the prosoma, followed by three parallel rows of larger eye pairs. A hard exoskeleton covers the body; younger spiders molt more often. During molting, enzymes release the body from the underlying tissue, and the spider escapes the old exoskeleton, leaving behind the exuviae. It takes about a year to mature, and adults can live two years or more.

Its exact native range is uncertain due to human spread, but it likely originated in subtropical parts of Afro-Eurasia, with recent authorities considering it native only to Asia. As a synanthropic species, its modern distribution has been shaped by human movement. It now occurs in most temperate countries on every continent. It cannot survive cold well, so in cooler regions it stays indoors—especially in human dwellings. It favors dim, dark, quiet spots, often in building corners, attics, or homes. Outdoor populations live in caves and rock crevices.

*P. phalangioides* is a carnivorous predator, feeding on insects, other spiders, and more.