Pholcidae

The Pholcidae family of araneomorph spiders includes over 2,000 species, known by many common names such as cellar spider, daddy long-legs spider, carpenter spider, daddy long-legger, vibrating spider, gyrating spider, long daddy, and angel spider. Carl Ludwig Koch first described the family in 1850, and it now comprises 94 genera. The name "daddy long-legs" is shared with harvestmen and crane flies, though it most commonly refers to *Pholcus phalangioides*.

These spiders have notably long, thin legs with flexible tarsi. Their eye arrangement sets them apart from other long-legged spiders: they typically have two groups of three eyes each, with a possible pair of small eyes in between, totaling eight. Some genera, like *Modisimus*, *Spermophora*, and *Spermophorides*, lack that middle pair and have only six eyes. The body is usually whitish or grey. Harvestmen, also called daddy longlegs, have just one pair of eyes and a body that appears as a single segment. Pholcids have two body segments: the prosoma, which may be evenly domed or have a furrow or pit, and the opisthosoma, which can be long and cylindrical, long and pointed at the back, or short. Body length varies from just over 1 millimeter (*Spermophorides lascars*) to 11 millimeters (*Artema atlanta*).

Pholcids live on every continent except Antarctica. They hang upside down in messy, irregular webs built in dark, damp places like caves, under rocks and loose bark, and in abandoned mammal burrows. In human homes, they spin webs in undisturbed areas such as high corners, attics, and cellars—hence the name "cellar spider."

Their webs lack adhesive and rely on an irregular structure to trap prey. When prey is detected, the spider quickly wraps it in silk, eating it immediately or storing it for later. After feeding, it cleans the web by dropping the carcass. Pholcids are passive toward humans. When disturbed by a touch to the web or by large entangled prey, some species vibrate rapidly in a gyrating motion, sometimes falling into a circular rhythm. This oscillation may match the web’s elasticity, creating a larger movement. This threat response, which gives them the name "vibrating spiders," may confuse predators, signal rivals, or help capture or further entangle prey. If the disturbance continues, the spider retreats or drops from the web to escape.

Pholcids eat insects but also invade other spiders’ webs to consume the host, eggs, or prey. Some vibrate another spider’s web to mimic trapped prey, luring the host closer. They prey on *Tegenaria* funnel weaver spiders, redback spiders, huntsman spiders, and house spiders. In regions with dense hobo spider populations, pholcids may help keep *Tegenaria* in check. They have also been observed feeding on *Steatoda nobilis* in Ireland and England.

*Pholcus phalangioides* commonly uses an alternating tetrapod gait—first right leg, then second left leg, then third right leg, and so on—though frequent variations occur.

A common urban legend claims that daddy long-legs spiders have the most potent venom of any spider but cannot bite humans due to small or weak fangs. This is false for pholcids, harvestmen, and crane flies. Pholcids can bite humans, but their venom is not medically significant. Harvestmen and crane flies lack venom or fangs entirely. Pholcids have a short, hooked fang structure called uncate, similar to brown recluse spiders, which can deliver medically significant bites. Possible explanations for the legend include that pholcid venom is not toxic to humans, their fangs are smaller than those of brown recluses, or recluses have stronger muscles for fang penetration. According to Rick Vetter of the University of California, Riverside, the daddy long-legs spider has never harmed a human, and there is no evidence it is dangerous. The legend may stem from the fact that pholcids prey on venomous spiders like redbacks and other *Latrodectus* widows.